2024-31402. Taking and Importing Marine Mammals; Taking Marine Mammals Incidental to the U.S. Navy Training and Testing Activities in the Hawaii-Southern California Training and Testing Study Area

Table 1—Marine Mammal Occurrence Within the HSTT Study Area

Common name	Scientific name	Stock	Status		Occurrence	Seasonal absence	Stock abundance (CV)/minimum population
			MMPA	ESA
Blue whale	Balaenoptera musculus	Eastern North Pacific	Strategic, Depleted	Endangered	Southern California	-	1,898 (0.085)/1,767.
		Central North Pacific	Strategic, Depleted	Endangered	Hawaii	Summer	133 (1.09)/63.
Bryde's whale	Balaenoptera brydei/edeni	Eastern Tropical Pacific	-	-	Southern California	-	unknown.
		Hawaii	-	-	Hawaii	-	791 (0.29)/623.
Fin whale	Balaenoptera physalus	CA/OR/WA	Strategic, Depleted	Endangered	Southern California	-	11,065 (0.405)/7,970.
		Hawaii	Strategic, Depleted	Endangered	Hawaii	Summer	203 (0.99)/101.
Humpback whale	Megaptera novaeangliae	Central America/Southern Mexico—CA/OR/WA	Strategic	Endangered 1	Southern California	Winter	1,496 (0.171)/1,284.
		Mainland Mexico—CA/OR/WA	Strategic	Threatened 1	Southern California	Winter	3,477 (0.101)/3,185.
		Hawai'i	-	- 1	Hawaii	Summer	11,278 (0.56)/7,265.
Minke whale	Balaenoptera acutorostrata	CA/OR/WA	-	-	Southern California	-	915 (0.792)/509.
		Hawaii	-	-	Hawaii	Summer	438 (1.05)/212.
Sei whale	Balaenoptera borealis	Eastern North Pacific	Strategic, Depleted	Endangered	Southern California	-	864 (0.40)/625.
		Hawaii	Strategic, Depleted	Endangered	Hawaii	Summer	391 (0.9)/204.
Gray whale	Eschrichtius robustus	Eastern North Pacific	-	-	Southern California	-	26,960 (0.05)/25,849.
		Western North Pacific	Strategic, Depleted	Endangered	Southern California	-	290 (NA)/271.
( print page 4967)
Sperm whale	Physeter macrocephalus	CA/OR/WA	Strategic, Depleted	Endangered	Southern California	-	2,606 (0.135)/2,011.
		Hawaii	Strategic, Depleted	Endangered	Hawaii	-	5,707 (0.23)/4,486.
Pygmy sperm whale	Kogia breviceps	CA/OR/WA	-	-	Southern California	Winter and Fall	4,111 (1.12)/1,924.
		Hawaii	-	-	Hawaii	-	42,083 (0.64) 25,695.
Dwarf sperm whale	Kogia sima	CA/OR/WA	-	-	Southern California	-	unknown.
		Hawaii	-	-	Hawaii	-	unknown.
Baird's beaked whale	Berardius bairdii	CA/OR/WA	-	-	Southern California	-	1,363 (0.53)/894.
Blainville's beaked whale	Mesoplodon densirostris	Hawaii	-	-	Hawaii	-	1,132 (0.99)/564.
Goose-beaked whale 2	Ziphius cavirostris	CA/OR/WA	-	-	Southern California	-	5,454 (0.27)/4,214.
		Hawaii	-	-	Hawaii	-	4,431 0.41/3,180.
Longman's beaked whale	Indopacetus pacificus	Hawaii	-	-	Hawaii	-	2,550 (0.67)/1,527.
Mesoplodont beaked whales	Mesoplodon spp.	CA/OR/WA	-	-	Southern California	-	3,044 (0.54)/1,967.
Common Bottlenose dolphin	Tursiops truncatus	California Coastal	-	-	Southern California	-	453 (0.06)/346.
		CA/OR/WA Offshore	-	-	Southern California	-	3,477 (0.696)/2,048.
		Hawaii Pelagic	-	-	Hawaii	-	unknown.
		Kauai and Niihau	-	-	Hawaii	-	112 (0.24)/92.
		Oahu	-	-	Hawaii	-	112 (0.17)/97.
		Maui Nui 3	-	-	Hawaii	-	64 (0.15)/56.
		Hawaii Island	-	-	Hawaii	-	136 (0.43)/96.
False killer whale	Pseudorca crassidens	Main Hawaiian Islands Insular 4	Strategic, Depleted	Endangered	Hawaii	-	167 (0.14)/149.
		Hawaii Pelagic	-	-	Hawaii	-	5,528 (0.35)/4,152.
		Northwestern Hawaiian Islands	-	-	Hawaii		477 (1.71)/178.
Fraser's dolphin	Lagenodelphis hosei	Hawaii			Hawaii	-	40,960 (0.7)/24,068.
Killer whale	Orcinus orca	Eastern North Pacific Offshore	-	-	Southern California	-	300 (0.1)/276.
		West Coast Transient	-	-	Southern California	-	349 (N/A)/349.
		Hawaii	-	-	Hawaii	-	161 (1.06)/78.
Long-beaked common dolphin	Delphinus capensis	California	-	-	Southern California	-	83,379 (0.216)/69,636.
Melon-headed whale	Peponocephala electra	Hawaiian Islands	-	-	Hawaii	-	40,647 (0.74)/23,301.
		Kohala Resident	-	-	Hawaii	-	unknown.
Northern right whale dolphin	Lissodelphis borealis	CA/OR/WA	-	-	Southern California	-	29,285 (0.72)/17,024.
Pacific white-sided dolphin	Lagenorhynchus obliquidens	CA/OR/WA	-	-	Southern California	-	34,999 (0.222)/29,090.
Pantropical spotted dolphin	Stenella attenuata	Oahu	-	-	Hawaii	-	unknown.
		Maui Nui 3	-	-	Hawaii	-	unknown.
		Hawaii Island	-	-	Hawaii	-	unknown.
		Hawaii Pelagic	-	-	Hawaii	-	67,313 (0.27)/53,839.
Pygmy killer whale	Feresa attenuata	Tropical	-	-	Southern California	Winter & Spring	unknown.
		Hawaii	-	-	Hawaii	-	10,328 (0.75)/5,885.
Risso's dolphins	Grampus griseus	CA/OR/WA	-	-	Southern California	-	6,336 (0.32)/4,817.
		Hawaii	-	-	Hawaii	-	6,979 (0.29)/5,283.
Rough-toothed dolphin	Steno bredanensis	NSD 5	-	-	Southern California	-	unknown.
		Hawaii	-	-	Hawaii	-	83,915 (0.49)/56,782.
Short-beaked common dolphin	Delphinus delphis	CA/OR/WA	-	-	Southern California	-	1,056,308 (0.21)/888,971.
Short-finned pilot whale	Globicephala macrorhynchus	CA/OR/WA	-	-	Southern California	-	836 (0.79)/466.
		Hawaii	-	-	Hawaii	-	19,242 (0.23)/15,894.
Spinner dolphin	Stenella longirostris	Hawaii Pelagic	-	-	Hawaii	-	unknown.
		Hawaii Island	-	-	Hawaii	-	665 (0.09)/617.
( print page 4968)
		Oahu and 4-Islands	-	-	Hawaii	-	unknown.
		Kauai and Niihau	-	-	Hawaii	-	unknown.
		Kure and Midway	-	-	Hawaii	-	unknown.
		Pearl and Hermes	-	-	Hawaii	-	unknown.
Striped dolphin	Stenella coeruleoalba	CA/OR/WA	-	-	Southern California	-	29,988 (0.3)/23,448.
		Hawaii	-	-	Hawaii	-	64,343 (0.28)/51,055.
Dall's porpoise	Phocoenoides dalli	CA/OR/WA	-	-	Southern California	-	16,498 (0.61)/10,286.
Harbor seal	Phoca vitulina	California	-	-	Southern California	-	30,968 (NA)/27,348.
Hawaiian monk seal	Neomonachus schauinslandi	Hawaii	Strategic, Depleted	Endangered	Hawaii	-	1,564 (0.05)/1,444.
Northern elephant seal	Mirounga angustirostris	California	-	-	Southern California	-	187,386 (NA)/85,369.
California sea lion	Zalophus californianus	U.S. Stock	-	-	Southern California	-	257,606 (NA)/233,515.
Guadalupe fur seal	Arctocephalus townsendi	Mexico to California	Strategic, Depleted	Threatened	Southern California	-	34,187 (NA)/31,019.
Northern fur seal	Callorhinus ursinus	California	Depleted	-	Southern California	-	14,050 (NA)/7,524.
Note: A “-” indicates that this column does not apply.
1  The Mainland Mexico—CA/OR/WA stock and the Mexico—North Pacific stock (which does not occur in the HSTT Study Area) of humpback whale comprise the Mexico DPS. The Hawai'i stock comprises the Hawai'i DPS. The Central America/Southern Mexico—CA/OR/WA stock comprises the Central America DPS.
2   Ziphius cavirostris has multiple common names. In the 2018 HSTT final rule, 2020 HSTT final rule, and 2023 HSTT proposed rule, NMFS used the common name Cuvier's beaked whale. In this final rule, NMFS uses the common name goose-beaked whale instead.
3  The “4-Islands” stocks of common bottlenose dolphin and pantropical spotted dolphin are now the “Maui Nui” stocks.
4  NMFS relied on the 2022 final SAR for this stock.
5  NSD—No stock designation. Rough-toothed dolphin has a range known to include the waters off Southern California, but there is no recognized stock or data available for the U.S. West Coast.

Unusual Mortality Events

An UME is defined under section 410(6) of the MMPA as a stranding that is unexpected, involves a significant die-off of any marine mammal population, and demands immediate response. From 1991 to the present, there have been 17 formally recognized UMEs affecting marine mammals in California and Hawaii and involving species under NMFS' jurisdiction.

At the time of publication of the 2023 HSTT proposed rule, there was an active UME for gray whales which NMFS fully considered in its analysis (88 FR 68290, October 3, 2023). This UME was closed on November 9, 2023. The UME involved 690 gray whale strandings, including 347 in the United States, 316 in Mexico, and 27 in Canada. Strandings occurred from Alaska to Mexico along the west coast of North America, including in the whale's wintering, migratory, and feeding areas. The Investigative Team concluded that the preliminary cause of the UME was localized ecosystem changes in the whale's Subarctic and Arctic feeding areas that led to changes in food, malnutrition, decreased birth rates, and increased mortality all documented during the UME. Please see https://www.fisheries.noaa.gov/​national/​marine-life-distress/​2019-2023-eastern-north-pacific-gray-whale-ume-closed for additional information on this UME.

Biologically Important Areas

Kratofil et al. (2023) identified updated BIAs in Hawaii. The HSTT Study Area overlaps the updated BIAs for small and resident populations of the following species in Hawaii: spinner dolphin, short-finned pilot whale, rough-toothed dolphin, pygmy killer whale, pantropical spotted dolphin, melon-headed whale, false killer whale, dwarf sperm whale, goose-beaked whale, common bottlenose dolphin, and Blainville's beaked whale. Further, the HSTT Study Area overlaps updated BIAs for humpback whale reproduction in Hawaii. The updated BIAs overlap critical Navy training and testing areas within the HSTT Study Area, including most of the internal Navy operating areas. Please see Kratofil et al. (2023) for additional details about the BIAs.

Since publication of the 2023 HSTT proposed rule, Calambokidis et al. (2024) identified updated BIAs on the West Coast of the U.S. The HSTT Study Area overlaps feeding BIAs for blue whale and fin whale in SOCAL. Additionally, it overlaps a reproductive BIA as well as northbound and southbound migratory BIAs for gray whale. Please see Calambokidis et al. (2024) for additional details about the BIAs.

Potential Effects of Specified Activities on Marine Mammals and Their Habitat

This section provides a discussion of the ways in which components of the specified activity may impact marine mammals and their habitat. The Estimated Take section later in this document includes a quantitative analysis of the number of individuals that are expected to be taken by this activity. The Analysis and Negligible Impact Determination section considers the content of this section, the Estimated Take section, and the Mitigation Measures section, to draw conclusions regarding the likely impacts of these activities on the reproductive success or survivorship of individuals and whether those impacts are reasonably expected to, or reasonably likely to, adversely affect the species or stock through effects on annual rates of recruitment or survival. In the Potential Effects of Specified Activities on Marine Mammals and Their Habitat section of the 2018 HSTT proposed and final rules, and as updated by the 2020 HSTT final rule, NMFS provided a description of the ways marine mammals may be affected by the same activities that the Navy will be conducting during the 7-year period analyzed in this rulemaking in the form of serious injury or mortality, physical trauma, sensory impairment (permanent and temporary threshold shifts and acoustic masking), ( print page 4969) physiological responses (particularly stress responses), behavioral disturbance, or habitat effects. Further, in the 2023 HSTT proposed rule, we summarized any new relevant information from the scientific literature since publication of the 2020 HSTT final rule. We do not repeat the information here, all of which remains current and applicable, but refer the reader to those rules and the 2018 HSTT FEIS/OEIS (chapter 3, section 3.7 Marine Mammals), which NMFS participated in the development of via our cooperating agency status and adopted to meet our NEPA requirements.

In the Potential Effects of Specified Activities on Marine Mammals and Their Habitat section of the 2018 HSTT final rule, we stated that it has been speculated for some time that beaked whales might have unusual sensitivities to sonar sound due to their likelihood of stranding in conjunction with MFAS use, although few definitive causal relationships between MFAS use and strandings have been documented, and no such findings have been documented with Navy use in Hawaii and southern California. On March 25, 2022, a beaked whale (species unknown) stranded in Honaunau Bay, Hawaii. The animal was observed swimming into shore and over rocks. Bystanders intervened to turn the animal off of the rocks, and it swam back out of the Bay on its own. Locals reported hearing a siren or alarm type of sound underwater on the same day, and a Navy vessel was observed from shore on the following day. The Navy confirmed it used CAS within 50 km (27 nmi) and 48 hours of the time of stranding, though the stranding has not been definitively linked to the Navy's CAS use.

An initial study of another deep diving odontocete, the sperm whale, found similar behavioral responses and reductions in foraging when whales were exposed to PAS and CAS at similar cumulative Sound Exposure Levels (SEL_cum), even though the CAS signal had a lower source level than the PAS signal. This may indicate that animals were, in this case, responding to the cumulative energy of a signal rather than the instantaneous amplitude (Cure et al. 2021, Isojunno et al. 2020). If a beaked whale were inshore of a Navy vessel using either PAS or CAS MFAS, and responded by moving away from the vessel, they could find themselves in shallow water and become disoriented, as may have happened in the case of Honaunau Bay. In addition, the animal was not seen after it returned to sea, so blood tissue samples could not be obtained. There has been a growing body of literature about the impacts of new pathogens on the health and stranding of marine mammals, including beaked whales in Hawaii and other locations in the Pacific ( e.g., Clifton et al. 2023 and West et al. 2013).

NMFS has reviewed new relevant information from the scientific literature since publication of the 2023 HSTT proposed rule. Further, in the 2023 HSTT proposed rule, we summarized any new relevant information from the scientific literature since publication of the 2020 HSTT final rule. Summaries of the new key scientific literature reviewed since publication of the 2023 HSTT proposed rule are presented below. The literature generally falls into the following topic areas: Vessel Strike; Hearing, Vocalization, and Masking; Hearing Loss (Temporary Threshold Shift (TTS) and Permanent Threshold Shift (PTS)); Behavioral Reactions; Stranding; Population Consequences of Disturbance and Cumulative Stressors; Methodology for Assessing Acoustic Impacts.

Vessel Strike

Dunlop (2024) studied migrating east Australian humpback whales' response to approaching vessels to determine if individuals exhibited an avoidance response. While some select groups did display changes in their movements, the sampled collective did not display any consistent vessel avoidance response. Furthermore, the degree of avoidance was lower as vessels approached at faster speeds. Overall, the results showed that humpbacks were generally unresponsive to approaching vessels regardless of the speed or noise level at which they approached. Female-calf pairs proved to be the biggest exception to this pattern; though this demographic did not exhibit a consistent response as a whole, these pairs were more likely to change their travel pattern more than any other group. Due to the lack of response from the population, the results suggest that implementation of vessel strike avoidance protocols is critical for successfully conserving large whale populations.

Redfern et al. (2024) developed a new metric for analyzing vessel strike risk reduction (“PLETHd”) and applied it to North Atlantic right, humpback, fin, and sei whale distributions along the U.S. East Coast. The metric is calculated using three parameters: the relationship between vessel speed and the probability that a strike is lethal, vessel transit distance, and whale distributions. The authors compared the impact of a 14 kn (25.9 km/hr) vs. 10 kn (18.5 km/hr) speed restriction and found that only the 10 kn (18.5 km/hr) reduction substantially reduced risk. The authors also found that applying a 10 kn (18.5 km/hr) speed restriction within multiple whale species' critical habitat zones was almost as effective as enacting the same speed restriction along the entire East Coast Exclusive Economic Zone (EEZ). The results suggest that 10 kn (18.5 km/hr) speed restrictions are a robust method for reducing vessel strike risk and that vessel restrictions within high-density core areas of a marine mammal's habitat can be highly impactful.

Hearing, Vocalization, and Masking

Parnell et al. (2024) studied the soundscapes of four underwater Hawaiian monk seal critical habitats, including measurement of ambient noise and characterization of detected sound sources. The authors observed diel patterns in both anthropogenic and biological sound sources that mask acoustic communication in Hawaiian monk seals. The measurements collected for this study provide a baseline for future research on impacts of anthropogenic activities on these soundscapes.

A multi-national team of scientists (U.S. and Norway) obtained the first hearing measurements of a mysticete species through auditory evoked potential (AEP) tests. During the 2023 field season, AEP tests were conducted on two adolescent female minke whales in Norway (Houser et al. 2024). Houser et al. (2024) indicate that the minke whale's upper-frequency limit of hearing occurs somewhere between 45 to 90 kHz. Minke whale's high-frequency sensitivity is hypothesized to support detection of the echolocation clicks of one their predators, the killer whale. The bandwidth of the tone-bursts used in the Houser et al. (2024) AEP testing was too broad to define the precise upper-frequency limit, but indicates this species is more sensitive to higher frequencies than previously predicted based on inner ear anatomy and vocalization data (Southall et al. 2019; NMFS 2024). Results from their final 2024 field season, which included further examination of the upper-frequency limit of hearing, are expected to be published in 2025, with preliminary data from two additional whales indicating that minke whale hearing is best around 32 kHz.

Hearing Loss (TTS and PTS)

Gransier and Kastelein (2024) examined TTS susceptibility in harbor porpoises and harbor seals based on exposures varying in frequency range and level. Specifically, exposures consisted of 100% duty cycle one-sixth- ( print page 4970) octave noise bands at frequencies covering the entire hearing range of each species. Despite these species having different audiograms and regions of best sensitivity ( i.e., underwater pinnipeds are sensitive to sounds ranging from approximately 0.01 to 40-60kHz, while most odontocetes are sensitive sounds ranging from approximately 0.25 to 80-125kHz), the frequency-specific susceptibility to TTS was similar amongst both species, with the greatest susceptibility to TTS occurring at frequencies from 22.5 to 50 kHz and least susceptible to sounds below 10 kHz. The frequency of minimum TTS for the harbor seal aligns with its frequency of best hearing, while frequency of minimum TTS for the harbor porpoise is well below the frequency of best hearing. This study illustrates that the audiogram does not always serve as a good predictor of frequency-dependent susceptibility to TTS, with the pattern of susceptibility to TTS in these two species being more comparable than their audiograms.

Brewer et al. (2023) described 41 call types of Cook Inlet beluga vocal behavior and classified them into three categories: (1) whistles, (2) pulsed calls, and (3) combined calls. These are the first descriptions of vocal repertoire of this species in two critical habitat locations and across multiple seasons. Call types were then used to investigate the potential for masking from commercial ship noise. It was found that call types (0-12 kHz) were partially masked by distant ship noise and completely masked by close ship noise. This study provides evidence that ship noise can impact vocal communication of this population. Specifically Cook Inlet beluga vocalizations in the Susitna area, seven of the beluga's most common calls are either partially or fully masked by commercial ship traffic.

Kastelein et al. (2024) examined TTS in two California sea lions exposed to one-sixth-octave noise band centered at 32 kHz for 60-minutes of exposure, resulting in cumulative sound exposure levels (SEL_cum) ranging from 168 to 192 dB. Hearing after exposure was examined at the center frequency of the fatiguing sound (32 kHz) and at half an octave (44.8 kHz) and one octave above the center frequency (63 kHz). Higher SEL_cum resulted in greater threshold shifts. Furthermore, the greatest TTS occurred at half an octave above the center frequency, with TTS onset (6 dB threshold shift) measured at 44.8 kHz occurring at a 179 dB SEL_cum. TTS patterns and recovery was similar between the two individuals, with TTSs up to 6.7 dB recovering within 8 minutes of exposure, TTSs up to 12 dB recovering within an hour, and only the highest TTS measured (12.9 dB) taking over an hour to recover. The results of this study were directly incorporated in the Navy's updated Phase IV AUD INJ/TTS criteria and indicate that California sea lions have lower AUD INJ/TTS onset than previously predicted (Southall et al. 2019).

Behavioral Reactions

Ceciarini et al. (2023) tested the efficacy of Acoustic Deterrent Devices for minimizing common bottlenose dolphin interactions with trammel nets in the Northern Tyrrhenian Sea. The authors used interactive pingers which emitted output signals “from 5 up to 500 kHz at 168 dB re 1 μPa at 1 m as random high-speed tones FM ranging from 100 μs up to seconds”. The study found that catch damage from dolphins was significantly lower in nets where pingers were used.

Elmegaard et al. (2023) exposed six harbor porpoises to Acoustic Harassment Devices (AHDs), commonly referred to as “seal scarers”, to determine if they would exhibit any physiological or behavioral reactions. The AHDs pulsed at 14 kHz with a source level of 189 dB re 1 µPa (rms) or sound exposure level of 184 dB re 1 µPa² s, with porpoise RLs ranging from 98-132 dB re 1 µPa. All individuals sampled exhibited a mixture of behavioral or physiological responses, including startling, increased distance from the sound source, increased swim speed, diving, altered echolocation patterns, cardiac responses, or altered respiration patterns. Overall, responses were observed in every individual up to 7 km or down to an RL of 98 dB re 1 µPa.

Frankish et al. (2023) followed ten harbor porpoises for 5 to 10 days to observe their reactions to ship traffic around Denmark. The porpoises spent over half of the study period within 10 km of a ship, and a third of the study period exposed to noise levels above ambient. The porpoises responded by moving away from ships during the day, and diving deep during the night. They had a higher likelihood of altering their movements when louder ships were nearby (maximum probability of deterrence = 12.2 percent during the day and 14.9 percent at night), and moved an average of 3.2 km away from 13.6 different ships every day. Deeper dives occurred less frequently, at a rate of 5.7 different ships per individual per night. The porpoises also reacted to loud ships that were far away (>2 km at 93 ± 14 dB re 1 μPa² ), though responses occurred less frequently (5 to 9 percent of the time vs. up to 14.9 percent of the time at close range).

Southall et al. (2023) used control exposure experiments (CEEs) to provide the first results in examining the impact of mid-frequency navy sonar (3.5-4.1 kHz) or pseudorandom noise (similar frequency, duration and source and received level compared to mid-frequency sonar) on fin whale behavior in feeding habitats of the Southern California Bight. Of the 15 exposed fin whales, only five individuals demonstrated a mild to moderate behavioral changes (avoidance, changes in feeding, diving, or respiration), with no changes demonstrated for whales in the six control exposures. Compared to blue whales, fin whale behavioral responses were more limited in occurrence, severity and duration and were found to be less dependent upon contextual aspects of exposure, with received level as the primary factor associated with behavioral responses. Additionally, foraging success was not compromised by exposures from this study. The authors note that differences observed between behavioral response in fin whales in this study and blue whales in previously published studies may be attributed to the smaller sample size associated with this study. However, as seen in blue whales, fin whale behavior returned to baseline conditions after noise exposure ended.

Methodology for Assessing Acoustic Impacts

Indeck et al. (2024) assessed North Atlantic right whale, fin, and blue whale detectability by Slocum gliders near heavily used shipping lanes in the Gulf of St. Lawrence, Canada. The goal of the study was to evaluate the gliders' suitability as a passive acoustic monitoring platform for whale detection in areas with high anthropogenic noise levels. The authors found that shipping lane noise did not substantially impact whale detectability, as calls from the highly trafficked areas were not masked significantly more than calls in quieter areas nearby. The gliders were therefore identified as a viable PAM platform to use in and around busy shipping areas. These results suggest that gliders could be an important tool for monitoring mysticetes in highly industrialized areas and assisting in ongoing dynamic management initiatives.

Conclusion for New Pertinent Science Since Publication of the 2023 HSTT Proposed Rule

Having considered the best scientific information available, specifically new relevant information published since the 2023 HSTT proposed rule, we have ( print page 4971) determined that there is no new information that substantively affects our analysis of impacts on marine mammals and their habitat that appeared in the 2020 HSTT final rule, all of which remains applicable and valid for our assessment of the effects of the Navy's activities during the 7-year period of this rulemaking.

Estimated Take of Marine Mammals

This section indicates the number of takes that NMFS is authorizing, which are based on the amount of take that NMFS anticipates could occur or is likely to occur, depending on the type of take and the methods used to estimate it, as described below. NMFS coordinated closely with the Navy in the development of their incidental take application and agrees that the methods the Navy has put forth described herein, in the 2019 HSTT proposed rule, 2020 HSTT final rule, and in the 2018 HSTT proposed and final rules to estimate take (including the model, thresholds, and density estimates), and the resulting numbers are based on the best available science and appropriate for authorization, with the exception of that of humpback whales, discussed further below. The number and type of incidental takes that could occur or are likely to occur annually remain identical to those authorized in the 2018 HSTT regulations and 2020 HSTT regulations, with the exception of authorized takes by serious injury or mortality by vessel strike and harassment takes of humpback whale stocks in Southern California (due to the new stock structure).

Takes are predominantly in the form of harassment, but a small number of serious injuries or mortalities could occur. For military readiness activities, the MMPA defines “harassment” as (i) any act that injures or has the significant potential to injure a marine mammal or marine mammal stock in the wild (Level A harassment); or (ii) any act that disturbs or is likely to disturb a marine mammal or marine mammal stock in the wild by causing disruption of natural behavioral patterns, including, but not limited to, migration, surfacing, nursing, breeding, feeding, or sheltering, to a point where such behavioral patterns are abandoned or significantly altered (Level B harassment).

Authorized takes will primarily be in the form of Level B harassment, as use of the acoustic and explosive sources ( i.e., sonar, air guns, pile driving, explosives) is more likely to result in the disruption of natural behavior patterns to a point where they are abandoned or significantly altered (as defined specifically at the beginning of this section but referred to generally as behavioral disturbance) or TTS for marine mammals. There is also the potential for Level A harassment in the form of auditory injury and/or tissue damage (the latter from explosives only) to result from exposure to the sound sources utilized in training and testing activities. Additionally, serious injuries or mortalities of mysticetes (except for sei whales, minke whales, Bryde's whales, Central North Pacific stock of blue whales, Hawaii stock of fin whales, Western North Pacific stock of gray whales, and sperm whales) could occur through vessel strike. Mitigation and monitoring measures are expected to minimize the severity of the taking to the extent practicable.

Generally speaking, for acoustic impacts, NMFS estimates the amount and type of harassment by considering: (1) acoustic thresholds above which NMFS believes the best available science indicates marine mammals would experience behavioral disturbance or incur some degree of temporary or permanent hearing impairment; (2) the area or volume of water that will be ensonified above these levels in a day or event; (3) the density or occurrence of marine mammals within these ensonified areas; and (4) the number of days of activities or events.

Acoustic Thresholds

Using the best available science, NMFS, in coordination with the Navy, has established acoustic thresholds that identify the most appropriate received level of underwater sound above which marine mammals exposed to these sound sources could be reasonably expected to experience a disruption in behavior patterns to a point where they are abandoned or significantly altered, either directly or via the effects of TTS (both equated to Level B harassment) or PTS of some degree (equated to Level A harassment). Thresholds have also been developed to identify the pressure levels above which animals may incur non-auditory injury from exposure to pressure waves from explosive detonation. We described the acoustic thresholds and the methods used to determine thresholds in detail in the Acoustic Thresholds section of the 2018 HSTT final rule; please see the 2018 HSTT final rule for detailed information. Further, in the 2020 HSTT final rule, and 2023 HSTT proposed rule, we described new relevant information from the scientific literature since publication of the 2018 HSTT final rule and 2020 HSTT final rule, respectively. Since publication of the 2023 HSTT proposed rule, NMFS has updated our Technical Guidance (NMFS, 2024) containing updated acoustic criteria for auditory injury (89 FR 36762, October 24, 2024). The Technical Guidance provides updated auditory injury thresholds, where appropriate, as well as revised weighting functions, in some cases. For impulsive sources, the Updated Technical Guidance's auditory injury thresholds generally remain identical or are higher compared to our 2018 Technical Guidance, meaning that received levels would need to be higher in order for marine mammals to be expected to incur auditory injury. The exceptions are for phocid pinnipeds (PW), where the cumulative SEL threshold, in the Updated Technical Guidance, is 2 dB lower and for otariid pinnipeds (OW) where the peak sound pressure level threshold is 2 dB lower and the cumulative SEL threshold is 18 dB lower. As for the Updated Technical Guidance's weighting functions, for MF cetaceans (now called HF cetaceans in the updated document) and HF cetaceans (now called VHF cetaceans in the updated document), the weighting functions reflect a higher susceptibility to auditory injury at frequencies below 10 kHz, as compared to the 2018 Technical Guidance. Other minor changes/shifts to weighting functions ( e.g., for LF cetaceans, PW pinnipeds, OW pinnipeds) were also included. This new information was not available in a timeframe in which NMFS could have incorporated it into the quantitative analysis supporting this final rulemaking; however, NMFS did consider the information qualitatively. While these changes in the auditory injury thresholds and weighting functions could result in minor increases in PTS exposure estimates for some species, given the conservative assumptions built into the take estimate methodology, they would not be expected to result in meaningful, if any, changes in take estimates and would not be expected to change any of the findings.

Navy's Acoustic Effects Model

The Navy proposed no changes to the Acoustic Effects Model as described in the 2018 HSTT final rule (and incorporated by reference in the 2020 HSTT final rule), and there is no new information that would affect the applicability or validity of the model. Please see the 2018 HSTT final and proposed rules and Appendix E of the 2018 HSTT FEIS/OEIS for detailed information, and see the discussion of the 2024 Technical Guidance in the Acoustic Thresholds section above. ( print page 4972)

Range to Effects

The Navy proposed no changes from the 2018 HSTT final rule (and subsequent 2020 HSTT final rule) to the type and nature of the specified activities to be conducted during the 7-year period analyzed in this final rule, including equipment and sources used and exercises conducted.

As described above in the Acoustic Thresholds section, since publication of the 2023 HSTT proposed rule, NMFS has updated our Technical Guidance (NMFS, 2024) containing updated acoustic criteria for auditory injury (89 FR 36762). Please see that section for a full discussion of the updates. This new information was not available in a timeframe in which NMFS could have incorporated it into the quantitative analysis supporting this final rulemaking; however, NMFS did consider the information qualitatively. While these changes in the auditory injury thresholds and weighting functions could result in minor increases in PTS exposure estimates for some species, given the conservative assumptions built into the take estimate methodology, they would not be expected to result in meaningful, if any, changes in take estimates and would not be expected to change any of the findings.

Therefore, the ranges to effects in this final rule are identical to those described and analyzed in the 2018 HSTT final rule and 2020 HSTT final rule, including received sound levels that may cause onset of significant behavioral response and TTS and PTS in hearing for each source type or explosives that may cause non-auditory injury. Please see the Range to Effects section and tables 24 through 40 of the 2018 HSTT final rule for detailed information.

Marine Mammal Density

The Navy proposed no changes to the methods used to estimate marine mammal density described in the 2018 HSTT final rule, and there is no new information that would affect the applicability or validity of these methods or change the results in a manner that would change the necessary determinations supporting the issuance of these regulations. The Navy's estimate of marine mammal density as described in the 2018 HSTT final rule remains valid, though, as described herein, NMFS has incorporated new information regarding humpback whale stock structure into its analysis. Please see the 2018 HSTT final rule, and below, for detailed information.

As noted above, NMFS regularly updates SARs, and in this rulemaking considers the 2023 final SARs (Carretta et al. 2024, Young et al. 2024). While these SARs contain updated information, the Navy's estimate of marine mammal density as described in the 2018 HSTT final rule remains valid for the following reasons. The Navy uses its Marine Species Density Database (NMSDD) for its analysis, which is derived from multiple sources, including but not limited to SARs. In contrast, for most cetacean species, the SAR is estimated using line-transect surveys or mark-recapture studies ( e.g., Barlow, 2010; Barlow and Forney, 2007; Calambokidis et al. 2008). The result provides one single abundance value for each species across broad geographic areas, but it does not provide information on the species density or concentrations within that area, and it does not estimate density for other timeframes or seasons that were not surveyed. A change in a stock's abundance indicated in a SAR does not necessarily indicate a change in that stock's density in any given area. Therefore, stocks in the HSTT Study Area with higher abundance estimates in the most recent SARs in comparison to the abundance estimates at the time that marine mammal densities were derived for the HSTT Study Area do not necessarily now occur in higher densities in the HSTT Study Area. For humpback whale, while the stock structure in the Pacific Ocean was revised in the 2022 final SARs (Carretta et al. 2023, Young et al. 2023), the discussion above remains true regarding density of humpback whales in the HSTT Study Area across all stocks.

Take Requests

As in the 2018 HSTT final rule and 2020 HSTT final rule, the Navy determined that the three stressors below could result in the incidental taking of marine mammals. NMFS has reviewed the Navy's data and analysis and determined that it is complete and accurate, and NMFS agrees that the following stressors have the potential to result in takes of marine mammals from the Navy's planned activities:

• Acoustics (sonar and other transducers; air guns; pile driving/extraction);
• Explosives (explosive shock wave and sound, assumed to encompass the risk due to fragmentation); and
• Physical Disturbance and Strike (vessel strike).

NMFS reviewed and agrees with the Navy's conclusion that acoustic and explosive sources have the potential to result in incidental takes of marine mammals by harassment, serious injury, or mortality. NMFS carefully reviewed the Navy's analysis and conducted its own analysis of vessel strikes, determining that the likelihood of any particular species of large whale being struck is quite low. However, as noted previously, in 2021, two separate U.S. Navy vessels struck unidentified large whales on two separate occasions, one whale in June 2021 and one whale in July 2021. In May 2023, the U.S. Navy struck a large whale, which based on available photos and video, NMFS and the Navy have determined was either a fin whale or sei whale. NMFS agrees that vessel strikes have the potential to result in incidental take from serious injury or mortality for certain species of large whales, and the Navy has specifically requested coverage for these species. Therefore, the likelihood of vessel strikes, and later the effects of the incidental take that is being authorized, has been fully analyzed and is described below.

