[Federal Register Volume 75, Number 37 (Thursday, February 25, 2010)]
[Pages 8652-8671]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2010-3869]



National Oceanic and Atmospheric Administration

RIN 0648-XT57

Incidental Takes of Marine Mammals During Specified Activities; 
Marine Geophysical Survey in the Commonwealth of the Northern Mariana 
Islands, April to June 2010

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

ACTION: Notice; proposed incidental take authorization; request for 


SUMMARY: NMFS has received an application from the Lamont-Doherty Earth 
Observatory (L-DEO), a part of

[[Page 8653]]

Columbia University, for an Incidental Harassment Authorization (IHA) 
to take small numbers of marine mammals, by harassment, incidental to 
conducting a marine seismic survey in the Commonwealth of the Northern 
Mariana Islands (CNMI) during April to June 2010. Pursuant to the 
Marine Mammal Protection Act (MMPA), NMFS requests comments on its 
proposal to authorize L-DEO to incidentally take, by Level B harassment 
only, small numbers of marine mammals during the aforementioned 

DATES: Comments and information must be received no later than March 
29, 2010.

ADDRESSES: Comments on the application should be addressed 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. The mailbox address for 
providing e-mail comments is [email protected]. NMFS is not 
responsible for e-mail comments sent to addresses other than the one 
provided here. Comments sent via e-mail, including all attachments, 
must not exceed a 10-megabyte file size.
    All comments received are a part of the public record and will 
generally be posted to http://www.nmfs.noaa.gov/pr/permits/incidental.htm without change. All Personal Identifying Information 
(for example, name, address, etc.) voluntarily submitted by the 
commenter may be publicly accessible. Do not submit Confidential 
Business Information or otherwise sensitive or protected information.
    A copy of the application containing a list of the references used 
in this document may be obtained by writing to the address specified 
above, telephoning the contact listed below (see FOR FURTHER 
INFORMATION CONTACT), or visiting the Internet at: http://www.nmfs.noaa.gov/pr/permits/incidental.htm. Documents cited in this 
notice may be viewed, by appointment, during regular business hours, at 
the aforementioned address.

FOR FURTHER INFORMATION CONTACT: Howard Goldstein or Jolie Harrison, 
Office of Protected Resources, NMFS, 301-713-2289.



    Sections 101(a)(5)(A) and (D) of the MMPA (16 U.S.C. 1361 et seq.) 
direct the Secretary of Commerce (Secretary) to allow, upon request, 
the incidental, but not intentional, taking of marine mammals by United 
States 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.
    An authorization for incidental taking of small numbers of marine 
mammals shall be granted if NMFS finds that the taking will have a 
negligible impact on the species or stock(s), will not have an 
unmitigable adverse impact on the availability of the species or 
stock(s) for subsistence uses, and if the permissible methods of taking 
and requirements pertaining to the mitigation, monitoring and reporting 
of such 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.'' The authorization must also 
set forth permissible methods of taking, other means of affecting the 
least practicable adverse impact on the species or stock and its 
habitat and requirements for monitoring and reporting such takings.
    Section 101(a)(5)(D) of the MMPA established an expedited process 
by which citizens of the United States can apply for an authorization 
not to exceed one year 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''].
    16 U.S.C. 1362(18)

    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 for any proposed authorizations for the incidental harassment of 
marine mammals. Within 45 days of the close of the comment period, 
NMFS, on behalf of the Secretary, makes the findings set forth in 
clause 101(a)(5)(D)(i) of the MMPA and must either issue the 
authorization with appropriate conditions to meet the requirements of 
clause 101(a)(5)(D)(ii) or deny it. NMFS will publish notice of 
issuance or denial of the authorization within thirty days of issuance 
or denial.

Summary of Request

    On December 16, 2009, NMFS received an IHA application and an 
Environmental Assessment (EA) from L-DEO for the taking, by Level B 
harassment only, of small numbers of several species of marine mammals 
incidental to conducting, with research funding from the National 
Science Foundation (NSF), a marine seismic survey in the CNMI during 
April to June, 2010. The CNMI is a commonwealth in a political union 
with the U.S. The survey will take place in the Exclusive Economic Zone 
(EEZ) of the U.S. in water depths greater than 2,000 m (6,561.7 ft). 
The seismic study will use a towed array of 36 airguns with a total 
discharge volume of approximately 6,600 in\3\.

Description of the Specified Activity

    L-DEO plans to conduct a seismic survey in the CNMI. The survey 
will occur in the area 16.5[deg] to 19[deg] North, 146.5[deg] to 
150[deg] East within the EEZ (see Figure 1 of L-DEO's application). The 
project is scheduled to occur from April 25 to June 6, 2010. Some minor 
deviation of these dates is possible, depending on logistics and 
weather (i.e., the cruise may depart earlier to be extended due to poor 
weather; there could be extra days (up to three) of seismic operations 
if collected data are of substandard quality.
    L-DEO plans to conduct the seismic survey over the Mariana outer 
forearc, the trench and the outer rise of the subducting and bending 
Pacific plate. The objective is to understand the water cycle within 
subduction-systems. Subduction systems are where the basic building 
blocks of continental crust are made and where Earth's great 
earthquakes occur. Little is known about either of these processes, but 
water cycling through the system is thought to be the primary 
controlling factor in both arc-crust generation and megathrust 
    An important new hypothesis has recently been suggested that, if 
correct, will transform our understanding of the water budget of 
subduction systems. This hypothesis holds that cracking attributable to 
bending of the subducting plate enables water to penetrate through the 
subducting crust into the mantle, where it hydrates the mantle by 
forming the hydrous mineral phase serpentine. This phase is stable to 
greater depths than the hydrous clay minerals of the crust, where most 
of the subducting water was previously believed to be held. Thus, if 

[[Page 8654]]

hypothesis is correct, it provides a mechanism for transporting water 
far beneath the mantle wedge, where it promotes melting and crust 
formation, and possibly even deeper into the mantle, providing a whole-
earth hydration mechanism that promotes the continued operation of 
plate tectonics, without which our planet would likely be unable to 
support life.
    The scientists involved in this program will test this hypothesis 
by measuring mantle seismic sounds speeds, which vary with degree of 
serpentinization. By comparing these measurements from the Mariana 
system, which is old and cold with the Costa Rica system, which is 
young and warm and where similar measurements have recently been made, 
we should be able to definitively determine whether or not substantial 
water is taken up by the mantle of subducting plates near the outer 
rise of seafloor trenches.
    The planned survey will involve one source vessel, the R/V Marcus 
G. Langseth (Langseth), which will occur in the CNMI. The Langseth will 
deploy an array of 36 airguns (6,600 in\3\) as an energy source at a 
tow depth of 9 m (30 ft). The receiving system will consist of a 6 km 
(3.7 mi) hydrophone streamer and approximately 85 ocean bottom 
seismometers (OBSs). As the airgun array is towed along the survey 
lines, the hydrophone streamer will receive the returning acoustic 
signals and transfer the data to the on-board processing system. The 
OBSs record the returning acoustic signals internally for later 
analysis. The OBSs to be used for the 2010 program will be deployed and 
most (approximately 60) will be retrieved during the cruise, whereas 25 
will be left in place for one year.
    The planned seismic survey will consist of approximately 2,800 km 
(1,739.8 mi) of transect lines within the CNMI (see Figure 1 of L-DEO's 
application). The survey will take place in water depths greater than 
2,000 m (6,561.7 ft). All planned geophysical data acquisition 
activities will be conducted by L-DEO with onboard assistance by the 
scientists who have proposed the study. The scientific team consists of 
Dr. Doug Wiens (Washington University, St. Louis, MO) and Daniel 
Lizarralde (Woods Hole Oceanographic Institution [WHOI], Woods Hole, 
MA). The vessel will be self-contained, and the crew will live aboard 
the vessel for the entire cruise.
    In addition to the operations of the airgun array, a Kongsberg EM 
multibeam echosounder (MBES) and a Knudsen 320B sub-bottom profiler 
(SBP) will be operated from the Langseth continuously throughout the 
CNMI cruise.

Vessel Specifications

    The Langseth will be used as the source vessel. The Langseth will 
tow the 36 airgun array along predetermined lines. The Langseth will 
also tow the hydrophone streamer, retrieve OBSs, and may also deploy 
OBSs. When the Langseth is towing the airgun array as well as the 
hydrophone streamer, the turning rate of the vessel while the gear is 
deployed is limited to five degrees per minute. Thus, the 
maneuverability of the vessel is limited during operations with the 
    The Langseth has a length of 71.5 m (234.6 ft), a beam of 17 m 
(55.8 ft), and a maximum draft of 5.9 m (19.4 ft). The ship was 
designed as a seismic research vessel, with a propulsion system 
designed to be as quiet as possible to avoid interference with the 
seismic signals. The ship is powered by two Bergen BRG-6 diesel 
engines, each producing 3,550 horse-power (hp), that drive the two 
propellers directly. Each propeller has four blades, and the shaft 
typically rotates at 750 revolutions per minute (rpm). The vessel also 
has an 800 hp bowthruster, which is not used during seismic 
acquisition. The operation speed during seismic acquisition is 
typically 7.4 to 9.3 km/hr (4 to 5 kt). When not towing seismic survey 
gear, the Langseth can cruise at 20 to 24 km/hr (11 to 13 kt). The 
Langseth has a range of 25,000 km (15,534 mi), which is the distance 
the vessel can travel without refueling. The Langseth will also serve 
as the platform from which vessel-based Protected Species Observers 
(PSOs) will watch for marine animals before and during airgun 
operations. NMFS believes that the realistic possibility of a ship-
strike of a marine mammal by the vessel during research operations and 
in-transit during the proposed survey is discountable.

Acoustic Source Specifications--Seismic Airguns

    During the proposed survey, the airgun array to be used will 
consist of 36 airguns, with a total volume of approximately 6,600 
in\3\. The airgun array will consist of a mixture of Bolt 1500LL and 
1900LL airguns. The airguns array will be configured as four identical 
linear arrays or ``strings'' (see Figure 2 in L-DEO's application). 
Each string will have 10 airguns; the first and last airguns in the 
strings are spaced 16 m (52.5 ft) apart. Nine airguns in each string 
will be fired simultaneously, while the tenth is kept in reserve as a 
spare, to be turned on in case of failure of another airgun. The four 
airgun strings will be distributed across an approximate area of 24 x 
16 m (78.7 x 52.5 ft) behind the Langseth and will be towed 
approximately 140 m (459 ft) behind the vessel. The shot interval will 
be 37.5 m (123.0 ft) or 150 m (492.1 ft) during the study. The shot 
interval will be relatively short (approximately 37.5 m or 
approximately 15 to 18 seconds [s]) for multi-channel seismic surveying 
with the hydrophone streamer, and relatively long (approximately 150 m 
or approximately 58 to 73 s) when recording data on the OBSs. The 
firing pressure of the array is 1,900 pounds per square inch (psi). 
During firing, a brief (approximately 0.1 s) pulse of sound is emitted. 
The airguns will be silent during the intervening periods.
    Because the actual source is a distributed source (36 airguns) 
rather than a single point source, the highest sound levels measurable 
at any location in the water will be less than the nominal source (265 
dB re 1 [mu] Pa[middot]m, peak-to-peak [pk-pk]). In addition, the 
effective source level for sound propagating in near-horizontal 
directions will be substantially lower than the nominal source level 
applicable to downward propagation because of the directional nature of 
the sound from the airgun array.

 Table 1--Distances To Which Sound Levels Greater Than or Equal to 190, 180, and 160 dB re 1 [mu]Pa (rms) Could
  be Received in Deep (Greater Than 1,000 m) Water During the Proposed Survey in the CNMI, April 25 to June 6,
                                                                            Predicted RMS distances (m)
       Source and volume         Tow depth (m)     Water depth   -----------------------------------------------
                                                                      190 dB          180 dB          160 dB
Single Bolt airgun (40 in3)...               9  Deep (>1,000 m).              12              40             385
4 strings, 36 airguns (6,600                 9  Deep (>1,000 m).             400             940           3,850

[[Page 8655]]

Acoustic Source Specifications--Multibeam Echosounder (MBES) and Sub-
bottom Profiler (SBP)

    Along with the airgun operations, two additional acoustical data 
acquisition systems will be operated during the survey. The ocean floor 
will be mapped with Kongsberg EM 122 MBES and Knudsen 320 SBP. These 
sound sources will be operated from the Langseth continuously 
throughout the cruise.
    The Kongsberg EM 122 MBES operates at 10.5 to 13 (usually 12) kHz 
and is hull-mounted on the Langseth. The transmitting beamwidth is 
1[deg] or 2[deg] fore-aft and 150[deg] athwartship. The maximum source 
level is 242 dB re 1 [mu]Pam (rms). Each ``ping'' consists of eight (in 
water greater than 1,000 m deep) or four (less than 1,000 m) successive 
fan-shaped transmissions, each ensonifying a sector that extends 1[deg] 
fore-aft. Continuous-wave (CW) pulses increase from two to 15 ms long 
in water depths up to 2,600 m (8,530 ft), and FM chirp pulses up to 100 
ms long are used in water greater than 2,600 m. The successive 
transmissions span an overall cross-track angular extent of about 
150[deg], with 2 ms gaps between pulses for successive sectors.
    The Knudsen 320B SBP is normally operated to provide information 
about the sedimentary features and the bottom topography that is being 
mapped simultaneously by the MBES. The SBP beam is transmitted as a 27 
degree cone, which is directed downward by a 3.5 kHz transducer in the 
hull of the Langseth. The maximum output is 1,000 watts (204 dB), but 
in practice, the output varies with water depth. The pulse interval is 
1 s, but a common mode of operation is to broadcast five pulses at 1 s 
intervals followed by a 5 s pause.

