Takes of Marine Mammals Incidental to Specified Activities: Taking Marine Mammals Incidental to U.S. Navy Surveillance Towed Array Sensor System Low Frequency Active Sonar Training and Testing in the Central and Western North Pacific Ocean and Eastern Indian Ocean

Federal RegisterMar 1, 2019

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DEPARTMENT OF COMMERCE

National Oceanic and Atmospheric Administration

50 CFR Part 218

[Docket No. 180809740-9103-01]

RIN 0648-BI42

Takes of Marine Mammals Incidental to Specified Activities: Taking Marine Mammals Incidental to U.S. Navy Surveillance Towed Array Sensor System Low Frequency Active Sonar Training and Testing in the Central and Western North Pacific Ocean and Eastern Indian Ocean

AGENCY:

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

ACTION:

Proposed rule; request for comments.

SUMMARY:

NMFS has received a request from the U.S. Navy (Navy) for authorization to take marine mammals incidental to the use of Surveillance Towed Array Sensor System Low Frequency Active (SURTASS LFA) sonar systems onboard U.S. Navy surveillance ships for training and testing activities conducted under the authority of the Secretary of the Navy in the western and central North Pacific Ocean and eastern Indian Ocean (SURTASS LFA sonar activities) beginning August 2019. Pursuant to section 101(a)(5)(A) of the MMPA, NMFS is requesting comments on its proposal to issue regulations to govern the incidental take of marine mammals by Level B harassment during SURTASS LFA sonar activities. The Fiscal Year 2019 (FY19) National Defense Authorization Act (NDAA), signed on August 13, 2018, amended the Marine Mammal Protection Act to extend the maximum authorization period of permitted incidental takings of marine mammals under section 101(a)(5)(A) in the course of specified military readiness activities by the Department of Defense from five to seven years. Therefore, the authorization, if issued, would be in effect from August 2019 to August 2026. NMFS will consider public comments prior to making any final decision on the issuance of the requested MMPA authorization and agency responses will be summarized in the final notice of our decision. The Navy's activities are considered military readiness activities pursuant to the Marine Mammal Protection Act (MMPA), as amended by the National Defense Authorization Act for Fiscal Year 2004 (FY 2004 NDAA).

DATES:

Comments and information must be received no later than April 1, 2019.

ADDRESSES:

You may submit comments on this document, identified by NOAA-NMFS-2019-0014, by any of the following methods:

•

Electronic submission:

Submit all electronic public comments via the Federal e-Rulemaking Portal. Go to

www.regulations.gov/#!docketDetail;D =NOAA-NMFS-2019-0014,

click the “Comment Now!” icon, complete the required fields, and enter or attach your comments.

•

Mail:

Submit written comments to Jolie Harrison, Chief, Permits and Conservation Division, Office of Protected Resources, National Marine Fisheries Service, 1315 East-West Highway, Silver Spring, MD 20910.

Instructions:

Comments sent by any other method, to any other address or individual, or received after the end of the comment period, may not be considered by NMFS. All comments received are a part of the public record and will generally be posted for public viewing on

www.regulations.gov

without change. All personal identifying information (

e.g.,

name, address), confidential business information, or otherwise sensitive information submitted voluntarily by the sender will be publicly accessible. 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, or Adobe PDF file formats only.

FOR FURTHER INFORMATION CONTACT:

Wendy Piniak, Office of Protected Resources, NMFS, (301) 427-8401.

SUPPLEMENTARY INFORMATION:

Availability

A copy of the Navy's application and any supporting documents, as well as a list of the references cited in this document, may be obtained online at:

https://www.fisheries.noaa.gov/national/marine-mammal-protection/incidental-take-authorizations-military-readiness-activities.

In case of problems accessing these documents, please call the contact listed above (see

FOR FURTHER INFORMATION CONTACT

Purpose and Need for Regulatory Action

NMFS received an application from the Navy requesting regulations and a related letter or letters of authorization (LOA) to take multiple species of marine mammals by Level B harassment incidental to SURTASS LFA sonar activities. Please see “Background” below for definitions of harassment. This proposed rule would establish a framework under the authority of the MMPA (16 U.S.C. 1361

et seq.

) to allow for the authorization of take of marine mammals incidental to the Navy's specified activities.

Legal Authority for the Proposed Action

Section 101(a)(5)(A) of the MMPA (16 U.S.C. 1371(a)(5)(A)) generally directs 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 for up to five years if, after notice and public comment, the agency makes certain findings and issues regulations that set forth permissible methods of taking and other means of effecting the least practicable adverse impact on the affected species or stocks and their habitat (see the discussion below in the Proposed Mitigation section), as well as monitoring and reporting requirements. Section 101(a)(5)(A) of the MMPA and the implementing regulations at 50 CFR part 216, subpart I provide the legal basis for issuing this proposed rule and any associated LOAs. As described in the next section, the MMPA has been amended in a number of ways when the specified activity is a military readiness activity, including most recently in 2018 to extend the maximum authorization period under section 101(a)(5)(A) to seven years for Department of Defense military readiness activities. As directed by this legal authority, this proposed rule contains mitigation, monitoring, and reporting requirements.

Background

The MMPA prohibits the “take” of marine mammals, with certain exceptions. Sections 101(a)(5)(A) and (D) of the MMPA (16 U.S.C. 1361

et seq.

) direct the Secretary of Commerce (as delegated to NMFS) 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, an incidental harassment authorization may be issued following notice and opportunity for public comment.

Authorization for incidental takings shall be granted if NMFS finds that the taking will have a negligible impact on the species or stock(s) and will not have

an unmitigable adverse impact on the availability of the species or stock(s) for taking for subsistence uses (where relevant). Further, NMFS must prescribe the permissible methods of taking and other means of effecting the least practicable adverse impact on the affected species or stocks and their habitat, paying particular attention to rookeries, mating grounds, and areas of similar significance, and on the availability of such species or stocks for taking for certain subsistence uses (referred to in shorthand as “mitigation”), and requirements pertaining to the monitoring and reporting of such takings.

The 2004 NDAA (Pub. L. 108-136) removed the “small numbers” and “specified geographical region” limitations indicated above and amended the definition of “harassment” as it applies to a “military readiness activity” to read as follows (Section 3(18)(B) of the MMPA): (i) Any act that injures or has the significant potential to injure a marine mammal or marine mammal stock in the wild (Level A Harassment); or (ii) Any act that disturbs or is likely to disturb a marine mammal or marine mammal stock in the wild by causing disruption of natural behavioral patterns, including, but not limited to, migration, surfacing, nursing, breeding, feeding, or sheltering, to a point where such behavioral patterns are abandoned or significantly altered (Level B Harassment). In addition, the FY 2004 NDAA amended the MMPA as it relates to military readiness activities and the incidental take authorization (ITA) process such that “least practicable adverse impact” shall include consideration of personnel safety, practicality of implementation, and impact on the effectiveness of the military readiness activity. As mentioned above, the NDAA for FY 2019 amended the MMPA to extend the authorized period of permitted incidental takings of marine mammals covered by section 101(a)(5)(A) in the course of specified military readiness activities from five to seven years.

The allowance of incidental taking under section 101(a)(5)(A) requires promulgation of activity-specific regulations. Under NMFS' implementing regulations for section 101(a)(5)(A), a Letter of Authorization (LOA) may be issued consistent with the activity-specific regulations, provided that the level of taking will be consistent with the findings made for the total taking allowable under the specific regulations. The promulgation of activity-specific regulations (with their associated prescribed mitigation, monitoring, and reporting) requires notice and opportunity for public comment.

National Marine Sanctuaries Act

NMFS will work with NOAA's Office of National Marine Sanctuaries to fulfill our responsibilities under the NMSA as warranted and will complete any NMSA requirements prior to a determination on the issuance of the final rule and LOAs.

National Environmental Policy Act

To comply with the National Environmental Policy Act of 1969 (NEPA; 42 U.S.C. 4321

et seq.

) and NOAA Administrative Order (NAO) 216-6A, NMFS must evaluate our proposed action (

i.e.,

the promulgation of regulations and issuance of the LOA) and alternatives with respect to potential impacts on the human environment. NMFS is a cooperating agency on the Navy's supplemental environmental impact statement/supplemental overseas environmental impact statement (SEIS/SOEIS). NMFS plans to adopt the Navy's SEIS/SOEIS for SURTASS LFA sonar training and testing activities, provided our independent evaluation of the document finds that it includes adequate information analyzing the effects on the human environment of issuing the incidental take regulations and LOA.

The Navy published a Notice of Availability of a DSEIS/SOEIS for employment of SURTASS LFA sonar in the

Federal Register

on September 7, 2018 (83 FR 45442), which was available for public review and comment until October 22, 2018. The public may view the DSEIS/SOEIS at:

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

NMFS will evaluate the comments received on the DSEIS/SOEIS and comments received as a result of this proposed rulemaking prior to concluding our NEPA process or making a final decision on the request for incidental take authorization.

Summary of Request

On June 4, 2018, NMFS received a request from the Navy for authorization to take, by harassment, 46 species of marine mammals incidental to the use of SURTASS LFA sonar onboard U.S. Navy surveillance ships for training and testing activities conducted under the authority of the Secretary of the Navy in the western and central North Pacific Ocean and eastern Indian Ocean beginning in August 2019. In light of the FY 2019 NDAA amending section 101(a)(5)(A), the period for which the regulations would be effective for issuing the LOA under this rulemaking would extend to August 2026. On July 13, 2018, NMFS published a notice of receipt (NOR) of the Navy's application in the

Federal Register

(83 FR 32615), and requested comments and information related to the Navy's request. The review and comment period for the NOR ended on August 13, 2018. We received one comment in response to the NOR from a private citizen requesting that NMFS deny Navy's incidental take authorization request to avoid harming or killing marine mammals. This comment is available online at:

https://www.fisheries.noaa.gov/national/marine-mammal-protection/incidental-take-authorizations-military-readiness-activities.

We note that the Navy has not requested, nor is NMFS anticipating or proposing to authorize any mortality or any form of Level A harassment and, as discussed in more detail below, impacts to marine mammals are anticipated to be limited to Level B harassment only.

The Navy submitted a revised application on November 13, 2018. This revision included a minor change to the mitigation measures provided in the June 2018 application that was available for public review during the review and comment period for the NOR. This revision does not represent a significant change to the proposed mitigation measures for this proposed rule; however, the revised application is available here:

https://www.fisheries .noaa.gov/action/incidental-take-authorization-us-navy-operations-surveillance-towed-array-sensor-system-0

(also see Proposed Mitigation section of this notice for more detail).

The Navy states, and NMFS concurs, that these SURTASS LFA sonar activities, classified as military readiness activities, may incidentally take marine mammals by exposing them to SURTASS LFA sonar at levels that constitute Level B harassment as defined above. The Navy requests authorization to take, by Level B Harassment, individuals from 139 stocks of 46 species of marine mammals (10 species of mysticete (baleen) whales, 31 species of odontocete (toothed) whales, and 5 species of pinnipeds (seals and sea lions)). This rule may also cover the authorization of take of animals from additional associated stocks of marine mammals not listed here, should one or more of the stocks identified in this rule be formally separated into multiple stocks, provided NMFS is able to confirm the necessary findings for the newly identified stocks. As discussed later in this document, incidental takes due to SURTASS LFA sonar will be limited to Level B behavioral harassment. No takes by

Level A harassment are proposed to be authorized as Level A harassment is considered unlikely and will be avoided through the implementation of the Navy's proposed mitigation measures, as discussed below.

In previous SURTASS LFA sonar rulemakings, NMFS authorized some Level A harassment takes in an abundance of caution even though Level A harassment takes were not anticipated. However, to the knowledge of the Navy and NMFS, no Level A harassment takes have resulted over the 17-year history of SURTASS LFA sonar activities. Additionally, the exposure criteria and thresholds for assessing Level A harassment have been modified since prior rules based on the best available science. Under these new metrics, the zone for potential injury is substantially reduced. Therefore, due to the small injury zones and the fact that mitigation measures would ensure that marine mammals would not be exposed to received levels associated with injury, the Navy has not requested authorization for Level A harassment takes, and NMFS is not proposing to authorize any takes by Level A harassment.

NMFS published the first incidental take rule for SURTASS LFA sonar, effective from August 2002 through August 2007, on July 16, 2002 (67 FR 46712); the second rule, effective from August 2007 through August 2012, on August 21, 2007 (72 FR 46846); and the third rule, effective from August 2012 through August 2017, on August 20, 2012 (77 FR 50290).

In 2016, the Navy submitted an application for a fourth incidental take regulation under the MMPA (DoN, 2016) for the taking of marine mammals by harassment incidental to the deployment of up to four SURTASS LFA sonar systems from August 15, 2017, through August 14, 2022. NMFS published a proposed rule on April 27, 2017 (82 FR 19460). On August 10, 2017, the Deputy Secretary of Defense, after conferring with the Secretary of Commerce, determined that it was necessary for the national defense to exempt all military readiness activities that use SURTASS LFA sonar from compliance with the requirements of the MMPA for a period of up to two years beginning August 13, 2017, through August 12, 2019, or until such time when NMFS issues regulations and an LOA under MMPA section 101(a)(5)(A) for military readiness activities associated with the use of SURTASS LFA sonar, whichever is earlier. During the exemption period, all military readiness activities that involve the use of SURTASS LFA sonar are required to comply with all mitigation, monitoring, and reporting measures set forth in the 2017 National Defense Exemption (NDE) for SURTASS LFA sonar, which were based on the measures included in NMFS' prior (2012) Final Rule (77 FR 50290; August 20, 2012) and 2017 Proposed Rule (82 FR 19460; April 27, 2017). As a result of the NDE (available at

http://www.surtass-lfa-eis.com/wp-content/uploads/2018/01/SURTASS_LFA_NDE_10Aug17.pdf

), NMFS did not finalize its April 2017 proposed rule.

