Takes of Marine Mammals Incidental to Specified Activities; Marine Geophysical Survey in the Pacific Ocean off Costa Rica, April Through June, 2011, 20325-20335 [2011-8734]

Agencies

• DEPARTMENT OF COMMERCE
• National Oceanic and Atmospheric Administration

[Federal Register Volume 76, Number 70 (Tuesday, April 12, 2011)]
[Notices]
[Pages 20325-20335]
From the Federal Register Online via the Government Printing Office [www.gpo.gov]
[FR Doc No: 2011-8734]


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DEPARTMENT OF COMMERCE

National Oceanic and Atmospheric Administration

RIN 0648-XA314


Takes of Marine Mammals Incidental to Specified Activities; 
Marine Geophysical Survey in the Pacific Ocean off Costa Rica, April 
Through June, 2011

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

ACTION: Notice; issuance of an incidental take authorization.

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SUMMARY: In accordance with the Marine Mammal Protection Act (MMPA) 
regulations, notification is hereby given that NMFS has issued an 
Incidental Harassment Authorization (IHA) to Lamont-Doherty Earth 
Observatory (L-DEO), a part of Columbia University, to take small 
numbers of marine mammals, by Level B harassment, incidental to 
conducting a marine geophysical survey in the eastern tropical Pacific 
(ETP) Ocean off Costa Rica, April through June, 2011.

DATES: Effective April 7 through June 6, 2011.

ADDRESSES: A copy of the IHA and application are available by writing 
to P. Michael Payne, Chief, Permits, Conservation and Education 
Division, Office of Protected Resources, National Marine Fisheries 
Service, 1315 East-West Highway, Silver Spring, MD 20910 or by 
telephoning the contacts listed here. A copy of the application 
containing a list of the references used in this document may be 
obtained by writing to the above address, telephoning the contact 
listed here (see FOR FURTHER INFORMATION CONTACT) or visiting the 
Internet at: https://www.nmfs.noaa.gov/pr/permits/incidental.htm#applications. The following associated documents are 
also available at the same internet address: Environmental Assessment 
(EA) prepared by NMFS, and the finding of no significant impact 
(FONSI). The NMFS Biological Opinion will be available online at: 
https://www.nmfs.noaa.gov/pr/consultation/opinions.htm. Documents cited 
in this notice may be viewed, by appointment, during regular business 
hours, at the aforementioned address. Documents cited in this notice 
may be viewed, by appointment, during regular business hours, at the 
aforementioned address.

FOR FURTHER INFORMATION CONTACT: Jeannine Cody, Office of Protected 
Resources, NMFS, (301) 713-2289, ext. 113.

SUPPLEMENTARY INFORMATION:

Background

    Section 101(a)(5)(D) of the MMPA (16 U.S.C. 1371 (a)(5)(D)) directs 
the Secretary of Commerce to authorize, upon request, the incidental, 
but not intentional, taking of small numbers of marine mammals of a 
species or population stock, 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, if the taking is 
limited to harassment, a notice of a proposed authorization is provided 
to the public for review.
    Authorization for the 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), and will not have an 
unmitigable adverse impact on the availability of the species or 
stock(s) for subsistence uses (where relevant). The authorization must 
set forth the permissible methods of taking, other means of effecting 
the least practicable adverse impact on the species or stock and its 
habitat, and requirements pertaining to the mitigation, monitoring and 
reporting of such takings. NMFS has defined ``negligible impact'' in 50 
CFR 216.103 as ``* * * an impact resulting from the specified activity 
that cannot be reasonably expected to, and is not reasonably likely to, 
adversely affect the species or stock through effects on annual rates 
of recruitment or survival.''
    Section 101(a)(5)(D) of the MMPA established an expedited process 
by which citizens of the United States can apply for an authorization 
to incidentally take small numbers of marine mammals by harassment. 
Section 101(a)(5)(D) of the MMPA establishes a 45-day time limit for 
NMFS' review of an application followed by a 30-day public notice and 
comment period on any proposed authorizations for the incidental 
harassment of small numbers of marine mammals. Within 45 days of the 
close of the public comment period, NMFS must either issue or deny the 
authorization. NMFS must publish a notice in the Federal Register 
within 30 days of its determination to issue or deny the authorization.
    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].

Summary of Request

    NMFS received an application on November 12, 2010, from L-DEO for 
the taking by harassment, of marine mammals, incidental to conducting a 
marine geophysical survey in the eastern tropical Pacific Ocean within 
the Exclusive Economic Zone (EEZ) of Costa Rica. L-DEO, with research 
funding from the U.S. National Science Foundation (NSF), plans to 
conduct the seismic survey from April 7, 2011, through May 9, 2011. 
Upon receipt of additional information, NMFS determined the application 
complete

[[Page 20326]]

and adequate on January 4, 2011. On February 4, 2011 NMFS published a 
notice in the Federal Register (76 FR 6430) disclosing the effects on 
marine mammals, making preliminary determinations and including a 
proposed IHA. The notice initiated a 30-day public comment period.
    L-DEO plans to use one source vessel, the R/V Marcus G. Langseth 
(Langseth) and a seismic airgun array to image the structures along a 
major plate-boundary fault off in the ETP off Costa Rica using three-
dimensional (3-D) seismic reflection techniques. L-DEO will use the 3-D 
seismic reflection data to determine the fault structure and the 
properties of the rocks that lie along the fault zone. In addition to 
the proposed operations of the seismic airgun array, L-DEO intends to 
operate a multibeam echosounder (MBES) and a sub-bottom profiler (SBP) 
continuously throughout the survey.
    Acoustic stimuli (i.e., increased underwater sound) generated 
during the operation of the seismic airgun array, has the potential to 
cause a short-term behavioral disturbance for marine mammals in the 
survey area. This is the only anticipated means of marine mammal taking 
associated with these specified activities. L-DEO has requested and 
NMFS has authorized the incidental take of 19 species marine mammals by 
Level B harassment. Take is not expected to result from the use of the 
MBES or SBP, for reasons discussed in this notice. While ship-strike is 
the cause of take of marine mammals, NMFS believes the possibility of 
take from collision with the vessel is so remote as to be discountable 
because it is a single vessel moving at a relatively slow speed during 
seismic acquisition within the survey for approximately 32 days. It is 
likely that any marine mammal would be able to avoid the vessel.

