[Federal Register Volume 78, Number 30 (Wednesday, February 13, 2013)]
[Notices]
[Pages 10137-10160]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2013-03321]
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DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
RIN 0648-XC238
Takes of Marine Mammals Incidental to Specified Activities;
Marine Geophysical Survey on the Mid-Atlantic Ridge in the Atlantic
Ocean, April 2013, Through June 2013
AGENCY: National Marine Fisheries Service, National Oceanic and
Atmospheric Administration (NOAA), Commerce.
ACTION: Notice; proposed incidental harassment authorization; request
for comments.
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SUMMARY: We have received an application from the Lamont-Doherty Earth
Observatory (Observatory), in collaboration with the National Science
Foundation (Foundation), for an Incidental Harassment Authorization to
take marine mammals, by harassment, incidental to conducting a marine
geophysical (seismic) survey on the Mid-Atlantic Ridge in the north
Atlantic Ocean in international waters, from April 2013 through May
2013. Per the Marine Mammal Protection Act, we are requesting comments
on our proposal to issue an Incidental Harassment Authorization to the
Observatory and the Foundation to incidentally harass by Level B
harassment only, 28 species of marine mammals during the 20-day seismic
survey.
DATES: Comments and information must be received no later than March
15, 2013.
ADDRESSES: Comments on the application should be addressed to P.
Michael Payne, Chief, Permits and Conservation Division, Office of
Protected Resources, National Marine Fisheries Service, 1315 East-West
Highway, Silver Spring, MD 20910-3225. The mailbox address for
providing email comments is [email protected]. Please include 0648-
XC238 in the subject line. We are not responsible for email comments
sent to other addresses other than the one provided here. Comments sent
via email to [email protected], including all attachments, must not
exceed a 10-megabyte file size.
All submitted comments are a part of the public record and we will
post to http://www.nmfs.noaa.gov/pr/permits/incidental.htm#applications
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.
To obtain an electronic copy of the application, write to the
previously mentioned address, telephone the contact listed here (see
FOR FURTHER INFORMATION CONTACT), or visit the internet at: http://www.nmfs.noaa.gov/pr/permits/incidental.htm#applications.
The following associated documents are also available at the same
internet address:
The Foundation's draft environmental analysis titled, ``Marine
geophysical survey by the R/V MARCUS G. LANGSETH on the mid-Atlantic
Ridge, April-May 2013,'' for their federal action of funding the
Observatory's seismic survey. LGL Ltd., Environmental Research
Associates (LGL), prepared this analysis on behalf of the Foundation
pursuant to Executive Order 12114: Environmental Effects Abroad of
Major Federal Actions. The Foundation's environmental analysis
evaluates the effects of the proposed seismic survey on the human
environment including impacts to marine mammals. We will prepare a
separate National Environmental Policy Act (NEPA: 42 U.S.C. 4321 et
seq.) analysis to evaluate the environmental effects related to the
scope of our federal action which is the proposed issuance of an
incidental take authorization to the Observatory and the Foundation. We
plan to incorporate the Foundation's environmental analysis, in whole
or part, by reference, into our NEPA document as that analysis provides
a detailed description of the planned survey and its anticipated
effects on marine mammals. This notice and the referenced document
present detailed information on the scope of our federal action under
NEPA (i.e., potential impacts to marine mammals from
[[Page 10138]]
issuing the proposed IHA including measures for mitigation, and
monitoring) and we will consider comments submitted in response to this
notice as we prepare our NEPA analysis.
The public can view documents cited in this notice by appointment,
during regular business hours, at the aforementioned address.
FOR FURTHER INFORMATION CONTACT: Jeannine Cody, National Marine
Fisheries Service, Office of Protected Resources, (301) 427-8401.
SUPPLEMENTARY INFORMATION:
Background
Section 101(a)(5)(D) of the Marine Mammal Protection Act of 1972,
as amended (MMPA; 16 U.S.C. 1361 et seq.) 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, after notice of a proposed authorization to the
public for review and public comment: (1) We make certain findings; and
(2) the taking is limited to harassment.
We shall grant authorization for the incidental taking of small
numbers of marine mammals if we find 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 taking. We have 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
our 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, we must either issue or deny the
authorization and must publish a notice in the Federal Register within
30 days of our 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
We received an application from the Observatory on December 7,
2012, requesting that we issue an Incidental Harassment Authorization
(Authorization) for the take, by Level B harassment only, of small
numbers of marine mammals incidental to conducting a marine seismic
survey in the north Atlantic Ocean in international waters from April
8, 2013, through May 13, 2013. We received a revised application from
the Observatory on December 23, 2012 and January 17, 2013, which
reflected updates to the mitigation safety zones, incidental take
requests for marine mammals, and information on marine protected areas.
Upon receipt of additional information, we determined the application
complete and adequate on January 18, 2013.
Project Purpose--The Observatory plans to conduct a two-dimensional
(2-D) seismic survey on the Mid-Atlantic Ridge in the north Atlantic
Ocean. Specifically, the proposed survey would image the Rainbow massif
to determine the characteristics of the magma body that supplies heat
to the Rainbow hydrothermal field; determine the distribution of the
different rock types that form the Rainbow massif; document large- and
small-scale faults in the vicinity and investigate their role in
controlling hydrothermal fluid discharge.
Vessel--The Observatory plans to use one source vessel, the R/V
Marcus G. LANGSETH (LANGSETH), a seismic airgun array, a single
hydrophone streamer, and ocean bottom seismometers (seismometers) to
conduct the seismic survey. In addition to the operations of the
seismic airgun array and hydrophone streamer, and the seismometers, the
Observatory intends to operate a multibeam echosounder and a sub-bottom
profiler continuously throughout the proposed survey.
Marine Mammal Take--Acoustic stimuli (i.e., increased underwater
sound) generated during the operation of the seismic airgun arrays, may
have the potential to cause behavioral disturbance for marine mammals
in the survey area. This is the principal means of marine mammal take
associated with these activities and the Observatory requested an
authorization to take 28 species of marine mammals by Level B
harassment.
In the Observatory's application, they did not request
authorization to take marine mammals by Level A Harassment because
their environmental analyses estimate that marine mammals would not be
exposed to levels of sound likely to result in Level A harassment (we
refer the reader to Appendix B of the Foundation's NEPA document
titled, ``2011 Final Programmatic Environmental Impact Statement/
Overseas Environmental Impact Statement (2011 PEIS) for Marine Seismic
Research funded by the National Science Foundation or Conducted by the
U.S. Geological Survey,'' (NSF/USGS, 2011) at http://www.nsf.gov/geo/oce/envcomp/usgs-nsf-marine-seismic-research/nsf-usgs-final-eis-oeis-with-appendices.pdf for details). Consequently, the Observatory's
request for take by Level A harassment is zero animals for any species.
We do not expect that the use of the multibeam echosounder, the
sub-bottom profiler, or the ocean bottom seismometer would result in
the take of marine mammals and will discuss our reasoning later in this
notice. Also, we do not expect take to result from a collision with the
LANGSETH during seismic acquisition activities because the vessel moves
at a relatively slow speed (approximately 8.3 kilometers per hour (km/
h); 5.2 miles per hour (mph); 4.5 knots (kts)), for a relatively short
period of time (approximately 20 operational days). It is likely that
any marine mammal would be able to avoid the vessel during seismic
acquisition activities. The Observatory has no recorded cases of a
vessel strike with a marine mammal during the conduct of over eight
years of seismic surveys covering over 160,934 km (86,897.4 nmi) of
transect lines.
Description of the Proposed Specified Activities
Survey Details
The Observatory's proposed seismic survey on the Mid-Atlantic Ridge
in the north Atlantic Ocean would commence
[[Page 10139]]
on April 8, 2013, and end on May 13, 2013. The LANGSETH would depart
from St. George's, Bermuda, on April 8, 2013, and transit to the
proposed survey area in international waters approximately 300 km
(186.4 miles (mi)) offshore of Pico and Faial Islands in the Azores. At
the conclusion of the proposed survey activities, the LANGSETH would
arrive in Ponta Delgada, Azores on May 13, 2012. The proposed study
area would encompass an area on the Mid-Atlantic Ridge bounded by the
following coordinates: Approximately 35.5 to 36.5[deg] North by 33.5 to
34.5[deg] West.
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, we propose to issue an
authorization that is effective from April 8, 2013, to June 24, 2013.
Typically, 2-D surveys acquire data along single track lines with
wide intervals; cover large areas; provide a coarse sampled subsurface
image; and project less acoustic energy into the environment than other
types of seismic surveys. During the survey, the LANGSETH would deploy
an 36-airgun array as an energy source, an 8-kilometer (km)-long (3.7
mi-long) hydrophone streamer, and 46 seismometers. The seismometers are
portable, self-contained passive receiver systems designed to sit on
the seafloor and record seismic signals generated primarily by airguns
and earthquakes.
The LANGSETH would transect approximately 2,582 km (1.6 mi) of
transect lines which are spaced 1 to 2 meters (m) (3.2 to 6.6 feet
(ft)) apart from one another (see Figure 1 in the Observatory's
application). As the LANGSETH tows the airgun array along the transect
lines, the hydrophone streamer would receive the returning acoustic
signals and transfer the data to the vessel's onboard processing
system. The seismometers also record and store the returning signals
for later analysis. The LANGSETH would retrieve the seismometers at the
conclusion of the survey.
The proposed study (e.g., equipment testing, startup, line changes,
repeat coverage of any areas, and equipment recovery) would require
approximately 20 days. At the proposed survey area, the LANGSETH would
conduct seismic acquisition activities in a grid pattern using the
seismometers as a receiver over a total of approximately 1,680 km
(1,044 mi) of survey lines and would also conduct seismic acquisition
activities in multichannel seismic (MCS) mode using the 8-km (3.7 mi)
streamer as the receiver over a total of approximately 900 km (559 mi).
The seismic lines are over water depths of approximately 900 to 3,000 m
(2,952 ft to 1.9 mi). Approximately 2,565 km (1,594 mi) of the survey
effort would occur in depths greater than 1,000 m (3,280 ft). The
remaining effort (17 km; 10.5 mi) would occur in water depths of 100 to
1,000 m (328 to 3,280 ft).
The proposed data acquisition would include approximately 480 hours
of airgun operations (i.e., 20 days over 24 hours), with airgun
discharges occurring on either a 3.25 minute interval with the
seismometers or a 16-second interval for the MCS seismic portion. The
Observatory would conduct all planned seismic activities with on-board
assistance by the scientists who have proposed the study, Drs. J.P.
Canales and R. Sohn of Woods Hole Oceanographic Institution and Dr. R.
Dunn of the University of Hawaii. The vessel is self-contained and the
crew would live aboard the vessel for the entire cruise.
Vessel Specifications
R/V LANGSETH
The LANGSETH, owned by the Foundation and operated by the
Observatory, is a seismic research vessel with a quiet propulsion
system that avoids interference with the seismic signals emanating from
the airgun array. The vessel is 71.5 m (235 ft) long; has a beam of
17.0 m (56 ft); a maximum draft of 5.9 m (19 ft); and a gross tonnage
of 3,834 pounds. Its two 3,550 horsepower (hp) Bergen BRG-6 diesel
engines drive two propellers. Each propeller has four blades and the
shaft typically rotates at 750 revolutions per minute. The vessel also
has an 800-hp bowthruster, which is not used during seismic
acquisition. The cruising speed of the vessel outside of seismic
operations is 18.5 km/h (11.5 mph; 10 kts).
The LANGSETH would tow the 36-airgun array, as well as the
hydrophone streamer during the first and last surveys, along
predetermined lines. When the LANGSETH is towing the airgun array and
the hydrophone streamer, the turning rate of the vessel is limited to
five degrees per minute. Thus, the maneuverability of the vessel is
limited during operations with the streamer.
The vessel also has an observation tower from which protected
species visual observers (observer) would watch for marine mammals
before and during the proposed seismic acquisition operations. When
stationed on the observation platform, the observer's eye level would
be approximately 21.5 m (71 ft) above sea level providing the observer
an unobstructed view around the entire vessel.
Acoustic Source Specifications
Seismic Airguns
The LANGSETH would deploy an 36-airgun array, with a total volume
of approximately 6,600 cubic inches (in\3\). The airguns are a mixture
of Bolt 1500LL and Bolt 1900LLX airguns ranging in size from 40 to 360
in\3\, with a firing pressure of 1,900 pounds per square inch. The
dominant frequency components range from zero to 188 Hertz (Hz). The
array configuration consists of four identical linear strings, with 10
airguns on each string; the first and last airguns would be spaced 16 m
(52 ft) apart. Of the 10 airguns, nine would fire simultaneously while
the tenth airgun would serve as a spare in case of failure of one of
the other airguns. The LANGSETH would distribute the array across an
area of approximately 24 x 16 m (78.7 x 52.5 ft) and would tow the
array approximately 30 m (98.4 ft) behind the vessel at a tow depth of
12 m (39.4 ft) (see Figure 2-11, page 2-25 in the Foundation's 2011
PEIS) (NSF/USGS, 2011). During firing, the airguns would emit a brief
(approximately 0.1 s) pulse of sound; during the intervening periods of
operations, the airguns are silent.
Metrics Used in This Document
This section includes a brief explanation of the sound measurements
frequently used in the discussions of acoustic effects in this
document. Sound pressure is the sound force per unit area, and is
usually measured in micropascals ([micro]Pa), where 1 pascal (Pa) is
the pressure resulting from a force of one newton exerted over an area
of one square meter. We express sound pressure level as the ratio of a
measured sound pressure and a reference level. The commonly used
reference pressure level in underwater acoustics is 1 [micro]Pa, and
the units for sound pressure levels are dB re: 1 [mu]Pa. Sound pressure
level (in decibels (dB)) = 20 log (pressure/reference pressure).
