Takes of Marine Mammals Incidental to Specified Activities; Low-Energy Marine Geophysical Survey in the Dumont d'Urville Sea Off the Coast of East Antarctica, January to March 2013

DEPARTMENT OF COMMERCE

National Oceanic and Atmospheric Administration

RIN 0648-XC779

Takes of Marine Mammals Incidental to Specified Activities; Low-Energy Marine Geophysical Survey in the Dumont d'Urville Sea Off the Coast of East Antarctica, January to March 2013

AGENCY:

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

ACTION:

Notice; proposed Incidental Harassment Authorization; request for comments.

SUMMARY:

NMFS has received an application from the National Science Foundation (NSF) Division of Polar Programs, and Antarctic Support Contract (ASC) on behalf of five research institutions: Colgate University, Columbia University, Texas A&M Research Foundation, University of South Florida, and University of Texas at Austin, for an Incidental Harassment Authorization (IHA) to take marine mammals, by harassment, incidental to conducting a low-energy marine geophysical (seismic) survey in the Dumont d'Urville Sea off the coast of East Antarctica, January to March 2014. Pursuant to the Marine Mammal Protection Act (MMPA), NMFS is requesting comments on its proposal to issue an IHA to NSF to incidentally harass, by Level B harassment only, 14 species of marine mammals during the specified activity.

DATES:

Comments and information must be received no later than February 3, 2014.

ADDRESSES:

Comments on the application should be addressed to P. Michael Payne, Chief, Permits and Conservation Division, Office of Protected Resources, National Marine Fisheries Service, 1315 East-West Highway, Silver Spring, MD 20910. The mailbox address for providing email comments is

ITP.Goldstein@noaa.gov.

NMFS is not responsible for email comments sent to addresses other than the one provided here. Comments sent via email, including all attachments, must not exceed a 10-megabyte file size.

All comments received are a part of the public record and will generally be posted to

http://www.nmfs.noaa.gov/pr/permits/incidental.htm#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.

A copy of the application containing a list of the references used in this document may be obtained by writing to the above address, telephoning the contact listed here (see

FOR FURTHER INFORMATION CONTACT

) or visiting the internet at:

http://www.nmfs.noaa.gov/pr/permits/incidental.htm#applications.

NSF and ASC have provided a “Draft Initial Environmental Evaluation/Environmental Assessment to Conduct a Marine-Based Studies of the Totten Glacier System and Marine Record of Cryosphere—Ocean Dynamics” (IEE/EA), prepared by AECOM, on behalf of NSF and ASC, which is also available at the same Internet address. Documents cited in this notice may be viewed, by appointment, during regular business hours, at the aforementioned address.

FOR FURTHER INFORMATION CONTACT:

Howard Goldstein or Jolie Harrison, Office of Protected Resources, NMFS, 301-427-8401.

SUPPLEMENTARY INFORMATION:

Background

Section 101(a)(5)(D) of the MMPA, as amended (16 U.S.C. 1371 (a)(5)(D)), directs the Secretary of Commerce (Secretary) 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 certain findings are made and, if the taking is limited to harassment, a notice of a proposed authorization is provided to the public for review.

Authorization for the incidental taking of small numbers of marine mammals shall be granted if NMFS finds 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. NMFS has defined “negligible impact” in 50 CFR 216.103 as “. . . an impact resulting from the specified activity that cannot be reasonably expected to, and is not reasonably likely to, adversely affect the species or stock through effects on annual rates of recruitment or survival.”

Section 101(a)(5)(D) of the MMPA 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 MMPA establishes a 45-day time limit for NMFS's 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, NMFS must either issue or deny the authorization.

Except with respect to certain activities not pertinent here, the MMPA defines “harassment” as: Any act of pursuit, torment, or annoyance which (i) has the potential to injure a marine mammal or marine mammal stock in the wild [Level A harassment]; or (ii) has the potential to disturb a marine mammal or marine mammal stock in the wild by causing disruption of behavioral patterns, including, but not limited to, migration, breathing, nursing, breeding, feeding, or sheltering [Level B harassment].

Summary of Request

On July 3, 2013, NMFS received an application from the NSF and ASC requesting that NMFS issue an IHA for the take, by Level B harassment only, of small numbers of marine mammals incidental to conducting a low-energy marine seismic survey in International Waters (i.e., high seas) and in the Southern Ocean off the coast of East Antarctica during January to March 2014. We received an addendum to the application from the NSF and ASC on December 18, 2013 which reflected updates to incidental take requests for marine mammals related to icebreaking activities.

The research would be conducted by five research institutions: Colgate University, Columbia University, Texas A&M Research Foundation, University of South Florida, and University of Texas at Austin. The NSF and ASC plans to use one source vessel, the R/VIB

Nathaniel B. Palmer

(

Palmer

), and a seismic airgun array to collect seismic data in the Southern Ocean. The vessel would be operated by ASC, which operates the United States Antarctic Program under contract to the NSF. In support of the United States Antarctic Program, the NSF and ASC plans to use conventional low-energy, seismic methodology to perform marine-based studies in the Dumont d'Urville Sea to include evaluation of geophysical and physical oceanographic features in two

areas along the coast of East Antarctica (see Figures 1, 2, and 3 of the IHA application). The primary area proposed for the study is the Totten Glacier system (preferred study area) including the Moscow University Ice Shelf along the Sabrina Coast, and a secondary area, the Mertz Glacier and Cook Ice Shelf, along the Oates Coast. In addition to the proposed operations of the seismic airgun array and hydrophone streamer, NSF and ASC intend to operate a single-beam echosounder, multi-beam echosounder, acoustic Doppler current profiler (ADCP), and sub-bottom profiler continuously throughout the survey.

Acoustic stimuli (i.e., increased underwater sound) generated during the operation of the seismic airgun array and from icebreaking activities may have the potential to cause a behavioral disturbance for marine mammals in the survey area. This is the principal means of marine mammal taking associated with these activities, and NSF and ASC has requested an authorization to take 14 species of marine mammals by Level B harassment. Take is not expected to result from the use of the single-beam echosounder, multi-beam echosounder, ADCP, acoustic locator, and sub-bottom profiler, as the brief exposure of marine mammals to one pulse, or small numbers of signals, in this particular case is not likely to result in the harassment of marine mammals. Also, NMFS does not expect take to result from collision with the source vessel because it is a single vessel moving at a relatively slow, constant cruise speed of 5 knots [kts]; 9.3 kilometers per hour [km/hr]; 5.8 miles per hour [mph]) during seismic acquisition within the survey, for a relatively short period of time (approximately 45 operational days). It is likely that any marine mammal would be able to avoid the vessel.

Description of the Proposed Specified Activity

NSF and ASC propose to conduct a low-energy seismic survey in the Dumont d'Urville Sea in the Southern Ocean off the coast of East Antarctica from January to March 2014. In addition to the low-energy seismic survey, scientific activities would include conducting a bathymetric profile survey of the seafloor using transducer based instruments such as a multi-beam echosounder and sub-bottom profiler; conducting magnetometry and imaging surveys using an underwater camera assembly; collecting sediment cores and dredge sampling; and collecting water samples and conductivity (salinity), temperature, depth (CTD) and current data through the deployment and recovery of short-term (in place for approximately one month) and long-term (in place for approximately one year) instrumentation moorings, CTD equipment casts, and the use of transducer-based ADCP instruments. Sea ice conditions will dictate areas where the ship and airguns can operate. Due to dynamic ice conditions, which cannot be predicted on a local scale, it is not possible to develop tracklines a priori. The seismic survey would be conducted in one or both of the two study areas depending on the sea ice conditions; however, the preferred study area is the Totten Glacier region (see Figure 2 of the IHA application). Water depths in the survey area range from 100 to 1,000 meters (m) (328.1 to 3,280.1 feet [ft]), and possibly exceeding 1,000 m in some areas. The seismic surveys are scheduled to occur for a total of less than or equal to 300 hours at one or both of the two study areas for approximately 45 operational days in January to March 2014. The operation hours and survey length would include equipment testing, ramp-up, line changes, and repeat coverage. The long transit time between port and the study site constrains how long the ship can be in the study area and effectively limits the maximum amount of time the airguns can operate. Some minor deviation from these dates would be possible, depending on logistics and weather.

The proposed survey of Totten Glacier and Moscow University Ice Shelf along the Sabrina Coast continental shelf is designed to address several critical questions. The Totten Glacier system, which drains one-eighth of the East Antarctic Ice Sheet and contains more ice volume than the entire West Antarctic Ice Sheet, remains the single largest and least understood glacial system which possesses a potentially unsteady dynamic. If it were to melt, sea-level would rise by more than 5 m (16.4 ft) worldwide. The proposed marine studies would help to understand both the dynamics and the controls of the Totten Glacier system, and to resolve ambiguity in large ice mass dynamic behavior. This research would be accomplished via the collection of glaciological, geological, and physical oceanographic data. In order to place the modern system, as well as more recent changes to the system, into a longer-term perspective, researchers would collect and interpret marine geologic, geochemical, and geophysical records of the longer term behavior and response of this system.

The proposed research would complement fieldwork studying other Antarctic ice shelves oceanographic studies near the Antarctic Peninsula, and ongoing development of ice sheet and other ocean models. It would facilitate learning at sea and ashore by students, help to fill important spatial and temporal gaps in a sparsely sampled region of coastal Antarctica, and communicate its findings via publications and outreach. Obtaining records of currents and oceanographic properties in this region are consistent with the objectives of the Southern Ocean Observing System for climate change. The work would enhance general understanding of air-sea-ice interactions, ocean circulation, ice shelf sensitivity to climate change, and the present and future roles of East Antarctic Ice Sheet on sea level.

The Principal Investigators are Dr. Amy Leventer of Colgate University, Dr. Donald Blankenship and Dr. Sean Gulick of the University of Texas at Austin, Dr. Eugene Domack of the University of South Florida, Mr. Bruce Huber of Columbia University, and Dr. Alejandro Orsi of Texas A&M Research Foundation.

The procedures to be used for the surveys would be similar to those used during previous low-energy seismic surveys by NSF and would use conventional seismic methodology. The proposed survey will involve one source vessel, the R/V

Nathaniel B. Palmer

(

Palmer

). NSF and ASC will deploy two (each with a discharge volume of 45 cubic inch [in

3

] with a total volume of 90 in

3

or each with a discharge volume of 105 in

3

with a total volume of 210 in

3

) Sercel Generator Injector (GI) airgun array as an energy source at a tow depth of up to 3 m (9.8 ft) below the surface (more information on the airguns can be found in Appendix B of the IHA application). The receiving system will consist of one 100 m (328.1 ft) long, 24-channel, solid-state hydrophone streamer towed behind the vessel. As the GI airguns are towed along the survey lines, the hydrophone streamer will receive the returning acoustic signals and transfer the data to the onboard processing system. All planned seismic data acquisition activities will be conducted by technicians provided by NSF and ASC with onboard assistance by the scientists who have proposed the study. The vessel will be self-contained, and the crew will live aboard the vessel for the entire cruise.