Description of the Specified Activity

    L-DEO's planned seismic survey in the ETP off Costa Rica is 
scheduled to commence on April 7, 2011 and continue for approximately 
32 days ending on May 9, 2011. L-DEO will operate the Langseth to 
deploy a seismic airgun array and hydrophone streamers to complete the 
survey. The Langseth will depart from Caldera, Costa Rica on April 7, 
2011 and transit to the survey area offshore from Costa Rica. Some 
minor deviation from these dates is possible, depending on logistics, 
weather conditions, and the need to repeat some lines if data quality 
is substandard. Therefore, NMFS plans to issue an authorization that 
extends to June 6, 2011.
    Geophysical survey activities will involve 3-D seismic 
methodologies to determine the fault structure and the properties of 
the rocks that lie along the fault zone and to assess the property 
changes along the fault and determine where the large stress 
accumulations that lead to large earthquakes occur along the fault 
zone.
    To obtain 3-D images of the fault zone which lies two to nine 
kilometers (km) below the seafloor, the Langseth will deploy a two-
string subarray of nine airguns each as an energy source. The identical 
subarrays will fire alternately, so that no more than 18 airguns will 
fire at any time during the survey. The receiving system will consist 
of four 6-km-long hydrophone streamers. As the airgun subarrays are 
towed along the survey lines, the hydrophone streamers will receive the 
returning acoustic signals and transfer the data to the on-board 
processing system. L-DEO also plans to use two or three small fishing 
vessels around the Langseth to ensure that other vessels do not 
entangle the streamers.
    The study (e.g., equipment testing, startup, line changes, repeat 
coverage of any areas, and equipment recovery) will take place in the 
EEZ of Costa Rica in water depths ranging from less than 100 meters (m) 
(328 feet (ft)) to greater than 2,500 m (1.55 miles (mi)). The survey 
will require approximately 32 days (d) to complete approximately 19 
transects in a racetrack configuration that will cover an area of 
approximately 57 x 12 km (35.4 x 7.5 mi). In all, the survey will 
complete approximately 2,145 km (1,333 mi) of survey lines with an 
additional 365 km (227 mi) of turns. Data acquisition will include 
approximately 672 hours (hr) of airgun operation (28 d x 24 hr).
    The scientific team consists of Drs. Nathan Bangs, Kirk McIntosh 
(Institute for Geophysics, University of Texas) and Eli Silver 
(University of California at Santa Cruz).
    NMFS outlined the purpose of the program in a previous notice for 
the proposed IHA (76 FR 6430, February 4, 2011). The activities to be 
conducted have not changed between the proposed IHA notice and this 
final notice announcing the issuance of the IHA. For a more detailed 
description of the authorized action, including vessel and acoustic 
source specifications, the reader should refer to the proposed IHA 
notice (76 FR 6430, February 4, 2011), the application and associated 
documents referenced above this section.

Comments and Responses

    A notice of receipt of the L-DEO application and proposed IHA was 
published in the Federal Register on February 4, 2011 (76 FR 6430). 
During the 30-day public comment period, NMFS received comments from 
the Marine Mammal Commission (Commission) only. The Commission's 
comments are online at: https://www.nmfs.noaa.gov/pr/permits/incidental.htm. Following are their comments and NMFS' responses.
    Comment 1: The Commission recommends that NMFS require Lamont-
Doherty Earth Observatory to: (1) Provide a full description of the 
Lamont-Doherty Earth Observatory model as it is used to estimate safety 
and buffer zones; and (2) rerun the model using site-specific 
information to determine safety and buffer zones and associated takes.
    Response: The NSF and L-DEO have revised Appendix A in the draft 
Environmental Analysis to include information from the calibration 
study conducted on the Langseth in 2007 and 2008. This information is 
now available in the final Environmental Analysis on NSF's Web site at 
https://www.nsf.gov/geo/oce/envcomp/index.jsp. The revised Appendix A 
describes the L-DEO modeling process and compares the model results 
with empirical results of the 2007-2008 Langseth calibration experiment 
in shallow, deep and intermediate water. The conclusions- identified in 
Appendix A-show that the model represents the actual produced levels, 
particularly within the first few kilometers, where the predicted 
safety radii lie. At greater distances, local oceanographic variations 
begin to take effect, and the model tends to over predict. Further, 
since the modeling matches the observed measurement data, the authors 
have concluded that the models can continue to be used for defining 
exclusion zones, including for predicting mitigation radii for various 
tow depths. The data results from the studies were peer reviewed and 
the calibration results, viewed as conservative, were used to determine 
the cruise-specific exclusion zones.
    At present, the L-DEO model does not account for site-specific 
environmental conditions. The calibration study of the L-DEO model 
predicted that using site-specific information may actually provide 
less conservative safety radii at greater distances. As the Commission 
noted, the Draft Programmatic Environmental Impact Statement/Overseas 
Environmental Impact Statement (draft PEIS) for Marine Seismic Research 
Funded by the

[[Page 20327]]