The NDE expires August 12, 2019. For this rulemaking, the Navy is proposing to continue using SURTASS LFA sonar systems onboard United States Naval Ship (USNS) surveillance ships for training and testing activities conducted under the authority of the Secretary of the Navy within the western and central North Pacific Ocean and eastern Indian Ocean. The operating features of the LFA sonar have remained the same since the 2001 FOEIS/EIS, except to note that the typical duty cycle of LFA sonar, based on historical SURTASS LFA sonar use, is 7.5 to 10 percent (DoN, 2007). The maximum duty cycle remained the same at 20 percent.

For this rulemaking, the Navy scoped the geographic extent of the area where the specified activity will occur (study area) to better reflect the areas where the Navy anticipates conducting SURTASS LFA sonar training and testing activities. Whereas the previous authorizations included certain routine military operations among the scope of actions analyzed, the Navy also has narrowed the scope of activities in the current request for authorization to training and testing activities only due to various statutory and practical considerations, as described in the SURTASS 2018 DSEIS/OEIS (DoN, 2018), Chapter 1, and discussed further below.

Under the proposed rule, the Navy would transmit a total of up to 496 LFA sonar transmission hours per year for its specified activity, as described below (see Description of the Specified Activities section), pooled across all SURTASS LFA sonar-equipped vessels in the first four years of the authorization, with an increase in usage to a total of up to 592 LFA transmission hours in years five through seven.

Description of the Specified Activities

Overview

The Navy's primary mission is to organize, train, and equip combat-ready naval forces capable of accomplishing American strategic objectives, deterring maritime aggression, and assuring freedom of navigation in ocean areas. This mission is mandated by Federal law in Section 5062 of Title 10 of the United States Code, which directs the Secretary of the Navy to ensure the readiness of the U.S. naval forces.

The Secretary of the Navy and the Chief of Navy Operations (CNO) have established that anti-submarine warfare (ASW) is a critical capability for achieving the Navy's mission, and it requires unfettered access to both the high seas and littoral environments to be prepared for all potential threats by maintaining ASW core competency. The Navy is challenged by the increased difficulty in locating undersea threats solely by using passive acoustic technologies due to the advancement and use of quieting technologies in diesel-electric and nuclear submarines. At the same time as the distance at which submarine threats can be detected decreases due to quieting technologies, improvements in torpedo and missile design have extended the effective range of these weapons.

One of the ways the Navy has addressed the changing requirements for ASW readiness was by developing SURTASS LFA sonar, which is able to reliably detect quieter and harder-to-find submarines at long range before these vessels can get within their effective weapons range to launch against their targets. SURTASS LFA sonar systems have a passive component (SURTASS), which is a towed line array of hydrophones used to detect sound emitted or reflected from submerged targets, and an active component (LFA), which is comprised of a set of acoustic transmitting elements. The active component detects objects by creating a sound pulse, or “ping” that is transmitted through the water and reflects off the target, returning in the form of an echo similar to echolocation used by some marine mammals to locate prey and navigate. SURTASS LFA sonar systems are long-range sensors that operate in the low-frequency (LF) band (

i.e.,

100-500 Hertz (Hz)). Because LF sound travels in seawater for greater distances than higher frequency sound, the SURTASS LFA sonar system would meet the need for improved detection and tracking of new-generation submarines at a longer range and would maximize the opportunity for U.S. armed forces to safely react to, and defend against, potential submarine threats while remaining a safe distance beyond a submarine's effective weapons range. Thus, the active acoustic component in the SURTASS LFA sonar is an important augmentation to its passive and tactical systems, as its long-range detection capabilities can effectively

counter the threat to the Navy and national security interests posed by quiet, diesel submarines.

The Navy's proposed specified activity for MMPA incidental take coverage is the continued employment of SURTASS LFA sonar systems onboard USNS surveillance ships for training and testing activities conducted under the authority of the Secretary of the Navy in the western and central Pacific Ocean and eastern Indian Ocean, which is classified as a military readiness activity, beginning August 13, 2019. The use of the SURTASS LFA sonar system would result in acoustic stimuli from the generation of sound or pressure waves in the water at or above levels that NMFS has determined would result in take of marine mammals under the MMPA. This is the principal means of marine mammal taking associated with these military readiness activities. In addition to the use of active acoustic sources, the Navy's activities include the movement of vessels. This document also analyzes the effects of this aspect of the activities. NMFS does not anticipate takes of marine mammals to result from ship strikes from any SURTASS LFA vessels because each vessel moves at a relatively slow speed (10 to 12 knots (kt) while transiting), especially when towing the SURTASS and LFA sonar systems (moving at 3 to 4 kt), and for a relatively short period of time. Combined with the use of mitigation measures as noted below, it is likely that surveillance vessels would be able to avoid any marine mammals.

The Navy will restrict SURTASS LFA sonar training and testing activities to the central and western North Pacific Ocean and eastern Indian Ocean. The Navy will not conduct training or testing utilizing SURTASS LFA sonar within the foreign territorial seas of other nations and will maintain SURTASS LFA sonar received levels below 180 decibels (dB) re 1 µPa (root-mean-square (rms)) within 12 nautical miles (nmi) (22 kilometers (km)) of any emerged land features or within the boundaries of designated Offshore Biologically Important Areas (OBIAs) during their effective periods (see Proposed Mitigation section below for OBIA details). In addition to these geographic mitigation measures, the Navy will implement procedural mitigation measures including monitoring for the presence of marine mammals (including visual as well as active and passive acoustic monitoring) and implementing shutdown procedures for marine mammals within a mitigation/buffer zone around the LFA sonar source (see Proposed Mitigation section below for further details).

Dates and Duration

This proposed rule (if made final) and associated LOA would be valid beginning August 13, 2019, through August 12, 2026. The Navy currently conducts SURTASS LFA sonar activities from four vessels. The Navy is planning to add new vessels to its ocean surveillance fleet. As new vessels are developed, the onboard LFA and High Frequency Marine Mammal Monitoring sonar (HF/M3 sonar) systems (discussed below) may need to be updated, modified, or even re-designed. Current indications are that future LFA sonar systems will have the same operational characteristics and that updates and modifications are focused toward miniaturizing the system components to reduce the weight and handling of the systems. If system parameters are modified as a result of these updates the Navy will determine if supplementary analysis would be required to cover the deployment of these new systems. As the new vessels and sonar system components are developed and constructed, at-sea testing would eventually be necessary. The Navy anticipates that new vessels, or new/updated sonar system components, would be ready for at-sea testing beginning in the fifth year of the time period covered by this proposed rule. Thus, the Navy's activity analysis included consideration of the sonar hours associated with future testing of new or updated LFA sonar system components and new ocean surveillance vessels. This consideration resulted in two scenarios of annual sonar transmit hours: Years 1 to 4 would entail 496 hours total per year across all SURTASS LFA sonar vessels, while years 5 to 7 would include an increase in LFA sonar transmit hours to 592 hours across all vessels.

The SURTASS LFA sonar transmission hours represent a distribution across six activities that include (with an approximate allocation of hours indicated):

• Contractor crew proficiency training (80 hours per year);

• Military crew (MILCREW) proficiency training (96 hours per year);

• Participation in or support of naval exercises (96 hours per year);

• Vessel and equipment maintenance (64 hours per year);

• Acoustic research testing (160 hours per year); and

• New SURTASS LFA sonar system testing (96 hours per year; would occur in years 5 to 7).

Each of these activities utilizes the SURTASS LFA sonar system within the operating profile described above; therefore, the number of hours designated for each activity is merely an estimate for planning purposes.

As noted above, this rulemaking would result in the fourth such regulation for the Navy's SURTASS LFA sonar activities. The Navy is currently conducting the specified activities under an NDE that will expire after August 12, 2019. Therefore, the Navy has requested MMPA rulemaking and a LOA for its SURTASS LFA sonar activities effective beginning August 13, 2019, to take marine mammals incidental to the SURTASS LFA sonar activities for a seven year period.

Potential SURTASS LFA Sonar Training and Testing Areas

The potential geographic scope of the SURTASS LFA sonar activities covered by this proposed rule are the western and central North Pacific Ocean and eastern Indian Ocean outside of the territorial seas of foreign nations (generally 12 nautical miles (nmi) (22 kilometers (km) from most foreign nations). Figure 1 depicts the potential areas of SURTASS LFA sonar activities. In areas within 12 nmi from any emergent land (coastal exclusion areas) and in areas identified as OBIAs, SURTASS LFA sonar training and testing would be conducted such that received levels of LFA sonar are below 180 dB re 1 μPa rms sound pressure level (SPL). This restriction would be observed year-round for coastal standoff zones and during known periods of biological importance for OBIAs.

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For this rulemaking, the Navy has scoped the geographic extent of its specified activities to better reflect the areas where the Navy anticipates conducting SURTASS LFA sonar training and testing activities now and into the reasonably foreseeable future. Fifteen representative model areas (shown in Figure 1 and listed in Table 1), with nominal modeling sites in each region, provide geographic context for the proposed SURTASS LFA sonar activities.

Table 1—Representative SURTASS LFA Sonar Modeling Areas That the Navy Modeled for the DSEIS/OEIS (DoN, 2018) and the MMPA Rulemaking/LOA Application

Modeled site

Location

(latitude/

longitude of

center of

modeling area)

Notes

East of Japan

38° N, 148° E

North Philippine Sea

29° N, 136° E

West Philippine Sea

22° N, 124° E

Offshore Guam

11° N, 145° E

Navy Mariana Islands Testing and Training Area.

Sea of Japan

39° N, 132° E

East China Sea

26° N, 125° E

South China Sea

14° N, 114° E

Offshore Japan 25° to 40° N

30° N, 165° E

Offshore Japan 10° to 25° N

15° N, 165° E

Hawaii North

25° N, 158° W

Navy Hawaii-Southern California Training and Testing Area.

Hawaii South

19.5° N, 158.5° W

Navy Hawaii-Southern California Training and Testing Area.

Offshore Sri Lanka

5° N, 85° E

Andaman Sea

7.5° N, 96° E

Northwest of Australia

18° S, 110° E

Northeast of Japan

52° N, 163° E

Detailed Description of the Specified Activities

SURTASS LFA Sonar

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

As mentioned previously, the SURTASS LFA sonar system is a long-range, all-weather LF sonar (operating between 100 and 500 Hertz (Hz)) system that has both active and passive components. LFA, the active system component (which allows for the detection of an object that is not generating noise), is comprised of source elements (called projectors) suspended vertically on a cable beneath the surveillance vessel. The projectors produce an active sound pulse by converting electrical energy to mechanical energy by setting up vibrations or pressure disturbances within the water to produce a ping. The Navy uses LFA as an augmentation to the passive SURTASS operations when passive system performance is inadequate. SURTASS, the passive part of the system, uses hydrophones (

i.e.,

underwater microphones) to detect sound emitted or reflected from submerged targets, such as submarines. The SURTASS hydrophones are mounted on a horizontal line array that is towed behind the surveillance vessel. The Navy processes and evaluates the returning signals or echoes, which are usually below background or ambient sound level, to identify and classify potential underwater targets.

LFA Active Component

—The active component of the SURTASS LFA sonar system consists of up to 18 projectors suspended beneath the surveillance vessel in a vertical line array. The SURTASS LFA sonar projectors transmit in the low-frequency band (between 100 and 500 Hz). The source level of an individual projector in the SURTASS LFA sonar array is approximately 215 dB re: 1 µPa at 1 m or less. Sound pressure is the sound force per unit area and is usually measured in micropascals (μPa), where one Pascal (Pa) is the pressure resulting from a force of one newton exerted over an area of one square meter. The commonly used reference pressure level in underwater acoustics is 1 μPa at 1 m, and the units for source level are decibels (dB) re: 1 μPa at 1 m). Because of the physics involved in acoustic beamforming (

i.e.,

a method of mapping noise sources by differentiating sound levels based upon the direction from which they originate) and sound transmission loss processes, the SURTASS LFA sonar array cannot have a SPL higher than the SPL of an individual projector.

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

i.e.,

the ratio of sound “on” time to total time) for LFA sonar is normally 7.5 to 10 percent and will not exceed a maximum duty cycle of 20 percent.

Compact LFA Active Component

—In addition to the LFA sonar system currently deployed on the USNS IMPECCABLE, the Navy developed a compact LFA (CLFA) sonar system, which is now deployed on its three smaller surveillance vessels (

i.e.,

the USNS ABLE, EFFECTIVE, and VICTORIOUS). The operational characteristics of the active component for CLFA sonar are comparable to the LFA system and the potential impacts from CLFA will be similar to the effects from the LFA sonar system. The CLFA sonar system consists of smaller projectors that weigh 142,000 lbs (64,410 kilograms (kg)), which is 182,000 lbs (82,554 kg) less than the weight of the LFA projectors on the USNS IMPECCABLE. The CLFA sonar system also consists of up to 18 projectors suspended beneath the surveillance vessel in a vertical line array and the CLFA sonar projectors transmit in the low-frequency band (also between 100 and 500 Hz) with the same duty cycle as described for LFA sonar. Similar to the active component of the LFA sonar system, the source level of an individual projector in the CLFA sonar array is approximately 215 dB re: 1 µPa or less.

