# Takes of Marine Mammals Incidental to Specified Activities; Three Marine Geophysical Surveys in the Northeast Pacific Ocean, June Through July 2012

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URL: https://www.frixlaw.com/law-library/documents/fr%3A2012-10627

## Record

- **Collection:** Federal Register
- **Document type:** Notice
- **Published:** May 2, 2012
- **Citation:** 77 FR 25966

## Text

DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
RIN 0648-XB105
Takes of Marine Mammals Incidental to Specified Activities; Three Marine Geophysical Surveys in the Northeast Pacific Ocean, June Through July 2012

AGENCY:

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

ACTION:

Notice; proposed incidental harassment authorization; request for comments.

SUMMARY:

We have received an application from the Lamont-Doherty Earth Observatory, a part of Columbia University, for an Incidental Harassment Authorization to take marine mammals, by harassment, incidental to conducting three consecutive marine geophysical surveys in the northeast Pacific Ocean, June through July 2012.

DATES:

Comments and information must be received no later than May 31, 2012.

ADDRESSES:

Comments on the application should be addressed to Tammy C. Adams, Acting Chief, Permits and Conservation Division, Office of Protected Resources, National Marine Fisheries Service, 1315 East-West Highway, Silver Spring, MD 20910-3225. The mailbox address for providing email comments is
ITP.Cody@noaa.gov.
We are 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 10-megabyte file size.

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

To obtain an electronic copy of the application containing a list of the references used in this document, write to the previously mentioned address, telephone the contact listed here (see
FOR FURTHER INFORMATION CONTACT
), or visit the Internet at:
http://www.nmfs.noaa.gov/pr/permits/incidental.htm#applications
.

The National Science Foundation's (Foundation) draft Environmental Assessment (Assessment) pursuant to the National Environmental Policy Act of 1969 and Executive Order 12114 is also available at the same Internet address. The Assessment incorporates an “Environmental Assessment of a marine geophysical survey by the R/V
Marcus G. Langseth
in the northeastern Pacific Ocean, June-July 2012,” prepared by LGL Limited environmental research associates, on behalf of the Foundation. The public can view documents cited in this notice by appointment, during regular business hours, at the aforementioned address.

FOR FURTHER INFORMATION CONTACT:

Jeannine Cody or Howard Goldstein, National Marine Fisheries Service, Office of Protected Resources, (301) 427-8401.

SUPPLEMENTARY INFORMATION:

Background

Section 101(a)(5)(D) of the Marine Mammal Protection Act of 1972, as amended (MMPA; 16 U.S.C. 1361
et seq.
) directs the Secretary of Commerce to authorize, upon request, the incidental, but not intentional, taking of small numbers of marine mammals of a species or population stock, by United States citizens who engage in a specified activity (other than commercial fishing) within a specified geographical region if: (1) We make certain findings; (2) the taking is limited to harassment; and (3) we provide a notice of a proposed authorization to the public for review.

We shall grant authorization for the incidental taking of small numbers of marine mammals if we find that the taking will have a negligible impact on the species or stock(s), and will not have an unmitigable adverse impact on the availability of the species or stock(s) for subsistence uses (where relevant). The authorization must set forth the permissible methods of taking; other means of effecting the least practicable adverse impact on the species or stock and its habitat; and requirements pertaining to the mitigation, monitoring and reporting of such takings. We have 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.”

Section 101(a)(5)(D) of the Marine Mammal Protection Act established an expedited process by which citizens of the United States can apply for an authorization to incidentally take small numbers of marine mammals by harassment. Section 101(a)(5)(D) of the Act establishes a 45-day time limit for our review of an application followed by a 30-day public notice and comment period on any proposed authorizations for the incidental harassment of small numbers of marine mammals. Within 45 days of the close of the public comment period, we must either issue or deny the authorization and must publish a notice in the
Federal Register
within 30 days of our determination to issue or deny the authorization.

Except with respect to certain activities not pertinent here, the Marine Mammal Protection Act 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

We received an application on January 27, 2012, from the Lamont-Doherty Earth Observatory (Observatory) for the taking by harassment, of small numbers of marine mammals, incidental to conducting three separate marine geophysical surveys in the northeast Pacific Ocean. We determined the application complete and adequate on March 27, 2012.

The Observatory, with research funding from the U.S. National Science Foundation (Foundation), plans to conduct three research studies on the Juan de Fuca Plate, the Cascadia thrust zone, and the Cascadia subduction margin in waters off the Oregon and Washington coasts. The Observatory has proposed to conduct the first survey from June 11 through July 5, 2012, the second survey from July 5 through July 8, 2012, and the third survey from July 12 through July 23, 2012.

The Observatory plans to use one source vessel, the R/V
Marcus G. Langseth
(
Langseth
), a seismic airgun array, a single hydrophone streamer, and ocean bottom seismometers to conduct the geophysical surveys.

The proposed surveys will provide data necessary to:

• Characterize the evolution and state of hydration of the Juan de Fuca plate at the Cascadia subduction zone;

• Provide information on the buried structures in the region; and

• Assess the location, physical state, fluid budget, and methane systems of the Juan de Fuca plate boundary and overlying crust.

The results of the three studies would provide background information for generating improved earthquake hazards analyses and a better understanding of the processes that control megathrust earthquakes which are produced by a sudden slip along the boundary between a subducting and an overriding plate.

In addition to the operations of the seismic airgun array and hydrophone streamer, and the ocean bottom seismometers (seismometers), the Observatory intends to operate a multibeam echosounder and a sub-bottom profiler continuously throughout the surveys.

Acoustic stimuli (i.e., increased underwater sound) generated during the operation of the seismic airgun arrays, may have the potential to cause a short-term behavioral disturbance for marine mammals in the survey area. This is the principal means of marine mammal taking associated with these activities and the Observatory has requested an authorization to take 26 species of marine mammals by Level B harassment. We do not expect that the use of the multibeam echosounder, the sub-bottom profiler, or the ocean bottom seismometer will result in the take of marine mammals and will discuss our reasoning later in this notice. Also, we do not expect take to result from a collision with the
Langseth
because it is a single vessel moving at relatively slow speeds (4.6 knots (kts); 8.5 kilometers per hour (km/h); 5.3 miles per hour (mph)) during seismic acquisition within the survey, for a relatively short period of time. It is likely that any marine mammal would be able to avoid the vessel.

Description of the Specified Activities

Juan de Fuca Plate Survey

The first proposed seismic survey would begin on June 11, 2012, and end on July 5, 2012. The
Langseth
would depart from Astoria, Oregon on June 11, 2012, and transit to the survey area in the northeast Pacific Ocean in international waters and the Exclusive Economic Zones of the United States and Canada. The study area will encompass an area bounded by approximately 43-48 degrees (°) North by approximately 124-130° East (see Figure 1 in the Observatory's Application #1). Water depths in the survey area range from approximately 50 to 3,000 meters (m) (164 feet (ft) to 1.9 miles (mi)). At the conclusion of the first survey, the
Langseth
would begin a second three-day seismic survey on July 5, 2012, in the same area.

Typically, two-dimensional surveys such as this one, acquire data along single track lines with wide intervals; cover large areas; provide a coarse sampled subsurface image; and project less acoustic energy into the environment than other types of seismic surveys. During this survey, the
Langseth
would deploy a 36-airgun array as an energy source, an 8-kilometer (km)-long (4.9 mi-long) hydrophone streamer, and 46 seismometers. The seismometers are portable, self-contained passive receiver systems designed to sit on the seafloor and record seismic signals generated primarily by airguns and earthquakes. As the
Langseth
tows the airgun array along the survey lines, the hydrophone streamer receives the returning acoustic signals and transfers the data to the vessel's on-board processing system. The seismometers also record and store the returning signals for later analysis.

The Observatory plans to discharge the airgun array along three long transect lines and three semi-circular arcs using the seismometers as the receivers and then repeat along the long transect lines in multichannel seismic mode using the 8-km streamer as the receiver (see Figure 1 in the Observatory's Application #1). Also, the Observatory will use one support vessel, the R/V
Oceanus
(
Oceanus
) to deploy 46 seismometers on the northern onshore-offshore line, retrieve the 46 seismometers from the northern line, and then deploy 39 seismometers on the southern onshore-offshore lines and retrieve them at the conclusion of the survey.

The first study (e.g., equipment testing, startup, line changes, repeat coverage of any areas, and equipment recovery) will require approximately 17 days to complete approximately 3,051 km (1,895.8 mi) of transect lines. The total survey effort including contingency will consist of approximately 2,878 km (1,788.3) of transect lines in depths greater than 1,000 m (621.3 mi), 102 km (63.4 mi) in depths 100 to 1,000 m (328 to 3,280 ft), and 71 km (44.1 mi) in water depths less than 100 m (328 ft). The northern and southern onshore-offshore lines are 70 to 310 km (43.4 to 192.6 mi) and 15 to 450 km (9.3 to 279.6 mi) from shore, respectively.

Data acquisition will include approximately 408 hours of airgun operations (i.e., 17 days over 24 hours). The Observatory, the
Langseth's
operator, will conduct all planned seismic activities, with on-board assistance by the scientists who have proposed the study. The Principal Investigators for the survey are Drs. S. Carbotte and H. Carton (Lamont Doherty Earth Observatory, New York) and P. Canales (Woods Hole Oceanographic Institution, Massachusetts). The vessel is self-contained and the crew will live aboard the vessel for the entire cruise.

Cascadia Thrust Zone Survey

The second proposed survey would begin on July 5, 2012, and end on July 8, 2012. The survey would take place in the U.S. Exclusive Economic Zone in waters off of the Oregon and Washington coasts. The study area will encompass an area bounded by approximately 43.5-47° North by approximately 124-125° East (see Figure 1 in the Observatory's Application #2). Water depths in the survey area range from approximately 50 to 1,000 m (164 ft to 0.62 mi). At the conclusion of this survey, the
Langseth
would return to Astoria, Oregon on July 8, 2012.

The
Langseth
would deploy a 36-airgun array as an energy source, 12 seismometers, and 48 seismometers (33  in Oregon and 15 in Washington) onshore (on land). As stated previously, as the
Langseth
tows the airgun array along the survey lines, the seismometers record the returning acoustic signals for later analysis. The Observatory proposes to use the
Oceanus
to deploy and retrieve the seismometers.

The Observatory plans to discharge the airgun array along a grid of lines off Oregon and along an onshore-offshore line off Washington (see Figure 1 in the Observatory's Application #2).

The proposed study (e.g., equipment testing, startup, line changes, repeat coverage of any areas, and equipment recovery) will require approximately 3 days to complete approximately 793 km (492.7 mi) of transect lines. The total survey effort including contingency will consist of approximately 5 km (3.1 mi) of transect lines in depths greater than 1,000 m (621.3 mi), 501 km (311.3 mi) in depths 100 to 1,000 m (328 to 3,280 ft), and 287 km (178.3 mi) in water depths less than 100 m (328 ft). The northern and southern legs of the onshore-offshore lines are 15 to 70 km (9.3 to 43.5 mi) and 15 to 50 km (9.3 to 31.1 mi) from shore, respectively.

Data acquisition will include approximately 72 hours of airgun operations (i.e., 3 days over 24 hours). The Principal Investigators for the

second survey are Drs. A.M Trehu (Oregon State University) and G. Abers and H. Carton (Lamont Doherty Earth Observatory, New York). The vessel is self-contained and the crew will live aboard the vessel for the entire cruise.