Sound pressure level is an instantaneous measurement and can be
expressed as the peak, the peak-peak (p-p), or the root mean square.
Root mean square, which is the square root of the arithmetic average of
the squared instantaneous pressure values, is typically used in
discussions of the effects of sounds on vertebrates and all references
to sound pressure level in this document refer to the root mean square
unless otherwise noted. Sound
[[Page 10140]]
pressure level does not take the duration of a sound into account.
Characteristics of the Airgun Pulses
Airguns function by venting high-pressure air into the water which
creates an air bubble. The pressure signature of an individual airgun
consists of a sharp rise and then fall in pressure, followed by several
positive and negative pressure excursions caused by the oscillation of
the resulting air bubble. The oscillation of the air bubble transmits
sounds downward through the seafloor and the amount of sound
transmitted in the near horizontal directions is reduced. However, the
airgun array also emits sounds that travel horizontally toward non-
target areas.
The nominal source levels of the airgun array on the LANGSETH is
236 to 265 dB re: 1 [micro]Pa(p-p) and the root mean square
value for a given airgun pulse is typically 16 dB re: 1 [mu]Pa lower
than the peak-to-peak value (Greene, 1997; McCauley et al., 1998,
2000a). However, the difference between root mean square and peak or
peak-to-peak values for a given pulse depends on the frequency content
and duration of the pulse, among other factors.
Accordingly, the Observatory predicted the received sound levels in
relation to distance and direction from the 36-airgun array and the
single Bolt 1900LL 40-in\3\ airgun.
Appendix H of the Foundation's PEIS (NSF/USGS, 2011) provides a
detailed description of the modeling for marine seismic source arrays
for species mitigation. These are the source levels applicable to
downward propagation. The effective source levels for horizontal
propagation are lower than those for downward propagation because of
the directional nature of the sound from the airgun array. We refer the
reader to the Observatory's authorization application and the
Foundation's PEIS for additional information.
Predicted Sound Levels for the Airguns
The Observatory has developed a model (Diebold et al., 2010) that
predicts received sound levels as a function of distance from the
airguns for the 36-airgun array and the single 40-in\3\ airgun. Their
modeling approach uses ray tracing (i.e., a graphical representation of
the effects of refracting sound waves) for the direct wave traveling
from the array to the receiver and its associated source ghost
(reflection at the air-water interface in the vicinity of the array),
in a constant-velocity half-space (infinite homogeneous ocean layer,
unbounded by a seafloor).
Additionally, Tolstoy et al., (2009) reported results for
propagation measurements of pulses from the LANGSETH's 36-airgun array
in shallow-water (approximately 50 m (164 ft)) and deep-water depths
(approximately 1,600 m (5,249 ft)) in the Gulf of Mexico in 2007 and
2008. Results of the Gulf of Mexico calibration study (Tolstoy et al.,
2009) showed that radii around the airguns for various received levels
varied with water depth and that sound propagation varied with array
tow depth.
The Observatory used the results from their algorithm for acoustic
modeling (Diebold et al., 2010) to calculate the exclusion zones for
the 36-airgun array and the single airgun. These values designate
mitigation zones used during power downs or shutdowns for marine
mammals. The Observatory uses the mitigation zones to estimate take
(described in greater detail in Chapter 7 of the application) for
marine mammals.
Comparison of the Tolstoy et al. (2009) calibration study with the
Observatory's model (Diebold et al., 2010) for the LANGSETH's 36-airgun
array indicated that the Observatory's model represents the actual
received levels, within the first few kilometers and the locations of
the predicted exclusions zones. Thus, the comparison of results from
the Tolstoy et al. (2009) calibration study with the Observatory's
model (Diebold et al., 2010) at short ranges for the same array tow
depth are in good agreement (see Figures 12 and 14 in Diebold et al.,
2010). As a consequence, isopleths falling within this domain can be
predicted reliably by the Observatory's model.
In contrast, for actual received levels at longer distances, the
Observatory found that their model (Diebold et al., 2010) was a more
robust tool for estimating mitigation radii in deep water as it did not
overestimate the received sound levels at a given distance. To estimate
mitigation radii in intermediate water depths, the Observatory applied
a correction factor (multiplication) of 1.5 to the deep water
mitigation radii. We refer the reader to Appendix H of the Foundation's
PEIS (NSF/USGS, 2011) for a detailed description of the modeling for
marine seismic source arrays for species mitigation.
Table 1 summarizes the predicted distances at which one would
expect to receive three sound levels (160-, 180-, and 190-dB) from the
36-airgun array and a single airgun. To avoid the potential for injury
or permanent physiological damage (Level A harassment), serious injury,
or mortality we have concluded that cetaceans and pinnipeds should not
be exposed to pulsed underwater noise at received levels exceeding 180
dB re: 1 [mu]Pa and 190 dB re: 1 [mu]Pa, respectively (NMFS, 1995,
2000). The 180-dB and 190-dB level shutdown criteria are applicable to
cetaceans and pinnipeds, respectively, specified by us (NMFS, 1995,
2000). Thus the Observatory used these received sound levels to
establish the mitigation zones. We also assume that marine mammals
exposed to levels exceeding 160 dB re: 1 [micro]Pa may experience Level
B harassment.
Table 1--Modeled Distances to Which Sound Levels Greater Than or Equal to 160 and 180 dB re: 1 [micro]Pa Could
Be Received During the Proposed Survey Over the Mid-Atlantic Ridge in the North Atlantic Ocean, During April
Through June, 2013
----------------------------------------------------------------------------------------------------------------
Predicted RMS
Tow depth Water depth distances\1\ (m)
Source and volume (in\3\) (m) (m) ---------------------
160 dB 180 dB
----------------------------------------------------------------------------------------------------------------
Single Bolt airgun (40 in\3\)................................. 12 > 1,000 388 100
100 to 1,000 582 100
36-Airgun Array (6,600 in\3\)................................. 12 > 1,000 6,908 1,116
100 to 1,000 10,362 1,674
----------------------------------------------------------------------------------------------------------------
\1\ Diebold, J.B., M. Tolstoy, L. Doermann, S.L. Nooner, S.C. Webb, and T.J. Crone. 2010. R/V Marcus G. Langseth
seismic source: Modeling and calibration. Geochem. Geophys. Geosyst.
[[Page 10141]]
Ocean Bottom Seismometers
The Observatory proposes to place 46 seismometers on the sea floor
prior to the initiation of the seismic survey. Each seismometer is
approximately 0.9 m (2.9 ft) high with a maximum diameter of 97
centimeters (cm) (3.1 ft). An anchor, made of a rolled steel bar grate
which measures approximately 7 by 91 by 91.5 cm (3 by 36 by 36 inches)
and weighs 45 kilograms (99 pounds) would anchor the seismometer to the
seafloor.
After the Observatory completes the proposed seismic survey, an
acoustic signal would trigger the release of each of the 46
seismometers from the ocean floor. The LANGSETH's acoustic release
transponder, located on the vessel, communicates with the seismometer
at a frequency of 9 to13 kilohertz (kHz). The maximum source level of
the release signal is 242 dB re: 1 [mu]Pa with an 8-millisecond pulse
length. The received signal activates the seismometer's double burn-
wire release assembly which then releases the seismometer from the
anchor. The seismometer then floats to the ocean surface for retrieval
by the LANGSETH. The steel grate anchors from each of the seismometers
would remain on the seafloor.
The LANGSETH crew would deploy the seismometers one-by-one from the
stern of the vessel while onboard protected species observers will
alert them to the presence of marine mammals and recommend ceasing
deploying or recovering the seismometers to avoid potential
entanglement with marine mammal. Thus, entanglement of marine mammals
is highly unlikely.
Although placement of the seismometers is dispersed over
approximately1,500 square km (km\2\) (579 square mi (mi\2\) of seafloor
habitat and may disturb benthic invertebrates, we and the Observatory
expect these impacts to be localized and short-term because of natural
sedimentation processes and the natural sinking of the anchors from
their own weight resulting in no long-term habitat impacts. Also, the
deep water habitat potentially affected by the placement of the
seismometers is not designated as a marine protected area.
Multibeam Echosounder
The LANGSETH would operate a Kongsberg EM 122 multibeam echosounder
concurrently during airgun operations to map characteristics of the
ocean floor. The hull-mounted echosounder emits brief pulses of sound
(also called a ping) (10.5 to 13.0 kHz) in a fan-shaped beam that
extends downward and to the sides of the ship. The transmitting
beamwidth is 1 or 2[deg] fore-aft and 150[deg] athwartship and the
maximum source level is 242 dB re: 1 [mu]Pa.
For deep-water operations, each ping consists of eight (in water
greater than 1,000 m; 3,280 ft) or four (less than 1,000 m; 3,280 ft)
successive, fan-shaped transmissions, from two to 15 milliseconds (ms)
in duration and each ensonifying a sector that extends 1[deg] fore-aft.
Continuous wave pulses increase from 2 to 15 ms long in water depths up
to 2,600 m (8,530 ft). The echosounder uses frequency-modulated chirp
pulses up to 100-ms long in water greater than 2,600 m (8,530 ft). The
successive transmissions span an overall cross-track angular extent of
about 150[deg], with 2-ms gaps between the pulses for successive
sectors.
Sub-Bottom Profiler
The LANGSETH would also operate a Knudsen Chirp 3260 sub-bottom
profiler concurrently during airgun and echosounder operations to
provide information about the sedimentary features and bottom
topography. The profiler is capable of reaching depths of 10,000 m (6.2
mi). The dominant frequency component is 3.5 kHz and a hull-mounted
transducer on the vessel directs the beam downward in a 27[ordm] cone.
The power output is 10 kilowatts (kW), but the actual maximum radiated
power is three kilowatts or 222 dB re: 1 [micro]Pa. The ping duration
is up to 64 ms with a pulse interval of one second, but a common mode
of operation is to broadcast five pulses at 1-s intervals followed by a
5-s pause.
We expect that acoustic stimuli resulting from the proposed
operation of the single airgun or the 36-airgun array has the potential
to harass marine mammals, incidental to the conduct of the proposed
seismic survey. We assume that during simultaneous operations of the
airgun array and the other sources, any marine mammals close enough to
be affected by the echosounder and sub-bottom profiler would already be
affected by the airguns. We also expect these disturbances to result in
a temporary modification in behavior and/or low-level physiological
effects (Level B harassment) of small numbers of certain species of
marine mammals.
We do not expect that the movement of the LANGSETH, during the
conduct of the seismic survey, has the potential to harass marine
mammals because of the relatively slow operation speed of the vessel
(4.6 kts; 8.5 km/hr; 5.3 mph) during seismic acquisition.
Description of the Marine Mammals in the Area of the Proposed Specified
Activity
Twenty-eight marine mammal species under our jurisdiction may occur
in the proposed survey area, including seven mysticetes (baleen
whales), and 21 odontocetes (toothed cetaceans) during April through
May, 2013. Six of these species are listed as endangered under the
Endangered Species Act of 1973 (ESA; 16 U.S.C. 1531 et seq.),
including: the blue (Balaenoptera musculus), fin (Balaenoptera
physalus), humpback (Megaptera novaeangliae), north Atlantic right
(Eubalaena glacialis), sei (Balaenoptera borealis), and sperm (Physeter
macrocephalus) whales.
Based on the best available data, the Observatory does not expect
to encounter the following species because of these species rare and/or
extralimital occurrence in the survey area. They include the: Atlantic
white-sided dolphin (Lagenorhynchus acutus), white-beaked dolphin
(Lagenorhynchus albirostris), harbor porpoise (Phocoena phocoena),
Clymene dolphin (Stenella clymene), Fraser's dolphin (Lagenodelphis
hosei), spinner dolphin (Stenella longirostris), melon-headed whale
(Peponocephala electra), Atlantic humpback dolphin (Souza teuszii),
long-beaked common dolphin (Delphinus capensis), and any pinniped
species. Accordingly, we did not consider these species in greater
detail and the proposed authorization would only address requested take
authorizations for the 28 species.
Of these 28 species, the most common marine mammals in the survey
area would be the: short-beaked common dolphin (Delphinus delphis),
striped dolphin (Stenella coeruleoalba), and short-finned pilot whale
(Globicephala macrorhynchus).
Table 2 presents information on the abundance, distribution, and
conservation status of the marine mammals that may occur in the
proposed survey area during April through June, 2013.
[[Page 10142]]
Table 2--Abundance Estimates, Mean Density, and ESA Status of Marine
Mammals That May Occur in the Proposed Seismic Survey Area Over the Mid-
Atlantic Ridge in the North Atlantic Ocean, During April Through June,
2013.
[See text and Table 2 in the Observatory's application for further
details]
------------------------------------------------------------------------
Estimated
Abundance in ESA Density (/100 km \2\)
Atlantic Ocean \b\
------------------------------------------------------------------------
Mysticetes:
North Atlantic right 396 \1\........ EN 0
whale.
Humpback whale.......... 11,570 \2\..... EN 0
Minke whale............. 121,000 \3\.... NL 0
Bryde's whale........... Not available.. NL 0.19
Sei whale............... 12-13,000 \4\.. EN 0.19
Fin whale............... 24,887 \5\..... EN 4.46
Blue whale.............. 937 \6\........ EN 1.49
Odontocetes:
Sperm whale............. 13,190 \7\..... EN 3.71
Pygmy sperm whale....... 395 \1\........ NL 0
Dwarf sperm whale....... 395 \1\........ NL 0
Cuvier's beaked whale... 3,513 \1,8\.... NL 0
Mesoplodon spp.......... 3,513 \1,8\.... NL 7.04
True's beaked whale..... 3,513 \1,8\.... NL 7.04
Gervais beaked whale.... 3,513 \1,8\.... NL 7.04
Sowerby's beaked whale.. 3,513 \1,8\.... NL 7.04
Blainville's beaked 3,513 \1,8\.... NL 7.04
whale.
