Marine Mammals; Incidental Take During Specified Activities; Proposed Incidental Harassment Authorization for Northern Sea Otters in Cook Inlet, Alaska; Availability of Draft Environmental Assessment; Request for Comments, 18330-18342 [2018-08760]

Agencies

• Fish and Wildlife Service
• DEPARTMENT OF THE INTERIOR

[Federal Register Volume 83, Number 81 (Thursday, April 26, 2018)]
[Notices]
[Pages 18330-18342]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2018-08760]


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DEPARTMENT OF THE INTERIOR

Fish and Wildlife Service

[FWS-R7-ES-2018-N010; FXES111607MRG01-189-FF07CAMM00]


Marine Mammals; Incidental Take During Specified Activities; 
Proposed Incidental Harassment Authorization for Northern Sea Otters in 
Cook Inlet, Alaska; Availability of Draft Environmental Assessment; 
Request for Comments

AGENCY: Fish and Wildlife Service, Interior.

ACTION: Notice of receipt of application; proposed incidental 
harassment authorization; availability of draft environmental 
assessment; 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 Hilcorp Alaska, LLC, propose to authorize nonlethal, incidental 
take by harassment of small numbers of northern sea otters between May 
23, 2018, and September 30, 2018. The applicant has requested this

[[Page 18331]]

authorization for take that may result from aircraft overflights in 
Cook Inlet, Alaska. Aerial surveys are needed to collect gravitational 
and magnetic data for oil and gas exploration. This proposed 
authorization, if finalized, will be for take by Level B harassment 
only; no take by injury or death will be authorized. The application 
package and the references cited herein are available for viewing at 
https://www.fws.gov/alaska/fisheries/mmm/iha.htm or may be requested as 
described under FOR FURTHER INFORMATION CONTACT.

DATES: Comments on the proposed incidental harassment authorization and 
draft environmental assessment will be accepted on or before May 29, 
2018.

ADDRESSES: Document availability: You may obtain a copy of the draft 
environmental assessment and a list of the references cited in this 
document by the methods set out below.
    Comment submission: You may submit comments by one of the following 
methods:
     U.S. mail or hand-delivery: Public Comments Processing, 
Attention: Ms. Kimberly Klein, U.S. Fish and Wildlife Service, MS 341, 
1011 East Tudor Road, Anchorage, Alaska 99503;
     Fax: (907) 786-3848, Attention: Ms. Kimberly Klein; or
     Email: [email protected].
    See Request for Public Comments below for more information.

FOR FURTHER INFORMATION CONTACT: Ms. Kimberly Klein, by mail (see 
ADDRESSES); by email at [email protected]; or by telephone at 1-
800-362-5148.

SUPPLEMENTARY INFORMATION: 

Background

    Section 101(a)(5)(D) of the Marine Mammal Protection Act of 1972, 
as amended (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 1 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'') make the 
following findings: (i) Take is of a small number of animals, (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 calls this ``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 calls this ``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 here, 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 may 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 November 2, 2017, Hilcorp Alaska, LLC (hereafter ``Hilcorp'' or 
``the applicant'') submitted a request to the Service's Marine Mammals 
Management Office (MMM) for authorization to take a small number of 
northern sea otters (Enhydra lutris kenyoni, hereafter ``sea otters'' 
or ``otters''). Hilcorp expects that take by unintentional harassment 
may occur during their planned oil and gas exploration activities in 
Cook Inlet, Alaska.
    Hilcorp originally requested an IHA for take of sea otters 
resulting from both aerial and in-water seismic surveys planned for 
April 1, 2018, through June 30, 2018. Aerial surveys measure the 
gravitational and magnetic signatures of the Earth's crust to detect 
subsurface oil and gas deposits. Seismic surveys measure sound waves 
reflected off the sea floor to detect offshore oil and gas deposits. 
Both survey types create noise that may cause sea otters to be 
harassed. Hilcorp later notified the Service that the seismic work will 
not be conducted as part of the 2018 project. On December 22, 2017, 
Hilcorp submitted an amended request withdrawing the seismic work. They 
retained the aerial survey work as originally planned and adjusted the 
proposed dates to the period May 23, 2018, through July 1, 2018. We 
evaluated possible effects of conducting the project between May 23, 
2018, and September 30, 2018, rather than between May 23, 2018, and 
June 30, 2018, in order to provide flexibility should additional time 
be needed to complete the proposed work. We evaluated the effects of 
conducting the same amount of work over a longer period, but we did not 
consider the effects of conducting additional work. There is no 
expected change in the amount of take that would be authorized.

Description of Specified Activities and Geographic Area

    The specified activity (the ``project'') consists of Hilcorp's 2018 
Lower Cook Inlet geophysical survey program. Hilcorp will conduct 
aerial surveys over Cook Inlet between May 23, 2018, and July 1, 2018. 
Data will be collected by

[[Page 18332]]

sensitive equipment mounted aboard aircraft. All data collection is 
passive; no signals will be emitted from the equipment.
    The surveys will be conducted by flying a prescribed pattern of 
transect lines over the Federal and State waters of lower Cook Inlet 
and the shoreline of Alaska between 151.7[deg] and 153.6[deg] W., and 
59.4[deg] and 60.5[deg] N. This is the specified geographic area of the 
project. Two aircraft types will be used, a fixed-wing Basler BT-67 
turboprop (a modified remanufactured Douglas DC-3) and an AS-350 B3 
helicopter. The helicopter will be flown over land and within 4.8 
kilometers (km) (3 miles (mi)) of the coast, while the DC-3 will be 
flown over the offshore waters only. The DC-3 will fly at about 333 
kilometers per hour (km/h) or 207 miles per hour (mi/h) while the AS-
350 will fly at about 100 km/h (62 mi/h).
    Fixed-wing transect lines will be flown in a northeast/southwest 
direction, generally parallel to the coast of Cook Inlet, and will be 
approximately 100 km (62 mi) long. Helicopter transects will run 
roughly east/west and will be about 25 km (15.5 mi) long. Both sets of 
transect lines will be spaced 500 m (0.3 mi) apart and will be 
connected by perpendicular tie lines at 5,000 meters (m) (3.1 mi) 
apart. The fixed-wing survey will be flown at approximately 152 m (500 
feet (ft)) above sea level (ASL), and the helicopter will fly at 91 to 
152 m (300 to 500 ft) above ground level (AGL).
    Aerial surveys are expected to take approximately 14 days total 
within a 2-month period, although work days may not be consecutive due 
to weather or equipment delays. Standard fixed-wing and helicopter 
operational limitations apply, and weather delays, flight ceilings, 
etc., will be at the discretion of the flight contractor.

