# Takes of Marine Mammals Incidental to Specified Activities; Taking Marine Mammals Incidental to Geophysical and Geotechnical Survey in Cook Inlet, Alaska

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URL: https://www.frixlaw.com/law-library/documents/fr%3A2015-16012

## Record

- **Collection:** Federal Register
- **Document type:** Notice
- **Published:** June 30, 2015
- **Citation:** 80 FR 37466

## Text

DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
RIN 0648-XE018
Takes of Marine Mammals Incidental to Specified Activities; Taking Marine Mammals Incidental to Geophysical and Geotechnical Survey in Cook Inlet, Alaska

AGENCY:

National Marine Fisheries Service (NMFS), National Oceanic and Atmospheric Administration (NOAA), Commerce.

ACTION:

Notice; proposed incidental harassment authorization; request for comments.

SUMMARY:

NMFS has received an application from ExxonMobil Alaska LNG LLC (AK LNG) for an Incidental Harassment Authorization (IHA) to take marine mammals, by harassment, incidental to a geophysical and geotechnical survey in Cook Inlet, Alaska. This action is proposed to occur for 84 days after August 7, 2015. Pursuant to the Marine Mammal Protection Act (MMPA), NMFS is requesting comments on its proposal to issue an IHA to AK LNG to incidentally take, by Level B Harassment only, marine mammals during the specified activity.

DATES:

Comments and information must be received no later than July 30, 2015.

ADDRESSES:

Comments on the application should be addressed to Jolie Harrison, Chief, Permits and Conservation Division, Office of Protected Resources, National Marine Fisheries Service, 1315 East-West Highway, Silver Spring, MD 20910. The mailbox address for providing email comments is
itp.young@noaa.gov
. Comments sent via email, including all attachments, must not exceed a 25-megabyte file size. NMFS is not responsible for comments sent to addresses other than those provided here.

Instructions:
All comments received are a part of the public record and will generally be posted to
http://www.nmfs.noaa.gov/pr/permits/incidental.htm
without change. All Personal Identifying Information (for example, name, address, etc.) voluntarily submitted by the commenter may be publicly accessible. Do not submit Confidential Business Information or otherwise sensitive or protected information.

An electronic copy of the application may be obtained by writing to the address specified above, telephoning the contact listed below (see
FOR FURTHER INFORMATION CONTACT
), or visiting the internet at:
http://www.nmfs.noaa.gov/pr/permits/incidental.htm
. The following associated documents are also available at the same internet address: Draft Environmental Assessment.

FOR FURTHER INFORMATION CONTACT:

Sara Young, Office of Protected Resources, NMFS, (301) 427-8484.

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.
) directs the Secretary of Commerce 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 geographical region if, after NMFS provides a notice of a proposed authorization to the public for review and comment: (1) NMFS makes certain findings; and (2) the taking is limited to harassment.

An Authorization for incidental takings shall be granted if NMFS finds that the taking will have a negligible impact on the species or stock(s), will not have an unmitigable adverse impact on the availability of the species or stock(s) for subsistence uses (where relevant), and if the permissible methods of taking and requirements pertaining to the mitigation, monitoring and reporting of such takings are set forth. NMFS has defined “negligible impact” in 50 CFR 216.103 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.”

Except with respect to certain activities not pertinent here, the MMPA defines “harassment” as: Any act of pursuit, torment, or annoyance which (i) has the potential to injure a marine mammal or marine mammal stock in the wild [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 [Level B harassment].

Summary of Request

On February 4, 2015, NMFS received an application from AK LNG for the taking of marine mammals incidental to a geotechnical and geophysical survey in Cook Inlet, Alaska. NMFS determined that the application was adequate and complete on June 8, 2015.

AK LNG proposes to conduct a geophysical and geotechnical survey in Cook Inlet to investigate the technical suitability of a pipeline study corridor across Cook Inlet and potential marine terminal locations near Nikiski. The proposed activity would occur for 12 weeks during the 2015 open water season after August 7, 2015. The following specific aspects of the proposed activities are likely to result in the take of marine mammals: Sub-bottom profiler (chirp and boomer), and a seismic airgun. Take, by Level B Harassment only, of individuals of four species is anticipated to result from the specified activities.

Description of the Specified Activity

Overview

The planned geophysical surveys involve remote sensors including single beam echo sounder, multibeam echo sounder, sub-bottom profilers (chirp and boomer), 0.983 L (60 in
3
) airgun, side scan sonar, geophysical resistivity meters, and magnetometer to characterize the bottom surface and subsurface. The planned shallow geotechnical investigations include vibracoring, sediment grab sampling, and piezo-cone penetration testing (PCPT) to directly evaluate seabed features and soil conditions. Geotechnical borings are planned at potential shoreline crossings and in the terminal boring subarea within the Marine Terminal survey area, and will be used to collect information on the mechanical properties of in-situ soils to support feasibility studies for construction crossing techniques and decisions on siting and design of pilings, dolphins, and other marine structures. Geophysical resistivity imaging will be conducted at the potential shoreline crossings. Shear wave velocity profiles (downhole geophysics) will be conducted within some of the boreholes. Further details of the planned operations are provided below.

Dates and Duration

Geophysical and geotechnical surveys that do not involve equipment that could acoustically harass listed marine mammals could begin as soon as April 2015, depending on the ice conditions. These surveys include echo sounders and side scan sonar surveys operating at frequencies above the hearing range of local marine mammals and geotechnical borings, which are not expected to produce underwater noise exceeding

ambient. The remaining surveys, including use of sub-bottom profilers and the small airgun, would occur soon after receipt of the IHA, if granted. These activities would be scheduled in such a manner as to minimize potential effects to marine mammals, subsistence activities, and other users of Cook Inlet waters. It is expected that approximately 12 weeks (84 work days) are required to complete the G&G Program. The work days would not all be consecutive due to weather, rest days, and any timing restrictions.

Specified Geographic Region

The Cook Inlet 2015 G&G Program will include geophysical surveys, shallow geotechnical investigations, and geotechnical borings. Two separate areas will be investigated and are shown in Figure 1 of the application: The pipeline survey area and the Marine Terminal survey area (which includes an LNG carrier approach zone). The pipeline survey area runs from the Kenai Peninsula, across the Inlet, up to Beluga, also considered the Upper Inlet. The Terminal area will include an area west and south of Nikiski, the northern edge of what is considered the Lower Inlet. The G&G Program survey areas (also referred to as the action area or action areas) are larger than the proposed pipeline route and the Marine Terminal site to ensure detection of all potential hazards, or to identify areas free of hazards. This provides siting flexibility should the pipeline corridor or Marine Terminal sites need to be adjusted to avoid existing hazards.

• Pipeline Survey Area—The proposed pipeline survey area (Figure 1) crosses Cook Inlet from Boulder Point on the Kenai Peninsula across to Shorty Creek about halfway between the village of Tyonek and the Beluga River. This survey area is approximately 45 km (28 mi) in length along the corridor centerline and averages about 13 km (8 mi) wide. The total survey area is 541 km2 (209 mi2). The pipeline survey area includes a subarea where vibracores will be conducted in addition to the geophysical surveys and shallow geotechnical investigations.

• Marine Terminal Survey Area—The proposed Marine Terminal survey area (Figure 1) encompassing 371 km2 (143 mi2) is located near Nikiski where potential sites and vessel routes for the Marine Terminal are being investigated. The Marine Terminal survey area includes two subareas: A seismic survey subarea where the airgun will be operated in addition to the other geophysical equipment, and a terminal boring subarea where geotechnical boreholes will be drilled in addition to the geophysical survey and shallow geotechnical investigations. The seismic survey subarea encompasses 25 km2 (8.5 mi2) and the terminal boring subarea encompasses 12 km2 (4.6 mi2).

Detailed Description of Activities

The details of this activity are broken down into two categories for further description and analysis: Geophysical surveys and geotechnical surveys.

Geophysical Surveys

The types of acoustical geophysical equipment planned for use in the Cook Inlet 2015 G&G Program are indicated, by survey area, in Table 1 in the application. The equipment includes: Single beam echo sounder, multibeam echo sounder, sub-bottom profilers (chirp and boomer), 0.983 L (60 in
3
) airgun, and side scan sonar. The magnetometer and resistivity system are not included in the table since they are not acoustical in nature and, thus, do not generate sound that might harass marine mammals, nor do they affect habitat.

Downhole geophysics is included in the table as a sound source, but is not considered further in this assessment as the energy source will not generate significant sound energy within the water column since the equipment will be located downhole within the geotechnical boreholes. The transmitter (source) and receiver are both housed within the same probe or tool that is lowered into the hole on a wireline. The suspension log transmitter is an electromechanical device. It consists of a metallic barrel (the hammer) disposed horizontally in the tool and actuated by an electromagnet (solenoid) to hit the inside of tool body (the plate). The fundamental H1 mode is at about 4.5 KHz, and H2 is at 9 KHz. An extra resonance (unknown) mode is also present at about 15Khz. An analysis performed to estimate the expected sound level of the proposed borehole logging equipment scaled the sound produced by a steel pile driven by a hammer (given that both are cylindrical noise sources and produce impulsive sounds) and concluded that the sound level produced at 25m by the borehole logging equipment would be less than 142 dB. This is not considering the confining effect of the borehole which would lower the sound level even further (I&R, 2015).

The other types of geophysical equipment proposed for the 2015 program will generate impulsive sound in the water column and are described below Information on the acoustic characteristics of geophysical and geotechnical sound sources is also summarized in Table 2 in the application, followed by a corresponding description of each piece of equipment to be used.

Single Beam Echo Sounders

Single beam echo sounders calculate water depth by measuring the time it takes for emitted sound to reflect off the seafloor bottom and return to the transducer. They are usually mounted on the vessel hull or a side-mounted pole. Echo sounding is expected to be conducted concurrently with sub-bottom profiling. Given an operating frequency of more than 200 kHz (Table 2), it is unlikely that the single beam echosounder will cause behavioral disturbance to marine mammals in the area (Wartzok and Ketten 1999, Southall et al. 2007, Reichmuth and Southall 2011, Castellote et al. 2014). While literature has shown pinniped behavioral reaction to sounds at 200kHz, as well as detection of subharmonics at 90 and 130 KHz by several odontocetes, the ambient noise levels in Cook Inlet make behavioral disturbance unlikely (Hastie et al. 2014, Deng et al. 2014). Further, single beam echo sounders operate at relatively low energy levels (146 dB re 1 μPa-m [rms]). The simultaneous operations of echo sounder with sub-bottom profiler should have no additive effect on marine mammals. The high ambient noise levels in Cook Inlet, as well as the low proposed source level of this technology will like not disturb marine mammals to the point of Level B harassment. Thus, this equipment is not further evaluated in this application

Multibeam Echo Sounders

Multibeam echo sounders emit a swath of sonar downward to the seafloor at source energy levels of 188 dB re 1 μPa-m (rms). The reflection of the sonar signal provides for the production of three dimensional seafloor images. These systems are usually side-mounted to the vessel. Echo sounding is expected to be conducted concurrently with sub-bottom profiling. Given the operating frequencies of the planned multibeam system (>200 kHz, Table 2), the generated underwater sound will be beyond the hearing range of Cook Inlet marine mammals (Wartzok and Ketten 1999, Kastelein et al. 2005, Southall et al. 2007, Reichmuth and Southall 2011, Castellote et al. 2014). Further, most sound energy is emitted directly downward from this equipment, not laterally. As with the single beam, the multibeam is not further evaluated because it far exceeds the maximum hearing frequency of local marine mammals. Due to this technology being

above the hearing frequency of local marine mammal species, the simultaneous operations of echo sounder with sub-bottom profiler should have no additive effect on marine mammals.

Side-Scan Sonar

Side-scan sonar emits a cone-shaped pulse downward to the seafloor with source energy of about 188 dB re 1 μPa-m (rms). Acoustic reflections provide a two-dimensional image of the seafloor and other features. The side-scan sonar system planned for use during this program will emit sound energy at frequencies of 400 and 1600 kHz (Table 2), which are well beyond the normal hearing range of Cook Inlet marine mammals (Wartzok and Ketten 1999, Kastelein et al. 2005, Southall et al. 2007, Reichmuth and Southall 2011, Castellote et al. 2014). Side-scan sonar is not further evaluated in this application.

Sub-Bottom Profiler—Chirp

The chirp sub-bottom profiler planned for use in this program is a precisely controlled “chirp” system that emits high-energy sounds with a resolution of one millisecond (ms) and is used to penetrate and profile the shallow sediments near the sea floor. At operating frequencies of 2 to 16 kHz (Table 2), this system will be operating at the lower end of the hearing range of beluga whales and well below the most sensitive hearing range of beluga whales (45-80 kHz, Castellote et al. 2014). The source level is estimated at 202 dB re 1 μPa-m (rms). The beam width is 24 degrees and pointed downward.

