Rule2026-07536
Taking and Importing Marine Mammals; Taking Marine Mammals Incidental to Geophysical Surveys in the Gulf of America
Primary source
Metadata and text below are from the Federal Register, a public-domain U.S. government work. Always verify the official published version before relying on it for any legal matter.
Published
April 17, 2026
Effective
April 20, 2026
Issuing agencies
Commerce DepartmentNational Oceanic and Atmospheric Administration
Abstract
In accordance with the regulations implementing the Marine Mammal Protection Act (MMPA), as amended, notification is hereby given that NMFS promulgates regulations to govern the incidental taking of marine mammals during geophysical survey activity conducted in the Gulf of America (GOA), over the course of 5 years. These regulations, which allow for the issuance of Letters of Authorization (LOA) to survey operators for the incidental take of marine mammals during the described activities and specified timeframe, prescribe the permissible methods of taking and other means of effecting the least practicable adverse impact on marine mammal species or stocks and their habitat, as well as requirements pertaining to the monitoring and reporting of such taking.
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<title>Federal Register, Volume 91 Issue 74 (Friday, April 17, 2026)</title>
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[Federal Register Volume 91, Number 74 (Friday, April 17, 2026)]
[Rules and Regulations]
[Pages 20784-20858]
From the Federal Register Online via the Government Publishing Office [<a href="http://www.gpo.gov">www.gpo.gov</a>]
[FR Doc No: 2026-07536]
[[Page 20783]]
Vol. 91
Friday,
No. 74
April 17, 2026
Part II
Department of Commerce
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National Oceanic and Atmospheric Administration
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50 CFR Part 217
Taking and Importing Marine Mammals; Taking Marine Mammals Incidental
to Geophysical Surveys in the Gulf of America; Final Rule
Federal Register / Vol. 91 , No. 74 / Friday, April 17, 2026 / Rules
and Regulations
[[Page 20784]]
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DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
50 CFR Part 217
[Docket No. 260414-0101]
RIN 0648-BO19
Taking and Importing Marine Mammals; Taking Marine Mammals
Incidental to Geophysical Surveys in the Gulf of America
AGENCY: National Marine Fisheries Service (NMFS), National Oceanic and
Atmospheric Administration (NOAA), Commerce.
ACTION: Final rule.
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SUMMARY: In accordance with the regulations implementing the Marine
Mammal Protection Act (MMPA), as amended, notification is hereby given
that NMFS promulgates regulations to govern the incidental taking of
marine mammals during geophysical survey activity conducted in the Gulf
of America (GOA), over the course of 5 years. These regulations, which
allow for the issuance of Letters of Authorization (LOA) to survey
operators for the incidental take of marine mammals during the
described activities and specified timeframe, prescribe the permissible
methods of taking and other means of effecting the least practicable
adverse impact on marine mammal species or stocks and their habitat, as
well as requirements pertaining to the monitoring and reporting of such
taking.
DATES: Effective from April 20, 2026, through April 19, 2031.
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: <a href="https://www.fisheries.noaa.gov/action/incidental-take-authorization-oil-and-gas-industry-geophysical-survey-activity-gulf-america">https://www.fisheries.noaa.gov/action/incidental-take-authorization-oil-and-gas-industry-geophysical-survey-activity-gulf-america</a>. In case of problems accessing these documents,
please call the contact listed below.
FOR FURTHER INFORMATION CONTACT: Ben Laws, Office of Protected
Resources, NMFS, (301) 427-8401.
SUPPLEMENTARY INFORMATION:
Purpose and Need for Regulatory Action
On January 19, 2021 (86 FR 5322), in response to a petition request
from the Bureau of Ocean Energy Management (BOEM), NMFS issued a final
rule implementing incidental take regulations (ITRs) under the MMPA, 16
U.S.C. 1361 et seq., governing the take of marine mammals incidental to
the conduct of geophysical survey activities in the GOA.\1\ The ITRs
provide a framework for authorization of incidental take through LOAs
upon request from individual applicants planning specific geophysical
survey activities. The ITRs became effective on April 19, 2021, and are
effective through April 19, 2026 (86 FR 5322, January 19, 2021).
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\1\ Pursuant to Executive Order 14172, ``Restoring Names That
Honor American Greatness,'' and Department of the Interior
Secretarial Order 3423, ``The Gulf of America,'' the body of water
formerly known as the Gulf of Mexico is now called the Gulf of
America. Accordingly, NMFS amended the incidental take regulations
to reflect the change. See 90 FR 38001 (August 7, 2025).
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NMFS subsequently discovered that the 2021 rule was based on
erroneous take estimates. We conducted another rulemaking to reassess
the statutorily required findings for issuance of the 2021 ITRs using
correct take estimates and other newly available and pertinent
information relevant to the analyses supporting some of the findings in
the 2021 final rule and the taking allowable under the regulations. We
issued a final rule affirming those findings in April 2024, effective
through April 19, 2026 (89 FR 31488, April 24, 2024). The 2024 rule did
not result in any changes to the existing ITRs.
On March 25, 2025, NMFS received an application from the EnerGeo
Alliance (EnerGeo) requesting development of ITRs governing the taking
of marine mammals incidental to geophysical survey activity conducted
in the GOA over the course of 5 years following the expiration of the
existing ITRs. Following receipt of NMFS' comments on the draft
application on April 15, 2025, EnerGeo submitted revised versions of
the application on July 14, August 8, and August 12, 2025, the last of
which was determined to be adequate and complete. NMFS determined at
that time, based on the date of submission of the adequate and complete
application, that it was unlikely a new rulemaking process could be
completed prior to expiration of the existing ITRs on April 19, 2026.
On August 28, 2025, NMFS Office of Protected Resources (OPR)
received a request from NMFS Office of Policy (Policy) for
reimplementation of the current ITRs to avoid a lapse in ITRs offering
incidental take coverage for GOA geophysical survey activities. The
request notes that the pending April 2026 expiration of the current
ITRs would affect regulatory certainty through loss of an efficient
permitting framework, and that reimplementation of the existing ITRs on
the basis of the same specified activity defined in the initial 2021
final rule and associated estimates of incidental take evaluated in the
2024 corrective rulemaking is consistent with the MMPA and appropriate
pursuant to Executive Orders 14156, ``Declaring a National Energy
Emergency,'' and 14154, ``Unleashing American Energy.'' On October 20,
2025, BOEM (the original petitioner for the current ITRs) submitted a
request to be included in the process as a co-petitioner.
NMFS has received multiple requests from industry survey operators
relating to specific survey activities that would extend beyond the
expiration date of the current ITRs, establishing the ongoing need for
the ITRs. The reimplementation of the regulations in effect continues
the current established framework for authorization of incidental take
through LOAs until superseded by new ITRs promulgated on the basis of
the separate EnerGeo request.
Legal Authority for the Action
Section 101(a)(5)(A) of the MMPA (16 U.S.C. 1371(a)(5)(A)) directs
the Secretary of Commerce 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 for up to 5 years if,
after notice and public comment, the agency makes certain findings and
issues regulations that set forth permissible methods of taking
pursuant to that activity and other means of effecting the ``least
practicable adverse impact'' (LPAI) on the affected species or stocks
and their habitat (see the discussion below in the Proposed Mitigation
section), as well as monitoring and reporting requirements. Under NMFS'
implementing regulations for section 101(a)(5)(A), NMFS issues LOAs to
individuals (including entities) seeking authorization for take under
the activity-specific incidental take regulations (50 CFR 216.106).
Severability
In the event a court were to invalidate some but not all aspects of
NMFS' small numbers interpretation/application, NMFS intends that the
remaining aspects of the rule and ITRs be severable to the extent
possible. The extent to which this is possible may depend on which
aspect is invalidated. The small numbers standard is a statutory
requirement that could be satisfied on an LOA-by-LOA basis in
accordance with the ruling of a court if for example the court upholds
NMFS' LOA-by-LOA
[[Page 20785]]
aspect of our interpretation but rules adversely on other aspects of
our small numbers interpretation.
Importantly, the negligible impact analysis for this 5-year rule is
the biologically relevant inquiry, and that analysis is based on the
total annual estimated taking for all activities the regulations will
govern over the five-year period. Our ability to issue LOAs to allow
the incidental take of marine mammals, subject to the mitigation,
monitoring, and reporting requirements, is based on our findings in
this final rule that the total taking over the five-year period of the
rule will have a negligible impact on the affected species or stocks;
that the mitigation and related monitoring required in the ITRs will
effect the least practicable adverse impact on those species or stocks;
and our determination in this rule that any LOA we issue must not
involve taking that exceeds one-third of the abundance for that species
or stock.
Summary of Major Provisions Within the Regulations
Following is a summary of the major provisions of this final rule
regarding geophysical survey activities. The regulations contain
requirements for mitigation, monitoring, and reporting, including:
<bullet> Standard detection-based mitigation measures, including
use of visual and acoustic observation to detect marine mammals and
shutdown of acoustic sources in certain circumstances;
<bullet> A time-area restriction designed to avoid effects to
bottlenose dolphins in times and places of particular importance;
<bullet> Vessel strike avoidance measures; and
<bullet> Monitoring and reporting requirements.
These measures are unchanged from those included in the current
ITRs. See 50 CFR 217.180 et seq.
Background
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 issued or, if
the taking is limited to harassment, a notice of a proposed
authorization is provided to the public for review.
An incidental take authorization shall be granted if NMFS finds
that the taking will have a negligible impact on the species or
stock(s), will not have an unmitigable adverse impact on the
availability of the species or stock(s) for subsistence uses (where
relevant), and if the permissible methods of taking and requirements
pertaining to the mitigation, monitoring, and reporting of such takings
are set forth.
NMFS has defined ``negligible impact'' in 50 CFR 216.103 as an
impact resulting from the specified activity that cannot be reasonably
expected to, and is not reasonably likely to, adversely affect the
species or stock through effects on annual rates of recruitment or
survival. The MMPA states that the term ``take'' means to harass, hunt,
capture, kill or attempt to harass, hunt, capture, or kill any marine
mammal.
Except with respect to certain activities not pertinent here, the
MMPA defines ``harassment'' as: any act of pursuit, torment, or
annoyance, which (i) has the potential to injure a marine mammal or
marine mammal stock in the wild (Level A harassment); or (ii) has the
potential to disturb a marine mammal or marine mammal stock in the wild
by causing disruption of behavioral patterns, including, but not
limited to, migration, breathing, nursing, breeding, feeding, or
sheltering (Level B harassment).
On January 19, 2021, we issued a final rule with ITRs to govern the
unintentional taking of marine mammals incidental to geophysical survey
activities conducted in U.S. waters of the GOA over the course of the
statutory maximum of 5 years (86 FR 5322, January 19, 2021). NMFS
subsequently discovered that the 2021 rule was based on erroneous take
estimates. We conducted another rulemaking to reassess the statutorily
required findings for issuance of the 2021 ITRs using correct take
estimates and other newly available and pertinent information relevant
to the analyses supporting some of the findings in the 2021 final rule
and the taking allowable under the regulations. We issued a final rule
affirming those findings in April 2024 (89 FR 31488, April 24, 2024).
The 2024 rule did not result in any changes to the existing ITRs, which
provide a framework for authorization of incidental take through LOAs
upon request from individual applicants planning specific geophysical
survey activities. The existing ITRs are in effect through April 19,
2026.
On March 25, 2025, NMFS received an application from EnerGeo
requesting development of ITRs governing the taking of marine mammals
incidental to geophysical survey activity conducted in the GOA over the
course of 5 years following the date of issuance. Following receipt of
NMFS' comments on the draft application on April 15, 2025, EnerGeo
submitted revised versions of the application on July 14, August 8, and
August 12, 2025. On September 24, 2025 (90 FR 45936), we published a
notice of receipt of the request in the Federal Register, requesting
comments and information related to the request.
On August 28, 2025, NMFS OPR received a request from NMFS Policy
for reimplementation of the current ITRs. The request notes that the
pending April 2026 expiration of the current ITRs would affect
regulatory certainty with loss of an efficient permitting framework,
and that reimplementation of the existing ITRs on the basis of the same
specified activity and activity levels defined in the initial 2021
final rule and associated estimates of incidental take evaluated in the
2024 corrective rulemaking is consistent with the MMPA and appropriate
pursuant to Executive Orders 14156, ``Declaring a National Energy
Emergency,'' and 14154, ``Unleashing American Energy.'' On September 3,
2025 (90 FR 42569), we published a notice of receipt of the request in
the Federal Register, requesting comments and information related to
the request. All comments received are available online at: <a href="https://www.fisheries.noaa.gov/action/incidental-take-authorization-oil-and-gas-industry-geophysical-survey-activity-gulf-america">https://www.fisheries.noaa.gov/action/incidental-take-authorization-oil-and-gas-industry-geophysical-survey-activity-gulf-america</a>. Among the
comments was a letter from EnerGeo and other industry trade
associations expressing support for NMFS' proposed issuance of
reimplemented ITRs until superseded by new ITRs promulgated on the
basis of the separate EnerGeo request. Please see the letters for full
comments.
On October 20, 2025, BOEM (the original petitioner for the current
ITRs) submitted a request to be included in the process as a co-
petitioner, expressing support for the requested reimplementation of
the existing ITRs. Both the NMFS Policy and BOEM requests are available
online at: <a href="https://www.fisheries.noaa.gov/action/incidental-take-authorization-oil-and-gas-industry-geophysical-survey-activity-gulf-america">https://www.fisheries.noaa.gov/action/incidental-take-authorization-oil-and-gas-industry-geophysical-survey-activity-gulf-america</a>.
This final rule provides analysis of the same activities and
activity levels considered for the 2021 final rule, which were
unchanged in the 2024 final rule, and utilizes the same modeling
methodology described in the 2024 final rule. We incorporate the best
available information, including information that was newly evaluated
in the 2024 final rule and any information that is newly available
since issuance of the 2024
[[Page 20786]]
final rule. The 2024 final rule incorporated expanded modeling results
relative to the 2021 final rule that estimate take utilizing the
existing methodology but also consider the effects of using smaller
airgun arrays (relative to the proxy source originally defined by BOEM)
that are currently prevalent as evidenced by LOA applications received
by NMFS to date (see <a href="https://www.fisheries.noaa.gov/action/incidental-take-authorization-oil-and-gas-industry-geophysical-survey-activity-gulf-america">https://www.fisheries.noaa.gov/action/incidental-take-authorization-oil-and-gas-industry-geophysical-survey-activity-gulf-america</a>).
There are no changes to the nature or level of the specified
activities within or across years or to the geographic scope of the
activity. There is no new information pertaining to the estimates of
marine mammal take presented in the 2024 final rule and, therefore, no
changes to those take numbers. Based on our assessment of the specified
activity in light of the 2024 revised take estimates and other new
information, we have determined that the proposed ITRs, which
reimplements the current ITRs and includes the required mitigation and
associated monitoring measures, satisfies the MMPA requirement to
prescribe the means of effecting the LPAI on the affected species or
stocks and their habitat, and contains the requirements pertaining to
monitoring and reporting.
Summary of the Action
This final rule provides analysis of the same activities and
activity levels considered for the 2024 final rule and utilizes the
same modeling methodology described in the 2024 final rule. There are
no changes to the nature or level of the specified activities within or
across years or to the geographic scope of the activity. Based on our
assessment of the specified activity in light of the take estimates,
which remain unchanged, we have determined that the total taking over
the five-year period of the specified activity will have a negligible
impact on the affected species or stocks of marine mammals.\2\
Additionally, the regulations promulgated here satisfy the MMPA
requirement to prescribe the means of effecting the least practicable
adverse impact on the affected species or stocks and their habitat and
contain monitoring and reporting requirements pertaining to the taking.
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\2\ There are no relevant subsistence uses implicated by this
action. Therefore the taking from the specified activity will not
have an unmitigable adverse impact on the availability of the
species for taking for relevant subsistence uses. See 16 U.S.C.
1371(a)(5)(A).
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Description of the Specified Activity
Overview
The specified activity for this action as requested by the NMFS'
Policy petition is unchanged from the specified activity considered for
the 2021 and 2024 rules, consisting of geophysical surveys conducted
for a variety of reasons. Actual total amounts of effort (including by
survey type and location) are not known in advance of receiving LOA
requests, but take in excess of what is analyzed in this rule would not
be authorized. Applicants seeking authorization for take of marine
mammals incidental to survey activities outside the geographic scope of
the rule (i.e., within the former Gulf of Mexico Energy Security Act
(GOMESA) (Sec. 104, Pub. L. 109-432) \3\ moratorium area) would need to
pursue a separate MMPA incidental take authorization (see figure 1).
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\3\ The Congressional moratorium in GOMESA was in place until
June 30, 2022. On September 8, 2020, the President withdrew, under
section 12 of the Outer Continental Shelf Lands Act, the same area
covered by the prior GOMESA moratorium from disposition by leasing
for 10 years, beginning on July 1, 2022, and ending on June 30,
2032.
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EnerGeo's 2025 ITR petition suggests that the existing level of
effort estimates, by survey type and location, are a reasonable
representation of the activities expected to occur under our final ITR
reimplementation rule (which EnerGeo supports). EnerGeo's petition,
available online at: <a href="https://www.fisheries.noaa.gov/action/incidental-take-authorization-oil-and-gas-industry-geophysical-survey-activity-gulf-america">https://www.fisheries.noaa.gov/action/incidental-take-authorization-oil-and-gas-industry-geophysical-survey-activity-gulf-america</a>, carries forward the same survey types and similar
estimated annual levels of effort by survey type and location as
specified by BOEM over a 10-year period (as adjusted in 2020 by BOEM to
account for removal from consideration of the area then under a
Congressional leasing moratorium under GOMESA). The most notable
difference is EnerGeo's estimate that approximately 40 percent of
forecast survey effort may be accomplished using alternative sources
that have less environmental impact than airgun arrays (e.g., tuned
pulse or dual barbell sources; additional descriptions of these source
types may be found in Federal Register notices of LOA issuance under
the existing ITRs, e.g., 86 FR 37309, July 15, 2021; 87 FR 55790,
September 12, 2022; 88 FR 72739, October 23, 2023). NMFS will address
these changes to survey effort in a future rulemaking on EnerGeo's
petition. For the current rulemaking, we have determined the specified
activity that is the subject of this final rule is a reasonable
projection on which to proceed.
Geophysical surveys are conducted to obtain information on marine
seabed and subsurface geology for a variety of reasons, including to
obtain data for hydrocarbon and mineral exploration and production; aid
in siting of oil and gas structures, facilities, and pipelines;
identify possible seafloor or shallow depth geologic hazards; and
locate potential archaeological resources and benthic habitats that
should be avoided.
Deep penetration seismic surveys using airgun arrays as an acoustic
source (sound sources are described in the Detailed Description of
Activities section) are a primary method of obtaining geophysical data
used to characterize subsurface structure. These surveys are designed
to illuminate deeper subsurface structures and formations. A deep
penetration survey uses an acoustic source suited to provide data on
geological formations that may be thousands of meters (m) beneath the
seafloor, as compared with a shallow penetration or high resolution
geophysical (HRG) survey that may be intended to evaluate shallow
subsurface formations or the seafloor itself (e.g., for hazards).
Deep penetration surveys may be two-dimensional (2D) or three-
dimensional (3D), and there are a variety of survey methodologies
designed to provide the specific data of interest. 2D surveys are
designed to acquire data over large areas (thousands of square miles)
in order to screen for potential hydrocarbon prospectivity, and provide
a cross-sectional image of the structure. In contrast, 3D surveys may
use similar acoustic sources but are designed to cover smaller areas
with greater resolution (e.g., with closer survey line spacing),
providing a volumetric image of underlying geological structures.
