BILLING CODE 3510-22-P
DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
[RTID 0648-XE032]
Takes of Marine Mammals Incidental to Specified Activities; Taking Marine
Mammals Incidental to a Marine Geophysical Survey of the Reykjanes Ridge in the
North Atlantic Ocean
AGENCY: National Marine Fisheries Service (NMFS), National Oceanic and
Atmospheric Administration (NOAA), Commerce.
ACTION: Notice; issuance of an incidental harassment authorization.
SUMMARY: In accordance with the regulations implementing the Marine Mammal
Protection Act (MMPA) as amended, notification is hereby given that NMFS has issued
an incidental harassment authorization (IHA) to the Lamont-Doherty Earth Observatory
of Columbia University (L-DEO) to incidentally harass marine mammals during survey
activities associated with a marine geophysical survey at the Reykjanes Ridge in the
North Atlantic Ocean.
DATES: This authorization is effective from June 27, 2024 through June 26, 2025.
ADDRESSES: Electronic copies of the application and supporting documents, as well as
a list of the references cited in this document, may be obtained online at:
https://www.fisheries.noaa.gov/national/marine-mammal-protection/incidental-takeauthorizations-research-and-other-activities. In case of problems accessing these
documents, please call the contact listed below.
FOR FURTHER INFORMATION CONTACT: Rachel Wachtendonk, Office of
Protected Resources, NMFS, (301) 427-8401.
SUPPLEMENTARY INFORMATION:
Background

The MMPA prohibits the “take” of marine mammals, with certain exceptions.
Sections 101(a)(5)(A) and (D) of the MMPA (16 U.S.C. 1361 et seq.) direct the Secretary
of Commerce (as delegated to NMFS) to allow, upon request, the incidental, but not
intentional, taking of small numbers of marine mammals by U.S. citizens who engage in
a specified activity (other than commercial fishing) within a specified geographical
region if certain findings are made and either regulations are proposed or, if the taking is
limited to harassment, a notice of a proposed IHA is provided to the public for review.
Authorization for incidental takings shall be granted if NMFS finds that the taking
will have a negligible impact on the species or stock(s) and will not have an unmitigable
adverse impact on the availability of the species or stock(s) for taking for subsistence
uses (where relevant). Further, NMFS must prescribe the permissible methods of taking
and other “means of effecting the least practicable adverse impact” on the affected
species or stocks and their habitat, paying particular attention to rookeries, mating
grounds, and areas of similar significance, and on the availability of the species or stocks
for taking for certain subsistence uses (referred to in shorthand as “mitigation”); and
requirements pertaining to the mitigation, monitoring and reporting of the takings are set
forth. The definitions of all applicable MMPA statutory terms cited above are included in
the relevant sections below.
Summary of Request
On December 27, 2023, NMFS received a request from L-DEO for an IHA to
take marine mammals incidental to conducting a marine geophysical survey of the
Reykjanes Ridge in the North Atlantic Ocean. NMFS received a final, revised version of
L-DEO’s application on February 26, 2024, which was deemed adequate and complete
on February 27, 2024. L-DEO’s request is for take of 25 marine mammal species by
Level B harassment and, for a subset of 5 of these species, by Level A harassment.
Neither L-DEO nor NMFS expect serious injury or mortality to result from this activity

and, therefore, an IHA is appropriate. There are no changes from the proposed IHA to the
final IHA.
Description of the Specified Activity
Overview
Researchers from the University of Birmingham, University of Southampton and
University of Cambridge, with funding from the Natural Environmental Research
Council (NERC), plan to conduct a high-energy seismic survey using airguns as the
acoustic source from the research vessel (R/V) Marcus G. Langseth (Langseth), which is
owned and operated by L-DEO. The planned survey will occur at the Reykjanes Ridge,
off southern Iceland, in the northwestern Atlantic Ocean during summer 2024. The
survey will occur within Iceland’s Exclusive Economic Zone (EEZ) and high seas. The
survey will occur in water depths ranging from approximately 600 to 3,000 meters (m),
with most of the survey effort (~78 percent) occurring in deep water (considered here to
be depths greater than 1000 m). To complete this survey, the R/V Langseth will tow a 36airgun array with a total discharge volume of ~6,600 cubic inches (in3) at a depth of 10 to
12 m. The airgun array receiving systems for the different survey segments will consist of
a 15 kilometer (km) long solid-state hydrophone streamer and approximately 150
deployments using a total of 50 Ocean Bottom Seismometers (OBS). The airguns will
fire at a shot interval of 50 m (~24 seconds (s)) during 2-dimensional (2-D) multi-channel
seismic (MCS) reflection surveys with the hydrophone streamer and at a 154.4 m (~60 s)
interval during OBS seismic refraction surveys. Approximately 2,754 km of total survey
trackline are planned, including 1,662 km of MCS seismic reflection data and 1,092 km
of OBS refraction data.
The purpose of the survey is to collect data in support of a research proposal
entitled ‘IMPULSE: Taking the Pulse of the Icelandic Mantle Plume’. IMPULSE will
make the first definite test of the Thermal Plume Pulsing (TPP) model, the shortest

predicted time period of transient mantle convections, which has been suggested as a
primary driver of some of the most remarkable perturbations to global climate,
ecosystems, and the carbon cycle in Earth’s history. The North Atlantic V-shaped Ridges
(VSR) are the basis for the TPP model, and the planned survey will acquire the first ever
full crustal seismic profiles across multiple complete VSR cycles.
Additional data will be collected using a multibeam echosounder (MBES), a subbottom profiler (SBP), and an Acoustic Doppler Current Profiler (ADCP), which will be
operated from R/V Langseth continuously during the seismic surveys, including during
transit. No take of marine mammals is expected to result from use of this equipment.
Dates and Duration
The planned survey is expected to last for approximately 38 days, with 9 days of
MCS seismic operations, 5 days of OBS seismic operations, 17 days of OBS deployment
and retrieval, 3 days of streamer deployment and retrieval, and 4 days of transit. R/V
Langseth will likely leave from and return to port in Reykjavik, Iceland during summer
2024.
Specific Geographic Region
The planned survey will occur within approximately 56-63° N, 24-34° W, within
Iceland’s EEZ and on the high seas, in water depths ranging from approximately 600 to
3,000 m. The closest approach of the planned survey lines to land off the south coast of
Iceland is ~130 km from Eldey and ~145 km from mainland Iceland. The region where
the survey is planned to occur is depicted in figure 1; the tracklines could occur anywhere
within the polygon shown in figure 1. Representative survey tracklines are shown;
however, some deviation in actual tracklines, including the order of survey operations,
could be necessary for reasons such as science drivers, poor data quality, inclement
weather, or mechanical issues with the research vessel and/or equipment.

Figure 1. Location of the Reykjanes Ridge Seismic Surveys in the Northwest
Atlantic Ocean
Representative survey tracklines are included in the figure; however, the tracklines could occur anywhere
within the survey area. Numbered sites correspond to the following Vulnerable Marine Ecosystems
(VMEs): (1) Northern Mid-Atlantic Ridge, (2) Mid Mid-Atlantic Ridge, (3) Hatton Bank, (4) Hatton Bank
Area 1, and (5) Hatton Bank Area 2. EBSA; Ecologically or Biologically Significant Marine Areas. MPA;
Marine Protected Area. NEAFC; North East Atlantic Fisheries.

A detailed description of the planned geophysical survey was provided in the
Federal Register notice of the proposed IHA (89 FR 41850, March 13, 2024). Since that
time, no changes have been made to the planned survey activities. Therefore, a detailed
description is not provided here. Please refer to that Federal Register notice for the
description of the specified activity.
Comments and Responses
A notice of NMFS' proposal to issue an IHA to L-DEO was published in the
Federal Register on March 13, 2024 (89 FR 41850). That notice described, in detail, LDEO’s activity, the marine mammal species that may be affected by the activity, and the
anticipated effects on marine mammals. In that notice, we requested public input on the

request for authorization described therein, our analyses, the proposed authorization, and
any other aspect of the notice of proposed IHA, and requested that interested persons
submit relevant information, suggestions, and comments. The proposed notice was
available for a 30-day public comment period. NMFS received no public comments.
Changes from the Proposed IHA to Final IHA
In the notice of the proposed IHA (89 FR 41850, March 13, 2024), NMFS stated
an intention to adopt the National Science Foundation's (NSF) Environmental
Assessment (EA) to comply with the National Environmental Policy Act of 1969
(NEPA). However, NMFS subsequently determined that this action is consistent with
categories of activities identified in Categorical Exclusion B4 (IHAs with no anticipated
serious injury or mortality) of the Companion Manual for NOAA Administrative Order
216-6A, which do not individually or cumulatively have the potential for significant
impacts on the quality of the human environment and for which we have not identified
any extraordinary circumstances that would preclude this categorical exclusion.
Accordingly, NMFS has determined that the issuance of the IHA qualifies to be
categorically excluded from further NEPA review.
Description of Marine Mammals in the Area of Specified Activities
Sections 3 and 4 of the application summarize available information regarding
status and trends, distribution and habitat preferences, and behavior and life history of the
potentially affected species. NMFS fully considered all of this information, and we refer
the reader to these descriptions, instead of reprinting the information. Additional
information about these species (e.g., physical and behavioral descriptions) may be found
on NMFS’ website (https://www.fisheries.noaa.gov/find-species). NMFS refers the reader
to the aforementioned source for general information regarding the species listed in table
1.

