[Federal Register Volume 89, Number 89 (Tuesday, May 7, 2024)]
[Notices]
[Pages 38167-38180]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2024-09895]
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DEPARTMENT OF THE INTERIOR
Fish and Wildlife Service
[Docket No. FWS-R7-ES-2024-0016; FXES111607MRG01-245-FF07CAMM00]
Marine Mammals; Incidental Take During Specified Activities;
Proposed Incidental Harassment Authorization for the Southeast Alaska
Stock of Northern Sea Otters in Sitka, Alaska
AGENCY: Fish and Wildlife Service, Interior.
ACTION: Notice of receipt of application; proposed incidental
harassment authorization; 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 the City and Borough of Sitka, Alaska, propose to authorize
nonlethal, incidental take by harassment of small numbers of Southeast
Alaska stock of northern sea otters (Enhydra lutris kenyoni) between
July 1, 2024, and July 1, 2025. The applicant requested this
authorization for take by harassment that may result from activities
associated with construction of a seaplane base in Sitka Channel,
Sitka, Alaska. We estimate that this project may result in the
nonlethal, incidental take by harassment of up to 36 sea otters from
the Southeast Alaska stock. This proposed authorization, if finalized,
will be for up to 36 takes of sea otters by Level B harassment only. No
take by injury or mortality is requested, expected, or proposed to be
authorized.
DATES: Comments on this proposed incidental harassment authorization
and the accompanying draft environmental assessment must be received by
June 6, 2024.
ADDRESSES: Document availability: You may view this proposed incidental
harassment authorization, the application package, supporting
information, draft environmental assessment, and the list of references
cited herein at https://www.regulations.gov under Docket No. FWS-R7-ES-
2024-0016, or you may request these documents from the person listed
under FOR FURTHER INFORMATION CONTACT.
[[Page 38168]]
Comment submission: You may submit comments on the proposed
authorization by one of the following methods:
Electronic submission: Federal eRulemaking Portal at:
https://www.regulations.gov. Follow the instructions for submitting
comments to Docket No. FWS-R7-ES-2024-0016.
U.S. mail: Public Comments Processing, Attn: Docket No.
FWS-R7-ES-2024-0016, Policy and Regulations Branch, U.S. Fish and
Wildlife Service, MS: PRB (JAO/3W), 5275 Leesburg Pike, Falls Church,
VA 22041-3803.
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: Charles Hamilton, U.S. Fish and
Wildlife Service, 1011 East Tudor Road, MS-341, Anchorage, AK 99503; by
email at [email protected], or by telephone at (907) 786-3800.
Individuals in the United States who are deaf, deafblind, hard of
hearing, or have a speech disability may dial 711 (TTY, TDD, or
TeleBraille) to access telecommunications relay services. Individuals
outside the United States should use the relay services offered within
their country to make international calls to the point-of-contact in
the United States.
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 by harassment of small numbers of marine mammals in
response to requests by U.S. citizens (as defined in title 50 of the
Code of Federal Regulations (CFR) in part 18, at 50 CFR 18.27(c))
engaged in a specified activity (other than commercial fishing) in a
specified geographic region during a period of not more than 1 year.
The Secretary has delegated authority for implementation of the MMPA to
the U.S. Fish and Wildlife Service (FWS, or we). The FWS shall allow
this incidental taking for a period of up to 1 year if we find that
such taking:
(1) will affect only small numbers of individuals of the species or
stock;
(2) will have no more than a negligible impact on the species or
stock; and
(3) will not have an unmitigable adverse impact on the availability
of the species or stock for taking for subsistence use by Alaska
Natives.
If the requisite findings are made, we issue an authorization that
sets forth the following, where applicable:
(1) permissible methods of taking;
(2) means of effecting the least practicable adverse impact on the
species or stock and its habitat and the availability of the species or
stock for subsistence uses; and
(3) requirements for monitoring and reporting of such taking by
harassment, including, in certain circumstances, requirements for the
independent peer review of proposed monitoring plans or other research
proposals.
The term ``take'' means to harass, hunt, capture, or kill, or to
attempt to harass, hunt, capture, or kill any marine mammal.
``Harassment'' for activities other than military readiness activities
or scientific research conducted by or on behalf of the Federal
Government means any act of pursuit, torment, or annoyance which (a)
has the potential to injure a marine mammal or marine mammal stock in
the wild (the MMPA defines this as ``Level A harassment''), or (b) 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'' and ``unmitigable adverse impact''
are defined in 50 CFR 18.27 (i.e., regulations governing small takes of
marine mammals incidental to specified activities) as follows:
``Negligible impact'' is 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. ``Unmitigable adverse impact''
means 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.
The term ``small numbers'' is also defined in 50 CFR 18.27.
However, we do not rely on that definition here as it conflates ``small
numbers'' with ``negligible impacts.'' We recognize ``small numbers''
and ``negligible impacts'' as two separate and distinct considerations
when reviewing requests for incidental harassment authorizations (IHA)
under the MMPA (see Natural Res. Def. Council, Inc. v. Evans, 232 F.
Supp. 2d 1003, 1025 (N.D. Cal. 2003)). Instead, for our small numbers
determination, we estimate the likely number of takes of marine mammals
and evaluate if that take is small relative to the size of the species
or stock.
The term ``least practicable adverse impact'' is not defined in the
MMPA or its enacting regulations. For this IHA, we ensure the least
practicable adverse impact by requiring mitigation measures that are
effective in reducing the impact of project activities, but they are
not so restrictive as to make project activities unduly burdensome or
impossible to undertake and complete.
If the requisite findings are made, we shall issue an IHA, which
may set forth the following, where applicable: (i) permissible methods
of taking; (ii) other means of effecting the least practicable impact
on the species or stock and its habitat, paying particular attention to
rookeries, mating grounds, and areas of similar significance, and on
the availability of the species or stock for taking for subsistence
uses by coastal-dwelling Alaska Natives (if applicable); and (iii)
requirements for monitoring and reporting take by harassment.
Summary of Request
On August 18, 2023, the City and Borough of Sitka (hereafter
``CBS'' or ``the applicant'') submitted a request to the FWS for the
nonlethal, incidental harassment of 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. The CBS expects that incidental take of sea otters by
harassment may occur during the construction of a new seaplane base in
Sitka Channel, Sitka, Alaska for the period July 2024 through July
2025. The FWS requested additional information on September 10, 2023,
and October 27, 2023. We received revised requests on October 13, 2023,
and November 16, 2023. The FWS deemed the November 16, 2023, request
adequate and complete (hereafter referred to as the ``Request'').
Description of Specified Activities and Specified Geographic Region
The specified activity (``the project'') involves the construction
of a new seaplane base by the CBS on the shore of Japonski Island in
Sitka, Alaska. Construction will include creation of an upland
approach, storage area and
[[Page 38169]]
parking, a seaplane ramp float, a drive-down float, a pedestrian and
vehicle transfer bridge, and an approach dock. Building these
components of the new seaplane base will require pile driving,
blasting, excavation, and deposition of fill material.
