Small Takes of Marine Mammals Incidental to Specified Activities; Rim of the Pacific Antisubmarine Warfare Exercise Training Events Within the Hawaiian Islands Operating Area, 38710-38738 [06-6050]
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DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric
Administration
I.D. 062806A
Small Takes of Marine Mammals
Incidental to Specified Activities; Rim
of the Pacific Antisubmarine Warfare
Exercise Training Events Within the
Hawaiian Islands Operating Area
National Marine Fisheries
Service (NMFS), National Oceanic and
Atmospheric Administration (NOAA),
Commerce.
ACTION: Notice; issuance of IHA.
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AGENCY:
SUMMARY: In accordance with the
provisions of the Marine Mammal
Protection Act (MMPA) as amended,
notification is hereby given that NMFS
has issued an Incidental Harassment
Authorization (IHA) to the U.S. Navy
(Navy) to take marine mammals, by
incidental Level B harassment only,
while conducting Rim of the Pacific
(RIMPAC) anti-submarine (ASW)
training events, in which submarines,
surface ships, and aircraft from the
United States and multiple foreign
nations participate in ASW training
exercises, utilizing mid-frequency sonar
(1 kilohertz (kHz) to 10 kHz), in the U.S.
Navy’s Hawaiian Operating Area
(OpArea) during July, 2006.
DATES: Effective June 27, 2006, through
August 15, 2006.
ADDRESSES: A copy of the IHA and the
application are available by writing to
Michael Payne, Chief, Permits,
Conservation, and Education Division,
Office of Protected Resources, National
Marine Fisheries Service, 1315 EastWest Highway, Silver Spring, MD
20910–3225, or by telephoning the
contact listed here. A copy of the
application containing a list of
references used in this document may
be obtained by writing to this address,
by telephoning the contact listed here
(see FOR FURTHER INFORMATION CONTACT)
or online at: https://www.nmfs.noaa.gov/
pr/permits/incidental.htm. Documents
cited in this notice may be viewed, by
appointment, during regular business
hours, at the aforementioned address.
FOR FURTHER INFORMATION CONTACT:
Donna Wieting, Office of Protected
Resources, NMFS, (301) 713–2289.
SUPPLEMENTARY INFORMATION:
Background
Sections 101(a)(5)(A) and (D) of the
MMPA (16 U.S.C. 1361 et seq.) direct
the Secretary of Commerce to allow,
upon request, the incidental, but not
intentional, taking of marine mammals
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by U.S. citizens who engage in a
specified activity (other than
commercial fishing) within a specified
geographical region if certain findings
are made and either regulations are
issued or, if the taking is limited to
harassment, a notice of a proposed
authorization is provided to the public
for review.
Authorization 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 that the permissible methods of
taking and requirements pertaining to
the mitigation, monitoring and reporting
of such takings are set forth. NMFS has
defined ‘‘negligible impact’’ in 50 CFR
216.103 as ’’...an impact resulting from
the specified activity that cannot be
reasonably expected to, and is not
reasonably likely to, adversely affect the
species or stock through effects on
annual rates of recruitment or survival.’’
Section 101(a)(5)(D) of the MMPA
established an expedited process by
which citizens of the United States can
apply for an authorization to
incidentally take small numbers of
marine mammals by harassment. The
National Defense Authorization Act of
2004 (NDAA) (Public Law 108–136)
removed the ‘‘small numbers’’
limitation and amended the definition
of ‘‘harassment’’ as it applies to a
‘‘military readiness activity’’ to read as
follows:
(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]
Section 101(a)(5)(D) establishes a 45day time limit for NMFS review of an
application followed by a 30-day public
notice and comment period on any
proposed authorizations for the
incidental harassment of marine
mammals. Within 45 days of the close
of the comment period, NMFS must
either issue or deny issuance of the
authorization.
Summary of Request
On March 16, 2006, NMFS received
an application from the Navy for the
taking, by harassment, of several species
of marine mammals incidental to
conducting RIMPAC ASW training
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events, in which submarines, surface
ships, and aircraft from the United
States and multiple foreign nations
participate in ASW training exercises, in
the OpArea, in the summer of 2006. The
RIMPAC ASW exercises are considered
a military readiness activity.
NMFS may not authorize the take of
marine mammals by non-U.S. citizens;
however, all foreign vessels
participating in RIMPAC 2006 will be
under the Operational Control (OPCON)
of Commander, U.S. THIRD Fleet in his
capacity as Officer Conducting the
Exercise (OCE) and Commander,
Combined Task Force (CCTF) RIMPAC
(i.e., the Navy can require that a foreign
vessel cease sonar operations).
Additionally, all forces assigned,
including foreign vessels, are required
to comply with the environmental
mitigation measures spelled out in the
Navy’s Annex L [Environmental], which
will include all of the measures in the
IHA, as a condition of participating in
the exercise. This is part of the
description of the activity.
Description of the Activity
RIMPAC 2006 ASW activities are
scheduled to take place from June 26,
2006, to about July 28, 2006, with ASW
training events planned on 21 days. The
OpArea is approximately 210,000
square nautical miles (nm), however,
the majority of RIMPAC ASW training
would occur in the six areas delineated
in Figure 2–1 in the Navy’s application
(approximate 46,000 square nm). ASW
events typically rotate between these six
modeled areas. These six areas were
used for analysis as being representative
of the marine mammal habitats and the
bathymetric, seabed, wind speed, and
sound velocity profile conditions within
the entire OpArea. For purposes of this
analysis, all likely RIMPAC ASW events
were modeled as occurring in these six
areas.
As a combined force during the
exercises, submarines, surface ships,
and aircraft will conduct ASW against
opposition submarine targets.
Submarine targets include real
submarines, target drones that simulate
the operations of an actual submarine,
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 SAGs for
RIMPAC 2006. For the purposes of
analysis, each event in which a SAG
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participates is counted as an ASW
operation. There will be approximately
44 ASW operations during RIMPAC
with an average event length of
approximately 12 hours.
One or more ASW events may occur
simultaneously within the OpArea.
Each event was identified and modeled
separately. If a break of more than 1
hour in ASW operations occurred, then
the subsequent event was modeled as a
separate event. Training event durations
ranged from 2 hours to 24 hours. A total
of 532 training hours were modeled for
RIMPAC acoustic exposures. This total
includes all potential ASW training that
is expected to occur during RIMPAC.
Active Acoustic Sources
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
sound energy reflected back from that
object.
Modern sonar technology has
developed a multitude of sonar sensor
and processing systems. In concept, the
simplest active sonars emit
omnidirectional pulses (‘‘pings’’) and
time the arrival of the reflected echoes
from the target object to determine
range. More sophisticated active sonar
emits an omnidirectional 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 in RIMPAC are designed to
detect submarines in tactical operational
scenarios. This task requires the use of
the sonar mid-frequency (MF) range (1
kilohertz [kHz] to 10 kHz)
predominantly.
The types of tactical acoustic sources
that would be used in training events
during RIMPAC are discussed in the
following paragraphs. For more
information regarding how the Navy’s
determined which sources should not
be included in their analysis, see the
Estimates of Take Section later in this
document.
Surface Ship Sonars–A variety of
surface ships participate in RIMPAC,
including guided missile cruisers,
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destroyers, guided missile destroyers,
and frigates. Some ships (e.g., aircraft
carriers) do not have any onboard active
sonar systems, other than fathometers.
Others, like guided missile cruisers, are
equipped with active as well as passive
sonars for submarine detection and
tracking. For purposes of the analysis,
all surface ship sonars were modeled as
equivalent to SQS–53 having the
nominal source level of 235 decibels
(dB) re 1mPa2–s (SEL). Since the SQS–
53 hull mounted sonar is the U.S.
Navy’s most powerful surface ship hull
mounted sonar, modeling this source is
a conservative assumption tending
towards an overestimation of potential
effects (although, the conservativeness
is offset some by the fact that the Navy
did not model for any of the times
(though brief and infrequent) that they
may use a source level higher than 235
dB). Sonar ping transmission durations
were modeled as lasting 1 second per
ping and directional with a footprint
that was 240 degrees wide, which is a
conservative assumption that
overestimates potential exposures, since
actual ping durations will be less than
1 second. The SQS–53 hull mounted
sonar transmits at center frequencies of
2.6 kHz and 3.3 kHz.
Submarine Sonars–Submarine sonars
can be used to detect and target enemy
submarines and surface ships. However,
submarine active sonar use is very rare
in the planned RIMPAC exercises, and,
when used, very brief. Therefore, use of
active sonar by submarines is unlikely
to have any effect on marine mammals,
and it was not modeled for RIMPAC
2006.
Aircraft Sonar Systems–Aircraft sonar
systems that would operate during
RIMPAC include sonobuoys and
dipping sonar. Sonobuoys may be
deployed by P–3 aircraft or helicopters;
dipping sonars are used by carrier-based
helicopters. A sonobuoy is an
expendable device used by aircraft for
the detection of underwater acoustic
energy and for conducting vertical water
column temperature measurements.
Most sonobuoys are passive, but some
can generate active acoustic signals as
well. Dipping sonar is an active or
passive sonar device lowered on cable
by helicopters to detect or maintain
contact with underwater targets. During
RIMPAC, these systems active modes
are only used briefly for localization of
contacts and are not used in primary
search capacity. Because active mode
dipping sonar use is very brief, it is
extremely unlikely its use would have
any effect on marine mammals. The AN/
AQS 13 (dipping sonar) used by carrier
based helicopters was determined in the
Environmental Assessment/Overseas
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Environmental Assessment of the SH–
60R Helicopter/ALFS Test Program,
October 1999, not to be problematic due
to its limited use and very short pulse
length. Therefore, the aircraft sonar
systems were not modeled for RIMPAC
2006.
Torpedoes–Torpedoes are the primary
ASW weapon used by surface ships,
aircraft, and submarines. The guidance
systems of these weapons can be
autonomous or electronically controlled
from the launching platform through an
attached wire. The autonomous
guidance systems are acoustically based.
They operate either passively,
exploiting the emitted sound energy by
the target, or actively, ensonifying the
target and using the received echoes for
guidance. All torpedoes used for ASW
during RIMPAC would be located in the
range area managed by Pacific Missile
Range Facility (PMRF) and would be
non-explosive and recovered after use.
Acoustic Device Countermeasures
(ADC)–ADCs are, in effect, submarine
simulators that make noise to act as
decoys to avert localization and/or
torpedo attacks. Previous classified
analysis has shown that, based on the
operational characteristics (source
output level and/or frequency) of these
acoustic sources, the potential to affect
marine mammals was unlikely, and
therefore they were not modeled for
RIMPAC 2006.
Training Targets–ASW training
targets are used to simulate target
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. Based on the
operational characteristics (source
output level and/or frequency) of these
acoustic sources, the potential to affect
marine mammals is unlikely, and
therefore they were not modeled for
RIMPAC 2006.
Range Sources–Range pingers are
active acoustic devices that allow each
of the in-water platforms on the range
(e.g., ships, submarines, target
simulators, and exercise torpedoes) to
be tracked by the range transducer
nodes. In addition to passively tracking
the pinger signal from each range
participant, the range transducer nodes
also are capable of transmitting acoustic
signals for a limited set of functions.
These functions include submarine
warning signals, acoustic commands to
submarine target simulators (acoustic
command link), and occasional voice or
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data communications (received by
participating ships and submarines on
range). Based on the operational
characteristics (source output level and/
or frequency) of these acoustic sources,
the potential to affect marine mammals
is unlikely, and therefore they were not
modeled for RIMPAC 2006.
For detailed information regarding the
proposed activity, please see the Navy’s
application and the associated
Environmental Assessment (EA) (see
ADDRESSES).
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Description of Marine Mammals
Potentially Affected by the Activity
There are 27 marine mammal species
with possible or confirmed occurrence
in the Navy’s OpArea (Table 1): 25
cetacean species (whales, dolphins, and
porpoises) and 2 pinnipeds (seals). In
addition, five species of sea turtles are
known to occur in the OpArea.
The most abundant marine mammals
are rough-toothed dolphins, dwarf
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sperm whales, and Fraser’s dolphins.
The most abundant large whales are
sperm whales. There are three
seasonally migrating baleen whale
species that winter in Hawaiian waters:
minke, fin, and humpback whales.
Humpback whales utilize Hawaiian
waters as a major breeding ground
during winter and spring (November
through April), but should not be
present during the RIMPAC exercise,
which takes place in July. Because
definitive information on the other two
migrating species is lacking, their
possible presence during the July
timeframe is assumed, although it is
considered unlikely. Seven marine
mammal species listed as federally
endangered under the Endangered
Species Act (ESA) occur in the area: the
humpback whale, North Pacific right
whale, sei whale, fin whale, blue whale,
sperm whale, and Hawaiian monk seal.
The Navy has used data compiled
from available sighting records,
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literature, satellite tracking, and
stranding and bycatch data to identify
the species of marine mammals present
in the OpArea. A combination of
inshore survey data (within 25 nm (46
km); Mobley et al., 2000) and offshore
data (from 25 nm (46 km) offshore out
to the U.S. Exclusive Economic Zone
(EEZ) (200 nm (370 km) (, Barlow 2003)
was used to estimate the density and
abundance of marine mammals within
the OpArea (Table 1). Additional
information regarding the status and
distribution of the 27 marine mammal
species that occur in the OpArea may be
found in the Navy’s application and the
associated EA (see ADDRESSES) and in
NMFS’ Stock Assessment Reports,
which are available at: https://
www.nmfs.noaa.gov/pr/PR2/Stockl
Assessment lProgram/ individuall
sars.html.
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Potential Effects on Marine Mammals
NMFS has issued an IHA to the Navy
for the take, by harassment, of marine
mammals incidental to RIMPAC ASW
exercises in the OpArea. Section
101(a)(5)(D) of the MMPA, the section
pursuant to which IHAs are issued, may
not be used to authorize mortality or
serious injury leading to mortality. The
Navy’s analysis of the RIMPAC ASW
exercises concluded that no mortality or
serious injury leading to mortality
would result from the proposed
activities. However, NMFS believes,
based on our interpretation of the
limited available data bearing on this
point, that some marine mammals may
react to mid-frequency sonar, at
received levels lower than those thought
to cause direct physical harm, with
behaviors that may, in some
circumstances, lead to physiological
harm, stranding, or, potentially, death.
Therefore, NMFS has required
additional mitigation and monitoring
measures that were not originally
proposed in the Navy’s application,
which are intended to ensure (in
addition to the standard statutory
requirement to effect the ‘‘least
practicable adverse impact upon the
affected species or stock’’) that mortality
or serious injury leading to mortality
does not result from the proposed
activities.
Below, NMFS describes the potential
effects on marine mammals of exposure
to tactical sonar.
Metrics Used in Acoustic Effect
Discussions
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.
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SPL
Sound pressure is the sound force per
unit area, and is usually measured in
micropascals (mPa), where 1 Pa is the
pressure resulting from a force of one
newton exerted over an area of one
square meter.
The sound levels to which most
mammals are sensitive extend over
many orders of magnitude and, for this
reason, it is convenient to use a
logarithmic scale (the decibel (dB) scale)
when measuring sound. 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 mPa,
and the units for SPLs are dB re: 1 mPa.
SPL (in dB) = 20 log (pressure /
reference pressure)
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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.
SPL does not take the duration of a
sound into account.
SEL
In this proposed authorization, effect
thresholds are expressed in terms of
sound exposure level SEL. SEL is an
energy metric that integrates the squared
instantaneous sound pressure over a
stated time interval. The units for SEL
are dB re: 1 mPa2–s.
SEL = SPL + 10log(duration)
As applied to tactical sonar, the SEL
includes both the ping SPL and the
duration. Longer-duration pings and/or
higher-SPL pings 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.
Since mammalian threshold shift (TS)
data show less effect from intermittent
exposures compared to continuous
exposures with the same energy (Ward,
1997), basing the effect thresholds on
the total received SEL may be a
conservative approach for treating
multiple pings; as some recovery may
occur between pings and lessen the
effect of a particular exposure.
The total SEL depends on the SPL,
duration, and number of pings received.
The acoustic effects on hearing that
result in temporary threshold shift
(TTS) and permanent threshold shift
(PTS), do not imply any specific SPL,
duration, or number of pings. The SPL
and duration of each received ping are
used to calculate the total SEL and
determine whether the received SEL
meets or exceeds the effect thresholds.
For example, the sub-TTS behavioral
effects threshold of 173 dB SEL would
be reached through any of the following
exposures:
A single ping with SPL = 173 dB re 1 mPa
and duration = 1 second.A single ping with
SPL = 170 dB re 1 mPa and duration = 2
seconds.Two pings with SPL = 170 dB re 1
mPa and duration = 1 second.Two pings with
SPL = 167 dB re 1 mPa and duration = 2
seconds.
Potential Physiological Effects
Physiological function is any of a
collection of processes ranging from
biochemical reactions to mechanical
interaction and operation of organs and
tissues within an animal. A
physiological effect may range from the
most significant of impacts (i.e.,
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mortality and serious injury) to lesser
effects that would define the lower end
of the physiological impact range, such
as non-injurious short-term impacts to
auditory tissues.
Exposure to some types of noise may
cause a variety of physiological effects
in mammals. For example, exposure to
very high sound levels may affect the
function of the visual system, vestibular
system, and internal organs (Ward,
1997). Exposure to high-intensity
sounds of sufficient duration may cause
injury to the lungs and intestines (e.g.,
Dalecki et al., 2002). Sudden, intense
sounds may elicit a ‘‘startle’’ response
and may be followed by an orienting
reflex (Ward, 1997; Jansen, 1998). The
primary physiological effects of sound,
however, are on the auditory system
(Ward, 1997).
Hearing Threshold Shift
In mammals, high-intensity sound
may rupture the eardrum, damage the
small bones in the middle ear, or overstimulate the electromechanical hair
cells that convert the fluid motions
caused by sound into neural impulses
that are sent to the brain. Lower level
exposures may cause hearing loss,
which is called a threshold shift (TS)
(Miller, 1974). Incidence of TS may be
either permanent, in which case it is
called a permanent threshold shift
(PTS), or temporary, in which case it is
called a temporary threshold shift
(TTS). PTS consists of non-recoverable
physical damage to the sound receptors
in the ear, which can include total or
partial deafness, or an impaired ability
to hear sounds in specific frequency
ranges. TTS is recoverable and is
considered to result from temporary,
non-injurious impacts to hearing-related
tissues. Hearing loss may affect an
animal’s ability to react normally to the
sounds around it.
The amplitude, duration, frequency,
and temporal pattern of sound exposure
all affect the amount of associated TS.
As amplitude and duration of sound
exposure increase, so, generally, does
the amount of TS. For continuous
sounds, exposures of equal energy will
lead to approximately equal effects
(Ward, 1997). 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). 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
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PTS, at least in terrestrial mammals
(Kryter, 1985).
Additional detailed information
regarding threshold shifts may be
viewed in the Navy’s RIMPAC
application and in the USWTR DEIS.
Acoustically Mediated Bubble Growth
One theoretical cause of injury to
marine mammals is rectified diffusion
(Crum and Mao, 1996), the process of
increasing the size of a bubble by
exposing it to a sound field. This
process could be facilitated if the
environment in which the ensonified
bubbles exist is supersaturated with gas.
Repetitive diving by marine mammals
can cause the blood and some tissues to
accumulate gas to a greater degree than
is supported by the surrounding
environmental pressure (Ridgway and
Howard, 1979). The deeper and longer
dives of some marine mammals (for
example, beaked whales) are
theoretically predicted to induce greater
supersaturation (Houser et al., 2001b). If
rectified diffusion were possible in
marine mammals exposed to high-level
sound, conditions of tissue
supersaturation could theoretically
speed the rate and increase the size of
bubble growth. Subsequent effects due
to tissue trauma and emboli would
presumably mirror those observed in
humans suffering from decompression
sickness.
It is unlikely that the short duration
of sonar pings 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 gassupersaturated state for a long enough
period of time for bubbles to become of
a problematic size. Yet another
hypothesis has speculated that rapid
ascent to the surface following exposure
to a startling sound might produce
tissue gas saturation sufficient for the
evolution of nitrogen bubbles (Jepson et
al., 2003). In this scenario, the rate of
ascent would need to be sufficiently
rapid to compromise behavioral or
physiological protections against
nitrogen bubble formation. Collectively,
these hypotheses can be referred to as
‘‘hypotheses of acoustically mediated
bubble growth.’’
Although theoretical predictions
suggest the possibility for acoustically
mediated bubble growth, there is
considerable disagreement among
scientists as to its likelihood (Piantadosi
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and Thalmann, 2004; Evans and Miller,
2003). To date, Energy Levels (ELs)
predicted to cause in vivo bubble
formation within diving cetaceans have
not been evaluated (NOAA, 2002b).
Further, although it has been argued
that traumas from some recent beaked
whale strandings are consistent with gas
emboli and bubble-induced tissue
separations (Jepson et al., 2003), there is
no conclusive evidence of this. Because
evidence supporting the potential for
acoustically mediated bubble growth is
debatable, this proposed IHA does not
give it any special treatment.
Additionally, the required mitigation
measures, which are designed to avoid
behavioral disruptions that could result
in abnormal vertical movement by
whales through the water column,
should also reduce the potential for
creating circumstances that theoretically
contribute to harmful bubble growth.
Additional information on the
physiological effects of sound on marine
mammals may be found in the Navy’s
IHA application and associated
Environmental Assessment, the USWTR
DEIS, and on the Ocean Acoustic
Program section of the NMFS website
(see ADDRESSES).
Stress Responses
In addition to PTS and TTS, exposure
to mid-frequency sonar is likely to result
in other physiological changes that have
other consequences for the health and
ecological fitness of marine mammals.
There is mounting evidence that wild
animals respond to human disturbance
in the same way that they respond to
predators (Beale and Monaghan, 2004;
Frid, 2003; Frid and Dill, 2002; Gill et
al., 2000; Gill and Sutherland, 2001;
Harrington and Veitch, 1992; Lima,
1998; Romero, 2004). These responses
manifest themselves as interruptions of
essential behavioral or physiological
events, alteration of an animal’s time or
energy budget, or stress responses in
which an animal perceives human
activity as a potential threat and
undergoes physiological changes to
prepare for a flight or fight response or
more serious physiological changes with
chronic exposure to stressors (Frid and
Dill, 2002; Romero, 2004; Sapolsky et
al., 2000; Walker et al., 2005).
Classic stress responses begin when
an animal’s central nervous system
perceives a potential threat to its
homeostasis. That perception triggers
stress responses regardless of whether a
stimulus actually threatens the animal;
the mere perception of a threat is
sufficient to trigger a stress response
(Sapolsky et al., 2005; Seyle, 1950).
Once an animal’s central nervous
system perceives a threat, it develops a
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biological response or defense that
consists of a combination of the four
general biological defense responses:
behavioral responses, autonomic
nervous system responses,
neuroendocrine responses, or immune
response.
The physiological mechanisms
behind stress responses involving the
hypothalamus-pituitary-adrenal glands
have been well-established through
controlled experiment in the laboratory
and natural settings (Korte et al. 2005;
McEwen and Seeman, 2000; Moberg,
1985; 2000; Sapolsky et al., 2005).
Relationships between these
physiological processes, animal
behavior, neuroendocrine responses,
immune responses, inhibition of
reproduction (by suppression of preovulatory luteinizing hormones), and
the costs of stress responses have also
been documented through controlled
experiment in both laboratory and freeliving animals (for examples see,
Holberton et al., 1996; Hood et al., 1998;
Jessop et al., 2003; Krausman et al.,
2004; Lankford et al., 2005; Reneerkens
et al., 2002; Thompson and Hamer,
2000; Tilbrook et al., 2000).
The available evidence suggests that:
with the exception of unrelieved pain or
extreme environmental conditions, in
most animals (including humans)
chronic stress results from exposure to
a series of acute stressors whose
cumulative biotic costs produce a
pathological or pre-pathological state in
an animal. The biotic costs can result
from exposure to an acute stressor or
from the accumulation of a series of
different stressors acting in concert
before the animal has a chance to
recover.
Although these responses have not
been explicitly identified in marine
mammals, they have been identified in
other vertebrate animals and every
vertebrate mammal that has been
studied, including humans. Because of
the physiological similarities between
marine mammals and other mammal
species, NMFS believes that acoustic
energy sufficient to trigger onset PTS or
TTS is likely to initiate physiological
stress responses. More importantly,
NMFS believes that marine mammals
might experience stress responses at
received levels lower than those
necessary to trigger onset TTS.
Potential Behavioral Effects
For a military readiness activity, Level
B Harassment is defined as ‘‘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,
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breeding, feeding, or sheltering, to a
point where such behavioral patterns
are abandoned or significantly altered.’’
