[Federal Register Volume 73, Number 86 (Friday, May 2, 2008)]
[Notices]
[Pages 24223-24235]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: E8-9717]


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DEPARTMENT OF COMMERCE

National Oceanic and Atmospheric Administration

RIN 0648-XH14


Incidental Takes of Marine Mammals During Specified Activities; 
Marine Geophysical Surveys in the Eastern Tropical Pacific Ocean in 
2008

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

ACTION:  Notice; issuance of an incidental take authorization.

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SUMMARY:  In accordance with regulations implementing the Marine Mammal 
Protection Act (MMPA), notification is hereby given that an Incidental 
Harassment Authorization to take marine mammals, by Level-B harassment, 
incidental to conducting two marine geophysical surveys by the Lamont-
Doherty Earth Observatory (L-DEO) in the Eastern Tropical Pacific Ocean 
(ETP), has been issued for a period of one year.

DATES:  The authorization is effective from April 24, 2008, until April 
23, 2009.

ADDRESSES:  Copies of the application, IHA, the Environmental 
Assessment of Two Marine Geophysical Surveys by the R/V Marcus G. 
Langseth in the Eastern Tropical Pacific, 2008, prepared for the L-DEO 
and the National Science Foundation (NSF) by the LGL Ltd., and/or a 
list of references used in this document may be obtained by writing to 
P. Michael Payne, Chief, Permits, Conservation and Education Division, 
Office of Protected Resources, National Marine Fisheries Service, 1315 
East-West Highway, Silver Spring, MD 20910-3225, or by telephoning one 
of the contacts listed here (see FOR FURTHER INFORMATION CONTACT).

FOR FURTHER INFORMATION CONTACT:  Shane Guan, Office of Protected 
Resources, NMFS, (301) 713-2289, ext 137.

SUPPLEMENTARY INFORMATION:

Background

    Sections 101(a)(5)(A) and (D) of the MMPA (16 U.S.C. 1361 et seq.) 
direct the Secretary of Commerce to allow, upon request, the 
incidental, but not intentional, taking of marine mammals by U.S. 
citizens who engage in a specified activity (other than commercial 
fishing) within a specified geographical region if certain findings are 
made and either regulations are issued or, if the taking is limited to 
harassment, a notice of a proposed authorization is provided to the 
public for review.
    Authorization shall be granted if NMFS finds that the taking will 
have a negligible impact on the species or stock(s), will not have an 
unmitigable adverse impact on the availability of the species or 
stock(s) for certain subsistence uses, and if the permissible methods 
of taking and requirements pertaining to the mitigation, monitoring and 
reporting of such takings are set forth. NMFS has defined ``negligible 
impact'' in 50 CFR 216.103 as ''...an impact resulting from the 
specified activity that cannot be reasonably expected to, and is not 
reasonably likely to, adversely affect the species or stock through 
effects on annual rates of recruitment or survival.''
    Section 101(a)(5)(D) of the MMPA established an expedited process 
by which citizens of the United States can apply for an authorization 
to incidentally take small numbers of marine mammals by harassment. 
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 authorization 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

    L-DEO submitted to NMFS an application from L-DEO for the taking, 
by Level B harassment, of several species of marine mammals incidental 
to conducting, with research funding from the NSF, two marine seismic 
surveys in the ETP. This project would be conducted with L-DEO's new 
seismic vessel, the R/V Marcus G. Langseth (Langseth), which would 
deploy different configurations of airguns and a different bottom-
mapping sonar than used previously by L-DEO. The first survey was 
planned to be approximately 39 days between September and October 2007, 
and the second one approximately 6 days in between November and 
December 2007. However, due to scheduling issues with the vessel, the 
39-day survey is rescheduled to June and August 2008, and the 6-day 
survey to April and May 2008.

Description of the Specified Activity

    The April-May 6-day survey would examine two important types of 
seismic behavior of the Quebrada, Discovery, and Gofar fault systems 
(QDG) to understand better the behavior of earthquakes and faults in 
general.
    The June-August 39-day survey would obtain seismic reflection 
imaging of the internal structure of the magmatic-hydrothermal system 
at the fast-spreading mid-ocean ridge of the East Pacific Rise (EPR).

[[Page 24224]]

    The seismic surveys will involve one vessel. The source vessel 
Langseth would deploy a 36-airgun array as an energy source. However, 
for the EPR study, two identical two-string sources will be firing 
alternately, so that no more than 18 airguns will be firing at any 
time, with a maximum discharge volume of 3,300 in\3\. The Langseth 
would also tow the receiving system, which consists of four 6-km (3.73-
mi) hydrophone streamers. For the QDG study, no more than 27 airguns 
would be fired at any time, with a maximum discharge volume of 4,950 
in\3\. The Langseth would also tow the receiving system, a single 8-km 
(4.97-mi) streamer, and would also deploy 40 long-term Ocean Bottom 
Seismometers (OBSs) that would be recovered 1 year after deployment, 
and another 8-10 short-term OBSs on each line that will be retrieved 
after the seismic surveys are completed.
    The EPR and QDG programs would consist of a maximum of 
approximately 7,992 km (4,967 mi) and 654 km (406 mi) of surveys, 
respectively.
    The QDG seismic survey would also occur in international waters of 
the ETP, approximately 2,265 km (1,408 mi) off the coast of Ecuador and 
approximately 1,300 km (808 mi) west of the Galapagos Islands. The 
overall area within which the seismic survey would occur is located 
between 3[deg] and 5[deg] S, and between 103[deg] and 106[deg] W. Water 
depths in the survey area are more than 3,000 m (9,843 ft) deep. The 
EPR seismic survey would take place in international waters of the ETP, 
offshore from Mexico and Central America at the East Pacific Rise. The 
closest land mass to this survey is Mexico, located approximately 890 
km (553 mi) away. The overall area within which the seismic survey will 
occur is located between 8.3[deg] and 10.2[deg] N, and between 
104.1[deg] and 104.5[deg] W. The survey would take place in water more 
than 2,000 m (6,562 ft) deep.
    In addition to the operations of the airgun array, a multi-beam 
bathymetric sonar would be operated from the source vessel continuously 
throughout the entire cruise, and a lower-energy sub-bottom profiler 
will also be operated during most of the survey.
    Detailed descriptions of these activities were published in the 
Federal Register on March 5, 2008 (72 FR 11876). No changes have been 
made to these proposed marine geophysical surveys.
    The Langseth would also serve as the platform from which vessel-
based visual marine mammal observers will watch for marine mammals 
before and during airgun operations. The characteristics of the Ewing 
that make it suitable for visual monitoring are described under 
Monitoring, later in this document.

Acoustic Source Specifications

Airguns
    The airgun array to be used will consist of 36 airguns, with 
maximum total discharge volume of approximately 6,600 in\3\. The 
airguns will comprise a mixture of Bolt 1500LL and Bolt 1900LLX 
airguns. The array will consist of four identical linear arrays or 
``strings.'' Each string would have ten airguns; the first and last 
airguns in the strings are spaced 16 m (52.5 ft) apart. Nine airguns 
would be fired simultaneously, while the tenth is kept in reserve as a 
spare, to be turned on in case of failure of another airgun. Two of the 
four strings would be fired during the EPR survey (18 airguns), and 
three strings would be fired during the QDG survey (27 airguns). The 
airgun strings would be distributed across an approximate area of 24 x 
16 m (78.7 x 52.5 ft) behind the Langseth and would be towed 
approximately 50 - 100 m (164 - 328 ft) behind the vessel. The firing 
pressure of the array is 2,000 psi. During firing, a brief (~0.1 s) 
pulse of sound is emitted. During the EPR survey, the shots would be 
emitted at intervals of ~15 s, corresponding to a shot interval of 
~37.5 m (~123 ft). During the QDG survey, the shots would be emitted at 
intervals of ~60 s, corresponding to a shot interval of ~150 m (492 
ft). The airguns would be towed at a depth of 7 m (23 ft) during both 
the QDG and the EPR surveys. The depth at which the source is towed 
affects the maximum near-field output and the shape of its frequency 
spectrum. In deeper water, the effective source level for sound 
propagating in near-horizontal directions is higher than in shallow 
water; however, the nominal source levels of the array at various tow 
depths are nearly identical.
    Because the actual source is a distributed sound source (up to 27 
airguns in these surveys) rather than a single point source, the 
highest sound levels measurable at any location in the water would be 
less than the nominal source level. In addition, the effective source 
level for sound propagating in near-horizontal directions would be 
substantially lower than the nominal source level applicable to 
downward propagation because of the directional nature of the sound 
from the airgun array.
    The specifications of each source planned for use are described in 
Table 1.