The populations of marine mammals found in the survey area do not occur within
the U.S. EEZ and therefore, are not assessed in NMFS' Stock Assessment Reports
(SARs). For most species, there are no stocks defined for management purposes in the
survey area, and NMFS is evaluating impacts at the species level and ranges for most
species evaluated here are considered to be the North Atlantic. As such, information on
potential biological removal level (PBR; defined by the MMPA as the maximum number
of animals, not including natural mortalities, that may be removed from a marine
mammal stock while allowing that stock to reach or maintain its optimum sustainable
population) and annual levels of serious injury and mortality from anthropogenic sources
are not available for these marine mammal populations. Abundance estimates for marine
mammals in the survey location are lacking; therefore, the modeled abundances presented
here are based on a variety of proxy sources, including the U.S Navy Atlantic Fleet
Training and Testing Area Marine Mammal Density (AFTT) model (Roberts et al., 2023)
and the North Atlantic Marine Mammal Commission (NAMMCO; NAMMCO, 2023).
The modeled abundance is considered the best scientific information available on the
abundance of marine mammal populations in the area.
Table 1 lists all species that occur in the survey area that may be taken as a result
of the planned survey and summarizes information related to the population, including
regulatory status under the MMPA and Endangered Species Act (ESA).
Table 1 -- Species Likely Impacted by the Specified Activities
Common name

Scientific name

ESA/MMPA
status;
Strategic
(Y/N)1

Modeled
abundance2

NA

E, D, Y

NA

E, D, Y

11,672

NA

-, -, N3

4,990

Stock

Order Artiodactyla – Cetacea – Mysticeti (baleen whales)
Family Balaenopteridae (rorquals)
Blue Whale
Fin Whale
Humpback
Whale

Balaenoptera
musculus
Balaenoptera
physalus
Megaptera
novaeangliae

Minke Whale

Balaenoptera
acutorostrata
Balaenoptera
borealis

NA

-, -, N

13,784

NA

E, D, Y

19,530

NA

E, D, Y

64,015

Mesoplodon
densirostris

NA

-, -, N

65,069 4

Ziphius cavirostris

NA

-, -, N

65,069 4

Northern
Bottlenose
Whale

Hyperoodon
ampullatus

NA

-, -, N

1,056

Sowerby's
Beaked Whale

Mesoplodon
bidens

NA

-, -, N

65,069 5

Killer Whale

Orcinus orca

NA

-, -, N

Long-Finned
Pilot Whale

Globicephala
melas

NA

-, -, N

264,907 6

Atlantic WhiteSided Dolphin

Lagenorhynchus
acutus

NA

-, -, N

175,299

Bottlenose
Dolphin

Tursiops truncatus

NA

-, -, N

418,151

Grampus griseus

NA

-, -, N

78,205

Delphinus delphis

NA

-, -, N

473,260

NA

-, -, N

412,729

NA

-, -, N

2,627

NA

-, -, N

94,583

Sei Whale

Odontoceti (toothed whales, dolphins, and porpoises)
Family Physeteridae
Sperm Whale

Physeter
macrocephalus

Family Ziphiidae (beaked whales)
Blainville's
Beaked Whale
Cuvier's Beaked
Whale

Family Delphinidae

Risso's Dolphin
Common
Dolphin
Striped Dolphin
White-Beaked
Dolphin

Stenella
coeruleoalba
Lagenorhynchus
albirostris

Family Phocoenidae (porpoises)
Harbor Porpoise

Phocoena
phocoena

Order Carnivora – Pinnipedia
Family Phocidae (earless seals)
Bearded Seal

Erignathus
barbatus barbatus

NA

-, -, N7

NA

Gray Seal

Halichoerus
grypus

NA

-, -, N

NA

NA

-, -, N

NA

NA

-, -, N

NA

NA

-, -, N

NA

Harbor Seal
Harp Seal
Hooded Seal

Phoca vitulina
Pagophilus
groenlandicus
Cystophora
cristata

ESA status: Endangered (E), Threatened (T)/MMPA status: Depleted (D). A dash (-) indicates that the
species is not listed under the ESA or designated as depleted under the MMPA. Under the MMPA, a
strategic stock is one for which the level of direct human-caused mortality exceeds PBR or which is
determined to be declining and likely to be listed under the ESA within the foreseeable future. Any species
or stock listed under the ESA is automatically designated under the MMPA as depleted and as a strategic
stock.
2 Modeled abundance value from U.S Navy AFTT Marine Mammal Density (Roberts et al., 2023).
3 Two humpback whale distinct population segments (DPSs) could occur in the survey area: the West
Indies DPS, which is not listed under the ESA; and the Cape Verde Islands/Northwest Africa DPS, which is
listed as endangered under the ESA.
4 Beaked whale guild.
5 2017 estimate for the U.K., Iceland, and Faroe Islands (NAMMCO 2023).
6 Pilot whale guild.
7 There are two concurrently recognized subspecies of the bearded seal. Only the Pacific subspecies is listed
under the ESA and MMPA.

All 25 species in table 1 temporally and spatially co-occur with the activity to the
degree that take is reasonably likely to occur. All species that could potentially occur in
the survey area are listed in section 3 of the application; however, 3 species (North
Atlantic right whale (Eubalaena glacialis), bowhead whale (Balaena mysticetus), and
ringed seal (Phoca hispida hispida)) are omitted from further analysis as they have been
infrequently sighted in the survey area or their temporal and/or spatial occurrence is such
that take is not expected to occur. They are not discussed further beyond the explanation
provided in the Federal Register notice for the proposed IHA (89 FR 41850, March 13,
2024).
A detailed description of the of the species likely to be affected by the
geophysical survey, including brief introductions to the species and relevant stocks as
well as available information regarding population trends and threats, and information
regarding local occurrence, were provided in the Federal Register notice for the
proposed IHA (89 FR 41850, March 13, 2024). Since that time, we are not aware of any
changes in the status of these species and stocks; therefore, detailed descriptions are not
provided here. Please refer to that Federal Register notice for these descriptions. Please
also refer to NMFS' website (https://www.fisheries.noaa.gov/find-species) for generalized
species accounts.
Marine Mammal Hearing

Hearing is the most important sensory modality for marine mammals underwater,
and exposure to anthropogenic sound can have deleterious effects. To appropriately
assess the potential effects of exposure to sound, it is necessary to understand the
frequency ranges marine mammals are able to hear. Not all marine mammal species have
equal hearing capabilities (e.g., Richardson et al., 1995; Wartzok and Ketten, 1999; Au
and Hastings, 2008). To reflect this, Southall et al. (2007, 2019) recommended that
marine mammals be divided into hearing groups based on directly measured (behavioral
or auditory evoked potential techniques) or estimated hearing ranges (behavioral response
data, anatomical modeling, etc.). Note that no direct measurements of hearing ability
have been successfully completed for mysticetes (i.e., low-frequency cetaceans).
Subsequently, NMFS (2018) described generalized hearing ranges for these marine
mammal hearing groups. Generalized hearing ranges were chosen based on the
approximately 65 decibel (dB) threshold from the normalized composite audiograms,
with the exception for lower limits for low-frequency cetaceans where the lower bound
was deemed to be biologically implausible and the lower bound from Southall et al.
(2007) retained. Marine mammal hearing groups and their associated hearing ranges are
provided in table 2.
Table 2 -- Marine Mammal Hearing Groups (NMFS, 2018)

Hearing Group
Low-frequency (LF) cetaceans
(baleen whales)

Generalized Hearing
Range*
7 Hz to 35 kHz

Mid-frequency (MF) cetaceans
(dolphins, toothed whales, beaked whales, bottlenose
whales)

150 Hz to 160 kHz

High-frequency (HF) cetaceans
(true porpoises, Kogia, river dolphins, Cephalorhynchid,
Lagenorhynchus cruciger & L. australis)

275 Hz to 160 kHz

Phocid pinnipeds (PW) (underwater)
(true seals)

50 Hz to 86 kHz

Otariid pinnipeds (OW) (underwater)
(sea lions and fur seals)

60 Hz to 39 kHz

* Represents the generalized hearing range for the entire group as a composite (i.e., all species within the
group), where individual species’ hearing ranges are typically not as broad. Generalized hearing range
chosen based on ~65 dB threshold from normalized composite audiogram, with the exception for lower
limits for LF cetaceans (Southall et al. 2007) and PW pinniped (approximation).

For more detail concerning these groups and associated frequency ranges, please
see NMFS (2018) for a review of available information.
Potential Effects of Specified Activities on Marine Mammals and Their Habitat
The effects of underwater noise from L-DEO's survey activities have the potential
to result in behavioral harassment of marine mammals in the vicinity of the survey area.
The notice of proposed IHA (89 FR 41850, March 13, 2024) included a discussion of the
effects of anthropogenic noise on marine mammals and the potential effects of
underwater noise from L-DEO on marine mammals and their habitat. That information
and analysis is incorporated by reference into this final IHA determination and is not
repeated here; please refer to the notice of proposed IHA (89 FR 41850, March 13, 2024).
Estimated Take of Marine Mammals
This section provides an estimate of the number of incidental takes authorized
through the IHA, which will inform both NMFS’ consideration of “small numbers,” and
the negligible impact determinations.

Harassment is the only type of take expected to result from these activities.
Except with respect to certain activities not pertinent here, section 3(18) of 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).
Authorized takes are primarily by Level B harassment, as use of the airgun array
has the potential to result in disruption of behavioral patterns for individual marine
mammals. There is also some potential for auditory injury (Level A harassment) to result
for species of certain hearing groups due to the size of the predicted auditory injury zones
for those groups. Auditory injury is less likely to occur for mid-frequency species due to
their relative lack of sensitivity to the frequencies at which the primary energy of an
airgun signal is found as well as such species’ general lower sensitivity to auditory injury
as compared to high-frequency cetaceans. As discussed in further detail below, we do not
expect auditory injury for mid-frequency cetaceans. No mortality is anticipated as a result
of these activities. Below we describe how the authorized take numbers are estimated.
For acoustic impacts, generally speaking, we estimate take by considering: (1)
acoustic thresholds above which NMFS believes the best available science indicates
marine mammals will be behaviorally harassed or incur some degree of permanent
hearing impairment; (2) the area or volume of water that will be ensonified above these
levels in a day; (3) the density or occurrence of marine mammals within these ensonified
areas; and (4) the number of days of activities. We note that while these factors can
contribute to a basic calculation to provide an initial prediction of potential takes,
additional information that can qualitatively inform take estimates is also sometimes
available (e.g., previous monitoring results or average group size). Below, we describe