Twelve 16-inch galvanized steel piles will be temporarily installed
as templates to guide permanent piles using a vibratory hammer for both
installation and removal, and an impact hammer for installation only.
Ten permanent 16-inch-diameter galvanized steel piles and 16 permanent
24-inch galvanized steel piles will be driven using a vibratory hammer,
socketed using down-the-hole drilling equipment, and driven with an
impact hammer. These piles will support the approach dock, pedestrian
and vehicle transfer bridge, drive-down float, and seaplane ramp float.
The upland project area will be developed through blasting and
excavation. Over a period of 62 days, approximately 7,263 cubic meters
(m\3\) (9,500 cubic yards (yd\3\)) above the high tide line will be
blasted, and an additional 4,530 cm (5,925 yd\3\) of rock, gravel, and
sediment will be excavated. Materials will be stored in an upland
location to dry, then used to fill both above and below the high tide
line to develop the areas needed for a bridge abutment, approach,
vehicle turnaround, parking, basic amenities, curb, and vehicle
driveway. Up to 26,492 m\3\ (34,650 yd\3\) of fill will be placed over
a period of 87 days using an excavator and dozer, and then compacted
using a vibratory soil compactor. Only 275 m\3\ (360 yd\3\) of fill
material will be placed in marine waters.
A material barge, construction barge, and skiff will be used to
transport materials, equipment, and personnel to the project location.
The materials barge will originate in Seattle, Washington, travelling
at an average of 6 knots, and be used on location as a staging area
during construction, tied to existing harbor structures. The
construction barge will originate in coastal Alaska, travelling at an
average of 6 knots, and will be used on location to support
construction, and will be secured in place by four mooring anchors. The
skiff will be used to transport personnel less than 91 meters (m) (300
feet (ft)) to the barge work platform multiple times a day at a speed
no higher than 5 knots. Additionally, standard barges, tugboats, and
other equipment may be used to place and position piles on the
substrate.
Project activities would begin as early as July 2024 and be
completed by July 2025. During this time, piling driving activities are
expected to occur for 46 hours over a period of 31 days with 18 days of
activity. Vibratory pile driving would occur for approximately 8.4
hours, impact pile driving would occur for approximately 3.1 hours, and
down-the-hole drilling would occur for approximately 34 hours. Fill in
marine waters would occur over a period of 11 hours and fill in
intertidal waters would occur over a period of 641 hours.
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.
[GRAPHIC] [TIFF OMITTED] TN07MY24.063
Description of Marine Mammals in the Specified Geographic Region
The northern sea otter is the only marine mammal under the FWS's
jurisdiction that normally occupies the Northeast Pacific Ocean. Sea
otters in Alaska are represented by three stocks: the Southwest Alaska
stock, the Southcentral Alaska stock, and the Southeast Alaska stock.
Those in the Northeast Pacific Ocean belong to the Southeast Alaska
stock. Detailed information about the biology of the Southeast Alaska
stock can be found in the most recent stock assessment report (88 FR
53510, August 8, 2023), available at: https://www.fws.gov/project/marine-mammal-stock-assessment-reports.
[[Page 38170]]
Sea otters may be distributed anywhere within the specific
geographic region other than upland areas; however, they generally
occur in shallow water near the shoreline. They are most commonly
observed within the 40-meter (m) (131-foot (ft)) depth contour (88 FR
53510, August 8, 2023), although they can be found in areas with deeper
water. Ocean depth is generally correlated with distance to shore, and
sea otters typically remain within 1 to 2 kilometers (km) (0.62 to 1.24
miles (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 1995-2012 survey data were combined with results from recent
aerial surveys conducted in Glacier Bay National Park and incorporated
into a spatiotemporal model of ecological diffusion using a Bayesian
hierarchical framework as described in Eisaguirre et al. (2021) (88 FR
53510, August 8, 2023). This model was used to develop the most recent
estimate of 27,285 otters in the Southeast Alaska stock and generated
otter abundance estimates at a resolution of 1000 m by 1000 m.
Abundance values within the project area ranged from 0.065 to 0.65
otters per square kilometer (km\2\) (0.39 square miles (mi\2\)).
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 nonmigratory 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 Impacts of the Specified Activities on Marine Mammals
Effects of Noise on Sea Otters
The project has the potential to result in take of sea otters by
Level B 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 sea otter from the sound source, the level and
intensity of sound the sea otter receives, background noise levels,
noise frequency, noise duration, and whether the noise is pulsed or
continuous. The actual noise level perceived by individual sea otters
will also depend on whether the sea otter is above or below water and
atmospheric and environmental conditions. Temporary disturbance of sea
otters or localized displacement reactions are the most likely effects
to occur from noise exposure. No lethal take is anticipated, nor was it
requested by the applicant. Therefore, none will be authorized.
Sea Otter Hearing
Seaplane base construction activities will fall within the hearing
range of sea otters. Controlled sound exposure trials on southern sea
otters (Enhydra lutris nereis) indicate that sea 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) sound than terrestrial mustelids, but was
similar to that of a California sea lion (Zalophus californianus).
However, the sea otter was still able to hear low-frequency sounds, and
the detection thresholds for sounds between 0.125 and 1 kHz were
between 116 and 101 decibels (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 under water; therefore, masking of
communications by anthropogenic sound is less of a concern than for
other marine mammals. However, sea otters, especially mothers and pups,
do use sound for communication in air (McShane et al. 1995), and sea
otters may monitor underwater sound to avoid predators (Davis et al.
1987).
Exposure Thresholds
Noise exposure criteria for identifying underwater noise levels
capable of causing Level A harassment (injury) to marine mammal
species, including sea otters, have been established using the same
methods as those used by National Marine Fisheries Service (NMFS)
(Southall et al. 2019). These criteria are based on estimated levels of
sound exposure capable of causing a permanent shift in hearing
sensitivity (i.e., a permanent threshold shift [PTS]) (NMFS 2018). PTS
occurs when noise exposure causes permanent damage to hair cells within
the inner ear system (Ketten 2012).
Sound exposure thresholds 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. PTS-based
injury criteria were developed from theoretical extrapolation of
observations of temporary threshold shifts (TTS) detected in lab
settings during sound exposure trials. The TTS is a noise-induced
threshold shift in hearing sensitivity that fully recovers over time
(Finneran 2015). Southall and colleagues (2019) predict that PTS for
sea otters, which are included in the ``other marine carnivores''
category, will occur at 232 dB peak or 203 dB cumulative sound exposure
(SELCUM) for impulsive underwater sound, and at 219 dB
SELCUM for nonimpulsive (continuous) underwater sound.
Thresholds based on TTS have been used as a proxy for Level B
harassment (70 FR 1871, January 11, 2005; 71 FR 3260, January 20, 2006;
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
[[Page 38171]]
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). Based
on these findings, Southall et al. (2019) developed TTS thresholds for
sea otters, which are included in the ``other marine carnivores''
category, of 188 dB SELCUM for impulsive sounds and 199 dB
SELCUM for nonimpulsive sounds.
