2023-23298. Taking and Importing Marine Mammals; Taking Marine Mammals Incidental to Geophysical Surveys Related to Oil and Gas Activities in the Gulf of Mexico

AGENCY:

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

ACTION:

Notice. Issuance of letter of authorization.

SUMMARY:

In accordance with the Marine Mammal Protection Act (MMPA), as amended, its implementing regulations, and NMFS' MMPA Regulations for Taking Marine Mammals Incidental to Geophysical Surveys Related to Oil and Gas Activities in the Gulf of Mexico, notification is hereby given that a Letter of Authorization (LOA) has been issued to WesternGeco for the take of marine mammals incidental to geophysical survey activity in the Gulf of Mexico.

DATES:

The LOA is effective from October 17, 2023 through April 30, 2024.

ADDRESSES:

The LOA, LOA request, and supporting documentation are available online at: https://www.fisheries.noaa.gov/​action/​incidental-take-authorization-oil-and-gas-industry-geophysical-survey-activity-gulf-mexico. In case of problems accessing these documents, please call the contact listed below (see FOR FURTHER INFORMATION CONTACT ).

FOR FURTHER INFORMATION CONTACT:

Jenna Harlacher, Office of Protected Resources, NMFS, (301) 427–8401.

SUPPLEMENTARY INFORMATION:

Background

Sections 101(a)(5)(A) and (D) of the MMPA (16 U.S.C. 1361 et seq.) direct the Secretary of Commerce 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 issued or, if the taking is limited to harassment, a notice of a proposed authorization is provided to the public for review.

An authorization for incidental takings shall be granted if NMFS finds that the taking will have a negligible impact on the species or stock(s), will not have an unmitigable adverse impact on the availability of the species or stock(s) for subsistence uses (where relevant), and if the permissible methods of taking and requirements pertaining to the mitigation, monitoring and reporting of such takings are set forth. NMFS has defined “negligible impact” in 50 CFR 216.103 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.

Except with respect to certain activities not pertinent here, the MMPA defines “harassment” as any act of pursuit, torment, or annoyance which: (i) has the potential to injure a marine mammal or marine mammal stock in the wild (Level A harassment); or (ii) has the potential to disturb a marine mammal or marine mammal stock in the wild by causing disruption of behavioral patterns, including, but not limited to, migration, breathing, nursing, breeding, feeding, or sheltering (Level B harassment).

On January 19, 2021, we issued a final rule with regulations to govern the unintentional taking of marine mammals incidental to geophysical survey activities conducted by oil and gas industry operators, and those persons authorized to conduct activities on their behalf (collectively “industry operators”), in U.S. waters of the Gulf of Mexico (GOM) over the course of 5 years (86 FR 5322, January 19, 2021). The rule was based on our findings that the total taking from the specified activities over the 5-year period will have a negligible impact on the affected species or stock(s) of marine mammals and will not have an unmitigable adverse impact on the availability of those species or stocks for subsistence uses. The rule became effective on April 19, 2021.

Our regulations at 50 CFR 217.180 et seq. allow for the issuance of LOAs to industry operators for the incidental take of marine mammals during geophysical survey activities and prescribe the permissible methods of taking and other means of effecting the least practicable adverse impact on marine mammal species or stocks and their habitat (often referred to as mitigation), as well as requirements pertaining to the monitoring and reporting of such taking. Under § 217.186 (e), issuance of an LOA shall be based on a determination that the level of taking will be consistent with the findings made for the total taking allowable under these regulations and a determination that the amount of take authorized under the LOA is of no more than small numbers.

Summary of Request and Analysis

WesternGeco plans to conduct a three-dimensional (3D) ocean bottom node (OBN) survey in the Green Canyon and Walker Ridge protraction areas, including approximately 795 lease blocks. Approximate water depths of the survey area range from 1,000 to 3,000 meters (m). See section F of the LOA application for a map of the area.

WesternGeco anticipates using two source vessels, towing low-frequency airgun sources known as Gemini (also referred to as a dual barbell source) or conventional airgun sources consisting of 28 elements, with a total volume of 5,240 cubic inches (in³ ). Please see WesternGeco's application for additional detail.