Cascadia Subduction Margin Survey

The last seismic survey would begin on July 12, 2012, and end on July 23, 2012. The
Langseth
would depart from Astoria, Oregon on July 12, 2012, and transit to waters off of the Washington coast. The study area encompasses an area bounded by approximately 46.5-47.5° North by approximately 124.5-126° East (see Figure 1 in the Observatory's Application #3). Water depths in the survey area range from approximately 95 to 2,650 m (311.7 ft to 1.6 mi). At the conclusion of this survey, the
Langseth
would return to Astoria, Oregon on July 23, 2012.

The
Langseth
would deploy a 36-airgun array as an energy source and an 8-km-long (4.9 mi-long) hydrophone streamer. The Observatory plans to discharge the airgun array along nine parallel lines that are spaced eight km apart. If time permits, the Langseth would survey an additional two lines perpendicular to the parallel lines (see Figure 1 in the Observatory's Application #3).

The proposed study (e.g., equipment testing, startup, line changes, repeat coverage of any areas, and equipment recovery) will require approximately 10 days to complete approximately 1,147 km (712.7 mi) of transect lines. The total survey effort including contingency will consist of approximately 785 km (487.8 mi) of transect lines in depths greater than1,000 m (621.3 mi), 350 km (217.5 mi) of transect lines in depths 100 to 1,000 m (328 to 3,280 ft), and 12 km (7.5 mi) of transect lines in water depths less than 100 m (328 ft). The survey area is 32 to 150 km (19.9 to 93.2 mi) from shore.

Data acquisition will include approximately 240 hours of airgun operations (i.e., 10 days over 24 hours). The Principal Investigators for the third survey are Drs. W.S. Holbrook (University of Wyoming), A.M. Trehu (Oregon State University), H.P. Johnson (University of Washington), G.M. Kent (University of Nevada), and K. Keranen (University of Oklahoma). The vessel is self-contained and the crew will live aboard the vessel for the entire cruise.

Vessel Specifications

The
Langseth,
owned by the Foundation, is a seismic research vessel with a quiet propulsion system that avoids interference with the seismic signals emanating from the airgun array. The vessel is 71.5 m (235 ft) long; has a beam of 17.0 m (56 ft); a maximum draft of 5.9 m (19 ft); and a gross tonnage of 3,834 pounds. It's two 3,550 horsepower (hp) Bergen BRG-6 diesel engines drive two propellers. Each propeller has four blades and the shaft typically rotates at 750 revolutions per minute. The vessel also has an 800-hp bowthruster, which is not used during seismic acquisition. The
Langseth's
operational speed during seismic acquisition will be approximately 4.6 kts (8.5 km/h; 5.3 mph) and the cruising speed of the vessel outside of seismic operations is 18.5 km/h (11.5 mph or 10 kts).

The
Langseth
will tow the 36-airgun array, as well as the hydrophone streamer during the first and last surveys, along predetermined lines. When the
Langseth
is towing the airgun array and the hydrophone streamer, the turning rate of the vessel is limited to five degrees per minute. Thus, the maneuverability of the vessel is limited during operations with the streamer.

The vessel also has an observation tower from which protected species visual observers (observer) will watch for marine mammals before and during the proposed airgun operations. When stationed on the observation platform, the observer's eye level will be approximately 21.5 m (71 ft) above sea level providing the observer an unobstructed view around the entire vessel.

Some minor deviation from these dates is possible, depending on logistics, weather conditions, and the need to repeat some lines if data quality is substandard. Therefore, we propose to issue an authorization to the Observatory that would be effective from June 9, 2012, to August 27, 2012.

Acoustic Source Specifications

Seismic Airguns

The
Langseth
will deploy a 36-airgun array, with a total volume of approximately 6,600 cubic inches (in
3
) at a tow depth of 9, 12, or 15 m (29.5, 39.4, or 49.2 ft). The airguns are a mixture of Bolt 1500LL and Bolt 1900LLX airguns ranging in size from 40 to 360 in
3
, with a firing pressure of 1,900 pounds per square inch. The dominant frequency components range from zero to 188 Hertz (Hz). The array configuration consists of four identical linear strings, with 10 airguns on each string. The
Langseth's
crew will space the first and last airguns 16 m (52 ft) apart from one another. Of the 10 airguns, nine will fire simultaneously while the tenth airgun will serve as a spare. The crew will turn on the spare airgun in case one of the other airguns fail. The
Langseth
will distribute the array across an area of approximately 24 by 16 m (78.7 by 52.5 ft) and will tow the array approximately 100 m (328 ft) behind the vessel.

Juan de Fuca Plate Survey:
This survey's array tow depth will be 9 m (29.5 ft) for the multichannel seismic survey using the hydrophone streamer and 12 m (39.4 ft) during the survey using the seismometers. During the multichannel seismic survey, each airgun array will emit a pulse at approximately 16-second (s) intervals which corresponds to a shot interval of approximately 37.5 m (123 ft). During the survey using the seismometers, each airgun array will emit a pulse at approximately 200-s intervals which corresponds to a shot interval of approximately 500 m (1,640.4 ft). During firing, the airguns will emit a brief (approximately 0.1 s) pulse of sound; during the intervening periods of operations, the airguns are silent.

Cascadia Thrust Zone Survey:
The survey's array tow depth will be 12 m (39.4 ft). During this survey, each airgun array will emit a pulse at approximately 40-s intervals which corresponds to a shot interval of approximately 100 m (328 ft). During firing, the airguns will emit a brief (approximately 0.1 s) pulse of sound; during the intervening periods of operations, the airguns are silent.

Cascadia Subduction Margin Survey:
The survey's array tow depth will be 15 m (49.2 ft). During this survey, each airgun array will emit a pulse at approximately 20-s intervals which corresponds to a shot interval of approximately 50 m (164 ft). During firing, the airguns will emit a brief (approximately 0.1 s) pulse of sound; during the intervening periods of operations, the airguns are silent.

Metrics Used in This Document

This section includes a brief explanation of the sound measurements frequently used in the discussions of acoustic effects in this document. Sound pressure is the sound force per unit area, and is usually measured in micropascals (µPa), where 1 pascal (Pa) is the pressure resulting from a force of one newton exerted over an area of one square meter. In this document, we express sound pressure level as the ratio of a measured sound pressure and a reference level. The commonly used reference pressure level in underwater acoustics is 1 FPa, and the units for sound pressure levels are dB re: 1 μPa.

Sound pressure level (in decibels (dB)) = 20 log (pressure/reference pressure)

Sound pressure level is an instantaneous measurement and can be expressed as the peak, the peak-peak (p-p), or the root mean square. Root mean square, which is the square root of the arithmetic average of the squared instantaneous pressure values, is typically used in discussions of the effects of sounds on vertebrates and all references to sound pressure level in this document refer to the root mean square unless otherwise noted. Sound pressure level does not take the duration of a sound into account.

Characteristics of the Airgun Pulses

Airguns function by venting high-pressure air into the water which creates an air bubble. The pressure signature of an individual airgun consists of a sharp rise and then fall in pressure, followed by several positive and negative pressure excursions caused by the oscillation of the resulting air bubble. The oscillation of the air bubble transmits sounds downward through the seafloor and the amount of sound transmitted in the near horizontal directions is reduced. However, the airgun array also emits sounds that travel horizontally toward non-target areas.

The nominal source levels of the airgun array used by the Observatory on the
Langseth
is 236 to 265 dB re: 1 μPa
(p-p)
and the root mean square value for a given airgun pulse is typically 16 dB re: 1 μPa lower than the peak-to-peak value (Greene, 1997; McCauley
et al.
, 1998, 2000a). However, the difference between root mean square and peak or peak-to-peak values for a given pulse depends on the frequency content and duration of the pulse, among other factors.

Accordingly, the Observatory has predicted the received sound levels in relation to distance and direction from the 36-airgun array and the single Bolt 1900LL 40-in
3
airgun, which will be used during power downs. Appendix A of the Foundation's Environmental Assessment provides a detailed description of the modeling for marine seismic source arrays for species mitigation and Appendix B(3) of the Assessment discusses the characteristics of the airgun pulses. These are the source levels applicable to downward propagation. The effective source levels for horizontal propagation are lower than those for downward propagation because of the directional nature of the sound from the airgun array. Refer to the authorization application and Assessment for additional information.

Predicted Sound Levels for the Airguns

Tolstoy
et al.
, (2009) reported results for propagation measurements of pulses from the
Langseth's
36-airgun, 6,600 in
3
array in shallow-water (approximately 50 m (164 ft)) and deep-water depths (approximately 1,600 m (5,249 ft)) in the Gulf of Mexico in 2007 and 2008. Results of the Gulf of Mexico calibration study (Tolstoy
et al.
, 2009) showed that radii around the airguns for various received levels varied with water depth and that sound propagation varied with array tow depth.

The Observatory used the results from the Gulf of Mexico study to determine the algorithm for its model that calculates the exclusion zones for the 36-airgun array and the single airgun. These values designate mitigation zones and the Observatory uses them to estimate take (described in greater detail in Section VII of the application and Section IV of the Foundation's Environmental Assessment) for marine mammals.

Comparison of the Tolstoy
et al.
(2009) calibration study with the Observatory's model for the
Langseth's
36-airgun array indicated that the model represents the actual received levels, within the first few kilometers and the locations of the predicted exclusions zones. However, the model for deep water (greater than 1,000 m; 3,280 ft) overestimated the received sound levels at a given distance but is still valid for defining exclusion zones at various tow depths. Because the tow depth of the array in the calibration study is less shallow (6 m; 19.7 ft) than the tow depths in the proposed surveys (9, 12, or 15 m; 29.5, 39.4, or 49.2 ft), the Observatory used the following correction factors for estimating the received levels during the proposed surveys (see Table 1). The correction factors are the ratios of the 160-,180-, and 190-dB distances from the modeled results for the 6,600 in
3
airgun array towed at 6 m (19.7 ft) versus 9, 12, or 15 m (29.5, 39.4, or 49.2 ft) (LGL, 2008).

Table 1—Correction Factors for Estimating the Received Levels for Three Proposed Surveys in the Northeast Pacific Ocean, during June-July 2012

Array tow depth
160-dB
180-dB
190-dB

9
1.285
1.338
1.364

12
1.467
1.577
1.545

15
1.647
1.718
1.727

For a single airgun, the tow depth has minimal effect on the maximum near-field output and the shape of the frequency spectrum for the single airgun; thus, the predicted exclusion zones are essentially the same at different tow depths. The Observatory's model does not allow for bottom interactions, and thus is most directly applicable to deep water.

Table 2 summarizes the predicted distances at which one would expect to receive three sound levels (160-, 180-, and 190-dB) from the 36-airgun array and a single airgun. To avoid the potential for injury or permanent physiological damage (Level A harassment), we (NMFS, 1995, 2000), we have concluded that cetaceans and pinnipeds should not be exposed to pulsed underwater noise at received levels exceeding 180 dB re: 1 μPa and 190 dB re: 1 μPa, respectively. The 180-dB and 190-dB level shutdown criteria are applicable to cetaceans and pinnipeds, respectively, specified by us (NMFS, 1995, 2000). The Observatory used these levels to establish the exclusion zones. We also assume that marine mammals exposed to levels exceeding 160 dB re: 1 µPa may experience Level B harassment.

Table 2—Measured (Array) or Predicted (Single Airgun) Distances to Which Sound Levels Greater Than or Equal to 160, 180, and 190 dB re: 1 μP
a
That Could Be Received During the Three Proposed Surveys in the Northeast Pacific Ocean, During June-July 2012

Source and volume (in
3
)

Tow depth
(m)

Water depth (m)

Predicted RMS distances
2
(m)

160 dB
180 dB
190 dB

Single Bolt airgun (40 in
3
)

1
6-15

>1,000
100 to 1,000
<100

385
578
1,050

40
60
296

12
18
150

36-Airgun Array (6,600 in
3
)

9

>1,000
100 to 1,000
<100

3,850
12,200
20,550

940
1,540
2,140

400
550
680

36-Airgun Array (6,600 in
3
)

12

>1,000
100 to 1,000
<100

4,400
13,935
23,470

1,100
1,810
2,250

460
615
770

36-Airgun Array (6,600 in
3
)

15

>1,000
100 to 1,000
<100

4,490
15,650
26,350

1,200
1,975
2,750

520
690
865

1
For a single airgun, the tow depth has minimal effect on the maximum near-field output and the shape of the frequency spectrum for the single airgun; thus, the predicted exclusion zones are essentially the same at different tow depths.