the factors considered here in more detail and present the take estimates.
Acoustic Thresholds
NMFS recommends the use of acoustic thresholds that identify the received level
of underwater sound above which exposed marine mammals would be reasonably
expected to be behaviorally harassed (equated to Level B harassment) or to incur
permanent threshold shift (PTS) of some degree (equated to Level A harassment).
Level B Harassment – Though significantly driven by received level, the onset of
behavioral disturbance from anthropogenic noise exposure is also informed to varying
degrees by other factors related to the source or exposure context (e.g., frequency,
predictability, duty cycle, duration of the exposure, signal-to-noise ratio, distance to the
source), the environment (e.g., bathymetry, other noises in the area, predators in the area),
and the receiving animals (hearing, motivation, experience, demography, life stage,
depth) and can be difficult to predict (e.g., Southall et al., 2007, 2021, Ellison et al.,
2012). Based on what the available science indicates and the practical need to use a
threshold based on a metric that is both predictable and measurable for most activities,
NMFS typically uses a generalized acoustic threshold based on received level to estimate
the onset of behavioral harassment. NMFS generally predicts that marine mammals are
likely to be behaviorally harassed in a manner considered to be Level B harassment when
exposed to underwater anthropogenic noise above root-mean-squared pressure received
levels (RMS SPL) of 120 dB (referenced to 1 micropascal (re 1 μPa)) for continuous
(e.g., vibratory pile driving, drilling) and above RMS SPL 160 dB re 1 μPa for nonexplosive impulsive (e.g., seismic airguns) or intermittent (e.g., scientific sonar) sources.
Generally speaking, Level B harassment take estimates based on these behavioral
harassment thresholds are expected to include any likely takes by temporary threshold
shift (TTS) as, in most cases, the likelihood of TTS occurs at distances from the source
less than those at which behavioral harassment is likely. TTS of a sufficient degree can

manifest as behavioral harassment, as reduced hearing sensitivity and the potential
reduced opportunities to detect important signals (conspecific communication, predators,
prey) may result in changes in behavior patterns that would not otherwise occur.
L-DEO’s survey includes the use of impulsive seismic sources (i.e., airguns), and
therefore the 160 dB re 1 μPa is applicable for analysis of Level B harassment.
Level A harassment – NMFS’ Technical Guidance for Assessing the Effects of
Anthropogenic Sound on Marine Mammal Hearing (Version 2.0) (Technical Guidance,
2018) identifies dual criteria to assess auditory injury (Level A harassment) to five
different marine mammal groups (based on hearing sensitivity) as a result of exposure to
noise from two different types of sources (impulsive or non-impulsive). L-DEO’s survey
includes the use of impulsive seismic sources (i.e., airguns).
These thresholds are provided in the table below. The references, analysis, and
methodology used in the development of the thresholds are described in NMFS’ 2018
Technical Guidance, which may be accessed at:
https://www.fisheries.noaa.gov/national/marine-mammal-protection/marine-mammalacoustic-technical-guidance.
Table 3 -- Thresholds Identifying the Onset of Permanent Threshold Shift.
PTS Onset Acoustic Thresholds*
(Received Level)
Hearing Group

Impulsive

Non-impulsive

Low-Frequency (LF)
Cetaceans

Cell 1
Lpk,flat: 219 dB
LE,LF,24h: 183 dB

Cell 2
LE,LF,24h: 199 dB

Mid-Frequency (MF)
Cetaceans

Cell 3
Lpk,flat: 230 dB
LE,MF,24h: 185 dB

Cell 4
LE,MF,24h: 198 dB

High-Frequency (HF)
Cetaceans

Cell 5
Lpk,flat: 202 dB
LE,HF,24h: 155 dB

Cell 6
LE,HF,24h: 173 dB

Phocid Pinnipeds (PW)
(Underwater)

Cell 7
Lpk,flat: 218 dB
LE,PW,24h: 185 dB

Cell 8
LE,PW,24h: 201 dB

Otariid Pinnipeds (OW)
(Underwater)

Cell 9
Lpk,flat: 232 dB
LE,OW,24h: 203 dB

Cell 10
LE,OW,24h: 219 dB

* Dual metric acoustic thresholds for impulsive sounds: Use whichever results in the
largest isopleth for calculating PTS onset. If a non-impulsive sound has the potential of
exceeding the peak sound pressure level thresholds associated with impulsive sounds,
these thresholds should also be considered.
Note: Peak sound pressure (Lpk) has a reference value of 1 µPa, and cumulative sound
exposure level (LE) has a reference value of 1µPa2s. In this table, thresholds are
abbreviated to reflect American National Standards Institute standards (ANSI, 2013).
However, peak sound pressure is defined by ANSI as incorporating frequency
weighting, which is not the intent for this Technical Guidance. Hence, the subscript
“flat” is being included to indicate peak sound pressure should be flat weighted or
unweighted within the generalized hearing range. The subscript associated with
cumulative sound exposure level thresholds indicates the designated marine mammal
auditory weighting function (LF, MF, and HF cetaceans, and PW and OW pinnipeds)
and that the recommended accumulation period is 24 hours. The cumulative sound
exposure level thresholds could be exceeded in a multitude of ways (i.e., varying
exposure levels and durations, duty cycle). When possible, it is valuable for action
proponents to indicate the conditions under which these acoustic thresholds will be
exceeded.
Ensonified Area
Here, we describe operational and environmental parameters of the activity that
are used in estimating the area ensonified above the acoustic thresholds, including source
levels and transmission loss coefficient.
When the Technical Guidance was published (NMFS, 2016), in recognition of the
fact that ensonified area/volume could be more technically challenging to predict because
of the duration component in the new thresholds, we developed a user spreadsheet that
includes tools to help predict a simple isopleth that can be used in conjunction with
marine mammal density or occurrence to help predict takes. We note that because of
some of the assumptions included in the methods used for these tools, we anticipate that
isopleths produced are typically going to be overestimates of some degree, which may
result in some degree of overestimate of Level A harassment take. However, these tools

offer the best way to predict appropriate isopleths when more sophisticated 3D modeling
methods are not available, and NMFS continues to develop ways to quantitatively refine
these tools and will qualitatively address the output where appropriate.
The planned survey will entail the use of a 36-airgun array with a total discharge
volume of 6,600 in3 at a tow depth of 10 m to 12 m. L-DEO’s model results are used to
determine the 160 dBrms radius for the airgun source down to a maximum depth of 2,000
m. Received sound levels have been predicted by L-DEO’s model (Diebold et al., 2010)
as a function of distance from the 36-airgun array. This modeling approach uses ray
tracing 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). In addition, propagation measurements of pulses from the 36-airgun array at a
tow depth of 6 m have been reported in deep water (~1,600 m), intermediate water depth
on the slope (~600–1,100 m), and shallow water (~50 m) in the Gulf of Mexico (Tolstoy
et al., 2009; Diebold et al., 2010).
For deep and intermediate water cases, the field measurements cannot be used
readily to derive the harassment isopleths, as at those sites the calibration hydrophone
was located at a roughly constant depth of 350-550 m, which may not intersect all the
SPL isopleths at their widest point from the sea surface down to the assumed maximum
relevant water depth (~2000 m) for marine mammals. At short ranges, where the direct
arrivals dominate and the effects of seafloor interactions are minimal, the data at the deep
sites are suitable for comparison with modeled levels at the depth of the calibration
hydrophone. At longer ranges, the comparison with the model—constructed from the
maximum SPL through the entire water column at varying distances from the airgun
array—is the most relevant.

In deep and intermediate water depths at short ranges, sound levels for direct
arrivals recorded by the calibration hydrophone and L-DEO model results for the same
array tow depth are in good alignment (see figures 12 and 14 in Diebold et al. 2010).
Consequently, isopleths falling within this domain can be predicted reliably by the LDEO model, although they may be imperfectly sampled by measurements recorded at a
single depth. At greater distances, the calibration data show that seafloor-reflected and
sub-seafloor-refracted arrivals dominate, whereas the direct arrivals become weak and/or
incoherent (see figures 11, 12, and 16 in Diebold et al. 2010). Aside from local
topography effects, the region around the critical distance is where the observed levels
rise closest to the model curve. However, the observed sound levels are found to fall
almost entirely below the model curve. Thus, analysis of the Gulf of Mexico calibration
measurements demonstrates that although simple, the L-DEO model is a robust tool for
conservatively estimating isopleths.
The planned high-energy survey will acquire data with the 36-airgun array at a
tow depth of 10 to 12 m. For deep water (>1,000 m), we use the deep-water radii
obtained from L-DEO model results down to a maximum water depth of 2,000 m for the
36-airgun array. The radii for intermediate water depths (100-1,000 m) are derived from
the deep-water ones by applying a correction factor (multiplication) of 1.5, such that
observed levels at very near offsets fall below the corrected mitigation curve (see figure
16 in Diebold et al. 2010).
L-DEO's modeling methodology is described in greater detail in L-DEO’s
application. The estimated distances to the Level B harassment isopleth for the planned
airgun configuration are shown in table 4.
Table 4 -- Predicted Radial Distances from the R/V Langseth Seismic Source to
Isopleth Corresponding to Level B Harassment Threshold
Airgun
Configuration

Tow Depth

(m)1

Water Depth (m)

Predicted
distances (in m) to
the Level B

harassment
threshold

4 strings, 36
airguns, 6,600 in3

>1,000

6,7332

100-1,000

10,1003

1Maximum

tow depth was used for conservative distances.
is based on L-DEO model results.
3Distance is based on L-DEO model results with a 1.5 × correction factor between deep and intermediate
water depths.
2Distance

Table 5 -- Modeled Radial Distance to Isopleths Corresponding to Level A
Harassment Thresholds
Low
Frequency
Cetaceans

Mid
Frequency
Cetaceans

High
Frequency
Cetaceans

Phocid
Pinnipeds

MCS Surveys
PTS SELcum

320.2

1

10.4

PTS Peak

38.9

13.6

268.3

43.7

OBS Surveys
PTS SELcum

103.6

0.3

3.4

PTS Peak

38.9

13.6

268.3

43.7

The largest distance (in bold) of the dual criteria (SEL cum or Peak) was used to estimate threshold
distances and potential takes by Level A harassment.

