[Federal Register Volume 70, Number 35 (Wednesday, February 23, 2005)]
[Notices]
[Pages 8768-8783]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 05-3442]


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DEPARTMENT OF COMMERCE

National Oceanic and Atmospheric Administration

[I.D. 101204B]


Small Takes of Marine Mammals Incidental to Specified Activities; 
Low-Energy Seismic Survey in the Southwest Pacific Ocean

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

ACTION: Notice of issuance of an incidental harassment authorization.

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SUMMARY: In accordance with provisions of the Marine Mammal Protection 
Act (MMPA) as amended, notification is hereby given that an Incidental 
Harassment Authorization (IHA) to take small numbers of marine mammals, 
by harassment, incidental to conducting oceanographic seismic surveys 
in the southwestern Pacific Ocean (SWPO) has been issued to the Scripps 
Institution of Oceanography, (Scripps).

DATES: Effective from February 10, 2005, through February 9, 2006.

ADDRESSES: The authorization and application containing a list of the 
references used in this document may be obtained by writing to this 
address or by telephoning the contact listed here. The application is 
also available at: http://www.nmfs.noaa.gov/prot_res/PR2/Small_Take/smalltake_info.htm#applications.

FOR FURTHER INFORMATION CONTACT: Kenneth Hollingshead, Office of 
Protected Resources, NMFS, (301) 713-2289, ext 128.

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.
    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.''
    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. 
Except with respect to certain activities not pertinent here, 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 [Level A harassment]; 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 
[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 October 6, 2004, NMFS received an application from Scripps for 
the taking, by harassment, of several species of marine mammals 
incidental to conducting a low-energy marine seismic survey program 
during early 2005 in the SWPO. The overall area within which the 
seismic survey will occur is located between approximately 25[deg] and 
50[deg]S, and between approximately 133[deg] and 162.5[deg]W. The 
survey will be conducted entirely in international waters. The purpose 
of the seismic survey is to collect the site survey data for a second 
Integrated Ocean Drilling Program transect to study the structure of 
the Eocene Pacific from the subtropics into the Southern Ocean. A 
future ocean-drilling program cruise (not currently scheduled) based on 
the data collected in the present program will better document and 
constrain the actual patterns of atmospheric and oceanic circulation on 
Earth at the time of extreme warmth in the early Eocene. Through the 
later ocean drilling program, it is anticipated that marine scientists 
will be able to (1) define the poleward extent of the sub-tropical 
gyre, (2) establish the position of the polar front, (3) determine sea-
surface temperatures and latitudinal temperature gradient, (4) 
determine the width and intensity of the high-productivity zone 
associated with these oceanographic features, (5) characterize the 
water masses formed in the sub-polar region, (6) determine the nature 
of the zonal winds and how they relate to oceanic surface circulation, 
and (7) document the changes in these systems as climate evolves from 
the warm early Eocene to the cold Antarctic of the early Oligocene. As 
presently scheduled, the seismic survey will occur from approximately 
February 11, 2005 to March 21, 2005.

Description of the Activity

    The seismic survey will involve one vessel. The source vessel, the 
R/V Melville, will deploy a pair of low-energy Generator-Injector (GI) 
airguns as an energy source (each with a discharge volume of 45 in\3\), 
plus a 450-meter (m) (1476-ft) long, 48-channel, towed hydrophone 
streamer. As the airguns are towed along the survey lines, the 
receiving system will receive the returning acoustic signals. The 
survey program will consist of approximately 11,000 kilometer (km) 
(5940 nautical mile (nm)) of surveys, including turns. Water depths 
within the seismic survey area are 4000-5000 m (13,123-16,400 ft) with 
no strong topographic features. The GI guns will be operated en route 
between piston-coring sites, where bottom sediment cores will be 
collected. There will be additional operations associated with 
equipment testing, start-

[[Page 8769]]

up, line changes, and repeat coverage of any areas where initial data 
quality is sub-standard.
    The energy to the airguns is compressed air supplied by compressors 
on board the source vessel. Seismic pulses will be emitted at intervals 
of 6-10 seconds. At a speed of 7 knots (about 13 km/h), the 6-10 sec 
spacing corresponds to a shot interval of approximately 21.5-36 m (71-
118 ft).
    The generator chamber of each GI gun, the one responsible for 
introducing the sound pulse into the ocean, is 45 in\3\. The larger 
(105 in\3\) injector chamber injects air into the previously-generated 
bubble to maintain its shape, and does not introduce more sound into 
the water. The two 45/105 in\3\ GI guns will be towed 8 m (26.2 ft) 
apart side by side, 21 m (68.9 ft) behind the Melville, at a depth of 2 
m (6.6 ft).

General-Injector Airguns

    Two GI-airguns will be used from the Melville during the proposed 
program. These 2 GI-airguns have a zero to peak (peak) source output of 
237 dB re 1 microPascal-m (7.2 bar-m) and a peak-to-peak (pk-pk) level 
of 243 dB (14.0 bar-m). However, these downward-directed source levels 
do not represent actual sound levels that can be measured at any 
location in the water. Rather, they represent the level that would be 
found 1 m (3.3 ft) from a hypothetical point source emitting the same 
total amount of sound as is emitted by the combined airguns in the 
airgun array. The actual received level at any location in the water 
near the airguns will not exceed the source level of the strongest 
individual source and actual levels experienced by any organism more 
than 1 m (3.3 ft) from any GI gun will be significantly lower.
    Further, the root mean square (rms) received levels that are used 
as impact criteria for marine mammals (see Richardson et al., 1995) are 
not directly comparable to these peak or pk-pk values that are normally 
used by acousticians to characterize source levels of airgun arrays. 
The measurement units used to describe airgun sources, peak or pk-pk 
decibels, are always higher than the rms decibels referred to in 
biological literature. For example, a measured received level of 160 dB 
rms in the far field would typically correspond to a peak measurement 
of about 170 to 172 dB, and to a pk-pk measurement of about 176 to 178 
decibels, as measured for the same pulse received at the same location 
(Greene, 1997; McCauley et al. 1998, 2000). The precise difference 
between rms and peak or pk-pk values depends on the frequency content 
and duration of the pulse, among other factors. However, the rms level 
is always lower than the peak or pk-pk level for an airgun-type source.
    The depth at which the sources are towed has a major impact on the 
maximum near-field output, because the energy output is constrained by 
ambient pressure. The normal tow depth of the sources to be used in 
this project is 2.0 m (6.6 ft), where the ambient pressure is 
approximately 3 decibars. This also limits output, as the 3 decibars of 
confining pressure cannot fully constrain the source output, with the 
result that there is loss of energy at the sea surface. Additional 
discussion of the characteristics of airgun pulses is provided in 
Scripps application and in previous Federal Register documents (see 69 
FR 31792 (June 7, 2004) or 69 FR 34996 (June 23, 2004)).
    Received sound levels have been modeled by L-DEO for two 105 in\3\ 
GI guns, but not for the two 45 in\3\ GI-guns, in relation to distance 
and direction from the airguns. The model does not allow for bottom 
interactions, and is therefore most directly applicable to deep water. 
Based on the modeling, estimates of the maximum distances from the GI 
guns where sound levels of 190, 180, 170, and 160 dB microPascal-m 
(rms) are predicted to be received are shown in Table 1. Because the 
model results are for the larger 105 in\3\ guns, those distances are 
overestimates of the distances for the 45 in\3\ guns.

   TABLE 1. Distances to which sound levels 190, 180, 170, and 160 dB
  microPascal-m (rms) might be received from two 105 in\3\ GI airguns,
   similar to the two 45 in\3\ GI airguns that will be used during the
   seismic survey in the SW Pacific Ocean during February-March 2005.
  Distances are based on model results provided by Lamont-Doherty Earth
                          Observatory (L-DEO).
              Estimated Distances at Received Levels (m/ft)
Water Depth >1000...............   190 dB   180 dB     170 dB     160 dB
                                    17/56   54/177    175/574   510/1673
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    Some empirical data concerning the 180-, and 160-dB distances have 
been acquired for several airgun configurations, including two GI-guns, 
based on measurements during an acoustic verification study conducted 
by L-DEO in the northern Gulf of Mexico (GOM) from 27 May to 3 June 
2003 (Tolstoy et al., 2004). Although the results are limited, the data 
showed that water depth affected the radii around the airguns where the 
received level would be 180 dB re 1 microPa (rms), NMFS' current injury 
threshold safety criterion applicable to cetaceans (NMFS, 2000). 
Similar depth-related variation is likely in the 190-dB distances 
applicable to pinnipeds. Correction factors were developed and 
implemented for previous IHAs for activities with water depths less 
than 1000 m (3281 ft). However, the proposed airgun survey will occur 
in depths 4000-5000 m (13,123-16,400 ft). As a result, NMFS has 
determined correction factors are not necessary here since the L-DEO 
model has been shown to result in more conservative (i.e,. protective) 
impact zones than indicated by the empirical measurements. Therefore, 
the assumed 180- and 190-dB radii are 54 m (177 ft) and 17 m (56 ft), 
respectively. Considering that the 2 GI-airgun array is towed 21 m (69 
ft) behind the Melville and the vessel is 85 m (270 ft) long, the 
forward aspect of the 180-dB isopleth (lines of equal pressure) at its 
greatest depth will not exceed approximately the mid-ship line of the 
Melville. At the water surface, an animal would need to be between the 
vessel and the 450-m (1476 ft) long hydrophone streamer to be within 
the 180-dB isopleth.