Regarding the quantification of expected takes from acoustic and explosive sources (by Level A and Level B harassment, as well as mortality resulting from exposure to explosives), the number of takes are based directly on the level of activities (days, hours, counts, etc., of different activities and events) in a given year. In the 2020 HSTT final rule, take estimates across the 7 years were based on the Navy conducting 4 years of a representative level of activity and 3 years of maximum level of activity. As in the 2020 HSTT final rule, the Navy uses the maximum annual level to calculate annual takes (which would remain identical to what was determined in the 2020 HSTT final rule, with the exception of attribution of takes to humpback whale stocks), and the sum of all years (4 representative and 3 maximum) to calculate the 7-year totals for this rulemaking.

The quantitative analysis process used for the 2018 HSTT FEIS/OEIS and the 2017 and 2019 Navy applications to estimate potential exposures to marine mammals resulting from acoustic and explosive stressors is detailed in the technical report titled Quantifying Acoustic Impacts on Marine Mammals and Sea Turtles: Methods and Analytical Approach for Phase III Training and Testing (U.S. Department of the Navy, 2018). The Navy Acoustic Effects Model estimates acoustic and explosive effects without taking mitigation into account; therefore, the model overestimates predicted impacts on marine mammals within mitigation zones. To account for mitigation for marine species in the take estimates, the ( print page 4973) Navy conducts a quantitative assessment of mitigation. The Navy conservatively quantifies the manner in which procedural mitigation is expected to reduce the risk for model-estimated PTS for exposures to sonars and for model-estimated mortality for exposures to explosives, based on species sightability, observation area, visibility, and the ability to exercise positive control over the sound source. Where the analysis indicates mitigation would effectively reduce risk, the model-estimated PTS are considered reduced to TTS and the model-estimated mortalities are considered reduced to injury. For a complete explanation of the process for assessing the effects of mitigation, see the 2017 Navy application and the Take Requests section of the 2018 HSTT final rule. The extent to which the mitigation areas reduce impacts on the affected species and stocks is addressed separately in the Analysis and Negligible Impact Determination section.

No changes have been made to the quantitative analysis process to estimate potential exposures to marine mammals resulting from acoustic and explosive stressors and calculate take estimates, with the exception of take of humpback whales to account for the change in stock structure. Please see the documents described in the paragraph above, the 2018 HSTT proposed rule, the 2018 HSTT final rule, and below for detailed descriptions of these analyses. While Oedekoven and Thomas (2022) suggest that detection of marine mammals is less certain than previously assumed at certain distances, NMFS has independently evaluated the Navy's method for application of mitigation effectiveness in estimating take and agrees that it is appropriately applied to augment the model in the prediction and authorization of injury and mortality as described in the rule, including after consideration of Oedekoven and Thomas (2022). In summary, we believe the Navy's methods, including the method for incorporating mitigation and avoidance, are the most appropriate methods for predicting PTS, TTS, and behavioral disturbance. But even with the consideration of mitigation and avoidance, given some of the more conservative components of the methodology ( e.g., the thresholds do not consider ear recovery between pulses), we would describe the application of these methods as identifying the maximum number of instances in which marine mammals would be reasonably expected to be taken through PTS, TTS, or behavioral disturbance.

Summary of Authorized Take From Training and Testing Activities

Based on the methods discussed in the previous sections and the Navy's model and quantitative assessment of mitigation, the Navy provided its take estimate and request for authorization of takes incidental to the use of acoustic and explosive sources for training and testing activities both annually (based on the maximum number of activities that could occur per 12-month period) and over the 7-year period in its 2019 rulemaking/LOA application. With the exception of changes to humpback whale take, described below, annual takes (based on the maximum number of activities that could occur per 12-month period) from the use of acoustic and explosive sources are identical to those presented in tables 41 and 42 and in the Explosives subsection of the Take Requests section of the 2018 HSTT final rule. The 2022 Navy application includes the Navy's updated take estimate and request for take by vessel strike due to vessel movement in the HSTT Study Area. NMFS reviewed the Navy's data, methodology, and analysis and determined that it was complete, but NMFS has reanalyzed the potential for vessel strike following the May 2023 strike, as described in the Authorized Take from Vessel Strikes and Explosives by Serious Injury or Mortality section. NMFS agrees that the estimates for incidental takes by harassment from all sources as well as the incidental takes by serious injury or mortality from explosives requested for authorization are the maximum number of instances in which marine mammals are reasonably expected to be taken at the time of Navy's request, and continues to be for all stocks other than humpback whales, for which changes are described below. NMFS also agrees that the takes by serious injury or mortality as a result of vessel strikes could occur. Note that, consistent with the 2020 HSTT final rule, the total amount of estimated incidental take from acoustic and explosive sources over the total 7-year period covered by the 2019 Navy application is less than the annual total multiplied by seven. Although the annual estimates are based on the maximum number of activities per year and therefore, the maximum possible estimated takes, the 7-year total take estimates are based on the sum of 3 maximum years and 4 representative years, with the exception of humpback whale stocks that occur in SOCAL for which 7-year total take is conservatively estimated as the annual total multiplied by seven. Not all activities occur every year. Some activities would occur multiple times within a year, and some activities would occur only a few times over the course of the 7-year period. Using 7 years of the maximum number of activities each year would vastly overestimate the amount of incidental take that would occur over the 7-year period where the Navy knows that it will not conduct the maximum number of activities each and every year for the 7 years.

As described above in the Description of Marine Mammals and Their Habitat in the Area of the Specified Activities section, the 2022 final SARs include a revision to the humpback whale stock structure in the Pacific Ocean. In the 2020 HSTT final rule, NMFS authorized take of the CA/OR/WA stock and Central North Pacific stock of humpback whale. Given the revised stock structure, in this final rule, NMFS has reanalyzed the potential for take of each stock of humpback whale and determined that the Central America/Southern Mexico-CA/OR/WA, Mainland Mexico-CA/OR/WA stock, and Hawaii stocks are likely to be taken by the Navy's activities.

Under the new stock structure, the Hawaii stock (Hawaii DPS) is the only stock that would occur in Hawaii. Therefore, the Hawaii stock of humpback whale is the only humpback whale stock anticipated to be taken by the Navy's activities in the HRC, and all takes of the Central North Pacific stock of humpback whale that were authorized in the 2020 HSTT final rule are anticipated to be of individuals from the new Hawaii stock. In SOCAL, the takes of individuals from the former CA/OR/WA stock that were authorized in the 2020 HSTT final rule are anticipated to be of individuals from the new Central America/Southern Mexico-CA/OR/WA and Mainland Mexico-CA/OR/WA stock.

Please see the Authorized Harassment Take from Testing Activities and Authorized Harassment Take from Training Activities sections below for the authorized annual and 7-year total number and type of Level A harassment and Level B harassment for each humpback whale stock.

Authorized Harassment Take From Training Activities

For training activities, table 11 of the 2020 HSTT final rule summarizes the Navy's take estimate and request in the 2019 Navy application and the maximum amount and type of Level A harassment and Level B harassment that NMFS concurred is reasonably expected to occur by species or stock and authorized in the 2020 HSTT LOA. In the 2022 Navy application, the Navy ( print page 4974) requested no change to this authorized take, though as described above, NMFS has since published the 2023 final, which include a revision to humpback whale stock structure. For the estimated 7-year total amount and type of Level A harassment and Level B harassment, see table 11 of the 2020 HSTT final rule for all species other than humpback whale. For the estimated amount and type of Level A harassment and Level B harassment annually, see table 41 in the 2018 HSTT final rule for all species other than humpback whale. Note that take by Level B harassment includes both behavioral disturbance and TTS. Navy figures 6-12 through 6-50 in section 6 of the 2017 Navy application illustrate the comparative amounts of TTS and behavioral disturbance for each species annually, noting that if a modeled marine mammal was “taken” through exposure to both TTS and behavioral disturbance in the model, it was recorded as a TTS.

Table 2—Humpback Whale Take From Acoustic and Explosive Effects for All Training Activities in the HSTT Study Area

Species	Stock	Annual		7-year total
		Level B harassment	Level A harassment	Level B harassment	Level A harassment
Humpback whale a	Hawaii	5,604	1	34,437	12
	Central America/Southern Mexico-CA/OR/WA (Central America DPS)	585	0	b  4,095	0
	Mainland Mexico—CA/OR/WA (Mexico DPS)	669	1	b  4,683	7
a  Combined takes from the Central America/Southern Mexico- CA/OR/WA stock and the Mainland Mexico CA/OR/WA stock are equal to takes of the CA/OR/WA stock authorized in the 2020 HSTT final rule.
b  Unlike other species and stocks, for the Central America/Southern Mexico-CA/OR/WA stock and Mainland Mexico-CA/OR/WA stock, NMFS estimated the 7-year take by Level B harassment by multiplying the annual estimated take by seven. However, between the two stocks, NMFS does not anticipate that the total number of takes by Level B harassment across all 7 years would exceed the 7,962 takes by Level B harassment from training activities that were authorized for the CA/OR/WA stock of humpback whales in the 2020 HSTT final rule.

Authorized Harassment Take From Testing Activities

For testing activities, table 12 of the 2020 HSTT final rule summarizes the Navy's take estimate and request in the 2019 Navy application and the maximum amount and type of Level A harassment and Level B harassment that NMFS concurred is reasonably expected to occur by species or stock and authorized in the 2020 HSTT LOA. In the 2022 Navy application, the Navy requested no change to this authorized take. For the estimated 7-year total amount and type of Level A harassment and Level B harassment, see table 12 of the 2020 HSTT final rule. For the estimated amount and type of Level A harassment and Level B harassment annually, see table 42 in the 2018 HSTT final rule. Note that take by Level B harassment includes both behavioral disturbance and TTS. Navy figures 6-12 through 6-50 in section 6 of the 2017 Navy application illustrate the comparative amounts of TTS and behavioral disturbance for each species annually, noting that if a modeled marine mammal was “taken” through exposure to both TTS and behavioral disturbance in the model, it was recorded as a TTS.

Table 3—Humpback Whale Take From Acoustic and Explosive Effects for All Testing Activities in the HSTT Study Area

Species	Stock	Annual		7-year total
		Level B harassment	Level A harassment	Level B harassment	Level A harassment
Humpback whale a	Hawaii	3,522	2	23,750	19
	Central America/Southern Mexico-CA/OR/WA	291	0	b  2,037	0
	Mainland Mexico—CA/OR/WA	449	0	b  3,143	0
a  Combined takes from the Central America/Southern Mexico- CA/OR/WA stock and the Mainland Mexico CA/OR/WA stock are equal to takes of the CA/OR/WA stock authorized in the 2020 HSTT final rule.
b  Unlike other species and stocks, for the Central America/Southern Mexico-CA/OR/WA stock and Mainland Mexico-CA/OR/WA stock, NMFS estimated the 7-year take by Level B harassment by multiplying the annual estimated take by seven. However, between the two stocks, NMFS does not anticipate that the total number of takes by Level B harassment across all 7 years would exceed the 4,961 takes by Level B harassment from testing activities that were authorized for the CA/OR/WA stock of humpback whales in the 2020 HSTT final rule.

Authorized Take From Vessel Strikes and Explosives by Serious Injury or Mortality

Vessel Strike

Vessel strikes from commercial, recreational, and military vessels are known to affect large whales and have resulted in serious injury and fatalities to cetaceans (Abramson et al. 2011; Berman-Kowalewski et al. 2010; Calambokidis, 2012; Douglas et al. 2008; Laggner, 2009; Lammers et al. 2003; Van der Hoop et al. 2012; Van der Hoop et al. 2013; Crum et al. 2019). Records of collisions date back to the early 17th century, and the worldwide number of collisions appears to have increased steadily during recent decades (Laist et al. 2001; Ritter 2012) due to increases in the number and speed of large vessels, increased reporting of strikes, and increased abundance of some large whales (Ransome et al. 2021), among other factors.

Numerous studies of interactions between surface vessels and marine ( print page 4975) mammals have demonstrated that free-ranging marine mammals often, but not always ( e.g., McKenna et al. 2015; Smultea et al. 2022; Szesciorka et al. 2019), engage in avoidance behavior when surface vessels move toward them. It is not clear whether these responses are caused by the physical presence of a surface vessel, the underwater noise generated by the vessel, or an interaction between the two (Amaral and Carlson, 2005; Au and Green, 2000; Bain et al. 2006; Bauer 1986; Bejder et al. 1999; Bejder and Lusseau, 2008; Bejder et al. 2009; Bryant et al. 1984; Corkeron, 1995; Erbe, 2002; Félix, 2001; Goodwin and Cotton, 2004; Lemon et al. 2006; Lusseau, 2003; Lusseau, 2006; Magalhaes et al. 2002; Nowacek et al. 2001; Richter et al. 2003; Scheidat et al. 2004; Simmonds, 2005; Watkins, 1986; Williams et al. 2002; Wursig et al. 1998). Several authors suggest that the noise generated during vessel movement is probably an important factor (Blane and Jaakson, 1994; Evans et al. 1992; Evans et al. 1994). Water disturbance may also be a factor. These studies suggest that the behavioral responses of marine mammals to surface vessels are similar to their behavioral responses to predators. Avoidance behavior is expected to be even stronger in the subset of instances during which the Navy is conducting training or testing activities using active sonar or explosives.

The marine mammals most vulnerable to vessel strikes are those that spend extended periods of time at the surface to restore oxygen levels within their tissues after deep dives ( e.g., sperm whales). In addition, some baleen whales seem generally unresponsive to vessel sound, making them more susceptible to vessel collisions (Nowacek et al. 2004). These species are primarily large whales.

Some researchers have suggested the relative risk of a vessel strike can be assessed as a function of animal density and the magnitude of vessel traffic ( e.g., Fonnesbeck et al. 2008; Vanderlaan et al. 2008). Differences among vessel types also influence the probability of a vessel strike. The ability of any ship to detect a marine mammal and avoid a collision depends on a variety of factors, including environmental conditions, ship design, size, speed, and ability and number of personnel observing, as well as the behavior of the animal. Vessel speed, size, and mass are all important factors in determining if injury or death of a marine mammal is likely due to a vessel strike. For large vessels, speed and angle of approach can influence the severity of a strike. For example, Vanderlaan and Taggart (2007) found that between vessel speeds of 8.6 and 15 kn (15.9 and 27.8 km per hour), the probability that a vessel strike is lethal increases from 0.21 to 0.79. Large whales also do not have to be at the water's surface to be struck. Silber et al. (2010) found when a whale is below the surface (about one to two times the vessel draft), there is likely to be a pronounced propeller suction effect. This suction effect may draw the whale into the hull of the ship, increasing the probability of propeller strikes.

There are some key differences between the operation of military and non-military vessels, which make the likelihood of a military vessel striking a whale lower than some other vessels ( e.g., commercial merchant vessels). Key differences include:

• Many military ships have their bridges positioned closer to the bow, offering better visibility ahead of the ship (compared to a commercial merchant vessel);
• There are often aircraft associated with the training or testing activity (which can serve as Lookouts), which can more readily detect cetaceans in the vicinity of a vessel or ahead of a vessel's present course before crew on the vessel would be able to detect them;
• Military ships are generally more maneuverable than commercial merchant vessels, and if cetaceans are spotted in the path of the ship, could be capable of changing course more quickly;
• The crew size on military vessels is generally larger than merchant ships, allowing for stationing more trained Lookouts on the bridge. At all times when vessels are underway, trained Lookouts and bridge navigation teams are used to detect objects on the surface of the water ahead of the ship, including cetaceans. Additional Lookouts, beyond those already stationed on the bridge and on navigation teams, are positioned as Lookouts during some training events; and
• When submerged, submarines are generally slow moving (to avoid detection), and therefore, marine mammals at depth with a submarine are likely able to avoid collision with the submarine. When a submarine is transiting on the surface, there are Lookouts serving the same function as they do on surface ships.

Vessel strike to marine mammals is not associated with any specific training or testing activity but is rather a limited and sporadic, but possible, accidental result of Navy vessel movement within the HSTT Study Area or while in transit.

In 2009, the Navy began implementing additional mitigation measures to further reduce the likelihood of vessel strikes. Prior to the recent strikes in 2021 and 2023, there were two recorded U.S. Navy vessel strikes of large whales in the HSTT Study Area between 2009 and April 2021, a period of approximately 12 years.

Since 2021 there have been five strikes of large whales in SOCAL attributed to naval vessels, three by the U.S. Navy and two by the Royal Australian Navy. As stated previously, the U.S. Navy struck a large whale in waters off Southern California in May 2023. Based on available photos and video, NMFS and the Navy have determined this whale was either a fin whale or sei whale. The U.S. Navy struck two unidentified large whales during the months of June and July 2021, and prior to that, on May 7, 2021, the Royal Australian Navy HMAS Sydney, a 147.5 m (161.3 yd) Hobart Class Destroyer, struck and killed two fin whales (a mother and her calf) while operating within SOCAL. In the case of the Royal Australian Navy strike, the carcasses were first sighted under the bow of the vessel while it was approaching the Naval Base in San Diego. The whales had been pinned to a sonar dome in the front of the vessel due to the force of water as the ship was underway. Based on interviews with HMAS Sydney personnel, the most likely time of impact with the two whales would have been around 6:25 a.m. when the vessel was located near Cortes Bank, and visibility was poor. The reported vessel speed at the estimated time of strike was 9 kn (16.7 km per hour). One minute before the estimated strike time a lookout reported whales off the starboard bow. The officer on-watch verbally acknowledged the report, slowed speed, and visually tracked the whales passing clear down the starboard side until they were clear of the ship. The morning of the strike, the HMAS Sydney was getting into position to participate in a U.S. Navy-led exercise later that day. Of note, throughout the remainder of the day visibility was poor and the vessel had implemented mitigation measures in multiple instances due to whale occurrence. In addition to being the only documented occurrence of a foreign military vessel strike of a large whale within the HSTT Study Area, the HMAS Sydney vessel strike was also somewhat unique, as compared to other reported military vessel strikes, in that two whales were apparently struck at one time, and both remained pinned to ( print page 4976) the front of the vessel until the vessel approached the port.

On June 29, 2021, a U.S. Navy cruiser struck an unknown whale species approximately 95 nmi (176 km) west of San Diego. The ship was returning from Hawaii, heading to a rendezvous with a fuel replenishment vessel (oiler) for an Underway Replenishment. Off-duty sailors noticed a group of whales approaching the ship from the port quarter ( i.e., left rear of the ship), an area unique to cruisers with some equipment structures blocking close aboard sight. The first indication of a whale within the 500-yd mitigation zone immediately prior to the strike was when an off-duty sailor on the flight deck witnessed the whale briefly surface on the aft port quarter before diving. Shortly after this occurred blood was noticed in the wake, and a floating whale body was eventually observed behind the ship. The ship's speed was 25 kn (46.3 km per hour) at the estimated time the strike occurred. The Navy also noted that, on the morning before the strike occurred, the ship had maneuvered several times to avoid whale blows beyond the 500-yd (457.2 m) mitigation zone, closer to 1,000 yd (914.4 m).

On July 11, 2021, a U.S. Navy cruiser struck an unknown whale species approximately 90 nmi (166.7 km) south-southwest of San Diego. The vessel was a participant in a MTE (Large Integrated Anti-Submarine Warfare—Composite Unit Training Exercise) within the SOCAL portion of the action area. The vessel was maneuvering for pending flight operations to receive an inbound helicopter. At 2:27 p.m., the starboard lookout sighted what they believed to be a whale crossing immediately under the vessel's bow. The conning officer attempted to maneuver the vessel by turning to port but internal watchstanders subsequently felt the ship shudder aft. The vessel's combat center observed a red slick 600 yd (548.6 m) astern on a flight deck camera and a brief surfacing of the whale itself, but no carcass was observed. There had not been any sightings of large whales off the bow leading up to the incident. Although the ship was traveling at 25-30 kn (46.3-55.6 km per hour) 1 hour before the estimated strike time, at 10 minutes before, the vessel changed course and reduced its speed to 17 kn (31.5 km per hour). These 2021 incidents were the first known U.S. Navy vessel strikes in the HSTT Study Area since 2009.

On May 20, 2023, a U.S. Navy aircraft carrier was at sea conducting independent, unit-level flight training for the embarked airwing approximately 70 nmi (129.6 km) west of San Diego. Training exercises concluded for the day at approximately 7:44 p.m. local time. Navy personnel discovered a whale impinged on the bow of the vessel at approximately 8:00 p.m. local time. The vessel was traveling at approximately 5 kn (9.3 km per hour) and had recently made a turn to reset position for the evening when the Navy personnel discovered the whale. Navy personnel captured video and photos of the carcass, and based on those images, NMFS and the Navy have determined this whale was either a fin whale or sei whale; the two species are very similar morphologically and are difficult to distinguish from one another at sea. Navy personnel stopped the vessel to allow lack of momentum to dislodge the carcass from the bow, and based on lack of further observations after the carcass dislodged, it is believed to have sunk around 9:30 p.m. local time. Navy personnel on board the vessel reported that they did not feel an impact from striking the whale. Prior to the strike, between 6:45 p.m. and 7:45 p.m., the forward Lookouts on the vessel observed two whales crossing the vessel's bow but did not provide a distance between the vessel and the whales. One Lookout reported seeing the blow and the other reported seeing `humps' (presumably the dorsal of the animal). Both whales were sighted past the ship's course to the northwest. Within the same time window, one of the aft Lookouts observed a single whale swimming parallel to the ship and soon passed astern of the ship. During the same time, independent of the sightings and for general movement reasons, the ship changed speed from 17 kn (31.5 km per hour) to 10 kn (18.5 km per hour) at 7:22 p.m.

While in this incident a whale was discovered impinged on the bow of a Navy vessel, this incident is very different from the discovery of two fin whales discovered impinged on the sonar dome of a Royal Australian Navy vessel in 2021 when the vessel came to port at Naval Base San Diego. While U.S. Navy cannot speculate on the configurations of other ships bows and even sonar dome specifications (that may be at the bow), the Navy believes it would be implausible for a marine mammal to become lodged on the sonar dome of a U.S. Navy ship and remain undetected due to a technological standard operating procedure. Sonar domes on U.S. Navy ships have a pressurized rubber window that maintains 150 pound-force per square inch (PSI) through the ship's fire main. If anything affects the pressure, an alarm sounds in the sonar control room. In the event of a whale strike in that location, this alarm would alert personnel that something hit the sonar dome. Further, the shape, hydrodynamic design, construction using a non-abrasive material, and regular hull cleaning procedures to remove barnacles and other growth on U.S. Navy ships also make it unlikely that a whale would become lodged and remain undetected on a U.S. Navy ship's bow or even sonar dome. While in the case of the May 2023 strike, described above, a whale also became lodged on the ship's bow, the aircraft carrier that struck the whale does not have active or passive sonar capabilities ( i.e., no sonar dome), nor does it have a bulbous bow, and the whale was more quickly discovered by Navy personnel.

In March 2024 a dead fin whale was discovered off of Pier 10 in Naval Station San Diego within the Navy's security barrier. The security barrier, which consists of a series of connected floating sections, is intended to discourage unauthorized boat entry to the piers. The necropsy indicated that vessel strike was the most likely cause of death. Given the location the whale was discovered, this could have been the result of a military vessel strike. However, the Navy reviewed its vessel activity during that time frame and available observations of those vessels coming and going to port, as well as at port, and determined it was unlikely that the whale was carried into port by a Navy vessel. Based on this and other information from Navy's investigation, we cannot determine whether this whale was struck by a Navy vessel during HSTT activities or was struck by a commercial or other vessel and drifted into the Navy pier area.

For the same reasons listed above describing why the likelihood of a military vessel striking a whale is lower than that of some other vessels striking whales, it is also highly unlikely that a Navy vessel would strike a whale, dolphin, porpoise, or pinniped without detecting it. Specifically, Navy vessels have Lookouts, including on the forward part of the ship that can visually detect a hit animal in the event ship personnel do not feel the strike (which has occurred). Accordingly, NMFS is confident that the Navy's reported strikes are accurate and appropriate for use in the analysis. The Navy has strict internal procedures and mitigation requirements include reporting of any vessel strikes of marine mammals, and the Navy's discipline, extensive training (not only for detecting marine mammals, but for detecting and reporting any potential navigational obstruction), and strict ( print page 4977) chain of command give NMFS a high level of confidence that all strikes are reported.

In order to better account for the accidental nature of vessel strikes to large whales in general and the potential risk from U.S. Navy vessel movement within the HSTT Study Area during the remaining period of the HSTT rule in particular, the Navy requested the HSTT rule be modified to authorize additional incidental takes by vessel strike based on probabilities derived from a Poisson distribution using vessel strike data between 2009-2021 in the HSTT Study Area (the time period from when current mitigations were instituted until the Navy conducted the analysis for the 2022 Navy application), as well as historical at-sea days in the HSTT Study Area from 2009-2015 and estimated at-sea days for the period from 2016 to 2025 covered by the current regulations. This distribution predicted the probabilities of a specific number of strikes (n = 0, 1, 2, etc.) over the remaining period of the regulations at the time of the Navy's analysis (2022-2025).

The Navy used the two fin whale strikes (2009) and two unidentified large whale strikes (2021) in their calculations to determine the number of strikes likely to result from its activities over the remaining 3 years of the rule (2023-2025, although worldwide strike information from all Navy activities and other sources was used to inform the species that may be struck). The Navy evaluated data beginning in 2009 as that was the start of the Navy's Marine Species Awareness Training and adoption of additional mitigation measures to address vessel strike, which will remain in place along with additional and modified mitigation measures during the 7 years of this rulemaking. From this analysis, the Navy concluded that there was a 27 percent chance that zero whales would be struck by Navy vessels over the remaining period of the rule (which, at the time that the application was submitted, was 4 years), and a 35, 23, and 10 percent chance that one, two, or three whales, respectively, would be struck over the remaining 4 years of the rule. Therefore, the Navy estimated that there was some probability that the Navy could strike, and take by serious injury or mortality, up to three large whales incidental to training and testing activities within the HSTT Study Area over what would have been the remaining 4 years of the current authorization, and the Navy requested authorization of two additional takes of large whales by serious injury or mortality by vessel strike, beyond the three takes authorized by the 2020 HSTT final rule (85 FR 41780, July 10, 2020).

NMFS has since updated this analysis to reflect that an additional strike of an unidentified large whale occurred in May 2023 (either a fin whale or sei whale, as stated above) and that additional time has passed since the Navy submitted the 2022 Navy application. Based on further discussions with the Navy, NMFS has also updated the way it calculated at-sea days. This is a different manner of calculating at-sea days for the purposes of the strike analysis rather than a change in Navy's activity levels. For 2010-2015, the at-sea days used in NMFS' calculation reflected historic at-sea days in the HSTT action area based on positional vessel data records (Mintz, 2016). While the actual annual at-sea days from 2016-present are currently classified, NMFS' updated calculation reflects an extrapolation of the 2010-2015 at-sea days (using the formula y = -64 x +131555) to estimate the number of at-sea days in 2016 (Navy, 2022). The number of at-sea days derived for 2016 was 2,056 at-sea days, which reflects the downward trend in HSTT vessel activity from 2010-2015. Since we do not have sufficient information to say whether or not this downward trend continued for the years 2017-2023, we conservatively estimate the average over these years was the same as the 2016 extrapolated value of 2,056 at-sea days. This analysis only included at-sea days for Navy warships greater than 65 feet ( i.e., destroyers are the smallest ship class included). Navy vessels smaller than 65 feet have never reported a whale strike in the Pacific, and therefore, we consider it unlikely that this would occur in the remaining period of the regulations.

Table 4—HSTT 2009 Through Mid-2023 At-Sea Days Used for the Vessel Strike Probability Calculation

Year	At-Sea days	Derivation
2009	4,233	Estimated average based on 2010-2015 data.
2010	5,207	Based on positional vessel data.
2011	4,483	Based on positional vessel data.
2012	4,081	Based on positional vessel data.
2013	4,041	Based on positional vessel data.
2014	4,272	Based on positional vessel data.
2015	3,311	Based on positional vessel data.
2016	2,056	Extrapolated from 2010-2015 regression.
2017	2,056	Extrapolated from 2010-2015 regression.
2018	2,056	Extrapolated from 2010-2015 regression.
2019	2,056	Extrapolated from 2010-2015 regression.
2020	2,056	Extrapolated from 2010-2015 regression.
2021	2,056	Extrapolated from 2010-2015 regression.
2022	2,056	Extrapolated from 2010-2015 regression.
2023 (first half of year)	1,028	Extrapolated from 2010-2015 regression, then reduced by half.
2009- Mid-2023 total	45,048

NMFS then used the number of past Navy vessel strikes and the at-sea days to calculate a vessel strike rate for 2009 through mid-2023. The estimated total number of Navy at-sea days (for vessels greater than 65 feet) for 2009 through mid-2023 was 45,048 days. Dividing the five known strikes during that period by the at-sea days ( i.e., 5 strikes/45,048 at-sea days) results in a strike rate of 0.000111 strikes per day.

As described above, NMFS conservatively assumed that the average number of at-sea days from mid-2023 through 2025 (the remaining period of the regulations at the time that the analysis was conducted) will be the same as the 2016 extrapolated value of 2,056. Therefore, the estimated at-sea days within the action area for the period from mid-2023 through 2025 is 5,140 days. NMFS multiplied the historic daily strike rate by the estimated at-sea days from mid-2023 ( print page 4978) through 2025 (0.000111 strikes per day × 5,140 days) to estimate the number of whale strikes anticipated during that period. This calculation predicts an estimated 0.57 strikes over the remaining 2.5 years of the regulations at the time the analysis was conducted (mid-2023 through 2025).

As explained above, according to the U.S. Navy, the May 2021 vessel strike of two fin whales by a Royal Australian Navy vessel did not occur while that vessel was participating in a U.S. Navy-led training exercise, and the strike of those two fin whales is not included in the estimated take by vessel strike calculation. Instead, as noted below, NMFS considered the 2021 vessel strike by the Royal Australian Navy along with other strike information when determining which species could be among the estimated large whales struck.

NMFS used a Poisson distribution to derive the probabilities of a specific number of strikes (n=0, 1, 2, etc.) from mid-2023 through 2025, given the estimated 0.57 strikes during that period. NMFS' probability analysis concluded that there is a 57 percent chance that zero whales would be struck by U.S. Navy vessels from mid-2023 through 2025, and a 32, 9, and 2 percent chance that one, two, or three whales, respectively, would be struck over that period. Further, there is an estimated 11 percent chance that the Navy would strike more than one large whale from mid-2023 through 2025. We have assessed these probabilities and determined that the strike of up to two large whales could occur over the remaining duration of the regulations, for a total of five takes by serious injury or mortality of large whales by vessel strike total over the 7-year duration of the regulations (three takes authorized in the 2020 HSTT final rule (85 FR 41780, July 10, 2020) which have occurred, plus two additional takes).

In addition to the reasons listed above that make it unlikely that the Navy will hit a large whale (more maneuverable ships, larger crew, etc.), vessel strike of dolphins, small whales, porpoises, and pinnipeds is considered very unlikely. Dating back more than 20 years and for as long as it has kept records, the Navy has no records of any pinnipeds being struck by a vessel as a result of Navy activities. Over the same time period, NMFS and the Navy have only one record of a dolphin, porpoise, or small whale being struck by a vessel as a result of Navy activities. A dolphin was accidentally struck by a Navy small boat in fall 2021 in Saint Andrew's Pass, Florida. The smaller size and maneuverability of dolphins, small whales, and pinnipeds generally make such strikes very unlikely. Other than this one reported strike of a dolphin in 2021, NMFS has never received any reports from other LOA or Incidental Harassment Authorization holders indicating that these species have been struck by vessels. In addition, worldwide vessel strike records show little evidence of strikes of these groups from the shipping sector and larger vessels, and the majority of the Navy's activities involving faster-moving vessels (that could be considered more likely to hit a marine mammal) are located in offshore areas where smaller delphinid, porpoise, and pinniped densities are lower. Based on this information, NMFS concurs with the Navy's assessment and recognizes the potential for (and is authorizing) incidental take by vessel strike of large whales only ( i.e., no dolphins, small whales, porpoises, or pinnipeds) over the course of the 7-year regulations from training and testing activities as discussed below.

Next, after determining that take of up to five large whales could occur, NMFS considered which species could be among the five large whales struck. As noted in the 2018 HSTT proposed and final rules, the 2019 HSTT proposed rule, 2020 HSTT final rule, and 2023 HSTT proposed rule, in the 2017 Navy rulemaking/LOA application, the Navy initially considered a weight of evidence approach that considered relative abundance, historical strike data over many years, and the overlap of Navy activities with the stock distribution in their request. NMFS updated this analysis to consider several factors, in addition to the overlap of Navy activities with stock distribution: (1) The relative likelihood of striking one stock versus another based on available strike data from all vessel types as denoted in the Carretta et al. (2021; referenced in the Pacific SARs), the Pacific and Alaska SARs (Carretta et al. 2024 and Young et al. 2024), and unpublished NMFS vessel strike data for 2019-2021; and (2) whether the Navy has ever struck an individual from a particular species or stock in the HSTT Study Area, and if so, how many times. (Note that since publication of the 2023 HSTT proposed rule, Carretta et al. (2023), which includes vessel strike data through 2021 has published, but NMFS included this data in its analysis through the unpublished NMFS vessel strike data for 2019-2021, referenced above). NMFS did not consider relative abundance, as was considered in previous analyses, given that the relative abundance of a stock does not necessarily inform its occurrence in a specific area. Further, NMFS did not consider the historical strike data from older years (prior to 2015), given that more recent data is more relevant to determining occurrence of, and strike risk to, various stocks. NMFS updated the analysis with NMFS' vessel strike probability analysis for the remaining period of the rule (2.5 years at the time of the analysis) and included new/updated vessel strike data from the SARs and NMFS records for California and Hawaii.

