Taking and Importing Marine Mammals; U.S. Navy Training in the Hawaii Range Complex, 35510-35577 [08-1371]

Agencies

• DEPARTMENT OF COMMERCE
• National Oceanic and Atmospheric Administration

[Federal Register Volume 73, Number 121 (Monday, June 23, 2008)]
[Proposed Rules]
[Pages 35510-35577]
From the Federal Register Online via the Government Printing Office [www.gpo.gov]
[FR Doc No: 08-1371]



[[Page 35509]]

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Part IV





Department of Commerce





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National Oceanic and Atmospheric Administration



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50 CFR Part 216



Taking and Importing Marine Mammals; U.S. Navy Training in the Hawaii 
Range Complex; Proposed Rule

Federal Register / Vol. 73, No. 121 / Monday, June 23, 2008 / 
Proposed Rules

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DEPARTMENT OF COMMERCE

National Oceanic and Atmospheric Administration

50 CFR Part 216

[Docket No. 080519680-8684-01]
RIN 0648-AW86


Taking and Importing Marine Mammals; U.S. Navy Training in the 
Hawaii Range Complex

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

ACTION: Proposed rule; request for comments.

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SUMMARY: NMFS has received a request from the U.S. Navy (Navy) for 
authorization to take marine mammals incidental to training activities 
conducted within the Hawaii Range Complex (HRC) for the period of 
December 2008 through December 2013. Pursuant to the Marine Mammal 
Protection Act (MMPA), NMFS is proposing regulations to govern that 
take and requesting information, suggestions, and comments on these 
proposed regulations.

DATES: Comments and information must be received no later than July 23, 
2008.

ADDRESSES: You may submit comments, identified by 0648-AW86, by any one 
of the following methods:
     Electronic Submissions: Submit all electronic public 
comments via the Federal eRulemaking Portal: https://
www.regulations.gov.
     Hand delivery or mailing of paper, disk, or CD-ROM 
comments should be addressed to Michael Payne, Chief, Permits, 
Conservation and Education Division, Office of Protected Resources, 
National Marine Fisheries Service, 1315 East-West Highway, Silver 
Spring, MD 20910-3225.
    Instructions: All comments received are a part of the public record 
and will generally be posted to https://www.regulations.gov without 
change. All Personal Identifying Information (for example, name, 
address, etc.) voluntarily submitted by the commenter may be publicly 
accessible. Do not submit Confidential Business Information or 
otherwise sensitive or protected information.
    NMFS will accept anonymous comments. Attachments to electronic 
comments will be accepted in Microsoft Word, Excel, WordPerfect, or 
Adobe PDF file formats only.
    Comments regarding the burden-hour estimates or other aspects of 
the collection-of-information requirements contained in this proposed 
rule should be submitted in writing to Michael Payne at the address 
above and to David Rostker, OMB, by e-mail at David_
Rostker@omb.eop.gov or by fax to 202-395-7285.

FOR FURTHER INFORMATION CONTACT: Jolie Harrison, Office of Protected 
Resources, NMFS, (301) 713-2289, ext. 166.

SUPPLEMENTARY INFORMATION:

Availability

    A copy of the Navy's application may be obtained by writing to the 
address specified above (See ADDRESSES), telephoning the contact listed 
above (see FOR FURTHER INFORMATION CONTACT), or visiting the Internet 
at: https://www.nmfs.noaa.gov/pr/permits/incidental.htm. The Navy's 
Final Environmental Impact Statement (FEIS) for the Hawaii Range 
Complex was published on May 9, 2008, and may be viewed at https://
www.govsupport.us/hrc. NMFS participated in the development of the 
Navy's FEIS as a cooperating agency under NEPA. Last, NMFS is preparing 
a Draft Environmental Assessment (EA) that analyzes the environmental 
effects of several different mitigation alternatives for the potential 
issuance of the proposed rule. The Draft EA will be posted on the 
following Web site as soon as it is complete: https://www.nmfs.noaa.gov/
pr/permits/incidental.htm.

Background

    Sections 101(a)(5)(A) and (D) of the MMPA (16 U.S.C. 1361 et seq.) 
direct the Secretary of Commerce (Secretary) to allow, upon request, 
the incidental, but not intentional taking of marine mammals by U.S. 
citizens who engage in a specified activity (other than commercial 
fishing) during periods of not more than five consecutive years each if 
certain findings are made and regulations are issued or, if the taking 
is limited to harassment, notice of a proposed authorization is 
provided to the public for review.
    Authorization shall be granted if NMFS finds that the taking will 
have a negligible impact on the species or stock(s), will not have an 
unmitigable adverse impact on the availability of the species or 
stock(s) for subsistence uses, and if the permissible methods of taking 
and requirements pertaining to the mitigation, monitoring and reporting 
of such taking are set forth.
    NMFS has defined ``negligible impact'' in 50 CFR 216.103 as:

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

    The National Defense Authorization Act of 2004 (NDAA) (Public Law 
108-136) removed the ``small numbers'' and ``specified geographical 
region'' limitations and amended the definition of ``harassment'' as it 
applies to a ``military readiness activity'' to read as follows 
(Section 3(18)(B) of the MMPA):

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

Summary of Request

    On June 25, 2007, NMFS received an application from the Navy 
requesting authorization for the take of 24 species of marine mammals 
incidental to upcoming Navy training activities to be conducted within 
the HRC, which covers 235,000 nm\2\ around the Main Hawaiian Islands 
(see map on page 17 of the application), over the course of 5 years. 
These training activities are classified as military readiness 
activities. The Navy states that these training activities may 
incidentally take marine mammals present within the HRC by exposing 
them to sound from mid-frequency or high frequency active sonar (MFAS/
HFAS) or to underwater detonations at levels that NMFS associates with 
the take of marine mammals. The Navy requests authorization to take 
individuals of 24 species of marine mammals by Level B Harassment. 
Further, though they do not anticipate it to occur, the Navy requests 
authorization to take, by injury or mortality, up to 10 individuals 
each of 10 species over the course of the 5-year period (bottlenose 
dolphin, Kogia spp., melon-headed whale, pantropical spotted dolphin, 
pygmy killer whale, short-finned pilot whale, striped dolphin, and 
Cuvier's, Longman's, and Blainville's beaked whale).

