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Federal Register / Vol. 86, No. 23 / Friday, February 5, 2021 / Notices
Estimated Take
consideration of small numbers and the negligible impact determination.
Harassment is the only type of take expected to result from these activities.
Except with respect to certain activities not pertinent here, section 318 of 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.
Authorized takes would primarily be by Level B harassment, as noise from pile driving and HRG surveys has the potential to result in disruption of behavioral patterns for individual marine mammals. There is also some potential for auditory injury Level A
harassment to result from impact pile driving. The proposed mitigation and monitoring measures are expected to minimize the severity of such taking to the extent practicable see Proposed Mitigation.
As described previously, no mortality is anticipated or proposed to be authorized for these activities. The approach by which take is estimated is described below.
Generally speaking, NMFS estimates take by considering: 1 Acoustic thresholds above which NMFS believes the best available science indicates marine mammals will be behaviorally harassed or incur some degree of permanent hearing impairment; 2 the area or volume of water that will be ensonified above these levels in a day;
3 the density or occurrence of marine mammals within these ensonified areas;
and, 4 and the number of days of activities. NMFS notes that while these basic factors can contribute to a basic calculation to provide an initial prediction of takes, additional information that can qualitatively inform take estimates is also sometimes available e.g., previous monitoring results or average group size. Below, NMFS describes the factors considered here in more detail and present the proposed take estimate.

This section provides an estimate of the number of incidental takes proposed for authorization through this IHA, which will inform both NMFS

Acoustic Thresholds NMFS recommends the use of acoustic thresholds that identify the received level of underwater sound
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SPLs of sufficient strength have been known to cause injury to fish and fish mortality. However, in most fish species, hair cells in the ear continuously regenerate and loss of auditory function likely is restored when damaged cells are replaced with new cells. Halvorsen et al. 2012a showed that a TTS of 46 dB was recoverable within 24 hours for one species. Impacts would be most severe when the individual fish is close to the source and when the duration of exposure is long. Injury caused by barotrauma can range from slight to severe and can cause death, and is most likely for fish with swim bladders.
Barotrauma injuries have been documented during controlled exposure to impact pile driving Halvorsen et al., 2012b; Casper et al., 2013. As described in the Proposed Mitigation section below, South Fork Wind would utilize a sound attenuation device which would reduce potential for injury to marine mammal prey.
The most likely impact to fish from impact and vibratory pile driving activities at the project areas would be temporary behavioral avoidance of the area. The duration of fish avoidance of an area after pile driving stops is unknown, but a rapid return to normal recruitment, distribution and behavior is anticipated. In general, impacts to marine mammal prey species are expected to be minor and temporary due to the expected short daily duration of individual pile driving events and the relatively small areas being affected.
Any behavioral avoidance by fish of the disturbed area would still leave significantly large areas of fish and marine mammal foraging habitat in the nearby vicinity. Based on the information discussed herein, NMFS
concludes that impacts of South Fork Winds activities are not likely to have more than short-term adverse effects on any prey habitat or populations of prey species. Further, any impacts to marine mammal habitat are not expected to result in significant or long-term consequences for individual marine mammals, or to contribute to adverse impacts on their populations.

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above which exposed marine mammals would be reasonably expected to be behaviorally harassed equated to Level B harassment or to incur PTS of some degree equated to Level A harassment.
Level B HarassmentThough significantly driven by received level, the onset of behavioral disturbance from anthropogenic noise exposure is also informed to varying degrees by other factors related to the source e.g., frequency, predictability, duty cycle, the environment e.g., bathymetry, and the receiving animals hearing, motivation, experience, demography, behavioral context and can be difficult to predict Southall et al., 2007, Ellison et al., 2012. Based on what the available science indicates and the practical need to use a threshold based on a factor that is both predictable and measurable for most activities, NMFS
uses a generalized acoustic threshold based on received level to estimate the onset of behavioral harassment. NMFS
predicts that marine mammals are likely to be behaviorally harassed in a manner we consider Level B harassment when exposed to underwater anthropogenic noise above received levels of 160 dB re 1 mPa rms for impulsive and/or intermittent sources. South Fork Winds proposed activity includes the use of impulsive and intermittent sources e.g., impact pile driving, HRG acoustic sources, and thus the 160 dB threshold applies.
Level A harassmentNMFS
Technical Guidance for Assessing the Effects of Anthropogenic Sound on Marine Mammal Hearing Version 2.0
Technical Guidance, 2018 identifies dual criteria to assess auditory injury Level A harassment to five different marine mammal groups based on hearing sensitivity as a result of exposure to noise from two different types of sources impulsive or nonimpulsive. The components of South Fork Winds proposed activity that may result in take of marine mammals include the use of impulsive and nonimpulsive sources.
These thresholds are provided in Table 5. The references, analysis, and methodology used in the development of the thresholds are described in NMFS
2018 Technical Guidance, which may be accessed at: www.fisheries.noaa.gov/
national/marine-mammal-protection/
marine-mammal-acoustic-technicalguidance.

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