To address number (1) above, for SOCAL, NMFS compiled information from Carretta et al. (2021) and unpublished NMFS vessel strike data for 2020-2021 (since published in Caretta et al. (2023)) for California on known annual rates of large whale serious injury or mortality from vessel collisions (this data includes the strike of two fin whales by the Royal Australian Navy in 2021, but does not include Navy strikes in 2021 and 2023 because the species struck is not known). Use of Carretta et al. (2021) rather than the Pacific SAR allows NMFS to separate strikes that occurred in California from strikes to the same stocks that occurred in other locations. For the HRC, NMFS compiled information from the Pacific and Alaska SARs and unpublished NMFS vessel strike data for 2019-2021 for Hawaii on known annual rates of large whale serious injury or mortality from vessel collisions. The annual rates of large whale serious injury or mortality from vessel collisions from those sources help inform the relative susceptibility of large whale species to vessel strike in SOCAL and the HRC; therefore, we considered only reported strikes where the species struck was identified with sufficient certainty ( i.e., “known strikes”). Additionally, the M/SI in the 2023 SAR considers modeled takes for some, but not most species and stocks ( i.e., M/SI for humpback whale includes modeled takes from Rockwood et al. (2017)). Using known strike data for all species and stocks allows us to consider-like metrics for this comparative analysis. (Note we rely on the M/SI estimates from the 2023 SAR (or draft 2023 SAR, where relevant) in our negligible impact analysis. We also consider modeled takes of species from Rockwood et al. (2017) in table 7). We summed the annual rates of serious injury or mortality from vessel collisions in California and Hawaii as calculated above and then divided each species' annual rate by this sum to get the proportion of strikes for each species/stock (table 5). ( print page 4979)

Table 5—Annual Rates of Serious Injury and Mortality From Vessel Strike and Percentage of Total Strikes by Species in SOCAL and the HRC

ESA status	Species	Stock	SOCAL annual known strikes (2015-2021)	HRC annual known strikes (2015-2021)	Percentage of total annual strikes
Listed	Blue whale	Central North Pacific		0	0.0
		Eastern North Pacific	0.57		6.5
	Fin whale a	California, Oregon, & Washington	1.57		17.8
		Hawaiian		0	0.0
	Humpback whale	Central America/Southern Mexico-CA/OR/WA (Central America DPS)	1 b		11.3
		Mainland Mexico- CA/OR/WA (Mexico DPS)
	Sei whale	Eastern North Pacific	0.14		1.6
		Hawaiian		0	0.0
	Gray whale	Western North Pacific	0		0.0
	Sperm whale	California, Oregon, & Washington	0		0.0
		Hawaiian		0	0.0
Not listed	Gray whale	Eastern North Pacific	2.14		24.3
	Bryde's whale	ETP stock	0		0.0
		Hawaiian		0	0.0
	Minke whale	CA/OR/WA	0		0.0
		Hawaii		0	0.0
	Humpback whale	Hawaii (Hawaii DPS)		3.4	38.5
Total			8.82
a  This includes the two fin whales struck by the Royal Australian Navy in May 2021.
b  This strike occurred to an individual of the CA/OR/WA stock under the previous stock structure. As such, in its analysis, NMFS assumed that this strike could have been of either stock.

To inform the likelihood of striking a particular species of large whale, we multiplied the percent of total annual strikes for a given species in table 5, by the total percent likelihood of striking at least one whale during the remaining period of the rule (2023-2025 at the time of the analysis; i.e., 43 percent, as described by the probability analysis above). We also calculated the percent likelihood of striking a particular species of large whale twice during the remaining period of the rule by squaring the value estimated for the probability of striking a particular species of whale once ( i.e., to calculate the probability of an event occurring twice, multiply the probability of the first event by the second). The results of these calculations are reflected in the last two columns of table 6. We note that these probabilities vary from year to year as the average annual mortality changes depending on the specific range of time considered; however, over the years and through updated data in the SARs and unpublished NMFS records, stocks tend to consistently maintain a relatively higher or relatively lower likelihood of being struck.

Table 6—Percent Likelihood of Striking Each Stock One or Two Times Over 2.5 Years and Total Known U.S. Navy Strikes in the HSTT Study Area

Species	Stock	Total known U.S Navy strikes in HSTT study area	Percent likelihood of 1 strike over 2.5 years	Percent likelihood of 2 strikes over 2.5 years
Blue whale	Central North Pacific	0	0.00	0.00
	Eastern North Pacific	1 in SOCAL (2004)	2.81	0.08
Fin whale	CA/OR/WA	3 in SOCAL (2009, 2023 a )	7.74 b	0.60 b
	Hawaiian	0	0.00	0.00
Humpback whale	Central America/Southern Mexico- CA/OR/WA (Central America DPS)	0	4.93	0.24
	Mainland Mexico- CA/OR/WA (Mexico DPS)
Sei whale	Eastern North Pacific	1 in SOCAL (2023 a )	0.69	0.00
	Hawaiian	0	0.00	0.00
Gray whale	Western North Pacific	0	0.00	0.00
Sperm whale	CA/OR/WA	0.00	0.00
	Hawaiian	1 in HRC (2007)	0.00	0.00
Gray whale	Eastern North Pacific	3 in SOCAL (1993, 1998)	10.55	1.11
Bryde's whale	ETP stock	0	0.00	0.00
	Hawaiian	0	0.00	0.00
Minke whale	CA/OR/WA	0	0.00	0.00
	Hawaii	0	0.00	0.00
( print page 4980)
Humpback whale	Hawaii (Hawaii DPS)	2 in HRC (2003)	16.76	2.81
a  Based on available photos and video, NMFS and the Navy have determined the May 2023 strike was of either a fin whale or sei whale. In the analysis herein, NMFS has assumed that this strike could have been of either species, and has therefore, accounted for it in both the fin whale and sei whale strike totals. Given that we are unable to identify the species of the whales struck by the U.S. Navy in 2021, NMFS did not include the two 2021 strikes in this part of the analysis.
b  This includes the two fin whales struck by the Royal Australian Navy in May 2021.

The percent likelihood calculated as described above are then considered in combination with the information indicating the known species that the Navy has hit in the HSTT Study Area since 1991 (since they started tracking consistently; table 6). We note that for the lethal take of species specifically denoted in table 7 below, 47 percent of those struck by the Navy (8 of 17 in the Pacific) remained unidentified (including the May 2023 strike, which as stated above, NMFS and the Navy have determined was of either a fin whale or sei whale). However, given the information on known stocks struck, the analysis below remains appropriate. We also note that Rockwood et al. (2017) modeled the likelihood of vessel strike of blue whales, fin whales, and humpback whales on the U.S. West Coast (discussed in more detail in the Serious Injury or Mortality subsection of the Analysis and Negligible Impact Determination section), and those numbers help inform the relative likelihood that the Navy could hit those stocks.

For each indicated stock, table 7 includes the percent likelihood of striking an individual whale from a particular stock during the remaining 2.5 years of the rule once based on SAR data, Carretta et al. (2021), and unpublished NMFS vessel strike data from 2019-2021 for Hawaii; total strikes from Navy vessels in the HSTT Study Area, and modeled vessel strikes from Rockwood et al. (2017). The last column indicates the authorized annual mortality.

Table 7—Summary of Factors Considered in Determining the Number of Individuals in Each Stock Potentially Struck by a Vessel

ESA status	Species	Stock	Percent likelihood of one strike over 2.5 years	Total known U.S Navy strikes in HSTT study area (1993-2009)	Rockwood et al. 2017 modeled vessel strikes 1	Annual authorized take from 2020 HSTT final rule	Annual authorized take
Listed	Blue whale	Central North Pacific	0.00	0			0
		Eastern North Pacific	2.81	1 in SOCAL (2004)	18	0.14	0.14
	Fin whale	CA/OR/WA	7.74 2	3 in SOCAL (2009, 2023 3 )	43	0.29	0.57
		Hawaii	0.00	0			0
	Humpback whale 4	Central America/Southern Mexico- CA/OR/WA (Central America DPS)	4.93	0	22	0.14	0
		Mainland Mexico-CA/OR/WA (Mexico DPS)					0.14
	Sei whale	Eastern North Pacific	0.69	1 in SOCAL(2023) 3			0.14
		Hawaii	0.00	0			0
	Gray whale	Western North Pacific	0.00	0			0
	Sperm whale	CA/OR/WA	0.00	0			0
		Hawaii	0.00	1 in HRC (2007)		0.14	0
Not listed	Gray whale	Eastern North Pacific	10.55	3 in SOCAL (1993, 1998)		0.29	0.57
	Bryde's whale	Eastern Tropical Pacific	0.00	0			0
		Hawaii	0.00	0			0
	Minke whale	CA/OR/WA	0.00	0			0
		Hawaii	0.00	0			0
	Humpback whale	Hawaii (Hawaii DPS) 5	16.76	2 in HRC (2003)		0.29	0.29
1  Rockwood et al. modeled likely annual vessel strikes off the West Coast for these three species only.
2  This includes the two fin whales struck by the Royal Australian Navy in May 2021.
3  Based on available photos and video, NMFS and the Navy have determined the May 2023 strike was of either a fin whale or sei whale. In the analysis herein, NMFS has assumed that this strike could have been of either species, and has therefore, accounted for it in both the fin whale and sei whale strike totals.
4  In the 2020 HSTT final rule, take of humpback whale by serious injury and mortality by vessel strike in SOCAL was attributed to the former CA/OR/WA stock and the Mexico DPS. Text explains why takes in SOCAL come from the Mexico DPS, and therefore the Mainland Mexico-CA/OR/WA stock.
5  The 2023 final SAR reports vessel strike data for the Hawaii stock of humpback whales in Alaska, Washington, and Hawaii. Only vessel strike data from Hawaii was incorporated into our analysis as Alaska and Washington are outside of the HSTT Study Area.

Accordingly, stocks that have no record of ever having been struck by any vessel are considered to have a zero percent likelihood of being struck by the Navy in the 7-year period of the rule. Stocks that have never been struck by the Navy, have rarely been struck by other vessels, and have a low percent likelihood based on the historical vessel strike calculation are also considered to have a zero percent likelihood to be struck by the Navy during the 7-year rule. We note that while vessel strike records have not differentiated between Eastern North Pacific and Western North Pacific gray whales, given their small population size and the comparative rarity with which individuals from the Western North Pacific stock are detected off the U.S. West Coast, it is highly unlikely that ( print page 4981) they would be encountered, much less struck. This rules out all but seven stocks. Further, it is unlikely that the Hawaii stock of sperm whale would be struck given the zero percent likelihood of striking a sperm whale as indicated by the quantitative analysis above, the fact that the last U.S. Navy strike of a Hawaii stock sperm whale was in 2007, before the mitigation updates discussed above, and that, with the exception of humpback whales, vessel strikes (both military and non-military) of other large whale species in the HRC are extremely rare events (Carretta 2021b; Carretta 2022). (The 2020 HSTT final rule authorized one take (0.14 annual take) by mortality of the Hawaii stock of sperm whale.)

As stated previously, based on available photos and video of the whale struck by the U.S. Navy in Southern California in 2023, NMFS and the Navy have determined this whale was either a fin whale or sei whale. While the species of the two whales struck by the U.S. Navy in 2021 are unknown, given the following factors, NMFS expects these strikes may have been CA/OR/WA fin whales or Eastern North Pacific (ENP) gray whales, or some combination of these two stocks. These species have the highest annual rates of M/SI from vessel collision in California (1.57, 2.14, respectively, as noted above; which is approximately one and a half to two times higher than the species with the next highest strike rate, humpback whale, and approximately two to four times higher than the strike rate of blue whale). Additionally, gray whale and fin whale have the most recorded vessel strike incidents by military vessels in SOCAL and are the only stocks known to have been hit more than one time by naval vessels in the SOCAL portion of the HSTT Study Area (three gray whale strikes by the U.S. Navy (1993, 1998), two or three fin whale strikes by the U.S. Navy (2009, potentially 2023), and two fin whale strikes by the Royal Australian Navy (2021)). Further, accounting for undocumented vessel strikes, Rockwood et al. (2021) estimated that in their study area off Southern California from 2012-2018, on average 8.9 blue, 4.6 humpback, and 9.7 fin whales were killed by civilian vessel strikes from June to November each year. In addition, they estimated that, on average, 5.7 humpback whales were killed by civilian vessel strike from January-April per year (Rockwood et al. 2021). For fin whales in particular, model-predicted densities of large whales in the Southern California Bight from May to July 2021 (the time period during which the 2021 strikes of two unidentified whales by the U.S. Navy occurred) estimated fin whale abundance as being nearly an order of magnitude higher than either blue or humpback whale abundance during this time period (Becker et al. 2020; Zickel et al. 2021). Ship-whale encounter models for the U.S. West Coast Exclusive Economic Zone also indicated that vessel strike mortality estimates for fin whales were significantly higher than for blue whales and humpback whales (Rockwood et al. 2017). The comparatively higher modeled vessel strike rates for fin whales result from both the larger population as well as the more offshore distribution that overlaps significantly with several major shipping routes for a much greater spatial extent (Rockwood et al. 2017). Based on 1,243 visual boat-based sightings of 2,638 fin whales from 1991-2011, Calambokidis et al. (2015) found fin whale concentration areas included the San Clemente Basin where the 2021 Navy vessel strikes occurred (Tanner and Cortez Banks area and the shelf edge west of San Nicolas Island were also reported as fin whale concentration areas). There are two different populations of fin whales that occur in the Southern California Bight: a seasonal population, and a population that occurs year-round with offshore/inshore movements (Campbell et al. 2015; Falcone et al. 2022). This would likely make fin whales more susceptible to vessel strike year-round, as compared to other large whale species that may occur seasonally within SOCAL. Based on all of these factors, there is a reasonable likelihood that the CA/OR/WA stock of fin whales or ENP stock of gray whales could be struck twice during the remaining period of the rule. Therefore, we find that, of the five total takes by serious injury or mortality by vessel strike of large whales authorized over the course of the 7-year rule, up to four of those takes could be of the CA/OR/WA stock of fin whale or the ENP stock of gray whale given that the two strikes of unidentified large whales in 2021 could have been of either stock. Further, consistent with the 2020 HSTT final rule, we expect that, of the five total takes by serious injury or mortality by vessel strike of large whales authorized, up to two of those takes could occur in Hawaii, and therefore be of individuals of the Hawaii stock of humpback whale.

Based on the information summarized in table 7 and the fact that there is the potential for up to two large whales to be struck over the remaining period of the rule (five strikes over the full 7-year rule period), one individual from the Eastern North Pacific stock of blue whale, Mainland Mexico-CA/OR/WA stock of humpback whale, or Eastern North Pacific stock of sei whale could be among the two whales struck during the remaining effective period of the regulations (2023-2025 at the time of the analysis). The total strikes of Eastern North Pacific blue whales and the percent likelihood of striking one based on the historic strike calculation above can both be considered moderate compared to other stocks, and the Navy struck a blue whale in 2004 (based on the historic strike calculation, the likelihood of striking two blue whales is well below one percent (table 6)). Therefore, we consider it reasonably likely that the Navy could strike one individual over the course of the 7-year rule, and given that we do not expect that the 2023 strike nor either of the 2021 U.S. Navy strikes of unidentified large whales were blue whales, we expect that this strike could occur during the remaining period of the rule. The total strikes of Eastern North Pacific sei whales are low compared to other stocks, but NMFS and the Navy think it is possible that the Navy may have struck a sei whale in SOCAL in 2023. Therefore, we consider it reasonably likely that the Navy could strike a sei whale over the remaining period of the rule. The Navy has not hit a humpback whale in the SOCAL portion of the HSTT Study Area. However, in 2016 a U.S. Coast Guard vessel participating in a Navy event struck a humpback whale in Hood Canal, and as a species, humpbacks have a moderate to high number of total strikes and percent likelihood of being struck. Although the likelihood of Central America/Southern Mexico- CA/OR/WA (Central America DPS) or Mainland Mexico-CA/OR/WA (Mexico DPS) humpback whales being struck by any vessel type is moderate to high relative to other stocks, the distribution of the Mexico DPS versus the Central America DPS, as well as the distribution of overall vessel strikes inside versus outside of the SOCAL area (the majority are outside), supports the reasonable likelihood that the Navy could strike one individual humpback whale from the Mainland Mexico-CA/OR/WA stock (Mexico DPS) over the 7-year duration of the rule, as described below.

Regarding the likelihood of striking a humpback whale from a particular DPS, we evaluated the relative abundance of each of these DPS in California waters. Curtis et al. (2022) estimated the abundance of the Central America DPS to be 1,496 whales. From Wade et al. (2017), about 93 percent (or 1,391 ( print page 4982) whales) of these humpbacks that winter in Central America will move to Oregon/California in the summer months. While there is currently no abundance estimate for the Mexico DPS, an estimated 3,477 whales from the Mexico DPS feed off the U.S. West Coast (Calambokidis and Barlow 2020; Curtis 2022). Based on this information, we estimate that approximately 30 percent of the humpback whales off the coast of California may be from the Central America DPS with the remaining 70 percent expected to be from the Mexico DPS. Therefore, we anticipate that if a Navy vessel strike of a humpback whale were to occur within SOCAL, it would likely be from the Mexico DPS. Last, Rockwood et al. (2017) supports a relative likelihood of 1:1:2 for striking blue whales, humpback whales, and fin whales off the U.S West Coast (though as noted above, more recent data suggests that the relative likelihood of striking a fin whale is higher and suggests that the two 2021 U.S. Navy vessel strikes of unidentified large whales may have been fin whales), which, in consideration of more recent data also supports the authorized take included in this rule, which is 1, 1, and 4, respectively over the 7-year period. For these reasons, one lethal take of a Mainland Mexico-CA/OR/WA humpback whale (Mexico DPS) could occur and is authorized.

For Hawaii stocks, given that all known vessel strikes between 2015 and 2021 were of humpback whales, we anticipate that any vessel strike of a large whale in Hawaii would be of the Hawaii stock of humpback whale. Given that this stock has the highest percentage of total annual strikes (38.5 percent) and a 2.81 percent chance of being struck twice over the remaining period of the rule (more than twice that of the species with the next highest percentage, gray whale), NMFS authorizes two lethal takes of Hawaii humpback whales.

As described above, the Navy's analysis suggests and NMFS' analysis concurs that the likelihood of vessel strikes to the stocks below is discountable due to the stocks' relatively low occurrence in the HSTT Study Area, particularly in core HSTT training and testing subareas, and the fact that the stocks have not been struck by the Navy and are rarely, if ever, recorded struck by other vessels. Therefore, NMFS is not authorizing lethal take for the following stocks: Blue whale (Central North Pacific stock), Bryde's whale (Eastern Tropical Pacific stock and Hawaii stock), fin whale (Hawaii stock), gray whale (Western North Pacific stock), humpback whale (Central America/Southern Mexico-CA/OR/WA stock, Central America DPS), minke whale (CA/OR/WA stock and Hawaii stock), sei whale (Hawaii stock), and sperm whale (CA/OR/WA stock and Hawaii stock).

Also of note, while information on past Navy vessel strikes can serve as a reasonable indicator of future vessel strike risk, future conditions may differ from the past in ways that could influence the likelihood of a large whale vessel strike occurring. In general, the magnitude of vessel strike risk may be increasing over time as many whale populations are gradually recovering from centuries of commercial whaling (Redfern et al. 2020). Increased vessel strike risk off California in recent decades has been associated with increases in the abundance of fin and humpback whale populations in the North Pacific (Redfern et al. 2020). It has also been suggested that the blue whale population in the Eastern North Pacific, inclusive of the SOCAL portion of the HSTT Study Area, is at carrying capacity and recovered to pre-whaling levels (Monnahan et al. 2014). In addition, the magnitude of risk may also be affected by shifts in whale distributions over time in response to environmental factors including climate change, marine heatwaves, and associated changes in prey distribution.

Historically, military vessel strikes of large whales within the HSTT Study Area have been rare events with only seven such strikes occurring over the past 14 years, five U.S. Navy strikes, and two Royal Australian Navy strikes. However, the fact that four of these strikes occurred within a 3-month period (May-July) in 2021, and two occurred within a 4-month period (February-May) in 2009, suggests that military vessel strikes in SOCAL can be both highly episodic and clustered. The four large whale strikes in 2021 (two strikes of unidentified large whales by the U.S. Navy and two fin whale strikes by the Royal Australian Navy) appear to be outliers in the time series of military vessel strikes in SOCAL for that period. However, particularly in consideration of the 2023 U.S. Navy strike, these strikes could also represent an early indicator of an increased military vessel strike risk within SOCAL based on the factors discussed above. Results from a survey of whale watching vessel operators and crew in Southern California, combined with remote sensing data in the area, suggest that the number of large whales may have been greater in May through July of 2021 compared with previous years in certain high military vessel traffic and “core” use HSTT areas off southern California, particularly farther offshore as well as closer to shore off San Diego Bay (Zickel MJ et al. 2021).

In conclusion, while take by vessel strike across any given year is sporadic, based on the information and analysis above, including consideration of the 2021 and 2023 strikes by the U.S. Navy, NMFS anticipates no more than five takes of large whales by M/SI could occur over the 7-year period of the rule. Of those five whales over the 7-years, no more than four may come from the following stocks: gray whale (Eastern North Pacific stock) and fin whale (CA/OR/WA stock). No more than two may come from the Hawaii stock of humpback whales. No more than one may come from the following stocks: blue whale (Eastern North Pacific stock), sei whale (Eastern North Pacific), and humpback whale (Mexico-North Pacific stock or Mainland Mexico-CA/OR/WA, Mexico DPS). Accordingly, NMFS has evaluated under the negligible impact standard the M/SI of 0.14, 0.29, or 0.57 whales annually from each of these species or stocks ( i.e., one, two, or four takes, respectively, divided by 7 years to get the annual number), along with the expected incidental takes by harassment.

Explosives

The Navy's model and quantitative analysis process used for the 2018 HSTT FEIS/OEIS and in the Navy's 2017 and 2019 applications to estimate potential exposures of marine mammals to explosive stressors is detailed in the technical report titled Quantifying Acoustic Impacts on Marine Mammals and Sea Turtles: Methods and Analytical Approach for Phase III Training and Testing report (U.S. Department of the Navy, 2018). Specifically, over the course of a modeled maximum year of training and testing, the Navy's model and quantitative analysis process estimates M/SI of two short-beaked common dolphin and one California sea lion as a result of exposure to explosive training and testing activities (please see section 6 of the 2017 Navy application where it is explained how maximum annual estimates are calculated). Over the 7‐year period of the 2020 HSTT regulations, M/SI of 8 short-beaked common dolphins and 5 California sea lions (13 marine mammals in total) is estimated as a result of exposure to explosive training and testing activities. NMFS makes no changes to the authorization of take by M/SI as a result of explosive use as the Navy made no changes to its activities from that described in the 2018 HSTT final rule, and after reviewing all new information, ( print page 4983) we find that our previous analyses remain applicable. Please refer to the 2018 HSTT final rule and 2020 HSTT final rule for additional information.

Mitigation Measures

Under section 101(a)(5)(A) of the MMPA, NMFS must set forth the permissible methods of taking pursuant to the activity, and other means of effecting the least practicable adverse impact on the species or stock(s) and its habitat, paying particular attention to rookeries, mating grounds, and areas of similar significance, and on the availability of the species or stock(s) for subsistence uses (“least practicable adverse impact”). NMFS does not have a regulatory definition for least practicable adverse impact. The 2004 NDAA amended the MMPA as it relates to military readiness activities and the incidental take authorization process such that a determination of “least practicable adverse impact” shall include consideration of personnel safety, practicality of implementation, and impact on the effectiveness of the military readiness activity. For the full discussion of how NMFS interprets least practicable adverse impact, including how it relates to the negligible-impact standard, see the Mitigation Measures section in the 2018 HSTT final rule.

Section 101(a)(5)(A)(i)(II) requires NMFS to issue, in conjunction with its authorization, binding—and enforceable—restrictions (in the form of regulations) setting forth how the activity must be conducted, thus ensuring the activity has the “least practicable adverse impact” on the affected species or stocks. In situations where mitigation is specifically needed to reach a negligible impact determination, section 101(a)(5)(A)(i)(II) also provides a mechanism for ensuring compliance with the “negligible impact” requirement. Finally, the least practicable adverse impact standard also requires consideration of measures for marine mammal habitat, with particular attention to rookeries, mating grounds, and other areas of similar significance, and for subsistence impacts, whereas the negligible impact standard is concerned solely with conclusions about the impact of an activity on annual rates of recruitment and survival.^[1] In evaluating what mitigation measures are appropriate, NMFS considers the potential impacts of the Specified Activities, the availability of measures to minimize those potential impacts, and the practicability of implementing those measures, as we describe below. This final rule includes all mitigation measures required by the 2020 HSTT final rule (though two have been modified in this final rule), and our discussion in that rule remains complete and accurate (including reference to the 2018 HSTT final rule), except as described below.

Implementation of Least Practicable Adverse Impact Standard

Our evaluation of potential mitigation measures includes consideration of two primary factors:

(1) The manner in which, and the degree to which, implementation of the potential measure(s) is expected to reduce adverse impacts to marine mammal species or stocks, their habitat, and their availability for subsistence uses (where relevant). This analysis considers such things as the nature of the potential adverse impact (such as likelihood, scope, and range), the likelihood that the measure will be effective if implemented, and the likelihood of successful implementation; and

(2) The practicability of the measure(s) for applicant implementation. Practicability of implementation may consider such things as cost, impact on activities, and, in the case of a military readiness activity, specifically considers personnel safety, practicality of implementation, and impact on the effectiveness of the military readiness activity.

While the language of the least practicable adverse impact standard calls for minimizing impacts to affected species or stocks, we recognize that the reduction of impacts to those species or stocks accrues through the application of mitigation measures that limit impacts to individual animals. Accordingly, NMFS' analysis focuses on measures that are designed to avoid or minimize impacts on individual marine mammals that are likely to increase the probability or severity of population-level effects.

While direct evidence of impacts to species or stocks from a specified activity is rarely available, and additional study is still needed to understand how specific disturbance events affect the fitness of individuals of certain species, there have been improvements in understanding the process by which disturbance effects are translated to the population. With recent scientific advancements (both marine mammal energetic research and the development of energetic frameworks), the relative likelihood or degree of impacts on species or stocks may often be inferred given a detailed understanding of the activity, the environment, and the affected species or stocks—and the best available science has been used here. This same information is used in the development of mitigation measures and helps us understand how mitigation measures contribute to lessening effects (or the risk thereof) to species or stocks. We also acknowledge that there is always the potential that new information, or a new recommendation could become available in the future and necessitate reevaluation of mitigation measures (which may be addressed through adaptive management) to see if further reductions of population impacts are possible and practicable.

In the evaluation of specific measures, the details of the specified activity will necessarily inform each of the two primary factors discussed above (expected reduction of impacts and practicability), and are carefully considered to determine the types of mitigation that are appropriate under the least practicable adverse impact standard. Analysis of how a potential mitigation measure may reduce adverse impacts on a marine mammal stock or species, consideration of personnel safety, practicality of implementation, and consideration of the impact on effectiveness of military readiness activities are not issues that can be meaningfully evaluated through a yes/no lens. The manner in which, and the degree to which, implementation of a measure is expected to reduce impacts, as well as its practicability in terms of these considerations, can vary widely. For example, a time/area restriction could be of very high value for decreasing population-level impacts ( e.g., avoiding disturbance of feeding females in an area of established biological importance) or it could be of lower value ( e.g., decreased disturbance in an area of high productivity but of less firmly established biological importance). Regarding practicability, a measure might involve restrictions in an area or time that impede the Navy's ability to certify a strike group (higher impact on mission effectiveness), or it could mean delaying a small in-port training event by 30 minutes to avoid exposure of a marine mammal to injurious levels of sound (lower impact). A responsible evaluation of “least practicable adverse impact” will consider the factors along these realistic scales. Accordingly, the greater the likelihood that a measure will contribute to reducing the probability or severity of adverse impacts to the ( print page 4984) species or stock or its habitat, the greater the weight that measure is given when considered in combination with practicability to determine the appropriateness of the mitigation measure, and vice versa. In the evaluation of specific measures, the details of the specified activity will necessarily inform each of the two primary factors discussed above (expected reduction of impacts and practicability), and will be carefully considered to determine the types of mitigation that are appropriate under the least practicable adverse impact standard. For more detail on how we apply these factors, see the discussion in the Mitigation Measures section of the 2018 HSTT final rule.

Assessment of Mitigation Measures for HSTT Rule

NMFS fully reviewed the Navy's specified activities and the mitigation measures for the 2020 HSTT final rule and determined, with the addition of the new and modified measures discussed herein, and after consideration of the new information and studies described above, that the mitigation measures would result in the least practicable adverse impact on marine mammals (see the 2019 Navy application and the 2018 HSTT final rule for detailed information on the Navy's mitigation measures, with the exception of the new and modified measures described herein). NMFS worked with the Navy in the development of the Navy's mitigation measures, which were informed by years of implementation and monitoring. A complete discussion of the Navy's evaluation process used to develop, assess, and select mitigation measures, which was informed by input from NMFS, can be found in chapter 5 ( Mitigation) of the 2018 HSTT FEIS/OEIS. The process described in chapter 5 ( Mitigation) of the 2018 HSTT FEIS/OEIS robustly supports NMFS' independent evaluation of whether the mitigation measures would meet the least practicable adverse impact standard. The Navy has implemented the mitigation measures under the 2020 HSTT regulations and will be required to continue implementation of the mitigation measures identified in this rulemaking for the full 7 years it covers to avoid or reduce potential impacts from acoustic, explosive, and physical disturbance and vessel strike stressors.

The Navy also evaluated numerous measures in the 2018 HSTT FEIS/OEIS that were not included in the 2017 Navy application, and NMFS independently reviewed and considered all new information, and continues to concur with Navy's analysis that their inclusion was not appropriate under the least practicable adverse impact standard. The Navy considered these additional potential mitigation measures in two groups. First, chapter 5 ( Mitigation) of the 2018 HSTT FEIS/OEIS, in the Measures Considered but Eliminated section, includes an analysis of an array of different types of mitigation that have been recommended over the years by NGOs or the public, through scoping or public comment on environmental compliance documents. Appendix K (Geographic Mitigation Assessment) of the 2018 HSTT FEIS/OEIS includes an in-depth analysis of time/area restrictions that have been recommended over time or previously implemented as a result of litigation.

Below, we summarize the mitigation measures (organized into procedural measures and mitigation areas) that NMFS has determined will ensure the least practicable adverse impact on all affected species and stocks and their habitat, including the specific considerations for military readiness activities, and including several measures that are new or modified since publication of the 2020 HSTT final rule.

In its 2022 application, the Navy proposed no changes to the procedural or geographic mitigation measures in the 2020 HSTT final rule. NMFS reviewed new information potentially pertinent to mitigation of the Navy's training and testing activities. While Lookouts are essential to detecting the potential for and potentially avoiding a vessel strike of a marine mammal, NMFS and the Navy have always acknowledged that Lookouts cannot prevent all vessel strikes. The recent U.S. Navy and Royal Australian Navy vessel strikes appear to confirm this, as these strikes occurred when Lookouts were posted. As acknowledged above, these recent incidents may represent an early indicator of an increased military vessel strike risk within SOCAL. Recent reports appear to reflect the sporadic, episodic, or clustered nature of vessel strike or may reflect a trend of increased large whale presence in this area in the early summer months. NMFS and the Navy have discussed the circumstances of each of the recent strikes, including the Royal Australian Navy strike, and discussed ways of improving strike mitigation. In these further conversations, NMFS and the Navy developed several new and modified mitigation measures in comparison to those included in the 2020 HSTT final rule.

For vessel movement, the 2020 HSTT final rule required that “When underway Navy personnel must observe the mitigation zone for marine mammals; if marine mammals are observed, Navy personnel must maneuver to maintain distance.” This measure has been updated to state that reducing speed may be an appropriate way to maneuver. The revised measure states that “When underway, Navy personnel must observe the mitigation zone for marine mammals; if marine mammals are observed, Navy personnel must maneuver (which may include reducing speed as the mission or circumstances allow) to maintain distance.” Of note, between 2009 and 2021 (the most recent year for which data is available), U.S. Navy vessels in the SOCAL portion of the HSTT Study Area maneuvered 316 times to avoid large whales during MTEs. The years 2017 and 2021 had the highest number of maneuvers (n=64 and n=82, respectively). In all years for which data is available (2009 to 2021), Navy cruisers and destroyers account for 51 to 100 percent of maneuvers during MTEs. With this modified measure, NMFS is emphasizing that Navy personnel should consider reducing speed (as mission or circumstances allow) when maneuvering to avoid marine mammals, though this modified measure does not require reduction of vessel speed for reasons explained in chapter 5 ( Mitigation) of the 2018 HSTT FEIS/OEIS, in the Measures Considered but Eliminated section ( i.e., requirements to reduce vessel speeds would have significant direct negative effects on mission effectiveness).

This final rule also requires that Navy personnel must send alerts to Navy vessels of increased risk of strike following any reported Navy vessel strike in the HSTT Study Area.

Further, the 2020 HSTT final rule included a requirement for Navy personnel to issue seasonal awareness notification messages to alert ships and aircraft to the possible presence of blue whales (June-October), humpback whales (November-April), gray whales (November-March), or fin whales (November-May). These messages assist in maintaining safety of navigation and in avoiding interactions with large whales during transits. Platforms must use the information from the awareness notification messages to assist their visual observation of applicable mitigation zones during training and testing activities and to aid in the implementation of procedural mitigation. This final rule requires the Navy to re-title the spring blue whale message (released in June) to a large whale awareness message inclusive of typical spring-summer large whales in southern California (mainly blue, fin, ( print page 4985) and humpback whales). Furthermore, rather than tying the message release to a specific month, the message would be for a period based on predicted oceanographic conditions for a given year ( e.g., May-November, April-November, etc.). The Navy will also evaluate information obtained from NMFS' Southwest Fisheries Science Center scientists, recently published West Coast BIAs (Calambokedis et al. 2024), and other oceanographic or predictive models for guiding message text descriptions of whale occurrence in Southern California. The improvement will emphasize that when a marine mammal is spotted, this may be an indicator that additional marine mammals are present and nearby, and increased vigilance and awareness of Navy personnel is warranted.

This final rule also contains a new mitigation measure in which Navy personnel would issue real-time notifications to Navy vessels of large whale aggregations (four or more whales) within 1 nmi (1.9 km) of a Navy vessel in a select area of SOCAL (Of note, the four whales do not have to be the same species and do not have to be part of the same group ( e.g., two whales of one species sighted at a distance off the port side at 500 yd (457.2 m) and two more whales of another species sighted off the starboard side at 500 yd (457.2 m) will be considered an aggregation under this measure)). This measure will apply to the area between 32-33 degrees North and 117.2-119.5 degrees West, which includes the locations where recent (2009, 2021, 2023) strikes occurred, and historic locations where strikes occurred when precise latitude and longitude were known.