Background of Navy Request

    The Navy's mission is to maintain, train, and equip combat-ready 
naval forces capable of winning wars, deterring aggression, and 
maintaining freedom of the seas. Title 10, U.S. Code (U.S.C.) section 
5062 directs the Chief of Naval Operations to train all naval forces 
for combat. The Chief of Naval Operations meets that direction, in 
part,

[[Page 35511]]

by conducting at-sea training exercises and ensuring naval forces have 
access to ranges, operating areas (OPAREAs) and airspace where they can 
develop and maintain skills for wartime missions and conduct research, 
development, test, and evaluation (RDT&E) of naval weapons systems.
    The HRC, where the Navy has, for more than 40 years, routinely 
conducted training and major exercises in the waters around the 
Hawaiian Islands, is a critical part of the Navy's mission, especially 
as it relates to training, for several reasons. Centrally located in 
the Pacific Ocean between the west coast of the United States and the 
naval stations in the western Pacific, and surrounding the most 
isolated islands in the world, the HRC has the infrastructure (i.e., 
extensive existing range assets and training capabilities) to support a 
large number of forces in a location both remote and under U.S. 
control. The range surrounds the major homeport of Naval Station Pearl 
Harbor, enabling re-supply and repairs to submarines and surface ships 
alike. The isolation of the range offers an invaluable facility on 
which to conduct missile testing and training. Able to link with the 
U.S. Army's Pohakuloa Training Area, as well as U.S. Air Force and U.S. 
Marine Corps bases where aircraft basing and amphibious training may 
occur, the HRC provides a superior joint training environment for all 
the U.S. armed services and advanced missile testing capability. Among 
the important assets of the HRC is the Pacific Missile Range Facility 
(PMRF), which is the world's largest instrumented, multi-environment, 
military test range capable of supporting subsurface, surface, air, and 
space training, and RDT&E. It consists of instrumented underwater 
ranges, controlled airspace, and a temporary operating area covering 
2.1 million square nautical miles (nm2) of ocean area. The 
Navy must have the flexibility and capacity to quickly surge required 
combat power in the event of a national crisis or contingency 
operation. Because of its location, training for sustained deployment 
at the HRC, rather than at ranges on the west coast, saves 10 transit 
days to the western Pacific from the west coast of the United States.
    The HRC complex consists of targets and instrumented areas, 
airspace, surface OPAREAS, and land range facilities. The Navy's 
proposed action includes conducting current and emerging training in 
the HRC. Although the Navy plans to conduct many different types of 
RDT&E on the land, in the air, and in the water, as well as implement 
infrastructure improvements (addressed comprehensively in the Navy's 
FEIS), this document specifically analyzes those activities in the HRC 
for which the Navy seeks MMPA incidental take authorization, i.e., 
those training activities that the Navy predicts would result in the 
generation of levels of sound in the water that NMFS has indicated are 
likely to result in the take of marine mammals (not counting SURTASS 
LFA sonar, for which the Navy has already obtained an MMPA 
authorization), either through the use of sonar (mid-frequency active 
sonar (MFAS) or high frequency active sonar (HFAS)) or from the use of 
live ordnance, including the detonation of explosives in the water. 
Table 1-1 in the Navy's application presents a summary of the training 
and RDT&E activities that will occur in the HRC and indicates the 
exercise types that the Navy's modeling indicated would likely result 
in the take of marine mammals.

Description of the Specified Activities

    As mentioned above, the Navy has requested MMPA authorization to 
take marine mammals incidental to training activities in the HRC that 
would result in the generation of sound in the water, at or above 
levels that NMFS has determined will likely result in take (see 
Acoustic Take Criteria Section), either through the use of MFAS/HFAS or 
the detonation of explosives in the water.

Activities Utilizing Active Tactical Sonar Sources

    For this operating area (HRC), the training activities that utilize 
active tactical sonar sources fall into the category of Anti-submarine 
Warfare (ASW) exercises. This section includes a description of the 
active acoustic devices used in ASW exercises, as well as the exercise 
types in which these acoustic sources are used.
Acoustic Sources Used for ASW Exercises in the HRC
    Tactical military sonars are designed to search for, detect, 
localize, classify, and track submarines. There are two types of 
sonars, passive and active:
     Passive sonars only listen to incoming sounds and, since 
they do not emit sound energy in the water, lack the potential to 
acoustically affect the environment.
     Active sonars generate and emit acoustic energy 
specifically for the purpose of obtaining information concerning a 
distant object from the received and processed reflected sound energy.
    Modern sonar technology includes a multitude of sonar sensor and 
processing systems. In concept, the simplest active sonars emit omni-
directional pulses (``pings'') and time the arrival of the reflected 
echoes from the target object to determine range. More sophisticated 
active sonar emits an omni-directional ping and then rapidly scans a 
steered receiving beam to provide directional, as well as range, 
information. More advanced sonars transmit multiple preformed beams, 
listening to echoes from several directions simultaneously and 
providing efficient detection of both direction and range.
    The tactical military sonars to be deployed during testing and 
training in the HRC are designed to detect submarines in tactical 
training scenarios. This task requires the use of the sonar mid-
frequency range (1 kilohertz [kHz] to 10 kHz) predominantly, as well as 
one source in the high frequency range (above 10 kHz) that operates at 
a level high enough to be considered in the modeling. The high 
frequency source will contribute a comparatively very small amount to 
the total amount of active sonar that marine mammals will be exposed to 
during the Navy's proposed activities, however, for this document we 
will refer to the collective high and mid-frequency sonar sources as 
MFAS/HFAS. A narrative description of the types of acoustic sources 
used in ASW training exercises is included below. Table 1 (below) 
summarizes the nominal characteristics of the acoustic sources used in 
the modeling to predict take of marine mammals.

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[GRAPHIC] [TIFF OMITTED] TP23JN08.001