Repeated 3D surveys are referred to as four-dimensional (4D), or time-
lapse, surveys that assess the depletion of a reservoir.
Shallow penetration and high-resolution surveys are designed to
highlight seabed and near-surface potential obstructions, archaeology,
and geohazards that may have safety implications during rig
installation or well and development facility siting. Shallow
penetration surveys may use a small airgun array, single airgun, or
similar sources, while high-resolution surveys (which are limited to
imaging the seafloor itself) may use a variety of sources, such as sub-
bottom profilers, single or multibeam echosounders, or side-scan
sonars.
[[Page 20787]]
Dates and Duration
The specified activities may occur at any time during the 5-year
period of validity of the regulations. Actual dates and duration of
individual surveys are not known. Although the period of validity is
for 5 years, the regulations would continue in effect only until
superseded by new ITRs promulgated on the basis of the separate EnerGeo
request.
Specified Geographical Region
Generally speaking, projected survey activity may occur within U.S.
waters within the GOA, outside of the former GOMESA moratorium area.
The specified geographical region (with modeling zones and depicting
the area withdrawn from leasing consideration) is depicted in figure 1.
[GRAPHIC] [TIFF OMITTED] TR17AP26.028
Figure 1--Specified Geographical Region
Representative Sound Sources
Because the specifics of acoustic sources to be used cannot be
known in advance of receiving LOA requests from industry operators, it
is necessary to define representative acoustic source parameters, as
well as representative survey patterns. The supporting modeling for the
2021 ITRs considered two specific airgun array sizes/configurations
(4,130 and 8,000 in\3\ arrays) as well as a single, 90-in\3\ airgun.
For the 2024 rule, modeling of a third representative airgun array size
(5,110-in\3\) was also specifically considered. In its petition for the
2021 ITRs, BOEM determined realistic representative proxy sound sources
and survey patterns. We note that EnerGeo's 2025 petition for new ITRs
carries forward these assumed proxies regarding survey patterns, as
well as the 5,110-in\3\ array modeled for the 2024 rule, as
representative of ongoing industry survey activities in the GOA.
Acoustic exposure modeling for the 8,000-in\3\ airgun array and 90-
in\3\ single airgun, which provided support for the 2021 rule, was
described in detail in ``Acoustic Propagation and Marine Mammal
Exposure Modeling of Geological and Geophysical Sources in the Gulf of
Mexico'' and ``Addendum to Acoustic Propagation and Marine Mammal
Exposure Modeling of Geological and Geophysical Sources in the Gulf of
Mexico'' (Zeddies et al., 2015, 2017a). Additional information,
including evaluation of the 4,130-in\3\ airgun array, was provided in
``Gulf of Mexico Acoustic Exposure Model Variable Analysis'' (Zeddies
et al., 2017b).
Modeling of the more representative 5,110-in\3\ airgun array for
NMFS' 2024 rule (in view of LOA applications received to date under the
current ITRs) was described in a 2022 memorandum (Weirathmueller et
al., 2022). These reports provide full detail regarding the modeled
acoustic sources and survey types and are available online at:
<a href="http://www.fisheries.noaa.gov/action/incidental-take-authorization-oil-and-gas-industry-geophysical-survey-activity-gulf-america">www.fisheries.noaa.gov/action/incidental-take-authorization-oil-and-gas-industry-geophysical-survey-activity-gulf-america</a>.
Representative sources for the modeling include the three different
airgun arrays, the single airgun, and an acoustic source package
including a sub-bottom profiler in combination with multibeam
echosounder and side-scan sonar. Two major survey types were
considered: large-area seismic (including 2D, 3D NAZ, 3D WAZ, and coil
surveys) and small-area, high-resolution geotechnical (including single
airgun surveys and HRG surveys using the aforementioned package of
sources). The nominal airgun sources used for analysis of this final
rule include a small single airgun (90-in\3\
[[Page 20788]]
airgun) and a large airgun array (8,000-in\3\). While the 5,110-in\3\
airgun array is considered most representative of the airgun sources
that are likely to be used during deep penetration surveys during the
period of effectiveness of these ITRs, the 8,000-in\3\ airgun array
results in larger take numbers for most species for which acoustic
exposures were modeled, and provides the basis for the analysis herein
to allow the flexibility for applicants to use larger sources when
survey objectives dictate. The modeling for the alternative 4,130- and
5,110-in\3\ arrays provides more realistic estimates of take for use in
survey-specific LOAs, depending on the actual acoustic sources planned
for use (see Letters of Authorization section). We note that while
high-resolution geophysical sources were included for consideration in
the 2021 final rule to allow for take authorization if necessary, these
types of sources would not typically be expected to cause the
incidental take of marine mammals (Ruppel et al., 2022).
New technologies and/or uses of existing technologies may come into
practice during the period of validity of these regulations. As under
the 2021 and 2024 final rules, NMFS will evaluate any such developments
on a case-specific basis to determine whether expected impacts on
marine mammals are consistent with those described or referenced in
this document and, therefore, whether any anticipated take incidental
to use of those new technologies or practices may appropriately be
authorized under the existing regulatory framework. See Letters of
Authorization for additional information.
Estimated Levels of Effort
Actual total amounts of effort by survey type and location cannot
be known in advance of receiving LOA requests from survey operators.
Therefore, BOEM's 2017 Programmatic Environmental Impact Statement
(PEIS) provided projections of survey level of effort for the different
survey types for a 10-year period (and BOEM refined those projections
following removal of the GOMESA area from the scope of activity in
2020). As noted above, and as confirmed by both EnerGeo and BOEM, these
estimated levels of effort are expected to remain representative of
expected survey activity on an ongoing basis and, therefore, are
carried forward unchanged. Table 1 provides those effort projections
for the next 5-year period.
BILLING CODE 3510-22-P
[[Page 20789]]
[GRAPHIC] [TIFF OMITTED] TR17AP26.029
BILLING CODE 3510-22-C
The preceding description of the specified activity is a summary.
The interested reader should refer to the notice of proposed rulemaking
(91 FR
[[Page 20790]]
9014, February 24, 2026) for additional detail regarding these
activities.
Comments and Responses
NMFS published a notice of proposed rulemaking in the Federal
Register on February 24, 2026 (91 FR 9014), beginning a 30-day comment
period. In that notice, we requested public input on the proposed rule,
including but not limited to NMFS' proposed or preliminary findings,
determinations, or conclusions regarding the MMPA standards, and the
information NMFS relies on in support of those findings,
determinations, or conclusions; and NMFS' preliminary decision to not
make changes to the 2021 final rule, and the information NMFS relies on
in support of those preliminary decisions, and requested that
interested persons submit relevant information, suggestions, and
comments.
During the 30-day comment period, we received nine comment letters.
Of this total, we received four letters from various organizations
(described below) and five submissions from private citizens.
Submissions from private citizens expressed a mix of generic support
for or opposition to the proposed issuance of the regulations, as well
as generic support for protection of marine mammals. We do not address
these comments further. A letter was submitted jointly by EnerGeo, the
American Petroleum Institute, the Louisiana Mid-Continent Oil and Gas
Association, the National Ocean Industries Association, and the
Offshore Operators Committee (hereafter, the ``Associations''). A
separate letter was submitted jointly by the Natural Resources Defense
Council (NRDC), Association of Zoos and Aquariums, Center for
Biological Diversity, Earthjustice, Sierra Club, and Turtle Island
Restoration Network (hereafter, ``NRDC''). Turtle Island Restoration
Network (TIRN) also submitted a letter independently, and an additional
letter was submitted by Animal Counsel. TIRN's independent letter
provided a generic statement in opposition to issuance of the rule, and
we do not address it further.
The Associations express support for issuance of the reimplemented
ITRs, stating that ``the record should reflect that the request is also
made on behalf of the regulated industry participants.'' The
Associations emphasize that they preserve all previously expressed
objections to the current ITRs, urge prompt issuance of new ITRs based
on the EnerGeo petition, and request that requested LOAs be issued
promptly under the reimplemented ITRs. NMFS does not further address
the Associations' letter.
NMFS has reviewed all public comments received on the 2026 proposed
rule. All relevant comments and our responses are described below. All
comments received are available online at: <a href="https://www.regulations.gov">https://www.regulations.gov</a>.
A direct link to these comments is provided at: <a href="https://www.fisheries.noaa.gov/action/incidental-take-authorization-oil-and-gas-industry-geophysical-survey-activity-gulf-america">https://www.fisheries.noaa.gov/action/incidental-take-authorization-oil-and-gas-industry-geophysical-survey-activity-gulf-america</a>.
Comment 1: Animal Counsel indicated a belief that NMFS' proposal to
issue the rule contradicts Congressional intent behind the MMPA and
would be incompatible with the original intent of the MMPA. Animal
Counsel additionally stated that the legislative history of the MMPA
makes clear that the precautionary principle must be applied and bias
must favor marine mammals.
Response 1: NMFS believes that this action is fully consistent with
the original public meaning of the relevant provisions of the statute,
and NMFS disagrees that this action contradicts any requirement of the
MMPA or is contrary to Congressional intent as expressed through the
enactment of the relevant provisions of the statute. Neither the MMPA
nor NMFS' implementing regulations include references to, or
requirements for, the precautionary approach, nor is there a clear,
agreed-upon description of what the precautionary approach is or would
entail in the context of the MMPA or any specific activity.
Nevertheless, the MMPA by nature is inherently protective, including
the requirement to mitigate to the lowest level practicable (``least''
practicable adverse impacts, or ``LPAI,'' on species or stocks and
their habitat). This requires that NMFS assess measures in light of the
LPAI standard. To ensure that we fulfill that requirement, NMFS
considers all potential measures (e.g., from recommendations or review
of available data) that have the potential to reduce impacts on marine
mammal species or stocks, their habitat, or subsistence uses of those
stocks, regardless of whether those measures are characterized as
``precautionary.''
Comment 2: Animal Counsel requests that NMFS extend the comment
period for the proposed rule to a minimum of 60 days and hold public
hearings. The request is primarily founded on the contention that an
announced March 2026 meeting of the Endangered Species Committee
demands delay, with Animal Counsel stating that the meeting ``is likely
to drastically change the outlook for marine mammals in the Gulf.''
Elsewhere in its letter, Animal Counsel highlights the independence of
the MMPA from the Endangered Species Act (ESA).
Response 2: We do not find Animal Counsel's rationale persuasive;
NMFS finds the 30-day comment period for the proposed rule sufficient.
Supporting material for this rule has been available for review during
public comment periods for prior rulemakings associated with oil and
gas industry geophysical survey activity in the GOA (see 83 FR 29212,
June 22, 2018; 88 FR 916, January 5, 2023). This rule covers the same
activity and reimplements the measures that were considered in those
rulemakings, which were the subject of extensive comment. As to the
Endangered Species Committee meeting, we disagree that the Committee's
March 31, 2026, action to exempt GOA oil and gas activities from the
requirements of ESA section 7 is likely to drastically change the
outlook for marine mammals in the GOA. Specifically, the oil and gas
activities considered by the Committee included oil and gas
exploration, development, and production activities in the Gulf as well
as the avoidance or minimization measures that are described in the
agency action analyzed in NMFS' 2025 biological opinion and in the U.S.
Fish and Wildlife Service's 2018 and 2025 consultation decisions. The
Committee's exemption order explicitly states that those avoidance and
minimization measures shall continue to be implemented. See Dep't of
the Interior, March 31, 2026, Endangered Species Committee Order,
<a href="https://www.doi.gov/endangered-species-committee">https://www.doi.gov/endangered-species-committee</a>. Thus we do not agree
that the Committee's order has drastically changed the outlook for
marine mammals in the GOA such that we should extend the public comment
period or hold public hearings on that basis.
Comment 3: NRDC claims that use of BOEM's programmatic estimates of
ongoing geophysical survey activity is arbitrary. NRDC's claim is based
on the age of BOEM's original projections, which were initially
included in its 2017 PEIS issued under the National Environmental
Policy Act (NEPA) before being revised as part of BOEM's 2020 revision
of the geographic scope of the program addressed in NMFS' 2021 final
rule, and on what NRDC describes as ``recent developments that are
likely to influence industry development of the Gulf,'' including
prospective future schedules for offshore oil and gas lease sales.
Response 3: NMFS disagrees with NRDC's claim. The programmatic
[[Page 20791]]
estimates of ongoing geophysical survey activity included in this rule
remain a reasonable representation of ongoing and future activity over
the 5-year duration of this rule. While the 10-year projections in the
PEIS indeed extended through 2027, they were based on generic
expectations regarding BOEM's program over the 10-year window of
analysis provided at that time, not on specific understanding of
conditions dictating oil and gas industry levels of effort. When
revising its level of effort projections in 2020 in support of its 2016
petition for ITRs, BOEM affirmed that the projections should be
considered an adequate representation of generic conditions informing
the need for survey activity in the GOA. Subsequently, EnerGeo (an
industry trade organization dedicated to the geophysical and
exploration industry and best positioned to understand future industry
demand for survey activity) affirmed the validity of these projections
by adopting them as an ongoing representation of future survey activity
in its 2025 petition for new ITRs. We also note that actual survey
effort under the current ITRs from 2021 to 2025 has been less than the
association projections, suggesting that the projections remain
reasonable and accommodating of potential future fluctuations in
demand.
NRDC's references to new developments relating to schedules for
future lease sales are not relevant to our analysis of expected survey
activity during the course of the next 5-year period. Future lease
sales may influence survey activity beyond the next 5-year period but
are unlikely to increase demand on the timeframe imagined by NRDC. NRDC
also suggests that speculative future lease sales in areas outside of
the geographic scope of this rule, i.e., in the eastern GOA, would
invalidate the level of effort projections considered here. However,
should this demand in the eastern GOA arise, it would necessarily be
subject to additional MMPA incidental take authorization requests, as
the area is not covered under this rule.
Comment 4: NRDC expressed concerns regarding NMFS' use of the
probabilistic response function described by Wood et al. (2012), in
which 10 percent, 50 percent, and 90 percent of individuals exposed are
assumed to produce a behavioral response (of a sufficient degree of
severity to constitute Level B harassment) at exposures of 140, 160,
and 180 dB root mean square (rms), respectively. (The function is
shifted for the more behaviorally sensitive beaked whales such that 50
percent and 90 percent response probabilities are assumed to occur at
120 and 140 dB rms, respectively.) NRDC stated that the function is
inconsistent with the best available science, asserting that behavioral
disruptions occur at higher percentages at lower noise exposure levels
than those suggested by Wood et al. (2012). NRDC's criticism of the
function also focused on the use of horizontal displacement studies as
the supposed basis of analysis for Wood et al. (2012), as well as on
the function's nature as a series of step functions. In addition, NRDC
expressed concerns that the use of frequency weighting in the Wood et
al. (2012) approach is inappropriate. Overall, NRDC claims that
reliance on this function results in underestimation of impacts and is
arbitrary and capricious. Similarly, Animal Counsel urges NMFS to adopt
different harassment thresholds.
Response 4: NMFS has historically been criticized for the use of
the single-step 160-dB rms approach. Those criticisms are based on the
idea that an approach reflecting a more complex multi-step
probabilistic function would more effectively represent the known
variation in responses at different levels due to differences in the
receivers, the context of the exposure, and other factors, as well as
the science indicating that animals may react in ways constituting
Level B harassment when exposed to lower received levels. In developing
the acoustic exposure analysis for the 2021 rule, we reviewed relevant
past public comments as well as the best available science, determining
that a more complex probabilistic function is indeed better reflective
of available scientific information and that it was appropriate to take
the fundamental step of recognizing the potential for Level B
harassment occurring at exposures to received levels below 160 dB rms
(as well as the potential for no Level B harassment occurring at
exposures above 160 dB rms). This approach also accounts for
differential hearing sensitivity by incorporating frequency-weighting
functions, as behavioral responses in cetaceans are best explained by
the interaction between sound source type and functional hearing group
(Gomez et al., 2016). NMFS has determined that the general approach
used for this rule--a probabilistic risk function that allows for the
likelihood of differential response probability at given received
levels on the basis of multiple factors, including behavioral context
and distance from the source, and that addresses particularly sensitive
species--is appropriate in light of the best available scientific
information.
However, because behavioral responses to sound depend on the
context in which an animal receives the sound, including the animal's
behavioral mode when it hears sounds, prior experience, additional
biological factors, and other contextual factors, predicting when sound
levels will be likely to disrupt behavioral patterns is extremely
difficult. Even experts have not previously been able to suggest
specific new criteria due to these difficulties (e.g., Southall et al.,
2007; Gomez et al., 2016). While we acknowledge our approach reduces a
complex suite of interactions to make reasonable inferences, it is
consistent with the best available science.
NRDC referenced ``recent'' research they claim is not consistent
with the recommendations of Wood et al. (2012). We note that, of the
nine studies cited by NRDC, five were published prior to the Wood et
al. (2012) study, and were therefore available for those authors'
consideration (and some were specifically referenced by those authors
in discussion of their recommendations). Further, we disagree that the
referenced findings are inconsistent with Wood et al. (2012). For
example, a detectable change in motion or vocalization in response to
noise exposure does not necessarily mean that a take by Level B
harassment under the MMPA has occurred, given that the definition
focuses on ``disruption of behavioral patterns.'' NRDC also suggests
that some of these studies were not incorporated into Wood et al.'s
recommendations, or our consideration of those and other potential
approaches in context of the available science, and criticize what they
view as an over-reliance on horizontal displacement studies as the
supposed basis of analysis. While it is true that the majority of
available behavioral data focus on avoidance responses, Wood et al.
(2012) does not mention excluding behavioral studies involving vocal
changes, and Southall et al. (2007) specifically incorporates numerous
studies that do mention changes in vocalization associated with sound
exposure. Thus, these datasets were not excluded and as discussed in
our notice of proposed rulemaking, we adequately considered all studies
addressed by NRDC.
Regarding baleen whales, we acknowledge that changes in
vocalization have been observed in association with exposure to airgun
surveys within migratory and non-migratory contexts (e.g., Castellote
et al., 2012; Blackwell et al., 2013; Cerchio et
[[Page 20792]]
al., 2014). The potential for such effects to occur over relatively
large spatial scales is not surprising for species with large
communication spaces (e.g., Clark et al., 2009), but we reiterate our
disagreement with NRDC's apparent contention that every detected change
to vocalizations rises to the level of a take. NRDC cites reports of
changes in vocalization, typically for baleen whales, as evidence in
support of lower thresholds, claiming these reactions result in
biological consequences indicating that the reaction was indeed a take.
However, NMFS is not aware of research that provides a well-supported
link between the reported reactions at lower received levels and the
putative consequences. In conflict with NRDC's interpretation of the
literature are documented instances of marine mammal exposure to
greater received levels that did not elicit any response (e.g., Malme
et al., 1983, 1984, 1985, 1988; McCauley et al., 1998, 2000a, 2000b;
Barkaszi et al., 2012; Stone, 2015a; Gailey et al., 2016; Barkaszi and
Kelly, 2018).
The received level associated with stoppage of calling for bowhead
whales (Balaena mysticetus) observed by Blackwell et al. (2013, 2015)--
a response that may arguably rise to the level of harassment--is
consistent with the Wood et al. (2012) scheme, in which the potential
for take upon exposure to received levels as low as 140 dB is accounted
for. Similarly, the findings of Pirotta et al. (2014) for harbor
porpoise (Phocoena phocoena) are consistent with the treatment of
behaviorally sensitive species by Wood et al. (2012), in which the
potential for take at even lower received levels is accounted for
(though irrelevant here, as harbor porpoise are not found in the GOA).
The response levels reported by McDonald et al. (1995) and Di Iorio and
Clark (2009) for blue whales (Balaenoptera musculus) also comport with
the Wood et al. (2012) function, if we assume that the observed
responses equate to harassment (though it is not clear that they do).