Description of Marine Mammals in the Specified Area

    The northern sea otter is currently the only marine mammal under 
the Service's jurisdiction that normally occupies Cook Inlet, Alaska. 
Sea otters in Alaska are represented by three stocks. Those in Cook 
Inlet belong to either the southwest Alaska stock or the southcentral 
Alaska stock, depending on whether they occur west or east of the 
center of Cook Inlet, respectively. A third stock occurs in southeast 
Alaska.
    The southwest stock of the northern sea otter corresponds to the 
southwestern Distinct Population Segment (DPS), which was listed as 
threatened under the Endangered Species Act of 1973 (ESA; 16 U.S.C. 
1531, et seq.) on August 9, 2005 (70 FR 46366). Detailed information 
about the biology and conservation status of the listed DPS can be 
found at https://www.fws.gov/alaska/fisheries/mmm/seaotters/otters.htm. 
Stock assessment reports for the listed DPS and non-listed populations 
are available at https://www.fws.gov/alaska/fisheries/mmm/stock/stock.htm.
    Sea otters may occur anywhere within the specified project area 
other than upland areas. The number of sea otters in Cook Inlet was 
estimated from an aerial survey conducted by the Service in cooperation 
with the U.S. Geological Survey (USGS) in May 2017 (USFWS and USGS, 
unpublished data). The sea otter survey was conducted in all areas of 
Cook Inlet south of approximately 60.3[deg] N. within the 40 m (131 ft) 
depth contour, including Kachemak Bay in southeastern Cook Inlet and 
Kamishak Bay in southwestern Cook Inlet. This survey was designed to 
estimate abundance in Cook Inlet while accounting for the variable 
densities and observability of sea otters in the region. Total 
abundance was estimated to be 19,889 sea otters (standard error = 
2,988). Within the project area, the highest densities of sea otters 
were found in the outer Kamishak Bay area, with 3.5 otters per square 
km (km\2\), followed by the eastern shore of Cook Inlet (1.7 otters per 
km\2\). Distribution of the population during Hilcorp's project is 
likely to be similar to that detected during sea otter surveys, as 
their work will be conducted during the same time of year that the sea 
otter surveys were completed.
    Sea otters generally occur in shallow water near the shoreline. 
They are most commonly observed within the 40 m (131 ft) depth contour 
(USFWS 2014a, b) although they can be found in areas with deeper water. 
Depth is 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 remain closer to shore during storms, but 
they venture farther out during good weather and calm seas (Lensink 
1962; Kenyon 1969).
    The documented home range sizes and movement patterns of sea otters 
illustrate the types of movements that could be seen among otters 
responding to Hilcorp's 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 remain for all or part of 
the year in a breeding territory covering up to 1 km (0.62 mi) of 
coastline. 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/h 
(3.4 mi/h) (Garshelis and Garshelis 1984). In eastern Cook Inlet, large 
numbers of sea otters have been observed riding the incoming tide 
northward and returning on the outgoing tide, especially in August. 
They are presumably feeding along the eastern shoreline of Cook Inlet 
during the slack tides when the weather is good and remaining in 
Kachemak Bay during periods of less favorable weather (Gill 2009; 
BlueCrest 2013). In western Cook Inlet, otters appear to move in and 
out of Kamishak Bay in response to seasonal changes in the presence of 
sea ice (Larned 2006).

Potential Effects of the Activities

Exposure of Sea Otters to Noise

    Hilcorp has requested authorization for Level B incidental 
harassment of sea otters. Sea otters in Cook Inlet will be exposed to 
the visual and auditory stimulation associated with Hilcorp's aerial 
surveys. Fixed-wing and helicopter traffic is common in Cook Inlet, and 
the visual presence of aircraft alone is unlikely to cause sea otters 
to be harassed. If sea otters are disturbed, it will more likely be due 
to the airborne noise associated with Hilcorp's flyovers, or possibly, 
the noise in tandem with the sight of the aircraft. Hilcorp's aerial 
surveys will generate noise that is louder and recurs more frequently 
than noise from regular air traffic due to the survey's particular 
aircraft, low flight altitudes, and parallel transect pattern. Flyovers 
may cause disruptions in the sea otter's normal behavioral patterns, 
thereby resulting in incidental take by Level B harassment.
    We expect the actual number of otters experiencing Level B take due 
to harassment by noise to be 578 or fewer. Otters may be taken more 
than once; the total number of incidental takes of sea otters is 
expected to be less than 693. Hilcorp's project, as it is currently 
proposed, will not introduce anything into the water, alter habitat, 
generate sound below the water's surface, or expose any marine mammals 
to direct contact with people, equipment, or vessels. Take will be 
limited to incidental, unintentional Level B

[[Page 18333]]

harassment; no take from other sources is expected.
Noise From Hilcorp's Aircraft
    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, duration, and whether the noise is pulsed or continuous. The 
actual noise level perceived by individual sea otters will depend on 
distance to the aircraft, whether the animal is above or below water, 
atmospheric and environmental conditions, and the operational 
conditions of the aircraft.
    Noise production has been measured for the DC-3 and the AS-350. 
Noise levels herein are given in decibels (dB) referenced to 20 
[micro]Pa for airborne sound. All dB levels are dBRMS unless 
otherwise noted; dBRMS refers to the root-mean-squared dB 
level, the square root of the average of the squared Sound Pressure 
Level (SPL) typically measured over 1 second. See Richardson et al. 
(1995), G[ouml]tz et al. (2009), Hopp et al. (2012), Navy (2014), or 
similar resources for descriptions of acoustical terms and measurement 
units in the context of ecological impact assessment.
    Standardized noise testing has been conducted for compliance with 
Federal Aviation Administration (FAA) regulations at 14 CFR part 36. 
During these tests, the DC-3 produced noise levels of 82.4 
dBEPN (Effective Perceived Noise level) during takeoff, and 
91.9 dBEPN on approach (USDOT 2012). Other field-testing of 
the DC-3 produced a peak SPL of 90 dBPEAK during level 
flyovers at 265 km/hr (165 mi/hr) measured at 305 m (1,000 ft) from the 
flightpath (Ollerhead 1971; Fink 1977). During a gliding flight path at 
152.4 m (500 ft) altitude and airspeeds around 278 km/hr (173 mi/h), a 
maximum of 79.6 dB was recorded (Healy 1974). See 14 CFR part 36 for 
calculation of dBEPN from field measurements of sound.
    Documented noise levels of the AS-350 recorded for FAA compliance 
measured 89.8 to 91.1 dBEPN during takeoff and 91.3 to 91.4 
dBEPN on approach; level straight-line flyovers at an 
altitude of 305 m (1,000 ft) produced noise levels from 86.8 to 87.1 
dBEPN (USDOT 2012). Newman and Rickley (1979) reported 91.2 
dBEPN on approach, 89.2 dBEPN during takeoff, and 
87.2 dBEPN during level flyovers at approximately 150 m (492 
ft) altitude. Falzarano and Levy (2007) reported that overflights by 
the AS-350 at a distance of 122 m (400 ft) AGL produced an FAA-
certified 83.5 dBA Sound Exposure Level (SEL; normally referenced to 20 
[mu]Pa\2\-s).
    Turboprop aircraft such as the DC-3 are generally perceived to 
produce noise levels 10 to 20 dB higher than helicopters, which in turn 
are 10 to 20 dB noisier than piston aircraft (Ollerhead 1971). Based on 
information on aircraft type, airspeed, and altitude, we assume the 
sound levels generated by Hilcorp's aircraft during aerial gravitation 
and magnetic surveys will not exceed a maximum of approximately 90 dB 
at the water's surface.
Sea Otter Hearing
    Sound frequencies produced by Hilcorp's aircraft will fall within 
the hearing range of sea otters and will be audible to animals during 
flyovers. Controlled sound exposure trials on southern sea otters (E. 
l. nereis) indicate that otters can hear frequencies between 125 hertz 
(Hz) and 38 kilohertz (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) sounds than 
terrestrial mustelids but similar to that of a sea lion. 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). During FAA testing, the test aircraft 
produced sound at all frequencies measured (50 Hz to 10 kHz) (Healy 
1974; Newman and Rickley 1979). At frequencies centered at 5 kHz, jets 
flying at 300 m (984 ft) produced \1/3\ octave band noise levels of 84 
to 124 dB, propeller-driven aircraft produced 75 to 90 dB, and 
helicopters produced 60 to 70 dB (Richardson et al. 1995).
    Exposure to high levels of sound may cause changes in behavior, 
masking of communications, temporary or permanent changes in hearing 
sensitivity, discomfort, and injury. Species-specific criteria for sea 
otters have not been identified for preventing harmful exposures to 
sound. Thresholds have been developed for other marine mammals, above 
which exposure is likely to cause behavioral disturbance and injuries 
(Southall et al. 2007; Finneran and Jenkins 2012; NMFS 2016). Because 
sea otter hearing abilities and sensitivities have not been fully 
evaluated, we relied on the closest related proxy to evaluate the 
potential effects of noise exposure.
    California sea lions (Zalophus californianus) (otariid pinnipeds) 
have shown a frequency range of hearing most similar to that of 
southern sea otters (Ghoul and Reichmuth 2014) and provide the closest 
related proxy for 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 communication rather than 
feeding).
Exposure Thresholds
    Noise exposure thresholds have been established by the National 
Marine Fisheries Service (NMFS) for identifying underwater noise levels 
capable of causing Level A harassment (injury) of marine mammals, 
including otariid pinnipeds (NMFS 2016). Those thresholds 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 2016)). Thresholds for non-impulse sound are based on cumulative 
SEL (SELcum) during a 24-hour period and include weighting adjustments 
for the sensitivity of different species to varying frequencies. These 
injury thresholds were developed from Temporary Threshold Shifts (TTS) 
detected in lab settings during sound exposure trials. Studies were 
summarized by Finneran (2015). 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).
    The NMFS (2016) guidance neither addresses thresholds for 
preventing injury or disturbance from airborne noise, nor provides 
thresholds for avoidance of Level B take. However, it does provide a 
framework for assessment of potential consequences of noise exposure. 
Exposure to airborne noise has been estimated to cause TTS in the 
California sea lion after 1.5 to 50 minutes of exposure to sound at 
SPLs of 94 to 133 dB; TTS onset was estimated to occur at 159 dB SELcum 
(Kastak et al. 2004, 2007). The U.S. Navy adopted 159 dB SELcum as a 
TTS threshold level and used it to estimate onset of PTS and set a 
threshold for otariid pinnipeds at 168 dB SELcum (Finneran and Jenkins, 
2012). Southall et al. (2007) reviewed the literature and recommended 
dual injury thresholds for PTS for sea lions exposed to discrete non-
pulsed airborne noise of 149 dBPEAK and 172.5 dB SELcum.
    Acoustic thresholds can be reached from acute exposure to high 
sound levels or from long periods of exposure to lower levels. Both the 
sound levels and durations of exposure from

