2024-02383. Takes of Marine Mammals Incidental To Specified Activities; Taking Marine Mammals Incidental to U.S. Navy 2024 Ice Exercise Activities in the Arctic Ocean

AGENCY:

National Marine Fisheries Service (NMFS), National Oceanic and Atmospheric Administration (NOAA), Commerce.

ACTION:

Notice; issuance of an incidental harassment authorization.

SUMMARY:

In accordance with the regulations implementing the Marine Mammal Protection Act (MMPA) as amended, notification is hereby given that NMFS has issued an incidental harassment authorization (IHA) to the U.S. Navy (Navy) to incidentally harass marine mammals during submarine training and testing activities associated with a 2024 Ice Exercise (ICEX24) Activities in the Arctic Ocean.

DATES:

This authorization is effective from February 1, 2024 through April 30, 2024.

ADDRESSES:

Electronic copies of the application and supporting documents, as well as a list of the references cited in this document, may be obtained online at: https://www.fisheries.noaa.gov/​national/​marine-mammal-protection/​incidental-take-authorizations-military-readiness-activities. In case of problems accessing these documents, please call the contact listed below.

FOR FURTHER INFORMATION CONTACT:

Leah Davis, Office of Protected Resources, NMFS, (301) 427–8401.

SUPPLEMENTARY INFORMATION:

Background

The MMPA prohibits the “take” of marine mammals, with certain exceptions. Sections 101(a)(5)(A) and (D) of the MMPA (16 U.S.C. 1361 et seq.) direct the Secretary of Commerce (as delegated to NMFS) to allow, upon request, the incidental, but not intentional, taking of small numbers of marine mammals by U.S. citizens who engage in a specified activity (other than commercial fishing) within a specified geographical region if certain findings are made and either regulations are proposed or, if the taking is limited to harassment, a notice of a proposed IHA is provided to the public for review.

Authorization for incidental takings shall be granted if NMFS finds that the taking will have a negligible impact on the species or stock(s) and will not have an unmitigable adverse impact on the availability of the species or stock(s) for taking for subsistence uses (where relevant). Further, NMFS must prescribe the permissible methods of taking and other “means of effecting the least practicable adverse impact” on the affected species or stocks and their habitat, paying particular attention to rookeries, mating grounds, and areas of similar significance, and on the availability of the species or stocks for taking for certain subsistence uses (referred to in shorthand as “mitigation”); and requirements pertaining to the mitigation, monitoring and reporting of the takings are set forth. The definitions of all applicable MMPA statutory terms cited above are included in the relevant sections below.

The 2004 National Defense Authorization Act (NDAA; Pub. L. 108–136) removed the “small numbers” and “specified geographical region” limitations indicated above and amended the definition of “harassment” as applied to a “military readiness activity.” The activity for which incidental take of marine mammals is being requested qualifies as a military readiness activity.

Summary of Request

On May 24, 2023, NMFS received a request from the Navy for an IHA to take marine mammals incidental to submarine training and testing activities including establishment of a tracking range on an ice floe in the Arctic Ocean, north of Prudhoe Bay, Alaska. Following NMFS' review of the application, the Navy submitted a revised application on October 13, 2023 that removed the request for take of bearded seal and included an updated take estimate for ringed seals. The application was deemed adequate and complete on October 19, 2023. The Navy's request is for take of ringed seal by Level B harassment. Neither the Navy nor NMFS expect serious injury or mortality to result from this activity and, therefore, an IHA is appropriate.

NMFS previously issued IHAs to the Navy for similar activities (83 FR 6522, February 14, 2018; 85 FR 6518, February 5, 2020; 87 FR 7803, February 10, 2022). The Navy complied with all the requirements ( e.g., mitigation, monitoring, and reporting) of the previous IHAs, and information regarding their monitoring results may be found in the Estimated Take of Marine Mammals section.

Description of the Specified Activity

The Navy proposes to conduct submarine training and testing activities, which includes the establishment of a tracking range and temporary ice camp, and research in the Arctic Ocean for six weeks beginning in February 2024. Submarine active acoustic transmissions may result in occurrence of Level B harassment, including direct behavioral disturbance or temporary hearing impairment (temporary threshold shift (TTS)), of ringed seals. A detailed description of the planned ICEX24 activities is provided in the Federal Register notice for the proposed IHA (88 FR 85244, December 7, 2023). Since that time, no changes have been made to the planned activities. Therefore, a detailed description is not provided here. Please refer to that Federal Register notice for the description of the specific activity.

Comments and Responses

A notice of NMFS' proposal to issue an IHA to the Navy was published in the Federal Register on December 7, 2023 (88 FR 85244). That notice described, in detail, the Navy's activity, the marine mammal species that may be affected by the activity, and the anticipated effects on marine mammals. In that notice, we requested public input on the request for authorization described therein, our analyses, the proposed authorization, and any other aspect of the notice of proposed IHA, and requested that interested persons submit relevant information, suggestions, and comments. During the 30-day public comment period, NMFS did not receive any public comments.

Changes From the Proposed IHA to Final IHA

Since publication of the proposed IHA, NMFS made two updates to the required mitigation measures. The proposed IHA required that fixed wing aircraft must operate at the highest altitudes practicable taking into account safety of personnel, meteorological conditions, and need to support safe operations of a drifting ice camp. Aircraft must not reduce altitude if a seal is observed on the ice. In general, cruising elevation must be 305 meters (m; 1,000 feet (ft)) or higher. This final IHA requires that cruising elevation must be 457 m (1,500 ft) or higher. This change aligns with NMFS' biological opinion and the U.S. Fish and Wildlife Service's requirements for polar bears. Further, NMFS updated its requirement for personnel on foot and operating on-ice vehicles to avoid areas of deep snowdrifts and pressure ridges to clarify that a deep snow drift is one that is >0.5 m, and these areas must be avoided by 0.8 kilometers (km), consistent with NMFS' biological opinion.

NMFS also added a requirement that when traveling away from camp, each snow machine must have a dedicated observer (not the vehicle operator) or each expeditionary team must have at least one observer. Observers must be capable of observing and recording marine mammal presence and behaviors, and accurately and completely record data. When traveling, observers will have no other primary duty than to watch for and report observations related to marine mammals and human/seal interactions. Dedicated observers can also serve as the communicator between the field party and camp. These changes and additions align with NMFS' biological opinion.

Last, NMFS added several reporting measures to this final IHA to align with NMFS' biological opinion. The Navy must report the following: the minimum distance between human activities and seals or seal lairs; the duration of time during which seals or seal lairs were known to be present within 150 m of human activities, and the behaviors exhibited by the seals during those observation periods; and an account of the status of all seal lairs located within 150 m of camps or ice trails through time.

Description of Marine Mammals in the Area of Specified Activities

Sections 3 and 4 of the application summarize available information regarding status and trends, distribution and habitat preferences, and behavior and life history of the potentially affected species. NMFS fully considered all of this information, and we refer the reader to these descriptions, instead of reprinting the information. Additional information regarding population trends and threats may be found in NMFS' Stock Assessment Reports (SARs; https://www.fisheries.noaa.gov/​national/​marine-mammal-protection/​marine-mammal-stock-assessments) and more general information about these species ( e.g., physical and behavioral descriptions) may be found on NMFS' website ( https://www.fisheries.noaa.gov/​find-species).

