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Federal Register / Vol. 86, No. 195 / Wednesday, October 13, 2021 / Proposed Rules Harp Seal The harp seal is a highly migratory species, and its range can extend from the Canadian Arctic to New Jersey. In U.S. waters, the species has an increasing presence in the coastal waters between Maine and New Jersey and are considered members of the western North Atlantic stock with general presence from January through May Hayes et al., 2019.
Harp seals in Rhode Island are known almost exclusively from strandings approximately 98 percent. Strandings are widespread on ocean-facing beaches throughout Long Island and Rhode Island and the records are almost entirely from spring approximately 68
percent and winter approximately 30
percent. Harp seals are nearly absent in summer and fall. Harp seals also make occasional appearances well inland up rivers Kenny and Vigness-Raposa, 2010. During late winter of 2020, a healthy harp seal was observed hauled out and resting near The Sisters haulout site DeAngelis, 2020.
Hooded Seal The hooded seal is a highly migratory species, and its range can extend from the Canadian Arctic to as far south as Puerto Rico Mignucci-Giannoni and Odell, 2001 as cited in Hayes et al., 2019. In U.S. waters, the species has an increasing presence in the coastal waters between Maine and Florida.
Hooded seals in the U.S. are considered members of the western North Atlantic
stock and generally occur in New England waters from January through May and further south off the southeast U.S. coast and in the Caribbean in the summer and fall seasons McAlpine et al. 1999; Harris et al. 2001; and Mignucci-Giannoni and Odell, 2001 as cited in Hayes et al., 2019.
Hooded seal occurrences in Rhode Island are predominantly from stranding records approximately 99 percent.
They are rare in summer and fall but most common in the area during spring and winter 45 percent and 36 percent of all records, respectively Kenney, 2005; Kenny and Vigness-Raposa, 2010.
Hooded seal strandings are broadly distributed across ocean-facing beaches in Rhode Island and they occasionally occur well up rivers, but less often than harp seals. Hooded seals have been recorded in Narragansett Bay but are considered occasional visitors and are expected to be the least encountered seal species in the bay RICRMC, 2010.
Unusual Mortality Events An unusual mortality event UME is defined under Section 4106 of the MMPA as a stranding that is unexpected; involves a significant dieoff of any marine mammal population;
and demands immediate response.
There are no active UME investigations for species affected in the project area.
Marine Mammal Hearing Hearing is the most important sensory modality for marine mammals
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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
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
Hearing group
Generalized hearing range

Low-frequency LF cetaceans baleen whales
Mid-frequency MF cetaceans dolphins, toothed whales, beaked whales, bottlenose whales
High-frequency HF cetaceans true porpoises, Kogia, river dolphins, cephalorhynchid, Lagenorhynchus cruciger & L. australis.
Phocid pinnipeds PW underwater true seals
Otariid pinnipeds OW underwater sea lions and fur seals

7 Hz to 35 kHz.
150 Hz to 160 kHz.
275 Hz to 160 kHz.
50 Hz to 86 kHz.
60 Hz to 39 kHz.

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Represents the generalized hearing range for the entire group as a composite i.e., all species within the group, where individual species hearing ranges are typically not as broad. Generalized hearing range chosen based on 65 dB threshold from normalized composite audiogram, with the exception for lower limits for LF cetaceans Southall et al. 2007 and PW pinniped approximation.

The pinniped functional hearing group was modified from Southall et al.
2007 on the basis of data indicating that phocid species have consistently demonstrated an extended frequency range of hearing compared to otariids, especially in the higher frequency range Hemila et al. 2006; Kastelein et al.
2009; Reichmuth and Holt, 2013.
For more detail concerning these groups and associated frequency ranges, please see NMFS 2018 for a review of available information. Seven marine
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mammal species three cetacean and four phocid pinniped species have the reasonable potential to co-occur with the proposed construction activities.
Please refer to Table 3. Of the cetacean species that may be present, two are classified as a mid-frequency cetacean i.e., dolphins, and one is classified as a high-frequency cetacean i.e., harbor porpoise.

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Potential Effects of Specified Activities on Marine Mammals and Their Habitat This section includes a summary and discussion of the ways that components of the specified activity may impact marine mammals and their habitat. The Estimated Take section later in this document includes a quantitative analysis of the number of individuals that are expected to be taken by this activity. The Negligible Impact Analysis and Determination section considers the content of this section, the Estimated
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