With regard to NRDC's citation of Clark and Gagnon (2006), a non-peer
reviewed white paper, NRDC incorrectly calculated the area over which
the effect was observed by an order of magnitude (the paper discusses
an area of 100 x 100 nmi, which equates to 10,000 nmi\2\--not 100,000
nmi\2\).
In regard to Cerchio et al. (2014), it is important to note that
received levels provided in this study are those recorded at locations
of their underwater recording devices. The authors indicated ``we did
not have the ability to locate the singers or the seismic survey
vessel, estimate the source level of the pulses, the distance between
the source and potentially impacted singers, or the received level of
the pulses at the singers.'' The same situation, i.e., actual received
levels at the location of the animals are unknown, is true for
Castellote et al. (2012) and Clark and Gagnon (2006), which provide
average background sound levels with and without the presence of airgun
surveys. Thus, not having the location of the animals at the time of
exposure makes it difficult to draw conclusions based strictly on
received level. NMFS has evaluated the papers and determined they are
not informative about appropriate Level B harassment thresholds.
Regarding sperm whales, NMFS disagrees that assuming a 100 percent
probability of take of sperm whales upon exposure to survey noise at
135 dB--as suggested by NRDC--is an accurate reflection of the results
of the Miller et al. (2009) study. While we agree that the work of
Miller et al. (2009) suggests that sperm whales in the GOA may be
susceptible to disruption of foraging behavior upon exposure to
relatively moderate sound levels, NRDC incorrectly interprets results
of the study in claiming that sperm whale ``foraging success'' was
found to ``decline significantly.'' Instead, the authors report that
buzz rates (a proxy for attempts to capture prey) were approximately 20
percent lower, meaning that the appropriate interpretation would be
that foraging activity (versus foraging success) was reduced by 20
percent (Jochens et al., 2008). Of the eight whales tagged in that
study, only one was observed to actually cease foraging.
Moreover, while we do believe that these study results support a
conclusion that exposure to survey noise can impact foraging activity,
others have interpreted them differently, e.g., by focusing on the
finding that exposed whales did not change behavioral state during
exposure or show horizontal avoidance (a finding replicated in other
studies, e.g., Madsen et al., 2002a; Winsor et al., 2017). Importantly,
the observed effect was not statistically significant and, as reported
by the authors, constituted ``subtle effects on their foraging
behavior.'' Furthermore, the authors of the Wood et al. (2012) study
explicitly described their consideration of Miller et al. (2009) in the
development of their recommended criteria. Therefore, the Wood et al.
(2012) recommendation is indeed consistent with the Miller et al.
(2009) study. In referencing Bowles et al. (1994), NRDC fails to state
that the observed cessation of vocalization was likely in response to a
low-frequency tone (dissimilar to airgun signals), though a distant
airgun survey was noted as producing signals that were detectable above
existing background noise.
Regarding other odontocetes, NRDC's representation of the available
scientific information is also inaccurate. Miller et al. (2005)
specifically state that ``[s]ighting rates at distances of 10-20 km
from the airgun array were significantly lower than those in areas 20-
30 km from the airgun array, where sighting rates were unexpectedly
high'' (i.e., the study indicates sighting rates of beluga whales
(Delphinapterus leucas) were lower, not ``100% avoidance'' as claimed
by NRDC). Miller et al. (2005) reported seven aerial beluga whale
sightings from 8 to 18 km from the survey vessel and two vessel-based
beluga whale sightings at 1.5 and 2.5 km from the survey vessel.
Furthermore, Southall et al. (2007) described the findings of the
Miller et al. (2005) study as temporary avoidance behaviors at these
lower received levels, while Gomez et al. (2016) (which NRDC agrees
reflects the best available science) evaluated Miller et al. (2005)
based on a received level of 150 dB. Thus, the Wood et al. (2012)
approach does capture responses associated with this study.
Additionally, Wood et al. (2012) has the advantage of accounting
for sensitive species such as beaked whales, meaning that a response of
a beaked whale at 140 dB (as cited by NRDC) is covered within the Wood
et al. (2012) recommended criteria (e.g., Wood et al. assumes 90
percent of an exposed beaked whale population will respond at 140 dB).
It should be noted that the systematic review by Gomez et al.
(2016), cited by NRDC and Animal Counsel in support of their positions,
found that received level was not appropriate as the sole indicator of
behavioral response. For example, this review shows that ``low''
effects were actually found to reach peak probability at a higher
received level than ``moderate'' effects for baleen whales. The results
of the Gomez et al. (2016) review are not inconsistent with Wood et al.
(2012). With regard to NRDC's comment that the authors consider their
results ``non-conservative,'' Gomez et al. (2016) only indicates that
they may have scored the severity of vocal responses higher if they had
more information on the ecological significance of these types of
responses. There is no indication elsewhere in Gomez et al. (2016) that
their overall results and analysis are ``non-conservative.'' Commenters
also
[[Page 20793]]
reference the ``more conservative approach'' of Nowacek et al. (2015),
suggesting that this approach is more appropriate. However, the more
substantive reviews presented by Southall et al. (2007) and Gomez et
al. (2016) were unable to present any firm recommendations, as noted
above. We note that Animal Counsel recommends that NMFS update
thresholds to ``reflect the findings of Gomez et al. (2016) and Nowacek
et al. (2015),'' but provide no specific recommendations. We addressed
Gomez et al. in further detail in this response, and note that NMFS has
addressed the brief, scientifically unsupported recommendation of
Nowacek et al. (2015) in detail in prior comment responses (e.g., 86 FR
5322, January 19, 2021).
NRDC also criticizes the use of weighting functions in evaluating
potential Level B harassment, and specifically criticizes use of the M-
weighting scheme of Southall et al. (2007). Gomez et al. (2016) suggest
that incorporation of frequency-weighting is necessary to account for
differential hearing sensitivity, as behavioral responses in cetaceans
are best explained by the interaction between sound source type and
functional hearing group. That is, implementing weighting functions
allows for consideration that different marine mammal groups do not
hear varying frequencies of sound equally well. Thus, it is appropriate
to account for sounds below a group's best hearing range having a lower
likelihood of resulting in a behavioral response (let alone that
animals are likely unable to effectively detect sounds at frequencies
completely outside their hearing range).
The M-weighting functions are described in Southall et al. (2007)
as ``intentionally precautionary (wide)'' (as opposed to the weighting
functions used in NMFS' Technical Guidance to account for noise-induced
hearing loss) and are used to account for the functional hearing ranges
of different marine mammal hearing groups. This frequency weighting
scheme (i.e., M-weighting) was intentionally selected because it is
more conservative in accounting for hearing sensitivity (as is
appropriate in evaluating potential Level B harassment) than are more
recently developed filters designed to better assess potential noise-
induced hearing loss.
NRDC asserts that because M-weighting assumes that high- and very
high-frequency (HF and VHF) cetaceans are relatively insensitive to
noise below 1 kHz, it is likely that the incorporation of M-weighting
has a significant downwards effect on take estimates. This is
incorrect. As demonstrated in NMFS' 2021 final rule, at 250 Hz and
above, the M-weighting functions do not result in a significant
reduction for HF or VHF cetaceans. Furthermore, the lower bound of the
functional hearing range of these groups is 150 Hz for MF cetaceans and
200 Hz for HF cetaceans (i.e., sounds below 100 Hz, where most energy
in airgun noise is found and where M-weighting results in the greatest
reductions, are outside functional hearing range). At 1 kHz, where
these species are most likely to be able to detect and respond to
airgun noise, there is very little assumed reduction in sensitivity.
Finally, NRDC advocates for the use of a linear risk function as
opposed to the multiple step function of Wood et al. (2012), stating
that linear risk functions are scientifically accepted methodology that
better acknowledge individuals may vary in responsiveness. Although
NRDC does not specifically define what they mean by ``linear risk
function,'' NMFS assumes a linear risk function is a smooth, continuous
function, as opposed to a function defined by multiple steps, as is the
case of Wood et al. (2012). NRDC states that Wood et al. (2012) ``has a
significant negative bias on take estimates'' where ``all exposures
from 140 dB to 159.9 dB are considered to produce the same risk.'' Wood
et al. (2012) does acknowledge that responsiveness varies with received
levels, while relying on broad steps, rather than a continuous
function. These broad steps allow for easier implementation of a risk
function and are more practical for most users, which is an important
consideration, especially in the context of users that may not have the
ability or access to more sophisticated modeling (in contrast to the
Navy). Therefore, if new linear risk functions become available, NMFS
may still provide a more simplistic function broken down in broad
steps, so that it can be applied by all users.
Overall, we reiterate the lack of scientific consensus regarding
what criteria might be most appropriate for evaluating Level B
harassment. Defining sound levels that disrupt behavioral patterns is
difficult because responses depend on complex, difficult to predict
contextual factors much more so than received level. Therefore, levels
at which responses occur are not necessarily consistent and can be
difficult to predict. However, although better methods of assessing
likely behavioral response to acoustic stimuli than the relatively
simple multi-step function used here may be forthcoming from the
scientific community, NMFS has determined that the recommendations of
Wood et al. (2012) adequately reflect the available science, and
commenters offer no alternative recommendation.
Comment 5: NRDC raised concerns regarding NMFS' Acoustic Technical
Guidance for evaluating the potential for marine mammal hearing loss,
claiming that the Technical Guidance is not based on the best available
science and leads to underestimation of potential auditory effects.
NRDC also asserts that NMFS fails to account for alternative mechanisms
of auditory injury, stating that permanent hearing loss (i.e., Level A
harassment) may occur through mechanisms other than PTS. NRDC states
that NMFS must account for these mechanisms in its assessment of
potential injury. Animal Counsel similarly expresses concern regarding
the potential for accumulated auditory effects resulting from repeated
temporary threshold shift exposures.
Response 5: We first acknowledge our use of the 2018 Revised
Technical Guidance (NMFS, 2018) in evaluating the potential for
auditory effects in the context of estimating take and refer the reader
to the Estimated Take section below for discussion of NMFS' use of the
2018 guidance for take estimation. Moreover, NMFS did consider the 2024
Technical Guidance. However, NRDC's critique relates to aspects of the
Technical Guidance that predate the 2024 update and, indeed, NMFS
considered similar comments from NRDC for issuance of the 2021 final
rule.
Regarding the updated 2024 Technical Guidance, the 2024 updated
acoustic thresholds (cumulative sound pressure level and peak sound
pressure level) for cetaceans either are identical or are higher than
those in the 2018 Revised Technical Guidance (i.e., level of exposure
has to be higher to result in PTS or AUD INJ compared to the 2018
thresholds). Additionally, the weighting functions were also updated,
but this update only resulted in minor changes for LF cetaceans and no
changes for the other two cetacean hearing groups, where the peak sound
pressure level metric thresholds, which are unweighted, result in the
largest isopleths. Furthermore, despite these changes, the Level A
harassment isopleths for LF cetaceans are still expected to be within
the shutdown zone and would not result in a change in the amount of
Level A harassment take expected for this species or any other cetacean
in the Gulf.
Each of NMFS' Technical Guidance documents (NMFS, 2016, 2018, 2024)
is a compilation, interpretation, and
[[Page 20794]]
synthesis of the scientific literature that provides the best available
information regarding the effects of anthropogenic sound on marine
mammals' hearing. In 2016, the initial iteration of the Technical
Guidance was classified as a Highly Influential Scientific Assessment
and, as such, underwent three independent peer reviews, at three
different stages in its development, including a follow-up to one of
the peer reviews, prior to its dissemination by NMFS. In addition,
there were three separate public comment periods, during which time
NMFS received and responded to similar comments on the guidance (81 FR
51694), and subsequent public and interagency review under Executive
Order 13795. While new information may help to improve the guidance in
the future, and NMFS will continue to review the available literature
to determine when revisions are appropriate, the science underlying the
Technical Guidance (2018 and 2024 update) reflects the best available
science, and all information received through peer review and public
comment. The concerns raised by NRDC have been addressed by NMFS in
responses associated with publication of the guidance (see
<a href="http://www.fisheries.noaa.gov/national/marine-mammal-protection/marine-mammal-acoustic-technical-guidance">www.fisheries.noaa.gov/national/marine-mammal-protection/marine-mammal-acoustic-technical-guidance</a>).
In light of these considerations, NRDC's argument that estimates
based on the guidance ``are based on methods and assumptions that have
no scientific basis'' is unpersuasive. NMFS considers the guidance to
represent the best scientific information currently available and,
given the incorporation of multiple peer reviews and public comment
opportunities during its development, we did not solicit and are not
responding in detail to comments concerning the contents of the
Technical Guidance (NMFS, 2016, 2018, 2024), as such comments are
outside the scope of this rulemaking.
NRDC also referenced information related to occupational noise
standards established by the National Institute of Occupational Safety
and Health (NIOSH). Human noise risk assessments (NIOSH, 1998) are not
equivalent (or applicable) to thresholds provided in the guidance,
because they are used to predict hearing loss based on a daily 8-h
occupational noise exposure over 40 years (i.e., current marine mammal
TTS data are only available to predict exposure periods of 24-h or less
and cannot be used to assess or predict risk associated with a lifetime
of exposure) and are based on larger sample sizes of human listeners
(e.g., NIOSH 1972 and 1997 risk assessments were based on a sample size
of 1,172 people). As pointed out in Wright (2015), NIOSH criteria
provide a 95 percent confidence interval for their human noise
standards but also allow for an excess risk of material hearing
impairment, defined as an average threshold elevation for both ears
that exceeds 25 dB, of eight percent (i.e., human noise standards
limits do allow for some risk; risk is not zero percent and
specifically that eight percent of the population is still capable of
developing noise-induced hearing loss exceeding 25 dB when exposed to
the 85 dB NIOSH level).
Finally, we note that a group of scientists published an update to
their original, seminal publication concerning noise exposure criteria
to predict the onset of auditory effects in marine mammals (Southall et
al., 2007, 2019a), the topic of this comment. The newer peer-reviewed
publication evaluates the recommendations of the original publication
in light of subsequent scientific findings, including those findings
that form the basis for the recommendations of NMFS (2018, 2024). While
Southall et al. (2019a) provide recommendations for future research
that could lead to revisions, the fundamental aspects of an evaluation
of the onset of auditory effects for the marine mammals considered in
these ITRs (i.e., auditory weighting functions and noise exposure
criteria) are identical to those presented by NMFS (2018, 2024) and
incorporated into the modeling process developed for these ITRs.
Regarding NRDC's suggestion that NMFS fails to account for
alternative mechanisms of auditory injury, NMFS is aware of the work by
Kujawa and Liberman (2009), which is cited by NRDC. The authors report
that in mice, despite completely reversible threshold shifts that leave
cochlear sensory cells intact, there were synaptic level changes and
delayed cochlear nerve degeneration. However, the large threshold
shifts measured (i.e., maximum 40 dB) that led to the synaptic changes
shown in this study are within the range of the large shifts used by
Southall et al. (2007, 2019a) and in NMFS' Technical Guidance to define
PTS onset (i.e., 40 dB). There are no data indicating that smaller
levels of TTS would lead to similar changes or what may be the long-
term implications of irreversible neural degeneration. The effects of
sound exposure on the nervous system are complex, and this will be re-
examined as more data become available. It is important to note that
NMFS' Technical Guidance incorporated various conservative factors,
such as a 6-dB threshold shift to represent TTS onset (i.e., minimum
amount of threshold shift that can be differentiated in most
experimental conditions); the incorporation of exposures only with
measured levels of TTS (i.e., did not incorporate exposures where TTS
did not occur); and assumed no potential of recovery between
intermittent exposures. NMFS disagrees that consideration of likely PTS
is not sufficient to account for reasonably expected incidents of
auditory injury.
NRDC also suggested that NMFS should ``revise its take estimates''
following the update to the definition of injury in the 2024 Technical
Guidance to include indirectly induced injury in addition to PTS.
However, this update in terminology is simply an acknowledgement that
in addition to PTS, there could be the potential for auditory injury
(which may or may not result in PTS). This updated terminology
acknowledges data available for terrestrial mammals and that, since the
mammalian cochlea is highly conserved, there is the potential for
similar auditory injury in marine mammals. However, this terminology
change does not numerically affect our acoustic criteria and,
therefore, nothing would change in terms of estimated take (i.e., the
criteria remain based on a 40 dB threshold shift, reflecting the same
threshold shifts associated with auditory injury seen in terrestrial
mammal studies). Thus, numerically the 2018 and 2024 criteria account
for the potential for auditory injury in the same way, but the updated
guidance has changed the terminology to more directly reflect this.
Comment 6: NRDC commented that the aversion adjustment applied to
estimates of Level A harassment proposed by NMFS for low- and very
high-frequency cetaceans is not supported. NRDC cites NMFS' statements
attributing the original modeling decision not to include a
quantitative adjustment for aversion to lack of information regarding
species-specific degree of aversion and level of onset as suggestive of
lack of an ``evidentiary basis'' for making such an adjustment.
Response 6: NMFS disagrees with these comments and clarifies our
position. Aversion is a known real-world phenomenon. It is well-known
that animals will avoid unpleasant stimuli, such as very high received
levels of sound. A large and growing literature has demonstrated
behavioral aversion in a number of contexts for many marine mammal
species in increasingly controlled and well-documented contexts. While
considerable species, individual, and
[[Page 20795]]
context-dependencies exist in terms of received noise levels associated
with behavioral aversion, clear patterns of behavioral aversion have
been demonstrated empirically within odontocetes and mysticetes (e.g.,
Miller et al., 2012, 2014; DeRuiter et al., 2013; Southall et al.,
2019b). This is particularly true for exposure scenarios in which
animals occur relatively close to sources and at the high levels that
would be required for even TTS (much less PTS) to occur. In some
instances, in these and other studies, behavioral avoidance has been
measured at received levels many orders of magnitude below those
required for predicted PTS onset and even below the nominal, 50 percent
behavioral response probability at 160 dB rms that NMFS has applied
historically.
However, accounting for aversion quantitatively in an acoustic
exposure modeling process is a significantly data-heavy endeavor and,
despite the growing body of evidence there still not sufficient data
regarding the specific degree of aversion and level of onset on a
species-specific basis. That is, in order to account for aversion
within the modeling process, one must program individual simulated
animals (animats) representing different species to respond at a
specific received level by changing their direction of travel by a
specific degree and assuming a specific rate of speed. Through a test
scenario evaluation (discussed in detail in the 2021 rulemaking and in
associated modeling reports that support this rule), we determined that
while this is possible to do, the specific values that must be used in
programming the animat response could not be adequately derived.
Instead, a nominal offset factor was applied to the modeled injurious
exposures based on published model result evaluation to account for
aversion.
Ellison et al. (2016) modeled scenarios using animal movement
models to evaluate predicted PTS in which no aversion was assumed
relative to scenarios where reasonable assumptions were made about
aversion, in line with historical response probability assumptions and
that existing scientific literature suggest are appropriate. Scenarios
where no aversion probability was used overestimated the potential for
high levels of exposure required for PTS by about five times.
Accordingly, for the 2021 final rule, total modeled injurious exposures
calculated without accounting for behavioral aversion (for low- and
high-frequency species) were multiplied by 0.2. NMFS consulted
scientific experts (referred to in the 2021 final rule as the ``Expert
Working Group,'' contracted by NMFS and BOEM to provide scientific
expertise in developing a risk assessment framework), including the
lead author of Ellison et al. (2016), in selecting the specific offset
factor, and discussed that selection again in context of the public
comments received on that rule. These experts agreed that the approach
and specific offset factor was a reasonable approach to addressing the
issue of aversion.