OBS Description and Deployment

    Approximately 85 OBSs will be deployed by the Langseth before the 
survey, in water depths 3,100 to 8,100 m (10,170.6 to 26,574.8 ft). 
There are three types of OBS deployment:
    (1) Approximately 20 broad-band OBSs located on the bottom in a 
wide two-dimensional (2D) array with a spacing of no more than 100 km 
(62.1 mi);
    (2) Approximately five short-period OBSs tethered in the water 
column above the trench areas deeper than 6 km; and
    (3) Approximately 60 short-period OBSs located on the bottom in a 
2D array with a spacing of about 75 km (46.6 mi).
    The first two types will be left in place for one year for passive 
recording, and the third type will be retrieved after the seismic 
operations. OBSs deployed in water deeper than 5,500 m (18,044.6 ft) 
will require a tether to keep the instruments at a depth of 5,500 to 
6,000 m (18,044.6 to 19,685 ft), as the instruments are rated to a 
maximum depth of 6,000 m. The lengths of the tethers will vary from 65 
to 2,600 m (213.3 to 8,530.2 ft). The tether will fall to the seafloor 
when the OBS is released.
    Two different types of OBSs may be used during the 2010 program. 
The WHOI ``D2'' OBS has a height of approximately 1 m (3.3 ft) and a 
maximum diameter of 50 cm (19.7 in). The anchor is made of hot-rolled 
steel and weighs 23 kg (50.7 lb). The anchor dimensions are 
2.5x30.5x38.1 cm. The LC4x4 OBS from the Scripps Institution of 
Oceanography (SIO) has a volume of approximately 1 m3, with 
an anchor that consists of a large piece of steel grating 
(approximately 1 m2). Once an OBS is ready to be retrieved, 
an acoustic release transponder interrogates the OBS at a frequency of 
9 to 11 kHz, and a response is received at a frequency of 9 to 13 kHz. 
The burn-wire release assembly is then activated, and the instrument is 
released from the anchor to float to the surface. The anchors will 
remain on the sea floor.

Proposed Dates, Duration, and Specific Geographic Area

    The survey will occur in the following specific geographic area: 
16.5[deg] to 19[deg] North, 146.5[deg] to 150[deg] East within the EEZ 
of the U.S. (see Figure 1 of L-DEO's application). Water depths in the 
survey area range from greater than 2,000 m to greater than 8,000 m 
(26,246.7 ft). The closest that the vessel will approach to any island 
is approximately 50 km (31.1 mi) from Alamagan. The exact dates of the 
activities depend on logistics and weather conditions. The Langseth 
will depart from Guam on April 25, 2010 and return to Guam on June 6, 
2010. Seismic operations will be carried out for 16 days, with the 
balance of the cruise occupied in transit (approximately 2 days) and in 
deployment and retrieval of OBSs and maintenance (25 days).

Description of Marine Mammals in the Proposed Activity Area

    A total of 27 cetacean species, including 20 odontocete (dolphins 
and small- and large-toothed whales) species and nine mysticetes 
(baleen whales) are known to occur in the area affected by the 
specified activities associated with the proposed CNMI marine 
geophysical survey (see Table 2 of L-DEO's application). Cetaceans and 
pinnipeds, which are the subject of this IHA application, are protected 
by the MMPA and managed by NMFS in accordance with its requirements. 
Information on the occurrence, distribution, population size, and 
conservation status for each of the 27 marine mammal species that may 
occur in the proposed project area is presented in the Table 2 of L-
DEO's application as well as here in the table below (Table 2). The 
status of certain marine mammal species as threatened or endangered is 
based on evaluation and listing procedures under the U.S. Endangered 
Species Act (ESA), the International Union for Conservation of Nature 
(IUCN) Red List of Threatened Species, and Convention on International 
Trade in Endangered Species (CITES). Several marine mammal species that 
may be affected by the proposed IHA are listed as Endangered under 
Section 4 of the ESA, including the North Pacific right, sperm, 
humpback, fin, sei, and blue whales.
    There are no reported sightings of pinnipeds in the CNMI (e.g., 
DON, 2005). The dugong (Dugong dugon), also listed under the ESA as 
Endangered, is distributed throughout most of the Indo-Pacific region 
between approximately 27[deg] North and south of the equator (Marsh, 
2002); it seems unlikely that dugongs have ever inhabited the Mariana 
Islands (Nishiwaki et al., 1979). There have been some extralimital 
sightings in Guam, including a single dugong in Cocos Lagoon in 1974 
(Randall et al., 1975) and several sightings of an individual in 1985 
along the southeastern coast (Eldredge, 2003).
    Table 2 below outlines the cetacean species, their habitat and 
abundance in the proposed project area, and the requested take levels. 
Additional information regarding the distribution of these species 
expected to be found in the project area and how the estimated 
densities were calculated may be found in L-DEO's application.

[[Page 8656]]

 Table 2--The Habitat, Regional Abundance, Conservation Status, and Best and Maximum Density Estimates of Marine
 Mammals That Could Occur in or Near the Proposed Seismic Survey Area in the CNMI. See Tables 2 to 4 in L-DEO's
                                         Application for Further Detail
                                                               Regional                      1000 km2   Density/
             Species                      Habitat        population size \a\     ESA \b\      (best)    1000 km2
                                                                                               \c\     (max) \d\
    North Pacific right whale      Pelagic and coastal.  Few 100s...........  EN..........       0.01       0.01
     (Eubalaena japonica).
    Humpback whale (Megaptera      Mainly nearshore      938-1107 \e\.......  EN..........       0.01       0.02
     novaeangliae).                 waters and banks.
    Minke whale (Balaenoptera      Pelagic and coastal.  25,000 \f\.........  NL..........       0.01       0.02
    Bryde's whale Balaenoptera     Pelagic and coastal.  20,000-30,000......  NL..........       0.41       0.62
    Sei whale (Balaenoptera        Primarily offshore,   7,260-12,620 \g\...  EN..........       0.29       0.44
     borealis).                     pelagic.
    Fin whale (Balaenoptera        Continental slope,    13.620-18.680 \h\..  EN..........       0.01       0.02
     physalus).                     mostly pelagic.
    Blue whale (Balaenoptera       Pelagic and coastal.  N.A................  EN..........       0.01       0.02
    Sperm whale (Physeter          Usually pelagic and   29,674 \i\.........  EN..........       1.23       1.85
     macrocephalus).                deep seas.
    Pygmy sperm whale (Kogia       Deep waters off       N.A................  NL..........       2.91       4.37
     breviceps).                    shelf.
    Dwarf sperm whale (Kogia       Deep waters off the   11,200 \j\.........  NL..........       7.14      10.71
     sima).                         shelf.
    Cuvier's beaked whale          Pelagic.............  20,000 \j\.........  NL..........       6.21       9.32
     (Ziphius cavirostris).
    Longman's beaked whale         Deep water..........  N.A................  NL..........       0.41       0.62
     (Indopacetus pacificus).
    Blainville's beaked whale      Pelagic.............  25,300 \k\.........  NL..........       1.17       1.76
     (Mesoplodon densirostris).
    Ginkgo-toothed beaked whale    Pelagic.............  N.A................  NL..........       0.01       0.02
     (Mesoplodon ginkgodens).
    Rough-toothed dolphin (Steno   Deep water..........  146,000 ETP \j\....  NL..........       0.29       0.44
    Common bottlenose dolphin      Coastal and oceanic,  243,500 ETP \j\....  NL..........       0.21       0.32
     (Tursiops truncatus).          shelf break.
    Pantropical spotted dolphin    Coastal and pelagic.  800,000 ETP \j\....  NL..........      22.60      33.90
     (Stenella attenuata).
    Spinner dolphin (Stenella      Coastal and pelagic.  800,000 ETP \j\....  NL..........       3.14       4.71
    Striped dolphin (Stenella      Off continental       1,000,000 ETP \j\..  NL..........       6.16       9.24
     coeruleoalba).                 shelf.
    Fraser's dolphin               Waters greater than   289,000 ETP \j\....  NL..........       4.17       6.26
     (Lagenodelphis hosei).         1,000 m.
    Short-beaked common dolphin    Shelf and pelagic,    3,000,000 ETP \j\..  NL..........       0.01       0.01
     (Delphinus delphis).           seamounts.
    Risso's dolphin (Grampus       Waters greater than   175,000 ETP \j\....  NL..........       0.97       1.46
     griseus).                      1,000 m, seamounts.
    Melon-headed whale             Oceanic.............  45,000 ETP \j\.....  NL..........       4.28       6.42
     (Peponocephala electra).
    Pygmy killer whale (Feresa     Deep, pantropical     39,000 ETP \j\.....  NL..........       0.14       0.21
     attenuata).                    waters.
    False killer whale (Pseudorca  Pelagic.............  40,000 \j\.........  NL..........       1.11       0.21
    Killer whale (Orcinus orca)..  Widely distributed..  8,500 ETP \j\......  NL..........       0.14       0.21
    Short-finned pilot whale       Mostly pelagic, high- 500,000 ETP \j\....  NL..........       1.59       2.39
     (Globicephala macrorhynchus).  relief topography.
Sirenians: Dugong (Dugong dugon).  Coastal.............  N.A................  EN..........       N.A.       N.A.
N.A.--Data not available or species status was not assessed,
\a\ North Pacific (Jefferson et al., 2008) unless otherwise indicated.
\b\ U.S. Endangered Species Act: EN = Endangered, NL = Not listed.
\c\ Best estimate as listed in Table 3 of the application.
\d\ Maximum estimate as listed in Table 3 of the application.
\e\ Western North Pacific (Calambokidis et al., 2008).
\f\ Northwest Pacific and Okhotsk Sea (IWC, 2007a).
\g\ North Pacific (Tillman, 1977).
\h\ North Pacific (Ohsumi and Wada, 1974).
\i\ Western North Pacific (Whitehead, 2002b).
\j\ Eastern Tropical Pacific = ETP (Wade and Gerrodette, 1993).
\k\ ETP; all Mesoplodon spp. (Wade and Gerodette, 1993).

Potential Effects on Marine Mammals

Potential Effects of Airgun Sounds

    The effects of sounds from airguns might result in one or more of 
the following: tolerance, masking of natural sounds, behavioral 
disturbances, temporary or permanent hearing impairment, or non-
auditory physical or physiological effects (Richardson et al., 1995; 
Gordon et al., 2004; Nowacek et al., 2007; Southall et al., 2007). 
Permanent hearing impairment, in the unlikely event that it occurred, 
would constitute injury, but temporary threshold shift (TTS) is not an 
injury (Southall et al., 2007). Although the possibility cannot be 
entirely excluded, it is unlikely that the project would result in any 
cases of temporary or especially permanent hearing impairment, or any 
significant non-auditory physical or physiological effects. Some 
behavioral disturbance is expected, but this would be localized and 
short-term. NMFS concurs with this determination.
    The root mean square (rms) received levels that are used as impact 
criteria for marine mammals are not directly comparable to the peak or 
peak-to-peak values normally used to characterize source levels of 
airgun arrays. The measurement units used to describe airgun sources, 
peak or peak-to-peak decibels, are always higher than the rms decibels 
referred to in biological literature. A measured received level of 160 
dB rms in the far field would typically correspond to a peak 
measurement of approximately 170 to 172 dB, and to a peak-to-peak 
measurement of approximately 176 to 178 dB, as measured for the same 
pulse received at the same location (Greene, 1997; McCauley et al., 
1998, 2000a). The precise difference between rms and peak or peak-to-
peak values depends on the frequency content and duration of the pulse, 
among other factors. However, the rms level is always lower

[[Page 8657]]

than the peak or peak-to-peak level for an airgun-type source.


    Numerous studies have shown that pulsed sounds from airguns are 
often readily detectable in the water at distances of many kilometers. 
For a summary of the characteristics of airgun pulses, see Appendix B 
(3) of the EA. Numerous studies have shown that marine mammals at 
distances more than a few kilometers from operating seismic vessels 
often show no apparent response--see Appendix B (5) of L-DEO's 
application. 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 the 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 usually seem to be more tolerant 
of exposure to airgun pulses than are cetaceans, with relative 
responsiveness of baleen and toothed whales being variable.


    Obscuring of sounds of interest by interfering sounds, generally at 
similar frequencies, is known as 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 few 
specific data of relevance. Because of the intermittent nature and low 
duty cycle of seismic pulses, animals can emit and receive sounds in 
the relatively quiet intervals between pulses. However in exceptional 
situations, reverberation occurs for much or all of the interval 
between pulses (Simard et al., 2005; Clark and Gagnon, 2006) which 
could mask calls. Some baleen and toothed whales are known to continue 
calling in the presence of seismic pulses. The airgun sounds are 
pulsed, with quiet periods between the pulses, and whale calls often 
can be heard between the seismic pulses (Richardson et al., 1986; 
McDonald et al., 1995; Greene et al., 1999; Nieukirk et al., 2004; 
Smultea et al., 2004; Holst et al., 2005a,b, 2006; Dunn et al., 2009). 
In the northeast Pacific Ocean, blue whale calls have been recorded 
during a seismic survey off Oregon (McDonald et al., 1995). Clark and 
Gagnon (2006) reported that fin whales in the northeast Pacific Ocean 
went silent for an extended period starting soon after the onset of a 
seismic survey in the area. Similarly, there has been one report that 
sperm whales ceased calling when exposed to pulses from a very distant 
seismic ship (Bowles et al., 1994). However, more recent studies found 
that they continued calling the presence of seismic pulses (Madsen et 
al., 2002; Tyack et al., 2003; Smultea et al., 2004; Holst et al., 
2006; Jochens et al., 2008). Dolphins and porpoises commonly are heard 
calling while airguns are operating (Gordon et al., 2004; Smultea et 
al., 2004; Holst et al., 2005a,b; Potter et al., 2007). The sounds 
important to small odontocetes are predominantly at much higher 
frequencies than the dominant components of airgun sounds, thus 
limiting the potential for masking. In general, masking effects of 
seismic pulses are expected to be minor, given the normally 
intermittent nature of seismic pulses. Masking effects on marine 
mammals are discussed further in Appendix B (4) of the L-DEO EA.

