Taking and Importing Marine Mammals; Navy Training Activities Conducted Within the Northwest Training Range Complex

DEPARTMENT OF COMMERCE

National Oceanic and Atmospheric Administration

50 CFR Part 218

[Docket No. 0906101030-91038-01]

RIN 0648-AX88

Taking and Importing Marine Mammals; Navy Training Activities Conducted Within the Northwest Training Range Complex

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 incidental to training activities conducted in the Northwest Training Range Complex (NWTRC), off the coasts of Washington, Oregon, and northern California, for the period of February 2010 through February 2015 (updated from initial request for October 2009 through September 2014). Pursuant to the Marine Mammal Protection Act (MMPA), NMFS is proposing regulations to govern that take and requesting information, suggestions, and comments on these proposed regulations.

DATES:

Comments and information must be received no later than August 12, 2009.

ADDRESSES:

You may submit comments, identified by 0648-AX88, 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 Michael Payne, Chief, Permits, Conservation and Education Division, Office of Protected Resources, National Marine Fisheries Service, 1315 East-West Highway, Silver Spring, MD 20910-3225.

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.

FOR FURTHER INFORMATION CONTACT:

Jolie Harrison, Office of Protected Resources, NMFS, (301) 713-2289, ext. 166.

SUPPLEMENTARY INFORMATION:

Availability

A copy of the Navy's application may be obtained by writing to the address specified above (

See

ADDRESSES

), telephoning the contact listed above (

see

FOR FURTHER INFORMATION CONTACT

), or visiting the Internet at:

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

. The Navy's Draft Environmental Impact Statement (DEIS) for NWTRC was published on December 29 2008, and may be viewed at

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

. NMFS is participating in the development of the Navy's EIS as a cooperating agency under NEPA.

Background

Sections 101(a)(5)(A) and (D) of the 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 marine mammals by U.S. citizens who engage in a specified activity (other than commercial fishing) 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, 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), will not have an unmitigable adverse impact on the availability of the species or stock(s) for subsistence uses, and if the permissible methods of taking and requirements pertaining to the mitigation, monitoring and reporting of such taking are set forth. NMFS has defined “negligible impact” in 50 CFR 216.103 as:

“An impact resulting from the specified activity that cannot be reasonably expected to, and is not reasonably likely to, adversely affect the species or stock through effects on annual rates of recruitment or survival.”

The National Defense Authorization Act of 2004 (NDAA) (Pub. L. 108-136) modified the MMPA by removing the “small numbers” and “specified geographical region” limitations and amended the definition of “harassment” as it applies to a “military readiness activity” 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 behavioral 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].

In January 2009, the Council on Environmental Quality requested that NOAA conduct a comprehensive review of the Navy's mitigation measures applicable to the use of sonar in it's training activities.

Summary of Request

In September 2008, NMFS received an application from the Navy requesting authorization for the take of individuals of 26 species of marine mammals incidental to upcoming Navy training activities to be conducted within the NWTRC, which extends west to 250 nautical miles (nm) (463 kilometers [km]) beyond the coast of Northern California, Oregon, and Washington and east to Idaho and encompasses 122,400 nm

2

(420,163 km

2

) of surface/subsurface ocean operating areas. These training activities are military readiness activities under the provisions of the NDAA. The Navy states, and NMFS concurs, that these military readiness activities may incidentally take marine mammals present within the NWTRC by exposing them to sound from mid-frequency or high frequency active sonar (MFAS/HFAS) or underwater detonations. The Navy requests authorization to take individuals of 26 species of marine mammals by Level B Harassment and 14 individuals of 10 species by Level A Harassment. The Navy's model, which did not factor in any potential benefits of mitigation measures, predicted that 14 individual marine mammals would be exposed to levels of sound or pressure that would result in injury; thus, NMFS is proposing to authorize the take, by Level A Harassment of 14 individuals. However, NMFS and the Navy have determined preliminarily that injury can be avoided through the implementation of the Navy's proposed mitigation measures. NMFS neither anticipates, nor does it propose to authorize mortality of marine mammals incidental to naval exercises in the NWTRC.

Background of Request

The Navy's mission is to maintain, train, and equip combat-ready naval forces capable of winning wars, deterring aggression, and maintaining freedom of the seas. Section 5062 of Title 10 of the United States Code directs the Chief of Naval Operations to train all naval forces for combat. The Chief of Naval Operations meets that direction, in part, by conducting at-sea training exercises and ensuring naval forces have access to ranges, operating areas (OPAREAs) and airspace where they can develop and maintain skills for wartime missions and conduct research, development, testing, and evaluation (RDT&E) of naval weapons systems.

The proposed action would result in selectively focused, but critical enhancements and increases in training that are necessary for the Navy to maintain a state of military readiness commensurate with the national defense mission. The Navy proposes to implement actions within the NWTRC to:

• Conduct training and Unmanned Aerial Systems (UAS) RDT&E activities of the same types as currently conducted, but also;

• Increase training activities from current levels as necessary in support of the Fleet Response Training Plan (FRTP);

• Accommodate force structure changes (new platforms and weapons systems); and

• Implement range enhancements associated with the NWTRC.

The proposed action would result in the following increases (above those conducted in previous years,

i.e.

, the No Action Alternative in the Navy's DEIS) in activities:

•

Antisubmarine Warfare

—10% increase.

•

Gunnery Exercises

—100% increase (increased from 90 to 176 events).

•

Bombing Exercises

—25% increase (increased from 24 to 30 sorties).

•

Sinking Exercises

—100% increase (increased from 1 to 2 exercises).

Overview of the NWTRC

The U.S. Navy has been training and operating in the area now defined as the NWTRC for over 60 years. The NWTRC includes ranges and airspace that extend west to 250 nm (463 km) beyond the coast of Northern California, Oregon, and Washington and east to Idaho. The components of the NWTRC encompass 122,461 nm

2

(420,163 km

2

) of surface/subsurface ocean operating areas (OPAREAs), 46,048 nm

2

(157,928 km

2

) of special use airspace (SUA), and 875 acres (354 hectares) of land. For range management and scheduling purposes, the NWTRC is divided into numerous sub-component ranges or training areas used to conduct training and RDT&E of military hardware, personnel, tactics, munitions, explosives, and electronic combat systems, as described in detail in the NWTRC DEIS. As the take of marine mammals is inherently tied to the surface/subsurface OPAREAs of the NWTRC, only those areas are discussed in more detail below.

The LOA application includes graphics (Figures 1-1, 2-1, and 2-2) that depict the sea, undersea, and air spaces used by the Navy. To aid in the description of the range complexes that will be addressed in this proposed rule, the ranges are divided into three major geographic and functional subdivisions. Each of the depicted individual ranges falls into one of these three major range subdivisions:

The Offshore Area

—The Pacific Northwest (PACNW) OPAREA (same footprint as Offshore Area) serves as maneuver water space for ships and submarines to conduct training and to use as transit lanes. It extends from the Strait of Juan de Fuca in the north, to approximately 50 nm (93 km) south of Eureka, California in the south, and from the coast line of Washington, Oregon, and California westward to 130° W. longitude. The PACNW OPAREA is approximately 510 nm (945 km) in length from the northern boundary to the southern boundary, and 250 nm (463 km) from the coastline to the western boundary at 130° W longitude. Total surface area of the PACNW OPAREA is 122,400 nm

2

(420,163 km

2

).

Commander Submarine Force, U.S. Pacific Fleet (COMSUBPAC) Pearl Harbor manages this water space as transit lanes for U.S. submarines. While the sea space is ample for all levels of Navy training, no infrastructure is currently in place to support training. There are no dedicated training frequencies, no permanent instrumentation, no meteorological and oceanographic activities (METOC) system, and no Opposition Forces (OPFOR) or Electronic Combat (EC) target systems. In this region of the Pacific Ocean, storms and high sea states can create challenges to surface ship training between October and April. In addition, strong undersea currents in the PACNW make it difficult to place permanent bottom-mounted instrumentation such as hydrophones.

The Offshore Area undersea space lies beneath the PACNW OPAREA as described above. The bathymetry chart depicts a 100-fathom (182-m) curve parallel to the coastline approximately 12 nm (22 km) to sea, and in places 20 nm (37 km) out to sea. The area of deeper water of more than 100 fathoms (182 m) is calculated to be approximately 115,800 nm

2

(397,194 km

2

), while the shallow water area of less than 100 fathoms (600 ft, 182 m) is all near shore and amounts to approximately 6,600 nm

2

(22,638 km

2

).

The Inshore Area

—This area includes all sea and undersea ranges and OPAREAs inland of the coastline, including Puget Sound. This area is composed of approximately 61 nm

2

of surface and subsurface area. NWTRC Inshore Areas include land ranges, airspace, and two surface/subsurface restricted areas—Navy 7 and 3. Activities conducted in each of these areas are not expected to take marine mammals, as defined by the MMPA and therefore, and will not be discussed further in this proposed rule. Also included in the Inshore Area, Explosive Ordnance Disposal (EOD) Ranges are land, sea, and undersea ranges used by NSW and EOD forces specifically for EOD training and are composed of approximately 0.4 nm

2

of surface and subsurface area within the area identified as the Inshore Area. EOD units located in the NWTRC conduct underwater detonations as part of mine countermeasure training. This training is conducted at one of three locations: Crescent Harbor Underwater EOD Range, offshore from the Seaplane Base at Naval Air Station Whidbey Island; at the Floral Point Underwater EOD Range, located in Hood Canal near NAVBASE Kitsap-Bangor; and the Indian Island Underwater EOD Range, adjacent to Indian Island.

Description of Specified Activities

As mentioned above, the Navy has requested MMPA authorization to take marine mammals incidental to training activities in the NWTRC that would result in the generation of sound or pressure waves in the water at or above levels that NMFS has determined will likely result in take (see Acoustic Take Criteria Section), either through the use of MFAS/HFAS or the detonation of explosives in the water. These activities are discussed in the subsections below. In addition to use of active sonar sources and explosives, these activities include the operation and movement of vessels that are necessary to conduct the training, and the effects of this part of the activities are also analyzed in this document.

The Navy's application also briefly summarizes Anti-Air Warfare Training, Naval Special Warfare Training and Support Operations; however, these activities are primarily land and air based and do not utilize sound sources

or explosives for the portions that are in the water and, therefore, no take of marine mammals is anticipated from these activities and they are not discussed further.

Activities Utilizing Active Sonar Sources

For the NWTRC, the training activities that utilize active tactical sonar sources fall primarily into the category of Anti-submarine Warfare (ASW) exercises (MFAS/HFAS is also used in the mine avoidance exercises, which are considered Mine Warfare Training (MIW) activities; however, it is in such a small amount that impacts to marine mammals are minimal). This section includes a description of ASW, the active acoustic devices used in ASW exercises, and the exercise types in which these acoustic sources are used. Of note, the use of MFAS/HFAS in the NWTRC is minimal as compared to previous rules issued by NMFS (approximately 110 hours annual use of the most powerful surface vessel sonar versus approximately 2,500 hours annual use of AN/SQS-53C and AN/SQS-56C sonar in the Southern California Range Complex), does not include major exercises that involve the use of more than one surface vessel MFAS (AN/SQS-53C or AN/SQS-56C) at a time, and will not occur in the inshore area (

i.e.

, inland from the mouth of the Strait of Juan de Fuca).

ASW Training and Active Sonar

ASW involves helicopter and sea control aircraft, ships, and submarines, operating alone or in combination, to locate, track, and neutralize submarines. Various types of active and passive sonars are used by the Navy to determine water depth, locate mines, and identify, track, and target submarines. Passive sonar “listens” for sound waves by using underwater microphones, called hydrophones, which receive, amplify and process underwater sounds. No sound is introduced into the water when using passive sonar. Passive sonar can indicate the presence, character and movement of submarines. However, passive sonar provides only a bearing (direction) to a sound-emitting source; it does not provide an accurate range (distance) to the source. Also, passive sonar relies on the underwater target itself to provide sufficient sound to be detected by hydrophones. Active sonar is needed to locate objects that emit little or no noise (such as mines or diesel-electric submarines operating in electric mode) and to establish both bearing and range to the detected contact.

Active sonar transmits pulses of sound that travel through the water, reflect off objects and return to a receiver. By knowing the speed of sound in water and the time taken for the sound wave to travel to the object and back, active sonar systems can quickly calculate direction and distance from the sonar platform to the underwater object. There are three types of active sonar: low frequency, mid-frequency, and high-frequency.