Northern bottlenose 40,000 \9\..... NL 0
whale.
Rough-toothed dolphin... Not available.. NL 0
Common bottlenose 81,588 \10\.... NL 8.35
dolphin.
Pantropical spotted 4,439 \1\...... NL 0
dolphin.
Atlantic spotted dolphin 50,978 \1\..... NL 20.03
Striped dolphin......... 94,462 \1\..... NL 185.50
Short-beaked common 120,741 \4\.... NL 379.52
dolphin.
Risso's dolphin......... 20,479 \4\..... NL 3.83
Pygmy killer whale...... Not available.. NL 0
False killer whale...... Not available.. NL 1.17
Killer whale............ Not available.. NL 0
Long-finned pilot whale. 12,619,\1\ NL 0
780,000 \11\.
Short-finned pilot whale 24,674,\1\ NL 120.96
780,000 \11\.
------------------------------------------------------------------------
\a\ ESA status codes: NL--not listed under the ESA; EN--Endangered; T--
Threatened
\b\ The Observatory used Waring et al., 2008 to calculate density from
sightings, effort, mean group sizes, and values for f(0) for the
southern part of the survey area.
\1\ Western North Atlantic, in U.S. and southern Canadian waters (Waring
et al., 2012)
\2\ Likely negatively biased (Stevick et al., 2003)
\3\ Central and Northeast Atlantic (IWC, 2012)
\4\ North Atlantic (Cattanach et al., 1993)
\5\ Central and Northeast Atlantic (V[iacute]kingsson et al., 2009)
\6\ Central and Northeast Atlantic (Pike et al., 2009).
\7\ For the northeast Atlantic, Faroes-Iceland, and the U.S. east coast
(Whitehead, 2002).
\8\ Ziphius and Mesoplodon spp. combined
\9\ Eastern North Atlantic (NAMMCO, 1995)
\10\ Offshore, Western North Atlantic (Waring et al., 2012)
\11\ Globicephala sp. combined, Central and Eastern North Atlantic (IWC,
2012)
Refer to Section 4 of the Observatory's application and Sections
3.6.3.4 and 3.7.3.4 of the 2011 PEIS (NSF/USGS, 2011) for detailed
information regarding the abundance and distribution, population
status, and life history and behavior of these species and their
occurrence in the proposed project area. We have reviewed these data
and determined them to be the best available scientific information for
the purposes of the proposed incidental harassment authorization.
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 proposed survey area.
The effects of sounds from airgun operations might include one or more
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 is not
an injury (Southall et al., 2007). Although we cannot exclude the
possibility entirely, it is unlikely that the proposed 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, we expect some
behavioral disturbance, but we expect the disturbance to be localized.
We refer the reader to a more comprehensive review of these issues in
the 2011 PEIS (NSF/USGS, 2011).
Tolerance
Studies on marine mammals' tolerance to sound in the natural
environment are relatively rare. Richardson et al. (1995) defined
[[Page 10143]]
tolerance as the occurrence of marine mammals in areas where they are
exposed to human activities or manmade noise. In many cases, tolerance
develops by the animal habituating to the stimulus (i.e., the gradual
waning of responses to a repeated or ongoing stimulus) (Richardson, et
al., 1995; Thorpe, 1963), but because of ecological or physiological
requirements, many marine animals may need to remain in areas where
they are exposed to chronic stimuli (Richardson, et al., 1995).
Numerous studies have shown that pulsed sounds from airguns are
often readily detectable in the water at distances of many kilometers.
Several studies have shown that marine mammals at distances more than a
few kilometers from operating seismic vessels often show no apparent
response. That is often true even in cases when the pulsed sounds must
be readily audible to the animals based on measured received levels and
the hearing sensitivity of the marine mammal group. Although various
baleen whales and toothed whales, and (less frequently) pinnipeds have
been shown to react behaviorally to airgun pulses under some
conditions, at other times marine mammals of all three types have shown
no overt reactions (Stone, 2003; Stone and Tasker, 2006; Moulton et al.
2005, 2006a; Weir 2008a for sperm whales), (MacLean and Koski, 2005;
Bain and Williams, 2006 for Dall's porpoises). The relative
responsiveness of baleen and toothed whales are quite variable.
Masking
The term masking refers to the inability of a subject to recognize
the occurrence of an acoustic stimulus as a result of the interference
of another acoustic stimulus (Clark et al., 2009). Introduced
underwater sound may, through masking, reduce the effective
communication distance of a marine mammal species if the frequency of
the source is close to that used as a signal by the marine mammal, and
if the anthropogenic sound is present for a significant fraction of the
time (Richardson et al., 1995).
We expect that the masking effects of pulsed sounds (even from
large arrays of airguns) on marine mammal calls and other natural
sounds will be limited, although there are very few specific data on
this. Because of the intermittent nature and low duty cycle of seismic
airgun pulses, animals can emit and receive sounds in the relatively
quiet intervals between pulses. However, in some situations,
reverberation occurs for much or the entire interval between pulses
(e.g., Simard et al., 2005; Clark and Gagnon, 2006) which could mask
calls. We understand that some baleen and toothed whales continue
calling in the presence of seismic pulses, and that some researchers
have heard these calls between the seismic pulses (e.g., 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; and Dunn and
Hernandez, 2009). However, 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 have found that they continued
calling in the presence of seismic pulses (Madsen et al., 2002; Tyack
et al., 2003; Smultea et al., 2004; Holst et al., 2006; and Jochens et
al., 2008). Several studies have reported hearing dolphins and
porpoises calling while airguns were operating (e.g., Gordon et al.,
2004; Smultea et al., 2004; Holst et al., 2005a, b; and Potter et al.,
2007). The sounds important to small odontocetes are predominantly at
much higher frequencies than are the dominant components of airgun
sounds, thus limiting the potential for masking.
Marine mammals are thought to be able to compensate for masking by
adjusting their acoustic behavior through shifting call frequencies,
increasing call volume, and increasing vocalization rates. For example,
blue whales are found to increase call rates when exposed to noise from
seismic surveys in the St. Lawrence Estuary (Dilorio and Clark, 2009).
The North Atlantic right whales exposed to high shipping noise
increased call frequency (Parks et al., 2007), while some humpback
whales respond to low-frequency active sonar playbacks by increasing
song length (Miller et al., 2000).
In general, we expect that the masking effects of seismic pulses
would be minor, given the normally intermittent nature of seismic
pulses.
Behavioral Disturbance
Marine mammals may behaviorally react to sound when exposed to
anthropogenic noise. Disturbance includes a variety of effects,
including subtle to conspicuous changes in behavior, movement, 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). These behavioral
reactions are often shown as: Changing durations of surfacing and
dives, number of blows per surfacing, or moving direction and/or speed;
reduced/increased vocal activities; changing/cessation of certain
behavioral activities (such as socializing or feeding); visible startle
response or aggressive behavior (such as tail/fluke slapping or jaw
clapping); avoidance of areas where noise sources are located; and/or
flight responses (e.g., pinnipeds flushing into the water from haul-
outs or rookeries). If a marine mammal does react briefly to an
underwater sound by changing its behavior or moving a small distance,
the impacts of the change are unlikely to be significant to the
individual, let alone the stock or population. 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).
The biological significance of many of these behavioral
disturbances is difficult to predict, especially if the detected
disturbances appear minor. However, the consequences of behavioral
modification could be expected to be biologically significant if the
change affects growth, survival, and/or reproduction. Some of these
significant behavioral modifications include:
Change in diving/surfacing patterns (such as those thought
to be causing beaked whale stranding due to exposure to military mid-
frequency tactical sonar);
Habitat abandonment due to loss of desirable acoustic
environment; and
Cessation of feeding or social interaction.
The onset of behavioral disturbance from anthropogenic noise
depends on both external factors (characteristics of noise sources and
their paths) and the receiving animals (hearing, motivation,
experience, demography) and is also difficult to predict (Richardson et
al., 1995; Southall et al., 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 would be
present within a particular distance of industrial activities and/or
exposed to a particular level of industrial sound. In most cases, this
approach likely overestimates the numbers of marine mammals that would
be affected in some biologically-important manner.
The sound criteria used to estimate how many marine mammals might
be
[[Page 10144]]
disturbed to some biologically-important degree by a seismic program
are based primarily on behavioral observations of a few species.
Scientists have conducted detailed studies on humpback, gray, bowhead
(Balaena mysticetus), and sperm whales. There are less detailed data
available for some other species of baleen whales and small toothed
whales, 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 (reviewed in Richardson
et al., 1995). 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, baleen whales
exposed to strong noise pulses from airguns often react by deviating
from their normal migration route and/or interrupting their feeding and
moving away from the area. In the cases of migrating gray and bowhead
whales, the observed changes in behavior appeared to be of little or no
biological consequence to the animals (Richardson et al., 1995). They
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 shown that
seismic pulses with received levels of 160 to 170 dB re: 1 [micro]Pa
seem to cause obvious avoidance behavior in a substantial fraction of
the animals exposed (Malme et al., 1986, 1988; Richardson et al.,
1995). In many areas, seismic pulses from large arrays of airguns
diminish to those levels at distances ranging from four to 15 km (2.5
to 9.3 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 Foundation's Assessment have shown
that some species of baleen whales, notably bowhead and humpback
whales, at times show strong avoidance at received levels lower than
160-170 dB re: 1 [micro]Pa.
Researchers have studied the responses of humpback whales to
seismic surveys during migration, feeding during the summer months,
breeding while offshore from Angola, and wintering offshore from
Brazil. McCauley et al. (1998, 2000a) studied the responses of humpback
whales off western Australia to a full-scale seismic survey with a 16-
airgun array (2,678-in\3\) and to a single, 20-in\3\ airgun with source
level of 227 dB re: 1 [micro]Pa (p-p). In the 1998 study, the
researchers documented that avoidance reactions began at five to eight
km (3.1 to 4.9 mi) from the array, and that those reactions kept most
pods approximately three to four km (1.9 to 2.5 mi) from the operating
seismic boat. In the 2000 study, McCauley et al. noted localized
displacement during migration of four to five km (2.5 to 3.1 mi) by
traveling pods and seven to 12 km (4.3 to 7.5 mi) by more sensitive
resting pods of cow-calf pairs. Avoidance distances with respect to the
single airgun were smaller but consistent with the results from the
full array in terms of the received sound levels. The mean received
level for initial avoidance of an approaching airgun was 140 dB re: 1
[micro]Pa for humpback pods containing females, and at the mean closest
point of approach distance, the received level was 143 dB re: 1
[micro]Pa. The initial avoidance response generally occurred at
distances of five to eight km (3.1 to 4.9 mi) from the airgun array and
two 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 [micro]Pa.
Data collected by observers during several seismic surveys in the
northwest Atlantic Ocean showed that sighting rates of humpback whales
were significantly greater during non-seismic periods compared with
periods when a full array was operating (Moulton and Holst, 2010). In
addition, humpback whales were more likely to swim away and less likely
to swim towards a vessel during seismic versus non-seismic periods
(Moulton and Holst, 2010).
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.
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. However, Moulton and Holst (2010)
reported that humpback whales monitored during seismic surveys in the
northwest Atlantic had lower sighting rates and were most often seen
swimming away from the vessel during seismic periods compared with
periods when airguns were silent.
Other studies have suggested that south Atlantic humpback whales
wintering off Brazil may be displaced or even strand upon exposure to
seismic surveys (Engel et al., 2004). Although, 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 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).
A few studies have documented reactions of migrating and feeding
(but not wintering) gray whales to seismic surveys. 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. They estimated, based on small sample sizes, that
50 percent of feeding gray whales stopped feeding at an average
received pressure level of 173 dB re: 1 [mu]Pa on an (approximate) root
mean square basis, and that 10 percent of feeding whales interrupted
feeding at received levels of 163 dB re: 1 [micro]Pa. 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 western Pacific
gray whales feeding off Sakhalin Island, Russia (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).
Observers have seen various species of Balaenoptera (blue, sei,
fin, and minke whales) in areas ensonified by airgun pulses (Stone,
2003; MacLean and Haley, 2004; Stone and Tasker, 2006), and have
localized calls from blue and fin whales in areas with airgun
operations (e.g., McDonald et al., 1995; Dunn and Hernandez, 2009;
Castellote et al., 2010). 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 vs. 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). Castellote et al. (2010)
observed
[[Page 10145]]
localized avoidance by fin whales during seismic airgun events in the
western Mediterranean Sea and adjacent Atlantic waters from 2006-2009
and reported that singing fin whales moved away from an operating
airgun array for a time period that extended beyond the duration of the
airgun activity.
Ship-based monitoring studies of baleen whales (including blue,
fin, sei, minke, and whales) in the northwest Atlantic found that
overall, this group had lower sighting rates during seismic versus non-
seismic periods (Moulton and Holst, 2010). Baleen whales as a group
were also seen significantly farther from the vessel during seismic
compared with non-seismic periods, and they were more often seen to be
swimming away from the operating seismic vessel (Moulton and Holst,
2010). Blue and minke whales were initially sighted significantly
farther from the vessel during seismic operations compared to non-
seismic periods; the same trend was observed for fin whales (Moulton
and Holst, 2010). Minke whales were most often observed to be swimming
away from the vessel when seismic operations were underway (Moulton and
Holst, 2010).
Data on short-term reactions by 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 have 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 (Appendix A in Malme et al.,
1984; Richardson et al., 1995; Allen and Angliss, 2011). The western
Pacific gray whale population did not appear affected by a seismic
survey in its feeding ground during a previous 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; Allen and Angliss, 2011). The
history of coexistence between seismic surveys and baleen whales
suggests that brief exposures to sound pulses from any single seismic
survey are unlikely to result in prolonged effects.