National Science Foundation or Conducted by the U.S. Geological Survey 
(draft PEIS) prepared pursuant to the National Environmental Policy Act 
(NEPA; 42 U.S.C. 4321 et seq.) did incorporate various site-specific 
environmental conditions in the modeling of the Detailed Analysis 
Areas. The NEPA process associated with the draft PEIS is still ongoing 
and the NSF has not yet issued a Record of Decision. Once the NEPA 
process for the PEIS has concluded, NSF will look at upcoming cruises 
on a site-specific basis for any impacts not already considered in the 
draft PEIS.
    The IHA issued to L-DEO, under section 101(a)(5)(D) of the MMPA, 
provides mitigation and monitoring requirements that will protect 
marine mammals from any injury or mortality. L-DEO is required to 
comply with the IHA's requirements. These analyses are supported by 
extensive scientific research and data. NMFS is confident in the peer-
reviewed results of the L-DEO seismic equipment calibration studies 
which, although viewed as conservative, are used to determine cruise-
specific exclusion zones and which factor into exposure estimates. NMFS 
has determined that these reviews are the best scientific data 
available for review of the IHA application and to support the 
necessary analyses and determinations under the MMPA, Endangered 
Species Act of 1973 (ESA; 16 U.S.C. 1531 et seq.) and NEPA.
    Based on NMFS' analysis of the likely effects of the specified 
activity on marine mammals and their habitat, and taking into 
consideration the implementation of the mitigation and monitoring 
measures, NMFS has determined that the exclusion zones identified in 
the IHA are appropriate for the survey and that additional field 
measurement is not necessary at this time. While exposures of marine 
mammals to acoustic stimuli are difficult to estimate, NMFS is 
confident that the levels of take authorized herein are estimated based 
upon the best available scientific information and estimation 
methodology. The exclusion zones used to estimate exposure are 
appropriate and sufficient for purposes of supporting NMFS's analyses 
and determinations required under section 101(a)(5)(D) of the MMPA and 
its implementing regulations.
    Comment 2: The Commission recommends that before issuing the 
requested IHA, NMFS provide additional justification for its 
preliminary determination that the planned monitoring program will be 
sufficient to detect with a high level of confidence, all marine 
mammals within or entering the identified exclusion zones.
    Response: NMFS believes that the planned monitoring program will be 
sufficient to detect (using visual detection and passive acoustic 
monitoring (PAM)), with reasonable certainty, marine mammals within or 
entering identified exclusion zones. This monitoring, along with the 
required mitigation measures, will result in the least practicable 
adverse impact on the affected species or stocks and will result in a 
negligible impact on the affected species or stocks.
    At present, NMFS views the combination of visual and passive 
acoustic monitoring as the most effective mitigation techniques 
available for detecting marine mammals within or entering the exclusion 
zone. The final monitoring and mitigation measures are the most 
effective feasible measures and NMFS is not aware of any additional 
measures which could meaningfully increase the likelihood of detecting 
marine mammals in and around the exclusion zone. Further, public 
comment has not revealed any additional mitigation or monitoring 
measures that could be feasibly implemented to increase the 
effectiveness of detection.
    L-DEO and NSF (the federal funding agency) are receptive to 
incorporating proven technologies and techniques to enhance the current 
monitoring and mitigation program. Until proven technological advances 
are made, nighttime mitigation measures during operations include 
combinations of the use of protected species visual observers (PSVOs) 
for ramp ups, PAM, night vision devices, and continuous shooting of a 
mitigation gun. Should the airgun array be powered-down, the operation 
of a single airgun would continue to serve as a sound source deterrent 
to marine mammals. In the event of a complete airgun array shut down at 
night for mitigation or repairs, L-DEO suspends the data collection 
until one half hour after civil dawn (when PSVO's are able to clear the 
safety zone). L-DEO will not activate the airguns until the entire 
safety radius is visible for at least 30 minutes.
    In cooperation with NMFS, L-DEO will be conducting efficacy 
experiments of night vision devices (NVD) during a future Langseth 
cruise. In addition, in response to a recommendation from NMFS, L-DEO 
is evaluating the use of handheld thermal imaging cameras to supplement 
nighttime mitigation practices. Another federal agency has successfully 
used these devices while conducting nighttime seismic operations.
    Comment 3: The Commission recommends that NMFS propose to L-DEO 
that it revise its survey design to add pre- and post-seismic survey 
assessments as a way to assess marine mammal abundance in an area 
before, during, and after the seismic survey to determine how those 
numbers differ and to obtain more realistic baseline abundance 
estimates of marine mammals.
    Response: NMFS acknowledges the Commission's concerns and will 
forward the recommendation to the NSF and L-DEO. Because the cruise's 
primary focus is marine geophysical research, extending or altering the 
cruise is not practicable from either an operational or research 
standpoint for the applicant. Due to the remote location of the survey 
and the length of time needed to conduct the requested research, there 
may be little time left for the vessel to operate without the need for 
refueling and servicing. Second, at sea data collection and analyses to 
estimate marine mammal abundance are time and resource intensive 
endeavors--even more so if the intent is to assess abundance in-situ, 
before, during, and after the seismic survey.
    Numerous studies have reported on the distribution of cetaceans 
inhabiting the ETP and L-DEO has incorporated this data into their 
analyses. For example, Ferguson and Barlow (2001, 2003) calculated 
cetacean densities in the ETP based on summer/fall research surveys in 
1986-1996; Gerrodette et al. (2008) calculated dolphin abundance in the 
ETP based on summer/fall research surveys in 1986-1990, 1998-2000, 
2003, and 2006; and Jackson et al., (2008) described cetacean sightings 
data collected in a survey area that overlaps with the seismic survey 
area. NMFS believes that L-DEO's current approach for estimating 
abundance in the survey area is believed to be the best available 
approach.
    To conclude, there will be significant amounts of transit time 
during the cruise, which PSVOs will be on watch prior to and after the 
seismic portions of the survey. The collection of this observational 
data by PSVOs may provide meaningful baseline data on marine mammals, 
but it is unlikely that the information would result in any 
statistically robust conclusions for this particular seismic survey.
    Comment 4: The Commission recommends that NMFS require the 
applicant: (1) To report on the number of marine mammals that were 
acoustically detected for which a power-down or shutdown of the airguns 
was initiated; (2) specify if the animals also were visually detected; 
and (3) compare

