Taking and Importing Marine Mammals: Taking Marine Mammals Incidental to U.S. Navy Operations of Surveillance Towed Array Sensor System Low Frequency Active Sonar

Federal RegisterJan 6, 2012

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DEPARTMENT OF COMMERCE

National Oceanic and Atmospheric Administration

50 CFR Part 218

[Docket No. 110808485-1534-01]

RIN 0648-BB14

Taking and Importing Marine Mammals: Taking Marine Mammals Incidental to U.S. Navy Operations of Surveillance Towed Array Sensor System Low Frequency Active Sonar

AGENCY:

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

ACTION:

Proposed rule; request for comments.

SUMMARY:

NMFS has received a request from the U.S. Navy (Navy) for authorization to take marine mammals, by harassment, incidental to conducting operations of Surveillance Towed Array Sensor System (SURTASS) Low Frequency Active (LFA) sonar in areas of the world's oceans (with the exception of Arctic and Antarctic waters and certain geographic restrictions), from August 16, 2012, through August 15, 2017. Pursuant to the Marine Mammal Protection Act (MMPA), NMFS is proposing regulations to govern that take and requests information, suggestions, and comments on these proposed regulations.

DATES:

Comments and information must be received no later than February 6, 2012.

ADDRESSES:

You may submit comments, identified by 0648-BB14, by any one of the following methods:

•

Electronic Submissions:

Submit all electronic public comments via the Federal eRulemaking Portal:

http://www.regulations.gov.

• Hand delivery or mailing of paper, disk, or CD-ROM comments should be addressed to P. Michael Payne, Chief, Permits, Conservation and Education Division, Office of Protected Resources, National Marine Fisheries Service, 1315 East-West Highway, Silver Spring, MD 20910.

Instructions:

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

http://www.regulations.gov

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.

NMFS will accept anonymous comments (enter N/A in the required fields if you wish to remain anonymous). Attachments to electronic comments will be accepted in Microsoft Word, Excel, WordPerfect, or Adobe PDF file formats only. To help NMFS process and review comments more efficiently, please use only one method to submit comments.

FOR FURTHER INFORMATION CONTACT:

Jeannine Cody, Office of Protected Resources, NMFS, (301) 427-8401.

SUPPLEMENTARY INFORMATION:

Availability

The public may obtain an electronic copy of the Navy's application by writing to the address specified above this section (see

ADDRESSES

), telephoning the contact listed above this section (see

FOR FURTHER INFORMATION CONTACT

), or by visiting the Internet at:

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

The Navy published a

Federal Register

Notice of Availability of a Draft Supplemental Environmental Impact Statement/Supplemental Overseas Environmental Impact Statement (DSEIS/SOEIS) for employment of SURTASS LFA sonar on August 19, 2011. The public may view the document at:

http://www.surtass-lfa-eis.com.

NMFS is participating in the development of the Navy's DSEIS/SOEIS as a cooperating agency under the National Environmental Policy Act of 1972.

Background

Sections 101(a)(5)(A) and (D) of the Marine Mammal Protection Act of 1972, as amended (MMPA; 16 U.S.C. 1361

et seq.

), direct the Secretary of Commerce (Secretary) to allow, upon request, the incidental, but not intentional, taking of small numbers of marine mammals by U.S. citizens who engage in a specified activity (other than commercial fishing) within a specified geographical region during periods of not more than five consecutive years each if certain findings are made and regulations are issued, or if the taking is limited to harassment, a notice of a proposed authorization is provided to the public for review.

Authorization 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 taking.

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.

The National Defense Authorization Act of 2004 (NDAA; Pub. L. 108-136) amended the MMPA by removing the “small numbers” and “specified geographical region” provisions and amended the definition of “harassment” as it applies to a “military readiness activity” (as defined in section 315(f) of Public Law 107-314; 16 U.S.C. 703 note) to read as follows (Section 3(18)(B) of the MMPA):

(i) Any act that injures or has the significant potential to injure a marine mammal or marine mammal stock in the wild [Level A Harassment]; or

(ii) Any act that disturbs or is likely to disturb a marine mammal or marine mammal stock in the wild by causing disruption of natural behavior patterns, including, but not limited to, migration, surfacing, nursing, breeding, feeding, or sheltering, to a point where such behavioral patterns are abandoned or significantly altered [Level B Harassment].

Summary of Request

On August 17, 2011, NMFS received an application from the U.S. Navy requesting authorization for the take of individuals of 94 species of marine mammals (70 cetaceans and 24 pinnipeds), by harassment, incidental to upcoming routine training and testing of the SURTASS LFA sonar system, as well as the use of the system on a maximum of four U.S. Naval ships during military operations in certain areas of the Pacific, Atlantic, and Indian Oceans and the Mediterranean Sea from August 16, 2012 through August 15, 2017. These routine training and testing and military operations are classified as military readiness activities. The Navy states, and NMFS concurs, that these military readiness activities may incidentally take marine mammals present within the Navy's operation areas by exposing them to sound from low-frequency active sonar sources. The Navy requests authorization to take individuals of 94 species of marine mammals by Level A and Level B Harassment, although as discussed later in this document, Level A Harassment will likely be avoided through the implementation of the Navy's proposed mitigation measures.

This is NMFS' third rule making for SURTASS LFA sonar operations under the MMPA. NMFS' current five-year

regulations governing incidental takings incidental to SURTASS LFA sonar activities and the related Letters of Authorizations (LOA) expire on August 15, 2012. NMFS published the first rule, effective from August 2002 through August 2007, on July 16, 2002 (67 FR 46712), and published the second rule on August 21, 2007 (72 FR 46846). For this proposed rule making, the Navy is proposing to conduct the same types of sonar activities as they have conducted over the past nine years.

Description of the Specified Activities

Purpose and Background

The Navy's mission is to maintain, train, equip, and operate combat-ready naval forces capable of accomplishing American strategic objectives, deterring maritime aggression, and maintaining freedom of the seas. Section 5062 of Title 10 of the United States Code directs the Secretary of the Navy and Chief of Naval Operations (CNO) to ensure the readiness of the U.S. naval forces.

The Secretary of the Navy and the CNO have established that anti-submarine warfare (ASW) is a critical part of the Navy's mission that requires access to both the open-ocean and littoral environments and continual training to prepare for all potential threats. The Navy is challenged by the increased difficulty in locating undersea threats solely by using passive acoustic technologies due to the advancement and use of quieting technologies in diesel-electric and nuclear submarines. The range at which the Navy's ASW assets are able to identify submarine threats is decreasing, and at the same time, improvements in torpedo design are extending the effective weapons range of subsea threats to the U.S. naval fleet.

To address these changing requirements for ASW readiness, the Navy developed SURTASS LFA sonar, which provides the Navy with a reliable and dependable system for long-range detection of quieter, harder-to-find submarines. Because low-frequency (LF) sound travels in seawater for greater distances than higher frequency sound, the Navy states that the SURTASS LFA sonar system would meet the need for improved detection and tracking of new-generation submarines at a longer range and would maximize the opportunity for U.S. armed forces to safely react to, and defend against, potential submarine threats while remaining a safe distance beyond a submarine's effective weapons range. Thus, the Navy believes that the active acoustic component in the SURTASS LFA sonar is an important augmentation to its passive and tactical systems, as its long-range detection capabilities can effectively counter the threat to the U.S. Navy and national security interests posed by quiet, diesel submarines.

Specified Activities

As previously mentioned, the Navy has requested MMPA authorization to take marine mammals incidental to the operation of up to four SURTASS LFA sonar systems for routine training and testing as well as for the use of the system during military operations from August 16, 2012 through August 15, 2017. The SURTASS LFA sonar system is a long-range, LF sonar (between 100 and 500 Hertz (Hz)) that has both active and passive components (see the Description of SURTASS LFA Sonar section later in this document). Use of the LFA sonar system could occur in the Pacific, Atlantic and Indian Oceans, and the Mediterranean Sea on a maximum of four naval surveillance vessels: the USNS ABLE, USNS EFFECTIVE, USNS IMPECCABLE, and the USNS VICTORIOUS. The Navy states that they will not operate SURTASS LFA sonar in Arctic and Antarctic waters. Further, the Navy also proposes to operate SURTASS LFA sonar such that the sound field does not exceed 180 decibels (dB) within 22 kilometers (km) (13.7 miles (mi); 12 nautical miles (nm) of land; or in proposed offshore biologically important areas (OBIA) for marine mammals, identified later in this document, in the Navy's application, and in the Navy's 2011 DSEIS/SOEIS (see Geographic Restrictions section later in this document).

Because of uncertainties in the world's political climate, the Navy cannot predict a detailed account of future operating locations and conditions. However, for analytical purposes, the Navy has developed a nominal annual deployment schedule and operational concept based on current LFA sonar operations since January 2003 and projected naval fleet requirements (See Table 1).

The Navy anticipates that a normal SURTASS LFA sonar deployment schedule for a single vessel would involve approximately 294 days per year at sea, which includes 240 days of active sonar transmissions and 54 days of transit. SURTASS LFA sonar would operate day and night in a variety of weather conditions. NMFS refers the reader to Table 1 for additional details on the nominal annual deployment schedule for SURTASS LFA sonar vessels.

Table 1—Example Annual Deployment Schedule for One Surveillance Vessel Using SURTASS LFA Sonar

On mission

Days

Off mission

Days

Transit

In-Port Upkeep

Active Operations:

432 transmission hours based on a 7.5% duty cycle

240

Regular Overhaul

Total Days on Mission

294

Total Days off Mission

Potential SURTASS LFA Sonar Operational Areas

Figure 1 depicts the potential areas of operation for SURTASS LFA sonar. Based on the Navy's current operational requirements, potential operations for SURTASS LFA sonar vessels from August 2012 through August 2017 would most likely include areas located in the Pacific, Indian, and Atlantic Oceans and Mediterranean Sea.

The Navy will not operate SURTASS LFA sonar in polar regions (i.e., Arctic and Antarctic waters) of the world (see shaded areas in Figure 1). The Arctic Ocean, the Bering Sea (including Bristol Bay and Norton Sound), portions of the Norwegian, Greenland, and Barents Seas north of 72° North (N) latitude, plus Baffin Bay, Hudson Bay, and the Gulf of St. Lawrence would be non-operational areas for SURTASS LFA sonar. In the Antarctic, the Navy will not conduct SURTASS LFA operations in areas south of 60° South (S) latitude. The Navy has excluded polar waters from operational planning because of the inherent inclement weather conditions and the navigational and operational (equipment) danger that icebergs pose to SURTASS LFA sonar vessels.

EP06JA12.000

The Navy must anticipate, or predict, where they have to operate in the next five years or so for the MMPA authorization. Naval forces are presently operating in several areas strategic to U.S national and international interests, including areas in the Atlantic Ocean, the Mediterranean Sea, the Indian Ocean and Persian Gulf, and the Pacific Rim. National Security needs may dictate that many of these operational areas will be close to ports and choke points, such as entrances to straits, channels, and canals. It is anticipated that many future naval conflicts are likely to occur within littoral or coastal areas. However, it is infeasible for the Navy to analyze all potential mission areas for all species and stocks for all seasons. Instead, the Navy projects where it intends to test, train, and operate for the next five-year authorization period based on today's political climate and provides NMFS with risk estimates for marine mammal stocks in the proposed areas of operation.

For this third rulemaking, the Navy has modeled and analyzed 19 operational areas for SURTASS LFA operations that would be relevant to U.S. national security interests (see Table 2). They include the following modeled areas: East of Japan; north Philippine Sea; west Philippine Sea; offshore Guam; Sea of Japan; East China Sea; the south China Sea; the northwest Pacific Ocean; the Hawai'i Range Complex; Offshore Southern California in the Southern California (SOCAL) Range Complex; the western Atlantic in the Atlantic Fleet Active Sonar (AFAST) Study Area/Jacksonville (JAX) operational area (OPAREA); the eastern North Atlantic (western approach); the Mediterranean and Ligurian Seas; the Arabian Sea; the Andaman Sea (approaches to the Strait of Malacca); the Panama Canal (western approach); and the northeast Australian Coast.

Table 2—Potential SURTASS LFA Sonar Operating Areas That the Navy Modeled for the DSEIS/OEIS (DoN, 2011) and the MMPA LOA Application

Modeled site

Location

(latitude/

longitude)

Modeled site

Location

(latitude/

longitude)

East of Japan

38° N, 148° E

Hawaii South (Hawai'i Range Complex)

19.5° N, 158.5° W.

North Philippine Sea

29° N, 136° E

Offshore Southern California (Southern California (SOCAL) Range Complex)

32° N, 120° W.

West Philippine Sea

22° N, 124° E

Western Atlantic (off Florida) (Atlantic Fleet Active Sonar (AFAST) Study Area/Jacksonville

30° N, 78° W.

Offshore Guam (Mariana Islands Range Complex, outside Mariana Trench)

11° N, 145° E

Eastern North Atlantic (western approach)

56.5° N, 10° W.

Sea of Japan

39° N, 132° E

Mediterranean Sea—Ligurian Sea

43° N, 8° E.

East China Sea

26° N, 125° E

Arabian Sea

20°N, 65°E.

South China Sea

21° N, 119° E

Andaman Sea (approaches to the Strait of Malacca)

7.5° N, 96° E.

NW Pacific 25° to 40° N

30° N, 165° E

Panama Canal (western approach)

5° N, 81° W.

NW Pacific 10° to 25° N

15° N, 165° E

Northeast Australian Coast

23° S, 155° E.

Hawai'i North (Hawai'i Range Complex)

25° N, 158° W

Acoustic stimuli (i.e., increased underwater sound) generated during the transmission of low-frequency acoustic signals by the SURTASS LFA sonar system has the potential to cause take of marine mammals in the operational areas. The operation of the SURTASS LFA sonar system during at-sea operations would result in the generation of sound or pressure waves in the water at or above levels that NMFS has determined would result in take. This is the principal means of marine mammal taking associated with these military readiness activities and the Navy has requested an authorization to take 94 species of marine mammals by Level A and Level B harassment. At no point are there expected to be more than four systems in use, and thus this proposed rule analyzes the impacts on marine mammals due to the deployment of up to four LFA sonar systems from 2012 through 2017.

In addition to the use of active acoustic sources, the Navy's activities include the operation and movement of vessels that are necessary to conduct the routine training and testing as well as the use of the system during military operations. This document also analyzes the effects of this part of the activities. However, NMFS does not anticipate take to result from collision with any of the four SURTASS LFA vessels because each vessel moves at a relatively slow speed, for a relatively short period of time. It is likely that any marine mammal would be able to avoid the surveillance vessels.

Description of SURTASS LFA Sonar

SONAR is an acronym for Sound Navigation and Ranging, and its definition includes any system (biological or mechanical) that uses underwater sound, or acoustics, for detection, monitoring, and/or communications. Active sonar is the transmission of sound energy for the purpose of sensing the environment by interpreting features of received signals. Active sonar detects objects by creating a sound pulse or ping that is transmitted through the water and reflects off the target, returning in the form of an echo. Passive sonar detects the transmission of sound waves created by an object.

The SURTASS LFA sonar system is a long-range, all-weather sonar system that has both active and passive components. LFA, the active system component (which allows for the detection of an object that is not generating noise), is comprised of source elements (called projectors) suspended vertically on a cable beneath the surveillance vessel. The projectors produce an active sound pulse (i.e., a ping) by converting electrical energy to mechanical energy by setting up vibrations or pressure disturbances within the water to produce a ping. The Navy uses LFA as an augmentation to SURTASS operations when passive system performance is inadequate. SURTASS, the passive part of the system, uses hydrophones (i.e., underwater microphones) to detect sound emitted or reflected from submerged targets, such as submarines. The SURTASS hydrophones are mounted on a horizontal line array that is towed behind the surveillance vessel. The Navy then processes and evaluates the returning signals or echoes, which are usually below background or ambient sound level, to identify and classify potential underwater targets.

