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Federal Register / Vol. 86, No. 134 / Friday, July 16, 2021 / Proposed Rules
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consequences for individual animals or populations, and even if some smaller subset of the takes are in the form of a longer several hours or a day and more severe responses, if they are not expected to be repeated over sequential days, impacts to individual fitness are not anticipated. Nearly all studies and experts agree that infrequent exposures of a single day or less are unlikely to impact an individuals overall energy budget Farmer et al., 2018; Harris et al., 2017; King et al., 2015; NAS 2017; New et al., 2014; Southall et al., 2007;
Villegas-Amtmann et al., 2015.
The analyses below in some cases address species and stocks collectively if they occupy the same functional hearing group i.e., low, mid, and highfrequency cetaceans and pinnipeds, share similar life history strategies, and/
or are known to behaviorally respond similarly to stressors. Because some of these groups or species share characteristics that inform the impact analysis similarly, it would be duplicative to repeat the same analysis for each species. In addition, similar species typically have the same hearing capabilities and behaviorally respond in the same manner.
Thus, our analysis below considers the effects of the Navys activities on each affected species even where discussion is organized by functional hearing group and/or information is evaluated at the group level. Where there are meaningful differences between species that would further differentiate the analysis, they are either described within the section or the discussion for those species is included as a separate subsection. Specifically, below we first give broad descriptions of the mysticete, odontocete, and pinniped groups and then differentiate into further groups and species as appropriate.
Mysticetes This section builds on the broader discussion above and brings together the discussion of the different types and amounts of take that different species are likely to incur, the applicable mitigation, and the status of the species to support the negligible impact determinations for each species. We have described above in the General Negligible Impact Analysis section the unlikelihood of any masking having effects that would impact the reproduction or survival of any of the individual marine mammals affected by the Navys activities. We also described in the Potential Effects of Specified Activities on Marine Mammals and their Habitat section of the proposed rule the unlikelihood of any habitat impacts
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having effects that would impact the reproduction or survival of any of the individual marine mammals affected by the Navys activities. There is no predicted non-auditory tissue damage from explosives for any species, and only one take by PTS of any mysticete fin whale annually. Much of the discussion below focuses on the behavioral effects and the mitigation measures that reduce the probability or severity of effects. Because there are species-specific considerations, at the end of the section we break out our findings on a species-specific basis.
In Table 31 above, we indicate for each species the total annual numbers of take by Level A and Level B harassment for mysticetes, and a number indicating the instances of total take as a percentage of abundance in the PMSR
Study Area. Note also that for mysticetes, the abundance within the PMSR Study Area represents only a portion of the species or stock abundance.
No Brydes whales, gray whales Western North Pacific stock, or sei whales would be taken by Level A
harassment or Level B harassment and therefore are not discussed further. For other mysticetes, exposure to explosives will result in small numbers of take: 1
14 Takes by Level B harassment by behavioral disturbance per species, and 47 by TTS per species. One take by PTS will result for fin whales and 0 for all other mysticetes. Based on this information, the majority of the Level B
harassment by behavioral disturbance is expected to be of low severity and of shorter duration. No non-auditory tissue damage from training and testing activities is anticipated or authorized for any species.
Research and observations show that if mysticetes are exposed to impulsive sounds such as those from explosives, they may react in a variety of ways, which may include alerting, startling, breaking off feeding dives and surfacing, diving or swimming away, changing vocalization, or showing no response at all DOD, 2017; Nowacek, 2007;
Richardson, 1995; Southall et al., 2007.
Overall and in consideration of the context for an exposure, mysticetes have been observed to be more reactive to acoustic disturbance when a noise source is located directly in their path or the source is nearby somewhat independent of the sound level Dunlop et al., 2016; Dunlop et al., 2018;
Ellison et al., 2011; Friedlaender et al., 2016; Henderson et al., 2019; Malme et al., 1985; Richardson et al., 1995;
Southall et al., 2007a. Mysticetes have been observed to be more reactive to acoustic disturbance when a noise
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source is located directly on their migration route. Mysticetes disturbed while migrating could pause their migration or route around the disturbance, while males en route to breeding grounds have been shown to be less responsive to disturbances.
Although some may pause temporarily, they will resume migration shortly after the exposure ends. Animals disturbed while engaged in other activities such as feeding or reproductive behaviors may be more likely to ignore or tolerate the disturbance and continue their natural behavior patterns. Because noise from most activities using explosives is short term and intermittent, and because detonations usually occur within a small area, behavioral reactions from mysticetes, if they occur at all, are likely to be short term and of little to no significance.
Noise from explosions is broadband with most energy below a few hundred Hz; therefore, any reduction in hearing sensitivity from exposure to explosive sounds is likely to be broadband with effects predominantly at lower frequencies. Mysticetes that do experience threshold shift i.e., TTS or the one instance of PTS for fin whale from exposure to explosives may have reduced ability to detect biologically important sounds e.g., social vocalizations. For example, during the short period that a mysticete experiences TTS, social calls from conspecifics could be more difficult to detect or interpret, the ability to detect predators may be reduced, and the ability to detect and avoid sounds from approaching vessels or other stressors might be reduced. Any TTS that would occur would be of short duration.
While NMFS can make a negligible impact determination on Navys estimated take numbers, the implementation of mitigation and the sightability of mysticetes especially given their large size reduces the potential for, and severity of, any threshold shift for mysticetes. When we look in ocean areas where the Navy has been intensively training and testing with explosive and other active acoustic sources for decades, there are no data suggesting any long-term consequences to reproduction or survival rates of mysticetes from explosives and other active acoustic sources. All the mysticete species discussed in this section will benefit from the mitigation measures described earlier in the Proposed Mitigation Measures section.
Below we compile and summarize the information that supports our determination that the Navys activities will not adversely affect any species through effects on annual rates of
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