Small Takes of Marine Mammals Incidental to Specified Activities; Oceanographic Surveys in the Hess Deep, Eastern Equatorial Pacific Ocean

Note: EPA no longer updates this information, but it may be useful as a reference or resource.
 [Federal Register: April 14, 2003 (Volume 68, Number 71)]
[Notices]
[Page 17909-17920]
From the Federal Register Online via GPO Access [wais.access.gpo.gov]
[DOCID:fr14ap03-26]

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DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
[I.D. 021203A]
 
Small Takes of Marine Mammals Incidental to Specified Activities; 
Oceanographic Surveys in the Hess Deep, Eastern Equatorial Pacific 
Ocean

AGENCY: National Marine Fisheries Service (NMFS), National Oceanic and 
Atmospheric Administration (NOAA), Commerce.
ACTION: Notice of receipt of application and proposed authorization for 
a small take exemption; request for comments.

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SUMMARY: NMFS has received an application from the Lamont-Doherty Earth 
Observatory (LDEO) for an Incidental Harassment Authorization (IHA) to 
take small numbers of marine

[[Page 17910]]

 mammals, by harassment, incidental to conducting oceanographic surveys 
in the Hess Deep in international waters of the Eastern Equatorial 
Pacific Ocean. Under the Marine Mammal Protection Act (MMPA), NMFS is 
requesting comments on its proposal to issue a small take authorization 
to LDEO to incidentally take, by harassment, small numbers of several 
species of cetaceans and pinnipeds for a limited period of time within 
the next year.

DATES: Comments and information must be received no later than May 14, 
2003.

ADDRESSES:  Comments on the application should be addressed to Chief, 
Marine Mammal Conservation 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, Environmental Assessment (EA) and/or a list of 
the references used in this document may be obtained by writing to this 
address or by telephoning the contact listed here. Comments cannot be 
accepted if submitted via e-mail or the Internet.

FOR FURTHER INFORMATION CONTACT:  Kenneth R. Hollingshead, Office of 
Protected Resources, NMFS, (301) 713-2055, ext 128,

SUPPLEMENTARY INFORMATION:

Background

    Sections 101(a)(5)(A) and (D) of the MMPA (16 U.S.C. 1361 et seq.) 
directs 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.
    Permission may be granted if NMFS finds that the taking will have a 
negligible impact on the species or stock(s) and will not have an 
unmitigable adverse impact on the availability of the species or 
stock(s) for subsistence uses and that the permissible methods of 
taking and requirements pertaining to the 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.''
    Subsection 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 MMPA defines ``harassment'' as:
    any act of pursuit, torment, or annoyance which (i) has the 
potential to injure a marine mammal or marine mammal stock in the 
wild; or (ii) has the potential to disturb a marine mammal or marine 
mammal stock in the wild by causing disruption of behavioral 
patterns, including, but not limited to, migration, breathing, 
nursing, breeding, feeding, or sheltering.
    (B) The term ``Level A harassment'' means harassment described 
in subparagraph (A)(i).
    (C) The term ``Level B harassment'' means harassment described 
in subparagraph (A)(ii).
    Subsection 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 
small numbers 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 January 29, 2003, NMFS received an application from LDEO for the 
taking, by harassment of several species of marine mammals incidental 
to conducting a seismic survey program in the Hess Deep portion of the 
Eastern Equatorial Pacific Ocean about 600 nautical miles (nm)(690 land 
miles; 1111.2 km) west of the Galapagos Islands during March and April 
2003, but rescheduled for July, 2003. The purpose of this survey is to 
obtain information on movements of the earth's plates and on formations 
associated with those movements. More specifically, the Hess Deep 
survey will obtain information on the geologic nature of boundaries of 
the earth's crust at fast-spreading and intermediate-spreading ridges 
at the boundaries of tectonic plates. Past studies have mapped these 
areas using manned submersibles and remotely piloted vehicles, but they 
have not provided a link between geologic and seismic structure. This 
study will provide the seismic data to assess the geologic nature of 
the previously mapped areas.

Description of the Activity

    The seismic survey will involve a single vessel, the R/V Maurice 
Ewing, which will deploy and retrieve the Ocean Bottom Seismometers 
(OBSs) and conduct the seismic work. The Maurice Ewing will deploy an 
array of airguns as an energy source, plus a 6-km (3.2-nm) towed 
streamer containing hydrophones to receive the returning acoustic 
signals.
    All planned geophysical data acquisition activities will be 
conducted by LDEO scientists, with the participation of scientists from 
the University of Texas at Austin, TX. Water depths in the Hess Deep 
survey area will range from approximately 2,000 to 3,400 m (6,560 to 
11,150 ft). A total of 912 km (492 nm) of MCS (Multi Channel Seismic) 
surveys using a 10-gun array and 189 km (102 nm) of OBS surveys using a 
12-gun array are planned to be conducted. These line-kilometer figures 
represent the planned production surveys. There will be additional 
operations associated with equipment testing, startup, line changes, 
and repeat coverage of any areas where initial data quality is sub-
standard.
    The procedures to be used for the 2003 seismic survey will be 
similar to those used during previous seismic surveys by LDEO, e.g., in 
the equatorial Pacific Ocean (Carbotte et al., 1998, 2000). The 
proposed program will use conventional seismic methodology with a towed 
airgun array as the energy source and a towed streamer containing 
hydrophones as the receiver system, sometimes in combination with OBS 
receivers placed on the bottom. The energy to the airgun array is 
compressed air supplied by compressors on board the source vessel. The 
specific configuration of the airgun array will differ between the OBS 
and MCS surveys, as described later in this document. In addition, a 
multi-beam bathymetric sonar will be operated from the source vessel at 
most times during the Hess Deep survey. A lower-energy sub-bottom 
profiler, which is routinely operated at the same time as the multi-
beam sonar during other projects, will not be operated during this 
cruise.
    The R/V Maurice Ewing will be used as the source vessel. It will 
tow the airgun array (either 10 or 12 guns) and a streamer containing 
hydrophones along predetermined lines. The vessel will travel at 4-5 
knots (7.4-9.3 km/hr), and seismic pulses will be emitted at intervals 
of 60-90 seconds (OBS lines) and approximately 20 seconds (all other 
lines). The 20-sec spacing corresponds to a shot interval of about 50 m 
(164 ft). The 60-90 sec spacing along OBS lines is to minimize previous 
shot noise during OBS data acquisition, and the exact spacing will 
depend on water depth. The 10-gun array will be used during MSC surveys 
and the 12-gun array will be used during OBS surveys. The airguns will 
be widely spaced in an approximate rectangle with dimensions 35 m 
(114.9 ft)(across track) by 9 m (29.5 ft)(along track). Individual 
airguns range

[[Page 17911]]

 in size from 80 to 850 in3, with total volumes of the arrays being 
3005 and 3721 in3 for the 10- and 12-gun arrays, respectively.
    The 10-airgun array will have a peak sound source level of 248 dB 
re 1 [mu]Pa or 255 dB peak-to-peak (P-P). The 12-airgun array will have 
a peak sound source level of 250 dB re 1 [mu]Pa or 257 dB P-P. These 
are the nominal source levels for the sound directed downward, and 
represent the theoretical source level close to a single point source 
emitting the same sound as that emitted by the array of 10 or 12 
sources. Because the actual source is a distributed sound source (10 or 
12 guns) rather than a single point source, the highest sound levels 
measurable at any location in the water will be less than the nominal 
source level. Also, because of the downward directional nature of the 
sound from these airgun arrays, the effective source level for sound 
propagating in near-horizontal directions will be substantially lower.
    Along selected lines, OBSs will be positioned by the R/V Maurice 
Ewing prior to the time when it begins airgun operations in that area. 
After OBS lines are shot, the R/V Maurice Ewing will retrieve the OBSs, 
download the data, and refurbish the units.
    Along with the airgun operations, one additional acoustical data 
acquisition activity will occur throughout most of the cruise. The 
ocean floor will be mapped with an Atlas Hydrosweep DS-2 multi-beam 
15.5-kHz bathymetric sonar. The Atlas Hydrosweep is mounted in the hull 
of the R/V Maurice Ewing, and it operates in three modes, depending on 
the water depth. The first mode is when water depth is <400 m (1312.3 
ft). The source output is 210 dB re 1 [mu]Pa-m rms and a single 1-
millisec pulse or ``ping'' per second is transmitted, with a beamwidth 
of 2.67 degrees fore-aft and 90 degrees in beamwidth. The beamwidth is 
measured to the 3 dB point, as is usually quoted for sonars. The other 
two modes are deep-water modes: The Omni mode is identical to the 
shallow-water mode except that the source output is 220 dB rms. The 
Omni mode is normally used only during start up. The Rotational 
Directional Transmission (RDT) mode is normally used during deep-water 
operation and has a 237 dB rms source output. In the RDT mode, each 
``ping'' consists of five successive transmissions, each ensonifying a 
beam that extends 2.67 degrees fore-aft and approximately 30 degrees in 
the cross-track direction. The five successive transmissions (segments) 
sweep from port to starboard with minor overlap, spanning an overall 
cross-track angular extent of about 140 degrees, with tiny (<1 
millisec) gaps between the pulses for successive 30-degree segments. 
The total duration of the ``ping'', including all 5 successive 
segments, varies with water depth but is 1 millisec in water depths 
£500 m (1640.4 ft) and 10 millisec in the deepest water. 
Additional information on the airgun array and Atlas Hydrosweep 
specifications is contained in the application, which is available upon 
request (see ADDRESSES).