LFA Active Component

The active component of the SURTASS LFA sonar system consists of up to 18 projectors suspended beneath the surveillance vessel in a vertical line array. The expected water depth at the center of the array is approximately 400 ft (121.9 m). The SURTASS LFA sonar projectors transmit in the low-frequency band (between 100 and 500 Hz) and the Navy will not transmit the SURTASS LFA sonar signal at a frequency greater than 500 Hz. The source level of an individual projector in the SURTASS LFA sonar array is approximately 215 dB re: 1 µPa at 1 m or less. (Sound pressure is the sound force per unit area and is usually measured in micropascals (μPa), where one Pascal (Pa) is the pressure resulting from a force of one newton exerted over an area of one square meter. The commonly used reference pressure level in underwater acoustics is 1 μPa at 1 m, and the units are decibels (dB) re: 1 μPa at 1 m). Because of the physics involved in acoustic beamforming (i.e., a method of mapping noise sources by differentiating sound levels based upon the direction from which they originate) and sound transmission loss processes, the SURTASS LFA sonar array cannot have a sound pressure level (SPL) higher than the SPL of an individual projector.

The SURTASS LFA sonar acoustic transmission is an omnidirectional beam (a full 360 degrees (°)) in the horizontal plane. The LFA sonar system also has a narrow vertical beam that the vessel's crew can steer above or below the horizontal plane. The typical SURTASS LFA sonar signal is not a constant tone, but rather a transmission of various signal types that vary in frequency and duration (including continuous wave (CW) and frequency-modulated (FM) signals). A complete sequence of sound transmissions, also referred to by the Navy as a “ping” or a wavetrain, can last as short as six seconds (sec) to as long as 100 sec with an average length of 60 sec. Within each ping, the duration of any continuous frequency sound transmission is no longer than 10 sec and the time between pings is typically from six to 15 minutes (min). Based on the Navy's historical operating parameters over the past nine years, the average duty cycle (i.e., the ratio of sound “on” time to total time) for LFA sonar is normally 7.5 to 10 percent and the duty cycle is not expected to exceed 20 percent.

Compact LFA Active Component

At present, the USNS IMPECCABLE is the only naval vessel with an operational LFA sonar system. To meet future undersea warfare requirements in littoral waters, the Navy has developed a compact LFA (CLFA) sonar system now deployed on its three smaller surveillance vessels (i.e., the USNS ABLE, EFFECTIVE, and VICTORIOUS). In the application, the Navy indicates that the operational characteristics of the active component CLFA are comparable to the existing LFA systems and that the potential impacts from CLFA will be similar to the effects from the existing LFA sonar system. CLFA consists of smaller projectors that weigh 142,000 lbs (64,410 kilograms (kg)), which is 182,000 lbs (82,554 kg) less that the mission weight of the LFA projectors on the USNS IMPECCABLE. The CLFA sonar system also consists of up to 18 projectors suspended beneath the surveillance vessel in a vertical line array and the CLFA sonar projectors transmit in the low-frequency band (also between 100 and 500 Hz). Similar to the active component of the LFA system, the source level of an individual projector in the CLFA sonar array is approximately 215 dB re: 1 µPa or less.

For the analysis in this document, NMFS will use the term LFA to refer to both the LFA sonar system and/or the CLFA sonar system, unless otherwise specified.

SURTASS Passive Component

The passive component of the SURTASS LFA system consists of a SURTASS Twin-line (TL-29A) horizontal line array mounted with hydrophones. The Y-shaped array is 1,000 ft (305 m) in length and has an operational depth of 500 to 1,500 ft (152.4 to 457.2 m). The SURTASS LFA sonar vessel typically maintains a speed of at least 3.4 mph (5.6 km/hr; 3 knots (kts)) to tow the array astern of the vessel in the correct horizontal configuration.

High-Frequency Active Sonar

Although technically not part of the SURTASS LFA sonar system, the Navy also proposes to use a high-frequency sonar system, called the High Frequency Marine Mammal Monitoring sonar (HF/M3 sonar), developed by the Navy and Scientific Solutions, Inc., to detect and locate marine mammals within the SURTASS LFA sonar operational areas. This enhanced commercial fish-finding sonar, mounted at the top of the SURTASS LFA sonar vertical line array, has a source level of 220 dB re: 1 µPa at 1 m with a frequency range from 30 to 40 kilohertz (kHz). The duty cycle is variable, but is normally below between three to four percent and the maximum pulse duration is 40 milliseconds. The HF/M3 sonar has four transducers with 8° horizontal and 10° vertical beamwidths, which sweep a full 360° in the horizontal plane every 45 to 60 sec with a maximum range of approximately 1.2 mi (2 km).

Vessel Specifications

The Navy proposes to deploy the SURTASS LFA sonar system on a maximum of four U.S. Naval ships: the USNS ABLE (T-AGOS 20), the USNS EFFECTIVE (T-AGOS 21), the USNS IMPECCABLE (T-AGOS 23) and the USNS VICTORIOUS (T-AGOS 19).

The USNS ABLE, EFFECTIVE, and VICTORIOUS, are twin-hulled ocean surveillance ships. Each vessel has a length of 235 feet (ft) (71.6 meters (m)); a beam of 93.6 ft (28.5 m); a maximum draft of 25 ft (7.6 m); and a full load displacement of 3,396 tons (3,451 metric tons). A twin-shaft diesel electric engine provides 3,200 horsepower (hp), which drives two propellers.

The USNS IMPECCABLE, also a twin-hulled ocean surveillance ship, has a length of 281.5 ft (85.8 m); a beam of 95.8 ft (29.2 m); a maximum draft of 26 ft (7.9 m); and a full load displacement of 5,368 tons (5,454 metric tons). A twin-shaft diesel electric engine provides 5,000 hp, which drives two propellers.

The operational speed of each vessel during sonar operations will be approximately 3.4 miles per hour (mph) (5.6 km per hour (km/hr); 3 kts) and each vessel's cruising speed outside of sonar operations would be approximately 11.5 to 14.9 mph (18.5 to 24.1 km/hr; 10 to 13 kts). The expected minimum water depth at which the SURTASS LFA vessel would operate is 656.2 ft (200 m) and the vessel will generally travel in straight lines or in oval-shaped (i.e., racetrack) patterns depending on the operational scenario. Also, each SURTASS LFA sonar vessel would operate independently of, or in conjunction with, other naval air, surface or submarine assets.

Each vessel also has an observation area on the bridge from where lookouts will monitor for marine mammals before and during the proposed sonar operations. When stationed on the bridge of the USNS ABLE, EFFECTIVE, or VICTORIOUS, the lookout's eye level will be approximately 32 ft (9.7 m) above sea level providing an unobstructed view around the entire vessel. For the USNS IMPECCABLE, the lookout's eye level will be approximately 45 ft (13.7 m) above sea level.

Description of Real-Time SURTASS LFA Sonar Sound Field Modeling

This section explains how the Navy will determine the propagation of LFA sonar signals in the ocean and the distance from the SURTASS LFA sonar source to the 180-dB re: 1 µPa at 1 m isopleth (i.e., the basis for the proposed LFA sonar mitigation zone for marine mammals). NMFS provides this description to aid the public's understanding of this action. However, the actual physics governing the propagation of SURTASS LFA sound signals is extremely complex and dependent on numerous in-situ environmental factors.

Prior to commencing and during SURTASS LFA transmissions, the sonar operators on the vessel will measure oceanic conditions (such as sea water temperature, salinity, and depth) in the proposed action area. This information is required for the sonar technicians to accurately determine the speed at which sound travels and to determine the path that the sound would take through the water column at a particular location (i.e., the speed of sound in seawater varies directly with depth, temperature, and salinity).

The sonar operators use the near-real time environmental data and the Navy's underwater acoustic performance prediction models (updated every 12 hours or more frequently when meteorological or oceanographic conditions change) to generate a plot of sound speed versus depth, typically referred to as a sound speed profile (SSP). The SSP enables the technicians to determine the sound field by predicting the received levels of sound at various distances from the SURTASS LFA sonar source location. Modeling of the sound field in near-real time provides the information necessary to modify SURTASS LFA operations, including the delay or suspension of LFA sonar transmissions for mitigation.

Subchapter 3.1.2 of the SURTASS LFA Sonar 2011 DSEIS/SOEIS (DoN, 2011) discusses some of the environmental factors affecting sound propagation. Appendix B of the 2001 SURTASS LFA Sonar FOEIS/EIS (DoN, 2001) also provides an understanding concerning the general conditions of sound speed in the oceans. NMFS refers the public to these documents at

http://www.surtass-lfa-eis.com

for additional information.

Comments and Responses

On August 30, 2011 NMFS published a notice of receipt of an application for an LOA in the

Federal Register

(76 FR 53884) and requested comments and information from the interested public for 30 days. During the 30-day comment period, NMFS received two comments. One commenter opposed the project on the grounds that it would cause mortality to marine mammals. NMFS notes that the Navy has not requested lethal take of marine mammals in its application and, for the reasons described in this document, NMFS does not anticipate that any mortality will occur as a result of the Navy's activities. Therefore, the proposed rule only envisions the authorization of Level A and Level B harassment of marine mammals. The other comment, from an environmental non-governmental organization, expressed concerns about the geographic mitigation proposed in the Navy's DSEIS/SOEIS, focusing particularly on the process for identifying proposed offshore biologically important areas (OBIAs). NMFS undertook a systematic and scientifically supportable process for identifying OBIAs for this proposed rule making. This process is summarized in the Mitigation section of this proposed rule and detailed in the Navy's DSEIS/SOEIS.

The Marine Mammal Commission (MMC) also submitted comments to the Navy and NMFS. Generally, the MMC agreed that NMFS should propose regulations governing the take of marine mammals incidental to operation of SURTASS LFA sonar for a third five-year period. However, the MMC recommended that the Navy amend its application and related DSEIS/SOEIS to: (1) clarify the Navy's take request for marine mammals by Level A harassment; and (2) specify the numbers of marine mammals that could be taken by Level A and B harassment incidental to operating SURTASS LFA sonar, rather than providing only the probabilities of such takes. With respect to the first point, NMFS notes that the Navy's application specifically requests authorization for Level A harassment of

marine mammals incidental to SURTASS LFA sonar operations.

With respect to the MMC's second point, the percentages given in Tables 6 through 27 in the Navy's application are not probabilities, but rather indicate the percent of the affected stock for a specific marine mammal species. For the Navy's Level A and Level B harassment take request, that percentage is then multiplied by the number of animals in the relevant species or stock to arrive at an estimated number of animals that may be harassed by SURTASS LFA sonar operations. The Navy's approach to estimating Level A harassment and Level B harassment takes is consistent with the approach used in previous rules for SURTASS LFA sonar.

This proposed rule does not specify the number of marine mammals that may be taken in the proposed locations because these are determined annually through various inputs such as mission location, mission duration, and season of operation. As with the previous two rulemakings, this proposed rule analyzes a maximum of 12 percent takes by Level B harassment per stock annually that will be taken per stock annually, regardless of the number of LFA sonar vessels operating. The Navy will use the 12 percent cap (i.e., the maximum percentage of a stock that could be taken annually, not the probability of take) to guide its mission planning and annual LOA applications. For the annual applications for LOAs, the Navy proposes to present both the estimated percentage of stock incidentally harassed as well as the estimated number of animals that may be potentially harassed by SURTASS LFA sonar.

Description of Marine Mammals in the Area of the Specified Activities

Ninety-four (94) marine mammal species or populations/stocks have confirmed or possible occurrence within potential SURTASS LFA operational areas in certain areas of the Pacific, Atlantic, and Indian Oceans and the Mediterranean Sea. Twelve species of baleen whales (mysticetes), 58 species of toothed whales, dolphins, or porpoises (odontocetes), and 24 species of seals or sea lions (pinnipeds) could be affected by SURTASS LFA sonar operations.

Fifteen of the 94 marine mammal species are listed as endangered and three of the 94 marine mammal species are listed as threatened under the Endangered Species Act of 1973 (ESA; 16 U.S.C. 1531

et seq.

). Marine mammal species under NMFS' jurisdiction listed as endangered include: the blue whale (

Balaenoptera musculus

); fin whale (

Balaenoptera physalus

); sei whale (

Balaenoptera borealis

); humpback whale (

Megaptera novaeangliae

); bowhead whale (

Balaena mysticetus

); North Atlantic right whale (

Eubalaena glacialis

); North Pacific right whale (

Eubalaena japonica

); southern right whale (

Eubalaena australis

); gray whale (

Eschrichtius robustus

); sperm whale (

Physeter macrocephalus

); the Cook Inlet stock of beluga whale (

Delphinapterus leucas

); the Southern Resident population of Killer whale (

Orca orcinus

); the western distinct population segment (DPS) of the Steller sea lion (

Eumetopias jubatus

); Mediterranean monk seal (

Monachus monachus

); and Hawaiian monk seal (

Monachus schauinslandi

). Marine mammal species under NMFS' jurisdiction listed as threatened include: the eastern DPS of the Steller sea lion; the Guadalupe fur seal (

Arctocephalus townsendi

) and the southern DPS of the spotted seal (

Phoca largha

). The aforementioned threatened and endangered marine mammal species also are depleted under the MMPA.

In addition, the Hawaiian insular DPS of false killer whale (

Pseudorca crassidens

) is a candidate for proposed listing under the ESA. Also, three of the 94 species are considered depleted under the MMPA. They are: the western north Atlantic coastal stock of bottlenose dolphin (

Tursiops truncatus

); the northeastern offshore stock of the pantropical spotted dolphin (

Stenella attenuata

); and the eastern stock of the spinner dolphin (

Stenella longirostris

Ringed seals (

Phoca hispida

), bearded seals (

Erignathus barbatus

), Chinese river dolphins (

Lipotes vexillifer

) and vaquita (

Phocoena sinus

) do not have stocks designated within potential SURTASS LFA sonar operational areas (see Potential SURTASS LFA Operational Areas section). The ringed seal is found in the Northern Hemisphere with a circumpolar distribution ranging from 35° N to the North Pole. Bearded seals have a circumpolar distribution south of 85° N latitude, extending south into the southern Bering Sea in the Pacific and into Hudson Bay and southern Labrador in the Atlantic. The distribution of the Chinese river dolphin is limited to the main channel of a river section between the cities of Jingzhou and Jiangyin. The vaquita's distribution is restricted to the upper portion of the northern Gulf of California, mostly within the Colorado River delta. Based on the rare occurrence of these species in the Navy's designated operational areas (i.e., outside of Arctic waters or outside of the coastal standoff distance of 22 km (13. mi; 11.8 nmi)), the Navy and NMFS do not anticipate any take of ringed seals, bearded seals, Chinese river dolphins, and vaquita and therefore these species are not addressed further in this document.

The U.S. Fish and Wildlife Service (USFWS) is responsible for managing the following marine mammal species: southern sea otter (

Enhydra lutris

), polar bear (

Ursus maritimus

), walrus (

Odobenus rosmarus

), west African manatee (

Trichechus senegalensis

), Amazonian manatee (

Trichechus inunguis

), west Indian manatee (

Trichechus manatus

), and dugong (

Dugong dugon

). None of these species occur in geographic areas that would overlap with SURTASS LFA sonar operational areas. Therefore, the Navy has determined that routine training and testing of SURTASS LFA sonar as well as the use of the system during military operations would have no effect on the endangered or threatened species or the critical habitat of the ESA-listed species under the jurisdiction of the USFWS. These species are not considered further in this notice.

Tables 3 through 21 summarize the abundance, status under the ESA, and density estimates of the marine mammals that have confirmed or possible occurrence within 19 SURTASS LFA sonar operating areas in the Pacific, Indian, and Atlantic Oceans and Mediterranean Sea. The Navy states that they selected these 19 areas based on relevance to national security interests for this application. Because it is infeasible for the Navy to model enough representative sites to cover all potential SURTASS LFA sonar operating areas, the Navy provided 19 sites, based on the current political climate, as examples of potential operating areas in their application.

Information on how the density and stock/abundance estimates were derived for the selected mission sites is in the Navy's application. These data are derived from current, published source documentation, and provide general area information for each mission area with species-specific information on the animals that could occur in that area, including estimates for their stock abundance and density. The Navy developed the majority of the abundance and density estimates by first using estimates from line-transect surveys that occurred in or near each of the 19 model sites (e.g., Barlow, 2006). When density estimates were not available from a survey in the operating area, the Navy extrapolated density estimates from a region with similar oceanographic characteristics to that operating area. For example, the eastern

tropical Pacific has been extensively surveyed and provides a comprehensive understanding of marine mammals in temperate oceanic waters (Ferguson and Barlow, 2001, 2003). Further, the Navy pooled density estimates for species of the same genus if sufficient data are not available to compute a density for individual species or the species are difficult to distinguish at sea.