The NMFS (2018) criteria do not identify sound level thresholds for
avoidance of Level B harassment. For pinnipeds under their jurisdiction
(seals and sea lions), the NMFS has adopted a 160-dB threshold for
Level B harassment from exposure to impulsive noise and a 120-dB
threshold for continuous noise (81 FR 51693, August 4, 2016; NMFS
2022). These thresholds were developed from observations of mysticete
(baleen) whales responding to airgun operations (Malme et al. 1983a, b;
Richardson et al. 1986, 1995) and from equating Level B harassment with
noise levels capable of causing TTS in lab settings. 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 from 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) 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.
We have evaluated these thresholds and determined that a Level B
harassment threshold of 120 dB for nonimpulsive noise is not applicable
to sea otters. The 120-dB threshold is based on studies in which gray
whales (Eschrichtius robustus) were exposed to experimental playbacks
of industrial noise (Malme et al. 1983a, b). During these playback
studies, southern sea otter responses to industrial noise were also
monitored (Riedman 1983, 1984). Gray whales exhibited avoidance to
industrial noise at the 120-dB threshold; however, 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.
Based on the best available scientific information about sea
otters, and closely related marine mammals when sea otter data are
limited, the FWS has set 160 dB of received underwater sound as a
threshold for Level B take by disturbance for sea otters for this IHA.
Exposure to unmitigated in-water noise levels between 125 Hz and 38 kHz
that are greater than 160 dB--for both impulsive and nonimpulsive sound
sources--will be considered by the FWS as Level B harassment.
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).
Table 1--Temporary Threshold Shift (TTS) and Permanent Threshold Shift (PTS) Thresholds Established by Southall et al. (2019) Through Modeling and
Extrapolation for ``Other Marine Carnivores,'' Which Includes Sea Otters
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TTS PTS
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Nonimpulsive Impulsive Nonimpulsive Impulsive
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SELCUM SELCUM Peak SPL SELCUM SELCUM Peak SPL
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Air................................................................ 157 146 170 177 161 176
Water.............................................................. 199 188 226 219 203 232
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Note: Values are weighted for other marine carnivores' hearing thresholds and given in cumulative sound exposure level (SELCUM dB re 20 micropascal
([micro]Pa) in air and SELCUM dB re 1 [micro]Pa in water) for impulsive and nonimpulsive sounds, and unweighted peak sound pressure level in air (dB
re 20[micro]Pa) and water (dB 1[micro]Pa) (impulsive sounds only).
Airborne Sounds
The NMFS (2018) guidance neither addresses thresholds for
preventing injury or disturbance from airborne noise, nor provides
thresholds for avoidance of Level B harassment. Southall et al. (2007)
suggested thresholds for PTS and TTS for sea lions exposed to non-
pulsed airborne noise of 172.5 and 159 dB re (20 [micro]Pa)2-s SEL.
Conveyance of underwater noise into the air is of little concern since
the effects of pressure release and interference at the water's surface
reduce underwater noise transmission into the air. For activities that
create both in-air and underwater sounds, we will estimate take based
on parameters for underwater noise transmission. This estimation will
also account for exposures to sea otters at the surface, as sound
energy travels more efficiently through water than through air.
Evidence From Sea Otter Studies
Sea otters may be more resistant to the effects of sound
disturbance and human activities than other marine mammals. For
example, southern sea otters were observed to not change their
presence, density, or behavior in response to underwater sounds from
industrial noise recordings at 110 dB and a frequency range of 50 Hz to
20 kHz, even at the closest distance of 0.5 nautical miles (<1 km or
0.6 mi) (Riedman 1983). Southern sea otters did not respond noticeably
to noise from a single 1,638 cubic centimeter (cm\3\) (100 cubic inch
(in\3\)) airgun, and no sea otter disturbance reactions were evident
when a 67,006 cm\3\ (4,089 in\3\) airgun array was as close as 0.9 km
(0.6 mi) to sea otters (Riedman 1983, 1984). However, southern sea
otters displayed slight reactions to airborne engine noise (Riedman
1983). Northern sea otters were observed to exhibit a limited response
to a variety of airborne and underwater sounds, including a warble
tone, sea otter pup calls, killer whale (Orcinus orca) calls (which are
predators to sea otters), air horns, and an underwater noise harassment
system designed to drive marine mammals away from crude oil spills
(Davis et al.
[[Page 38172]]
1988). These sounds elicited reactions from northern sea otters,
including startle responses and movement away from noise sources.
However, these reactions were only observed when northern sea otters
were within 100-200 m (328-656 ft) of noise sources. Further, northern
sea otters appeared to become habituated to the noises within 2 hours
or, at most, 3-4 days (Davis et al. 1988).
Noise exposure may be influenced by the amount of time sea otters
spend at the water's surface. Noise at the water's surface can be
attenuated by turbulence from wind and waves more quickly compared to
within 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 traveling through the water beneath it.
The average amount of time that sea otters spend above the water each
day while resting and grooming varies between males and females and
across seasons (Esslinger et al. 2014, Zellmer et al. 2021). For
example, female sea otters foraged for an average of 8.78 hours per day
compared to male sea otters, which foraged for an average of 7.85 hours
per day during the summer months (Esslinger et al. 2014). Male and
female sea otters spend an average of 63 to 67 percent of their day at
the surface resting and grooming during the summer months (Esslinger et
al. 2014). Few studies have evaluated foraging times during the winter
months. Garshelis et al. (1986) found that foraging times increased
from 5.1 hours per day to 16.6 hours per day in the winter; however,
Gelatt et al. (2002) did not find a significant difference in seasonal
foraging times. It is likely that seasonal variation is determined by
seasonal differences in energetic demand and the quality and
availability of prey sources (Esslinger et al. 2014). These findings
suggest that the large portion of the day sea otters spend at the
surface may help limit sea otters' exposure during noise-generating
operations.
Sea otter sensitivity to industrial activities may be influenced by
the overall level of human activity within the sea otter population's
range. In locations that lack frequent human activity, sea otters
appear to have a lower threshold for disturbance. Sea otters in Alaska
exhibited escape behaviors in response to the presence and approach of
vessels (Udevitz et al. 1995). Behaviors included diving or actively
swimming away from a vessel, sea otters on haulouts entering the water,
and groups of sea otters disbanding and swimming in multiple directions
(Udevitz et al. 1995). Alaskan sea otters were observed to avoid areas
with heavy boat traffic and return to these areas during seasons with
less vessel traffic (Garshelis and Garshelis 1984). In Cook Inlet, sea
otters drifting on a tide trajectory that would have taken them within
500 m (0.3 mi) of an active offshore drilling rig were observed to swim
in order to avoid a close approach of the drilling rig despite near-
ambient noise levels (BlueCrest 2013). Sea otter responses to
disturbance can result in energetic costs, which increases the amount
of prey required by sea otters (Barrett 2019). This increased prey
consumption may impact sea otter prey availability and cause sea otters
to spend more time foraging and less time resting (Barrett 2019).