The Gemini source was not included in the acoustic exposure modeling developed in support of the rule. However, our rule anticipated the possibility of new and unusual technologies (NUT) and determined they would be evaluated on a case-by case basis (86 FR 5322, 5442, January 19, 2021). This source was previously evaluated as a NUT in 2020 (prior to issuance of the 2021 final rule) pursuant to the requirements of NMFS' 2020 Biological Opinion on BOEM's Gulf of Mexico oil and gas program as well as the issuance of the rule. An associated report produced by Jasco Applied Sciences (Grooms et al., 2019) provides information related to the acoustic output of the Gemini source, which informs our evaluation here.

The Gemini source operates on the same basic principles as a traditional airgun source in that it uses compressed air to create a bubble in the water column which then goes through a series of collapses and expansions creating primarily low-frequency sounds. However, the Gemini source consists of one physical element with two large chambers of 4,000 (in³ ) each (total volume of 8,000 in³ ). This creates a larger bubble resulting in more of the energy being concentrated in low frequencies, with a fundamental frequency of 3.7 Hertz. In addition to concentrating energy at lower frequencies, the Gemini source is expected to produce lower overall sound levels than the conventional airgun proxy source. The number of airguns in an array is highly influential on overall sound energy output, because the output increases approximately linearly with the number of airgun elements. In this case, because the same air volume is used to operate two very large guns, rather than tens of smaller guns, the array produces lower sound levels than a conventional array of equivalent total volume.

The modeled distances described in the aforementioned Jasco report show expected per-pulse sound pressure level threshold distances to the 160-dB level of 4.29 kilometers (km). When frequency-weighted, i.e., considering the low frequency output of the source relative to the hearing sensitivities of different marine mammal hearing groups, the estimated distance is decreased to approximately 1 km for the low-frequency cetacean hearing group and to de minimis levels for mid- and high-frequency cetacean hearing groups, significantly less than comparable modeled distances for the proxy 72-element, 8,000 in³ array evaluated in the rule.

These factors lead to a conclusion that take by Level B harassment associated with use of the Gemini source would be less than would occur for a similar survey instead using the modeled airgun array as a sound source. Based on the foregoing, we have determined there will be no effects of a magnitude or intensity different from those evaluated in support of the rule. Moreover, use of modeling results relating to use of the 72 element, 8,000 in³ airgun array are expected to be significantly conservative as a proxy for use in evaluating potential impacts of use of the Gemini source.

Consistent with the preamble to the final rule, the survey effort proposed by WesternGeco in its LOA request was used to develop LOA-specific take estimates based on the acoustic exposure modeling results described in the preamble (86 FR 5398, January 19, 2021). In order to generate the appropriate take numbers for authorization, the following information was considered: (1) survey type; (2) location (by modeling zone ^[1] ); (3) number of days; and (4) season.^[2] The acoustic exposure modeling performed in support of the rule provides 24-hour exposure estimates for each species, specific to each modeled survey type in each zone and season.

No 3D OBN surveys were included in the modeled survey types, and use of existing proxies ( i.e., two-dimensional (2D), 3D narrow-azimuth (NAZ), 3D wide-azimuth (WAZ), Coil) is generally conservative for use in evaluation of 3D OBN survey effort, largely due to the greater area covered by the modeled proxies. Summary descriptions of these modeled survey geometries are available in the preamble to the proposed rule (83 FR 29220, June 22, 2018). Coil was selected as the best available proxy survey type in this case because the spatial coverage of the planned survey is most similar to the coil survey pattern.

The planned 3D OBN survey will involve two source vessels sailing along survey lines averaging 83 km in length. The coil survey pattern was assumed to cover approximately 144 kilometers squared (km² ) per day (compared with approximately 795 km² , 199 km² , and 845 km² per day for the 2D, 3D NAZ, and 3D WAZ survey patterns, respectively). Among the different parameters of the modeled survey patterns ( e.g., area covered, line spacing, number of sources, shot interval, total simulated pulses), NMFS considers area covered per day to be most influential on daily modeled exposures exceeding Level B harassment criteria. Although WesternGeco is not proposing to perform a survey using the coil geometry, its planned 3D OBN survey is expected to cover approximately 99.6 km² per day, meaning that the coil proxy is most representative of the effort planned by WesternGeco in terms of predicted Level B harassment exposures. In addition, all available acoustic exposure modeling results assume use of a 72-element, 8,000 in³ array. Thus, as discussed above, estimated take numbers for this LOA are considered conservative due to differences between the acoustic source planned for use (Gemini or 28 element, 5,240 in³ airgun array) and the proxy array modeled for the rule.