2
The Observatory has based the radii for the array on data in Tolstoy
et al.
(2009) and has corrected for tow depth using modeled results. They have based the predicted radii for a single airgun upon their model (see Figure 3 in application #1).

Ocean Bottom Seismometers

The Observatory proposes to use the Woods Hole Oceanographic Institution “D2” seismometer during the cruise. The seismometer is approximately one meter in height and has a maximum diameter of 50 centimeters (cm). The anchor (2.5 x 30.5 x 38.1 cm) is hot-rolled steel and weighs 23 kilograms. The acoustic release transponder, located on the vessel, communicates with the seismometer at a frequency of 9 to 11 kilohertz (kHz). The source level of the release signal is 190 dB re: 1 μPa. The received signal activates the seismometer's burn-wire release assembly which then releases the seismometer from the anchor. The seismometer then floats to the ocean surface for retrieval by the
Oceanus.

Multibeam Echosounder

The
Langseth
will operate a Kongsberg EM 122 multibeam echosounder concurrently during airgun operations to map characteristics of the ocean floor. The hull-mounted echosounder emits brief pulses of sound (also called a ping) (10.5 to 13 kHz) in a fan-shaped beam that extends downward and to the sides of the ship. The transmitting beamwidth is 1 or 2° fore-aft and 150° athwartship and the maximum source level is 242 dB re: 1  μPa.

For deep-water operations, each ping consists of eight (in water greater than 1,000 m; 3,280 ft) or four (less than 1,000 m; 3,280 ft) successive, fan-shaped transmissions, from two to 15 milliseconds (ms) in duration and each ensonifying a sector that extends 1° fore-aft. Continuous wave pulses increase from 2 to 15 ms long in water depths up to 2,600 m (8,530 ft). The echosounder uses frequency-modulated chirp pulses up to 100-ms long in water greater than 2,600 m (8,530 ft). The successive transmissions span an overall cross-track angular extent of about 150°, with 2-ms gaps between the pulses for successive sectors.

Sub-Bottom Profiler

The
Langseth
will also operate a Knudsen Chirp 3260 sub-bottom profiler concurrently during airgun and echosounder operations to provide information about the sedimentary features and bottom topography. The profiler is capable of reaching depths of 10,000 m (6.2 mi). The dominant frequency component is 3.5 kHz and a hull-mounted transducer on the vessel directs the beam downward in a 27° cone. The power output is 10 kilowatts (kW), but the actual maximum radiated power is three kilowatts or 222 dB re: 1 μPa. The ping duration is up to 64 ms with a pulse interval of one second, but a common mode of operation is to broadcast five pulses at 1-s intervals followed by a 5-s pause.

We expect that acoustic stimuli resulting from the proposed operation of the single airgun or the 36-airgun array has the potential to harass marine mammals, incidental to the conduct of the proposed seismic survey. We also expect these disturbances to be temporary and result in a temporary modification in behavior and/or low-level physiological effects (Level B harassment only) of small numbers of certain species of marine mammals.

We do not expect that the movement of the
Langseth,
during the conduct of the seismic survey, has the potential to harass marine mammals because of the relatively slow operation speed of the vessel (4.6 kts; 8.5 km/hr; 5.3 mph) during seismic acquisition.

Description of the Marine Mammals in the Area of the Specified Activity

Thirty-one marine mammal species under our jurisdiction may occur in the proposed survey areas, including 19 odontocetes (toothed cetaceans), seven mysticetes (baleen whales), and five species of pinniped during June through July, 2012. Six of these species and two stocks are listed as endangered under the Endangered Species Act of 1973 (ESA; 16 U.S.C. 1531
et seq.
), including the blue (
Balaenoptera musculus
), fin (
Balaenoptera physalus
), humpback (
Megaptera novaeangliae
), north Pacific right (
Eubalaena japonica
), sei (
Balaenoptera borealis
), and sperm (
Physeter macrocephalus
) whales; the southern resident stock of killer (
Orcinus orca
) whales; and the eastern U.S. stock of the Steller sea lion (
Eumetopias jubatus
).

The U.S. Fish and Wildlife Service manages the northern sea otter (
Enhydra lutis
) (listed under the Endangered Species Act). Because this species is not under our jurisdiction, we do not consider this species further in this notice.

Based on available data, the Observatory does not expect to encounter five of the 31 species in the proposed survey areas. They include the: the north Pacific right, false killer (
Pseudorca crassidens
), and short-finned pilot (
Globicephala macrorhynchus
) whales; the California sea lion (
Zalophus californianus
); and the bottlenose dolphin (
Tursiops truncatus
) because of these species' rare and/or extralimital occurrence in the survey areas. Accordingly, we did not consider these species in greater detail and the proposed authorization will only address requested take authorizations for 26 species: Six mysticetes, 16 odontocetes, and four species of pinniped.

Of these 26 species, the most common marine mammals in the survey area would be the: harbor porpoise (
Phocoena phocoena
), Dall's porpoise (
Phocoenoides dalli
), northern fur seal (
Callorhinus ursinus
), and northern elephant seal (Mirounga angustirostris).

Table 3 presents information on the abundance, distribution, and conservation status of the marine mammals that may occur in the proposed survey area June through July 2012.

Table 3—Habitat, Abundance, Density, and ESA Status of Marine Mammals That May Occur in or Near the Proposed Seismic Survey Areas in the Northeast Pacific Ocean
[See text and Tables 2 and 3 in the Observatory's applications and the Foundation's Environmental Assessment for further details.]

Species

Occurrence
in area

Habitat

Abundance
in the

NW Pacific
1

ESA
2

Density
3

#/1,000 km
2

Mysticetes

North Pacific right whale
Rare
Coastal, shelf, offshore

4
31

EN
0

Gray whale
Common *
Coastal, shallow shelf

5
19,126

DL
3.21

Humpback whale
Common *
Mainly nearshore and banks

6
20,800

EN
0.81

Minke whale
Rare
Nearshore, offshore

7
9,000

NL
0.46

Sei whale
Rare
Mostly pelagic

8
12,620

EN
0.16

Fin whale
Common
Slope, pelagic

9
13,620-18,680

EN
1.29

Blue whale
Rare
Pelagic and coastal
2,497
EN
0.18

Odontocetes

Sperm whale
Common
Pelagic, steep topography

10
24,000

EN
1.02

Pygmy sperm whale
Rare
Deep, off shelf
N.A.
NL
0.71

Dwarf sperm whale
Rare
Deep, shelf, slope
N.A.
NL
0.71

Cuvier's beaked whale
Common
Pelagic
2,143
NL
0.43

Baird's beaked whale
Common
Pelagic
907
NL
1.18

Blainville's beaked whale
Rare
Pelagic

11
1,024

NL
1.75

Hubb's beaked whale
Rare
Slope, offshore

11
1,024

NL
1.75

Stejneger's beaked whale
Common
Slope, offshore

11
1,024

NL
1.75

Common bottlenose dolphin
Rare
Coastal, shelf, deep

12
1,006

NL
0

Striped dolphin
Rare
Off continental shelf
10,908
NL
0.04

Short-beaked common dolphin
Common
Shelf, pelagic, mounts
411,211
NL
10.28

Pacific white-sided dolphin
Abundant
Offshore, slope
26,930
NL
34.91

Northern right whale dolphin
Common
Slope, offshore waters
8,334
NL
12.88

Risso's dolphin
Common
Shelf, slope, mounts
6,272
NL
11.19

False killer whale
Rare
Pelagic
N.A.
NL
0

Killer whale
Common
Widely distributed
2,250-2,700

NL/EN
13

1.66

Short-finned pilot whale
Rare
Pelagic, high-relief
760
NL
0

Harbor porpoise
Abundant
Coastal and inland waters

13
55,255

NL
632.4

Dall's porpoise
Abundant
Shelf, slope, offshore
42,000
NL
83.82

Pinnipeds

Northern fur seal
Common
Pelagic, offshore

5
653,171

NL
83.62

California sea lion
Rare
Coastal, shelf
296,750
NL
0

Steller sea lion
Common *
Coastal, shelf

5
58,334-72,223

T
13.12

Harbor seal
Abundant *
Coastal

14
24,732

NL
292.3

Northern elephant seal
Common
Coastal, pelagic in migration

15
124,000

NL
45.81

N.A.—Data not available or species status was not assessed.
* In nearshore survey areas, rare elsewhere.

1
Abundance given for the California/Oregon/Washington or Eastern North Pacific stock (Carretta et al. 2011a,b), unless otherwise stated.

2
Endangered Species Act: EN = Endangered, T = Threatened, DL = Delisted, NL = Not listed.

3
Density estimate as listed in Table 3 of the Observatory's applications. Refer to pg. 48 of application #1, pg. 47 of application #2, and pg. 47 of application #3 for specific references.

4
Bering Sea (Wade et al. 2010).

5
Eastern North Pacific (Allen and Angliss 2011).

6
North Pacific (Barlow et al. 2009).

7
North Pacific (Wada 1976).

8
North Pacific (Tillman 1977).

9
North Pacific (Ohsumi and Wada 1974).

10
Eastern Temperate North Pacific (Whitehead 2002a).

11
All mesoplodont whales.

12
Offshore stock (Carretta et al. 2011a).

13
The Eastern North Pacific Southern Resident Stock of killer whales is listed as Endangered under the ESA.

14
Northern Oregon/Washington Coast and Northern California/Southern Oregon stocks.

15
Oregon/Washington Coastal Stock (Carretta et al. 2011a).

Refer to Sections III and IV of the Observatory's applications for detailed information regarding the abundance and distribution, population status, and life history and behavior of these species and their occurrence in the proposed project area. The applications also present how the Observatory calculated the estimated densities for the marine mammals in the proposed survey area. We have reviewed these data and determined them to be the best available scientific information for the purposes of the proposed incidental harassment authorization.

Potential Effects on Marine Mammals

Acoustic stimuli generated by the operation of the airguns, which introduce sound into the marine environment, may have the potential to cause Level B harassment of marine mammals in the proposed survey area. The effects of sounds from airgun operations might include one or more of the following: tolerance, masking of natural sounds, behavioral disturbance, temporary or permanent impairment, or non-auditory physical or physiological effects (Richardson
et al.,
1995; Gordon
et al.,
2004; Nowacek
et al.,
2007; Southall
et al.,
2007).

Permanent hearing impairment, in the unlikely event that it occurred, would constitute injury, but temporary threshold shift is not an injury (Southall
et al.,
2007). Although we cannot exclude the possibility entirely, it is unlikely that the proposed project would result in any cases of temporary or permanent hearing impairment, or any significant non-auditory physical or physiological effects. Based on the available data and studies described in this document, we expect some behavioral disturbance, but we expect the disturbance to be localized.

Tolerance

Studies on marine mammals' tolerance to sound in the natural environment are relatively rare. Richardson
et al.
(1995) defined tolerance as the occurrence of marine mammals in areas where they are exposed to human activities or manmade noise. In many cases, tolerance develops by the animal habituating to the stimulus (i.e., the gradual waning of responses to a repeated or ongoing stimulus) (Richardson,
et al.,
1995; Thorpe, 1963), but because of ecological or physiological requirements, many marine animals may need to remain in areas where they are exposed to chronic stimuli (Richardson,
et al.,
1995).