Individual sea otters in Sitka will likely show a range of
responses to noise from pile driving activities. Some sea otters will
likely show startle responses, change direction of travel, dive, or
prematurely surface. Sea otters reacting to survey activities may
divert time and attention from biologically important behaviors, such
as feeding and nursing pups. Some sea otters may abandon the project
area and return when the disturbance has ceased. Based on the observed
movement patterns of sea otters (Lensink 1962; Kenyon 1969, 1981;
Garshelis and Garshelis 1984; Riedman and Estes 1990; Tinker and Estes
1996), we expect some individuals will respond to pile driving
activities by dispersing to nearby areas of suitable habitat; however,
other sea otters, especially territorial adult males, will not be
displaced.
Vessel Activities
Vessel collisions with marine mammals can result in death or
serious injury. Wounds resulting from vessel strike may include massive
trauma, hemorrhaging, broken bones, or propeller lacerations (Knowlton
and Kraus 2001). An individual may be harmed by a vessel if the vessel
runs over the animal at the surface, the animal hits the bottom of a
vessel while the animal is surfacing, or the animal is cut by a
vessel's propeller. Mortality associated with vessel strike has been
determined based on recovery of carcasses with lacerations indicative
of propeller injuries (Wild and Ames 1974; Morejohn et al. 1975).
Vessel strike has been documented as a cause of death across all three
stocks of northern sea otters in Alaska. In a review of sea otter
mortality that occurred during a 10-year period (2002-12), 10
individuals out of 483 with an identifiable cause of death were
determined to die due to trauma from a boat strike (Burek-Huntington et
al. 2021). These events occurred in across central and southeast
Alaska, with fatalities occurring in the specified geographic region of
Sitka. In many boat strike cases, trauma was determined to be the
ultimate cause of death; however, there was a contributing factor, such
as disease or biotoxin exposure, which incapacitated the sea otter and
made it more vulnerable to vessel strike (88 FR 53510, August 8, 2023).
Vessel speed influences the likelihood of vessel strikes involving
sea otters. The probability of death or serious injury to a marine
mammal increases as vessel speed increases (Laist et al. 2001;
Vanderlaan and Taggart 2007). Sea otters spend a considerable portion
of their time at the water's surface (Esslinger et al. 2014), and are
typically visually aware of approaching vessels and can move away if a
vessel is not traveling too quickly. The CBS has committed to speeds of
6 knots for their materials and construction barges and 5 knots for
their personnel skiffs. These speeds are slow enough to allow nearby
sea otters to move away from vessels if needed, and significantly
reduce the risk of potential boat strike.
Sea otters exhibit behavioral flexibility in response to vessels,
and their responses may be influenced by the intensity and duration of
the vessel's activity. For example, sea otter populations in Alaska
were observed to avoid areas with heavy vessel traffic but return to
those same areas during seasons with less vessel traffic (Garshelis and
Garshelis 1984). Sea otters have also shown signs of disturbance or
escape behaviors in response to the presence and approach of survey
vessels, including: sea otters diving and/or actively swimming away
from a vessel; sea otters on haulouts entering the water; and groups of
sea otters disbanding and swimming in multiple different directions
(Udevitz et al. 1995).
Additionally, sea otter responses to vessels may be influenced by
the sea otter's previous experience with vessels. Sea otters in
different study locations in California were found to exhibit markedly
different responses to kayakers, suggesting a different level of
tolerance between the groups (Gunvalson 2011). Benham (2006) found
evidence that the sea otters exposed to high levels of recreational
activity may have become more tolerant than individuals in less-
disturbed areas. Sea otters off the California coast showed only mild
interest in vessels passing
[[Page 38173]]
within hundreds of meters and appeared to have habituated to vessel
traffic (Riedman 1983, Curland 1997). The project area is within an
active harbor used year-round by commercial and recreational vessels
and is immediately adjacent to the flight path of aircraft landing at
Sitka Rocky Gutierrez Airport. As such, it is probable that sea otters
in the area have been frequently exposed to boating and aircraft
activity and would not regard the project's vessel activities as novel
stimuli.
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 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 that lost feeding opportunities due
to vessel traffic faced a substantial (18 percent) estimated decrease
in energy intake (Williams et al. 2002). Such disturbance effects can
have population-level consequences. Increased disturbance rates have
been associated with a decline in bottlenose dolphin (Tursiops spp.)
abundance (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 haulout
patterns and distribution (Benham et al. 2006, Maldini et al. 2012).
Chronic stress can also lead to weakened reflexes, lowered learning
responses (Welch and Welch 1970, van Polanen Petel et al. 2006),
compromised immune function, decreased body weight, and abnormal
thyroid function (Seyle 1979).
Changes in behavior resulting from anthropogenic disturbance can
include increased agonistic interactions between individuals or
temporary or permanent abandonment of an area (Barton et al. 1998). The
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 Sea Otter Habitat and Prey
Physical and biological features of habitat essential to the
conservation of sea otters include the benthic invertebrates (e.g., red
sea urchins (Mesocentrotus franciscanus), blue mussels (Mytilus spp.),
butter clams (Saxidomus giganteus), etc.) eaten by sea otters, shallow
rocky areas, and kelp (e.g., bull kelp (Nereocystis luetkeana) and
dragon kelp (Eualaria fistulosa)) beds that provide cover from
predators. Important sea otter habitat in the project area includes
coastal areas within the 40-m (131-ft) depth contour where high
densities of sea otters have been detected.
Construction activities, such as pile driving and fill placement,
may generate in-water noise at levels which can temporarily displace
sea otters from important habitat and impact sea otter prey species.
The primary prey species for sea otters are sea urchins, abalone,
clams, mussels, crabs, and squid (Tinker and Estes 1996). When
preferential prey are scarce, sea otters will also eat kelp, slow-
moving benthic fishes, sea cucumbers, egg cases of rays, 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; Davis and Bodkin 2021). Several studies have addressed the
effects of noise on invertebrates (Tidau and Briffa 2016; Carroll et
al. 2017). Behavioral changes, such as an increase in lobster (Homanus
americanus) feeding levels (Payne et al. 2007), an increase in
avoidance behavior by wild-caught captive reef squid (Sepioteuthis
australis) (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 observed in response to increased sound levels, including changes
in serum biochemistry and hepatopancreatic cells in lobsters (Payne et
al. 2007) and long-term damage to the statocysts required for hearing
in several cephalopod species (Andr[eacute] et al. 2011; Sol[eacute] et
al. 2013, 2019). De Soto 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 (6.6 ft)) was far higher than
the proposed project activities will produce. Industrial noise can also
impact larval settlement by masking the natural acoustic settlement
cues for crustaceans and fish (Pine et al. 2012, Simpson et al. 2016,
Tidau and Briffa 2016).
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 project 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.