As discussed above, TTS consists of
temporary, short-term impacts to
auditory tissue that alter physiological
function, but that are fully recoverable
without the requirement for tissue
replacement or regeneration. An animal
that experiences a temporary reduction
in hearing sensitivity suffers no
permanent injury to its auditory system,
but, for an initial time post-exposure,
may not perceive some sounds due to
the reduction in sensitivity. As a result,
the animal may not respond to sounds
that would normally produce a
behavioral reaction (such as a predator
or the social calls of conspecifics, which
play important roles in mother-calf
relations, reproduction, foraging, and
warning of danger). This lack of
response qualifies as a temporary
disruption of normal behavioral patterns
- the animal is impeded from
responding in a normal manner to an
acoustic stimulus.
NMFS also considers disruption of
the behavior of marine mammals that
can result from sound levels lower than
those considered necessary for TTS to
occur (often referred to as sub-TTS
behavioral disruption). Though few
studies have specifically documented
the effects of tactical mid-frequency
sonar on the behavior of marine
mammals in the wild, many studies
have reported the effects of a wide range
of intense anthropogenic acoustic
stimuli on specific facets of marine
mammal behavior, including migration
(Malme et al., 1984; Ljungblad et al.,
1988; Richardson et al., 1999), feeding
(Malme et al., 1988), and surfacing
(Nowachek et al., 2004). Below, NMFS
summarizes the results of two studies
and one after-the-fact investigation
wherein the natural behavior patterns of
marine mammals exposed to levels of
tactical mid-frequency sonar, or sounds
similar to mid-frequency sonar, lower
than those thought to induce TTS were
disrupted to the point where it was
abandoned or significantly altered:
(1) Finneran and Schlundt (2004)
analyzed behavioral observations from
related TTS studies (Schlundt et al.,
2000; Finneran et al., 2001; 2003) to
calculate cetacean behavioral reactions
as a function of known noise exposure.
During the TTS experiments, four
dolphins and two white whales were
exposed during a total of 224 sessions
to 1–s pulses between 160 and 204 dB
re 1 mPa (root-mean-square sound
pressure level (SPL)), at 0.4, 3, 10, 20,
and 75 kHz. Finneran and Schlundt
(2004) evaluated the behavioral
observations in each session and
determined whether a ‘‘behavioral
alteration’’ (ranging from modifications
of response behavior during hearing
sessions to attacking the experimental
equipment) occurred. For each
frequency, the percentage of sessions in
which behavioral alterations occurred
was calculated as a function of received
noise SPL. By pooling data across
individuals and test frequencies,
respective SPL levels coincident with
responses by 25, 50, and 75 percent
behavioral alteration were documented.
190 dB re 1 mPa (SPL) is the point at
which 50 percent of the animals
exposed to 3, 10, and 20 kHz tones were
deemed to respond with some
behavioral alteration, and the threshold
that the Navy originally proposed for
sub-TTS behavioral disturbance.
(2) Nowacek et al. (2004) conducted
controlled exposure experiments on
North Atlantic right whales using ship
noise, social sounds of con-specifics,
and an alerting stimulus (frequency
modulated tonal signals between 500 Hz
and 4.5 kHz). Animals were tagged with
acoustic sensors (D-tags) that
simultaneously measured movement in
three dimensions. Whales reacted
strongly to alert signals at received
levels of 133–148 dB SPL, mildly to
conspecific signals, and not at all to
ship sounds or actual vessels. The alert
stimulus caused whales to immediately
cease foraging behavior and swim
rapidly to the surface. Although SEL
values were not directly reported, based
on received exposure durations,
approximate received values were on
the order of 160 dB re: 1 mPa2–s.
(3) NMFS (2005) evaluated the
acoustic exposures and coincident
behavioral reactions of killer whales in
the presence of tactical mid-frequency
sonar. In this case, none of the animals
were directly fitted with acoustic
dosimeters. However, based on a Naval
Research Laboratory (NRL) analysis that
took advantage of the fact that calibrated
measurements of the sonar signals were
made in situ and using advanced
modeling to bound likely received
exposures, estimates of received sonar
signals by the killer whales were
possible. Received SPL values ranged
from 121 to 175 dB re: 1 mPa. The most
probable SEL values were 169.1 to 187.4
dB re: 1 mPa2–s; worst-case estimates
ranged from 177.7 to 195.8 dB re: 1
mPa2–s. Researchers observing the
animals during the course of sonar
exposure reported unusual alterations in
swimming, breathing, and diving
behavior.
For more detailed information
regarding how marine mammals may
respond to sound, see the Navy’s IHA
application, the Navy’s associated EA,
Richardson’s Marine Mammals and
Noise (1995), or the references cited on
NMFS’ Ocean Acoustic Program website
(see ADDRESSES)
Harassment Thresholds
For the purposes of this IHA, NMFS
recognizes three levels of take; Level A
Harassment (Injury), Level B
Harasssment (Behavioral Disruption),
and mortality (or serious injury that may
lead to mortality) (Table 2). Mortality, or
serious injury leading to mortality, may
not be authorized with an IHA.
NMFS has determined that for
acoustic effects, acoustic thresholds are
the most effective way to consistently
both apply measures to avoid or
minimize the impacts of an action and
to quantitatively estimate the effects of
an action. Thresholds are commonly
used in two ways: (1) To establish a
shut-down or power down zone, i.e., if
an animal enters an area calculated to be
ensonified above the level of an
established threshold, a sound source is
powered down or shut down; and (2) to
calculate take, for example, if the Level
A Harassment threshold is 215 dB, a
model may be used to calculate the area
around the sound source that will be
ensonified to that level or above, then,
based on the estimated density of
animals and the distance that the sound
source moves, NMFS can estimate the
number of marine mammals exposed to
215 dB. The rationale behind the
acoustic thresholds proposed for this
authorization are discussed below.
TABLE 2. THE THREE LEVELS OF TAKE ADDRESSED IN THE MMPA, HOW NMFS MEASURES THEM IN REGARD TO ACOUSTIC
EFFECTS, AND THE PROPOSED THRESHOLDS FOR THIS AUTHORIZATION
Basis of Threshold
Proposed Threshold
Permanent Threshold Shift (PTS) ................................
Temporary Threshold Shift (TTS) ................................
Sub–TTS Behavioral Effects ........................................
215 dB (SEL).
195 dB (SEL) .......
173 dB (SEL).
Levels of Take Pursuant to the MMPA
Level A Harassment (Injury)
Level B Harassment (Behavioral Effects)
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TABLE 2. THE THREE LEVELS OF TAKE ADDRESSED IN THE MMPA, HOW NMFS MEASURES THEM IN REGARD TO ACOUSTIC
EFFECTS, AND THE PROPOSED THRESHOLDS FOR THIS AUTHORIZATION—Continued
Basis of Threshold
Proposed Threshold
Not enough information for quantitative threshold .......
May not be
authorized with an
IHA.
Levels of Take Pursuant to the MMPA
Mortality, or Serious Injury That May Lead to Mortality (Stranding)
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TTS
Because it is non-injurious, NMFS
considers TTS as Level B harassment
(behavioral disruption) that is mediated
by physiological effects on the auditory
system. The smallest measurable
amount of TTS (onset-TTS) is taken as
the best indicator for slight temporary
sensory impairment. However, as
mentioned earlier, NMFS believes that
behavioral disruptions may result from
received levels of tactical sonar lower
than those thought to induce TTS and,
therefore, NMFS does not consider onset TTS to be the lowest level at which
Level B Harassment may occur. NMFS
considers the threshold for Level B
Harasment as the received levels from
which sub-TTS behavioral disruptions
are likely to result (discussed in SubTTS sub-section). However, the
threshold for Level A Harassment (PTS)
is derived from the threshold for TTS
and, therefore, it is necessary to describe
how the TTS threshold was developed.
The proposed TTS threshold is
primarily based on the cetacean TTS
data from Schlundt et al. (2000). These
tests used short-duration tones similar
to sonar pings, and they are the most
directly relevant data for the
establishing TTS criteria. The mean
exposure EL required to produce onsetTTS in these tests was 195 dB re 1
mPa2–s. This result is corroborated by
the short-duration tone data of Finneran
et al. (2000, 2003) and the long-duration
noise data from Nachtigall et al.
(2003a,b). Together, these data
demonstrate that TTS in cetaceans is
correlated with the received EL and that
onset-TTS exposures are fit well by an
equal-energy line passing through 195
dB re 1 mPa2–s.
The justification for establishing the
195 dB acoustic criteria for TTS is
described in detail in both the Navy’s
RIMPAC IHA application and the
USWTR DEIS (see ADDRESSES).
PTS
PTS consists of non-recoverable
physical damage to the sound receptors
in the ear and is, therefore, classified as
Level A harassment under the MMPA.
For acoustic effects, because the tissues
of the ear appear to be the most
susceptible to the physiological effects
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of sound, and because threshold shifts
(TSs) tend to occur at lower exposures
than other more serious auditory effects,
NMFS has determined that permanent
threshold shift (PTS) is the best
indicator for the smallest degree of
injury that can be measured. Therefore,
the acoustic exposure associated with
onset-PTS is used to define the lower
limit of the Level A harassment.
PTS data do not currently exist for
marine mammals and are unlikely to be
obtained due to ethical concerns.
However, PTS levels for these animals
may be estimated using TTS data and
relationships between TTS and PTS.
NMFS proposes the use of 215 dB re 1
mPa2–s as the acoustic threshold for
PTS. This threshold is based on a 20 dB
increase in exposure EL over that
required for onset-TTS (195 dB).
Extrapolations from terrestrial mammal
data indicate that PTS occurs at 40 dB
or more of TS, and that TS growth
occurs at a rate of approximately 1.6 dB
TS per dB increase in EL. There is a 34–
dB TS difference between onset-TTS (6
dB) and onset-PTS (40 dB). Therefore,
an animal would require approximately
20dB of additional exposure (34 dB
divided by 1.6 dB) above onset-TTS to
reach PTS.
The justification for establishing the
215–dB acoustic criteria for PTS is
described in detail in both the Navy’s
RIMPAC IHA application and the
Undersea Warfare Training Range
USWTR DEIS.
Sub-TTS Behavioral Disruption
NMFS believes that behavioral
disruption of marine mammals may
result from received levels of midfrequency sonar lower than those
believed necessary to induce TTS, and
further, that the lower limit of Level B
Harassment may be defined by the
received sound levels associated with
these sub-TTS behavioral disruptions.
As of yet, no controlled exposure
experiments have been conducted
wherein wild cetaceans are deliberately
exposed to tactical mid-frequency sonar
and their reactions carefully observed.
However, NMFS believes that in the
absence of controlled exposure
experiments, the following
investigations and reports (described
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previously in the Behavioral Effects
section) constitute the best available
scientific information for establishing an
appropriate acoustic threshold for subTTS behavioral disruption: (1) Finneran
and Schlundt (2004), in which
behavioral observations from TTS
studies of captive bottlenose dophins
and beluga whales are analyzed as a
function of known noise exposure; (2)
Nowachek et al. (2004), in which
controlled exposure experiments were
conducted on North Atlantic right
whales using ship noise, social sounds
of con-specifics, and an alerting
stimulus; and (3) NMFS (2005), in
which the behavioral reactions of killer
whales in the presence of tactical midfrequency sonar were observed, and
analyzed after the fact. Based on these
three studies, NMFS has set the sub-TTS
behavioral disruption threshold at 173
dB re 1 mPa2–s (SEL).
The Finneran and Schlundt (2004)
analysis is an important piece in the
development of an appropriate acoustic
threshold for sub-TTS behavioral
disruption because: (1) researchers had
superior control over and ability to
quantify noise exposure conditions; (2)
behavioral patterns of exposed marine
mammals were readily observable and
definable; and, (3) fatiguing noise
consisted of tonal noise exposures with
frequencies contained in the tactical
mid-frequency sonar bandwidth. In
Finneran and Schlundt (2004) 190 dB re
1 mPa (SPL) is the point at which 50
percent of the animals exposed to 3, 10,
and 20 kHz tones were deemed to
respond with some behavioral
alteration. This 50 percent behavior
alteration level (190 dB SPL) may be
converted to an SEL criterion of 190 dB
re 1 mPa2–s (the numerical values are
identical because exposure durations
were 1–s), which provides consistency
with the Level A (PTS) effects threshold,
which are also expressed in SEL. The
Navy proposed 190 dB (SEL) as the
acoustic threshold for sub-TTS
behavioral disruption in the first IHA
application they submitted to NMFS.
NMFS acknowledges the advantages
arising from the use of behavioral
observations in controlled laboratory
conditions; however, there is
considerable uncertainty regarding the
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validity of applying data collected from
trained captives conditioned to not
respond to noise exposure in
establishing thresholds for behavioral
reactions of naive wild individuals to a
sound source that apparently evokes
strong reactions in some marine
mammals. Although wide-ranging in
terms of sound sources, context, and
type/extent of observations reported, the
large and growing body of literature
regarding behavioral reactions of wild,
naive marine mammals to
anthropogenic exposure generally
suggests that wild animals are
behaviorally affected at significantly
lower levels than those determined for
captive animals by Finneran and
Schlundt (2004). For instance, some
cetaceans exposed to human noise
sound sources, such as seismic airgun
sounds and low frequency sonar signals,
have been shown to exhibit avoidance
behavior when the animals are exposed
to noise levels of 140–160 dB re: 1 mPa
under certain conditions (Malme et al.,
1983; 1984; 1988; Ljungblad et al., 1988;
Tyack and Clark, 1998). Richardson et
al. (1995) reviewed the behavioral
response data for many marine mammal
species and a wide range of human
sound sources.
Two specific situations for which
exposure conditions and behavioral
reactions of free-ranging marine
mammals exposed to sounds very
similar to those proposed for use in
RIMPAC are considered by Nowacek et
al. (2004) and NMFS (2005) (described
previously in Behavioral Effects
subsection). In the Nowacek et al. (2004)
study, North Atlantic right whales
reacted strongly to alert signals at
received levels of 133–148 dB SPL,
which, based on received exposure
durations, is approximately equivalent
to 160 dB re: 1 mPa2–s (SEL). In the
NMFS (2005) report, unusual alterations
in swimming, breathing, and diving
behaviors of killer whales observed by
researchers in Haro Strait were
correlated, after the fact, with the
presence of estimated received sound
levels between 169.1and 187.4 dB re: 1
mPa2–s (SEL).
While acknowledging the limitations
of all three of these studies and noting
that they may not necessarily be
predictive of how wild cetaceans might
react to mid-frequency sonar signals in
the OpArea, NMFS believes that these
three studies are the best available
science to support the selection of an
acoustic sub-TTS behavioral
disturbance threshold at this time.
Taking into account all three studies,
NMFS has established 173 dB re: 1
mPa2 (SEL) as the threshold for sub-TTS
behavioral disturbance.
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Stranding and Mortality
Over the past 10 years, there have
been four stranding events coincident
with military mid-frequency sonar use
that are believed to most likely have
been caused by exposure to the sonar.
These occurred in Greece (1996), the
Bahamas (2000), Madeira (2000) and
Canary Islands (2002). In 2004, during
the RIMPAC exercises, between 150–
200 usually pelagic melon-headed
whales occupied the shallow waters of
the Hanalei Bay, Kaua’i, Hawaii for over
28 hours. NMFS determined that the
mid-frequency sonar was, a plausible, if
not likely, contributing factor in what
may have been a confluence of events
that led to the Hanalei Bay stranding. A
number of other stranding events
coincident with the operation of midfrequency sonar and resulting in the
death of beaked whales or other species
(minke whales, dwarf sperm whales,
pilot whales) have been reported,
though the majority have not been
investigated to the level of the Bahamas
stranding and, therefore, other causes
cannot be ruled out.
Greece, Madeira, and Canary Islands
Twelve Cuvier’s beaked whales
stranded along the western coast of
Greece in 1996. The test of a low- and
mid-frequency active sonar system
conducted by NATO was correlated
with the strandings by an analysis
published in Nature. A subsequent
NATO investigation found the
strandings to be closely related, in time,
to the movements of the sonar vessel,
and ruled out other physical factors as
a cause.
In 2000, four beaked whales stranded
in Madeira while several NATO ships
were conducting an exercise near shore.
Scientists investigating the stranding
found that the injuries, which included
blood in and around the eyes, kidney
lesions, and pleural hemorrhage, as well
as the pattern of the stranding suggested
that a similar pressure event
precipitated or contributed to strandings
in both Madeira and Bahamas (see
Bahamas sub-section).
In 2002, at least 14 beaked whales of
three different species stranded in the
Canary Islands while a naval exercise
including Spanish vessels, U.S. vessels,
and at least one vessel equipped with
mid-frequency sonar was conducted in
the vicinity. Four more beaked whales
stranded over the next several days. The
subsequent investigation, which was
reported in both Nature and Veterinary
Pathology, revealed a variety of traumas,
including emboli and lesions suggestive
of decompression sickness.
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Bahamas
NMFS and the Navy prepared a joint
report addressing the multi-species
stranding in the Bahamas in 2000,
which took place within 24 hours of
U.S. Navy ships using active midfrequency sonar as they passed through
the Northeast and Northwest Providence
Channels. Of the 17 cetaceans that
stranded (Cuvier’s beaked whales,
Blainsville’s beaked whales, Minke
whales, and a spotted dolphin), seven
animals died on the beach (5 Cuvier’s
beaked whales, 1 Blainsville’s beaked
whale, and the spotted dolphin) and the
other 10 were returned to the water
alive (though their fate is unknown). A
comprehensive investigation was
conducted and all possible causes of the
stranding event were considered,
whether they seemed likely at the outset
or not. The only possible contributory
cause to the strandings and cause of the
lesions that could not be ruled out was
intense acoustic signals (the dolphin
necropsy revealed a disease and the
death is considered unrelated to the
others).
Based on the way in which the
strandings coincided with ongoing
naval activity involving tactical midfrequency sonar use, in terms of both
time and geography, the nature of the
physiological effects experienced by the
dead animals, and the absence of any
other acoustic sources, the investigation
team concluded that mid-frequency
sonars aboard U.S. Navy ships that were
in use during the sonar exercise in
question were the most plausible source
of this acoustic or impulse trauma. This
sound source was active in a complex
environment that included the presence
of a surface duct, unusual and steep
bathymentry, a constricted channel with
limited egress, intensive use of multiple,
active sonar units over an extended
period of time, and the presence of
beaked whales that appear to be
sensitive to the frequencies produced by
these sonars. The investigation team
concluded that the cause of this
stranding event was the confluence of
the Navy mid-frequency sonar and these
contributory factors working together,
and further recommended that the Navy
avoid operating mid-frequency sonar in
situations where these five factors
would be likely to occur. This report
does not conclude that all five of these
factors must be present for a stranding
to occur, nor that beaked whales are the
only species that could potentially be
affected by the confluence of the other
factors. Based on this, NMFS believes
that the presence of surface ducts, steep
bathymetry, and/or constricted channels
added to the operation of mid-frequency
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sonar in the presence of cetaceans
(especially beaked whales and,
potentially, deep divers) may increase
the likelihood of producing a sound
field with the potential to cause
cetaceans to strand, and therefore,
necessitates caution.
Hanalei Bay
On July 3–4, 2004, between 150–200
melon-headed whales occupied the
shallow waters of the Hanalei Bay,
Kaua’i, Hawaii for over 28 hours.
Attendees of a canoe blessing observed
the animals entering the Bay in a single
wave formation at 7 a.m. on July 3,
2004. The animals were observed
moving back into the shore from the
mouth of the Bay at 9 a.m. The usually
pelagic animals milled in the shallow
bay and were returned to deeper water
with human assistance beginning at 9:30
a.m. on July 4, 2004, and were out of
sight by 10:30 a.m.
Only one animal, a calf, was known
to have died (on July 5, 2004) following
this event. The animal was noted alive
and alone in the Bay on the afternoon
of July 4, 2004 and was found dead in
the Bay the morning of July 5, 2004. On
July 7, 2004, a full necropsy, magnetic
resonance imaging, and computerized
tomography examination were
performed on the calf to determine the
manner and cause of death. The
combination of imaging, necropsy and
histological analyses found no evidence
of infectious, internal traumatic,
congenital, or toxic factors. Although
cause of death could not be definitively
determined, it is likely that maternal
separation, poor nutritional condition,
and dehydration contributed to the final
demise of the animal. Although we do
not know when the calf was separated
from its mother, the movement into the
Bay, the milling and re-grouping may
have contributed to the separation or
lack of nursing especially if the
maternal bond was weak or this was a
primiparous calf.
Environmental factors, abiotic and
biotic, were analyzed for any anomalous
occurrences that would have
contributed to the animals entering and
remaining in Hanalei Bay. The Bay’s
bathymetry is similar to many other
sites within the Hawaiian Island chain
and dissimilar to sites that have been
associated with mass strandings in other
parts of the United States. The weather
conditions appeared to be normal for
that time of year with no fronts or other
significant features noted. There was no
evidence of unusual distribution or
occurrence of predator or prey species,
or unusual harmful algal blooms.
Weather patterns and bathymetry that
have been associated with mass
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strandings elsewhere were not found to
occur in this instance.
This event was spatially and
temporally correlated with RIMPAC.
Official sonar training and tracking
exercises in the Pacific Missile Range
Facility (PMRF) warning area did not
commence until approximately 8 a.m.
on July 3 and were thus ruled out as a
possible trigger for the initial movement
into the Bay.
However, the six naval surface vessels
transiting to the operational area on July
2 intermittently transmitted active sonar
(for approximately 9 hours total from
1:15 p.m. to 12:30 a.m.) as they
approached from the south. The
potential for these transmissions to have
triggered the whales’ movement into
Hanalei Bay was investigated. Analyses
with the information available indicated
that animals to the south and east of
Kaua’i could have detected active sonar
transmissions on July 2, and reached
Hanalei Bay on or before 7 a.m. on July
3, 2004. However, data limitations
regarding the position of the whales
prior to their arrival in the Bay, the
magnitude of sonar exposure, behavioral
responses of melon-headed whales to
acoustic stimuli, and other possible
relevant factors preclude a conclusive
finding regarding the role of sonar in
triggering this event. Propagation
modeling suggest that transmissions
from sonar use during the July 3
exercise in the PMRF warning area may
have been detectable at the mouth of the
Bay. If the animals responded negatively
to these signals, it may have contributed
to their continued presence in the Bay.
The U.S. Navy ceased all active sonar
transmissions during exercises in this
range on the afternoon of July 3, 2004.
Subsequent to the cessation of sonar
use, the animals were herded out of the
Bay.
While causation of this stranding
event may never be unequivocally
determined, we consider the active
sonar transmissions of July 2–3, 2004, a
plausible, if not likely, contributing
factor in what may have been a
confluence of events. This conclusion is
based on: (1) the evidently anomalous
nature of the stranding; (2) its close
spatiotemporal correlation with widescale, sustained use of sonar systems
previously associated with stranding of
deep-diving marine mammals; (3) the
directed movement of two groups of
transmitting vessels toward the
southeast and southwest coast of Kaua’i;
(4) the results of acoustic propagation
modeling and an analysis of possible
animal transit times to the Bay; and (5)
the absence of any other compelling
causative explanation. The initiation
and persistence of this event may have
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resulted from an interaction of
biological and physical factors. The
biological factors may have included the
presence of an apparently uncommon,
deep-diving cetacean species (and
possibly an offshore, non-resident
group), social interactions among the
animals before or after they entered the
Bay, and/or unknown predator or prey
conditions. The physical factors may
have included the presence of nearby
deep water, multiple vessels transiting
in a directed manner while transmitting
active sonar over a sustained period, the
presence of surface sound ducting
conditions, and/or intermittent and
random human interactions while the
animals were in the Bay.
Beaked Whales
Recent beaked whale strandings have
prompted inquiry into the relationship
between mid-frequency active sonar and
the cause of those strandings. A review
of world-wide cetacean mass stranding
data reveals that beaked whales have
been the most common taxa involved in
stranding events (approximately 67
percent of all strandings include beaked
whales), with Cuvier’s beaked whales
accounting for about 90 percent of the
individual beaked whales. Although the
confluence of Navy mid-frequency
active tactical sonar with the other
contributory factors noted in the report
was identified as the cause of the 2000
Bahamas stranding event, the specific
mechanisms that led to that stranding
are not understood, and there is
uncertainty regarding the ordering of
effects that led to the stranding. It is
uncertain whether beaked whales were
directly injured by sound (a
physiological effect) prior to stranding
or whether a behavioral response to
sound occurred that ultimately caused
the beaked whales to strand and be
injured.
Several potential physiological
outcomes caused by behavioral
responses to high-intensity sounds have
been suggested by Cox et al. (in press).
These include: gas bubble formation
caused by excessively fast surfacing;
remaining at the surface too long when
tissues are supersaturated with nitrogen;
or diving prematurely when extended
time at the surface is necessary to
eliminate excess nitrogen. Baird et al.
