`[Federal Register Volume 88, Number 190 (Tuesday, October 3, 2023)]
[Proposed Rules]
[Pages 68290-68367]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2023-21499]



[[Page 68289]]

Vol. 88

Tuesday,

No. 190

October 3, 2023

Part II





Department of Commerce





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





 National Oceanic and Atmospheric Administration





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





50 CFR Part 218





Taking and Importing Marine Mammals; Taking Marine Mammals Incidental 
to the U.S. Navy Training and Testing Activities in the Hawaii-Southern 
California Training and Testing Study Area; Proposed Rule

  Federal Register / Vol. 88 , No. 190 / Tuesday, October 3, 2023 / 
Proposed Rules  

[[Page 68290]]


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

DEPARTMENT OF COMMERCE

National Oceanic and Atmospheric Administration

50 CFR Part 218

[Docket No. 230817-0197]
RIN 0648-BL72


Taking and Importing Marine Mammals; Taking Marine Mammals 
Incidental to the U.S. Navy Training and Testing Activities in the 
Hawaii-Southern California Training and Testing Study Area

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

ACTION: Proposed rule; request for comments and information.

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

SUMMARY: NMFS has received a request from the U.S. Navy (Navy) to 
modify the regulations and Letters of Authorization (LOAs) authorizing 
the take of marine mammals incidental to Navy training and testing 
activities conducted in the Hawaii-Southern California Training and 
Testing (HSTT) Study Area between 2018 and 2025. In 2021, two separate 
U.S. Navy vessels struck unidentified large whales on two separate 
occasions, one whale in June 2021 and one whale in July 2021, in waters 
off Southern California. The takes by vessel strike of the two whales 
by the U.S. Navy were covered by the existing regulations and LOAs, 
which authorize the U.S. Navy to take up to three large whales by 
serious injury or mortality by vessel strike between 2018 and 2025. The 
Navy reanalyzed the potential of vessel strike in the HSTT Study Area, 
including the recent strikes and as a result, requested two additional 
takes of large whales by serious injury or mortality by vessel strike 
for the remainder of the current regulatory period. In May 2023, a U.S. 
Navy vessel struck a large whale in waters off Southern California. 
NMFS reanalyzed the potential for vessel strike following the May 2023 
strike and proposes to authorize two additional takes of large whales 
by serious injury or mortality by vessel strike for the remainder of 
the current regulatory period (two takes in addition to the three takes 
authorized in the current regulations). Pursuant to the Marine Mammal 
Protection Act (MMPA), NMFS is requesting comments on the proposed 
promulgation of modified regulations and associated LOAs for the Navy 
governing this additional incidental taking of marine mammals. NMFS 
will consider public comments prior to issuing any final rule and 
making final decisions on the issuance of the requested LOAs. Agency 
responses to public comments will be provided in the notice of the 
final decision. The Navy's activities qualify as military readiness 
activities pursuant to the MMPA, as amended by the National Defense 
Authorization Act for Fiscal Year 2004 (2004 NDAA).

DATES: Comments and information must be received no later than November 
17, 2023.

ADDRESSES: Submit all electronic public comments via the Federal e-
Rulemaking Portal. Go to https://www.regulations.gov and enter NOAA-
NMFS-2023-0102 in the Search box. Click on the ``Comment'' icon, 
complete the required fields, and enter or attach your comments.
    Instructions: Comments sent by any other method, to any other 
address or individual, or received after the end of the comment period 
may not be considered by NMFS. All comments received are a part of the 
public record and will generally be posted for public viewing on 
www.regulations.gov without change. All personal identifying 
information (e.g., name, address), confidential business information, 
or otherwise sensitive information submitted voluntarily by the sender 
will be publicly accessible. NMFS will accept anonymous comments (enter 
``N/A'' in the required fields if you wish to remain anonymous).
    A copy of the Navy's applications, NMFS' proposed and final rules 
and subsequent LOAs for the existing (2020) and previous (2018) 
regulations, and other supporting documents and documents cited herein 
may be obtained online at: www.fisheries.noaa.gov/national/marine-mammal-protection/incidental-take-authorizations-military-readiness-activities. In case of problems accessing these documents, please use 
the contact listed here (see FOR FURTHER INFORMATION CONTACT).

FOR FURTHER INFORMATION CONTACT: Leah Davis, Office of Protected 
Resources, NMFS, (301) 427-8401.

SUPPLEMENTARY INFORMATION:

Purpose of Regulatory Action

    These proposed regulations, issued under the authority of the MMPA 
(16 U.S.C. 1361 et seq.), would modify the current regulations, which 
allow for the authorization of take of marine mammals incidental to the 
Navy's training and testing activities (which qualify as military 
readiness activities) from the use of sonar and other transducers, in-
water detonations, air guns, impact pile driving/vibratory extraction, 
and the movement of vessels throughout the HSTT Study Area (50 CFR part 
218, subpart H; hereafter ``2020 HSTT regulations'').
    NMFS received a request from the Navy to modify the existing 
regulations and LOAs to authorize two additional takes of large whales 
by serious injury or mortality by vessel strike over the remainder of 
the HSTT regulatory period. The current HSTT regulations and LOAs 
authorize the incidental take, by serious injury or mortality, of three 
large whales by vessel strike. Here, in consideration of the best 
available science, including updated information related to vessel 
strikes, NMFS analyzes and proposes to authorize the incidental serious 
injury or mortality by vessel strike of five large whales over the 
effective period of the regulations (December 2018-December 2025). The 
effective period remains unchanged from the existing regulations. 
Further, the Navy's proposed activities remain unchanged; however, this 
proposed rule includes two additional mitigation measures and revision 
of two existing mitigation measures to further reduce the probability 
of vessel strike. With the exception of these new mitigation measures 
and revisions to two existing mitigation measures, the required 
mitigation and monitoring measures remain unchanged.

Background

    The MMPA prohibits the ``take'' of marine mammals, with certain 
exceptions. Sections 101(a)(5)(A) and (D) of the MMPA (16 U.S.C. 1361 
et seq.) direct the Secretary of Commerce (as delegated to NMFS) to 
allow, upon request, the incidental, but not intentional, taking of 
small numbers of marine mammals by U.S. citizens who engage in a 
specified activity (other than commercial fishing) within a specified 
geographical region if certain findings are made and either regulations 
are issued or, if the taking is limited to harassment, the public is 
provided with notice of the proposed incidental take authorization and 
the opportunity to review and submit comments.
    An authorization for incidental takings shall be granted if NMFS 
finds that the taking will have a negligible impact on the species or 
stock(s) and will not have an unmitigable adverse impact on the 
availability of the species or stock(s) for taking for subsistence uses 
(where relevant). Further, NMFS must prescribe the permissible methods 
of taking and other means of effecting the least practicable adverse 
impact on the affected species or stocks and their habitat, paying 
particular attention to rookeries, mating grounds, and areas of

[[Page 68291]]

similar significance, and on the availability of such species or stocks 
for taking for certain subsistence uses (referred to in this rulemaking 
as ``mitigation measures''); and requirements pertaining to the 
monitoring and reporting of such takings. The MMPA defines ``take'' to 
mean to harass, hunt, capture, or kill, or attempt to harass, hunt, 
capture, or kill any marine mammal. The Preliminary Analysis and 
Negligible Impact Determination section below discusses the definition 
of ``negligible impact.''
    The 2004 NDAA (Pub. L. 108-136) amended section 101(a)(5) of the 
MMPA to remove the ``small numbers'' and ``specified geographical 
region'' provisions indicated above and amended the definition of 
``harassment'' as applied to a ``military readiness activity.'' The 
definition of harassment for military readiness activities (section 
3(18)(B) of the MMPA) is (i) any act that injures or has the 
significant potential to injure a marine mammal or marine mammal stock 
in the wild (Level A Harassment); or (ii) any act that disturbs or is 
likely to disturb a marine mammal or marine mammal stock in the wild by 
causing disruption of natural behavioral patterns, including, but not 
limited to, migration, surfacing, nursing, breeding, feeding, or 
sheltering, to a point where such behavioral patterns are abandoned or 
significantly altered (Level B harassment). In addition, the 2004 NDAA 
amended the MMPA as it relates to military readiness activities such 
that the least practicable adverse impact analysis shall include 
consideration of personnel safety, practicality of implementation, and 
impact on the effectiveness of the military readiness activity.
    The NDAA for Fiscal Year 2019 (2019 NDAA) (Pub. L. 115-232), 
amended the MMPA to allow incidental take rules for military readiness 
activities under section 101(a)(5)(A) to be issued for up to 7 years. 
Prior to this amendment, all incidental take rules under section 
101(a)(5)(A) were limited to 5 years.
    Under the MMPA implementing regulations, incidental take 
regulations may be modified, in whole or in part, as new information is 
developed and after notice and opportunity for public comment (50 CFR 
216.105). An LOA must be withdrawn or suspended if, after notice and 
opportunity for public comment, NMFS determines that the regulations 
are not being substantially complied with, or the taking is having, or 
may have, more than a negligible impact on species or stock. Id. at 
216.106(e). Note, in its application, Navy relied on Sec. Sec.  218.76, 
and 218.77. These sections outline the process for modification of an 
LOA without modifying the applicable incidental take regulation. These 
sections do not apply here because the Navy requested modification of 
the 2020 HSTT regulations.

Summary of Request

    On December 27, 2018, NMFS issued a 5-year final rule governing the 
taking of marine mammals incidental to Navy training and testing 
activities conducted in the HSTT Study Area (83 FR 66846; hereafter 
``2018 HSTT final rule''). Previously, on August 13, 2018, and towards 
the end of the time period in which NMFS was processing the Navy's 
request for the 2018 regulations, the 2019 NDAA amended the MMPA for 
military readiness activities to allow incidental take regulations to 
be issued for up to 7 years instead of the previous 5 years. The Navy's 
training and testing activities conducted in the HSTT Study Area 
qualify as military readiness activities pursuant to the MMPA, as 
amended by the 2004 NDAA. On March 11, 2019, the Navy submitted an 
application requesting that NMFS extend the 2018 HSTT regulations and 
associated LOAs such that they would cover take incidental to 7 years 
of training and testing activities instead of 5, extending the 
expiration date from December 20, 2023 to December 20, 2025. On July 
10, 2020, NOAA Fisheries issued regulations to govern the taking of 
marine mammals incidental to the training and testing activities 
conducted in the HSTT Study Area over the course of 7 years, 
effectively extending the effective period from December 20, 2023 to 
December 20, 2025.
    On March 31, 2022, NMFS received an adequate and complete 
application (2022 Navy application) from the Navy requesting that NMFS 
modify the existing regulations and LOAs to authorize two additional 
takes of large whales by serious injury or mortality by vessel strike 
over the remainder of the HSTT authorization period. The 2020 HSTT 
regulations (50 CFR part 218, subpart H) and LOAs authorize the take of 
marine mammals from the Navy's training and testing activities in the 
HSTT Study Area through December 20, 2025. These regulations and LOAs 
authorize the take of three large whales by serious injury or mortality 
by vessel strike.
    The Navy's 2022 request is based upon new information regarding 
U.S. Navy vessel strikes off the coast of Southern California. As 
described in the 2022 Navy application, in 2021, two separate U.S. Navy 
vessels struck unidentified large whales off the coast of Southern 
California on two separate occasions, one whale in June 2021 and one 
whale in July 2021. Separately, a foreign naval vessel struck two fin 
whales off the coast of Southern California in May 2021.
    In the 2022 Navy application, the Navy proposes no changes to the 
nature of the specified activities covered by the 2020 HSTT final rule. 
The Navy states that the level of activity within and between years 
would be consistent with that previously analyzed in the 2020 HSTT 
final rule, and all activities would be conducted within the same 
boundaries of the HSTT Study Area identified in the 2020 HSTT final 
rule. The training and testing activities (e.g., equipment and sources 
used, exercises conducted) are identical to those described and 
analyzed in the 2020 HSTT final rule, and the mitigation, monitoring, 
and reporting measures are similar to those described and analyzed in 
the 2020 HSTT final rule. The only changes included in the Navy's 
request are for additional take by serious injury or mortality by 
vessel strike.
    The Navy's mission is to organize, train, equip, and maintain 
combat-ready naval forces capable of winning wars, deterring 
aggression, and maintaining freedom of the seas. This mission is 
mandated by Federal law (10 U.S.C. 8062), which ensures the readiness 
of the naval forces of the United States. The Navy executes this 
responsibility by establishing and executing training programs, 
including at-sea training and exercises, and ensuring naval forces have 
access to the ranges, operating areas (OPAREAs), and airspace needed to 
develop and maintain skills for conducting naval activities.
    For a summary of the training and testing activities within the 
HSTT Study Area, see the Navy's previous rulemaking and LOA 
applications submitted for HSTT Phase III activities (October 13, 2017 
initial rulemaking and LOA application (hereafter ``2017 Navy 
application'') and March 11, 2019 extension rulemaking and LOA 
application (hereafter ``2019 Navy application'')) and the 2020 HSTT 
regulations that were subsequently promulgated, which can be found at: 
https://www.fisheries.noaa.gov/national/marine-mammal-protection/incidental-take-authorizations-military-readiness-activities. These 
activities are deemed by the Navy necessary to accomplish military 
readiness requirements and are anticipated to continue into the 
reasonably foreseeable future. The 2022 Navy application and this 
proposed rule cover training and testing activities that would occur 
over the remainder of the effective period of the current regulations, 
valid from the

[[Page 68292]]

publication date of the final rule, if issued, through December 20, 
2025.

Summary of the Proposed Regulations

    NMFS is proposing to modify the incidental take regulations and 
associated LOAs to cover the same Navy activities covered by the 2020 
HSTT regulations but authorize five takes of large whales by serious 
injury or mortality by vessel strike (two takes in addition to the 
three takes authorized in the current regulations). In its 2022 
application, the Navy proposes no additional changes and explains that 
its training and testing activities, including the level of vessel use, 
remain unchanged. Nearly all mitigation, monitoring, and reporting 
measures remain unchanged with the exception of two additional 
mitigation measures, revision of two existing mitigation measures, and 
an additional reporting measure resulting from discussions between the 
Navy and NMFS.
    In response to the Navy's request, we focus our analysis on the new 
information related to vessel strike. We also review any new 
information that may be pertinent to our analysis of the impacts from 
all other activities that comprise Navy's specified activity, and our 
analysis of mitigation, monitoring, and reporting. Where there is any 
new information pertinent to the descriptions, analyses, or findings 
required to authorize the incidental take for military readiness 
activities under MMPA section 101(a)(5)(A), that information is 
provided in the appropriate sections below. Where there is no new 
information or any new information does not change our previous 
analysis or findings, we indicate as such and refer the reader to the 
original analysis in the 2018 HSTT proposed and final rule, 2020 HSTT 
final rule or the 2019 HSTT Final Environmental Impact Statement 
(FEIS)/Overseas Environmental Impact Statement (OEIS).
    After reviewing all new information and as discussed below, we 
largely find that our previous analyses and findings remain current and 
applicable. For vessel strike, we provide a new analysis and propose 
authorizing two additional takes of large whales, for a total of five 
takes by serious injury or mortality by vessel strike over the 7-year 
period. We consider authorizing these additional takes after analyzing 
the best available information and after considering the effects of the 
entire specified activity and the total taking as required by MMPA 
section 101(a)(5)(A). When setting forth the permissible methods of 
taking pursuant to the activity and other means of effecting the least 
practicable adverse impact on the species or stock, we propose 
requiring new and modified mitigation and also consider whether to 
require any new or modified mitigation for the entire specified 
activity.
    The proposed regulatory language included at the end of this 
proposed rule, which would be published at 50 CFR part 218, subpart H, 
remains largely the same as that under the HSTT 2020 regulations, 
except for a small number of technical changes related to the Navy's 
2022 request, new and revised mitigation measures, and a new reporting 
measure. Therefore, in this proposed rule, we refer the reader to 
complete analyses described in the 2018 HSTT final rule or an updated 
analysis in the 2020 HSTT final rule, where appropriate.
    Below is a list of the regulatory documents referenced in this 
proposed rule. The list indicates the short name by which the document 
is referenced in this proposed rule as well as the full titles of the 
cited documents. All of the documents can be found at: 
www.fisheries.noaa.gov/national/marine-mammal-protection/incidental-take-authorizations-military-readiness-activities and http://www.hstteis.com/.
     NMFS June 26, 2018, Hawaii-Southern California Training 
and Testing (HSTT) proposed rule (83 FR 29872; 2018 HSTT proposed 
rule);
     NMFS December 27, 2018, Hawaii-Southern California 
Training and Testing (HSTT) final rule (83 FR 66846; 2018 HSTT final 
rule);
     NMFS September 13, 2019, Hawaii-Southern California 
Training and Testing (HSTT) proposed rule (84 FR 48388; 2019 HSTT 
proposed rule);
     NMFS July 10, 2020, Hawaii-Southern California Training 
and Testing (HSTT) final rule (85 FR 41780; 2020 HSTT final rule);
     Navy October 13, 2017, MMPA rulemaking and LOA application 
(2017 Navy application);
     Navy March 11, 2019, MMPA rulemaking and LOA extension 
application (2019 Navy application);
     Navy March 31, 2022, MMPA rulemaking and LOA revision 
application (2022 Navy application); and
     October 26, 2018, Hawaii-Southern California Training and 
Testing (HSTT) Final Environmental Impact Statement/Overseas 
Environmental Impact Statement (FEIS/OEIS) (2018 HSTT FEIS/OEIS).

Description of the Specified Activity

    The Navy requests authorization to take marine mammals incidental 
to conducting training and testing activities. The Navy has determined 
that acoustic and explosives stressors are most likely to result in 
impacts on marine mammals that could rise to the level of harassment. 
In addition to take by harassment, the Navy has determined that vessel 
movement may result in serious injury or mortality to marine mammals. 
Detailed descriptions of these activities are provided in chapter 2 of 
the 2018 HSTT FEIS/OEIS and in the 2017 Navy application.

Overview of Training and Testing Activities

    The Navy routinely trains in the HSTT Study Area in preparation for 
national defense missions. Training and testing activities and 
components covered in the 2022 Navy application are described in detail 
in the Overview of Training and Testing Activities sections of the 2018 
HSTT proposed rule, the 2018 HSTT final rule, and chapter 2 
(Description of Proposed Action and Alternatives) of the 2018 HSTT 
FEIS/OEIS (http://www.hstteis.com/). Each military training and testing 
activity described meets mandated Fleet requirements to deploy ready 
forces. The Navy proposes no changes to the specified activities 
described and analyzed in the 2018 HSTT final rule and subsequent 2020 
HSTT final rule. The boundaries of the HSTT Study Area (see figure 2-1 
of the 2019 Navy application); the dates and duration of the 
activities; and the training and testing activities (e.g., equipment 
and sources used, exercises conducted) analyzed in this proposed rule 
are identical to those described and analyzed in the 2020 HSTT final 
rule and therefore, are not repeated herein. Please see the 2020 HSTT 
final rule for more information. The manner of vessel movement 
presented in this proposed rule is also identical to that analyzed in 
the 2020 HSTT final rule.

Vessel Strike

    Vessel strikes are not specific to any particular training or 
testing activity but rather, a limited, sporadic, and incidental result 
of Navy vessel movement within the HSTT Study Area. Vessel strikes from 
commercial, recreational, and military vessels are known to seriously 
injure and occasionally kill cetaceans (Abramson et al. 2011; Berman-
Kowalewski et al. 2010; Calambokidis, 2012; Douglas et al. 2008; 
Laggner, 2009; Lammers et al. 2003; Van der Hoop et al. 2012; Van der 
Hoop et al. 2013; Crum et al. 2019), although reviews of the literature 
on vessel strikes mainly involve collisions between commercial vessels 
and whales (Jensen and Silber, 2003; Laist et al. 2001). Vessel speed, 
size, and mass are

[[Page 68293]]

all important factors in determining both the potential likelihood and 
impacts of a vessel strike to marine mammals (Conn and Silber, 2013; 
Gende et al. 2011; Silber et al. 2010; Vanderlaan and Taggart, 2007; 
Wiley et al. 2016). For large vessels, speed and angle of approach can 
influence the severity of a strike.
    Navy vessels transit at speeds that are optimal for fuel 
conservation or to meet training and testing requirements. Small craft 
(for purposes of this analysis, less than 18 m in length) have much 
more variable speeds (0-50+ knots (kn; 0-92.6 kilometers (km) per 
hour), dependent on the activity). Submarines generally operate at 
speeds in the range of 8-13 kn (14.8-24.1 km per hour), and the average 
speed of large Navy ships range between 10 and 15 kn (18.5 and 27.8 km 
per hour). While these speeds are considered averages and 
representative of most events, some vessels need to operate outside of 
these parameters for certain times or during certain activities. For 
example, to produce the required relative wind speed over the flight 
deck, an aircraft carrier engaged in flight operations must adjust its 
speed through the water accordingly. Also, there are other instances 
such as launch and recovery of a small rigid hull inflatable boat; 
vessel boarding, search, and seizure training events; or retrieval of a 
target when vessels would be dead in the water or moving slowly ahead 
to maintain steerage. There are a few specific events, including high-
speed tests of newly constructed vessels, where vessels would operate 
at higher speeds. By comparison, this is slower than most commercial 
vessels where full speed for a container ship is typically 24 kn (44.4 
km per hour; Bonney and Leach, 2010).
    Large Navy vessels (greater than 18 m in length) within the 
offshore areas of range complexes and testing ranges operate 
differently from commercial vessels in ways that may reduce the 
probability of whale collisions. Surface ships operated by or for the 
Navy have multiple personnel assigned to stand watch at all times when 
a ship or surfaced submarine is moving through the water (underway). A 
primary duty of personnel standing watch on surface ships is to detect 
and report all objects and disturbances sighted in the water that may 
indicate a threat to the vessel and its crew, such as debris, a 
periscope, surfaced submarine, or surface disturbance. Per vessel 
safety requirements, personnel standing watch also report any marine 
mammals sighted in the path of the vessel as a standard collision 
avoidance procedure. All vessels proceed at a safe speed so they can 
take proper and effective action to avoid a collision with any sighted 
object or disturbance and can be stopped within a distance appropriate 
to the prevailing circumstances and conditions. As described in the 
Standard Operating Procedures section, the Navy utilizes Lookouts to 
avoid collisions, and Lookouts are also trained to spot marine mammals 
so that vessels may change course or take other appropriate action to 
avoid collisions. Should a vessel strike occur, we consider that it 
would likely result in incidental take in the form of serious injury 
and/or mortality and, accordingly, for the purposes of the analysis, we 
assume that any vessel strike would result in serious injury or 
mortality.
    The Navy proposes no changes to the nature of the specified 
activities, the training and testing activities, the manner of vessel 
movement, the speeds at which vessels operate, the number of vessels 
that would be used during various activities, or the locations in which 
Navy vessel activity would be concentrated within the HSTT Study Area 
described in the 2018 HSTT final rule and referenced in the 2020 HSTT 
final rule.

Vessel Movement

    Vessels used as part of the planned activities include ships, 
submarines, unmanned vessels, and boats ranging in size from small, 22 
ft (7 m) rigid hull inflatable boats to aircraft carriers with lengths 
up to 1,092 ft (333 m). The average speed of large Navy ships ranges 
between 10 and 15 kn (18.5 and 27.8 km per hour) and submarines 
generally operate at speeds in the range of 8-13 kn (14.8-24.1 km per 
hour) while a few specialized vessels can travel at faster speeds. 
Small craft (for purposes of this analysis, less than 18 m in length) 
have much more variable speeds (0-50+ kn (0-92.6 km per hour), 
dependent on the activity) but generally range from 10 to 14 kn (18.5 
to 25.9 km per hour). From unpublished Navy data, average median speed 
for large Navy ships in the HSTT Study Area from 2011-2015 varied from 
5-10 kn (9.2-18.5 km per hour) with variations by ship class and 
location (i.e., slower speeds close to the coast). While these speeds 
for large and small craft are representative of most events, some 
vessels need to temporarily operate outside of these parameters. 
Typical speed of Navy vessels in HSTT core high use areas from 2014-
2018 were between 10 and 15 kn (18.5 and 27.8 km per hour; Starcovic 
and Mintz 2021). This core area is a region including the approaches to 
San Diego, and immediate offshore areas west of San Diego, centered 
north and south of San Clemente Island. A full description of Navy 
vessels that are used during training and testing activities can be 
found in the 2017 Navy application and chapter 2 (Description of 
Proposed Action and Alternatives) of the 2018 HSTT FEIS/OEIS.
    The number of Navy vessels used in the HSTT Study Area varies based 
on military training and testing requirements, deployment schedules, 
annual budgets, and other dynamic factors. Most training and testing 
activities involve the use of vessels. These activities could be widely 
dispersed throughout the HSTT Study Area but would typically be 
conducted near naval ports, piers, and range areas. Navy vessel traffic 
would be especially concentrated near San Diego, California and Pearl 
Harbor, Hawaii. Based on historical data, we anticipate the annual 
number of at-sea hours by U.S. Navy vessels in the HSTT action area 
will be around 26,800 hours per year (Starcovic and Mintz 2021). We 
expect that about 25 percent of this vessel activity would occur within 
the Hawaii Range Complex (HRC) and 75 percent within the Southern 
California Range Complex (SOCAL; Mintz 2016). There is no seasonal 
differentiation in Navy vessel use because of continual operational 
requirements from Combatant Commanders. The majority of large vessel 
traffic occurs between the installations and the OPAREAs. The transit 
corridor, notionally defined by the great circle route (e.g., shortest 
distance) from San Diego to the center of the HRC, as depicted in the 
2018 HSTT FEIS/OEIS, is generally used by ships transiting between 
SOCAL and HRC. While in transit, ships and aircraft would, at times, 
conduct basic and routine unit-level activities such as gunnery, 
bombing, and sonar training and maintenance. Of note, support craft 
would be more concentrated in the coastal waters in the areas of naval 
installations, ports, and ranges. Activities involving vessel movements 
occur intermittently and are variable in duration, ranging from a few 
hours up to weeks. More information on Navy and non-Navy vessel traffic 
patterns in the HSTT Study Area may be found in several studies 
prepared by the Navy (Starcovic and Mintz 2021; Mintz, 2016; Mintz and 
Filadelfo, 2011; Mintz, 2012; Mintz and Parker, 2006).

Foreign Navies

    In addition, we note that in some cases, foreign militaries may 
participate in U.S. Navy training or testing activities in the HSTT 
Study Area. The Navy does not consider these foreign

[[Page 68294]]

military activities as part of the ``specified activity'' under the 
MMPA, and NMFS defers to the applicant to describe the scope of its 
request for an authorization.
    The participation of foreign navies varies from year to year, but 
overall is infrequent compared with Navy's total training and testing 
activities. The most significant joint training event is the Rim of the 
Pacific (RIMPAC), a multi-national training exercise held every-other-
year primarily in the HRC. The participation level of foreign military 
vessels in U.S. Navy-led training or testing events within the HRC and 
within SOCAL differs greatly between RIMPAC and non-RIMPAC years. For 
example, in 2019 (a non-RIMPAC year), there were 0.1 foreign navy at-
sea days (i.e., 1 day = 24 hours) within HRC and 20 foreign navy at-sea 
days within SOCAL (Navy 2021). Out of 56 U.S.-led training events in 
2019, 4 involved foreign navy vessels, with an average time per event 
of 8.7 hours. In 2020, a RIMPAC year, foreign vessels participating in 
U.S. Navy-led events accounted for 32 at-sea days in the HRC from 
August through September (some of this activity occurred after the 
RIMPAC exercise). During RIMPAC 2022, foreign vessels operated and/or 
transited through the HRC for 576 hours (24 days). Even in a RIMPAC 
year, the days at sea for foreign militaries engaged in a Navy-led 
training or testing activity accounts for a very small percentage 
compared to the U.S. Navy activities. For instance, the 2020 foreign 
military participation (a RIMPAC-year) was 1.5 percent of the U.S. 
Navy's average days at sea (32 days out of an estimated 2,056 days at 
sea).
    According to the U.S. Navy, consistent with customary international 
law, when a foreign military vessel participates in a U.S. Navy 
exercise within the U.S. territorial sea (i.e., 0 to 12 nmi (0 to 22.2 
km) from shore), the U.S. Navy will request that the foreign vessel 
follow the U.S. Navy's mitigation measures for that particular event. 
When a foreign military vessel participates in a U.S. Navy exercise 
beyond the U.S. territorial sea but within the U.S. Exclusive Economic 
Zone, the U.S. Navy will encourage the foreign vessel to follow the 
U.S. Navy's mitigation measures for that particular event (Navy 2022a; 
Navy 2022b). In either scenario (i.e., both within and beyond the 
territorial sea), U.S. Navy personnel will provide the foreign vessels 
participating with a description of the mitigation measures to follow. 
If a foreign military is not participating in a U.S. Navy training or 
testing exercise, foreign military vessels operating within the HSTT 
Study Area are expected to adhere to their own standard operating 
procedures and environmental mitigation measures.
    According to the U.S. Navy, the May 2021 vessel strike of two fin 
whales by an Australian navy vessel did not occur while that vessel was 
participating in a U.S. Navy-led training exercise. The Royal 
Australian Navy vessel was adhering to its standard operating 
procedures at the time of the strike. The Royal Australian Navy 
provided a report of the incident, which is discussed below to inform 
our analysis.
    NMFS analyzes the effects of these foreign military activities in 
two ways. First, effects of all past foreign military activities are 
captured in the baseline for the analysis, through marine mammal 
abundance estimates and population trends found in the SARs. Second, 
NMFS considers foreign military activities, including recent strikes, 
qualitatively in this proposed rule. For instance, in preparing this 
rulemaking, NMFS and the U.S. Navy discussed the nature, frequency, and 
control over joint or U.S. Navy-led training and testing activities 
with foreign entities to identify opportunities to encourage foreign 
militaries to adopt mitigation. NMFS and the U.S. Navy examined the 
Royal Australian Navy strike report for any lessons that could inform 
U.S. Navy strike mitigation. NMFS considered the Royal Australian Navy 
strikes along with other recent U.S. Navy strikes to determine whether 
these strikes indicate an increased risk of strike by the U.S. Navy in 
this region during the early summer months. NMFS also considered the 
species struck in this incident, fin whales, along with other 
literature, when considering the likelihood of certain species to be 
struck by the U.S. Navy. Finally, NMFS considered the fact that two fin 
whales were struck by the Royal Australian Navy qualitatively when 
considering other fin whale population and mortality trends, as well as 
the take proposed for authorization, as part of the negligible impact 
analysis.

Standard Operating Procedures

    For training and testing to be effective, personnel must be able to 
safely use their sensors and weapon systems as they are intended to be 
used in a real-world situation and to their optimum capabilities. While 
standard operating procedures (SOPs) are designed for the safety of 
personnel and equipment and to ensure the success of training and 
testing activities, their implementation often yields additional 
benefits on environmental, socioeconomic, public health and safety, and 
cultural resources. Because standard operating procedures are essential 
to safety and mission success, the Navy considers them to be part of 
the proposed activities under NEPA and included them in the 
environmental analysis. We consider standard operating procedures as 
part of Navy's specified activity for the purposes of MMPA but also, 
where procedures are utilized (even in part) to reduce impacts to 
marine mammal species and Navy's commitment to follow the measures are 
practicable, certain SOPs may also be required as mitigation. Details 
on standard operating procedures were provided in the 2018 HSTT 
proposed rule; please see the 2018 HSTT proposed rule, the 2017 Navy 
application, and Chapter 2 (Description of Proposed Action and 
Alternatives) of the 2018 HSTT FEIS/OEIS for more information.
    As stated in its 2022 application, in 2018, the Navy updated its 
SOPs related to vessel safety to incorporate revised procedures 
regarding Lookouts for certain ship classes as per the 2021 Surface 
Ship Navigation Department Organization and Regulations Manual 
(NAVDORM). The 2021 NAVDORM requires the use of three Lookouts on Navy 
cruisers and destroyers as compared to the previous requirement of one 
Lookout when a vessel was underway and not engaged in sonar training or 
testing. However, as discussed in the Proposed Mitigation Measures 
section below, the Navy informed NMFS that requiring the additional 
Lookouts as mitigation is not practicable because this SOP may change 
in response to manning issues and national security needs. Further, 
since submission of its 2022 application, the Navy has updated its 
Lookout Training Handbook and implemented other training improvements, 
as described in the Proposed Mitigation Measures section (September 
2022).

Description of Marine Mammals and Their Habitat in the Area of the 
Specified Activities

    Marine mammal species and their associated stocks that have the 
potential to occur in the HSTT Study Area are presented in table 1 
along with the best/minimum abundance estimate and associated 
coefficient of variation value. Consistent with the 2018 HSTT final 
rule and 2020 HSTT final rule, the Navy anticipates the take of 
individuals from 38 marine mammal species by Level A harassment and 
Level B harassment incidental to training and testing activities from 
the use of sonar and other transducers, in-water detonations,

[[Page 68295]]

air guns, and impact pile driving/vibratory extraction activities. As 
described in detail later, serious injury or mortality of six species 
is also analyzed and proposed for authorization.
    In the 2018 HSTT proposed rule and 2018 HSTT final rule, we 
presented a detailed discussion of marine mammals and their occurrence 
in the HSTT Study Area, inclusive of important marine mammal habitat 
(e.g., ESA-designated critical habitat), biologically important areas 
(BIAs), national marine sanctuaries (NMSs), and unusual mortality 
events (UMEs). Please see these rules and the 2017 and 2019 Navy 
applications for additional information beyond what is provided herein. 
While there have been some minor changes described here, there have 
been no changes to important marine mammal habitat, NMSs, or ESA 
designated critical habitat since the issuance of the 2018 HSTT final 
rule that change our determination of which species or stocks have the 
potential to be affected by the Navy's activities or the information in 
the Description of Marine Mammals and Their Habitat in the Area of the 
Specified Activities section in the 2019 HSTT proposed rule and 2020 
HSTT final rule. Therefore, the information presented in those sections 
of the 2019 HSTT proposed rule and 2020 HSTT final rule remains current 
and valid with the exception of the information about UMEs, BIAs, and 
revised humpback whale stock structures, discussed below.
    On April 21, 2021, NMFS designated critical habitat for the 
endangered Western North Pacific Distinct Population Segment (DPS), the 
endangered Central America DPS, and the threatened Mexico DPS of 
humpback whales (86 FR 21082). Areas proposed as critical habitat 
include specific marine areas located off the coasts of California, 
Oregon, Washington, and Alaska. None of the designated critical habitat 
overlaps with the HSTT Study Area. One of the proposed areas, critical 
habitat Unit 19, would have overlapped with the SOCAL range in the HSTT 
Study Area but was excluded after consideration of potential national 
security and economic impacts of designation. NMFS, in the final rule 
designating critical habitat for humpback whales, identified prey 
species, primarily euphausiids and small pelagic schooling fishes of 
sufficient quality, abundance, and accessibility within humpback whale 
feeding areas to support feeding and population growth, as an essential 
habitat feature. NMFS, through a critical habitat review team (CHRT), 
also considered inclusion of migratory corridors and passage features, 
as well as sound and the soundscape, as essential habitat features. 
NMFS did not include either in the final critical habitat, however, as 
the CHRT concluded that the best available science did not allow for 
identification of any consistently used migratory corridors or 
definition of any physical, essential migratory or passage conditions 
for whales transiting between or within habitats of the three DPSs. The 
best available science also currently does not enable NMFS to identify 
particular sound levels or to describe a certain soundscape feature 
that is essential to the conservation of humpback whales. Regardless of 
whether critical habitat is designated for a particular area, NMFS has 
considered all applicable information regarding marine mammals and 
their habitat in the analysis supporting these proposed regulations.
    NMFS has reviewed the 2022 final Stock Assessment Reports (SARs; 
Carretta et al. 2023, Young et al. 2023). For all species except 
humpback whale, NMFS determined that neither the SARs nor any other new 
information changes our determination of which species or stocks have 
the potential to be affected by the Navy's activities. For humpback 
whale, the 2022 final SARs include a revision to the humpback whale 
stock structure in the Pacific Ocean. In the 2020 HSTT final rule, NMFS 
authorized take of the CA/OR/WA stock and Central North Pacific stock 
of humpback whale. Given the revised stock structure, in this proposed 
rule, NMFS has reanalyzed the potential for take of each stock of 
humpback whale and determined that the Central America/Southern Mexico-
CA/OR/WA, Mainland Mexico--CA/OR/WA stock, and Hawaii stocks are likely 
to be taken by the Navy's activities. Please refer to the 2022 Alaska 
and Pacific Ocean SARs for additional information about these new 
stocks.)
    The species considered but not carried forward for analysis are two 
American Samoa stocks of spinner dolphins--(1) the Kure and Midway 
stock and (2) the Pearl and Hermes stock. There is no potential for 
overlap with any stressors from Navy activities and therefore there 
would be no incidental takes, in which case, these stocks are not 
considered further.

                                              Table 1--Marine Mammal Occurrence Within the HSTT Study Area
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                   Status                                                Stock abundance
          Common name            Scientific name         Stock       ----------------------------------   Occurrence       Seasonal       (CV)/minimum
                                                                            MMPA             ESA                            absence        population
--------------------------------------------------------------------------------------------------------------------------------------------------------
Blue whale....................  Balaenoptera       Eastern North      Strategic,       Endangered       Southern          --            1,898 (0.085)/
                                 musculus.          Pacific.           Depleted                          California                      1,767.
                                Central North      Strategic,         Endangered       Hawaii           Summer          133 (1.09)/63.
                                 Pacific.           Depleted.
Bryde's whale.................  Balaenoptera       Eastern Tropical     --               --             Southern          --            unknown.
                                 brydei/edeni.      Pacific.                                             California
                                                   Hawaii...........    --               --             Hawaii            --            602 (0.22)/501.
Fin whale.....................  Balaenoptera       CA/OR/WA.........  Strategic,       Endangered       Southern          --            11,065 (0.405)/
                                 physalus.                             Depleted                          California                      7,970.
                                                   Hawaii...........  Strategic,       Endangered       Hawaii          Summer          203 (0.99)/101.
                                                                       Depleted
Humpback whale................  Megaptera          Central America/   Strategic        Endangered \1\   Southern        Winter          1,496 (0.171)/
                                 novaeangliae.      Southern Mexico--                                    California                      1,284.
                                                    CA/OR/WA.
                                                   Mainland Mexico--  Strategic        Threatened\1\    Southern        Winter          3,477 (0.101)/
                                                    CA/OR/WA.                                            California                      3,185.
                                                   Hawai[revaps]i...    --               --\1\          Hawaii          Summer          11,278 (0.56)/
                                                                                                                                         7,265.
Minke whale...................  Balaenoptera       CA/OR/WA.........    --               --             Southern          --            915 (0.792)/509.
                                 acutorostrata.                                                          California
                                                   Hawaii...........    --               --             Hawaii          Summer          438 (1.05)/212.
Sei whale.....................  Balaenoptera       Eastern North      Strategic,       Endangered       Southern          --            519 (0.40)/374.
                                 borealis.          Pacific.           Depleted                          California
                                                   Hawaii...........  Strategic,       Endangered       Hawaii          Summer          391 (0.9)/204.
                                                                       Depleted

[[Page 68296]]

 
Gray whale....................  Eschrichtius       Eastern North        --               --             Southern          --            26,960 (0.05)/
                                 robustus.          Pacific.                                             California                      25,849.
                                                   Western North      Strategic,       Endangered       Southern          --            290 (NA)/271.
                                                    Pacific.           Depleted                          California
Sperm whale...................  Physeter           CA/OR/WA.........  Strategic,       Endangered       Southern          --            1,997 (0.57)/
                                 macrocephalus.                        Depleted                          California                      1,270.
                                                   Hawaii...........  Strategic,       Endangered       Hawaii            --            5,707 (0.23)/
                                                                       Depleted                                                          4,486.
Pygmy sperm whale.............  Kogia breviceps..  CA/OR/WA.........    --               --             Southern        Winter and      4,111 (1.12)/
                                                                                                         California      Fall            1,924.
                                                   Hawaii...........    --               --             Hawaii            --            42,083 (0.64)
                                                                                                                                         25,695.
Dwarf sperm whale.............  Kogia sima.......  CA/OR/WA.........    --               --             Southern          --            unknown.
                                                                                                         California
                                                   Hawaii...........    --               --             Hawaii            --            unknown.
Baird's beaked whale..........  Berardius bairdii  CA/OR/WA.........    --               --             Southern          --            1,363 (0.53)/
                                                                                                         California                      894.
Blainville's beaked whale.....  Mesoplodon         Hawaii...........    --               --             Hawaii            --            1,132 (0.99)/
                                 densirostris.                                                                                           564.
Cuvier's beaked whale.........  Ziphius            CA/OR/WA.........    --               --             Southern          --            5,454 (0.27)/
                                 cavirostris.                                                            California                      4,214.
                                                   Hawaii...........    --               --             Hawaii            --            4,431 0.41/
                                                                                                                                         3,180.
Longman's beaked whale........  Indopacetus        Hawaii...........    --               --             Hawaii            --            2,550 (0.67)/
                                 pacificus.                                                                                              1,527.
Mesoplodont beaked whales.....  Mesoplodon spp...  CA/OR/WA.........    --               --             Southern          --            3,044 (0.54)/
                                                                                                         California                      1,967.
Common Bottlenose dolphin.....  Tursiops           California           --               --             Southern          --            453 (0.06)/346.
                                 truncatus.         Coastal.                                             California
                                                   CA/OR/WA Offshore    --               --             Southern          --            3,477 (0.696)/
                                                                                                         California                      2,048.
                                                   Hawaii Pelagic...    --               --             Hawaii            --            unknown.
                                                   Kauai and Niihau.    --               --             Hawaii            --            NA NA/97.
                                                   Oahu.............    --               --             Hawaii            --            NA.
                                                   4-Islands........    --               --             Hawaii            --            NA.
                                                   Hawaii Island....    --               --             Hawaii            --            unknown.
False killer whale............  Pseudorca          Main Hawaiian      Strategic,       Endangered       Hawaii            --            167 (0.14)/149.
                                 crassidens.        Islands Insular.   Depleted
                                                   Hawaii Pelagic...    --               --             Hawaii            --            2,086 (0.35)/
                                                                                                                                         1,567.
                                                   Northwestern         --               --             Hawaii            --            477 (1.71)/178.
                                                    Hawaiian Islands.
Fraser's dolphin..............  Lagenodelphis      Hawaii...........    --               --             Hawaii            --            40,960 (0.7)/
                                 hosei.                                                                                                  24,068.
Killer whale..................  Orcinus orca.....  Eastern North        --               --             Southern          --            300 (0.1)/276.
                                                    Pacific Offshore.                                    California
                                                   West Coast           --               --             Southern          --            349 (N/A)/349.
                                                    Transient.                                           California
                                                   Hawaii...........    --               --             Hawaii            --            161 (1.06)/78.
Long-beaked common dolphin....  Delphinus          California.......    --               --             Southern          --            83,379 (0.216)/
                                 capensis.                                                               California                      69,636.
Melon-headed whale............  Peponocephala      Hawaiian Islands.    --               --             Hawaii            --            40,647 (0.74)/
                                 electra.                                                                                                23,301.
                                                   Kohala Resident..    --               --             Hawaii            --            unknown.
Northern right whale dolphin..  Lissodelphis       CA/OR/WA.........    --               --             Southern          --            29,285 (0.72)/
                                 borealis.                                                               California                      17,024.
Pacific white-sided dolphin...  Lagenorhynchus     CA/OR/WA.........    --               --             Southern          --            34,999 (0.222)/
                                 obliquidens.                                                            California                      29,090.
Pantropical spotted dolphin...  Stenella           Oahu.............    --               --             Hawaii            --            unknown.
                                 attenuata.
                                                   4-Islands........    --               --             Hawaii            --            unknown.
                                                   Hawaii Island....    --               --             Hawaii            --            unknown.
                                                   Hawaii Pelagic...    --               --             Hawaii            --            39,768 (0.51)/
                                                                                                                                         25,548.
Pygmy killer whale............  Feresa attenuata.  Tropical.........    --               --             Southern        Winter &        unknown.
                                                                                                         California      Spring
                                                   Hawaii...........    --               --             Hawaii            --            10,328 (0.75)/
                                                                                                                                         5,885.
Risso's dolphins..............  Grampus griseus..  CA/OR/WA.........    --               --             Southern          --            6,336 (0.32)/
                                                   Hawaii...........  --               --                California     --               4,817.
                                                                                                        Hawaii                          7,385 (0.22)/
                                                                                                                                         6,150.
                                Steno bredanensis  NSD \2\..........    --               --             Southern          --            unknown.
                                                                                                         California
Rough-toothed dolphin.........                     Hawaii...........    --               --             Hawaii            --            76,357 (0.41)/
                                                                                                                                         54,804.
Short-beaked common dolphin...  Delphinus delphis  CA/OR/WA.........    --               --             Southern          --            1,056,308 (0.21)/
                                                                                                         California                      888,971.
Short-finned pilot whale......  Globicephala       CA/OR/WA.........    --               --             Southern          --            836 (0.79)/466.
                                 macrorhynchus.                                                          California
                                                   Hawaii...........    --               --             Hawaii            --            12,607 (0.18)/
                                                                                                                                         10,847.
Spinner dolphin...............  Stenella           Hawaii Pelagic...    --               --             Hawaii            --            unknown.
                                 longirostris.
                                                   Hawaii Island....    --               --             Hawaii            --            665 (0.09)/617.
                                                   Oahu and 4-          --               --             Hawaii            --            unknown.
                                                    Islands.
                                                   Kauai and Niihau.    --               --             Hawaii            --            unknown.
                                                   Kure and Midway..    --               --             Hawaii            --            unknown.
                                                   Pearl and Hermes.    --               --             Hawaii            --            unknown.
Striped dolphin...............  Stenella           CA/OR/WA.........    --               --             Southern          --            29,988 (0.3)/
                                 coeruleoalba.                                                           California                      23,448.

[[Page 68297]]

 
                                                   Hawaii...........    --               --             Hawaii            --            35,179 (0.23)/
                                                                                                                                         29,058.
Dall's porpoise...............  Phocoenoides       CA/OR/WA.........    --               --             Southern          --            16,498 (0.61)/
                                 dalli.                                                                  California                      10,286.
Harbor seal...................  Phoca vitulina...  California.......    --               --             Southern          --            30,968 (NA)/
                                                                                                         California                      27,348.
Hawaiian monk seal............  Neomonachus        Hawaii...........  Strategic,       Endangered       Hawaii            --            1,465 \3\ (0.03)/
                                 schauinslandi.                        Depleted                                                          1,431.
Northern elephant seal........  Mirounga           California.......    --               --             Southern          --            187,386 (NA)/
                                 angustirostris.                                                         California                      85,369.
California sea lion...........  Zalophus           U.S. Stock.......    --               --             Southern          --            257,606 (NA)/
                                 californianus.                                                          California                      233,515.
Guadalupe fur seal............  Arctocephalus      Mexico to          Strategic,       Threatened       Southern          --            34,187 (NA)/
                                 townsendi.         California.        Depleted                          California                      31,019.
Northern fur seal.............  Callorhinus        California.......  Depleted           --             Southern          --            14,050 (NA)/
                                 ursinus.                                                                California                      7,524.
--------------------------------------------------------------------------------------------------------------------------------------------------------
Note: A ``--'' indicates that this column does not apply.
\1\ The Mainland Mexico-CA-OR-WA stock and the Mexico-North Pacific stock (which does not occur in the HSTT Study Area) of humpback whale comprise the
  Mexico DPS. The Hawai[revaps]i stock comprises the Hawai[revaps]i DPS. The Central America/Southern Mexico-CA-OR-WA stock comprises the Central
  America DPS.
\2\ NSD--No stock designation. Rough-toothed dolphin has a range known to include the waters off Southern California, but there is no recognized stock
  or data available for the U.S. West Coast.
\3\ The best official estimate of the total population size from the NMFS 2022 Stock Assessment Report (Carretta et al. 2023) is 1,465. This estimate is
  based on available data through 2020 data for Kure and Midway Atolls, Nihoa Island, and the MHI, and through 2019 for all other subpopulations. More
  recent survey data for 2021 and 2022 indicate an increasing trend in population size. NMFS estimates a total population size for 2022 of 1,605 (NOAA
  2023).

Unusual Mortality Events

    An UME is defined under section 410(6) of the MMPA as a stranding 
that is unexpected, involves a significant die-off of any marine mammal 
population, and demands immediate response. From 1991 to the present, 
there have been 17 formally recognized UMEs affecting marine mammals in 
California and Hawaii and involving species under NMFS' jurisdiction. 
There is one UME that is applicable to our evaluation of the Navy's 
activities in the HSTT Study Area. The gray whale UME along the west 
coast of North America is active and involves ongoing investigations. 
At the time of publication of the 2020 HSTT final rule, there was an 
active UME for Guadalupe fur seal, which NMFS fully considered in its 
analysis (85 FR 41780, July 10, 2020). This UME was closed on September 
2, 2021, and therefore, it is not discussed further beyond the 
information provided here. The UME was closed because conditions under 
which the UME was declared are no longer occurring or have become 
persistent. Scientists documented a reduction in strandings compared to 
peak UME years. The team of scientists who investigated this UME 
determined the cause of the UME as being due to malnutrition in 
Guadalupe fur seal pups and yearlings from ecological factors (e.g., 
warm water events) in the Pacific Ocean causing suboptimal prey 
conditions. Please see https://www.fisheries.noaa.gov/national/marine-life-distress/unusual-mortality-event-2015-2021-guadalupe-fur-seal-and-2015 for additional information on this UME.
    Gray Whale UME
    Since January 1, 2019, elevated gray whale strandings have occurred 
along the west coast of North America, from Mexico to Canada. As of 
June 25, 2023, there have been a total of 674 strandings along the 
coasts of the U.S., Canada, and Mexico, with 333 of those strandings 
occurring along the U.S. coast. Of the strandings on the U.S. coast, 
135 have occurred in Alaska, 83 in Washington, 22 in Oregon, and 93 in 
California. Full or partial necropsy examinations were conducted on a 
subset of the whales. Preliminary findings in several of the whales 
have shown evidence of emaciation. These findings are not consistent 
across all of the whales examined, so more research is needed. As part 
of the UME investigation process, NOAA has assembled an independent 
team of scientists to coordinate with the Working Group on Marine 
Mammal Unusual Mortality Events to review the data collected, sample 
stranded whales, consider possible causal-linkages between the 
mortality event and recent ocean and ecosystem perturbations, and 
determine the next steps for the investigation. Please refer to: 
https://www.fisheries.noaa.gov/national/marine-life-distress/2019-2023-gray-whale-unusual-mortality-event-along-west-coast-and for more 
information on this UME. See the Preliminary Analysis and Negligible 
Impact Determination section for additional information on how NMFS has 
considered this UME in this proposed rule.

Biologically Important Areas

    Since publication of the 2020 HSTT final rule, Kratofil et al. 
(2023) identified updated BIAs in Hawaii. The HSTT Study Area overlaps 
the updated BIAs for small and resident populations of the following 
species in Hawaii: spinner dolphin, short-finned pilot whale, rough-
toothed dolphin, pygmy killer whale, pantropical spotted dolphin, 
melon-headed whale, false killer whale, dwarf sperm whale, Cuvier's 
beaked whale, common bottlenose dolphin, and Blainville's beaked whale. 
Further, the HSTT Study Area overlaps updated BIAs for humpback whale 
reproduction in Hawaii. The updated BIAs overlap critical Navy training 
and testing areas within the HSTT Study Area, including most of the 
internal Navy operating areas. Please see Kratofil et al. (2023) for 
additional details about the BIAs.

Potential Effects of Specified Activities on Marine Mammals and Their 
Habitat

    This section provides a discussion of the ways in which components 
of the specified activity may impact marine mammals and their habitat. 
The Estimated Take section later in this document includes a 
quantitative analysis of the number of individuals that are expected to 
be taken by this activity. The Negligible Impact Analysis and 
Determination section considers the content of this section, the 
Estimated Take section, and the Proposed 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

[[Page 68298]]

survival. In the Potential Effects of Specified Activities on Marine 
Mammals and Their Habitat section of the 2018 HSTT proposed and final 
rules, and as updated by the 2020 HSTT final rule, NMFS provided a 
description of the ways marine mammals may be affected by the same 
activities that the Navy will be conducting during the 7-year period 
analyzed in this rulemaking in the form of serious injury or mortality, 
physical trauma, sensory impairment (permanent and temporary threshold 
shifts and acoustic masking), physiological responses (particularly 
stress responses), behavioral disturbance, or habitat effects. We do 
not repeat the information here, all of which remains current and 
applicable, and instead summarize any new relevant information from the 
scientific literature. For more information we refer the reader to 
those rules and the 2018 HSTT FEIS/OEIS (Chapter 3, Section 3.7 Marine 
Mammals), which NMFS participated in the development of via our 
cooperating agency status and adopted to meet our NEPA requirements.
    In the Potential Effects of Specified Activities on Marine Mammals 
and Their Habitat section of the 2018 HSTT final rule, we stated that 
it has been speculated for some time that beaked whales might have 
unusual sensitivities to sonar sound due to their likelihood of 
stranding in conjunction with mid-frequency active sonar (MFAS) use, 
although few definitive causal relationships between MFAS use and 
strandings have been documented, and no such findings have been 
documented with Navy use in Hawaii and southern California. On March 
25, 2022, a beaked whale (species unknown) stranded in Honaunau Bay, 
Hawaii. The animal was observed swimming into shore and over rocks. 
Bystanders intervened to turn the animal off of the rocks, and it swam 
back out of the Bay on its own. Locals reported hearing a siren or 
alarm type of sound underwater on the same day, and a Navy vessel was 
observed from shore on the following day. The Navy confirmed it used 
continuous active sonar (CAS) within 50 km (27 nmi) and 48 hours of the 
time of stranding, though the stranding has not been definitively 
linked to the Navy's CAS use.
    An initial study of another deep diving odontocete, the sperm 
whale, found similar behavioral responses and reductions in foraging 
when whales were exposed to pulsed active sonar (PAS) and CAS at 
similar cumulative Sound Exposure Levels (SELcum), even 
though the CAS signal had a lower source level than the PAS signal. 
This may indicate that animals were, in this case, responding to the 
cumulative energy of a signal rather than the instantaneous amplitude 
(Cure et al. 2021, Isojunno et al. 2020). If a beaked whale were 
inshore of a Navy vessel using either PAS or CAS MFAS, and responded by 
moving away from the vessel, they could find themselves in shallow 
water and become disoriented, as may have happened in the case of 
Honaunau Bay. In addition, the animal was not seen after it returned to 
sea, so blood tissue samples could not be obtained. There has been a 
growing body of literature about the impacts of new pathogens on the 
health and stranding of marine mammals, including beaked whales in 
Hawaii and other locations in the Pacific (e.g., Clifton et al. 2023 
and West et al. 2013).

