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Federal Register / Vol. 86, No. 38 / Monday, March 1, 2021 / Notices
Mitigation and Monitoring In order to issue an IHA under Section 101a5D of the MMPA, the Service must set forth the permissible methods of taking pursuant to the activity, and other means of affecting the least practicable impact on the species or stock and its habitat, paying particular attention to habitat areas of significance and the availability of sea otters for subsistence uses by coastaldwelling Alaska Natives, although this factor is not applicable for this action.
In evaluating how mitigation may or may not be appropriate to ensure the least practicable impact on species or stocks and their habitat, as well as subsistence uses where applicable, we carefully consider two primary factors:
1 The manner in which, and the degree to which, the successful implementation of the measures is expected to reduce impacts to marine mammals, marine mammal species or stocks, and their habitat. This considers the nature of the potential adverse impact being mitigated i.e., 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.
To reduce the potential for disturbance to marine mammals caused by acoustic stimuli associated with IHA
activities, NSF has proposed to implement mitigation measures for the northern sea otter including, but not limited to, the following:
Development of marine mammal monitoring and mitigation plans;
Reduced survey transect lines and daylight-only operations in area of highest sea otter densities;
Establishment of shutdown and monitoring zones;
Vessel-based visual mitigation monitoring by Protected Species Observers;
Site clearing before start-up;
Soft-start and shutdown procedures.
The specific methods to be implemented are further specified in the Services draft EA USFWS 2020
available at: http www.regulations.gov, Docket No. FWSR1ES20200131.

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Estimated Take by Incidental Harassment of Northern Sea Otters In a previous section, we discussed the components of the project activities that have the potential to affect sea otters and the physiological and behavioral effects that can be expected.
Here, we discuss how the Service characterizes these effects under the MMPA.
An individual sea otters reaction to human activity will depend on the otters prior exposure to the activity, its need to be in the particular area, its physiological status, or other intrinsic factors. The location, timing, frequency, intensity, and duration of the encounter are among the external factors that will also influence the animals response.
Intermediate reactions that disrupt biologically significant behaviors are considered Level B harassment under the MMPA. The Service has identified the following sea otter behaviors as indicating possible Level B harassment:
Swimming away at a fast pace on belly i.e., porpoising;
Repeatedly raising the head vertically above the water to get a better view spy hopping while apparently agitated or while swimming away;
In the case of a pup, repeatedly spy hopping while hiding behind and holding onto its mothers head;
Abandoning prey or feeding area;
Ceasing to nurse and/or rest applies to dependent pups;
Ceasing to rest applies to independent animals;
Ceasing to use movement corridors along the shoreline;
Ceasing mating behaviors;
Shifting/jostling/agitation in a raft so that the raft disperses;
Sudden diving of an entire raft; or Flushing animals off of a haulout.
This list is not meant to encompass all possible behaviors; other situations may also indicate Level B harassment.
Reactions capable of causing injury are characterized as Level A harassment events. However, it is also important to note that, depending on the duration and severity of the above-described Level B behaviors, such responses could constitute take by Level A harassment.
For example, while a single flushing event would likely indicate Level B
harassment, repeatedly flushing sea otters from a haulout may constitute Level A harassment.
Calculating Estimate of Takes In the sections below, we estimate take by harassment of the numbers of sea otters from the Washington stock in Oregon and Washington that are likely to be affected during the proposed
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activities. We assumed all animals exposed to underwater sound levels that meet the acoustic exposure criteria would experience Level A >232 dBRMS
or Level B 160232 dBRMS harassment.
To determine the number of otters that may be exposed to these sound levels, we created spatially explicit zones of ensonification using the proposed reduced survey transect lines and determined the number of otters present in the ensonification zones using density information generated from minimum population estimates in Jeffries et al. 2019, which subdivides the surveyed area into Cape Flattery to La Push and La Push to north entrance of Grays Harbor. An in-depth explanation of the process used can be found in the Services draft EA USFWS
2020 available at: http
www.regulations.gov, Docket No. FWS
R1ES20200131.
The Level A and Level B underwater sound thresholds were used to create spatially explicit ensonification zones surrounding the proposed project transects. We created a buffer with a 46m 151-ft width around the proposed project transects to account for the Level A ensonified area on either side of the 24-m-wide 79-ft-wide airgun array. To determine the Level B ensonified area, we placed a 12,650-m 7.9-mi buffer around transects in water <100 m 328
ft deep, and a 9,468-m 5.9-mi buffer around transects in water 1001,000 m 3283,280 ft deep.
The minimum population estimate from Jeffries et al. 2019 can be specifically applied to the surveyed area, which included the Washington coastline between Cape Flattery and Grays Harbor in the nearshore areas less than 25-m 82-ft depth contour. Sea otters are overwhelmingly observed 95
percent within the 40-m 131-ft depth contour Laidre et al. 2009; Tinker et al.
2019, thus for the purposes of this analysis, the population estimated by Jeffries et al. 2019 is assumed to apply to the 40-m 131-ft depth contour for the waters between Grays Harbor and Cape Flattery. The minimum abundance estimates from Jeffries et al. 2019 were divided north and south of the Quillayute River, thus for this analysis habitat was divided into subregions, Cape Flattery south to Quillayute River subregion north and Quillayute River to Grays Harbor subregion mid.
Density estimates for the north and mid subregions were calculated by dividing the population estimate for that subregion Jeffries et al. 2019 by the area from shore to the 40-m 131-ft depth contour. See Table 1 for projected sea otter abundance and density estimates.

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