Sub-Bottom Profiler—Boomer

A boomer sub-bottom profiling system with a penetration depth of up to 600 ms and resolution of 2 to 10 ms will be used to penetrate and profile the Cook Inlet sediments to an intermediate depth. The system will be towed behind the vessel. With a sound energy source level of about 205 dB re 1 μPa-m (rms) at frequencies of 0.5 to 6 kHz (Table 2), most of the sound energy generated by the boomer will be at frequencies that are well below peak hearing sensitivities of beluga whales (45-80 kHz; Castellote et al. 2014), but would still be detectable by these animals. The boomer is pointed downward but the equipment is omni-directional so the physical orientation is irrelevant.

Airgun

A 0.983 L (60 in
3
) airgun will be used to gather high resolution profiling at greater depths below the seafloor. The published source level from Sercel (the manufacturer) for a 0.983 L (60 in
3
) airgun is 216 dB re 1 μPa-m (equating to about 206 dB re 1 μPa-m (rms). These airguns typically produce sound levels at frequencies of less than 1 kHz (Richardson et al. 1995, Zykov and Carr 2012), or below the most sensitive hearing of beluga whales (45-80 kHz; Castellote et al. 2014), but within the functional hearing of these animals (>75 Hz; Southall et al. 2007). The airgun will only be used during geophysical surveys conducted in the smaller seismic survey subarea within the Marine Terminal survey area (Lower Inlet).

Geotechnical Surveys

Shallow Geotechnical Investigations—Vibracores

Vibracoring is conducted to obtain cores of the seafloor sediment from the surface down to a depth of about 6.1 m (20 ft). The cores are later analyzed in the laboratory for moisture, organic and carbonate content, shear strength, and grain size. Vibracore samplers consist of a 10-cm (4.0-in) diameter core barrel and a vibratory driving mechanism mounted on a four-legged frame, which is lowered to the seafloor. The electric motor driving mechanism oscillates the core barrel into the sediment where a core sample is then extracted. The duration of the operation varies with substrate type, but generally the sound source (driving mechanism) is operable for only the one or two minutes it takes to complete the 6.1-m (20-ft) bore and the entire setup process often takes less than one hour.

Chorney et al. (2011) conducted sound measurements on an operating vibracorer in Alaska and found that it emitted a sound pressure level at 1-m source of 187.4 dB re 1 μPa-m (rms), with a frequency range of between 10 Hz and 20 kHz (Table 2). Vibracoring will result in the largest zone of influence (ZOI; area ensonified by sound energy greater than the 120 dB threshold) among the continuous sound sources. Vibracoring would also have a very small effect on the benthic habitat.

Vibracoring will be conducted at approximate intervals of one core every 4.0 km (2.5 mi) along the pipeline corridor centerline for a total of about 22 samplings total. Approximately 33 vibracores will also be collected within the Marine Terminal survey area. Only about three or four vibracorings per day are expected to be conducted over about 14 days of vibracoring activity, but given the expected duration per vibracore the total time the sound source would be operating is expected to be about 2.0 hours or less.

Because of the very brief duration within a day (up to four 1 or 2-minute periods) of this continuous, non-impulsive sound, combined with the small number of days the source will be used overall, NMFS does not believe that the vibracore operations will result in the take of marine mammals. However, because the applicant requested take from this source and included a quantitative analysis in their application, that analysis will be included here for reference and opportunity for public comment.

Geotechnical Borings

Geotechnical borings will be conducted within the Marine Terminal survey area and within the pipeline survey area near potential shoreline crossings. Geotechnical borings will be conducted by collecting geotechnical samples from borings 15.2 to 70.0 m (50-200 ft) deep using a rotary drilling unit mounted on a small jack-up platform. Geotechnical borings provide geological information at greater sediment depths than vibracores. These data are required to help inform proper designs and construction techniques for pipeline crossing and terminal facilities. The number of and general locations for the planned geotechnical boreholes are provided below in Table 3.

The jack-up platform is expected to be the Seacore
Skate 3
modular jack-up or a similar jack-up. The Skate 3 modular platform is supported by four 76-cm (30-in) diameter legs. The borings will be drilled with a Comacchio MC-S conventional rotary geotechnical drill rig mounted on rubber skids. Four geotechnical boreholes will be drilled at each of the two shoreline crossings (8 total), and up to 34 boreholes will be drilled in the terminal boring subarea within the Marine Terminal survey area.

Sound source verifications of large jack-up drilling rigs in Cook Inlet (
Spartan 151
and
Endeavour
) have shown that underwater sound generated by rotary drilling from elevated platforms on jack-ups generally does not exceed the underwater ambient sound levels at the source (MAI 2011, I&R 2014). Underwater sound generated by these larger drill rigs was identified as being associated with the rigs' large hotel generators or with underwater deep-well pumps, neither of which type of equipment is used by the Skate 3, which should therefore make the operational noise quieter than the sound source levels measured for the
Spartan 151
and
Endeavour
. The Skate 3 is equipped with only a small deck-mounted pump and generator. Sound source information is not available for the
Skate 3,
however, the rubber tracks

of the skid and the narrow legs of the rig greatly limit the transmission of sound (via vibrations) from the drilling table into the water column. Underwater sound generated from the Skate 3 from geotechnical borings is expected to be much less than those in the sound source verifications for the rigs mentioned above (MAI, 2011; I&R, 2014); the borings are therefore not further evaluated as potential noise impact. However, the intrusive borings will affect benthic habitat and is later described.

Sediment Grab Samples

Grab sampling will involve using a Van Veen grab sampler that will be lowered with its “jaws” open to the seafloor from the geophysical vessel at which point the mechanical closing mechanism is activated, thus “grabbing” a sample of bottom sediment. The sampler is retrieved to the vessel deck and a sample of the sediments collected for environmental and geotechnical analysis, such as soil description and sieve analyses. Grab sampling does not produce significant underwater sound, but will have a small effect on the benthic habitat. Grab samples will be obtained as warranted to aid interpretation of geophysical data.

Piezo-Cone Penetration Testing

Piezo-cone penetration testing (PCPT) involves placing a metal frame on the ocean bottom and then pushing an instrumented cone into the seafloor at a controlled rate, measuring the resistance and friction of the penetration. The results provide a measure of the geotechnical engineering property of the soil, including load bearing capacity and stratigraphy. The target depth is about 4.9 m (16 ft). PCPTs will be conducted at intervals of about one per 8.0 km (5.0 mi) along the pipeline corridor centerline and elsewhere in the pipeline survey area and Marine Terminal survey area. Precise target locations will be determined in the field and will be adjusted by onboard personnel after the preliminary geophysical data has been made available to select sample locations that better identify soil transition zones and/or other features. PCPT will have an inconsequential effect on benthic habitat as well as local marine mammal populations

Vessels

The geophysical surveys will be conducted from one of two source vessels with the smaller of the two used in more shallow, nearshore water conditions. Vibracoring will be conducted from a third vessel as noted in Table 4 in the application. Geotechnical borings will be conducted from a jack-up platform. The jack-up platform is not self-powered, and will be positioned over each sampling location by a tug. The proposed vessels are: Three source vessels, one jack-up platform, and one tug. The contracted vessels will either be these vessels or similar vessels with similar configurations.

Description of Marine Mammals in the Area of the Specified Activity

Marine mammals that regularly inhabit upper Cook Inlet and Nikiski activity areas are the beluga whale (
Delphinapterus leucas
), harbor porpoise (
Phocoena phocoena
), and harbor seal (
Phoca vitulina
) (Table 6). However, these species are found there in relatively low numbers, and generally only during the summer fish runs (Nemeth
et al.
2007, Boveng
et al.
2012). Killer whales (
Orcinus orca
) are occasionally observed in upper Cook Inlet where they have been observed attempting to prey on beluga whales (Shelden et al. 2003). Based on a number of factors, Shelden et al. (2003) concluded that the killer whales found in upper Cook Inlet to date are the transient type, while resident types occasionally enter lower Cook Inlet. Marine mammals occasionally found in lower Cook Inlet include humpback whales (
Megaptera novaeangliae
), gray whales (
Eschrichtius robustus
), minke whales (
Balaenoptera acutorostrata
), Dall's porpoise (
Phocoena dalli
), and Steller sea lion (
Eumetopias jubatus).
Background information of species evaluated in this proposed Authorization is detailed in Table 1 below.

Table 1—Marine Mammals Inhabiting the Cook Inlet Action Area

Species
Stock

ESA/MMPA status
1
; strategic (Y/N)

Stock abundance (CV, N
min
, most recent abundance survey)
2

Relative occurrence in Cook Inlet; season of occurrence

Killer whale
Alaska Resident
-;N
2,347 (N/A; 2,084; 2009)
Occasionally sighted in Lower Cook Inlet.

Alaska Transient
-:N
345 (N/A; 303; 2003)

Beluga whale
Cook Inlet
E/D;Y
312 (0.10; 280; 2012)
Use upper Inlet in summer and lower in winter: Annual.

Harbor porpoise
Gulf of Alaska
-;Y
31,046 (0.214; 25,987; 1998)
Widespread in the Inlet: Annual (less in winter).

Harbor seal
Cook Inlet/Shelikof
-;N
22,900 (0.053; 21,896; 2006)
Frequently found in upper and lower inlet; annual (more in northern Inlet in summer).

Beluga Whale (Delphinapterus leucas)

The Cook Inlet beluga whale Distinct Population Stock (DPS) is a small geographically isolated population that is separated from other beluga populations by the Alaska Peninsula. The population is genetically (mtDNA) distinct from other Alaska populations suggesting that the Peninsula is an effective barrier to genetic exchange (O'Corry-Crowe et al. 1997) and that these whales may have been separated from other stocks at least since the last ice age. Laidre et al. (2000) examined data from over 20 marine mammal surveys conducted in the northern Gulf of Alaska and found that sightings of belugas outside Cook Inlet were exceedingly rare, and these were composed of a few stragglers from the Cook Inlet DPS observed at Kodiak Island, Prince William Sound, and Yakutat Bay. Several marine mammal surveys specific to Cook Inlet (Laidre et al. 2000, Speckman and Piatt 2000), including those that concentrated on beluga whales (Rugh et al. 2000, 2005a), clearly indicate that this stock largely confines itself to Cook Inlet. There is no indication that these whales make forays into the Bering Sea where they might intermix with other Alaskan stocks.

The Cook Inlet beluga DPS was originally estimated at 1,300 whales in

1979 (Calkins 1989) and has been the focus of management concerns since experiencing a dramatic decline in the 1990s. Between 1994 and 1998 the stock declined 47%, which has been attributed to overharvesting by subsistence hunting. During that period, subsistence hunting was estimated to have annually removed 10-15% of the population. Only five belugas have been harvested since 1999, yet the population has continued to decline (Allen and Angliss 2014), with the most recent estimate at only 312 animals (Allen and Angliss 2014). The NMFS listed the population as “depleted” in 2000 as a consequence of the decline, and as “endangered” under the Endangered Species Act (ESA) in 2008 when the population failed to recover following a moratorium on subsistence harvest. In April 2011, the NMFS designated critical habitat for the Cook Inlet beluga whale under the ESA (Figure 2 in the application).

Prior to the decline, this DPS was believed to range throughout Cook Inlet and occasionally into Prince William Sound and Yakutat (Nemeth et al. 2007). However, the range has contracted coincident with the population reduction (Speckman and Piatt 2000). During the summer and fall, beluga whales are concentrated near the Susitna River mouth, Knik Arm, Turnagain Arm, and Chickaloon Bay (Nemeth et al. 2007) where they feed on migrating eulachon (
Thaleichthys pacifcus
) and salmon (Onchorhynchus spp.) (Moore et al. 2000). The limits of Critical Habitat Area 1 reflect the summer distribution (Figure 3 in the application). During the winter, beluga whales concentrate in deeper waters in the mid-inlet to Kalgin Island, and in the shallow waters along the west shore of Cook Inlet to Kamishak Bay. The limits of Critical Habitat Area 2 reflect the winter distribution. Some whales may also winter in and near Kachemak Bay.

Goetz et al. (2012) modeled beluga use in Cook Inlet based on the NMFS aerial surveys conducted between 1994 and 2008. The combined model results shown in Figure 3 in the application indicate a very clumped distribution of summering beluga whales, and that lower densities of belugas are expected to occur in most of the pipeline survey area (but not necessarily specific G&G survey locations; see Section 6.3 in the application) and the vicinity of the proposed Marine Terminal. However, beluga whales begin moving into Knik Arm around August 15 where they spend about a month feeding on Eagle River salmon. The area between Nikiski, Kenai, and Kalgin Island provides important wintering habitat for Cook Inlet beluga whales. Use of this area would be expected between fall and spring, with animals largely absent during the summer months when G&G surveys would occur (Goetz
et al.
2012).

Killer Whale (Orcinus orca)

Two different stocks of killer whales inhabit the Cook Inlet region of Alaska: The Alaska Resident Stock and the Gulf of Alaska, Aleutian Islands, Bering Sea Transient Stock (Allen and Angliss 2014). The Alaska Resident stock is estimated at 2,347 animals and occurs from Southeast Alaska to the Bering Sea (Allen and Angliss 2014). Resident whales feed exclusively on fish and are genetically distinct from transient whales (Saulitis et al. 2000).