Table 3—Abundance and Density Estimates for the Marine Mammal Species, Species Groups, and Stocks Associated With the East of Japan Operational Area

Species

Stock name

Abundance

Density (animals/Km

)

ESA

Status

Blue whale (

Balaenoptera musculus

)

9,250

0.0002

Fin whale (

Balaenoptera physalus

)

9,250

0.0002

Sei whale (

Balaenoptera borealis

)

8,600

0.0006

Bryde's whale (

Balaenoptera edeni

)

WNP

20,501

0.0006

Minke whale (

Balaenoptera acutorostrata

)

WNP “O” Stock

25,049

0.0022

North Pacific right whale (

Eubalaena japonica

)

WNP

922

< 0.00001

Sperm whale (

Physeter macrocephalus

)

102,112

0.0010

Pygmy sperm whale (

Kogia breviceps

) Dwarf sperm whale (

Kogia sima

)

350,553

0.0031

Baird's beaked whale (

Berardius bairdii

)

WNP

8,000

0.0029

Cuvier's beaked whale (

Ziphius cavirostris

)

90,725

0.0054

Ginkgo-toothed beaked whale (

Mesoplodon ginkgodens

)

22,799

0.0005

Hubbs beaked whale (

Mesoplodon carhubbsi

)

22,799

0.0005

False killer whale (

Pseudorca crassidens

)

WNP-Pelagic

16,668

0.0036

Pygmy killer whale (

Feresa attenuata

)

WNP

30,214

0.0021

Short-finned pilot whale (

Globicephala macrorhynchus

)

WNP

53,608

0.0128

Risso's dolphin (

Grampus griseus

)

WNP

83,289

0.0097

Common dolphin (

Delphinus delphis

)

WNP

3,286,163

0.0761

Fraser's dolphin (

Lagenodelphis hosei

)

WNP

220,789

0.0040

Bottlenose dolphin (

Tursiops truncatus

)

WNP

168,791

0.0171

Pantropical spotted dolphin (

Stenella attenuata

)

WNP

438,064

0.0259

Striped dolphin (

Stenella coeruleoalba

)

WNP

570,038

0.0111

Spinner dolphin (

Stenella longirostris

)

WNP

1,015,059

0.0005

Pacific white-sided dolphin (

Lagenorhynchus obliquidens

)

WNP

931,000

0.0082

Rough-toothed dolphin (

Steno bredanensis

)

WNP

145,729

0.0059

NP = north Pacific; WNP = western north Pacific.

Refer to Table 5 of the Navy's application for literature references associated with abundance estimates presented in this table.

Refer to Table 5 of the Navy's application for literature references associated with density estimates presented in this table.

ESA Status: EN = Endangered; T = Threatened; NL = Not Listed.

Table 4—Abundance and Density Estimates for the Marine Mammal Species, Species Groups, and Stocks Associated With the North Philippine Sea Operational Area

Species

Stock name

Abundance

Density (animals/Km

)

ESA

Status

Bryde's whale

WNP

20,501

0.0006

Minke whale

WNP “O” Stock

25,049

0.0044

North Pacific right whale

WNP

922

< 0.00001

Sperm whale

102,112

0.0028

Pygmy sperm and Dwarf sperm whale

350,553

0.0031

Cuvier's beaked whale

90,725

0.0054

Blainville's beaked whale (

Mesoplodon densirostris

)

8,032

0.0005

Ginkgo-toothed beaked whale

22,799

0.0005

Killer whale (

Orca orcinus

)

12,256

0.0004

False killer whale

WNP-Pelagic

16,668

0.0029

Pygmy killer whale

WNP

30,214

0.0021

Melon-headed whale (

Peponocephala electra

)

WNP

36,770

0.0012

Short-finned pilot whale

WNP

53,608

0.0153

Risso's dolphin

WNP

83,289

0.0106

Common dolphin

WNP

3,286,163

0.0562

Fraser's dolphin

WNP

220,789

0.0040

Bottlenose dolphin

WNP

168,791

0.0146

Pantropical spotted dolphin

WNP

438,064

0.0137

Striped dolphin

WNP

570,038

0.0329

Spinner dolphin

WNP

1,015,059

0.0005

Pacific white-sided dolphin

WNP

931,000

0.0119

Rough-toothed dolphin

WNP

145,729

0.0059

NP = north Pacific; WNP = western north Pacific.

Refer to Table 5 of the Navy's application for literature references associated with abundance estimates presented in this table.

Refer to Table 5 of the Navy's application for literature references associated with density estimates presented in this table.

ESA Status: EN = Endangered; T = Threatened; NL = Not Listed.

Table 5—Abundance and Density Estimates for the Marine Mammal Species, Species Groups, and Stocks Associated With the West Philippine Sea Operational Area

Species

Stock name

Abundance

Density (animals/Km

)

ESA

Status

Fin whale

9,250

0.0002

Bryde's whale

WNP

20,501

0.0006

Minke whale

WNP “O” Stock

25,049

0.0033

Humpback whale

WNP

1,107

0.0008

Sperm whale

102,112

0.0010

Pygmy sperm and Dwarf sperm whale

350,553

0.0017

Cuvier's beaked whale

90,725

0.0003

Blainville's beaked whale

8,032

0.0005

Ginkgo-toothed beaked whale

22,799

0.0005

False killer whale

WNP-Pelagic

16,668

0.0029

Pygmy killer whale

WNP

30,214

0.0021

Melon-headed whale

WNP

36,770

0.0012

Short-finned pilot whale

WNP

53,608

0.0076

Risso's dolphin

WNP

83,289

0.0106

Common dolphin

WNP

3,286,163

0.0562

Fraser's dolphin

WNP

220,789

0.0040

Bottlenose dolphin

WNP

168,791

0.0146

Pantropical spotted dolphin

WNP

438,064

0.0137

Striped dolphin

WNP

570,038

0.0164

Spinner dolphin

WNP

1,015,059

0.0005

Pacific white-sided dolphin

WNP

931,000

0.0245

Rough-toothed dolphin

WNP

145,729

0.0059

NP = north Pacific; WNP = western north Pacific.

Refer to Table 5 of the Navy's application for literature references associated with abundance estimates presented in this table.

Refer to Table 5 of the Navy's application for literature references associated with density estimates presented in this table.

ESA Status: EN = Endangered; T = Threatened; NL = Not Listed.

Table 6—Abundance and Density Estimates for the Marine Mammal Species, Species Groups, and Stocks Associated With the Offshore Guam Operational Area

Species

Stock name

Abundance

Density (animals/Km

)

ESA

Status

Blue whale

ENP

2,842

0.0001

Fin whale

ENP

9,250

0.0003

Sei whale

8,600

0.0003

Bryde's whale

WNP

20,501

0.0004

Minke whale

WNP “O” Stock

25,049

0.0003

Humpback whale

CNP

10,103

0.0069

Sperm whale

102,112

0.0012

Pygmy sperm and Dwarf sperm whale

350,553

0.0101

Cuvier's beaked whale

90,725

0.0062

Blainville's beaked whale

8,032

0.0012

Ginkgo-toothed beaked whale

22,799

0.0005

Longman's beaked whale (

Indopacetus pacificus

)

CNP

1,007

0.0004

Killer whale

CNP

349

0.0001

False killer whale

WNP-Pelagic

16,668

0.0011

Pygmy killer whale

WNP

30,214

0.0001

Melon-headed whale

WNP

36,770

0.0043

Short-finned pilot whale

WNP

53,608

0.0016

Risso's dolphin

WNP

83,289

0.0010

Common dolphin

WNP

3,286,163

0.0021

Fraser's dolphin

CNP

10,226

0.0042

Bottlenose dolphin

WNP

168,791

0.0002

Pantropical spotted dolphin

WNP

438,064

0.0226

Striped dolphin

WNP

570,038

0.0062

Spinner dolphin

WNP

1,015,059

0.0031

Rough-toothed dolphin

WNP

145,729

0.0003

CNP = central north Pacific; ENP = eastern north Pacific; NP = north Pacific; WNP = western north Pacific.

Refer to Table 5 of the Navy's application for literature references associated with abundance estimates presented in this table.

Refer to Table 5 of the Navy's application for literature references associated with density estimates presented in this table.

ESA Status: EN = Endangered; T = Threatened; NL = Not Listed.

Table 7—Abundance and Density Estimates for the Marine Mammal Species, Species Groups, and Stocks Associated With the Sea of Japan Operational Area

Species

Stock name

Abundance

Density (animals/Km

ESA

Status

Fin whale

9,250

0.0009

Bryde's whale

WNP

20,501

0.0001

Minke whale

WNP “O” Stock

25,049

0.0004

Minke whale

WNP “J” Stock

893

0.0002

North Pacific right whale

WNP

922

< 0.00001

Gray whale (

Eschrichtius robustus

)

WNP

121

< 0.00001

Sperm whale

102,112

0.0008

Stejneger's beaked whale (

Mesoplodon stejnegeri

)

8,000

0.0014

Baird's beaked whale

WNP

8,000

0.0003

Cuvier's beaked whale

90,725

0.0043

Ginkgo-toothed beaked whale

22,799

0.0005

False killer whale

IA-Pelagic

9,777

0.0027

Melon-headed whale

WNP

36,770

0.00001

Short-finned pilot whale

WNP

53,608

0.0014

Risso's dolphin

WNP

83,289

0.0073

Common dolphin

WNP

3,286,163

0.0860

Bottlenose dolphin

105,138

0.0009

Pantropical spotted dolphin

WNP

219,032

0.0137

Spinner dolphin

WNP

1,015,059

0.00001

Pacific white-sided dolphin

WNP

931,000

0.0030

Dall's porpoise (

Phocoenoides dalli

)

SOJ

76,720

0.0520

IA = Inshore Archipelago; NP = north Pacific; SOJ = Sea of Japan; WNP = western north Pacific.

Refer to Table 5 of the Navy's application for literature references associated with abundance estimates presented in this table.

Refer to Table 5 of the Navy's application for literature references associated with density estimates presented in this table.

ESA Status: EN = Endangered; T = Threatened; NL = Not Listed.

Only the western Pacific population of gray whale is endangered under the ESA.

Table 8—Abundance and Density Estimates for the Marine Mammal Species, Species Groups, and Stocks Associated With the East China Sea Operational Area

Species

Stock name

Abundance

Density (animals/Km

)

ESA

Status

Fin whale

ECS

500

0.0002

Bryde's whale

WNP

20,501

0.0006

Minke whale

WNP “O” Stock

25,049

0.0044

Minke whale

WNP “J” Stock

893

0.0018

North Pacific right whale

WNP

922

< 0.00001

Gray whale

WNP

121

< 0.00001

Sperm whale

102,112

0.0012

Pygmy sperm and Dwarf sperm whale

350,553

0.0031

Cuvier's beaked whale

90,725

0.0062

Blainville's beaked whale

8,032

0.0012

Ginkgo-toothed beaked whale

22,799

0.0005

False killer whale

IA-Pelagic

9,777

0.0011

Pygmy killer whale

WNP

30,214

0.0001

Melon-headed whale

WNP

36,770

0.0043

Short-finned pilot whale

WNP

53,608

0.0016

Risso's dolphin

WNP

83,289

0.0106

Common dolphin

WNP

3,286,163

0.0461

Fraser's dolphin

WNP

220,789

0.0040

Bottlenose dolphin

105,138

0.0146

Pantropical spotted dolphin

WNP

219,032

0.0137

Striped dolphin

WNP

570,038

0.0164

Spinner dolphin

WNP

1,015,059

0.0031

Pacific white-sided dolphin

WNP

931,000

0.0028

Rough-toothed dolphin

WNP

145,729

0.0059

ECS = East China Sea; IA = Inshore Archipelago; NP = north Pacific; WNP = western north Pacific.

Refer to Table 5 of the Navy's application for literature references associated with abundance estimates presented in this table.

Refer to Table 5 of the Navy's application for literature references associated with density estimates presented in this table.

ESA Status: EN = Endangered; T = Threatened; NL = Not Listed.

Only the western Pacific population of gray whale is endangered under the ESA.

Table 9—Abundance and Density Estimates for the Marine Mammal Species, Species Groups, and Stocks Associated With the South China Sea Operational Area

Species

Stock name

Abundance

Density (animals/Km

)

ESA

Status

Fin whale

WNP

9,250

0.0002

Bryde's whale

WNP

20,501

0.0006

Minke whale

WNP “O” Stock

25,049

0.0033

North Pacific right whale

WNP

922

< 0.00001

Gray whale

WNP

121

< 0.0001

Sperm whale

102,112

0.0012

Pygmy sperm and Dwarf sperm whale

350,553

0.0017

Cuvier's beaked whale

90,725

0.0003

Blainville's beaked whale

8,032

0.0005

Ginkgo-toothed beaked whale

22,799

0.0005

False killer whale

IA-Pelagic

9,777

0.0011

Pygmy killer whale

WNP

30,214

0.0001

Melon-headed whale

WNP

36,770

0.0043

Short-finned pilot whale

WNP

53,608

0.0016

Risso's dolphin

WNP

83,289

0.0106

Common dolphin

WNP

3,286,163

0.0461

Fraser's dolphin

WNP

220,789

0.0040

Bottlenose dolphin

105,138

0.0146

Pantropical spotted dolphin

WNP

219,032

0.0137

Striped dolphin

WNP

570,038

0.0164

Spinner dolphin

WNP

1,015,059

0.3140

Rough-toothed dolphin

WNP

145,729

0.0040

IA = Inshore Archipelago; NP = north Pacific; WNP = western north Pacific.

Refer to Table 5 of the Navy's application for literature references associated with abundance estimates presented in this table.

Refer to Table 5 of the Navy's application for literature references associated with density estimates presented in this table.

ESA Status: EN = Endangered; T = Threatened; NL = Not Listed.

Only the western Pacific population of gray whale is endangered under the ESA.

Table 10—Abundance and Density Estimates for the Marine Mammal Species, Species Groups, and Stocks Associated With the Operational Area Offshore Japan (25° to 40° N)

Species

Stock name

Abundance

Density (animals/Km

)

ESA

Status

Blue whale

9,250

0.0003

Fin whale

9,250

0.0001

Sei whale

37,000

0.0003

Bryde's whale

WNP

20,501

0.0004

Minke whale

WNP “O” Stock

25,049

0.0003

Sperm whale

102,112

0.0003

Pygmy sperm and Dwarf sperm whale

350,553

0.0049

Baird's beaked whale

WNP

8,000

0.0001

Cuvier's beaked whale

90,725

0.0017

Mesoplodon

spp.

22,799

0.0005

False killer whale

WNP-Pelagic

16,668

0.0036

Pygmy killer whale

WNP

30,214

0.0001

Melon-headed whale

WNP

36,770

0.0012

Short-finned pilot whale

WNP

53,608

0.0001

Risso's dolphin

WNP

83,289

0.0010

Common dolphin

WNP

3,286,163

0.0863

Bottlenose dolphin

WNP

168,791

0.0005

Pantropical spotted dolphin

WNP

438,064

0.0181

Striped dolphin

WNP

570,038

0.0500

Spinner dolphin

WNP

1,015,059

0.00001

Pacific white-sided dolphin

WNP

67,769

0.0048

Rough-toothed dolphin

WNP

145,729

0.0003

Hawaiian monk seal

(

Monachus schauinslandi

)

Hawaii

1,129

< 0.00001

NP = north Pacific; WNP = western north Pacific.

Refer to Table 5 of the Navy's application for literature references associated with abundance estimates presented in this table.

Refer to Table 5 of the Navy's application for literature references associated with density estimates presented in this table.

ESA Status: EN = Endangered; T = Threatened; NL = Not Listed.

Table 11—Abundance and Density Estimates for the Marine Mammal Species, Species Groups, and Stocks Associated With the Operational Area Offshore Japan (10° to 25° N)

Species

Stock name

Abundance

Density (animals/Km

)

ESA

Status

Bryde's whale

WNP

20,501

0.0004

Sperm whale

102,112

0.0004

Pygmy sperm and Dwarf sperm whale

350,553

0.0009

Cuvier's beaked whale

90,725

0.0017

False killer whale

WNP-Pelagic

16,668

0.0021

Melon-headed whale

WNP

36,770

0.0012

Short-finned pilot whale

WNP

53,608

0.0009

Risso's dolphin

WNP

83,289

0.0026

Common dolphin

WNP

3,286,163

0.0863

Bottlenose dolphin

WNP

168,791

0.0007

Pantropical spotted dolphin

WNP

438,064

0.0226

Striped dolphin

WNP

570,038

0.0110

Spinner dolphin

WNP

1,015,059

0.0031

Rough-toothed dolphin

WNP

145,729

0.0003

NP = north Pacific; WNP = western north Pacific.