New Pertinent Science Since Publication of the 2020 HSTT Final Rule

    NMFS has reviewed new relevant information from the scientific 
literature since publication of the 2020 HSTT final rule. Summaries of 
the new key scientific literature reviewed since publication of the 
2020 HSTT final rule are presented below. The literature generally 
falls into the following topic areas: Vessel Strike; Aircraft Noise; 
Hearing, Vocalization, and Masking; Hearing Loss (Temporary Threshold 
Shift (TTS) and Permanent Threshold Shift (PTS)); Behavioral Reactions; 
Stranding; Population Consequences of Disturbance and Cumulative 
Stressors; Methodology for Assessing Acoustic Impacts.

Vessel Strike

    Crum et al. (2019) analyzed a modeling framework using encounter 
theory to estimate the risk of lethal commercial vessel strike to North 
Atlantic right whales. Seasonal mortality rates of right whales 
decreased by 22 percent on average after a speed rule was implemented, 
indicating that the rule is effective at reducing lethal collisions. 
The rule's effect on risk was greatest where right whales were abundant 
and vessel traffic was heavy but varied considerably across time and 
space.
    Keen et al. (2019) compared vessel traffic patterns in the Southern 
California Bight, San Francisco, and the Pacific Northwest and found 
fin whales had a higher risk of nighttime vessel strikes with the 
nighttime risk being double daytime risk. The authors concluded that 
the shipping lanes contained 14 percent of all traffic volume and 
contributed 13 percent of all strike risk similar to conclusions 
reached by Rockwood et al. (2017). However, the authors also point out 
that a California Current Ecosystem (CCE) wide shipping speed 
reductions would not be practicable. Instead, they proposed 24-hour 
speed restrictions around and within shipping lanes would be more 
effective and feasible than nighttime only speed restrictions 
elsewhere. Keen et al. (2019b) reported high fin whale habitat 
suitability throughout the Southern California Bight, in particular 
inshore in winter and in southern portions of the Bight, which include 
HSTT SOCAL Study Area.
    Leaper (2019) estimated that a global 10 percent reduction in 
shipping speeds could result in a reduction of underwater sound 
associated with shipping by approximately 40 percent and vessel strike 
risk by around 50 percent by 2050. The vessel strike risk reduction 
done by the author is highly variable based solely on the relationship 
between ship speed and risk, qualitative in its findings, and 
speculative.
    Redfern et al. (2019) compared risk of vessel strike to baleen 
whales around the Santa Barbara Channel based on 8 years of shipping 
data (2008-2015). Species evaluated include blue whales, fin whales, 
and humpback whales using available spatial habitat models and 
satellite tagging results. Spatial habitat modeling data included the 
years 1991, 1993, 1996, 2001, 2005, 2008, and 2009. The authors defined 
collision risk based on the co-occurrence of whales and ships for 
various management scenarios focused on adding shipping routes, 
expanding existing area to be avoided, and reducing shipping speed 
associated with these areas. Encounter rate theory was used to predict 
relative mortality resulting from vessel strikes by estimating (a) the 
encounter rate; (b) the number of encounters that result in a 
collision; and (c) the probability that a collision is lethal (Martin 
et al. 2016, Rockwood et al. 2017, Crum et al. 2019). The authors 
concluded that expanding the existing areas to be avoided and speed 
reductions within shipping lanes and their approaches would be the most 
effective solutions. Ship speeds declined in the Bight from 2008 to 
2015 because California air pollution regulations and economic factors 
made slow[hyphen]steaming strategies more favorable, therefore 
reduction in risk from slowing ships was greatest in 2008 and lowest in 
2015.
    Rockwood and Jahncke (2019) estimated that humpback whale mortality 
from January to April in Southern California alone was 6.5 whales 
(1.63/month), based upon modeling using updated abundance

[[Page 68299]]

estimates for humpback whales off Southern California. When added to 
the estimated mortality from July to November, the total estimated 
annual humpback mortality from vessel strikes in California alone was 
23.4 deaths (16.9 + 6.5). This study did not include information for 
January to April for fin or blue whales and did not estimate humpback 
mortality in central or Northern California. Thus, even this updated 
study may underestimate whale mortality. The author's focus was 
exclusively on shipping approaches to San Francisco Bay (Northern 
California) and Los Angeles/Long Beach (Southern California) based on 
Rockwood et al. 2017 with new local fine scale analysis. The paper 
postulated potential mortality from models, not actual reported 
strikes. The model is used to predict whale mortality based on factors 
listed in Rockwood et al. 2017. In the model results, cargo vessels, 
especially container ships, accounted for more than half of the 
predicted mortality for all whale species in both Northern and Southern 
California with oil tankers accounting for the second highest 
mortality. The author's recommendation concludes with commercial 
industry-wide shipping speed reduction recommendations given the model 
is biased on mortality as a function of speed. In summary, Rockwood and 
Jahncke (2019) only addresses commercial shipping strike risk 
associated with major California commercial ports, and therefore, the 
paper may have limited applicability to how the Navy trains and tests 
in SOCAL.
    S[egrave]be et al. (2019) assesses previous publications on whale 
vessel strike risk methodology and proposed a systematic approach to 
addressing the issue called the Formal Safety Assessment: (1) 
identification of hazards, (2) assessment of risks, (3) risk control 
options, (4) cost-benefit assessment, and (5) recommendations for 
decision-making. The authors provided a case study based on data from 
Rockwood et al. (2017). No new data analysis is presented in the paper. 
Caveats to S[egrave]be et al. (2019) are similar to those mentioned for 
Rockwood et al. (2017, 2019): older marine mammal data that may not be 
reflective of current or future distribution and focus on limited 
navigation within shipping approaches by commercial ships means that 
this study may have somewhat limited applicability to how the Navy 
trains and tests in SOCAL.
    Szesciorka et al. (2019) concluded that while whales have some cues 
to avoid ships, this is true only at close range, under certain 
oceanographic conditions and if the whale is not otherwise distracted 
by feeding, breeding, or other behaviors. The paper is based on a 
single blue whale reaction observed in the Santa Barbara Channel, north 
of, and outside of, SOCAL. The blue whale was tagged as part of the 
U.S. Navy-funded Southern California Behavioral Response Study (SOCAL 
BRS) 2010-2015 and exposed to simulated MFAS when a closest point of 
approach of 93 m from a passing commercial container ship was noted. 
The whale was only tagged for a couple of hours before tag detachment. 
As other published papers report from the SOCAL BRS and as cited in the 
2018 HSTT FEIS/OEIS, there can be significant individual variation in 
response to anthropogenic sources, which in this case would include 
vessel transit.
    Blondin et al. (2020) estimated blue whale vessel strike risk in 
the Southern California Bight by combining predicted daily whale 
distributions with continuous vessel movement data for 4 years (2011, 
2013, 2015, 2017). The study focuses on the northern Southern 
California Bight associated with the commercial vessel traffic 
separation zone through Santa Barbara Channel approaching the Port of 
Los Angeles/Long Beach. This area is north of and outside of SOCAL. The 
authors found that vessel traffic activity across years (2011, 2013, 
2015, 2017) was variable and whale spatial probability was also 
variable based on inter-annual fluctuations in environmental 
conditions. Similar to previous monitoring efforts in Southern 
California, blue whales are typically in higher concentrations north of 
SOCAL from July-November (Mate et al. 2018), and Blondin et al. (2021) 
also picked up on this seasonal variability in their analysis. 
Oceanographic conditions favorable for krill development and 
concentration (i.e., cool water periods) would lead to increased blue 
whale occurrence and higher strike risk as evidenced during the higher 
number of blue whale strikes in 2007 (Berman-Kowalewski et al. 2010). 
Finally, the coarse level of data analyzed by the authors does not 
account for short-term patchy prey conditions influencing blue whale 
occurrence and may result in overestimation of average risk.
    Redfern et al. (2020) revised their 2019 assessments of vessel 
strike risk off California using interannual variability of risk across 
multiple years for blue whale, fin whale and humpback whale. The 
authors showed higher concentrations of both blue and fin whales along 
the Central California coast as compared to within SOCAL. Magnitude of 
vessel strike risk was influenced by the ship traffic scenario. In 
addition, interannual species variability (1991, 1993, 1996, 2001, 
2005, 2008, and 2009) also influenced the magnitude of vessel strike 
risk, but did not change whether nearshore or offshore scenarios had 
higher risk. The author's conclusions were similar to Redfern et al. 
(2019). Figure 2 from Redfern et al. (2020) illustrates mean blue 
whale, fin whale, and humpback whale vessel strike risk for California 
based on data through 2009. Results from more recent NMFS surveys in 
2014 and 2018 may or may not change this assessment in the future.
    Rockwood et al. (2020b) calculated expected blue whale and humpback 
whale mortality for hypothetical compliance scenarios by imposing speed 
caps within and adjacent to vessel traffic lanes leading to the Port of 
San Francisco in Central California, 400 miles (643.7 km) north of 
SOCAL. Rookwood et al. (2020a) had already demonstrated this area off 
Central California had concentrated krill prey with associated higher 
distributions of blue whales and humpback whales. Rookwood et al. 
(2020b) used better temporal resolution density data than previous 
modeling efforts reported by Rookwood et al. (2017). Biological data 
analysis for Rookwood et al. (2020b) was based on regional monthly 
krill and whale surveys from 2004-2017. Rockwood et al.'s (2020b) 
overall modeling conclusions were that lower commercial ship speeds 
within the vessel traffic lanes could potentially reduce whale 
mortality from vessel strike. The authors acknowledge that local 
changes in whale abundance can have strong effects on both inter-annual 
and long-term patterns of ship-strike mortality.
    Bernknopf et al. (2021) examined the socioeconomic benefits of 
using remotely-sensed information instead of in situ observations for 
determining blue whale occurrence in the eastern North Pacific Ocean. 
Their analysis used blue whale spatial distribution through 1991-2009 
projects as representative of 2017 densities (Becker et al. 2012) 
combined with automatic identification system (AIS) derived measures of 
civilian commercial vessel traffic to predict blue whale vessel strike 
risk, called the Reference Case by the authors. The authors then 
compared estimated blue whale strike risk in a second analysis that, 
instead of using empirically measured blue whale observations converted 
into spatial habitat maps, used satellite tracking and environmental 
data to identify the spatial and temporal distribution of blue

[[Page 68300]]

whales, called the Counterfactual Case by the authors (Hazen et al. 
2017). Estimated mean fatal strikes to blue whales for the Reference 
Case based on empirical density data from 1991-2009 ranged from 0.0490 
to 2.5877 (max. values >1.000 between June to October) (see Table 2 in 
Bernknopf et al. 2021). Estimated mean fatal strikes to blue whales for 
the Counterfactual Case based on environmental estimates of blue whale 
density in 2017 ranged from 0.0286 to 2.1556 (max. values >1.000 
between August to October). An important caveat to this research is 
that the two approaches result in different strike risks due to using 
different blue whale density estimates.
    Barkaszi et al. (2021) designed a model to estimate risks to large 
whales from shipping associated with offshore wind development along 
the U.S. Atlantic Coast. A key caveat for the model is that it is based 
on civilian vessel types associated with wind energy construction 
(e.g., tugs, service craft, etc.) with relatively fixed, direct routes 
to offshore wind sites. Therefore, while lower vessel speeds can reduce 
mortality, prediction and implementation of reduced speed zones are a 
far more complex challenge (Barkaszi et al. 2021). Vessel speed has 
less effect on strike risk over a fixed distance with fixed target 
density when there are no behavioral components considered (Yin et al. 
2019). Vessel speed has a significant effect on strike risk only when 
behavioral components are considered, thus the ability for the user to 
input animal or vessel aversion is an important variable that can 
provide insights to the encounter risk based on vessel speeds.
    Cusato (2021) discusses the merits of vessel traffic separation 
changes or mandatory commercial ship speed reductions in the Santa 
Barbara Channel to reduce the risk of vessel strikes to large whales. 
The author compares it to similar restrictions on the U.S. East Coast 
for North Atlantic right whales. The paper is a policy discussion 
rather than an analysis of current biological distribution of large 
whales and associated risk. Cusato (2021) focuses on reducing risk from 
commercial ships in the current vessel traffic separation scheme within 
the Santa Barbara Channel. Speed restrictions in the Channel would need 
to be implemented through either Federal regulations or Federal 
statute. The author also correctly points out legitimate concerns that 
operating large vessels at slow speeds in certain conditions could pose 
a safety risk because large vessels are more difficult to control and 
steer at slower speeds.
    Hausner et al. (2021) examined tradeoffs of blue whale vessel 
strikes and speed reduction mitigation over a 17-year period from 2002 
to 2018 in the Southern California Bight under two management scenarios 
verses a ``fixed strategy'' that implements speed reductions for a 
fixed time period each year. The two management strategies were (1) a 
``daily strategy'' implementing speed reductions in response to whale 
habitat conditions on a daily basis, and (2) a ``seasonal strategy'' 
implementing speed reductions in response to whale habitat conditions 
on a seasonal basis. The period of the author's data analysis also 
covers the abnormal marine heat wave along the U.S. West Coast (2014-
2016). The study's focus was exclusively with the traffic separation 
lanes leading from the Santa Barbara Channel to the Ports of Los 
Angeles and Long Beach, a narrow corridor north of and outside of 
SOCAL. The daily and seasonal management strategies were more effective 
in reducing blue whale strike risk in the Santa Barbara channel than 
the fixed strategy. The daily management strategy had the highest 
protective effect. This apparent difference in strategies also applied 
during and after the 2014-2016 marine heat wave where the daily 
strategy added even extra protection. The authors acknowledged that 
interannual variation on blue whale presence in the shipping lanes 
added some variability to their analysis. In addition, their study only 
considered blue whales sighted within the Traffic Separation Scheme, as 
opposed to the broader region where vessels transit through or a blue 
whale could occur.
    Ransome et al. (2021) documented 40 vessel strikes to large whales 
in the Eastern Tropical Pacific Ocean between 1905 and 2017 off the 
coasts of 10 Central and South American countries (Mexico to Columbia). 
The authors concluded that vessel strikes to large whales are more 
prolific in this region than previously reported. For instance, the 
author's findings of 40 vessel strikes was over three times greater 
than previous reporting and still is likely under reporting total whale 
strikes. The majority of whale strikes occurred from the 1950s onward 
with the growth of modern shipping and whale watching. Humpback whales 
were the most commonly struck species (45 percent) although 30 percent 
of the species were not identified in their data.
    Rockwood et al. (2021), similar to Rockwood et al. (2020b), 
calculated potential whale strike mortalities using AIS vessel data and 
whale density data to estimate mortality under several management 
scenarios within the commercial shipping lanes passing through Santa 
Barbara Channel and San Pedro Channel to and from the Ports of Los 
Angeles and Long Beach. While the Santa Barbara Channel is 
approximately 100 miles (160.9 km) north of SOCAL, Rockwood et al.'s 
study area also included the southern vessel traffic approach to Los 
Angeles and Long Beach which did extend into the northeast coastal 
portion of SOCAL. Recent whale surveys were not available for this 
effort, so the authors used long-term average blue, fin, and humpback 
whale densities from Becker et al. (2016). The author's model also 
predicted a higher level of whale vessel strikes from commercial ships 
than Rockwood et al. (2017), although the authors acknowledged that for 
the 2020 publication they included more vessel classes than for the 
2017 publication.
    Silber et al. (2021) examined the risk to gray whales from 
commercial shipping in the North Pacific. Vessel strike risk was 
highest for gray whales including the Western North Pacific Distinct 
Population Segment (WNP DPS) along most of the migratory routes. 
Highest risk to the WNP DPS of gray whales was outside of the SOCAL in 
the western Bering Sea, along the east coast of the Kamchatka peninsula 
(Russia), and coastlines of Japan. For both Eastern North Pacific and 
WNP DPSs of gray whales, the greatest vessel strike risk along the U.S. 
West Coast was from Washington to Central California.
    Helm et al. (2023) looked at strike risk to foraging humpback 
whales surfacing around large cruise ships transiting Glacier Bay 
National Park, Alaska. The authors concluded that the probability of 
foraging humpback whales remaining near the surface after first 
sightings was relatively high. While this puts humpback whales at 
increased risk of ship strike, it also allows shipboard observers more 
time to spot whales in order to maneuver the ship to avoid a strike.
Lookout Effectiveness
    A recent study by Oedekoven and Thomas (2022) was designed to 
evaluate the effectiveness of Navy Lookouts at detecting marine mammals 
before they entered a defined set of mitigation zones (i.e., 200, 500, 
and 1,000 yd (182.9, 457.2, and 914.4 m)) during MFAS training 
activities. This study also compared Lookout effectiveness with that of 
trained marine mammal observers. Lookout teams were comprised of 
varying numbers of Lookouts depending on the type of ship and the 
training activity that was occurring (noting that the data was

[[Page 68301]]

collected prior to the Navy's change in its SOPs to require the use of 
three Lookouts on Navy cruisers and destroyers.) Marine mammal observer 
teams consisted of two dedicated observers. Results of this study 
indicate that Navy Lookout Teams, which include Lookouts and other crew 
members, have approximately an 80 percent chance of failing to detect a 
pod of large baleen whales (rorquals) before they come closer than a 
mitigation range of 200 yd (182.9 m), compared with a 49 percent chance 
for trained marine mammal observers. The probability of a pod remaining 
undetected by Lookouts was greater for larger mitigation zones (i.e., 
85 percent at 500 yd (457.2 m); 91 percent at 1,000 yd (914.4 m)). 
These values require some level of interpretation with regard to the 
numerical results. For instance, the study's statistical model assumed 
that Navy ships moved in a straight line at a set speed for the 
duration of the field trials, and that animals could not move in a 
direction perpendicular to a ship. Violation of this model assumption 
would underestimate Lookout effectiveness for some data points. The 
values for both Navy Lookouts and the Marine Mammal Observers include 
animals under the water that would not have been available for 
detection by a Lookout. This study suggests that detection of marine 
mammals is less certain than previously assumed at certain distances.
Hearing, Vocalization, and Masking
    Branstetter et al. (2021) measured underwater, masked hearing 
thresholds for frequencies between 0.5 and 80 kilohertz (kHz) in two 
killer whales. Critical ratios computed from the threshold measurements 
ranged from 16 to 32 decibels (dB). For communication signals in the 
1.5-15 kHz range, killer whales would require the signal to be up to 26 
dB above background Gaussian noise to be detected. The authors noted 
that ambient background noise in the marine environment is not 
Gaussian, the tones used in this study do not contain as much frequency 
information as biologically relevant signals, and the temporal and 
spectral characteristics of actual signals and noise may result in some 
degree of release from masking. These results are consistent with 
critical ratio measurements from other odontocete species, despite 
differences in hearing ability and head size.
    Fournet et al. (2021) measured call amplitudes from male bearded 
seals in the Beaufort Sea under different ambient noise conditions. The 
results showed that estimated source levels of seal calls increased 
with ambient noise up to approximately 100-105 dB root-mean-squared 
(rms), above which no further Lombard effect was observed. This 
suggests that masking of bearded seal mating calls may occur, resulting 
in reduced communication range, which could reduce the ability of 
bearded seals to detect one another, mate, and reproduce.
    Mercado (2021) aimed to characterize how units within humpback 
whale songs were systematically varied using a large dataset of 
recordings from off the coast of Kona, Hawaii. The data showed that 
narrowband, reverberant units repeated at regular time intervals and 
dominated most song sessions, while broadband units were less 
predictable and occupied frequency bands that did not overlap with the 
narrowband units. The persistent production of narrowband units at 
regular time intervals resulted in consistent reverberation, which 
could either function to increase the range at which the song can be 
detected, or listen for fluctuations in echoes to indicate the presence 
of whale-sized targets.
    Rey-Baquero et al. (2021) collected theodolite and passive acoustic 
data on humpback whales in a pristine environment along the Colombian 
Pacific for 2 months. When acoustic data (n=34 files) were analyzed for 
unit duration and inter-unit interval before and after boats passed, 
song unit lengths were shorter and more variable when boats were 
present. The second aim of this study was to model the whales' 
communication space during ambient noise or one to two boats traveling 
slowly. The most common peak frequency of this stock's song (350 Hz) 
was used in the model, and, along with a whale's location along the 
coast, informed calculations of transmission loss. However, the source 
level of ``typical whale-watching boats'' (145 dB re 1 uPa (decibels 
referenced to 1 micropascal) at 1 m; (Erbe et al. 2012)) and humpback 
whales (153 dB re 1 uPa at 1 m; (Au et al. 2006)) were taken from 
previous studies. Authors found that the infrequent addition of ecotour 
boat noise could temporarily reduce the ``very audible area'' (>10 dB 
SNR) in their song's commonly used peak frequency (350 Hz) by 63 
percent.
    Ruscher et al. (2021) measured aerial behavioral hearing thresholds 
in a Hawaiian monk seal (Neomonachus schauinslandi). The results showed 
a hearing range between 0.1 and 33 kHz with relatively poor sensitivity 
compared to Phocinae seals. The most sensitive thresholds were 40 dB re 
20 [mu]Pa measured at 800 Hz and 3.2 kHz. The resulting audiogram was 
most similar to the northern elephant seal, which is the only other 
species of Monachinae seal with audiogram data (Reichmuth et al. 2013). 
This study suggested that hearing sensitivity of Monachinae seals is 
substantially reduced compared to other species within their functional 
hearing group (phocid carnivores in air; PCA); therefore, the use of 
the PCA weighting function to predict auditory impacts is likely 
conservative for Hawaiian monk seals.
    Sills et al. (2021) measured underwater auditory detection 
thresholds in a male Hawaiian monk seal, and the range of most 
sensitive hearing was between 0.2 and 33 kHz. Peak hearing sensitivity 
of 73 dB re 1 [mu]Pa was observed at 1.6 kHz. The audiogram for this 
individual was similar but narrower and elevated compared to the 
hearing group (phocid carnivores in water; PCW) composite audiogram 
used to assess impacts to this species. Underwater vocalizations were 
also measured, and 6 call types were identified, which had peak energy 
between 55 and 400 Hz. The number of calls produced per minute 
fluctuated seasonally and peaked in the breeding season with the 
highest call rates recorded in December.
    Sweeney et al. (2022) examined the difference between noise impact 
analyses using unweighted broadband sound pressure levels (SPLs) and 
analyses using auditory weighting functions. The recordings used to 
conduct parallel analyses in three marine mammal species groups were 
from a shipping route in Canada. Since shipping noise was predominantly 
in the low-frequency spectrum, bowhead whales perceived similar 
weighted and unweighted SPLs while narwhals and ringed seals 
experienced lower SPLs when auditory weighting functions were used. The 
data provide a real-world example to support the use of weighting 
functions based on hearing sensitivity when estimating audibility and 
potential impact of vessel noise on marine mammals.
    A study by von Benda-Beckmann et al. (2021) modeled the effect of 
pulsed and continuous 1-2 kHz active sonar on sperm whale echolocation 
clicks and found that the presence of upper harmonics in the sonar 
signal increased masking of clicks produced in the search phase of 
foraging compared to buzz clicks produced during prey capture. 
Different levels of sonar caused intermittent to continuous masking 
(120 to 160 dB re 1 [mu]Pa2, respectively), but varied based on click 
level, whale orientation, and prey target strength. CAS resulted in a 
greater percentage of

[[Page 68302]]

time that echolocation clicks were masked compared to PAS.
    Kastelein et al. (2021c) compared the ability of harbor porpoises 
to detect signals in constant-amplitude noise with amplitude-modulated 
noise. Underwater, behavioral hearing thresholds were measured from 
harbor porpoises at 4 kHz under three conditions: ambient noise 
(control), sinusoidally amplitude modulated (SAM) masking noise, and 
Gaussian (constant amplitude) masking noise. Both masker types were 
centered at 4 kHz with a one-third octave bandwidth and were tested at 
various SPLs. The SAM noise was also tested at modulation rates from 1-
90 hertz (Hz). The 4 kHz hearing test signals were 0.5, 1, and 2 
seconds in duration. The results showed that, compared to Gaussian 
noise, up to 14.5 dB of masking release (from ``dip listening'') was 
observed in lower-modulation rate (1-5 Hz) SAM noise. The effect of 
masking on communication space is often modeled using constant-
amplitude noise, whereas most Navy sources contain gaps, more like 
amplitude-modulated noise. This study suggests that the signal 
duration, masker level, and masker modulation rate and depth should be 
considered when modeling the effect of noise on signal detection.
    Isojunno et al. (2021) used data from 15 tagged sperm whales 
(Isojunno et al. 2020) to evaluate odontocete echolocation behavior as 
a function of received sonar exposures. Statistical analysis revealed 
small reductions in the number of buzzes and movement during sonar, but 
the most apparent change in echolocation behavior was a Lombard effect 
observed during higher sea states (increased surface noise). No 
behavioral changes in orientation relative to the sonar source were 
observed that would suggest an anti-masking strategy for spatial 
release from masking. Theoretical modeling of masking potential in 
terms of detection range revealed that search phase clicks would likely 
be masked during both PAS and CAS, but the buzz clicks would not. For 
regular search phase clicks to be continuously masked, SELs would have 
to be equal to or greater than 160 and 173 dB re 1 [mu]Pa\2\s (dB 
referenced to 1 micropascal squared seconds) for PAS and CAS, 
respectively. Overall, the data showed more evidence for masking by 
increases in ambient noise (surface noise from higher sea states), than 
for sonar. This result could be due, in part, to the 1-2 kHz narrowband 
sonar masker, which is not comparable to broadband maskers such as 
ambient noise or shipping noise.
    Matthews and Parks (2021) reviewed the existing literature on North 
Atlantic right whale acoustic behavior and summarize information on 
acoustic behavior of the Southern right whale, North Pacific right 
whale, and bowhead whale. The authors reviewed primary literature on 
whale vocalizations, anatomical modeling, and behavioral responses to 
playbacks to conclude that the North Atlantic right whale might have a 
hearing range of 20 Hz to 22 kHz. However, vocalization data cannot be 
used to directly estimate audible range since there are many examples 
of mammals (including marine mammals) that vocalize with energy below 
the frequency of best hearing, and calls can also contain high-
frequency harmonics that are above the upper limit of hearing. The 
anatomical model developed by Ketten (1994) was used by Parks et al. 
(2007) to estimate a functional hearing range of 15 Hz to 18 kHz for 
this species.
    Jacobson et al. (2022) modeled the probability of Blainville's 
beaked whale group vocal periods (GVPs) on the Pacific Missile Range 
Facility during periods of no naval activity, naval activity without 
hull-mounted MFAS, and naval activity with hull-mounted MFAS. Data were 
collected from bottom-mounted hydrophones on the range before, during, 
and after six Submarine Commanders Course (SCC) exercises. At an MFAS 
received level of 150 dB re 1 [mu]Pa rms (root mean square), the 
probability of GVP detection decreased by 77 percent (95 percent CI: 67 
percent-84 percent) compared to periods when general training activity 
was ongoing and by 87 percent (95 percent CI: 81 percent-91 percent) 
compared to baseline conditions. This study found a greater reduction 
in p(GVP) with MFAS than observed in a prior study of Blainville's 
beaked whales at the Atlantic Undersea Test and Evaluation Center 
(AUTEC) (Moretti et al. 2014). The authors suggest that this may be due 
to the baseline period in the AUTEC study including naval activity 
without MFAS, potentially lowering the baseline p(GVP), or due to 
differences in the residency of the populations at each range.
    Branstetter and Sills (2022) reviewed direct laboratory (i.e., 
psychoacoustic) studies of marine mammal hearing in noise. 
Psychoacoustic studies of auditory masking in marine mammals were 
described in detail and categorized by the type of signal and masker 
(e.g., tone in white noise), and specific conditions under which 
masking is reduced (i.e., release from masking). Specifically, 
comodulation masking release, or the reduction in masking due to 
amplitude or frequency modulation differences between the signal and 
noise, and spatial release from masking, or the reduction in masking 
due to spatial separation between signal and noise and the directional 
hearing ability of the listener, are discussed. Finally, energetic 
masking, or the ability of the listener to detect a signal was compared 
to informational masking, or the ability of the listener to comprehend 
the signal was reviewed. The authors point out that while the body of 
scientific evidence thus far shows that processes of the ear result in 
energetic masking, more research on informational masking is needed to 
develop realistic communication space models. This is because current 
communication space models are based on 50 percent signal detection 
rather than some threshold of successful signal recognition or 
interpretation by the listener.
Hearing Loss (TTS and PTS)
    Houser (2021) reviews existing literature on the relationship 
between auditory threshold shift and tissue destruction in mammals. 
According to small terrestrial mammal literature, TTSs of approximately 
30-50 dB measured 24 hours after sound exposure induced progressive 
tissue damage despite the return of normal hearing thresholds. Although 
large TTSs allow for full recovery of hearing, pathological tissue 
destruction may occur; however, smaller-magnitude TTSs are unlikely to 
result in tissue damage. The author concludes that the current criteria 
of 40 dB of TTS measured within minutes of the noise exposure as the 
onset of injury is likely to encompass recoverable auditory threshold 
shift without tissue damage. This publication supports the use of 
current definitions of auditory injury in marine mammals.
    Kastelein et al. (2022a) measured underwater behavioral hearing 
thresholds in two California sea lions at 0.6, 0.85, and 1.2 kHz before 
and after exposure to a one-sixth-octave noise band centered at 0.6 kHz 
for 60-minutes. Hearing tests were also conducted at 1, 1.4, and 2 kHz 
after exposure to a one-sixth-octave noise band centered at 1 kHz for 
60-minutes. For the 0.6 kHz exposure, the maximum TTS was 7.5 dB (6.7 
dB mean) for a 210 dB cumulative SEL (SELcum) exposure at 
the hearing test frequency one-half octave above the center frequency 
of the fatiguing stimulus (0.85 kHz), which recovered after 
approximately 12 minutes. For the 1 kHz exposure, the maximum TTS was 
10.6 dB (9.6 dB mean) after a 195 dB SELcum exposure at the 
hearing test frequency one-half octave above the center frequency of 
the fatiguing

[[Page 68303]]

stimulus (1.4 kHz). Mean threshold shift (TS) greater than 6 dB (mean = 
8.0 dB, min = 7.2 dB, max = 8.5 dB) was also observed after exposure to 
the 1 kHz fatiguing stimulus at 195 dB SELcum for the 1 kHz 
hearing test frequency. For this exposure frequency, hearing recovered 
within 24 minutes. The results of this study show individuals 
exhibiting onset of TTS in water at lower received levels than the 
otariid thresholds in ``Criteria and Thresholds for U.S. Navy Acoustic 
and Explosive Effects Analysis (Phase III)'' (Navy, 2017).
    Kastelein et al. (2022b) measured underwater behavioral hearing 
thresholds in two California sea lions at 8, 11.3, and 16kHz before and 
after exposure to a one-sixth-octave noise band centered at 8 kHz for 
60-minutes. Hearing tests were also conducted at 32 kHz after exposure 
to a one-sixth-octave noise band centered at 16 kHz for 60-minutes. For 
the 8kHz exposure, the maximum TTS was 20.2 dB (18 dB mean) for a 190 
dB SELcum exposure at the hearing test frequency one-half 
octave above the center frequency of the fatiguing stimulus (11.3 kHz), 
which recovered after approximately 12 minutes. For the 16 kHz 
exposure, the maximum TTS was 19.7 dB (16.3 dB mean) after a 207 dB 
SELcum exposure at the hearing test frequency one-half 
octave above the center frequency of the fatiguing stimulus (22.4 kHz). 
For these exposure frequencies and scenarios, hearing recovered within 
72 minutes or less. The results of this study show TTS onset in-water 
occurred at lower received levels than what the current otariid 
criteria in ``Criteria and Thresholds for U.S. Navy Acoustic and 
Explosive Effects Analysis (Phase III'') (Navy, 2017) suggest.
    Kastelein et al. (2021a) measured underwater behavioral hearing 
thresholds at 0.5, 0.71, and 1 kHz in one harbor porpoise before and 
after exposure to one-sixth-octave band noise centered at 0.5 kHz. 
Maximum TTS was 8.9 dB (mean = 7.6 dB) at the 0.5 kHz hearing test 
frequency after a 205-dB SELcum exposure. For the 0.71 and 1 
kHz hearing test frequencies, no mean TTS > 6 dB was observed. However, 
at 0.71 kHz, maximum TTS was 6.5 dB (mean = 5.8 dB) was observed after 
a 205-dB SELcum exposure. At 1 kHz, a maximum of 6.3 dB of 
TTS (mean = 5.7 dB) occurred after 206-dB SELcum exposures. 
All shifts < 5 dB recovered within 12 minutes and shifts > 6 dB 
recovered within 60 minutes. These results are consistent with the 
criteria and thresholds described in ``Criteria and Thresholds for U.S. 
Navy Acoustic and Explosive Effects Analysis (Phase III)'' (Navy, 
2017).
    Kastelein et al. (2021b) measured behavioral, underwater hearing 
thresholds at 2, 2.8, and 4.2 kHz in two sea lions before and after 
exposure to band-limited noise centered at 2 kHz. Sea lion hearing was 
also tested at 4.2, 5.6, 8 kHz before and after exposure to noise 
centered at 4 kHz. Maximum TTS was 24.1 dB (22.4 dB mean) at the 5.6 
kHz test frequency after a 205-dB SELcum exposure centered 
at 4 kHz. Threshold shifts greater than or equal to 6 dB occurred at 
187, 181, and 187 dB SELcum for 4.2, 5.6, and 8 kHz test 
frequencies respectively. After exposure to the 2-kHz noise, maximum 
TTS of 11.1 dB (10.5 dB mean) occurred for 203 dB SELcum at 
the 2 kHz test frequency. Threshold shifts greater than or equal to 6 
dB occurred at SELcum of 192, 186, and 198 dB for test 
frequencies 2, 2.8, and 4.2 kHz respectively. These data suggest that 
one-half octave above the exposure frequency is the most sensitive to 
noise exposure. TTS between 6 and 10 dB recovered within 60 minutes, 
10-15 dB of TTS recovered within 120 min, and TTS up to 24.1 dB 
recovered after 240 minutes. The results of this study show individuals 
exhibiting onset of TTS in-water at lower received levels than the 
current otariid criteria (``Criteria and Thresholds for U.S. Navy 
Acoustic and Explosive Effects Analysis (Phase III)'' (Navy, 2017)).
    Kastelein et al. (2020a) measured underwater, behavioral hearing 
thresholds in one harbor porpoise before and after exposure to 
playbacks of one-sixth-octave band noise centered at 1.5 kHz and a 6.5 
kHz continuous wave. Following exposure to the 1.5 kHz noise band at 
201 dB SELcum, a maximum of a 7.8 dB, 9.8 dB, and 7 dB TTS 
was observed for 1.5, 2.1, and 3 kHz hearing frequencies respectively. 
After exposure to the 6.5 kHz continuous wave at 184 dB 
SELcum, a maximum of a 7.5, 16.7, and 11.8 dB TTS was 
observed for 6.5, 9.2, and 13 kHz hearing frequencies respectively. For 
the 6.5 kHz exposure, a mean TTS > 6 dB was observed for the 178 and 
180 dB SELcum when the hearing test frequency was 9.2 kHz, 
and for the 180 dB SELcum when the hearing test frequency 
was 13 kHz. The results of this study show that the animal incurred 
onset of TTS at higher received levels than what the current HF 
cetacean criteria in ``Criteria and Thresholds for U.S. Navy Acoustic 
and Explosive Effects Analysis (Phase III)'' (Navy, 2017) indicate for 
both 1.5 and 6.5 kHz.
    Kastelein et al. (2020b) measured underwater, behavioral hearing 
thresholds in two harbor seals before and after exposure to playbacks 
of one-sixth-octave band noise centered at 0.5, 1, and 2 kHz. Hearing 
tests were conducted at the center frequency, one-half octave above, 
and 1 octave above center frequency. No TTS > 6 dB was observed for any 
hearing frequency after 204, 210, or 211 dB SELcum exposures 
to the 0.5 kHz noise band. For the 1 kHz exposure frequency, max TTS of 
7.4 dB (6.1 mean) was observed after a 207 dB SELcum 
exposure at a hearing frequency of 1.4 kHz. For this exposure 
frequency, no other test condition produced TTS > 6 dB; although, a 5.9 
dB shift (at 1.4 kHz) occurred at 206 dB SELcum. For the 2 
kHz noise band, after a 201 dB SELcum exposure, max TTS of 
12 dB was measured one octave above the center frequency (4 kHz). For 
this exposure frequency, TTS > 6 dB was observed at SELcum > 
201, 198, and 192 dB for hearing frequencies 2, 2.8, and 4 kHz 
respectively. All shifts recovered within 1 hour. These results of this 
study show that the animal incurred lower TTS (i.e., smaller threshold 
shifts) at higher received levels than what the current phocid pinniped 
criteria in ``Criteria and Thresholds for U.S. Navy Acoustic and 
Explosive Effects Analysis (Phase III)'' (Navy, 2017) indicate.
    Kastelein et al. (2020c) measured underwater, behavioral hearing 
thresholds in one harbor porpoise before and after exposure to 
playbacks of one-sixth-octave band noise centered at 88.4 kHz. Maximum 
TTS of 13.6 dB was observed at 197 dB SELcum for the 100 kHz 
hearing test frequency. No TTS > 6 dB was observed for any 
SELcum at the 88.4 kHz test frequency. For 125 kHz, shifts > 
6 dB were observed for 191, 194, and 197 dB SELcum 
exposures, with a mean TTS of 5.4, 6.1, and 5.9 dB, respectively. The 
results of this study show that the animal incurred TTS at higher 
received levels than what the current HF cetacean criteria in 
``Criteria and Thresholds for U.S. Navy Acoustic and Explosive Effects 
Analysis (Phase III)'' (Navy, 2017) suggest.
    Kastelein et al. (2020d) measured underwater, behavioral hearing 
thresholds in one harbor porpoise before and after exposure to airgun 
impulses (``shots''). Exposure conditions varied with regard to number 
of airguns, number of shots, light cues, and position of the dolphin 
relative to the airguns. Hearing test frequencies were 2, 4, and 8 kHz, 
and no TTS > 6 dB was observed. The results of this study show that the 
animal would incur TTS onset at higher received levels than what the 
current HF cetacean criteria in ``Criteria and Thresholds for U.S. Navy 
Acoustic and Explosive Effects Analysis (Phase III)'' (Navy, 2017) 
suggest.

[[Page 68304]]

    Kastelein et al. (2020e) measured underwater, behavioral hearing 
thresholds in two harbor seals before and after exposure to playbacks 
of one-sixth-octave band noise centered at 40 kHz. For the 50 kHz 
hearing test frequency, a maximum TTS of 30.7 dB was observed 12-16 
minutes after the 189 dB SELcum, and a mean TTS > 6 dB was 
observed for all SELcum 177 dB and above. The 30-dB shift 
recovered after 3 days. No TTS > 6 dB was observed for any 
SELcum at the 63 kHz test frequency for either seal. At 40 
kHz, mean TTS of 9.2 dB was observed after a 189-dB SEL. The results of 
this study show that the animal incurred TTS at lower received levels 
than what the current phocid criteria in ``Criteria and Thresholds for 
U.S. Navy Acoustic and Explosive Effects Analysis (Phase III)'' (Navy, 
2017) suggest.
    Sills et al. (2020) exposed one bearded seal to multiple impulsive 
underwater noise exposures (seismic air gun ``shots''). Hearing tests 
were conducted at 100 Hz and 400 Hz after exposures to 2, 4, and 10 
shots. After a 4-shot (191 dB SELcum) exposure, max TTS of 
9.4 dB was observed, but no other TTS > 6 dB was demonstrated, despite 
four 10-shot (194-195 dB SELcum) exposures. It is possible 
that TTS recovered during the measurements, as quantified by a mean 
``first miss'' of 7.5 dB for the 10-shot exposures (mean TTS was 2.2 
dB). The results of this study show that the animal incurred TTS onset 
at lower received levels than what the current criteria in ``Criteria 
and Thresholds for U.S. Navy Acoustic and Explosive Effects Analysis 
(Phase III)'' (Navy, 2017) suggest. Behavioral responses were also 
scored and averaged across three observers. For most exposures, the 
seal exhibited mild/detectable responses, and all scores indicated that 
the seal did not move more than half his body and consistently 
participated in the study.
    Tougaard et al. (2022) reviewed the most recent temporary TTS data 
from phocid seals and harbor porpoises and compared empirical data to 
the predictive exposure functions put forth by Southall et al. (2019), 
which were based on data collected prior to 2015. The authors concluded 
that more recent data supports the thresholds used for harbor porpoises 
(categorized as `very high frequency', or VHF cetaceans), which over-
estimated the hearing impact for sounds above 20 kHz in frequency. 
Similarly, the new data for phocid seals show TTS onset thresholds that 
are well-above the predicted levels for sounds below 5 kHz in 
frequency. However, phocid seals might be more sensitive to higher 
frequency sound exposures than predicted, as the TTS onset data for 
frequencies higher than 20 kHz was below the predicted levels.
    von Benda-Beckmann et al. (2022) assessed whether correcting for 
kurtosis, a measure of sound impulsiveness, improved the ability to 
predict TTS in a marine mammal. Two different kurtosis correction 
factors were tested by applying them to frequency-weighted sound 
exposure levels (SELcum) and fitting (linear least squares) 
previously collected harbor porpoise TTS data to create dose-response 
functions, then comparing the resulting R\2\ values to that of the 
standard function used to fit TTS growth data. TTS data from both 
continuous and intermittent sound exposures were used. For intermittent 
and continuous 1-2 kHz exposures combined, kurtosis-corrected fits were 
poorer (R\2\ = 0.47, 0.68) than SELcum-based fits (R\2\ = 
0.73). For intermittent exposures of different types, one of the 
kurtosis-corrections resulted in a better fit (R\2\ = 0.84) than 
SELcum (R\2\ = 0.64), but only when a model fitting 
parameter denoting the relationship between SELcum and risk 
of permanent hearing loss was specifically derived from harbor porpoise 
TTS growth data. The conclusions from this study were that the 
kurtosis-corrected SELs did not explain differences in TTS between 
intermittent and continuous sound exposures, likely because silent 
intervals provided an opportunity for hearing recovery that could not 
be accounted for by these models. Kurtosis might still be useful for 
evaluating sound exposure criteria for different types of sounds having 
various degrees of impulsiveness.
Behavioral Reactions
    In a study by Benti et al. (2021), vocalizations from Northeast 
Atlantic herring-feeding killer whales and Northeast Pacific mammal-
eating killer whales were played back to humpback whales in Norwegian 
waters while their behavior was monitored through animal-borne tags and 
visual observations. In five of six cases the humpback whales 
approached the fish-eating killer whales, suggesting some attraction. 
The response to the mammal-eating killer whales varied with the 
behavioral context of the humpback whales. The results suggested that 
the calls of the fish-eating killer whales may have acted like a 
dinner-bell and initiated approach and foraging behavior in the 
humpback whales, while the unfamiliar sounds of the mammal-eating 
killer whales may have been perceived as a threat in offshore waters, 
but led to mixed behavior during inshore herring foraging by humpback 
whales. These results indicated that the humpback whales were able to 
discriminate between the different call types and respond with 
different behavioral strategies.
    Boisseau et al. (2021) exposed foraging minke whales in Icelandic 
waters to an acoustic deterrent device that emitted 15 kHz pure tones 
with a source level of 198 dB rms. Pulse length and the number of 
pulses in a block were randomized but average pulse length was 752 
millisecond (ms) with a 10 percent duty cycle. The source was deployed 
from a Zodiac boat 500 m away from an animal for the first two 
exposures, and 1000 m away in the remaining 8 exposures (max received 
level of 150 dB RMS at a minimum distance of 338 m). Video-range 
tracking was used to track animals before, during, and after the 
exposures and dive duration (sec), swim speed (km/h), reoxygenation 
rate (blows/min), and path predictability were also examined. During 
the exposure, animal speed and dive duration increased, measures of 
path predictability increased indicating straighter paths, and 
reoxygenation rate decreased. Path predictability had a strong 
relationship with received level whereas speed and dive duration did 
not, which suggested those two metrics were more influenced by the 
presence of the exposure signal than the received sound level.
    Cur[eacute] et al. (2021) conducted controlled exposure experiments 
using both PAS (5 percent duty cycle) and CAS (95 percent duty cycle) 
to measure and score tagged sperm whale behavioral responses. No sonar 
control exposures resulted in significantly fewer and less severe 
behavioral responses than sonar exposures. No significant differences 
were observed between sonar types, but the presence of killer whales or 
pilot whales did significantly increase the number of responses. The 
probability of observing low and medium severity responses increased 
with cumulative sound exposure level (SEL, dB re 1 [mu]Pa2 s), reaching 
a probability of 0.5 at approximately 173 dB SEL for low severity 
responses. Medium severity responses reached a probability of 
approximately 0.35 at cumulative SELs between 179 and 189 dB. This 
study suggested that both PAS and CAS exposure resulted in a greater 
number of behavioral changes in sperm whales as compared to the vessel 
(control) alone, and the types of behavioral responses might differ 
across sonar types.
    Czapanskiy et al. (2021) modeled energetic costs associated with 
behavioral response to MFAS using

[[Page 68305]]

datasets from 11 cetaceans' feeding rates, prey characteristics, 
avoidance behavior, and metabolic rates. Authors found that the short-
term energetic cost was influenced more by lost foraging opportunities 
than increased locomotor effort during avoidance. Additionally, the 
model found that mysticetes incurred more energetic cost than 
odontocetes, even during mild behavioral responses to sonar.
    Durbach et al. (2021) analyzed acoustic tracks from minke whales 
detected on the Pacific Missile Range Facility (PMRF) in Hawaii in 3 
years before, during, and after major Navy training exercises. These 
tracks were fit using a continuous-time correlated random walk at 5-
minute interpolated locations. During sonar periods, fast movement 
became more northerly and more directed (less turning), with less 
movement south and east in the direction of the training activity, and 
this more northerly movement continued after sonar cessation. 
Specifically, whales to the north of the training activity were more 
likely to head north, while whales that were west of the activity were 
more likely to head west. Headings did not appear to change for slow, 
undirected movement during sonar. In addition, fast movement was more 
likely to occur during sonar than during any other period (70 percent 
during vs 35-41 percent in the other periods). Finally, whales were 
more likely to stop calling when in the fast state although not 
necessarily more during sonar than in other periods; in contrast, slow 
moving whales were more likely to stop calling during sonar than other 
periods. These results demonstrated that minke whales moved faster and 
movements were more directed during periods of active sonar. Minke 
whales also avoided the locations of the ships producing the sonar and 
were more likely to cease calling during sonar.
    Fernandez-Betelu et al. (2021) used passive acoustic data recorded 
over a 10-year time period to assess the effects of impulsive noise 
produced during offshore activities on coastal bottlenose dolphin 
occurrence. Offshore activities included seismic surveys and pile 
driving from wind farm construction. Echolocation detections of 
dolphins were compared across years with and without offshore activity 
and also across days with and without impulsive noise. The effect of 
distance from the noise-producing activities on dolphin detections was 
also investigated by placing recorders (CPODs) at locations expected to 
be the most (impact areas) and least (reference areas) impacted by 
noise. No consistent relationship was found between annual dolphin 
occurrence and impulsive noise, but significantly more detections were 
observed on days with impulsive noise. The results showed that dolphins 
were not displaced by impulsive noise levels up to 141 dB re 1 [mu]Pa 
and as close as 20 km (10.8 nmi) from the impact area. These results 
suggest that the increase in dolphin detections during far-field noise 
was likely due to an increase in the number and/or amplitude of 
echolocation vocalizations.
    Hastie et al. (2021) studied how the number and severity of 
avoidance events may be an outcome of marine mammal cognition and risk 
assessment. Five captive grey seals were given the option to forage in 
a high- or low-density prey patch while continuously exposed to 
silence, pile driving, or tidal turbine playbacks (source levels = 148 
dB re 1 [mu]Pa at 1 m) for 1 hour. One prey patch was closer to the 
speaker, so had a higher received level in experimental exposures. 
Overall, seals avoided both anthropogenic noise playback conditions 
with higher received levels when the prey density was limited but would 
forage successfully and for as long as control conditions when the prey 
density was higher, demonstrating a classic cognitive approach utilized 
with predation risk and profit balancing.
    In a study by Holt et al. (2021a), DTAGs (miniature sound and 
movement recording tags) were attached with suction cups to Southern 
Resident Killer Whales in the Salish Sea to investigate the 
relationship between probability of prey capture and vessel and sound 
variables. The predicted probability of prey capture was lower when 
vessels increased their speed. Received noise level did not 
significantly affect the probability of prey capture. The rate of 
descent during dives was slower when echosounders were on. The observed 
effects of echosounders suggest that whales prolonged their foraging 
efforts to successfully hunt, which could be caused by acoustic masking 
or increased attention to vessels. The rate of descent increased with 
increasing broadband noise levels and decreasing vessel distance. 
Decrease prey abundance also decreased the probability of predicted 
prey capture.
    Holt et al. (2021b) attached DTAGs to 23 Southern Resident Killer 
Whales in the San Juan Islands over 3 field seasons in order to 
investigate the effects of vessel distance on underwater foraging 
behavior. When vessels were less than 366 m away, whales (n=13) 
decreased the number of dives associated with prey capture and the 
amount of time spent in these dives. Additionally, female killer whales 
were more likely to stop foraging, socializing, and prey-sharing and 
instead start traveling when vessels approached at this distance. At 
the same distance from vessels, male orcas were more likely to 
transition from close prey capture to socializing and prey-sharing, but 
would not stop general foraging behavior, such as searching for prey at 
deeper depths. Female orcas may therefore be at greater risk than males 
during close vessel interactions.
    Kates Varghese et al. (2021) analyzed the effect of two separate 
surveys using a 12 kHz multibeam echosounder (i.e., downward directed, 
unlike ASW sonar) over the Southern California Antisubmarine Warfare 
Range (SOAR) hydrophone array on Cuvier's beaked whale foraging. The 
authors conducted a spatial analysis, building off a temporal analysis 
of a previously presented dataset (Varghese et al. 2020). There were 
differences in spatial use of the SOAR for foraging between the 2 
survey years. While no change in overall foraging effort was detected 
before, during, and after the surveys each year, some localized spatial 
shifts in foraging hot spots were detected during and after the survey 
in the second year. Because of the known heterogeneity of prey patches 
on SOAR, lack of evidence of avoidance of the sound source, and no 
observed change in overall foraging effort, the authors suggest that 
the observed spatial shifts were most likely due to prey dynamics.
    K[ouml]nigson et al. (2021) tested the efficacy of Banana Pingers 
(300 ms, 59-130 kHz frequency modulated, 133-139 dB rms re 1 [micro]Pa 
at 1 m source level) as a deterrent for harbor porpoise in Sweden. As 
described previously, these pingers were designed to avoid potential 
pinniped responses. Authors used recorded echolocation clicks with C-
PODs to measure the presence or absence of porpoise in the area. 
Porpoise were less likely to be detected at 0 m and within 100 m of an 
active pinger, but a pinger at 400 m appeared to have no effect.
    In a study by Laborie et al. (2021), unmanned aerial vehicles 
(UAVs) were flown at three altitudes (25, 20, and 15 m) over Weddell 
seals, including adult males and females and females with pups. There 
was generally little response; 88 percent of the time the animals 
showed mild vigilance or no responses, and mothers rarely ended 
nursing. Agitation or escape responses only occurred in 12 percent of 
observations. The strongest response was in females with pups when wind 
speeds were lowest and therefore ambient noise levels were at their 
lowest. The probability of response

