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Federal Register / Vol. 86, No. 38 / Monday, March 1, 2021 / Notices
Potential Impacts of the Proposed Seismic Survey on Northern Sea Otters in Washington and Oregon This section includes a summary of the ways that components of the specified activity may impact sea otters and their habitat. A more in-depth analysis can be found in the Services draft EA USFWS 2020. The Estimated Take by Incidental Harassment of Sea Otters section later in this document includes a quantitative analysis of the number of sea otters that are expected to be taken by this activity. The Negligible Impact section considers the content of the Estimated Take by Incidental Harassment of Sea Otters section, and the Mitigation and Monitoring section, to draw conclusions regarding the likely impacts of these activities on the reproductive success or survivorship of individuals and how those impacts on individuals are likely to impact sea otters.
Otters may be impacted while at the surface by the presence of the vessels traveling to/from the ports to the transects and operating along the transects. Otters underwater may be impacted by the OBS/OBNs as they are deployed and the acoustic effects from the airguns, OBS/SBP/ADCP/
echosounders, and ship noise.
Anthropogenic sounds cover a broad range of frequencies and sound levels and can have a range of highly variable impacts on marine life, from none or minor to potentially severe responses, depending on signal characteristics, received levels, duration of exposure, behavioral context, and whether the sea otter is above or below the water surface. Underwater sounds are not likely to affect sea otters at the surface, due to the pressure release effect. Thus, the susceptibility of sea otters from underwater sounds would be restricted to behaviors during which the head or body is submerged, such as during foraging dives and underwater swimming and, intermittently, during grooming bouts. The proposed activities include underwater sound sources that are impulsive airguns and nonimpulsive OBS/SBP/ADCP/
echosounders and ship noise. Potential effects from impulsive sound sources can range in severity from effects such as behavioral disturbance or tactile perception to physical discomfort, slight to severe injury of the internal organs and the auditory system, or mortality Yelverton et al. 1973; Yelverton and Richmond 1981; Turnpenny and Nedwell 1994; Turnpenny et al. 1994.
Marine mammals exposed to highintensity sound, or to lower-intensity sound for prolonged periods, can
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experience a hearing threshold shift TS, which is the loss of hearing sensitivity at certain frequency ranges Finneran 2015. TS can be permanent PTS, in which case there is physical damage to the sound receptors in the ear i.e., tissue damage and the loss of hearing sensitivity is not fully recoverable, or temporary TTS, in which case there is primarily tissue fatigue and the animals hearing threshold would recover over time Southall et al. 2007. Repeated sound exposure that leads to TTS could cause PTS. Temporary or permanent loss of hearing will occur almost exclusively for noise within an animals hearing range. Given the longer exposure duration necessary to cause PTS as compared with TTS, it is considerably less likely that PTS would occur as a result of project activities because a sea otter could remove itself from exposure by coming to the surface. However, a sea otter underwater in close proximity to the higher level of sound could experience PTS. In addition, otters startled by the sound while foraging in deeper waters will be underwater longer and potentially be exposed to more acoustic sound.
Behavioral disturbance may include a variety of effects, including subtle changes in behavior e.g., minor or brief avoidance of an area, changes in vocalizations, or changes in antipredator response, more conspicuous changes in similar behavioral activities, and more sustained and/or potentially severe reactions, such as displacement from or abandonment of high-quality habitat.
Reactions by sea otters to anthropogenic noise can be manifested as visible startle responses, flight responses flushing into water from haulouts or splashdown alarm behavior in surface-resting rafts, changes in moving direction and/
or speed, changes in or cessation of certain behaviors such as grooming, socializing, or feeding, or avoidance of areas where noise sources are located.
The biological significance of these behavioral disturbances is difficult to predict, especially if the detected disturbances appear minor. However, the consequences of behavioral modification would be expected to be biologically significant if the change affected growth, survival, or reproduction.
Potentially significant behavioral modifications include disturbance of resting sea otters, marked disruption of foraging behaviors, separation of mothers from pups, or disruption of spatial and social patterns sexual segregation and male territoriality.
Foraging is energetically costly to sea otters, more so than other marine
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mammals, because of their buoyancy and swimming style Yeates et al. 2007, thus displacement from or reduction of foraging in high-quality habitat could result in increased energy expenditures.
The energy expense and associated physiological effects could ultimately lead to reduced survival and reproduction Gill and Sutherland 2000;
Frid and Dill 2002.
Disturbances can also have indirect effects; for example, response to noise disturbance is considered a nonlethal stimulus that is similar to an antipredator response Frid and Dill 2002. Sea otters are susceptible to predation, particularly from sharks and eagles, and have a well-developed antipredator response to perceived threats, which includes actively looking above and beneath the water. Although an increase in vigilance or a flight response is nonlethal, a tradeoff occurs between risk avoidance and energy conservation. An animals reactions to noise disturbance may cause stress and direct an animals energy away from fitness-enhancing activities such as feeding and mating Frid and Dill 2002;
Goudie and Jones 2004. For example, southern sea otters in areas with heavy recreational boat traffic demonstrated changes in behavioral time budgeting showing decreased time resting and changes in haul-out patterns and distribution Benham 2006; Maldini et al. 2012.
Chronic stress can also lead to weakened reflexes, lowered learning responses Welch and Welch 1970; van Polanen Petel et al. 2006, compromised immune function, decreased body weight, and abnormal thyroid function Seyle 1979. Changes in behavior resulting from anthropogenic disturbance can include increased agonistic interactions between individuals or temporary or permanent abandonment of an area Barton et al.
1998. The type and extent of response may be influenced by intensity of the disturbance Cevasco et al. 2001, the extent of previous exposure to humans Holcomb et al. 2009, the type of disturbance Andersen et al. 2012, and the age or sex of the individuals Shaughnessy et al. 2008; Holcomb et al.
2009.
Exposure ThresholdsAlthough no specific thresholds have been developed for sea otters, several alternative behavioral response thresholds have been developed for otariid pinnipeds.
Otariid pinnipeds e.g., California sea lions Zalophus californianus have a frequency range of hearing most similar to that measured in a southern sea otter Ghoul and Reichmuth 2014 and provide the closest related proxy for
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