Of note, in order to improve mitigation effectiveness, in fall 2022 the Navy made several changes to its Lookout training. The Navy revised its basic Lookout training materials to improve marine mammal awareness and spotting techniques through updates to the Marine Mammal chapter of the Navy's September 2022 Lookout Training Handbook. Further, the Navy integrated improved Lookout training into a new generation of a shipboard simulator at its recruit training center in the Great Lakes. This simulator enhances new sailor knowledge and skill under realistic training scenarios. Last, the Navy will evaluate future revisions to online or DVD Marine Species Awareness Training video training to emphasize that when a protected species is spotted, this may be an indicator that additional marine mammals are present and nearby, and the vessel should take this into consideration when transiting.

In addition to Lookouts required under this rule, the Navy mandates the number of Lookouts on underway vessels per internal policy documents, including the Surface Ship NAVDORM. As described in the Standard Operating Procedures section, in 2021, NAVDORM policy changed to require three Lookouts on most classes of surface ship, including destroyers and cruisers. However, the Navy asserts that always including three Lookouts on these vessels in the future as a required mitigation measure is not practicable because lookout numbers are subject to change based on national security needs, including manning and staffing requirements. As such, although the Navy describes these additional Lookouts in its application under the mitigation section, NMFS has not considered the potential presence of two additional lookouts when considering Navy's mitigation effectiveness. Please see the Reporting section for additional detail on this requirement.

With the exception of Oedekoven and Thomas (2022) described above, there is no new information that affects NMFS' assessment of the applicability or effectiveness of the measures included in the 2018 HSTT final rule over the remainder of the 7-year period. As stated above in the Potential Effects of Specified Activities on Marine Mammals and Their Habitat section, while (Oedekoven and Thomas, 2022) suggests that detection of marine mammals is less certain than previously assumed at certain distances, model assumptions may still underestimate Lookout effectiveness in some cases. Additionally, maneuvering data summarized above demonstrates that Navy vessels are successfully maneuvering to avoid striking sighted marine mammals in most cases, despite the Oedekoven and Thomas (2022) results. Further, as described above, Navy and NMFS have developed modified or new mitigation in this final rule which are anticipated to further reduce the risk of vessel strike of large whales.

In summary, and as described in more detail above regarding vessel strike, the Navy has agreed to procedural mitigation measures that will reduce the probability and/or severity of impacts expected to result from acute exposure to acoustic sources or explosives, vessel strike, and impacts to marine mammal habitat. Specifically, the Navy will use a combination of delayed starts, powerdowns, and shutdowns to minimize or avoid M/SI and minimize the likelihood or severity of PTS or other injury, and reduce instances of TTS or more severe behavioral disturbance caused by acoustic sources or explosives. The Navy will also implement multiple time/area restrictions (several of which were added in the 2018 HSTT final rule since the previous HSTT MMPA incidental take rule) that would reduce take of marine mammals in areas or at times where they are known to engage in important behaviors, such as feeding or calving, where the disruption of those behaviors would have a higher probability of resulting in impacts on reproduction or survival of individuals that could lead to population-level impacts. Table 8 provides the Navy's required procedural mitigation measures for environmental awareness and education and vessel movement as well as summaries of the Navy's procedural mitigation measures for other activities. Table 9 provides summaries of mitigation areas for the HSTT Study Area.

NMFS and the Navy considered additional mitigation areas (beyond those already identified with associated measures to reduce impacts to marine mammals) to further protect marine mammals, including odontocetes with small or resident populations in the HSTT Study Area, and large whales with feeding, reproductive, and migratory BIAs in the HSTT Study Area. This includes consideration of new mitigation areas that could be based on newly identified BIAs in Hawaii (Kratofil et al. 2023) and on the West Coast (Calambokidis et al. 2024). The HRC overlaps BIAs identified in Kratofil et al. (2023) for humpback whale, spinner dolphin, short-finned pilot whale, rough-toothed dolphin, pygmy killer whale, pantropical spotted dolphin, melon-headed whale, false killer whale, dwarf sperm whale, goose-beaked whale, common bottlenose dolphin, and Blainville's beaked whale. All of the BIAs that overlap the HRC are small and resident population BIAs, with the exception of the humpback whale reproductive BIA. SOCAL overlaps BIAs identified in Calambokidis et al. (2024) for blue whale (feeding area), fin whale (feeding area), and gray whale (migratory route).

Additional restrictions in mitigation areas beyond those restrictions and areas included in the 2020 HSTT final rule (including mitigation to reduce vessel strike risk such as vessel speed restrictions, and in consideration of the newly identified BIAs (Kratofil et al. 2023 and Calambokidis et al. 2024)) is impracticable given overlap with critical Navy training areas in the HRC and SOCAL. However, many of the BIAs ( print page 4986) identified in Kratofil et al. 2023 and Calambokidis et al. (2024) partially or fully overlap the mitigation areas included in the 2020 HSTT final rule and this final rule and are aimed at reducing impacts to the same species for which Kratofil et al. 2023 and Calambokidis et al. (2024) identified BIAs. In the HRC, the existing mitigation areas are targeted and expected to reduce impacts to humpback whales, false killer whales, dwarf sperm whales, pygmy killer whales, short-finned pilot whales, melon-headed whales, bottlenose dolphins, spotted dolphins, spinner dolphins, rough-toothed dolphins, goose-beaked whales, and Blainville's beaked whales ( i.e., all species for which Kratofil et al. (2023) identified BIAs). In SOCAL, the existing mitigation areas are aimed at reducing impacts to blue whales, fin whales, and gray whales ( i.e., all species for which Calambokidis et al. (2024) identified BIAs). Further, as included in the 2023 HSTT proposed rule, this final rule requires that Navy personnel must issue real-time notifications to Navy vessels of large whale aggregations (four or more whales) within 1 nmi (1.9 km) of a Navy vessel in a select area of SOCAL, and that Navy personnel must send alerts to Navy vessels of increased risk of strike following any reported Navy vessel strike in the HSTT Study Area. Last, this final rule includes modification of two mitigation measures from the 2020 HSTT final rule (85 FR 41780; July 10, 2020) to further reduce the potential for vessel strike.

Table 8—Summary of Procedural Mitigation

Stressor or activity	Mitigation zone sizes and other requirements
Environmental Awareness and Education	• This mitigation applies to all training and testing activities, as applicable. • Mitigation Requirements:
	○ Appropriate Navy personnel (including civilian personnel) involved in mitigation and training or testing activity reporting under the specific activities must complete one or more modules of the U.S. Navy Afloat Environmental Compliance Training Series, as identified in their career path training plan. Modules include:
	Introduction to the U.S. Navy Afloat Environmental Compliance Training Series. The introductory module provides information on environmental laws ( e.g., ESA, MMPA) and the corresponding responsibilities that are relevant to Navy training and testing activities. The material explains why environmental compliance is important in supporting the Navy's commitment to environmental stewardship.
	Marine Species Awareness Training. All bridge watch personnel, Commanding Officers, Executive Officers, maritime patrol aircraft aircrews, anti-submarine warfare and mine warfare rotary-wing aircrews, Lookouts, and equivalent civilian personnel must successfully complete the Marine Species Awareness Training prior to standing watch or serving as a Lookout. The Marine Species Awareness Training provides information on sighting cues, visual observation tools and techniques, and sighting notification procedures. Navy biologists developed Marine Species Awareness Training to improve the effectiveness of visual observations for biological resources, focusing on marine mammals and sea turtles, and including floating vegetation, jellyfish aggregations, and flocks of seabirds.
	U.S. Navy Protective Measures Assessment Protocol. This module provides the necessary instruction for accessing mitigation requirements during the event planning phase using the Protective Measures Assessment Protocol software tool.
	U.S. Navy Sonar Positional Reporting System and Marine Mammal Incident Reporting. This module provides instruction on the procedures and activity reporting requirements for the Sonar Positional Reporting System and marine mammal incident reporting.
Active Sonar	Depending on sonar source:
	• 1,000 yd (914.4 m) power down, 500 yd (457.2 m) power down, and 200 yd (182.9 m) shut down. • 200 yd (182.9 m) shut down.
Air Guns	• 150 yd (137.2 m).
Pile Driving	• 100 yd (91.4 m).
Weapons Firing Noise	• 30 degrees on either side of the firing line out to 70 yd (64 m).
Explosive Sonobuoys	• 600 yd (548.6 m).
Explosive Torpedoes	• 2,100 yd (1,920.2 m).
Explosive Medium-Caliber and Large-Caliber Projectiles	• 1,000 yd (914.4 m; large-caliber projectiles). • 600 yd (548.6 m; medium-caliber projectiles during surface-to-surface activities). • 200 yd (182.9 m; medium-caliber projectiles during air-to-surface activities).
Explosive Missiles and Rockets	• 2,000 yd (1,828.8 m; 21-500 lb. net explosive weight). • 900 yd (823 m; 0.6-20 lb. net explosive weight).
Explosive Bombs	• 2,500 yd (2,286 m).
Sinking Exercises	• 2.5 nmi (4.6 km).
Explosive Mine Countermeasure and Neutralization Activities	• 2,100 yd (1,929.2 m; 6-650 lb net explosive weight). • 600 yd (548.6 m; 0.1-5 lb net explosive weight).
Explosive Mine Neutralization Activities Involving Navy Divers	• 1,000 yd (914.4 m; 21-60 lb net explosive weight for positive control charges and charges using time-delay fuses). • 500 yd (457.2 m; 0.1-20 lb net explosive weight for positive control charges).
Underwater Demolition Multiple Charge—Mat Weave and Obstacle Loading	• 700 yd (640.1 m).
Maritime Security Operations—Anti-Swimmer Grenades	• 200 yd (182.9 m).
Vessel Movement	• The mitigation must not be applied if: (1) The vessel's safety is threatened, (2) the vessel is restricted in its ability to maneuver ( e.g., during launching and recovery of aircraft or landing craft, during towing activities, when mooring), (3) the vessel is operated autonomously, or (4) when impractical based on mission requirements ( e.g., during Amphibious Assault—Battalion Landing exercises). • Number of Lookouts and Observation Platform:
	○ Lookout must be on the vessel that is underway.1
	• Mitigation Requirements:
	○ Mitigation zones:—500 yd (457.2 m) around whales.—200 yd (182.9 m) around other marine mammals (except bow-riding dolphins and pinnipeds hauled out on man-made navigational structures, port structures, and vessels).
	○ When a vessel is underway, Navy personnel must observe the mitigation zone for marine mammals; if marine mammals are observed, Navy personnel must maneuver (which may include reducing speed as the mission or circumstances allow) to maintain distance.
	• Additional requirements:
	○ If a marine mammal vessel strike occurs, Navy personnel must follow the established incident reporting procedures. Navy personnel must also send alerts to Navy vessels of increased risk of strike following any reported Navy vessel strike in the HSTT Study Area.
( print page 4987)
	○ Navy personnel must issue real-time notifications to Navy vessels of large whale aggregations (four or more whales) within 1 nmi (1.9 km) of a Navy vessel in the area between 32-33 degrees North and 117.2-119.5 degrees West. These notifications would be issued to Navy vessels within this boundary only.
Towed In-Water Devices	• 250 yd (228.6 m; marine mammals).
Small-, Medium-, and Large-Caliber Non-Explosive Practice Munitions	• 200 yd (182.9 m).
Non-Explosive Missiles and Rockets	• 900 yd (823 m).
Non-Explosive Bombs and Mine Shapes	• 1,000 yd (914.4 m).
Note: lb: pounds; nmi: nautical miles; yd: yards; m: meters.
1  Underway vessels will maintain at least one Lookout. For ship classes required to maintain more than one Lookout, the specific requirement is subject to change over time in accordance with Navy navigation instruction ( e.g., the Surface Ship NAVDORM). Navy personnel will notify NMFS as soon as practicable should its Lookout policies change, including in the NAVDORM.

Summary of mitigation area requirements

Hawaii Island Mitigation Area (year-round)

• Navy personnel must not conduct more than 300 hours of MF1 surface ship hull-mounted mid-frequency active sonar or 20 hours of MF4 dipping sonar, or use explosives that could potentially result in takes of marine mammals during training and testing.¹

4-Islands Region Mitigation Area (November 15-April 15 for active sonar; year-round for explosives)

• Navy personnel must not use MF1 surface ship hull-mounted mid-frequency active sonar or explosives that could potentially result in takes of marine mammals during training and testing.¹

Humpback Whale Special Reporting Areas (December 15-April 15)

• Navy personnel must report the total hours of surface ship hull-mounted mid-frequency active sonar used in the special reporting areas in its annual training and testing activity reports submitted to NMFS.

San Diego Arc, San Nicolas Island, and Santa Monica/Long Beach Mitigation Areas (June 1-October 31)

• Navy personnel must not conduct more than a total of 200 hours of MF1 surface ship hull-mounted mid-frequency active sonar in the combined areas, excluding normal maintenance and systems checks, during training and testing.¹

• Within the San Diego Arc Mitigation Area, Navy personnel must not use explosives that could potentially result in the take of marine mammals during large-caliber gunnery, torpedo, bombing, and missile (including 2.75” rockets) activities during training and testing.¹

• Within the San Nicolas Island Mitigation Area, Navy personnel must not use explosives that could potentially result in the take of marine mammals during mine warfare, large-caliber gunnery, torpedo, bombing, and missile (including 2.75” rockets) activities during training.¹

• Within the Santa Monica/Long Beach Mitigation Area, Navy personnel must not use explosives that could potentially result in the take of marine mammals during mine warfare, large-caliber gunnery, torpedo, bombing, and missile (including 2.75” rockets) activities during training and testing.¹

Santa Barbara Island Mitigation Area (year-round)

• Navy personnel must not use MF1 surface ship hull-mounted mid-frequency active sonar during training and testing, or explosives that could potentially result in the take of marine mammals during medium-caliber or large-caliber gunnery, torpedo, bombing, and missile (including 2.75″ rockets) activities during training.¹

Awareness Notification Message Areas (seasonal according to species)

• Navy personnel must issue spring awareness notification messages to alert ships and aircraft to the possible presence of large whales during a period based on predicted oceanographic conditions for a given year. The message must emphasize to personnel on vessels that when a marine mammal is spotted, this may be an indicator that additional marine mammals are present and nearby, and increased vigilance and awareness of Navy personnel is warranted. Navy personnel must also issue awareness notification messages to alert ships and aircraft to the possible presence of gray whales (November-March) and fin whales (November-May).

¹  If Naval units need to conduct more than the specified amount of training or testing, they will obtain permission from the appropriate designated Command authority prior to commencement of the activity. The Navy will provide NMFS with advance notification and include the information in its annual activity reports submitted to NMFS.

Mitigation Conclusions

NMFS has carefully evaluated the Navy's mitigation measures from the 2020 rule—many of which were developed with NMFS' input during the previous phases of Navy training and testing authorizations and none of which have changed since our evaluation during the 2018 HSTT rulemaking, with the exception of the changes described herein—and considered a broad range of other measures ( i.e., the measures considered but eliminated in the 2018 HSTT FEIS/OEIS, which reflect many of the comments that have arisen via NMFS or public input in past years) in the context of ensuring that NMFS prescribes the means of effecting the least practicable adverse impact on the affected marine mammal species and stocks and their habitat. Our evaluation of potential measures included consideration of the following factors in relation to one another: the manner in which, and the degree to which, the successful implementation of the mitigation measures is expected to reduce the likelihood and/or magnitude of adverse impacts to marine mammal species and stocks and their habitat; the proven or likely efficacy of the measures; and the practicability of the measures for applicant implementation, including consideration of personnel safety, practicality of implementation, and impact on the effectiveness of the military readiness activity. After considering all new information, including consideration of new information regarding vessel strike, NMFS is requiring two additional mitigation measures and revision of two existing mitigation measures as described above.

Based on our evaluation of the Navy's current mitigation measures (which are being implemented under the 2020 HSTT regulations), as well as modified and new measures described above, NMFS has determined that the mitigation measures are appropriate means of effecting the least practicable adverse impact on marine mammal species or stocks and their habitat, paying particular attention to rookeries, mating grounds, and areas of similar significance, and considering specifically personnel safety, practicality of implementation, and impact on the effectiveness of the military readiness activity. Additionally, as described in more detail below, the 2020 HSTT final rule includes an adaptive management provision, which NMFS has included in this final rule, which ensures that mitigation is regularly assessed and ( print page 4988) provides a mechanism to improve the mitigation, based on the factors above, through modification as appropriate.

Monitoring

Section 101(a)(5)(A) of the MMPA states that in order to authorize incidental take for an activity, NMFS must set forth requirements pertaining to the monitoring and reporting of such taking. The MMPA implementing regulations at 50 CFR 216.104(a)(13) indicate that requests for incidental take authorizations must include the suggested means of accomplishing the necessary monitoring and reporting that will result in increased knowledge of the species and of the level of taking or impacts on populations of marine mammals that are expected to be present.

In its 2022 application, the Navy proposed no changes to the monitoring described in the 2018 HSTT final rule and 2020 HSTT final rule. They would continue implementation of the robust Integrated Comprehensive Monitoring Program and Strategic Planning Process described in the 2018 HSTT final rule. The Navy's monitoring strategy, currently required by the 2018 HSTT regulations, is well-designed to work across Navy ranges to help better understand the impacts of the Navy's activities on marine mammals and their habitat by focusing on learning more about marine mammal occurrence in different areas and exposure to Navy stressors, marine mammal responses to different sound sources, and the consequences of those exposures and responses on marine mammal populations. Similarly, these modified regulations would include identical adaptive management provisions and reporting requirements as the 2018 HSTT regulations. There is no new information that would indicate that the monitoring measures put in place under the 2018 HSTT final rule would not remain applicable and appropriate for the 7-year period of this rule. See the Monitoring section of the 2018 HSTT final rule for more details on the monitoring program that would be required under this rule. In addition, please see the 2019 Navy application, which references chapter 13 of the 2017 Navy application for full details on the monitoring and reporting proposed by the Navy.

Within the SOCAL portion of HSTT, the Navy has been primarily focused on beaked whale monitoring since 2018 through two separate ongoing projects that are expected to continue until 2025. These projects use passive acoustic devices, visual surveys, satellite tagging, genetic analysis, photoID, and response to anthropogenic sounds to refine population status of beaked whales in SOCAL. There is also one concurrent project with fin whales using visual surveys, satellite tagging, and photoID to gather additional data on fin whale populations in Southern California. Finally, the Navy continues to fund marine mammal sighting data collected during California Cooperative Oceanic Fisheries Investigations (CALCOFI) https://calcofi.org/​. These data are collected on a much more frequent basis than NMFS' West Coast visual survey which typically occur once every 5 years in the summer. CALCOFI surveys occur quarterly every year to include winter and spring seasons NMFS does not survey. Sufficient marine mammal sightings have been accumulated since the Navy started funding in 2004 for the data to be incorporated into ongoing NMFS spatial habitat models, including new models for select species. The Navy also annually funds continued NMFS spatial habitat model improvements as new data and techniques become available. These models benefit the Navy and other Federal partners such as the Bureau of Ocean Energy Management and NMFS, for use in future regional marine mammal density derivation. For additional information, please see the Navy's Marine Species Monitoring program website, https://www.navymarinespeciesmonitoring.us/​regions/​pacific/​current-projects/​.

Adaptive Management

The 2020 HSTT regulations governing the take of marine mammals incidental to Navy training and testing activities in the HSTT Study Area contain an adaptive management component. Our understanding of the effects of Navy training and testing activities ( e.g., acoustic and explosive stressors) on marine mammals continues to evolve, which makes the inclusion of an adaptive management component both valuable and necessary within the context of 7-year regulations. The 2022 Navy application proposed no changes to the adaptive management component included in the 2020 HSTT final rule.

The reporting requirements associated with this rule are designed to provide NMFS with monitoring data from the previous year to allow NMFS to consider whether any changes to existing mitigation and monitoring requirements are appropriate. The use of adaptive management allows NMFS to consider new information from different sources to determine (with input from the Navy regarding practicability) on an annual or biennial basis if mitigation or monitoring measures should be modified (including additions or deletions). Mitigation measures could be modified if new data suggests that such modifications would have a reasonable likelihood of more effectively accomplishing the goals of the mitigation and monitoring and if the measures are practicable. If the modifications to the mitigation, monitoring, or reporting measures are substantial, NMFS will publish a notice of the planned LOA in the Federal Register and solicit public comment.

The following are some of the possible sources of applicable data to be considered through the adaptive management process: (1) results from monitoring and exercises reports, as required by MMPA authorizations; (2) compiled results of Navy funded R&D studies; (3) results from specific stranding investigations; (4) results from general marine mammal and sound research; and (5) any information which reveals that marine mammals may have been taken in a manner, extent, or number not authorized by these regulations or subsequent LOAs. The results from monitoring reports and other studies may be viewed at https://www.navymarinespeciesmonitoring.us.

Reporting

In order to issue incidental take authorization for an activity, section 101(a)(5)(A) of the MMPA states that NMFS must set forth requirements pertaining to the monitoring and reporting of such taking. Effective reporting is critical both to compliance as well as ensuring that the most value is obtained from the required monitoring. Reports from individual monitoring events, results of analyses, publications, and periodic progress reports for specific monitoring projects will be posted to the Navy's Marine Species Monitoring web portal: http://www.navymarinespeciesmonitoring.us. The 2019 Navy application and 2022 Navy application proposed no changes to the reporting requirements, though as noted above, the Navy has since proposed to report changes to Lookout SOPs to NMFS. Except as discussed below, reporting requirements would remain identical to those described in the 2018 HSTT final rule and 2020 HSTT final rule, and there is no new information that would indicate that the reporting requirements put in place under the 2020 HSTT final rule would not remain applicable and appropriate for the remaining duration of the 7-year period of this rule. See the Reporting section of the 2018 HSTT final rule for more details on the reporting that would be required under this rulemaking. In addition, the 2018 HSTT proposed and final rules unintentionally failed to ( print page 4989) include the requirement for the Navy to submit a final activity “close out” report at the end of the regulatory period. That oversight was corrected through the 2020 HSTT final rule. Please see the 2020 HSTT final rule for the detailed requirements for that report.

In addition to the reporting requirements included in the 2020 HSTT final rule, in 2023, we proposed requiring the Navy to report changes in its Lookout policies to NMFS as soon as practicable after a change is made. This final rule requires the Navy to implement that reporting measure, as well as two new measures that were not included in the 2023 HSTT proposed rule, described below.

The Navy's annual HSTT Training Exercise Report and Testing Activity Report must include information that tracks the Navy's implementation of the new SOCAL large whale aggregation real-time reporting mitigation measure. The report must include the following information for each instance that an aggregation of large whales is reported: (1) the date, time and general location ( e.g., approximately 10-12 nmi (18.5 to 22.2 km) SE of San Clemente Island) of the whales when the aggregation was first sighted; (2) the total number of whales observed within 1 nmi (1.8 km) of a Navy vessel that make up the aggregation; and (3) the approximate distance (or distances if more than one group of whales is sighted) of the vessel from the whales in the aggregation when the whales were first sighted. To the extent practicable, this information should be provided in the Navy's unclassified version of these reports.

The Navy's annual HSTT Training Exercise Report and Testing Activity Report must include a confirmation that foreign military use of sonar and explosives, when such militaries are participating in a U.S. Navy-led exercise or event, combined with the U.S. Navy's use of sonar and explosives, would not cause exceedance of the analyzed levels (within each NAEMO modeled sonar and explosive bin) used for estimating predicted impacts, which formed the basis of the acoustic impacts effects analysis used to estimate take in this final rule. The purpose of this new reporting measure is for the Navy to confirm annually that the Navy has accounted for foreign military participation in its annual report, without requiring the Navy to quantitatively account for foreign military activity. The Navy informed NMFS that it would be difficult for the Navy to quantify foreign military activities as a subset of its total activities because the Navy does not track activities conducted by foreign vessels in this manner. Furthermore, the annual reported takes from Navy activities are calculated the same regardless of whether the activity was conducted by a foreign military or not.

Analysis and Negligible Impact Determination

NMFS has defined negligible impact as an impact resulting from the specified activity that cannot be reasonably expected to, and is not reasonably likely to, adversely affect the species or stock through effects on annual rates of recruitment or survival (50 CFR 216.103). A negligible impact finding is based on the lack of likely adverse effects on annual rates of recruitment or survival ( i.e., population-level effects). While this final rule consists of a modification of take by M/SI by vessel strike, NMFS considers the impacts of the entire specified activity and the total taking in the negligible impact determination. An estimate of the number of takes alone is not enough information on which to base an impact determination. In addition to considering estimates of the number of marine mammals that might be taken through mortality, serious injury, and Level A or Level B harassment (as presented in tables 11 and 12 of the 2020 HSTT final rule), NMFS considers other factors, such as the likely nature of any responses ( e.g., intensity, duration), the context of any responses ( e.g., critical reproductive time or location, migration), as well as effects on habitat, and the likely effectiveness of the mitigation. We also assess the number, intensity, and context of estimated takes by evaluating this information relative to population status. Consistent with the 1989 preamble for NMFS' implementing regulations (54 FR 40338, September 29, 1989), the impacts from other past and ongoing anthropogenic activities (including foreign military activities) are incorporated into this analysis via their impacts on the environmental baseline ( e.g., as reflected in the regulatory status of the species, population size and growth rate where known, other ongoing sources of human-caused mortality, ambient noise levels, and specific consideration of take by Level A harassment or M/SI previously authorized for other NMFS activities).

In the Estimated Take of Marine Mammals sections of this final rule and the 2020 HSTT final rule (where the activities, species and stocks, potential effects, and mitigation measures (except as modified above) are the same as for this rulemaking), we identified the subset of potential effects that would be expected to rise to the level of takes both annually and over the 7-year period covered by this rulemaking and then identified the number of each of those mortality takes that we believe could occur or the maximum number of harassment takes that are reasonably expected to occur based on the methods described. The impact that any given take will have is dependent on many case-specific factors that need to be considered in the negligible impact analysis ( e.g., the context of behavioral exposures such as duration or intensity of a disturbance, the health of impacted animals, the status of a species that incurs fitness-level impacts to individuals, etc.). For this final rule, we evaluated the likely impacts of the enumerated maximum number of harassment takes that were reasonably expected to occur and are authorized, in the context of the specific circumstances surrounding these predicted takes. We also assessed M/SI takes that could occur, as well as considering the traits and statuses of the affected species and stocks. Last, we collectively evaluated this information, as well as other more taxa-specific information and mitigation measure effectiveness, in group-specific assessments that support our negligible impact conclusions for each stock or species. Because all of the Navy's specified activities would occur within the ranges of the marine mammal stocks identified in the rule, all negligible impact analyses and determinations are at the stock level ( i.e., additional species-level determinations are not needed).

The Navy proposed no changes to the nature or level of the specified activities or the boundaries of the HSTT Study Area, and therefore, the training and testing activities ( e.g., equipment and sources used, exercises conducted) are the same as those analyzed in the 2020 HSTT final rule. In addition, the mitigation, monitoring, and nearly all reporting measures are identical to those described and analyzed in the 2018 HSTT final rule with the exception of changes to mitigation measures and the additional reporting requirements described previously. There is no new information since the publication of the 2020 HSTT final rule regarding the impacts of the specified activities on marine mammals, the status and distribution of any of the affected marine mammal species or stocks, or the effectiveness of the mitigation and monitoring measures that would change the content of our analyses, with the exception of that described below. First, naval vessel strikes have occurred in the HSTT and Atlantic Fleet Training and Testing (AFTT) Study Areas since ( print page 4990) publication of the 2020 HSTT final rule (one fin or sei whale struck by the U.S. Navy in the HSTT Study Area (2023), two unidentified large whales struck by the U.S. Navy in the HSTT Study Area (2021), two fin whales struck by a foreign navy in the HSTT Study Area (2021), and one dolphin struck by the U.S. Navy in the AFTT Study Area (2021)). Second, for gray whales, we have considered the latest effects of the recently closed UME on the west coast of North America along with the effects of the Navy's activities in the negligible impact analysis. Third, a new study suggests that Lookout detection of marine mammals is less certain than previously assumed (Oedekoven and Thomas, 2022). Fourth, stock assessments have been updated for multiple stocks in the 2023 Pacific and Alaska SARs (Carretta et al. 2024; Young et al. 2024).

As described above, since publication of the 2023 HSTT proposed rule, NMFS has updated our Technical Guidance (NMFS, 2024) containing updated acoustic criteria for auditory injury (89 FR 36762, October 24, 2024). The Technical Guidance provides updated auditory injury thresholds, where appropriate, as well as revised weighting functions, in some cases. For impulsive sources, the Updated Technical Guidance's auditory injury thresholds generally remain identical or are higher compared to our 2018 Technical Guidance, meaning that received levels would need to be higher in order for marine mammals to be expected to incur auditory injury. The exceptions are for phocid pinnipeds (PW), where the cumulative SEL threshold, in the Updated Technical Guidance, is 2 dB lower and for otariid pinnipeds (OW) where the peak sound pressure level threshold is 2 dB lower and the cumulative SEL threshold is 18 dB lower. As for the Updated Technical Guidance's weighting functions, for MF cetaceans (now called HF cetaceans in the updated document) and HF cetaceans (now called VHF cetaceans in the updated document), the weighting functions reflect a higher susceptibility to auditory injury at frequencies below 10 kHz, as compared to the 2018 Technical Guidance. Other minor changes/shifts to weighting functions ( e.g., for LF cetaceans, PW pinnipeds, OW pinnipeds) were also included. This new information was not available in a timeframe in which NMFS could have incorporated it into the quantitative analysis supporting this final rulemaking; however, NMFS did consider the information qualitatively. While these changes in the auditory injury thresholds and weighting functions could result in minor increases in PTS exposure estimates for some species, given the conservative assumptions built into the take estimate methodology, they would not be expected to result in meaningful, if any, changes in take estimates and would not be expected to change any of the findings.

Harassment

As described in the Estimated Take of Marine Mammals section, the annual number of takes authorized and reasonably expected to occur by Level A harassment and Level B harassment (based on the maximum number of activities per 12-month period) are identical to those presented in tables 41 and 42 in the Take Requests section of the 2018 HSTT final rule, with the exception of humpback whale, which are presented in tables 2 and 3 herein. As such, the negligible impact analyses and determinations of the effects of the estimated Level A harassment and Level B harassment takes on annual rates of recruitment or survival for each species and stock are nearly identical to and substantively unchanged from those presented in the 2020 HSTT final rule. The differences in the analysis is our removal of consideration of California Sea Lion UME and gray whale UME, which have been closed since publication of the 2020 HSTT final rule and 2023 HSTT proposed rule, respectively, and incorporation of the revised stock structure for humpback whales. This does not affect the results of the analyses or our determinations. For detailed discussion of the impacts that affected individuals may experience given the specific characteristics of the specified activities and required mitigation ( e.g., from behavioral disruption, masking, and temporary or permanent threshold shift), along with the effects of the expected Level A harassment and Level B harassment take on reproduction and survival, see the applicable subsections in the Analysis and Negligible Impact Determination section of the 2018 HSTT final rule (83 FR 66977-67018; also incorporated by reference in the 2020 HSTT final rule).

Serious Injury or Mortality

Based on the information and methods discussed in the Estimated Take of Marine Mammals section (which are identical to those used in the 2018 HSTT final rule for explosives and revised for vessel strike), NMFS is authorizing five mortalities of large whales due to vessel strike over the 7-year period of this rulemaking, two more strikes than what was authorized in the 2018 HSTT final rule and 2020 HSTT final rule. Across the 7-year duration of the rule, take of an annual average of 0.57 gray whales (Eastern North Pacific stock) and fin whales (CA/OR/WA stock), an annual average of 0.29 humpback whales (Hawaii stock) and an annual average of 0.14 blue whales (Eastern North Pacific stock), sei whales (Eastern North Pacific stock) and humpback whales (Mainland Mexico-CA/OR/WA stock, Mexico DPS), as described in table 7 ( i.e., one, two, or four take(s) over 7 years divided by seven to get the annual number) could occur and are authorized.

Table 10—Summary Information Related to Mortalities Requested for Vessel Strike, 2018-2025

Species (stock)	Stock abundance (Nbest) *	Annual authorized take by serious injury or mortality 1	Total annual M/SI * 2	Fisheries interactions (Y/N); annual rate of M/SI from fisheries interactions *	Annual rate of M/SI from vessel collision *	PBR *	Residual PBR (PBR minus annual M/SI) 3	Stock trend * 4	Recent UME (Y/N); number and year (since 2007)
Fin whale (CA/OR/WA stock)	11,065	0.57	≥43.4	Y; ≥0.41	Y, 43	80	36.6	↑	N
Gray whale (Eastern North Pacific stock)	26,960	0.57	131	Y, 9.3	Y, 1.8	801	670	5  ↑	Y; 690; 2019
Humpback whale (Mainland Mexico-CA/OR/WA stock, Mexico DPS)	3,477	0.14	22	Y; 11.4	6  Y, 10.15	65	7  43	Unknown	N
Humpback whale (Hawaii stock)	11,278	0.29	27.09	Y; 8.39	8  Y, 10.59	127	99.91	Unknown	Y; 52; 2015
( print page 4991)
Blue whale (Eastern North Pacific Stock)	1,898	0.14	≥18.6	Y; ≥0.61	Y, 18	4.1	−14.5	Unknown	Y; 3, 2007
Sei whale (Eastern North Pacific Stock)	864	0.14	≥0	N; 0	Y, 0	1.25	1.25	Unknown	N
* Presented in the 2023 final SARs.
1 This column represents the annual take by serious injury or mortality (M/SI) by vessel collision and was calculated by the number of mortalities authorized divided by 7 years (the length of the rule and LOAs).
2 This column represents the total number of incidents of M/SI that could potentially accrue to the specified species or stock. This number comes from the SAR, but deducts the takes accrued from either Navy strikes or NMFS' Southwest Fisheries Science Center (SWFSC) takes in the SARs to ensure not double-counted against PBR. However, for these species, there were no takes from either other Navy activities or SWFSC in the SARs to deduct that would be considered double-counting.
3 This value represents the calculated PBR less the average annual estimate of ongoing anthropogenic mortalities ( i.e., total annual human-caused M/SI, which is presented in the SARs).
4 See relevant SARs for more information regarding stock status and trends.
5 The Pacific 2023 SAR indicates that the stock trend is increasing. However, recent (2023-2024) surveys conducted by NMFS' Southwest Fisheries Science Center indicated that the estimated total abundance of gray whales during the 2023-2024 southbound migration was 19,260, though the authors note that this stock has historically shown a pattern of population growth and decline that has not impacted the population in the long term (Eguchi et al. 2024).
6 Vessel strike of the Mainland Mexico-CA/OR/WA stock was calculated by applying a prorated portion of humpback whale strikes modeled by Rockwood et al. (2017) to this stock.
7 For this stock, PBR is currently set at 43 for U.S. waters and 65 for the stock's entire range. As the HSTT Study Area extends beyond U.S. waters and activities have the potential to impact the entire stock, we present the analysis using the PBR for the stock's entire range.
8 Annual vessel strike for this stock reported in the 2023 final SAR was calculated by summing vessel strike data from Hawaii, Alaska, and Washington. All observed strikes in Hawaii were assigned to the Hawaii stock, and a portion of observed strikes in Alaska were assigned to the Hawaii stock. Vessel strike of the Hawaii stock in Washington waters was calculated by applying a prorated portion of humpback whale strikes modeled by Rockwood et al. (2017) to the Hawaii stock.

