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Federal Register / Vol. 86, No. 23 / Friday, February 5, 2021 / Notices Stock occurs south of the project area.
Bottlenose dolphins are expected to occur in the project area in relatively high numbers. They were the second most frequently observed species of dolphin in aerial surveys conducted from 20112015 in the project area, and were observed in every month of the year except January and March Kraus et al., 2016.
Rissos Dolphin Rissos dolphins are distributed worldwide in tropical and temperate seas, and in the Northwest Atlantic occur from Florida to eastern Newfoundland Leatherwood et al.
1976; Baird and Stacey 1991. Off the northeastern U.S. coast, Rissos dolphins are distributed along the continental shelf edge from Cape Hatteras northward to Georges Bank during spring, summer, and autumn CETAP 1982; Payne et al. 1984, with the range extending outward into oceanic waters in the winter Payne et al., 1984. Rissos dolphins are not expected to be common in the project area due to the relatively shallow water depths. In aerial surveys conducted from 20112015 in the project there were only two confirmed sightings of Rissos dolphins, both of which occurred in the spring Kraus et al., 2016.
Harbor Porpoise Harbor porpoises occur from the coastline to deep waters >1800 m;
Westgate et al. 1998, although the majority of the population is found over the continental shelf Hayes et al., 2020. In the project area, only the Gulf of Maine/Bay of Fundy stock of harbor porpoise may be present. This stock is found in U.S. and Canadian Atlantic waters and is concentrated in the northern Gulf of Maine and southern Bay of Fundy region, generally in waters less than 150 m deep Waring et al., 2016. In aerial surveys conducted from 20112015 in the project area, sightings of harbor porpoise occurred from November through May, with the highest number of detections occurring in April and almost none during June September Kraus et al., 2016.

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Harbor Seal The harbor seal is found in all nearshore waters of the North Atlantic
and North Pacific Oceans and adjoining seas above about 30 N Burns, 2009. In the western North Atlantic, harbor seals are distributed from the eastern Canadian Arctic and Greenland south to southern New England and New York, and occasionally to the Carolinas Hayes et al., 2020. Haulout and pupping sites are located off Manomet, MA and the Isles of Shoals, ME Waring et al., 2016.
Based on harbor seal sightings reported at sea in shipboard surveys conducted by the NMFS Northeast Fisheries Science Center from 19952011, harbor seals would be expected to occur in the project area from September to May Hayes et al., 2020. Harbor seals are expected to be relatively common in the project area. Since July 2018, elevated numbers of harbor seal and gray seal mortalities have occurred across Maine, New Hampshire and Massachusetts.
This event has been declared a UME.
Additionally, stranded seals have shown clinical signs as far south as Virginia, although not in elevated numbers; therefore, the UME
investigation now encompasses all seal strandings from Maine to Virginia. Full or partial necropsy examinations have been conducted on some of the seals and samples have been collected for testing. Based on tests conducted thus far, the main pathogen found in the seals is phocine distemper virus. NMFS
is performing additional testing to identify any other factors that may be involved in this UME. Information on this UME is available online at:
www.fisheries.noaa.gov/new-englandmid-atlantic/marine-life-distress/20182019-pinniped-unusual-mortality-eventalong.
Gray Seal There are three major populations of gray seals found in the world: Eastern Canada western North Atlantic stock, northwestern Europe, and the Baltic Sea. Gray seals in the project area belong to the western North Atlantic stock. The range for this stock is from New Jersey to Labrador. Current population trends show that gray seal abundance is likely increasing in the U.S. Atlantic EEZ Hayes et al., 2020.
Although the rate of increase is unknown, surveys conducted since their arrival in the 1980s indicate a steady increase in abundance in both Maine
and Massachusetts Hayes et al., 2020.
It is believed that recolonization by Canadian gray seals is the source of the U.S. population Hayes et al., 2020.
Gray seals are expected to be relatively common in the project area. As described above, elevated seal mortalities, including gray seals, have occurred across Maine, New Hampshire and Massachusetts, and as far south as Virginia, since July 2018. This event has been declared a UME, with phocine distemper virus identified as the main pathogen found in the seals. NMFS is performing additional testing to identify any other factors that may be involved in this UME.
Marine Mammal Hearing Hearing is the most important sensory modality for marine mammals underwater, and exposure to anthropogenic sound can have deleterious effects. To appropriately assess the potential effects of exposure to sound, it is necessary to understand the frequency ranges marine mammals are able to hear. Current data indicate that not all marine mammal species have equal hearing capabilities e.g., Richardson et al., 1995; Wartzok and Ketten, 1999; Au and Hastings, 2008.
To reflect this, Southall et al. 2007, 2019 recommended that marine mammals be divided into functional hearing groups based on directly measured or estimated hearing ranges on the basis of available behavioral response data, audiograms derived using auditory evoked potential techniques, anatomical modeling, and other data. Note that no direct measurements of hearing ability have been successfully completed for mysticetes i.e., low-frequency cetaceans. Subsequently, NMFS 2018
described generalized hearing ranges for these marine mammal hearing groups.
Generalized hearing ranges were chosen based on the approximately 65 decibel dB threshold from the normalized composite audiograms, with the exception for lower limits for lowfrequency cetaceans where the lower bound was deemed to be biologically implausible and the lower bound from Southall et al. 2007 retained. Marine mammal hearing groups and their associated hearing ranges are provided in Table 4.

TABLE 4MARINE MAMMAL HEARING GROUPS
NMFS, 2018
Generalized hearing range

Hearing group Low-frequency LF cetaceans baleen whales

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7 Hz to 35 kHz.