Numerous studies have shown that pulsed sounds from airguns are often readily detectable in the water at distances of many kilometers. Several studies have shown that marine mammals at distances more than a few kilometers from operating seismic vessels often show no apparent response (see Appendix B(5) in the Environmental Assessment). That is often true even in cases when the pulsed sounds must be readily audible to the animals based on measured received levels and the hearing sensitivity of the marine mammal group. Although various baleen whales and toothed whales, and (less frequently) pinnipeds have been shown to react behaviorally to airgun pulses under some conditions, at other times marine mammals of all three types have shown no overt reactions (Stone, 2003; Stone and Tasker, 2006; Moulton
et al.
2005, 2006a; Weir 2008a for sperm whales), (MacLean and Koski, 2005; Bain and Williams, 2006 for Dall's porpoises). The relative responsiveness of baleen and toothed whales are quite variable.

Masking of Natural Sounds

The term masking refers to the inability of a subject to recognize the occurrence of an acoustic stimulus as a result of the interference of another acoustic stimulus (Clark
et al.,
2009). Introduced underwater sound may, through masking, reduce the effective communication distance of a marine mammal species if the frequency of the source is close to that used as a signal by the marine mammal, and if the anthropogenic sound is present for a significant fraction of the time (Richardson
et al.,
1995).

We expect that the masking effects of pulsed sounds (even from large arrays of airguns) on marine mammal calls and other natural sounds will be limited, although there are very few specific data on this. Because of the intermittent nature and low duty cycle of seismic airgun pulses, animals can emit and receive sounds in the relatively quiet intervals between pulses. However, in some situations, reverberation occurs for much or the entire interval between pulses (e.g., Simard
et al.,
2005; Clark and Gagnon, 2006) which could mask calls. We understand that some baleen and toothed whales continue calling in the presence of seismic pulses, and that some researchers have heard these calls between the seismic pulses (e.g., Richardson
et al.,
1986; McDonald
et al.,
1995; Greene
et al.,
1999; Nieukirk
et al.,
2004; Smultea
et al.,
2004; Holst
et al.,
2005a,b, 2006; and Dunn and Hernandez, 2009). However, Clark and Gagnon (2006) reported that fin whales in the northeast Pacific Ocean went silent for an extended period starting soon after the onset of a seismic survey in the area. Similarly, there has been one report that sperm whales ceased calling when exposed to pulses from a very distant seismic ship (Bowles
et al.,
1994). However, more recent studies have found that they continued calling in the presence of seismic pulses (Madsen
et al.,
2002; Tyack
et al.,
2003; Smultea
et al.,
2004; Holst
et al.,
2006; and Jochens
et al.,
2008). Several studies have reported hearing dolphins and porpoises calling while airguns were operating (e.g., Gordon
et al.,
2004; Smultea
et al.,
2004; Holst
et al.,
2005a, b; and Potter
et al.,
2007). The sounds important to small odontocetes are predominantly at much higher frequencies than are the dominant components of airgun sounds, thus limiting the potential for masking.

In general, we expect that the masking effects of seismic pulses will be minor, given the normally intermittent nature of seismic pulses. Refer to Appendix B(4) of the Foundation's Assessment for a more detailed discussion of masking effects on marine mammals.

Behavioral Disturbance

Disturbance includes a variety of effects, including subtle to conspicuous changes in behavior, movement, and displacement. Reactions to sound, if any, depend on species, state of maturity, experience, current activity, reproductive state, time of day, and many other factors (Richardson
et al.,
1995; Wartzok
et al.,
2004; Southall
et al.,
2007; Weilgart, 2007). If a marine mammal does react briefly to an underwater sound by changing its behavior or moving a small distance, the impacts of the change are unlikely to be significant to the individual, let alone the stock or population. However, if a sound source displaces marine mammals from an important feeding or breeding area for a prolonged period, impacts on individuals and populations could be significant (e.g., Lusseau and Bejder, 2007; Weilgart, 2007). Given the many uncertainties in predicting the quantity and types of impacts of noise on marine mammals, it is common practice to estimate how many mammals would be present within a particular distance of industrial activities and/or exposed to a particular level of industrial sound. In most cases, this approach likely overestimates the numbers of marine mammals that would be affected in some biologically-important manner.

The sound criteria used to estimate how many marine mammals might be disturbed to some biologically-important degree by a seismic program are based primarily on behavioral observations of a few species. Scientists have conducted detailed studies on humpback, gray, bowhead (
Balaena mysticetus
), and sperm whales. There are less detailed data available for some other species of baleen whales, small toothed whales, and sea otters (
Enhydra lutris
), but for many species there are no data on responses to marine seismic surveys.

Baleen Whales
—Baleen whales generally tend to avoid operating airguns, but avoidance radii are quite variable (reviewed in Richardson
et al.,
1995). 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 longer distances. However, as reviewed in Appendix B(5) of the Foundation's Assessment, baleen whales exposed to strong noise pulses from airguns often react by deviating from their normal migration route and/or interrupting their feeding and moving away from the area. In the cases of migrating gray and bowhead whales, the observed changes in behavior appeared to be of little or no biological consequence to the animals (Richardson
et al.,
1995). They avoided the sound source by displacing their migration route to varying degrees, but within the natural boundaries of the migration corridors.

Studies of gray, bowhead, and humpback whales have shown that seismic pulses with received levels of 160 to 170 dB re: 1 μPa seem to cause obvious avoidance behavior in a substantial fraction of the animals exposed (Malme
et al.,
1986, 1988; Richardson
et al.,
1995). In many areas, seismic pulses from large arrays of airguns diminish to those levels at distances ranging from four to 15 km (2.5 to 9.3 mi) from the source. A substantial proportion of the baleen whales within those distances may show avoidance or other strong behavioral reactions to the airgun array. Subtle behavioral changes sometimes become evident at somewhat lower received levels, and studies summarized in Appendix B(5) of the Foundation's Assessment have shown that some species of baleen whales, notably bowhead and humpback whales, at times show strong avoidance at received levels lower than 160-170 dB re: 1 μPa.

Researchers have studied the responses of humpback whales to seismic surveys during migration, feeding during the summer months, breeding while offshore from Angola, and wintering offshore from Brazil. McCauley
et al.
(1998, 2000a) studied the responses of humpback whales off western Australia to a full-scale seismic survey with a 16-airgun array (2,678-in
3
) and to a single, 20-in
3
airgun with source level of 227 dB re: 1 μPa (p-p). In the 1998 study, the researchers documented that avoidance reactions began at five to eight km (3.1 to 4.9 mi) from the array, and that those reactions kept most pods approximately three to four km (1.9 to 2.5 mi) from the operating seismic boat. In the 2000 study, McCauley
et al.
noted localized displacement during migration of four to five km (2.5 to 3.1 mi) by traveling pods and seven to 12 km (4.3 to 7.5 mi) by more sensitive resting pods of cow-calf pairs. Avoidance distances with respect to the single airgun were smaller but consistent with the results from the full array in terms of the received sound levels. The mean received level for initial avoidance of an approaching airgun was 140 dB re: 1 μPa for humpback pods containing females, and at the mean closest point of approach distance, the received level was 143 dB re: 1 μPa. The initial avoidance response generally occurred at distances of five to eight km (3.1 to 4.9 mi) from the airgun array and two km (1.2 mi) from the single airgun. However, some individual humpback whales, especially males, approached within distances of 100 to 400 m (328 to 1,312 ft), where the maximum received level was 179 dB re: 1 μPa.

Data collected by observers during several seismic surveys in the northwest Atlantic Ocean showed that sighting rates of humpback whales were significantly greater during non-seismic periods compared with periods when a full array was operating (Moulton and Holst, 2010). In addition, humpback whales were more likely to swim away and less likely to swim towards a vessel during seismic versus non-seismic periods (Moulton and Holst, 2010).

Humpback whales on their summer feeding grounds in Frederick Sound and Stephens Passage, Alaska did not exhibit persistent avoidance when exposed to seismic pulses from a 1.64-L (100-in
3
) airgun (Malme
et al.,
1985). Some humpbacks seemed “startled” at received levels of 150 to 169 dB re: 1 μPa. Malme
et al.
(1985) concluded that there was no clear evidence of avoidance, despite the possibility of subtle effects, at received levels up to 172 re: 1 μPa.

Other studies have suggested that south Atlantic humpback whales wintering off Brazil may be displaced or even strand upon exposure to seismic surveys (Engel
et al.,
2004). Although, the evidence for this was circumstantial and subject to alternative explanations (IAGC, 2004). Also, the evidence was not consistent with subsequent results from the same area of Brazil (Parente
et al.,
2006), or with direct studies of humpbacks exposed to seismic surveys in other areas and seasons. After allowance for data from subsequent years, there was “no observable direct correlation” between strandings and seismic surveys (IWC, 2007: 236).

There are no data on reactions of right whales to seismic surveys, but results from the closely-related bowhead whale show that their responsiveness can be quite variable depending on their activity (migrating versus feeding). Bowhead whales migrating west across the Alaskan Beaufort Sea in autumn, in particular, are unusually responsive, with substantial avoidance occurring out to distances of 20 to 30 km (12.4 to 18.6 mi) from a medium-sized airgun source at received sound levels of approximately 120 to 130 dB re: 1 μPa (Miller
et al.,
1999; Richardson
et al.,
1999; see Appendix B(5) of the Foundation's Assessment). However, more recent research on bowhead whales (Miller
et al.,
2005; Harris
et al.,
2007) corroborates earlier evidence that, during the summer feeding season, bowheads are not as sensitive to seismic sources. Nonetheless, subtle but statistically significant changes in surfacing-respiration-dive cycles were evident upon statistical analysis (Richardson
et al.,
1986). In the summer, bowheads typically begin to show avoidance reactions at received levels of about 152 to 178 dB re: 1 μPa (Richardson
et al.,
1986, 1995; Ljungblad
et al.,
1988; Miller
et al.,
2005).

A few studies have documented reactions of migrating and feeding (but not wintering) gray whales to seismic surveys. Malme
et al.
(1986, 1988) studied the responses of feeding eastern Pacific 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 percent of feeding gray whales stopped feeding at an average received pressure level of 173 dB re: 1 μPa on an (approximate) root mean square basis, and that 10 percent of feeding whales interrupted feeding at received levels of 163 dB re: 1 μPa. Those findings were generally consistent with the results of experiments conducted on larger numbers of gray whales that were migrating along the California coast (Malme
et al.,
1984; Malme and Miles, 1985), and western Pacific gray whales feeding off Sakhalin Island, Russia (Wursig
et al.,
1999; Gailey
et al.,
2007; Johnson
et al.,
2007; Yazvenko
et al.,
2007a,b), along with data on gray whales off British Columbia (Bain and Williams, 2006).

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

(mainly fin and sei whales) were similar when large arrays of airguns were shooting vs. silent (Stone, 2003; Stone and Tasker, 2006). However, these whales tended to exhibit localized avoidance, remaining significantly further (on average) from the airgun array during seismic operations compared with non-seismic periods (Stone and Tasker, 2006). Castellote
et al.
(2010) also observed localized avoidance by fin whales during seismic airgun events in the western Mediterranean Sea and adjacent Atlantic waters from 2006-2009. They reported that singing fin whales moved away from an operating airgun array for a time period that extended beyond the duration of the airgun activity.