Description of Habitat and Marine Mammals Affected by the Activity

    A detailed description of the Eastern Equatorial Pacific Ocean and 
its associated marine mammals can be found in a number of documents 
referenced in the LDEO application and is not repeated here. 
Approximately 27 species of cetaceans and possibly two species of 
pinnipeds may inhabit the area of the Hess Deep. These species are the 
sperm whale (Physeter macrocephalus), pygmy sperm whale (Kogia 
breviceps), dwarf sperm whale (Kogia sima), Cuvier's beaked whale 
(Ziphius cavirostris), Longman's beaked whale (Indopacetus pacificus), 
pygmy beaked whale (Mesoplodon peruvianus), Ginkgo-toothed beaked whale 
(Mesoplodon ginkgodens), Blainville's beaked whale (Mesoplodon 
densirostris), rough-toothed dolphin (Steno bredanensis), bottlenose 
dolphin (Tursiops truncatus), pantropical spotted dolphin (Stenella 
attenuata), spinner dolphin (Stenella longirostris), striped dolphin 
(Stenella coeruleoalba), short-beaked common dolphin (Delphinus 
delphis), Fraser's dolphin (Lagenodelphis hosei), Risso's dolphin 
(Grampus griseus), melon-headed whale (Peponocephala electra), pygmy 
killer whale (Feresa attenuata), false killer whale (Pseudorca 
crassidens), killer whale (Orcinus orca), short-finned pilot whale 
(Globicephala macrorhynchus), humpback whale (Megaptera novaeangliae), 
minke whale (Balaenoptera acutorostrata), Bryde's whale (Balaenoptera 
edeni), sei whale (Balaenoptera borealis), fin whale (Balaenoptera 
physalus), and the blue whale (Balaenoptera musculus), Galapagos fur 
seal (Arctocephalus galapagoensis) and Galapagos sea lion (Zalophus 
wollebaeki). Additional information on most of these species is 
contained in Caretta et al. (2001, 2002) which is available at: 
http://www.nmfs.noaa.gov/prot_res/PR2/Stock_Assessment_Program/sars.html. 


Potential Effects on Marine Mammals

    As outlined in several previous NMFS documents, the effects of 
noise on marine mammals are highly variable, and can be categorized as 
follows (based on Richardson et al., 1995):
    (1) The noise may be too weak to be heard at the location of the 
animal (i.e., lower than the prevailing ambient noise level, the 
hearing threshold of the animal at relevant frequencies, or both);
    (2) The noise may be audible but not strong enough to elicit any 
overt behavioral response;
    (3) The noise may elicit reactions of variable conspicuousness and 
variable relevance to the well being of the marine mammal; these can 
range from temporary alert responses to active avoidance reactions such 
as vacating an area at least until the noise event ceases;
    (4) Upon repeated exposure, a marine mammal may exhibit diminishing 
responsiveness (habituation), or disturbance effects may persist; the 
latter is most likely with sounds that are highly variable in 
characteristics, infrequent and unpredictable in occurrence (as are 
vehicle launches), and associated with situations that a marine mammal 
perceives as a threat;
    (5) Any anthropogenic noise that is strong enough to be heard has 
the potential to reduce (mask) the ability of a marine mammal to hear 
natural sounds at similar frequencies, including calls from 
conspecifics, and underwater environmental sounds such as surf noise;
    (6) If mammals remain in an area because it is important for 
feeding, breeding or some other biologically important purpose even 
though there is chronic exposure to noise, it is possible that there 
could be noise-induced physiological stress; this might (in turn) have 
negative effects on the well-being or reproduction of the animals 
involved; and
    (7) Very strong sounds have the potential to cause temporary or 
permanent reduction in hearing sensitivity. In terrestrial mammals, and 
presumably marine mammals, received sound levels must far exceed the 
animal's hearing threshold for there to be any temporary threshold 
shift (TTS). For transient sounds, the sound level necessary to cause 
TTS is inversely related to the duration of the sound. Received sound 
levels must be even higher for there to be risk of permanent hearing 
impairment. In addition, intense acoustic or explosive events may cause 
trauma to tissues associated with organs vital for hearing, sound 
production, respiration and other functions. This trauma may include 
minor to severe hemorrhage.

[[Page 17912]]

Characteristics of Airgun Pulses

    Airguns function by venting high-pressure air into the water. The 
pressure signature of an individual airgun consists of a sharp rise and 
then fall in pressure, followed by several positive and negative 
pressure excursions caused by oscillation of the resulting air bubble. 
The sizes, arrangement and firing times of the individual airguns in an 
array are designed and synchronized to suppress the pressure 
oscillations subsequent to the first cycle. The resulting downward-
directed pulse has a duration of only 10 to 20 ms, with only one strong 
positive and one strong negative peak pressure (Caldwell and Dragoset, 
2000). Most energy emitted from airguns is at relatively low 
frequencies. For example, typical high-energy airgun arrays emit most 
energy at 10-120 Hz. However, the pulses contain some energy up to 500-
1000 Hz and above (Goold and Fish, 1998). The pulsed sounds associated 
with seismic exploration have higher peak levels than other industrial 
sounds to which whales and other marine mammals are routinely exposed. 
The P-P source levels of the 20-gun array (not proposed to be used for 
the Hess Deep work), and the 12-gun array and 10-gun arrays (that will 
be used for the Hess Deep), are 262, 257, and 255 dB re 1 [mu]Pa-m, 
respectively. These are the nominal source levels applicable to 
downward propagation. (The effective source level for horizontal 
propagation is lower.) The only sources with higher or comparable 
effective source levels are explosions and high-power sonars operating 
near maximum power.
    Several important mitigating factors need to be kept in mind. (1) 
Airgun arrays produce intermittent sounds, involving emission of a 
strong sound pulse for a small fraction of a second followed by several 
seconds of near silence. In contrast, some other acoustic sources 
produce sounds with lower peak levels, but their sounds are continuous 
or discontinuous but continuing for much longer durations than seismic 
pulses. (2) Airgun arrays are designed to transmit strong sounds 
downward through the seafloor, and the amount of sound transmitted in 
near-horizontal directions is considerably reduced. Nonetheless, they 
also emit sounds that travel horizontally toward non-target areas. (3) 
An airgun array is a distributed source, not a point source. The 
nominal source level is an estimate of the sound that would be measured 
from a theoretical point source emitting the same total energy as the 
airgun array. That figure is useful in calculating the expected 
received levels in the far field (i.e., at moderate and long 
distances). Because the airgun array is not a single point source, 
there is no one location within the near field (or anywhere else) where 
the received level is as high as the nominal source level.
    The strengths of airgun pulses can be measured in different ways, 
and it is important to know which method is being used when 
interpreting quoted source or received levels. Geophysicists usually 
quote P-P levels, in bar-meters or dB re 1 [mu]Pa-m. The peak (= zero-
to-peak) level for the same pulse is typically about 6 dB less. In the 
biological literature, levels of received airgun pulses are often 
described based on the ``average'' or ``root-mean-square'' (rms) level 
over the duration of the pulse. The rms value for a given pulse is 
typically about 10 dB lower than the peak level, and 16 dB lower than 
the P-P value (Greene, 1997; McCauley et al., 1998, 2000a). A fourth 
measure that is sometimes used is the energy level, in dB re 1 
[mu]Pa\2\s. Because the pulses are £1 sec in duration, the 
numerical value of the energy is lower than the rms pressure level (but 
the units are different). Because the level of a given pulse will 
differ substantially depending on which of these measures is being 
applied, it is important to be aware which measure is in use when 
interpreting any quoted pulse level. In the past, NMFS has commonly 
referenced the rms levels when discussing levels of pulsed sounds that 
might ``harass'' marine mammals.
    Seismic sound received at any given point will arrive via a direct 
path, indirect paths that include reflection from the sea surface and 
bottom, and often indirect paths including segments through the bottom 
sediments. Sounds propagating via indirect paths travel longer 
distances and often arrive later than sounds arriving via a direct 
path. (However, sound travel in the bottom may travel faster than that 
in the water, and thus may arrive earlier than the direct arrival 
despite traveling a greater distance.) These variations in travel time 
have the effect of lengthening the duration of the received pulse. At 
the source, seismic pulses are about 10 to 20 ms in duration. In 
comparison, the pulse duration as received at long horizontal distances 
can be much greater. For example, for one airgun array operating in the 
Beaufort Sea, pulse duration was about 300 ms at a distance of 8 km 
(4.3 nm), 500 ms at 20 km (10.8 nm), and 850 ms at 73 km (39.4 nm) 
(Greene and Richardson, 1988).
    Another important aspect of sound propagation is that received 
levels of low-frequency underwater sounds diminish close to the surface 
because of pressure-release and interference phenomena that occur at 
and near the surface (Urick, 1983; Richardson et al., 1995). Paired 
measurements of received airgun sounds at depths of 3 m (9.8 ft) vs. 9 
or 18 m (29.5 or 59 ft) have shown that received levels are typically 
several decibels lower at 3 m (9.8. ft)(Greene and Richardson, 1988). 
For a mammal whose auditory organs are within 1/2 or 1 m ( 1.6 or 3.3 
ft) of the surface, the received level of the predominant low-frequency 
components of the airgun pulses would be further reduced.
    Pulses of underwater sound from open-water seismic exploration are 
often detected 50 to 100 km (30 to 54 nm) from the source location, 
even during operations in nearshore waters (Greene and Richardson, 
1988; Burgess and Greene, 1999). At those distances, the received 
levels on an approximate rms basis are low (below 120 dB re 1 mPa). 
However, faint seismic pulses are sometimes detectable at even greater 
ranges (e.g., Bowles et al., 1994; Fox et al., 2002). Considerably 
higher levels can occur at distances out to several kms from an 
operating airgun array. With 12-gun and 10-gun arrays, the distances at 
which seismic pulses are expected to diminish to received levels of 
190, 180, 170 dB and 160 dB re 1 [mu]Pa, on an rms basis) are as 
follows:

