Quiero saber acerca de...

30422

Federal Register / Vol. 86, No. 108 / Tuesday, June 8, 2021 / Notices
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 3.

TABLE 3MARINE MAMMAL HEARING GROUPS
NMFS, 2018
Generalized hearing range

Hearing group 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.

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.

jbell on DSKJLSW7X2PROD with NOTICES

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. As mentioned previously, five marine mammal species one cetacean and four pinniped all phocid species have the reasonable potential to co-occur with the construction activities. Please refer to Table 2. The only cetacean species that may be present, the harbor porpoise, is classified as a high-frequency cetacean.
Potential Effects of Specified Activities on Marine Mammals and Their Habitat The effects of underwater noise from impact pile driving, vibratory pile driving and removal, drilling, and blasting activities for the Navys modification and expansion of DD1
have the potential to result in Level B
harassment behavioral disturbance, TTS for marine mammal species authorized for take. Level A harassment injury in the form of PTS may also occur in limited numbers of animals. No other forms of Level A harassment would occur, nor would serious injury or mortality. The project would not result in permanent impacts to habitats used directly by marine mammals, such
VerDate Sep<11>2014

16:36 Jun 07, 2021

Jkt 253001

as haulout sites, but may have potential short-term impacts to food sources such as forage fish and impacts to the substrate during installation and removal of piles and as a result of bedrock removal. The Federal Register notice of the proposed IHA 86 FR
18244; April 8, 2021 included a discussion of the potential effects to marine mammals and their associated habitat, therefore, that information is not repeated here; please refer to the notice of proposed IHA for more details.
Estimated Take This section provides an estimate of the number of incidental takes authorized by the IHA, which informed both NMFS 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 be primarily by Level B behavioral harassment, as noise generated from in-water pile
PO 00000

Frm 00022

Fmt 4703

Sfmt 4703

driving vibratory and impact, drilling, and blasting has the potential to result in disruption of behavioral patterns for individual marine mammals. The use of the explosive source i.e., blasting for a very short period each day has the potential to result in Temporary Threshold Shift TTS, which is another form of Level B harassment. There is also some potential for auditory injury Level A harassment to result from impact pile driving and blasting in the form of Permanent Threshold Shift PTS. The required mitigation and monitoring measures see Mitigation Requirements and Monitoring and Reporting Requirements sections are expected to minimize the severity of such taking to the extent practicable.
The primary relevant mitigation measure to minimize Level A
harassment is delaying these activities, to the extent practicable, when any marine mammal is observed in the Level A harassment zones for PTS. While this requirement is expected to minimize take by Level A harassment, NMFS is authorizing takes by Level A harassment in the form of PTS to account for the possibility that marine mammals escape observation in the PTS zone and because the shutdown zones see Mitigation Requirements section are, in most cases, smaller than the Level A
harassment zones. The distances to thresholds associated with the onset of and 50 percent probability of injury to the gastrointestinal tract for harbor porpoises 5 meters m and phocids 9

E:FRFM08JNN1.SGM

08JNN1