The transient whales feed primarily on marine mammals (Saulitis et al. 2000). The transient population inhabiting the Gulf of Alaska shares mitochondrial DNA haplotypes with whales found along the Aleutian Islands and the Bering Sea, suggesting a common stock, although there appears to be some subpopulation genetic structuring occurring to suggest the gene flow between groups is limited (see Allen and Angliss 2014). For the three regions combined, the transient population has been estimated at 587 animals (Allen and Angliss 2014).

Killer whales are occasionally observed in lower Cook Inlet, especially near Homer and Port Graham (Shelden et al. 2003, Rugh et al. 2005a). The few whales that have been photographically identified in lower Cook Inlet belong to resident groups more commonly found in nearby Kenai Fjords and Prince William Sound (Shelden et al. 2003). Prior to the 1980s, killer whale sightings in upper Cook Inlet were very rare. During aerial surveys conducted between 1993 and 2004, killer whales were observed on only three flights, all in the Kachemak and English Bay area (Rugh et al. 2005a). However, anecdotal reports of killer whales feeding on belugas in upper Cook Inlet began increasing in the 1990s, possibly in response to declines in sea lion and harbor seal prey elsewhere (Shelden et al. 2003). These sporadic ventures of transient killer whales into beluga summering grounds have been implicated as a possible contributor to the decline of Cook Inlet belugas in the 1990s, although the number of confirmed mortalities from killer whales is small (Shelden et al. 2003). If killer whales were to venture into upper Cook Inlet in 2015, they might be encountered during the G&G Program.

Harbor Porpoise (Phocoena phocoena)

Harbor porpoise are small (approximately 1.2 m [4 ft] in length), relatively inconspicuous toothed whales. The Gulf of Alaska Stock is distributed from Cape Suckling to Unimak Pass and was most recently estimated at 31,046 animals (Allen and Angliss 2014). They are found primarily in coastal waters less than 100 m (328 ft) deep (Hobbs and Waite 2010) where they feed on Pacific herring (
Clupea pallasii
), other schooling fishes, and cephalopods.

Although they have been frequently observed during aerial surveys in Cook Inlet, most sightings of harbor porpoise are of single animals, and are concentrated at Chinitna and Tuxedni bays on the west side of lower Cook Inlet (Rugh et al. 2005a). Dahlheim et al. (2000) estimated the 1991 Cook Inlet-wide population at only 136 animals. Also, during marine mammal monitoring efforts conducted in upper Cook Inlet by Apache from 2012 to 2014, harbor porpoise represented less than 2% of all marine mammal sightings. However, they are one of the three marine mammals (besides belugas and harbor seals) regularly seen in upper Cook Inlet (Nemeth et al. 2007), especially during spring eulachon and summer salmon runs. Because harbor porpoise have been observed throughout Cook Inlet during the summer months, including mid-inlet waters, they represent species that might be encountered during G&G Program surveys in upper Cook Inlet.

Harbor Seal (Phoca vitulina)

At over 150,000 animals state-wide (Allen and Angliss 2014), harbor seals are one of the more common marine mammal species in Alaskan waters. They are most commonly seen hauled out at tidal flats and rocky areas. Harbor seals feed largely on schooling fish such as Alaska pollock (Theragra chalcogramma), Pacific cod (Gadus macrocephalus), salmon, Pacific herring, eulachon, and squid. Although harbor seals may make seasonal movements in response to prey, they are resident to Alaska and do not migrate.

The Cook Inlet/Shelikof Stock, ranging from approximately Anchorage down along the south side of the Alaska Peninsula to Unimak Pass, has been recently estimated at a stable 22,900 (Allen and Angliss 2014). Large numbers concentrate at the river mouths and embayments of lower Cook Inlet, including the Fox River mouth in Kachemak Bay (Rugh et al. 2005a). Montgomery et al. (2007) recorded over 200 haulout sites in lower Cook Inlet

alone. However, only a few dozen to a couple hundred seals seasonally occur in upper Cook Inlet (Rugh et al. 2005a), mostly at the mouth of the Susitna River where their numbers vary with the spring eulachon and summer salmon runs (Nemeth et al. 2007, Boveng et al. 2012). Review of NMFS aerial survey data collected from 1993-2012 (Shelden et al. 2013) finds that the annual high counts of seals hauled out in Cook Inlet ranged from about 100-380, with most of these animals hauling out at the mouths of the Theodore and Lewis Rivers. There are certainly thousands of harbor seals occurring in lower Cook Inlet, but no references have been found showing more than about 400 harbor seals occurring seasonally in upper Cook Inlet. In 2012, up to 100 harbor seals were observed hauled out at the mouths of the Theodore and Lewis rivers (located about 16 km [10 mi] northeast of the pipeline survey area) during monitoring activity associated with Apache's 2012 Cook Inlet seismic program, and harbor seals constituted 60 percent of all marine mammal sightings by Apache observers during 2012 to 2014 survey and monitoring efforts (L. Parker, Apache, pers. comm.). Montgomery et al. (2007) also found that seals elsewhere in Cook Inlet move in response to local steelhead (
Onchorhynchus mykiss
) and salmon runs. Harbor seals may be encountered during G&G surveys in Cook Inlet.

Humpback Whale (Megaptera novaeangliae)

Although there is considerable distributional overlap in the humpback whale stocks that use Alaska, the whales seasonally found in lower Cook Inlet are probably of the Central North Pacific stock. Listed as endangered under the Endangered Species Act (ESA), this stock has recently been estimated at 7,469, with the portion of the stock that feeds in the Gulf of Alaska estimated at 2,845 animals (Allen and Angliss 2014). The Central North Pacific stock winters in Hawaii and summers from British Columbia to the Aleutian Islands (Calambokidis et al. 1997), including Cook Inlet.

Humpback use of Cook Inlet is largely confined to lower Cook Inlet. They have been regularly seen near Kachemak Bay during the summer months (Rugh et al. 2005a), and there is a whale-watching venture in Homer capitalizing on this seasonal event. There are anecdotal observations of humpback whales as far north as Anchor Point, with recent summer observations extending to Cape Starichkof (Owl Ridge 2014). Because of the southern distribution of humpbacks in Cook Inlet, it is unlikely that they will be encountered during this activity in close enough proximity to cause Level B harassment and are not considered further in this proposed Authorization.

Gray Whale (Eschrichtius robustus)

Each spring, the Eastern North Pacific stock of gray whale migrates 8,000 kilometers (5,000 miles) northward from breeding lagoons in Baja California to feeding grounds in the Bering and Chukchi seas, reversing their travel again in the fall (Rice and Wolman 1971). Their migration route is for the most part coastal until they reach the feeding grounds. A small portion of whales do not annually complete the full circuit, as small numbers can be found in the summer feeding along the Oregon, Washington, British Columbia, and Alaskan coasts (Rice et al. 1984, Moore et al. 2007).

Human exploitation reduced this stock to an estimated “few thousand” animals (Jones and Schwartz 2002). However, by the late 1980s, the stock was appearing to reach carrying capacity and estimated to be at 26,600 animals (Jones and Schwartz 2002). By 2002, that stock had been reduced to about 16,000 animals, especially following unusually high mortality events in 1999 and 2000 (Allen and Angliss 2014). The stock has continued to grow since then and is currently estimated at 19,126 animals with a minimum estimate of 18,017 (Carretta et al. 2013). Most gray whales migrate past the mouth of Cook Inlet to and from northern feeding grounds. However, small numbers of summering gray whales have been noted by fisherman near Kachemak Bay and north of Anchor Point. Further, summering gray whales were seen offshore of Cape Starichkof by marine mammal observers monitoring Buccaneer's Cosmopolitan drilling program in 2013 (Owl Ridge 2014). Regardless, gray whales are not expected to be encountered in upper Cook Inlet, where the activity is concentrated, north of Kachemak Bay. Therefore, it is unlikely that they will be encountered during this activity in close enough proximity to cause Level B harassment and are not considered further in this proposed Authorization.

Minke Whale (Balaenoptera acutorostrata)

Minke whales are the smallest of the rorqual group of baleen whales reaching lengths of up to 35 feet. They are also the most common of the baleen whales, although there are no population estimates for the North Pacific, although estimates have been made for some portions of Alaska. Zerbini et al. (2006) estimated the coastal population between Kenai Fjords and the Aleutian Islands at 1,233 animals.

During Cook Inlet-wide aerial surveys conducted from 1993 to 2004, minke whales were encountered only twice (1998, 1999), both times off Anchor Point 16 miles northwest of Homer. A minke whale was also reported off Cape Starichkof in 2011 (A. Holmes, pers. comm.) and 2013 (E. Fernandez and C. Hesselbach, pers. comm.), suggesting this location is regularly used by minke whales, including during the winter. Recently, several minke whales were recorded off Cape Starichkof in early summer 2013 during exploratory drilling conducted there (Owl Ridge 2014). There are no records north of Cape Starichkof, and this species is unlikely to be seen in upper Cook Inlet. There is little chance of encountering a minke whale during these activities and they are not analyzed further.

Dall's Porpoise (Phocoenoides dalli)

Dall's porpoise are widely distributed throughout the North Pacific Ocean including Alaska, although they are not found in upper Cook Inlet and the shallower waters of the Bering, Chukchi, and Beaufort Seas (Allen and Angliss 2014). Compared to harbor porpoise, Dall's porpoise prefer the deep offshore and shelf slope waters. The Alaskan population has been estimated at 83,400 animals (Allen and Angliss 2014), making it one of the more common cetaceans in the state. Dall's porpoise have been observed in lower Cook Inlet, including Kachemak Bay and near Anchor Point (Owl Ridge 2014), but sightings there are rare. The concentration of sightings of Dall's porpoise in a southerly part of the Inlet suggest it is unlikely they will be encountered during AK LNG's activities and they are therefore not considered further in this analysis.

Steller Sea Lion (Eumetopias jubatus)

The Western Stock of the Steller sea lion is defined as all populations west of longitude 144° W to the western end of the Aleutian Islands. The most recent estimate for this stock is 45,649 animals (Allen and Angliss 2014), considerably less than that estimated 140,000 animals in the 1950s (Merrick et al. 1987). Because of this dramatic decline, the stock was listed under the ESA as a threatened DPS in 1990, and relisted as endangered in 1997. Critical habitat was designated in 1993, and is defined as a 20-nautical-mile radius around all major rookeries and haulout sites. The 20-nautical-mile buffer was established based on telemetry data that indicated these sea lions concentrated their

summer foraging effort within this distance of rookeries and haul outs.

Steller sea lions inhabit lower Cook Inlet, especially in the vicinity of Shaw Island and Elizabeth Island (Nagahut Rocks) haulout sites (Rugh
et al.
2005a), but are rarely seen in upper Cook Inlet (Nemeth
et al.
2007). Of the 42 Steller sea lion groups recorded during Cook Inlet aerial surveys between 1993 and 2004, none were recorded north of Anchor Point and only one in the vicinity of Kachemak Bay (Rugh
et al.
2005a). Marine mammal observers associated with Buccaneer's drilling project off Cape Starichkof did observe seven Steller sea lions during the summer of 2013 (Owl Ridge 2014).

The upper reaches of Cook Inlet may not provide adequate foraging conditions for sea lions for establishing a major haul out presence. Steller sea lions feed largely on walleye pollock (
Theragra chalcogramma
), salmon (
Onchorhyncus spp.
), and arrowtooth flounder (
Atheresthes stomias
) during the summer, and walleye pollock and Pacific cod (
Gadus macrocephalus
) during the winter (Sinclair and Zeppelin 2002), none of which, except for salmon, are found in abundance in upper Cook Inlet (Nemeth
et al.
2007). Steller sea lions are unlikely to be encountered during operations in upper Cook Inlet, as they are primarily encountered along the Kenai Peninsula, especially closer to Anchor Point, and therefore they are not considered further in this proposed Authorization.

Potential Effects of the Specified Activity on Marine Mammals and Their Habitat

This section includes a summary and discussion of the ways that components (
e.g.,
seismic airgun operations, sub-bottom profiler chirper and boomer) of the specified activity may impact marine mammals. The “Estimated Take by Incidental Harassment” section later in this document will include a quantitative analysis of the number of individuals that NMFS expects to be taken by this activity. The “Negligible Impact Analysis” section will include the analysis of how this specific proposed activity would impact marine mammals and will consider the content of this section, the “Estimated Take by Incidental Harassment” section, the “Proposed Mitigation” section, and the “Anticipated Effects on Marine Mammal Habitat” section to draw conclusions regarding the likely impacts of this activity on the reproductive success or survivorship of individuals and from that on the affected marine mammal populations or stocks.

NMFS intends to provide a background of potential effects of AK LNG's activities in this section. Operating active acoustic sources have the potential for adverse effects on marine mammals. The majority of anticipated impacts would be from the use of these sources.