Noise-generating activities that interact with the seabed can
produce vibrations, resulting in the disturbance of sediment and
increased turbidity in the water. Although turbidity is likely to have
little impact on sea otters and prey species (Todd et al. 2015), there
may be some impacts from vibrations and increased sedimentation. For
example, mussels (Mytilus edulis) exhibited changes in valve gape and
oxygen demand, and hermit crabs (Pagurus bernhardus) exhibited limited
behavioral changes in response to
[[Page 38174]]
vibrations caused by pile driving (Roberts et al. 2016). Increased
sedimentation is likely to reduce sea otter visibility, which may
result in reduced foraging efficiency and a potential shift to less-
preferred prey species. These outcomes may cause sea otters to spend
more energy on foraging or processing the prey items; however, the
impacts of a change in energy expenditure are not likely to be seen at
the population level (Newsome et al. 2015). Additionally, the benthic
invertebrates may be impacted by increased sedimentation, resulting in
higher abundances of opportunistic species that recover quickly from
industrial activities that increase sedimentation (Kotta et al. 2009).
The impacts of increased turbidity at the project site will be
temporary. Conversely, placement of fill below the high tide line and
construction of a new upland peninsula will result in the permanent
removal of 1.3 acres of sea otter habitat. However, sea otter habitat
is abundant throughout the Sitka area, and loss of a small amount of
habitat is unlikely to apply density-dependent pressure on the
population, as it is estimated to be well below carrying capacity
(estimated K=47 percent (Tinker et al. 2019).
Potential Impacts on Subsistence Uses
The proposed specified activities will occur near marine
subsistence harvest areas used by Alaska Native Peoples from Sitka and
the surrounding areas. Subsistence harvest of sea otters in the Sitka
subregion has been consistent over time. Between 1988 and 2015, it is
estimated that 12,546 sea otters were harvested in southeast Alaska. Of
these harvests, 2,744, or roughly 22 percent, occurred in the Sitka
subregion.
The proposed project is immediately adjacent to Sitka Airport and
the Sitka harbor. Active subsistence harvest does not typically occur
in these heavily used areas. Construction activities will not preclude
access to hunting areas or interfere in any way with individuals
wishing to hunt. In September 2018, the Alaska Harbor Seal Commission,
the Alaska Sea Otter and Steller Sea Lion Commission, and the Sitka
Tribe of Alaska were contacted by CBS to discuss a project in Sitka
Channel and request comments. The Commissions and Sitka Tribe of Alaska
did not express concerns with the project impacting the harvest of
marine mammals. However, the Sitka Tribe of Alaska did request that no
pile driving be conducted from March 15 to May 31 to protect herring,
and the CBS will honor the request. If any conflicts are identified in
the future, the CBS will develop a plan of cooperation (POC) specifying
the particular steps necessary to minimize any effects the project may
have on subsistence harvest.
Mitigation Measures
If an IHA for the project is issued, it must specify means for
effecting 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 the following:
Development of a marine mammal monitoring and mitigation
plan;
Establishment of shutdown and monitoring zones;
Monitoring by designated protected species observers
(PSOs);
Clearance of the site before startup;
Limiting in-water activity to daylight hours;
Use of silt curtains to prevent sedimentation and
turbidity during down-the-hold drilling;
Adherence to soft-start procedures; and
Shutdown procedures.
These measures are further specified under Proposed Authorization,
part B. Avoidance and Minimization. The FWS has not identified any
additional (i.e., not already incorporated into the CBS's request)
mitigation or monitoring measures that are practicable and would
further reduce potential impacts to sea otters and their habitat.
Estimated Take
Definitions of Incidental Take Under the Marine Mammal Protection Act
Below we provide definitions of three potential types of take of
sea otters. The FWS does not anticipate and is not authorizing lethal
take or Level A harassment as a part of this proposed IHA; however, the
definitions of these take types are provided for context and
background.
Lethal Take--Human activity may result in biologically significant
impacts to sea otters. In the most serious interactions human actions
can result in the mortality of sea otters.
Level A Harassment--Human activity may result in the injury of sea
otters. Level A harassment for nonmilitary readiness activities is
defined as any act of pursuit, torment, or annoyance that has the
potential to injure a marine mammal or marine mammal stock in the wild.
The specified action is not anticipated to result in Level A harassment
due to exposure of sea otters to noise capable of causing PTS.
Level B Harassment--The applicant requested authorization for only
take by Level B harassment, and the FWS is proposing to authorize only
take by Level B harassment for this IHA. Level B harassment for
nonmilitary readiness activities means any act of pursuit, torment, or
annoyance that has the potential to disturb a marine mammal or marine
mammal stock in the wild by causing disruption of behaviors or
activities, including, but not limited to, migration, breathing,
nursing, feeding, or sheltering. Human-caused changes in behavior that
disrupt biologically significant behaviors or activities for the
affected animal indicate take by Level B harassment under the MMPA.
The FWS has identified the following sea otter behaviors as
indicating possible Level B harassment:
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
behavioral responses may also be indicative of Level B harassment.
Relatively minor changes in behavior such as the animal raising its
head or temporarily changing
[[Page 38175]]
its direction of travel are not likely to disrupt biologically
important behavioral patterns, and the FWS does not view such minor
changes in behavior as indicative of a take by Level B harassment. It
is also important to note that eliciting behavioral responses that
equate to take by Level B harassment repeatedly may result in 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
The FWS does not anticipate, nor do we propose to authorize, the
Level A or Level B harassment of sea otters as a result of vessel
operations or placement of fill in the waterway. Vessels will be
operated in areas with year-round boat traffic at conservatively slow
speeds, significantly reducing the probability of sea otter harassment.
Deposition of fill material is not anticipated to generate appreciable
underwater noise (Dickerson et al. 2001, Nedwell and Howell 2004).
Finally, otters are not anticipated to be physically injured due to
fill deposition due to the use of protected species observers and
shutdown zones.
We assumed all animals exposed to underwater sound levels from pile
driving operations 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. Spatially explicit zones of
ensonification were established around the proposed construction
location to estimate the number of otters that may be exposed to these
sound levels.
The project can be divided into three major components: down-the-
hole drilling, vibratory hammering, and pile-driving using an impact
hammer. Each of these components will generate a different type of in-
water noise. Vibratory hammering will produce nonimpulsive or
continuous noise, impact driving will produce impulsive noise, and
down-the-hole drilling is considered to produce both impulsive and
continuous noise (NMFS 2020).