[[Page 18334]]

Hilcorp's aircraft will depend primarily on a sea otter's distance from 
the transect during a flyover. Airborne sound attenuation rates are 
affected by characteristics of the atmosphere and topography, but can 
be conservatively generalized for line sources (such as flight lines) 
over acoustically ``hard'' surfaces like water (rather than ``soft'' 
surfaces like snow) by a loss of 3 dB per doubling of distance from the 
source. At this attenuation rate, a sound registering 90 dB directly 
below a flyover at 91 to 152 m (300 to 500 ft) ASL will attenuate to 80 
dB in 1 to 1.5 km (0.6 to 0.9 mi). The same noise level will attenuate 
to 68 dB (the upper range of ambient conditions near Cook Inlet per 
Blackwell (2005)) within 15 to 24 km (9 to 15 mi).
    At rates of speed proposed for Hilcorp's aircraft (333 km/hr (207 
mi/h) for the DC-3 and 100 km/hr (62 mi/h) for the AS-350 helicopter) 
sea otters will be exposed to sound levels between 80 and 90 dB for up 
to 1 minute per flyover by either aircraft. Sea otters will experience 
sound levels less than 80 dB but greater than ambient for up to 2.5 
minutes as the DC-3 passes by, and up to 13.5 minutes when the AS-350 
helicopter flies by. About 15 to 18 passes per day will be required to 
complete the survey during the allotted period. This scenario suggests 
that otters within the helicopter survey area could potentially be 
exposed to continual sound levels that are higher than ambient for the 
duration of each day's work.
    No value representing the upper limit of safety for prolonged 
exposure has been identified for sea otters, but a sea lion exposed to 
an SPL of 94 dB for 12 minutes did not show a statistically significant 
TTS (Kastak et al. 2007). In humans, prolonged exposure to 80 dBA is 
unlikely to cause hearing loss (dBA is the decibel level weighted at 
frequencies sensitive to human hearing). Although the decibel levels 
here have not been weighted for the sensitivity of sea otters to 
specific frequencies, weighting adjustments generally reduce the dB 
level of sounds at frequencies outside of the range of greatest 
sensitivity. We therefore assume prolonged exposure to 80 dB 
(unweighted) will not cause TTS in sea otters.
    We then considered the potential effect of repeated 1-minute 
exposures to SPLs greater than 80 dB. The SELcum of a sea otter 
positioned below the aircraft can be estimated based on the duration of 
exposure and sound level at the location of the animal. Cumulative SEL 
is linearly related to the SPL and logarithmically related to the 
exposure time, meaning that SELcum will increase or decrease on a 1:1 
basis with increasing or decreasing SPL, and increase or decrease by 3 
dB for each doubling or halving of exposure time, respectively 
(Finneran et al. 2015). Based on this relationship, we can estimate the 
SELcum from flyover exposures. For example, using a simple equation SPL 
+ 10log10 (duration of exposure, expressed in seconds) (NMFS 
2016), SELcum may reach 120 dB for the anticipated activities (90 + 
10log10 (1,080) [ap] 120.3 dB, where 1,080 represents 18 
passes at 60 seconds each). This specific model is generally used in 
underwater applications, and it assumes a constant received sound level 
that does not change over space and time (e.g., Urick 1983; ANSI 1986; 
Madsen 2005). Additionally, Hilcorp's flight lines do not cover the 
same area multiple times, so sea otters are unlikely to be exposed to 
sound from all passes in a day. Therefore, this model is expected to 
overestimate a sea otter's cumulative exposure to sound during 
flyovers, but it demonstrates that the airborne noise generated by 
Hilcorp's aircraft during gravitational and magnetic surveys will not 
cause TTS in sea otters, even for an otter located at the closest point 
of approach during multiple flyovers.