------------------------------------------------------------------------
                               18-Airgun Array (2    27-Airgun Array (3
                                    Strings)              Strings)
------------------------------------------------------------------------
Energy Source                 18, 2,000 psi Bolt    27, 2,000 psi Bolt
                               airguns of 40-360     airguns of 40-360
                               in\3\                 in\3\
------------------------------------------------------------------------
Source output (downward)      0-pk: 252 dB re 1     0-pk: 256 dB re 1
                               microPa-m;pk-pk:      microPa-m;pk-pk:
                               259 dB re 1 microPa-  262 dB re 1 microPa-
                               m                     m
------------------------------------------------------------------------
Air discharge volume          Approximately 3,300   Approximately 4,950
                               in\3\                 in\3\
------------------------------------------------------------------------
Towing depth of energy        7 m (23 ft)           7 m (23 ft)
 source
------------------------------------------------------------------------
Dominant frequency            0 - 188 Hz            0 - 188 Hz
 components
------------------------------------------------------------------------
Table 1. L-DEO airgun configuration and specification of each source
  planned for use in the proposed projects.

    A detailed discussion of the characteristics of airgun pulses has 
been provided in L-DEO's application, and in previous Federal Register 
notices (see 69 FR 31792 (June 7, 2004) or 69 FR 34996 (June 23, 
2004)). Reviewers are referred to those documents for additional 
information.
    Received sound levels have been predicted by L-DEO in relation to 
distance and direction from the airguns for the 36-airgun array with 18 
and 27 airguns firing and for a single 1900LL 40-in\3\ airgun, which 
would be used during power downs.
    The predicted sound contours are shown as sound exposure levels 
(SEL) in decibels (dB) re 1 microPa\2\-s. SEL is a measure of the 
received energy in the pulse and represents the sound pressure level 
(SPL) that would be measured if the pulse energy were spread evenly 
across a 1-s period. Because actual

[[Page 24225]]

seismic pulses are less than 1 s in duration, this means that the SEL 
value for a given pulse is lower than the SPL calculated for the actual 
duration of the pulse. The advantage of working with SEL is that the 
SEL measure accounts for the total received energy in the pulse, and 
biological effects of pulsed sounds probably depend mainly on pulse 
energy. SPL for a given pulse depends greatly on pulse duration. A 
pulse with a given SEL can be long or short depending on the extent to 
which propagation effects have ``stretched'' the pulse duration. The 
SPL will be low if the duration is long and higher if the duration is 
short, even though the pulse energy (and presumably the biological 
effects) is the same.
    Although SEL may be a better measure than SPL when dealing with 
biological effects of pulsed sound, SPL is the measure that has been 
most commonly used in studies of marine mammal reactions to airgun 
sounds and in NMFS practice concerning levels above which ``taking'' 
might occur. SPL is often referred to as rms or ``root mean square'' 
pressure, averaged over the pulse duration. As noted above, the rms 
received levels that are used as impact criteria for marine mammals are 
not directly comparable to pulse energy (SEL). The SPL (i.e., rms sound 
pressure) for a given pulse is typically 10 - 15 dB higher than the SEL 
value for the same pulse as measured at the same location (Greene et 
al., 1997; McCauley et al., 1998; 2000). For this project, L-DEO 
assumes that rms pressure levels of received seismic pulses would be 10 
dB higher than the SEL values predicted by L-DEO's model. Thus, the L-
DEO assumes that 170 dB SEL can be viewed as 180 dB rms. NMFS considers 
that this assumption is valid.
    It should be noted that neither the SEL nor the SPL (rms) measure 
is directly comparable to the peak or peak-to-peak pressure levels 
normally used by geophysicists to characterize source levels of 
airguns. Peak and peak-to-peak pressure levels for airgun pulses are 
always higher than the rms dB referred to in much of the biological 
literature (Greene et al., 1997; McCauley et al., 1998; 2000). For 
example, a measured received level of 160 dB rms in the far field would 
typically correspond to a peak measurement of 170 - 172 dB re 1 
microPa, and to a peak-to-peak measurement of 176 - 178 dB, as measured 
for the same pulse received at the same location (Greene et al., 1997; 
McCauley et al., 1998; 2000). The precise difference between rms and 
peak or peak-to-peak values for a given pulse depends on the frequency 
content and duration of the pulse, among other factors. However, the 
rms level is always lower than the peak or peak-to-peak level, and 
higher than the SEL value, for an airgun-type source.
    Empirical data concerning 190, 180, 170, and 160 dB (rms) isopleths 
in deep and shallow water were acquired for various airgun 
configurations during the acoustic calibration study of the Ewing's 20-
airgun, 8,600-in\3\ array in 2003 (Tolstoy et al., 2004a; 2004b). The 
results showed that radii around the airguns where the received level 
was 180 dB re 1 microPa (rms), the onset point for estimating temporary 
hearing threshold shift (TTS) in cetaceans (NMFS, 2000), varied with 
water depth. Similar depth-related variation is likely for 190-dB, the 
onset point used for estimating TTS in pinnipeds, although these were 
not measured. The empirical data indicated that, for deep water (>1,000 
m, or 3,280 ft), the L-DEO model overestimates the received sound 
levels at a given distance (Tolstoy et al., 2004a; 2004b). However, to 
be conservative, the Ewing's modeled distances would be applied to 
deep-water areas during the proposed study. As very few, if any, 
mammals are expected to occur below 2,000 m (6,562 ft), this depth was 
used as the maximum relevant depth.
    For the proposed programs in the ETP, the modeled distances are 
used to estimate deep-water mitigation safety zones; no correction 
factors are necessary because all activities will take place in deep 
(>2,000 m, or 6,562 ft) water. The 180 and 190 dB re 1 microPa (rms) 
distances define the safety criteria, used for mitigation for cetaceans 
and pinnipeds, respectively.
    The predicted distances to which sound levels higher than 190, 180, 
and 160 dB re 1 microPa (rms) could be received, based on the model 
calculation, are shown in Table 2.

--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                                  Predicted RMS Radii (m)
--------------------------------------------------------------------------------------------------------------------------------------------------------
          Source and Volume                 Min. Water Depth                  190 dB                       160 dB                       180 dB
--------------------------------------------------------------------------------------------------------------------------------------------------------
Single Bolt airgun (40 in\3\)         3000 m                       12                           40                           385
--------------------------------------------------------------------------------------------------------------------------------------------------------
36-airgun array: 3 strings (4950      3000 m                       200                          650                          4400
 in\3\)
--------------------------------------------------------------------------------------------------------------------------------------------------------
36-airgun array: 2 strings (3300      2000 m                       140                          450                          3800
 in\3\)
--------------------------------------------------------------------------------------------------------------------------------------------------------
Table 2. Predicted distances to which sound levels higher than 190, 180, and 160 dB re 1 microPa (rms) could be received from the airgun array and
  single airgun planned for use during the surveys in the ETP.

Bathymetric Sonar and Sub-bottom Profiler
    Along with the airgun operations, two additional acoustical data 
acquisition systems would be operated during parts of the Langseth's 
cruises. The ocean floor would be mapped with the 12-kHz Kongsberg 
Simrad EM 120 MBB sonar, and a 2.5 - 7 kHz sub-bottom profiler would 
also be operated along with the MBB sonar. These sound sources would be 
operated from the Langseth, at times simultaneously with the airgun 
array.
    The Kongsberg Simrad EM 120 operates at 11.25 - 12.6 kHz and would 
be mounted in a sonar pod hung below the hull of the Langseth. The 
beamwidth is 1o fore-aft and 150[deg] athwartship. The maximum source 
level is 242 dB re 1 microPa at 1 m (rms). For deep-water operation, 
each ``ping'' consists of nine successive fan-shaped transmissions, 
each 15 ms in duration and each ensonifying a sector that extends 
1[deg] fore-aft. The nine successive transmissions span an overall 
cross-track angular extent of about 150[deg], with 16 ms gaps between 
the pulses for successive sectors. A receiver in the overlap area 
between two sectors would receive two 15-ms pulses separated by a 16-ms 
gap. In shallower water, the pulse duration is reduced to 2 ms, and the 
number of transmit beams is also reduced. The ping interval varies with 
water depth, from ~5 s at 1,000 m (3,280 ft) to 20 s at 4,000 m (13,123 
ft).
    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 MBB sonar. The energy from the sub-
bottom profiler is directed

[[Page 24226]]

downward by a 3.5-kHz transducer in the hull of the Langseth. The 
output varies with water depth from 50 watts in shallow water to 800 
watts in deep water. Pulse interval is 1 second but a common mode of 
operation is to broadcast five pulses at 1-s intervals followed by a 5-
s pause.