(2005) found that slow ascent rates from
deep dives and long periods of time
spent within 50 m of the surface were
typical for both Cuvier’s and
Blainsville’s beaked whales, the two
species involved in mass strandings
related to naval sonar. These two
behavioral mechanisms may be
necessary to purge excessive dissolved
nitrogen concentrated in their tissues
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during their frequent long dives (Baird
et al., 2005). Baird et al. (2005) further
suggests that abnormally rapid ascents
or premature dives in response to highintensity sonar could indirectly result in
physical harm to the beaked whales,
through the mechanisms described
above (gas bubble formation or nonelimination of excess nitrogen).
During the RIMPAC exercise there
will be use of multiple sonar units in an
area where three beaked whale species
may be present. A surface duct may be
present in a limited area for a limited
period of time. Although most of the
ASW training events will take place in
the deep ocean, some will occur in areas
of high bathymetric relief. However,
none of the training events will take
place in a location having a constricted
channel with limited egress similar to
the Bahamas. Consequently, not all five
of the environmental factors believed to
contribute to the Bahamas stranding
(mid-frequency sonar, beaked whale
presence, surface ducts, steep
bathymetry, and constricted channels
with limited egress) will be present
during RIMPAC ASW exercises.
However, as mentioned previously,
NMFS believes caution should be used
anytime either steep bathymetry, surface
ducting conditions, or a constricted
channel is present in addition to the
operation of mid-frequency tactical
sonar and the presence of cetaceans
(especially beaked whales).
Estimated Take by Incidental
Harassment
In order to estimate acoustic
exposures from the RIMPAC ASW
operations, acoustic sources to be used
were examined with regard to their
operational characteristics. Systems
with acoustic source levels below 205
dB re 1 mPa were not included in the
analysis given that at this source level
(205 dB re 1 mPa) or below, a 1-second
ping would attenuate below the Level B
Harassment behavioral disturbance
threshold of 173 dB at a distance of
about 100 meters, which is well within
the required shutdown zone. Also,
animals are expected to avoid the
exercises by a distance greater than that
and their detectibility is higher at that
distance. In addition, systems with an
operating frequency greater than 100
kHz were not analyzed in the detailed
modeling, as these signals attenuate
rapidly, resulting in very short
propagation distances. Acoustic
countermeasures were previously
examined and found not to be
problematic. The AN/AQS 13 (dipping
sonar) used by carrier based helicopters
was determined in the Environmental
Assessment/Overseas Environmental
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Assessment of the SH–60R Helicopter/
ALFS Test Program, October 1999, not
to be problematic due to its limited use
and very short pulse length (2 to 5
pulses of 3.5 to 700 msec). Since 1999,
during the time of the test program,
there have been over 500 hours of
operation, with no environmental
effects observed. The Directional
Command Activated Sonobuoy System
(DICASS) sonobuoy was determined not
to be problematic, having a source level
of 201 dB re 1 mPa. These acoustic
sources, therefore, did not require
further examination in this analysis.
Based on the information above, only
hull mounted mid-frequency active
tactical sonar was determined to have
the potential to affect marine mammals
during RIMPAC ASW training events.
Model
An analysis was conducted for
RIMPAC 2006, modeling the potential
interaction of hull mounted midfrequency active tactical sonar with
marine mammals in the OpArea. The
model incorporates site-specific
bathymetric data, time-of-year-specific
sound speed information, the sound
source’s frequency and vertical beam
pattern, and multipath pressure
information as a function of range,
depth and bearing. Results were
calculated based on the typical ASW
activities planned for RIMPAC 2006.
Acoustic propagation and mammal
population and density data were
analyzed for the July timeframe since
RIMPAC occurs in July. The modeling
occurred in five broad steps, listed
below.
Step 1. Perform a propagation analysis
for the area ensonified using spherical
spreading loss and the Navy’s CASS/
GRAB program, respectively.
Step 2. Convert the propagation data
into a two-dimensional acoustic
footprint for the acoustic sources
engaged in each training event as they
move through the six acoustic exposure
model areas.
Step 3. Calculate the total energy flux
density level for each ensonified area
summing the accumulated energy of all
received pings.
Step 4. Compare the total energy flux
density to the thresholds and determine
the area at or above the threshold to
arrive at a predicted marine mammal
exposure area.
Step 5. Multiply the exposure areas by
the corresponding mammal population
density estimates. Sum the products to
produce species sound exposure rate.
Analyze this rate based on the annual
number of events for each exercise
scenario to produce annual acoustic
exposure estimates.
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Based on the modeled estimate,
NMFS anticipates take of 21 cetaceans
and no pinnipeds. The results of the
model (estimated Level B Harassment
takes) are presented in Table 1. The
model actually estimated potential take
of 1 Hawaiian monk seal, however,
because of the anticipated effectiveness
of the mitigation measures and distance
of the majority of the exercises from
land, NMFS does not anticipate any take
of monk seals, and it is not authorized.
When analyzing the results of the
acoustic exposure modeling to provide
an estimate of effects, it is important to
understand that there are limitations to
the ecological data used in the model,
and that the model results must be
interpreted within the context of a given
species’ ecology and biology.
NMFS believes that the model take
estimates may be overestimates for the
following reasons:
(1) The implementation of the
extensive mitigation and monitoring
that will be required by the IHA
(Including large power-down/shutdown zones, geographic restrictions,
and monitors that will almost certainly
sight groups of animals, if not
individuals, in time to avoid/minimize
impacts) have not been taken into
account.
(2) In the model the Navy used to
estimate take, marine mammals remain
stationary as the sound source passes by
and their immediate area is ensonified.
NMFS believes that some, if not the
majority of animals, will move away
from the sound to some degree, thus
receiving a lower level of energy than
estimated by the model.
(3) In the Navy’s model, sound levels
were calculated for every 5 m (16 ft)
wide by 5 m (16 ft) long by 2 m (7 ft)
deep section within the ensonified area.
Then, for each 5 m (16 ft) by 5 m (16
ft) column of the ocean, the sound level
through that entire water column was
assumed to be whatever the sound level
was in the loudest 2 m (7 ft) deep
section of that water column.
(4) NMFS interprets the results of the
Navy’s model as the number of times
marine mammals might be exposed to
particular received levels of sound.
However, NMFS believes it would be
unrealistic, considering the fast-paced,
multi-vessel nature of the exercise and
the fact that the exercise continues over
the course of a month in an area with
resident populations of cetaceans, to
assume that each exposure involves a
different whale; some whales are likely
to be exposed once, while others are
likely to be exposed more than
once.Some elements of the Navy’s
modeling, such as its calculation of
received levels without regard to where
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animals occur in the water column, are
conservative. Other elements, such as its
evaluation of some but not all acoustic
sources that would be used during the
exercise, may not be conservative. It is
NMFS view that an extensive set of
mitigation and monitoring requirements
like those set forth in this notice would
ensure that impacts on species and
stocks are negligible. This conclusion
would not necessarily apply to other
naval acoustic activities whose
operational and environmental
parameters may differ.
Potential Effects on Habitat
The primary source of marine
mammal habitat impact is acoustic
exposures resulting from ASW
activities. However, the exposures do
not constitute a long term physical
alteration of the water column or bottom
topography, as the occurrences are of
limited duration and are intermittent in
time. Surface vessels associated with the
activities are present in limited duration
and are intermittent as well.
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Potential Effects on Subsistence Harvest
of Marine Mammals
There is no known legal subsistence
hunting for marine mammals in or near
the survey area, so the proposed
activities will not have any impact on
the availability of the species or stocks
for subsistence users.
Comments and Responses
On April 24, 2006 (71 FR 20987),
NMFS published a notice of a proposed
IHA for the Navy’s request to take
marine mammals incidental to the
RIMPAC ASW exercises and requested
comments, information and suggestions
concerning the request. During the 30day public comment period, NMFS
received approximately 125 comments
from private citizens and several sets of
comments from non-governmental
organizations, including the Marine
Mammal Commission (MMC), the
Natural Resources Defense Council
(which commented on behalf of the
International Fund for Animal Welfare,
Cetacean Society International, the
League for Coastal Protection, Ocean
Futures Society, Jean-Michel Cousteau,
the Humane Society of the United
States, the Center for Biological
Diversity, and Oceana) (NRDC et al.),
the Cascadia Research Collective (CRC),
Seaflow, the Animal Welfare Institute
(AWI), the Pacific Whale Foundation
(PWF), the Whale and Dolphin
Conservation Society (WDCS), and the
Center for Regulatory Effectiveness
(CRE). The comments have been sorted
into general topic areas and are
addressed below.
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Mitigation Measures
Comment 1: The coastal exclusion
zone recommended in the proposed IHA
(25 km (13.5 nm) is not large enough to
adequately protect island associated
populations of odontocetes from
significant impacts, as aerial surveys
indicate that short-finned pilot whales,
spotted dolphins, spinner dolphins, and
bottlenose dolphins occur in greater
densities within 25 nm (46 km) of shore.
Additionally, the comments point out,
during the Hanalei stranding in 2004,
signals from ships in the PMRF, some
40–50 km (21–26 nm) away, peaked
above 150 dB re 1 miPa at the mouth of
Hanalei Bay.
Response: The main reasons behind
requiring the Navy to maintain a 25 km
coastal exclusion zone around the 200
m (656 ft) isobath were to avoid the
confluence of the factors that we know
contributed to the stranding in the
Bahamas (see Strandings section), to
avoid driving deep-diving animals up
onto the shelf-break where they might
become disoriented, and to minimize
impacts to island associated animals. In
an effort to reduce the possibility of a
repeat of the circumstances present
during the Hanalei event (and to
generally better avoid the confluence of
the five Bahamas factors), NMFS did
propose an additional mitigation
measure that would require a 25–nm
(46–km) (plus 2–nm (3.7–buffer) coastal
exclusion zone. Following is an
explanation from the Navy explaining
why the 25–nm (46–km) buffer is
impracticable:
Littoral waterspace is where the
enemy will operate. The littoral
waterspace is also the most challenging
area to operate in due to a diverse
acoustic environment found there. It is
not realistic to refrain from training in
the areas that are the most challenging
and operationally unavoidable. The [25
nm (46 km) buffer] would remove
realism from precursor operations and
tactical development culminating in
choke point transits. The proposal
would remove ASW operations from the
AMPHIB phase of the training, which is
arguably the highest period of risk for
our forces.
NMFS must balance protective
measures with practicability and we
believe that the 25 km (13.5 nm) buffer
effectively reduces the effects to island
associated cetaceans while allowing the
Navy to effectively carry out their
mission.
Comment 2: Two commenters
recommended that NMFS implement a
sonar exclusion zone around sea
mounts, where species associated with
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steep, sloping areas may be exposed,
and cyclonic eddies, which can result in
significant increases in primary
productivity and have been linked to
significant increases in higher trophic
species.
Response: In regard to cyclonic
eddies, NMFS believes that the
impracticability to the Navy of avoiding
these features outweighs the potential
conservation gain. Though many species
may congregate near cyclonic eddies,
cyclonic eddies are very large, and, so
restricting access to the full extent of
these features to avoid animals that may
congregate in a small subset of the total
areas is not practicable. NMFS proposed
a mitigation measure that would require
the Navy to avoid seamounts, however,
the Navy informed NMFS that this
restriction would be impracticable
because of the following operational
impacts of having to steer clear of
seamounts:
Submarine tracking is a long and
complicated tactical procedure. The
training value of these procedures
would be lost if operations were
terminated when nearing seamounts
prior to reaching the training objectives.
Seamounts impact the way sound
travels in water as well as our ability to
search and track submarines. If we do
not train near seamounts and
understand how they affect our ability
to search and track a submarine, we will
be unable to do so when required
against an actual threat. Submarine
search planning is a detailed process
that requires flexibility and large
operating areas. If we avoided searching
or tracking submarines near sea mounts,
ASW operators will be severely limited
in their ability to execute effective
plans.
Comment 3: One commenter points
out that pursuant to Executive Order
(E.O.) 13158, NMFS must consider and
‘‘to the maximum extent practicable’’
avoid harm to the protected natural and
cultural resources of all Federal and
State-designated protected areas (Marine
Protected Areas (MPAs)) including, but
not limited to, the Hawaiian Islands
Humpback Whale National Marine
Sanctuary.
Response: Both the Hawaiian Islands
Humpback Whale National Marine
Sanctuary (HIHWNMS) and the newly
designated Northwestern Hawaiian
Islands Marine National Monument fall
within in the Navy’s Hawaiian Islands
OpArea, and at times during RIMPAC
exercises portions of their waters may
be ensonified. Though the HIHWNMS is
an important breeding area for
Humpback whales during the winter
and spring, the exercises will be
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conducted in July when no humpback
whales are expected to be present.
The Northwestern Hawaiian Islands
Marine National Monument
proclamation contains the following
language ‘‘The prohibitions required by
this proclamation shall not apply to
activities and exercises of the Armed
Forces (including those carried out by
the United States Coast Guard) that are
consistent with applicable laws.’’
As mentioned above, the effects of
this action are temporary and acoustic
in nature, and NMFS does not expect
them to result in harm to the protected
natural and cultural resources of these
areas.
Comment 4: One commenter
suggested NMFS should not authorize
sonar use during ship transits between
exercises, as this is the same activity
(same levels, same area), according to
the NMFS Hanalei Bay Stranding
Report, that was a ‘‘plausible, if not
likely’’ contributor to the 2004 mass
stranding event of melon-headed whales
in Hanalei Bay.
Response: According to the Navy, the
sonar use that occurred prior to the
Hanalei event was part of a designated
exercise, not sonar use while in transit
between exercises. Though the Navy
could potentially operate sonar in the
same place and manner it did during
RIMPAC 2004, it does not necessarily
mean that the other contributing factors
to the stranding would be in place
again. Also, unlike 2004, NMFS has
included in the IHA a specific set of
shutdown criteria that require the Navy
cease operating sonar as soon as a
‘‘milling out of habitat’’ event involving
a group of ten or more animals (such as
in Hanalei) is verified.
Comment 5: Several commenters
noted that the Navy plans not to operate
sonar over 235 dB except for occasional,
short periods of time. These
commenters further assert that the Navy
did not model marine mammal take at
levels above 235 dB and, therefore,
NMFS has failed to assess all reasonably
foreseeable impacts as required by
National Environmental Policy Act
(NEPA) and the MMPA. One commenter
thought that the Navy should define
what ‘‘occasional short periods’’ are and
identify the higher source level while
another commenter recommended
limiting sonar output to 235 dB
throughout the exercise.
Response: NMFS proposed an
additional mitigation measure that
would have required the Navy not
operate sonar over 235 dB, however, the
Navy informed us that they could not
implement the measure because it is
impracticable for the following reasons:
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This measure limits tactical options and
the specific reasons that it should not be
agreed to are classified. Generally, however,
realistic training requires flexibility to
operate sonar as fits the tactical scenario and
environment encountered. Sonar
configuration and operation is dependent
upon the environment. These conditions
cannot be predicted a month in advance and
a ship may find it necessary to transmit at
power levels above 235 dB to address a
situation as they would during a real world
ASW event. To place an artificial
requirement as requested decreases the
training value and does not allow our sailors
to train as we expect them to fight.
In a ‘‘classified’’ document, the Navy
provided information to the appropriate
recipients at NMFS that discusses when
and under what circumstances the
source level above 235 dB is used. After
reviewing the document, NMFS
determined that the occasional
operation of sonar above 235 dB does
not affect our conclusions pursuant to
NEPA, ESA, or MMPA.
NMFS proposed an additional
mitigation measure that would have
required the Navy not operate sonar
over 235 dB, however, the Navy
informed us that they could not
implement the measure because it is
impracticable for the following reasons:
This measure limits tactical options and
the specific reasons that it should not be
agreed to are classified. Generally, however,
realistic training requires flexibility to
operate sonar as fits the tactical scenario and
environment encountered. Sonar
configuration and operation is dependent
upon the environment. These conditions
cannot be predicted a month in advance and
a ship may find it necessary to transmit at
power levels above 235 dB to address a
situation as they would during a real world
ASW event. To place an artificial
requirement as requested decreases the
training value and does not allow our sailors
to train as we expect them to fight.
Comment 6: One commenter suggests
that because of the considerable
reduction in the range of effects gained
by a reduction in source level, NMFS
must consider requiring the Navy to
operate at source levels below 235 dB
throughout the exercise or at least in
some circumstances.Response: NMFS is
requiring the Navy to operate sonar at
lower levels under some circumstances
through monitoring of safety zones, and
with larger safety zones in surface duct
conditions and low visibility situations.
Comment 7: NMFS received several
comments regarding the proposed safety
zones. One commenter suggested that
the proposed outer safety zones (1000 m
(3280 ft), or 2000 m (6561 ft) in special
circumstances) are inadequate because
they are inconsistent with NMFS 173 dB
threshold. They further suggested that
the distances are arbitrary and
capricious.
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Response: NMFS marine mammal
incidental take authorizations typically
require a shutdown zone that
corresponds to the isopleth associated
with the Level A harassment threshold.
NMFS does not require shutdown at the
threshold associated with the onset of
Level B Harassment (173 dB in this
case), as that would effectively be an
avoidance of take, which would render
a take authorization unnecessary. In the
case of RIMPAC, the 1000 m safety zone
(at which powerdown begins) is
estimated as corresponding to the more
conservative (than typical PTS
shutdown threshold) TTS threshold
(195 SEL), and as such, is neither
arbitrary nor inadequate.
Comment 8: One commenter
suggested that the proposed safety zones
fail to meet the ‘‘least practicable
impact’’ standard because the
Australian Navy uses a 4000–m (2.2 nm)
safety zone for sonar systems operating
below 235 dB
Response: NMFS has implemented a
1000–m (3280 ft) safety zone under
normal conditions, a 2000 m (6561 ft)
safety zone in low visibility conditions
and surface-ducting conditions, and a
2000 m (6561 ft) ‘‘clear zone’’ prior to
startup in a chokepoint exercise. NMFS
believes that these zones will effectively
minimize take of marine mammals to
the maximum extent practicable
through this type of measure. Once the
safety zones are enlarged past this point,
NMFS believes detectability decreases
notably and impracticability increases
notably. The Navy observers will still be
looking beyond the safety zone and will
use the information to help implement
the current safety zone measures.
Comment 9: One commenter
suggested that NMFS require sonar
shutdown at 1000 m (3280 ft), instead
of powerdown, and that the Navy not be
authorized to operate sonar at all in
strong surface-ducting conditions.
Response: Powering down when an
animal enters the 1000–m (3280 ft)
safety zone ensures that a marine
mammal will not be exposed to levels
of sound above approximately 195 dB,
the threshold established for TTS.
Because the next powerdown is at 500
m (1640 ft), the animal would again not
be exposed to levels above
approximately 195 dB. If the animal
were then to approach to 200 m (656 ft),
it might be exposed to levels slightly
above 195, but then sonar will shut
down at 200 m (656 ft). NMFS believes
that these shutdown zones are
protective enough, especially when
balanced against the impracticability of
shutting down at 1000 m (3280 ft).
Comment 10: One commenter notes
that the 6 dB powerdown requirement if
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animals enter the 1000–m (3280–ft)
safety zone still only lowers the sound
produced to 229 dB, which is still
significantly higher than the 145–150
dB level that caused the Bahamas and
Hanalei Bay strandings.
Response: The 229 dB in this
comment refers to the sound level at 1
m (3.3 ft) from the actual sound source,
whereas the 145–150 dB level refers to
a sound level that was modeled for a
particular location where animals may
have been, based on the known
locations of the implicated sound
sources. NMFS does not expected
marine mammals to approach within
several hundred meters, much less 1 m
of the sonar dome. Additionally, neither
of the reports concluded that the listed
sound levels ’caused’’ the stranding, in
Hanalei, NMFS concluded that sonar
was a plausible, if not likely, contributor
to the event. In the Bahamas, the
Department of Defense and Department
of Commerce found that sonar was the
only possible contributory cause that
could not be ruled out.
Comment 11: One commenter
recommended that after a shutdown the
Navy wait 45 minutes, instead of 30,
before reinitiating sonar operations to
account for deep-diving animals.
Response: NMFS believes that
because of the fast-moving nature of the
exercise, the vessel will have moved a
significant distance from where the
animal was seen, and, therefore, we did
not include that measure.
Comment 12: One commenter notes
that shutdown is required by NMFS, in
normal conditions, at 200 m. The
commenter further suggests that within
that distance of the sonar dome, the
animal would have likely received noise
levels of such intensity that mortality is
almost certain. Additionally, the
commenter notes, if the animal has
gotten that close, the observation
mitigation has obviously failed.
Response: As noted in an above
comment, if an animal were to approach
and be detected (visually or otherwise)
successive powerdowns would precede
the shutdown, and this would prevent
exposure to levels above those thought
to potentially cause TTS. If an animal
were first detected right at 200 m, it
could potentially be exposed to levels
approaching those thought capable of
causing PTS. NMFS does not believe
that detection of marine mammals will
be 100 percent in the RIMPAC exercises,
however because most animals will
avoid the noise and activities
surrounding the exercises, we do not
anticipate animals approaching within
200 m of any hull-mounted sonar.
Comment 13: One commenter
recommends a mitigation measure
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wherein the Navy would be required to
shut down or relocate if they detected
beaked whales or aggregations anywhere
within their sight (not just within the
safety zone zone). They noted that
NMFS recently required the U.S. Air
Force to relocate its ordnance exercises
offshore the Eglin Air Force Base should
its fixed-wing aircraft spot any marine
mammals or sea turtles within its orbit
cycle (9.3 km).
Response: A measure that is
practicable for one activity is not
necessarily practicable or appropriate
for another. First, NMFS does not
believe that observers will be able to
recognize beaked whales versus another
species beyond the distance of the safety
zone. Second, NMFS believes that the
required safety zones are adequate for
minimizing take and the Navy will
easily be able to implement the
appropriate powerdowns (or avoid the
animals, if preferable) in the presence of
aggregations. RIMPAC is a highly
complex and coordinated exercise, and
shutting down or relocating in response
to animals detected outside the safety
zones is impracticable.
Comment 14: Several commenters
recommended that the Navy not operate
sonar at night-time because animals
cannot be detected as far out as the
safety zone.
Response: NMFS proposed a
mitigation measure that would have
required the Navy to refrain from
conducting chokepoint exercises at
night. The Navy informed NMFS that it
would be unable to comply with that
measure for the following reasons:
Operating at night is a warfighting
requirement. Night time conduct of ASW
events is required for at least the following
reasons:
-Exercise realism: ASW is as much an art
as a technical application. Commanders must
learn how best to effectively employ the
assets available. There is not a universal
solution applicable across the board. ASW is
very much dependent upon the geography,
water conditions, available assets, time
available for mission accomplishment and
many other factors. Training for this
complicated warfighting skill must be
conducted in a variety of locations, situations
and environmental conditions. ASW can
occur at any time of day or night and requires
that ships and aircraft be adept at operating
in close proximity to each other in darkness
and low visibility.
-ASW is a lengthy and involved process. It
can take many hours for the tactical situation
to develop. It is impractical to halt a
complicated scenario at sunset.
-Exercise safety of other major events.
Other events (e.g. gunnery and missile
exercises) requiring more stringent safety
measures are conducted in daylight,
affording the best visibility for range
observance. Scheduling within a relatively
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short exercise period requires ASW to take
place in twilight or night conditions.
-Darkness provides the enemy one of his
greatest tactical advantages and therefore the
need to train 24 hours a day is a necessary
requirement to prepare U.S. forces to defend
our country. There may be an additional risk
to mammals at night, only insofar as there are
no aerial surveys available, but that is a
necessary risk in support of national defense.
Comment 15: Several commenters
made recommendations regarding the
limitation of sonar activities during low
visibility conditions, surface-ducting
conditions, or chokepoint exercises
including operating sonar at 6 dB down
or shutting down sonar.
Response: NMFS proposed a
mitigation measure in which the Navy
would be required to cease operating
sonar during strong surface-ducting
conditions during the chokepoint
exercises. However, the Navy was
unable to accept that measure for the
following reason:
We already have mitigations imposed for
significant surface ducting conditions. Our
Sailors need to practice warfighting in all
conditions. The enemy uses choke points to
his tactical advantage, and this is the reason
we need to train in a restricted water
environment. The confluence of currents and
sea state conditions in the Hawaiian channels
make it less likely that these conditions will
be present in the channels.
NMFS’ IHA requires the Navy to
powerdown sonar by 6 dB if they cannot
detect marine mammals out to the
prescribed safety zone and in strong
surface-ducting conditions.
Monitoring
Comment 16: The monitoring for nonchoke-point exercises is inadequate, in
that it consists of nothing more than a
single, non-dedicated observer,
watching for marine mammals while
performing other duties on deck. It is
well-established that single, nondedicated observers-even if welltrained-spot only a fraction of the
marine mammals that multiple,
dedicated observers do. Additionally,
another commenter notes that
observations should be made from all
platforms, day and night.