[[Page 68306]]

increased with lower altitude flights, so at altitudes over 25 m a low 
level of impact to Weddell seal behavior would be expected.
    Manzano-Roth et al. (2022) found that cross seamount beaked whales 
reduced clusters of foraging pulses (Group Vocal Periods) during 
Submarine Command Course events and remained low for a minimum of 3 
days after the MFA sonar activity.
    An analysis subsequent to Varghese et al. (2020) suggested that the 
observed spatial shifts of Cuvier's beaked whales during multibeam 
echosounder activity on the Southern California Antisubmarine Warfare 
Range were most likely due to prey dynamics (Kates Varghese et al. 
2021).
    Ramesh et al. (2021) explored environmental drivers and the impact 
of shipping noise on fin whale vocalizations in Ireland. Approximately 
3 months of passive acoustic fin whale call data from spring 2016 used 
in the habitat model found that fin whale calls increased at night, 
along with signs of higher prey availability. Fin whale calls were also 
less likely to be detected for every 1 dB re 1 [mu]Pa/minute increase 
in shipping noise levels (rms). However, these results should be used 
cautiously since the model was more likely to predict the absence of 
fin whale detections, rather than their presence.
    Santos-Carvallo et al. (2021) monitored fin whale behavior before, 
during, and after the presence of whale watching vessels in Caleta 
Cha[ntilde]aral de Aceituno to determine if the whale watching activity 
was having any adverse impacts on the fin whales. Whale watching 
activities were only conducted by local artisanal fishers; 39 boats 
have permission but less than 20 conduct the whale watching activity. 
Land-based observations were conducted in January and February of 2015-
2018 via binocular scans and focal follow tracking using a theodolite. 
Groups of whales were tracked through the area with continuous sampling 
of position, behavior, and presence of boats for every surfacing until 
they were no longer visible. Behavior was classified as traveling or 
resting, and the groups' swim speed, reorientation, and directness 
index, and these were modeled relative to the number of boats and 
whether the time period was before, during, or after the boats were 
present. Most observations occurred within the presence of at least one 
boat, but no more than three boats at one time. Travel swim speeds 
increased in the after period, while reorientation increased and 
directness decreased during and after the presence of boats. During 
rest behavior, reorientation increased during the presence of boats 
compared to before the boats were present, and directness decreased 
during the presence of boats. These results indicate that when whale 
watching vessels were present, the fin whales changed their direction 
of movement more frequently, with less linear movement than occurred 
before the boats arrived; this behavior may represent evasion or 
avoidance of the boats. The increase in travel swim speeds after the 
boats left the area may be related to the vessel's rapid speeds when 
leaving, sometimes in front of animals, leading to more avoidance 
behavior after the boats departed.
    Arranz et al. (2021) conducted a noise exposure experiment which 
compared behavioral reactions of resting short-finned pilot whale 
mother-calf pairs during controlled approaches by a tour boat with two 
electric (136-140 dB) or petrol engines (139-150 dB). Approach speed 
(<4 kn (7.4 km per hour)), distance of passes (60 m (65.6 yd)), and 
vessel features other than engine noise remained the same between the 
two experimental conditions. Behavioral data was collected via unmanned 
aerial vehicle (UAV) and activity budgets were calculated from 
continuous focal follows. Mother pilot whales rested less, and calves 
nursed less, in response to both types of boat engines compared to 
control conditions (vessel >300 m (328 yd), stationary in neutral). 
However, they found no significant impact on whale behaviors when the 
boat approached with the quieter electric engine, while resting 
behavior decreased 29 percent and nursing decreased 81 percent when the 
louder petrol engine was installed in the same vessel.
    Hiley et al. (2021) exposed groups of harbor porpoises to ``startle 
sounds'', which were 200-ms in duration and were band limited (5.5-20.5 
kHz) with a peak frequency of 10.5 kHz and a source level of 176 dB re 
1 [micro]Pa. There were 13 exposure sequences in which the startle 
sound was repeated for 15 minutes at a 0.6 percent duty cycle, and 11 
control sequences in which vessels operated but no startle sounds were 
played. Despite a larger distance between porpoise groups and vessels 
during sound exposure trials (152 m) as compared to control trials (90 
m), avoidance responses during exposures were significant whereas no 
avoidance was observed for controls. Porpoises avoided the area where 
sound exposures took place for approximately 30-60 minutes, and no 
long-term exclusion effect was observed.
    Pellegrini et al. (2021) examined how boat presence impacts a 
unique subspecies of bottlenose dolphin (Tursiops truncatus gephyreus, 
Lahille's bottlenose) that vocalizes while foraging cooperatively with 
local fishermen who cast nets onto dolphin-herded fish while standing 
in coastal waters in Brazil. Dolphin vocalizations changed in response 
to the number, type, and speed of boats within 250 m. When more than 
one boat was present, dolphins produced fewer whistles and had a lower 
click rate and a longer whistle duration; initial and maximum frequency 
increased as well, especially when group size or calf presence 
increased. Whistles were longer duration when boat speed increased as 
well.
    Martin et al. (2022) exposed a wild Cape fur seal breeding colony 
in Africa to playback recordings of boat noise and sea-side car 
traffic. Focal groups of at least six seals were approached by an 
experimenter who crawled within 6 m to avoid disturbing the seals. 
Seals were exposed to low (60-64 dB re 20 [micro]Pa rms SPL, broadcast 
at 6 m), medium (64-70 dB, broadcast at 3 m), or high (70-80 dB, 
broadcast at 1 m) levels, depending on the individual's distance to the 
speaker. No behavioral differences were found between low, medium, and 
high-level groups. Video recorded behavioral analysis demonstrated that 
mother-pup pairs spent less time nursing (15-31 percent) and more time 
awake (13-26 percent), vigilant (7-31 percent), and mobile (2-4 
percent) during boat noise conditions compared to control conditions. 
Mothers were more vigilant (26 percent) than pups (7 percent) to medium 
levels of boat noise.
    Jones[hyphen]Todd et al. (2021) analyzed the movement of seven 
Blainville's beaked whales tagged at (AUTEC) relative to MFAS use 
during the SCC training event. Data from these tags was previously 
reported by Joyce et al. (2019). A continuous time correlated random 
walk movement model accounted for location accuracy by modeling 100 
track imputations for each tag and arranged samples in equal time 
intervals. The probability of whale presence within the boundary of the 
instrumented range (on range), and outside the boundary of the 
instrumented range (off range) was modeled relative to the time since 
the last MFAS transmission. Results show there was a higher probability 
that whales on the range would go off range when there were MFAS 
transmissions, and that whales off the range would stay off the range 
when there were MFAS transmissions. These results indicate a response 
to MFAS that lasted for 3 days since transition rates on-off and off-on 
the range returned to baseline levels

[[Page 68307]]

after that amount of time. There was also variability in transition 
rates and time spent on/off range between individuals, which highlights 
the need to analyze a larger sample size of whales.
    Durban et al. (2022) tested new methods of observing behavioral 
responses of groups of small delphinids to sonar, where the use of tags 
is challenging, and the response of the group is more salient than that 
of the individual. They tested the use of a land-based observation 
platform coupled with a drone and multiple acoustic recorders to 
observe the vocal behavior, group cohesion, group size, and group 
behavior before, during, and after a simulated sonar exposure. In a 
group of short-beaked common dolphins, the authors found the number of 
whistles and sub-groups to increase during the exposure period, but the 
directivity of the tracked subgroup did not change much.
    K[ouml]nigson et al. (2022) tested the efficacy of Banana Pingers 
(300 ms, 59-130 kHz frequency modulated, 133-139 dBrms re 1 
[micro]Pa at 1 m source level) as a deterrent for harbor porpoise in 
Sweden. As described previously, these pingers were designed to avoid 
potential pinniped responses. Authors used recorded echolocation clicks 
with C-PODs to measure the presence or absence of porpoise in the area. 
Porpoise were less likely to be detected at 0 m and within 100 m of an 
active pinger, but a pinger 400 m appeared to have no effect.
    Miller et al. (2022) investigated the risk disturbance hypothesis 
that an animal's response decision is a trade-off between perceived 
risk and the cost of a missed opportunity (the reward of foraging). The 
authors predicted that species that are more vulnerable to predation 
would be more likely to respond to both predator sounds and 
anthropogenic stressors. Using data collected from 2008 to 2017 during 
the 3S project in Norway, changes in foraging duration during killer 
whale playbacks and changes in foraging duration during mid-frequency 
sonar were positively correlated across the four species examined 
(listed in order of increasing sensitivity to foraging disruption: 
sperm whales, long-finned pilot whales, humpback whales, and northern 
bottlenose whales). This suggests that tolerance of predation risk may 
play a role in sensitivity to sonar disturbance.
    Paitach et al. (2022) tested the efficacy of Banana Pingers (300 
ms, 50-120 kHz frequency modulated, 145 dB +/- 3 dB at 1 m source 
level) as a deterrent and entanglement mitigation for Franciscana 
dolphins in Brazil. These pingers were designed to emit sound outside 
of the best hearing range for pinnipeds and were therefore less likely 
to incite a ``dinner bell'' effect. Authors used recorded echolocation 
clicks with C-PODs to measure the presence or absence of dolphins in 
the area. Dolphins were 19 percent and 15 percent less likely to be 
detected nearby and within 100 m of an active pinger respectively, but 
dolphins 400 m from the pinger did not appear to avoid it. While a 
reduction in vocalizations does not always equate to a reduction in 
presence, this species has been previously seen departing from areas 
with active pingers. Authors did not witness any habituation to the 
pinger during the length of the experiment (64 days), and although they 
recorded fewer dolphins in the area over time, they believe this was 
due to seasonality rather than habitat displacement.
    Siegal et al. (2022) used Dtag data from 15 northern bottlenose 
whales tagged during 3S efforts off Norway (2013-2016) to estimate body 
density (to represent body condition by lipid energy stores) using 
hydrodynamic models and obtain foraging and anti-predator indicators 
based on vocal behavior and dive metrics. The authors compared relative 
anti-predator/foraging indices to body condition and found that 
relative anti-predator to foraging indices typically did not depend on 
body condition. This finding is inconsistent with the needs/assets 
hypothesis; an individual in poor condition would accept more risk 
(i.e., engage in less anti-predator behavior) for foraging 
opportunities, whereas healthy animals can afford to be more risk 
averse (i.e., have a relatively higher anti-predator to foraging index 
ratio). The authors suggest that this result may be due to an 
insufficient range of body conditions in the data set to determine a 
relationship, or a selection of bolder individuals in the tagging 
effort. The authors also suggest that animals in good condition may 
take greater predation risks because they may successfully flee. Three 
of the 15 whales were exposed to sonar (presented in prior 3S 
publications). The authors compared foraging and anti-predator metrics 
pre- and post-exposure, showing that all three animals increased their 
anti-predator index and reduced their foraging index.
    Stanistreet et al. (2022) used passive acoustic recordings during a 
multinational navy activity to assess marine mammal acoustic presence 
and behavioral response to especially long bouts of sonar lasting up to 
13 consecutive hours, occurring repeatedly over 8 days (median and 
maximum SPL = 120 dB and 164 dB). Cuvier's beaked whales and sperm 
whales substantially reduced how often they produced clicks during 
sonar, indicating a decrease or cessation in foraging behavior. Few 
previous studies have shown sustained changes in foraging or 
displacement of sperm whales, but there was an absence of sperm whale 
clicks for 6 consecutive days of sonar activity. Sperm whales returned 
to baseline levels of clicks within days after the activity, but beaked 
whale detection rates remained low even 7 days after the exercise. In 
addition, there were no detections from a Mesoplodon beaked whale 
species within the area during and at least 7 days after the sonar 
activity. Clicks from northern bottlenose whales and Sowerby's beaked 
whales were also detected but were not frequent enough at the recording 
site used to compare clicks between baseline and sonar conditions.
    Benhemma-Le Gall et al. (2021) compared harbor porpoise presence 
and foraging activity between periods of baseline and construction at 
two Scottish offshore windfarms with arrays of echolocation click 
detectors (C-PODs). Noise levels were measured with calibrated noise 
recorders, and vessel presence was tracked with AIS data. Authors found 
an 8-17 percent decline in porpoise presence compared to baseline, with 
more porpoises (more buzzing) further from vessels, construction sites, 
and related higher levels of noise. The probability of porpoise 
occurrence by source vessels decreased by 9-23 percent without piling 
activity, and by 40-54 percent during pile driving. Porpoises were 
displaced up to 12 km (6.5 nmi) from pile driving and 4 km (2.2 nmi) 
from construction vessels. At an average vessel distance of 2 km (1.1 
nmi), porpoise occurrence decreased by up to 35 percent. Outside piling 
hours, porpoise detection decreased by 17 percent (0.26), and foraging 
(buzzes) decreased by up to 41.5 percent (0.03) with increasing noise 
levels (159 and 155 dB re 1 [micro]Pa, respectively). During piling 
activities, porpoise occurrence began lower (0.16, 102 dB) but 
occurrence still decreased by 9 percent (0.07), and foraging (buzzes, 
beginning at 0.76, 104 dB) also decreased by 61.8 percent (0.15) with 
increasing noise levels (161 and 155 dB re 1 [micro]Pa, respectively).
    Kastelein et al. (2022c) recorded pile driving sounds 100 m from 
construction for an offshore windfarm turbine, and six versions of the 
sound were created with varying frequency content using low-pass 
filters at 44.1, 6.3, 3.2, 1.5, 1.0,

[[Page 68308]]

and 0.5 kHz, at levels of 135 dB re 1 [micro]Pa\2\s. When authors 
played these impulsive sounds back to a single harbor porpoise in a 
pool, she increased swim speed, respiration rate, distance from the 
transducer, and occasionally jumped in response to the sounds with 
higher frequencies present (i.e., the sounds with a wider bandwidth, 
especially sounds low-pass filtered at 44.1 and 6.3 kHz). However, the 
porpoise still moved away from the three most narrowband sounds, just 
not as far. Results indicate that frequency weighting of SEL may 
improve prediction of harbor porpoise behavioral responses, and authors 
present the argument that weighted SELs should be used for reporting 
behavioral response threshold levels for criteria.
    Todd et al. (2022) detected harbor porpoises with C-PODS before, 
during, and after pile driving for an oil and gas platform from 2015-
2020. Pile driving single strike SEL at 750 m was 160-164 dB re 1 
[micro]Pa\2\s. Porpoise detections significantly decreased at the 
beginning of the construction project, but detections appeared to 
return to baseline levels within 5 months. According to the authors, 
the lack of significant trend over years indicated that porpoises 
returned to the area and did not experience habitat displacement for 
the entire 5-year period.

Physiological Responses and Stress

    Elmegaard et al. (2021) exposed two captive harbor porpoises to 
sonar sweeps (6-9 kHz, 500 msec duration, 50-100 msec rise time, 
varying received levels (RL)) and pulsed sounds (50 msec duration, peak 
frequency 40 kHz, half power bandwidth of ~5 kHz, rise time < 5 msec, 
varying RL) to investigate startle reflex and changes in heart rate. 
The sonar exposures did not elicit startle responses; the initial two 
to three exposures induced bradycardia (a slow heart rate), with 
subsequent habituation. This habituation was conserved after a 3-year 
pause in exposures. The authors suggest that the initial bradycardia 
allows ``a prolonged breath-hold to assess the nature of a novel 
stimuli or flee in crypsis if needed;'' in na[iuml]ve wild cetaceans, 
the reduced peripheral perfusion caused by this response may reduce 
N2 diffusion from supersaturated tissues during dive 
ascents, increasing risk of decompression sickness. Startle responses 
to the pulse exposures were directly correlated to RL. The 50 percent 
motor-startle probability threshold was around 130 dB re 1 [mu]Pa 
(rms50). This is ~85 dB above hearing threshold and is similar to that 
observed in bottlenose dolphins (~90 dB over hearing threshold) (Gotz 
et al. 2020). No significant change in heart rate was observed. The 
authors suggest that the parasympathetic cardiac dive response may 
override any transient sympathetic response, or that diving mammals may 
not have the cardiac startle response seen in terrestrial mammals in 
order to maintain volitional cardiovascular control at depth.
    Fahlman et al. (2021) reviews decompression theory and the 
mechanisms dolphins have evolved to prevent high N2 levels and gas 
emboli (i.e., bends-like symptoms) in normal conditions. However, in 
times of high stress, the selective gas exchange hypothesis states that 
this mechanism can break down. In addition, circulating microparticles 
may be useful biomarkers for decompression stress in cetaceans.
    Yang et al. (2021) measured cortisol concentrations in blood 
samples of two captive bottlenose dolphins and found significantly 
higher levels after exposure to high sound level (140 dB re 1 [mu]Pa) 
impulsive noise playbacks, compared to control and low sound levels (0 
and 120 dB re 1 [mu]Pa, respectively). Six cytokine gene transcriptions 
were also measured in blood samples and two (IL-10 and IFN-[gamma]) 
showed significant changes at high sound level exposure, compared to 
control and low sound levels. Results suggest that repeated exposures 
or sustained stress response to impulsive sounds may increase an 
affected individual's susceptibility to pathogens, affect growth and 
reproduction, etc. In addition, no avoidance behavior was observed 
during the trials, indicating that stress-induced physiological changes 
could be present despite the absence of behavioral changes.
    Williams et al. (2022) measured physiological and behavioral 
responses in narwhals in the Arctic during seismic airgun impulse 
exposure compared to control conditions. Responses were measured using 
heart rate-accelerometer-depth recorders and changes in locomotor, 
cardiovascular, and respiratory responses were observed following 
exposure. Airgun SELs, as received at 10 m depth during sound source 
verifications, were approximately 152 dB re 1 [micro]Pa\2\s at 1 km 
(0.5 nmi) range and decreased to approximately 120 dB re 1 
[micro]Pa\2\s at 10 km (5.4 nmi) dives. The response to seismic and 
vessel noise was a reduction in gliding descents and prolonged periods 
of high intensity activity associated with periods of elevated stroke 
frequencies. Noise exposure also resulted in periods of prolonged and 
intense bradycardia (i.e., slowed heart rate). An increase in post-dive 
respiratory rates occurred during recovery from noise-exposed dives 
compared to control dives.

Stranding

    Danil et al. (2021) document the findings of NOAA's investigation 
of the strandings of three coastal bottlenose dolphins in 2015 at 
Silver Strand Training Complex in NOAA Technical Memorandum NMFS-SWFSC-
641. On October 21, 2015, two dolphins were found stranded dead near 
each other on the beach. Because a Navy major training exercise (MTE) 
was underway, these strandings met the criteria of an Uncommon 
Stranding Event in accordance with the Southern California Stranding 
Response Plan in the Navy's Phase 2 LOA for HSTT. A third decomposed 
dolphin was found in the same area 10 days later. Examination of the 
dolphins resulted in findings indicative of severe acute trauma, 
including lower jaw subcutaneous hemorrhage, emphysema, and cervical 
blubber hemorrhage. Additional signs of injury to the cerebrum and 
heart, or lipids in the lungs were also discovered. No hemorrhage was 
found near the ears. At least two of the dolphins showed signs of 
feeding before stranding, and all were in robust condition. There were 
no external signs of strike or entanglement. These observations and 
lack of others did not clearly determine the cause of the acute trauma. 
Based on previous case studies, the investigators determined that 
underwater detonation, peracute underwater entrapment (i.e., fisheries 
interaction), or sonar were the most plausible causes. The Navy notes 
that sonar has not been associated with these kinds of symptoms before, 
nor has there ever been any association between dolphin mortality and 
sonar. No anti-submarine (ASW) sonar or explosive use was associated 
with the Navy MTE; however, unit level training with MF1 sonar occurred 
on October 19 (for 35 minutes) and October 20 (62 minutes in total), 
with sonar use as close as 6 nmi (11.1 km) to the stranding location. 
No known squid or bait fishing efforts within U.S. waters occurred in 
the vicinity preceding the strandings. The Navy notes that it is 
unknown what fishing efforts occurred in Mexican territorial waters 
immediately south of the stranding location.
    Wang et al. (2021) conducted an auditory-evoked potential (AEP) 
hearing test on a single stranded 19-year-old male melon-headed whale 
in the 9.5--181 kHz frequency range. Tone pip trains were presented 
underwater at a depth of 0.3 m and 1 m distance from the whale, and 
AEPs were recorded by suction cup electrodes on the skin surface. 
Hearing was measured in this

[[Page 68309]]

individual after it had been stranded and during attempted 
rehabilitation in a concrete pool. Eighteen frequencies were measured 
once, and eight frequencies were measured twice, yielding an audiogram 
that showed elevated hearing thresholds (compared to the pygmy killer 
whale) between 10 and 100 kHz. There are no data from normal-hearing 
individuals of the melon-headed whale species to which this study's 
data can be compared.

Population Consequences of Disturbance and Cumulative Stressors

    Southall et al. (2021) provided updated guidance and methods to 
assess the severity of behavioral responses by marine mammals to 
several types of anthropogenic noise sources. The criteria developed in 
the 2007 effort were updated by explicitly distinguishing between 
captive and field studies, decoupling their respective severity scales, 
and splitting the severity scale into three categories of foraging, 
survival, and reproduction. In addition, the updated guidance changed 
the categorization of noise sources and began to consider long term 
consequences of exposures rather than just immediate responses. 
Additional and consistent metrics to be reported in behavioral response 
studies are recommended, including subject-specific metrics (e.g., 
functional hearing group, age class, sex, behavioral state, presence of 
calf), exposure context metrics (e.g., exposure type, range to source, 
source and animal depth, presence of other species or other noise 
sources), and noise exposure metrics (e.g. exposure duration, rise 
time, number of exposures, SPL [rms and p-p], SEL, SNR). The authors 
then applied the severity scale to acute exposure studies using sonar 
sources, continuous (industrial) sources, pile driving sources, and 
airgun sources. For the long-term exposure analysis, a set of factors 
developed by Bejder and Samuels (2003) were applied to long-term 
studies on whale-watching and other long-term exposure or multi-
exposure datasets. These factors included metrics of short-term impacts 
and long-term survival measures, characteristics of the studies, and 
sources of anthropogenic disturbance. The applied examples of scoring 
both acute and long-term studies of behavioral response provide a 
framework for other researchers to apply the same metrics to their own 
studies.
    Migrating humpback whale mother-calf pairs' responses to seismic 
surveys were modeled by Dunlop et al. (2021) using both a forwards and 
backward approach. While a typical forwards approach can determine if a 
stressor would have population-level consequences, authors demonstrated 
that working backwards through a population consequences of disturbance 
(PCoD) model can be used to assess the ``worst case'' scenario for an 
interaction of a target species and stressor. Assumptions for the 
extreme scenario were likely exaggerated (e.g., in area for > 48 hours, 
exposed to > 3 air gun events) but lack data to inform humpback nursing 
behavior and calf survivability during acoustic stressors. The results 
demonstrated that migrating whales would not likely experience enough 
of a delay as a result of disturbance to result in population 
consequences, but whales disturbed in breeding or resting areas would 
be more vulnerable to consequences of disturbance.
    Greenfield et al. (2020) demonstrated that bottlenose dolphins who 
had been injured from boat strike or entanglement experienced a decline 
in their social network's preferred associations, and as a result were 
more vulnerable to predation and less fecund.
    Hin et al. (2021) used a previously published energy budget model 
for pilot whales (Hin et al. 2019) to examine how lost foraging days 
affect individuals in a population at carrying capacity. In this model, 
depletion of prey is dependent on whale density, and prey density 
limits the energy available for growth, reproduction, and survival. The 
authors assumed extreme disturbance events for this study: consecutive 
days of no foraging affecting all individuals in a population. The 
undisturbed whale population was regulated through the effect of prey 
availability on calf survival and pregnancy rates and on age at first 
reproduction of females. During a disturbance event, population decline 
was generally attributed to loss of lactating females and calves due to 
reduced body condition. The subsequent increase in prey density and per 
capita prey availability, however, resulted in improved body condition 
in the population overall and decreased age at first calf. As 
disturbance duration was increased (~40 days of no foraging), the 
population would enter extreme decline towards extinction.
    Murray et al. (2021) conducted a cumulative effects assessment on 
Northern and Southern Resident killer whales, which involved both a 
Pathways of Effects conceptual model and a Population Viability 
Analysis quantitative simulation model. Authors found that both 
populations were highly sensitive to prey abundance and were also 
impacted by the interaction of low prey abundance with vessel strike, 
vessel noise, and polychlorinated biphenyls contaminants. However, more 
research is needed to validate the mechanisms of vessel disturbance and 
environmental contaminants.
    Pirotta et al. (2020) reformulated their previous dynamic energy 
budget model (Pirotta et al. 2018) to investigate the state-dependent 
life history strategies of female long-finned pilot whales and trade-
offs between their body condition (i.e., ability to offset starvation 
during pregnancy and provide milk), prey availability, and decision to 
reproduce in situations with and without disturbance. Many whales in 
this model attempted to reproduce young, and while that had no cost in 
situations without disturbance, young mothers would starve and die when 
foraging was prevented by some disturbance event or because resources 
were low (winter). Whale reproductive strategies resulted in lower 
lifetime reproductive output, compared to the model used in Hin et al. 
(2019).
    Pirotta et al. (2021) integrated different sources of data (e.g., 
controlled exposure data, activity monitoring, telemetry tracking, and 
prey sampling) into a bioenergetic model, which was used to predict 
effects from sonar on a blue whale's daily energy intake. Approximately 
half of the simulated whales had no change in daily net energy intake 
because they either had no response or were not exposed. However, the 
other half experienced a decrease in net energy intake. A portion (11 
percent) of those simulated whales had negative net energy even after 
brief (e.g., 6-30 min) or weak (e.g., 160-180 dB re 1 [mu]Pa source 
level) events, which indicated that they would not be able to cover 
that day's energetic cost. This dichotomy in results was due to the 
variation in activity budgets, lunging rates and ranging patterns 
between tagged whales. This evidence suggests that context can 
influence the predicted costs of disturbance even more than body size 
or prey density distribution on a daily scale (although prey 
availability and abundance affected behavioral patterns).
    Pirotta et al. (2022) evaluated potential long-term effects of 
changing environmental conditions and military sonar by modeling vital 
rates of Eastern North Pacific blue whales. Previous work from Pirotta 
et al. (2021) was used as a foundation for incorporating the most 
recent best available science into the vital rate model presented in 
this study. Using data and underlying models of behavioral patterns, 
energy budgets, body condition, contextual responses to noise, and prey 
resources, the model predicted female vital rates

[[Page 68310]]

including survival (age at death), and reproductive success (number of 
female calves). The model simulation results showed that 
``[e]nvironmental changes were predicted to severely affect vital 
rates, while the current regime of sonar activities was not.'' The case 
study used an annual sonar regime in SOCAL based on the description of 
the action in the Navy's 2018 HSTT FEIS/OEIS. Additional military sonar 
scenarios were modeled, and a ten-fold increase in sonar activity 
combined with a shift in geographical location to overlap with main 
feeding areas of blue whales resulted in a moderate decrease in 
lifetime reproductive success (Cohen's d = 0.47). However, there was no 
effect on survival (Cohen's d = 0.05).
    Pirotta (2022) covered the development of bioenergetic models 
[``any mechanistic model where the principles of metabolic ecology are 
used to describe how an individual animal acquires energy from food 
resources (i.e., energy intake) and allocates assimilated energy to 
various life history functions (i.e., energy costs, including 
maintenance and survival, growth and reproduction)''] with a focus on 
applications to marine mammals. This article provided a thorough 
overview of the history of marine mammal bioenergetic models, defined 
relevant terminology, and explained the differences between general 
types of models.
    McHuron et al. (2021) developed a state-dependent behavioral and 
life history model to predict the probability of Western gray whale 
mother-calf pair survival with and without acoustic disturbance and 
with or without adequate prey availability on their summer foraging 
grounds. Pregnant mother movement, feeding behavior, fat mass and fetal 
length were input data for the model. Since prey availability was co-
dependent on whales having access to high-density offshore areas by 
mid-July, nearshore seismic surveys had no impact on population 
fecundity or mother-calf survival. This model overcomes a key challenge 
in PCoD literature by providing a link between behavioral responses and 
vital rates; authors recommend focusing on species that are data rich 
to accurately characterize the biology of the focal species, metrics of 
fitness, and key qualities of their environment.
    Joy et al. (2022) presented a hypothetical case study for fin 
whales off Southern California exposed to stationary single-ship 53C 
sonar events over the course of a year, using the Navy's Phase 3 
behavioral response function (BRF). Two model runs were compared: using 
[alpha] = 0.05 (average 20-minute movement disruption) and [alpha]= 
0.99 (average 3 days movement disruption). When animals returned to 
baseline behavior after a short disturbance ([alpha] = 0.05), there was 
less regional displacement and thus more instances of behavioral 
disturbance over the course of a year. When animals returned to 
baseline behavior after a longer period ([alpha]=0.99), there were 
fewer instances of behavioral disturbances over the course of a year 
due to cumulative displacement from habitat near the sonar source.
    Keen et al. (2021) reviewed 15+ years of PCoD modeling and 
identified the most critical factors for determining long-term impacts 
to populations. Critical factors include life-history traits, 
disturbance source characteristics, and environmental conditions. No 
specific model or quantitative assessment was proposed.
Methodology for Assessing Acoustic Impacts
    Palmer et al. (2022) recorded North Atlantic right whale upcalls 
using 10 Marine Autonomous Recording Units deployed in Cape Cod Bay 
from February to May 2009. A modified equation was provided for 
determining the effective survey area, including a Lombard coefficient, 
for single sensor applications. The authors state manual annotation or 
verification is nearly always used to confirm automated detector 
outputs prior to near-real-time conservation measures due to 
limitations in automatic detector capabilities.
Aircraft Noise
    Kuehne et al. (2020) measured in-air and underwater sound from low-
altitude EA-18G Growler flights in the immediate vicinity of Ault Field 
at Naval Air Station Whidbey Island (NASWI). Data were collected by two 
in-air recorders and one hydrophone placed just off the runway at a 
depth of 30 meters. The underwater 10-flight average sound measurement 
was 134  3 dB re 1 [mu]Pa rms in the highest 1-second 
window. The results showed that the peak frequency range of the Growler 
overflight noise both in air and underwater was between 50 and 1,000 
Hz, which is typically a frequency range with high background noise 
underwater, particularly in areas with large amounts of vessel traffic 
(Erbe et al. 2012). The study did not include behavioral observations 
of wildlife, and the authors' conclusions about potential impacts to 
wildlife were unsupported by data from the study. In a separate effort, 
Kuehne and Olden (2020) relied on volunteers to identify military 
aircraft noise in recordings taken on land on the Olympic Peninsula. 
This study also did not examine impacts to or responses by wildlife to 
aircraft.
    We reiterate that NMFS reviewed the Navy's analysis and conclusions 
that aircraft noise will not result in incidental take of marine 
mammals, and finds the analysis and conclusions complete and 
supportable, as stated in the 2018 HSTT final rule. Please see section 
3.7 (Marine Mammals) of the 2018 HSTT FEIS/OEIS for additional 
information.
Conclusion for New Pertinent Science Since Publication of the 2020 HSTT 
Final Rule
    Having considered the best scientific information available, 
specifically new relevant information published since the 2020 HSTT 
final rule, we have preliminarily determined that there is no new 
information that substantively affects our analysis of impacts on 
marine mammals and their habitat that appeared in the 2020 HSTT final 
rule, all of which remains applicable and valid for our assessment of 
the effects of the Navy's activities during the 7-year period of this 
rulemaking.

Estimated Take of Marine Mammals

    This section indicates the number of takes that NMFS is proposing 
for authorization, which are based on the amount of take that NMFS 
anticipates could occur or is likely to occur, depending on the type of 
take and the methods used to estimate it, as described below. NMFS 
coordinated closely with the Navy in the development of their 
incidental take application and preliminarily agrees that the methods 
the Navy has put forth described herein, in the 2019 HSTT proposed 
rule, 2020 HSTT final rule, and in the 2018 HSTT proposed and final 
rules to estimate take (including the model, thresholds, and density 
estimates), and the resulting numbers are based on the best available 
science and appropriate for authorization, with the exception of that 
of humpback whales, discussed further below. The number and type of 
incidental takes that could occur or are likely to occur annually 
remain identical to those authorized in the 2018 HSTT regulations and 
2020 HSTT regulations, with the exception of proposed takes by serious 
injury or mortality by vessel strike and harassment takes of humpback 
whale stocks in Southern California (due to the new stock structure).
    Takes are predominantly in the form of harassment, but a small 
number of serious injuries or mortalities could

[[Page 68311]]

occur. For military readiness activities, the MMPA defines 
``harassment'' as (i) any act that injures or has the significant 
potential to injure a marine mammal or marine mammal stock in the wild 
(Level A harassment); or (ii) any act that disturbs or is likely to 
disturb a marine mammal or marine mammal stock in the wild by causing 
disruption of natural behavioral patterns, including, but not limited 
to, migration, surfacing, nursing, breeding, feeding, or sheltering, to 
a point where such behavioral patterns are abandoned or significantly 
altered (Level B harassment).
    Proposed authorized takes would primarily be in the form of Level B 
harassment, as use of the acoustic and explosive sources (i.e., sonar, 
air guns, pile driving, explosives) and is more likely to result in the 
disruption of natural behavior patterns to a point where they are 
abandoned or significantly altered (as defined specifically at the 
beginning of this section but referred to generally as behavioral 
disturbance) or TTS for marine mammals. There is also the potential for 
Level A harassment in the form of auditory injury and/or tissue damage 
(the latter from explosives only) to result from exposure to the sound 
sources utilized in training and testing activities. Additionally, 
serious injuries or mortalities of mysticetes (except for sei whales, 
minke whales, Bryde's whales, Central North Pacific stock of blue 
whales, Hawaii stock of fin whales, Western North Pacific stock of gray 
whales, and sperm whales) could occur through vessel strike. Proposed 
mitigation and monitoring measures are expected to minimize the 
severity of the taking to the extent practicable.
    Generally speaking, for acoustic impacts, NMFS estimates the amount 
and type of harassment by considering: (1) acoustic thresholds above 
which NMFS believes the best available science indicates marine mammals 
would experience behavioral disturbance or incur some degree of 
temporary or permanent hearing impairment; (2) the area or volume of 
water that will be ensonified above these levels in a day or event; (3) 
the density or occurrence of marine mammals within these ensonified 
areas; and (4) and the number of days of activities or events.
Acoustic Thresholds
    Using the best available science, NMFS, in coordination with the 
Navy, has established acoustic thresholds that identify the most 
appropriate received level of underwater sound above which marine 
mammals exposed to these sound sources could be reasonably expected to 
experience a disruption in behavior patterns to a point where they are 
abandoned or significantly altered or to incur TTS (equated to Level B 
harassment) or permanent threshold shift (PTS) of some degree (equated 
to Level A harassment). Thresholds have also been developed to identify 
the pressure levels above which animals may incur non-auditory injury 
from exposure to pressure waves from explosive detonation.
    We described the acoustic thresholds and the methods used to 
determine thresholds, none of which have changed, in detail in the 
Acoustic Thresholds section of the 2018 HSTT final rule; please see the 
2018 HSTT final rule for detailed information. Further, in the 2020 
HSTT final rule, we described new relevant information from the 
scientific literature since publication of the 2018 HSTT final rule. 
Since publication of the 2020 HSTT final rule, a number of additional 
studies have published, including several associated with TTS in harbor 
porpoises and seals (e.g., Kastelein et al. 2020d; Kastelein et al. 
2021a and 2021b; Sills et al. 2020). NMFS is aware of these recent 
papers, summarized above in the New Pertinent Science Since Publication 
of the 2020 HSTT Final Rule section. NMFS is currently working with the 
Navy to update NMFS' Technical Guidance for Assessing the Effects of 
Anthropogenic Sound on Marine Mammal Hearing Version 2.0 (Acoustic 
Technical Guidance; NMFS 2018) to reflect relevant papers that have 
been published since the 2018 update on our 3-5 year update schedule in 
the Acoustic Technical Guidance. First, we note that the recent peer-
reviewed updated marine mammal noise exposure criteria by Southall et 
al. (2019) provide identical PTS and TTS thresholds and weighting 
functions to those provided in NMFS' Acoustic Technical Guidance.
    NMFS will continue to review and evaluate new relevant data as it 
becomes available and consider the impacts of those studies on the 
Acoustic Technical Guidance to determine what revisions or updates may 
be appropriate. However, any such revisions must undergo peer and 
public review before being adopted, as described in the Acoustic 
Technical Guidance methodology. While some of the relevant data may 
potentially suggest changes to TTS/PTS thresholds for some species, any 
such changes would not be expected to change the predicted take 
estimates in a manner that would change the necessary determinations 
supporting the issuance of these regulations, and the data and values 
used in this proposed rule reflect the best available science.

Navy's Acoustic Effects Model

    The Navy proposes no changes to the Acoustic Effects Model as 
described in the 2018 HSTT final rule (and incorporated by reference in 
the 2020 HSTT final rule), and there is no new information that would 
affect the applicability or validity of the model. Please see the 2018 
HSTT final and proposed rules and Appendix E of the 2018 HSTT FEIS/OEIS 
for detailed information.

Range to Effects

    The Navy proposes no changes from the 2018 HSTT final rule (and 
subsequent 2020 HSTT final rule) to the type and nature of the 
specified activities to be conducted during the 7-year period analyzed 
in this proposed rule, including equipment and sources used and 
exercises conducted. NMFS has reviewed and will continue to review and 
evaluate new relevant data as it becomes available and consider the 
impacts of those studies on the Acoustic Technical Guidance to 
determine what revisions/updates may be appropriate. However, any such 
revisions must undergo peer and public review before being adopted, as 
described in the Acoustic Guidance methodology. While some of the 
relevant data may potentially suggest changes to TTS/PTS thresholds for 
some species (e.g., Kastelein et al. (2020a) shows onset of TTS 
incurred by a harbor porpoise at higher received levels than would have 
been anticipated based on the existing criteria, while Kastelein et al. 
(2022a) shows onset of TTS in otariids in water at lower received 
levels than the existing criteria), our assessment suggests that any 
such changes would not be expected to change the predicted take 
estimates in a manner that would change the necessary determinations 
supporting the issuance of these regulations, and the data and values 
used in the 2018 HSTT final rule, 2020 HSTT final rule, and this 
proposed rule reflect the best available science. Therefore, the ranges 
to effects in this proposed rule are identical to those described and 
analyzed in the 2018 HSTT final rule and 2020 HSTT final rule, 
including received sound levels that may cause onset of significant 
behavioral response and TTS and PTS in hearing for each source type or 
explosives that may cause non-auditory injury. Please see the Range to 
Effects section and tables 24 through 40 of the 2018 HSTT final rule 
for detailed information.

[[Page 68312]]

Marine Mammal Density

    The Navy proposes no changes to the methods used to estimate marine 
mammal density described in the 2018 HSTT final rule, and there is no 
new information that would affect the applicability or validity of 
these methods or change the results in a manner that would change the 
necessary determinations supporting the issuance of these regulations. 
The Navy's estimate of marine mammal density as described in the 2018 
HSTT final rule remains valid, though, as described herein, NMFS has 
incorporated new information regarding humpback whale stock structure 
into its analysis. Please see the 2018 HSTT final rule, and below, for 
detailed information.
    As noted above, NMFS regularly updates SARs, and in this rulemaking 
considers the 2022 final SARs (Carretta et al. 2023, Young et al. 
2023). While these SARs contain updated information, the Navy's 
estimate of marine mammal density as described in the 2018 HSTT final 
rule remains valid for the following reasons. The Navy uses its Marine 
Species Density Database (NMSDD) for its analysis, which is derived 
from multiple sources, including but not limited to SARs. In contrast, 
for most cetacean species, the SAR is estimated using line-transect 
surveys or mark-recapture studies (e.g., Barlow, 2010; Barlow and 
Forney, 2007; Calambokidis et al. 2008). The result provides one single 
abundance value for each species across broad geographic areas, but it 
does not provide information on the species density or concentrations 
within that area, and it does not estimate density for other timeframes 
or seasons that were not surveyed. A change in a stock's abundance 
indicated in a SAR does not necessarily indicate a change in that 
stock's density in any given area. Therefore, stocks in the HSTT Study 
Area with higher abundance estimates in the most recent SARs in 
comparison to the abundance estimates at the time that marine mammal 
densities were derived for the HSTT Study Area do not necessarily now 
occur in higher densities in the HSTT Study Area. For humpback whale, 
while the stock structure in the Pacific Ocean was revised in the 2022 
final SARs, the discussion above remains true regarding density of 
humpback whales in the HSTT Study Area across all stocks.

Take Requests

    As in the 2018 HSTT final rule and 2020 HSTT final rule, the Navy 
determined that the three stressors below could result in the 
incidental taking of marine mammals. NMFS has reviewed the Navy's data 
and analysis and determined that it is complete and accurate, and NMFS 
agrees that the following stressors have the potential to result in 
takes of marine mammals from the Navy's planned activities:
     Acoustics (sonar and other transducers; air guns; pile 
driving/extraction);
     Explosives (explosive shock wave and sound, assumed to 
encompass the risk due to fragmentation); and
     Physical Disturbance and Strike (vessel strike).
    NMFS reviewed and agrees with the Navy's conclusion that acoustic 
and explosive sources have the potential to result in incidental takes 
of marine mammals by harassment, serious injury, or mortality. NMFS 
carefully reviewed the Navy's analysis and conducted its own analysis 
of vessel strikes, determining that the likelihood of any particular 
species of large whale being struck is quite low. However, as noted 
previously, in 2021, two separate U.S. Navy vessels struck unidentified 
large whales on two separate occasions, one whale in June 2021 and one 
whale in July 2021. In May 2023, the U.S. Navy struck a large whale, 
which based on available photos and video, NMFS and the Navy have 
determined was either a fin whale or sei whale. NMFS agrees that vessel 
strikes have the potential to result in incidental take from serious 
injury or mortality for certain species of large whales, and the Navy 
has specifically requested coverage for these species. Therefore, the 
likelihood of vessel strikes, and later the effects of the incidental 
take that is being proposed to be authorized, has been fully analyzed 
and is described below.
    Regarding the quantification of expected takes from acoustic and 
explosive sources (by Level A and Level B harassment, as well as 
mortality resulting from exposure to explosives), the number of takes 
are based directly on the level of activities (days, hours, counts, 
etc., of different activities and events) in a given year. In the 2020 
HSTT final rule, take estimates across the 7 years were based on the 
Navy conducting 4 years of a representative level of activity and 3 
years of maximum level of activity. As in the 2020 HSTT final rule, the 
Navy proposes to use the maximum annual level to calculate annual takes 
(which would remain identical to what was determined in the 2020 HSTT 
final rule, with the exception of attribution of takes to humpback 
whale stocks), and the sum of all years (4 representative and 3 
maximum) to calculate the 7-year totals for this rulemaking.
    The quantitative analysis process used for the 2018 HSTT FEIS/OEIS 
and the 2017 and 2019 Navy applications to estimate potential exposures 
to marine mammals resulting from acoustic and explosive stressors is 
detailed in the technical report titled Quantifying Acoustic Impacts on 
Marine Mammals and Sea Turtles: Methods and Analytical Approach for 
Phase III Training and Testing (U.S. Department of the Navy, 2018). The 
Navy Acoustic Effects Model estimates acoustic and explosive effects 
without taking mitigation into account; therefore, the model 
overestimates predicted impacts on marine mammals within mitigation 
zones. To account for mitigation for marine species in the take 
estimates, the Navy conducts a quantitative assessment of mitigation. 
The Navy conservatively quantifies the manner in which procedural 
mitigation is expected to reduce the risk for model-estimated PTS for 
exposures to sonars and for model-estimated mortality for exposures to 
explosives, based on species sightability, observation area, 
visibility, and the ability to exercise positive control over the sound 
source. Where the analysis indicates mitigation would effectively 
reduce risk, the model-estimated PTS are considered reduced to TTS and 
the model-estimated mortalities are considered reduced to injury. For a 
complete explanation of the process for assessing the effects of 
mitigation, see the 2017 Navy application and the Take Requests section 
of the 2018 HSTT final rule. The extent to which the mitigation areas 
reduce impacts on the affected species and stocks is addressed 
separately in the Preliminary Analysis and Negligible Impact 
Determination section.
    No changes have been made to the quantitative analysis process to 
estimate potential exposures to marine mammals resulting from acoustic 
and explosive stressors and calculate take estimates, with the 
exception of take of humpback whales to account for the change in stock 
structure. Please see the documents described in the paragraph above, 
the 2018 HSTT proposed rule, the 2018 HSTT final rule, and below for 
detailed descriptions of these analyses. While Oedekoven and Thomas 
(2022) suggest that detection of marine mammals is less certain than 
previously assumed at certain distances, NMFS has independently 
evaluated the Navy's method for application of mitigation effectiveness 
in estimating take and agrees that it is appropriately applied to 
augment the model in the prediction and authorization of injury and

[[Page 68313]]

mortality as described in the rule, including after consideration of 
Oedekoven and Thomas (2022). In summary, we believe the Navy's methods, 
including the method for incorporating mitigation and avoidance, are 
the most appropriate methods for predicting PTS, TTS, and behavioral 
disturbance. But even with the consideration of mitigation and 
avoidance, given some of the more conservative components of the 
methodology (e.g., the thresholds do not consider ear recovery between 
pulses), we would describe the application of these methods as 
identifying the maximum number of instances in which marine mammals 
would be reasonably expected to be taken through PTS, TTS, or 
behavioral disturbance.

Summary of Requested Take From Training and Testing Activities

    Based on the methods discussed in the previous sections and the 
Navy's model and quantitative assessment of mitigation, the Navy 
provided its take estimate and request for authorization of takes 
incidental to the use of acoustic and explosive sources for training 
and testing activities both annually (based on the maximum number of 
activities that could occur per 12-month period) and over the 7-year 
period in its 2019 rulemaking/LOA application. With the exception of 
changes to humpback whale take, described below, annual takes (based on 
the maximum number of activities that could occur per 12-month period) 
from the use of acoustic and explosive sources are identical to those 
presented in tables 41 and 42 and in the Explosives subsection of the 
Take Requests section of the 2018 HSTT final rule. The 2022 Navy 
application includes the Navy's updated take estimate and request for 
take by vessel strike due to vessel movement in the HSTT Study Area. 
NMFS reviewed the Navy's data, methodology, and analysis and determined 
that it was complete, but NMFS has reanalyzed the potential for vessel 
strike following the May 2023 strike, as described in the Estimated 
Take from Vessel Strikes and Explosives by Serious Injury or Mortality 
section. NMFS agrees that the estimates for incidental takes by 
harassment from all sources as well as the incidental takes by serious 
injury or mortality from explosives requested for authorization are the 
maximum number of instances in which marine mammals are reasonably 
expected to be taken at the time of Navy's request, and continues to be 
for all stocks other than humpback whales, for which changes are 
described below. NMFS also agrees that the takes by serious injury or 
mortality as a result of vessel strikes could occur. Note that, 
consistent with the 2020 HSTT final rule, the total amount of estimated 
incidental take from acoustic and explosive sources over the total 7-
year period covered by the 2019 Navy application is less than the 
annual total multiplied by seven. Although the annual estimates are 
based on the maximum number of activities per year and therefore, the 
maximum possible estimated takes, the 7-year total take estimates are 
based on the sum of 3 maximum years and 4 representative years, with 
the exception of humpback whale stocks that occur in SOCAL for which 7-
year total take is conservatively estimated as the annual total 
multiplied by seven. Not all activities occur every year. Some 
activities would occur multiple times within a year, and some 
activities would occur only a few times over the course of the 7-year 
period. Using 7 years of the maximum number of activities each year 
would vastly overestimate the amount of incidental take that would 
occur over the 7-year period where the Navy knows that it will not 
conduct the maximum number of activities each and every year for the 7 
years.
    As described above in the Description of Marine Mammals and Their 
Habitat in the Area of the Specified Activities section, the 2022 final 
SARs include a revision to the humpback whale stock structure in the 
Pacific Ocean. In the 2020 HSTT final rule, NMFS authorized take of the 
CA/OR/WA stock and Central North Pacific stock of humpback whale. Given 
the revised stock structure, in this proposed rule, NMFS has reanalyzed 
the potential for take of each stock of humpback whale and determined 
that the Central America/Southern Mexico-CA/OR/WA, Mainland Mexico--CA/
OR/WA stock, and Hawaii stocks are likely to be taken by the Navy's 
activities.
    Under the new stock structure, the Hawaii stock (Hawaii DPS) is the 
only stock that would occur in Hawaii. Therefore, the Hawaii stock of 
humpback whale is the only humpback whale stock anticipated to be taken 
by the Navy's activities in the HRC, and all takes of the Central North 
Pacific stock of humpback whale that were authorized in the 2020 HSTT 
final rule are anticipated to be of individuals from the new Hawaii 
stock. In SOCAL, the takes of individuals from the former CA/OR/WA 
stock that were authorized in the 2020 HSTT final rule are anticipated 
to be of individuals from the new Central America/Southern Mexico-CA/
OR/WA and Mainland Mexico-CA/OR/WA stock.
    Please see the Estimated Harassment Take from Testing Activities 
and Estimated Harassment Take from Training Activities sections below 
for the estimated annual and 7-year total number and type of Level A 
harassment and Level B harassment for each humpback whale stock.
Estimated Harassment Take From Training Activities
    For training activities, table 11 of the 2020 HSTT final rule 
summarizes the Navy's take estimate and request in the 2019 Navy 
application and the maximum amount and type of Level A harassment and 
Level B harassment that NMFS concurred is reasonably expected to occur 
by species or stock and authorized in the 2020 HSTT LOA. In the 2022 
Navy application, the Navy requested no change to this authorized take, 
though as described above, NMFS has since published the 2022 final 
SARs, which include a revision to humpback whale stock structure. For 
the estimated 7-year total amount and type of Level A harassment and 
Level B harassment, see table 11 of the 2020 HSTT final rule for all 
species other than humpback whale. For the estimated amount and type of 
Level A harassment and Level B harassment annually, see table 41 in the 
2018 HSTT final rule for all species other than humpback whale. Note 
that take by Level B harassment includes both behavioral disturbance 
and TTS. Navy Figures 6-12 through 6-50 in Section 6 of the 2017 Navy 
application illustrate the comparative amounts of TTS and behavioral 
disturbance for each species annually, noting that if a modeled marine 
mammal was ``taken'' through exposure to both TTS and behavioral 
disturbance in the model, it was recorded as a TTS.

[[Page 68314]]



 Table 2--Humpback Whale Take From Acoustic and Explosive Effects for All Training Activities in the HSTT Study
                                                      Area
----------------------------------------------------------------------------------------------------------------
                                                              Annual                       7-Year total
                                                 ---------------------------------------------------------------
            Species                   Stock           Level B         Level A         Level B         Level A
                                                    harassment      harassment      harassment      harassment
----------------------------------------------------------------------------------------------------------------
Humpback whale \a\............  Hawaii..........           5,604               1          34,437              12
                                Central America/             585               0       \b\ 4,095               0
                                 Southern Mexico-
                                 CA/OR/WA
                                 (Central
                                 America DPS).
                                Mainland Mexico--            669               1       \b\ 4,683               7
                                 CA/OR/WA
                                 (Mexico DPS).
----------------------------------------------------------------------------------------------------------------
\a\ Combined, takes from the Central America/Southern Mexico- CA/OR/WA stock and the Mainland Mexico CA/OR/WA
  stock are equal to takes of the CA/OR/WA stock authorized in the 2020 HSTT final rule.
\b\ Unlike other species and stocks, for the Central America/Southern Mexico-CA/OR/WA stock and Mainland Mexico-
  CA/OR/WA stock, NMFS estimated the 7-year take by Level B harassment by multiplying the annual estimated take
  by seven. However, between the two stocks, NMFS does not anticipate that the total number of takes by Level B
  harassment across all 7 years would exceed the 7,962 takes by Level B harassment from training activities that
  were authorized for the CA/OR/WA stock of humpback whales in the 2020 HSTT final rule.

Estimated Harassment Take From Testing Activities
    For testing activities, table 12 of the 2020 HSTT final rule 
summarizes the Navy's take estimate and request in the 2019 Navy 
application and the maximum amount and type of Level A harassment and 
Level B harassment that NMFS concurred is reasonably expected to occur 
by species or stock and authorized in the 2020 HSTT LOA. In the 2022 
Navy application, the Navy requested no change to this authorized take. 
For the estimated 7-year total amount and type of Level A harassment 
and Level B harassment, see table 12 of the 2020 HSTT final rule. For 
the estimated amount and type of Level A harassment and Level B 
harassment annually, see table 42 in the 2018 HSTT final rule. Note 
that take by Level B harassment includes both behavioral disturbance 
and TTS. Navy Figures 6-12 through 6-50 in section 6 of the 2017 Navy 
application illustrate the comparative amounts of TTS and behavioral 
disturbance for each species annually, noting that if a modeled marine 
mammal was ``taken'' through exposure to both TTS and behavioral 
disturbance in the model, it was recorded as a TTS.

  Table 3--Humpback Whale Take From Acoustic and Explosive Effects for All Testing Activities in the HSTT Study
                                                      Area
----------------------------------------------------------------------------------------------------------------
                                                              Annual                       7-Year total
                                                 ---------------------------------------------------------------
            Species                   Stock           Level B         Level A         Level B         Level A
                                                    harassment      harassment      harassment      harassment
----------------------------------------------------------------------------------------------------------------
Humpback whale \a\............  Hawaii..........           3,522               2          23,750              19
                                Central America/             291               0       \b\ 2,037               0
                                 Southern
                                 Mexico--CA/OR/
                                 WA.
                                Mainland Mexico--            449               0       \b\ 3,143               0
                                 CA/OR/WA.
----------------------------------------------------------------------------------------------------------------
\a\ Combined, takes from the Central America/Southern Mexico-CA/OR/WA stock and the Mainland Mexico CA/OR/WA
  stock are equal to takes of the CA/OR/WA stock authorized in the 2020 HSTT final rule.
\b\ Unlike other species and stocks, for the Central America/Southern Mexico-CA/OR/WA stock and Mainland Mexico-
  CA/OR/WA stock, NMFS estimated the 7-year take by Level B harassment by multiplying the annual estimated take
  by seven. However, between the two stocks, NMFS does not anticipate that the total number of takes by Level B
  harassment across all 7 years would exceed the 4,961 takes by Level B harassment from testing activities that
  were authorized for the CA/OR/WA stock of humpback whales in the 2020 HSTT final rule.

