Marine Mammals; Incidental Take During Specified Activities; Proposed Incidental Harassment Authorization for Southeast Alaska Stock of Northern Sea Otters in the Queen Charlotte Fault Region, Alaska, 30613-30625 [2021-12134]

Agencies

• Fish and Wildlife Service
• DEPARTMENT OF THE INTERIOR

[Federal Register Volume 86, Number 109 (Wednesday, June 9, 2021)]
[Notices]
[Pages 30613-30625]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2021-12134]



[[Page 30613]]

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DEPARTMENT OF THE INTERIOR

Fish and Wildlife Service

[Docket No. FWS-R7-ES-2020-0132; FXES111607MRG01-212-FF07CAMM00]


Marine Mammals; Incidental Take During Specified Activities; 
Proposed Incidental Harassment Authorization for Southeast Alaska Stock 
of Northern Sea Otters in the Queen Charlotte Fault Region, Alaska

AGENCY: Fish and Wildlife Service, Interior.

ACTION: Notice of receipt of application; proposed incidental 
harassment authorization; request for comments.

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SUMMARY: We, the U.S. Fish and Wildlife Service, in response to a 
request under the Marine Mammal Protection Act of 1972, as amended, 
from the National Science Foundation and the Lamont-Doherty Earth 
Observatory, propose to authorize nonlethal, incidental take by 
harassment of small numbers of the Southeast Alaska stock of northern 
sea otters between July 1, 2021, and August 31, 2021. The applicants 
have requested this authorization for take that may result from high-
energy seismic surveys in the Queen Charlotte Fault region of Southeast 
Alaska. Seismic surveys are being conducted to characterize crustal and 
uppermost mantle velocity structure, fault zone architecture and 
rheology, and seismicity in the Queen Charlotte Fault. We estimate that 
this project may result in the nonlethal incidental take of up to 27 
northern sea otters from the Southeast Alaska stock. This proposed 
authorization, if finalized, will be for up to 49 takes of 27 northern 
sea otters by Level B harassment only. No injury or mortality is 
expected or will be authorized.

DATES: Comments on the proposed incidental harassment authorization and 
draft environmental assessment must be received by July 9, 2021.

ADDRESSES: Document availability: You may view this proposed 
authorization, the application package, supporting information, and the 
lists of references cited herein at https://www.regulations.gov under 
Docket No. FWS-R7-ES-2020-0132, or these documents may be requested as 
described under FOR FURTHER INFORMATION CONTACT.
    Comment submission: You may submit comments on this proposed 
authorization by one of the following methods:
     U.S. mail: Public Comments Processing, Attn: Docket No. 
FWS-R7-ES-2020-0132, U.S. Fish and Wildlife Service, MS: PRB/3W, 5275 
Leesburg Pike, Falls Church, Virginia 22041-3803.
     Electronic submission: Federal eRulemaking Portal at: 
https://www.regulations.gov. Follow the instructions for submitting 
comments to Docket No. FWS-R7-ES-2020-0132. We will post all comments 
at https://www.regulations.gov. You may request that we withhold 
personal identifying information from public review; however, we cannot 
guarantee that we will be able to do so. See Request for Public 
Comments for more information.

FOR FURTHER INFORMATION CONTACT: Marine Mammals Management, U.S. Fish 
and Wildlife Service, MS-341, 1011 East Tudor Road, Anchorage, Alaska, 
99503, by email at [email protected]; or by telephone at 1-800-
362-5148. Persons who use a telecommunications device for the deaf 
(TDD) may call the Federal Relay Service (FRS) at 1-800-877-8339, 24 
hours a day, 7 days a week.

SUPPLEMENTARY INFORMATION:

Background

    Section 101(a)(5)(D) of the Marine Mammal Protection Act of 1972 
(MMPA; 16 U.S.C. 1361, et seq.), authorizes the Secretary of the 
Interior (Secretary) to allow, upon request, the incidental but not 
intentional taking of small numbers of marine mammals of a species or 
population stock by U.S. citizens who engage in a specified activity 
(other than commercial fishing) within a specified region during a 
period of not more than one year. Incidental take may be authorized 
only if statutory and regulatory procedures are followed and the U.S. 
Fish and Wildlife Service (hereafter, ``the Service'' or ``we'') makes 
the following findings: (i) Take is of a small number of marine mammals 
of a species or population stock, (ii) take will have a negligible 
impact on the species or stock, and (iii) take will not have an 
unmitigable adverse impact on the availability of the species or stock 
for subsistence uses by coastal-dwelling Alaska Natives.
    The term ``take,'' as defined by the MMPA, means to harass, hunt, 
capture, or kill, or to attempt to harass, hunt, capture, or kill any 
marine mammal (16 U.S.C. 1362(13)). Harassment, as defined by the MMPA, 
means any act of pursuit, torment, or annoyance that (i) has the 
potential to injure a marine mammal or marine mammal stock in the wild 
(the MMPA defines this as ``Level A harassment''), or (ii) has the 
potential to disturb a marine mammal or marine mammal stock in the wild 
by causing disruption of behavioral patterns, including, but not 
limited to, migration, breathing, nursing, breeding, feeding, or 
sheltering (the MMPA defines this as ``Level B harassment'').
    The terms ``negligible impact,'' ``small numbers,'' and 
``unmitigable adverse impact'' are defined in the Code of Federal 
Regulations at 50 CFR 18.27, the Service's regulations governing take 
of small numbers of marine mammals incidental to specified activities. 
``Negligible impact'' is defined as an impact resulting from the 
specified activity that cannot be reasonably expected to and is not 
reasonably likely to adversely affect the species or stock through 
effects on annual rates of recruitment or survival. ``Small numbers'' 
is defined as a portion of a marine mammal species or stock whose 
taking would have a negligible impact on that species or stock. 
However, we do not rely on that definition, as it conflates the terms 
``small numbers'' and ``negligible impact,'' which we recognize as two 
separate and distinct requirements (see Natural Res. Def. Council, Inc. 
v. Evans, 232 F. Supp. 2d 1003, 1025 (N.D. Cal. 2003)). Instead, in our 
small numbers determination, we evaluate whether the number of marine 
mammals likely to be taken is small relative to the size of the overall 
population. ``Unmitigable adverse impact'' is defined as an impact 
resulting from the specified activity (1) that is likely to reduce the 
availability of the species to a level insufficient for a harvest to 
meet subsistence needs by (i) causing the marine mammals to abandon or 
avoid hunting areas, (ii) directly displacing subsistence users, or 
(iii) placing physical barriers between the marine mammals and the 
subsistence hunters; and (2) that cannot be sufficiently mitigated by 
other measures to increase the availability of marine mammals to allow 
subsistence needs to be met.
    If the requisite findings are made, we will issue an Incidental 
Harassment Authorization (IHA), which sets forth the following: (i) 
Permissible methods of taking; (ii) other means of effecting the least 
practicable impact on marine mammals and their habitat, paying 
particular attention to rookeries, mating grounds, and areas of similar 
significance, and on the availability of marine mammals for taking for 
subsistence uses by coastal-dwelling Alaska Natives; and (iii) 
requirements for monitoring and reporting take.

Summary of Request

    On December 2, 2019, the National Science Foundation and Lamont-
Doherty Earth Observatory (hereafter

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``NSF/L-DEO'' or ``the applicant'') submitted a request to the 
Service's Marine Mammals Management Office (MMM) for authorization to 
take by Level B harassment a small number of northern sea otters 
(Enhydra lutris kenyoni, hereafter ``sea otters'' or ``otters'' unless 
another species is specified) from the Southeast Alaska stock. NSF/L-
DEO expects that take by unintentional harassment may occur during 
their planned high-energy marine seismic surveys at the Queen Charlotte 
Fault (QCF) in the Northeast Pacific Ocean within the U.S. Exclusive 
Economic Zone (EEZ).

