# Takes of Marine Mammals Incidental to Specified Activities; Taking Marine Mammals Incidental to BlueCrest Alaska Operating, LLC Drilling Activities at Cosmopolitan State Unit, Alaska, 2016

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URL: https://www.frixlaw.com/law-library/documents/fr%3A2016-12886

## Record

- **Collection:** Federal Register
- **Document type:** Notice
- **Published:** June 2, 2016
- **Citation:** 81 FR 35548

## Text

DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
RIN 0648-XE497
Takes of Marine Mammals Incidental to Specified Activities; Taking Marine Mammals Incidental to BlueCrest Alaska Operating, LLC Drilling Activities at Cosmopolitan State Unit, Alaska, 2016

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 BlueCrest Alaska Operating, LLC (BlueCrest) for an Incidental Harassment Authorization (IHA) to take marine mammals, by harassment, incidental to conducting an oil and gas production drilling program in lower Cook Inlet, AK, on State of Alaska Oil and Gas Lease 384403 under the program name of Cosmopolitan State during the 2016 open water season. Pursuant to the Marine Mammal Protection Act (MMPA), NMFS is requesting comments on its proposal to issue an IHA to BlueCrest 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 5, 2016.

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.Youngkin@noaa.gov
. NMFS is not responsible for email comments sent to addresses other than the one provided here. Comments sent via email, including all attachments, must not exceed a 25-megabyte file size.

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 (
e.g.,
name, address) 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, NMFS' Draft Programmatic Environmental Assessment (EA) for activities in Cook Inlet, and a list of the references used in this document may be obtained by visiting the Internet at:
http://www.nmfs.noaa.gov/pr/permits/incidental.htm
. In case of problems accessing these documents, please call the contact listed below. Documents cited in this notice may also be viewed, by appointment, during regular business hours, at the aforementioned address.

FOR FURTHER INFORMATION CONTACT:

Dale Youngkin, Office of Protected Resources, NMFS, (301) 427-8401.

SUPPLEMENTARY INFORMATION:

Background

Sections 101(a)(5)(A) and (D) of the MMPA (16 U.S.C. 1361
et seq.
) direct the Secretary of Commerce to allow, upon request, the incidental, but not intentional, taking of small numbers of marine mammals by U.S. citizens who engage in a specified activity (other than commercial fishing) within a specified geographical region if certain findings are made and either regulations are issued or, if the taking is limited to harassment, a notice of a proposed authorization is provided to the public for review.

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; other means of effecting the least practicable impact on the species or stock and its habitat; 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 September 28, 2015 NMFS received an IHA application from BlueCrest for the taking of marine mammals incidental to an oil and gas production drilling program in lower Cook Inlet, AK, during the 2016 open water season. Typically, the open water (
i.e.,
ice-free) season is mid-April through October; however, BlueCrest would only operate during a portion of this season, from August 1, 2016 through October 31, 2016. NMFS determined that the application was adequate and complete on April 12, 2016.

BlueCrest proposes to conduct and oil and gas production drilling program using the
Spartan 151
drill rig (or similar rig) in lower Cook Inlet. This work would include drilling up to three wells with a total operating time of approximately 91 days during the 2016 open-water season, (August 1 through October 31). In 2013, BlueCrest, then in partnership with Buccaneer Energy, conducted exploratory oil and gas drilling at the Cosmopolitan State #A-1 well site (then called Cosmopolitan State #1). Beginning in 2016, BlueCrest intends to drill two more wells (Cosmopolitan State #A-2 and #A-3). These directionally drilled wells have top holes located a few meters from the original Cosmopolitan State #A-1, and together would feed to a future single offshore platform. Both #A-2 and #A-3 may involve test drilling into oil layers. After testing, the oil horizons will be plugged and abandoned, while the gas zones will be suspended pending platform construction. A third well (#B-1) will be located approximately 1.7 kilometers (km; 1 mile [mi]) southeast of the other wells. This well will be drilled into oil formations to collect geological information. After testing, the oil horizon will be plugged and abandoned, while the gas zones will be suspended pending platform construction. All four wells (one existing and up to three new) would be located within Lease 384403. Specific locations (latitude and longitude and depth) of each well is provided in Table 1-1 and depicted in Figure 1-1 of BlueCrest's application.

The following specific aspects of the proposed activities are likely to result in the take of marine mammals: (1) Impact hammering of the drive pipe at the well prior to drilling, and (2) vertical seismic profiling (VSP). Underwater noise associated with drilling and rig operation associated with the specified activity has been determined to have little effect on marine mammals (based on Marine Acoustics, Inc.'s [2011] acoustical testing of the
Spartan 151
while drilling). Take, by Level B harassment only, of nine marine mammal species is anticipated to result from the specified activity.

Description of the Specified Activity

Overview

BlueCrest proposes to conduct oil and gas production drilling operations at up to three sites in lower Cook Inlet during the 2016 open water (ice-free) season (August 1 through October 31), using the
Spartan 151
jack-up drill rig, depending on availability. The activities of relevance to this IHA request include: Impact hammering of the drive pipe and VSP seismic operations. BlueCrest proposes to mobilize and demobilize the drill rig to and from the well locations, and will utilize both helicopters and vessels to conduct resupply, crew change, and other logistics during the drilling program. These mobilization/demobilization activities, and actual drilling/operation of the rig, are also part of the proposed activity but are not considered activities of relevance to this IHA because take is not being authorized for those activities. More information regarding these activities and why they are/are not considered activities of relevance to this IHA can be found in the Detailed Description of Activities section below.

Dates and Duration

The 2016 drilling program (which is the subject of this IHA request) would occur during the 2016 open water season (August 1 through October 31). BlueCrest estimates that the drilling period could take up to 91 days in the above time period. The exact start date is currently unknown, and dependent on the scheduling availability of the proposed drill rig. It is expected that each well will take approximately 30 days to complete, including well testing time.

During this time period, drive pipe hammering would only occur for a period of 1 to 3 days at each well site (although actual sound generation would occur only intermittently during this time period), and VSP seismic operations would only occur for a period of less than 1 to 2 days at each well site. This IHA (if issued) would be effective for 1 year, beginning on August 1, 2016.

Specified Geographic Region

BlueCrest's proposed program would occur at Cosmopolitan State #B-1 (originally Cosmopolitan #2), Cosmopolitan State #A-1 (originally Cosmopolitan State #1), #A-2, and #A-3 in lower Cook Inlet, AK. The exact location of BlueCrest's well sites can be seen in Figure 1-1 in BlueCrest's IHA application and location information (latitude/longitude and water depth) is provided in Table 1-1 in the IHA application.

Detailed Description of Activities

1. Drill Rig Mobilization and Towing

BlueCrest proposes to conduct its production and exploratory drilling using the
Spartan 151
drill rig or similar rig (see Figure 1-2 of the IHA application). The
Spartan 151
is a 150 H class independent leg, cantilevered jack-up drill rig, with a drilling capability of 25,000 ft but can operate in maximum water depths up to only 150 ft. The rig will be towed by ocean-going tugs licensed to operate in Cook Inlet. While under tow, the rig operations will be monitored by BlueCrest and the drilling contractor management, both aboard the rig and onshore.

The
Spartan 151
is currently moored at the Seward Marine Industrial Center, directly across Resurrection Bay from the City of Seward. The intention is to move the drill rig to the Cosmopolitan Site #B-1 well site in July, a distance of approximately 314 km (195 miles [mi]). It is anticipated that this tow would be accomplished within three days. Any move post-project will be controlled by the owner of the drilling rig. The rig will be towed between locations by ocean-going tugs that are licensed to operate in Cook Inlet. Move plans will receive close scrutiny from the rig owner's tow master as well as the owner's insurers, and will be conducted in accordance with state and federal regulations. Rig moves will be conducted in a manner to minimize any potential risk regarding safety as well as cultural or environmental impact.

The rig will be wet-towed by two or three ocean-going tugs licensed to operate in Cook Inlet. Ship strike of marine mammals during tow is not an issue of major concern. Most strikes of marine mammals occur when vessels are traveling at speeds between 24 and 44 km/hr (13 and 24 knots [kt]) (
http://www.nmfs.noaa.gov/pr/pdfs/shipstrike/ss_speed.pdf
), well above the 1.9- to 7.4-km/hr (1- to 4-kt) drill rig tow speed expected. However, noise from towing was considered as a potential impact. Tugs generate their loudest sounds while towing due to propeller cavitation. While these continuous sounds have been measured at up to 171 dB re 1 μPa-m (rms) at 1-meter source (broadband), they are generally emitted at dominant frequencies of less than 5 kHz (Miles
et al.,
1987; Richardson
et al.,
1995a, Simmonds
et al.,
2004). For the most part, the dominant noise frequencies from propeller cavitation are significantly lower than the dominant hearing frequencies for pinnipeds and toothed whales, including beluga whales (Wartzok and Ketten, 1999), so towing activities are not considered an activity that would `take' marine mammals.

2. Drive Pipe Hammering

A drive pipe is a relatively short, large-diameter pipe driven into the sediment prior to the drilling of oil wells. This section of tubing serves to support the initial sedimentary part of the well, preventing the looser surface layer from collapsing and obstructing the wellbore. Drive pipes are usually installed using pile driving techniques. The term `drive pipe' is often synonymous to the term `conductor pipe'; however, a 50.8-centimeter (cm; 20-inch [in]) conductor pipe will be drilled (not hammered) inside the drive pipe, and will be used to transport (conduct) drillhead cuttings to the surface. Therefore, there is no noise concern associated with the conductor pipe drilling, and the potential for acoustical harassment of marine mammals is due to the hammering of the drive pipe. BlueCrest proposes to drive approximately 200 ft (60 m) below mudline of 30-inch drive pipe at each of the well sites prior to drilling using a Delmar D62-22 impact hammer. This hammer has impact weight of 13,640 pounds (6,200 kg) and reaches maximum impact energy of 165,215 foot-pounds (224 kilonewton-meters) at a drop height of 12 ft (3.6 m).