The Navy also requested a small number of takes by M/SI from explosives in the 2017 Navy application. To calculate the annual average of mortalities for explosives in table 11, we used the same method as described for vessel strikes. The annual average is the total number of takes over 7 years divided by seven. Specifically, NMFS is authorizing the following M/SI takes from explosives: five California sea lions and eight short-beaked common dolphins over the 7-year period (therefore 0.71 mortalities annually for California sea lions and 1.14 mortalities annually for short-beaked common dolphin), as described in table 11. As this annual number is the same as that analyzed and authorized in the 2020 HSTT final rule, and no other relevant information about the status, abundance, or effects of mortality on each species or stock has changed, the analysis of the effects of explosives is identical to that presented in the 2020 HSTT final rule.

Table 11—Summary Information Related to Mortalities from Explosives, 2018-2025

Species (stock)	Stock abundance (nbest) *	Annual authorized take by serious injury or mortality 1	Total annual M/SI * 2	Fisheries interactions (Y/N); annual rate of M/SI from fisheries interactions *	PBR *	SWFSC authorized take (annual) 3	Residual PBR- PBR minus annual M/SI and SWFSC 4	Stock trend * 5	UME (Y/N); number and year
California sea lion (U.S. stock)	257,606	0.71	≥321	Y; ≥197	14,011	6	13,684	↑	N
Short-beaked common dolphin (CA/OR/WA stock)	1,056,308	1.14	≥30.5	Y; ≥30.5	8,889	2.8	8,855.7	unknown	N
* Presented in the 2023 SARs.
1  This column represents the annual take by serious injury or mortality (M/SI) during explosive detonations and was calculated by the number of mortalities planned for authorization divided by 7 years (the length of the rule and LOAs).
2  This column represents the total number of incidents of M/SI that could potentially accrue to the specified species or stock. This number comes from the SAR.
3  This column represents annual take authorized through NMFS' SWFSC rulemaking/LOAs (86 FR 3840, January 15, 2021).
4  This value represents the calculated PBR less the average annual estimate of ongoing anthropogenic mortalities ( i.e., total annual human-caused M/SI column and the annual authorized take from the SWFSC column. In the case of California sea lion the M/SI column (321) and the annual authorized take from the SWFSC (6) were subtracted from the calculated PBR of 14,011. In the case of short-beaked common dolphin the M/SI column (30.5) and the annual authorized take from the SWFSC (2.8) were subtracted from the calculated PBR of 8,889.
5  See relevant SARs for more information regarding stock status and trends.

See the Serious Injury or Mortality subsection in the Analysis and Negligible Impact Determination section of the 2018 HSTT final rule (83 FR 66985-66993, December 27, 2018) for detailed discussions of the impacts of M/SI, including a description of how the agency uses the PBR metric and other factors to inform our analysis and an analysis of the impacts on each species and stock for which M/SI is authorized, including the relationship of potential mortality for each species to the insignificance threshold and residual PBR, except as updated below.

Stocks With M/SI Below the Insignificance Threshold

As noted in the Serious Injury or Mortality subsection of the Analysis and Negligible Impact Determination section in the 2018 HSTT final rule and 2020 HSTT final rule, for a species or stock with incidental M/SI less than 10 percent of residual PBR, we consider M/SI from the specified activities to represent an insignificant incremental increase in ongoing anthropogenic M/SI that alone ( i.e., in the absence of any other take and barring any other unusual circumstances) will clearly not adversely affect annual rates of recruitment and survival. In this case, as ( print page 4992) shown in table 10 and table 11, the following species or stocks have potential or estimated M/SI from vessel strike and explosive takes, respectively, and authorized below their insignificance threshold: fin whale (CA/OR/WA stock), gray whale (Eastern North Pacific stock), humpback whale (Hawaii stock and Mainland Mexico-CA/OR/WA stock), California sea lion (U.S stock), and short-beaked common dolphin (CA/OR/WA stock). While the authorized M/SI of gray whales (Eastern North Pacific stock) is below the insignificance threshold, because of the recent UME, we further address how the authorized M/SI and the UME inform the negligible impact determination immediately below. For the other five stocks with authorized M/SI below the insignificance threshold, there are no other known factors, information, or unusual circumstances that indicate anticipated M/SI below the insignificance threshold could have adverse effects on annual rates of recruitment or survival and they are not discussed further. For the remaining stocks with anticipated potential M/SI above the insignificance threshold, how that M/SI compares to residual PBR, as well as additional factors, as appropriate, are discussed below as well.

Gray Whales (Eastern North Pacific Stock)

The estimated and authorized lethal take of gray whale (Eastern North Pacific stock) is well below the insignificance threshold (0.57 as compared to a residual PBR of 670). Nonetheless, we consider here how the 2019-2023 West Coast Gray Whale UME informs our negligible impact determination. Strandings of eastern North Pacific gray whales occurred in the United States, Canada and Mexico along the west coast of North America. They occurred in wintering, migratory, and feeding areas. Stranding rates have returned back to normal and expected levels, and the prevalence of thin live or thin dead whales has also decreased. The Investigative Team concluded localized ecosystem changes, including both access to and quality of prey, in the northern Bering and Chukchi seas caused the UME. These changes contributed to the poor nutritional condition observed in live whales in the wintering areas of Mexico and dead stranded gray whales in all three countries. This malnutrition led to increased mortality during the whales' annual northward migration (from Mexico to Alaska) and decreased production of calves. This resulted in an overall decline in population abundance. Because of the abundance and residual PBR of this stock, as well as the fact that the UME is closed and increased mortality stopped in late 2023 (with peak strandings ending in December 2020), this UME is not expected to have any impacts on individuals during the period of this final rule, nor is it thought to have had impacts on the population rate when it was occurring that would influence our evaluation of the effects of the mortality authorized on the stock.

Stocks with M/SI Above the Insignificance Threshold

Blue Whale (Eastern North Pacific Stock)

For blue whales (Eastern North Pacific stock), PBR is currently set at 4.1 and the total annual M/SI is estimated at greater than or equal to 18.6, yielding a residual PBR of −14.5. This is slightly higher than the 2020 HSTT final rule (−16.7) and 2023 HSTT proposed rule (−15.4). NMFS authorizes one M/SI for the Navy over the 7-year duration of the rule (indicated as 0.14 annually for the purposes of comparing to PBR and evaluating overall effects on annual rates of recruitment and survival), which means that residual PBR is exceeded by 14.5. However, as described in the 2018 and 2020 rules, given that the negligible impact determination is based on the assessment of take of the activity being analyzed, when total annual mortality from human activities is higher, but the impacts from the specific activity being analyzed are very small, NMFS may still find the impact of the authorized take from a specified activity to be negligible even if total human-caused mortality exceeds PBR if the authorized mortality is less than 10 percent of PBR and management measures are being taken to address serious injuries and mortalities from the other activities causing mortality ( i.e., other than the specified activities covered by the incidental take authorization in consideration). When those considerations are applied here, the authorized lethal take (0.14 annually) of blue whales from the Eastern North Pacific stock is less than 10 percent of PBR (which is 4.1), and there are management measures in place to address M/SI from activities other than those the Navy is conducting (as discussed below). Perhaps more importantly, the available data suggests that the current number of vessel strikes is not likely to have an adverse impact on the population, despite the fact that it exceeds PBR, with the Navy's minimal additional mortality of one whale in the 7 years not creating the likelihood of adverse impact. Immediately below, we explain the information that supports our finding that the Navy's authorized M/SI is not expected to result in more than a negligible impact on this stock. As described previously, NMFS must also ensure that impacts by the applicant on the species or stock from other types of take ( i.e., harassment) do not combine with the impacts from mortality to adversely affect the species or stock via impacts on annual rates of recruitment or survival, which occurs further below in the stock-specific conclusion sections.

As discussed in the 2018 HSTT final rule and the 2020 HSTT final rule, the 2018 draft SAR and the more recent SARs rely on a new method to estimate annual deaths by vessel strike utilizing an encounter theory model that combined species distribution models of whale density, vessel traffic characteristics, and whale movement patterns obtained from satellite-tagged animals in the region to estimate encounters that would result in mortality (Rockwood et al. 2017). The model predicts 18 annual mortalities of blue whales from vessel strikes, which, with the additional M/SI of 1.54 from fisheries interactions, results in the current estimate of residual PBR being −15.4. Although NMFS' Permits and Conservation Division in the Office of Protected Resources has independently reviewed the vessel strike model and its results and agrees that it is appropriate for estimating blue whale mortality by vessel strike on the U.S. West Coast, for analytical purposes we also note that if the historical method were used to predict vessel strike ( i.e., using observed mortality by vessel strike, or 0.6, instead of 18), then total human-caused mortality including the Navy's potential take would not exceed PBR. We further note that the authors (Rockwood et al. 2017) do not suggest that vessel strike suddenly increased to 18 recently. In fact, the model is not specific to a year, but rather offers a generalized prediction of vessel strike off the U.S. West Coast. Therefore, if the Rockwood et al. (2017) model is an accurate representation of vessel strike, then similar levels of vessel strike have been occurring in past years as well. Put another way, if the model is correct, for some number of years total-human-caused mortality has been significantly underestimated and PBR has been similarly exceeded by a notable amount, and yet, the Eastern North Pacific stock of blue whales remains stable nevertheless. ( print page 4993)

NMFS' 2023 SAR states that the current population trend is unknown, though there may be evidence of a population size increase since the 1990s. The SAR further cites to Monnahan et al. (2015), which used a population dynamics model to estimate that the Eastern North Pacific blue whale population was at 97 percent of carrying capacity in 2013 and to suggest that the observed lack of a population increase since the early 1990s was explained by density dependence, not impacts from vessel strike. This would mean that this stock of blue whales shows signs of stability and is not increasing in population size because the population size is at or nearing carrying capacity for its available habitat. In fact, we note that this population has maintained this status throughout the years that the Navy has consistently tested and trained at similar levels (with similar vessel traffic) in areas that overlap with blue whale occurrence, which would be another indicator of population stability.

Monnahan et al. (2015) modeled vessel numbers, vessel strikes, and the population of the Eastern North Pacific blue whale population from 1905 out to 2050 using a Bayesian framework to incorporate informative biological information and assign probability distributions to parameters and derived quantities of interest. The authors tested multiple scenarios with differing assumptions, incorporated uncertainty, and further tested the sensitivity of multiple variables. Their results indicated that there is no immediate threat ( i.e., through 2050) to the population from any of the scenarios tested, which included models with 10 and 35 strike mortalities per year. Broadly, the authors concluded that, unlike other blue whale stocks, the Eastern North Pacific blue whales have recovered from 70 years of whaling and are in no immediate threat from vessel strikes. They further noted that their conclusion conflicts with the depleted and strategic designation under the MMPA as well as PBR specifically.

As discussed, we also take into consideration management measures in place to address M/SI caused by other activities. The Channel Islands NMS staff coordinates, collects, and monitors whale sightings in and around the Vessel Speed Reduction (VSR) zones and the Channel Islands NMS region. Redfern et al. (2013) note that the most risky area for blue whales is the Santa Barbara Channel, where shipping lanes intersect with common feeding areas. The seasonally established Southern California VSR zone spans from Point Arguello to Dana Point, including the Traffic Separation Schemes in the Santa Barbara Channel and San Pedro Channel. Vessels transiting the area from May 1 through December 15, 2023 are recommended to exercise caution and voluntarily reduce speed to 10 kn (18.5 km per hour) or less for blue, humpback, and fin whales. (Note this is an expanded timeframe from the Whale Advisory Zone discussed in the 2020 HSTT final rule, which spanned June through November, though the effective period could change in future years.) Channel Island NMS observers collect information from aerial surveys conducted by NOAA, the U.S. Coast Guard, California Department of Fish and Game, and U.S. Navy chartered aircraft. Information on seasonal presence, movement, and general distribution patterns of large whales is shared with mariners, NMFS Office of Protected Resources, U.S. Coast Guard, California Department of Fish and Game, the Santa Barbara Museum of Natural History, the Marine Exchange of Southern California, and whale scientists. Real time and historical whale observation data collected from multiple sources can be viewed on the Point Blue Whale Database.

In this case, 0.14 M/SI means one mortality in 1 of the 7 years and zero mortalities in 6 of those 7 years. Therefore, the Navy would not be contributing to the total human-caused mortality at all in 6 of the 7, or 85.7 percent, of the years covered by this rulemaking. That means that even if a blue whale were to be struck, in 6 of the 7 years there could be no effect on annual rates of recruitment or survival from Navy-caused M/SI. Additionally, the loss of a male would have far less, if any, effect on population rates and absent any information suggesting that one sex is more likely to be struck than another, we can reasonably assume that there is a 50 percent chance that the single strike authorized by this rulemaking would be a male, thereby further decreasing the likelihood of impacts on the population rate. In situations like this where potential M/SI is fractional, consideration must be given to the lessened impacts anticipated due to the absence of M/SI in 6 of the 7 years and the fact that the single strike could be a male. Lastly, we reiterate that PBR is a conservative metric and also not sufficiently precise to serve as an absolute predictor of population effects upon which mortality caps would appropriately be based. This is especially important given the minor difference between zero and one across the 7-year period covered by this rulemaking, which is the smallest distinction possible when considering mortality. As noted above, Wade et al. (1998), authors of the paper from which the current PBR equation is derived, note that “Estimating incidental mortality in 1 year to be greater than the PBR calculated from a single abundance survey does not prove the mortality will lead to depletion; it identifies a population worthy of careful future monitoring and possibly indicates that mortality-mitigation efforts should be initiated.” The information included here indicates that the current population trend of this blue whale stock is unknown but likely approaching carrying capacity and has leveled off because of density-dependence, not human-caused mortality, in spite of what might be otherwise indicated from the calculated PBR. Further, potential (and authorized) M/SI is below 10 percent of PBR and management actions are in place to minimize vessel strike from other vessel activity in one of the highest-risk areas for strikes. Based on the presence of the factors described above, we do not expect lethal take from Navy activities, alone, to adversely affect Eastern North Pacific blue whales through effects on annual rates of recruitment or survival. Nonetheless, the fact that total human-caused mortality exceeds PBR necessitates close attention to the remainder of the impacts ( i.e., harassment) on the Eastern North Pacific stock of blue whales from the Navy's activities to ensure that the total authorized takes have a negligible impact on the species or stock. Therefore, this information will be considered in combination with our assessment of the impacts of authorized harassment takes in the Group and Species-Specific Analyses section that follows.

Sei Whale (Eastern North Pacific Stock)

For sei whales (Eastern North Pacific stock), PBR is currently set at 1.25. The total annual M/SI is estimated at greater than or equal to 0 in the 2023 SAR, yielding a residual PBR of 1.25. NMFS authorizes one M/SI for the Navy over the 7-year duration of the rule (indicated as 0.14 annually for the purposes of comparing to PBR and evaluating overall effects on annual rates of recruitment and survival), which means that residual PBR is 1.11.

We acknowledge that the 2023 vessel strike by the U.S. Navy could have been of a sei whale or a CA/OR/WA fin whale, and this strike is not quantitatively included in this PBR analysis (nor is it quantitatively included in the PBR analysis for CA/ ( print page 4994) OR/WA fin whale if both of the 2021 U.S. Navy strikes were fin whales) which relies on the 2023 SARs. However, consideration of the 2023 strike would not change the total M/SI which NMFS compares to PBR, as the 2023 U.S. Navy strike occurred outside of the time period considered in the vessel strike analysis in the 2023 SAR. Therefore, while we acknowledge the 2023 U.S. Navy strike, in the quantitative analysis it is treated the same as other non-U.S. Navy strikes that occurred outside of the timeframe reflected in the total M/SI.

Immediately below, we explain the information that supports our finding that the Navy's authorized M/SI is not expected to result in more than a negligible impact on this stock. As described previously, NMFS must also ensure that impacts by the applicant on the species or stock from other types of take ( i.e., harassment) do not combine with the impacts from mortality to adversely affect the species or stock via impacts on annual rates of recruitment or survival, which occurs further below in the stock-specific conclusion sections.

Of note, management measures are in place to address M/SI caused by other activities. The Channel Islands NMS staff coordinates, collects, and monitors whale sightings in and around the VSR zones and the Channel Islands NMS region. The seasonally established Southern California VSR zone spans from Point Arguello to Dana Point, including the Traffic Separation Schemes in the Santa Barbara Channel and San Pedro Channel. Vessels transiting the area from May 1 through December 15, 2023 are recommended to exercise caution and voluntarily reduce speed to 10 kn (18.5 km per hour) or less. While the VSR zone is aimed at reducing risk of fatal vessel strike of blue, humpback, and fin whales, this measure is also anticipated to reduce risk to sei whales (note, this is an expanded timeframe from the Whale Advisory Zone discussed in the 2020 HSTT final rule, which spanned June through November, though the effective period could change in future years). Channel Island NMS observers collect information from aerial surveys conducted by NOAA, the U.S. Coast Guard, California Department of Fish and Game, and U.S. Navy chartered aircraft. Information on seasonal presence, movement, and general distribution patterns of large whales is shared with mariners, NMFS Office of Protected Resources, U.S. Coast Guard, California Department of Fish and Game, the Santa Barbara Museum of Natural History, the Marine Exchange of Southern California, and whale scientists. Real time and historical whale observation data collected from multiple sources can be viewed on the Point Blue Whale Database.

Further, as stated in the 2023 SAR, the California swordfish drift gillnet fishery is the most likely U.S. fishery to interact with Eastern North Pacific sei whales, though there are zero estimated annual takes from this fishery given no observed entanglements from 1990-2021 across 9,246 observed fishing sets (Carretta et al. (2022)). NMFS established the Pacific Offshore Cetacean Take Reduction Team in 1996 and prepared an associated Plan (PCTRP) to reduce the risk of M/SI via fisheries interactions. In 1997, NMFS published final regulations formalizing the requirements of the PCTRP, including the use of pingers following several specific provisions and the employment of Skipper education workshops.

In this case, 0.14 M/SI means one authorized mortality in 1 of the 7 years and zero authorized mortalities in 6 of those 7 years. Therefore, the Navy's authorized take would not be contributing to the total human-caused mortality at all in 6 of the 7, or 85.7 percent, of the years covered by this rulemaking. That means that even if a sei whale were to be struck, in 6 of the 7 years there could be no effect on annual rates of recruitment or survival from Navy-caused M/SI. Additionally, the loss of a male would have far less, if any, effect on population rates and absent any information suggesting that one sex is more likely to be struck than another, we can reasonably assume that there is a 50 percent chance that the single strike authorized by this rulemaking would be a male, thereby further decreasing the likelihood of impacts on the population rate. In situations like this where potential M/SI is fractional, consideration must be given to the lessened impacts anticipated due to the absence of M/SI in 6 of the 7 years and the fact that the single strike could be a male.

Lastly, we reiterate that PBR is a conservative metric and also not sufficiently precise to serve as an absolute predictor of population effects upon which mortality caps would appropriately be based. This is especially important given the minor difference between zero and one across the 7-year period covered by this rulemaking, which is the smallest distinction possible when considering mortality. As noted above, Wade et al. (1998), authors of the paper from which the current PBR equation is derived, note that “Estimating incidental mortality in 1 year to be greater than the PBR calculated from a single abundance survey does not prove the mortality will lead to depletion; it identifies a population worthy of careful future monitoring and possibly indicates that mortality-mitigation efforts should be initiated.” Even after qualitatively considering the possibility that the whale struck by Navy in 2023 was a sei whale, and based on the presence of the factors described above, we do not expect one authorized lethal take from Navy activities, alone, to adversely affect Eastern North Pacific sei whales through effects on annual rates of recruitment or survival. This information will be considered in combination with our assessment of the impacts of authorized harassment takes in the Group and Species-Specific Analyses section that follows.

Group and Species-Specific Analyses

In addition to broader analyses of the impacts of the Navy's activities on mysticetes, odontocetes, and pinnipeds, the 2018 HSTT final rule contained detailed analyses of the effects of the Navy's activities in the HSTT Study Area on each affected species and stock and was updated, as appropriate, in the 2020 HSTT final rule. All of that information and analyses remain applicable and valid for our analyses of the effects of the same Navy activities on the same species and stocks, with the exception of humpback whale, for which the stock structure has been revised, and NMFS has updated its analyses accordingly for this final rule. See the Group and Species-Specific Analyses subsection in the Analysis and Negligible Impact Determination section of the 2018 HSTT final rule (83 FR 66993-67018). In addition, apart from the additional authorized incidental take by vessel strike of two large whales, the resulting changes to the average annual mortality estimates discussed above, and the revised humpback whale stock structure, no new information has been received since the publication of the 2020 HSTT final rule that significantly changes the analyses of the effects of the Navy's activities on each species and stock presented in the 2020 HSTT final rule (new information regarding vessel strike, the potential impact of the gray whale UME (now closed), and the revised humpback whale stock structure were discussed earlier in the rule).

In the discussions below, the estimated Level B harassment takes represent instances of take, not the number of individuals taken (the much lower and less frequent Level A harassment takes are far more likely to ( print page 4995) be associated with separate individuals), and in many cases, some individuals are expected to be taken more than one time while in other cases, a portion of individuals will not be taken at all. Below, we compare the total take numbers (including PTS, TTS, and behavioral disturbance) for species or stocks to their associated abundance estimates to evaluate the magnitude of impacts across the species or stock and to individuals. Specifically, when an abundance percentage comparison is below 100, it means that percentage or less of the individuals in the stock will be affected ( i.e., some individuals will not be taken at all), that the average for those taken is 1 day per year, and that we would not expect any individuals to be taken more than a few times in a year. When it is more than 100 percent, it means there will definitely be some number of repeated takes of individuals. For example, if the percentage is 300, the average would be each individual is taken on 3 days in a year if all were taken, but it is more likely that some number of individuals will be taken more than three times and some number of individuals fewer times or not at all. While it is not possible to know the maximum number of days across which individuals of a stock might be taken, in acknowledgement of the fact that it is more than the average, for the purposes of this analysis, we assume a number approaching twice the average. For example, if the percentage of take compared to the abundance is 800, we estimate that some individuals might be taken as many as 16 times. Those comparisons are included in the sections below. For some stocks, these numbers have been adjusted slightly (with these adjustments being in the single digits) so as to more consistently apply this approach, but these minor changes did not change the analysis or findings.

To assist in understanding what this analysis means, we clarify a few issues related to estimated takes and the analysis here. An individual that incurs a PTS or TTS take may sometimes, for example, also be subject to behavioral disturbance at the same time. As described in the Harassment subsection of the Analysis and Negligible Impact Determination section of the 2018 HSTT final rule, the degree of PTS, and the degree and duration of TTS, expected to be incurred from the Navy's activities are not expected to impact marine mammals such that their reproduction or survival could be affected. Similarly, data do not suggest that a single instance in which an animal accrues PTS or TTS and is also subjected to behavioral disturbance would result in impacts to reproduction or survival. Alternately, we recognize that if an individual is subjected to behavioral disturbance repeatedly for a longer duration and on consecutive days, effects could accrue to the point that reproductive success is jeopardized (as discussed below in the stock-specific summaries). Accordingly, in analyzing the number of takes and the likelihood of repeated and sequential takes (which could result in reproductive impacts), we consider the total takes, not just the Level B harassment takes by behavioral disturbance, so that individuals potentially exposed to both threshold shift and behavioral disturbance are appropriately considered. We note that the same reasoning applies with the potential addition of behavioral disturbance to tissue damage from explosives, the difference being that we do already consider the likelihood of reproductive impacts whenever tissue damage occurs. Further, the number of Level A harassment takes by either PTS or tissue damage are so low compared to abundance numbers that it is considered highly unlikely that any individual would be taken at those levels more than once.

Having considered all of the information and analyses previously presented in the 2018 HSTT final rule, including the Group and Species-Specific Analyses discussions organized by the different groups and species, below we present tables showing instances of total take as a percentage of stock abundance for each group, updated with the new vessel strike calculations and humpback stock structure. We then summarize the information for each species or stock, considering the analysis from the 2018 HSTT final rule, 2020 HSTT final rule, and any new analysis. The analyses below in some cases address species collectively if they occupy the same functional hearing group ( i.e., low, mid, and high-frequency cetaceans and pinnipeds in water), share similar life history strategies, and/or are known to behaviorally respond similarly to acoustic stressors. Because some of these groups or species share characteristics that inform the impact analysis similarly, it would be duplicative to repeat the same analysis for each species or stock. In addition, animals belonging to each stock within a species typically have the same hearing capabilities and behaviorally respond in the same manner as animals in other stocks within the species.

Mysticetes

In tables 12 and 13 below for mysticetes, we indicate the total annual mortality, Level A harassment, and Level B harassment, and a number indicating the instances of total take as a percentage of abundance. Tables 12 and 13 have been updated from tables 18 and 19 in the 2020 HSTT final rule, as appropriate, with the 2023 final SARs and updated information on mortality, as discussed above. For additional information and analysis supporting the negligible-impact analysis, see the Mysticetes discussion in the Group and Species-Specific Analyses section of the 2018 HSTT final rule, all of which remains applicable to this rule unless specifically noted.

Table 12—Annual Estimated Takes by Level B Harassment, Level A Harassment, and Mortality for Mysticetes in the HRC Portion of the HSTT Study Area and Number Indicating the Instances of Total Take as a Percentage of Stock Abundance

Species	Stock	Instances of indicated types of incidental take (not all takes represent separate individuals, especially for disturbance)					Total takes a		Abundance		Instance of total take as percent of abundance
		Level B harassment		Level A harassment		Mortality b	Total takes (entire study area)	Takes (within Navy EEZ)	Total Navy abundance inside and outside of EEZ (HRC)	Within EEZ Navy abundance (HRC)	Total take as percentage of total Navy abundance (HRC)	EEZ take as percentage of Navy EEZ abundance (HRC)
		Behavioral disturbance	TTS (may also include disturbance)	PTS	Tissue damage
Blue whale	Central North Pacific	15	33	0	0	0	48	40	43	33	112	121
( print page 4996)
Bryde's whale	Hawaii	40	106	0	0	0	146	123	108	89	135	138
Fin whale	Hawaii	21	27	0	0	0	48	41	52	40	92	103
Humpback whale	Hawaii	2,837	6,289	3	0	0.29	9,129	7,389	5,078	4,595	180	161
Minke whale	Hawaii	1,233	3,697	2	0	0	4,932	4,030	3,652	2,835	135	142
Sei whale	Hawaii	46	121	0	0	0	167	135	138	107	121	126
Note: For the Hawaii take estimates, we compare predicted takes to abundance estimates generated from the same underlying density estimates (as described in the Estimated Take of Marine Mammals section of the 2018 HSTT final rule), both in and outside of the U.S. EEZ. Because the portion of the Navy's study area inside the U.S. EEZ is generally concomitant with the area used to generate the abundance estimates in the SARs, and the abundance predicted by the same underlying density estimates is the preferred abundance to use, there is no need to separately compare the take to the SARs abundance estimate.
a  Total takes inside and outside U.S. EEZ represent the sum of annual Level A and Level B harassment from training and testing activities.
b  The annual mortality of 0.29 is the result of no more than two mortalities over the course of 7 years from vessel strikes as described above in the Estimated Take of Marine Mammals section.

Table 13—Annual Estimated Takes by Level B Harassment, Level A Harassment, and Mortality for Mysticetes in the SOCAL Portion of the HSTT Study Area and Number Indicating the Instances of Total Take as a Percentage of Stock Abundance

Species	Stock	Instances of indicated types of incidental take (not all takes represent separate individuals, especially for disturbance)					Total takes a	Abundance		Instance of total take as percent of abundance
		Level B harassment		Level A harassment		Mortality b	Total takes (entire study area)	Navy abundance in action area (SOCAL)	NMFS SARs abundance	Total take as percentage of total Navy abundance in action area	Total take as percentage of total SAR abundance
		Behavioral disturbance	TTS (may also include disturbance)	PTS	Tissue damage
Blue whale	Eastern North Pacific	792	1,196	1	0	0.14	1,989	785	1,898	253	105
Bryde's whale	Eastern Tropical Pacific	14	27	0	0	0	41	1.3	unknown	3,154	unknown
Fin whale	CA/OR/WA	835	1,390	1	0	0.57	2,227	363	11,065	613	20
Humpback whale	Central America/Southern Mexico-CA/OR/WA	282	594	0	0	0	876	c  74	1,496	1,184	59
	Mainland Mexico- CA/OR/WA	198	920	1	0	0.14	1,119	c  173	3,477	647	32
Minke whale	CA/OR/WA	259	666	1	0	0	926	163	915	568	101
Sei whale	Eastern North Pacific	27	52	0	0	0.14	79	3	864	2,633	9
Gray whale	Eastern North Pacific	1,316	3,355	7	0	0.57	4,679	193	26,960	2,424	17
Gray whale	Western North Pacific	2	4	0	0	0	6	0	290	0	2
Note: For the SOCAL take estimates, because of the manner in which the Navy study area overlaps the ranges of many MMPA stocks ( i.e., a stock may range far north to Washington state and beyond and abundance may only be predicted within the U.S. EEZ, while the Navy study area is limited to Southern California and northern Mexico, but extends beyond the U.S. EEZ), we compare predicted takes to both the abundance estimates for the study area, as well as the SARs (as described in the Estimated Take of Marine Mammals section of the 2018 HSTT final rule).
a  Total takes inside and outside U.S. EEZ represent the sum of annual Level A and Level B harassment from training and testing activities.
b  The annual mortality of 0.14 is the result of no more than one mortality over the course of 7 years from vessel strikes as described above in the Estimated Take of Marine Mammals section. The annual mortality of 0.57 is the result of no more than four mortalities over the course of 7 years from vessel strikes.
c  In the 2020 HSTT final rule, NMFS reported a Navy abundance in Action Area (SOCAL) of 247 CA/OR/WA humpback whales. As explained in more detail in the Authorized Take From Vessel Strikes and Explosives by Serious Injury or Mortality section, NMFS estimates that approximately 30 percent of the humpback whales off the coast of California may be from the Central America DPS with the remaining 70 percent are expected to be from the Mexico DPS. Therefore, of the estimated 247 humpback whales in SOCAL, NMFS anticipates that 74 would be of the Central America/Southern Mexico-CA/OR/WA stock (Central America DPS), and 173 would be of the Mainland Mexico-CA/OR/WA stock (Mexico DPS).

( print page 4997)

Below we compile and summarize the information that supports our determination that the Navy's activities will not adversely affect any species or stocks through effects on annual rates of recruitment or survival for any of the affected mysticete species and stocks.

Blue Whale (Eastern North Pacific Stock)

Blue whales are listed as endangered under the ESA, and the current population trend for the Eastern North Pacific stock is unknown. We further note that this stock was originally listed under the ESA as a result of the impacts from commercial whaling, which is no longer affecting the species. NMFS authorizes one mortality over the 7 years covered by this rulemaking or 0.14 mortality annually. With the addition of this 0.14 annual mortality, residual PBR is exceeded, resulting in the total human-caused mortality exceeding PBR by 14.5. However, as described in more detail in the Serious Injury or Mortality section above, when total human-caused mortality exceeds PBR, we consider whether the incremental addition of a small amount of authorized mortality from the specified activity may still result in a negligible impact, in part by identifying whether it is less than 10 percent of PBR. In this case, the authorized mortality is well below 10 percent of PBR, management measures are in place to reduce mortality from other sources, and the incremental addition of a single mortality over the course of the 7-year Navy rule is not expected to, alone, lead to adverse impacts on the stock through effects on annual rates of recruitment or survival.

Regarding the magnitude of Level B harassment takes (TTS and behavioral disturbance), the number of estimated total instances of take compared to the abundance (measured against both the Navy-estimated abundance and the SAR) is 253 and 105 percent, respectively (table 13). Given the range of blue whales, this information suggests that only some portion of individuals in the stock are likely impacted, but that there will likely be some repeat exposure (maybe 5 or 6 days within a year) of some subset of individuals that spend extended time within SOCAL. Regarding the severity of those individual Level B harassment takes by behavioral disturbance, the duration of any exposure is expected to be between minutes and hours ( i.e., relatively short) and the received sound levels largely below 172 dB with a portion up to 178 dB ( i.e., of a moderate or lower level, less likely to evoke a severe response). Additionally, the Navy implements time/area mitigation in SOCAL in the majority of the BIAs identified by Calambokidis et al. (2015). These areas overlap a portion of the blue whale feeding BIAs (parent and child; see Harrison et al. 2023) identified in Calambokidis et al. (2024) and will reduce the severity of impacts to blue whales by reducing interference in feeding that could result in lost feeding opportunities or necessitate additional energy expenditure to find other good opportunities. Regarding the severity of TTS takes, we have explained in the 2018 HSTT final rule that they are expected to be low-level, of short duration, and mostly not in a frequency band that would be expected to interfere with blue whale communication or other important low-frequency cues—and that the associated lost opportunities and capabilities are not at a level that will impact reproduction or survival. For similar reasons (as described in the 2018 HSTT final rule) the single estimated Level A harassment take by PTS for this stock is unlikely to have any effect on the reproduction or survival of that one individual, even if it were to be experienced by an animal that also experiences one or more Level B harassment takes by behavioral disturbance.

Altogether, only a small portion of the stock is anticipated to be impacted and any individual blue whale is likely to be disturbed at a low-moderate level, with likely many animals exposed only once or twice and a subset potentially disturbed across 5 or 6 days but minimized in BIAs. This low magnitude and severity of harassment effects is not expected to result in impacts on the reproduction or survival of any individuals and, therefore, when combined with the authorized mortality (which our earlier analysis indicated will not, alone, have more than a negligible impact on this stock of blue whales), the total take is not expected to adversely affect this stock through impacts on annual rates of recruitment or survival. For these reasons, we have determined, in consideration of all of the effects of the Navy's activities combined, that the authorized take will have a negligible impact on the Eastern North Pacific stock of blue whales.