The planned seismic survey (e.g., equipment testing, start-up, line changes, repeat coverage of any areas, and equipment recovery) will consist of approximately 2,800 kilometer (km) (1,511.9 nautical miles [nmi]) of transect lines (including turns) in the survey area in the Dumont d'Urville Sea of the

Southern Ocean (see Figures 1, 2, and 3 of the IHA application). In addition to the operation of the airgun array, a single-beam and multi-beam echosounder, ADCP, and a sub-bottom profiler will also likely be operated from the

Palmer

continuously throughout the cruise between the first and last survey sites. There will be additional seismic operations associated with equipment testing, ramp-up, and possible line changes or repeat coverage of any areas where initial data quality is sub-standard. In NSF and ASC's estimated take calculations, 25% has been added for those additional operations.

Table 1—Proposed Low-Energy Seismic Survey Activities in the Dumont d'Urville Sea Off the Coast of East Antarctica

Survey length

(km)

Cumulative duration

(hr)

1

Airgun array total volume

Time between airgun shots

(distance)

Streamer length

(m)

2,800 (1,511.9 nmi)

≤300

2 × 45 in

3

(2 × 737 cm

3

) or

2 × 105 in

3

(2 × 1,720 cm

3

)

5 seconds (12.5 m or 41 ft)

100 (328.1 ft).

1

Airgun operations are planned for no more than 16 continuous hours at a time.

Vessel Specifications

The

Palmer,

a research vessel owned by Edison Chouest Offshore, Inc. and operated by NSF and ACS (under a long-term charter with Edison Chouest Offshore, Inc.), will tow the two GI airgun array, as well as the hydrophone streamer. When the

Palmer

is towing the airgun array and the relatively short hydrophone streamer, the turning rate of the vessel while the gear is deployed is much higher than the limit of 5 degrees per a minute for a seismic vessel towing a streamer of more typical length (much greater than 1 km [0.5 nmi]), which is approximately 20 degrees. Thus, the maneuverability of the vessel is not limited much during operations with the streamer.

The U.S.-flagged vessel has a length of 94 m (308.5 ft); a beam of 18.3 m (60 ft); a maximum draft of 6.8 m (22.5 ft); and a gross tonnage of 6,174. The ship is powered by four Caterpillar 3608 diesel engines (3,300 brake horsepower [hp] at 900 rotations per minute [rpm]) and a 1,400 hp flush-mounted, water jet azimuthing bowthruster. Electrical power is provided by four Catepillar 3512, 1,050 kiloWatt (kW) diesel generators. The

Palmer'

s operation speed during seismic acquisition is typically approximately 9.3 km/hr (5 kts) (varying between 7.4 to 11.1 km/hr [4 to 6 kts]). When not towing seismic survey gear, the

Palmer

typically cruises at 18.7 km/hr (10.1 kts) and has a maximum speed of 26.9 km/hr (14.5 kts). The

Palmer

has an operating range of approximately 27,780 km (15,000 nmi) (the distance the vessel can travel without refueling), which is approximately 70 to 75 days. The vessel can accommodate 37 scientists and 22 crew members.

The vessel also has two locations as likely observation stations from which Protected Species Observers (PSO) will watch for marine mammals before and during the proposed airgun operations on the

Palmer.

Observing stations will be at the bridge level with PSO's eye level approximately 16.5 m (54.1 ft) above sea level with an approximately 270° view around the vessel, and an aloft observation tower that is approximately 24.4 m (80.1 ft) above sea level that is protected from the weather and has an approximately 360° view around the vessel. More details of the

Palmer

can be found in the IHA application and online at:

http://www.nsf.gov/geo/plr/support/nathpalm.jsp

and

http://www.usap.gov/vesselScienceAndOperations/contentHandler.cfm?id=1561

.

Acoustic Source Specifications

Seismic Airguns

The

Palmer

will deploy an airgun array, consisting of two 45 in

3

or two 105 in

3

GI airguns as the primary energy source and a 100 m streamer containing hydrophones. The airgun array will have a supply firing pressure of 2,000 pounds per square inch (psi) and 2,200 psi when at high pressure stand-by (i.e., shut-down). The regulator is adjusted to ensure that the maximum pressure to the GI airguns is 2,000 psi, but there are times when the GI airguns may be operated at pressures as low as 1,750 to 1,800 psi Seismic pulses for the GI airguns will be emitted at intervals of approximately 5 seconds. At speeds of approximately 9.3 km/hr, the shot intervals correspond to spacing of approximately will be 12.5 m (41 ft) during the study. There would be approximately 720 shots per hour. During firing, a brief (approximately 0.03 second) pulse sound is emitted; the airguns will be silent during the intervening periods. The dominant frequency components range from two to 188 Hertz (Hz).

The GI airguns would be used in harmonic mode, that is, the volume of the injector chamber (I) of each GI airgun is equal to that of its generator chamber (G): 45 in

3

and 105 in

3

for each airgun array. Each airgun would be initially configured to a displacement volume of 45 in

3

for the generator and injector. The generator chamber of each GI airgun in the primary source, the one responsible for introducing the sound pulse into the ocean, is 45 in

3

. The injector chamber injects air into the previously-generated bubble to maintain its shape, and does not introduce more sound into the water. The airguns would fire the compressed air volume in unison in a harmonic mode. In harmonic mode, the injector volume is designed to destructively interfere with the reverberations of the generator (source component). Firing the airguns in harmonic mode maximizes resolution in the data and minimizes any excess noise in the water column or data caused by the reverberations (or bubble pulses). The two GI airguns will be spaced approximately 3 or 6 m (9.8 or 19.7 ft) apart, side-by-side, between 15 and 40 m (49.2 and 131.2 ft) behind the

Palmer,

at a depth of up to 3 m during the surveys. If needed to improve penetration of the strata, the two airguns may be reconfigured to a displacement volume of 105 in

3

each and would still be considered a low-energy acoustic source as defined in the NSF/USGS PEIS. Therefore, there are three possible two airgun array configurations: Two 45/45 in

3

airguns separated by 3 m, two 45/45 in

3

airguns separated by 6 m, and two 105/105 in

3

airguns separated by 3 m. The two 45/45 in

3

airguns separated by 3 m layout is preferred, the two 45/45 in

3

separated by 6 m layout would be used in the event the middle of the three 45/45 in

3

airgun fails, and the two 105/105 in

3

airguns separated by 3 m would be used only if additional penetration is needed. To summarize, two strings of GI airguns would be available: (1) Three 45/45 in

3

airguns on a single string where one of these is used as a “hot spare” in the event of

failure of one of the other two airguns, these three GI airguns are separated by 3 m; and (2) two 105/105 in

3

airguns on a second string without a “hot spare.” The total effective volume will be 90 or 210 in

3

. The two strings would be spaced 14 m (45.9 ft) apart, on either side of the midline of the vessel, however, only one string at a time would be used.

The Nucleus modeling software used at Lamont-Doherty Earth Observatory of Columbia University (L-DEO) does not include GI airguns as part of its airgun library, however signatures and mitigation models have been obtained for two 45 in

3

G airguns at 2 m tow depth and two 105 in

3

G airguns at 3 m tow depth that are close approximations. For the two 45 in

3

airgun array, the source output (downward) is 230.6 dB re: 1 μPam for 0-to-peak and 235.9 dB re: 1 μPam for peak-to-peak. For the two 105 in

3

airgun array, the source output (downward) is 234.4 dB re: 1 μPam 0-to-peak and 239.8 dB re: 1 μPam for peak-to-peak. These numbers were determined using the aforementioned G-airgun approximation to the GI airgun and using signatures filtered with DFS V out-256 Hz 72 dB/octave. The dominant frequency range would be 20 to 160 Hz for a pair of GI airguns towed at 3 m depth and 35 to 230 Hz for a pair of GI airguns towed at 2 m depth.

During the low-energy seismic survey, the vessel would attempt to maintain a constant cruise speed of approximately 5 knots. The airguns would operate continuously for no more than 16 hours at a time and duration of continuous operation is dependent on ice concentration. The cumulative duration of the airgun operations will not exceed 200 hrs. The relatively short, 24-channel hydrophone streamer would provide operational flexibility to allow the seismic survey to proceed along the designated cruise track with minimal interruption due to variable sea ice conditions. The design of the seismic equipment is to achieve high-resolution images of the glacial marine sequence stratigraphy with the ability to correlate to the ultra-high frequency sub-bottom profiling data and provide cross-sectional views to pair with the seafloor bathymetry. The cruise path would be designated once in the study area and would take care to avoid heavy ice conditions such as icebergs or dense areas of pack ice that could potentially damage the airguns or streamer and minimize proximity to potential marine receptors.

Weather conditions that could affect the movement of sea ice and hinder the hydrophone streamer would be closely monitored, as well as conditions that could limit visibility. If situations are encountered which pose a risk to the equipment, impede data collection, or require the vessel to stop forward progress, the seismic survey equipment would be shut-down and retrieved until conditions improve. In general, the hydrophone streamer and sources could be retrieved in less than 30 minutes.

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. Sound pressure level (SPL) is expressed as the ratio of a measured sound pressure and a reference level. The commonly used reference pressure level in underwater acoustics is 1 μPa, and the units for SPLs are dB re: 1 μPa. SPL (in decibels [dB]) = 20 log (pressure/reference pressure).

SPL is an instantaneous measurement and can be expressed as the peak, the peak-to-peak (p-p), or the root mean square (rms). 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 SPL in this document refer to the root mean square unless otherwise noted. SPL 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 downward-directed source levels of the airgun arrays used by NSF and ASC on the

Palmer

do not represent actual sound levels that can be measured at any location in the water. Rather, they represent the level that would be found 1 m (3.3 ft) from a hypothetical point source emitting the same total amount of sound as is emitted by the combined GI airguns. The actual received level at any location in the water near the GI airguns will not exceed the source level of the strongest individual source. In this case, that will be about 224.6 dB re 1 μPam peak, or 229.8 dB re 1 μPam peak-to-peak for the two 45 in

3

airgun array, and 228.2 dB re 1 μPam peak or 233.5 dB re 1 μPam peak-to-peak for the two 105 in

3

airgun array. However, the difference between rms and peak or peak-to-peak values for a given pulse depends on the frequency content and duration of the pulse, among other factors. Actual levels experienced by any organism more than 1 m from either GI airgun will be significantly lower.

Accordingly, Lamont-Doherty Earth Observatory of Columbia University (L-DEO) has predicted and modeled the received sound levels in relation to distance and direction from the two GI airgun array. A detailed description of L-DEO's modeling for this survey's marine seismic source arrays for protected species mitigation is provided in the NSF/USGS PEIS. These are the nominal source levels applicable to downward propagation. The NSF/USGS PEIS discusses the characteristics of the airgun pulses. NMFS refers the reviewers to those documents for additional information.