Blackwell (2005) measured the noise produced by a Delmar D62-22 driving 36-inch steel pipe in upper Cook Inlet and found sound pressure levels (SPLs) to exceed 190 dB re 1μPa-m (rms) at about 200 ft (60 m), 180 dB re 1μPa-m (rms) at about 820 ft (250 m), and 160 dB re 1μPa-m (rms) at just less than 1.2 mi (1.9 km). Illingworth and Rodkin (2014) measured the hammer noise operating from another rig, the
Endeavour,
in 2013 and found SPLs to exceed 190 dB re 1μPa-m (rms) at about 180 ft (55 m), 180 dB re 1μPa-m (rms) at about 560 ft (170 m), and 160 dB re 1μPa-m (rms) at 1 mi (1.6 km). The drive pipe driving event is expected to last 1 to 3 days at each well site, although actual sound generation (pounding) would occur only intermittently during this period.

3. Drilling and Standard Operation

The
Spartan 151
was hydro-acoustically measured by Marine Acoustics, Inc. while operating in 2011. The survey results showed that continuous noise levels exceeding 120 dB re 1μPa (NMFS' current threshold for estimating Level B harassment from continuous underwater noise) extended

out only 164 ft (50 m), and that this sound was largely associated with the diesel engines used as hotel power generators.

Deep well pumps were not identified as a sound source by Marine Acoustics, Inc. (2011) during their acoustical testing of the
Spartan 151,
and are not considered an activity that would `take' marine mammals.

4. Vertical Seismic Profiling

Once a well is drilled, accurate follow-up seismic data can be collected by placing a receiver at known depths in the borehole and shooting a seismic airgun at the surface near the borehole. These gathered data not only provide high resolution images of the geological layers penetrated by the borehole but can be used to accurately correlate (or correct) the original surface seismic data. The procedure is known as vertical seismic profiling (VSP).

BlueCrest intends to conduct VSP operations at the end of drilling each well using an array of airguns with total volumes of between 600 and 880 cubic inches (in
3
). The VSP operation is expected to last less than 1 or 2 days at each well site. Assuming a 1-meter source level of 227 dB re 1μPa (based on manufacturer's specifications) for an 880 in
3
array and using Collins
et al.'
s (2007) transmission loss model for Cook Inlet (227 − 18.4 Log(R) − 0.00188), the 190 dB radius from the source was estimated at 330 ft (100 m), the 180 dB radius at 1,090 ft (332 m), and the 160 dB radius at 1.53 mi (2.46 km). 190 dB and 180 dB are the current NMFS thresholds for estimating Level A harassment from underwater noise exposure for pinnipeds and cetaceans, respectively, and 160 dB is the current NMFS threshold for estimating Level B harassment from exposure to underwater impulse noises. Therefore, VSP operations are considered an activity that has the potential to `take' marine mammals.

Illingworth and Rodkin (2014) measured the underwater sound levels associated with a July 2013 VSP operation using a 750 in
3
array and found sound levels exceeding 160 dB re 1 μPa (rms) extended out 1.54 mi (2.47 km), virtually identical to the modeled distance. The measured radius to 190 dB was 394 ft (120 m) and to 180 dB was 787 ft (240 m).

5. Helicopter and Supply Vessel Support

Helicopter logistics for project operations will include transportation for personnel, groceries, and supplies. Helicopter support will consist of a twin turbine Bell 212 (or equivalent) helicopter certified for instrument flight rules land and over water operations. Helicopter crews and support personnel will be housed in existing Kenai area facilities. The helicopter will be based at the Kenai Airport to support rig crew changes and cargo handling. Fueling will take place at these facilities. No helicopter refueling will take place on the rig.

Helicopter flights to and from the rig are expected to average two per day. Flight routes will follow a direct route to and from the rig location, and flight heights will be maintained 1,000 to 1,500 feet above ground level to avoid take of marine mammals (Richardson
et al.,
1995a). At these altitudes, there are not expected to be impacts from sound generation on marine mammals, and are not considered an activity that would `take' marine mammals. The aircraft will be dedicated to the drilling operation and will be available for service 24 hours per day. A replacement aircraft will be available when major maintenance items are scheduled.

Major supplies will be staged on-shore at the Kenai OSK Dock. Required supplies and equipment will be moved from the staging area by contracted supply vessels and loaded aboard the rig when the rig is established on a drilling location. Major supplies will include fuel, drilling water, mud materials, cement, casing, and well service equipment. Supply vessels also will be outfitted with fire-fighting systems as part of fire prevention and control as required by Cook Inlet Spill Prevention and Response, Inc. The specific supply vessels have not been identified; however, typical offshore drilling support work vessels are of steel construction with strengthened hulls to give the capability of working in extreme conditions. Additional information about logistics and fuel and waste management can be found in Section 1.2 of BlueCrest's IHA application.

Description of Marine Mammals in the Area of the Specified Activity

Several marine mammal species occur in lower Cook Inlet. The marine mammal species under NMFS's jurisdiction include: Beluga whale (
Delphinapterus leucas
); harbor porpoise (
Phocoena phocoena
); killer whale (
Orcinus orca
); gray whale (
Eschrichtius robustus
); minke whale (
Balaenoptera acutorostrata
); Dall's porpoise (
Phocoenoides dalli
); humpback whale (
Megaptera novaeangliae
); harbor seal (
Phoca vitulina richardsi
); and Steller sea lion (
Eumetopias jubatus
).

Data collected during marine mammal monitoring at Cosmopolitan State #A-1 during summer 2013 recorded at least 154 harbor porpoise (152 within 1.2 mi (2 km) of operation, 12 of which were observed inside 853 ft (260 m) of the rig); 77 harbor seals (18 of these within 853 ft [260 m] of the active drill rig); 42 minke whales (all except for three recorded over 984 ft (300 m) from the active drill rig; 19 Dall's porpoise (none in close proximity to the active drill rig); 12 gray whales (observed offshore of Cape Starichkof; none closely approached drilling operations); seven Steller sea lions (none in close proximity to the active drill rig); 18 killer whales (17 within 1.2 mi (2 km) of operations); and one beluga whale (observed at a distance well beyond 1.8 mi (3 km) between May and August 2013 (112 days of monitoring). Based on their seasonal patterns, gray whales could be encountered in low numbers during operations. Minke whales have been considered migratory in Alaska (Allen and Angliss, 2014) but have recently been observed off Cape Starichkof and Anchor Point, including in winter. The remaining species could be encountered year-round. Humpback whales are common in the very southern part of Cook Inlet and typically do not venture north of Kachemak Bay (B. Mahoney, NMFS, pers. comm., August 2014), which is south of the proposed Cosmopolitan drilling site. Therefore, while it is unlikely that humpback whales, gray whales, or minke whales would be encountered during the proposed project, it is still a possibility based on observations from past monitoring efforts, and therefore take of these species was requested.

Of these marine mammal species, Cook Inlet beluga whales, humpback whales, and the western distinct population segment (DPS) of Steller sea lions are listed as endangered under the Endangered Species Act (ESA). The eastern DPS of Steller sea lions was recently removed from the endangered species list (78 FR 66139, November 4, 2013) but currently retains its status as “depleted” under the MMPA along with the western DPS, Cook Inlet beluga whales, and humpback whales.

Despite these designations, Cook Inlet beluga whales and the western DPS of Steller sea lions have not made significant progress towards recovery. Data indicate that the Cook Inlet population of beluga whales decreased at a rate of 0.6 percent annually between 2002 and 2012 (Allen and Angliss, 2014). The NMFS 2014 Stock Assessment Report (SAR) estimated 312 Cook Inlet beluga whales, which is a three-year average. However, the most

recent abundance estimate is 340 beluga whales (Shelden
et al.,
2015).

Regional variation in trends in Western DPS Steller sea lion pup counts in 2000-2012 is similar to that of non-pup counts (Johnson and Fritz, 2014). Overall, there is strong evidence that pup counts in the western stock in Alaska increased (1.45 percent annually). Between 2004 and 2008, Alaska western non-pup counts increased only 3%: Eastern Gulf of Alaska (Prince William Sound area) counts were higher and Kenai Peninsula through Kiska Island counts were stable, but western Aleutian counts continued to decline. Johnson and Fritz (2014) analyzed western Steller sea lion population trends in Alaska and noted that there was strong evidence that non-pup counts in the western stock in Alaska increased between 2000 and 2012 (average rate of 1.67 percent annually). However, there continues to be considerable regional variability in recent trends across the range in Alaska, with strong evidence of a positive trend east of Samalga Pass and strong evidence of a decreasing trend to the west (Allen and Angliss, 2014).

The Central North Pacific humpback whale stock, consisting of winter/spring populations of the Hawaiian Islands which migrate primarily to northern British Columbia/Southeast Alaska, the Gulf of Alaska, and the Bering Sea/Aleutian Islands (Baker
et al.,
1990; Perry
et al.,
1990; Calambokidis
et al.,
1997), has increased over the past two decades. Different studies and sampling techniques in Hawaii and Alaska have indicated growth rates ranging from 4.9-10 percent per year in the 1980s, 1990s, and early 2000s (Mobley
et al.,
2001; Mizroch
et al.,
2004; Zerbini
et al.,
2006; Calambokidis
et al.,
2008). It is also clear that the abundance has increased in Southeast Alaska, though a trend for the Southeast Alaska portion of this stock cannot be estimated from the data because of differences in methods and areas covered (Allen and Angliss, 2013). On April 21, 2015, NMFS published a notice in the
Federal Register
requesting comments on a proposal to revise the listing status of humpback whales by delineating the species into 14 DPS, changing the Central North Pacific stock of humpback whales to become the Hawaii DPS. NMFS also proposed to delist the Hawaii DPS (80 FR 22304).