Response: Though the observers on
Navy vessels are not dedicated marine
mammal observers, they are dedicated
observers and do not have other duties
on the deck. Additionally, people on all
of the vessels, aircraft, etc. involved in
the exercise have been briefed on
marine mammals and instructed to alert
the commanding officer if one is
spotted.
Comment 17: One commenter
suggests that monitors should be
specifically trained in marine mammal
observation, extensive theoretical
training (underwater acoustics, etc.),
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and should have vision tests and be well
rested. Another commenter added that
observers should be independent nonNavy personnel.
Response: At least one watchstander
who has recieved training from a NMFSapproved instructor will be on duty at
all times during the operation of hullmounted tactical sonar, and all RIMPAC
participants will be briefed on marine
mammals, see an associated training
video, and be instructed to alert the
commanding officer if a marine
mammal is sighted. Watchstanders are
professional observers, and NMFS will
assume that, due to the importance of
their job, the Navy ensures that
watchstanders are well-rested and cared
for as it relates to their vision. NMFS
does not believe that instruction in the
fundamentals of underwater acoustics is
necessary to be an effective observer,
and therefore does not require it of
observers.
Comment 18: Several commenters
note that effectiveness of vessel-based
marine mammal monitoring is low
(Navy document indicates
approximately 5 percent) and that the
chance of a trained observer seeing a
beaked whale on an ideal day for
observations is approximately 2 percent.
Additionally, some commenters believe
that cetaceans cannot be reliably
detected out to the extent of the 2000–
m (6561–ft) safety zone, especially in
low visibility conditions.
Response: NMFS acknowledges the
limitations of vessel-based monitoring
and has instituted other methods of
detection in low visibility conditions
and during chokepoint exercises. NMFS
also requires a powerdown in low
visibility conditions.
Comment 19: Some commenters
pointed out the fact that passive
acoustic monitoring is not very effective
(Navy estimates 5 percent) and has
significant drawbacks such as the fact
that it cannot detect non-vocalizing
animals and cannot detect the distance
or location of the animals. Another
commenter suggested that passive
acoustic monitoring should be used
throughout the exercise, not just before,
that the technology should be further
developed to increase localization and
range-finding abilities, and that specific
Passive Acoustic Monitoring guidelines
should be established.
Response: NMFS acknowledges that
passive acoustics has limitations,
however it also adds a dimension of
detection to the monitoring and NMFS
believes that it adds value to the
monitoring. Though some standard
passive acoustic systems cannot localize
or determine the distance to a source,
NMFS notes that with towed arrays,
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instrumented ranges, active sonar, or
other passive acoustic systems, better
detection and localization of marine
mammals is possible. NMFS proposed a
mitigation measure that required the
Navy to implement additional passive
(or active) acoustic measures to use to
improve detection rates during the
RIMPAC exercises, however, the Navy
was unable to comply for the following
reasons:
The Navy has no additional measures for
detection of marine mammals. Passive
detection will only serve to cue lookouts to
more vigilance since localization via passive
detection is not possible. We will use all
measures available to us, including passive
monitoring, but passive monitoring would be
difficult while actively transmitting as the
outgoing signal blanks some receive
capability.
The High Frequency Marine Mammal
Monitoring System (HF/M3) measure is
drawn from SURTASS LFA mitigation
measures. SURTASS is very slow moving, is
a very different design, and is deployed very
differently from surface combatant vessels.
The SURTASS LFA and Mid-Frequency
Antisubmarine Sonar (MFAS) are two
different systems, deployed and operated
differently with very different capabilities.
Comment 20: Several odontocetes
(beaked whales, Kogia sp., and others)
will have a very low probability of being
detected through aerial overflights due
to their long dive times. The commenter
cites ‘‘the effective search width for
beaked whales is typically only 250–500
m (820–1640 ft) on each side of the
aircraft for aerial observers searching by
naked eye in good to excellent sighting
conditions’’. The high winds typically
present in the channels in which the
chokepoint exercises will be conducted
will reduce detection rates further.
Response: NMFS acknowledges the
limitations in detecting cryptic species
by aerial reconnaissance and have taken
them into consideration in our
conclusions.
Comment 21: Land-based monitoring
in the Alenuihaha Channel during the
chokepoint exercise is not adequate
(monitoring will occur along 2 km (1.1
nm) of shore, but the border of
chokepoint exercise is 28 km (15 nm)
long). Additionally, the area is gently
sloping and less than 200–m (656 ft)
deep, and the animals that are thought
to be more susceptible to high-intensity
sound are not found in these areas.
Response: Though the entire border of
the exercise will not be monitored,
NMFS believes that this mitigation adds
to the detectability of injured or dead
animals and even though it is not an
area where the species susceptible to
strandings would usually be present, if
they were responding to sonar in the
way we are concerned about, they could
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potentially go into areas we do not
usually see them (milling out of habitat).
NMFS does not believe that it would be
practicable to ask the Navy to monitor
28 km (15 nm) of shore.
Comment 22: The Navy should
establish a public hotline for strandings
during RIMPAC.
Response: NMFS has established
stranding response procedures,
including a hotline, and does not want
the Navy to establish another line, as it
could only confound the response.
Comment 23: Longterm monitoring
should be conducted to assess the
affects of RIMPAC on resident
populations.
Response: The Navy is currently
coordinating long monitoring of the
marine mammal populations within the
OpArea (see Conservation Measures
(Research), in Mitigation section, below)
Comment 24: No information is
presented on the statistical power of the
monitoring and mitigation plan. Based
on the level of monitoring outlined, the
density of marine mammals in Hawaii,
and the low likelihood of detecting long
diving and cryptic species, the
commenter concludes that the power to
assess the presence of animals
(especially beaked whales) to reduce
impacts is low and the power to detect
impacts if they occur is low. In addition,
the prevailing direction of currents in
Hawaii and the large number of sharks
that scavenge carcasses makes the
likelihood of dead animals stranding
low.
Response: NMFS acknowledges the
challenges in detecting animals in order
to implement mitigation measures and
in detecting injured or dead animals in
order to assess effects. NMFS has
implemented several measures intended
to increase the detectability of impacts.
Aerial or vessel surveys will be
conducted 1–2 days after an exercise to
look for dead or injured animals. NMFS
has also implemented shutdown
protocols to use in the event of a
verified stranding during RIMPAC (see
Mitigation).
Comment 25: One commenter
recommended that NMFS require the
Navy to conduct fewer ASW exercises to
lessen the impacts.
Response: The Navy’s purpose and
need for the activity (for the EA) is to
‘‘implement a selected set of exercises
that is combined into a sea control/
power projection fleet training exercise
in a multi-threat environment’’. NMFS
interprets the action put forth in the
IHA application as the ‘‘selected set’’
and did not discuss an alteration of the
proposed action with the Navy. Instead,
NMFS endeavored to minimize impacts
by limiting exercises near features
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associated with strandings, limiting
sonar output during strong surfaceducting conditions, requiring additional
monitoring during chokepoint exercises,
and instituting specific shutdown
criteria.
Comment 26: One commenter states
that NMFS must clearly define the
circumstances under which both the
exercise and RIMPAC 2006 will be shut
down. This commenter adds that it is
particularly important that clear nondiscretionary triggers are set for the
suspension of RIMPAC.
Response: NMFS has developed and
implemented within the IHA a set of
shutdown criteria that include specific
triggers for temporary sonar shutdown
subsequent to the verification of an
uncommon stranding event, and
indicate the framework within which
NMFS will make a determination
regarding modification, suspension, or
revocation of the Navy’s IHA. The
shutdown criteria are included in the
Mitigation section of this document.
Impact Assessment
Comment 27: Much of the abundance
data for the inshore populations (within
25 nm (46 km) of shore) of the main
Hawaiian Islands marine mammals is
based on the Mobley et al. (2000) aerial
survey data, which underestimate the
abundance of deep-diving/cryptic
species. Mobley notes that the
abundance estimates presented in the
proposed IHA notice for beaked and
sperm whales probably underestimate
the true abundance by a factor of at least
two to five. The commenter is
concerned that this underestimate of
abundance will be reflected in the take
estimate.
Response: If the abundance of some of
these species has been underestimated
then NMFS also may have
underestimated the number of animals
taken; accordingly, within this
mathematical adjustment the percent of
the population affected would remain
the same. Since the increase in numbers
taken is not related to a biologically
important area, this information does
not affect NMFS’ negligible impact
determination.
Comment 28: In the case of spinner
dolphins and bottlenose dolphins, there
appears to be additional population
structure within the main Hawaiian
Islands, with genetic differentiation and
no evidence of movements of
individuals among the four main groups
of islands. Response: The study cited for
genetic differentiation of spinner
dolphins discusses two different social
systems of spinner dolphins, one in the
main Hawaiian Islands and one in the
northwestern atolls. The study further
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suggests that low diversity at a
particular mDNA microsatellite is likely
caused by geographic isolation of small
populations that might experience some
inbreeding. The study does not suggest
different sub-populations within the
main Hawaiian Islands or, therefore,
within the Hawaiian OpArea. The cited
bottlenose dolphin study revealed that
there may be genetically differentiated
populations stratified by both site
fidelity to a particular island, and in one
case, depth. Because the RIMPAC
exercises are distributed throughout the
islands and 2–24 hours in duration
each, because the potentially genetically
differentiated populations are not
known to be limited to an area smaller
than a whole island, and because of the
high detectability of bottlenose dolphins
(which increases mitigation
effectiveness), NMFS does not expect
this additional information to affect our
negligible impact determination.
Comment 29: One commenter notes
that several species are genetically
differentiated between the Hawaiian
Islands population and the tropical
Pacific population
Response: As described, the Hawaiian
populations extend to an unknown
distance beyond the EEZ, so this
observation does not affect the
negligible effect determination.
Comment 30: The additional
mitigation measures do not take into
account the cumulative and synergistic
effects of multiple noise sources being
employed at any one time or over time.
Such effects should be addressed before
any authorization is issued.
Response: The Navy’s model sums the
received energy from multiple sources
and calculates the SEL around the sonar
sources. This SEL, which is an energy
metric, does take into account the
effects of multiple sources over time.
The Navy’s model does incorporate
synergism to some degree, as conditions
in the model are based on nominal
conditions calculated from a generalized
digitalized monthly average, which
includes surface-ducting conditions.
Though synergistic possibilities exist
that are not addressed by the model, the
Navy has incorporated several
conservative features into the model
that help balance other inadequacies of
the model (such as the fact that animals
are assumed to remain stationary in the
presence of the ASW activities and the
fact that animals are assumed to be
located at the loudest depth within the
water column).
Comment 31: Most of the papers cited
to support the evaluation of the Level B
harassment behavioral threshold
involved either sinusoidal tones or
impulses. When developing thresholds
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for mid-frequency sonar, NMFS should
use studies that employ complex, sonarlike signals.
Response: In this regard, NMFS is
constrained by the available science.
The one known incident (Haro Strait,
see Sub-TTS Behavioral Threshold
section) in which cetaceans were
actually exposed to mid-frequency
tactical sonar signals from naval vessels,
and scientists, having some information
about exposure conditions (including
duration) were able to estimate their
received level in terms of sound
exposure level has been included in our
development of the 173–dB threshold.
Comment 32: Regarding the
estimation of PTS onset relative to TTS
levels used in the development of the
Level A Harassment threshold, the Navy
incorporates the maximum recoverable
TTS that humans (and cats, in one
study) can recover from without
permanently damaging their hearing.
The commenter points out that both
humans and cats are highly visually
adapted species (though cats less so
than humans), and from the relationship
between their different recoverable TTS
levels he deduces that animals that are
more dependent on sound cues are less
able to recover from extreme TTS. The
commenter further asserts that it might
easily follow that cetaceans that rely
almost exclusively on acoustical cues
would be even less likely to recover
from extreme TTS. Through further
alternative interpretations of the data
that the Navy used to estimate the onset
of PTS, the commenter suggests that
PTS onset could be estimated at 210 dB
or as low as 200 dB.
Response: The extrapolation that the
Navy uses to estimate PTS onset from
known TTS levels consists of several
discrete steps, and in each of these
separate calculations the Navy has built
in conservative approximations to help
offset the lack of taxa-specific data and
other data gaps, such as that which the
commenter highlights. Additionally,
Navy researchers have exposed captive
dolphins to sound levels in certain
conditions to exposures exceeding 220
dB peak and 200 dB SEL and been
unable to elicit TTS, much less PTS.
Comment 33: Several commenters
note different sound levels (145–165
SPL, 174 SEL) cited in the Bahamas and
Hanalei Bay Stranding reports and
assert that NMFS should base our Level
B Harassment behavioral threshold on
these numbers.
Response: The sound levels cited in
these reports are, for the most part, the
modeled received sound at a particular
location, based on the known locations
of different sound sources present near
the time of the stranding event and the
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best guess of the sound speed profile in
the area based on available
environmental data. While this
information is valuable for many
reasons, we do not know where any of
the animals were actually located in
relation to the known sound sources
when the behavioral or physiological
response that led to either of these
strandings was triggered. The Level B
Harassment behavioral threshold that
NMFS has chosen is based primarily on
two studies and one incident in which
actual received levels were measured
and/or we know the source level and
the approximate distance of the animal
from the sound source leading to
relatively precise modeling estimates.
Comment 34: NMFS has not
considered the full breadth of available
information on bubble growth in its
potential effects analysis. For example,
some researchers suggest that gas
bubbles could be activated in
supersaturated marine mammal tissue
on brief exposure to sounds of 150 dB
(rms) re 1 miPa or lower and then grow
significantly, causing injury as the
animal rises to the surface. Further, the
commenter mentions the investigation
of the 2002 Canary Islands strandings,
whose findings concerning fat and gas
emboli were recently published, but not
mentioned in our analysis.
Response: Though NMFS did not
mention the specific results cited above
in the discussion of bubble growth in
the proposed IHA, adequate coverage of
the topic was provided through a
summary discussion of acoustically
mediated bubble growth, which
discussed the destabilization of stable
bubbles by high-level sound exposures
such that bubble growth occurs through
static diffusion of gas out of the tissues,
the evolution of nitrogen bubbles
through rapid ascent to the surface, and
rectified diffusion. Additionally, based
on the available science, the exact
mechanisms for bubble growth are
unknown, and the predicted received
levels to induce bubble growth are
estimated to exceed those required to
induce TTS. NMFS believes that the
mitigation measures designed to avoid
serious injury or mortality and effect the
least practicable adverse impact also
function to minimize the chances of
bubble growth.
Comment 35: NMFS’ injury threshold
does not reflect non-auditory
physiological impacts, as from stress
and from chronic exposure during
development.
Response: NMFS acknowledges the
importance of potential physiological
effects of mid-frequency tactical sonar
on marine mammals and they are
addressed in this document. However,
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information regarding the sound levels,
frequencies, and duration/repetition
conditions these types of effects result
in is unavailable and, therefore, cannot
contribute to the development of the
injury threshold.
Comment 36: NMFS should use a
dual threshold (SPL and SEL, not just
SEL) for injury, as a 2003 Office of
Naval Research report suggests that peak
power may have more to do with the
way beaked whales respond to sound
(and potentially strand).
Response: Because of the equal energy
line applied by Finneran (2002) to the
TTS data of several researchers, NMFS
believes that SEL can be effectively used
to predict when TTS and PTS (from
extrapolation) will occur in marine
mammals. There is little data relating to
mid-frequency tactical sonar in
particular, however, the larger body of
data related to high-intensity sound in
general suggests that context and SPL
are also important in how animals
behaviorally react to sound. While SEL
may not be the only metric important in
predicting the response of marine
mammals to sound, NMFS chose the
behavioral threshold for this
authorization based on three studies/
events thought to be most closely
representative of how mid-frequency
sonar affects marine mammals for which
SEL exposures are available.
Additionally, the pulse length and
signal types produced by RIMPAC are
known (vs. explosions) and NMFS
believes that in this particular case, SEL
is an appropriate metric for the
behavioral harassment threshold. NMFS
is currently developing acoustic criteria,
which may include dual critieria, but
the wide-ranging evidence regarding at
what levels marine mammals
behaviorally respond to high-intensity
sound has made the behavioral
threshold part of that process difficult
both in terms of metrics and absolute
numbers.
Comment 37: For the SURTASS LFA
sonar authorization, the Navy used a
study that showed resonance damage to
small mammals (submerged) at 205 dB
to establish their proposed Level A
injury threshold. Why was that
threshold not used in this
authorization?
Response: NMFS believes that
extrapolation to PTS from the specific
marine mammal TTS onset data is the
more appropriate way to establish the
threshold. The size and nature of the air
spaces within small mammal ears may
affect the way sound affects the tissues
of the ear such that these results are not
as applicable to marine mammals.
Comment 38: TTS is physiological
damage that can last from minutes to
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days, and can increase the chances of
being injured or killed. TTS should be
considered Level A Harassment.
Response: TTS may be considered to
be an adaptive process (analogous to the
dark adaptation in visual systems)
wherein sensory cells change their
response patterns to sound. Tissues are
not irreparably damaged with the onset
of TTS, the effects are temporary
(particularly for onset-TTS), and NMFS
does not believe that this effect qualifies
as an injury. Therefore TTS-onset is
treated as the upper bound of Level B
Harassment.
Comment 39: For the development of
the TTS threshold, the Navy’s
extrapolation of data from bottlenose
dolphins and belugas to all cetaceans is
not justifiable because they do not have
the most sensitive hearing of all
cetaceans and some studies suggest that
hearing sensitivity may be variable as a
function of signal production and/or
other parameters.
Response: The absolute hearing
sensitivity at the frequency of tactical,
mid-frequency sonar is similar for most
odontocetes that have been tested.
Additionally, onset-TTS values used for
the calculation of PTS onset represent
the most sensitive of the animals tested.
Presumably, any modulation of
sensitivity that served to protect the
cetacean auditory system from
overexposure to noise would be
activated by intense noise exposure. It
would be expected to operate, if it in
fact exists, in captive marine mammals
involved in the TTS studies as well as
animals exposed to loud noise in the
wild. There is no empirical comparative
data on these phenomena with which to
modify/adjust the TTS onset or growth
estimates. Comment 40: The Finneran
equal energy line applied to multiple
TTS datasets was used to justify the 195
dB TTS threshold (and by extrapolation,
the 215 PTS threshold) in this
authorization. This line could have
justifiably been drawn at 190 dB
(without giving such weight to the
single Natchtigall point), and would
have been more conservative.
Response: While acknowledging the
limitations of current data and the
existing criticisms of an equal energy
approach in the terrestrial mammalian
literature at this time, NMFS believes
that the 195–SEL equal energy line is a
reasonable interpretation of the current
data at this time. Both TTS onset and
the estimation of PTS onset as a
demarcation of physical injury have
several precautions built into the
assumptions. The equal-energy line
through the existing cetacean TTS data
is not a least-squares regression of the
data but rather an expression of pressure
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magnitude of exposure as a function of
duration. That the long duration
exposures from Nachtigall et al. fall so
close to this line (they are not used to
derive it) is one of a number of
arguments in favor of the use of SEL as
a means of comparing TTS-onset across
extremely variable exposure conditions.
Finally, the 195–dB SEL line was
selected based on the empirical
measures of TTS-onset for 195 dBrms 1–
s exposures and extrapolated to other
exposures of variable sound pressure
magnitude and duration using the equal
energy relationship.
Comment 41: Several commenters
suggest that the animals used in the
studies the Navy used to develop their
proposed TTS threshold were old and
test-habituated, and that studies
involving younger, less test-habituated
animals should be given more weight.
Another commenter noted that the
animals used in the TTS study may not
adequately represent the range of
variation within their own species.
Response: NMFS acknowledges that
the test-animals may not fully represent
the range of hearing responses across
multiple taxa, within their own species,
or in some cases even within
individuals whose sensitivity may
change over time however, we have
used the best science available to
develop these thresholds. Also, though
NMFS believes that habituation to
exposure may affect how animals
respond to noises in a behavioral
context, but that from a sensorineural
point of view there is likely less
dependence on exposure history. NMFS
is aware of some data on terrestrial
mammals indicating a ‘‘toughening’’ of
auditory systems repeatedly exposed to
noise, but notes that such data are
generally unavailable for marine
mammals but not indicated in the
exposure sequences of subjects that
have been tested. In fact, some data exist
indicating a slight apparent
improvement in the hearing sensitivity
(lower thresholds over time) of marine
mammals at a particular sound
frequency for which TTS is tested,
likely as a result of the increased
relevance of those particular signals to
the animals in the context of foodreward tasks.
Comment 42: Pinniped data should
have been used in the development of
the threshold.
Response: NMFS does not anticipate
take of pinnipeds as a result of this
action and, therefore, did not consider
the incorporation of pinniped data into
the thresholds (or the development of
separate pinniped thresholds)
necessary.
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Comment 43: A recent study of
threshold shift in pinnipeds found that
the amount of hearing loss an animal
experiences does not increase linearly
with the energy it receives. As the
energy intensifies, its rate of hearing
loss increases, to such a degree that
projections of permanent threshold shift
according to traditional, linear models
are likely to result in underestimates of
harm. The Navy should lower its
threshold.
Response: Kastak et al (2005) note the
non-linear growth of TTS for relatively
small magnitude shifts (< 6dB) and the
innadequacy of a linear model using
only these data in predicting the growth
of TTS with exposure level for a wider
range of exposures. It is well known that
the TTS growth function is sigmoidal
and thus it is misleading to describe it
solely based on exposures that generate
only small-magnitude TTS (where the
slope of the growth function is relatively
shallow). For a wide range of exposures,
however, there is a steeper, linear
portion of the sigmoidal function and a
fairly consistent relationship between
exposure magnitude and growth of TTS.
The slope of this relationship is
relatively well-known for humans (on
the order of 1.6 dB TTS/dB noise (Ward
et al., 1958; 1959)). While it is not wellunderstood for marine mammals
(because studies to date have yet to
induce sufficiently large TTS values to
properly assess it), the slope of this
portion of the function predicted by the
Kastak et al (2005) data fit with the
curvilinear approximation (based on
Maslen, 1981) was found to be
comparable. Therefore, estimations of
PTS from TTS onset that use a linear
growth function with the steepest slope
from a curvilinear function are very
likely appropriate and in fact a
conservative approximation, based on
the information available at this time.
Comment 44: The 173–dB behavioral
threshold is not supportable, as
significant behavioral changes have
been demonstrated in a controlled
exposure experiment (Nowacek et al.,
2004) at 154 dB SEL. It is not
appropriate to use the 25th percentile
results of the Finneran study (173 dB),
as the captive animals in that study
cannot adequately represent the
responses of wild animals.
Alternatively, NMFS received one
comment in support of the issuance of
the IHA, but that commenter believed
that the 190–dB behavioral threshold
was supported, not the 190–dB
threshold.
Response: As discussed in the text,
NMFS used the three examples
(Finneran and Schlundt, 2004, Nowacek
et al., 2004; and NMFS Haro Strait
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38727
analysis) of cetacean responses to high
intensity sound that we believe are the
most predictive for marine mammal
responses to tactical sonar to develop
the threshold. Generally, NMFS
interprets the received SELs in these
studies as approximately 50 percent
disturbance = 190 dB SEL (Finneran),
approximately maximum SEL:160 dB
(Nowacek), and approximately 165–175
dB SEL (Haro Strait). Where using a
single threshold, instead of the likely
more appropriate but currently
unknown dose-response sigmoidal
relationship, NMFS acknowledges that
some animals exposed above the
threshold may not be harassed by the
sound and, conversely, some animals
exposed to a sound below the threshold
may be harassed. Therefore, NMFS
believes that an appropriate threshold is
a number somewhere between the
lowest and highest mid-frequency signal
exposure levels to which animals have
demonstrated profound behavioral
disturbance, which is why we chose 173
dB SEL for this authorization.
Comment 45: NMFS’ analysis of
effects should include more information
on the avoidance behavior and
behavioral response data of mysticetes
to high-intensity sound.
Response: The majority of data
addressing mysticete avoidance and
behavioral responses to sound relates to
low frequency sound. Because of
differences in how animals react to
these two different types of sound and
differences in how these sounds
propagate, the Navy and NMFS limited
the analysis to primarily mid-frequency/
tactical sonar-type data. However, one
of three datum used to develop the
behavioral harassment threshold was
derived from right whale responses
(Nowachek).
Comment 46: The model the Navy
uses to calculate take is flawed because
it does not take into consideration
reverberation, surface-ducting, or
sources above 205 dB.
Response: The model does indirectly
incorporate surface-ducting, as
conditions in the model are based on
nominal conditions calculated from a
generalized digitalized monthly average.