Predicted Sound Levels for the Airguns

To determine exclusion zones for the airgun array to be used in the intermediate and deep water of the Gulf of Mexico (GOM), received sound levels have been modeled by L-DEO for a number of airgun configurations, including two 45 in

3

and two 105 in

3

G airguns, in relation to distance and direction from the airguns (see Figure 2 and 3 in Attachment B of the IHA application). The model does not allow for bottom interactions, and is most directly applicable to deep water. Because the model results are for G airguns, which have more energy than GI airguns of the same size, those distances overestimate (by approximately 10%) the distances for the two 45 in

3

GI airguns and two 105 in

3

GI airguns, respectively. Although the distances are overestimated, no adjustments for this have been made to the radii distances in Table 2 (below). Based on the modeling, estimates of the maximum distances from the GI airguns where sound levels of 190, 180, and 160 dB re 1 μPa (rms) are predicted to be received in shallow, intermediate, and deep water are shown in Table 2 (see Table 1 of Attachment B of the IHA application).

Empirical data concerning the 190, 180, and 160 dB (rms) distances were acquired for various airgun arrays based on measurements during the acoustic verification studies conducted by L-DEO in the northern GOM in 2003 (Tolstoy

et al.,

2004) and 2007 to 2008 (Tolstoy

et al.,

2009; Diebold

et al.,

2010). Results of the 18 and 36 airgun array are not relevant for the two GI airguns to be used in the proposed survey. The empirical data for the 6, 10, 12, and 20 airgun arrays indicate that, for deep water, the L-DEO model tends to overestimate the received sound levels at a given distance (Tolstoy

et al.,

2004). Measurements were not made for the two GI airgun array in deep water; however, NSF and ASC proposes to use the buffer and exclusion zones predicted by L-DEO's model for the proposed GI airgun operations in deep water, although they are likely conservative given the empirical results for the other arrays. Using the L-DEO model, Table 2 (below) shows the distances at which three rms sound levels are expected to be received from the two GI airguns. The 180 and 190 dB re 1 μPam (rms) distances are the safety criteria for potential Level A harassment as specified by NMFS (2000) and are applicable to cetaceans and pinnipeds, respectively. If marine mammals are detected within or about to enter the appropriate exclusion zone, the airguns will be shut-down immediately.

Table 2 summarizes the predicted distances at which sound levels (160, 180, and 190 dB [rms]) are expected to be received from the two airgun array (45 in

3

or 105 in

3

) operating in shallow (less than 100 m [328 ft]), intermediate (100 to 1,000 m [328 to 3,280 ft]), and deep water (greater than 1,000 m [3,280 ft]) depths.

Table 2— Predicted and modeled (two 45 in

3

and two 105 in

3

GI airgun array) distances to which sound levels ≥190, 180 and 160 dB re: 1 μPa (rms) could be received in shallow, intermediate, and deep water during the proposed low-energy seismic survey in the Dumont d'Urville Sea of the Southern Ocean, January to March 2014.

Source and total volume

Tow depth

(m)

Water depth

(m)

Predicted RMS radii distances

(m) for 2 GI airgun array

160 dB

180 dB

190 dB

Two GI Airguns (45 in

3

)

3

Shallow (<100)

1,176

(3,858.3 ft)

296

(971.1 ft)

147.

(482.3 ft).

Two GI Airguns (45 in

3

)

3

Intermediate (100 to 1,000)

600

(1,968.5 ft)

100

(328ft)

15.

(49.2 ft).

Two GI Airguns (45 in

3

)

3

Deep (>1,000)

400

(1,312.3 ft)

100

(328 ft)

10.

(32.8 ft).

Two GI Airguns (105 in

3

)

3

Shallow (<100)

1,970

(6,463.3 ft)

511

(1,676.5 ft)

294.

(964.6 ft).

Two GI Airguns (105 in

3

)

3

Intermediate (100 to 1,000)

1,005

(3,297.2 ft)

100

30.

(98.4 ft).

Two GI Airguns (105 in

3

)

3

Deep (>1,000)

670

(2,198.2 ft)

100

20.

(65.6 ft).

NMFS expects that acoustic stimuli resulting from the proposed operation of the two GI airgun array has the potential to harass marine mammals. NMFS does not expect that the movement of the

Palmer,

during the conduct of the low-energy seismic survey, has the potential to harass marine mammals because of the relatively slow operation speed of the vessel (approximately 5 kts; 9.3 km/hr; 5.8 mph) during seismic acquisition.

Bathymetric Survey

Along with the low-energy airgun operations, other additional geophysical measurements would be made using swath bathymetry, backscatter sonar imagery, high-resolution sub-bottom profiling (“CHIRP”), imaging, and magnetometer instruments. In addition, several other transducer-based instruments onboard the vessel would be operated continuously during the cruise for operational and navigational purposes. Operating characteristics for the instruments to be used are described below.

Single-Beam Echosounder (Knudsen 3260)—The hull-mounted CHIRP sonar would be operated continuously during all phases of the cruise. This instrument is operated at 12 kHz for bottom-tracking purposes or at 3.5 kHz in the sub-bottom profiling mode. The sonar emits energy in a 30° beam from the bottom of the ship.

Single-Beam Echosounder (Bathy 2000)—The hull-mounted sonar characteristics of the Bathy 2000 are similar to the Knudsen 3260. Only one hull-mounted echosounder can be operated a time, and this source would be operated instead of the Knudsen 3260 only if needed (i.e., only one would be in continuous operation during the cruise).

Multi-Beam Sonar (Simrad EM120)—The hull-mounted multi-beam sonar would be operated continuously during the cruise. This instrument operates at a frequency of 12 kHz, has an estimated maximum source energy level of 242 dB re 1μPa (rms), and emits a very narrow (<2°) beam fore to aft and 150° in cross-track. The multi-beam system emits a series of nine consecutive 15 ms pulses.

Acoustic Doppler Current Profiler (ADCP Teledyne RDI VM-150)—The hull-mounted ADCP would be operated continuously throughout the cruise. The ADCP operates at a frequency of 150 kHz with an estimated acoustic output level at the source of 223.6 dB re 1μPa (rms). Sound energy from the ADCP is emitted as a 30° conically-shaped beam.

Acoustic Doppler Current Profiler (ADCP Ocean Surveyor OS-38)—The characteristics of this backup hull-mounted ADCP unit are similar to the Teledyne VM-150 and would be continuously operated.

Acoustic Locator (Pinger)—An acoustic locator (i.e., pinger) would be deployed when using the Smith-McIntyre grab sampler and multi-corer (Mega-corer) to enable these devices to be located in the event they become detached from their lines. A pinger typically operates at a frequency of 12 kHz, generates a 5 ms pulse per second, and has an acoustical output of 162 dB re 1μPa (rms). A maximum total of 30 samples would be obtained using these devices and require approximately one hour per sample; therefore, the pinger would operate for a total of 30 hours.

Passive Instruments—During the seismic survey in the Dumont d'Urville Sea, a precession magnetometer and Air-Sea gravity meter would be deployed. In addition, numerous (approximately 24) expendable bathythermograph (XBTs) probes would

also be released (and none would be recovered) over the course of the cruise to obtain temperature data necessary to calculate sound velocity profiles used by the multi-beam sonar.

Core and Dredge Sampling

The primary sampling goals involve the acquisition of marine sediment cores of various lengths up to 25 m (82 ft). It is anticipated that up to 65 sediment cores and grab samples and 12 rock dredge samples would be collected as summarized in Table 3 (Table 3 of the IHA application). Each core or grab sample would require approximately one hour per sample. All cores and dredges would be deployed using a steel cable/winch system.

Approximately 75 m

2

(807.3 ft

2

) of seafloor would be disturbed by each of four deployments of the dredge at three different sites (resulting in a total of 900 m

2

[9,687.5 ft

2

] of affected seafloor for the project). The selection of the bottom sampling locations and sampling method would be based on observations of the seafloor, subsurface reflectivity, sediment type, and accessibility due to ice and weather conditions. Bottom sampling in the Mertz Glacier area would be limited to strategically selected locations including possible re-sampling at a previous core site.

Table 3—Proposed Coring and Dredging Activities in the Dumont d'Urville Sea

Sampling device

Number of

deployments

Smith-MycIntyre grab sampler

10 to 15.

Multi-corer (Mega-corer)

10 to 15.

Kasten corer (regular or jumbo)

20 to 25.

Jumbo piston corer

8 to 10.

Box cage dredge

10 to 12.

Limited sampling of rock material would be conducted using a dredge that would be towed along the seafloor for short distances (approximately 50 m [164 ft]) to collect samples of bedrock and ice rafted debris. The available dredges, which have openings of 0.5 to 1.5 m (1.6 to 4.9 ft), would be deployed on rocky substrates. The locations of the proposed dredge sites are limited to the inner shelf (southern) perimeter of three areas: The Mertz Trough and two regions along the Sabrina Coast. Final selection of dredge sites will include review to ensure that the seamounts or corals in the area are avoided (AOA, 2011).

The Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR) has adopted conservation measures (i.e., 22-06, 22-07, and 22-09) to protect vulnerable marine ecosystems (VME), which include seamounts, hydrothermal vents, cold water corals, and sponge fields. The conservation measure 22-07 includes mitigation and reporting requirements if VME are encountered. The science team would follow these requirements (see Attachment C of the IHA application) if VME's are encountered while sampling the sea bottom.

In addition, a camera and towed video system would be deployed at up to 25 sites. This device would lightly touch the seafloor to establish a baseline and rise to an optimum elevation to obtain the desired images.

Water Sampling and Current Measurements

High-resolution conductivity, depth, and temperature (CTD) measurements would be collected to characterize the summer regional water mass stratification and circulation, and the meridional exchange of waters between the oceanic and shelf regimes. These physical measurements would involve approximately SeaBird CTD system casts including the use of a lowered ADCP (LADCP).

The LADCP would consist of two Teledyne RDI Workhorse Monitor ADCPs mounted on the CTD/rosette frame and one oriented upward and the other downward. The LADCP and frame would be raised and lowered by cable and winch. The LADCPs would operate at a frequency of 307.2 kHz, with an estimated output acoustic pressure along each 4 beams of 216.3 dB re 1μPa at 1 m. The beams are angled at 20 degrees from the centerline of the ADCP head, with a beam angle of 4 degrees for the individual beams. Typical pulse duration is 5.7 ms, with a typical repetition rate of 1.75 s. The upward and downward-looking ADCPs are operated in master-salve mode so that only one head pings at a time. The LADCP would be operated approximately one hour at every CTD/rosette station (maximum of 100 stations) for a total of 100 hours of operation.

These instruments would be used to profile the full water column for temperature, salinity (conductivity), dissolved oxygen and currents at a series of transects in the study area. Discrete water samples would be collected for salinity and dissolved oxygen to monitor CTD/rosette performance, and for oxygen isotopes to assess meltwater content. Water samples would also be collected for development and interpretation of marine sediment proxies using Niskin bottles.