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

SURTASS Passive Component

—The passive component of the SURTASS LFA sonar system consists of a SURTASS Twin-line (TL-29A) horizontal line array mounted with hydrophones. The Y-shaped array is 1,000 ft (305 m) in length and has an operational depth of 500 to 1,500 ft (152.4 to 457.2 m).

High-Frequency Marine Mammal Monitoring Active Sonar (HF/M3)

—Although technically not part of the SURTASS LFA sonar system, the Navy also proposes to use a high-frequency sonar system, called the HF/M3 sonar, to detect and locate marine mammals

within the SURTASS LFA sonar mitigation and buffer zones, as described later in this proposed rule. This enhanced commercial fish-finding sonar, mounted at the top of the SURTASS LFA sonar vertical line array, has a source level of 220 dB re: 1 µPa at 1 m with a frequency range from 30 to 40 kilohertz (kHz). The duty cycle is variable, but is normally below three to four percent and the maximum pulse duration is 40 milliseconds. The HF/M3 sonar has four transducers with 8° horizontal and 10° vertical beamwidths, which sweep a full 360° in the horizontal plane every 45 to 60 sec with a maximum range of approximately 1.2 mi (2 km).

Vessel Specifications

—The Navy currently deploys SURTASS LFA sonar on four twin-hulled ocean surveillance vessels that are 235 to 282 ft (72 to 86 m) in length, with twin-shafted diesel electric engines capable of providing 3,200 to 5,000 horsepower. Each vessel has an observation area on the bridge that is more than 30 ft above sea level from where lookouts will monitor for marine mammals whenever SURTASS LFA sonar is transmitting. As stated previously, the Navy may develop and field additional SURTASS LFA equipped vessels, either to replace or complement the Navy's current SURTASS LFA capable fleet, and these vessels may be in use beginning in the fifth year of the time period covered by this proposed rulemaking.

The operational speed of each vessel during sonar activities will be approximately 3.4 miles per hour (mph) (5.6 km per hour (km/hr); 3 knots (kt)) and each vessel's cruising speed outside of sonar activities would be a maximum of approximately 11.5 to 14.9 mph (18.5 to 24.1 km/hr; 10 to 13 kts). During sonar activities, the SURTASS LFA sonar vessels will generally travel in straight lines or in oval-shaped (

i.e.,

racetrack) patterns depending on the training or testing scenario.

Notice of Receipt Comments and Responses

On July 13, 2018, NMFS published a notice of receipt (NOR) of an application for rulemaking in the

Federal Register

(83 FR 32615) and invited comments and information from the interested public. During the 30-day comment period, which ended on August 13, 2018, NMFS received one comment from a private individual. This comment requested NMFS deny the request to authorize the incidental take of marine mammals and stop the Navy from performing SURTASS LFA sonar training and testing activities, citing concern for assault and mortality of marine mammals. As described below, no mortality of marine mammals is anticipated to occur due to SURTASS LFA sonar activities. Therefore, the Navy has not requested and NMFS is not proposing to authorize any mortality of marine mammals. In addition, no injury (Level A harassment) is anticipated as a result of the SURTASS LFA sonar training and testing activities, so Navy has not requested nor has NMFS proposed authorizing takes due to Level A harassment. Therefore, the incidental take of marine mammals associated with the proposed SURTASS LFA sonar activities would be limited to behavioral effects (Level B harassment).

Description of Marine Mammals in the Area of the Specified Activities

Forty-six species of marine mammals, including 10 baleen whale (mysticete); 31 toothed whale (odontocete); and 5 seal/sea lion (pinniped) species that represent 139 stocks (as currently classified) have confirmed or possible occurrence within potential SURTASS LFA sonar activity areas in the central and western North Pacific Ocean and eastern Indian Ocean. Multiple stocks of some species are affected, and independent assessments are conducted to make the necessary findings and determinations for each of these.

There are 11 marine mammal species under NMFS' jurisdiction listed as endangered or threatened under the Endangered Species Act (ESA; 16 U.S.C. 1531

et seq.

) with confirmed or possible occurrence in the study area for SURTASS LFA sonar training and testing activities. Marine mammal species under NMFS' jurisdiction in the study area listed as endangered are: North Pacific right whale (

Eubalaena japonica

); gray whale (

Eschrichtius robustus

); blue whale (

Balaenoptera musculus

); fin whale (

Balaenoptera physalus

); Western North Pacific distinct population segment (DPS) of humpback whale (

Megaptera novaeangliae

); sei whale (

Balaenoptera borealis

); sperm whale (

Physeter macrocephalus

); Main Hawaiian Islands Insular DPS of false killer whale (

Pseudorca crassidens

); Western DPS of the Steller sea lion (

Eumetopias jubatus

); and Hawaiian monk seal (

Neomonachus schauinslandi

). The southern DPS of the spotted seal (

Phoca largha

) is listed as threatened under the ESA and is within the study area for SURTASS LFA sonar activities. The aforementioned threatened and endangered marine mammal species also are depleted under the MMPA.

Chinese river dolphins (

Lipotes vexillifer

) do not have stocks designated within the SURTASS LFA sonar study area (see Potential SURTASS LFA Study Area section). The distribution of the Chinese river dolphin is limited to the main channel of a river section between the cities of Jingzhou and Jiangyin. Based on the extremely rare occurrence of these species in the Navy's Study Area and due to the coastal standoff range (

i.e.,

distance of 22 km (13 mi; 12 nmi) from land), take of Chinese river dolphins is not considered a reasonable likelihood; therefore, this species is not addressed further in this document. Similarly, the Taiwanese humpback dolphin, a subspecies of the Indo-Pacific humpback dolphin, is found only in a small, narrow stretch of estuarine waters off the western coast of Taiwan. Take of this species is also not considered a reasonable likelihood and this species is not addressed further in this document.

None of the marine mammal species which the U.S. Fish and Wildlife Service (USFWS) is responsible for managing occur in geographic areas that would overlap with the SURTASS LFA sonar Study Area. Therefore, the Navy has determined that SURTASS LFA sonar activities would have no effect on the endangered or threatened species or the critical habitat of the ESA-listed species under the jurisdiction of the USFWS. These species are not considered further in this notice.

To accurately assess the potential effects of SURTASS LFA sonar activities, the Navy modeled 15 representative sites in the SURTASS LFA sonar activity area. Tables 2 through 16 (below) summarize the abundance, status under the ESA, and density estimates of the marine mammal species and stocks that have confirmed or possible occurrence within the 15 SURTASS LFA sonar modeling areas in the central and western North Pacific Ocean and eastern Indian Ocean.

Table 2—Abundance and Density Estimates for the Marine Mammal Species, Species Groups, and Stocks Associated With Model Area 1, the East of Japan

Species

Stock name

Stock

abundance

Density

(animals/km

)

Winter

Spring

Summer

Fall

ESA

status

Blue whale

WNP

9,250

0.00001

Bryde's whale

WNP

20,501

0.0006

Common minke whale

WNP “OE”

25,049

0.0022

Fin whale

WNP

9,250

0.0002

Humpback whale

WNP stock and DPS

1,328

0.00036

North Pacific right whale

WNP

922

0.00001

Sei whale

7,000

0.0006

Baird's beaked whale

WNP

5,688

0.0029

Common dolphin

WNP

3,286,163

0.0761

Common bottlenose dolphin

WNP Northern Offshore

100,281

0.0171

Cuvier's beaked whale

WNP

90,725

0.0031

Dall's porpoise (

truei

)

WNP

truei

178,157

0.0390

0.0520

False killer whale

WNP

16,668

0.0036

Ginkgo-toothed beaked whale

22,799

0.0005

Harbor porpoise

WNP

31,046

0.0190

Hubbs beaked whale

22,799

0.0005

Killer whale

WNP

12,256

0.0001

Kogia

spp.

WNP

350,553

0.0031

Pacific white-sided dolphin

931,000

0.0082

Pantropical spotted dolphin

WNP

130,002

0.0259

Pygmy killer whale

WNP

30,214

0.0021

Risso's dolphin

WNP

143,374

0.0097

Rough-toothed dolphin

WNP

5,002

0.00224

Short-finned pilot whale

WNP Northern

20,884

0.0128

Sperm whale

102,112

0.00123

Spinner dolphin

WNP

1,015,059

0.00083

Stejneger's beaked whale

WNP

8,000

0.0005

Striped dolphin

WNP Northern Offshore

497,725

0.0111

Northern fur seal

503,609

0.368

0.158

NP=north Pacific; OE=Offshore Japan; WP=western Pacific; WNP=western north Pacific.

Refer to Table 3-2 of the Navy's application for literature references associated with abundance estimates presented in this table.

Refer to Table 3-2 of the Navy's application for literature references associated with density estimates presented in this table. No value for density indicates that species is not expected to occur in the model area during that season.

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

Pygmy and dwarf sperm whales are difficult to distinguish at sea, and abundance estimates are pooled for

Kogia

spp. as reported in Ferguson and Barlow, 2001 and 2003.

Table 3—Abundance and Density Estimates for the Marine Mammal Species, Species Groups, and Stocks Associated With Model Area 2, North Philippine Sea

Species

Stock name

Abundance

Density

(animals/km

)

Winter

Spring

Summer

Fall

ESA

status

Blue whale

WNP

9,250

0.00001

Bryde's whale

WNP

20,501

0.0006

Common minke whale

WNP “OE”

25,049

0.0044

Fin whale

WNP

9,250

0.0002

Humpback whale

WNP and DPS

1,328

0.00089

.00089

North Pacific right whale

WNP

922

0.00001

Omura's whale

WNP

1,800

0.00004

Blainville's beaked whale

WNP

8,032

0.0005

Common dolphin

WNP

3,286,163

0.0562

Common bottlenose dolphin

Japanese Coastal

3,516

0.0146

Cuvier's beaked whale

WNP

90,725

0.0054

False killer whale

WNP

16,668

0.0029

Fraser's dolphin

WNP

220,789

0.0069

Ginkgo-toothed beaked whale

22,799

0.0005

Killer whale

WNP

12,256

0.00009

Kogia

spp.

WNP

350,553

0.0031

Longman's beaked whale

WNP

7,619

0.00025

Melon-headed whale

WNP

56,213

0.00428

Pacific white-sided dolphin

931,000

0.0119

Pantropical spotted dolphin

WNP

130,002

0.0137

Pygmy killer whale

WNP

30,214

0.0021

Risso's dolphin

WNP

143,374

0.0106

Rough-toothed dolphin

WNP

5,002

0.00224

Short-finned pilot whale

WNP Southern

31,396

0.0153

Sperm whale

102,112

0.00123

Spinner dolphin

WNP

1,015,059

0.00083

Striped dolphin

Japanese Coastal

19,631

0.0329

NP=north Pacific; OE=Offshore Japan; WNP=western north Pacific.

Refer to Table 3-2 of the Navy's application for literature references associated with abundance estimates presented in this table.

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

Pygmy and dwarf sperm whales are difficult to distinguish at sea, and abundance estimates are pooled for

Kogia

spp. as reported in Ferguson and Barlow, 2001 and 2003.

Table 4—Abundance and Density Estimates for the Marine Mammal Species, Species Groups, and Stocks Associated With Model Area 3, West Philippine Sea

Species

Stock name

Abundance

Density

(animals/km

)

Winter

Spring

Summer

Fall

ESA

status

Blue whale

WNP

9,250

0.00001

Bryde's whale

WNP

20,501

0.0006

Common minke whale

WNP “OE”

25,049

0.0033

Fin whale

WNP

9,250

0.0002

Humpback whale

WNP and DPS

1,328

0.00089

Omura's whale

WNP

1,800

0.00004

Blainville's beaked whale

WNP

8,032

0.0005

Common dolphin

WNP

3,286,163

0.1158

Common bottlenose dolphin

WNP Southern Offshore

40,769

0.0146

Cuvier's beaked whale

WNP

90,725

0.0003

Deraniyagala's beaked whale

22,799

0.0005

False killer whale

WNP

16,668

0.0029

Fraser's dolphin

WNP

220,789

0.0069

Ginkgo-toothed beaked whale

22,799

0.0005

Killer whale

WNP

12,256

0.00009

Kogia

spp.

WNP

350,553

0.0017

Longman's beaked whale

WNP

7,619

0.00025

Melon-headed whale

WNP

56,213

0.00428

Pantropical spotted dolphin

WNP

130,002

0.0137

Pygmy killer whale

WNP

30,214

0.0021

Risso's dolphin

WNP

143,374

0.0106

Rough-toothed dolphin

WNP

5,002

0.00224

Short-finned pilot whale

WNP Southern

31,396

0.0076

Sperm whale

102,112

0.00123

Spinner dolphin

WNP

1,015,059

0.00083

Striped dolphin

WNP Southern Offshore

52,682

0.0164

NP=north Pacific; OE=Offshore Japan; WNP=western north Pacific.

Refer to Table 3-2 of the Navy's application for literature references associated with abundance estimates presented in this table.

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

Pygmy and dwarf sperm whales are difficult to distinguish at sea, and abundance estimates are pooled for

Kogia

spp. as reported in Ferguson and Barlow, 2001 and 2003.