    Surface Ship Sonars--A variety of surface ships participate in 
testing and training events. Some ships (e.g., aircraft carriers, 
amphibious assault ships) do not have any onboard active sonar systems, 
other than fathometers. Others, like guided missile cruisers, are 
equipped with active as well as passive tactical sonars for mine 
avoidance and submarine detection and tracking. Within Navy ASW 
exercises in the HRC, two types of hull-mounted sonar sources account 
for the majority of the estimated impacts to marine mammals. The AN/
SQS-53 hull-mounted sonar, which has a nominal source level of 235 
decibels (dB) re 1 [mu]Pa and transmits at center frequencies of 2.6 
kHz and 3.3 kHz, is the Navy's most powerful sonar source used in ASW 
exercises in the HRC. The AN/SQS-56 hull-mounted sonar has a nominal 
source level of 225 dB re 1 [mu]Pa and transmits at a center frequency 
of 7.5 kHz. Sonar ping transmission durations were modeled as lasting 1 
second per ping and omni-directional, which is a conservative 
assumption that may overestimate potential effects. Actual ping 
durations will be less than 1 second. Details concerning the tactical 
use of specific frequencies and the repetition rate for the sonar pings 
is classified but was modeled based on the required tactical training 
setting. The AN/SQS-53 and the AN/SQS-56 were modeled using the number 
of hours of predicted use (typically at two pings per minute; meaning 
an hour of sonar operation results in approximately 120 one-second 
pings). Based on modeling results, the Navy anticipates that the 
operation of these two sources will likely result in take of marine 
mammals (see Estimated Take of Marine Mammals Section).
    Hull-mounted sonars occasionally operate in a mode called 
``Kingfisher,'' which is designed to better detect smaller objects. The 
Kingfisher mode uses the same source level and frequency as normal 
search modes, however, it uses a different waveform (designed for small 
objects), a shorter pulse length (< 1 sec), a higher pulse repetition 
rate (due to the short ranges), and the ping is not omnidirectional, 
but directed forward. All Kingfisher use in the HRC (approximately 27 
hours/year) was modeled as AN/SQS-53, though the less powerful AN/SQS-
56 likely accounts for part of the total Kingfisher use as well.
    Submarine Sonars--Submarine sonars (AN/BQQ-10, AN/BQQ-5, or AN/BSY-
1) are used to detect and target enemy submarines and surface ships. 
Because they are trying to avoid being detected, a submarine's use of 
MFAS is generally rare, very brief, using minimal power, and may be 
narrowly focused. Modeling for the AN/BQQ-10 (all three submarine types 
were modeled as AN/BQQ-10, the most powerful submarine sonar source) 
assumes sonar use of two pings an hour (which is higher than typical), 
for one second each, at 235 dB re 1 [mu]Pa, and using an omni-
directional transmission. The AN/BQQ-10 was modeled using the number of 
hours of predicted use (at two pings per hour). Based on modeling 
results, the Navy anticipates that the operation of this source may 
result in some take of marine mammals (see Estimated Take of Marine 
Mammals Section).
    Aircraft Sonar Systems--Aircraft sonar systems that would operate 
in the HRC include sonobuoys (SSQ-62) and dipping sonar (AN/AQS-22). A 
sonobuoy is an expendable device, which may be deployed by maritime 
patrol aircraft or helicopters, used for the detection of underwater 
acoustic energy and for conducting vertical water column temperature 
measurements. Most sonobuoys are passive, but some, like the SSQ-62, 
can also generate active acoustic signals. The SSQ-62 has a nominal 
source level of 201 dB re 1 [mu]Pa and transmits at a center frequency 
of 8 kHz. Dipping sonar is an active or passive sonar device lowered on 
cable helicopters to detect or maintain contact with underwater 
targets. During ASW training, these systems active modes are only used 
briefly for localization of contacts and are not used in primary search 
capacity. The AN/AQS-22 has a nominal source level of 217 dB re 1 
[mu]Pa and transmits at a center frequency of 4.1 kHz. Based on 
modeling results, the Navy anticipates that the operation of these two 
sources may result in some take of marine mammals (see Estimated Take 
of Marine Mammals Section).
    Torpedoes--Torpedoes are the primary ASW weapon used by surface 
ships, aircraft, and submarines. The guidance systems of these weapons 
can be autonomous (acoustically based) or electronically controlled 
from the launching platform through an attached wire. They operate 
either passively, exploiting the emitted sound energy by the target, or 
actively, ensonifying the target and using the received echoes for 
guidance. We know that the MK-48 operates in the high frequency range 
(>10 kHZ), however, the nominal source level and the center frequency 
are classified. Based on modeling results, the Navy anticipates that 
the operation of this source may result in some take of marine mammals 
(see Estimated Take of Marine Mammals Section). In addition to the HFA 
sonar source used to guide the torpedo, the MK-48 is discussed in the 
``Activities Utilizing Underwater Detonations'' Section.
    Other Acoustic Sources--The Navy uses other acoustic sources in ASW 
exercises. However, based on operational characteristics (such as 
frequency and source level), the Navy determined that use of the 
following acoustic sources would not likely result in the take of 
marine mammals:
     Acoustic Device Countermeasures (ADC)--submarine 
simulators that make sound to act as decoys to avert localization and/
or torpedo attacks.
     Training Targets--ASW training targets consisting of MK-30 
and/or MK-39 Expendable Mobile ASW Training

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Target (EMATT) are used to simulate opposition submarines. They are 
equipped with one or a combination of the following devices: (1) 
Acoustic projectors emanating sounds to simulate submarine acoustic 
signatures; (2) echo repeaters to simulate the characteristics of the 
echo of a particular sonar signal reflected from a specific type of 
submarine; and (3) magnetic sources to trigger magnetic detectors.
     Range pingers are active acoustic devices that allow 
inwater platforms on the range (e.g., submarines, target simulators, 
and exercise torpedoes) to be tracked by hydrophones on the seafloor 
such as those at the underwater instrumented range at PMRF. The range 
hydrophones are also tied in with transducer nodes that are capable of 
transmitting acoustic signals for a limited set of functions, including 
submarine warning signals, acoustic commands to submarine target 
simulators (acoustic command link), and occasional voice or data 
communications (received by participating ships and submarines on 
range).
Types of ASW Exercises in the HRC
    ASW training conducted within the HRC involves the use of surface 
ships, submarines, aircraft, non-explosive and explosive exercise 
weapons, and other training-related devices. ASW training involves the 
use of active and passive acoustic devices with training activities 
occurring in both offshore (<12 nm (22 km) from shore) and open ocean 
(>12 nm (22 km) from shore) areas. A description of the different 
exercise types is provided below. Table 2 lists the types of ASW 
exercises and indicates the areas they are conducted in, the average 
duration of an exercise, the average number of exercises/per year, and 
the time of year they are conducted. Table 3, at the end of this 
section, indicates the total number of hours for each source type 
anticipated for each year for each exercise type.
[GRAPHIC] [TIFF OMITTED] TP23JN08.002

    Anti-Submarine Warfare Tracking Exercise (ASW TRACKEX)--An ASW 
TRACKEX trains aircraft, ship, and submarine crews in tactics, 
techniques, and procedures for search, detection, and tracking of 
submarines. No torpedoes are fired during a TRACKEX. ASW TRACKEX 
includes ships, fixed wing aircraft, helicopters, torpedo targets, 
submarines, and weapons recovery boats and/or helicopters. As a unit-
level exercise, an aircraft, ship, or submarine is typically used 
versus one target submarine or simulated target. TRACKEXs can include 
the use of hull-mounted sonar, submarines, or sonobuoys. No explosive 
ordnance is used in TRACKEX exercises.
    The target may be non-evading while operating on a specified track 
or it may be fully evasive, depending on the state of training of the 
ASW unit. Duration of a TRACKEX is highly dependent on the tracking 
platform and its available on-station time. A maritime patrol aircraft 
can remain on station for eight hours, and typically conducts tracking 
exercises that last three to six hours. An ASW helicopter has a much 
shorter on-station time, and conducts a typical TRACKEX in one to two 
hours. Surface ships and submarines, which measure their on-station 
time in days, conduct tracking exercises exceeding eight hours and 
averaging up to 18 hours. For modeling purposes, TRACKEX and TORPEX 
(explained in next section) sonar hours are averaged, resulting in a 
sonar time of 13.5 hours.
    ASW TRACKEX events are conducted on ranges within PMRF Warning Area 
W-188, the Hawaii Offshore Areas and/or the open ocean. Whenever 
aircraft use the ranges for ASW training, range clearance procedures 
include a detailed visual range search for marine mammals and 
unauthorized boats and planes by the aircraft releasing the inert 
torpedoes, range safety boats/aircraft, and range controllers. TRACKEXs 
can include the use of hull-mounted sonar, submarines, or sonobuoys, 
which can result in the take of marine mammals.
    Anti-Submarine Warfare Torpedo Exercises (ASW TORPEX)--Anti-
Submarine Warfare Torpedo Exercises (ASW TORPEX) train crews in 
tracking and attack of submerged targets, firing one or more 
Recoverable Exercise Torpedoes. TORPEX targets used in the Offshore 
Areas include submarines, MK-30 ASW training targets, and MK-39 
Expendable Mobile ASW Training Targets. The target may be non-evading 
while operating on a specified track, or it may be fully evasive, 
depending on the training requirements. Submarines periodically conduct 
torpedo firing training exercises within the Hawaii Offshore OPAREA. 
Typical duration of a submarine TORPEX event is 22.7 hours, while air 
and surface ASW platform TORPEX events are considerably shorter. For 
modeling purposes, TRACKEX and TORPEX sonar hours are averaged 
resulting in a sonar time of 13.5 hours. TORPEXs can