Description of Specified Activities and Geographic Region

    The specified activity (the ``project'') consists of Lamont-Doherty 
Earth Observatory's (L-DEO) 2021 Marine Geophysical Surveys by the 
Research Vessel (R/V) Marcus G. Langseth (Langseth) of the QCF in the 
Northeast Pacific Ocean from July 1, 2021, to August 31, 2021. High-
energy two-dimensional (2-D) seismic surveys will be used to 
characterize crustal and uppermost mantle velocity structure, fault 
zone architecture and rheology, and seismicity of the QCF. The 2-D 
seismic surveys will be conducted along transect lines within the area 
of 52-57[deg] N and 131-137[deg] W (Figure 1). Some deviation in actual 
transects, including order of survey operations, could be necessary due 
to poor data quality, inclement weather, or mechanical issues with the 
research vessel or equipment. The surveys are proposed to occur within 
the EEZs of the United States and Canada, including U.S. Federal 
Waters, State of Alaska Waters, and Canadian Territorial Waters ranging 
from 50 to 2,800 meters (m; 164 to 9,186 feet (ft)) in depth. The 
Service cannot and is not authorizing the incidental take of marine 
mammals in waters not under the jurisdiction of the United States. 
Therefore, the Service's calculation of estimated incidental take is 
limited to the specified activity occurring in United States 
jurisdictional waters within the stock's range. The proposed surveys 
are anticipated to last for 36 days, including approximately 27 days of 
seismic operations, approximately 2 days of transit to and from the 
survey area, 3 days for equipment deployment/recovery, and 4 days of 
contingency. The R/V Langseth will likely leave out of and return to 
the port of Ketchikan, AK, during summer 2021.
    The R/V Langseth will tow 4 strings containing an array of 36 
airguns at a depth of 12 m (39 ft), creating a discharge volume of 
approximately 0.11 cubic meter (m\3\; 6,600 cubic inches (in\3\)). The 
peak sound pressure 1 m (3.2 ft) from the center of the airgun array is 
258.6 decibels (Tolstoy et al. 2009). Noise levels herein are given in 
decibels (dB) referenced to 1 [micro]Pa (dB re: 1 [mu]Pa) for 
underwater sound. All dB levels are dBRMS (root-mean-squared 
dB level) unless otherwise noted; dBRMS refers to the square 
root of the average of the squared sound pressure level typically 
measured over 1 second. Other important metrics include the sound 
exposure level (SEL; represented as dB re: 1 [mu]Pa\2\-s), which 
represents the total energy contained within a pulse and considers both 
intensity and duration of exposure, and the peak sound pressure (also 
referred to as the zero-to-peak sound pressure or 0-p). Peak sound 
pressure is the maximum instantaneous sound pressure measurable in the 
water at a specified distance from the source and is represented in the 
same units as the dBRMS sound pressure. See Richardson et 
al. (1995), G[ouml]tz et al. (2009), Hopp et al. (2012), Navy (2014), 
for descriptions of acoustical terms and measurement units in the 
context of ecological impact assessment.
    The seismic array produces broadband energy that ranges from a few 
hertz (Hz) to kilohertz (kHz). However, all but a small fraction of the 
energy is focused in the 10-300 Hz range (Tolstoy et al. 2009). The 
survey will also include the use of a single 655-cubic-centimeter 
(cm\3\; 40-in\3\) airgun that will be used when the full array is 
powered down.
    The receiving system will consist of a 15-kilometer (km; 9.3-mile 
(mi)) hydrophone streamer and approximately 60 short-period and 28 
broadband Ocean Bottom Seismometer (OBS) devices, which will be 
primarily deployed from a second vessel, the Canadian Coast Guard R/V 
John P. Tully (however, R/V Langseth may also deploy OBSs). The OBSs 
will be deployed at approximately 10-km (6.2-mi) intervals with 5-km 
(3.1 mi) spacing over the central 40 km (25 mi) of the fault zone. The 
OBSs have a height and diameter of 1 m (3.2 ft) and an 80-kilogram 
(176-pound) anchor.
    Additional project details may be reviewed in the application 
materials available as described under ADDRESSES or may also be 
requested as described under FOR FURTHER INFORMATION CONTACT.

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[GRAPHIC] [TIFF OMITTED] TN09JN21.038

Description of Marine Mammals in the Specified Activity Area

    The northern sea otter is the only marine mammal under the 
Service's jurisdiction that normally occupies the Northeast Pacific 
Ocean. Sea otters in Alaska are represented by three stocks. Those in 
the Northeast Pacific Ocean belong to the Southeast Alaska stock. Two 
other stocks occur in Southcentral and Southwest Alaska. Detailed 
information about the biology of the Southeast Alaska stock can be 
found in the most recent stock assessment report (USFWS 2014), which 
can be found at: https://www.fws.gov/r7/fisheries/mmm/stock/Revised_April_2014_Southeast_Alaska_Sea_Otter_SAR.pdf.
    Sea otters may be distributed anywhere within the specified project 
area other than upland areas; however, they generally occur in shallow 
water near the shoreline. They are most commonly observed within the 
40-m (131-ft) depth contour (USFWS 2014), although they can be found in 
areas with deeper water. Ocean depth is

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generally correlated with distance to shore, and sea otters typically 
remain within 1 to 2 km (0.62 to 1.24 mi) of shore (Riedman and Estes 
1990). They tend to be found closer to shore during storms, but they 
venture farther out during good weather and calm seas (Lensink 1962; 
Kenyon 1969). In the 14 aerial surveys conducted from 1995 to 2012 in 
Southeast Alaska, 95 percent of otters were found in areas shallower 
than 40 m (131 ft) (Tinker et al. 2019). Areas important to mating for 
the Southeast Alaska stock include marine coastal regions containing 
adequate food resources within the 40-m (131-ft) depth contour.
    The most recent estimate of the number of sea otters in the 
Southeast Alaska stock is 25,584 otters (standard error = 3,679; Tinker 
et al. 2019). The estimate was developed using a Bayesian hierarchical 
modeling framework based on survey and harvest count data. The survey 
data comprised results from 14 aerial surveys conducted in Southeast 
Alaska from 1995 to 2012, totaling more than 20,000 km (12,427 mi) of 
aerial transects. The Service conducted large-scale surveys in 
cooperation with the U.S. Geological Survey in 2003 and 2010 in 
southern Southeast Alaska (from Kake to Duke Island and Cape Chacon) 
and in 2002 and 2011 in northern Southeast Alaska (from Icy Point to 
Cape Ommaney). In these aerial surveys, transects were flown over high-
density otter habitat (<40-m (131-ft) ocean depth) with a spacing of 2 
km (1.2 mi) between transects and low-density otter habitat (40- to 
100-m (131- to 328-ft) ocean depth) with a spacing of 8 km (5 mi) 
between transects.
    Otter densities within the Southeast Alaska stock have been 
calculated for 24 subdivisions (Tinker et al. 2019). The density of 
otters in the affected subdivisions ranged from 0.175 to 1.333 otters 
per km\2\. Distribution of the population during the proposed project 
is likely to be similar to that detected during sea otter surveys, as 
work will occur during the same time of the year that these surveys 
were conducted.
    The documented home range sizes and movement patterns of sea otters 
illustrate the types of movements that could be seen among otters 
responding to the proposed activities. Sea otters are non-migratory and 
generally do not disperse over long distances (Garshelis and Garshelis 
1984). They usually remain within a few kilometers of their established 
feeding grounds (Kenyon 1981). Breeding males stay for all or part of 
the year in a breeding territory covering up to 1 km (0.62 mi) of 
coastline while adult females have home ranges of approximately 8 to 16 
km (5 to 10 mi), which may include one or more male territories. 
Juveniles move greater distances between resting and foraging areas 
(Lensink 1962; Kenyon 1969; Riedman and Estes 1990; Estes and Tinker 
1996). Although sea otters generally remain local to an area, they are 
capable of long-distance travel. Otters in Alaska have shown daily 
movement distances greater than 3 km (1.9 mi) at speeds up to 5.5 km 
per hour (km/hr; 3.4 mi per hour (mi/h)) (Garshelis and Garshelis 
1984).

Potential Effects of the Specified Activities

Exposure of Sea Otters to Noise

    We do not expect the operations outlined in the Description of 
Specified Activities and Geographic Region and described in the 
applicant's petition to lead to take from vessel presence or 
anthropogenic presence. The tracklines for the vessels will not 
physically enter low-density or high-density sea otter habitat. Thus, 
we do not anticipate human-otter interactions that would lead to Level 
B harassment or other forms of take.
    The operations have the potential to result in take of sea otters 
by harassment from noise. Here, we characterize ``noise'' as sound 
released into the environment from human activities that exceeds 
ambient levels or interferes with normal sound production or reception 
by sea otters. The terms ``acoustic disturbance'' or ``acoustic 
harassment'' are disturbances or harassment events resulting from noise 
exposure. Potential effects of noise exposure are likely to depend on 
the distance of the otter from the sound source and the level of sound 
the otter receives. Temporary disturbance or localized displacement 
reactions are the most likely to occur. No lethal take is anticipated, 
nor can the Service authorize lethal take through an Incidental Take 
Authorization. Therefore, none will be authorized.
    Whether a specific noise source will affect a sea otter depends on 
several factors, including the distance between the animal and the 
sound source, the sound intensity, background noise levels, the noise 
frequency, the noise duration, and whether the noise is pulsed or 
continuous. The actual noise level perceived by individual sea otters 
will depend on distance to the source, whether the animal is above or 
below water, atmospheric and environmental conditions as well as 
aspects of the noise emitted.
    From the discussion below, we expect the actual number of otters 
experiencing Level B take due to harassment by noise to be 27 or fewer. 
While individual otters may be taken more than once, the total number 
of incidental takes of sea otters is expected to be less than 49.