The survey will take place over approximately 85 days, including 65 days of sound source operation. The survey plan includes approximately half the days within Zone 5 and half the days within Zone 7. We modeled 33 days in each zone for take estimates. The seasonal distribution of survey days is not known in advance. Therefore, the take estimates for each species are based on the season that produces the greater value.

For some species, take estimates based solely on the modeling yielded results that are not realistically likely to occur when considered in light of other relevant information available during the rulemaking process regarding marine mammal occurrence in the GOM. The approach used in the acoustic exposure modeling, in which seven modeling zones were defined over the U.S. GOM, necessarily averages fine-scale information about marine mammal distribution over the large area of each modeling zone. This can result in unrealistic projections regarding the likelihood of encountering particularly rare species and/or species not expected to occur outside particular habitats. Thus, although the modeling conducted for the rule is a natural starting point for estimating take, our rule acknowledged that other information could be considered ( e.g.,86 FR 5322, January 19, 2021), discussing the need to provide flexibility and make efficient use of previous public and agency review of other information and identifying that additional public review is not necessary unless the model or inputs used differ substantively from those that were previously reviewed by NMFS and the public). For this survey, NMFS has other relevant information reviewed during the rulemaking that indicates use of the acoustic exposure modeling to generate a take estimate for Rice's whales and killer whales produces results inconsistent with what is known regarding their occurrence in the GOM. Accordingly, we have adjusted the calculated take estimates for those species as described below.

NMFS' final rule described a “core habitat area” for Rice's whales (formerly known as GOM Bryde's whales) ^[3] located in the northeastern GOM in waters between 100 and 400 m depth along the continental shelf break (Rosel et al., 2016). However, whaling records suggest that Rice's whales historically had a broader distribution within similar habitat parameters throughout the GOM (Reeves et al., 2011; Rosel and Wilcox, 2014). In addition, habitat-based density modeling identified similar habitat ( i.e., approximately 100–400 m water depths along the continental shelf break) as being potential Rice's whale habitat (Roberts et al., 2016), although the core habitat area contained approximately 92 percent of the predicted abundance of Rice's whales. See discussion provided at, e.g.,83 FR 29228, June 22, 2018; 83 FR 29280, June 22, 2018; 86 FR 5418, January 19, 2021.

Although Rice's whales may occur outside of the core habitat area, we expect that any such occurrence would be limited to the narrow band of suitable habitat described above ( i.e., 100–400 m) and that, based on the few available records, these occurrences would be rare. WesternGeco's planned activities will occur in water depths of approximately 1,000–3,000 m in the central GOM. Thus, NMFS does not expect there to be the reasonable potential for take of Rice's whale in association with this survey and, accordingly, does not authorize take of Rice's whale through the LOA.

Killer whales are the most rarely encountered species in the GOM, typically in deep waters of the central GOM (Roberts et al., 2015; Maze-Foley and Mullin, 2006). As discussed in the final rule, the density models produced by Roberts et al. (2016) provide the best available scientific information regarding predicted density patterns of cetaceans in the U.S. GOM. The predictions represent the output of models derived from multi-year observations and associated environmental parameters that incorporate corrections for detection bias. However, in the case of killer whales, the model is informed by few data, as indicated by the coefficient of variation associated with the abundance predicted by the model (0.41, the second-highest of any GOM species model; Roberts et al., 2016). The model's authors noted the expected non-uniform distribution of this rarely-encountered species (as discussed above) and expressed that, due to the limited data available to inform the model, it “should be viewed cautiously” (Roberts et al., 2015). NOAA surveys in the GOM from 1992 to 2009 reported only 16 sightings of killer whales, with an additional 3 encounters during more recent survey effort from 2017 to 2018 (Waring et al., 2013; https://www.boem.gov/​gommapps ). Two other species were also observed on fewer than 20 occasions during the 1992–2009 NOAA surveys (Fraser's dolphin and false killer whale ^[4] ). However, observational data collected by protected species observers (PSO) on industry geophysical survey vessels from 2002 to 2015 distinguish the killer whale in terms of rarity. During this period, killer whales were encountered on only 10 occasions, whereas the next most rarely encountered species.⁴ However, note that these species have been observed over a greater range of water depths in the GOM than have killer whales. (Fraser's dolphin) was recorded on 69 occasions (Barkaszi and Kelly, 2019). The false killer whale and pygmy killer whale were the next most rarely encountered species, with 110 records each. The killer whale was the species with the lowest detection frequency during each period over which PSO data were synthesized (2002–2008 and 2009–2015). This information qualitatively informed our rulemaking process, as discussed at 86 FR 5322 and 86 FR 5334 (January 19, 2021), and similarly informs our analysis here.