NRDC acknowledges that aversion is a meaningful real-world
phenomenon that is significantly influential on actual occurrence of
Level A harassment, stating that ``it is certainly true that some
marine mammals will flee the sound.'' Ignoring this phenomenon would
result in unrealistically high estimates of auditory injury for marine
mammals in the GOA. As described above, there is extensive information
supporting the aversion concept in marine mammals, but limited
quantitative data with which to develop precise, species-specific
offset factors. Accordingly, utilizing the available data and expert
input, NMFS applied its professional judgement in order to account for
this meaningful phenomenon, and has determined it appropriate to retain
this approach for the present rule.
Comment 7: Animal Counsel expressed concern that density estimates
available for Rice's whale are based on visual survey data and do not
include acoustic detections.
Response 7: We agree that ideally, passive acoustic data could be
incorporated to the spatial density models to improve the model
predictions. However, incorporation of visual and acoustic data to
spatial density models remains cutting edge science, and such models
have only rarely been produced. The long-term cetacean density modeling
effort presented by Roberts et al. (2016) and subsequent, related
publications provides an example of the difficulty of doing so. This
U.S. Navy-funded effort has been responsible for continually improved
iterations of spatial density models for cetaceans along the U.S. East
Coast since 2015. However, to date, acoustic data have been
incorporated only into models for beaked whales and sperm whales (two
species that are most amenable to acoustic surveys and for which
acoustic detections are most important to understanding occurrence),
and only in the most recently updated model iterations. This required 7
years and a model version 7 for beaked whales and model version 8 for
sperm whales (<a href="https://seamap.env.duke.edu/models/Duke/EC/">https://seamap.env.duke.edu/models/Duke/EC/</a>). Acoustic
data have been used to qualitatively verify density model predictions
for certain mysticetes, but have not been incorporated to date into any
East Coast mysticete density model. Efforts to evaluate the feasibility
and utility of combining visual and acoustic survey data in the GOA
have only recently been conducted as a pilot study (Frasier et al.,
2021).
We note that the same areas in which the acoustic detections were
made are predicted by the spatial density model as being suitable
Rice's whale habitat and, in fact, density predictions within areas
expected to provide suitable habitat for Rice's whale increased
compared with the predictions provided by Roberts et al. (2016) (e.g.,
Rice's whale density value in Zone 5, which includes areas of the
central GOA where acoustic detections were made, increased by 71
percent; see Appendix A of Weirathmueller et al., 2022).
Comment 8: NRDC and Animal Counsel assert that NMFS has failed to
account adequately for the effects of masking or stress on marine
mammals.
Response 8: The potential impacts of masking were properly
considered. We acknowledge that masking may impact marine mammals,
particularly baleen whales such as the Rice's whale, and particularly
when considered in the context of the full suite of regulated and
unregulated anthropogenic sound contributions overlaying an animal's
acoustic habitat. We acknowledge that masking can constitute a take,
depending on the particular circumstances, but do not agree that
masking effects from the incremental noise contributions of individual
activities or sound sources always rise to the level of take. Further,
not all takes are readily quantifiable. In this case, while masking is
considered in the analysis, we do not believe it will result in take of
marine mammals beyond those that have already been quantified as taken
by behavioral harassment. Specifically, in the case of these proposed
activities, in the event that some masking incidents rise to the level
of a take, we would expect them to be accounted for in the quantified
exposures above the harassment thresholds. Given the short duration of
expected noise exposures, any take by masking in the case of these
surveys would be most likely to be incurred by individuals either
exposed briefly to notably higher levels or those that are generally in
the wider vicinity of the source for comparatively longer times. Both
of these situations would be captured in the enumeration of takes by
Level B harassment, which accounts for
[[Page 20796]]
takes that may occur upon exposure at relatively low levels of received
sound (e.g., 140 dB).
In addition, Animal Counsel suggests that NMFS should evaluate
``the proposed activity's acoustic contribution against the natural,
pre-industrial baseline rather than the existing anthropogenic
soundscape;'' however, no recommendation is provided as to how it
believes this analysis should be accomplished absent data relating to
the ``natural, pre-industrial baseline.'' In addition, this
recommendation runs afoul of the MMPA requirement for NMFS to evaluate
the effects of the specified activity alone.
In addition to the comment that NMFS has underestimated takes that
may result from masking, commenters disregard the consideration given
to masking effects in NMFS' risk assessment framework (see Negligible
Impact Analysis and Determinations). Broadly, the results of the
analysis for any given species are based on the integration of two
components: the severity of the impacts (which reflects the extent of
the activities overlaid with the presence and distribution of the given
species) and the vulnerability of that species based on multiple
biological and environmental risk factors, including explicit
consideration of masking. Expected consequences of masking account for
20 percent of a species' vulnerability rating, and is a substantial
proportion of the vulnerability score.
NMFS recognizes that masking is not necessarily co-extensive with
harassment and explicitly recognizes this in our discussion of effects,
although we also note that the distances at which behavioral harassment
is quantified for this rule are farther than those contemplated in the
past, due to the behavioral harassment thresholds used (see the
Estimated Take section and comment responses later in this section for
further discussion of acoustic thresholds). As discussed in detail in
NMFS' 2021 final rule, NMFS designed and supported the implementation
of a chronic and cumulative effects analysis, which is incorporated in
NMFS' discussion of the potential effects of the specified activity
here for the specific purpose of addressing the effects of these
activities on the listening space of all species and the communication
space of Rice's whales specifically (see Negligible Impact Analysis and
Determinations). This modeling effort explicitly considered the effects
of masking over realistic spatial scales.
Similarly, we addressed the available literature regarding
potential impacts of stress resulting from noise exposure in marine
mammals. As described in that discussion, stress responses are
complicated and may or may not have meaningful impacts on marine
mammals. NRDC implies that NMFS must (1) enumerate takes resulting from
stress alone and (2) specifically address stress in its negligible
impact analysis. The effects of stress are not straightforward, and
there is no information available to inform an understanding of whether
it is reasonably likely that an animal may experience a stress response
upon noise exposure that would not be accounted for in NMFS' existing
enumeration of takes via exposure to noise, which includes an
accounting for exposures above received levels as low as 140 dB rms
(and as low as 120 dB rms for beaked whales). NRDC provides nothing
informative regarding how such an analysis might be carried out. With
regard to NMFS' negligible impact analysis, we believe that the
potential effects of stress are addressed and subsumed within NMFS'
considerations of severity of effect and vulnerability of affected
populations. Similarly, NRDC provides no justification as to why stress
would appropriately be considered separately in this analysis, and no
useful recommendation as to how to do so, if appropriate. We believe we
have appropriately acknowledged the potential effects of stress, and
that these potential effects are accounted for within our overall
assessment of potential effects on marine mammals.
Comment 9: NRDC states that NMFS uses an ``arbitrary'' method to
convert area-specific risk scores into a ``basis for making Gulf-wide
negligible impact determinations.'' NRDC takes issue with NMFS' use of
the median of zone-specific risk ratings (for those zones including at
least 0.05 percent of GOA-wide abundance for a particular species),
suggesting that the application of this method inappropriately
minimizes findings of ``high'' to ``very high'' risk for certain
species in Zone 5, where there is a confluence of relatively high
levels of survey activity and high proportions of GOA-wide abundance
for some species, resulting in high take numbers. NRDC expressed
concern that using the median does not allow for appropriate
consideration of the importance of specific areas to a particular
species, i.e., that this approach ``smooths'' away granularity of the
risk assessment.
Response 9: We disagree with NRDC's comments on this topic, and
note that NRDC provided no alternative recommendation. On the contrary,
NMFS' approach explicitly incorporates considerations of the importance
of a particular area to a species, or the particular localized threats
faced by a species, through the zone-specific vulnerability assessment
that contributes to the overall risk rating. In addition, NMFS'
approach is specifically designed to retain considerations of zone-
specific impacts and vulnerability beyond simply the inclusion of the
vulnerability scoring. For example, an alternative approach to
generating a GOA-wide risk rating would be to employ a wholly different
paradigm in which aggregate GOA-wide vulnerability and severity scores
are assessed, versus taking a median value of zone-specific ratings.
NMFS retained the median value approach precisely because we believe
that evaluating risk for such a large and variable area (i.e., the
entire U.S. GOA) with species and activities that are each highly
localized would provide only a very general and less informative answer
regarding risk. The approach employed by NMFS highlights the
fundamental importance of the spatiotemporal intersection of animals
and activity as the fundamental driver in evaluating risk, while also
allowing us to avoid exactly the effect of concern to NRDC (blurring of
localized scoring) by avoiding the influence of areas where a
particular species essentially does not occur on the overall risk
rating for that species.
NRDC is incorrect that use of the median value is inappropriate or
that it has ``no biological basis.'' We note that mean (or average)
values can be more heavily skewed by outliers with small sample size
than median values. Thus, we chose the median as a better descriptor of
central tendency, which is a more appropriate perspective for the risk
analysis. (We also rounded up values of 0.5 (e.g., median score of 3.5
would be rounded to a 4), a mathematically valid approach that builds
in a reasonable degree of conservatism.)
One of the fundamental values of the analytical framework is that
it is structured in a spatially explicit way that can be applied at
multiple scales, based on the scope of the action and the information
available, to inform an assessment of the risk associated with the
activity (or suite of activities). This allows one to generate overall
risk ratings while also evaluating risk on finer scales. In this case,
severity ratings were generated on the basis of seven different GOA
zones, allowing an understanding not only of the relative scenario-
specific risk across the entire GOA, as is demanded for this analysis,
but also to better understand the particular zones where risk may be
[[Page 20797]]
relatively high (depending on actual future survey effort) and what
part of the stock's range may be subject to relatively high risk.
NRDC cites the Expert Working Group (EWG) Report in support of its
comment, stating it was ``[telling]'' that ``report did not contrive a
Gulf-wide risk assessment'' and that ``doing so would have belied the
very different purpose underlying its design: a relative risk
assessment across multiple species and geographies.'' Although the
initial EWG report (Southall et al., 2017) made available for public
review of the framework concept did not derive GOA-wide risk ratings,
the EWG did so in a later draft report that NMFS adopted in producing
the risk evaluation presented in its 2021 final rule.
Comment 10: NRDC asserts that NMFS has failed to appropriately
account for stock structure and the importance of certain habitat in
its negligible impact analysis, highlighting bottlenose dolphins and
sperm whales.
Response 10: Regarding bottlenose dolphins, NRDC criticizes the use
of generic risk ratings that homogenize risk for three shelf and
coastal bottlenose dolphin stocks. NRDC's comment dramatically inflates
this issue through reference to the total 36 stocks of bottlenose
dolphin found in the GOA. In fact, 31 of these stocks are comprised of
bay, sound, and estuarine populations that are not expected to be
affected by the specified activity considered herein. We described and
discounted the potential for impacts to these stocks of bottlenose
dolphin in the 2018 notice of proposed rulemaking (83 FR 29212, June
22, 2018). As described there, estuarine stocks of bottlenose dolphin
primarily inhabit inshore waters of bays, sounds, and estuaries (BSE),
and stocks are defined throughout waters adjacent to the specified
geographical region. However, estuarine stock ranges are generally
described as including coastal waters (i.e., waters adjacent to shore,
barrier islands, or presumed outer bay boundaries and outside of
typical inshore ranges) to approximately 1-3 km. For example,
bottlenose dolphins that were captured in Texas and outfitted with
radio transmitters largely remained within the bays, with three
individuals tracked to 1 km offshore (Lynn and W[uuml]rsig, 2002).
Radio-tracking of dolphins in the St. Joseph Bay, Florida area showed
that most dolphins stayed within the bay and that, although some
individuals ranged more than 40 km along the coastline from the study
site, they never ventured outside of immediate nearshore waters (Balmer
et al., 2008). Dolphins captured in Barataria Bay, Louisiana were
fitted with satellite-linked transmitters, showing that most dolphins
remained within the bay, while those that entered nearshore coastal
waters remained within 1.75 km (Wells et al., 2017). Therefore, these
stocks would not generally be expected to be impacted by the described
geophysical surveys. If a deep penetration seismic survey were
occurring in nearshore Federal waters (i.e., at least 3 miles from
shore but 9 miles from shore off Texas and Florida), it is possible
that a dolphin belonging to a BSE stock could be affected. However,
such surveys are expected to be rare in such shallow waters, and given
the fact that BSE dolphins in sheltered inshore waters would largely
not be impacted by noise generated offshore, we believe that impacts
from the specified activities that could potentially be considered as a
``take'' (as defined by the MMPA) should be considered discountable.
Further, the eastern coastal stock of bottlenose dolphin range is
entirely outside the specified geographical region, and the segregation
of density models into ocean and shelf/coastal domains means that
stock-specific risk ratings may be attributed to the oceanic stock of
bottlenose dolphin. Therefore, the issue described by NRDC is limited
to three stocks of bottlenose dolphin: the continental shelf and
western and northern coastal stocks, for which homogenized risk ratings
are provided for Zones 2 and 3.
Overall, species-level take and abundance estimates are used to
support risk ratings for bottlenose dolphins in Zones 2 and 3 out of
necessity. As acknowledged in our negligible impact analysis, the best
available information (Garrison et al., 2023) was used to inform
combined stock values for these zones and did not support further
quantitative apportionment of estimated take or abundances to stocks.
However, NRDC's criticism of the development of risk ratings for these
stocks of bottlenose dolphins is unwarranted. The risk rating is
comprised of the severity score, reflecting the homogenous take
information available for the three stocks in Zones 2 and 3, and the
vulnerability score, which is designed to incorporate stock-specific
information regarding status and threats. The population portion of the
vulnerability score comprises three components: status, i.e., is the
stock listed under the ESA and/or designated as depleted under the
MMPA; trend, i.e., does information over the available time series of
abundance estimates indicate a trend; and size, i.e., is the population
defined as small (less than 2,500). None of the designated stocks of
bottlenose dolphin in Federal waters of the GOA are listed under the
ESA or designated as depleted under the MMPA, and none would be classed
as small. Regarding trend, for each of the three stocks, two point
estimates of abundance are available based on aerial data from surveys
during 2011-2012 and 2017-2018 (Garrison et al., 2021). Each of these
surveys had a similar design and was conducted using the same aircraft
and observer configuration. For each of the three stocks, the 2017-2018
estimate is larger than the 2011-2012 estimate. While a formal trends
analysis is not possible based on two point estimates, the information
does suggest an increasing trend for these stocks for the purposes of
the trend component of the population score. We recognize that the
effects of the Deepwater Horizon (DWH) oil spill included likely
population reductions for all GOA marine mammal stocks; however, the
best available information indicates that these reductions were likely
modest for all bottlenose dolphin stocks other than the northern
coastal stock, and no more recent population abundance estimates that
might reflect any potential reduction are yet available. While the
likely decline in population abundance for northern coastal bottlenose
dolphins is subsumed within the population score assigned for
bottlenose dolphins at the species level for Zones 2 and 3,
vulnerability scoring is necessarily performed at the species level
such that it may appropriately be integrated with the take-based
severity scoring and used to generate an overall zone-specific risk
rating. As mentioned above, the best available scientific information
does not allow for stock-specific parsing of take for bottlenose
dolphins in Zones 2 and 3. Moreover, the trend component of the
population score is a relatively small contribution to the overall
vulnerability scoring. The likely decline in population abundance for
northern coastal bottlenose dolphins, although not reflected in the
existing vulnerability scoring, is insignificant as a contribution to
the overall vulnerability score for bottlenose dolphins as a species.
As noted above, the effects of the DWH oil spill are separately
accounted for in the vulnerability scoring and, in summary, the stock-
specific status concerns described by NRDC are incorporated to the risk
ratings (though we reiterate that NRDC's references to concern relating
to the Barataria Bay stock of bottlenose dolphins is in error, as this
stock will not be impacted by the specified activities). Importantly,
and also not accounted for in the risk assessment
[[Page 20798]]
framework, we include significant mitigation (time-area restriction)
intended to alleviate impacts to northern coastal bottlenose dolphins
during periods of greatest importance for their reproductive behavior.
NRDC contends that through use of homogenous relative risk ratings
addressing the combination of bottlenose dolphin stocks residing in
Zones 2 and 3, the actual authorization of take of bottlenose dolphins
through LOAs could result in greater than a negligible impact through
disproportionate impact to the shelf and two coastal stocks of
bottlenose dolphin that may be impacted by survey activity occurring in
Zones 2 and 3. However, we reiterate that the issues of concern to NRDC
are applicable only to the shelf and coastal bottlenose dolphin stocks
and Zones 2 and 3, while the majority of projected bottlenose dolphin
takes would be expected to accrue to oceanic stock dolphins, reflecting
the greater amount of survey effort projected for Zones 4-7. Moreover,
as discussed earlier, the risk ratings are only one component of NMFS'
negligible impact analysis for each respective stock. Even for these
stocks, the implementation of the rule is bound by the description of
the specified activity that informs the analysis. That is, the
specified activity is comprised of zone- and year-specific effort
projections that inform the take estimates and, therefore, the analysis
supporting issuance of the rule. Were actual effort to occur in a
manner inconsistent with the specified activity, it would not be within
the analysis contemplated by the rule. NRDC's comment addresses a
hypothetical that cannot occur and still be within the bounds of the
rule.
NRDC's additional suggestion, using sperm whales as a case study,
that the ``averaging of zones disregards the heightened relevance of
certain areas to species ecology,'' has no merit. Leaving aside that we
do not ``average zones''--elsewhere in its letter, NRDC criticizes
NMFS' use of median values to derive Gulf-wide risk ratings--as
explained above, both the Gulf-wide and zone-specific relative risk
ratings factor into NMFS' negligible impact analysis, as does
consideration independent of the risk ratings of impacts to habitat.
Comment 11: Animal Counsel states that NMFS must provide species-
specific impact analyses for each species within the blackfish, beaked
whale, and Kogia guilds rather than relying solely on guild-level
estimates.
Response 11: NMFS has performed the requisite species- and stock-
level analyses. We acknowledge that stock-specific take estimates
cannot be derived based on the available scientific information, which
is resolved for the referenced groups only at the guild level. As
described in the Estimated Take and Negligible Impact Analysis and
Determinations sections, sightings of these species that provide the
basis for both abundance estimates provided in NMFS' Stock Assessment
Reports (SARs) and for the density models comprising the best
scientific information available regarding marine mammal occurrence in
the GOA typically cannot be resolved to the species level. These
species are first rarely sighted due to their pelagic distribution and
typical high availability bias due to deep-diving behavior and cryptic
nature when at the surface, and are generally difficult to distinguish
between species when visually observed in the field. Accordingly,
abundance estimates in NMFS SARs are recorded for Mesoplodon spp. (and,
separately, for the goose-beaked whale) and Kogia spp. For the broader
beaked whale and blackfish guilds, available sightings data, including
often unresolved sightings, must be combined in order to develop
habitat-based density models, as were used to inform our acoustic
exposure modeling effort. Therefore, density and take estimates in this
rule are similarly lumped for the referenced guilds, and there is no
additional information by which NMFS could appropriately apportion
impacts other than equally/proportionally across the constituent
species. Animal Counsel appears to misunderstand our description of
these issues, suggesting that these issues are only superficial
(``grouping based on superficial similarity in looks'') and therefore
unjustified compared with grouping that may be based on ecological
similarity. In this case, these issues are indistinguishable: as
described above, the reliance on undifferentiated sightings for members
of these guilds is in fact due to similarities in ecological function
as well as to visual similarity. However, of greater importance is that
Animal Counsel appears to misunderstand our treatment of the
constituent species of these guilds in the negligible impact analysis.
We reiterate and confirm here that, while we are unable to precisely
apportion estimated take to the species level (reflecting the
scientific information available to inform the take estimates), we
import species-specific considerations to qualitative aspects of the
negligible impact analysis and, in so doing, reach the requisite
species- and stock-specific negligible impact determinations.