Though the model does not consider
reverberations, these effects are
generally at received levels many orders
of magnitude below those of direct
exposures (as demonstrated in the Haro
Strait analysis) and thus contribute
essentially nothing to the cumulative
SEL exposure. The Navy did not include
sources below 205 dB in its model
because sound is expected to attenuate
to below 173 dB within 100 m (328 ft)
around these sources (animals are
expected to avoid the dynamic exercise
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at that distance and/or monitors are
largely expected to detect and shut
down sonar (within 200 m (656 ft))) and
because larger sources will usually be
operating in the vicinity, adding to the
likelihood of avoidance.
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NEPA Compliance
Comment 47: The Navy should revise
the EA based on the findings of the final
Hanalei Bay report to reflect ‘‘significant
new information’’.
Response: Though the final Hanalei
report was not published when the
Navy issued the April draft of its EA
and the event was not discussed in the
necessary detail in that draft, NMFS
considered the event in more detail, as
demonstrated in both this final IHA
notice and the associated Finding of No
Significant Impact (FONSI) .
Comment 48: The Navy suggests at
points in the EA that its analysis of
extraterritorial activities, those activities
that would take place outside U.S.
territorial waters, was prepared under
the authority of Executive Order 12114
rather than under NEPA. The Navy’s
position on the scope of the review is
inconsistent with the statute. For NMFS,
adopting such a position is clearly
insupportable, given that the Federal
action to which its NEPA review
applies, the decision to authorize
RIMPAC, takes place entirely within the
territory of the U.S. NMFS should
indicate its derogation from the Navy’s
EA on this point.
Response: Pursuant to NOAA
Administrative Order 216–6, NMFS
applies NEPA in the EEZ, and has
complied with NEPA for this action.
Comment 49: One commenter
believes that the Navy’s purpose and
need is too narrow.
Response: The Navy’s stated purpose
is to ‘‘implement a selected set of
exercises that is combined into a sea
control/power projection fleet training
exercise in a multi-threat environment’’.
NMFS does not believe that this stated
purpose is inherently too narrow.
Comment 50: The Navy does not do
an adequate alternatives analysis. The
alternatives consist of the preferred
alternative, the no action alternative,
and previously considered alternatives.
The Navy does not consider alternate
geographical locations or any other
alternatives. NMFS should not adopt the
EA.
Response: For the purposes of NMFS’
federal action--the issuance of an
MMPA authorization--the alternatives
are adequate: no action, preferred action
(ASW with added mitigation), and the
previously considered alternative (ASW
with no added mitigation).
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Comment 51: An overarching concern
is the blanket exclusion of fish and
invertebrates from consideration [in the
EA] in terms of acoustic impacts.
Response: The Navy provided a
supplemental analysis of the effects of
mid-frequency sonar on fish and NMFS
has included it in the FONSI.
Comment 52: The Navy’s EA did not
adequately consider cumulative effects.
NMFS must assess the potential for
synergistic adverse effects, as from noise
in combination with ship stripes,
properly assess the cumulative impacts
of holding biannual RIMPAC exercises
in the same areas off Hawaii, and
consider whether individual naval
exercises in the Hawaiian Islands
Operating Area and other activities
could combine with RIMPAC to
produce a significant effect.
Response: NMFS acknowledges the
need for additional analysis of
cumulative effects in the NEPA analysis
and has addressed cumulative effects in
the FONSI
Comment 53: With regard to noiseproducing activities the Navy must
describe source levels, frequency ranges,
duty cycles, and other technical
paramenters relevant to determining
potential impacts on marine life.
Response: NMFS requested this
information early in the process and the
Navy informed NMFS that the majority
of the information was ‘‘classified’’.
Comment 54: For Data Quality Act
compliance, the models used in this
analysis need to be available to the
public.
Response: MatLab is a commercially
available program. CASSGRAB is
available to the public from the Federal
Government through leasing
arrangements. The other components of
the Navy’s model are not published and
can be discussed with the Navy.
Comment 55: Several commenters
were concerned that NMFS could not
satisfy the criteria necessary to issue a
Finding of No Significant Impact.
Response: NMFS issued a FONSI on
June 27, 2006, addressing all the
required criteria.
MMPA Compliance
Comment 56: Pursuant to the MMPA
(16 U.S.C. 1371(a)(5)(D)(i)), an IHA can
only be granted for harassment, not
serious injury or mortality. NMFS
cannot say with confidence that serious
injury or mortality will not occur
incidental to this action, especially
during the chokepoint exercises, which
present four of five conditions for
heightened risk: (1) the use of tactical
sonar, (2) in places where as many as
three species of beaked whale may
occur, (3) areas with steep bathymetry,
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and (4) areas that offer surface-ducting
conditions.
Response: NMFS has required a suite
of mitigation measures in the IHA that
reduces the likelihood of a stranding
resulting from the RIMPAC ASW
activities. However, several points that
were emphasized in the public
comments (i.e., the difficulty (in ideal
conditions) of detecting beaked whales,
which have been among the species in
most of the strandings associated with
sonar, and the fact that choke-point
exercises will be conducted both at
night and in surface-ducting conditions)
and the published conclusions of the
Hanalei Bay melon-headed whale report
do not allow NMFS to rule out the
possibility of a stranding resulting from
the RIMPAC ASW activities.
Consequently, NMFS has included
specific shutdown criteria (see
Mitigation and Monitoring, above),
which are intended to ensure MMPA
compliance. These criteria require the
Navy to temporarily cease operating
sonar in a designated area when a
stranding is verified during the RIMPAC
ASW exercise. NMFS will then conduct
an investigation, and if NMFS finds that
the Navy’s activities may have
contributed to the stranding, NMFS will
modify, revoke, or suspend the IHA.
Comment 57: NMFS can not reach a
negligible impact determination for
beaked whales as the activity is
projected to affect over 16 percent of
each population of beaked whales and
the mitigation measures are know to be
ineffective due to the low detectability
of beaked whales.
Response: As discussed in more detail
in the Negligible Impact Determination
section, NMFS does not believe that
over 16 percent of each beaked whale
species will be harassed by these
activities. NMFS believes that the initial
take numbers generated by the Navy’s
model are overestimates, that the
mitigation measures will reduce that
percent somewhat (especially through
measures that don’t depend on
detection, such as exclusion zones and
circumstantial powerdowns), and that
the beaked whale populations extend
past the EEZ (make sure spelled out first
time in document), which means that a
smaller percent of the population will
be affected by the activities within the
EEZ that what was modeled. This,
coupled with the temporary nature of
the exercise and the implementation of
the new shutdown criteria, leads NMFS
to believe the activity will have a
negligible impact on beaked whale
populations.
Comment 58: NMFS cannot make
negligible impact determinations for
species other than beaked whales
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because the portions of the populations
affected by the activity are too high.
Response: As mentioned in the prior
response and in the Negligible Impact
Determination section, NMFS believes
that the actual portion of the
populations affected by the RIMPAC
exercises is significantly smaller than
modeled number of individuals taken
divided by the estimated abundance in
the EEZ. In addition to the reasons
stated in the previous response, the
percent of the population affected is
even smaller for animals with
significantly larger densities inshore
than offshore (due to the 25–km (13.5–
nm) exclusion zone) and for animals
with large average group sizes or large
body size (far more detectable through
monitoring). Tables 3 and 4 discuss
what factors were considered in the
negligible impact determination.
Comment 59: NMFS must also
consider other RIMPAC exercises that
might impact marine mammals that are
intertwined with anti-submarine
warfare exercises, such as air-to-surface
gunnery exercises, mine
countermeasures, etc.
Response: The Navy applied for an
authorization for take of marine
mammals incidental to ASW exercises.
As described in the application, the
ASW exercises are discrete exercises.
Comment 60: NMFS’ notice states that
RIMPAC will not have an unmitigable
adverse impact on the availability of the
species or stocks for subsistence uses.
The notice should clarify that only the
subsistence hunting of marine mammals
by Alaska natives is considered in the
findings under either 101(a)(5)(A) or
101(a)(5)(D) of the MMPA.
Response: After reviewing the statute,
NMFS believes the commenter is correct
and has removed the reference to that
finding from the appropriate
documents.Other Comments
Comment 61: Foreign vessels and
crews cannot avail themselves of an IHA
for the harassment of marine mammals
in the U.S. Exclusive Economic Zone
because section 101(a)(5)(D) of the
MMPA is available only to ‘‘citizens of
the United States.’’
Response: This doesn’t have an
associated comment-think it belongs
one or two pages up where there’s no
response to a comment on this issue.
The U.S. Navy is the applicant for
purposes of this IHA for RIMPAC 2006
exercises and qualifies as a U.S. citizen
under NMFS regulations. NMFS has
issued the IHA to the Navy, which is
hosting the exercises. As the holder of
the IHA, the Navy is responsible for
implementing the terms and conditions
of the IHA, which requires that all
participants in RIMPAC ASW activities
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abide by the IHA’s mitigation and
monitoring requirements. The Navy has
indicated that all foreign vessels
participating in RIMPAC 2006 will be
under the Operational Control (OPCON)
of Commander, U.S. THIRD Fleet in his
capacity as Officer Conducting the
Exercise (OCE) and Commander,
Combined Task Force (CCTF) RIMPAC.
As such, all forces assigned, including
foreign vessels and aircraft operating
under CCTF RIMPAC OPCON, are
required to comply with the
environmental mitigation measures
spelled out in Annex L to the RIMPAC
2006 OPORDER as a condition of
participating in the exercise. Under
Annex L and two other annexes, all
vessels, including foreign ships, are
required to make sonar use reports in
the daily operational summary.
Comment 62: NMFS sets the injury
threshold at 215 dB (for PTS); yet we
say that ‘‘some marine mammals may
react to mid-frequency sonar, at
received levels lower than those thought
to cause direct physical harm, with
behaviors that may, in some
circumstances, lead to physiological
harm, stranding, or, potentially, death’’.
If this is the case, the Level A
harassment threshold should be lower.
Response: Thresholds represent
sound levels at which NMFS predicts
marine mammals are likely to be
harassed in a certain way or to a certain
level. The behavioral Level B
harassment threshold represents the
level at which NMFS believes marine
mammals are likely behaviorally
harassed. Within the range of potential
behavioral responses rising to the level
of harassment, a small subset of the
animals exposed may respond
behaviorally or physiologically in a way
that leads to a stranding. Such an
extreme reaction by some animals does
not necessarily justify the establishment
of a general threshold, but instead an
awareness of the possibility of this
response and implementation of
mitigation measures to address it, such
as those contained in this IHA (e.g., 25–
km (13.5 nm) exclusion zone, extra
monitoring, etc.). Additionally, the
exact mechanisms that lead to a
stranding are not well understood, and
it is believed that there are often other
(unknown) contributing factors
involved. NMFS does not believe it is
appropriate to use sound levels that
represent the onset of the behavioral
disturbance to also represent the onset
of injury when other contributing
factors may be necessary to get to injury
from the initial behavioral disturbance.
Comment 63: The Navy should keep,
and make available to NMFS if a
stranding occurs, a detailed log of sonar
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38729
use. The detailed report required to
NMFS should be made available to
NMFS within a given amount of time
after RIMPAC is completed.
Response: The Navy keeps very
specific records of when and where
sonar is operated. The Navy will make
both classified ‘‘secret’ and unclassified
reports to NMFS after RIMPAC. In the
event of a stranding, the Navy will
coordinate with NMFS to provide the
needed information regarding the
positioning of the operating sonar
within the OpArea. Unclassified reports
from the Navy are immediately available
to the public. Classified reports will be
made available as they are unclassified.
Comment 64: The commenter is
concerned that the RIMPAC proposal is
using the Navy’s draft EIS for the
USWTR proposal even while the
assumptions, methodologies, and
substantiating information are still in
draft and are still under review.
Response: Some of the information in
the Navy’s draft EIS for USWTR
constitutes the best available science,
even if it is still in review.
Comment 65: The commenter is
troubled that conservation organizations
need to continually expend their
resources and energies attempting to
stem the destruction of marine habitat
by the U.S. Navy. The commenter states
that the ‘‘burden of proof’’ falls upon
those who are attempting to conserve
marine mammal habitat, and not the
U.S. Navy, who are proposing assaults
and compromises to the environment.
Response: NMFS cannot address this
issue.
Comment 66: NMFS received
approximately 120 general comments of
opposition within the comment period,
and approximately 100 additional
comments of general opposition after
the comment period closed. Many of the
commenters did not think that NMFS
should authorize the Navy to injure or
kill the animals and many expressed the
thought that we should avoid impacts to
marine mammals.
Response: NMFS appreciates the
outpouring of concern for the well-being
of the marine mammals around the
Hawaiian Islands. As a clarification,
NMFS has not authorized the injury or
mortality of marine mammals and has
including mitigation and monitoring
measures to reduce the potential for
injury or mortality, as well as instituting
stranding shutdown protocols for use in
the event of any stranding. Further,
though NMFS does not ask for
protective measures meant to entirely
avoid disturbance of marine mammals,
which would preclude the need for an
authorization, we have included
measures intended to affect the least
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practicable adverse impact on the
species.
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Mitigation, Monitoring, and Reporting
The Navy has requested an IHA from
NMFS for the take, by harassment, of
marine mammals incidental to RIMPAC
ASW exercises in the OpArea. Section
101(a)(5)(D) of the MMPA, the section
pursuant to which IHAs are issued, may
not be used to authorize mortality or
serious injury leading to mortality. The
Navy’s analysis of the RIMPAC ASW
exercises concluded that no mortality or
serious injury leading to mortality
would result from the proposed
activities. However, NMFS believes that
some marine mammals may react to
mid-frequency sonar, at received levels
lower than those thought to cause direct
physical harm, with behaviors that may
lead to physiological harm, stranding,
or, potentially, death. Therefore, in
processing the Navy’s IHA request,
NMFS has required additional
mitigation and monitoring than
originally proposed in the Navy’s
application, which is intended to ensure
that mortality or serious injury leading
to mortality does not result from the
proposed activities.
In any IHA issued there is the
requirement to supply the ‘‘means of
effecting the least practicable [adverse]
impact upon the affected species.’’
NMFS’ determination of ‘‘the least
practicable adverse impact on the
affected species’’ includes consideration
of personnel safety, practicality of
implementation, and impact on the
effectiveness of military readiness
activities. While NMFS’ proposed
mitigation and monitoring requirements
discussed below are intended to effect
the ‘‘least practicable adverse impact’’,
they are also designed to ensure that no
mortality or serious injury leading to
mortality occurs, so that an IHA may be
legally issued under the MMPA.
Changes Made in the IHA Since the
Proposed IHA was published in the FR
Three changes have occurred in the
authorization since the proposed IHA
was published in the Federal Register:
(1) a mitigation measure was added
wherein during chokepoint exercises
the Navy must ensure that a 2000 m
(6561 ft) (vs. 1000 m (3280 ft) in nonchokepoint exercises) radius is clear of
marine mammals prior to startup of
sonar; (2) stranding shutdown protocols
were included in the IHA; and (3) the
Navy requested they be allowed to
conduct 6.5 hours of sonar operations
within the part of the PMRF that falls
within 25 km (13.5 nm) of the 200–m
(656–ft) isobath, and NMFS
subsequently made the requested
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modification to the IHA and added a
mitigation measure that requires the
Navy abide by the applicable existing
chokepoint mitigation measures when
conducting these activities. These
changes are addressed in more detail in
the ‘‘Additional Mitigation, Monitoring,
and Reporting Measures Required by
NMFS’’ section below.
Standard Operating Procedures
Proposed in Navy Application
Navy shipboard lookout(s) are highly
qualified and experienced observers of
the marine environment. Their duties
require that they report all objects
sighted in the water to the Officer of the
Deck (e.g., trash, a periscope, a marine
mammal) and all disturbances (e.g.,
surface disturbance, discoloration) that
may be indicative of a threat to the
vessel and its crew. There are personnel
serving as lookouts on station at all
times (day and night) when a ship or
surfaced submarine is moving through
the water.
Navy lookouts undergo extensive
training in order to qualify as a
watchstander. This training includes onthe-job instruction under the
supervision of an experienced
watchstander, followed by completion
of the Personal Qualification Standard
program, certifying that they have
demonstrated the necessary skills (such
as detection and reporting of partially
submerged objects). In addition to these
requirements, many Fleet lookouts
periodically undergo a 2-day refresher
training course.
The Navy includes marine species
awareness as part of its training for its
bridge lookout personnel on ships and
submarines. Marine species awareness
training was updated in 2005 and the
additional training materials are now
included as required training for Navy
lookouts. This training addresses the
lookout’s role in environmental
protection, laws governing the
protection of marine species, Navy
stewardship commitments, and general
observation information to aid in
avoiding interactions with marine
species. Marine species awareness and
training is reemphasized by the
following means:
Bridge personnel on ships and
submarines–Personnel utilize marine
species awareness training techniques
as standard operating procedure, they
have available the ‘‘whale wheel’’
identification aid when marine
mammals are sighted, and they receive
updates to the current marine species
awareness training as appropriate.
Aviation units–All pilots and aircrew
personnel, whose airborne duties during
ASW operations include searching for
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submarine periscopes, report the
presence of marine species in the
vicinity of exercise participants.
Sonar personnel on ships,
submarines, and ASW aircraft–Both
passive and active sonar operators on
ships, submarines, and aircraft utilize
protective measures relative to their
platform.
The Environmental Annex to the
RIMPAC Operational Order mandates
specific actions to be taken if a marine
mammal is detected and these actions
are standard operating procedure
throughout the exercise.
Implementation of these protective
measures is a requirement and involves
the chain of command with supervision
of the activities and consequences for
failing to follow orders. Activities
undertaken on a Navy vessel or aircraft
are highly controlled. Very few actions
are undertaken on a Navy vessel or
aircraft without oversight by and
knowledge of the chain of command.
Failure to follow the orders of one’s
superior in the chain of command can
result in disciplinary action.
Operating Procedures
The following procedures are
implemented to maximize the ability of
operators to recognize instances when
marine mammals are close aboard and
avoid adverse effects to listed species:
Visual detection/ships and
submarines–Ships and surfaced
submarines have personnel on lookout
with binoculars at all times when the
vessel is moving through the water.
Standard operating procedure requires
these lookouts maintain surveillance of
the area visible around their vessel and
to report the sighting of any marine
species, disturbance to the water’s
surface, or object (unknown or
otherwise) to the Officer in Command.
Visual detection/aircraft–Aircraft
participating in RIMPAC ASW events
will conduct and maintain, whenever
possible, surveillance for marine species
prior to and during the event. The
ability to effectively perform visual
searches by participating aircraft crew
will be heavily dependent upon the
primary duties assigned as well as
weather, visibility, and sea conditions.
Sightings would be immediately
reported to ships in the vicinity of the
event as appropriate.
Passive detection for submarines Submarine sonar operators will review
detection indicators of close-aboard
marine mammals prior to the
commencement of ASW operations
involving active mid-frequency sonar.
When marine mammals are detected
close aboard, all ships, submarines, and
aircraft engaged in ASW would reduce
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mid-frequency active sonar power levels
in accordance with the following
specific actions:
(1) Helicopters shall observe/survey
the vicinity of an event location for 10
minutes before deploying active
(dipping) sonar in the water. Helicopters
shall not dip their sonar within 200
yards of a marine mammal and shall
secure pinging if a marine mammal
closes within 200 yards after pinging
has begun.
(2) Note: Safety radii, power-down,
and shut-down zones proposed by the
Navy have been replaced with more
conservative measures required by
NMFS and are discussed in the next
section.
The RIMPAC Operational Order
Environmental includes specific
measures, including the measures
required by NMFS’ IHA, that are to be
followed by all exercise participants,
including non-U.S. participants.
The Navy proposes that training be
provided to exercise participants and
NOAA officials before and during the in
port phase of RIMPAC (26–30 Jun 06).
This will consist of exercise participants
(CO/XO/Ops) reviewing the C3F Marine
Mammal Brief, available OPNAV N45
video presentations, and a NOAA brief
presented by C3F on marine mammal
issues in the Hawaiian Islands. The
Navy will also provide the following
training for RIMPAC participants:
(1) NUWC will train observers on
marine mammal identification
observation techniques
(2) Third fleet will brief all
participants on marine mammal
mitigation requirements
(3) Participants will receive video
training on marine mammal awareness
(4) Navy offers NOAA/NMFS
opportunity to send a representative to
the ashore portion of the exercise to
address participants and/or observe
training.
Conservation Measures (Research)
The Navy will continue to fund
ongoing marine mammal research in the
Hawaiian Islands. Results of
conservation efforts by the Navy in
other locations will also be used to
support efforts in the Hawaiian Islands.
The Navy is coordinating long term
monitoring/ studies of marine mammals
on various established ranges and
operating areas:
(1) Coordinating with NMFS to
conduct surveys within the selected
Hawaiian Islands Operating Area as part
of a baseline monitoring program.
(2) Implementing a long-term
monitoring program of marine mammal
populations in the OpArea, including
evaluation of trends.
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(3) Continuing Navy research and
Navy contribution to university/external
research to improve the state of the
science regarding marine species
biology and acoustic effects.
(4) Sharing data with NMFS and the
public, via the literature, for research
and development efforts.
The Navy has contracted with a
consortium of researchers from Duke
University, University of North Carolina
at Wilmington, University of St.
Andrews, and the NMFS Northeast
Fisheries Science Center to conduct a
pilot study analysis and develop a
survey and monitoring plan that lays
out the recommended approach for
surveys (aerial/shipboard, frequency,
spatial extent, etc.) and data analysis
(standard line-transect, spatial
modeling, etc.) necessary to establish a
baseline of protected species
distribution and abundance and monitor
for changes that might be attributed to
ASW operations on the Atlantic Fleet
Undersea Warfare Training Range. The
Research Design for the project will be
utilized in evaluating the potential for
implementing similar programs in the
Hawaiian Islands ASW operations areas.
In addition, a Statement of Interest has
been promulgated to initiate a similar
research and monitoring project in the
Hawaiian Islands and the remainder of
the Pacific Fleet OPAREAs. The
execution of funding to begin the
resultant monitoring is planned for the
fall of 2006.
Reporting
The RIMPAC Operational Order
Environmental Annex (see example in
Appendix A of the application) includes
specific reporting requirements related
to marine mammals.
Additional Proposed Mitigation,
Monitoring, and Reporting Measures
Required by NMFS
The following protective mitigation
and monitoring measures will be
implemented in addition to the standard
operating procedures discussed in the
previous section:
(1) The Navy will operate sonar at the
lowest practicable level, not to exceed
235 dB, except for occasional short
periods of time to meet tactical training
objectives.
(2) Safety Zones - When marine
mammals are detected by any means
(aircraft, lookout, or acoustically) within
1000 m (3280 ft) of the sonar dome (the
bow), the ship or submarine will limit
active transmission levels to at least 6
dB below normal operating levels. Ships
and submarines will continue to limit
maximum ping levels by this 6–dB
factor until the animal has been seen to
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leave the area, has not been seen for 30
minutes, or the vessel has transited
more than 2000 m beyond the location
of the sighting.
Should a marine mammal be detected
within or closing to inside 500 m (1640
ft) of the sonar dome, active sonar
transmissions will be limited to at least
10 dB below the equipment’s normal
operating level. Ships and submarines
will continue to limit maximum ping
levels by this 10–dB factor until the
animal has been seen to leave the area,
has not been seen for 30 minutes, or the
vessel has transited more than 1500 m
(4920 ft) beyond the location of the
sighting.
Should the marine mammal be
detected within or closing to inside 200
m (656 ft) of the sonar dome, active
sonar transmissions will cease. Sonar
will not resume until the animal has
been seen to leave the area, has not been
seen for 30 minutes, or the vessel has
transited more than 1200 m beyond the
location of the sighting.
If the Navy is operating sonar above
235 dB and any of the conditions
necessitating a powerdown arise ((f), (g),
or (h)), the Navy shall follow the
requirements as though they were
operating at 235 dB - the normal
operating level (i.e., the first
powerdown will be to 229 dB,
regardless of at what level above 235
sonar was being operated).
(3) In strong surface ducting
conditions, the Navy will enlarge the
safety zones such that a 6–dB powerdown will occur if a marine mammal
enters the zone within a 2000 m (6561
ft) radius around the source, a 10–dB
power-down will occur if an animal
enters the 1000 m (3280 ft) zone, and
shut down will occur when an animal
closes within 500 m (1640 ft) of the
sound source.
(4) In low visibility conditions (i.e.,
whenever the entire safety zone cannot
be effectively monitored due to
nighttime, high sea state, or other
factors), the Navy will use additional
detection measures, such as infrared (IR)
or enhanced passive acoustic detection.
If detection of marine mammals is not
possible out to the prescribed safety
zone, the Navy will power down sonar
(per the safety zone criteria above) as if
marine mammals are present
immediately beyond the extent of
detection. (For example, if detection of
marine mammals is only possible out to
700 m (2296 ft), the Navy must
implement a 6–dB powerdown, as
though an animal is present at 701 m
(2299 ft), which is inside the 1000–m
(3280–ft) safety zone)
(5) With the exception of three
specific choke-point exercises (special
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measures outlined in item 8), the Navy
will not conduct sonar activities in
constricted channels or canyon-like
areas.