Response to Disturbance

    The potential that Hilcorp's aerial surveys will cause take due to 
changes in the hearing abilities (TTS or PTS) of sea otters is 
negligible. However, the project may result in Level B take by 
harassment due to an individual's reaction to project noise. The actual 
number of takes will depend on the number of times individual sea 
otters perceive Hilcorp's activities and respond with a significant 
behavioral change in a biologically important activity.
Direct and Indirect Effects
    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 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). In an example described by Pavez et al., (2015), 
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. 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, Limbaugh (1961) reported that sea otters were 
apparently undisturbed by the presence of a harbor seal (Phoca 
vitulina), but they were quite concerned with the appearance of a 
California sea lion. They demonstrated their fear by actively looking 
above and beneath the water when a sea lion was swimming nearby.
    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 haulout 
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 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

[[Page 18335]]

disturbance (Andersen et al., 2012), and the age and/or sex of the 
individuals (Shaughnessy et al. 2008; Holcomb et al., 2009). Despite 
the importance of understanding the effects of disturbance from sound, 
few controlled experiments or field observations have been conducted on 
sea otters to address this topic.
Evidence From Sea Otter Studies
    The available studies of sea otter behavior indicate that sea 
otters are somewhat more resistant to the effects of sound than other 
marine mammals (Riedman 1983, 1984; Ghoul et al., 2012a, b; Reichmuth 
and Ghoul 2012). Southern sea otters off the California coast showed 
only mild interest in boats passing within hundreds of meters and 
appeared to have habituated to boat traffic (Riedman 1983; Curland 
1997). Southern sea otters in an area with frequent railroad noise 
appeared to be relatively undisturbed by pile-driving activities, many 
showing no response and generally reacting more strongly to passing 
vessels than to the sounds of pile driving equipment (ESA 2016). When 
sea otters have displayed behavioral disturbance in response to 
acoustic stimuli, these responses were short-lived, and the otters 
quickly become habituated and resumed normal activity (Ghoul et al., 
2012b). Sea otters may be less sensitive to noise because whereas many 
marine mammals depend on acoustic cues for vital biological functions 
such as orientation, communication, locating prey, and avoiding 
predators, sea otters do not rely on sound to orient themselves, locate 
prey, or communicate underwater.
    In locations without frequent human activity, sea otters appear to 
be more easily disturbed. Sea otters in Alaska have shown signs of 
disturbance (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 were observed riding the tides past a new offshore 
drilling platform while drilling was being conducted; otters drifting 
on a trajectory that would have taken them within 500 m (0.3 mi) of the 
rig tended to swim to change their angle of drift to avoid a close 
approach although noise levels from the work were near the ambient 
level of underwater noise (BlueCrest 2013).
    Disturbances of sea otters due to aircraft have been observed in 
Alaska. Biologists conducting aerial surveys for the Service and the 
USGS to determine sea otter abundance between 2008 and 2015 reported 
disturbances of sea otters (USFWS and USGS unpublished data). Bodkin 
and Udevitz (1999) conducted sea otter surveys and reported 
disturbances caused by various flight patterns. Sea otter disturbances 
were also reported between 2009 and 2012 during aerial surveys 
conducted to determine bird and marine mammal distribution in Cook 
Inlet (ABR, Inc. 2010-2013). From all sources, the mean rate of 
disturbance during aerial surveys was 18.3 percent (2,288 out of 30,611 
sea otters observed), ranging from 8.0 to 29.2 percent (USFWS and USGS 
unpublished data, Bodkin and Udevitz 1999, ABR, Inc. 2010-2013). Most 
of the disturbances involved otters diving, swimming out of the area, 
or swimming erratically during overflights. Flying a more intensive 
search pattern (circling overhead) or flying at lower altitudes 
resulted in greater disturbance rates than straight-line flights at 
higher altitudes. Among these surveys, the reported rate of Level B 
harassment was below 0.1 percent (0 to 0.8 percent); 18 confirmed Level 
B takes were recorded among 19,500 animals observed (USFWS and USGS 
unpublished data).
    Some degree of disturbance is possible from Hilcorp's activities. 
Individual sea otters in Cook Inlet will show a range of responses to 
noise from Hilcorp's aircraft. Some 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, and others) we expect some individuals, independent juveniles, 
for example, will respond to Hilcorp's proposed activities by 
dispersing to areas of suitable habitat nearby, while others, 
especially breeding-age adult males, will not be displaced by 
overflights.
    Some otters will likely show startle responses, change direction of 
travel, or dive. Sea otters reacting to overflights may divert time and 
attention from biologically important behaviors, such as feeding. Some 
effects may be undetectable in observations of behavior, especially the 
physiological effects of chronic noise exposure. Air traffic, 
commercial and recreational, is routine in Cook Inlet. Some sea otters 
in the area of activity may become habituated to noise caused by the 
project due to the existing continual air traffic in the area and will 
have little, if any, reaction to flyovers. However, noise levels from 
aircraft will be louder and will recur more frequently than that from 
regular air traffic in the region.

Effects on Habitat

    Habitat areas of significance for sea otters exist near the project 
area. Sea otter critical habitat was designated under the ESA (74 FR 
51988, October 8, 2009). In Cook Inlet, critical habitat occurs along 
the western shoreline south of approximately Redoubt Point. It extends 
from mean high tide line out to 100 m (328.1 ft) from shore or to the 
20 m (65.6 ft) depth contour. Physical and biological features of 
critical habitat essential to the conservation of sea otters include 
the benthic invertebrates (urchins, mussels, clams, etc.) eaten by 
otters and the shallow rocky areas and kelp beds that provide cover 
from predators. Other important habitat in the Hilcorp project area 
includes outer Kamishak Bay between Augustine Island and Iniskin Bay 
within the 40 m (131 ft) depth contour where high densities of otters 
have been detected. Sea otters within this important area and within 
the critical habitat may be affected by aerial surveys conducted by 
Hilcorp. The MMPA allows the Service to identify avoidance and 
minimization measures for effecting the least practicable impact of the 
specified activity on important habitats. However, the project, as 
currently proposed, will have no effect on habitat.

Mitigation and Monitoring

    If an IHA for Hilcorp's project is issued, it must specify means 
for effecting the least practicable impact on sea otters and their 
habitat, paying particular attention to habitat areas of significance, 
and on the availability of sea otters for taking for subsistence uses 
by coastal-dwelling Alaska Natives. Hilcorp has proposed to minimize 
the effects of their action by maintaining minimum flight altitudes, 
providing training to aircraft pilots to identify and monitor otters, 
reporting observations of otters to the Service, and coordinating with 
subsistence hunting communities. These measures are specified under 
Proposed Authorization, part B. Avoidance and Minimization.
    We evaluated various alternatives to these proposed mitigation 
measures to determine the means of effecting the least practicable 
impact to sea otters and their availability for subsistence use. 
Decreasing the survey length and increasing flight altitudes were not 
considered practicable for accomplishing the magnetic and

[[Page 18336]]

gravitational survey. Hilcorp suggested temporarily increasing flight 
altitude or diverting away from the flight path when groups of sea 
otters were encountered. We evaluated this option, but at the requisite 
flight speeds and initial altitudes, it is unlikely that otters can be 
spotted until the survey aircraft is too close to avoid disturbance. 
Evasive maneuvers such as an abrupt increase in altitude or change in 
direction will result in increased noise production due to the 
additional engine power and changes in aircraft configuration necessary 
for these tasks. These maneuvers would probably increase, rather than 
decrease, the level of noise exposure. Additionally, the pilot would 
later need to return to the same flight path to complete the transect, 
potentially encountering the same otters and causing another 
disturbance.