Toothed Whales--There is little systematic information available
about reactions of toothed whales to noise pulses. There are few
studies on toothed whales similar to the more extensive baleen whale/
seismic pulse work summarized earlier in this notice. However, there
are recent systematic studies on sperm whales (e.g., 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 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; Moulton and Holst, 2010).
Seismic operators and protected species observers (observers) on
seismic vessels regularly see dolphins and other small toothed whales
near operating airgun arrays, but in general there is a tendency for
most delphinids to show some avoidance of operating seismic vessels
(e.g., 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; Moulton and
Holst, 2010). 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 arrays of airguns are firing (e.g., Moulton and Miller, 2005).
Nonetheless, 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 (e.g., Stone and
Tasker, 2006; Weir, 2008, Barry et al., 2010; Moulton and Holst, 2010).
In most cases, the avoidance radii for delphinids appear to be small,
on the order of one km or less, and some individuals show no apparent
avoidance.
Captive bottlenose dolphins (Tursiops truncatus) and beluga whales
(Delphinapterus leucas) 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). 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 (Phocoena phocoena) show stronger
avoidance of seismic operations than do Dall's porpoises (Stone, 2003;
MacLean and Koski, 2005; 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 operating 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 (Richardson et al., 1995; Southall et al.,
2007).
Most studies of sperm whales exposed to airgun sounds indicate that
the whale shows considerable tolerance of airgun pulses (e.g., Stone,
2003; Moulton et al., 2005, 2006a; Stone and Tasker, 2006; Weir, 2008).
In most cases the whales do not show strong avoidance, and they
continue to call. However, controlled exposure experiments in the Gulf
of Mexico indicate that foraging behavior was altered upon exposure to
airgun sound (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, some northern bottlenose
whales (Hyperoodon ampullatus) remained in the general area and
continued to produce high-frequency clicks when exposed to sound pulses
from distant seismic surveys (Gosselin and Lawson, 2004; Laurinolli and
Cochrane, 2005; Simard et al., 2005). Most beaked whales tend to avoid
approaching vessels of other types (e.g., Wursig et al., 1998). They
may also dive for an extended period when approached by a vessel (e.g.,
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). Based on a
single observation, Aguilar-Soto et al. (2006) suggested that foraging
efficiency of Cuvier's beaked whales (Ziphius cavirostris) may be
reduced by close approach of vessels. In any event, it is likely that
most beaked whales would also show strong avoidance of an approaching
seismic vessel, although this has not been documented explicitly. In
fact, Moulton and Holst (2010) reported 15 sightings of beaked whales
during seismic studies in the northwest Atlantic; seven of those
sightings were made at times when at least one airgun was operating.
There was little evidence to indicate that beaked whale behavior was
affected by airgun operations; sighting rates and distances were
similar during seismic and non-seismic periods (Moulton and Holst,
2010).
There are increasing indications that some beaked whales tend to
strand when naval exercises involving mid-frequency sonar operation are
underway
[[Page 10146]]
within the vicinity of the animals (e.g., Simmonds and Lopez-Jurado,
1991; Frantzis, 1998; NOAA and USN, 2001; Jepson et al., 2003;
Hildebrand, 2005; Barlow and Gisiner, 2006; see also the Stranding and
Mortality section in this notice). These types of strandings are
apparently a disturbance response, although auditory or other injuries
or other physiological effects may also be involved. Whether beaked
whales would ever react similarly to seismic surveys is unknown.
Seismic survey sounds are quite different from those of the sonar in
operation during the above-cited incidents.
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. However, other data suggest that some odontocete species,
including harbor porpoises, may be more responsive than might be
expected given their poor low-frequency hearing. Reactions at longer
distances may be particularly likely when sound propagation conditions
are conducive to transmission of the higher frequency components of
airgun sound to the animals' location (DeRuiter et al., 2006; Goold and
Coates, 2006; Tyack et al., 2006; Potter et al., 2007).
Hearing Impairment and Other Physical Effects
Exposure to high intensity sound for a sufficient duration may
result in auditory effects such as a noise-induced threshold shift--an
increase in the auditory threshold after exposure to noise (Finneran et
al., 2005). Factors that influence the amount of threshold shift
include the amplitude, duration, frequency content, temporal pattern,
and energy distribution of noise exposure. The magnitude of hearing
threshold shift normally decreases over time following cessation of the
noise exposure. The amount of threshold shift just after exposure is
called the initial threshold shift. If the threshold shift eventually
returns to zero (i.e., the threshold returns to the pre-exposure
value), it is called temporary threshold shift (Southall et al., 2007).
Researchers have studied temporary threshold shift in certain
captive odontocetes and pinnipeds exposed to strong sounds (reviewed in
Southall et al., 2007). However, there has been no specific
documentation of temporary threshold shift let alone permanent hearing
damage, (i.e., permanent threshold shift, in free-ranging marine
mammals exposed to sequences of airgun pulses during realistic field
conditions).
Temporary Threshold Shift--This is the mildest form of hearing
impairment that can occur during exposure to a strong sound (Kryter,
1985). While experiencing temporary threshold shift, the hearing
threshold rises and a sound must be stronger in order to be heard. At
least in terrestrial mammals, temporary threshold shift can last from
minutes or hours to (in cases of strong shifts) days. For sound
exposures at or somewhat above the temporary threshold shift threshold,
hearing sensitivity in both terrestrial and marine mammals recovers
rapidly after exposure to the noise ends. There are few data on sound
levels and durations necessary to elicit mild temporary threshold shift
for marine mammals, and none of the published data focus on temporary
threshold shift elicited by exposure to multiple pulses of sound.
Southall et al. (2007) summarizes available data on temporary threshold
shift in marine mammals. Table 1 (introduced earlier in this document)
presents the estimated distances from the LANGSETH's airguns at which
the received energy level (per pulse, flat-weighted) would be greater
than or equal to 180 or 190 dB re: 1 [micro]Pa.
To avoid the potential for Level A harassment, serious injury or
mortality we (NMFS 1995, 2000) concluded that cetaceans should not be
exposed to pulsed underwater noise at received levels exceeding 180 dB
re: 1 [mu]Pa. We do not consider the established 180 criterion to be
the level above which temporary threshold shift might occur. Rather, it
is a received level above which, in the view of a panel of bioacoustics
specialists convened by us before temporary threshold shift
measurements for marine mammals started to become available, one could
not be certain that there would be no injurious effects, auditory or
otherwise, to marine mammals. We also assume that cetaceans exposed to
levels exceeding 160 dB re: 1 [mu]Pa may experience Level B harassment.
For toothed whales, researchers have derived temporary threshold
shift information for odontocetes from studies on the bottlenose
dolphin and beluga. The experiments show that exposure to a single
impulse at a received level of 207 kilopascals (or 30 psi, p-p), which
is equivalent to 228 dB re: 1 Pa (p-p), resulted in a 7 and 6 dB
temporary threshold shift in the beluga whale at 0.4 and 30 kHz,
respectively. Thresholds returned to within 2 dB of the pre-exposure
level within four minutes of the exposure (Finneran et al., 2002). For
the one harbor porpoise tested, the received level of airgun sound that
elicited onset of temporary threshold shift was lower (Lucke et al.,
2009). If these results from a single animal are representative, it is
inappropriate to assume that onset of temporary threshold shift occurs
at similar received levels in all odontocetes (cf. Southall et al.,
2007). Some cetaceans apparently can incur temporary threshold shift at
considerably lower sound exposures than are necessary to elicit
temporary threshold shift in the beluga or bottlenose dolphin.
For baleen whales, there are no data, direct or indirect, on levels
or properties of sound that are required to induce temporary threshold
shift. The frequencies to which baleen whales are most sensitive are
assumed to be lower than those to which odontocetes are most 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, one could suspect that received
levels causing temporary threshold shift onset may also be higher in
baleen whales (Southall et al., 2007).
In pinnipeds, researchers have not measured temporary threshold
shift thresholds associated with exposure to brief pulses (single or
multiple) of underwater sound. Initial evidence from more prolonged
(non-pulse) exposures suggested that some pinnipeds (harbor seals in
particular) incur temporary threshold shift at somewhat lower received
levels than do small odontocetes exposed for similar durations (Kastak
et al., 1999, 2005; Ketten et al., 2001). The indirectly estimated
temporary threshold shift threshold for pulsed sounds (in sound
pressure level) would be approximately 181 to 186 dB re: 1 [mu]Pa
(Southall et al., 2007), or a series of pulses for which the highest
sound exposure level values are a few decibels lower.
Permanent Threshold Shift--When permanent threshold shift 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, 1985). There is no specific evidence that exposure to
pulses of airgun sound can cause permanent threshold shift 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 temporary threshold shift, there has been further speculation
about the
[[Page 10147]]
possibility that some individuals occurring very close to airguns might
incur permanent threshold shift (e.g., Richardson et al., 1995, p.
372ff; Gedamke et al., 2008). Single or occasional occurrences of mild
temporary threshold shift are not indicative of permanent auditory
damage, but repeated or (in some cases) single exposures to a level
well above that causing temporary threshold shift onset might elicit
permanent threshold shift.
Relationships between temporary and permanent threshold shift
thresholds have not been studied in marine mammals, but are assumed to
be similar to those in humans and other terrestrial mammals. Permanent
threshold shift might occur at a received sound level at least several
decibels above that inducing mild temporary threshold shift if the
animal were exposed to strong sound pulses with rapid rise times. Based
on data from terrestrial mammals, a precautionary assumption is that
the permanent threshold shift threshold for impulse sounds (such as
airgun pulses as received close to the source) is at least six decibels
higher than the temporary threshold shift threshold on a peak-pressure
basis, and probably greater than 6 dB (Southall et al., 2007).
Given the higher level of sound necessary to cause permanent
threshold shift as compared with temporary threshold shift, it is
considerably less likely that permanent threshold shift would occur.
Baleen whales generally avoid the immediate area around operating
seismic vessels, as do some other marine mammals.
Stranding and Mortality
When a living or dead marine mammal swims or floats onto shore and
becomes ``beached'' or incapable of returning to sea, the event is
termed a ``stranding'' (Geraci et al., 1999; Perrin and Geraci, 2002;
Geraci and Lounsbury, 2005; NMFS, 2007). The legal definition for a
stranding under the MMPA is that ``(A) a marine mammal is dead and is
(i) on a beach or shore of the United States; or (ii) in waters under
the jurisdiction of the United States (including any navigable waters);
or (B) a marine mammal is alive and is (i) on a beach or shore of the
United States and is unable to return to the water; (ii) on a beach or
shore of the United States and, although able to return to the water,
is in need of apparent medical attention; or (iii) in the waters under
the jurisdiction of the United States (including any navigable waters),
but is unable to return to its natural habitat under its own power or
without assistance''.
Marine mammals are known to strand for a variety of reasons, such
as infectious agents, biotoxicosis, starvation, fishery interaction,
ship strike, unusual oceanographic or weather events, sound exposure,
or combinations of these stressors sustained concurrently or in series.
However, the cause or causes of most strandings are unknown (Geraci et
al., 1976; Eaton, 1979; Odell et al., 1980; Best, 1982). Numerous
studies suggest that the physiology, behavior, habitat relationships,
age, or condition of cetaceans may cause them to strand or might pre-
dispose them to strand when exposed to another phenomenon. These
suggestions are consistent with the conclusions of numerous other
studies that have demonstrated that combinations of dissimilar
stressors commonly combine to kill an animal or dramatically reduce its
fitness, even though one exposure without the other does not produce
the same result (Chroussos, 2000; Creel, 2005; DeVries et al., 2003;
Fair and Becker, 2000; Foley et al., 2001; Moberg, 2000; Relyea, 2005a;
2005b, Romero, 2004; Sih et al., 2004).
Strandings Associated with Military Active Sonar--Several sources
have published lists of mass stranding events of cetaceans in an
attempt to identify relationships between those stranding events and
military active sonar (Hildebrand, 2004; IWC, 2005; Taylor et al.,
2004). For example, based on a review of stranding records between 1960
and 1995, the International Whaling Commission (2005) identified ten
mass stranding events and concluded that, out of eight stranding events
reported from the mid-1980s to the summer of 2003, seven had been
coincident with the use of mid-frequency active sonar and most involved
beaked whales.
Over the past 12 years, there have been five stranding events
coincident with military mid-frequency active sonar use in which
exposure to sonar is believed to have been a contributing factor to
strandings: Greece (1996); the Bahamas (2000); Madeira (2000); Canary
Islands (2002); and Spain (2006). Refer to Cox et al. (2006) for a
summary of common features shared by the strandings events in Greece
(1996), Bahamas (2000), Madeira (2000), and Canary Islands (2002); and
Fernandez et al., (2005) for an additional summary of the Canary
Islands 2002 stranding event.
Potential for Stranding from Seismic Surveys--Marine mammals close
to underwater detonations of high explosives can be killed or severely
injured, and the auditory organs are especially susceptible to injury
(Ketten et al., 1993; Ketten, 1995). However, explosives are no longer
used in marine waters for commercial seismic surveys or (with rare
exceptions) for seismic research. These methods 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
specific evidence that they can cause serious injury, death, or
stranding even in the case of large airgun arrays.
However, the association of strandings of beaked whales with naval
exercises involving mid-frequency active sonar and, in one case, the
co-occurrence of a Lamont-Doherty's 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 (e.g., Hildebrand,
2005; Southall et al., 2007).
