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Federal Register / Vol. 86, No. 33 / Monday, February 22, 2021 / Notices
fish may avoid the immediate area due to the temporary loss of this foraging habitat during pile driving activities.
The duration of fish avoidance of this area after pile driving stops is unknown, but we anticipate a rapid return to normal recruitment, distribution and behavior Hastings and Popper, 2005, Popper and Hastings, 2009. Further, in the In-water Construction Effects on Potential Prey section of the notice of proposed IHA and this notice, NMFS
acknowledges that sound pressure levels SPLs of sufficient strength have been known to cause injury to fish and fish mortality, however, the West Dock area already has limited prey availability, and therefore, even if fish mortality did occur, we would expect that marine mammals would forage elsewhere in the vast foraging area available to marine mammals outside of the immediate project area.
Comment 29: A commenter stated that NMFS underestimated take because its density estimates were wrong. For example, the density estimates for ringed seals were not corrected for unobserved animals. Also, lacking data for the summer and fall, NMFS simply cut density estimates by 50 percent without any rational basis for choosing this percentage.
Importantly, NMFS not only relied on old density data for winter, but it also incorrectly calculated the density.
While NMFS said that the most recent ASAMM surveys did not specify species, it is worth noting that NMFS
relied on proportionality measures for determining the density of other seal species and could have done the same to use newer survey data. For example, for spotted seals NMFS assumes that they are 20 percent of seals and bearded seals are 17 percent of sightings. This same approach could be used to determine seal densities with more recent surveys Clarke et al., 2020.
Response: NMFS worked directly with Dr. Megan Ferguson of the National Marine Mammal Laboratory NMML, one of the authors of the ASAMM reports, to calculate the cetacean densities using the available ASAMM survey data at the time through 2018. NMFS has discussed the more recent 2019 surveys in the Marine Mammal Occurrence and Estimated Take sections of this notice. Further, while we expect that new ASAMM data will likely become available between the time that this IHA is issued and when AGDC begins work, given that the new data would be averaged with previous observations beginning in 2011 for bowhead and gray whale and 2014 for beluga whale, we do not expect that new survey data would have
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more than a minor effect on the densities or estimated take calculations for cetaceans.
Regarding the phocids take estimates, NMFS noted the limited availability of recent data in the notice of proposed IHA. As stated by the commenter, and in the notice of the proposed IHA, the ringed seal densities used to estimate take are not corrected for unobserved animals, and therefore may result in an underestimated density. However, as also noted, the fact that density calculations were conservatively calculated only from sightings observed in water depths greater than 10 ft. 3 m Moulton et al., 2002a, Moulton et al., 2002b, Richardson and Williams, 2003, while the water surrounding the project site is shallow less than 14.2 ft. 4.3 m at West Dock, is likely to result in some degree of overestimation of density.
Also for ringed seals, as stated by the commenter, NMFS estimated that the summer ringed seal density would be 50
percent of the spring density, as also calculated for the Liberty Drilling and Production Island Final Rule 84 FR
70274; December 20, 2019. The surveys were flown in the spring, when the greatest percentage of seals have abandoned their lairs and are hauled out on the ice Kelly et al., 2010 and therefore provide the best available information on ringed seal densities.
During the summer, ringed seals range considerable distances; ringed seals make trips farther offshore to find sea ice during the summer Von Duyke et al., 2020, supporting the expected lower densities in the coastal project area during the summer months in comparison to the spring when ringed seals mostly haul out on the ice.
Therefore, NMFS continued to estimate the summer ringed seal density as 50
percent of the spring ringed seal density in the final IHA. NMFS has appropriately considered the best available, though limited, data regarding the density of ringed seals in both the density and take estimates.
The commenter recommended that NMFS use the 2019 ASAMM surveys Clarke et al., 2020 which were conducted during summer and fall 2019, to apply a method of estimating proportionality of seal species with that data, similar to which NMFS did in the proposed IHA with the Northstar data.
While the ASAMM data is more recent, most ASAMM pinniped observations are not identified to species, and pinniped observations in the ASAMM
surveys include walrus observations.
The reports used in the take calculation in this IHA to determine proportionality of seals in the project area do not all include walrus observations. Therefore,
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it is not appropriate to apply these same proportions to the ASAMM data. NMFS
is unaware of, and the commenter has not offered, more recent alternative sources that are appropriate for calculating proportions of all pinnipeds in the Beaufort Sea, including walrus.
Comment 30: A commenter stated that NMFS decision that take would only occur on 123 days rather than the AGDCs estimated 164 days is arbitrary and underestimates take. NMFS says that AGDC will complete construction during the April to October season and therefore the take will overlap with some piles being installed on the same day and thus only occur on 123 days, and therefore, NMFS also cuts the estimated marine mammal take by 25
percent. But then it allows for a contingency period in case the construction takes longer. The commenter states that activities during the contingency period will have increased impacts that have not been adequately analyzed. Moreover, NMFS
states that AGDC will only operate one hammer at a time during all pile driving; which may mean that not more than one pile is installed on the same day. This underestimates both the negligible impact and small numbers determination.
Response: As stated in the notice of the proposed IHA, AGDC expects to conduct the planned construction between July and October. As described in that notice, NMFS recognizes that AGDC may work outside of this period in their February to April contingency period; however, we expect that if AGDC works during the contingency period, it would be because of construction delays and therefore, days on which they did not work during their planned open water work season, rather than additional construction activity or time, and we expect that construction during that period would be very limited. Therefore, work during the contingency period is already accounted for in the take estimate and is not expected to meaningfully change the number of takes of marine mammals.
Additionally, as stated in the Description of Marine Mammals in the Area of Specified Activities section of the notice of the proposed IHA, ringed seals and bearded seals are the only species of marine mammals that may occur in the project area during the winter/spring contingency period.
Therefore, for all other species, work during the contingency period rather than the open water season would likely reduce the number of takes from the project. Bearded seal densities are expected to be much lower in the
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