Estimated Incidental Take

Characterizing Take by Level B Harassment

    An individual sea otter's reaction will depend on its prior 
exposure to low-flying aircraft, its need or desire to be in the 
particular area, 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.
    Relatively minor reactions such as increased vigilance or a short-
term change in direction of travel are not likely to disrupt 
biologically important behavioral patterns and are not considered take 
by harassment as defined by the MMPA. These types of responses typify 
the most likely reactions of the majority of sea otters that will be 
exposed to Hilcorp's activities. Extreme behavioral reactions capable 
of causing injury are characterized as Level A harassment events, which 
are unlikely to result from the proposed project and will not be 
authorized. Examples include separation of mothers from young or 
repeatedly flushing sea otters from a haulout.
    Intermediate reactions that disrupt biologically significant 
behaviors and may potentially result in decreased fitness for the 
affected animal meet the criteria for Level B harassment under the 
MMPA. In 2014, the Service 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 along the shoreline;
     Ceasing mating behaviors;
     Shifting/jostling/agitation in a raft so that the raft 
disperses;
     Sudden diving of an entire raft;
     Flushing animals off a haulout.
    This list is not meant to encompass all possible behaviors, other 
situations may also indicate Level B take.

Estimating Exposure Rates

    To estimate the numbers of sea otters likely to experience Level B 
take, we first calculated the number of otters in Cook Inlet that occur 
within the Hilcorp project area. Number of otters was calculated from 
density multiplied by project area. Density was estimated according to 
region in Cook Inlet. Density data for Kamishak and the East side of 
Cook Inlet along the shore of the Kenai Peninsula was derived from 
aerial surveys conducted in May 2017 (USFWS and USGS, unpublished 
data). Surveys were not conducted for central Cook Inlet in 2017, and 
2017 surveys did not yield useful results for western Cook Inlet north 
of Kamishak, so the density for those regions was derived from the 2002 
surveys conducted by Bodkin et al. (2003) and corrected for population 
growth proportional to the growth rate of Cook Inlet as a whole, as 
determined from comparison of the 2002 and 2017 surveys. Density values 
(in otters per km\2\) were 1.7 in East Cook Inlet (excluding Kachemak 
Bay and the outer Coast of Kenai Peninsula south and east of Seldovia), 
3.5 in Kamishak Bay, and 0.026 in West and Central Cook Inlet.
    Hilcorp's project area boundary contains about 6,625 km\2\ (2,558 
square mi (mi\2\)) excluding land. Of this area, 1,039 km\2\ (401 
mi\2\) is in East Cook Inlet, 830 km\2\ (310 mi\2\) in Kamishak Bay, 
and 1,870 km\2\ (722 mi\2\) in West and Central Cook Inlet. The total 
number of otters within the Hilcorp project area was calculated to be 
4,753 otters ((1,039 x 1.7) + (831 x 3.53) + (1,870 x 0.026) [ap] 
4,753).

Predicting Behavioral Response Rates

    Although we cannot predict the outcome of each encounter between a 
sea otter and one of Hilcorp's aircraft, it is possible to consider the 
most likely reactions. The best predictor of behavioral response for 
sea otters exposed to airborne sound is the distance at which the 
encounter occurs in relation to the sound level produced.
    To predict the total number of Level B takes, we distributed a 
questionnaire to professional biologists with experience conducting 
aerial surveys in regions with sea otters. The survey requested 
information about the respondent, the aircraft used, the flight 
altitude, and the reactions of otters to aircraft. Six useable 
responses were received in the time allotted; four were from 
professional sea otter biologists who have each conducted more than 
five sea otter surveys.
    Survey responses reported that, on average, 26 percent of sea 
otters located directly below the aircraft appear to react to the 
presence of the aircraft. Survey respondents reported that at a point 
on the water's surface 100 m (328 ft) perpendicular to the flight line, 
the disturbance rate dropped to just below 20 percent. At 250 m (820 
ft) from the flight line, just over 10 percent of sea otters reacted to 
aircraft, and at 500 m (1,640 ft) away, less than seven percent 
reacted. At 1,000 m (3,281 ft), less than one percent of otters were 
disturbed by aircraft overflights.
    We then evaluated whether Hilcorp's project will expose sea otters 
to comparable noise levels to those during surveys conducted by 
questionnaire respondents. Hilcorp will use an AS-350 and a modified 
DC-3. Hilcorp's aerial surveys will be conducted at 92 to 152 m (300 to 
500 ft) for the AS-350 and 152 m (500 ft) for the DC-3. Small fixed-
wing aircraft such as the Piper PA-18 Super Cub, Cessna 185 and 206, 
and 18-GCBC Scout were most often used by questionnaire respondents and 
were generally flown at 92 to 152 m (300 to 500 ft) ASL. Larger twin-
engine aircraft were also used, including the Aero Commander and the 
Partenavia P.68. Questionnaire respondents indicated the use of the 
Partenavia P.68 flown at 61 m (200 ft) ASL during surveys for southern 
sea otters. Helicopters used during sea otter surveys included the 
Hughes 500 and Hughes 369 flown at 92 to 152 m (300 to 500 ft) ASL.
    Field tests for the Hughes 500 have demonstrated a maximum overall 
SPL of 87.6 dB as measured at ground level on the centerline of the 
flight path during straight-line flyovers at 150 m (492 ft) altitude 
and at a stable airspeed of 111 km/h (69 mi/h) (Newman and Rickley 
1979). The Hughes 500 and the AS-350 should generally produce a similar 
level of noise at the same altitude, although the AS-350 will be

[[Page 18337]]

slightly louder. Indeed, Newman et al. 1982 reported signatures for the 
AS-350 that were about 5 to 7 dB higher than those of the Hughes 500.
    The Aero Commander was the largest aircraft used during sea otter 
surveys. It produces a maximum of 75.4 dB during a gliding flight path 
at 152.4 m (500 ft) altitude and airspeeds up to 324 km/hr (201 mi/hr) 
(Healy 1974). The Aero Commander is expected to be roughly 5 dB quieter 
than the DC-3. The second largest aircraft, the Partenavia, produced 
noise levels measured for FAA compliance up to 78.2 dBA during flyovers 
at 305 m (1000 ft). The Piper PA-18 produced 65.9 dBA, and the Cessna 
206 ranged from 75.4 to 79.4 dBA at 305 m (1,000 ft) (USDOT 2012).
    For the Partenavia, back calculating from FAA standards using an 
estimated 3 to 6 dB loss per doubling of distance indicates this 
aircraft at 200 ft ASL may have exposed sea otters to 85 to 92 dB while 
a Cessna 206 at 300 ft would have generated from 84.6 to 89.8 dB. Both 
of these are within the possible range of noise produced by the DC-3. 
The Piper PA-18 flying at 91 m (300 ft) would likely expose sea otters 
to sound pressure levels ranging from 71.1 to 76.4 dB.
    In conclusion, there is overlap in the sound levels that will be 
produced by Hilcorp's project and those generated during sea otter 
surveys conducted by questionnaire respondents. Therefore, disturbance 
rates from Hilcorp's activities will be adequately represented by the 
rates of sea otter disturbance reported by biologists.