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 (Richardson et al., 1995; Wartzok et al., 2004; Southall 
et al., 2007; Weilgart, 2007). If a marine mammal does react to an 
underwater sound by changing its behavior or moving a small distance, 
the response may or may not rise to the level of ``harassment'' to the 
individual, or affect the stock or the species population as a whole. 
However, if a sound source displaces marine mammals from an important 
feeding or breeding area for a prolonged period, impacts on individuals 
and populations could be significant (e.g., Lusseau and Bejder, 2007; 
Weilgart, 2007). Given the many uncertainties in predicting the 
quantity and types of impacts of noise on marine mammals, it is common 
practice to estimate how many mammals are likely to be present within a 
particular distance of industrial activities, and/or exposed to a 
particular level of industrial sound. In most cases, this practice 
potentially overestimates the numbers of marine mammals that would be 
affected in some biologically-important manner.
    The sound exposure criteria used to estimate how many marine 
mammals might be disturbed to some biologically-important degree by a 
seismic program are based primarily on behavioral observations of 
several species. However, information is lacking for many species. 
Detailed studies have been done on humpback, gray, bowhead, and sperm 
whales. Less detailed data are available for some other species of 
baleen whales, small toothed whales, and sea otters, but for many 
species there are no data on responses to marine seismic surveys.
    Baleen Whales--Baleen whales generally tend to avoid operating 
airguns, but avoidance radii are quite variable. Whales are often 
reported to show no overt reactions to pulses from large arrays of 
airguns at distances beyond a few kilometers, even though the airgun 
pulses remain well above ambient noise levels out to much longer 
distances. However, as reviewed in Appendix B (5) of the L-DEO EA, 
baleen whales exposed to strong noise pulses from airguns often react 
by deviating from their normal migration route and/or interrupting 
their feeding activities and moving away from the sound source. In the 
case of the migrating gray and bowhead whales, the observed changes in 
behavior appeared to be of little or no biological consequence to the 
animals. They simply avoided the sound source by displacing their 
migration route to varying degrees, but within the natural boundaries 
of the migration corridors.
    Studies of gray, bowhead, and humpback whales have demonstrated 
that seismic pulses with received levels of 160 to 170 dB re 1 [mu]Pa 
(rms) seem to cause obvious avoidance behavior in a substantial 
fraction of the animals exposed (Richardson et al., 1995). In many 
areas, seismic pulses from large arrays of airguns diminish to those 
levels at distances ranging from 4 to 15 km (2.8 to 9 mi) from the 
source. A substantial proportion of the baleen whales within those 
distances may show avoidance or other strong behavioral reactions to 
the airgun array. Subtle behavioral changes sometimes become evident at 
somewhat lower received levels, and studies summarized in Appendix B(5) 
of the L-DEO EA have shown that some species of baleen whales, notably 
bowhead and humpback whales, at times show strong avoidance at received 
levels lower than 160 to 170 dB re 1 [mu]Pa (rms).
    Responses of humpback whales to seismic surveys have been studied 
during migration, on the summer feeding grounds, and on Angolan winter 
breeding grounds; there has also been discussion of effects on the 
Brazilian wintering grounds. McCauley et al. (1998, 2000a) studied the 
responses of humpback whales off Western Australia to a full-scale 
seismic survey with a 16 airgun, 2,678 in\3\ array, and to a single 20 
in\3\ airgun with a source level of 227

[[Page 8658]]

dB re 1 [mu]Pam peak-to-peak. McCauley et al. (1998) documented that 
initial avoidance reactions began at 5 to 8 km (3.1 to 5 mi) from the 
array, and that those reactions kept most pods approximately 3 to 4 km 
(1.9 to 2.5 mi) from the operating seismic boat. McCauley et al. 
(2000a) noted localized displacement during migration of 4 to 5 km (2.5 
to 3.1 mi) by traveling pods and 7 to 12 km (4.3 to 7.5 mi) by cow-calf 
pairs. Avoidance distances with respect to the single airgun were 
smaller (2 km [1.2 mi]) but consistent with the results from the full 
array in terms of received sound levels. The mean received level for 
initial avoidance of an approaching airgun was 140 dB re 1 [mu]Pa (rms) 
for humpback whale pods containing females, and at the mean closest 
point of approach (CPA) distance the received level was 143 dB re 1 
[mu]Pa (rms). The initial avoidance response generally occurred at 
distances of 5 to 8 km (3.1 to 5 mi) from the airgun array and 2 km 
(1.2 mi) from the single airgun. However, some individual humpback 
whales, especially males, approached within distances of 100 to 400 m 
(328 to 1,312 ft), where the maximum received level was 179 dB re 1 
[mu]Pa (rms).
    Humpback whales on their summer feeding grounds in southeast Alaska 
did not exhibit persistent avoidance when exposed to seismic pulses 
from a 1.64-L (100 in\3\) airgun (Malme et al., 1985). Some humpbacks 
seemed ``startled'' at received levels of 150 to 169 dB re 1 [mu]Pa on 
an approximate rms basis. Malme et al. (1985) concluded that there was 
no clear evidence of avoidance, despite the possibility of subtle 
effects, at received levels up to 172 re 1 [mu]Pa on an approximate rms 
    It has been suggested that South Atlantic humpback whales wintering 
off Brazil may be displaced or even strand upon exposure to seismic 
surveys (Engel et al., 2004). The evidence for this was circumstantial 
and subject to alternative explanations (IAGC, 2004). Also, the 
evidence was not consistent with subsequent results from the same area 
of Brazil (Parente et al., 2006), or with results from direct studies 
of humpbacks exposed to seismic surveys in other areas and seasons. 
After allowance for data from subsequent years, there was ``no 
observable direct correlation'' between strandings and seismic surveys 
(IWC, 2007:236).
    There are no data on reactions of right whales to seismic surveys, 
but results from the closely-related bowhead whale show that their 
responsiveness can be quite variable depending on the activity 
(migrating vs. feeding). Bowhead whales migrating west across the 
Alaskan Beaufort Sea in autumn, in particular, are unusually 
responsive, with substantial avoidance occurring out to distances of 20 
to 30 km (12.4 to 18.6 mi) from a medium-sized airgun source at 
received sound levels of around 120 to 130 dB re 1 [mu]Pa (rms) (Miller 
et al., 1999; Richardson et al., 1999; see Appendix B (5) of the EA). 
However, more recent research on bowhead whales (Miller et al., 2005a; 
Harris et al., 2007) corroborates earlier evidence that, during the 
summer feeding season, bowheads are not as sensitive to seismic 
sources. Nonetheless, subtle but statistically significant changes in 
surfacing-respiration-dive cycles were evident upon statistical 
analysis (Richardson et al., 1986). In summer, bowheads typically begin 
to show avoidance reactions at a received level of about 152 to 178 dB 
re 1 [mu]Pa (rms) (Richardson et al., 1986, 1995; Ljungblad et al., 
1988; Miller et al., 2005a).
    Reactions of migrating and feeding (but not wintering) gray whales 
to seismic surveys have been studied. Malme et al. (1986, 1988) studied 
the responses of feeding Eastern Pacific gray whales to pulses from a 
single 100 in\3\ airgun off St. Lawrence Island in the northern Bering 
Sea. Malme et al. (1986, 1988) estimated, based on small sample sizes, 
that 50 percent of feeding gray whales ceased feeding at an average 
received pressure level of 173 dB re 1 [mu]Pa on an (approximate) rms 
basis, and that 10 percent of feeding whales interrupted feeding at 
received levels of 163 dB dB re 1 [mu]Pa (rms). Those findings were 
generally consistent with the results of experiments conducted on 
larger numbers of gray whales that were migrating along the California 
coast (Malme et al., 1984; Malme and Miles, 1985), and with 
observations of Western Pacific gray whales feeding off Sakhalin 
Island, Russia, when a seismic survey was underway just offshore of 
their feeding area (Wursig et al., 1999; Gailey et al., 2007; Johnson 
et al., 2007; Yazvenko et al. 2007a,b), along with data on gray whales 
off British Columbia (Bain and Williams, 2006).
    Various species of Balaenoptera (blue, sei, fin, Bryde's, and minke 
whales) have occasionally been reported in areas ensonified by airgun 
pulses (Stone, 2003; MacLean and Haley, 2004; Stone and Tasker, 2006), 
and calls from blue and fin whales have been localized in areas with 
airgun operations (e.g. McDonald et al., 1995; Dunn et al., 2009). 
Sightings by observers on seismic vessels off the United Kingdom from 
1997 to 2000 suggest that, during times of good sightability, sighting 
rates for mysticetes (mainly fin and sei whales) were similar when 
large arrays of airguns were shooting and not shooting (silent) (Stone, 
2003; Stone and Tasker, 2006). However, these whales tended to exhibit 
localized avoidance, remaining significantly further (on average) from 
the airgun array during seismic operations compared with non-seismic 
periods (Stone and Tasker, 2006). In a study off Nova Scotia, Moulton 
and Miller (2005) found little difference in sighting rates (after 
accounting for water depth) and initial sighting distances of 
balaenopterid whales when airguns were operating vs. silent. However, 
there were indications that these whales were more likely to be moving 
away when seen during airgun operations. Similarly, ship-based 
monitoring studies of blue, fin, sei, and minke whales offshore of 
Newfoundland (Orphan Basin and Laurentian Sub-basin) found no more than 
small differences in sighting rates and swim direction during seismic 
vs. non-seismic periods (Moulton et al., 2005, 2006a,b).
    Data on short-term reactions (or lack of reactions) of cetaceans to 
impulsive noises are not necessarily indicative of long-term or 
biologically significant effects. It is not known whether impulsive 
sounds affect reproductive rate or distribution and habitat use in 
subsequent days or years. However, gray whales continued to migrate 
annually along the west coast of North America with substantial 
increases in the population over recent years, despite intermittent 
seismic exploration (and much ship traffic) in that area for decades 
(see Appendix A in Malme et al., 1984; Richardson et al., 1995; Angliss 
and Outlaw, 2008). The Western Pacific gray whale population did not 
seem affected by a seismic survey in its feeding ground during a prior 
year (Johnson et al., 2007). Similarly, bowhead whales have continued 
to travel to the eastern Beaufort Sea each summer, and their numbers 
have increased notably, despite seismic exploration in their summer and 
autumn range for many years (Richardson et al., 1987; Angliss and 
Outlaw, 2008).
    Toothed Whales--Little systematic information is available about 
reactions of toothed whales to noise pulses. Few studies similar to the 
more extensive baleen whale/seismic pulse work summarized above and (in 
more detail) in Appendix B or the EA have been reported for toothed 
whales. However, recent systematic studies on sperm whales have been 
done (Gordon et al., 2006; Madsen et al., 2006; Winsor and Mate, 2006; 
Jochens et al., 2008; Miller et al., 2009). There is an increasing 
amount of information about responses

