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Federal Register / Vol. 86, No. 181 / Wednesday, September 22, 2021 / Notices
0.41, the second-highest of any GOM
species model; Roberts et al., 2016. The models authors noted the expected non-uniform distribution of this rarelyencountered 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 19922009 reported only 16 sightings of killer whales, with an additional three encounters during more recent survey effort from 201718 Waring et al., 2013;
www.boem.gov/gommapps. Two other species were also observed on fewer than 20 occasions during the 19922009
NOAA surveys Frasers dolphin and false killer whale 3. However, observational data collected by protected species observers PSOs on industry geophysical survey vessels from 20022015 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 Frasers 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 20022008 and 2009
2015. This information qualitatively informed our rulemaking process, as discussed at 86 FR 5322, 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 2.32.4 minutes, and Hooker et al. 2012 reported that killer whales spent 78 percent of their time at depths between 010 meters m.
Similarly, Kvadsheim et al. 2012
reported data from a study of four killer whales, noting that the whales performed 20 times as many dives 130
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. 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.
NMFS determination in reflection of the data 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, 5403;
January 19, 2021. In this case, use of the acoustic exposure modeling produces an estimate of three killer whale exposures. Given the foregoing, it is unlikely that even one killer whale would be encountered during this 5-day survey, and accordingly no take of killer whales is authorized through this LOA.
Based on the results of our analysis, NMFS has determined that the level of taking expected for this survey and authorized through the LOA is consistent with the findings made for the total taking allowable under the regulations. See Table 1 in this notice
and Table 9 of the final 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 MMPAs small numbers requirement provided in the final rule 86 FR 5322, 5438; January 19, 2021.
The take numbers for authorization, which are determined as described above, are used by NMFS in making the necessary small numbers determinations, through comparison with the best available abundance estimates see discussion at 86 FR 5322, 5391; January 19, 2021. For this comparison, NMFS approach is to use the maximum theoretical population, determined through review of current stock abundance reports SAR;
www.fisheries.noaa.gov/national/
marine-mammal-protection/marinemammal-stock-assessments and modelpredicted 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 monthto-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 1TAKE ANALYSIS
Authorized take 1

Species Brydes whale 3
Kogia sp
Beaked whales
Bottlenose dolphin
Short-finned pilot whale
Sperm whale
Atlantic spotted dolphin

Abundance 2
0

4 66

944
648
70
178
245

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

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51
4,373
3,768
176,108
1,981
2,207
74,785

Percent abundance n/a 1.5
25.1
0.4
3.5
8.1
0.3