[Federal Register Volume 89, Number 191 (Wednesday, October 2, 2024)]
[Notices]
[Pages 80214-80227]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2024-22724]


-----------------------------------------------------------------------

DEPARTMENT OF COMMERCE

National Oceanic and Atmospheric Administration

[RTID 0648-XE190]


Takes of Marine Mammals Incidental to Specified Activities; 
Taking Marine Mammals Incidental to a Marine Geophysical Survey of the 
Chain Transform Fault in the Equatorial 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 Chain Transform Fault in the 
equatorial Atlantic Ocean.

DATES: The authorization is effective from September 27, 2024 through 
September 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-take-authorizations-research-and-other-activities. In case of problems accessing these documents, please 
call the contact listed below.

FOR FURTHER INFORMATION CONTACT: Jenna Harlacher, 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

[[Page 80215]]

taking for certain subsistence uses (referred to in shorthand as 
``mitigation''); and requirements pertaining to the monitoring and 
reporting of the takings. The definitions of all applicable MMPA 
statutory terms cited above are included in the relevant sections 
below.

Summary of Request

    On April 15, 2024, NMFS received a request from L-DEO for an IHA to 
take marine mammals incidental to conducting a marine geophysical 
survey of the Chain Transform Fault in the equatorial Atlantic Ocean. 
Following NMFS review of the application and additional clarifying 
information from L-DEO, NMFS deemed the application adequate and 
complete on May 22, 2024. L-DEO's request is for take of 28 marine 
mammal species by Level B harassment, and for take of 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 Activity

    Researchers from the Woods Hole Oceanographic Institution, 
University of Delaware, University of New Hampshire, Boise State 
University and Boston College, with funding from the National Science 
Foundation, 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 survey 
would occur at the Chain Transform Fault, off the coast of Africa, in 
the equatorial Atlantic Ocean during austral summer 2024 in the 
Southern Hemisphere (i.e., between October 2024 and February 2025). The 
survey would occur within International Waters more than 600 kilometers 
(km) in the Gulf of Guinea, Africa, in water depths ranging from 
approximately 2,000 to 5,500 meters (m). To complete this survey, the 
R/V Langseth would tow a 36-airgun array with a total discharge volume 
of approximately (~) 6,600 cubic inches (in\3\) at a depth of 9 to 12 
m. The airgun array receiving system would consist of a 15 km long 
solid-state hydrophone streamer and 20 Ocean Bottom Seismometers (OBS). 
The airguns would fire at a shot interval of 37.5 m (~18 seconds (s)) 
during seismic acquisition. Approximately 2,058 km of total survey 
trackline are planned. Airgun arrays would introduce underwater sounds 
that may result in take, by Level A and Level B harassment, of marine 
mammals.
    A detailed description of the planned geophysical survey was 
provided in the Federal Register notice of the proposed IHA (89 FR 
56158, July 8, 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 July 8, 2024 (89 FR 56158). That notice 
described, in detail, L-DEO'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.

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 regarding population trends and threats may be found in 
NMFS' Stock Assessment Reports (SARs; https://www.fisheries.noaa.gov/national/marine-mammal-protection/marine-mammal-stock-assessments) and 
more general 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. exclusive economic zone (EEZ) and therefore, are 
not assessed in NMFS' 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. 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 
International Whaling Commission (IWC) Population (Abundance) Estimates 
(IWC 2024). 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
----------------------------------------------------------------------------------------------------------------
                                                                                 ESA/MMPA
                                                                                  status;      Modeled abundance
           Common name               Scientific name            Stock          strategic (Y/          \2\
                                                                                  N) \1\
----------------------------------------------------------------------------------------------------------------
                             Order Artiodactyla--Cetacea--Mysticeti (baleen whales)
----------------------------------------------------------------------------------------------------------------
Family Balaenopteridae
 (rorquals):
    Blue Whale...................  Balaenoptera         NA..................  E, D, Y          \2\ 191/2,\4\ 300
                                    musculus.