[[Page 35514]]

include the use of hull-mounted sonar, submarines, sonobuoys, or MK-48 
torpedoes (inert), which can result in the take of marine mammals.
    Rim of the Pacific (RIMPAC)--RIMPAC is a multi-threat maritime 
exercise where submarines, surface ships, and aircraft from the U.S. 
and other countries conduct many different exercise events, including 
ASW against opposition submarine targets to improve coordination and 
interoperability of combined, bilateral and joint forces of 
participating nations. RIMPAC occurs during the summer over a 1-month 
period every other year (currently in even numbered years). Submarine 
targets include real submarines, targets that simulate the operations 
of an actual submarine including those described previously under 
TORPEX, and virtual submarines interjected into the training events by 
exercise controllers. ASW training events are complex and highly 
variable. For RIMPAC, the primary event involves a Surface Action Group 
(SAG), consisting of one to five surface ships equipped with sonar, 
with one or more helicopters, and a P-3 aircraft searching for one or 
more submarines. There will be approximately four to eight SAGs for a 
typical RIMPAC. For the purposes of analysis, each SAG event is counted 
as an ASW training activity. One or more ASW events may occur 
simultaneously within the HRC. There will be approximately 44 ASW 
training events during a typical RIMPAC, with an average event length 
of approximately 12 hours (ranging from 2-24 hours).
    In addition to including potential training with of all of the 
acoustic sources mentioned previously, RIMPAC includes training events 
that involve underwater detonations (described in the next section: 
Activities Utilizing Underwater Detonations), including Sinking 
Exercise, Air-to-Surface Gunnery Exercise, Surface-to-Surface Gunnery 
Exercise, Naval Surface Fire Support, Air-to-Surface Missile Exercise, 
Surface-to-Surface Missile Exercise, Bombing Exercise, Mine 
Neutralization Exercise, and IEER/EER Exercise. Both the use of the 
acoustic sources as well as the underwater detonations could result in 
the take of marine mammals. These exercises involving underwater 
detonations do not overlap in space and time with sonar exercises. 
Explosives from RIMPAC have been included in the training events 
described in the next Section.
    Undersea Warfare Exercise (USWEX)--Carrier Strike Groups (CSGs) and 
Expeditionary Strike Groups (ESGs) that deploy from the west coast of 
the United States will experience realistic submarine combat conditions 
and assess submarine warfare training capabilities postures in the HRC 
prior to their deployment to real world operations elsewhere. As a 
combined force, submarines, surface ships, and aircraft will conduct 
ASW against opposition submarine targets, which include real 
submarines, targets that simulate the operations of an actual 
submarine, and virtual submarines interjected into the training events 
by exercise controllers. USWEX training events are complex and highly 
variable. The primary event involves from one to five surface ships 
equipped with sonar, with one or more helicopters, and a P-3 aircraft 
searching for one or more submarines. A total of five exercises using 
MFAS/HFAS, lasting three to four days each, could occur throughout the 
year for USWEX.
    In addition to the use of hull-mounted sonar (AN/SQS-53 and AN/SQS-
56), submarine sonar, helicopter dipping sonar, and sonobuoys, USWEX 
includes training events that involve underwater detonations as 
described in the next section (Activities Utilizing Underwater 
Detonations), including Air-to-Surface Gunnery Exercise, Air-to-Surface 
Missile Exercise, and Bombing Exercise. Both the use of the acoustic 
sources as well as the underwater detonations could result in the take 
of marine mammals. These exercises utilizing underwater detonations do 
not overlap in space and time with sonar exercises. Explosives from 
USWEX have been included in the training events described in the next 
section.
    Multiple Strike Group Exercise--A Multiple Strike Group Exercise 
consists of events that involve Navy assets engaging in a schedule of 
events battle scenario, with U.S. forces (blue forces) pitted against a 
notional opposition force (red force). Participants use and build upon 
previously gained training skill sets to maintain and improve the 
proficiency needed for a mission-capable, deployment-ready unit. The 
exercise would occur over a 5-day to 10-day period at any time during 
the year. As described above for USWEX, as a combined force, 
submarines, surface ships, and aircraft will conduct ASW against 
opposition submarine targets.
    In addition to the use of hull-mounted sonar (AN/SQS-53 and AN/SQS-
56), submarine sonar, helicopter dipping sonar, and sonobuoys , the 
Multiple Strike Group Exercise includes training events that involve 
underwater detonations as described in the next Section (Activities 
Utilizing Underwater Detonations), including Sinking Exercise, Air-to-
Surface Missile Exercise, Mine Neutralization Exercise, and EER/IEER 
Exercise. Both the use of the acoustic sources as well as the 
underwater detonations could result in the take of marine mammals. 
These exercises utilizing underwater detonations do not overlap in 
space and time with sonar exercises. Explosives from the Multiple 
Strike Group Exercise have been included in the events described in the 
next Section.

[[Page 35515]]

[GRAPHIC] [TIFF OMITTED] TP23JN08.003

Activities Utilizing Underwater Detonations

    Underwater detonation activities can occur at various depths 
depending on the activity (sinking exercise [SINKEX] and mine 
neutralization), but may also include activities which may have 
detonations at or just below the surface (SINKEX, gunnery exercise 
[GUNEX], or missile exercise [MISSILEX]). When the weapons hit the 
target except for live torpedo shot, there is no explosion in the 
water, and so a ``hit'' is not modeled (i.e., the energy (either 
acoustic or pressure) from the hit is not expected to reach levels that 
would result in take of marine mammals). When a live weapon misses, it 
is modeled as exploding below the water surface at 1 ft (5-inch naval 
gunfire, 76mm rounds), 2 meters (Maverick, Harpoon, MK-82, MK-83, MK-
84), or 50-ft (MK-48 torpedo) as shown in Appendix A of the Navy's 
application, Table A-7 (the depth is chosen to represent the worst case 
of the possible scenarios as related to potential marine mammals 
impacts). Exercises may utilize either live or inert ordnance of the 
types listed in Table 4. Additionally, successful hit rates are known 
to the Navy and are utilized in the effects modeling. Training events 
that involve explosives and underwater detonations occur throughout the 
year and are described below and summarized in Table 5 at the end of 
this section.
[GRAPHIC] [TIFF OMITTED] TP23JN08.004

    Sinking Exercise (SINKEX)--In a SINKEX, a specially prepared, 
deactivated vessel is deliberately sunk using multiple weapons systems. 
The exercise provides training to ship and submarine and aircraft crews 
in delivering both live and inert ordnance on a real target. These 
target vessels are remediated to standards set by the Environmental 
Protection Agency. A SINKEX target is towed to sea and set adrift at 
the SINKEX location. The duration of a SINKEX is unpredictable since it 
ends when the target sinks, sometimes immediately after the first 
weapon impact and sometimes only after multiple impacts by a variety of 
weapons. Typically, the exercise lasts for four to eight hours over one 
to two days. SINKEXs typically occur only once or twice a year in the 
HRC.