Sea Otter Hearing

    The NSF/L-DEO's 36-airgun array will produce sound frequencies that 
fall within the hearing range of sea otters and will be audible to 
animals. Controlled sound exposure trials on southern sea otters (E. l. 
nereis) indicate that otters can hear frequencies between 125 Hz and 38 
kHz with best sensitivity between 1.2 and 27 kHz (Ghoul and Reichmuth 
2014). Aerial and underwater audiograms for a captive adult male 
southern sea otter in the presence of ambient noise suggest the sea 
otter's hearing was less sensitive to high-frequency (greater than 22 
kHz) and low-frequency (less than 2 kHz) sound than terrestrial 
mustelids but was similar to that of a California sea lion (Zalophus 
californianus). However, the subject otter was still able to hear low-
frequency sounds, and the detection thresholds for sounds between 
0.125-1 kHz were between 116-101 dB, respectively. Dominant frequencies 
of southern sea otter vocalizations are between 3 and 8 kHz, with some 
energy extending above 60 kHz (McShane et al. 1995; Ghoul and Reichmuth 
2012).
    Exposure to high levels of sound may cause changes in behavior, 
masking of communications, temporary or permanent changes in hearing 
sensitivity, discomfort, and injury to marine mammals. Unlike other 
marine mammals, sea otters do not rely on sound to orient themselves, 
locate prey, or communicate underwater; therefore, masking of 
communications by anthropogenic sound is less of a concern than for 
other marine mammals. However, sea otters do use sound for 
communication in air (especially mothers and pups; McShane et al. 1995) 
and may avoid predators by monitoring underwater sound (Davis et al. 
1987).
    Thresholds have been developed for some marine mammals above which 
exposure is likely to cause behavioral disturbance and injuries 
(Southall et al. 2007; Finneran and Jenkins 2012; NMFS 2016). However, 
species-specific criteria for sea otters has not been identified. 
Because sea otter hearing abilities and sensitivities have not been 
fully evaluated, we relied on the most similar proxy to evaluate the 
potential effects of noise exposure.
    California sea lions (otariid pinnipeds) have a frequency range of 
hearing most similar to that of southern sea otters (Ghoul and 
Reichmuth 2014) and provide the closest related proxy for

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which data are available. Sea otters and pinnipeds share a common 
mammalian aural physiology (Echteler et al. 1994; Solntseva 2007). Both 
are adapted to amphibious hearing, and both use sound in the same way 
(primarily for in-air communication rather than feeding).

Exposure Thresholds

    The National Marine Fisheries Service (NMFS) established noise 
exposure criteria for identifying underwater noise levels capable of 
causing Level A harassment (injury) of otariid pinnipeds (NMFS 2018). 
Sea otter-specific criteria have not been determined. However, because 
of their biological similarities, we assume that NMFS' noise exposure 
criteria for otariid pinniped injury is a suitable surrogate for sea 
otter impacts. Those criteria are based on estimated levels of sound 
exposure capable of causing a permanent shift in sensitivity of hearing 
(e.g., a permanent threshold shift (PTS) (NMFS 2018)). A PTS occurs 
when noise exposure causes hairs within the inner ear system to die.
    The NMFS (2018) criteria for sound exposure incorporate two metrics 
of exposure: The peak level of instantaneous exposure likely to cause 
PTS, and the cumulative sound exposure level during a 24-hour period 
(SELcum). They also include weighting adjustments for the sensitivity 
of different species to varying frequencies. The PTS-based injury 
criteria were developed from theoretical extrapolation of observations 
of temporary threshold shifts (TTS) detected in lab settings during 
sound exposure trials. Studies were summarized by Finneran (2015). For 
otariid pinnipeds, PTS is predicted to occur at 232 dB peak or 203 dB 
SELcum for impulsive sound, or 219 dB SELcum for 
non-impulsive (continuous) sound.
    The NMFS criteria for take by Level A harassment represents the 
best available information for predicting injury from exposure to 
underwater sound among pinnipeds, and in the absence of data specific 
to otters, we assume these criteria also represent appropriate exposure 
limits for Level A take of sea otters.
    The NMFS (2018) criteria do not identify thresholds for avoidance 
of Level B take. For pinnipeds, the NMFS has adopted a 160-dB threshold 
for Level B take from exposure to impulse noise and a 120-dB threshold 
for continuous noise (NMFS 1998; HESS 1999; NMFS undated). These 
thresholds were developed from observations of mysticete (baleen) 
whales responding to airgun operations (e.g., Malme et al. 1983a, b; 
Richardson et al. 1986, 1995) and from equating Level B take with noise 
levels capable of causing TTS in lab settings.
    We have evaluated these thresholds and determined that the Level B 
threshold of 120-dB for non-impulsive noise is not applicable to sea 
otters. The 120-dB threshold is based on studies conducted by Malme et 
al. in the 1980s, during which gray whales (Eschrichtius robustus) were 
exposed to experimental playbacks of industrial noise. Gray whales are 
in the group of marine mammals believed to be most sensitive to low-
frequency sounds, with an estimated audible frequency range of 
approximately 10 Hz to 30 kHz (Finneran 2015). During the study, 
conducted at St. Lawrence Island, Alaska, Malme et al. (1988) observed 
the behavioral responses of gray whales to the playback of drillship 
noise and concluded that ``exposure to levels of 120 dB or more would 
probably cause avoidance of the area by more than one-half of the gray 
whales.'' Sea otters do not usually occur at St. Lawrence Island, 
Alaska, but similar playback studies conducted off the coast of 
California (Malme 1983a, 1984) included a southern sea otter monitoring 
component (Riedman 1983, 1984). While the 1983 and 1984 studies 
detected probabilities of avoidance in gray whales comparable to those 
reported in Malme et al. (1988), there was no evidence of disturbance 
reactions or avoidance in southern sea otters. Thus, given the 
different range of frequencies to which sea otters and gray whales are 
sensitive, the NMFS 120-dB threshold based on gray whale behavior is 
not appropriate for predicting sea otter behavioral responses, 
particularly for low-frequency sound.
    Although no specific thresholds have been developed for sea otters, 
several alternative behavioral response thresholds have been developed 
for pinnipeds. Southall et al. (2007, 2019) assessed behavioral 
response studies and found considerable variability among pinnipeds. 
The authors determined that exposures between approximately 90 to 140 
dB generally do not appear to induce strong behavioral responses in 
pinnipeds in water. However, they found behavioral effects, including 
avoidance, become more likely in the range between 120 to 160 dB, and 
most marine mammals showed some, albeit variable, responses to sound 
between 140 to 180 dB. Wood et al. (2012) later adapted the approach 
identified in Southall et al. (2007) to develop a probabilistic scale 
for marine mammal taxa at which 10 percent, 50 percent, and 90 percent 
of individuals exposed are assumed to produce a behavioral response. 
For many marine mammals, including pinnipeds, these response rates were 
set at sound pressure levels of 140, 160, and 180 dB, respectively.
    Based on the lack of sea otter disturbance response or any other 
reaction to the 1980's playback studies and the absence of a clear 
pattern of disturbance or avoidance behaviors attributable to 
underwater sound levels up to about 160 dB resulting from low-frequency 
broadband noise, we assume 120 dB is not an appropriate behavioral 
response threshold for sea otters exposed to continuous underwater 
noise.
    Thresholds based on TTS have been used as a proxy for Level B 
harassment (i.e., 70 FR 1871, January 11, 2005; 71 FR 3260, January 20, 
2006; and 73 FR 41318, July 18, 2008). Southall et al. (2007) derived 
TTS thresholds for pinnipeds based on 212 dB peak and 171 dB 
SELcum. Exposures resulting in TTS in pinnipeds were found 
to range from 152 to 174 dB (183 to 206 dB SEL) (Kastak et al. 2005), 
with a persistent TTS, if not a PTS, after 60 seconds of 184 dB SEL 
(Kastak et al. 2008). Kastelein et al. (2012) found small but 
statistically significant TTSs at approximately 170 dB SEL (136 dB, 60 
minutes (min)) and 178 dB SEL (148 dB, 15 min). Finneran (2015) 
summarized these and other studies, and the NMFS (2018) has used the 
data to develop TTS threshold for otariid pinnipeds of 188 dB 
SELcum for impulsive sounds and 199 dB SELcum for 
non-impulsive sounds.
    Exposure to impulsive sound levels greater than 160 dB can elicit 
behavioral changes in marine mammals that may lead to detrimental 
disruption of normal behavioral routines. Thus, using information 
available for other marine mammals as a surrogate and taking into 
consideration the best available scientific information about sea 
otters, the Service has set 160 dB of received underwater sound as a 
threshold for Level B take by disturbance for sea otters for this 
proposed IHA based on the work of Ghoul and Reichmuth (2012a, b), 
McShane et al. (1995), NOAA (2005), Riedman (1983), Richardson et al. 
(1995), and others. Exposure to unmitigated in-water noise levels 
between 125 Hz and 38 kHz that are greater than 160 dB--for both 
impulsive and non-impulsive sound sources--will be considered by the 
Service as Level B take; thresholds for potentially injurious Level A 
take will be 232 dB peak or 203 dB SEL for impulsive sounds and 219 dB 
SEL for continuous sounds (Table 1).
    The area in which underwater noise in the frequency range of sea 
otter hearing will exceed thresholds is termed

[[Page 30618]]

the ``zone of ensonification.'' The ensonification zone in which noise 
levels exceed thresholds for Level A harassment is often referred to as 
the Level A harassment zone. The Level B harassment zone likewise 
includes areas ensonified to thresholds for Level B harassment of sea 
otters and extends from the sound source to the 160-dB isopleth.