[[Page 8659]]

of various odontocetes to seismic surveys based on monitoring studies 
(e.g., Stone, 2003; Smultea et al., 2004; Moulton and Miller, 2005; 
Bain and Williams, 2006; Holst et al., 2006; Stone and Tasker, 2006; 
Potter et al., 2007; Hauser et al., 2008; Holst and Smultea, 2008; 
Weir, 2008; Barkaszi et al., 2009; Richardson et al., 2009).
    Seismic operators and observers on seismic vessels regularly see 
dolphins and other small toothed whales near operating airgun arrays, 
but in general there seems to be a tendency for most delphinids to show 
some avoidance of operating seismic vessels (Goold, 1996a,b,c; 
Calambokidis and Osmek, 1998; Stone, 2003; Moulton and Miller, 2005; 
Holst et al., 2006; Stone and Tasker, 2006; Weir, 2008; Richardson et 
al., 2009; Barkaszi et al., 2009). However, some dolphins seem to be 
attracted to the seismic vessel and floats, and some ride the bow wave 
of the seismic vessel even when large airgun arrays are firing (Moulton 
and Miller, 2005). Nonetheless, there have been indications that small 
toothed whales more often tend to head away, or to maintain a somewhat 
greater distance from the vessel, when a large array of airguns is 
operating than when it is silent (Stone and Tasker, 2006; Weir, 2008). 
In most cases, the avoidance radii for delphinids appear to be small, 
on the order of 1 km (0.62 mi) or less, and some individuals show no 
apparent avoidance. The beluga is a species that (at least at times) 
shows long-distance avoidance of seismic vessels. Aerial surveys during 
seismic operations in the southeastern Beaufort Sea during summer found 
that sighting rates of beluga whales were significantly lower at 
distances 10 to 20 km (6.2 to 12.4 mi) compared with 20 to 30 km (mi) 
from an operating airgun array, and observers on seismic boats in that 
area rarely see belugas (Miller et al., 2005; Harris et al., 2007).
    Captive bottlenose dolphins and beluga whales exhibited changes in 
behavior when exposed to strong pulsed sounds similar in duration to 
those typically used in seismic surveys (Finneran et al., 2000, 2002, 
2005; Finneran and Schlundt, 2004). However, the animals tolerated high 
received levels of sound before exhibiting aversive behaviors.
    Results for porpoises depend on species. The limited available data 
suggest that harbor porpoises show stronger avoidance of seismic 
operations than do Dall's porpoises (Stone, 2003; Bain and Williams, 
2006; Stone and Tasker, 2006). Dall's porpoises seem relatively 
tolerant of airgun operations (MacLean and Koski, 2005; Bain and 
Williams, 2006), although they too have been observed to avoid large 
arrays of operations airguns (Calambokidis and Osmek, 1998; Bain and 
Williams, 2006). This apparent difference in responsiveness of these 
two porpoise species is consistent with their relative responsiveness 
to boat traffic and some other acoustic sources in general (Richardson 
et al., 1995; Southall et al., 2007).
    Most studies of sperm whales exposed to airgun sounds indicate that 
the sperm whale shows considerable tolerance of airgun pulses (Stone, 
2003; Moulton et al., 2005, 2006a; Stone and Tasker, 2006; Weir, 2008). 
In most cases, the whales do not show strong avoidance and continue to 
call (see Appendix B in the L-DEO EA). However, controlled exposure 
experiments in the Gulf of Mexico indicate that foraging behavior was 
altered upon exposure to airgun sounds (Jochens et al., 2008; Miller et 
al., 2009; Tyack, 2009).
    There are almost no specific data on the behavioral reactions of 
beaked whales to seismic surveys. However, northern bottlenose whales 
(Hyperodon ampullatus) continued to produce high-frequency clicks when 
exposed to sound pulses from distant seismic surveys (Laurinolli and 
Cochrane, 2005; Simard et al., 2005). Most beaked whales tend to avoid 
approaching vessels of other types (Wursig et al., 1998). They may also 
dive for an extended period when approached by a vessel (Kasuya, 1986), 
although it is uncertain how much longer such dives may be as compared 
to dives by undisturbed beaked whales, which also are often quite long 
(Baird et al., 2006; Tyack et al., 2006). It is likely that these 
beaked whales would normally show strong avoidance of an approaching 
seismic vessel, but this has not been documented explicitly.
    Odontocete reactions to large arrays of airguns are variable and, 
at least for delphinids and Dall's porpoises, seem to be confined to a 
smaller radius than has been observed for the more responsive of the 
mysticetes, belugas, and harbor porpoises (Appendix B of the L-DEO EA).

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 will be developing new noise exposure criteria for marine 
mammals that take account of the now-available scientific data on 
temporary threshold shift (TTS), the expected offset between the TTS 
and permanent threshold shift (PTS) thresholds, differences in the 
acoustic frequencies to which different marine mammal groups are 
sensitive, and other relevant factors. Detailed recommendations for new 
science-based noise exposure criteria were published in late 2007 
(Southall et al., 2007).
    Several aspects of the planned monitoring and mitigation measures 
for this project (see below) 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. In addition, many 
cetaceans are likely to show some avoidance of the area where received 
levels of airgun sound are high enough such that hearing impairment 
could potentially occur. 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 might (in theory) 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 (i.e., beaked whales) 
may be especially susceptible to injury and/or stranding when exposed 
to strong pulsed sounds. However, as discussed below, 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 especially 
unlikely that any effects of these types would occur during the present 
project given the brief duration of exposure of any given mammal, the 
deep water in the study area, and the proposed monitoring and 
mitigation measures (see below). The following subsections discuss in 
somewhat more detail the possibilities of TTS, PTS, and non-auditory 
physical effects.
    Temporary Threshold Shift--TTS is the mildest form of hearing 
impairment that can occur during exposure to a strong sound (Kryter, 
1985). While experiencing TTS, the hearing threshold rises and a sound 
must be stronger in order to be heard. At least in terrestrial mammals, 
TTS can last from minutes or hours to (in cases of strong TTS) days. 
For sound exposures at or somewhat above the TTS threshold, hearing 
sensitivity in both terrestrial and marine mammals recovers rapidly 
after exposure to the noise ends. Few data on sound levels and 
durations necessary to elicit mild TTS have been obtained for

[[Page 8660]]

marine mammals, and none of the published data concern TTS elicited by 
exposure to multiple pulses of sound. Available data on TTS in marine 
mammals are summarized in Southall et al. (2007). Based on these data, 
the received energy level of a single seismic pulse (with no frequency 
weighting) might need to be approximately 186 dB re 1 
[mu]Pa\2\[middot]s (i.e., 186 dB SEL or approximately 196 to 201 re 1 
[mu]Pa [rms]) in order to produce brief, mild TTS. Exposure to several 
strong seismic pulses that each have received levels near 190 re 1 
[mu]Pa (rms) might result in cumulative exposure of approximately 186 
dB SEL and thus slight TTS in a small odontocete, assuming the TTS 
threshold is (to a first approximation) a function of the total 
received pulse energy; however, this `equal energy' concept is an 
oversimplification. The distance from the Langseth's airguns at which 
the received energy level (per pulse, flat-weighted) would be expected 
to be greater than or equal to 190 dB re 1 [mu]Pa (rms) are estimated 
in Table 1 of L-DEO's application and above. Levels greater than or 
equal to 190 dB re 1 [mu]Pa (rms) are expected to be restricted to 
radii no more than 400 m. For an odontocete closer to the surface, the 
maximum radius with greater than or equal to 190 dB re 1 [mu]Pa (rms) 
would be smaller.
    The above TTS information for odontocetes is derived from studies 
on the bottlenose dolphin and beluga. For the one harbor porpoise 
tested, the received level of airgun sound that elicited onset of TTS 
was lower (Lucke et al., 2009). If these results from a single animal 
are representative, it is inappropriate to assume that onset of TTS 
occurs at similar received levels in all odontocetes (Southall et al., 
2007). Some cetaceans apparently can incur TTS at considerably lower 
sound exposures than are necessary to elicit TTS in the beluga or 
bottlenose dolphin.
    For baleen whales, there are no data, direct or indirect, on levels 
or properties of sound required to induce TTS. The frequencies to which 
baleen whales are most sensitive are lower than those to which 
odontocetes are more sensitive, and natural background noise levels at 
those low frequencies tend to be higher. As a result, auditory 
thresholds of baleen whales within their frequency band of best hearing 
are believed to be higher (less sensitive) than are those of 
odontocetes at their best frequencies (Clark and Ellison, 2004). From 
this, it is suspected that received levels causing TTS onset may also 
be higher in baleen whales (Southall et al., 2007). In any event, no 
cases of TTS are expected given three considerations:
    (1) The relatively low abundance of baleen whales expected in the 
planned study areas;
    (2) 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; and
    (3) The mitigation measures that are planned.
    To avoid the potential for injury, NMFS (1995, 2000) concluded that 
cetaceans and pinnipeds should not be exposed to pulsed underwater 
noise at received levels exceeding 180 and 190 dB re 1 [mu]Pa (rms), 
respectively. This sound level is not considered to be the level above 
which TTS might occur. Rather, it was the received levels above which, 
in the view of a panel of bioacoustics specialists convened by NMFS 
before TTS measurements for marine mammals started to become available, 
one could not be certain that there would be no injurious effects, 
auditory or otherwise, to cetaceans. As summarized above and in 
Southall et al. (2007), data that are now available imply that TTS is 
unlikely to occur in most odontocetes (and probably mysticetes as well) 
unless they are exposed to a sequence of several airgun pulses stronger 
than 190 dB re 1 [mu]Pa (rms).
    Permanent Threshold Shift--When PTS occurs, there is physical 
damage to the sound receptors in the ear. In severe cases, there can be 
total or partial deafness, whereas in other cases, the animal has an 
impaired ability to hear sounds in specific frequency ranges (Kryter, 
    There is no specific evidence that exposure to pulses of airgun 
sound can cause PTS in any marine mammal, even with large arrays of 
airguns. However, given the possibility that mammals close to an airgun 
array might incur at least mild TTS, there has been further speculation 
about the possibility that some individuals occurring very close to 
airguns might incur PTS (Richardson et al., 1995; Gedamke et al., 
2008). Single or occasional occurrences of mild TTS are not indicative 
of permanent auditory damage, but repeated or (in some cases) single 
exposures to a level well above that causing TTS onset might elicit 
    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. PTS might occur at a received sound level at 
least several decibels above that inducing mild TTS if the animal were 
exposed to strong sound pulses with rapid rise time (see Appendix B (6) 
of the L-DEO EA). Based on data from terrestrial mammals, a 
precautionary assumption is that the PTS threshold for impulse sounds 
(such as airgun pulses as received close to the source) is at least 6 
dB higher than the TTS threshold on a peak-pressure basis, and probably 
greater than 6 dB (Southall et al., 2007). On an SEL basis, Southall et 
al. (2007) estimated that received levels would need to exceed the TTS 
threshold by at least 15 dB for there to be risk of PTS. Thus, for 
cetaceans they estimate that the PTS threshold might be an M-weighted 
SEL (for the sequence of received pulses) of approximately 198 dB re 1 
[mu]Pa2[middot]s (15 dB higher than the Mmf -
weighted TTS threshold, in a beluga, for a watergun impulse), where the 
SEL value is cumulated over the sequence of pulses.
    Southall et al. (2007) also note that, regardless of the SEL, there 
is concern about the possibility of PTS if a cetacean or pinniped 
receives one or more pulses with peak pressure exceeding 230 or 218 dB 
re 1 [mu]Pa (peak), respectively. Thus PTS might be expected upon 
exposure of cetaceans to either SEL greater than or equal to 198 dB re 
1 [mu]Pa2[middot]s or peak pressure greater than or equal to 
230 dB re 1 [mu]Pa. Corresponding proposed dual criteria for pinnipeds 
(at least harbor seals) are greater than or equal to 186 dB SEL and 
greater than or equal to 218 dB peak pressure (Southall et al., 2007). 
These estimates are all first approximations, given the limited 
underlying data, assumptions, species differences, and evidence that 
the ``equal energy'' model may not be entirely correct. A peak pressure 
of 230 dB re 1 [mu]Pa (3.2 bar [middot] m, 0-pk), which would only be 
found within a few meters of the largest (360 in3) airguns 
in the planned airgun array (Caldwell and Dragoset, 2000). A peak 
pressure of 218 dB re 1 [mu]Pa could be received somewhat farther away; 
to estimate that specific distance, one would need to apply a model 
that accurately calculates peak pressures in the near-field around an 
array of airguns.
    Given the higher level of sound necessary to cause PTS as compared 
with TTS, it is considerably less likely that PTS could occur. Baleen 
whales generally avoid the immediate area around operating seismic 
vessels, as do some other marine mammals. The planned monitoring and 
mitigation measures, including visual monitoring, passive acoustic 
monitoring (PAM) to complement visual observations (if practicable), 
power-downs, and shut-downs of the airguns when mammals are seen within 
or approaching the EZs will further reduce the probability of exposure 
of marine mammals to sounds strong enough to induce PTS.

[[Page 8661]]

