# Takes of Marine Mammals Incidental to Specified Activities; U.S. Navy Training and Testing Activities in the Hawaii-Southern California Training and Testing Study Area > Briefs, arguments, decisions, and more. URL: https://www.frixlaw.com/law-library/documents/fr%3A2013-01808 ## Record - **Collection:** Federal Register - **Document type:** Proposed Rule - **Published:** January 31, 2013 - **Citation:** 78 FR 6978 ## Text DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration 50 CFR Part 218 [Docket No. 130107014-3024-01] RIN 0648-BC52 Takes of Marine Mammals Incidental to Specified Activities; U.S. Navy Training and Testing Activities in the Hawaii-Southern California Training and Testing Study Area AGENCY: National Marine Fisheries Service (NMFS), National Oceanic and Atmospheric Administration (NOAA), Commerce. ACTION: Proposed rule; request for comments and information. SUMMARY: NMFS has received a request from the U.S. Navy (Navy) for authorization to take marine mammals incidental to the training and testing activities conducted in the Hawaii-Southern California Training and Testing (HSTT) study area from January 2014 through January 2019. Pursuant to the Marine Mammal Protection Act (MMPA), NMFS is requesting comments on its proposal to issue regulations and subsequent Letters of Authorization (LOAs) to the Navy to incidentally harass marine mammals. DATES: Comments and information must be received no later than March 11, 2013. ADDRESSES: You may submit comments, identified by 0648-BC52, by either of the following methods: • Electronic submissions: Submit all electronic public comments via the Federal eRulemaking Portal http://www.regulations.gov. • Hand delivery or mailing of paper, disk, or CD-ROM comments should be addressed to P. Michael Payne, Chief, Permits and Conservation 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: Michelle Magliocca, Office of Protected Resources, NMFS, (301) 427-8401. SUPPLEMENTARY INFORMATION: Availability A copy of the Navy's application may be obtained by visiting the internet at: http://www.nmfs.noaa.gov/pr/permits/incidental.htm#applications. The Navy's Draft Environmental Impact Statement/Overseas Environmental Impact Statement (DEIS/OEIS) for HSTT was made available to the public on May 11, 2012 (77 FR 27743) and may also be viewed at http://www.nmfs.noaa.gov/pr/permits/incidental.htm#applications. Documents cited in this notice may also be viewed, by appointment, during regular business hours, at the aforementioned address. Background Sections 101(a)(5)(A) and (D) of the MMPA (16 U.S.C. 1361 et seq.) direct the Secretary of Commerce to allow, upon request, the incidental, but not intentional, taking of small numbers of marine mammals by U.S. citizens who engage in a specified activity (other than commercial fishing) within a specified geographical region if certain findings are made and either regulations are issued or, if the taking is limited to harassment, a notice of a proposed authorization is provided to the public for review. Authorization for incidental takings shall be granted if NMFS finds that the taking will have a negligible impact on the species or stock(s), will not have an unmitigable adverse impact on the availability of the species or stock(s) for subsistence uses (where relevant), and if the permissible methods of taking and requirements pertaining to the mitigation, monitoring, and reporting of such takings are set forth. NMFS has defined “negligible impact” in 50 CFR 216.103 as “an impact resulting from the specified activity that cannot be reasonably expected to, and is not reasonably likely to, adversely affect the species or stock through effects on annual rates of recruitment or survival.” The National Defense Authorization Act of 2004 (NDAA) (Pub. L. 108-136) removed the “small numbers” and “specified geographical region” limitations indicated above and amended the definition of “harassment” as 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].” Summary of Request On April 13, 2012, NMFS received an application from the Navy requesting two LOAs for the take of 39 species of marine mammals incidental to Navy training and testing activities to be conducted in the HSTT Study Area over 5 years. The Navy submitted an addendum on September 24, 2012 and the application was considered complete. The Navy is requesting regulations that would establish a process for authorizing take, via two separate 5-year LOAs, of marine mammals for training activities and testing activities, each proposed to be conducted from 2014 through 2019. The Study Area includes three existing range complexes (Southern California (SOCAL) Range Complex, Hawaii Range Complex (HRC), and Silver Strand Training Complex (SSTC)) plus pierside locations and areas on the high seas where maintenance, training, or testing may occur. The proposed activities are classified as military readiness activities. Marine mammals present in the Study Area may be exposed to sound from active sonar, underwater detonations, and/or pile driving and removal. In addition, incidental takes of marine mammals may occur from ship strikes. The Navy is requesting authorization to take 38 marine mammal species by Level B harassment and 24 marine mammal species by Level A harassment or mortality. The Navy's application and the HSTT DEIS/OEIS contain proposed acoustic criteria and thresholds that would, in some instances, represent changes from what NMFS has used to evaluate the Navy's proposed activities for past incidental take authorizations. The revised thresholds are based on evaluation of recent scientific studies; a detailed explanation of how they were derived is provided in the HSTT DEIS/OEIS Criteria and Thresholds Technical Report. NMFS is currently updating and revising all of its acoustic criteria and thresholds. Until that process is complete, NMFS will continue its long-standing practice of considering specific modifications to the acoustic criteria and thresholds currently employed for incidental take authorizations only after providing the public with an opportunity for review and comment. NMFS is requesting comments on all aspects of the proposed rule, and specifically requests comments on the proposed acoustic criteria and thresholds. 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 military 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 systems. The Navy proposes to continue conducting training and testing activities within the HSTT Study Area, which have been ongoing since the 1940s. Recently, most of these activities were analyzed in three separate EISs completed between 2008 and 2011; the Hawaii Range Complex (HRC) EIS/OEIS (U.S. Department of the Navy, 2008a), the Southern California (SOCAL) Range Complex EIS/OEIS (U.S. Department of the Navy, 2008b), and the Silver Strand Training Complex (SSTC) EIS (U.S. Department of the Navy, 2011a). These documents, among others, and their associated MMPA regulations and authorizations, describe the baseline of training and testing activities currently conducted in the Study Area. The tempo and types of training and testing activities have fluctuated due to changing requirements; new technologies; the dynamic nature of international events; advances in warfighting doctrine and procedures; and changes in basing locations for ships, aircraft, and personnel. Such developments influence the frequency, duration, intensity, and location of required training and testing. The Navy's LOA request covers training and testing activities that would occur for a 5-year period following the expiration of the current MMPA authorizations. The Navy has also prepared a DEIS/OEIS analyzing the effects on the human environment of implementing their preferred alternative (among others). Description of the Specified Activity The Navy is requesting authorization to take marine mammals incidental to conducting training and testing activities. The Navy has determined that sonar use, underwater detonations, pile driving and removal, and ship strike are the stressors most likely to result in impacts on marine mammals that could rise to the level of harassment. Detailed descriptions of these activities are provided in the HSTT DEIS/OEIS and LOA application ( http://www.nmfs.noaa.gov/pr/permits/incidental.htm ) and are summarized here. Overview of Training Activities The Navy routinely trains in the HSTT Study Area in preparation for national defense missions. Training activities are categorized into eight functional warfare areas (anti-air warfare; amphibious warfare; strike warfare; anti-surface warfare; anti-submarine warfare; electronic warfare; mine warfare; and naval special warfare). The Navy determined that the following stressors used in these warfare areas are most likely to result in impacts on marine mammals: • Amphibious warfare (underwater detonations, pile driving and removal) • Anti-surface warfare (underwater detonations) • Anti-submarine warfare (active sonar, underwater detonations) • Mine warfare (active sonar, underwater detonations, and marine mammal systems (see description below)) • Naval special warfare (underwater detonations) The Navy's activities in anti-air warfare, strike warfare, and electronic warfare do not involve stressors that could result in harassment of marine mammals. Therefore, these activities are not discussed further. Amphibious Warfare The mission of amphibious warfare is to project military power from the sea to the shore through the use of naval firepower and Marine Corps landing forces. The Navy uses amphibious warfare to attack a threat located on land by a military force embarked on ships. Amphibious warfare training ranges from individual, crew, and small unit events to large task force exercises. Individual and crew training include amphibious vehicles and naval gunfire support training for shore assaults, boat raids, airfield or port seizures, and reconnaissance. Large-scale amphibious exercises involve ship-to-shore maneuver, naval fire support, such as shore bombardment, and air strike and close air support training. However, the Navy only analyzed those portions of amphibious warfare training that occur at sea, in particular, underwater detonations associated with naval gunfire support training. The Navy conducts other amphibious warfare support activities that could potentially affect marine mammals (such as pile driving and removal) in the near shore region from the beach to about 914 meters (m) from shore. Anti-Surface Warfare The mission of anti-surface warfare is to defend against enemy ships or boats. When conducting anti-surface warfare, aircraft use cannons, air-launched cruise missiles, or other precision-guided munitions; ships use torpedoes, naval guns, and surface-to-surface missiles; and submarines use torpedoes or submarine-launched, anti-ship cruise missiles. Anti-surface warfare training includes surface-to-surface gunnery and missile exercises, air-to-surface gunnery and missile exercises, and submarine missile or exercise torpedo launch events. Anti-Submarine Warfare The mission of anti-submarine warfare is to locate, neutralize, and