[[Page 20328]]

the results from the two methods (visual versus acoustic) to help 
identify their respective weaknesses.
    Response: L-DEO reports on the number of acoustic detections made 
by the PAM system within the post-cruise monitoring reports as required 
by the IHA. The report also includes a description of any acoustic 
detections that were concurrent with visual sightings, which allows for 
a comparison of acoustic and visual detection methods for each cruise.
    The post-cruise monitoring reports also include on the following 
information: the total operational effort in daylight (hours); the 
total operation effort at night (hours); the total number of hours of 
visual observations conducted, the total number of sightings, and the 
total number of hours of acoustic detections conducted.
    LGL Ltd., Environmental Research Associates (LGL), a contractor for 
L-DEO, has processed sighting and density and data, and their 
publications can be viewed online at: https://www.lgl.com/index.php?option=com_content&view=article&id=69&Itemid=162&lang=en. 
Post-cruise monitoring reports are currently available on the NMFS' 
MMPA Incidental Take Program website and future reports will also be 
available on the NSF website should there be interest in further 
analysis of this data by the public.
    Comment 5: The Commission recommends that NMFS condition the 
authorization to prohibit an eight-minute pause before ramping up after 
either a power-down or shutdown of the airguns, based on the presence 
of a marine mammal in the exclusion zone and the Langseth's movement. 
The Commission believes that this limit is inappropriate because it 
fails to account for the position, swim speed and heading of the 
observed marine mammal. If a marine mammal sighted in the exclusion 
zone is moving in the same direction as the Langseth, or if it is 
moving in a different direction but changes its heading, it may remain 
in the exclusion zone for periods longer than eight minutes.
    Response: To clarify, in the instance of a power-down or shutdown 
based on the presence of a marine mammal in the exclusion zone, L-DEO 
will restart the airguns to the full operating source level (i.e., 
3,300 cubic inches (in\3\)) only if the PSVO visually observes the 
marine mammal exiting the exclusion zone for the full source level 
within an eight-minute period of the shut-down or power down. The 
eight-minute period is based on the 180-dB radius for the 18-airgun 
subarray towed at a depth of seven m (23 ft) in relation to the minimum 
planned speed of the Langseth while shooting (8.5 km/h; 5.3 mph; 4.6 
kts). In the event that a marine mammal would re-enter the exclusion 
zone after reactivating the airguns, L-DEO would reinitiate a shut-down 
or power down as required by the IHA.
    Should the airguns be inactive or powered down for more than 8 
minutes, and the PSVO does not observe the marine mammal leaving the 
exclusion zone, then L-DEO must wait 15 minutes (for small odontocetes 
or pinnipeds) or 30 minutes (for mysticetes and large odontocetes) 
after the last sighting before L-DEO can initiate ramp-up procedures. 
However, ramp up will not occur as long as a marine mammal is detected 
within the exclusion zone, which provides more time for animals to 
leave the exclusion zone, and accounts for the position, swim speed and 
heading of marine mammals within the exclusion zone.
    Finally, L-DEO may need to temporarily perform a shut-down due to 
equipment failure or maintenance. In this instance, L-DEO will restart 
the airguns to the full source level within an 8-minute period of the 
shut-down only if the PSVOs do not observe marine mammals within 
exclusion zone for the full source level. If the airguns are inactive 
or powered down for more than eight minutes, then L-DEO would follow 
the ramp-up procedures required by the IHA. L-DEO would restart the 
airguns beginning with the smallest airgun in the array and add airguns 
in a sequence such that the source level of the array does not exceed 6 
decibels (dB) per 5-minute period over a total duration of 
approximately 30 minutes. Again, the PSVOs would monitor the exclusion 
zones for marine mammals during this time and would initiate a power-
down or a shutdown, as required by the IHA.
    Comment 6: Extend the monitoring period to at least one hour before 
initiation of seismic activities and at least one hour before the 
resumption of airgun activities after a shutdown because of a marine 
mammal sighting within an exclusion zone.
    Response: As the Commission points out, several species of deep-
diving cetaceans are capable of remaining underwater for more than 30 
minutes; however, for the following reasons NMFS believes that 30 
minutes is an adequate length for the monitoring period prior to the 
start-up of airguns:
    (1) Because the Langseth is required to monitor before ramp-up of 
the airgun array, the time of monitoring prior to start-up of any but 
the smallest array is effectively longer than 30 minutes (ramp-up will 
begin with the smallest airgun in the array and airguns will be added 
in sequence such that the source level of the array will increase in 
steps not exceeding approximately 6 dB per 5-minute period over a total 
duration of 20 to 30 minutes);
    (2) In many cases PSVOs are observing during times when L-DEO is 
not operating the seismic airguns and would actually observe the area 
prior to the 30-minute observation period anyway;
    (3) The majority of the species that may be exposed do not stay 
underwater more than 30 minutes; and
    (4) All else being equal and if deep-diving individuals happened to 
be in the area in the short time immediately prior to the pre-start-up 
monitoring, if an animal's maximum underwater dive time is 45 minutes, 
then there is only a one in three chance that the last random surfacing 
would occur prior to the beginning of the required 30-minute monitoring 
period and that the animal would not be seen during that 30-minute 
period.
    Also, seismic vessels are moving continuously (because of the long, 
towed array) and NMFS believes that unless the animal submerges and 
follows at the speed of the vessel (highly unlikely, especially when 
considering that a significant part of their movements is vertical 
[deep-diving]), the vessel will be far beyond the length of the 
exclusion zone radii within 30 minutes, and therefore it will be safe 
to start the airguns again.
    The effectiveness of monitoring is science-based and the 
requirement that mitigation measures be ``practicable.'' NMFS believes 
that the framework for visual monitoring will: (1) Be effective at 
spotting almost all species for which take is requested; and (2) that 
imposing additional requirements, such as those suggested by the 
Commission, would not meaningfully increase the effectiveness of 
observing marine mammals approaching or entering the EZs and thus 
further minimize the potential for take.
    Comment 7: The Commission recommends that, before issuing the 
requested IHA, NMFS require that observers collect and analyze data on 
the effectiveness of ramp-up as a mitigation measures during all such 
procedures.
    Response: The IHA requires that PSVOs on the Langseth make 
observations for 30 minutes prior to ramp-up, during all ramp-ups, and 
during all daytime seismic operations and record the following 
information when a marine mammal is sighted:
    (i) Species, group size, age/size/sex categories (if determinable), 
behavior