Estimated Take From Vessel Strikes and Explosives by Serious Injury or 
Mortality Vessel Strike

    Vessel strikes from commercial, recreational, and military vessels 
are known to affect large whales and have resulted in serious injury 
and fatalities to cetaceans (Abramson et al. 2011; Berman-Kowalewski et 
al. 2010; Calambokidis, 2012; Douglas et al. 2008; Laggner, 2009; 
Lammers et al. 2003; Van der Hoop et al. 2012; Van der Hoop et al. 
2013; Crum et al. 2019). Records of collisions date back to the early 
17th century, and the worldwide number of collisions appears to have 
increased steadily during recent decades (Laist et al. 2001; Ritter 
2012) due to increases in the number and speed of large vessels, 
increased reporting of strikes, and increased abundance of some large 
whales (Ransome et al. 2021), among other factors.
    Numerous studies of interactions between surface vessels and marine 
mammals have demonstrated that free-ranging marine mammals often, but 
not always (e.g., McKenna et al. 2015; Smultea et al. 2022; Szesciorka 
et al. 2019), engage in avoidance behavior when surface vessels move 
toward them. It is not clear whether these responses are caused by the 
physical presence of a surface vessel, the underwater noise generated 
by the vessel, or an interaction between the two (Amaral and Carlson, 
2005; Au and Green, 2000; Bain et al. 2006; Bauer 1986; Bejder et al. 
1999; Bejder and Lusseau, 2008; Bejder et al. 2009; Bryant et al. 1984; 
Corkeron, 1995; Erbe, 2002; F[eacute]lix, 2001; Goodwin and Cotton, 
2004; Lemon et al. 2006; Lusseau, 2003; Lusseau, 2006; Magalhaes et al. 
2002; Nowacek et al. 2001; Richter et al. 2003; Scheidat et al. 2004; 
Simmonds, 2005; Watkins, 1986; Williams et al. 2002; Wursig et al. 
1998). Several authors suggest that the noise generated during vessel 
movement is probably an important factor (Blane and Jaakson, 1994; 
Evans et al. 1992; Evans et al. 1994). Water disturbance may also be a 
factor. These studies suggest that the behavioral responses of marine 
mammals to surface vessels are similar to their behavioral responses to

[[Page 68315]]

predators. Avoidance behavior is expected to be even stronger in the 
subset of instances during which the Navy is conducting training or 
testing activities using active sonar or explosives.
    The marine mammals most vulnerable to vessel strikes are those that 
spend extended periods of time at the surface to restore oxygen levels 
within their tissues after deep dives (e.g., sperm whales). In 
addition, some baleen whales seem generally unresponsive to vessel 
sound, making them more susceptible to vessel collisions (Nowacek et 
al. 2004). These species are primarily large, slow-moving whales.
    Some researchers have suggested the relative risk of a vessel 
strike can be assessed as a function of animal density and the 
magnitude of vessel traffic (e.g., Fonnesbeck et al. 2008; Vanderlaan 
et al. 2008). Differences among vessel types also influence the 
probability of a vessel strike. The ability of any ship to detect a 
marine mammal and avoid a collision depends on a variety of factors, 
including environmental conditions, ship design, size, speed, and 
ability and number of personnel observing, as well as the behavior of 
the animal. Vessel speed, size, and mass are all important factors in 
determining if injury or death of a marine mammal is likely due to a 
vessel strike. For large vessels, speed and angle of approach can 
influence the severity of a strike. For example, Vanderlaan and Taggart 
(2007) found that between vessel speeds of 8.6 and 15 kn (15.9 and 27.8 
km per hour), the probability that a vessel strike is lethal increases 
from 0.21 to 0.79. Large whales also do not have to be at the water's 
surface to be struck. Silber et al. (2010) found when a whale is below 
the surface (about one to two times the vessel draft), there is likely 
to be a pronounced propeller suction effect. This suction effect may 
draw the whale into the hull of the ship, increasing the probability of 
propeller strikes.
    There are some key differences between the operation of military 
and non-military vessels, which make the likelihood of a military 
vessel striking a whale lower than some other vessels (e.g., commercial 
merchant vessels). Key differences include:
     Many military ships have their bridges positioned closer 
to the bow, offering better visibility ahead of the ship (compared to a 
commercial merchant vessel);
     There are often aircraft associated with the training or 
testing activity (which can serve as Lookouts), which can more readily 
detect cetaceans in the vicinity of a vessel or ahead of a vessel's 
present course before crew on the vessel would be able to detect them;
     Military ships are generally more maneuverable than 
commercial merchant vessels, and if cetaceans are spotted in the path 
of the ship, could be capable of changing course more quickly;
     The crew size on military vessels is generally larger than 
merchant ships, allowing for stationing more trained Lookouts on the 
bridge. At all times when vessels are underway, trained Lookouts and 
bridge navigation teams are used to detect objects on the surface of 
the water ahead of the ship, including cetaceans. Additional Lookouts, 
beyond those already stationed on the bridge and on navigation teams, 
are positioned as Lookouts during some training events; and
     When submerged, submarines are generally slow moving (to 
avoid detection), and therefore, marine mammals at depth with a 
submarine are likely able to avoid collision with the submarine. When a 
submarine is transiting on the surface, there are Lookouts serving the 
same function as they do on surface ships.
    Vessel strike to marine mammals is not associated with any specific 
training or testing activity but is rather a limited and sporadic, but 
possible, accidental result of Navy vessel movement within the HSTT 
Study Area or while in transit.
    In 2009, the Navy began implementing additional mitigation measures 
to further reduce the likelihood of vessel strikes. Prior to the recent 
strikes in 2021 and 2023, there were two recorded U.S. Navy vessel 
strikes of large whales in the HSTT Study Area between 2009 and April 
2021, a period of approximately 12 years.
    Since 2021 there have been five documented strikes of large whales 
in SOCAL by naval vessels, three by the U.S. Navy and two by the Royal 
Australian Navy. As stated previously, the U.S. Navy struck a large 
whale in waters off Southern California in May 2023. Based on available 
photos and video, NMFS and the Navy have determined this whale was 
either a fin whale or sei whale. The U.S. Navy struck two unidentified 
large whales during the months of June and July 2021, and prior to 
that, on May 7, 2021, the Royal Australian Navy HMAS Sydney, a 147.5 m 
(161.3 yd) Hobart Class Destroyer, struck and killed two fin whales (a 
mother and her calf) while operating within SOCAL. In the case of the 
Royal Australian Navy strike, the carcasses were first sighted under 
the bow of the vessel while it was approaching the Naval Base in San 
Diego. The whales had been pinned to a sonar dome in the front of the 
vessel due to the force of water as the ship was underway. Based on 
interviews with HMAS Sydney personnel, the most likely time of impact 
with the two whales would have been around 6:25 a.m. when the vessel 
was located near Cortes Bank, and visibility was poor. The reported 
vessel speed at the estimated time of strike was 9 kn (16.7 km per 
hour). One minute before the estimated strike time a lookout reported 
whales off the starboard bow. The officer on-watch verbally 
acknowledged the report, slowed speed, and visually tracked the whales 
passing clear down the starboard side until they were clear of the 
ship. The morning of the strike, the HMAS Sydney was getting into 
position to participate in a U.S. Navy-led exercise later that day. Of 
note, throughout the remainder of the day visibility was poor and the 
vessel had implemented mitigation measures in multiple instances due to 
whale occurrence. In addition to being the only documented occurrence 
of a foreign military vessel strike of a large whale within the HSTT 
Study Area, the HMAS Sydney vessel strike was also somewhat unique, as 
compared to other reported military vessel strikes, in that two whales 
were apparently struck at one time, and both remained pinned to the 
front of the vessel until the vessel approached the port.
    On June 29, 2021, a U.S. Navy cruiser struck an unknown whale 
species approximately 95 nmi west of San Diego. The ship was returning 
from Hawaii, heading to a rendezvous with a fuel replenishment vessel 
(oiler) for an Underway Replenishment. Off-duty sailors noticed a group 
of whales approaching the ship from the port quarter (i.e., left rear 
of the ship), an area unique to cruisers with some equipment structures 
blocking close aboard sight. The first indication of a whale within the 
500-yd mitigation zone immediately prior to the strike was when an off-
duty sailor on the flight deck witnessed the whale briefly surface on 
the aft port quarter before diving. Shortly after this occurred blood 
was noticed in the wake, and a floating whale body was eventually 
observed behind the ship. The ship's speed was 25 kn (46.3 km per hour) 
at the estimated time the strike occurred. The Navy also noted that, on 
the morning before the strike occurred, the ship had maneuvered several 
times to avoid whale blows beyond the 500-yd (457.2 m) mitigation zone, 
closer to 1,000 yd (914.4 m).
    On July 11, 2021, a U.S. Navy cruiser struck an unknown whale 
species

[[Page 68316]]

approximately 90 nmi (166.7 km) south-southwest of San Diego. The 
vessel was a participant in a MTE (Large Integrated Anti-Submarine 
Warfare--Composite Unit Training Exercise) within the SOCAL portion of 
the action area. The vessel was maneuvering for pending flight 
operations to receive an inbound helicopter. At 2:27 p.m., the 
starboard lookout sighted what they believed to be a whale crossing 
immediately under the vessel's bow. The conning officer attempted to 
maneuver the vessel by turning to port but internal watchstanders 
subsequently felt the ship shudder aft. The vessel's combat center 
observed a red slick 600 yd (548.6 m) astern on a flight deck camera 
and a brief surfacing of the whale itself, but no carcass was observed. 
There had not been any sightings of large whales off the bow leading up 
to the incident. Although the ship was traveling at 25-30 kn (46.3-55.6 
km per hour) one hour before the estimated strike time, at ten minutes 
before, the vessel changed course and reduced its speed to 17 kn (31.5 
km per hour). These 2021 incidents were the first known U.S. Navy 
vessel strikes in the HSTT Study Area since 2009.
    On May 20, 2023, a U.S. Navy aircraft carrier was at sea conducting 
independent, unit-level flight training for the embarked airwing 
approximately 70 nmi west of San Diego. Training exercises concluded 
for the day at approximately 7:44 p.m. local time. Navy personnel 
discovered a whale impinged on the bow of the vessel at approximately 
8:00 p.m. local time. The vessel was traveling at approximately 5 kn 
and had recently made a turn to reset position for the evening when the 
Navy personnel discovered the whale. Navy personnel captured video and 
photos of the carcass, and based on those images, NMFS and the Navy 
have determined this whale was either a fin whale or sei whale; the two 
species are very similar morphologically and are difficult to 
distinguish from one another at sea. Navy personnel stopped the vessel 
to allow lack of momentum to dislodge the carcass from the bow, and 
based on lack of further observations after the carcass dislodged, it 
is believed to have sunk around 9:30 p.m. local time. Navy personnel on 
board the vessel reported that they did not feel an impact from 
striking the whale. Prior to the strike, between 6:45 p.m. and 7:45 
p.m., the forward Lookouts on the vessel observed two whales crossing 
the vessel's bow but did not provide a distance between the vessel and 
the whales. One Lookout reported seeing the blow and the other reported 
seeing `humps' (presumably the dorsal of the animal). Both whales were 
sighted past the ship's course to the northwest. Within the same time 
window, one of the aft Lookouts observed a single whale swimming 
parallel to the ship and soon passed astern of the ship. During the 
same time, independent of the sightings and for general movement 
reasons, the ship changed speed from 17 knots to 10 knots at 7:22 p.m.
    For the same reasons listed above describing why the likelihood of 
a military vessel striking a whale is lower than that of some other 
vessels striking whales, it is also highly unlikely that a Navy vessel 
would strike a whale, dolphin, porpoise, or pinniped without detecting 
it. Specifically, Navy ships have Lookouts, including on the forward 
part of the ship that can visually detect a hit animal in the event 
ship personnel do not feel the strike (which has occurred). 
Accordingly, NMFS is confident that the Navy's reported strikes are 
accurate and appropriate for use in the analysis. Navy's strict 
internal procedures and mitigation requirements include reporting of 
any vessel strikes of marine mammals, and the Navy's discipline, 
extensive training (not only for detecting marine mammals, but for 
detecting and reporting any potential navigational obstruction), and 
strict chain of command give NMFS a high level of confidence that all 
strikes actually get reported.
    As noted above, the 2021 Royal Australian Navy vessel strikes were 
first observed when the vessel came to port at Naval Base San Diego. 
However, such a scenario is unlikely on a U.S. Navy vessel. While U.S. 
Navy cannot speculate on the configurations of other ships bows and 
even sonar dome specifications (that may be at the bow), the Navy 
believes it would be implausible for a marine mammal to become lodged 
on the sonar dome of a U.S. Navy ship and remain undetected due to a 
technological standard operating procedure. Sonar domes on U.S. Navy 
ships have a pressurized rubber window that maintains 150 pound-force 
per square inch (PSI) through the ship's fire main. If anything affects 
the pressure, an alarm sounds in the sonar control room. In the event 
of a whale strike in that location, this alarm would alert personnel 
that something hit the sonar dome. Further, the shape, hydrodynamic 
design, construction using a non-abrasive material, and regular hull 
cleaning procedures to remove barnacles and other growth on U.S. Navy 
ships also make it unlikely that a whale would become lodged and remain 
undetected on a U.S. Navy ship's bow or even sonar dome. While in the 
case of the May 2023 strike, described above, a whale also became 
lodged on the ship's bow, the aircraft carrier that struck the whale 
does not have active or passive sonar capabilities (i.e., no sonar 
dome), nor does it have a bulbous bow, and the whale was more quickly 
discovered by Navy personnel.
    In order to better account for the accidental nature of vessel 
strikes to large whales in general and the potential risk from U.S. 
Navy vessel movement within the HSTT Study Area during the remaining 
period of the HSTT rule in particular, the Navy requested the HSTT rule 
be modified to authorize additional incidental takes by vessel strike 
based on probabilities derived from a Poisson distribution using vessel 
strike data between 2009-2021 in the HSTT Study Area (the time period 
from when current mitigations were instituted until the Navy conducted 
the analysis for the 2022 Navy application), as well as historical at-
sea days in the HSTT Study Area from 2009-2015 and estimated at-sea 
days for the period from 2016 to 2025 covered by the current 
regulations. This distribution predicted the probabilities of a 
specific number of strikes (n=0, 1, 2, etc.) over the remaining period 
of the regulations at the time of the Navy's analysis (2022-2025).
    The Navy used the two fin whale strikes (2009) and two unidentified 
large whale strikes (2021) in their calculations to determine the 
number of strikes likely to result from its activities over the 
remaining 3 years of the rule (2023-2025, although worldwide strike 
information from all Navy activities and other sources was used to 
inform the species that may be struck). The Navy evaluated data 
beginning in 2009 as that was the start of the Navy's Marine Species 
Awareness Training and adoption of additional mitigation measures to 
address vessel strike, which will remain in place along with additional 
and modified mitigation measures during the 7 years of this rulemaking. 
From this analysis, the Navy concluded that there was a 27 percent 
chance that zero whales would be struck by Navy vessels over the 
remaining period of the rule (which, at the time that the application 
was submitted, was 4 years), and a 35, 23, and 10 percent chance that 
one, two, or three whales, respectively, would be struck over the 
remaining 4 years of the rule. Therefore, the Navy estimated that there 
was some probability that the Navy could strike, and take by serious 
injury or mortality, up to three large whales incidental to training 
and testing

[[Page 68317]]

activities within the HSTT Study Area over what would have been the 
remaining 4 years of the current authorization, and the Navy requested 
authorization of two additional takes of large whales by serious injury 
or mortality by vessel strike, beyond the three takes authorized by the 
2020 HSTT final rule (85 FR 41780, July 10, 2020).
    NMFS has since updated this analysis to reflect that an additional 
strike of an unidentified large whale occurred in May 2023 (either a 
fin whale or sei whale, as stated above) and that additional time has 
passed since the Navy submitted the 2022 Navy application. Based on 
further discussions with the Navy, NMFS has also updated the way it 
calculated at-sea days. This is a different manner of calculating at-
sea days for the purposes of the strike analysis rather than a change 
in Navy's activity levels. For 2010-2015, the at-sea days used in NMFS' 
calculation reflected historic at-sea days in the HSTT action area 
based on positional vessel data records (Mintz, 2016). While the actual 
annual at-sea days from 2016-present are currently classified, NMFS' 
updated calculation reflects an extrapolation of the 2010-2015 at-sea 
days (using the formula y = -64x + 131555) to estimate the number of 
at-sea days in 2016 (Navy, 2022). The number of at-sea days derived for 
2016 was 2,056 at-sea days, which reflects the downward trend in HSTT 
vessel activity from 2010-2015. Since we do not have sufficient 
information to say whether or not this downward trend continued for the 
years 2017-2022, we conservatively estimate the average over these 
years was the same as the 2016 extrapolated value of 2,056 at-sea days. 
This analysis only included at-sea days for Navy warships greater than 
65 feet (i.e., destroyers are the smallest ship class included). Navy 
vessels smaller than 65 feet have never reported a whale strike in the 
Pacific, and therefore, we consider it unlikely that this would occur 
in the remaining 2.5 years of the regulations.

       Table 4--HSTT 2009 Through Mid-2023 At-Sea Days Used for the Vessel Strike Probability Calculation
----------------------------------------------------------------------------------------------------------------
                     Year                         At-sea days                      Derivation
----------------------------------------------------------------------------------------------------------------
2009..........................................           4,233  Estimated average based on 2010-2015 data.
2010..........................................           5,207  Based on positional vessel data.
2011..........................................           4,483  Based on positional vessel data.
2012..........................................           4,081  Based on positional vessel data.
2013..........................................           4,041  Based on positional vessel data.
2014..........................................           4,272  Based on positional vessel data.
2015..........................................           3,311  Based on positional vessel data.
2016..........................................           2,056  Extrapolated from 2010-2015 regression.
2017..........................................           2,056  Extrapolated from 2010-2015 regression.
2018..........................................           2,056  Extrapolated from 2010-2015 regression.
2019..........................................           2,056  Extrapolated from 2010-2015 regression.
2020..........................................           2,056  Extrapolated from 2010-2015 regression.
2021..........................................           2,056  Extrapolated from 2010-2015 regression.
2022..........................................           2,056  Extrapolated from 2010-2015 regression.
2023 (first half of year).....................           1,028  Extrapolated from 2010-2015 regression, then
                                                                 reduced by half.
                                               ----------------
    2009-Mid-2023 total.......................          45,048
----------------------------------------------------------------------------------------------------------------

    NMFS then used the number of past Navy vessel strikes and the at-
sea days to calculate a vessel strike rate for 2009 through mid-2023. 
The estimated total number of Navy at-sea days (for vessels greater 
than 65 feet) for 2009 through mid-2023 was 45,048 days. Dividing the 
five known strikes during that period by the at-sea days (i.e., 5 
strikes/45,048 at-sea days) results in a strike rate of 0.000111 
strikes per day.
    As described above, NMFS conservatively assumed that the average 
number of at-sea days from mid-2023 through 2025 (the remaining period 
of the regulations) will be the same as the 2016 extrapolated value of 
2,056. Therefore, the estimated at-sea days within the action area for 
the period from mid-2023 through 2025 is 5,140 days. NMFS multiplied 
the historic daily strike rate by the estimated at-sea days from mid-
2023 through 2025 (0.000111 strikes per day x 5,140 days) to estimate 
the number of whale strikes anticipated during that period. This 
calculation predicts an estimated 0.57 strikes over the remaining 2.5 
years of the regulations (mid-2023 through 2025).
    As explained above, according to the U.S. Navy, the May 2021 vessel 
strike of two fin whales by a Royal Australian Navy vessel did not 
occur while that vessel was participating in a U.S. Navy-led training 
exercise, and the strike of those two fin whales is not included in the 
estimated take by vessel strike calculation. Instead, as noted below, 
NMFS considered the 2021 vessel strike by the Royal Australian Navy 
along with other strike information when determining which species 
could be among the estimated large whales struck.
    NMFS used a Poisson distribution to derive the probabilities of a 
specific number of strikes (n=0, 1, 2, etc.) from mid-2023 through 
2025, given the estimated 0.57 strikes during that period. NMFS' 
probability analysis concluded that there is a 57 percent chance that 
zero whales would be struck by U.S. Navy vessels over the remaining 
period of the rule (mid-2023 through 2025), and a 32, 9, and 2 percent 
chance that one, two, or three whales, respectively, would be struck 
over the remaining 2.5 years of the regulations. Further, there is an 
estimated 11 percent chance that the Navy would strike more than one 
large whale over the remaining period of the rule (mid-2023 through 
2025). We have assessed these probabilities and determined that the 
strike up to two large whales could occur over the remaining duration 
of the regulations, for a total of five takes by serious injury or 
mortality of large whales by vessel strike total over the 7-year 
duration of the regulations (three takes authorized in the 2020 HSTT 
final rule (85 FR 41780, July 10, 2020) which have occurred, plus two 
additional takes).
    In addition to the reasons listed above that make it unlikely that 
the Navy will hit a large whale (more maneuverable ships, larger crew, 
etc.), vessel strike of dolphins, small whales, porpoises, and 
pinnipeds is considered very unlikely. Dating back more than 20 years 
and for as long as it has kept records, the Navy has no records of any 
small whales or

[[Page 68318]]

pinnipeds being struck by a vessel as a result of Navy activities. Over 
the same time period, NMFS and the Navy have only one record of a 
dolphin being struck by a vessel as a result of Navy activities. The 
dolphin was accidentally struck by a Navy small boat in fall 2021 in 
Saint Andrew's Pass, Florida. The smaller size and maneuverability of 
dolphins, small whales, and pinnipeds generally make such strikes very 
unlikely. Other than this one reported strike of a dolphin in 2021, 
NMFS has never received any reports from other LOA or Incidental 
Harassment Authorization holders indicating that these species have 
been struck by vessels. In addition, worldwide vessel strike records 
show little evidence of strikes of these groups from the shipping 
sector and larger vessels, and the majority of the Navy's activities 
involving faster-moving vessels (that could be considered more likely 
to hit a marine mammal) are located in offshore areas where smaller 
delphinid, porpoise, and pinniped densities are lower. Based on this 
information, NMFS concurs with the Navy's assessment and recognizes the 
potential for (and is proposing for authorization) incidental take by 
vessel strike of large whales only (i.e., no dolphins, small whales, 
porpoises, or pinnipeds) over the course of the 7-year regulations from 
training and testing activities as discussed below.
    Next, after determining that take of up to five large whales could 
occur, NMFS considered which species could be among the five large 
whales struck. As noted in the 2018 HSTT proposed and final rules, the 
2019 HSTT proposed rule, and 2020 HSTT final rule, in the 2017 Navy 
rulemaking/LOA application, the Navy initially considered a weight of 
evidence approach that considered relative abundance, historical strike 
data over many years, and the overlap of Navy activities with the stock 
distribution in their request. NMFS updated this analysis to consider 
several factors, in addition to the overlap of Navy activities with 
stock distribution: (1) The relative likelihood of striking one stock 
versus another based on available strike data from all vessel types as 
denoted in the Carretta et al. (2021; referenced in the Pacific SARs), 
the Pacific and Alaska SARs (Carretta et al. 2023 and Young et al. 
2023), and unpublished NMFS vessel strike data for 2019-2021; and (2) 
whether the Navy has ever struck an individual from a particular 
species or stock in the HSTT Study Area, and if so, how many times. 
NMFS did not consider relative abundance, as was considered in previous 
analyses, given that the relative abundance of a stock does not 
necessarily inform its occurrence in a specific area. Further, NMFS did 
not consider the historical strike data from older years (prior to 
2015), given that more recent data is more relevant to determining 
occurrence of, and strike risk to, various stocks. NMFS updated the 
analysis with NMFS' vessel strike probability analysis for the 
remaining 2.5 years of the rule and included new/updated vessel strike 
data from the SARs and NMFS records for California and Hawaii.
    To address number (1) above, for SOCAL, NMFS compiled information 
from Carretta et al. (2021) and unpublished NMFS vessel strike data for 
2020-2021 for California on known annual rates of large whale serious 
injury or mortality from vessel collisions (this data includes the 
strike of 2 fin whales by the Royal Australian Navy in 2021, but does 
not include Navy strikes in 2021 and 2023 because the species struck is 
not known). Use of Carretta et al. (2021) rather than the Pacific SAR 
allows NMFS to separate strikes that occurred in California from 
strikes to the same stocks that occurred in other locations. For the 
HRC, NMFS compiled information from the Pacific and Alaska SARs and 
unpublished NMFS vessel strike data for 2019-2021 for Hawaii on known 
annual rates of large whale serious injury or mortality from vessel 
collisions. The annual rates of large whale serious injury or mortality 
from vessel collisions from those sources help inform the relative 
susceptibility of large whale species to vessel strike in SOCAL and the 
HRC; therefore, we considered only reported strikes where the species 
struck was identified with sufficient certainty (i.e., ``known 
strikes''). Additionally, the M/SI in the 2022 SAR considers modeled 
takes for some, but not most species and stocks (i.e., M/SI for 
humpback whale includes modeled takes from Rockwood et al. (2017)). 
Using known strike data for all species and stocks allows us to 
consider-like metrics for this comparative analysis. (Note we rely on 
the M/SI estimates from the 2022 SAR in our Negligible Impact Analysis. 
We also consider modeled takes of species from Rockwood et al. (2017) 
in table 7). We summed the annual rates of serious injury or mortality 
from vessel collisions in California and Hawaii as calculated above and 
then divided each species' annual rate by this sum to get the 
proportion of strikes for each species/stock (table 5).

   Table 5--Annual Rates of Serious Injury and Mortality From Vessel Strike and Percentage of Total Strikes by
                                          Species in SOCAL and the HRC
----------------------------------------------------------------------------------------------------------------
                                                                 SOCAL annual     HRC annual      Percentage of
      ESA status              Species              Stock         known strikes   known strikes    total annual
                                                                  (2015-2021)     (2015-2021)        strikes
----------------------------------------------------------------------------------------------------------------
Listed................  Blue whale........  Central North       ..............               0               0.0
                                             Pacific.
                                            Eastern North                 0.57  ..............               6.5
                                             Pacific.
                        Fin whale \a\.....  California,                   1.57  ..............              17.8
                                             Oregon, &
                                             Washington.
                                            Hawaiian..........  ..............               0               0.0
                        Humpback whale....  Central America/             \b\ 1  ..............              11.3
                                             Southern Mexico-
                                             CA/OR/WA (Central
                                             America DPS).
                                            Mainland Mexico-CA/
                                             OR/WA (Mexico
                                             DPS).
                        Sei whale.........  Eastern North                 0.14  ..............               1.6
                                             Pacific.
                                            Hawaiian..........  ..............               0               0.0
                        Gray whale........  Western North                    0  ..............               0.0
                                             Pacific.
                        Sperm whale.......  California,                      0  ..............               0.0
                                             Oregon, &
                                             Washington.
                                            Hawaiian..........  ..............               0               0.0
Not listed............  Gray whale........  Eastern North                 2.14  ..............              24.3
                                             Pacific.
                        Bryde's whale.....  ETP stock.........               0  ..............               0.0
                                            Hawaiian..........  ..............               0               0.0
                        Minke whale.......  CA/OR/WA..........               0  ..............               0.0

[[Page 68319]]

 
                                            Hawaiian..........  ..............               0               0.0
                        Humpback whale....  Hawaii (Hawaii      ..............             3.4              38.5
                                             DPS).
                                                               -------------------------------------------------
    Total.............  ..................  ..................               8.82               ................
----------------------------------------------------------------------------------------------------------------
\a\ This includes the two fin whales struck by the Royal Australian Navy in May 2021.
\b\ This strike occurred to an individual of the CA/OR/WA stock under the previous stock structure. As such, in
  its analysis, NMFS assumed that this strike could have been of either stock.

    To inform the likelihood of striking a particular species of large 
whale, we multiplied the percent of total annual strikes for a given 
species in table 5, by the total percent likelihood of striking at 
least one whale during the remaining period of the rule (2023-2025; 
i.e., 43 percent, as described by the probability analysis above). We 
also calculated the percent likelihood of striking a particular species 
of large whale twice during the remaining period of the rule by 
squaring the value estimated for the probability of striking a 
particular species of whale once (i.e., to calculate the probability of 
an event occurring twice, multiply the probability of the first event 
by the second). The results of these calculations are reflected in the 
last two columns of table 6. We note that these probabilities vary from 
year to year as the average annual mortality changes depending on the 
specific range of time considered; however, over the years and through 
updated data in the SARs and unpublished NMFS records, stocks tend to 
consistently maintain a relatively higher or relatively lower 
likelihood of being struck.

  Table 6--Percent Likelihood of Striking Each Stock One or Two Times Over 2.5 Years and Total Known U.S. Navy
                                         Strikes in the HSTT Study Area
----------------------------------------------------------------------------------------------------------------
                                                                                      Percent         Percent
                                                           Total known U.S. Navy   likelihood of   likelihood of
              Species                       Stock          strikes in HSTT study   1 strike over  2 strikes over
                                                                    area             2.5 years       2.5 years
----------------------------------------------------------------------------------------------------------------
Blue whale........................  Central North Pacific  0....................            0.00            0.00
                                    Eastern North Pacific  1 in SOCAL (2004)....            2.81            0.08
Fin whale.........................  CA/OR/WA.............  3 in SOCAL (2009,            \b\ 7.74        \b\ 0.60
                                                            2023 \a\).
                                    Hawaiian.............  0....................            0.00            0.00
Humpback whale....................  Central America/       0....................            4.93            0.24
                                     Southern Mexico-CA/
                                     OR/WA (Central
                                     America DPS).
                                    Mainland Mexico-CA/OR/
                                     WA (Mexico DPS).
Sei whale.........................  Eastern North Pacific  1 in SOCAL (2023 \a\)            0.69            0.00
                                    Hawaiian.............  0....................            0.00            0.00
Gray whale........................  Western North Pacific  0....................            0.00            0.00
Sperm whale.......................  CA/OR/WA.............  0.00.................            0.00
                                    Hawaiian.............  1 in HRC (2007)......            0.00            0.00
Gray whale........................  Eastern North Pacific  3 in SOCAL (1993,               10.55            1.11
                                                            1998).
Bryde's whale.....................  ETP stock............  0....................            0.00            0.00
                                    Hawaiian.............  0....................            0.00            0.00
Minke whale.......................  CA/OR/WA.............  0....................            0.00            0.00
                                    Hawaii...............  0....................            0.00            0.00
Humpback whale....................  Hawaii (Hawaii DPS)..  2 in HRC (2003)......           16.76            2.81
----------------------------------------------------------------------------------------------------------------
\a\ Based on available photos and video, NMFS and the Navy have determined the May 2023 strike was of either a
  fin whale or sei whale. In the analysis herein, NMFS has assumed that this strike could have been of either
  species, and has therefore, accounted for it in both the fin whale and sei whale strike totals. Given that we
  are unable to identify the species of the whales struck by the U.S. Navy in 2021, NMFS did not include the two
  2021 strikes in this part of the analysis.
\b\ This includes the two fin whales struck by the Royal Australian Navy in May 2021.

    The percent likelihood calculated as described above are then 
considered in combination with the information indicating the known 
species that the Navy has hit in the HSTT Study Area since 1991 (since 
they started tracking consistently; table 6). We note that for the 
lethal take of species specifically denoted in table 7 below, 47 
percent of those struck by the Navy (8 of 17 in the Pacific) remained 
unidentified (including the May 2023 strike, which as stated above, 
NMFS and the Navy have determined was of either a fin whale or sei 
whale). However, given the information on known stocks struck, the 
analysis below remains appropriate. We also note that Rockwood et al. 
(2017) modeled the likelihood of vessel strike of blue whales, fin 
whales, and humpback whales on the U.S. West Coast (discussed in more 
detail in the Serious Injury or Mortality subsection of the Preliminary 
Analysis and Negligible Impact Determination section), and those 
numbers help inform the relative likelihood that the Navy could hit 
those stocks.
    For each indicated stock, table 7 includes the percent likelihood 
of

[[Page 68320]]

striking an individual whale from a particular stock during the 
remaining 2.5 years of the rule once based on SAR data, Carretta et al. 
(2021), and unpublished NMFS vessel strike data from 2019-2021 for 
Hawaii; total strikes from Navy vessels in the HSTT Study Area, and 
modeled vessel strikes from Rockwood et al. (2017). The last column 
indicates the annual mortality proposed to be authorized.

              Table 7--Summary of Factors Considered in Determining the Number of Individuals in Each Stock Potentially Struck by a Vessel
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                               Percent                             Rockwood et     Annual
                                                                              likelihood   Total known U.S. Navy     al. 2017    authorized    Proposed
       ESA status                  Species                   Stock              of one     strikes in HSTT study     modeled     take from      annual
                                                                             strike over      area (1993-2009)        vessel     2020 HSTT    authorized
                                                                              2.5 years                            strikes \1\   final rule      take
--------------------------------------------------------------------------------------------------------------------------------------------------------
Listed..................  Blue whale..............  Central North Pacific..         0.00  0......................  ...........  ...........            0
                                                    Eastern North Pacific..         2.81  1 in SOCAL (2004)......           18         0.14         0.14
                          Fin whale...............  CA/OR/WA...............     \2\ 7.74  3 in SOCAL (2009, 2023            43         0.29         0.57
                                                                                           \3\).
                                                    Hawaii.................         0.00  0......................  ...........  ...........            0
                          Humpback whale \4\......  Central America/                4.93  0......................           22         0.14            0
                                                     Southern Mexico-CA/OR/
                                                     WA (Central America
                                                     DPS).
                                                    Mainland Mexico-CA/OR/                                                                          0.14
                                                     WA (Mexico DPS).
                          Sei whale...............  Eastern North Pacific..         0.69  1 in SOCAL(2023) \3\...  ...........  ...........         0.14
                                                    Hawaii.................         0.00  0......................  ...........  ...........            0
                          Gray whale..............  Western North Pacific..         0.00  0......................  ...........  ...........            0
                          Sperm whale.............  CA/OR/WA...............         0.00  0......................  ...........  ...........            0
                                                    Hawaii.................         0.00  1 in HRC (2007)........  ...........         0.14            0
Not listed..............  Gray whale..............  Eastern North Pacific..        10.55  3 in SOCAL (1993, 1998)  ...........         0.29         0.57
                          Bryde's whale...........  Eastern Tropical                0.00  0......................  ...........  ...........            0
                                                     Pacific.
                                                    Hawaii.................         0.00  0......................  ...........  ...........            0
                          Minke whale.............  CA/OR/WA...............         0.00  0......................  ...........  ...........            0
                                                    Hawaii.................         0.00  0......................  ...........  ...........            0
                          Humpback whale..........  Hawaii (Hawaii DPS) \5\        16.76  2 in HRC (2003)........  ...........         0.29         0.29
--------------------------------------------------------------------------------------------------------------------------------------------------------
\1\ Rockwood et al. modeled likely annual vessel strikes off the West Coast for these three species only.
\2\ This includes the two fin whales struck by the Royal Australian Navy in May 2021.
\3\ Based on available photos and video, NMFS and the Navy have determined the May 2023 strike was of either a fin whale or sei whale. In the analysis
  herein, NMFS has assumed that this strike could have been of either species, and has therefore, accounted for it in both the fin whale and sei whale
  strike totals.
\4\ In the 2020 HSTT final rule, take of humpback whale by serious injury and mortality by vessel strike in Southern California was attributed to the
  former CA/OR/WA stock and the Mexico DPS. Text explains why takes in SOCAL come from the Mexico DPS, and therefore the Mainland Mexico-CA/OR/WA stock.
\5\ The 2022 final SAR reports vessel strike data for the Hawaii stock of humpback whales in Alaska, Washington, and Hawaii. Only vessel strike data
  from Hawaii was incorporated into our analysis as Alaska and Washington are outside of the HSTT Study Area.

    Accordingly, stocks that have no record of ever having been struck 
by any vessel are considered to have a zero percent likelihood of being 
struck by the Navy in the 7-year period of the rule. Stocks that have 
never been struck by the Navy, have rarely been struck by other 
vessels, and have a low percent likelihood based on the historical 
vessel strike calculation are also considered to have a zero percent 
likelihood to be struck by the Navy during the 7-year rule. We note 
that while vessel strike records have not differentiated between 
Eastern North Pacific and Western North Pacific gray whales, given 
their small population size and the comparative rarity with which 
individuals from the Western North Pacific stock are detected off the 
U.S. West Coast, it is highly unlikely that they would be encountered, 
much less struck. This rules out all but seven stocks. Further, it is 
unlikely that the Hawaii stock of sperm whale would be struck given the 
zero percent likelihood of striking a sperm whale as indicated by the 
quantitative analysis above, the fact that the last U.S. Navy strike of 
a Hawaii stock sperm whale was in 2007, before the mitigation updates 
discussed above, and that, with the exception of humpback whales, 
vessel strikes (both military and non-military) of other large whale 
species in the HRC are extremely rare events (Carretta 2021b; Carretta 
2022). (The 2020 HSTT final rule authorized 1 take (0.14 annual take) 
by mortality of the Hawaii stock of sperm whale.)
    As stated previously, based on available photos and video of the 
whale struck by the U.S. Navy in Southern California in 2023, NMFS and 
the Navy have determined this whale was either a fin whale or sei 
whale. While the species of the two whales struck by the U.S. Navy in 
2021 are unknown, given the following factors, NMFS expects these 
strikes may have been CA/OR/WA fin whales or Eastern North Pacific 
(ENP) gray whales, or some combination of these two stocks. These 
species have the highest annual rates of mortality/serious injury (M/
SI) from vessel collision in California (1.57, 2.14, respectively, as 
noted above; which is approximately one and a half to two times higher 
than the species with the next highest strike rate, humpback whale, and 
approximately two to four times higher than the strike rate of blue 
whale). Additionally, gray whale and fin whale have the most recorded 
vessel strike incidents by military vessels in SOCAL and are the only 
stocks known to have been hit more than one time by naval vessels in 
the SOCAL portion of the HSTT Study Area (3 gray whale strikes by the 
U.S. Navy (1993, 1998), 2 or 3 fin whale strikes by the U.S. Navy 
(2009, potentially 2023), and 2 fin whale strikes by the Royal 
Australian Navy (2021)). Further, accounting for undocumented vessel 
strikes, Rockwood et al. (2021) estimated that in their study area off 
Southern California from 2012-2018, on average 8.9 blue, 4.6 humpback, 
and 9.7 fin whales were killed by civilian vessel strikes from June to 
November each year. In addition, they estimated that, on average, 5.7 
humpback whales were killed by civilian vessel strike from January-
April per year (Rockwood et al. 2021). For fin whales in particular, 
model-predicted densities of large whales in the Southern California 
Bight from May to July 2021 (the time period during which the 2021 
strikes of two unidentified whales by the U.S. Navy occurred) estimated 
fin whale abundance as being nearly an order of magnitude higher than 
either blue or humpback whale abundance during this time period (Becker 
et al. 2020; Zickel

[[Page 68321]]

et al. 2021). Ship-whale encounter models for the U.S. West Coast 
Exclusive Economic Zone also indicated that vessel strike mortality 
estimates for fin whales were significantly higher than for blue whales 
and humpback whales (Rockwood et al. 2017). The comparatively higher 
modeled vessel strike rates for fin whales result from both the larger 
population as well as the more offshore distribution that overlaps 
significantly with several major shipping routes for a much greater 
spatial extent (Rockwood et al. 2017). Based on 1,243 visual boat-based 
sightings of 2,638 fin whales from 1991-2011, Calambokidis et al. 
(2015) found fin whale concentration areas included the San Clemente 
Basin where the 2021 Navy vessel strikes occurred (Tanner and Cortez 
Banks area and the shelf edge west of San Nicolas Island were also 
reported as fin whale concentration areas). There are two different 
populations of fin whales that occur in the Southern California Bight: 
a seasonal population, and a population that occurs year-round with 
offshore/inshore movements (Campbell et al. 2015; Falcone et al. 2022). 
This would likely make fin whales more susceptible to vessel strike 
year-round, as compared to other large whale species that may occur 
seasonally within SOCAL. Based on all of these factors, there is a 
reasonable likelihood that the CA/OR/WA stock of fin whales or ENP 
stock of gray whales could be struck twice during the remaining 2.5 
years of the rule. Therefore, we propose that, of the five total takes 
by serious injury or mortality by vessel strike of large whales 
proposed to be authorized, up to four of those takes could be of the 
CA/OR/WA stock of fin whale or the ENP stock of gray whale given that 
the two strikes of unidentified large whales in 2021 could have been of 
either stock. Further, consistent with the 2020 HSTT final rule, we 
propose that, of the five total takes by serious injury or mortality by 
vessel strike of large whales proposed to be authorized, up to two of 
those takes could occur in Hawaii, and therefore be of individuals of 
the Hawaii stock of humpback whale.
    Based on the information summarized in table 7 and the fact that 
there is the potential for up to two large whales to be struck over the 
remaining 2.5 years of the rule (five strikes over the full 7-year rule 
period), one individual from the Eastern North Pacific stock of blue 
whale, Mainland Mexico-CA/OR/WA stock of humpback whale, or Eastern 
North Pacific stock of sei whale could be among the two whales struck 
during the remaining effective period of the regulations (2023-2025). 
The total strikes of Eastern North Pacific blue whales and the percent 
likelihood of striking one based on the historic strike calculation 
above can both be considered moderate compared to other stocks, and the 
Navy struck a blue whale in 2004 (based on the historic strike 
calculation, the likelihood of striking two blue whales is well below 
one percent (table 6)). Therefore, we consider it reasonably likely 
that the Navy could strike one individual over the course of the 7-year 
rule, and given that we do not expect that the 2023 strike nor either 
of the 2021 U.S. Navy strikes of unidentified large whales were blue 
whales, we expect that this strike could occur during the remaining 2.5 
years of the rule. The total strikes of Eastern North Pacific sei 
whales are low compared to other stocks, but NMFS and the Navy think it 
is possible that the Navy may have struck a sei whale in SOCAL in 2023. 
Therefore, we consider it reasonably likely that the Navy could strike 
a sei whale over the remaining 2.5 years of the rule. The Navy has not 
hit a humpback whale in the SOCAL portion of the HSTT Study Area. 
However, in 2016 a U.S. Coast Guard vessel participating in a Navy 
event struck a humpback whale in Hood Canal, and as a species, 
humpbacks have a moderate to high number of total strikes and percent 
likelihood of being struck. Although the likelihood of Central America/
Southern Mexico-CA/OR/WA (Central America DPS) or Mainland Mexico-CA/
OR/WA (Mexico DPS) humpback whales being struck by any vessel type is 
moderate to high relative to other stocks, the distribution of the 
Mexico DPS versus the Central America DPS, as well as the distribution 
of overall vessel strikes inside versus outside of the SOCAL area (the 
majority are outside), supports the reasonable likelihood that the Navy 
could strike one individual humpback whale from the Mainland Mexico-CA/
OR/WA stock (Mexico DPS) over the 7-year duration of the rule, as 
described below.
    Regarding the likelihood of striking a humpback whale from a 
particular DPS, we evaluated the relative abundance of each of these 
DPS in California waters. Curtis et al. (2022) estimated the abundance 
of the Central America DPS to be 1,496 whales. From Wade et al. (2017), 
about 93 percent (or 1,391 whales) of these humpbacks that winter in 
Central America will move to Oregon/California in the summer months. 
While there is currently no abundance estimate for the Mexico DPS, an 
estimated 3,477 whales from the Mexico DPS feed off the U.S. West Coast 
(Calambokidis and Barlow 2020; Curtis 2022). Based on this information, 
we estimate that approximately 30 percent of the humpback whales off 
the coast of California may be from the Central America DPS with the 
remaining 70 percent are expected to be from the Mexico DPS. Therefore, 
we anticipate that if a Navy vessel strike of a humpback whale were to 
occur within SOCAL, it would likely be from the Mexico DPS. Last, 
Rockwood et al. (2017) supports a relative likelihood of 1:1:2 for 
striking blue whales, humpback whales, and fin whales off the U.S West 
Coast (though as noted above, more recent data suggests that the 
relative likelihood of striking a fin whale is higher and suggests that 
the two 2021 U.S. Navy vessel strikes of unidentified large whales may 
have been fin whales), which, in consideration of more recent data also 
supports the proposed authorized take included in this rule, which is 
1, 1, and 4, respectively over the 7-year period. For these reasons, 
one lethal take of a Mainland Mexico-CA/OR/WA humpback whale (Mexico 
DPS) could occur and is proposed for authorization.
    For Hawaii stocks, given that all known vessel strikes between 2015 
and 2021 were of humpback whales, we anticipate that any vessel strike 
of a large whale in Hawaii would be of the Hawaii stock of humpback 
whale. Given that this stock has the highest percentage of total annual 
strikes (38.5 percent) and a 2.81 percent chance of being struck twice 
over the remaining 2.5 years (more than twice that of the species with 
the next highest percentage, gray whale), NMFS proposes to authorize 
two lethal takes of Hawaii humpback whales.
    As described above, the Navy's analysis suggests and NMFS' analysis 
concurs that the likelihood of vessel strikes to the stocks below is 
discountable due to the stocks' relatively low occurrence in the HSTT 
Study Area, particularly in core HSTT training and testing subareas, 
and the fact that the stocks have not been struck by the Navy and are 
rarely, if ever, recorded struck by other vessels. Therefore, NMFS is 
not proposing to authorize lethal take for the following stocks: Blue 
whale (Central North Pacific stock), Bryde's whale (Eastern Tropical 
Pacific stock and Hawaii stock), fin whale (Hawaii stock), gray whale 
(Western North Pacific stock), humpback whale (Central America/Southern 
Mexico-CA/OR/WA stock, Central America DPS), minke whale (CA/OR/WA 
stock and Hawaii stock), sei whale (Hawaii stock), and sperm

[[Page 68322]]

whale (CA/OR/WA stock and Hawaii stock).
    Also of note, while information on past Navy vessel strikes can 
serve as a reasonable indicator of future vessel strike risk, future 
conditions may differ from the past in ways that could influence the 
likelihood of a large whale vessel strike occurring. In general, the 
magnitude of vessel strike risk may be increasing over time as many 
whale populations are gradually recovering from centuries of commercial 
whaling (Redfern et al. 2020). Increased vessel strike risk off 
California in recent decades has been associated with increases in the 
abundance of fin and humpback whale populations in the North Pacific 
(Redfern et al. 2020). It has also been suggested that the blue whale 
population in the Eastern North Pacific, inclusive of the SOCAL portion 
of the action area, is at carrying capacity and recovered to pre-
whaling levels (Monnahan et al. 2014). In addition, the magnitude of 
risk may also be affected by shifts in whale distributions over time in 
response to environmental factors including climate change, marine 
heatwaves, and associated changes in prey distribution.
    Historically, military vessel strikes of large whales within the 
HSTT Study Area have been rare events with only seven such strikes 
occurring over the past 14 years, five U.S. Navy strikes, and two Royal 
Australian Navy strikes. However, the fact that four of these strikes 
occurred within a 3-month period (May-July) in 2021, and two occurred 
within a 4-month period (February-May) in 2009, suggests that military 
vessel strikes in SOCAL can be both highly episodic and clustered. The 
four large whale strikes in 2021 (two strikes of unidentified large 
whales by the U.S. Navy and two fin whale strikes by the Royal 
Australian Navy) appear to be outliers in the time series of military 
vessel strikes in SOCAL for that period. However, particularly in 
consideration of the 2023 U.S. Navy strike, these strikes could also 
represent an early indicator of an increased military vessel strike 
risk within SOCAL based on the factors discussed above. Results from a 
survey of whale watching vessel operators and crew in Southern 
California, combined with remote sensing data in the area, suggest that 
the number of large whales may have been greater in May through July of 
2021 compared with previous years in certain high military vessel 
traffic and ``core'' use HSTT areas off southern California, 
particularly farther offshore as well as closer to shore off San Diego 
Bay (Zickel MJ et al. 2021).
    In conclusion, while take by vessel strike across any given year is 
sporadic, based on the information and analysis above, including 
consideration of the 2021 and 2023 strikes by the U.S. Navy, NMFS 
anticipates no more than five takes of large whales by M/SI could occur 
over the 7-year period of the rule. Of those five whales over the 7-
years, no more than four may come from the following stocks: gray whale 
(Eastern North Pacific stock) and fin whale (CA/OR/WA stock). No more 
than two may come from the Hawaii stock of humpback whales. No more 
than one may come from the following stocks: blue whale (Eastern North 
Pacific stock), sei whale (Eastern North Pacific), and humpback whale 
(Mexico-North Pacific stock or Mainland Mexico-CA/OR/WA, Mexico DPS). 
Accordingly, NMFS has evaluated under the negligible impact standard 
the M/SI of 0.14, 0.29, or 0.57 whales annually from each of these 
species or stocks (i.e., 1, 2, or 4 takes, respectively, divided by 7 
years to get the annual number), along with the expected incidental 
takes by harassment.

Explosives

    The Navy's model and quantitative analysis process used for the 
2018 HSTT FEIS/OEIS and in the Navy's 2017 and 2019 applications to 
estimate potential exposures of marine mammals to explosive stressors 
is detailed in the technical report titled Quantifying Acoustic Impacts 
on Marine Mammals and Sea Turtles: Methods and Analytical Approach for 
Phase III Training and Testing report (U.S. Department of the Navy, 
2018). Specifically, over the course of a modeled maximum year of 
training and testing, the Navy's model and quantitative analysis 
process estimates M/SI of two short-beaked common dolphin and one 
California sea lion as a result of exposure to explosive training and 
testing activities (please see section 6 of the 2017 Navy application 
where it is explained how maximum annual estimates are calculated). 
Over the 7[hyphen]year period of the 2020 HSTT regulations, M/SI of 8 
short-beaked common dolphins and 5 California sea lions (13 marine 
mammals in total) is estimated as a result of exposure to explosive 
training and testing activities. NMFS proposes no changes to the 
authorization of take by M/SI as a result of explosive use as the Navy 
proposes no changes to its activities from that described in the 2018 
HSTT final rule, and after reviewing all new information, we find that 
our previous analyses remain applicable. Please refer to the 2018 HSTT 
final rule and 2020 HSTT final rule for additional information.