Comment 12: NRDC asserts that NMFS has erroneously used the
relativistic assessment produced through the risk assessment framework
as the basis for the negligible impact determination, incorrectly
applying it as though it evaluated absolute risk.
Response 12: NMFS disagrees with the comment. The relative risk
ratings produced through the framework did not replace our judgments
regarding the absolute risk to stocks from the specified activity
represented by the negligible impact determinations. The relative risk
ratings, both Gulf-wide and zone-specific, are one factor in NMFS'
stock specific negligible impact determinations. Despite thorough
discussion of all relevant factors for each stock in the Negligible
Impact Analysis and Determinations section, NRDC confuses our reference
to the straightforward risk rating terms (e.g., low, moderate, high) as
being solely determinative of the negligible impact determinations.
The risk assessment analysis is an important component of the
negligible impact analysis, but is not the sole basis for our
determination. Similarly, implicit in NRDC's complaints regarding NMFS'
method of evaluating Gulf-wide risk is the suggestion that NMFS did not
also consider zone-specific risk in its negligible impact
determinations. These claims are incorrect. We incorporate the Gulf-
wide relative risk ratings to our negligible impact analysis, but also
provide appropriate focus to the specific zones for each species or
guild where relative risk was evaluated to be highest. While the risk
assessment analysis comprehensively considered the spatial and temporal
overlay of the activities and the marine mammals in the GOA, as well as
the number of takes predicted by the described modeling, there are
details about the nature of any ``take'' anticipated to result from
these activities that were not considered directly in the risk
assessment analysis and which warrant explicit consideration in the
negligible impact analysis. Accordingly, NMFS' analysis considers the
results of the risk assessment analysis, the effects of the required
mitigation, and the nature and context of the takes that are predicted
to occur. NMFS' analysis also explicitly considers the effects of
predicted Level A harassment, duration of Level B harassment events,
and impacts to marine mammal habitat, which respectively were not
integrated into or included in the risk ratings. These components of
the full analysis, along with any germane species or stock-specific
information, are integrated and
[[Page 20799]]
summarized for each species or stock in the Species and Stock-specific
Negligible Impact Analysis Summaries section of the negligible impact
analysis.
In addition, while the risk assessment framework comprehensively
considers the aggregate impacts to marine mammal populations from the
activities addressed in this rule in the context of both the severity
of the impacts and the vulnerability of the affected species, it does
not fully consider the absence of survey activity in the eastern GOA.
While this is to some degree reflected in the updated take estimates,
and thereby incorporated into the risk ratings, the absence of survey
activities within areas of greater biological importance for certain
species benefits those species GOA-wide beyond what is simply reflected
in the updated take numbers. The negligible impact analysis considers
the beneficial effects of the absence of survey activity in the eastern
GOA regarding both acute and chronic effects.
Also, we note that while the risk assessment framework produces
relativistic risk ratings, its components consist of absolute concepts,
some of which are also absolutely quantified (e.g., whether the
specified activity area contains greater than 30 percent of total
region-wide estimated population, between 30 and 15 percent, between 15
and 5 percent, or less than 5 percent). Further, NMFS provided
substantive input into the scoring used in implementing the EWG
framework for the GOA, to ensure that the categories associated with
different scores, the scores themselves, and the weight of the scores
within the overall risk rating all reflected meaningful biological,
activity, or environmental distinctions that would appropriately inform
the negligible impact analysis. Accordingly, and as intended, we used
our understanding of the framework and best professional judgment to
interpret the relativistic results of the risk assessment analysis
appropriately into the larger negligible impact analysis, with the
other factors discussed above, to make the necessary findings specific
to the effects of the total taking on the affected species and stocks.
Comment 13: NRDC asserts that the rule allows for take in excess of
the estimates used in its negligible impact determinations.
Response 13: NRDC's comment suggests a misunderstanding of the
acoustic exposure modeling process. The comment assumes that because
the modeling involved placement of one survey simulation area in each
of the seven original modeling zones, real-world surveys taking place
at other locations would take place under conditions (e.g., acoustic
propagation, marine mammal density) different than those modeled. That
comment confuses the smaller survey boxes with the simulation areas
within which sound exposure was modeled, stating that ``none of the
nominal surveys, save for the survey modeled for zone 4, appear to take
place within the proposed critical habitat of Rice's whale'' despite
the fact that six out of the seven simulation areas overlap the 100-400
m isobaths that mark the proposed designation of Rice's whale critical
habitat.
A fundamental component of the modeling approach was the
thoroughness with which Gulf-wide conditions were represented in the
modeling. Key modeling aspects with geospatial dependence include
acoustic propagation conditions and marine mammal density. For the
former, propagation conditions were modeled at each of 10 locations
representing a full range of static conditions (depths and bottom type)
in both the central and western Gulf, with conditions at each of these
10 locations modeled in multiple seasons to understand the full range
of dynamic conditions (sound speed profiles). The resulting sound
fields were then used in animal movement modeling within the simulation
areas to represent the full range of potential conditions that marine
mammals may encounter throughout the Gulf and throughout the year.
Similarly, average marine mammal density values for each zone were then
used to scale the modeled exposure estimates according to real-world
density values. While the use of zone-wide average density values does
smooth spatial variability in likelihood of encountering particular
species of marine mammal, the overall result, both within and across
surveys, is a reasonable representation of the likelihood of exposing
particular species to sound exceeding harassment criteria.
NMFS acknowledges that a real-world survey occurring in an area
with marine mammal occurrence higher than the zonal average may
encounter more marine mammals than expected, just as a survey occurring
in an area with marine mammal occurrence lower than the zonal average
may encounter fewer marine mammals than expected. Overall, during the
course of rule implementation, there is no fundamental aspect of the
modeling that would result in directionally more marine mammals being
impacted than we assume here, regardless of location or season.
Comment 14: NRDC states that NMFS' analysis of the consequences of
exposure in support of the negligible impact analysis ``contradicts the
factual record,'' asserting that NMFS wrongly assumed low severity for
certain exposure durations and disregarded repeated exposures. Animal
Counsel similarly suggests that NMFS ignores the consequences of
exposure, referring to the ``cumulative impacts of repeat harassment.''
Response 14: While NMFS evaluated exposure durations, which are
critical to understanding how the authorized takes are likely to impact
individual marine mammals, the negligible impact analysis is not
dependent on this or any other single factor, as described fully in the
Negligible Impact Analysis and Determinations section. Exposure
duration was not addressed in the risk assessment framework but was
incorporated into the negligible impact analysis.
As we indicate in the Negligible Impact Analysis and Determinations
discussion of this final rule, to put the predicted amount of take into
meaningful context, it is useful to understand the duration of exposure
at or above a given level of received sound (as well as the likely
number of repeated exposures across days). While even a momentary
exposure above the criteria for Level B harassment counts as an
instance of take, that accounting does not make any distinction between
fleeting exposures and encounters in which an animal may be exposed to
that received level of sound for a longer period of time. This
information is meaningful to an understanding of the likely severity of
the exposure, which is relevant to the negligible impact evaluation.
For example, for bottlenose dolphin exposed to noise from 3D WAZ
surveys in Zone 6, the modeling report shows that approximately 72
takes (Level B harassment) would be expected to occur in a 24-hr
period. However, each animat modeled has a record or time history of
received levels of sound over the course of the modeled 24-hr period.
The 50th percentile of the cumulative distribution function indicates
that the time spent exposed to levels of sound above 160 dB rms SPL
(i.e., the 50 percent midpoint for Level B harassment) would be only
1.8 minutes--a minimal amount of exposure carrying little potential for
significant disruption of behavioral activity.
The Species and Stock-specific Negligible Impact Analysis Summaries
discussion considers the relative impact ratings in conjunction with
required mitigation and other relevant contextual information--
including exposure durations at the various thresholds--to produce an
assessment of impact to the
[[Page 20800]]
stock or species, i.e., the negligible impact determinations. For
beaked whales, take is estimated on the basis of a risk function
shifted down such that 90 percent of the animals exposed to received
levels above 140 dB and 50 percent exposed to received levels above 120
dB are predicted to be harassed. We used this approach based on the
documented behavioral sensitivity of beaked whales. However, as NRDC
acknowledges, context is important when assessing behavioral responses
to sound. The exposures above 120 dB here occur at significant distance
from the source (i.e., greater than 50 km). It is generally accepted
that an animal's distance from the sound source plays an important role
in the animal's behavioral response to a received sound level (e.g.,
Gomez et al., 2016). NMFS believes that exposures to the relevant
harassment thresholds at significant modeled distances from the actual
sound source, although included in the take estimates based on the risk
function, will not carry significant consequences for the potentially
exposed animals. Rather, these exposures are likely to result in
significantly less severe responses (if any). Examples provided by NRDC
purporting to demonstrate greater severity of response than we have
assumed include irrelevant examples--beaked whales are known to respond
with greater severity to mid-frequency active military sonar than to
other sources, as discussed in greater detail in the Potential Effects
of the Specified Activities on Marine Mammals and Their Habitat section
of the proposed rule--and examples of ``responses'' entailing changes
to vocalization patterns over longer durations, but these responses do
not necessarily rise to the level of a take, much less a take event of
significant severity.
Regarding repeated exposures, despite the figures cited by NRDC
concerning potential days of activity, it is unlikely that any given
individual animal would in fact experience repeated take events of the
magnitude suggested. Each of the GOA zones is an extremely large area
(average zone size approximately 100,000 km\2\), and the likely
harassment ``footprint'' of any given survey would be relatively small.
Modeled isopleth distances to the 160-dB threshold are approximately 12
km for low-frequency cetaceans (i.e., the Rice's whale), 7 km for high-
frequency cetaceans (i.e., sperm whales, beaked whales, dolphins), and
6 km for very high-frequency cetaceans (i.e., Kogia spp.). Distances to
the 140-dB isopleths are substantially larger, but we again emphasize
that only 10 percent of the animals exposed at that level would be
expected to incur harassment, while 50 percent of the animals exposed
at the 160-dB level would be expected to incur harassment. It is clear
that, in reality, there is a relatively low chance of any given
individual marine mammal being repeatedly taken within relatively short
timeframes, much less that such events would result in fitness
consequences for those individuals. Additionally, NRDC suggests that
NMFS fails to consider repeated takes at all, when in fact this
likelihood is inherently addressed through the severity rating of the
risk assessment.
Comment 15: NRDC claims that NMFS' negligible impact analysis is
inappropriately reliant upon the prescribed mitigation and, further,
that the mitigation will be ineffective. NRDC further expressed concern
regarding the efficacy of the prescribed visual and acoustic monitoring
methods, stating that species could go undetected. NRDC also repeats an
erroneous claim from prior letters that acoustic shutdowns for sperm
whales are not required under the ITRs.
Response 15: NMFS did not rely on the mitigation in the negligible
impact analysis to the degree NRDC implies. As is stated in the
analysis, consideration of the implementation of prescribed mitigation
is one factor in the analysis but is not determinative in any case. In
certain circumstances, mitigation is more important in reaching the
negligible impact determination, e.g., when mitigation helps to
alleviate the likely significance of taking by avoiding or reducing
impacts in important areas.
NRDC misunderstands the degree to which NMFS relies on shutdowns
for sensitive or vulnerable species, including beaked whales, at
extended distances. We agree that these measures in and of themselves
will have limited benefit for cryptic species such as beaked whales
that are unlikely to be observed. However, we believe it makes sense to
minimize the duration and intensity of exposure for these species when
they are observed, and because shutdowns are practicable we include
them in the suite of prescribed measures and discuss them where
appropriate. For more readily detected species, such as the sperm
whale, which is easily detected when at the surface and vocalizes
frequently while underwater, the extended distance shutdowns (for both
visual and acoustic detections) should appropriately be considered
influential in our assessment of impacts to affected individuals and,
therefore, ultimately on the stock. In summary, we consider these
measures appropriately as mitigating factors when considering context
as part of our negligible impact analysis.
While NMFS disagrees with some specific comments regarding
efficacy, we generally agree with the overall point that there are
limitations on what may reasonably be expected from either visual or
acoustic monitoring. While visual and acoustic monitoring effectively
complement each other, and acoustic monitoring is the more effective
monitoring method (for certain species) during periods of impaired
visibility, there is no expectation that these methods will detect all
marine mammals present. In general, NRDC appears to misunderstand what
NMFS claims with regard to what such monitoring may reasonably be
expected to accomplish and/or the extent to which we rely on
assumptions regarding the efficacy of monitoring in reaching the
necessary findings. We acknowledge these limitations in prescribing
these monitoring requirements, while stating why NMFS believes that
visual and acoustic monitoring, and the related protocols we have
prescribed, are an appropriate part of the suite of mitigation measures
here that satisfy the MMPA's least practicable adverse impact standard.
However, the negligible impact finding is not conditioned on the
presumption of a specific degree of monitoring efficacy.
Regarding NRDC's claim that ``NMFS hasn't included an acoustic
shutdown requirement for sperm whales in its proposed regulation,'' we
clarify that the requirement to shut down ``upon detection of a sperm
whale,'' which was described in detail in the notice of proposed
rulemaking and is included in this final rule, includes detection by
either visual or acoustic means.
Comment 16: NRDC asserts that NMFS ``arbitrarily dismissed high
number of injuries'' for Kogia spp. Animal Counsel also expressed
concern regarding Kogia spp., suggesting similarly that the estimated
takes of these species were significantly greater than the total
population.
Response 16: As basis for its claim that the assessed Level A
harassment events are of such magnitude as to call into question NMFS'
negligible impact determinations, NRDC states that the annual number of
injuries ``would amount to 2.4 times the size'' of the Kogia spp.
population and ``exceed potential biological removal by some 6700
percent.'' (We note that although irrelevant, NRDC's calculations for
both values are incorrect.) However, these values are based on the
severely negatively biased abundance estimate of 336 provided in NMFS'
SAR. Animal
[[Page 20801]]
Counsel similarly compares the estimated takes of these species to the
SAR abundance estimate of 336. As discussed in the notice of proposed
rulemaking (and below), but omitted by NRDC, NMFS' SARs state that the
abundance estimate provided for Kogia spp. is likely a severe
underestimate because it was not corrected for the probability of
detection on the trackline, and because Kogia spp. are often difficult
to see, present little of themselves at the surface, do not fluke when
they dive, and have long dive times. In addition, they exhibit
avoidance behavior towards ships and changes in behavior towards
approaching survey aircraft. As a result, as stated in the notice of
proposed rulemaking, we appropriately refer to the model-generated
estimated abundance of 1,385 as the most appropriate estimate of
abundance available for Kogia spp.
NRDC's argument is based entirely on its premise that if the
estimated instances of Level A harassment are so large in comparison
with the affected population, it cannot be true that the population-
level effects of the assessed Level A harassment events can be mild,
i.e., that a majority of the population would experience repeated
hearing loss, leading to greater injury. Therefore, the invalid basis
for the premise renders the comment irrelevant.
Comment 17: Animal Counsel suggests that NMFS' analysis related to
Rice's whale is deficient, stating that NMFS must ``conduct a separate,
dedicated Rice's whale impact analysis incorporating post-2024 passive
acoustic data, the multi-year NOAA trophic ecology study, and a
population viability model.'' Animal Counsel separately suggests that
NMFS' consideration of prey species impacts is deficient.
Response 17: NMFS fully considered the information Animal Counsel
references. In our view, these investigations solidify NMFS' previous
understanding of the importance of continental slope waters between
approximately 100-400 m water depth as Rice's whale habitat. The
previously used spatial density model for Rice's whale (Roberts et al.,
2016) identified waters of approximately 100-400 m depth on the
continental slope throughout the GOA as potential habitat, and the
updated density model (which, as discussed previously, incorporates new
data on Rice's whale habitat associations) predictions do not markedly
differ (Garrison et al., 2023).
NMFS fully considered new information concerning acoustic
detections of Rice's whales in areas along the shelf break in the
central and western GOA, which demonstrates year-round Rice's whale
occurrence in areas outside of the previously identified core habitat.
Soldevilla et al. (2022) detected Rice's whale calls at sites in the
central GOA south of Louisiana. A subsequent study placed acoustic
recorders in shelf break waters in the same central GOA area and added
a location in the western GOA offshore of Texas (Soldevilla et al.,
2024). This information provides additional evidence of the regular
occurrence of Rice's whales outside the northeastern GOA, with Rice's
whale calls recorded on 33 and 25 percent of days at the central and
western GOA sites, respectively. As in the prior study, calls were
recorded throughout the year. Continued study has demonstrated the
persistence of Rice's whale presence in the western GOA (Debich et al.,
2025a,b).
In summary, available data related to marine mammal presence and
habitat, including impacts to prey species, were considered in the
negligible impact analysis. Animal Counsel does not provide adequate
detail regarding either the manner in which it believes we did not
adequately consider the cited factors, or provide sufficiently detailed
recommendations regarding the impact analysis it suggests be conducted,
including how it should be conducted differently than or incorporated
differently to the impact analysis we present in the Negligible Impact
Analysis and Determinations section.
Comment 18: Animal Counsel raises concerns regarding NMFS'
negligible impact analysis through comparison of take estimates to
NMFS' Potential Biological Removal values.
Response 18: PBR is defined in the MMPA (16 U.S.C. 1362(20)) 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 is
a measure to be considered when evaluating the effects of mortality or
serious injury on a marine mammal species or stock. Harassment is not
equivalent to serious injury and does not ``remove'' an individual from
a stock. Therefore, the PBR metric is not relevant to an evaluation of
the effects of harassment on a stock in the manner suggested by the
commenter.
Comment 19: Animal Counsel suggests that NMFS should discount
consideration of practicability in determining the appropriate suite of
mitigation requirements.
Response 19: Animal Counsel states that practicability should not
hold equal weight with consideration of the effectiveness of a measure
when evaluating measures towards achieving the MMPA standard of ``least
practicable adverse impact.'' Because mitigation requirements are
inherently burdensome, Animal Counsel suggests that consideration of
this factor is in conflict with the MMPA. However, this reading is in
contradiction with the statutory requirement to prescribe the ``means
of effecting the least practicable adverse impact.'' Consideration of
practicability is ingrained in the very standard that Animal Counsel
urges NMFS to meet, and disregarding practicability would contradict
the requirements of the MMPA.
Animal Counsel also suggests that consideration of practicability
is at odds with the need to based decisions on the best scientific
information available. However, relevant data are not limited to
consideration of mitigation effectiveness, but also contribute to an
understanding of the operational impacts of a measure, i.e.,
practicability. In either case (consideration of mitigation
effectiveness and practicability), NMFS must consider the available
data and make judgments regarding these two primary factors.
In the evaluation of specific measures, the details of the
specified activity will necessarily inform each of the two primary
factors discussed above (expected reduction of impacts and
practicability) and are carefully considered to determine the types of
mitigation that are appropriate under the least practicable adverse
impact standard. Analysis of how a potential mitigation measure may
reduce adverse impacts on a marine mammal stock or species and
practicability of implementation are not issues that can be
meaningfully evaluated through a yes/no lens. The manner in which, and
the degree to which, implementation of a measure is expected to reduce
impacts, as well as its practicability, can vary widely. For example, a
time-area restriction could be of very high value for reducing the
potential for, or severity of, population-level impacts (e.g., avoiding
disturbance of feeding females in an area of established biological
importance) or it could be of lower value (e.g., decreased disturbance
in an area of high productivity but of less firmly established
biological importance). Regarding practicability, a measure might
involve restrictions in an area or time that impede the operator's
ability to acquire necessary data (higher impact), or it could mean
incremental delays that increase operational costs but still allow the
activity to be conducted (lower impact). A
[[Page 20802]]
responsible evaluation of ``least practicable adverse impact'' will
consider the factors along these realistic scales. Expected effects of
the activity and of the mitigation as well as status of the stock all
weigh into these considerations. Accordingly, the greater the
likelihood that a measure will contribute to reducing the probability
or severity of adverse impacts to the species or stock or their
habitat, the greater the weight that measure is given when considered
in combination with practicability to determine the appropriateness of
the mitigation measure, and vice versa.