[[Page 20329]]

when first sighted and after initial sighting, heading (if consistent), 
bearing and distance from seismic vessel, sighting cue, apparent 
reaction to the airguns or vessel (e.g., none, avoidance, approach, 
paralleling, etc., and including responses to ramp-up), and behavioral 
pace; and
    (ii) Time, location, heading, speed, activity of the vessel 
(including number of airguns operating and whether in state of ramp-up 
or power-down), Beaufort wind force sea state, visibility, and sun 
glare.
    One of the primary purposes of monitoring is to result in 
``increased knowledge of the species'' and the effectiveness of 
monitoring and mitigation measures; the effectiveness of marine mammals 
reaction to ramp-up would be useful information in this regard. NMFS 
has asked NSF and L-DEO to gather all data that could potentially 
provide information regarding the effectiveness of ramp-ups as a 
mitigation measure. However, considering the low numbers of marine 
mammal sightings and low numbers of ramp-ups, it is unlikely that the 
information will result in any statistically robust conclusions for 
this particular seismic survey. Over the long term, these requirements 
may provide information regarding the effectiveness of ramp-up as a 
mitigation measure, provided animals are detected during ramp-up.

Description of the Marine Mammals in the Area of the Specified Activity

    Twenty-eight marine mammal species may seasonally occur in the 
survey area, including 20 odontocetes (toothed cetaceans), 6 mysticetes 
(baleen whales) and two pinnipeds. Of these, 19 cetacean species are 
likely to occur in the survey area in the ETP during April through 
June. Five of these species are listed as endangered under the ESA, 
including the humpback (Megaptera novaeangliae), sei (Balaenoptera 
borealis), fin (Balaenoptera physalus), blue (Balaenoptera musculus), 
and sperm (Physeter macrocephalus) whale.
    The species of marine mammals expected to be most common in the 
survey area (all delphinids) include the short-beaked common dolphin 
(Delphinus delphis), spinner dolphin (Stenella longirostris), 
pantropical spotted dolphin (Stenella attenuata), striped dolphin 
(Stenella coeruleoalba), melon-headed whale (Peponocephala electra), 
and bottlenose dolphin (Tursiops truncatus).
    Two pinnipeds, the California sea lion (Zalophus californianus) and 
the Gal[aacute]pagos sea lion (Zalophus wollebaeki), have the potential 
to transit in the vicinity of the seismic survey, although any 
occurrence would be rare as they are vagrants to the area. Accordingly, 
the IHA only addresses requested take authorizations for mysticetes and 
odontocetes.
    NMFS has presented a more detailed discussion of the status of 
these stocks and their occurrence in the northeastern Pacific Ocean, as 
well as other marine mammal species that occur in area offshore Costa 
Rica in the notice of the proposed IHA (76 FR 6430, February 4, 2011).

Potential Effects on Marine Mammals

    Acoustic stimuli generated by the operation of the airguns, which 
introduce sound into the marine environment, may have the potential to 
cause Level B harassment of marine mammals in the survey area. The 
effects of sounds from airgun operations might include one of the 
following: tolerance, masking of natural sounds, behavioral 
disturbance, temporary or permanent 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 permanent hearing impairment, or 
any significant non-auditory physical or physiological effects. Based 
on the available data and studies described here, some behavioral 
disturbance is expected, but NMFS expects the disturbance to be 
localized and short-term.
    The notice of the proposed IHA (76 FR 6430, February 4, 2011) 
included a discussion of the effects of sounds from airguns on 
mysticetes and odontocetes including tolerance, masking, behavioral 
disturbance, hearing impairment, and other non-auditory physical 
effects. NMFS refers the reader to L-DEO's application, environmental 
analysis and NMFS' EA for additional information on the behavioral 
reactions (or lack thereof) by all types of marine mammals to seismic 
vessels.

Anticipated Effects on Marine Mammal Habitat, Fish and Invertebrates

    NMFS included a detailed discussion of the potential effects of 
this action on marine mammal habitat, including physiological and 
behavioral effects on marine fish and invertebrates in the notice of 
the proposed IHA (76 FR 6430, February 4, 2011). While NMFS anticipates 
that the specified activity may result in marine mammals avoiding 
certain areas due to temporary ensonification, this impact to habitat 
is temporary and reversible which NMFS considered in further detail in 
the notice of the proposed IHA (76 FR 6430, February 4, 2011) as 
behavioral modification. The main impact associated with the activity 
would be temporarily elevated noise levels and the associated direct 
effects on marine mammals.

Mitigation

    In order to issue an incidental take authorization (ITA) 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 the availability of 
such species or stock for taking for certain subsistence uses.
    L-DEO has based the mitigation measures described herein, to be 
implemented for the seismic survey, on the following:
    (1) Protocols used during previous L-DEO seismic research cruises 
as approved by NMFS;
    (2) Previous IHA applications and IHAs approved and authorized by 
NMFS; and
    (3) Recommended best practices in Richardson et al. (1995), Pierson 
et al. (1998), and Weir and Dolman, (2007).
    To reduce the potential for disturbance from acoustic stimuli 
associated with the activities, L-DEO and/or its designees would 
implement the following mitigation measures for marine mammals:
    (1) Exclusion zones;
    (2) Power-down procedures;
    (3) Shutdown procedures; and
    (4) Ramp-up procedures.
    Exclusion Zones--L-DEO uses safety radii to designate exclusion 
zones (EZ) and to estimate take for marine mammals. Table 1 shows the 
distances at which two sound levels (160- and 180-dB) are expected to 
be received from the 18-airgun subarray and a single airgun. NMFS 
(1995, 2000) concluded that cetaceans should not be exposed to pulsed 
underwater noise at received levels exceeding 180 dB re: 1 [mu]Pa. NMFS 
believes that to avoid the potential for permanent physiological damage 
(Level A harassment), cetaceans should not be exposed to pulsed 
underwater noise at received levels exceeding 180 dB re: 1 [mu]Pa. The 
180-dB level is a shutdown criterion applicable

[[Page 20330]]

to cetaceans, as specified by NMFS (2000). NMFS also assumes that 
cetaceans exposed to levels exceeding 160 dB re: 1 [mu]Pa (rms) may 
experience Level B harassment. L-DEO used these levels to establish the 
EZ.
    If the protected species visual observer (PSVO) detects marine 
mammal(s) within or about to enter the appropriate exclusion zone, the 
Langseth crew will immediately power down the airgun subarrays, or 
perform a shut down if necessary (see Shut-down Procedures).