Table 5—Abundance and Density Estimates for the Marine Mammal Species, Species Groups, and Stocks Associated With Model Area 4, Offshore Guam

Species

Stock name

Abundance

Density

(animals/km

)

Winter

Spring

Summer

Fall

ESA

status

Blue whale

WNP

9,250

0.00001

Bryde's whale

WNP

20,501

0.0004

Common minke whale

WNP “OE”

25,049

0.00015

Fin whale

WNP

9,250

0.00001

Humpback whale

WNP and DPS

1,328

0.00089

Omura's whale

WNP

1,800

0.00004

Sei whale

7,000

0.00029

Blainville's beaked whale

WNP

8,032

0.00086

Common bottlenose dolphin

WNP Southern Offshore

40,769

0.00899

Cuvier's beaked whale

WNP

90,725

0.0003

Deraniyagala's beaked whale

22,799

0.00093

Dwarf sperm whale

WNP

350,553

0.00714

False killer whale

WNP

16,668

0.00111

Fraser's dolphin

CNP

16,992

0.02104

Ginkgo-toothed beaked whale

22,799

0.00093

Killer whale

WNP

12,256

0.00006

Longman's beaked whale

WNP

7,619

0.00311

Melon-headed whale

WNP

56,213

0.00428

Pantropical spotted dolphin

WNP

130,002

0.0226

Pygmy killer whale

WNP

30,214

0.00014

Pygmy sperm whale

WNP

350,553

0.00291

Risso's dolphin

WNP

143,374

0.00474

Rough-toothed dolphin

WNP

5,002

0.00185

Short-finned pilot whale

WNP Southern

31,396

0.00797

Sperm whale

102,112

0.00123

Spinner dolphin

WNP

1,015,059

0.00083

Striped dolphin

WNP Southern Offshore

52,682

0.00616

CNP=central north Pacific; NP=north Pacific; OE=Offshore Japan; WNP=western north Pacific.

Refer to Table 3-2 of the Navy's application for literature references associated with abundance estimates presented in this table.

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

Table 6—Abundance and Density Estimates for the Marine Mammal Species, Species Groups, and Stocks Associated With Model Area 5, Sea of Japan

Species

Stock name

Abundance

Density

(animals/km

)

Winter

Spring

Summer

Fall

ESA

Status

Bryde's whale

WNP

20,501

0.0001

Common minke whale

WNP “JW” Stock

2,611

0.00016

Fin whale

WNP

9,250

0.0009

North Pacific right whale

WNP

922

0.00001

Omura's whale

WNP

1,800

0.00004

Western North Pacific gray whale

WNP Western DPS

140

0.00001

Baird's beaked whale

WNP

5,688

0.0003

Common dolphin

WNP

279,182

0.1158

Common bottlenose dolphin

105,138

0.00077

Cuvier's beaked whale

WNP

90,725

0.0031

Dall's porpoise

SOJ

dalli

173,638

0.0520

False killer whale

9,777

0.0027

Harbor porpoise

WNP

31,046

0.0190

Killer whale

WNP

12,256

0.00009

Kogia

spp

WNP

350,553

0.0017

Pacific white-sided dolphin

931,000

0.0030

Risso's dolphin

143,374

0.0073

Rough-toothed dolphin

WNP

5,002

0.00224

Sperm whale

102,112

0.00123

Spinner dolphin

WNP

1,015,059

0.00083

Stejneger's beaked whale

WNP

8,000

0.0005

Northern fur seal

503,609

0.368

0.158

Spotted seal

Southern and DPS

3,500

0.00001

IA=Inshore Archipelago; JW=Sea of Japan (minke); NP=north Pacific; SOJ=Sea of Japan; WNP=western north Pacific.

Refer to Table 3-2 of the Navy's application for literature references associated with abundance estimates presented in this table.

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

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

Pygmy and dwarf sperm whales are difficult to distinguish at sea, and abundance estimates are pooled for

Kogia

spp as reported in Ferguson and Barlow, 2001 and 2003.

Table 7—Abundance and Density Estimates for the Marine Mammal Species, Species Groups, and Stocks Associated With Model Area 6, East China Sea

Species

Stock name

Abundance

Density

(animals/km

)

Winter

Spring

Summer

Fall

ESA

status

Bryde's whale

ECS

137

0.0003

Common minke whale

4,492

0.0018

Fin whale

ECS

500

0.0002

North Pacific right whale

WNP

922

0.00001

Omura's whale

WNP

1,800

0.00004

Western North Pacific gray whale

WNP and Western DPS

140

0.00001

Blainville's beaked whale

WNP

8,032

0.0005

Common dolphin

WNP

279,182

0.1158

Common bottlenose dolphin

105,138

0.00077

Cuvier's beaked whale

WNP

90,725

0.0003

False killer whale

9,777

0.00111

Fraser's dolphin

WNP

220,789

0.00694

Ginkgo-toothed beaked whale

22,799

0.0005

Killer whale

WNP

12,256

0.00009

Kogia

spp

WNP

350,553

0.0017

Longman's beaked whale

WNP

7,619

0.00025

Melon-headed whale

WNP

56,213

0.00428

Pacific white-sided dolphin

931,000

0.0028

Pantropical spotted dolphin

WNP

130,002

0.01374

Pygmy killer whale

WNP

30,214

0.00014

Risso's dolphin

143,374

0.0106

Rough-toothed dolphin

WNP

5,002

0.00224

Sperm whale

102,112

0.00123

Spinner dolphin

WNP

1,015,059

0.00083

Spotted seal

Southern and DPS

1,000

0.00001

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

Refer to Table 3-2 of the Navy's application for literature references associated with abundance estimates presented in this table.

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

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

Pygmy and dwarf sperm whales are difficult to distinguish at sea, and abundance estimates are pooled for

Kogia

spp. as reported in Ferguson and Barlow, 2001 and 2003.

Table 8—Abundance and Density Estimates for the Marine Mammal Species, Species Groups, and Stocks Associated With Model Area 7, South China Sea

Species

Stock name

Abundance

Density

(animals/km

)

Winter

Springer

Summer

Fall

ESA

status

Bryde's whale

WNP

20,501

0.0006

Common minke whale

4,492

0.0018

Fin whale

WNP

9,250

0.0002

Humpback whale

WNP and DPS

1,328

0.00036

North Pacific right whale

WNP

922

0.00001

Omura's whale

WNP

1,800

0. 00004

Western North Pacific gray whale

WNP and Western DPS

140

0.00001

Blainville's beaked whale

WNP

8,032

0.0005

Common dolphin

WNP

279,182

0.1158

Common bottlenose dolphin

105,138

0.00077

Cuvier's beaked whale

WNP

90,725

0.0003

Deraniyagala's beaked whale

22,799

0.0005

False killer whale

9,777

0.00111

Fraser's dolphin

WNP

220,789

0.00694

Ginkgo-toothed beaked whale

22,799

0.0005

Killer whale

WNP

12,256

0.00009

Kogia

spp

WNP

350,553

0.0017

Longman's beaked whale

WNP

7,619

0.00025

Melon-headed whale

WNP

56,213

0.00428

Pantropical spotted dolphin

WNP

130,002

0.01374

Pygmy killer whale

WNP

30,214

0.00014

Risso's dolphin

143,374

0.0106

Rough-toothed dolphin

WNP

5,002

0.00224

Short-finned pilot whale

WNP Southern

31,396

0.00159

Sperm whale

102,112

0.0012

Spinner dolphin

WNP

1,015,059

0.00083

Striped dolphin

WNP Southern Offshore

52,682

0.00584

IA=Inshore Archipelago; NP=north Pacific; WNP=western north Pacific; YS=Yellow Sea.

Refer to Table 3-2 of the Navy's application for literature references associated with abundance estimates presented in this table.

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

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

Pygmy and dwarf sperm whales are difficult to distinguish at sea, and abundance estimates are pooled for

Kogia

spp. as reported in Ferguson and Barlow, 2001 and 2003.

Table 9—Abundance and Density Estimates for the Marine Mammal Species, Species Groups, and Stocks Associated With Model Area 8, Offshore Japan 25° to 40° N

Species

Stock name

Abundance

Density

(animals/km

)

Winter

Spring

Summer

Fall

ESA

status

Blue whale

WNP

9,250

0.00001

Bryde's whale

WNP

20,501

0.0003

Common minke whale

WNP “OE”

25,049

0.0003

Fin whale

WNP

9,250

0.0001

Humpback whale

WNP and DPS

1,328

0.00036

Sei whale

7,000

0.00029

Baird's beaked whale

WNP

5,688

0.0001

Blainville's beaked whale

WNP

8,032

0.0007

Common dolphin

WNP

3,286,163

0.0863

Common bottlenose dolphin

WNP Northern Offshore

100,281

0.00077

Cuvier's beaked whale

WNP

90,725

0.00374

Dall's porpoise

WNP

dalli

162,000

0.0390

0.0520

Dwarf sperm whale

WNP

350,553

0.0043

False killer whale

WNP

16,668

0.0036

Hubb's beaked whale

22,799

0.0005

Killer whale

WNP

12,256

0.00009

Longman's beaked whale

WNP

7,619

0.00025

Melon-headed whale

WNP

56,213

0.0027

Mesoplodon

spp

WNP

22,799

0.0005

Northern right whale dolphin

68,000

0.00001

Pacific white-sided dolphin

931,000

0.0048

Pantropical spotted dolphin

WNP

130,002

0.0113

Pygmy killer whale

WNP

30,214

0.0001

Pygmy sperm whale

WNP

350,553

0.0018

Risso's dolphin

WNP

143,374

0.0005

Rough-toothed dolphin

WNP

5,002

0.0019

Short-finned pilot whale

WNP Northern

20,884

0.0021

Sperm whale

102,112

0.0022

Spinner dolphin

WNP

1,015,059

0.0019

Stejneger's beaked whale

WNP

8,000

0.0005

Striped dolphin

WNP Northern Offshore

497,725

0.0058

Hawaiian monk seal

Hawaii

1,427

0.00001

Northern fur seal

503,609

0.0123

NP=north Pacific; OE=Offshore Japan; WNP=western north Pacific; WP=Western Pacific.

Refer to Table 3-2 of the Navy's application for literature references associated with abundance estimates presented in this table.

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

No methods are available to distinguish between the species of

Mesoplodon

beaked whales in the WNP stocks (Blainville's beaked whale (

M. densirostris

), Perrin's beaked whale (

M. perrini

), Lesser beaked whale (

M. peruvianus

), Stejneger's beaked whale (

M. stejnegeri

), Gingko-toothed beaked whale (

M. gingkodens

), and Hubbs' beaked whale (

M. carlhubbsi

)) when observed during at-sea surveys (Carretta

et al.,

2018). As reported in Ferguson and Barlow, 2001 and 2003, data on these species were pooled. These six species are managed as one unit.

Table 10—Abundance and Density Estimates for the Marine Mammal Species, Species Groups, and Stocks Associated With Model Area 9, Offshore Japan 10° to 25° N

Species

Stock name

Abundance

Density

(animals/km

)

Winter

Spring

Summer

Fall

ESA

status

Blue whale

WNP

9,250

0.00001

Bryde's whale

WNP

20,501

0.0003

Fin whale

WNP

9,250

0.00001

Humpback whale

WNP and DPS

1,328

0.00036

Omura's whale

WNP

1,800

0.00004

Sei whale

7,000

0.0029

Blainville's beaked whale

WNP

8,032

0.0007

Common bottlenose dolphin

WNP Southern Offshore

40,769

0.00077

Cuvier's beaked whale

WNP

90,725

0.00374

Deraniyagala's beaked whale

22,799

0.00093

Dwarf sperm whale

WNP

350,553

0.0043

False killer whale

WNP

16,668

0.00057

Fraser's dolphin

CNP

16,992

0.00251

Ginkgo-toothed beaked whale

22,799

0.00093

Killer whale

WNP

12,256

0.00009

Longman's beaked whale

WNP

7,619

0.00025

Melon-headed whale

WNP

56,213

0.00267

Pantropical spotted dolphin

WNP

130,002

0.01132

Pygmy killer whale

WNP

30,214

0.00006

Pygmy sperm whale

WNP

350,553

0.00176

Risso's dolphin

WNP

143,374

0.00046

Rough-toothed dolphin

WNP

5,002

0.00185

Short-finned pilot whale

WNP Southern

31,396

0.00211

Sperm whale

102,112

0.00222

Spinner dolphin

WNP

1,015,059

0.00187

Striped dolphin

WNP Southern Offshore

52,682

0.00584

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

Refer to Table 3-2 of the Navy's application for literature references associated with abundance estimates presented in this table.

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

Table 11—Abundance and Density Estimates for the Marine Mammal Species, Species Groups, and Stocks Associated With Model Area 10, Northern Hawaii

Species

Stock name

Abundance

Density

(animals/km

)

Winter

Spring

Summer

Fall

ESA

status

Blue whale

CNP

133

0.00005

Bryde's whale

Hawaii

1,751

0.000085

Common minke whale

Hawaii

25,049

0.00423

Fin whale

Hawaii

154

0.00006

Humpback whale

CNP and Hawaii DPS

10,103

0.00529

Sei whale

Hawaii

391

0.00016

Blainville's beaked whale

Hawaii

2,105

0.00086

Common bottlenose dolphin

Hawaii pelagic

21,815

0.00118

Kauai/Niihau

184

0.065

4 Islands

191

0.017

Oahu

743

0.187

Hawaii Island

128

0.028

Cuvier's beaked whale

Hawaii

723

0.0003

Dwarf sperm whale

Hawaii

17,519

0.00714

False killer whale

Hawaii-Pelagic

1,540

0.0006

Main HI Islands Insular and DPS

167

0.0008

NW HI Islands

617

0.0006

Fraser's dolphin

Hawaii

51,491

0.02104

Killer whale

Hawaii

146

0.00006

Longman's beaked whale

Hawaii

7,619

0.00311

Melon-headed whale

Hawaiian Islands

8,666

0.002

0.0020

Kohala Resident

447

0.1000

Pantropical spotted dolphin

Hawaiian Pelagic

55,795

0.00369

Hawaiian Island

220

0.061

Oahu

220

0.072

4 Islands

220

0.061

Pygmy killer whale

Hawaii

10,640

0.00435

Pygmy sperm

Hawaii

7,138

0.0029

Risso's dolphin

Hawaii

11,613

0.00474

Rough-toothed dolphin

Hawaii

72,528

0.00224

Short-finned pilot whale

Hawaii

19,503

0.00459

Sperm whale

Hawaii

4,559

0.00158

Spinner dolphin

Hawaii Pelagic

3,351

0.00159

Kauai/Niihau

601

0.097

Hawaiian Island

631

0.066

Oahu/4 Islands

355

0.023

Kure/Midway Atoll

260

0.0070

Pearl and Hermes Reef

300

0.0070

Striped dolphin

Hawaii

61,201

0.00385

Hawaiian monk seal

Hawaii

1,427

0.00004

CNP=central north Pacific.

