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Federal Register / Vol. 86, No. 23 / Friday, February 5, 2021 / Notices and exclusion zones larger than the Level A harassment zone. Any individuals that are exposed above the Level B harassment threshold are expected to move away from the sound source and temporarily avoid the areas of pile driving. Therefore, North Atlantic right whales taken by the activity are likely to be exposed to lower noise levels closer to the 120dB
threshold than the Level A harassment threshold and therefore, behavioral reactions are expected to be less intense than during exposures to louder sounds but still below the Level A harassment threshold. NMFS expects that any avoidance of the project area by North Atlantic right whales would be temporary in nature and that any North Atlantic right whales that avoid the project area during construction would not be permanently displaced. Even limited repeated Level B harassment of some small subset of the overall stock, although not expected to occur given the transitory nature of marine mammals in the project area, is unlikely to result in any significant realized decrease in fitness or viability for the affected individuals, and thus would not result in any adverse impact to the stock as a whole.
Prey for North Atlantic right whales are mobile and broadly distributed throughout the project area; therefore, North Atlantic right whales that may be temporarily displaced during construction activities are expected to be able to resume foraging once they have moved away from areas with disturbing levels of underwater noise.
Because of the temporary nature of the disturbance and the availability of similar habitat and resources in the surrounding area, the impacts to North Atlantic right whales and the food sources that they utilize are not expected to cause significant or longterm consequences for individual North Atlantic right whales or their population. In addition, there are no North Atlantic right whale mating or calving areas within the proposed project area.
As described above, North Atlantic right whales are experiencing an ongoing UME. However, as described above, no injury of North Atlantic right whales as a result of the proposed project is expected or proposed for authorization, and Level B harassment takes of North Atlantic right whales are expected to be in the form of avoidance of the immediate area of construction.
As no injury or mortality is expected or proposed for authorization, and Level B
harassment of North Atlantic right whales will be reduced to the level of least practicable adverse impact through
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use of proposed mitigation measures, the proposed authorized takes of North Atlantic right whales would not exacerbate or compound the effects of the ongoing UME in any way.
NMFS concludes that the additional proposed mitigation measures would ensure that any exposures above the Level B harassment threshold would result in only short-term effects to individuals exposed. With implementation of the proposed mitigation requirements, take by Level A harassment is unlikely and is therefore not proposed for authorization. Potential impacts associated with Level B harassment would include only low-level, temporary behavioral modifications, most likely in the form of avoidance behavior or potential alteration of vocalizations.
Although acoustic masking may occur, based on the acoustic characteristics of noise associated with impact pile driving e.g., frequency spectra, short duration and HRG
surveys e.g., higher frequency, intermittent signals and the limited duration of vibratory pile driving activity, NMFS expects masking effects to be minimal e.g., pile driving to none e.g., HRG surveys. As mentioned previously, masking events that might be considered Level B harassment have already been accounted for in the exposure analysis as they would be expected to occur within the behavioral harassment zones predetermined for pile driving. Avoidance of the SFWF or SFEC during construction would represent a potential manifestation of behavioral disturbance. Although the project area is located within the migratory BIA for North Atlantic right whales, impact pile driving of monopile foundations would only occur on 16
days one pile would be driven per day for a maximum of 3 hours, and vibratory pile driving would be limited to a maximum of 36 hours of the 12month project. Further, seasonal restrictions preclude impact pile driving during the months in which North Atlantic right whale occurrence is expected to be highest January through April. If avoidance of the project area by North Atlantic right whales occurs, it is expected to be temporary. Finally, consistent North Atlantic right whale utilization of the habitat south of Marthas Vineyard and Nantucket Islands Oleson et al., 2020 indicates that suitable alternative nearby habitat would be available to North Atlantic right whales that might avoid the project area during construction.
In order to evaluate whether or not individual behavioral responses, in
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combination with other stressors, impact animal populations, scientists have developed theoretical frameworks which can then be applied to particular case studies when the supporting data are available. One such framework is the population consequences of disturbance model PCoD, which attempts to assess the combined effects of individual animal exposures to stressors at the population level NAS 2017. Nearly all PCoD studies considering multiple marine mammal species and experts agree that infrequent exposures of a single day or less are unlikely to impact individual fitness, let alone lead to population level effects Booth et al., 2016; Booth et al., 2017; Christiansen and Lusseau 2015; Farmer et al., 2018;
Harris et al., 2017; Harwood et al., 2014;
Harwood and Booth 2016; King et al., 2015; McHuron et al., 2018; NAS 2017;
New et al., 2014; Pirotta et al., 2018;
Southall et al., 2007; Villegas-Amtmann et al., 2015. Since NMFS expects that any exposures would be brief no more than 3 hours per day for impact pile driving or 36 hours over 6 days for vibratory pile driving, and likely less given probable avoidance response, and repeat exposures to the same individuals are unlikely, any behavioral responses that would occur due to animals being exposed to construction activity are expected to be temporary, with behavior returning to a baseline state shortly after the acoustic stimuli ceases, similar to findings during European wind farm construction.
Given this, and NMFS evaluation of the available PCoD studies, any such behavioral responses are not expected to impact individual animals health or have effects on individual animals survival or reproduction, thus no detrimental impacts at the population level are anticipated. North Atlantic right whales may temporarily avoid the immediate area but are not expected to permanently abandon the area. NMFS
does not anticipate North Atlantic right whales takes that would result from the proposed project would impact annual rates of recruitment or survival. Thus, any takes that occur would not result in population level impacts.
All Other Marine Mammal Species Impact pile driving has source characteristics short, sharp pulses with higher peak levels and sharper rise time to reach those peaks that are potentially injurious or more likely to produce severe behavioral reactions. No Level A
harassment from HRG surveys or vibratory pile driving is expected, even in the absence of mitigation; therefore, our discussion regarding auditory injury is limited to impact pile driving.

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