defeat hostile submarine threats to surface forces. Anti-submarine warfare is based on the principle of a layered defense of surveillance and attack aircraft, ships, and submarines all searching for hostile submarines. These forces operate together or independently to gain early warning and detection, and to localize, track, target, and attack hostile submarine threats. Anti-submarine warfare training addresses basic skills such as detection and classification of submarines, distinguishing between sounds made by enemy submarines and those of friendly submarines, ships, and marine life. More advanced, integrated anti-submarine warfare training exercises are conducted in coordinated, at-sea training events involving submarines, ships, and aircraft. This training integrates the full spectrum of anti-submarine warfare from detecting and tracking a submarine to attacking a target using either exercise torpedoes or simulated weapons. Mine Warfare The mission of mine warfare is to detect, and avoid or neutralize mines to protect Navy ships and submarines and to maintain free access to ports and shipping lanes. Mine warfare also includes offensive mine laying to gain control or deny the enemy access to sea space. Naval mines can be laid by ships, submarines, or aircraft. Mine warfare training includes exercises in which ships, aircraft, submarines, underwater vehicles, or marine mammal detection systems search for mines. Certain personnel train to destroy or disable mines by attaching and detonating underwater explosives to simulated mines. Other neutralization techniques involve impacting the mine with a bullet-like projectile or intentionally triggering the mine to detonate. Finally, the Navy deploys California sea lions in the HSTT Study Area for integrated training involving two primary missions areas: To find objects such as inert mine shapes, and to detect swimmers or other intruders around Navy facilities such as piers. When deployed, the animals are part of what the Navy refers to as marine mammal systems. These systems include one or more motorized small boats, several crew members, and a trained marine mammal. Each trained animal is deployed under behavioral control to find the intruding swimmer or submerged object. Naval Special Warfare The mission of naval special warfare is to conduct unconventional warfare, direct action, combat terrorism, special reconnaissance, information warfare, security assistance, counter-drug operations, and recovery of personnel from hostile situations. Naval special warfare operations are highly specialized and require continual and intense training. Naval special warfare units are required to utilize a combination of specialized training, equipment, and tactics, including insertion and extraction operations using parachutes, submerged vehicles, rubber boats, and helicopters; boat-to-shore and boat-to-boat gunnery; underwater demolition training; reconnaissance; and small arms training. Overview of Testing Activities The Navy researches, develops, tests, and evaluates new platforms, systems, and technologies. Testing activities may occur independently of or in conjunction with training activities. Many testing activities are conducted similarly to Navy training activities and are also categorized under one of the primary mission areas. Other testing activities are unique and are described within their specific testing categories. The Navy determined that stressors used during the following testing activities are most likely to result in impacts on marine mammals: • Naval Air Systems Command (NAVAIR) Testing ○ Anti-surface warfare testing (underwater detonations) ○ Anti-submarine warfare testing (active sonar, underwater detonations) ○ Mine warfare testing (active sonar, underwater detonations) • Naval Sea Systems command (NAVSEA) Testing ○ New ship construction (active sonar, underwater detonations) ○ Life cycle activities (active sonar, underwater detonations) ○ Anti-surface warfare/anti-submarine warfare testing (active sonar, underwater detonations) ○ Mine warfare testing (active sonar, underwater detonations) ○ Ship protection systems and swimmer defense testing (active sonar, airguns) ○ Unmanned vehicle testing (active sonar) ○ Other testing (active sonar) • Space and Naval Warfare Systems Commands (SPAWAR) Testing ○ SPAWAR research, development, test, and evaluation (active sonar) • Office of Naval Research (ONR) and Naval Research Laboratory (NRL) Testing ○ ONR/NRL research, development, test, and evaluation (active sonar) Other Navy testing activities do not involve stressors that could result in marine mammal harassment. Therefore, these activities are not discussed further. Naval Air Systems Command Testing (NAVAIR) NAVAIR events include testing of new aircraft platforms, weapons, and systems before delivery to the fleet for training activities. NAVAIR also conducts lot acceptance testing of weapons and systems, such as sonobuoys. In general, NAVAIR conducts its testing activities the same way the fleet conducts its training activities. However, NAVAIR testing activities may occur in different locations than equivalent fleet training activities and testing of a particular system may differ slightly from the way the fleet trains with the same system. Anti-surface Warfare Testing —Anti-surface warfare testing includes air-to-surface gunnery, missile, and rocket exercises. Testing is required to ensure the equipment is fully functional for defense from surface threats. Testing may be conducted on new guns or run rounds, missiles, rockets, and aircraft, and also in support of scientific research to assess new and emerging technologies. Testing events are often integrated into training activities and in most cases the systems are used in the same manner in which they are used for fleet training activities. Anti-submarine Warfare Testing —Anti-submarine warfare testing addresses basic skills such as detection and classification of submarines, distinguishing between sounds made by enemy submarines and those of friendly submarines, ships, and marine life. More advanced, integrated anti-submarine warfare testing is conducted in coordinated, at-sea training events involving submarines, ships, and aircraft. This testing integrates the full spectrum of anti-submarine warfare from detecting and tracking a submarine to attacking a target using various torpedoes and weapons. Mine Warfare Testing —Mine warfare testing includes activities in which aircraft detection systems are used to search for and record the location of mines for subsequent neutralization. Mine neutralization tests evaluate a system's effectiveness at intentionally detonating or otherwise disabling the mine. Different mine neutralization systems are designed to neutralize mines either at the sea surface or deployed deeper within the water column. All components of these systems are tested in the at-sea environment to ensure they meet mission requirements. Naval Sea Systems Command Testing (NAVSEA) NAVSEA testing activities are aligned with its mission of new ship construction, life cycle support, and other weapon systems development and testing. New Ship Construction Activities —Ship construction activities include pierside testing of ship systems, tests to determine how the ship performs at sea (sea trials), and developmental and operational test and evaluation programs for new technologies and systems. Pierside and at-sea testing of systems aboard a ship may include sonar, acoustic countermeasures, radars, and radio equipment. During sea trials, each new ship propulsion engine is operated at full power and subjected to high-speed runs and steering tests. At-sea test firing of shipboard weapon systems, including guns, torpedoes, and missiles, are also conducted. Life Cycle Activities —Testing activities are conducted throughout the life of a Navy ship to verify performance and mission capabilities. Sonar system testing occurs pierside during maintenance, repair, and overhaul availabilities, and at sea immediately following most major overhaul periods. A Combat System Ship Qualification Trial is conducted for new ships and for ships that have undergone modification or overhaul of their combat systems. Radar cross signature testing of surface ships is conducted on new vessels and periodically throughout a ship's life to measure how detectable the ship is by radar. Electromagnetic measurements of off-board electromagnetic signature are also conducted for submarines, ships, and surface craft periodically. Other Weapon Systems Development and Testing —Numerous test activities and technical evaluations, in support of NAVSEA's systems development mission, often occur with fleet activities within the Study Area. Tests within this category include, but are not limited to, anti-surface, anti-submarine, and mine warfare, using torpedoes, sonobuoys, and mine detection and neutralization systems. Space and Naval Warfare Systems Command Testing (SPAWAR) The mission of SPAWAR is to acquire, develop, deliver, and sustain decision superiority for the warfighter at the right time and for the right cost. SPAWAR Systems Center Pacific is the research and development part of SPAWAR focused on developing and transitioning technologies in the area of command, control, communications, computers, intelligence, surveillance, and reconnaissance. SPAWAR Systems Center Pacific conducts research, development, test, and evaluation projects to support emerging technologies for intelligence, surveillance, and reconnaissance; anti-terrorism and force protection; mine countermeasures; anti-submarine warfare; oceanographic research; remote sensing; and communications. These activities include, but are not limited to, the testing of unmanned undersea and surface vehicles, a wide variety of intelligence, surveillance, and reconnaissance sensor systems, underwater surveillance technologies, and underwater communications. Office of Naval Research and Naval Research Laboratory Testing (ONR and NRL) As the Navy's science and technology provider, ONR and NRL provide technology solutions for Navy and Marine Corps needs. ONR's mission is to plan, foster, and encourage scientific research in recognition of its paramount importance as related to the maintenance of future naval power, and the preservation of national security. Further, ONR manages the Navy's basic, applied, and advanced research to foster transition from science and technology to higher levels of research, development, test, and evaluation. The Ocean Battlespace Sensing Department explores science and technology in the areas of oceanographic and meteorological observations, modeling, and prediction in the battlespace environment; submarine detection and classification (anti-submarine warfare); and mine warfare applications for detecting and neutralizing mines in both the ocean and littoral environment. ONR events include research, development, test, and evaluation activities; surface processes acoustic communications experiments; shallow water acoustic communications experiments; sediment acoustics experiments; shallow water acoustic propagation experiments; and