Refer to Table 3-2 of the Navy's application for literature references associated with abundance estimates presented in this table.

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

Table 12—Abundance and Density Estimates for the Marine Mammal Species, Species Groups, and Stocks Associated With Model Area 11, Southern Hawaii

Species

Stock name

Abundance

Density

(animals/km

)

Winter

Spring

Summer

Fall

ESA

status

Blue whale

CNP

133

0.00005

Bryde's whale

Hawaii

798

0.00012

Common minke whale

Hawaii

25,049

0.00423

Fin whale

Hawaii

154

0.00006

Humpback whale

CNP/Hawaii DPS

10,103

0.00631

Sei whale

Hawaii

391

0.00016

Blainville's beaked whale

Hawaii

2,105

0.00086

Common bottlenose dolphin

Hawaii Pelagic

21,815

0.00126

Oahu

743

0.187

4 Islands

191

0.017

Hawaii Island

128

0.028

Kauai/Niihau

184

0.065

Cuvier's beaked whale

Hawaii

723

0.0003

Deraniyagala's beaked whale

22,799

0.00093

Dwarf sperm whale

Hawaii

17,519

0.00714

False killer whale

Hawaii-Pelagic

1,540

0.00086

Main Hawaiian Island Insular

167

0.0008

Fraser's dolphin

Hawaii

51,491

0.02104

Killer whale

Hawaii

146

0.00006

Longman's beaked whale

Hawaii

7,619

0.00311

Melon-headed whale

Hawaiian Islands

8,666

0.0020

Kohala Resident

447

0.1000

Pantropical spotted dolphin

Hawaiian Pelagic

55,795

0.00541

Hawaii Island

220

0.061

Oahu

220

0.072

4 Islands

220

0.061

Pygmy killer whale

Hawaii

10,640

0.00435

Pygmy sperm whale

Hawaii

7,138

0.0029

Risso's dolphin

Hawaii

11,613

0.00474

Rough toothed dolphin

Hawaii

75,528

0.00257

Short-finned pilot whale

Hawaii

19,503

0.00549

Sperm whale

Hawaii

4,559

0.00131

Spinner dolphin

Hawaii Pelagic

3,351

0.00348

Oahu/4-Islands

601

0.023

Hawaii Island

631

0.066

Kauai/Niihau

355

0.097

Striped dolphin

Hawaii

61,201

0.00475

Hawaiian monk seal

Hawaii

1,427

0.00004

CNP=central north Pacific; NP=north Pacific.

Refer to Table 3-2 of the Navy's application for literature references associated with abundance estimates presented in this table.

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

Table 13—Abundance and Density Estimates for the Marine Mammal Species, Species Groups, and Stocks Associated With Model Area 12, Offshore Sri Lanka

Species

Stock name

Abundance

Density

(animals/km

)

Winter

Spring

Summer

Fall

ESA

status

Blue whale

NIND

3,691

0.00004

Bryde's whale

NIND

9,176

0.00041

Common minke whale

IND

257,000

0.00001

Fin whale

IND

1,846

0.00001

Omura's whale

NIND

9,176

0.00041

Sei whale

NIND

9,176

0.00041

Blainville's beaked whale

IND

16,867

0.00105

Common dolphin

IND

1,819,982

0.00513

0.00516

0.00541

0.00538

Common bottlenose dolphin

NIND

785,585

0.04839

0.04829

0.04725

0.04740

Cuvier's beaked whale

NIND

27,272

0.00506

0.00508

0.00505

Deraniyagala's beaked whale

IND

16,867

0.00513

0.00516

0.00541

0.00538

Dwarf sperm whale

IND

10,541

0.00005

False killer whale

IND

144,188

0.00024

Fraser's dolphin

IND

151,554

0.00207

Indo-Pacific bottlenose dolphin

IND

7,850

0.00048

0.00047

Killer whale

IND

12,593

0.00697

0.00155

0.00693

0.00694

Longman's beaked whale

IND

16,867

0.00513

0.00516

0.00541

0.00538

Melon-headed whale

IND

64,600

0.00921

0.00920

0.00937

0.00936

Pantropical spotted dolphin

IND

736,575

0.00904

Pygmy killer whale

IND

22,029

0.00138

0.00137

0.00152

0.00153

Pygmy sperm whale

IND

10,541

0.00001

Risso's dolphin

IND

452,125

0.08641

0.08651

0.08435

0.08466

Rough-toothed dolphin

IND

156,690

0.00071

Short-finned pilot whale

IND

268,751

0.03219

0.03228

0.03273

0.03279

Sperm whale

NIND

24,446

0.00129

0.00118

0.00126

0.00121

Spinner dolphin

IND

634,108

0.00678

Striped dolphin

IND

674,578

0.14601

0.14629

0.14780

0.14788

IND=Indian Ocean; NIND=northern Indian Ocean.

Refer to Table 3-2 of the Navy's application for literature references associated with abundance estimates presented in this table.

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

Table 14—Abundance and Density Estimates for the Marine Mammal Species, Species Groups, and Stocks Associated With Model Area 13, Andaman Sea

Species

Stock name

Abundance

Density

(animals/km

)

Winter

Spring

Summer

Fall

ESA

status

Blue whale

NIND

3,691

0.00003

Bryde's whale

NIND

9,176

0.00038

0.000036

0.00037

Common minke whale

IND

257,000

0.00001

0.00968

0.00001

Fin whale

IND

1,846

0.00001

Omura's whale

NIND

9,176

0.00038

0.00036

0.00037

Blainville's beaked whale

IND

16,867

0.00094

0.00089

0.00094

0.00099

Common bottlenose dolphin

NIND

785,585

0.07578

0.07781

0.07261

0.07212

Cuvier's beaked whale

NIND

27,272

0.00466

0.00482

0.00480

0.00473

Deraniyagala's beaked whale

IND

16,867

0.00094

0.00092

0.00097

0.00099

Dwarf sperm whale

IND

10,541

0.00005

0.00006

0.00005

False killer whale

IND

144,188

0.00023

0.00024

0.00023

Fraser's dolphin

IND

151,554

0.00176

0.00179

0.00180

Ginkgo-toothed beaked whale

IND

16,867

0.00094

0.00092

0.00097

0.00099

Indo-Pacific bottlenose dolphin

IND

7,850

0.00076

0.00078

0.00073

0.00072

Killer whale

IND

12,593

0.00744

0.00178

0.00730

0.00734

Longman's beaked whale

IND

16,867

0.00444

0.00429

0.00459

0.00440

Melon-headed whale

IND

64,600

0.00884

0.00878

0.00846

Pantropical spotted dolphin

IND

736,575

0.00868

0.00841

0.00829

0.00873

Pygmy killer whale

IND

22,029

0.00121

0.00113

0.00125

0.00131

Pygmy sperm whale

IND

10,541

0.00001

Risso's dolphin

IND

452,125

0.09197

0.09215

0.09173

0.09366

Rough-toothed dolphin

IND

156,690

0.00077

0.00078

0.00077

0.00074

Short-finned pilot whale

IND

268,751

0.03354

0.03364

0.03543

0.03504

Sperm whale

NIND

24,446

0.00109

0.00099

0.00107

0.00105

Spinner dolphin

IND

634,108

0.00736

0.00711

0.00701

0.00726

Striped dolphin

IND

674,578

0.14413

0.14174

0.14123

0.14402

IND=Indian Ocean; NIND=northern Indian Ocean.

Refer to Table 3-2 of the Navy's application for literature references associated with abundance estimates presented in this table.

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

Table 15—Abundance and Density Estimates for the Marine Mammal Species, Species Groups, and Stocks Associated With Model Area 14, Northwestern Australia

Species

Stock name

Abundance

Density

(animals/km

)

Winter

Spring

Summer

Fall

ESA

status

Antarctic minke whale

ANT

90,000

0.00001

Blue whale/Pygmy blue whale

SIND

1,657

0.00003

Bryde's whale

SIND

13,854

0.00032

Common minke whale

IND

257,500

0.01227

0.01929

0.01947

Fin whale

SIND

38,185

0.00001

0.00099

0.00128

0.00121

Humpback whale

Western Australia stock and DPS

13,640

0.00007

Omura's whale

SIND

13,854

0.00032

Sei whale

SIND

13,854

0.00001

Blainville's beaked whale

IND

16,867

0.00083

0.00082

0.00083

Common bottlenose dolphin

WAU

3,000

0.03630

0.03652

0.03459

0.03725

Cuvier's beaked whale

76,500

0.00399

0.00406

0.00402

0.00405

Dwarf sperm whale

IND

10,541

0.00004

False killer whale

IND

144,188

0.00020

0.00019

0.00020

Fraser's dolphin

IND

151,554

0.00145

0.00148

0.00149

0.00147

Killer whale

IND

12,593

0.00585

0.00435

0.00588

0.00580

Longman's beaked whale

IND

16,867

0.00393

0.00403

0.00412

Melon-headed whale

IND

64,600

0.00717

0.00635

0.00637

Pantropical spotted dolphin

IND

736,575

0.00727

0.00715

0.00746

Pygmy killer whale

IND

22,029

0.00100

0.00104

0.00101

0.00097

Risso's dolphin

IND

452,125

0.07152

0.07214

0.06944

0.07173

Rough-toothed dolphin

IND

156,690

0.00059

0.00060

0.00059

Short-finned pilot whale

IND

268,751

0.02698

0.02759

0.02689

0.02716

Southern bottlenose whale

IND

599,300

0.00083

0.00082

0.00083

Spade-toothed beaked whale

IND

16,867

0.00083

0.00082

0.00083

Sperm whale

SIND

24,446

0.00096

0.00087

0.00097

0.00092

Spinner dolphin

IND

634,108

0.00561

0.00549

0.00568

0.00563

Striped dolphin

IND

674,578

0.12018

0.12041

0.11680

0.11727

ANT=Antarctic; SIND=southern Indian Ocean; IND=Indian Ocean; SH=Southern Hemisphere; WAU=Western Australia.

Refer to Table 3-2 of the Navy's application for literature references associated with abundance estimates presented in this table.

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

Table 16—Abundance and Density Estimates for the Marine Mammal Species, Species Groups, and Stocks Associated With Model Area 15, Northeast of Japan

Species

Stock name

Abundance

Density

(animals/km

)

Winter

Spring

Summer

Fall

ESA

status

Blue whale

WNP

9,250

0.00001

Common minke whale

WNP “OE”

25,049

0.0022

Fin whale

WNP

9,250

0.0002

Humpback whale

WNP and DPS

1,328

0.000498

North Pacific right whale

WNP

922

0.00001

Sei whale

7,000

0.00029

Western North Pacific gray whale

Western and DPS

140

0.00001

Baird's beaked whale

WNP

5,688

0.0015

0.0029

Common dolphin

WNP

3,286,163

0.0863

Cuvier's beaked whale

WNP

90,725

0.0054

Dall's porpoise

WNP

dalli

162,000

0.0390

0.0520

0.0650

0.0520

Killer whale

WNP

12,256

0.0036

Pacific white-sided dolphin

931,000

0.0048

Sperm whale

102,112

0.0017

0.0022

Stejneger's beaked whale

WNP

8,000

0.0005

Northern fur seal

Western Pacific

503,609

0.00689

0.01378

Ribbon seal

365,000

0.0904

0.0452

Spotted seal

Alaska/Bering Sea DPS

461,625

0.2770

0.1385

Steller sea lion

West-Asian and Western DPS

71,221

0.00001

IND=Indian Ocean; NP=northern Pacific; WNP=western north Pacific; OE=Offshore Japan.

Refer to Table 3-2 of the Navy's application for literature references associated with abundance estimates presented in this table.

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

Information on how the density and abundance stock estimates were derived for the selected mission sites is in the Navy's application (refer to section 3.2). These data are derived from the best available published source documentation and provide general area information for each model area with species-specific information on the animals that could occur in that area, including estimates for their stock, abundance, and density. The Navy developed the abundance and density estimates by first using estimates from line-transect surveys that occurred in or near each of the 15 model sites (

e.g.,

Bradford

et al.,

2017). When density estimates were not available from a survey in the model area, the Navy extrapolated density estimates from a region with similar oceanographic

characteristics to that model area. For example, the eastern tropical Pacific has been extensively surveyed and provides a comprehensive understanding of marine mammals in temperate oceanic waters (Ferguson and Barlow, 2001, 2003). Density estimates for some model areas were also derived from the Navy's Marine Species Density Database (DoN, 2018). In addition, density estimates are usually not available for rare marine mammal species or for those that have been newly defined (

e.g.,

the Deraniyagala's beaked whale). For these species, the lowest density estimate of 0.0001 animals/square kilometer (0.0001 animals/km

) was used in the take analysis to reflect the low probability of occurrence in a specific SURTASS LFA sonar model area. Further, the Navy pooled density estimates for species of the same genus if sufficient data were not available to compute a density for individual species or the species are difficult to distinguish at sea, which is often the case for beaked whales (

e.g., Mesoplodon

spp.), as well as the pygmy and dwarf sperm whales (

Kogia

spp.). Density estimates are available for species groups rather than the individual species for

Kogia

spp. in model areas 1, 2, 3, 5, 6, and 7 and for

Mesoplodon

spp. in model area 8, as the best available data (Ferguson and Barlow, 2001 and 2003) were reported as pooled data.