Acoustic Impacts

When considering the influence of various kinds of sound on the marine environment, it is necessary to understand that different kinds of marine life are sensitive to different frequencies of sound. Current data indicate that not all marine mammal species have equal hearing capabilities (Richardson
et al.,
1995; Southall
et al.,
1997; Wartzok and Ketten, 1999; Au and Hastings, 2008).

Southall
et al.
(2007) designated “functional hearing groups” for marine mammals based on available behavioral data; audiograms derived from auditory evoked potentials; anatomical modeling; and other data. Southall
et al.
(2007) also estimated the lower and upper frequencies of functional hearing for each group. However, animals are less sensitive to sounds at the outer edges of their functional hearing range and are more sensitive to a range of frequencies within the middle of their functional hearing range.

The functional groups applicable to this proposed survey and the associated frequencies are:

• Low frequency cetaceans (13 species of mysticetes): Functional hearing estimates occur between approximately 7 Hertz (Hz) and 25 kHz (extended from 22 kHz based on data indicating that some mysticetes can hear above 22 kHz; Au
et al.,
2006; Lucifredi and Stein, 2007; Ketten and Mountain, 2009; Tubelli
et al.,
2012);

• Mid-frequency cetaceans (32 species of dolphins, six species of larger toothed whales, and 19 species of beaked and bottlenose whales): Functional hearing estimates occur between approximately 150 Hz and 160 kHz;

• High-frequency cetaceans (eight species of true porpoises, six species of river dolphins,
Kogia,
the franciscana, and four species of
cephalorhynchids
): Functional hearing estimates occur between approximately 200 Hz and 180 kHz; and

• Pinnipeds in water: Phocid (true seals) functional hearing estimates occur between approximately 75 Hz and 100 kHz (Hemila
et al.,
2006; Mulsow
et al.,
2011; Reichmuth
et al.,
2013) and otariid (seals and sea lions) functional hearing estimates occur between approximately 100 Hz to 40 kHz.

As mentioned previously in this document, four marine mammal species (3 odontocetes and 1 phocid) would likely occur in the proposed action area. Table 2 presents the classification of these species into their respective functional hearing group. NMFS consider a species' functional hearing group when analyzing the effects of exposure to sound on marine mammals.

Table 2—Classification of Marine Mammals That Could Potentially Occur in the Proposed Activity Area in Cook Inlet, 2015 by Functional Hearing Group (Southall
et al.,
2007)

Mid-frequency hearing range
Beluga whale, killer whale.

High Frequency Hearing Range
Harbor porpoise.

Pinnipeds in Water Hearing Range
Harbor seal.

1. Potential Effects of Airgun Sounds on Marine Mammals

The effects of sounds from airgun operations might include one or more of the following: Tolerance, masking of natural sounds, behavioral disturbance, temporary or permanent impairment, or non-auditory physical or physiological effects (Richardson
et al.,
1995; Gordon
et al.,
2003; Nowacek
et al.,
2007; Southall
et al.,
2007). The effects of noise on marine mammals are highly variable, often depending on species and contextual factors (based on Richardson
et al.,
1995).

Tolerance

Studies on marine mammals' tolerance to sound in the natural environment are relatively rare. Richardson
et al.
(1995) defined tolerance as the occurrence of marine mammals in areas where they are exposed to human activities or manmade noise. In many cases, tolerance develops by the animal habituating to the stimulus (
i.e.,
the gradual waning of responses to a repeated or ongoing stimulus) (Richardson,
et al.,
1995), but because of ecological or physiological requirements, many marine animals may need to remain in areas where they are exposed to chronic stimuli (Richardson,
et al.,
1995).

Numerous studies have shown that pulsed sounds from airguns are often readily detectable in the water at distances of many kilometers. Several studies have also shown that marine mammals at distances of more than a few kilometers from operating seismic vessels often show no apparent

response. That is often true even in cases when the pulsed sounds must be readily audible to the animals based on measured received levels and the hearing sensitivity of the marine mammal group. Although various baleen whales and toothed whales, and (less frequently) pinnipeds have been shown to react behaviorally to airgun pulses under some conditions, at other times marine mammals of all three types have shown no overt reactions (Stone, 2003; Stone and Tasker, 2006; Moulton
et al.
2005, 2006) and (MacLean and Koski, 2005; Bain and Williams, 2006).

Weir (2008) observed marine mammal responses to seismic pulses from a 24 airgun array firing a total volume of either 5,085 in
3
or 3,147 in
3
in Angolan waters between August 2004 and May 2005. Weir (2008) recorded a total of 207 sightings of humpback whales (n = 66), sperm whales (n = 124), and Atlantic spotted dolphins (n = 17) and reported that there were no significant differences in encounter rates (sightings per hour) for humpback and sperm whales according to the airgun array's operational status (
i.e.,
active versus silent).

Bain and Williams (2006) examined the effects of a large airgun array (maximum total discharge volume of 1,100 in
3
) on six species in shallow waters off British Columbia and Washington: harbor seal, California sea lion (
Zalophus californianus
), Steller sea lion (
Eumetopias jubatus
), gray whale (
Eschrichtius robustus
), Dall's porpoise (
Phocoenoides dalli
), and harbor porpoise. Harbor porpoises showed reactions at received levels less than 155 dB re: 1 μPa at a distance of greater than 70 km (43 mi) from the seismic source (Bain and Williams, 2006). However, the tendency for greater responsiveness by harbor porpoise is consistent with their relative responsiveness to boat traffic and some other acoustic sources (Richardson,
et al.,
1995; Southall,
et al.,
2007). In contrast, the authors reported that gray whales seemed to tolerate exposures to sound up to approximately 170 dB re: 1 μPa (Bain and Williams, 2006) and Dall's porpoises occupied and tolerated areas receiving exposures of 170-180 dB re: 1 μPa (Bain and Williams, 2006; Parsons,
et al.,
2009). The authors observed several gray whales that moved away from the airguns toward deeper water where sound levels were higher due to propagation effects resulting in higher noise exposures (Bain and Williams, 2006). However, it is unclear whether their movements reflected a response to the sounds (Bain and Williams, 2006). Thus, the authors surmised that the lack of gray whale responses to higher received sound levels were ambiguous at best because one expects the species to be the most sensitive to the low-frequency sound emanating from the airguns (Bain and Williams, 2006).

Pirotta
et al.
(2014) observed short-term responses of harbor porpoises to a two-dimensional (2-D) seismic survey in an enclosed bay in northeast Scotland which did not result in broad-scale displacement. The harbor porpoises that remained in the enclosed bay area reduced their buzzing activity by 15 percent during the seismic survey (Pirotta,
et al.,
2014). Thus, the authors suggest that animals exposed to anthropogenic disturbance may make trade-offs between perceived risks and the cost of leaving disturbed areas (Pirotta,
et al.,
2014).

Masking

Marine mammals use acoustic signals for a variety of purposes, which differ among species, but include communication between individuals, navigation, foraging, reproduction, avoiding predators, and learning about their environment (Erbe and Farmer, 2000; Tyack, 2000).

The term masking refers to the inability of an animal to recognize the occurrence of an acoustic stimulus because of interference of another acoustic stimulus (Clark
et al.,
2009). Thus, masking is the obscuring of sounds of interest by other sounds, often at similar frequencies. It is a phenomenon that affects animals that are trying to receive acoustic information about their environment, including sounds from other members of their species, predators, prey, and sounds that allow them to orient in their environment. Masking these acoustic signals can disturb the behavior of individual animals, groups of animals, or entire populations.

Introduced underwater sound may, through masking, reduce the effective communication distance of a marine mammal species if the frequency of the source is close to that used as a signal by the marine mammal, and if the anthropogenic sound is present for a significant fraction of the time (Richardson
et al.,
1995).

Marine mammals are thought to be able to compensate for masking by adjusting their acoustic behavior through shifting call frequencies, increasing call volume, and increasing vocalization rates. For example in one study, blue whales increased call rates when exposed to noise from seismic surveys in the St. Lawrence Estuary (Di Iorio and Clark, 2010). Other studies reported that some North Atlantic right whales exposed to high shipping noise increased call frequency (Parks
et al.,
2007) and some humpback whales responded to low-frequency active sonar playbacks by increasing song length (Miller
et al.,
2000). Additionally, beluga whales change their vocalizations in the presence of high background noise possibly to avoid masking calls (Au
et al.,
1985; Lesage
et al.,
1999; Scheifele
et al.,
2005).

Studies have shown that some baleen and toothed whales continue calling in the presence of seismic pulses, and some researchers have heard these calls between the seismic pulses (
e.g.,
Richardson
et al.,
1986; McDonald
et al.,
1995; Greene
et al.,
1999; Nieukirk
et al.,
2004; Smultea
et al.,
2004; Holst
et al.,
2005a, 2005b, 2006; and Dunn and Hernandez, 2009).

In contrast, Clark and Gagnon (2006) reported that fin whales in the northeast Pacific Ocean went silent for an extended period starting soon after the onset of a seismic survey in the area. Similarly, NMFS is aware of one report that observed sperm whales ceased calls when exposed to pulses from a very distant seismic ship (Bowles
et al.,
1994). However, more recent studies have found that sperm whales continued calling in the presence of seismic pulses (Madsen
et al.,
2002; Tyack
et al.,
2003; Smultea
et al.,
2004; Holst
et al.,
2006; and Jochens
et al.,
2008).

Risch
et al.
(2012) documented reductions in humpback whale vocalizations in the Stellwagen Bank National Marine Sanctuary concurrent with transmissions of the Ocean Acoustic Waveguide Remote Sensing (OAWRS) low-frequency fish sensor system at distances of 200 km (124 mi) from the source. The recorded OAWRS produced series of frequency modulated pulses and the signal received levels ranged from 88 to 110 dB re: 1 μPa (Risch,
et al.,
2012). The authors hypothesized that individuals did not leave the area but instead ceased singing and noted that the duration and frequency range of the OAWRS signals (a novel sound to the whales) were similar to those of natural humpback whale song components used during mating (Risch
et al.,
2012). Thus, the novelty of the sound to humpback whales in the study area provided a compelling contextual probability for the observed effects (Risch
et al.,
2012). However, the authors did not state or imply that these changes had long-term effects on individual animals or populations (Risch
et al.,
2012).

Several studies have also reported hearing dolphins and porpoises calling while airguns were operating (
e.g.,

Gordon
et al.,
2004; Smultea
et al.,
2004; Holst
et al.,
2005a, b; and Potter
et al.,
2007). The sounds important to small odontocetes are predominantly at much higher frequencies than the dominant components of airgun sounds, thus limiting the potential for masking in those species.

Although some degree of masking is inevitable when high levels of manmade broadband sounds are present in the sea, marine mammals have evolved systems and behavior that function to reduce the impacts of masking. Odontocete conspecifics may readily detect structured signals, such as the echolocation click sequences of small toothed whales even in the presence of strong background noise because their frequency content and temporal features usually differ strongly from those of the background noise (Au and Moore, 1988, 1990). The components of background noise that are similar in frequency to the sound signal in question primarily determine the degree of masking of that signal.

Redundancy and context can also facilitate detection of weak signals. These phenomena may help marine mammals detect weak sounds in the presence of natural or manmade noise. Most masking studies in marine mammals present the test signal and the masking noise from the same direction. The sound localization abilities of marine mammals suggest that, if signal and noise come from different directions, masking would not be as severe as the usual types of masking studies might suggest (Richardson
et al.,
1995). The dominant background noise may be highly directional if it comes from a particular anthropogenic source such as a ship or industrial site. Directional hearing may significantly reduce the masking effects of these sounds by improving the effective signal-to-noise ratio. In the cases of higher frequency hearing by the bottlenose dolphin, beluga whale, and killer whale, empirical evidence confirms that masking depends strongly on the relative directions of arrival of sound signals and the masking noise (Penner
et al.,
1986; Dubrovskiy, 1990; Bain
et al.,
1993; Bain and Dahlheim, 1994). Toothed whales and probably other marine mammals as well, have additional capabilities besides directional hearing that can facilitate detection of sounds in the presence of background noise. There is evidence that some toothed whales can shift the dominant frequencies of their echolocation signals from a frequency range with a lot of ambient noise toward frequencies with less noise (Au
et al.,
1974, 1985; Moore and Pawloski, 1990; Thomas and Turl, 1990; Romanenko and Kitain, 1992; Lesage
et al.,
1999). A few marine mammal species increase the source levels or alter the frequency of their calls in the presence of elevated sound levels (Dahlheim, 1987; Au, 1993; Lesage
et al.,
1993, 1999; Terhune, 1999; Foote
et al.,
2004; Parks
et al.,
2007, 2009; Di Iorio and Clark, 2010; Holt
et al.,
2009).