(6) With the exception of three
specific ‘‘choke-point’’ exercises
(special measures outlined in item 8),
and events occurring on range areas
managed by PMRF, the Navy will not
operate mid-frequency sonar within 25
km (13.5 nm) of the 200 m (656 ft)
isobath.
(7) Navy watchstanders, the
individuals responsible for detecting
marine mammals in the Navy’s standard
operating procedures, will participate in
marine mammal observer training by a
NMFS-approved instructor (NMFS will
work with Navy to develop appropriate
format, potentially to be presented to
Navy personnel during the port phase of
RIMPAC, June 26–30). Training will
focus on identification cues and
behaviors that will assist in the
detection of marine mammals and the
recognition of behaviors potentially
indicative of injury or stranding.
Training will also include information
aiding in the avoidance of marine
mammals and the safe navigation of the
vessel, as well as species identification
review (with a focus on beaked whales
and other species likely to strand). At
least one individual who has received
this training will be present, and on
watch, at all times during operation of
tactical mid-frequency sonar, on each
vessel operating mid-frequency sonar.
(8) The Navy will conduct no more
than three ‘‘choke-point’’ exercises.
These exercises will occur in the
Kaulakahi Channel (between Kauai and
Niihau) and the Alenuihaha Channel
(between Maui and Hawaii). These
exercises fall outside of the
requirements listed above in 5 and 6,
i.e., to avoid canyon-like areas and to
operate sonar farther than 25 km (13.5
nm) from the 200 m (656 ft) isobath. The
additional measures required for these
three choke-point exercises are as
follows:
(a) The Navy will provide NMFS
(Stranding Coordinator and Protected
Resources, Headquarters) and the
Hawaii marine patrol with information
regarding the time and place for the
choke-point exercises 24 hours in
advance of the exercises.
(b) The Navy will have at least one
dedicated Navy marine mammal
observer who has received the NMFSapproved training mentioned above in
7, on board each ship and conducting
observations during the operation of
mid-frequency tactical sonar during the
choke-point exercises. The Navy has
also authorized the presence of two
experienced marine mammal observers
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(non-Navy personnel) to embark on
Navy ships for observation during the
exercise.
(c) Prior to start up or restart of sonar,
the Navy will ensure that a 2000–m
(6561–ft) radius around the sound
source is clear of marine mammals.
(d) The Navy will coordinate a
focused monitoring effort around the
choke-point exercises, to include preexercise monitoring (2 hours), duringexercise monitoring, and post-exercise
monitoring (1–2 days). This monitoring
effort will include at least one dedicated
aircraft or one dedicated vessel for
realtime monitoring from the prethrough post-monitoring time period,
except at night. The vessel or airplane
may be operated by either dedicated
Navy personnel, or non-Navy scientists
contracted by the Navy, who will be in
regular communication with a Tactical
Officer with the authority to shut-down,
power-down, or delay the start-up of
sonar operations. These monitors will
communicate with this Officer to ensure
the 2000–m (6561–ft) safety zone is
clear prior to sonar start-up, to
recommend power-down and shutdown during the exercise, and to
extensively search for potentially
injured or stranding animals in the area
and down-current of the area postexercise.
(e) The Navy will further contract an
experienced cetacean researcher to
conduct systematic aerial
reconnaissance surveys and
observations before, during, and after
the choke-point exercises with the
intent of closely examining local
populations of marine mammals during
the RIMPAC exercise.
(f) Along the Kaulakahi Channel
(between Kauai and Niihau), shoreline
reconnaissance and nearshore
observations will be undertaken by a
team of observers located at Kekaha (the
approximate mid point of the Channel).
Additional observations will be made
on a daily basis by range vessels while
enroute from Port Allen to the range at
PMRF (a distance of approximately 16
nm (30 km) and upon their return at the
end of each day’s activities. Finally,
surveillance of the beach shoreline and
nearshore waters bounding PMRF will
occur randomly around the clock a
minimum four times in each 24 hour
period.
(g) In the Alenuihaha Channel
(between Maui and Hawaii), the Navy
will conduct shoreline reconnaissance
and nearshore observations by a team of
observers rotating between Mahukona
and Lapakahi before, during, and after
the exercise.
(9) The Navy will conduct five
exercises in the Pacific Missile Range
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Facilities that fall within 25 km (13.5
nm) of the 200–m (656–ft) isobath. The
live sonar component of these 5
exercises will total approximately 6.5
hours. During these exercises, the Navy
will conduct the monitoring described
in (8)(b), (c), and (d).
(10) NMFS and the Navy will
continue coordination on the
‘‘Communications and Response
Protocol for Stranded Marine Mammal
Events During Navy Operations in the
Pacific Islands Region’’ that is currently
under preparation by NMFS PIRO to
facilitate communication during
RIMPAC. The Navy will coordinate with
the NMFS Stranding Coordinator for
any unusual marine mammal behavior,
including stranding, beached live or
dead cetacean(s), floating marine
mammals, or out-of-habitat/milling live
cetaceans that may occur at any time
during or shortly after RIMPAC
activities. After RIMPAC, NMFS and the
Navy (CPF) will prepare a coordinated
report on the practicality and
effectiveness of the protocol that will be
provided to Navy/NMFS leadership.
(11)The Navy will provide a report to
NMFS after the completion of RIMPAC
that includes:
(a) An estimate of the number of
marine mammals affected by the
RIMPAC ASW exercises and a
discussion of the nature of the effects,
if observed, based on both modeled
results of real-time exercises and
sightings of marine mammals.
(b) An assessment of the effectiveness
of the mitigation and monitoring
measures with recommendations of how
to improve them.
(c) Results of all of the marine species
monitoring (real-time Navy monitoring
from all platforms, independent aerial
monitoring, shore-based monitoring at
chokepoints, etc.) before, during, and
after the RIMPAC exercises.
(d) As much information (unclassified
and, to appropriate recipients, classified
‘‘secret’’) as the Navy can provide
including, but not limited to, where and
when sonar was used (including sources
not considered in take estimates, such
as submarine and aircraft sonars) in
relation to any measured received levels
(such as at sonobuoys or on PMRF
range), source levels, numbers of
sources, and frequencies, so it can be
coordinated with observed cetacean
behaviors.
The mitigation and monitoring
proposed in this IHA are intended to
function adaptively, and NMFS fully
expects to refine them for future
authorizations based on the reporting
input from the Navy.
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Shutdown Criteria
Pursuant to section101(a)(5)(D)(iv) of
the MMPA, The Secretary of Commerce
shall modify, suspend, or revoke an
authorization if the Secretary finds that
the provisions of clauses (i) or (ii) of
section 101(a)(5)(D) are not being met.
Marine mammal strandings are a
common event in Hawaii and over the
course of the 22 days of ASW exercises,
NMFS expects that 1 or 2 single-animal
strandings may occur that are not
related to RIMPAC. To distinguish these
strandings from a stranding that NMFS
believes may occur as a result of
exposure to the hull-mounted MidFrequency Active Sonar (MFAS)
activities covered in this authorization,
NMFS and the U.S. Navy have
established this ‘‘shutdown criteria’’ to
provide the necessary time for the
Secretary to investigate the cause of
uncommon marine mammal stranding
events and determine whether the IHA
should be modified, suspended, or
revoked. The established protocols in
place between NMFS Stranding
Coordinator Pacific and COMPACFLT
Environmental Coordinator are the basis
for this document.
Definitions
Shutdown area–An area within 50 km
(27 nm) of the half of the island
centered on the place where the animal
was found.
Limited Chokepoint Shutdown–
Temporary suspension of the hullmounted MFAS during the choke point
exercises.
Uncommon Stranding Event–An
event involving any one of the
following:
• Two or more individuals of a
commonly stranded species found dead
or live beached within a two day period
(not including mother/calf pairs), or
• A single uncommonly stranded
whale found dead or live beached, or
• A group of 10 or more animals
milling out of habitat (e.g. such as
occurred with melon headed whales in
Hanalei Bay in 2004)
Commonly Stranded Odontocete
Species–spinner dolphin, striped
dolphin, Kogia sp, Tursiops sp, melonheaded whale, pilot whale, and sperm
whales.
Investigation–consists of the
following components and can be
conducted within 3 days of notification
of a stranding event
(1) NMFS will undertake a survey
around stranding site to search for other
stranded/out of habitat animals
(2) Physical Exam of animal (and
blood work if live animals) to
investigate and verify presence or
absences
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(a) Of impacts on the hearing of live
stranded mammals. If feasible and if
medical condition of the animal allows,
Acoustic Brainstem Response (ABR) and
Auditory Evoke Potential (AEP) will be
conducted to rapidly assess whether the
hearing of a live stranded animal has
been affected.
(b) Of long term illness (based on
body condition), life threatening
infection, blunt force traumas or fishery
interaction that would indicate the
likely cause of death
(c) Of gross lesions or CT/MRI
findings that have been documented in
previous sonar related strandings (i.e.,
gas emboli or fat emboli, hemorrhages in
organs, hemorrhage in ears). Note: Care
must be taken to control and document
the conditions under which the carcass
is handled. The investigation of
microscopic histology can be
compromised by the decomposition,
freeze/thaw, transport conditions and
subsequent necropsy of the mammal.
(3) Evaluation of environmental
conditions (through remote sensing,
modeling and direct observations)
preceding and during the stranding or
out of habitat event to determine if
environmental factors that are known to
contribute to such events were in place,
such as fronts, swells, particular
currents, Kona winds, prey abundance,
seismic events, lunar phase, toxins or
predators in area. Navy will assist in
providing environmental data that is
otherwise collected for tactical
purposes.
• Strong evidence of environmental
factors that might contribute to
stranding event were present
• Weak to no evidence of
environmental factors that might
contribute to stranding were present
(4) Within 72 hours of notification of
an Uncommon Stranding Event, Navy
will provide information regarding
where and what (or where not) the Navy
was operating sonar leading up to the
stranding.
start time and duration of any recent
choke-point exercises.
3. The Navy will cease hull-mounted
MFAS activities in the shutdown area.
Additionally, if the uncommon
stranding event occurred during or
within 48 hours of the end of a choke
point exercise the Navy will invoke the
limited choke point shutdown for up to
4 days.
4. NMFS will conduct its
investigation and inform the Navy of its
findings as soon as possible, but no later
than 4 days from the date the
Uncommon Stranding Event was
verified.
5. If the results of the investigation
indicate that the stranding resulted from
causes other than activities covered by
this authorization NMFS will inform the
Navy that exercises authorized by this
IHA may resume.
6. If NMFS determines that the Navy’s
activities authorized under the IHA may
have contributed to the uncommon
marine mammal stranding event NMFS
will advise the Navy whether the IHA
should be modified, suspended, or
revoked.
Shutdown Protocol:
1. NMFS will respond to all reports of
marine mammal strandings during the
exercise. If a stranding is suspected to
be an Uncommon Stranding Event, the
NMFS Stranding Coordinator Pacific
will immediately notify the
COMPACFLT Environmental
Coordinator. The Coordinators will
utilize existing protocols as amplified
by this document to verify whether or
not an event constitutes an Uncommon
Stranding Event.
2. If an Uncommon Stranding Event is
verified, NMFS will inform the Navy
and will identify the shutdown area.
NMFS will also confirm with Navy the
Negligible Impact Determination and
Avoidance of Mortality of Marine
Mammals
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Communication
Effective communication is critical to
the successful implementation of this
protocol.
• NMFS will provide Navy with a list
of NMFS staff, empowered to inform the
Navy to implement the appropriate
shutdown protocol as described above.
These individuals will be reachable 24
hours/day for 22 consecutive days (a
pre-identified group will be on call in
shifts to make these decisions and a
phone tree will be available). Week-end
on call will be designated for HQ staff
by noon on Friday.
• Navy will provide NMFS a list of
people empowered to implement the
shut down protocol, at least one of
whom will be reachable at any hour
during the 22 days of ASW exercises
prior to the initiation of the exercise
Negligible Impact
Negligible impact is defined 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.’’ Because NMFS
does not authorize or expect any
mortality or injury to result from these
activities, NMFS believes the authorized
takings, by harassment, can be
reasonably expected not to adversely
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affect the species or stock through
effects on annual rates of survival.
NMFS acknowledges that Level B
Harassment to large enough portions of
a species or stock or over a long enough
time could potentially adversely affect
survival rates, however, due to the
required mitigation and monitoring
during this proposed activity (which
reduce the numbers of animals exposed
and the levels they are exposed to), as
well as the duration and nature of the
activities, NMFS does not believe the
RIMPAC ASW exercises will adversely
affect survival of any of the affected
species.
As discussed earlier (see Stress
Responses), some portion of the animals
exposed to SELs greater than 173 dB
during the RIMPAC exercises will
undergo a physiological stress response.
Relationships between stress responses
and inhibition of reproduction (by
suppression of pre-ovulatory luteinizing
hormones, for example) have been well-
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documented. However, NMFS believes
the manner in which individual animals
respond to different stressors varies
across a continuum that is normally
distributed with hyper-sensitive and
hypo-sensitive animals being on the
tails of the curve. Therefore, NMFS does
not believe that much more than a small
portion of animals exposed to sound
levels above 173 dB would respond in
a manner that physiologically inhibits
reproduction. Additionally, suppression
of pre-ovulatory luteinizing hormones
would only be of a concern to species
whose period of reproductive activity
overlaps in time and space with
RIMPAC. NMFS also believes that due
to the enhanced nature of the
monitoring required in this
authorization, combined with the
shutdown zones, the likelihood of
seeing and avoiding mother/calf pairs or
animals engaged in social reproductive
behaviors is high. Consequently, NMFS
believes it is unlikely the authorized
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takings will adversely affect the species
or stocks through effects on annual rates
of recruitment.
Table 3 summarizes the reasoning
behind NMFS’ negligible impact
determination, in terms of how
mitigation measures contribute towards
it and what other factors were
considered. Several of the measures
addressed have a visual monitoring
component, which NMFS recognizes is
most effective in reducing impacts to
larger animals and species that travel in
larger groups. However, NMFS has also
included coastal and steep bathymetry
restrictions, and extended power-down/
shut-down zones, which will
significantly reduce the numbers of
animals taken, regardless of whether
they are cryptic or easily seen, and will
effectively reduce the likelihood of
mortality, or serious injury, of marine
mammals.
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As mentioned in Table 3, the number
of individuals estimated to be harassed,
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in relation to the abundance of the
species or stock, factors into the
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negligible impact determination. In
Table 4, NMFS shows the raw percent
of the Navy’s modeled exposures for
each species divided by the estimated
abundance of each species within the
Hawaiian EEZ. Though NMFS uses
these numbers as a starting point for
assessing approximately what portion of
any affected population may be affected
by Level B Harassment through this
activity, these numbers suggest impacts
to a far greater portion of the
populations than NMFS believes will
actually occur because they do not take
into account several important factors
discussed below. Though no particular
numeric reduction of the raw modeled
percentages can be justified, they are
semi-quantitatively addressed in Table
4, which illustrates how certain factors
and protective measures reduce the
percent of population affected by these
activities for each species. Below are the
reasons NMFS believes that the
percentages of each stock affected are
lower:
(1) The effectiveness of mitigation
measures has not been taken into
account. The following measures will
reduce the numbers of individuals
harassed:
(a) The 25 km (13.5 nm) coastal
exclusion area - For species that have
significantly higher densities inshore
(10 - 40 times greater within 25 nm (46
km) of the shore), the Navy is excluded
from operating sonar within 25 km (13.5
nm) of shore, which significantly
reduces the numbers of individuals
exposed to sonar. This an especially
important point for the spinner dolphin,
which has an inshore density of 40
times that of the offshore density.
(b) Monitoring and implementation of
powerdowns, shutdowns, and
avoidance maneuvers - Species of large
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body size and large average group size
are significantly more likely to be
detected by monitoring (active
submarine sonar prior to startup, and
visual monitoring during the exercise)
than those animals that are deep divers
or cryptic and the surface, and,
therefore, powerdowns and shutdowns
are expected to be especially effective in
reducing the numbers of these species
affected.
(2) The estimated percentage of the
portion of the population or stock
harassed was calculated by dividing the
modeled Level B harassment takes by
the estimated abundance in the
Hawaiian EEZ. NMFS beleives that the
modeled number of takes is an
overestimate of the actual number for
the following reasons:
(a) As discussed in more detail in the
sub-section entitled ‘‘Model’’ in the
‘‘Estimated Number of Takes’’ section
previously, NMFS believes that the
model overestimates the take of marine
mammals significantly by assuming that
animals remain stationary throughout
their overlap with the ensonified area
and by assuming that an animal is
always located in the loudest point in
any column of ensonified water.
(b) Additionally, when further
analyzing the effects of these takes on
the affected species and stocks, NMFS
believes it would be unrealistic,
considering the fast-paced, multi-vessel
nature of the exercise and the fact that
the exercise continues over the course of
a month in an area with resident
populations of cetaceans, to assume that
each exposure involves a different
whale. Some whales are likely to be
exposed once, while others are likely to
be exposed more than once. One way to
numerically address this concept is to
assume that the exposure events would
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be distributed normally, with the
exposures that each affect a different
whale falling within one standard
deviation (68.26 percent), the exposures
assumed to affect different whales each
twice within 2 standard deviations
(27.18 percent), the exposures assumed
to affect different whales each 3 times
within 3 standard deviations (4.28
percent), and so on, if the populations
are larger. If this relationship is applied
to estimated numbers of exposures
produced by the Navy’s model, the
calculated number of affected animals is
approximately 16 percent less than the
estimated number of exposures for any
given species. NMFS acknowledges the
lack of specific sonar/marine mammal
data to support this approach, however,
NMFS believes that this approach will
help us more closely approximate the
number of animals potentially taken
than an assumption that each sonar ping
affects a different cetacean.
(3) As mentioned in number 2, the
estimated percentage of the portion of
the population or stock harassed was
calculated by dividing the modeled
Level B harassment takes by the
estimated abundance in the Hawaiian
EEZ. However, almost all of the
biological populations extend past the
boundary of the Hawaiian EEZ, some to
an unknown distance, some
pantropically, some to the northern
Pacific, and some farther. This means
that the percentages of populations
effected are further lower than the
percentages reported in Table. This
point may be less applicable to spinner
dolphins and bottlenose dolphins as
there may be additional population subdivision within the Hawaiian Islands.
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being published in the Federal Register,
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NMFS published the Final Report
addressing the melon-headed whale
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event that occurred in Hanalei Bay
during the RIMPAC exercises last year.
This report concluded that midfrequency sonar operation in the area
was a plausible, if not likely, contributor
to the event. NMFS recognizes that the
deaths of these animals could
potentially have resulted measurable
effects on the population. To minimize
that possibility in the future, NMFS will
implement Shutdown Critieria during
RIMPAC that require the Navy to cease
sonar operations if an uncommon
stranding event (such as the Hanalei
event) is verified (see Mitigation,
Monitoring, and Reporting above).
NMFS has determined that, based on
the nature and duration of the proposed
activities, and dependent upon the full
implementation of the required
mitigation and monitoring measures,
which will reduce both the severity of
effects on animals that may be
potentially exposed and the numbers of
animals potentially exposed, the
RIMPAC ASW exercises will result in
the Level B Harassment of the species
addressed here, consisting primarily of
temporary behavioral modifications, in
the form of temporary displacement
from feeding or sheltering areas, lowlevel physiological stress responses,
and, to a lesser extent, TTS. NMFS has
further determined that these takings, by
harassment, will result in a negligible
impact to the affected species or stocks.
Avoidance of Serious Injury or Mortality
cprice-sewell on PROD1PC66 with NOTICES2
NMFS has required a suite of
mitigation measures in the IHA that
reduces the likelihood of a stranding
resulting from the RIMPAC ASW
activities. However, several points that
were emphasized in the public
comments (i.e., the difficulty (even in
ideal conditions) of detecting beaked
whales, which have been among the
species stranded in most of the
strandings associated with sonar, and
the fact that choke-point exercises will
be conducted both at night and in
surface-ducting conditions) and the
published conclusions of the melonheaded whale stranding report do not
VerDate Aug<31>2005
15:49 Jul 06, 2006
Jkt 208001
allow NMFS to rule out the possibility
of a stranding resulting from the
RIMPAC ASW activities. Consequently,
NMFS has included specific shutdown
criteria (see Mitigation and Monitoring,
above), which are intended to ensure
MMPA compliance. These criteria
require the Navy to temporarily cease
operating sonar in a designated area
when a stranding is verified during the
RIMPAC ASW exercise. NMFS will then
conduct an investigation, and if NMFS
finds that the Navy’s activities may have
contributed to the stranding, NMFS will
modify, revoke, or suspend the IHA.
Endangered Species Act (ESA)
There are seven marine mammal
species and five sea turtle species that
are listed as endangered or threatened
under the ESA with confirmed or
possible occurrence in the RIMPAC
ASW area: humpback whale, North
Pacific right whale, sei whale, fin whale,
blue whale, sperm whale, and Hawaiian
monk seal, loggerhead sea turtle, the
green sea turtle, hawksbill sea turtle,
leatherback sea turtle, and olive ridley
sea turtle.
Under section 7 of the ESA, the Navy
consulted with NMFS on the proposed
RIMPAC ASW exercises. NMFS also
consulted internally on the issuance of
an IHA under section 101(a)(5)(D) of the
MMPA for this activity. The Endangered
Species Division, NMFS, issued a
Biological Opinion (BiOp) that
concluded that the proposed action is
not likely to result in jeopardy to the
species or in the destruction or adverse
modification of critical habitat..
The BiOp includes an incidental take
statement for harassment of sperm
whales, fin whales, and sei whales,
which also contains the same required
terms and conditions (mitigation,
monitoring, and reporting) as those
contained in the IHA.
National Environmental Policy Act
(NEPA)
In April, 2006, the Navy prepared a
revised 2006 Supplement on the 2002
Programmatic Environmental
Assessment (EA) on RIMPAC. NMFS
PO 00000
Frm 00030
Fmt 4701
Sfmt 4703
has adopted the Navy’s EA and issued
an associated Finding of No Significant
Impact (FONSI).
Conclusions
A determination of negligible impact
is required for NMFS to authorize
incidental take of marine mammals. By
regulation, an activity has a ‘‘negligible
impact’’ on a species or stock when it
is determined that the total taking is not
likely to reduce annual rates of adult
survival or recruitment (i.e., offspring
survival, birth rates). Based on each
species’ life history information, the
expected behavioral patterns of the
animals in the RIMPAC locations, the
duration of the activity, the anticipated
implementation of the required
mitigation and monitoring measures,
and an analysis of the behavioral
disturbance levels in comparison to the
overall populations, an analysis of the
potential impacts of the Proposed
Action on species recruitment or
survival support the conclusion that
proposed RIMPAC ASW training events
would have a negligible impact on the
affected species or stocks. NMFS has
also determined that the issuance of the
IHA would not have an unmitigable
adverse impact on the availability of the
affected species or stocks for subsistence
use. Additionally, NMFS has set forth in
its IHA the permissible methods of
taking and requirements pertaining to
the mitigation, monitoring and reporting
of such takings.
Authorization
NMFS has issued an IHA to the Navy
for conducting ASW exercises, using
tactical mid-frequency sonar, in the
Hawaiian Islands OpArea, provided the
previously mentioned mitigation,
monitoring, and reporting requirements
are incorporated.
Dated: June 29, 2006.
James H. Lecky,
Director, Office of Protected Resources,
National Marine Fisheries Service.
[FR Doc. 06–6050 Filed 7–6–06; 8:45 am]
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Agencies
[Federal Register Volume 71, Number 130 (Friday, July 7, 2006)]
[Notices]
[Pages 38710-38738]
From the Federal Register Online via the Government Printing Office [www.gpo.gov]
[FR Doc No: 06-6050]
[[Page 38709]]
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Part III
Department of Commerce
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National Oceanic and Atmospheric Administration
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Small Takes of Marine Mammals Incidental to Specified Activities; Rim
of the Pacific Antisubmarine Warfare Exercise Training Events Within
the Hawaiian Islands Operating Area; Notice
Federal Register / Vol. 71, No. 130 / Friday, July 7, 2006 /
Notices
[[Page 38710]]
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DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
I.D. 062806A
Small Takes of Marine Mammals Incidental to Specified Activities;
Rim of the Pacific Antisubmarine Warfare Exercise Training Events
Within the Hawaiian Islands Operating Area
AGENCY: National Marine Fisheries Service (NMFS), National Oceanic and
Atmospheric Administration (NOAA), Commerce.
ACTION: Notice; issuance of IHA.