[[Page 80216]]

 
    Fin Whale....................  Balaenoptera         NA..................  E, D, Y                     11,672
                                    physalus.
    Humpback Whale...............  Megaptera            NA..................  -, -, N              \2\ 4,990/\5\
                                    novaeangliae.                                                         42,000
    Common Minke Whale...........  Balaenoptera         NA..................  -, -, N                     13,784
                                    acutorostrata.
    Antarctic Minke Whale........  Balaenoptera         NA..................  -, -, N                \3\ 515,000
                                    bonaerensis.
    Sei Whale....................  Balaenoptera         NA..................  E, D, Y                     19,530
                                    borealis.
    Bryde's Whale................  Balaenoptera edeni.  NA..................  -, -, N                        536
----------------------------------------------------------------------------------------------------------------
                              Odontoceti (toothed whales, dolphins, and porpoises)
----------------------------------------------------------------------------------------------------------------
Family Physeteridae:
    Sperm Whale..................  Physeter             NA..................  E, D, Y                     64,015
                                    macrocephalus.
Family Kogiidae:
    Pygmy Sperm Whale............  Kogia breviceps....  NA..................  -, -, N                 \7\ 26,043
    Dwarf Sperm Whale............  Kogia sima.........  NA..................  -, -, N
Family Ziphiidae (beaked whales):
    Blainville's Beaked Whale....  Mesoplodon           NA..................  -, -, N                 \8\ 65,069
                                    densirostris.
    Cuvier's Beaked Whale........  Ziphius cavirostris  NA..................  -, -, N
    Gervais' Beaked Whale........  Mesoplodon           NA..................  -, -, N
                                    europaeus.
Family Delphinidae:
    Killer Whale.................  Orcinus orca.......  NA..................  -, -, N                        972
    Short-Finned Pilot Whale.....  Globicephala melas.  NA..................  -, -, N                \6\ 264,907
    Rough-toothed Dolphin........  Steno bredanensis..  NA..................  -, -, N                     32,848
    Bottlenose Dolphin...........  Tursiops truncatus.  NA..................  -, -, N                    418,151
    Risso's Dolphin..............  Grampus griseus....  NA..................  -, -, N                     78,205
    Common Dolphin...............  Delphinus delphis..  NA..................  -, -, N                    473,260
    Striped Dolphin..............  Stenella             NA..................  -, -, N                    412,729
                                    coeruleoalba.
    Pantropical Spotted Dolphin..  Stenella attenuata.  NA..................  -, -, N                    321,740
    Atlantic Spotted Dolphin.....  Stenella frontalis.  NA..................  -, -, N                    259,519
    Spinner Dolphin..............  Stenella             NA..................  -, -, N                    152,511
                                    longirostris.
    Clymene Dolphin..............  Stenella clymene...  NA..................  -, -, N                    181,209
    Fraser's Dolphin.............  Lagenodelphis hosei  NA..................  -, -, N                     19,585
    Melon-headed Whale...........  Peponocephala        NA..................  -, -, N                     64,114
                                    electra.
    Pygmy Killer Whale...........  Feresa attenuata...  NA..................  -, -, N                      9,001
    False Killer Whale...........  Pseudorca            NA..................  -, -, N                     12,682
                                    crassidens.
----------------------------------------------------------------------------------------------------------------
\1\ 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 Atlantic Fleet Training and Testing Area Marine Mammal Density (AFTT)
  (Roberts et al., 2023) unless otherwise noted.
\3\ Abundance of minke whales (species unspecified) for the Southern Hemisphere (IWC 2024)
\4\ Abundance of blue whales (excluding pygmy blue whales) for Southern Hemisphere (IWC 2024)
\5\ Abundance of humpback whales on Antarctic feeding grounds (IWC 2024)
\6\ Pilot whale guild.
\7\ Estimate includes dwarf and pygmy sperm whales.
\8\ Beaked whale guild.