LFA sonar is not presently utilized in the NWTRC, and is not part of the Proposed Action.

MFAS, as defined in the Navy's NWTRC LOA application, operates between 1 and 10 kHz, with detection ranges up to 10 nm (19 km). Because of this detection ranging capability, MFAS is the Navy's primary tool for conducting ASW. Many ASW experiments and exercises have demonstrated that this improved capability for long range detection of adversary submarines before they are able to conduct an attack is essential to U.S. ship survivability. Today, ASW is the Navy's number one war-fighting priority. Navies across the world utilize modern, quiet, diesel-electric submarines that pose the primary threat to the U.S. Navy's ability to perform a number of critical missions. Extensive training is necessary if Sailors, ships, and strike groups are to gain proficiency in using MFAS. If a strike group does not demonstrate MFAS proficiency, it cannot be certified as combat ready.

HFAS, as defined in the Navy's NWTRC LOA application, operates at frequencies greater than 10 kilohertz (kHz). At higher acoustic frequencies, sound rapidly dissipates in the ocean environment, resulting in short detection ranges, typically less than five nm (9 km). High-frequency sonar is used primarily for determining water depth, hunting mines and guiding torpedoes.

Acoustic Sources Used for ASW Exercises in the NWTRC

Modern sonar technology has developed a multitude of sonar sensor and processing systems. In concept, the simplest active sonars emit omni-directional pulses (“pings”) and time the arrival of the reflected echoes from the target object to determine range. More sophisticated active sonar emits an omni-directional ping and then rapidly scans a steered receiving beam to provide directional, as well as range, information. More advanced active sonars transmit multiple preformed beams, listening to echoes from several directions simultaneously and providing efficient detection of both direction and range. The types of active sonar sources employed during ASW active sonar training exercises in the NWTRC are identified in Table 1.

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ASW sonar systems are deployed from certain classes of surface ships, submarines, and fixed-wing maritime patrol aircraft (MPA). Maritime patrol aircraft is a category of fixed-wing aircraft that includes the current P-3C Orion, and the future P-8 Poseidon multimission maritime aircraft. No ASW helicopters train in the NWTRC. The

surface ships used are typically equipped with hull-mounted sonars (passive and active) for the detection of submarines. Fixed-wing MPA are used to deploy both active and passive sonobuoys to assist in locating and tracking submarines or ASW targets during the exercise. Submarines are equipped with passive sonar sensors used to locate and prosecute other submarines and/or surface ships during the exercise. The platforms used in ASW exercises are identified below.

Surface Ship Sonars

—A variety of surface ships participate in training events. Of the ships that operate in the NWTRC, only two classes employ MFAS: the Fast Frigate (FFG) and the Guided Missile Destroyer (DDG). These two classes of ship are equipped with active as well as passive tactical sonars for mine avoidance and submarine detection and tracking. DDG class ships are equipped with the AN/SQS-53C sonar system (the most powerful system), with a nominal source level of 235 decibels (dB) re 1 μPa @ 1 m. The FFG class ship uses the SQS-56 sonar system, with a nominal source level of 225 decibels (dB) re 1 μPa @ 1 m. Sonar ping transmission durations were modeled as lasting 1 second per ping and omni-directional, which is a conservative assumption that will overestimate potential effects. Actual ping durations will be less than 1 second. The AN/SQS-53C hull-mounted sonar transmits at a center frequency of 3.5 kHz. The SQS-56 transmits at a center frequency of 7.5 kHz. Details concerning the tactical use of specific frequencies and the repetition rate for the sonar pings is classified but was modeled based on the required tactical training setting.

Submarine Sonars

—Submarine active sonars are not used for ASW training in the NWTRC. However, the AN/BQS-15 sonar would be used for mine detection training. The AN/BQS-15, installed on guided missile nuclear submarines (SSGN) and fast attack nuclear submarines (SSN), uses high frequency (> 10 kHz) active sonar to locate mine shapes. A total of seven mine avoidance exercises would take place annually in the NWTRC. Each exercise would last six hours, for a total of 42 hours annually.

Aircraft Sonar Systems

—Sonobuoys are the only aircraft sonar systems that would operate in the NWTRC. Sonobuoys are deployed by MPAs and are expendable devices used for the detection of submarines. Most sonobuoys are passive, but some can generate active acoustic signals, as well as listen passively. During ASW training, these systems' active modes are used for localization of contacts and are not typically used in primary search capacity. The AN/SSQ-62 Directional Command Activated Sonobuoy System (DICASS) is the only MFAS sonobuoy used in the NWTRC. Because no ASW helicopters train in the NWTRC, no dipping sonar system is carried forward for any further analysis of effects.

Extended Echo Ranging and Improved Extended Echo Ranging (EER/IEER) Systems

—EER/IEER are airborne ASW systems used to conduct “large area” searches for submarines. These systems are made up of airborne avionics ASW acoustic processing and sonobuoy types that are deployed in pairs. The EER/IEER System's active sonobuoy component, the AN/SSQ-110A Sonobuoy, generates an explosive sound impulse and a passive sonobuoy (ADAR, AN/SSQ-101A) would “listen” for the return echo that has been bounced off the surface of a submarine. These sonobuoys are designed to provide underwater acoustic data necessary for naval aircrews to quickly and accurately detect submerged submarines. The sonobuoy pairs are dropped from a maritime patrol aircraft into the ocean in a predetermined pattern with a few buoys covering a very large area. The AN/SSQ-110A Sonobuoy Series is an expendable and commandable sonobuoy. Upon command from the aircraft, the explosive charge would detonate, creating the sound impulse. Within the sonobuoy pattern, only one detonation is commanded at a time. Twelve to twenty SSQ-110A source sonobuoys are used in a typical exercise. Both charges of each sonobuoy would be detonated during the course of the training, either tactically to locate the submarine, or when the sonobuoys are commanded to scuttle at the conclusion of the exercise. The AN/SSQ-110A is listed in this table because it functions like a sonar ping, however, the source creates an explosive detonation and its effects are considered in the underwater explosive section.

Advanced Extended Echo Ranging (AEER) System

—The proposed AEER system is operationally similar to the existing EER/IEER system. The AEER system will use the same ADAR sonobuoy (SSQ-101A) as the acoustic receiver and will be used for a large area ASW search capability in both shallow and deep water. However, instead of using an explosive AN/SQS-110A as an impulsive source for the active acoustic wave, the AEER system will use a battery powered (electronic) source for the AN/SSQ 125 sonobuoy. The output and operational parameters for the AN/SSQ-125 sonobuoy (source levels, frequency, wave forms,

etc.

) are classified. However, this sonobuoy is intended to replace the EER/IEER's use of explosives and is scheduled to enter the fleet in 2011. Acoustic impact analysis for the AN/SSQ-125 in this document assumes a similar per-buoy effect as that modeled for the DICASS sonobuoy. For purposes of analysis, replacement of the EER/IEER system by the AEER system will be assumed to occur at 25% per year as follows: 2011—25% replacement; 2012—50% replacement; 2013—75% replacement; 2014—100% replacement with no further use of the EER/IEER system beginning in 2015 and beyond.

Torpedoes

—Torpedoes are the primary ASW weapon used by surface ships, aircraft, and submarines. The guidance systems of these weapons can be autonomous or electronically controlled from the launching platform through an attached wire. The autonomous guidance systems are acoustically based. They operate either passively, exploiting the emitted sound energy by the target, or actively, ensonifying the target and using the received echoes for guidance. The MK-48 submarine-launched torpedo, used in its anti-surface ship mode, was modeled for active sonar transmissions in Sinking Exercises conducted within the NWTRC.

Portable Undersea Tracking Range

—The Portable Undersea Tracking Range (PUTR) has been developed to support ASW training in areas where the ocean depth is between 300 ft and 12,000 ft and at least 3 nm from land. This proposed project would temporarily instrument 25-square-mile or smaller areas on the seafloor, and would provide high fidelity feedback and scoring of crew performance during ASW training activities. When training is complete, the PUTR equipment would be recovered. All of the potential PUTR areas have been used for ASW training for decades.

No on-shore construction would take place. Seven electronics packages, each approximately 3 ft long by 2 ft in diameter, would be temporarily installed on the seafloor by a range boat, in water depths greater than 600 ft. The anchors used to keep the electronics packages on the seafloor would be either concrete or sand bags, approximately 1.5 ft-by-1.5 ft and 300 pounds. Each package consists of a hydrophone that receives pinger signals, and a transducer that sends an acoustic “uplink” of locating data to the range boat. The uplink signal is transmitted at 8.8 kilohertz (kHz), 17 kHz, or 40 kHz, at a source level of 190 decibels (dB). The Portable Undersea Tracking Range

system also incorporates an underwater voice capability that transmits at 8-11 kHz and a source level of 190 dB. Each of these packages is powered by a D cell alkaline battery. After the end of the battery life, the electronic packages would be recovered and the anchors would remain on the seafloor. The Navy proposes to deploy this system for 3 months of the year (approximately June-August), and to conduct TRACKEX activities for 10 days per month in an area beyond 3 nm from shore. During each of the 30 days of annual operation, the PUTR would be in use for 5 hours each day. No additional ASW activity is proposed as a result of PUTR use. Operation of this range requires that underwater participants transmit their locations via pingers and that the receiving transducers transmit that information the range boat via the Uplink transmitter (

see

“Range Tracking Pingers” and uplink transmitter “below”).

Range Tracking Pingers

—MK-84 range tracking pingers would be used on ships, submarines, and ASW targets when ASW TRACKEX training is conducted on the PUTR. The MK-84 pinger generates a 12.93 kHz sine wave in pulses with a maximum duty cycle of 30 milliseconds (3% duty cycle) and has a design power of 194 dB re 1 micro-Pascal at 1 meter. Although the specific exercise, and number and type of participants will determine the number of pingers in use at any time, a minimum of one and a maximum of three pingers would be used for each ASW training activity. On average, two pingers would be in use for 3 hours each during PUTR operational days.

Uplink Transmitters

—Each package consists of a hydrophone that receives pinger signals, and a transducer that sends an acoustic “uplink” of locating data to the range boat. The uplink signal is transmitted at 8.8 kilohertz (kHz), 17 kHz, or 40 kHz, at a source level of 190 decibels (dB). The Portable Undersea Tracking Range system also incorporates an underwater voice capability that transmits at 8-11 kHz and a source level of 190 dB. Under the proposed action, the uplink transmitters would operate 30 days per year, for 5 hours each day of use. The total time of use would be 150 hours annually.

Exercises Utilizing MFAS in the NWTRC

ASW Tracking Exercises are the exercises that primarily utilize MFAS and HFAS sources in the NWTRC, although Mine Avoidance MIW exercises also utilize a less powerful HFAS source. ASW Tracking Exercise (TRACKEX) trains aircraft, ship, and submarine crews in tactics, techniques, and procedures for search, detection, localization, and tracking of submarines with the goal of determining a firing solution that could be used to launch a torpedo and destroy the submarine. ASW Tracking Exercises occur during both day and night. A typical unit-level exercise involves one (1) ASW unit (aircraft, ship, or submarine) versus one (1) target—either a MK-39 Expendable Mobile ASW Training Target (EMATT), or a live submarine. The target may be non-evading while operating on a specified track or fully evasive. Participating units use active and passive sensors, including hull-mounted sonar, towed arrays, and sonobuoys for tracking. If the exercise continues into the firing of a practice torpedo it is termed a Torpedo Exercise (TORPEX). The ASW TORPEX usually starts as a TRACKEX to achieve the firing solution. No torpedoes are fired during ASW training conducted in the NWTRC. The exercise types that utilize MFAS/HFAS are described below and summarized in Table 2, which also includes a summary of the exercise types utilizing explosives.

ASW TRACKEX (Maritime Patrol Aircraft)

—During an ASW TRACKEX (MPA), a typical scenario would involve a single MPA dropping sonobuoys, from an altitude below 3,000 ft (914 m) above mean sea level (MSL), and sometimes as low as 400 ft (122 m), into specific patterns designed for both the anticipated threat submarine and the specific water conditions. These patterns vary in size and coverage area based on the threat and water conditions.

Typically, passive sonobuoys will be used first, so the threat submarine is not alerted. Active buoys will be used as required either to locate extremely quiet submarines, or to further localize and track submarines previously detected by passive buoys. A TRACKEX (MPA) usually takes two to four hours. TheP-8 Multi-mission Maritime Aircraft (MMA), a modified Boeing 737 that is the Navy's replacement for the agingP-3 Orion aircraft, is a long-range aircraft that is capable of broad-area, maritime and littoral activities. As P-8 live training is expected to be supplemented with virtual training to a greater degree than P-3 training, P-8 training activities in the NWTRC are likely to be less numerous than those currently conducted by P-3 aircraft crews. P-3 replacement is expected to begin by 2013. None of the potential marine mammal impacts associated with the P-3 aircraft are expected to differ as a result of the P-3 being replaced by the MMA.