Bathymetric Sonar and Sub-bottom Profiler

    In addition to the 2 GI-airguns, a multi-beam bathymetric sonar and 
a low-energy 3.5-kHz sub-bottom profiler will be used during the 
seismic profiling and continuously when underway.
    Sea Beam 2000 Multi-beam Sonar - The hull-mounted Sea Beam 2000 
sonar images the seafloor over a 120[deg]-wide swath to 4600 m (15092 
ft) under the vessel. In ``deep'' mode (400-1000 m

[[Page 8770]]

(1312-3281 ft), it has a beam width of 2[deg], fore-and-aft, uses very 
short (7-20 msec) transmit pulses with a 2-22 s repetition rate and a 
12.0 kHz frequency sweep. The maximum source level is 234 dB microPa 
(rms).
    Sub-bottom Profiler - The sub-bottom profiler is normally operated 
to provide information about the sedimentary features and the bottom 
topography that is simultaneously being mapped by the multi-beam sonar. 
The energy from the sub-bottom profiler is directed downward by a 3.5-
kHz transducer mounted in the hull of the Melville. The output varies 
with water depth from 50 watts in shallow water to 800 watts in deep 
water. Pulse interval is 1 second (s) but a common mode of operation is 
to broadcast five pulses at 1-s intervals followed by a 5-s pause. The 
beamwidth is approximately 30[deg] and is directed downward. Maximum 
source output is 204 dB re 1 microPa (800 watts) while normal source 
output is 200 dB re 1 microPa (500 watts). Pulse duration will be 4, 2, 
or 1 ms, and the bandwith of pulses will be 1.0 kHz, 0.5 kHz, or 0.25 
kHz, respectively.
    Although the sound levels have not been measured directly for the 
sub-bottom profiler used by the Melville, Burgess and Lawson (2000) 
measured sounds propagating more or less horizontally from a sub-bottom 
profiler similar to the Scripps unit with similar source output (i.e., 
205 dB re 1 microPa m). For that profiler, the 160- and 180-dB re 1 
microPa (rms) radii in the horizontal direction were estimated to be, 
respectively, near 20 m (66 ft) and 8 m (26 ft) from the source, as 
measured in 13 m (43 ft) water depth. The corresponding distances for 
an animal in the beam below the transducer would be greater, on the 
order of 180 m (591 ft) and 18 m (59 ft) respectively, assuming 
spherical spreading. Thus the received level for the Scripps sub-bottom 
profiler would be expected to decrease to 160 and 180 dB about 160 m 
(525 ft) and 16 m (52 ft) below the transducer, respectively, assuming 
spherical spreading. Corresponding distances in the horizontal plane 
would be lower, given the directionality of this source (30[deg] 
beamwidth) and the measurements of Burgess and Lawson (2000).

Characteristics of Airgun Pulses

    Discussion of the characteristics of airgun pulses was provided in 
several previous Federal Register documents (see 69 FR 31792 (June 7, 
2004) or 69 FR 34996 (June 23, 2004)) and is not repeated here. 
Reviewers are referred to those documents for additional information.

Comments and Responses

    A notice of receipt and request for 30-day public comment on the 
application and proposed authorization was published on December 3, 
2004 (69 FR 70236). During the 30-day public comment period, NMFS 
received two comments. One commenter expressed the opinion that marine 
mammals should not be killed and that these killings are not small. As 
noted in this document, NMFS believes that no marine mammals are likely 
to be seriously injured or killed as a result of this L-DEO conducting 
seismic surveys.The concerns of the second commenter, the Center for 
Regulatory Effectiveness (CRE), are discussed here.
    Comment 1: There is no scientific basis for the use of 190, 180, 
170, and 160 dB micro-Pascal (RMS) as criteria for potential injury to 
marine mammals from seismic operations. NMFS uses these criteria along 
with L-DEO (Lamont-Doherty Earth Observatory) modeling, to determine 
the safety (shut-down) radii for seismic surveys. The comment states 
that those criteria are arbitrary and without scientific basis, were 
established without external peer review or published reports, and were 
not based on empirical data.
    Response: NMFS disagrees that there is no factual or scientific 
basis to support the 190, 180, and 160 dB thresholds (we note that 170 
dB is not used by NMFS). At the same time we recognize the limitations 
of these thresholds and, in the interest of transparency, acknowledge 
and disclose them. These limitations largely stem from the data gaps 
for many species of marine mammals, individual intra-species 
variability, and the difficulties inherent in conducting field studies 
in this area of inquiry (both logistic and ethical). NMFS makes its 
data, and the analysis of these data, available to the public and 
solicits public comment. However, there are factual studies that 
support the threshold values used here.
    The 160-dB isopleth for onset of Level B (behavioral) harassment is 
supported by research conducted by Malme et al. (1983, 1984) in their 
study on the California gray whale when exposed to seismic sounds. They 
found that migrating gray whales showed definite avoidance reactions 
and other behavioral changes when exposed to seismic pulses with 
received levels exceeding about 160 dB re 1 micro Pa (rms). The 
received levels at which 10 percent, 50 percent and 90 percent of the 
whales exhibited avoidance were estimated to be 164, 170, and 180 dB 
(Malme et al., 1989; Richardson et al., 1995).
    More recently, McCauley et al. (1998) documented localized 
avoidance by humpback whales of both the seismic array and a single 
airgun (16-gun 2678-in\3\ array and a single 20 in\3\ airgun with a 
source level 227 dB re 1 microPa-m (p-p)). The standoff range (i.e., 
the closest point of approach of the airgun to the whales) corresponded 
to received levels around 140 dB re 1 microPa. The initial avoidance 
response generally occurred at distances of 5 to 8 km (2.7 to 4.3 nm) 
from the airgun array and 2 km (1.0 nm) from the single gun, with 
estimated received levels at 140 dB and 143 dB re 1 microPa rms, 
respectively. However, some individual humpback whales, especially 
males, approached the vessel within distances 100 to 400 m (328 to 1312 
ft), where the maximum received level was 179 dB re 1 microPa rms.
    With respect to the 180 and 190 dB thresholds, data that are now 
available imply that, at least for dolphins, temporary threshold shift 
(TTS)in marine mammals is unlikely to occur unless the dolphins are 
exposed to airgun pulses stronger than 180 dB re 1 microPa (rms). 
However, safety zones must be implemented to protect those species 
believed to be most sensitive to low-frequency seismic noise: mysticete 
whales, sperm whales, and likely beaked whales (although beaked whales' 
best hearing is at significantly higher frequencies than low frequency 
seismic, it is possible that non-auditory injury may occur at lower 
sound pressure levels). As a result, NMFS has established the 180- and 
190-dB safety zones based on the most sensitive species at the 
estimated best hearing frequencies. If information is available that 
sensitive species will not be within the affected area, or empirical 
data are presented that marine mammal stocks within the affected area 
do not have hearing capabilities within the source frequencies, then 
the appropriate safety zones might be reduced in size.
    In some cases mitigation safety zones are perhaps larger than 
necessary to avoid Level A harassment of a particular species or the 
mitigation measures are one-size-fits-all in nature. This reflects the 
different sensitivities of affected species and the lack of data. Where 
different mitigation measures for different species are not practical, 
NMFS manages for the most sensitive species when multiple species are 
present. The safety zone for this seismic survey also affords the 
applicant a set of mitigation measures that can be practically 
implemented and will promote enforceability of the IHA. In this manner 
the applicant can move forward with the project in a timely