The rarity of encounter during seismic surveys is not likely to be the product of high bias on the probability of detection. Unlike certain cryptic species with high detection bias, such as Kogia spp. or beaked whales, or deep-diving species with high availability bias, such as beaked whales or sperm whales, killer whales are typically available for detection when present and are easily observed. Roberts et al. (2015) stated that availability is not a major factor affecting detectability of killer whales from shipboard surveys, as they are not a particularly long-diving species. Baird et al. (2005) reported that mean dive durations for 41 fish-eating killer whales for dives greater than or equal to 1 minute in duration was 2.3–2.4 minutes, and Hooker et al. (2012) reported that killer whales spent 78 percent of their time at depths between 0 and 10 m. Similarly, Kvadsheim et al. (2012) reported data from a study of 4 killer whales, noting that the whales performed 20 times as many dives 1–30 m in depth than to deeper waters, with an average depth during those most common dives of approximately 3 m.

In summary, killer whales are the most rarely encountered species in the GOM and typically occur only in particularly deep water. This survey would take place in deep waters that would overlap with depths in which killer whales typically occur. While this information is reflected through the density model informing the acoustic exposure modeling results, there is relatively high uncertainty associated with the model for this species, and the acoustic exposure modeling applies mean distribution data over areas where the species is in fact less likely to occur. In addition, as noted above in relation to the general take estimation methodology, the assumed proxy source (72-element, 8,000-in³ array) results in a significant overestimate of the actual potential for take to occur. NMFS' determination in reflection of the information discussed above, which informed the final rule, is that use of the generic acoustic exposure modeling results for killer whales will generally result in estimated take numbers that are inconsistent with the assumptions made in the rule regarding expected killer whale take (86 FR 5322, January 19, 2021; 86 FR 5403, January 19, 2021).

In past authorizations, NMFS has often addressed situations involving the low likelihood of encountering a rare species such as killer whales in the GOM through authorization of take of a single group of average size ( i.e., representing a single potential encounter). See 83 FR 63268, December 7, 2018; 86 FR 29090, May 28, 2021; 85 FR 55645, September 9, 2020. For the reasons expressed above, NMFS determined that a single encounter of killer whales is more likely than the model-generated estimates and has authorized take associated with a single group encounter ( i.e., up to seven animals for killer whales).

Based on the results of our analysis, NMFS has determined that the level of taking authorized through the LOA is consistent with the findings made for the total taking allowable under the regulations for the affected species or stocks of marine mammals. See Table 1 in this notice and Table 9 of the rule (86 FR 5322, January 19, 2021).

Small Numbers Determination

Under the GOM rule, NMFS may not authorize incidental take of marine mammals in an LOA if it will exceed “small numbers.” In short, when an acceptable estimate of the individual marine mammals taken is available, if the estimated number of individual animals taken is up to, but not greater than, one-third of the best available abundance estimate, NMFS will determine that the numbers of marine mammals taken of a species or stock are small. For more information please see NMFS' discussion of the MMPA's small numbers requirement provided in the final rule (86 FR 5438, January 19, 2021).

The take numbers for authorization are determined as described above in the Summary of Request and Analysis section. Subsequently, the total incidents of harassment for each species are multiplied by scalar ratios to produce a derived product that better reflects the number of individuals likely to be taken within a survey (as compared to the total number of instances of take), accounting for the likelihood that some individual marine mammals may be taken on more than 1 day (see 86 FR 5404, January 19, 2021). The output of this scaling, where appropriate, is incorporated into adjusted total take estimates that are the basis for NMFS' small numbers determinations, as depicted in Table 1.

