Je veux savoir à propos de…

30620

Federal Register / Vol. 86, No. 109 / Wednesday, June 9, 2021 / Notices
Mitigation and Monitoring If an IHA for the NSF/LDEO project is issued, it must specify means for affecting the least practicable adverse impact on sea otters and their habitat, paying particular attention to rookeries, mating grounds, and areas of similar significance and the availability of sea otters for subsistence uses by coastaldwelling Alaska Natives.
In evaluating what mitigation measures are appropriate to ensure the least practicable adverse impact on species or stocks and their habitat, as well as subsistence uses, we considered the manner and degree to which the successful implementation of the measures are expected to achieve this goal. We considered the nature of the potential adverse impact being mitigated likelihood, scope, range, the likelihood that the measures will be effective if implemented, and the likelihood of effective implementation.
We also considered the practicability of the measures for applicant implementation e.g., cost, impact on operations.
To reduce the potential for disturbance from acoustic stimuli associated with the activities, the applicants have proposed mitigation measures including, but not limited to, the following:
Development of a marine mammal monitoring and mitigation plan;
Establishment of shutdown and monitoring zones;
Visual mitigation monitoring by designated Protected Species Observers PSO;
Site clearance before startup;
Soft-start procedures;
Shutdown procedures; and Vessel strike avoidance measures.
These measures are further specified under Proposed Authorization, part B.
Avoidance and Minimization. The Service has not identified any additional mitigation or monitoring measures not already incorporated into NSFs request that are practicable and would further reduce potential impacts to sea otters and their habitat.
Estimated Incidental Take
lotter on DSK11XQN23PROD with NOTICES1

Characterizing Take by Level B
Harassment In the previous section, we discussed the components of the project activities that have the potential to affect sea otters. Here, we describe and categorize the physiological and behavioral effects that can be expected based on documented responses to human activities observed during sea otter studies. We also discuss how these
VerDate Sep<11>2014

18:13 Jun 08, 2021

Jkt 253001

behaviors are characterized under the MMPA.
As we described in Evidence from Sea Otter Studies, an individual sea otters reaction to human activity will depend on the otters prior exposure to the activity, the potential benefit that may be realized by the individual from its current location, 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 take:
Swimming away at a fast pace on belly i.e., porpoising;
Repeatedly raising the head vertically above the water to get a better view spyhopping while apparently agitated or while swimming away;
In the case of a pup, repeatedly spyhopping 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;
Ceasing mating behaviors;
Shifting/jostling/agitation in a raft so that the raft disperses;
Sudden diving of an entire raft; or Flushing animals off a haulout.
This list is not meant to encompass all possible behaviors; other situations may also indicate Level B take.
Reactions capable of causing injury are characterized as Level A harassment events. The proposed action is not anticipated to result in Level A
harassment due to exposure of otters to noise capable of causing PTS. 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 Take We assumed all animals exposed to underwater sound levels that meet the acoustic exposure criteria shown in Table 1 will experience, at a minimum, take by Level B harassment due to exposure to underwater noise. To estimate the number of otters that may be exposed to these sound levels, we
PO 00000

Frm 00035

Fmt 4703

Sfmt 4703

worked closely with the applicant to create spatially explicit zones of ensonification around the proposed survey transects based on expected sound source levels and attenuation models. We determined the number of otters present in the ensonification zones using density information generated by Tinker et al. 2019 for the subgroups that comprise the Southeast Alaska stock.
Zones of Level A and Level B
ensonification were created using the proposed R/V Langseth transects along the Southeast Alaskan coast. We developed sound level isopleths through acoustic modeling by NSF/L
DEO for deep water and an analysis of empirical data collected in a 2012
survey by the R/V Langseth along the Cascadia Margin in coastal Washington Crone et al. 2014 for intermediate and shallow waters. The 2012 survey in Cascadia was conducted using a 4-string 0.11-m3 6,600-in3 airgun array at a tow depth of 9 m 29.5 ft, while the proposed activities in Southeast Alaska will use a 0.11-m3 6,600-in3 airgun array at a tow depth of 12 m 39 ft. To account for this difference, the applicant used a scaling factor see the application available as described under ADDRESSES
for details. The largest resulting Level A isopleth calculated from the NSF/L
DEO modeling where sound levels will be greater than 232 dB peak encompassed areas up to 10.6 m 34.7
ft from the sound source. The Level B
isopleth where sound levels will be between 160231 dB was based on empirical data and encompassed areas up to 12.65 km 7.9 mi from the sound source when the R/V Langseth was in shallow water <100 m or 328 ft ocean depth and up to 9.2 km 5.7 mi when the vessel was in intermediate depths 1001,000 m or 3283,280 ft ocean depth.
The Level A and Level B isopleths were then used to create spatially explicit ensonification zones surrounding the proposed project transects using ArcGIS Pro 2018. Using the proximity toolset in ArcGIS Pro, we created a buffer with a 45-m 148-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, points were first placed along the proposed project transects every 500 m 0.3 mi. We then used bathymetry data to determine ocean depth at each point along the transect. We placed a 12.65km 7.9-mi buffer around points in water less than 100 m 328 ft deep, and a 9.2-km 5.7-mi buffer around points in water 1001,000 m 3283,280 ft
E:FRFM09JNN1.SGM

09JNN1