The level of sound anticipated from each project component was
established using recorded data from pile-driving in Friday Harbor,
Washington, Bangor Naval Base, Washington, and Trinidad Bay, California
(a proxy for vibratory hammering; NAVFAC 2015); Rodeo, California (a
proxy for impact hammering of 24-inch piles; Caltrans 2020); Anderson,
California (a proxy for impact hammering of 16-inch piles; Caltrans
2020); Tenakee Springs, Alaska (a proxy for down-the-hole drilling of
16-inch and 24-inch piles; Heyvaert and Reyff 2021); and Biorka Island,
Alaska (a proxy for down-the-hole drilling of 24-inch piles; Guan and
Miner 2020). The NMFS Technical Guidance and User Spreadsheet (NMFS
2018, 2020) was used to determine the distance at which sound levels
would attenuate to Level A harassment thresholds, and we used the NMFS
Multi-species pile driving calculator to determine the distance at
which sound levels would attenuate to Level B harassment thresholds
(table 2). The weighting factor adjustment included in the NMFS User
Spreadsheet accounts for sound created in portions of an organism's
hearing range where they have less sensitivity. We used the weighting
factor adjustment for otariid pinnipeds (2), as they are the closest
available physiological and anatomical proxy for sea otters. Both tools
incorporate a transmission loss coefficient, which accounts for the
reduction in sound level outward from a sound source. We used the NMFS-
recommended transmission loss coefficient of 15 for coastal pile-
driving activities to indicate simple spread (NMFS 2020).
Table 2--Summary by Project Component of Sound Level, Timing of Sound Production, Distance From Sound Source to Below Level B Harassment Thresholds,
Days of Impact, Otters in Level B Harassment Ensonification Area, and Total Otters Expected To Be Harassed Through Behavioral Disturbance
--------------------------------------------------------------------------------------------------------------------------------------------------------
Down-the-hole Vibratory hammering
Sound source drilling (16-inch Down-the-hole drilling (16 and 24-inch steel Impact hammer (16-inch Impact hammer (24-
steel piles) (24-inch steel piles) piles) steel piles) inch steel piles)
--------------------------------------------------------------------------------------------------------------------------------------------------------
Sound level at 10 meters:
dB RMS........................ 167.................. 173................... 161................... 185................... 190
dB SEL........................ 146.................. 159................... ...................... 175................... 177
dB peak....................... 172.................. 184................... ...................... 200................... 203
Literature reference.............. Heyvaert and Reyff Heyvaert and Reyff NAVFAC 2015........... Caltrans 2020......... Caltrans 2020
2021 (dB RMS); Guan 2021.
and Miner 2020 (dB
SEL and dB peak).
Timing per pile................... 60 minutes/pile...... 90 minutes/pile....... 10 minutes/pile....... 5 minutes/pile........ 5 minutes/pile
Strikes per pile.................. 36,000 strikes/pile.. 54,000 strikes/pile... ...................... 175 strikes/pile...... 175 strikes/pile
Maximum piles per day............. 2.................... 2..................... 6..................... 4..................... 4
Maximum number of days............ 5.................... 8..................... 9..................... 6..................... 4
Distance to below Level A 2.3.................. 22.2.................. 0.3................... 9..................... 12.2
harassment threshold in meters.
Distance to below Level B 30................... 75.................... 20.................... 465................... 1,000
harassment threshold in meters.
Estimated sea otter density in 0.85................. 0.85.................. 0.85.................. 0.85.................. 0.85
affected area.
Potential sea otters affected by 0 *.................. 2..................... 0 *................... 2..................... 2
sound.
Days of activity.................. 5.................... 8..................... 9..................... 6..................... 4
Potential harassment events....... 0.................... 16.................... 0..................... 12.................... 8
--------------------------------------------------------------------------------------------------------------------------------------------------------
* The project shutdown zone extends 30 meters from the sound source. Therefore, we do not anticipate sea otters to experience Level B harassment as a
result of down-the-hole drilling of 16-inch steel piles or vibratory hammering of 16-inch or 24-inch steel piles.
Note: Sound levels for all sources are unweighted and given in dB re 1 [micro]Pa. Nonimpulsive sounds are in the form of mean maximum root mean square
(RMS) sound pressure level (SPL) as it is more conservative than cumulative sound exposure level (SEL) or peak SPL for these activities. Impulsive
sound sources are in the form of SEL for a single strike (s-s).
Recent estimates of the number of sea otters in the project area
are less than one otter per square kilometer. Tinker et al. (2019)
estimated an average of 0.85 otters/km\2\ in the sub-region that
includes the project area (N05). Similarly, fine-scale ecological
diffusion models have estimated 0.062 otters/km\2\ inside the harbor
breakwater and 0.65 otters/km\2\ outside the harbor breakwater
Eisaguirre et al. (2023). Given these values, we assume up to
[[Page 38176]]
one otter per square kilometer may be in the area during construction
activities. However, the project is within an area that may provide
refuge for mom-pup pairs. Northern sea otters enter estrus immediately
following pup loss or weaning (Monson et al. 2000) and may have pups
year-round. Thus, when estimating the number of potential Level B
harassment events, we account for the possibility of the otter having a
dependent pup by assuming two otters per square kilometer during
project activities.
To determine the number of sea otters that may experience in-water
sound greater than 160 dB, we calculated the area of potential impact
for each project activity (i.e., down-the-hole drilling and impact
hammering) that would generate noise >160 dB beyond the project's 30-
meter shutdown zone. Impact areas were drawn and their area calculated
in ArcPro 3.1.4 using geospatial files of the project location,
adjacent coastline, and the harbor breakwater to account for sound
attenuation by land shadows (figure 2). These impact areas were
multiplied by the number of otters/km\2\ and rounded to account for the
possibility of a mom-pup pair (table 1).
[GRAPHIC] [TIFF OMITTED] TN07MY24.064
Although sea otters are non-migratory, they typically move amongst
focal areas within their home ranges to rest and forage (Garshelis and
Garshelis 1984, Laidre et al. 2009). It is possible that given the
density of sea otters in the region, the large variability in
individual home range sizes, and the potential for up to daily movement
in and out of foraging or resting areas, that a different mom-pup pair
could be found within the ensonification zone each day of the project.
Thus, the FWS conservatively assumes that the 36 estimated harassment
events may impact up to 36 different sea otters. However, should an
individual or mom-pup pair remain in the impact area more than one day,
and therefore experience Level B harassment more than once, we do not
anticipate repeated exposure events to lead to harassment greater than
Level B. No Level A harassment (i.e., injury) is anticipated or
proposed to be authorized. While in-water noise will be at a level
capable of causing PTS from up to 22.2 m from the source location
(during down-the-hole drilling of 24-inch piles), operations will be
shut down should any marine mammal come within 30 m of project
activities.
Critical Assumptions
We estimate 36 takes of 36 sea otters by Level B harassment will
occur due to the proposed specified activities. To conduct this
analysis and estimate the potential amount of Level B harassment,
several critical assumptions were made.
Otter density was calculated using a state-space model created by
Tinker et al. (2019) and a Bayesian hierarchical model created by
Eisaguirre et al. (2021), which includes assumptions that can be found
in the original publications. The northern sea otter southeast stock
Stock Assessment Report (88 FR 53510, August 8, 2023) also elaborates
on the inclusion of Glacier Bay National Park aerial surveys into the
most recent iteration of the Eisaguirre et al. (2021) Bayesian
hierarchical model.
Sound level estimates for construction activities were generated
using sound source verification from recent pile-driving activities in
several locations in California, Washington, and Alaska. Environmental
conditions in these locations, including water depth, substrate, and
ambient sound levels are similar to those in the project location but
not identical. Further, estimation of ensonification zones were based
on sound attenuation models using a simple spreading loss model. These
factors may lead to actual sound values differing slightly from those
estimated here.