Table 5 presents the modeled PTS isopleths for each cetacean hearing group
based on L-DEO modeling incorporated in the companion user spreadsheet, for the highenergy surveys with the shortest shot interval (i.e. greatest potential to cause PTS based
on accumulated sound energy) (NMFS 2018).
Predicted distances to Level A harassment isopleths, which vary based on marine
mammal hearing groups, were calculated based on modeling performed by L-DEO using
the Nucleus software program and the NMFS user spreadsheet, described below. The
acoustic thresholds for impulsive sounds contained in the NMFS Technical Guidance
were presented as dual metric acoustic thresholds using both SELcum and peak sound

pressure metrics (NMFS, 2016). As dual metrics, NMFS considers onset of PTS (Level A
harassment) to have occurred when either one of the two metrics is exceeded (i.e., metric
resulting in the largest isopleth). The SELcum metric considers both level and duration of
exposure, as well as auditory weighting functions by marine mammal hearing group.
The SELcum for the 36-airgun array is derived from calculating the modified
farfield signature. The farfield signature is often used as a theoretical representation of
the source level. To compute the farfield signature, the source level is estimated at a large
distance (right) below the array (e.g., 9 km), and this level is back projected
mathematically to a notional distance of 1 m from the array's geometrical center.
However, it has been recognized that the source level from the theoretical farfield
signature is never physically achieved at the source when the source is an array of
multiple airguns separated in space (Tolstoy et al., 2009). Near the source (at short
ranges, distances <1 km), the pulses of sound pressure from each individual airgun in the
source array do not stack constructively as they do for the theoretical farfield signature.
The pulses from the different airguns spread out in time such that the source levels
observed or modeled are the result of the summation of pulses from a few airguns, not the
full array (Tolstoy et al., 2009). At larger distances, away from the source array center,
sound pressure of all the airguns in the array stack coherently, but not within one time
sample, resulting in smaller source levels (a few dB) than the source level derived from
the far-field signature. Because the far-field signature does not take into account the large
array effect near the source and is calculated as a point source, the far-field signature is
not an appropriate measure of the sound source level for large arrays. See L-DEO’s
application for further detail on acoustic modeling.
Auditory injury is unlikely to occur for mid-frequency cetaceans, given the very
small modeled zones of injury for those species (all estimated zones are less than 15 m
for mid-frequency cetaceans), in context of distributed source dynamics.

In consideration of the received sound levels in the near-field as described above,
we expect the potential for Level A harassment of mid-frequency cetaceans to be de
minimis, even before the likely moderating effects of aversion and/or other compensatory
behaviors (e.g., Nachtigall et al., 2018) are considered. We do not anticipate that Level A
harassment is a likely outcome for any mid-frequency cetacean and do not authorize any
take by Level A harassment for these species.
The Level A and Level B harassment estimates are based on a consideration of
the number of marine mammals that could be within the area around the operating airgun
array where received levels of sound ≥160 dB re 1 µPa rms are predicted to occur. The
estimated numbers are based on the densities (numbers per unit area) of marine mammals
expected to occur in the area in the absence of seismic surveys. To the extent that marine
mammals tend to move away from seismic sources before the sound level reaches the
criterion level and tend not to approach an operating airgun array, these estimates likely
overestimate the numbers actually exposed to the specified level of sound.
Marine Mammal Occurrence
In this section, we provide information about the occurrence of marine mammals,
including density or other relevant information which will inform the take calculations.
Habitat-based stratified marine mammal densities for the North Atlantic are taken
from the US Navy Atlantic Fleet Training and Testing Area Marine Mammal Density
(Roberts et al., 2023; Mannocci et al., 2017), which represent the best available
information regarding marine mammal densities in the region. This density information
incorporates visual line-transect surveys of marine mammals for over 35 years, resulting
in various studies that estimated the abundance, density, and distributions of marine
mammal populations. The habitat-based density models consisted of 5 km x 5 km grid
cells. The AFTT model does not overlap the survey area but provides density data for
marine mammals at the same latitudes and water depths as the planned survey area. The

model covers an area of approximately 15-65° N, and from the east coast of the U.S. and
Canada to 45° W. More information is available online at
https://seamap.env.duke.edu/models/Duke/AFTT/. The range of most populations extends
past the coverage of the model.
For most species, only annual densities were available. For some baleen whale
species, seasonal densities were available; thus, densities that overlapped the timing of
the planned survey (i.e., summer) were used.
Take Estimation
Here, we describe how the information provided above is synthesized to produce
a quantitative estimate of the take that is reasonably likely to occur and authorized. In
order to estimate the number of marine mammals predicted to be exposed to sound levels
that would result in Level A or Level B harassment, radial distances from the airgun array
to the predicted isopleth corresponding to the Level A harassment and Level B
harassment thresholds are calculated, as described above. Those radial distances were
then used to calculate the area(s) around the airgun array predicted to be ensonified to
sound levels that exceed the harassment thresholds. The distance for the 160-dB Level B
harassment threshold and PTS (Level A harassment) thresholds (based on L-DEO model
results) was used to draw a buffer around the area expected to be ensonified (i.e., the
survey area). The ensonified areas were then increased by 25 percent to account for
potential delays, which is equivalent to adding 25 percent to the planned line km to be
surveyed. The density for each species was then multiplied by the daily ensonified areas
(increased as described above) and then multiplied by the number of survey days (14) to
estimate potential takes (see appendix B of L-DEO’s application for more information).
L-DEO assumed that their estimates of marine mammal exposures above
harassment thresholds equate to take and requested authorization of those takes. Those
estimates in turn form the basis for our take authorization numbers. For the species for

which NMFS does not expect there to be a reasonable potential for take by Level A
harassment to occur (i.e., mid-frequency cetaceans and phocid seals), we have added LDEO’s estimated exposures above Level A harassment thresholds to their estimated
exposures above the Level B harassment threshold to produce a total number of incidents
of take by Level B harassment that are authorized. Estimated exposures and authorized
take numbers for authorization are shown in table 6.
Table 6 -- Estimated Take Authorized
Species
Humpback whale3
Minke whale
Fin whale
Sei whale
Blue whale
Sperm whale
Northern bottlenose
whale
Beaked whales4
Risso’s dolphin
Atlantic white-sided
dolphin
Bottlenose dolphin
Striped dolphin
White-beaked dolphin
Common dolphin

Estimated Take
Level
Level A
B
80
3
84
3
82
3
113
4
1
0
214
Authorized Take

Percent of
modeled
abundance2

Level B

Level A

Modeled
Abundance1

80
84
82
113
1
3
3
3
4
0
4,990
13,784
11,672
19,530
191
64,015

1.66
0.63
0.73
0.60
0.53
0.33

0

0

1,056

0.23

0

0

65,069

0.39

2

0

78,205

1.17

4,052

4,060

175,299

2.23

974
148
46
13,44
2
0
976
148
0
0
418,151
412,729
2,627

0.23
0.04
1.76

13,468

418,151

2.85

Long-finned pilot
1,020
2
1,022
0
264,907
0.39
whale5
Killer whale
24
0
24
0
972
2.48
94,583
Harbor porpoise
1,181
45
1,181
45
1.30
Phocid Seals6
5,844
35
5,879
0
150,075
3.92
1 Modeled abundance (Roberts et al., 2023) or North Atlantic abundance (NAMMCO, 2023), where
applicable.
2 Requested take authorization is expressed as percent of population for the AFTT Area (Roberts et al.,
2023).
3 Based on the best population estimates of 10,752 individuals for the West Indies breeding population
(Stevick et al., 2003), and 260 individuals for the Cape Verde breeding population (Ryan et al., 2014); the
ratio for these 2 populations was applied to estimate 2 takes for the Cape Verde/Northwest Africa DPS and
81 takes for the West Indies DPS.
4 Beaked whale guild. Includes Cuvier’s beaked whale, Blainville’s beaked whale, and Sowerby’s beaked
whale. Most takes are assumed to be for Cuvier’s beaked whale, as they are most likely to be encountered
in the survey area.
5 Takes based on density for Globicephala sp. All takes are assumed to be for long-finned pilot whales as
short-finned pilot whales are only found in tropical, subtropical, and warm temperate waters (Olson, 2018)
and are not expected to be found at this latitude.

6 Seal

guild. Includes hooded seal, harp seal, bearded seal, gray seal and harbor seal. Most takes are
assumed to be for hooded seal and harp seal, as they are the most likely to be encountered in the survey
area.

Mitigation
In order to issue an IHA under section 101(a)(5)(D) of the MMPA, NMFS must
set forth the permissible methods of taking pursuant to the activity and other means of
effecting the least practicable impact on the species or stock and its habitat, paying
particular attention to rookeries, mating grounds, and areas of similar significance, and on
the availability of the species or stock for taking for certain subsistence uses (latter not
applicable for this action). NMFS regulations require applicants for incidental take
authorizations to include information about the availability and feasibility (economic and
technological) of equipment, methods, and manner of conducting the activity or other
means of effecting the least practicable adverse impact upon the affected species or
stocks, and their habitat (50 CFR 216.104(a)(11)).
In evaluating how mitigation may or may not be appropriate to ensure the least
practicable adverse impact on species or stocks and their habitat, as well as subsistence
uses where applicable, NMFS considers two primary factors:
(1) The manner in which, and the degree to which, the successful implementation
of the measure(s) is expected to reduce impacts to marine mammals, marine mammal
species or stocks, and their habitat. This considers the nature of the potential adverse
impact being mitigated (likelihood, scope, range). It further considers the likelihood that
the measure will be effective if implemented (probability of accomplishing the mitigating
result if implemented as planned), the likelihood of effective implementation (probability
implemented as planned); and
(2) The practicability of the measures for applicant implementation, which may
consider such things as cost and impact on operations.
Vessel-Based Visual Mitigation Monitoring