Observations of the thermal structure along other portions of the cruise track would be made using an underway CTD system and XBTs while the seafloor is swath-mapped. The number and spacing of stations would be adjusted according to ocean features discovered through multi-beam swath mapping and the sea ice conditions. If portions of the study area are inaccessible to the NBP, a contingency sampling focused on the inflows of MDCW would be pursued in adjacent shelf troughs.

It is noted that underway ADCP on the

Palmer

can, under ideal conditions, obtain profiles of ocean currents to depths greater than 800 m (2,624.7 ft). On continental shelves where depths may be less than the range of the ADCP, the underway profiles cannot resolve the deepest 15% of the water column due to side lobe reflections from the bottom which contaminate the water column Doppler returns. For a depth of 800 m, expected in the MCDW, currents in the lower 120 m (393.7 ft) could not be measured by the ship ADCP; therefore, the lowered ADCP can provide accurate current profiles to within a few meters of the bottom and provide complete coverage of the velocity field at each CTD station.

Instrumentation Moorings

Four instrumented moorings would be deployed during the proposed cruise to measure current, temperature, and salinity (conductivity) continuously. Two of the moorings would be deployed for approximately one month (short-term moorings) and two moorings would be deployed for approximately one year (long-term moorings). The two short-term moorings and one long-term mooring would include ADCP paired with CTD recorders, and additional intermediate T (i.e., temperature) recorders. The characteristics of the ADCP units deployed on the moorings are similar to the Teledyne VM-150; the moored ADCPs operate at frequencies of 75 kHz (one unit) and 300 kHz (two units). The fourth mooring would be equipped with sediment traps, a CTD recorder and intermediate T recorders, and be deployed for approximately one year (long-term mooring). The two long-term moorings would be retrieved approximately one year later by a U.S. Arctic Program (USAP) vessel or collaborators from other countries.

Subject to sea ice conditions, these moorings would preferably be placed in front of Totten Glacier, but otherwise as close as possible inside adjacent cross-shelf troughs. If access to the inner shelf is not allowed by sea ice conditions we would attempt mooring deployments within the outer shelf close to the

troughs mouth, where the Totten Glacier is more directly connected to inflows from the oceanic domain offshore. The two long-term moorings would be deployed within 16 km of each other. The short-term moorings would be within a few kilometers of each other and no farther than 32 km (17.3 nmi) from the long-term moorings. All instruments would be kept at depths below 250 m (820.2 ft) to minimize damage or loss by icebergs.

The moorings would temporarily attached to anchors and be recovered using acoustic release mechanisms. The mooring recovery process would be similar regardless of mooring type or when they would be retrieved. Locating the moorings and releasing the moorings from the steel railroad wheel anchors (which would not be recovered) would be accomplished by transmitting sound over a period of several seconds. This is done with an acoustic deck command unit that sends a sequence of coded pulses to the receiving units, the acoustic releases, connected to the mooring anchors. The acoustic releases response to acknowledge the receipt of commands from the deck unit is by transmitting a short sequence of pulses back. Both of the acoustic units (onboard deck unit and moored releases) operate at frequencies between approximately 7 and 15 kHz. The beam pattern is approximately omnidirectional. The acoustic source level is less than 192 dB re 1μPa at 1 m.

In addition to the U.S. moorings described above, three new moorings would be deployed on behalf of Australia's national science agency the Commonwealth of Scientific and Industrial Research Organisation (CSIRO) Physical Oceanography group in the Totten Glacier region by the project team. These moorings would be retrieved approximately one year later by collaborators from other countries. Also, during this cruise, three CSIRO moorings that were deployed over a year ago in the western outlet of the Mertz-Ninnis Trough would be recovered. The recovery process and acoustic sources described above for the U.S. moorings would be used for recovery of the CSIRO moorings.

Icebreaking

Icebreaking is considered by NMFS to be a continuous sound and NMFS estimates that harassment occurs when marine mammals are exposed to continuous sounds at a received sound level of 120 dB SPL or above. Potential takes of marine mammals may ensue from icebreaking activity in which the

Palmer

is expected to engage in Antarctic waters (i.e., along the George V and Oates Coast of East Antarctica, >65° South, between 140° and 165° East). While breaking ice, the noise from the ship, including impact with ice, engine noise, and propeller cavitation, will exceed 120 dB (rms) continuously. If icebreaking does occur in Antarctic waters, NMFS, NSF and ASC expect it will occur during transit and non-seismic operations to gain access to coring, dredging, or other sampling locations and not during seismic airgun operations. The research activities and associated contingencies are designed to avoid areas of heavy sea ice condition. The buffer zone (160 dB [rms]) for the marine mammal Level B harassment threshold during the proposed activities is greater than the calculated radius during icebreaking. Therefore, if the

Palmer

breaks ice during seismic operations within the Antarctic waters (within the Dumont d'Urville Sea or other areas of the Southern Ocean), the more conservative and larger radius (i.e., that for seismic operations) will be used and supercede the buffer zone for icebreaking.

In 2008, acousticians from Scripps Institution of Oceanography Marine Physical Laboratory and University of New Hampshire Center for Coastal and Ocean Mapping conducted measurements of SPLs of the

Healy

icebreaking under various conditions (Roth and Schmidt, 2010). The results indicated that the highest mean SPL (185 dB) was measured at survey speeds of 4 to 4.5 kts in conditions of 5/10 ice and greater. Mean SPL under conditions where the ship was breaking heavy ice by backing and ramming was actually lower (180 dB). In addition, when backing and ramming, the vessel is essentially stationary, so the ensonified area is limited for a short period (on the order of minutes to tens of minutes) to the immediate vicinity of the vessel until the ship breaks free and once again makes headway.

The 120 dB received sound level radius around the

Healy

while icebreaking was estimated by researchers (USGS, 2010). Using a spherical spreading model, a source level of 185 dB decays to 120 dB in about 1,750 m (5,741.5 ft). This model is corroborated by Roth and Schmidt (2010). Therefore, as the ship travels through the ice, a watch 3,500 m (11,482.9 ft) wide would be subject to sound levels greater than or equal to 120 dB. This results in potential exposure of 3,500 km

2

(1,020.4 nmi

2

) to sounds greater than or equal to 120 dB from icebreaking.

Data characterizing the sound levels generated by icebreaking activities conducted by the

Palmer

are not available; therefore, data for noise generating from an icebreaking vessel such as the U.S. Coast Guard Cutter (USCGC)

Healy

will be used as a proxy. It is noted that the

Palmer

is a smaller vessel and has less icebreaking capability than the U.S. Coast Guard's other polar icebreakers, being only capable of breaking ice up to 1 m thick at speeds of 3 kts (5.6 km/hr or 3 nmi). Therefore, the sound levels that may be generated by the

Palmer

are expected to be lower than the conservative levels estimated and measured for the

Healy.

Researchers will work to minimize time spent breaking ice as science operations are more difficult to conduct in icy conditions since the ice noise degrades the quality of the seismic and ADCP data and time spent breaking ice takes away from time supporting scientific research. Logistically, if the vessel were in heavy ice conditions, researchers would not tow the airgun array and streamer, as this would likely damage equipment and generate noisy data. It is possible that the seismic survey can be performed in low ice conditions if the Palmer could generate an open path behind the vessel.

Because the

Palmer

is not rated to break multi-year ice routinely, operations generally avoid transiting through older ice (i.e., 2 years or older, thicker than 1 m). If sea ice is encountered during the cruise, it is anticipated the

Palmer

will proceed primarily through one year sea ice, and possibly some new, very thin ice, and would follow leads wherever possible. Satellite imagery from the Totten region documents that sea ice is at its minimum extent during the month of February. The most recent image for the region, from November 21, 2013, shows that the sea ice is currently breaking up, with a significant coastal lead of open water. Based on a maximum sea ice extent of 250 km (135 nmi) and estimating that NSF and ASC will transit to the innermost shelf and back into open water twice, a round trip transit in each of the potential work regions, NSF and ASC estimate that the

Palmer

will actively break ice up to a distance of 1,000 km (540 nmi). Based on a ship's speed of 5 kts under moderate ice conditions, this distance represents approximately 108 hrs of icebreaking operations. It is noted that typical transit through areas primarily open water and containing brash ice or pancake ice will not be considered icebreaking.

Dates, Duration, and Specified Geographic Region

The proposed project and survey sites are located in selected regions of the Dumont d'Urville Sea in the Southern Ocean off the coast of East Antarctica and focus on the Totten Glacier and Moscow University Ice Shelf, located on the Sabrina Coast, from greater than approximately 64° South and between approximately 95 to 135° East (see Figure 2 of the IHA application), and the Mertz Glacier and Cook Ice Shelf systems located on the George V and Oates Coast, from greater than approximately 65° South and between approximately 140 to 165° East in International Waters. The proposed study sites are characterized by heavy ice cover, with a seasonal break-up in the ice that structures biological patterns. The proposed studies would occur in both areas, or entirely in one or the other, depending on ice conditions. Figure 3 of the IHA application illustrates the limited detailed bathymetry of the two study areas. Ice conditions encountered during the previous surveys in the region limited the area where bathymetric data could be collected. Water depths in the survey area range from approximately 100 to 1,000 m, and possibly exceeding 1,000 m in some areas. There is limited information on the depths in the study area and therefore more detailed information on bathymetry is not available. Figures 2 and 3 of the IHA application illustrate the limited available detailed bathymetry of the two proposed study areas due to ice conditions encountered during previous surveys in the region. The proposed seismic survey would be within an area of approximately 5,628 km

2

(1,640.9 nmi

2

). This estimate is based on the maximum number of kilometers for the seismic survey (2,800 km) times the predicted rms radii (m) based on modeling and empirical measurements (assuming 100% use of the two 105 in

3

GI airguns in 100 to 1,000 m water depths) which was calculated to be 1,005 m (3,297.2 ft).

The icebreaking will occur, as necessary, between approximately 66 to 70° South and between 140 to 165° East. The total distance in the region of the vessel will travel include the proposed seismic survey and transit to dredging or sampling locations and will represent approximately 5,600 km (3,023.8 nmi). Based on a maximum sea ice extent of 250 km (135 nmi) and estimating that NSF and ASC will transit to the innermost shelf and back into open water twice, a round trip transit in each of the potential work regions, NSF and ASC estimate that the Palmer will actively break ice up to a distance of 1,000 km (540 nmi). Based on a ship's speed of 5 kts under moderate ice conditions, this distance represents approximately 108 hrs of icebreaking operations.

The

Palmer

is expected to depart from Hobart, Tasmania on approximately January 29, 2014 and arrive at Hobart, Tasmania on approximately March 16, 2014. Research operations would be over a span of 45-days, including to and from port. Ice-free or very low concentrations of sea ice are required in order to collect high quality seismic data and not impede passage of the vessel between sampling locations. This requirement restricts the cruise to operating in mid to late austral summer when the ice concentrations are typically the lowest. Some minor deviation from this schedule is possible, depending on logistics and weather (i.e., the cruise may depart earlier or be extended due to poor weather; there could be additional days of seismic operations if collected data are deemed to be of substandard quality).