long range acoustic propagation experiments. Sonar, Ordnance, Targets, and Other Systems The Navy uses a variety of sensors, platforms, weapons, and other devices to meet its mission. Training and testing with these systems may introduce acoustic (sound) energy into the environment. This section describes and organizes sonar systems, ordnance, munitions, targets, and other systems to facilitate understanding of the activities in which these systems are used. Underwater sound is described as one of two types for the purposes of the Navy's application: impulsive and non-impulsive. Underwater detonations of explosives and other percussive events are impulsive sounds. Sonar and similar sound producing systems are categorized as non-impulsive sound sources. Sonar and Other Non-impulsive Sources —Modern sonar technology includes a variety of sonar sensor and processing systems. The simplest active sonar emits sound waves, or “pings,” sent out in multiple directions and the sound waves then reflect off of the target object in multiple directions. The sonar source calculates the time it takes for the reflected sound waves to return; this calculation determines the distance to the target object. More sophisticated active sonar systems emit a ping and then rapidly scan or listen to the sound waves in a specific area. This provides both distance to the target and directional information. Even more advanced sonar systems use multiple receivers to listen to echoes from several directions simultaneously and provide efficient detection of both direction and distance. The Navy rarely uses active sonar continuously throughout activities. When sonar is in use, the pings occur at intervals, referred to as a duty cycle, and the signals themselves are very short in duration. For example, sonar that emits a 1-second ping every 10 seconds has a 10-percent duty cycle. The Navy utilizes sonar systems and other acoustic sensors in support of a variety of mission requirements. Primary uses include the detection of and defense against submarines (anti-submarine warfare) and mines (mine warfare); safe navigation and effective communications; use of unmanned undersea vehicles; and oceanographic surveys. Ordnance and Munitions —Most ordnance and munitions used during training and testing events fall into three basic categories: Projectiles (such as gun rounds), missiles (including rockets), and bombs. Ordnance can be further defined by their net explosive weight, which considers the type and quantity of the explosive substance without the packaging, casings, bullets, etc. Net explosive weight (NEW) is the trinitrotoluene (TNT) equivalent of energetic material, which is the standard measure of strength of bombs and other explosives. For example, a 12.7-centimeter(cm) shell fired from a Navy gun is analyzed at about 9.5 pounds (lb) (4.3 kilograms (kg)) of NEW. The Navy also uses non-explosive ordnance in place of high explosive ordnance in many training and testing events. Non-explosive ordnance munitions look and perform similarly to high explosive ordnance, but lack the main explosive charge. Defense Countermeasures —Naval forces depend on effective defensive countermeasures to protect themselves against missile and torpedo attack. Defensive countermeasures are devices designed to confuse, distract, and confound precision guided munitions. Defensive countermeasures analyzed in this LOA application include acoustic countermeasures, which are used by surface ships and submarines to defend against torpedo attack. Acoustic countermeasures are either released from ships and submarines, or towed at a distance behind the ship. Mine Warfare Systems —The Navy divides mine warfare systems into two categories: mine detection and mine neutralization. Mine detection systems are used to locate, classify, and map suspected mines, on the surface, in the water column, or on the sea floor. The Navy analyzed the following mine detection systems for potential impacts to marine mammals: • Towed or hull-mounted mine detection systems. These detection systems use acoustic and laser or video sensors to locate and classify suspect mines. Fixed and rotary wing platforms, ships, and unmanned vehicles are used for towed systems, which can rapidly assess large areas. • Unmanned/remotely operated vehicles. These vehicles use acoustic and video or lasers to locate and classify mines and provide unique capabilities in nearshore littoral areas, surf zones, ports, and channels. • Marine mammal systems. The Navy deploys trained Atlantic bottlenose dolphins ( Tursiops truncatus ) and California sea lions ( Zalopus californianus ) for integrated training involving two primary mission areas: to find objects such as inert mine shapes, and to detect swimmers or other intruders around Navy facilities such as piers. These systems also include one or more motorized small boats and several crew members for each trained marine mammal. When not engaged in training, Navy marine mammals are housed in temporary enclosures either on land or aboard ships. Mine Neutralization Systems —Mine neutralization systems disrupt, disable, or detonate mines to clear ports and shipping lanes, as well as littoral, surf, and beach areas in support of naval amphibious operations. The Navy analyzed the following mine neutralization systems for potential impacts to marine mammals: • Towed influence mine sweep systems. These systems use towed equipment that mimic a particular ship's magnetic and acoustic signature triggering the mine and causing it to explode. • Unmanned/remotely operated mine neutralization systems. Surface ships and helicopters operate these systems, which place explosive charges near or directly against mines to destroy the mine. • Airborne projectile-based mine clearance systems. These systems neutralize mines by firing a small or medium-caliber non-explosive, supercavitating projectile from a hovering helicopter. • Diver emplaced explosive charges. Operating from small craft, divers put explosive charges near or on mines to destroy the mine or disrupt its ability to function. Classification of Non-Impulsive and Impulsive Sources Analyzed In order to better organize and facilitate the analysis of about 300 sources of underwater non-impulsive sound or impulsive energy, the Navy developed a series of source classifications, or source bins. This method of analysis provides the following benefits: • Allows for new sources to be covered under existing authorizations, as long as those sources fall within the parameters of a “bin;” • Simplifies the data collection and reporting requirements anticipated under the MMPA; • Ensures a conservative approach to all impact analysis because all sources in a single bin are modeled as the loudest source (e.g., lowest frequency, highest source level, longest duty cycle, or largest net explosive weight within that bin); • Allows analysis to be conducted more efficiently, without compromising the results; • Provides a framework to support the reallocation of source usage (hours/explosives) between different source bins, as long as the total number and severity of marine mammal takes remain within the overall analyzed and authorized limits. This flexibility is required to support evolving Navy training and testing requirements, which are linked to real world events. A description of each source classification is provided in Tables 1-3. Non-impulsive sources are grouped into bins based on the frequency, source level when warranted, and how the source would be used. Impulsive bins are based on the net explosive weight of the munitions or explosive devices. The following factors further describe how non-impulsive sources are divided: • Frequency of the non-impulsive source: ○ Low-frequency sources operate below 1 kilohertz (kHz) ○ Mid-frequency sources operate at or above 1 kHz, up to and including 10 kHz ○ High-frequency sources operate above 10 kHz, up to and including 100 kHz ○ Very high-frequency sources operate above 100, but below 200 kHz • Source level of the non-impulsive source: ○ Greater than 160 decibels (dB), but less than 180 dB ○ Equal to 180 dB and up to 200 dB ○ Greater than 200 dB How a sensor is used determines how the sensor's acoustic emissions are analyzed. Factors to consider include pulse length (time source is on); beam pattern (whether sound is emitted as a narrow, focused beam, or, as with most explosives, in all directions); and duty cycle (how often a transmission occurs in a given time period during an event). There are also non-impulsive sources with characteristics that are not anticipated to result in takes of marine mammals. These sources have low source levels, narrow beam widths, downward directed transmission, short pulse lengths, frequencies beyond known hearing ranges of marine mammals, or some combination of these factors. These sources were not modeled by the Navy, but are qualitatively analyzed in Table 1-4 of the LOA application and the HSTT DEIS/OEIS. Table 1—Impulsive Training and Testing Source Classes Analyzed Source class Representative munitions Net explosive weight (lbs) E1 Medium-caliber projectiles 0.1-0.25 (45.4-113.4 g) E2 Medium-caliber projectiles 0.26-0.5 (117.9-226.8 g) E3 Large-caliber projectiles >0.5-2.5 (>226.8 g-1.1 kg) E4 Improved Extended Echo Ranging Sonobuoy >2.5-5.0 (1.1-2.3 kg) E5 5 in. (12.7 cm) projectiles >5-10 (>2.3-4.5 kg) E6 15 lb. (6.8 kg) shaped charge >10-20 (>4.5-9.1 kg) E7 40 lb. (18.1 kg) demo block/shaped charge >20-60 (>9.1-27.2 kg) E8 250 lb. (113.4 kg) bomb >60-100 (>27.2-45.4 kg) E9 500 lb. (226.8 kg) bomb >100-250 (>45.4-113.4 kg) E10 1,000 lb. (453.6 kg) bomb >250-500 (>113.4-226.8 kg) E11 650 lb. (294.8 kg) mine >500-650 (>226.8-294.8 kg) E12 2,000 lb. (907.2 kg) bomb >650-1,000 (>294.8-453.6 kg) E13 1,200 lb. (544.3 kg) HBX charge >1,000-1,740 (>453.6-789.3 kg) Table 2—Non-Impulsive Training Source Classes Analyzed Source class category Source class Description Mid-Frequency (MF): Tactical and non-tactical sources that produce mid-frequency (1 to 10 kHz) signals MF1 Active hull-mounted surface ship sonar (e.g., AN/SQS-53C and AN/SQS-60). MF1K Kingfisher object avoidance mode associated with MF1 sonar. MF2 Active hull-mounted surface ship sonar (e.g., AN/SQS-56). MF2K Kingfisher mode associated with MF2 sonar. MF3 Active hull-mounted submarine sonar (e.g., AN/BQQ-10). MF4 Active helicopter-deployed dipping sonar (e.g., AN/AQS-22 and AN/AQS-13). MF5 Active acoustic sonobuoys (e.g., AN/SSQ-62 DICASS). MF6 Active underwater sound signal devices (e.g., MK-84). MF11 Hull-mounted surface ship sonar with an active duty cycle greater than 80%. MF12 High duty cycle—variable depth sonar. High-Frequency (HF) and Very High-Frequency (VHF): Tactical and non-tactical sources that produce high-frequency (greater than 10 kHz but less than 200 kHz) signals HF1 HF4 Active hull-mounted submarine sonar (e.g., AN/BQQ-15). Active mine detection, classification, and neutralization sonar (e.g., AN/SQS-20). Anti-Submarine Warfare (ASW): Tactical sources such as active sonobuoys and acoustic countermeasures systems used during ASW training activities ASW1 