Bryde's Whale (Eastern Tropical Pacific Stock)

Little is known about this stock or its status, and it is not listed under the ESA. No mortality or Level A harassment is anticipated or authorized. Regarding the magnitude of Level B harassment takes (TTS and behavioral disturbance), the number of estimated total instances of take compared to the abundance is 3,154 percent; however, the abundance upon which this percentage is based (1.3 whales from the Navy estimate, which is extrapolated from density estimates based on very few sightings) is clearly erroneous and the SAR does not include an abundance estimate because all of the survey data is outdated (table 13). However, the abundance in the early 1980s was estimated as 22,000 to 24,000, a portion of the stock was estimated at 13,000 in 1993, and the minimum number in the Gulf of California was estimated at 160 in 1990. Given this information and the fact that 41 total takes of Bryde's whales were estimated, this information suggests that only a small portion of the individuals in the stock are likely impacted, and few, if any, are likely taken over more than 1 day. Regarding the severity of those individual Level B harassment takes by behavioral disturbance, the duration of any exposure is expected to be between minutes and hours ( i.e., relatively short) and the received sound levels largely below 172 dB with a portion up to 178 dB ( i.e., of a moderate or lower level, less likely to evoke a severe response). Regarding the severity of TTS takes, they are expected to be low-level, of short duration, and mostly not in a frequency band that would be expected to interfere with Bryde's whale communication or other important low-frequency cues. Any associated lost opportunities and capabilities are not at a level that will impact reproduction or survival.

Altogether, only a small portion of the stock is anticipated to be impacted and any individual Bryde's whale is likely to be disturbed at a low-moderate level, with few, if any, individuals exposed over more than 1 day in the year. This low magnitude and severity of harassment effects is not expected to result in impacts on individual reproduction or survival, much less annual rates of recruitment or survival. For these reasons, we have determined, in consideration of all of the effects of the Navy's activities combined, that the authorized take will have a negligible impact on the Eastern Tropical Pacific stock of Bryde's whales.

Fin Whale (CA/OR/WA Stock)

The SAR identifies this stock as “increasing,” even though the larger species is listed as endangered under the ESA. NMFS authorizes four mortalities over the 7 years covered by this rulemaking, or 0.57 mortality annually. The addition of this 0.57 annual mortality still leaves the total human-caused mortality well under residual PBR. ( print page 4998)

We acknowledge the 2021 vessel strike of two fin whales by the Royal Australian Navy, and that the 2021 and 2023 vessel strikes by the U.S. Navy could have been CA/OR/WA fin whales. While the Royal Australian Navy strikes are not quantitatively included in the estimated take by vessel strike, even if they were, and if we presumed that the 2021 and 2023 U.S. Navy strikes were all fin whales, M/SI of this stock would still fall well below PBR (80).

Regarding the magnitude of Level B harassment takes (TTS and behavioral disturbance), the number of estimated total instances of take compared to the abundance (measured against both the Navy-estimated abundance and the SAR) is 613 and 20 percent, respectively (table 13). This information suggests that only some portion (less than 25 percent) of individuals in the stock are likely impacted but that there is likely some repeat exposure (perhaps up to 12 days within a year) of some subset of individuals that spend extended time within the SOCAL complex. Some of these takes could occur on a few sequential days for some small number of individuals, for example, if they resulted from a multi-day exercise on a range while individuals were in the area for multiple days feeding. Regarding the severity of those individual Level B harassment takes by behavioral disturbance, the duration of any exposure is expected to be between minutes and hours ( i.e., relatively short) and the received sound levels largely below 172 dB with a portion up to 178 dB ( i.e., of a moderate or lower level, less likely to evoke a severe response). Additionally, Calambokidis et al. (2024) identifies feeding BIAs for fin whales in SOCAL. The Navy implements time/area mitigation in SOCAL in blue whale BIAs identified by Calambokidis et al. (2015), and fin whales are known to sometimes feed in some of the same areas. Additionally, these mitigation areas designed for blue whales overlap a portion of the fin whale feeding BIAs (parent and child; see Harrison et al. 2023) identified by Calambokidis et al. (2024) which means fin whales could potentially accrue some benefits from the mitigation. Regarding the severity of TTS takes, they are expected to be low-level, of short duration, and mostly not in a frequency band that would be expected to interfere with fin whale communication or other important low-frequency cues—and that the associated lost opportunities and capabilities are not at a level that will impact reproduction or survival. For similar reasons (as described in the 2018 HSTT final rule) the single estimated Level A harassment take by PTS for this stock is unlikely to have any effects on the reproduction or survival of that one individual.

Altogether, this population is increasing, only a small portion of the stock is anticipated to be impacted, and any individual fin whale is likely to be disturbed at a low-moderate level, with the taken individuals likely exposed between 1 and 12 days, with a few individuals potentially taken on a few sequential days. This low magnitude and severity of harassment effects is not expected to result in impacts on individual reproduction or survival, and therefore, when combined with the authorized mortality (which our earlier analysis indicated will not, alone, have more than a negligible impact on this stock of fin whales), the total take is not expected to adversely affect this stock through impacts on annual rates of recruitment or survival. For these reasons, we have determined, in consideration of all of the effects of the Navy's activities combined, that the authorized take will have a negligible impact on the CA/OR/WA stock of fin whales.

Humpback Whale (Central America/Southern Mexico-CA/OR/WA Stock)

The SAR identifies this stock as increasing, though the growth rate is uncertain. Animals in this stock are of the Central America DPS which is designated as endangered under the ESA.

Regarding the magnitude of Level B harassment takes (TTS and behavioral disturbance), the number of estimated total instances of take compared to the abundance (measured against both the Navy-estimated abundance and the SAR) is 1,184 and 59 percent, respectively (table 13). Given the range of humpback whales, this information suggests that only some portion of individuals in the stock are likely impacted but that there is likely some repeat exposure (perhaps up to 23 days within a year) of some subset of individuals that spend extended time within the SOCAL complex. Regarding the severity of those individual Level B harassment takes by behavioral disturbance, the duration of any exposure is expected to be between minutes and hours ( i.e., relatively short) and the received sound levels largely below 172 dB with a portion up to 178 dB ( i.e., of a moderate or lower level, less likely to evoke a severe response). Some of these takes could occur on several sequential days for some small number of individuals, for example, if they resulted from a multi-day exercise on a range while individuals were in the area for multiple days feeding. However, these amounts are still not expected to adversely impact reproduction or survival of any individuals.

Regarding the severity of TTS takes, they are expected to be low-level, of short duration, and mostly not in a frequency band that would be expected to interfere with humpback whale communication or other important low-frequency cues—and that the associated lost opportunities and capabilities are not at a level that will impact reproduction or survival. Altogether, only a small portion of the stock is anticipated to be impacted and any individual humpback whale is likely to be disturbed at a low-moderate level, with likely many animals exposed only once or twice and a subset potentially disturbed up to 23 days, but with no reason to think that more than a few of those days would be sequential. This low magnitude and severity of harassment effects is not expected to result in impacts on the reproduction or survival of any individuals and, therefore, the total take is not expected to adversely affect this stock through impacts on annual rates of recruitment or survival. For these reasons, we have determined, in consideration of all of the effects of the Navy's activities combined, that the authorized take will have a negligible impact on the Central America/Southern Mexico-CA/OR/WA stock of humpback whales.

Humpback Whale (Mainland Mexico-CA/OR/WA Stock)

The status of this stock is unknown. Animals in this stock are of the Mexico DPS which is designated as threatened under the ESA. NMFS authorizes one mortality over the 7 years covered by this rulemaking, or 0.14 mortality annually. The addition of this 0.14 annual mortality still leaves the total human-caused mortality well under residual PBR.

Regarding the magnitude of Level B harassment takes (TTS and behavioral disturbance), the number of estimated total instances of take compared to the abundance (measured against both the Navy-estimated abundance and the SAR) is 647 and 32 percent, respectively (table 13). Given the range of humpback whales, this information suggests that only some portion of individuals in the stock are likely impacted but that there is likely some repeat exposure (perhaps up to 13 days within a year) of some subset of individuals that spend extended time within the SOCAL complex. Regarding the severity of those individual Level B harassment takes by behavioral disturbance, the duration of any exposure is expected to be between ( print page 4999) minutes and hours ( i.e., relatively short) and the received sound levels largely below 172 dB with a portion up to 178 dB ( i.e., of a moderate or lower level, less likely to evoke a severe response). Some of these takes could occur on several sequential days for some small number of individuals, for example, if they resulted from a multi-day exercise on a range while individuals were in the area for multiple days feeding. However, these amounts are still not expected to adversely impact reproduction or survival of any individuals.

Regarding the severity of TTS takes, they are expected to be low-level, of short duration, and mostly not in a frequency band that would be expected to interfere with humpback whale communication or other important low-frequency cues—and that the associated lost opportunities and capabilities are not at a level that will impact reproduction or survival. For similar reasons (as described in the 2018 HSTT final rule) the single estimated Level A harassment take by PTS for this stock is unlikely to have any effects on the reproduction or survival of that one individual.

Altogether, only a small portion of the stock is anticipated to be impacted and any individual humpback whale is likely to be disturbed at a low-moderate level, with likely many animals exposed only once or twice and a subset potentially disturbed up to 13 days, but with no reason to think that more than a few of those days would be sequential. This low magnitude and severity of harassment effects is not expected to result in impacts on the reproduction or survival of any individuals and, therefore, when combined with the authorized mortality (which our earlier analysis indicated will not, alone, have more than a negligible impact on this stock of humpback whales), the total take is not expected to adversely affect this stock through impacts on annual rates of recruitment or survival. For these reasons, we have determined, in consideration of all of the effects of the Navy's activities combined, that the authorized take will have a negligible impact on the CA/OR/WA stock of humpback whales.

Minke Whale (CA/OR/WA Stock)

The status of this stock is unknown and it is not listed under the ESA. No mortality from vessel strike or tissue damage from explosive exposure is anticipated or authorized for this species. Regarding the magnitude of Level B harassment takes (TTS and behavioral disturbance), the number of estimated total instances of take compared to the abundance (measured against both the Navy-estimated abundance and the SAR) is 568 and 101 percent, respectively (table 13). Based on the behaviors of minke whales, which often occur along continental shelves and sometimes establish home ranges along the West Coast, this information suggests that only a portion of individuals in the stock are likely impacted but that there is likely some repeat exposure (perhaps up to 11 days within a year) of some subset of individuals that spend extended time within the SOCAL complex. Some of these takes could occur on a few sequential days for some small number of individuals, for example, if they resulted from a multi-day exercise on a range while individuals were in the area for multiple days feeding. Regarding the severity of those individual Level B harassment takes by behavioral disturbance, the duration of any exposure is expected to be between minutes and hours ( i.e., relatively short) and the received sound levels largely below 172 dB with a portion up to 178 dB ( i.e., of a moderate or lower level, less likely to evoke a severe response). Regarding the severity of TTS takes, they are expected to be low-level, of short duration, and mostly not in a frequency band that would be expected to interfere with minke whale communication or other important low-frequency cues—and that the associated lost opportunities and capabilities are not at a level that will impact reproduction or survival. For similar reasons (as described in the 2018 HSTT final rule) the single estimated Level A harassment take by PTS for this stock is unlikely to have any effects on the reproduction or survival of that individual.

Altogether, only a portion of the stock is anticipated to be impacted and any individual minke whale is likely to be disturbed at a low-moderate level, with the taken individuals likely exposed between 1 and 11 days, with a few individuals potentially taken on a few sequential days. This low magnitude and severity of harassment effects is not expected to result in impacts on individual reproduction or survival, much less annual rates of recruitment or survival. For these reasons, we have determined, in consideration of all of the effects of the Navy's activities combined, that the authorized take will have a negligible impact on the CA/OR/WA stock of minke whales.

Sei Whale (Eastern North Pacific Stock)

The status of this stock is unknown, and sei whales are listed under the ESA. NMFS authorizes one mortality over the 7 years covered by this rulemaking or 0.14 mortality annually. The addition of this 0.14 annual mortality still leaves the total human-caused mortality under residual PBR. After additionally considering several qualitative factors described above, including that the 2023 strike could have been a sei whale (or fin whale), we do not expect one authorized lethal take from Navy activities, alone, to adversely affect Eastern North Pacific sei whales through effects on annual rates of recruitment or survival. No Level A harassment is anticipated or authorized.

Regarding the magnitude of Level B harassment takes (TTS and behavioral disturbance), the number of estimated total instances of take compared to the abundance (measured against both the Navy-estimated abundance and the SAR) is 2,633 and 9 percent, respectively (table 13), however, the abundance upon which the Navy percentage is based (3 from the Navy estimate, which is extrapolated from density estimates based on very few sightings) is likely an underestimate of the number of individuals in the HSTT study Area, resulting in an overestimated percentage. Given this information and the large range of sei whales, and the fact that only 79 total Level B harassment takes of sei whales were estimated, it is likely that some very small number of sei whales would be taken repeatedly, potentially up to 15 days in a year (typically 2,633 percent would lead to the estimate of 52 days/year, however, given that there are only 79 sei whale total takes, we used the conservative assumption that five individuals might be taken up to 15 times, with the few remaining takes distributed among other individuals). Regarding the severity of those individual Level B harassment takes by behavioral disturbance, the duration of any exposure is expected to be between minutes and hours ( i.e., relatively short) and the received sound levels largely below 172 dB with a portion up to 178 dB ( i.e., of a moderate or lower level, less likely to evoke a severe response). Some of these takes could occur on a few sequential days for some small number of individuals, for example, if they resulted from a multi-day exercise on a range while individuals were in the area for multiple days feeding, however, these amounts are still not expected to adversely impact reproduction or survival of any individuals. Regarding the severity of TTS takes, they are expected to be low-level, of short duration, and mostly not in a frequency band that would be expected to interfere with sei whale communication or other important low-frequency cues—and that ( print page 5000) the associated lost opportunities and capabilities are not at a level that will impact reproduction or survival.

Altogether, only a small portion of the stock is anticipated to be impacted and any individual sei whale is likely to be disturbed at a low-moderate level, with only a few individuals exposed over one to 15 days in a year, with no more than a few sequential days. This low magnitude and severity of harassment effects is not expected to result in impacts on individual reproduction or survival, and therefore, when combined with the authorized mortality (which our earlier analysis indicated will not, alone, have more than a negligible impact on this stock of sei whales), the total take is not expected to adversely affect this stock through impacts on annual rates of recruitment or survival. For these reasons, we have determined, in consideration of all of the effects of the Navy's activities combined, that the authorized take will have a negligible impact on the Eastern North Pacific stock of sei whales.

Gray Whale (Eastern North Pacific Stock)

The Eastern North Pacific stock of gray whale is not ESA-listed and the SAR indicates that the stock is increasing. However, recent (2021-2022) surveys conducted by NMFS' Southwest Fisheries Science Center estimated that the population has declined to 16,650 whales, though the authors note that this stock has historically shown a pattern of population growth and decline that has not impacted the population in the long term (Eguchi et al. 2022). NMFS is authorizing four mortalities over the 7 years covered by this rulemaking, or 0.57 mortality annually. The addition of this 0.57 annual mortality still leaves the total human-caused mortality well under the insignificance threshold of residual PBR (670). We acknowledge that the 2021 vessel strikes by the U.S. Navy could have been Eastern North Pacific gray whales. If we presumed that the 2021 U.S. Navy strikes were both gray whales, M/SI of this stock would still fall well below PBR (801).

We also consider here how the 2019-2023 West Coast Gray Whale UME informs our negligible impact determination. Because of the abundance and residual PBR of this stock, as well as the fact that the UME is closed and increased mortality stopped in late 2023 (with peak strandings ending in December 2020), this UME is not expected to have any impacts on individuals during the period of this final rule, nor is it thought to have had impacts on the population rate when it was occurring that would influence our evaluation of the effects of the mortality authorized on the stock.

Regarding the magnitude of Level B harassment takes (TTS and behavioral disturbance), the number of estimated total instances of take compared to the abundance (measured against both the Navy-estimated abundance and the SAR) is 2,424 and 17 percent, respectively (table 13). (Note that in comparison to the recent Eguchi et al. 2024 abundance estimate, the number of estimated total instances of take compared to the abundance would be 24 percent.) This information suggests that only some small portion of individuals in the stock are likely impacted (less than 17 percent) but that there is likely some level of repeat exposure of some subset of individuals that spend extended time within the SOCAL complex. Typically 2,424 percent would lead to the estimate of 48 days/year, however, given that a large number of gray whales are known to migrate through the SOCAL complex and the fact that there are 4,679 total takes, we believe that it is more likely that a larger number of individuals will be taken one to a few times, while a small number staying in an area to feed for several days may be taken on 5-10 days. Regarding the severity of those individual Level B harassment takes by behavioral disturbance, the duration of any exposure is expected to be between minutes and hours ( i.e., relatively short) and the received sound levels largely below 172 dB with a portion up to 178 dB ( i.e., of a moderate or lower level, less likely to evoke a severe response). Some of these takes could occur on a couple of sequential days for some small number of individuals; however, these amounts are still not expected to adversely impact reproduction or survival of any individuals.

Regarding the severity of TTS takes, they are expected to be low-level, of short duration, and mostly not in a frequency band that would be expected to interfere with gray whale communication or other important low-frequency cues and that the associated lost opportunities and capabilities are not at a level that will impact reproduction or survival. For these same reasons (low level and frequency band), while a small permanent loss of hearing sensitivity may include some degree of energetic costs for compensating or may mean some small loss of opportunities or detection capabilities, at the expected scale the seven estimated Level A harassment takes by PTS for gray whales are unlikely to impact behaviors, opportunities, or detection capabilities to a degree that would interfere with reproductive success or survival of any individuals.

Altogether, we have considered the impacts of the recent (now closed) gray whale UME, the Eastern North Pacific stock of gray whales is not endangered or threatened under the ESA. The SAR indicates that the stock is increasing. However, recent (2023-2024) surveys conducted by NMFS' Southwest Fisheries Science Center estimated that the population has declined since the most recent Eastern North Pacific gray whale SAR was published (Eguchi et al. 2024). Only a small portion of the stock is anticipated to be impacted and any individual gray whale is likely to be disturbed at a low-moderate level, with likely many animals exposed only once or twice and a subset potentially disturbed across 5 to 10 days. This low magnitude and severity of harassment effects is not expected to result in impacts to reproduction or survival for any individuals and, therefore, when combined with the authorized mortality of four whales over the 7 year period (which our earlier analysis indicated will not, alone, have more than a negligible impact on this stock of gray whales), the total take is not expected to adversely affect this stock through impacts on annual rates of recruitment or survival. For these reasons, we have determined, in consideration of all of the effects of the Navy's activities combined, that the authorized take will have a negligible impact on the Eastern North Pacific stock of gray whales.

Gray Whale (Western North Pacific Stock)

The Western North Pacific stock of gray whales is reported as increasing in the 2023 final SAR but is listed as endangered under the ESA. No mortality or Level A harassment is anticipated or authorized. This stock is expected to incur the very small number of 6 Level B harassment takes (2 behavioral disruption and 4 TTS) to a stock with a SAR-estimated abundance of 290 (table 13). These takes will likely accrue to different individuals, the behavioral disturbances will be of a low-moderate level, and the TTS instances will be at a low level and short duration. This low magnitude and severity of harassment effects is not expected to result in impacts on individual reproduction or survival, much less to adversely affect this stock through impacts on annual rates of recruitment or survival. For these reasons, we have determined, in consideration of all of the effects of the Navy's activities combined, that the authorized take will have a negligible impact on the Western North Pacific stock of gray whales. ( print page 5001)

Humpback Whale (Hawaii Stock)

The status of this stock is unknown. Animals in this stock are of the Hawaii DPS which is not listed under the ESA. No Level A harassment by tissue damage is authorized. NMFS authorizes two mortalities over the 7 years covered by this rulemaking, or 0.29 mortalities annually. The addition of this 0.29 annual mortality still leaves the total human-caused mortality well under the insignificance threshold for residual PBR.

Regarding the magnitude of Level B harassment takes (TTS and behavioral disturbance), the number of estimated instances of take compared to the abundance, both throughout the HSTT Study Area and within the U.S. EEZ, respectively, is 180 and 161 percent (table 12). This information and the complicated far-ranging nature of the stock structure suggests that some portion of the stock (but not all) are likely impacted, over 1 to several days per year, with little likelihood of take across sequential days. Regarding the severity of those individual Level B harassment takes by behavioral disturbance, the duration of any exposure is expected to be between minutes and hours ( i.e., relatively short) and the received sound levels largely below 172 dB with a portion up to 178 dB ( i.e., of a moderate or lower level, less likely to evoke a severe response). Additionally, as noted above, there are two mitigation areas implemented by the Navy that span a large area of the important humpback reproductive areas (BIA, parent and child; see Harrison et al. 2023) identified in Kratofil et al. (2023) and minimize impacts by limiting the use of MF1 active sonar and explosives, thereby reducing both the number and severity of takes of humpback whales. Regarding the severity of TTS takes, they are expected to be low-level, of short duration, and mostly not in a frequency band that would be expected to interfere with humpback whale communication or other important low-frequency cues, and that the associated lost opportunities and capabilities are not at a level that will impact reproduction or survival. For these same reasons (low level and frequency band), while a small permanent loss of hearing sensitivity may include some degree of energetic costs for compensating or may mean some small loss of opportunities or detection capabilities, at the expected scale the 3 estimated Level A harassment takes by PTS for humpback whales are unlikely to impact behaviors, opportunities, or detection capabilities to a degree that would interfere with reproductive success or survival of any individuals.

Altogether, this stock's status is unknown and the DPS is not listed as endangered or threatened under the ESA. Only a small portion of the stock is anticipated to be impacted and any individual humpback whale is likely to be disturbed at a low-moderate level, with the taken individuals likely exposed between 1 to several days per year, with little likelihood of take across sequential days. This low magnitude and severity of harassment effects is not expected to result in impacts on individual reproduction or survival, and therefore, when combined with the authorized mortality (which our earlier analysis indicated will not, alone, have more than a negligible impact on this stock of humpback whales), the total take is not expected to adversely affect this stock through effects on annual rates of recruitment or survival. For these reasons, we have determined, in consideration of all of the effects of the Navy's activities combined, that the authorized take will have a negligible impact on the Hawaii stock of humpback whales.

Blue Whale (Central North Pacific Stock) and the Hawaii Stocks of Bryde's Whale, Fin Whale, Minke Whale, and Sei Whale

The status of these stocks are not identified in the SARs. Blue whale (Central North Pacific stock) and the Hawaii stocks of fin whale and sei whale are listed as endangered under the ESA; the Hawaii stocks of minke whales and Bryde's whales are not listed under the ESA. No mortality or Level A harassment by tissue damage is anticipated or authorized for any of these stocks.

Regarding the magnitude of Level B harassment takes (TTS and behavioral disturbance), the number of estimated instances of take compared to the abundance, both throughout the HSTT Study Area and within the U.S. EEZ, respectively, is 92-135 and 103-142 percent (table 12). This information suggests that some portion of the stocks (but not all) are likely impacted, over 1 to several days per year, with little likelihood of take across sequential days. Regarding the severity of those individual Level B harassment takes by behavioral disturbance, the duration of any exposure is expected to be between minutes and hours ( i.e., relatively short) and the received sound levels largely below 172 dB with a portion up to 178 dB ( i.e., of a moderate or lower level, less likely to evoke a severe response). Regarding the severity of TTS takes, they are expected to be low-level, of short duration, and mostly not in a frequency band that would be expected to interfere with mysticete communication or other important low-frequency cues—and that the associated lost opportunities and capabilities are not at a level that will impact reproduction or survival. For similar reasons (as described in the 2018 HSTT final rule) the two estimated Level A harassment takes by PTS for the Hawaii stock of minke whales are unlikely to have any effects on the reproduction or survival of any individuals.

Altogether, only a portion of these stocks are anticipated to be impacted and any individuals of these stocks are likely to be disturbed at a low-moderate level, with the taken individuals likely exposed between 1 and several days, with little chance that any are taken across sequential days. This low magnitude and severity of harassment effects is not expected to result in impacts on individual reproduction or survival, much less have impacts on annual rates of recruitment or survival. For these reasons, we have determined, in consideration of all of the effects of the Navy's activities combined, that the authorized take will have a negligible impact on these stocks.

Odontocetes

Sperm Whale, Dwarf Sperm Whale, and Pygmy Sperm Whale

In table 14 and table 15 below for sperm whale, dwarf sperm whale, and pygmy sperm whale, we indicate the total annual mortality (0 for all stocks; the 2020 HSTT final rule included 0.14 annual takes by mortality of the Hawaii stock of sperm whale), Level A and Level B harassment, and a number indicating the instances of total take as a percentage of abundance. Table 14 and table 15 are unchanged from tables 20 and 21 in the 2020 HSTT final rule, except for updated information on mortality for the Hawaii stock of sperm whales, as discussed above. For additional information and analysis supporting the negligible-impact analysis, see the Odontocetes discussion as well as the Sperm Whales, Dwarf Sperm Whales, and Pygmy Sperm Whales discussion in the Group and Species-Specific Analyses section of the 2018 HSTT final rule, all of which remains applicable to this rule unless specifically noted. ( print page 5002)

Table 14—Annual Estimated Takes by Level B Harassment, Level A Harassment, and Mortality for Sperm Whales, Dwarf Sperm Whales, and Pygmy Sperm Whales in the HRC Portion of the HSTT Study Area and Number Indicating the Instances of Total Take as a Percentage of Stock Abundance

Species	Stock	Instances of indicated types of incidental take (not all takes represent separate individuals, especially for disturbance)					Total takes		Abundance		Instances of total take as percent of abundance
		Level B harassment		Level A harassment		Mortality	Total takes (entire study area)	Takes (within NAVY EEZ)	Total Navy abundance inside and outside EEZ (HRC)	Within EEZ Navy abundance (HRC)	Total take as percentage of total Navy abundance (HRC)	EEZ take as percentage of EEZ abundance (HRC)
		Behavioral disturbance	TTS (may also include disturbance)	PTS	Tissue damage
Dwarf sperm whale	Hawaii	5,870	14,550	64	0	0	20,484	15,310	8,218	6,379	249	240
Pygmy sperm whale	Hawaii	2,329	5,822	29	0	0	8,180	6,098	3,349	2,600	244	235
Sperm whale	Hawaii	2,466	30	0	0	0	2,496	1,317	1,656	1,317	151	147
Note: For the Hawaii take estimates, we compare predicted takes to abundance estimates generated from the same underlying density estimates (as described in the Estimated Take of Marine Mammals section of the 2018 HSTT final rule), both in and outside of the U.S. EEZ. Because the portion of the Navy's study area inside the U.S. EEZ is generally concomitant with the area used to generate the abundance estimates in the SARs, and the abundance predicted by the same underlying density estimates is the preferred abundance to use, there is no need to separately compare the take to the SARs abundance estimate.
Total takes inside and outside U.S. EEZ represent the sum of annual Level A and Level B harassment from training and testing activities.

Table 15—Annual Estimated Takes by Level B Harassment, Level A Harassment, and Mortality for Sperm Whales, Dwarf Sperm Whales, and Pygmy Sperm Whales in the SOCAL Portion of the HSTT Study Area and Number Indicating the Instances of Total Take as a Percentage of Stock Abundance

Species	Stock	Instances of indicated types of incidental take (not all takes represent separate individuals, especially for disturbance)					Total takes	Abundance		Instances of total take as percent of abundance
		Level B harassment		Level A harassment		Mortality	Total takes (entire study area)	Navy abundance in action area	NMFS SARS abundance	Total take as percentage of total Navy abundance in action area	Total take as percentage of total SAR abundance
		Behavioral disturbance	TTS (may also include disturbance)	PTS	Tissue damage
Kogia whales	CA/OR/WA	2,779	6,353	38	0	0	9,170	757	4,111	1,211	223
Sperm whale	CA/OR/WA	2,437	56	0	0	0	2,493	273	2,606	913	96
Note: For the SOCAL take estimates, because of the manner in which the Navy study area overlaps the ranges of many MMPA stocks ( i.e., a stock may range far north to Washington state and beyond and abundance may only be predicted within the U.S. EEZ, while the Navy study area is limited to Southern California and northern Mexico, but extends beyond the U.S. EEZ), we compare predicted takes to both the abundance estimates for the study area, as well as the SARs (as described in the Estimated Take of Marine Mammals section of the 2018 HSTT final rule).
Total takes inside and outside U.S. EEZ represent the sum of annual Level A and Level B harassment from training and testing activities.

Below we compile and summarize the information that supports our determination that the Navy's activities will not adversely affect any species or stocks through effects on annual rates of recruitment or survival for any of the affected species and stocks addressed in this section. Sperm Whale, Dwarf Sperm Whale, and Pygmy Sperm Whale (CA/OR/WA Stocks)

The SAR identifies the CA/OR/WA stock of sperm whales as “stable”, and the species is listed as endangered under the ESA. The status of the CA/OR/WA stocks of pygmy and dwarf sperm whales is unknown and neither are listed under the ESA. Neither mortality nor Level A harassment by tissue damage from exposure to explosives is expected or authorized for any of these three stocks.

Due to their pelagic distribution, small size, and cryptic behavior, pygmy sperm whales and dwarf sperm whales are rarely sighted during at-sea surveys and are difficult to distinguish between when visually observed in the field. Many of the relatively few observations of Kogia spp. off the U.S. West Coast were not identified to species. All at-sea sightings of Kogia spp. have been identified as pygmy sperm whales or Kogia spp. Stranded dwarf sperm and pygmy sperm whales have been found on the U.S. West Coast, however dwarf sperm whale strandings are rare. NMFS SARs suggest that the majority of Kogia sighted off the U.S. West Coast were likely pygmy sperm whales. As such, the stock estimate in the NMFS SAR for pygmy sperm whales is the estimate derived for all Kogia spp. in the region (Barlow, 2016), and no separate abundance estimate can be determined for dwarf sperm whales, though some low number likely reside in the U.S. EEZ. Due to the lack of abundance estimate, it is not possible to predict the take of dwarf sperm whales and take estimates are identified as Kogia spp. (including both pygmy and dwarf sperm whales). We assume only a small portion of those takes are likely to be dwarf sperm whales as the density and abundance in the U.S. EEZ is thought to be low.

Regarding the magnitude of Level B harassment takes (TTS and behavioral disturbance), the number of estimated total instances of take compared to the abundance (measured against both the Navy-estimated abundance and the SAR) is, respectively, 913 and 96 for sperm whales and 1,211 and 223 for Kogia spp., with a large proportion of these anticipated to be pygmy sperm whales due to the low abundance and density of dwarf sperm whales in the HSTT Study Area (table 15). Given the ( print page 5003) range of these stocks (which extends the entire length of the West Coast, as well as beyond the U.S. EEZ boundary), this information suggests that some portion of the individuals in these stocks will not be impacted but that there is likely some repeat exposure (perhaps up to 24 days within a year for Kogia spp. and 18 days a year for sperm whales) of some small subset of individuals that spend extended time within the SOCAL Range. Additionally, while interrupted feeding bouts are a known response and concern for odontocetes, we also know that there are often viable alternative habitat options in the relative vicinity. Regarding the severity of those individual Level B harassment takes by behavioral disturbance, the duration of any exposure is expected to be between minutes and hours ( i.e., relatively short) and the received sound levels largely below 172 dB ( i.e., of a lower, to occasionally moderate, level and less likely to evoke a severe response). However, some of these takes could occur on a fair number of sequential days for some number of individuals.

Regarding the severity of TTS takes, they are expected to be low-level, of short duration, and mostly not in a frequency band that would be expected to interfere with sperm whale communication or other important low-frequency cues, and that the associated lost opportunities and capabilities are not at a level that will impact reproduction or survival. For these same reasons (low level and frequency band), while a small permanent loss of hearing sensitivity (PTS) may include some degree of energetic costs for compensating or may mean some small loss of opportunities or detection capabilities, at the expected scale the estimated Level A harassment takes by PTS for the dwarf and pygmy sperm whale stocks are unlikely to impact behaviors, opportunities, or detection capabilities to a degree that would interfere with reproductive success or survival of any individuals. Thus, the 38 total Level A harassment takes by PTS for these 2 stocks are unlikely to affect rates of recruitment and survival for the stocks.

Altogether, most members of the stocks will likely be taken by Level B harassment (at a low to occasionally moderate level) over several days a year, and some smaller portion of the stocks are expected to be taken on a relatively moderate to high number of days (up to 18 or 24) across the year, some of which could be sequential days. Though the majority of impacts are expected to be of a lower to sometimes moderate severity, the larger number of takes for a subset of individuals makes it more likely that a small number of individuals could be interrupted during foraging in a manner and amount such that impacts to the energy budgets of females (from either losing feeding opportunities or expending considerable energy to find alternative feeding options) could cause them to forego reproduction for a year. Energetic impacts to males are generally meaningless to population rates unless they cause death, and it takes extreme energy deficits beyond what would ever be likely to result from these activities to cause the death of an adult marine mammal. As discussed in the 2020 HSTT final rule, however, foregone reproduction (especially for 1 year, which is the maximum predicted because the small number anticipated in any 1 year makes the probability that any individual would be impacted in this way twice in 7 years very low) has far less of an impact on population rates than mortality, and a small number of instances of foregone reproduction are not expected to adversely affect these stocks through effects on annual rates of recruitment or survival. We also note that residual PBR is 19 for pygmy sperm whales and 3.5 for sperm whales. Both the abundance and PBR are unknown for dwarf sperm whales, however, we know that take of this stock is likely significantly lower in magnitude and severity ( i.e., lower number of total takes and repeated takes any individual) than pygmy sperm whales. For these reasons, in consideration of all of the effects of the Navy's activities combined, we have determined that the authorized take will have a negligible impact on the CA/OR/WA stocks of sperm whales and pygmy and dwarf sperm whales.

Sperm Whale (Hawaii Stock)

The SAR does not identify a trend for this stock and the species is listed as endangered under the ESA. No mortality or Level A harassment by PTS or tissue damage is expected or authorized.

Regarding the magnitude of Level B harassment takes (TTS and behavioral disturbance), the number of estimated instances of take compared to the abundance, both throughout the HSTT Study Area and within the U.S. EEZ, respectively, is 151 and 147 percent (table 14). This information and the sperm whale stock range suggest that likely only a smaller portion of the stock will be impacted, over 1 to several days per year, with little likelihood of take across sequential days. Regarding the severity of those individual Level B harassment takes by behavioral disturbance, the duration of any exposure is expected to be between minutes and hours ( i.e., relatively short) and the received sound levels largely below 172 dB ( i.e., of a lower, to occasionally moderate, level and less likely to evoke a severe response). Regarding the severity of TTS takes, they are expected to be low-level, of short duration, and mostly not in a frequency band that would be expected to interfere with sperm whale communication or other important low-frequency cues, and that the associated lost opportunities and capabilities are not at a level that will impact reproduction or survival.

