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Federal Register / Vol. 86, No. 23 / Friday, February 5, 2021 / Notices biologically significant if the change affects growth, survival, or reproduction. Significant behavioral modifications that could lead to effects on growth, survival, or reproduction, such as drastic changes in diving/
surfacing patterns or significant habitat abandonment are considered extremely unlikely in the case of the proposed project, as it is expected that mitigation measures, including clearance zones and soft start described in detail below, see Proposed Mitigation will minimize the potential for marine mammals to be exposed to sound levels that would result in more extreme behavioral responses. In addition, marine mammals in the project area are expected to avoid any area that would be ensonified at sound levels high enough for the potential to result in more severe acute behavioral responses, as the offshore environment would allow marine mammals the ability to freely move to other areas without restriction.
In the case of impact pile driving, sound sources would be active for relatively short durations 2 to 3 hours per pile, and only one pile would be driven per day. The acoustic frequencies produced during pile driving activity are lower than those used by most species for communication or foraging expected to be present in the project area. Given the short duration and the frequency spectra produced by pile driving, NMFS expects minimal masking impacts from these activities.
Further, any masking events that might qualify as Level B harassment under the MMPA would be expected to occur concurrently within the zones of behavioral harassment already estimated for pile driving, and have, therefore, already been taken into account in the exposure analysis. The zones of behavioral harassment estimated for vibratory pile driving are large see Estimated Take, but the short duration of this activity coupled with the ephemeral use by LF cetaceans the group most susceptible to potential masking from these activities of the nearshore habitat will limit masking impacts. Finally, masking effects from HRG survey activities are not anticipated due to the characteristics of the acoustic sources intermittent and higher frequency signals, the small isopleths generated by those signals, and the influence of the proposed mitigation.
Anticipated Effects on Marine Mammal Habitat The proposed activities would result in the placement of 16 permanent structures i.e., the monopiles and associated scour protection supporting
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the WTGs and OSS and a temporary cofferdam in the marine environment.
HRG surveys would not impact marine mammal habitat beyond the noise transmission discussed above, and are, therefore, not discussed further in this section. Based on the best available information, the long-term presence of the WTGs and OSS is not expected to have negative impacts on habitats used by marine mammals, and may ultimately have beneficial impacts on those habitats as a result of increased presence of prey species in the project area due to the WTGs and OSS acting as artificial reefs Russell et al., 2014.
Although studies assessing the impacts of offshore wind development on marine mammals are limited, the repopulation of wind energy areas by harbor porpoises Brandt et al., 2016;
Lindeboom et al., 2011 and harbor seals Lindeboom et al., 2011; Russell et al., 2016 following the installation of wind turbines are promising. SFWF would be located within the migratory corridor BIA for North Atlantic right whales;
however, the 13,000 acre 62.5 km2
lease area occupies a fraction of the available habitat for North Atlantic right whales migrating through the region.
Additionally, SFWF would operate a relatively small number of WTGs 15
compared to the number of foundations in offshore wind farms assessed in e.g., Brandt et al. 2016 range: 3081; mean:
62, making the footprint comparatively small once installation is complete.
There are no known foraging hotspots, or other ocean bottom structures of significant biological importance to marine mammals present in the project area. The proposed activities may have potential short-term impacts to food sources such as forage fish and could also affect acoustic habitat see Auditory Masking discussion above, but meaningful impacts are unlikely.
Therefore, the main impact issue associated with the proposed activity would be temporarily elevated sound levels and the associated direct effects on marine mammals, as discussed previously. The most likely impact to marine mammal habitat occurs from impact and vibratory pile driving effects on marine mammal prey e.g., fish.
Impacts to the immediate substrate during installation of piles are anticipated, but these would be limited to minor, temporary suspension of sediments, which could impact water quality and visibility for a short amount of time, but which would not be expected to have any effects on individual marine mammals. Impacts to substrate are therefore not discussed further.

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Effects to PreySound may affect marine mammals through impacts on the abundance, behavior, or distribution of prey species e.g., crustaceans, cephalopods, fish, zooplankton. Marine mammal prey varies by species, season, and location and, for some, is not well documented. Here, we describe studies regarding the effects of noise on known marine mammal prey.
Fish utilize the soundscape and components of sound in their environment to perform important functions such as foraging, predator avoidance, mating, and spawning e.g., Zelick et al., 1999; Fay, 2009.
Depending on their hearing anatomy and peripheral sensory structures, which vary among species, fishes hear sounds using pressure and particle motion sensitivity capabilities and detect the motion of surrounding water Fay et al., 2008. The potential effects of noise on fishes depends on the overlapping frequency range, distance from the sound source, water depth of exposure, and species-specific hearing sensitivity, anatomy, and physiology.
Key impacts to fishes may include behavioral responses, hearing damage, barotrauma pressure-related injuries, and mortality.
Fish react to sounds which are especially strong and/or intermittent low-frequency sounds, and behavioral responses such as flight or avoidance are the most likely effects. Short duration, sharp sounds can cause overt or subtle changes in fish behavior and local distribution. The reaction of fish to noise depends on the physiological state of the fish, past exposures, motivation e.g., feeding, spawning, migration, and other environmental factors. Hastings and Popper 2005 identified several studies that suggest fish may relocate to avoid certain areas of sound energy.
Additional studies have documented effects of pile driving on fish, although several are based on studies in support of large, multiyear bridge construction projects e.g., Scholik and Yan, 2001, 2002; Popper and Hastings, 2009.
Several studies have demonstrated that impulse sounds might affect the distribution and behavior of some fishes, potentially impacting foraging opportunities or increasing energetic costs e.g., Fewtrell and McCauley, 2012; Pearson et al., 1992; Skalski et al., 1992; Santulli et al., 1999; Paxton et al., 2017. However, some studies have shown no or slight reaction to impulse sounds e.g., Pena et al., 2013; Wardle et al., 2001; Jorgenson and Gyselman, 2009; Cott et al., 2012. More commonly, though, the impacts of noise on fish are temporary.

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