[[Page 35516]]

Underwater detonation of several different explosive types could result 
in the take of marine mammals. Some or all of the following weapons may 
be employed in a SINKEX: Three HARPOON surface-to-surface and air-to-
surface missiles; two to eight air-to-surface Maverick missiles; two to 
four MK-82 General Purpose Bombs; two Hellfire air-to-surface missiles; 
one SLAM-ER air-to-surface missile; two-hundred and fifty rounds for a 
5-inch gun; and one MK-48 heavyweight submarine-launched torpedo.
    Surface-to-Surface Gunnery Exercise (S-S GUNEX)--Surface gunnery 
exercises (GUNEX) take place in the open ocean to provide gunnery 
practice for Navy and Coast Guard ship crews. GUNEX training events 
conducted in the Offshore OPAREA involve stationary targets such as a 
MK-42 FAST or a MK-58 marker (smoke) buoy. The gun systems employed 
against surface targets include the 5-inch, 76 millimeter (mm), 25-mm 
chain gun, 20-mm Close-in Weapon System (CIWS), and .50 caliber machine 
gun. Typical ordnance expenditure for a single GUNEX is a minimum of 21 
rounds of 5-inch or 76-mm ammunition, and approximately 150 rounds of 
25-mm or .50-caliber ammunition. Both live and inert training rounds 
are used. After impacting the water, the rounds and fragments sink to 
the bottom of the ocean. A S-S GUNEX lasts approximately two to four 
hours, depending on target services and weather conditions. Detonation 
of the live 5-inch and 76-mm rounds could result in the take of marine 
mammals.
    Naval Surface Fire Support Exercise--Navy surface combatants 
conduct fire support exercise (FIREX) training events at PMRF on a 
virtual range against ``Fake Island'', located on Barking Sands 
Tactical Underwater Range (BARSTUR). Fake Island is unique in that it 
is a virtual landmass simulated in three dimensions. Ships conducting 
FIREX training against targets on the island are given the coordinates 
and elevation of targets. PMRF is capable of tracking fired rounds to 
an accuracy of 30 feet (9.1 m). Detonation of the live 5-inch and 76-mm 
rounds fired into ocean during this exercise could result in the take 
of marine mammals.
    Air-to-Surface Missile Exercise (A-S MISSILEX)--The A-S MISSILEX 
consists of the attacking platform releasing a forward-fired, guided 
weapon at the designated towed target. The exercise involves locating 
the target, then designating the target, usually with a laser.
    A-S MISSILEX training can take place without the release of a live 
weapon if the attacking platform is carrying a captive air training 
missile (CATM) simulating the weapon involved in the training. The CATM 
MISSILEX is identical to a live-fire exercise in every aspect except 
that a weapon is not released, nor does it contain any explosives or 
propellant. The event requires a laser-safe range as the target is 
designated just as in a live-fire exercise.
    From 1 to 16 aircraft, carrying live, inert, or CATMs, or flying 
without ordnance (dry runs) are used during the exercise. At sea, 
seaborne powered targets (SEPTARs), Improved Surface Towed Targets 
(ISTTs), and decommissioned hulks are used as targets. A-S MISSILEX 
assets include helicopters and/or one to 16 fixed wing aircraft with 
air-to-surface missiles and anti-radiation missiles (electromagnetic 
radiation source seeking missiles). When a high-speed anti-radiation 
missile (HARM) is used, the exercise is called a HARMEX. Targets 
include SEPTARs, ISTTs, and decommissioned ship hulks. Detonation of 
live ordnance could result in the take of marine mammals.
    Surface-to-Surface Missile Exercise (S-S MISSILEX)--Surface-to-
surface missile exercise (S-S MISSILEX) involves the attack of surface 
targets at sea by use of cruise missiles or other missile systems, 
usually by a single ship conducting training in the detection, 
classification, tracking and engagement of a surface target. Engagement 
is usually with Harpoon missiles or Standard missiles in the surface-
to-surface mode. Targets could include virtual targets or the SEPTAR or 
ship deployed surface target. S-S MISSILEX training is routinely 
conducted on individual ships with embedded training devices. A S-S 
MISSILEX could include four to 20 surface-to-surface missiles, SEPTARs, 
a weapons recovery boat, and a helicopter for environmental and photo 
evaluation. All missiles are equipped with instrumentation packages or 
a warhead. Surface-to-air missiles can also be used in a surface-to-
surface mode. S-S MISSILEX activities are conducted within PMRF Warning 
area W-188. Each exercise typically lasts five hours, though future S-S 
MISSILEXs could range from four to 35 hours. Missile detonation could 
result in the take of marine mammals.
    Bombing Exercise (BOMBEX)--Fixed-wing aircraft conduct BOMBEX 
events against stationary targets (MK-42 FAST or MK-58 smoke buoy) at 
sea. An aircraft will clear the area, deploy a smoke buoy or other 
floating target, and then set up a racetrack pattern, dropping on the 
target with each pass. At PMRF, a range boat might be used to deploy 
the target for an aircraft to attack. A BOMBEX may involve either live 
or inert ordnance. Underwater detonation of live ordnance could result 
in the take of marine mammals.
    Mine Neutralization--Mine Neutralization events involve the 
detection, identification, evaluation, rendering safe, and disposal of 
mines and unexploded ordnance (UXO) that constitutes a threat to ships 
or personnel. Mine neutralization training can be conducted by a 
variety of air, surface and subsurface assets. Tactics for 
neutralization of ground or bottom mines involve a diver placing a 
specific amount of explosives, which when detonated underwater at a 
specific distance from a mine results in neutralization of the mine. 
Floating, or moored, mines involve the diver placing a specific amount 
of explosives directly on the mine. Floating mines encountered by Fleet 
ships in open ocean areas will be detonated at the surface. Inert dummy 
mines are used in the exercises. The total net explosive weight used 
against each mine ranges from less than one pound to 20 pounds (0.5 to 
9.1 kg). Mine neutralization training takes place offshore in Puuloa 
Underwater Range, Lima Landing, Naval Inactive Ship Maintenance 
Facility, MCBH, MCTAB, Barters Point Range, Ewa Training Minefield; and 
in open-ocean areas. Detonation of live ordnance could result in the 
take of marine mammals.
    All demolition activities are conducted in accordance with current 
Navy directives and approved standard operating procedures. Before any 
explosive is detonated, divers are transported a safe distance away 
from the explosive. Standard practices for tethered mines in Hawaiian 
waters require ground mine explosive charges to be suspended 10 feet 
(3.0 m) below the surface of the water.
    EER/IEER AN/SSQ-110A--The Extended Echo Ranging and Improved 
Extended Echo Ranging (EER/IEER) Systems are air-launched ASW systems 
used in conducting ``large area'' searches for submarines. These 
systems are made up of airborne avionics ASW acoustic processing and 
sonobuoy types that are deployed in pairs. The IEER System's active 
sonobuoy component, the AN/SSQ-110A Sonobuoy, would generate a ``ping'' 
(small detonation) and the passive AN/SSQ-101 ADAR Sonobuoy would 
``listen'' for the return echo of the sonar ping that has been bounced 
off the surface of a submarine. These sonobuoys are designed to provide 
underwater acoustic data necessary for naval aircrews to quickly