Proposed Mitigation Measures

    Under section 101(a)(5)(A) of the MMPA, NMFS must set forth the 
permissible methods of taking pursuant to the activity, and other means 
of effecting the least practicable adverse impact on the species or 
stock(s) and its habitat, paying particular attention to rookeries, 
mating grounds, and areas of similar significance, and on the 
availability of the species or stock(s) for subsistence uses (``least 
practicable adverse impact''). NMFS does not have a regulatory 
definition for least practicable adverse impact. The 2004 NDAA amended 
the MMPA as it relates to military readiness activities and the 
incidental take authorization process such that a determination of 
``least practicable adverse impact'' shall include consideration of 
personnel safety, practicality of implementation, and impact on the 
effectiveness of the military readiness activity. For the full 
discussion of how NMFS interprets least practicable adverse impact, 
including how it relates to the negligible-impact standard, see the 
Mitigation Measures section in the 2018 HSTT final rule.
    Section 101(a)(5)(A)(i)(II) requires NMFS to issue, in conjunction 
with its authorization, binding--and enforceable--restrictions (in the 
form of regulations) setting forth how the activity must be conducted, 
thus ensuring the activity has the ``least practicable adverse impact'' 
on the affected species or stocks. In situations where mitigation is 
specifically needed to reach a negligible impact determination, section 
101(a)(5)(A)(i)(II) also provides a mechanism for ensuring compliance 
with the ``negligible impact'' requirement. Finally, the least 
practicable adverse impact standard also requires consideration of 
measures for marine mammal habitat, with particular attention to 
rookeries, mating grounds, and other areas of similar significance, and 
for subsistence impacts, whereas the negligible impact standard is 
concerned solely with conclusions about the impact of an activity on 
annual rates of recruitment and survival.\1\ In evaluating what 
mitigation measures are appropriate, NMFS considers the potential 
impacts of the Specified Activities, the availability of measures to 
minimize those potential impacts, and the practicability of 
implementing those measures, as we

[[Page 68323]]

describe below. This proposed rule includes all mitigation measures 
required by the 2020 HSTT final rule (though two have been modified in 
this proposed rule), and our discussion in that rule remains complete 
and accurate (including reference to the 2018 HSTT final rule), except 
as described below.
---------------------------------------------------------------------------

    \1\ Outside of the military readiness context, mitigation may 
also be appropriate to ensure compliance with the ``small numbers'' 
language in MMPA sections 101(a)(5)(A) and (D).
---------------------------------------------------------------------------

Implementation of Least Practicable Adverse Impact Standard

    Our evaluation of potential mitigation measures includes 
consideration of two primary factors:
    (1) The manner in which, and the degree to which, implementation of 
the potential measure(s) is expected to reduce adverse impacts to 
marine mammal species or stocks, their habitat, and their availability 
for subsistence uses (where relevant). This analysis considers such 
things as the nature of the potential adverse impact (such as 
likelihood, scope, and range), the likelihood that the measure will be 
effective if implemented, and the likelihood of successful 
implementation; and
    (2) The practicability of the measure(s) for applicant 
implementation. Practicability of implementation may consider such 
things as cost, impact on activities, and, in the case of a military 
readiness activity, specifically considers personnel safety, 
practicality of implementation, and impact on the effectiveness of the 
military readiness activity.
    While the language of the least practicable adverse impact standard 
calls for minimizing impacts to affected species or stocks, we 
recognize that the reduction of impacts to those species or stocks 
accrues through the application of mitigation measures that limit 
impacts to individual animals. Accordingly, NMFS' analysis focuses on 
measures that are designed to avoid or minimize impacts on individual 
marine mammals that are likely to increase the probability or severity 
of population-level effects.
    While direct evidence of impacts to species or stocks from a 
specified activity is rarely available, and additional study is still 
needed to understand how specific disturbance events affect the fitness 
of individuals of certain species, there have been improvements in 
understanding the process by which disturbance effects are translated 
to the population. With recent scientific advancements (both marine 
mammal energetic research and the development of energetic frameworks), 
the relative likelihood or degree of impacts on species or stocks may 
often be inferred given a detailed understanding of the activity, the 
environment, and the affected species or stocks--and the best available 
science has been used here. This same information is used in the 
development of mitigation measures and helps us understand how 
mitigation measures contribute to lessening effects (or the risk 
thereof) to species or stocks. We also acknowledge that there is always 
the potential that new information, or a new recommendation could 
become available in the future and necessitate reevaluation of 
mitigation measures (which may be addressed through adaptive 
management) to see if further reductions of population impacts are 
possible and practicable.
    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, 
consideration of personnel safety, practicality of implementation, and 
consideration of the impact on effectiveness of military readiness 
activities 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 in terms of these considerations, can vary widely. 
For example, a time/area restriction could be of very high value for 
decreasing 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 Navy's ability to certify a strike group 
(higher impact on mission effectiveness), or it could mean delaying a 
small in-port training event by 30 minutes to avoid exposure of a 
marine mammal to injurious levels of sound (lower impact). A 
responsible evaluation of ``least practicable adverse impact'' will 
consider the factors along these realistic scales. 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 
its 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. 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 will be 
carefully considered to determine the types of mitigation that are 
appropriate under the least practicable adverse impact standard. For 
more detail on how we apply these factors, see the discussion in the 
Mitigation Measures section of the 2018 HSTT final rule.
Assessment of Mitigation Measures for HSTT Rule
    NMFS fully reviewed the Navy's specified activities and the 
mitigation measures for the 2020 HSTT final rule and determined, with 
the addition of the new and modified measures discussed herein, and 
after consideration of the new information and studies described above, 
that the proposed mitigation measures would result in the least 
practicable adverse impact on marine mammals (see the 2019 Navy 
application and the 2018 HSTT final rule for detailed information on 
the Navy's mitigation measures, with the exception of the new and 
modified measures described herein). NMFS worked with the Navy in the 
development of the Navy's mitigation measures, which were informed by 
years of implementation and monitoring. A complete discussion of the 
Navy's evaluation process used to develop, assess, and select 
mitigation measures, which was informed by input from NMFS, can be 
found in Chapter 5 (Mitigation) of the 2018 HSTT FEIS/OEIS. The process 
described in Chapter 5 (Mitigation) of the 2018 HSTT FEIS/OEIS robustly 
supports NMFS' independent evaluation of whether the mitigation 
measures would meet the least practicable adverse impact standard. The 
Navy has implemented the mitigation measures under the 2020 HSTT 
regulations and would be required to continue implementation of the 
mitigation measures identified in this rulemaking for the full 7 years 
it covers to avoid or reduce potential impacts from acoustic, 
explosive, and physical disturbance and vessel strike stressors.
    The Navy also evaluated numerous measures in the 2018 HSTT FEIS/
OEIS that were not included in the 2017 Navy application, and NMFS 
independently reviewed and considered all new information, and 
continues to concur with Navy's analysis that their inclusion

[[Page 68324]]

was not appropriate under the least practicable adverse impact 
standard. The Navy considered these additional potential mitigation 
measures in two groups. First, Chapter 5 (Mitigation) of the 2018 HSTT 
FEIS/OEIS, in the Measures Considered but Eliminated section, includes 
an analysis of an array of different types of mitigation that have been 
recommended over the years by NGOs or the public, through scoping or 
public comment on environmental compliance documents. Appendix K 
(Geographic Mitigation Assessment) of the 2018 HSTT FEIS/OEIS includes 
an in-depth analysis of time/area restrictions that have been 
recommended over time or previously implemented as a result of 
litigation.
    Below, we summarize the mitigation measures (organized into 
procedural measures and mitigation areas) that NMFS has determined will 
ensure the least practicable adverse impact on all affected species and 
stocks and their habitat, including the specific considerations for 
military readiness activities, and including several measures that are 
new or modified since publication of the 2020 HSTT final rule.
    In its 2022 application, the Navy proposed no changes to the 
procedural or geographic mitigation measures in the 2020 HSTT final 
rule. NMFS reviewed new information potentially pertinent to mitigation 
of the Navy's training and testing activities. While Lookouts are 
essential to detecting the potential for and potentially avoiding a 
vessel strike of a marine mammal, NMFS and the Navy have always 
acknowledged that Lookouts cannot prevent all vessel strikes. The 
recent U.S. Navy and Royal Australian Navy vessel strikes appear to 
confirm this, as these strikes occurred when Lookouts were posted. As 
acknowledged above, these recent incidents may represent an early 
indicator of an increased military vessel strike risk within SOCAL. 
Recent reports appear to reflect the sporadic, episodic, or clustered 
nature of vessel strike or may reflect a trend of increased large whale 
presence in this area in the early summer months. NMFS and Navy have 
discussed the circumstances of each of the recent strikes, including 
the Royal Australian Navy strike, and discussed ways of improving 
strike mitigation. In these further conversations, NMFS and the Navy 
developed several new and modified mitigation measures in comparison to 
those included in the 2020 HSTT final rule.
    For vessel movement, the 2020 HSTT final rule required that ``When 
underway Navy personnel must observe the mitigation zone for marine 
mammals; if marine mammals are observed, Navy personnel must maneuver 
to maintain distance.'' This measure has been updated to state that 
reducing speed may be an appropriate way to maneuver. The revised 
measure states that ``When underway, Navy personnel must observe the 
mitigation zone for marine mammals; if marine mammals are observed, 
Navy personnel must maneuver (which may include reducing speed as the 
mission or circumstances allow) to maintain distance.'' Of note, 
between 2009 and 2021 (the most recent year for which data is 
available), U.S. Navy vessels in the SOCAL portion of the HSTT Study 
Area maneuvered 316 times to avoid large whales during MTEs. The years 
2017 and 2021 had the highest number of maneuvers (n=64 and n=82, 
respectively). In all years for which data is available (2009 to 2021), 
Navy cruisers and destroyers account for 51 to 100 percent of maneuvers 
during MTEs. With this modified measure, NMFS is emphasizing that Navy 
personnel should consider reducing speed (as mission or circumstances 
allow) when maneuvering to avoid marine mammals, though this modified 
measure does not require reduction of vessel speed for reasons 
explained in Chapter 5 (Mitigation) of the 2018 HSTT FEIS/OEIS, in the 
Measures Considered but Eliminated section (i.e., requirements to 
reduce vessel speeds would have significant direct negative effects on 
mission effectiveness).
    This proposed rule also requires that Navy personnel must send 
alerts to Navy vessels of increased risk of strike following any 
reported Navy vessel strike in the HSTT Study Area.
    Further, the 2020 HSTT final rule included a requirement for Navy 
personnel to issue seasonal awareness notification messages to alert 
ships and aircraft to the possible presence of blue whales (June-
October), humpback whales (November-April), gray whales (November-
March), or fin whales (November-May). These messages assist in 
maintaining safety of navigation and in avoiding interactions with 
large whales during transits. Platforms must use the information from 
the awareness notification messages to assist their visual observation 
of applicable mitigation zones during training and testing activities 
and to aid in the implementation of procedural mitigation. This 
proposed rule requires the Navy to re-title the spring blue whale 
message (released in June) to a large whale awareness message inclusive 
of typical spring-summer large whales in southern California (mainly 
blue, fin, and humpback whales). Furthermore, rather than tying the 
message release to a specific month, the message would be for a period 
based on predicted oceanographic conditions for a given year (e.g., 
May-November, April-November, etc.). The Navy will also evaluate 
information obtained from NMFS' Southwest Fisheries Science Center 
scientists, soon to be promulgated revised West Coast BIAs, and other 
oceanographic or predictive models for guiding message text 
descriptions of whale occurrence in Southern California. The 
improvement will emphasize that when a marine mammal is spotted, this 
may be an indicator that additional marine mammals are present and 
nearby, and increased vigilance and awareness of Navy personnel is 
warranted.
    The proposed rule also contains a new mitigation measure in which 
Navy personnel would issue real-time notifications to Navy vessels of 
large whale aggregations (four or more whales) within 1 nmi (1.9 km) of 
a Navy vessel in a select area of SOCAL (Of note, the four whales do 
not have to be the same species and do not have to be part of the same 
group (e.g., two whales of one species sighted at a distance off the 
port side at 500 yd (457.2 m) and two more whales of another species 
sighted off the starboard side at 500 yd (457.2 m) would be considered 
an aggregation under this measure)). This measure would apply to the 
area between 32-33 degrees North and 117.2-119.5 degrees West, which 
includes the locations where recent (2009, 2021, 2023) strikes 
occurred, and historic locations where strikes occurred when precise 
latitude and longitude were known.
    Of note, in order to improve mitigation effectiveness, in fall 2022 
the Navy made several changes to its Lookout training. The Navy revised 
its basic Lookout training materials to improve marine mammal awareness 
and spotting techniques through updates to the Marine Mammal chapter of 
the Navy's September 2022 Lookout Training Handbook. Further, the Navy 
integrated improved Lookout training into a new generation of a 
shipboard simulator at its recruit training center in the Great Lakes. 
This simulator enhances new sailor knowledge and skill under realistic 
training scenarios. Last, the Navy will evaluate future revisions to 
online or DVD Marine Species Awareness Training video training to 
emphasize that when a protected species is spotted, this may be an 
indicator that additional marine mammals are present and nearby, and 
the vessel should take this into consideration when transiting.

[[Page 68325]]

    In addition to Lookouts required under this proposed rule, the Navy 
mandates the number of Lookouts on underway vessels per internal policy 
documents, including the Surface Ship NAVDORM. As described in the 
Standard Operating Procedures section, in 2021, NAVDORM policy changed 
to require three Lookouts on most classes of surface ship, including 
destroyers and cruisers. However, the Navy asserts that always 
including three Lookouts on these vessels in the future as a required 
mitigation measure is not practicable because lookout numbers are 
subject to change based on national security needs, including manning 
and staffing requirements. As such, although the Navy describes these 
additional Lookouts in its application under the mitigation section, 
NMFS has not considered the potential presence of two additional 
lookouts when considering Navy's mitigation effectiveness. Please see 
the Proposed Reporting section for additional detail on this proposed 
requirement.
    With the exception of Oedekoven and Thomas (2022) described above, 
there is no new information that affects NMFS' assessment of the 
applicability or effectiveness of the measures included in the 2018 
HSTT final rule over the remainder of the 7-year period. As stated 
above in the Potential Effects of Specified Activities on Marine 
Mammals and Their Habitat section, while (Oedekoven and Thomas, 2022) 
suggests that detection of marine mammals is less certain than 
previously assumed at certain distances, model assumptions may still 
underestimate Lookout effectiveness in some cases. Additionally, 
maneuvering data summarized above demonstrates that Navy vessels are 
successfully maneuvering to avoid striking sighted marine mammals in 
most cases, despite the Oedekoven and Thomas (2022) results. Further, 
as described above, Navy and NMFS have developed modified or new 
mitigation in this proposed rule which are anticipated to further 
reduce the risk of vessel strike of large whales.
    In summary, and as described in more detail above regarding vessel 
strike, the Navy has agreed to procedural mitigation measures that will 
reduce the probability and/or severity of impacts expected to result 
from acute exposure to acoustic sources or explosives, vessel strike, 
and impacts to marine mammal habitat. Specifically, the Navy will use a 
combination of delayed starts, powerdowns, and shutdowns to minimize or 
avoid M/SI and minimize the likelihood or severity of PTS or other 
injury, and reduce instances of TTS or more severe behavioral 
disturbance caused by acoustic sources or explosives. The Navy will 
also implement multiple time/area restrictions (several of which were 
added in the 2018 HSTT final rule since the previous HSTT MMPA 
incidental take rule) that would reduce take of marine mammals in areas 
or at times where they are known to engage in important behaviors, such 
as feeding or calving, where the disruption of those behaviors would 
have a higher probability of resulting in impacts on reproduction or 
survival of individuals that could lead to population-level impacts. 
Table 8 provides the Navy's required procedural mitigation measures for 
environmental awareness and education and vessel movement as well as 
summaries of the Navy's procedural mitigation measures for other 
activities. Table 9 provides summaries of mitigation areas for the HSTT 
Study Area.
    NMFS and the Navy considered mitigation areas to protect marine 
mammals, including odontocetes with small or resident populations in 
the HSTT Study Area. This included consideration of new mitigation 
areas based on newly identified BIAs in Hawaii (Kratofil et al. 2023). 
Including additional mitigation areas beyond that included in the 2020 
HSTT final rule is impracticable given overlap with critical Navy 
training areas in the HRC. However, many of the BIAs identified in 
Kratofil et al. 2023 partially or fully overlap the mitigation areas 
included in the 2020 HSTT final rule and proposed herein.

                Table 8--Summary of Procedural Mitigation
------------------------------------------------------------------------
                                         Mitigation zone sizes and other
          Stressor or activity                     requirements
------------------------------------------------------------------------
Environmental Awareness and Education..   This mitigation
                                          applies to all training and
                                          testing activities, as
                                          applicable.
                                          Mitigation
                                          Requirements:
                                            [cir] Appropriate Navy
                                             personnel (including
                                             civilian personnel)
                                             involved in mitigation and
                                             training or testing
                                             activity reporting under
                                             the specific activities
                                             must complete one or more
                                             modules of the U.S. Navy
                                             Afloat Environmental
                                             Compliance Training Series,
                                             as identified in their
                                             career path training plan.
                                             Modules include:
                                              [ssquf] Introduction to
                                               the U.S. Navy Afloat
                                               Environmental Compliance
                                               Training Series. The
                                               introductory module
                                               provides information on
                                               environmental laws (e.g.,
                                               ESA, MMPA) and the
                                               corresponding
                                               responsibilities that are
                                               relevant to Navy training
                                               and testing activities.
                                               The material explains why
                                               environmental compliance
                                               is important in
                                               supporting the Navy's
                                               commitment to
                                               environmental
                                               stewardship.
                                              [ssquf] Marine Species
                                               Awareness Training. All
                                               bridge watch personnel,
                                               Commanding Officers,
                                               Executive Officers,
                                               maritime patrol aircraft
                                               aircrews,
                                               anti[hyphen]submarine
                                               warfare and mine warfare
                                               rotary-wing aircrews,
                                               Lookouts, and equivalent
                                               civilian personnel must
                                               successfully complete the
                                               Marine Species Awareness
                                               Training prior to
                                               standing watch or serving
                                               as a Lookout. The Marine
                                               Species Awareness
                                               Training provides
                                               information on sighting
                                               cues, visual observation
                                               tools and techniques, and
                                               sighting notification
                                               procedures. Navy
                                               biologists developed
                                               Marine Species Awareness
                                               Training to improve the
                                               effectiveness of visual
                                               observations for
                                               biological resources,
                                               focusing on marine
                                               mammals and sea turtles,
                                               and including floating
                                               vegetation, jellyfish
                                               aggregations, and flocks
                                               of seabirds.
                                              [ssquf] U.S. Navy
                                               Protective Measures
                                               Assessment Protocol. This
                                               module provides the
                                               necessary instruction for
                                               accessing mitigation
                                               requirements during the
                                               event planning phase
                                               using the Protective
                                               Measures Assessment
                                               Protocol software tool.
                                              [ssquf] U.S. Navy Sonar
                                               Positional Reporting
                                               System and Marine Mammal
                                               Incident Reporting. This
                                               module provides
                                               instruction on the
                                               procedures and activity
                                               reporting requirements
                                               for the Sonar Positional
                                               Reporting System and
                                               marine mammal incident
                                               reporting.
Active Sonar...........................  Depending on sonar source:

[[Page 68326]]

 
                                             1,000 yd (914.4 m)
                                             power down, 500 yd (457.2
                                             m) power down, and 200 yd
                                             (182.9 m) shut down
                                             200 yd (182.9 m)
                                             shut down.
Air Guns...............................   150 yd (137.2 m).
Pile Driving...........................   100 yd (91.4 m).
Weapons Firing Noise...................   30 degrees on either
                                          side of the firing line out to
                                          70 yd (64 m).
Explosive Sonobuoys....................   600 yd (548.6 m).
Explosive Torpedoes....................   2,100 yd (1,920.2 m).
Explosive Medium-Caliber and Large-       1,000 yd (914.4 m;
 Caliber Projectiles.                     large-caliber projectiles).
                                          600 yd (548.6 m;
                                          medium-caliber projectiles
                                          during surface-to-surface
                                          activities).
                                          200 yd (182.9 m;
                                          medium-caliber projectiles
                                          during air-to-surface
                                          activities).
Explosive Missiles and Rockets.........   2,000 yd (1,828.8 m;
                                          21-500 lb. net explosive
                                          weight).
                                          900 yd (823 m; 0.6-20
                                          lb. net explosive weight).
Explosive Bombs........................   2,500 yd (2,286 m).
Sinking Exercises......................   2.5 nmi (4.6 km).
Explosive Mine Countermeasure and         2,100 yd (1,929.2 m; 6-
 Neutralization Activities.               650 lb net explosive weight).
                                          600 yd (548.6 m; 0.1-5
                                          lb net explosive weight).
Explosive Mine Neutralization             1,000 yd (914.4 m; 21-
 Activities Involving Navy Divers.        60 lb net explosive weight for
                                          positive control charges and
                                          charges using time-delay
                                          fuses).
                                          500 yd (457.2 m; 0.1-
                                          20 lb net explosive weight for
                                          positive control charges).
Underwater Demolition Multiple Charge--   700 yd (640.1 m).
 Mat Weave and Obstacle Loading.
Maritime Security Operations--Anti-       200 yd (182.9 m).
 Swimmer Grenades.
Vessel Movement........................   The mitigation must
                                          not be applied if: (1) The
                                          vessel's safety is threatened,
                                          (2) the vessel is restricted
                                          in its ability to maneuver
                                          (e.g., during launching and
                                          recovery of aircraft or
                                          landing craft, during towing
                                          activities, when mooring), (3)
                                          the vessel is operated
                                          autonomously, or (4) when
                                          impractical based on mission
                                          requirements (e.g., during
                                          Amphibious Assault--Battalion
                                          Landing exercises).
                                          Number of Lookouts and
                                          Observation Platform:
                                            [cir] 1 Lookout must be on
                                             the vessel that is
                                             underway.\1\
                                          Mitigation
                                          Requirements:
                                            [cir] Mitigation zones:--500
                                             yd (457.2 m) around
                                             whales.--200 yd (182.9 m)
                                             around other marine mammals
                                             (except bow-riding dolphins
                                             and pinnipeds hauled out on
                                             man-made navigational
                                             structures, port
                                             structures, and vessels).
                                            [cir] During the activity:--
                                             When underway, Navy
                                             personnel must observe the
                                             mitigation zone for marine
                                             mammals; if marine mammals
                                             are observed, Navy
                                             personnel must maneuver
                                             (which may include reducing
                                             speed as the mission or
                                             circumstances allow) to
                                             maintain distance.
                                          Additional
                                          requirements:
                                            [cir] If a marine mammal
                                             vessel strike occurs, Navy
                                             personnel must follow the
                                             established incident
                                             reporting procedures. Navy
                                             personnel must also send
                                             alerts to Navy vessels of
                                             increased risk of strike
                                             following any reported Navy
                                             vessel strike in the HSTT
                                             Study Area.
                                            [cir] Navy personnel must
                                             issue real-time
                                             notifications to Navy
                                             vessels of large whale
                                             aggregations (four or more
                                             whales) within 1 nmi (1.9
                                             km) of a Navy vessel in the
                                             area between 32-33 degrees
                                             North and 117.2-119.5
                                             degrees West.
Towed In-Water Devices.................   250 yd (228.6 m;
                                          marine mammals).
Small-, Medium-, and Large-Caliber Non-   200 yd (182.9 m).
 Explosive Practice Munitions.
Non-Explosive Missiles and Rockets.....   900 yd (823 m).
Non-Explosive Bombs and Mine Shapes....   1,000 yd (914.4 m).
------------------------------------------------------------------------
Note: lb: pounds; nmi: nautical miles; yd: yards; m: meters.
\1\ Underway vessels will maintain at least one Lookout. For ship
  classes required to maintain more than one Lookout, the specific
  requirement is subject to change over time in accordance with Navy
  navigation instruction (e.g., the Surface Ship NAVDORM). Navy
  personnel will notify NMFS as soon as practicable should its Lookout
  policies change, including in the NAVDORM.


         Table 9--Summary of Mitigation Areas for Marine Mammals
------------------------------------------------------------------------
                 Summary of mitigation area requirements
-------------------------------------------------------------------------
Hawaii Island Mitigation Area (year-round):
     Navy personnel must not conduct more than 300 hours of MF1
     surface ship hull-mounted mid-frequency active sonar or 20 hours of
     MF4 dipping sonar, or use explosives that could potentially result
     in takes of marine mammals during training and testing.\1\
4-Islands Region Mitigation Area (November 15-April 15 for active sonar;
 year-round for explosives):
     Navy personnel must not use MF1 surface ship hull-mounted
     mid-frequency active sonar or explosives that could potentially
     result in takes of marine mammals during training and testing.\1\
Humpback Whale Special Reporting Areas (December 15-April 15):
     Navy personnel must report the total hours of surface ship
     hull-mounted mid-frequency active sonar used in the special
     reporting areas in its annual training and testing activity reports
     submitted to NMFS.
San Diego Arc, San Nicolas Island, and Santa Monica/Long Beach
 Mitigation Areas (June 1-October 31):
     Navy personnel must not conduct more than a total of 200
     hours of MF1 surface ship hull-mounted mid-frequency active sonar
     in the combined areas, excluding normal maintenance and systems
     checks, during training and testing.\1\
     Within the San Diego Arc Mitigation Area, Navy personnel
     must not use explosives that could potentially result in the take
     of marine mammals during large-caliber gunnery, torpedo, bombing,
     and missile (including 2.75'' rockets) activities during training
     and testing.\1\
     Within the San Nicolas Island Mitigation Area, Navy
     personnel must not use explosives that could potentially result in
     the take of marine mammals during mine warfare, large-caliber
     gunnery, torpedo, bombing, and missile (including 2.75'' rockets)
     activities during training.\1\
     Within the Santa Monica/Long Beach Mitigation Area, Navy
     personnel must not use explosives that could potentially result in
     the take of marine mammals during mine warfare, large-caliber
     gunnery, torpedo, bombing, and missile (including 2.75'' rockets)
     activities during training and testing.\1\
Santa Barbara Island Mitigation Area (year-round):

[[Page 68327]]

 
     Navy personnel must not use MF1 surface ship hull-mounted
     mid-frequency active sonar during training and testing, or
     explosives that could potentially result in the take of marine
     mammals during medium-caliber or large-caliber gunnery, torpedo,
     bombing, and missile (including 2.75'' rockets) activities during
     training.\1\
Awareness Notification Message Areas (seasonal according to species):
     Navy personnel must issue awareness notification messages
     to alert ships and aircraft to the possible presence of large
     whales during a period based on predicted oceanographic conditions
     for a given year. The message must emphasize that when a marine
     mammal is spotted, this may be an indicator that additional marine
     mammals are present and nearby, and increased vigilance and
     awareness of Navy personnel is warranted. Navy personnel must also
     issue awareness notification messages to alert ships and aircraft
     to the possible presence of gray whales (November-March) and fin
     whales (November-May).
------------------------------------------------------------------------
\1\ If Naval units need to conduct more than the specified amount of
  training or testing, they will obtain permission from the appropriate
  designated Command authority prior to commencement of the activity.
  The Navy will provide NMFS with advance notification and include the
  information in its annual activity reports submitted to NMFS.

Mitigation Conclusions

    NMFS has carefully evaluated the Navy's mitigation measures from 
the 2020 rule--many of which were developed with NMFS' input during the 
previous phases of Navy training and testing authorizations and none of 
which have changed since our evaluation during the 2018 HSTT 
rulemaking, with the exception of the changes described herein--and 
considered a broad range of other measures (i.e., the measures 
considered but eliminated in the 2018 HSTT FEIS/OEIS, which reflect 
many of the comments that have arisen via NMFS or public input in past 
years) in the context of ensuring that NMFS prescribes the means of 
effecting the least practicable adverse impact on the affected marine 
mammal species and stocks and their habitat. Our evaluation of 
potential measures included consideration of the following factors in 
relation to one another: the manner in which, and the degree to which, 
the successful implementation of the mitigation measures is expected to 
reduce the likelihood and/or magnitude of adverse impacts to marine 
mammal species and stocks and their habitat; the proven or likely 
efficacy of the measures; and the practicability of the measures for 
applicant implementation, including consideration of personnel safety, 
practicality of implementation, and impact on the effectiveness of the 
military readiness activity. After considering all new information, 
including consideration of new information regarding vessel strike, 
NMFS proposes two additional mitigation measures and revision of two 
existing mitigation measures as described above.
    Based on our evaluation of the Navy's current mitigation measures 
(which are being implemented under the 2020 HSTT regulations), as well 
as modified and new measures described above, NMFS has preliminarily 
determined that the proposed mitigation measures are appropriate means 
of effecting the least practicable adverse impact on marine mammal 
species or stocks and their habitat, paying particular attention to 
rookeries, mating grounds, and areas of similar significance, and 
considering specifically personnel safety, practicality of 
implementation, and impact on the effectiveness of the military 
readiness activity. Additionally, as described in more detail below, 
the 2020 HSTT final rule includes an adaptive management provision, 
which the Navy proposes to extend, which ensures that mitigation is 
regularly assessed and provides a mechanism to improve the mitigation, 
based on the factors above, through modification as appropriate.
    The proposed rule comment period provides the public an opportunity 
to submit recommendations, views, and/or concerns regarding the Navy's 
activities and the proposed mitigation measures. While NMFS has 
preliminarily determined that the proposed mitigation measures would 
effect the least practicable adverse impact on the affected species or 
stocks and their habitat, NMFS will consider all public comments to 
help inform our final decision. Consequently, the proposed mitigation 
measures may be refined, modified, removed, or added to prior to the 
issuance of the final rule based on public comments received, and where 
appropriate, further analysis of any additional mitigation measures.

Proposed Monitoring

    Section 101(a)(5)(A) of the MMPA states that in order to authorize 
incidental take for an activity, NMFS must set forth requirements 
pertaining to the monitoring and reporting of such taking. The MMPA 
implementing regulations at 50 CFR 216.104(a)(13) indicate that 
requests for incidental take authorizations must include the suggested 
means of accomplishing the necessary monitoring and reporting that will 
result in increased knowledge of the species and of the level of taking 
or impacts on populations of marine mammals that are expected to be 
present.
    In its 2022 application, the Navy proposes no changes to the 
monitoring described in the 2018 HSTT final rule and 2020 HSTT final 
rule. They would continue implementation of the robust Integrated 
Comprehensive Monitoring Program and Strategic Planning Process 
described in the 2018 HSTT final rule. The Navy's monitoring strategy, 
currently required by the 2018 HSTT regulations, is well-designed to 
work across Navy ranges to help better understand the impacts of the 
Navy's activities on marine mammals and their habitat by focusing on 
learning more about marine mammal occurrence in different areas and 
exposure to Navy stressors, marine mammal responses to different sound 
sources, and the consequences of those exposures and responses on 
marine mammal populations. Similarly, these proposed modified 
regulations would include identical adaptive management provisions and 
reporting requirements as the 2018 HSTT regulations. There is no new 
information that would indicate that the monitoring measures put in 
place under the 2018 HSTT final rule would not remain applicable and 
appropriate for the 7-year period of this proposed rule. See the 
Monitoring section of the 2018 HSTT final rule for more details on the 
monitoring program that would be required under this rule. In addition, 
please see the 2019 Navy application, which references Chapter 13 of 
the 2017 Navy application for full details on the monitoring and 
reporting proposed by the Navy.
    Within the SOCAL portion of HSTT, the Navy has been primarily 
focused on beaked whale monitoring since 2018 through two separate 
ongoing projects that are expected to continue until 2025. These 
projects use passive acoustic devices, visual surveys, satellite 
tagging, genetic analysis, photoID, and response to anthropogenic 
sounds to refine population status of beaked whales in SOCAL. There is 
also one concurrent project with fin whales using visual surveys, 
satellite tagging, and photoID to gather additional data on fin whale

[[Page 68328]]

populations in Southern California. Finally, the Navy continues to fund 
marine mammal sighting data collected during California Cooperative 
Oceanic Fisheries Investigations (CALCOFI) https://calcofi.org/. These 
data are collected on a much more frequent basis than NMFS' West Coast 
visual survey which typically occur once every 5 years in the summer. 
CALCOFI surveys occur quarterly every year to include winter and spring 
seasons NMFS does not survey. Sufficient marine mammal sightings have 
been accumulated since the Navy started funding in 2004 for the data to 
be incorporated into ongoing NMFS spatial habitat models, including new 
models for select species. The Navy also annually funds continued NMFS 
spatial habitat model improvements as new data and techniques become 
available. These models benefit the Navy and other Federal partners 
such as the Bureau of Ocean Energy Management and NMFS, for use in 
future regional marine mammal density derivation. For additional 
information, please see the Navy's Marine Species Monitoring program 
website, https://www.navymarinespeciesmonitoring.us/regions/pacific/current-projects/.

Adaptive Management

    The 2020 HSTT regulations governing the take of marine mammals 
incidental to Navy training and testing activities in the HSTT Study 
Area contain an adaptive management component. Our understanding of the 
effects of Navy training and testing activities (e.g., acoustic and 
explosive stressors) on marine mammals continues to evolve, which makes 
the inclusion of an adaptive management component both valuable and 
necessary within the context of 7-year regulations. The 2022 Navy 
application proposes no changes to the adaptive management component 
included in the 2020 HSTT final rule.
    The reporting requirements associated with this rule are designed 
to provide NMFS with monitoring data from the previous year to allow 
NMFS to consider whether any changes to existing mitigation and 
monitoring requirements are appropriate. The use of adaptive management 
allows NMFS to consider new information from different sources to 
determine (with input from the Navy regarding practicability) on an 
annual or biennial basis if mitigation or monitoring measures should be 
modified (including additions or deletions). Mitigation measures could 
be modified if new data suggests that such modifications would have a 
reasonable likelihood of more effectively accomplishing the goals of 
the mitigation and monitoring and if the measures are practicable. If 
the modifications to the mitigation, monitoring, or reporting measures 
are substantial, NMFS will publish a notice of the planned LOA in the 
Federal Register and solicit public comment.
    The following are some of the possible sources of applicable data 
to be considered through the adaptive management process: (1) results 
from monitoring and exercises reports, as required by MMPA 
authorizations; (2) compiled results of Navy funded R&D studies; (3) 
results from specific stranding investigations; (4) results from 
general marine mammal and sound research; and (5) any information which 
reveals that marine mammals may have been taken in a manner, extent, or 
number not authorized by these regulations or subsequent LOAs. The 
results from monitoring reports and other studies may be viewed at 
https://www.navymarinespeciesmonitoring.us.

Proposed Reporting

    In order to issue incidental take authorization for an activity, 
section 101(a)(5)(A) of the MMPA states that NMFS must set forth 
requirements pertaining to the monitoring and reporting of such taking. 
Effective reporting is critical both to compliance as well as ensuring 
that the most value is obtained from the required monitoring. Reports 
from individual monitoring events, results of analyses, publications, 
and periodic progress reports for specific monitoring projects will be 
posted to the Navy's Marine Species Monitoring web portal: http://www.navymarinespeciesmonitoring.us. The 2019 Navy application and 2022 
Navy application proposed no changes to the reporting requirements, 
though as noted above, the Navy has since proposed to report changes to 
Lookout SOPs to NMFS. Except as discussed below, reporting requirements 
would remain identical to those described in the 2018 HSTT final rule 
and 2020 HSTT final rule, and there is no new information that would 
indicate that the reporting requirements put in place under the 2020 
HSTT final rule would not remain applicable and appropriate for the 
remaining duration of the 7-year period of this proposed rule. See the 
Reporting section of the 2018 HSTT final rule for more details on the 
reporting that would be required under this rulemaking. In addition, 
the 2018 HSTT proposed and final rules unintentionally failed to 
include the requirement for the Navy to submit a final activity ``close 
out'' report at the end of the regulatory period. That oversight was 
corrected through the 2020 HSTT final rule. Please see the 2020 HSTT 
final rule for the detailed requirements for that report.
    In addition to the reporting requirements included in the 2020 HSTT 
final rule, the Navy must report changes in its Lookout policies to 
NMFS as soon as practicable after a change is made.

Preliminary Analysis and Negligible Impact Determination

    NMFS has defined negligible impact as an impact resulting from the 
specified activity that cannot be reasonably expected to, and is not 
reasonably likely to, adversely affect the species or stock through 
effects on annual rates of recruitment or survival (50 CFR 216.103). A 
negligible impact finding is based on the lack of likely adverse 
effects on annual rates of recruitment or survival (i.e., population-
level effects). While this proposed rule consists of a modification of 
take by M/SI by vessel strike, NMFS considers the impacts of the entire 
specified activity and the total taking in the negligible impact 
determination. An estimate of the number of takes alone is not enough 
information on which to base an impact determination. In addition to 
considering estimates of the number of marine mammals that might be 
taken through mortality, serious injury, and Level A or Level B 
harassment (as presented in tables 11 and 12 of the 2020 HSTT final 
rule), NMFS considers other factors, such as the likely nature of any 
responses (e.g., intensity, duration), the context of any responses 
(e.g., critical reproductive time or location, migration), as well as 
effects on habitat, and the likely effectiveness of the mitigation. We 
also assess the number, intensity, and context of estimated takes by 
evaluating this information relative to population status. Consistent 
with the 1989 preamble for NMFS' implementing regulations (54 FR 40338; 
September 29, 1989), the impacts from other past and ongoing 
anthropogenic activities (including foreign military activities) are 
incorporated into this analysis via their impacts on the environmental 
baseline (e.g., as reflected in the regulatory status of the species, 
population size and growth rate where known, other ongoing sources of 
human-caused mortality, ambient noise levels, and specific 
consideration of take by Level A harassment or M/SI previously 
authorized for other NMFS activities).
    In the Estimated Take of Marine Mammals sections of this proposed 
rule and the 2020 HSTT final rule (where the activities, species and 
stocks, potential effects, and mitigation measures are the same as for 
this rulemaking), we

[[Page 68329]]

identified the subset of potential effects that would be expected to 
rise to the level of takes both annually and over the 7-year period 
covered by this rulemaking and then identified the number of each of 
those mortality takes that we believe could occur or the maximum number 
of harassment takes that are reasonably expected to occur based on the 
methods described. The impact that any given take will have is 
dependent on many case-specific factors that need to be considered in 
the negligible impact analysis (e.g., the context of behavioral 
exposures such as duration or intensity of a disturbance, the health of 
impacted animals, the status of a species that incurs fitness-level 
impacts to individuals, etc.). For this proposed rule, we evaluated the 
likely impacts of the enumerated maximum number of harassment takes 
that are reasonably expected to occur and proposed for authorization, 
in the context of the specific circumstances surrounding these 
predicted takes. We also assessed M/SI takes that could occur, as well 
as considering the traits and statuses of the affected species and 
stocks. Last, we collectively evaluated this information, as well as 
other more taxa-specific information and mitigation measure 
effectiveness, in group-specific assessments that support our 
negligible impact conclusions for each stock or species. Because all of 
the Navy's specified activities would occur within the ranges of the 
marine mammal stocks identified in the rule, all negligible impact 
analyses and determinations are at the stock level (i.e., additional 
species-level determinations are not needed).
    The Navy proposes no changes to the nature or level of the 
specified activities or the boundaries of the HSTT Study Area, and 
therefore, the training and testing activities (e.g., equipment and 
sources used, exercises conducted) are the same as those analyzed in 
the 2020 HSTT final rule. In addition, the mitigation, monitoring, and 
nearly all reporting measures are identical to those described and 
analyzed in the 2018 HSTT final rule with the exception of changes to 
mitigation measures described previously and the additional reporting 
requirement for Navy to report changes in its Lookout policies to NMFS 
as soon as practicable after a change is made. There is no new 
information since the publication of the 2020 HSTT final rule regarding 
the impacts of the specified activities on marine mammals, the status 
and distribution of any of the affected marine mammal species or 
stocks, or the effectiveness of the mitigation and monitoring measures 
that would change the content of our analyses, with the exception of 
that described below. First, naval vessel strikes have occurred in the 
HSTT and Atlantic Fleet Training and Testing (AFTT) Study Areas since 
publication of the 2020 HSTT final rule (one fin or sei whale struck by 
the U.S. Navy in the HSTT Study Area (2023), two unidentified large 
whales struck by the U.S. Navy in the HSTT Study Area (2021), two fin 
whales struck by a foreign navy in the HSTT Study Area (2021), and one 
dolphin struck by the U.S. Navy in the AFTT Study Area (2021)). Second, 
for gray whales, we have considered the latest effects of the UME on 
the west coast of North America along with the effects of the Navy's 
activities in the negligible impact analysis. Third, a new study 
suggests that Lookout detection of marine mammals is less certain than 
previously assumed (Oedekoven and Thomas, 2022). Fourth, stock 
assessments have been updated for multiple stocks in the 2022 Pacific 
and Alaska SARs (Carretta et al. 2023; Young et al. 2023).
    As described above and in the 2022 Navy application, a number of 
additional studies have been published, including several studies 
associated with TTS in harbor porpoises and seals (e.g., Kastelein et 
al. 2020d; Kastelein et al. 2021a and 2021b; Sills et al. 2020). NMFS 
is aware of these recent papers and is currently working with the Navy 
to update NMFS' Technical Guidance for Assessing the Effects of 
Anthropogenic Sound on Marine Mammal Hearing Version 2.0 (Acoustic 
Technical Guidance; NMFS 2018) to reflect relevant papers that have 
been published since the 2018 update on our 3-5 year update schedule in 
the Acoustic Technical Guidance. We note that the recent peer-reviewed, 
updated marine mammal noise exposure criteria by Southall et al. (2019) 
provide identical PTS and TTS thresholds and weighting functions to 
those provided in NMFS' Acoustic Technical Guidance. NMFS will continue 
to review and evaluate new relevant data as it becomes available and 
consider the impacts of those studies on the Acoustic Technical 
Guidance to determine what revisions/updates may be appropriate. 
However, any such revisions must undergo peer and public review before 
being adopted, as described in the Acoustic Guidance methodology. While 
some of the relevant data may potentially suggest changes to TTS/PTS 
thresholds for some species, any such changes would not be expected to 
change the predicted take estimates in a manner that would change the 
necessary determinations supporting the issuance of these regulations, 
and the data and values used in this rulemaking reflect the best 
available science.

Harassment

    As described in the Estimated Takes of Marine Mammals section, the 
annual number of takes proposed for authorization and reasonably 
expected to occur by Level A harassment and Level B harassment (based 
on the maximum number of activities per 12-month period) are identical 
to those presented in tables 41 and 42 in the Take Requests section of 
the 2018 HSTT final rule, with the exception of humpback whale, which 
are presented in tables 2 and 3 herein. As such, the negligible impact 
analyses and determinations of the effects of the estimated Level A 
harassment and Level B harassment takes on annual rates of recruitment 
or survival for each species and stock are nearly identical to and 
substantively unchanged from those presented in the 2020 HSTT final 
rule. The differences in the analysis is our removal of consideration 
of California Sea Lion UME, which has been closed since publication of 
the 2020 HSTT final rule, and incorporation of the revised stock 
structure for humpback whales. This does not affect the results of the 
analyses or our determinations. For detailed discussion of the impacts 
that affected individuals may experience given the specific 
characteristics of the specified activities and required mitigation 
(e.g., from behavioral disruption, masking, and temporary or permanent 
threshold shift), along with the effects of the expected Level A 
harassment and Level B harassment take on reproduction and survival, 
see the applicable subsections in the Analysis and Negligible Impact 
Determination section of the 2018 HSTT final rule (83 FR 66977-67018; 
also incorporated by reference in the 2020 HSTT final rule).

Serious Injury or Mortality

    Based on the information and methods discussed in the Estimated 
Take of Marine Mammals section (which are identical to those used in 
the 2018 HSTT final rule for explosives and revised for vessel strike), 
NMFS is proposing to authorize five mortalities of large whales due to 
vessel strike over the 7-year period of this rulemaking, two more 
strikes than what was authorized in the 2018 HSTT final rule and 2020 
HSTT final rule. Across the 7-year duration of the rule, take of an 
annual average of 0.57 gray whales (Eastern North Pacific stock) and 
fin

[[Page 68330]]

whales (CA/OR/WA stock), an annual average of 0.29 humpback whales 
(Hawaii stock) and an annual average of 0.14 blue whales (Eastern North 
Pacific stock), sei whales (Eastern North Pacific stock) and humpback 
whales (Mainland Mexico-CA/OR/WA stock, Mexico DPS), as described in 
table 8 (i.e., one, two, or four take(s) over 7 years divided by seven 
to get the annual number) could occur and are proposed for 
authorization.

                                                        Table 10--Summary Information Related to Mortalities Requested for Vessel Strike
                                                                                           [2018-2025]
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
                                                   Annual
                                                 authorized                                                                            Residual
                                        Stock      take by     Total     Fisheries interactions     Annual rate of M/SI    Potential   PBR (PBR                              Recent UME (Y/N);
          Species (stock)             abundance    serious   annual M/  (Y/N); annual rate of M/   from vessel collision  biological     minus       Stock trend * \4\    number and year (since
                                      (Nbest) *   injury or   SI * \2\      SI from fisheries                *              removal    annual M/                                   2007)
                                                  mortality                  interactions *                                 (PBR) *     SI) \3\
                                                     \1\
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Fin whale (CA/OR/WA stock).........      11,065        0.57     >=43.6  Y; >=0.64...............  Y, 43.................          80        36.4  [uarr]................  N.
Gray whale (Eastern North Pacific        26,960        0.57        131  Y, 9.3..................  Y, 1.8................         801         670  \5\ [uarr]............  Y; 674; 2019 (as of
 stock).                                                                                                                                                                   June 25, 2023).
Humpback whale (Mainland Mexico-CA/       3,477        0.14         22  Y; 11.4.................  Y, 10.15..............          65      \6\ 43  Unknown...............  N.
 OR/WA stock, Mexico DPS).
Humpback whale (Hawaii stock)......      11,278        0.29      27.09  Y; 8.39.................  \7\ Y, 10.59..........         127       99.91  Unknown...............  Y; 2015; 52.]
Blue whale (Eastern North Pacific         1,898        0.14     >=19.5  Y; >=1.54...............  Y, 0.8................         4.1       -15.4  Unknown...............  Y; 3, 2007.
 Stock).
Sei whale (Eastern North Pacific            519        0.14      >=0.2  N; 0....................  Y, 0.2................        0.75        0.55  Unknown...............  N.
 Stock).
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
* Presented in the 2022 final SARs.
\1\ This column represents the annual take by serious injury or mortality (M/SI) by vessel collision and was calculated by the number of mortalities proposed for authorization divided by 7
  years (the length of the rule and LOAs).
\2\ This column represents the total number of incidents of M/SI that could potentially accrue to the specified species or stock. This number comes from the SAR, but deducts the takes accrued
  from either Navy strikes or NMFS' Southwest Fisheries Science Center (SWFSC) takes in the SARs to ensure not double-counted against PBR. However, for these species, there were no takes from
  either other Navy activities or SWFSC in the SARs to deduct that would be considered double-counting.
\3\ This value represents the calculated PBR less the average annual estimate of ongoing anthropogenic mortalities (i.e., total annual human-caused M/SI, which is presented in the SARs).
\4\ See relevant SARs for more information regarding stock status and trends.
\5\ The Pacific 2022 SAR indicates that the stock trend is increasing. However, recent (2021-2022) surveys conducted by NMFS' Southwest Fisheries Science Center estimated that the population
  has declined to 16,650 whales, though the authors note that this stock has historically shown a pattern of population growth and decline that has not impacted the population in the long term
  (Eguchi et al. 2022).
\6\ Vessel strike of the Mainland Mexico-CA/OR/WA stock was calculated by applying a prorated portion of humpback whale strikes modeled by Rockwood et al. (2017) to this stock.
\7\ For this stock, PBR is currently set at 43 for U.S. waters and 65 for the stock's entire range. As the HSTT Study Area extends beyond U.S. waters and activities have the potential to
  impact the entire stock, we present the analysis using the PBR for the stock's entire range.
\8\ Annual vessel strike for this stock reported in the 2022 final SAR was calculated by summing vessel strike data from Hawaii, Alaska, and Washington. All observed strikes in Hawaii were
  assigned to the Hawaii stock, and a portion of observed strikes in Alaska were assigned to the Hawaii stock. Vessel strike of the Hawaii stock in Washington waters was calculated by applying
  a prorated portion of humpback whale strikes modeled by Rockwood et al. (2017) to the Hawaii stock.

    The Navy also requested a small number of takes by M/SI from 
explosives in the 2017 Navy application. To calculate the annual 
average of mortalities for explosives in table 11, we used the same 
method as described for vessel strikes. The annual average is the total 
number of takes over 7 years divided by seven. Specifically, NMFS is 
proposing to authorize the following M/SI takes from explosives: five 
California sea lions and eight short-beaked common dolphins over the 7-
year period (therefore 0.71 mortalities annually for California sea 
lions and 1.14 mortalities annually for short-beaked common dolphin), 
as described in table 11. As this annual number is the same as that 
analyzed and authorized in the 2020 HSTT final rule, and no other 
relevant information about the status, abundance, or effects of 
mortality on each species or stock has changed, the analysis of the 
effects of explosives is identical to that presented in the 2020 HSTT 
final rule.

                                          Table 11--Summary Information Related to Mortalities From Explosives
                                                                       [2018-2025]
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                               Annual
                                             authorized                   Fisheries                    SWFSC       Residual
                                    Stock      take by     Total     interactions (Y/N);             authorized    PBR--PBR                  UME (Y/N);
        Species (stock)           abundance    serious   annual M/   annual rate of M/SI    PBR *       take        minus        Stock       number and
                                  (Nbest) *   injury or   SI* \2\      from fisheries                 (annual)   annual M/SI   trend* \5\       year
                                              mortality                interactions *                   \3\       and SWFSC
                                                 \1\                                                                 \4\
--------------------------------------------------------------------------------------------------------------------------------------------------------
California sea lion (U.S.           257,606        0.71      >=321  Y; >=197............    14,011            6       13,684      [uarr]   N
 stock).
Short-beaked common dolphin (CA/  1,056,308        1.14     >=30.5  Y; >=30.5...........     8,889          2.8      8,855.7           ?   N
 OR/WA stock).
--------------------------------------------------------------------------------------------------------------------------------------------------------
* Presented in the 2022 draft SARs or most recent SAR.
\1\ This column represents the annual take by serious injury or mortality (M/SI) during explosive detonations and was calculated by the number of
  mortalities planned for authorization divided by 7 years (the length of the rule and LOAs).
\2\ This column represents the total number of incidents of M/SI that could potentially accrue to the specified species or stock. This number comes from
  the SAR.
\3\ This column represents annual take authorized through NMFS' SWFSC rulemaking/LOAs (86 FR 3840; January 15, 2021).
\4\ This value represents the calculated PBR less the average annual estimate of ongoing anthropogenic mortalities (i.e., total annual human-caused M/SI
  column and the annual authorized take from the SWFSC column. In the case of California sea lion the M/SI column (321) and the annual authorized take
  from the SWFSC (6) were subtracted from the calculated PBR of 14,011. In the case of short-beaked common dolphin the M/SI column (30.5) and the annual
  authorized take from the SWFSC (2.8) were subtracted from the calculated PBR of 8,889.
\5\ See relevant SARs for more information regarding stock status and trends.


[[Page 68331]]

    See the Serious Injury or Mortality subsection in the Analysis and 
Negligible Impact Determination section of the 2018 HSTT final rule (83 
FR 66985-66993) for detailed discussions of the impacts of M/SI, 
including a description of how the agency uses the PBR metric and other 
factors to inform our analysis and an analysis of the impacts on each 
species and stock for which M/SI is proposed for authorization, 
including the relationship of potential mortality for each species to 
the insignificance threshold and residual PBR, except as updated below.

Stocks With M/SI Below the Insignificance Threshold

    As noted in the Serious Injury or Mortality subsection of the 
Negligible Impact Analysis and Determination section in the 2018 HSTT 
final rule and 2020 HSTT final rule, for a species or stock with 
incidental M/SI less than 10 percent of residual PBR, we consider M/SI 
from the specified activities to represent an insignificant incremental 
increase in ongoing anthropogenic M/SI that alone (i.e., in the absence 
of any other take and barring any other unusual circumstances) will 
clearly not adversely affect annual rates of recruitment and survival. 
In this case, as shown in table 10 and table 11, the following species 
or stocks have potential or estimated M/SI from vessel strike and 
explosive takes, respectively, and proposed for authorization below 
their insignificance threshold: fin whale (CA/OR/WA stock), gray whale 
(Eastern North Pacific stock), humpback whale (Hawaii stock and 
Mainland Mexico-CA/OR/WA stock), California sea lion (U.S stock), and 
short-beaked common dolphin (CA/OR/WA stock). While the proposed 
authorized M/SI of gray whales (Eastern North Pacific stock) is below 
the insignificance threshold, because of the recent UME, we further 
address how the proposed authorized M/SI and the UME inform the 
negligible impact determination immediately below. For the other four 
stocks with proposed authorized M/SI below the insignificance 
threshold, there are no other known factors, information, or unusual 
circumstances that indicate anticipated M/SI below the insignificance 
threshold could have adverse effects on annual rates of recruitment or 
survival and they are not discussed further. For the remaining stocks 
with anticipated potential M/SI above the insignificance threshold, how 
that M/SI compares to residual PBR, as well as additional factors, as 
appropriate, are discussed below as well.

Gray Whales (Eastern North Pacific Stock)

    Since January 2019, gray whale strandings along the west coast of 
North America have been significantly higher than the previous 18-year 
averages. Preliminary findings from necropsies have shown evidence of 
emaciation. These findings are not consistent across all of the whales 
examined, so more research is needed. The seasonal pattern of elevated 
strandings in the spring and summer months is similar to that of the 
previous gray whale UME in 1999-2000. If strandings continue to follow 
a similar pattern, we would anticipate a decrease in strandings in late 
summer and fall. However, combined with other annual human-caused 
mortalities and viewed through the PBR lens (for human-caused 
mortalities), total human-caused mortality would still fall below 
residual PBR. Given the small number of takes by serious injury or 
mortality proposed for authorization, the proposed takes are not 
anticipated to exacerbate the ongoing UME.