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 vestibular 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. However, 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
from one another, 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 one kHz. Typical military mid-frequency sonar
emits non-impulse
[[Page 10148]]
sounds at frequencies of two to 10 kHz, generally with a relatively
narrow bandwidth at any one time. A further difference between seismic
surveys and naval exercises is that naval exercises can involve sound
sources on more than one vessel. Thus, it is not appropriate to assume
that there is a direct correlation between the potential effects of
military sonar on marine mammals and those caused by seismic surveys
using airguns. However, evidence that sonar signals can, in special
circumstances, lead (at least indirectly) to physical damage and
mortality (e.g., Balcomb and Claridge, 2001; NOAA and USN, 2001; Jepson
et al., 2003; Fern[aacute]ndez et al., 2004, 2005; Hildebrand 2005; Cox
et al., 2006) suggests that caution is warranted when dealing with
exposure of marine mammals to any high-intensity 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) were not well founded (IAGC, 2004; IWC, 2007). In September 2002,
two Cuvier's beaked whales stranded in the Gulf of California, Mexico
while Lamont-Doherty's R/V Maurice Ewing had been operating a 20-airgun
(8,490 in\3\) array in the general area. The link between the stranding
and the seismic surveys was inconclusive and not based on any physical
evidence (Hogarth, 2002; Yoder, 2002). Nonetheless, the Gulf of
California incident plus the beaked whale strandings near naval
exercises involving use of mid-frequency sonar suggests a need for
caution in conducting seismic surveys in areas occupied by beaked
whales until more is known about effects of seismic surveys on those
species (Hildebrand, 2005).
We anticipate no injuries of beaked whales during the proposed
study because of:
(1) The likelihood that any beaked whales nearby would avoid the
approaching vessel before being exposed to high sound levels; and
(2) Differences between the sound sources operated by the LANGSETH
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
formations (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.
Potential Effects of Other Acoustic Devices
Multibeam Echosounder
The Observatory would operate the Kongsberg EM 122 multibeam
echosounder from the source vessel during the planned study. Sounds
from the multibeam echosounder are very short pulses, occurring for two
to 15 ms once every five to 20 s, depending on water depth. Most of the
energy in the sound pulses emitted by this echosounder is at
frequencies near 12 kHz, and the maximum source level is 242 dB re: 1
[mu]Pa. 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 (less 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 segments. Also, marine mammals
that encounter the Kongsberg EM 122 are unlikely to be subjected to
repeated pulses because of the narrow fore aft width of the beam and
will receive only limited amounts of pulse energy because of the short
pulses. Animals close to the vessel (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 echosounder emits a pulse is small. The animal
would have to pass the transducer at close range and be swimming at
speeds similar to the vessel in order to receive the multiple pulses
that might result in sufficient exposure to cause temporary threshold
shift.
Navy sonars linked to avoidance reactions and stranding of
cetaceans: (1) Generally have longer pulse duration than the Kongsberg
EM 122; and (2) are often directed close to horizontally versus more
downward for the echosounder. The area of possible influence of the
echosounder is much smaller--a narrow band below the source vessel.
Also, the duration of exposure for a given marine mammal can be much
longer for naval sonar. During the Observatory's operations, the
individual pulses will be very short, and a given mammal would not
receive many of the downward-directed pulses as the vessel passes by
the animal. The following section outlines possible effects of an
echosounder on marine mammals.
Masking--Marine mammal communications would not be masked
appreciably by the echosounder's signals given the low duty cycle of
the echosounder and the brief period when an individual mammal is
likely to be within its beam. Furthermore, in the case of baleen
whales, the echosounder's signals (12 kHz) do not overlap with the
predominant frequencies in the calls, which would avoid any significant
masking.
Behavioral Responses--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 (Globicephala melas)
(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]Pa, gray whales reacted
by orienting slightly away from the source and being deflected from
their course by approximately 200 m (Frankel, 2005). When a 38-kHz
[[Page 10149]]
echosounder and a 150-kHz acoustic Doppler current profiler were
transmitting during studies in the eastern tropical Pacific Ocean,
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 would be emitted by the Observatory's echosounder, 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
duration as compared with those from an echosounder.
Hearing Impairment and Other Physical Effects--Given recent
stranding events that have been associated with the operation of naval
sonar, there is concern that mid-frequency sonar sounds can cause
serious impacts to marine mammals (see above). However, the echosounder
proposed for use by the LANGSETH is quite different than sonar used for
navy operations. The echosounder's pulse duration is very short
relative to the naval sonar. Also, at any given location, an individual
marine mammal would be in the echosounder's beam for much less time
given the generally downward orientation of the beam and its narrow
fore-aft beamwidth; navy sonar often uses near-horizontally-directed
sound. Those factors would all reduce the sound energy received from
the echosounder relative to that from naval sonar.
Based upon the best available science, we believe that the brief
exposure of marine mammals to one pulse, or small numbers of signals,
from the echosounder is not likely to result in the harassment of
marine mammals.
Sub-Bottom Profiler
The Observatory would also operate a sub-bottom profiler from the
source vessel during the proposed survey. The profiler's sounds are
very short pulses, occurring for one to four ms once every second. Most
of the energy in the sound pulses emitted by the profiler is at 3.5
kHz, and the beam is directed downward. The sub-bottom profiler on the
LANGSETH has a maximum source level of 222 dB re: 1 [micro]Pa. 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 a profiler more powerful than that on the LANGSETH--if the
animal was in the area, it would have to pass the transducer at close
range and in order to be subjected to sound levels that could cause
temporary threshold shift.
Masking--Marine mammal communications would not be masked
appreciably by the profiler's signals given the 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
profiler's signals do not overlap with the predominant frequencies in
the calls, which would avoid significant masking.
Behavioral Responses--Marine mammal behavioral reactions to other
pulsed sound sources are discussed above, and responses to the profiler
are likely to be similar to those for other pulsed sources if received
at the same levels. However, the pulsed signals from the profiler are
considerably weaker than those from the echosounder. Therefore,
behavioral responses are not expected unless marine mammals are very
close to the source.
Hearing Impairment and Other Physical Effects--It is unlikely that
the profiler produces pulse levels strong enough to cause hearing
impairment or other physical injuries even in an animal that is
(briefly) in a position near the source. The profiler operates
simultaneously with other higher-power acoustic sources. Many marine
mammals would 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 profiler
Potential Effects of Vessel Movement and Collisions
Vessel movement in the vicinity of marine mammals has the potential
to result in either a behavioral response or a direct physical
interaction. Both scenarios are discussed below this section.
Behavioral Responses to Vessel Movement
There are limited data concerning marine mammal behavioral
responses to vessel traffic and vessel noise, and a lack of consensus
among scientists with respect to what these responses mean or whether
they result in short-term or long-term adverse effects. In those cases
where there is a busy shipping lane or where there is a large amount of
vessel traffic, marine mammals may experience acoustic masking
(Hildebrand, 2005) if they are present in the area (e.g., killer whales
in Puget Sound; Foote et al., 2004; Holt et al., 2008). In cases where
vessels actively approach marine mammals (e.g., whale watching or
dolphin watching boats), scientists have documented that animals
exhibit altered behavior such as increased swimming speed, erratic
movement, and active avoidance behavior (Bursk, 1983; Acevedo, 1991;
Baker and MacGibbon, 1991; Trites and Bain, 2000; Williams et al.,
2002; Constantine et al., 2003), reduced blow interval (Ritcher et al.,
2003), disruption of normal social behaviors (Lusseau, 2003; 2006), and
the shift of behavioral activities which may increase energetic costs
(Constantine et al., 2003; 2004)). A detailed review of marine mammal
reactions to ships and boats is available in Richardson et al. (1995).
For each of the marine mammal taxonomy groups, Richardson et al. (1995)
provides the following assessment regarding reactions to vessel
traffic:
Toothed whales: ``In summary, toothed whales sometimes show no
avoidance reaction to vessels, or even approach them. However,
avoidance can occur, especially in response to vessels of types used to
chase or hunt the animals. This may cause temporary displacement, but
we know of no clear evidence that toothed whales have abandoned
significant parts of their range because of vessel traffic.''
Baleen whales: ``When baleen whales receive low-level sounds from
distant or stationary vessels, the sounds often seem to be ignored.
Some whales approach the sources of these sounds. When vessels approach
whales slowly and non-aggressively, whales often exhibit slow and
inconspicuous avoidance maneuvers. In response to strong or rapidly
changing vessel noise, baleen whales often interrupt their normal
behavior and swim rapidly away. Avoidance is especially strong when a
boat heads directly toward the whale.''
Behavioral responses to stimuli are complex and influenced to
varying degrees by a number of factors, such as species, behavioral
contexts, geographical regions, source characteristics (moving or
stationary, speed, direction, etc.), prior experience of the animal and
physical status of the animal. For example, studies have shown that
beluga whales' reactions varied when exposed to vessel noise and
traffic. In some cases, naive beluga whales exhibited rapid swimming
from ice-breaking vessels up to 80 km (49.7 mi) away, and showed
changes in
[[Page 10150]]
surfacing, breathing, diving, and group composition in the Canadian
high Arctic where vessel traffic is rare (Finley et al., 1990). In
other cases, beluga whales were more tolerant of vessels, but responded
differentially to certain vessels and operating characteristics by
reducing their calling rates (especially older animals) in the St.
Lawrence River where vessel traffic is common (Blane and Jaakson,
1994). In Bristol Bay, Alaska, beluga whales continued to feed when
surrounded by fishing vessels and resisted dispersal even when
purposefully harassed (Fish and Vania, 1971).
In reviewing more than 25 years of whale observation data, Watkins
(1986) concluded that whale reactions to vessel traffic were ``modified
by their previous experience and current activity: Habituation often
occurred rapidly, attention to other stimuli or preoccupation with
other activities sometimes overcame their interest or wariness of
stimuli.'' Watkins noticed that over the years of exposure to ships in
the Cape Cod area, minke whales changed from frequent positive interest
(e.g., approaching vessels) to generally uninterested reactions; fin
whales changed from mostly negative (e.g., avoidance) to uninterested
reactions; right whales apparently continued the same variety of
responses (negative, uninterested, and positive responses) with little
change; and humpbacks dramatically changed from mixed responses that
were often negative to reactions that were often strongly positive.
Watkins (1986) summarized that ``whales near shore, even in regions
with low vessel traffic, generally have become less wary of boats and
their noises, and they have appeared to be less easily disturbed than
previously. In particular locations with intense shipping and repeated
approaches by boats (such as the whale-watching areas of Stellwagen
Bank), more and more whales had positive reactions to familiar vessels,
and they also occasionally approached other boats and yachts in the
same ways.''
Although the radiated sound from the LANGSETH would be audible to
marine mammals over a large distance, it is unlikely that animals would
respond behaviorally (in a manner that we would consider MMPA
harassment) to low-level distant shipping noise as the animals in the
area are likely to be habituated to such noises (Nowacek et al., 2004).
In light of these facts, we do not expect the LANGSETH's movements to
result in Level B harassment.
Vessel Strike
Ship strikes of cetaceans can cause major wounds, which may lead to
the death of the animal. An animal at the surface could be struck
directly by a vessel, a surfacing animal could hit the bottom of a
vessel, or an animal just below the surface could be cut by a vessel's
propeller. The severity of injuries typically depends on the size and
speed of the vessel (Knowlton and Kraus, 2001; Laist et al., 2001;
Vanderlaan and Taggart, 2007).
The most vulnerable marine mammals are those that spend extended
periods of time at the surface in order to restore oxygen levels within
their tissues after deep dives (e.g., the sperm whale). In addition,
some baleen whales, such as the North Atlantic right whale, seem
generally unresponsive to vessel sound, making them more susceptible to
vessel collisions (Nowacek et al., 2004). These species are primarily
large, slow moving whales. Smaller marine mammals (e.g., bottlenose
dolphin) move quickly through the water column and are often seen
riding the bow wave of large ships. Marine mammal responses to vessels
may include avoidance and changes in dive pattern (NRC, 2003).
An examination of all known ship strikes from all shipping sources
(civilian and military) indicates vessel speed is a principal factor in
whether a vessel strike results in death (Knowlton and Kraus, 2001;
Laist et al., 2001; Jensen and Silber, 2003; Vanderlaan and Taggart,
2007). In assessing records in which vessel speed was known, Laist et
al. (2001) found a direct relationship between the occurrence of a
whale strike and the speed of the vessel involved in the collision. The
authors concluded that most deaths occurred when a vessel was traveling
in excess of 24.1 km/h (14.9 mph;13 kts).
The Observatory's proposed operation of one vessel for the proposed
survey is relatively small in scale compared to the number of
commercial ships transiting at higher speeds in the same areas on an
annual basis. The probability of vessel and marine mammal interactions
occurring during the proposed survey is unlikely due to the LANGSETH's
slow operational speed, which is typically 4.6 kts (8.5 km/h; 5.3 mph).
Outside of seismic operations, the LANGSETH's cruising speed would be
approximately 11.5 mph (18.5 km/h; 10 kts) which is generally below the
speed at which studies have noted reported increases of marine mammal
injury or death (Laist et al., 2001).
As a final point, the LANGSETH has a number of other advantages for
avoiding ship strikes as compared to most commercial merchant vessels,
including the following: The LANGSETH's bridge offers good visibility
to visually monitor for marine mammal presence; observers posted during
operations scan the ocean for marine mammals and must report visual
alerts of marine mammal presence to crew; and the observers receive
extensive training that covers the fundamentals of visual observing for
marine mammals and information about marine mammals and their
identification at sea.
Entanglement
Entanglement can occur if wildlife becomes immobilized in survey
lines, cables, nets, or other equipment that is moving through the
water column. The proposed seismic survey would require towing
approximately 8.0 km (4.9 mi) of equipment and cables. This large of an
array carries the risk of entanglement for marine mammals. Wildlife,
especially slow moving individuals, such as large whales, have a low
probability of becoming entangled due to slow speed of the survey
vessel and onboard monitoring efforts. The Observatory has no recorded
cases of entanglement of marine mammals during the conduct of over 8
years of seismic surveys covering over 160,934 km (86,897.4 nmi) of
transect lines.