Refer to Table 5 of the Navy's application for literature references associated with abundance estimates presented in this table.

Refer to Table 5 of the Navy's application for literature references associated with density estimates presented in this table.

ESA Status: EN = Endangered; T = Threatened; NL = Not Listed.

Table 12—Abundance and Density Estimates for the Marine Mammal Species, Species Groups, and Stocks Associated With the Northern Hawaii Operational Area

Species

Stock name

Abundance

Density (animals/Km

)

ESA

Status

Blue whale

WNP

1,548

0.0002

Fin whale

Hawaii

2,099

0.0007

Bryde's whale

Hawaii

469

0.0002

Minke whale

WNP

25,000

0.0002

Humpback whale

Hawaii

10,103

< 0.0001

Sperm whale

CNP

6,919

0.0028

Pygmy sperm and Dwarf sperm whale

Hawaii

24,657

0.0101

Cuvier's beaked whale

Hawaii

15,242

0.0062

Blainville's beaked whale

Hawaii

2,872

0.0012

Longman's beaked whale

Hawaii

1,007

0.0004

Killer whale

Hawaii

349

0.0001

False killer whale

Hawaii-Pelagic

484

0.0002

Pygmy killer whale

Hawaii

956

0.0004

Melon-headed whale

Hawaii

2,950

0.0012

Short-finned pilot whale

Hawaii

8,870

0.0036

Risso's dolphin

Hawaii

2,372

0.0010

Fraser's dolphin

Hawaii

10,226

0.0042

Bottlenose dolphin

Hawaii

3,215

0.0013

Pantropical spotted dolphin

Hawaii

8,978

0.0037

Striped dolphin

Hawaii

13,143

0.0054

Spinner dolphin

Hawaii

3,351

0.0014

Rough-toothed dolphin

Hawaii

8,709

0.0036

Hawaiian monk seal

Hawaii

1,129

< 0.0001

CNP = central north Pacific; WNP = western north Pacific.

Refer to Table 5 of the Navy's application for literature references associated with abundance estimates presented in this table.

Refer to Table 5 of the Navy's application for literature references associated with density estimates presented in this table.

ESA Status: EN = Endangered; T = Threatened; NL = Not Listed.

Table 13—Abundance and Density Estimates for the Marine Mammal Species, Species Groups, and Stocks Associated With the Southern Hawaii Operational Area

Species

Stock name

Abundance

Density

(animals/Km

)

ESA

Status

Blue whale

WNP

1,548

0.0002

Fin whale

Hawaii

2,099

0.0007

Bryde's whale

Hawaii

469

0.0002

Minke whale

Hawaii

25,000

0.0002

Humpback whale

Hawaii

10,103

0.0008

Sperm whale

CNP

6,919

0.0028

Pygmy sperm and Dwarf sperm whale

Hawaii

24,657

0.0101

Cuvier's beaked whale

Hawaii

15,242

0.0062

Blainville's beaked whale

Hawaii

2,872

0.0012

Longman's beaked whale

Hawaii

1,007

0.0004

Killer whale

Hawaii

349

0.0001

False killer whale

Hawaii-Pelagic

484

0.0002

Pygmy killer whale

Hawaii

956

0.0004

Melon-headed whale

Hawaii

2,950

0.0012

Short-finned pilot whale

Hawaii

8,870

0.0036

Risso's dolphin

Hawaii

2,372

0.0010

Fraser's dolphin

Hawaii

10,226

0.0042

Bottlenose dolphin

Hawaii

3,215

0.0013

Pantropical spotted dolphin

Hawaii

8,978

0.0037

Striped dolphin

Hawaii

13,143

0.0054

Spinner dolphin

Hawaii

3,351

0.0014

Rough-toothed dolphin

Hawaii

8,709

0.0036

Hawaiian monk seal

Hawaii

1,129

< 0.0001

CNP = central north Pacific; WNP = western north Pacific.

Refer to Table 5 of the Navy's application for literature references associated with abundance estimates presented in this table.

Refer to Table 5 of the Navy's application for literature references associated with density estimates presented in this table.

ESA Status: EN = Endangered; T = Threatened; NL = Not Listed.

Table 14—Abundance and Density Estimates for the Marine Mammal Species, Species Groups, and Stocks Associated With the Operational Area Offshore Southern California (SOCAL OPAREA)

Species

Stock name

Abundance

Density (animals/Km

)

ESA

Status

Blue whale

ENP

2,842

0.0014

Fin whale

CA/OR/WA

2,099

0.0018

Sei whale

ENP

0.0001

Bryde's whale

ENP

13,000

0.00001

Northern minke whale

CA/OR/WA

823

0.0007

Humpback whale

CA/OR/WA

942

0.0008

Gray whale

ENP

18,813

0.051

Sperm whale

CA/OR/WA

1,934

0.0017

Pygmy sperm whale

CA/OR/WA

1,237

0.0011

Stejneger's beaked whale

CA/OR/WA

1,177

0.0010

Baird's beaked whale

CA/OR/WA

1,005

0.0009

Cuvier's beaked whale

CA/OR/WA

4,342

0.0038

Blainville's beaked whale

CA/OR/WA

1,177

0.0010

Ginkgo-toothed beaked whale

CA/OR/WA

1,177

0.0010

Hubbs beaked whale

CA/OR/WA

1,177

0.0010

Longman's beaked whale

Hawaii

1,177

0.0010

Perrin's beaked whale (

Mesoplodon perrini

)

CA/OR/WA

1,177

0.0010

Pygmy beaked whale (

Mesoplodon peruvianus

)

CA/OR/WA

1,177

0.0010

Killer whale (offshore)

ENP

810

0.0007

Short-finned pilot whale

CA/OR/WA

350

0.0003

Risso's dolphin

CA/OR/WA

11,910

0.0105

Long-beaked common dolphin (

Delphinus capensis

)

CA/OR/WA

21,902

0.0192

Short-beaked common dolphin (

Delphinus delphis

)

CA/OR/WA

352,069

0.3094

Bottlenose dolphin (offshore)

CA/OR/WA

2,026

0.0018

Striped dolphin

CA/OR/WA

18,976

0.0167

Pacific white-sided dolphin

CA/OR/WA

23,817

0.0209

Northern right whale dolphin (

Lissodelphis borealis

)

CA/OR/WA

11,097

0.0098

Dall's porpoise

CA/OR/WA

85,955

0.0753

Guadalupe fur seal (

Arctocephalus townsendi

)

Mexico

7,408

0.007

Northern fur seal (

Callorhinus ursinus

)

SMI

9,424

California sea lion (

Zalophus californianus

)

California

238,000

0.54

California sea lion

California

238,000

Harbor seal (

Phoca vitulina

)

California

34,233

0.0095

Northern elephant seal (

Mirounga angustirostris

)

CA-Breeding

124,000

0.0045

Northern elephant seal

CA-Breeding

124,000

CA/OR/WA = California, Oregon, and Washington; ENP = eastern north Pacific; SMI = San Miguel Island.

Refer to Table 5 of the Navy's application for literature references associated with abundance estimates presented in this table.

Refer to Table 5 of the Navy's application for literature references associated with density estimates presented in this table.

ESA Status: EN = Endangered; T = Threatened; NL = Not Listed.

Only the western Pacific population of gray whale is endangered under the ESA.

Table 15—Abundance and Density Estimates for the Marine Mammal Species, Species Groups, and Stocks Associated With the Northwestern Atlantic Operational Area Off Florida (JAX OPAREA)

Species

Stock name

Abundance

Density

(animals/Km

)

ESA

Status

Humpback whale

WNA

11,570

0.0006

North Atlantic right whale (on shelf)

WNA

438

0.0012

Sperm whale (on shelf)

WNA

4,804

Sperm whale (off shelf)

WNA

4,804

0.0005

Pygmy sperm and Dwarf sperm whale

WNA

580

0.0010

Beaked whales (on shelf)

WNA

3,513

Beaked whales (off shelf)

WNA

3,513

0.0006

Cuvier's beaked whale

WNA

3,513

0.0006

Blainville's beaked whale

WNA

3,513

0.0006

Gervais' beaked whale (

Mesoplodon europaeus

)

WNA

3,513

0.0006

Sowerby's beaked whale (

Mesoplodon bidens

)

WNA

3,513

0.0006

True's beaked whale (

Mesoplodon mirus

)

WNA

3,513

0.0006

Short-finned pilot whale (on shelf)

WNA

31,139

0.00004

Short-finned pilot whale (off shelf)

WNA

31,139

0.0271

Risso's dolphin (on shelf)

WNA

20,479

0.0009

Risso's dolphin (off shelf)

WNA

20,479

0.0181

Common dolphin

WNA

120,743

0.00002

Bottlenose dolphin (on shelf)

WNA

81,588

0.2132

Bottlenose dolphin (off shelf)

WNA

81,588

0.1163

Pantropical spotted dolphin

WNA

12,747

0.0223

Striped dolphin

WNA

94,462

0.00003

Atlantic spotted dolphin (on shelf) (

Stenella frontalis

)

WNA

50,978

0.4435

Atlantic spotted dolphin (off shelf)

WNA

50,978

0.0041

Clymene dolphin (

Stenella clymene

)

WNA

6,086

0.0106

Rough-toothed dolphin

WNA

274

0.0005

WNA = western north Atlantic.

Refer to Table 5 of the Navy's application for literature references associated with abundance estimates presented in this table.

Refer to Table 5 of the Navy's application for literature references associated with density estimates presented in this table.

ESA Status: EN = Endangered; T = Threatened; NL = Not Listed.

Table 16—Abundance and Density Estimates for the Marine Mammal Species, Species Groups, and Stocks Associated With the Operational Area in the Northeastern Atlantic Off the United Kingdom.

Species

Stock name

Abundance

Density

(animals/Km

)

ESA

Status

Blue whale

ENA

100

0.00001

Fin whale

ENA

10,369

0.0031

Sei whale

ENA

14,152

0.0113

Northern minke whale

ENA

107,205

0.0068

Humpback whale

ENA

4,695

0.0019

Sperm whale

ENA

6,375

0.0049

Pygmy sperm and Dwarf sperm whale

ENA

580

0.0001

Cuvier's beaked whale

ENA

3,513

0.0013

Blainville's beaked whale

ENA

3,513

0.0013

Sowerby's beaked whale

ENA

3,513

0.0013

Northern bottlenose whale (

Hyperodon ampullatus

)

ENA

5,827

0.0003

Killer whale

ENA

6,618

0.0001

False killer whale

ENA

484

0.0001

Long-finned pilot whale (

Globicephala melas

)

ENA

778,000

0.0121

Risso's dolphin

ENA

20,479

0.0063

Common dolphin

ENA

273,150

0.238

Bottlenose dolphin

ENA

81,588

0.0094

Striped dolphin

ENA

94,462

0.0765

Atlantic white-sided dolphin (

Lagenorhynchus acutus

)

ENA

11,760

0.0027

White-beaked dolphin (

Lagenorhynchus albirostris

)

ENA

11,760

0.0027

Harbor porpoise (

Phocoena phocoena

)

ENA

341,366

0.2299

Harbor seal (

Phoca vitulina

)

Ireland/Scotland

23,500

0.0230

Gray seal (

Halichoerus grypus

)

ENA

113,300

0.027

ENA = eastern north Atlantic.

Refer to Table 5 of the Navy's application for literature references associated with abundance estimates presented in this table.

Refer to Table 5 of the Navy's application for literature references associated with density estimates presented in this table.

ESA Status: EN = Endangered; T = Threatened; NL = Not Listed.

Table 17—Abundance and Density Estimates for the Marine Mammal Species, Species Groups, and Stocks Associated With the Operational Area in the Western Mediterranean Sea and the Ligurian Sea

Species

Stock name

Abundance

Density

(Animals/Km

)

ESA

Status

Fin whale

MED

3,583

0.004

Sperm whale

WMED

6,375

0.0049

Cuvier's beaked whale

ENA

3,513

0.0013

Long-finned pilot whale

ENA

778,000

0.0121

Risso's dolphin

WMED

5,320

0.0075

Common dolphin

WMED

19,428

0.0144

Bottlenose dolphin

WMED

23,304

0.041

Striped dolphin

WMED

117,880

0.24

ENA = eastern north Atlantic; MED = Mediterranean; WMED = western Mediterranean.

Refer to Table 5 of the Navy's application for literature references associated with abundance estimates presented in this table.

Refer to Table 5 of the Navy's application for literature references associated with density estimates presented in this table.

ESA Status: EN = Endangered; T = Threatened; NL = Not Listed.

Table 18—Abundance and Density Estimates for the Marine Mammal Species, Species Groups, and Stocks Associated With the Operational Area in the Northern Arabian Sea

Species

Stock name

Abundance

Density

(animals/Km

)

ESA

Status

Bryde's whale

IND

9,176

0.0001

Humpback whale

XAR

200

0.0004

Sperm whale

IND

24,446

0.0125

Dwarf sperm whale

IND

10,541

0.0145

Cuvier's beaked whale

IND

27,272

0.0001

Blainville's beaked whale

IND

16,867

0.0016

Ginkgo-toothed beaked whale

IND

16,867

0.0016

Longman's beaked whale

IND

16,867

0.0016

False killer whale (pelagic)

IND

144,188

0.0003

Pygmy killer whale

IND

22,029

0.0026

Melon-headed whale

IND

64,600

0.0661

Short-finned pilot whale

IND

268,751

0.0034

Risso's dolphin

IND

452,125

0.0125

Common dolphin

IND

1,819,882

0.0265

Bottlenose dolphin

IND

785,585

0.0164

Pantropical spotted dolphin

IND

736,575

0.0127

Striped dolphin

IND

674,578

0.0706

Spinner dolphin

IND

634,108

0.01

Rough-toothed dolphin

IND

156,690

0.0081

IND = Indian Ocean; XAR = Stock X Arabian Sea.

Refer to Table 5 of the Navy's application for literature references associated with abundance estimates presented in this table.

Refer to Table 5 of the Navy's application for literature references associated with density estimates presented in this table.

ESA Status: EN = Endangered; T = Threatened; NL = Not Listed.

Table 19—Abundance and Density Estimates for the Marine Mammal Species, Species Groups, and Stocks Associated With the Operational Area in the Andaman Sea Off Myanmar

Species

Stock name

Abundance

Density

(animals/Km

)

ESA

Status

Bryde's whale

IND

9,176

0.0001

Sperm whale

IND

24,446

0.0125

Dwarf sperm whale

IND

10,541

0.0145

Cuvier's beaked whale

IND

27,272

0.0001

Blainville's beaked whale

IND

16,867

0.0016

Ginkgo-toothed beaked whale

IND

16,867

0.0016

Longman's beaked whale

IND

16,867

0.0016

Killer whale

IND

12,593

0.0001

False killer whale (pelagic)

IND

144,188

0.0003

Pygmy killer whale

IND

22,029

0.0026

Melon-headed whale

IND

64,600

0.0661

Short-finned pilot whale

IND

268,751

0.0034

Risso's dolphin

IND

452,125

0.0125

Common dolphin

IND

1,819,882

0.0265

Bottlenose dolphin

IND

785,585

0.0164

Pantropical spotted dolphin

IND

736,575

0.0127

Striped dolphin

IND

674,578

0.0706

Spinner dolphin

IND

634,108

0.01

Rough-toothed dolphin

IND

156,690

0.0081

IND = Indian Ocean.

Refer to Table 5 of the Navy's application for literature references associated with abundance estimates presented in this table.

Refer to Table 5 of the Navy's application for literature references associated with density estimates presented in this table.

ESA Status: EN = Endangered; T = Threatened; NL = Not Listed.