    Strandings and Mortality--Marine mammals close to underwater 
detonations of high explosives can be killed or severely injured, and 
their auditory organs are especially susceptible to injury (Ketten et 
al., 1993; Ketten, 1995). However, explosives are no longer used for 
marine waters for commercial seismic surveys or (with rare exceptions) 
for seismic research; they have been replaced entirely by airguns or 
related non-explosive pulse generators. 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 and, in one case, an L-DEO seismic survey 
(Malakoff, 2002; Cox et al., 2006), 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 (Hildebrand, 2005; Southall et al., 2007). Appendix B(6) of 
the L-DEO EA provides additional details.
    Specific sound-related processes that lead to strandings and 
mortality are not well documented, but may include:
    (1) Swimming in avoidance of a sound into shallow water;
    (2) A change in behavior (such as a change in diving behavior) that 
might contribute to tissue damage, gas bubble formation, hypoxia, 
cardiac arrhythmia, hypertensive hemorrhage or other forms of trauma;
    (3) A physiological change such as a vetibular response leading to 
a behavioral change or stress-induced hemorrhagic diathesis, leading in 
turn to tissue damage; and
    (4) Tissue damage directly from sound exposure, such as through 
acoustically mediated bubble formation and growth or acoustic resonance 
of tissues.
    Some of these mechanisms are unlikely to apply in the case of 
impulse sounds. However, there are increasing indications that gas-
bubble disease (analogous to ``the bends''), induced in supersaturated 
tissue by a behavioral response to acoustic exposure, could be a 
pathologic mechanism for the strandings and mortality of some deep-
diving cetaceans exposed to sonar. The evidence for this remains 
circumstantial and associated with exposure to naval mid-frequency 
sonar, not seismic surveys (Cox et al., 2006; Southall et al., 2007).
    Seismic pulses and mid-frequency sonar signals are quite different, 
and some mechanisms by which sonar sounds have been hypothesized to 
affect beaked whales are unlikely to apply to airgun pulses. Sounds 
produced by airgun arrays are broadband impulses 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. 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 (at least indirectly) to physical 
damage and mortality (Balcomb and Claridge, 2001; NOAA and USN, 2001; 
Jepson et al., 2003; Fern[aacute]ndez et al., 2004, 2005a; Cox et al., 
2006) suggests that caution is warranted when dealing with exposure of 
marine mammals to any high-intensity pulsed sound.
    There is no conclusive evidence of cetacean strandings or deaths at 
sea as a result of exposure to seismic surveys, but a few cases of 
strandings in the general area where a seismic survey was ongoing have 
led to speculation concerning a possible link between seismic surveys 
and strandings. Suggestions that there was a link between seismic 
surveys and strandings of humpback whales in Brazil (Engel et al., 
2004) was not well founded based on available data (IAGC, 2004; IWC, 
2007b). In September 2002, there was a stranding of two Cuvier's beaked 
whales in the Gulf of California, Mexico, when the L-DEO vessel R/V 
Maurice Ewing (Ewing) was operating a 20 airgun, 8,490 in\3\ array in 
the general area. The link between the stranding and the seismic survey 
was inconclusive and not based on any physical evidence (Hogarth, 2002; 
Yoder, 2002). Nonetheless, the Gulf of California incident plus the 
beaked whale strandings near naval exercises involving use of mid-
frequency sonar suggests a need for caution when conducting seismic 
surveys in areas occupied by beaked whales until more is known about 
effects of seismic surveys on those species (Hildebrand, 2005). No 
injuries of beaked whales are anticipated during the proposed study 
because of:
    (1) The high likelihood that any beaked whales nearby would avoid 
the approaching vessel before being exposed to high sound levels;
    (2) The proposed monitoring and mitigation measures; and
    (3) Differences between the sound sources operated by L-DEO and 
those involved in the naval exercises associated with strandings.
    Non-auditory Physiological Effects--non-auditory physiological 
effects or injuries that theoretically might occur in marine mammals 
exposed to strong underwater sound include stress, neurological 
effects, bubble formation, resonance, and other types of organ or 
tissue damage (Cox et al., 2006; Southall et al., 2007). Studies 
examining such effects are limited. However, resonance effects (Gentry, 
2002) and direct noise-induced bubble formation (Crum et al., 2005) are 
implausible in the case of exposure to an impulsive broadband source 
like an airgun array. If seismic surveys disrupt diving patterns of 
deep-diving species, this might perhaps result in bubble formation and 
a form of ``the bends,'' as speculated to occur in beaked whales 
exposed to sonar. However, there is no specific evidence of this upon 
exposure to airgun pulses.
    In general, very little is known about the potential for seismic 
survey sounds (or other types of strong underwater sounds) to cause 
non-auditory physical effects in marine mammals. Such effects, if they 
occur at all, would presumably be limited to short distances and to 
activities that extend over a prolonged period. The available data do 
not allow identification of a specific exposure level above which non-
auditory effects can be expected (Southall et al., 2007), or any 
meaningful quantitative predictions of the numbers (if any) of marine 
mammals that might be affected in those ways. Marine mammals that show 
behavioral avoidance of seismic vessels, including most baleen whales 
and some odontocetes, are especially unlikely to incur non-auditory 
physical effects. Also, the planned monitoring and mitigation measures, 
including shut-down of the airguns, will reduce any such effects that 
might otherwise occur.

Potential Effects of Other Acoustic Devices--MBES Signals

    The Kongsberg EM 122 MBES will be operated from the source vessel 
during the planned study. Sounds from the MBES are very short pulses, 
occurring for 2 to 15 ms once every 5 to 20 s, depending on water 
depth. Most of the energy in the sound pulses emitted by the MBES is at 
frequencies centered at 12 kHz, and the maximum source level is 242 dB 
re 1 [micro]Pa (rms). The beam is narrow (1 to 2[deg]) in fore-aft 
extent and wide (150[deg]) in the cross-track extent. Each ping 
consists of eight (in water greater than 1,000 m deep) or four (greater 
than 1,000 m deep) 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 MBES are unlikely to 
be subjected to

[[Page 8662]]

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 2 to 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 MBES 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 in order to receive the multiple pulses 
that might result in sufficient exposure to cause TTS. Burkhardt et al. 
(2007) concluded that immediate direct auditory injury was possible 
only if a cetacean dived under the vessel into the immediate vicinity 
of the transducer.
    Navy sonars that have been linked to avoidance reactions and 
stranding of cetaceans (1) generally have a longer pulse duration that 
the Kongsberg EM 122, and (2) are often directed close to horizontally 
vs. more downward for the MBES. The area of possible influence of the 
MBES 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. During L-DEO's operations, the individual pulses will be 
very short, and a given marine mammal would not receive many of the 
downward-directed pulses as the vessel passes by.
    Marine mammal communications will not be masked appreciably by the 
MBES signals given its low duty cycle and the brief period when an 
individual mammal is likely to be within its beam. Furthermore, in the 
case of baleen whales, the signals (12 kHz) do not overlap with the 
predominant frequencies in the calls, which would avoid significant 
    Behavioral reactions of free-ranging marine mammals to sonars, 
echosounders, and other sound sources 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 beachings by beaked whales. During exposure to a 
21 to 25 kHz ``whale-finding'' sonar with a source level of 215 dB re 1 
[mu]Pam, gray whales reacted by orienting slightly away from the source 
and being deflected from their course by approximately 200 m (656 ft) 
(Frankel, 2005). When a 38 kHz echosounder and a 150 kHz acoustic 
Doppler current profiler were transmitting during studies in the 
Eastern Tropical Pacific, baleen whales showed no significant 
responses, while spotted and spinner dolphins were detected slightly 
more often and beaked whales less often during visual surveys 
(Gerrodette and Pettis, 2005).
    Captive bottlenose dolphins and a beluga whale exhibited changes in 
behavior when exposed to 1 s tonal signals at frequencies similar to 
those that will be emitted by the MBES used by L-DEO, 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; Finneran and Schlundt, 
2004). The relevance of those data to free-ranging odontocetes is 
uncertain, and in any case, the test sounds were quite different in 
either duration as compared with those from an MBES.
    NMFS believes that the brief exposure of marine mammals to one 
pulse, or small numbers of signals, from the MBES are not likely to 
result in the harassment of marine mammals.

Potential Effects of Other Acoustic Devices--SBP Signals

    A SBP will be operated from the source vessel during the planned 
study. Sounds from the SBP are very short pulses, occurring for 1 to 4 
ms once every second. Most of the energy in the sound pulses emitted by 
the SBP is at 3.5 kHz, and the cone-shaped beam is directed downward. 
The SBP on the Langseth has a maximum source level of 204 dB re 1 
[micro]Pam. Kremser et al. (2005) noted that the probability of a 
cetacean swimming through the area of exposure when a bottom profiler 
emits a pulse is small--even for an SBP more powerful than that on the 
Langseth--if the animal was in the area, it would have to pass the 
transducer at close range in order to be subjected to sound levels that 
could cause TTS.
    Marine mammal communications will not be masked appreciably by the 
SBP signals given their directionality of the signal and the brief 
period when an individual mammal is likely to be within its beam. 
Furthermore, in the case of most baleen whales, the SBP signals do not 
overlap with the predominant frequencies in the calls, which would 
avoid significant masking.
    Marine mammal behavioral reactions to other pulsed sound sources 
are discussed above, and responses to the SBP are likely to be similar 
to those for other pulsed sources if received at the same levels. The 
pulsed signals from the SBP are somewhat weaker than those from the 
MBES. Therefore, behavioral responses are not expected unless marine 
mammals are very close to the source.
    It is unlikely that the SBP 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 SBP is operated 
simultaneously with other higher-power acoustic sources, including the 
airguns. 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 SBP. In the case of 
mammals that do not avoid the approaching vessel and its various sound 
sources, monitoring and mitigation measures that would be applied to 
minimize effects of other sources would further reduce or eliminate any 
minor effects of the SBP.
    NMFS believes that to avoid the potential for permanent 
physiological damage (Level A harassment), cetaceans and pinnipeds 
should not be exposed to pulsed underwater noise at received levels 
exceeding, respectively, 180 and 190 dB re 1 [mu]Pa (rms). The 
precautionary nature of these criteria is discussed in the L-DEO EA, 
including the fact that 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 and 
the level associated with the onset of TTS is often considered to be a 
level below which there is no danger of permanent damage. NMFS also 
assumes that cetaceans or pinnipeds exposed to levels exceeding 160 dB 
re 1 [mu]Pa (rms) may experience Level B harassment.

Possible Effects of Acoustic Release Signals

    The acoustic release transponder used to communicate with the OBSs 
uses frequencies of 9 to 13 kHz. These signals will be used very 
intermittently. It is unlikely that the acoustic release signals would 
have significant effects on marine mammals through masking, 
disturbance, or hearing impairment. Any effects likely would be 
negligible given the brief exposure at presumable low levels.

Estimated Take of Marine Mammals by Incidental Harassment

    All anticipated takes would be ``takes by Level B harassment,'' 
involving temporary changes in behavior. The proposed monitoring and 
mitigation measures are expected to minimize the possibility of 
injurious takes or mortality. However, as noted earlier, there is no 
specific information

[[Page 8663]]

demonstrating that injurious ``takes'' or mortality would occur even in 
the absence of the planned mitigation measures. NMFS believes, 
therefore, that injurious take or mortality to the affected species 
marine mammals is extremely unlikely to occur as a result of the 
specified activities within the specified geographic area for which L-
DEO seeks the IHA. The sections below describe methods to estimate 
``take by harassment'', and present estimates of the numbers of marine 
mammals that could be affected during the proposed seismic program. The 
estimates of ``take by harassment'' are based on consideration of the 
number of marine mammals that might be disturbed appreciably by 
operations with the 36 airgun array to be used during approximately 
2,800 km of seismic surveys in the CNMI study area. The sources of 
distributional and numerical data used in deriving the estimates are 
described below.
    It is assumed that, during simultaneous operations of the airgun 
array and the other sources, any marine mammals close enough to be 
affected by the MBES and SBP would already be affected by the airguns. 
However, whether or not the airguns are operating simultaneously with 
the other sources, marine mammals are expected to exhibit no more than 
short-term and inconsequential responses to the MBES and SBP given 
their characteristics (e.g., narrow downward-directed beam) and other 
considerations. Such reactions are not considered to constitute 
``taking'' (NMFS, 2001). Therefore, no additional allowance is included 
for animals that could be affected by sound sources other than airguns.
    The only systematic marine mammal survey conducted in the CNMI was 
a ship-based survey conducted by the U.S. Navy during January to April, 
2007 in four legs: January 16 to February 2, February 6 to 25, March 1 
to 20, and March 24 to April 12 (SRS--Parsons et al., 2007). The cruise 
area was defined by the boundaries 10[deg] to 18[deg] North, 142[deg] 
to 148[deg] East, encompassing an area approximately 585,000 km\2\ 
including the islands of Guam and the southern CNMI almost as far north 
as Pagan. The systematic line-transect survey effort was conducted from 
the flying bridge (10.5 m or 34.5 ft above sea level) of the 56 m 
(183.7 ft) long M/V Kahana using standard line-transect protocols 
developed by NMFS Southwest Fisheries Science Center (SWFSC). Observers 
visually surveyed 11,033 km (6,855.6 mi) of tracklines, mostly in high 
sea states (88 percent of the time in Beaufort Sea states 4 to 6).
    L-DEO used the densities calculated in SRS--Parsons et al. (2007) 
for the 12 species sighted in that survey. For eight species not 
sighted in that survey, but expected to occur in the CNMI, relevant 
densities are available for the ``outer EEZ stratum'' of Hawaiian 
waters, based on a 13,500 km (mi) survey conducted by NMFS SWFSC in 
August to November, 2002 (Barlow, 2006). Another potential source of 
relevant densities is the SWFSC surveys conducted in the ETP during 
summer/fall 1986 to 1996 (Ferguson and Barlow, 2001). However, for five 
of the remaining seven species that could occur in the survey area, 
there were no sightings in offshore tropical strata during those 
surveys, and for another (the humpback whale), there was only one 
sighting in more than 50 offshore tropical (less than 20[deg] latitude) 
5[deg] x 5[deg] strata. For those six species, an arbitrary low density 
was assigned. The short-beaked common dolphin was sighted in a number 
of offshore tropical strata, so its density was calculated as the mean 
of densities in the 17 offshore 5[deg] x 5[deg] strata between 10[deg] 
North and 20[deg] North.
    The densities mentioned above had been corrected, by the original 
authors, for detectability bias, and in two of the three areas, for 
availability bias. Detectability bias is associated with diminishing 
sightability with increasing lateral distance from the track line 
[[fnof](0)]. Availability bias refers to the fact that there is less 
than 100 percent probability of sighting an animal that is present 
along the survey track line, and it is measured by g(0). SRS--Parsons 
et al. (2007) did not correct the Marianas densities for g(0), which 
for all but large (greater than 20) groups of dolphins [where g(0) = 
1], resulted in underestimates of density.
    There is some uncertainty about the representativeness of the 
density data and the assumptions used in the calculations. For example, 
the timing of the surveys was either before (Marianas) or after (Hawaii 
and ETP) the proposed surveys. Also, most of the Marianas survey was in 
high sea states that would have prevented detection of many marine 
mammals, especially cryptic species such as beaked whales and Kogia 
spp. However, the approach used here is believed to be the best 
available approach. To provide some allowance for these uncertainties, 
particularly underestimates of densities present and numbers of marine 
mammals potentially affected have been derived; maximum estimates are 
1.5x the best estimates. Densities calculated or estimated as described 
above are given in Table 3 of L-DEO's application.
    The estimated numbers of individuals potentially exposed are based 
on the 160 dB re 1 Pa (rms) Level B harassment exposure threshold for 
all cetaceans, see Table 4 of L-DEO's application. It is assumed that 
the species of marine mammals affected by the proposed survey, if 
exposed to airgun sounds at these levels, might change their behavior 
sufficiently to be considered ``take by Level B harassment.''
    It should be noted that the following estimates of exposures to 
various sound levels and related incidental takes by Level B harassment 
assume that the proposed marine geophysical surveys will be completed. 
As is typical during offshore ship surveys, inclement weather and 
equipment malfunctions are likely to cause delays and may limit the 
number of useful line-km of seismic operations that can be undertaken. 
Furthermore, any marine mammals sightings within or near the designated 
EZs will result in the power-down or shut-down of seismic operations as 
a mitigation measure. Thus the following estimates of the numbers of 
marine mammals potentially exposed to 160 dB re 1 [mu]Pam (rms) sounds 
are precautionary and probably overestimate the actual numbers of 
marine mammals that might be involved. These estimates assume that 
there will be no weather, equipment, or mitigation delays, which is 
highly unlikely.
    Table 4 of L-DEO's application shows the best and maximum estimated 
number of exposures and the number of different individuals potentially 
exposed during the seismic survey if no animals moved away from the 
survey vessel. The requested take authorization, given in the far right 
column of Table 4 of L-DEO's application, is based on the maximum 
estimates rather than the best estimates of the numbers of individuals 
exposed, because of uncertainties associated with applying density data 
from one area to another.
    The number of different individuals that may be exposed to airgun 
sounds with received levels >=160 dB re 1 [mu]Pa (rms) on one or more 
occasions was 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. The number of possible exposures (including 
repeated exposures of the same individuals) can be estimated by 
considering the total marine area that would be within the 160 dB 
radius around the operating airguns, including areas of overlap. In the 
proposed survey, the seismic lines are widely spaced in the proposed 
survey area, so an