Stocks With M/SI Above the Insignificance Threshold

Blue Whale (Eastern North Pacific Stock)

    For blue whales (Eastern North Pacific stock), PBR is currently set 
at 4.1 and the total annual M/SI is estimated at greater than or equal 
to 19.5, yielding a residual PBR of -15.4. This is slightly higher than 
the 2020 HSTT final rule (was -16.7). NMFS proposes to authorize one M/
SI for the Navy over the 7-year duration of the rule (indicated as 0.14 
annually for the purposes of comparing to PBR and evaluating overall 
effects on annual rates of recruitment and survival), which means that 
residual PBR is exceeded by 15.54. However, as described in the 2018 
and 2020 rules, given that the negligible impact determination is based 
on the assessment of take of the activity being analyzed, when total 
annual mortality from human activities is higher, but the impacts from 
the specific activity being analyzed are very small, NMFS may still 
find the impact of the proposed authorized take from a specified 
activity to be negligible even if total human-caused mortality exceeds 
PBR if the proposed authorized mortality is less than 10 percent of PBR 
and management measures are being taken to address serious injuries and 
mortalities from the other activities causing mortality (i.e., other 
than the specified activities covered by the incidental take 
authorization in consideration). When those considerations are applied 
here, the authorized lethal take (0.14 annually) of blue whales from 
the Eastern North Pacific stock is less than 10 percent of PBR (which 
is 4.1), and there are management measures in place to address M/SI 
from activities other than those the Navy is conducting (as discussed 
below). Perhaps more importantly, the available data suggests that the 
current number of vessel strikes is not likely to have an adverse 
impact on the population, despite the fact that it exceeds PBR, with 
the Navy's minimal additional mortality of one whale in the 7 years not 
creating the likelihood of adverse impact. Immediately below, we 
explain the information that supports our finding that the Navy's 
proposed authorized M/SI is not expected to result in more than a 
negligible impact on this stock. As described previously, NMFS must 
also ensure that impacts by the applicant on the species or stock from 
other types of take (i.e., harassment) do not combine with the impacts 
from mortality to adversely affect the species or stock via impacts on 
annual rates of recruitment or survival, which occurs further below in 
the stock-specific conclusion sections.
    As discussed in the 2018 HSTT final rule and the 2020 HSTT final 
rule, the 2018 draft SAR and the more recent SARs rely on a new method 
to estimate annual deaths by vessel strike utilizing an encounter 
theory model that combined species distribution models of whale 
density, vessel traffic characteristics, and whale movement patterns 
obtained from satellite-tagged animals in the region to estimate 
encounters that would result in mortality (Rockwood et al. 2017). The 
model predicts 18 annual mortalities of blue whales from vessel 
strikes, which, with the additional M/SI of 1.54 from fisheries 
interactions, results in the current estimate of residual PBR being -
15.4. Although NMFS' Permits and Conservation Division in the Office of 
Protected Resources has independently reviewed the vessel strike model 
and its results and agrees that it is appropriate for estimating blue 
whale mortality by vessel strike on the U.S. West Coast, for analytical 
purposes we also note that if the historical method were used to 
predict vessel strike (i.e., using observed mortality by vessel strike, 
or 0.8, instead of 18), then total human-caused mortality including the 
Navy's potential take would not exceed PBR. We further note that the 
authors (Rockwood et al. 2017) do not suggest that vessel strike 
suddenly increased to 18 recently. In fact, the model is not specific 
to a year, but rather offers a generalized

[[Page 68332]]

prediction of vessel strike off the U.S. West Coast. Therefore, if the 
Rockwood et al. (2017) model is an accurate representation of vessel 
strike, then similar levels of vessel strike have been occurring in 
past years as well. Put another way, if the model is correct, for some 
number of years total-human-caused mortality has been significantly 
underestimated and PBR has been similarly exceeded by a notable amount, 
and yet, the Eastern North Pacific stock of blue whales remains stable 
nevertheless.
    NMFS' 2022 final SAR states that the current population trend is 
unknown, though there may be evidence of a population size increase 
since the 1990s. The SAR further cites to Monnahan et al. (2015), which 
used a population dynamics model to estimate that the Eastern North 
Pacific blue whale population was at 97 percent of carrying capacity in 
2013 and to suggest that the observed lack of a population increase 
since the early 1990s was explained by density dependence, not impacts 
from vessel strike. This would mean that this stock of blue whales 
shows signs of stability and is not increasing in population size 
because the population size is at or nearing carrying capacity for its 
available habitat. In fact, we note that this population has maintained 
this status throughout the years that the Navy has consistently tested 
and trained at similar levels (with similar vessel traffic) in areas 
that overlap with blue whale occurrence, which would be another 
indicator of population stability.
    Monnahan et al. (2015) modeled vessel numbers, vessel strikes, and 
the population of the Eastern North Pacific blue whale population from 
1905 out to 2050 using a Bayesian framework to incorporate informative 
biological information and assign probability distributions to 
parameters and derived quantities of interest. The authors tested 
multiple scenarios with differing assumptions, incorporated 
uncertainty, and further tested the sensitivity of multiple variables. 
Their results indicated that there is no immediate threat (i.e., 
through 2050) to the population from any of the scenarios tested, which 
included models with 10 and 35 strike mortalities per year. Broadly, 
the authors concluded that, unlike other blue whale stocks, the Eastern 
North Pacific blue whales have recovered from 70 years of whaling and 
are in no immediate threat from vessel strikes. They further noted that 
their conclusion conflicts with the depleted and strategic designation 
under the MMPA as well as PBR specifically.
    As discussed, we also take into consideration management measures 
in place to address M/SI caused by other activities. The Channel 
Islands NMS staff coordinates, collects, and monitors whale sightings 
in and around the Vessel Speed Reduction (VSR) zones and the Channel 
Islands NMS region. Redfern et al. (2013) note that the most risky area 
for blue whales is the Santa Barbara Channel, where shipping lanes 
intersect with common feeding areas. The seasonally established 
Southern California VSR zone spans from Point Arguello to Dana Point, 
including the Traffic Separation Schemes in the Santa Barbara Channel 
and San Pedro Channel. Vessels transiting the area from May 1 through 
December 15, 2023 are recommended to exercise caution and voluntarily 
reduce speed to 10 kn (18.5 km per hour) or less for blue, humpback, 
and fin whales. (Note this is an expanded timeframe from the Whale 
Advisory Zone discussed in the 2020 HSTT final rule, which spanned June 
through November, though the effective period could change in future 
years.) Channel Island NMS observers collect information from aerial 
surveys conducted by NOAA, the U.S. Coast Guard, California Department 
of Fish and Game, and U.S. Navy chartered aircraft. Information on 
seasonal presence, movement, and general distribution patterns of large 
whales is shared with mariners, NMFS Office of Protected Resources, 
U.S. Coast Guard, California Department of Fish and Game, the Santa 
Barbara Museum of Natural History, the Marine Exchange of Southern 
California, and whale scientists. Real time and historical whale 
observation data collected from multiple sources can be viewed on the 
Point Blue Whale Database.
    In this case, 0.14 M/SI means one mortality in 1 of the 7 years and 
zero mortalities in 6 of those 7 years. Therefore, the Navy would not 
be contributing to the total human-caused mortality at all in 6 of the 
7, or 85.7 percent, of the years covered by this rulemaking. That means 
that even if a blue whale were to be struck, in 6 of the 7 years there 
could be no effect on annual rates of recruitment or survival from 
Navy-caused M/SI. Additionally, the loss of a male would have far less, 
if any, effect on population rates and absent any information 
suggesting that one sex is more likely to be struck than another, we 
can reasonably assume that there is a 50 percent chance that the single 
strike authorized by this rulemaking would be a male, thereby further 
decreasing the likelihood of impacts on the population rate. In 
situations like this where potential M/SI is fractional, consideration 
must be given to the lessened impacts anticipated due to the absence of 
M/SI in 6 of the 7 years and the fact that the single strike could be a 
male. Lastly, we reiterate that PBR is a conservative metric and also 
not sufficiently precise to serve as an absolute predictor of 
population effects upon which mortality caps would appropriately be 
based. This is especially important given the minor difference between 
zero and one across the 7-year period covered by this rulemaking, which 
is the smallest distinction possible when considering mortality. As 
noted above, Wade et al. (1998), authors of the paper from which the 
current PBR equation is derived, note that ``Estimating incidental 
mortality in 1 year to be greater than the PBR calculated from a single 
abundance survey does not prove the mortality will lead to depletion; 
it identifies a population worthy of careful future monitoring and 
possibly indicates that mortality-mitigation efforts should be 
initiated.'' The information included here indicates that the current 
population trend of this blue whale stock is unknown but likely 
approaching carrying capacity and has leveled off because of density-
dependence, not human-caused mortality, in spite of what might be 
otherwise indicated from the calculated PBR. Further, potential (and 
proposed for authorization) M/SI is below 10 percent of PBR and 
management actions are in place to minimize vessel strike from other 
vessel activity in one of the highest-risk areas for strikes. Based on 
the presence of the factors described above, we do not expect lethal 
take from Navy activities, alone, to adversely affect Eastern North 
Pacific blue whales through effects on annual rates of recruitment or 
survival. Nonetheless, the fact that total human-caused mortality 
exceeds PBR necessitates close attention to the remainder of the 
impacts (i.e., harassment) on the Eastern North Pacific stock of blue 
whales from the Navy's activities to ensure that the total authorized 
takes have a negligible impact on the species or stock. Therefore, this 
information will be considered in combination with our assessment of 
the impacts of proposed harassment takes in the Group and Species-
Specific Analyses section that follows.

Sei Whale (Eastern North Pacific Stock)

    For sei whales (Eastern North Pacific stock), PBR is currently set 
at 0.75. The total annual M/SI is estimated at greater than or equal to 
0.2 in the 2022 final SAR, which reflects one strike over 5

[[Page 68333]]

years, yielding a residual PBR of 0.55. However, more recent 
information suggests that the total annual M/SI reflected in the SAR 
may be overestimated because the one mortality considered in the 
calculation may not have been caused by a vessel strike. Carretta et 
al. (2021) elected to omit this strike from its report summarizing 
sources of human-related injury and mortality for U.S. Pacific west 
coast marine mammal stock assessments after reviewing the stranding 
narrative. The narrative indicated that the strike likely occurred 
post-mortem, evidenced by a lack of hemorrhaging in the whale's 
tissues. NMFS proposes to authorize one M/SI for the Navy over the 7-
year duration of the rule (indicated as 0.14 annually for the purposes 
of comparing to PBR and evaluating overall effects on annual rates of 
recruitment and survival), which means that residual PBR is 0.41 with 
the conservative inclusion of the likely post-mortem strike discussed 
above.
    We acknowledge that the 2023 vessel strike by the U.S. Navy could 
have been of a sei whale or a CA/OR/WA fin whale, and this strike is 
not quantitatively included in this PBR analysis (nor is it 
quantitatively included in the PBR analysis for CA/OR/WA fin whale if 
both of the 2021 U.S. Navy strikes were fin whales) which rely on the 
2022 final SARs. However, consideration of the 2023 strike would not 
change the total M/SI which NMFS compares to PBR, as the single strike 
from 2012-2016 used to calculate the vessel strike rate in the 2022 
final SAR occurred in 2015 (which, as noted above, likely occurred 
post-mortem, and therefore, inclusion of this strike in the annual 
total M/SI is inherently conservative), and the 2023 U.S. Navy strike 
occurred outside of the 2012-2016 time period. Therefore, while we 
acknowledge the 2023 U.S. Navy strike, in the quantitative analysis it 
is treated the same as other non-U.S. Navy strikes that occurred 
outside of the timeframe reflected in the total M/SI (2012-2016).
    Immediately below, we explain the information that supports our 
finding that the Navy's proposed authorized M/SI is not expected to 
result in more than a negligible impact on this stock. As described 
previously, NMFS must also ensure that impacts by the applicant on the 
species or stock from other types of take (i.e., harassment) do not 
combine with the impacts from mortality to adversely affect the species 
or stock via impacts on annual rates of recruitment or survival, which 
occurs further below in the stock-specific conclusion sections.
    Of note, management measures are in place to address M/SI caused by 
other activities. The Channel Islands NMS staff coordinates, collects, 
and monitors whale sightings in and around the Vessel Speed Reduction 
(VSR) zones and the Channel Islands NMS region. The seasonally 
established Southern California VSR zone spans from Point Arguello to 
Dana Point, including the Traffic Separation Schemes in the Santa 
Barbara Channel and San Pedro Channel. Vessels transiting the area from 
May 1 through December 15, 2023 are recommended to exercise caution and 
voluntarily reduce speed to 10 kn (18.5 km per hour) or less. While the 
VSR zone is aimed at reducing risk of fatal vessel strike of blue, 
humpback, and fin whales, this measure is also anticipated to reduce 
risk to sei whales (note, this is an expanded timeframe from the Whale 
Advisory Zone discussed in the 2020 HSTT final rule, which spanned June 
through November, though the effective period could change in future 
years). Channel Island NMS observers collect information from aerial 
surveys conducted by NOAA, the U.S. Coast Guard, California Department 
of Fish and Game, and U.S. Navy chartered aircraft. Information on 
seasonal presence, movement, and general distribution patterns of large 
whales is shared with mariners, NMFS Office of Protected Resources, 
U.S. Coast Guard, California Department of Fish and Game, the Santa 
Barbara Museum of Natural History, the Marine Exchange of Southern 
California, and whale scientists. Real time and historical whale 
observation data collected from multiple sources can be viewed on the 
Point Blue Whale Database.
    Further, as stated in the 2022 final SAR, the California swordfish 
drift gillnet fishery is the most likely U.S. fishery to interact with 
Eastern North Pacific sei whales, though there are zero estimated 
annual takes from this fishery given no observed entanglements from 
1990-2016 across 8,845 monitored fishing sets (Carretta et al. 
(2018b)). NMFS established the Pacific Offshore Cetacean Take Reduction 
Team in 1996 and prepared an associated Plan (PCTRP) to reduce the risk 
of M/SI via fisheries interactions. In 1997, NMFS published final 
regulations formalizing the requirements of the PCTRP, including the 
use of pingers following several specific provisions and the employment 
of Skipper education workshops.
    In this case, 0.14 M/SI means one authorized mortality in 1 of the 
7 years and zero authorized mortalities in 6 of those 7 years. 
Therefore, the Navy's authorized take would not be contributing to the 
total human-caused mortality at all in 6 of the 7, or 85.7 percent, of 
the years covered by this rulemaking. That means that even if a sei 
whale were to be struck, in 6 of the 7 years there could be no effect 
on annual rates of recruitment or survival from Navy-caused M/SI. 
Additionally, the loss of a male would have far less, if any, effect on 
population rates and absent any information suggesting that one sex is 
more likely to be struck than another, we can reasonably assume that 
there is a 50 percent chance that the single strike authorized by this 
rulemaking would be a male, thereby further decreasing the likelihood 
of impacts on the population rate. In situations like this where 
potential M/SI is fractional, consideration must be given to the 
lessened impacts anticipated due to the absence of M/SI in 6 of the 7 
years and the fact that the single strike could be a male.
    Lastly, we reiterate that PBR is a conservative metric and also not 
sufficiently precise to serve as an absolute predictor of population 
effects upon which mortality caps would appropriately be based. This is 
especially important given the minor difference between zero and one 
across the 7-year period covered by this rulemaking, which is the 
smallest distinction possible when considering mortality. As noted 
above, Wade et al. (1998), authors of the paper from which the current 
PBR equation is derived, note that ``Estimating incidental mortality in 
1 year to be greater than the PBR calculated from a single abundance 
survey does not prove the mortality will lead to depletion; it 
identifies a population worthy of careful future monitoring and 
possibly indicates that mortality-mitigation efforts should be 
initiated.'' Even after qualitatively considering the possibility that 
the whale struck by Navy in 2023 was a sei whale, and based on the 
presence of the factors described above, we do not expect one 
authorized lethal take from Navy activities, alone, to adversely affect 
Eastern North Pacific sei whales through effects on annual rates of 
recruitment or survival. This information will be considered in 
combination with our assessment of the impacts of proposed harassment 
takes in the Group and Species-Specific Analyses section that follows.

Group and Species-Specific Analyses

    In addition to broader analyses of the impacts of the Navy's 
activities on mysticetes, odontocetes, and pinnipeds, the 2018 HSTT 
final rule contained detailed analyses of the effects of the

[[Page 68334]]

Navy's activities in the HSTT Study Area on each affected species and 
stock and was updated, as appropriate, in the 2020 HSTT final rule. All 
of that information and analyses remain applicable and valid for our 
analyses of the effects of the same Navy activities on the same species 
and stocks, with the exception of humpback whale, for which the stock 
structure has been revised, and NMFS has updated its analyses 
accordingly for this proposed rule. See the Group and Species-Specific 
Analyses subsection in the Analysis and Negligible Impact Determination 
section of the 2018 HSTT final rule (83 FR 66993-67018). In addition, 
apart from the additional proposed incidental take by vessel strike of 
two large whales, the resulting changes to the average annual mortality 
estimates discussed above, and the revised humpback whale stock 
structure, no new information has been received since the publication 
of the 2020 HSTT final rule that significantly changes the analyses of 
the effects of the Navy's activities on each species and stock 
presented in the 2020 HSTT final rule (new information regarding vessel 
strike, the potential impact of the new gray whale UME, and the revised 
humpback whale stock structure were discussed earlier in the rule).
    In the discussions below, the estimated Level B harassment takes 
represent instances of take, not the number of individuals taken (the 
much lower and less frequent Level A harassment takes are far more 
likely to be associated with separate individuals), and in many cases, 
some individuals are expected to be taken more than one time while in 
other cases, a portion of individuals will not be taken at all. Below, 
we compare the total take numbers (including PTS, TTS, and behavioral 
disturbance) for species or stocks to their associated abundance 
estimates to evaluate the magnitude of impacts across the species or 
stock and to individuals. Specifically, when an abundance percentage 
comparison is below 100, it means that percentage or less of the 
individuals in the stock will be affected (i.e., some individuals will 
not be taken at all), that the average for those taken is 1 day per 
year, and that we would not expect any individuals to be taken more 
than a few times in a year. When it is more than 100 percent, it means 
there will definitely be some number of repeated takes of individuals. 
For example, if the percentage is 300, the average would be each 
individual is taken on 3 days in a year if all were taken, but it is 
more likely that some number of individuals will be taken more than 
three times and some number of individuals fewer times or not at all. 
While it is not possible to know the maximum number of days across 
which individuals of a stock might be taken, in acknowledgement of the 
fact that it is more than the average, for the purposes of this 
analysis, we assume a number approaching twice the average. For 
example, if the percentage of take compared to the abundance is 800, we 
estimate that some individuals might be taken as many as 16 times. 
Those comparisons are included in the sections below. For some stocks, 
these numbers have been adjusted slightly (with these adjustments being 
in the single digits) so as to more consistently apply this approach, 
but these minor changes did not change the analysis or findings.
    To assist in understanding what this analysis means, we clarify a 
few issues related to estimated takes and the analysis here. An 
individual that incurs a PTS or TTS take may sometimes, for example, 
also be subject to behavioral disturbance at the same time. As 
described in the Harassment subsection of the Analysis and Negligible 
Impact Determination section of the 2018 HSTT final rule, the degree of 
PTS, and the degree and duration of TTS, expected to be incurred from 
the Navy's activities are not expected to impact marine mammals such 
that their reproduction or survival could be affected. Similarly, data 
do not suggest that a single instance in which an animal accrues PTS or 
TTS and is also subjected to behavioral disturbance would result in 
impacts to reproduction or survival. Alternately, we recognize that if 
an individual is subjected to behavioral disturbance repeatedly for a 
longer duration and on consecutive days, effects could accrue to the 
point that reproductive success is jeopardized (as discussed below in 
the stock-specific summaries). Accordingly, in analyzing the number of 
takes and the likelihood of repeated and sequential takes (which could 
result in reproductive impacts), we consider the total takes, not just 
the Level B harassment takes by behavioral disturbance, so that 
individuals potentially exposed to both threshold shift and behavioral 
disturbance are appropriately considered. We note that the same 
reasoning applies with the potential addition of behavioral disturbance 
to tissue damage from explosives, the difference being that we do 
already consider the likelihood of reproductive impacts whenever tissue 
damage occurs. Further, the number of Level A harassment takes by 
either PTS or tissue damage are so low compared to abundance numbers 
that it is considered highly unlikely that any individual would be 
taken at those levels more than once.
    Having considered all of the information and analyses previously 
presented in the 2018 HSTT final rule, including the Group and Species-
Specific Analyses discussions organized by the different groups and 
species, below we present tables showing instances of total take as a 
percentage of stock abundance for each group, updated with the new 
vessel strike calculations and humpback stock structure. We then 
summarize the information for each species or stock, considering the 
analysis from the 2018 HSTT final rule, 2020 HSTT final rule, and any 
new analysis. The analyses below in some cases address species 
collectively if they occupy the same functional hearing group (i.e., 
low, mid, and high-frequency cetaceans and pinnipeds in water), share 
similar life history strategies, and/or are known to behaviorally 
respond similarly to acoustic stressors. Because some of these groups 
or species share characteristics that inform the impact analysis 
similarly, it would be duplicative to repeat the same analysis for each 
species or stock. In addition, animals belonging to each stock within a 
species typically have the same hearing capabilities and behaviorally 
respond in the same manner as animals in other stocks within the 
species.
Mysticetes
    In table 12 and table 13 below for mysticetes, we indicate the 
total annual mortality, Level A harassment, and Level B harassment, and 
a number indicating the instances of total take as a percentage of 
abundance. Table 12 and table 13 have been updated from tables 18 and 
19 in the 2020 HSTT final rule, as appropriate, with the 2022 final 
SARs and updated information on mortality, as discussed above. For 
additional information and analysis supporting the negligible-impact 
analysis, see the Mysticetes discussion in the Group and Species-
Specific Analyses section of the 2018 HSTT final rule, all of which 
remains applicable to this proposed rule unless specifically noted.

[[Page 68335]]



 Table 12--Annual Estimated Takes by Level B Harassment, Level A Harassment, and Mortality for Mysticetes in the HRC Portion of the HSTT Study Area and Number Indicating the Instances of Total
                                                                             Take as a Percentage of Stock Abundance
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                    Instances of indicated types of incidental take (not all    Total takes \a\          Abundance        Instance of total take
                                                                      takes represent separate individuals, especially for   --------------------------------------------      as percent of
                                                                                          disturbance)                                                                           abundance
                                                                   ----------------------------------------------------------                                            -----------------------
                                                                        Level B harassment          Level A                     Total             Total Navy                 Total     EEZ  take
                Species                            Stock           ---------------------------    harassment                    takes     Takes    abundance  Within EEZ    take as       as
                                                                                              ------------------               (entire   (within     inside       Navy    percentage  percentage
                                                                                   TTS  (may                      Mortality     study     Navy        and      abundance    of total    of Navy
                                                                     Behavioral  also include           Tissue       \b\        area)     EEZ)    outside of     (HRC)       Navy         EEZ
                                                                    disturbance  disturbance)   PTS     damage                                     EEZ (HRC)               abundance   abundance
                                                                                                                                                                             (HRC)       (HRC)
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Blue whale.............................  Central North Pacific....           15            33      0          0            0        48        40          43          33         112         121
Bryde's whale..........................  Hawaii...................           40           106      0          0            0       146       123         108          89         135         138
Fin whale..............................  Hawaii...................           21            27      0          0            0        48        41          52          40          92         103
Humpback whale.........................  Hawaii...................        2,837         6,289      3          0         0.29     9,129     7,389       5,078       4,595         180         161
Minke whale............................  Hawaii...................        1,233         3,697      2          0            0     4,932     4,030       3,652       2,835         135         142
Sei whale..............................  Hawaii...................           46           121      0          0            0       167       135         138         107         121         126
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Note: For the Hawaii take estimates, we compare predicted takes to abundance estimates generated from the same underlying density estimates (as described in the Estimated Take of Marine
  Mammals section of the 2018 HSTT final rule), both in and outside of the U.S. EEZ. Because the portion of the Navy's study area inside the U.S. EEZ is generally concomitant with the area
  used to generate the abundance estimates in the SARs, and the abundance predicted by the same underlying density estimates is the preferred abundance to use, there is no need to separately
  compare the take to the SARs abundance estimate.
\a\ Total takes inside and outside U.S. EEZ represent the sum of annual Level A and Level B harassment from training and testing activities.
\b\ The annual mortality of 0.29 is the result of no more than two mortalities over the course of 7 years from vessel strikes as described above in the Estimated Take of Marine Mammals
  section.


   Table 13--Annual Estimated Takes by Level B Harassment, Level A Harassment, and Mortality for Mysticetes in the SOCAL Portion of the HSTT Study Area and Number Indicating the Instances of
                                                                          Total Take as a Percentage of Stock Abundance
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                 Instances of indicated types of incidental take (not     Total          Abundance        Instance of total take
                                                                                 all takes represent separate individuals, especially     takes  ------------------------      as percent of
                                                                                                   for disturbance)                        \a\                                   abundance
                                                                              -------------------------------------------------------------------                        -----------------------
                                                                                   Level B harassment         Level A                                                        Total
                                                                              ---------------------------    harassment                              Navy                   take as      Total
                   Species                                 Stock                                         -----------------                Total    abundance   NMFS SARS  percentage    take as
                                                                                              TTS  (may                     Mortality     takes    in action   abundance   of total   percentage
                                                                                Behavioral      also                           \b\       (entire     area                    Navy      of total
                                                                               disturbance     include     PTS    Tissue                  study     (SOCAL)                abundance      SAR
                                                                                            disturbance)          damage                  Area)                            in action   abundance
                                                                                                                                                                             area
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Blue whale..................................  Eastern North Pacific..........          792         1,196      1         0         0.14     1,989         785       1,898         253         105
Bryde's whale...............................  Eastern Tropical Pacific.......           14            27      0         0            0        41         1.3     unknown       3,154     unknown
Fin whale...................................  CA/OR/WA.......................          835         1,390      1         0         0.57     2,227         363      11,065         613          20
Humpback whale..............................  Central America/Southern Mexico-         282           594      0         0            0       876      \c\ 74       1,496       1,184          59
                                               CA/OR/WA.
                                              Mainland Mexico- CA/OR/WA......          198           920      1         0         0.14     1,119     \c\ 173       3,477         647          32
Minke whale.................................  CA/OR/WA.......................          259           666      1         0            0       926         163         915         568         101
Sei whale...................................  Eastern North Pacific..........           27            52      0         0         0.14        79           3         519       2,633          15
Gray whale..................................  Eastern North Pacific..........        1,316         3,355      7         0         0.57     4,679         193      26,960       2,424          17
Gray whale..................................  Western North Pacific..........            2             4      0         0            0         6           0         290           0           2
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Note: For the SOCAL take estimates, because of the manner in which the Navy study area overlaps the ranges of many MMPA stocks (i.e., a stock may range far north to Washington state and beyond
  and abundance may only be predicted within the U.S. EEZ, while the Navy study area is limited to Southern California and northern Mexico, but extends beyond the U.S. EEZ), we compare
  predicted takes to both the abundance estimates for the study area, as well as the SARs (as described in the Estimated Take of Marine Mammals section of the 2018 HSTT final rule).
\a\ Total takes inside and outside U.S. EEZ represent the sum of annual Level A and Level B harassment from training and testing activities.
\b\ The annual mortality of 0.14 is the result of no more than one mortality over the course of 7 years from vessel strikes as described above in the Estimated Take of Marine Mammals section.
  The annual mortality of 0.57 is the result of no more than four mortalities over the course of 7 years from vessel strikes.
\c\ In the 2020 HSTT final rule, NMFS reported a Navy abundance in Action Area (SOCAL) of 247 CA/OR/WA humpback whales. As explained in more detail in the Estimated Take from Vessel Strikes
  and Explosives by Serious Injury or Mortality, NMFS estimates that approximately 30 percent of the humpback whales off the coast of California may be from the Central America DPS with the
  remaining 70 percent are expected to be from the Mexico DPS. Therefore, of the estimated 247 humpback whales in SOCAL, NMFS anticipates that 74 would be of the Central America/Southern
  Mexico-CA/OR/WA stock (Central America DPS), and 173 would be of the Mainland Mexico-CA/OR/WA stock (Mexico DPS).


[[Page 68336]]

    Below we compile and summarize the information that supports our 
preliminary determination that the Navy's activities would not 
adversely affect any species or stocks through effects on annual rates 
of recruitment or survival for any of the affected mysticete species 
and stocks.

Blue Whale (Eastern North Pacific Stock)

    Blue whales are listed as endangered under the ESA, and the current 
population trend for the Eastern North Pacific stock is unknown. We 
further note that this stock was originally listed under the ESA as a 
result of the impacts from commercial whaling, which is no longer 
affecting the species. NMFS proposes to authorize one mortality over 
the 7 years covered by this rulemaking or 0.14 mortality annually. With 
the addition of this 0.14 annual mortality, residual PBR is exceeded, 
resulting in the total human-caused mortality exceeding PBR by 15.54. 
However, as described in more detail in the Serious Injury or Mortality 
section above, when total human-caused mortality exceeds PBR, we 
consider whether the incremental addition of a small amount of 
authorized mortality from the specified activity may still result in a 
negligible impact, in part by identifying whether it is less than 10 
percent of PBR. In this case, the authorized mortality is well below 10 
percent of PBR, management measures are in place to reduce mortality 
from other sources, and the incremental addition of a single mortality 
over the course of the 7-year Navy rule is not expected to, alone, lead 
to adverse impacts on the stock through effects on annual rates of 
recruitment or survival.
    Regarding the magnitude of Level B harassment takes (TTS and 
behavioral disturbance), the number of estimated total instances of 
take compared to the abundance (measured against both the Navy-
estimated abundance and the SAR) is 253 and 105 percent, respectively 
(table 13). Given the range of blue whales, this information suggests 
that only some portion of individuals in the stock are likely impacted, 
but that there will likely be some repeat exposure (maybe 5 or 6 days 
within a year) of some subset of individuals that spend extended time 
within SOCAL. Regarding the severity of those individual Level B 
harassment takes by behavioral disturbance, the duration of any 
exposure is expected to be between minutes and hours (i.e., relatively 
short) and the received sound levels largely below 172 dB with a 
portion up to 178 dB (i.e., of a moderate or lower level, less likely 
to evoke a severe response). Additionally, the Navy implements time/
area mitigation in SOCAL in the majority of the BIAs, which will reduce 
the severity of impacts to blue whales by reducing interference in 
feeding that could result in lost feeding opportunities or necessitate 
additional energy expenditure to find other good opportunities. 
Regarding the severity of TTS takes, we have explained in the 2018 HSTT 
final rule that they are expected to be low-level, of short duration, 
and mostly not in a frequency band that would be expected to interfere 
with blue whale communication or other important low-frequency cues--
and that the associated lost opportunities and capabilities are not at 
a level that would impact reproduction or survival. For similar reasons 
(as described in the 2018 HSTT final rule) the single estimated Level A 
harassment take by PTS for this stock is unlikely to have any effect on 
the reproduction or survival of that one individual, even if it were to 
be experienced by an animal that also experiences one or more Level B 
harassment takes by behavioral disturbance.
    Altogether, only a small portion of the stock is anticipated to be 
impacted and any individual blue whale is likely to be disturbed at a 
low-moderate level, with likely many animals exposed only once or twice 
and a subset potentially disturbed across 5 or 6 days but minimized in 
biologically important areas. This low magnitude and severity of 
harassment effects is not expected to result in impacts on the 
reproduction or survival of any individuals and, therefore, when 
combined with the proposed authorized mortality (which our earlier 
analysis indicated would not, alone, have more than a negligible impact 
on this stock of blue whales), the total take is not expected to 
adversely affect this stock through impacts on annual rates of 
recruitment or survival. For these reasons, we have preliminarily 
determined, in consideration of all of the effects of the Navy's 
activities combined, that the authorized take proposed would have a 
negligible impact on the Eastern North Pacific stock of blue whales.

Bryde's Whale (Eastern Tropical Pacific Stock)

    Little is known about this stock or its status, and it is not 
listed under the ESA. No mortality or Level A harassment is anticipated 
or proposed to be authorized. Regarding the magnitude of Level B 
harassment takes (TTS and behavioral disturbance), the number of 
estimated total instances of take compared to the abundance is 3,154 
percent; however, the abundance upon which this percentage is based 
(1.3 whales from the Navy estimate, which is extrapolated from density 
estimates based on very few sightings) is clearly erroneous and the SAR 
does not include an abundance estimate because all of the survey data 
is outdated (table 13). However, the abundance in the early 1980s was 
estimated as 22,000 to 24,000, a portion of the stock was estimated at 
13,000 in 1993, and the minimum number in the Gulf of California was 
estimated at 160 in 1990. Given this information and the fact that 41 
total takes of Bryde's whales were estimated, this information suggests 
that only a small portion of the individuals in the stock are likely 
impacted, and few, if any, are likely taken over more than 1 day. 
Regarding the severity of those individual Level B harassment takes by 
behavioral disturbance, the duration of any exposure is expected to be 
between minutes and hours (i.e., relatively short) and the received 
sound levels largely below 172 dB with a portion up to 178 dB (i.e., of 
a moderate or lower level, less likely to evoke a severe response). 
Regarding the severity of TTS takes, they are expected to be low-level, 
of short duration, and mostly not in a frequency band that would be 
expected to interfere with Bryde's whale communication or other 
important low-frequency cues. Any associated lost opportunities and 
capabilities are not at a level that would impact reproduction or 
survival.
    Altogether, only a small portion of the stock is anticipated to be 
impacted and any individual Bryde's whale is likely to be disturbed at 
a low-moderate level, with few, if any, individuals exposed over more 
than 1 day in the year. This low magnitude and severity of harassment 
effects is not expected to result in impacts on individual reproduction 
or survival, much less annual rates of recruitment or survival. For 
these reasons, we have preliminarily determined, in consideration of 
all of the effects of the Navy's activities combined, that the 
authorized take proposed would have a negligible impact on the Eastern 
Tropical Pacific stock of Bryde's whales.

Fin Whale (CA/OR/WA Stock)

    The SAR identifies this stock as ``increasing,'' even though the 
larger species is listed as endangered under the ESA. NMFS proposes to 
authorize four mortalities over the 7 years covered by this rulemaking, 
or 0.57 mortality annually. The addition of this 0.57 annual mortality 
still leaves the total human-caused mortality well under residual PBR.

[[Page 68337]]

    We acknowledge the 2021 vessel strike of two fin whales by the 
Royal Australian Navy, and that the 2021 and 2023 vessel strikes by the 
U.S. Navy could have been CA/OR/WA fin whales. While the Royal 
Australian Navy strikes are not quantitatively included in the 
estimated take by vessel strike, even if they were, and if we presumed 
that the 2021 and 2023 U.S. Navy strikes were all fin whales, M/SI of 
this stock would still fall well below PBR (80).
    Regarding the magnitude of Level B harassment takes (TTS and 
behavioral disturbance), the number of estimated total instances of 
take compared to the abundance (measured against both the Navy-
estimated abundance and the SAR) is 613 and 20 percent, respectively 
(table 13). This information suggests that only some portion (less than 
25 percent) of individuals in the stock are likely impacted but that 
there is likely some repeat exposure (perhaps up to 12 days within a 
year) of some subset of individuals that spend extended time within the 
SOCAL complex. Some of these takes could occur on a few sequential days 
for some small number of individuals, for example, if they resulted 
from a multi-day exercise on a range while individuals were in the area 
for multiple days feeding. Regarding the severity of those individual 
Level B harassment takes by behavioral disturbance, the duration of any 
exposure is expected to be between minutes and hours (i.e., relatively 
short) and the received sound levels largely below 172 dB with a 
portion up to 178 dB (i.e., of a moderate or lower level, less likely 
to evoke a severe response). Additionally, while there are no known 
BIAs for fin whales in the SOCAL range, the Navy implements time/area 
mitigation in SOCAL in blue whale BIAs, and fin whales are known to 
sometimes feed in some of the same areas, which means they could 
potentially accrue some benefits from the mitigation. Regarding the 
severity of TTS takes, they are expected to be low-level, of short 
duration, and mostly not in a frequency band that would be expected to 
interfere with fin whale communication or other important low-frequency 
cues--and that the associated lost opportunities and capabilities are 
not at a level that would impact reproduction or survival. For similar 
reasons (as described in the 2018 HSTT final rule) the single estimated 
Level A harassment take by PTS for this stock is unlikely to have any 
effects on the reproduction or survival of that one individual.
    Altogether, this population is increasing, only a small portion of 
the stock is anticipated to be impacted, and any individual fin whale 
is likely to be disturbed at a low-moderate level, with the taken 
individuals likely exposed between 1 and 12 days, with a few 
individuals potentially taken on a few sequential days. This low 
magnitude and severity of harassment effects is not expected to result 
in impacts on individual reproduction or survival, and therefore, when 
combined with the proposed authorized mortality (which our earlier 
analysis indicated would not, alone, have more than a negligible impact 
on this stock of fin whales), the total take is not expected to 
adversely affect this stock through impacts on annual rates of 
recruitment or survival. For these reasons, we have preliminarily 
determined, in consideration of all of the effects of the Navy's 
activities combined, that the authorized take proposed would have a 
negligible impact on the CA/OR/WA stock of fin whales.

Humpback Whale (Central America/Southern Mexico-CA/OR/WA Stock)

    The SAR identifies this stock as increasing, though the growth rate 
is uncertain. Animals in this stock are of the Central America DPS 
which is designated as endangered under the ESA.
    Regarding the magnitude of Level B harassment takes (TTS and 
behavioral disturbance), the number of estimated total instances of 
take compared to the abundance (measured against both the Navy-
estimated abundance and the SAR) is 1,184 and 59 percent, respectively 
(table 11). Given the range of humpback whales, this information 
suggests that only some portion of individuals in the stock are likely 
impacted but that there is likely some repeat exposure (perhaps up to 
23 days within a year) of some subset of individuals that spend 
extended time within the SOCAL complex. Regarding the severity of those 
individual Level B harassment takes by behavioral disturbance, the 
duration of any exposure is expected to be between minutes and hours 
(i.e., relatively short) and the received sound levels largely below 
172 dB with a portion up to 178 dB (i.e., of a moderate or lower level, 
less likely to evoke a severe response). Some of these takes could 
occur on several sequential days for some small number of individuals, 
for example, if they resulted from a multi-day exercise on a range 
while individuals were in the area for multiple days feeding. However, 
in these amounts, it would still not be expected to adversely impact 
reproduction or survival of any individuals.
    Regarding the severity of TTS takes, they are expected to be low-
level, of short duration, and mostly not in a frequency band that would 
be expected to interfere with humpback whale communication or other 
important low-frequency cues--and that the associated lost 
opportunities and capabilities are not at a level that would impact 
reproduction or survival. Altogether, only a small portion of the stock 
is anticipated to be impacted and any individual humpback whale is 
likely to be disturbed at a low-moderate level, with likely many 
animals exposed only once or twice and a subset potentially disturbed 
up to 23 days, but with no reason to think that more than a few of 
those days would be sequential. This low magnitude and severity of 
harassment effects is not expected to result in impacts on the 
reproduction or survival of any individuals and, therefore, the total 
take is not expected to adversely affect this stock through impacts on 
annual rates of recruitment or survival. For these reasons, we have 
preliminarily determined, in consideration of all of the effects of the 
Navy's activities combined, that the authorized take proposed would 
have a negligible impact on the Central America/Southern Mexico-CA/OR/
WA stock of humpback whales.
Humpback Whale (Mainland Mexico-CA/OR/WA Stock)
    The status of this stock is unknown. Animals in this stock are of 
the Mexico DPS which is designated as threatened under the ESA. NMFS 
proposes to authorize one mortality over the 7 years covered by this 
rulemaking, or 0.14 mortality annually. The addition of this 0.14 
annual mortality still leaves the total human-caused mortality well 
under residual PBR.
    Regarding the magnitude of Level B harassment takes (TTS and 
behavioral disturbance), the number of estimated total instances of 
take compared to the abundance (measured against both the Navy-
estimated abundance and the SAR) is 647 and 32 percent, respectively 
(table 13). Given the range of humpback whales, this information 
suggests that only some portion of individuals in the stock are likely 
impacted but that there is likely some repeat exposure (perhaps up to 
13 days within a year) of some subset of individuals that spend 
extended time within the SOCAL complex. Regarding the severity of those 
individual Level B harassment takes by behavioral disturbance, the 
duration of any exposure is expected to be between minutes and hours 
(i.e., relatively short) and the received sound levels largely below 
172 dB with a portion up to 178

[[Page 68338]]

dB (i.e., of a moderate or lower level, less likely to evoke a severe 
response). Some of these takes could occur on several sequential days 
for some small number of individuals, for example, if they resulted 
from a multi-day exercise on a range while individuals were in the area 
for multiple days feeding. However, in these amounts, it would still 
not be expected to adversely impact reproduction or survival of any 
individuals.
    Regarding the severity of TTS takes, they are expected to be low-
level, of short duration, and mostly not in a frequency band that would 
be expected to interfere with humpback whale communication or other 
important low-frequency cues--and that the associated lost 
opportunities and capabilities are not at a level that would impact 
reproduction or survival. For similar reasons (as described in the 2018 
HSTT final rule) the single estimated Level A harassment take by PTS 
for this stock is unlikely to have any effects on the reproduction or 
survival of that one individual.
    Altogether, only a small portion of the stock is anticipated to be 
impacted and any individual humpback whale is likely to be disturbed at 
a low-moderate level, with likely many animals exposed only once or 
twice and a subset potentially disturbed up to 13 days, but with no 
reason to think that more than a few of those days would be sequential. 
This low magnitude and severity of harassment effects is not expected 
to result in impacts on the reproduction or survival of any individuals 
and, therefore, when combined with the proposed authorized mortality 
(which our earlier analysis indicated would not, alone, have more than 
a negligible impact on this stock of humpback whales), the total take 
is not expected to adversely affect this stock through impacts on 
annual rates of recruitment or survival. For these reasons, we have 
preliminarily determined, in consideration of all of the effects of the 
Navy's activities combined, that the authorized take proposed would 
have a negligible impact on the CA/OR/WA stock of humpback whales.

Minke Whale (CA/OR/WA Stock)

    The status of this stock is unknown and it is not listed under the 
ESA. No mortality from vessel strike or tissue damage from explosive 
exposure is anticipated or proposed for authorization for this species. 
Regarding the magnitude of Level B harassment takes (TTS and behavioral 
disturbance), the number of estimated total instances of take compared 
to the abundance (measured against both the Navy-estimated abundance 
and the SAR) is 568 and 101 percent, respectively (table 11). Based on 
the behaviors of minke whales, which often occur along continental 
shelves and sometimes establish home ranges along the West Coast, this 
information suggests that only a portion of individuals in the stock 
are likely impacted but that there is likely some repeat exposure 
(perhaps up to 11 days within a year) of some subset of individuals 
that spend extended time within the SOCAL complex. Some of these takes 
could occur on a few sequential days for some small number of 
individuals, for example, if they resulted from a multi-day exercise on 
a range while individuals were in the area for multiple days feeding. 
Regarding the severity of those individual Level B harassment takes by 
behavioral disturbance, the duration of any exposure is expected to be 
between minutes and hours (i.e., relatively short) and the received 
sound levels largely below 172 dB with a portion up to 178 dB (i.e., of 
a moderate or lower level, less likely to evoke a severe response). 
Regarding the severity of TTS takes, they are expected to be low-level, 
of short duration, and mostly not in a frequency band that would be 
expected to interfere with minke whale communication or other important 
low-frequency cues--and that the associated lost opportunities and 
capabilities are not at a level that would impact reproduction or 
survival. For similar reasons (as described in the 2018 HSTT final 
rule) the single estimated Level A harassment take by PTS for this 
stock is unlikely to have any effects on the reproduction or survival 
of that individual.
    Altogether, only a portion of the stock is anticipated to be 
impacted and any individual minke whale is likely to be disturbed at a 
low-moderate level, with the taken individuals likely exposed between 1 
and 11 days, with a few individuals potentially taken on a few 
sequential days. This low magnitude and severity of harassment effects 
is not expected to result in impacts on individual reproduction or 
survival, much less annual rates of recruitment or survival. For these 
reasons, we have preliminarily determined, in consideration of all of 
the effects of the Navy's activities combined, that the authorized take 
proposed would have a negligible impact on the CA/OR/WA stock of minke 
whales.

Sei Whale (Eastern North Pacific Stock)

    The status of this stock is unknown, and sei whales are listed 
under the ESA. NMFS proposes to authorize one mortality over the 7 
years covered by this rulemaking or 0.14 mortality annually. The 
addition of this 0.14 annual mortality still leaves the total human-
caused mortality under residual PBR. After additionally considering 
several qualitative factors described above, including that the 2023 
strike could have been a sei whale (or fin whale), we do not expect one 
authorized lethal take from Navy activities, alone, to adversely affect 
Eastern North Pacific sei whales through effects on annual rates of 
recruitment or survival. No Level A harassment is anticipated or 
proposed for authorization.
    Regarding the magnitude of Level B harassment takes (TTS and 
behavioral disturbance), the number of estimated total instances of 
take compared to the abundance (measured against both the Navy-
estimated abundance and the SAR) is 2,633 and 15 percent, respectively 
(table 13), however, the abundance upon which the Navy percentage is 
based (3 from the Navy estimate, which is extrapolated from density 
estimates based on very few sightings) is likely an underestimate of 
the number of individuals in the HSTT study Area, resulting in an 
overestimated percentage. Given this information and the large range of 
sei whales, and the fact that only 79 total Level B harassment takes of 
sei whales were estimated, it is likely that some very small number of 
sei whales would be taken repeatedly, potentially up to 15 days in a 
year (typically 2,633 percent would lead to the estimate of 52 days/
year, however, given that there are only 79 sei whale total takes, we 
used the conservative assumption that five individuals might be taken 
up to 15 times, with the few remaining takes distributed among other 
individuals). Regarding the severity of those individual Level B 
harassment takes by behavioral disturbance, the duration of any 
exposure is expected to be between minutes and hours (i.e., relatively 
short) and the received sound levels largely below 172 dB with a 
portion up to 178 dB (i.e., of a moderate or lower level, less likely 
to evoke a severe response). Some of these takes could occur on a few 
sequential days for some small number of individuals, for example, if 
they resulted from a multi-day exercise on a range while individuals 
were in the area for multiple days feeding, however, in these amounts 
it would still not be expected to adversely impact reproduction or 
survival of any individuals. Regarding the severity of TTS takes, they 
are expected to be low-level, of short duration, and mostly not in a 
frequency band that would be expected to interfere with sei whale

[[Page 68339]]

communication or other important low-frequency cues--and that the 
associated lost opportunities and capabilities are not at a level that 
would impact reproduction or survival.
    Altogether, only a small portion of the stock is anticipated to be 
impacted and any individual sei whale is likely to be disturbed at a 
low-moderate level, with only a few individuals exposed over one to 15 
days in a year, with no more than a few sequential days. This low 
magnitude and severity of harassment effects is not expected to result 
in impacts on individual reproduction or survival, and therefore, when 
combined with the proposed authorized mortality (which our earlier 
analysis indicated would not, alone, have more than a negligible impact 
on this stock of sei whales), the total take is not expected to 
adversely affect this stock through impacts on annual rates of 
recruitment or survival. For these reasons, we have preliminarily 
determined, in consideration of all of the effects of the Navy's 
activities combined, that the authorized take proposed would have a 
negligible impact on the Eastern North Pacific stock of sei whales.

Gray Whale (Eastern North Pacific Stock)

    The Eastern North Pacific stock of gray whale is not ESA-listed and 
the SAR indicates that the stock is increasing. However, recent (2021-
2022) surveys conducted by NMFS' Southwest Fisheries Science Center 
estimated that the population has declined to 16,650 whales, though the 
authors note that this stock has historically shown a pattern of 
population growth and decline that has not impacted the population in 
the long term (Eguchi et al. 2022). NMFS is proposing to authorize four 
mortalities over the 7 years covered by this rulemaking, or 0.57 
mortality annually. The addition of this 0.57 annual mortality still 
leaves the total human-caused mortality well under the insignificance 
threshold of residual PBR (670). On May 31, 2019, NMFS declared the 
unusual spike in strandings of gray whales along the west coast of 
North America since January 1, 2019 an UME. As of June 25, 2023, 674 
gray whales have stranded along the west coast of North America (in the 
U.S., Canada, and Mexico) under this UME. Given the small number of 
takes by serious injury or mortality proposed for authorization, the 
proposed takes are not anticipated to exacerbate the ongoing UME.
    Regarding the magnitude of Level B harassment takes (TTS and 
behavioral disturbance), the number of estimated total instances of 
take compared to the abundance (measured against both the Navy-
estimated abundance and the SAR) is 2,424 and 16 percent, respectively 
(table 13). (Note that in comparison to the recent Eguchi et al. 2022 
abundance estimate, the number of estimated total instances of take 
compared to the abundance would be 28 percent.) This information 
suggests that only some small portion of individuals in the stock are 
likely impacted (less than 17 percent) but that there is likely some 
level of repeat exposure of some subset of individuals that spend 
extended time within the SOCAL complex. Typically 2,424 percent would 
lead to the estimate of 48 days/year, however, given that a large 
number of gray whales are known to migrate through the SOCAL complex 
and the fact that there are 4,679 total takes, we believe that it is 
more likely that a larger number of individuals would be taken one to a 
few times, while a small number staying in an area to feed for several 
days may be taken on 5-10 days. Regarding the severity of those 
individual Level B harassment takes by behavioral disturbance, the 
duration of any exposure is expected to be between minutes and hours 
(i.e., relatively short) and the received sound levels largely below 
172 dB with a portion up to 178 dB (i.e., of a moderate or lower level, 
less likely to evoke a severe response). Some of these takes could 
occur on a couple of sequential days for some small number of 
individuals; however, in these amounts it would still not be expected 
to adversely impact reproduction or survival of any individuals.
    Regarding the severity of TTS takes, they are expected to be low-
level, of short duration, and mostly not in a frequency band that would 
be expected to interfere with gray whale communication or other 
important low-frequency cues and that the associated lost opportunities 
and capabilities are not at a level that would impact reproduction or 
survival. For these same reasons (low level and frequency band), while 
a small permanent loss of hearing sensitivity may include some degree 
of energetic costs for compensating or may mean some small loss of 
opportunities or detection capabilities, at the expected scale the 
seven estimated Level A harassment takes by PTS for gray whales would 
be unlikely to impact behaviors, opportunities, or detection 
capabilities to a degree that would interfere with reproductive success 
or survival of any individuals.
    Altogether, we have considered the impacts of the gray whale UME, 
the Eastern North Pacific stock of gray whales is not endangered or 
threatened under the ESA. The SAR indicates that the stock is 
increasing. However, recent (2021-2022) surveys conducted by NMFS' 
Southwest Fisheries Science Center estimated that the population has 
declined (Eguchi et al. 2022). Only a small portion of the stock is 
anticipated to be impacted and any individual gray whale is likely to 
be disturbed at a low-moderate level, with likely many animals exposed 
only once or twice and a subset potentially disturbed across 5 to 10 
days. This low magnitude and severity of harassment effects is not 
expected to result in impacts to reproduction or survival for any 
individuals and, therefore, when combined with the proposed authorized 
mortality of four whales over the 7 year period (which our earlier 
analysis indicated would not, alone, have more than a negligible impact 
on this stock of gray whales), the total take is not expected to 
adversely affect this stock through impacts on annual rates of 
recruitment or survival. For these reasons, we have preliminarily 
determined, in consideration of all of the effects of the Navy's 
activities combined, that the authorized take proposed would have a 
negligible impact on the Eastern North Pacific stock of gray whales.

Gray Whale (Western North Pacific stock)

    The Western North Pacific stock of gray whales is reported as 
increasing in the 2022 final SAR but is listed as endangered under the 
ESA. No mortality or Level A harassment is anticipated or proposed for 
authorization. This stock is expected to incur the very small number of 
6 Level B harassment takes (2 behavioral disruption and 4 TTS) to a 
stock with a SAR-estimated abundance of 290 (table 11). These takes 
will likely accrue to different individuals, the behavioral 
disturbances will be of a low-moderate level, and the TTS instances 
will be at a low level and short duration. This low magnitude and 
severity of harassment effects is not expected to result in impacts on 
individual reproduction or survival, much less to adversely affect this 
stock through impacts on annual rates of recruitment or survival. For 
these reasons, we have preliminarily determined, in consideration of 
all of the effects of the Navy's activities combined, that the 
authorized take proposed would have a negligible impact on the Western 
North Pacific stock of gray whales.

Humpback Whale (Hawaii Stock)

    The status of this stock is unknown. Animals in this stock are of 
the Hawaii

[[Page 68340]]

DPS which is not listed under the ESA. No Level A harassment by tissue 
damage is proposed for authorization. NMFS proposes to authorize two 
mortalities over the 7 years covered by this rulemaking, or 0.29 
mortalities annually. The addition of this 0.29 annual mortality still 
leaves the total human-caused mortality well under the insignificance 
threshold for residual PBR.
    Regarding the magnitude of Level B harassment takes (TTS and 
behavioral disturbance), the number of estimated instances of take 
compared to the abundance, both throughout the HSTT Study Area and 
within the U.S. EEZ, respectively, is 180 and 161 percent (table 12). 
This information and the complicated far-ranging nature of the stock 
structure suggests that some portion of the stock (but not all) are 
likely impacted, over 1 to several days per year, with little 
likelihood of take across sequential days. Regarding the severity of 
those individual Level B harassment takes by behavioral disturbance, 
the duration of any exposure is expected to be between minutes and 
hours (i.e., relatively short) and the received sound levels largely 
below 172 dB with a portion up to 178 dB (i.e., of a moderate or lower 
level, less likely to evoke a severe response). Additionally, as noted 
above, there are two mitigation areas implemented by the Navy that span 
a large area of the important humpback reproductive area (BIA) and 
minimize impacts by limiting the use of MF1 active sonar and 
explosives, thereby reducing both the number and severity of takes of 
humpback whales. Regarding the severity of TTS takes, they are expected 
to be low-level, of short duration, and mostly not in a frequency band 
that would be expected to interfere with humpback whale communication 
or other important low-frequency cues, and that the associated lost 
opportunities and capabilities are not at a level that would impact 
reproduction or survival. For these same reasons (low level and 
frequency band), while a small permanent loss of hearing sensitivity 
may include some degree of energetic costs for compensating or may mean 
some small loss of opportunities or detection capabilities, at the 
expected scale the 3 estimated Level A harassment takes by PTS for 
humpback whales would be unlikely to impact behaviors, opportunities, 
or detection capabilities to a degree that would interfere with 
reproductive success or survival of any individuals.
    Altogether, this stock's status is unknown and the DPS is not 
listed as endangered or threatened under the ESA. Only a small portion 
of the stock is anticipated to be impacted and any individual humpback 
whale is likely to be disturbed at a low-moderate level, with the taken 
individuals likely exposed between 1 to several days per year, with 
little likelihood of take across sequential days. This low magnitude 
and severity of harassment effects is not expected to result in impacts 
on individual reproduction or survival, and therefore, when combined 
with the proposed authorized mortality (which our earlier analysis 
indicated would not, alone, have more than a negligible impact on this 
stock of humpback whales), the total take is not expected to adversely 
affect this stock through effects on annual rates of recruitment or 
survival. For these reasons, we have preliminarily determined, in 
consideration of all of the effects of the Navy's activities combined, 
that the authorized take proposed would have a negligible impact on the 
Hawaii stock of humpback whales.