    All 28 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 planned survey area are 
listed in section 3 of the application.
    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 56158, July 8, 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.). 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-

[[Page 80217]]

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                 Generalized hearing range *
------------------------------------------------------------------------
Low-frequency (LF) cetaceans (baleen   7 Hz to 35 kHz.
 whales).
Mid-frequency (MF) cetaceans           150 Hz to 160 kHz.
 (dolphins, toothed whales, beaked
 whales, bottlenose whales).
High-frequency (HF) cetaceans (true    275 Hz to 160 kHz.
 porpoises, Kogia, river dolphins,
 Cephalorhynchid, Lagenorhynchus
 cruciger & L. australis).
Phocid pinnipeds (PW) (underwater)     50 Hz to 86 kHz.
 (true seals).
Otariid pinnipeds (OW) (underwater)    60 Hz to 39 kHz.
 (sea lions and fur seals).
------------------------------------------------------------------------
* 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 
56158, July 8, 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 56158, July 8, 2024).

Estimated Take of Marine Mammals

    This section provides an estimate of the number of incidental takes 
authorized through the IHA, which will inform 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).
    Anticipated takes would primarily be by Level B harassment, as the 
noise from 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 (LF and HF) 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 or serious 
injury 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). Acoustic thresholds used in 
this analysis were discussed in detail in the notice of proposed IHA 
(89 FR 56158, July 8, 2024) and not repeated here. Please see that 
notice for additional detail.

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

[[Page 80218]]

qualitatively address the output where appropriate.
    The planned survey would entail the use of a 36-airgun array with a 
total discharge volume of 6,600 in\3\ at a tow depth of 9 m to 12 m. L-
DEO's model results are used to determine the 160 dB root mean square 
(rms) 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 sound pressure 
level (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 L-DEO 
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 would acquire data with the 36-
airgun array at a tow depth of 9 to 12 m. For this survey, which occurs 
only in 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.
    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 airgun configuration are shown in table 3.

  Table 3--Predicted Radial Distances From the R/V Langseth Seismic Source to Isopleth Corresponding to Level B
                                              Harassment Threshold
----------------------------------------------------------------------------------------------------------------
                                                                                                   Predicted
                                                                                               distances (in m)
                Airgun configuration                   Tow depth (m) \1\    Water depth (m)     to the Level B
                                                                                                  harassment
                                                                                                   threshold
----------------------------------------------------------------------------------------------------------------
4 strings, 36 airguns, 6,600 in\3\..................                 12              >1,000           \2\ 6,733
----------------------------------------------------------------------------------------------------------------
\1\ Maximum tow depth was used for conservative distances.
\2\ Distance is based on L-DEO model results.


          Table 4--Modeled Radial Distance to Isopleths Corresponding to Level A Harassment Thresholds
----------------------------------------------------------------------------------------------------------------
                                                           Low frequency      Mid frequency      High frequency
                                                             cetaceans          cetaceans          cetaceans
----------------------------------------------------------------------------------------------------------------
PTS SELcum.............................................              426.9                  0                1.3
PTS Peak...............................................               38.9               13.6              268.3
----------------------------------------------------------------------------------------------------------------
The largest distance (in bold) of the dual criteria (cumulative sound exposure level (SELcum) or Peak) was used
  to estimate threshold distances and potential takes by Level A harassment.

    Table 4 presents the modeled PTS isopleths for each cetacean 
hearing group based on L-DEO modeling incorporated in the companion 
user spreadsheet, for the high-energy 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 
SEL<INF>cum</INF> 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 SEL<INF>cum</INF> metric 
considers both level and duration of exposure, as well as auditory 
weighting functions by marine mammal hearing group.
    The SEL<INF>cum</INF> 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

[[Page 80219]]