We acknowledge that in some cases, certain mitigation may be
necessary in order to make a ``negligible impact'' finding for an
affected species or stock, which is a fundamental requirement of
issuing an authorization--in these cases, consideration of
practicability may be a lower priority for decision-making if impacts
to marine mammal species or stocks would not be negligible in the
measure's absence. However, this circumstance is not present in the
analysis presented herein, and practicability must be given due
consideration.
Comment 20: NRDC comments that, overall, NMFS has not prescribed
mitigation measures sufficient to meet the MMPA's LPAI standard, and
specifically that NMFS must prescribe an area closure for Rice's whale
in order to meet this standard. Animal Counsel expresses similar
concerns regarding NMFS' assessment of the available science regarding
Rice's whale habitat and its LPAI analysis.
Response 20: NRDC provides no actionable recommendation beyond the
assertion that NMFS must ``provide an area closure'' for Rice's whale.
As discussed at length in the Mitigation section of this final rule, we
find that, while there is now robust evidence that Rice's whales
utilize areas of the Gulf within roughly the 100-400 m depth isobaths
outside of their northeastern GOA core habitat area, key questions
remain about Rice's whale abundance, density, habitat use, demography,
and stock structure in the central and western GOA. As was acknowledged
by NMFS in its proposed rule to designate critical habitat for Rice's
whale, aside from visual and acoustic detections indicating presence,
this area hosts features that comprise characteristics of habitat that
is essential to the species. However, it does not follow that the area
must be closed to activity of a certain sector, in this case
geophysical survey activity. And as described in the notice of proposed
rulemaking and later in this rule, there is no available scientific
information that would enable NMFS to identify any particular portion
of this broad swath of suitable habitat throughout the GOA that is of
particular importance, or to identify any time of year when this
habitat may be of particular importance. Absent this information, NMFS
is left to contemplate a complete, year-round closure to geophysical
survey effort of the 100-400 m isobaths across the entire central to
western GOA, based solely on data establishing that the habitat
contains features making it suitable for Rice's whale use, and scant
information establishing that Rice's whales are present in unknown
numbers in this area. NRDC does not dispute that the available
information does not enable identification of any area or time that
could be subject to meaningful consideration as a closure, and it does
not attempt to identify and recommend any such area. Instead, NRDC
implies that the entire area should be closed by asserting that the
MMPA ``places no ceiling on the amount of habitat that may be subject
to mitigation'' and that the entire area should be closed as a result
of its assertion that the MMPA demands ``overprotection'' rather than
``underprotection,'' without acknowledging that the measures included
in the rule may be the right amount of protection.
NRDC's argument in favor of some sort of area closure rests on a
misunderstanding of the acoustic exposure modeling supporting the
rule's take estimates. NRDC wrongly asserts that NMFS' modeling
``placed its nominal surveys entirely or almost entirely outside the
[Rice's] whale's habitat,'' leading to the misguided assertion that
``the rule itself is insufficient to ensure that actual take remains
within authorized numbers.'' As we address in greater detail above, the
exposure modeling is representative of all habitat, including Rice's
whale habitat, that may be traversed by projected survey effort, and
the assertion that much greater impacts than have been modeled would
result is unsupported.
As discussed in detail in the notice of proposed rulemaking, the
rate of call detections throughout the year is considerably higher in
the eastern GOA than at the central GOA sites where calls were most
commonly detected, with at least 8.3 calls/hour among four eastern GOA
sites over 110 deployment days (Rice et al., 2014) compared to 0.3
calls/hour over the 299-day deployment at the central GOA site where
calls were detected most frequently during the Soldevilla et al. (2022)
study. During that study, approximately 2,000 total calls were detected
at the central site over 10 months, compared to more than 66,000 total
detections at the eastern GOA deployment site over 11 months
(approximately 30 times more calls detected at the eastern GOA site)
(Soldevilla et al., 2022). Similarly, Soldevilla et al. (2024) reported
detecting 0.2 calls/hour at the western GOA site off Texas (1,694
detections over 8,547 hours of recording). While continued monitoring
off Texas demonstrates ongoing, regular presence of whales (Debich et
al., 2025a,b), available information continues to suggest that density
and abundance of Rice's whales is likely lower in the central and
western GOA than in the species' core habitat area in the eastern GOA.
Regarding the suggestion that NMFS has not adequately considered
habitat in its consideration of mitigation, we disagree. Habitat value
is generally informed by marine mammal presence and use, and the
available data can support the consideration and discussion of impacts
to (and mitigation for) both marine mammals and their habitat
simultaneously. The discussion above clearly considers physical
features that can drive habitat use (e.g., depth), as well as detailed
information related to relative presence in the eastern versus the
central and western GOA, which is indicative of preferred habitat in
the east. Because habitat value is generally informed by marine mammal
presence and use, in some cases, there may be overlap in measures for
the species or stock and for use of habitat. NRDC has not presented any
information that would suggest habitat we did not consider for
mitigation.
In summary, the newly available data related to marine mammal
presence and habitat were considered under the LPAI standard, and we
concluded additional mitigation for Rice's whale was not warranted
under that standard. NRDC provides no persuasive argument to the
contrary.
Comment 21: NRDC finds fault with NMFS' consideration of
practicability concerning possible closure of potential Rice's whale
habitat in the central and western GOA to future survey activity,
suggesting that NMFS' reference to analysis presented in its Regulatory
Impact Analysis (RIA) for the 2021 rule is not relevant. Animal Counsel
similarly recommends that NMFS must implement restrictions on survey
activity in Rice's whale habitat (waters 100-400 m depth throughout the
Gulf). NRDC also suggests that NMFS must consider that the Outer
Continental Shelf Lands Act (OCSLA) ``requires a balancing between the
development of
[[Page 20803]]
offshore energy resources and the protection of marine resources.''
Response 21: As was acknowledged in the proposed rule, the RIA did
not directly evaluate a potential closure of potentially suitable
habitat in the central and western GOA outside of the Rice's whale core
distribution area. However, we disagree that the RIA is not relevant to
our practicability analysis here. The RIA's assessment of potential
restrictions in the northeastern GOA provided a useful framework for
considering practicability relating to a broad closure of potential
Rice's whale habitat to future survey activity.
To bolster that discussion, we turned to the same sources of data
referenced in the RIA in analysis of potential closure areas considered
therein (see <a href="https://www.data.boem.gov/Main/Default.aspx">https://www.data.boem.gov/Main/Default.aspx</a>). While areas
of Rice's whale habitat (i.e., water depths of 100-400 m on the
continental shelf break) contain less oil and gas industry
infrastructure than do shallower, more mature waters, and have been
subject to less leasing activity than deeper waters with greater
expected potential reserves, they nonetheless host significant industry
activity. BOEM provides summary information by water depth bin,
including water depths of 201-400 m. Omitting information regarding
water depths of 100-200 m, the area overlaps 33 active leases, with 17
active platforms and over 1,200 approved applications to drill. In the
past 20 years, over 500 wells have been drilled in water depths of 100-
400 m. These data confirm that there is substantial oil and gas
industry activity in this area and, therefore, the inability to collect
new seismic data could affect oil and gas development given that oil
companies typically use targeted seismic to refine their geologic
analysis before drilling a well. In addition, year-round occurrence of
Rice's whales in waters 100-400 m deep precludes the use of seasonal
closures to minimize exposure of Rice's whales. Therefore, we analyzed
the potential for a year-round closure, which exacerbates the potential
for effects on oil and gas productivity in the GOA because operators
have no ability to plan around the closure. While the area is not as
important to regional oil and gas productivity as the prospective
deepwater central GOA closure analyzed in the RIA (as we acknowledged
in the proposed rule), the more area-specific data provided above
continue to support NMFS' previous conclusions, which we affirm here:
(1) We are unable to delineate specific areas of Rice's whale habitat
in the central and western GOA where restrictions on survey activity
would be appropriate because there is currently uncertainty about
Rice's whale density, abundance, habitat usage patterns and other
factors in the central and western GOA; and (2) there is high
likelihood that closures or other restrictions on survey activity in
all waters of 100-400 m depth in the central and western GOA would have
significant economic impacts. Finally, we note that despite NRDC's
concerns, it does not recommend any particular closure that it believes
NMFS should evaluate.
Regarding NRDC's suggestions concerning OCSLA--a statute
administered by BOEM--NMFS' statutory obligations arise under the MMPA
(with associated requirements under the ESA, NEPA, and Administrative
Procedure Act (APA), among others). NMFS has no statutory obligation
relative to OCSLA. Similarly, NMFS' obligations under the MMPA require
that we prescribe the means of effecting the LPAI on the affected
species or stock and their habitat, which we have done here.
Comment 22: NRDC states that NMFS ``fails to consider mitigation
measures'' for Rice's whale, suggesting that NMFS consider: (1)
allowing some survey activities in Rice's whale habitat (i.e., the 100-
400 m isobaths), such as surveys undertaken by leaseholders to develop
their lease blocks, while prohibiting others; (2) extending
geographically vessel strike avoidance measures ``presently in effect
for industry''; and (3) requiring use of ``lowest practicable source
levels within the whales' communication frequencies for activities
taking place in the vicinity of the whales' habitat.'' Animal Counsel
also states that NMFS must impose a mandatory 10-knot vessel speed
restriction for all project vessels within Rice's whale habitat.
Response 22: NRDC does not provide supporting detail regarding its
recommended mitigation requirements. As such, NMFS is unable to fully
evaluate the suggested measures.
Regarding the suggestion to allow some surveys but prohibit others,
section 101(a)(5)(A) of the MMPA requires NMFS to make a determination
that the take incidental to a ``specified activity'' will have a
negligible impact on the affected species or stocks of marine mammals,
and will not result in an unmitigable adverse impact on the
availability of marine mammals for taking for subsistence uses. NMFS'
implementing regulations require applicants to include in their request
a detailed description of the specified activity or class of activities
that can be expected to result in incidental taking of marine mammals.
50 CFR 216.104(a)(1). Thus, the ``specified activity'' for which
incidental take coverage is being sought under section 101(a)(5)(A) is
generally defined and described by the applicant. Here, BOEM, having
joined the NMFS Policy request as co-petitioner, is an applicant for
the ITRs in support of industry operators, and we are responding to the
specified activity as requested, i.e., carrying forward the specified
activity underlying the 2021 rule (and making the necessary findings on
that basis). BOEM's initial petition made no distinction between
surveys that may be speculative or otherwise fall into a category of
surveys that NRDC suggests should be prohibited, and those that are
not.
Moreover, NRDC does not describe any useful metric for determining
which surveys should be allowed, aside from reference to ``surveys
undertaken by leaseholders to develop their lease blocks.'' The
suggestions are not sufficiently developed to allow for adequate
consideration.
Regarding vessel strike avoidance measures, NRDC does not specify
what measures it is referring to. However, the ITRs already contains a
suite of vessel strike avoidance measures that apply wherever survey
activity is occurring and, regarding Animal Counsel's recommendation,
these measures include practicable measures expected to avoid the risk
of vessel strike, including separation distance requirements from
whales and recommendations to slow speeds in the presence of whales.
Animal Counsel suggests that the rule is internally contradictory in
its ``reliance on 5-knot towing speeds;'' however, we are not reliant
on this fact in determining that strike is unlikely. We acknowledge
that support vessels and other vessels not towing gear may travel at
speeds in excess of 5 knots. However, it remains that a contributing
factor to our assessment of vessel strike risk is the fact that survey
vessels are typically slow-moving.
Finally, NRDC does not describe any useful scheme by which ``lowest
practicable source levels within the whales' communication
frequencies'' might be defined. An expert panel, convened by BOEM to
determine whether it would be feasible to develop standards to
determine a lowest practicable source level, determined that it would
not be reasonable or practicable to develop such metrics (see Appendix
L in BOEM, 2017). The subject matter is outside NMFS' expertise, and we
have no basis upon which to doubt the panel's published findings.
[[Page 20804]]
Comment 23: Animal Counsel presents certain mitigation
recommendations, including that NMFS should (1) require dedicated,
independent third-party marine mammal observers for all survey
operations, not only those where they are currently mandated; (2)
prohibit survey operations from continuing during any passive acoustic
monitoring (PAM) malfunction beyond the minimum time necessary for
troubleshooting; and, (3) increase exclusion and buffer zones to at
least 500 meters for all survey types and eliminate the dolphin
exception for shutdown requirements.
Response 23: NMFS has thoroughly evaluated all of Animal Counsel's
recommendations in this and prior related rulemakings, and has
previously addressed all of these issues. With regard to the suggestion
that third-party marine mammal observers should be required for all
survey operations, this is a requirement of the rule.
Regarding the allowance that survey operations may continue during
brief periods of PAM malfunction, we retain this feature as reasonable
consideration of both overall impacts of the suite of mitigation
requirements as well as practicability. It would serve little purpose
to require cessation of operations during such brief periods, as the
overall survey duration would be significantly extended due to the
frequent brief disruptions. Each cessation of survey operations
requires extended time to reposition the source vessels and engage in
necessary pre-clearance and ramp-up periods, and the amount of sound
energy in the water overall would be increased. Animal Counsel's
recommendation is short-sighted. In addition, the comment references at
length other issues associated with broader malfunction than is at
issue here, including hypothetical safety issues associated with
continued operation during malfunction of acoustic source equipment.
This provision of mitigation is solely with respect to malfunction of
the PAM listening devices.
Regarding its recommendation to increase exclusion and buffer
zones, Animal Counsel offers no supporting rationale other than the
unsupported premise that larger is better, claiming that NMFS' required
zones are arbitrary ``by NMFS' own admission.'' Nowhere in the record
has NMFS stated or suggested that its required zones are arbitrary.
NMFS provided a detailed rationale for both the size of the specified
zones and for the associated dolphin exemption.
Comment 24: NRDC states that NMFS ``fails to reconsider prescribing
quieter alternatives to conventional seismic airguns, despite evidence
of the availability of such alternatives,'' and claims that NMFS has
not adequately analyzed the practicability of such a requirement.
Animal Counsel states that NMFS must require similar measures.
Response 24: NMFS acknowledges that there are an increasing number
of sources that may reasonably be considered as environmentally
preferable to conventional airguns, including sources operating at
lower frequencies and without the high peak pressure output associated
with airguns. In fact, such sources have been used during certain
surveys conducted under NMFS-issued LOAs. However, imposing
requirements to use certain technologies, or prescribing the manner in
which geophysical survey data must be acquired, would exceed NMFS'
authority under the MMPA. Survey funders and operators define survey
objectives and methodologies, including which acoustic sources are
used, on the basis of data needs that are beyond NMFS' technical
expertise to judge. NRDC argues that specific mandates are not
required, versus a generic ``best available technology'' requirement,
but offers no recommended metrics. NMFS agrees that increased use of
environmentally preferable sources is an appropriate goal, but it would
be more appropriate to continue working with industry to incentivize
use of such sources and techniques rather than require them.
Comment 25: NRDC states that NMFS must consider ``measures to
eliminate duplicative surveys.''
Response 25: BOEM has historically been the subject matter expert
regarding whether and which surveys are ``duplicative.'' NRDC fails to
explain how this is within NMFS' statutory authority or suggest ways to
appropriately apportion the amount of effort that it believes should be
allowed. NMFS cannot arbitrarily limit planned effort and has no
legitimate means of changing the specified activity absent a conclusion
that the activity would have more than a negligible impact. However,
NMFS has made the necessary findings under the MMPA for issuance of
this rule. Similarly, NRDC states that NMFS should ``require BOEM to
eliminate unnecessary duplication of survey effort'' but does not
explain how they believe that this suggestion is within NMFS' statutory
authority. As the permitting agency, BOEM has the authority to require
permit applicants to submit statements indicating that existing data
are not available to meet the data needs identified for the applicant's
survey (i.e., non-duplicative survey statement), but such requirements
are not within NMFS' purview. NMFS may not demand that BOEM discharge
its authority under OCSLA in any particular manner. As stated
previously, NMFS considers the specified activity described by an
applicant in reviewing a request for an incidental take authorization.
Nothing in the statute provides authority to direct consolidation or
removal of activities based on some presumption of duplication that
NMFS is not qualified to judge.
NMFS also notes that, although surveys may be perceived as
``duplicative'' simply because other surveys have also occurred in the
same location, they are in fact designed specifically to produce
proprietary data that satisfies the needs of survey funders. As noted
by NRDC, BOEM convened an expert panel to study the issue of
duplicative surveys (see Appendix L in BOEM, 2017) and developed
standards for consideration of what surveys are duplicative. NRDC
provides extensive discussion of their thoughts regarding the
insufficiency of BOEM's duplicative survey standard and its
implementation. These comments are more appropriately directed to BOEM.
Comment 26: Animal Counsel suggests that NMFS must incorporate
enforceable adaptive management triggers into the regulatory text,
including automatic review upon finalization of Rice's whale critical
habitat, completion of a recovery plan, or updated stock assessments.
Response 26: As acknowledged by Animal Counsel, the ITRs include
adaptive management provisions that would allow NMFS to modify the
existing mitigation, monitoring, or reporting measures if doing so is
practicable and creates a reasonable likelihood of more effectively
accomplishing the goals of the mitigation and monitoring set forth in
this final rule. Separate from the adaptive management provisions, the
ITRs allow that NMFS may modify the requirements without regard for
practicability if it determines that an emergency exists that poses a
significant risk to the well-being of the affected species or stocks of
marine mammals. Animal Counsel does not clarify how it believes its
recommendation differs from these provisions, which were included in
the proposed rule and in this final rule.
Comment 27: Animal Counsel suggests that NMFS cannot satisfy the
MMPA's small numbers requirement, as
[[Page 20805]]
the estimated take numbers exceed population estimates.
Response 27: We refer the commenter to the detailed description of
NMFS' implementation of the small numbers requirement later in this
rule, entailing the appropriate evaluation of small numbers at the LOA
stage (see Small Numbers). However, we also note Animal Counsel's
reference to inappropriate population abundance estimates in support of
its comment. NMFS provides detailed discussion, in this rule and in the
notice of proposed rulemaking, regarding its approach to evaluation of
the most appropriate abundance estimate for purposes of evaluating
``small numbers.'' As an example, Animal Counsel cites to NMFS' SARs
estimate for the Clymene dolphin of 513 (CV = 1.03). As explained
later, the most appropriate abundance estimate for this species is the
modeled abundance value of over 6,000. NMFS' series of SAR abundance
estimates for this stock have fluctuated between 129 and 17,355
animals, i.e., varying by a maximum factor of more than 100. For most
species, such fluctuations across these ``snapshot'' abundance
estimates (i.e., that are based on only the most recent year of survey
data) reflect interannual variations in dynamic oceanographic
characteristics that influence whether animals will be seen when
surveying in predetermined locations, rather than any true increase or
decline in population abundance. In fact, NMFS' SARs typically caution
that trends should not be inferred from multiple such estimates, that
differences in temporal abundance estimates are difficult to interpret
without an understanding of range-wide stock abundance, and that
temporal shifts in abundance or distribution cannot be effectively
detected by surveys that only cover portions of a stock's range (i.e.,
U.S. waters). The corresponding density model for Clymene dolphins
predicts a mean abundance of over 6,000 dolphins. Therefore, in this
example, Animal Counsel would have us compare takes predicted by a
model in which 6,000 dolphins are assumed to exist against an abundance
estimate of 513 dolphins. Our goal in assessing predicted takes is to
generate a meaningful comparison, which is accomplished through use of
the model-predicted abundance.