Blue Whale (Central North Pacific Stock) and the Hawaii Stocks of 
Bryde's Whale, Fin Whale, Minke Whale, and Sei Whale

    The status of these stocks are not identified in the SARs. Blue 
whale (Central North Pacific stock) and the Hawaii stocks of fin whale 
and sei whale are listed as endangered under the ESA; the Hawaii stocks 
of minke whales and Bryde's whales are not listed under the ESA. No 
mortality or Level A harassment by tissue damage is anticipated or 
proposed for authorization for any of these stocks.
    Regarding the magnitude of Level B harassment takes (TTS and 
behavioral disturbance), the number of estimated instances of take 
compared to the abundance, both throughout the HSTT Study Area and 
within the U.S. EEZ, respectively, is 92-135 and 103-142 percent (table 
12). This information suggests that some portion of the stocks (but not 
all) are likely impacted, over 1 to several days per year, with little 
likelihood of take across sequential days. Regarding the severity of 
those individual Level B harassment takes by behavioral disturbance, 
the duration of any exposure is expected to be between minutes and 
hours (i.e., relatively short) and the received sound levels largely 
below 172 dB with a portion up to 178 dB (i.e., of a moderate or lower 
level, less likely to evoke a severe response). Regarding the severity 
of TTS takes, they are expected to be low-level, of short duration, and 
mostly not in a frequency band that would be expected to interfere with 
mysticete communication or other important low-frequency cues--and that 
the associated lost opportunities and capabilities are not at a level 
that would impact reproduction or survival. For similar reasons (as 
described in the 2018 HSTT final rule) the two estimated Level A 
harassment takes by PTS for the Hawaii stock of minke whales are 
unlikely to have any effects on the reproduction or survival of any 
individuals.
    Altogether, only a portion of these stocks are anticipated to be 
impacted and any individuals of these stocks are likely to be disturbed 
at a low-moderate level, with the taken individuals likely exposed 
between 1 and several days, with little chance that any are taken 
across sequential days. This low magnitude and severity of harassment 
effects is not expected to result in impacts on individual reproduction 
or survival, much less have impacts on annual rates of recruitment or 
survival. For these reasons, we have preliminarily determined, in 
consideration of all of the effects of the Navy's activities combined, 
that the authorized take proposed would have a negligible impact on 
these stocks.
Odontocetes

Sperm Whale, Dwarf Sperm Whale, and Pygmy Sperm Whale

    In table 14 and table 15 below for sperm whale, dwarf sperm whale, 
and pygmy sperm whale, we indicate the total annual mortality (0 for 
all stocks; the 2020 HSTT final rule included 0.14 annual takes by 
mortality of the Hawaii stock of sperm whale), Level A and Level B 
harassment, and a number indicating the instances of total take as a 
percentage of abundance. Table 14 and table 15 are unchanged from 
tables 20 and 21 in the 2020 HSTT final rule, except for updated 
information on mortality for the Hawaii stock of sperm whales, as 
discussed above. For additional information and analysis supporting the 
negligible-impact analysis, see the Odontocetes discussion as well as 
the Sperm Whales, Dwarf Sperm Whales, and Pygmy Sperm Whales discussion 
in the Group and Species-Specific Analyses section of the 2018 HSTT 
final rule, all of which remains applicable to this proposed rule 
unless specifically noted.

[[Page 68341]]



Table 14--Annual Estimated Takes by Level B Harassment, Level A Harassment, and Mortality for Sperm Whales, Dwarf Sperm Whales, and Pygmy Sperm Whales in the HRC Portion of the HSTT Study Area
                                                      and Number Indicating the Instances of Total Take as a Percentage of Stock Abundance
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                    Instances of indicated types of incidental             Total takes                   Abundance          Instances of total
                                                                      take (not all takes represent separate    ---------------------------------------------------------   take as percent of
                                                                     individuals, especially for disturbance)                                                                    abundance
                                                                  ----------------------------------------------                                                         -----------------------
                                                                       Level B harassment          Level A                      Total             Total Navy              Total take
                Species                           Stock           ---------------------------     harassment                    takes     Takes    abundance  Within EEZ      as       EEZ take
                                                                                             -------------------  Mortality    (entire   (within  inside and     Navy     percentage      as
                                                                                  TTS (may                                      study     NAVY      outside    abundance   of total   percentage
                                                                    Behavioral  also include           Tissue                   area)     EEZ)     EEZ (HRC)     (HRC)       Navy       of EEZ
                                                                   disturbance  disturbance)   PTS     damage                                                              abundance   abundance
                                                                                                                                                                             (HRC)       (HRC)
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Dwarf sperm whale.....................  Hawaii...................        5,870        14,550     64           0            0    20,484    15,310       8,218       6,379         249         240
Pygmy sperm whale.....................  Hawaii...................        2,329         5,822     29           0            0     8,180     6,098       3,349       2,600         244         235
Sperm whale...........................  Hawaii...................        2,466            30      0           0            0     2,496     1,317       1,656       1,317         151         147
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Note: For the Hawaii take estimates, we compare predicted takes to abundance estimates generated from the same underlying density estimates (as described in the Estimated Take of Marine
  Mammals section of the 2018 HSTT final rule), both in and outside of the U.S. EEZ. Because the portion of the Navy's study area inside the U.S. EEZ is generally concomitant with the area
  used to generate the abundance estimates in the SARs, and the abundance predicted by the same underlying density estimates is the preferred abundance to use, there is no need to separately
  compare the take to the SARs abundance estimate.
Total takes inside and outside U.S. EEZ represent the sum of annual Level A and Level B harassment from training and testing activities.


  Table 15--Annual Estimated Takes by Level B Harassment, Level A Harassment, and Mortality for Sperm Whales, Dwarf Sperm Whales, and Pygmy Sperm Whales in the SOCAL Portion of the HSTT Study
                                                    Area and Number Indicating the Instances of Total Take as a Percentage of Stock Abundance
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                              Instances of indicated types of incidental        Total takes              Abundance          Instances of total
                                                                                take (not all takes represent separate    -----------------------------------------------   take as percent of
                                                                               individuals, especially for disturbance)                                                          abundance
                                                                            ----------------------------------------------                                               -----------------------
                                                                                 Level B harassment          Level A                                                      Total take
                                                                            ---------------------------     harassment                    Total      Navy                     as      Total take
                  Species                                 Stock                                        -------------------                takes    abundance   NMFS SARS  percentage      as
                                                                                                                            Mortality    (entire   in action   abundance   of total   percentage
                                                                              Behavioral    TTS (may                                      study      area                    Navy      of total
                                                                             disturbance  also include   PTS     Tissue                   area)                            abundance      SAR
                                                                                          disturbance)           damage                                                    in Action   abundance
                                                                                                                                                                             Area
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Kogia whales...............................  CA/OR/WA......................        2,779         6,353     38           0            0     9,170         757       4,111       1,211         223
Sperm whale................................  CA/OR/WA......................        2,437            56      0           0            0     2,493         273       1,997         913         125
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Note: For the SOCAL take estimates, because of the manner in which the Navy study area overlaps the ranges of many MMPA stocks (i.e., a stock may range far north to Washington state and beyond
  and abundance may only be predicted within the U.S. EEZ, while the Navy study area is limited to Southern California and northern Mexico, but extends beyond the U.S. EEZ), we compare
  predicted takes to both the abundance estimates for the study area, as well as the SARs (as described in the Estimated Take of Marine Mammals section of the 2018 HSTT final rule).
Total takes inside and outside U.S. EEZ represent the sum of annual Level A and Level B harassment from training and testing activities.

    Below we compile and summarize the information that supports our 
preliminary determination that the Navy's activities would not 
adversely affect any species or stocks through effects on annual rates 
of recruitment or survival for any of the affected species and stocks 
addressed in this section.
Sperm Whale, Dwarf Sperm Whale, and Pygmy Sperm Whale (CA/OR/WA Stocks)
    The SAR identifies the CA/OR/WA stock of sperm whales as 
``stable'', and the species is listed as endangered under the ESA. The 
status of the CA/OR/WA stocks of pygmy and dwarf sperm whales is 
unknown and neither are listed under the ESA. Neither mortality nor 
Level A harassment by tissue damage from exposure to explosives is 
expected or proposed for authorization for any of these three stocks.
    Due to their pelagic distribution, small size, and cryptic 
behavior, pygmy sperm whales and dwarf sperm whales are rarely sighted 
during at-sea surveys and are difficult to distinguish between when 
visually observed in the field. Many of the relatively few observations 
of Kogia spp. off the U.S. West Coast were not identified to species. 
All at-sea sightings of Kogia spp. have been identified as pygmy sperm 
whales or Kogia spp. Stranded dwarf sperm and pygmy sperm whales have 
been found on the U.S. West Coast, however dwarf sperm whale strandings 
are rare. NMFS SARs suggest that the majority of Kogia sighted off the 
U.S. West Coast were likely pygmy sperm whales. As such, the stock 
estimate in the NMFS SAR for pygmy sperm whales is the estimate derived 
for all Kogia spp. in the region (Barlow, 2016), and no separate 
abundance estimate can be determined for dwarf sperm whales, though 
some low number likely reside in the U.S. EEZ. Due to the lack of 
abundance estimate, it is not possible to predict the take of dwarf 
sperm whales and take estimates are identified as Kogia spp. (including 
both pygmy and dwarf sperm whales). We assume only a small portion of 
those takes are likely to be dwarf sperm whales as the density and 
abundance in the U.S. EEZ is thought to be low.
    Regarding the magnitude of Level B harassment takes (TTS and 
behavioral disturbance), the number of estimated total instances of 
take compared to the abundance (measured against both the Navy-
estimated abundance and the SAR) is, respectively, 913 and 125 for 
sperm whales and 1,211 and 223 for Kogia spp., with a large proportion 
of

[[Page 68342]]

these anticipated to be pygmy sperm whales due to the low abundance and 
density of dwarf sperm whales in the HSTT Study Area. (Table 15). Given 
the range of these stocks (which extends the entire length of the West 
Coast, as well as beyond the U.S. EEZ boundary), this information 
suggests that some portion of the individuals in these stocks will not 
be impacted but that there is likely some repeat exposure (perhaps up 
to 24 days within a year for Kogia spp. and 18 days a year for sperm 
whales) of some small subset of individuals that spend extended time 
within the SOCAL Range. Additionally, while interrupted feeding bouts 
are a known response and concern for odontocetes, we also know that 
there are often viable alternative habitat options in the relative 
vicinity. Regarding the severity of those individual Level B harassment 
takes by behavioral disturbance, the duration of any exposure is 
expected to be between minutes and hours (i.e., relatively short) and 
the received sound levels largely below 172 dB (i.e., of a lower, to 
occasionally moderate, level and less likely to evoke a severe 
response). However, some of these takes could occur on a fair number of 
sequential days for some number of individuals.
    Regarding the severity of TTS takes, they are expected to be low-
level, of short duration, and mostly not in a frequency band that would 
be expected to interfere with sperm whale communication or other 
important low-frequency cues, and that the associated lost 
opportunities and capabilities are not at a level that would impact 
reproduction or survival. For these same reasons (low level and 
frequency band), while a small permanent loss of hearing sensitivity 
(PTS) may include some degree of energetic costs for compensating or 
may mean some small loss of opportunities or detection capabilities, at 
the expected scale the estimated Level A harassment takes by PTS for 
the dwarf and pygmy sperm whale stocks would be unlikely to impact 
behaviors, opportunities, or detection capabilities to a degree that 
would interfere with reproductive success or survival of any 
individuals. Thus, the 38 total Level A harassment takes by PTS for 
these two stocks would be unlikely to affect rates of recruitment and 
survival for the stocks.
    Altogether, most members of the stocks will likely be taken by 
Level B harassment (at a low to occasionally moderate level) over 
several days a year, and some smaller portion of the stocks are 
expected to be taken on a relatively moderate to high number of days 
(up to 18 or 24) across the year, some of which could be sequential 
days. Though the majority of impacts are expected to be of a lower to 
sometimes moderate severity, the larger number of takes for a subset of 
individuals makes it more likely that a small number of individuals 
could be interrupted during foraging in a manner and amount such that 
impacts to the energy budgets of females (from either losing feeding 
opportunities or expending considerable energy to find alternative 
feeding options) could cause them to forego reproduction for a year. 
Energetic impacts to males are generally meaningless to population 
rates unless they cause death, and it takes extreme energy deficits 
beyond what would ever be likely to result from these activities to 
cause the death of an adult marine mammal. As discussed in the 2020 
HSTT final rule, however, foregone reproduction (especially for 1 year, 
which is the maximum predicted because the small number anticipated in 
any 1 year makes the probability that any individual would be impacted 
in this way twice in 7 years very low) has far less of an impact on 
population rates than mortality and a small number of instances of 
foregone reproduction would not be expected to adversely affect these 
stocks through effects on annual rates of recruitment or survival. We 
also note that residual PBR is 19 for pygmy sperm whales and 1.9 for 
sperm whales. Both the abundance and PBR are unknown for dwarf sperm 
whales, however, we know that take of this stock is likely 
significantly lower in magnitude and severity (i.e., lower number of 
total takes and repeated takes any individual) than pygmy sperm whales. 
For these reasons, in consideration of all of the effects of the Navy's 
activities combined, we have preliminarily determined that the 
authorized take proposed would have a negligible impact on the CA/OR/WA 
stocks of sperm whales and pygmy and dwarf sperm whales.
Sperm Whale (Hawaii Stock)
    The SAR does not identify a trend for this stock and the species is 
listed as endangered under the ESA. No mortality or Level A harassment 
by PTS or tissue damage is expected or proposed for authorization.
    Regarding the magnitude of Level B harassment takes (TTS and 
behavioral disturbance), the number of estimated instances of take 
compared to the abundance, both throughout the HSTT Study Area and 
within the U.S. EEZ, respectively, is 151 and 147 percent (table 14). 
This information and the sperm whale stock range suggest that likely 
only a smaller portion of the stock would be impacted, over 1 to 
several days per year, with little likelihood of take across sequential 
days. Regarding the severity of those individual Level B harassment 
takes by behavioral disturbance, the duration of any exposure is 
expected to be between minutes and hours (i.e., relatively short) and 
the received sound levels largely below 172 dB (i.e., of a lower, to 
occasionally moderate, level and less likely to evoke a severe 
response). Regarding the severity of TTS takes, they are expected to be 
low-level, of short duration, and mostly not in a frequency band that 
would be expected to interfere with sperm whale communication or other 
important low-frequency cues, and that the associated lost 
opportunities and capabilities are not at a level that would impact 
reproduction or survival.
    Altogether, a relatively small portion of this stock is anticipated 
to be impacted and any individuals are likely to be disturbed at a low-
moderate level, with the taken individuals likely exposed between 1 and 
several days, with little chance that any are taken across sequential 
days. This low magnitude and severity of harassment effects is not 
expected to result in impacts on individual reproduction or survival, 
much less annual rates of recruitment or survival. For these reasons, 
we have preliminarily determined, in consideration of all of the 
effects of the Navy's activities combined, that the authorized take 
proposed would have a negligible impact on the Hawaii stock of sperm 
whales.
Pygmy and Dwarf Sperm Whales (Hawaii Stocks)
    The SAR does not identify a trend for these stocks and the species 
are not listed under the ESA. No Level A harassment by tissue damage is 
anticipated or proposed for authorization. Regarding the magnitude of 
Level B harassment takes (TTS and behavioral disturbance), the number 
of estimated instances of take compared to the abundance, both 
throughout the HSTT Study Area and within the U.S. EEZ, respectively, 
is 244-249 and 235-240 percent (table 12). This information and the 
pygmy and dwarf sperm whale stock ranges (at least throughout the U.S. 
EEZ around the entire Hawaiian Islands) suggest that likely a fair 
portion of each stock is not impacted, but that a subset of individuals 
may be taken over one to perhaps 5 days per year, with little 
likelihood of take across sequential days. Regarding the severity of 
those individual Level B harassment takes by behavioral disturbance, 
the duration of any exposure is expected to

[[Page 68343]]

be between minutes and hours (i.e., relatively short) and the received 
sound levels largely below 172 dB (i.e., of a lower, to occasionally 
moderate, level and less likely to evoke a severe response). 
Additionally, as discussed earlier, within the Hawaii Island Mitigation 
Area, explosives are not used and the use of MF1 and MF4 active sonar 
is limited, greatly reducing the severity of impacts within the small 
and resident population BIA for dwarf sperm whales (Kratofil et al., 
2023), which is entirely contained within this mitigation area.
    Regarding the severity of TTS takes, they are expected to be low-
level, of short duration, and mostly not in a frequency band that would 
be expected to interfere with sperm whale communication or other 
important low-frequency cues--and that the associated lost 
opportunities and capabilities are not at a level that would impact 
reproduction or survival. For these same reasons (low level and 
frequency band), while a small permanent loss of hearing sensitivity 
may include some degree of energetic costs for compensating or may mean 
some small loss of opportunities or detection capabilities, at the 
expected scale, estimated Level A harassment takes by PTS for dwarf and 
pygmy sperm whales would be unlikely to impact behaviors, 
opportunities, or detection capabilities to a degree that would 
interfere with reproductive success or survival of any individuals, 
even if it were to be experienced by an animal that also experiences 
one or more instances of Level B harassment by behavioral disturbance. 
Thus the 29 and 64 total Level A harassment takes by PTS for dwarf and 
pygmy sperm whales, respectively, would be unlikely to affect rates of 
recruitment and survival for these stocks.
    Altogether, a portion of these stocks are likely to be impacted and 
any individuals are likely to be disturbed at a low-moderate level, 
with the taken individuals likely exposed between 1 and 5 days, with 
little chance that any are taken across sequential days. This low 
magnitude and severity of Level A and Level B harassment effects is not 
expected to result in impacts on individual reproduction or survival, 
much less impacts on annual rates of recruitment or survival. For these 
reasons, we have preliminarily determined, in consideration of all of 
the effects of the Navy's activities combined, that the expected and 
authorized take proposed would have a negligible impact on the Hawaii 
stocks of pygmy and dwarf sperm whales.

Beaked Whales

    In table 16 and table 17 below for beaked whales, we indicate the 
total annual mortality, Level A and Level B harassment, and a number 
indicating the instances of total take as a percentage of abundance. 
Table 16 and table 17 are unchanged from table 22 and table 23 in the 
2020 HSTT final rule, with the exception of a correction to a rounding 
error as noted. For additional information and analysis supporting the 
negligible-impact analysis, see the Odontocetes discussion as well as 
the Beaked Whales discussion in the Group and Species-Specific Analyses 
section of the 2018 HSTT final rule, all of which remains applicable to 
this proposed rule unless specifically noted.

  Table 16--Annual Estimated Takes by Level B Harassment, Level A Harassment, and Mortality for Beaked Whales in the HRC Portion of the HSTT Study Area and Number Indicating the Instances of
                                                                          Total Take as a Percentage of Stock Abundance
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                    Instances of indicated types of incidental take (not all      Total takes            Abundance          Instances of total
                                                                      takes represent separate individuals, especially for   --------------------------------------------   take as percent of
                                                                                          disturbance)                                                                           abundance
                                                                  -----------------------------------------------------------                                            -----------------------
                                                                       Level B harassment           Level A harassment          Total             Total Navy              Total take
                Species                           Stock           -----------------------------------------------------------   Takes     Takes    abundance  Within EEZ      as       EEZ take
                                                                                                                               (entire   (within  inside and     Navy     percentage      as
                                                                                  TTS (may                                      Study     Navy      outside    abundance   of total   percentage
                                                                    Behavioral  also include     PTS      Tissue   Mortality    Area)     EEZ)     EEZ (HRC)     (HRC)       Navy       of EEZ
                                                                   disturbance  disturbance)              damage                                                           abundance   abundance
                                                                                                                                                                             (HRC)       (HRC)
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Blainville's beaked whale.............  Hawaii...................        5,369            16          0         0          0     5,385     4,140         989         768     \a\ 544         539
Cuvier's beaked whale.................  Hawaii...................        1,792             4          0         0          0     1,796     1,377         345         268         521         514
Longman's beaked whale................  Hawaii...................       19,152            81          0         0          0    19,233    14,585       3,568       2,770         539         527
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Note: For the Hawaii take estimates, we compare predicted takes to abundance estimates generated from the same underlying density estimates (as described in the Estimated Take of Marine
  Mammals section of the 2018 HSTT final rule), both in and outside of the U.S. EEZ. Because the portion of the Navy's study area inside the U.S. EEZ is generally concomitant with the area
  used to generate the abundance estimates in the SARs, and the abundance predicted by the same underlying density estimates is the preferred abundance to use, there is no need to separately
  compare the take to the SARs abundance estimate.
Total takes inside and outside U.S. EEZ represent the sum of annual Level A and Level B harassment from training and testing activities.
\a\ The 2020 final rule unintentionally presented this percentage as 545. The correct value is provided here. This error does not affect the conclusions in the 2020 HSTT final rule.


[[Page 68344]]


 Table 17--Annual Estimated Takes by Level B Harassment, Level A Harassment, and Mortality for Beaked Whales in the SOCAL Portion of the HSTT Study Area and Number Indicating the Instances of
                                                                          Total Take as a Percentage of Stock Abundance
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                              Instances of indicated types of incidental        Total takes              Abundance          Instances of total
                                                                                take (not all takes represent separate    -----------------------------------------------   take as percent of
                                                                               individuals, especially for disturbance)                                                          abundance
                                                                            ----------------------------------------------                                               -----------------------
                                                                                 Level B harassment          Level A                                                      Total take
                                                                            ---------------------------     harassment                    Total      Navy                     as      Total take
                  Species                                 Stock                                        -------------------                Takes    abundance   NMFS SARS  percentage      as
                                                                                                                            Mortality    (entire   in action   abundance   of total   percentage
                                                                              Behavioral    TTS (may                                      study      area                    Navy      of total
                                                                             disturbance  also include   PTS     Tissue                   area)                            abundance      SAR
                                                                                          disturbance)           damage                                                    in action   abundance
                                                                                                                                                                             area
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Baird's beaked whale.......................  CA/OR/WA......................        2,030            14      0           0            0     2,044          74       1,363       2,762         150
Cuvier's beaked whale......................  CA/OR/WA......................       11,373           127      1           0            0    11,501         520       5,454       2,212         211
Mesoplodon species.........................  CA/OR/WA......................        6,125            68      1           0            0     6,194          89       3,044       6,960         203
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Note: For the SOCAL take estimates, because of the manner in which the Navy study area overlaps the ranges of many MMPA stocks (i.e., a stock may range far north to Washington state and beyond
  and abundance may only be predicted within the U.S. EEZ, while the Navy study area is limited to Southern California and northern Mexico, but extends beyond the U.S. EEZ), we compare
  predicted takes to both the abundance estimates for the study area, as well as the SARs (as described in the Estimated Take of Marine Mammals section of the 2018 HSTT final rule).
Total takes inside and outside U.S. EEZ represent the sum of annual Level A and Level B harassment from training and testing activities.

    Below we compile and summarize the information that supports our 
determination that the Navy's activities would not adversely affect any 
species or stocks through effects on annual rates of recruitment or 
survival for any of the affected species or stocks addressed in this 
section.
Blainville's, Cuvier's, and Longman's Beaked Whales (Hawaii Stocks)
    The SAR does not identify a trend for these stocks and the species 
are not listed under the ESA. No mortality or Level A harassment are 
expected or proposed for authorization for any of these three stocks. 
Regarding the magnitude of Level B harassment takes (TTS and behavioral 
disturbance), the number of estimated instances of take compared to the 
abundance, both throughout the HSTT Study Area and within the U.S. EEZ, 
respectively, is 521-544 and 514-539 percent (table 16). This 
information and the stock ranges (at least of the small, resident 
island associated stocks around Hawaii) suggest that likely a fair 
portion of the stocks (but not all) will be impacted, over 1 to perhaps 
11 days per year, with little likelihood of much take across sequential 
days. Regarding the severity of those individual Level B harassment 
takes by behavioral disturbance, the duration of any exposure is 
expected to be between minutes and hours (i.e., relatively short) and 
the received sound levels largely below 160 dB, though with beaked 
whales, which are considered somewhat more sensitive, this could mean 
that some individuals will leave preferred habitat for a day or 2 
(i.e., moderate level takes). However, while interrupted feeding bouts 
are a known response and concern for odontocetes, we also know that 
there are often viable alternative habitat options nearby. 
Additionally, as noted earlier, within the Hawaii Island mitigation 
area (which overlaps a large portion of the BIAs for Cuvier's and 
Blainville's beaked whales), explosives are not used and the use of MF1 
and MF4 active sonar is limited, greatly reducing the severity of 
impacts within these two small resident populations.
    Regarding the severity of TTS takes, they are expected to be low-
level, of short duration, and mostly not in a frequency band that would 
be expected to interfere with beaked whale communication or other 
important low-frequency cues, and that the associated lost 
opportunities and capabilities are not at a level that would impact 
reproduction or survival.
    Altogether, a fair portion of these stocks are anticipated to be 
impacted and any individuals are likely to be disturbed at a moderate 
level, with the taken individuals likely exposed between 1 and 11 days, 
with little chance that individuals are taken across more than a few 
sequential days. This low, to occasionally moderate, magnitude and 
severity of harassment effects is not expected to result in impacts on 
individual reproduction or survival, much less have impacts on annual 
rates of recruitment or survival. For these reasons, we have 
preliminarily determined, in consideration of all of the effects of the 
Navy's activities combined, that the authorized take proposed would 
have a negligible impact on the Hawaii stocks of beaked whales.
Baird's and Cuvier's Beaked Whales and Mesoplodon Species (All CA/OR/WA 
Stocks)
    The species are not listed under the ESA and their populations have 
been identified as ``increasing,'' ``decreasing,'' and ``increasing,'' 
respectively. No mortality is expected or proposed for authorization 
for any of these three stocks and only two takes by Level A harassment 
(PTS) are proposed for authorization.
    No methods are available to distinguish between the six species of 
Mesoplodon beaked whale CA/OR/WA stocks (Blainville's beaked whale (M. 
densirostris), Perrin's beaked whale (M. perrini), Lesser beaked whale 
(M. peruvianus), Stejneger's beaked whale (M. stejnegeri), Gingko-
toothed beaked whale (M. gingkodens), and Hubbs' beaked whale (M. 
carlhubbsi)) when observed during at-sea surveys (Carretta et al. 
2018a). Bycatch and stranding records from the region indicate that the 
Hubbs' beaked whale is most commonly encountered (Carretta et al. 2008, 
Moore and Barlow, 2013). As indicated in the SAR, no species-specific 
abundance estimates are available, the abundance estimate includes all 
CA/OR/WA Mesoplodon spp, and the six species are managed as one unit. 
Due to the lack of species-specific abundance estimates, it is not 
possible to predict the take of individual species and take estimates 
are identified as Mesoplodon spp.
    Regarding the magnitude of Level B harassment takes (TTS and 
behavioral disturbance), the number of estimated total instances of 
take compared to the abundance for these stocks is 2,762, 2,212, and 
6,960 percent (measured against Navy-estimated abundance) and

[[Page 68345]]

150, 211, and 203 percent (measured against the SAR) for Baird's beaked 
whales, Cuvier's beaked whales, and Mesoplodon spp., respectively 
(table 15). Given the ranges of these stocks, this information suggests 
that some smaller portion of the individuals of these stocks will be 
taken, and that some subset of individuals within the stock will be 
taken repeatedly within the year (perhaps up to 20-25 days, and 
potentially more for Cuvier's)--potentially over a fair number of 
sequential days, especially where individuals spend extensive time in 
the SOCAL Range. Note that we predict lower days of repeated exposure 
for these stocks than their percentages might have suggested because of 
the number of overall takes--i.e., using the higher percentage would 
suggest that an unlikely portion of the takes are taken up by a small 
portion of the stock incurring a very large number of repeat takes, 
with little room for take resulting from few or moderate numbers of 
repeats, which is unlikely. While interrupted feeding bouts are a known 
response and concern for odontocetes, we also know that there are often 
viable alternative habitat options in the relative vicinity. Regarding 
the severity of those individual Level B harassment takes by behavioral 
disturbance, we have explained that the duration of any exposure is 
expected to be between minutes and hours (i.e., relatively short) and 
the received sound levels largely below 160 dB, though with beaked 
whales, which are considered somewhat more sensitive, this could mean 
that some individuals will leave preferred habitat for a day or 2 
(i.e., of a moderate level). In addition, as noted, some of these takes 
could occur on a fair number of sequential days for these stocks.
    The severity of TTS takes is expected to be low-level, of short 
duration, and mostly not in a frequency band that would be expected to 
interfere significantly with conspecific communication, echolocation, 
or other important low-frequency cues. Therefore, the associated lost 
opportunities and capabilities would not be expected to impact 
reproduction or survival. For similar reasons (as described in the 2020 
HSTT final rule) the single estimated Level A harassment take by PTS 
for this stock is unlikely to have any effects on the reproduction or 
survival of any individuals.
    Altogether, a portion of these stocks will likely be taken (at a 
moderate or sometimes low level) over several days a year, and some 
smaller portion of the stock is expected to be taken on a relatively 
moderate to high number of days across the year, some of which could be 
sequential days. Though the majority of impacts are expected to be of a 
moderate severity, the repeated takes over a potentially fair number of 
sequential days for some individuals makes it more likely that a small 
number of individuals could be interrupted during foraging in a manner 
and amount such that impacts to the energy budgets of females (from 
either losing feeding opportunities or expending considerable energy to 
find alternative feeding options) could cause them to forego 
reproduction for a year. Energetic impacts to males are generally 
meaningless to population rates unless they cause death, and it takes 
extreme energy deficits beyond what would ever be likely to result from 
these activities to cause the death of an adult marine mammal. As noted 
previously, however, foregone reproduction (especially for 1 year, 
which is the maximum predicted because the small number anticipated in 
any 1 year makes the probability that any individual would be impacted 
in this way twice in 7 years very low) has far less of an impact on 
population rates than mortality and a small number of instances of 
foregone reproduction would not be expected to adversely affect these 
stocks through effects on annual rates of recruitment or survival, 
especially given the residual PBR of these three beaked whale stocks 
(8.7, 41.9, and 19.9, respectively).
    Further, Navy activities have been conducted in SOCAL for many 
years at similar levels and the SAR considers Mesoplodon spp. and 
Baird's beaked whales as increasing. While NMFS' SAR indicates that 
Cuvier's beaked whales on the U.S. West Coast are declining based on a 
Bayesian trend analysis of NMFS' survey data collected from 1991 
through 2014, results from passive acoustic monitoring and other 
research have estimated regional Cuvier's beaked whale densities that 
were higher than indicated by NMFS' broad-scale visual surveys for the 
U.S. West Coast (Debich et al. 2015a; Debich et al. 2015b; Falcone and 
Schorr, 2012, 2014; Hildebrand et al. 2009; Moretti, 2016; 
[Scaron]irovi[cacute] et al. 2016; Smultea and Jefferson, 2014). 
Research also indicates higher than expected residency in the Navy's 
instrumented Southern California Anti-Submarine Warfare Range in 
particular (Falcone and Schorr, 2012) and photo identification studies 
in the SOCAL have identified approximately 100 individual Cuvier's 
beaked whale individuals with 40 percent having been seen in one or 
more prior years, with re-sightings up to 7 years apart (Falcone and 
Schorr, 2014). The documented residency by many Cuvier's beaked whales 
over multiple years suggests that a stable population may exist in that 
small portion of the stock's overall range (Falcone et al. 2009; 
Falcone and Schorr, 2014; Schorr et al. 2017).
    For these reasons, in consideration of all of the effects of the 
Navy's activities combined, we have preliminarily determined that the 
authorized take proposed would have a negligible impact on the CA/OR/WA 
stocks of Baird's and Cuvier's beaked whales, as well as all six 
species included within the Mesoplodon spp.

Small Whales and Dolphins

    In table 18 and table 19 below for dolphins and small whales, we 
indicate the total annual mortality, Level A and Level B harassment, 
and a number indicating the instances of total take as a percentage of 
abundance. Table 18 and table 19 are updated from tables 24 and 25 in 
the 2020 HSTT final rule as appropriate with the 2022 final SARs. For 
additional information and analysis supporting the negligible-impact 
analysis, see the Odontocetes discussion as well as the Small Whales 
and Dolphins discussion in the Group and Species-Specific Analyses 
section of the 2018 HSTT final rule, all of which remains applicable to 
this proposed rule unless specifically noted.

[[Page 68346]]



   Table 18--Annual Estimated Takes by Level B Harassment, Level A Harassment, and Mortality for Dolphins and Small Whales in the HRC Portion of the HSTT Study Area and Number Indicating the
                                                                   Instances of Total Take as a Percentage of Stock Abundance
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                    Instances of indicated types of incidental take (not all      Total takes            Abundance        Instance of total take
                                                                      takes represent separate individuals, especially for   --------------------------------------------      as percent of
                                                                                          disturbance)                                                                           abundance
                                                                  -----------------------------------------------------------                        Total               -----------------------
                                                                       Level B harassment          Level A                      Total                Navy                    Total     EEZ  take
                Species                           Stock           ---------------------------     harassment                    takes     Takes    abundance    Within      take as       as
                                                                                             -------------------               (entire   (within  inside and   EEZ  Navy  percentage  percentage
                                                                                  TTS  (may                       Mortality     study     Navy      outside    abundance    of total    of Navy
                                                                    Behavioral      also               Tissue                   area)     EEZ)      of EEZ       (HRC)       Navy         EEZ
                                                                   disturbance     include     PTS     damage                                        (HRC)                 abundance   abundance
                                                                                disturbance)                                                                                 (HRC)       (HRC)
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Bottlenose dolphin....................  Hawaii Pelagic...........        3,196           132      0           0            0     3,328     2,481       1,528       1,442         218         172
Bottlenose dolphin....................  Kauai & Niihau...........          534            31      0           0            0       565       264         184         184         307         143
Bottlenose dolphin....................  Oahu.....................        8,600            61      1           0            0     8,662     8,376         743         743   \a\ 1,166   \a\ 1,127
Bottlenose dolphin....................  4-Island.................          349            10      0           0            0       359       316         189         189         190         167
Bottlenose dolphin....................  Hawaii...................           74             6      0           0            0        80        42         131         131          61          32
False killer whale....................  Hawaii Pelagic...........          999            42      0           0            0     1,041       766         645         507         161         151
False killer whale....................  Main Hawaiian Islands              572            17      0           0            0       589       476         147         147     \b\ 401         324
                                         Insular.
False killer whale....................  Northwestern Hawaiian              365            16      0           0            0       381       280         215         169         177         166
                                         Islands.
Fraser's dolphin......................  Hawaii...................       39,784         1,289      2           0            0    41,075    31,120       5,408      18,763         760         166
Killer whale..........................  Hawaii...................          118             6      0           0            0       124        93          69          54         180         172
Melon-headed whale....................  Hawaii Islands...........        3,261           231      0           0            0     3,492     2,557       1,782       1,782         196         143
Melon-headed whale....................  Kohala Resident..........          341             9      0           0            0       350       182         447         447          78          41
Pantropical spotted dolphin...........  Hawaii Island............        3,767           227      0           0            0     3,994     2,576       2,405       2,405         166         107
Pantropical spotted dolphin...........  Hawaii Pelagic...........        9,973           476      0           0            0    10,449     7,600       5,462       4,637         191         164
Pantropical spotted dolphin...........  Oahu.....................        4,284            45      0           0            0     4,329     4,194         372         372       1,164       1,127
Pantropical spotted dolphin...........  4-Island.................          701            17      0           0            0       718       634         657         657         109          96
Pygmy killer whale....................  Hawaii...................        8,122           402      0           0            0     8,524     6,538       4,928       3,931         173         166
Pygmy killer whale....................  Tropical.................          710            50      0           0            0       760       490         159          23         478       2,130
Risso's dolphin.......................  Hawaii...................        8,950           448      0           0            0     9,398     7,318       1,210       4,199         777         174
Rough-toothed dolphin.................  Hawaii...................        6,112           373      0           0            0     6,485     4,859       3,054       2,808         212         173
Short-finned pilot whale..............  Hawaii...................       12,499           433      0           0            0    12,932     9,946       6,433       5,784         201         172
Spinner dolphin.......................  Hawaii Island............          279            12      0           0            0       291        89         629         629          46          14
Spinner dolphin.......................  Hawaii Pelagic...........        4,332           202      0           0            0     4,534     3,491       2,885       2,229         157         157
Spinner dolphin.......................  Kauai & Niihau...........        1,683            63      0           0            0     1,746       812         604         604         289         134

[[Page 68347]]

 
Spinner dolphin.......................  Oahu & 4-Island..........        1,790            34      1           0            0     1,825     1,708         354         354         516         482
Striped dolphin.......................  Hawaii...................        7,379           405      0           0            0     7,784     6,034       4,779       3,646         163         165
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Note: For the Hawaii take estimates, we compare predicted takes to abundance estimates generated from the same underlying density estimates (as described in the Estimated Take of Marine
  Mammals section of the 2018 HSTT final rule), both in and outside of the U.S. EEZ. Because the portion of the Navy's study area inside the U.S. EEZ is generally concomitant with the area
  used to generate the abundance estimates in the SARs, and the abundance predicted by the same underlying density estimates is the preferred abundance to use, there is no need to separately
  compare the take to the SARs abundance estimate.
Total takes inside and outside U.S. EEZ represent the sum of annual Level A and Level B harassment from training and testing activities.
\a\ The 2020 final rule unintentionally presented these percentages as 1,169 and 1,130. The correct values are provided here. These errors do not affect the conclusions in the 2020 HSTT final
  rule.
\b\ The 2020 final rule unintentionally presented this percentage as 400. The correct value is provided here. This rounding error does not affect the conclusions in the 2020 HSTT final rule.


  Table 19--Annual Estimated Takes by Level B Harassment, Level A Harassment, and Mortality for Dolphins and Small Whales in the SOCAL Portion of the HSTT Study Area and Number Indicating the
                                                                   Instances of Total Take as a Percentage of Stock Abundance
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                            Instances of indicated types of incidental take (not all     Total           Abundance        Instance of total take
                                                                              takes represent separate individuals, especially for       takes   ------------------------      as percent of
                                                                                                  disturbance)                       ------------                                abundance
                                                                          -----------------------------------------------------------                                    -----------------------
                                                                               Level B harassment          Level A                                                           Total
                                                                          ---------------------------     harassment                     Total       Navy                   take as      Total
                  Species                               Stock                                        -------------------                 takes     abundance  NMFS  SARS  percentage    take as
                                                                                          TTS  (may                                     (entire    in action   abundance    of total  percentage
                                                                            Behavioral      also                          Mortality      study       area                    Navy       of total
                                                                           disturbance     include     PTS     Tissue                    area)      (SOCAL)                abundance      SAR
                                                                                        disturbance)           damage                                                      in action   abundance
                                                                                                                                                                             area
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Bottlenose dolphin........................  California Coastal...........        1,771            38      0           0            0       1,809         238         453         760         399
Bottlenose dolphin........................  CA/OR/WA Offshore............       51,727         3,695      3           0            0      55,425       5,946       3,477         932       1,594
Killer whale..............................  ENP Offshore.................           96            11      0           0            0         107           4         300       2,675          36
Killer whale..............................  ENP Transient/West Coast               179            20      0           0            0         199          30         349         663          57
                                             Transient.
Long-beaked common dolphin................  California...................      233,485        13,787     18           2            0     247,292      10,258      83,379       2,411         297
Northern right whale dolphin..............  CA/OR/WA.....................       90,052         8,047     10           1            0      98,110       7,705      29,285       1,273         335
Pacific white-sided dolphin...............  CA/OR/WA.....................       69,245         6,093      5           0            0      75,343       6,626      34,999       1,137         215
Risso's dolphin...........................  CA/OR/WA.....................      116,143        10,118      9           0            0     126,270       7,784       6,336       1,622       1,993
Short-beaked common dolphin...............  CA/OR/WA.....................    1,374,048       118,525     79          10         1.14   1,492,664     261,438   1,056,308         571         141
Short-finned pilot whale..................  CA/OR/WA.....................        1,789           124      1           0            0       1,914         208         836         920         229
Striped dolphin...........................  CA/OR/WA.....................      163,640        11,614      3           0            0     175,257      39,862      29,988         440         584
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Note: For the SOCAL take estimates, because of the manner in which the Navy study area overlaps the ranges of many MMPA stocks (i.e., a stock may range far north to Washington state and beyond
  and abundance may only be predicted within the U.S. EEZ, while the Navy study area is limited to Southern California and northern Mexico, but extends beyond the U.S. EEZ), we compare
  predicted takes to both the abundance estimates for the study area, as well as the SARs (as described in the Estimated Take of Marine Mammals section of the 2018 HSTT final rule).
Total takes inside and outside U.S. EEZ represent the sum of annual Level A and Level B harassment from training and testing activities.
For mortality takes there is an annual average of 1.14 short-beaked common dolphins (i.e., where eight takes could potentially occur divided by 7 years to get the annual number of mortalities/
  serious injuries).

    Below we compile and summarize the information that supports our 
determination that the Navy's activities would not adversely affect any 
species or stocks through effects on annual rates of recruitment or 
survival for any of the affected species or stocks addressed in this 
section.

[[Page 68348]]

Long-Beaked Common Dolphin (California Stock), Northern Right Whale 
Dolphin (CA/OR/WA Stock), and Short-Beaked Common Dolphin (CA/OR/WA 
Stock)
    None of these stocks are listed under the ESA and their stock 
statuses are considered ``increasing,'' ``unknown,'' and 
``increasing,'' respectively. Eight mortalities or serious injuries of 
short-beaked common dolphins are proposed for authorization over the 7-
year rule, or 1.14 M/SI annually. The addition of this 1.14 annual 
mortality still leaves the total human-caused mortality well under the 
insignificance threshold for residual PBR. The three stocks are 
expected to accrue 2, 1, and 10 Level A harassment takes from tissue 
damage resulting from exposure to explosives, respectively. As 
described in detail in the 2018 HSTT final rule, the impacts of a Level 
A harassment take by tissue damage could range in impact from minor to 
something just less than M/SI that could seriously impact fitness. 
However, given the Navy's procedural mitigation, exposure closer to the 
source and more severe end of the spectrum is less likely and we 
cautiously assume some moderate impact for these takes that could lower 
the affected individual's fitness within the year such that a female 
(assuming a 50 percent chance of it being a female) might forego 
reproduction for 1 year. As noted previously, foregone reproduction has 
less of an impact on population rates than death (especially for only 1 
year in 7, which is the maximum predicted because the small number 
anticipated in any 1 year makes the probability that any individual 
would be impacted in this way twice in 7 years very low), and 1 to 10 
instances would not be expected to impact annual rates of recruitment 
or survival for these stocks.
    Regarding the magnitude of Level B harassment takes (TTS and 
behavioral disturbance), the number of estimated total instances of 
take compared to the abundance (measured against both the Navy-
estimated abundance and the SAR) is 2,411, 1,273, and 571 percent 
(respective to the stocks listed in the heading) and 297, 335, and 141 
percent (respective to the stocks listed in the heading) (table 19). 
Given the range of these stocks, this information suggests that likely 
some portion (but not all or even the majority) of the individuals in 
the northern right whale dolphin and short-beaked common dolphin stocks 
are likely impacted while it is entirely possible that most or all of 
the range-limited long-beaked common dolphin is taken. All three stocks 
likely will experience some repeat Level B harassment exposure (perhaps 
up to 48, 25, or 11 days within a year, respective to the stocks listed 
in the heading) of some subset of individuals that spend extended time 
within the SOCAL range complex. While interrupted feeding bouts are a 
known response and concern for odontocetes, we also know that there are 
often viable alternative habitat options in the relative vicinity. 
Regarding the severity of those individual Level B harassment takes by 
behavioral disturbance, the duration of any exposure is expected to be 
between minutes and hours (i.e., relatively short) and the received 
sound levels largely below 172 dB with a portion up to 178 dB (i.e., of 
a moderate or lower level, less likely to evoke a severe response). 
However, some of these takes could occur on a fair number of sequential 
days for long-beaked common dolphins or northern right whale dolphins, 
or even some number of short-beaked common dolphins, given the high 
number of total takes (i.e., the probability that some number of 
individuals get taken on a higher number of sequential days is higher, 
because the total take number is relatively high, even though the 
percentage is not that high).
    The severity of TTS takes is expected to be low-level, of short 
duration, and mostly not in a frequency band that would be expected to 
interfere significantly with conspecific communication, echolocation, 
or other important low-frequency cues, and the associated lost 
opportunities and capabilities would not be expected to impact 
reproduction or survival. For these same reasons (low level and 
frequency band), while a small permanent loss of hearing sensitivity 
may include some degree of energetic costs for compensating or may mean 
some small loss of opportunities or detection capabilities, as 
discussed in the 2020 HSTT final rule, it would be unlikely to impact 
behaviors, opportunities, or detection capabilities to a degree that 
would interfere with reproductive success or survival of any 
individuals.
    Altogether and as described in more detail above, 1.14 annual 
lethal takes of short-beaked common dolphins are proposed for 
authorization, all three stocks may experience a very small number of 
takes by tissue damage or PTS (relative to the stock abundance and 
PBR), and a moderate to large portion of all three stocks will likely 
be taken (at a low to occasionally moderate level) over several days a 
year, and some smaller portion of these stocks is expected to be taken 
on a relatively moderate to high number of days across the year, some 
of which could be sequential days. Though the majority of impacts are 
expected to be of a lower to sometimes moderate severity, the larger 
number of takes (in total and for certain individuals) makes it more 
likely (probabilistically) that a small number of individuals could be 
interrupted during foraging in a manner and amount such that impacts to 
the energy budgets of females (from either losing feeding opportunities 
or expending considerable energy to find alternative feeding options) 
could cause them to forego reproduction for a year. Energetic impacts 
to males are generally meaningless to population rates unless they 
cause death, and it takes extreme energy deficits beyond what would 
ever be likely to result from these activities to cause the death of an 
adult marine mammal. As noted previously, however, foregone 
reproduction (especially for only 1 year out of 7, which is the maximum 
predicted because the small number anticipated in any 1 year makes the 
probability that any individual would be impacted in this way twice in 
7 years very low) has far less of an impact on population rates than 
mortality and a small number of instances of foregone reproduction 
(including in combination with that which might result from the small 
number of tissue damage takes) would not be expected to adversely 
affect the stocks through effects on annual rates of recruitment or 
survival, especially given the very high residual PBRs of these stocks 
(638.3, 156.4, and 8,858.5, respectively). For these reasons, in 
consideration of all of the effects of the Navy's activities combined 
(mortality, Level A harassment, and Level B harassment), we have 
preliminarily determined that the authorized take proposed would have a 
negligible impact on these three stocks of dolphins.
All Other SOCAL Dolphin Stocks (Except Long-Beaked Common Dolphin, 
Northern Right Whale Dolphin, and Short-Beaked Common Dolphin)
    None of these stocks are listed under the ESA and their stock 
statuses are considered ``unknown,'' except for the bottlenose dolphin 
(California coastal stock) and killer whale (Eastern North Pacific 
stock), which are considered ``stable.'' No M/SI or Level A harassment 
via tissue damage from exposure to explosives is expected or proposed 
for authorization for these stocks.
    Regarding the magnitude of Level B harassment takes (TTS and 
behavioral disturbance), the number of estimated total instances of 
take compared to the

[[Page 68349]]

abundance (measured against both the Navy-estimated abundance and the 
SAR) is from 440 to 2,675 percent and 36 to 1,993 percent, respectively 
(table 19). Given the range of these stocks (along the entire U.S. West 
Coast, or even beyond, with some also extending seaward of the HSTT 
Study Area boundaries), this information suggests that some portion 
(but not all or even the majority) of the individuals of any of these 
stocks will be taken, with the exception that most or all of the 
individuals of the more range-limited California coastal stock of 
bottlenose dolphin may be taken. It is also likely that some subset of 
individuals within most of these stocks will be taken repeatedly within 
the year (perhaps up to 10-15 days within a year) but with no more than 
several potentially sequential days, although the CA/OR/WA stocks of 
bottlenose dolphins, Pacific white-sided dolphins, and Risso's dolphins 
may include individuals that are taken repeatedly within the year over 
a higher number of days (up to 57, 22, and 40 days, respectively) and 
potentially over a fair number of sequential days, especially where 
individuals spend extensive time in the SOCAL range complex. Note that 
though percentages are high for the Eastern North Pacific stock of 
killer whales and short-finned pilot whales, given the low overall 
number of takes, it is highly unlikely that any individuals would be 
taken across the number of days their percentages would suggest. While 
interrupted feeding bouts are a known response and concern for 
odontocetes, we also know that there are often viable alternative 
habitat options in the relative vicinity. Regarding the severity of 
those individual Level B harassment takes by behavioral disturbance, we 
have explained that the duration of any exposure is expected to be 
between minutes and hours (i.e., relatively short) and the received 
sound levels largely below 172 dB (i.e., of a lower, or sometimes 
moderate level, less likely to evoke a severe response). However, as 
noted, some of these takes could occur on a fair number of sequential 
days for the three stocks listed earlier.
    The severity of TTS takes is expected to be low-level, of short 
duration, and mostly not in a frequency band that would be expected to 
interfere significantly with conspecific communication, echolocation, 
or other important low-frequency cues. For these same reasons (low 
level and frequency band), while a small permanent loss of hearing 
sensitivity may include some degree of energetic costs for compensating 
or may mean some small loss of opportunities or detection capabilities, 
it would be unlikely to impact behaviors, opportunities, or detection 
capabilities to a degree that would interfere with reproductive success 
or survival of any individuals.
    Altogether, a portion of all of these stocks will likely be taken 
(at a low to occasionally moderate level) over several days a year, and 
some smaller portion of CA/OR/WA stocks of bottlenose dolphins, Pacific 
white-sided dolphins, and Risso's dolphins, specifically, are expected 
to be taken on a relatively moderate to high number of days across the 
year, some of which could be sequential days. Though the majority of 
impacts are expected to be of a lower to sometimes moderate severity, 
the larger number of takes (in total and for certain individuals) for 
the CA/OR/WA stocks of bottlenose dolphins, Pacific white-sided 
dolphins, and Risso's dolphins makes it more likely (probabilistically) 
that a small number of individuals could be interrupted during foraging 
in a manner and amount such that impacts to the energy budgets of 
females (from either losing feeding opportunities or expending 
considerable energy to find alternative feeding options) could cause 
them to forego reproduction for a year. Energetic impacts to males are 
generally meaningless to population rates unless they cause death, and 
it takes extreme energy deficits beyond what would ever be likely to 
result from these activities to cause the death of an adult marine 
mammal. As noted previously, however, foregone reproduction (especially 
for only 1 year in 7, which is the maximum predicted because the small 
number anticipated in any 1 year makes the probability that any 
individual would be impacted in this way twice in 7 years very low) has 
far less of an impact on population rates than mortality and a small 
number of instances of foregone reproduction would not be expected to 
adversely affect the stocks through effects on annual rates of 
recruitment or survival, especially given the residual PBRs of the CA/
OR/WA stocks of bottlenose dolphins, Pacific white-sided dolphins, and 
Risso's dolphins (18.9, 272, and 42.3, respectively). For these 
reasons, in consideration of all of the effects of the Navy's 
activities combined, we have preliminarily determined that the 
authorized take proposed would have a negligible impact on these stocks 
of dolphins.
All HRC Dolphin Stocks
    With the exception of the Main Hawaiian Island stock of false 
killer whales (listed as endangered under the ESA, with the MMPA stock 
identified as ``decreasing''), none of these stocks are listed under 
the ESA and their stock statuses are considered ``unknown.'' No M/SI or 
Level A harassment via tissue damage from exposure to explosives is 
expected or proposed for authorization for these stocks.
    Regarding the magnitude of Level B harassment takes (TTS and 
behavioral disturbance), the number of estimated total instances of 
take compared to the abundance (measured against both the Navy-
estimated abundance and the SAR) is from 46 to 1,166 percent and 14 to 
2,130 percent, respectively (table 16). Given the ranges of these 
stocks (many of them are small, resident, island-associated stocks), 
this information suggests that a fairly large portion of the 
individuals of many of these stocks will be taken but that most 
individuals will only be impacted across a smaller to moderate number 
of days within the year (1-15), and with no more than several 
potentially sequential days, although two stocks (the Oahu stocks of 
bottlenose dolphin and pantropical spotted dolphin) have a slightly 
higher percentage, suggesting they could be taken up to 23 days within 
a year, with perhaps a few more of those days being sequential. We note 
that although the percentage is higher for the tropical stock of pygmy 
killer whale within the U.S. EEZ (2,130), given (1) the low overall 
number of takes (760) and (2) the fact that the small within-U.S. EEZ 
abundance is not a static set of individuals, but rather individuals 
moving in and out of the U.S. EEZ making it more appropriate to use the 
percentage comparison for the total takes versus total abundance--it is 
highly unlikely that any individuals would be taken across the number 
of days the within-U.S. EEZ percentage suggests (42). While interrupted 
feeding bouts are a known response and concern for odontocetes, we also 
know that there are often viable alternative habitat options in the 
relative vicinity. Regarding the severity of those individual Level B 
harassment takes by behavioral disturbance, the duration of any 
exposure is expected to be between minutes and hours (i.e., relatively 
short) and the received sound levels largely below 172 dB (i.e., of a 
lower, or sometimes moderate level, less likely to evoke a severe 
response). However, as noted, some of these takes could occur on a fair 
number of sequential days for the Oahu stocks of bottlenose dolphin and 
pantropical spotted dolphins.
    Regarding the severity of TTS takes, they are expected to be low-
level, of short duration, and mostly not in a frequency band that would 
be expected

[[Page 68350]]

to interfere significantly with conspecific communication, 
echolocation, or other important low-frequency cues. For these same 
reasons (low level and frequency band), while a small permanent loss of 
hearing sensitivity may include some degree of energetic costs for 
compensating or may mean some small loss of opportunities or detection 
capabilities, they would be unlikely to impact behaviors, 
opportunities, or detection capabilities to a degree that would 
interfere with reproductive success or survival of any individuals, 
even if accrued to individuals that are also taken by behavioral 
harassment at the same time.
    Altogether, most of these stocks (all but the Oahu stocks of 
bottlenose dolphin and pantropical spotted dolphins) will likely be 
taken (at a low to occasionally moderate level) over several days a 
year, with some smaller portion of the stock potentially taken on a 
more moderate number of days across the year (perhaps up to 15 days for 
Fraser's dolphin, though others notably less), some of which could be 
across a few sequential days, which is not expected to affect the 
reproductive success or survival of individuals. For the Oahu stocks of 
bottlenose dolphin and pantropical spotted dolphins, some subset of 
individuals could be taken up to 23 days in a year, with some small 
number being taken across several sequential days, such that a small 
number of individuals could be interrupted during foraging in a manner 
and amount such that impacts to the energy budgets of females (from 
either losing feeding opportunities or expending considerable energy to 
find alternative feeding options) could cause them to forego 
reproduction for a year. Energetic impacts to males are generally 
meaningless to population rates unless they cause death, and it takes 
extreme energy deficits beyond what would ever be likely to result from 
these activities to cause the death of an adult marine mammal. As noted 
previously, however, foregone reproduction (especially for 1 year, 
which is the maximum predicted because the small number anticipated in 
any 1 year makes the probability that any individual would be impacted 
in this way twice in 7 years very low) has far less of an impact on 
population rates than mortality and a small number of instances of 
foregone reproduction would not be expected to adversely affect these 
two stocks through effects on annual rates of recruitment or survival. 
For these reasons, in consideration of all of the effects of the Navy's 
activities combined, we have preliminarily determined that the 
authorized take proposed would have a negligible impact on all of the 
stocks of dolphins found in the vicinity of the HRC.