------------------------------------------------------------------------
                                           RMS Radii (m/ft)
        Airgun Array         -------------------------------------------
                                190 dB     180 dB     170 dB     160 dB
------------------------------------------------------------------------
12 airguns..................    300/984   880/2887  2680/8793      7250/
                                                                   23786
10 airguns..................    250/820   830/2723  2330/7644      6500/
                                                                   21325
------------------------------------------------------------------------

[[Page 17913]]

    Additional information can be found in the LDEO application.

Effects of Seismic Surveys on Marine Mammals

    The LDEO application provides the following information on what is 
known about the effects, on marine mammals, of the types of seismic 
operations planned by LDEO. The types of effects considered here are 
(1) masking, (2) disturbance, and (3) potential hearing impairment and 
other physical effects. Additional discussion on species specific 
effects can be found in the LDEO application.

Masking

    Masking effects on marine mammal calls and other natural sounds are 
expected to be limited. Seismic sounds are short pulses occurring for 
less than 1 sec every 20 or 60-90 sec in this project. Sounds from the 
multibeam sonar are very short pulses, occurring for 1-10 msec once 
every 1 to 15 sec, depending on water depth. (During operations in deep 
water, the duration of each pulse from the multibeam sonar as received 
at any one location would actually be only 1/5\th\ or at most 2/5\th\ 
of 1-10 msec, given the segmented nature of the pulses.) Some whales 
are known to continue calling in the presence of seismic pulses. Their 
calls can be heard between the seismic pulses (e.g., Richardson et al., 
1986; McDonald et al., 1995; Greene et al., 1999). Although there has 
been one report that sperm whales cease calling when exposed to pulses 
from a very distant seismic ship (Bowles et al., 1994), a recent study 
reports that sperm whales continued calling in the presence of seismic 
pulses (Madsen et al., 2002). Masking effects of seismic pulses are 
expected to be negligible in the case of the smaller odontocete 
cetaceans, given the intermittent nature of seismic pulses plus the 
fact that sounds important to them are predominantly at much higher 
frequencies than are airgun sounds.
    Most of the energy in the sound pulses emitted by airgun arrays is 
at low frequencies, with strongest spectrum levels below 200 Hz and 
considerably lower spectrum levels above 1000 Hz. These frequencies are 
mainly used by mysticetes, but not by odontocetes or pinnipeds. An 
industrial sound source will reduce the effective communication or 
echolocation distance only if its frequency is close to that of the 
cetacean signal. If little or no overlap occurs between the industrial 
noise and the frequencies used, as in the case of many marine mammals 
vs. airgun sounds, communication and echolocation are not expected to 
be disrupted. Furthermore, the discontinuous nature of seismic pulses 
makes significant masking effects unlikely even for mysticetes.
    A few cetaceans are known to increase the source levels of their 
calls in the presence of elevated sound levels, or possibly to shift 
their peak frequencies in response to strong sound signals (Dahlheim, 
1987; Au, 1993; Lesage et al., 1999; Terhune, 1999; reviewed in 
Richardson et al., 1995:233ff, 364ff). These studies involved exposure 
to other types of anthropogenic sounds, not seismic pulses, and it is 
not known whether these types of responses ever occur upon exposure to 
seismic sounds. If so, these adaptations, along with directional 
hearing and preadaptation to tolerate some masking by natural sounds 
(Richardson et al., 1995), would all reduce the importance of masking.

Disturbance by Seismic Surveys

    Disturbance includes a variety of effects, including subtle changes 
in behavior, more conspicuous dramatic changes in activities, and 
displacement. Disturbance is the primary concern for this project. 
Based on previous determinations by NMFS regarding minor behavioral 
response by marine mammals, LDEO presumes here that simple exposure to 
sound, or brief reactions that do not disrupt behavioral patterns in a 
potentially significant manner, do not constitute Level B harassment or 
``taking''. By potentially significant, LDEO means ``in a manner that 
might have deleterious effects to the well-being of individual marine 
mammals or their populations.''
    However, there are difficulties in defining which marine mammals 
should be counted as ``taken by harassment''. For many species and 
situations, scientists do not have detailed information about their 
reactions to noise, including reactions to seismic (and sonar) pulses. 
Behavioral reactions of marine mammals to sound are difficult to 
predict. Reactions to sound, if any, depend on species, state of 
maturity, experience, current activity, reproductive state, time of 
day, and many other factors. If a marine mammal does react to an 
underwater sound by changing its behavior or moving a small distance, 
the impacts of the change may not be significant to the individual let 
alone the stock or the species as a whole. However, if a sound source 
displaces marine mammals from an important feeding or breeding area for 
a prolonged period, impacts on the animals could be significant. Given 
the many uncertainties in predicting the quantity and types of impacts 
of noise on marine mammals, scientists often resort to estimating how 
many mammals were present within a particular distance of industrial 
activities, or exposed to a particular level of industrial sound. This 
likely overestimates the numbers of marine mammals that are affected in 
some biologically important manner. The sound criteria used to estimate 
how many marine mammals might be disturbed to some biologically-
important degree by a seismic program are based on behavioral 
observations during studies of several species. However, information is 
lacking for many other species. This is discussed further in the LDEO 
application.

Hearing Impairment and Other Physical Effects

    Temporary or permanent hearing impairment is a possibility when 
marine mammals are exposed to very strong sounds. The minimum sound 
level necessary to cause permanent hearing impairment is higher, by a 
variable and generally unknown amount, than the level that induces 
barely-detectable temporary threshold shift (TTS). The level associated 
with the onset of TTS is often considered to be a level below which 
there is no danger of damage. Current NMFS policy regarding exposure of 
marine mammals to high-level sounds is that cetaceans and pinnipeds 
should not be exposed to impulsive sounds exceeding 180 and 190 dB re 1 
micro Pa (rms), respectively.
    Several aspects of the planned monitoring and mitigation measures 
for this project are designed to detect marine mammals occurring near 
the airgun array (and multi-beam sonar), and to avoid exposing them to 
sound pulses that might cause hearing impairment. In addition, many 
cetaceans are likely to show some avoidance of the area with ongoing 
seismic operations. In these cases, the avoidance responses of the 
animals themselves will reduce or avoid the possibility of hearing 
impairment.
    Non-auditory physical effects may also occur in marine mammals 
exposed to strong underwater pulsed sound. Possible types of non-
auditory physiological effects or injuries that might (in theory) occur 
include stress, neurological effects, bubble formation, resonance 
effects, and other types of organ or tissue damage. It is possible that 
some marine mammal species (i.e., beaked whales) may be especially 
susceptible to injury and/or stranding when exposed to strong pulsed 
sounds.