Table 1 lists all species or stocks for which take is expected and authorized for this activity, and summarizes information related to the population or stock, including regulatory status under the MMPA and Endangered Species Act (ESA) and potential biological removal (PBR), where known. PBR is defined by the MMPA as the maximum number of animals, not including natural mortalities, that may be removed from a marine mammal stock while allowing that stock to reach or maintain its optimum sustainable population (as described in NMFS' SARs). While no serious injury or mortality is anticipated or authorized here, PBR and annual serious injury and mortality from anthropogenic sources are included here as gross indicators of the status of the species or stocks and other threats. That said, in this case for the Arctic stock of ringed seals and as explained in footnote 5 of table 1, the lack of complete population information significantly impacts the usefulness of PBR in considering the status of the stock, as explained below.

Marine mammal abundance estimates presented in this document represent the total number of individuals that make up a given stock or the total number estimated within a particular study or survey area. NMFS' stock abundance estimates for most species represent the total estimate of individuals within the geographic area, if known, that comprises that stock. For some species, this geographic area may extend beyond U.S. waters. All managed stocks in this region are assessed in NMFS' U.S. Alaska SARs (Young et al. 2023). All values presented in table 2 are the most recent available at the time of publication and are available online at: https://www.fisheries.noaa.gov/​national/​marine-mammal-protection/​marine-mammal-stock-assessments. However, for the same reason noted above and as described in footnote 5 of table 1, the lack of complete population information for the Arctic stock of ringed seals impacts the usefulness of these numbers in considering the impacts of the anticipated take on the stock.

Table 1—Species Likely Impacted by the Specified Activities ¹

Common name	Scientific name	Stock	ESA/ MMPA status; strategic (Y/N) 2	Stock abundance (CV, N min , most recent abundance survey) 3	PBR	Annual M/SI 4
Ringed Seal	Pusa hispida	Arctic	T, D, Y	UND 5 (UND, UND, 2013)	UND	6  6,459
1  Information on the classification of marine mammal species can be found on the web page for The Society for Marine Mammalogy's Committee on Taxonomy ( https://marinemammalscience.org/​science-and-publications/​list-marine-mammal-species-subspecies/​; Committee on Taxonomy (2022)).
2  ESA status: Endangered (E), Threatened (T)/MMPA status: Depleted (D). Under the MMPA, a strategic stock is one for which the level of direct human-caused mortality exceeds PBR or which is determined to be declining and likely to be listed under the ESA within the foreseeable future. Any species or stock listed under the ESA is automatically designated under the MMPA as depleted and as a strategic stock.
3  NMFS marine mammal SARs online at: https://www.fisheries.noaa.gov/​national/​marine-mammal-protection/​marine-mammal-stock-assessment-reports-region. CV is coefficient of variation; N min is the minimum estimate of stock abundance.
4  These values, found in NMFS's SARs, represent annual levels of human-caused mortality plus serious injury from all sources combined ( e.g., commercial fisheries, ship strike). Annual M/SI often cannot be determined precisely and is in some cases presented as a minimum value or range. A CV associated with estimated mortality due to commercial fisheries is presented in some cases.
5  A reliable population estimate for the entire stock is not available. Using a sub-sample of data collected from the U.S portion of the Bering Sea, an abundance estimate of 171,418 ringed seals has been calculated, but this estimate does not account for availability bias due to seals in the water or in the shorefast ice zone at the time of the survey. The actual number of ringed seals in the U.S. portion of the Bering Sea is likely much higher. Using the N min based upon this negatively biased population estimate, the PBR is calculated to be 4,755 seals, although this is also a negatively biased estimate.
6  The majority of the M/SI for this stock (6,454 of 6,459 animals) is a result of the Alaska Native subsistence harvest. While M/SI appears to exceed PBR, given that the reported PBR is based on a partial stock abundance estimate, and is therefore an underestimate for the full stock, M/SI likely does not exceed PBR.

As indicated in table 1, ringed seals (with one managed stock) temporally and spatially co-occur with the activity to the degree that take is reasonably likely to occur. While beluga whales ( Delphinapterus leucas), gray whales ( Eschrichtius robustus), bowhead whales ( Balaena mysticetus), and spotted seals ( Phoca largha) may occur in the ICEX24 Study Area, the temporal and/or spatial occurrence of these species is such that take is not expected to occur, and they are not discussed further beyond the explanation provided here. Bowhead whales are unlikely to occur in the ICEX24 Study Area between February and April, as they spend winter (December to April) in the northern Bering Sea and southern Chukchi Sea, and migrate north through the Chukchi Sea and Beaufort Sea during April and May (Young et al. 2023). On their spring migration, the earliest that bowhead whales reach Point Hope in the Chukchi Sea, well south of Point Barrow, is late March to mid-April (Braham et al. 1980). Although the ice camp location is not known with certainty, the distance between Point Barrow and the closest edge of the Ice Camp Study Area is over 200 km (124.3 miles (mi)). The distance between Point Barrow and the closest edge of the Navy Activity Study Area is over 50 km (31 mi), and the distance between Point Barrow and Point Hope is an additional 525 km (326.2 mi; straight line distance); accordingly, bowhead whales are unlikely to occur in the ICEX24 Study Area before ICEX24 activities conclude. Beluga whales follow a migration pattern similar to bowhead whales. They typically overwinter in the Bering Sea and migrate north during the spring to the eastern Beaufort Sea where they spend the summer and early fall months (Young et al. 2023). Though the beluga whale migratory path crosses through the ICEX24 Study Area, they are unlikely to occur in the ICEX24 Study Area between February and April. (Of note, the ICEX24 Study Area does overlap the northernmost portion of the North Bering Strait, East Chukchi, West Beaufort Sea beluga whale migratory Biologically Important Area (BIA; April and May), though the data support for this BIA is low, the boundary certainty is low, and the importance score is moderate. Given the spring migratory direction, the northernmost portion of the BIA is likely more important later in the April and May period, and overlap with this BIA does not imply that belugas are likely to be in the ICEX24 Study Area during the Navy's activities.) Gray whales feed primarily in the Beaufort Sea, Chukchi Sea, and Northwestern Bering Sea during the summer and fall, but migrate south to winter in Baja California lagoons (Young et al. 2023). Typically, northward migrating gray whales do not reach the Bering Sea before May or June (Frost and Karpovich 2008), after the ICEX24 activities would occur, and several hundred kilometers south of the ICEX24 Study Area. Further, gray whales are primarily bottom feeders (Swartz et al. 2006) in water less than 60 m (196.9 ft) deep (Pike 1962). Therefore, on the rare occasion that a gray whale does overwinter in the Beaufort Sea (Stafford et al. 2007), we would expect an overwintering individual to remain in shallow water over the continental shelf where it could feed. Therefore, gray whales are not expected to occur in the ICEX24 Study Area during the ICEX24 activity period. Spotted seals may also occur in the ICEX24 Study Area during summer and fall, but they are not expected to occur in the ICEX24 Study Area during the ICEX24 timeframe (Muto et al. 2020).

