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Federal Register / Vol. 86, No. 181 / Wednesday, September 22, 2021 / Notices 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 Federal waters of the U.S. 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 stocks 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 50 CFR
217.186e, 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 Anadarko plans to conduct a zero offset vertical seismic profile VSP
survey after reaching total depth at Lease Block 129 in the Mississippi Canyon. See map in Section F of
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Anadarkos application. Anadarko plans to use one of four possible airgun arrays for this survey: A 12-element array, with a total volume of 2,400 cubic inches in3; an array consisting of 6
elements with total volume of 1,500 in3;
an array consisting of 6 elements, with a total volume of 1,200 in3; or an array consisting of 8 elements with a total volume of 1,170 in3. Please see Anadarkos application for additional detail.
Consistent with the preamble to the final rule, the survey effort proposed by Anadarko 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 5322, 5398; January 19, 2021. In order to generate the appropriate take number 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 VSP surveys were included in the modeled survey types, and use of existing proxies i.e., 2D, 3D NAZ, 3D
WAZ, Coil is generally conservative for use in evaluation of VSP survey effort.
Summary descriptions of these modeled survey geometries are available in the preamble to the proposed rule 83 FR
29212, 29220; June 22, 2018. Zero offset VSP surveys are significantly different from modeled survey geometries in that they are conducted from a stationary or near-stationary deployment very close to an active drilling platform. For this survey, the seismic source array will be deployed from a drillship at or near the borehole, with the seismic receivers i.e., geophones deployed in the borehole on wireline at specified depth intervals. Use of the 2D proxy for zero offset VSP surveys is expected to be significantly conservative. In addition, all available acoustic exposure modeling results assume use of a 72 element, 8,000 in3 array. In this case, take numbers authorized through the LOA
are considered very conservative i.e., they likely overestimate take due to differences in both the airgun array and the survey geometry planned by Anadarko, as compared to those modeled for the rule. The survey is planned to occur for 5 days in Zone 5.
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 DecemberMarch and Summer AprilNovember.

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Although the survey is planned to occur in September 2021, the LOA is effective from September 18, 2021March 17, 2022 to account for potential delay.
Therefore, the take estimates for each species are based on the season that has the greater value for the species i.e., winter or summer.
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 killer whales produces results inconsistent with what is known regarding their occurrence in the GOM. Accordingly, we have adjusted the calculated take estimates for that species as described below.
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
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