[[Page 17914]]

TTS

    TTS is the mildest form of hearing impairment that can occur during 
exposure to a strong sound (Kryter, 1985). When an animal experiences 
TTS, its hearing threshold rises and a sound must be stronger in order 
to be heard. TTS can last from minutes or hours to (in cases of strong 
TTS) days. The magnitude of TTS depends on the level and duration of 
noise exposure, among other considerations (Richardson et al., 1995). 
For sound exposures at or somewhat above the TTS threshold, hearing 
sensitivity recovers rapidly after exposure to the noise ends. Only a 
few data on sound levels and durations necessary to elicit mild TTS 
have been obtained for marine mammals.
    Currently, NMFS believes that, whenever possible to avoid Level A 
harassment, cetaceans should not be exposed to pulsed underwater noise 
at received levels exceeding 180 dB re 1 [mu]Pa (rms). The 
corresponding limit for pinnipeds has been set at 190 dB. The predicted 
180- and 190-dB distances for the airgun arrays operated by LDEO during 
this activity were summarized previously in this document. These sound 
levels are not considered to be the levels at or above which TTS might 
occur. Rather, they are the received levels above which, in the view of 
a panel of bioacoustics specialists convened by NMFS, one cannot be 
certain that there will be no injurious effects, auditory or otherwise, 
to marine mammals. It has been shown that most whales tend to avoid 
ships and associated seismic operations. Thus, whales will likely not 
be exposed to such high levels of airgun sounds. Any whales close to 
the trackline could move away before the sounds become sufficiently 
strong for there to be any potential for hearing impairment. Therefore, 
there is little potential for whales being close enough to an array to 
experience TTS. In addition, ramping up airgun arrays, which has become 
standard operational protocol for many seismic operators including 
LDEO, should allow cetaceans to move away from the seismic source and 
to avoid being exposed to the full acoustic output of the airgun array.

Permanent Threshold Shift (PTS)

    When PTS occurs, there is physical damage to the sound receptors in 
the ear. In some cases, there can be total or partial deafness, while 
in other cases, the animal has an impaired ability to hear sounds in 
specific frequency ranges. Physical damage to a mammal's hearing 
apparatus can occur if it is exposed to sound impulses that have very 
high peak pressures, especially if they have very short rise times 
(time required for sound pulse to reach peak pressure from the baseline 
pressure). Such damage can result in a permanent decrease in functional 
sensitivity of the hearing system at some or all frequencies.
    Single or occasional occurrences of mild TTS do not cause permanent 
auditory damage in terrestrial mammals, and presumably do not do so in 
marine mammals. However, very prolonged exposure to sound strong enough 
to elicit TTS, or shorter-term exposure to sound levels well above the 
TTS threshold, can cause PTS, at least in terrestrial mammals (Kryter, 
1985). In terrestrial mammals, the received sound level from a single 
sound exposure must be far above the TTS threshold for any risk of 
permanent hearing damage (Kryter, 1994; Richardson et al., 1995). 
Relationships between TTS and PTS thresholds have not been studied in 
marine mammals but are assumed to be similar to those in humans and 
other terrestrial mammals.
    Some factors that contribute to onset of PTS are as follows:
    (1) exposure to single very intense noises, (2) repetitive exposure 
to intense sounds that individually cause TTS but not PTS, and (3) 
recurrent ear infections or (in captive animals) exposure to certain 
drugs.
    Cavanagh (2000) has reviewed the thresholds used to define TTS and 
PTS. Based on his review and SACLANT (1998), it is reasonable to assume 
that PTS might occur at a received sound level 20 dB or more above that 
which induces mild TTS. However, for PTS to occur at a received level 
only 20 dB above the TTS threshold, it is probable that the animal 
would have to be exposed to the strong sound for an extended period.
    Sound impulse duration, peak amplitude, rise time, and number of 
pulses are the main factors thought to determine the onset and extent 
of PTS. Based on existing data, Ketten (1994) has noted that the 
criteria for differentiating the sound pressure levels that result in 
PTS (or TTS) are location and species-specific. PTS effects may also be 
influenced strongly by the health of the receiver's ear.
    Given that marine mammals are unlikely to be exposed to received 
levels of seismic pulses that could cause TTS, it is highly unlikely 
that they would sustain permanent hearing impairment. If we assume that 
the TTS threshold for exposure to a series of seismic pulses may be on 
the order of 220 dB re 1 [mu]Pa (P-P) in odontocetes, then the PTS 
threshold might be about 240 dB re 1 [mu]Pa (P-P). In the units used by 
geophysicists, this is 10 bar-m. Such levels are found only in the 
immediate vicinity of the largest airguns (Richardson et al., 1995:137; 
Caldwell and Dragoset, 2000). It is very unlikely that an odontocete 
would remain within a few meters of a large airgun for sufficiently 
long to incur PTS. The TTS (and thus PTS) thresholds of baleen whales 
and pinnipeds may be lower, and thus may extend to a somewhat greater 
distance. However, baleen whales generally avoid the immediate area 
around operating seismic vessels, so it is unlikely that a baleen whale 
could incur PTS from exposure to airgun pulses. Some pinnipeds do not 
show strong avoidance of operating airguns. However, pinnipeds are 
expected to be (at most) uncommon in the Hess Deep survey area. 
Although it is unlikely that the planned seismic surveys could cause 
PTS in any marine mammals, caution is warranted given the limited 
knowledge about noise-induced hearing damage in marine mammals, 
particularly baleen whales.

Strandings and Mortality

    Marine mammals close to underwater detonations of high explosives 
can be killed or severely injured, and the auditory organs are 
especially susceptible to injury (Ketten et al., 1993; Ketten, 1995). 
Airgun pulses are less energetic and have slower rise times, and there 
is no evidence that they can cause serious injury, death, or stranding. 
However, the association of mass strandings of beaked whales with naval 
exercises and, in a recent case, an LDEO seismic survey has raised the 
possibility that beaked whales may be especially susceptible to injury 
and/or stranding when exposed to strong pulsed sounds.
    In March 2000, several beaked whales that had been exposed to 
repeated pulses from high intensity, mid-frequency military sonars 
stranded and died in the Providence Channels of the Bahamas Islands, 
and were subsequently found to have incurred cranial and ear damage 
(NOAA and USN, 2001). Based on post-mortem analyses, it was concluded 
that an acoustic event caused hemorrhages in and near the auditory 
region of some beaked whales. These hemorrhages occurred before death. 
They would not necessarily have caused death or permanent hearing 
damage, but could have compromised hearing and navigational ability 
(NOAA and USN, 2001). The researchers concluded that acoustic exposure 
caused this damage and triggered stranding, which resulted in 
overheating, cardiovascular collapse, and physiological shock that 
ultimately

[[Page 17915]]

led to the death of the stranded beaked whales. During the event, five 
naval vessels used their AN/SQS-53C or -56 hull-mounted active sonars 
for a period of 16 h. The sonars produced narrow (<100 Hz) bandwidth 
signals at center frequencies of 2.6 and 3.3 kHz (-53C), and 6.8 to 8.2 
kHz (-56). The respective source levels were usually 235 and 223 dB re 
1 [mu]
Pa, but the -53C briefly operated at an unstated but 
substantially higher source level. The unusual bathymetry and 
constricted channel where the strandings occurred were conducive to 
channeling sound. This, and the extended operations by multiple sonars, 
apparently prevented escape of the animals to the open sea. In addition 
to the strandings, there are reports that beaked whales were no longer 
present in the Providence Channel region after the event, suggesting 
that other beaked whales either abandoned the area or (perhaps) died at 
sea (Balcomb and Claridge, 2001).
    Other strandings of beaked whales associated with operation of 
military sonars have also been reported (e.g., Simmonds and Lopez-
Jurado, 1991; Frantzis, 1998). In these cases, it was not determined 
whether there were noise-induced injuries to the ears or other organs. 
Another stranding of beaked whales (15 whales) happened on 24-25 
September 2002 in the Canary Islands, where naval maneuvers were taking 
place.
    It is important to note that seismic pulses and mid-frequency sonar 
pulses are quite different. Sounds produced by the types of airgun 
arrays used to profile sub-sea geological structures are broadband with 
most of the energy below 1 kHz. Typical military mid-frequency sonars 
operate at frequencies of 2 to 10 kHz, generally with a relatively 
narrow bandwidth at any one time (though the center frequency may 
change over time). Because seismic and sonar sounds have considerably 
different characteristics and duty cycles, it is not appropriate to 
assume that there is a direct connection between the effects of 
military sonar and seismic surveys on marine mammals. However, evidence 
that sonar pulses can, in special circumstances, lead to hearing damage 
and, indirectly, mortality suggests that caution is warranted when 
dealing with exposure of marine mammals to any high-intensity pulsed 
sound.
    In addition to the sonar-related strandings, there was a recent 
(September 2002) stranding of two Cuvier's beaked whales in the Gulf of 
California (Mexico) when a seismic survey by the National Science 
Foundation/LDEO vessel R/V Maurice Ewing was underway in the general 
area (Malakoff, 2002). The airgun array in use during that project was 
the Ewing's 20-gun 8490-in\3\ array. This might be a first indication 
that seismic surveys can have effects, at least on beaked whales, 
similar to the suspected effects of naval sonars. However, the evidence 
linking the Gulf of California strandings to the seismic surveys is 
inconclusive, and to this date is not based on any physical evidence 
(Hogarth, 2002; Yoder, 2002). The ship was also operating its multi-
beam bathymetric sonar at the same time but, as discussed later in this 
document, this sonar had much less potential than these naval sonars to 
affect beaked whales. Although the link between the Gulf of California 
strandings and the seismic (plus multi-beam sonar) survey is 
inconclusive, this plus the various incidents involving beaked whale 
strandings associated with naval exercises suggests a need for caution 
in conducting seismic surveys in areas occupied by beaked whales.