[[Page 35517]]

and accurately detect submerged submarines. The expendable and 
commandable sonobuoy pairs are dropped from a fixed-wing aircraft into 
the ocean in a predetermined pattern (array) with a few buoys covering 
a very large area. Upon command from the aircraft, the bottom payload 
is released to sink to a designated operating depth. A second command 
is required from the aircraft to cause the second payload to release 
and detonate generating a ``ping''. There is only one detonation in the 
pattern of buoys at a time. Detonation of the buoys could result in the 
take of marine mammals.
    Air-to-Surface Gunnery Exercise (A-S GUNEX)--Air-to-Surface GUNEX 
events are conducted by rotary-wing aircraft against stationary targets 
(Floating at-sea Target [FAST] and smoke buoy). Rotary-wing aircraft 
involved in this training activity would include a single SH-60 using 
either 7.62-mm or .50-caliber door-mounted machine guns. A typical A-S 
GUNEX will last approximately one hour and involve the expenditure of 
approximately 400 rounds of 50-caliber or 7.62-mm ammunition. Due to 
the use of small, inert rounds, A-S GUNEXs are not expected to result 
in the take of marine mammals.
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    Additional information on the Navy's proposed activities may be 
found in the LOA Application and the FEIS (Section 2 and Appendices D, 
E, and J).

Description of Marine Mammals in the Area of the Specified Activities

    There are 27 marine mammal species with possible or confirmed 
occurrence in the HRC. As indicated in Table 6, there are 25 cetacean 
species (7 mysticetes and 18 odontocetes) and two pinnipeds. Table 6 
also includes the estimated abundance, estimated group size, and 
estimated probability of detection (based on Barlow 2006) of the 
species that occur in the HRC. Seven marine mammal species listed as 
federally endangered under the Endangered Species Act (ESA) occur in 
the HRC: the humpback whale, North Pacific right whale, sei whale, fin 
whale, blue whale, sperm whale, and Hawaiian monk seal. The most 
abundant marine mammals appear to be dwarf sperm whales, striped 
dolphins, and Fraser's dolphins. The most abundant large whales are 
sperm whales.
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[[Page 35519]]


    The Navy has compiled information on the abundance, behavior, 
status and distribution, and vocalizations of marine mammal species in 
the Hawaiian waters from peer reviewed literature, the Navy Marine 
Resource Assessment, NMFS Stock Assessment Reports, and marine mammal 
surveys using acoustics or visual observations from aircraft or ships. 
This information may be viewed in the Navy's LOA application and/or the 
Navy's FEIS for the HRC (see Availability). Additional information is 
available in NMFS Stock Assessment Reports, which may be viewed at: 
https://www.nmfs.noaa.gov/pr/sars/species.htm.
    Based on their rare occurrence in the HRC, the Navy and NMFS do not 
anticipate any effects to Blue whales, North Pacific right whales, or 
Northern elephant seals and, therefore, they are not addressed further 
in this document.

Important Reproductive Areas

    Because the consideration of areas where marine mammals are known 
to selectively breed or calve are important to both the negligible 
impact finding necessary for the issuance of an MMPA authorization and 
the need for NMFS to put forth the means of effecting the least 
practicable adverse impact paying particular attention to rookeries, 
mating grounds, and other areas of similar significance, we are 
emphasizing important reproductive areas within this section. Little is 
known about the breeding and calving behaviors of many of the marine 
mammals that occur in the HRC. Some delphinid species have calving 
peaks once or twice a year, but give birth throughout their ranges. The 
mysticete species that may occur in the HRC are generally thought to 
migrate from higher to lower latitudes to breed and calve in the 
winter. With one notable exception, no breeding or calving areas have 
been identified in the HRC for the species that occur there. However, 
the main Hawaiian Islands constitute one of the world's most important 
habitats for the endangered humpback whale. Nearly two-thirds of the 
entire North Pacific population of humpback whales migrates to Hawaii 
each winter to engage in breeding, calving and nursing activities 
important for the survival of their species. The available sighting 
information and the known preferred breeding habitat (shallow water) 
indicates that humpback whale densities are much higher (up to almost 
four whales/square mile) in certain areas and that humpback mothers and 
calves are concentrated within the 200-m isobath. The Hawaiian Humpback 
Whale National Marine Sanctuary worked with Dr. Joe Mobley to compile a 
figure that generally illustrates humpback whale survey data collected 
between 1993 and 2003 and indicates areas of high and low density 
(Mobley 2004, Figure 1).

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[[Page 35521]]

