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Federal Register / Vol. 86, No. 233 / Wednesday, December 8, 2021 / Notices
are expected to cover approximately 15.7 km2 per day, meaning that the coil proxy is most representative of the effort planned by Shell 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, estimated take numbers for this LOA are considered conservative due to differences in both the airgun array 32
elements, 5,110 in3 and the daily survey area planned by Shell 15.7 km2, as compared to those modeled for the rule.
The Ursa survey will take place over 61 days, including 45 days of sound source operation. The Europa survey will take place over 122 days, including 20 days of sound source operation. Both surveys will occur within Zone 5. For both surveys, 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.
Additionally, 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. 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 see, e.g., 86 FR 5322, 5442 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 certain marine mammal species 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.
Rices whales formerly known as GOM Brydes whales 3 are generally found within a small area in the northeastern GOM in waters between 100400 m depth along the continental shelf break Rosel et al., 2016. Whaling 3 The final rule refers to the GOM Brydes whale Balaenoptera edeni. These whales were subsequently described as a new species, Rices whale Balaenoptera ricei Rosel et al., 2021.

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records suggest that Rices whales historically had a broader distribution within similar habitat parameters throughout the GOM Reeves et al., 2011; Rosel and Wilcox, 2014, and a NOAA survey reported observation of a Rices whale in the western GOM in 2017 NMFS, 2018. Habitat-based density modeling identified similar habitat i.e., approximately 100400 m water depths along the continental shelf break as being potential Rices whale habitat Roberts et al., 2016, although a core habitat area defined in the northeastern GOM outside the scope of the rule contained approximately 92
percent of the predicted abundance of Rices whales. See discussion provided at, e.g., 83 FR 29212, 29228, 29280 June 22, 2018; 86 FR 5322, 5418 January 19, 2021.
Although it is possible that Rices whales may occur outside of their core habitat, NMFS expects that any such occurrence would be limited to the narrow band of suitable habitat described above i.e., 100400 m.
Shells planned activities will occur in water depths of approximately 600
1,800 m and 8001,400 Ursa and Europa, respectively in the central GOM. Thus, NMFS does not expect there to be the reasonable potential for take of Rices whale in association with this survey and, accordingly, does not authorize take of Rices whale through this 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. 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. NMFS
has determined that the approach results in unrealistic projections regarding the likelihood of encountering killer whales.
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
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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 less than 20 occasions during the 19922009
NOAA surveys Frasers dolphin and false killer whale 4. 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 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 to 1
4 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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