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Federal Register / Vol. 86, No. 106 / Friday, June 4, 2021 / Proposed Rules delphinids may choose to bow ride the source vessel; in which case exposure is expected to have no effect on behavior.
For the majority of species, the amount of proposed annual take by Level B
harassment is very low less than 1
percent in relation to the population abundance estimate. For stocks above 1
percent n=3, the amount of proposed annual take by Level B harassment is less than 12 percent.
We have produced what we believe to be conservative estimates of potential incidents of Level B harassment. The procedure for producing these estimates, described in detail in the notice of proposed rulemaking for the initial LOA 80 FR 39542, July 9, 2015
and summarized earlier in the Estimated Take Due to Acoustic Harassment section, represents NMFS
best effort towards balancing the need to quantify the potential for occurrence of Level B harassment due to production of underwater sound with a general lack of information related to the specific way that these acoustic signals, which are generally highly directional and transient, interact with the physical environment and to a meaningful understanding of marine mammal perception of these signals and occurrence in the areas where the NEFSC operates. The sources considered here have moderate to high output frequencies 10 to 200 kHz, generally short ping durations, and are typically focused highly directional to serve their intended purpose of mapping specific objects, depths, or environmental features. In addition, some of these sources can be operated in different output modes e.g., energy can be distributed among multiple output beams that may lessen the likelihood of perception by and potential impacts on marine mammals in comparison with the quantitative estimates that guide our take authorization.
In particular, low-frequency hearing specialists i.e., mysticetes are less likely to perceive or, given perception, to react to these signals. As described previously, NEFSC determined that the EK60, ME 70, and DSM 300 sources comprise the total effective exposures relative to line-kilometers surveyed.
Acoustic disturbance takes are calculated for these three dominant sources. Of these dominant acoustic sources, only the EK 60 can use a frequency within the hearing range of baleen whales 18k Hz. Therefore, Level B harassment of baleen whales is only expected for exposure to the EK60.
The other two dominant sources are outside of their hearing range. There is some minimal potential for temporary
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effects to hearing for certain marine mammals, but most effects would likely be limited to temporary behavioral disturbance. Effects on individuals that are taken by Level B harassment will likely be limited to reactions such as increased swimming speeds, increased surfacing time, or decreased foraging if such activity were occurring, reactions that are considered to be of low severity e.g., Southall et al., 2007. There is the potential for behavioral reactions of greater severity, including displacement, but because of the directional nature of the sources considered here and because the source is itself moving, these outcomes are unlikely and would be of short duration if they did occur. Although there is no information on which to base any distinction between incidents of harassment and individuals harassed, the same factors, in conjunction with the fact that NEFSC survey effort is widely dispersed in space and time, indicate that repeated exposures of the same individuals would be unlikely.
The acoustic sources proposed to be used by NEFSC are generally of low source level, higher frequency, and narrow beamwidth. As described previously, there is some minimal potential for temporary effects to hearing for certain marine mammals, but most effects would likely be limited to temporary behavioral disturbance.
Effects on individuals that are taken by Level B harassment will likely be limited to reactions such as increased swimming speeds, increased surfacing time, or decreased foraging if such activity were occurring, reactions that are considered to be of low severity e.g., Ellison et al., 2012. Individuals may move away from the source if disturbed; however, because the source is itself moving and because of the directional nature of the sources considered here, there is unlikely to be even temporary displacement from areas of significance and any disturbance would be of short duration. The areas ensonified above the Level B
harassment threshold during NEFSC
surveys are extremely small relative to the overall survey areas. Although there is no information on which to base any distinction between incidents of harassment and individuals harassed, the same factors, in conjunction with the fact that NEFSC survey effort is widely dispersed in space and time, indicate that repeated exposures of the same individuals would be very unlikely. The short term, minor behavioral responses that may occur incidental to NEFSC use of acoustic sources, are not expected to result in
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impacts the reproduction or survival of any individuals, much less have an adverse impact on the population.
Similarly, disturbance of pinnipeds by researchers are expected to be infrequent and cause only a temporary disturbance on the order of minutes.
This level of periodic incidental harassment would have temporary effects and would not be expected to alter the continued use of the tidal ledges by seals. Anecdotal reports from previous monitoring show that the pinnipeds returned to the various sites and did not permanently abandon haulout sites after the NEFSC conducted their research activities. Monitoring results from other activities involving the disturbance of pinnipeds and relevant studies of pinniped populations that experience more regular vessel disturbance indicate that individually significant or population level impacts are unlikely to occur.
When considering the individual animals likely affected by this disturbance, only a small fraction of the estimated population abundance of the affected stocks would be expected to experience the disturbance. Therefore, the NEFSC activity cannot be reasonably expected to, and is not reasonably likely to, adversely affect species or stocks through effects on annual rates of recruitment or survival.
Conclusions In summary, as described in the Serious Injury and Mortality section, the proposed takes by serious injury or mortality from NEFSC activities, alone, are unlikely to adversely affect any species or stock through effects on annual rates of recruitment or survival.
Further, the low severity and magnitude of expected Level B harassment is not predicted to affect the reproduction or survival of any individual marine mammals, much less the rates of recruitment or survival of any species or stock. Therefore, the authorized Level B
harassment, alone or in combination with the M/SI authorized for some species or stocks, will result in a negligible impact on the effected stocks and species.
Based on the analysis contained herein of the likely effects of the specified activity on marine mammals and their habitat, and taking into consideration the implementation of the proposed monitoring and mitigation measures, NMFS preliminarily finds that the total marine mammal take from the proposed activity will have a negligible impact on all affected marine mammal species or stocks.

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