A Brief Background on Sound

    An understanding of the basic properties of underwater sound is 
necessary to comprehend many of the concepts and analyses presented in 
this document. A summary is included below.
    Sound is a wave of pressure variations propagating through a medium 
(for the sonar considered in this proposed rule, the medium is marine 
water). Pressure variations are created by compressing and relaxing the 
medium. Sound measurements can be expressed in two forms: intensity and 
pressure. Acoustic intensity is the average rate of energy transmitted 
through a unit area in a specified direction and is expressed in watts 
per square meter (W/m\2\). Acoustic intensity is rarely measured 
directly, it is derived from ratios of pressures; the standard 
reference pressure for underwater sound is 1 microPascal ([mu]Pa); for 
airborne sound, the standard reference pressure is 20 [mu]Pa 
(Richardson et al., 1995).
    Acousticians have adopted a logarithmic scale for sound 
intensities, which is denoted in decibels (dB). Decibel measurements 
represent the ratio between a measured pressure value and a reference 
pressure value (in this case 1 [mu]Pa or, for airborne sound, 20 
[mu]Pa). The logarithmic nature of the scale means that each 10 dB 
increase is a ten-fold increase in power (e.g., 20 dB is a 100-fold 
increase, 30 dB is a 1,000-fold increase). Humans perceive a 10-dB 
increase in noise as a doubling of sound level, or a 10 dB decrease in 
noise as a halving of sound level. The term ``sound pressure level'' 
implies a decibel measure and a reference pressure that is used as the 
denominator of the ratio. Throughout this document, NMFS uses 1 
microPascal (denoted re: 1 [mu]Pa) as a standard reference pressure 
unless noted otherwise.
    It is important to note that decibels underwater and decibels in 
air are not the same and cannot be directly compared. To estimate a 
comparison between sound in air and underwater, because of the 
different densities of air and water and the different decibel 
standards (i.e., reference pressures) in water and air, a sound with 
the same intensity (i.e., power) in air and in water would be 
approximately 63 dB quieter in air. Thus a sound that is 160 dB loud 
underwater would have the same approximate effective intensity as a 
sound that is 97 dB loud in air.
    Sound frequency is measured in cycles per second, or Hertz 
(abbreviated Hz), and is analogous to musical pitch; high-pitched 
sounds contain high frequencies and low-pitched sounds contain low 
frequencies. Natural sounds in the ocean span a huge range of 
frequencies: from earthquake noise at 5 Hz to harbor porpoise clicks at 
150,000 Hz (150 kHz). These sounds are so low or so high in pitch that 
humans cannot even hear them; acousticians call these infrasonic and 
ultrasonic sounds, respectively. A single sound may be made up of many 
different frequencies together. Sounds made up of only a small range of 
frequencies are called ``narrowband'', and sounds with a broad range of 
frequencies are called ``broadband''; airguns are an example of a 
broadband sound source and tactical sonars are an example of a 
narrowband sound source.
    When considering the influence of various kinds of sound on the 
marine environment, it is necessary to understand that different kinds 
of marine life are sensitive to different frequencies of sound. Based 
on available behavioral data, audiograms derived using auditory evoked 
potential, anatomical modeling, and other data, Southall et al. (2007) 
designate ``functional hearing groups'' and estimate the lower and 
upper frequencies of functional hearing of the groups. Further, the 
frequency range in which each group's hearing is estimated as being 
most sensitive is represented in the flat part of the M-weighting 
functions developed for each group. More specific data is available for 
certain species (Table 17). The functional groups and the associated 
frequencies are indicated below:
     Low frequency cetaceans (13 species of mysticetes): 
Functional hearing is estimated to occur between approximately 7 Hz and 
22 kHz.
     Mid-frequency cetaceans (32 species of dolphins, six 
species of larger toothed whales, and 19 species of beaked and 
bottlenose whales): Functional hearing is estimated to occur between 
approximately 150 Hz and 160 kHz.
     High frequency cetaceans (eight species of true porpoises, 
six species of river dolphins, Kogia, the franciscana, and four species 
of cephalorhynchids): Functional hearing is estimated to occur between 
approximately 200 Hz and 180 kHz.
     Pinnipeds in Water: Functional hearing is estimated to 
occur between approximately 75 Hz and 75 kHz, with the greatest 
sensitivity between approximately 700 Hz and 20 kHz.
     Pinnipeds in Air: Functional hearing is estimated to occur 
between approximately 75 Hz and 30 kHz.
    Because ears adapted to function underwater are physiologically 
different from human ears, comparisons using decibel measurements in 
air would still not be adequate to describe the effects of a sound on a 
whale. When sound travels away from its source, its loudness decreases 
as the distance traveled (propagates) by the sound increases. Thus, the 
loudness of a sound at its source is higher than the loudness of that 
same sound a kilometer distant. Acousticians often refer to the 
loudness of a sound at its source (typically measured one meter from 
the source) as the source level and the loudness of sound elsewhere as 
the received level. For example, a humpback whale three kilometers from 
an airgun that has a source level of 230 dB may only be exposed to 
sound that is 160 dB loud, depending on how the sound propagates. As a 
result, it is important not to confuse source levels and received 
levels when discussing the loudness of sound in the ocean.
    As sound travels from a source, its propagation in water is 
influenced by various physical characteristics, including water 
temperature, depth, salinity, and surface and bottom properties that 
cause refraction, reflection, absorption, and scattering of sound 
waves. Oceans are not homogeneous and the contribution of each of these 
individual factors is extremely complex and interrelated. The physical 
characteristics that determine the sound's speed through the water will 
change with depth, season, geographic location, and with time of day 
(as a result, in actual sonar operations, crews will measure oceanic 
conditions, such as sea water temperature and depth, to calibrate 
models that determine the path the sonar signal will take as it travels 
through the ocean and how strong the sound signal will be at a given 
range along a particular transmission path). As sound travels through 
the ocean, the intensity associated with the wavefront diminishes, or 
attenuates. This decrease in intensity is referred to as propagation 
loss, also commonly called transmission loss.

Metrics Used in This Document

    This section includes a brief explanation of the two sound 
measurements (sound pressure level (SPL) and sound exposure level 
(SEL)) frequently used in the discussions of acoustic effects in this 
document.
SPL
    Sound pressure is the sound force per unit area, and is usually 
measured in micropascals ([mu]Pa), where 1 Pa is the pressure resulting 
from a force of one newton exerted over an area of one

[[Page 35522]]

square meter. SPL is expressed as the ratio of a measured sound 
pressure and a reference level. The commonly used reference pressure 
level in underwater acoustics is 1 [mu]Pa, and the units for SPLs are 
dB re: 1 [mu]Pa.

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

    SPL is an instantaneous measurement and can be expressed as the 
peak, the peak-peak, or the root mean square (rms). Root mean square, 
which is the square root of the arithmetic average of the squared 
instantaneous pressure values, is typically used in discussions of the 
effects of sounds on vertebrates and all references to SPL in this 
document refer to the root mean square. SPL does not take the duration 
of a sound into account. SPL is the applicable metric used in the risk 
continuum, which is used to estimate behavioral harassment takes (see 
Level B Harassment Risk Function (Behavioral Harassment) Section).
SEL
    SEL is an energy metric that integrates the squared instantaneous 
sound pressure over a stated time interval. The units for SEL are dB 
re: 1 [mu]Pa\2\s.

SEL = SPL + 10log(duration in seconds)