Finally, the pile-driving activities described here will also
create in-air noise. Because sea otters spend over half of their day
with their heads above water (Esslinger et al. 2014), they will be
exposed to increases in in-air noise from
[[Page 38177]]
construction equipment. However, we have calculated Level B harassment
with the assumption that an individual may be harassed only one time
per 24-hour period, and underwater sound levels will be more disturbing
and extend farther than in-air noise. Thus, while sea otters may be
disturbed by noise both in air and underwater, we have relied on the
more conservative underwater estimates.
Determinations and Findings
Sea otters exposed to 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
harassment). 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 a longer time period than the proposed project activities
(Southall et al. 2019). With the adoption of the mitigation measures
proposed in the request and required by this proposed IHA, estimated
take was reduced.
Small Numbers
For our small numbers determination, we consider whether the
estimated number of sea otters to be subjected to incidental take is
small relative to the population size of the species or stock. We
estimate the CBS's specified activities in the specified geographic
region will take no more than 36 takes of sea otters by Level B
harassment during the 1-year period of this proposed IHA (see
Calculating Take). Take of 36 animals is 0.13 percent of the best
available estimate of the current Southeast Alaska stock size of 27,285
animals ((36 / 27,285) x 100 [ap] 0.13), and represents a ``small
number'' of sea otters of that stock.
Negligible Impact
We propose a finding that any incidental take by Level B harassment
resulting from the specified activities cannot be reasonably expected
to, and is not reasonably likely to, adversely affect the Southeast
Alaska stock of northern sea otters through effects on annual rates of
recruitment or survival and will, therefore, have no more than a
negligible impact on the stock. 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 planned activities with
temporary behavioral modification or temporary displacement. These
reactions are not anticipated 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. Sea otters may move
in and out of the project area during pile driving activities, leading
to as many as 36 individuals experiencing one day of exposure. However,
it is possible that an individual or a mom-pup pair may enter the
ensonification area more than once during the project. At most, if the
same mom-pup pair enters the ensonification area every day pile driving
occurs, the mom-pup pair would experience Level B harassment for 18
days. However, injuries (i.e., Level A harassment or PTS) due to
chronic sound exposure are estimated to occur over a longer time scale
(Southall et al. 2019). The greatest area that will experience noise
greater than Level B thresholds due to pile driving is small (less than
0.7 km\2\), and an animal that may be disturbed could escape the noise
by moving to nearby quiet areas. Further, sea otters spend over half of
their time above the surface during the summer months (Esslinger et al.
2014), and likely no more than 70 percent of their time foraging during
winter months (Gelatt et al. 2002); thus, their ears will not be
exposed to continuous noise, and the amount of time it may take for
permanent injury is considerably longer than that of mammals primarily
under water. Some animals may exhibit some of the stronger responses
typical of Level B harassment, such as fleeing, interruption of
feeding, or flushing from a haulout. These responses could have
temporary biological impacts for affected individuals, but are not
anticipated to result in measurable changes in survival or
reproduction.
The total number of animals affected and severity of impact are not
sufficient to change the current population dynamics at the stock
scale. Although the specified activities may result in approximately 36
incidental takes of up to 36 sea 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 specified activities as mitigated by the
avoidance and minimization measures identified in the City and Borough
of Sitka'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
specified project will have a negligible impact on the Southeast Alaska
stock of northern sea otters.
Least Practicable Adverse Impacts
To reduce the potential for disturbance from their specified
activities, the CBS will implement mitigation measures as described in
Mitigation Measures and further specified under Proposed Authorization,
part B. Avoidance and Minimization. We find that the mitigation
measures required by this proposed IHA will affect the least
practicable adverse impacts on the stock from any incidental take
likely to occur in association with the specified activities. In making
this finding, we considered the biological characteristics of sea
otters, the nature of the specified activities, the potential effects
of the activities on sea otters, the documented
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impacts of similar activities on sea otters, and alternative mitigation
measures.
We evaluated the manner and degree to which the successful
implementation of the measures are expected to ensure the least
practicable adverse impact on species or stocks and their habitat, as
well as subsistence uses. 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). We assessed whether any additional
practicable requirements could be implemented to further reduce effects
and did not identify any.
During the IHA application process, the FWS coordinated closely
with the applicant to discuss potential mitigation measures and their
practicability. A comprehensive list of these measures can be found in
the supplemental information for this proposed IHA. One notable measure
considered by both the FWS and CBS but deemed to be impracticable was
the use of bubble curtains during pile driving. The CBS has stated the
small-diameter piles used in this project will be placed closely
together, and this close placement will not allow enough space to
deploy bubble curtains, sound mitigation screens, or nets to dampen
sound.
Following the discussion of potential mitigation measures with the
applicant, the FWS has not identified any additional (i.e., not already
incorporated into the applicant's request) mitigation or monitoring
measures that are practicable and would further reduce potential
impacts to sea otters and their habitat.
Impact on Subsistence Use
We propose a finding that the CBS'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)
We have prepared a draft environmental assessment in accordance
with the NEPA (42 U.S.C. 4321 et seq.). We have preliminarily concluded
that authorizing the nonlethal, incidental, unintentional take by Level
B harassment of up to 36 northern sea otters from the Southeast Alaska
stock during the specified activities would not significantly affect
the quality of the human environment and, thus, preparation of an
environmental impact statement for this incidental harassment
authorization is not required by section 102(2) of NEPA or its
implementing regulations. We are accepting comments on the draft
environmental assessment as specified above in DATES and ADDRESSES.
Endangered Species Act
Under the Endangered Species Act (ESA) (16 U.S.C. 1536(a)(2)), 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 specified activities would occur entirely within
the range of the Southeast Alaska stock of northern sea otters, which
is not listed as threatened or endangered under the ESA.
The authorization of incidental take of sea otters and the measures
included in the proposed IHA would not affect other listed species or
designated critical habitat.
Government-to-Government Consultation
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 the Interior's policies on consultation with
Alaska Native Tribes and organizations.
We have evaluated possible effects of the specified 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.
The FWS does not anticipate impacts to Alaska Native Tribes or Alaska
Native Claims Settlement Act corporations and does not anticipate
requesting consultation; however, we invite continued discussion,
either about the project and its impacts or about our coordination and
information exchange throughout the IHA/POC process.
Paperwork Reduction Act
This rule does not contain any new collection of information that
require approval by the Office of Management and Budget (OMB) under the
Paperwork Reduction Act of 1995 (44 U.S.C. 3501 et seq.). OMB has
previously approved the information collection requirements associated
with IHAs and assigned OMB Control Number 1018-0194 (expires 08/31/
2026). An agency may not conduct or sponsor, and a person is not
required to respond to, a collection of information unless it displays
a currently valid OMB control number.