Ship-based monitoring studies of baleen whales (including blue, fin, sei, minke, and whales) in the northwest Atlantic found that overall, this group had lower sighting rates during seismic versus non-seismic periods (Moulton and Holst, 2010). Baleen whales as a group were also seen significantly farther from the vessel during seismic compared with non-seismic periods, and they were more often seen to be swimming away from the operating seismic vessel (Moulton and Holst, 2010). Blue and minke whales were initially sighted significantly farther from the vessel during seismic operations compared to non-seismic periods; the same trend was observed for fin whales (Moulton and Holst, 2010). Minke whales were most often observed to be swimming away from the vessel when seismic operations were underway (Moulton and Holst, 2010).

Data on short-term reactions by cetaceans to impulsive noises are not necessarily indicative of long-term or biologically significant effects. We do not know whether impulsive sounds affect reproductive rate or distribution and habitat use in subsequent days or years. However, gray whales have continued to migrate annually along the west coast of North America with substantial increases in the population over recent years, despite intermittent seismic exploration (and much ship traffic) in that area for decades (Appendix A in Malme
et al.,
1984; Richardson
et al.,
1995; Allen and Angliss, 2011). The western Pacific gray whale population did not appear affected by a seismic survey in its feeding ground during a previous year (Johnson
et al.,
2007). Similarly, bowhead whales have continued to travel to the eastern Beaufort Sea each summer, and their numbers have increased notably, despite seismic exploration in their summer and autumn range for many years (Richardson
et al.,
1987; Allen and Angliss, 2011).

Toothed Whales
—There is little systematic information available about reactions of toothed whales to noise pulses. There are few studies on toothed whales similar to the more extensive baleen whale/seismic pulse work summarized earlier in Appendix B of the Foundation's Assessment. However, there are recent systematic studies on sperm whales (e.g., Gordon
et al.,
2006; Madsen
et al.,
2006; Winsor and Mate, 2006; Jochens
et al.,
2008; Miller
et al.,
2009). There is an increasing amount of information about responses of various odontocetes to seismic surveys based on monitoring studies (
e.g.,
Stone, 2003; Smultea
et al.,
2004; Moulton and Miller, 2005; Bain and Williams, 2006; Holst
et al.,
2006; Stone and Tasker, 2006; Potter
et al.,
2007; Hauser
et al.,
2008; Holst and Smultea, 2008; Weir, 2008; Barkaszi
et al.,
2009; Richardson
et al.,
2009; Moulton and Holst, 2010).

Seismic operators and protected species observers (observers) on seismic vessels regularly see dolphins and other small toothed whales near operating airgun arrays, but in general there is a tendency for most delphinids to show some avoidance of operating seismic vessels (e.g., Goold, 1996a,b,c; Calambokidis and Osmek, 1998; Stone, 2003; Moulton and Miller, 2005; Holst
et al.,
2006; Stone and Tasker, 2006; Weir, 2008; Richardson
et al.,
2009; Barkaszi
et al.,
2009; Moulton and Holst, 2010). Some dolphins seem to be attracted to the seismic vessel and floats, and some ride the bow wave of the seismic vessel even when large arrays of airguns are firing (e.g., Moulton and Miller, 2005). Nonetheless, small toothed whales more often tend to head away, or to maintain a somewhat greater distance from the vessel, when a large array of airguns is operating than when it is silent (e.g., Stone and Tasker, 2006; Weir, 2008, Barry
et al.,
2010; Moulton and Holst, 2010). In most cases, the avoidance radii for delphinids appear to be small, on the order of one km or less, and some individuals show no apparent avoidance. The beluga whale (
Delphinapterus leucas
) is a species that (at least at times) shows long-distance avoidance of seismic vessels. Summer aerial surveys conducted in the southeastern Beaufort Sea reported that sighting rates of beluga whales were significantly lower at distances of 10 to 20 km (6.2 to 12.4 mi) from an operating airgun array compared to distances of 20 to 30 km (12.4 to 18.6 mi). Further, observers on seismic boats in that area have rarely reported sighting beluga whales (Miller
et al.,
2005; Harris
et al.,
2007).

Captive bottlenose dolphins (
Tursiops truncatus
) and beluga whales exhibited changes in behavior when exposed to strong pulsed sounds similar in duration to those typically used in seismic surveys (Finneran
et al.,
2000, 2002, 2005). However, the animals tolerated high received levels of sound before exhibiting aversive behaviors.

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

Most studies of sperm whales exposed to airgun sounds indicate that the whale shows considerable tolerance of airgun pulses (e.g., Stone, 2003; Moulton
et al.,
2005, 2006a; Stone and Tasker, 2006; Weir, 2008). In most cases the whales do not show strong avoidance, and they continue to call (see Appendix B of the Foundation's Assessment for review). However, controlled exposure experiments in the Gulf of Mexico indicate that foraging behavior was altered upon exposure to airgun sound (Jochens
et al.,
2008; Miller
et al.,
2009; Tyack, 2009).

There are almost no specific data on the behavioral reactions of beaked whales to seismic surveys. However, some northern bottlenose whales (
Hyperoodon ampullatus
) remained in the general area and continued to produce high-frequency clicks when exposed to sound pulses from distant seismic surveys (Gosselin and Lawson, 2004; Laurinolli and Cochrane, 2005; Simard
et al.,
2005). Most beaked whales tend to avoid approaching vessels of other types (e.g., Wursig
et al.,
1998). They may also dive for an extended period when approached by a vessel (e.g., Kasuya, 1986), although it is uncertain how much longer such dives may be as compared to dives by undisturbed beaked whales, which also are often quite long (Baird
et al.,
2006; Tyack
et al.,
2006). Based on a single observation, Aguilar-Soto
et al.
(2006) suggested that foraging efficiency of Cuvier's beaked whales (

Ziphius

cavirostris

) may be reduced by close approach of vessels. In any event, it is likely that most beaked whales would also show strong avoidance of an approaching seismic vessel, although this has not been documented explicitly. In fact, Moulton and Holst (2010) reported 15 sightings of beaked whales during seismic studies in the Northwest Atlantic; seven of those sightings were made at times when at least one airgun was operating. There was little evidence to indicate that beaked whale behavior was affected by airgun operations; sighting rates and distances were similar during seismic and non-seismic periods (Moulton and Holst, 2010).

There are increasing indications that some beaked whales tend to strand when naval exercises involving mid-frequency sonar operation are underway within the vicinity of the animals (e.g., Simmonds and Lopez-Jurado, 1991; Frantzis, 1998; NOAA and USN, 2001; Jepson
et al.,
2003; Hildebrand, 2005; Barlow and Gisiner, 2006; see also the Stranding and Mortality section in this notice). These strandings are apparently a disturbance response, although auditory or other injuries or other physiological effects may also be involved. Whether beaked whales would ever react similarly to seismic surveys is unknown. Seismic survey sounds are quite different from those of the sonar in operation during the above-cited incidents.

Odontocete reactions to large arrays of airguns are variable and, at least for delphinids and Dall's porpoises, seem to be confined to a smaller radius than has been observed for the more responsive of the mysticetes, belugas, and harbor porpoises (See Appendix B of the Foundation's Assessment).

Pinnipeds
—Pinnipeds are not likely to show a strong avoidance reaction to the airgun array. Visual monitoring from seismic vessels has shown only slight (if any) avoidance of airguns by pinnipeds, and only slight (if any) changes in behavior, see Appendix B(5)(3) of the Foundation's Assessment. In the Beaufort Sea, some ringed seals avoided an area of 100 m (328 ft) to (at most) a few hundred meters around seismic vessels, but many seals remained within 100 to 200 m (328 to 656 ft) of the trackline as the operating airgun array passed by (e.g., Harris
et al.,
2001; Moulton and Lawson, 2002; Miller
et al.,
2005). Ringed seal sightings averaged somewhat farther away from the seismic vessel when the airguns were operating than when they were not, but the difference was small (Moulton and Lawson, 2002). Similarly, in Puget Sound, sighting distances for harbor seals and California sea lions tended to be larger when airguns were operating (Calambokidis and Osmek, 1998). Previous telemetry work suggests that avoidance and other behavioral reactions may be stronger than evident to date from visual studies (Thompson
et al.,
1998).

Hearing Impairment and Other Physical Effects

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

Researchers have studied temporary threshold shift in certain captive odontocetes and pinnipeds exposed to strong sounds (reviewed in Southall
et al.,
2007). However, there has been no specific documentation of temporary threshold shift let alone permanent hearing damage, i.e., permanent threshold shift, in free-ranging marine mammals exposed to sequences of airgun pulses during realistic field conditions.

Temporary Threshold Shift
—This is the mildest form of hearing impairment that can occur during exposure to a strong sound (Kryter, 1985). While experiencing temporary threshold shift, the hearing threshold rises and a sound must be stronger in order to be heard. At least in terrestrial mammals, temporary threshold shift can last from minutes or hours to (in cases of strong shifts) days. For sound exposures at or somewhat above the temporary threshold shift threshold, hearing sensitivity in both terrestrial and marine mammals recovers rapidly after exposure to the noise ends. There are few data on sound levels and durations necessary to elicit mild temporary threshold shift for marine mammals, and none of the published data focus on temporary threshold shift elicited by exposure to multiple pulses of sound. Southall
et al.
(2007) summarizes available data on temporary threshold shift in marine mammals. Table 2 (introduced earlier in this document) presents the estimated distances from the
Langseth's
airguns at which the received energy level (per pulse, flat-weighted) would be greater than or equal to 180 or 190 dB re: 1 µPa.

Researchers have derived temporary threshold shift information for odontocetes from studies on the bottlenose dolphin and beluga. For the one harbor porpoise tested, the received level of airgun sound that elicited onset of temporary threshold shift was lower (Lucke
et al.,
2009). If these results from a single animal are representative, it is inappropriate to assume that onset of temporary threshold shift occurs at similar received levels in all odontocetes (cf. Southall
et al.,
2007). Some cetaceans apparently can incur temporary threshold shift at considerably lower sound exposures than are necessary to elicit temporary threshold shift in the beluga or bottlenose dolphin.

For baleen whales, there are no data, direct or indirect, on levels or properties of sound that are required to induce temporary threshold shift. The frequencies to which baleen whales are most sensitive are assumed to be lower than those to which odontocetes are most sensitive, and natural background noise levels at those low frequencies tend to be higher. As a result, auditory thresholds of baleen whales within their frequency band of best hearing are believed to be higher (less sensitive) than are those of odontocetes at their best frequencies (Clark and Ellison, 2004). From this, it is suspected that received levels causing temporary threshold shift onset may also be higher in baleen whales (Southall
et al.,
2007). For this proposed study, the Observatory expects no cases of temporary threshold shift given the low abundance of baleen whales in the planned study area at the time of the survey, and the strong likelihood that baleen whales would avoid the approaching airguns (or vessel) before being exposed to levels high enough for temporary threshold shift to occur.

In pinnipeds, researchers have not measured temporary threshold shift thresholds associated with exposure to brief pulses (single or multiple) of underwater sound. Initial evidence from more prolonged (non-pulse) exposures suggested that some pinnipeds (harbor seals in particular) incur temporary threshold shift at somewhat lower received levels than do small odontocetes exposed for similar durations (Kastak
et al.,
1999, 2005; Ketten
et al.,
2001). The indirectly estimated temporary threshold shift threshold for pulsed sounds would be approximately 181 to 186 dB re: 1 μPa

(Southall
et al.,
2007), or a series of pulses for which the highest sound exposure level values are a few decibels lower. Corresponding values for California sea lions and northern elephant seals are likely to be higher (Kastak
et al.,
2005).