Further, while the Navy initially requested take of bearded seals ( Erignathus barbatus), which do occur in the ICEX24 Study Area during the project timeframe, NMFS does not expect that bearded seals would occur in the areas near the ice camp or where submarine activities involving active acoustics would occur, and therefore incidental take is not anticipated to occur and has not been proposed for authorization. Bearded seals are not discussed further beyond the explanation provided here. The Navy anticipates that the ice camp would be established 100–200 nautical miles (nmi; 185–370 km) north of Prudhoe Bay in water depths of 800 m (2,625 ft) or more, and also that submarine training and testing activities would occur in water depths of 800 m (2,625 ft) or more. Although acoustic data indicate that some bearded seals remain in the Beaufort Sea year round (MacIntyre et al. 2013, 2015; Jones et al. 2014), satellite tagging data (Boveng and Cameron 2013; ADF&G 2017) show that large numbers of bearded seals move south in fall/winter with the advancing ice edge to spend the winter in the Bering Sea, confirming previous visual observations (Burns and Frost 1979; Frost et al. 2008; Cameron and Boveng 2009). The southward movement of bearded seals in the fall means that very few individuals are expected to occur along the Beaufort Sea continental shelf in February through April, the timeframe for ICEX24 activities. The northward spring migration through the Bering Strait, begins in mid-April (Burns and Frost 1979).

In the event some bearded seals were to remain in the Beaufort Sea during the season when ICEX24 activities will occur, the most probable area in which bearded seals might occur during winter months is along the continental shelf. Bearded seals feed extensively on benthic invertebrates ( e.g., clams, gastropods, crabs, shrimp, bottom-dwelling fish; Quakenbush et al. 2011; Cameron et al. 2010) and are typically found in water depths of 200 m (656 ft) or less (Burns 1970). The Bureau of Ocean Energy Management (BOEM) conducted an aerial survey from June through October that covered the shallow Beaufort and Chukchi Sea shelf waters and observed bearded seals from Point Barrow to the border of Canada (Clarke et al. 2015). The farthest from shore that bearded seals were observed was the waters of the continental slope (though this study was conducted outside of the ICEX24 time frame). The Navy anticipates that the ice camp will be established 185–370 km (100–200 nmi) north of Prudhoe Bay in water depths of 800 m (2,625 ft) or more. The continental shelf near Prudhoe Bay is approximately 55 nmi (100 km) wide. Therefore, even if the ice camp were established at the closest estimated distance (100 nmi from Prudhoe Bay), it would still be approximately 45 nmi (83 km) distant from habitat potentially occupied by bearded seals. Empirical evidence has not shown responses to sonar that would constitute take beyond a few km from an acoustic source, and therefore, NMFS and the Navy conservatively set a distance cutoff of 10 km (6.2 mi). Regardless of the source level at that distance, take is not estimated to occur beyond 10 km (6.2 mi) from the source. Although bearded seals occur 20 to 100 nmi (37 to 185 km) offshore during spring (Simpkins et al. 2003, Bengtson et al. 2005), they feed heavily on benthic organisms (Hamilton et al. 2018; Hjelset et al. 1999; Fedoseev 1965), and during winter bearded seals are expected to select habitats where food is abundant and easily accessible to minimize the energy required to forage and maximize energy reserves in preparation for whelping, lactation, mating, and molting. Bearded seals are not known to dive as deep as 800 m (2,625 ft) to forage (Boveng and Cameron, 2013; Cameron and Boveng 2009; Cameron et al. 2010; Gjertz et al. 2000; Kovacs 2002), and it is highly unlikely that they would occur near the ice camp or where the submarine activities would be conducted. This conclusion is supported by the fact that the Navy did not visually observe or acoustically detect bearded seals during the 2020 or 2022 ice exercises.

In addition, the polar bear ( Ursus maritimus) may be found in the ICEX24 Study Area. However, polar bears are managed by the U.S. Fish and Wildlife Service and are not considered further in this document.

A detailed description of the of the Arctic stock of ringed seals, including brief introductions to the species and stock as well as available information regarding population trends and threats, and information regarding local occurrence, were provided in the Federal Register notice for the proposed IHA (88 FR 85244, December 7, 2023); since that time, we are not aware of any changes in the status of these species and stocks; therefore, detailed descriptions are not provided here. Please refer to that Federal Register notice for these descriptions. Please also refer to NMFS' website ( https://www.fisheries.noaa.gov/​find-species) for generalized species accounts.

Marine Mammal Hearing

Hearing is the most important sensory modality for marine mammals underwater, and exposure to anthropogenic sound can have deleterious effects. To appropriately assess the potential effects of exposure to sound, it is necessary to understand the frequency ranges marine mammals are able to hear. Not all marine mammal species have equal hearing capabilities ( e.g., Richardson et al. 1995; Wartzok and Ketten, 1999; Au and Hastings, 2008). To reflect this, Southall et al. (2007, 2019) recommended that marine mammals be divided into hearing groups based on directly measured (behavioral or auditory evoked potential techniques) or estimated hearing ranges (behavioral response data, anatomical modeling, etc.). Note that no direct measurements of hearing ability have been successfully completed for mysticetes ( i.e., low-frequency cetaceans). Subsequently, NMFS (2018) described generalized hearing ranges for these marine mammal hearing groups. Generalized hearing ranges were chosen based on the approximately 65 decibels (dB) threshold from the normalized composite audiograms, with the exception for lower limits for low-frequency cetaceans where the lower bound was deemed to be biologically implausible and the lower bound from Southall et al. (2007) retained. Marine mammal hearing groups and their associated hearing ranges are provided in table 2.

Table 2—Marine Mammal Hearing Groups

[NMFS, 2018]

Hearing group	Generalized hearing range *
Low-frequency (LF) cetaceans (baleen whales)	7 Hz to 35 kHz.
Mid-frequency (MF) cetaceans (dolphins, toothed whales, beaked whales, bottlenose whales)	150 Hz to 160 kHz.
High-frequency (HF) cetaceans (true porpoises, Kogia, river dolphins, Cephalorhynchid, Lagenorhynchus cruciger & L. australis)	275 Hz to 160 kHz.
Phocid pinnipeds (PW) (underwater) (true seals)	50 Hz to 86 kHz.
Otariid pinnipeds (OW) (underwater) (sea lions and fur seals)	60 Hz to 39 kHz.
* Represents the generalized hearing range for the entire group as a composite ( i.e., all species within the group), where individual species' hearing ranges are typically not as broad. Generalized hearing range chosen based on ~65 dB threshold from normalized composite audiogram, with the exception for lower limits for LF cetaceans (Southall et al. 2007) and PW pinniped (approximation).

The pinniped functional hearing group was modified from Southall et al. (2007) on the basis of data indicating that phocid species have consistently demonstrated an extended frequency range of hearing compared to otariids, especially in the higher frequency range (Hemilä et al. 2006; Kastelein et al. 2009; Reichmuth and Holt, 2013).

For more detail concerning these groups and associated frequency ranges, please see NMFS (2018) for a review of available information.