[[Page 8771]]

manner and NMFS' legal mandate is satisfied.
    NMFS is striving to improve the quality of the information it 
relies upon. We are developing sound exposure guidelines that will 
incorporate the current state of knowledge and take into account 
variations based on sound source, species type, and energy level. These 
guidelines will guide agency decisions and give the regulated 
communities and the public better information for planning, 
enforcement, and understanding. NMFS expects these guidelines to 
reflect the evolving understanding and appreciation of how sound 
affects marine mammals. As part of the process, NMFS has announced its 
intent to prepare an environmental impact statement and initiated 
public scoping to fully involve the public (70 FR 1871 (January 11, 
2005)). The science underlying those guidelines will undergo external 
peer review.
    Comment 2: The comment states there is no basis for correlating the 
effects, if any, on marine mammals of sonar and seismic operations.
    Response: NMFS agrees that the properties of seismic and sonar are 
quite different and will take that into account when developing its 
acoustic guidelines.
    Comment 3: NMFS' reliance on the L-DEO propagation model to 
determine the safety (shut-down) radii for seismic operations is 
unjustified and unsupported. NMFS has stated that for deep water the L-
DEO model overestimates the received sound levels at a given distance. 
The L-DEO model is also inappropriate for use in shallow and 
intermediate depths because it cannot account for bottom interactions 
with sound waves.
    Response: We have previously acknowledged the limitations of the 
model, as has the applicant. The acoustic verification/ calibration 
study in May/June 2003 in the GOM showed that water depth affected 
sound propagation (and, accordingly, the size of the safety radii). As 
a result, correction factors were developed for water depths 100-1000 m 
(328-3281 ft) and less than 100 m (328 ft). Those correction factors 
are not relevant for this survey, which will take place in water depths 
between 4000 and 5000 m (13123 and 16404 ft). Empirical data indicate 
that for water deeper than 1000 m (3281 ft), L-DEO's model tends to 
overestimate the received sound levels at any given distance (Tolstoy 
et al., 2004). Pending acquisition of additional empirical data, 
Scripps' safety radii will be the values predicted by the model. This 
approach will ensure that marine mammals are not inadvertently exposed 
to sound levels greater than what were calculated in the GOM 
verification study.
    Another alternative for estimating propagation would be to conduct 
simple calculations similar to those found in the Minerals Management 
Service's (MMS) Environmental Assessment for Geological and Geophysical 
Seismic Surveys in the GOM. This methodology is illustrated in Appendix 
C of that document (available at http://www.gomr.mms.gov/homepg/regulate/environ/nepa/2004-054.pdf). NMFS believes this methodology 
would need to be improved prior to use for incidental take 
authorizations because it does not take into account the fact that 
marine mammals dive into deeper water where the sound fields normally 
propagate to greater distances than at the surface. Similarly, using 
simple propagation logarithms (e.g., Lr = Ls- 20 Log R for deep water 
propagation) also has shortcomings, in that they overestimate 
horizontal propagation (seismic airgun arrays project sounds towards 
the bottom and not horizontally). As a result, until improved models 
are developed, NMFS believes that using the L-DEO model, with fully 
explained correction factors where necessary (shallow and intermediate 
water depths) provides a reasonable methodology for calculating the 
zones of impact from vertically propagating seismic arrays.
    Comment 4: According to the abstract of the calibration study 
report (Tolstoy et al., 2004)), ``Received [sound] levels in deep water 
were lower than anticipated based on [L-DEO] modeling, and in shallow 
water they were higher.'' In other words, the L-DEO model is inaccurate 
and unreliable in deep and shallow water.
    Response: The L-DEO model is a general one that does not take into 
account the variation in propagation characteristics for the specific 
water bodies. In the GOM, sound propagation levels in deep water were 
lower and in shallow water were higher than that estimated by the L-DEO 
model. Under the MMPA and ESA, NMFS is charged with using the best 
information available. To the best of NMFS' knowledge, the L-DEO model 
provides a practical alternative to the use of standard propagation and 
attenuation calculations. Therefore, a more accurate statement would be 
that in that part of the GOM received sound levels in deep water were 
lower than anticipated based on the L-DEO model, and in shallow water 
they were higher the L-DEO model. Without making acoustic propagation 
measurements in advance of conducting seismic in each operating area, 
conservative estimates of sound propagation and attenuation were made. 
For this Scripps' seismic survey, the R/V Melville will conduct 
approximately 11,000 kilometers (km) (5940 nautical miles (nm)) of 
straight line seismic transects during the survey. Stopping the vessel 
to calibrate sound speed profiles for a particular water mass body, 
while possible, would result in increased costs through time and 
additional personnel and equipment needed onboard the R/V Melville. As 
an alternative, Scripps erred on the side of marine mammals protection 
and adopted conservative estimates for sound attenuation to the 160-, 
180-, and 190-dB isopleths. For this cruise, NMFS has adopted those 
conservative estimates.
    Comment 5:To the best of CRE's knowledge, the L-DEO model is not 
publically available, and NMFS has not demonstrated that it is 
sufficiently accurate and reliable to use. If NMFS intends to continue 
to use or rely on the L-DEO model, then the Agency should: (1) make the 
model publically available for comment; (2) validate use of the model 
for all contexts in which NMFS uses or relies on it; and (3) document 
use of the model and its results for each specific application in 
question, and make that documentation available for public comment 
along with the application itself in sufficient detail to allow third 
parties to reproduce the model results. If there is some reason why 
NMFS must rely on models that cannot be disclosed, then the agency must 
perform, document and produce the ``especially vigorous robustness 
checks'' that NMFS performed on these models. CRE recommends that NMFS 
adopt the Environmental Protection Agency's (EPA) definition of 
``especially rigorous robustness checks.'' If and when NMFS attempts to 
validate the L-DEO model, CRE recommends that NMFS follow EPA's model 
validation guidance. (EPA draft guidance is available at: http://www.epa.gov/osp/crem/library/CREM%20Guidance% Draft%2012--03.pdf.
    Response: The L-DEO model is available to the public by contacting 
L-DEO (see the L-DEO application for the address). In addition, the 
model is explained in Diebold (2004, unpublished). A copy of this 
article is available upon request (see ADDRESSES). The 2003 GOM seismic 
airgun calibration study referenced in this document (Tolstoy et al., 
2004) was the result of an IHA issued to L-DEO for seismic work in the 
GOM (68 FR 9991, March 3, 2003). That report has been cited in a number 
of recent authorizations, and Chapter 3 of that

[[Page 8772]]

report has been available since mid-2004 on our homepage where seismic 
incidental take applications are posted. We consider all references 
cited in our Federal Register notices to be part of our administrative 
record. Whenever an article is not generally available publically, we 
strive to make a copy available.
    Chapter 3 of the 2003 GOM 90-day monitoring report was also 
rewritten, submitted for publication, peer-reviewed and finally 
published in the AGU's Geophysical Research Letters (Tolstoy, M., J.B. 
Diebold, S.C. Webb, D.R. Bohnenstiehl, E. Chapp, R.C. Holmes, and M. 
Rawson. 2004. Broadband Calibration of the R/V Ewing Seismic Sources. 
Geophys. Res. Lett., 31, doi:10.1029/ 2004GL020234, 2004). This 
scientific article is publically available through subscription, 
scientific libraries, or Inter-Library loan.
    As to other modeling approaches and software that could be used to 
verify or refute the L-DEO model, there are commercial products 
available, such as Bellhop, PE, and one called Nucleus that produce 
illustrations similar to the L-DEO model, but this latter product 
provides peak levels only, and has several of the same limitations 
contained in the L-DEO model. There are also publically available 
packages that include complex water column velocity structure, and 
seafloor interactions, but most of these have other kinds of 
limitations (e.g., typically, they do not include arrays of sound 
sources, and do not analyze for broadband frequencies).
    Comment 6: The CRE believes that NMFS should be concerned only with 
biologically significant effects on marine mammals, citing as support 
National Research Council reports (NRC 2004, NRC 2000).
    Response: NMFS' decisions are made in accordance with the relevant 
provisions of the MMPA and its implementing regulations. MMPA section 
101(a)(5)(D) requires the Secretary to authorize the taking of marine 
mammals incidental to otherwise lawful activities, provided that the 
activity will have no more than a negligible impact on the affected 
species or stocks of marine mammals. ``Negligible impact'' is defined 
in 50 CFR 216.103 (repeated earlier in this document). This is the 
relevant standard for the Secretary's decision. Although the term 
``biologically significant'' is not used, this concept is captured 
through application of NMFS' definition of ``negligible impact.''