Pursuant to the ESA, critical habitat has been designated for Cook Inlet beluga whales and Steller sea lions. The proposed drilling program does not fall within critical habitat designated in Cook Inlet for beluga whales or within critical habitat designated for Steller sea lions. The Cosmopolitan State unit is nearly 100 miles south of beluga whale Critical Habitat Area 1 and approximately 27 miles south of Critical Habitat Area 2. It is also located about 25 miles north of the isolated patch of Critical Habitat Area 2 found in Kachemak Bay. Area 2 is based on dispersed fall and winter feeding and transit areas in waters where whales typically appear in smaller densities or deeper waters (76 FR 20180, April 11, 2011). No critical habitat has been designated for humpback whales.

BlueCrest is requesting take of belugas, humpback whales and Steller sea lions, which have been observed in close proximity to the Cosmopolitan site (G. Green, Owl Ridge, personal communication). In addition, BlueCrest is requesting take of gray, minke, and killer whales, harbor and Dall's porpoise, and harbor seals. See Table 1 below for more information on the habitat, range, population, and status of these species.

Table 1—The Habitat, Abundance, and Conservation Status of Marine Mammals

Species
Habitat
Range

Best Population Estimate (Minimum)
1

ESA
2

MMPA
3

Humpback whale (
Megaptera novaeangliae)

Coastal and inland waters
Worldwide in all ocean basins
10,103—Central N. Pacific Stock
EN
D, S.

Minke Whale (
Balaenoptera acutorostra
)

Coastal and inland waters
Bering and Chukchi Seas south to near the Equator

1,233
2
—Alaska stock

NL
NC.

Gray Whale (
Eschrichtius robustus
)

Coastal and inland waters
North Pacific from Alaska to Mexico

20,990
3
—E. North Pacific Stock

NL
NC.

Beluga Whale (
Delphinapterus leucas
)

Offshore waters in winter; coastal/estuarine waters in spring
Ice-covered arctic and subartic waters of the Northern Hemisphere
340—Cook Inlet stock
EN
D, S.

Killer Whale (
Orcinus orca
)

Offshore to inland waterways
Throughout North Pacific; along west coast of North America; entire Alaskan coast
2,347—Alaska resident stock/587 Alaska transient stock
NL
NC.

Harbor Porpoise (
Phocoena phocoena
)

Coastal
Point Barrow, Alaska to Point Conception, California
31,046—Gulf of Alaska stock
NL
S.

Dall's Porpoise
(Phocoenoides dalli
)

Over continental shelf adjacent to slope and over deep oceanic waters
Throughout North Pacific
83,400—Alaska stock
NL
NC.

Pacific harbor seal (Phoca vitulina richardii)
Coastal and Estuarine
Coastal temperate to polar regions in Northern Hemisphere
22,900—Cook Inlet/Shelikof stock
NL
NC.

Steller Sea Lion (
Eumetopias jubatus
)

Coastal
Northern Pacific Rim from northern Japan to California
55,422—W. U.S. stock
NL
D, S.

NA = Not available or not assessed.

1
Allen and Angliss (2015).

2
Zerbini
et al.
(2006).

3
Caretta
et al.
(2015).

4
U.S. Endangered Species Act: EN = Endangered, T = Threatened, DL = Delisted, and NL = Not listed.

5
U.S. Marine Mammal Protection Act: D = Depleted, S = Strategic, and NC = Not classified.

Cetaceans

Beluga Whale
(Delphinapterus leucas)

The Cook Inlet beluga whale 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 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 more than 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 percent which was attributed to overharvesting by subsistence hunting. Subsistence hunting was estimated to annually remove 10 to 15 percent of the population during this period. Only five belugas have been harvested since 1999, yet the population has continued to decline, with the most recent estimate at only 312 animals (Allen and Angliss 2014). 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, NMFS designated critical habitat for the beluga under the ESA (Figure 1).

BILLING CODE 3510-22-P

EN02JN16.026

BILLING CODE 3510-22-C

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 pacificus
) and salmon (
Onchorhyncus spp.
) (Moore
et al.
2000). Critical Habitat Area

1 reflects this summer distribution (Figure 1). 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 (Critical Habitat Area 2; Figure 1). Some whales may also winter in and near Kachemak Bay.

The Cosmopolitan State lease does not fall within beluga whale critical habitat. Based on Goetz et al. (2012) beluga whale densities, both along the route from Port Graham and at the well site, are very low (<0.01 whales/km
2
). In the past, beluga whales have been observed in Kachemak Bay, which presumably could have travelled between the bay and upper Cook Inlet following a route past the current location of the Cosmopolitan State lease. Reported observations since 1975 show most whale activity in Kachemak Bay occurred prior to 2000. However, in 2013 a single beluga was sighted a few kilometers from Cosmopolitan State well site #A-1 (Owl Ridge 2014).

Killer Whales (
Orcinus orca
)

Two different killer whale stocks inhabit the Cook Inlet region of Alaska: the Alaska resident stock (resident stock) and the Gulf of Alaska, Aleutian Islands, Bering Sea transient stock (transient stock) (Allen and Angliss, 2014). The Alaska resident stock occurs from Southeast Alaska to the Bering Sea (Allen and Angliss, 2014) and feeds exclusively on fish, while transient killer whales feed primarily on marine mammals (Saulitis
et al.,
2000). Killer whales are occasionally observed in lower Cook Inlet, especially near Homer and Port Graham (Shelden
et al.,
2003; Rugh
et al.,
2005). A concentration of sightings near Homer and inside Kachemak Bay may represent high killer whale use or high observer-effort given most records are from a whale-watching venture based in Homer. During aerial surveys conducted between 1993 and 2004, killer whales were only observed on three flights, all in the Kachemak Bay and English Bay area (Rugh
et al.,
2005). Eighteen killer whales (it is unknown which stock these belonged to) were recorded during the May to August 2013 marine mammal monitoring activities at Cosmopolitan State #A-1 (Owl Ridge 2014). Based on these sightings, it is possible that killer whales will occur in the vicinity of the proposed drilling activity.

Harbor Porpoise (
Phocoena phocoena
)

The most recent estimated density for harbor porpoises in Cook Inlet is 7.2 per 1,000 km
2
(Dahlheim
et al.,
2000) indicating that only a small number use Cook Inlet. Harbor porpoise have been reported in lower Cook Inlet from Cape Douglas to the West Foreland, Kachemak Bay, and offshore (Rugh
et al.,
2005). Harbor porpoises are found primarily in coastal waters less than 328 ft deep (Hobbs and Waite, 2010) where they feed primarily on Pacific herring, other schooling fish, and cephalopods. The diet of harbor porpoise within Cook Inlet is unknown, although seasonal distribution patterns of porpoise (Shelden et al. 2014) coincident with eulachon, longfin smelt, capelin, herring, and salmon concentrations (Moulton 1997) suggest these fish are important prey items for Cook Inlet harbor porpoise. Small numbers of harbor porpoises have been consistently reported in upper Cook Inlet between April and October, except for a recent survey that recorded higher than usual numbers (Prevel Ramos
et al.,
2008). In addition, recent passive acoustic research in Cook Inlet by the Alaska Department of Fish and Game and the National Marine Mammal Laboratory (NMML) have indicated that harbor porpoises occur more frequently than previously thought, particularly in the West Foreland area in the spring (NMML, 2011); however overall numbers are still unknown at this time. Also, harbor porpoises were the most frequently sighted marine mammal species during monitoring in 2013 at the Cosmopolitan State #A-1 well. At least 154 harbor porpoises were recorded during the 2013 monitoring, but only 12 were observed inside 853 ft (260 m) of the drill rig.

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.

In the North Pacific, humpback whiles feed primarily on krill (especially euphausiids) and small schooling fish such including herring, sand lance, capelin, and eulachon (Clapham 2002). Based on both fecal samples and isotope analysis, Witteveen et al. (2011) found humpback whales near Kodiak Island to feed largely on euphausiids, capelin, Pacific sand lance, and juvenile walleye pollock. It is unknown what humpback whales seasonally occurring in Kachemak Bay and near Anchor Point are feeding on, but Cook Inlet seabird and forage fish studies (Piatt and Roseneau 1997) found large concentrations of sand lance in this region. 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 very few records to the latitude of the Cosmopolitan State lease area. However, 29 sightings of 48 humpback whales were recorded by marine mammal observers during the 2013 monitoring program at Cosmopolitan State well site #A-1 (Owl Ridge 2014), although nearly all of these animals were observed at a distance well south of the well site, many records were repeat sightings of the same animals, and none were recorded inside an active harassment zone. Due to these sightings, humpback whales may be encountered in the vicinity of the project and were included in the application for incidental take.

Gray Whale (
Eschrichtius robustus
)

The gray whale is a large baleen whale known to have one of the longest migrations of any mammal. This whale can be found all along the shallow coastal waters of the North Pacific Ocean. The Eastern North Pacific stock, which includes those whales that travel along the coast of Alaska, was delisted from the ESA in 1994 after a distinction was made between the western and eastern populations (59 FR 31094, June 16, 1994). The most recent estimate of abundance for the Eastern North Pacific stock of gray whales is 19,126, based on the 2006/2007 southbound survey (Laake
et al.,
2009).

Gray whales typically do not feed during their northward migration through Alaskan waters until they reach the Chukchi Sea where they spend the summer feeding mostly on ampeliscid amphipods, a benthic crustacean (Rice and Wolman 1971, Highsmith and Coyle 1992, Nelson et al. 1994). However, small groups of whales may opportunistically feed along route (Nerini 1984), with some groups actually becoming “resident” at areas of high localized prey densities (Calambokidis et al. 2004, Estes 2006). One “resident” group, known as the Kodiak group, has been observed year-round at Ugak Bay (Kodiak Island)

feeding on dense populations of hooded shrimp or cumaceans (Diastylidae), a benthic crustacean (Moore et al. 2007). Groups of gray whales were recorded at the Cosmopolitan State lease site in 2013 (Owl Ridge 2014), mostly in July, but it was noted that these may have been repeated sightings of the same one or two small groups, suggesting seasonal foraging use of the Anchor Point area by a few whales. There is no information the diet of gray whales using lower Cook Inlet, but available prey could be similar to that found at Ugak Bay.