Comments and Responses

    A notice of receipt and request for public comment on the 
application and proposed authorization was published on March 5, 2008 
(73 FR 11874). During the 30-day public comment period, NMFS received 
the following comments from the Marine Mammal Commission (Commission).
    Comment 1: The Commission recommends to extend to one hour the 
monitoring period imposed prior to the initiation of seismic activities 
and resumption of airgun activities after a power-down.
    Response: NMFS acknowledges that several species of deep-diving 
cetaceans are capable of remaining underwater for more than 30 minutes. 
However, for the following reasons, NMFS believes that 30 minutes is an 
adequate duration for the monitoring period prior to the start-up of 
airguns: (1) because the Langseth is required to ramp-up, the time of 
monitoring prior to start-up of any but the smallest array is 
effectively longer than 30 minutes (i.e., ramp-up will begin with the 
smallest gun in the array and airguns will be added in a sequence such 
that the source level of the array will increase in steps not exceeding 
approximately 6 dB per 5-min period over a total duration of 20-40 
min); (2) L-DEO decides to conduct marine mammal monitoring during 
transient even though the airguns are not in operation, so that all 
safety redii will be under monitoring prior to the 30-min observation 
period anyway; and (3) the majority of the species that may be exposed 
do not stay underwater more than 30 minutes.
    Comment 2: The Commission recommends that NMFS require marine 
mammal monitoring be made during all ramp-up procedures to gather data 
regarding the effectiveness of ramp-up as a mitigation tool.
    Response: NMFS concurs with the Commission's recommendation that 
all ramp-up procedures will be visually monitored when visibility 
permits. For ramp-up during low-light hours, visual monitoring is 
ineffective, nonetheless, passive acoustic monitoring will be 
implemented during all ramp-up procedures.

Description of Marine Mammals in the Activity Area

    A total of 34 cetacean species and 6 species of pinnipeds are known 
to or may occur in the ETP. Of the 34 cetacean species, 27 are likely 
to occur in the proposed survey area.
    Five of those 27 cetacean species are listed under the U.S. 
Endangered Species Act (ESA) as endangered: sperm whale (Physeter 
macrocephalus), humpback whale (Megaptera novaeangliae), blue whale 
(Balaenoptera musculus), fin whale (B. physalus), and sei whale (B. 
borealis).
    The other 22 species that are likely to occur in the proposed 
survey areas are: Minke whale (B. acutorostrata), Bryde's whale (B. 
edeni), Pygmy sperm whale (Kogia breviceps), Dwarf sperm whale (K. 
simus), Cuvier's beaked whale (Ziphius cavirostris), Longman's beaked 
whale (Indopacetus pacificus), Pygmy beaked whale (Mesoplodon 
peruvianus), Ginkgo-toothed beaked whale (M. ginkgodens), Blainville's 
beaked whale (M. densirostris), Rough-toothed dolphin (Steno 
bredanensis), Bottlenose dolphin (Tursiops truncatus), Pantropical 
spotted dolphin (Stenella attenuata), Spinner dolphin (S. 
longirostris), Striped dolphin (S. coeruleoalba), Fraser's dolphin 
(Lagenodelphis hosei), Short-beaked common dolphin (Delphinus delphis), 
Risso's dolphin (Grampus griseus), Melon-headed whale (Peponocephala 
electra), Pygmy killer whale (Feresa attenuata), False killer whale 
(Pseudorca crassidens), Killer whale (Orcinus orca), and Short-finned 
pilot whale (Globicephala macrorhynchus).
    A detailed description of the biology, population estimates, and 
distribution and abundance of these species is provided in the L-DEO's 
IHA application and in the March 5, 2008 Federal Register notice (73 FR 
11874). Therefore, it is not repeated here. Additional information 
regarding the stock assessment of these species are be found in NMFS 
Pacific Marine Mammal Stock Assessment Report (Carretta et al., 2007), 
and can also be accessed via the following URL link: http://www.nmfs.noaa.gov/pr/pdfs/sars/po2006.pdf.

Summary of Potential Effects of Airgun Sounds on Marine Mammals

    The effects of sounds from airguns might include one or more of the 
following: tolerance, masking of natural sounds, behavioral 
disturbance, and at least in theory, temporary or permanent hearing 
impairment, or non-auditory physical or physiological effects 
(Richardson et al., 1995). These effects are discussed below, but also 
in further detail in Appendix B of L-DEO's application.
     The potential effects of airguns discussed below are presented 
without consideration of the required mitigation measures described 
below. When these measures are taken into account, it is unlikely that 
this project would result in temporary, or especially, permanent 
hearing impairment or any non-auditory physical or physiological 
effects.

Tolerance

    Numerous studies have shown that pulsed sounds from airguns are 
often readily detectable in the water at distances of many kilometers. 
A summary of the characteristics of airgun pulses is provided in 
Appendix B of L-DEO's application. Studies have also shown that marine 
mammals at distances more than a few kilometers from operating seismic 
vessels often show no apparent response (tolerance) (Appendix B (e)). 
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. Although various baleen 
whales, toothed whales, and (less frequently) 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.

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, although there are very few specific data of relevance. 
Some whales are known to continue calling in the presence of seismic 
pulses. Their calls can be heard between the seismic pulses (e.g., 
Richardson et al., 1986; McDonald et al., 1995; Greene et al., 1999; 
Nieukirk et al., 2004). Although there has been one report that sperm 
whales ceased calling when exposed to pulses from a very distant 
seismic ship (Bowles et al., 1994), a more recent study reports that 
sperm whales off northern Norway continued calling in the presence of 
seismic pulses (Madsen et al., 2002). That has also been shown during 
recent work in the Gulf of Mexico (Tyack et al., 2003; Smultea et al., 
2004). 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. Dolphins and porpoises commonly are

[[Page 24227]]

heard calling while airguns are operating (e.g., Gordon et al., 2004; 
Smultea et al., 2004; Holst et al., 2005a; 2005b). Also, the sounds 
important to small odontocetes are predominantly at much higher 
frequencies than are airgun sounds. Masking effects, in general, are 
discussed further in LDEO's application Appendix B (d).

Disturbance Reactions

    Disturbance includes a variety of effects, including subtle changes 
in behavior, more conspicuous changes in activities, and displacement.
    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 briefly to an underwater 
sound by slightly changing its behavior or moving a small distance, the 
impacts of the change are unlikely to be significant to the individual, 
let alone the stock or the species as a whole. However, if a sound 
source displaces a marine mammal(s) from an important feeding or 
breeding area for a prolonged period, impacts on the animal(s) could be 
significant.
    There are many uncertainties in predicting the quantity and types 
of impacts of noise on marine mammals. NMFS uses exposures to 180 and 
190 dB re 1 microPa rms to estimate the number of animals that may be 
harassed by a particular sound source in a given area (and also uses 
those SPLs for use in the development of shutdown zones for 
mitigation). These estimates are based on behavioral observations 
during studies of several species. However, information is lacking for 
many species. Detailed studies have been done on humpback, gray, and 
bowhead whales, and on ringed seals. Less detailed data are available 
for some other species of baleen whales, sperm whales, and small 
toothed whales.

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 sequences 
of airgun pulses. NMFS' incidental take authorizations generally 
protect against exposure to impulsive sounds greater than 180 and 190 
dB re 1 microPa (rms), for cetaceans and pinnipeds, respectively (NMFS, 
2000). Those criteria have been used in defining the safety (shut down) 
radii planned for the proposed seismic surveys.
    Several aspects of the monitoring and mitigation measures required 
for this project are designed to detect marine mammals occurring near 
the airguns to avoid exposing them to sound pulses that might, at least 
in theory, cause hearing impairment (see Mitigation and Monitoring 
section below). In addition, many cetaceans are likely to show some 
avoidance of the area with high received levels of airgun sound. In 
those cases, the avoidance responses of the animals themselves will 
reduce or (most likely) avoid any 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, and other types of organ or 
tissue damage. It is possible that some marine mammal species (e.g., 
beaked whales) may be especially susceptible to injury and/or stranding 
when exposed to strong pulsed sounds. However, there is no definitive 
evidence that any of these effects occur even for marine mammals in 
close proximity to large arrays of airguns. It is unlikely that any 
effects of these types would occur during the proposed project given 
the brief duration of exposure of any given mammal, and the planned 
monitoring and mitigation measures (see below).