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

Potential Effects of Specified Activities on Marine Mammals

Exposure to MFAS/HFAS

    The Navy has requested authorization for the take of marine mammals 
that may occur incidental to training activities in the HRC utilizing 
MFAS/HFAS or underwater explosives. The Navy has analyzed other Navy 
activities in the HRC, both ongoing and proposed, and in consultation 
with NMFS as a cooperating agency for the HRC EIS, has determined that 
take of marine mammals incidental to other Navy activities is unlikely 
and, therefore, has not requested authorization for take of marine 
mammals that might occur incidental to any other activities. Therefore, 
NMFS will analyze the potential effects on marine mammals from MFAS/
HFAS and underwater detonations, but not from other activities.
    For the purposes of MMPA authorizations, NMFS's effects assessments 
have three primary purposes: (1) To put forth the permissible methods 
of taking within the context of MMPA Level B Harassment (behavioral 
harassment), Level A Harassment (injury), and mortality (i.e., identify 
the number and types of take that will occur); (2) to determine whether 
the specified activity will have a negligible impact on the affected 
species or stocks of marine mammals (based on the likelihood that the 
activity will adversely affect the species or stock through effects on 
annual rates of recruitment or survival); and (3) to determine whether 
the specified activity will have an unmitigable adverse impact on the 
availability of the species or stock(s) for subsistence uses (however, 
there are no subsistence communities that would be affected in the HRC, 
so this determination is inapplicable for the HRC).
    More specifically, for activities involving active tactical sonar 
or underwater detonations, NMFS's analysis will identify the 
probability of lethal responses, physical trauma, sensory impairment 
(permanent and temporary threshold shifts and acoustic masking), 
physiological responses (particular stress responses), behavioral 
disturbance (that rises to the level of harassment), and social 
responses that would be classified as behavioral harassment or injury 
and/or would be likely to adversely affect the species or stock through 
effects on annual rates of recruitment or survival. In this section, we 
will focus qualitatively on the different ways that MFAS/HFAS and 
underwater explosive detonations may affect marine mammals (some of 
which NMFS would not classify as harassment). Then, in the Estimated 
Take of Marine Mammals Section, NMFS will relate the potential effects 
to marine mammals from MFAS/HFAS and underwater detonation of 
explosives to the MMPA regulatory definitions of Level A and Level B 
Harassment and attempt to quantify those effects.
    In its April 14, 2008, Biological Opinion of the U.S. Navy's 
proposal to conduct four training exercises in the Cherry Point, 
Virginia Capes, and Jacksonville, Range Complexes NMFS presented a 
conceptual model of the potential responses of endangered and 
threatened species upon being exposed to active sonar and the pathways 
by which those responses might affect the fitness of individual animals 
that have been exposed, which may then affect the reproduction and/or 
survival of those individuals. Literature supporting the framework, 
with examples drawn from many taxa (both aquatic and terrestrial) was 
included in the ``Application of this Approach'' and ``Response 
Analyses'' sections of that document (available at: https://
www.nmfs.noaa.gov/pr/permits/incidental.htm). This conceptual framework 
may also be used to describe the responses and pathways for non-
endangered and non-threatened species and is included in this document 
for reference (Figure 2).
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[[Page 35524]]

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

Threshold Shift (Noise-Induced Loss of Hearing)

    When animals exhibit reduced hearing sensitivity (i.e., sounds must 
be louder for an animal to recognize them) following exposure to a 
sufficiently intense sound, it is referred to as a noise-induced 
threshold shift (TS). An animal can experience temporary threshold 
shift (TTS) or permanent threshold shift (PTS). TTS can last from 
minutes or hours to days (i.e., there is recovery), occurs in specific 
frequency ranges (i.e., an animal might only have a temporary loss of 
hearing sensitivity between the frequencies of 1 and 10 kHz)), and can 
be of varying amounts (for example, an animal's hearing sensitivity 
might be reduced by only 6 dB or reduced by 30 dB). PTS is permanent 
(i.e., there is no recovery), but also occurs in a specific frequency 
range and amount as mentioned.
    The following physiological mechanisms are thought to play a role 
in inducing auditory TSs: Effects to sensory hair cells in the inner 
ear that reduce their sensitivity, modification of the chemical 
environment within the sensory cells, residual muscular activity in the 
middle ear, displacement of certain inner ear membranes, increased 
blood flow, and post-stimulatory reduction in both efferent and sensory 
neural output (Southall et al., 2007). The amplitude, duration, 
frequency, temporal pattern, and energy distribution of sound exposure 
all affect the amount of associated TS and the frequency range in which 
it occurs. As amplitude and duration of sound exposure increase, so, 
generally, does the amount of TS. For continuous sounds, exposures of 
equal energy (the same SEL) will lead to approximately equal effects. 
For intermittent sounds, less TS will occur than from a continuous 
exposure with the same energy (some recovery will occur between 
exposures) (Kryter et al., 1966; Ward, 1997). For example, one short 
but loud (higher SPL) sound exposure may induce the same impairment as 
one longer but softer sound, which in turn may cause more impairment 
than a series of several intermittent softer sounds with the same total 
energy (Ward, 1997). Additionally, though TTS is temporary, very 
prolonged exposure to sound strong enough to elicit TTS, or shorter-
term exposure to sound levels well above the TTS threshold, can cause 
PTS, at least in terrestrial mammals (Kryter, 1985) (although in the 
case of MFAS/HFAS, animals are not expected to be exposed to levels 
high enough or durations long enough to result in PTS).
    PTS is considered auditory injury (Southall et al., 2007). 
Irreparable damage to the inner or outer cochlear hair cells may cause 
PTS, however, other mechanisms are also involved, such as exceeding the 
elastic limits of certain tissues and membranes in the middle and inner 
ears and resultant changes in the chemical composition of the inner ear 
fluids (Southall et al., 2007).
    Although the published body of scientific literature contains 
numerous theoretical studies and discussion papers on hearing 
impairments that can occur with exposure to a loud sound, only a few 
studies provide empirical information on the levels at which noise-
induced loss in hearing sensitivity occurs in nonhuman animals. For 
cetaceans, published data are limited to the captive bottlenose dolphin 
and beluga (Finneran et al., 2000, 2002b, 2005a; Schlundt et al., 2000; 
Nachtigall et al., 2003, 2004). For pinnipeds in water, data is limited 
to Kastak et al.'s measurement of TTS in one harbor seal, one elephant 
seal, and one California sea lion.
    Marine mammal hearing plays a critical role in communication with 
conspecifics, and interpreting environmental cues for purposes such as 
predator avoidance and prey capture. Depending on the degree (dB), 
duration, and frequency range of TTS, and the context in which it is 
experienced, TTS can have effects on marine mammals ranging from 
discountable to serious (similar to those discussed in auditory 
masking, below). For example, a marine mammal may be able to readily 
compensate for a brief, relatively small amount of TTS in a non-
critical frequency range that takes place during a time when the animal 
is traveling through the open ocean, where ambient noise is lower and 
there are not as many competing sounds present. Alternatively, a larger 
amount and longer duration of TTS sustained during time when 
communication is critical for successful mother/calf interactions could 
have more serious impacts. Also, depending on the degree and frequency 
range, the effects of PTS on an animal could range in severity, 
although it is considered generally more serious because it is a long 
term condition. Of note, reduced hearing sensitivity as a simple 
function of development and aging has been observed in marine mammals, 
as well as humans and other taxa (Southall et al., 2007), so we can 
infer that strategies exist for coping with this condition to some 
degree, though likely not without cost. There is no empirical evidence 
that exposure to MFAS/HFAS can cause PTS in any marine mammals; instead 
the probability of PTS has been inferred from studies of TTS (see 
Richardson et al. 1995).

Acoustically Mediated Bubble Growth

    One theoretical cause of injury to marine mammals is rectified 
diffusion (Crum and Mao, 1996), the process of increasing the size of a 
bubble by exposing it to a sound field. This process could be 
facilitated if the environment in which the ensonified bubbles exist is 
supersaturated with gas. Repetitive diving by marine mammals can cause 
the blood and some tissues to accumulate gas to a greater degree than 
is supported by the surrounding environmental pressure (Ridgway and 
Howard, 1979). The deeper and longer dives of some marine mammals (for 
example, beaked whales) are theoretically predicted to induce greater 
supersaturation (Houser et al., 2001b). If rectified diffusion were 
possible in marine mammals exposed to high