ASW TRACKEX (EER/IEER or AEER)

—This activity is an at-sea flying event, typically conducted below 3,000 ft (914 m) MSL, that is designed to train P-3 crews in the deployment and use of the EER/IEER (and in the future, AEER) sonobuoy systems. These systems use the SSQ-110A as the signal source and the SSQ-77 (VLAD) as the receiver buoy. The signal source is a small explosive charge that detonates underwater. The SSQ-110A sonobuoy has two charges, each being individually detonated during the exercise. This activity typically lasts six hours, with one hour for buoy pattern deployment and five hours for active search. Between 12 and 20 SSQ-110A source sonobuoys and approximately 20 SSQ-77 passive sonobuoys are used in a typical exercise.

ASW TRACKEX (Surface Ship)

—In the PACNW OPAREA, locally based surface ships do not routinely conduct ASW Tracking exercises. However, MFAS is used during ship transits through the OPAREA. In a typical year, 24 DDG ship transits and 36 FFG transits will take place, with 1.5 hours of active sonar use during each transit. All surface ship MFAS use is documented in this training activity description. 10% of surface ship MFAS used in NWTRC is training associated with the PUTR.

ASW TRACKEX (Submarine)

—ASW TRACKEX is a primary training exercise for locally based submarines. Training is conducted within the NWTRC and involves aircraft approximately 30% of the time. Training events in which aircraft are used typically last 8 to 12 hours. During these activities submarines use passive sonar sensors to search, detect, classify, localize and track the threat submarine with the goal of developing a firing solution that could be used to launch a torpedo and destroy the threat submarine. However, no torpedoes are fired during this training activity. All submarine ASW TRACKEX conducted in the NWTRC is passive only; therefore, these activities are not carried forward for any further analysis of effects. All aircraft ASW is analyzed under ASW TRACKEX (MPA).

Mine Avoidance

—Mine avoidance exercises train ship and submarine crews to detect and avoid underwater mines. In the NWTRC, submarine crews will use the AN/BQS-15 high frequency active sonar to locate mine shapes in a training minefield in the PACNW OPAREA. A small-scale underwater minefield will be added in the NWTRC for these exercises. Each mine avoidance exercise involves one submarine operating the AN/BQS-15 sonar for six hours to navigate through

the training minefield. A total of seven mine avoidance exercises will occur in the NWTRC annually.

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Activities Utilizing Underwater Detonations

Underwater detonation activities can occur at various depths depending on the activity, but may also include activities which may have detonations at or just below the surface (such as SINKEX or gunnery exercise [GUNEX]). When the weapons hit the target, except for live torpedo shots, there is no explosion in the water, and so a “hit” is not modeled (

i.e.

, the energy (either acoustic or pressure) from the hit is not expected to reach levels that would result in take of marine mammals). When a live weapon misses, it is modeled as exploding below the water surface at 1 ft (5-inch naval gunfire, 76mm rounds), 2 meters (Maverick, Harpoon, MK-82, MK-83, MK-84), or 50-ft (MK-48 torpedo) as shown in Appendix A of the Navy's application (the depth is chosen to represent the worst case of the possible scenarios as related to potential marine mammal impacts). Exercises may utilize either live or inert ordnance of the types listed in Table 3. Additionally, successful hit rates are known to the Navy and are utilized in the effects modeling. Training events that involve explosives and underwater detonations occur throughout the year and are described below and summarized in Table 2. Of note, the only Inshore Area exercises that use explosives are on EOD ranges described under Mine Countermeasures (No more than 4 total detonations of 2.5 lb. charges annually).

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Anti-Surface Warfare Training (ASUW)

Anti-Surface Warfare (ASUW) is the category of activity that addresses combat (or interdiction) activities training by air, surface, or submarine forces against hostile surface ships and boats. The ASUW exercises conducted in NWTRC are described in the sections below. Because all of the rounds used in GUNEX in the NWTRC are inert, no take of marine mammals is anticipated to

result from the activity. However, a description is included here for comparison and clarity as NMFS has authorized take of marine mammals incidental to these activities in the past when explosive rounds were used instead of inert rounds.

Air-to-Surface Bombing Exercise

—During an Air-to-Surface Bombing Exercise (BOMBEX A-S), fixed-wing aircraft deliver bombs against simulated surface maritime targets, typically a smoke float, with the goal of destroying or disabling enemy ships or boats. MPA use bombs to attack surfaced submarines and surface craft that would not present a major threat to the MPA itself. A single MPA approaches the target at a low altitude. In most training exercises, the aircrew drops inert training ordnance, such as the Bomb Dummy Unit (BDU-45) on a MK-58 smoke float used as the target. Historically, ordnance has been released throughout W-237 (off WA State), just south of W-237, and in international waters in accordance with international laws, rules, and regulations. Annually, 120 pieces of ordnance, consisting of 10 MK-82 live bombs and 110 BDU 45 inert bombs, are dropped in the NWTRC. In accordance with the regulations for the Olympic Coast National Marine Sanctuary (OCNMS) the Navy dos not conduct live bombing in the sanctuary. Each BOMBEX A-S can take up to 4 hours to complete.

Sinking Exercise

—A Sinking Exercise (SINKEX) is typically conducted by aircraft, surface ships, and submarines in order to take advantage of a full size ship target and an opportunity to fire live weapons. The target is typically a decommissioned combatant or merchant ship that has been made environmentally safe for sinking. In accordance with EPA permits, it is towed out to sea (at least 50 nm [92.6 km]) and set adrift at the SINKEX location in deep water (at least 1,000 fathoms [6,000 feet]) where it will not be a navigation hazard to other shipping. The Environmental Protection Agency (EPA) granted the Department of the Navy a general permit through the Marine Protection, Research, and Sanctuaries Act to transport vessels “for the purpose of sinking such vessels in ocean waters * * *” (40 CFR Part 229.2). Subparagraph (a)(3) of this regulation states “All such vessel sinkings shall be conducted in water at least 1,000 fathoms (6,000 feet) deep and at least 50 nautical miles from land.”

Ship, aircraft, and submarine crews typically are scheduled to attack the target with coordinated tactics and deliver live ordnance to sink the target. Inert ordnance is often used during the first stages of the event so that the target may be available for a longer time. The duration of a SINKEX is unpredictable because it ends when the target sinks, but the goal is to give all forces involved in the exercise an opportunity to deliver their live ordnance. Sometimes the target will begin to sink immediately after the first weapon impact and sometimes only after multiple impacts by a variety of weapons. Typically, the exercise lasts 4 to 8 hours, especially if inert ordnance such as 5-inch gun projectiles or MK-76 dummy bombs are used during the first hours. In the worst case of maximum exposure, the following ordnance are all expended (in the indicated amounts): MK82 Live Bomb (4); MK83 Live Bomb (4); MK84 Live Bomb (4); HARM Missile (2); AGM-114 Hellfire Missile (1); M-65 Maverick Missile (3); M-84 Harpoon Missile (3); AM ER Missile (1); 5 in/62 Shell (500); 76 mm Shell (200); 48 ADCAP Torpedo (1). If the hulk is not sunk by weapons, it will be sunk by Explosive Ordnance Disposal (EOD) personnel setting off demolition charges previously placed on the ship. Since the target may sink at any time during the exercise, the actual number of weapons used can vary widely.

Surface-to-Surface Gunnery Exercise

—Surface-to-Surface Gunnery Exercises (S-S GUNEX) take place in the open ocean to provide gunnery practice for Navy ship crews. Exercises can involve a variety of surface targets that are either stationary or maneuverable. Gun systems employed against surface targets include the 5″, 76 mm, 57 mm, .50 caliber and the 7.62 mm. A GUNEX lasts approximately one to two hours, depending on target services and weather conditions. All rounds fired are inert, containing no explosives.

Mine Warfare Training (MIW)

Mine Warfare Training includes Mine Countermeasures and Mine Avoidance. Mine Avoidance includes use of an active sonar source (although in very small amounts) and, therefore, was addressed in the appropriate section previously. Because of the location of the EOD ranges, the very limited use of explosives (4 individual explosions) proposed annually for these Mine Countermeasure exercises, and the likely effectiveness of the mitigation (

e.g.

, marine mammal take is only expected within 180 m of the impact area, which is well within the shutdown zone of 700 yds from the point of impact), take of marine mammals is not anticipated to occur in the NWTRC. However, a description is included here for comparison as NMFS has authorized take of marine mammals incidental to these activities in other areas where the amount of activity is significantly greater.

Mine Countermeasures

—Naval EOD personnel require proficiency in underwater mine neutralization. Mine neutralization activities consist of underwater demolitions designed to train personnel in the destruction of mines, unexploded ordnance (UXO), obstacles, or other structures in an area to prevent interference with friendly or neutral forces and non-combatants. EOD units conduct underwater demolition training in Crescent Harbor Underwater EOD Range, Indian Island Underwater EOD Range, and Floral Point Underwater EOD Range. A 2.5 lb (1.1 kg) charge of C-4 is used, consisting of one surface or one subsurface detonation. No more than two detonations will take place annually at Crescent Harbor, and no more than one each at Indian Island and Floral Point. The total duration of the exercise is four hours for an underwater detonation and one hour for a surface detonation. Small boats such as the MK-5 Combat Rubber Raiding Craft and MK-7, or 9 (meters in length, respectively) Rigid Hull Inflatable Boats (RHIB) are used to insert personnel for underwater activities and either a helicopter (H-60) or RHIB is used for insertion for surface activities.

Vessel Movement

The operation and movement of vessels that is necessary to conduct the training described above is also analyzed here. Training exercises involving vessel movements occur intermittently and are variable in duration, ranging from a few hours up to 2 weeks. During training, speeds vary and depend on the specific type of activity, although 10-14 knots is considered the typical speed. Approximately 490 training activities that involve Navy vessels occur within the Study Area during a typical year. Training activities are widely dispersed throughout the large OPAREA, which encompasses 122,468 nm

2

(420,054 km

2

). Consequently, the density of Navy ships within the Study Area at any given time is low.

Research, Development, Testing, and Evaluation

RDT&E proposed in this action is limited to Unmanned Aerial Systems (UAS) activities, the use of which is not anticipated to result in the take of marine mammals because it utilizes small, relatively quiet airborne, not undersea, gliders. Undersea RDT&E in the Pacific Northwest is conducted at

the Naval Sea Systems Command (NAVSEA) Keyport range and is analyzed in the NAVSEA Naval Undersea Warfare Center (NUWC) Keyport Range Extension EIS/OEIS.

Additional information on the Navy's proposed activities may be found in the LOA Application and the Navy's NWTRC DEIS.

Description of Marine Mammals in the Area of the Specified Activities

The California Current passes through the NWTRC, creating a mixing of temperate and tropical waters, thereby making this area one of the most productive ocean systems in the world (Department of the Navy [DoN], 2002a). Because of this productive environment, there is a rich marine mammal fauna, as evidenced in abundance and species diversity (Leatherwood

et al.

, 1988; Bonnell and Dailey, 1993). In addition to many marine mammal species that live here year-round and use the region's coasts and islands for breeding and hauling out, there is a community of seasonal residents and migrants. The narrow continental shelf along the Pacific coast and the presence of the cold California Current sweeping down from Alaska allows cold-water marine mammal species to reach nearshore waters as far south as Baja California.

Thirty-three marine mammal species or populations/stocks have confirmed or possible occurrence within the NWTRC, including six species of baleen whales (mysticetes), 21 species of toothed whales (odontocetes), five species of seals and sea lions (pinnipeds), and the sea otter (mustelids). Table 4 summarizes their abundance, Endangered Species Act (ESA) status, population trends, and occurrence in the area. Most of these species are listed as “common” in the table, indicating that they occur routinely, either year-round or during annual migrations into or through the area. The other species are indicated as “rare” because of sporadic sightings or as “very rare” because they have been documented once or twice as appearing outside their normal range. All of the species that occur in the NWTRC are either cosmopolitan (occur worldwide), or associated with the temperate and sub-Arctic oceans (Leatherwood

et al.

, 1988). Seven of the species are ESA-listed and considered depleted under the MMPA: Blue whale; fin whale; humpback whale; sei whale; sperm whale; southern resident killer whale; and Steller sea lion.