Strandings and Mortality

    Marine mammals close to underwater detonations of high explosive 
can be killed or severely injured, and the auditory organs are 
especially susceptible to injury (Ketten et al., 1993; Ketten, 1995). 
Airgun pulses are less energetic and have slower rise times, and there 
is no proof that they can cause serious injury, death, or stranding 
even in the case of large airgun arrays. However, the association of 
mass strandings of beaked whales with naval exercises involving mid-
frequency sonar and, in one case, an L-DEO seismic survey, has raised 
the possibility that beaked whales exposed to strong pulsed sounds may 
be especially susceptible to injury and/or behavioral reactions that 
can lead to stranding.
    Seismic pulses and mid-frequency sonar pulses are quite different. 
Sounds produced by airgun arrays are broadband with most of the energy 
below 1 kHz. Typical military mid-frequency sonars operate at 
frequencies of 2-10 kHz, generally with a relatively narrow bandwidth 
at any one time. Thus, 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 mortality (NOAA and 
USN, 2001; Jepson et al., 2003; Fernandez et al., 2005a), even if only 
indirectly, suggests that caution is warranted when dealing with 
exposure of marine mammals to any high-intensity pulsed sound.
    In September, 2002, there was a stranding of two Cuvier's beaked 
whales in the Gulf of California, Mexico, when the L-DEO vessel Maurice 
Ewing was operating a 20 airgun, 8,490 in\3\ airgun array in the 
general area. The link between the stranding and the seismic surveys 
was inconclusive and not based on any physical evidence (Hogarth, 2002; 
Yoder, 2002). Nonetheless, that together with the incidents involving 
beaked whale strandings near naval exercises suggests a need for 
caution in conducting seismic surveys in areas occupied by beaked 
whales. No injuries of beaked whales are anticipated during the 
proposed study, due to the required monitoring and mitigation measures.

Possible Effects of Multibeam Bathymetric (MBB) Sonar Signals

    The Kongsberg Simrad EM 120 12-kHz sonar will be operated from the 
source vessel at some times during the planned study. As discussed 
above, sounds from the MBB sonar are very short pulses, occurring for 
15 ms once every 5 - 20 s, depending on water depth. Most of the energy 
in the sound pulses emitted by this MBB sonar is at frequencies 
centered at 12 kHz. The beam is narrow (1[deg]) in fore-aft extent and 
wide (150[deg]) in the cross-track extent. Each ping consists of nine 
successive fan-shaped transmissions (segments) at different cross-track 
angles. Any given mammal at depth near the trackline would be in the 
main beam for only one or two of the nine segments. Also, marine 
mammals that encounter the Kongsberg Simrad EM 120 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. Animals close to the ship (where the beam is 
narrowest) are especially unlikely to be ensonified for more than one 
15 ms pulse (or two pulses if in the overlap area). Similarly, Kremser 
et al. (2005) noted that the probability of a cetacean swimming through 
the area of exposure when an MBB sonar emits a pulse is small. The 
animal would have to pass the transducer at close range and be swimming 
at speeds similar to the vessel in order to be subjected to sound 
levels that could cause TTS.

[[Page 24228]]

    Navy sonars that have been linked to avoidance reactions and 
stranding of cetaceans (1) generally have a longer pulse duration than 
the Kongsberg Simrad EM 120, and (2) are often directed close to 
horizontally vs. downward for the Kongsberg Simrad EM 120. The area of 
possible influence of the EM 120 is much smaller-a narrow band below 
the source vessel. The duration of exposure for a given marine mammal 
can be much longer for a Navy sonar. Possible effects of sonar on 
marine mammals are outlined below.

Possible Effects of Sub-bottom Profiler Signals

    A sub-bottom profiler would be operated from the source vessel 
during the planned study. As discussed before, sounds from the sub-
bottom profiler are very short pulses, occurring for 1, 2, or 4 ms once 
every second. Most of the energy in the sound pulses emitted by this 
sub-bottom profiler is at mid frequencies, centered at 3.5 kHz. The 
beam width is approximately 30[deg] and is directed downward.
    Sound levels have not been measured directly for the sub-bottom 
profiler used by the Langseth, but Burgess and Lawson (2000) measured 
sounds propagating more or less horizontally from a similar unit with 
similar source output (205 dB re 1 microPa at 1 m). The 160 and 180 dB 
re 1 microPa (rms) radii, in the horizontal direction, were estimated 
to be, respectively, near 20 m (65.6 ft) and 8 m (26.2 ft) from the 
source, as measured in 13 m (42.7 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.
    The sub-bottom profiler on the Langseth has a stated maximum source 
level of 204 dB re 1 microPa at 1 m. Thus, the received level would be 
expected to decrease to 160 and 180 dB about 160 m (525 ft) and 16 m 
(53 ft) below the transducer, respectively, again assuming spherical 
spreading. Corresponding distances in the horizontal plane would be 
lower, given the directionality of this source (30[deg] beam width) and 
the measurements of Burgess and Lawson (2000).

Numbers of Marine Mammals Estimated to be Taken

    All anticipated takes would be takes by Level B harassment, 
involving temporary changes in behavior. The required mitigation 
measures will prevent the possibility of injurious takes. The basis for 
the take estimates from the airgun array is described in this section.
    The anticipated radii of influence of the MBB sonar are less than 
those for the airgun array. It is assumed that, during simultaneous 
operations of the airgun array and sonar, any marine mammals close 
enough to be affected by the sonar would already be affected by the 
airguns. However, whether or not the airguns are operating 
simultaneously with the sonar, marine mammals are not expected to be 
``taken'' by the sonar given its characteristics (e.g., narrow 
downward-directed beam) and other considerations described above. 
Therefore, no additional allowance is included for animals that might 
be affected by sound sources other than airguns.

Basis for Take Estimates

    As discussed above, several extensive marine mammal surveys have 
been conducted in the ETP over numerous years. The most comprehensive 
data available for the regions encompassing the proposed survey areas 
are the Ferguson and Barlow (2001) data collected from late July to 
early December 1986-1996.
    Because the proposed QDG survey is planned for April-May 2008, data 
collected by Ferguson and Barlow (2001) in July - December may not be 
as representative for the QDG survey. Again, however, it is the best 
available information. For some species, the densities derived from 
past surveys may not be representative of the densities that would be 
encountered during the actual proposed seismic studies. For example, 
the density of cetaceans sighted during L-DEO's 2003 Hess Deep survey 
was considerably lower (only one sighting) than the densities 
anticipated to occur there based on the Ferguson and Barlow (2001) 
data. The Hess Deep survey occurred in mid-July, and was apparently not 
well represented by the Ferguson and Barlow (2001) data collected 
during the fall, beginning just after the Hess Deep survey.
    Despite the above caveats, the Ferguson and Barlow (2001) data 
still represent the best available data for estimating numbers of 
animals potentially exposed to the proposed seismic sounds. Average and 
maximum densities for marine mammals from Ferguson and Barlow (2001) 
were calculated for each of the project areas based on encompassing and 
adjacent survey blocks. Maximum densities were either the highest 
estimated density in any of the blocks or, if that number was zero, the 
average group size for that species. The densities reported in Ferguson 
and Barlow (2001) were corrected for both detectability [f(0)] and 
availability [g(0)] biases, and therefore, are relatively unbiased.

Estimated Number of Takes by Harassment

    The number of individuals that may be exposed to airgun sounds with 
received levels higher than 160 dB re 1 microPa (rms) on one or more 
occasions can be estimated by considering the total marine area that 
would be within the 160-dB radius around the operating airgun array on 
at least one occasion. In the QDG survey, the proposed seismic lines do 
not run parallel to each other in close proximity, and only one 
transect line might be surveyed a second time, which minimizes the 
number of times an individual mammal may be exposed during the survey. 
In the EPR survey, the seismic lines are parallel and in close 
proximity, and the entire grid may be surveyed more than twice, which 
may result in individuals being exposed on two or more occasions. It is 
not known how much time will pass between the first and the second 
transit along each line, so it is also possible that different marine 
mammals could occur in the area during the second pass. Thus, the best 
estimates in this section are based on a single pass of all survey 
lines (including turns), and maximum estimates are based on maximum 
densities, i.e., the highest single-block density among all of the 
blocks used in the calculations. Tables 3 and 4 show the best and 
maximum estimates of the number of marine mammals that could 
potentially be affected during the EPR and QDG seismic surveys, 
respectively.
    The number of individuals potentially exposed to 160 dB re 1 
microPa (rms) or higher in each area was calculated by multiplying
     The expected species density, either ``mean'' (i.e., best 
estimate) or ``maximum'' (maximum estimate) times by
     The anticipated minimum area to be ensonified to that 
level during airgun operations.
    The area expected to be ensonified was determined by entering the 
planned survey lines into a MapInfo Geographic Information System 
(GIS), using the GIS to identify the relevant areas by ``drawing'' the 
applicable 160-dB buffer around each seismic line and then calculating 
the total area within the buffers. Areas where overlap occurred 
(because of intersecting lines) were included only once to determine 
the minimum area expected to be ensonified to higher than 160 dB re 1 
microPa at least once.