Table 20—Abundance and Density Estimates for the Marine Mammal Species, Species Groups, and Stocks Associated With the Panama Canal Operational Area (West Approach)

Species

Stock name

Abundance

Density

(animals/Km

)

ESA

Status

Blue whale

ENP

2,842

0.0001

Bryde's whale

ETP

13,000

0.0003

Humpback whale

ENP

1,391

0.0004

Sperm whale

ETP

22,700

0.0047

Dwarf sperm whale

ETP

11,200

0.0145

Cuvier's beaked whale

ETP

20,000

0.0025

Blainville's beaked whale

ETP

25,300

0.0013

Ginkgo-toothed beaked whale

ETP

25,300

0.0016

Longman's beaked whale

ETP

25,300

0.0003

Pygmy beaked whale (

Mesoplodon peruvianus

)

ETP

25,300

0.0016

Killer whale

ETP

8,500

0.0002

False killer whale (pelagic)

ETP

39,800

0.0004

Pygmy killer whale

ETP

38,900

0.0014

Melon-headed whale

ETP

45,400

0.0174

Short-finned pilot whale

ETP

160,200

0.0058

Risso's dolphin

ETP

110,457

0.0161

Common dolphin

ETP

3,127,203

0.049

Fraser's dolphin

ETP

289,300

0.001

Bottlenose dolphin

ETP

335,834

0.0157

Pantropical spotted dolphin

NEOP

640,000

0.0669

Striped dolphin

ETP

964,362

0.1199

Spinner dolphin

Eastern

450,000

0.007

Rough-toothed dolphin

ETP

107,633

0.0146

ETP = eastern tropical Pacific; NEOP = northeastern offshore Pacific.

Refer to Table 5 of the Navy's application for literature references associated with abundance estimates presented in this table.

Refer to Table 5 of the Navy's application for literature references associated with density estimates presented in this table.

ESA Status: EN = Endangered; T = Threatened; NL = Not Listed.

Table 21—Abundance and Density Estimates for the Marine Mammal Species, Species Groups, and Stocks Associated With the Operational Area Off the Northeastern Australian Coast

Species

Stock name

Abundance

Density

(animals/Km

)

ESA

Status

Blue whale

WSP

9,250

0.0002

Fin whale

WSP

9,250

0.0002

Bryde's whale

WSP

22,000

0.0006

Northern minke whale

WSP

25,000

0.0044

Humpback whale

GVEA

3,500

0.0143

Sperm whale

WSP

102,112

0.0029

Pygmy sperm and Dwarf sperm whale

WSP

350,553

0.0031

Cuvier's beaked whale

WSP

90,725

0.0054

Blainville's beaked whale

WSP

8,032

0.0005

Arnoux's beaked whale (

Berardius arnuxii

)

WSP

22,799

0.0005

Ginkgo-toothed beaked whale

WSP

22,799

0.0005

Longman's beaked whale

WSP

22,799

0.0005

Southern bottlenose whale (

Hyperodon planifrons

)

WSP

22,799

0.0005

Killer whale

WSP

12,256

0.0004

False killer whale (pelagic)

WSP

16,668

0.0029

Pygmy killer whale

WSP

30,214

0.0021

Melon-headed whale

WSP

36,770

0.0012

Globicephala

spp.

WSP

53,608

0.0153

Risso's dolphin

WSP

83,289

0.0106

Common dolphin

WSP

3,286,163

0.0562

Fraser's dolphin

WSP

220,789

0.004

Bottlenose dolphin

WSP

168,791

0.0146

Pantropical spotted dolphin

WSP

438,064

0.0137

Striped dolphin

WSP

570,038

0.0329

Spinner dolphin

WSP

1,015,059

0.0005

Dusky dolphin (

Lagenorhynchus obscurus

)

WSP

12,626

0.0002

Rough-toothed dolphin

WSP

145,729

0.0059

GVEA = group V east Australia; WSP = western south Pacific.

Refer to Table 5 of the Navy's application for literature references associated with abundance estimates presented in this table.

Refer to Table 5 of the Navy's application for literature references associated with density estimates presented in this table.

ESA Status: EN = Endangered; T = Threatened; NL = Not Listed.

The Navy provides detailed descriptions of the distribution, abundance, diving behavior, life history, and hearing vocalization information for each affected marine mammal species with confirmed or possible occurrence within SURTASS LFA sonar operational areas in section 4 (pages 38-97) of the application, which is available online at

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

Although not repeated in this document, NMFS has reviewed these data, determined them to be the best available scientific information for the purposes of the proposed rulemaking, and considers this information part of the administrative record for this action. Additional information is available in NMFS' Marine Mammal Stock Assessment Reports, which may be viewed at

http://www.nmfs.noaa.gov/pr/sars/species.htm

. Also, NMFS refers the public to Table 5 (page 37) of the Navy's application for literature references associated with abundance and density estimates presented in these tables.

Brief Background on Sound, Marine Mammal Hearing, and Vocalization

Acoustic Source Specifications

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 at 1 m, and the units for SPLs are decibels (dB) re: 1 μPa at 1 m. SPL (in dB) = 20 log (pressure/reference pressure). SPL is an instantaneous measurement and can be expressed as the peak, the peak-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.

SPL and the Single Ping Equivalent (SPE)

To model potential impacts to marine animals from exposure to SURTASS LFA sonar sound, the Navy has developed a methodology to estimate the total exposure of modeled animals exposed to multiple pings over an extended period of time. The Navy's acoustic model analyzes the following components: (1) The LFA sonar source modeled as a point source, with an effective source level (SL) in dB re: 1 μPa at 1 m (SPL); (2) a 60-sec duration signal; and (3) a beam pattern that is correct for the number and spacing of the individual projectors (source elements). This source model, when combined with the three-dimensional transmission loss (TL) field generated by the Parabolic Equation (PE) acoustic propagation model, defines the received level (RL) (in SPL) sound field surrounding the source for a 60-sec LFA sonar signal. To estimate the total exposure of animals exposed to multiple pings, the Navy models the RLs for each modeled location and any computer-simulated marine mammals (also called animats) within the location, records the exposure history of each animat, and generates a single ping equivalent (SPE) value. Thus, the Navy can model the SURTASS LFA sound field, providing a four-dimensional (position and time) representation of a sound pressure field within the marine environment and estimates of an animal's exposure to sound.

Figure 2 shows the Navy calculation that converts SPL values to SPE values in order to estimate impacts to marine mammals from SURTASS LFA sonar transmissions. For a more detailed explanation of the SPE calculations, NMFS refers the public to Appendix C of the Navy's 2011 DSEIS/SOEIS.

EP06JA12.001

Underwater Sound

An understanding of the basic properties of underwater sound is necessary to comprehend many of the concepts and analyses presented in this document.

Sound is a wave of pressure variations propagating through a medium (for the sonar considered in this proposed rulemaking, the medium is seawater). Pressure variations are created by compressing and relaxing the medium. Sound measurements can be expressed in two forms: Intensity and pressure. Acoustic intensity is the average rate of energy transmitted through a unit area in a specified direction and is expressed in watts per square meter (W/m

). Acoustic intensity is rarely measured directly, it is derived from ratios of pressures; the standard reference pressure for underwater sound is 1 μPa at 1 m (Richardson

et al.,

1995).

Acousticians have adopted a logarithmic scale for sound intensities, which is denoted in dB. The logarithmic nature of the scale means that each 10 dB increase is a ten-fold increase in power (e.g., 20 dB is a 100-fold increase, 30 dB is a 1,000-fold increase). Humans perceive a 10-dB increase in noise as a doubling of sound level, or a 10-dB decrease in noise as a halving of sound level. Sound pressure level or SPL implies a decibel measure and a reference pressure that is used as the denominator of the ratio.

Sound frequency is measured in cycles per second, referred to as Hertz (Hz), and is analogous to musical pitch; high-pitched sounds contain high frequencies and low-pitched sounds contain low frequencies. Natural sounds in the ocean span a huge range of frequencies: From earthquake noise at five Hz to harbor porpoise clicks at 150,000 Hz (150 kilohertz (kHz)). These sounds are so low or so high in pitch that humans cannot even hear them; acousticians call these infrasonic (typically below 20 Hz) and ultrasonic (typically above 20,000 Hz) sounds, respectively. A single sound may be made up of many different frequencies together. Sounds made up of only a small range of frequencies are called narrowband, and sounds with a broad range of frequencies are called broadband. Explosives are an example of a broadband sound source and tactical sonars are an example of a narrowband sound source.

Marine Mammal Hearing

Cetaceans have an auditory anatomy that follows the basic mammalian pattern, with some changes to adapt to the demands of hearing in the sea. The typical mammalian ear is divided into an outer ear, middle ear, and inner ear. The outer ear is separated from the inner ear by a tympanic membrane, or eardrum. In terrestrial mammals, the outer ear, eardrum, and middle ear transmit airborne sound to the inner ear, where the sound waves are propagated through the cochlear fluid. Since the impedance of water (i.e., the product of density and sound speed) is close to that of the tissues of a cetacean, the outer ear is not required to transduce sound energy as it does when sound waves travel from air to fluid (inner ear). Sound waves traveling through the inner ear cause the basilar membrane to vibrate. Specialized cells, called hair cells, respond to the vibration and produce nerve pulses that are transmitted to the central nervous system. Acoustic energy causes the basilar membrane in the cochlea to vibrate. Sensory cells at different positions along the basilar membrane are excited by different frequencies of sound (Pickles, 1998).

When considering the influence of various kinds of sound on the marine environment, it is necessary to understand that different kinds of marine life are sensitive to different frequencies of sound. Based on available behavioral data, audiograms derived using auditory evoked potential (AEP) techniques, anatomical modeling, and other data, Southall

et al.

(2007) designated “functional hearing groups” for marine mammals and estimated the lower and upper frequencies of functional hearing (i.e., the frequencies that the species can actually hear) of these groups. The functional groups and the associated frequencies are described here (though animals are less sensitive to sounds at the outer edge of their functional range and most sensitive to sounds of frequencies within a smaller range somewhere in the middle of their functional hearing range):

• Low frequency (LF) cetaceans (13 species of mysticetes): Southall

et al.

(2007) estimates that functional hearing occurs between approximately seven Hz and 22 kHz;

• Mid-frequency (MF) cetaceans (32 species of dolphins, six species of larger toothed whales, and 19 species of beaked and bottlenose whales): Southall

et al.

(2007) estimates that functional hearing occurs between approximately 150 Hz and 160 kHz;

• High frequency (HF) cetaceans (eight species of true porpoises, six species of river dolphins,

Kogia,

the franciscana, and four species of cephalorhynchids): Southall

et al.

(2007) estimates that functional hearing occurs between approximately 200 Hz and 180 kHz.

• Pinnipeds in Water: Southall

et al.

(2007) estimates that functional hearing occurs between approximately 75 Hz and 75 kHz, with the greatest sensitivity between approximately 700 Hz and 20 kHz.

Marine Mammal Functional Hearing Groups and LFA Sonar

Baleen (mysticete) whales (members of the LF functional hearing group) have inner ears that appear to be specialized for low-frequency hearing. Conversely, most odontocetes (i.e., sperm whales, dolphins and porpoises) have inner ears that are specialized to hear mid and high frequencies. Pinnipeds, which lack the highly specialized active biosonar systems of odontocetes, have inner ears that are specialized to hear a broad range of frequencies in water (Southall

et al.,

2007). Based on an extensive suite of reported laboratory measurements (DoN, 2001, Ketten, 1997, Southall

et al.,

2007), the LFA sound source is below the range of best hearing sensitivity for MF and HF odontocete and pinnipeds in water hearing specialists (Clark and Southall, 2009).

Marine Mammal Vocalization

Marine mammal vocalizations often extend both above (higher than 20 kHz) and below (lower than 20 Hz) the range of human hearing (National Research Council, 2003; Figure 4-1). Measured data on the hearing abilities of cetaceans are sparse, particularly for the larger cetaceans such as the baleen whales. The auditory thresholds of some of the smaller odontocetes have been determined in captivity. It is generally believed that cetaceans should at least be sensitive to the frequencies of their own vocalizations. Comparisons of the anatomy of cetacean inner ears and models of the structural properties and the response to vibrations of the ear's components in different species provide an indication of likely sensitivity to various sound frequencies. Thus, the ears of small toothed whales are optimized for receiving high-frequency sound, while baleen whale inner ears are best suited for low frequencies, including to infrasonic frequencies (Ketten, 1992; 1997; 1998).

Baleen whale (i.e., mysticete) vocalizations are composed primarily of frequencies below one kHz, and some contain fundamental frequencies as low as 16 Hz (Watkins

et al.,

1987; Richardson

et al.,

1995; Rivers, 1997; Moore

et al.,

1998; Stafford

et al.,

1999; Wartzok and Ketten, 1999) but can be as high as 24 kHz (humpback whale; Au

et al.,

2006). Clark and Ellison (2004) suggested that baleen whales use low frequency sounds not only for long-range communication, but also as a simple form of echo ranging, using echoes to navigate and orient relative to physical features of the ocean. Information on auditory function in mysticetes is extremely lacking. Sensitivity to low frequency sound by baleen whales has been inferred from observed vocalization frequencies, observed reactions to playback of sounds, and anatomical analyses of the auditory system. Although there is apparently much variation, the source levels of most baleen whale vocalizations lie in the range of 150-190 dB re: 1 μPa at 1 m. Low-frequency vocalizations made by baleen whales and their corresponding auditory anatomy suggest that they have good low-frequency hearing (Ketten, 2000), although specific data on sensitivity, frequency or intensity discrimination, or localization abilities are lacking. Marine mammals, like all mammals, have typical U-shaped audiograms that begin with relatively low sensitivity (high threshold) at some specified low frequency with increased sensitivity (low threshold) to a species-specific optimum followed by a generally steep rise at higher frequencies (high threshold) (Fay, 1988).

Toothed whales (i.e., odontocetes) produce a wide variety of sounds, which include species-specific broadband “clicks” with peak energy between 10 and 200 kHz, individually variable “burst pulse” click trains, and constant frequency or frequency-modulated (FM) whistles ranging from 4 to 16 kHz (Wartzok and Ketten, 1999). The general consensus is that the tonal vocalizations (whistles) produced by toothed whales play an important role in maintaining contact between dispersed individuals, while broadband clicks are used during echolocation (Wartzok and Ketten, 1999). Burst pulses have also been strongly implicated in communication, with some scientists suggesting that they play an important role in agonistic encounters (McCowan and Reiss, 1995), while others have proposed that they represent “emotive” signals in a broader sense, possibly representing graded communication signals (Herzing, 1996). Sperm whales, however, are known to produce only clicks, which are used for both communication and echolocation (Whitehead, 2003). Most of the energy of toothed whales social vocalizations is concentrated near 10 kHz, with source levels for whistles as high as 100-180 dB re 1 μPa at 1 m (Richardson

et al.,

1995). No odontocete has been shown audiometrically to have acute hearing (less than 80 dB re 1 μPa at 1 m) below 500 Hz (DoN, 2001; Ketten, 1998). Sperm whales produce clicks, which may be used to echolocate (Mullins

et al.,

1988), with a frequency range from less than 100 Hz to 30 kHz and source levels up to 230 dB re 1 μPa at 1 m or greater (Mohl

et al.,

2000).

Brief Background on the Navy's Assessment of the Potential Impacts on Marine Mammals

Acoustic Modeling Scenarios. The Navy based their analysis of potential impacts on marine mammals from SURTASS LFA sonar on literature review, the Navy's Low Frequency Sound Scientific Research Program (LFS SRP), and a comprehensive program of underwater acoustical modeling.

To assess the potential impacts on marine mammals by the SURTASS LFA sonar source operating at a given site, the Navy must predict the sound field that a given marine mammal species could be exposed to over time. This is a multi-part process involving: (1) The ability to measure or estimate an animal's location in space and time; (2) The ability to measure or estimate the three-dimensional sound field at these times and locations; (3) The integration of these two data sets into the Acoustic Integration Model (AIM) to estimate the total acoustic exposure for each animal in the modeled population; and (4) Converting the resultant cumulative exposures (within the post-AIM analysis) for a modeled population into an estimate of the risk of a significant disturbance of a biologically important behavior (i.e., a take estimate for Level B harassment of marine mammals based upon an estimated percentage of each stock affected by SURTASS LFA sonar operations) or an assessment of risk in terms of injury of marine mammals (i.e., a take estimate for Level A harassment of marine mammals based on a cumulative exposure of greater than or equal to 180-dB SPE). In the post-AIM analysis, as mentioned in number (4), the Navy developed a relationship for converting the resultant cumulative exposures for a modeled population into an estimate of the risk to the entire population of a significant disruption of a biologically important behavior and of injury. This process assessed risk in relation to received level (RL) and repeated exposure. The Navy's risk continuum is based on the assumption that the threshold of risk is variable and occurs over a range of conditions rather than at a single threshold. Taken together, the LFS SRP results, the acoustic propagation modeling, and the Navy's risk assessment model provide an estimate of takes of marine mammals.