These data demonstrating adaptations for reduced masking pertain mainly to the very high frequency echolocation signals of toothed whales. There is less information about the existence of corresponding mechanisms at moderate or low frequencies or in other types of marine mammals. For example, Zaitseva
et al.
(1980) found that, for the bottlenose dolphin, the angular separation between a sound source and a masking noise source had little effect on the degree of masking when the sound frequency was 18 kHz, in contrast to the pronounced effect at higher frequencies. Studies have noted directional hearing at frequencies as low as 0.5-2 kHz in several marine mammals, including killer whales (Richardson
et al.,
1995a). This ability may be useful in reducing masking at these frequencies. In summary, high levels of sound generated by anthropogenic activities may act to mask the detection of weaker biologically important sounds by some marine mammals. This masking may be more prominent for lower frequencies. For higher frequencies, such as that used in echolocation by toothed whales, several mechanisms are available that may allow them to reduce the effects of such masking.

Behavioral Disturbance

Marine mammals may behaviorally react to sound when exposed to anthropogenic noise. Reactions to sound, if any, depend on species, state of maturity, experience, current activity, reproductive state, time of day, and many other factors (Richardson
et al.,
1995; Wartzok
et al.,
2004; Southall
et al.,
2007; Weilgart, 2007).

Types of behavioral reactions can include the following: Changing durations of surfacing and dives, number of blows per surfacing, or moving direction and/or speed; reduced/increased vocal activities; changing/cessation of certain behavioral activities (such as socializing or feeding); visible startle response or aggressive behavior (such as tail/fluke slapping or jaw clapping); avoidance of areas where noise sources are located; and/or flight responses (
e.g.,
pinnipeds flushing into water from haulouts or rookeries).

The biological significance of many of these behavioral disturbances is difficult to predict, especially if the detected disturbances appear minor. However, one could expect the consequences of behavioral modification to be biologically significant if the change affects growth, survival, and/or reproduction (
e.g.,
Lusseau and Bejder, 2007; Weilgart, 2007). Examples of behavioral modifications that could impact growth, survival, or reproduction include:

• Drastic changes in diving/surfacing patterns (such as those associated with beaked whale stranding related to exposure to military mid-frequency tactical sonar);

• Permanent habitat abandonment due to loss of desirable acoustic environment; and

• Disruption of feeding or social interaction resulting in significant energetic costs, inhibited breeding, or cow-calf separation.

The onset of behavioral disturbance from anthropogenic noise depends on both external factors (characteristics of noise sources and their paths) and the receiving animals (hearing, motivation, experience, demography) and is also difficult to predict (Richardson
et al.,
1995; Southall
et al.,
2007). Many studies have also shown that marine mammals at distances more than a few kilometers away often show no apparent response when exposed to seismic activities (
e.g.,
Madsen & Mohl, 2000 for sperm whales; Malme
et al.,
1983, 1984 for gray whales; and Richardson
et al.,
1986 for bowhead whales). Other studies have shown that marine mammals continue important behaviors in the presence of seismic pulses (
e.g.,
Dunn & Hernandez, 2009 for blue whales; Greene Jr.
et al.,
1999 for bowhead whales; Holst and Beland, 2010; Holst and Smultea, 2008; Holst
et al.,
2005; Nieukirk
et al.,
2004; Richardson,
et al.,
1986; Smultea
et al.,
2004).

Baleen Whales:
Studies have shown that underwater sounds from seismic activities are often readily detectable by baleen whales in the water at distances of many kilometers (Castellote
et al.,
2012 for fin whales).

Observers have seen various species of
Balaenoptera
(blue, sei, fin, and minke whales) in areas ensonified by airgun pulses (Stone, 2003; MacLean and Haley, 2004; Stone and Tasker, 2006), and have localized calls from blue and fin whales in areas with airgun operations (
e.g.,
McDonald
et al.,
1995; Dunn and Hernandez, 2009; Castellote
et al.,
2010). Sightings by observers on seismic vessels off the United Kingdom from 1997 to 2000 suggest that, during

times of good visibility, sighting rates for mysticetes (mainly fin and sei whales) were similar when large arrays of airguns were shooting versus silent (Stone, 2003; Stone and Tasker, 2006). However, these whales tended to exhibit localized avoidance, remaining significantly further (on average) from the airgun array during seismic operations compared with non-seismic periods (Stone and Tasker, 2006).

Ship-based monitoring studies of baleen whales (including blue, fin, sei, minke, and humpback whales) in the northwest Atlantic found that overall, this group had lower sighting rates during seismic versus non-seismic periods (Moulton and Holst, 2010). The authors observed that baleen whales as a group were significantly farther from the vessel during seismic compared with non-seismic periods. Moreover, the authors observed that the whales swam away more often from the operating seismic vessel (Moulton and Holst, 2010). Initial sightings of blue and minke whales were significantly farther from the vessel during seismic operations compared to non-seismic periods and the authors observed the same trend for fin whales (Moulton and Holst, 2010). Also, the authors observed that minke whales most often swam away from the vessel when seismic operations were underway (Moulton and Holst, 2010).

Toothed Whales:
Few systematic data are available describing reactions of toothed whales to noise pulses. However, systematic work on sperm whales is underway (
e.g.,
Gordon
et al.,
2006; Madsen
et al.,
2006; Winsor and Mate, 2006; Jochens
et al.,
2008; Miller
et al.,
2009) and there is an increasing amount of information about responses of various odontocetes, including killer whales and belugas, to seismic surveys based on monitoring studies (
e.g.,
Stone, 2003; Smultea
et al.,
2004; Moulton and Miller, 2005; Bain and Williams, 2006; Holst
et al.,
2006; Stone and Tasker, 2006; Potter
et al.,
2007; Hauser
et al.,
2008; Holst and Smultea, 2008; Weir, 2008; Barkaszi
et al.,
2009; Richardson
et al.,
2009; Moulton and Holst, 2010). Reactions of toothed whales to large arrays of airguns are variable and, at least for delphinids, seem to be confined to a smaller radius than has been observed for mysticetes.

Observers stationed on seismic vessels operating off the United Kingdom from 1997-2000 have provided data on the occurrence and behavior of various toothed whales exposed to seismic pulses (Stone, 2003; Gordon
et al.,
2004). The studies note that killer whales were significantly farther from large airgun arrays during periods of active airgun operations compared with periods of silence. The displacement of the median distance from the array was approximately 0.5 km (0.3 mi) or more. Killer whales also appear to be more tolerant of seismic shooting in deeper water (Stone, 2003; Gordon
et al.,
2004).

The beluga may be a species that (at least in certain geographic areas) shows long-distance avoidance of seismic vessels. Aerial surveys during seismic operations in the southeastern Beaufort Sea recorded much lower sighting rates of beluga whales within 10-20 km (6.2-12.4 mi) of an active seismic vessel. These results were consistent with the low number of beluga sightings reported by observers aboard the seismic vessel, suggesting that some belugas might have been avoiding the seismic operations at distances of 10-20 km (6.2-12.4 mi) (Miller
et al.,
2005).

Delphinids

Seismic operators and protected species observers (observers) on seismic vessels regularly see dolphins and other small toothed whales near operating airgun arrays, but in general there is a tendency for most delphinids to show some avoidance of operating seismic vessels (
e.g.,
Goold, 1996a,b,c; Calambokidis and Osmek, 1998; Stone, 2003; Moulton and Miller, 2005; Holst
et al.,
2006; Stone and Tasker, 2006; Weir, 2008; Richardson
et al.,
2009; Barkaszi
et al.,
2009; Moulton and Holst, 2010). Some dolphins seem to be attracted to the seismic vessel and floats, and some ride the bow wave of the seismic vessel even when large arrays of airguns are firing (
e.g.,
Moulton and Miller, 2005). Nonetheless, there have been indications that small toothed whales sometimes move away or maintain a somewhat greater distance from the vessel when a large array of airguns is operating than when it is silent (
e.g.,
Goold, 1996a,b,c; Stone and Tasker, 2006; Weir, 2008, Barry
et al.,
2010; Moulton and Holst, 2010). In most cases, the avoidance radii for delphinids appear to be small, on the order of one km or less, and some individuals show no apparent avoidance.

Captive bottlenose dolphins exhibited changes in behavior when exposed to strong pulsed sounds similar in duration to those typically used in seismic surveys (Finneran
et al.,
2000, 2002, 2005). However, the animals tolerated high received levels of sound (pk-pk level >200 dB re 1 μPa) before exhibiting aversive behaviors.

Porpoises

Results for porpoises depend upon the species. The limited available data suggest that harbor porpoises show stronger avoidance of seismic operations than do Dall's porpoises (Stone, 2003; MacLean and Koski, 2005; Bain and Williams, 2006; Stone and Tasker, 2006). Dall's porpoises seem relatively tolerant of airgun operations (MacLean and Koski, 2005; Bain and Williams, 2006), although they too have been observed to avoid large arrays of operating airguns (Calambokidis and Osmek, 1998; Bain and Williams, 2006). This apparent difference in responsiveness of these two porpoise species is consistent with their relative responsiveness to boat traffic and some other acoustic sources (Richardson
et al.,
1995; Southall
et al.,
2007).

Pinnipeds

Pinnipeds are not likely to show a strong avoidance reaction to the airgun sources proposed for use. Visual monitoring from seismic vessels has shown only slight (if any) avoidance of airguns by pinnipeds and only slight (if any) changes in behavior. Monitoring work in the Alaskan Beaufort Sea during 1996-2001 provided considerable information regarding the behavior of Arctic ice seals exposed to seismic pulses (Harris
et al.,
2001; Moulton and Lawson, 2002). These seismic projects usually involved arrays of 6 to 16 airguns with total volumes of 560 to 1,500 in
3
. The combined results suggest that some seals avoid the immediate area around seismic vessels. In most survey years, ringed seal (
Phoca hispida
) sightings tended to be farther away from the seismic vessel when the airguns were operating than when they were not (Moulton and Lawson, 2002). However, these avoidance movements were relatively small, on the order of 100 m (328 ft) to a few hundreds of meters, and many seals remained within 100-200 m (328-656 ft) of the trackline as the operating airgun array passed by the animals. Seal sighting rates at the water surface were lower during airgun array operations than during no-airgun periods in each survey year except 1997. Similarly, seals are often very tolerant of pulsed sounds from seal-scaring devices (Mate and Harvey, 1987; Jefferson and Curry, 1994; Richardson
et al.,
1995). However, initial telemetry work suggests that avoidance and other behavioral reactions by two other species of seals to small airgun sources may at times be stronger than evident to date from visual studies of pinniped reactions to airguns (Thompson
et al.,
1998).

Hearing Impairment

Exposure to high intensity sound for a sufficient duration may result in

auditory effects such as a noise-induced threshold shift—an increase in the auditory threshold after exposure to noise (Finneran
et al.,
2005). Factors that influence the amount of threshold shift include the amplitude, duration, frequency content, temporal pattern, and energy distribution of noise exposure. The magnitude of hearing threshold shift normally decreases over time following cessation of the noise exposure. The amount of threshold shift just after exposure is the initial threshold shift. If the threshold shift eventually returns to zero (
i.e.,
the threshold returns to the pre-exposure value), it is a temporary threshold shift (Southall
et al.,
2007).

Threshold Shift (noise-induced loss of hearing)
—When animals exhibit reduced hearing sensitivity (
i.e.,
sounds must be louder for an animal to detect them) following exposure to an intense sound or sound for long duration, it is referred to as a noise-induced threshold shift (TS). An animal can experience temporary threshold shift (TTS) or permanent threshold shift (PTS). TTS can last from minutes or hours to days (
i.e.,
there is complete recovery), can occur in specific frequency ranges (
i.e.,
an animal might only have a temporary loss of hearing sensitivity between the frequencies of 1 and 10 kHz), and can be of varying amounts (for example, an animal's hearing sensitivity might be reduced initially by only 6 dB or reduced by 30 dB). PTS is permanent, but some recovery is possible. PTS can also occur in a specific frequency range and amount as mentioned above for TTS.

The following physiological mechanisms are thought to play a role in inducing auditory TS: Effects to sensory hair cells in the inner ear that reduce their sensitivity, modification of the chemical environment within the sensory cells, residual muscular activity in the middle ear, displacement of certain inner ear membranes, increased blood flow, and post-stimulatory reduction in both efferent and sensory neural output (Southall
et al.,
2007). The amplitude, duration, frequency, temporal pattern, and energy distribution of sound exposure all can affect the amount of associated TS and the frequency range in which it occurs. As amplitude and duration of sound exposure increase, so, generally, does the amount of TS, along with the recovery time. For intermittent sounds, less TS could occur than compared to a continuous exposure with the same energy (some recovery could occur between intermittent exposures depending on the duty cycle between sounds) (Kryter
et al.,
1966; Ward, 1997). For example, one short but loud (higher SPL) sound exposure may induce the same impairment as one longer but softer sound, which in turn may cause more impairment than a series of several intermittent softer sounds with the same total energy (Ward, 1997). Additionally, though TTS is temporary, prolonged exposure to sounds strong enough to elicit TTS, or shorter-term exposure to sound levels well above the TTS threshold, can cause PTS, at least in terrestrial mammals (Kryter, 1985). Although in the case of the proposed seismic survey, NMFS does not expect that animals would experience levels high enough or durations long enough to result in PTS given that the airgun is a very low volume airgun, and the use of the airgun will be restricted to seven days in a small geographic area.