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SUMMARY: In accordance with the provisions of the Marine Mammal
Protection Act (MMPA) as amended, notification is hereby given that
NMFS has issued an Incidental Harassment Authorization (IHA) to the
U.S. Navy (Navy) to take marine mammals, by incidental Level B
harassment only, while conducting Rim of the Pacific (RIMPAC) anti-
submarine (ASW) training events, in which submarines, surface ships,
and aircraft from the United States and multiple foreign nations
participate in ASW training exercises, utilizing mid-frequency sonar (1
kilohertz (kHz) to 10 kHz), in the U.S. Navy's Hawaiian Operating Area
(OpArea) during July, 2006.
DATES: Effective June 27, 2006, through August 15, 2006.
ADDRESSES: A copy of the IHA and the application are available by
writing 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, or by
telephoning the contact listed here. A copy of the application
containing a list of references used in this document may be obtained
by writing to this address, by telephoning the contact listed here (see
FOR FURTHER INFORMATION CONTACT) or online at: https://
www.nmfs.noaa.gov/pr/permits/incidental.htm. Documents cited in this
notice may be viewed, by appointment, during regular business hours, at
the aforementioned address.
FOR FURTHER INFORMATION CONTACT: Donna Wieting, Office of Protected
Resources, NMFS, (301) 713-2289.
SUPPLEMENTARY INFORMATION:
Background
Sections 101(a)(5)(A) and (D) of the MMPA (16 U.S.C. 1361 et seq.)
direct the Secretary of Commerce to allow, upon request, the
incidental, but not intentional, taking of marine mammals by U.S.
citizens who engage in a specified activity (other than commercial
fishing) within a specified geographical region if certain findings are
made and either regulations are issued or, if the taking is limited to
harassment, a notice of a proposed authorization is provided to the
public for review.
Authorization 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 that the permissible methods of
taking and requirements pertaining to the mitigation, monitoring and
reporting of such takings are set forth. NMFS has defined ``negligible
impact'' in 50 CFR 216.103 as ''...an impact resulting from the
specified activity that cannot be reasonably expected to, and is not
reasonably likely to, adversely affect the species or stock through
effects on annual rates of recruitment or survival.''
Section 101(a)(5)(D) of the MMPA established an expedited process
by which citizens of the United States can apply for an authorization
to incidentally take small numbers of marine mammals by harassment. The
National Defense Authorization Act of 2004 (NDAA) (Public Law 108-136)
removed the ``small numbers'' limitation and amended the definition of
``harassment'' as it applies to a ``military readiness activity'' to
read as follows:
(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]
Section 101(a)(5)(D) establishes a 45-day time limit for NMFS
review of an application followed by a 30-day public notice and comment
period on any proposed authorizations for the incidental harassment of
marine mammals. Within 45 days of the close of the comment period, NMFS
must either issue or deny issuance of the authorization.
Summary of Request
On March 16, 2006, NMFS received an application from the Navy for
the taking, by harassment, of several species of marine mammals
incidental to conducting RIMPAC ASW training events, in which
submarines, surface ships, and aircraft from the United States and
multiple foreign nations participate in ASW training exercises, in the
OpArea, in the summer of 2006. The RIMPAC ASW exercises are considered
a military readiness activity.
NMFS may not authorize the take of marine mammals by non-U.S.
citizens; however, all foreign vessels participating in RIMPAC 2006
will be under the Operational Control (OPCON) of Commander, U.S. THIRD
Fleet in his capacity as Officer Conducting the Exercise (OCE) and
Commander, Combined Task Force (CCTF) RIMPAC (i.e., the Navy can
require that a foreign vessel cease sonar operations). Additionally,
all forces assigned, including foreign vessels, are required to comply
with the environmental mitigation measures spelled out in the Navy's
Annex L [Environmental], which will include all of the measures in the
IHA, as a condition of participating in the exercise. This is part of
the description of the activity.
Description of the Activity
RIMPAC 2006 ASW activities are scheduled to take place from June
26, 2006, to about July 28, 2006, with ASW training events planned on
21 days. The OpArea is approximately 210,000 square nautical miles
(nm), however, the majority of RIMPAC ASW training would occur in the
six areas delineated in Figure 2-1 in the Navy's application
(approximate 46,000 square nm). ASW events typically rotate between
these six modeled areas. These six areas were used for analysis as
being representative of the marine mammal habitats and the bathymetric,
seabed, wind speed, and sound velocity profile conditions within the
entire OpArea. For purposes of this analysis, all likely RIMPAC ASW
events were modeled as occurring in these six areas.
As a combined force during the exercises, submarines, surface
ships, and aircraft will conduct ASW against opposition submarine
targets. Submarine targets include real submarines, target drones that
simulate the operations of an actual submarine, 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 SAGs for RIMPAC 2006. For the purposes
of analysis, each event in which a SAG
[[Page 38711]]
participates is counted as an ASW operation. There will be
approximately 44 ASW operations during RIMPAC with an average event
length of approximately 12 hours.
One or more ASW events may occur simultaneously within the OpArea.
Each event was identified and modeled separately. If a break of more
than 1 hour in ASW operations occurred, then the subsequent event was
modeled as a separate event. Training event durations ranged from 2
hours to 24 hours. A total of 532 training hours were modeled for
RIMPAC acoustic exposures. This total includes all potential ASW
training that is expected to occur during RIMPAC.
Active Acoustic Sources
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 sound energy
reflected back from that object.
Modern sonar technology has developed a multitude of sonar sensor
and processing systems. In concept, the simplest active sonars emit
omnidirectional pulses (``pings'') and time the arrival of the
reflected echoes from the target object to determine range. More
sophisticated active sonar emits an omnidirectional 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 in RIMPAC are designed
to detect submarines in tactical operational scenarios. This task
requires the use of the sonar mid-frequency (MF) range (1 kilohertz
[kHz] to 10 kHz) predominantly.
The types of tactical acoustic sources that would be used in
training events during RIMPAC are discussed in the following
paragraphs. For more information regarding how the Navy's determined
which sources should not be included in their analysis, see the
Estimates of Take Section later in this document.
Surface Ship Sonars-A variety of surface ships participate in
RIMPAC, including guided missile cruisers, destroyers, guided missile
destroyers, and frigates. Some ships (e.g., aircraft carriers) do not
have any onboard active sonar systems, other than fathometers. Others,
like guided missile cruisers, are equipped with active as well as
passive sonars for submarine detection and tracking. For purposes of
the analysis, all surface ship sonars were modeled as equivalent to
SQS-53 having the nominal source level of 235 decibels (dB) re 1mPa\2\-
s (SEL). Since the SQS-53 hull mounted sonar is the U.S. Navy's most
powerful surface ship hull mounted sonar, modeling this source is a
conservative assumption tending towards an overestimation of potential
effects (although, the conservativeness is offset some by the fact that
the Navy did not model for any of the times (though brief and
infrequent) that they may use a source level higher than 235 dB). Sonar
ping transmission durations were modeled as lasting 1 second per ping
and directional with a footprint that was 240 degrees wide, which is a
conservative assumption that overestimates potential exposures, since
actual ping durations will be less than 1 second. The SQS-53 hull
mounted sonar transmits at center frequencies of 2.6 kHz and 3.3 kHz.
Submarine Sonars-Submarine sonars can be used to detect and target
enemy submarines and surface ships. However, submarine active sonar use
is very rare in the planned RIMPAC exercises, and, when used, very
brief. Therefore, use of active sonar by submarines is unlikely to have
any effect on marine mammals, and it was not modeled for RIMPAC 2006.
Aircraft Sonar Systems-Aircraft sonar systems that would operate
during RIMPAC include sonobuoys and dipping sonar. Sonobuoys may be
deployed by P-3 aircraft or helicopters; dipping sonars are used by
carrier-based helicopters. A sonobuoy is an expendable device used by
aircraft for the detection of underwater acoustic energy and for
conducting vertical water column temperature measurements. Most
sonobuoys are passive, but some can generate active acoustic signals as
well. Dipping sonar is an active or passive sonar device lowered on
cable by helicopters to detect or maintain contact with underwater
targets. During RIMPAC, these systems active modes are only used
briefly for localization of contacts and are not used in primary search
capacity. Because active mode dipping sonar use is very brief, it is
extremely unlikely its use would have any effect on marine mammals. The
AN/AQS 13 (dipping sonar) used by carrier based helicopters was
determined in the Environmental Assessment/Overseas Environmental
Assessment of the SH-60R Helicopter/ALFS Test Program, October 1999,
not to be problematic due to its limited use and very short pulse
length. Therefore, the aircraft sonar systems were not modeled for
RIMPAC 2006.
Torpedoes-Torpedoes are the primary ASW weapon used by surface
ships, aircraft, and submarines. The guidance systems of these weapons
can be autonomous or electronically controlled from the launching
platform through an attached wire. The autonomous guidance systems are
acoustically based. They operate either passively, exploiting the
emitted sound energy by the target, or actively, ensonifying the target
and using the received echoes for guidance. All torpedoes used for ASW
during RIMPAC would be located in the range area managed by Pacific
Missile Range Facility (PMRF) and would be non-explosive and recovered
after use.
Acoustic Device Countermeasures (ADC)-ADCs are, in effect,
submarine simulators that make noise to act as decoys to avert
localization and/or torpedo attacks. Previous classified analysis has
shown that, based on the operational characteristics (source output
level and/or frequency) of these acoustic sources, the potential to
affect marine mammals was unlikely, and therefore they were not modeled
for RIMPAC 2006.
Training Targets-ASW training targets are used to simulate target
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. Based on the operational characteristics (source
output level and/or frequency) of these acoustic sources, the potential
to affect marine mammals is unlikely, and therefore they were not
modeled for RIMPAC 2006.
Range Sources-Range pingers are active acoustic devices that allow
each of the in-water platforms on the range (e.g., ships, submarines,
target simulators, and exercise torpedoes) to be tracked by the range
transducer nodes. In addition to passively tracking the pinger signal
from each range participant, the range transducer nodes also are
capable of transmitting acoustic signals for a limited set of
functions. These functions include submarine warning signals, acoustic
commands to submarine target simulators (acoustic command link), and
occasional voice or
[[Page 38712]]
data communications (received by participating ships and submarines on
range). Based on the operational characteristics (source output level
and/or frequency) of these acoustic sources, the potential to affect
marine mammals is unlikely, and therefore they were not modeled for
RIMPAC 2006.
For detailed information regarding the proposed activity, please
see the Navy's application and the associated Environmental Assessment
(EA) (see ADDRESSES).
Description of Marine Mammals Potentially Affected by the Activity
There are 27 marine mammal species with possible or confirmed
occurrence in the Navy's OpArea (Table 1): 25 cetacean species (whales,
dolphins, and porpoises) and 2 pinnipeds (seals). In addition, five
species of sea turtles are known to occur in the OpArea.
The most abundant marine mammals are rough-toothed dolphins, dwarf
sperm whales, and Fraser's dolphins. The most abundant large whales are
sperm whales. There are three seasonally migrating baleen whale species
that winter in Hawaiian waters: minke, fin, and humpback whales.
Humpback whales utilize Hawaiian waters as a major breeding ground
during winter and spring (November through April), but should not be
present during the RIMPAC exercise, which takes place in July. Because
definitive information on the other two migrating species is lacking,
their possible presence during the July timeframe is assumed, although
it is considered unlikely. Seven marine mammal species listed as
federally endangered under the Endangered Species Act (ESA) occur in
the area: the humpback whale, North Pacific right whale, sei whale, fin
whale, blue whale, sperm whale, and Hawaiian monk seal.
The Navy has used data compiled from available sighting records,
literature, satellite tracking, and stranding and bycatch data to
identify the species of marine mammals present in the OpArea. A
combination of inshore survey data (within 25 nm (46 km); Mobley et
al., 2000) and offshore data (from 25 nm (46 km) offshore out to the
U.S. Exclusive Economic Zone (EEZ) (200 nm (370 km) (, Barlow 2003) was
used to estimate the density and abundance of marine mammals within the
OpArea (Table 1). Additional information regarding the status and
distribution of the 27 marine mammal species that occur in the OpArea
may be found in the Navy's application and the associated EA (see
ADDRESSES) and in NMFS' Stock Assessment Reports, which are available
at: https://www.nmfs.noaa.gov/pr/PR2/Stock_Assessment_Program/
individual_sars.html.
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Potential Effects on Marine Mammals
NMFS has issued an IHA to the Navy for the take, by harassment, of
marine mammals incidental to RIMPAC ASW exercises in the OpArea.
Section 101(a)(5)(D) of the MMPA, the section pursuant to which IHAs
are issued, may not be used to authorize mortality or serious injury
leading to mortality. The Navy's analysis of the RIMPAC ASW exercises
concluded that no mortality or serious injury leading to mortality
would result from the proposed activities. However, NMFS believes,
based on our interpretation of the limited available data bearing on
this point, that some marine mammals may react to mid-frequency sonar,
at received levels lower than those thought to cause direct physical
harm, with behaviors that may, in some circumstances, lead to
physiological harm, stranding, or, potentially, death. Therefore, NMFS
has required additional mitigation and monitoring measures that were
not originally proposed in the Navy's application, which are intended
to ensure (in addition to the standard statutory requirement to effect
the ``least practicable adverse impact upon the affected species or
stock'') that mortality or serious injury leading to mortality does not
result from the proposed activities.
Below, NMFS describes the potential effects on marine mammals of
exposure to tactical sonar.
Metrics Used in Acoustic Effect Discussions
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 (mPa), where 1 Pa is the pressure resulting
from a force of one newton exerted over an area of one square meter.
The sound levels to which most mammals are sensitive extend over
many orders of magnitude and, for this reason, it is convenient to use
a logarithmic scale (the decibel (dB) scale) when measuring sound. 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 mPa, and the units for SPLs are dB re: 1 mPa.
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. SPL does not take the duration of a
sound into account.
SEL
In this proposed authorization, effect thresholds are expressed in
terms of sound exposure level SEL. SEL is an energy metric that
integrates the squared instantaneous sound pressure over a stated time
interval. The units for SEL are dB re: 1 mPa\2\-s.
SEL = SPL + 10log(duration)
As applied to tactical sonar, the SEL includes both the ping SPL
and the duration. Longer-duration pings and/or higher-SPL pings 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. Since mammalian
threshold shift (TS) data show less effect from intermittent exposures
compared to continuous exposures with the same energy (Ward, 1997),
basing the effect thresholds on the total received SEL may be a
conservative approach for treating multiple pings; as some recovery may
occur between pings and lessen the effect of a particular exposure.
The total SEL depends on the SPL, duration, and number of pings
received. The acoustic effects on hearing that result in temporary
threshold shift (TTS) and permanent threshold shift (PTS), do not imply
any specific SPL, duration, or number of pings. The SPL and duration of
each received ping are used to calculate the total SEL and determine
whether the received SEL meets or exceeds the effect thresholds. For
example, the sub-TTS behavioral effects threshold of 173 dB SEL would
be reached through any of the following exposures:
A single ping with SPL = 173 dB re 1 mPa and duration = 1
second.A single ping with SPL = 170 dB re 1 mPa and duration = 2
seconds.Two pings with SPL = 170 dB re 1 mPa and duration = 1
second.Two pings with SPL = 167 dB re 1 mPa and duration = 2
seconds.
Potential Physiological Effects
Physiological function is any of a collection of processes ranging
from biochemical reactions to mechanical interaction and operation of
organs and tissues within an animal. A physiological effect may range
from the most significant of impacts (i.e., mortality and serious
injury) to lesser effects that would define the lower end of the
physiological impact range, such as non-injurious short-term impacts to
auditory tissues.
Exposure to some types of noise may cause a variety of
physiological effects in mammals. For example, exposure to very high
sound levels may affect the function of the visual system, vestibular
system, and internal organs (Ward, 1997). Exposure to high-intensity
sounds of sufficient duration may cause injury to the lungs and
intestines (e.g., Dalecki et al., 2002). Sudden, intense sounds may
elicit a ``startle'' response and may be followed by an orienting
reflex (Ward, 1997; Jansen, 1998). The primary physiological effects of
sound, however, are on the auditory system (Ward, 1997).
Hearing Threshold Shift
In mammals, high-intensity sound may rupture the eardrum, damage
the small bones in the middle ear, or over-stimulate the
electromechanical hair cells that convert the fluid motions caused by
sound into neural impulses that are sent to the brain. Lower level
exposures may cause hearing loss, which is called a threshold shift
(TS) (Miller, 1974). Incidence of TS may be either permanent, in which
case it is called a permanent threshold shift (PTS), or temporary, in
which case it is called a temporary threshold shift (TTS). PTS consists
of non-recoverable physical damage to the sound receptors in the ear,
which can include total or partial deafness, or an impaired ability to
hear sounds in specific frequency ranges. TTS is recoverable and is
considered to result from temporary, non-injurious impacts to hearing-
related tissues. Hearing loss may affect an animal's ability to react
normally to the sounds around it.
The amplitude, duration, frequency, and temporal pattern of sound
exposure all affect the amount of associated TS. As amplitude and
duration of sound exposure increase, so, generally, does the amount of
TS. For continuous sounds, exposures of equal energy will lead to
approximately equal effects (Ward, 1997). 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). 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
[[Page 38715]]
PTS, at least in terrestrial mammals (Kryter, 1985).
Additional detailed information regarding threshold shifts may be
viewed in the Navy's RIMPAC application and in the USWTR DEIS.
Acoustically Mediated Bubble Growth
One theoretical cause of injury to marine mammals is rectified
diffusion (Crum and Mao, 1996), the process of increasing the size of a
bubble by exposing it to a sound field. This process could be
facilitated if the environment in which the ensonified bubbles exist is
supersaturated with gas. Repetitive diving by marine mammals can cause
the blood and some tissues to accumulate gas to a greater degree than
is supported by the surrounding environmental pressure (Ridgway and
Howard, 1979). The deeper and longer dives of some marine mammals (for
example, beaked whales) are theoretically predicted to induce greater
supersaturation (Houser et al., 2001b). If rectified diffusion were
possible in marine mammals exposed to high-level sound, conditions of
tissue supersaturation could theoretically speed the rate and increase
the size of bubble growth. Subsequent effects due to tissue trauma and
emboli would presumably mirror those observed in humans suffering from
decompression sickness.
It is unlikely that the short duration of sonar pings would be long
enough to drive bubble growth to any substantial size, if such a
phenomenon occurs. However, an alternative but related hypothesis has
also been suggested: stable bubbles could be destabilized by high-level
sound exposures such that bubble growth then occurs through static
diffusion of gas out of the tissues. In such a scenario the marine
mammal would need to be in a gas-supersaturated state for a long enough
period of time for bubbles to become of a problematic size. Yet another
hypothesis has speculated that rapid ascent to the surface following
exposure to a startling sound might produce tissue gas saturation
sufficient for the evolution of nitrogen bubbles (Jepson et al., 2003).
In this scenario, the rate of ascent would need to be sufficiently
rapid to compromise behavioral or physiological protections against
nitrogen bubble formation. Collectively, these hypotheses can be
referred to as ``hypotheses of acoustically mediated bubble growth.''
Although theoretical predictions suggest the possibility for
acoustically mediated bubble growth, there is considerable disagreement
among scientists as to its likelihood (Piantadosi and Thalmann, 2004;
Evans and Miller, 2003). To date, Energy Levels (ELs) predicted to
cause in vivo bubble formation within diving cetaceans have not been
evaluated (NOAA, 2002b). Further, although it has been argued that
traumas from some recent beaked whale strandings are consistent with
gas emboli and bubble-induced tissue separations (Jepson et al., 2003),
there is no conclusive evidence of this. Because evidence supporting
the potential for acoustically mediated bubble growth is debatable,
this proposed IHA does not give it any special treatment. Additionally,
the required mitigation measures, which are designed to avoid
behavioral disruptions that could result in abnormal vertical movement
by whales through the water column, should also reduce the potential
for creating circumstances that theoretically contribute to harmful
bubble growth.
Additional information on the physiological effects of sound on
marine mammals may be found in the Navy's IHA application and
associated Environmental Assessment, the USWTR DEIS, and on the Ocean
Acoustic Program section of the NMFS website (see ADDRESSES).
Stress Responses
In addition to PTS and TTS, exposure to mid-frequency sonar is
likely to result in other physiological changes that have other
consequences for the health and ecological fitness of marine mammals.
There is mounting evidence that wild animals respond to human
disturbance in the same way that they respond to predators (Beale and
Monaghan, 2004; Frid, 2003; Frid and Dill, 2002; Gill et al., 2000;
Gill and Sutherland, 2001; Harrington and Veitch, 1992; Lima, 1998;
Romero, 2004). These responses manifest themselves as interruptions of
essential behavioral or physiological events, alteration of an animal's
time or energy budget, or stress responses in which an animal perceives
human activity as a potential threat and undergoes physiological
changes to prepare for a flight or fight response or more serious
physiological changes with chronic exposure to stressors (Frid and
Dill, 2002; Romero, 2004; Sapolsky et al., 2000; Walker et al., 2005).
Classic stress responses begin when an animal's central nervous
system perceives a potential threat to its homeostasis. That perception
triggers stress responses regardless of whether a stimulus actually
threatens the animal; the mere perception of a threat is sufficient to
trigger a stress response (Sapolsky et al., 2005; Seyle, 1950). Once an
animal's central nervous system perceives a threat, it develops a
biological response or defense that consists of a combination of the
four general biological defense responses: behavioral responses,
autonomic nervous system responses, neuroendocrine responses, or immune
response.
The physiological mechanisms behind stress responses involving the
hypothalamus-pituitary-adrenal glands have been well-established
through controlled experiment in the laboratory and natural settings
(Korte et al. 2005; McEwen and Seeman, 2000; Moberg, 1985; 2000;
Sapolsky et al., 2005). Relationships between these physiological
processes, animal behavior, neuroendocrine responses, immune responses,
inhibition of reproduction (by suppression of pre-ovulatory luteinizing
hormones), and the costs of stress responses have also been documented
through controlled experiment in both laboratory and free-living
animals (for examples see, Holberton et al., 1996; Hood et al., 1998;
Jessop et al., 2003; Krausman et al., 2004; Lankford et al., 2005;
Reneerkens et al., 2002; Thompson and Hamer, 2000; Tilbrook et al.,
2000).
The available evidence suggests that: with the exception of
unrelieved pain or extreme environmental conditions, in most animals
(including humans) chronic stress results from exposure to a series of
acute stressors whose cumulative biotic costs produce a pathological or
pre-pathological state in an animal. The biotic costs can result from
exposure to an acute stressor or from the accumulation of a series of
different stressors acting in concert before the animal has a chance to
recover.
Although these responses have not been explicitly identified in
marine mammals, they have been identified in other vertebrate animals
and every vertebrate mammal that has been studied, including humans.
Because of the physiological similarities between marine mammals and
other mammal species, NMFS believes that acoustic energy sufficient to
trigger onset PTS or TTS is likely to initiate physiological stress
responses. More importantly, NMFS believes that marine mammals might
experience stress responses at received levels lower than those
necessary to trigger onset TTS.
Potential Behavioral Effects
For a military readiness activity, Level B Harassment is defined as
``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,
[[Page 38716]]
breeding, feeding, or sheltering, to a point where such behavioral
patterns are abandoned or significantly altered.''
As discussed above, TTS consists of temporary, short-term impacts
to auditory tissue that alter physiological function, but that are
fully recoverable without the requirement for tissue replacement or
regeneration. An animal that experiences a temporary reduction in
hearing sensitivity suffers no permanent injury to its auditory system,
but, for an initial time post-exposure, may not perceive some sounds
due to the reduction in sensitivity. As a result, the animal may not
respond to sounds that would normally produce a behavioral reaction
(such as a predator or the social calls of conspecifics, which play
important roles in mother-calf relations, reproduction, foraging, and
warning of danger). This lack of response qualifies as a temporary
disruption of normal behavioral patterns - the animal is impeded from
responding in a normal manner to an acoustic stimulus.
NMFS also considers disruption of the behavior of marine mammals
that can result from sound levels lower than those considered necessary
for TTS to occur (often referred to as sub-TTS behavioral disruption).