Visual monitoring requires the use of trained observers (herein referred to as
visual protected species observers (PSOs)) to scan the ocean surface for the presence of
marine mammals. The area to be scanned visually includes primarily the shutdown zone
(SZ), within which observation of certain marine mammals requires shutdown of the
acoustic source, a buffer zone, and to the extent possible depending on conditions, the
surrounding waters. The buffer zone means an area beyond the SZ to be monitored for
the presence of marine mammals that may enter the SZ. During pre-start clearance
monitoring (i.e., before ramp-up begins), the buffer zone also acts as an extension of the
SZ in that observations of marine mammals within the buffer zone would also prevent
airgun operations from beginning (i.e., ramp-up). The buffer zone encompasses the area
at and below the sea surface from the edge of the 0–500 m SZ, out to a radius of 1,000 m
from the edges of the airgun array (500–1,000 m). This 1,000-m zone (SZ plus buffer)
represents the pre-start clearance zone. Visual monitoring of the SZ and adjacent waters
(buffer plus surrounding waters) is intended to establish and, when visual conditions
allow, maintain zones around the sound source that are clear of marine mammals, thereby
reducing or eliminating the potential for injury and minimizing the potential for more
severe behavioral reactions for animals occurring closer to the vessel. Visual monitoring
of the buffer zone is intended to (1) provide additional protection to marine mammals that
may be in the vicinity of the vessel during pre-start clearance, and (2) during airgun use,
aid in establishing and maintaining the SZ by alerting the visual observer and crew of
marine mammals that are outside of, but may approach and enter, the SZ.
During survey operations (e.g., any day on which use of the airgun array is
planned to occur and whenever the airgun array is in the water, whether activated or not),
a minimum of two visual PSOs must be on duty and conducting visual observations at all
times during daylight hours (i.e., from 30 minutes prior to sunrise through 30 minutes
following sunset). Visual monitoring of the pre-start clearance zone must begin no less

than 30 minutes prior to ramp-up and monitoring must continue until 1 hour after use of
the airgun array ceases or until 30 minutes past sunset. Visual PSOs shall coordinate to
ensure 360° visual coverage around the vessel from the most appropriate observation
posts and shall conduct visual observations using binoculars and the naked eye while free
from distractions and in a consistent, systematic, and diligent manner.
PSOs shall establish and monitor the SZ and buffer zone. These zones shall be
based upon the radial distance from the edges of the airgun array (rather than being based
on the center of the array or around the vessel itself). During use of the airgun array (i.e.,
anytime airguns are active, including ramp-up), detections of marine mammals within the
buffer zone (but outside the SZ) shall be communicated to the operator to prepare for the
potential shutdown of the airgun array. Visual PSOs will immediately communicate all
observations to the on duty acoustic PSO(s), including any determination by the PSO
regarding species identification, distance, and bearing and the degree of confidence in the
determination. Any observations of marine mammals by crew members shall be relayed
to the PSO team. During good conditions (e.g., daylight hours; Beaufort sea state (BSS) 3
or less), visual PSOs shall conduct observations when the airgun array is not operating
for comparison of sighting rates and behavior with and without use of the airgun array
and between acquisition periods, to the maximum extent practicable.
Visual PSOs may be on watch for a maximum of 4 consecutive hours followed by
a break of at least 1 hour between watches and may conduct a maximum of 12 hours of
observation per 24-hour period. Combined observational duties (visual and acoustic but
not at same time) may not exceed 12 hours per 24-hour period for any individual PSO.
Passive Acoustic Monitoring
Passive acoustic monitoring (PAM) means the use of trained personnel
(sometimes referred to as PAM operators, herein referred to as acoustic PSOs) to operate
PAM equipment to acoustically detect the presence of marine mammals. Acoustic

monitoring involves acoustically detecting marine mammals regardless of distance from
the source, as localization of animals may not always be possible. Acoustic monitoring is
intended to further support visual monitoring (during daylight hours) in maintaining a SZ
around the sound source that is clear of marine mammals. In cases where visual
monitoring is not effective (e.g., due to weather, nighttime), acoustic monitoring may be
used to allow certain activities to occur, as further detailed below.
PAM will take place in addition to the visual monitoring program. 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. Acoustic monitoring can be used in addition to visual
observations to improve detection, identification, and localization of cetaceans. The
acoustic monitoring would serve to alert visual PSOs (if on duty) when vocalizing
cetaceans are detected. It is only useful when marine mammals vocalize, but it can be
effective either by day or by night and does not depend on good visibility. It will be
monitored in real time so that the visual observers can be advised when cetaceans are
detected.
The R/V Langseth will use a towed PAM system, which must be monitored by at
a minimum one on duty acoustic PSO beginning at least 30 minutes prior to ramp-up and
at all times during use of the airgun array. Acoustic PSOs may be on watch for a
maximum of 4 consecutive hours followed by a break of at least 1 hour between watches
and may conduct a maximum of 12 hours of observation per 24-hour period. Combined
observational duties (acoustic and visual but not at same time) may not exceed 12 hours
per 24-hour period for any individual PSO.
Survey activity may continue for 30 minutes when the PAM system malfunctions
or is damaged, while the PAM operator diagnoses the issue. If the diagnosis indicates that
the PAM system must be repaired to solve the problem, operations may continue for an

additional 10 hours without acoustic monitoring during daylight hours only under the
following conditions:
●

Sea state is less than or equal to BSS 4;

●

No marine mammals (excluding delphinids) detected solely by PAM in

the SZ in the previous 2 hours;
●

NMFS is notified via email as soon as practicable with the time and

location in which operations began occurring without an active PAM system; and
●

Operations with an active airgun array, but without an operating PAM

system, do not exceed a cumulative total of 10 hours in any 24-hour period.
Establishment of Shutdown and Pre-Start Clearance Zones
A SZ is a defined area within which occurrence of a marine mammal triggers
mitigation action intended to reduce the potential for certain outcomes (e.g., auditory
injury, disruption of critical behaviors). The PSOs will establish a minimum SZ with a
500-m radius. The 500-m SZ will be based on radial distance from the edge of the airgun
array (rather than being based on the center of the array or around the vessel itself). With
certain exceptions (described below), if a marine mammal appears within or enters this
zone, the airgun array will be shut down.
The pre-start clearance zone is defined as the area that must be clear of marine
mammals prior to beginning ramp-up of the airgun array and includes the SZ plus the
buffer zone. Detections of marine mammals within the pre-start clearance zone would
prevent airgun operations from beginning (i.e., ramp-up).
The 500-m SZ is intended to be precautionary in the sense that it would be
expected to contain sound exceeding the injury criteria for all cetacean hearing groups,
(based on the dual criteria of SELcum and peak SPL), while also providing a consistent,
reasonably observable zone within which PSOs would typically be able to conduct
effective observational effort. Additionally, a 500-m SZ is expected to minimize the

likelihood that marine mammals will be exposed to levels likely to result in more severe
behavioral responses. Although significantly greater distances may be observed from an
elevated platform under good conditions, we expect that 500 m is likely regularly
attainable for PSOs using the naked eye during typical conditions. The pre-start clearance
zone simply represents the addition of a buffer to the SZ, doubling the SZ size during
pre-clearance.
An extended SZ of 1,500 m must be enforced for all beaked whales, a large whale
with a calf, and groups of six or more large whales. No buffer of this extended SZ is
required, as NMFS concludes that this extended SZ is sufficiently protective to mitigate
harassment to these groups.
Pre-start Clearance and Ramp-up
Ramp-up (sometimes referred to as "soft start") means the gradual and systematic
increase of emitted sound levels from an airgun array. Ramp-up begins by first activating
a single airgun of the smallest volume, followed by doubling the number of active
elements in stages until the full complement of an array's airguns are active. Each stage
should be approximately the same duration, and the total duration should not be less than
approximately 20 minutes. The intent of pre-start clearance observation (30 minutes) is to
ensure no marine mammals are observed within the pre-start clearance zone (or extended
SZ, for beaked whales, a large whale with a calf, and groups of six or more large whales)
prior to the beginning of ramp-up. During the pre-start clearance period is the only time
observations of marine mammals in the buffer zone would prevent operations (i.e., the
beginning of ramp-up). The intent of ramp-up is to warn marine mammals of pending
seismic survey operations and to allow sufficient time for those animals to leave the
immediate vicinity prior to the sound source reaching full intensity. A ramp-up
procedure, involving a step-wise increase in the number of airguns firing and total array
volume until all operational airguns are activated and the full volume is achieved, is

required at all times as part of the activation of the airgun array. All operators must
adhere to the following pre-start clearance and ramp-up requirements:
●

The operator must notify a designated PSO of the planned start of ramp-up

as agreed upon with the lead PSO; the notification time should not be less than 60
minutes prior to the planned ramp-up in order to allow the PSOs time to monitor the prestart clearance zone (and extended SZ) for 30 minutes prior to the initiation of ramp-up
(pre-start clearance);
●

Ramp-ups shall be scheduled so as to minimize the time spent with the

source activated prior to reaching the designated run-in;
●

One of the PSOs conducting pre-start clearance observations must be

notified again immediately prior to initiating ramp-up procedures and the operator must
receive confirmation from the PSO to proceed;
●

Ramp-up may not be initiated if any marine mammal is within the

applicable shutdown or buffer zone. If a marine mammal is observed within the pre-start
clearance zone (or extended SZ, for beaked whales, a large whale with a calf, and groups
of six or more large whales) during the 30 minute pre-start clearance period, ramp-up
may not begin until the animal(s) has been observed exiting the zones or until an
additional time period has elapsed with no further sightings (15 minutes for small
odontocetes and pinnipeds, and 30 minutes for all mysticetes and all other odontocetes,
including sperm whales, beaked whales, and large delphinids, such as pilot whales);
●

Ramp-up shall begin by activating a single airgun of the smallest volume

in the array and shall continue in stages by doubling the number of active elements at the
commencement of each stage, with each stage of approximately the same duration.
Duration shall not be less than 20 minutes. The operator must provide information to the
PSO documenting that appropriate procedures were followed;

●

PSOs must monitor the pre-start clearance zone and extended SZ during

ramp-up, and ramp-up must cease and the source must be shut down upon detection of a
marine mammal within the applicable zone. Once ramp-up has begun, detections of
marine mammals within the buffer zone do not require shutdown, but such observation
shall be communicated to the operator to prepare for the potential shutdown;
●

Ramp-up may occur at times of poor visibility, including nighttime, if

appropriate acoustic monitoring has occurred with no detections in the 30 minutes prior
to beginning ramp-up. Airgun array activation may only occur at times of poor visibility
where operational planning cannot reasonably avoid such circumstances;
●

If the airgun array is shut down for brief periods (i.e., less than 30

minutes) for reasons other than implementation of prescribed mitigation (e.g., mechanical
difficulty), it may be activated again without ramp-up if PSOs have maintained constant
visual and/or acoustic observation and no visual or acoustic detections of marine
mammals have occurred within the pre-start clearance zone (or extended SZ, where
applicable). For any longer shutdown, pre-start clearance observation and ramp-up are
required; and
●

Testing of the airgun array involving all elements requires ramp-up.