Temperate and warm-water toothed whales often change their distribution and abundance as oceanographic conditions vary both seasonally (Forney and Barlow, 1998) and inter-annually (Forney, 2000). Forney and Barlow (1998) noted significant north/south shifts in distribution for Dall's porpoises, common dolphins, and Pacific white-sided dolphins, and they identified significant inshore/offshore differences for northern right whale dolphins and humpback whales. Several authors have noted the impact of the El Niño events of 1982/1983 and 1997/1998 on marine mammal occurrence patterns and population dynamics in the waters off California (Wells

et al.

, 1990; Forney and Barlow, 1998; Benson

et al.

, 2002).

The distribution of some marine mammal species is based on the presence of salmon, an important prey source. Seals and sea lions congregate near areas where migrating salmon run. For example, in the San Juan Islands, harbor seals (

Phoca vitulina richardii

) congregate near a constricted channel where incoming tidal currents funnel migrating salmon (Zamon, 2001). In Oregon, harbor seals wait for chum salmon runs during the incoming tide near a constriction in Netarts Bay (Brown and Mat, 1983). During the summer, southern resident killer whales (

Orcinus orca

) congregate at locations associated with high densities of migrating salmon (Heimlich-Boran, 1986; Nichol and Shackleton, 1996; Olson, 1998; National Marine Fisheries Service [NMFS], 2005i). Their strong preference for Chinook salmon may influence the year-round distribution patterns of southern resident killer whales in the NWTRC (Ford and Ellis, 2005).

The Navy has compiled information on the abundance, behavior, status and distribution, and vocalizations of marine mammal species in the NWTRC waters from the Navy Marine Resource Assessment for NWTRC (which was recently updated, during the development of the application for this rule, based on peer-reviewed literature and government reports such as NMFS' Stock Assessment Reports) and marine mammal experts engaged in current research utilizing tagging and tracking. This information may be viewed in the Navy's LOA application and/or the Navy's DEIS for NWTRC (

see

Availability), and is incorporated by reference herein. Included below, however, are summaries of some important biological issues that are needed to further inform the MMPA effects analysis. Additional information is available in NMFS Stock Assessment Reports, which may be viewed at:

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

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Species Not Considered Further

The North Pacific right whale is classified as endangered under the ESA. Although there is designated critical habitat for this species in the western Gulf of Alaska and an area in the southeastern Bering Sea (NMFS, 2006), there is no designated critical habitat for this species within the NWTRC. Census data are too limited to suggest a population trend for this species. In the western North Pacific, the population may number in the low hundreds (Brownell

et al.

, 2001; Clapham

et al.

, 2004). The eastern population likely now numbers in the tens of animals. Right whales were probably never common along the west coast of North America (Scarff, 1986; Brownell

et al.

, 2001). Historical whaling records provide the most complete information on likely North Pacific right whale

distribution. Presently, sightings are extremely rare, occurring primarily in the Okhotsk Sea and the eastern Bering Sea (Brownell

et al.

, 2001; Shelden

et al.

, 2005; Shelden and Clapham, 2006; Wade

et al.

, 2006). There were no sightings of North Pacific right whales during ship surveys conducted off California, Oregon, and Washington from 1991 through 2005 (Barlow and Forney, 2007), although recent deployment of directional sonobuoys (focused on the gunshot call) in the southeastern Bering Sea has resulted in multiple recordings of the rarely detected marine mammals (Berchok

et al.

, 2009). The area of densest concentration in the Gulf of Alaska is east from 170° W to 150° W and south to 52° N (Shelden and Clapham, 2006). Based upon the extremely low probability of encountering this species anywhere in the coastal and offshore waters in the NWTRC, this species will not be included in this analysis.

Designated Critical Habitat

Southern Resident Killer Whale

NMFS designated critical habitat for the southern resident killer whale (

Orcinus orca

) distinct population segment (DPS). Three specific areas (which comprise approximately 2,560 square miles (6,630 sq km) of marine habitat) are designated:

(1)

The Summer Core Area in Haro Strait and waters around the San Juan Islands

—Occurrence of Southern Residents in Area 1 coincides with concentrations of salmon, and is more consistent and concentrated in the summer months of June through August, though they have been sighted in Area 1 during every month of the year;

(2)

Puget Sound

—southern resident killer whale occurrence in Area 2 has been correlated with fall salmon runs; and

(3)

The Strait of Juan de Fuca

—All pods regularly use the Strait of Juan de Fuca for passage from Areas 1 and 2 to outside waters in the Pacific Ocean and to access outer coastal water feeding grounds.

The designated physical and biological features which are essential to the conservation of southern resident killer whales and that may require special management considerations or protection (Primary Constituent Elements/PCEs) are as follows:

(1)

Water quality to support growth and development

—Because of their long life span, position at the top of the food chain, and their blubber stores, southern resident killer whales accumulate high concentrations of contaminants;

(2)

Prey species of sufficient quantity, quality and availability to support individual growth, reproduction and development, as well as overall population growth

—Fish are the major dietary component of southern resident killer whales in the northeastern Pacific. Salmon comprise the southern resident killer whales' preferred prey, and are likely consumed in large amounts; and

(3)

Passage conditions to allow for migration, resting, and foraging

—In order to move between important habitat areas, find prey, and fulfill other life history requirements, southern resident killer whales require open waterways that are free from obstruction.

As noted previously, the Navy's proposed action does not include the use of MFAS/HFAS in southern resident killer whale critical habitat, and explosive use is limited to four detonations of 2.5-lb charges annually in EOD exercises.

Steller Sea Lion

In California and Oregon, major Steller sea lion rookeries and associated air and aquatic zones are designated as critical habitat. Critical habitat includes an air zone extending 3,000 ft above rookery areas historically occupied by sea lions and an aquatic zone extending 3,000 seaward. Three rookeries located along the southern Oregon Coast have been designated as critical habitat sites in the NWTRC. These include: Orford Reef (Long Brown Rock); Oxrord Reef (Seal Rock); Rogue Reef (Pyramid Rock). The PCEs for Steller sea lions are: Nearshore waters around rookeries and haulouts and prey resources and foraging habitats.

Gray Whale Migration

The gray whale makes a well-defined seasonal north-south migration. Most of the population summers in the shallow waters of the northern Bering Sea, the Chukchi Sea, and the western Beaufort Sea (Rice and Wolman, 1971), whereas some individuals also summer along the Pacific coast from Vancouver Island to central California (Rice and Wolman, 1971; Darling 1984; Nerini, 1984). In October and November, the whales begin to migrate southeast through Unimak Pass and follow the shoreline south to breeding grounds on the west coast of Baja California and the southeastern Gulf of California (Braham, 1984; Rugh, 1984). The average gray whale migrates 7,500-10,000 km at a rate of 147 km/d (Rugh

et al.

, 2001; Jones and Swartz, 2002). Although some calves are born along the coast of California, most are born in the shallow, protected waters on the Pacific coast of Baja California from Morro de Santo Domingo (28° N) south to Isla Creciente (24° N) (Urban

et al.

, 2003). The main calving sites are Laguna Guerrero Negro, Laguna Ojo de Liebre, Laguna San Ignacio, and Estero Soledad (Rice

et al.

, 1981).

Gray whales occur in the Pacific Northwest OPAREA and Puget Sound throughout the year. In addition, larger numbers of migratory animals transit along the coast of Washington, Oregon, and California during migrations between breeding and feeding grounds. Peak sightings in the NWTRC during the southbound migration occur in January (Rugh

et al.

, 2001). There are two phases of the northbound migration, including an early phase from mid-February through April and a later phase, which consists of mostly cows and calves, from late April through May (Herzing and Mate, 1984).

Marine Mammal Hearing and Vocalizations

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 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). Baleen whales have inner ears that appear to be specialized for low-frequency hearing. Conversely, dolphins and porpoises have ears that are specialized to hear high frequencies.

Marine mammal vocalizations often extend both above and below the range of human hearing; vocalizations with frequencies lower than 18 Hertz (Hz) are labeled as infrasonic and those higher than 20 kHz as ultrasonic (National Research Council [NRC], 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. The ears of small toothed whales are optimized for receiving high-frequency sound, while baleen whale inner ears are best in low to infrasonic frequencies (Ketten, 1992; 1997; 1998).

Baleen whale vocalizations are composed primarily of frequencies below 1 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).

The toothed whales 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 (<80 dB re 1 μPa) below 500 Hz (DoN, 2001). 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 1 m or greater (Mohl

et al.

, 2000).

Table 5 includes a summary of the vocalizations of the species found in the NWTRC. The “Brief Background on Sound” section contained a description of the functional hearing groups designated by Southall

et al.,

(2007), which includes the functional hearing range of various marine mammal groups (

i.e.

, what frequencies that can actually hear).

Marine Mammal Density Estimates

Understanding the distribution and abundance of a particular marine mammal species or stock is necessary to analyze the potential impacts of an action on that species or stock. Further, in order to assess quantitatively the likely acoustic impacts of a potential action on individuals and to estimate take it is necessary to know the density of the animals in the affected area. Density estimates for cetaceans were obtained from the Marine Mammal and Sea Turtle Density Estimates for the Pacific Northwest Study Area (DoN, 2007a). The abundance of most cetaceans was derived from shipboard surveys conducted by the Southwest Fisheries Science Center in 1991, 1993, 1996, 2001, and 2005 (Barlow, 1995; Barlow, 2003; Barlow and Forney, 2007). These estimates are used to develop NMFS Stock Assessment Reports (Carretta

et al.

, 2007); interpret the impacts of human-caused mortality associated with fishery bycatch, ship strikes, and other sources; and evaluate the ecological role of cetaceans in the eastern North Pacific. In the density study, predictive species-habitat models were built for species with sufficient numbers of sightings to estimate densities for the NWTRC (described in detail Appendix B of the Navy's application). For species with insufficient numbers of sightings, density estimates were obtained from Barlow and Forney (2007).

There are limited depth distribution data for most marine mammals. This is especially true for cetaceans, as they must be tagged at-sea and by using a tag that either must be implanted in the skin/blubber in some manner or adhere to the skin. There is slightly more data for some pinnipeds, as they can be tagged while on shore during breeding or molting seasons and the tags can be glued to the pelage rather than implanted. There are a few different methodologies/techniques that can be used to determine depth distribution percentages, but by far the most widely used technique currently is the time-depth recorder. These instruments are attached to the animal for a fairly short period of time (several hours to a few days) via a suction cup or glue, and then retrieved immediately after detachment or when the animal returns to the beach. Depth information can also be collected via satellite tags, sonic tags, digital tags, and, for sperm whales, via acoustic tracking of sounds produced by the animal itself.

There are somewhat suitable depth distribution data for a few marine mammal species. Sample sizes are usually extremely small, nearly always fewer than 10 animals total and often only one or two animals. Depth distribution information often must be interpreted from other dive and/or preferred prey characteristics. Depth distributions for species for which no data are available are extrapolated from similar species.

Density is nearly always reported for an area,

e.g.

, animals/km

2

. Analyses of survey results using Distance Sampling techniques include correction factors for animals at the surface but not seen as well as animals below the surface and not seen. Therefore, although the area (

e.g.

, km

2

) appears to represent only the surface of the water (two-dimensional), density actually implicitly includes animals anywhere within the water column under that surface area. Density assumes that animals are uniformly distributed within the prescribed area,

even though this is likely rarely true. Marine mammals are usually clumped in areas of greater importance (and often in groups), for example, areas of high productivity, lower predation, safe calving,

etc.

Density can occasionally be calculated for smaller areas that are used regularly by marine mammals, but more often than not there are insufficient data to calculate density for small areas. Therefore, assuming an even distribution within the prescribed area remains the norm.

Assuming that marine mammals are distributed evenly within the water column is not accurate. The ever-expanding database of marine mammal behavioral and physiological parameters obtained through tagging and other technologies has demonstrated that marine mammals use the water column in various ways, with some species capable of regular deep dives (<800 m) and others regularly diving to <200 m, regardless of the bottom depth. Assuming that all species are evenly distributed from surface to bottom is almost never appropriate and can present a distorted view of marine mammal distribution in any region.

By combining marine mammal density with depth distribution information, a more accurate three-dimensional density estimate is possible. These 3-D estimates allow more accurate modeling of potential marine mammal exposures from specific noise sources. Density estimates are included in Table 4.