Description of Habitat and Marine Mammals Affected by the Activity

    A detailed description of the SWPO area and its associated marine 
mammals can be found in the Scripps application and a number of 
documents referenced in that application, and is not repeated here. 
Forty species of cetacean, including 31 odontocete (dolphins and small- 
and large-toothed whales) species and nine mysticete (baleen whales) 
species, are believed by scientists to occur in the southwest Pacific 
in the proposed seismic survey area. Table 2 in the Scripps application 
summarizes the habitat, occurrence, and regional population estimate 
for these species. A more detailed discussion of the following species 
is also provided in the application: Sperm whale, pygmy and dwarf sperm 
whales, southern bottlenose whale, Arnoux's beaked whale, Cuvier's 
beaked whale, Shepherd's beaked whale, Mesoplodont beaked whales 
(Andrew's beaked whale, Blainville's beaked whale, gingko-toothed 
whale, Gray's beaked whale, Hector's beaked whale, spade-toothed whale, 
strap-toothed whale), melon-headed whale, pygmy killer whale, false 
killer whale, killer whale, long-finned pilot whale, short-finned pilot 
whale, rough-toothed dolphin, bottlenose dolphin, pantropical spotted 
dolphin, spinner dolphin, striped dolphin, short-beaked common dolphin, 
hourglass dolphin, Fraser's dolphin, Risso's dolphin, southern right 
whale dolphin, spectacled porpoise, humpback whale, southern right 
whale, pygmy right whale, common minke whale, Antarctic minke whale. 
Bryde's whale, sei whale, fin whale and blue whale. Because the 
proposed survey area spans a wide range of latitudes (25-500 S), 
tropical, temperate, and polar species are all likely to be found 
there. The survey area is all in deep-water habitat but is close to 
oceanic island (Society Islands, Australes Islands) habitats, so both 
coastal and oceanic species might be encountered. However, abundance 
and density estimates of cetaceans found there are provided for 
reference only, and are not necessarily the same as those that likely 
occur in the survey area.
    Five species of pinnipeds could potentially occur in the proposed 
seismic survey area: southern elephant seal, leopard seal, crabeater 
seal, Antarctic fur seal, and the sub-Antarctic fur seal. All are 
likely to be rare, if they occur at all, as their normal distributions 
are south of the Scripps survey area. Outside the breeding season, 
however, they disperse widely in the open ocean (Boyd, 2002; King, 
1982; Rogers, 2002). Only three species of pinniped are known to wander 
regularly into the area (SPREP, 1999): the Antarctic fur seal, the sub-
Antarctic fur seal, and the leopard seal. Leopard seals are seen are 
far north as the Cook Islands (Rogers, 2002).
    More detailed information on these species is contained in the 
Scripps application, which is available at: http://www.nmfs.noaa.gov/prot_res/PR2/Small_Take/smalltake_info.htm#applications.

Potential Effects on Marine Mammals

    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, 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

[[Page 8773]]

be any TTS in its hearing ability. For transient sounds, the sound 
level necessary to cause TTS is inversely related to the duration of 
the sound. Received sound levels must be even higher for there to be 
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.

Effects of Seismic Surveys on Marine Mammals

    The Scripps' application provides the following information on what 
is known about the effects on marine mammals of the types of seismic 
operations planned by Scripps. The types of effects considered here are 
(1) tolerance, (2) masking of natural sounds, (2) behavioral 
disturbance, and (3) potential hearing impairment and other non-
auditory physical effects (Richardson et al., 1995). Given the 
relatively small size of the airguns planned for the present project, 
the effects are anticipated to be considerably less than would be the 
case with a large array of airguns. Scripps and NMFS believe it is very 
unlikely that there would be any cases of temporary or especially 
permanent hearing impairment, or non-auditory physical effects. Also, 
behavioral disturbance is expected to be limited to distances less than 
500 m (1640 ft), the zone calculated for 160 dB or the onset of Level B 
harassment. Additional discussion on species-specific effects can be 
found in the Scripps application.

Tolerance

    Numerous studies (referenced in Scripps, 2004) have shown that 
pulsed sounds from airguns are often readily detectable in the water at 
distances of many kilometers, but that marine mammals at distances more 
than a few kilometers from operating seismic vessels often show no 
apparent response. That is often true even in cases when the pulsed 
sounds must be readily audible to the animals based on measured 
received levels and the hearing sensitivity of that mammal group. 
However, most measurements of airgun sounds that have been reported 
concerned sounds from larger arrays of airguns, whose sounds would be 
detectable farther away than that planned for use in the proposed 
survey. Although various baleen whales, toothed whales, and pinnipeds 
have been shown to react behaviorally to airgun pulses under some 
conditions, at other times mammals of all three types have shown no 
overt reactions. In general, pinnipeds and small odontocetes seem to be 
more tolerant of exposure to airgun pulses than are baleen whales. 
Given the relatively small and low-energy airgun source planned for use 
in this project, mammals are expected to tolerate being closer to this 
source than would be the case for a larger airgun source typical of 
most seismic surveys.

Masking

    Masking effects of pulsed sounds (even from large arrays of 
airguns) on marine mammal calls and other natural sounds are expected 
to be limited (due in part to the small size of the GI airguns), 
although there are very few specific data on this. Given the small 
acoustic source planned for use in the SWPO, there is even less 
potential for masking of baleen or sperm whale calls during the present 
research than in most seismic surveys (Scripps, 2004). GI-airgun 
seismic sounds are short pulses generally occurring for less than 1 sec 
every 6-10 seconds or so. The 6-10 sec spacing corresponds to a shot 
interval of approximately 21.5-36 m (71-118 ft). Sounds from the multi-
beam sonar are very short pulses, occurring for 7-20 msec once every 2 
to 22 sec, depending on water depth.
    Some whales are known to continue calling in the presence of 
seismic pulses. Their calls can be heard between the seismic pulses 
(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). Given the 
relatively small source planned for use during this survey, there is 
even less potential for masking of sperm whale calls during the present 
study than in most seismic surveys. 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 and the 
relatively low source level of the airguns to be used in the SWPO. 
Also, the sounds important to small odontocetes 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 low frequencies 
are mainly used by mysticetes, but generally 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 marine mammal signal. If little or no overlap occurs 
between the industrial noise and the frequencies used, as in the case 
of many marine mammals relative to 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; as reviewed in 
Richardson et al., 1995). 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, pre-
adaptation to tolerate some masking by natural sounds (Richardson et 
al., 1995) and the relatively low-power acoustic sources being used in 
this survey, would all reduce the importance of masking marine mammal 
vocalizations.

Disturbance by Seismic Surveys

    Disturbance includes a variety of effects, including subtle changes 
in behavior, more conspicuous dramatic changes in activities, and 
displacement. 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 rise to the level of a disruption of 
a behavioral pattern. However, if a sound source would displace marine 
mammals from an important feeding or breeding area, such a disturbance 
may constitute Level B harassment under the MMPA. Given the many 
uncertainties in predicting the quantity and types of impacts of noise 
on marine mammals, it is appropriate to resort to estimating how many 
mammals may be present within a particular distance of industrial

[[Page 8774]]

activities or exposed to a particular level of industrial sound. With 
the possible exception of beaked whales, NMFS believes that this is a 
conservative approach and likely overestimates the numbers of marine 
mammals that are affected in some biologically important manner.
    The sound exposure criteria used to estimate how many marine 
mammals might be harassed behaviorally by the seismic survey are based 
on behavioral observations during studies of several species. However, 
information is lacking for many species. Detailed information on 
potential disturbance effects on baleen whales, toothed whales, and 
pinnipeds can be found in Scripps's SWPO application and its Appendix 
A.

Hearing Impairment and Other Physical Effects

    Temporary or permanent hearing impairment is a possibility when 
marine mammals are exposed to very strong sounds, but there has been no 
specific documentation of this for marine mammals exposed to airgun 
pulses. Based on current information, NMFS precautionarily sets 
impulsive sounds equal to or greater than 180 and 190 dB re 1 microPa 
(rms) as the exposure thresholds for onset of Level A harassment for 
cetaceans and pinnipeds, respectively (NMFS, 2000). Those criteria have 
been used in setting the safety (shut-down) radii for seismic surveys. 
As discussed in the Scripps application and summarized here.
    1. The 180-dB criterion for cetaceans is probably quite 
precautionary, i.e., lower than necessary to avoid TTS let alone 
permanent auditory injury, at least for delphinids.
    2. 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 TTS.
    3. The level associated with the onset of TTS is considered to be a 
level below which there is no danger of permanent damage.
    Because of the small size of the two 45 in\3\ GI-airguns, along 
with the planned monitoring and mitigation measures, there is little 
likelihood that any marine mammals will be exposed to sounds 
sufficiently strong to cause even the mildest (and reversible) form of 
hearing impairment. Several aspects of the planned monitoring and 
mitigation measures for this project are designed to detect marine 
mammals occurring near the 2 GI-airguns (and bathymetric sonar), and to 
avoid exposing them to sound pulses that might (at least in theory) 
cause hearing impairment. In addition, research and monitoring studies 
on gray whales, bowhead whales and other cetacean species indicate that 
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 theoretically might 
occur in mammals close to a strong sound source 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. However, Scripps 
and NMFS believe that it is especially unlikely that any of these non-
auditory effects would occur during the proposed survey given the small 
size of the acoustic sources, the brief duration of exposure of any 
given mammal, and the planned mitigation and monitoring measures. The 
following paragraphs discuss the possibility of TTS, permanent 
threshold shift (PTS), and non-auditory physical effects.