  Table 1--Summary of Thresholds for Predicting Level A and Level B Take of Northern Sea Otters From Underwater
                               Sound Exposure in the Frequency Range 125 Hz-38 kHz
----------------------------------------------------------------------------------------------------------------
                                               Injury (Level A) threshold               Disturbance  (Level B)
                                    ------------------------------------------------          threshold
           Marine mammals                                                           ----------------------------
                                          Impulsive \1\         Non-impulsive \1\                All
----------------------------------------------------------------------------------------------------------------
Sea otters.........................  232 dB peak; 203 dB     219 dB SELCUM \2\.....  160 dBRMS.
                                      SELCUM.
----------------------------------------------------------------------------------------------------------------
\1\ Based on National Marine Fisheries Service acoustic exposure criteria for take of otariid pinnipeds (NMFS
  2018).
\2\ SELCUM = cumulative sound exposure level.

Evidence From Sea Otter Studies

    The available studies of sea otter behavior suggest that sea otters 
may be more resistant to the effects of sound disturbance and human 
activities than other marine mammals. For example, at Soberanes Point, 
California, Riedman (1983) examined changes in the behavior, density, 
and distribution of southern sea otters that were exposed to recorded 
noises associated with oil and gas activity. The underwater sound 
sources were played at a level of 110 dB and a frequency range of 50 Hz 
to 20 kHz and included production platform activity, drillship, 
helicopter, and semi-submersible sounds. Riedman (1983) also observed 
the sea otters during seismic airgun shots fired at decreasing 
distances from the nearshore environment (50, 20, 8, 3.8, 3, 1, and 0.5 
nautical miles (nm)) at a firing rate of 4 shots per minute and a 
maximum air volume of 4,070 in\3\. Riedman (1983) observed no changes 
in the presence, density, or behavior of sea otters as a result of 
underwater sounds from recordings or airguns, even at the closest 
distance of 0.5 nm (<1 km or 0.6 mi). However, otters did display 
slight reactions to airborne engine noise. Riedman (1983, 1984) also 
monitored the behavior of sea otters along the California coast while 
they were exposed to a single 1,638-cm\3\ (100-in\3\) airgun and a 
67,006-cm\3\ (4,089-in\3\) airgun array. Sea otters did not respond 
noticeably to the single airgun, and no disturbance reactions were 
evident when the airgun array was as close as 0.9 km (0.6 mi).
    While at the surface, turbulence from wind and waves attenuates 
noise more quickly than in deeper water, reducing potential noise 
exposure (Greene and Richardson 1988; Richardson et al. 1995). 
Additionally, turbulence at the water's surface limits the transference 
of sound from water to air. A sea otter with its head above water will 
be exposed to only a small fraction of the sound energy travelling 
through the water beneath it. The average time spent above the water 
each day resting and grooming varies between male and female sea otters 
and seasonally. Esslinger et al. (2014) found in the summer months 
(i.e., the season when the proposed action will take place), female 
otters foraged for an average of 8.78 hours per day, while male otters 
foraged for an average of 7.85 hours per day. Male and female sea 
otters spent an average of 63 to 67 percent of their summer days at the 
surface resting and grooming. The amount of total time spent at the 
surface may help limit sea otters' exposure during noise-generating 
operations.
    Sea otters generally show a high degree of tolerance to noise. In 
another study using prerecorded sounds, Davis et al. (1988) exposed 
both northern sea otters in Simpson Bay, Alaska, and southern sea 
otters in Morro Bay, California, to a variety of airborne and 
underwater sounds, including a warble tone, sea otter pup calls, killer 
whale calls, air horns, and an underwater noise harassment system 
designed to drive marine mammals away from crude oil spills. The sounds 
were projected at a variety of frequencies, decibel levels, and 
intervals. The authors noted that certain noises could cause a startle 
response and result in movement away from a noise source. However, the 
effects were limited in range (no responses were observed for otters 
approximately 100-200 m (328-656 ft) from the source of the stimuli), 
and otters stopped moving away as a result of the stimuli within hours 
or, at most, 3 to 4 days.
    In locations that lack frequent human activity, sea otters appear 
to have a lower threshold for outward signs of disturbance. Sea otters 
in Alaska have exhibited escape behaviors in response to the presence 
and approach of vessels. Behaviors included diving or actively swimming 
away from a boat, hauled-out sea otters entering the water, and groups 
of sea otters disbanding and swimming in multiple different directions 
(Udevitz et al. 1995). Sea otters in Alaska have also been shown to 
avoid areas with heavy boat traffic but return to those same areas 
during seasons with less traffic (Garshelis and Garshelis 1984). In 
Cook Inlet, otters drifting on a tide trajectory that would have taken 
them within 500 m (0.3 mi) of an active offshore drilling rig tended to 
swim to change their angle of drift to avoid a close approach despite 
near-ambient noise levels from the work (BlueCrest 2013).
    Individual sea otters in Southeast Alaska will likely show a range 
of responses to noise from NSF/L-DEO's survey equipment and vessels. 
Some otters will likely show startle responses, change direction of 
travel, diving, or premature surfacing. Sea otters reacting to survey 
activities may divert time and attention from biologically important 
behaviors, such as feeding. Some animals may abandon the survey area 
and return when the disturbance has ceased. Based on the observed 
movement patterns of wild sea otters (i.e., Lensink 1962; Kenyon 1969, 
1981; Garshelis and Garshelis 1984; Riedman and Estes 1990; Estes and 
Tinker 1996), we expect some individuals, independent juveniles, for 
example, will respond to NSF/L-DEO's proposed survey by dispersing to 
areas of suitable habitat nearby, while others, especially breeding-age 
adult males, will not be displaced by vessels.

Consequences of Disturbance

    The reactions of wildlife to disturbance can range from short-term 
behavioral changes to long-term impacts that affect survival and 
reproduction. When disturbed by noise, animals may respond behaviorally 
(e.g., escape response) or physiologically (e.g., increased heart rate, 
hormonal response) (Harms et al. 1997; Tempel and

[[Page 30619]]

Gutierrez 2003). The energy expense and associated physiological 
effects could ultimately lead to reduced survival and reproduction 
(Gill and Sutherland 2000; Frid and Dill 2002). For example, South 
American sea lions (Otaria byronia) visited by tourists exhibited an 
increase in the state of alertness and a decrease in maternal 
attendance and resting time on land, thereby potentially reducing 
population size (Pavez et al. 2015). In another example, killer whales 
(Orcinus orca) that lost feeding opportunities due to boat traffic 
faced a substantial (18 percent) estimated decrease in energy intake 
(Williams et al. 2006). Such disturbance effects can have population-
level consequences. Increased disturbance rates have been associated 
with a decline in abundance of bottlenose dolphins (Tursiops sp.; 
Bejder et al. 2006; Lusseau et al. 2006).
    These examples illustrate direct effects on survival and 
reproductive success, but disturbances can also have indirect effects. 
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 killer whales and 
eagles, and have a well-developed antipredator response to perceived 
threats. For example, the presence of a harbor seal (Phoca vitulina) 
did not appear to disturb sea otters, but they demonstrated a fear 
response in the presence of a California sea lion by actively looking 
above and beneath the water (Limbaugh 1961).
    Although an increase in vigilance or a flight response is 
nonlethal, a tradeoff occurs between risk avoidance and energy 
conservation. An animal's reactions to noise disturbance may cause 
stress and direct an animal's 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 et al. 2005; 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 
intensity of 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) may influence the type 
and extent of response.

Effects on Habitat and Prey

    Physical and biological features of habitat essential to the 
conservation of sea otters include the benthic invertebrates (urchins, 
mussels, clams, etc.) that otters eat and the shallow rocky areas and 
kelp beds that provide cover from predators. Important sea otter 
habitat in the NSF/L-DEO project area include coastal areas within the 
40-m (131-ft) depth contour where high densities of otters have been 
detected. The MMPA allows the Service to identify avoidance and 
minimization measures for effecting the least practicable impact of the 
specified activity on important habitats. Geophysical surveys conducted 
by NSF/L-DEO may impact sea otters within this important habitat, 
however, the project is not likely to cause lasting effects to habitat.
    The primary prey species for sea otters are sea urchins, abalone, 
clams, mussels, crabs, and squid (Tinker and Estes 1999). When 
preferential prey are scarce, otters will also eat kelp, turban snails 
(Tegula spp.), octopuses (e.g., Octopus spp.), barnacles (Balanus 
spp.), sea stars (e.g., Pycnopodia helianthoides), scallops (e.g., 
Patinopecten caurinus), rock oysters (Saccostrea spp.), worms (e.g., 
Eudistylia spp.), and chitons (e.g., Mopalia spp.) (Riedman and Estes 
1990). A shift to less-preferred prey species may result in more energy 
spent foraging or processing the prey items; however, the impacts of a 
change in energy expenditure is not likely seen at the population level 
(Newsome et al. 2015).
    Several recent reviews and empirical studies have addressed the 
effects of noise on invertebrates (Carroll et al. 2017). Behavioral 
changes, such as an increase in lobster (Homanus americanus) feeding 
levels (Payne et al. 2007), an increase in wild-caught captive reef 
squid (Sepioteuthis australis) avoidance behavior (Fewtrell and 
McCauley 2012), and deeper digging by razor clams (Sinonovacula 
constricta; Peng et al. 2016) have been observed following experimental 
exposures to sound. Physical changes have also been seen in response to 
increased sound levels, including changes in serum biochemistry and 
hepatopancreatic cells in a lobster species (H. americanus; Payne et 
al. 2007) and long-term damage to the statocysts required for hearing 
in several cephalopod species (Andre et al. 2011; Sole et al. 2013).
    The effects of increased sound levels on benthic invertebrate 
larvae have been mixed. Desoto et al. (2013) found impaired embryonic 
development in scallop (Pecten novaezelandiae) larvae when exposed to 
160 dB. Christian et al. (2004) noted a reduction in the speed of egg 
development of bottom-dwelling crabs following exposure to noise; 
however, the sound level (221 dB at 2 m or 6.6 ft) was far higher than 
the proposed seismic array will produce.
    While these studies provide evidence of deleterious effects to 
invertebrates as a result of increased sound levels, Carroll et al. 
(2017) caution that there is a wide disparity between results obtained 
in field and laboratory settings. In experimental settings, changes 
were observed only when animals were housed in enclosed tanks and many 
were exposed to prolonged bouts of continuous, pure tones. We would not 
expect similar results in open marine conditions. It is unlikely that 
noises generated by survey activities will have any lasting effect on 
sea otter prey given the short-term duration of sounds produced by each 
component of the proposed work.