Permanent Threshold Shift
—When permanent threshold shift occurs, there is physical damage to the sound receptors in the ear. In severe cases, there can be total or partial deafness, whereas in other cases, the animal has an impaired ability to hear sounds in specific frequency ranges (Kryter, 1985). There is no specific evidence that exposure to pulses of airgun sound can cause permanent threshold shift in any marine mammal, even with large arrays of airguns. However, given the possibility that mammals close to an airgun array might incur at least mild temporary threshold shift, there has been further speculation about the possibility that some individuals occurring very close to airguns might incur permanent threshold shift (e.g., Richardson
et al.,
1995, p. 372
ff;
Gedamke
et al.,
2008). Single or occasional occurrences of mild temporary threshold shift are not indicative of permanent auditory damage, but repeated or (in some cases) single exposures to a level well above that causing temporary threshold shift onset might elicit permanent threshold shift.

Relationships between temporary threshold shift and permanent threshold shift thresholds have not been studied in marine mammals, but are assumed to be similar to those in humans and other terrestrial mammals. Permanent threshold shift might occur at a received sound level at least several decibels above that inducing mild temporary threshold shift if the animal were exposed to strong sound pulses with rapid rise times—see Appendix B(6) of the Foundation's Assessment. Based on data from terrestrial mammals, a precautionary assumption is that the permanent threshold shift threshold for impulse sounds (such as airgun pulses as received close to the source) is at least six decibels higher than the temporary threshold shift threshold on a peak-pressure basis, and probably greater than six decibels (Southall
et al.,
2007).

Given the higher level of sound necessary to cause permanent threshold shift as compared with temporary threshold shift, it is considerably less likely that permanent threshold shift would occur. Baleen whales generally avoid the immediate area around operating seismic vessels, as do some other marine mammals.

Stranding and Mortality

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

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

Strandings Associated with Military Active Sonar
—Several sources have published lists of mass stranding events of cetaceans in an attempt to identify relationships between those stranding events and military active sonar (Hildebrand, 2004; IWC, 2005; Taylor
et al.,
2004). For example, based on a review of stranding records between 1960 and 1995, the International Whaling Commission (2005) identified ten mass stranding events and concluded that, out of eight stranding events reported from the mid-1980s to the summer of 2003, seven had been coincident with the use of mid-frequency active sonar and most involved beaked whales.

Over the past 12 years, there have been five stranding events coincident with military mid-frequency active sonar use in which exposure to sonar is believed to have been a contributing factor to strandings: Greece (1996); the Bahamas (2000); Madeira (2000); Canary Islands (2002); and Spain (2006). Refer to Cox
et al.
(2006) for a summary of common features shared by the strandings events in Greece (1996), Bahamas (2000), Madeira (2000), and Canary Islands (2002); and Fernandez
et al.,
(2005) for an additional summary of the Canary Islands 2002 stranding event.

Potential for Stranding from Seismic Surveys
-The association of strandings of beaked whales with naval exercises involving mid-frequency active sonar and, in one case, an Observatory's seismic survey (Malakoff, 2002; Cox
et al.,
2006), has raised the possibility that beaked whales exposed to strong “pulsed” sounds may be especially susceptible to injury and/or behavioral reactions that can lead to stranding (
e.g.,
Hildebrand, 2005; Southall
et al.,
2007). Appendix B (6) of the Foundation's Assessment provides additional details.

Specific sound-related processes that lead to strandings and mortality are not well documented, but may include:

(1) Swimming in avoidance of a sound into shallow water;

(2) A change in behavior (such as a change in diving behavior) that might contribute to tissue damage, gas bubble formation, hypoxia, cardiac arrhythmia, hypertensive hemorrhage or other forms of trauma;

(3) A physiological change such as a vestibular response leading to a behavioral change or stress-induced hemorrhagic diathesis, leading in turn to tissue damage; and

(4) Tissue damage directly from sound exposure, such as through acoustically-mediated bubble formation and growth or acoustic resonance of tissues. Some of these mechanisms are unlikely to apply in the case of impulse sounds. However, there are increasing indications that gas-bubble disease (analogous to the bends), induced in supersaturated tissue by a behavioral response to acoustic exposure, could be a pathologic mechanism for the strandings and mortality of some deep-diving cetaceans exposed to sonar. However, the evidence for this remains circumstantial and associated with exposure to naval mid-frequency sonar,

not seismic surveys (Cox
et al.,
2006; Southall
et al.,
2007).

Seismic pulses and mid-frequency sonar signals are quite different, and some mechanisms by which sonar sounds have been hypothesized to affect beaked whales are unlikely to apply to airgun pulses. Sounds produced by airgun arrays are broadband impulses with most of the energy below one kHz. Typical military mid-frequency sonar emits non-impulse sounds at frequencies of two to 10 kHz, generally with a relatively narrow bandwidth at any one time. A further difference between seismic surveys and naval exercises is that naval exercises can involve sound sources on more than one vessel. Thus, it is not appropriate to assume that there is a direct connection between the effects of military sonar and seismic surveys on marine mammals. However, evidence that sonar signals can, in special circumstances, lead (at least indirectly) to physical damage and mortality (e.g., Balcomb and Claridge, 2001; NOAA and USN, 2001; Jepson
et al.,
2003; Fernández
et al.,
2004, 2005; Hildebrand 2005; Cox
et al.,
2006) suggests that caution is warranted when dealing with exposure of marine mammals to any high-intensity “pulsed” sound.

There is no conclusive evidence of cetacean strandings or deaths at sea as a result of exposure to seismic surveys, but a few cases of strandings in the general area where a seismic survey was ongoing have led to speculation concerning a possible link between seismic surveys and strandings. Suggestions that there was a link between seismic surveys and strandings of humpback whales in Brazil (Engel
et al.,
2004) were not well founded (IAGC, 2004; IWC, 2007). In September 2002, two Cuvier's beaked whales stranded in the Gulf of California, Mexico while the Observatory's R/V
Maurice Ewing
had been operating a 20-airgun (8,490 in
3
) array in the general area. The link between the stranding and the seismic surveys was inconclusive and not based on any physical evidence (Hogarth, 2002; Yoder, 2002). Nonetheless, the Gulf of California incident plus the beaked whale strandings near naval exercises involving use of mid-frequency sonar suggests a need for caution in conducting seismic surveys in areas occupied by beaked whales until more is known about effects of seismic surveys on those species (Hildebrand, 2005). We anticipate no injuries of beaked whales during the proposed study because of:

(1) The likelihood that any beaked whales nearby would avoid the approaching vessel before being exposed to high sound levels; and

(2) Differences between the sound sources operated by the Observatory and those involved in the naval exercises associated with strandings.

Non-Auditory Physiological Effects

Non-auditory physiological effects or injuries that theoretically might occur in marine mammals exposed to strong underwater sound include stress, neurological effects, bubble formation, resonance, and other types of organ or tissue damage (Cox
et al.,
2006; Southall
et al.,
2007). Studies examining such effects are limited. However, 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 perhaps 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 seismic survey sounds (or other types of strong 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. Marine mammals that show behavioral avoidance of seismic vessels, including most baleen whales and some odontocetes, are especially unlikely to incur non-auditory physical effects.

Potential Effects of Other Acoustic Devices

Multibeam Echosounder

The Observatory will operate the Kongsberg EM 122 multibeam echosounder from the source vessel during the planned study. Sounds from the multibeam echosounder are very short pulses, occurring for two to 15 ms once every five to 20 s, depending on water depth. Most of the energy in the sound pulses emitted by this echosounder is at frequencies near 12 kHz, and the maximum source level is 242 dB re: 1 μPa. The beam is narrow (1 to 2°) in fore-aft extent and wide (150°) in the cross-track extent. Each ping consists of eight (in water greater than 1,000 m deep) or four (less than 1,000 m deep) successive fan-shaped transmissions (segments) at different cross-track angles. Any given mammal at depth near the trackline would be in the main beam for only one or two of the segments. Also, marine mammals that encounter the Kongsberg EM 122 are unlikely to be subjected to repeated pulses because of the narrow fore-aft width of the beam and will receive only limited amounts of pulse energy because of the short pulses. Animals close to the vessel (where the beam is narrowest) are especially unlikely to be ensonified for more than one 2- to 15-ms pulse (or two pulses if in the overlap area). Similarly, Kremser
et al.
(2005) noted that the probability of a cetacean swimming through the area of exposure when an echosounder emits a pulse is small. The animal would have to pass the transducer at close range and be swimming at speeds similar to the vessel in order to receive the multiple pulses that might result in sufficient exposure to cause temporary threshold shift.

Navy sonars linked to avoidance reactions and stranding of cetaceans: (1) Generally have longer pulse duration than the Kongsberg EM 122; and (2) are often directed close to horizontally versus more downward for the echosounder. The area of possible influence of the echosounder is much smaller—a narrow band below the source vessel. Also, the duration of exposure for a given marine mammal can be much longer for naval sonar. During the Observatory's operations, the individual pulses will be very short, and a given mammal would not receive many of the downward-directed pulses as the vessel passes by the animal. The following section outlines possible effects of an echosounder on marine mammals.

Masking
—Marine mammal communications will not be masked appreciably by the echosounder's signals given the low duty cycle of the echosounder and the brief period when an individual mammal is likely to be within its beam. Furthermore, in the case of baleen whales, the echosounder's signals (12 kHz) do not overlap with the predominant frequencies in the calls, which would avoid any significant masking.

Behavioral Responses
—Behavioral reactions of free-ranging marine mammals to sonars, echosounders, and other sound sources appear to vary by species and circumstance. Observed reactions have included silencing and dispersal by sperm whales (Watkins
et al.,
1985), increased vocalizations and

no dispersal by pilot whales (
Globicephala melas
) (Rendell and Gordon, 1999), and the previously-mentioned beachings by beaked whales. During exposure to a 21 to 25 kHz “whale-finding” sonar with a source level of 215 dB re: 1 µPa, gray whales reacted by orienting slightly away from the source and being deflected from their course by approximately 200 m (Frankel, 2005). When a 38-kHz echosounder and a 150-kHz acoustic Doppler current profiler were transmitting during studies in the eastern Tropical Pacific Ocean, baleen whales showed no significant responses, while spotted and spinner dolphins were detected slightly more often and beaked whales less often during visual surveys (Gerrodette and Pettis, 2005).

Captive bottlenose dolphins and a beluga whale exhibited changes in behavior when exposed to 1-s tonal signals at frequencies similar to those that will be emitted by the Observatory's echosounder, and to shorter broadband pulsed signals. Behavioral changes typically involved what appeared to be deliberate attempts to avoid the sound exposure (Schlundt
et al.,
2000; Finneran
et al.,
2002; Finneran and Schlundt, 2004). The relevance of those data to free-ranging odontocetes is uncertain, and in any case, the test sounds were quite different in duration as compared with those from an echosounder.

Hearing Impairment and Other Physical Effects
—Given recent stranding events that have been associated with the operation of naval sonar, there is concern that mid-frequency sonar sounds can cause serious impacts to marine mammals (see above). However, the echosounder proposed for use by the Observatory is quite different than sonar used for navy operations. The echosounder's pulse duration is very short relative to the naval sonar. Also, at any given location, an individual marine mammal would be in the echosounder's beam for much less time given the generally downward orientation of the beam and its narrow fore-aft beamwidth; navy sonar often uses near-horizontally-directed sound. Those factors would all reduce the sound energy received from the echosounder relative to that from naval sonar.

Based upon the best available science, we believe that the brief exposure of marine mammals to one pulse, or small numbers of signals, from the echosounder is not likely to result in the harassment of marine mammals.

Sub-Bottom Profiler

The Observatory will also operate a sub-bottom profiler from the source vessel during the proposed survey. The profiler's sounds are very short pulses, occurring for one to four ms once every second. Most of the energy in the sound pulses emitted by the profiler is at 3.5 kHz, and the beam is directed downward. The sub-bottom profiler on the
Langseth
has a maximum source level of 222 dB re: 1 µPa.