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 the 
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 referenced to 1 micropascal (re 1 [micro]Pa) 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. As the AFTT model does not 
overlap the planned survey area, the average densities in the grid 
cells for the AFTT area that encompassed a similar-sized area as the 
planned survey area in the southeastern-most part of the AFTT area were 
used (between ~21.1[deg] N-22.5[deg] N and ~45.1[deg] W-49.5[deg] W). 
Even though these densities are for the western Atlantic Ocean, they 
are for an area of the Mid-Atlantic Ridge, which would be most 
representative of densities occurring at the Mid-Atlantic Ridge in the 
planned survey area. More information is available online at https://seamap.env.duke.edu/models/Duke/AFTT/.
    Since there was no density data available for the actual survey 
area, L-DEO used OBIS sightings, available literature, and regional 
distribution maps of the actual survey area (or greater region) to 
determine which species would be expected to be encountered in the 
survey area. From the AFTT models, L-DEO excluded the following 
species, as they were not expected to occur in the survey area: seals, 
northern bottlenose whales, North Atlantic right whale (these had 
densities of zero) and harbor porpoise, white-beaked dolphin, and 
Atlantic white-sided dolphin (these species had non-zero densities). 
There were no additional species that might occur in the survey area 
that were not available in the AFTT model.
    For most species, only annual densities were available. For some 
baleen whale species (fin, sei and humpback whale), monthly densities 
were available. For these species, the highest monthly densities were 
used. Densities for fin whales were near zero and the calculations did 
not result in any estimated takes. However, because this species could 
be encountered in the survey area, we authorize take of one individual.

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 (11.5) 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 authorized 
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), we have added L-
DEO'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 is 
authorized. Estimated exposures and authorized take numbers are shown 
in table 5.

[[Page 80220]]



                                                                Table 5--Authorized Take
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                  Estimated take                  Authorized take
                         Species                         ----------------------------------------------------------------     Modeled       Percent of
                                                              Level B         Level A         Level B         Level A      abundance \1\   abundance \2\
--------------------------------------------------------------------------------------------------------------------------------------------------------
Humpback whale..........................................              39               2              39               2           4,990            0.82
Bryde's whale...........................................               4               0               4               0             536            0.75
Minke whale \3\.........................................              23               1              23               1          13,784            0.17
Fin whale...............................................               0               0               1               0          11,672            0.01
Sei whale...............................................              11               1              11               1          19,530            0.06
Blue whale..............................................               1               0               1               0             191            0.52
Sperm whale.............................................             110               0             110               0          64,015            0.17
Beaked whales \4\.......................................             106               0             106               0          65,069            0.16
Risso's dolphin.........................................              88               0              88               0          78,205            0.11
Rough-toothed dolphin...................................             166               0             166               0          32,848            0.51
Bottlenose dolphin......................................           1,229               2           1,231               0         418,151            0.30
Pantropical spotted dolphin.............................              46               0          \7\ 76               0         321,740            0.02
Atlantic spotted dolphin................................             435               1             436               0         259,519            0.17
Spinner dolphin.........................................             898               2             900               0         152,511            0.59
Striped dolphin.........................................              55               0          \7\ 73               0         412,729            0.02
Clymene dolphin.........................................           1,038               2           1,040               0         181,209            0.57
Fraser's dolphin........................................             110               0             110               0          19,585            0.56
Common dolphin..........................................              27               0          \7\ 92               0         473,206            0.02
Short-finned pilot whale \5\............................           1,301               2           1,303               0         264,907            0.49
Melon-headed whale......................................             502               1             503               0          64,114            0.78
False killer whale......................................              99               0              99               0          12,682            0.78
Pygmy killer whale......................................              71               0              71               0           9,001            0.79
Killer whale............................................               1               0           \7\ 5               0             972            0.51
Kogia spp \6\...........................................             122               5             122               5          26,043            0.49
--------------------------------------------------------------------------------------------------------------------------------------------------------
\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 only (Roberts et al. 2023).
\3\ Takes assigned equally between Common minke whales (11 Level B takes and 1 Level A take) and Antarctic minke whales (12 Level B takes).
\4\ Beaked whale guild. Includes Cuvier's beaked whale, Blaineville's beaked whale, and Gervais' beaked whale.
\5\ Takes based on density for Globicephala sp. All takes are assumed to be for short-finned pilot whales.
\6\ Kogia spp. Includes Pygmy sperm whale and Dwarf sperm whale.
\7\ Takes rounded to a mean group size (Weir 2011).