Potential Impacts on Subsistence Uses

    The proposed activities will occur near marine subsistence harvest 
areas used by Alaska Natives from the villages of Pelican, Sitka, and 
Port Alexander. Between 1989 and 2019, approximately 5,617 sea otters 
were harvested from these villages, averaging 187 per year (although 
numbers from 2019 are preliminary). The large majority (95 percent) 
were taken by hunters based in Sitka. However, harvest activity takes 
place in coves where the sounds produced by survey equipment will not 
harass sea otters.
    The proposed project area will not occur in inshore waters and, 
therefore, will avoid significant overlap with subsistence harvest 
areas. NSF/L-DEO's activities will not preclude access to hunting areas 
or interfere in any way with individuals wishing to hunt. NSF/L-DEO 
will coordinate with Native villages and Tribal organizations to 
identify and avoid potential conflicts. If any conflicts are 
identified, NSF/L-DEO will develop a Plan of Cooperation (POC) 
specifying the particular steps necessary to minimize any effects the 
project may have on subsistence harvest.

[[Page 30620]]

Mitigation and Monitoring

    If an IHA for the NSF/L-DEO project is issued, it must specify 
means for affecting the least practicable adverse impact on sea otters 
and their habitat, paying particular attention to rookeries, mating 
grounds, and areas of similar significance and the availability of sea 
otters for subsistence uses by coastal-dwelling Alaska Natives.
    In evaluating what mitigation measures are appropriate to ensure 
the least practicable adverse impact on species or stocks and their 
habitat, as well as subsistence uses, we considered the manner and 
degree to which the successful implementation of the measures are 
expected to achieve this goal. We considered the nature of the 
potential adverse impact being mitigated (likelihood, scope, range), 
the likelihood that the measures will be effective if implemented, and 
the likelihood of effective implementation. We also considered the 
practicability of the measures for applicant implementation (e.g., 
cost, impact on operations).
    To reduce the potential for disturbance from acoustic stimuli 
associated with the activities, the applicants have proposed mitigation 
measures including, but not limited to, the following:
     Development of a marine mammal monitoring and mitigation 
plan;
     Establishment of shutdown and monitoring zones;
     Visual mitigation monitoring by designated Protected 
Species Observers (PSO);
     Site clearance before startup;
     Soft-start procedures;
     Shutdown procedures; and
     Vessel strike avoidance measures.
    These measures are further specified under Proposed Authorization, 
part B. Avoidance and Minimization. The Service has not identified any 
additional mitigation or monitoring measures not already incorporated 
into NSF's request that are practicable and would further reduce 
potential impacts to sea otters and their habitat.

Estimated Incidental Take

Characterizing Take by Level B Harassment

    In the previous section, we discussed the components of the project 
activities that have the potential to affect sea otters. Here, we 
describe and categorize the physiological and behavioral effects that 
can be expected based on documented responses to human activities 
observed during sea otter studies. We also discuss how these behaviors 
are characterized under the MMPA.
    As we described in Evidence from Sea Otter Studies, an individual 
sea otter's reaction to human activity will depend on the otter's prior 
exposure to the activity, the potential benefit that may be realized by 
the individual from its current location, its physiological status, or 
other intrinsic factors. The location, timing, frequency, intensity, 
and duration of the encounter are among the external factors that will 
also influence the animal's response. Intermediate reactions that 
disrupt biologically significant behaviors are considered Level B 
harassment under the MMPA. The Service has identified the following sea 
otter behaviors as indicating possible Level B take:
     Swimming away at a fast pace on belly (i.e., porpoising);
     Repeatedly raising the head vertically above the water to 
get a better view (spyhopping) while apparently agitated or while 
swimming away;
     In the case of a pup, repeatedly spyhopping while hiding 
behind and holding onto its mother's head;
     Abandoning prey or feeding area;
     Ceasing to nurse and/or rest (applies to dependent pups);
     Ceasing to rest (applies to independent animals);
     Ceasing to use movement corridors;
     Ceasing mating behaviors;
     Shifting/jostling/agitation in a raft so that the raft 
disperses;
     Sudden diving of an entire raft; or
     Flushing animals off a haulout.
    This list is not meant to encompass all possible behaviors; other 
situations may also indicate Level B take.
    Reactions capable of causing injury are characterized as Level A 
harassment events. The proposed action is not anticipated to result in 
Level A harassment due to exposure of otters to noise capable of 
causing PTS. However, it is also important to note that, depending on 
the duration and severity of the above-described Level B behaviors, 
such responses could constitute take by Level A harassment. For 
example, while a single flushing event would likely indicate Level B 
harassment, repeatedly flushing sea otters from a haulout may 
constitute Level A harassment.

Calculating Take

    We assumed all animals exposed to underwater sound levels that meet 
the acoustic exposure criteria shown in Table 1 will experience, at a 
minimum, take by Level B harassment due to exposure to underwater 
noise. To estimate the number of otters that may be exposed to these 
sound levels, we worked closely with the applicant to create spatially 
explicit zones of ensonification around the proposed survey transects 
based on expected sound source levels and attenuation models. We 
determined the number of otters present in the ensonification zones 
using density information generated by Tinker et al. (2019) for the 
subgroups that comprise the Southeast Alaska stock.
    Zones of Level A and Level B ensonification were created using the 
proposed R/V Langseth transects along the Southeast Alaskan coast. We 
developed sound level isopleths through acoustic modeling by NSF/L-DEO 
for deep water and an analysis of empirical data collected in a 2012 
survey by the R/V Langseth along the Cascadia Margin in coastal 
Washington (Crone et al. 2014) for intermediate and shallow waters. The 
2012 survey in Cascadia was conducted using a 4-string 0.11-m\3\ 
(6,600-in\3\) airgun array at a tow depth of 9 m (29.5 ft), while the 
proposed activities in Southeast Alaska will use a 0.11-m\3\ (6,600-
in\3\) airgun array at a tow depth of 12 m (39 ft). To account for this 
difference, the applicant used a scaling factor (see the application 
available as described under ADDRESSES for details). The largest 
resulting Level A isopleth calculated from the NSF/L-DEO modeling 
(where sound levels will be greater than 232 dB peak) encompassed areas 
up to 10.6 m (34.7 ft) from the sound source. The Level B isopleth 
(where sound levels will be between 160-231 dB) was based on empirical 
data and encompassed areas up to 12.65 km (7.9 mi) from the sound 
source when the R/V Langseth was in shallow water (<100 m or 328 ft 
ocean depth) and up to 9.2 km (5.7 mi) when the vessel was in 
intermediate depths (100-1,000 m or 328-3,280 ft ocean depth).
    The Level A and Level B isopleths were then used to create 
spatially explicit ensonification zones surrounding the proposed 
project transects using ArcGIS Pro (2018). Using the proximity toolset 
in ArcGIS Pro, we created a buffer with a 45-m (148-ft) width around 
the proposed project transects to account for the Level A ensonified 
area on either side of the 24 m-wide (79 ft-wide) airgun array. To 
determine the Level B ensonified area, points were first placed along 
the proposed project transects every 500 m (0.3 mi). We then used 
bathymetry data to determine ocean depth at each point along the 
transect. We placed a 12.65-km (7.9-mi) buffer around points in water 
less than 100 m (328 ft) deep, and a 9.2-km (5.7-mi) buffer around 
points in water 100-1,000 m (328-3,280 ft)