The Navy provides detailed descriptions of the distribution, abundance, diving behavior, life history, and hearing vocalization information for each affected marine mammal species with confirmed or possible occurrence within SURTASS LFA sonar study areas in section 4 (pages 4-1 through 4-44) of the application, which is available online at

https://www.fisheries.noaa .gov/national/marine-mammal-protection/incidental-take-authorizations-military-readiness-activities.

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

https://www.fisheries.noaa .gov/national/marine-mammal-protection/marine-mammal-stock-assessments.

NMFS refers the public to Table 3-2 (pages 3-6 through 3-25) of the Navy's application for literature references associated with abundance and density estimates presented in these tables.

Brief Background on Sound, Marine Mammal Hearing, and Vocalization

Underwater Sound

An understanding of the basic properties of underwater sound is necessary to comprehend many of the concepts and analyses presented in this document. Sound travels in waves, the basic components of which are frequency, wavelength, velocity, and amplitude. Sound frequency is measured in cycles per second, referred to as Hertz (Hz), and is analogous to musical pitch; high-pitched sounds contain high frequencies and low-pitched sounds contain low frequencies. Frequency, or the “pitch” of a sound, is the number of pressure waves that pass by a reference point per unit of time and is measured in Hz or cycles per second. Wavelength is the distance between two peaks or corresponding points of a sound wave (length of one cycle). Higher frequency sounds have shorter wavelengths than lower frequency sounds, and typically attenuate (decrease) more rapidly, except in certain cases in shallower water. Amplitude is the height of the sound pressure wave or the “loudness” of a sound and is typically described using the relative unit of the dB. A sound pressure level (SPL) in dB is described as the ratio between a measured pressure and a reference pressure (for underwater sound, this is 1 microPascal (μPa)) and is a logarithmic unit that accounts for large variations in amplitude; therefore, a relatively small change in dB corresponds to large changes in sound pressure. The source level (SL) represents the SPL referenced at a distance of 1 m from the source (referenced to 1 μPa), while the received level is the SPL at the listener's position (referenced to 1 μPa).

Natural sounds in the ocean span a large range of frequencies: From earthquake noise at five Hz to harbor porpoise clicks at 150,000 Hz (150 kilohertz (kHz)). These sounds are so low or so high in pitch that humans cannot even hear them; acousticians call these infrasonic (typically below 20 Hz, which is considered the low frequency bound of human hearing) and ultrasonic (typically above 20,000 Hz, which is considered the upper bound of human hearing) sounds, respectively. A single sound may be made up of multiple frequencies. Sounds made up of only a small range of frequencies are called narrowband, and sounds with a broad range of frequencies are called broadband. Explosives are an example of a broadband sound source and tactical military sonars are an example of a narrowband sound source.

When underwater objects vibrate or activity occurs, sound-pressure waves are created. These waves alternately compress and decompress the water as the sound wave travels. Underwater sound waves radiate in a manner similar to ripples on the surface of a pond and may be either directed in a beam or beams or may radiate in all directions (omnidirectional sources), as is the case for sound produced by LFA sonar. The compressions and decompressions associated with sound waves are detected as changes in pressure by aquatic life and man-made sound receptors such as hydrophones.

Sounds are often considered to fall into one of two general types: Impulsive and non-impulsive (described below). The distinction between these two sound types is important because they have differing potential to cause physical effects, particularly with regard to hearing (

e.g.,

Ward, 1997 in Southall

et al.,

2007). Please see Southall

et al.

(2007) for an in-depth discussion of these concepts. The distinction between these two sound types is not always obvious, as certain signals share properties of both pulsed and non-pulsed sounds. A signal near a source could be categorized as a pulse, but due to propagation effects as it moves farther from the source, the signal duration becomes longer (

e.g.,

Greene and Richardson, 1988).

Impulsive sound sources (

e.g.,

airguns, explosions, gunshots, sonic booms, impact pile driving) produce signals that are brief (typically considered to be less than one second), broadband, atonal transients (ANSI, 1986, 2005; Harris, 1998; NIOSH, 1998; ISO, 2003) and occur either as isolated events or repeated in some succession. Impulsive sounds are all characterized by a relatively rapid rise from ambient pressure to a maximal pressure value followed by a rapid decay period that may include a period of diminishing, oscillating maximal and minimal pressures, and generally have an increased capacity to induce physical injury as compared with sounds that lack these features.

Non-impulsive sounds can be tonal, narrowband, or broadband, brief or prolonged, and may be either continuous or intermittent (ANSI, 1995; NIOSH, 1998). Some of these non-impulsive sounds can be transient signals of short duration but without the essential properties of pulses (

e.g.,

rapid rise time). Examples of non-impulsive sounds include those produced by vessels, aircraft, machinery operations such as drilling or dredging, and vibratory pile driving. The duration of such sounds, as received at a distance,

can be greatly extended in a highly reverberant environment. Given the non-pulsed nature of the LFA sonar source, it is appropriate to consider it a non-impulsive source for estimation of permanent and temporary threshold shifts (PTS and TTS, respectively). The Navy derived the potential for Level B harassment directly from data obtained during experiments exposing marine mammals (mysticetes) to low frequency sonar. Refer to the “Estimated Take” section for more information regarding the estimation of take by harassment.

Metrics Used in This Document

This section includes a brief explanation of the sound measurement metrics frequently used in the discussions of acoustic effects in this document.

Sound Pressure Level

Sound pressure level (SPL) is expressed as the ratio of a measured sound pressure and a reference level. The commonly used reference pressure level in underwater acoustics is 1 μPa, and the units for SPLs are decibels (dB) re: 1 μPa. SPL (in dB) = 20 log (pressure/reference pressure). SPL is an instantaneous measurement and can be expressed as the peak (pk), the peak-peak (p-p), or the root mean square (RMS). SPL does not directly take the duration of exposure to a sound into account, though the duration over which the root mean square pressure is averaged should be noted since it influences the result. Root mean square pressure, which is the square root of the arithmetic average of the squared instantaneous pressure values (Urick, 1983), is typically used in discussions of behavioral effects of sounds on vertebrates in part because behavioral effects, which often result from auditory cues, may be better expressed through averaged units than by peak pressures. SPL

is applicable to impulsive, or pulsed, noise (such as airguns, explosions, gunshots, sonic booms, and impact pile driving); as such it is not applicable to SURTASS LFA sonar and therefore is not used for estimation of PTS (Level A harassment) in this rulemaking. All references to SPL in this document refer to the RMS unless otherwise noted. In addition, the Navy uses a Single Ping Equivalent (SPE) metric for the estimation of Level B harassment, as described below.

Cumulative Sound Exposure Level

Sound exposure level (SEL; represented as dB re 1 μPa

-s) represents the total energy contained within a pulse, and considers both exposure level and duration of exposure.

To assess potential for auditory injury of marine mammals from sound exposure, NMFS' 2018 Revision to Technical Guidance for Assessing the Effects of Anthropogenic Sound on Marine Mammal Hearing (Acoustic Technical Guidance) identifies specific injury thresholds for impulsive and non-impulsive sources, and divides marine mammals into hearing groups based on measured or estimated generalized hearing ranges. The Acoustic Technical Guidance uses a dual metric approach for impulsive sounds (

i.e.,

peak SPL (SPL

) and cumulative SEL (SEL

cum

)), but since SURTASS LFA sonar is a non-impulsive source, only the cumulative SEL

cum

metric is used to account for the total energy received over the specified duration of sound exposure (

i.e.,

the metric accounts for both received level and duration of exposure) (Southall

et al.,

2007; NMFS, 2018). NMFS' Acoustic Technical Guidance builds upon the foundation provided by Southall

et al.

(2007), while incorporating updated information that since became available on marine mammal hearing and impacts of noise on hearing (

e.g.,

DoN, 2017). NMFS (2018) recommends 24 hours as the default maximum accumulation period relative to SEL

cum

thresholds.

Note that NMFS' SEL

cum

acoustic thresholds also incorporate marine mammal auditory weighting functions, which take into account what is known about marine mammal hearing sensitivity and susceptibility to noise-induced hearing loss, and can be applied to a sound-level measurement to account for frequency-dependent hearing (NMFS, 2018). See Houser (2017) for a review of the development of auditory weighting functions for marine mammals. For further discussion of auditory weighting functions and their application or metrics associated with evaluating noise-induced hearing loss, see also NMFS (2018).

Table 17 displays auditory impact thresholds for onset of temporary and permanent threshold shifts (TTS and PTS, respectively) in hearing (from NMFS (2018)).

Table 17—TTS and PTS Onset Thresholds for Non-Impulsive Sounds

Hearing group

Cumulative

sound exposure

level for TTS

(dB)

Cumulative

sound exposure

level for PTS

(dB)

Low-frequency cetaceans

179

199

Mid-frequency cetaceans

178

198

High-frequency cetaceans

153

173

Phoicid pinnipeds (PW) (Underwater)

181

201

Otariid pinnipeds (OW) (Underwater)

199

219

Referenced to 1 μPa

s; weighted according to appropriate auditory weighting function.

Single Ping Equivalent (SPE)

To model potential behavioral impacts to marine animals from exposure to SURTASS LFA sonar sound, the Navy has developed a methodology to estimate the total exposure of modeled animals exposed to multiple pings over an extended period of time. The Navy's acoustic model analyzes the following components: (1) The LFA sonar source modeled as a point source, with an effective source level (SL) of approximately 240 dB re: 1 μPa at 1 m (SPL); (2) a 60-sec duration signal; and (3) a beam pattern that is correct for the number and spacing of the individual projectors (source elements). This source model, when combined with the three-dimensional transmission loss (TL) field generated by the Parabolic Equation (PE) acoustic propagation model, defines the received level (RL) (in SPL) sound field surrounding the source for a 60-sec LFA sonar signal (

i.e.,

the SPE metric accounts for received level and exposure from multiple pings). To estimate the total exposure of animals exposed to multiple pings, the Navy models the RLs for each modeled location and any computer-simulated marine mammals (animats) within the location, records the exposure history of each animat, and generates a SPE value. Thus, the Navy can model the SURTASS LFA sound

field, providing a four-dimensional (position and time) representation of a sound pressure field within the marine environment and estimates of an animal's exposure to sound over a period of 24 hours.

Figure 2 shows the Navy calculation that converts SPL values to SPE values in order to estimate impacts to marine mammals from SURTASS LFA sonar transmissions. For a more detailed explanation of the SPE calculations, NMFS refers the public to Appendix B of the SURTASS 2018 DSEIS/SOEIS.

EP01MR19.001

Marine Mammal Hearing

Hearing is the most important sensory modality for marine mammals underwater, and exposure to anthropogenic sound can have deleterious effects. To appropriately assess the potential effects of exposure to sound, it is necessary to understand the frequency ranges marine mammals are able to hear. Current data indicate that not all marine mammal species have equal hearing capabilities (

e.g.,

Richardson

et al.,

1995; Wartzok and Ketten, 1999; Au and Hastings, 2008). To reflect this, Southall

et al.

(2007) recommended that marine mammals be divided into functional hearing groups based on directly measured or estimated hearing ranges on the basis of available behavioral response data, audiograms derived using auditory evoked potential techniques, anatomical modeling, and other data. Note that no direct measurements of hearing ability have been successfully completed for mysticetes (

i.e.,

low-frequency cetaceans).

Subsequently, NMFS (2018) described generalized hearing ranges for these marine mammal hearing groups. Generalized hearing ranges were chosen based on the approximately 65 dB threshold from the normalized composite audiograms, with an exception for lower limits for low-frequency cetaceans where the result was deemed to be biologically implausible, and the lower bound from Southall

et al.

(2007) was retained while the lower frequency range for phocid pinnipeds was approximated. The generalized hearing groups and the associated frequencies are indicated below (note that these frequency ranges correspond to the range for the composite group, with the entire range not necessarily reflecting the capabilities of every species within that group):

• Low-frequency (LF) cetaceans (mysticetes): Generalized hearing is estimated to occur between approximately 7 Hz and 35 kHz;

• Mid-frequency (MF) cetaceans (larger toothed whales, beaked whales, and most delphinids): Generalized hearing is estimated to occur between approximately 150 Hz and 160 kHz;

• High-frequency (HF) cetaceans (porpoises, river dolphins, and members of the genera

Kogia

and

Cephalorhynchus

; including two members of the genus

Lagenorhynchus,

on the basis of recent echolocation data and genetic data): Generalized hearing is estimated to occur between approximately 275 Hz and 160 kHz;

• Pinnipeds in water; Phocidae (true seals): Generalized hearing is estimated to occur between approximately 50 Hz to 86 kHz;

• Pinnipeds in water; Otariidae (eared seals): Generalized hearing is estimated to occur between 60 Hz and 39 kHz for Otariidae.