Calculating Take

    We then used the estimated response rates of sea otters, as 
described by questionnaire responses provided by professional 
biologists, to predict the total number of possible reactions that 
could result from Hilcorp's project. To do this, we multiplied the size 
of the project area by the density of otters and the probability of 
disturbance according to the distance from the flight line. Details 
follow.
    The area within which sea otters may be disturbed was calculated on 
a per day basis in ArcGIS[supreg] using transect lines provided by 
Hilcorp. The total transect length was divided into 14 polygons 
representing 4 helicopter and 10 fixed-wing ``flight days.'' The ends 
of fixed-wing transects were connected by a line of the minimum length 
necessary to circle a 1-nautical-mile perimeter, based on the turn 
radius of a DC-3. The ends of helicopter transects were joined with 
straight lines to connect one to the next. Both fixed-wing and 
helicopter transect lines were connected in a zigzag pattern to 
simulate minimal off-transect travel routes. Transects in each of the 
14 flight days were then buffered to represent the area per day of 
potential disturbance effects.
    Multi-ring buffers were created around transect lines to represent 
zones with variable probabilities of disturbance determined by distance 
from the center line of the flight path as measured along the water's 
surface to a point directly below the aircraft. Rings were established 
at distance categories of 20, 100, 250, 500, 750, and 1,000 m (66, 328, 
820, 1,640, 2,461, and 3,281 ft) from the transect lines. Overlapping 
rings within the same distance categories were merged within, but not 
between flight days. The total area of each ring was summed in 
ArcGIS[supreg]. Table 1 shows the area calculated within each ring by 
distance from the transect.
    Next, the density of otters within each region in Cook Inlet was 
multiplied by the area within each transect buffer to represent the 
number of otters potentially affected by Hilcorp's project according to 
categorical distance from the centerline of the nearest overflight. 
Table 2 shows the calculated numbers of otters within each transect 
buffer ring by region in Cook Inlet.
    A probability multiplier was then applied to each ring to represent 
the probability of disturbance for otters within a given distance from 
a transect. Alternately, the multipliers represent the declining sound 
exposure levels with increasing distance from an aircraft flight line. 
As described previously, the multipliers were identified by polling sea 
otter biologists regarding the likelihood of disturbance during 
overflights when otters were located at each respective distance from 
the centerline of a survey flight path. The questionnaire responses 
were averaged to determine the appropriate probability multiplier for 
each distance category. The maximum distance at which a reaction could 
possibly be expected was predicted to be 1,000 m (3,281 ft). This 
distance was supported in the responses given by survey respondents. 
Multipliers are given in Table 3 as the proportion of otters in each 
distance category that are likely to be disturbed during flyovers.
    Finally, the total number of disturbances in response to Hilcorp's 
flyovers was estimated by multiplying the number of otters within each 
distance category (Table 2) by the applicable probability multiplier 
for each category of distance from the centerline of a survey flight 
path (Table 3). The total number of disturbances was then summed by 
region in Cook Inlet and by stock. A total of 693 behavioral responses 
are likely. Of these, 523 and 170 will occur among otters belonging to 
the southwestern and southcentral stocks, respectively.
    To estimate the number of individual otters taken, we again 
calculated the area within each distance category; but this time, we 
merged polygons both within and between flight days to remove repeated 
exposures. All other calculations were repeated. We estimated 578 
individual otters could be disturbed by Hilcorp's project. Of these, 
410 belong to the southwest stock, and 168 belong to the southcentral 
stock (Table 5).
    Table 1. Area (km\2\) of potential aircraft disturbance within 
specified distances (m) from aircraft flight lines by region of Cook 
Inlet. Area within each distance category was measured in 
ArcGIS[supreg] by creating concentric buffers of the specified width 
extending outward from the aircraft flight lines. Area is given by 
region within Cook Inlet (CI) and by stock (SC=Southcentral, 
SW=Southwestern).

----------------------------------------------------------------------------------------------------------------
                                                     Area (km\2\) within distance categories
  Region in cook inlet (stock)  --------------------------------------------------------------------------------
                                     20 m        100 m        250 m        500 m        750 m         1000 m
----------------------------------------------------------------------------------------------------------------
Kamishak (SW)..................        74.10       292.75       533.01       104.80        95.45           92.57
Upper West (SC)................       119.67       476.95       897.08       188.25       174.83          172.86
East Cook Inlet (SW)...........        50.20       198.65       371.20        52.59        47.08           47.34
Central CI (SC)................        87.44       348.42       648.00       124.23       116.10          109.88
Central CI (SW)................       121.49       484.49       901.24       164.51       157.44          151.76
----------------------------------------------------------------------------------------------------------------


[[Page 18338]]

    Table 2. Estimated number of otters within specified distances (m) 
of Hilcorp's proposed flight lines by region of Cook Inlet. Numbers 
were estimated by multiplying density of sea otters in each region by 
area within distance categories given in Table 1.

--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                              Density                                  Distance categories
               Region in Cook Inlet (stock)                 (sea otters --------------------------------------------------------------------------------
                                                             per km\2\)      20 m        100 m        250 m        500 m        750 m         1000 m
--------------------------------------------------------------------------------------------------------------------------------------------------------
Kamishak (SW).............................................        3.530       261.58      1033.48      1881.66       369.98       336.97          326.78
Upper West (SC)...........................................        0.026         3.11        12.39        23.30         4.89         4.54            4.49
East Cook Inlet (SW)......................................        1.705        85.57       338.65       632.79        89.66        80.25           80.69
Central CI (SC)...........................................        0.026         2.27         9.05        16.83         3.23         3.02            2.85
Central CI (SW)...........................................        0.026         3.16        12.58        23.41         4.27         4.09            3.94
--------------------------------------------------------------------------------------------------------------------------------------------------------

    Table 3. Estimated probability of behavioral responses of sea 
otters by distance from flight line, as measured outward across the 
water surface from a point directly below the flight line transect.

----------------------------------------------------------------------------------------------------------------
       Distance (meters)              20          100          250          500          750           1000
----------------------------------------------------------------------------------------------------------------
Probability....................        0.258        0.198        0.107        0.068        0.030           0.004
----------------------------------------------------------------------------------------------------------------

    Table 4. Estimated number of behavioral responses (Level B takes) 
calculated as the total number of disturbances potentially caused by 
aircraft overflights according to distance from the flightpath. Entries 
were calculated by multiplying values in Table 2 by those in Table 3.

--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                                                       Total number of disturbances by
             Distance (meters)                  20          100         250         500         750        1000                    region
--------------------------------------------------------------------------------------------------------------------------------------------------------
Region (Stock):
    Kamishak (SW).........................       67.58      204.97      200.71       25.29       10.11        1.31  509.96.
    Upper West (SW).......................        0.80        2.46        2.49        0.33        0.14        0.02  6.23.
    East Cook Inlet (SC)..................       22.11       67.17       67.50        6.13        2.41        0.32  165.63.
    Central CI (SC).......................        0.59        1.79        1.80        0.22        0.09        0.01  4.50.
    Central CI (SW).......................        0.82        2.50        2.50        0.29        0.12        0.02  6.24.
                                           -------------------------------------------------------------------------------------------------------------
        Total Number of Disturbances, by         91.89      278.89      274.99       32.26       12.87        1.68  Overall Total: 692.56.
         Distance from Flightpath.
--------------------------------------------------------------------------------------------------------------------------------------------------------

    Totals by Stock SW: 522.43: SC: 170.13.
    Table 5. Estimated number of otters experiencing disturbance (Level 
B take) from aircraft overflights by distance from flightpath, region, 
and stock. Entries were calculated in the same manner as for Table 4, 
with the exception that in areas where project activities overlapped 
between days, behavioral responses were counted only once.