Though few studies have specifically documented the effects of tactical
mid-frequency sonar on the behavior of marine mammals in the wild, many
studies have reported the effects of a wide range of intense
anthropogenic acoustic stimuli on specific facets of marine mammal
behavior, including migration (Malme et al., 1984; Ljungblad et al.,
1988; Richardson et al., 1999), feeding (Malme et al., 1988), and
surfacing (Nowachek et al., 2004). Below, NMFS summarizes the results
of two studies and one after-the-fact investigation wherein the natural
behavior patterns of marine mammals exposed to levels of tactical mid-
frequency sonar, or sounds similar to mid-frequency sonar, lower than
those thought to induce TTS were disrupted to the point where it was
abandoned or significantly altered:
(1) Finneran and Schlundt (2004) analyzed behavioral observations
from related TTS studies (Schlundt et al., 2000; Finneran et al., 2001;
2003) to calculate cetacean behavioral reactions as a function of known
noise exposure. During the TTS experiments, four dolphins and two white
whales were exposed during a total of 224 sessions to 1-s pulses
between 160 and 204 dB re 1 mPa (root-mean-square sound pressure level
(SPL)), at 0.4, 3, 10, 20, and 75 kHz. Finneran and Schlundt (2004)
evaluated the behavioral observations in each session and determined
whether a ``behavioral alteration'' (ranging from modifications of
response behavior during hearing sessions to attacking the experimental
equipment) occurred. For each frequency, the percentage of sessions in
which behavioral alterations occurred was calculated as a function of
received noise SPL. By pooling data across individuals and test
frequencies, respective SPL levels coincident with responses by 25, 50,
and 75 percent behavioral alteration were documented. 190 dB re 1 mPa
(SPL) is the point at which 50 percent of the animals exposed to 3, 10,
and 20 kHz tones were deemed to respond with some behavioral
alteration, and the threshold that the Navy originally proposed for
sub-TTS behavioral disturbance.
(2) Nowacek et al. (2004) conducted controlled exposure experiments
on North Atlantic right whales using ship noise, social sounds of con-
specifics, and an alerting stimulus (frequency modulated tonal signals
between 500 Hz and 4.5 kHz). Animals were tagged with acoustic sensors
(D-tags) that simultaneously measured movement in three dimensions.
Whales reacted strongly to alert signals at received levels of 133-148
dB SPL, mildly to conspecific signals, and not at all to ship sounds or
actual vessels. The alert stimulus caused whales to immediately cease
foraging behavior and swim rapidly to the surface. Although SEL values
were not directly reported, based on received exposure durations,
approximate received values were on the order of 160 dB re: 1 mPa\2\-s.
(3) NMFS (2005) evaluated the acoustic exposures and coincident
behavioral reactions of killer whales in the presence of tactical mid-
frequency sonar. In this case, none of the animals were directly fitted
with acoustic dosimeters. However, based on a Naval Research Laboratory
(NRL) analysis that took advantage of the fact that calibrated
measurements of the sonar signals were made in situ and using advanced
modeling to bound likely received exposures, estimates of received
sonar signals by the killer whales were possible. Received SPL values
ranged from 121 to 175 dB re: 1 mPa. The most probable SEL values were
169.1 to 187.4 dB re: 1 mPa\2\-s; worst-case estimates ranged from
177.7 to 195.8 dB re: 1 mPa\2\-s. Researchers observing the animals
during the course of sonar exposure reported unusual alterations in
swimming, breathing, and diving behavior.
For more detailed information regarding how marine mammals may
respond to sound, see the Navy's IHA application, the Navy's associated
EA, Richardson's Marine Mammals and Noise (1995), or the references
cited on NMFS' Ocean Acoustic Program website (see ADDRESSES)
Harassment Thresholds
For the purposes of this IHA, NMFS recognizes three levels of take;
Level A Harassment (Injury), Level B Harasssment (Behavioral
Disruption), and mortality (or serious injury that may lead to
mortality) (Table 2). Mortality, or serious injury leading to
mortality, may not be authorized with an IHA.
NMFS has determined that for acoustic effects, acoustic thresholds
are the most effective way to consistently both apply measures to avoid
or minimize the impacts of an action and to quantitatively estimate the
effects of an action. Thresholds are commonly used in two ways: (1) To
establish a shut-down or power down zone, i.e., if an animal enters an
area calculated to be ensonified above the level of an established
threshold, a sound source is powered down or shut down; and (2) to
calculate take, for example, if the Level A Harassment threshold is 215
dB, a model may be used to calculate the area around the sound source
that will be ensonified to that level or above, then, based on the
estimated density of animals and the distance that the sound source
moves, NMFS can estimate the number of marine mammals exposed to 215
dB. The rationale behind the acoustic thresholds proposed for this
authorization are discussed below.
Table 2. The three levels of take addressed in the MMPA, how NMFS
measures them in regard to acoustic effects, and the proposed thresholds
for this authorization
------------------------------------------------------------------------
Levels of Take Pursuant to the
MMPA Basis of Threshold Proposed Threshold
------------------------------------------------------------------------
Level A Harassment (Injury) Permanent 215 dB (SEL)
Threshold Shift
(PTS).
Level B Harassment (Behavioral Temporary 195 dB (SEL)
Effects) Threshold Shift 173 dB (SEL)
(TTS).
Sub-TTS Behavioral
Effects.
[[Page 38717]]
Mortality, or Serious Injury Not enough May not be
That May Lead to Mortality information for authorized with an
(Stranding) quantitative IHA
threshold.
------------------------------------------------------------------------
TTS
Because it is non-injurious, NMFS considers TTS as Level B
harassment (behavioral disruption) that is mediated by physiological
effects on the auditory system. The smallest measurable amount of TTS
(onset-TTS) is taken as the best indicator for slight temporary sensory
impairment. However, as mentioned earlier, NMFS believes that
behavioral disruptions may result from received levels of tactical
sonar lower than those thought to induce TTS and, therefore, NMFS does
not consider on-set TTS to be the lowest level at which Level B
Harassment may occur. NMFS considers the threshold for Level B
Harasment as the received levels from which sub-TTS behavioral
disruptions are likely to result (discussed in Sub-TTS sub-section).
However, the threshold for Level A Harassment (PTS) is derived from the
threshold for TTS and, therefore, it is necessary to describe how the
TTS threshold was developed.
The proposed TTS threshold is primarily based on the cetacean TTS
data from Schlundt et al. (2000). These tests used short-duration tones
similar to sonar pings, and they are the most directly relevant data
for the establishing TTS criteria. The mean exposure EL required to
produce onset-TTS in these tests was 195 dB re 1 mPa\2\-s. This result
is corroborated by the short-duration tone data of Finneran et al.
(2000, 2003) and the long-duration noise data from Nachtigall et al.
(2003a,b). Together, these data demonstrate that TTS in cetaceans is
correlated with the received EL and that onset-TTS exposures are fit
well by an equal-energy line passing through 195 dB re 1 mPa\2\-s.
The justification for establishing the 195 dB acoustic criteria for
TTS is described in detail in both the Navy's RIMPAC IHA application
and the USWTR DEIS (see ADDRESSES).
PTS
PTS consists of non-recoverable physical damage to the sound
receptors in the ear and is, therefore, classified as Level A
harassment under the MMPA. For acoustic effects, because the tissues of
the ear appear to be the most susceptible to the physiological effects
of sound, and because threshold shifts (TSs) tend to occur at lower
exposures than other more serious auditory effects, NMFS has determined
that permanent threshold shift (PTS) is the best indicator for the
smallest degree of injury that can be measured. Therefore, the acoustic
exposure associated with onset-PTS is used to define the lower limit of
the Level A harassment.
PTS data do not currently exist for marine mammals and are unlikely
to be obtained due to ethical concerns. However, PTS levels for these
animals may be estimated using TTS data and relationships between TTS
and PTS. NMFS proposes the use of 215 dB re 1 mPa\2\-s as the acoustic
threshold for PTS. This threshold is based on a 20 dB increase in
exposure EL over that required for onset-TTS (195 dB). Extrapolations
from terrestrial mammal data indicate that PTS occurs at 40 dB or more
of TS, and that TS growth occurs at a rate of approximately 1.6 dB TS
per dB increase in EL. There is a 34-dB TS difference between onset-TTS
(6 dB) and onset-PTS (40 dB). Therefore, an animal would require
approximately 20dB of additional exposure (34 dB divided by 1.6 dB)
above onset-TTS to reach PTS.
The justification for establishing the 215-dB acoustic criteria for
PTS is described in detail in both the Navy's RIMPAC IHA application
and the Undersea Warfare Training Range USWTR DEIS.
Sub-TTS Behavioral Disruption
NMFS believes that behavioral disruption of marine mammals may
result from received levels of mid-frequency sonar lower than those
believed necessary to induce TTS, and further, that the lower limit of
Level B Harassment may be defined by the received sound levels
associated with these sub-TTS behavioral disruptions. As of yet, no
controlled exposure experiments have been conducted wherein wild
cetaceans are deliberately exposed to tactical mid-frequency sonar and
their reactions carefully observed. However, NMFS believes that in the
absence of controlled exposure experiments, the following
investigations and reports (described previously in the Behavioral
Effects section) constitute the best available scientific information
for establishing an appropriate acoustic threshold for sub-TTS
behavioral disruption: (1) Finneran and Schlundt (2004), in which
behavioral observations from TTS studies of captive bottlenose dophins
and beluga whales are analyzed as a function of known noise exposure;
(2) Nowachek et al. (2004), in which controlled exposure experiments
were conducted on North Atlantic right whales using ship noise, social
sounds of con-specifics, and an alerting stimulus; and (3) NMFS (2005),
in which the behavioral reactions of killer whales in the presence of
tactical mid-frequency sonar were observed, and analyzed after the
fact. Based on these three studies, NMFS has set the sub-TTS behavioral
disruption threshold at 173 dB re 1 mPa\2\-s (SEL).
The Finneran and Schlundt (2004) analysis is an important piece in
the development of an appropriate acoustic threshold for sub-TTS
behavioral disruption because: (1) researchers had superior control
over and ability to quantify noise exposure conditions; (2) behavioral
patterns of exposed marine mammals were readily observable and
definable; and, (3) fatiguing noise consisted of tonal noise exposures
with frequencies contained in the tactical mid-frequency sonar
bandwidth. In Finneran and Schlundt (2004) 190 dB re 1 mPa (SPL) is the
point at which 50 percent of the animals exposed to 3, 10, and 20 kHz
tones were deemed to respond with some behavioral alteration. This 50
percent behavior alteration level (190 dB SPL) may be converted to an
SEL criterion of 190 dB re 1 mPa\2\-s (the numerical values are
identical because exposure durations were 1-s), which provides
consistency with the Level A (PTS) effects threshold, which are also
expressed in SEL. The Navy proposed 190 dB (SEL) as the acoustic
threshold for sub-TTS behavioral disruption in the first IHA
application they submitted to NMFS.
NMFS acknowledges the advantages arising from the use of behavioral
observations in controlled laboratory conditions; however, there is
considerable uncertainty regarding the
[[Page 38718]]
validity of applying data collected from trained captives conditioned
to not respond to noise exposure in establishing thresholds for
behavioral reactions of naive wild individuals to a sound source that
apparently evokes strong reactions in some marine mammals. Although
wide-ranging in terms of sound sources, context, and type/extent of
observations reported, the large and growing body of literature
regarding behavioral reactions of wild, naive marine mammals to
anthropogenic exposure generally suggests that wild animals are
behaviorally affected at significantly lower levels than those
determined for captive animals by Finneran and Schlundt (2004). For
instance, some cetaceans exposed to human noise sound sources, such as
seismic airgun sounds and low frequency sonar signals, have been shown
to exhibit avoidance behavior when the animals are exposed to noise
levels of 140-160 dB re: 1 mPa under certain conditions (Malme et al.,
1983; 1984; 1988; Ljungblad et al., 1988; Tyack and Clark, 1998).
Richardson et al. (1995) reviewed the behavioral response data for many
marine mammal species and a wide range of human sound sources.
Two specific situations for which exposure conditions and
behavioral reactions of free-ranging marine mammals exposed to sounds
very similar to those proposed for use in RIMPAC are considered by
Nowacek et al. (2004) and NMFS (2005) (described previously in
Behavioral Effects subsection). In the Nowacek et al. (2004) study,
North Atlantic right whales reacted strongly to alert signals at
received levels of 133-148 dB SPL, which, based on received exposure
durations, is approximately equivalent to 160 dB re: 1 mPa\2\-s (SEL).
In the NMFS (2005) report, unusual alterations in swimming, breathing,
and diving behaviors of killer whales observed by researchers in Haro
Strait were correlated, after the fact, with the presence of estimated
received sound levels between 169.1and 187.4 dB re: 1 mPa\2\-s (SEL).
While acknowledging the limitations of all three of these studies
and noting that they may not necessarily be predictive of how wild
cetaceans might react to mid-frequency sonar signals in the OpArea,
NMFS believes that these three studies are the best available science
to support the selection of an acoustic sub-TTS behavioral disturbance
threshold at this time. Taking into account all three studies, NMFS has
established 173 dB re: 1 mPa\2\ (SEL) as the threshold for sub-TTS
behavioral disturbance.
Stranding and Mortality
Over the past 10 years, there have been four stranding events
coincident with military mid-frequency sonar use that are believed to
most likely have been caused by exposure to the sonar. These occurred
in Greece (1996), the Bahamas (2000), Madeira (2000) and Canary Islands
(2002). In 2004, during the RIMPAC exercises, between 150-200 usually
pelagic melon-headed whales occupied the shallow waters of the Hanalei
Bay, Kaua'i, Hawaii for over 28 hours. NMFS determined that the mid-
frequency sonar was, a plausible, if not likely, contributing factor in
what may have been a confluence of events that led to the Hanalei Bay
stranding. A number of other stranding events coincident with the
operation of mid-frequency sonar and resulting in the death of beaked
whales or other species (minke whales, dwarf sperm whales, pilot
whales) have been reported, though the majority have not been
investigated to the level of the Bahamas stranding and, therefore,
other causes cannot be ruled out.
Greece, Madeira, and Canary Islands
Twelve Cuvier's beaked whales stranded along the western coast of
Greece in 1996. The test of a low- and mid-frequency active sonar
system conducted by NATO was correlated with the strandings by an
analysis published in Nature. A subsequent NATO investigation found the
strandings to be closely related, in time, to the movements of the
sonar vessel, and ruled out other physical factors as a cause.
In 2000, four beaked whales stranded in Madeira while several NATO
ships were conducting an exercise near shore. Scientists investigating
the stranding found that the injuries, which included blood in and
around the eyes, kidney lesions, and pleural hemorrhage, as well as the
pattern of the stranding suggested that a similar pressure event
precipitated or contributed to strandings in both Madeira and Bahamas
(see Bahamas sub-section).
In 2002, at least 14 beaked whales of three different species
stranded in the Canary Islands while a naval exercise including Spanish
vessels, U.S. vessels, and at least one vessel equipped with mid-
frequency sonar was conducted in the vicinity. Four more beaked whales
stranded over the next several days. The subsequent investigation,
which was reported in both Nature and Veterinary Pathology, revealed a
variety of traumas, including emboli and lesions suggestive of
decompression sickness.
Bahamas
NMFS and the Navy prepared a joint report addressing the multi-
species stranding in the Bahamas in 2000, which took place within 24
hours of U.S. Navy ships using active mid-frequency sonar as they
passed through the Northeast and Northwest Providence Channels. Of the
17 cetaceans that stranded (Cuvier's beaked whales, Blainsville's
beaked whales, Minke whales, and a spotted dolphin), seven animals died
on the beach (5 Cuvier's beaked whales, 1 Blainsville's beaked whale,
and the spotted dolphin) and the other 10 were returned to the water
alive (though their fate is unknown). A comprehensive investigation was
conducted and all possible causes of the stranding event were
considered, whether they seemed likely at the outset or not. The only
possible contributory cause to the strandings and cause of the lesions
that could not be ruled out was intense acoustic signals (the dolphin
necropsy revealed a disease and the death is considered unrelated to
the others).
Based on the way in which the strandings coincided with ongoing
naval activity involving tactical mid-frequency sonar use, in terms of
both time and geography, the nature of the physiological effects
experienced by the dead animals, and the absence of any other acoustic
sources, the investigation team concluded that mid-frequency sonars
aboard U.S. Navy ships that were in use during the sonar exercise in
question were the most plausible source of this acoustic or impulse
trauma. This sound source was active in a complex environment that
included the presence of a surface duct, unusual and steep bathymentry,
a constricted channel with limited egress, intensive use of multiple,
active sonar units over an extended period of time, and the presence of
beaked whales that appear to be sensitive to the frequencies produced
by these sonars. The investigation team concluded that the cause of
this stranding event was the confluence of the Navy mid-frequency sonar
and these contributory factors working together, and further
recommended that the Navy avoid operating mid-frequency sonar in
situations where these five factors would be likely to occur. This
report does not conclude that all five of these factors must be present
for a stranding to occur, nor that beaked whales are the only species
that could potentially be affected by the confluence of the other
factors. Based on this, NMFS believes that the presence of surface
ducts, steep bathymetry, and/or constricted channels added to the
operation of mid-frequency
[[Page 38719]]
sonar in the presence of cetaceans (especially beaked whales and,
potentially, deep divers) may increase the likelihood of producing a
sound field with the potential to cause cetaceans to strand, and
therefore, necessitates caution.
Hanalei Bay
On July 3-4, 2004, between 150-200 melon-headed whales occupied the
shallow waters of the Hanalei Bay, Kaua'i, Hawaii for over 28 hours.
Attendees of a canoe blessing observed the animals entering the Bay in
a single wave formation at 7 a.m. on July 3, 2004. The animals were
observed moving back into the shore from the mouth of the Bay at 9 a.m.
The usually pelagic animals milled in the shallow bay and were returned
to deeper water with human assistance beginning at 9:30 a.m. on July 4,
2004, and were out of sight by 10:30 a.m.
Only one animal, a calf, was known to have died (on July 5, 2004)
following this event. The animal was noted alive and alone in the Bay
on the afternoon of July 4, 2004 and was found dead in the Bay the
morning of July 5, 2004. On July 7, 2004, a full necropsy, magnetic
resonance imaging, and computerized tomography examination were
performed on the calf to determine the manner and cause of death. The
combination of imaging, necropsy and histological analyses found no
evidence of infectious, internal traumatic, congenital, or toxic
factors. Although cause of death could not be definitively determined,
it is likely that maternal separation, poor nutritional condition, and
dehydration contributed to the final demise of the animal. Although we
do not know when the calf was separated from its mother, the movement
into the Bay, the milling and re-grouping may have contributed to the
separation or lack of nursing especially if the maternal bond was weak
or this was a primiparous calf.
Environmental factors, abiotic and biotic, were analyzed for any
anomalous occurrences that would have contributed to the animals
entering and remaining in Hanalei Bay. The Bay's bathymetry is similar
to many other sites within the Hawaiian Island chain and dissimilar to
sites that have been associated with mass strandings in other parts of
the United States. The weather conditions appeared to be normal for
that time of year with no fronts or other significant features noted.
There was no evidence of unusual distribution or occurrence of predator
or prey species, or unusual harmful algal blooms. Weather patterns and
bathymetry that have been associated with mass strandings elsewhere
were not found to occur in this instance.
This event was spatially and temporally correlated with RIMPAC.
Official sonar training and tracking exercises in the Pacific Missile
Range Facility (PMRF) warning area did not commence until approximately
8 a.m. on July 3 and were thus ruled out as a possible trigger for the
initial movement into the Bay.
However, the six naval surface vessels transiting to the
operational area on July 2 intermittently transmitted active sonar (for
approximately 9 hours total from 1:15 p.m. to 12:30 a.m.) as they
approached from the south. The potential for these transmissions to
have triggered the whales' movement into Hanalei Bay was investigated.
Analyses with the information available indicated that animals to the
south and east of Kaua'i could have detected active sonar transmissions
on July 2, and reached Hanalei Bay on or before 7 a.m. on July 3, 2004.
However, data limitations regarding the position of the whales prior to
their arrival in the Bay, the magnitude of sonar exposure, behavioral
responses of melon-headed whales to acoustic stimuli, and other
possible relevant factors preclude a conclusive finding regarding the
role of sonar in triggering this event. Propagation modeling suggest
that transmissions from sonar use during the July 3 exercise in the
PMRF warning area may have been detectable at the mouth of the Bay. If
the animals responded negatively to these signals, it may have
contributed to their continued presence in the Bay. The U.S. Navy
ceased all active sonar transmissions during exercises in this range on
the afternoon of July 3, 2004. Subsequent to the cessation of sonar
use, the animals were herded out of the Bay.
While causation of this stranding event may never be unequivocally
determined, we consider the active sonar transmissions of July 2-3,
2004, a plausible, if not likely, contributing factor in what may have
been a confluence of events. This conclusion is based on: (1) the
evidently anomalous nature of the stranding; (2) its close
spatiotemporal correlation with wide-scale, sustained use of sonar
systems previously associated with stranding of deep-diving marine
mammals; (3) the directed movement of two groups of transmitting
vessels toward the southeast and southwest coast of Kaua'i; (4) the
results of acoustic propagation modeling and an analysis of possible
animal transit times to the Bay; and (5) the absence of any other
compelling causative explanation. The initiation and persistence of
this event may have resulted from an interaction of biological and
physical factors. The biological factors may have included the presence
of an apparently uncommon, deep-diving cetacean species (and possibly
an offshore, non-resident group), social interactions among the animals
before or after they entered the Bay, and/or unknown predator or prey
conditions. The physical factors may have included the presence of
nearby deep water, multiple vessels transiting in a directed manner
while transmitting active sonar over a sustained period, the presence
of surface sound ducting conditions, and/or intermittent and random
human interactions while the animals were in the Bay.
Beaked Whales
Recent beaked whale strandings have prompted inquiry into the
relationship between mid-frequency active sonar and the cause of those
strandings. A review of world-wide cetacean mass stranding data reveals
that beaked whales have been the most common taxa involved in stranding
events (approximately 67 percent of all strandings include beaked
whales), with Cuvier's beaked whales accounting for about 90 percent of
the individual beaked whales. Although the confluence of Navy mid-
frequency active tactical sonar with the other contributory factors
noted in the report was identified as the cause of the 2000 Bahamas
stranding event, the specific mechanisms that led to that stranding are
not understood, and there is uncertainty regarding the ordering of
effects that led to the stranding. It is uncertain whether beaked
whales were directly injured by sound (a physiological effect) prior to
stranding or whether a behavioral response to sound occurred that
ultimately caused the beaked whales to strand and be injured.
Several potential physiological outcomes caused by behavioral
responses to high-intensity sounds have been suggested by Cox et al.
(in press). These include: gas bubble formation caused by excessively
fast surfacing; remaining at the surface too long when tissues are
supersaturated with nitrogen; or diving prematurely when extended time
at the surface is necessary to eliminate excess nitrogen. Baird et al.
(2005) found that slow ascent rates from deep dives and long periods of
time spent within 50 m of the surface were typical for both Cuvier's
and Blainsville's beaked whales, the two species involved in mass
strandings related to naval sonar. These two behavioral mechanisms may
be necessary to purge excessive dissolved nitrogen concentrated in
their tissues
[[Page 38720]]
during their frequent long dives (Baird et al., 2005). Baird et al.
(2005) further suggests that abnormally rapid ascents or premature
dives in response to high-intensity sonar could indirectly result in
physical harm to the beaked whales, through the mechanisms described
above (gas bubble formation or non-elimination of excess nitrogen).
During the RIMPAC exercise there will be use of multiple sonar
units in an area where three beaked whale species may be present. A
surface duct may be present in a limited area for a limited period of
time. Although most of the ASW training events will take place in the
deep ocean, some will occur in areas of high bathymetric relief.
However, none of the training events will take place in a location
having a constricted channel with limited egress similar to the
Bahamas. Consequently, not all five of the environmental factors
believed to contribute to the Bahamas stranding (mid-frequency sonar,
beaked whale presence, surface ducts, steep bathymetry, and constricted
channels with limited egress) will be present during RIMPAC ASW
exercises. However, as mentioned previously, NMFS believes caution
should be used anytime either steep bathymetry, surface ducting
conditions, or a constricted channel is present in addition to the
operation of mid-frequency tactical sonar and the presence of cetaceans
(especially beaked whales).
Estimated Take by Incidental Harassment
In order to estimate acoustic exposures from the RIMPAC ASW
operations, acoustic sources to be used were examined with regard to
their operational characteristics. Systems with acoustic source levels
below 205 dB re 1 mPa were not included in the analysis given that at
this source level (205 dB re 1 mPa) or below, a 1-second ping would
attenuate below the Level B Harassment behavioral disturbance threshold
of 173 dB at a distance of about 100 meters, which is well within the
required shutdown zone. Also, animals are expected to avoid the
exercises by a distance greater than that and their detectibility is
higher at that distance. In addition, systems with an operating
frequency greater than 100 kHz were not analyzed in the detailed
modeling, as these signals attenuate rapidly, resulting in very short
propagation distances. Acoustic countermeasures were previously
examined and found not to be problematic. The AN/AQS 13 (dipping sonar)
used by carrier based helicopters was determined in the Environmental
Assessment/Overseas Environmental Assessment of the SH-60R Helicopter/
ALFS Test Program, October 1999, not to be problematic due to its
limited use and very short pulse length (2 to 5 pulses of 3.5 to 700
msec). Since 1999, during the time of the test program, there have been
over 500 hours of operation, with no environmental effects observed.
The Directional Command Activated Sonobuoy System (DICASS) sonobuoy was
determined not to be problematic, having a source level of 201