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Federal Register / Vol. 86, No. 134 / Friday, July 16, 2021 / Proposed Rules
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they are expected to be low-level, of short duration not at a level that will impact reproduction or survival.
Altogether, minke whales are not listed under the ESA and with no known population trend. Our analysis suggests that a very small portion of the stock will be taken and disturbed at a low level, with those individuals disturbed likely one day within a year.
No Level A harassment, serious injury, or mortality is anticipated or proposed for authorization. This low magnitude and severity of harassment effects is not expected to result in impacts on the reproduction or survival of any individuals, let alone have impacts on annual rates of recruitment or survival.
Therefore, the total take will not adversely affect this species through impacts on annual rates of recruitment or survival. For these reasons, we have preliminarily determined, in consideration of all of the effects of the Navys activities combined, that the proposed take will have a negligible impact on minke whales.
Odontocetes 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 for each species, 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 this proposed rule the unlikelihood of any habitat impacts 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 PTS
from explosives for most odontocetes, with the exception of a few species, which is discussed below. There is no predicted non-auditory tissue damage from explosives for any species. Much of the discussion below focuses on the behavioral effects and the mitigation measures that reduce the probability or severity of effects. Here, we include information that applies to all of the odontocete species, which are then further divided and discussed in more detail in the following subsections:
Kogia whales; sperm whales; beaked whales; porpoise, and dolphins and small whales. These subsections include
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more specific information about the groups, as well as conclusions for each species represented.
In Table 31 above, we indicate for each species the total annual numbers of take by Level A and Level B harassment for odontocetes, and a number indicating the instances of total take as a percentage of abundance in the PMSR
Study Area. Note also that, for all odontocetes where estimated take is requested, their abundance within the PMSR Study Area represents only a portion of their respective species population.
No Bairds beaked whale, Cuviers beaked whale, Mesoplodont spp. harbor porpoise, bottlenose dolphin California coastal stock, killer whale, or shortfinned pilot whale will be taken by Level A harassment or Level B
harassment and therefore are not discussed further.
Odontocete echolocation occurs predominantly at frequencies significantly higher than 20 kHz, though there may be some small overlap at the lower part of their echolocating range for some species, which means that there is little likelihood that threshold shift, either temporary or permanent would interfere with feeding behaviors.
Many of the other critical sounds that serve as cues for navigation and prey e.g., waves, fish, invertebrates occur below a few kHz and the threshold shift that might be incurred by individuals exposed to explosives would likely be lower frequency 5 kHz or less and spanning a wider frequency range, which could slightly lower an individuals sensitivity to navigational or prey cues, or a small portion of communication calls, for several minutes to hours if temporary or permanently. There is no reason to think that any of the individual odontocetes taken by TTS would incur these types of takes over more than one day, and therefore they are unlikely to result in impacts on reproduction or survival. The number of PTS takes from these activities are very low 0 annually for most, 115 for a few species, and 49
for Dalls porpoise, and as discussed previously because of the low degree of PTS i.e., low amount of hearing sensitivity loss, it is unlikely to affect reproduction or survival of any individuals.
The range of potential behavioral effects of sound exposure on marine mammals generally, and odontocetes specifically, has been discussed in detail previously. There are behavioral patterns that differentiate the likely impacts on odontocetes as compared to mysticetes. First, odontocetes echolocate to find prey, which means
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that they actively send out sounds to detect their prey. While there are many strategies for hunting, one common pattern, especially for deeper diving species, is many repeated deep dives within a bout, and multiple bouts within a day, to find and catch prey. As discussed above, studies demonstrate that odontocetes may cease their foraging dives in response to sound exposure. If enough foraging interruptions occur over multiple sequential days, and the individual either does not take in the necessary food, or must exert significant effort to find necessary food elsewhere, energy budget deficits can occur that could potentially result in impacts to reproductive success, such as increased cow/calf intervals the time between successive calving. Second, while many mysticetes rely on seasonal migratory patterns that position them in a geographic location at a specific time of the year to take advantage of ephemeral large abundances of prey i.e., invertebrates or small fish, which they eat by the thousands, odontocetes forage more homogeneously on one fish or squid at a time. Therefore, if odontocetes are interrupted while feeding, it is often possible to find more prey relatively nearby.
Dwarf Sperm Whales and Pygmy Sperm Whales Kogia speciesThis section builds on the broader odontocete discussion above and brings together the discussion of the different types and amounts of take that these two species are likely to incur, the applicable mitigation, and the status of the species to support the negligible impact determinations for each species.
Some Level A harassment by PTS is anticipated annually 6 takes for Dwarf and pygmy whale, see Table 31.
In Table 31 above, we indicate for each species the total annual numbers of take by Level A and Level B harassment above for dwarf sperm whales and pygmy sperm whales, and a number indicating the instances of total take as a percentage of the abundance within the PMSR Study Area. Note also that, for dwarf and pygmy sperm whales and all odontocetes, the abundance within the PMSR Study Area represents only a portion of the species abundance.
As discussed above, the majority of takes by Level B harassment by behavioral disturbance of odontocetes, and thereby dwarf and pygmy sperm whales, is expected to be in the form of low severity of a shorter duration. As discussed earlier in this section, we anticipate more severe effects from takes when animals are exposed to higher received levels or for longer durations.
Occasional milder Level B harassment
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