The Navy modeled acoustic propagation using its standard acoustical performance prediction transmission loss model-PE version 3.4. The results of this model are the primary input to the AIM, which the Navy used to estimate marine mammal sound exposures. AIM integrates simulated movements (including dive patterns) of marine mammals, a schedule of SURTASS LFA sonar transmissions, and the predicted sound field for each transmission to estimate acoustic exposure during a hypothetical SURTASS LFA sonar operation. Description of the PE and AIM models, including AIM input parameters for animal movement, diving behavior, and marine mammal distribution, abundance, and density, are described in detail in the Navy's application and in the DSEIS/SOEIS (see Subchapter 4.4 and Appendix C) and are not discussed further in this document.

For this application for rulemaking, the Navy has used the same analytical methodology utilized in the first and second five-year rules and LOAs to provide reasonable and realistic estimates of the potential effects to marine mammals specific to the

potential mission areas as presented in the application. Although this proposed rule uses the same analytical methodology the Navy used for the 2002-2007 rule, the Navy continuously updates the analysis with new marine mammal biological data (behavior, distribution, abundance and density) whenever new information becomes available.

The Navy initially developed 31 acoustic modeling scenarios for the major ocean regions in the SURTASS LFA sonar FOEIS/EIS (DoN, 2001); 11 acoustic modeling scenarios for the 2007 FSEIS and the 2007 rulemaking and LOAs; and eight additional sites for the 2011 DSEIS/SOEIS.

In the initial modeling effort for the 2001 FOEIS/EIS, the Navy selected locations to represent the greatest potential effects for each of the three major ocean acoustic regimes where SURTASS LFA sonar could potentially be used. These acoustic regimes were: (1) Deep-water convergence zone propagation, (2) near surface duct propagation, and (3) shallow water bottom interaction propagation. The Navy selected these sites to model the greatest potential for effects from the use of SURTASS LFA sonar incorporating the following factors: (1) closest plausible proximity to land (from a SURTASS LFA sonar operations standpoint), and/or OBIAs for marine mammals most likely to be affected; (2) acoustic propagation conditions that allow minimum propagation loss, or transmission loss (TL) (i.e., longest acoustic transmission ranges); and (3) time of year selected for maximum animal abundance. These 31 sites presented in the Navy's 2001 FOEIS/EIS represented the upper bound of impacts (in terms of both possible acoustic propagation conditions and marine mammal population and density) that could be expected from operation of the SURTASS LFA sonar system.

In the 2007 FSEIS, the Navy provided a risk assessment case study that included nine additional sites based on reasonable and realistic choices for potential SURTASS LFA sonar testing, training, and operations during the proposed period of the rulemaking and LOA application. Subsequent to the publication of the 2007 FSEIS, the Navy added two additional sites in the waters north and south of the Hawaiian Islands. The most recent risk assessment analyses provided in the Navy's application and 2011 DSEIS/SOEIS proves updated modeling for the 11 sites under the 2007 rulemaking and eight additional sites using the most up-to-date marine mammal abundance, density, and behavioral information available. These 19 operating sites are in areas of potential strategic importance and/or areas of possible naval fleet exercises.

Overall, the Navy's total effort for underwater acoustic modeling includes all 50 potential operational sites for SURTASS LFA sonar. The analysis of the 50 potential sites provides the foundation for the analysis of potential effects of SURTASS LFA sonar operations on the overall marine environment.

If the Navy conducts SURTASS LFA sonar operations in an area that was not acoustically modeled in the 2001 FOEIS/EIS (DoN, 2001), the 2007 FSEIS (DoN, 2007) or the 2011 DSEIS/SOEIS (DoN, 2011), the Navy states that the potential effects would most likely be less than those analyzed for the most similar site in the analyses because the modeled sites represent the upper bound of effects. NMFS concurs with this approach, as any site not modeled in the Navy's analyses should fall within or under the modeled bounds of impacts of possible acoustic propagation conditions and marine mammal densities. The assumptions of the 2001 FOEIS/EIS (DoN, 2001) and the 2007 FSEIS (DoN, 2007) are still valid and there are no new data to contradict the conclusions made in the Navy's documents.

Risk Analysis. To determine the potential impacts that exposure to LF sound from SURTASS LFA sonar operations could have on marine mammals, the Navy defined biological risk standards with associated measurement parameters. The Navy's measurement parameters for determining exposure were RLs in dB, the pulse repetition interval (time between pings), and the number of pings received. To address the potential for accumulation of effects on marine mammals over a seven to 20-day period (i.e., the estimated maximum SURTASS LFA sonar mission period, allowing for varying RLs and a duty cycle of 20 percent or less), the Navy developed a function that translates the modeled history of repeated exposures (as calculated in the AIM) into an equivalent RL for a single exposure with a comparable risk (as previously discussed in the SPL and the Single Ping Equivalent (SPE) section). Based upon the best available information, NMFS believes that the Navy's assumptions are still valid and there are no new data to contradict the conclusions made by the Navy's risk analysis. NMFS refers the reader to Section 6.4.3 of the Navy's application and Appendix C of the 2011 DSEIS/SOEIS for more detailed information on the Navy's risk assessment approach.

Potential Effects of the Specified Activity on Marine Mammals

The Navy has requested authorization for the incidental take of marine mammals that may result from upcoming training, testing, and military operations using SURTASS LFA sonar on a maximum of four U.S. Naval ships in certain areas of the Pacific, Atlantic, and Indian Oceans and the Mediterranean Sea. In addition to the use of LFA and HF/M3 sonar, the Navy has analyzed the potential impact of ship strike to marine mammals from SURTASS LFA sonar operations, and, in consultation with NMFS as a cooperating agency for the SURTASS LFA sonar 2011 DSEIS/SOEIS, has determined that take of marine mammals incidental to this non-acoustic component of the Navy's operations is unlikely and, therefore, has not requested authorization for take of marine mammals that might occur incidental to vessel ship strike. In this document, NMFS analyzes the potential effects on marine mammals from exposure to LFA and HF/M3 sonar, but also includes some additional analysis of the potential impacts from vessel operations.

For the purpose of MMPA authorizations, NMFS' effects assessments serve four primary purposes: (1) Identification of the permissible methods of taking, meaning: The nature of the take (e.g., resulting from anthropogenic noise versus from ship strike, etc.); the regulatory level of take (i.e., mortality versus Level A or Level B harassment) and the estimated amount of take; (2) Informing the prescription of means of effecting the least practicable adverse impact on such species or stock and its habitat (i.e., mitigation); (3) Supporting the determination of whether the specified activity will have a negligible impact on the affected species or stocks of marine mammals (based on the likelihood that the activity will adversely affect the species or stock through effects on annual rates of recruitment or survival); and (4) Determining whether the specified activity will have an unmitigable adverse impact on the availability of the species or stock(s) for subsistence uses.

NMFS' analysis of potential impacts from SURTASS LFA operations including lethal responses, physical trauma, sensory impairment (permanent and temporary threshold shifts and acoustic masking), physiological responses (particularly stress responses), and behavioral disturbance

is outlined below this section. NMFS will focus qualitatively on the different ways that SURTASS LFA sonar operations may affect marine mammals (some of which may not classify as take). Then, in the Estimated Take of Marine Mammals Section, NMFS will relate the potential effects to marine mammals from SURTASS LFA sonar operations to the MMPA definitions of take, including Level A and Level B Harassment, and attempt to quantify those effects.

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

Potential Effects of Exposure to SURTASS LFA Sonar Operations

Based on the literature, the potential effects of sound from the proposed activities associated with SURTASS LFA sonar might include one or more of the following: Behavioral changes, masking, non-auditory injury, and noise-induced loss of hearing sensitivity (more commonly called “threshold shift”). Separately, an animal's behavioral reaction to an acoustic exposure might lead to physiological effects that might ultimately lead to injury or death. NMFS discusses this potential effect later in the Stranding section.

The effects of underwater noise on marine mammals are highly variable, and one can categorize the effects as follows (Richardson

et al.,

1995; Nowacek

et al.,

2007; Southall

et al.,

2007):

(1) The noise may be too weak to be heard at the location of the animal (i.e., lower than the prevailing ambient noise level, the hearing threshold of the animal at relevant frequencies, or both);

(2) The noise may be audible but not strong enough to elicit any overt behavioral response;

(3) The noise may elicit behavioral reactions of variable conspicuousness and variable relevance to the well-being of the animal; these can range from temporary alert responses to active avoidance reactions such as vacating an area at least until the noise event ceases but potentially for longer periods of time;

(4) Upon repeated exposure, a marine mammal may exhibit diminishing responsiveness (habituation), or disturbance effects may persist; the latter is most likely with sounds that are highly variable in characteristics, infrequent, and unpredictable in occurrence, and associated with situations that the animal perceives as a threat;

(5) Any anthropogenic (human-made) noise that is strong enough to be heard has the potential to reduce (mask) the ability of a marine mammal to hear natural sounds at similar frequencies, including calls from conspecifics (i.e., an organism of the same species), and underwater environmental sounds such as surf noise;

(6) If mammals remain in an area because it is important for feeding, breeding, or some other biologically important purpose even though there is a chronic exposure to noise, it is possible that there could be noise-induced physiological stress; this might in turn have negative effects on the well-being or reproduction of the animals involved; and

(7) Very strong sounds have the potential to cause temporary or permanent reduction in hearing sensitivity, also known as threshold shift. In terrestrial mammals and presumably marine mammals, received sound levels must far exceed the animal's hearing threshold for there to be any temporary threshold shift (TTS) in its hearing ability. For transient sounds, the sound level necessary to cause TTS is inversely related to the duration of the sound. Received sound levels must be even higher for there to be risk of permanent hearing impairment. In addition, intense acoustic or explosive events (not relevant for this proposed activity) may cause trauma to tissues associated with organs vital for hearing, sound production, respiration and other functions. This trauma may include minor to severe hemorrhage.

Direct Physiological Effects

Threshold Shift (Noise-Induced Loss of Hearing)

When animals exhibit reduced hearing sensitivity within their auditory range (i.e., sounds must be louder for an animal to detect them) following exposure to a sufficiently intense sound or a less intense sound for a sufficient duration, it is referred to as a noise-induced threshold shift (TS). An animal can experience a temporary threshold shift (TTS) and/or permanent threshold shift (PTS). TTS can last from minutes or hours to days (i.e., there is recovery back to baseline/pre-exposure levels), can occur within a specific frequency range (i.e., an animal might only have a temporary loss of hearing sensitivity within a limited frequency band of its auditory range), and can be of varying amounts (for example, an animal's hearing sensitivity might be reduced by only six dB or reduced by 30 dB). PTS is permanent (i.e., there is incomplete recovery back to baseline/pre-exposure levels), but also can occur in a specific frequency range and amount as mentioned above for TTS.

The following physiological mechanisms are thought to play a role in inducing auditory TSs: Effects to sensory hair cells in the inner ear that reduce their sensitivity, modification of the chemical environment within the sensory cells, residual muscular activity in the middle ear (at least in terrestrial mammals), displacement of certain inner ear membranes, increased blood flow, and post-stimulatory reduction in both efferent and sensory neural output (Southall

et al.,

2007). As amplitude and duration of sound exposure increase, so, generally, does the amount of TS, along with the recovery time. Human non-impulsive noise exposure guidelines are based on the assumption that exposures of equal energy (the same Sound Exposure Level (SEL)) producing equal amounts of hearing impairment regardless of how the sound energy is distributed in time (NIOSH, 1998). Until recently, previous marine mammal TTS studies have also generally supported this equal energy relationship (Southall

et al.,

2007). The amplitude, duration, frequency, temporal pattern, and energy distribution of sound exposure all affect the amount of associated TS and the frequency range in which it occurs. Three studies, two by Mooney

et al.

(2009a, 2009b) on a single bottlenose dolphin either exposed to playbacks of Navy MF active sonar or octave-band noise (4-8 kHz) and one by Kastak

et al.

(2007) on a single California sea lion exposed to airborne octave-band noise (centered at 2.5 kHz), concluded that for all noise exposure situations the equal energy relationship may not be the best indicator to predict TTS onset levels. All three of these studies highlight the inherent complexity of predicting TTS onset in marine mammals, as well as the importance of considering exposure duration when assessing potential impacts. Generally, with sound exposures of equal energy, those that were quieter (lower sound pressure level (SPL)) with longer duration were found to induce TTS onset at lower levels than those of louder (higher SPL) and shorter duration. For intermittent sounds, less TS will occur than from a continuous exposure with the same energy (some recovery can occur between intermittent exposures) (Kryter

et al.,

1966; Ward, 1997; Mooney

et al.

2009a, 2009b; Finneran

et al.

2010). For example, one short but loud (higher SPL) sound exposure may induce the same impairment as one longer but softer (lower SPL) sound, which in turn may cause more impairment than a series of several intermittent softer sounds with the same total energy (Ward, 1997). Additionally, though TTS is temporary, very prolonged or repeated exposure to sound strong enough to elicit TTS, or shorter-term exposure to sound levels well above the TTS threshold can cause PTS, at least in terrestrial mammals (Kryter, 1985; Lonsbury-Martin

et al.

1987) (although in the case of SURTASS LFA, animals are not expected to be exposed to levels high enough or durations long enough to result in PTS).

PTS is considered auditory injury (Southall

et al.,

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

et al.,

2007). Although the published body of scientific literature contains numerous theoretical studies and discussion papers on hearing impairments that can occur with exposure to a loud sound, only a few studies provide empirical information on the levels at which noise-induced loss in hearing sensitivity occurs in nonhuman animals. For cetaceans, published data on the onset of TTS are limited to the captive bottlenose dolphin, beluga, harbor porpoise, and Yangtze finless porpoise (Finneran

et al.,

2000, 2002b, 2005a, 2007, 2010a, 2010b; Schlundt

et al.,

2000; Nachtigall

et al.,

2003, 2004; Mooney

et al.,

2009a, 2009b; Lucke

et al.,

2009; Finneran and Schlundt, 2010; Popov

et al.,

2011). For pinnipeds in water, data are limited to Kastak

et al.'

s (1999, 2005) measurement of TTS in one captive harbor seal, one captive elephant seal, and one captive California sea lion (Finneran

et al.,

2003 tried to induce TTS in two California sea lions but could not).

Marine mammal hearing plays a critical role in communication with conspecifics and in interpretation of environmental cues for purposes such as predator avoidance and prey capture. Depending on the degree (elevation of threshold in dB), duration (i.e., recovery time), and frequency range of TTS, and the context in which it is experienced, TTS can have effects on marine mammals ranging from discountable to serious (similar to those discussed in auditory masking, below). For example, a marine mammal may be able to readily compensate for a brief, relatively small amount of TTS in a non-critical frequency range that takes place during a time when the animal is traveling through the open ocean, where ambient noise is lower and there are not as many competing sounds present. Alternatively, a larger amount and longer duration of TTS sustained during a time when communication is critical for successful mother/calf interactions could have more serious impacts if it were in the same frequency band as the necessary vocalizations and of a severity that impeded communication. The fact that animals exposed to levels and durations of sound that would be expected to result in this physiological response would also be expected to have behavioral responses of a comparatively more severe or sustained nature is potentially more significant than simple existence of a TTS.

Also, depending on the degree and frequency range, the effects of PTS on an animal could range in severity, although it is considered generally more serious than TTS because it is a permanent condition. Of note, reduced hearing sensitivity as a simple function of aging has been observed in marine mammals, as well as humans and other taxa (Southall

et al.,

2007), so we can infer that strategies exist for coping with this condition to some degree, though likely not without cost. There is no empirical evidence that exposure to SURTASS LFA sonar can cause PTS in any marine mammals; instead the possibility of PTS has been inferred from studies of TTS on captive marine mammals (see Richardson

et al.,

1995).

Acoustically Mediated Bubble Growth

One theoretical cause of injury to marine mammals is rectified diffusion (Crum and Mao, 1996), the process of increasing the size of a bubble by exposing it to a sound field. This process could be facilitated if the environment in which the ensonified bubbles exist is supersaturated with gas. Repetitive diving by marine mammals can cause the blood and some tissues to accumulate gas to a greater degree than is supported by the surrounding environmental pressure (Ridgway and Howard, 1979). The deeper and longer dives of some marine mammals (e.g., beaked whales) are theoretically predicted to induce greater supersaturation (Houser

et al.,

2001b), although recent preliminary empirical data suggests that there is no increase in blood nitrogen levels or formation of bubbles in diving bottlenose dolphins (Houser, 2009). If rectified diffusion were possible in marine mammals exposed to high-level sound, conditions of tissue supersaturation could theoretically speed the rate and increase the size of bubble growth. Subsequent effects due to tissue trauma and emboli would presumably mirror those observed in humans suffering from decompression sickness.