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. Richardson et al. (1995) note that the magnitude of TTS 
depends on the level and duration of noise exposure, among other 
considerations. For sound exposures at or somewhat above the TTS 
threshold, hearing sensitivity recovers rapidly after exposure to the 
noise ends. Little data on sound levels and durations necessary to 
elicit mild TTS have been obtained for marine mammals.
    For toothed whales exposed to single short pulses, the TTS 
threshold appears to be, to a first approximation, a function of the 
energy content of the pulse (Finneran et al., 2002). Given the 
available data, the received level of a single seismic pulse might need 
to be on the order of 210 dB re 1 microPa rms (approx. 221 226 dB pk 
pk) in order to produce brief, mild TTS. Exposure to several seismic 
pulses at received levels near 200 205 dB (rms) might result in slight 
TTS in a small odontocete, assuming the TTS threshold is (to a first 
approximation) a function of the total received pulse energy (Finneran 
et al., 2002). Seismic pulses with received levels of 200 205 dB or 
more are usually restricted to a zone of no more than 100 m (328 ft) 
around a seismic vessel operating a large array of airguns. Because of 
the small airgun source planned for use during this project, such sound 
levels would be limited to distances within a few meters directly 
astern of the Melville.
    There are no data, direct or indirect, on levels or properties of 
sound that are required to induce TTS in any baleen whale. However, TTS 
is not expected to occur during this survey given the small size of the 
source limiting these sound pressure levels to the immediate proximity 
of the vessel, and the strong likelihood that baleen whales would avoid 
the approaching airguns (or vessel) before being exposed to levels high 
enough for there to be any possibility of TTS.
    TTS thresholds for pinnipeds exposed to brief pulses (single or 
multiple) have not been measured, although exposures up to 183 dB re 1 
microPa (rms) have been shown to be insufficient to induce TTS in 
California sea lions (Finneran et al., 2003). However, prolonged 
exposures show that some pinnipeds may incur TTS at somewhat lower 
received levels than do small odontocetes exposed for similar durations 
(Kastak et al., 1999; Ketten et al., 2001; Au et al., 2000). For this 
research cruise therefore, TTS is unlikely for pinnipeds.
    A marine mammal within a zone of less than 100 m (328 ft) around a 
typical large array of operating airguns might be exposed to a few 
seismic pulses with levels of [gteqt]205 dB, and possibly more pulses 
if the mammal moved with the seismic vessel. Also, around smaller 
arrays, such as the 2 GI-airgun array proposed for use during this 
survey, a marine mammal would need to be even closer to the source to 
be exposed to levels greater than or equal to 205 dB. However, as noted 
previously, most cetacean species tend to avoid operating airguns, 
although not all individuals do so. In addition, ramping up airgun 
arrays, which is now standard operational protocol for U.S. and some 
foreign seismic operations, should allow cetaceans to move away from 
the seismic source and to avoid being exposed to the full acoustic 
output of the airgun array. Even with a large airgun array, it is 
unlikely that these cetaceans would be exposed to airgun pulses at a 
sufficiently high level for a sufficiently long period to cause more 
than mild TTS, given the relative

[[Page 8775]]

movement of the vessel and the marine mammal. However, with a large 
airgun array, TTS would be more likely in any odontocetes that bow-ride 
or otherwise linger near the airguns. While bow-riding, odontocetes 
would be at or above the surface, and thus not exposed to strong sound 
pulses given the pressure-release effect at the surface. However, bow-
riding animals generally dive below the surface intermittently. If they 
did so while bow-riding near airguns, they would be exposed to strong 
sound pulses, possibly repeatedly. During this project, the anticipated 
180-dB distance is less than 54 m (177 ft), the array is towed 21 m (69 
ft) behind the Melville and the bow of the Melville will be 106 m (348 
ft) ahead of the airguns and the 205-dB zone would be less than 50 m 
(165 ft). Thus, TTS would not be expected in the case of odontocetes 
bow riding during airgun operations and if some cetaceans did incur TTS 
through exposure to airgun sounds, it would very likely be a temporary 
and reversible phenomenon.
    NMFS believes that, to avoid Level A harassment, cetaceans should 
not be exposed to pulsed underwater noise at received levels exceeding 
180 dB re 1 microPa (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 Scripps during this activity are summarized 
in Table 1 in this document. It has also 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. 
Because of the slow ship speed, 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, as mentioned previously, ramping up the airgun array, 
which has become standard operational protocol for many seismic 
operators including Scripps, should allow cetaceans to move away from 
the seismic source and to avoid being exposed to the full acoustic 
output of the GI airguns.

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. Although there is no specific evidence that 
exposure to pulses of airgun sounds can cause PTS in any marine 
mammals, even with the largest airgun arrays, physical damage to a 
mammal's hearing apparatus can potentially 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 are not indicative of 
permanent auditory damage in terrestrial 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). 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. The low-to-moderate levels of TTS that have been induced in 
captive odontocetes and pinnipeds during recent controlled studies of 
TTS have been confirmed to be temporary, with no measurable residual 
PTS (Kastak et al., 1999; Schlundt et al., 2000; Finneran et al., 2002; 
Nachtigall et al., 2003). In terrestrial mammals, the received sound 
level from a single non-impulsive sound exposure must be far above the 
TTS threshold for any risk of permanent hearing damage (Kryter, 1994; 
Richardson et al., 1995). For impulse sounds with very rapid rise times 
(e.g., those associated with explosions or gunfire), a received level 
not greatly in excess of the TTS threshold may start to elicit PTS. 
Rise times for airgun pulses are rapid, but less rapid than for 
explosions.
    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 odontocetes for exposure to a series of seismic 
pulses may be on the order of 220 dB re 1 microPa (pk-pk) 
(approximately 204 dB re 1 microPa rms), then the PTS threshold might 
be about 240 dB re 1 microPa (pk-pk). 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; 
Caldwell and Dragoset, 2000). However, 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 from the source. 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. In summary, it is highly unlikely that marine mammals could 
receive sounds strong enough (and over a sufficient period of time) to 
cause permanent hearing impairment during this project. In the proposed 
project marine mammals are unlikely to be exposed to received levels of 
seismic pulses strong enough to cause TTS, and because of the higher 
level of sound necessary to cause PTS, it is even less likely that PTS 
could occur. This is due to the fact that even levels immediately 
adjacent to the 2 GI-airguns may not be sufficient to induce PTS 
because the mammal would not be exposed to more than one strong pulse 
unless it swam alongside an airgun for a period of time.

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. While 
there is no documented evidence that airgun arrays can cause serious

[[Page 8776]]

injury, death, or stranding, the association of strandings of beaked 
whales with naval exercises and an L-DEO seismic survey in 2002 have 
raised the possibility that beaked whales may be especially susceptible 
to injury and/or stranding when exposed to strong pulsed sounds. 
Information on recent beaked whale strandings may be found in Appendix 
A of the Scripps application and in several previous Federal Register 
documents (see 69 FR 31792 (June 7, 2004) or 69 FR 34996 (June 23, 
2004)).
    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 physical 
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 September, 
2002 stranding of two Cuvier's beaked whales in the Gulf of California 
(Mexico) when a seismic survey by the 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 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 this sonar had much less 
potential than 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 when conducting seismic surveys in areas 
occupied by beaked whales. However, the present project will involve a 
much smaller sound source than used in typical seismic surveys. 
Considering this and the required monitoring and mitigation measures, 
any possibility for strandings and mortality is expected to be 
eliminated.

Non-auditory Physiological Effects

    Possible types of non-auditory physiological effects or injuries 
that might theoretically occur in marine mammals exposed to strong 
underwater sound might include stress, neurological effects, bubble 
formation, resonance effects, and other types of organ or tissue 
damage. There is no evidence that any of these effects occur in marine 
mammals exposed to sound from airgun arrays (even large ones). 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 might be exposed 
at close range for unusually long periods.
    It is doubtful that any single marine mammal would be exposed to 
strong seismic sounds for sufficiently long that significant 
physiological stress would develop. That is especially so in the case 
of the present project where the airguns are small, the ship's speed is 
relatively fast (7 knots or approximately 13 km/h), and for the most 
part the survey lines are widely spaced with little or no overlap.
    Gas-filled structures in marine animals have an inherent 
fundamental resonance frequency. If stimulated at that frequency, the 
ensuing resonance could cause damage to the animal. There may also 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 workshop (Gentry [ed.] 2002) was held to discuss whether the 
stranding of beaked whales in the Bahamas in 2000 (Balcomb and 
Claridge, 2001; NOAA and USN, 2001) 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.
    Until recently, it was assumed that diving marine mammals are not 
subject to the bends or air embolism. However, a short paper concerning 
beaked whales stranded in the Canary Islands in 2002 suggests that 
cetaceans might be subject to decompression injury in some situations 
(Jepson et al., 2003). If so, that might occur if they ascend unusually 
quickly when exposed to aversive sounds. However, the interpretation 
that the effect was related to decompression injury is unproven 
(Piantadosi and Thalmann, 2004; Fernandez et al., 2004). Even if that 
effect can occur during exposure to mid-frequency sonar, there is no 
evidence that this type of effect occurs in response to low-frequency 
airgun sounds. It is especially unlikely in the case of this project 
involving only two small GI-airguns.
    In summary, little is known about the potential for seismic survey 
sounds to cause either auditory impairment or other non-auditory 
physical effects in marine mammals. Available data suggest that such 
effects, if they occur at all, would be limited to short distances 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. Also, the planned mitigation and 
monitoring measures are expected to minimize any possibility of serious 
injury, mortality or strandings.