 Table 1--Predicted Distances To Which Sound Levels >=, 180, and 160 dB re: 1 [mu]Parms Could Be Received During
   the Survey Using a 18-Airgun Subarray, as Well as a Single Airgun Towed at a Depth of 7 m in the ETP During
                                                 April-May, 2011
                            [Distances are based on model results provided by L-DEO.]
----------------------------------------------------------------------------------------------------------------
                                                                                  Predicted RMS distances (m)
              Source and volume                         Water depth          -----------------------------------
                                                                                   180 dB            160 dB
----------------------------------------------------------------------------------------------------------------
Single Bolt airgun (40 in\3\)...............  Shallow < 100 m...............               296             1,050
                                              Intermediate 100-1,000 m......                60               578
                                              Deep > 1,000 m................                40               385
18-Airgun subarray (3,300 in\3\)............  Shallow < 100 m...............             1,030          * 19,500
                                              Intermediate 100-1,000 m......               675             5,700
                                              Deep > 1,000 m................               450            3,800
----------------------------------------------------------------------------------------------------------------
* This is likely an overestimate, as the measured distance for the 36-airgun array operating in shallow waters
  of the northern Gulf of Mexico was 17,500 m (17.5 km).

    Power-down Procedures--A power-down involves decreasing the number 
of airguns in use such that the radius of the 180-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 subarray can also occur when the 
vessel is moving from one seismic line to another. During a power-down 
for mitigation, L-DEO will operate one airgun. 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 
the Langseth suspends all airgun activity.
    If the PSVO detects a marine mammal outside the EZ, but it is 
likely to enter the EZ, L-DEO will power down the airguns before the 
animal is within the EZ. Likewise, if a mammal is already within the 
EZ, when first detected L-DEO will power down the airguns immediately. 
During a power down of the airgun array, L-DEO will also operate the 
40-in\3\ airgun. If a marine mammal is detected within or near the 
smaller EZ around that single airgun (Table 1), L-DEO will shut down 
the airgun (see next section).
    Following a power-down, L-DEO will not resume airgun activity until 
the marine mammal has cleared the safety zone. L-DEO will consider the 
animal to have cleared the EZ if
     A PSVO has visually observed the animal leave the EZ, or
     A PSVO has not sighted the animal within the EZ for 15 min 
for small odontocetes, or 30 min for mysticetes and large odontocetes, 
including sperm, pygmy sperm, dwarf sperm, and beaked whales.
    During airgun operations following a power-down (or shut-down) 
whose duration has exceeded the time limits specified previously, L-DEO 
will ramp-up the airgun array gradually (see Shut-down Procedures).
    Shut-down Procedures--L-DEO will shut down the operating airgun(s) 
if a marine mammal is seen within or approaching the EZ for the single 
airgun. L-DEO will implement a shut-down:
    (1) If an animal enters the EZ of the single airgun after L-DEO has 
initiated a power down, or (2) If a an animal is initially seen within 
the EZ of the single airgun when more than one airgun (typically the 
full airgun array) is operating.
    L-DEO will not resume airgun activity until the marine mammal has 
cleared the EZ, or until the PSVO is confident that the animal has left 
the vicinity of the vessel. Criteria for judging that the animal has 
cleared the EZ will be as described in the preceding section.
    Ramp-up Procedures--L-DEO will follow a ramp-up procedure when the 
airgun subarrays begin operating after a specified period without 
airgun operations or when a power down has exceeded that period. L-DEO 
proposes that, for the present cruise, this period would be 
approximately eight minutes. This period is based on the 180-dB radius 
for the 18-airgun subarray towed at a depth of seven m (23 ft) in 
relation to the minimum planned speed of the Langseth while shooting 
(8.5 km/h; 5.3 mph; 4.6 knots). L-DEO has used similar periods (8-10 
min) 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 six dB per five-
minute period over a total duration of approximately 30 min. During 
ramp-up, the PSVOs will monitor the EZ, and if marine mammals are 
sighted, L-DEO will implement a power down or shut down as though the 
full airgun array were operational.
    If the complete EZ has not been visible for at least 30 minutes 
prior to the start of operations in either daylight or nighttime, L-DEO 
will not commence the ramp-up 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 safety zone 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. L-DEO will not initiate a ramp-up of the 
airguns if a marine mammal is sighted within or near the applicable EZs 
during the day or close to the vessel at night.
    NMFS has carefully evaluated the applicant's proposed mitigation 
measures and has considered a range of other measures in the context of 
ensuring that NMFS prescribes the means of effecting the least 
practicable adverse impact on the affected marine mammal species and 
stocks and their habitat. Our evaluation of potential measures included 
consideration of the

[[Page 20331]]

following factors in relation to one another: (1) The manner in which, 
and the degree to which, the successful implementation of the measure 
is expected to minimize adverse impacts to marine mammals; (2) the 
proven or likely efficacy of the specific measure to minimize adverse 
impacts as planned; and (3) the practicability of the measure for 
applicant implementation.
    Based on our evaluation of the applicant's proposed measures, as 
well as other measures considered by NMFS or recommended by the public, 
NMFS has determined that the mitigation measures provide the means of 
effecting the least practicable adverse impacts on marine mammals 
species or stocks and their habitat, paying particular attention to 
rookeries, mating grounds, and areas of similar significance.

Monitoring and Reporting

    In order to issue an IHA 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) indicate 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 in the action area.