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

[[Page 80221]]

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[deg] 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 visual 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 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 would 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 would 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:
    <bullet> Sea state is less than or equal to BSS 4;
    <bullet> No marine mammals (excluding delphinids) detected solely 
by PAM in the SZ in the previous 2 hours;
    <bullet> 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
    <bullet> 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 would establish a minimum SZ with a 500-m radius. The 500-m SZ 
would 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 would 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 
SEL<INF>cum</INF> 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, 
Kogia spp, 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

[[Page 80222]]

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, Kogia spp, 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 the 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 stepwise 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:
    <bullet> 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 pre-start clearance zone 
(and extended SZ) for 30 minutes prior to the initiation of ramp-up 
(pre-start clearance);
    <bullet> Ramp-ups shall be scheduled so as to minimize the time 
spent with the source activated prior to reaching the designated run-
in;
    <bullet> 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;
    <bullet> 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 30 minutes for all 
mysticetes and all other odontocetes, including sperm whales, beaked 
whales, and large delphinids, such as pilot whales);
    <bullet> 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;
    <bullet> 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;
    <bullet> 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;
    <bullet> 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
    <bullet> 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 
watch 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 the 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 would not resume until the 
marine mammal has cleared the SZ. The animal would 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 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 the 
specific genera of small dolphins (Delphinus, Lagenodelphis, Stenella, 
Steno and Tursiops).
    We include this 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 mid-frequency

[[Page 80223]]

cetaceans (e.g., 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 
R/V 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 mid-frequency 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 R/V 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 an extended 
shutdown of 1,500 m 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.

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 large whale (defined in this context as 
sperm whales or baleen whales), or other marine mammals.
    Vessel speeds must be reduced to 10 kn (18.5 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 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.
    L-DEO must use dedicated, trained, and NMFS-approved PSOs. The PSOs 
must have no tasks other than to conduct observational effort, record 
observational data, and communicate with and instruct relevant vessel 
crew with regard to the presence of marine mammals and mitigation 
requirements. PSO resumes shall be provided to NMFS for advance 
approval (prior to embarking on the vessel).
    At least one of the visual and two of the acoustic PSOs (discussed 
below) 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.
    Monitoring and reporting requirements prescribed by NMFS

[[Page 80224]]

should contribute to improved understanding of one or more of the 
following:
    <bullet> Occurrence of marine mammal species or stocks in the area 
in which take is anticipated (e.g., presence, abundance, distribution, 
density);
    <bullet> 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);
    <bullet> Individual marine mammal responses (behavioral or 
physiological) to acoustic stressors (acute, chronic, or cumulative), 
other stressors, or cumulative impacts from multiple stressors;
    <bullet> How anticipated responses to stressors impact either: (1) 
long-term fitness and survival of individual marine mammals; or (2) 
populations, species, or stocks;
    <bullet> Effects on marine mammal habitat (e.g., marine mammal prey 
species, acoustic habitat, or other important physical components of 
marine mammal habitat); and,
    <bullet> Mitigation and monitoring effectiveness.