Marine Mammal Hearing Groups and LFA Sonar

Baleen (mysticete) whales (members of the LF hearing group) have inner ears that appear to be specialized for low-frequency hearing. Conversely, most odontocetes (

i.e.,

dolphins and porpoises) have inner ears that are specialized to hear mid and high frequencies. Pinnipeds, which lack the highly specialized active biosonar systems of odontocetes, have inner ears that are specialized to hear a broad range of frequencies in water (Southall

et al.,

2007 and NMFS, 2018). Based on measured hearing thresholds, the LFA sound source is below the range of known highest hearing sensitivity for MF and HF odontocetes and pinnipeds in water (Au, 1993; Au and Hastings, 2008; Gentry, 2009; Hall and Johnson, 1972; Houser

et al.,

2008; Kastelein

et al.,

2009, 2005, 2003, and 2002; Montie

et al.,

2011; Mooney

et al.,

2015; Mulsow and Reichmuth, 2010; Nedwell

et al.,

2004; Richardson

et al.,

1995; Ridgeway and Carder, 2001; Pacini

et al.,

2011; Schlundt

et al.,

2011; Sills

et al.,

2014; Southall

et al.,

2007; Szymanski

et al.,

1999; Thomas

et al.,

1990; Yuen

et al.,

2005).

Marine Mammal Vocalization

Marine mammal vocalizations often extend both above and below the range of human hearing (higher than 20 kHz and lower than 20 Hz; Research Council, 2003). Measured data on the hearing abilities of cetaceans are sparse or non-existent, particularly for the larger cetaceans such as the baleen whales (mysticetes). 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 and those of conspecifics (

i.e.,

an organism of the same or similar species). Comparisons of the anatomy of cetacean inner ears and models of the structural properties and the response to vibrations of the ear's components in different species provide an indication of likely sensitivity to various sound frequencies. Thus, the ears of small toothed whales are optimized for receiving high-frequency sound, while baleen whale inner ears are best suited for low frequencies, including to infrasonic frequencies (Ketten, 1992; 1994; 1997; 1998).

Baleen whale (

i.e.,

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

et al.,

1987; Richardson

et al.,

1995; Rivers, 1997;

Moore

et al.,

1998; Stafford

et al.,

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

et al.,

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

Toothed whales (

i.e.,

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

i.e.,

odontocetes) social vocalizations is concentrated near 10 kHz, with source levels for whistles as high as 100-180 dB re 1 μPa at 1 m (Richardson

et al.,

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

et al.,

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

et al.,

2000).

Potential Effects of the Specified Activity on Marine Mammals and Their Habitat

This section includes a summary and discussion of the ways that components of the specified activities (

e.g.,

use of acoustic sources) may impact marine mammals and their habitat. The “Estimated Take” section later in this document includes a quantitative analysis of the number of individuals that are expected to be taken by this activity. The “Negligible Impact Analysis and Determination” section considers the content of this section and the material it references, the “Estimated Take” section, and the “Proposed Mitigation” section to draw conclusions regarding the likely impacts of these activities on the reproductive success or survivorship of individuals and how those impacts on individuals are likely to impact marine mammal species or stocks.

The Navy has requested authorization for the incidental take of marine mammals that may result from upcoming use of SURTASS LFA sonar during training and testing activities on U.S. Naval ships in certain areas of the central and western North Pacific Ocean and eastern Indian Ocean. In addition to the use of LFA and HF/M3 sonar, the Navy has analyzed the potential impact of ship strike to marine mammals from SURTASS LFA sonar activities and, in consultation with NMFS as a cooperating agency for the SURTASS LFA sonar 2018 DSEIS/SOEIS, has determined that take of marine mammals incidental to this non-acoustic component of the Navy's training and testing activities is not reasonably likely to occur. This is due to the low speed at which the SURTASS LFA sonar vessels test and train (10 to 12 knots (kt)) and the suite of mitigation and monitoring efforts employed, including a three-pronged monitoring effort that involves visual and passive acoustic monitoring for marine mammals as well as use of the HF/M3 sonar (please see the Proposed Mitigation section below for more detail), which has been shown to be highly effective at detecting marine mammals. The Navy has not requested authorization for take of marine mammals that might occur incidental to vessel ship strike. In this document, NMFS analyzes the potential effects on marine mammals from exposure to LFA and HF/M3 sonar, but also includes some additional analysis of the potential impacts from vessel operations.

Overview of Potential Effects of Exposure to SURTASS LFA Sonar Activities

The potential effects of sound from the proposed SURTASS LFA sonar training and testing activities might include one or more of the following: Behavioral changes, masking, non-auditory injury (

i.e.,

gas bubble formation/rectified diffusion), and noise-induced loss of hearing sensitivity (more commonly called threshold shift). NMFS discusses these potential effects in more detail below.

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

et al.,

1995; Nowacek

et al.,

2007; Southall

et al.,

2007):

(1) The noise may be too weak to be heard at the location of the animal (

i.e.,

lower than the prevailing ambient noise level, the hearing threshold of the animal at relevant frequencies, or both);

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

(3) The noise may elicit behavioral reactions of variable conspicuousness and relevance to the well-being of the animal. These can range from temporary alert responses to active avoidance reactions such as vacating an area at least until the noise event ceases, but potentially for longer periods of time. Depending on the nature and duration of these the disturbances, they could have effects on the well-being or reproduction of the animals involved;

(4) Upon repeated exposure, a marine mammal may exhibit diminishing responsiveness (habituation), disturbance effects may persist, or disturbance effects could increase (sensitization, or becoming more sensitive to exposure). Persistent disturbance and sensitization are more likely with sounds that are highly variable in characteristics, infrequent, and unpredictable in occurrence, and associated with situations that the animal perceives as a threat. Marine mammals are not likely to be exposed enough to SURTASS LFA sonar to exhibit habituation or increased sensitization, due to the fact that SURTASS LFA sonar is a mobile source

operating in open water, and animals are likely to move away and/or would not be receiving pings in the way that small resident populations would receive with a stationary source;

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

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

(7) Very strong sounds have the potential to cause temporary or permanent reduction in hearing sensitivity, also known as threshold shift. In terrestrial mammals and presumably marine mammals, received sound levels must far exceed the animal's hearing threshold for there to be any temporary threshold shift (TTS) in its hearing ability. For transient sounds, the sound level necessary to cause TTS is inversely related to the duration of the sound. Received sound levels must be even higher for there to be the possibility of permanent hearing impairment. In addition, intense acoustic events may cause trauma to tissues associated with organs vital for hearing, sound production, respiration and other functions. This trauma may include minor to severe hemorrhage.

Direct Physiological Effects

Below we discuss the potential direct physiological effects of exposure to SURTASS LFA sonar, which include threshold shift (permanent and temporary) and acoustically mediated bubble growth.

Threshold Shift (Noise-Induced Loss of Hearing in Certain Frequencies)

When animals exhibit reduced hearing sensitivity within their auditory range (

i.e.,

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

i.e.,

there is recovery back to baseline/pre-exposure levels), can occur within a specific frequency range (

i.e.,

an animal might only have a temporary loss of hearing sensitivity within a limited frequency band of its auditory range), and can be of varying amounts (for example, an animal's hearing sensitivity might be reduced by only six dB or reduced by 30 dB). PTS is permanent (

i.e.,

there is incomplete recovery back to baseline/pre-exposure levels), but also can occur in a specific frequency range and amount as mentioned above for TTS.

The following physiological mechanisms are thought to play a role in inducing auditory 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. Generally, the amount of TS, and the time needed to recover from the effect, increase as amplitude and duration of sound exposure increases. Human non-impulsive noise exposure guidelines are based on the assumption that exposures of equal energy (the same SEL) produce equal amounts of hearing impairment regardless of how the sound energy is distributed in time (NIOSH, 1998). Previous marine mammal TTS studies have also generally supported this equal energy relationship (Southall

et al.,

2007). However, some more recent studies concluded that for all noise exposure situations the equal energy relationship may not be the best indicator to predict TTS onset levels (Mooney

et al.,

2009a and 2009b; Kastak

et al.,

2007). These studies highlight the inherent complexity of predicting TTS onset in marine mammals, as well as the importance of considering exposure duration when assessing potential impacts. Generally, with sound exposures of equal energy, those that were quieter (lower sound pressure level (SPL)) with longer duration were found to induce TTS onset at lower levels than those of louder (higher SPL) and shorter duration. Less TS will occur from intermittent sounds than from a continuous exposure with the same energy (some recovery can occur between intermittent exposures) (Kryter

et al.,

1966; Ward, 1997; Mooney

et al.,

2009a, 2009b; Finneran

et al.,

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

et al.,

1987). However, in the case of the proposed SURTASS LFA sonar activities, animals are not expected to be exposed to levels high enough or durations long enough to result in PTS due to the nature of the activities. The potential for PTS becomes even more unlikely when mitigation measures are considered. 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. The NMFS 2018 Acoustic Technical Guidance, which was used in the assessment of effects for this action, compiled, interpreted, and synthesized the best available scientific information for noise-induced hearing effects for marine mammals to derive updated thresholds for assessing the impacts of noise on marine mammal hearing, as noted above. For cetaceans, published data on the onset of TTS are limited to the captive bottlenose dolphin, beluga, harbor porpoise, and Yangtze finless porpoise (summarized in DoN, 2017). TTS studies involving exposure to SURTASS LFA or other low-frequency sonar (below 1 kHz) have never been conducted due to logistical difficulties of conducting experiments with low frequency sound sources. However, there are TTS measurements for exposures to other LF sources, such as seismic airguns. Finneran

et al.

(2015) suggest that the potential for airguns to cause hearing loss in dolphins is lower than previously predicted, perhaps as a result of the low-frequency content of airgun impulses compared to the high-

frequency hearing ability of dolphins. For pinnipeds in water, measurements of TTS are limited to harbor seals, elephant seals, and California sea lions (summarized in Finneran, 2015).

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

i.e.,

recovery time), and frequency range of TTS, and the context in which it is experienced, TTS can have effects on marine mammals ranging from discountable to serious, similar to those discussed in auditory masking, below. Available data (of mid-frequency hearing specialists exposed to mid- or high-frequency sounds; Southall

et al.,

2007) suggest that most TTS occurs in the frequency range of the source up to one octave higher than the source (with the maximum TTS at

1/2

octave above). The Navy's SURTASS LFA source utilizes the 100-500 Hz frequency band, which suggests that if TTS were to be induced it would be in a frequency band somewhere between approximately 200 Hz and 1 kHz (but likely more in the middle of that range), which is in the range of most communication calls for mysticetes, some for pinnipeds, but below the range of most communication calls for odontocetes. While there are some broadband clicks in this range, most echolocation calls used by odontocetes for foraging are also below this frequency. Also, a marine mammal may be able to readily compensate for a brief, relatively small amount of TTS in a non-critical frequency range that takes place during a time when the animal is traveling through the open ocean, where ambient noise is lower and there are not as many competing sounds present. Alternatively, a larger amount and longer duration of TTS sustained during a time when communication is critical for successful mother/calf interactions could have more serious impacts if it were in the same frequency band as the necessary vocalizations and of a severity that impeded communication. The fact that animals exposed to high levels of sound that would be expected to result in this physiological response would also be expected to have behavioral responses of a comparatively more severe or sustained nature is potentially more significant than simple existence of a TTS. However, it is important to note that TTS can result from longer exposures to sound at lower levels where a behavioral response may not be elicited.

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

et al.,

2007), so we can infer that strategies exist for coping with this condition to some degree, though likely not without some cost to the animal. There is no empirical evidence that exposure to SURTASS LFA sonar can cause PTS in any marine mammals, especially given the proximity to and duration that an animal would need to be exposed; instead the possibility of PTS has been inferred from studies of TTS on captive marine mammals.

As stated in the SURTASS DSEIS/SOEIS (section 4.5.2.1.3), modeling results show that all hearing groups except LF cetaceans would need to be within 22 feet (ft) (7 meters (m)) for an entire LFA transmission (60 seconds) to potentially experience PTS. A LF cetacean would need to be within 135 ft (41 m) for an entire LFA transmission to potentially experience PTS. Based on the mitigation procedures used during SURTASS LFA sonar activities, and the fact that animals reasonably can be expected to move away from disturbances, the chances of this occurring are negligible. This conclusion is supported by the fact that a marine mammal would have to match its swim speed with that of the SURTASS LFA sonar vessel while also remaining undetected by the HF/M3 mitigation system as it moved through the 2,000-yard LFA Mitigation Zone, and remain close to the source for a 60-second ping.

Acoustically Mediated Bubble Growth

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

e.g.,

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

et al.,

2001b). A study of repetitive diving in trained bottlenose dolphins found no increase in blood nitrogen levels or formation of bubbles (Houser

et al.,

2009). If rectified diffusion were possible in marine mammals exposed to high-level sound, conditions of tissue supersaturation could theoretically speed the rate and increase the size of bubble growth. Subsequent effects due to tissue trauma and emboli would presumably mirror those observed in humans suffering from decompression sickness.

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

ex vivo

supersaturated bovine tissues suggests that, for a 37 kHz signal, a sound exposure of approximately 215 dB re 1µPa would be required before microbubbles became destabilized and grew (Crum

et al.,

2005). Furthermore, tissues in the study were supersaturated by exposing them to pressures of 400-700 kiloPascals for periods of hours and then releasing them to ambient pressures. Assuming the equilibration of gases with the tissues occurred when the tissues were exposed to high pressures, levels of supersaturation in the tissues could have been as high as 400-700 percent. These levels of tissue supersaturation are substantially higher than model predictions for marine mammals (Houser

et al.,

2001; Saunders

et al.,

2008). Both the degree of supersaturation and exposure levels observed to cause microbubble destabilization are unlikely to occur, either alone or in concert.