--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                                                    Total number of otters disturbed, by
             Distance (meters)                  20          100         250         500         750        1000                    region
--------------------------------------------------------------------------------------------------------------------------------------------------------
Region (Stock):
    Kamishak (SW).........................       54.55      166.43      165.54        8.76        3.12        0.41  398.80.
    Upper West (SW).......................        0.79        2.42        2.46        0.06        0.02        0.00  5.75.
    East Cook Inlet (SC)..................       22.11       67.17       67.32        4.98        1.70        0.21  163.48.
    Central CI (SC).......................        0.59        1.80        1.79        0.03        0.01        0.00  4.23.
    Central CI (SW).......................        0.82        2.49        2.49        0.02        0.01        0.00  5.83.
                                           -------------------------------------------------------------------------------------------------------------
        Total Number of Otters Disturbed,        91.89      278.89      274.99       32.26       12.87        1.68  Overall total: 578.10.
         by Distance from Flight Path.
--------------------------------------------------------------------------------------------------------------------------------------------------------

    Totals by Stock SW: 410.38: SC: 167.71.

Critical Assumptions

    We propose to authorize up to 693 takes of 578 sea otters by Level 
B harassment from Hilcorp's aerial survey program. In order to conduct 
this analysis and estimate the potential amount of Level B take, 
several critical assumptions were made.
    Level B take by harassment is equated herein with behavioral 
responses that indicate harassment or disturbance. There are likely to 
be a proportion of animals that respond in ways that indicate some 
level of disturbance but do not experience significant biological 
consequences. A correction factor was not applied, although we 
considered using the rate of Level B take reported by Service 
biologists during sea otter surveys conducted between 2008 and 2015 
(below 0.01 percent; USFWS and USGS, unpublished data). The Service's 
2014 efforts to characterize behaviors that indicate take were applied 
in the field in 2016. The reported rate of take prior to 2016 may not 
represent the current definition; and therefore, it was not deemed 
appropriate for use in determining the ratio of behavioral response to 
Level B take. This will result in overestimation in take calculations.
    We assumed that the mean behavioral response rates of sea otters 
indicated by

[[Page 18339]]

the questionnaires returned by biologists are representative of 
responses of sea otters exposed to Hilcorp's work. There are several 
underlying assumptions. Noise levels produced by aircraft used by 
biologists versus those used by Hilcorp were examined and found to be 
comparable. The otters in Cook Inlet are assumed to exhibit a similar 
range of reactions to comparable levels of aircraft noise. The validity 
of this assumption has not been examined, but mean disturbance rates 
reported by questionnaire respondents (Table 3) are within the expected 
range reported by Bodkin and Udevitz (1999), the Service and the USGS 
(unpublished data), and ABR, Inc., (2010-2013), suggesting that these 
disturbance rates may also be appropriate in Cook Inlet.
    Our estimates do not account for variable responses by age and sex. 
The available information suggests that sea otters are generally 
resilient to low levels of disturbance. Females with dependent pups and 
with pups that have recently weaned are physiologically the most 
sensitive (Thometz et al. 2014) and most likely to experience take from 
disturbance. There is not enough information on composition of the Cook 
Inlet sea otter population in the Hilcorp survey area to incorporate 
individual variability based on age and sex or to predict its influence 
on take estimates. Our estimates are derived from a variety of sample 
populations with various age and sex structures, and we assume the 
response rates are applicable.
    The estimates of behavioral response presented here do not account 
for the individual movements of animals away from the Hilcorp survey 
area or habituation of animals to the survey noise. Our assessment 
assumes animals remain stationary; i.e., density does not change. There 
is not enough information about the movement of sea otters in response 
to specific disturbances to refine this assumption. This situation is 
likely to result in overestimation of take.
    Level B harassment due to Hilcorp's project will be some fraction 
of the estimated number of behavioral responses elicited from sea 
otters; but, because of the unresolved assumptions and lack of 
information, we have conservatively estimated Level B take to equal 
rates of disturbance. For this reason, we propose to authorize up to 
693 takes of 578 sea otters by Level B harassment from Hilcorp's aerial 
survey program.

Potential Impacts on the Sea Otter Stock

    The estimated level of take by harassment is small relative to the 
most recent stock abundance estimates for the sea otter. Take of 578 
otters includes 410 from the southwest stock, and 168 from the 
southcentral stock. Take of 410 animals is 1 percent of the best 
available estimate of the current population size of 45,064 animals in 
the southwest stock (USFWS 2014a) (410/45,064 [ap] 0.009). Take of 168 
is about 1 percent of the 18,297 animals in the southcentral stock 
(USFWS 2014b) (168/18,297 [ap] 0.009). Although an estimated 693 
instances of take of 578 otters by Level B harassment are possible, 
most events are unlikely to have significant consequences for the 
health, reproduction, or survival of affected animals.
    Noise levels are not expected to reach levels capable of causing 
harm. Animals in the area are not expected to incur hearing impairment 
(i.e., TTS or PTS). Level A harassment is not expected to occur. 
Aircraft noise may cause behavioral disturbances. Sea otters exposed to 
sound produced by the project are likely to respond with temporary 
behavioral modification or displacement. With the adoption of the 
measures proposed in Hilcorp's mitigation and monitoring plan and 
required by this proposed IHA, we conclude that the only anticipated 
effects from noise generated by the proposed project would be the 
short-term temporary behavioral alteration of sea otters.
    Aircraft activities could temporarily interrupt the feeding, 
resting, and movement of sea otters. Because activities are expected to 
occur for 14 days during a 60- to 150-day period, impacts associated 
with the project are likely to be temporary and localized. The 
anticipated effects include short-term behavioral reactions and 
displacement of sea otters near active operations.
    Animals that encounter the proposed activities may exert more 
energy than they would otherwise due to temporary cessation of feeding, 
increased vigilance, and retreat from the project area, but we expect 
that most would tolerate this exertion without measurable effects on 
health or reproduction. In sum, we do not anticipate injuries or 
mortalities to result from Hilcorp's operation, and none will be 
authorized. The takes that are anticipated would be from short-term 
Level B harassment in the form of startling reactions or temporary 
displacement.

Potential Impacts on Subsistence Uses

    The proposed activities will occur near marine subsistence harvest 
areas used by Alaska Natives from the villages of Ninilchik, Salamatof, 
Tyonek, Nanwalek, Seldovia, and Port Graham. Between 2013 and 2017, 
approximately 145 sea otters were harvested from Cook Inlet, averaging 
29 per year (although numbers from 2017 are preliminary). The large 
majority were taken in Kachemak Bay. Harvest occurs year-round, but 
peaks in April and May, with about 40 percent of the total taken at 
this time. February and March are also high harvest periods, with about 
10 percent of the total annual harvest occurring in each of these 
months.
    The proposed project area will avoid Kachemak Bay and therefore 
avoid significant overlap with subsistence harvest areas. Hilcorp's 
activities will not preclude access to hunting areas or interfere in 
any way with individuals wishing to hunt. Hilcorp's aircraft may 
displace otters, resulting in changes to availability of otters for 
subsistence use during the project period. Otters may be more vigilant 
during periods of disturbance, which could affect hunting success 
rates. Hilcorp will coordinate with Native villages and Tribal 
organizations to identify and avoid potential conflicts. If any 
conflicts are identified, Hilcorp will develop a Plan of Cooperation 
(POC) specifying the particular steps that will be taken to minimize 
any effects the project might have on subsistence harvest.