Altogether, a relatively small portion of this stock is anticipated to be impacted and any individuals are likely to be disturbed at a low-moderate level, with the taken individuals likely exposed between 1 and several days, with little chance that any are taken across sequential days. This low magnitude and severity of harassment effects is not expected to result in impacts on individual reproduction or survival, much less annual rates of recruitment or survival. For these reasons, we have determined, in consideration of all of the effects of the Navy's activities combined, that the authorized take will have a negligible impact on the Hawaii stock of sperm whales.

Pygmy and Dwarf Sperm Whales (Hawaii Stocks)

The SAR does not identify a trend for these stocks and the species are not listed under the ESA. No Level A harassment by tissue damage is anticipated or authorized. Regarding the magnitude of Level B harassment takes (TTS and behavioral disturbance), the number of estimated instances of take compared to the abundance, both throughout the HSTT Study Area and within the U.S. EEZ, respectively, is 244-249 and 235-240 percent (table 14). This information and the pygmy and dwarf sperm whale stock ranges (at least throughout the U.S. EEZ around the entire Hawaiian Islands) suggest that likely a fair portion of each stock is not impacted, but that a subset of individuals may be taken over one to perhaps 5 days per year, with little likelihood of take across sequential days. Regarding the severity of those individual Level B harassment takes by behavioral disturbance, the duration of any exposure is expected to be between minutes and hours ( i.e., relatively short) and the received sound levels largely below 172 dB ( i.e., of a lower, to occasionally moderate, level and less likely to evoke a severe response). Additionally, as discussed earlier, within the Hawaii Island Mitigation ( print page 5004) Area, explosives are not used and the use of MF1 and MF4 active sonar is limited, greatly reducing the severity of impacts within the small and resident population BIA for dwarf sperm whales (Kratofil et al. 2023), which is entirely contained within this mitigation area.

Regarding the severity of TTS takes, they are expected to be low-level, of short duration, and mostly not in a frequency band that would be expected to interfere with sperm whale communication or other important low-frequency cues—and that the associated lost opportunities and capabilities are not at a level that will impact reproduction or survival. For these same reasons (low level and frequency band), while a small permanent loss of hearing sensitivity may include some degree of energetic costs for compensating or may mean some small loss of opportunities or detection capabilities, at the expected scale, estimated Level A harassment takes by PTS for dwarf and pygmy sperm whales are unlikely to impact behaviors, opportunities, or detection capabilities to a degree that would interfere with reproductive success or survival of any individuals, even if it were to be experienced by an animal that also experiences one or more instances of Level B harassment by behavioral disturbance. Thus the 29 and 64 total Level A harassment takes by PTS for dwarf and pygmy sperm whales, respectively, are unlikely to affect rates of recruitment and survival for these stocks.

Altogether, a portion of these stocks are likely to be impacted and any individuals are likely to be disturbed at a low-moderate level, with the taken individuals likely exposed between 1 and 5 days, with little chance that any are taken across sequential days. This low magnitude and severity of Level A and Level B harassment effects is not expected to result in impacts on individual reproduction or survival, much less impacts on annual rates of recruitment or survival. For these reasons, we have determined, in consideration of all of the effects of the Navy's activities combined, that the expected and authorized take will have a negligible impact on the Hawaii stocks of pygmy and dwarf sperm whales.

Beaked Whales

In table 16 and table 17 below for beaked whales, we indicate the total annual mortality, Level A and Level B harassment, and a number indicating the instances of total take as a percentage of abundance. Table 16 and table 17 are unchanged from table 22 and table 23 in the 2020 HSTT final rule, with the exception of a correction to a rounding error as noted. For additional information and analysis supporting the negligible-impact analysis, see the Odontocetes discussion as well as the Beaked Whales discussion in the Group and Species-Specific Analyses section of the 2018 HSTT final rule, all of which remains applicable to this rule unless specifically noted.

Table 16—Annual Estimated Takes by Level B Harassment, Level A Harassment, and Mortality for Beaked Whales in the HRC Portion of the HSTT Study Area and Number Indicating the Instances of Total Take as a Percentage of Stock Abundance

Species	Stock	Instances of indicated types of incidental take (not all takes represent separate individuals, especially for disturbance)					Total takes		Abundance		Instances of total take as percent of abundance
		Level B harassment		Level A harassment		Mortality	Total takes (entire study area)	Takes (within Navy EEZ)	Total Navy abundance inside and outside EEZ (HRC)	Within EEZ Navy abundance (HRC)	Total take as percentage of total Navy abundance (HRC)	EEZ take as percentage of EEZ abundance (HRC)
		Behavioral disturbance	TTS (may also include disturbance)	PTS	Tissue damage
Blainville's beaked whale	Hawaii	5,369	16	0	0	0	5,385	4,140	989	768	a  544	539
Goose-beaked whale	Hawaii	1,792	4	0	0	0	1,796	1,377	345	268	521	514
Longman's beaked whale	Hawaii	19,152	81	0	0	0	19,233	14,585	3,568	2,770	539	527
Note: For the Hawaii take estimates, we compare predicted takes to abundance estimates generated from the same underlying density estimates (as described in the Estimated Take of Marine Mammals section of the 2018 HSTT final rule), both in and outside of the U.S. EEZ. Because the portion of the Navy's study area inside the U.S. EEZ is generally concomitant with the area used to generate the abundance estimates in the SARs, and the abundance predicted by the same underlying density estimates is the preferred abundance to use, there is no need to separately compare the take to the SARs abundance estimate.
Total takes inside and outside U.S. EEZ represent the sum of annual Level A and Level B harassment from training and testing activities.
a The 2020 final rule unintentionally presented this percentage as 545. The correct value is provided here. This error does not affect the conclusions in the 2020 HSTT final rule.

Table 17—Annual Estimated Takes by Level B Harassment, Level A Harassment, and Mortality for Beaked Whales in the SOCAL Portion of the HSTT Study Area and Number Indicating the Instances of Total Take as a Percentage of Stock Abundance

Species	Stock	Instances of indicated types of incidental take (not all takes represent separate individuals, especially for disturbance)					Total takes	Abundance		Instances of total take as percent of abundance
		Level B harassment		Level A harassment		Mortality	Total takes (entire study area)	Navy abundance in action area	NMFS SARs abundance	Total take as percentage of total Navy abundance in action area	Total take as percentage of total SAR abundance
		Behavioral disturbance	TTS (may also include disturbance)	PTS	Tissue damage
Baird's beaked whale	CA/OR/WA	2,030	14	0	0	0	2,044	74	1,363	2,762	150
Goose-beaked whale	CA/OR/WA	11,373	127	1	0	0	11,501	520	5,454	2,212	211
( print page 5005)
Mesoplodon species	CA/OR/WA	6,125	68	1	0	0	6,194	89	3,044	6,960	203
Note: For the SOCAL take estimates, because of the manner in which the Navy study area overlaps the ranges of many MMPA stocks ( i.e., a stock may range far north to Washington state and beyond and abundance may only be predicted within the U.S. EEZ, while the Navy study area is limited to Southern California and northern Mexico, but extends beyond the U.S. EEZ), we compare predicted takes to both the abundance estimates for the study area, as well as the SARs (as described in the Estimated Take of Marine Mammals section of the 2018 HSTT final rule).
Total takes inside and outside U.S. EEZ represent the sum of annual Level A and Level B harassment from training and testing activities.

Below we compile and summarize the information that supports our determination that the Navy's activities will not adversely affect any species or stocks through effects on annual rates of recruitment or survival for any of the affected species or stocks addressed in this section.

Blainville's, Goose-Beaked, and Longman's Beaked Whales (Hawaii Stocks)

The SAR does not identify a trend for these stocks and the species are not listed under the ESA. No mortality or Level A harassment are expected or authorized for any of these three stocks. Regarding the magnitude of Level B harassment takes (TTS and behavioral disturbance), the number of estimated instances of take compared to the abundance, both throughout the HSTT Study Area and within the U.S. EEZ, respectively, is 521-544 and 514-539 percent (table 16). This information and the stock ranges (at least of the small, resident island associated stocks around Hawaii) suggest that likely a fair portion of the stocks (but not all) will be impacted, over 1 to perhaps 11 days per year, with little likelihood of much take across sequential days. Regarding the severity of those individual Level B harassment takes by behavioral disturbance, the duration of any exposure is expected to be between minutes and hours ( i.e., relatively short) and the received sound levels largely below 160 dB, though with beaked whales, which are considered somewhat more sensitive, this could mean that some individuals will leave preferred habitat for a day or 2 ( i.e., moderate level takes). However, while interrupted feeding bouts are a known response and concern for odontocetes, we also know that there are often viable alternative habitat options nearby. Additionally, as noted earlier, within the Hawaii Island mitigation area (which overlaps a large portion of the BIAs for goose-beaked and Blainville's beaked whales identified in Kratofil et al. 2023), explosives are not used and the use of MF1 and MF4 active sonar is limited, greatly reducing the severity of impacts within these two small resident populations.

Regarding the severity of TTS takes, they are expected to be low-level, of short duration, and mostly not in a frequency band that would be expected to interfere with beaked whale communication or other important low-frequency cues, and that the associated lost opportunities and capabilities are not at a level that will impact reproduction or survival.

Altogether, a fair portion of these stocks are anticipated to be impacted and any individuals are likely to be disturbed at a moderate level, with the taken individuals likely exposed between 1 and 11 days, with little chance that individuals are taken across more than a few sequential days. This low, to occasionally moderate, magnitude and severity of harassment effects is not expected to result in impacts on individual reproduction or survival, much less have impacts on annual rates of recruitment or survival. For these reasons, we have determined, in consideration of all of the effects of the Navy's activities combined, that the authorized take will have a negligible impact on the Hawaii stocks of beaked whales.

Baird's Beaked Whale, Goose-Beaked Whale and Mesoplodon Species (All CA/OR/WA Stocks)

The species are not listed under the ESA and their populations have been identified as “increasing,” “decreasing,” and “increasing,” respectively. No mortality is expected or authorized for any of these three stocks and only two takes by Level A harassment (PTS) are authorized.

No methods are available to distinguish between the six species of Mesoplodon beaked whale CA/OR/WA stocks (Blainville's beaked whale ( M. densirostris), Perrin's beaked whale ( M. perrini), Lesser beaked whale ( M. peruvianus), Stejneger's beaked whale ( M. stejnegeri), Gingko-toothed beaked whale ( M. gingkodens), and Hubbs' beaked whale ( M. carlhubbsi)) when observed during at-sea surveys (Carretta et al. 2018a). Bycatch and stranding records from the region indicate that the Hubbs' beaked whale is most commonly encountered (Carretta et al. 2008, Moore and Barlow, 2013). As indicated in the SAR, no species-specific abundance estimates are available, the abundance estimate includes all CA/OR/WA Mesoplodon spp, and the six species are managed as one unit. Due to the lack of species-specific abundance estimates, it is not possible to predict the take of individual species and take estimates are identified as Mesoplodon spp.

Regarding the magnitude of Level B harassment takes (TTS and behavioral disturbance), the number of estimated total instances of take compared to the abundance for these stocks is 2,762, 2,212, and 6,960 percent (measured against Navy-estimated abundance) and 150, 211, and 203 percent (measured against the SAR) for Baird's beaked whales, goose-beaked beaked whales, and Mesoplodon spp., respectively (table 17). Given the ranges of these stocks, this information suggests that some smaller portion of the individuals of these stocks will be taken, and that some subset of individuals within the stock will be taken repeatedly within the year (perhaps up to 20-25 days, and potentially more for goose-beaked)— ( print page 5006) potentially over a fair number of sequential days, especially where individuals spend extensive time in the SOCAL Range. Note that we predict lower days of repeated exposure for these stocks than their percentages might have suggested because of the number of overall takes— i.e., using the higher percentage would suggest that an unlikely portion of the takes are taken up by a small portion of the stock incurring a very large number of repeat takes, with little room for take resulting from few or moderate numbers of repeats, which is unlikely. While interrupted feeding bouts are a known response and concern for odontocetes, we also know that there are often viable alternative habitat options in the relative vicinity. Regarding the severity of those individual Level B harassment takes by behavioral disturbance, we have explained that the duration of any exposure is expected to be between minutes and hours ( i.e., relatively short) and the received sound levels largely below 160 dB, though with beaked whales, which are considered somewhat more sensitive, this could mean that some individuals will leave preferred habitat for a day or 2 ( i.e., of a moderate level). In addition, as noted, some of these takes could occur on a fair number of sequential days for these stocks.

The severity of TTS takes is expected to be low-level, of short duration, and mostly not in a frequency band that would be expected to interfere significantly with conspecific communication, echolocation, or other important low-frequency cues. Therefore, the associated lost opportunities and capabilities are not expected to impact reproduction or survival. For similar reasons (as described in the 2020 HSTT final rule) the single estimated Level A harassment take by PTS for this stock is unlikely to have any effects on the reproduction or survival of any individuals.

Altogether, a portion of these stocks will likely be taken (at a moderate or sometimes low level) over several days a year, and some smaller portion of the stock is expected to be taken on a relatively moderate to high number of days across the year, some of which could be sequential days. Though the majority of impacts are expected to be of a moderate severity, the repeated takes over a potentially fair number of sequential days for some individuals makes it more likely that a small number of individuals could be interrupted during foraging in a manner and amount such that impacts to the energy budgets of females (from either losing feeding opportunities or expending considerable energy to find alternative feeding options) could cause them to forego reproduction for a year. Energetic impacts to males are generally meaningless to population rates unless they cause death, and it takes extreme energy deficits beyond what would ever be likely to result from these activities to cause the death of an adult marine mammal. As noted previously, however, foregone reproduction (especially for 1 year, which is the maximum predicted because the small number anticipated in any 1 year makes the probability that any individual would be impacted in this way twice in 7 years very low) has far less of an impact on population rates than mortality and a small number of instances of foregone reproduction are not expected to adversely affect these stocks through effects on annual rates of recruitment or survival, especially given the residual PBR of these three beaked whale stocks (8.7, 41.9, and 19.9, respectively).

Further, Navy activities have been conducted in SOCAL for many years at similar levels and the SAR considers Mesoplodon spp. and Baird's beaked whales as increasing. While NMFS' SAR indicates that goose-beaked whales on the U.S. West Coast are declining based on a Bayesian trend analysis of NMFS' survey data collected from 1991 through 2014, results from passive acoustic monitoring and other research have estimated regional goose-beaked whale densities that were higher than indicated by NMFS' broad-scale visual surveys for the U.S. West Coast (Debich et al. 2015a; Debich et al. 2015b; Falcone and Schorr, 2012, 2014; Hildebrand et al. 2009; Moretti, 2016; Širović et al. 2016; Smultea and Jefferson, 2014). Research also indicates higher than expected residency in the Navy's instrumented Southern California Anti-Submarine Warfare Range in particular (Falcone and Schorr, 2012) and photo identification studies in the SOCAL have identified approximately 100 individual goose-beaked whale individuals with 40 percent having been seen in one or more prior years, with re-sightings up to 7 years apart (Falcone and Schorr, 2014). The documented residency by many goose-beaked whales over multiple years suggests that a stable population may exist in that small portion of the stock's overall range (Falcone et al. 2009; Falcone and Schorr, 2014; Schorr et al. 2017).

For these reasons, in consideration of all of the effects of the Navy's activities combined, we have determined that the authorized take will have a negligible impact on the CA/OR/WA stocks of Baird's and goose-beaked whales, as well as all six species included within the Mesoplodon spp.

Small Whales and Dolphins

In tables 18 and 19 below for dolphins and small whales, we indicate the total annual mortality, Level A and Level B harassment, and a number indicating the instances of total take as a percentage of abundance. Tables 18 and 19 are updated from tables 24 and 25 in the 2020 HSTT final rule as appropriate with the 2023 final SARs. For additional information and analysis supporting the negligible-impact analysis, see the Odontocetes discussion as well as the Small Whales and Dolphins discussion in the Group and Species-Specific Analyses section of the 2018 HSTT final rule, all of which remains applicable to this rule unless specifically noted.

Table 18—Annual Estimated Takes by Level B Harassment, Level A Harassment, and Mortality for Dolphins and Small Whales in the HRC Portion of the HSTT Study Area and Number Indicating the Instances of Total Take as a Percentage of Stock Abundance

Species	Stock	Instances of indicated types of incidental take (not all takes represent separate individuals, especially for disturbance)					Total takes		Abundance		Instance of total take as percent of abundance
		Level B harassment		Level A harassment		Mortality	Total takes (entire study area)	Takes (within Navy EEZ)	Total Navy abundance inside and outside of EEZ (HRC)	Within EEZ Navy abundance (HRC)	Total take as percentage of total Navy abundance (HRC)	EEZ take as percentage of Navy EEZ abundance (HRC)
		Behavioral disturbance	TTS (may also include disturbance)	PTS	Tissue damage
Bottlenose dolphin	Hawaii Pelagic	3,196	132	0	0	0	3,328	2,481	1,528	1,442	218	172
( print page 5007)
Bottlenose dolphin	Kauai & Niihau	534	31	0	0	0	565	264	184	184	307	143
Bottlenose dolphin	Oahu	8,600	61	1	0	0	8,662	8,376	743	743	a  1,166	a  1,127
Bottlenose dolphin	4-Island	349	10	0	0	0	359	316	189	189	190	167
Bottlenose dolphin	Hawaii	74	6	0	0	0	80	42	131	131	61	32
False killer whale	Hawaii Pelagic	999	42	0	0	0	1,041	766	645	507	161	151
False killer whale	Main Hawaiian Islands Insular	572	17	0	0	0	589	476	147	147	b  401	324
False killer whale	Northwestern Hawaiian Islands	365	16	0	0	0	381	280	215	169	177	166
Fraser's dolphin	Hawaii	39,784	1,289	2	0	0	41,075	31,120	5,408	18,763	760	166
Killer whale	Hawaii	118	6	0	0	0	124	93	69	54	180	172
Melon-headed whale	Hawaii Islands	3,261	231	0	0	0	3,492	2,557	1,782	1,782	196	143
Melon-headed whale	Kohala Resident	341	9	0	0	0	350	182	447	447	78	41
Pantropical spotted dolphin	Hawaii Island	3,767	227	0	0	0	3,994	2,576	2,405	2,405	166	107
Pantropical spotted dolphin	Hawaii Pelagic	9,973	476	0	0	0	10,449	7,600	5,462	4,637	191	164
Pantropical spotted dolphin	Oahu	4,284	45	0	0	0	4,329	4,194	372	372	1,164	1,127
Pantropical spotted dolphin	4-Island	701	17	0	0	0	718	634	657	657	109	96
Pygmy killer whale	Hawaii	8,122	402	0	0	0	8,524	6,538	4,928	3,931	173	166
Pygmy killer whale	Tropical	710	50	0	0	0	760	490	159	23	478	2,130
Risso's dolphin	Hawaii	8,950	448	0	0	0	9,398	7,318	1,210	4,199	777	174
Rough-toothed dolphin	Hawaii	6,112	373	0	0	0	6,485	4,859	3,054	2,808	212	173
Short-finned pilot whale	Hawaii	12,499	433	0	0	0	12,932	9,946	6,433	5,784	201	172
Spinner dolphin	Hawaii Island	279	12	0	0	0	291	89	629	629	46	14
Spinner dolphin	Hawaii Pelagic	4,332	202	0	0	0	4,534	3,491	2,885	2,229	157	157
Spinner dolphin	Kauai & Niihau	1,683	63	0	0	0	1,746	812	604	604	289	134
Spinner dolphin	Oahu & 4-Island	1,790	34	1	0	0	1,825	1,708	354	354	516	482
Striped dolphin	Hawaii	7,379	405	0	0	0	7,784	6,034	4,779	3,646	163	165
Note: For the Hawaii take estimates, we compare predicted takes to abundance estimates generated from the same underlying density estimates (as described in the Estimated Take of Marine Mammals section of the 2018 HSTT final rule), both in and outside of the U.S. EEZ. Because the portion of the Navy's study area inside the U.S. EEZ is generally concomitant with the area used to generate the abundance estimates in the SARs, and the abundance predicted by the same underlying density estimates is the preferred abundance to use, there is no need to separately compare the take to the SARs abundance estimate.
Total takes inside and outside U.S. EEZ represent the sum of annual Level A and Level B harassment from training and testing activities. ( print page 5008)
a  The 2020 final rule unintentionally presented these percentages as 1,169 and 1,130. The correct values are provided here. These errors do not affect the conclusions in the 2020 HSTT final rule.
b  The 2020 final rule unintentionally presented this percentage as 400. The correct value is provided here. This rounding error does not affect the conclusions in the 2020 HSTT final rule.

Table 19—Annual Estimated Takes by Level B Harassment, Level A Harassment, and Mortality for Dolphins and Small Whales in the SOCAL Portion of the HSTT Study Area and Number Indicating the Instances of Total Take as a Percentage of Stock Abundance

Species	Stock	Instances of indicated types of incidental take (not all takes represent separate individuals, especially for disturbance)					Total takes	Abundance		Instance of total take as percent of abundance
		Level B harassment		Level A harassment		Mortality	Total takes (entire study area)	Navy abundance in action area (SOCAL)	NMFS SARs abundance	Total take as percentage of total Navy abundance in action area	Total take as percentage of total SAR abundance
		Behavioral disturbance	TTS (may also include disturbance)	PTS	Tissue damage
Bottlenose dolphin	California Coastal	1,771	38	0	0	0	1,809	238	453	760	399
Bottlenose dolphin	CA/OR/WA Offshore	51,727	3,695	3	0	0	55,425	5,946	3,477	932	1,594
Killer whale	ENP Offshore	96	11	0	0	0	107	4	300	2,675	36
Killer whale	ENP Transient/West Coast Transient	179	20	0	0	0	199	30	349	663	57
Long-beaked common dolphin	California	233,485	13,787	18	2	0	247,292	10,258	83,379	2,411	297
Northern right whale dolphin	CA/OR/WA	90,052	8,047	10	1	0	98,110	7,705	29,285	1,273	335
Pacific white-sided dolphin	CA/OR/WA	69,245	6,093	5	0	0	75,343	6,626	34,999	1,137	215
Risso's dolphin	CA/OR/WA	116,143	10,118	9	0	0	126,270	7,784	6,336	1,622	1,993
Short-beaked common dolphin	CA/OR/WA	1,374,048	118,525	79	10	1.14	1,492,664	261,438	1,056,308	571	141
Short-finned pilot whale	CA/OR/WA	1,789	124	1	0	0	1,914	208	836	920	229
Striped dolphin	CA/OR/WA	163,640	11,614	3	0	0	175,257	39,862	29,988	440	584
Note: For the SOCAL take estimates, because of the manner in which the Navy study area overlaps the ranges of many MMPA stocks ( i.e., a stock may range far north to Washington state and beyond and abundance may only be predicted within the U.S. EEZ, while the Navy study area is limited to Southern California and northern Mexico, but extends beyond the U.S. EEZ), we compare predicted takes to both the abundance estimates for the study area, as well as the SARs (as described in the Estimated Take of Marine Mammals section of the 2018 HSTT final rule).
Total takes inside and outside U.S. EEZ represent the sum of annual Level A and Level B harassment from training and testing activities.
For mortality takes there is an annual average of 1.14 short-beaked common dolphins ( i.e., where eight takes could potentially occur divided by 7 years to get the annual number of mortalities/serious injuries).

Below we compile and summarize the information that supports our determination that the Navy's activities will not adversely affect any species or stocks through effects on annual rates of recruitment or survival for any of the affected species or stocks addressed in this section.

Long-Beaked Common Dolphin (California Stock), Northern Right Whale Dolphin (CA/OR/WA Stock), and Short-Beaked Common Dolphin (CA/OR/WA Stock)

None of these stocks are listed under the ESA and their stock statuses are considered “increasing,” “unknown,” and “increasing,” respectively. Eight mortalities or serious injuries of short-beaked common dolphins are authorized over the 7-year rule, or 1.14 M/SI annually. The addition of this 1.14 annual mortality still leaves the total human-caused mortality well under the insignificance threshold for residual PBR. The 3 stocks are expected to accrue 2, 1, and 10 Level A harassment takes from tissue damage resulting from exposure to explosives, respectively. As described in detail in the 2018 HSTT final rule, the impacts of a Level A harassment take by tissue damage could range in impact from minor to something just less than M/SI that could seriously impact fitness. However, given the Navy's procedural mitigation, exposure closer to the source and more severe end of the spectrum is less likely and we cautiously assume some moderate impact for these takes that could lower the affected individual's fitness within the year such that a female (assuming a 50 percent chance of it being a female) might forego reproduction for 1 year. As noted previously, foregone reproduction has less of an impact on population rates than death (especially for only 1 year in 7, which is the maximum predicted because the small number anticipated in any 1 year makes the probability that any individual would be impacted in this way twice in 7 years very low), and 1 to 10 instances would not be expected to impact annual rates of recruitment or survival for these stocks.

Regarding the magnitude of Level B harassment takes (TTS and behavioral disturbance), the number of estimated total instances of take compared to the abundance (measured against both the Navy-estimated abundance and the SAR) is 2,411, 1,273, and 571 percent (respective to the stocks listed in the heading) and 297, 335, and 141 percent (respective to the stocks listed in the heading) (table 19). Given the range of these stocks, this information suggests that likely some portion (but not all or even the majority) of the individuals in the northern right whale dolphin and short-beaked common dolphin stocks are likely impacted while it is entirely possible that most or all of the range-limited long-beaked common dolphin is ( print page 5009) taken. All three stocks likely will experience some repeat Level B harassment exposure (perhaps up to 48, 25, or 11 days within a year, respective to the stocks listed in the heading) of some subset of individuals that spend extended time within the SOCAL range complex. While interrupted feeding bouts are a known response and concern for odontocetes, we also know that there are often viable alternative habitat options in the relative vicinity. Regarding the severity of those individual Level B harassment takes by behavioral disturbance, the duration of any exposure is expected to be between minutes and hours ( i.e., relatively short) and the received sound levels largely below 172 dB with a portion up to 178 dB ( i.e., of a moderate or lower level, less likely to evoke a severe response). However, some of these takes could occur on a fair number of sequential days for long-beaked common dolphins or northern right whale dolphins, or even some number of short-beaked common dolphins, given the high number of total takes ( i.e., the probability that some number of individuals get taken on a higher number of sequential days is higher, because the total take number is relatively high, even though the percentage is not that high).

The severity of TTS takes is expected to be low-level, of short duration, and mostly not in a frequency band that would be expected to interfere significantly with conspecific communication, echolocation, or other important low-frequency cues, and the associated lost opportunities and capabilities are not expected to impact reproduction or survival. For these same reasons (low level and frequency band), while a small permanent loss of hearing sensitivity may include some degree of energetic costs for compensating or may mean some small loss of opportunities or detection capabilities, as discussed in the 2020 HSTT final rule, it is unlikely to impact behaviors, opportunities, or detection capabilities to a degree that would interfere with reproductive success or survival of any individuals.

Altogether and as described in more detail above, 1.14 annual lethal takes of short-beaked common dolphins are authorized, all three stocks may experience a very small number of takes by tissue damage or PTS (relative to the stock abundance and PBR), and a moderate to large portion of all three stocks will likely be taken (at a low to occasionally moderate level) over several days a year, and some smaller portion of these stocks is expected to be taken on a relatively moderate to high number of days across the year, some of which could be sequential days. Though the majority of impacts are expected to be of a lower to sometimes moderate severity, the larger number of takes (in total and for certain individuals) makes it more likely (probabilistically) that a small number of individuals could be interrupted during foraging in a manner and amount such that impacts to the energy budgets of females (from either losing feeding opportunities or expending considerable energy to find alternative feeding options) could cause them to forego reproduction for a year. Energetic impacts to males are generally meaningless to population rates unless they cause death, and it takes extreme energy deficits beyond what would ever be likely to result from these activities to cause the death of an adult marine mammal. As noted previously, however, foregone reproduction (especially for only 1 year out of 7, which is the maximum predicted because the small number anticipated in any 1 year makes the probability that any individual would be impacted in this way twice in 7 years very low) has far less of an impact on population rates than mortality and a small number of instances of foregone reproduction (including in combination with that which might result from the small number of tissue damage takes) are not expected to adversely affect the stocks through effects on annual rates of recruitment or survival, especially given the very high residual PBRs of these stocks (638.3, 156.4, and 8,858.5, respectively). For these reasons, in consideration of all of the effects of the Navy's activities combined (mortality, Level A harassment, and Level B harassment), we have determined that the authorized take will have a negligible impact on these three stocks of dolphins.

All Other SOCAL Dolphin Stocks (Except Long-Beaked Common Dolphin, Northern Right Whale Dolphin, and Short-Beaked Common Dolphin)

None of these stocks are listed under the ESA and their stock statuses are considered “unknown,” except for the bottlenose dolphin (California coastal stock) and killer whale (Eastern North Pacific stock), which are considered “stable.” No M/SI or Level A harassment via tissue damage from exposure to explosives is expected or authorized for these stocks.

Regarding the magnitude of Level B harassment takes (TTS and behavioral disturbance), the number of estimated total instances of take compared to the abundance (measured against both the Navy-estimated abundance and the SAR) is from 440 to 2,675 percent and 36 to 1,993 percent, respectively (table 19). Given the range of these stocks (along the entire U.S. West Coast, or even beyond, with some also extending seaward of the HSTT Study Area boundaries), this information suggests that some portion (but not all or even the majority) of the individuals of any of these stocks will be taken, with the exception that most or all of the individuals of the more range-limited California coastal stock of bottlenose dolphin may be taken. It is also likely that some subset of individuals within most of these stocks will be taken repeatedly within the year (perhaps up to 10-15 days within a year) but with no more than several potentially sequential days, although the CA/OR/WA stocks of bottlenose dolphins, Pacific white-sided dolphins, and Risso's dolphins may include individuals that are taken repeatedly within the year over a higher number of days (up to 57, 22, and 40 days, respectively) and potentially over a fair number of sequential days, especially where individuals spend extensive time in the SOCAL range complex. Note that though percentages are high for the Eastern North Pacific stock of killer whales and short-finned pilot whales, given the low overall number of takes, it is highly unlikely that any individuals would be taken across the number of days their percentages would suggest. While interrupted feeding bouts are a known response and concern for odontocetes, we also know that there are often viable alternative habitat options in the relative vicinity. Regarding the severity of those individual Level B harassment takes by behavioral disturbance, we have explained that the duration of any exposure is expected to be between minutes and hours ( i.e., relatively short) and the received sound levels largely below 172 dB ( i.e., of a lower, or sometimes moderate level, less likely to evoke a severe response). However, as noted, some of these takes could occur on a fair number of sequential days for the three stocks listed earlier.

The severity of TTS takes is expected to be low-level, of short duration, and mostly not in a frequency band that would be expected to interfere significantly with conspecific communication, echolocation, or other important low-frequency cues. For these same reasons (low level and frequency band), while a small permanent loss of hearing sensitivity may include some degree of energetic costs for compensating or may mean some small loss of opportunities or detection capabilities, it is unlikely to impact ( print page 5010) behaviors, opportunities, or detection capabilities to a degree that would interfere with reproductive success or survival of any individuals.

Altogether, a portion of all of these stocks will likely be taken (at a low to occasionally moderate level) over several days a year, and some smaller portion of CA/OR/WA stocks of bottlenose dolphins, Pacific white-sided dolphins, and Risso's dolphins, specifically, are expected to be taken on a relatively moderate to high number of days across the year, some of which could be sequential days. Though the majority of impacts are expected to be of a lower to sometimes moderate severity, the larger number of takes (in total and for certain individuals) for the CA/OR/WA stocks of bottlenose dolphins, Pacific white-sided dolphins, and Risso's dolphins makes it more likely (probabilistically) that a small number of individuals could be interrupted during foraging in a manner and amount such that impacts to the energy budgets of females (from either losing feeding opportunities or expending considerable energy to find alternative feeding options) could cause them to forego reproduction for a year. Energetic impacts to males are generally meaningless to population rates unless they cause death, and it takes extreme energy deficits beyond what would ever be likely to result from these activities to cause the death of an adult marine mammal. As noted previously, however, foregone reproduction (especially for only 1 year in 7, which is the maximum predicted because the small number anticipated in any 1 year makes the probability that any individual would be impacted in this way twice in 7 years very low) has far less of an impact on population rates than mortality and a small number of instances of foregone reproduction are not expected to adversely affect the stocks through effects on annual rates of recruitment or survival, especially given the residual PBRs of the CA/OR/WA stocks of bottlenose dolphins, Pacific white-sided dolphins, and Risso's dolphins (18.9, 272, and 42.3, respectively). For these reasons, in consideration of all of the effects of the Navy's activities combined, we have determined that the authorized take will have a negligible impact on these stocks of dolphins.

All HRC Dolphin Stocks

With the exception of the Main Hawaiian Island stock of false killer whales (listed as endangered under the ESA, with the MMPA stock identified as “decreasing”), none of these stocks are listed under the ESA and their stock statuses are considered “unknown.” No M/SI or Level A harassment via tissue damage from exposure to explosives is expected or authorized for these stocks.

Regarding the magnitude of Level B harassment takes (TTS and behavioral disturbance), the number of estimated total instances of take compared to the abundance (measured against both the Navy-estimated abundance and the SAR) is from 46 to 1,166 percent and 14 to 2,130 percent, respectively (table 18). Given the ranges of these stocks (many of them are small, resident, island-associated stocks), this information suggests that a fairly large portion of the individuals of many of these stocks will be taken but that most individuals will only be impacted across a smaller to moderate number of days within the year (1-15), and with no more than several potentially sequential days, although two stocks (the Oahu stocks of bottlenose dolphin and pantropical spotted dolphin) have a slightly higher percentage, suggesting they could be taken up to 23 days within a year, with perhaps a few more of those days being sequential. We note that although the percentage is higher for the tropical stock of pygmy killer whale within the U.S. EEZ (2,130), given (1) the low overall number of takes (760) and (2) the fact that the small within-U.S. EEZ abundance is not a static set of individuals, but rather individuals moving in and out of the U.S. EEZ making it more appropriate to use the percentage comparison for the total takes versus total abundance—it is highly unlikely that any individuals would be taken across the number of days the within-U.S. EEZ percentage suggests (42). While interrupted feeding bouts are a known response and concern for odontocetes, we also know that there are often viable alternative habitat options in the relative vicinity. Regarding the severity of those individual Level B harassment takes by behavioral disturbance, the duration of any exposure is expected to be between minutes and hours ( i.e., relatively short) and the received sound levels largely below 172 dB ( i.e., of a lower, or sometimes moderate level, less likely to evoke a severe response). However, as noted, some of these takes could occur on a fair number of sequential days for the Oahu stocks of bottlenose dolphin and pantropical spotted dolphins.