Non-auditory Physiological Effects

    Possible types of non-auditory physiological effects or injuries 
that might occur in marine mammals exposed to strong underwater sound 
might, in theory, include stress, neurological effects, bubble 
formation, resonance effects, and other types of organ or tissue 
damage. There is no proof that any of these effects occur in marine 
mammals exposed to sound from airgun arrays. However, there have been 
no direct studies of the potential for airgun pulses to elicit any of 
these effects. If any such effects do occur, they would probably be 
limited to unusual situations when animals mightbe exposed at close 
range for unusually long periods.
    Long-term exposure to anthropogenic noise may have the potential to 
cause physiological stress that could affect the health of individual 
animals or their reproductive potential, which could theoretically 
cause effects at the population level (Gisner (ed.), 1999). However, 
there is essentially no information about the occurrence of noise-
induced stress in marine mammals. Also, it is doubtful that any single 
marine mammal would be exposed to strong seismic sounds for 
sufficiently long that significant physiological stress would develop. 
This is particularly so in the case of broad-scale seismic surveys of 
the type planned by LDEO (see Fig. 1 in LDEO (2003)), where the 
tracklines are generally not as closely spaced as in many 3-dimensional 
industry surveys.
    Gas-filled structures in marine animals have an inherent 
fundamental resonance frequency. If stimulated at this frequency, the 
ensuing resonance could cause damage to the animal. Diving marine 
mammals are not subject to the bends or air embolism because, unlike a 
human SCUBA diver, they only breath air at sea level pressure and have 
protective adaptations against getting the bends. There may be a 
possibility that high sound levels could cause bubble formation in the 
blood of diving mammals that in turn could cause an air embolism, 
tissue separation, and high, localized pressure in nervous tissue 
(Gisner (ed.), 1999; Houser et al., 2001).
    A recent workshop (Gentry (ed.), 2002) was held to discuss whether 
the stranding of beaked whales in the Bahamas in 2000 might have been 
related to air cavity resonance or bubble formation in tissues caused 
by exposure to noise from naval sonar. A panel of experts concluded 
that resonance in air-filled structures was not likely to have caused 
this stranding. Among other reasons, the air spaces in marine mammals 
are too large to be susceptible to resonant frequencies emitted by mid- 
or low-frequency sonar; lung tissue damage has not been observed in any 
mass, multi-species stranding of beaked whales; and the duration of 
sonar pings is likely too short to induce vibrations that could damage 
tissues (Gentry (ed.), 2002). Opinions were less conclusive about the 
possible role of gas (nitrogen) bubble formation/growth in the Bahamas 
stranding of beaked whales. Workshop participants did not rule out the 
possibility that bubble formation/growth played a role in the stranding 
and participants acknowledged that more research is needed in this 
area. The only available information on acoustically-mediated bubble 
growth in marine mammals is modeling that assumes prolonged exposure to 
sound.
    In summary, little is known about the potential for seismic survey 
sounds to cause auditory impairment or other physical effects in marine 
mammals. Available data suggest that such effects, if they occur at 
all, would be limited to situations where the marine mm where the 
marine mammal is located at a short distance from the sound source. 
However, the available data do not allow for meaningful quantitative 
predictions of the numbers (if any) of marine mammals that might be 
affected in these ways. Marine mammals that show behavioral avoidance 
of seismic vessels, including most baleen whales, some odontocetes, and 
some pinnipeds, are unlikely to incur auditory impairment or other 
physical effects.

[[Page 17916]]

Possible Effects of Mid-Frequency Sonar Signals

    A multi-beam bathymetric sonar (Atlas Hydrosweep DS-2, 15.5-kHz) 
will be operated from the source vessel at most times during the Hess 
Deep survey. Sounds from the multibeam sonar are very short pulses, 
occurring for 1-10 msec once every 1 to 15 sec, depending on water 
depth. Most of the energy in the sound pulses emitted by this multi-
beam sonar is at high frequencies, centered at 15.5 kHz. The beam is 
narrow (2.67[deg]) in fore-aft extent, and wide (140[deg]) in the 
cross-track extent. Each ping consists of five successive transmissions 
(segments) at different cross-track angles. Any given mammal at depth 
near the trackline would be in the main beam for only one or two of the 
five segments, i.e. for 1/5\th\ or at most 2/5\th\ of the 1- 10 msec.
    Navy sonars that have been linked to avoidance reactions and 
stranding of cetaceans (1) generally are more powerful than the Atlas 
Hydrosweep, (2) have a longer pulse duration, and (3) are directed 
close to horizontally (vs. downward for the Hydrosweep). The area of 
possible influence of the Hydrosweep is much smaller (a narrow band 
below the source vessel). Marine mammals that encounter the Hydrosweep 
at close range are unlikely to be subjected to repeated pulses because 
of the narrow fore-aft width of the beam, and will receive only limited 
amounts of pulse energy because of the short pulses.

Masking by Mid-Frequency Sonar Signals

    There is little chance that marine mammal communications will be 
masked appreciably by the multibeam sonar signals given the low duty 
cycle of the sonar and the brief period when an individual mammal is 
likely to be within its beam. Furthermore, in the case of baleen 
whales, the sonar signals do not overlap with the predominant 
frequencies in the calls, which would avoid significant masking.

Behavioral Responses Resulting from Mid-Frequency Sonar Signals

    Marine mammal behavioral reactions to military and other sonars 
appear to vary by species and circumstance. Sperm whales reacted to 
military sonar, apparently from a submarine, by dispersing from social 
aggregations, moving away from the sound source, remaining relatively 
silent and becoming difficult to approach (Watkins et al., 1985). Other 
early and generally limited observations were summarized in Richardson 
et al. (1995, p. 301ff). More recently, Rendell and Gordon (1999) 
recorded vocal behavior of pilot whales during periods of active naval 
sonar transmission. The sonar signal was made up of several components 
each lasting 0.17 sec and sweeping up from 4 to 5 kHz. The pilot whales 
were significantly more vocal while the pulse trios were being emitted 
than during the intervening quiet periods, but did not leave the area 
even after several hours of exposure to the sonar.
    Reactions of beaked whales near the Bahamas to mid-frequency naval 
sonars were summarized earlier. Following extended exposure to pulses 
from a variety of ships, some individuals beached themselves, and 
others may have abandoned the area (Balcomb and Claridge, 2001; NOAA 
and USN, 2001). Pulse durations from these sonars were much longer than 
those of the LDEO multi-beam sonar, and a given mammal would probably 
receive many pulses. All of these observations are of limited relevance 
to the present situation because exposures to multi-beam pulses are 
expected to be brief as the vessel passes by, and the individual pulses 
will be very short.
    Captive bottlenose dolphins and a white whale exhibited changes in 
behavior when exposed to 1 sec pulsed sounds at frequencies similar to 
those that will be emitted by the multi-beam sonar used by LDEO 
(Ridgway et al., 1997; Schlundt et al., 2000), and to shorter broadband 
pulsed signals (Finneran et al., 2000, 2002). Behavioral changes 
typically involved what appeared to be deliberate attempts to avoid the 
sound exposure or to avoid the location of the exposure site during 
subsequent tests (Schlundt et al., 2000; Finneran et al., 2002). 
Dolphins exposed to 1-sec intense tones exhibited short-term changes in 
behavior above received sound levels of 178 to 193 dB re 1 [mu]Pa rms 
and belugas did so at received levels of 180 to 196 dB and above. 
Received levels necessary to elicit such reactions to shorter pulses 
were higher (Finneran et al., 2000, 2002). Test animals sometimes 
vocalized after exposure to pulsed, mid-frequency sound from a watergun 
(Finneran et al., 2002). In some instances, animals exhibited 
aggressive behavior toward the test apparatus (Ridgway et al., 1997; 
Schlundt et al., 2000). The relevance of these data to free-ranging 
odontocetes is uncertain. In the wild, cetaceans sometimes avoid sound 
sources well before they are exposed to the levels listed above, and 
reactions in the wild may be more subtle than those described by 
Ridgway et al. (1997) and Schlundt et al.(2000).
    LDEO is not aware of any data on the reactions of pinnipeds to 
sonar sounds, although it is likely the pinniped species can detect 
these sounds given their hearing abilities (Kastak and Schusterman, 
1995, 1998, 1999; see also a review in Richardson et al., 1995). Some 
harp seals (Pagophilus groenlandicus) seemed to alter their swimming 
patterns (exhibited avoidance) when they were exposed to the beam of an 
echosounder, nominally operating at 200 kHz (Terhune, 1976); that 
frequency is above the range of effective hearing of seals. However, 
there was significant energy at lower frequencies that would be audible 
to a harp seal (Richardson et al., 1995). The behavior of ringed (Phoca 
hispida) and Weddell (Leptonychotes weddelli) seals fitted with 
acoustic pingers, transmitting at 60 to 69 kHz, did not seem to be 
affected by the sounds from these devices. Mate (1993) described 
experiments where aperiodic 12-17 kHz sound pulses of varying duration 
were effective, at source levels of 187 dB, in reducing harbor seal 
abundance near fish hatcheries (although a few older seals may have 
habituated and foraged nearby with modified techniques such that they 
were not seen as frequently). For California sea lions, the same system 
produced a dramatic initial startle response but was otherwise 
ineffective. Mate (1993) noted that many marine mammals will react to 
moving sound sources even if strong stationary sources are tolerated. 
Mate also noted that, by not using swept frequencies, this experimental 
acoustic source lost the illusion of motion that would have been 
simulated by Doppler-like frequency sweeps.
    In summary, cetacean behavioral reactions to military and other 
sonars appear to vary by species and circumstance. While there may be a 
link between naval sonar use and changes in cetacean vocalization rates 
and movements, it is unclear what impact these behavioral changes 
(which are likely to be short-term) might have on the animals. Data on 
the reactions of pinnipeds to sonar sounds are lacking, but the few 
reports available on their reactions to other pulsed sounds suggest 
that they too would exhibit either no, or short-term, behavioral 
responses. Therefore, as mentioned previously, because simple momentary 
behavioral reactions that are within normal behavioral patterns for 
that species are not considered to be a taking, the very brief exposure 
of cetaceans to signals from the Hydrosweep is unlikely to result in a 
``take'' by harassment.