Potential Effects of Specified Activities on Marine Mammals and Their Habitat

The underwater noise from the Navy's submarine training and testing activities has the potential to result in behavioral harassment of marine mammals in the vicinity of the ICEX24 Study Area. The notice of proposed IHA (88 FR 85244, December 7, 2023) included a discussion of the effects of anthropogenic noise on marine mammals and the potential effects of underwater noise from Navy's activities on marine mammals and their habitat. That information and analysis is referenced in this final IHA determination and is not repeated here; please refer to the notice of proposed IHA (88 FR 85244, December 7, 2023).

Estimated Take of Marine Mammals

This section provides an estimate of the number of incidental takes authorized through this IHA, which will inform NMFS' consideration of the negligible impact determinations and impacts on subsistence uses.

Harassment is the only type of take expected to result from these activities. For this military readiness activity, 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 the behavioral patterns are abandoned or significantly altered (Level B harassment).

Authorized takes for individual marine mammals resulting from exposure to acoustic transmissions are by Level B harassment only, in the form of direct behavioral disturbance including TTS, which can be associated with disruptions in behavioral patterns resulting from an animal missing some acoustic cues during the time that their hearing sensitivity is reduced. Based on the nature of the activity, Level A harassment is neither anticipated nor authorized. As described previously, no serious injury or mortality is anticipated nor authorized for this activity. Below we describe how the take numbers are estimated.

For acoustic impacts, generally speaking, we estimate take by considering: (1) acoustic thresholds above which NMFS believes the best available science indicates marine mammals will be behaviorally harassed or incur some degree of permanent hearing impairment; (2) the area or volume of water that will be ensonified above these levels in a day; (3) the density or occurrence of marine mammals within these ensonified areas; and (4) the number of days of activities. We note that while these factors can contribute to a basic calculation to provide an initial prediction of potential takes, additional information that can qualitatively inform take estimates is also sometimes available ( e.g., previous monitoring results or average group size). Below, we describe the factors considered here in more detail and present the take estimates.

Acoustic Thresholds

NMFS recommends the use of acoustic thresholds that identify the received level of underwater sound above which exposed marine mammals would be reasonably expected to be behaviorally harassed (equated to Level B harassment) or to incur permanent threshold shift (PTS) of some degree (equated to Level A harassment).

Level B Harassment —In coordination with NMFS, the Navy developed behavioral thresholds to support environmental analyses for the Navy's testing and training military readiness activities utilizing active sonar sources; these behavioral harassment thresholds are used here to evaluate the potential effects of the active sonar components of the proposed specified activities. Though significantly driven by received level, the onset of behavioral disturbance from anthropogenic noise exposure is also informed to varying degrees by other factors related to the source or exposure context ( e.g., frequency, predictability, duty cycle, duration of the exposure, signal-to-noise ratio, distance to the source), the environment ( e.g., bathymetry, other noises in the area, predators in the area), and the receiving animals (hearing, motivation, experience, demography, life stage, depth) and can be difficult to predict ( e.g., Southall et al. 2007, 2021; Ellison et al. 2012).

The Navy's Phase III proposed pinniped behavioral threshold was updated based on controlled exposure experiments on the following captive animals: Hooded seal, gray seal, and California sea lion (Götz et al. 2010; Houser et al. 2013a; Kvadsheim et al. 2010). Overall exposure levels were 110–170 dB referenced to 1 micropascal (re 1 μPa) for hooded seals, 140–180 dB re 1 μPa for gray seals, and 125–185 dB re 1 μPa for California sea lions; responses occurred at received levels ranging from 125–185 dB re 1 μPa. However, the means of the response data were between 159 and 170 dB re 1 μPa. Hooded seals were exposed to increasing levels of sonar until an avoidance response was observed, while the grey seals were exposed first to a single received level multiple times, then an increasing received level. Each individual California sea lion was exposed to the same received level 10 times. These exposure sessions were combined into a single response value, with an overall response assumed if an animal responded in any single session. Because these data represent a dose-response type relationship between received level and a response, and because the means were all tightly clustered, the Bayesian biphasic Behavioral Response Function for pinnipeds most closely resembles a traditional sigmoidal dose-response function at the upper received levels and has a 50 percent probability of response at 166 dB re 1 μPa. Additionally, to account for proximity to the source discussed above and based on the best scientific information, a conservative distance of 10 km is used beyond which exposures would not constitute a take under the military readiness definition of Level B harassment.

Level A harassment —NMFS' Technical Guidance for Assessing the Effects of Anthropogenic Sound on Marine Mammal Hearing (Version 2.0) (Technical Guidance, 2018) identifies dual criteria to assess auditory injury (Level A harassment) to five different marine mammal groups (based on hearing sensitivity) as a result of exposure to noise from two different types of sources (impulsive or non-impulsive). The Navy's activities include the use of non-impulsive (active sonar) sources.

These thresholds are provided in the table below. The references, analysis, and methodology used in the development of the thresholds are described in NMFS' 2018 Technical Guidance, which may be accessed at: https://www.fisheries.noaa.gov/​national/​marine-mammal-protection/​marine-mammal-acoustic-technical-guidance.

For previous ICEXs, the Navy's PTS/TTS analysis began with mathematical modeling to predict the sound transmission patterns from Navy sources, including sonar. These data were then coupled with marine species distribution and abundance data to determine the sound levels likely to be received by various marine species. These criteria and thresholds were applied to estimate specific effects that animals exposed to Navy-generated sound may experience. For weighting function derivation, the most critical data required were TTS onset exposure levels as a function of exposure frequency. These values can be estimated from published literature by examining TTS as a function of sound exposure level (SEL) for various frequencies.

Table 3 below provides the weighted criteria and thresholds used in previous ICEX analyses for estimating quantitative acoustic exposures of marine mammals from the specified activities.

Table 3—Acoustic Thresholds Identifying the Onset of Behavioral Disturbance, TTS, and PTS for Non-Impulsive Sound Sources ¹

Functional hearing group	Species	Behavioral criteria	Physiological criteria
			TTS threshold SEL (weighted)	PTS threshold SEL (weighted)
Phocid Pinnipeds (Underwater)	Ringed seal	Pinniped Dose Response Function 2	181 dB SEL cumulative	201 dB SEL cumulative.
1  The threshold values provided are assumed for when the source is within the animal's best hearing sensitivity. The exact threshold varies based on the overlap of the source and the frequency weighting.
2  See Figure 6–1 in the Navy's IHA application.
Note: SEL thresholds in dB re: 1 μPa2 s.

Marine Mammal Occurrence and Take Calculation and Estimation

In previous ICEX analyses, the Navy has performed a quantitative analysis to estimate the number of ringed seals that could be harassed by the underwater acoustic transmissions during the proposed specified activities using marine mammal density estimates (Kaschner et al. 2006; Kaschner 2004), marine mammal depth occurrence distributions (U.S Department of the Navy, 2017), oceanographic and environmental data, marine mammal hearing data, and criteria and thresholds for levels of potential effects. Given the lack of recent density estimates for the ICEX Study Area and the lack of ringed seal observations and acoustic detections during ICEXs in the recent past (described in further detail below), NMFS expects that the ringed seal density relied upon in previous ICEX analyses was an overestimate to a large degree, and that the resulting take estimates were likely overestimates as well. Please see the notice of the final IHA for ICEX 22 for additional information on that analysis (87 FR 7803, January 10, 2022).