ASW2 MF active Deep Water Active Distributed System (DWADS). MF active Multistatic Active Coherent (MAC) sonobuoy (e.g., AN/SSQ-125). ASW3 MF active towed active acoustic countermeasure systems (e.g., AN/SLQ-25 NIXIE). ASW4 MF active expendable active acoustic device countermeasures (e.g., MK-3). Torpedoes (TORP): Source classes associated with active acoustic signals produced by torpedoes TORP1 HF active lightweight torpedo sonar (e.g., MK-46, MK-54, or Anti-Torpedo Torpedo). TORP2 HF active heavyweight torpedo sonar (e.g., MK-48). Table 3—Non-Impulsive Testing Source Classes Analyzed Source class category Source class Description Low-Frequency (LF): Sources that produce low-frequency (less than 1 kilohertz [kHz]) signals LF4 Low-frequency sources equal to 180 dB and up to 200 dB. LF5 Low-frequency sources less than 180 dB. LF6 Low-frequency sonar currently in development (e.g., anti-submarine warfare sonar associated with the Littoral Combat Ship). Mid-Frequency (MF): Tactical and non-tactical sources that produce mid-frequency (1 to 10 kHz) signals MF1 MF1K Hull-mounted surface ship sonar (e.g., AN/SQS-53C and AN/SQS-60). Kingfisher mode associated with MF1 sonar (Sound Navigation and Ranging). MF2 Hull-mounted surface ship sonar (e.g., AN/SQS-56). MF3 Hull-mounted submarine sonar (e.g., AN/BQQ-10). MF4 Helicopter-deployed dipping sonar (e.g., AN/AQS-22 and AN/AQS-13). MF5 Active acoustic sonobuoys (e.g., DICASS). MF6 Active underwater sound signal devices (e.g., MK-84). MF8 Active sources (greater than 200 dB). MF9 Active sources (equal to 180 dB and up to 200 dB). MF10 Active sources (greater than 160 dB, but less than 180 dB) not otherwise binned. MF12 High duty cycle—variable depth sonar. High-Frequency (HF) and Very High-Frequency (VHF): Tactical and non-tactical sources that produce high-frequency (greater than 10 kHz but less than 200 kHz) signals HF1 HF3 HF4 Hull-mounted submarine sonar (e.g., AN/BQQ-10). Hull-mounted submarine sonar (classified). Mine detection, classification, and neutralization sonar (e.g., AN/SQS-20). HF5 Active sources (greater than 200 dB). HF6 Active sources (equal to 180 dB and up to 200 dB). Anti-Submarine Warfare (ASW): Tactical sources such as active sonobuoys and acoustic countermeasures systems used during the conduct of anti-submarine warfare testing activities ASW1 Mid-frequency Deep Water Active Distributed System (DWADS). ASW2 ASW2H Mid-frequency Multistatic Active Coherent sonobuoy (e.g., AN/SSQ-125). Mid-frequency sonobuoy (e.g., high duty cycle)—Sources that are analyzed by hours. ASW3 Mid-frequency towed active acoustic countermeasure systems (e.g., AN/SLQ-25). ASW4 Mid-frequency expendable active acoustic device countermeasures (e.g., MK-3). Torpedoes (TORP): Source classes associated with the active acoustic signals produced by torpedoes TORP1 Lightweight torpedo (e.g., MK-46, MK-54, or Surface Ship Defense System). TORP2 Heavyweight torpedo (e.g., MK-48). Acoustic Modems (M): Systems used to transmit data acoustically through water M3 Mid-frequency acoustic modems (greater than 190 dB). Swimmer Detection Sonar (SD): Systems used to detect divers and submerged swimmers SD1-SD2 High-frequency sources with short pulse lengths, used for the detection of swimmers and other objects for the purpose of port security. Airguns (AG): Underwater airguns are used during swimmer defense and diver deterrent training and testing activities AG Up to 60 cubic inch airguns (e.g., Sercel Mini-G). Synthetic Aperture Sonar (SAS): Sonar in which active acoustic signals are post-processed to form high-resolution images of the seafloor SAS1 SAS2 SAS3 MF SAS systems. HF SAS systems. VHF SAS systems. Proposed Action The Navy proposes to continue conducting training and testing activities within the HSTT Study Area. The Navy has been conducting military readiness training and testing activities in the HSTT Study Area since the 1940s. Recently, these activities were analyzed in three separate EISs completed between 2008 and 2011; the Hawaii Range Complex (HRC) EIS/OEIS (U.S. Department of the Navy 2008a), the SOCAL Range Complex EIS/OEIS (U.S. Department of the Navy 2008b), and the Silver Strand Training Complex (SSTC) EIS (U.S. Department of the Navy 2011a). These documents, among others, and their associated MMPA regulations and authorizations, describe the baseline of training and testing activities currently conducted in the Study Area. The tempo and types of training and testing activities have fluctuated due to changing requirements; the introduction of new technologies; the dynamic nature of international events; advances in warfighting doctrine and procedures; and changes in basing locations for ships, aircraft, and personnel (force structure changes). Such developments have influenced the frequency, duration, intensity, and location of required training and testing. Training The Navy proposes to conduct training activities in the Study Area as described in Tables 4 and 5. Detailed information about each proposed activity (stressor, training event, description, sound source, duration, and geographic location) can be found in Appendix A of the HSTT DEIS/OEIS. NMFS used the detailed information in Appendix A of the HSTT DEIS/OEIS to analyze the potential impacts to marine mammals. Table 4 describes the annual number of impulsive source detonations during testing activities within the HSTT Study Area, and Table 5 describes the annual number of hours or items of non-impulsive sources used during training within the HSTT Study Area. The Navy's proposed action is an adjustment to existing baseline training activities to accommodate the following: • Force structure changes including the relocation of ships, aircraft, and personnel; • Planned new aircraft platforms, new vessel classes, and new weapons systems; • Ongoing training activities that were not addressed in previous documentation; and • New range capabilities, such as hydrophone modifications, upgrades, and replacement at instrumented Navy underwater tracking ranges. Table 4—Proposed Annual Number of Impulsive Source Detonations During Training in the HSTT Study Area Explosive class Net explosive weight (NEW) Annual in-water detonations (training) E1 (0.1 lb.-0.25 lb.) 19,840 E2 (0.26 lb.-0.5 lb.) 1,044 E3 (0.6 lb.-2.5 lb.) 3,020 E4 (>2.5 lb.-5 lb.) 668 E5 (>5 lb.-10 lb.) 8,154 E6 (>10 lb.-20 lb.) 538 E7 (>20 lb.-60 lb.) 407 E8 (>60 lb.-100 lb.) 64 E9 (>100 lb.-250 lb.) 16 E10 (>250 lb.-500 lb.) 19 E11 (>500 lb.-650 lb.) 8 E12 (>650 lb.-1000 lb.) 224 E13 (>1000 lb.-1,740 lb.) 9 Table 5—Annual Hours and Items of Non-Impulsive Sources Used During Training Within the HSTT Study Area Source class category Source class Annual use Mid-Frequency (MF) Active sources from 1 to 10 kHz MF1 11,588 hours. MF1K 88 hours. MF2 3,060 hours. MF2K 34 hours. MF3 2,336 hours. MF4 888 hours. MF5 13,718 items. MF11 1,120 hours. MF12 1,094 hours. High-Frequency (HF) and Very High-Frequency (VHF) tactical and non-tactical sources that produce signals greater than 10kHz but less than 200 kHz HF1 1,754 hours. HF4 4,848 hours. Anti-Submarine Warfare (ASW) ASW1 224 hours. Active ASW sources ASW2 1,800 items. ASW3 16,561 hours. ASW4 1,540 items. Torpedoes (TORP) TORP1 170 items. Active torpedo sonar TORP2 400 items. Testing The Navy's proposed testing activities are described in Tables 6 and 7. Detailed information about each proposed activity (stressor, testing event, description, sound source, duration, and geographic location) can be found in Appendix A of the HSTT DEIS/OEIS. NMFS used the detailed information in Appendix A of the HSTT DEIS/OEIS to analyze the potential impacts from testing activities on marine mammals. Table 6 describes the annual number of impulsive source detonations during testing activities within the HSTT Study Area, and Table 7 describes the annual number of hours or items of non-impulsive sources used during testing within the HSTT Study Area. Table 6—Proposed Annual Number of Impulsive Source Detonations During Testing Activities Within the HSTT Study Area Explosive class Net explosive weight (NEW) Annual in-water detonations (testing) E1 (0.1 lb.-0.25 lb.) 14,501 E2 (0.26 lb.-0.5 lb.) 0 E3 (0.6 lb.-2.5 lb.) 2,990 E4 (>2.5 lb.-5 lb.) 753 E5 (>5 lb.-10 lb.) 202 E6 (>10 lb.-20 lb.) 37 E7 (>20 lb.-60 lb.) 21 E8 (>60 lb.-100 lb.) 12 E9 (>100 lb.-250 lb.) 0 E10 (>250 lb.-500 lb.) 31 E11 (>500 lb.-650 lb.) 14 E12 (>650 lb.-1000 lb.) 0 E13 (>1000 lb.-1,740 lb.) 0 Table 7—Annual Hours and Items of Non-Impulsive Sources Used During Testing Within the HSTT Study Area Source class category Source class Annual use Low-Frequency (LF) Sources that produce signals less than 1 kHz LF4 52 hours. LF5 2,160 hours. LF6 192 hours. Mid-Frequency (MF) Tactical and non-tactical sources that produce signals from 1 to 10 kHz MF1 180 hours. MF1K 18 hours. MF2 84 hours. MF3 392 hours. MF4 693 hours. MF5 5,024 items. MF6 540 items. MF8 2 hours. MF9 3,039 hours. MF10 35 hours. MF12 336 hours. High-Frequency (HF) and Very High-Frequency (VHF): Tactical and non-tactical sources that produce signals greater than 10kHz but less than 200kHz HF1 1,025 hours. HF3 273 hours. HF4 1,336 hours. HF5 1,094 hours. HF6 3,460 hours. Anti-Submarine Warfare (ASW) Tactical sources used during anti-submarine warfare training and testing activities ASW1 224 hours. ASW2 2,260 items. ASW2H 255 hours. ASW3 1,278 hours. ASW4 477 items. Torpedoes (TORP) Source classes associated with active acoustic signals produced by torpedoes TORP1 701 items. TORP2 732 items. Acoustic Modems (M) Transmit data acoustically through the water M3 4,995 hours. Swimmer Detection Sonar (SD) Used to detect divers and submerged swimmers SD1 38 hours. Airguns (AG) Used during swimmer defense and diver deterrent training and testing activities AG 5 uses. Synthetic Aperture Sonar (SAS): Sonar in which active acoustic signals are post-processed to form high-resolution images of the seafloor SAS1 2,700 hours. SAS2 4,956 hours. SAS3 3,360 hours. Vessels Vessels used as part of the proposed action include ships, submarines, boats, and Unmanned Undersea Vehicles (UUVs) ranging in size from small, 5-m Rigid Hull Inflatable Boats to 333-m long aircraft carriers. Representative Navy vessel types, lengths, and speeds used in both training and testing activities are shown in Table 8. While these speeds are representative, some vessels operate outside of these speeds due to unique training or safety requirements for a given event. Examples include increased speeds needed for flight operations, full speed runs to test engineering equipment, time critical positioning needs, etc. Examples of decreased speeds include speeds less than 5 knots or completely stopped for launching small boats, certain tactical maneuvers, target launch or retrievals, UUVs etc. The number of Navy vessels in the HSTT Study Area varies based on training and testing schedules. Most activities include either one or two vessels, with an average of one vessel per activity, and last from a few hours up to two weeks. Multiple ships, however, can be involved with major training events. Vessel movement and the use of