Possible Effects of Mid-frequency Sonar Signals

    A multi-beam bathymetric sonar (Sea Beam 2000, 12 kHz) and a sub-
bottom profiler will be operated from the source vessel essentially 
continuously during the planned survey. Details about these sonars were 
provided previously in this document.
    Navy sonars that have been linked to avoidance reactions and 
stranding of cetaceans generally (1) are more powerful than the Sea 
Beam 2000 sonar, (2) have a longer pulse duration, and (3) are directed 
close to horizontally (vs. downward for the Sea Beam 2000). The area of 
possible influence of the Sea Beam 2000 is much smaller-a narrow band 
oriented in the cross-track

[[Page 8777]]

direction below the source vessel. Marine mammals that encounter the 
Sea Beam 2000 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 and vessel speed. Therefore, as harassment or injury from pulsed 
sound is a function of total energy received, the actual harassment or 
injury threshold for the bathymetric sonar signals (approximately 10 
ms) would be at a much higher dB level than that for longer duration 
pulses such as seismic signals. As a result, NMFS believes that marine 
mammals are unlikely to be harassed or injured from the multi-beam 
sonar.

Masking by Mid-frequency Sonar Signals

    Marine mammal communications will not be masked appreciably by the 
multi-beam sonar signals or the sub-bottom profiler given the low duty 
cycle and directionality of the sonars 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 from the Sea Beam 2000 sonar 
do not overlap with the predominant frequencies of the calls, which 
would avoid significant masking.
    For the sub-bottom profiler, marine mammal communications will not 
be masked appreciably because of their relatively low power output, low 
duty cycle, directionality (for the profiler), and the brief period 
when an individual mammal may be within the sonar's beam. In the case 
of most odonotocetes, the sonar signals from the profiler do not 
overlap with the predominant frequencies in their calls. In the case of 
mysticetes, the pulses from the pinger do not overlap with their 
predominant frequencies.

Behavioral Responses Resulting from Mid-frequency Sonar Signals

    Behavioral reactions of free-ranging marine mammals to military and 
other sonars appear to vary by species and circumstance. Observed 
reactions have included silencing and dispersal by sperm whales 
(Watkins et al., 1985), increased vocalizations and no dispersal by 
pilot whales (Rendell and Gordon, 1999), and the previously-mentioned 
strandings by beaked whales. Also, Navy personnel have described 
observations of dolphins bow-riding adjacent to bow-mounted mid-
frequency sonars during sonar transmissions. However, all of these 
observations are of limited relevance to the present situation. Pulse 
durations from these sonars were much longer than those of the Scripps 
multi-beam sonar, and a given mammal would have received many pulses 
from the naval sonars. During Scripps' operations, the individual 
pulses will be very short, and a given mammal would not receive many of 
the downward-directed pulses as the vessel passes by.
    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 Scripps and 
to shorter broadband pulsed signals. Behavioral changes typically 
involved what appeared to be deliberate attempts to avoid the sound 
exposure (Schlundt et al., 2000; Finneran et al., 2002). The relevance 
of these data to free-ranging odontocetes is uncertain and in any case 
the test sounds were quite different in either duration or bandwidth as 
compared to those from a bathymetric sonar.
    Scripps and NMFS are not aware of any data on the reactions of 
pinnipeds to sonar sounds at frequencies similar to those of the 12.0 
kHz frequency of the Melville's multi-beam sonar. Based on observed 
pinniped responses to other types of pulsed sounds, and the likely 
brevity of exposure to the bathymetric sonar sounds, pinniped reactions 
are expected to be limited to startle or otherwise brief responses of 
no lasting consequences to the individual animals. The pulsed signals 
from the sub-bottom profiler are much weaker than those from the multi-
beam sonar and somewhat weaker than those from the 2 GI-airgun array. 
Therefore, significant behavioral responses are not expected.

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 on Marine Mammals). However, the multi-beam sonars 
proposed for use by Scripps are quite different than sonars used for 
navy operations. Pulse duration of the bathymetric sonars 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 beam-width. (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. Therefore, hearing impairment 
by multi-beam bathymetric sonar is unlikely.
    Source levels of the sub-bottom profiler are much lower than those 
of the airguns and the multi-beam sonar. Sound levels from a sub-bottom 
profiler similar to the one on the Melville were estimated to decrease 
to 180 dB re 1 microPa (rms) at 8 m (26 ft) horizontally from the 
source (Burgess and Lawson, 2000), and at approximately 18 m downward 
from the source. Furthermore, received levels of pulsed sounds that are 
necessary to cause temporary or especially permanent hearing impairment 
in marine mammals appear to be higher than 180 dB (see earlier 
discussion). Thus, it is unlikely that the sub-bottom profiler produces 
pulse levels strong enough to cause hearing impairment or other 
physical injuries even in an animal that is (briefly) in a position 
near the source.
    The sub-bottom profiler is usually operated simultaneously with 
other higher-power acoustic sources. Many marine mammals will move away 
in response to the approaching higher-power sources or the vessel 
itself before the mammals would be close enough for there to be any 
possibility of effects from the less intense sounds from the sub-bottom 
profiler. In the case of mammals that do not avoid the approaching 
vessel and its various sound sources, mitigation measures that would be 
applied to minimize effects of the higher-power sources would further 
reduce or eliminate any minor effects of the sub-bottom profiler.

Estimates of Take by Harassment for the SWPO Seismic Survey

    Given the proposed mitigation (see Mitigation later in this 
document), all anticipated takes involve a temporary change in behavior 
that may constitute Level B harassment. The proposed mitigation 
measures will minimize or eliminate the possibility of Level A 
harassment or mortality. Scripps has calculated the ``best estimates'' 
for the numbers of animals that could be taken by level B harassment 
during the proposed SWPO seismic survey using data on marine mammal 
density (numbers per unit area) and estimates of the size of the 
affected area, as shown in the predicted RMS radii table (see Table 1). 
Because there is very little information on marine mammal densities in 
the proposed survey area, densities were used from two of Longhurst's 
(1998) biogeographic provinces north of the survey area that are 
oceanographically similar to the two

[[Page 8778]]

provinces in which most of the seismic activities will take place.
    These estimates are based on a consideration of the number of 
marine mammals that might be exposed to sound levels greater than 160 
dB, the criterion for the onset of Level B harassment, by operations 
with the 2 GI-gun array planned to be used for this project. The 
anticipated zone of influence of the multi-beam sonar and sub-bottom 
profiler are less than that for the airguns, so it is assumed that 
during simultaneous operations of these instruments that any marine 
mammals close enough to be affected by the multi-beam and sub-bottom 
profiler sonars would already be affected by the airguns. Therefore, no 
additional incidental takings are included for animals that might be 
affected by the multi-beam sonar. Given their characteristics 
(described previously), no Level B harassment takings are considered 
likely when the multi-beam and sub-bottom profiler are operating but 
the airguns are silent.
    Table 2 provides the best estimate of the numbers of each species 
that would be exposed to seismic sounds greater than 160 dB. A detailed 
description on the methodology used by Scripps to arrive at the 
estimates of Level B harassment takes that are provided in Table 2 can 
be found in Scripps's IHA application for the SWPO survey.
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Conclusions