In May, 2011, there was one recorded entanglement of an olive
ridley sea turtle (Lepidochelys olivacea) in the LANGSETH's barovanes
after the conclusion of a seismic survey off Costa Rica. There have
cases of baleen whales, mostly gray whales (Heyning, 1990), becoming
entangled in fishing lines. The probability for entanglement of marine
mammals is considered not significant because of the vessel speed and
the monitoring efforts onboard the survey vessel.
The potential effects to marine mammals described in this section
of the document do not take into consideration the proposed monitoring
and mitigation measures described later in this document (see the
``Proposed Mitigation'' and ``Proposed Monitoring and Reporting''
sections) which, as noted are designed to effect the least practicable
adverse impact on affected marine mammal species and stocks.
Anticipated Effects on Marine Mammal Habitat
The proposed seismic survey is not anticipated to have any
permanent impact on habitats used by the marine mammals in the proposed
survey area, including the food sources they use (i.e., fish and
invertebrates). Additionally, no physical damage to any habitat is
[[Page 10151]]
anticipated as a result of conducting the proposed seismic survey.
While it is anticipated that the specified activity may result in
marine mammals avoiding certain areas due to temporary ensonification,
this impact to habitat is temporary and reversible and was considered
in further detail earlier in this document, as behavioral modification.
The main impact associated with the proposed activity would be
temporarily elevated noise levels and the associated direct effects on
marine mammals, previously discussed in this notice. The next section
discusses the potential impacts of anthropogenic sound sources on
common marine mammal prey in the proposed survey area (i.e., fish and
invertebrates).
Anticipated 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. There are three types of potential effects of
exposure to seismic surveys: (1) Pathological, (2) physiological, and
(3) behavioral. Pathological effects involve lethal and temporary or
permanent sub-lethal injury. Physiological effects involve temporary
and permanent primary and secondary stress responses, such as changes
in levels of enzymes and proteins. Behavioral effects refer to
temporary and (if they occur) permanent changes in exhibited behavior
(e.g., startle and avoidance behavior). The three categories are
interrelated in complex ways. For example, it is possible that certain
physiological and behavioral changes could potentially lead to an
ultimate pathological effect on individuals (i.e., mortality).
The 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.
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 the
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 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. 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. As
far as the Observatory, and we know, there are only two papers with
proper experimental methods, controls, and careful pathological
investigation implicating sounds produced by actual seismic survey
airguns in causing adverse anatomical effects. One such study indicated
anatomical damage, and the second indicated temporary threshold shift
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 temporary threshold shift (as determined by
auditory brainstem response) in two of three fish species from the
Mackenzie River Delta. This study found that broad whitefish (Coregonus
nasus) exposed to five airgun shots were not significantly different
from those of controls. 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
airguns (less than 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 (i.e., the cutoff 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 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).
An experiment of the effects of a single 700 in\3\ airgun was
conducted in Lake Meade, Nevada (USGS, 1999). The data were used in an
Environmental Assessment of the effects of a marine reflection survey
of the Lake Meade fault system by the National Park Service (Paulson et
al., 1993, in USGS, 1999). They suspended the airgun 3.5 m (11.5 ft)
above a school of threadfin shad in Lake Meade and fired three
successive times at a 30 second interval. Neither surface inspection
nor diver observations of the water column and bottom found any dead
fish.
For a proposed seismic survey in Southern California, USGS (1999)
conducted a review of the literature on the effects of airguns on fish
and fisheries. They reported a 1991 study of the Bay Area Fault system
from the continental shelf to the Sacramento River, using a 10 airgun
(5,828 in\3\) array. Brezzina and Associates were hired by USGS to
monitor the effects of the surveys, and concluded that airgun
operations were not responsible for the
[[Page 10152]]
death of any of the fish carcasses observed, and the airgun profiling
did not appear to alter the feeding behavior of sea lions, seals, or
pelicans observed feeding during the seismic surveys.
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 mortality/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
insignificant.
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; Santulli et al.,
1999; McCauley et al., 2000a,b). The periods necessary for the
biochemical changes to return to normal are variable and depend on
numerous aspects of the biology of the species and of the sound
stimulus.
Behavioral Effects--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 (e.g., 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.
The Minerals Management Service (MMS, 2005) assessed the effects of
a proposed seismic survey in Cook Inlet, Alaska. The seismic survey
proposed using three vessels, each towing two, four-airgun arrays
ranging from 1,500 to 2,500 in\3\. The Minerals Management Service
noted that the impact to fish populations in the survey area and
adjacent waters would likely be very low and temporary and also
concluded that seismic surveys may displace the pelagic fishes from the
area temporarily when airguns are in use. However, fishes displaced and
avoiding the airgun noise are likely to backfill the survey area in
minutes to hours after cessation of seismic testing. Fishes not
dispersing from the airgun noise (e.g., demersal species) may startle
and move short distances to avoid airgun emissions.
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 effects of
airguns on fish, particularly under realistic at-sea conditions.
Anticipated 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).
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 in Appendix E of the 2011 PEIS (NSF/USGS,
2011).
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
the article provides little evidence to support this claim.
Tenera Environmental (2011b) reported that Norris and Mohl (1983,
summarized in Mariyasu et al., 2004) observed lethal effects in squid
(Loligo vulgaris) at levels of 246 to 252 dB after 3 to 11 minutes.
Andre et al. (2011) exposed four cephalopod species (Loligo
vulgaris, Sepia officinalis, Octopus vulgaris, and Ilex coindetii) to
two hours of continuous sound from 50 to 400 Hz at 157 5
dB re: 1 [mu]Pa. They reported lesions to the sensory hair cells of the
statocysts of the exposed animals that
[[Page 10153]]
increased in severity with time, suggesting that cephalopods are
particularly sensitive to low-frequency sound. The received sound
pressure level was 157 5 dB re: 1 [micro]Pa, with peak
levels at 175 dB re 1 [micro]Pa. As in the McCauley et al. (2003) paper
on sensory hair cell damage in pink snapper as a result of exposure to
seismic sound, the cephalopods were subjected to higher sound levels
than they would be under natural conditions, and they were unable to
swim away from the sound source.
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). It was
noted however, than no behavioral impacts were exhibited by crustaceans
(Christian et al., 2003, 2004; DFO, 2004). 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 effects of exposure to seismic survey sound on crustaceans
and cephalopods have been conducted on both uncaged and caged animals.
In some cases, invertebrates exhibited startle responses (e.g., squid
in McCauley et al., 2000a,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
method).
Proposed Mitigation
In order to issue an incidental take authorization under section
101(a)(5)(D) of the MMPA, we 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.
The Observatory has reviewed the following source documents and
have incorporated a suite of proposed mitigation measures into their
project description.
(1) Protocols used during previous Foundation and Observatory-
funded seismic research cruises as approved by us and detailed in the
Foundation's 2011 PEIS;
(2) Previous incidental harassment authorizations applications and
authorizations that we have approved and authorized; 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, the Observatory, and/or its designees
have proposed to implement the following mitigation measures for marine
mammals:
(1) Vessel-based visual mitigation monitoring;
(2) Proposed exclusion zones;
(3) Power down procedures;
(4) Shutdown procedures;
(5) Ramp-up procedures; and
(6) Speed and course alterations.
Vessel-Based Visual Mitigation Monitoring
The Observatory would position observers aboard the seismic source
vessel to watch for marine mammals near the vessel during daytime
airgun operations and during any start-ups at night. Observers would
also watch for marine mammals near the seismic vessel for at least 30
minutes prior to the start of airgun operations after an extended
shutdown (i.e., greater than approximately eight minutes for this
proposed cruise). When feasible, the observers would 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 the
observations, the LANGSETH would power down or shutdown the airguns
when marine mammals are observed within or about to enter a designated
180-dB exclusion zone.
During seismic operations, at least four protected species
observers would be aboard the LANGSETH. The Observatory would appoint
the observers with our concurrence and they would conduct observations
during ongoing daytime operations and nighttime ramp-ups of the airgun
array. During the majority of seismic operations, two observers would
be on duty from the observation tower to monitor marine mammals near
the seismic vessel. Using two observers would increase the
effectiveness of detecting animals near the source vessel. However,
during mealtimes and bathroom breaks, it is sometimes difficult to have
two observers on effort, but at least one observer would be on watch
during bathroom breaks and mealtimes. Observers would be on duty in
shifts of no longer than four hours in duration.
Two observers on the LANGSETH would also be on visual watch during
all nighttime ramp-ups of the seismic airguns. A third observer would
monitor the passive acoustic monitoring 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 observers
(visual) on duty from the observation tower, and an observer (acoustic)
on the passive acoustic monitoring system. Before the start of the
seismic survey, the Observatory would instruct the vessel's crew to
assist in detecting marine mammals and implementing mitigation
requirements.
The LANGSETH is a suitable platform for marine mammal observations.
When stationed on the observation platform, the eye level would be
approximately 21.5 m (70.5 ft) above sea level, and the observer would
have a good view around the entire vessel. During daytime, the
observers would 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
would 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) would 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;
[[Page 10154]]
that is done primarily with the reticles in the binoculars.
When the observers see marine mammals within or about to enter the
designated exclusion zone, the LANGSETH would immediately power down or
shutdown the airguns. The observer(s) would continue to maintain watch
to determine when the animal(s) are outside the exclusion zone by
visual confirmation. Airgun operations would not resume until the
observer has confirmed that the animal has left the zone, or if not
observed after 15 minutes for species with shorter dive durations
(small odontocetes and pinnipeds) or 30 minutes for species with longer
dive durations (mysticetes and large odontocetes, including sperm,
pygmy sperm, dwarf sperm, killer, and beaked whales).
Proposed Exclusion Zones--The Observatory would use safety radii to
designate exclusion zones and to estimate take for marine mammals.
Table 1 (presented earlier in this document) shows the distances at
which one would expect to receive three sound levels (160- and 180-dB)
from the 36-airgun array and a single airgun. The 180-dB level shutdown
criteria are applicable to cetaceans as specified by us (2000). The
Observatory used these levels to establish the exclusion zones.
If the protected species visual observer detects marine mammal(s)
within or about to enter the appropriate exclusion zone, the LANGSETH
crew would immediately power down the airgun array, or perform a
shutdown if necessary (see Shut-down Procedures).
Power Down Procedures-A power down involves decreasing the number
of airguns in use such that the radius of the 180-dB zone is smaller to
the extent that marine mammals are no longer within or about to enter
the exclusion zone. 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, the LANGSETH would operate one airgun (40
in\3\). The continued operation of one airgun is intended to alert
marine mammals to the presence of the seismic vessel in the area. A
shutdown occurs when the LANGSETH suspends all airgun activity.
If the observer detects a marine mammal outside the exclusion zone
and the animal is likely to enter the zone, the crew would power down
the airguns to reduce the size of the 180-dB exclusion zone before the
animal enters that zone. Likewise, if a mammal is already within the
zone when first detected, the crew would power-down the airguns
immediately. During a power down of the airgun array, the crew would
operate a single 40-in\3\ airgun which has a smaller exclusion zone. If
the observer detects a marine mammal within or near the smaller
exclusion zone around the airgun (Table 1), the crew would shut down
the single airgun (see next section).
Resuming Airgun Operations After a Power Down--Following a power-
down, the LANGSETH crew would not resume full airgun activity until the
marine mammal has cleared the 180-dB exclusion zone (see Table 1). The
observers would consider the animal to have cleared the exclusion zone
if:
The observer has visually observed the animal leave the
exclusion zone; or
An observer has not sighted the animal within the
exclusion zone for 15 minutes for species with shorter dive durations
(i.e., small odontocetes or pinnipeds), or 30 minutes for species with
longer dive durations (i.e., mysticetes and large odontocetes,
including sperm, pygmy sperm, dwarf sperm, and beaked whales); or
The LANGSETH crew would resume operating the airguns at full power
after 15 minutes of sighting any species with short dive durations
(i.e., small odontocetes or pinnipeds). Likewise, the crew would resume
airgun operations at full power after 30 minutes of sighting any
species with longer dive durations (i.e., mysticetes and large
odontocetes, including sperm, pygmy sperm, dwarf sperm, and beaked
whales).
We estimate that the LANGSETH would transit outside the original
180-dB exclusion zone after an 8-minute wait period. This period is
based on the 180-dB exclusion zone for the 36-airgun array towed at a
depth of 12 m (39.4 ft) in relation to the average speed of the
LANGSETH while operating the airguns (8.5 km/h; 5.3 mph). Because the
vessel has transited away from the vicinity of the original sighting
during the 8-minute period, implementing ramp-up procedures for the
full array after an extended power down (i.e., transiting for an
additional 35 minutes from the location of initial sighting) would not
meaningfully increase the effectiveness of observing marine mammals
approaching or entering the exclusion zone for the full source level
and would not further minimize the potential for take. The LANGSETH's
observers are continually monitoring the exclusion zone for the full
source level while the mitigation airgun is firing. On average,
observers can observe to the horizon (10 km; 6.2 mi) from the height of
the LANGSETH's observation deck and should be able to say with a
reasonable degree of confidence whether a marine mammal would be
encountered within this distance before resuming airgun operations at
full power.
Shutdown Procedures--The LANGSETH crew would shutdown the operating
airgun(s) if a marine mammal is seen within or approaching the
exclusion zone for the single airgun. The crew would implement a
shutdown:
(1) If an animal enters the exclusion zone of the single airgun
after the crew has initiated a power down; or
(2) If an animal is initially seen within the exclusion zone of the
single airgun when more than one airgun (typically the full airgun
array) is operating.