Although observations of gray whales are rare within Cook Inlet, marine mammal observers noted individual gray whales on nine occasions in upper Cook Inlet in 2012 while conducting marine mammal monitoring for seismic survey activities under an IHA NMFS issued to Apache Alaska Corporation: Four times in May; twice in June; and three times in July (Apache, 2013). Annual surveys conducted by NMFS in Cook Inlet since 1993 have resulted in a total of five gray whale sightings (Rugh
et al.,
2005). Although Cook Inlet is not believed to comprise either essential feeding or social ground, there may be some encounters in lower Cook Inlet. Small numbers of summering gray whales have been noted by fishermen near Kachemak Bay and north of Anchor Point. Further, summer gray whales were recorded a dozen times offshore of Cape Starichkof by observers monitoring BlueCrest's Cosmopolitan #A-1 drilling program between May and August 2013. However, as noted above, these may have been repeat sightings of the same one or two small groups.

Minke Whale (
Balaenoptera acutorostrata
)

Minke whales are the smallest of the rorqual group of baleen whales. 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 mi 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. There are no records north of Cape Starichkof. However, 42 minke whales were recorded at Cosmopolitan State site #A-1 between May and August 2013 in patterns suggesting the presence of a small, yet conspicuous summer population (at least) within the Cosmopolitan State unit. All but three of the minke whales observed during the 2013 monitoring season were recorded over 984 ft (300 m) from the active drill rig.

Minke whales have a very catholic diet feeding on preferred prey most abundant at a given time and location (Leatherwood and Reeves 1983). In the southern hemisphere they feed largely on krill, while in the North Pacific they feed on schooling fish such as herring, sandlance, and walleye pollock (Reeves et al. 2002). There is no dietary information specific to Alaska although anecdotal observations of minke whales feeding on shoaling fish off Anchor Point have been reported to NMFS (Brad Smith, pers. comm.).

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). 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 prefer the deep offshore and shelf slope waters where they feed largely on mesopelagic fish and squid, but also herring in more nearshore waters (Jefferson 2002). There is no diet information specific to Cook Inlet. Dall's porpoise have been observed in lower Cook Inlet, including Kachemak Bay and near Anchor Point (Glenn Johnson, pers. comm.), but sightings there are rare, as expected, given they prefer waters exceeding 180 meters deep. During 112 days of monitoring during the Cosmopolitan State #1 drilling operation between May and August 2013, 19 Dall's porpoise were recorded (all during the month of August), but none were observed in close proximity of the drill rig (
i.e.,
they were greater than 853 ft [260 m away]).

Pinnipeds

Harbor Seals (
Phoca vitulina
)

Harbor seals inhabit the coastal and estuarine waters of Cook Inlet and are one of the more common marine mammal species in Alaskan waters. Harbor seals are non-migratory; their movements are associated with tides, weather, season, food availability, and reproduction. The major haulout sites for harbor seals are located in lower Cook Inlet, and their presence in the upper inlet coincides with seasonal runs of prey species. For example, harbor seals are commonly observed along the Susitna River and other tributaries along upper Cook Inlet during the eulachon and salmon migrations (NMFS, 2003). During aerial surveys of upper Cook Inlet in 2001, 2002, and 2003, harbor seals were observed 24 to 96 km (15 to 60 mi) south-southwest of Anchorage at the Chickaloon, Little Susitna, Susitna, Ivan, McArthur, and Beluga Rivers (Rugh
et al.,
2005). Montgomery
et al.
(2007) recorded over 200 haulout sites in lower Cook Inlet alone. Montgomery
et al.
(2007) also found seals elsewhere in Cook Inlet to move in response to local steelhead and salmon runs. However, aerial surveys conducted in June 2013 for the proposed Susitna Dam project noted nearly 700 harbor seals in the Susitna Delta region (Alaska Energy Authority, 2013). During the marine mammal monitoring associated with the 2013 drilling activities at Cosmopolitan State, 77 harbor seals were recorded. Harbor seals may be encountered during BlueCrest's lower Cook Inlet proposed drilling program.

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 as threatened under ESA in 1990, and was 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 which, except for salmon, are found in abundance in upper Cook Inlet (Nemeth
et al.
2007). Small numbers of Steller sea lions are likely to be encountered during BlueCrest's planned operations in 2016 based on the observations of sea lions made at the lease site in 2013 (Owl Ridge 2014), but on of which was observed within 50m of the drill rig during the 2013 monitoring program.

Summary

BlueCrest's application contains information on the status, distribution, seasonal distribution, and abundance of each of the species under NMFS jurisdiction mentioned in this document. Please refer to the application for that information (see
ADDRESSES
). Additional information can also be found in the NMFS Stock Assessment Reports (SAR). The Alaska 2014 SAR is available on the Internet at:
http://www.nmfs.noaa.gov/pr/sars/pdf/ak2014_final.pdf.

Potential Effects of the Specified Activity on Marine Mammals

This section includes a summary and discussion of the ways that the types of stressors associated with the specified activity (
e.g.,
impact hammering of the drive pipe and VSP) has been observed to, or are thought to, 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 are expected to be taken by this activity. The “Negligible Impact Analysis” section will include the analysis of how this specific activity will impact marine mammals and will consider the content of this section, the “Estimated Take by Incidental Harassment” section, the “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.

The likely or possible impacts of the proposed drilling program in lower Cook Inlet on marine mammals could involve both non-acoustic and acoustic stressors. Potential non-acoustic stressors include the physical presence of the equipment and personnel. Petroleum development and associated activities introduce sound into the marine environment. Impacts to marine mammals are expected to primarily be acoustic in nature. Potential acoustic effects on marine mammals relate to impact hammering of drive pipe and the VSP airgun array.

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. Based on available behavioral data, audiograms have been derived using auditory evoked potentials, anatomical modeling, and other data, Southall
et al.
(2007) designate “functional hearing groups” for marine mammals and estimate the lower and upper frequencies of functional hearing of the groups. The functional groups and the associated frequencies are indicated below (though animals are less sensitive to sounds at the outer edge of their functional range and most sensitive to sounds of frequencies within a smaller range somewhere in the middle of their functional hearing range):

• Low frequency cetaceans (13 species of mysticetes): functional hearing is estimated to occur between approximately 7 Hz and 25 kHz;

• Mid-frequency cetaceans (32 species of dolphins, six species of larger toothed whales, and 19 species of beaked and bottlenose whales): functional hearing is estimated to 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 is estimated to occur between approximately 200 Hz and 180 kHz;

• Phocid pinnipeds in Water: functional hearing is estimated to occur between approximately 75 Hz and 100 kHz; and

• Otariid pinnipeds in Water: functional hearing is estimated to occur between approximately 100 Hz and 48 kHz.

As mentioned previously in this document, nine marine mammal species (seven cetacean and two pinniped species) may occur in the drilling area of BlueCrest's lower Cook Inlet project. Of the seven cetacean species likely to occur in the proposed project area and for which take is requested, three are classified as low-frequency cetaceans (
i.e.,
humpback, minke, and gray whales), two are classified as a mid-frequency cetacean (
i.e.,
beluga and killer whales), and two are classified as high-frequency cetaceans (
i.e.,
harbor and Dall's porpoises) (Southall
et al.,
2007). A species' functional hearing group is a consideration when we analyze the effects of exposure to sound on marine mammals.

1. Tolerance

Numerous studies have shown that underwater sounds from industry activities are often readily detectable by marine mammals in the water at distances of many kilometers. Numerous studies have also shown that marine mammals at distances more than a few kilometers away often show no apparent response to industry activities of various types (Miller
et al.,
2005; Bain and Williams, 2006). This is often true even in cases when the sounds must be readily audible to the animals based on measured received levels and the hearing sensitivity of that mammal group. Although various baleen whales, toothed whales, and (less frequently) pinnipeds have been shown to react behaviorally to underwater sound such as airgun pulses or vessels under some conditions, at other times mammals of all three types have shown no overt reactions (
e.g.,
Malme
et al.,
1986; Richardson
et al.,
1995a; Madsen and Mohl, 2000; Croll
et al.,
2001; Jacobs and Terhune, 2002; Madsen
et al.,
2002; Miller
et al.,
2005). 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 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/hr) for humpback and sperm whales according to the airgun array's operational status (
i.e.,
active versus silent). The airgun arrays used in the Weir (2008) study were much larger than the array proposed for use during the limited VSP (total discharge volumes of 600 to 880 in
3
for 1 to 2 days). In general, pinnipeds and small odontocetes seem to be more tolerant of exposure to some types of underwater sound than are baleen whales. Richardson
et al.
(1995a) found that vessel noise does not seem to strongly affect pinnipeds that are already in the water. Richardson
et al.
(1995a) went on to explain that seals on haul-outs sometimes respond strongly to the presence of vessels and at other times appear to show considerable tolerance of vessels.

2. Masking

Masking is the obscuring of sounds of interest by other sounds, often at similar frequencies. 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). Masking, or auditory interference, generally occurs when sounds in the environment are louder than, and of a similar frequency as, auditory signals an animal is trying to receive. Masking 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 in situations where the temporal and spatial scope of the masking activities is extensive.

Masking occurs when anthropogenic sounds and signals (that the animal utilizes) overlap at both spectral and temporal scales. The sounds generated by the proposed equipment for the drilling program will consist of low frequency sources (most under 500 Hz). Lower frequency man-made sounds are more likely to affect detection of communication calls of low-frequency specialists and other potentially important natural sounds such as surf and prey noise. There is less concern regarding masking of conspecific vocalizations near the jack-up rig during drilling operations, as the species most likely to be found in the vicinity are mid- to high-frequency cetaceans or pinnipeds and not low-frequency cetaceans. Additionally, masking is not expected to be a concern from airgun usage due to the brief duration of use (less than a day to up to 2 days) and the low-frequency sounds that are produced by the airguns. However, at long distances (over tens of kilometers away), due to multipath propagation and reverberation, the durations of airgun pulses can be “stretched” to seconds with long decays (Madsen
et al.,
2006), although the intensity of the sound is greatly reduced.