Proposed Authorization
We propose to authorize the nonlethal, incidental take by Level B
harassment of 36 Southeast Alaska stock northern sea otters. Authorized
take will be limited to disruption of behavioral patterns that may be
caused by construction of a seaplane base, and support activities
conducted by the City and Borough of Sitka in the Sitka Channel, Sitka,
Alaska, between July 1, 2024 and July 1, 2025. We do not anticipate or
propose to authorize any lethal take or Level A harassment.
A. General Conditions for This IHA
(1) Activities must be conducted in the manner described in the
revised Request dated November 16, 2023, for an IHA and in accordance
with all applicable conditions and mitigations measures. The taking of
sea otters whenever the required conditions,
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mitigation, monitoring, and reporting measures are not fully
implemented as required by the IHA is prohibited. Failure to follow the
measures specified both in the Request and within this proposed
authorization may result in the modification, suspension, or revocation
of the IHA.
(2) If project activities cause unauthorized take (i.e., take of
more than 36 Southeast Alaska stock northern sea otters, a form of take
other than Level B harassment, or take of one or more sea otters
through methods not described in the IHA), the City and Borough of
Sitka 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 FWS within 48 hours;
and
(iii) suspend further activities until the FWS has reviewed the
circumstances and determined whether additional mitigation measures are
necessary to avoid further unauthorized taking.
(3) All operations managers, vehicle operators, and vessel
operators must receive a copy of this 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) This IHA will apply to activities associated with the specified
project as described in this document and in the City and Borough of
Sitka's Request. Changes to the specified project without prior
authorization may invalidate the IHA.
(5) The City and Borough of Sitka's Request is approved and fully
incorporated into this IHA unless exceptions are specifically noted
herein. The Request includes:
(i) The City and Borough of Sitka's original request for an IHA,
dated August 18, 2023;
(ii) Revised requests, dated October 13, 2023, and November 16,
2023; and
(iii) Geospatial files of the project location and ensonification
areas.
(6) Operators will allow FWS personnel or the FWS's designated
representative to visit project work sites to monitor for 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 City and Borough of Sitka's
authority, including all contractors and subcontractors.
B. Avoidance and Minimization
(7) Construction activities must be conducted using equipment that
generates the lowest practicable levels of underwater sound within the
range of frequencies audible to sea otters.
(8) During all pile-installation activities, regardless of
predicted sound levels, a physical interaction shutdown zone of 30 m
(98 ft) must be enforced. If a sea otter enters the shutdown zone, in-
water activities must be delayed until either the animal has been
visually observed outside the shutdown zone, or 30 minutes have elapsed
since the last observation time without redetection of the animal.
(9) If the impact driver has been idled for more than 30 minutes,
an initial set of 3 strikes from the impact driver must be delivered at
reduced energy, followed by a 1-minute waiting period, and then two
subsequent 3-strike sets before full-powered proofing strikes.
(10) In-water activity must be conducted in daylight. If
environmental conditions prevent visual detection of sea otters within
the shutdown zone, in-water activities must be stopped until visibility
is regained.
C. Mitigation Measures for Vessel Operators
Vessel operators must take every precaution to avoid harassment of
sea otters when a vessel is operating near these animals. The applicant
must carry out the following measures:
(11) Vessels must remain at least 500 m (0.3 mi) from rafts of 10
or more sea otters, unless safety is a factor. Vessels must reduce
speed and maintain a distance of 100 m (328 ft) from all sea otters,
unless safety is a factor.
(12) Vessels must not be operated in such a way as to separate
members of a group of sea otters from other members of the group, and
must avoid alongshore travel in shallow water (<20 m (66 ft)) whenever
practicable.
(13) When weather conditions require, such as when visibility
drops, vessels must adjust speed accordingly to avoid the likelihood of
injury to sea otters.
(14) Vessel operators must be provided written guidance for
avoiding collisions and minimizing disturbances to sea otters. Guidance
will include measures identified in paragraphs (C)(11) through (13) of
this section.
D. Monitoring
(15) Operators shall work with protected species observers (PSO) 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 personnel.
(16) Duties of the 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 operators to implement all appropriate
mitigation measures.
(17) A sufficient number of PSOs will be available to meet the
following criteria: 100 percent monitoring of exclusion zones during
all daytime periods of underwater noise-generating work; a maximum of 4
consecutive hours on watch per PSO; a maximum of approximately 12 hours
on watch per day per PSO.
(18) 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 sea otter observer will
supervise the PSO team. Initially, 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 FWS to review.
(19) Observers will be provided with reticule binoculars (7x50 or
better), 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.
(20) Observers will collect data using the following procedures:
(i) All data will be recorded onto a field form or database.
(ii) Global positioning system data, sea state, wind force, and
weather will be collected at the beginning and end of a monitoring
period, every hour in between, at the change of an observer, and upon
sightings of sea otters.
(iii) Observation records of sea otters will include date; time;
the observer's locations, heading, and speed (if moving); weather;
visibility; number of animals; group size and composition (adults/
juveniles); and the location of the animals (or distance and direction
from the observer).
(iv) Observation records will also include initial behaviors of the
sea otters, descriptions of project activities and underwater sound
levels being generated, the position of sea otters relative to
applicable monitoring and mitigation zones, any mitigation measures
applied, and any apparent reactions to the project activities before
and after mitigation.
(v) For all sea otters in or near a mitigation zone, observers will
record
[[Page 38180]]
the distance from the sound source to the sea otter upon initial
observation, the duration of the encounter, and the distance at last
observation in order to monitor cumulative sound exposures.
(vi) Observers will note any instances of animals lingering close
to or traveling with vessels for prolonged periods of time.
(21) Monitoring of the shutdown zone must continue for 30 minutes
following completion of pile installation.
E. Measures To Reduce Impacts to Subsistence Users
(22) Prior to conducting the work, the City and Borough of Sitka
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 Southeast Alaska villages and traditional councils;
(iii) Identify and work to resolve concerns of stakeholders
regarding the project's effects on subsistence hunting of sea otters;
and
(iv) If any concerns remain, develop a POC in consultation with the
FWS and subsistence stakeholders to address these concerns.
F. Reporting Requirements
(23) The City and Borough of Sitka must notify the FWS at least 48
hours prior to commencement of activities.
(24) Reports will be submitted to the FWS's MMM weekly during
project activities. The reports will summarize project work and
monitoring efforts.
(25) A final report will be submitted to the FWS'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 the City and
Borough of Sitka'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.
(26) 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 FWS
within 24 hours of discovery. Photographs, video, location information,
or any other available documentation shall be provided to the FWS.
(27) All reports shall be submitted by email to
[email protected].
(28) The City and Borough of Sitka must notify the FWS 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 either 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 FWS will consider all comments
that are received before the close of the comment period (see DATES).
The FWS does not anticipate extending the public comment period beyond
the 30 days required under section 101(a)(5)(D)(iii) of the MMPA.
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.
Peter Fasbender,
Assistant Regional Director for Fisheries and Ecological Services,
Alaska Region.
[FR Doc. 2024-09895 Filed 5-6-24; 8:45 am]
BILLING CODE 4333-15-P