For ICEX24, rather than relying on a density estimate, the Navy estimated take of ringed seals based on an occurrence estimate of ringed seals within the ICEX Study Area. Ringed seal presence in the ICEX Study Area was obtained using sighting data from the Ocean Biodiversity Information System-Spatial Ecological Analysis of Megavertebrate Populations (OBIS–SEAMAP; Halpin et al. 2009). The ICEX Study Area was overlaid on the OBIS–SEAMAP ringed seal sightings map that included sightings for years 2000 to 2007 and 2013. Sighting data were only available for the mid-to-late summer and fall months. Due to the paucity of winter and spring data, the average number of individual ringed seals per year was assumed to be present in the ICEX Study Area during ICEX24; therefore, it is assumed that three ringed seals would be present in the ICEX Study Area.

Table 4 provides range to effects for active acoustic sources proposed for ICEX24 to phocid pinniped-specific criteria. Phocids within these ranges would be predicted to receive the associated effect. Range to effects can be important information for predicting acoustic impacts, but also in determining adequate mitigation ranges to avoid higher level effects, especially physiological effects, to marine mammals.

Table 4—Range to Behavioral Disturbance, TTS, and PTS in the ICEX24 Study Area

Source/exercise	Range to effects (m)
	Behavioral disturbance	TTS	PTS
Submarine Exercise	10,000 a	5,050	130 b
a  Empirical evidence has not shown responses to sonar that would constitute take beyond a few km from an acoustic source, which is why NMFS and the Navy conservatively set a distance cutoff of 10 km. Regardless of the source level at that distance, take is not estimated to occur beyond 10 km from the source.
b  The distance represents the range to effects for all ICEX24 activities.

Though likely conservative given the size of the ICEX Study Area in comparison to the size of the anticipated Level B harassment zone (10,000 m), Navy estimated that three ringed seals may be taken by Level B harassment per day of activity within the ICEX Study Area. Navy anticipates conducting active acoustic transmissions on 42 days, and therefore requested 126 takes by Level B harassment of ringed seals (3 seals per day × 42 days = 126 takes by Level B harassment; table 5). NMFS concurs and proposes to authorize 126 takes by Level B harassment. Modeling for the three previous ICEXs (2018, 2020, and 2022), which employed similar acoustic sources, did not result in any estimated takes by PTS; therefore, particularly in consideration of the fact that total takes were likely overestimated for those ICEX activities given the density information used in the analyses (NMFS anticipates that the density of ringed seals is actually much lower) and the relatively small range to effects for PTS (130 m), the Navy did not request, and NMFS has not authorized, take by Level A harassment of ringed seal.

Table 5—Quantitative Modeling Results of Potential Exposures for ICEX Activities

Species	Level B harassment	Level A harassment	Total
Ringed seal	126	0	126

During monitoring for the 2018 IHA covering similar military readiness activities in the ICEX22 Study Area, the Navy did not visually observe or acoustically detect any marine mammals (U.S. Navy, 2018). During monitoring for the 2020 IHA covering similar military readiness activities in the ICEX22 Study Area, the Navy also did not visually observe any marine mammals (U.S. Navy, 2020). Acoustic monitoring associated with the 2020 IHA did not detect any discernible marine mammal vocalizations (Henderson et al. 2021). The monitoring report states that “there were a few very faint sounds that could have been (ringed seal) barks or yelps.” However, these were likely not from ringed seals, given that ringed seal vocalizations are generally produced in series (Jones et al. 2014). Henderson et al. (2021) expect that these sounds were likely ice-associated or perhaps anthropogenic. While the distance at which ringed seals could be acoustically detected is not definitive, Henderson et al. (2021) states that Expendable Mobile ASW Training Targets (EMATTs) “traveled a distance of 10 nmi (18.5 km) away and were detected the duration of the recordings; although ringed seal vocalization source levels are likely far lower than the sounds emitted by the EMATTs, this gives some idea of the potential detection radius for the cryophone. The periods when the surface anthropogenic activity is occurring in close proximity to the cryophone are dominated by those broadband noises due to the shallow hydrophone placement in ice (only 10 centimeters (cm) down), and any ringed seal vocalizations that were underwater could have been masked.” During monitoring for the 2022 IHA covering similar military readiness activities in the ICEX24 Study Area, the Navy also did not visually observe any marine mammals (U.S. Navy, 2022). With the exception of passive acoustic monitoring (PAM) conducted during activities for mitigation purposes (no detections), PAM did not occur in 2022 because the ice camp ice flow broke up, and therefore, Navy had to relocate camp. Given the lost time, multiple research projects were canceled, including the under-ice PAM that the Naval Postgraduate School was planning to conduct.

Mitigation

In order to issue an IHA under section 101(a)(5)(D) of the MMPA, NMFS must set forth the permissible methods of taking pursuant to the activity, and other means of effecting the least practicable impact on the species or stock and its habitat, paying particular attention to rookeries, mating grounds, and areas of similar significance, and on the availability of the species or stock for taking for certain subsistence uses. NMFS regulations require applicants for incidental take authorizations to include information about the availability and feasibility (economic and technological) of equipment, methods, and manner of conducting the activity or other means of effecting the least practicable adverse impact upon the affected species or stocks, and their habitat (50 CFR 216.104(a)(11)). The 2004 NDAA amended the MMPA as it relates to military readiness activities and the incidental take authorization process such that “least practicable impact” shall include consideration of personnel safety, practicality of implementation, and impact on the effectiveness of the military readiness activity.

In evaluating how mitigation may or may not be appropriate to ensure the least practicable adverse impact on species or stocks and their habitat, as well as subsistence uses where applicable, NMFS considers two primary factors:

(1) The manner in which, and the degree to which, the successful implementation of the measure(s) is expected to reduce impacts to marine mammals, marine mammal species or stocks, and their habitat, as well as subsistence uses. This considers the nature of the potential adverse impact being mitigated (likelihood, scope, range). It further considers the likelihood that the measure will be effective if implemented (probability of accomplishing the mitigating result if implemented as planned), the likelihood of effective implementation (probability implemented as planned); and

(2) The practicability of the measures for applicant implementation, which may consider such things as cost, impact on operations, and, in the case of a military readiness activity, personnel safety, practicality of implementation, and impact on the effectiveness of the military readiness activity.

The IHA requires that appropriate personnel (including civilian personnel) involved in mitigation and training or testing activity reporting under the specified activities must complete Arctic Environmental and Safety Awareness Training. Modules include: Arctic Species Awareness and Mitigations, Environmental Considerations, Hazardous Materials Management, and General Safety.