Vessel-Based Visual Monitoring

    As described above, PSO observations would take place during 
daytime airgun operations. During seismic survey operations, at least 
five visual PSOs would be based aboard the R/V Langseth. Two visual 
PSOs would be on duty at all times during daytime hours. Monitoring 
shall be conducted in accordance with the following requirements:
    <bullet> The operator shall provide PSOs with bigeye reticle 
binoculars (e.g., 25 x 150; 2.7 view angle; individual ocular focus; 
height control) of appropriate quality solely for PSO use. These 
binoculars 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
    <bullet> 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:
    <bullet> PSOs shall be independent, dedicated, trained visual and 
acoustic PSOs and must be employed by a third-party observer provider;
    <bullet> 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);
    <bullet> 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;
    <bullet> 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;
    <bullet> 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;
    <bullet> 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;
    <bullet> 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
    <bullet> 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.
    <bullet> 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:
    [cir] Vessel name, vessel size and type, maximum speed capability 
of vessel;
    [cir] Dates (MM/DD/YYYY) of departures and returns to port with 
port name;
    [cir] PSO names and affiliations, PSO ID (initials or other 
identifier);
    [cir] Date (MM/DD/YYYY) and participants of PSO briefings;
    [cir] Visual monitoring equipment used (description);
    [cir] PSO location on vessel and height (meters) of observation 
location above water surface;
    [cir] Watch status (description);
    [cir] 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;
    [cir] Vessel location (decimal degrees) when survey effort began 
and ended and vessel location at beginning and end of visual PSO duty 
shifts;
    [cir] Vessel location (decimal degrees) at 30-second intervals if 
obtainable from data collection software, otherwise at practical 
regular interval;
    [cir] Vessel heading (compass heading) and speed (knots) at 
beginning and end of visual PSO duty shifts and upon any change;
    [cir] Water depth (meters) (if obtainable from data collection 
software);
    [cir] 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;
    [cir] 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
    [cir] Vessel/Survey activity information (and changes thereof) 
(description),

[[Page 80225]]

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.).
    <bullet> Upon visual observation of any marine mammals, the 
following information must be recorded:
    [cir] Sighting ID (numeric);
    [cir] Watch status (sighting made by PSO on/off effort, 
opportunistic, crew, alternate vessel/platform);
    [cir] Location of PSO/observer (description);
    [cir] Vessel activity at the time of the sighting (e.g., deploying, 
recovering, testing, shooting, data acquisition, other);
    [cir] PSO who sighted the animal/ID;
    [cir] Time/date of sighting (GMT/UTC, MM/DD/YYYY);
    [cir] Initial detection method (description);
    [cir] Sighting cue (description);
    [cir] Vessel location at time of sighting (decimal degrees);
    [cir] Water depth (meters);
    [cir] Direction of vessel's travel (compass direction);
    [cir] Speed (knots) of the vessel from which the observation was 
made;
    [cir] Direction of animal's travel relative to the vessel 
(description, compass heading);
    [cir] Bearing to sighting (degrees);
    [cir] 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;
    [cir] Species reliability (an indicator of confidence in 
identification) (1 = unsure/possible, 2 = probable, 3 = definite/sure, 
9 = unknown/not recorded);
    [cir] Estimated distance to the animal (meters) and method of 
estimating distance;
    [cir] Estimated number of animals (high/low/best) (numeric);
    [cir] Estimated number of animals by cohort (adults, yearlings, 
juveniles, calves, group composition, etc.);
    [cir] 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);
    [cir] 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);
    [cir] Animal's closest point of approach (meters) and/or closest 
distance from any element of the airgun array;
    [cir] Description of any actions implemented in response to the 
sighting (e.g., delays, shutdown, ramp-up) and time and location of the 
action.
    [cir] Photos (Yes/No);
    [cir] Photo Frame Numbers (List of numbers); and
    [cir] Conditions at time of sighting (Visibility; Beaufort Sea 
State).
    If a marine mammal is detected while using the PAM system, the 
following information should be recorded:
    <bullet> An acoustic encounter identification number, and whether 
the detection was linked with a visual sighting;
    <bullet> Date and time when first and last heard;
    <bullet> Types and nature of sounds heard (e.g., clicks, whistles, 
creaks, burst pulses, continuous, sporadic, strength of signal); and
    <bullet> 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 time-stamped 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. 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) as soon as feasible. The report must include 
the following information:
    <bullet> Time, date, and location (latitude/longitude) of the first 
discovery (and updated location information if known and applicable);
    <bullet> Species identification (if known) or description of the 
animal(s) involved;
    <bullet> Condition of the animal(s) (including carcass condition if 
the animal is dead);
    <bullet> Observed behaviors of the animal(s), if alive;
    <bullet> If available, photographs or video footage of the 
animal(s); and
    <bullet> General circumstances under which the animal was 
discovered.
    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 as soon as feasible. The report must 
include the following information:
    <bullet> Time, date, and location (latitude/longitude) of the 
incident;
    <bullet> Vessel's speed during and leading up to the incident;
    <bullet> Vessel's course/heading and what operations were being 
conducted (if applicable);
    <bullet> Status of all sound sources in use;
    <bullet> 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;
    <bullet> Environmental conditions (e.g., wind speed and direction, 
BSS, cloud cover, visibility) immediately preceding the strike;
    <bullet> Species identification (if known) or description of the 
animal(s) involved;
    <bullet> Estimated size and length of the animal that was struck;