in-water devices as part of the proposed action would be concentrated in portions of the Study Area within SOCAL, naval installations at San Diego and Pearl Harbor, and on instrumented underwater ranges. Surface and sub-surface vessel operations in the Study Area may result in marine mammal strikes. Table 8—Typical Navy Boat and Vessel Types With Length Greater Than 18 Meters Used Within the HSTT Study Area Vessel type (>18 m) Example(s) (specifications in meters (m) for length, metric tons (mt) for mass, and knots for speed) Typical operating speed (knots) Aircraft Carrier Aircraft Carrier (CVN) length: 333 m beam: 41 m draft: 12 m displacement: 81,284 mt max. speed: 30+ knots 10 to 15. Surface Combatants Cruiser (CG) length: 173 m beam: 17 m draft: 10 m displacement: 9,754 mt max. speed: 30+ knots 10 to 15. Destroyer (DDG) length: 155 m beam: 18 m draft: 9 m displacement: 9,648 mt max. speed: 30+ knots Frigate (FFG) length: 136 m beam: 14 m draft: 7 m displacement: 4,166 mt max. speed: 30+ knots Littoral Combat Ship (LCS) length: 115 m beam: 18 m draft: 4 m displacement: 3,000 mt max. speed: 40+ knots Amphibious Warfare Ships Amphibious Assault Ship (LHA, LHD) length: 253 m beam: 32 m draft: 8 m displacement: 42,442 mt max. speed: 20+ knots 10 to 15. Amphibious Transport Dock (LPD) length: 208 m beam: 32 m draft: 7 m displacement: 25,997 mt max. speed: 20+ knots Dock Landing Ship (LSD) length: 186 m beam: 26 m draft: 6 m displacement: 16,976 mt max. speed: 20+ knots Mine Warship Ship Mine Countermeasures Ship (MCM) length: 68 m beam: 12 m draft: 4 m displacement: 1,333 max. speed: 14 knots 5 to 8. Submarines Attack Submarine (SSN) length: 115 m beam: 12 m draft: 9 m displacement: 12,353 mt max. speed: 20+ knots 8 to 13. Guided Missile Submarine (SSGN) length: 171 m beam: 13 m draft: 12 m displacement: 19,000 mt max. speed: 20+ knots Combat Logistics Force Ships* Fast Combat Support Ship (T-AOE) length: 230 m beam: 33 m draft: 12 m displacement: 49,583 max. speed: 25 knots 8 to 12. Dry Cargo/Ammunition Ship (T-AKE) length: 210 m beam: 32 m draft: 9 m displacement: 41,658 mt max speed: 20 knots Fleet Replenishment Oilers (T-AO) length: 206 m beam: 30 m draft: 11 displacement: 42,674 mt max. speed: 20 knots Fleet Ocean Tugs (T-ATF) length: 69 m beam: 13 m draft: 5 m displacement: 2,297 max. speed: 14 knots Support Craft/Other Landing Craft, Utility (LCU) length: 41m beam: 9 m draft: 2 m displacement: 381 mt max. speed: 11 knots 3 to 5. Landing Craft, Mechanized (LCM) length: 23 m beam: 6 m draft: 1 m displacement: 107 mt max. speed: 11 knots Support Craft/Other Specialized High Speed MK V Special Operations Craft length: 25 m beam: 5 m displacement: 52 mt max. speed: 50 knots Variable. * CLF vessels are not homeported in Pearl Harbor or San Diego, but are frequently used for various fleet support and training support events in the HSTT Study Area. Duration and Location Training and testing activities would be conducted in the HSTT Study Area from January 2014 through January 2019. The HSTT Study Area is comprised of established operating and warning areas across the north-central Pacific Ocean, from Southern California to Hawaii and the International Date Line. The defined Study Area has expanded beyond the areas included in previous Navy authorizations to include transit routes and pierside locations. This expansion is not an increase in the Navy's training and testing area, but rather an increase in the area to be analyzed (i.e., not previously analyzed) under an incidental take authorization in support of the HSTT EIS/OEIS. The Study Area includes three existing range complexes: the Hawaii Range Complex (HRC), the Southern California (SOCAL) Range Complex, and the Silver Strand Training Complex (SSTC). Each range complex is an organized and designated set of specifically bounded geographic areas, which includes a water component (above and below the surface), airspace, and sometimes a land component. Operating areas (OPAREAs) and special use airspace are established within each range complex. These designations are further described in Chapter 2 of the Navy's LOA application. In addition to Navy range complexes, the Study Area includes Navy pierside locations where sonar maintenance and testing activities occur (San Diego Bay, Pearl Harbor) and transit corridors on the high seas where training and sonar testing may occur during vessel transit. Hawaii Range Complex (HRC) —The HRC geographically encompasses ocean areas located around the Hawaiian Islands chain. The largest component of the HRC is the temporary operating area, which extends north and west from the island of Kauai and totals over 2 million square nautical miles (nm 2 ) of air and sea space. This area is used for Navy ship transit throughout the year and for missile defense testing activities as required to support missile defense testing activities. Nearly all of the training and testing activities within the HRC take place within the smaller Hawaii OPAREA, which consists of 235,000 nm 2 of special use airspace, and sea and undersea space. The Hawaii OPAREA is the portion of the range complex immediately surrounding the island chain of Hawaii. Military activities and exercises were excluded from the list of prohibitions triggered when the Monument was established in 2006, so long as the activities are “carried out in a manner that avoids, to the extent practicable and consistent with operational requirements, adverse impacts on monument resources and qualities.” More detailed information on the HRC, including maps, is provided in Chapter 2 of the Navy's LOA application ( http://www.nmfs.noaa.gov/pr/permits/incidental.htm#applications ). Southern California (SOCAL) Range Complex —The SOCAL Range Complex is situated between Dana Point and San Diego, and extends more than 600 nm southwest into the Pacific Ocean. The two primary components of the SOCAL Range Complex are the ocean operating areas and the special use airspace. The SOCAL Range Complex includes San Diego Bay and a small portion of the Point Mugu Sea Range. The Silver Strand Training Complex is also included as part of the Southern California portion for this application. More detailed information on the SOCAL Range Complex, including maps, is provided in Chapter 2 of the Navy's LOA application ( http://www.nmfs.noaa.gov/pr/permits/incidental.htm#applications ). Transit Corridor —In addition to the three range complexes, a transit corridor outside the bounds of existing range complexes is included in the Navy's request. This transit corridor is important to the Navy in that it provides adequate air, sea, and undersea space in which ships and aircraft can conduct training and some sonar maintenance and testing while en route between Southern California and Hawaii. The transit corridor is an area encompassing the shortest distance from San Diego to the center of the HRC. While in transit, ships and aircraft would, at times, conduct basic and routine unit level training as long as the training does not interfere with the primary objective of reaching their intended destination. Ships would also conduct sonar maintenance, which includes active sonar transmissions. The portion of the transit corridor to the east of 140° west longitude is included in the analysis of SOCAL activities and the area to the west of that meridian is included in the analysis of HRC activities since these portions of the corridor correspond with the marine mammal stocks in those range complexes. Pierside Locations —The Study Area also includes select pierside locations where Navy surface ship and submarine sonar maintenance testing occur. These pierside locations include channels and transit routes in ports, and facilities associated with ports and shipyards at Navy piers in San Diego, California, and Navy piers, shipyards, and the Intermediate Maintenance Facility in Pearl Harbor, Hawaii. Description of Marine Mammals in the Area of the Specified Activities Thirty-nine marine mammal species are known to occur in the Study Area, including seven mysticetes (baleen whales), 25 odontocetes (dolphins and toothed whales), six pinnipeds (seals and sea lions), and the Southern sea otter. Among these species, there are 72 stocks managed by NMFS or the U.S. Fish and Wildlife Service (USFWS) in the U.S. Exclusive Economic Zone (EEZ). These species and their numbers are presented in Table 9 and relevant information on their status, distribution, and seasonal distribution (when applicable) is presented in Chapter 4 of the Navy's LOA application ( http://www.nmfs.noaa.gov/pr/permits/incidental.htm#applications ). Consistent with NMFS most recent Pacific Stock Assessment Report, a single species may include multiple stocks recognized for management purposes (e.g., spinner dolphin), while other species are grouped into a single stock due to limited species-specific information (e.g., beaked whales belonging to the genus Mesoplodon ). Species that may have once inhabited and transited the Study Area, but have not been sighted in recent years, include the North Pacific right whale ( Eubalaena japonica ), harbor porpoise ( Phocoena phocoena ), and Steller sea lion ( Eumetopias jubatus ). These species are not expected to be exposed to or affected by any project activities and, therefore, are not discussed further. Table 9—Marine Mammals With Possible or Confirmed Presence Within the HSTT Study Area Common name Scientific name Study area Stock Stock abundance CV Study area abundance (CV) Occurrence in study area ESA/MMPA Status Order Cetacea Suborder Mysticeti (Baleen Whales) Family Balaenopteridae (Rorquals) Humpback whale Megaptera novaeangliae SOCAL California, Oregon, & Washington 2,043 −0.1 36 −0.51 Seasonal; More sightings around the northern Channel Islands Endangered/Depleted. HRC Central North Pacific 10,103 (N/A) 4,491 (N/A) Seasonal; Throughout known breeding grounds during winter and spring (most common November through April) Endangered/Depleted. Blue whale Balaenoptera musculus SOCAL Eastern North Pacific 2,497 −0.24 842 −0.2 Seasonal; arrive April-May; more common late summer to fall Endangered/Depleted. HRC Central North Pacific No data. No data. Seasonal; infrequent winter migrant; few sightings Endangered/Depleted. Fin whale Balaenoptera physalus SOCAL California, Oregon, & Washington 3,044 −0.18 359 −0.4 Year-round presence Endangered/Depleted. HRC Hawaiian 174 −0.72 174 −0.72 Seasonal; mainly fall and winter although considered rare in HRC Endangered/Depleted. Sei whale Balaenoptera borealis SOCAL Eastern North Pacific 126 −0.53 7 −1.07 Rare; infrequently sighted in California. Only nine confirmed sightings on WA/OR/CA surveys from 1991-2008 Endangered/Depleted. HRC Hawaiian 77 −1.06 77 −1.06 Rare; limited sightings of seasonal migrants that feed at higher latitudes Endangered/Depleted. Bryde's whale Balaenoptera edeni SOCAL Eastern Tropical Pacific 13,000 −0.2 7 −1.07 Limited summer occurrence HRC Hawaiian 469 −0.45 469 −0.45 Uncommon; distributed throughout the Hawaii Exclusive Economic Zone Minke whale Balaenoptera acutorostrata SOCAL California, Oregon, & Washington 478 −1.36 226 −1.02 Less common in summer; small numbers around northern Channel Islands HRC Hawaiian No data. No data. Regular but seasonal occurrence (November-March) Family Eschrichtildae (Gray Whale) Gray whale Eschrichtius robustus SOCAL Eastern North Pacific 18,813 −0.07 Population migrates through SOCAL Transient during seasonal migrations HRC No known occurrence Suborder Odontoceti (Toothed Whales) Family Physeteridae (Sperm Whale) Sperm whale Physeter macrocephalus SOCAL California, Oregon, & Washington 971 −0.31 607 −0.57 Common year round; more likely in waters > 1,000 m, most often > 2,000 m Endangered/Depleted. HRC Hawaiian 6,919 −0.81 6,919 −0.81 Widely distributed year round; more likely in waters > 1,000 m, most often > 2,000 m Endangered/Depleted. Family Kogiidae (Pygmy and Dwarf Sperm Whale) Pygmy sperm whale Kogia breviceps SOCAL California, Oregon, & Washington 579 −1.02 Seaward of 500-1000 m; limited sightings over entire Southern Cal. Bight HRC Hawaiian 7,138 −1.12 7,138 −1.12 Stranding numbers suggest this species is more common than infrequent sightings during survey (Barlow 2006) indicated. Dwarf sperm whale Kogia sima SOCAL California, Oregon, & Washington Unknown Seaward of 500-1000 m; no confirmed sightings over entire Southern Cal. Bight (all Kogia spp. or Kogia breviceps) HRC Hawaiian 17,519 −0.74 17,519 −0.74 Stranding numbers suggest this species is more common than infrequent sightings during survey (Barlow 2006) indicated Family Delphinidae (Dolphins) Killer whale Orcinus orca SOCAL Eastern North Pacific Offshore 240 −0.49 30 −0.73 Uncommon; occurs infrequently; more likely in winter SOCAL Eastern North Pacific Transient 451 −0.49 Uncommon; occurs infrequently; more likely in winter HRC Hawaiian 349 −0.98 349 −0.98 Uncommon; infrequent sightings False killer whale Pseudorca crassidens SOCAL Eastern Tropical Pacific Unknown Uncommon; warm water species; although stranding records from the Channel Islands HRC Hawaii Insular [7],[8] 151 −0.2 151 −0.2 Regular Endangered. HRC Hawaii Pelagic 7 1,503 −0.66 1,503 −0.66 Regular HRC Northwest Hawaiian Islands 7 522 −1.09 522 −1.09 Regular Pygmy killer whale Feresa attenuata SOCAL Tropical Unknown Extralimital. Extralimital within the south-west boundary of the SOCAL Range Complex HRC Hawaiian 956 −0.83 956 −0.83 Year-round resident; abundance based on 3 sightings (Barlow 2006). Short-finned pilot whale Globicephala macrorhynchus SOCAL California, Oregon, & Washington 760 −0.64 118 −1.04 Uncommon; more common before 1982 HRC Hawaiian 8,870 −0.38 8,870 −0.38 Commonly observed around main Hawaiian Islands and Northwestern Hawaiian Islands Melon-headed whale Peponocephala electra SOCAL No known occurrence HRC Hawaiian 2,950 −1.17 2,950 −1.17 Regular. Long-beaked common dolphin Delphinus capensis SOCAL California 27,046 −0.59 17,530 −0.57 Common; more inshore distribution (within 50 nm of coast) HRC No known occurrence Short-beaked common dolphin Delphinus delphis SOCAL California, Oregon, & Washington 411,211 −0.21 165,400 −0.19 Common; one of the most abundant SOCAL dolphins; higher summer densities HRC No known occurrence Bottlenose dolphin Tursiops truncatus SOCAL California Coastal 323 −0.13 323 −0.13 Limited, small population within 1 km of shore SOCAL California, Oregon, & Washington Offshore 1,006 −0.48 1,831 −0.47 Common HRC Hawaii Pelagic 3,178 −0.59 3,178 −0.59 Common in deep offshore waters HRC Kauai and Niihau 147 −0.11 147 −0.11 Common in shallow nearshore waters (1000 m or less) HRC Oahu 594 −0.54 594 −0.54 Common in shallow nearshore waters (1000 m or less) HRC 4-Islands Region 153 −0.24 153 −0.24 Common in shallow nearshore waters (1000 m or less) HRC Hawaii Island 102 −0.13 102 −0.13 Common in shallow nearshore waters (1000 m or less) Pantropical spotted dolphin Stenella attenuata SOCAL Eastern Tropical Pacific Unknown. Rare; associated with warm tropical surface waters HRC Hawaiian 8,978 −0.48 8,978 −0.48 Common; primary occurrence between 100 and 4,000 meters depth Striped dolphin Stenella coerulealba SOCAL California, Oregon, & Washington 10,908 −0.34 8,697 −0.34 Occasional visitor; warm water oceanic species HRC Hawaiian 13,143 −0.46 13,143 −0.46 Occurs regularly year round but infrequent sighting data Spinner dolphin Stenella longirostris SOCAL No known occurrence HRC Hawaii Pelagic Unknown. 3,351 −0.74 for entire Hawaiian Islands Stock Complex Common year round in offshore waters HRC Hawaii Island Unknown. 3,351 −0.74 for entire Hawaiian Islands Stock Complex Common year round; rest in nearshore waters during the day and move offshore to feed at night HRC Oahu/4-Islands Unknown. 3,351 −0.74 for entire Hawaiian Islands Stock Complex Common year round; rest in nearshore waters during the day and move offshore to feed at night HRC Kauai/Niihau Unknown. 3,351 −0.74 for entire Hawaiian Islands Stock Complex Common year round; rest in nearshore waters during the day and move offshore to feed at night HRC Pearl and Hermes Reef Unknown. 3,351 −0.74 for entire Hawaiian Islands Stock Complex Common year round; rest in nearshore waters during the day and move offshore to feed at night HRC Kure/Midway Unknown. 3,351 −0.74 for entire Hawaiian Islands Stock Complex Common year round; rest in nearshore waters during the day and move offshore to feed at night Rough-toothed dolphin Steno bredanensis SOCAL Tropical and warm temperate Unknown. Rare; more tropical offshore species HRC Hawaiian 8,709 −0.45 8,709 −0.45 Common throughout the main Hawaiian Islands and Hawaii Exclusive Economic Zone Pacific white-sided dolphin Lagenorhynchus obliquidens SOCAL California, Oregon, & Washington 26,930 −0.28 2,196 −0.71 Common; year-round cool water species; more abundant November-April HRC No known occurrence Northern right whale dolphin Lissodelphis borealis SOCAL California, Oregon, & Washington 8,334 −0.4 1,172 −0.52 Common; cool water species; more abundant November-April HRC No known occurrence Fraser's dolphin Lagenodelphis hosei SOCAL No known occurrence HRC Hawaiian 10,226 −1.16 10,226 −1.16 Tropical species only recently documented within Hawaii Exclusive Economic Zone (2002 survey) Risso's dolphins Grampus griseus SOCAL California, Oregon, & Washington 6,272 −0.3 3,418 −0.31 Common; present in summer, but higher densities November-April HRC Hawaiian 2,372 −0.97 2,372 −0.97 Have been considered rare but six sightings in Hawaii Exclusive Economic Zone during 2002 survey Family Phocoenidae (Porpoises) Dall's porpoise Phocoenoidea dalli SOCAL California, Oregon, & Washington 42,000 −0.33 727 −0.99 Common in cold water periods; more abundant November-April HRC No known occurrence Family Ziphiidae (Beaked Whales) Cuvier's beaked whale Ziphius cavirostris SOCAL California, Oregon, & Washington 2,143 −0.65 911 −0.68 Possible year-round occurrence but difficult to detect due to diving behavior HRC Hawaiian 15,242 −1.43 15,242 −1.43 Year-round occurrence but difficult to detect due to diving behavior Baird's beaked whale Berardius bairdii SOCAL California, Oregon, & Washington 907 −0.49 127 −1.14 Primarily along continental slope from late spring to early fall HRC No known occurrence Longman's beaked whale Indopacetus pacificus SOCAL No known occurrence HRC Hawaiian 1,007 −1.26 1,007 −1.26 One of the rarest and least known cetacean species; abundance based on Barlow 2006 with 3 sightings, however, multiple sightings during 2010 HICEAS Blainville's beaked whale Mesoplodon densirostris SOCAL California, Oregon, & Washington 603 −1.16 132 (0.96; for Mesoplodon spp.). Distributed throughout deep waters and continental slope regions; difficult to detect given diving behavior HRC Hawaiian 2,872 −1.25 2,872 −1.25 Year-round occurrence but difficult to detect due to diving behavior Mesoplodont beaked whales (SOCAL estimates also include Blainville's beaked whale listed separately above) Mesoplodon spp. SOCAL California, Oregon, & Washington 1,024 −0.77 132 −0.96 Distributed throughout deep waters and continental slope regions; difficult to detect given diving behavior. Limited sightings; generally seaward of 500-1000 m HRC No known occurrence of five Mesoplodon species (M. carlhubbsi, M. ginkgodens, M. perrini, M. peruvianus, M. stejnegeri) Suborder Pinnipedia [9, 10] Family Otariidae (Fur Seals and Sea Lions) California sea lion Zalophus californianus SOCAL U.S. Stock 238,000 Most common pinniped, Channel Islands breeding sites in summer HRC No known occurrence Northern fur seal Callorhinus ursinus SOCAL San Miguel Island 9,968 Stock is outside of SOCAL. Common; small population breeds on San Miguel Island. May-October HRC No known occurrence Guadalupe fur seal Arctocephalus townsendi SOCAL Mexico 7,408 Rare; Occasional visitor to northern Channel Islands; mainly breeds on Guadalupe Island, Mexico, May-July Threatened/Depleted. HRC No known occurrence Family Phocidae (True Seals) Hawaiian monk seal Monachus schauinslandi SOCAL No known occurrence HRC Hawaiian 1,161 1,161 Predominantly occur at Northwestern Hawaiian Islands; approximately 150 in Main Hawaiian Islands Endangered/Depleted. Northern elephant seal Mirounga angustirostris SOCAL California Breeding 124,000 SNI 9,794 pups in 2000. SCI up to 16 through 2000 Common; Channel Island haul-outs of different age classes; including SCI December-March and April-August; spend 8-10 months at sea HRC Extralimital Harbor seal Phoca vitulina SOCAL California 34,233 5,271 (All age classes from aerial counts). Common; Channel Islands haul-outs including SCI and La Jolla; bulk of stock found north of Pt. Conception HRC No known occurrence Information on the status, distribution, abundance, and vocalizations of marine mammal species in the Study Area may be viewed in Chapter 4 of their LOA application ( http://www.nmfs.noaa.gov/pr/permits/incidental.htm#applications ). Further information on the general biology and ecology of marine mammals is included in the HSTT Draft EIS/OEIS. In addition, NMFS publishes annual stock assessment reports for marine mammals, including stocks that occur within the Study Area ( http://www.nmfs.noaa.gov/pr/species/mammals ). 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 underwater. 