Testing limited to individual source elements or strings does not require ramp-up but
does require pre-start clearance of 30 minutes.
Shutdown
The shutdown of an airgun array requires the immediate de-activation of all
individual airgun elements of the array. Any PSO on duty will have the authority to call
for shutdown of the airgun array if a marine mammal is detected within the applicable
SZ. The operator must also establish and maintain clear lines of communication directly
between PSOs on duty and crew controlling the airgun array to ensure that shutdown
commands are conveyed swiftly while allowing PSOs to maintain watch. When both

visual and acoustic PSOs are on duty, all detections will be immediately communicated
to the remainder of the on-duty PSO team for potential verification of visual observations
by the acoustic PSO or of acoustic detections by visual PSOs. When the airgun array is
active (i.e., anytime one or more airguns is active, including during ramp-up) and (1) a
marine mammal appears within or enters the applicable SZ and/or (2) a marine mammal
(other than delphinids, see below) is detected acoustically and localized within the
applicable SZ, the airgun array will be shut down. When shutdown is called for by a
PSO, the airgun array will be immediately deactivated and any dispute resolved only
following deactivation. Additionally, shutdown will occur whenever PAM alone (without
visual sighting), confirms presence of marine mammal(s) in the SZ. If the acoustic PSO
cannot confirm presence within the SZ, visual PSOs will be notified but shutdown is not
required.
Following a shutdown, airgun activity will not resume until the marine mammal
has cleared the SZ. The animal will be considered to have cleared the SZ if it is visually
observed to have departed the SZ (i.e., animal is not required to fully exit the buffer zone
where applicable), or it has not been seen within the SZ for 15 minutes for small
odontocetes or 30 minutes for all mysticetes and all other odontocetes, including sperm
whales, beaked whales, and large delphinids, such as pilot whales.
The shutdown requirement is waived for pinnipeds and specific genera of small
dolphins if an individual is detected within the SZ. The small dolphin group is intended to
encompass those members of the Family Delphinidae most likely to voluntarily approach
the source vessel for purposes of interacting with the vessel and/or airgun array (e.g., bow
riding). This exception to the shutdown requirement applies solely to pinnipeds and the
specific genera of small dolphins (Delphinus, Lagenodelphis, Stenella, and Tursiops).
We include this pinniped and small dolphin exception because shutdown
requirements for these species under all circumstances represent practicability concerns

without likely commensurate benefits for the animals in question. Small dolphins are
generally the most commonly observed marine mammals in the specific geographic
region and would typically be the only marine mammals likely to intentionally approach
the vessel. As described above, auditory injury is extremely unlikely to occur for midfrequency cetaceans (e.g., phocid seals and delphinids), as this group is relatively
insensitive to sound produced at the predominant frequencies in an airgun pulse while
also having a relatively high threshold for the onset of auditory injury (i.e., permanent
threshold shift).
A large body of anecdotal evidence indicates that small dolphins commonly
approach vessels and/or towed arrays during active sound production for purposes of bow
riding with no apparent effect observed (e.g., Barkaszi et al., 2012, Barkaszi and Kelly,
2018). The potential for increased shutdowns resulting from such a measure would
require the Langseth to revisit the missed track line to reacquire data, resulting in an
overall increase in the total sound energy input to the marine environment and an increase
in the total duration over which the survey is active in a given area. Although other midfrequency hearing specialists (e.g., large delphinids) are no more likely to incur auditory
injury than are small dolphins, they are much less likely to approach vessels. Therefore,
retaining a shutdown requirement for large delphinids would not have similar impacts in
terms of either practicability for the applicant or corollary increase in sound energy
output and time on the water. We do anticipate some benefit for a shutdown requirement
for large delphinids in that it simplifies somewhat the total range of decision-making for
PSOs and may preclude any potential for physiological effects other than to the auditory
system as well as some more severe behavioral reactions for any such animals in close
proximity to the Langseth.
Visual PSOs shall use best professional judgment in making the decision to call
for a shutdown if there is uncertainty regarding identification (i.e., whether the observed

marine mammal(s) belongs to one of the delphinid genera for which shutdown is waived
or one of the species with a larger SZ).
L-DEO must implement shutdown if a marine mammal species for which take
was not authorized or a species for which authorization was granted but the authorized
takes have been met approaches the Level A or Level B harassment zones. L-DEO must
also implement shutdown if any large whale (defined as a sperm whale or any mysticete
species) with a calf (defined as an animal less than two-thirds the body size of an adult
observed to be in close association with an adult) and/or an aggregation of six or more
large whales are observed within the extended SZ (1,500 m).
Vessel Strike Avoidance Mitigation Measures
Vessel personnel should use an appropriate reference guide that includes
identifying information on all marine mammals that may be encountered. Vessel
operators must comply with the below measures except under extraordinary
circumstances when the safety of the vessel or crew is in doubt or the safety of life at sea
is in question. These requirements do not apply in any case where compliance would
create an imminent and serious threat to a person or vessel or to the extent that a vessel is
restricted in its ability to maneuver and, because of the restriction, cannot comply.
Vessel operators and crews must maintain a vigilant watch for all marine
mammals and slow down, stop their vessel, or alter course, as appropriate and regardless
of vessel size, to avoid striking any marine mammal. A single marine mammal at the
surface may indicate the presence of submerged animals in the vicinity of the vessel;
therefore, precautionary measures should always be exercised. A visual observer aboard
the vessel must monitor a vessel strike avoidance zone around the vessel (separation
distances stated below). Visual observers monitoring the vessel strike avoidance zone
may be third-party observers (i.e., PSOs) or crew members, but crew members
responsible for these duties must be provided sufficient training to 1) distinguish marine

mammals from other phenomena; and 2) broadly to identify a marine mammal as a right
whale, other whale (defined in this context as sperm whales or baleen whales other than
right whales), or other marine mammals.
Vessel speeds must be reduced to 10 knots (kn; 18.5 kilometers per hour (kph)) or
less when mother/calf pairs, pods, or large assemblages of cetaceans are observed near a
vessel. All vessels must maintain a minimum separation distance of 100 m from sperm
whales and all other baleen whales. All vessels must, to the maximum extent practicable,
attempt to maintain a minimum separation distance of 50 m from all other marine
mammals, with an understanding that at times this may not be possible (e.g., for animals
that approach the vessel).
When marine mammals are sighted while a vessel is underway, the vessel shall
take action as necessary to avoid violating the relevant separation distance (e.g., attempt
to remain parallel to the animal’s course, avoid excessive speed or abrupt changes in
direction until the animal has left the area). If marine mammals are sighted within the
relevant separation distance, the vessel must reduce speed and shift the engine to neutral,
not engaging the engines until animals are clear of the area. This does not apply to any
vessel towing gear or any vessel that is navigationally constrained.
Based on our evaluation of the applicant’s planned measures, as well as other
measures considered by NMFS, NMFS has determined that the mitigation measures
provide the means of effecting the least practicable impact on the affected species or
stocks and their habitat, paying particular attention to rookeries, mating grounds, and
areas of similar significance.
Monitoring and Reporting
In order to issue an IHA for an activity, section 101(a)(5)(D) of the MMPA states
that NMFS must set forth requirements pertaining to the monitoring and reporting of such
taking. The MMPA implementing regulations at 50 CFR 216.104(a)(13) indicate that

requests for authorizations must include the suggested means of accomplishing the
necessary monitoring and reporting that will result in increased knowledge of the species
and of the level of taking or impacts on populations of marine mammals that are expected
to be present while conducting the activities. Effective reporting is critical both to
compliance as well as ensuring that the most value is obtained from the required
monitoring.
Monitoring and reporting requirements prescribed by NMFS should contribute to
improved understanding of one or more of the following:
●

Occurrence of marine mammal species or stocks in the area in which take

is anticipated (e.g., presence, abundance, distribution, density);
●

Nature, scope, or context of likely marine mammal exposure to potential

stressors/impacts (individual or cumulative, acute or chronic), through better
understanding of: (1) action or environment (e.g., source characterization, propagation,
ambient noise); (2) affected species (e.g., life history, dive patterns); (3) co-occurrence of
marine mammal species with the activity; or (4) biological or behavioral context of
exposure (e.g., age, calving or feeding areas);
●

Individual marine mammal responses (behavioral or physiological) to

acoustic stressors (acute, chronic, or cumulative), other stressors, or cumulative impacts
from multiple stressors;
●

How anticipated responses to stressors impact either: (1) long-term fitness

and survival of individual marine mammals; or (2) populations, species, or stocks;
●

Effects on marine mammal habitat (e.g., marine mammal prey species,

acoustic habitat, or other important physical components of marine mammal habitat); and
●

Mitigation and monitoring effectiveness.

Vessel-Based Visual Monitoring

As described above, PSO observations will take place during daytime airgun
operations. During seismic survey operations, at least five visual PSOs will be based
aboard the Langseth. Two visual PSOs will be on duty at all times during daytime hours.
Monitoring shall be conducted in accordance with the following requirements:
●

The operator shall provide PSOs with bigeye binoculars (e.g., 25 x 150;

2.7 view angle; individual ocular focus; height control) of appropriate quality solely for
PSO use. These shall be pedestal-mounted on the deck at the most appropriate vantage
point that provides for optimal sea surface observation, PSO safety, and safe operation of
the vessel; and
●

The operator will work with the selected third-party observer provider to

ensure PSOs have all equipment (including backup equipment) needed to adequately
perform necessary tasks, including accurate determination of distance and bearing to
observed marine mammals.
PSOs must have the following requirements and qualifications:
●

PSOs shall be independent, dedicated, trained visual and acoustic PSOs

and must be employed by a third-party observer provider;
●

PSOs shall have no tasks other than to conduct observational effort (visual

or acoustic), collect data, and communicate with and instruct relevant vessel crew with
regard to the presence of protected species and mitigation requirements (including brief
alerts regarding maritime hazards);
●

PSOs shall have successfully completed an approved PSO training course

appropriate for their designated task (visual or acoustic). Acoustic PSOs are required to
complete specialized training for operating PAM systems and are encouraged to have
familiarity with the vessel with which they will be working;

●

PSOs can act as acoustic or visual observers (but not at the same time) as

long as they demonstrate that their training and experience are sufficient to perform the
task at hand;
●

NMFS must review and approve PSO resumes accompanied by a relevant

training course information packet that includes the name and qualifications (i.e.,
experience, training completed, or educational background) of the instructor(s), the
course outline or syllabus, and course reference material as well as a document stating
successful completion of the course;
●

PSOs must successfully complete relevant training, including completion

of all required coursework and passing (80 percent or greater) a written and/or oral
examination developed for the training program;
●