This product is used by NMFS in making the necessary small numbers determinations through comparison with the best available abundance estimates (see discussion at 86 FR 5322, January 19, 2021; 86 FR 5391, January 19, 2021). For this comparison, NMFS' approach is to use the maximum theoretical population, determined through review of current stock assessment reports (SAR; https://www.fisheries.noaa.gov/​national/​marine-mammal-protection/​marine-mammal-stock-assessment-reports-species-stock) and model-predicted abundance information ( https://seamap.env.duke.edu/​models/​Duke/​GOM/​). For the latter, for taxa where a density surface model could be produced, we use the maximum mean seasonal ( i.e., 3-month) abundance prediction for purposes of comparison as a precautionary smoothing of month-to-month fluctuations and in consideration of a corresponding lack of data in the literature regarding seasonal distribution of marine mammals in the GOM. Information supporting the small numbers determinations is provided in Table 1.

Table 1—Take Analysis

Species	Authorized take	Scaled take 1	Abundance 2	Percent abundance
Rice's whale	0	n/a	51	n/a
Sperm whale	1,043	441	2,207	20.0
Kogia spp.	3  426	129	4,373	3.5
Beaked whales	5,374	543	3,768	14.4
Rough-toothed dolphin	946	271	4,853	5.6
Bottlenose dolphin	3,129	898	176,108	0.5
Clymene dolphin	2,611	749	11,895	6.3
Atlantic spotted dolphin	1,247	358	74,785	0.5
Pantropical spotted dolphin	15,927	4,571	102,361	4.5
Spinner dolphin	2,430	697	25,114	2.8
Striped dolphin	1,117	321	5,229	6.1
Fraser's dolphin	332	95	1,665	5.7
Risso's dolphin	667	197	3,764	5.2
Melon-headed whale	1,706	503	7,003	7.2
Pygmy killer whale	524	155	2,126	7.3
False killer whale	725	214	3,204	6.7
Killer whale	7	n/a	267	2.6
Short-finned pilot whale	391	115	1,981	5.8
1  Scalar ratios were applied to “Authorized Take” values as described at 86 FR 5322 and 86 FR 5404 (January 19, 2021) to derive scaled take numbers shown here.
2  Best abundance estimate. For most taxa, the best abundance estimate for purposes of comparison with take estimates is considered here to be the model-predicted abundance (Roberts et al., 2016). For those taxa where a density surface model predicting abundance by month was produced, the maximum mean seasonal abundance was used. For those taxa where abundance is not predicted by month, only mean annual abundance is available. For Rice's whale and the killer whale, the larger estimated SAR abundance estimate is used.
3  Includes 26 takes by Level A harassment and 400 takes by Level B harassment. Scalar ratio is applied to takes by Level B harassment only; small numbers determination made on basis of scaled Level B harassment take plus authorized Level A harassment take.

Based on the analysis contained herein of WesternGeco's proposed survey activity described in its LOA application and the anticipated take of marine mammals, NMFS finds that small numbers of marine mammals will be taken relative to the affected species or stock sizes ( i.e., less than one-third of the best available abundance estimate) and therefore the taking is of no more than small numbers.

Authorization

NMFS has determined that the level of taking for this LOA request is consistent with the findings made for the total taking allowable under the incidental take regulations and that the amount of take authorized under the LOA is of no more than small numbers. Accordingly, we have issued an LOA to WesternGeco authorizing the take of marine mammals incidental to its geophysical survey activity, as described above.

Dated: October 17, 2023.

Kim Damon-Randall,

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

Footnotes

1.  For purposes of acoustic exposure modeling, the GOM was divided into seven zones. Zone 1 is not included in the geographic scope of the rule.

2.  For purposes of acoustic exposure modeling, seasons include winter (December–March) and summer (April–November).

3.  The final rule refers to the GOM Bryde's whale ( Balaenoptera edeni). These whales were subsequently described as a new species, Rice's whale ( Balaenoptera ricei) (Rosel et al., 2021).

4.  However, note that these species have been observed over a greater range of water depths in the GOM than have killer whales.