Further, the following general mitigation measures are required to prevent incidental take of ringed seals on the ice floe associated with the ice camp (further explanation of certain mitigation measures is provided in parentheses following the measure):

• The ice camp and runway must be established on first-year and multi-year ice without pressure ridges. (This will minimize physical impacts to subnivean lairs and impacts to sea ice habitat suitable for lairs);

• Ice camp deployment must begin no later than mid-February 2024, and be gradual, with activity increasing over the first 5 days. Camp deployment must be completed by March 15, 2024. (Given that mitigation measures require that the ice camp and runway be established on first-year or multi-year ice without pressure ridges, as well as the average ringed seal lair density in the area, and the relative footprint of the Navy's planned ice camp (2 km² 0.8 mi² ), it is extremely unlikely that a ringed seal would build a lair in the vicinity of the ice camp. Additionally, based on the best available science, Arctic ringed seal whelping is not expected to occur prior to mid-March, and therefore, construction of the ice camp will be completed prior to whelping in the area of ICEX24. Further, as noted above, ringed seal lairs are not expected to occur in the ice camp study area, and therefore, NMFS does not expect ringed seals to relocate pups due to human disturbance from ice camp activities, including construction);

• Personnel on all on-ice vehicles must observe for marine and terrestrial animals;
• Snowmobiles must follow established routes, when available. On-ice vehicles must not be used to follow any animal, with the exception of actively deterring polar bears in accordance with U.S. Fish and Wildlife Service requirements or guidance if the situation requires;
• Personnel on foot and operating on-ice vehicles must avoid areas of deep (>0.5 m) snowdrifts and pressure ridges by 0.8 km. (These areas are preferred areas for subnivean lair development);
• Personnel must maintain a 100 m (328 ft) avoidance distance from all observed marine mammals; and

• All material ( e.g., tents, unused food, excess fuel) and wastes ( e.g., solid waste, hazardous waste) must be removed from the ice floe upon completion of ICEX24 activities.

The following mitigation measures are required for activities involving acoustic transmissions (further explanation of certain mitigation measures is provided in parentheses following the measure):

• Personnel must begin PAM for vocalizing marine mammals 15 minutes prior to the start of activities involving active acoustic transmissions from submarines. (This PAM would be conducted for the area around the submarine in real time by technicians on board the submarine.);
• Personnel must delay active acoustic transmissions if a marine mammal is detected during pre-activity PAM and must shutdown active acoustic transmissions if a marine mammal is detected during acoustic transmissions; and
• Personnel must not restart acoustic transmissions until 15 minutes have passed with no marine mammal detections.

Ramp up procedures for acoustic transmissions are not required as the Navy determined, and NMFS concurs, that they would result in impacts on military readiness and on the realism of training that would be impracticable.

The following mitigation measures are required for aircraft activities to prevent incidental take of marine mammals due to the presence of aircraft and associated noise.

• Fixed wing aircraft must operate at the highest altitudes practicable taking into account safety of personnel, meteorological conditions, and need to support safe operations of a drifting ice camp. Aircraft must not reduce altitude if a seal is observed on the ice. In general, cruising elevation must be 457 m (1,500 ft) or higher;
• Unmanned Aircraft Systems (UAS) must maintain a minimum altitude of at least 15.2 m (50 ft) above the ice. They must not be used to track or follow marine mammals;
• Helicopter flights must use prescribed transit corridors when traveling to or from Prudhoe Bay and the ice camp. Helicopters must not hover or circle above marine mammals or within 457 m (1,500 ft) of marine mammals;
• Aircraft must maintain a minimum separation distance of 1.6 km (1 mi) from groups of 5 or more seals; and
• Aircraft must not land on ice within 800 m (0.5 mi) of hauled-out seals.

Based on our evaluation of the required measures, as well as other measures considered by NMFS as described above, NMFS has determined that the mitigation measures provide the means of effecting the least practicable impact on the affected species or stocks and their habitat, paying particular attention to rookeries, mating grounds, and areas of similar significance.

Monitoring and Reporting

In order to issue an IHA for an activity, section 101(a)(5)(D) of the MMPA states that 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 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 while conducting the activities. Effective reporting is critical both to compliance as well as ensuring that the most value is obtained from the required monitoring.

Monitoring and reporting requirements prescribed by NMFS should contribute to improved understanding of one or more of the following:

• Occurrence of marine mammal species or stocks in the area in which take is anticipated ( e.g., presence, abundance, distribution, density);

• Nature, scope, or context of likely marine mammal exposure to potential stressors/impacts (individual or cumulative, acute or chronic), through better understanding of: (1) action or environment ( e.g., source characterization, propagation, ambient noise); (2) affected species ( e.g., life history, dive patterns); (3) co-occurrence of marine mammal species with the activity; or (4) biological or behavioral context of exposure ( e.g., age, calving or feeding areas);

• Individual marine mammal responses (behavioral or physiological) to acoustic stressors (acute, chronic, or cumulative), other stressors, or cumulative impacts from multiple stressors;
• How anticipated responses to stressors impact either: (1) long-term fitness and survival of individual marine mammals; or (2) populations, species, or stocks;

• Effects on marine mammal habitat ( e.g., marine mammal prey species, acoustic habitat, or other important physical components of marine mammal habitat); and

• Mitigation and monitoring effectiveness.

The Navy has coordinated with NMFS to develop an overarching program, the Integrated Comprehensive Monitoring Program (ICMP), intended to coordinate marine species monitoring efforts across all regions and to allocate the most appropriate level and type of effort for each range complex based on a set of standardized objectives, and in acknowledgement of regional expertise and resource availability. The ICMP was created in direct response to Navy requirements established in various MMPA regulations and ESA consultations. As a framework document, the ICMP applies by regulation to those activities on ranges and operating areas for which the Navy is seeking or has sought incidental take authorizations.

The ICMP is focused on Navy training and testing ranges where the majority of Navy activities occur regularly, as those areas have the greatest potential for being impacted by the Navy's activities. In comparison, ICEX is a short duration exercise that occurs approximately every other year. Due to the location and expeditionary nature of the ice camp, the number of personnel on site is extremely limited and is constrained by the requirement to be able to evacuate all personnel in a single day with small planes. As such, the Navy asserts that a dedicated ICMP monitoring project is not feasible as it would require additional personnel and equipment, and NMFS concurs. However, the Navy is exploring the potential of implementing an environmental DNA (eDNA) study on ice seals.

Nonetheless, the Navy must conduct the following monitoring and reporting under the IHA. Ice camp personnel must generally monitor for marine mammals in the vicinity of the ice camp and record all observations of marine mammals, regardless of distance from the ice camp, as well as the additional data indicated below. Additionally, Navy personnel must conduct PAM during all active sonar use. Ice camp personnel must also maintain an awareness of the surrounding environment and document any observed marine mammals. When traveling away from camp, each snow machine must have a dedicated observer (not the vehicle operator) or each expeditionary team must have at least one observer. Observers must be capable of observing and recording marine mammal presence and behaviors, and accurately and completely record data. When traveling, observers will have no other primary duty than to watch for and report observations related to marine mammals and human/seal interactions. Dedicated observers can also serve as the communicator between the field party and camp.