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

The marine mammals that generally occur in the proposed action area belong to three taxonomic groups: Mysticetes (baleen whales), odontocetes (toothed whales), and pinnipeds (seals and sea lions). The marine mammal species that potentially occur within the Southern Ocean in proximity to the proposed action area in the Dumont d'Urville Sea include 28 species of cetaceans and 6 species of pinnipeds.

The Dumont d'Urville Sea may be a feeding ground for many of these marine mammals. Many of the species that may be potentially present in the study area seasonally migrate to higher latitudes along the east coast of Antarctica. In general, most species (except for the killer whale) migrate north in the middle of the austral winter and return to Antarctica in the early austral summer. Some species, particularly Antarctic minke (

Balaenopter

a

bonaerensis

) and killer whales (

Orcinus orca

), are expected to be present in higher concentrations along the ice edge (SCAR, 2002). The 6 species of pinnipeds that are found in the Southern Ocean and which may be present in the proposed study area include the crabeater (

Lebodon carcinophagus

), leopard (

Hydrurga leptonyx

), Wedell (

Leptonychotes weddellii

), Ross (

Ommatophoca rossii

), southern elephant (

Mirounga leonina

), and Antarctic fur seal (

Arctocephalus gazella

). Many of these pinniped species breed on either the pack ice or sub-Antarctic islands. Since the southern elephant seal and Antarctic fur seal haul-outs and rookeries are located on sub-Antarctic islands and prefer beaches, they are more common north of the seasonally shifting pack ice found in the proposed study area; therefore, these two species have not been considered further. Marine mammal species listed as endangered under the U.S. Endangered Species Act of 1973 (ESA; 16 U.S.C. 1531

et seq.

), includes the southern right (

Eubalaena australis

), humpback (

Megaptera novaeangliae

), sei (

Balaenoptera borealis

), fin (

Balaenoptera physalus

), blue (

Balaenoptera musculus

), and sperm (

Physeter macrocephalus

) whale. Of those endangered species, the humpback, sei, fin, blue, and sperm whale are likely to be encountered in the proposed survey area.

Various national Antarctic research programs along the coast of East Antarctica have conducted scientific cruises that included data on marine mammal sightings. These observations were made primarily between 30° East and 170° East and north to 60° South. The reported cetacean sightings are summarized in Tables 5 to 7 of the IHA application. For pinnipeds, observations made during a scientific cruise over a 13-day period in East Antarctica are summarized in Table 8 of the IHA application. These observations were made below 60° South and between 110° East to 165° East and include sightings of individual animals in the water as well as individuals that were hauled-out (i.e., resting on the surface of the sea ice).

Records from the International Whaling Commission's Southern Ocean Whale and Ecosystem Research (IWC-SOWER) circumpolar cruises were also considered. In addition to the 14 species known to occur in the Dumont d'Urville Sea of the Southern Ocean, there are 18 cetacean species with ranges that are known to occur in the sub-Antarctic waters of the study area which may also feed and/or migrate to the Southern Ocean during the austral summer, these include the southern right, pygmy right (

Caperea marginata

), Bryde's (

Balaenoptera brydei

), dwarf minke (

Balaenoptera acutorostrata

spp.), pygmy blue (

Balaenoptera musculus

brevicauda

), pygmy dwarf sperm whale (

Kogia breviceps

), Arnoux's beaked (

Berardius arnuxii

), Blainville's beaked whale (

Mesoplodon densirostris

), Cuvier's beaked (

Ziphius cavirostris

), Shepherd's beaked (

Tasmacetus shepherdi

), Southern bottlenose (

Hyperoodon planifrons

), Andrew's

beaked (

Mesoplodon bowdoini

), Hector's beaked (

Mesoplodon hectori

), Gray's beaked (

Mesoplodon grayi

), strap-toothed beaked (

Mesoplodon layardii

), spade-toothed beaked (

Mesoplodon traversii

), southern right whale dolphin (

Lissodelphis peronii

), Dusky (

Lagenorhynchus obscurus

), and bottlenose dolphin (

Tursiops truncatus

). However, these species have not been sighted and are not expected to occur where the proposed activities would take place. These species are not considered further in this document. Table 4 (below) presents information on the abundance, distribution, population status, conservation status, and population trend of the species of marine mammals that may occur in the proposed study area during February to March 2014.

Table 4—The Habitat, Regional Abundance, and Conservation Status of Marine Mammals That May Occur In or Near the Proposed Low-Energy Seismic Survey Area in the Antarctic Area of the Southern Ocean

[See text and Tables 4 in NSF and ASC's application for further details]

Species

Habitat

Population estimate

ESA

1

MMPA

2

Population trend

Mysticetes:

Southern right whale (

Eubalaena australis

)

Coastal, pelagic

8,000

3

to 15,000

4

EN

D

Increasing.

Pygmy right whale (

Caperea marginata

)

Coastal, pelagic

NA

NL

NC

NA.

Humpback whale (

Megaptera novaeangliae

)

Pelagic, nearshore waters, and banks

35,000 to 40,000

3

—Worldwide

9,484

5

—Scotia Sea and Antarctica Peninsula

EN

D

Increasing.

Dwarf minke whale (

Balaenoptera acutorostrata

sub-species)

Pelagic and coastal

NA

NL

NC

NA.

Antarctic minke whale (

Balaenoptera bonaerensis

)

Pelagic, ice floes

Several 100,000

3

—Worldwide

18,125

5

—Scotia Sea and Antarctica Peninsula

NL

NC

Stable.

Bryde's whale (

Balaenoptera brydei

)

Pelagic and coastal

NA

NL

NC

NA.

Sei whale (

Balaenoptera borealis

)

Primarily offshore, pelagic

80,000

3

—Worldwide

EN

D

NA.

Fin whale (

Balaenoptera physalus

)

Continental slope, pelagic

140,000

3

—Worldwide

4,672

5

—Scotia Sea and Antarctica Peninsula

EN

D

NA.

Blue whale (

Balaenoptera musculus

)

Pelagic, shelf, coastal

8,000 to 9,000

3

—Worldwide

1,700

6

—Southern Ocean

EN

D

NA.

Odontocetes:

Sperm whale (

Physeter macrocephalus

)

Pelagic, deep sea

360,000

3

—Worldwide

9,500

3

—Antarctic

EN

D

NA.

Pygmy sperm whale (Kogia breviceps)

Pelagic, slope

NA

NL

NC

NA.

Arnoux's beaked whale (

Berardius arnuxii

)

Pelagic

NA

NL

NC

NA.

Blainville's beaked whale (

Mesoplodon densirostris

)

Pelagic

NA

NL

NC

NA.

Cuvier's beaked whale (

Ziphius cavirostris

)

Pelagic

NA

NL

NC

NA.

Shepherd's beaked whale (Tasmacetus shepherdi)

Pelagic

NA

NL

NC

NA.

Southern bottlenose whale (

Hyperoodon planifrons

)

Pelagic

500,000

3

—South of Antarctic Convergence

NL

NC

NA.

Andrew's beaked whale (Mesoplodon bowdoini)

Pelagic

NA

NL

NC

NA.

Hector's beaked whale (Mesoplodon hectori)

Pelagic

NA

NL

NC

NA.

Gray's beaked whale (

Mesoplodon grayi

)

Pelagic

NA

NL

NC

NA.

Strap-toothed beaked whale (

Mesoplodon layardii

)

Pelagic

NA

NL

NC

NA.

Spade-toothed beaked whale (Mesoplodon traversii)

Pelagic

NA

NL

NC

NA.

Killer whale (

Orcinus orca

)

Pelagic, shelf, coastal, pack ice

80,000

3

—South of Antarctic Convergence

25,000

7

—Southern Ocean

NL

NC

NA.

Long-finned pilot whale (

Globicephala melas

)

Pelagic, shelf, coastal

200,000

3 8

—South of Antarctic Convergence

NL

NC

NA.

Bottlenose dolphin (

Tursiops truncatus

)

Offshore, inshore, coastal, estuaries

>625,500

3

—Worldwide

NL

NC

NA.

Southern right whale dolphin (

Lissodelphis peronii

)

Pelagic

NA

NL

NC

NA.

Dusky dolphin (Lagenorhynchus obscurus)

Coastal, continental shelf and slope

NA

NL

NC

NA.

Hourglass dolphin (

Lagenorhynchus cruciger

)

Pelatic, ice edge

144,000

3

NL

NC

NA.

Spectacled porpoise (

Phocoena dioptrica

)

Coastal, pelagic

NA

NL

NC

NA.

Pinnipeds:

Crabeater seal (

Lobodon carcinophaga

)

Coastal, pack ice

5,000,000 to 15,000,000

3 9

NL

NC

Increasing.

Leopard seal (

Hydrurga leptonyx

)

Pack ice, sub-Antarctic islands

220,000 to 440,000

3 10

NL

NC

NA.

Ross seal (

Ommatophoca rossii

)

Pack ice, smooth ice floes, pelagic

130,000

3

NL

NC

NA.

Wedell seal (

Leptonychotes weddellii

)

Fast ice, pack ice, sub-Antarctic islands

500,000 to 1,000,000

3 11

NL

NC

NA.

Southern elephant seal (

Mirounga leonina

)

Coastal, pelagic, sub-Antarctic waters

640,000

12

to 650,000

3

NL

NC

Decreasing, increasing or stable depending on breeding population.

Antarctic fur seal (

Arctocephalus gazella

)

Shelf, rocky habitats

1,600,000

13

to 3,000,000

3

NL

NC

Increasing.

NA = Not available or not assessed.

1

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

2

U.S. Marine Mammal Protection Act: D = Depleted, S = Strategic, NC = Not Classified.

3

Jefferson

et al.,

2008.

4

Kenney, 2009.

5

Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR) survey area (Reilly

et al.,

2004).

6

Sears and Perrin, 2009.

7

Ford, 2009.

8

Olson, 2009.

9

Bengston, 2009.

10

Rogers, 2009.

11

Thomas and Terhune, 2009.

12

Hindell and Perrin, 2009.

13

Arnould, 2009.

Refer to sections 3 and 4 of NSF and ASC's IHA application for detailed information regarding the abundance and distribution, population status, and life history and behavior of these other marine mammal species and their occurrence in the proposed project area. The IHA application also presents how NSF and ASC calculated the estimated densities for the marine mammals in the proposed survey area. NMFS has reviewed these data and determined them to be the best available scientific information for the purposes of the proposed IHA.

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 hearing 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 (TTS) is not an injury (Southall

et al.,

2007). Although the possibility cannot be entirely excluded, 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 here, some behavioral disturbance is expected. A more comprehensive review of these issues can be found in the “Programmatic Environmental

Impact Statement/Overseas Environmental Impact Statement prepared for Marine Seismic Research that is funded by the National Science Foundation and conducted by the U.S. Geological Survey” (NSF/USGS, 2011).