It is unlikely that the short duration of the SURTASS LFA sonar pings would be long enough to drive bubble growth to any substantial size, if such a phenomenon occurs. However, an alternative but related hypothesis has also been suggested; stable bubbles could be destabilized by high-level sound exposures such that bubble growth then occurs through static diffusion of gas out of the tissues. In such a scenario the marine mammal would need to be in a gas-supersaturated state for a long enough period of time for bubbles to become of a problematic size.

Yet another hypothesis (decompression sickness) speculates that rapid ascent to the surface following exposure to a startling sound might produce tissue gas saturation sufficient for the evolution of nitrogen bubbles (Jepson

et al.,

2003; Fernandez

et al.,

2005). In this scenario, the rate of ascent would need to be sufficiently rapid to compromise behavioral or physiological protections against nitrogen bubble formation. Alternatively, Tyack

et al.

(2006) studied the deep diving behavior of beaked whales and concluded that: “Using current models of breath-hold diving, we infer that their natural diving behavior is inconsistent with known problems of acute nitrogen supersaturation and embolism.” Collectively, these hypotheses (rectified diffusion and decompression sickness) can be referred to as “hypotheses of acoustically-mediated bubble growth.”

Although theoretical predictions suggest the possibility for acoustically mediated bubble growth, there is considerable disagreement among scientists as to its likelihood (Piantadosi and Thalmann, 2004; Evans and Miller, 2003; Cox

et al.,

2006; Rommel

et al.,

2006). Crum and Mao (1996) hypothesized that received levels would have to exceed 190 dB in order for there to be the possibility of significant bubble growth due to supersaturation of gases in the blood (i.e., rectified diffusion). More recent work conducted by Crum

et al.

(2005) demonstrated the possibility of rectified diffusion for short duration signals, but at exposure levels and tissue saturation levels that are highly improbable to occur in diving marine mammals. To date, energy levels predicted to cause in vivo bubble

formations within diving cetaceans have not been evaluated (NOAA, 2002b). Although it has been argued that traumas from some recent beaked whale strandings are consistent with gas emboli and bubble-induced tissue separations (Jepson

et al.,

2003), there is no conclusive evidence of this (Rommel

et al.,

2006). However, Jepson

et al.

(2003, 2005) and Fernandez

et al.

(2004, 2005) concluded that in vivo bubble formation, which may be exacerbated by deep, long-duration, repetitive dives, may explain why beaked whales appear to be particularly vulnerable to MF/HF active sonar exposures.

In 2009, Hooker

et al.

(2009) tested two mathematical models to predict blood and tissue tension N2 (P

) using field data from three beaked whale species: Northern bottlenose whales, Cuvier's beaked whales, and Blainville's beaked whales. The researchers aimed to determine if physiology (body mass, diving lung volume, and dive response) or dive behavior (dive depth and duration, changes in ascent rate, and diel behavior) would lead to differences in P

levels and thereby decompression sickness risk between species.

In their study, they compared results for previously published time depth recorder data (Hooker and Baird, 1999; Baird

et al.,

2006, 2008) from Cuvier's beaked whale, Blainville's beaked whale, and northern bottlenose whale. They reported that diving lung volume and extent of the dive response had a large effect on end-dive P

. Also, results showed that dive profiles had a larger influence on end-dive P

than body mass differences between species. Despite diel changes (i.e., variation that occurs regularly every day or most days) in dive behavior, P

levels showed no consistent trend. Model output suggested that all three species live with tissue P

levels that would cause a significant proportion of decompression sickness cases in terrestrial mammals. The authors concluded that the dive behavior of Cuvier's beaked whale was different from both Blainville's beaked whale, and northern bottlenose whale, and resulted in higher predicted tissue and blood N2 levels (Hooker

et al.,

2009) and suggested that the prevalence of Cuvier's beaked whales stranding after naval sonar exercises could be explained by either a higher abundance of this species in the affected areas or by possible species differences in behavior and/or physiology related to MF active sonar (Hooker

et al.,

2009).

The hypotheses for gas bubble formation related to beaked whale strandings is that beaked whales potentially have strong avoidance responses to MF active sonars because they sound similar to their main predator, the killer whale (Cox

et al.,

2006; Southall

et al.,

2007; Zimmer and Tyack, 2007; Baird

et al.,

2008; Hooker

et al.,

2009). Because SURTASS LFA sonar transmissions are lower in frequency (less than 500 Hz) and dissimilar in characteristics from those of marine mammal predators, or MF active sonars the SURTASS LFA sonar transmissions are not expected to cause gas bubble formation or beaked whale strandings. Further investigation is needed to further assess the potential validity of these hypotheses.

Acoustic Masking

Marine mammals use acoustic signals for a variety of purposes, which differ among species, but include communication between individuals, navigation, foraging, reproduction, and learning about their environment (Erbe and Farmer, 2000; Tyack, 2000). Masking, or auditory interference, generally occurs when sounds in the environment are louder than, and of a similar frequency as, auditory signals an animal is trying to receive. Masking is a phenomenon that affects animals that are trying to receive acoustic information about their environment, including sounds from other members of their species, predators, prey, and sounds that allow them to orient in their environment. Masking these acoustic signals can disturb the behavior of individual animals, groups of animals, or entire populations.

The extent of the masking interference depends on the spectral, temporal, and spatial relationships between the signals an animal is trying to receive and the masking noise, in addition to other factors. In humans, significant masking of tonal signals occurs as a result of exposure to noise in a narrow band of similar frequencies. As the sound level increases, the detection of frequencies above those of the masking stimulus decreases. This principle is expected to apply to marine mammals as well because of common biomechanical cochlear properties across taxa.

Richardson

et al.

(1995b) argued that the maximum radius of influence of an industrial noise (including broadband low-frequency sound transmission) on a marine mammal is the distance from the source to the point at which the noise can barely be heard. This range is determined by either the hearing sensitivity of the animal or the background noise level present. Industrial masking is most likely to affect some species' ability to detect communication calls and natural sounds (i.e., surf noise, prey noise, etc.) (Richardson

et al.,

1995).

The echolocation calls of toothed whales are subject to masking by high-frequency sound. Human data indicate that low-frequency sounds can mask high-frequency sounds (i.e., upward masking). Studies on captive odontocetes by Au

et al.

(1974, 1985, 1993) indicate that some species may use various processes to reduce masking effects (e.g., adjustments in echolocation call intensity or frequency as a function of background noise conditions). There is also evidence that the directional hearing abilities of odontocetes are useful in reducing masking at the higher frequencies these cetaceans use to echolocate, but not at the low-to-moderate frequencies they use to communicate (Zaitseva

et al.,

1980). A study by Nachtigall and Supin (2008) showed that false killer whales adjust their hearing to compensate for ambient sounds and the intensity of returning echolocation signals. Holt

et al.

(2009) measured killer whale call source levels and background noise levels in the one to 40 kHz band and reported that the whales increased their call source levels by one dB SPL for every one dB SPL increase in background noise level. Similarly, another study on St. Lawrence River belugas reported a similar rate of increase in vocalization activity in response to passing vessels (Scheifele

et al.,

2005).

Parks

et al.

(2007) provided evidence of behavioral changes in the acoustic behaviors of the endangered North Atlantic right whale, and the South Atlantic right whale, and suggested that these were correlated to increased underwater noise levels. The study indicated that right whales might shift the frequency band of their calls to compensate for increased in-band background noise. The significance of their result is the indication of potential species-wide behavioral change in response to gradual, chronic increases in underwater ambient noise. Di Iorio and Clark (2010) showed that blue whale calling rates vary in association with seismic sparker survey activity, with whales calling more on days with survey than on days without surveys. They suggested that the whales called more during seismic survey periods as a way to compensate for the elevated noise conditions.

As mentioned previously, the functional hearing ranges of mysticetes overlap with the frequencies of the SURTASS LFA sonar sources used in the Navy's training and testing, as well as during military operations. The closer the characteristics of the masking signal to the signal of interest, the more likely masking is to occur. The masking effects of the SURTASS LFA sonar signal are

expected to be limited for a number of reasons. First, the frequency range (bandwidth) of the system is limited to approximately 30 Hz, and the instantaneous bandwidth at any given time of the signal is small, on the order of 10 Hz. Second, the average duty cycle is always less than 20 percent and, based on past LFA sonar operational parameters (2003 to 2012), is nominally 7.5 to 10 percent. Third, given the average maximum pulse length (60 sec), and the fact that the signals vary and do not remain at a single frequency for more than 10 sec, SURTASS LFA sonar is not likely to cause significant masking. The Navy provided an analysis of marine mammal hearing and masking in Subchapter 4.6.1.2 of the 2007 FSEIS and 4.2.5 in the 2011 DSEIS/SOEIS. In other words, the LFA sonar transmissions are coherent, narrow bandwidth signals of six to 100 sec in length followed by a quiet period of six to 15 minutes. Therefore, the effect of masking will be limited because animals that use this frequency range typically use broader bandwidth signals. As a result, the chances of an LFA sonar sound actually overlapping whale calls at levels that would interfere with their detection and recognition would be extremely low.

Impaired Communication

In addition to making it more difficult for animals to perceive acoustic cues in their environment, anthropogenic sound presents separate challenges for animals that are vocalizing. When they vocalize, animals are aware of environmental conditions that affect the “active space” of their vocalizations, which is the maximum area within which their vocalizations can be detected before they drop to the level of ambient noise (Brenowitz, 2004; Brumm

et al.,

2004; Lohr

et al.,

2003). Animals are also aware of environmental conditions that affect whether listeners can discriminate and recognize their vocalizations from other sounds, which is more important than simply detecting that a vocalization is occurring (Brenowitz, 1982; Brumm

et al.,

2004; Dooling, 2004, Marten and Marler, 1977; Patricelli

et al.,

2006). Most animals that vocalize have evolved with an ability to make adjustments to their vocalizations to increase the signal-to-noise ratio, active space, and recognizability/distinguishability of their vocalizations in the face of temporary changes in background noise (Brumm

et al.,

2004; Patricelli

et al.,

2006). Vocalizing animals can make adjustments to vocalization characteristics such as the frequency structure, amplitude, temporal structure and temporal delivery.

Many animals will combine several of these strategies to compensate for high levels of background noise. Anthropogenic sounds which reduce the signal-to-noise ratio of animal vocalizations, increase the masked auditory thresholds of animals listening for such vocalizations, or reduce the active space of an animal's vocalizations impair communications between animals. Most animals that vocalize have evolved strategies to compensate for the effects of short-term or temporary increases in background or ambient noise on their songs or calls. Although the fitness consequences of these vocal adjustments remain unknown, like most other trade-offs animals must make, some of these strategies probably come at a cost (Patricelli

et al.,

2006). For example, vocalizing more loudly in noisy environments may have energetic costs that decrease the net benefits of vocal adjustment and alter a bird's energy budget (Brumm, 2004; Wood and Yezerinac, 2006). Shifting songs and calls to higher frequencies may also impose energetic costs (Lambrechts, 1996).

Stress Responses

Classic stress responses begin when an animal's central nervous system perceives a potential threat to its homeostasis. That perception triggers stress responses regardless of whether a stimulus actually threatens the animal; the mere perception of a threat is sufficient to trigger a stress response (Moberg, 2000; Sapolsky

et al.,

2005; Seyle, 1950). Once an animal's central nervous system perceives a threat, it mounts a biological response or defense that consists of a combination of the four general biological defense responses: Behavioral responses, autonomic nervous system responses, neuroendocrine responses, or immune responses.

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

An animal's third line of defense to stressors involves its neuroendocrine or sympathetic nervous systems; the system that has received the most study has been the hypothalmus-pituitary-adrenal system (also known as the HPA axis in mammals or the hypothalamus-pituitary-interrenal axis in fish and some reptiles). Unlike stress responses associated with the autonomic nervous system, virtually all neuro-endocrine functions that are affected by stress—including immune competence, reproduction, metabolism, and behavior—are regulated by pituitary hormones. Stress-induced changes in the secretion of pituitary hormones have been implicated in failed reproduction (Moberg, 1987; Rivier, 1995), altered metabolism (Elasser

et al.,

2000), reduced immune competence (Blecha, 2000), and behavioral disturbance. Increases in the circulation of glucocorticosteroids (cortisol, corticosterone, and aldosterone in marine mammals; see Romano

et al.,

2004) have been equated with stress for many years.

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

Relationships between these physiological mechanisms, animal behavior, and the costs of stress responses have also been documented

fairly well through controlled experiments; because this physiology exists in every vertebrate that has been studied, it is not surprising that stress responses and their costs have been documented in both laboratory and free-living animals (for examples see, Holberton

et al.,

1996; Hood

et al.,

1998; Jessop

et al.,

2003; Krausman

et al.,

2004; Lankford

et al.,

2005; Reneerkens

et al.,

2002; Thompson and Hamer, 2000).

There is limited information on the physiological responses of marine mammals to anthropogenic sound exposure, as most observations have been limited to short-term behavioral responses, which included cessation of feeding, resting, or social interactions. Despite the dearth of information on stress responses for marine mammals exposed to anthropogenic sounds, studies of other marine animals and terrestrial animals lead us to expect some marine mammals to experience physiological stress responses and, perhaps, physiological responses that would be classified as “distress” upon exposure to low-frequency sounds. For example, Jansen (1998) reported on the relationship between acoustic exposures and physiological responses that are indicative of stress responses in humans (e.g., elevated respiration and increased heart rates). Jones (1998) reported on reductions in human performance when faced with acute, repetitive exposures to acoustic disturbance. Trimper

et al.

(1998) reported on the physiological stress responses of osprey to low-level aircraft noise while Krausman

et al.

(2004) reported on the auditory and physiology stress responses of endangered Sonoran pronghorn to military overflights. Smith

et al.

(2004a, 2004b) identified noise-induced physiological transient stress responses in hearing-specialist fish (i.e., goldfish) that accompanied short- and long-term hearing losses. Welch and Welch (1970) reported physiological and behavioral stress responses that accompanied damage to the inner ears of fish and several mammals.

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

Behavioral Disturbance

Behavioral responses to sound are highly variable and context-specific. Many different variables can influence an animal's perception of and response to (in both nature and magnitude) an acoustic event. An animal's prior experience with a sound or sound source affects whether it is less likely (habituation) or more likely (sensitization) to respond to certain sounds in the future (animals can also be innately pre-disposed to respond to certain sounds in certain ways) (Southall

et al.,

2007). Related to the sound itself, the perceived nearness of the sound, bearing of the sound (approaching vs. retreating), similarity of the sound to biologically relevant sounds in the animal's environment (i.e., calls of predators, prey, or conspecifics), and familiarity of the sound may affect the way an animal responds to the sound (Southall

et al.,

2007). Individuals (of different age, gender, reproductive status, etc.) among most populations will have variable hearing capabilities, and differing behavioral sensitivities to sounds that will be affected by prior conditioning, experience, and current activities of those individuals. Often, specific acoustic features of the sound and contextual variables (i.e., proximity, duration, or recurrence of the sound or the current behavior that the marine mammal is engaged in or its prior experience), as well as entirely separate factors such as the physical presence of a nearby vessel, may be more relevant to the animal's response than the received level alone.

Exposure of marine mammals to sound sources can result in, but is not limited to, no response or any of the following observable responses: increased alertness; orientation or attraction to a sound source; vocal modifications; cessation of feeding; cessation of social interaction; alteration of movement or diving behavior; avoidance; habitat abandonment (temporary or permanent); and, in severe cases, panic, flight, stampede, or stranding, potentially resulting in death (Southall

et al.,

2007). A review of marine mammal responses to anthropogenic sound was first conducted by Richardson (1995). A more recent review (Nowacek

et al.,

2007) addresses studies conducted since 1995 and focuses on observations where the received sound level of the exposed marine mammal(s) was known or could be estimated. The following subsections provide examples of behavioral responses that provide an idea of the variability in behavioral responses that would be expected given the different sensitivities of marine mammal species to sound and the wide range of potential acoustic sources to which a marine mammal may be exposed. Estimates of the types of behavioral responses that could occur for a given sound exposure should be determined from the literature that is available for each species or extrapolated from closely related species when no information exists.