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

et al.,

2003; Fernandez

et al.,

2005; Fernandez

et al.,

2012). In this scenario, the rate of ascent would need to be sufficiently rapid to compromise behavioral or physiological protections against nitrogen bubble formation. Alternatively, Tyack

et al.

(2006) studied the deep diving behavior of beaked whales and concluded that: “Using current models of breath-hold diving, we infer that their natural diving behavior is inconsistent with known problems of acute nitrogen

supersaturation and embolism.” Collectively, these hypotheses (rectified diffusion and decompression sickness) can be referred to as “hypotheses of acoustically-mediated bubble growth.”

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

et al.,

2006; Rommel

et al.,

2006). Crum and Mao (1996) hypothesized that received levels would have to exceed 190 dB in order for there to be the possibility of significant bubble growth due to supersaturation of gases in the blood (

i.e.,

rectified diffusion). Work conducted by Crum

et al.

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

et al.

(2007) and Southall

et al.

(2007) reviewed potential types of non-auditory injury to marine mammals from active sonar transmissions, including acoustically mediated bubble growth within tissues from supersaturated dissolved nitrogen gas. Detailed descriptions and information on these types of non-auditory impacts were provided in previous documentation for SURTASS LFA sonar (DoN, 2007, 2012, 2017), and no new data have emerged to contradict any of the assumptions or conclusions in previous LFA documentation, especially the conclusion that SURTASS LFA sonar transmissions are not expected to cause gas bubble formation or strandings. Although it has been argued that traumas from some beaked whale strandings are consistent with gas emboli and bubble-induced tissue separations (Jepson

et al.,

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

et al.,

2006). However, Jepson

et al.

(2003, 2005) and Fernandez

et al.

(2004, 2005, 2012) concluded that in vivo bubble formation, which may be exacerbated by deep, long-duration, repetitive dives, may explain why beaked whales appear to be particularly vulnerable to MF and HF active sonar exposures. This has not been demonstrated for LF sonar exposures, such as SURTASS LFA sonar.

In 2009, Hooker

et al.

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

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

levels and thereby decompression sickness risk between species.

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

et al.,

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

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

than body mass differences between species. Despite diel changes (

i.e.,

variation that occurs regularly every day or most days) in dive behavior, P

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

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

et al.,

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

et al.,

2009).

Bernaldo de Quiros

et al.

(2012) showed that, among evaluated stranded whales, deep diving species of whales had higher abundances of gas bubbles compared to shallow diving species. Kvadsheim

et al.

(2012) estimated blood and tissue P

levels in species representing shallow, intermediate, deep diving cetaceans following behavioral responses to sonar and their comparisons found that deep diving species had higher end-dive blood and tissue N

levels, indicating a higher risk of developing gas bubble emboli compared with shallow diving species. Fahlmann

et al.

(2014) evaluated dive data recorded from sperm, killer, long-finned pilot, Blainville's beaked and Cuvier's beaked whales before and during exposure to low (1-2 kHz) and mid (2-7 kHz) frequency active sonar in an attempt to determine if either differences in dive behavior or physiological responses to sonar are plausible risk factors for bubble formation. Note that SURTASS LFA sonar is transmitted between 100-500 Hz, which is well below the low frequency sonar in these studies. The authors suggested that CO

may initiate bubble formation and growth, while elevated levels of N

may be important for continued bubble growth. The authors also suggest that if CO

plays an important role in bubble formation, a cetacean escaping a sound source may experience increased metabolic rate, CO

production, and alteration in cardiac output, which could increase risk of gas bubble emboli. However, as discussed in Kvadsheim

et al.

(2012), the actual observed behavioral responses to sonar from the species in their study (sperm, killer, long-finned pilot, Blainville's beaked, and Cuvier's beaked whales) did not imply any significantly increased risk of decompression sickness due to high levels of N

Therefore, further information is needed to understand the relationship between exposure to stimuli, behavioral response (discussed in more detail below), elevated N

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

et al.,

2006; Southall

et al.,

2007; Zimmer and Tyack, 2007; Baird

et al.,

2008; Hooker

et al.,

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

To summarize, there are few data related to the potential for strong, anthropogenic underwater sounds to cause non-auditory physical effects in marine mammals. Such effects, if they occur at all, would presumably be limited to situations where marine mammals were exposed to high powered sounds at close range over a prolonged period of time. The available data do not allow identification of a specific exposure level above which non-auditory effects can be expected (Southall

et al.,

2007) or any meaningful quantitative predictions of the numbers (if any) of marine mammals that might be affected in those ways. However, as noted above, non-auditory physical effects are not likely to result from the use of SURTASS LFA sonar because of the required mitigation and unlikelihood of marine mammals being exposed to high powered sounds at close range.

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 other sounds in the environment are of a similar frequency and are louder than auditory signals an animal is trying to receive. Masking is a phenomenon that affects animals 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 disrupt the behavior of individual animals, groups of animals, or, when over large spatial and temporal scales, entire populations.

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

Richardson

et al.

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

i.e.,

surf noise, prey noise, etc.) (Richardson

et al.,

1995).

Erbe

et al.

(2016) reviewed the current state of understanding of masking in marine mammals, including anti-masking strategies for both receivers and senders. When a signal and noise are received from different directions, a receiver with directional hearing can reduce the masking impact. This is known as spatial release from masking, and this ability has been found in dolphins, killer whales and harbor seals. Given the hearing abilities of marine mammals, it is likely that most, if not all, species have this ability to some extent.

The echolocation calls of toothed whales are subject to masking by high-frequency sound. Human data indicate that low-frequency sounds can mask high-frequency sounds (

i.e.,

upward masking). Studies on captive odontocetes by Au

et al.

(1974, 1985, and 1993) indicate that some species may use various processes to reduce masking effects (

e.g.,

adjustments in echolocation call intensity or frequency as a function of background noise conditions). There is also evidence that the directional hearing abilities of odontocetes are useful in reducing masking at the higher frequencies these cetaceans use to echolocate, but not at the low-to-moderate frequencies they use to communicate (Zaitseva

et al.,

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

et al.

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

et al.,

2005).

Parks

et al.

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

Risch

et al.

(2012) documented reductions in humpback whale vocalizations in the Stellwagen Bank National Marine Sanctuary concurrent with transmissions of the Ocean Acoustic Waveguide Remote Sensing (OAWRS) low-frequency fish sensor system at distances of 200 km (124 mi) from the source. The recorded OAWRS produced a series of frequency-modulated pulses and the signal received levels ranged from 88 to 110 dB re: 1 μPa (Risch

et al.,

2012). The authors hypothesized that individuals did not leave the area but instead ceased singing and noted that the duration and frequency range of the OAWRS signals (a novel sound to the whales) were similar to those of natural humpback whale song components used during mating (Risch

et al.,

2012). Thus, the novelty of the sound to humpback whales in the study area provided a compelling contextual probability for the observed effects (Risch

et al.,

2012). However, the authors did not state or imply that these changes had long-term effects on individual animals or populations (Risch

et al.,

2012). Gong

et al.,

(2014) assessed the effects of the OAWRS transmissions on calling rates on Georges Bank and determined constant vocalization rates of humpback whales, with a reduction occurring before the OAWRS system began transmitting. Risch

et al.

(2014) pointed out that the results of Risch

et al.

(2012) and Gong

et al.

(2014) are not contradictory, but rather highlight the principal point of their original paper that behavioral responses depend on many factors, including range to source, RL above background noise level, novelty of signal, and differences in behavioral state.

Redundancy and context can also facilitate detection of weak signals. These phenomena may help marine mammals detect weak sounds in the presence of natural or manmade noise. Most masking studies in marine mammals present the test signal and the masking noise from the same direction. The sound localization abilities of marine mammals suggest that, if signal and noise come from different directions, masking would not be as severe as some masking studies might suggest (Richardson

et al.,

1995). The dominant background noise may be highly directional if it comes from a particular anthropogenic source such as a ship or industrial site. Directional hearing may significantly reduce the masking effects of these sounds by improving the effective signal-to-noise ratio.

As mentioned previously, the hearing ranges of mysticetes overlap with the frequencies of the SURTASS LFA sonar sources. The closer the characteristics of the masking signal to the signal of interest, the more likely masking is to occur. The Navy provided an analysis of marine mammal hearing and masking in Subchapter 4.5.2.1.3 of the DSEIS/

SOEIS, and the masking effects of the SURTASS LFA sonar signal are expected to be limited for a number of reasons. First, the frequency range (bandwidth) of the system is limited to approximately 30 Hz, and the instantaneous bandwidth at any given time of the signal is small, on the order of 10 Hz. Second, the average duty cycle is always less than 20 percent and, based on past SURTASS LFA sonar operational parameters (2003 to 2018), is normally 7.5 to 10 percent. Third, given the average maximum pulse length (60 sec), and the fact that the signals vary and do not remain at a single frequency for more than 10 sec, SURTASS LFA sonar is not likely to cause significant masking. In other words, the LFA sonar transmissions are coherent, narrow bandwidth signals of six to 100 sec in length followed by a quiet period of six to 15 minutes. Therefore, the effect of masking will be limited because animals that use this frequency range typically use broader bandwidth signals. As a result, the chances of an LFA sonar sound actually overlapping whale calls at levels that would interfere with their detection and recognition will be extremely low.

Impaired Communication

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

et al.,

2004; Lohr

et al.,

2003). Animals are also aware of environmental conditions that affect whether listeners can discriminate and recognize their vocalizations apart 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 species that vocalize are able to adapt by adjusting 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, impairing communications between animals. Most animals that vocalize have evolved strategies to compensate for the effects of short-term or temporary increases in background or ambient noise on their songs or calls. Although the fitness consequences of these vocal adjustments are not directly known in all instances, like most other trade-offs animals must make, some of these strategies probably come at a cost (Patricelli

et al.,

2006). Shifting songs and calls to higher frequencies may also impose energetic costs (Lambrechts, 1996). For example in birds, 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).

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 sometimes 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.

According to Moberg (2000), in the case of many stressors, an animal's first and most economical (in terms of biotic costs) response is behavioral avoidance of the potential stressor or avoidance of continued exposure to a stressor. An animal's second line of defense to stressors involves the sympathetic part of the autonomic nervous system and the classical “fight or flight” response which includes the cardiovascular system, the gastrointestinal system, the exocrine glands, and the adrenal medulla to produce changes in heart rate, blood pressure, and gastrointestinal activity that humans commonly associate with “stress.” These responses have a relatively short duration and may or may not have significant long-term effect on an animal's welfare.

An animal's third line of defense to stressors involves its neuroendocrine or sympathetic nervous systems; the system that has received the most study has been the hypothalmus-pituitary-adrenal system (also known as the HPA axis in mammals or the hypothalamus-pituitary-interrenal axis in fish and some reptiles). Unlike stress responses associated with the autonomic nervous system, virtually all neuro-endocrine functions that are affected by stress—including immune competence, reproduction, metabolism, and behavior—are regulated by pituitary hormones. Stress-induced changes in the secretion of pituitary hormones have been implicated in failed reproduction (Moberg, 1987; Rivier and Rivest, 1991), altered metabolism (Elasser

et al.,

2000), reduced immune competence (Blecha, 2000), and behavioral disturbance (Moberg, 1987; Blecha, 2000). Increases in the circulation of glucocorticosteroids (cortisol, corticosterone, and aldosterone in marine mammals; see Romano

et al.,

2004) have been equated with stress for many years.

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

Relationships between these physiological mechanisms, animal behavior, and the costs of stress responses have also been documented fairly well through controlled experiments; because this physiology exists in every vertebrate that has been studied, it is not surprising that stress

responses and their costs have been documented in both laboratory and free-living animals (for examples see, Holberton

et al.,

1996; Hood

et al.,

1998; Jessop

et al.,

2003; Krausman

et al.,

2004; Lankford

et al.,

2005; Thompson and Hamer, 2000).

There is limited information on the physiological responses of marine mammals to anthropogenic sound exposure, as most observations have been limited to short-term behavioral responses, which included cessation of feeding, resting, or social interactions. Information has been collected on the physiological responses of marine mammals to anthropogenic sounds (Fair and Becker, 2000; Romano

et al.,

2002; Wright

et al.,

2008), and various efforts have been undertaken to investigate the impact from vessels including whale watching vessels as well as general vessel traffic noise (Bain, 2002; Erbe, 2002; Noren

et al.,

2009; Williams

et al.,

2006, 2009, 2014a, 2014b; Read

et al.,

2014; Rolland

et al.,

2012; Pirotta

et al.,

2015). This body of research for the most part has investigated impacts associated with the presence of chronic stressors (

e.g.,

whale watch vessels), which differ significantly from the proposed Navy SURTASS LFA sonar activities. For example, in the analysis of energy costs to killer whales, Williams

et al.

(2009) suggested that whale-watching in Canada's Johnstone Strait resulted in lost feeding opportunities due to vessel disturbance, which could carry higher costs than other measures of behavioral change might suggest. Ayres

et al.

(2012) reported on research in the Salish Sea (state of Washington) involving the measurement of southern resident killer whale fecal hormones to assess two potential threats to the species recovery: Lack of prey (salmon) and impacts to behavior from vessel traffic. The authors suggested that the lack of prey overshadowed any population-level physiological impacts on southern resident killer whales from vessel traffic. 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 (NRC, 2005). 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). Ultimately, the PCAD working group issued a report (Cochrem, 2014) that summarized information compiled from 239 papers or book chapters relating to stress in marine mammals and concluded that stress responses can last from minutes to hours and, while we typically focus on adverse stress responses, stress response is part of a natural process to help animals adjust to changes in thei

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