Tolerance

Richardson

et al.

(1995) defines tolerance as the occurrence of marine mammals in areas where they are exposed to human activities or man-made 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. 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. The relative responsiveness of baleen and toothed whales are quite variable.

Masking

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).

The airguns for the proposed low-energy seismic survey have dominant frequency components of 2 to 188 Hz. This frequency range fully overlaps the lower part of the frequency range of odontocete calls and/or functional hearing (full range about 150 Hz to 180 kHz). Airguns also produce a small portion of their sound at mid and high frequencies that overlap most, if not all, frequencies produced by odontocetes. While it is assumed that mysticetes can detect acoustic impulses from airguns and vessel sounds (Richardson

et al.,

1995a), sub-bottom profilers, pingers, and most of the multi-beam echosounders would likely be detectable by some mysticetes based on presumed mysticete hearing sensitivity. Odontocetes are presumably more sensitive to mid to high frequencies produced by the mulit-beam echosounders, sub-bottom profilers, and pingers than to the dominant low frequencies produced by the airguns and vessel. A more comprehensive review of the relevant background information for odontocetes appears in Section 3.6.4.3, Section 3.7.4.3 and Appendix E of the NSF/USGS PEIS (2011).

Masking effects of pulsed sounds (even from large arrays of airguns) on marine mammal calls and other natural sounds are expected to be limited. 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. Some baleen and toothed whales are known to continue calling in the presence of seismic pulses, and their calls can usually be heard 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 North Atlantic 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 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). Dilorio and Clark (2009) found evidence of increased calling by blue whales during operations by a lower-energy seismic source (i.e., sparker). Dolphins and porpoises commonly are heard calling while airguns are 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.

Pinnipeds have the most sensitive hearing and/or produce most of their sounds in frequencies higher than the dominant components of airgun sound, but there is some overlap in the frequencies of the airgun pulses and the calls. However, the intermittent nature of airgun pules presumably reduces the potential for masking.

Marine mammals are thought to be able to compensate for masking by adjusting their acoustic behavior through shifting call frequencies, increasing call volume, and increasing vocalization rates. For example blue whales are found to increase call rates when exposed to noise from seismic surveys in the St. Lawrence Estuary (Dilorio and Clark, 2009). The North Atlantic right whales (

Eubalaena glacialis

) exposed to high shipping noise increased call frequency (Parks

et al.,

2007), while some humpback whales respond to low-frequency active sonar playbacks by increasing song length (Miller

et al.,

2000). In general, NMFS expects the masking effects of seismic pulses to be minor, given the normally intermittent nature of seismic pulses.

Behavioral Disturbance

Marine mammals may behaviorally react to sound when exposed to anthropogenic noise. 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). These behavioral reactions are often shown as: Changing durations of surfacing and dives, number of blows per surfacing, or moving direction and/or speed; reduced/increased vocal activities; changing/cessation of certain behavioral activities (such as socializing or feeding); visible startle response or aggressive behavior (such as tail/fluke slapping or jaw clapping); avoidance of areas where noise sources are located; and/or flight responses (e.g., pinnipeds flushing into the water from haul-outs or rookeries). 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).

The biological significance of many of these behavioral disturbances is difficult to predict, especially if the detected disturbances appear minor. However, the consequences of behavioral modification could be expected to be biologically significant if the change affects growth, survival, and/or reproduction. Some of these significant behavioral modifications include:

• Change in diving/surfacing patterns (such as those thought to be causing beaked whale stranding due to exposure to military mid-frequency tactical sonar);

• Habitat abandonment due to loss of desirable acoustic environment; and

• Cessation of feeding or social interaction.

The onset of behavioral disturbance from anthropogenic noise depends on both external factors (characteristics of noise sources and their paths) and the receiving animals (hearing, motivation, experience, demography) and is also difficult to predict (Richardson

et al.,

1995; Southall

et al.,

2007). 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 sound. In most cases, this approach likely overestimates the numbers of marine mammals that would be affected in some biologically-important manner.

Baleen Whales

—Baleen whales generally tend to avoid operating airguns, but avoidance radii are quite variable (reviewed in Richardson

et al.,

1995; Gordon

et al.,

2004). 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, 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. In the cases of migrating gray (

Eschrichtius robustus

) and bowhead (

Balaena mysticetus

) whales, the observed changes in behavior appeared to be of little or no biological consequence to the animals (Richardson,

et al.,

1995). They simply 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 (rms) 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 4 to 15 km (2.2 to 8.1 nmi) 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 have shown that some species of baleen whales, notably bowhead, gray, and humpback whales, at times, show strong avoidance at received levels lower than 160 to 170 dB re 1 μPa (rms).

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 airgun (20 in

3

) with source level of 227 dB re 1 µPa (p-p). In the 1998 study, they documented that avoidance reactions began at 5 to 8 km (2.7 to 4.3 nmi) from the array, and that those reactions kept most pods approximately 3 to 4 km (1.6 to 2.2 nmi) from the operating seismic boat. In the 2000 study, they noted localized displacement during migration of 4 to 5 km (2.2 to 2.7 nmi) by traveling pods and 7 to 12 km (3.8 to 6.5 nmi) 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 (rms) for humpback pods containing females, and at the mean closest point of approach distance the received level was 143 dB re 1 μPa (rms). The initial avoidance response generally occurred at distances of 5 to 8 km (2.7 to 4.3 nmi) from the airgun array and 2 km (1.1 nmi) 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 (rms).

Data collected by observers during several seismic surveys in the Northwest Atlantic 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 vs. non-seismic periods (Moulton and Holst, 2010).

Humpback whales on their summer feeding grounds in southeast 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 dB re 1 μPa (rms). However, Moulton and Holst (2010) reported that humpback whales monitored during seismic surveys in the Northwest Atlantic had lower sighting rates and were most often seen swimming away from the vessel during seismic periods compared with periods when airguns were silent.

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). 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).

Reactions of migrating and feeding (but not wintering) gray whales to seismic surveys have been studied. 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) rms basis, and that 10 percent of feeding whales interrupted feeding at received levels of 163 dB re 1 µPa (rms). 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).

Various species of

Balaenoptera

(blue, sei, fin, and minke whales) have occasionally been seen in areas ensonified by airgun pulses (Stone, 2003; MacLean and Haley, 2004; Stone and Tasker, 2006), and calls from blue and fin whales have been localized 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 versus silent (Stone, 2003; Stone and Tasker, 2006). However, these whales tended to exhibit localized avoidance, remaining significantly further (on average) from the airgun array during seismic operations compared with non-seismic periods (Stone and Tasker, 2006). Castellote

et al.

(2010) reported that singing fin whales in the Mediterranean moved away from an operating airgun array.

Ship-based monitoring studies of baleen whales (including blue, fin, sei, minke, and humpback whales) in the Northwest Atlantic found that overall, this group had lower sighting rates during seismic vs. 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. It is not known 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, 2010). The western Pacific gray whale population did not seem 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, 2010). The history of coexistence between seismic surveys and baleen whales suggests that brief exposures to sound pulses from any single seismic survey are unlikely to result in prolonged effects.

Toothed Whales

—Little systematic information is available about reactions of toothed whales to noise pulses. Few studies similar to the more extensive baleen whale/seismic pulse work summarized above have been reported for toothed whales. 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 PSOs 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. Captive bottlenose dolphins and beluga whales (

Delphinapterus leucas

) 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 of 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 (

Phocoenoides dalli

) (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 sperm 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. 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 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 ongoing nearby (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, seem to be confined to a smaller radius than has been observed for the more responsive of some mysticetes. However, other data suggest that some odontocete species, including harbor porpoises, may be more responsive than might be expected given their poor low-frequency hearing. Reactions at longer distances may be particularly likely when sound propagation conditions are conducive to transmission of the higher frequency components of airgun sound to the animals' location (DeRuiter

et al.,

2006; Goold and Coates, 2006; Tyack

et al.,

2006; Potter

et al.,

2007).

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. In the Beaufort Sea, some ringed seals avoided an area of 100 m 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 (

Pusa hispida

) 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 (

Phoca vitulina

) and California sea lions (

Zalophus californianus

) 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).

During seismic exploration off Nova Scotia, gray seals (

Halichoerus grypus

) exposed to noise from airguns and linear explosive charges did not react strongly (J. Parsons in Greene

et al.,

1985). Pinnipeds in both water and air, sometimes tolerate strong noise pulses from non-explosive and explosive scaring devices, especially if attracted to the area for feeding and reproduction (Mate and Harvey, 1987; Reeves

et al.,

1996). Thus pinnipeds are expected to be rather tolerant of, or habituate to, repeated underwater sounds from distant seismic sources, at least when the animals are strongly attracted to the area.

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, Carder, Schlundt, and Ridgway, 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 (TTS) (Southall

et al.,

2007). Researchers have studied TTS in certain captive odontocetes and pinnipeds exposed to strong sounds (reviewed in Southall

et al.,

2007). However, there has been no specific documentation of TTS let alone permanent hearing damage, i.e., permanent threshold shift (PTS), in free-ranging marine mammals exposed to sequences of airgun pulses during realistic field conditions.

Temporary Threshold Shift

—TTS is the mildest form of hearing impairment that can occur during exposure to a strong sound (Kryter, 1985). While experiencing TTS, the hearing threshold rises and a sound must be stronger in order to be heard. At least in terrestrial mammals, TTS can last from minutes or hours to (in cases of strong TTS) days. For sound exposures at or somewhat above the TTS threshold, hearing sensitivity in both terrestrial and marine mammals recovers rapidly after exposure to the noise ends. Few data on sound levels and durations necessary to elicit mild TTS have been obtained for marine mammals, and none of the published data concern TTS elicited by exposure to multiple pulses of sound. Available data on TTS in marine mammals are summarized in Southall

et al.

(2007). Table 2 (above) presents the estimated distances from the

Palmer'

s airguns at which the received energy level (per pulse, flat-weighted) would be expected to be greater than or equal to 180 and 190 dB re 1 μPa (rms).

To avoid the potential for injury, NMFS (1995, 2000) concluded that cetaceans and pinnipeds should not be exposed to pulsed underwater noise at received levels exceeding 180 and 190 dB re 1 μPa (rms). NMFS believes that to avoid the potential for Level A harassment, cetaceans and pinnipeds should not be exposed to pulsed underwater noise at received levels exceeding 180 and 190 dB re 1 μPa (rms), respectively. The established 180 and 190 dB (rms) criteria are not considered to be the levels above which TTS might occur. Rather, they are the received levels above which, in the view of a panel of bioacoustics specialists convened by NMFS before TTS measurements for marine mammals started to become available, one could not be certain that there would be no injurious effects, auditory or otherwise, to marine mammals. NMFS also assumes that cetaceans and pinnipeds exposed to levels exceeding 160 dB re 1 μPa (rms) may experience Level B harassment.