Within the Hawaii Island mitigation area (which overlaps a large portion of the BIAs for common bottlenose dolphin, dwarf sperm whale, false killer whale, melon-headed whale, pantropical spotted dolphin, pygmy killer whale, rough-toothed dolphin, short-finned pilot whale, and spinner dolphin identified in Kratofil et al. 2023), the Navy will not use explosives and will limit the use of MF1 and MF4 active sonar. The 4-Islands mitigation area overlaps a portion of the BIAs identified in Kratofil et al. (2023) for common bottlenose dolphin, false killer whale, pantropical spotted dolphin, rough-toothed dolphin, and spinner dolphin. Within the 4-Islands mitigation area (November 15-April 15), the Navy will not use MF1 surface ship hull-mounted mid-frequency active sonar or explosives that could potentially result in takes of marine mammals. The mitigation required in these two areas will reduce the severity of impacts within these small and resident populations.

Regarding the severity of TTS takes, they are expected to be low-level, of short duration, and mostly not in a frequency band that would be expected to interfere significantly with conspecific communication, echolocation, or other important low-frequency cues. For these same reasons (low level and frequency band), while a small permanent loss of hearing sensitivity may include some degree of energetic costs for compensating or may mean some small loss of opportunities or detection capabilities, they are unlikely to impact behaviors, opportunities, or detection capabilities to a degree that would interfere with reproductive success or survival of any individuals, even if accrued to individuals that are also taken by behavioral harassment at the same time.

Altogether, most of these stocks (all but the Oahu stocks of bottlenose dolphin and pantropical spotted dolphins) will likely be taken (at a low to occasionally moderate level) over several days a year, with some smaller portion of the stock potentially taken on a more moderate number of days across the year (perhaps up to 15 days for Fraser's dolphin, though others notably less), some of which could be across a few sequential days, which is not expected to affect the reproductive success or survival of individuals. For the Oahu stocks of bottlenose dolphin and pantropical spotted dolphins, some subset of individuals could be taken up to 23 days in a year, with some small number being taken across several sequential days, such that a small number of individuals could be interrupted during foraging in a manner and amount such that impacts to the energy budgets of females (from either losing feeding opportunities or expending considerable energy to find alternative feeding options) could cause them to forego reproduction for a year. Energetic impacts to males are generally meaningless to population rates unless ( print page 5011) they cause death, and it takes extreme energy deficits beyond what would ever be likely to result from these activities to cause the death of an adult marine mammal. As noted previously, however, foregone reproduction (especially for 1 year, which is the maximum predicted because the small number anticipated in any 1 year makes the probability that any individual would be impacted in this way twice in 7 years very low) has far less of an impact on population rates than mortality and a small number of instances of foregone reproduction are not expected to adversely affect these two stocks through effects on annual rates of recruitment or survival. For these reasons, in consideration of all of the effects of the Navy's activities combined, we have determined that the authorized take will have a negligible impact on all of the stocks of dolphins found in the vicinity of the HRC.

Dall's Porpoise

In table 20 below for porpoises, we indicate the total annual mortality, Level A harassment and Level B harassment, and a number indicating the instances of total take as a percentage of abundance. Table 20 is updated from table 26 in the 2020 HSTT final rule with the 2023 final SARs. For additional information and analysis supporting the negligible-impact analysis, see the Odontocetes discussion as well as the Dall's Porpoise discussion in the Group and Species-Specific Analyses section of the 2018 HTT final rule, all of which remains applicable to this rule unless specifically noted.

Table 20—Annual Estimated Takes by Level B Harassment, Level A Harassment, and Mortality for Porpoises in the HSTT Study Area and Number Indicating the Instances of Total Take as a Percentage of Stock Abundance

Species	Stock	Instances of indicated types of incidental take (not all takes represent separate individuals, especially for disturbance)					Total takes	Abundance		Instances of total take as percent of abundance
		Level B harassment		Level A harassment		Mortality	Total takes (entire study area)	Navy abundance in Action Area	NMFS SARs abundance	Total take as percentage of total Navy abundance in Action Area	Total take as percentage of total SAR abundance
		Behavioral disturbance	TTS (may also include disturbance)	PTS	Tissue damage
Dall's porpoise	CA/OR/WA	14,482	29,891	209	0	0	44,582	2,054	16,498	2,170	270
Note: For the SOCAL take estimates, because of the manner in which the Navy study area overlaps the ranges of many MMPA stocks ( i.e., a stock may range far north to Washington state and beyond and abundance may only be predicted within the U.S. EEZ, while the Navy study area is limited to Southern California and northern Mexico, but extends beyond the U.S. EEZ), we compare predicted takes to both the abundance estimates for the study area, as well as the SARs (as described in the Estimated Take of Marine Mammals section of the 2018 HSTT final rule).
Total takes inside and outside U.S. EEZ represent the sum of annual Level A and Level B harassment from training and testing activities.

Below we compile and summarize the information that supports our determination that the Navy's activities will not adversely affect Dall's porpoises through effects on annual rates of recruitment or survival.

Dall's porpoise is not listed under the ESA and the stock status is considered “unknown.” No M/SI or Level A harassment via tissue damage from exposure to explosives is expected or authorized for this stock.

Most Level B harassments to Dall's porpoise from hull-mounted sonar (MF1) in the HSTT Study Area will result from received levels between 154 and 166 dB SPL (85 percent). While harbor porpoises have been observed to be especially sensitive to human activity, the same types of responses have not been observed in Dall's porpoises. Dall's porpoises are typically notably longer than and weigh more than twice as much as harbor porpoises making them generally less likely to be preyed upon and likely differentiating their behavioral repertoire somewhat from harbor porpoises. Further, they are typically seen in large groups and feeding aggregations or exhibiting bow-riding behaviors, which is very different from the group dynamics observed in the more typically solitary, cryptic harbor porpoises, which are not often seen bow-riding. For these reasons, Dall's porpoises are not treated as especially sensitive species (as compared to harbor porpoises, which have a lower threshold for Level B harassment by behavioral disturbance and more distant cutoff) but, rather, are analyzed similarly to other odontocetes. Therefore, the majority of Level B harassment takes are expected to be in the form of milder responses compared to higher level exposures. As discussed more fully in the 2018 HSTT final rule, we anticipate more severe effects from takes when animals are exposed to higher received levels.

Regarding the magnitude of Level B harassment takes (TTS and behavioral disturbance), the number of estimated total instances of take compared to the abundance (measured against both the Navy-estimated abundance and the SAR) is 2,170 and 270 percent, respectively (table 20). Given the range of this stock (up the U.S. West Coast through Washington and sometimes beyond the U.S. EEZ), this information suggests that some smaller portion of the individuals of this stock will be taken, and that some subset of individuals within the stock will be taken repeatedly within the year (perhaps up to 42 days)—potentially over a fair number of sequential days, especially where individuals spend extensive time in the SOCAL range complex. While interrupted feeding bouts are a known response and concern for odontocetes, we also know that there are often viable alternative habitat options in the relative vicinity. Regarding the severity of those individual Level B harassment takes by behavioral disturbance, the duration of any exposure is expected to be between minutes and hours ( i.e., relatively short) and the received sound levels largely below 172 dB ( i.e., of a lower, or sometimes moderate level, less likely to evoke a severe response). However, as noted, some of these takes could occur on a fair number of sequential days for this stock.

The severity of TTS takes is expected to be low-level, of short duration, and mostly not in a frequency band that would be expected to interfere significantly with conspecific communication, echolocation, or other important low-frequency cues. Therefore, the associated lost opportunities and capabilities are not expected to impact reproduction or survival. For these same reasons (low level and the likely frequency band), while a small permanent loss of hearing sensitivity may include some degree of energetic costs for compensating or may ( print page 5012) mean some small loss of opportunities or detection capabilities, the estimated 209 takes by Level A harassment by PTS for Dall's porpoise are unlikely to impact behaviors, opportunities, or detection capabilities to a degree that would interfere with reproductive success or survival for most individuals. Because of the high number of PTS takes, however, we acknowledge that a few animals could potentially incur permanent hearing loss of a higher degree that could potentially interfere with their successful reproduction and growth. Given the status of the stock, even if this occurred, it would not adversely impact rates of recruitment or survival.

Altogether, a portion of this stock will likely be taken (at a low to occasionally moderate level) over several days a year, and some smaller portion of the stock is expected to be taken on a relatively moderate to high number of days across the year, some of which could be sequential days. Though the majority of impacts are expected to be of a lower to sometimes moderate severity, the larger number of takes (in total and for certain individuals) for the Dall's porpoise makes it more likely (probabilistically) that a small number of individuals could be interrupted during foraging in a manner and amount such that impacts to the energy budgets of females (from either losing feeding opportunities or expending considerable energy to find alternative feeding options) could cause them to forego reproduction for a year. Energetic impacts to males are generally meaningless to population rates unless they cause death, and it takes extreme energy deficits beyond what would ever be likely to result from these activities to cause the death of an adult marine mammal. Similarly, we acknowledge the potential for this to occur to a few individuals out of the 209 total that might incur a higher degree of PTS. As noted previously, however, foregone reproduction (especially for only 1 year in 7, which is the maximum predicted because the small number anticipated in any 1 year makes the probability that any individual would be impacted in this way twice in 7 years very low) has far less of an impact on population rates than mortality. Further, the small number of instances of foregone reproduction that could potentially result from PTS and/or the few repeated, more severe Level B harassment takes by behavioral disturbance are not expected to adversely affect the stock through effects on annual rates of recruitment or survival, especially given the status of the species (not endangered or threatened; minimum population of 10,286 just within the U.S. EEZ) and residual PBR of Dall's porpoise (98.3). For these reasons, in consideration of all of the effects of the Navy's activities combined, we have determined that the authorized take will have a negligible impact on Dall's porpoise.

Pinnipeds

In tables 21 and 22 below for pinnipeds, we indicate the total annual mortality, Level A harassment and Level B harassment, and a number indicating the instances of total take as a percentage of abundance. Tables 21 and 22 have been updated from tables 27 and 28 in the 2020 HSTT final rule with the 2023 final SARs. For additional information and analysis supporting the negligible-impact analysis, see the Pinnipeds discussion in the Group and Species-Specific Analyses section of the 2018 HSTT final rule, all of which remains applicable to this rule unless specifically noted.

Table 21—Annual Estimated Takes by Level B Harassment, Level A Harassment, and Mortality for Pinnipeds in the HRC Portion of the HSTT Study Area and Number Indicating the Instances of Total Take as a Percentage of Stock Abundance

Species	Instances of indicated types of incidental take (not all takes represent separate individuals, especially for disturbance)					Total takes		Abundance		Instance of total take as percent of abundance
	Level B harassment		Level A harassment		Mortality	Total takes (entire study area)	Takes (within Navy EEZ)	Total Navy abundance inside and outside of EEZ (HRC)	Within EEZ Navy abundance (HRC)	Total take as percentage of total Navy abundance (HRC)	EEZ take as percentage of Navy EEZ abundance (HRC)
	Behavioral disturbance	TTS (may also include disturbance)	PTS	Tissue damage
Hawaiian monk seal	143	62	1	0	0	206	195	169	169	122	115
Note: For the Hawaii take estimates, we compare predicted takes to abundance estimates generated from the same underlying density estimates (as described in the Estimated Take of Marine Mammals section of the 2018 HSTT final rule), both in and outside of the U.S. EEZ. Because the portion of the Navy's study area inside the U.S. EEZ is generally concomitant with the area used to generate the abundance estimates in the SARs, and the abundance predicted by the same underlying density estimates is the preferred abundance to use, there is no need to separately compare the take to the SARs abundance estimate.
Total takes inside and outside U.S. EEZ represent the sum of annual Level A and Level B harassment from training and testing activities.

Table 22—Annual Estimated Takes by Level B Harassment, Level A Harassment, and Mortality for Pinnipeds in the SOCAL Portion of the HSTT Study Area and Number Indicating the Instances of Total Take as a Percentage of Stock Abundance

Species	Stock	Instances of indicated types of incidental take (not all takes represent separate individuals, especially for disturbance)					Total Takes	Abundance		Instance of total take as percent of abundance
		Level B harassment		Level A harassment		Mortality	Total takes (entire study area)	Navy abundance in action area (SOCAL)	NMFS SARs abundance	Total take as percentage of total Navy abundance in action area	Total take as percentage of total SAR abundance
		Behavioral disturbance	TTS (may also include disturbance)	PTS	Tissue damage
California sea lion	U.S.	113,419	4,789	87	9	0.71	118,305	4,085	257,606	2,896	46
Guadalupe fur seal	Mexico	1,442	15	0	0	0	1,457	1,171	34,187	124	4
( print page 5013)
Northern fur seal	California	15,167	124	1	0	0	15,292	886	14,050	1,726	109
Harbor seal	California	2,450	2,994	8	0	0	5,452	321	30,968	1,698	18
Northern elephant seal	California	42,916	17,955	97	2	0	60,970	4,108	187,386	1,484	33
Note: For the SOCAL take estimates, because of the manner in which the Navy action area overlaps the ranges of many MMPA stocks ( i.e., a stock may range far north to Washington state and beyond and abundance may only be predicted within the U.S. EEZ, while the Navy action area is limited to Southern California and northern Mexico, but extends beyond the U.S. EEZ), we compare predicted takes to both the abundance estimates for the action area, as well as the SARs.
For mortality takes there is an annual average of 0.71 California sea lions ( i.e., where five takes could potentially occur divided by 7 years to get the annual number of mortalities/serious injuries).

Below we compile and summarize the information that supports our determination that the Navy's activities would not adversely affect any pinnipeds through effects on annual rates of recruitment or survival for any of the affected species or stocks addressed in this section.

Five M/SI takes of California sea lions are authorized and when this mortality is combined with the other human-caused mortality from other sources, it still falls well below the insignificance threshold for residual PBR (13,684). A small number of Level A harassment takes by tissue damage are also authorized (nine and two for California sea lions and northern elephant seals, respectively), which, as discussed in the 2020 HSTT final rule, could range in impact from minor to something just less than M/SI that could seriously impact fitness. However, given the Navy's mitigation, exposure at the closer to the source and more severe end of the spectrum is less likely. Nevertheless, we cautiously assume some moderate impact on the individuals that experience these small numbers of take that could lower the individual's fitness within the year such that a female (assuming a 50 percent chance of it being a female) might forego reproduction for 1 year. As noted previously, foregone reproduction has less of an impact on population rates than death (especially for only one within 7 years, which is the maximum predicted because the small number anticipated in any 1 year makes the probability that any individual would be impacted in this way twice in 7 years very low) and these low numbers of instances (especially assuming the likelihood that only 50 percent of the takes would affect females) are not expected to impact annual rates of recruitment or survival, especially given the population sizes of these species.

Regarding the magnitude of Level B harassment takes (TTS and behavioral disturbance), for Hawaiian monk seals and Guadalupe fur seals, the two species listed under the ESA, the estimated instances of takes as compared to the stock abundance does not exceed 124 percent, which suggests that some portion of these two stocks would be taken on 1 to a few days per year. For the remaining stocks, the number of estimated total instances of take compared to the abundance (measured against both the Navy-estimated abundance and the SAR) is 1,484 to 2,896 percent and 18 to 46 percent, respectively (table 22). Given the ranges of these stocks ( i.e., very large ranges, but with individuals often staying in the vicinity of haulouts), this information suggests that some very small portion of the individuals of these stocks will be taken, but that some subset of individuals within the stock will be taken repeatedly within the year (perhaps up to 58 days)—potentially over a fair number of sequential days. Regarding the severity of those individual Level B harassment takes by behavioral disturbance, the duration of any exposure is expected to be between minutes and hours ( i.e., relatively short) and the received sound levels largely below 172 dB, which is considered a relatively low to occasionally moderate level for pinnipeds. However, as noted, some of these takes could occur on a fair number of sequential days for this stock.

As described in the 2018 HSTT final rule and 2020 HSTT final rule, the Hawaii and 4-Islands mitigation areas protect (by not using explosives and limiting MFAS within) a significant portion of the designated critical habitat for Hawaiian monk seals in the Main Hawaiian Islands, including all of it around the islands of Hawaii and Lanai, most around Maui, and good portions around Molokai and Kaho'olawe. As discussed, this protection reduces the overall number of takes and further reduces the severity of effects by minimizing impacts near pupping beaches and in important foraging habitat.

The severity of TTS takes are expected to be low-level, of short duration, and mostly not in a frequency band that would be expected to interfere significantly with conspecific communication, echolocation, or other important low-frequency cues that would affect the individual's reproduction or survival. For these same reasons (low level and frequency band), while a small permanent loss of hearing sensitivity may include some degree of energetic costs for compensating or may mean some small loss of opportunities or detection capabilities, the one to eight estimated Level A harassment takes by PTS for monk seals, northern fur seals, and harbor seals are unlikely to impact behaviors, opportunities, or detection capabilities to a degree that would interfere with reproductive success or survival of any individuals. Because of the high number of PTS takes for California sea lions and northern elephant seals (87 and 97, respectively), we acknowledge that a few animals could potentially incur permanent hearing loss of a higher degree that could potentially interfere with their successful reproduction and growth. Given the status of the stocks, even if this occurred, it would not adversely impact rates of recruitment or ( print page 5014) survival (residual PBR of 13,684 and 5,108, respectively).

Altogether, an individual Hawaiian monk seal and Guadalupe fur seal would be taken no more than a few days in any year with none of the expected take anticipated to affect individual reproduction or survival, let alone annual rates of recruitment and survival. With all other stocks, only a very small portion of the stock will be taken in any manner. Of those taken, some individuals will be taken by Level B harassment (at a moderate or sometimes low level) over several days a year, and some smaller portion of those taken will be on a relatively moderate to high number of days across the year (up to 58), a fair number of which will likely be sequential days. Though the majority of impacts are expected to be of a lower to sometimes moderate severity, the repeated takes over a potentially fair number of sequential days for some individuals makes it more likely that some number of individuals could be interrupted during foraging in a manner and amount such that impacts to the energy budgets of females (from either losing feeding opportunities or expending considerable energy to find alternative feeding options) could cause them to forego reproduction for a year (energetic impacts to males are generally meaningless to population rates unless they cause death, and it takes extreme energy deficits beyond what would ever be likely to result from these activities to cause the death of an adult marine mammal). As noted previously, however, foregone reproduction (especially for only 1 year within 7, which is the maximum predicted because the small number anticipated in any 1 year makes the probability that any individual would be impacted in this way twice in 7 years very low) has far less of an impact on population rates than mortality and a relatively small number of instances of foregone reproduction (as compared to the stock abundance and residual PBR) are not expected to adversely affect the stock through effects on annual rates of recruitment or survival, especially given the status of these stocks. Accordingly, we do not anticipate the relatively small number of individual northern fur seals or harbor seals that might be taken over repeated days within the year in a manner that results in 1 year of foregone reproduction to adversely affect the stocks through effects on rates of recruitment or survival, given the status of the stocks, which are respectively increasing and stable with abundances and residual PBRs of 14,050/30,968 and 449/1,598.

For California sea lions, given the very high abundance and residual PBR (257,606 and 13,684, respectively), as well as the increasing status of the stock in the presence of similar levels of Navy activities over past years—the impacts of 0.71 annual mortalities, potential foregone reproduction for up to nine individuals in a year taken by tissue damage, and some relatively small number of individuals taken as a result of repeated behavioral harassment over a fair number of sequential days are not expected to adversely affect the stock through effects on annual rates of recruitment or survival. Similarly, for northern elephant seals, given the very high abundance and residual PBR (187,386 and 5,108, respectively), as well as the increasing status of the stock in the presence of similar levels of Navy activities over past years, the impacts of potential foregone reproduction for up to 2 individuals in a year taken by tissue damage and some relatively small number of individuals taken as a result of repeated behavioral harassment over a fair number of sequential days are not expected to adversely affect the stock through effects on annual rates of recruitment or survival. For these reasons, in consideration of all of the effects of the Navy's activities combined (M/SI, Level A harassment, and Level B harassment), we have determined that the authorized take will have a negligible impact on all pinniped species and stocks.

Determination

The 2018 HSTT final rule included a detailed discussion of all of the anticipated impacts on the affected species and stocks from serious injury or mortality, Level A harassment, and Level B harassment; impacts on habitat; and how the Navy's mitigation and monitoring measures reduce the number and/or severity of adverse effects. We have evaluated how these impacts as well as additional take of two large whales by serious injury or mortality by vessel strike, and the required mitigation measures are expected to combine, annually, to affect individuals of each species and stock. Those effects were then evaluated in the context of whether they are reasonably likely to impact reproductive success or survivorship of individuals and then, if so, further analyzed to determine whether there would be effects on annual rates of recruitment or survival that would adversely affect the species or stock.

As described above, the basis for the negligible impact determination is the assessment of effects on annual rates of recruitment and survival. Accordingly, the analysis included in the 2018 HSTT final rule and 2020 HSTT final rule used annual activity levels, the best available science, and approved methods to predict the annual impacts to marine mammals, which were then analyzed in the context of whether each species or stock would incur more than a negligible impact based on anticipated adverse impacts to annual rates of recruitment or survival. As we have described above, none of the factors upon which the conclusions in the 2020 HSTT final rule were based have changed, with the exception of estimated take by vessel strike. Therefore, even though this final rule includes two additional takes by vessel strike, little has changed that would change our 2018 HSTT final rule and subsequent 2020 HSTT final rule analyses, and it is appropriate to rely on those analyses, as well as the new information and analysis discussed above, for this final rule.

Based on the applicable information and analysis from the 2018 HSTT final rule and 2020 HSTT final rule, as updated with the information and analysis contained herein on the potential and likely effects of the specified activities on the affected marine mammals and their habitat, and taking into consideration the implementation of the monitoring and mitigation measures, NMFS finds that the incidental take from the specified activities will have a negligible impact on all affected marine mammal species and stocks.

Subsistence Harvest of Marine Mammals

There are no subsistence uses or harvest of marine mammals in the geographic area affected by the specified activities. Therefore, NMFS has determined that the total taking affecting species or stocks would not have an unmitigable adverse impact on the availability of such species or stocks for taking for subsistence purposes.

Classification

Endangered Species Act

There are nine marine mammal species under NMFS jurisdiction that are listed as endangered or threatened under the ESA with confirmed or possible occurrence in the HSTT Study Area: blue whale, fin whale, gray whale (Western North Pacific DPS), humpback whale (Mexico and Central America DPSs), sei whale, sperm whale, false killer whale (Main Hawaiian Islands Insular DPS), Hawaiian monk seal, and ( print page 5015) Guadalupe fur seal. There is also ESA-designated critical habitat for Hawaiian monk seals and Main Hawaiian Islands Insular false killer whales. The Navy consulted with NMFS pursuant to section 7 of the ESA for HSTT activities. NMFS also consulted internally on the issuance of the 2018 HSTT regulations and LOAs under section 101(a)(5)(A) of the MMPA.

NMFS issued a Biological Opinion on December 10, 2018 concluding that the issuance of the 2018 HSTT final rule and subsequent LOAs are not likely to jeopardize the continued existence of the threatened and endangered species under NMFS' jurisdiction and are not likely to result in the destruction or adverse modification of critical habitat in the HSTT Study Area. The 2018 Biological Opinion included specified conditions under which NMFS would be required to reinitiate section 7 consultation. NMFS reviewed these specified conditions for the 2020 HSTT rulemaking and determined that reinitiation of consultation was not warranted. The incidental take statement that accompanied the 2018 Biological Opinion was amended to cover the 7-year period of the 2020 HSTT rule. The 2018 Biological Opinion for this action is available at https://www.fisheries.noaa.gov/​national/​marine-mammal-protection/​incidental-take-authorizations-military-readiness-activities.

The 2018 Biological Opinion reinitiation clause (2), states that formal consultation should be reinitiated if “new information reveals effects of the agency action that may affect ESA-listed species or critical habitat in a manner or to an extent not previously considered.” Given the new information regarding the recent occurrence of large whale strikes by naval vessels in the southern California portion of the HSTT Study Area, as described herein, the Navy reinitiated consultation with NMFS pursuant to section 7 of the ESA for HSTT Study Area activities, and NMFS also reinitiated consultation internally on the issuance of these revised regulations and LOAs under section 101(a)(5)(A) of the MMPA.

NMFS issued a reinitiated Biological and Conference Opinion on June 3, 2024 concluding that the issuance of the 2024 HSTT final rule and subsequent LOAs are not likely to jeopardize the continued existence of the threatened and endangered species under NMFS' jurisdiction and are not likely to result in the destruction or adverse modification of critical habitat in the HSTT Study Area. The opinion is available at https://doi.org/​10.25923/​7y9x-vw84.

National Marine Sanctuaries Act

Federal agency actions that are likely to injure national marine sanctuary resources are subject to consultation with the Office of National Marine Sanctuaries (ONMS) under section 304(d) of the National Marine Sanctuaries Act (NMSA). There are two national marine sanctuaries in the HSTT Study Area, the Hawaiian Islands Humpback Whale National Marine Sanctuary and the Channel Islands National Marine Sanctuary. NMFS has fulfilled its responsibilities and completed all requirements under the NMSA.

National Environmental Policy Act

To comply with the National Environmental Policy Act of 1969 (NEPA; 42 U.S.C. 4321 et seq.) and NOAA Administrative Order (NAO) 216-6A, NMFS must evaluate our proposed actions and alternatives with respect to potential impacts on the human environment. NMFS participated as a cooperating agency on the 2018 HSTT FEIS/OEIS (published on October 26, 2018, http://www.hstteis.com) which evaluated impacts from Navy training and testing activities in the HSTT Study Area for the reasonably foreseeable future (including through 2025). In accordance with 40 CFR 1506.3, NMFS independently reviewed and evaluated the 2018 HSTT FEIS/OEIS and determined that it was adequate and sufficient to meet our responsibilities under NEPA for the issuance of the 2018 HSTT final rule and associated LOAs. NMFS therefore adopted the 2018 HSTT FEIS/OEIS.

In accordance with 40 CFR 1502.9 and the information and analysis contained in this final rule, NMFS has determined that this final rule and any subsequent LOAs will not result in impacts that were not fully considered in the 2018 HSTT FEIS/OEIS. As indicated in this final rule, the Navy has made no substantial changes to the activities that are relevant to environmental concerns nor are there substantial new circumstances or information about the significance of adverse effects that bear on the analysis. Therefore, NMFS has determined that the 2018 HSTT FEIS/OEIS remains valid, and there is no need to supplement the document for this rulemaking. NOAA therefore, has adopted the 2018 HSTT FEIS/OEIS. NMFS has prepared a separate Record of Decision. NMFS' Record of Decision for adoption of the 2018 HSTT FEIS/OEIS and issuance of this final rule and subsequent LOAs can be found at https://www.fisheries.noaa.gov/​national/​marine-mammal-protection/​incidental-take-authorizations-military-readiness-activities.

Regulatory Flexibility Act

The Office of Management and Budget has determined that this rule is not significant for purposes of Executive Order 12866.

Pursuant to the Regulatory Flexibility Act (RFA), the Chief Counsel for Regulation of the Department of Commerce has certified to the Chief Counsel for Advocacy of the Small Business Administration during the proposed rule stage that this action would not have a significant economic impact on a substantial number of small entities. The factual basis for the certification was published in the proposed rule and is not repeated here. No comments were received regarding this certification. As a result, a regulatory flexibility analysis was not required and none was prepared.

Waiver of Delay in Effective Date Under the Administrative Procedure Act

NMFS has determined that there is good cause under the Administrative Procedure Act (5 U.S.C. 553(d)) to waive the 30-day delay of the effective date for this rule. This rule relieves the Navy from the restrictions of the take prohibitions under the MMPA by granting the Navy's request for incidental take authorization under MMPA section 101(a)(5)(A). In addition, there is good cause to waive the 30-day effective date period because a delay would be contrary to the public interest and unnecessary. A delay in effectiveness is contrary to public interest because this rule allows the Navy to continue training and testing activities that are necessary for national security in compliance with the MMPA. Further, a delay is unnecessary because this rule is not generally applicable to the public. The Navy is the only entity affected by the regulations, the Navy specifically requested the modification to the regulations, and the Navy has fully agreed to the requirements included herein. The Navy is anticipating finalization of the rule and, as such, is ready to comply immediately upon publication. As such, there is good cause to waive the 30-day delay in effective date.

List of Subjects in 50 CFR Part 218

• Administrative practice and procedure
• Endangered and threatened species
• Fish
• Fisheries
• Marine mammals
• Penalties
• Reporting and recordkeeping requirements
• Transportation
• Wildlife

( print page 5016)

Dated: December 23, 2024.

Samuel D. Rauch III,

Deputy Assistant Administrator for Regulatory Programs, National Marine Fisheries Service.

For reasons set forth in the preamble, 50 CFR part 218 is amended as follows:

PART 218—REGULATIONS GOVERNING THE TAKING AND IMPORTING OF MARINE MAMMALS

1. The authority citation for part 218 continues to read as follows:

Authority: 16 U.S.C. 1361 et seq.

2. Revise subpart H to read as follows:

Subpart H—Taking and Importing Marine Mammals; U.S. Navy's Hawaii-Southern California Training and Testing (HSTT)

218.70

Specified activity and geographical region.

218.71

Effective dates.

218.72

Permissible methods of taking.

218.73

Prohibitions.

218.74

Mitigation requirements.

218.75

Requirements for monitoring and reporting.

218.76

Letters of Authorization (LOA).

218.77

Renewals and modifications of Letters of Authorization.

218.78-218.79

[Reserved]

Subpart H—Taking and Importing Marine Mammals; U.S. Navy's Hawaii-Southern California Training and Testing (HSTT)

§ 218.70

Specified activity and geographical region.

(a) Regulations in this subpart apply only to the U.S. Navy (Navy) for the taking of marine mammals that occurs in the area described in paragraph (b) of this section and that occurs incidental to the activities listed in paragraph (c) of this section.

(b) The taking of marine mammals by the Navy under this subpart may be authorized in Letters of Authorization (LOAs) only if it occurs within the Hawaii-Southern California Training and Testing (HSTT) Study Area, which includes established operating and warning areas across the north-central Pacific Ocean, from the mean high tide line in Southern California west to Hawaii and the International Date Line. The HSTT Study Area includes the at-sea areas of three existing range complexes, the Hawaii Range Complex (HRC), the Southern California Range Complex (SOCAL), and the Silver Strand Training Complex, and overlaps a portion of the Point Mugu Sea Range (PMSR). Also included in the HSTT Study Area are Navy pierside locations in Hawaii and Southern California, Pearl Harbor, San Diego Bay, and the transit corridor on the high seas where sonar training and testing may occur.

(c) The taking of marine mammals by the Navy is only authorized if it occurs incidental to the Navy conducting training and testing activities:

(1) Training. (i) Amphibious warfare;

(ii) Anti-submarine warfare;

(iii) Electronic warfare;

(iv) Expeditionary warfare;

(v) Mine warfare;

(vi) Surface warfare; and

(vii) Pile driving.

(2) Testing. (i) Naval Air Systems Command Testing Activities;

(ii) Naval Sea System Command Testing Activities;

(iii) Office of Naval Research Testing Activities; and

(iv) Naval Information Warfare Systems Command.

§ 218.71

Effective dates.

This subpart is effective from January 16, 2025, through December 20, 2025.

§ 218.72

Permissible methods of taking.

(a) Under LOAs issued pursuant to §§ 216.106 of this chapter and 218.76, the Holder of the LOAs (hereinafter “Navy”) may incidentally, but not intentionally, take marine mammals within the area described in § 218.70(b) by Level A harassment and Level B harassment associated with the use of active sonar and other acoustic sources and explosives as well as serious injury or mortality associated with vessel strikes and explosives, provided the activity is in compliance with all terms, conditions, and requirements of these regulations in this subpart and the applicable LOAs.

(b) The incidental take of marine mammals by the activities listed in § 218.70(c) is limited to the following species:

Table 1 to Paragraph ( b )

Species	Stock
Blue whale	Central North Pacific
Blue whale	Eastern North Pacific
Bryde's whale	Eastern Tropical Pacific
Bryde's whale	Hawaii
Fin whale	CA/OR/WA
Fin whale	Hawaii
Humpback whale	Central America/Southern Mexico-CA/OR/WA
Humpback whale	Mainland Mexico-CA/OR/WA
Humpback whale	Hawaii
Minke whale	CA/OR/WA
Minke whale	Hawaii
Sei whale	Eastern North Pacific
Sei whale	Hawaii
Gray whale	Eastern North Pacific
Gray whale	Western North Pacific
Sperm whale	CA/OR/WA
Sperm whale	Hawaii
Dwarf sperm whale	Hawaii
Pygmy sperm whale	Hawaii
Kogia whales	CA/OR/WA
Baird's beaked whale	CA/OR/WA
Blainville's beaked whale	Hawaii
Goose-beaked whale	CA/OR/WA
Goose-beaked whale	Hawaii
Longman's beaked whale	Hawaii
Mesoplodon spp.	CA/OR/WA
( print page 5017)
Bottlenose dolphin	California Coastal
Bottlenose dolphin	CA/OR/WA Offshore
Bottlenose dolphin	Hawaii Pelagic
Bottlenose dolphin	Kauai & Niihau
Bottlenose dolphin	Oahu
Bottlenose dolphin	4-Island
Bottlenose dolphin	Hawaii
False killer whale	Hawaii Pelagic
False killer whale	Main Hawaiian Islands Insular
False killer whale	Northwestern Hawaiian Islands
Fraser's dolphin	Hawaii
Killer whale	Eastern North Pacific (ENP) Offshore
Killer whale	ENP Transient/West Coast Transient
Killer whale	Hawaii
Long-beaked common dolphin	California
Melon-headed whale	Hawaiian Islands
Melon-headed whale	Kohala Resident
Northern right whale dolphin	CA/OR/WA
Pacific white-sided dolphin	CA/OR/WA
Pantropical spotted dolphin	Hawaii Island
Pantropical spotted dolphin	Hawaii Pelagic
Pantropical spotted dolphin	Oahu
Pantropical spotted dolphin	4-Island
Pygmy killer whale	Hawaii
Pygmy killer whale	Tropical
Risso's dolphin	CA/OR/WA
Risso's dolphin	Hawaii
Rough-toothed dolphin	Hawaii
Short-beaked common dolphin	CA/OR/WA
Short-finned pilot whale	CA/OR/WA
Short-finned pilot whale	Hawaii
Spinner dolphin	Hawaii Island
Spinner dolphin	Hawaii Pelagic
Spinner dolphin	Kauai & Niihau
Spinner dolphin	Oahu & 4-Island
Striped dolphin	CA/OR/WA
Striped dolphin	Hawaii
Dall's porpoise	CA/OR/WA
California sea lion	U.S.
Guadalupe fur seal	Mexico
Northern fur seal	California
Harbor seal	California
Hawaiian monk seal	Hawaii
Northern elephant seal	California
Note to Table 1: CA/OR/WA = California/Oregon/Washington.