Monitoring

    L-DEO would sponsor marine mammal monitoring during the present 
project, in order to implement the mitigation measures that require 
real-time monitoring, and to satisfy the anticipated monitoring 
requirements of the IHA. L-DEO's Monitoring Plan is described below 
this section. 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

    L-DEO's PSVOs will be based aboard the seismic source vessel and 
will watch for marine mammals near the vessel during daytime airgun 
operations and during any start-ups at night. PSVOs will also watch for 
marine mammals near the seismic vessel for at least 30 min prior to the 
start of airgun operations after an extended shut down.
    PSVOs will conduct observations during daytime periods when the 
seismic system is not operating for comparison of sighting rates and 
behavior with and without airgun operations and between acquisition 
periods. Based on PSVO observations, the airguns will be powered down 
or shut down when marine mammals are observed within or about to enter 
a designated EZ.
    During seismic operations off Costa Rica, at least three PSVOs will 
be based aboard the Langseth. L-DEO will appoint the PSVOs with NMFS' 
concurrence. During all daytime periods, two PSVOs will be on duty from 
the observation tower to monitor and PSVOs will be on duty in shifts of 
duration no longer than four hours.
    During mealtimes it is sometimes difficult to have two PSVOs on 
effort, but at least one PSVO will be on watch during bathroom breaks 
and mealtimes. Use of two simultaneous observers increases the 
effectiveness of detecting animals near the source vessel. However, 
during meal times, only one PSVO may be on duty.
    Two PSVOs will also be on visual watch during all nighttime start-
ups of the seismic airguns. A third PSVO will monitor the PAM equipment 
24 hours a day to detect vocalizing marine mammals present in the 
action area. In summary, a typical daytime cruise would have scheduled 
two PSVOs on duty from the observation tower, and a third PSVO on PAM.
    L-DEO will also instruct other crew to assist in detecting marine 
mammals and implementing mitigation requirements (if practical). Before 
the start of the seismic survey, L-DEO will give the crew additional 
instruction regarding how to accomplish this task.
    The Langseth is a suitable platform for marine mammal observations. 
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 daytime, the PSVOs 
will scan the area around the vessel systematically with reticle 
binoculars (e.g., 7 x 50 Fujinon), Big-eye binoculars (25 x 150), 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 range-finding binoculars (Leica 
LRF 1200 laser rangefinder or equivalent) will be available to assist 
with distance estimation. Those are useful in training observers 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.

Passive Acoustic Monitoring

    Passive Acoustic Monitoring (PAM) will complement the visual 
monitoring program, when practicable. Visual monitoring typically is 
not effective during periods of poor visibility or at night, and even 
with good visibility, is unable to detect marine mammals when they are 
below the surface or beyond visual range.
    Besides the three PSVOs, an additional acoustic Protected Species 
Observer (PSO) with primary responsibility for PAM will also be aboard 
the vessel. L-DEO can use acoustical monitoring 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 towed hydrophone 
array that is connected to the vessel by a cable. The lead in from the 
hydrophone array is approximately 400 m (1,312 ft) long, the active 
section of the array is approximately 56 m (184 ft) long, and the 
hydrophone array is typically towed at depths of less than 20 m (66 
ft).
    The deck cable is connected from the array to a computer in the 
laboratory where signal conditioning and processing takes place. The 
digitized signal is then sent to the main laboratory, where the 
acoustic PSO monitors the system.
    The acoustic PSO will monitor the towed hydrophones 24 h per day 
during airgun operations and during most periods when the Langseth is 
underway while the airguns are not operating. However, PAM may not be 
possible if damage occurs to both the primary and back-up hydrophone 
the arrays during operations. The primary PAM streamer on the Langseth 
is a digital hydrophone streamer. Should the digital streamer fail, 
back-up systems should include an analog spare streamer and a hull-

[[Page 20332]]

mounted hydrophone. Every effort would be made to have a working PAM 
system during the cruise. In the unlikely event that all three of these 
systems were to fail, L-DEO would continue science acquisition with the 
visual-based observer program. The PAM system is a supplementary 
enhancement to the visual monitoring program. If weather conditions 
were to prevent the use of PAM then conditions would also likely 
prevent the use of the airgun array.
    One acoustic PSO 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. Acoustic PSOs monitoring the 
acoustical data will be on shift for one to six hours at a time. 
Besides the PSVO, an additional acoustic PSO with primary 
responsibility for PAM will also be aboard the source vessel. All PSVOs 
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 visual PSVO immediately, to 
alert him/her to the presence of cetaceans (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 call will be entered into a 
database. Data entry will 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.

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 airguns 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, age/size/sex categories (if determinable), 
behavior when first sighted and after initial sighting, heading (if 
consistent), bearing and distance from seismic vessel, sighting cue, 
apparent reaction to the airguns or vessel (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) 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 and power downs or shut downs will be recorded in 
a standardized format. Data will be entered into an electronic 
database. The accuracy of the 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 from the vessel-based observations will provide:
    1. The basis for real-time mitigation (airgun power down or shut 
down).
    2. Information needed to estimate the number of marine mammals 
potentially taken by harassment, which must be reported to NMFS.
    3. Data on the occurrence, distribution, and activities of marine 
mammals and turtles in the area where the seismic study is conducted.
    4. Information to compare the distance and distribution of marine 
mammals and turtles relative to the source vessel at times with and 
without seismic activity.
    5. Data on the behavior and movement patterns of marine mammals 
seen at times with and without seismic activity.
    L-DEO will submit a report 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 and turtles near the 
operations. The report will provide 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 number and nature of exposures that could result in 
``takes'' of marine mammals by harassment or in other ways.
    L-DEO will report all injured or dead marine mammals (regardless of 
cause) to NMFS as soon as practicable. The report should include the 
species or description of the animal, the condition of the animal, 
location, time first found, observed behaviors (if alive) and photo or 
video, if available.

Estimated Take by Incidental 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].