The “stretching” of sound described above could affect communication signals used by low frequency mysticetes when they occur near the noise band and thus reduce the communication space of animals (
e.g.,
Clark
et al.,
2009) and cause increased stress levels (
e.g.,
Foote
et al.,
2004; Holt
et al.,
2009); however, only low numbers of baleen whales are expected to occur within the proposed action area. Marine mammals are thought to sometimes be able to compensate for masking by adjusting their acoustic behavior by shifting call frequencies, and/or increasing call volume and vocalization rates. For example, blue whales are found to increase call rates when exposed to seismic survey noise in the St. Lawrence Estuary (Di Iorio and Clark, 2010). The North Atlantic right whales (Eubalaena glacialis) exposed to high shipping noise increase call frequency (Parks
et al.,
2007), while some humpback whales respond to low-frequency active sonar playbacks by increasing song length (Miller el al., 2000). Additionally, beluga whales have been known to 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). Although some degree of masking is inevitable when high levels of manmade broadband sounds are introduced into the sea, marine mammals have evolved systems and behavior that function to reduce the impacts of masking. Structured signals, such as the echolocation click sequences of small toothed whales, may be readily detected 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.,
1995a). 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 are known to 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, 2009; 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. Directional hearing has been demonstrated 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.

3. Behavioral Disturbance

Behavioral responses to sound are highly variable and context-specific. Many different variables can influence an animal's perception of and response to (in both nature and magnitude) an acoustic event. An animal's prior

experience with a sound or sound source affects whether it is less likely (habituation) or more likely (sensitization) to respond to certain sounds in the future (animals can also be innately pre-disposed to respond to certain sounds in certain ways; Southall
et al.,
2007). Related to the sound itself, the perceived nearness of the sound, bearing of the sound (approaching vs. retreating), similarity of a sound to biologically relevant sounds in the animal's environment (
i.e.,
calls of predators, prey, or conspecifics), and familiarity of the sound may affect the way an animal responds to the sound (Southall
et al.,
2007). Individuals (of different age, gender, reproductive status, etc.) among most populations will have variable hearing capabilities and differing behavioral sensitivities to sounds that will be affected by prior conditioning, experience, and current activities of those individuals. Often, specific acoustic features of the sound and contextual variables (
i.e.,
proximity, duration, or recurrence of the sound or the current behavior that the marine mammal is engaged in or its prior experience), as well as entirely separate factors such as the physical presence of a nearby vessel, may be more relevant to the animal's response than the received level alone.

Exposure of marine mammals to sound sources can result in (but is not limited to) no response or any of the following observable responses: Increased alertness; orientation or attraction to a sound source; vocal modifications; cessation of feeding; cessation of social interaction; alteration of movement or diving behavior; avoidance; habitat abandonment (temporary or permanent); and, in severe cases, panic, flight, stampede, or stranding, potentially resulting in death (Southall
et al.,
2007). The biological significance of many of these behavioral disturbances is difficult to predict.

The following sub-sections provide examples of the variability in behavioral responses that could be expected given the different sensitivities of marine mammal species to sound.

Baleen Whales
—Richardson
et al.
(1995b) reported changes in surfacing and respiration behavior and the occurrence of turns during surfacing in bowhead whales exposed to playback of underwater sound from drilling activities. These behavioral effects were localized and occurred at distances up to 1.2-2.5 mi (2-4 km).

Richardson
et al.
(2008) reported a slight change in the distribution of bowhead whale calls in response to operational sounds on BP's Northstar Island. The southern edge of the call distribution ranged from 0.47 to 1.46 mi (0.76 to 2.35 km) farther offshore, apparently in response to industrial sound levels. However, this result was only achieved after intensive statistical analyses, and it is not clear that this represented a biologically significant effect.

Richardson
et al.
(1995a) and Moore and Clarke (2002) reviewed a few studies that observed responses of gray whales to aircraft. Cow-calf pairs were quite sensitive to a turboprop survey flown at 1,000 ft (305 m) altitude on the Alaskan summering grounds. In that survey, adults were seen swimming over the calf, or the calf swam under the adult (Ljungblad
et al.,
1983, cited in Richardson
et al.,
1995a and Moore and Clarke, 2002). However, when the same aircraft circled for more than 10 minutes at 1,050 ft (320 m) altitude over a group of mating gray whales, no reactions were observed (Ljungblad
et al.,
1987, cited in Moore and Clarke, 2002). Malme
et al.
(1984, cited in Richardson
et al.,
1995a and Moore and Clarke, 2002) conducted playback experiments on migrating gray whales. They exposed the animals to underwater noise recorded from a Bell 212 helicopter (estimated altitude = 328 ft [100 m]), at an average of three simulated passes per minute. The authors observed that whales changed their swimming course and sometimes slowed down in response to the playback sound but proceeded to migrate past the transducer. Migrating gray whales did not react overtly to a Bell 212 helicopter at greater than 1,394 ft (425 m) altitude, occasionally reacted when the helicopter was at 1,000-1,198 ft (305-365 m), and usually reacted when it was below 825 ft (250 m; Southwest Research Associates, 1988, cited in Richardson
et al.,
1995a and Moore and Clarke, 2002). Reactions noted in that study included abrupt turns or dives or both. Green
et al.
(1992, cited in Richardson
et al.,
1995a) observed that migrating gray whales rarely exhibited noticeable reactions to a straight-line overflight by a Twin Otter at 197 ft (60 m) altitude. Overflights are likely to have little or no disturbance effects on baleen whales. Any disturbance that may occur would likely be temporary and localized.

Southall
et al.
(2007, Appendix C) reviewed a number of papers describing the responses of marine mammals to non-pulsed sound, such as that produced during drilling operations. In general, little or no response was observed in animals exposed at received levels from 90-120 dB re 1 µPa (rms). Probability of avoidance and other behavioral effects increased when received levels were from 120-160 dB re 1 µPa (rms). Some of the relevant reviews contained in Southall
et al.
(2007) are summarized next.

Baker
et al.
(1982) reported some avoidance by humpback whales to vessel noise when received levels were 110-120 dB (rms) and clear avoidance at 120-140 dB (sound measurements were not provided by Baker but were based on measurements of identical vessels by Miles and Malme, 1983).

Malme
et al.
(1983, 1984) used playbacks of sounds from helicopter overflight and drilling rigs and platforms to study behavioral effects on migrating gray whales. Received levels exceeding 120 dB induced avoidance reactions. Malme
et al.
(1984) calculated 10%, 50%, and 90% probabilities of gray whale avoidance reactions at received levels of 110, 120, and 130 dB, respectively. Malme
et al.
(1986) observed the behavior of feeding gray whales during four experimental playbacks of drilling sounds (50 to 315 Hz; 21-min overall duration and 10% duty cycle; source levels of 156-162 dB). In two cases for received levels of 100-110 dB, no behavioral reaction was observed. However, avoidance behavior was observed in two cases where received levels were 110-120 dB.

Richardson
et al.
(1990) performed 12 playback experiments in which bowhead whales in the Alaskan Arctic were exposed to drilling sounds. Whales generally did not respond to exposures in the 100 to 130 dB range, although there was some indication of minor behavioral changes in several instances.

McCauley
et al.
(1996) reported several cases of humpback whales responding to vessels in Hervey Bay, Australia. Results indicated clear avoidance at received levels between 118 to 124 dB in three cases for which response and received levels were observed/measured.

Palka and Hammond (2001) analyzed line transect census data in which the orientation and distance off transect line were reported for large numbers of minke whales. The authors developed a method to account for effects of animal movement in response to sighting platforms. Minor changes in locomotion speed, direction, and/or diving profile were reported at ranges from 1,847 to 2,352 ft (563 to 717 m) at received levels of 110 to 120 dB.

Biassoni
et al.
(2000) and Miller
et al.
(2000) reported behavioral observations for humpback whales exposed to a low-frequency sonar stimulus (160- to 330-Hz frequency band; 42-s tonal signal repeated every 6 min; source levels 170 to 200 dB) during playback experiments. Exposure to measured received levels

ranging from 120 to 150 dB resulted in variability in humpback singing behavior. Croll
et al.
(2001) investigated responses of foraging fin and blue whales to the same low frequency active sonar stimulus off southern California. Playbacks and control intervals with no transmission were used to investigate behavior and distribution on time scales of several weeks and spatial scales of tens of kilometers. The general conclusion was that whales remained feeding within a region for which 12 to 30 percent of exposures exceeded 140 dB.

Frankel and Clark (1998) conducted playback experiments with wintering humpback whales using a single speaker producing a low-frequency “M-sequence” (sine wave with multiple-phase reversals) signal in the 60 to 90 Hz band with output of 172 dB at 1 m. For 11 playbacks, exposures were between 120 and 130 dB re 1 µPa (rms) and included sufficient information regarding individual responses. During eight of the trials, there were no measurable differences in tracks or bearings relative to control conditions, whereas on three occasions, whales either moved slightly away from (n = 1) or towards (n = 2) the playback speaker during exposure. The presence of the source vessel itself had a greater effect than did the M-sequence playback.

Finally, Nowacek
et al.
(2004) used controlled exposures to demonstrate behavioral reactions of northern right whales to various non-pulse sounds. Playback stimuli included ship noise, social sounds of conspecifics, and a complex, 18-min “alert” sound consisting of repetitions of three different artificial signals. Ten whales were tagged with calibrated instruments that measured received sound characteristics and concurrent animal movements in three dimensions. Five out of six exposed whales reacted strongly to alert signals at measured received levels between 130 and 150 dB (
i.e.,
ceased foraging and swam rapidly to the surface). Two of these individuals were not exposed to ship noise, and the other four were exposed to both stimuli. These whales reacted mildly to conspecific signals. Seven whales, including the four exposed to the alert stimulus, had no measurable response to either ship sounds or actual vessel noise.