In addition, the Navy is required to provide NMFS with a draft exercise monitoring report within 90 days of the conclusion of the specified activity. A final report must be prepared and submitted within 30 calendar days following receipt of any NMFS comments on the draft report. If no comments are received from NMFS within 30 calendar days of receipt of the draft report, the report shall be considered final. The report, at minimum, must include:

• Marine mammal monitoring effort including date, time, duration of observation efforts;
• The minimum distance between human activities and seals or seal lairs;
• Duration of time during which seals or seal lairs were known to be present within 150 m of human activities, and the behaviors exhibited by the seals during those observation periods;
• Account of the status of seal lairs located within 150 m of camps or ice trails through time;

• Ice camp activities occurring during each monitoring period ( e.g., construction, demobilization, safety watch, field parties);

• Number of marine mammals detected;
• Upon observation of a marine mammal, record the following information:

○ Environmental conditions when animal was observed, including relevant weather conditions such as cloud cover, snow, sun glare, and overall visibility, and estimated observable distance;

○ Lookout location and ice camp activity at time of sighting (or location and activity of personnel who made observation, if observed outside of designated monitoring periods);

○ Time and approximate location of sighting;

○ Identification of the animal(s) ( e.g., seal, or unidentified), also noting any identifying features;

○ Distance and location of each observed marine mammal relative to the ice camp location for each sighting;

○ Estimated number of animals (min/max/best estimate); and

○ Description of any marine mammal behavioral observations ( e.g., observed behaviors such as traveling), including an assessment of behavioral responses thought to have resulted from the activity ( e.g., no response or changes in behavioral state such as ceasing feeding, changing direction, flushing).

Also, all sonar usage will be collected via the Navy's Sonar Positional Reporting System database. The Navy is required to provide data regarding sonar use and the number of shutdowns during ICEX24 activities in the Atlantic Fleet Training and Testing (AFTT) Letter of Authorization 2025 annual classified report. The Navy is also required to analyze any declassified underwater recordings collected during ICEX24 for marine mammal vocalizations and report that information to NMFS, including the types and nature of sounds heard ( e.g., clicks, whistles, creaks, burst pulses, continuous, sporadic, strength of signal) and the species or taxonomic group (if determinable). This information will also be submitted to NMFS with the 2025 annual AFTT declassified monitoring report.

Finally, in the event that personnel discover an injured or dead marine mammal, personnel must report the incident to OPR, NMFS and to the Alaska regional stranding network as soon as feasible. The report must include the following information:

• Time, date, and location (latitude/longitude) of the first discovery (and updated location information if known and applicable);
• Species identification (if known) or description of the animal(s) involved;
• Condition of the animal(s) (including carcass condition if the animal is dead);
• Observed behaviors of the animal(s), if alive;
• If available, photographs or video footage of the animal(s); and

• General circumstances under which the animal(s) was discovered ( e.g., during submarine activities, observed on ice floe, or by transiting aircraft).

Negligible Impact Analysis and 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). 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 harassment, NMFS considers other factors, such as the likely nature of any impacts or responses ( e.g., intensity, duration), the context of any impacts or responses ( e.g., critical reproductive time or location, foraging impacts affecting energetics), 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 are incorporated into this analysis via their impacts on the baseline ( e.g., as reflected in the regulatory status of the species, population size and growth rate where known, ongoing sources of human-caused mortality, or ambient noise levels).

Underwater acoustic transmissions associated with ICEX24, as outlined previously, have the potential to result in Level B harassment of ringed seals in the form of behavioral disturbance and TTS. Given the nature of the activity, no take by Level A harassment, serious injury, or mortality are anticipated to result from this activity even absent mitigation, and no such takes are authorized. Further, at close ranges and high sound levels approaching those that could cause PTS, seals would likely avoid the area immediately around the sound source.

NMFS anticipates that take of ringed seals by TTS could occur from the submarine activities. TTS is a temporary impairment of hearing and can last from minutes or hours to days (in cases of strong TTS) and which can result in disruptions to behavioral patterns from missing acoustic cues associated with, for example, conspecific communication or prey detection. In many cases, however, hearing sensitivity recovers rapidly after exposure to the sound ends. This activity has the potential to result in only minor levels of TTS, and hearing sensitivity of affected animals would be expected to recover quickly. Though TTS may occur as indicated, the overall fitness of the impacted individuals is unlikely to be affected given the temporary nature of TTS and the minor levels of TTS expected from these activities. Negative impacts on the reproduction or survival of affected ringed seals as well as impacts on the stock are not anticipated.

Effects on individuals that are taken by Level B harassment by behavioral disturbance could include alteration of dive behavior, alteration of foraging behavior, effects to breathing, interference with or alteration of vocalization, avoidance, and flight. More severe behavioral responses are not anticipated due to the localized, intermittent use of active acoustic sources and mitigation using PAM, which would limit exposure to active acoustic sources. Most likely, individuals would be temporarily displaced by moving away from the sound source. As described previously in the Acoustic Impacts section, seals exposed to non-impulsive sources with a received sound pressure level within the range of calculated exposures, (142–193 dB re 1 μPa), have been shown to change their behavior by modifying diving activity and avoidance of the sound source (Götz et al. 2010, Kvadsheim et al. 2010). Although a minor change to a behavior may occur as a result of exposure to the sound sources associated with the proposed specified activity, these changes would be within the normal range of behaviors for the animal ( e.g., the use of a breathing hole further from the source, rather than one closer to the source). Further, given the limited number of total instances of takes and the unlikelihood that any single individuals would be taken repeatedly, multiple times over sequential days, these takes are unlikely to impact the reproduction or survival of any individuals.

The Navy's activities are localized and of relatively short duration. While the total ICEX24 Study Area is large, the Navy expects that most activities would occur within the Ice Camp Study Area in relatively close proximity to the ice camp. The larger Navy Activity Study Area depicts the range where submarines may maneuver during the exercise. The ice camp would be in existence for up to 6 weeks with acoustic transmission occurring intermittently over approximately 4 weeks.

The project is not expected to have significant adverse effects on marine mammal habitat. The project activities are limited in time and would not modify physical marine mammal habitat. While the activities may cause some fish to leave a specific area ensonified by acoustic transmissions, temporarily impacting marine mammals' foraging opportunities, these fish would likely return to the affected area. As such, the impacts to marine mammal habitat are not expected to cause significant or long-term negative consequences.

For on-ice activity, Level A harassment, Level B harassment, serious injury, and mortality are not anticipated, given the nature of the activities, the lack of previous ringed seal observations, and the mitigation measures NMFS has required in the IHA. The ringed seal pupping season on the ice lasts for 5 to 9 weeks during late winter and spring. As stated in the Potential Effects of Specified Activities on Marine Mammals and Their Habitat section, March 1 is generally expected to be the onset of ice seal lairing season. The ice camp and runway would be established on first-year ice or multi-year ice without pressure ridges, as ringed seals tend to build their lairs near pressure ridges. Ice camp deployment will begin no later than mid-February, and be gradual, with activity increasing over the first 5 days. Ice camp deployment will be completed by March 15, before the pupping season. Displacement of seal lair construction or relocation to existing lairs outside of the ice camp area is unlikely, given the low average density of lairs (the average ringed seal lair density in the vicinity of Prudhoe Bay, Alaska is 1.58 lairs per km² ), the relative footprint of the Navy's planned ice camp (2 km² ; 0.77 mi² ), the lack of previous ringed seal observations on the ice during ICEX activities, and mitigation requirements that require the Navy to construct the ice camp and runway on first-year or multi-year ice without pressure ridges and require personnel to avoid areas of deep snow drift or pressure ridges.