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Brief Background on Sound

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

Sound is a wave of pressure variations propagating through a medium (for the MFAS/HFAS considered in this proposed rule, the medium is marine water). 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

2

). Acoustic intensity is rarely measured directly, it is derived from ratios of pressures; the standard reference pressure for underwater sound is 1 microPascal (μPa); for airborne sound, the standard reference pressure is 20 μPa (Richardson

et al.

, 1995).

Acousticians have adopted a logarithmic scale for sound intensities, which is denoted in decibels (dB). Decibel measurements represent the ratio between a measured pressure value and a reference pressure value (in this case 1 μPa or, for airborne sound, 20 μPa). 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 loudness, or a 10 dB decrease in noise as a halving of loudness. The term “sound pressure level” implies a decibel measure and a reference pressure that is used as the denominator of the ratio. Throughout this document, NMFS uses 1 microPascal (denoted re: μPa) as a standard reference pressure unless noted otherwise.

It is important to note that decibels underwater and decibels in air are not the same and cannot be directly compared. To estimate a comparison between sound in air and underwater, because of the different densities of air and water and the different decibel standards (

i.e.

, reference pressures) in water and air, a sound with the same intensity (

i.e.

, power) in air and in water would be approximately 63 dB quieter in air. Thus a sound that is 160 dB loud underwater would have the same approximate effective intensity as a sound that is 97 dB loud in air.

Sound frequency is measured in cycles per second, or Hertz (abbreviated 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 5 Hz to harbor porpoise clicks at 150,000 Hz (150 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 active tactical sonars are an example of a narrowband sound source.

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) designate “functional hearing groups” for marine mammals and estimate the lower and upper frequencies of functional hearing of the groups. Further, the frequency range in which each group's hearing is estimated as being most sensitive is represented in the flat part of the M-weighting functions developed for each group. The functional groups and the associated frequencies are indicated below (though, again, animals are less sensitive to sounds at the outer edge of their functional range and most sensitive to sounds of frequencies within a smaller range somewhere in the middle of their functional hearing range):

• Low frequency cetaceans (13 species of mysticetes): Functional hearing is estimated to occur between approximately 7 Hz and 22 kHz;

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

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

•

Pinnipeds in Water:

Functional hearing is estimated to occur between approximately 75 Hz and 75 kHz, with the greatest sensitivity between approximately 700 Hz and 20 kHz.

Because ears adapted to function underwater are physiologically different from human ears, comparisons using decibel measurements in air would still not be adequate to describe the effects of a sound on a whale. When sound travels away from its source, its loudness decreases as the distance traveled (propagates) by the sound increases. Thus, the loudness of a sound at its source is higher than the loudness of that same sound a kilometer distant. Acousticians often refer to the loudness of a sound at its source (typically measured one meter from the source) as the source level and the loudness of sound elsewhere as the received level. For example, a humpback whale three kilometers from an airgun that has a source level of 230 dB may only be exposed to sound that is 160 dB loud, depending on how the sound propagates (in this example, it is spherical spreading). As a result, it is important not to confuse source levels and received levels when discussing the loudness of sound in the ocean or its impacts on the marine environment.

As sound travels from a source, its propagation in water is influenced by various physical characteristics, including water temperature, depth, salinity, and surface and bottom properties that cause refraction, reflection, absorption, and scattering of sound waves. Oceans are not homogeneous and the contribution of each of these individual factors is extremely complex and interrelated. The physical characteristics that determine the sound's speed through the water will change with depth, season, geographic location, and with time of day (as a result, in actual MFAS/HFAS operations, crews will measure oceanic conditions, such as sea water temperature and depth, to calibrate models that determine the path the sonar signal will take as it travels through the ocean and how strong the sound signal will be at a given range along a particular transmission path). As sound travels through the ocean, the intensity associated with the wavefront diminishes, or attenuates. This decrease in intensity is referred to as propagation loss, also commonly called transmission loss.

Metrics Used in This Document

This section includes a brief explanation of the two sound measurements (sound pressure level (SPL) and sound exposure level (SEL)) frequently used in the discussions of acoustic effects in this document.

SPL

Sound pressure is the sound force per unit area, and is usually measured in micropascals (μPa), where 1 Pa is the pressure resulting from a force of one newton exerted over an area of one square meter. SPL is expressed as the ratio of a measured sound pressure and a reference level. The commonly used reference pressure level in underwater acoustics is 1 μPa, and the units for SPLs are dB re: 1 μPa.

SPL (in dB) = 20 log (pressure / reference pressure)

SPL is an instantaneous measurement and can be expressed as the peak, the peak-peak, 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. SPL does not take the duration of a sound into account. SPL is the applicable metric used in the risk continuum, which is used to estimate behavioral harassment takes (

see

Level B Harassment Risk Function (Behavioral Harassment) Section).

SEL

SEL is an energy metric that integrates the squared instantaneous sound pressure over a stated time interval. The units for SEL are dB re: 1 μPa

2

−s.

SEL = SPL + 10log (duration in seconds)

As applied to MFAS/HFAS, the SEL includes both the SPL of a sonar ping and the total duration. Longer duration pings and/or pings with higher SPLs will have a higher SEL. If an animal is exposed to multiple pings, the SEL in each individual ping is summed to calculate the total SEL. The total SEL depends on the SPL, duration, and number of pings received. The thresholds that NMFS uses to indicate at what received level the onset of temporary threshold shift (TTS) and permanent threshold shift (PTS) in hearing are likely to occur are expressed in SEL.

Potential Effects of Specified Activities on Marine Mammals

The Navy has requested authorization for the take of marine mammals that may occur incidental to training activities in the NWTRC utilizing MFAS/HFAS or underwater detonations. In addition to MFAS/HFAS and underwater detonations, the Navy has analyzed other potential impacts to marine mammals from training activities in the NWTRC DEIS, including ship strike, aerial overflights, ship noise and movement, and others, and, in consultation with NMFS as a cooperating agency for the NWTRC DEIS, has determined that take of marine mammals incidental to these non-acoustic components of the NWTRC is unlikely and, therefore, has not requested authorization for take of marine mammals that might occur incidental to these non-acoustic components. In this document, NMFS analyzes the potential effects on marine mammals from exposure to MFAS/HFAS and underwater detonations, but also includes some additional analysis of the potential impacts from vessel operation in the NWTRC.

For the purpose of MMPA authorizations, NMFS' effects assessments serve four primary purposes: (1) To help identify the permissible methods of taking, meaning: the nature of the take (

e.g.

, resulting from anthropogenic noise vs. from ship strike, etc.); the regulatory level of take (

i.e.

, mortality vs. Level A or Level B harassment), and; the amount of take; (2) to inform the prescription of means of affecting the least practicable adverse impact on such species or stock and its habitat (

i.e.

, mitigation); (3) to support 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) to determine whether the specified activity will have an unmitigable adverse impact on the availability of the species or stock(s) for subsistence uses (however, there are no subsistence communities that would be affected in the NWTRC).

More specifically, for activities involving sonar or underwater detonations, NMFS' analysis will identify the probability of lethal responses, physical trauma, sensory impairment (permanent and temporary threshold shifts and acoustic masking), physiological responses (particular stress responses), behavioral disturbance (that rises to the level of harassment), and social responses that would be classified as behavioral harassment or injury and/or would be likely to adversely affect the species or stock through effects on annual rates of recruitment or survival. In this section, we will focus qualitatively on the different ways that MFAS/HFAS and underwater explosive detonations may affect marine mammals (some of which NMFS would not classify as harassment). Then, in the Estimated Take of Marine Mammals Section, NMFS will relate the potential effects to marine mammals from MFAS/HFAS and underwater detonation of explosives to the MMPA regulatory definitions of Level A and Level B Harassment and attempt to quantify those effects.

Exposure to MFAS/HFAS

In the subsections below, the following types of impacts are discussed in more detail: Direct physiological impacts, stress responses, acoustic masking and impaired communication, behavioral disturbance, and strandings. An additional useful graphic tool for better understanding the layered nature of potential marine mammal responses to anthropogenic sound is presented in NMFS' January 14, 2009 Programmatic biological opinion on the U.S. Navy's proposal to conduct training exercises in the Southern California Range Complex from January 2009 to January 2014 (available at:

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

). This document presents a conceptual model of the potential responses of endangered and threatened species upon being exposed to MFAS/HFAS and the pathways by which those responses might affect the fitness of individual animals that have been exposed, and the resulting impact on the individual animal's ability to reproduce or survive. Literature supporting the framework, with examples drawn from many taxa (both aquatic and terrestrial) was included in the “Application of this Approach” and “Response Analyses” sections of that document.

Direct Physiological Effects

Based on the literature, there are two basic ways that MFAS/HFAS might directly result in physical trauma or damage: Noise-induced loss of hearing sensitivity (more commonly-called “threshold shift”) and acoustically mediated bubble growth. Separately, an animal's behavioral reaction to an acoustic exposure might lead to physiological effects that might ultimately lead to injury or death, which is discussed later in the Stranding section.

Threshold Shift (Noise-Induced Loss of Hearing)

When animals exhibit reduced hearing sensitivity (

i.e.

, sounds must be louder for an animal to recognize them) following exposure to a sufficiently intense sound, it is referred to as a noise-induced threshold shift (TS). An animal can experience temporary threshold shift (TTS) or permanent threshold shift (PTS). TTS can last from minutes or hours to days (

i.e.

, there is

recovery), occurs in specific frequency ranges (

i.e.

, an animal might only have a temporary loss of hearing sensitivity between the frequencies of 1 and 10 kHz), and can be of varying amounts (for example, an animal's hearing sensitivity might be reduced by only 6 dB or reduced by 30 dB). PTS is permanent (

i.e.

, there is no recovery), but also occurs 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, displacement of certain inner ear membranes, increased blood flow, and post-stimulatory reduction in both efferent and sensory neural output (Southall

et al.

, 2007). The amplitude, duration, frequency, temporal pattern, and energy distribution of sound exposure all affect the amount of associated TS and the frequency range in which it occurs. As amplitude and duration of sound exposure increase, so, generally, does the amount of TS, along with the recovery time. Human non-impulsive noise exposure guidelines are based on exposures of equal energy (the same 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). Three newer studies, two by Mooney

et al.

, (2009a, 2009b) on a single bottlenose dolphin either exposed to playbacks of Navy MFAS 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 levels. All three of these studies highlight the inherent complexity of TTS in marine mammals, as well the importance of considering exposure duration when assessing impacts. With exposures of equal energy, quieter, longer duration exposures were found to induce greater levels of TTS than those of exposures that were louder and of shorter duration (more similar to MFAS). For intermittent sounds, less TS will occur than from a continuous exposure with the same energy (some recovery will occur between intermittent exposures) (Kryter

et al.

, 1966; Ward, 1997). For example, one short but loud (higher SPL) sound exposure may induce the same impairment as one longer but softer sound, which in turn may cause more impairment than a series of several intermittent softer sounds with the same total energy (Ward, 1997). Additionally, though TTS is temporary, very prolonged 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) (although in the case of MFAS/HFAS, 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 and beluga (Finneran

et al.,

2000, 2002b, 2005a; Schlundt

et al.,

2000; Nachtigall

et al.,

2003, 2004). For pinnipeds in water, data are limited to Kastak

et al.'s

measurement of TTS in one harbor seal, one elephant seal, and one California sea lion.

Marine mammal hearing plays a critical role in communication with conspecifics, and interpretation of environmental cues for purposes such as predator avoidance and prey capture. Depending on the degree (elevation of threshold in dB), duration (

i.e.,

recovery time), and frequency range of TTS, and the context in which it is experienced, TTS can have effects on marine mammals ranging from discountable to serious (similar to those discussed in auditory masking, below). For example, a marine mammal may be able to readily compensate for a brief, relatively small amount of TTS in a non-critical frequency range that 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 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 it impeded communication. Also, depending on the degree and frequency range, the effects of PTS on an animal could range in severity, although it is considered generally more serious because it is a permanent condition. Of note, reduced hearing sensitivity as a simple function of development and 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 MFAS/HFAS can cause PTS in any marine mammals; instead the probability of PTS has been inferred from studies of TTS (

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 (for example, beaked whales) are theoretically predicted to induce greater supersaturation (Houser

et al.,

2001b). 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 MFAS 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) has speculated 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. Collectively, these hypotheses 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). 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 SELs and tissue saturation levels that are highly improbable to occur in diving marine mammals. To date, Energy Levels (ELs) predicted to cause in vivo bubble formation 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. 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 MFAS/HFAS exposures. Further investigation is needed to further assess the potential validity of these hypotheses. More information regarding hypotheses that attempt to explain how behavioral responses to MFAS/HFAS can lead to strandings is included in the Behaviorally Mediated Bubble Growth Section, after the summary of strandings.