For toothed whales, researchers have derived TTS information for odontocetes from studies on the bottlenose dolphin and beluga. The experiments show that exposure to a single impulse at a received level of 207 kPa (or 30 psi, p-p), which is equivalent to 228 dB re 1 Pa (p-p), resulted in a 7 and 6 dB TTS in the beluga whale at 0.4 and 30 kHz, respectively. Thresholds returned to within 2 dB of the pre-exposure level within 4 minutes of the exposure (Finneran

et al.,

2002). For the

one harbor porpoise tested, the received level of airgun sound that elicited onset of TTS was lower (Lucke

et al.,

2009). If these results from a single animal are representative, it is inappropriate to assume that onset of TTS occurs at similar received levels in all odontocetes (

cf.

Southall

et al.,

2007). Some cetaceans apparently can incur TTS at considerably lower sound exposures than are necessary to elicit TTS 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 TTS. 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 TTS onset may also be higher in baleen whales than those of odontocetes (Southall

et al.,

2007).

In pinnipeds, researchers have not measured TTS 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 TTS at somewhat lower received levels than do small odontocetes exposed for similar durations (Kastak

et al.,

1999, 2005; Ketten

et al.,

2001). The TTS threshold for pulsed sounds has been indirectly extimated as being an SEL of approximately 171 dB re 1 μPa

2

·s (Southall

et al.,

2007) which would be equivalent to a single pulse with a received level of approximately 181 to 186 dB re 1 μPa (rms), or a series of pulses for which the highest rms values are a few dB lower. Corresponding values for California sea lions and northern elephant seals (

Mirounga angustirostris

) are likely to be higher (Kastak

et al.,

2005).

Permanent Threshold Shift

—When PTS 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 PTS 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 TTS, there has been further speculation about the possibility that some individuals occurring very close to airguns might incur PTS (e.g., Richardson

et al.,

1995, p. 372

ff;

Gedamke

et al.,

2008). Single or occasional occurrences of mild TTS are not indicative of permanent auditory damage, but repeated or (in some cases) single exposures to a level well above that causing TTS onset might elicit PTS.

Relationships between TTS and PTS thresholds have not been studied in marine mammals but are assumed to be similar to those in humans and other terrestrial mammals (Southall

et al.,

2007). PTS might occur at a received sound level at least several dBs above that inducing mild TTS if the animal were exposed to strong sound pulses with rapid rise times. Based on data from terrestrial mammals, a precautionary assumption is that the PTS threshold for impulse sounds (such as airgun pulses as received close to the source) is at least 6 dB higher than the TTS threshold on a peak-pressure basis, and probably greater than 6 dB (Southall

et al.,

2007).

Given the higher level of sound necessary to cause PTS as compared with TTS, it is considerably less likely that PTS 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

—Marine mammals close to underwater detonations of high explosives can be killed or severely injured, and the auditory organs are especially susceptible to injury (Ketten

et al.,

1993; Ketten, 1995). However, explosives are no longer used in marine waters for commercial seismic surveys or (with rare exceptions) for seismic research. These methods have been replaced entirely by airguns or related non-explosive pulse generators. Airgun

pulses are less energetic and have slower rise times, and there is no specific evidence that they can cause serious injury, death, or stranding even in the case of large airgun arrays. However, the association of strandings of beaked whales with naval exercises involving mid-frequency active sonar (non-pulse sound) and, in one case, the co-occurrence of an L-DEO seismic survey (Malakoff, 2002; Cox

et al.,

2006), has raised the possibility that beaked whales exposed to strong “pulsed” sounds could also be susceptible to injury and/or behavioral reactions that can lead to stranding (e.g., Hildebrand, 2005; Southall

et al.,

2007).

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 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. 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 2 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 expect that the same to marine mammals will result from military sonar and seismic surveys. 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 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, there was a stranding of two Cuvier's beaked whales in the Gulf of California, Mexico, when the L-DEO vessel R/V

Maurice Ewing

was 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). No injuries of beaked whales are anticipated during the proposed study because of:

(1) The high 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 L-DEO 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, some odontocetes, and some pinnipeds, are especially unlikely to incur non-auditory physical effects.

Potential Effects of Other Acoustic Devices and Sources

Multibeam Echosounder

NSF and ASC will operate the Simrad EM120 multibeam echosounder from the source vessel during the planned study. Sounds from the multibeam echosounder are very short pulses, occurring for 15 ms, depending on water depth. Most of the energy in the sound pulses emitted by the multibeam echosounder is at frequencies near 12 kHz, and the maximum source level is 242 dB re 1 μPa (rms). The beam is narrow (1 to 2°) in fore-aft extent and wide (150°) in the cross-track extent. Each ping consists of nine (in water greater than 1,000 m deep) consecutive 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 nine segments. Also, marine mammals that encounter the Simrad EM120 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 ship (where the beam is narrowest) are especially unlikely to be ensonified for more than one 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 a multibeam 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 TTS.

Navy sonars that have been linked to avoidance reactions and stranding of cetaceans: (1) Generally have longer pulse duration than the Simrad EM120; and (2) are often directed close to horizontally, as well as omnidirectional, versus more downward and narrowly for the multibeam echosounder. The area of possible influence of the multibeam 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 NSF and ASC'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. Possible effects of a multibeam echosounder on marine mammals are described below.

Masking

—Marine mammal communications will not be masked appreciably by the multibeam echosounder 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 multibeam echosounder 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 (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 (656.2 ft) (Frankel, 2005). When a 38 kHz echosounder and a 150 kHz acoustic Doppler current profiler were transmitting during studies in the Eastern Tropical Pacific, 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 second tonal signals at frequencies similar to those that will be emitted by the multibeam echosounder used by NSF and ASC, 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 a multibeam echosounder.

Hearing Impairment and Other Physical Effects

—Given several stranding events that have been associated with the operation of naval sonar in specific circumstances, there is concern that mid-frequency sonar sounds can cause serious impacts to marine mammals (see above). However, the multibeam echosounder proposed for use by NSF and ASC is quite different than sonar used for Navy operations. Pulse duration of the multibeam echosounder is very short relative to the naval sonar. Also, at any given location, an individual marine mammal would be in the beam of the multibeam echosounder 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 multibeam echosounder rather drastically relative to that from naval sonar.

NMFS believes that the brief exposure of marine mammals to one pulse, or small numbers of signals, from the multi-beam echosounder in this particular case is not likely to result in the harassment of marine mammals.

Single-Beam Echosounder

NSF and ASC will operate the Knudsen 3260 and Bathy 2000 single-beam echosounders from the source vessel during the planned study. Sounds from the single-beam echosounder are very short pulses, depending on water depth. Most of the energy in the sound pulses emitted by the singlebeam echosounder is at frequencies near 12 kHz for bottom-tracking purposes or at 3.5 kHz in the sub-bottom profiling mode. The sonar emits energy in a 30° beam from the bottom of the ship. Marine mammals that encounter the Simrad EM120 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 ship (where the beam is narrowest) are especially unlikely to be ensonified for more than one 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 a multibeam 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 TTS.

Navy sonars that have been linked to avoidance reactions and stranding of cetaceans: (1) Generally have longer pulse duration than the Simrad EM120; and (2) are often directed close to horizontally versus more downward for the echosounder. The area of possible influence of the single-beam 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 NSF and ASC'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. Possible effects of a single-beam echosounder on marine mammals are described below.

Masking

—Marine mammal communications will not be masked appreciably by the single-beam echosounder 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 single-beam echosounder signals (12 or 3.5 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 (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 (656.2 ft) (Frankel, 2005). When a 38 kHz echosounder and a 150 kHz ADCP were transmitting during studies in the Eastern Tropical Pacific, 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 second tonal signals at frequencies similar to those that will be emitted by the single-beam echosounder used by NSF and ASC, 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 a single-beam 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 single-beam echosounder proposed for use by NSF and ASC is quite different than sonar used for Navy operations. Pulse duration of the single-beam echosounder is very short relative to the naval sonar. Also, at any given location, an individual marine mammal would be in the beam of the single-beam echosounder 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 single-beam echosounder rather drastically relative to that from naval sonar.

NMFS believes that the brief exposure of marine mammals to one pulse, or small numbers of signals, from the single-beam echosounder in this particular case is not likely to result in the harassment of marine mammals.

Acoustic Doppler Current Profilers

NSF and ASC will operate the ADCP Teledyne RDI VM-150 and ADCP Ocean Surveyor OS-38 from the source vessel during the planned study. Most of the energy in the sound pulses emitted by the ADCPs operate at frequencies near 150 kHz, and the maximum source level is 223.6 dB re 1 μPa (rms). Sound energy from the ADCP is emitted as a 30° conically-shaped beam. Marine mammals that encounter the ADCPs 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 ship (where the beam is narrowest) are especially unlikely to be ensonified for more than one 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 the ADCPs 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 TTS.

Navy sonars that have been linked to avoidance reactions and stranding of cetaceans: (1) Generally have longer pulse duration than the ADCPs; and (2) are often directed close to horizontally versus more downward for the ADCPs. The area of possible influence of the multibeam 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 NSF and ASC'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. Possible effects of the ADCPs on marine mammals are described below.

Masking

—Marine mammal communications will not be masked appreciably by the ADCP signals given the low duty cycle of the ADCPs and the brief period when an individual mammal is likely to be within its beam. Furthermore, in the case of baleen whales, the ADCP signals (150 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 (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 (656.2 ft) (Frankel, 2005). When a 38 kHz echosounder and a 150 kHz ADCP were transmitting during studies in the Eastern Tropical Pacific, 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 second tonal signals at frequencies similar to those that will be emitted by the multibeam echosounder used by NSF and ASC, 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 a multibeam 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 multibeam echosounder proposed for use by NSF and ASC is quite different than sonar used for Navy operations. Pulse duration of the ADCP is very short relative to the naval sonar. Also, at any given location, an individual marine mammal would be in the beam of the multibeam echosounder 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 multibeam echosounder rather drastically relative to that from naval sonar.

NMFS believes that the brief exposure of marine mammals to one pulse, or small numbers of signals, from the multi-beam echosounder in this particular case is not likely to result in the harassment of marine mammals.

Acoustic Locator

NSF and ASC will operate the acoustic locator from the source vessel during the planned study during sampling. Sounds from the locator are very short pulses, occurring for 5 ms. Most of the energy in the sound pulses emitted by the acoustic locator is at frequencies near 12 kHz, and the maximum source level is 162 dB re 1 μPa (rms). Animals close to the ship (where the beam is narrowest) are especially unlikely to be ensonified for more than one 5 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 a

multibeam 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 TTS.

Masking

—Marine mammal communications will not be masked appreciably by the acoustic locator signals given the low duty cycle and the low source level. Furthermore, in the case of baleen whales, the acoustic locator 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 (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 (656.2 ft) (Frankel, 2005). When a 38 kHz echosounder and a 150 kHz ADCP were transmitting during studies in the Eastern Tropical Pacific, 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).

NMFS believes that the brief exposure of marine mammals to one pulse, or small numbers of signals, from the acoustic locator is not likely to result in the harassment of marine mammals.