[[Page 30621]]

deep. The resulting ocean depth-informed ensonification zone was then 
modified to remove ``land shadows'' (marine areas behind land 
features). To do this, we created lines representing ensonification 
that radiated from each point along the proposed project transects. 
Lines were then clipped with a landform shapefile to identify areas 
where underwater sound will be absorbed by land features.
    As we described in Description of Marine Mammals in the Specified 
Area, sea otters are overwhelmingly observed (95 percent) within the 
40-m (131-ft) depth contour, although they can be found in areas with 
deeper water. Thus, high-density sea otter habitat was delineated by 
the 40-m (131-ft) depth contour, and low-density otter habitat was 
between the 40-m and 100-m (131-ft to 328-ft) depth contours. Habitat 
was further divided into subregions established by Tinker et al. (2019) 
as densities of otters in these subregions differed. Otter densities 
for the affected subregions were determined using 2012 abundance 
estimates generated using the Bayesian hierarchical model developed by 
Tinker et al. (2019). Abundance estimates are traditionally generated 
using aerial survey data from high-density habitat (<40 m or 131 ft in 
depth). To calculate the density of otters in low-density habitat (40-
100 m or 131-328 ft ocean depth), we multiplied the density of the 
adjacent high-density habitat by 0.05. The resulting density estimate 
accounts for the five percent of otters found in low-density areas.
    The Level A ensonification zone did not overlap with either high- 
or low-density habitat areas. To determine the amount (km\2\) of Level 
B ensonified habitat in each subregion, the high- and low-density 
habitat shapefiles were clipped using the Level B ensonification 
shapefiles in ArcGIS Pro. The area impacted in each subregion was 
multiplied by the estimated otter density in that region to determine 
the number of otters that will experience Level B sound levels (Table 
2). The total number of takes was predicted by estimating the projected 
days of activity in each subregion using survey start points supplied 
by the applicant. In several areas, the length and direction of the 
proposed survey transects make it highly unlikely that impacts will 
last only one day. In these instances, we estimated two days of 
disturbance, and thus two takes for each otter.

                    Table 2--Estimated Number of Otters Ensonified By Sound Levels Greater Than 160 dB Due to the Proposed Activities
[Level B take was calculated by multiplying the area ensonified in each subregion by that subregion's modeled sea otter density, then multiplying by the
                                                            projected days of ensonification]
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                                          Area                   Projected    Estimated
                     Subreg.                                 Habitat type                 Density       impacted    Estimated     days of       survey
                                                                                      (otters/km\2\)    (km\2\)      take/day       take     total takes
--------------------------------------------------------------------------------------------------------------------------------------------------------
N06.............................................  High (<40 m)......................           0.778         4.66            4            1            4
S05.............................................  High (<40 m)......................           1.333         8.74           12            2           24
S12.............................................  High (<40 m)......................          0.1748         2.56            1            2            2
N06.............................................  Low (40-100 m)....................           0.034        15.69            1            1            1
S01.............................................  Low (40-100 m)....................           0.084        42.31            4            2            8
S05.............................................  Low (40-100 m)....................           0.123        31.32            4            2            8
S12.............................................  Low (40-100 m)....................          0.0092       647.62            1            2            2
                                                 -------------------------------------------------------------------------------------------------------
    Total.......................................  ..................................  ..............  ...........           27  ...........           49
                                                 -------------------------------------------------------------------------------------------------------
        Current Stock Total.....................  ..................................          25,584  ...........  ...........  ...........  ...........
        Percentage of Stock.....................  ..................................  ..............  ...........        0.001  ...........  ...........
--------------------------------------------------------------------------------------------------------------------------------------------------------

Critical Assumptions

    We estimate 49 takes of 27 sea otters by Level B harassment will 
occur due to NSF/L-DEO's proposed high-energy seismic surveys. In order 
to conduct this analysis and estimate the potential amount of Level B 
take, several critical assumptions were made.
    Otter density was calculated using a Bayesian hierarchical model 
created by Tinker et al. (2019), which includes assumptions that can be 
found in the original publication. The most recently available density 
estimates and those used for our analysis were for the year 2012. Low-
density otter populations exhibit a growth rate that is typically 
directly related to resource availability, with growth rates slowing as 
the populations approach carrying capacity (Estes 1990). The 
populations in Southeast Alaska vary in their densities and estimated 
carrying capacities (Tinker et al. 2019), making it difficult to 
predict current density values. Thus, we relied on 2012 density 
estimates to calculate projected take. One subregion within the impact 
area, S12, was not included in the Tinker et al. (2019) published 
densities. To calculate otter density in this subregion, we used the 
2012 aerial survey data that served as the model's primary input. Thus, 
the S12 density estimate does not benefit from the additional 
information included in the Bayesian model provided by Tinker et al. 
(2019).
    Estimation of ensonification zones used sound attenuation models 
that focused on absorption and dispersion rather than reflection and 
refraction. Our models assumed that points of land intercepting high-
level noise will effectively attenuate sound levels above 160 dB, and 
sea otters in areas behind those land features (in land shadows) will 
be exposed to sound less than 160 dB. This assumption is adequate for 
this analysis given the offshore location of the survey transects.
    Finally, we estimated the repeated take of a portion of the otters 
affected by the proposed action due to the presence of the R/V Langseth 
for more than one day. We assume, due to the proposed survey transects, 
start points, and speed of the R/V Langseth, that otters within 
subregions S01, S05, and S12 will be ensonified for two days each. The 
applicant has listed a number of potential yet unanticipated reasons 
the R/V Langseth may remain in one area for an extended period of time, 
including poor data quality, inclement weather, or mechanical issues 
with the research vessel and/or equipment. However, except for the case 
of a reshoot due to poor data quality, the vessel's airgun array (i.e., 
the source of

[[Page 30622]]

take) will not be operational during extended delays of operations.
    We estimate 49 instances of take by Level B harassment of 27 
northern sea otters from the Southeast Alaska stock due to behavioral 
responses or TTS associated with noise exposure. These levels represent 
a small proportion of the most recent stock abundance estimate for the 
Southeast Alaska stock. Take of 27 otters is less than one percent of 
the best available estimate of the current population size of 25,584 
animals in the Southeast Alaska stock (Tinker et al. 2019) (27/
25,584=0.00105). Although an estimated 49 instances of take of 27 
otters by Level B harassment are possible, most events are unlikely to 
have significant consequences for the health, reproduction, or survival 
of affected animals.
    Sea otters exposed to sound project-produced sounds are likely to 
respond with temporary behavioral modification or displacement. Project 
activities could temporarily interrupt the feeding, resting, and 
movement of sea otters. Because activities will occur during a limited 
amount of time and in a localized region, the impacts associated with 
the project are likewise temporary and localized. The anticipated 
effects are primarily short-term behavioral reactions and displacement 
of sea otters near active operations.
    Sea otters that encounter the specified activity may exert more 
energy than they would otherwise due to temporary cessation of feeding, 
increased vigilance, and retreat from the project area. We expect that 
affected sea otters will tolerate this exertion without measurable 
effects on health or reproduction. Most of the anticipated takes will 
be due to short-term Level B harassment in the form of TTS, startling 
reactions, or temporary displacement. Chronic exposure to sound levels 
that cause TTS may lead to PTS (which would constitute Level A injury). 
While more research into the relationship between chronic noise 
exposure and PTS is needed (Finneran 2015), it is likely that the 
transition from temporary effects to permanent cellular damage occurs 
over weeks, months, or years (Southall et al 2019).
    With the adoption of the measures proposed in NSF/L-DEO's 
application and required by this proposed IHA, estimated take was 
reduced.

Findings

Small Numbers

    For small numbers analyses, the statute and legislative history do 
not expressly require a specific type of numerical analysis, leaving 
the determination of ``small'' to the agency's discretion. In this 
case, we propose a finding that the NSF/L-DEO project may result in 
approximately 49 incidental takes of 27 otters from the Southeast 
Alaska stock. This represents less than one percent of the estimated 
stock. Predicted levels of take were determined based on estimated 
density of sea otters in the project area and an ensonification zone 
developed using empirical evidence from a similar geographic area and 
corrected for the methodology proposed by NSF/L-DEO for this project. 
Based on these numbers, we propose a finding that the NSF/L-DEO project 
will take only a small number of animals.

Negligible Impact

    We propose a finding that any incidental take by harassment 
resulting from the proposed project cannot be reasonably expected to, 
and is not reasonably likely to, adversely affect the sea otter through 
effects on annual rates of recruitment or survival and will, therefore, 
have no more than a negligible impact on the Southeast Alaska stock of 
northern sea otters. In making this finding, we considered the best 
available scientific information, including: The biological and 
behavioral characteristics of the species, the most recent information 
on species distribution and abundance within the area of the specified 
activities, the current and expected future status of the stock 
(including existing and foreseeable human and natural stressors), the 
potential sources of disturbance caused by the project, and the 
potential responses of marine mammals to this disturbance. In addition, 
we reviewed applicant provided materials, information in our files and 
datasets, published reference materials, and species experts.
    Sea otters are likely to respond to proposed activities with 
temporary behavioral modification or displacement. These reactions are 
unlikely to have consequences for the long-term health, reproduction, 
or survival of affected animals. Most animals will respond to 
disturbance by moving away from the source, which may cause temporary 
interruption of foraging, resting, or other natural behaviors. Affected 
animals are expected to resume normal behaviors soon after exposure 
with no lasting consequences. Twenty-one otters are estimated to be 
exposed to seismic noise for two days and thus, will have repeated 
exposure. However, permanent (i.e., Level A) injury due to chronic 
sound exposure is estimated to occur at the scale of weeks, months, or 
years (Southall et al. 2019). Some animals may exhibit more severe 
responses typical of Level B harassment, such as fleeing, ceasing 
feeding, or flushing from a haul-out. These responses could have 
temporary, yet significant, biological impacts for affected individuals 
but are unlikely to result in measurable changes in survival or 
reproduction.
    The total number of animals affected and severity of impact is not 
sufficient to change the current population dynamics at the stock 
scale. Although the specified activities may result in approximately 49 
incidental takes of 27 otters from the Southeast Alaska stock, we do 
not expect this level of harassment to affect annual rates of 
recruitment or survival or result in adverse effects on the stock.
    Our proposed finding of negligible impact applies to incidental 
take associated with the proposed activities as mitigated by the 
avoidance and minimization measures identified in NSF/L-DEO's 
mitigation and monitoring plan. These mitigation measures are designed 
to minimize interactions with and impacts to sea otters. These measures 
and the monitoring and reporting procedures are required for the 
validity of our finding and are a necessary component of the proposed 
IHA. For these reasons, we propose a finding that the 2021 NSF/L-DEO 
project will have a negligible impact on the Southeast Alaska stock of 
northern sea otters.