PSOs must have successfully attained a bachelor's degree from an

accredited college or university with a major in one of the natural sciences, a minimum of
30 semester hours or equivalent in the biological sciences, and at least one undergraduate
course in math or statistics; and
●

The educational requirements may be waived if the PSO has acquired the

relevant skills through alternate experience. Requests for such a waiver shall be
submitted to NMFS and must include written justification. Requests shall be granted or
denied (with justification) by NMFS within 1 week of receipt of submitted information.
Alternate experience that may be considered includes, but is not limited to (1) secondary
education and/or experience comparable to PSO duties; (2) previous work experience
conducting academic, commercial, or government-sponsored protected species surveys;
or (3) previous work experience as a PSO; the PSO should demonstrate good standing
and consistently good performance of PSO duties.
●

At least one of the visual and two of the acoustic PSOs aboard the vessel

must have a minimum of 90 days at-sea experience working in those roles, respectively,

with no more than 18 months elapsed since the conclusion of the at-sea experience. One
visual PSO with such experience shall be designated as the lead for the entire protected
species observation team. The lead PSO shall serve as primary point of contact for the
vessel operator and ensure all PSO requirements per the IHA are met. To the maximum
extent practicable, the experienced PSOs should be scheduled to be on duty with those
PSOs with appropriate training but who have not yet gained relevant experience.
●

For data collection purposes, PSOs shall use standardized electronic data

collection forms. PSOs shall record detailed information about any implementation of
mitigation requirements, including the distance of animals to the airgun array and
description of specific actions that ensued, the behavior of the animal(s), any observed
changes in behavior before and after implementation of mitigation, and if shutdown was
implemented, the length of time before any subsequent ramp-up of the airgun array. If
required mitigation was not implemented, PSOs should record a description of the
circumstances. At a minimum, the following information must be recorded:
â—‹ Vessel name, vessel size and type, maximum speed capability of vessel;
â—‹ Dates (MM/DD/YYYY) of departures and returns to port with port name;
â—‹ PSO names and affiliations, PSO ID (initials or other identifier);
â—‹ Date (MM/DD/YYYY) and participants of PSO briefings;
â—‹ Visual monitoring equipment used (description);
â—‹ PSO location on vessel and height (meters) of observation location above
water surface;
â—‹ Watch status (description);
â—‹ Dates (MM/DD/YYYY) and times (Greenwich Mean Time/UTC) of
survey on/off effort and times (GMC/UTC) corresponding with PSO
on/off effort;

â—‹ Vessel location (decimal degrees) when survey effort began and ended and
vessel location at beginning and end of visual PSO duty shifts;
â—‹ Vessel location (decimal degrees) at 30-second intervals if obtainable
from data collection software, otherwise at practical regular interval;
â—‹ Vessel heading (compass heading) and speed (knots) at beginning and end
of visual PSO duty shifts and upon any change;
â—‹ Water depth (meters) (if obtainable from data collection software);
â—‹ Environmental conditions while on visual survey (at beginning and end of
PSO shift and whenever conditions changed significantly), including BSS
and any other relevant weather conditions including cloud cover, fog, sun
glare, and overall visibility to the horizon;
â—‹ Factors that may have contributed to impaired observations during each
PSO shift change or as needed as environmental conditions changed
(description) (e.g., vessel traffic, equipment malfunctions); and
â—‹ Vessel/Survey activity information (and changes thereof) (description),
such as airgun power output while in operation, number and volume of
airguns operating in the array, tow depth of the array, and any other notes
of significance (i.e., pre-start clearance, ramp-up, shutdown, testing,
shooting, ramp-up completion, end of operations, streamers, etc.).
●

Upon visual observation of any marine mammals, the following
information must be recorded:
â—‹ Sighting ID (numeric);
â—‹ Watch status (sighting made by PSO on/off effort, opportunistic, crew,
alternate vessel/platform);
â—‹ Location of PSO/observer (description);

â—‹ Vessel activity at the time of the sighting (e.g., deploying, recovering,
testing, shooting, data acquisition, other);
â—‹ PSO who sighted the animal/ID;
â—‹ Time/date of sighting (GMT/UTC, MM/DD/YYYY);
â—‹ Initial detection method (description);
â—‹ Sighting cue (description);
â—‹ Vessel location at time of sighting (decimal degrees);
â—‹ Water depth (meters);
○ Direction of vessel’s travel (compass direction);
â—‹ Speed (knots) of the vessel from which the observation was made;
○ Direction of animal’s travel relative to the vessel (description, compass
heading);
â—‹ Bearing to sighting (degrees);
â—‹ Identification of the animal (e.g., genus/species, lowest possible
taxonomic level, or unidentified) and the composition of the group if there
is a mix of species;
â—‹ Species reliability (an indicator of confidence in identification) (1 =
unsure/possible, 2 = probable, 3 = definite/sure, 9 = unknown/not
recorded);
â—‹ Estimated distance to the animal (meters) and method of estimating
distance;
â—‹ Estimated number of animals (high/low/best) (numeric);
â—‹ Estimated number of animals by cohort (adults, yearlings, juveniles,
calves, group composition, etc.);

â—‹ Description (as many distinguishing features as possible of each individual
seen, including length, shape, color, pattern, scars or markings, shape and
size of dorsal fin, shape of head, and blow characteristics);
â—‹ Detailed behavior observations (e.g., number of blows/breaths, number of
surfaces, breaching, spyhopping, diving, feeding, traveling; as explicit and
detailed as possible; note any observed changes in behavior);
○ Animal’s closest point of approach (meters) and/or closest distance from
any element of the airgun array;
â—‹ Description of any actions implemented in response to the sighting (e.g.,
delays, shutdown, ramp-up) and time and location of the action;
â—‹ Photos (Yes/No);
â—‹ Photo Frame Numbers (List of numbers); and
â—‹ Conditions at time of sighting (Visibility; BSS).
If a marine mammal is detected while using the PAM system, the following
information should be recorded:
●

An acoustic encounter identification number, and whether the detection

was linked with a visual sighting;
●

Date and time when first and last heard;

●

Types and nature of sounds heard (e.g., clicks, whistles, creaks, burst

pulses, continuous, sporadic, strength of signal); and
●

Any additional information recorded such as water depth of the

hydrophone array, bearing of the animal to the vessel (if determinable), species or
taxonomic group (if determinable), spectrogram screenshot, and any other notable
information.
Reporting

L-DEO shall submit a draft comprehensive report on all activities and monitoring
results within 90 days of the completion of the survey or expiration of the IHA,
whichever comes sooner. The report must describe all activities conducted and sightings
of marine mammals, must provide full documentation of methods, results, and
interpretation pertaining to all monitoring, and must summarize the dates and locations of
survey operations and all marine mammal sightings (dates, times, locations, activities,
associated survey activities). The draft report shall also include geo-referenced timestamped vessel tracklines for all time periods during which airgun arrays were operating.
Tracklines should include points recording any change in airgun array status (e.g., when
the sources began operating, when they were turned off, or when they changed
operational status such as from full array to single gun or vice versa). Geographic
Information System files shall be provided in Environmental Systems Research Institute
shapefile format and include the UTC date and time, latitude in decimal degrees, and
longitude in decimal degrees. All coordinates shall be referenced to the WGS84
geographic coordinate system. In addition to the report, all raw observational data shall
be made available. The report must summarize data collected as described above in
Monitoring and Reporting. A final report must be submitted within 30 days following
resolution of any comments on the draft report.
The report must include a validation document concerning the use of PAM, which
should include necessary noise validation diagrams and demonstrate whether background
noise levels on the PAM deployment limited achievement of the planned detection goals.
Copies of any vessel self-noise assessment reports must be included with the report.
Reporting Injured or Dead Marine Mammals
Discovery of injured or dead marine mammals—In the event that personnel
involved in the survey activities discover an injured or dead marine mammal, the L-DEO

shall report the incident to the Office of Protected Resources (OPR) and NMFS as soon
as feasible. The report must include the following information:
●

Time, date, and location (latitude/longitude) of the first discovery (and

updated location information if known and applicable);
●

Species identification (if known) or description of the animal(s) involved;

●

Condition of the animal(s) (including carcass condition if the animal is

●

Observed behaviors of the animal(s), if alive;

●

If available, photographs or video footage of the animal(s); and

●

General circumstances under which the animal was discovered.

dead);

Vessel strike—In the event of a strike of a marine mammal by any vessel involved
in the activities covered by the authorization, L-DEO shall report the incident to OPR and
NMFS as soon as feasible. The report must include the following information:
●

Time, date, and location (latitude/longitude) of the incident;

●

Vessel's speed during and leading up to the incident;

●

Vessel's course/heading and what operations were being conducted (if

applicable);
●

Status of all sound sources in use;

●

Description of avoidance measures/requirements that were in place at the

time of the strike and what additional measure were taken, if any, to avoid strike;
●

Environmental conditions (e.g., wind speed and direction, BSS, cloud

cover, visibility) immediately preceding the strike;
●

Species identification (if known) or description of the animal(s) involved;

●

Estimated size and length of the animal that was struck;

●

Description of the behavior of the marine mammal immediately preceding

and following the strike;

●

If available, description of the presence and behavior of any other marine

mammals present immediately preceding the strike;
●

Estimated fate of the animal (e.g., dead, injured but alive, injured and

moving, blood or tissue observed in the water, status unknown, disappeared); and
●

To the extent practicable, photographs or video footage of the animal(s).