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 to, 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, though, the detection of frequencies above those of the masking stimulus decreases also. 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 low-frequency sound 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 high frequencies these cetaceans use to echolocate, but not at the low-to-moderate frequencies they use to communicate (Zaitseva

et al.,

1980). A recent 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.

As mentioned previously, the functional hearing ranges of odontocetes, pinnipeds underwater, and mysticetes all encompass the frequencies of the MFAS/HFAS sources used in the Navy's MFAS/HFAS training exercises (although some mysticete's best hearing capacities are likely at frequencies somewhat lower than MFAS). Additionally, in almost all species, vocal repertoires span across the frequencies of these MFAS/HFAS sources used by the Navy. The closer the characteristics of the masking signal to the signal of interest, the more likely masking is to occur. For hull-mounted MFAS/HFAS—which accounts for the largest part of the takes of marine mammals (because of the source strength and number of hours it's conducted), the pulse length and duty cycle of the MFAS/HFAS signal (~1 second pulse twice a minute) makes it less likely that masking will occur as a result.

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 it drops 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 one or more of the following adjustments to their vocalizations: Adjust the frequency structure; adjust the amplitude; adjust temporal structure; or adjust temporal delivery (

see

Biological Opinion).

Many animals will combine several of these strategies to compensate for high levels of background noise.

Anthropogenic sounds that 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 communication 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 response.

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

An animal's third line of defense to stressors involves its neuroendocrine or sympathetic nervous systems; the system that has received the most study has been the hypothalmus-pituitary-adrenal system (also known as the HPA axis in mammals or the hypothalamus-pituitary-interrenal axis in fish and some reptiles). Unlike stress responses associated with the autonomic nervous system, virtually all 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) and 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 impairs 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 its 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.

Relationships between these physiological mechanisms, animal behavior, and the costs of stress responses have also been documented fairly well through controlled experiment; because this physiology exists in every vertebrate that has been studied, it is not surprising that stress responses and their costs have been documented in both laboratory and free-living animals (for examples

see

, Holberton

et al.,

1996; Hood

et al.,

1998; Jessop

et al.,

2003; Krausman

et al.,

2004; Lankford

et al.,

2005; Reneerkens

et al.,

2002; Thompson and Hamer, 2000). Although no information has been collected on the physiological responses of marine mammals to exposure to anthropogenic sounds, studies of other marine animals and terrestrial animals would lead us to expect some marine mammals to experience physiological stress responses and, perhaps, physiological responses that would be classified as “distress” upon exposure to high frequency, mid-frequency and 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 (for example, 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 to 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 (nature and magnitude) an acoustic event. An animal's prior experience with a sound or sound source affects whether it is less likely (habituation) or more likely (sensitization) to respond to certain sounds in the future (animals can also be innately pre-disposed to respond to certain sounds in certain ways) (Southall

et al.,

2007). Related to the sound itself, the perceived nearness of the sound, bearing of the sound (approaching vs. retreating), similarity of a sound to biologically relevant sounds in the animal's environment (

i.e.,

calls of predators, prey, or conspecifics), and familiarity of the sound may affect the way an animal responds to the sound (Southall

et al.,

2007). Individuals (of different age, gender, reproductive status,

etc.

) among most populations will have variable hearing capabilities, and differing behavioral sensitivities to sounds that will be affected by prior conditioning, experience, and current activities of those individuals. Often, specific acoustic features of the sound and contextual variables (

i.e.,

proximity, duration, or recurrence of the sound or the current behavior that the marine mammal is engaged in or its prior experience), as well as entirely separate factors such as the physical presence of a nearby vessel, may be more relevant to the animal's response than the received level alone.

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

et al.,

2007). 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 sub-sections provide examples of behavioral responses that provide an idea of the variability in behavioral responses that would be expected given the differential 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, an action, 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 speed of approach, 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 equivocal 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 in western grey 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 low-frequency signals similar to the ATOC sound source demonstrated no variation in foraging activity (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 at the animals 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 seismic activities in that region. 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 feeding area of these whales and the whales left the feeding area and moved to areas farther south in the Sea of Okhotsk. They only returned to the feeding area 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 is 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 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. Disruption of social relationships therefore depends on the disruption of other behaviors (

e.g.,

avoidance, masking,

etc.

). 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). Social disruptions must be considered, however, in context of the relationships that are affected. While some disruptions may not have deleterious effects, long-term 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, respectively.

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. It 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. Longer term displacement is possible, however, which can lead to changes in abundance or distribution patterns of the species in the affected region if they do not become acclimated to the presence of the 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 has 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 longer term or repetitive/chronic displacement for some dolphin groups and for manatees has been suggested to be due to the presence of chronic vessel noise (Haviland-Howell

et al.,

2007; Miksis-Olds

et al.,

2007).

Maybaum (1993) conducted sound playback experiments to assess the effects of mid-frequency active sonar on humpback whales in Hawaiian waters. Specifically, he 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 1,000 Hz to 10,000 Hz (IWC 2005).

Kvadsheim

et al.,

(2007) conducted a controlled exposure experiment in which killer whales (

Orcinus orca

) that had been 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 seconds for 10 minutes; Source B: with a 1.0 s upsweep 197 dB @ 6-7 kHz every 10 s 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, 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 immediately swimming away (horizontally) from the source of the sound; by engaging in a series of erratic and frequently deep dives that seem to take it below the sound field; or by 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 the series of behavioral response studies conducted by NMFS and other scientists showed one beaked whale (

Mesoplodon densirostris

) responding to an MFAS 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) 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, 2008)

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. Flight responses have been speculated as being a component of marine mammal strandings associated with MFAS 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). The probability of avoidance responses should also increase as received levels of active sonar increase (and the ship is, therefore, closer) and as ship speeds increase (that is, as approach speeds increase). For example, 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 approached groups of these animals more directly (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 vary with different behaviors and variations in respiration rate as a function of acoustic exposure can be expected to 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 the whale feeding 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, exposure of 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 in understanding species differences in the tolerance of underwater noise when determining the potential for impacts resulting from anthropogenic sound exposure.

Continued Pre-Disturbance Behavior, Habituation, or No Response

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 become aware of the 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, animals that continue their behavior but experience stress responses (that is, animals that cope with disturbance), animals that habituate to disturbance (that is, they may have experienced low-level stress responses initially, but those responses abated over time), and animals that do not respond to the potential disturbance. Watkins (1986) reviewed data on the behavioral reactions of fin, humpback, right and minke whales that were exposed to continuous, broadband low-frequency shipping and industrial noise in Cape Cod Bay. He concluded that underwater sound was the primary cause of behavioral reactions in these species of whales and that the whales responded behaviorally to acoustic stimuli within their respective hearing ranges. Watkins also noted that whales showed the strongest behavioral reactions to sounds in the 15 Hz to 28 kHz range, although negative reactions (avoidance, interruptions in vocalizations,

etc.

) were generally associated with sounds that were either unexpected, too loud, suddenly louder or different, or perceived as being associated with a potential threat (such as an approaching ship on a collision course). In particular, whales seemed to react negatively when they were within 100 m of the source or when received levels increased suddenly in excess of 12 dB relative to ambient sounds. At other times, the whales ignored the source of the signal and all four species habituated to these sounds.

Nevertheless, Watkins concluded that whales ignored most sounds in the background of ambient noise, including the sounds from distant human activities even though these sounds may have had considerable energies at frequencies well within the whales' range of hearing. Further, he noted that of the whales observed, fin whales were the most sensitive of the four species, followed by humpback whales; right whales were the least likely to be disturbed and generally did not react to low-amplitude engine noise. By the end of his period of study, Watkins (1986) concluded that fin and humpback whales have generally habituated to the continuous and broad-band noise of Cape Cod Bay while right whales did not appear to change their response. As mentioned above, animals that habituate to a particular disturbance may have experienced low-level stress responses initially, but those responses abated over time. In most cases, this likely means a lessened immediate potential effect from a disturbance; however, concern exists where the habituation occurs in a potentially more harmful situation, for example: animals may become more vulnerable to vessel strikes once they habituate to vessel traffic (Swingle

et al.

, 1993; Wiley

et al.

, 1995).

Aicken

et al.

, (2005) monitored the behavioral responses of marine mammals to a new low-frequency active sonar system that was being developed for use by the British Navy. During those trials, fin whales, sperm whales, Sowerby's beaked whales, long-finned pilot whales (

Globicephala melas

), Atlantic white-sided dolphins, and common bottlenose dolphins were observed and their vocalizations were recorded. These monitoring studies detected no evidence of behavioral responses that the investigators could attribute to exposure to the low-frequency active sonar during these trials.

Behavioral Responses (Southall et al. (2007))

Southall

et al.

, (2007) reports the results of the efforts of a panel of experts in acoustic research from behavioral, physiological, and physical disciplines that convened and reviewed the available literature on marine mammal hearing and physiological and behavioral responses to human-made sound with the goal of proposing exposure criteria for certain effects. This peer-reviewed compilation of literature is very valuable, though Southall

et al.

, (2007) note that not all data are equal, some have poor statistical power, insufficient controls, and/or limited information on received levels, background noise, and other potentially important contextual variables—such data were reviewed and sometimes used for qualitative illustration but were not included in the quantitative analysis for the criteria recommendations. All of the studies considered, however, contain an estimate of the received sound level when the animal exhibited the indicated response.

In the Southall

et al.

, (2007) publication, for the purposes of

analyzing responses of marine mammals to anthropogenic sound and developing criteria, the authors differentiate between single pulse sounds, multiple pulse sounds, and non-pulse sounds. MFAS/HFAS is considered a non-pulse sound. Southall

et al.

, (2007) summarize the studies associated with low-frequency, mid-frequency, and high-frequency cetacean and pinniped responses to non-pulse sounds, based strictly on received level, in Appendix C of their article (incorporated by reference and summarized in the three paragraphs below).

The studies that address responses of low frequency cetaceans to non-pulse sounds include data gathered in the field and related to several types of sound sources (of varying similarity to MFAS/HFAS) including: vessel noise, drilling and machinery playback, low-frequency M-sequences (sine wave with multiple phase reversals) playback, tactical low-frequency active sonar playback, drill ships, Acoustic Thermometry of Ocean Climate (ATOC) source, and non-pulse playbacks. These studies generally indicate no (or very limited) responses to received levels in the 90 to 120 dB re: 1 μPa range and an increasing likelihood of avoidance and other behavioral effects in the 120 to 160 dB range. As mentioned earlier, though, contextual variables play a very important role in the reported responses and the severity of effects are not linear when compared to received level. Also, few of the laboratory or field datasets had common conditions, behavioral contexts or sound sources, so it is not surprising that responses differ.

The studies that address responses of mid-frequency cetaceans to non-pulse sounds include data gathered both in the field and the laboratory and related to several different sound sources (of varying similarity to MFAS/HFAS) including: Pingers, drilling playbacks, ship and ice-breaking noise, vessel noise, Acoustic Harassment Devices (AHDs), Acoustic Deterrent Devices (ADDs), MFAS, and non-pulse bands and tones. Southall

et al.

, (2007) were unable to come to a clear conclusion regarding the results of these studies. In some cases, animals in the field showed significant responses to received levels between 90 and 120 dB, while in other cases these responses were not seen in the 120 to 150 dB range. The disparity in results was likely due to contextual variation and the differences between the results in the field and laboratory data (animals typically responded at lower levels in the field).

The studies that address responses of high frequency cetaceans to non-pulse sounds include data gathered both in the field and the laboratory and related to several different sound sources (of varying similarity to MFAS/HFAS) including: Pingers, AHDs, and various laboratory non-pulse sounds. All of these data were collected from harbor porpoises. Southall

et al.

, (2007) concluded that the existing data indicate that harbor porpoises are likely sensitive to a wide range of anthropogenic sounds at low received levels (~90-120 dB), at least for initial exposures. All recorded exposures above 140 dB induced profound and sustained avoidance behavior in wild harbor porpoises (Southall

et al.

, 2007). Rapid habituation was noted in some but not all studies. There is no data to indicate whether other high frequency cetaceans are as sensitive to anthropogenic sound as harbor porpoises are.