Impact on Subsistence

    We propose a finding that NSF/L-DEO's anticipated harassment will 
not have an unmitigable adverse impact on the availability of the 
Southeast Alaska stock of northern sea otters for taking for 
subsistence uses. In making this finding, we considered the timing and 
location of the proposed activities and the timing and location of 
subsistence harvest activities in the area of the proposed project. We 
also considered the applicant's consultation with subsistence 
communities, proposed measures for avoiding impacts to subsistence 
harvest, and commitment to development of a POC, should any concerns be 
identified.

Required Determinations

National Environmental Policy Act (NEPA)

    Per the National Environmental Policy Act (NEPA; 42 U.S.C. 4321, et 
seq.), the Service must evaluate the effects of the proposed action on 
the human environment. We plan to adopt

[[Page 30623]]

NSF's environmental assessment (EA), as we have preliminarily concluded 
that, as written, the draft EA contains adequate information analyzing 
the effects on the human environment of issuing the IHA. NSF's EA is 
available at https://www.nsf.gov/geo/oce/envcomp/. If the Service 
determines that impacts from issuing the IHA would not significantly 
affect the human environment, we may prepare a Finding of No 
Significant Impact that would conclude the Service's NEPA process.
    We will review all comments submitted in response to this notice as 
indicated above in DATES and ADDRESSES prior to concluding our NEPA 
process or making a final decision on the IHA.

Endangered Species Act (ESA)

    Under the ESA, all Federal agencies are required to ensure the 
actions they authorize are not likely to jeopardize the continued 
existence of any threatened or endangered species or result in 
destruction or adverse modification of critical habitat. The proposed 
activities will occur entirely within the range of the Southeast Alaska 
stock of the northern sea otter, which is not listed as threatened or 
endangered under the ESA. The measures included in the proposed IHA 
will not affect other listed species or designated critical habitat.

Government-to-Government Coordination

    It is our responsibility to communicate and work directly on a 
Government-to-Government basis with federally recognized Tribes in 
developing programs for healthy ecosystems. We are also required to 
consult with Alaska Native Corporations. We seek their full and 
meaningful participation in evaluating and addressing conservation 
concerns for protected species. It is our goal to remain sensitive to 
Alaska Native culture and to make information available to Alaska 
Natives. Our efforts are guided by the following policies and 
directives:
    (1) The Native American Policy of the Service (January 20, 2016);
    (2) the Alaska Native Relations Policy (currently in draft form);
    (3) Executive Order 13175 (January 9, 2000);
    (4) Department of the Interior Secretarial Orders 3206 (June 5, 
1997), 3225 (January 19, 2001), 3317 (December 1, 2011), and 3342 
(October 21, 2016); and
    (5) the Department of the Interior's policies on consultation with 
Tribes and with Alaska Native Corporations.
    We have evaluated possible effects of the proposed activities on 
federally recognized Alaska Native Tribes and organizations. Through 
the IHA process identified in the MMPA, the applicant has presented a 
communication process, culminating in a POC if needed, with the Native 
organizations and communities most likely to be affected by their work. 
NSF/L-DEO has engaged these groups in informational meetings. We invite 
continued discussion, either about the project and its impacts or about 
our coordination and information exchange throughout the IHA/POC 
process.

Proposed Authorization

    We propose to authorize up to 49 incidental takes of 27 Northern 
sea otters from the Southeast Alaska stock. We authorize take limited 
to disruption of behavioral patterns that may be caused by geophysical 
surveys and support activities conducted by NSF/L-DEO in Southeast 
Alaska, from July 1 to August 31, 2021. We anticipate no take by injury 
or death to northern sea otters resulting from these surveys.

A. General Conditions for Issuance of the Proposed IHA

    1. The taking of Northern sea otters from the Southeast Alaska 
stock whenever the required conditions, mitigation, monitoring, and 
reporting measures are not fully implemented as required by the IHA 
will be prohibited. Failure to follow measures specified may result in 
the suspension or revocation of the IHA.
    2. If take exceeds the level or type identified in the proposed 
authorization (e.g., greater than 49 incidents of incidental take of 27 
otters by Level B harassment), the IHA will be invalidated and the 
Service will reevaluate its findings. If project activities cause 
unauthorized take, such as any injury due to seismic noise, acute 
distress, or any indication of the separation of mother from pup, NSF/
L-DEO must take the following actions: (i) Cease its activities 
immediately (or reduce activities to the minimum level necessary to 
maintain safety); (ii) report the details of the incident to the 
Service's MMM within 48 hours; and (iii) suspend further activities 
until the Service has reviewed the circumstances, determined whether 
additional mitigation measures are necessary to avoid further 
unauthorized taking, and notified NSF/L-DEO that it may resume project 
activities.
    3. All operations managers and vessel operators must receive a copy 
of the IHA and maintain access to it for reference at all times during 
project work. These personnel must understand, be fully aware of, and 
be capable of implementing the conditions of the IHA at all times 
during project work.
    4. The IHA will apply to activities associated with the proposed 
project as described in this document and in NSF/L-DEO's amended 
application (LGL 2020). Changes to the proposed project without prior 
authorization may invalidate the IHA.
    5. NSF/L-DEO's IHA application will be approved and fully 
incorporated into the IHA, unless exceptions are specifically noted 
herein or in the final IHA. The application includes:
     NSF/L-DEO's original request for an IHA, dated December 
19, 2019;
     NSF/L-DEO's response to requests for additional 
information from the Service, dated January 22, February 19, and 
February 26, 2020; and
     A revised application, dated October 29, 2020.
    6. Operators will allow Service personnel or the Service's 
designated representative to visit project work sites to monitor 
impacts to sea otters and subsistence uses of sea otters at any time 
throughout project activities so long as it is safe to do so. 
``Operators'' are all personnel operating under the NSF/L-DEO's 
authority, including all contractors and subcontractors.

B. Avoidance and Minimization

    7. Seismic surveys must be conducted using equipment that generates 
the lowest practicable levels of underwater sound within the range of 
frequencies audible to sea otters.
    8. Vessels will not approach within 100 m (328 ft) of individual 
sea otters or 500 m (0.3 mi) of rafts of otters. Operators will reduce 
vessel speed if a sea otter approaches or surfaces within 100 m (328 
ft) of a vessel.
    9. Vessels may not be operated in such a way as to separate members 
of a group of sea otters from other members of the group.
    10. All vessels must avoid areas of active or anticipated 
subsistence hunting for sea otters as determined through community 
consultations.

C. Mitigation During Seismic Activities

    11. Designated trained and qualified PSOs must be employed to 
monitor for the presence of sea otters, initiate mitigation measures, 
and monitor, record, and report the effects of the activities on sea 
otters. NSF/L-DEO is responsible for providing training to PSOs to 
carry out mitigation and monitoring.
    12. NSF/L-DEO must establish mitigation zones for their 2D seismic

[[Page 30624]]

surveys, which generate underwater sound levels at or more than or 160 
dB between 125 Hz and 38 kHz. Mitigation zones must include all in-
water areas where work-related sound received by sea otters will match 
the levels and frequencies above. Mitigation zones will be designated 
as follows:
     Exclusion Zones (EZ) will be established with the 
following minimum radii: 500 m (0.3 mi) from the source for the full 
seismic array and 100 m (328 ft) for the single bolt airgun (655 cm\3\ 
or 40 in\3\).
     A Safety Zone (SZ) is an area larger than the EZ and will 
include all areas within which sea otters may be exposed to noise 
levels that will likely result in Level B take.
     Both the EZ and SZ will be centered on the sound source 
(the seismic array).
     The radius of the SZs are shown in Table 3 (as calculated 
based on modeling techniques described herein and in Appendix A of NSF/
L-DEO's application).