Baleen whale responses to pulsed sound (
e.g.,
seismic airguns) have been studied more thoroughly than responses to continuous sound (
e.g.,
drill rigs). Baleen whales generally tend to avoid operating airguns, but avoidance radii are quite variable. Whales are often reported to show no overt reactions to pulses from large arrays of airguns at distances beyond a few kilometers, even though the airgun pulses remain well above ambient noise levels out to much greater distances (Miller
et al.,
2005). However, baleen whales exposed to strong noise pulses often react by deviating from their normal migration route (Richardson
et al.,
1999). Migrating gray and bowhead whales were observed avoiding the sound source by displacing their migration route to varying degrees but within the natural boundaries of the migration corridors (Schick and Urban, 2000; Richardson
et al.,
1999; Malme
et al.,
1983). Baleen whale responses to pulsed sound however may depend on the type of activity in which the whales are engaged. Some evidence suggests that feeding bowhead whales may be more tolerant of underwater sound than migrating bowheads (Miller
et al.,
2005; Lyons
et al.,
2009; Christie
et al.,
2010).

Results of studies of gray, bowhead, and humpback whales have determined that received levels of pulses in the 160-170 dB re 1 µPa rms range seem to cause obvious avoidance behavior in a substantial fraction of the animals exposed. In many areas, seismic pulses from large arrays of airguns diminish to those levels at distances ranging from 2.8-9 mi (4.5-14.5 km) from the source. For the much smaller airgun array used during the VSP survey (total discharge volume between 600 and 880 in
3
), the distance to a received level of 160 dB re 1 µPa rms is estimated to be 1.53 mi (2.47 km). Baleen whales within those sound isopleths may show avoidance or other strong disturbance reactions to the airgun array.

Malme
et al.
(1986, 1988) studied the responses of feeding eastern gray whales to pulses from a single 100 in
3
airgun off St. Lawrence Island in the northern Bering Sea. They estimated, based on small sample sizes, that 50% of feeding gray whales ceased feeding at an average received pressure level of 173 dB re 1 µPa on an (approximate) rms basis, and that 10% of feeding whales interrupted feeding at received levels of 163 dB. Those findings were generally consistent with the results of experiments conducted on larger numbers of gray whales that were migrating along the California coast and on observations of the distribution of feeding Western Pacific gray whales off Sakhalin Island, Russia, during a seismic survey (Yazvenko
et al.,
2007).

Data on short-term reactions (or lack of reactions) of cetaceans to impulsive noises do not necessarily provide information about long-term effects. While it is not certain whether impulsive noises affect reproductive rate or distribution and habitat use in subsequent days or years, certain species have continued to use areas ensonified by airguns and have continued to increase in number despite successive years of anthropogenic activity in the area. Behavioral responses to noise exposure are generally highly variable and context dependent (Wartzok
et al.
2004). Travelling blue and fin whales (
Balaenoptera physalus
) exposed to seismic noise from airguns have been reported to stop emitting redundant songs (McDonald
et al.
1995; Clark & Gagnon 2006). By contrast, Iorio and Clark (2010) found increased production of transient, non-redundant calls of blue whales during seismic sparker operations. In any event, the brief exposures to sound pulses from the proposed airgun source (the airguns will only be fired for a few hours at a time over the course of 1 to 2 days) are highly unlikely to result in prolonged effects.

Toothed Whales
—Most toothed whales have their greatest hearing sensitivity at frequencies much higher than that of baleen whales and may be less responsive to low-frequency sound commonly associated with oil and gas industry exploratory drilling activities. Richardson
et al.
(1995b) reported that beluga whales did not show any apparent reaction to playback of underwater drilling sounds at distances greater than 656-1,312 ft (200-400 m). Reactions included slowing down, milling, or reversal of course after which the whales continued past the projector, sometimes within 164-328 ft (50-100 m). The authors concluded (based on a small sample size) that the playback of drilling sounds had no biologically significant effects on migration routes of beluga whales migrating through pack ice and along the seaward side of the nearshore lead east of Point Barrow in spring.

At least six of 17 groups of beluga whales appeared to alter their migration path in response to underwater playbacks of icebreaker sound (Richardson
et al.,
1995b). Received levels from the icebreaker playback were estimated at 78-84 dB in the
1/3
-octave band centered at 5,000 Hz, or 8-14 dB above ambient. If beluga whales reacted to an actual icebreaker at received levels of 80 dB, reactions would be expected to occur at distances on the order of 6.2 mi (10 km). Finley
et al.
(1990) also reported beluga avoidance of icebreaker activities in the Canadian High Arctic at distances of 22-31 mi (35-50 km). In addition to avoidance, changes in dive behavior and pod integrity were also noted. However,

no icebreakers will be used during this proposed program.

Patenaude
et al.
(2002) reported changes in beluga whale diving and respiration behavior, and some whales veered away when a helicopter passed at ≤820 ft (250 m) lateral distance at altitudes up to 492 ft (150 m). However, some belugas showed no reaction to the helicopter. Belugas appeared to show less response to fixed-wing aircraft than to helicopter overflights.

In reviewing responses of cetaceans with best hearing in mid-frequency ranges, which includes toothed whales, Southall
et al.
(2007) reported that combined field and laboratory data for mid-frequency cetaceans exposed to non-pulse sounds did not lead to a clear conclusion about received levels coincident with various behavioral responses. In some settings, individuals in the field showed profound (significant) behavioral responses to exposures from 90-120 dB, while others failed to exhibit such responses for exposure to received levels from 120-150 dB. Contextual variables other than exposure received level, and probable species differences, are the likely reasons for this variability. Context, including the fact that captive subjects were often directly reinforced with food for tolerating noise exposure, may also explain why there was great disparity in results from field and laboratory conditions—exposures in captive settings generally exceeded 170 dB before inducing behavioral responses. A summary of some of the relevant material reviewed by Southall
et al.
(2007) is next.

Buckstaff (2004) reported elevated bottlenose dolphin (
Tursiops trancatus
) whistle rates with received levels from oncoming vessels in the 110 to 120 dB range in Sarasota Bay, Florida. These hearing thresholds were apparently lower than those reported by a researcher listening with towed hydrophones. Morisaka
et al.
(2005) compared whistles from three populations of Indo-Pacific bottlenose dolphins (
Tursiops aduncus
). One population was exposed to vessel noise with spectrum levels of approximately 85 dB/Hz in the 1- to 22-kHz band (broadband received levels approximately 128 dB) as opposed to approximately 65 dB/Hz in the same band (broadband received levels approximately 108 dB) for the other two sites. Dolphin whistles in the noisier environment had lower fundamental frequencies and less frequency modulation, suggesting a shift in sound parameters as a result of increased ambient noise.

Morton and Symonds (2002) used census data on killer whales in British Columbia to evaluate avoidance of non-pulse acoustic harassment devices (AHDs). Avoidance ranges were about 2.5 mi (4 km). Also, there was a dramatic reduction in the number of days “resident” killer whales were sighted during AHD-active periods compared to pre- and post-exposure periods and a nearby control site.

Monteiro-Neto
et al.
(2004) studied avoidance responses of tucuxi (
Sotalia fluviatilis
), a freshwater dolphin, to Dukane® Netmark acoustic deterrent devices. In a total of 30 exposure trials, approximately five groups each demonstrated significant avoidance compared to 20 “pinger off” and 55 “no-pinger” control trials over two quadrants of about 0.19 mi
2
(0.5 km
2
). Estimated exposure received levels were approximately 115 dB.

Awbrey and Stewart (1983) played back semi-submersible drillship sounds (source level: 163 dB) to belugas in Alaska. They reported avoidance reactions at 984 and 4,921 ft (300 and 1,500 m) and approach by groups at a distance of 2.2 mi (3.5 km; received levels were approximately 110 to 145 dB over these ranges assuming a 15 log R transmission loss). Similarly, Richardson
et al.
(1990) played back drilling platform sounds (source level: 163 dB) to belugas in Alaska. They conducted aerial observations of eight individuals among approximately 100 spread over an area several hundred meters to several kilometers from the sound source and found no obvious reactions. Moderate changes in movement were noted for three groups swimming within 656 ft (200 m) of the sound projector.

Two studies deal with issues related to changes in marine mammal vocal behavior as a function of variable background noise levels. Foote
et al.
(2004) found increases in the duration of killer whale calls over the period 1977 to 2003, during which time vessel traffic in Puget Sound, and particularly whale-watching boats around the animals, increased dramatically. Scheifele
et al.
(2005) demonstrated that belugas in the St. Lawrence River increased the levels of their vocalizations as a function of the background noise level (the “Lombard Effect”).

Several researchers conducting laboratory experiments on hearing and the effects of non-pulse sounds on hearing in mid-frequency cetaceans have reported concurrent behavioral responses. Nachtigall
et al.
(2003) reported that noise exposures up to 179 dB and 55-min duration affected the trained behaviors of a bottlenose dolphin participating in a temporary threshold shift (TTS) experiment. Finneran and Schlundt (2004) provided a detailed, comprehensive analysis of the behavioral responses of belugas and bottlenose dolphins to 1-s tones (received levels 160 to 202 dB) in the context of TTS experiments. Romano
et al.
(2004) investigated the physiological responses of a bottlenose dolphin and a beluga exposed to these tonal exposures and demonstrated a decrease in blood cortisol levels during a series of exposures between 130 and 201 dB. Collectively, the laboratory observations suggested the onset of a behavioral response at higher received levels than did field studies. The differences were likely related to the very different conditions and contextual variables between untrained, free-ranging individuals vs. laboratory subjects that were rewarded with food for tolerating noise exposure.