The studies that address the responses of pinnipeds in water to non-pulse sounds include data gathered both in the field and the laboratory and related to several different sound sources (of varying similarity to MFAS/HFAS) including: AHDs, ATOC, various non-pulse sounds used in underwater data communication; underwater drilling, and construction noise. Few studies exist with enough information to include them in the analysis. The limited data suggested that exposures to non-pulse sounds between 90 and 140 dB generally do not result in strong behavioral responses in pinnipeds in water, but no data exist at higher received levels.

In addition to summarizing the available data, the authors of Southall

et al.

, (2007) developed a severity scaling system with the intent of ultimately being able to assign some level of biological significance to a response. Following is a summary of their scoring system, a comprehensive list of the behaviors associated with each score may be found in the report:

• 0-3 (Minor and/or brief behaviors) includes, but is not limited to: No response; minor changes in speed or locomotion (but with no avoidance); individual alert behavior; minor cessation in vocal behavior; minor changes in response to trained behaviors (in laboratory);

• 4-6 (Behaviors with higher potential to affect foraging, reproduction, or survival) includes, but is not limited to: Moderate changes in speed, direction, or dive profile; brief shift in group distribution; prolonged cessation or modification of vocal behavior (duration > duration of sound), minor or moderate individual and/or group avoidance of sound; brief cessation of reproductive behavior; or refusal to initiate trained tasks (in laboratory);

• 7-9 (Behaviors considered likely to affect the aforementioned vital rates) includes, but is not limited to: Extensive of prolonged aggressive behavior; moderate, prolonged or significant separation of females and dependent offspring with disruption of acoustic reunion mechanisms; long-term avoidance of an area; outright panic, stampede, stranding; threatening or attacking sound source (in laboratory).

In Table 6 we have summarized the scores that Southall

et al.

, (2007) assigned to the papers that reported behavioral responses of low-frequency cetaceans, mid-frequency cetaceans, and pinnipeds in water to non-pulse sounds. This table is included simply to summarize the findings of the studies and opportunistic observations (all of which were capable of estimating received level) that Southall

et al.

, (2007) compiled in the effort to develop acoustic criteria.

EP13JY09.146

Potential Effects of Behavioral Disturbance

The different ways that marine mammals respond to sound are sometimes indicators of the ultimate effect that exposure to a given stimulus will have on the well-being (survival, reproduction,

etc.

) of an animal. There is little quantitative marine mammal data relating the exposure of marine mammals to sound to effects on reproduction or survival, though data exists for terrestrial species to which we can draw comparisons for marine mammals. Several authors have reported that disturbance stimuli cause animals to abandon nesting and foraging sites, Sutherland and Crockford, 1993), cause animals to increase their activity levels and suffer premature deaths or reduced reproductive success when their energy expenditures exceed their energy budgets (Daan

et al.

, 1996, Feare 1976, Giese 1996, Mullner

et al.

, 2004, Waunters

et al.

, 1997), or cause animals to experience higher predation rates when they adopt risk-prone foraging or migratory strategies (Frid and Dill, 2002). Each of these studies addressed the consequences that result when animals shift from one behavioral state (for example, resting or foraging) to another behavioral state (avoidance or escape behavior) because of human disturbance or disturbance stimuli.

One consequence of behavioral avoidance results from changing the energetics of marine mammals because of the energy required to avoid surface vessels or the sound field associated with active sonar (Frid and Dill, 2002). Most animals can avoid that energetic cost by swimming away at slow speeds or those speeds that are at or near the minimum cost of transport (Miksis-Olds, 2006), as has been demonstrated in Florida manatees (Hartman, 1979, Miksis-Olds, 2006).

Those costs increase, however, when animals shift from a resting state, which is designed to conserve an animal's energy, to an active state that consumes energy the animal would have conserved had it not been disturbed. Marine mammals that have been disturbed by anthropogenic noise and vessel approaches are commonly reported to shift from resting behavioral states to active behavioral states, which would imply that they incur an energy cost. Morete

et al.

, (2007) reported that undisturbed humpback whale cows that were accompanied by their calves were frequently observed resting while their calves circled them (milling) and rolling interspersed with dives. When vessels approached, the amount of time cows and calves spent resting and milling, respectively declined significantly. These results are similar to those reported by Scheidat

et al.

(2004) for the humpback whales they observed off the coast of Ecuador.

Constantine and Brunton (2001) reported that bottlenose dolphins in the Bay of Islands, New Zealand only engaged in resting behavior 5% of the time when vessels were within 300 meters compared with 83% of the time when vessels were not present. Miksis-Olds (2006) and Miksis-Olds

et al.

(2005) reported that Florida manatees in Sarasota Bay, Florida, reduced the amount of time they spent milling and increased the amount of time they spent feeding when background noise levels increased. Although the acute costs of these changes in behavior are not likely to exceed an animals' ability to compensate, the chronic costs of these behavioral shifts are uncertain.

Attention is the cognitive process of selectively concentrating on one aspect of an animal's environment while ignoring other things (Posner, 1994). Because animals (including humans) have limited cognitive resources, there is a limit to how much sensory information they can process at any time. The phenomenon called “attentional capture” occurs when a stimulus (usually a stimulus that an animal is not concentrating on or attending to) “captures” an animal's attention. This shift in attention can occur consciously or unconsciously (for example, when an animal hears sounds that it associates with the approach of a predator) and the shift in attention can be sudden (Dukas, 2002; van Rij, 2007). Once a stimulus has captured an animal's attention, the animal can respond by ignoring the stimulus, assuming a “watch and wait” posture, or treat the stimulus as a disturbance and respond accordingly, which includes scanning for the source of the stimulus or “vigilance” (Cowlishaw

et al.

, 2004).

Vigilance is normally an adaptive behavior that helps animals determine the presence or absence of predators, assess their distance from conspecifics, or to attend cues from prey (Bednekoff and Lima, 1998; Treves, 2000). Despite those benefits, however, vigilance has a cost of time: when animals focus their attention on specific environmental cues, they are not attending to other activities such a foraging. These costs have been documented best in foraging animals, where vigilance has been shown to substantially reduce feeding rates (Saino, 1994; Beauchamp and Livoreil, 1997; Fritz

et al.

, 2002). Animals will spend more time being vigilant, which may translate to less time foraging or resting, when disturbance stimuli approach them more directly, remain at closer distances, have a greater group size (for example, multiple surface vessels, which, of note, will not be utilized in the NWTRC), or when they co-occur with times that an animal perceives increased risk (for example, when they are giving birth or accompanied by a calf). Most of the published literature, however, suggests that direct approaches will increase the amount of time animals will dedicate to being vigilant. For example, bighorn sheep and Dall's sheep dedicated more time to

being vigilant, and less time resting or foraging, when aircraft made direct approaches over them (Frid, 2001; Stockwell

et al.

, 1991).

Several authors have established that long-term and intense disturbance stimuli can cause population declines by reducing the body condition of individuals that have been disturbed, followed by reduced reproductive success, reduced survival, or both (Daan

et al.

, 1996; Madsen, 1994; White, 1983). For example, Madsen (1994) reported that pink-footed geese (

Anser brachyrhynchus

) in undisturbed habitat gained body mass and had about a 46-percent reproductive success rate compared with geese in disturbed habitat (being consistently scared off the fields on which they were foraging) which did not gain mass and has a 17% reproductive success rate. Similar reductions in reproductive success have been reported for mule deer (

Odocoileus hemionus

) disturbed by all-terrain vehicles (Yarmoloy

et al.

, 1988), caribou disturbed by seismic exploration blasts (Bradshaw

et al.

, 1998), caribou disturbed by low-elevation military jet-fights (Luick

et al.

, 1996), and caribou disturbed by low-elevation jet flights (Harrington and Veitch, 1992). Similarly, a study of elk (

Cervus elaphus

) that were disturbed experimentally by pedestrians concluded that the ratio of young to mothers was inversely related to disturbance rate (Phillips and Alldredge, 2000).

The primary mechanism by which increased vigilance and disturbance appear to affect the fitness of individual animals is by disrupting an animal's time budget and, as a result, reducing the time they might spend foraging and resting (which increases an animal's activity rate and energy demand). For example, a study of grizzly bears (

Ursus horribilis

) reported that bears disturbed by hikers reduced their energy intake by an average of 12 kcal/min (50.2 × 10

3

kJ/min), and spent energy fleeing or acting aggressively toward hikers (White

et al.

, 1999). Alternately, Ridgway

et al.

, (2006) reported that increased vigilance in bottlenose dolphins exposed to sound over a five day period did not cause any sleep deprivation or stress effects such as changes in cortisol or epinephrine levels.

On a related note, many animals perform vital functions, such as feeding, resting, traveling, and socializing, on a diel cycle (24-hr cycle). Substantive behavioral reactions to noise exposure (such as disruption of critical life functions, displacement, or avoidance of important habitat) are more likely to be significant if they last more than one diel cycle or recur on subsequent days (Southall

et al.

, 2007). Consequently, a behavioral response lasting less than one day and not recurring on subsequent days is not considered particularly severe unless it could directly affect reproduction or survival (Southall

et al.

, 2007).

Stranding and Mortality

When a live or dead marine mammal swims or floats onto shore and becomes “beached” or incapable of returning to sea, the event is termed a “stranding” (Geraci

et al.

, 1999; Perrin and Geraci, 2002; Geraci and Lounsbury, 2005; National Marine Fisheries Service, 2007p). The legal definition for a stranding within the United States is that (A) “a marine mammal is dead and is (i) on a beach or shore of the United States; or (ii) in waters under the jurisdiction of the United States (including any navigable waters); or (B) a marine mammal is alive and is (i) on a beach or shore of the United States and is unable to return to the water; (ii) on a beach or shore of the United States and, although able to return to the water, is in need of apparent medical attention; or (iii) in the waters under the jurisdiction of the United States (including any navigable waters), but is unable to return to its natural habitat under its own power or without assistance.” (16 U.S.C. 1421h).

Marine mammals are known to strand for a variety of reasons, such as infectious agents, biotoxicosis, starvation, fishery interaction, ship strike, unusual oceanographic or weather events, sound exposure, or combinations of these stressors sustained concurrently or in series. However, the cause or causes of most strandings are unknown (Geraci

et al.

, 1976; Eaton, 1979, Odell

et al.

, 1980; Best, 1982). Numerous studies suggest that the physiology, behavior, habitat relationships, age, or condition of cetaceans may cause them to strand or might pre-dispose them to strand when exposed to another phenomenon. These suggestions are consistent with the conclusions of numerous other studies that have demonstrated that combinations of dissimilar stressors commonly combine to kill an animal or dramatically reduce its fitness, even though one exposure without the other does not produce the same result (Chroussos, 2000; Creel, 2005; DeVries

et al.

, 2003; Fair and Becker, 2000; Foley

et al.

, 2001; Moberg, 2000; Relyea, 2005a; 2005b, Romero, 2004; Sih

et al.

, 2004).

Several sources have published lists of mass stranding events of cetaceans in an attempt to identify relationships between those stranding events and military active sonar (Hildebrand, 2004; IWC, 2005; Taylor

et al.

, 2004). For example, based on a review of stranding records between 1960 and 1995, the International Whaling Commission (2005) identified ten mass stranding events of Cuvier's beaked whales that had been reported and one mass stranding of four Baird's beaked whale (

Berardius bairdii

). The IWC concluded that, out of eight stranding events reported from the mid-1980s to the summer of 2003, seven had been coincident with the use of MFAS, one of those seven had been associated with the use of tactical low-frequency sonar, and the remaining stranding event had been associated with the use of seismic airguns.

Most of the stranding events reviewed by the IWC involved beaked whales. A mass stranding of Cuvier's beaked whales in the eastern Mediterranean Sea occurred in 1996 (Franzis, 1998) and mass stranding events involving Gervais' beaked whales, Blainville's beaked whales, and Cuvier's beaked whales occurred off the coast of the Canary Islands in the late 1980s (Simmonds and Lopez-Jurado, 1991). The stranding events that occurred in the Canary Islands and Kyparissiakos Gulf in the late 1990s and the Bahamas in 2000 have been the most intensively-studied mass stranding events and have been associated with naval exercises involving the use of MFAS.

Strandings Associated With MFAS

Over the past 12 years, there have been five stranding events coincident with military mid-frequency active sonar use in which exposure to sonar is believed by NMFS and the Navy to have been a contributing factor: Greece (1996); the Bahamas (2000); Madeira (2000); Canary Islands (2002); and Spain (2006). Additionally, in 2004, during the RIMPAC exercises, between 150-200 usually pelagic melon-headed whales occupied the shallow waters of the Hanalei Bay, Kaua'i, Hawaii for over 28 hours. NMFS determined that the mid-frequency sonar was a plausible, if not likely, contributing factor in what may have been a confluence of events that led to the Hanalei Bay stranding. A number of other stranding events coincident with the operation of MFAS including the death of beaked whales or other species (minke whales, dwarf sperm whales, pilot whales) have been reported; however, the majority have not been investigated to the degree necessary to determine the cause of the stranding.