Table 3--Estimated Radial Distances From the Seismic Sound Source to the
                             160-dB Isopleth
  [The area within the isopleth is designated as the Safety Zone (SZ)]
------------------------------------------------------------------------
                                                             Predicted
                                                          distances  (in
         Source and volume            Water depth  (m)    m)  to the 160
                                                           dB  received
                                                            sound level
------------------------------------------------------------------------
Single Bolt airgun, 40 in \3\.....  >1,000 m............         \1\ 431
                                    100-1,000 m.........         \2\ 647
                                    <100 m..............       \3\ 1,041
                                    <1000 m.............       \1\ 6,733
4 strings, 36 airguns, 6600 in \3\  100-1,000m..........       \4\ 9,468
                                    <100m...............      \4\ 12,650
------------------------------------------------------------------------
\1\ Distance is based on L-DEO model results.
\2\ Distance is based on L-DEO model results with a 1.5 x correction
  factor between deep and intermediate water depths.
\3\ Distance is based on empirically derived measurements in the GOM
  with scaling applied to account for differences in tow depth.
\4\ Based on empirical data from Crone et al. (2014); see Appendix A of
  the NSF/L-2012;DEO IHA application for details.

    13. PSOs must conduct visual monitoring of the entire EZ and the 
visible SZ continuously during all seismic work occurring in daylight 
hours.
    14. Prior to seismic work, a ``ramp-up'' procedure must be used to 
increase the levels of underwater sound at a gradual rate.
     A ramp-up will be used at the initial start of airgun 
operations and prior to restarting after any period greater than 30 
minutes (min) without airgun operations, including a power-down or 
shutdown event.
     Visual monitoring must begin at least 30 min prior to and 
continue throughout ramp-up efforts.
     During geophysical work, the number and total volume of 
airguns will be increased incrementally until the full volume is 
achieved.
     The rate of ramp-up will be no more than 6 dB per 5-min 
period. Ramp-up will begin with the smallest gun in the array that is 
being used for all airgun array configurations. During the ramp-up, the 
applicable mitigation zones (based on type of airgun and sound levels 
produced) must be maintained.
     It will not be permissible to ramp-up the full array from 
a complete shutdown in thick fog or at other times when the outer part 
of the EZ is not visible.
     Ramp-up of the airguns will not be initiated if a sea 
otter is sighted within the EZ at any time.
     If sea otters are observed during a ramp-up effort or 
prior to startup, a PSO must record the observation and monitor the 
animal's position until it moves out of visual range. Seismic work may 
commence if, after a full and gradual effort to ramp up the underwater 
sound level, the sea otter is outside of the EZ and does not show signs 
of visible distress (for example, vocalizing, repeatedly spy-hopping, 
or fleeing).
    15. The following actions must be taken in response to sea otters 
in mitigation zones:
     Seismic work will be shut down completely if a sea otter 
is observed within the 500-m (0.3-mi) EZ for the full array or the 100-
m (328-ft) EZ for the 40-cui array.
     When sea otters are observed in visible distress (for 
example, vocalizing, repeatedly spy-hopping, or fleeing), seismic work 
must be immediately shut down or powered down to reduce noise exposure.
     The shutdown procedure will be accomplished within several 
seconds of the determination that a sea otter is in the applicable EZ 
or as soon as practicable considering worker safety and equipment 
integrity.
     Following a shutdown, seismic work will not resume until 
the sea otter has cleared the EZ. The animal will be considered to have 
cleared the EZ if it is visually observed to have left the EZ or has 
not been seen within the EZ for 30 minutes or longer.
     Any shutdown due to sea otters sighted within the EZ must 
be followed by a 30-minute all-clear period and then a standard full 
ramp-up.
     Any shutdown for other reasons resulting in the cessation 
of seismic work for a period greater than 30 minutes must also be 
followed by full ramp-up procedures.
    16. Operators may reduce power to seismic equipment as an 
alternative to a shutdown to prevent a sea otter from entering the EZ. 
A power-down procedure involves reducing the volume of underwater sound 
generated. Vessel speed or course may be altered to achieve the same 
task.
     Whenever a sea otter is detected outside the EZ and, based 
on its position and motion relative to the seismic work, appears likely 
to enter the EZ but has not yet done so, the operator may power down to 
reduce high-level noise exposure.
     When a sea otter is detected in the SZ, an operator may 
choose to power down when practicable to reduce Level B take, but is 
not required to do so.
     During a power-down, the number of airguns in use will be 
reduced to a single mitigation airgun (airgun of small volume such as 
the 655-cm\3\ (40-in\3\) gun), such that the EZ is reduced, making the 
sea otters unlikely to enter the EZ.
     After a power-down, noise-generating work will not resume 
until the sea otter has cleared the EZ for the full airgun array. The 
animal will be

[[Page 30625]]

considered to have cleared the EZ if it is visually observed to have 
left the EZ and has not been seen within the zone for 30 minutes.
    17. Visual monitoring must continue for 30 minutes after the use of 
the acoustic source ceases or the sun sets, whichever is later.

D. Monitoring

    18. Operators shall work with PSOs to apply mitigation measures and 
shall recognize the authority of PSOs up to and including stopping 
work, except where doing so poses a significant safety risk to vessels 
and personnel.
    19. Duties of PSOs include watching for and identifying sea otters, 
recording observation details, documenting presence in any applicable 
monitoring zone, identifying and documenting potential harassment, and 
working with vessel operators to implement all appropriate mitigation 
measures.
    20. A sufficient number of PSOs will be onboard to meet the 
following criteria: 100 percent monitoring coverage during all daytime 
periods of seismic activity; a maximum of four consecutive hours on 
watch per PSO; a maximum of approximately 12 hours on watch per day per 
PSO; and at least one observer each on the source vessel and support 
vessel.
    21. All PSOs will complete a training course designed to 
familiarize individuals with monitoring and data collection procedures. 
A field crew leader with prior experience as a marine mammal observer 
will supervise the PSO team. New or inexperienced PSOs will be paired 
with experienced PSOs so that the quality of marine mammal observations 
and data recording is kept consistent. Resumes for candidate PSOs will 
be made available for the Service to review.
    22. Observers will be provided with reticule binoculars (10x42), 
big-eye binoculars or spotting scopes (30x), inclinometers, and range 
finders. Field guides, instructional handbooks, maps and a contact list 
will also be made available.

E. Measures To Reduce Impacts to Subsistence Users

    23. Prior to conducting the work, NSF/L-DEO will take the following 
steps to reduce potential effects on subsistence harvest of sea otters:
     Avoid work in areas of known sea otter subsistence 
harvest;
     Discuss the planned activities with subsistence 
stakeholders including Southeast Alaska villages and traditional 
councils;
     Identify and work to resolve concerns of stakeholders 
regarding the project's effects on subsistence hunting of sea otters; 
and
     If any concerns remain, develop a POC in consultation with 
the Service and subsistence stakeholders to address these concerns.

F. Reporting Requirements

    24. NSF/L-DEO must notify the Service at least 48 hours prior to 
commencement of activities.
    25. Reports will be submitted to the Service's MMM weekly during 
project activities. The reports will summarize project work and 
monitoring efforts.
    26. A final report will be submitted to the Service's MMM within 90 
days after completion of work or expiration of the IHA. It will 
summarize all monitoring efforts and observations, describe all project 
activities, and discuss any additional work yet to be done. Factors 
influencing visibility and detectability of marine mammals (e.g., sea 
state, number of observers, fog, and glare) will be discussed. The 
report will describe changes in sea otter behavior resulting from 
project activities and any specific behaviors of interest. Sea otter 
observation records will be provided in the form of electronic database 
or spreadsheet files. The report will assess any effects NSF/-DEO's 
operations may have had on the availability of sea otters for 
subsistence harvest and if applicable, evaluate the effectiveness of 
the POC for preventing impacts to subsistence users of sea otters.
    27. Injured, dead, or distressed sea otters that are not associated 
with project activities (e.g., animals found outside the project area, 
previously wounded animals, or carcasses with moderate to advanced 
decomposition or scavenger damage) must be reported to the Service 
within 24 hours of discovery. Photographs, video, location information, 
or any other available documentation shall be provided to the Service.
    28. All reports shall be submitted by email to 
[email protected].
    29. NSF/L-DEO must notify the Service upon project completion or 
end of the work season.

Request for Public Comments

    If you wish to comment on this proposed authorization, the 
applicability of NSF's draft EA to the proposed action, or the proposed 
adoption of NSF's EA, you may submit your comments by any of the 
methods described in ADDRESSES. Please identify if you are commenting 
on the proposed authorization, draft EA, or both, make your comments as 
specific as possible, confine them to issues pertinent to the proposed 
authorization or draft EA, and explain the reason for any changes you 
recommend. Where possible, your comments should reference the specific 
section or paragraph that you are addressing. The Service will consider 
all comments that are received before the close of the comment period 
(see DATES).
    Comments, including names and street addresses of respondents, will 
become part of the administrative record for this proposal. Before 
including your address, telephone number, email address, or other 
personal identifying information in your comment, be advised that your 
entire comment, including your personal identifying information, may be 
made publicly available at any time. While you can ask us in your 
comments to withhold from public review your personal identifying 
information, we cannot guarantee that we will be able to do so.

Gregory Siekaniec,
Regional Director, Alaska Region.
[FR Doc. 2021-12134 Filed 6-8-21; 8:45 am]
BILLING CODE 4333-15-P