[[Page 8664]]

individual mammal would most likely not be exposed numerous times 
during the survey; the area including overlap is only 1.4x the area 
excluding overlap. Moreover, it is unlikely that a particular animal 
would stay in the area during the entire survey.
    The number of different individuals potentially exposed to received 
levels >=160 dB re 1 [micro]Pa (rms) was calculated by multiplying:
     The expected species density, either ``mean'' (i.e., best 
estimate) or ``maximum,'' times,
     The anticipated minimum area to be ensonified to that 
level during airgun operations excluding overlap (exposures), or
     The anticipated area to be ensonified to that level during 
airgun operations excluding overlap (individuals).
    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 (see Table 1 of L-DEO's application) around 
each seismic line, and then calculating the total area within the 
buffers. Areas where overlap were included only once when estimating 
the number of individuals exposed.
    Applying the approach described above, approximately 15,685 km\2\ 
(6,056 mi\2\) would be within the 160 dB isopleth on one or more 
occasions during the survey, where as 21,415 km\2\ (8,268.4 mi\2\) is 
the area ensonified to greater than or equal to 160 dB when overlap is 
included. Because this approach does not allow for turnover in the 
mammal populations in the study area during the course of the survey, 
the actual number of individuals exposed could be underestimated. 
However, the approach assumes that no cetaceans will move away from or 
toward the trackline as the Langseth approaches in response to 
increasing sound levels prior to the time the levels reach 160 dB, 
which will result in overestimates for those species known to avoid 
seismic vessels.

 Table 3--The Estimates of the Possible Numbers of Marine Mammals Exposed to Sound Levels Greater Than or Equal
              to 160 dB During L-DEO's Proposed Seismic Survey in the CNMI in April to June, 2010*
                                                                    No. of           No. of      Approx. percent
                                                                 individuals      individuals      of regional
                           Species                              exposed (best)   exposed (max)     popu lation
                                                                     \1\              \1\           (best) \2\
                                                                            0                1                0
    North Pacific right whale................................
    (Eubalaena japonica).....................................
    Humpback whale...........................................               0                2                0
    (Megaptera novaeangliae).................................
    Minke whale..............................................               0                0                0
    (Balaenoptera acutorostrata).............................
    Bryde's whale............................................               6               10             0.03
    (Balaenoptera brydei)....................................
    Sei whale................................................               5                7             0.05
    (Balaenoptera borealis)..................................
    Fin whale................................................               0                2                0
    (Balaenoptera physalus)..................................
    Blue whale...............................................               0                2                0
    (Balaenoptera musculus)..................................
                                                                           19               29             0.07
    Sperm whale..............................................
    (Physeter macrocephalus).................................
    Pygmy sperm whale........................................              46               68             N.A.
    (Kogia breviceps)........................................
    Dwarf sperm whale........................................             112              168            <0.01
    (Kogia sima).............................................
    Cuvier's beaked whale....................................              97              146             0.49
    (Ziphius cavirostris)....................................
    Longman's beaked whale...................................               9               13             N.A.
    (Indopacetus pacificus)..................................
    Blainville's beaked whale................................              18               28             0.07
    (Mesoplodon densirostris)................................
    Ginkgo-toothed beaked whale..............................               0                0             N.A.
    (Mesoplodon ginkgodens)..................................
    Rough-toothed dolphin....................................               5                7            <0.01
    (Steno bredanensis)......................................
    Bottlenose dolphin.......................................               3                5            <0.01
    (Tursiops truncatus).....................................
    Pantropical spotted dolphin..............................             355              532             0.04
    (Stenella attenuata).....................................
    Spinner dolphin..........................................              49               74            <0.01
    (Stenella longirostris)..................................
    Striped dolphin..........................................              97              145             0.01
    (Stenella coeruleoalba)..................................
    Fraser's dolphin.........................................              65               98             0.02
    (Lagenodelphis hosei)....................................
    Short-beaked common dolphin..............................               0                0                0
    (Delphinus delphis)......................................

[[Page 8665]]

    Risso's dolphin..........................................              15               23             0.01
    (Grampus griseus)........................................
    Melon-headed whale.......................................              67              101             0.15
    (Peponocephala electra)..................................
    Pygmy killer whale.......................................               2                3            <0.01
    (Feresa attenuata).......................................
    False killer whale.......................................              17               26            <0.01
    (Pseudorca crassidens)...................................
    Killer whale.............................................               2                3             0.04
    (Orcinus orca)...........................................
    Short-finned pilot whale.................................              25               37            <0.01
    (Globicephala macrorhynchus).............................
Sirenians: Dugong............................................               0                0            N.A.
(Dugong dugon)...............................................
* The proposed sound source consists of a 36 airgun, 6,600 in\3\ array. Received levels are expressed in dB re 1
  [mu]Pa (rms) (averaged over pulse duration), consistent with NMFS' practice. Not all marine mammals will
  change their behavior when exposed to these sound levels, but some may alter their behavior when levels are
  lower (see text). See Tables 2 to 4 in L-DEO's application for further detail.
N.A.--Data not available or species status was not assessed
\1\ Best estimate and maximum density estimates are from Table 3 of L-DEO's application.
\2\ Regional population size estimates are from Table 2.

    Table 4 of L-DEO's application shows the best and maximum estimates 
of the number of exposures and the number of different individual 
marine mammals that potentially could be exposed to greater than or 
equal to 160 dB re 1 [mu]Pa (rms) during the seismic survey if no 
animals moved away from the survey vessel. For ESA listed species, the 
maximum estimate and Requested Take Authorization have been increased 
to the mean group size for the particular species in cases where the 
calculated maximum number of individuals exposed was between 0.05 and 
the mean group size (i.e., for North Pacific, right, humpback, fin, and 
blue whales).
    The ``best estimate'' of the total number of individual marine 
mammals that could be exposed to seismic sounds with received levels 
greater than or equal to 160 dB re 1 [micro]Pa (rms) during the survey 
is 1,011 animals and is shown in Table 4 of L-DEO's application and 
Table 3 (shown above). These estimates were derived from the best 
density estimates calculated for these species in the area. That total 
includes 11 baleen whales, five of which are ESA-listed sei whales, or 
0.05 percent of the regional population. In addition, 19 ESA-listed 
sperm whales or 0.07 percent of the regional population could be 
exposed during the survey, and 121 beaked whales including Cuvier's, 
Longman's, and Blainville's beaked whales. Most (69.4 percent) of the 
cetaceans exposed are delphinids; pantropical spotted, striped, and 
Fraser's dolphins and melon-headed whales are estimated to be the most 
common species in the area, with best estimates of 355 (0.04 percent of 
the regional population), 97 (0.01 percent), 65 (0.02 percent), and 67 
(0.15 percent) exposed to greater or equal to 160 dB re 1 [mu]Pa (rms) 

Potential Effects on Marine Mammal Habitat

    The proposed L-DEO seismic survey will not result in any permanent 
impact on habitats used by marine mammals, including the food sources 
they use. The main impact issue associated with the proposed activity 
will be temporarily elevated noise levels and the associated direct 
effects on marine mammals, as described above. The following sections 
briefly review effects of airguns on fish and invertebrates, and more 
details are included in Appendices C and D of the L-DEO EA, 

Potential Effects on Fish

    One reason for the adoption of airguns as the standard energy 
source for marine seismic surveys is that, unlike explosives, they have 
not been associated with large-scale fish kills. However, existing 
information on the impacts of seismic surveys on marine fish 
populations is limited (see Appendix D of the EA). There are three 
types of potential effects on fish and invertebrates from 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 potentially could lead to an ultimate pathological 
effect on individuals (i.e., mortality).
    The specific received sound levels at which permanent adverse 
effects to fish potentially could occur are little studied and largely 
unknown. Furthermore, the available information on the impacts of 
seismic surveys on marine fish is from studies of individuals or 
portions of a population; there have been no studies at the population 
scale. The studies of individual fish have often been on caged fish 
that were exposed to airgun pulses in situations not representative of 
an actual seismic survey. Thus, available information provides limited 
insight on possible real-world effects at the ocean or population 
scale. This makes drawing conclusions about impacts on fish problematic 
because ultimately, the most important aspect of potential impacts 
relates to how exposure to seismic survey sound affects marine fish 
populations and their viability, including their availability to 

[[Page 8666]]

    Hastings and Popper (2005), Popper (2009), and Popper and Hastings 
(2009a,b) provided recent critical reviews of the known effects of 
sound on fish. The following sections provide a general synopsis of 
available information on the effects of exposure to seismic and other 
anthropogenic sound as relevant to fish. The information comprises 
results from scientific studies of varying degrees of rigor plus some 
anecdotal information. Some of the data sources may have serious 
shortcomings in methods, analysis, interpretation, and reproducibility 
that must be considered when interpreting their results (see Hastings 
and Popper, 2005). Potential adverse effects of the program's sound 
sources on marine fish are then noted.
    Pathological Effects--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 (see Appendix D of the L-DEO EA). For a given sound to result 
in hearing loss, the sound must exceed, by some substantial 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 are unknown; however, they likely depend 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.
    Little is known about the mechanisms and characteristics of damage 
to fish that may be inflicted by exposure to seismic survey sounds. Few 
data have been presented in the peer-reviewed scientific literature. 
There are only two known valid papers with proper experimental methods, 
controls, and careful pathological investigation implicating sounds 
produced by actual seismic survey airguns with adverse anatomical 
effects. One such study indicated anatomical damage and the second 
indicated TTS in fish hearing. The anatomical case is McCauley et al. 
(2003), who 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) documented only TTS (as determined by 
auditory brainstem response) in two of three fish species from the 
Mackenzie River Delta. This study found that broad whitefish 
(Coreogonus nasus) that received a sound exposure level of 177 dB re 1 
[micro]Pa\2\[middot]s showed no hearing loss. 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 approximately 400 Hz in 
the study by McCauley et al. (2003) and less than approximately 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 in the 
former case and less than 2 m in the latter). Water depth sets a lower 
limit on the lowest sound frequency that will propagate (the ``cut-off 
frequency'') at about one-quarter wavelength (Urick, 1983; Rogers and 
Cox, 1988).
    Wardle et al. (2001) suggested that in water, acute injury and 
death of organisms exposed to seismic energy depends primarily on two 
features of the sound source: (1) The received peak pressure, and (2) 
the time required for the pressure to rise and decay. Generally, as 
received pressure increases, the period for the pressure to rise and 
decay decreases, and the chance of acute pathological effects 
increases. 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 and invertebrates 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,b, 
2003; Bjarti, 2002; Thomsen, 2002; Hassel et al., 2003; Popper et al., 
2005; Boeger et al., 2006).
    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. However, Payne et al. (2009) reported no 
statistical differences in morality/morbidity between control and 
exposed groups of capelin eggs or monkfish larvae. 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 
    Physiological Effects--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 (see Appendix D of the 
    Behavioral Effects--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.
    There is general concern about potential adverse effects of seismic 
operations on fisheries, namely a potential reduction in the 
``catchability'' of fish involved in fisheries. Although reduced catch 
rates have been observed in some marine fisheries during seismic 
testing, in a number of cases the findings are confounded by other 
sources of disturbance (Dalen and Raknes, 1985; Dalen and Knutsen, 
1986; L[oslash]kkeborg, 1991; Skalski et al., 1992; Engas et al., 
1996). In other airgun experiments, there was no change in catch per 
unit effort (CPUE) of fish when airgun pulses were emitted, 
particularly in the immediate vicinity of the seismic survey (Pickett 
et al., 1994; La Bella et al., 1996). For some species, reductions in 
catch may have resulted from a change in behavior of the fish, e.g., a 
change in vertical or horizontal distribution, as reported in Slotte et 
al., (2004).
    In general, any adverse effects on fish behavior or fisheries 
attributable to seismic testing may depend on the species in question 
and the nature of the fishery (season, duration, fishing method). They 
may also depend on the age of the fish, its motivational state, its 
size, and numerous other factors that are difficult, if not impossible, 
to quantify at this point, given such limited data on