Effects on Cetaceans
    Strong avoidance reactions by several species of mysticetes to 
seismic vessels have been observed at ranges up to 6-8 km (3.2-4.3 nm) 
and occasionally as far as 20-30 km (10.8-16.2 nm) from the source 
vessel when large arrays have been used. However, reactions at the 
longer distances appear to be atypical of most species and situations, 
and to large arrays. Furthermore, if they are encountered, the numbers 
of mysticetes estimated to occur within the 160-dB isopleth in the 
survey area are expected to be low. In addition, the estimated numbers 
presented in Table 2 are considered overestimates of actual numbers for 
three primary reasons. First, because the survey is scheduled for the 
end of the austral summer, some of the mysticetes and some species of 
odontocetes are expected to be present in feeding areas south of the 
survey area. Second, the estimated 160-dB radii used here are probably 
overestimates of the actual 160-dB radii at deep-water sites (Tolstoy 
et al. 2004) such as the SWPO survey area. Third, Scripps plans to use 
smaller GI guns than those on which the radii are based.
    Odontocete reactions to seismic pulses, or at least the reactions 
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 into account the small size and the relatively low sound 
output of the 2 GI-airguns to be used, and the mitigation measures that 
are planned, effects on cetaceans are generally expected to be limited 
to avoidance of a very small area around the seismic operation and 
short-term changes in behavior, falling within the MMPA definition of 
Level B harassment. Furthermore, the estimated numbers of animals 
potentially exposed to sound levels sufficient to cause appreciable 
disturbance are very low percentages of the affected populations.
    Based on the 160-dB criterion, the best estimates of the numbers of 
individual cetaceans that may be exposed to sounds [gteqt]160 dB re 1 
microPa (rms) represent 0 to approximately 0.2 percent of the 
populations of each species that may be encountered in the survey area. 
The assumed population sizes used to calculate the percentages are 
presented in Table 2 of the Scripps application. For species listed as 
endangered under the ESA, the estimates are significantly less than 0.1 
percent of the SWPO population of sperm, humpback, sei, and fin whales; 
probably less than 0.1 percent of southern right whales; and 0.1 
percent of blue whales (Table 2). In the cases of mysticetes, beaked 
whales, and sperm whales, the potential reactions are expected to 
involve no more than small numbers (2-32) of individual cetaceans. The 
sperm whale is the endangered species that is most likely to be 
exposed, and their SWPO population is approximately 140,000 (data of 
Butterworth et al. 1994 with g(0) correction from Barlow (1999) 
applied).
    Larger numbers of delphinids may be affected by the proposed 
seismic study, but the population sizes of species likely to occur in 
the operating area are large, and the numbers potentially affected are 
small relative to the population sizes (see Table 2). The best estimate 
of number of individual delphinids that might be exposed to sounds 160 
dB re 1 microPa (rms) represents significantly less than 0.01 percent 
of the approximately 8,200,000 dolphins estimated to occur in the SWPO, 
and 0-0.2 percent of the populations of each species occurring there 
(Table 2).
    Mitigation measures such as controlled speed, course alteration, 
observers, ramp ups, and power downs or shut downs when marine mammals 
are seen within defined ranges should further reduce short-term 
reactions, and minimize any effects on hearing. In all cases, the 
effects are expected to be short-term, with no lasting biological 
consequence. In light of the type of take expected and the small 
percentages of affected stocks of cetaceans, the action is expected to 
have no more than a negligible impact on the affected species or stocks 
of cetaceans.

Effects on Pinnipeds

    Five pinniped species-the sub-Antarctic fur seal, Antarctic fur 
seal, crabeater seal, leopard seal, and southern elephant seal-may be 
encountered at the survey sites, but their distribution and numbers 
have not been documented in the proposed survey area. An estimated 22-
45 individuals of each species of seal may be exposed to airgun sounds 
with received levels > 160 dB re 1 microPa (rms). The estimates of 
pinnipeds that may be exposed to received levels > 160 dB are probably 
overestimates of the actual numbers that will be affected 
significantly. The proposed survey would have, at most, a short-term 
effect on their behavior and no long-term impacts on individual 
pinnipeds or their populations. 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. As is the 
case for cetaceans, the short-term exposures to sounds from the two GI-
guns are not expected to result in any long-term consequences for the 
individuals or their populations and the activity is expected to have 
no more than a negligible impact on the affected species or stocks of 
pinnipeds.

Potential Effects on Habitat

    The proposed seismic survey will not result in any permanent impact 
on habitats used by marine mammals, or to the food sources they 
utilize. The main impact issue associated with the proposed activity 
will be temporarily elevated noise levels and the associated direct 
effects on marine mammals.
    One of the reasons for the adoption of airguns as the standard 
energy source for marine seismic surveys was that they (unlike the 
explosives used in the distant past) do not result in any appreciable 
fish kill. Various experimental studies showed that airgun discharges 
cause little or no fish kill, and that any injurious effects were 
generally limited to the water within a meter or so of an airgun. 
However, it has recently been found that injurious effects on captive 
fish, especially on fish hearing, may occur at somewhat greater 
distances than previously thought (McCauley et al., 2000a,b, 2002; 
2003). Even so, any injurious effects on fish would be limited to short 
distances from the source. Also, many of the fish that might otherwise 
be within the injury-zone are likely to be displaced from this region 
prior to the approach of the airguns through avoidance reactions to the 
passing seismic vessel or to the airgun sounds as received at distances 
beyond the injury radius.
    Fish often react to sounds, especially strong and/or intermittent 
sounds of low frequency. Sound pulses at received levels of 160 dB re 1 
microPa (peak) may cause subtle changes in behavior. Pulses at levels 
of 180 dB (peak) may cause noticeable changes in behavior (Chapman and 
Hawkins, 1969; Pearson et al., 1992; Skalski et al., 1992). It also 
appears that fish often habituate to repeated strong sounds rather 
rapidly, on time scales of minutes to an hour. However, the habituation 
does not endure, and resumption of the

[[Page 8781]]

disturbing activity may again elicit disturbance responses from the 
same fish.
    Fish near the airguns are likely to dive or exhibit some other kind 
of behavioral response. This might have short-term impacts on the 
ability of cetaceans to feed near the survey area. However, only a 
small fraction of the available habitat would be ensonified at any 
given time, and fish species would return to their pre-disturbance 
behavior once the seismic activity ceased. Thus, the proposed surveys 
would have little impact on the abilities of marine mammals to feed in 
the area where seismic work is planned. Some of the fish that do not 
avoid the approaching airguns (probably a small number) may be subject 
to auditory or other injuries.
    Zooplankton that are very close to the source may react to the 
airgun's shock wave. These animals have an exoskeleton and no air sacs; 
therefore, little or no mortality is expected. Many crustaceans can 
make sounds and some crustacea and other invertebrates have some type 
of sound receptor. However, the reactions of zooplankton to sound are 
not known. Some mysticetes feed on concentrations of zooplankton. A 
reaction by zooplankton to a seismic impulse would only be relevant to 
whales if it caused a concentration of zooplankton to scatter. Pressure 
changes of sufficient magnitude to cause this type of reaction would 
probably occur only very close to the source, so few zooplankton 
concentrations would be affected. Impacts on zooplankton behavior are 
predicted to be negligible, and this would translate into negligible 
impacts on feeding mysticetes.

Potential Effects on Subsistence Use of Marine Mammals

    There is no known legal subsistence hunting for marine mammals in 
the SWPO, so the proposed Scripps activities will not have any impact 
on the availability of these species or stocks for subsistence users.

Mitigation

    For the proposed seismic survey in the SWPO during February-March 
2005, Scripps will deploy 2-GI airguns as an energy source, with a 
total discharge volume of 90 in\3\. The energy from the airguns will be 
directed mostly downward. The directional nature of the airguns to be 
used in this project is an important mitigating factor. This 
directionality will result in reduced sound levels at any given 
horizontal distance as compared with the levels expected at that 
distance if the source were omnidirectional with the stated nominal 
source level. Also, the small size of these airguns is an inherent and 
important mitigation measure that will reduce the potential for effects 
relative to those that might occur with large airgun arrays. This 
measure is in conformance with NMFS encouraging seismic operators to 
use the lowest intensity airguns practical to accomplish research 
objectives.
    The following mitigation measures, as well as marine mammal visual 
monitoring (discussed later in this document), will be implemented for 
the subject seismic surveys: (1) Speed and course alteration (provided 
that they do not compromise operational safety requirements); (2) shut-
down procedures; and (3) ramp-up procedures. Because the safety radius 
for cetaceans is only 54 m (177 ft) the use of passive acoustics to 
detect vocalizing marine mammals is not warranted for this survey. 
Similarly, and because the Melville will be transiting a distance of 
approximately 11,000 km (5940 nm) during the survey period at a speed 
of approximately 7 knots, aerial and secondary vessel support is not 
warranted.

Speed and Course Alteration

    If a marine mammal is detected outside its respective safety zone 
(180 dB for cetaceans, 190 dB for pinnipeds) and, based on its position 
and the relative motion, is likely to enter the safety zone, the 
vessel's speed and/or direct course may, when practical and safe, 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 zone. If the mammal 
appears likely to enter the safety zone, further mitigative actions 
will be taken (i.e., either further course alterations or shut-down of 
the airguns).

Shut-down Procedures

    If a marine mammal is detected outside the safety radius but is 
likely to enter the safety radius, and if the vessel's course and/or 
speed cannot be changed to avoid having the animal enter the safety 
radius, the airguns will be shut down before the animal is within the 
safety radius. Likewise, if a marine mammal is already within the 
safety radius when first detected, the airguns will be shut down 
immediately.
    Following a shut-down, airgun activity will not resume until the 
marine mammal has cleared the safety zone. The animal will be 
considered to have cleared the safety zone if it (1) is visually 
observed to have left the safety zone, or (2) has not been seen within 
the zone for 15 min in the case of small odontocetes and pinnipeds, or 
(3) has not been seen within the zone for 30 min in the case of 
mysticetes and large odontocetes, including sperm, pygmy sperm, dwarf 
sperm, bottlenose and beaked whales.