PTS is considered auditory injury (Southall
et al.,
2007). Irreparable damage to the inner or outer cochlear hair cells may cause PTS; however, other mechanisms are also involved, such as exceeding the elastic limits of certain tissues and membranes in the middle and inner ears and resultant changes in the chemical composition of the inner ear fluids (Southall
et al.,
2007).

Although the published body of scientific literature contains numerous theoretical studies and discussion papers on hearing impairments that can occur with exposure to a loud sound, only a few studies provide empirical information on the levels at which noise-induced loss in hearing sensitivity occurs in non-human animals.

Recent studies by Kujawa and Liberman (2009) and Lin
et al.
(2011) found that despite completely reversible threshold shifts that leave cochlear sensory cells intact, large threshold shifts could cause synaptic level changes and delayed cochlear nerve degeneration in mice and guinea pigs, respectively. NMFS notes that the high level of TTS that led to the synaptic changes shown in these studies is in the range of the high degree of TTS that Southall
et al.
(2007) used to calculate PTS levels. It is unknown whether smaller levels of TTS would lead to similar changes. NMFS, however, acknowledges the complexity of noise exposure on the nervous system, and will re-examine this issue as more data become available.

For marine mammals, published data are limited to the captive bottlenose dolphin, beluga, harbor porpoise, and Yangtze finless porpoise (Finneran
et al.,
2000, 2002b, 2003, 2005a, 2007, 2010a, 2010b; Finneran and Schlundt, 2010; Lucke
et al.,
2009; Mooney
et al.,
2009a, 2009b; Popov
et al.,
2011a, 2011b; Kastelein
et al.,
2012a; Schlundt
et al.,
2000; Nachtigall
et al.,
2003, 2004). For pinnipeds in water, data are limited to measurements of TTS in harbor seals, an elephant seal, and California sea lions (Kastak
et al.,
1999, 2005; Kastelein
et al.,
2012b).

Lucke
et al.
(2009) found a threshold shift (TS) of a harbor porpoise after exposing it to airgun noise with a received sound pressure level (SPL) at 200.2 dB (peak-to-peak) re: 1 μPa, which corresponds to a sound exposure level of 164.5 dB re: 1 μPa2 s after integrating exposure. NMFS currently uses the root-mean-square (rms) of received SPL at 180 dB and 190 dB re: 1 μPa as the threshold above which permanent threshold shift (PTS) could occur for cetaceans and pinnipeds, respectively. Because the airgun noise is a broadband impulse, one cannot directly determine the equivalent of rms SPL from the reported peak-to-peak SPLs. However, applying a conservative conversion factor of 16 dB for broadband signals from seismic surveys (McCauley,
et al.,
2000) to correct for the difference between peak-to-peak levels reported in Lucke
et al.
(2009) and rms SPLs, the rms SPL for TTS would be approximately 184 dB re: 1 μPa, and the received levels associated with PTS (Level A harassment) would be higher. This is still above NMFS' current 180 dB rms re: 1 μPa threshold for injury. However, NMFS recognizes that TTS of harbor porpoises is lower than other cetacean species empirically tested (Finneran & Schlundt, 2010; Finneran
et al.,
2002; Kastelein and Jennings, 2012).

A recent study on bottlenose dolphins (Schlundt,
et al.,
2013) measured hearing thresholds at multiple frequencies to determine the amount of TTS induced before and after exposure to a sequence of impulses produced by a seismic air gun. The air gun volume and operating pressure varied from 40-150 in
3
and 1000-2000 psi, respectively. After three years and 180 sessions, the authors observed no significant TTS at any test frequency, for any combinations of air gun volume, pressure, or proximity to the dolphin during behavioral tests (Schlundt,
et al.,
2013). Schlundt
et al.
(2013) suggest that the potential for airguns to cause hearing loss in dolphins is lower than previously predicted, perhaps as a result of the low-frequency content of air gun impulses compared to the high-frequency hearing ability of dolphins.

Marine mammal hearing plays a critical role in communication with conspecifics, and interpretation of environmental cues for purposes such as predator avoidance and prey capture.

Depending on the degree (elevation of threshold in dB), duration (
i.e.,
recovery time), and frequency range of TTS, and the context in which it is experienced, TTS can have effects on marine mammals ranging from discountable to serious (similar to those discussed in auditory masking, below). For example, a marine mammal may be able to readily compensate for a brief, relatively small amount of TTS in a non-critical frequency range that occurs during a time where ambient noise is lower and there are not as many competing sounds present. Alternatively, a larger amount and longer duration of TTS sustained during time when communication is critical for successful mother/calf interactions could have more serious impacts. Also, depending on the degree and frequency range, the effects of PTS on an animal could range in severity, although it is considered generally more serious because it is a permanent condition. Of note, reduced hearing sensitivity as a simple function of aging has been observed in marine mammals, as well as humans and other taxa (Southall
et al.,
2007), so one can infer that strategies exist for coping with this condition to some degree, though likely not without cost.

Given the higher level of sound necessary to cause PTS as compared with TTS, it is considerably less likely that PTS would occur during the proposed seismic survey, although TTS is possible but unlikely. Cetaceans generally avoid the immediate area around operating seismic vessels, as do some other marine mammals. Some pinnipeds show avoidance reactions to airguns, but their avoidance reactions are generally not as strong or consistent compared to cetacean reactions.

Non-auditory Physical Effects:
Non-auditory physical effects might occur in marine mammals exposed to strong underwater pulsed sound. Possible types of non-auditory physiological effects or injuries that theoretically might occur in mammals close to a strong sound source include stress, neurological effects, bubble formation, and other types of organ or tissue damage. Some marine mammal species (
i.e.,
beaked whales) may be especially susceptible to injury and/or stranding when exposed to strong pulsed sounds.

Classic stress responses begin when an animal's central nervous system perceives a potential threat to its homeostasis. That perception triggers stress responses regardless of whether a stimulus actually threatens the animal; the mere perception of a threat is sufficient to trigger a stress response (Moberg, 2000; Sapolsky
et al.,
2005; Seyle, 1950). Once an animal's central nervous system perceives a threat, it mounts a biological response or defense that consists of a combination of the four general biological defense responses: Behavioral responses; autonomic nervous system responses; neuroendocrine responses; or immune responses.

In the case of many stressors, an animal's first and most economical (in terms of biotic costs) response is behavioral avoidance of the potential stressor or avoidance of continued exposure to a stressor. An animal's second line of defense to stressors involves the sympathetic part of the autonomic nervous system and the classical “fight or flight” response, which includes the cardiovascular system, the gastrointestinal system, the exocrine glands, and the adrenal medulla to produce changes in heart rate, blood pressure, and gastrointestinal activity that humans commonly associate with stress. These responses have a relatively short duration and may or may not have significant long-term effects on an animal's welfare.

An animal's third line of defense to stressors involves its neuroendocrine or sympathetic nervous systems; the system that has received the most study has been the hypothalmus-pituitary-adrenal system (also known as the HPA axis in mammals or the hypothalamus-pituitary-interrenal axis in fish and some reptiles). Unlike stress responses associated with the autonomic nervous system, the pituitary hormones regulate virtually all neuroendocrine functions affected by stress—including immune competence, reproduction, metabolism, and behavior. Stress-induced changes in the secretion of pituitary hormones have been implicated in failed reproduction (Moberg, 1987; Rivier, 1995), altered metabolism (Elasser
et al.,
2000), reduced immune competence (Blecha, 2000), and behavioral disturbance. Increases in the circulation of glucocorticosteroids (cortisol, corticosterone, and aldosterone in marine mammals; see Romano
et al.,
2004) have been equated with stress for many years.

The primary distinction between stress (which is adaptive and does not normally place an animal at risk) and distress is the biotic cost of the response. During a stress response, an animal uses glycogen stores that the body quickly replenishes after alleviation of the stressor. In such circumstances, the cost of the stress response would not pose a risk to the animal's welfare. However, when an animal does not have sufficient energy reserves to satisfy the energetic costs of a stress response, it diverts energy resources from other biotic functions, which impair those functions that experience the diversion. For example, when mounting a stress response diverts energy away from growth in young animals, those animals may experience stunted growth. When mounting a stress response diverts energy from a fetus, an animal's reproductive success and fitness will suffer. In these cases, the animals will have entered a pre-pathological or pathological state called “distress” (
sensu
Seyle, 1950) or “allostatic loading” (
sensu
McEwen and Wingfield, 2003). This pathological state will last until the animal replenishes its biotic reserves sufficient to restore normal function. Note that these examples involved a long-term (days or weeks) stress response exposure to stimuli.

Relationships between these physiological mechanisms, animal behavior, and the costs of stress responses have also been documented fairly well through controlled experiment; because this physiology exists in every vertebrate that has been studied, it is not surprising that stress responses and their costs have been documented in both laboratory and free-living animals (for examples see, Holberton
et al.,
1996; Hood
et al.,
1998; Jessop
et al.,
2003; Krausman
et al.,
2004; Lankford
et al.,
2005; Reneerkens
et al.,
2002; Thompson and Hamer, 2000). Although no information has been collected on the physiological responses of marine mammals to anthropogenic sound exposure, studies of other marine animals and terrestrial animals would lead us to expect some marine mammals to experience physiological stress responses and, perhaps, physiological responses that would be classified as “distress” upon exposure to anthropogenic sounds.

For example, Jansen (1998) reported on the relationship between acoustic exposures and physiological responses that are indicative of stress responses in humans (
e.g.,
elevated respiration and increased heart rates). Jones (1998) reported on reductions in human performance when faced with acute, repetitive exposures to acoustic disturbance. Trimper
et al.
(1998) reported on the physiological stress responses of osprey to low-level aircraft noise while Krausman
et al.
(2004) reported on the auditory and physiology stress responses of endangered Sonoran pronghorn to military overflights. Smith
et al.
(2004a, 2004b) identified noise-induced physiological transient stress responses in hearing-specialist fish (
i.e.,
goldfish) that accompanied short- and long-term hearing losses. Welch and Welch (1970) reported physiological

and behavioral stress responses that accompanied damage to the inner ears of fish and several mammals.

Hearing is one of the primary senses marine mammals use to gather information about their environment and communicate with conspecifics. Although empirical information on the relationship between sensory impairment (TTS, PTS, and acoustic masking) on marine mammals remains limited, we assume that reducing a marine mammal's ability to gather information about its environment and communicate with other members of its species would induce stress, based on data that terrestrial animals exhibit those responses under similar conditions (NRC, 2003) and because marine mammals use hearing as their primary sensory mechanism. Therefore, NMFS assumes that acoustic exposures sufficient to trigger onset PTS or TTS would be accompanied by physiological stress responses. More importantly, marine mammals might experience stress responses at received levels lower than those necessary to trigger onset TTS. Based on empirical studies of the time required to recover from stress responses (Moberg, 2000), NMFS also assumes that stress responses could persist beyond the time interval required for animals to recover from TTS and might result in pathological and pre-pathological states that would be as significant as behavioral responses to TTS.

Resonance effects (Gentry, 2002) and direct noise-induced bubble formations (Crum
et al.,
2005) are implausible in the case of exposure to an impulsive broadband source like an airgun array. If seismic surveys disrupt diving patterns of deep-diving species, this might result in bubble formation and a form of the bends, as speculated to occur in beaked whales exposed to sonar. However, there is no specific evidence of this upon exposure to airgun pulses.

In general, there are few data about the potential for strong, anthropogenic underwater sounds to cause non-auditory physical effects in marine mammals. Such effects, if they occur at all, would presumably be limited to short distances and to activities that extend over a prolonged period. The available data do not allow identification of a specific exposure level above which non-auditory effects can be expected (Southall
et al.,
2007) or any meaningful quantitative predictions of the numbers (if any) of marine mammals that might be affected in those ways. There is no definitive evidence that any of these effects occur even for marine mammals in close proximity to large arrays of airguns. In addition, marine mammals that show behavioral avoidance of seismic vessels, including some pinnipeds, are unlikely to incur non-auditory impairment or other physical effects. The low volume of the airgun proposed for this activity combined with the limited scope of use proposed makes non-auditory physical effects from airgun use, including stress, unlikely. Therefore, we do not anticipate such effects would occur given the brief duration of exposure during the proposed survey.

Stranding and Mortality

When a living or dead marine mammal swims or floats onto shore and becomes “beached” or incapable of returning to sea, the event is a “stranding” (Geraci
et al.,
1999; Perrin and Geraci, 2002; Geraci and Lounsbury, 2005; NMFS, 2007). The legal definition for a stranding under the MMPA is that “(A) a marine mammal is dead and is (i) on a beach or shore of the United States; or (ii) in waters under the jurisdiction of the United States (including any navigable waters); or (B) a marine mammal is alive and is (i) on a beach or shore of the United States and is unable to return to the water; (ii) on a beach or shore of the United States and, although able to return to the water, is in need of apparent medical attention; or (iii) in the waters under the jurisdiction of the United States (including any navigable waters), but is unable to return to its natural habitat under its own power or without assistance”.