Comment 28: NRDC asserts that NMFS' interpretation of the MMPA's
small numbers requirement is contrary to law, stating its belief that
NMFS must make a small numbers determination in the rule, rather than
for issuance of individual LOAs; that NMFS must evaluate the same
amount of take in order to separately determine that the total take
will both meet the small numbers standard and have a negligible impact;
that NMFS must analyze whether the estimated amount of takes over the
5-year ITRs will exceed small numbers for each affected species; and
that NMFS' approach impermissibly cuts the public out of the agency's
findings.
Response 28: Based on NMFS' analysis of the language and structure
of section 101(a)(5)(A) and the implementing regulations for that
provision, NMFS disagrees that the small numbers finding must be based
on the total of all take over the five-year (or less) period from all
potential survey activity. The MMPA does not define small numbers or
explain how to apply the term in either section 101(a)(5)(A) or the
similar provision for incidental harassment authorizations (IHAs) in
section 101(a)(5)(D),\4\ including how to apply the term in a way that
allows for consistency across those two provisions that are similar but
allow for potentially different time and activity scales. (See Small
Numbers below.) Especially when taken together with NMFS' implementing
regulations, our approach is consistent with the structure of section
101(a)(5)(A), which provides:
---------------------------------------------------------------------------
\4\ Section 101(a)(5)(D) states in relevant part:
(i) Upon request therefor by citizens of the United States who
engage in a specified activity (other than commercial fishing)
within a specific geographic region, the Secretary shall authorize,
for periods of not more than 1 year, subject to such conditions as
the Secretary may specify, the incidental, but not intentional,
taking by harassment of small numbers of marine mammals of a species
or population stock by such citizens while engaging in that activity
within that region if the Secretary finds that such harassment
during each period concerned--
(I) will have a negligible impact on such species or stock, and
(II) will not have an unmitigable adverse impact on the
availability of such species or stock for taking for subsistence
uses . . . .
(i) Upon request therefor by citizens of the United States who
engage in a specified activity (other than commercial fishing)
within a specified geographical region, the Secretary shall allow,
during periods of not more than five consecutive years each, the
incidental, but not intentional, taking by citizens while engaging
in that activity within that region of small numbers of marine
mammals of a species or population stock if the Secretary, after
notice (in the Federal Register and in newspapers of general
circulation, and through appropriate electronic media, in the
coastal areas that may be affected by such activity) and opportunity
for public comment--
(I) finds that the total of such taking during each five-year
(or less) period concerned will have a negligible impact on such
species or stock and will not have an unmitigable adverse impact on
the availability of such species or stock for taking for subsistence
uses . . . .
(Emphasis added.)
Section 101(a)(5)(A)(i)(I) is explicit that the ``negligible
impact'' determination for a specified activity must take into account
the ``total of such taking'' (i.e., all of the taking that the
Secretary may conceivably allow (or authorize) under individual LOAs
during the five year (or less) period considered for the rule). In
contrast, the ``small numbers'' language in 101(a)(5)(A) is not subject
to the same time period requirement of five years (or less in cases
where the period being considered for a rule is less than five years).
In our view, the statutory language for small numbers and the
negligible impact finding indicates that the negligible impact finding
is made based on consideration of an aggregation of potential
authorizations (LOAs) for taking small numbers of marine mammals, and
allows for different temporal periods in applying the two different
standards. The statute contemplates that the Secretary shall allow
taking during the five year (or less) period, which, in our view, also
implies that there could be multiple allowances or authorizations
(i.e., LOAs), so long as the maximum total taking from all of those
authorizations combined is considered in the upfront assessment of
whether the negligible impact standard is met for the total taking
allowable under the regulations.
As we note in our Small Numbers section, the regulatory vehicle for
authorizing (i.e., allowing) the take of marine mammals is the LOA, a
creature of NMFS' long-standing implementing regulations that is not in
the statute. See 50 CFR 216.106. Those 1989 implementing regulations
requiring an LOA to effectuate an authorization were in effect when
Congress amended the MMPA in 1994 to add section 101(a)(5)(D) for
issuance of one-year IHAs, and over the years when Congress amended
section 101(a)(5)(A) for various reasons (including most recently in
2018, to extend the maximum authorization period to seven years for
military readiness activities, Public Law 115-232 (John S. McCain
National Defense Authorization Act for Fiscal Year 2019) (Aug. 13,
2018)).
Under NMFS' approach, the negligible impact analysis for the
rulemaking is conducted for the time period covered by the rule (five
years in this case, the maximum under the statute for a non-military
readiness activity), but the small numbers analysis attaches to the
instrument that actually ``allows'' or authorizes taking, i.e., the
LOA. The statute does not preclude
[[Page 20806]]
NMFS from issuing an LOA that comports with the small numbers level set
forth in the relevant rule for the specified activity. Consistent with
the MMPA requirement, here the Secretary (through NMFS) has prescribed
the necessary specified activity regulations after notice and comment.
At that point, once the regulations are effective, NMFS thereafter may
authorize incidental take through the issuance of LOAs, provided that
they satisfy the requirements set forth in the rule and regulations,
including the small numbers standard articulated in the rule.
NRDC cites Conservation Council for Hawaii v. NMFS, 97 F. Supp. 3d
1210 (D. Hawaii 2015), in stating that the MMPA ``plainly requires that
the agency evaluate both whether there will be small numbers of take
and whether there will be a negligible impact'' before issuing
regulations, and that these determinations ``must be based on the same
amount of take.'' We disagree with the second proposition. In NMFS'
view, Conservation Council for Hawaii stands for the proposition that
NMFS cannot authorize more take than it has analyzed under the
negligible impact standard. 97 F. Supp. 3d at 1221. There the court
found that there were substantial differences between the anticipated
take numbers, which were the basis for the negligible impact finding,
and the amount of take that NMFS was prepared to authorize incidental
to U.S. Navy military readiness activities. That case did not involve
the small numbers provision, which does not apply in the case of
military readiness activities. 16 U.S.C. 1371(a)(5)(F)(i). The court in
Conservation Council for Hawaii did not consider or make any
pronouncements about whether the small numbers provision must be
applied to the total annual taking under the rule or whether it could
be applied at the LOA stage.
We disagree with NRDC's view that the word ``such'' in the phrase
``total of such taking'' for determining negligible impact means that
the analysis for small numbers must also consider the total taking
allowable under the regulations. The phrase ``total of such taking'' in
clause (I) clearly refers to what must be considered in making a
negligible impact determination, and does not qualify the small numbers
requirement. In addition, the statute's reference to ``citizens'' in
the plural contemplates that there could be more than one entity making
a request for take under a regulation for a specified activity. Under
the statute, the Secretary (through NMFS) shall allow the take of small
numbers of marine mammals by citizens--which, as in this case, could
entail more than one requester--provided that NMFS can make the
negligible impact finding for the total of all the taking that may be
authorized under the regulations.
NRDC repeatedly states that the negligible impact and small numbers
provisions must have separate meaning. NMFS agrees that the two
provisions have separate meanings, and this rule satisfies that
requirement. Each LOA must meet the small numbers requirement as NMFS
has interpreted it in this rule. In other words, it is not sufficient
for the survey activity described in an LOA application to fall within
the scope of the activity analyzed for the rule and NMFS' negligible
impact determination. The small numbers limitation set forth in this
rule also must be satisfied. For example, NMFS may receive an
application for an LOA where the take estimates exceed the small
numbers standard identified in the rule. In that case, the request
would be denied, even if the amount of taking was considered in the
negligible impact evaluation. Thus the negligible impact and small
numbers inquiries are separate and have different meanings.
To summarize, the MMPA is silent on how to apply ``small numbers''
in either section 101(a)(5)(A) or (D), including in a way that allows
for consistency across those two very similar provisions. Moreover,
NMFS' implementing regulations for section 101(a)(5)(A) make it clear
that LOAs are the instrument for authorizing (or ``allowing'') take.
Thus, the mere existence of regulations issued under section
101(a)(5)(A) for a specified activity is not sufficient to authorize
take under that provision. An LOA is required.
As we have previously stated, the small numbers standard has
limited biological relevance (i.e., there is a lack of a biological
underpinning for the concept), but NMFS' application of the small
numbers standard at the LOA stage does not rely on that view for the
approach taken here. NMFS' interpretation and approach are based on
analysis of the governing section 101(a)(5)(A) and limited legislative
history, and our long-standing approach to implementing section
101(a)(5)(A) through separate LOAs, as well as consideration of section
101(a)(5)(D). In the absence of further congressional guidance on the
meaning of the term ``small numbers'' and how it must be applied, we
have determined our interpretation and application of small numbers is
the best reading of the statute, consistent with the U.S. Supreme
Court's opinion in Loper Bright Enters. v. Raimondo, 603 U.S. 369.
Importantly, the final rule, which was subject to notice and
comment, sets the small numbers standard for future LOAs issued under
the rule. Moreover, contrary to NRDC's assertions, NMFS has set the
total taking allowable for all LOAs issued under the rule for this
specified activity--i.e., the taking that was analyzed for the
negligible impact determination. If an LOA application for a survey
provides take estimates that are within the small numbers threshold set
in this rule, then the LOA for that survey will be deemed to satisfy
the small numbers requirement.
As NRDC correctly points out, NMFS' implementing regulations
require issuance of LOAs to be consistent with the ``total taking
allowable'' under the activity-specific regulations. The regulations
for the specified activity also reflect this. The rulemaking for these
regulations evaluated the level of activity projected in BOEM's update
for its original petition as well as the updated take estimates for the
2024 rule and other available information, and NMFS' negligible impact
determination is based on consideration of that level (and the
corresponding take estimates). Any LOA must be within the amount
analyzed for the scope of the rule, and the total amount of take under
all issued LOAs combined cannot exceed the amount analyzed and
``allowable'' under the rule for this activity.
NRDC also states that ``NMFS must analyze whether the estimated
amount of takes over the 5-year proposed ITRs will rise above small
numbers for each affected marine mammal species,'' referencing NMFS'
use of species-specific scalar ratios (see Estimated Take) and
recommending that NMFS ``should use the scaled numbers it derived to
engage in a small numbers analysis.'' Although NRDC's recommendation is
unclear, we disagree with NRDC's position regarding the need to conduct
a small numbers analysis for the total allowable taking over the 5-year
ITRs, as discussed elsewhere in this response. However, we do use the
``scaled numbers'' for purposes of the LOA-by-LOA small numbers
analyses, as described in Small Numbers. In addition, NRDC recommends
that NMFS should invite comment on the ``details of the mathematical
modelling used to produce these ratios.'' However, this aspect of the
rulemaking has been described in detail and available for public review
and comment in NMFS' 2018 (83 FR 29212, June 22, 2018) and 2026 (91 FR
9014, February 24, 2026) rulemakings.
Finally, NRDC's statement that the public is impermissibly cut out
of the
[[Page 20807]]
agency's findings is incorrect. Both the proposed and this final rule
set forth the maximum total taking and annual taking that would be
allowable (via the issuance of LOAs) for the five-year period that the
regulations will be effective. The proposed rule included a 30-day
public comment period. We also believe that our rulemaking afforded a
full and focused opportunity for public review of and comment on the
full scope of survey activities and proposed mitigation, rather than
through dozens of individual IHAs, each with separate public comment
periods. Thus the public had a meaningful opportunity to comment.
Comment 29: NRDC states that the interpretation of ``small
numbers'' presented by NMFS in the notice of proposed rulemaking is
contrary to the plain meaning and purpose of the MMPA, in part because
NMFS allegedly did not provide a reasoned basis for the take limit
proposed (i.e., one-third of the best available species or stock
abundance estimate). NRDC makes three specific claims. First, NRDC
states that one-third cannot be considered a ``small number'' within
the plain meaning of the word. Second, NRDC states that Congress
intended that takes be limited to ``infrequent, unavoidable, or
accidental'' occurrences, but that NMFS has not explained why the
taking of up to one-third would be infrequent or unavoidable. Third,
NRDC contends that NMFS should define different small numbers
thresholds on the basis of the conservation status of individual
species.
Response 29: NMFS disagrees with these arguments. Although there is
limited legislative history available to guide NMFS and an apparent
lack of biological underpinning to the concept, we have worked to
develop a reasoned approach to small numbers. In the discussion of
Small Numbers in this and our 2021 rule for this specified activity,
NMFS explains the concept of ``small numbers'' in recognition that
there could also be quantities of individuals taken that would
correspond with ``medium'' and ``large'' numbers. As such, NMFS has
established that one-third of the most appropriate population abundance
number--as compared with the assumed number of individuals taken--is an
appropriate limit with regard to ``small numbers.'' This relative
approach is consistent with the statement from the legislative history
that ``[small numbers] is not capable of being expressed in absolute
numerical limits'' (H.R. Rep. No. 97-228, at 19 (September 16, 1981)),
and relevant case law (Center for Biological Diversity v. Salazar, 695
F.3d 893, 907 (9th Cir. 2012) (holding that the U.S. Fish and Wildlife
Service reasonably interpreted ``small numbers'' by analyzing take in
relative or proportional terms)).
NRDC claims that a number may be considered small only if it is
``little or close to zero'' or ``limited in degree.'' This selectively
picks a definition in support of the commenter's favored position. But
the definition of ``small'' in Webster's New Collegiate Dictionary
(1981) included ``having little size, esp. as compared with other
similar things.'' See also <a href="http://www.merriam-webster.com/dictionary/small">www.merriam-webster.com/dictionary/small</a>
(defining ``small'' as ``having comparatively little size''). These
definitions comport with the small numbers method developed by NMFS,
which utilizes a proportionality approach. NRDC's comment also ignores
the grammar in the relevant legislative history language when stating
that NMFS has not explained why the taking of up to one-third would be
``infrequent or unavoidable.'' The actual statement from the
legislative history is that taking of marine mammals should be
``infrequent, unavoidable, or accidental.'' H.R. Rep. No. 97-228, at 19
(September 16, 1981) (emphasis added). Like the term ``small,''
infrequent is a relative term that has multiple meanings. In addition,
this disjunctive language in the series suggests that taking that is
unavoidable or accidental may qualify as small numbers, even if not
infrequent.
Finally, the argument to establish a small numbers threshold on the
basis of stock-specific conservation status is unnecessarily
duplicative of the required negligible impact finding, in which
relevant biological and contextual factors are considered in
conjunction with the amount of take.
Comment 30: NRDC states that NMFS' severability clause regarding
small numbers is inoperable.
Response 30: Our small numbers interpretation and application
contains several aspects. In the event a court were to invalidate some
but not all aspects of NMFS' small numbers interpretation/application,
NMFS intends that the remaining aspects of the rule and ITRs be
severable to the extent possible. The extent to which this is possible
may depend on which aspect is invalidated. The small numbers standard
is a statutory requirement that could be satisfied on an LOA-by-LOA
basis in accordance with the ruling of a court if, for example, the
court upholds NMFS' LOA-by-LOA aspect of our interpretation but rules
adversely on other aspects of our small numbers interpretation.
Importantly, the negligible impact analysis for this five-year rule is
the biologically relevant inquiry, and that analysis is based on the
total annual estimated taking for all activities the regulations will
govern over the 5-year period. Our ability to issue LOAs to allow the
incidental take of marine mammals, subject to the mitigation,
monitoring, and reporting requirements, is based on our findings in
this final rule that the total taking over the 5-year period of the
rule will have a negligible impact on the affected species or stocks;
that the mitigation and related monitoring required in the ITRs will
effect the least practicable adverse impact on those species or stocks;
and our determination in this rule that any LOA we issue must not
involve taking that exceeds one-third of the abundance for that species
or stock.
Comment 31: NRDC asserts that the MMPA ``does not authorize NMFS to
reissue an incidental take regulation after five consecutive years have
passed'' and that NMFS is ignoring new information that has become
available over the past 5 years. Commenters also suggest that, simply
because of the nature of NMFS' action, i.e., reimplementation of the
rule, that its necessary determinations (which incorporate all relevant
newly available information) are not ``fresh.''
Response 31: NRDC mischaracterizes the nature of this action,
stating that NMFS is ``attempting to extend the duration of its 2021
rule beyond 5 years by freezing its previous findings in amber.'' To
the contrary, NMFS has followed all requirements under both MMPA
section 101(a)(5)(A) and the APA by conducting a new notice and comment
rulemaking; we do not seek to extend the duration of the 2021 rule
beyond 5 years without performing the required analysis, making the
necessary determinations, and engaging the public as required. While it
is correct that NMFS is using the same estimated take numbers from our
recent 2024 rule and reimplementing the previously prescribed
mitigation, monitoring, and reporting requirements, all necessary
analyses have been performed in light of new information. Commenters
ignore the substantive changes to estimated take numbers considered for
NMFS' 2024 final rule, which incorporated new information available
since issuance of the 2021 final rule. No new information is available
since 2024 that would impact NMFS' take estimates. Similarly, NMFS has
not frozen its previous findings ``in amber,'' but has revised its
negligible impact analysis and least practicable adverse impact
analysis to consider all relevant new information available since
issuance of the 2021 rule. NMFS has appropriately conducted a new
action, has performed
[[Page 20808]]
new analysis incorporating new information, and has made the necessary
findings to issue this final rule and ITRs.
Comment 32: NRDC asserts that NMFS cannot rely upon BOEM's 2017
PEIS to support issuance of a new rule, stating that a new NEPA
analysis must be prepared for a new action and that, at minimum, NMFS
must supplement the analysis. NRDC also states that NMFS cannot rely on
the PEIS because it ``does not adequately address NMFS' own actions and
responsibilities under the MMPA,'' given that BOEM's PEIS is ``framed
around a fundamentally different purpose and need'' relating to its
mandates under OCSLA that is ``incongruent with NMFS obligations under
the MMPA.'' Finally, NRDC states that BOEM's PEIS, as it relates to
marine mammals, is deficient on its face due to the range of
alternatives and mitigation considered, significance criteria, take and
impact estimates, and cumulative impacts analysis. Animal Counsel
similarly suggests that the 2017 PEIS must be supplemented.
Response 32: NRDC suggests that NMFS' adoption of BOEM's PEIS and
issuance of a Record of Decision (ROD) is not sufficient analysis to
address site-specific actions, claims that ``neither NMFS nor BOEM ever
envisioned that the 2017 PEIS would itself be sufficient to constitute
a hard look at future actions not yet contemplated by the agencies,''
and, without evidence, states that the PEIS is not sufficient to
satisfy NMFS' NEPA obligations for actions implementing its ongoing
program of issuing requested incidental take authorizations. NMFS' ROD
refutes these assertions in part. Of relevance, the ROD states that
``unless [future] applications vary substantially from the analysis
provided in the 2017 Final PEIS and final rule, this ROD forms the
basis for NMFS' decision under NEPA, with no further site-specific
analysis necessary.'' As described in detail herein, the current
application and action is the same as that analyzed in the PEIS. The
ROD further announces NMFS' decision ``to issue . . . future ITAs on a
case-by-case basis, if appropriate, consistent with the analyses in the
2017 Final PEIS and mitigation measures specified in the final ITR.''
Therefore, NMFS' expressed intentions regarding future reliance on
BOEM's PEIS were clearly stated in its ROD.
Regarding the suggestion that NMFS can no longer rely on the 2017
PEIS absent supplementation, NMFS has carefully evaluated relevant new
information and circumstances over the intervening period and
determined that supplementation is not required. This inquiry, in part,
entails an evaluation as to whether new information not previously
considered in the PEIS is now available. Given the new information
available since the 2017 PEIS, we evaluate whether that information
changes the impact analysis for marine mammals contained in the PEIS,
and if the impact analyses are different, whether the new information
and impact analyses change the impact conclusions provided in the PEIS.