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 Hilcorp project may result in 
approximately 693 takes of 578 otters, of which, 522 takes of 410 
animals will be from the southwest stock and 170 takes of 168 otters 
will be from the southcentral stock. This represents about 1 percent of 
each stock, respectively (USFWS 2014a, b). Predicted levels of take 
were determined based on estimated density of sea otters in the project 
area and the mean rates of aircraft disturbance based on the opinions 
of professional biologists in the field of study. Based on these 
numbers, we propose a finding that the Hilcorp 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

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of recruitment or survival and would, therefore, have no more than a 
negligible impact on the species or stocks. 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 potential sources of disturbance 
caused by the project, and the potential responses of animals to this 
disturbance. In addition, we reviewed material supplied by the 
applicant, other operators in Alaska, 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 health, reproduction, or survival 
of affected animals. Sound production is not expected to reach levels 
capable of causing harm, and Level A harassment is not authorized. 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. Some 
animals may exhibit more severe responses typical of Level B 
harassment, such as fleeing, ceasing feeding, or flushing from a 
haulout. These responses could have significant biological impacts for 
a few affected individuals, but most animals will also tolerate this 
type of disturbance without lasting effects. Thus, although the Hilcorp 
project may result in approximately 522 takes of 410 animals from the 
southwest stock and 170 takes of 168 otters from the southcentral 
stock, we do not expect this type of harassment to affect annual rates 
of recruitment or survival or result in adverse effects on the species 
or stocks.
    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 Hilcorp'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 IHA. For these 
reasons, we propose a finding that the 2018 Hilcorp project will have a 
negligible impact on sea otters.

Impact on Subsistence

    We propose a finding that the anticipated harassment caused by 
Hilcorp's activities would not have an unmitigable adverse impact on 
the availability of 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 adverse impacts be identified.

Required Determinations

National Environmental Policy Act (NEPA)

    We have prepared a draft Environmental Assessment in accordance 
with the NEPA (42 U.S.C. 4321 et seq.). We have preliminarily concluded 
that approval and issuance of an authorization for the nonlethal, 
incidental, unintentional take by Level B harassment of small numbers 
of sea otters in Alaska during activities conducted by Hilcorp in 2018 
would not significantly affect the quality of the human environment, 
and that the preparation of an environmental impact statement for these 
actions is not required by section 102(2) of NEPA or its implementing 
regulations.

Endangered Species Act

    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 
southwestern DPS of the northern sea otter was listed as threatened on 
August 9, 2005 (70 FR 46366). A portion of Hilcorp's project will occur 
within sea otter critical habitat. Prior to issuance of this IHA, the 
Service will complete intra-Service consultation under section 7 of the 
ESA on our proposed issuance of an IHA, which will consider whether the 
effects of the proposed project will adversely affect sea otters or 
their critical habitat. These evaluations and findings will be made 
available on the Service's website at https://www.fws.gov/alaska/fisheries/mmm/iha.htm.

Government-to-Government Coordination

    It is our responsibility to communicate and work directly on a 
Government-to-Government basis with federally recognized Alaska Native 
tribes and organizations in developing programs for healthy ecosystems. 
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); (5) the Alaska Government-to-Government Policy (a departmental 
memorandum issued January 18, 2001); and (6) the Department of 
Interior's policies on consultation with Alaska Native tribes and 
organizations.
    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. 
Hilcorp has engaged these groups in informational meetings.
    Through these various interactions, we have determined that the 
issuance of this proposed IHA is permissible. 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 522 takes of 410 animals from the 
southwest stock and 170 takes of 168 otters from the southcentral 
stock. Authorized take will be limited to disruption of behavioral 
patterns that may be caused by aircraft overflights conducted by 
Hilcorp in Cook Inlet, Alaska, between May 23 and September 30, 2018. 
We anticipate no take by injury or death to northern sea otters 
resulting from these aircraft overflights.

A. General Conditions for Issuance of the Proposed IHA

    1. The taking of sea otters 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

[[Page 18341]]

the modification, suspension, or revocation of the IHA.
    2. If take exceeds the level or type identified in the proposed 
authorization (e.g., greater than 693 incidents of take of 578 otters 
by Level B harassment, separation of mother from young, injury, or 
death), the IHA will be invalidated and the Service will reevaluate its 
findings. If project activities cause unauthorized take, Hilcorp 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 Hilcorp that it may resume project activities.
    3. All operations managers and aircraft pilots 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 Hilcorp's amended 
application (Fairweather Science 2017a). Changes to the proposed 
project without prior authorization may invalidate the IHA.
    5. Hilcorp'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:
     Hilcorp's original request for an IHA, dated November 2, 
2017;
     Hilcorp's response to a request for additional information 
from the Service, dated November 30, 2017;
     The letter requesting an amendment to the original 
application, dated December 22, 2017; and
     The Marine Mammal Monitoring and Mitigation Plan prepared 
by Fairweather Science, LLC (2017b).
    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 Hilcorp's authority, 
including all contractors and subcontractors.

B. Avoidance and Minimization

    7. Aircraft operators must take reasonable precautions to avoid 
harassment to sea otters.
    8. Aircraft must maintain a minimum altitude of 305 m (1,000 ft) 
when approaching and departing survey areas to avoid unnecessary 
harassment of sea otters outside of the survey areas, except when a 
lower flight altitude is necessary for safety due to weather or 
restricted visibility.
    9. Aircraft 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 aircraft must avoid areas of active or anticipated 
subsistence hunting for sea otters as determined through community 
consultations.

C. Monitoring

    11. Pilots will be provided training and resources for identifying 
and collecting information on sea otters. Pilots will record 
information during aerial surveys when it is safe and practical to do 
so.
    12. Data collection will include locations and numbers of sea 
otters and the dates and times of the corresponding aerial surveys. 
When feasible, data will also include aircraft heading, speed, and 
altitude; visibility, group size, and composition (adults/juveniles); 
initial behaviors of the sea otters before responding to aircraft; and 
descriptions of any apparent reactions to the aircraft.

D. Measures To Reduce Impacts to Subsistence Users

    13. Prior to conducting the work, Hilcorp will take the following 
steps to reduce potential effects on subsistence harvest of sea otters: 
(i) Avoid work in areas of known sea otter subsistence harvest; (ii) 
discuss the planned activities with subsistence stakeholders including 
Cook Inlet villages, traditional councils, and the Cook Inlet Regional 
Citizens Advisory Council; (iii) identify and work to resolve concerns 
of stakeholders regarding the project's effects on subsistence hunting 
of sea otters; and (iv) if any unresolved or ongoing concerns remain, 
develop a POC in consultation with the Service and subsistence 
stakeholders to address these concerns.

E. Reporting Requirements

    14. Hilcorp must notify the Service at least 48 hours prior to 
commencement of activities.
    15. Reports will be submitted to the Service's MMM weekly during 
project activities. The reports will summarize project work and 
monitoring efforts.
    16. 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 include 
a summary of monitoring efforts and observations. All project 
activities will be described, along with 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 Hilcorp'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.
    17. 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 48 hours of discovery. Photographs, video, location information, 
or any other available documentation shall be provided to the Service.
    18. All reports shall be submitted by email to 
[email protected].
    19. Hilcorp 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 
associated draft environmental assessment, or both documents, you may 
submit your comments by any of the methods described in ADDRESSES. 
Please identify if you are commenting on the proposed authorization, 
draft environmental assessment or both, make your comments as specific 
as possible, confine them to issues pertinent to the proposed 
authorization, 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,

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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.

    Dated: March 27, 2018.
Karen P. Clark
Acting Regional Director, Alaska Region.
[FR Doc. 2018-08760 Filed 4-25-18; 8:45 am]
 BILLING CODE 4333-15-P