Marine mammals strand for a variety of reasons, such as infectious agents, biotoxicosis, starvation, fishery interaction, ship strike, unusual oceanographic or weather events, sound exposure, or combinations of these stressors sustained concurrently or in series. However, the cause or causes of most strandings are unknown (Geraci
et al.,
1976; Eaton, 1979; Odell
et al.,
1980; Best, 1982). Numerous studies suggest that the physiology, behavior, habitat relationships, age, or condition of cetaceans may cause them to strand or might pre-dispose them to strand when exposed to another phenomenon. These suggestions are consistent with the conclusions of numerous other studies that have demonstrated that combinations of dissimilar stressors commonly combine to kill an animal or dramatically reduce its fitness, even though one exposure without the other does not produce the same result (Chroussos, 2000; Creel, 2005; DeVries
et al.,
2003; Fair and Becker, 2000; Foley
et al.,
2001; Moberg, 2000; Relyea, 2005a; 2005b, Romero, 2004; Sih
et al.,
2004). Given the low volume and source level of the proposed airgun, standing and mortality are not anticipated due to use of the airgun proposed for this activity.

2. Potential Effects of Other Acoustic Devices

Sub-Bottom Profiler

AK LNG would also operate a sub-bottom profiler chirp and boomer from the source vessel during the proposed survey. The chirp's sounds are very short pulses, occurring for one ms, six times per second. Most of the energy in the sound pulses emitted by the profiler is at 2-6 kHz, and the beam is directed downward. The chirp has a maximum source level of 202 dB re: 1 µPa, with a tilt angle of 90 degrees below horizontal and a beam width of 24 degrees. The sub-bottom profiler boomer will shoot approximately every 3.125m, with shots lasting 1.5 to 2 seconds. Most of the energy in the sound pulses emitted by the boomer is concentrated between 0.5 and 6 kHz, with a source level of 205dB re: 1μPa.The tilt of the boomer is 90 degrees below horizontal, but the emission is omnidirectional. Kremser
et al.
(2005) noted that the probability of a cetacean swimming through the area of exposure when a bottom profiler emits a pulse is small—because if the animal was in the area, it would have to pass the transducer at close range in order to be subjected to sound levels that could cause temporary threshold shift and would likely exhibit avoidance behavior to the area near the transducer rather than swim through at such a close range.

Masking:
Both the chirper and boomer sub-bottom profilers produce impulsive sound exceeding 160 dB re 1 μPa-m (rms). The louder boomer operates at a source value of 205 dB re 1 μPa-m (rms), but with a frequency between 0.5 and 6 kHz, which is lower than the maximum sensitivity hearing range of any the local species (belugas—40-130 kHz;, killer whales—7-30 kHz; harbor porpoise—100-140 kHz; and harbor seals—10-30 kHz; Wartzok and Ketten 1999, Southall et al. 2007, Kastelein et al. 2002). While the chirper is not as loud (202 dB re 1 μPa-m [rms]), it does operate at a higher frequency range (2-16 kHz), and within the maximum sensitive range of all of the local species except beluga whales.

Marine mammal communications would not likely be masked appreciably by the profiler's signals given the directionality of the signal and the brief period when an individual mammal is likely to be within its beam. Furthermore, despite the fact that the profiler overlaps with hearing ranges of

many marine mammal species in the area, the profiler's signals do not overlap with the predominant frequencies in the calls, which would avoid significant masking.

Behavioral Responses:
Responses to the profiler are likely to be similar to the other pulsed sources discussed earlier if received at the same levels. The behavioral response of local marine mammals to the operation of the sub-bottom profilers is expected to be similar to that of the small airgun. The odontocetes are likely to avoid the sub-bottom profiler activity, especially the naturally shy harbor porpoise, while the harbor seals might be attracted to them out of curiosity. However, because the sub-bottom profilers operate from a moving vessel, and the maximum radius to the 160 dB harassment threshold is only 263 m (863 ft), the area and time that this equipment would be affecting a given location is very small.

Hearing Impairment and Other Physical Effects:
It is unlikely that the sub-bottom profilers produce sound levels strong enough to cause hearing impairment or other physical injuries even in an animal that is (briefly) in a position near the source (Wood et al. 2012). The likelihood of marine mammals moving away from the source make if further unlikely that a marine mammal would be able to approach close to the transducers.

Animals may avoid the area around the survey vessels, thereby reducing exposure. Any disturbance to marine mammals is likely to be in the form of temporary avoidance or alteration of opportunistic foraging behavior near the survey location.

Vibracore

AK LNG would conduct vibracoring in a corridor across a northern portion of Cook Inlet. While duration is dependent on sediment type, the driving mechanism, which emits sound at a source level of 187dB re: 1µPa, will only bore for 1 to 2 minutes. The sound is emitted at a frequency of 10Hz to 20kHz. Cores will be bored at approximately every 4 km along the pipeline corridor, for about 22 cores in that area. Approximately 33 cores will be taken in the Marine Terminal area.

Masking:
It is unlikely that masking will occur due to vibracore operations. Chorney et al. (2011) conducted sound measurements on an operating vibracorer in Alaska and found that it emitted a sound pressure level at 1-m source of 188 dB re 1 μPa-m (rms), with a frequency range of between 10 Hz and 20 kHz. While the frequency range overlaps the lower ends of the maximum sensitivity hearing ranges of harbor porpoises, killer whales, and harbor seals, and the continuous sound extends 2.54 km (1.6 mi) to the 120 dB threshold, the vibracorer will operate about the one or two minutes it takes to drive the core pipe 7 m (20 ft) into the sediment, and approximately twice per day. Therefore, there is very little opportunity for this activity to mask the communication of local marine mammals.

Behavioral Response:
It is unlikely that vibracoring will elicit behavioral responses from marine mammal species in the area. An analysis of similar survey activity in New Zealand classified the likely effects from vibracore and similar activity to be some habitat degradation and prey species effects, but primarily behavioral responses, although the species in the analyzed area were different to those found in Cook Inlet (Thompson, 2012).

There are no data on the behavioral response to vibracore activity of marine mammals in Cook Inlet. The closest analog to vibracoring might be exploratory drilling, although there is a notable difference in magnitude between an oil and gas drilling operation and collecting sediment samples with a vibracorer. Thomas et al. (1990) played back drilling sound to four captive beluga whales and found no statistical difference in swim patterns, social groups, respiration and dive rates, or stress hormone levels before and during playbacks. There is no reason to believe that beluga whales or any other marine mammal exposed to vibracoring sound would behave any differently, especially since vibracoring occurs for only one or two minutes.

Hearing Impairment and Other Physical Effects:
The vibracorer operates for only one or two minutes at a time with a 1-m source of 187.4 dB re 1 μPa-m (rms). It is neither loud enough nor does it operate for a long enough duration to induce either TTS or PTS.

Stranding and Mortality

Stress, Stranding, and Mortality Safety zones will be established to prevent acoustical injury to local marine mammals, especially injury that could indirectly lead to mortality. Also, G&G sound is not expected to cause resonate effects to gas-filled spaces or airspaces in marine mammals based on the research of Finneran (2003) on beluga whales showing that the tissue and other body masses dampen any potential effects of resonance on ear cavities, lungs, and intestines. Chronic exposure to sound could lead to physiological stress eventually causing hormonal imbalances (NRC 2005). If survival demands are already high, and/or additional stressors are present, the ability of the animal to cope decreases, leading to pathological conditions or death (NRC 2005). Potential effects may be greatest where sound disturbance can disrupt feeding patterns including displacement from critical feeding grounds. However, all G&G exposure to marine mammals would be of duration measured in minutes.

Specific sound-related processes that lead to strandings and mortality are not well documented, but may include (1) swimming in avoidance of a sound into shallow water; (2) a change in behavior (such as a change in diving behavior) that might contribute to tissue damage, gas bubble formation, hypoxia, cardiac arrhythmia, hypertensive hemorrhage, or other forms of trauma; (3) a physiological change such as a vestibular response leading to a behavioral change or stress-induced hemorrhagic diathesis, leading in turn to tissue damage; and, (4) tissue damage directly from sound exposure, such as through acoustically mediated bubble formation and growth or acoustic resonance of tissues (Wood et al. 2012). Some of these mechanisms are unlikely to apply in the case of impulse G&G sounds, especially since airguns and sub-bottom profilers produce broadband sound with low pressure rise. Strandings to date which have been attributed to sound exposure related to date from military exercises using narrowband mid-frequency sonar with a much greater likelihood to cause physical damage (Balcomb and Claridge 2001, NOAA and USN, 2001, Hildebrand 2005).

The low intensity, low frequency, broadband sound associated with airguns and sub-bottom profilers, combined with the shutdown safety zone mitigation measure for the airgun would prevent physical damage to marine mammals. The vibracoring would also be unlikely to have the capability of causing physical damage to marine mammals because of its low intensity and short duration.

3. Potential Effects of Vessel Movement and Collisions

Vessel movement in the vicinity of marine mammals has the potential to result in either a behavioral response or a direct physical interaction. We discuss both scenarios here.

Behavioral Responses to Vessel Movement:
There are limited data concerning marine mammal behavioral responses to vessel traffic and vessel noise, and a lack of consensus among scientists with respect to what these responses mean or whether they result in short-term or long-term adverse

effects. In those cases where there is a busy shipping lane or where there is a large amount of vessel traffic, marine mammals may experience acoustic masking (Hildebrand, 2005) if they are present in the area (
e.g.,
killer whales in Puget Sound; Foote et al., 2004; Holt et al., 2008). In cases where vessels actively approach marine mammals (
e.g.,
whale watching or dolphin watching boats), scientists have documented that animals exhibit altered behavior such as increased swimming speed, erratic movement, and active avoidance behavior (Bursk, 1983; Acevedo, 1991; Baker and MacGibbon, 1991; Trites and Bain, 2000; Williams et al., 2002; Constantine et al., 2003), reduced blow interval (Ritcher et al., 2003), disruption of normal social behaviors (Lusseau, 2003; 2006), and the shift of behavioral activities which may increase energetic costs (Constantine et al., 2003; 2004). A detailed review of marine mammal reactions to ships and boats is available in Richardson et al. (1995). For each of the marine mammal taxonomy groups, Richardson et al. (1995) provides the following assessment regarding reactions to vessel traffic:

Pinnipeds:
Reactions by pinnipeds to vessel disturbance largely involve relocation. Harbor seals hauled out on mud flats have been documented returning to the water in response to nearing boat traffic. Vessels that approach haulouts slowly may also elicit alert reactions without flushing from the haulout. Small boats with slow, constant speed elicit the least noticeable reactions. However, in Alaska specifically, harbor seals are documented to tolerate fishing vessels with no discernable reactions, and habituation is common (Burns, 1989).

Porpoises:
Harbor porpoises are often seen changing direction in the presence of vessel traffic. Avoidance has been documented up to 1km away from an approaching vessel, but the avoidance response is strengthened in closer proximity to vessels (Barlow, 1998; Palka, 1993). This avoidance behavior is not consistent across all porpoises, as Dall's porpoises have been observed approaching boats.

Toothed whales:
In summary, toothed whales sometimes show no avoidance reaction to vessels, or even approach them. However, avoidance can occur, especially in response to vessels of types used to chase or hunt the animals. This may cause temporary displacement, but we know of no clear evidence that toothed whales have abandoned significant parts of their range because of vessel traffic.

Behavioral responses to stimuli are complex and influenced to varying degrees by a number of factors, such as species, behavioral contexts, geographical regions, source characteristics (moving or stationary, speed, direction, etc.), prior experience of the animal and physical status of the animal. For example, studies have shown that beluga whales' reactions varied when exposed to vessel noise and traffic. In some cases, naive beluga whales exhibited rapid swimming from ice-breaking vessels up to 80 km (49.7 mi) away, and showed changes in surfacing, breathing, diving, and group composition in the Canadian high Arctic where vessel traffic is rare (Finley et al., 1990). In other cases, beluga whales were more tolerant of vessels, but responded differentially to certain vessels and operating characteristics by reducing their calling rates (especially older animals) in the St. Lawrence River where vessel traffic is common (Blane and Jaakson, 1994). In Bristol Bay, Alaska, beluga whales continued to feed when surrounded by fishing vessels and resisted dispersal even when purposefully harassed (Fish and Vania, 1971).