[[Page 17917]]

Hearing Impairment and Other Physical Effects

    Given recent stranding events that have been associated with the 
operation of naval sonar, there is much concern that sonar noise can 
cause serious impacts to marine mammals (for discussion see Effects of 
Seismic Surveys). It is worth noting that the multi-beam sonar proposed 
for use by LDEO is quite different than sonars used for navy 
operations. Pulse duration of the multi-beam sonar is very short 
relative to the naval sonars. Also, at any given location, an 
individual marine mammal would be in the beam of the multi-beam sonar 
for much less time given the generally downward orientation of the beam 
and its narrow fore-aft beamwidth. (Navy sonars often use near-
horizontally-directed sound.) These factors would all reduce the sound 
energy received from the multi-beam sonar rather drastically relative 
to that from the sonars used by the Navy.

Estimates of Take by Harassment for the Hess Deep Cruise

    As described previously in this document and in the LDEO 
application, animals subjected to sound levels above 160 dB may alter 
their behavior or distribution, and therefore might be considered to be 
taken by Level B harassment. However, the 160 dB criterion is based on 
studies of baleen whales. Odontocete hearing at low frequencies is 
relatively insensitive, and the dolphins generally appear to be more 
tolerant of strong sounds than are most baleen whales. For that reason, 
it has been suggested that for purposes of estimating incidental 
harassment of odontocetes, a 170 dB criterion might be appropriate.
    Based on summer marine mammal survey data collected by NMFS and 
density calculations by Ferguson and Barlow (2001), LDEO used their 
average marine mammal density to compute a ``best estimate'' of the 
number of marine mammals that may be exposed to seismic sounds 
[gteqt]160 dB re 1[mu]Pa (rms). The average densities were then 
multiplied by the proposed survey effort (912 and 189 km for the 10-gun 
and 12-gun array, respectively) and twice the 160 dB radius from the 
source vessel (the 160 dB radius was 6.5 and 7.25 km for the 10-gun and 
12-gun array, respectively) to estimate the ``best estimate'' of the 
numbers of animals that might be exposed to sound levels [gteqt]160 dB 
re 1[mu]Pa (rms) during the proposed seismic survey program. Separate 
estimates were made for the 10-gun and 12-gun arrays because the 160 dB 
radius was different for the two arrays (see Tables 5 and 6 in LDEO 
(2003)). Based on this method, the ``best estimate'' of the number of 
marine mammals that would be exposed to [gteqt]160 dB (rms) and thus 
potentially taken by Level B harassment during the proposed survey is 
8,901, including animals taken by both the 10-gun and 12-gun arrays. Of 
these, 12 animals would be endangered species, sperm whales (11) and a 
single blue whale. The species composition of cetaceans within the 
species groups shown in Tables 5 and 6 in LDEO (2003) is expected to be 
roughly in proportion to the densities shown for each species in Table 
3 in LDEO (2003). Based on those densities, the numbers of each species 
that might be taken by Level B harassment are shown in Table 7 in LDEO 
(2003).
    Dolphins would account for 96 percent of the overall estimate for 
potential taking by harassment (i.e., 8,532 of 8,901). While there is 
no agreement regarding any alternative ``take'' criterion for dolphins 
exposed to airgun pulses, if only those dolphins exposed to 170 dB re 1 
[mu]Pa (rms) were affected sufficiently to be considered taken by Level 
B harassment, then the best estimate for dolphins would be 3,076 rather 
than 8,532. This is based on the predicted 170-dB radius around the 10- 
and 12-airgun arrays (2,330 and 2,680 m (7,644 and 7,742 ft), 
respectively), and is considered to be a more realistic estimate of the 
number of dolphins that may be disturbed. Therefore, the total number 
of animals likely to react behaviorally is considerably lower than the 
8,901 that LDEO has estimated in Tables 5 and 6 (LDEO, 2003).

Conclusions--Effects on Cetaceans

    Strong avoidance reactions by several species of mysticetes to 
seismic vessels have been observed at ranges up to 6 to 8 km and 
occasionally as far as 20-30 km from the source vessel. Some bowhead 
whales avoided waters within 30 km of the seismic operation. However, 
reactions at such long distances appear to be atypical of other species 
of mysticetes, and even for bowheads may only apply during migration.
    Odontocete reactions to seismic pulses, or at least those of 
dolphins, are expected to extend to lesser distances than are those of 
mysticetes. Odontocete low-frequency hearing is less sensitive than 
that of mysticetes, and dolphins are often seen from seismic vessels. 
In fact, there are documented instances of dolphins approaching active 
seismic vessels. However, dolphins as well as some other types of 
odontocetes sometimes show avoidance responses and/or other changes in 
behavior when near operating seismic vessels.
    Taking account of the mitigation measures that are planned, effects 
on cetaceans are generally expected to be limited to avoidance of the 
area around the seismic operation and short-term changes in behavior, 
falling within the MMPA definition of ``Level B harassment.'' In the 
cases of mysticetes, these reactions are expected to involve small 
numbers of individual cetaceans because few mysticetes occur in the 
areas where seismic surveys are proposed. LDEO's ``best estimate'' is 
that 10 Bryde's whales, or 0.1 percent of the estimated Eastern 
Equatorial Bryde's whale population, will be exposed to sound levels 
£160 dB re 1 [mu]Pa (rms) and potentially affected, and 1 
blue whale, or 0.1 percent of the ``endangered'' ETP blue whale 
population, would receive £160 dB. Therefore, these potential 
takings by Level B harassment will have a negligible impact on their 
populations.
    Larger numbers of odontocetes may be affected by the proposed 
activities, but the population sizes of the main species are large and 
the numbers potentially affected are small (<0.1 percent) relative to 
the population sizes. The total number of odontocetes that might be 
exposed to [gteqt]160 dB re 1 [mu]Pa (rms) in the Hess Deep area is 
estimated as 8,890. Of these, 8,532 are delphinids, and of these about 
3,076 might be exposed to [gteqt]170 dB. These figures are <0.1 percent 
of the Eastern Equatorial populations of these combined species, and 
the 3,076 value (based on the £170 dB criterion) is believed 
to be a more accurate estimate of the number that could potentially be 
harassed under Level B.
    The many cases of apparent tolerance by cetaceans of seismic 
exploration, vessel traffic, and some other human activities show that 
co-existence is possible. Mitigation measures such as controlled speed, 
look-outs, non-pursuit, ramp-ups, avoidance of start-ups during periods 
of darkness when possible, and shut-down when within defined ranges 
(See Mitigation) should further reduce short-term reactions to 
disturbance, and minimize any effects on hearing sensitivity.

Conclusions--Effects on Pinnipeds

    Very few if any pinnipeds are expected to be encountered in the 
Hess Deep area. Thus a maximum of 20 pinnipeds in the Hess Deep area 
may be affected by the proposed seismic surveys. If pinnipeds are 
encountered, the proposed seismic activities would have, at most, a 
short-termed effect on their behavior and no long-term impacts on 
individual seals or their populations.