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). Marine mammal vocalizations often extend both above and below the range of human hearing; vocalizations with frequencies lower than 20 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 baleen whales 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 whale social vocalizations is concentrated near 10 kHz, with source levels for whistles as high as 100 to 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). Marine Mammal Density Estimates A quantitative analysis of impacts on a species requires data on the abundance and distribution of the species population in the potentially impacted area. One metric for performing this type of analysis is density, which is the number of animals present per unit area. The Navy compiled existing, publically available density data for use in the quantitative acoustic impact analysis. There is no single source of density data for every area of the world, species, and season because of the costs, resources, and effort required to provide adequate survey coverage to sufficiently estimate density. Therefore, to estimate marine mammal densities for large areas like the HSTT Study Area, the Navy compiled data from several sources. The Navy developed a hierarchy of density data sources to select the best available data based on species, area, and time (season). The resulting Geographic Information System database, called the Navy Marine Species Density Database, includes seasonal density values for every marine mammal species present within the HSTT Study Area (Navy, 2012). The Navy Marine Species Density Database includes a compilation of the best available density data from several primary sources and published works including survey data from NMFS within the U.S. Exclusive Economic Zone. The Navy ranked their modeling methods as follows: 1. Density spatial model based estimates will be used when available (e.g., NMFS' Southwest Fisheries Science Center models for the California Current Ecosystem and the Central Pacific). 2. If no density spatial model based estimates are available, the following can be used in order of preference: a. Density estimates using designed-based methods incorporating line-transect survey data and involving spatial stratification (i.e., estimates split by depth strata or arbitrary survey sub-regions). b. Density estimates using designed-based methods incorporating only line-transect survey data (i.e., regional density estimate, stock assessment report). c. Density estimates derived using a Relative Environmental Suitability (RES) model in conjunction with survey data from Sea Mammal Research Unit (SMRU) Ltd or in conjunction with a global population estimate from Kaschner et al.' s (2006) density data. In some cases, extrapolation from neighboring regional density estimates or population/stock assessments is appropriate based on expert opinion. This is often preferred over using RES models because of discrepancies identified by local expert knowledge. This includes an extrapolation of no occurrence based on other sources of data such as the NMFS stock assessment reports or expert judgment. Additional information on the density data sources and how the database was applied to the HSTT Study Area is detailed in the Navy Marine Species Density Database Technical Report ( hstteis.com/DocumentsandReferences/HSTTDocuments/SupportingTechnicalDocuments.aspx ). 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 (e.g., 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, but rather 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 acoustic power (and a 20-dB increase is then a 100-fold increase in power; and a 30-dB increase is a 1,000-fold increase in power). A ten-fold increase in acoustic power does not mean that the sound is perceived as being ten times louder, however. Humans perceive a 10-dB increase in sound level as a doubling of loudness, and a 10-dB decrease in sound level 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: 1µPa) as a standard reference pressure unless noted otherwise. It is important to note that decibel values underwater and decibel values in air are not the same (different reference pressures and densities/sound speeds between media) and should not be directly compared. Because of the different densities of air and water and the different decibel standards (i.e., reference pressures) in air and water, a sound with the same level in air and in water would be approximately 62 dB lower in air. Thus, a sound that measures 160 dB (re 1 µPa) underwater would have the same approximate effective level as a sound that is 98 dB (re 20 µPa) 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 behavioral protocols or 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 (which are derived from the audiograms described above; see Figure 1 in Southall et al., 2007) developed for each broad 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—functional hearing is estimated to occur between approximately 7 Hz and 30 kHz; • Mid-frequency cetaceans—functional hearing is estimated to occur between approximately 150 Hz and 160 kHz; • High-frequency cetaceans—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. The estimated hearing range for low-frequency cetaceans has been extended slightly from previous analyses (from 22 to 30 kHz). This decision is based on data from Watkins et al. (1986) for numerous mysticete species, Au et al. (2006) for humpback whales, an abstract from Frankel (2005) and paper from Lucifredi and Stein (2007) on gray whales, and an unpublished report (Ketten and Mountain, 2009) and abstract (Tubelli et al., 2012) for minke whales. As more data from more species and/or individuals become available, these estimated hearing ranges may require modification. When sound travels (propagates) from its source, its loudness decreases as the distance traveled by the sound increases. Thus, the loudness of a sound at its source is higher than the loudness of that same sound a kilometer away. Acousticians often refer to the loudness of a sound at its source (typically referenced to one meter from the source) as the source level and the loudness of sound elsewhere as the received level (i.e., typically the receiver). For example, a humpback whale 3 km from a device that has a source level of 230 dB may only be exposed to sound that is 160 dB loud, depending on how the sound travels through water (e.g., spherical spreading [3 dB reduction with doubling of distance] was used in this example). As a result, it is important to understand the difference between 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 active sonar 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 to describe sound levels in the discussions of acoustic effects in this document. Sound pressure level (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. SPL (in dB) = 20 log (pressure/reference pressure) The commonly used reference pressure level in underwater acoustics is 1 µPa, and the units for SPLs are dB re: 1 µPa. SPL is an instantaneous pressure measurement and can be expressed as the peak, the peak-peak, or the root mean square (rms). Root mean square pressure, 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 exposure 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). Sound exposure level (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. Below is a simplified formula for SEL. SEL = SPL + 10log(duration in seconds) As applied to active sonar, 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 cumulative SEL. The cumulative 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 as cumulative 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 and testing activities in the Study Area. The Navy has analyzed potential impacts to marine mammals from impulsive and non-impulsive sound sources and vessel strike. Other potential impacts to marine mammals from training activities in the Study Area were analyzed in the Navy's HSTT DEIS/OEIS, in consultation with NMFS as a cooperating agency, and determined to be unlikely to result in marine mammal harassment. Therefore, the Navy has not requested authorization for take of marine mammals that might occur incidental to other components of their proposed activities. In this document, NMFS analyzes the potential effects on marine mammals from exposure to non-impulsive sound sources (sonar and other active acoustic sources), impulsive sound sources (underwater detonations and pile driving), and vessel strikes. For the purpose of MMPA authorizations, NMFS' effects assessments serve four primary purposes: (1) To prescribe the permissible methods of taking (i.e., Level B harassment (behavioral harassment), Level A harassment (injury), or mortality, including an identification of the number and types of take that could occur by harassment or mortality) and to prescribe other means of effecting the least practicable adverse impact on such species or stock and its habitat (i.e., mitigation); (2) to determine whether the specified activity would have a negligible impact on the affected species or stocks of marine mammals (based on the likelihood that the activity would adversely affect the species or stock through effects on annual rates of recruitment or survival); (3) to determine whether the specified activity would have an unmitigable adverse impact on the availability of the species or stock(s) for subsistence uses; and (4) to prescribe requirements pertaining to monitoring and reporting. More specifically, for activities involving non-impulsive or impulsive sources, 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 (effects to social relationships) that would be classified as a take and whether such take would have a negligible impact on such species or stocks. Vessel strikes, which have the potential to result in incidental take from direct injury and/or mortality, will be discussed in more detail in the Estimated Take of Marine Mammals section. In this section, we will focus qualitatively on the different ways that non-impulsive and impulsive sources may affect marine mammals (some of which NMFS would not classify as harassment). Then, in the Estimated Take of Marine Mammals section, we will relate the potential effects to marine mammals from non-impulsive and impulsive sources to the MMPA definitions of Level A and Level B Harassment, along with the potential effects from vessel strikes, and attempt to quantify those effects. Non-Impulsive Sources Direct Physiological Effects Based on the literature, there are two basic ways that non-impulsive sources 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 detect them) following exposure to an intense sound or sound for long duration, it is referred to as a noise-induced threshold shift (TS). An animal can experience temporary threshold shift (TTS) or permanent threshold shift (PTS). TTS can last from minutes or hours to days (i.e., there is complete recovery), can occur in specific frequency ranges (i.e., an animal might only have a temporary loss of hearing sensitivity between the frequencies of 1 and 10 kHz), and can be of varying amounts (for example, an animal's hearing sensitivity might be reduced initially by only 6 dB or reduced by 30 dB). PTS is permanent, but some recovery is possible. PTS can also occur in a specific frequency range and amount as mentioned above for TTS. The following physiological mechanisms are thought to play a role in inducing auditory TS: Effects to sensory hair cells in the inner ear that reduce their sensitivity, modification of the chemical environment within the sensory cells, residual muscular activity in the middle ear, displacement of certain inner ear membranes, increased blood flow, and post-stimulatory reduction in both efferent and sensory neural output (Southall et al., 2007). The amplitude, duration, frequency, temporal pattern, and energy distribution of sound exposure all can affect the amount of associated TS and the frequency range in which it occurs. As amplitude and duration of sound exposure increase, so, generally, does the amount of TS, along