[[Page 24229]]



----------------------------------------------------------------------------------------------------------------
                        Number of individuals exposed to SPL > 160 dB re 1 microPa (rms)
-----------------------------------------------------------------------------------------------------------------
                                                                Percent of regional
             Species                    Best estimate         population based on best       Maximum estimate
                                                                      estimate
----------------------------------------------------------------------------------------------------------------
Humpback whale                     0                        0.00                         2
----------------------------------------------------------------------------------------------------------------
Minke whale                        0                        NA                           1
----------------------------------------------------------------------------------------------------------------
Bryde's whale                      3                        0.02                         7
----------------------------------------------------------------------------------------------------------------
Sei whale                          0                        NA                           2
----------------------------------------------------------------------------------------------------------------
Fin whale                          0                        0.00                         2
----------------------------------------------------------------------------------------------------------------
Blue whale                         0                        0.03                         1
----------------------------------------------------------------------------------------------------------------
Sperm whale                        2                        0.01                         4
----------------------------------------------------------------------------------------------------------------
Pygmy sperm whale                  0                        NA                           1
----------------------------------------------------------------------------------------------------------------
Dwarf sperm whale                  66                       0.59                         87
----------------------------------------------------------------------------------------------------------------
Cuvier's beaked whale              16                       0.08                         30
----------------------------------------------------------------------------------------------------------------
Longman's beaked whale             0                        0.00                         4
----------------------------------------------------------------------------------------------------------------
Pygmy beaked whale                 0                        NA                           4
----------------------------------------------------------------------------------------------------------------
Blainville's beaked whale          0                        NA                           4
----------------------------------------------------------------------------------------------------------------
Mesoplodon sp.                     8                        0.03                         .......................
----------------------------------------------------------------------------------------------------------------
Rough-toothed dolphin              27                       0.02                         109
----------------------------------------------------------------------------------------------------------------
Bottlenose dolphin                 18                       0.01                         38
----------------------------------------------------------------------------------------------------------------
Spotted dolphin                    697                      0.03                         1327
----------------------------------------------------------------------------------------------------------------
Spinner dolphin                    342                      0.02                         695
----------------------------------------------------------------------------------------------------------------
Striped dolphin                    303                      0.02                         792
----------------------------------------------------------------------------------------------------------------
Fraser's dolphin                   5                        0.00                         47
----------------------------------------------------------------------------------------------------------------
Short-beaked common dolphin        7                        0.00                         835
----------------------------------------------------------------------------------------------------------------
Risso's dolphin                    18                       0.01                         53
----------------------------------------------------------------------------------------------------------------
Melon-headed whale                 5                        0.01                         30
----------------------------------------------------------------------------------------------------------------
Pygmy killer whale                 9                        0.02                         46
----------------------------------------------------------------------------------------------------------------
False killer whale                 3                        0.01                         8
----------------------------------------------------------------------------------------------------------------
Killer whale                       1                        0.01                         3
----------------------------------------------------------------------------------------------------------------
Short-finned pilot whale           20                       0.01                         41
----------------------------------------------------------------------------------------------------------------
Table 3. Estimates of the numbers of different individual marine mammals that might be exposed to sound levels >
  160 dB re 1 microPa (rms) during L-DEO's proposed EPR seismic program in the ETP. The proposed sound source is
  an 18-airgun array with a total volume of 3,300 in\3\. ''NA'' indicates that no percentage of population data
  were available due to the lack of population estimate.


----------------------------------------------------------------------------------------------------------------
                        Number of individuals exposed to SPL > 160 dB re 1 microPa (rms)
-----------------------------------------------------------------------------------------------------------------
                                                                Percent of regional
             Species                    Best estimate         population based on best       Maximum estimate
                                                                      estimate
----------------------------------------------------------------------------------------------------------------
Humpback whale                     0                        0.00                         2
----------------------------------------------------------------------------------------------------------------
Minke whale                        0                        NA                           1
----------------------------------------------------------------------------------------------------------------
Bryde's whale                      3                        0.02                         7
----------------------------------------------------------------------------------------------------------------
Sei whale                          0                        NA                           2
----------------------------------------------------------------------------------------------------------------
Fin whale                          0                        0.00                         2
----------------------------------------------------------------------------------------------------------------

[[Page 24230]]

 
Blue whale                         0                        0.03                         1
----------------------------------------------------------------------------------------------------------------
Sperm whale                        4                        0.01                         13
----------------------------------------------------------------------------------------------------------------
Pygmy sperm whale                  0                        NA                           1
----------------------------------------------------------------------------------------------------------------
Dwarf sperm whale                  0                        0.00                         2
----------------------------------------------------------------------------------------------------------------
Cuvier's beaked whale              48                       0.24                         81
----------------------------------------------------------------------------------------------------------------
Longman's beaked whale             0                        0.00                         3
----------------------------------------------------------------------------------------------------------------
Pygmy beaked whale                 0                        NA                           3
----------------------------------------------------------------------------------------------------------------
Blainville's beaked whale          0                        NA                           3
----------------------------------------------------------------------------------------------------------------
Mesoplodon sp.                     7                        0.03                         .......................
----------------------------------------------------------------------------------------------------------------
Rough-toothed dolphin              24                       0.02                         166
----------------------------------------------------------------------------------------------------------------
Bottlenose dolphin                 17                       0.01                         48
----------------------------------------------------------------------------------------------------------------
Spotted dolphin                    468                      0.02                         1236
----------------------------------------------------------------------------------------------------------------
Spinner dolphin                    226                      0.01                         431
----------------------------------------------------------------------------------------------------------------
Striped dolphin                    482                      0.03                         599
----------------------------------------------------------------------------------------------------------------
Fraser's dolphin                   43                       0.01                         151
----------------------------------------------------------------------------------------------------------------
Short-beaked common dolphin        30                       0.00                         2089
----------------------------------------------------------------------------------------------------------------
Risso's dolphin                    16                       0.01                         68
----------------------------------------------------------------------------------------------------------------
Melon-headed whale                 7                        0.01                         38
----------------------------------------------------------------------------------------------------------------
Pygmy killer whale                 3                        0.01                         16
----------------------------------------------------------------------------------------------------------------
False killer whale                 11                       0.03                         47
----------------------------------------------------------------------------------------------------------------
Killer whale                       1                        0.01                         2
----------------------------------------------------------------------------------------------------------------
Short-finned pilot whale           35                       0.02                         105
----------------------------------------------------------------------------------------------------------------
Table 4. Estimates of the numbers of different individual marine mammals that might be exposed to sound levels >
  160 dB re 1 microPa (rms) during L-DEO's proposed QDG seismic program in the ETP. The proposed sound source is
  an 27-airgun array with a total volume of 4,950 in\3\. ''NA'' indicates that no percentage of population data
  were available due to the lack of population estimate.

    Applying the approach described above, 2,492 km\2\ (923 mi\2\) 
would be within the 160-dB isopleth on one or more occasions during the 
EPR survey, and 2,911 km\2\ (1,224 mi\2\) would be ensonified on one or 
more occasions during the QDG survey. This approach does not allow for 
turnover in the marine mammal populations in the study areas during the 
course of the studies. That might underestimate actual numbers of 
individuals exposed, although the conservative distances used to 
calculate the area may offset this. In addition, the approach assumes 
that no cetaceans would move away or toward the trackline as the 
Langseth approaches in response to increasing sound levels prior to the 
time the levels reach 160 dB. Another way of interpreting the estimates 
that follow is that they represent the number of individuals that are 
expected (in the absence of a seismic program) to occur in the waters 
that will be exposed to 160 dB re 1 microPa (rms) or higher.
    The ``best estimate'' of the number of individual marine mammals 
that might be exposed to seismic sounds with received levels of 160 dB 
re 1 microPa (rms) or higher during the EPR survey includes 2 
endangered whales (both sperm whales), 24 beaked whales, and 3 Bryde's 
whales. Pantropical spotted, spinner, and striped dolphins are 
estimated to be the most common species exposed; the best estimates for 
those species are 697, 342, and 303, respectively. Estimates for other 
species are lower (Table 3).
    The ``best estimate'' of the number of individual marine mammals 
that might be exposed to seismic sounds with received levels of 160 dB 
re 1 microPa (rms) or higher during the QDG survey includes 5 
endangered whales (4 sperm whales and 1 blue whale), 55 beaked whales, 
and 6 Bryde's whales. Striped, spotted, and spinner dolphins are 
estimated to be the most common species exposed; the best estimates for 
those species are 482, 468, and 226, respectively. Estimates for other 
species are lower (Table 4).
    The ``best estimate'' of the total number of individual marine 
mammals that might be exposed to seismic sounds with received levels of 
160 dB re 1 microPa (rms) or higher for both surveys, along with the 
percentage of regional population, is listed in Table 5. It includes 
two ESA-listed species (6 sperm whales and 1 blue whale), 79

[[Page 24231]]

beaked whales, and 9 Bryde's whales. Striped, spotted, and spinner 
dolphins are estimated to be the most common species exposed; the best 
estimates for those species are 785, 1,165, and 568, respectively. 
Estimates for other species are lower (Table 5).