One component of new information available since issuance of the PEIS
is NMFS' revised take estimates, produced through incorporation of new
information in NMFS' 2024 final rule. These revised take estimates,
incorporating the current best available scientific information, are
uniformly and dramatically lower than those upon which the PEIS
analysis is founded. As a result, the PEIS impact conclusions remain
robust.
Commenters imply that the PEIS must be supplemented simply due to
its age. However, they provide no detailed discussion as to how they
believe that the information that is newly available would influence
the relevant impact analysis. By design, the PEIS provided analysis of
a substantial program of industry survey activity, including evaluation
of estimated marine mammal takes substantially greater than those at
issue here. Regarding Rice's whale, while the regulatory status of the
species has changed in the intervening years, the information
underlying that status change, which dates to NMFS' 2016 status review,
adequately informed the PEIS's analysis such that it is robust to the
evolution of scientific knowledge.
The proposed action at issue in the PEIS is BOEM's issuance of
permits or authorizations for survey activities in the GOA. PEIS
Chapter 1.1.1. The PEIS also recognizes that NMFS' proposed action is a
decision on whether to approve requests for incidental take regulations
and is not bound to a particular timeframe or specific request. NOAA
was a cooperating agency on BOEM's PEIS, as NOAA has jurisdiction by
law and special expertise over marine resources impacted by the
proposed action, including marine mammals and federally listed
threatened and endangered species. The PEIS explicitly recognizes that
the PEIS would be used in support of NMFS' decision on requests for
incidental take regulations. See PEIS Appendix B.
It is accepted NEPA practice for NOAA to adopt a lead agency's NEPA
analysis when, after independent review, NOAA determines the document
to be sufficient. Specifically here, NOAA is satisfied that BOEM's PEIS
adequately addresses the impacts of issuing MMPA incidental take
authorizations and that NOAA's comments and concerns have been
adequately addressed. There is no requirement that NMFS, as a
cooperating agency, issue a separate purpose and need statement in
order to ensure adequacy and sufficiency for adoption. Nevertheless,
the statement of Purpose and Need in the PEIS explicitly acknowledges
NMFS' own separate action of issuing an MMPA incidental take
authorization, and the PEIS is replete with discussion of issues
relating to the issuance of an MMPA authorization, including discussion
of marine mammal impacts, mitigation, and take estimates. NMFS' early
participation in the NEPA process and the agency's continuing role in
shaping and informing analyses using its special expertise ensured that
the analysis in the PEIS is sufficient for purposes of NMFS' own NEPA
obligations related to its issuance of an incidental take authorization
under the MMPA.
Regarding the alternatives, NMFS' early involvement in the
development of the PEIS and role in evaluating the effects of
incidental take under the MMPA ensured that the PEIS would include
adequate analysis of a reasonable range of alternatives for NMFS. The
PEIS includes a no action alternative specifically to address what
could happen if NMFS did not issue an MMPA authorization. See PEIS,
Chapter 2.9.1, pp. 2-20 to 2-22. Some of the alternatives explicitly
reference marine mammals or mitigation designed for marine mammals in
their title. More importantly, these alternatives fully analyze a
comprehensive variety of mitigation measures for marine mammals. This
mitigation analysis supported NMFS' evaluation of our options in
potentially issuing an MMPA authorization. This approach to evaluating
a reasonable range of alternatives is consistent with NMFS' policy and
practice for issuing MMPA incidental take authorizations. NOAA
independently reviewed and evaluated the PEIS, including the purpose
and need statement and range of alternatives, and determined that the
PEIS fully satisfies NMFS' NEPA obligations related to its decision to
issue the MMPA final rule requested by BOEM, as well as future
incidental take authorizations.
Regarding NRDC's reiterating of comments it submitted during the
PEIS development process, as a cooperating agency NMFS reviewed all
responses to comments on the draft PEIS that were relevant to its
management authorities
[[Page 20809]]
and provided input where we deemed it appropriate. See Appendix M of
the Final PEIS.
Description of Marine Mammals in the Area of the Specified Activities
Table 2 lists all species with expected potential for occurrence in
the GOA and summarizes information related to the population or stock,
including potential biological removal (PBR). 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, is
considered in concert with known sources of ongoing anthropogenic
mortality (as described in NMFS' SARs). For status of species, we
provide information regarding U.S. regulatory status under the MMPA and
ESA.
In some cases, species are treated as guilds. In general ecological
terms, a guild is a group of species that have similar requirements and
play a similar role within a community. However, for purposes of stock
assessment or density modeling, certain species may be treated together
as a guild because they are difficult to distinguish visually and many
observations are ambiguous. For example, NMFS' GOA SARs assess stocks
of Mesoplodon spp. and Kogia spp. as guilds. Following this approach,
we consider beaked whales and Kogia spp. as guilds. In this rule,
reference to ``beaked whales'' includes the goose-beaked whale \5\ and
Blainville's and Gervais' beaked whales, and reference to ``Kogia
spp.'' includes both the dwarf and pygmy sperm whale.
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\5\ Note that this species is referred to in NMFS' SARs as the
``Cuvier's beaked whale.''
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The use of guilds herein follows the best available density
information (i.e., Garrison et al., 2023). The density models treat
beaked whales and Kogia spp. as guilds and consolidate four species
into an undifferentiated blackfish guild. These species include the
melon-headed whale, false killer whale, pygmy killer whale, and killer
whale. The model authors determined that, for this group of species,
there were insufficient sightings of any individual species to generate
a species-specific model (Garrison et al., 2023). Therefore, reference
to blackfish hereafter includes the melon-headed whale, false killer
whale, pygmy killer whale, and killer whale.\6\ Twenty-one species
(with 24 managed stocks) have the potential to co-occur with the
prospective survey activities. All managed stocks in this region are
assessed in NMFS' U.S. Atlantic SARs. All values presented in table 2
are the most recent available. For more information, please see
information presented in the SARs (available online at: <a href="https://www.fisheries.noaa.gov/national/marine-mammal-protection/marine-mammal-stock-assessment-reports">https://www.fisheries.noaa.gov/national/marine-mammal-protection/marine-mammal-stock-assessment-reports</a>).
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\6\ This rule provides a single take estimate for the melon-
headed whale, false killer whale, pygmy killer whale, and killer
whale grouped together as the ``blackfish.'' This approach reflects
the best available scientific information (Garrison et al., 2023).
These species are encountered only occasionally during any given
vessel survey, and these relatively infrequent encounters make it
difficult to fit species-specific detection and habitat models. For
each of these models, the authors detail analyses and decisions
relevant to model development, as well as notes of caution regarding
use of the models given the associated uncertainty resulting from
development of a model based on few sightings. The Garrison et al.
(2023) models are based on survey data from 2003 to 2019. Notably,
surveys conducted after 2009 were conducted in ``passing'' mode,
where the ship did not deviate from the trackline to approach and
verify species identifications for detected marine mammal groups,
resulting in an increase in observed marine mammal groups that could
not be identified to species. As a result of these factors, the
model authors determined it appropriate to develop a single spatial
model based on sightings of unidentified blackfish, in addition to
the relatively few sightings where species identification could be
confirmed.
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In table 2 above, we report two sets of abundance estimates: those
from NMFS' SARs and those predicted by habitat-based cetacean density
models. Please see footnote 3 of table 2 for more detail. NMFS' SAR
estimates are typically generated from the most recent shipboard and/or
aerial surveys conducted. GOA oceanography is dynamic, and the spatial
scale of the GOA is small relative to the ability of most cetacean
species to travel. U.S. waters only comprise about 40 percent of the
entire GOA, and 65 percent of GOA oceanic waters are south of the U.S.
Exclusive Economic Zone (EEZ). Studies based on abundance and
distribution surveys restricted to U.S. waters are unable to detect
temporal shifts in distribution beyond U.S. waters that might account
for any changes in abundance within U.S. waters. NMFS' SAR estimates
also in some cases do not incorporate correction for detection bias.
Therefore, for cryptic or long-diving species (e.g., beaked whales,
Kogia spp., sperm whales), estimates should generally be considered
underestimates (see footnotes 5 and 7 of table 2).
The model-based abundance estimates represent the output of
predictive models derived from multi-year observations and associated
environmental parameters and incorporate corrections for detection bias
(the same models and data from which the density estimates are
derived). Incorporating more data over multiple years of observation
can yield different results in either direction, as the result is not
as readily influenced by fine-scale shifts in species habitat
preferences or by the absence of a species in the study area during a
given year. NMFS' SAR abundance estimates show substantial year-to-year
variability in some cases. Incorporation of correction for detection
bias should systematically result in greater abundance predictions. For
these reasons, the model-based estimates are generally more realistic
and, for the purposes of assessing estimated exposures relative to
abundance--used in this case to understand the scale of the predicted
takes compared to the population--NMFS generally believes that the
model-based abundance predictions are the best available information
and most appropriate because they were used to generate the exposure
estimates and therefore provide the most relevant comparison.
As part of our evaluation of the environmental baseline, which is
considered as part of the negligible impact analysis, we consider any
known areas of importance as marine mammal habitat. We also consider
other relevant information, such as unusual mortality events (UME) and
the 2010 Deepwater Horizon oil spill.
Habitat--Important habitat areas may include areas of known
importance for reproduction, feeding, or migration, or areas where
small and resident populations are known to occur. They may have
independent regulatory status such as designated critical habitat for
ESA-listed species (as defined by section 3 of the ESA) or be
identified through other means (e.g., recognized Biologically Important
Areas (BIA)).
No critical habitat has yet been designated for the Rice's whale,
though a proposed rule to do so was published (88 FR 47453, July 24,
2023). The proposal references the same supporting information
discussed herein in suggesting that GOA continental slope waters
between 100 and 400 m water depth be designated as critical habitat. In
addition, a BIA has been recognized since 2015 (LaBrecque et al.,
2015). A detailed description of available information relating to
Rice's whale habitat was provided in the notice of proposed rulemaking
(91 FR 9014, February 24, 2026). That information is not repeated here;
please see that notice for further information.
In summary, available data indicates the presence of a core habitat
area in the northeastern GOA (outside the geographic scope of this
rule), and the presence of Rice's whales in western and central GOA
waters. In particular, passive acoustic data provide evidence that
waters 100-400 m deep in the central and western GOA are Rice's whale
habitat and are being used by Rice's whales in all seasons, although it
remains unknown whether animals are moving between the northwestern and
the northeastern GOA or whether these represent different groups of
animals (Soldevilla et al., 2022).
Additional recent data continues to show calling activity in the
western GOA, with whales acoustically present between 20 and 50 percent
of recording days across multiple sites off Texas (Debich et al.,
2025a, b). Furthermore, updated photo-identification catalogs suggest
potential movement of individuals in and out of the core area, though
sightings outside this region remain rare (Aichinger Dias et al.,
2025). While these data refine our understanding of the species' range,
this information does not reveal information on range different from
those previously analyzed.
The available information is consistent with the predictions of
Rice's whale density modeling, on which basis NMFS has anticipated and
evaluated the potential for and effects of takes of Rice's whale in
western and central GOA waters. Little is known about the number of
whales that may be present, the nature of these individuals' use of the
habitat, or the timing, duration, or frequency of occurrence for
individual whales. Conversely, the importance of northeastern GOA
waters to Rice's whale recovery is clear (Rosel et al., 2016). A
comparison of acoustic and sightings data from the central/western and
eastern GOA, even acknowledging the limitations of those data, suggests
that occurrence of whales in the northeastern GOA core habitat is
[[Page 20813]]
significantly greater and that the area provides the habitat of
greatest importance to the species.
Deepwater Horizon Oil Spill--In 2010, the Macondo well blowout and
explosion aboard the Deepwater Horizon drilling rig (also known as the
Deepwater Horizon explosion, oil spill, and response; hereafter
referred to as the DWH oil spill) caused oil, natural gas, and other
substances to flow into the GOA for 87 days before the well was sealed.
Total oil discharge was estimated at 3.19 million barrels (134 million
gallons), resulting in the largest marine oil spill in history (DWH
NRDA Trustees, 2016). In addition, the response effort involved
extensive application of dispersants at the seafloor and at the
surface, and controlled burning of oil at the surface was also used
extensively as a response technique. The oil, dispersant, and burn
residue compounds continue to present ecological challenges in the
region. NMFS discussed the impacts of the DWH oil spill on marine
mammals in detail in its 2018 notice of proposed rulemaking (83 FR
29212; June 22, 2018), and we refer the reader to that document for
additional detail. The 2018 proposed rule provided detailed discussion
of the DWH oil spill. Comprehensive monitoring programs (2020-2025) led
by NMFS' Southeast Fisheries Science Center and partners have provided
updated further insights into post-DWH cetacean distribution and
density (Frasier et al., 2024a, b). Recent analysis indicates that many
species continue to exhibit densities significantly below pre-spill
levels, suggesting a lack of recovery for affected populations.
Estimates of annual mortality for many stocks over the period 2014-2018
include mortality attributed to the effects of the DWH oil spill (see
table 2) (Hayes et al., 2023), and these mortality estimates are
considered as part of the environmental baseline. NMFS similarly treats
the effects of the DWH oil spill as part of the baseline in considering
the likely resilience of these populations to the effects of the
activities considered in this final rule.
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.). Generalized hearing ranges were
chosen based on the ~65 decibel (dB) threshold from composite
audiograms, previous analyses in NMFS (2018), and/or data from Southall
et al. (2007) and Southall et al. (2019).
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For more detail concerning these groups and associated frequency
ranges, please see NMFS (2024) for a review of available information.
Potential Effects of the Specified Activities on Marine Mammals and
Their Habitat
In NMFS' notice of proposed rulemaking (91 FR 9014, February 24,
2026), this section (Potential Effects) included a comprehensive
summary and discussion of the ways that the specified activity may
impact marine mammals and their habitat, including general background
information on sound and specific discussion of potential effects to
marine mammals from noise produced through use of the acoustic sources
considered herein. We do not repeat that discussion here,
[[Page 20814]]
instead referring the reader to the notice of proposed rulemaking.
The Estimated Take section that follows includes a quantitative
analysis of the number of individuals that are expected to be taken by
the specified activity. The Negligible Impact Analysis and
Determinations section includes an analysis of how these activities
will impact marine mammals and considers the analysis of Potential
Effects presented in the notice of proposed rulemaking, the Estimated
Take section, and the Mitigation section, to draw conclusions regarding
the likely impacts of these activities on the reproductive success or
survivorship of individuals and whether those impacts are reasonably
expected to, or reasonably likely to, adversely affect the species or
stock through effects on annual rates of recruitment or survival.
Estimated Take
This section provides an estimate of the numbers and type of
incidental takes that may be expected to occur under the specified
activity, which informs NMFS' negligible impact determinations.
Realized incidental takes would be determined by the actual levels of
activity at specific times and places that occur under any issued LOAs
and by the actual acoustic sources used. Take estimates are available
for the three different airgun array configurations described
previously. The highest modeled estimated take (annual and 5-year
total) for each species is analyzed for the negligible impact analysis.
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). Harassment is the only
type of take expected to result from these activities. It is unlikely
that lethal takes would occur even in the absence of the mitigation and
monitoring measures, and no such takes are anticipated or will be
authorized.
Anticipated takes would primarily be by Level B harassment, as use
of the described acoustic sources, particularly airgun arrays, is
likely to disrupt behavioral patterns of marine mammals upon exposure
to sound at certain levels. There is also some potential for auditory
injury (Level A harassment) to result for LF and VHF species due to the
size of the predicted auditory injury zones for those species, though
none is predicted to occur for Rice's whales (the only LF cetacean in
the GOA). NMFS does not expect auditory injury to occur for HF species.
Detailed discussion of this determination was provided in the Estimated
take section of the notice of proposed rulemaking (91 FR 9014, February
24, 2026), and is not repeated here.
Below, we summarize how the take that may be authorized was
estimated using acoustic thresholds, sound field modeling, and marine
mammal density data. In addition to discussion provided below, please
see associated companion documents available on NMFS' website, for
additional detail (Zeddies et al., 2015, 2017a; Weirathmueller et al.,
2022). A summary overview of the take estimation process, as well as
full discussion related to the development of estimated take numbers,
is provided below.
Acoustic Thresholds
NMFS uses acoustic thresholds that identify the received level of
underwater sound above which exposed marine mammals generally would be
reasonably expected to exhibit disruption of behavioral patterns (Level
B harassment) or to incur AUD INJ of some degree (Level A harassment).
Level B Harassment--NMFS carries forward the approach to evaluation
of potential take by Level B harassment used for the 2021 and 2024
final rules. Based on the practical need to use a relatively simple
threshold based on available information that is both predictable and
measurable for most activities, NMFS typically uses a generalized
acoustic threshold based on received level to estimate the onset of
Level B harassment (e.g., the historical 160 dB rms threshold for
intermittent sources, which include the impulsive sources evaluated
herein). In this case, NMFS identified a more complex probabilistic
risk function for use in evaluating the potential effects of the
specified activity. This function, first described in Wood et al.
(2012), differs from the single-step 160 dB rms criterion primarily by
acknowledging the potential for Level B harassment at exposures to
received levels below 160 dB rms as well as the potential that animals
exposed to received levels above 160 dB rms will not respond in ways
constituting Level B harassment. The approach described by Wood et al.
(2012) also accounts for differential hearing sensitivity by
incorporating the Type I frequency-weighting functions described by
Southall et al. (2007). The broader Type I filters are appropriately
retained for use in evaluating potential behavioral disturbance in
conjunction with the probabilistic response function. The criteria are
described in table 4.
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Level A harassment--Modeling supporting the 2021 and 2024 final
rules relied on NMFS' Revised Technical Guidance for Assessing the
Effects of Anthropogenic Sound on Marine Mammal Hearing (Version 2.0;
NMFS, 2018) (table 5). Since issuance of those rules, NMFS completed
Updated Technical Guidance (NMFS, 2024) (table 6). Both versions of the
technical guidance identify dual criteria, using the cumulative sound
exposure level metric and peak sound pressure level metric, to assess
auditory injury (Level A harassment) to five different marine mammal
groups (based on hearing sensitivity) as a result of exposure to noise
from two different types of sources (impulsive or non-impulsive). This
final rule carries forward the modeling and resulting take estimates
(as updated for the 2024 rule) based on the 2018 Technical Guidance
(NMFS, 2018), based on our determination that those estimates of Level
A harassment remain sufficiently representative of any incidents of
Level A harassment that
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may reasonably be expected to occur (described next).
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These thresholds are provided in tables 5 and 6. The references,
analysis, and methodology used in the development of the thresholds are
described in NMFS' 2018 Revised Technical Guidance and NMFS' 2024
Updated Technical Guidance, both of which may be accessed at: <a href="https://www.fisheries.noaa.gov/national/marine-mammal-protection/marine-mammal-acoustic-technical-guidance">https://www.fisheries.noaa.gov/national/marine-mammal-protection/marine-mammal-acoustic-technical-guidance</a>. The specified activity considered herein
includes the use of impulsive seismic sources (i.e., airguns).
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In summary, the peak pressure threshold for LF cetaceans increased
by 3 dB, while the cumulative SEL threshold (upon which estimates of
potential AUD INJ for LF cetaceans is based in this case) is unchanged.
As discussed below, no Level A harassment is likely to occur for HF
cetaceans, though we note that the cumulative SEL threshold for the
hearing group increased by 8 dB. The peak pressure threshold for VHF
cetaceans (upon which estimates of potential AUD INJ are based in this
case) is unchanged, while the cumulative SEL threshold increased by 4
dB (see tables 5 and 6). Regarding the underlying frequency
sensitivities, the generalized hearing range for LF cetaceans remains
essentially the same (currently estimated as 7 Hz-36 kHz versus 7 Hz-35
kHz in
[…truncated; see source link]Indexed from Federal Register on April 17, 2026.
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