Considering the conservation status for north Pacific right whales,
the LANGSETH crew would shutdown the airgun(s) immediately in the
unlikely event that this species is observed, regardless of the
distance from the vessel. The LANGSETH would only begin ramp-up would
only if the north Pacific right whale has not been seen for 30 minutes.
Resuming Airgun Operations After a Shutdown--Following a shutdown
in excess of eight minutes, the LANGSETH crew would initiate a ramp-up
with the smallest airgun in the array (40-in\3\). The crew would turn
on additional airguns in a sequence such that the source level of the
array would increase in steps not exceeding 6 dB per five-minute period
over a total duration of approximately 30 minutes. During ramp-up, the
observers would monitor the exclusion zone, and if he/she sights a
marine mammal, the LANGSETH crew would implement a power down or
shutdown as though the full airgun array were operational.
During periods of active seismic operations, there are occasions
when the LANGSETH crew would need to temporarily shut down the airguns
due to equipment failure or for maintenance. In this case, if the
airguns are inactive longer than eight minutes, the crew would follow
ramp-up procedures for a shutdown described earlier and the observers
would monitor the full exclusion zone and would implement a power down
or shutdown if necessary.
If the full exclusion zone is not visible to the observer for at
least 30 minutes prior to the start of operations in either daylight or
nighttime, the LANGSETH crew would not commence 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 vessel's crew would not ramp up the airgun array
from a complete shutdown at night or in thick fog, because the outer
part of the zone
[[Page 10155]]
for that array would not be visible during those conditions.
If one airgun has operated during a power down period, ramp-up to
full power would be permissible at night or in poor visibility, on the
assumption that marine mammals would be alerted to the approaching
seismic vessel by the sounds from the single airgun and could move
away. The vessel's crew would not initiate a ramp-up of the airguns if
a marine mammal is sighted within or near the applicable exclusion
zones during the day or close to the vessel at night.
Ramp-Up Procedures--Ramp-up of an airgun array provides a gradual
increase in sound levels, and involves a step-wise increase in the
number and total volume of airguns firing until the full volume of the
airgun array is achieved. The purpose of a ramp-up is to ``warn''
marine mammals in the vicinity of the airguns, and to provide the time
for them to leave the area and thus avoid any potential injury or
impairment of their hearing abilities. The Observatory would follow a
ramp-up procedure when the airgun array begins operating after an 8
minute period without airgun operations or when shut down has exceeded
that period. The Observatory has used similar waiting periods
(approximately eight to 10 minutes) during previous seismic surveys.
Ramp-up would begin with the smallest airgun in the array (40
in\3\). The crew would add airguns in a sequence such that the source
level of the array would increase in steps not exceeding six dB per
five minute period over a total duration of approximately 30 to 35
minutes. During ramp-up, the observers would monitor the exclusion
zone, and if marine mammals are sighted, the Observatory would
implement a power-down or shut-down as though the full airgun array
were operational.
If the complete exclusion zone has not been visible for at least 30
minutes prior to the start of operations in either daylight or
nighttime, the Observatory would 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 crew would not ramp up the airgun array from a
complete shut-down at night or in thick fog, because the outer part of
the exclusion zone for that array would not be visible during those
conditions. If one airgun has operated during a power-down period,
ramp-up to full power would be permissible at night or in poor
visibility, on the assumption that marine mammals would be alerted to
the approaching seismic vessel by the sounds from the single airgun and
could move away. The Observatory would not initiate a ramp-up of the
airguns if a marine mammal is sighted within or near the applicable
exclusion zones.
Speed and Course Alterations
If during seismic data collection, the Observatory detects marine
mammals outside the exclusion zone and, based on the animal's position
and direction of travel, is likely to enter the exclusion zone, the
LANGSETH would change speed and/or direction if this does not
compromise operational safety. Due to the limited maneuverability of
the primary survey vessel, altering speed and/or course can result in
an extended period of time to realign onto the transect. However, if
the animal(s) appear likely to enter the exclusion zone, the LANGSETH
would undertake further mitigation actions, including a power down or
shut down of the airguns.
We have carefully evaluated the applicant's proposed mitigation
measures and have considered a range of other measures in the context
of ensuring that we have prescribed 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 following factors in relation to one another:
(1) The manner in which, and the degree to which, we expect that
the successful implementation of the measure would 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.
Proposed Monitoring and Reporting
In order to issue an incidental take authorization for an activity,
section 101(a)(5)(D) of the MMPA states that we must set forth
``requirements pertaining to the monitoring and reporting of such
taking.'' The Act's implementing regulations at 50 CFR 216.104 (a)(13)
indicate that requests for an authorization must include the suggested
means of accomplishing the necessary monitoring and reporting that
would result in increased knowledge of the species and our expectations
of the level of taking or impacts on populations of marine mammals
present in the action area.
Proposed Monitoring
The Observatory proposes to sponsor marine mammal monitoring during
the present project to supplement the mitigation measures that require
real-time monitoring, and to satisfy the monitoring requirements of the
Incidental Harassment Authorization. The Observatory understands that
this monitoring plan would be subject to review by us, and that we may
require refinements to the plan. The Observatory planned the monitoring
work as a self-contained project independent of any other related
monitoring projects that may occur in the same regions at the same
time. Further, the Observatory is prepared to discuss coordination of
its monitoring program with any other related work that might be
conducted by other groups working insofar as it is practical and
desirable.
Vessel-Based Passive Acoustic Monitoring
Passive acoustic monitoring would complement the visual mitigation
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. Passive acoustical monitoring
can be used in conjunction with visual observations to improve
detection, identification, and localization of cetaceans. The passive
acoustic monitoring would 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. The acoustic observer would monitor
the system in real time so that he/she can advise the visual observers
if they acoustic detect cetaceans.
The passive acoustic monitoring 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 tow cable.
The tow cable is 250 m (820.2 ft) long, and the hydrophones are fitted
in the last 10 m (32.8 ft) of cable. A depth gauge is attached to the
free end of the cable, and the cable is typically towed at depths less
than 20 m (65.6 ft). The LANGSETH crew would deploy the array from a
winch located on the back deck. A deck cable would connect the tow
cable to the electronics unit in the main computer lab where the
acoustic station, signal conditioning, and processing system would be
located. The acoustic signals received by the hydrophones are
amplified, digitized, and then processed by the Pamguard software. The
system
[[Page 10156]]
can detect marine mammal vocalizations at frequencies up to 250 kHz.
One acoustic observer, an expert bioacoustician with primary
responsibility for the passive acoustic monitoring system would be
aboard the LANGSETH in addition to the four visual observers. The
acoustic observer would monitor the towed hydrophones 24 hours per day
during airgun operations and during most periods when the LANGSETH is
underway while the airguns are not operating. However, passive acoustic
monitoring may not be possible if damage occurs to both the primary and
back-up hydrophone arrays during operations. The primary passive
acoustic monitoring 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-mounted hydrophone.
One acoustic observer would monitor the acoustic detection system
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. The observer monitoring the
acoustical data would be on shift for one to six hours at a time. The
other observers would rotate as an acoustic observer, although the
expert acoustician would be on passive acoustic monitoring duty more
frequently.
When the acoustic observer detects a vocalization while visual
observations are in progress, the acoustic observer on duty would
contact the visual observer immediately, to alert him/her to the
presence of cetaceans (if they have not already been seen), so that the
vessel's crew can initiate a power down or shutdown, if required. The
observer would enter the information regarding the call into a
database. Data entry would 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.
Observer Data and Documentation
Observers would record data to estimate the numbers of marine
mammals exposed to various received sound levels and to document
apparent disturbance reactions or lack thereof. They would use the data
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 exclusion zone.
When an observer makes a sighting, they will record the following
information:
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 observer will record the data listed under (2) 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.
Observers will record all observations and power downs or shutdowns
in a standardized format and will enter data into an electronic
database. The observers will verify the accuracy of the data entry by
computerized data validity checks as the data are entered and by
subsequent manual checking of the database. These procedures will allow
the preparation of initial summaries of data 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
shutdown).
2. Information needed to estimate the number of marine mammals
potentially taken by harassment, which the Observatory must report to
the Office of Protected Resources.
3. Data on the occurrence, distribution, and activities of marine
mammals and turtles in the area where the Observatory would conduct the
seismic study.
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
detected during non-active and active seismic operations.
Proposed Reporting
The Observatory would submit a report to us and to the Foundation
within 90 days after the end of the cruise. The report would describe
the operations that were conducted and sightings of marine mammals and
turtles near the operations. The report would provide full
documentation of methods, results, and interpretation pertaining to all
monitoring. The 90-day report would summarize the dates and locations
of seismic operations, and all marine mammal sightings (dates, times,
locations, activities, associated seismic survey activities). The
report would also include estimates of the number and nature of
exposures that could result in ``takes'' of marine mammals by
harassment or in other ways.
In the unanticipated event that the specified activity clearly
causes the take of a marine mammal in a manner not permitted by the
authorization (if issued), such as an injury, serious injury, or
mortality (e.g., ship-strike, gear interaction, and/or entanglement),
the Observatory shall immediately cease the specified activities and
immediately report the incident to the Incidental Take Program
Supervisor, Permits and Conservation Division, Office of Protected
Resources, NMFS, at 301-427-8401 and/or by email to
[email protected] and [email protected]. The report must include
the following information:
Time, date, and location (latitude/longitude) of the
incident;
Name and type of vessel involved;
Vessel's speed during and leading up to the incident;
Description of the incident;
Status of all sound source use in the 24 hours preceding
the incident;
Water depth;
Environmental conditions (e.g., wind speed and direction,
Beaufort sea state, cloud cover, and visibility);
Description of all marine mammal observations in the 24
hours preceding the incident;
Species identification or description of the animal(s)
involved;
Fate of the animal(s); and
Photographs or video footage of the animal(s) (if
equipment is available).
The Observatory shall not resume its activities until we are able
to review the circumstances of the prohibited take. We shall work with
the Observatory to determine what is necessary to minimize the
likelihood of further prohibited take and ensure MMPA compliance. The
Observatory may not resume their activities until notified by us via
letter, email, or telephone.
In the event that the Observatory discovers an injured or dead
marine
[[Page 10157]]
mammal, and the lead visual observer determines that the cause of the
injury or death is unknown and the death is relatively recent (i.e., in
less than a moderate state of decomposition as we describe in the next
paragraph), the Observatory will immediately report the incident to the
Incidental Take Program Supervisor, Permits and Conservation Division,
Office of Protected Resources, at 301-427-8401 and/or by email to
[email protected] and [email protected]. The report must include
the same information identified in the paragraph above this section.
Activities may continue while we review the circumstances of the
incident. We would work with the Observatory to determine whether
modifications in the activities are appropriate.
In the event that the Observatory discovers an injured or dead
marine mammal, and the lead visual observer determines that the injury
or death is not associated with or related to the authorized activities
(e.g., previously wounded animal, carcass with moderate to advanced
decomposition, or scavenger damage), the Observatory would report the
incident to the Incidental Take Program Supervisor, Permits and
Conservation Division, Office of Protected Resources, at 301-427-8401
and/or by email to [email protected] and [email protected],
within 24 hours of the discovery. The Observatory would provide
photographs or video footage (if available) or other documentation of
the stranded animal sighting to us.
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].
We propose to authorize take by Level B harassment for the proposed
seismic survey. Acoustic stimuli (i.e., increased underwater sound)
generated during the operation of the seismic airgun array may have the
potential to result in the behavioral disturbance of some marine
mammals. There is no evidence that planned activities could result in
serious injury or mortality within the specified geographic area for
the requested authorization. The required mitigation and monitoring
measures would minimize any potential risk for serious injury or
mortality.
The following sections describe the Observatory's methods to
estimate take by incidental harassment and present their estimates of
the numbers of marine mammals that could be affected during the
proposed seismic program. The estimates are based on a consideration of
the number of marine mammals that could be harassed by seismic
operations with the 36-airgun array during approximately 5,572 km\2\
(2,151 mi\2\) of transect lines on the Mid-Atlantic Ridge in the north
Atlantic Ocean, as depicted in Figure 1 of the application.
We assume that during simultaneous operations of the airgun array
and the other sources, any marine mammals close enough to be affected
by the echosounder and sub-bottom profiler would already be affected by
the airguns. However, whether or not the airguns are operating
simultaneously with the other sources, we expect that the marine
mammals would exhibit no more than short-term and inconsequential
responses to the echosounder and profiler given their characteristics
(e.g., narrow downward-directed beam) and other considerations
described previously. Based on the best available information, we do
not consider that these reactions constitute a ``take'' (NMFS, 2001).
Therefore, the Observatory did not provide any additional allowance for
animals that could be affected by sound sources other than the airguns.
Ensonified Area Calculations--Because the Observatory assumes that
the LANGSETH may need repeat some tracklines, accommodate the turning
of the vessel, address equipment malfunctions, or conduct equipment
testing to complete the survey; they have increased the proposed number
of line-kilometers for the seismic operations by 25 percent (i.e.,
contingency lines).
Density Information--The Observatory based the density estimates on
information calculated from sightings, effort, mean group sizes, and
values for f(0) for the southern part of the survey area in Waring et
al. (2008), which extends from the Azores at approximately 38[deg] N to
53[deg] N. The allocated densities calculated for undifferentiated
``common/striped dolphins'' to common and striped dolphins in
proportion to the calculated densities of the two species. The density
calculated for ``unidentified dolphin'' was allocated to bottlenose,
Atlantic spotted, and Risso's dolphins, species that could occur in the
proposed survey area based on their presence in the Azores, in
proportion to the number of sightings in the OBIS database for those
species around the Azores. The density calculated for ``unidentified
small whale'' was allocated to the false killer whale, the one small
whale species that could occur in the proposed survey area based on its
presence in the Azores. The four ``long-finned/short-finned pilot
whales'' sighted in the southern part of the survey area by Waring et
al. (2008) were assumed to be short-finned pilot whales based on OBIS
sightings around the Azores. The density calculated for the one ``sei/
Bryde's whale'' sighting in the southern part of the survey area was
allocated to sei and Bryde's whales in equal proportions. The authors'
calculated value of f(0) for the sei whale was used for calculating
densities of Bryde's, fin, and blue whales, and that for ``small
Delphinidae'' was used for calculating densities of Mesoplodon spp.,
dolphins, the false killer whale, and the short-finned pilot whale.