Alteration of Diving or Movement. Changes in dive behavior can vary widely. They may consist of increased or decreased dive times and surface intervals as well as changes in the rates of ascent and descent during a dive. Variations in dive behavior may reflect interruptions in biologically significant activities (e.g., foraging) or they may be of little biological significance. Variations in dive behavior may also expose an animal to potentially harmful conditions (e.g., increasing the chance of ship-strike) or may serve as an avoidance response that enhances survivorship. The impact of a variation in diving resulting from an acoustic exposure depends on what the animal is doing at the time of the exposure and the type and magnitude of the response.

Nowacek

et al.

(2004) reported disruptions of dive behaviors in foraging North Atlantic right whales when exposed to an alerting stimulus, a reaction, they noted, that could lead to an increased likelihood of ship strike. However, the whales did not respond to playbacks of either right whale social sounds or vessel noise, highlighting the importance of the sound characteristics in producing a behavioral reaction. Conversely, Indo-Pacific humpback dolphins have been observed to dive for longer periods of time in areas where vessels were present and/or approaching (Ng and Leung, 2003). In both of these studies, the influence of

the sound exposure cannot be decoupled from the physical presence of a surface vessel, thus complicating interpretations of the relative contribution of each stimulus to the response. Indeed, the presence of surface vessels, their approach, and the speed of approach, all seemed to be significant factors in the response of the Indo-Pacific humpback dolphins (Ng and Leung, 2003). Low-frequency signals of the Acoustic Thermometry of Ocean Climate (ATOC) sound source were not found to affect dive times of humpback whales in Hawaiian waters (Frankel and Clark, 2000) or to overtly affect elephant seal dives (Costa

et al.,

2003). They did, however, produce subtle effects that varied in direction and degree among the individual seals, illustrating the varied nature of behavioral effects and consequent difficulty in defining and predicting them.

Foraging. Disruption of feeding behavior can be difficult to correlate with anthropogenic sound exposure, so it is usually inferred by observed displacement from known foraging areas, the appearance of secondary indicators (e.g., bubble nets or sediment plumes), or changes in dive behavior. Noise from seismic surveys was not found to impact the feeding behavior of western gray whales off the coast of Russia (Yazvenko

et al.,

2007) and sperm whales engaged in foraging dives did not abandon dives when exposed to distant signatures of seismic airguns (Madsen

et al.,

2006). Balaenopterid whales exposed to moderate SURTASS LFA sonar demonstrated no responses or change in foraging behavior that could be attributed to the low-frequency sounds (Croll

et al.,

2001), whereas five out of six North Atlantic right whales exposed to an acoustic alarm interrupted their foraging dives (Nowacek

et al.,

2004). Although the received sound pressure level was similar in the latter two studies, the frequency, duration, and temporal pattern of signal presentation were different. These factors, as well as differences in species sensitivity, are likely contributing factors to the differential response. A determination of whether foraging disruptions incur fitness consequences will require information on or estimates of the energetic requirements of the individuals and the relationship between prey availability, foraging effort and success, and the life history stage of the animal.

Brownell (2004) reported the behavioral responses of western gray whales off the northeast coast of Sakhalin Island to sounds produced by local seismic activities. In 1997, the gray whales responded to seismic activities by changing their swimming speed and orientation, respiration rates, and distribution in waters around the seismic surveys. In 2001, seismic activities were conducted in a known foraging ground and the whales left the area and moved farther south to the Sea of Okhotsk. They only returned to the foraging ground several days after the seismic activities stopped. The potential fitness consequences of displacing these whales, especially mother-calf pairs and “skinny whales,” outside of their normal feeding area are not known; however, because gray whales, like other large whales, must gain enough energy during the summer foraging season to last them the entire year, sounds or other stimuli that cause them to abandon a foraging area for several days could disrupt their energetics (i.e., the measurement of energy flow through an animal, from what goes into an animal as food (prey) to how the animal converts that energy for growth, reproduction, maintenance, and metabolism) and force them to make trade-offs like delaying their migration south, delaying reproduction, reducing growth, or migrating with reduced energy reserves.

Social Relationships.

Social interactions between mammals can be affected by noise via the disruption of communication signals or by the displacement of individuals. Sperm whales responded to military sonar, apparently from a submarine, by dispersing from social aggregations, moving away from the sound source, remaining relatively silent, and becoming difficult to approach (Watkins

et al.,

1985). In contrast, sperm whales in the Mediterranean that were exposed to submarine sonar continued calling (J. Gordon pers. comm. cited in Richardson

et al.,

1995). Social disruptions must be considered, however, in context of the relationships that are affected. While some disruptions may not have deleterious effects, long-term or repeated disruptions of mother/calf pairs or interruption of mating behaviors have the potential to affect the growth and survival or reproductive effort/success of individuals.

Vocalizations.

(also see Masking Section)—Vocal changes in response to anthropogenic noise can occur across the repertoire of sound production modes used by marine mammals, such as whistling, echolocation click production, calling, and singing. Changes may result in response to a need to compete with an increase in background noise or may reflect an increased vigilance or startle response. For example, in the presence of low-frequency active sonar, humpback whales have been observed to increase the length of their “songs” (Miller

et al.,

2000; Fristrup

et al.,

2003), possibly due to the overlap in frequencies between the whale song and the low-frequency active sonar. A similar compensatory effect for the presence of low-frequency vessel noise has been suggested for right whales; right whales have been observed to shift the frequency content of their calls upward while reducing the rate of calling in areas of increased anthropogenic noise (Parks

et al.,

2007). Killer whales off the northwestern coast of the United States have been observed to increase the duration of primary calls once a threshold in observing vessel density (e.g., whale watching) was reached, which has been suggested as a response to increased masking noise produced by the vessels (Foote

et al.,

2004). In contrast, both sperm and pilot whales potentially ceased sound production during the Heard Island feasibility test (Bowles

et al.,

1994), although it cannot be absolutely determined whether the inability to acoustically detect the animals was due to the cessation of sound production or the displacement of animals from the area.

Avoidance.

Avoidance is the displacement of an individual from an area as a result of the presence of a sound. Richardson

et al.

(1995) noted that avoidance reactions are the most obvious manifestations of disturbance in marine mammals. Avoidance is qualitatively different from the flight response, but also differs in the magnitude of the response (i.e., directed movement, rate of travel, etc.). Oftentimes, avoidance is temporary and animals return to the area once the noise has ceased. However, longer term displacement is possible and can lead to changes in abundance or distribution patterns of the species in the affected region if animals do not become acclimated to the presence of the chronic sound (Blackwell

et al.,

2004; Bejder

et al.,

2006; Teilmann

et al.,

2006). Acute avoidance responses have been observed in captive porpoises and pinnipeds exposed to a number of different sound sources (Kastelein

et al.,

2001; Finneran

et al.,

2003; Kastelein

et al.,

2006a; Kastelein

et al.,

2006b). Short-term avoidance of seismic surveys, low-frequency emissions, and acoustic deterrents have also been noted in wild populations of odontocetes (Bowles

et al.,

1994; Goold, 1996; 1998; Stone

et al.,

2000; Morton and Symonds, 2002) and to some extent in mysticetes (Gailey

et al.,

2007), while

long-term or repetitive/chronic displacement for some dolphin groups and for manatees has been suggested to result from the presence of chronic vessel noise (Haviland-Howell

et al.,

2007; Miksis-Olds

et al.,

2007).

In 1998, the Navy conducted a Low Frequency Sonar Scientific Research Program (LFS SRP) to investigate avoidance behavior of gray whales to low frequency sound signals. The objective was to determine whether whales respond more strongly to received levels (RL), sound gradient, or distance from the source, and to compare whale avoidance responses to an LF source in the center of the migration corridor versus in the offshore portion of the migration corridor. A single source was used to broadcast LFA sonar sounds up to 200 dB. The Navy reported that the whales showed some avoidance responses when the source was moored one mile (1.8 km) offshore, in the migration path, but returned to their migration path when they were a few kilometers from the source. When the source was moored two miles (3.7 km) offshore, responses were much less, even when the source level was increased to 200 dB re: 1 µPa, to achieve the same RL for most whales in the middle of the migration corridor. Also, the researchers noted that the offshore whales did not seem to avoid the louder offshore source.

Also during the LFS SRP, researchers sighted numerous odontocete and pinniped species in the vicinity of the sound exposure tests with LFA sonar. The MF and HF hearing specialists present in the study area showed no immediately obvious responses or changes in sighting rates as a function of source conditions. Consequently, the researchers concluded that none of these species had any obvious behavioral reaction to LFA signals at received levels similar to those that produced only minor but short-term behavioral responses in the baleen whales (i.e., LF hearing specialists) (Clark and Southall, 2009). Thus, for odontocetes, the chances of injury and/or significant behavioral responses to SURTASS LFA sonar would be low given the MF/HF specialists' observed lack of response to LFA sounds during the LFS SRP and due to the MF/HF frequencies to which these animals are adapted to hear (Clark and Southall, 2009).

Maybaum (1993) conducted sound playback experiments to assess the effects of mid-frequency active sonar on humpback whales in Hawaiian waters. Specifically, she exposed focal pods to sounds of a 3.3-kHz sonar pulse, a sonar frequency sweep from 3.1 to 3.6 kHz, and a control (blank) tape while monitoring the behavior, movement, and underwater vocalizations. The two types of sonar signals differed in their effects on the humpback whales, but both resulted in avoidance behavior. The whales responded to the pulse by increasing their distance from the sound source and responded to the frequency sweep by increasing their swimming speeds and track linearity. In the Caribbean, sperm whales avoided exposure to mid-frequency submarine sonar pulses, in the range of 1000 Hz to 10,000 Hz (IWC 2005).

Kvadsheim

et al.,

(2007) conducted a controlled exposure experiment in which killer whales fitted with D-tags were exposed to mid-frequency active sonar (Source A: A 1.0 s upsweep 209 dB @ 1-2 kHz every 10 sec for 10 minutes; Source B: With a 1.0 s upsweep 197 dB @ 6-7 kHz every 10 sec for 10 min). When exposed to Source A, a tagged whale and the group it was traveling with did not appear to avoid the source. When exposed to Source B, the tagged whales along with other whales that had been carousel feeding (where killer whales cooperatively herd fish schools into a tight ball towards the surface and feed on the fish which have been stunned by tailslaps and subsurface feeding (Simila, 1997) ceased feeding during the approach of the sonar and moved rapidly away from the source. When exposed to Source B, Kvadsheim and his co-workers reported that a tagged killer whale seemed to try to avoid further exposure to the sound field by the following behaviors: Immediately swimming away (horizontally) from the source of the sound; engaging in a series of erratic and frequently deep dives that seemed to take it below the sound field; or swimming away while engaged in a series of erratic and frequently deep dives. Although the sample sizes in this study are too small to support statistical analysis, the behavioral responses of the orcas were consistent with the results of other studies.

In 2007, the first in a series of behavioral response studies (BRS) on deep diving odontocetes conducted by NMFS and other scientists showed one beaked whale (

Mesoplodon densirostris

) responding to an MF active sonar playback. The BRS-07 cruise report indicates that the playback began when the tagged beaked whale was vocalizing at depth (at the deepest part of a typical feeding dive), following a previous control with no sound exposure. The whale appeared to stop clicking significantly earlier than usual, when exposed to mid-frequency signals in the 130-140 dB (rms) received level range. After a few more minutes of the playback, when the received level reached a maximum of 140-150 dB, the whale ascended on the slow side of normal ascent rates with a longer than normal ascent, at which point the exposure was terminated. The BRS-07 cruise report notes that the results are from a single experiment and that a greater sample size is needed before robust and definitive conclusions can be drawn (NMFS, 2008a).

In the 2008 BRS study, researchers identified an emerging pattern of responses of deep-diving beaked whales to MF active sonar playbacks. For example, Blainville's beaked whales—a resident species within the Tongue of the Ocean, Bahamas study area—appear to be sensitive to noise at levels well below expected TTS (approximately 160 dB re: 1μPa at 1 m). This sensitivity is manifest by an adaptive movement away from a sound source. This response was observed irrespective of whether the signal transmitted was within the band width of MF active sonar, which suggests that beaked whales may not respond to the specific sound signatures. Instead, they may be sensitive to any pulsed sound from a point source in the frequency range of the MF active sonar transmission. The response to such stimuli appears to involve the beaked whale increasing the distance between it and the sound source (NMFS, 2008b).

In the 2010 BRS study, researchers again used controlled exposure experiments (CEE) to carefully measure behavioral responses of individual animals to sound exposures of MF active sonar and pseudo-random noise. For each sound type, some exposures were conducted when animals were in a surface feeding (approximately 164 ft (50 m) or less) and/or socializing behavioral state and others while animals were in a deep feeding (greater than 164 ft (50 m)) and/or traveling mode. The researchers conducted the largest number of CEEs on blue whales (n=19) and of these, 11 CEEs involved exposure to the MF active sonar sound type.

For the majority of CEE transmissions of either sound type, they noted few obvious behavioral responses detected either by the visual observers or on initial inspection of the tag data. The researchers observed that throughout the CEE transmissions, up to the highest received sound level (absolute RMS value approximately 160 dB re: 1μPa with signal-to-noise ratio values over 60 dB), two blue whales continued surface feeding behavior and remained at a range of around 3,820 ft (1,000 m) from the sound source (Southall

et al.,

2011).

In contrast, another blue whale (later in the day and greater than 11.5 mi (18.5 km; 10 nmi) from the first CEE location) exposed to the same stimulus (MFA) while engaged in a deep feeding/travel state exhibited a different response. In that case, the blue whale responded almost immediately following the start of sound transmissions when received sounds were just above ambient background levels (Southall

et al.,

2011). However, the authors note that this kind of temporary avoidance behavior was not evident in any of the nine CEEs involving blue whales engaged in surface feeding or social behaviors, but was observed in three of the ten CEEs for blue whales in deep feeding/travel behavioral modes (one involving MFA sonar; two involving pseudo-random noise) (Southall

et al.,

2011). The results of this study further illustrate the importance of behavioral context in understanding and predicting behavioral responses.

Flight Response.

A flight response is a dramatic change in normal movement to a directed and rapid movement away from the perceived location of a sound source. Relatively little information on flight responses of marine mammals to anthropogenic signals exist, although observations of flight responses to the presences of predators have occurred (Connor and Heithaus, 1996). Flight responses have been speculated as being a component of marine mammal strandings associated with MF active sonar activities (Evans and England, 2001). If marine mammals respond to Navy vessels that are transmitting active sonar in the same way that they might respond to a predator, their probability of flight responses should increase when they perceive that Navy vessels are approaching them directly, because a direct approach may convey detection and intent to capture (Burger and Gochfeld, 1981, 1990; Cooper, 1997, 1998). In addition to the limited data on flight response for marine mammals, there are examples for terrestrial species. For instance, the probability of flight responses in Dall's sheep

Ovis dalli dalli

(Frid, 2001a, 2001b), ringed seals

Phoca hispida

(Born

et al.,

1999), Pacific brant (

Branta bernicl nigricans

), and Canada geese (

B. Canadensis

) increased as a helicopter or fixed-wing aircraft more directly approached groups of these animals (Ward

et al.,

1999). Bald eagles (

Haliaeetus leucocephalus

) perched on trees alongside a river were also more likely to flee from a paddle raft when their perches were closer to the river or were closer to the ground (Steidl and Anthony, 1996).

Breathing.

Variations in respiration naturally occur with different behaviors. Variations in respiration rate as a function of acoustic exposure can co-occur with other behavioral reactions, such as a flight response or an alteration in diving. However, respiration rates in and of themselves may be representative of annoyance or an acute stress response. Mean exhalation rates of gray whales at rest and while diving were found to be unaffected by seismic surveys conducted adjacent to foraging grounds (Gailey

et al.,

2007). Studies with captive harbor porpoises showed increased respiration rates upon introduction of acoustic alarms (Kastelein

et al.,

2001; Kastelein

et al.,

2006a) and emissions for underwater data transmission (Kastelein

et al.,

2005). However, exposing the same acoustic alarm to a striped dolphin under the same conditions did not elicit a response (Kastelein

et al.,

2006a), again highlighting the importance of understanding species differences in the tolerance of underwater noise when determining the potential for impacts resulting from anthropogenic sound exposure.

Continued Pre-disturbance Behavior and Habituation.

Under some circumstances, some of the individual marine mammals that are exposed to active sonar transmissions will continue their normal behavioral activities; in other circumstances, individual animals will respond to sonar transmissions at lower received levels and move to avoid additional exposure or exposures at higher received levels (Richardson

et al.,

1995).

It is difficult to distinguish between animals that continue their pre-disturbance behavior without stress responses

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