In reviewing more than 25 years of whale observation data, Watkins (1986) concluded that whale reactions to vessel traffic were “modified by their previous experience and current activity: Habituation often occurred rapidly, attention to other stimuli or preoccupation with other activities sometimes overcame their interest or wariness of stimuli.” Watkins noticed that over the years of exposure to ships in the Cape Cod area, minke whales changed from frequent positive interest (
e.g.,
approaching vessels) to generally uninterested reactions; fin whales changed from mostly negative (
e.g.,
avoidance) to uninterested reactions; right whales apparently continued the same variety of responses (negative, uninterested, and positive responses) with little change; and humpbacks dramatically changed from mixed responses that were often negative to reactions that were often strongly positive. Watkins (1986) summarized that “whales near shore, even in regions with low vessel traffic, generally have become less wary of boats and their noises, and they have appeared to be less easily disturbed than previously. In particular locations with intense shipping and repeated approaches by boats (such as the whale-watching areas of Stellwagen Bank), more and more whales had positive reactions to familiar vessels, and they also occasionally approached other boats and yachts in the same ways.”

Vessel Strike

Ship strikes of cetaceans can cause major wounds, which may lead to the death of the animal. An animal at the surface could be struck directly by a vessel, a surfacing animal could hit the bottom of a vessel, or a vessel's propeller could injure an animal just below the surface. The severity of injuries typically depends on the size and speed of the vessel (Knowlton and Kraus, 2001; Laist et al., 2001; Vanderlaan and Taggart, 2007).

The most vulnerable marine mammals are those that spend extended periods of time at the surface in order to restore oxygen levels within their tissues after deep dives (
e.g.,
the sperm whale). In addition, some baleen whales, such as the North Atlantic right whale, seem generally unresponsive to vessel sound, making them more susceptible to vessel collisions (Nowacek et al., 2004). These species are primarily large, slow moving whales. Smaller marine mammals (
e.g.,
bottlenose dolphin) move quickly through the water column and are often seen riding the bow wave of large ships. Marine mammal responses to vessels may include avoidance and changes in dive pattern (NRC, 2003).

An examination of all known ship strikes from all shipping sources (civilian and military) indicates vessel speed is a principal factor in whether a vessel strike results in death (Knowlton and Kraus, 2001; Laist et al., 2001; Jensen and Silber, 2003; Vanderlaan and Taggart, 2007). In assessing records with known vessel speeds, Laist et al. (2001) found a direct relationship between the occurrence of a whale strike and the speed of the vessel involved in the collision. The authors concluded that most deaths occurred when a vessel was traveling in excess of 24.1 km/h (14.9 mph; 13 kts).

Entanglement

Entanglement can occur if wildlife becomes immobilized in survey lines, cables, nets, or other equipment that is moving through the water column. The proposed seismic survey would require towing approximately 8.0 km (4.9 mi) of equipment and cables. This size of the array generally carries a lower risk of entanglement for marine mammals. Wildlife, especially slow moving individuals, such as large whales, have a low probability of entanglement due to the low amount of slack in the lines, slow speed of the survey vessel, and onboard monitoring. Pinnipeds and porpoises are the least likely to entangle in equipment, as most documented

cases of entanglement involve fishing gear and prey species. There are no reported cases of entanglement from geophysical equipment in the Cook Inlet area.

Anticipated Effects on Marine Mammal Habitat

The G&G Program survey areas are primarily within upper Cook Inlet, although the Marine Terminal survey area is located near Nikiski just south of the East Foreland (technically in Lower Cook Inlet), which includes habitat for prey species of marine mammals, including fish as well as invertebrates eaten by Cook Inlet belugas. This area contains Critical Habitat for Cook Inlet belugas, is near the breeding grounds for the local harbor seal population, and serves as an occasional feeding ground for killer whales and harbor porpoises. Cook Inlet is a large subarctic estuary roughly 299 km (186 mi) in length and averaging 96 km (60 mi) in width. It extends from the city of Anchorage at its northern end and flows into the Gulf of Alaska at its southernmost end. For descriptive purposes, Cook Inlet is separated into unique upper and lower sections, divided at the East and West Forelands, where the opposing peninsulas create a natural waistline in the length of the waterway, measuring approximately 16 km (10 mi) across (Mulherin et al. 2001).

Potential effects on beluga habitat would be limited to noise effects on prey; direct impact to benthic habitat from jack-up platform leg placement, and sampling with grabs, coring, and boring; and small discharges of drill cuttings and drilling mud associated with the borings. Portions of the survey areas include waters of Cook Inlet that are <9.1 m (30 ft) in depth and within 8.0 km (5.0 mi) of anadromous streams. Several anadromous streams (Three-mile Creek, Indian Creek, and two unnamed streams) enter the Cook Inlet within the survey areas. Other anadromous streams are located within 8.0 km (5.0 mi) of the survey areas. The survey program will not prevent beluga access to the mouths of these streams and will result in no short-term or long-term loss of intertidal or subtidal waters that are <9.1 m (30 ft) in depth and within 8.0 km (5.0 mi) of anadromous streams. Minor seafloor impacts will occur in these areas from grab samples, PCPTs, vibracores, or geotechnical borings but will have no effect on the area as beluga habitat once the vessel or jack-up platform has left. The survey program will have no effect on this Primary Constituent Element.

Belugas may avoid areas ensonified by the geophysical or geotechnical activities that generate sound with frequencies within the beluga hearing range and at levels above threshold values. This includes the chirp sub-bottom profiler with a radius of 184 m (604 ft), the boomer sub-bottom profiler with a radius of 263 m (863 ft), the airgun with a radius of 300 m (984 ft) and the vibracores with a radius of 2.54 km (1.58 mi). The sub-bottom profilers and the airgun will be operated from a vessel moving at speeds of about 4 kt. The operation of a vibracore has a duration of approximately 1-2 minutes. All of these activities will be conducted in relatively open areas of the Cook Inlet within Critical Habitat Area 2. Given the size and openness of the Cook Inlet in the survey areas, and the relatively small area and mobile/temporary nature of the zones of ensonification, the generation of sound by the G&G activities is not expected to result in any restriction of passage of belugas within or between critical habitat areas. The jack-up platform from which the geotechnical borings will be conducted will be attached to the seafloor with legs, and will be in place at a given location for up to 4-5 days, but given its small size (Table 4 in the application) would not result in any obstruction of passage by belugas. The program will have no effect on this Primary Constituent Element.

Upper Cook Inlet comprises the area between Point Campbell (Anchorage) down to the Forelands, and is roughly 95 km (59 mi) in length and 24.9 km (15.5 mi) in width (Mulherin et al. 2001). Five major rivers (Knik, Matanuska, Susitna, Little Susitna, and Beluga) deliver freshwater to upper Cook Inlet, carrying a heavy annual sediment load of over 40 million tons of eroded materials and glacial silt (Brabets 1999). As a result, upper Cook Inlet is relatively shallow, averaging 18.3 m (60 ft) in depth. It is characterized by shoals, mudflats, and a wide coastal shelf, less than 17.9 m (59 ft) deep, extending from the eastern shore. A deep trough exists between Trading Bay and the Middle Ground Shoal, ranging from 35 to 77 m (114-253 ft) deep (NOAA Nautical Chart 16660). The substrate consists of a mixture of coarse gravels, cobbles, pebbles, sand, clay, and silt (Bouma et al. 1978, Rappeport 1982).

Upper Cook Inlet experiences some of the most extreme tides in the world, demonstrated by a mean tidal range from 4.0 m (13 ft) at the Gulf of Alaska end to 8.8 m (29 ft) near Anchorage (U.S. Army Corps of Engineers 2013). Tidal currents reach 3.9 kts per second (Mulherin et al. 2001) in upper Cook Inlet, increasing to 5.7-7.7 kts per second near the Forelands where the inlet is constricted. Each tidal cycle creates significant turbulence and vertical mixing of the water column in the upper inlet (U.S. Army Corps of Engineers 2013), and are reversing, meaning that they are marked by a period of slack tide followed an acceleration in the opposite direction (Mulherin et al. 2001).

Because of scouring, mixing, and sediment transport from these currents, the marine invertebrate community is very limited (Pentec 2005). Of the 50 stations sampled by Saupe et al. 2005 for marine invertebrates in Southcentral Alaska, their upper Cook Inlet station had by far the lowest abundance and diversity. Further, the fish community of upper Cook Inlet is characterized largely by migratory fish—eulachon and Pacific salmon—returning to spawning rivers, or outmigrating salmon smolts. Moulton (1997) documented only 18 fish species in upper Cook Inlet compared to at least 50 species found in lower Cook Inlet (Robards et al. 1999).

Lower Cook Inlet extends from the Forelands southwest to the inlet mouth demarked by an approximate line between Cape Douglas and English Bay. Water circulation in lower Cook Inlet is dominated by the Alaska Coastal Current (ACC) that flows northward along the shores of the Kenai Peninsula until it turns westward and is mixed by the combined influences of freshwater input from upper Cook Inlet, wind, topography, tidal surges, and the coriolis effect (Field and Walker 2003, MMS 1996). Upwelling by the ACC brings nutrient-rich waters to lower Cook Inlet and contributes to a biologically rich and productive ecology (Sambrotto and Lorenzen 1986). Tidal currents average 2-3 kt per second and are rotary in that they do not completely go slack before rotating around into an opposite direction (Gatto 1976, Mulherin et al. 2001). Depths in the central portion of lower Cook Inlet are 60-80 m (197-262 ft) and decrease steadily toward the shores (Muench 1981). Bottom sediments in the lower inlet are coarse gravel and sand that grade to finer sand and mud toward the south (Bouma 1978).

Coarser substrate support a wide variety of invertebrates and fish including Pacific halibut, Dungeness crab (Metacarcinus magister), tanner crab (Chionoecetes bairdi), pandalid shrimp (Pandalus spp.), Pacific cod, and rock sole (Lepidopsetta bilineata), while the soft-bottom sand and silt communities are dominated by polychaetes, bivalves and other flatfish (Field and Walker 2003). These species constitute prey species for several

marine mammals in Cook Inlet, including pinnipeds and Cook Inlet belugas. Sea urchins (Strongylocentrotus spp.) and sea cucumbers are important otter prey and are found in shell debris communities. Razor clams (Siliqua patula) are found all along the beaches of the Kenai Peninsula. In general, the lower Cook Inlet marine invertebrate community is of low abundance, dominated by polychaetes, until reaching the mouth of the inlet (Saupe et al. 2005). Overall, the lower Cook Inlet marine ecosystem is fed by midwater communities of phytoplankton and zooplankton, with the latter composed mostly of copepods and barnacle and crab larvae (Damkaer 1977, English 1980).

G&G Program activities that could potentially impact marine mammal habitats include sediment sampling (vibracore, boring, grab sampling) on the sea bottom, placement of the jack-up platform spud cans, and acoustical injury of prey resources. However, there are few benthic resources in the survey area that could be impacted by collection of the small samples (Saupe et al. 2005).

Acoustical effects to marine mammal prey resources are also limited. Christian et al. (2004) studied seismic energy impacts on male snow crabs (Chionoecetes sp.) and found no significant increases in physiological stress due to exposure to high sound pressure levels. No acoustical impact studies have been conducted to date on the above fish species, but studies have been conducted on Atlantic cod (Gadus morhua) and sardine (Clupea sp). Davis et al. (1998) cited various studies that found no effects to Atlantic cod eggs, larvae, and fry when received levels were 222 dB. Effects found were to larval fish within about 5.0 m (16 ft), and from air guns with volumes between 49,661 and 65,548 cm
3
(3,000 and 4,000 in
3
). Similarly, effects to sardine were greatest on eggs and 2-day larvae, but these effects were greatest at 0.5 m (1.6 ft), and again confined to 5.0 m (16 ft). Further, Greenlaw et al. (1988) found no evidence of gross histological damage to eggs and larvae of northern anchovy (Engraulis mordax) exposed to seismic air guns, and concluded that noticeable effects would result only from multiple, close exposures. Based on these results, much lower energy impulsive geophysical equipment planned for this program would not damage larval fish or any other marine mammal prey resource.

Potential damage to the Cook Inlet benthic community will be limited to the actual surface area of the four spud cans that form the “foot” of each 0.762-m (30-in) diameter leg, the 42 0.1524-m (6-in) diameter borings, and the 55 0.0762-m (3-in) diameter vibracore samplings (plus several grab and PCPT samples). Collectively, these samples would temporarily damage about a hundred square meters of benthic habitat relative to the size (nearly 21,000 km
2
/8,108 mi
2
) of Cook Inlet. Overall, sediment sampling and acoustical effects on prey resources will have a negligible effect at most on the marine mammal habitat within the G&G Program survey area. Some prey resources might be temporarily displaced, but no long-term effects are expected.

The Cook Inlet 2015 G&G Program will result in a number of minor discharges to the waters of Cook Inlet. Discharges associated with the geotechnical borings will include: (1) The discharge of drill cuttings and drilling fluids and (2) the discharge of deck drainage (runoff of precipitation and deck wash water) from the geotechnical drilling platform. Other vessels associated with the G&G surveys will discharge wastewaters that are normally associated with the operation of vessels in transit including deck drainage, ballast water, bilge water, non-contact cooling water, and gray water.

The discharges of drill cuttings, drilling fluids, and deck drainage associated with the geotechnical borings will be within limitations authorized by the

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Source: Frix Law Library, https://www.frixlaw.com/law-library/documents/fr%3A2015-16012. Public record. Not legal advice.