Negligible Impact Analysis and Determination
NMFS has defined negligible impact 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 (50
CFR 216.103). A negligible impact finding is based on the lack of likely adverse effects
on annual rates of recruitment or survival (i.e., population-level effects). An estimate of
the number of takes alone is not enough information on which to base an impact
determination. In addition to considering estimates of the number of marine mammals
that might be “taken” through harassment, NMFS considers other factors, such as the
likely nature of any impacts or responses (e.g., intensity, duration), the context of any
impacts or responses (e.g., critical reproductive time or location, foraging impacts
affecting energetics), as well as effects on habitat, and the likely effectiveness of the
mitigation. We also assess the number, intensity, and context of estimated takes by
evaluating this information relative to population status. Consistent with the 1989
preamble for NMFS’ implementing regulations (54 FR 40338, September 29, 1989), the
impacts from other past and ongoing anthropogenic activities are incorporated into this
analysis via their impacts on the baseline (e.g., as reflected in the regulatory status of the
species, population size and growth rate where known, ongoing sources of human-caused
mortality, or ambient noise levels).
To avoid repetition, the discussion of our analysis applies to all the species listed
in table 1, given that the anticipated effects of this activity on these different marine

mammal stocks are expected to be similar. Where there are meaningful differences
between species or stocks they are included as separate subsections below. NMFS does
not anticipate that serious injury or mortality would occur as a result of L-DEO’s planned
survey, even in the absence of mitigation, and no serious injury or mortality is authorized.
As discussed in the Potential Effects of Specified Activities on Marine Mammals and
Their Habitat section above, non-auditory physical effects and vessel strike are not
expected to occur. NMFS expects that the majority of potential takes would be in the
form of short-term Level B behavioral harassment, resulting from temporary avoidance
of the area or decreased foraging (if such activity was occurring), reactions that are
considered to be of low severity and with no lasting biological consequences (e.g.,
Southall et al., 2007).
We have authorized a limited number of Level A harassment events of five
species in the form of PTS (humpback whale, minke whale, fin whale, sei whale, and
harbor porpoise) and Level B harassment only of the remaining marine mammal species.
If any PTS is incurred in marine mammals as a result of the specified activity, we expect
only a small degree of PTS that would not result in severe hearing impairment because of
the constant movement of both the Langseth and of the marine mammals in the project
areas, as well as the fact that the vessel is not expected to remain in any one area in which
individual marine mammals would be expected to concentrate for an extended period of
time. Additionally, L-DEO will shut down the airgun array if marine mammals approach
within 500 m (with the exception of specific genera of dolphins, see Mitigation), further
reducing the expected duration and intensity of sound and therefore, the likelihood of
marine mammals incurring PTS. Since the duration of exposure to loud sounds will be
relatively short, it would be unlikely to affect the fitness of any individuals. Also, as
described above, we expect that marine mammals would likely move away from a sound
source that represents an aversive stimulus, especially at levels that would be expected to

result in PTS, given sufficient notice of the Langseth's approach due to the vessel's
relatively low speed when conducting seismic surveys.
In addition, the maximum expected Level B harassment zone around the survey
vessel is 6,733 m for water depths greater than 1,000 m (and up to 10,100 m in water
depths of 100 to 1,000 m), with 78% of the survey occurring in depths greater than 1,000
m. Therefore, the ensonified area surrounding the vessel is relatively small compared to
the overall distribution of animals in the area and their use of the habitat. Feeding
behavior is not likely to be significantly impacted as prey species are mobile and are
broadly distributed throughout the survey area; therefore, marine mammals that may be
temporarily displaced during survey activities are expected to be able to resume foraging
once they have moved away from areas with disturbing levels of underwater noise.
Because of the short duration (14 survey days) and temporary nature of the disturbance
and the availability of similar habitat and resources in the surrounding area, the impacts
to marine mammals and marine mammal prey species are not expected to cause
significant or long-term fitness consequences for individual marine mammals or their
populations.
Additionally, the acoustic “footprint” of the survey is very small relative to the
ranges of all marine mammals that would potentially be affected. Sound levels will
increase in the marine environment in a relatively small area surrounding the vessel
compared to the range of the marine mammals within the survey area. The seismic array
will be active 24 hours per day throughout the duration of the planned survey. However,
the very brief overall duration of the planned survey (14 survey days) will further limit
potential impacts that may occur as a result of the activity.
Of the marine mammal species that are likely to occur in the project area, the
following species are listed as endangered under the ESA: humpback whales (Cape
Verde/Northwest Africa DPS), blue whales, fin whales, sei whales, and sperm whales.

The take numbers authorized for these species (table 6) are minimal relative to their
modeled population sizes; therefore, we do not expect population-level impacts to any of
these species. Moreover, the actual range of the populations extends past the area covered
by the model, so modeled population sizes are likely smaller than their actual population
size. The other marine mammal species that may be taken by harassment during NSF's
seismic survey are not listed as threatened or endangered under the ESA. There is no
designated critical habitat for any ESA-listed marine mammals within the project area.
There are no rookeries, mating, or calving grounds known to be biologically
important to marine mammals within the survey area, and there are no feeding areas
known to be biologically important to marine mammals within the survey area.
Marine Mammal Species with Active UMEs
As discussed above, there are several active unusual mortality events (UMEs) for
marine mammal populations that occur in the survey area. Elevated humpback whale
mortalities have occurred along the Atlantic coast from Maine through Florida since
January 2016. Of the cases examined, approximately half had evidence of human
interaction (ship strike or entanglement). The UME does not yet provide cause for
concern regarding population-level impacts. Only the West Indies DPS is potentially
impacted by this UME, and their current population remains stable at approximately
12,000 individuals.
The mitigation measures are expected to reduce, to the extent practicable, the
intensity and/or duration of takes for all species listed in table 1. In particular, they would
provide animals the opportunity to move away from the sound source throughout the
survey area before seismic survey equipment reaches full energy, thus, preventing them
from being exposed to sound levels that have the potential to cause injury (Level A
harassment) or more severe Level B harassment.

In summary and as described above, the following factors primarily support our
determination that the impacts resulting from this activity are not expected to adversely
affect any of the species or populations through effects on annual rates of recruitment or
survival:
●

No serious injury or mortality is anticipated or authorized;

●

We have authorized a limited number of Level A harassment events of

five species in the form of PTS; if any PTS is incurred as a result of the specified activity,
we expect only a small degree of PTS that would not result in severe hearing impairment
because of the constant movement of both the vessel and of the marine mammals in the
project areas, as well as the fact that the vessel is not expected to remain in any one area
in which individual marine mammals would be expected to concentrate for an extended
period of time;
●

The planned activity is temporary and of relatively short duration (38 days

total with 14 days of planned survey activity);
●

The vast majority of anticipated impacts of the planned activity on marine

mammals would be temporary behavioral changes due to avoidance of the ensonified
area, which is relatively small (see table 4);
●

The availability of alternative areas of similar habitat value for marine

mammals to temporarily vacate the survey area during the planned survey to avoid
exposure to sounds from the activity is readily abundant;
●

The potential adverse effects on fish or invertebrate species that serve as

prey species for marine mammals from the planned survey would be temporary and
spatially limited and impacts to marine mammal foraging would be minimal; and
●

The planned mitigation measures are expected to reduce the number and

severity of takes, to the extent practicable, by visually and/or acoustically detecting

marine mammals within the established zones and implementing corresponding
mitigation measures (e.g., delay; shutdown).
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 monitoring and mitigation measures, NMFS finds that the marine
mammal take from the planned activity will have a negligible impact on all affected
marine mammal species or populations.
Small Numbers
As noted previously, only take of small numbers of marine mammals may be
authorized under sections 101(a)(5)(A) and (D) of the MMPA for specified activities
other than military readiness activities. The MMPA does not define small numbers and
so, in practice, where estimated numbers are available, NMFS compares the number of
individuals taken to the most appropriate estimation of abundance of the relevant species
or population in our determination of whether an authorization is limited to small
numbers of marine mammals. When the predicted number of individuals to be taken is
fewer than one-third of the species or population abundance, the take is considered to be
of small numbers. Additionally, other qualitative factors may be considered in the
analysis, such as the temporal or spatial scale of the activities.
The number of takes NMFS authorized is below one-third of the modeled
abundance for all relevant populations (specifically, take of individuals is less than four
percent of the modeled abundance of each affected population, see table 6). This is
conservative because the modeled abundance represents a population of the species and
we assume all takes are of different individual animals, which is likely not the case. Some
individuals may be encountered multiple times in a day, but PSOs will count them as
separate individuals if they cannot be identified.

Based on the analysis contained herein of the planned activity, including the
mitigation and monitoring measures, and the authorized take of marine mammals, NMFS
finds that small numbers of marine mammals would be taken relative to the size of the
affected species or populations.
Unmitigable Adverse Impact Analysis and Determination
There are no relevant subsistence uses of the affected marine mammal stocks or
species implicated by this action. Therefore, NMFS has determined that the total taking
of affected species or stocks would not have an unmitigable adverse impact on the
availability of such species or stocks for taking for subsistence purposes.
Endangered Species Act
Section 7(a)(2) of the ESA of 1973 (16 U.S.C. 1531 et seq.) requires that each
Federal agency insure that any action it authorizes, funds, or carries out is not likely to
jeopardize the continued existence of any endangered or threatened species or result in
the destruction or adverse modification of designated critical habitat. To ensure ESA
compliance for the issuance of IHAs, NMFS consults internally whenever we propose to
authorize take for endangered or threatened species.
The NMFS OPR ESA Interagency Cooperation Division issued a Biological
Opinion under section 7 of the ESA, on the issuance of an IHA to NSF under section
101(a)(5)(D) of the MMPA by the NMFS OPR Permits and Conservation Division. The
Biological Opinion concluded that the action is not likely to jeopardize the continued
existence of ESA-listed humpback whales (Cape Verde/Northwest Africa DPS), blue
whales, fin whales, sei whales, and sperm whales. There is no designated critical habitat
in the action area for any ESA-listed marine mammal species.
National Environmental Policy Act

To comply with the NEPA of 1969 (42 U.S.C. 4321 et seq.) and NOAA
Administrative Order (NAO) 216-6A, NMFS must review our proposed action (i.e., the
issuance of an IHA) with respect to potential impacts on the human environment.
This action is consistent with categories of activities identified in Categorical
Exclusion B4 (IHAs with no anticipated serious injury or mortality) of the Companion
Manual for NOAA Administrative Order 216-6A, which do not individually or
cumulatively have the potential for significant impacts on the quality of the human
environment and for which we have not identified any extraordinary circumstances that
would preclude this categorical exclusion. Accordingly, NMFS has determined that the
issuance of the IHA qualifies to be categorically excluded from further NEPA review.
Authorization
MFS has issued an IHA to L-DEO for the potential harassment of small numbers
of 25 marine mammal species incidental to the marine geophysical survey at the
Reykjanes Ridge in the North Atlantic Ocean that includes the previously explained
mitigation, monitoring and reporting requirements.
Dated: June 27, 2024.
Kimberly Damon-Randall,
Director, Office of Protected Resources,
National Marine Fisheries Service.
[FR Doc. 2024-14578 Filed: 7/1/2024 8:45 am; Publication Date: 7/2/2024]