Given that mitigation measures require that the ice camp and runway be established on first-year or multi-year ice without pressure ridges, where ringed seals tend to build their lairs, it is extremely unlikely that a ringed seal would build a lair in the vicinity of the ice camp. This measure, together with the other mitigation measures required for operation of the ice camp, are expected to avoid impacts to the construction and use of ringed seal subnivean lairs, particularly given the already low average density of lairs, as described above. Given that ringed seal lairs are not expected to occur in the ice camp study area, NMFS does not expect ringed seals to relocate pups due to human disturbance from ice camp activities.

Additional mitigation measures are also expected to prevent damage to and disturbance of ringed seals and their lairs that could otherwise result from on-ice activities. Personnel on on-ice vehicles are required to observe for marine mammals, and must follow established routes when available, to avoid potential damage to or disturbance of lairs. Personnel on foot and operating on-ice vehicles must avoid deep (>0.5 m) snow drifts and pressure ridges by 0.8 km, also to avoid potential damage to or disturbance of lairs. Further, personnel must maintain a 100 m (328 ft) distance from all observed marine mammals to avoid disturbing the animals due to the personnel's presence. Implementation of these measures will prevent ringed seal lairs from being crushed or damaged during ICEX24 activities.

In summary and as described above, the following factors primarily support our determination that the impacts resulting from this activity are not expected to adversely affect any of the species or stocks through effects on annual rates of recruitment or survival:

• No Level A harassment (injury), serious injury, or mortality is anticipated or authorized;
• Impacts would be limited to Level B harassment, primarily in the form of behavioral disturbance that results in minor changes in behavior;
• TTS is expected to affect only a limited number of animals and is expected to be minor and short term;
• The number of takes authorized are low relative to the estimated abundances of the affected stock, even given the extent to which abundance is significantly underestimated;
• Submarine training and testing activities will occur over only 4 weeks of the total 6-week activity period;
• There will be no loss or modification of ringed seal habitat and minimal, temporary impacts on prey;
• Physical impacts to ringed seal subnivean lairs will be avoided; and
• Mitigation requirements for ice camp activities are expected to prevent impacts to ringed seals during the pupping season.

Based on the analysis contained herein of the likely effects of the specified activity on marine mammals and their habitat, and taking into consideration the implementation of the required monitoring and mitigation measures, NMFS finds that the total marine mammal take from the planned activity will have a negligible impact on all affected marine mammal species or stocks.

Unmitigable Adverse Impact Analysis and Determination

In order to issue an IHA, NMFS must find that the specified activity will not have an “unmitigable adverse impact” on the subsistence uses of the affected marine mammal species or stocks by Alaskan Natives. NMFS has defined “unmitigable adverse impact” in 50 CFR 216.103 as an impact resulting from the specified activity: (1) That is likely to reduce the availability of the species to a level insufficient for a harvest to meet subsistence needs by: (i) Causing the marine mammals to abandon or avoid hunting areas; (ii) Directly displacing subsistence users; or (iii) Placing physical barriers between the marine mammals and the subsistence hunters; and (2) That cannot be sufficiently mitigated by other measures to increase the availability of marine mammals to allow subsistence needs to be met.

Impacts to marine mammals from the specified activity would mostly include limited, temporary direct behavioral disturbances of ringed seals; however, some TTS is also anticipated. No Level A harassment (injury), serious injury, or mortality of marine mammals is expected or authorized, and the activities are not expected to have any impacts on reproductive or survival rates of any marine mammal species.

The specified activity and associated harassment of ringed seals would not be expected to impact marine mammals in numbers or locations sufficient to reduce their availability for subsistence harvest given the short-term, temporary nature of the activities, and the distance offshore from known subsistence hunting areas. The specified activity would occur for a brief period of time outside of the primary subsistence hunting season, and though seals are harvested for subsistence uses off the North Slope of Alaska, the ICEX24 Study Area is seaward of known subsistence hunting areas. (The Study Area boundary is approximately 50 km from shore at the closest point, though exercises will occur farther offshore.)

The Navy will provide advance public notice to local residents and other users of the Prudhoe Bay region of Navy activities and measures used to reduce impacts on resources. This includes notification to local Alaska Natives who hunt marine mammals for subsistence. If any Alaska Natives express concerns regarding project impacts to subsistence hunting of marine mammals, the Navy would further communicate with the concerned individuals or community. The Navy would provide project information and clarification of the mitigation measures that will reduce impacts to marine mammals.

Based on the description of the specified activity, the measures described to minimize adverse effects on the availability of marine mammals for subsistence purposes, and the required mitigation and monitoring measures, NMFS has determined that there will not be an unmitigable adverse impact on subsistence uses from the Navy's proposed activities.

Endangered Species Act

Section 7(a)(2) of the ESA of 1973 (16 U.S.C. 1531 et seq.) requires that each Federal agency insure that any action it authorizes, funds, or carries out is not likely to jeopardize the continued existence of any endangered or threatened species or result in the destruction or adverse modification of designated critical habitat. To ensure ESA compliance for the issuance of IHAs, NMFS consults internally whenever we propose to authorize take for endangered or threatened species, in this case with NMFS' Alaska Regional Office (AKRO).

The NMFS Office of Protected Resources is authorizing take of ringed seals, which are listed under the ESA. The NMFS AKRO Protected Resources Division issued a Biological Opinion on January 11, 2024, which concluded that the Navy's activities and NMFS' issuance of an IHA are not likely to jeopardize the continued existence of the Arctic stock of ringed seals, and is not likely to destroy or adversely modify their critical habitat.

National Environmental Policy Act

In compliance with the National Environmental Policy Act of 1969 (42 U.S.C. 4321 et seq.), as implemented by the regulations published by the Council on Environmental Quality (40 CFR parts 1500–1508), the Navy prepared a Supplemental Environmental Assessment/Overseas Environmental Assessment (SEA/OEA) to consider the direct, indirect and cumulative effects to the human environment resulting from ICEX24, focusing on changes between ICEX24, and ICEX22 ( e.g., no torpedo training exercises in ICEX24 and new available science). This SEA/OEA supplements an EA/OEA published in 2022 for ICEX22 that was finalized in February 2022. NMFS adopted that EA/OEA and signed a Finding of No Significant Impact (FONSI) on February 4, 2022.

The Navy's SEA/OEA was made available for public comment at https://www.nepa.navy.mil/​icex/​ from September 29, 2023 to October 13, 2023. In the notice of proposed IHA (88 FR 85244, December 7, 2023), NMFS described its plan to adopt the Navy's SEA/OEA, provided our independent evaluation of the document found that it includes adequate information analyzing the effects on the human environment of issuing the IHA. In compliance with NEPA and the CEQ regulations, as well as NOAA Administrative Order 216–6A, NMFS has reviewed the Navy's SEA/OEA, determined it to be sufficient, and adopted that SEA/OEA and signed a FONSI on January 31, 2024.

Authorization

NMFS has issued an IHA to the Navy for the potential harassment of ringed seals incidental to ICEX24 in the Arctic Ocean that includes the previously explained mitigation, monitoring and reporting requirements.

Dated: February 1, 2024.

Catherine Marzin,

Acting Director, Office of Protected Resources, National Marine Fisheries Service.