Ramp-up Procedure

    A ``ramp-up'' procedure will be followed when the airguns begin 
operating after a period without airgun operations. The 2-GI guns will 
be added in sequence 5 minutes apart. During ramp-up procedures, the 
safety radius for the 2-GI guns will be maintained.
    During the day or night, ramp-up cannot begin from a shut-down 
unless the entire 180-dB safety radius has been visible for at least 30 
minutes prior to the ramp up (i.e., no ramp-up can begin in heavy fog 
or high sea states). During nighttime operations, if the entire safety 
radius is visible using either vessel lights or night-vision devices 
(NVDs), then start up of the airguns from a shut down may occur. 
Considering that the safety zone will be an area approximately from 
mid-ship sternward to the area of the hydrophone streamer and extending 
only about 46 m ( ft) beyond the vessel, NMFS believes that either deck 
lighting or NVDs will be capable of locating any marine mammal that 
might enter the safety zone at night.
    Comments on past IHAs raised the issue of prohibiting nighttime 
operations as a practical mitigation measure. However, this is not 
practicable due to cost considerations and ship time schedules. The 
daily cost to the federal government to operate vessels such as 
Melville is approximately $33,000-$35,000 /day (Ljunngren, pers. comm. 
May 28, 2003). If the vessels were prohibited from operating during 
nighttime, each trip could require an additional three to five days to 
complete, or up to $175,000 more, depending on average daylight at the 
time of work.
    If a seismic survey vessel is limited to daylight seismic 
operations, efficiency would also be much reduced. Without commenting 
specifically on how that would affect the present project, for seismic 
operators in general, a daylight-only requirement would be expected to 
result in one or more of the following outcomes: cancellation of 
potentially valuable seismic surveys; reduction in the total number of 
seismic cruises annually due to longer cruise durations; a need for 
additional vessels to conduct the seismic operations; or work conducted 
by non-U.S. operators or non-U.S. vessels when in waters not subject to 
U.S. law.

[[Page 8782]]

Marine Mammal Monitoring

    Scripps must have at least two visual observers on board the 
Melville, and at least one must be an experienced marine mammalsw 
observer that NMFS has approved in advance of the start of the PO 
cruise. These observers will be on duty in shifts of no longer than 4 
hours.
    The visual observers will monitor marine mammals and sea turtles 
near the seismic source vessel during all daytime airgun operations, 
during any nighttime start-ups of the airguns and at night. During 
daylight, vessel-based observers will watch for marine mammals and sea 
turtles near the seismic vessel during periods with shooting (including 
ramp-ups), and for 30 minutes prior to the planned start of airgun 
operations after a shut-down. NMFS has determined that a monitoring 
requirement for observers to be on watch at night whenever daytime 
monitoring resulted in one or more shut-down situations due to marine 
mammal presence is not warranted for this operation since the Melville 
will be transiting the area and not remaining in the area where this 
requirement would provide protection for marine mammals. With a ship 
speed of 7 knots, the Melville may be a number of miles from the marine 
mammal siting/shut-down area by night-time.
    Use of multiple observers will increase the likelihood that marine 
mammals near the source vessel are detected. Scripps bridge personnel 
will also assist in detecting marine mammals and implementing 
mitigation requirements whenever possible (they will be given 
instruction on how to do so), especially during ongoing operations at 
night when the designated observers are on stand-by and not required to 
be on watch at all times. The observer(s) and bridge watch will watch 
for marine mammals from the highest practical vantage point on the 
vessel or from the stern of the vessel, whichever provides the greatest 
total visibility of the safety zone.
    In addition, biological observers are required to record biological 
information on marine mammals sighted outside the safety zone, but 
within the 160-dB isopleth. For this activity, the observer(s) will 
systematically scan the area around the vessel with Big Eyes 
binoculars, reticle binoculars (e.g., 7 X 50 Fujinon) and with the 
naked eye during the daytime. Laser range-finding binoculars (Leica 
L.F. 1200 laser rangefinder or equivalent) will be available to assist 
with distance estimation. The observers will be used to determine when 
a marine mammal or sea turtle is in or near the safety radii so that 
the required mitigation measures, such as course alteration and power-
down or shut-down, can be implemented. If the GI-airguns are shut down, 
observers will maintain watch to determine when the animal is outside 
the safety radius.
    Observers are not required to be on duty during ongoing seismic 
operations at night (although they may do so); bridge personnel will 
watch for marine mammals during this time and will call for the airguns 
to be shut-down if marine mammals are observed in or about to enter the 
safety radii. However, a biological observer must be on standby at 
night and available to assist the bridge watch if marine mammals are 
detected. If the airguns are ramped-up at night (see previous section), 
two marine mammal observers will monitor for marine mammals for 30 
minutes prior to ramp-up and during the ramp-up using either deck 
lighting or NVDs that will be available (ITT F500 Series Generation 3 
binocular image intensifier or equivalent).
    Taking into consideration the additional costs of prohibiting 
nighttime operations and the likely impact of the activity (including 
all mitigation and monitoring), NMFS has determined that the proposed 
mitigation and monitoring ensures that the activity will have the least 
practicable impact on the affected species or stocks. Marine mammals 
will have sufficient notice of a vessel approaching with operating 
seismic airguns, thereby giving them an opportunity to avoid the 
approaching array; if ramp-up is required, two marine mammal observers 
will be required to monitor the safety radii using shipboard lighting 
or NVDs for at least 30 minutes before ramp-up begins and verify that 
no marine mammals are in or approaching the safety radii; ramp-up may 
not begin unless the entire safety radii are visible.

Reporting

    Scripps will submit a report to NMFS within 90 days after the end 
of the cruise, which is currently predicted to occur during February 
and March, 2004. The report will describe the operations that were 
conducted and the marine mammals that were detected. The report must 
provide full documentation of methods, results, and interpretation 
pertaining to all monitoring tasks. The report will summarize the dates 
and locations of seismic operations, 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)

    NMFS has issued a biological opinion regarding the effects of this 
action on ESA-listed species and critical habitat under the 
jurisdiction of NMFS. That biological opinion concluded that this 
action is not likely to jeopardize the continued existence of listed 
species or result in the destruction or adverse modification of 
critical habitat. A copy of the Biological Opinion is available upon 
request (see ADDRESSES).

National Environmental Policy Act (NEPA)

    The NSF made a FONSI determination on September 30, 2004, based on 
information contained within its EA, that implementation of the subject 
action is not a major Federal action having significant effects on the 
environment within the meaning of NEPA. NSF determined, therefore, that 
an environmental impact statement would not be prepared. On December 3, 
2004 (69 FR 70236), NMFS noted that the NSF had prepared an EA for the 
SWPO surveys and made this EA available upon request. In accordance 
with NOAA Administrative Order 216-6 (Environmental Review Procedures 
for Implementing the National Environmental Policy Act, May 20, 1999), 
NMFS has reviewed the information contained in NSF's EA and determined 
that the NSF EA accurately and completely describes the proposed action 
alternative, and the potential impacts on marine mammals, endangered 
species, and other marine life that could be impacted by the preferred 
alternative and the other alternatives. Accordingly, NMFS adopted the 
NSF EA under 40 CFR 1506.3 and made its own FONSI. The NMFS FONSI also 
takes into consideration additional mitigation measures required by the 
IHA that are not in NSF's EA. Therefore, it is not necessary to issue a 
new EA, supplemental EA or an environmental impact statement for the 
issuance of an IHA to L-DEO for this activity. A copy of the EA and the 
NMFS FONSI for this activity is available upon request (see ADDRESSES).

Determinations

    NMFS has determined that the impact of conducting the seismic 
survey in the SWPO off may result, at worst, in a temporary 
modification in behavior by certain species of marine mammals. This 
activity is expected to result in no more than a negligible impact on 
the affected species or stocks.

[[Page 8783]]

    For reasons stated previously in this document, this determination 
is supported by (1) the likelihood that, given sufficient notice 
through slow ship speed and ramp-up, marine mammals are expected to 
move away from a noise source that it is annoying prior to its becoming 
potentially injurious; (2) recent research that indicates that TTS is 
unlikely (at least in delphinids) until levels closer to 200-205 dB re 
1 microPa are reached rather than 180 dB re 1 microPa; (3) the fact 
that 200-205 dB isopleths would be well within a few dozen meters of 
the vessel because of the small acoustic source; and (4) the likelihood 
that marine mammal detection ability by trained observers is close to 
100 percent during daytime and remains high at night to the distance 
from the seismic vessel to the 180-dB isopleth. As a result, no take by 
injury or death is anticipated, and the potential for temporary or 
permanent hearing impairment is very low and will be avoided through 
the incorporation of the proposed mitigation measures mentioned in this 
document.
    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, the proposed seismic 
program will not interfere with any legal subsistence hunts, since 
seismic operations will not take place in subsistence whaling and 
sealing areas and will not affect marine mammals used for subsistence 
purposes.

Authorization

    NMFS has issued an IHA to L-DEO to take marine mammals, by 
harassment, incidental to conducting seismic surveys in the SWPO for a 
1-year period, provided the mitigation, monitoring, and reporting 
requirements are undertaken.

    Dated: February 10, 2005.
Laurie K. Allen,
Director, Office of Protected Resources, National Marine Fisheries 
Service.
[FR Doc. 05-3442 Filed 2-22-05; 8:45 am]
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