[[Page 8667]]

effects of airguns on fish, particularly under realistic at-sea 

Potential 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, thereby justifying further discussion and 
analysis of this issue. 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; see Appendix E 
of the L-DEO EA).
    The only information available on the impacts of seismic surveys on 
marine invertebrates involves studies of individuals; there have been 
no studies at the population scale. Thus, available information 
provides limited insight on possible real-world effects at the regional 
or ocean scale. The most important aspect of potential impacts concerns 
how exposure to seismic survey sound ultimately affects invertebrate 
populations and their viability, including availability to fisheries.
    Literature reviews of the effects of seismic and other underwater 
sound on invertebrates were provided by Moriyasu et al. (2004) and 
Payne et al. (2008). The following sections provide a synopsis of 
available information on the effects of exposure to seismic survey 
sound on species of decapod crustaceans and cephalopods, the two 
taxonomic groups of invertebrates on which most such studies have been 
conducted. The available information is from studies with variable 
degrees of scientific soundness and from anecdotal information. A more 
detailed review of the literature on the effects of seismic survey 
sound on invertebrates is provided in Appendix E of the L-DEO EA.
    Pathological Effects--In water, lethal and sub-lethal injury to 
organisms exposed to seismic survey sound appears to depend on at least 
two features of the sound source: (1) the received peak pressure, and 
(2) the time required for the pressure to rise and decay. Generally, as 
received pressure increases, the period for the pressure to rise and 
decay decreases, and the chance of acute pathological effects 
increases. 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, at most; however, very few specific data are available on 
levels of seismic signals that might damage these animals. 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,b) 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--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. Primary and secondary 
stress responses (i.e., changes in haemolymph levels of enzymes, 
proteins, etc.) of crustaceans have been noted several days or months 
after exposure to seismic survey sounds (Payne et al., 2007). 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.
    Behavioral Effects--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 
catchability by fisheries. Studies investigating the possible 
behavioral effect 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,b). In other cases, no behavioral impacts 
were noted (e.g., crustaceans in Christian et al., 2003, 2004; DFO, 
2004). There have been anecdotal reports of reduced catch rates of 
shrimp shortly after exposure to seismic surveys; however, other 
studies have not observed any significant changes in shrimp catch rate 
(Andriguetto-Filho et al., 2005). Similarly, Parry and Gason (2006) did 
not find any evidence that lobster catch rates were affected by seismic 
surveys. Any adverse effects on crustacean and cephalopod behavior or 
fisheries attributable to seismic survey sound depend on the species in 
question and the nature of the fishery (season, duration, fishing 
    During the proposed study, 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. The proposed seismic program is predicted to have negligible to 
low behavioral effects on the various life stages of the fish and 
invertebrates during its relatively short duration and extent.
    Because of the reasons noted above and the nature of the proposed 
activities, the proposed operations are not expected to have any 
habitat-related effects that could cause significant or long-term 
consequences for individual marine mammals or their populations or 
stocks. Similarly, any effects to food sources are expected to be 

Proposed Mitigation

    In order to issue an Incidental Take Authorization (ITA) for small 
numbers of marine mammals under Section 101(a)(5)(D) of the MMPA, NMFS 
must set forth the permissible methods of taking pursuant to such 
activity and other means of effecting the least practicable adverse 
impact on such species or stock and its habitat, paying particular 
attention to rookeries, mating grounds, and areas of similar 
significance, and on the availability of such species or stock for 
taking for certain subsistence uses. As noted, NMFS has determined that 
the proposed IHA would not impact marine mammals for purposes of their 
use for subsistence.
    Mitigation and monitoring measures and procedures described herein 
to be implemented for the proposed seismic survey have been developed 
and refined during previous L-DEO seismic research cruises as approved 
by NMFS, and associated environmental assessments (EAs), IHA 
applications, and IHAs, and on recommended best practices in Richardson 
et al. (1995), Pierson et al. (1998), and Weir and Dolman (2007). The 
following information provides more detailed

[[Page 8668]]

information about the mitigation measures that would be an integral 
part of the planned activities designed to affect the least practicable 
impact on stocks and species of affected marine mammals and their 
habitat. The measures are described in detail below.

Planning Phase

    In designing the proposed seismic survey, L-DEO and NSF have 
considered potential environmental impacts including seasonal, 
biological, and weather factors; ship schedules; and equipment 
availability during a preliminary assessment carried out when ship 
schedules were still flexible. Part of the considerations was whether 
the research objectives could be met with a smaller source or with a 
different survey design that involves less prolonged seismic 

Proposed Exclusion Zones (EZ)

    Received sound levels have been predicted by L-DEO, in relation to 
distance and direction from the airguns, for the 36 airgun array and 
for a single 1900LL 40 in\3\ airgun, which will be used during power-
downs. Results were recently reported for propagation measurements of 
pulses from the 36 airgun array in two water depths (approximately 
1,600 m and 50 m) in the Gulf of Mexico in 2007 to 2008 (Tolstoy et 
al., 2009). It would be prudent to use the empirical values that 
resulted to determine EZs for the airgun array. Measurements were not 
reported for the mitigation airgun, so model results will not be used.
    Results of the propagation measurements (Tolstoy et al., 2009) 
showed that radii around the airguns for various received levels varied 
with water depth. During the proposed study, all survey effort will 
take place in deep (greater than 1,000 m) water, so propagation in 
shallow water is not relevant here. However, the depth of the array was 
different in the Gulf of Mexico calibration study (6 m or 20 ft) than 
in the proposed survey (9 m or 30 ft). Because propagation varies with 
array depth, correction factors have been applied to the distances 
reported by Tolstoy et al. (2009). The correction factors used were the 
ratios of the 160, 180, and 190 dB distances from the modeled results 
for the 6,600 in\3\ airgun array towed at 6 m and 9 m depths; these 
distances were used for the L-DEO seismic survey in the Northeast 
Pacific Ocean (see Table 1 in LGL Ltd., 2009). The factors are 1.34 to 
1.38 for the 180 to 190 dB distances, and 1.29 for the 160 dB distance. 
Using the corrected measurements (array) or model (mitigation gun), 
Table 1 shows the distances at which four rms sound levels are expected 
to be received from the 36 airgun array and a single airgun. The 180 
and 190 dB levels are shut-down criteria applicable to cetaceans and 
pinnipeds, respectively, as specified by NMFS (2000); these levels were 
used to establish the EZs. If the PSVO detects marine mammal(s) within 
or about to enter the appropriate EZ, the airguns will be powered-down 
(or shut-down if necessary) immediately (see below).
    Detailed recommendations for new science-based noise exposure 
criteria were published in early 2008 (Southall et al., 2007). L-DEO 
will be prepared to revise its procedures for estimating numbers of 
mammals ``taken,'' EZs, etc., as may be required by any new guidelines 
that result. As yet, NMFS has not specified a new procedure for 
determining EZs. Such procedures, if applicable would be implemented 
through a modification to the IHA if issued.
    Mitigation measures that will be adopted during the proposed CNMI 
survey include:
    (1) Power-down procedures;
    (2) Shut-down procedures; and
    (3) Ramp-up procedures;
    Power-down Procedures--A power-down involves reducing the number of 
airguns in use such that the radius of the 180 dB (or 190 dB) zone is 
decreased to the extent that marine mammals are no longer in or about 
to enter the EZ. A power-down of the airgun array can also occur when 
the vessel is moving from one seismic line to another. During a power-
down for mitigation, one airgun will be operated. The continued 
operation of one airgun is intended to alert marine mammals to the 
presence of the seismic vessel in the area. In contrast, a shut-down 
occurs when all airgun activity is suspended.
    If a marine mammal (other than right whales [immediate shut-down, 
see end of section]) is detected outside the EZ but is likely to enter 
the EZ, the airguns will be powered-down to a single airgun before the 
animal is within the EZ. Likewise, if a mammal is already within the EZ 
when first detected, the airguns will be powered-down immediately. 
During a power-down of the airgun array, the 40 in\3\ airgun will be 
operated. If a marine mammal is detected within or near the smaller EZ 
around that single airgun (see Table 1 of L-DEO's application and Table 
1 above), all airguns will be shut down (see next subsection).
    Following a power-down, airgun activity will not resume until the 
marine mammal is outside the EZ for the full array. The animal will be 
considered to have cleared the EZ if it:
    (1) Is visually observed to have left the EZ, or
    (2) Has not been seen within the EZ for 15 minutes in the case for 
species with shorter dive durations (e.g., small odontocetes); or
    (3) Has not been seen within the EZ for 30 minutes in the case for 
species with longer dive durations (e.g., mysticetes and large 
odontocetes, including sperm, pygmy sperm, dwarf sperm, killer, and 
beaked whales).
    During airgun operations following a power-down (or shut-down) 
whose duration has exceeded the limits specified above and subsequent 
animal departures, the airgun array will be ramped-up gradually. Ramp-
up procedures are described below.
    Shut-down Procedures--The operating airguns(s) will be shut-down if 
a marine mammal is detected within or approaching the EZ for a single 
airgun source. Shut-downs will be implemented (1) if an animal enters 
the EZ of the single airgun after a power-down has been initiated, or 
(2) if an animal is initially seen within the EZ of a single airgun 
when more than one airgun (typically the full array) is operating. 
Airgun activity will not resume until the marine mammal has cleared the 
EZ, or until the PSVO is confident that the animal has left the 
vicinity of the vessel (or the PSVO not observing the animal(s) within 
the EZ for 15 or 30 min depending upon the species). Criteria for 
judging that the animal has cleared the EZ will be as described in the 
preceding subsection.
    Ramp-up Procedures--A ramp-up procedure will be followed when the 
airgun array begins operating after a specified period without airgun 
operations or when a power-down has exceeded that period. It is 
proposed that, for the present cruise, this period would be 
approximately 8 minutes. This period is based on the largest modeled 
180 dB radius for the 36 airgun array (940 m or 3,084 ft) in relation 
to the minimum planned speed of the Langseth while shooting (7.4 km/hr 
or 4.6 mi/hr). Similar periods (approximately 8 to 10 minutes) were 
used during previous L-DEO surveys.
    Ramp-up will begin with the smallest airgun 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 
over a total duration of approximately 35 minutes. During ramp-up, the 
PSVOs will monitor the EZ, and if marine mammals are sighted, a power-
down or shut-down will be

[[Page 8669]]

implemented as though the full array were operational.
    If the complete EZ has not been visible for at least 30 min prior 
to the start of operations in either daylight or nighttime, ramp up 
will not commence unless at least one airgun (40 in\3\ or similar) has 
been operating during the interruption of seismic survey operations. 
Given these provisions, it is likely that the airgun array will not be 
ramped-up from a complete shut-down at night or in thick fog, because 
the outer part of the EZ for that array will not be visible during 
those conditions. If one airgun has operated during a power-down 
period, ramp-up to full power will be permissible at night or in poor 
visibility, on the assumption that marine mammals will be alerted to 
the approaching seismic vessel by the sounds from the single airgun and 
could move away if they choose. Ramp-up of the airguns will not be 
initiated if a marine mammal is sighted within or near the applicable 
EZ during the day or close to the vessel at night.
    Procedures for Species of Particular Concern--One species of 
particular concern could occur in the study area.
    Considering the conservation status for North Pacific right whales, 
the airgun(s) will be shut-down immediately in the unlikely event that 
this species is observed, regardless of the distance from the Langseth. 
Ramp-up will only begin if the right whale has not been seen for 30 

Proposed Monitoring and Reporting

    In order to issue an ITA for an activity, Section 101(a)(5)(D) of 
the MMPA states that NMFS must set forth ``requirements pertaining to 
the monitoring and reporting of such taking.'' The MMPA implementing 
regulations at 50 CFR 216.104(a)(13) require that requests for IHAs 
must include the suggested means of accomplishing the necessary 
monitoring and reporting that will result in increased knowledge of the 
species and of the level of taking or impacts on populations of marine 
mammals that are expected to be present.
    L-DEO proposes to sponsor marine mammal monitoring during the 
proposed project, in order to implement the proposed mitigation 
measures that require real-time monitoring, and to satisfy the 
anticipated monitoring requirements of the IHA. L-DEO's proposed 
Monitoring Plan is described below as well as in their IHA application. 
L-DEO understands that this Monitoring Plan will be subject to review 
by NMFS, and that refinements may be required as part of the MMPA 
consultation process.
    The monitoring work described here has been planned as a self-
contained project independent of any other related monitoring projects 
that may be occurring simultaneously in the same regions. L-DEO is 
prepared to discuss coordination of its monitoring program with any 
related work that might be done by other groups insofar as this is 
practical and desirable.