Core and Dredge Sampling

During coring and dredging, the noise created by the mechanical action of the devices on the seafloor is expected to be perceived by nearby fish and other marine organisms and deter them from swimming toward the source. Coring and dredging activities would be highly localized and short-term in duration and would not be expected to significantly interfere with marine mammal behavior. The potential direct effects include temporary localized disturbance or displacement from associated sounds and/or physical movement/actions of the operations. Additionally, the potential indirect effects may consist of very localized and transitory/short-term disturbance of bottom habitat and associated prey in shallow-water areas as a result of coring, dredging, and sediment sampling (NSF/USGS PEIS, 2011). NMFS believes that the brief exposure of marine mammals to noise created from the mechanical action of the devices for core and dredge sampling is not likely to result in the harassment of marine mammals.

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 in 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 (especially low frequency specialists) 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' reaction varied when exposed to vessel noise and traffic. In some cases, beluga whales exhibited rapid swimming from ice-breaking vessels up to 80 km (43.2 nmi) 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; 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

Palmer

will be audible to marine mammals over a large distance, it is unlikely that marine mammals will respond behaviorally (in a manner that NMFS would consider harassment under the MMPA) 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, NMFS does not expect the

Palmer'

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 13 kts (24.1 km/hr, 14.9 mph).

NSF and ASC's proposed operation of one source vessel for the proposed low-energy seismic 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 low-energy seismic survey is unlikely due to the

Palmer'

s slow operational speed, which is typically 5 kts. Outside of seismic operations, the

Palmer'

s cruising speed would be approximately 10.1 to 14.5 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

Palmer

has a number of other advantages for avoiding ship strikes as compared to most commercial merchant vessels, including the following: the

Palmer'

s bridge and aloft observation tower offers good visibility to visually monitor for marine mammal presence; PSOs posted during operations scan the ocean for marine mammals and must report visual alerts of marine mammal presence to crew; and the PSOs receive extensive training that covers the fundamentals of visual observing for marine mammals and information about marine mammals and their identification at sea.

Entanglement

Entanglement can occur if wildlife becomes immobilized in survey lines, cables, nets, or other equipment that is moving through the water column. The proposed low-energy seismic survey would require towing approximately a single 100 m cable streamer. This large of an array carries the risk of entanglement for marine mammals. Wildlife, especially slow moving individuals, such as large whales, have a low probability of becoming entangled due to slow speed of the survey vessel and onboard monitoring efforts. In May 2011, there was one recorded entanglement of an olive ridley sea turtle (

Lepidochelys olivacea

) in the R/V

Marcus G. Langseth

's barovanes after the conclusion of a seismic survey off Costa Rica. There have been cases of baleen whales, mostly gray whales (Heyning, 1990), becoming entangled in fishing lines. The probability for entanglement of marine mammals is considered not significant because of the vessel speed and the monitoring efforts onboard the survey vessel.

Icebreaking Activities

Icebreakers produce more noise while breaking ice than ships of comparable size due, primarily, to the sounds of propeller cavitating (Richardson

et al.,

1995). Multi-year ice, which is expected to be encountered in the proposed survey area. Icebreakers commonly back and ram into heavy ice until losing momentum to make way. The highest noise levels usually occur while backing full astern in preparation to ram forward through the ice. Overall the noise generated by an icebreaker pushing ice was 10 to 15 dB greater than the noise produced by the ship underway in open water (Richardson

et al.,

1995). In general, the Antarctic and Southern Ocean is a noisy environment. Calving and grounding icebergs as well as the break-up of ice sheets, can produce a large amount of underwater noise. Little information is available about the increased sound levels due to icebreaking.

Cetaceans

—Few studies have been conducted to evaluate the potential interference of icebreaking noise with marine mammal vocalizations. Erbe and Farmer (1998) measured masked hearing thresholds of a captive beluga whale. They reported that the recording of a CCG ship,

Henry Larsen,

ramming ice in the Beaufort Sea, masked recordings of beluga vocalizations at a noise to signal pressure ratio of 18 dB, when the noise pressure level was eight times as high as the call pressure. Erbe and Farmer (2000) also predicted when icebreaker noise would affect beluga whales through software that combined a sound propagation model and beluga whale impact threshold models. They again used the data from the recording of the

Henry Larsen

in the Beaufort Sea and predicted that masking of beluga whale vocalizations could extend between 40 and 71 km (21.6 and 38.3 nmi) near the surface. Lesage

et al.

(1999) report that beluga whales changed their call type and call frequency when exposed to boat noise. It is possible that the whales adapt to the ambient noise levels and are able to communicate despite the sound. Given the documented reaction of belugas to ships and icebreakers it is highly unlikely that beluga whales would remain in the proximity of vessels where vocalizations would be masked.

Beluga whales have been documented swimming rapidly away from ships and icebreakers in the Canadian high Arctic when a ship approaches to within 35 to 50 km (18.9 to 27 nmi), and they may travel up to 80 km (43.2 nmi) from the vessel's track (Richardson

et al.,

1995). It is expected that belugas avoid

icebreakers as soon as they detect the ships (Cosens and Dueck, 1993). However, the reactions of beluga whales to ships vary greatly and some animals may become habituated to high levels of ambient noise (Erbe and Darmber, 2000).

There is little information about the effects of icebreaking ships on baleen whales. Migrating bowhead whales appeared to avoid an area around a drill site by greater than 25 km (13.5 mi) where an icebreaker was working in the Beaufort Sea. There was intensive icebreaking daily in support of the drilling activities (Brewer

et al.,

1993). Migrating bowheads also avoided a nearby drill site at the same time of year where little icebreaking was being conducted (LGL and Greeneridge, 1987). It is unclear as to whether the drilling activities, icebreaking operations, or the ice itself might have been the cause for the whale's diversion. Bowhead whales are not expected to occur in the proximity of the proposed action area.

Pinnipeds—Brueggeman

et al.

(1992) reported on the reactions of seals to an icebreaker during activities at two prospects in the Chukchi Sea. Reactions of seals to the icebreakers varied between the two prospects. Most (67%) seals did not react to the icebreaker at either prospect. Reaction at one prospect was greatest during icebreaking activity (running/maneuvering/jogging) and was 0.23 km (0.12 nmi) of the vessel and lowest for animals beyond 0.93 km (0.5 nmi). At the second prospect however, seal reaction was lowest during icebreaking activity with higher and similar levels of response during general (non-icebreaking) vessel operations and when the vessel was at anchor or drifting. The frequency of seal reaction generally declined with increasing distance from the vessel except during general vessel activity where it remained consistently high to about 0.46 km (0.25 nmi) from the vessel before declining.

Similarly, Kanik

et al.

(1980) found that ringed (

Pusa hispida

) and harp seals (

Pagophilus groenlandicus

) often dove into the water when an icebreaker was breaking ice within 1 km (0.5 nmi) of the animals. Most seals remained on the ice when the ship was breaking ice 1 to 2 km (0.5 to 1.1 nmi) away.

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 airgun operations during the proposed low-energy 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 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 in any particular area of the approximately 5,628 km

2

proposed project area, previously discussed in this notice.

The

Palmer

is designed for continuous passage at 3 kts through ice 1 m thick. During the proposed project the

Palmer

will typically encounter first- or second-year ice while avoiding thicker ice floes, particularly large intact multi-year ice, whenever possible. In addition, the vessel will follow leads when possible while following the survey route. As the vessel passes through the ice, the ship causes the ice to part and travel alongside the hull. This ice typically returns to fill the wake as the ship passes. The effects are transitory (i.e., hours at most) and localized (i.e., constrained to a relatively narrow swath perhaps 10 m (32.1 ft) to each side of the vessel. The

Palmer'

s maximum beam is 18.3 m (60 ft). Applying the maximum estimated amount of icebreaking (1,000 km), to the corridor opened by the ship, NSF and ASC anticipate that a maximum of approximately 18 km

2

(5.3 nmi

2

) of ice may be disturbed. This represents an inconsequential amount of the total ice present in the Southern Ocean.

Sea ice is important for pinniped life functions such as resting, breeding, and molting. Icebreaking activities may damage seal breathing holes and will also reduce the haul-out area in the immediate vicinity of the ship's track. Icebreaking along a maximum of 1,000 km of trackline will alter local ice conditions in the immediate vicinity of the vessel. This has the potential to temporarily lead to a reduction of suitable seal haul-out habitat. However, the dynamic sea-ice environment requires that seals be able to adapt to changes in sea, ice, and snow conditions, and they therefore create new breathing holes and lairs throughout the winter and spring (Hammill and Smith, 1989). In addition, seals often use open leads and cracks in the ice to surface and breathe (Smith and Stirling, 1975). Disturbance of the ice will occur in a very small area relative to the Southern Ocean ice-pack and no significant impact on marine mammals is anticipated by icebreaking during the proposed low-energy seismic survey. 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 and invertebrate populations is limited. 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. This makes drawing conclusions about impacts on fish problematic because, ultimately, the most important issues concern effects on marine fish populations, their

viability, and their availability to fisheries.

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 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. 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 NSF, ASC, and NMFS 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 TTS 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 TTS (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 nine 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 (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).

An experiment of the effects of a single 700 in

3

airgun was conducted in Lake Meade, Nevada (USGS, 1999). The data were used in an Environmental Assessment of the effects of a marine reflection survey of the Lake Meade fault system by the National Park Service (Paulson

et al.,

1993, in USGS, 1999). The airgun was suspended 3.5 m (11.5 ft) above a school of threadfin shad in Lake Meade and was fired three successive times at a 30 second interval. Neither surface inspection nor diver observations of the water column and bottom found any dead fish.

For a proposed seismic survey in Southern California, USGS (1999) conducted a review of the literature on the effects of airguns on fish and fisheries. They reported a 1991 study of the Bay Area Fault system from the continental shelf to the Sacramento River, using a 10 airgun (5,828 in

3

) array. Brezzina and Associates were hired by USGS to monitor the effects of the surveys and concluded that airgun operations were not responsible for the death of any of the fish carcasses observed. They also concluded that the airgun profiling did not appear to alter the feeding behavior of sea lions, seals, or pelicans observed feeding during the seismic surveys.

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.

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.

The Minerals Management Service (MMS, 2005) assessed the effects of a proposed seismic survey in Cook Inlet. The seismic survey proposed using three vessels, each towing two, four-airgun arrays ranging from 1,500 to 2,500 in

3

. MMS noted that the impact to fish populations in the survey area and adjacent waters would likely be very low and temporary. MMS also concluded that seismic surveys may displace the pelagic fishes from the area temporarily when airguns are in use. However, fishes displaced and avoiding the airgun noise are likely to backfill the survey area in minutes to hours after cessation of seismic testing. Fishes not dispersing from the airgun noise (e.g., demersal species) may startle and move short distances to avoid airgun emissions.

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 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).

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 provided in Appendix D of NSF/USGS's PEIS.

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 charac

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