Kremser
et al.
(2005) noted that the probability of a cetacean swimming through the area of exposure when a bottom profiler emits a pulse is small—even for a profiler more powerful than that on the
Langseth
—if the animal was in the area, it would have to pass the transducer at close range and in order to be subjected to sound levels that could cause temporary threshold shift.

Masking
—Marine mammal communications will not be masked appreciably by the profiler's signals given the directionality of the signal and the brief period when an individual mammal is likely to be within its beam. Furthermore, in the case of most baleen whales, the profiler's signals do not overlap with the predominant frequencies in the calls, which would avoid significant masking.

Behavioral Responses
—Marine mammal behavioral reactions to other pulsed sound sources are discussed above, and responses to the profiler are likely to be similar to those for other pulsed sources if received at the same levels. However, the pulsed signals from the profiler are considerably weaker than those from the echosounder. Therefore, behavioral responses are not expected unless marine mammals are very close to the source.

Hearing Impairment and Other Physical Effects
—It is unlikely that the profiler produces pulse levels strong enough to cause hearing impairment or other physical injuries even in an animal that is (briefly) in a position near the source. The profiler operates simultaneously with other higher-power acoustic sources. Many marine mammals will move away in response to the approaching higher-power sources or the vessel itself before the mammals would be close enough for there to be any possibility of effects from the less intense sounds from the profiler. Based upon the best available science, we believe that the brief exposure of marine mammals to signals from the profiler is not likely to result in the harassment of marine mammals.

Potential Effects of Vessel Movement and Collisions

Vessel movement in the vicinity of marine mammals has the potential to result in either a behavioral response or a direct physical interaction. Both scenarios are discussed below this section.

Behavioral Responses to Vessel Movement

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

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

Baleen whales: “When baleen whales receive low-level sounds from distant or stationary vessels, the sounds often seem to be ignored. Some whales approach the sources of these sounds. When vessels approach whales slowly and non-aggressively, whales often exhibit slow and inconspicuous avoidance maneuvers. In response to

strong or rapidly changing vessel noise, baleen whales often interrupt their normal behavior and swim rapidly away. Avoidance is especially strong when a boat heads directly toward the whale.”

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

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

Although the radiated sound from the
Langseth
will be audible to marine mammals over a large distance, it is unlikely that animals will respond behaviorally (in a manner that we would consider MMPA harassment) to low-level distant shipping noise as the animals in the area are likely to be habituated to such noises (Nowacek
et al.,
2004). In light of these facts, we do not expect the
Langseth's
movements to result in Level B harassment.

Vessel Strike

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

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

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

The Observatory's proposed operation of one vessel for the proposed survey is relatively small in scale compared to the number of commercial ships transiting at higher speeds in the same areas on an annual basis. The probability of vessel and marine mammal interactions occurring during the proposed survey is unlikely due to the
Langseth's
slow operational speed, which is typically 4.6 kts (8.5 km/h; 5.3 mph). Outside of operations, the Langseth's cruising speed would be approximately 11.5 mph (18.5 km/h; 10 kts) which is generally below the speed at which studies have noted reported increases of marine mammal injury or death (Laist
et al.,
2001).

As a final point, the
Langseth
has a number of other advantages for avoiding ship strikes as compared to most commercial merchant vessels, including the following: the Langseth's bridge offers good visibility to visually monitor for marine mammal presence; observers posted during operations scan the ocean for marine mammals and must report visual alerts of marine mammal presence to crew; and the observers receive extensive training that covers the fundamentals of visual observing for marine mammals and information about marine mammals and their identification at sea.

The potential effects to marine mammals described in this section of the document do not take into consideration the proposed monitoring and mitigation measures described later in this document (see the “Proposed Mitigation” and “Proposed Monitoring and Reporting” sections) which, as noted are designed to effect the least practicable adverse impact on affected marine mammal species and stocks.

Anticipated Effects on Marine Mammal Habitat

The proposed seismic survey is not anticipated to have any permanent impact on habitats used by the marine mammals in the proposed survey area, including the food sources they use (i.e., fish and invertebrates). Additionally, no physical damage to any habitat is anticipated as a result of conducting the proposed seismic survey. While it is anticipated that the specified activity may result in marine mammals avoiding certain areas due to temporary ensonification, this impact to habitat is temporary and reversible and was considered in further detail earlier in this document, as behavioral modification.

The main impact associated with the proposed activity will be temporarily elevated noise levels and the associated direct effects on marine mammals, previously discussed in this notice. The next section discusses the potential impacts of anthropogenic sound sources

on common marine mammal prey in the proposed survey area (i.e., fish and invertebrates).

Anticipated Effects on Fish

One reason for the adoption of airguns as the standard energy source for marine seismic surveys is that, unlike explosives, they have not been associated with large-scale fish kills. However, existing information on the impacts of seismic surveys on marine fish populations is limited (see Appendix D of the Foundation's Assessment). There are three types of potential effects of exposure to seismic surveys: (1) Pathological, (2) physiological, and (3) behavioral. Pathological effects involve lethal and temporary or permanent sub-lethal injury. Physiological effects involve temporary and permanent primary and secondary stress responses, such as changes in levels of enzymes and proteins. Behavioral effects refer to temporary and (if they occur) permanent changes in exhibited behavior (e.g., startle and avoidance behavior). The three categories are interrelated in complex ways. For example, it is possible that certain physiological and behavioral changes could potentially lead to an ultimate pathological effect on individuals (i.e., mortality).

The specific received sound levels at which permanent adverse effects to fish potentially could occur are little studied and largely unknown. Furthermore, the available information on the impacts of seismic surveys on marine fish is from studies of individuals or portions of a population; there have been no studies at the population scale. The studies of individual fish have often been on caged fish that were exposed to airgun pulses in situations not representative of an actual seismic survey. Thus, available information provides limited insight on possible real-world effects at the ocean or population scale.

Hastings and Popper (2005), Popper (2009), and Popper and Hastings (2009a,b) provided recent critical reviews of the known effects of sound on fish. The following sections provide a general synopsis of the available information on the effects of exposure to seismic and other anthropogenic sound as relevant to fish. The information comprises results from scientific studies of varying degrees of rigor plus some anecdotal information. Some of the data sources may have serious shortcomings in methods, analysis, interpretation, and reproducibility that must be considered when interpreting their results (see Hastings and Popper, 2005). Potential adverse effects of the program's sound sources on marine fish are then noted.

Pathological Effects
—The potential for pathological damage to hearing structures in fish depends on the energy level of the received sound and the physiology and hearing capability of the species in question (see Appendix D of the Foundation's Assessment). For a given sound to result in hearing loss, the sound must exceed, by some substantial amount, the hearing threshold of the fish for that sound (Popper, 2005). The consequences of temporary or permanent hearing loss in individual fish on a fish population are unknown; however, they likely depend on the number of individuals affected and whether critical behaviors involving sound (e.g., predator avoidance, prey capture, orientation and navigation, reproduction, etc.) are adversely affected.

Little is known about the mechanisms and characteristics of damage to fish that may be inflicted by exposure to seismic survey sounds. Few data have been presented in the peer-reviewed scientific literature. As far as we know, there are only two papers with proper experimental methods, controls, and careful pathological investigation implicating sounds produced by actual seismic survey airguns in causing adverse anatomical effects. One such study indicated anatomical damage, and the second indicated temporary threshold shift in fish hearing. The anatomical case is McCauley
et al.
(2003), who found that exposure to airgun sound caused observable anatomical damage to the auditory maculae of pink snapper (
Pagrus auratus
). This damage in the ears had not been repaired in fish sacrificed and examined almost two months after exposure. On the other hand, Popper
et al.
(2005) documented only temporary threshold shift (as determined by auditory brainstem response) in two of three fish species from the Mackenzie River Delta. This study found that broad whitefish (
Coregonus nasus
) exposed to five airgun shots were not significantly different from those of controls. During both studies, the repetitive exposure to sound was greater than would have occurred during a typical seismic survey. However, the substantial low-frequency energy produced by the airguns (less than 400 Hz in the study by McCauley
et al.
(2003) and less than approximately 200 Hz in Popper
et al.
(2005)) likely did not propagate to the fish because the water in the study areas was very shallow (approximately 9 m in the former case and less than two m in the latter). Water depth sets a lower limit on the lowest sound frequency that will propagate (i.e., the cutoff frequency) at about one-quarter wavelength (Urick, 1983; Rogers and Cox, 1988).

Wardle
et al.
(2001) suggested that in water, acute injury and death of organisms exposed to seismic energy depends primarily on two features of the sound source: (1) The received peak pressure, and (2) the time required for the pressure to rise and decay. Generally, as received pressure increases, the period for the pressure to rise and decay decreases, and the chance of acute pathological effects increases. According to Buchanan
et al.
(2004), for the types of seismic airguns and arrays involved with the proposed program, the pathological (mortality) zone for fish would be expected to be within a few meters of the seismic source. Numerous other studies provide examples of no fish mortality upon exposure to seismic sources (Falk and Lawrence, 1973; Holliday
et al.,
1987; La Bella
et al.,
1996; Santulli
et al.,
1999; McCauley
et al.,
2000a,b, 2003; Bjarti, 2002; Thomsen, 2002; Hassel
et al.,
2003; Popper
et al.,
2005; Boeger
et al.,
2006).

Some studies have reported, some equivocally, that mortality of fish, fish eggs, or larvae can occur close to seismic sources (Kostyuchenko, 1973; Dalen and Knutsen, 1986; Booman
et al.,
1996; Dalen
et al.,
1996). Some of the reports claimed seismic effects from treatments quite different from actual seismic survey sounds or even reasonable surrogates. However, Payne
et al.
(2009) reported no statistical differences in mortality/morbidity between control and exposed groups of capelin eggs or monkfish larvae. Saetre and Ona (1996) applied a worst-case scenario, mathematical model to investigate the effects of seismic energy on fish eggs and larvae. They concluded that mortality rates caused by exposure to seismic surveys are so low, as compared to natural mortality rates, that the impact of seismic surveying on recruitment to a fish stock must be regarded as insignificant.

Physiological Effects
—Physiological effects refer to cellular and/or biochemical responses of fish to acoustic stress. Such stress potentially could affect fish populations by increasing mortality or reducing reproductive success. Primary and secondary stress responses of fish after exposure to seismic survey sound appear to be temporary in all studies done to date (Sverdrup
et al.,
1994; Santulli
et al.,
1999; McCauley
et al.,
2000a,b). The periods necessary for the biochemical changes to return to normal are variable and depend on numerous aspects of the biology of the species and

of the sound stimulus (see Appendix D of the Foundation's Assessment).

Behavioral Effects
—Behavioral effects include changes in the distribution, migration, mating, and catchability of fish populations. Studies investigating the possible effects of sound (including seismic survey sound) on fish behavior have been conducted on both uncaged and caged individuals (e.g., Chapman and Hawkins, 1969; Pearson
et al.,
1992; Santulli
et al.,
1999; Wardle
et al.,
2001; Hassel
et al.,
2003). Typically, in these studies fish exhibited a sharp startle response at the onset of a sound followed by habituation and a return to normal behavior after the sound ceased.

In general, any adverse effects on fish behavior or fisheries attributable to seismic testing may depend on the species in question and the nature of the fishery (season, duration, fishing method). They may also depend on the age of the fish, its motivational state, its size, and numerous other factors that are difficult, if not impossible, to quantify at this point, given such limited data on effects of airguns on fish, particularly under realistic at-sea conditions.