Vessel-Based Visual Monitoring

    Protected Species Visual Observers (PSVOs) will be based aboard the 
seismic source vessel and will watch for marine mammals and other 
protected species near the vessel during daytime airgun operations and 
during start-ups of airguns at night. PSVOs will also watch for marine 
mammals near the seismic vessel for at least 30 minutes prior to the 
start of airgun operations and after an extended shut-down of the 
airguns. When feasible, PSVOs will also observe during daytime periods 
when the seismic system is not operating for comparison of sighting 
rates and animal behavior with vs. without airgun operations. Based on 
PSVO observations, the airguns will be powered-down or shut-down (see 
below) when marine mammals are detected within or about to enter a 
designated EZ, and in the case of the North Pacific right whale 
immediately when any individuals of that species is spotted at any 
distance. The PSVOs will continue to maintain watch to determine when 
the animal(s) are outside the EZ in accordance with the criteria 
established above in the mitigation section, and airgun operations will 
not resume until the animal has left that EZ. The predicted distances 
for the safety radius are listed according to the sound source, water 
depth, and received isopleths in Table 1. The EZ is a region in which a 
possibility exists of adverse effects on animal hearing or other 
physical effects.
    During seismic operations in CNMI, five PSOs will be based aboard 
the Langseth. PSOs will be appointed by L-DEO with NMFS concurrence. At 
least one PSVO, and when practical two PSVOs, will monitor for marine 
mammals and other specified protected species near the seismic vessel 
during ongoing daytime operations and nighttime start-ups of the 
airguns. Use of two simultaneous PSVOs will increase the effectiveness 
of detecting animals near the sound source. PSVO(s) will be on duty in 
shift of duration no longer than 4 hours. The vessel crew will also be 
instructed to assist in detecting marine mammals and other specified 
protected species, and implementing mitigation measures (if practical). 
Before the start of the seismic survey the crew will be given 
additional instruction regarding how to do so.
    The Langseth is a suitable platform for observations for marine 
mammals and other protected species. When stationed on the observation 
platform, the eye level will be approximately 21.5 m (70.5 ft) above 
sea level, and the observer will have a good view around the entire 
vessel. During the daytime, the PSVO(s) will scan the area around the 
vessel systematically with reticle binoculars (e.g., 7x50 Fujinon), 
Big-eye binoculars (25x150), and with the naked eye. During darkness, 
night vision devices (NVDs) will be available (ITT F500 Series 
Generation 3 binocular-image intensifier or equivalent), when required. 
Laser rangefinding binoculars (Leica LRF 1200 laser rangefinder or 
equivalent) will be available to assist with distance estimation. Those 
are useful in training PSVOs to estimate distances visually, but are 
generally not useful in measuring distances to animals directly; that 
is done primarily with the reticles in the binoculars' lenses.

Passive Acoustic Monitoring (PAM)

    PAM will take place to complement the visual monitoring program, 
when practicable. Visual monitoring typically is not effective during 
periods of poor visibility (e.g., 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. Acoustical monitoring can be 
used in addition to visual observations to improve detection, 
identification, and localization of cetaceans. The acoustic monitoring 
will serve to alert visual observers (if on duty) when vocalizing 
cetaceans are detected. It is only useful when marine mammals call, but 
it can be effective either by day or by night and does not depend on 
good visibility. It will be monitored in real time so that the visual 
observers can be advised when cetaceans are detected. When bearings 
(primary and mirror-image) to calling cetacean(s) are determined, the 
bearings will be relayed to the visual observer to help him/her sight 
the calling animal(s).
    The PAM system consists of hardware (i.e., hydrophones) and 
software. The ``wet end'' of the system consists of a low-noise, towed 
hydrophone array that is connected to the vessel by a ``hairy'' faired 
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 condition and processing system 
will be located. The lead-in from the hydrophone array

[[Page 8670]]

is approximately 400 m (1,312 ft) long, and the active part of the 
hydrophone is approximately 56 m (184 ft) long. The hydrophone array is 
typically towed at depths less than 20 m (65.6 ft).
    The towed hydrophone array will be monitored 24 hours per day while 
at the survey area during airgun operations, and during most periods 
when the Langseth is underway while the airguns are not operating. One 
Protected Species Observer will monitor the acoustic 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 frequency ranges produced by cetaceans. PSOs monitoring the 
acoustical data will be on a shift for one to six hours. Besides the 
visual PSOs, an additional PSO with primary responsibility for PAM will 
also be aboard. All PSOs are expected to rotate through the PAM 
position, although the most experienced with acoustics will be on PAM 
duty more frequently.
    When a vocalization is detected while visual observations are in 
progress, the acoustic PSO will contact the PSVO immediately to alert 
him/her to the presence of the cetacean(s) (if they have not already 
been seen), and to allow a power-down or shut-down to be initiated, if 
required. The information regarding the vocalization will be entered 
into a database. The data to be entered include an acoustic encounter 
identification number, whether it was linked with a visual sighting, 
date, time when first and last heard and whenever any additional 
information was recorded, position and water depth when first detected, 
bearing if determinable, species or species group (e.g., unidentified 
dolphin, sperm whale), types and nature of sounds heard (e.g., clicks, 
continuous, sporadic, whistles, creaks, burst pulses, strength of 
signal, etc.), and any other notable information. The acoustic 
detection can also be recorded for further analysis.
    L-DEO will coordinate the planned protected species monitoring 
program associated with the CNMI seismic survey with other parties that 
may have interest in the area and/or be conducting marine mammal 
studies in the same region during the proposed seismic survey. L-DEO 
and NSF will coordinate with applicable U.S. agencies (e.g., NMFS), and 
will comply with their requirements.

PSVO Data and Documentation

    PSVOs 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 (as defined in the 
MMPA). They will also provide information needed to order a power-down 
or shut-down of the seismic source when a marine mammal is within or 
near the EZ.
    When a sighting is made, the following information about the 
sighting will be recorded:
    (1) Species, group size, and 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 seismic source or vessel (e.g., 
none, avoidance, approach, paralleling, etc.); and behavioral pace.
    (2) Time, location, heading, speed, activity of the vessel, sea 
state, visibility, and sun glare.
    The data listed under (2) above 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 seismic source 
power-downs and shut-downs, will be recorded in a standardized format. 
The accuracy of data entry will be verified by computerized data 
validity checks as the data are entered and by subsequent manual 
checking of the database. These procedures will allow initial summaries 
of data to be prepared during and shortly after the field program, and 
will facilitate transfer of the data to statistical, graphical, and 
other programs for further processing and archiving.
    Results for the vessel-based observations will provide:
    (1) The basis for real-time mitigation (airgun power-down or shut-
    (2) Information needed to estimate the number of marine mammals 
potentially taken by harassment, which must be reported to NMFS per 
terms of MMPA authorizations or regulations.
    (3) Data on the occurrence, distribution, and activities of marine 
mammals in the area where the seismic study is conducted.
    (4) Information to compare the distance and distribution of marine 
mammals relative to the source vessel at times with and without seismic 
    (5) Data on the behavior and movement patterns of marine mammals 
seen at times with and without seismic activity.
    A report will be submitted to NMFS and NSF 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 be providing full documentation of methods, results, and 
interpretation pertaining to all monitoring. The 90-day report will 
summarize the dates and locations of seismic operations, and all marine 
mammal sightings (dates, times, locations, activities, associated 
seismic survey activities). The report will also include estimates of 
the amount and nature of potential ``take'' of marine mammals by 
harassment or in other ways.
    All injured or dead marine mammals (regardless of cause) will be 
reported to NMFS as soon as practicable. Report should include species 
or description of animal, condition of animal, location, time first 
found, observed behaviors (if alive) and photo or video, if available.

Negligible Impact and Small Numbers of Marine Mammals Analysis and 

    The Secretary, in accordance with paragraph 101(a)(5)(D) of the 
MMPA, shall authorize the take of small numbers of marine mammals 
incidental to specified activities other than commercial fishing within 
a specific geographic region if, among other things, he determines that 
the authorized incidental take will have a ``negligible impact'' on 
species or stocks affected by the authorization. NMFS implementing 
regulations codified at 50 CFR 216.103 states that a ``negligible 
impact is 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.''
    Based on the analysis contained herein, of the likely effects of 
the specified activity on marine mammals and their habitat within the 
specific area of study for the CNMI marine geophysical survey, and 
taking into consideration the implementation of the mitigation and 
monitoring measures, NMFS, on behalf the Secretary, preliminarily finds 
that L-DEO's proposed activities would result in the incidental take of 
small numbers of marine mammals, by Level B harassment only, and that 
the total taking from the proposed seismic survey would have a 
negligible impact on the affected species or stocks of marine mammals.

Impact on Availability of Affected Species for Taking for Subsistence 

    There is no subsistence hunting for marine mammals in the waters 
off of the coast of the CNMI that implicates MMPA Section 101(a)(5)(D).

[[Page 8671]]

Endangered Species Act (ESA)

    Under Section 7 of the ESA, NSF has initiated formal consultation 
with the NMFS, Office of Protected Resources, Endangered Species 
Division, on this proposed seismic survey. NMFS Office of Protected 
Resources, Permits, Conservation and Education Division, has initiated 
formal consultation under Section 7 of the ESA with NMFS Office of 
Protected Resources, Endangered Species Division, to obtain a 
Biological Opinion evaluating the effects of issuing the IHA on 
threatened and endangered marine mammals and, if appropriate, 
authorizing incidental take. NMFS will conclude formal Section 7 
consultation prior to making a determination on whether or not to issue 
the IHA. If the IHA is issued, L-DEO will be required to comply with 
the Terms and Conditions of the Incidental Take Statement corresponding 
to NMFS' Biological Opinion issued to both NSF and NMFS Office of 
Protected Resources.

National Environmental Policy Act (NEPA)

    With its complete application, L-DEO provided NMFS an EA analyzing 
the direct, indirect and cumulative environmental impacts of the 
proposed specified activities on marine mammals including those listed 
as threatened or endangered under the ESA. The EA, prepared by LGL 
Environmental Research Associated (LGL) on behalf of NSF and L-DEO is 
entitled Environmental Assessment of a Marine Geophysical Survey by the 
R/V Marcus G. Langseth in the Commonwealth of the Northern Mariana 
Islands, April-June 2010 (L-DEO EA). Prior to making a final decision 
on the IHA application, NMFS will either prepare an independent EA, or, 
after review and evaluation of the L-DEO EA for consistency with the 
regulations published by the Council of Environmental Quality (CEQ) and 
NOAA Administrative Order 216-6, Environmental Review Procedures for 
Implementing the National Environmental Policy Act, adopt the L-DEO EA 
and make a decision of whether or not to issue a Finding of No 
Significant Impact (FONSI).

Preliminary Determinations

    NMFS has preliminarily determined that the impact of conducting the 
specific seismic survey activities described in this notice and the IHA 
request in the specific geographic region within the U.S. EEZ within 
the CNMI may result, at worst, in a temporary modification in behavior 
(Level B harassment) of small numbers of marine mammals. Further, this 
activity is expected to result in a negligible impact on the affected 
species or stocks of marine mammals. The provision requiring that the 
activity not have an unmitigable impact on the availability of the 
affected species or stock of marine mammals for subsistence uses is not 
implicated for this proposed action.
    For reasons stated previously in this document, the specified 
activities associated with the proposed survey are not likely to cause 
TTS, PTS or other non-auditory injury, serious injury, or death to 
affected marine mammals because:
    (1) The likelihood that, given sufficient notice through relatively 
slow ship speed, marine mammals are expected to move away from a noise 
source that is annoying prior to its becoming potentially injurious;
    (2) The fact that cetaceans would have to be closer than 940 m (0.6 
mi) in deep water when the full array is in use at a 9 m (29.5 ft) tow 
depth from the vessel to be exposed to levels of sound (180 dB) 
believed to have even a minimal chance of causing PTS;
    (3) The fact that marine mammals would have to be closer than 3,850 
m (2.4 mi) in deep water when the full array is in use at a 9 m (29.5 
ft) tow depth from the vessel to be exposed to levels of sound (160 dB) 
believed to have even a minimal chance at causing TTS; and
    (4) The likelihood that marine mammal detection ability by trained 
observers is high at that short distance from the vessel.
    As a result, no take by injury, serious injury, or death is 
anticipated or authorized, and the potential for temporary or permanent 
hearing impairment is very low and will be avoided through the 
incorporation of the proposed monitoring and mitigation measures.
    While the number of marine mammals potentially incidentally 
harassed will depend on the distribution and abundance of marine 
mammals in the vicinity of the survey activity, the number of potential 
Level B incidental harassment takings (see Table 3 above) is estimated 
to be small, less than a few percent of any of the estimated population 
sizes based on the data disclosed in Table 2 of this notice, and has 
been mitigated to the lowest level practicable through incorporation of 
the monitoring and mitigation measures mentioned previously in this 
document. Also, there are no known important reproduction or feeding 
areas in the proposed action area.

Proposed Authorization

    As a result of these preliminary determinations, NMFS proposes to 
issue an IHA to L-DEO for conducting a marine geophysical survey in the 
CNMI from April to June, 2010, provided the previously mentioned 
mitigation, monitoring, and reporting requirements are incorporated. 
The duration of the IHA would not exceed one year from the date of its 

Information Solicited

    NMFS requests interested persons to submit comments and information 
concerning this proposed project and NMFS' preliminary determination of 
issuing an IHA (see ADDRESSES). Concurrent with the publication of this 
notice in the Federal Register, NMFS is forwarding copies of this 
application to the Marine Mammal Commission and its Committee of 
Scientific Advisors.

    Dated: February 19, 2010.
James H. Lecky,
Director, Office of Protected Resources, National Marine Fisheries 
[FR Doc. 2010-3869 Filed 2-24-10; 8:45 am]