with the recovery time. For intermittent sounds, less TS could occur than compared to a continuous exposure with the same energy (some recovery could occur between intermittent exposures depending on the duty cycle between sounds) (Kryter et al., 1966; Ward, 1997). For example, one short but loud (higher SPL) sound exposure may induce the same impairment as one longer but softer sound, which in turn may cause more impairment than a series of several intermittent softer sounds with the same total energy (Ward, 1997). Additionally, though TTS is temporary, prolonged exposure to sounds strong enough to elicit TTS, or shorter-term exposure to sound levels well above the TTS threshold, can cause PTS, at least in terrestrial mammals (Kryter, 1985). Although in the case of mid- and high-frequency active sonar (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 marine mammals, published data are limited to the captive bottlenose dolphin, beluga, harbor porpoise, and Yangtze finless porpoise (Finneran et al., 2000, 2002b, 2003, 2005a, 2007, 2010a, 2010b; Finneran and Schlundt, 2010; Lucke et al., 2009; Mooney et al., 2009a, 2009b; Popov et al., 2011a, 2011b; Kastelein et al., 2012a; Schlundt et al., 2000; Nachtigall et al., 2003, 2004). For pinnipeds in water, data are limited to measurements of TTS in harbor seals, an elephant seal, and California sea lions (Kastak et al., 1999, 2005; Kastelein et al., 2012b). Marine mammal hearing plays a critical role in communication with conspecifics, and interpretation of environmental cues for purposes such as predator avoidance and prey capture. Depending on the degree (elevation of threshold in dB), duration (i.e., recovery time), and frequency range of TTS, and the context in which it is experienced, TTS can have effects on marine mammals ranging from discountable to serious (similar to those discussed in auditory masking, below). For example, a marine mammal may be able to readily compensate for a brief, relatively small amount of TTS in a non-critical frequency range that occurs during a time where ambient noise is lower and there are not as many competing sounds present. Alternatively, a larger amount and longer duration of TTS sustained during time when communication is critical for successful mother/calf interactions could have more serious impacts. Also, depending on the degree and frequency range, the effects of PTS on an animal could range in severity, although it is considered generally more serious because it is a permanent condition. Of note, reduced hearing sensitivity as a simple function of aging has been observed in marine mammals, as well as humans and other taxa (Southall et al., 2007), so we can infer that strategies exist for coping with this condition to some degree, though likely not without cost. 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 sonar pings or explosion sounds 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. Alternatively, Tyack et al. (2006) studied the deep diving behavior of beaked whales and concluded that: “Using current models of breath-hold diving, we infer that their natural diving behavior is inconsistent with known problems of acute nitrogen supersaturation and embolism.” Collectively, these hypotheses 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 sonar 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 non-impulsive sources can lead to strandings is included in the Stranding and Mortality section. 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 mysticetes, odontocetes, and pinnipeds underwater all encompass the frequencies of the sonar sources used in the Navy's MFAS/HFAS training exercises. Additionally, almost all species' vocal repertoires span across the frequencies of these sonar 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 sonar, which accounts for the largest takes of marine mammals (because of the source strength and number of hours it's conducted), the pulse length and low duty cycle of the MFAS/HFAS signal makes it less likely that masking would 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 adjustments to vocalization characteristics such as the frequency structure, amplitude, temporal structure, and temporal delivery. Many animals will combine several of these strategies to compensate for high levels of background noise. Anthropogenic sounds 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 responses. In the case of many stressors, an animal's first and sometimes most economical (in terms of biotic costs) response is behavioral avoidance of the potential stressor or avoidance of continued exposure to a stressor. An animal's second line of defense to stressors involves the sympathetic part of the autonomic nervous system and the classical “fight or flight” response which includes the cardiovascular system, the gastrointestinal system, the exocrine glands, and the adrenal medulla to produce changes in heart rate, blood pressure, and gastrointestinal activity that humans commonly associate with “stress.” These responses have a relatively short duration and may or may not have significant long-term effect on an animal's welfare. An animal's third line of defense to stressors involves its neuroendocrine systems; the system that has received the most study has been the hypothalmus-pituitary-adrenal system (also known as the HPA axis in mammals or the hypothalamus-pituitary-interrenal axis in fish and some reptiles). Unlike stress responses associated with the autonomic nervous system, virtually all neuro-endocrine functions that are affected by stress—including immune competence, reproduction, metabolism, and behavior—are regulated by pituitary hormones. Stress-induced changes in the secretion of pituitary hormones have been implicated in failed reproduction (Moberg, 1987; Rivier, 1995), altered metabolism (Elasser et al., 2000), reduced immune competence (Blecha, 2000), and behavioral disturbance. Increases in the circulation of glucocorticosteroids (cortisol, corticosterone, and aldosterone in marine mammals; see Romano et al., 2004) have been equated with stress for many years. The primary distinction between stress (which is adaptive and does not normally place an animal at risk) and distress is the biotic cost of the response. During a stress response, an animal uses glycogen stores that can be quickly replenished once the stress is alleviated. In such circumstances, the cost of the stress response would not pose a risk to the animal's welfare. However, when an animal does not have sufficient energy reserves to satisfy the energetic costs of a stress response, energy resources must be diverted from other biotic function, 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. Note that these examples involved a long-term (days or weeks) stress response exposure to stimuli. Relationships between these physiological mechanisms, animal behavior, and the costs of stress responses have also been documented fairly well through controlled experiments; because this physiology exists in every vertebrate that has been studied, it is not surprising that stress responses and their costs have been documented in both laboratory and free-living animals (for examples see, Holberton et al., 1996; Hood et al., 1998; Jessop et al., 2003; Krausman et al., 2004; Lankford et al., 2005; Reneerkens et al., 2002; Thompson and Hamer, 2000). Information has also been collected on the physiological responses of marine mammals to exposure to anthropogenic sounds (Fair and Becker, 2000; Romano et al., 2002; Wright et al., 2008). For example, Rolland et al. (2012) found that noise reduction from reduced ship traffic in the Bay of Fundy was associated with decreased stress in North Atlantic right whales. In a conceptual model developed by the Population Consequences of Acoustic Disturbance (PCAD) working group, serum hormones were identified as possible indicators of behavioral effects that are translated into altered rates of reproduction and mortality. The Office of Naval Research hosted a workshop (Effects of Stress on Marine Mammals Exposed to Sound) in 2009 that focused on this very topic (ONR, 2009). Studies of other marine animals and terrestrial animals would also 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), for example, 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), we also assume that stress responses are likely to 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 effects 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 no response or responses including, but not limited to: increased alertness; orientation or attraction to a sound source; vocal modifications; cessation of feeding; cessation of social interaction; alteration of movement or diving behavior; 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 and others in 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. Flight Response —A flight response is a dramatic change in normal movement to a directed and rapid movement away from the perceived location of a sound source. Relatively little information on flight responses of marine mammals to anthropogenic signals exist, although observations of flight responses to the presence of predators have occurred (Connor and Heithaus, 1996). Flight responses have been speculated as being a component of marine mammal strandings associated with sonar activities (Evans and England, 2001). Response to Predator —Evidence suggests that at least some marine mammals have the ability to acoustically identify potential predators. For example, harbor seals that reside in the coastal waters off British Columbia are frequently targeted by certain groups of killer whales, but not others. The seals discriminate between the calls of threatening and non-threatening killer whales (Deecke et al., 2002), a capability that should increase survivorship while reducing the energy required for attending to and responding to all killer whale calls. The occurrence of masking or hearing impairment provides a means by which marine mammals may be prevented from responding to the acoustic cues produced by their predators. Whether or not this is a possibility depends on the duration of the masking/hearing impairment and the likelihood of encountering a predator during the time that predator cues are impeded. Diving —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. Due to past incidents of beaked whale strandings associated with sonar operations, feedback paths are provided between avoidance and diving and indirect tissue effects. This feedback accounts for the hypothesis that variations in diving behavior and/or avoidance responses can possibly result in nitrogen tissue supersaturation and nitrogen off-gassing, possibly to the point of deleterious vascular bubble formation (Jepson et al., 2003). Although hypothetical, discussions surrounding this potential process are controversial. 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 si [Text truncated at 120,000 characters. The full text is on the page linked above.] --- Source: Frix Law Library, https://www.frixlaw.com/law-library/documents/fr%3A2013-01808. Public record. Not legal advice.