Greece (1996)

Twelve Cuvier's beaked whales stranded atypically (in both time and space) along a 38.2-kilometer strand of the coast of the Kyparissiakos Gulf on May 12 and 13, 1996 (Frantzis, 1998). From May 11 through May 15, the NATO research vessel Alliance was conducting active sonar tests with signals of 600 Hz and 3 kHz and source levels of 228 and 226 dB re: 1 μPa, respectively (D'Amico and Verboom, 1998; D'Spain

et al.

, 2006). The timing and the location of the testing encompassed the time and location of the whale strandings (Frantzis, 1998).

Necropsies of eight of the animals were performed but were limited to basic external examination and sampling of stomach contents, blood, and skin. No ears or organs were collected, and no histological samples were preserved. No apparent abnormalities or wounds were found (Frantzis, 2004). Examination of photos of the animals, taken soon after their death, revealed that the eyes of at least four of the individuals were bleeding. Photos were taken soon after their death (Frantzis, 2004). Stomach contents contained the flesh of cephalopods, indicating that feeding had recently taken place (Frantzis, 1998).

All available information regarding the conditions associated with this stranding event were compiled, and many potential causes were examined including major pollution events, prominent tectonic activity, unusual physical or meteorological events, magnetic anomalies, epizootics, and conventional military activities (International Council for the Exploration of the Sea, 2005a). However, none of these potential causes coincided in time or space with the mass stranding, or could explain its characteristics (International Council for the Exploration of the Sea, 2005a). The robust condition of the animals, plus the recent stomach contents, is inconsistent with pathogenic causes (Frantzis, 2004). In addition, environmental causes can be ruled out as there were no unusual environmental circumstances or events before or during this time period and within the general proximity (Frantzis, 2004).

Because of the rarity of this mass stranding of Cuvier's beaked whales in the Kyparissiakos Gulf (first one in history), the probability for the two events (the military exercises and the strandings) to coincide in time and location, while being independent of each other, was thought to be extremely low (Frantzis, 1998). However, because full necropsies had not been conducted, and no abnormalities were noted, the cause of the strandings could not be precisely determined (Cox

et al.

, 2006). A Bioacoustics Panel convened by NATO concluded that the evidence available did not allow them to accept or reject sonar exposures as a causal agent in these stranding events. Their official finding was “An acoustic link can neither be clearly established, nor eliminated as a direct or indirect cause for the May 1996 strandings.” The analysis of this stranding event provided support for, but no clear evidence for, the cause-and-effect relationship of active sonar training activities and beaked whale strandings (Cox

et al.

, 2006).

Bahamas (2000)

NMFS and the Navy prepared a joint report addressing the multi-species stranding in the Bahamas in 2000, which took place within 24 hours of U.S. Navy ships using MFAS as they passed through the Northeast and Northwest Providence Channels on March 15-16, 2000. The ships, which operated both AN/SQS-53C and AN/SQS-56, moved through the channel while emitting MFAS pings approximately every 24 seconds. Of the 17 cetaceans that stranded over a 36-hr period (Cuvier's beaked whales, Blainville's beaked whales, Minke whales, and a spotted dolphin), seven animals died on the beach (5 Cuvier's beaked whales, 1 Blainville's beaked whale, and the spotted dolphin), while the other 10 were returned to the water alive (though their ultimate fate is unknown). As discussed in the Bahamas report (DOC/DON, 2001), there is no likely association between the minke whale and spotted dolphin strandings and the operation of MFAS.

Necropsies were performed on five of the stranded beaked whales. All five necropsied beaked whales were in good body condition, showing no signs of infection, disease, ship strike, blunt trauma, or fishery related injuries, and three still had food remains in their stomachs. Auditory structural damage was discovered in four of the whales, specifically bloody effusions or hemorrhaging around the ears. Bilateral intracochlear and unilateral temporal region subarachnoid hemorrhage, with blood clots in the lateral ventricles, were found in two of the whales. Three of the whales had small hemorrhages in their acoustic fats (located along the jaw and in the melon).

A comprehensive investigation was conducted and all possible causes of the stranding event were considered, whether they seemed likely at the outset or not. Based on the way in which the strandings coincided with ongoing naval activity involving tactical MFAS use, in terms of both time and geography, the nature of the physiological effects experienced by the dead animals, and the absence of any other acoustic sources, the investigation team concluded that MFAS aboard U.S. Navy ships that were in use during the active sonar exercise in question were the most plausible source of this acoustic or impulse trauma to beaked whales. This sound source was active in a complex environment that included the presence of a surface duct, unusual and steep bathymetry, a constricted channel with limited egress, intensive use of multiple, active sonar units over an extended period of time, and the presence of beaked whales that appear to be sensitive to the frequencies produced by these active sonars. The investigation team concluded that the cause of this stranding event was the confluence of the Navy MFAS and these contributory factors working together, and further recommended that the Navy avoid operating MFAS in situations where these five factors would be likely to occur. This report does not conclude that all five of these factors must be present for a stranding to occur, nor that beaked whales are the only species that could potentially be affected by the confluence of the other factors. Based on this, NMFS believes that the operation of MFAS in situations where surface ducts exist, or in marine environments defined by steep bathymetry and/or constricted channels, may increase the likelihood of producing a sound field with the potential to cause cetaceans (especially beaked whales) to strand, and therefore suggests the need for increased vigilance while operating MFAS in these areas, especially when beaked whales (or potentially other deep divers) are likely present.

Madeira, Spain (2000)

From May 10-14, 2000, three Cuvier's beaked whales were found atypically stranded on two islands in the Madeira archipelago, Portugal (Cox

et al.

, 2006). A fourth animal was reported floating in the Madeiran waters by fishermen but did not come ashore (Woods Hole Oceanographic Institution, 2005). Joint NATO amphibious training peacekeeping exercises involving participants from 17 countries and 80 warships, took place in Portugal during May 2-15, 2000.

The bodies of the three stranded whales were examined post mortem (Woods Hole Oceanographic Institution, 2005), though only one of the stranded whales was fresh enough (24 hours after stranding) to be necropsied (Cox

et al.

,

2006). Results from the necropsy revealed evidence of hemorrhage and congestion in the right lung and both kidneys (Cox

et al.

, 2006). There was also evidence of intercochlear and intracranial hemorrhage similar to that which was observed in the whales that stranded in the Bahamas event (Cox

et al.

, 2006). There were no signs of blunt trauma, and no major fractures (Woods Hole Oceanographic Institution, 2005). The cranial sinuses and airways were found to be clear with little or no fluid deposition, which may indicate good preservation of tissues (Woods Hole Oceanographic Institution, 2005).

Several observations on the Madeira stranded beaked whales, such as the pattern of injury to the auditory system, are the same as those observed in the Bahamas strandings. Blood in and around the eyes, kidney lesions, pleural hemorrhages, and congestion in the lungs are particularly consistent with the pathologies from the whales stranded in the Bahamas, and are consistent with stress and pressure related trauma. The similarities in pathology and stranding patterns between these two events suggest that a similar pressure event may have precipitated or contributed to the strandings at both sites (Woods Hole Oceanographic Institution, 2005).

Even though no definitive causal link can be made between the stranding event and naval exercises, certain conditions may have existed in the exercise area that, in their aggregate, may have contributed to the marine mammal strandings (Freitas, 2004): Exercises were conducted in areas of at least 547 fathoms (1,000 m) depth near a shoreline where there is a rapid change in bathymetry on the order of 547 to 3,281 (1,000-6,000 m) fathoms occurring across a relatively short horizontal distance (Freitas, 2004); multiple ships were operating around Madeira, though it is not known if MFAS was used, and the specifics of the sound sources used are unknown (Cox

et al.

, 2006, Freitas, 2004); exercises took place in an area surrounded by land masses separated by less than 35 nm (65 km) and at least 10 nm (19 km) in length, or in an embayment. Exercises involving multiple ships employing MFA near land may produce sound directed towards a channel or embayment that may cut off the lines of egress for marine mammals (Freitas, 2004).

Canary Islands, Spain (2002)

The southeastern area within the Canary Islands is well known for aggregations of beaked whales due to its ocean depths of greater than 547 fathoms (1,000 m) within a few hundred meters of the coastline (Fernandez

et al.

, 2005). On September 24, 2002, 14 beaked whales were found stranded on Fuerteventura and Lanzarote Islands in the Canary Islands (International Council for Exploration of the Sea, 2005a). Seven whales died, while the remaining seven live whales were returned to deeper waters (Fernandez

et al.

, 2005). Four beaked whales were found stranded dead over the next 3 days either on the coast or floating offshore. These strandings occurred within near proximity of an international naval exercise that utilized MFAS and involved numerous surface warships and several submarines. Strandings began about 4 hours after the onset of MFAS activity (International Council for Exploration of the Sea, 2005a; Fernandez

et al.

, 2005).

Eight Cuvier's beaked whales, one Blainville's beaked whale, and one Gervais' beaked whale were necropsied, six of them within 12 hours of stranding (Fernandez

et al.

, 2005). No pathogenic bacteria were isolated from the carcasses (Jepson

et al.

, 2003). The animals displayed severe vascular congestion and hemorrhage especially around the tissues in the jaw, ears, brain, and kidneys, displaying marked disseminated microvascular hemorrhages associated with widespread fat emboli (Jepson

et al.

, 2003; International Council for Exploration of the Sea, 2005a). Several organs contained intravascular bubbles, although definitive evidence of gas embolism

in vivo

is difficult to determine after death (Jepson

et al.

, 2003). The livers of the necropsied animals were the most consistently affected organ, which contained macroscopic gas-filled cavities and had variable degrees of fibrotic encapsulation. In some animals, cavitary lesions had extensively replaced the normal tissue (Jepson

et al.

, 2003). Stomachs contained a large amount of fresh and undigested contents, suggesting a rapid onset of disease and death (Fernandez

et al.

, 2005). Head and neck lymph nodes were enlarged and congested, and parasites were found in the kidneys of all animals (Fernandez

et al.

, 2005).

The association of NATO MFAS use close in space and time to the beaked whale strandings, and the similarity between this stranding event and previous beaked whale mass strandings coincident with active sonar use, suggests that a similar scenario and causative mechanism of stranding may be shared between the events. Beaked whales stranded in this event demonstrated brain and auditory system injuries, hemorrhages, and congestion in multiple organs, similar to the pathological findings of the Bahamas and Madeira stranding events. In addition, the necropsy results of the Canary Islands stranding event lead to the hypothesis that the presence of disseminated and widespread gas bubbles and fat emboli were indicative of nitrogen bubble formation, similar to what might be expected in decompression sickness (Jepson

et al.

, 2003; Fernández

et al.

, 2005).

Spain (2006)

The Spanish Cetacean Society reported an atypical mass stranding of four beaked whales that occurred January 26, 2006, on the southeast coast of Spain, near Mojacar (Gulf of Vera) in the Western Mediterranean Sea. According to the report, two of the whales were discovered the evening of January 26 and were found to be still alive. Two other whales were discovered during the day on January 27, but had already died. The fourth animal was found dead on the afternoon of January 27, a few kilometers north of the first three animals. From January 25-26, 2006, Standing North Atlantic Treaty Organization (NATO) Response Force Maritime Group Two (five of seven ships including one U.S. ship under NATO Operational Control) had conducted active sonar training against a Spanish submarine within 50 nm (93 km) of the stranding site.

Veterinary pathologists necropsied the two male and two female Cuvier's beaked whales. According to the pathologists, the most likely primary cause of this type of beaked whale mass stranding event was anthropogenic acoustic activities, most probably anti-submarine MFAS used during the military naval exercises. However, no positive acoustic link was established as a direct cause of the stranding. Even though no causal link can be made between the stranding event and naval exercises, certain conditions may have existed in the exercise area that, in their aggregate, may have contributed to the marine mammal strandings (Freitas, 2004): exercises were conducted in areas of at least 547 fathoms (1000 m) depth near a shoreline where there is a rapid change in bathymetry on the order of 547 to 3,281 fathoms (1000-6000 m) occurring across a relatively short horizontal distance (Freitas, 2004); multiple ships (in this instance, five) were operating MFAS in the same area over extended periods of time (in this case, 20 hours) i

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