Potential Impacts to Subsistence Harvest of Marine Mammals

    The proposed activities will not have any impact on the 
availability of the species or stocks for subsistence use described in 
section 101(a)(5)(D)(i)(II).

------------------------------------------------------------------------
 Total number of individuals exposed to SPL > 160 dB re 1 microPa (rms)
-------------------------------------------------------------------------
                                                    Percent of regional
           Species               Best estimate      population based on
                                                       best estimate
------------------------------------------------------------------------
Humpback whale                0                   0.00
------------------------------------------------------------------------
Minke whale                   0                   NA
------------------------------------------------------------------------
Bryde's whale                 9                   0.07
------------------------------------------------------------------------
Sei whale                     0                   NA
------------------------------------------------------------------------
Fin whale                     0                   0.00
------------------------------------------------------------------------
Blue whale                    1                   0.04
------------------------------------------------------------------------
Sperm whale                   6                   0.02
------------------------------------------------------------------------
Pygmy sperm whale             0                   NA
------------------------------------------------------------------------
Dwarf sperm whale             66                  0.59
------------------------------------------------------------------------
Cuvier's beaked whale         64                  0.32
------------------------------------------------------------------------
Longman's beaked whale        0                   0.00
------------------------------------------------------------------------
Pygmy beaked whale            0                   NA
------------------------------------------------------------------------
Blainville's beaked whale     0                   NA
------------------------------------------------------------------------
Mesoplodon sp.                15                  0.06
------------------------------------------------------------------------
Rough-toothed dolphin         51                  0.04
------------------------------------------------------------------------
Bottlenose dolphin            35                  0.02
------------------------------------------------------------------------
Spotted dolphin               1,165               0.05
------------------------------------------------------------------------
Spinner dolphin               568                 0.03
------------------------------------------------------------------------
Striped dolphin               785                 0.05
------------------------------------------------------------------------
Fraser's dolphin              48                  0.01
------------------------------------------------------------------------
Short-beaked common dolphin   37                  0.00
------------------------------------------------------------------------
Risso's dolphin               34                  0.02
------------------------------------------------------------------------
Melon-headed whale            12                  0.02
------------------------------------------------------------------------
Pygmy killer whale            12                  0.03
------------------------------------------------------------------------
False killer whale            14                  0.04
------------------------------------------------------------------------
Killer whale                  2                   0.02
------------------------------------------------------------------------
Short-finned pilot whale      55                  0.03
------------------------------------------------------------------------
Table 5. Estimates of the numbers of different individual marine mammals
  that might be exposed to sound levels > 160 dB re 1 microPa (rms)
  during L-DEO's two proposed seismic program in the ETP. ''NA''
  indicates that no percentage of population data were available due to
  the lack of population estimate.

Potential Impacts on Habitat and Prey

    The proposed seismic survey would not result in any permanent or 
significant impact on habitats used by marine mammals, or to the food 
sources they use. The main impact issue associated with the proposed 
activity would be temporarily elevated noise levels and the associated 
direct effects on marine mammals, as discussed above. The following 
sections briefly review effects of airguns on fish and invertebrates 
(both marine mammal prey sources), and more details are

[[Page 24232]]

included in Appendices C and D of the L-DEO's IHA application, 
respectively.

Effects on Fish

    There are three types of potential effects of exposure to seismic 
surveys: (1) pathological, (2) physiological, and (3) behavioral. 
Pathological effects involve lethal and temporary or permanent sub-
lethal injury. Physiological effects involve temporary and permanent 
primary and secondary stress responses, such as changes in levels of 
enzymes and proteins. Behavioral effects refer to temporary and (if 
they occur) permanent changes in exhibited behavior (e.g., startle and 
avoidance behavior). The three categories are interrelated in complex 
ways. For example, it is possible that certain physiological and 
behavioral changes could potentially lead to an ultimate pathological 
effect on individuals (i.e., mortality).
    The potential for pathological damage to hearing structures in fish 
depends on the energy level of the received sound and the physiology 
and hearing capability of the species in question. For a given sound to 
result in hearing loss, the sound must exceed, by some specific amount, 
the hearing threshold of the fish for that sound (Popper, 2005). The 
consequences of temporary or permanent hearing loss in individual fish 
on a fish population is unknown; however, it likely depends on the 
number of individuals affected and whether critical behaviors involving 
sound (e.g. predator avoidance, prey capture, orientation and 
navigation, reproduction, etc.) are adversely affected. McCauley et al. 
(2003) found that exposure to airgun sound caused observable anatomical 
damage to the auditory maculae of ``pink snapper'' (Pagrus auratus). 
This damage in the ears had not been repaired in fish sacrificed and 
examined almost two months after exposure. On the other hand, Popper et 
al. (2005) found that received sound exposure levels of 177 dB re 1 
microPa\2\-s caused no hearing loss in broad whitefish (Coreogonus 
nasus). During both studies, the repetitive exposure to sound was 
greater than would have occurred during a typical seismic survey. 
However, the substantial low-frequency energy produced by the airgun 
arrays (less than 400 Hz in the study by McCauley et al. (2003) and 
less than 200 Hz in Popper et al. (2005)) likely did not propagate to 
the fish because the water in the study areas was very shallow 
(approximately 9 m (29.5 ft) in the former case and less than 2 m (6.6 
ft) in the latter). Water depth sets a lower limit on the lowest sound 
frequency that will propagate at about one-quarter wavelength (Urick, 
1983; Rogers and Cox, 1988).
    Except for these two studies, at least with airgun-generated sound 
treatments, most contributions rely on rather subjective assays such as 
fish ``alarm'' or ``startle response'' or changes in catch rates by 
fishers. These observations are important in that they attempt to use 
the levels of exposures that are likely to be encountered by most free-
ranging fish in actual survey areas. However, the associated sound 
stimuli are often poorly described, and the biological assays are 
varied (Hastings and Popper, 2005). According to Buchanan et al. 
(2004), for the types of seismic airguns and arrays involved with the 
proposed program, the pathological (mortality) zone for fish would be 
expected to be within a few meters of the seismic source. Numerous 
other studies provide examples of no fish mortality upon exposure to 
seismic sources (Falk and Lawrence, 1973; Holliday et al., 1987; La 
Bella et al., 1996; Santulli et al., 1999; McCauley et al., 2000a; 
2000b; 2003; Bjarti, 2002; Hassel et al., 2003; Popper et al., 2005).
    Some studies have reported, some equivocally, that mortality of 
fish, fish eggs, or larvae can occur close to seismic sources 
(Kostyuchenko, 1973; Dalen and Knutsen, 1986; Booman et al., 1996; 
Dalen et al., 1996). Some of the reports claimed seismic effects from 
treatments quite different from actual seismic survey sounds or even 
reasonable surrogates. Saetre and Ona (1996) applied a ``worst-case 
scenario'' mathematical model to investigate the effects of seismic 
energy on fish eggs and larvae. They concluded that mortality rates 
caused by exposure to seismic surveys are so low, as compared to 
natural mortality rates, that the impact of seismic surveying on 
recruitment to a fish stock must be regarded as insignificant.
    Physiological effects refer to cellular and/or biochemical 
responses of fish to acoustic stress. Such stress potentially could 
affect fish populations by increasing mortality or reducing 
reproductive success. Primary and secondary stress responses of fish 
after exposure to seismic survey sound appear to be temporary in all 
studies done to date (Sverdrup et al., 1994; McCauley et al., 2000a; 
2000b). The periods necessary for the biochemical changes to return to 
normal are variable, and depend on numerous aspects of the biology of 
the species and of the sound stimulus.
    Behavioral effects include changes in the distribution, migration, 
mating, and catchability of fish populations. Studies investigating the 
possible effects of sound (including seismic survey sound) on fish 
behavior have been conducted on both uncaged and caged individuals 
(Chapman and Hawkins, 1969; Pearson et al., 1992; Santulli et al., 
1999, Wardle et al., 2001, Hassel et al., 2003). Typically, in these 
studies fish exhibited a sharp ``startle'' response at the onset of a 
sound followed by habituation and a return to normal behavior after the 
sound ceased.