Because the survey effort in the southern stratum of Waring et al.
(2008) is limited (1,047 km; 650 mi), the survey area is north of the
proposed seismic area (38-52[deg] N versus 36-36.5[deg] N), and the
survey was conducted during a somewhat different season (June versus
April-May), there is some uncertainty about the representativeness of
the data and the assumptions used in the calculations.
Exposure Estimation--The Observatory estimated the number of
different individuals that could 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 repeat 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, excluding areas
of overlap. Some individuals may be exposed multiple times since the
survey tracklines are spaced close together, however, 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 (rms) was
calculated by multiplying:
(1) The expected species density (in number/km\2\), times
(2) The anticipated area to be ensonified to that level during
airgun operations (5,571 km\2\; (2,151 mi\2\).
[[Page 10158]]
The Observatory's estimates of exposures to various sound levels
assume that the proposed surveys would be carried out in full (i.e.,
approximately 20 days of seismic airgun operations), however, the
ensonified areas calculated using the planned number of line-kilometers
have been increased by 25 percent to accommodate lines that may need to
be repeated, equipment testing, account for repeat exposure, etc. 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.
Table 3--Estimates of the Possible Numbers of Marine Mammals Exposed to Sound Levels Greater Than or Equal to
160 dB re: 1 [mu]Pa During the Proposed Seismic Survey Over the Mid-Atlantic Ridge in the North Atlantic Ocean,
During April Through June, 2013
----------------------------------------------------------------------------------------------------------------
Estimated number of
individuals exposed Requested or Approx.
Species to sound levels adjusted take Regional percent of
>=160 dB re: 1 authorization population \3\ regional
[micro]Pa\1\ \2\ population \3\
----------------------------------------------------------------------------------------------------------------
Mysticetes:
North Atlantic right whale........... 0 0 0 0
Humpback whale....................... 0 \4\ 2 0 0
Minke whale.......................... 0 \4\ 3 0 0
Bryde's whale........................ 1 1 N/A N/A
Sei whale............................ 1 1 13,000 0.01
Fin whale............................ 25 25 24,887 0.10
Blue whale........................... 8 8 937 0.89
Odontocetes ................... 21 .............. 0.16
Sperm whale.......................... 21 ................ 13,190 ..............
Pygmy sperm whale.................... 0 0 395 0
Dwarf sperm whale.................... 0 0 395 0
Cuvier's beaked whale................ 0 \4\ 7 3,513 0.2
Mesoplodon spp....................... ................... ................ .............. ..............
True's beaked whale.................. ................... ................ .............. ..............
Gervais beaked whale................. 39 39 .............. 1.12
Sowerby's beaked whale............... ................... ................ .............. ..............
Blainville's beaked whale............ ................... ................ 3,502 ..............
Northern bottlenose whale............ 0 \4\ 4 ~40,000 0
Rough-toothed dolphin................ 0 0 N/A 0
Common bottlenose dolphin............ 47 47 81,588 0.06
Pantropical spotted dolphin.......... 0 0 4,439 0
Atlantic spotted dolphin............. 112 112 50,978 0.22
Striped dolphin...................... 1,034 1,034 94,462 1.09
Short-beaked common dolphin.......... 2,115 2,115 120,741 1.75
Risso's dolphin...................... 21 21 20,479 0.10
Pygmy killer whale................... 0 0 N/A 0
False killer whale................... 7 7 N/A N/A
Killer whale......................... 0 \4\ 5 N/A 0
Long-finned pilot whale.............. 0 0 780,000 0
Short-finned pilot whale............. 674 674 780,000 0.09
----------------------------------------------------------------------------------------------------------------
N/A = Not Available.
\1\ Estimates are based on densities in Table 2 and an ensonified area of (5,571 km\2\; (2,151 mi\2\)
\2\ Requested or adjusted take includes a 25 percent contingency for repeated exposures due to the overlap of
parallel survey tracks.
\3\ Regional population size estimates are from Table 2.
\4\ Requested take authorization increased to group size for species for which densities were not calculated but
for which there were OBIS sightings around the Azores.
Encouraging and Coordinating Research
The Observatory would coordinate the planned marine mammal
monitoring program associated with the seismic survey on the Mid-
Atlantic Ridge in the north Atlantic Ocean with other parties that may
have interest in the area and/or may be conducting marine mammal
studies in the same region during the seismic surveys.
Negligible Impact and Small Numbers Analysis and Determination
We have 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.'' In making a negligible impact determination,
we consider:
(1) The number of anticipated injuries, serious injuries, or
mortalities;
(2) The number, nature, and intensity, and duration of Level B
harassment (all relatively limited); and
(3) The context in which the takes occur (i.e., impacts to areas of
significance, impacts to local populations, and cumulative impacts when
taking into account successive/contemporaneous actions when added to
baseline data);
(4) The status of stock or species of marine mammals (i.e.,
depleted, not depleted, decreasing, increasing, stable, impact relative
to the size of the population);
(5) Impacts on habitat affecting rates of recruitment/survival; and
(6) The effectiveness of monitoring and mitigation measures.
For reasons stated previously in this document and based on the
following factors, the specified activities associated with the marine
seismic surveys are not likely to cause permanent threshold shift, or
other non-auditory injury, serious injury, or death. They include:
[[Page 10159]]
(1) The likelihood that, given sufficient notice through relatively
slow ship speed, we expect marine mammals to move away from a noise
source that is annoying prior to its becoming potentially injurious;
(2) The potential for temporary or permanent hearing impairment is
relatively low and that we would likely avoid this impact through the
incorporation of the required monitoring and mitigation measures
(including power-downs and shutdowns); and
(3) The likelihood that marine mammal detection ability by trained
visual observers is high at close proximity to the vessel.
We do not anticipate that any injuries, serious injuries, or
mortalities would occur as a result of the Observatory's planned marine
seismic surveys, and we do not propose to authorize injury, serious
injury or mortality for this survey. We anticipate only behavioral
disturbance to occur during the conduct of the survey activities.
Table 4 in this document outlines the number of requested Level B
harassment takes that we anticipate as a result of these activities.
Due to the nature, degree, and context of Level B (behavioral)
harassment anticipated and described (see ``Potential Effects on Marine
Mammals'' section in this notice), we do not expect the activity to
impact rates of recruitment or survival for any affected species or
stock.
Further, the seismic surveys would not take place in areas of
significance for marine mammal feeding, resting, breeding, or calving
and would not adversely impact marine mammal habitat.
Many animals perform vital functions, such as feeding, resting,
traveling, and socializing, on a diel cycle (i.e., 24 hour cycle).
Behavioral reactions to noise exposure (such as disruption of critical
life functions, displacement, or avoidance of important habitat) are
more likely to be significant if they last more than one diel cycle or
recur on subsequent days (Southall et al., 2007). While we anticipate
that the seismic operations would occur on consecutive days, the
estimated duration of the survey would last no more than 20 days.
Additionally, the seismic survey would be increasing sound levels in
the marine environment in a relatively small area surrounding the
vessel (compared to the range of the animals), which is constantly
travelling over distances, and some animals may only be exposed to and
harassed by sound for shorter less than day.
Of the 28 marine mammal species under our jurisdiction that are
known to occur or likely to occur in the study area, six of these
species are listed as endangered under the ESA, including: The blue,
fin, humpback, north Atlantic right, sei, and sperm whales. These
species are also categorized as depleted under the MMPA. With the
exception of the north Atlantic right whale, the Observatory has
requested authorized take for these listed species.
As mentioned previously, we estimate that 28 species of marine
mammals under our jurisdiction could be potentially affected by Level B
harassment over the course of the proposed authorization. For each
species, these take numbers are small (most estimates are less than or
equal to two percent) relative to the regional or overall population
size and we have provided the regional population estimates for the
marine mammal species that may be taken by Level B harassment in Table
4 in this document.
Our practice has been to apply the 160 dB re: 1 [micro]Pa received
level threshold for underwater impulse sound levels to determine
whether take by Level B harassment occurs. Southall et al. (2007)
provides a severity scale for ranking observed behavioral responses of
both free-ranging marine mammals and laboratory subjects to various
types of anthropogenic sound (see Table 4 in Southall et al. [2007]).
We have preliminarily determined, provided that the aforementioned
mitigation and monitoring measures are implemented, that the impact of
conducting a proposed survey on the Mid-Atlantic Ridge in the north
Atlantic Ocean in international waters, from April 2013 through June
2013, may result, at worst, in a modification in behavior and/or low-
level physiological effects (Level B harassment) of certain species of
marine mammals.
While these species may make behavioral modifications, including
temporarily vacating the area during the operation of the airgun(s) to
avoid the resultant acoustic disturbance, the availability of alternate
areas within these areas and the short and sporadic duration of the
research activities, have led us to preliminary determine that this
action would have a negligible impact on the species in the specified
geographic region.
Based on the analysis contained herein 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, we preliminarily find that the Observatory's planned research
activities would result in the incidental take of small numbers of
marine mammals, by Level B harassment only, and that the required
measures mitigate impacts to affected species or stocks of marine
mammals to the lowest level practicable.
Impact on Availability of Affected Species or Stock for Taking for
Subsistence Uses
Section 101(a)(5)(D) of the Marine Mammal Protection Act also
requires us to determine that the authorization would not have an
unmitigable adverse effect on the availability of marine mammal species
or stocks for subsistence use. There are no relevant subsistence uses
of marine mammals in the study area (on the Mid-Atlantic Ridge in the
north Atlantic Ocean in international waters) that implicate section
101(a)(5)(D) of the Marine Mammal Protection Act.
Endangered Species Act
Of the species of marine mammals that may occur in the proposed
survey area, several are listed as endangered under the Endangered
Species Act, including the blue, fin, humpback, north Atlantic right,
sei, and sperm whales. The Observatory did not request take of
endangered north Atlantic right whales because of the low likelihood of
encountering these species during the cruise.
Under section 7 of the Act, the Foundation has initiated formal
consultation with the Service's, Office of Protected Resources,
Endangered Species Act Interagency Cooperation Division, on this
proposed seismic survey. We (i.e., National Marine Fisheries Service,
Office of Protected Resources, Permits and Conservation Division), have
also initiated formal consultation under section 7 of the Act with the
Endangered Species Act Interagency Cooperation Division to obtain a
Biological Opinion (Opinion) evaluating the effects of issuing an
incidental harassment authorization for threatened and endangered
marine mammals and, if appropriate, authorizing incidental take. Both
agencies would conclude the formal section 7 consultation (with a
single Biological Opinion for the Foundation's Division of Ocean
Sciences and NMFS' Office of Protected Resources, Permits and
Conservation Division federal actions) prior to making a determination
on whether or not to issue the authorization. If we issue the take
authorization, the Foundation and the Observatory must comply with the
mandatory Terms and Conditions of the Opinion's Incidental Take
Statement which would incorporate the mitigation and monitoring
requirements included
[[Page 10160]]
in the Incidental Harassment Authorization.
National Environmental Policy Act (NEPA)
To meet our NEPA requirements for the issuance of an IHA to the
Observatory, we intend to prepare an Environmental Assessment (EA)
titled ``Issuance of an Incidental Harassment Authorization to the
Lamont-Doherty Earth Observatory to Take Marine Mammals by Harassment
Incidental to a Marine Geophysical on the Mid-Atlantic Ridge in the
north Atlantic Ocean, from April 2013 through June 2013.'' This EA
would incorporate as appropriate the Foundation's Environmental
Analysis Pursuant To Executive Order 12114 (NSF, 2010) titled, ``Marine
geophysical survey by the R/V MARCUS G. Langseth on the mid-Atlantic
Ridge, April-May 2013,'' by reference pursuant to 40 CFR 1502.21 and
NOAA Administrative Order (NAO) 216-6 Sec. 5.09(d). Prior to making a
final decision on the IHA application, we would decide whether or not
to issue a Finding of No Significant Impact (FONSI).
The Foundation's environmental analysis is available for review at
the addresses set forth earlier in this notice. This notice and the
documents it references provide all relevant environmental information
related to our proposal to issue the IHA. We invite the public's
comment and will consider any comments related to environmental effects
related to the proposed issuance of the IHA submitted in response to
this as we conduct and finalize our NEPA analysis.
Proposed Authorization
As a result of these preliminary determinations, we propose to
authorize the take of marine mammals incidental to the Observatory's
proposed marine seismic surveys on the Mid-Atlantic Ridge in the north
Atlantic Ocean from April 2013, through June 2013, provided the
previously mentioned mitigation, monitoring, and reporting requirements
are incorporated. The duration of the incidental harassment
authorization would not exceed one year from the date of its issuance.
Information Solicited
We request interested persons to submit comments and information
concerning this proposed project and our preliminary determination of
issuing a take authorization (see ADDRESSES). Concurrent with the
publication of this notice in the Federal Register, we will forward
copies of this application to the Marine Mammal Commission and its
Committee of Scientific Advisors.
Dated: February 6, 2013.
Matthew J. Brookhart,
Acting Director, Office of Protected Resources, National Marine
Fisheries Service.
[FR Doc. 2013-03321 Filed 2-12-13; 8:45 am]
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