    Only take by Level B harassment is anticipated and authorized as a 
result of the marine geophysical survey off Costa Rica. Acoustic 
stimuli (i.e., increased underwater sound) generated during the 
operation of the seismic airgun array, may have the potential to cause 
marine mammals in the survey area to be exposed to sounds at or greater 
than 160 decibels (dB) or cause temporary, short-term changes in 
behavior. There is no evidence that the planned activities are likely 
to result in injury, serious injury or mortality to marine mammals 
within the specified geographic area for which NMFS has issued the IHA. 
Take by injury, serious injury or mortality is thus neither anticipated 
nor authorized. NMFS has determined that the he required mitigation and 
monitoring measures will minimize any potential risk for injury, 
serious injury or mortality.
    NMFS included an in-depth discussion of the methods used to 
calculate the densities of the marine mammals in the area of the 
seismic survey in a previous notice for the proposed IHA (76 FR 6430, 
February 4, 2011). A summary is included here.
    L-DEO's estimates are based on a consideration of the number of 
marine mammals that could be disturbed appreciably by operations with 
the 18-airgun subarray to be used during approximately 2,145 km (1,333 
mi) of survey lines with an additional 365 km (227 mi) of turns 
offshore Costa Rica.
    Density data on the marine mammal species in the proposed survey 
area are

[[Page 20333]]

available from extensive ship-based surveys for marine mammals in the 
ETP conducted by NMFS' Southwest Fisheries Science Center (SWFSC). L-
DEO used densities from two sources: (1) The SWFSC's habitat models 
that predict density for 15 cetacean species in the ETP; and (2) 
densities from the surveys conducted during summer and fall 1986-1996, 
as summarized by Ferguson and Barlow (2001, 2003) for species sighted 
in SWFSC surveys whose sample sizes were too small to model density.
    For the predictive models, the SWFSC developed habitat modeling as 
a method to estimate cetacean densities on a finer spatial scale 
compared to traditional line-transect analyses by using a continuous 
function of habitat variables, e.g., sea surface temperature, depth, 
distance from shore, and prey density (Barlow et al., 2009). The SWFSC 
incorporated the models into a web-based Geographic Information System 
(GIS) developed by Duke University's Department of Defense Strategic 
Environmental Research and Development Program (SERDP) team and L-DEO 
used the GIS to obtain mean and maximum densities for 11 cetacean 
species in the model in the proposed survey area.
    L-DEO also used the densities calculated from Ferguson and Barlow 
(2003) for 5[deg] x 5[deg] blocks that include the proposed survey area 
(Block 138) and blocks adjacent to 138 that include coastal waters: 
Blocks 119, 137, 138, 139, 158, and 159. Those blocks included 18,385 
km (11,423 mi) of survey effort in Beaufort sea states 0-5, and 3,899 
square kilometers (km\2\) (1,505 square miles (mi\2\)) of survey effort 
in Beaufort sea states 0-2. L-DEO also obtained densities for an 
additional seven species that were sighted in one or more of those 
blocks.
    For two endangered species for which there are only unconfirmed 
sightings in the region, the sei and fin whales, L-DEO assigned low 
density values (equal to the density of the species with the lowest 
calculated density). The false killer whale has been sighted near the 
survey area but not in the seven blocks of Ferguson and Barlow (2003), 
so it was also assigned the same low density value.
    Oceanographic conditions, including occasional El Ni[ntilde]o and 
La Ni[ntilde]a events, influence the distribution and numbers of marine 
mammals present in the ETP, resulting in considerable year-to-year 
variation in the distribution and abundance of many marine mammal 
species (e.g., Escorza-Trevino, 2009). Thus, for some species the 
densities derived from recent surveys may not be representative of the 
densities that will be encountered during the proposed seismic survey.
    L-DEO's estimates of exposures to various sound levels assume that 
the proposed 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-kilometers of 
seismic operations that can be undertaken. L-DEO has included an 
additional 25 percent of line transects to account for mission 
uncertainty and follow a precautionary approach. Furthermore, any 
marine mammal sightings within or near the designated exclusion zones 
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 sound levels of 160 dB re: 1 
[micro]Pa are precautionary and probably overestimate the actual 
numbers of marine mammals that might be involved. These estimates also 
assume that there will be no weather, equipment, or mitigation delays, 
which is highly unlikely.
    L-DEO estimated the number of different individuals that may be 
exposed to airgun sounds with received levels greater than or equal to 
160 dB re: 1 [micro]Pa on one or more occasions by considering the 
total marine area that would be within the 160-dB radius around the 
operating airgun array on at least one occasion and the expected 
density of marine mammals. 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 
planned survey, the seismic lines are parallel and in close proximity; 
thus individuals could be exposed on two or more occasions. The area 
including overlap is 31.9 times the area excluding overlap. Thus a 
marine mammal that stayed in the survey area during the entire survey 
could be exposed 32 times (14 times), on average. Given the pattern of 
the seismic lines, the interval between exposures of a stationary 
animal would be approximately 18 hours. 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 
greater than or equal to 160 re: 1 [micro]Pa was calculated by 
multiplying:
    (1) The expected species density, either ``mean'' (i.e., best 
estimate) or ``maximum'', times
    (2) The anticipated area to be ensonified to that level during 
airgun operations excluding overlap, which is approximately 3,225 km\2\ 
(2,003 mi\2\).
    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) around each seismic line, and 
then calculating the total area within the buffers. Areas of overlap 
were included only once when estimating the number of individuals 
exposed. Applying this approach, approximately 3,225 km\2\ (1,245 
mi\2\) would be within the 160-dB isopleth on one or more occasions 
during the survey. 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.
    The total `maximum estimate' of the number of individual cetaceans 
that could be exposed to seismic sounds with received levels greater 
than or equal to 160 dB re: 1 [mu]Pa during the proposed survey is 
7,078 (see Table 2). That total includes 38 species of baleen whales, 
four of which are endangered including: 18 humpback whales or 1.2 
percent of the regional population; one sei whale, one fin whale (less 
than 0.01 percent); and eight blue whales (0.6 percent). In addition, 
40 sperm whales (also listed as endangered under the ESA) or 0.15 
percent of the regional population could be exposed during the survey, 
and 19 beaked whales. Most (97 percent) of the cetaceans that could be 
potentially exposed are delphinids (e.g., short-beaked common, striped, 
pantropical spotted, striped and spinner dolphins) with maximum 
estimates ranging from two to 3,077 exposed to levels greater than or 
equal to 160 dB re: 1 [mu]Pa.

[[Page 20334]]



  Table 2--Estimates of the Possible Numbers of Marine Mammals Exposed to Different Sound Levels During L-DEO's
                                Seismic Survey in the ETP During April-Jun