Seismic operators and marine mammal observers sometimes see dolphins and other small toothed whales near operating airgun arrays, but, in general, there seems to be a tendency for most delphinids to show some limited avoidance of seismic vessels operating large airgun systems. However, 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. 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; Calambokidis and Osmek, 1998; Stone, 2003). The beluga may be a species that (at least at times) 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 6.2-12.4 mi (10-20 km) 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 be avoiding the seismic operations at distances of 6.2-12.4 mi (10-20 km) (Miller
et al.,
2005).

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). Killer whales were found to be significantly farther from large airgun arrays during periods of shooting compared with periods of no

shooting. 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.

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

Pinnipeds
—Pinnipeds generally seem to be less responsive to exposure to industrial sound than most cetaceans. Pinniped responses to underwater sound from some types of industrial activities such as seismic exploration appear to be temporary and localized (Harris
et al.,
2001; Reiser
et al.,
2009).

Southall
et al.
(2007) reviewed literature describing responses of pinnipeds to non-pulsed sound and reported that the limited data suggest exposures between approximately 90 and 140 dB generally do not appear to induce strong behavioral responses in pinnipeds exposed to non-pulse sounds in water; no data exist regarding exposures at higher levels. It is important to note that among these studies, there are some apparent differences in responses between field and laboratory conditions. In contrast to the mid-frequency odontocetes, captive pinnipeds responded more strongly at lower levels than did animals in the field. Again, contextual issues are the likely cause of this difference.

Jacobs and Terhune (2002) observed harbor seal reactions to Acoustic Harassment Devices (AHD) (source level in this study was 172 dB) deployed around aquaculture sites. Seals were generally unresponsive to sounds from the AHDs. During two specific events, individuals came within 141 and 144 ft (43 and 44 m) of active AHDs and failed to demonstrate any measurable behavioral response; estimated received levels based on the measures given were approximately 120 to 130 dB.

Costa
et al.
(2003) measured received noise levels from an Acoustic Thermometry of Ocean Climate (ATOC) program sound source off northern California using acoustic data loggers placed on translocated elephant seals. Subjects were captured on land, transported to sea, instrumented with archival acoustic tags, and released such that their transit would lead them near an active ATOC source (at 939-m depth; 75-Hz signal with 37.5-Hz bandwidth; 195 dB maximum source level, ramped up from 165 dB over 20 min) on their return to a haul-out site. Received exposure levels of the ATOC source for experimental subjects averaged 128 dB (range 118 to 137) in the 60- to 90-Hz band. None of the instrumented animals terminated dives or radically altered behavior upon exposure, but some statistically significant changes in diving parameters were documented in nine individuals. Translocated northern elephant seals exposed to this particular non-pulse source began to demonstrate subtle behavioral changes at exposure to received levels of approximately 120 to 140 dB.

Kastelein
et al.
(2006) exposed nine captive harbor seals in an approximately 82 × 98 ft (25 × 30 m) enclosure to non-pulse sounds used in underwater data communication systems (similar to acoustic modems). Test signals were frequency modulated tones, sweeps, and bands of noise with fundamental frequencies between 8 and 16 kHz; 128 to 130 [±3] dB source levels; 1- to 2-s duration [60-80 percent duty cycle]; or 100 percent duty cycle. They recorded seal positions and the mean number of individual surfacing behaviors during control periods (no exposure), before exposure, and in 15-min experimental sessions (n = 7 exposures for each sound type). Seals generally swam away from each source at received levels of approximately 107 dB, avoiding it by approximately 16 ft (5 m), although they did not haul out of the water or change surfacing behavior. Seal reactions did not appear to wane over repeated exposure (
i.e.,
there was no obvious habituation), and the colony of seals generally returned to baseline conditions following exposure. The seals were not reinforced with food for remaining in the sound field.

Potential effects to pinnipeds from aircraft activity could involve both acoustic and non-acoustic effects. It is uncertain if the seals react to the sound of the helicopter or to its physical presence flying overhead. Typical reactions of hauled out pinnipeds to aircraft that have been observed include looking up at the aircraft, moving on the ice or land, entering a breathing hole or crack in the ice, or entering the water. Ice seals hauled out on the ice have been observed diving into the water when approached by a low-flying aircraft or helicopter (Burns and Harbo, 1972, cited in Richardson
et al.,
1995a; Burns and Frost, 1979, cited in Richardson
et al.,
1995a). Richardson
et al.
(1995a) note that responses can vary based on differences in aircraft type, altitude, and flight pattern.

Blackwell
et al.
(2004a) observed 12 ringed seals during low-altitude overflights of a Bell 212 helicopter at Northstar in June and July 2000 (nine observations took place concurrent with pipe-driving activities). One seal showed no reaction to the aircraft while the remaining 11 (92%) reacted, either by looking at the helicopter (n = 10) or by departing from their basking site (n = 1). Blackwell
et al.
(2004a) concluded that none of the reactions to helicopters were strong or long lasting, and that seals near Northstar in June and July 2000 probably had habituated to industrial sounds and visible activities that had occurred often during the preceding winter and spring. There have been few systematic studies of pinniped reactions to aircraft overflights, and most of the available data concern pinnipeds hauled out on land or ice rather than pinnipeds in the water (Richardson
et al.,
1995a; Born
et al.,
1999).

Reactions of harbor seals to the simulated sound of a 2-megawatt wind power generator were measured by Koschinski
et al.
(2003). Harbor seals surfaced significantly further away from the sound source when it was active and did not approach the sound source as closely. The device used in that study produced sounds in the frequency range of 30 to 800 Hz, with peak source levels of 128 dB at 1 m at the 80- and 160-Hz frequencies.

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 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. 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.,
1995a). 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). Even if reactions of the species occurring in the present study area are as strong as those evident in the telemetry study, reactions are expected to be confined to relatively small distances and durations.

4. 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). However, in the case of the proposed drilling program, animals are not expected to be exposed to levels high enough or durations long enough to result in PTS, as described in detail in the paragraphs below.

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 nonhuman animals. 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).

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 we 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 drilling program in Cook Inlet due to the relatively short duration of activities producing these higher level sounds in combination with mitigation and monitoring efforts to avoid such effects.

5. Non-Auditory Physical Effects

Non-auditory physical effects might occur in marine mammals exposed to strong underwater 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, virtually all neuroendocrine functions that are affected by stress—including immune competence, reproduction, metabolism, and behavior—are regulated by pituitary hormones. 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 can be quickly replenished once the stress is alleviated. 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, energy resources must be diverted 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 which is 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 effects of 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, we assume that acoustic exposures sufficient to trigger onset PTS or TTS would be accompanied by physiological stress responses. 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. The source level of the jack-up rig is not loud enough to induce PTS or likely even 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, very little is known 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, which are not proposed for use during this program. For the most part, only low-level continuous sounds would be produced during the drilling program as impact hammering and VSP would occur for only short periods of time and most of the sound produced would be from the ongoing operation/drilling. In addition, marine mammals that show

behavioral avoidance of industry activities, including belugas and some pinnipeds, are especially unlikely to incur non-auditory impairment or other physical effects.

6. Stranding and Mortality

Marine mammals close to underwater detonations of high explosive can be killed or severely injured, and the auditory organs are especially susceptible to injury (Ketten
et al.,
1993; Ketten, 1995). Airgun pulses are less energetic and their peak amplitudes have slower rise times. To date, there is no evidence that serious injury, death, or stranding by marine mammals can occur from exposure to airgun pulses, even in the case of large airgun arrays. Additionally, the airguns used during VSP are used for short periods of time. The continuous sounds produced by the drill rig are also far less energetic.

It should be noted that strandings known, or thought, to be related to sound exposure have not been recorded for marine mammal species in Cook Inlet. Beluga whale strandings in Cook Inlet are not uncommon; however, these events often coincide with extreme tidal fluctuations (“spring tides”) or killer whale sightings (Shelden
et al.,
2003). For example, in August 2012, a group of Cook Inlet beluga whales stranded in the mud flats of Turnagain Arm during low tide and were able to swim free with the flood tide. NMFS does not expect any marine mammals will incur serious injury or mortality in Cook Inlet or strand as a result of the proposed drilling program.

Vessel Impacts

Vessel activity and noise associated with vessel activity will temporarily increase in the action area during BlueCrest's oil and gas production drilling program as a result of the operation of a jack-up drill rig and the use of tow and other support vessels. While under tow, the rig and the tow vessels move at slow speeds (2-4 knots). The support barges supplying pipe to the drill rig can typically run at 7-8 knots but may move slower inside Cook Inlet. Based on this information, NMFS does not anticipate and does not propose to authorize take from vessel strikes.

Odontocetes, such as beluga whales, killer whales, and harbor porpoises, often show tolerance to vessel activity; however, they may react at long distances if they are confined by ice, shallow water, or were previously harassed by vessels (Richardson
et al.,
1995a). Beluga whale response to vessel noise varies greatly from tolerance to extreme sensitivity depending on the activity of the whale and previous experience with vessels (Richardson
et al.,
1995a). Reactions to vessels depends on whale activities and experience, habitat, boat type, and boat behavior (Richardson
et al.,
1995a) and may include behavioral responses, such as altered headings or avoidance (Blane and Jaakson, 1994; Erbe and Farmer, 2000); fast swimming; changes in vocalizations (Lesage
et al.,
1999; Scheifele
et al.,
2005); and changes in dive, surfacing, and respiration patterns.

There are few data published on pinniped responses to vessel activity, and most of the information is anecdotal (Richardson
et al.,
1995a). Generally, sea lions in water show tolerance to close and frequently approaching vessels and sometimes show interest in fishing vessels. They are less tolerant when hauled out on land; however, they rarely react unless the vessel approaches within 100-200 m (330-660 ft; reviewed in Richardson
et al.,
1995a).