Effects on Invertebrates

    The existing body of information on the impacts of seismic survey 
sound on marine invertebrates is very limited. However, there is some 
unpublished and very limited evidence of the potential for adverse 
effects on invertebrates. The three types of potential effects of 
exposure to seismic surveys on marine invertebrates are pathological, 
physiological, and behavioral. Based on the physical structure of their 
sensory organs, marine invertebrates appear to be specialized to 
respond to particle displacement components of an impinging sound field 
and not to the pressure component (Popper et al., 2001).
    For the type of airgun array planned for the proposed program, the 
pathological (mortality) zone for crustaceans and cephalopods is 
expected to be within a few meters of the seismic source. This premise 
is based on the peak pressure and rise/decay time characteristics of 
seismic airgun arrays currently in use around the world.
    Some studies have suggested that seismic survey sound has a limited 
pathological impact on early developmental stages of crustaceans 
(Pearson et al., 1994; Christian et al., 2003; DFO, 2004). However, the 
impacts appear to be either temporary or insignificant compared to what 
occurs under natural conditions. Controlled field experiments on adult 
crustaceans (Christian et al., 2003; 2004; DFO, 2004) and adult 
cephalopods (McCauley et al., 2000a; 2000b) exposed to seismic survey 
sound have not resulted in any significant pathological impacts on the 
animals. It has been suggested that exposure to commercial seismic 
survey activities has injured giant squid (Guerra et al., 2004), but 
there is no evidence to support such claims.
    Physiological effects refer mainly to biochemical responses by 
marine invertebrates to acoustic stress. Such stress potentially could 
affect invertebrate populations by increasing mortality or reducing 
reproductive success. Any primary and secondary stress responses (i.e., 
changes in haemolymph levels of enzymes,

[[Page 24233]]

proteins, etc.) of crustaceans after exposure to seismic survey sounds 
appear to be temporary (hours to days) in studies done to date. The 
periods necessary for these biochemical changes to return to normal are 
variable and depend on numerous aspects of the biology of the species 
and of the sound stimulus.
    There is increasing interest in assessing the possible direct and 
indirect effects of seismic and other sounds on invertebrate behavior, 
particularly in relation to the consequences for fisheries. Changes in 
behavior could potentially affect such aspects as reproductive success, 
distribution, susceptibility to predation, and prey availability to 
marine mammals. Studies investigating the possible behavioral effects 
of exposure to seismic survey sound on crustaceans and cephalopods have 
been conducted on both uncaged and caged animals. In some cases, 
invertebrates exhibited startle responses (e.g., squid in McCauley et 
al., 2000a; 2000b). In other cases, no behavioral impacts were noted 
(e.g., crustaceans in Christian et al., 2003; 2004; DFO, 2004).

Effects on Marine Mammal Habitat

    The effects of the planned activity on marine mammal habitats and 
food resources are expected to be negligible, as described above. A 
small minority of the marine mammals that are present near the proposed 
activity may be temporarily displaced as much as a few kilometers by 
the planned activity.
    During the proposed survey, most marine mammals will be dispersed 
throughout the study area. However, concentrations of marine mammals 
and/or marine mammal prey species have been reported to occur in and 
near the proposed study area at the time of year when the seismic 
programs are planned. The countercurrent thermocline ridge at 
approximately 10[deg]N (in the EPR study area) has been reported to be 
an important area to cetacean species, as has the Costa Rica Dome, 
located several hundreds of kilometer to the east of the study area. 
Although these areas are thought to be important feeding grounds for 
some marine mammal species, they are not considered critical feeding 
areas for any of the species that are found there at that time of year.
    The proposed activity is not expected to have any habitat-related 
effects that could cause significant or long-term consequences for 
individual marine mammals or their populations, since operations at the 
various sites will be limited in duration.

Monitoring and Mitigation Measures

Monitoring

    For the issuance of the IHA, NMFS requires that L-DEO sponsor 
marine mammal monitoring during the present project.
(1) Safety Zones
    Received sound levels have been predicted by L-DEO in relation to 
distance and direction from the airguns for the 36-airgun array with 18 
and 27 airguns firing and for a single 1900LL 40 in3 airgun, which will 
be used during power downs. Those corresponding radii were described 
above under Acoustic Source Specifications and are set out in Table 2 
above. A detailed description of the modeling effort is provided in 
Appendix A of the L-DEO's IHA application.
    If marine mammals are detected within or about to enter the 
relevant safety zone (180 dB for cetaceans, 190 dB for pinnipeds), the 
airguns will be powered down (or shut down if necessary) immediately.
(2) Vessel-based Visual Monitoring
    A minimum of two (2) vessel-based marine mammal observers (MMOs) 
will be on board the seismic source vessel, and they will watch for 
marine mammals near the vessel during daytime airgun operations and 
during ramp-ups of airguns at night from power-down only. MMOs will 
also watch for marine mammals near the seismic vessel for at least 30 
minutes prior to the start of airgun operations after an extended 
shutdown (a shutdown lasting more than 30 minutes). When feasible, MMOs 
will also make observations during daytime periods when the seismic 
systems are not operating for comparison of animal abundance and 
behavior. Based on MMO observations, airguns will be powered down (see 
below) or, if necessary, shut down completely, when marine mammals are 
observed within or about to enter the relevant safety zone (see below).
    MMOs will be appointed by L-DEO, with NMFS approval. At least one 
MMO will monitor the safety zone during daytime airgun operations and 
any nighttime ramp-ups. MMOs will work in shifts of 4 hour duration or 
less. The vessel crew will also be instructed to assist in detecting 
marine mammals.
    The Langseth is a suitable platform for marine mammal observations. 
When stationed on the observation platform, the eye level will be 
approximately 17.8 m (58.4 ft) above sea level, and the observer will 
have a good view around the entire vessel. During daytime, the MMO will 
scan the area around the vessel systematically with reticule binoculars 
(e.g., 7 50 Fujinon), Big-eye binoculars (25 150), and with the naked 
eye. Night vision devices will be available for use (ITT F500 Series 
Generation 3 binocular-image intensifier or equivalent), although they 
are considered of limited effectiveness in detecting marine mammals. 
Laser rangefinding binoculars (Leica LRF 1200 laser rangefinder or 
equivalent) will be available to assist in distance estimation.
(3) Passive Acoustic Monitoring (PAM)
    Passive acoustic monitoring (PAM) will take place to complement the 
visual monitoring program. PAM will involve towing hydrophones that 
detect frequencies produced by vocalizing marine mammals. Two or more 
hydrophones are used to allow some localization of the bearing 
(direction) of the animal from the vessel. PAM can be effective at 
detecting some animals before they are detected visually (Smultea and 
Holst, 2003; Smultea et al., 2004). Visual monitoring typically is not 
effective during periods of bad weather or at night, and even with good 
visibility, is unable to detect marine mammals when they are below the 
surface or beyond visual range. Therefore, acoustic monitoring can 
improve detection, identification, localization, and tracking of marine 
mammals in these circumstances. PAM's value is limited, however, by 
bottom configuration (water depth) and other environmental factors, and 
in some cases towing the PAM equipment is not practicable. PAM would be 
operated or overseen by personnel with acoustic expertise.
    The PAM system consists of hardware (i.e., hydrophones) and 
software. The ``wet end'' of the hydrophone array system consists of a 
low-noise, towed hydrophone array that is connected to the vessel by a 
cable. The array will be deployed from a winch located on the back 
deck. A deck cable will connect from the winch to the main computer lab 
where the acoustic station and signal conditioning and processing 
system will be located.
    Proper steps should be taken to ensure appropriate protection from 
electric, electronic, and electro magnetic interferences (power supply, 
radar pulses, GPS etc.) that could introduce noises into the PAM 
system. An airgun shoots blanking mechanism should be incorporated into 
the PAM system so that adequate signal gain for PAM can be achieved to 
detect vocalizing marine mammals in the vicinity.
    The acoustical array will be monitored 24 h per day while at the 
survey area during airgun operations. One MMO will monitor the acoustic

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detection system at any one time, by listening to the signals from two 
channels via headphones and/or speakers and watching the real-time 
spectrographic display for vocalizations produced by cetaceans. MMOs 
monitoring the acoustical data will be on shift for 1 - 6 h. When a 
vocalization is detected, the acoustic MMO will contact the visual MMO 
immediately, to alert him/her to the presence of cetaceans (if they 
have not already been seen). The information regarding the call will be 
entered into a database. The data to be entered include whether the 
detection is linked with a visual sighting, date, time when first and 
last heard, if possible, and whenever any additional information was 
recorded, position and water depth when first detected, bearing if 
determinable, species or species group, types and nature of sounds 
heard, and any other notable information. The acoustic detection can 
also be recorded for further analysis.