[[Page 17918]]

 Responses of pinnipeds to acoustic disturbance are variable, but 
usually quite limited. Effects are expected to be limited to short-term 
and localized behavioral changes falling within the MMPA definition of 
Level B harassment.

Mitigation

    For the proposed seismic operations in the Hess Deep, a 12-gun 
array with a total volume of 3721 in3 and a 10-gun array of 3005 in\3\ 
will be used. The airguns comprising these arrays will be spread out 
horizontally, so that the energy from the array will be directed mostly 
downward. Modeled results for the 10- and 12-gun arrays indicate 
received levels to the 180 dB re 1 [mu]Pa (rms) isopleth (the criterion 
applicable to cetaceans) were 830 and 880 m (2,723 and 2,887 ft), 
respectively. The radii around the 10- and 12-gun arrays where the 
received level would be 190 dB re 1 [mu]Pa (rms) isopleth (lines of 
equal pressure), the criterion (applicable to pinnipeds), were 
estimated as 250 and 300 m (820 and 984 ft), respectively. Vessel-based 
observers will monitor marine mammals in the vicinity of the arrays. A 
calibration study planned for late May and/or June 2003 in the Gulf of 
Mexico is expected to determine the actual radii corresponding to each 
sound level. If the modeled radii have not been verified by the time of 
the Hess Deep surveys, LDEO proposes to use 1.5 times the 180- 
(cetaceans) and 190- (pinnipeds) dB radii predicted by the model as the 
safety radii until the radii have been verified. Thus, during the Hess 
Deep cruise the proposed safety radii for cetaceans are 1,245 and 1,320 
m (4,085 and 4,331 ft), respectively, for the 10- and 12-gun arrays, 
and the proposed safety radii for pinnipeds are 375 and 450 m (1,230 
and 1,476 ft), respectively. LDEO proposes to shut down the seismic 
source if marine mammals are observed within the proposed safety radii.
    Also, LDEO proposes to use a ramp-up procedure when commencing 
operations. Ramp-up will begin with the smallest gun in the array that 
is being used (80 in\3\ for the 10- and 12-gun arrays), and guns will 
be added in a sequence such that the source level of the array will 
increase at a rate no greater than 6 dB per 5-minutes.

Operational Mitigation

    The directional nature of the two alternative airgun arrays to be 
used in this project is an important mitigating factor, resulting in 
reduced sound levels at any given horizontal distance than would be 
expected at that distance if the source were omnidirectional with the 
stated nominal source level. Also, the use of the 10- or 12-gun array 
of 3,005 or 3,721 in3 rather than the largest airgun array that the 
LDEO's source vessel can deploy (20 airguns totaling almost 8600 in3) 
is another significant mitigation measure.

Marine Mammal Monitoring

    Vessel-based observers will monitor marine mammals near the seismic 
source vessel during all daylight airgun operations and during any 
nighttime startups of the airguns. Airgun operations will be suspended 
when marine mammals are observed within, or about to enter, designated 
safety zones where there is a possibility of significant effects on 
hearing or other physical effects. Vessel-based observers will watch 
for marine mammals near the seismic vessel during daylight periods with 
shooting, and for at least 30 minutes prior to the planned start of 
airgun operations. Observers will not be on duty during ongoing seismic 
operations at night; bridge personnel will watch for marine mammals 
during this period and will call for the airguns to be shut down if 
marine mammals are observed in or about to enter the safety radii. If 
the airguns are started up at night, two marine mammal observers will 
monitor marine mammals near the source vessel for 30 minutes prior to 
start up using night vision devices as described later (see Monitoring 
and Reporting).
    Two observers will be stationed on the R/V Maurice Ewing during 
seismic operations in the Hess Deep area. The R/V Maurice Ewing is a 
suitable platform for marine mammal observations. The observer's eye 
level will be approximately 11 m (36 ft) above sea level when stationed 
on the bridge, allowing for good visibility within a 210[deg]
arc for 
each observer. The proposed monitoring plan is summarized later in this 
document.

Proposed Safety Radii

    Received sound levels have been modeled for the 10-, 12-, and 20-
air gun arrays (but the 20-gun array will not be used during the Hess 
Deep Project). Based on the modeling, estimates of the 190, 180, 170, 
and 160 dB re 1 [mu]Pa (rms) distances (safety radii) for these arrays 
have been provided previously in this document. Acoustic measurements 
in shallow and deep water will be taken, in order to check the modeled 
received sound levels from these arrays. This verification is expected 
to occur in June 2003 in the Gulf of Mexico. If verification of the 
safety radii does not occur before the start of the proposed program, 
then conservative safety radii will be used during the proposed Hess 
Deep seismic surveys. Conservative radii will be 1.5 times the 
distances indicated for the 10- and 12-airgun arrays to be used in the 
Hess Deep area. Thus, during the Hess Deep cruise the proposed 
conservative safety radii for cetaceans are 1,245 and 1,320 m (4,085 
and 4,331 ft), for the 10- and 12-gun arrays, respectively, and the 
proposed conservative safety radii for pinnipeds are 375 and 450 m 
(1,230 and 1,476 ft), respectively.
    Airgun operations will be suspended immediately when cetaceans are 
seen within or about to enter the appropriate 180-dB (rms) radius, or 
if pinnipeds are seen within or about to enter the 190-dB (rms) radius. 
These 190 and 180 dB criteria are consistent with guidelines listed for 
pinnipeds and cetaceans by NMFS (2000) and other guidance by NMFS.

Mitigation During Operations

    The following mitigation measures, as well as marine mammal 
monitoring, will be adopted during the Hess Deep seismic survey program 
and the acoustic verification program, provided that doing so will not 
compromise operational safety requirements:
    (1) Course alteration; (2) Shut-down procedures; and (3) Ramp-up 
procedures.

Course Alteration

    If a marine mammal is detected outside the safety radius and, based 
on its position and the relative motion, is likely to enter the safety 
radius, alternative ship tracks will be plotted against anticipated 
mammal locations. The vessel's direct course and/or speed will be 
changed in a manner that also minimizes the effect to the planned 
science objectives. The marine mammal activities and movements relative 
to the seismic vessel will be closely monitored to ensure that the 
marine mammal does not approach within the safety radius. If the mammal 
appears likely to enter the safey radius, further mitigative actions 
will be taken, i.e., either further course alterations or shutdown of 
the airguns.

Shutdown Procedures

    Vessel-based observers will monitor marine mammals near the seismic 
vessel during daylight and for 30 minutes prior to start up during 
darkness throughout the program. Airgun operations will be suspended 
immediately when marine mammals are observed within, or about to enter, 
designated safety zones where there is a possibility of physical 
effects, including effects on hearing (based on the 180 and 190 dB 
criteria specified by NMFS). The

[[Page 17919]]

 shutdown procedure should be accomplished within several seconds or 
one shot period of the determination that a marine mammal is within or 
about to enter the safety zone. Airgun operations will not resume until 
the marine mammal is outside the safety radius. Once the safety zone is 
clear of marine mammals, the observer will advise that seismic surveys 
can re-commence. The ``ramp-up'' procedure will then be followed.

Ramp-up Procedure

    A ``ramp-up'' procedure will be followed when the airgun arrays 
begin operating after a specified-duration period without airgun 
operations. Under normal operational conditions (vessel speed 4-5 
knots), a ramp-up would be required after a ``no shooting'' period 
lasting 2 minutes or longer. At 4 knots, the source vessel would travel 
247 m (810 ft) during a 2-minute period. If the towing speed is reduced 
to 3 knots or less, as sometimes required when maneuvering in shallow 
water (not a factor in Hess Deep), it is proposed that a ramp-up would 
be required after a ``no shooting'' period lasting 3 minutes or longer. 
At towing speeds not exceeding 3 knots, the source vessel would travel 
no more than 277 m (909 ft) in 3 minutes. These guidelines would 
require modification if the normal shot interval were more than 2 or 3 
min, respectively, but that is not expected to occur during the Hess 
Deep project.
    Ramp-up will begin with the smallest gun in the array that is being 
used (80 in\3\ for the 10- and 12-gun arrays). Guns will be added in a 
sequence such that the source level of the array will increase in steps 
not exceeding 6 dB per 5-minute period over a total duration of 
approximately 18-20 min (10-12 gun arrays).

Monitoring and Reporting

    LDEO proposes to conduct marine mammal monitoring of its 2003 
seismic program in the Hess Deep and acoustical verification of safety 
radii, in order to satisfy the anticipated requirements of the IHA.