Oil Spill and Discharge Impacts

As noted above, the specified activity involves towing the rig, drilling of wells, and other associated support activities in lower Cook Inlet during the 2016 open water season. The primary stressors to marine mammals that are reasonably expected to occur will be acoustic in nature. The likelihood of a large oil spill occurring during BlueCrest's proposed drilling program is remote and effects from an event of this nature are not authorized. Offshore oil spill records in Cook Inlet during 1994-2011 show three spills during oil exploration (ADNR Division of Oil and Gas, 2011 unpub. data): Two oil spills at the UNOCAL Dillion Platform in June 2011 (two gallons) and December 2001 (three gallons); and one oil spill at the UNOCAL Monopod Platform in January 2002 (one gallon). During this same time period, 71 spills occurred offshore in Cook Inlet during oil production. Most spills ranged from 0.0011 to 1 gallon (42 spills), and only three spills were larger than 200 gallons: 210 gallons in July 2001 at the Cook Inlet Energy Stewart facility; 250 gallons in February 1998 at the King Salmon platform; and 504 gallons in October 1999 at the UNOCAL Dillion platform. All 71 crude oil spills from the offshore platforms, both exploration and production, totaled less than 2,140 gallons. Based on historical data, most oil spills have been small. Moreover, during more than 60 years of oil and gas exploration and development in Cook Inlet, there has not been a single oil well blowout, making it difficult to assign a specific risk factor to the possibility of such an event in Cook Inlet. However, the probability of such an event is thought to be extremely low.

BlueCrest will have various measures and protocols in place that will be implemented to prevent oil releases from the wellbore. BlueCrest has planned formal routine rig maintenance and surveillance checks, as well as normal inspection and equipment checks to be conducted on the jack-up rig daily. The following steps will be in place to prevent oil from entering the water:

• Required inspections will follow standard operating procedures.

• Personnel working on the rig will be directed to report any unusual conditions to appropriate personnel.

• Oily equipment will be regularly wiped down with oil absorbent pads to collect free oil. Drips and small spillage from equipment will be controlled through use of drip pans and oil absorbent drop clothes.

• Oil absorbent materials used to contain oil spills or seeps will be collected and disposed of in sealed plastic bags or metal drums and closed containers.

• The platform surfaces will be kept clean of waste materials and loose debris on a daily basis.

• Remedial actions will be taken when visual inspections indicate deterioration of equipment (tanks) and/or their control systems.

• Following remedial work, and as appropriate, tests will be conducted to determine that the systems function correctly.

Drilling and completion fluids provide primary well control during drilling, work over, or completion operations. These fluids are designed to exert hydrostatic pressure on the wellbore that exceeds the pore pressures within the subsurface formations. This prevents undesired fluid flow into the wellbore. Surface mounted blowout preventer (BOP) equipment provides secondary well control. In the event that primary well control is lost, this surface equipment is used to contain the influx of formation fluid and then safely circulate it out of the wellbore.

The BOP is a large, specialized valve used to seal, control, and monitor oil and gas wells. BOPs come in variety of styles, sizes, and pressure ratings. For Cook Inlet, the BOP equipment used by BlueCrest will consist of:

• Three BOPs pressure safety levels of: (1) 5,000 pounds per square inch (psi), (2) 10,000 psi, and (3) 15,000 psi;

• A minimum of three 35 cm (13
5/8
in), 10,000 psi WP ram type preventers;

• One 35 cm (13
5/8
in) annular preventer;

• Choke and kill lines that provide circulating paths from/to the choke manifold;

• A two choke manifold that allows for safe circulation of well influxes out of the well bore; and

• A hydraulic control system with accumulator backup closing.

The wellhead, associated valves, and control systems provide blowout prevention during well production. These systems provide several layers of redundancy to ensure pressure containment is maintained. Well control planning is performed in accordance with Alaska Oil and Gas Conservation Commission (AOGCC) and the Department of the Interior's Bureau of Safety and Environment Enforcement (BSEE) regulations. The operator's policies and recommended practices are, at a minimum, equivalent to BSEE regulations. BOP test drills are performed on a frequent basis to ensure the well will be shut in quickly and properly. BOP testing procedures will meet American Petroleum Institute Recommended Practice No. 53 and AOGCC specifications. The BOP tests will be conducted with a nonfreezing fluid when the ambient temperature around the BOP stack is below 0 °C (32 °F). Tests will be conducted at least weekly and before drilling out the shoe of each casing string. The AOGCC will be contacted before each test is conducted, and will be onsite during BOP tests unless an inspection waiver is approved.

BlueCrest developed an Oil Discharge Prevention and Contingency Plan (ODPCP) and has submitted it for approval to Alaska's Department of Environmental Conservation (ADEC). NMFS reviewed the previous ODPCP covering the Cosmopolitan drilling program (prepared by Buccaneer Alaska Operations LLC) during the ESA consultation process for Cosmopolitan leases and found that with implementation of the safety features mentioned above that the risk of an oil spill was discountable. As an oil spill is not a likely occurrence, it is not a component of BlueCrest's specified activity for which NMFS is proposing to authorize take.

Anticipated Effects on Marine Mammal Habitat

The primary potential impacts to marine mammals and other marine species are associated with elevated sound levels produced by the drilling program (
i.e.
towing of the drill rig and the airguns). However, other potential impacts are also possible to the surrounding habitat from physical disturbance, discharges, and an oil spill (which we do not anticipate or authorize). This section describes the potential impacts to marine mammal habitat from the specified activity, including impacts on fish and invertebrate species typically preyed upon by marine mammals in the area.

Common Marine Mammal Prey in the Proposed Drilling Area

Fish are the primary prey species for marine mammals in Cook Inlet. Beluga whales feed on a variety of fish, shrimp, squid, and octopus (Burns and Seaman, 1986). Common prey species in Knik Arm include salmon, eulachon and cod. Harbor seals feed on fish such as pollock, cod, capelin, eulachon, Pacific herring, and salmon, as well as a variety of benthic species, including crabs, shrimp, and cephalopods. Harbor seals are also opportunistic feeders with their diet varying with season and location. The preferred diet of the harbor seal in the Gulf of Alaska consists of pollock, octopus, capelin, eulachon, and Pacific herring (Calkins, 1989). Other prey species include cod, flat fishes, shrimp, salmon, and squid (Hoover, 1988). Harbor porpoises feed primarily on Pacific herring, cod, whiting (hake), pollock, squid, and octopus (Leatherwood
et al.,
1982). In the Cook Inlet area, harbor porpoise feed on squid and a variety of small schooling fish, which would likely include Pacific herring and eulachon (Bowen and Siniff, 1999; NMFS, unpublished data). Killer whales feed on either fish or other marine mammals depending on genetic type (resident versus transient respectively). Killer whales in Knik Arm are typically the transient type (Shelden
et al.,
2003) and feed on beluga whales and other marine mammals, such as harbor seal and harbor porpoise. The Steller sea lion diet consists of a variety of fishes (capelin, cod, herring, mackerel, pollock, rockfish, salmon, sand lance, etc.), bivalves, squid, octopus, and gastropods.

Potential Impacts From Seafloor Disturbance on Marine Mammal Habitat

There is a possibility of seafloor disturbance or increased turbidity in the vicinity of the drill sites. Seafloor disturbance could occur with bottom founding of the drill rig legs and anchoring system. These activities could lead to direct effects on bottom fauna, through either displacement or mortality. Increase in suspended sediments from seafloor disturbance also has the potential to indirectly affect bottom fauna and fish. The amount and duration of disturbed or turbid conditions will depend on sediment material.

The potential direct habitat impact by the BlueCrest drilling operation is limited to the actual drill-rig footprint defined as the area occupied and enclosed by the drill-rig legs. The jack-up rig will temporarily disturb one offshore location in lower Cook Inlet, where the wells are proposed to be drilled. Bottom disturbance would occur in the area where the three legs of the rig would be set down and where the actual wells would be drilled. The jack-up drill rig footprint would occupy three steel piles at 14 m (46 ft) diameter. The well casing would be a 76 cm (30 in) diameter pipe extending from the seafloor to the rig floor. The casing would only be in place during drilling activities at each potential well location. The total area of disturbance was calculated as 0.54 acres during the land use permitting process. The collective 2-acre footprint of the wells represents a very small fraction of the 7,300 square mile Cook Inlet surface area. Potential damage to the Cook Inlet benthic community will be limited to the actual surface area of the three spudcans (1,585 square feet each or 4,755 square feet total) that form the “foot” of each leg. Given the high tidal energy at the well site locations, drilling footprints are not expected to support benthic communities equivalent to shallow lower energy sites found in nearshore waters where harbor seals mostly feed. The presence of the drill rig is not expected to result in direct loss of marine mammal habitat.

Potential Impacts From Sound Generation

With regard to fish as a prey source for odontocetes and seals, fish are known to hear and react to sounds and to use sound to communicate (Tavolga
et al.,
1981) and possibly avoid predators (Wilson and Dill, 2002). Experiments have shown that fish can sense both the strength and direction of sound (Hawkins, 1981). Primary factors determining whether a fish can sense a sound signal, and potentially react to it, are the frequency of the signal and the strength of the signal in relation to the natural background noise level.

Fish produce sounds that are associated with behaviors that include territoriality, mate search, courtship, and aggression. It has also been speculated that sound production may provide the means for long distance communication and communication under poor underwater visibility conditions (Zelick
et al.,
1999), although the fact that fish communicate at low-frequency sound levels where the masking effects of ambient noise are naturally highest suggests that very long

distance communication would rarely be possible. Fish have evolved a diversity of sound generating organs and acoustic signals of various temporal and spectral contents. Fish sounds vary in structure, depending on the mechanism used to produce them (Hawkins, 1993). Generally, fish sounds are predominantly composed of low frequencies (less than 3 kHz).

Since objects in the water scatter sound, fish are able to detect these objects through monitoring the ambient noise. Therefore, fish are probably able to detect prey, predators, conspecifics, and physical features by listening to environmental sounds (Hawkins, 1981). There are two sensory systems that enable fish to monitor the vibration-based information of their surroundings. The two sensory

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Source: Frix Law Library, https://www.frixlaw.com/law-library/documents/fr%3A2016-12886. Public record. Not legal advice.