Anticipated Effects on Fisheries

It is possible that the
Langseth's
streamer may become entangled with various types of fishing gear. The Observatory will employ avoidance tactics as necessary to prevent conflict. It is not expected that the Observatory's operations will have a significant impact on fisheries in the western Pacific Ocean. Nonetheless, the Observatory will minimize the potential to have a negative impact on the fisheries by avoiding areas where fishing is actively underway.

There is general concern about potential adverse effects of seismic operations on fisheries, namely a potential reduction in the catchability of fish involved in fisheries. Although reduced catch rates have been observed in some marine fisheries during seismic testing, in a number of cases the findings are confounded by other sources of disturbance (Dalen and Raknes, 1985; Dalen and Knutsen, 1986; Lokkeborg, 1991; Skalski
et al.,
1992; Engas
et al.,
1996). In other airgun experiments, there was no change in catch per unit effort of fish when airgun pulses were emitted, particularly in the immediate vicinity of the seismic survey (Pickett
et al.,
1994; La Bella
et al.,
1996). For some species, reductions in catch may have resulted from a change in behavior of the fish, (e.g., a change in vertical or horizontal distribution), as reported in Slotte
et al.
(2004).

Anticipated Effects on Invertebrates

The existing body of information on the impacts of seismic survey sound on marine invertebrates is very limited. However, there is some unpublished and very limited evidence of the potential for adverse effects on invertebrates, thereby justifying further discussion and analysis of this issue. The three types of potential effects of exposure to seismic surveys on marine invertebrates are pathological, physiological, and behavioral. Based on the physical structure of their sensory organs, marine invertebrates appear to be specialized to respond to particle displacement components of an impinging sound field and not to the pressure component (Popper
et al.,
2001; see also Appendix E of the Foundation's Assessment).

The only information available on the impacts of seismic surveys on marine invertebrates involves studies of individuals; there have been no studies at the population scale. Thus, available information provides limited insight on possible real-world effects at the regional or ocean scale. The most important aspect of potential impacts concerns how exposure to seismic survey sound ultimately affects invertebrate populations and their viability, including availability to fisheries.

Literature reviews of the effects of seismic and other underwater sound on invertebrates were provided by Moriyasu
et al.
(2004) and Payne
et al.
(2008). The following sections provide a synopsis of available information on the effects of exposure to seismic survey sound on species of decapod crustaceans and cephalopods, the two taxonomic groups of invertebrates on which most such studies have been conducted. The available information is from studies with variable degrees of scientific soundness and from anecdotal information. A more detailed review of the literature on the effects of seismic survey sound on invertebrates is in Appendix E of the Foundation's Assessment.

Pathological Effects
—In water, lethal and sub-lethal injury to organisms exposed to seismic survey sound appears to depend on at least two features of the sound source: (1) The received peak pressure; and (2) the time required for the pressure to rise and decay. Generally, as received pressure increases, the period for the pressure to rise and decay decreases, and the chance of acute pathological effects increases. For the type of airgun array planned for the proposed program, the pathological (mortality) zone for crustaceans and cephalopods is expected to be within a few meters of the seismic source, at most; however, very few specific data are available on levels of seismic signals that might damage these animals. This premise is based on the peak pressure and rise/decay time characteristics of seismic airgun arrays currently in use around the world.

Some studies have suggested that seismic survey sound has a limited pathological impact on early developmental stages of crustaceans (Pearson
et al.,
1994; Christian
et al.,
2003; DFO, 2004). However, the impacts appear to be either temporary or insignificant compared to what occurs under natural conditions. Controlled field experiments on adult crustaceans (Christian
et al.,
2003, 2004; DFO, 2004) and adult cephalopods (McCauley
et al.,
2000a,b) exposed to seismic survey sound have not resulted in any significant pathological impacts on the animals. It has been suggested that exposure to commercial seismic survey activities has injured giant squid (Guerra
et al.,
2004), but the article provides little evidence to support this claim.

Andre
et al.
(2011) exposed four cephalopod species (
Loligo vulgaris,

Sepia officinalis,

Octopus vulgaris,
and
Ilex coindetii
) to two hours of continuous sound from 50 to 400 Hz at 157 ± 5 dB re: 1 μPa. They reported lesions to the sensory hair cells of the statocysts of the exposed animals that increased in severity with time, suggesting that cephalopods are particularly sensitive to low-frequency sound. The received sound pressure level was 157 v 5 dB re: 1 μPa, with peak levels at 175 dB re: 1 μPa. As in the McCauley
et al.
(2003) paper on sensory hair cell damage in pink snapper as a result of exposure to seismic sound, the cephalopods were subjected to higher sound levels than they would be under natural conditions, and they were unable to swim away from the sound source.

Physiological Effects
—Physiological effects refer mainly to biochemical responses by marine invertebrates to acoustic stress. Such stress potentially could affect invertebrate populations by increasing mortality or reducing reproductive success. Primary and secondary stress responses (i.e., changes in haemolymph levels of enzymes, proteins, etc.) of crustaceans have been noted several days or months after exposure to seismic survey sounds (Payne
et al.,
2007). The periods necessary for these biochemical changes to return to normal are variable and depend on numerous aspects of the

biology of the species and of the sound stimulus.

Behavioral Effects
—There is increasing interest in assessing the possible direct and indirect effects of seismic and other sounds on invertebrate behavior, particularly in relation to the consequences for fisheries. Changes in behavior could potentially affect such aspects as reproductive success, distribution, susceptibility to predation, and catchability by fisheries. Studies investigating the possible behavioral effects of exposure to seismic survey sound on crustaceans and cephalopods have been conducted on both uncaged and caged animals. In some cases, invertebrates exhibited startle responses (e.g., squid in McCauley
et al.,
2000a,b). In other cases, no behavioral impacts were noted (e.g., crustaceans in Christian
et al.,
2003, 2004; DFO, 2004). There have been anecdotal reports of reduced catch rates of shrimp shortly after exposure to seismic surveys; however, other studies have not observed any significant changes in shrimp catch rate (Andriguetto-Filho
et al.,
2005). Similarly, Parry and Gason (2006) did not find any evidence that lobster catch rates were affected by seismic surveys. Any adverse effects on crustacean and cephalopod behavior or fisheries attributable to seismic survey sound depend on the species in question and the nature of the fishery (season, duration, fishing method).

Proposed Mitigation

In order to issue an incidental take authorization under section 101(a)(5)(D) of the Marine Mammal Protection Act, we must set forth the permissible methods of taking pursuant to such activity, and other means of effecting the least practicable adverse impact on such species or stock and its habitat, paying particular attention to rookeries, mating grounds, and areas of similar significance, and the availability of such species or stock for taking for certain subsistence uses.

The Observatory has based the mitigation measures which they will implement during the proposed seismic survey, on the following:

(1) Protocols used during previous seismic research cruises as approved by  us;

(2) Previous incidental harassment authorizations applications and authorizations that we have approved and authorized; and

(3) Recommended best practices in Richardson
et al.
(1995), Pierson
et al.
(1998), and Weir and Dolman, (2007).

To reduce the potential for disturbance from acoustic stimuli associated with the activities, the Observatory and/or its designees would implement the following mitigation measures for marine mammals:

(1) Proposed exclusion zones;

(2) Power down procedures;

(3) Shutdown procedures; and

(4) Ramp-up procedures.

Proposed Exclusion Zones
—The Observatory uses safety radii to designate exclusion zones and to estimate take for marine mammals. Table 2 (presented earlier in this document) shows the distances at which one would expect to receive three sound levels (160-, 180-, and 190-dB) from the 36-airgun array and a single airgun. The 180-dB and 190-dB level shutdown criteria are applicable to cetaceans and pinnipeds, respectively, as specified by us (2000). The Observatory used these levels to establish the exclusion zones.

If the protected species visual observer detects marine mammal(s) within or about to enter the appropriate exclusion zone, the
Langseth
crew will immediately power down the airgun array, or perform a shutdown if necessary (see Shut-down Procedures).

Power Down Procedures
—A power down involves decreasing the number of airguns in use such that the radius of the 180-dB (or 190-dB) zone is smaller to the extent that marine mammals are no longer within or about to enter the exclusion zone. A power down of the airgun array can also occur when the vessel is moving from one seismic line to another. During a power down for mitigation, the Observatory will operate one airgun (40 in
3
). The continued operation of one airgun is intended to alert marine mammals to the presence of the seismic vessel in the area. In contrast, a shutdown occurs when the
Langseth
suspends all airgun activity.

If the observer detects a marine mammal outside the exclusion zone and the animal is likely to enter the zone, the crew will power down the airguns to reduce the size of the 180-dB exclusion zone before the animal enters that zone.

Likewise, if a mammal is already within the zone when first detected, the crew will power-down the airguns immediately. During a power down of the airgun array, the crew will operate a single 40-in
3
airgun which has a smaller exclusion zone. If the observer detects a marine mammal within or near the smaller exclusion zone around the airgun (Table 2), the crew will shut down the single airgun (see next section).

Shutdown Procedures
—The
Langseth
crew will shutdown the operating airgun(s) if a marine mammal is seen within or approaching the exclusion zone for the single airgun. The crew will implement a shutdown:

(1) If an animal enters the exclusion zone of the single airgun after the crew has initiated a power down; or

(2) If an animal is initially seen within the exclusion zone of the single airgun when more than one airgun (typically the full airgun array) is operating.

Considering the conservation status for north Pacific right whales, the
Langseth
crew will shutdown the airgun(s) immediately in the unlikely event that this species is observed, regardless of the distance from the vessel.

Resuming Airgun Operations After a Power Down

Following a power-down, the Langseth crew will not resume full airgun activity until the marine mammal has cleared the 180-dB exclusion zone (see Table 2). The observers will consider the animal to have cleared the exclusion zone if:

• The observer has visually observed the animal leave the exclusion zone, or

• An observer has not sighted the animal within the exclusion zone for 15 minutes for species with shorter dive durations (i.e., small odontocetes or pinnipeds), or 30 minutes for species with longer dive durations (i.e., mysticetes and large odontocetes, including sperm, pygmy sperm, dwarf sperm, and beaked whales); or

• The vessel has transited outside the original 180-dB exclusion zone after an 8-minute wait period. This period is based on the 180-dB exclusion zone for the 36-airgun array (940 m) towed at a depth of 9 m (29.5 ft) in relation to the average speed of the
Langseth
while operating the airguns (8.5 km/h; 5.3 mph).

The
Langseth
crew will resume operating the airguns at full power after 15 minutes of sighting any species with short dive durations (i.e., small odontocetes or pinnipeds). Likewise, the crew will resume airgun operations at full power after 30 minutes of sighting any species with longer dive durations (i.e., mysticetes and large odontocetes, including sperm, pygmy sperm, dwarf sperm, and beaked whales).

Because the vessel has transited 1.13 km (3,707 feet) away from the vicinity of the original sighting during the 8-minute period, implementing ramp-up procedures for the full array after an extended power down (i.e., transiting for an additional 35 minutes from the location of initial sighting) would not meaningfully increase the effectiveness of observing marine mammals approaching or entering the exclusion zone for the full source level and would

not further minimize the potential for take. The
Langseth's
observers are continually monitoring the exclusion zone for the full source level while the mitigation airgun is firing. On average, observers can observe to the horizon (10 km; 6.2 mi) from the height of the
Langseth's
observation deck and should be able to say with a reasonable degree of confidence whether a marine mammal would be encountered within this distance before resuming airgun operations at full power.

Resuming Airgun Operations After a Shutdown

Following a shutdown, the
Langseth
crew will initiate a ramp-up with the smallest airgun in the array (40-in
3
). The crew will turn on additional airguns in a sequence such that the s

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Source: Frix Law Library, https://www.frixlaw.com/law-library/documents/fr%3A2012-10627. Public record. Not legal advice.