Vessel-based Visual Monitoring

    Two observers dedicated to marine mammal observations will be 
stationed aboard LDEO's seismic survey vessel for the seismic survey in 
the Hess Deep area. It is proposed that one or both marine mammal 
observers aboard the seismic vessel will search for and observe marine 
mammals whenever seismic operations are in progress during daylight 
hours. When feasible, two observers will be on duty for at least 30 
minutes prior to the start of seismic shooting and during ramp-up 
procedures. The 30-minute observation period is only required prior to 
commencing seismic operations following an extended shut down period.
    If ramp-up procedures must be performed at night, two observers 
will be on duty 30 minutes prior to the start of seismic shooting and 
during the subsequent ramp-up procedures. Otherwise, no observers will 
be on duty during seismic operations at night. However, LDEO bridge 
personnel (port and starboard seamen and one mate) will assist in 
marine mammal observations whenever possible, and especially during 
operations at night, when designated marine mammal observers will not 
normally be on duty. A marine mammal observer will be on ``standby'' at 
night, in case bridge personnel see a marine mammal. An image-
intensifier night-vision device (NVD) will be available for use at 
night, although past experience has shown that NVDs are of limited 
value for this purpose.
    The observer(s) will watch for marine mammals from the bridge, the 
highest practical vantage point on the vessel. The observer's eye level 
will be approximately 11 m (36 ft) above see level when stationed on 
the bridge, allowing for good visibility within a 210[deg]
arc. The 
observer(s) will systematically scan the area around the vessel with 7 
X 50 Fujinon reticle binoculars or with the naked eye during the 
daytime. At night, night vision equipment will be available (ITT F500 
Series Generation 3 binocular image intensifier or equivalent), if 
required. Laser rangefinding binoculars (Bushnell Lytespeed 800 laser 
rangefinder with 4 optics or equivalent) will be available to assist 
with distance estimation. If a marine mammal is seen well outside the 
safety radius, the vessel may be maneuvered to avoid having the mammal 
come within the safety radius (see Mitigation). When mammals are 
detected within or about to enter the designated safety radii, the 
airguns will be shut down immediately. The observer(s) will continue to 
maintain watch to determine when the animal is outside the safety 
radius. Airgun operations will not resume until the animal is outside 
the safety radius.
    The vessel-based monitoring will provide data required to estimate 
the numbers of marine mammals exposed to various received sound levels, 
to document any apparent disturbance reactions, and thus to estimate 
the numbers of mammals potentially taken by Level B harassment. It will 
also provide the information needed in order to shut down the airguns 
at times when mammals are present in or near the safety zone. When a 
mammal sighting is made, the following information about the sighting 
will be recorded: (1) Species, group size, age/size/sex categories (if 
determinable), behavior when first sighted and after initial sighting, 
heading (if consistent), bearing and distance from seismic vessel, 
sighting cue, apparent reaction to seismic vessel (e.g., none, 
avoidance, approach, paralleling, etc.), and behavioral pace; and (2) 
Time, location, heading, speed, activity of the vessel (shooting or 
not), sea state, visibility, cloud cover, and sun glare. The data 
listed under (2) will also be recorded at the start and end of each 
observation watch and during a watch, whenever there is a change in one 
or more of the variables.
    All mammal observations and airgun shutdowns will be recorded in a 
standardized format. Data will be entered into a custom database using 
a laptop computer when observers are off-duty. The accuracy of the data 
entry will be verified by computerized validity data checks as the data 
are entered and by subsequent manual checking of the database. These 
procedures will allow initial summaries of data to be prepared during 
and shortly after the field program, and will facilitate transfer of 
the data to statistical, graphical or other programs for further 
processing and archiving.
    At least one experienced marine mammal observer will be on duty 
aboard the seismic vessel. During seismic operations in the Hess Deep 
area, two observers, including one qualified contract biologist and one 
observer appointed by LDEO, will be based aboard the vessel. Observers 
appointed by LDEO will complete a one-day training/refresher course on 
marine mammal monitoring procedures, given by a contract employee 
experienced in vessel-based seismic monitoring projects.
    Observers will be on duty in shifts of duration no longer than 4 
hours. The second observer will also be on watch part of the time, 
including the 30 minute periods preceding startup of the airguns and 
during ramp ups. Use of two simultaneous observers will increase the 
proportion of the marine mammals present near the source vessel that 
are detected. Bridge personnel additional to the dedicated marine 
mammal observers will also assist in detecting marine mammals and 
implementing mitigation requirements, and before the start of the 
seismic survey will be given instruction in how to do so.

[[Page 17920]]

    Results from the vessel-based observations will provide (1) The 
basis for real-time mitigation (airgun shutdown); (2) Information 
needed to estimate the number of marine mammals potentially taken by 
harassment, which must be reported to NMFS; (3) Data on the occurrence, 
distribution, and activities of marine mammals in the area where the 
seismic study is conducted; (4) Information to compare the distance and 
distribution of marine mammals relative to the source vessel at times 
with and without seismic activity; and (5) Data on the behavior and 
movement patterns of marine mammals seen at times with and without 
seismic activity.

Acoustical Measurements

    The acoustic measurement program is designed to verify the safety 
radii that will be used to determine when the air guns will be shut 
down to prevent marine mammals from being exposed to seismic sounds 180 
(cetaceans) or 190 dB re 1[mu]Pa (rms) (pinnipeds)(see Mitigation). It 
will also provide the specific acoustic data needed to document the 
seismic sounds to which marine mammals are exposed at various distances 
from the seismic source, as necessary to improve the estimates of 
potential take by harassment and to interpret the observations of 
marine mammal distribution, behavior, and headings. It appears most 
likely that acoustical measurements will be conducted in the Gulf of 
Mexico during June when LDEO's vessel will be in that area for other 
purposes. Acoustic studies will obtain data on characteristics of the 
seismic survey sounds as a function of distance in deep and shallow 
water.
    Additional details about the methods, timing and location of the 
acoustical verification study are provided in the LDEO application; 
additional information on monitoring will be provided by LDEO in an 
addendum to its application as plans for this effort become more 
specific. That addendum will address the marine mammals that might be 
exposed to airgun sounds during the verification study.
    A report will be submitted to NMFS within 90 days after the end of 
the seismic program in the Hess Deep area. The end of the Hess Deep 
program is predicted to occur on or about July 28, 2003. The report 
will cover the seismic surveys in the Hess Deep area and will be 
submitted to NMFS, providing full documentation of methods, results, 
and interpretation pertaining to all monitoring tasks. The 90-day 
report will summarize the dates and locations of seismic operations, 
sound measurement data, marine mammal sightings (dates, times, 
locations, activities, associated seismic survey activities), and 
estimates of the amount and nature of potential ``take'' of marine 
mammals by harassment or in other ways.

Endangered Species Act (ESA)

    Under section 7 of the ESA, NMFS has begun consultation on the 
proposed issuance of an IHA under section 101(a)(5)(D) of the MMPA for 
this activity. Consultation will be concluded prior to the issuance of 
an IHA.

National Environmental Policy Act (NEPA)

    The NSF has prepared an EA for the Hess Deep survey. NMFS is 
reviewing this EA and will either adopt it or prepare its own NEPA 
document before making a determination on the issuance of an IHA. A 
copy of the NSF EA for this activity is available upon request (see 
ADDRESSES).

Preliminary Conclusions

    NMFS has preliminarily determined that the short-term impact of 
conducting a seismic survey program in the Hess Deep portion of the 
Eastern Equatorial Pacific Ocean will result, at worst, in a temporary 
modification in behavior by certain species of marine mammals. While 
behavioral modifications may be made by these species as a result of 
seismic survey activities, this behavioral change is expected to result 
in no more than a negligible impact on the affected species.
    While the number of potential incidental harassment takes will 
depend on the distribution and abundance of marine mammals in the 
vicinity of the survey activity, the number of potential harassment 
takings is estimated to be small. In addition, no take by injury and/or 
death is anticipated, and the potential for temporary or permanent 
hearing impairment is low and will be avoided through the incorporation 
of the mitigation measures mentioned in this document.

Proposed Authorization

    NMFS proposes to issue an IHA to LDEO for conducting a seismic 
survey program in the Hess Deep portion of the Eastern Equatorial 
Pacific Ocean, provided the previously mentioned mitigation, 
monitoring, and reporting requirements are incorporated. NMFS has 
preliminarily determined that the proposed activity would result in the 
harassment of only small numbers of marine mammals; would have no more 
than a negligible impact on the affected marine mammal stocks; and 
would not have an unmitigable adverse impact on the availability of 
stocks for subsistence uses.

Information Solicited

    NMFS requests interested persons to submit comments and information 
concerning this request (see ADDRESSES).

    Dated: April 7, 2003.
Laurie K. Allen,
Acting Director, Office of Protected Resources, National Marine 
Fisheries Service.
[FR Doc. 03-9057 Filed 4-11-03; 8:45 am]
BILLING CODE 3510-22-S
Notices For
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Small Takes of Marine Mammals Incidental to Specified Activities; Oceanographic Surveys in the Hess Deep, Eastern Equatorial Pacific Ocean

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