[[Page 80226]]

    <bullet> Description of the behavior of the marine mammal 
immediately preceding and following the strike;
    <bullet> If available, description of the presence and behavior of 
any other marine mammals present immediately preceding the strike;
    <bullet> 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
    <bullet> 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 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 are authorizing a limited number of Level A harassment events of 
five species in the form of PTS (humpback whale, minke whale, sei 
whale, and Kogia spp (i.e., pygmy and dwarf sperm whales)) and Level B 
harassment of all 28 marine mammal species (table 5. 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 R/V 
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 would 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 R/V 
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. 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 (11.5 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 planned survey 
would be very small relative to the ranges of all marine mammals that 
would potentially be affected. Sound levels would 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 would be active 24 hours per day throughout the duration 
of the survey. However, the very brief overall duration of the survey 
(30 survey days) would 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: blue whales, fin whales, sei whales, and sperm whales. The take 
numbers authorized for these species (table 5) 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 
L-DEO'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.
    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

[[Page 80227]]

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:
    <bullet> No serious injury or mortality is anticipated or 
authorized;
    <bullet> We are authorizing 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.
    <bullet> The activity is temporary and of relatively short duration 
(11.5 days of planned survey activity);
    <bullet> The vast majority of anticipated impacts of the activity 
on marine mammals would be temporary behavioral changes due to 
avoidance of the ensonified area, which is relatively small (see table 
3);
    <bullet> The availability of alternative areas of similar habitat 
value for marine mammals to temporarily vacate the survey area during 
the survey to avoid exposure to sounds from the activity is readily 
abundant;
    <bullet> The potential adverse effects on fish or invertebrate 
species that serve as prey species for marine mammals from the survey 
would be temporary and spatially limited and impacts to marine mammal 
foraging would be minimal;
    <bullet> The 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 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 
stock 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 stock 
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 is authorizing is below one-third of the 
most appropriate abundance estimate for all relevant populations 
(specifically, take of individuals is less than 1 percent of the 
modeled abundance of each affected population, see table 5). 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 would 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 anticipated 
take of marine mammals, NMFS finds that small numbers of marine mammals 
would be taken relative to the population size of the affected species 
or stocks.

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 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 National Environmental Policy Act of 1969 (NEPA; 
42 U.S.C. 4321 et seq.) and NOAA Administrative Order (NAO) 216-6A, 
NMFS must review our 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 NAO 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

    NMFS has issued an IHA to L-DEO for the potential harassment of 
small numbers of 28 marine mammal species incidental to the marine 
geophysical survey at the Chain Transform Fault in the equatorial 
Atlantic Ocean that includes the previously explained mitigation, 
monitoring and reporting requirements.

    Dated: September 27, 2024.
Kimberly Damon-Randall,
Director, Office of Protected Resources, National Marine Fisheries 
Service.
[FR Doc. 2024-22724 Filed 10-1-24; 8:45 am]
BILLING CODE 3510-22-P