Mitigation

    Mitigation measures include (1) vessel speed or course alteration, 
provided that doing so will not compromise operational safety 
requirements, (2) airgun array power down, (3) airgun array shut down, 
and (4) airgun array ramp up.
(1) Speed or Course Alteration
    If a marine mammal is detected outside the safety zone but is 
likely to enter it based on relative movement of the vessel and the 
animal, then if safety and scientific objectives allow, the vessel 
speed and/or course will be adjusted to minimize the likelihood of the 
animal entering the safety zone. NMFS acknowledges that major course 
and speed adjustments are often impractical when towing long seismic 
streamers and large source arrays, thus for surveys involving large 
sources. Therefore the other mitigation measures often will be 
required.
(2) Power-down Procedures
    A power down involves reducing the number of airguns operating to a 
single airgun in order to reduce the size of the safety zone. The 
continued operation of one airgun is intended to alert marine mammals 
to the presence of the seismic vessel nearby.
    If a marine mammal is detected within, or is likely to enter, the 
safety zone of the array in use, and if vessel course and/or speed 
changes are impractical or will not be effective to prevent the animal 
from entering the safety zone, then the array will be powered down to 
ensure that the animal remains outside the smaller safety zone of the 
single 40-in\3\ airgun. If the size of the safety zone for the single 
airgun will not prevent the animal from entering it, then a shutdown 
will be required, as described below.
    Following a power down, airgun activity will not resume until the 
marine mammal is outside the safety zone for the full array. The animal 
will be considered to have cleared the safety zone if it (1) is 
visually observed to have left the relevant safety zone; or (2) has not 
been seen within the safety zone for 15 min in the case of small 
odontocetes; or has not been seen within the safety zone for 30 min in 
the case of mysticetes and large odontocetes, including sperm, pygmy 
sperm, dwarf sperm, and beaked whales.
    Following a power down and subsequent animal departure as above, 
the airgun array may resume operations following ramp-up procedures 
described below.
(3) Shut-down Procedures
    If a marine mammal is within or about to enter the safety zone for 
the single airgun, all airguns will be shut down immediately. Airgun 
activity will not resume until the animal has cleared the safety zone, 
as described above.
(4) Ramp-up Procedures
    A ramp-up procedure will be followed when an airgun array begins 
operating after a specified period without operations or at single 
airgun operation. For the present cruise, this period would be 4-5 min. 
This period is based on the largest modeled 180-dB radius for the 
airgun array to be used in relation to the planned speed of the 
Langseth while shooting.
    Ramp up will begin with the smallest gun in the array (40 in\3\). 
Airguns will be added in a sequence such that the source level of the 
array will increase in steps not exceeding 6 dB per 5-min period. 
During ramp-up, the MMOs will monitor the safety zone, and if marine 
mammals are sighted, decisions about course/speed changes, power down 
and shutdown will be implemented as though the full array were 
operational.
    Initiation of ramp-up procedures from shutdown requires that the 
full safety zone must be visible by the MMOs. This requirement will 
preclude starts at night or in thick fog. Ramp-up is allowed from a 
power down under reduced visibility conditions, but only if at least 
one airgun has operated continuously with a source level of at least 
180 dB re microPa (rms) throughout the survey interruption. It is 
assumed that the single airgun will alert marine mammals to the 
approaching seismic vessel, allowing them to move away if they choose. 
Ramp-up procedures will not be initiated if a marine mammal is observed 
within the safety zone of the airgun array to be operated.

Data Collection and Reporting

    MMOs will record data to estimate the numbers of marine mammals 
exposed to various received sound levels and to document apparent 
disturbance reactions or lack thereof. Data will be used to estimate 
numbers of animals potentially ``taken'' by harassment. They will also 
provide information needed to order a power down or shutdown of airguns 
when marine mammals are within or near the safety zone.
    When a sighting is made, the following information about the 
sighting will be recorded:
    (1) Species, group size, age/size/sex categories (if determinable), 
behavior when first sighted and after initial sighting, heading (if 
consistent), bearing and distance from seismic vessel, sighting cue, 
apparent reaction to the airguns or vessel, and behavioral pace.
    (2) Time, location, heading, speed, activity of the vessel 
(including whether and the level at which airguns are operating), sea 
state, visibility, and sun glare.
    The data listed under (2) will also be recorded at the start and 
end of each observation watch, and during a watch whenever there is a 
change in one or more of the variables.
    All observations, as well as information regarding airgun power 
down and shutdown, will be recorded in a standardized format. Data 
accuracy will be verified by the MMOs at sea, and preliminary reports 
will be prepared during the field program and summaries forwarded to 
the operating institution's shore facility and to NSF weekly or more 
frequently. MMO observations will provide the following information:
    (1) The basis for decisions about powering down or shutting down 
airgun arrays.
    (2) Information needed to estimate the number of marine mammals 
potentially taken by harassment as described above.
    (3) Data on the occurrence, distribution, and activities of marine 
mammals in the area where the seismic study is conducted.
    (4) Data on the behavior and movement patterns of marine mammals 
seen at times with and without seismic activity.
    A final report will be submitted to NMFS within 90 days after the 
end of the cruise. The report will describe the operations that were 
conducted and sightings of marine mammals near the operations. The 
report will also provide full documentation of methods, results, and 
interpretation pertaining to all monitoring. The report will summarize

[[Page 24235]]

the dates and locations of seismic operations, and all marine mammal 
sightings (dates, times, locations, activities, associated seismic 
survey activities), and the amount and nature of potential take of 
marine mammals by harassment or in other ways.

Endangered Species Act

    On March 5, 2007, NMFS concluded consultation with NSF under 
section 7 of the ESA on the proposed marine geophysical surveys in the 
ETP and issued a biological opinion on April 22, 2008. The finding of 
that consultation was that the marine geophysical surveys in the ETP 
may adversely affect, but is not likely to jeopardize, the continued 
existence of blue and sperm whales, and leatherback, green, olive 
ridley, hawksbill, and loggerhead turtles. The proposed marine 
geophysical surveys are not likely to adversely affect sei or fin 
whales. NMFS' IHA will not have impacts beyond what was analyzed in the 
biological opinion. Therefore, additional consultation is not required.

National Environmental Policy Act (NEPA)

    In April 2007, LGL Ltd. (LGL) prepared a draft Environmental 
Assessment of Two Marine Geophysical Surveys by the R/V Marcus G. 
Langseth in the Eastern Tropical Pacific, 2007 (EA) for L-DEO and NSF. 
NMFS has reviewed this EA and has adopted it. Therefore, the 
preparation of another EIS or EA is not warranted. NMFS issued a 
Finding of No Significant Impact Statement on April 23, 2008.

Determination

    Based on the preceding information, and provided that the 
aforementioned mitigation and monitoring measures are incorporated, 
NMFS has determined that the impact of conducting the marine seismic 
survey in the ETP may result, at worst, in a temporary modification in 
behavior of small numbers of certain species of marine mammals. While 
behavioral and avoidance reactions may be made by these species in 
response to the resultant noise from the airguns, these behavioral 
changes are expected to have a negligible impact on the affected 
species and stocks of marine mammals.
    While the number of potential incidental harassment takes will 
depend on the distribution and abundance of marine mammals in the area 
of seismic operations, the number of potential harassment takings is 
estimated to be relatively small in light of the population sizes (see 
Tables 3, 4, and 5). NMFS anticipates the actual take of individuals to 
be even lower than the numbers depicted in the tables, because those 
numbers do not reflect either the implementation of the mitigation 
numbers or the fact that some animals likely will avoid the sound at 
levels lower than those expected to result in harassment.
    In addition, no take by death and/or injury is anticipated, and the 
potential for temporary or permanent hearing impairment will be avoided 
through the incorporation of the mitigation measures described in this 
document.

Authorization

    NMFS has issued an IHA to L-DEO for the potential Level B 
harassment of small numbers of cetaceans incidental to conducting 
marine geophysical surveys in the ETP, provided the previously 
mentioned mitigation, monitoring, and reporting requirements are 
incorporated.

    Dated: April 23, 2008.
James H. Lecky,
Director, Office of Protected Resources, National Marine Fisheries 
Service.
[FR Doc. E8-9717 Filed 5-1-08; 8:45 am]
BILLING CODE 3510-22-S