Dall's Porpoise

    In table 20 below for porpoises, we indicate the total annual 
mortality, Level A harassment and Level B harassment, and a number 
indicating the instances of total take as a percentage of abundance. 
Table 20 is updated from table 26 in the 2020 HSTT final rule with the 
2022 final SARs. For additional information and analysis supporting the 
negligible-impact analysis, see the Odontocetes discussion as well as 
the Dall's Porpoise discussion in the Group and Species-Specific 
Analyses section of the 2018 HTT final rule, all of which remains 
applicable to this proposed rule unless specifically noted.

Table 20--Annual Estimated Takes by Level B Harassment, Level A Harassment, and Mortality for Porpoises in the HSTT Study Area and Number Indicating the Instances of Total Take as a Percentage
                                                                                       of Stock Abundance
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                       Instances of indicated types of incidental take (not all      Total            Abundance          Instances of total take
                                                                         takes represent separate individuals, especially for        takes   --------------------------  as percent of abundance
                                                                                             disturbance)                         -----------                          -------------------------
                                                                   ---------------------------------------------------------------                                      Total  take
                                                                        Level B harassment       Level A harassment                                                          as      Total  take
                Species                            Stock           -------------------------------------------------                 Total        Navy                   percentage       as
                                                                                                                                     takes     abundance    NMFS  SARS    of total    percentage
                                                                                    TTS  (may                          Mortality    (entire    in action    abundance       Navy       of total
                                                                     Behavioral       also        PTS      Tissue                    study        area                   abundance       SAR
                                                                     disturbance     include               damage                    area)                               in action    abundance
                                                                                  disturbance)                                                                              area
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Dall's porpoise........................  CA/OR/WA.................       14,482        29,891     209            0             0     44,582        2,054       16,498        2,170          270
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Note: For the SOCAL take estimates, because of the manner in which the Navy study area overlaps the ranges of many MMPA stocks (i.e., a stock may range far north to Washington state and beyond
  and abundance may only be predicted within the U.S. EEZ, while the Navy study area is limited to Southern California and northern Mexico, but extends beyond the U.S. EEZ), we compare
  predicted takes to both the abundance estimates for the study area, as well as the SARs (as described in the Estimated Take of Marine Mammals section of the 2018 HSTT final rule).
Total takes inside and outside U.S. EEZ represent the sum of annual Level A and Level B harassment from training and testing activities.

    Below we compile and summarize the information that supports our 
determination that the Navy's activities would not adversely affect 
Dall's porpoises through effects on annual rates of recruitment or 
survival.
    Dall's porpoise is not listed under the ESA and the stock status is 
considered ``unknown.'' No M/SI or Level A harassment via tissue damage 
from exposure to explosives is expected or proposed for authorization 
for this stock.
    Most Level B harassments to Dall's porpoise from hull-mounted sonar 
(MF1) in the HSTT Study Area would result from received levels between 
154 and 166 dB SPL (85 percent). While harbor porpoises have been 
observed to be especially sensitive to human activity, the same types 
of responses have not been observed in Dall's porpoises. Dall's 
porpoises are typically notably longer than and weigh more than twice 
as much as harbor porpoises making them generally less likely to be 
preyed upon and likely differentiating their behavioral repertoire 
somewhat from harbor porpoises. Further, they are typically seen in 
large groups and feeding aggregations or exhibiting bow-riding 
behaviors, which is very different from the group dynamics observed in 
the more typically solitary, cryptic harbor porpoises, which are not 
often seen bow-riding. For these reasons, Dall's porpoises are not 
treated as especially sensitive species (as compared to harbor 
porpoises, which have a lower threshold for Level B harassment by 
behavioral disturbance and more distant cutoff) but, rather, are 
analyzed similarly to other odontocetes. Therefore, the majority of 
Level B harassment takes are expected to be in the form of milder 
responses compared to higher level exposures. As discussed more fully 
in the 2018 HSTT final rule, we anticipate more severe effects from 
takes when animals are exposed to higher received levels.

[[Page 68351]]

    Regarding the magnitude of Level B harassment takes (TTS and 
behavioral disturbance), the number of estimated total instances of 
take compared to the abundance (measured against both the Navy-
estimated abundance and the SAR) is 2,170 and 270 percent, respectively 
(table 20). Given the range of this stock (up the U.S. West Coast 
through Washington and sometimes beyond the U.S. EEZ), this information 
suggests that some smaller portion of the individuals of this stock 
will be taken, and that some subset of individuals within the stock 
will be taken repeatedly within the year (perhaps up to 42 days)--
potentially over a fair number of sequential days, especially where 
individuals spend extensive time in the SOCAL range complex. While 
interrupted feeding bouts are a known response and concern for 
odontocetes, we also know that there are often viable alternative 
habitat options in the relative vicinity. Regarding the severity of 
those individual Level B harassment takes by behavioral disturbance, 
the duration of any exposure is expected to be between minutes and 
hours (i.e., relatively short) and the received sound levels largely 
below 172 dB (i.e., of a lower, or sometimes moderate level, less 
likely to evoke a severe response). However, as noted, some of these 
takes could occur on a fair number of sequential days for this stock.
    The severity of TTS takes is expected to be low-level, of short 
duration, and mostly not in a frequency band that would be expected to 
interfere significantly with conspecific communication, echolocation, 
or other important low-frequency cues. Therefore, the associated lost 
opportunities and capabilities would not be expected to impact 
reproduction or survival. For these same reasons (low level and the 
likely frequency band), while a small permanent loss of hearing 
sensitivity may include some degree of energetic costs for compensating 
or may mean some small loss of opportunities or detection capabilities, 
the estimated 209 takes by Level A harassment by PTS for Dall's 
porpoise would be unlikely to impact behaviors, opportunities, or 
detection capabilities to a degree that would interfere with 
reproductive success or survival for most individuals. Because of the 
high number of PTS takes, however, we acknowledge that a few animals 
could potentially incur permanent hearing loss of a higher degree that 
could potentially interfere with their successful reproduction and 
growth. Given the status of the stock, even if this occurred, it would 
not adversely impact rates of recruitment or survival.
    Altogether, a portion of this stock will likely be taken (at a low 
to occasionally moderate level) over several days a year, and some 
smaller portion of the stock is expected to be taken on a relatively 
moderate to high number of days across the year, some of which could be 
sequential days. Though the majority of impacts are expected to be of a 
lower to sometimes moderate severity, the larger number of takes (in 
total and for certain individuals) for the Dall's porpoise makes it 
more likely (probabilistically) that a small number of individuals 
could be interrupted during foraging in a manner and amount such that 
impacts to the energy budgets of females (from either losing feeding 
opportunities or expending considerable energy to find alternative 
feeding options) could cause them to forego reproduction for a year. 
Energetic impacts to males are generally meaningless to population 
rates unless they cause death, and it takes extreme energy deficits 
beyond what would ever be likely to result from these activities to 
cause the death of an adult marine mammal. Similarly, we acknowledge 
the potential for this to occur to a few individuals out of the 209 
total that might incur a higher degree of PTS. As noted previously, 
however, foregone reproduction (especially for only 1 year in 7, which 
is the maximum predicted because the small number anticipated in any 1 
year makes the probability that any individual would be impacted in 
this way twice in 7 years very low) has far less of an impact on 
population rates than mortality. Further, the small number of instances 
of foregone reproduction that could potentially result from PTS and/or 
the few repeated, more severe Level B harassment takes by behavioral 
disturbance would not be expected to adversely affect the stock through 
effects on annual rates of recruitment or survival, especially given 
the status of the species (not endangered or threatened; minimum 
population of 10,286 just within the U.S. EEZ) and residual PBR of 
Dall's porpoise (98.3). For these reasons, in consideration of all of 
the effects of the Navy's activities combined, we have preliminarily 
determined that the authorized take proposed would have a negligible 
impact on Dall's porpoise.

Pinnipeds

    In table 21 and table 22 below for pinnipeds, we indicate the total 
annual mortality, Level A harassment and Level B harassment, and a 
number indicating the instances of total take as a percentage of 
abundance. Table 21 and table 22 have been updated from tables 27 and 
28 in the 2020 HSTT final rule with the 2022 final SARs, as 
appropriate. For additional information and analysis supporting the 
negligible-impact analysis, see the Pinnipeds discussion in the Group 
and Species-Specific Analyses section of the 2018 HSTT final rule, all 
of which remains applicable to this proposed rule unless specifically 
noted.

 Table 21--Annual Estimated Takes by Level B Harassment, Level A Harassment, and Mortality for Pinnipeds in the HRC Portion of the HSTT Study Area and Number Indicating the Instances of Total
                                                                             Take as a Percentage of Stock Abundance
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
                                                            Instances of indicated types of incidental take (not all         Total takes              Abundance          Instance of total take
                                                              takes represent separate individuals, especially for     ------------------------------------------------  as percent of abundance
                                                                                  disturbance)                                                                         -------------------------
                                                        ---------------------------------------------------------------                                                 Total  take   EEZ  take
                                                             Level B harassment       Level A harassment                  Total      Takes    Total  Navy  Within  EEZ       as           as
                        Species                         -------------------------------------------------                 takes     (within     abundance      Navy      percentage   percentage
                                                                                                                         (entire      Navy     inside and   abundance     of total     of Navy
                                                          Behavioral     TTS (may               Tissue      Mortality     study       EEZ)     outside of     (HRC)         Navy         EEZ
                                                          disturbance  also include    PTS      damage                    area)                EEZ (HRC)                 abundance    abundance
                                                                       disturbance)                                                                                        (HRC)        (HRC)
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Hawaiian monk seal.....................................          143            62       1            0             0        206        195          169          169          122          115
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Note: For the Hawaii take estimates, we compare predicted takes to abundance estimates generated from the same underlying density estimates (as described in the Estimated Take of Marine
  Mammals section of the 2018 HSTT final rule), both in and outside of the U.S. EEZ. Because the portion of the Navy's study area inside the U.S. EEZ is generally concomitant with the area
  used to generate the abundance estimates in the SARs, and the abundance predicted by the same underlying density estimates is the preferred abundance to use, there is no need to separately
  compare the take to the SARs abundance estimate.
Total takes inside and outside U.S. EEZ represent the sum of annual Level A and Level B harassment from training and testing activities.


[[Page 68352]]


Table 22--Annual Estimated Takes by Level B Harassment, Level A Harassment, and Mortality for Pinnipeds in the SOCAL Portion of the HSTT Study Area and Number Indicating the Instances of Total
                                                                             Take as a Percentage of Stock Abundance
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                              Instances of indicated types of incidental take (not all    Total          Abundance        Instance of total take
                                                                                takes represent separate individuals, especially for      takes  ------------------------      as percent of
                                                                                                    disturbance)                       ----------                                abundance
                                                                            -----------------------------------------------------------                                  -----------------------
                                                                                 Level B harassment          Level A                                                         Total
                                                                            ---------------------------     harassment                    Total      Navy                   take as      Total
                  Species                                 Stock                                        -------------------                takes    abundance  NMFS  SARS  percentage    take as
                                                                                            TTS  (may                                    (entire   in action   abundance    of total  percentage
                                                                              Behavioral      also                          Mortality     study      area                    Navy       of total
                                                                             disturbance     include     PTS     Tissue                   area)     (SOCAL)                abundance      SAR
                                                                                          disturbance)           damage                                                    in action   abundance
                                                                                                                                                                             area
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
California sea lion........................  U.S...........................      113,419         4,789     87           9         0.71   118,305       4,085     257,606       2,896          46
Guadalupe fur seal.........................  Mexico........................        1,442            15      0           0            0     1,457       1,171      34,187         124           4
Northern fur seal..........................  California....................       15,167           124      1           0            0    15,292         886      14,050       1,726         109
Harbor seal................................  California....................        2,450         2,994      8           0            0     5,452         321      30,968       1,698          18
Northern elephant seal.....................  California....................       42,916        17,955     97           2            0    60,970       4,108     187,386       1,484          33
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Note: For the SOCAL take estimates, because of the manner in which the Navy action area overlaps the ranges of many MMPA stocks (i.e., a stock may range far north to Washington state and
  beyond and abundance may only be predicted within the U.S. EEZ, while the Navy action area is limited to Southern California and northern Mexico, but extends beyond the U.S. EEZ), we compare
  predicted takes to both the abundance estimates for the action area, as well as the SARs.
For mortality takes there is an annual average of 0.71 California sea lions (i.e., where five takes could potentially occur divided by 7 years to get the annual number of mortalities/serious
  injuries).

    Below we compile and summarize the information that supports our 
determination that the Navy's activities would not adversely affect any 
pinnipeds through effects on annual rates of recruitment or survival 
for any of the affected species or stocks addressed in this section.
    Five M/SI takes of California sea lions are proposed for 
authorization and when this mortality is combined with the other human-
caused mortality from other sources, it still falls well below the 
insignificance threshold for residual PBR (13,684). A small number of 
Level A harassment takes by tissue damage are also proposed for 
authorization (nine and two for California sea lions and northern 
elephant seals, respectively), which, as discussed in the 2020 HSTT 
final rule, could range in impact from minor to something just less 
than M/SI that could seriously impact fitness. However, given the 
Navy's mitigation, exposure at the closer to the source and more severe 
end of the spectrum is less likely. Nevertheless, we cautiously assume 
some moderate impact on the individuals that experience these small 
numbers of take that could lower the individual's fitness within the 
year such that a female (assuming a 50 percent chance of it being a 
female) might forego reproduction for 1 year. As noted previously, 
foregone reproduction has less of an impact on population rates than 
death (especially for only one within 7 years, which is the maximum 
predicted because the small number anticipated in any 1 year makes the 
probability that any individual would be impacted in this way twice in 
7 years very low) and these low numbers of instances (especially 
assuming the likelihood that only 50 percent of the takes would affect 
females) would not be expected to impact annual rates of recruitment or 
survival, especially given the population sizes of these species.
    Regarding the magnitude of Level B harassment takes (TTS and 
behavioral disturbance), for Hawaiian monk seals and Guadalupe fur 
seals, the two species listed under the ESA, the estimated instances of 
takes as compared to the stock abundance does not exceed 124 percent, 
which suggests that some portion of these two stocks would be taken on 
1 to a few days per year. For the remaining stocks, the number of 
estimated total instances of take compared to the abundance (measured 
against both the Navy-estimated abundance and the SAR) for these stocks 
is 1,484 to 2,896 percent and 18 to 46 percent, respectively (table 
21). Given the ranges of these stocks (i.e., very large ranges, but 
with individuals often staying in the vicinity of haulouts), this 
information suggests that some very small portion of the individuals of 
these stocks will be taken, but that some subset of individuals within 
the stock will be taken repeatedly within the year (perhaps up to 58 
days)--potentially over a fair number of sequential days. Regarding the 
severity of those individual Level B harassment takes by behavioral 
disturbance, the duration of any exposure is expected to be between 
minutes and hours (i.e., relatively short) and the received sound 
levels largely below 172 dB, which is considered a relatively low to 
occasionally moderate level for pinnipeds. However, as noted, some of 
these takes could occur on a fair number of sequential days for this 
stock.
    As described in the 2018 HSTT final rule and 2020 HSTT final rule, 
the Hawaii and 4-Islands mitigation areas protect (by not using 
explosives and limiting MFAS within) a significant portion of the 
designated critical habitat for Hawaiian monk seals in the Main 
Hawaiian Islands, including all of it around the islands of Hawaii and 
Lanai, most around Maui, and good portions around Molokai and 
Kaho'olawe. As discussed, this protection reduces the overall number of 
takes and further reduces the severity of effects by minimizing impacts 
near pupping beaches and in important foraging habitat.
    The severity of TTS takes are expected to be low-level, of short 
duration, and mostly not in a frequency band that would be expected to 
interfere significantly with conspecific communication, echolocation, 
or other important low-frequency cues that would affect the 
individual's reproduction or survival. For these same reasons (low 
level and frequency band), while a small permanent loss of hearing 
sensitivity may include some degree of energetic costs for compensating 
or may mean some small loss of opportunities or detection capabilities, 
the one to eight estimated Level A harassment takes by PTS for monk 
seals, northern fur seals, and harbor seals would be unlikely to impact 
behaviors, opportunities, or detection capabilities to a degree that 
would interfere with

[[Page 68353]]

reproductive success or survival of any individuals. Because of the 
high number of PTS takes for California sea lions and northern elephant 
seals (87 and 97, respectively), we acknowledge that a few animals 
could potentially incur permanent hearing loss of a higher degree that 
could potentially interfere with their successful reproduction and 
growth. Given the status of the stocks, even if this occurred, it would 
not adversely impact rates of recruitment or survival (residual PBR of 
13,684 and 5,108, respectively).
    Altogether, an individual Hawaiian monk seal and Guadalupe fur seal 
would be taken no more than a few days in any year with none of the 
expected take anticipated to affect individual reproduction or 
survival, let alone annual rates of recruitment and survival. With all 
other stocks, only a very small portion of the stock will be taken in 
any manner. Of those taken, some individuals will be taken by Level B 
harassment (at a moderate or sometimes low level) over several days a 
year, and some smaller portion of those taken will be on a relatively 
moderate to high number of days across the year (up to 58), a fair 
number of which would likely be sequential days. Though the majority of 
impacts are expected to be of a lower to sometimes moderate severity, 
the repeated takes over a potentially fair number of sequential days 
for some individuals makes it more likely that some number of 
individuals could be interrupted during foraging in a manner and amount 
such that impacts to the energy budgets of females (from either losing 
feeding opportunities or expending considerable energy to find 
alternative feeding options) could cause them to forego reproduction 
for a year (energetic impacts to males are generally meaningless to 
population rates unless they cause death, and it takes extreme energy 
deficits beyond what would ever be likely to result from these 
activities to cause the death of an adult marine mammal). As noted 
previously, however, foregone reproduction (especially for only 1 year 
within 7, which is the maximum predicted because the small number 
anticipated in any 1 year makes the probability that any individual 
would be impacted in this way twice in 7 years very low) has far less 
of an impact on population rates than mortality and a relatively small 
number of instances of foregone reproduction (as compared to the stock 
abundance and residual PBR) would not be expected to adversely affect 
the stock through effects on annual rates of recruitment or survival, 
especially given the status of these stocks. Accordingly, we do not 
anticipate the relatively small number of individual northern fur seals 
or harbor seals that might be taken over repeated days within the year 
in a manner that results in 1 year of foregone reproduction to 
adversely affect the stocks through effects on rates of recruitment or 
survival, given the status of the stocks, which are respectively 
increasing and stable with abundances and residual PBRs of 14,050/
30,968 and 449/1,598.
    For California sea lions, given the very high abundance and 
residual PBR (257,606 and 13,684, respectively), as well as the 
increasing status of the stock in the presence of similar levels of 
Navy activities over past years--the impacts of 0.71 annual 
mortalities, potential foregone reproduction for up to nine individuals 
in a year taken by tissue damage, and some relatively small number of 
individuals taken as a result of repeated behavioral harassment over a 
fair number of sequential days are not expected to adversely affect the 
stock through effects on annual rates of recruitment or survival. 
Similarly, for northern elephant seals, given the very high abundance 
and residual PBR (187,386 and 5,108, respectively), as well as the 
increasing status of the stock in the presence of similar levels of 
Navy activities over past years, the impacts of potential foregone 
reproduction for up to two individuals in a year taken by tissue damage 
and some relatively small number of individuals taken as a result of 
repeated behavioral harassment over a fair number of sequential days 
are not expected to adversely affect the stock through effects on 
annual rates of recruitment or survival. For these reasons, in 
consideration of all of the effects of the Navy's activities combined 
(M/SI, Level A harassment, and Level B harassment), we have 
preliminarily determined that the authorized take proposed would have a 
negligible impact on all pinniped species and stocks.

Preliminary Determination

    The 2018 HSTT final rule included a detailed discussion of all of 
the anticipated impacts on the affected species and stocks from serious 
injury or mortality, Level A harassment, and Level B harassment; 
impacts on habitat; and how the Navy's mitigation and monitoring 
measures reduce the number and/or severity of adverse effects. We have 
evaluated how these impacts as well as an additional proposed take of 
two large whales by serious injury or mortality by vessel strike, and 
the proposed mitigation measures are expected to combine, annually, to 
affect individuals of each species and stock. Those effects were then 
evaluated in the context of whether they are reasonably likely to 
impact reproductive success or survivorship of individuals and then, if 
so, further analyzed to determine whether there would be effects on 
annual rates of recruitment or survival that would adversely affect the 
species or stock.
    As described above, the basis for the negligible impact 
determination is the assessment of effects on annual rates of 
recruitment and survival. Accordingly, the analysis included in the 
2018 HSTT final rule and 2020 HSTT final rule used annual activity 
levels, the best available science, and approved methods to predict the 
annual impacts to marine mammals, which were then analyzed in the 
context of whether each species or stock would incur more than a 
negligible impact based on anticipated adverse impacts to annual rates 
of recruitment or survival. As we have described above, none of the 
factors upon which the conclusions in the 2020 HSTT final rule were 
based have changed, with the exception of estimated take by vessel 
strike. Therefore, even though this proposed rule includes two 
additional takes by vessel strike, little has changed that would change 
our 2018 HSTT final rule and subsequent 2020 HSTT final rule analyses, 
and it is appropriate to rely on those analyses, as well as the new 
information and analysis discussed above, for this proposed rule.
    Based on the applicable information and analysis from the 2018 HSTT 
final rule and 2020 HSTT final rule, as updated with the information 
and analysis contained herein on the potential and likely effects of 
the specified activities on the affected marine mammals and their 
habitat, and taking into consideration the implementation of the 
monitoring and mitigation measures, NMFS preliminarily finds that the 
incidental take from the specified activities will have a negligible 
impact on all affected marine mammal species and stocks.

Subsistence Harvest of Marine Mammals

    There are no subsistence uses or harvest of marine mammals in the 
geographic area affected by the specified activities. Therefore, NMFS 
has preliminarily determined that the total taking affecting species or 
stocks would not have an unmitigable adverse impact on the availability 
of such species or stocks for taking for subsistence purposes.

[[Page 68354]]

Classification

Endangered Species Act

    There are nine marine mammal species under NMFS jurisdiction that 
are listed as endangered or threatened under the ESA with confirmed or 
possible occurrence in the HSTT Study Area: blue whale (Eastern and 
Central North Pacific stocks), fin whale (CA/OR/WA and Hawaii stocks), 
gray whale (Western North Pacific stock), humpback whale (Mexico and 
Central America DPSs), sei whale (Eastern North Pacific and Hawaii 
stocks), sperm whale (CA/OR/WA and Hawaii stocks), false killer whale 
(Main Hawaiian Islands Insular), Hawaiian monk seal (Hawaii stock), and 
Guadalupe fur seal (Mexico to California). There is also ESA-designated 
critical habitat for Hawaiian monk seals and Main Hawaiian Islands 
Insular false killer whales. The Navy consulted with NMFS pursuant to 
section 7 of the ESA for HSTT activities. NMFS also consulted 
internally on the issuance of the 2018 HSTT regulations and LOAs under 
section 101(a)(5)(A) of the MMPA.
    NMFS issued a Biological Opinion on December 10, 2018 concluding 
that the issuance of the 2018 HSTT final rule and subsequent LOAs are 
not likely to jeopardize the continued existence of the threatened and 
endangered species under NMFS' jurisdiction and are not likely to 
result in the destruction or adverse modification of critical habitat 
in the HSTT Study Area. The 2018 Biological Opinion included specified 
conditions under which NMFS would be required to reinitiate section 7 
consultation. NMFS reviewed these specified conditions for the 2020 
HSTT rulemaking and determined that reinitiation of consultation was 
not warranted. The incidental take statement that accompanied the 2018 
Biological Opinion was amended to cover the 7-year period of the 2020 
HSTT rule. The 2018 Biological Opinion for this action is available at 
https://www.fisheries.noaa.gov/national/marine-mammal-protection/incidental-take-authorizations-military-readiness-activities.
    The 2018 Biological Opinion reinitiation clause (2), states that 
formal consultation should be reinitiated if ``new information reveals 
effects of the agency action that may affect ESA-listed species or 
critical habitat in a manner or to an extent not previously 
considered.'' Given the new information regarding the recent occurrence 
of large whale strikes by naval vessels in the southern California 
portion of the HSTT Study Area, as described herein, the Navy has 
reinitiated consultation with NMFS pursuant to section 7 of the ESA for 
HSTT Study Area activities, and NMFS has also reinitiated consultation 
internally on the issuance of these proposed, revised regulations and 
LOAs under section 101(a)(5)(A) of the MMPA.

National Marine Sanctuaries Act

    Federal agency actions that are likely to injure national marine 
sanctuary resources are subject to consultation with the Office of 
National Marine Sanctuaries (ONMS) under section 304(d) of the National 
Marine Sanctuaries Act (NMSA). There are two national marine 
sanctuaries in the HSTT Study Area, the Hawaiian Islands Humpback Whale 
National Marine Sanctuary and the Channel Islands National Marine 
Sanctuary. NMFS will work with NOAA's ONMS to fulfill our 
responsibilities under the NMSA as warranted and will complete any NMSA 
requirements prior to a determination on the issuance of the final rule 
and LOAs.

National Environmental Policy Act

    To comply with the National Environmental Policy Act of 1969 (NEPA; 
42 U.S.C. 4321 et seq.) and NOAA Administrative Order (NAO) 216-6A, 
NMFS must evaluate our proposed actions and alternatives with respect 
to potential impacts on the human environment. NMFS participated as a 
cooperating agency on the 2018 HSTT FEIS/OEIS (published on October 26, 
2018, http://www.hstteis.com) which evaluated impacts from Navy 
training and testing activities in the HSTT Study Area for the 
reasonably foreseeable future (including through 2025). In accordance 
with 40 CFR 1506.3, NMFS independently reviewed and evaluated the 2018 
HSTT FEIS/OEIS and determined that it was adequate and sufficient to 
meet our responsibilities under NEPA for the issuance of the 2018 HSTT 
final rule and associated LOAs. NMFS therefore adopted the 2018 HSTT 
FEIS/OEIS.
    In accordance with 40 CFR 1502.9 and the information and analysis 
contained in this proposed rule, the Navy and NMFS as a cooperating 
agency have made a preliminary determination that this proposed rule 
and any subsequent LOAs would not result in significant impacts that 
were not fully considered in the 2018 HSTT FEIS/OEIS. As indicated in 
this proposed rule, the Navy has made no substantial changes to the 
activities nor are there significant new circumstances or information 
relevant to environmental concerns or their impacts. NMFS will make a 
final NEPA determination prior to a decision whether to issue a final 
rule.

Regulatory Flexibility Act

    The Office of Management and Budget has determined that this 
proposed rule is not significant for purposes of Executive Order 12866.
    Pursuant to the Regulatory Flexibility Act (RFA), the Chief Counsel 
for Regulation of the Department of Commerce has certified to the Chief 
Counsel for Advocacy of the Small Business Administration that this 
proposed rule, if adopted, would not have a significant economic impact 
on a substantial number of small entities. The RFA requires Federal 
agencies to prepare an analysis of a rule's impact on small entities 
whenever the agency is required to publish a notice of proposed 
rulemaking. However, a Federal agency may certify, pursuant to 5 U.S.C. 
605(b), that the action will not have a significant economic impact on 
a substantial number of small entities. The Navy is the sole entity 
that would be affected by this rulemaking, and the Navy is not a small 
governmental jurisdiction, small organization, or small business, as 
defined by the RFA. Any requirements imposed by an LOA issued pursuant 
to these regulations, and any monitoring or reporting requirements 
imposed by these regulations, would be applicable only to the Navy. 
NMFS does not expect the issuance of these regulations or the 
associated LOAs to result in any impacts to small entities pursuant to 
the RFA. Because this action, if adopted, would directly affect the 
Navy and not a small entity, NMFS concludes the action would not result 
in a significant economic impact on a substantial number of small 
entities.

List of Subjects in 50 CFR Part 218

    Exports, Fish, Imports, Incidental take, Indians, Labeling, Marine 
mammals, Navy, Penalties, Reporting and recordkeeping requirements, 
Seafood, Sonar, Transportation.

    Dated: September 26, 2023.
Samuel D. Rauch III,
Deputy Assistant Administrator for Regulatory Programs, National Marine 
Fisheries Service.

    For reasons set forth in the preamble, NMFS proposes to amend 50 
CFR part 218 as follows:

PART 218--REGULATIONS GOVERNING THE TAKING AND IMPORTING OF MARINE 
MAMMALS

0
1. The authority citation for part 218 continues to read as follows:


[[Page 68355]]


    Authority:  16 U.S.C. 1361 et seq.

0
2. Revise subpart H to read as follows:

Subpart H--Taking and Importing Marine Mammals; U.S. Navy's Hawaii-
Southern California Training and Testing (HSTT)

Sec.
218.70 Specified activity and geographical region.
218.71 Effective dates.
218.72 Permissible methods of taking.
218.73 Prohibitions.
218.74 Mitigation requirements.
218.75 Requirements for monitoring and reporting.
218.76 Letters of Authorization.
218.77 Renewals and modifications of Letters of Authorization.
218.78 and 218.79 [Reserved]

Subpart H--Taking and Importing Marine Mammals; U.S. Navy's Hawaii-
Southern California Training and Testing (HSTT)


Sec.  218.70  Specified activity and geographical region.

    (a) Regulations in this subpart apply only to the U.S. Navy (Navy) 
for the taking of marine mammals that occurs in the area described in 
paragraph (b) of this section and that occurs incidental to the 
activities listed in paragraph (c) of this section.
    (b) The taking of marine mammals by the Navy under this subpart may 
be authorized in Letters of Authorization (LOAs) only if it occurs 
within the Hawaii-Southern California Training and Testing (HSTT) Study 
Area, which includes established operating and warning areas across the 
north-central Pacific Ocean, from the mean high tide line in Southern 
California west to Hawaii and the International Date Line. The HSTT 
Study Area includes the at-sea areas of three existing range complexes, 
the Hawaii Range Complex (HRC), the Southern California Range Complex 
(SOCAL), and the Silver Strand Training Complex, and overlaps a portion 
of the Point Mugu Sea Range (PMSR). Also included in the HSTT Study 
Area are Navy pierside locations in Hawaii and Southern California, 
Pearl Harbor, San Diego Bay, and the transit corridor on the high seas 
where sonar training and testing may occur.
    (c) The taking of marine mammals by the Navy is only authorized if 
it occurs incidental to the Navy conducting training and testing 
activities, including:
    (1) Training. (i) Amphibious warfare;
    (ii) Anti-submarine warfare;
    (iii) Electronic warfare;
    (iv) Expeditionary warfare;
    (v) Mine warfare;
    (vi) Surface warfare; and
    (vii) Pile driving.
    (2) Testing. (i) Naval Air Systems Command Testing Activities;
    (ii) Naval Sea System Command Testing Activities;
    (iii) Office of Naval Research Testing Activities; and
    (iv) Naval Information Warfare Systems Command.


Sec.  218.71  Effective dates.

    Regulations in this subpart are effective from [date of publication 
of a final rule in the Federal Register] through December 20, 2025.


Sec.  218.72  Permissible methods of taking.

    (a) Under LOAs issued pursuant to Sec. Sec.  216.106 of this 
chapter and 218.76, the Holder of the LOAs (hereinafter ``Navy'') may 
incidentally, but not intentionally, take marine mammals within the 
area described in Sec.  218.70(b) by Level A harassment and Level B 
harassment associated with the use of active sonar and other acoustic 
sources and explosives as well as serious injury or mortality 
associated with vessel strikes and explosives, provided the activity is 
in compliance with all terms, conditions, and requirements of these 
regulations in this subpart and the applicable LOAs.
    (b) The incidental take of marine mammals by the activities listed 
in Sec.  218.70(c) is limited to the following species:

                        Table 1 to Paragraph (b)
------------------------------------------------------------------------
                Species                               Stock
------------------------------------------------------------------------
Blue whale.............................  Central North Pacific.
Blue whale.............................  Eastern North Pacific.
Bryde's whale..........................  Eastern Tropical Pacific.
Bryde's whale..........................  Hawaii.
Fin whale..............................  CA/OR/WA.
Fin whale..............................  Hawaii.
Humpback whale.........................  Central America/Southern
                                          Mexico--CA/OR/WA.
Humpback whale.........................  Mainland Mexico--CA/OR/WA.
Humpback whale.........................  Hawaii.
Minke whale............................  CA/OR/WA.
Minke whale............................  Hawaii.
Sei whale..............................  Eastern North Pacific.
Sei whale..............................  Hawaii.
Gray whale.............................  Eastern North Pacific.
Gray whale.............................  Western North Pacific.
Sperm whale............................  CA/OR/WA.
Sperm whale............................  Hawaii.
Dwarf sperm whale......................  Hawaii.
Pygmy sperm whale......................  Hawaii.
Kogia whales...........................  CA/OR/WA.
Baird's beaked whale...................  CA/OR/WA.
Blainville's beaked whale..............  Hawaii.
Cuvier's beaked whale..................  CA/OR/WA.
Cuvier's beaked whale..................  Hawaii.
Longman's beaked whale.................  Hawaii.
Mesoplodon spp.........................  CA/OR/WA.
Bottlenose dolphin.....................  California Coastal.
Bottlenose dolphin.....................  CA/OR/WA Offshore.
Bottlenose dolphin.....................  Hawaii Pelagic.
Bottlenose dolphin.....................  Kauai & Niihau.
Bottlenose dolphin.....................  Oahu.
Bottlenose dolphin.....................  4-Island.

[[Page 68356]]

 
Bottlenose dolphin.....................  Hawaii.
False killer whale.....................  Hawaii Pelagic.
False killer whale.....................  Main Hawaiian Islands Insular.
False killer whale.....................  Northwestern Hawaiian Islands.
Fraser's dolphin.......................  Hawaii.
Killer whale...........................  Eastern North Pacific (ENP)
                                          Offshore.
Killer whale...........................  ENP Transient/West Coast
                                          Transient.
Killer whale...........................  Hawaii.
Long-beaked common dolphin.............  California.
Melon-headed whale.....................  Hawaiian Islands.
Melon-headed whale.....................  Kohala Resident.
Northern right whale dolphin...........  CA/OR/WA.
Pacific white-sided dolphin............  CA/OR/WA.
Pantropical spotted dolphin............  Hawaii Island.
Pantropical spotted dolphin............  Hawaii Pelagic.
Pantropical spotted dolphin............  Oahu.
Pantropical spotted dolphin............  4-Island.
Pygmy killer whale.....................  Hawaii.
Pygmy killer whale.....................  Tropical.
Risso's dolphin........................  CA/OR/WA.
Risso's dolphin........................  Hawaii.
Rough-toothed dolphin..................  Hawaii.
Short-beaked common dolphin............  CA/OR/WA.
Short-finned pilot whale...............  CA/OR/WA.
Short-finned pilot whale...............  Hawaii.
Spinner dolphin........................  Hawaii Island.
Spinner dolphin........................  Hawaii Pelagic.
Spinner dolphin........................  Kauai & Niihau.
Spinner dolphin........................  Oahu & 4-Island.
Striped dolphin........................  CA/OR/WA.
Striped dolphin........................  Hawaii.
Dall's porpoise........................  CA/OR/WA.
California sea lion....................  U.S.
Guadalupe fur seal.....................  Mexico.
Northern fur seal......................  California.
Harbor seal............................  California.
Hawaiian monk seal.....................  Hawaii.
Northern elephant seal.................  California.
------------------------------------------------------------------------
Note to Table 1: CA/OR/WA = California/Oregon/Washington.

Sec.  218.73  Prohibitions.

    Notwithstanding incidental takings contemplated in Sec.  218.72(a) 
and authorized by LOAs issued under Sec. Sec.  216.106 of this chapter 
and 218.76, no person in connection with the activities listed in Sec.  
218.70(c) may:
    (a) Violate, or fail to comply with, the terms, conditions, and 
requirements of this subpart or an LOA issued under Sec. Sec.  216.106 
of this chapter and 218.76;
    (b) Take any marine mammal not specified in Sec.  218.72(b);
    (c) Take any marine mammal specified in Sec.  218.72(b) in any 
manner other than as specified in the LOAs; or
    (d) Take a marine mammal specified in Sec.  218.72(b) if NMFS 
determines such taking results in more than a negligible impact on the 
species or stocks of such marine mammal.


Sec.  218.74  Mitigation requirements.

    When conducting the activities identified in Sec.  218.70(c), the 
mitigation measures contained in any LOAs issued under Sec. Sec.  
216.106 of this chapter and 218.76 must be implemented. These 
mitigation measures include, but are not limited to:
    (a) Procedural mitigation. Procedural mitigation is mitigation that 
the Navy must implement whenever and wherever an applicable training or 
testing activity takes place within the HSTT Study Area for each 
applicable activity category or stressor category and includes acoustic 
stressors (i.e., active sonar, air guns, pile driving, weapons firing 
noise), explosive stressors (i.e., sonobuoys, torpedoes, medium-caliber 
and large-caliber projectiles, missiles and rockets, bombs, sinking 
exercises, mines, anti-swimmer grenades, and mat weave and obstacle 
loading), and physical disturbance and strike stressors (i.e., vessel 
movement; towed in-water devices; small-, medium-, and large-caliber 
non-explosive practice munitions; non-explosive missiles and rockets; 
and non-explosive bombs and mine shapes).
    (1) Environmental awareness and education. Appropriate Navy 
personnel (including civilian personnel) involved in mitigation and 
training or testing activity reporting under the specified activities 
will complete one or more modules identified in their career path 
training plan, as specified in the LOAs.
    (2) Active sonar. Active sonar includes low-frequency active sonar, 
mid-frequency active sonar, and high-frequency active sonar. For 
vessel-based activities, mitigation applies only to sources that are 
positively controlled and deployed from manned surface vessels (e.g., 
sonar sources towed from manned surface platforms). For aircraft-based 
activities, mitigation applies only to sources that are positively 
controlled and deployed from manned aircraft that do not operate at 
high altitudes (e.g., rotary-wing aircraft). Mitigation does not apply 
to active sonar sources deployed from unmanned aircraft or aircraft 
operating at high altitudes (e.g., maritime patrol aircraft).
    (i) Number of Lookouts and observation platform--(A) Hull-mounted 
sources. One Lookout for

[[Page 68357]]

platforms with space or manning restrictions while underway (at the 
forward part of a small boat or ship) and platforms using active sonar 
while moored or at anchor (including pierside); and two Lookouts for 
platforms without space or manning restrictions while underway (at the 
forward part of the ship).
    (B) Sources that are not hull-mounted sources. One Lookout on the 
ship or aircraft conducting the activity.
    (ii) Mitigation zone and requirements. During the activity, at 
1,000 yards (yd) Navy personnel must power down 6 decibels (dB), at 500 
yd (457.2 m) Navy personnel must power down an additional 4 dB (for a 
total of 10 dB), and at 200 yd (182.9 m) Navy personnel must shut down 
for low-frequency active sonar >=200 dB and hull-mounted mid-frequency 
active sonar; or at 200 yd (182.9 m) Navy personnel must shut down for 
low-frequency active sonar <200 dB, mid-frequency active sonar sources 
that are not hull-mounted, and high-frequency active sonar.
    (A) Prior to activity. Prior to the start of the activity (e.g., 
when maneuvering on station), Navy personnel must observe the 
mitigation zone for floating vegetation; if floating vegetation is 
observed, Navy personnel must relocate or delay the start of active 
sonar transmission until the mitigation zone is clear. Navy personnel 
must also observe the mitigation zone for marine mammals; if marine 
mammals are observed, Navy personnel must relocate or delay the start 
of active sonar transmission.
    (B) During the activity for low-frequency active sonar at or above 
200 dB and hull-mounted mid-frequency active sonar. During the activity 
for low-frequency active sonar at or above 200 dB and hull-mounted mid-
frequency active sonar, Navy personnel must observe the mitigation zone 
for marine mammals and power down active sonar transmission by 6 dB if 
marine mammals are observed within 1,000 yd (914.4 m) of the sonar 
source; power down by an additional 4 dB (for a total of 10 dB total) 
if marine mammals are observed within 500 yd (457.2 m) of the sonar 
source; and cease transmission if marine mammals are observed within 
200 yd (182.9 m) of the sonar source.
    (C) During the activity for low-frequency active sonar below 200 
dB, mid-frequency active sonar sources that are not hull mounted, and 
high-frequency active sonar. During the activity for low-frequency 
active sonar below 200 dB, mid-frequency active sonar sources that are 
not hull mounted, and high-frequency active sonar, Navy personnel must 
observe the mitigation zone for marine mammals and cease active sonar 
transmission if marine mammals are observed within 200 yd (182.9 m) of 
the sonar source.
    (D) Commencement/recommencement conditions after a marine mammal 
sighting before or during the activity. Navy personnel must allow a 
sighted marine mammal to leave the mitigation zone prior to the initial 
start of the activity (by delaying the start) or during the activity 
(by not recommencing or powering up active sonar transmission) until 
one of the following conditions has been met:
    (1) Observed exiting. The animal is observed exiting the mitigation 
zone;
    (2) Thought to have exited. The animal is thought to have exited 
the mitigation zone based on a determination of its course, speed, and 
movement relative to the sonar source;
    (3) Clear from additional sightings. The mitigation zone has been 
clear from any additional sightings for 10 minutes (min) for aircraft-
deployed sonar sources or 30 min for vessel-deployed sonar sources;
    (4) Sonar source transit. For mobile activities, the active sonar 
source has transited a distance equal to double that of the mitigation 
zone size beyond the location of the last sighting; or
    (5) Bow-riding dolphins. For activities using hull-mounted sonar 
where a dolphin(s) is observed in the mitigation zone, the Lookout 
concludes that the dolphin(s) are deliberately closing in on the ship 
to ride the ship's bow wave, and are therefore out of the main 
transmission axis of the sonar (and there are no other marine mammal 
sightings within the mitigation zone).
    (3) Air guns--(i) Number of Lookouts and observation platform. One 
Lookout positioned on a ship or pierside.
    (ii) Mitigation zone and requirements. 150 yd (137.2 m) around the 
air gun.
    (A) Prior to activity. Prior to the initial start of the activity 
(e.g., when maneuvering on station), Navy personnel must observe the 
mitigation zone for floating vegetation; if floating vegetation is 
observed, Navy personnel must relocate or delay the start until the 
mitigation zone is clear. Navy personnel must also observe the 
mitigation zone for marine mammals; if marine mammals are observed, 
Navy personnel must relocate or delay the start of air gun use.
    (B) During activity. During the activity, Navy personnel must 
observe the mitigation zone for marine mammals; if marine mammals are 
observed, Navy personnel must cease air gun use.
    (C) Commencement/recommencement conditions after a marine mammal 
sighting before or during the activity. Navy personnel must allow a 
sighted marine mammal to leave the mitigation zone prior to the initial 
start of the activity (by delaying the start) or during the activity 
(by not recommencing air gun use) until one of the following conditions 
has been met:
    (1) Observed exiting. The animal is observed exiting the mitigation 
zone;
    (2) Thought to have exited. The animal is thought to have exited 
the mitigation zone based on a determination of its course, speed, and 
movement relative to the air gun;
    (3) Clear from additional sightings. The mitigation zone has been 
clear from any additional sightings for 30 min; or
    (4) Air gun transit. For mobile activities, the air gun has 
transited a distance equal to double that of the mitigation zone size 
beyond the location of the last sighting.
    (4) Pile driving. Pile driving and pile extraction sound during 
Elevated Causeway System training.
    (i) Number of Lookouts and observation platform. One Lookout must 
be positioned on the shore, the elevated causeway, or a small boat.
    (ii) Mitigation zone and requirements. 100 yd (91.4 m) around the 
pile driver.
    (A) Prior to activity. Prior to the initial start of the activity 
(for 30 min), Navy personnel must observe the mitigation zone for 
floating vegetation; if floating vegetation is observed, Navy personnel 
must delay the start until the mitigation zone is clear. Navy personnel 
also must observe the mitigation zone for marine mammals; if marine 
mammals are observed, Navy personnel must delay the start of pile 
driving or vibratory pile extraction.
    (B) During activity. During the activity, Navy personnel must 
observe the mitigation zone for marine mammals; if marine mammals are 
observed, Navy personnel must cease impact pile driving or vibratory 
pile extraction.
    (C) Commencement/recommencement conditions after a marine mammal 
sighting before or during the activity. Navy personnel must allow a 
sighted marine mammal to leave the mitigation zone prior to the initial 
start of the activity (by delaying the start) or during the activity 
(by not recommencing pile driving or pile extraction) until one of the 
following conditions has been met:
    (1) Observed exiting. The animal is observed exiting the mitigation 
zone;
    (2) Thought to have exited. The animal is thought to have exited 
the mitigation zone based on a determination of its course, speed, and 
movement relative to the pile driving location; or

[[Page 68358]]

    (3) Clear from additional sightings. The mitigation zone has been 
clear from any additional sightings for 30 minutes.
    (5) Weapons firing noise. Weapons firing noise associated with 
large-caliber gunnery activities.
    (i) Number of Lookouts and observation platform. One Lookout must 
be positioned on the ship conducting the firing. Depending on the 
activity, the Lookout could be the same as the one provided for under 
``Explosive medium-caliber and large-caliber projectiles'' or under 
``Small-, medium-, and large-caliber non-explosive practice munitions'' 
in paragraphs (a)(8)(i) and (a)(18)(i) of this section.
    (ii) Mitigation zone and requirements. Thirty degrees on either 
side of the firing line out to 70 yd from the muzzle of the weapon 
being fired.
    (A) Prior to activity. Prior to the start of the activity, Navy 
personnel must observe the mitigation zone for floating vegetation; if 
floating vegetation is observed, Navy personnel must relocate or delay 
the start of weapons firing until the mitigation zone is clear. Navy 
personnel must also observe the mitigation zone for marine mammals; if 
marine mammals are observed, Navy personnel must relocate or delay the 
start of weapons firing.
    (B) During activity. During the activity, Navy personnel must 
observe the mitigation zone for marine mammals; if marine mammals are 
observed, Navy personnel must cease weapons firing.
    (C) Commencement/recommencement conditions after a marine mammal 
sighting before or during the activity. Navy personnel must allow a 
sighted marine mammal to leave the mitigation zone prior to the initial 
start of the activity (by delaying the start) or during the activity 
(by not recommencing weapons firing) until one of the following 
conditions has been met:
    (1) Observed exiting. The animal is observed exiting the mitigation 
zone;
    (2) Thought to have exited. The animal is thought to have exited 
the mitigation zone based on a determination of its course, speed, and 
movement relative to the firing ship;
    (3) Clear from additional sightings. The mitigation zone has been 
clear from any additional sightings for 30 min; or
    (4) Firing ship transit. For mobile activities, the firing ship has 
transited a distance equal to double that of the mitigation zone size 
beyond the location of the last sighting.
    (6) Explosive sonobuoys--(i) Number of Lookouts and observation 
platform. One Lookout must be positioned in an aircraft or on small 
boat. If additional platforms are participating in the activity, Navy 
personnel positioned in those assets (e.g., safety observers, 
evaluators) must support observing the mitigation zone for applicable 
biological resources while performing their regular duties.
    (ii) Mitigation zone and requirements. 600 yd (548.6 m) around an 
explosive sonobuoy.
    (A) Prior to activity. Prior to the initial start of the activity 
(e.g., during deployment of a sonobuoy field, which typically lasts 20-
30 min), Navy personnel must observe the mitigation zone for floating 
vegetation; if floating vegetation is observed, Navy personnel must 
relocate or delay the start of sonobuoy or source/receiver pair 
detonations until the mitigation zone is clear. Navy personnel must 
conduct passive acoustic monitoring for marine mammals and use 
information from detections to assist visual observations. Navy 
personnel also must visually observe the mitigation zone for marine 
mammals; if marine mammals are observed, Navy personnel must relocate 
or delay the start of sonobuoy or source/receiver pair detonations.
    (B) During activity. During the activity, Navy personnel must 
observe the mitigation zone for marine mammals; if marine mammals are 
observed, Navy personnel must cease sonobuoy or source/receiver pair 
detonations.
    (C) Commencement/recommencement conditions after a marine mammal 
sighting before or during the activity. Navy personnel must allow a 
sighted marine mammal to leave the mitigation zone prior to the initial 
start of the activity (by delaying the start) or during the activity 
(by not recommencing detonations) until one of the following conditions 
has been met:
    (1) Observed exiting. The animal is observed exiting the mitigation 
zone;
    (2) Thought to have exited. The animal is thought to have exited 
the mitigation zone based on a determination of its course, speed, and 
movement relative to the sonobuoy; or
    (3) Clear from additional sightings. The mitigation zone has been 
clear from any additional sightings for 10 min when the activity 
involves aircraft that have fuel constraints (e.g., helicopter), or 30 
min when the activity involves aircraft that are not typically fuel 
constrained.
    (D) After activity. After completion of the activity (e.g., prior 
to maneuvering off station), when practical (e.g., when platforms are 
not constrained by fuel restrictions or mission-essential follow-on 
commitments), Navy personnel must observe for marine mammals in the 
vicinity of where detonations occurred; if any injured or dead marine 
mammals are observed, Navy personnel must follow established incident 
reporting procedures. If additional platforms are supporting this 
activity (e.g., providing range clearance), these Navy assets must 
assist in the visual observation of the area where detonations 
occurred.
    (7) Explosive torpedoes--(i) Number of Lookouts and observation 
platform. One Lookout positioned in an aircraft. If additional 
platforms are participating in the activity, Navy personnel positioned 
in those assets (e.g., safety observers, evaluators) must support 
observing the mitigation zone for applicable biological resources while 
performing their regular duties.
    (ii) Mitigation zone and requirements. 2,100 yd around the intended 
impact location.
    (A) Prior to activity. Prior to the initial start of the activity 
(e.g., during deployment of the target), Navy personnel must observe 
the mitigation zone for floating vegetation and jellyfish aggregations; 
if floating vegetation or jellyfish aggregations are observed, Navy 
personnel must relocate or delay the start of firing until the 
mitigation zone is clear. Navy personnel must conduct passive acoustic 
monitoring for marine mammals and use the information from detections 
to assist visual observations. Navy personnel also must visually 
observe the mitigation zone for marine mammals; if marine mammals are 
observed, Navy personnel must relocate or delay the start of firing.
    (B) During activity. During the activity, Navy personnel must 
observe for marine mammals and jellyfish aggregations; if marine 
mammals or jellyfish aggregations are observed, Navy personnel must 
cease firing.
    (C) Commencement/recommencement conditions after a marine mammal 
sighting before or during the activity. Navy personnel must allow a 
sighted marine mammal to leave the mitigation zone prior to the initial 
start of the activity (by delaying the start) or during the activity 
(by not recommencing firing) until one of the following conditions has 
been met:
    (1) Observed exiting. The animal is observed exiting the mitigation 
zone;
    (2) Thought to have exited. The animal is thought to have exited 
the mitigation zone based on a determination of its course, speed, and 
movement relative to the intended impact location; or
    (3) Clear from additional sightings. The mitigation zone has been 
clear from any additional sightings for 10 min when the activity 
involves aircraft that have fuel constraints, or 30 min when

[[Page 68359]]

the activity involves aircraft that are not typically fuel constrained.
    (D) After activity. After completion of the activity (e.g., prior 
to maneuvering off station), Navy personnel must when practical (e.g., 
when platforms are not constrained by fuel restrictions or mission-
essential follow-on commitments), observe for marine mammals in the 
vicinity of where detonations occurred; if any injured or dead marine 
mammals are observed, Navy personnel must follow established incident 
reporting procedures. If additional platforms are supporting this 
activity (e.g., providing range clearance), these Navy assets must 
assist in the visual observation of the area where detonations 
occurred.
    (8) Explosive medium-caliber and large-caliber projectiles. Gunnery 
activities using explosive medium-caliber and large-caliber 
projectiles. Mitigation applies to activities using a surface target.
    (i) Number of Lookouts and observation platform. One Lookout must 
be on the vessel or aircraft conducting the activity. For activities 
using explosive large-caliber projectiles, depending on the activity, 
the Lookout could be the same as the one described in ``Weapons firing 
noise'' in paragraph (a)(5)(i) of this section. If additional platforms 
are participating in the activity, Navy personnel positioned in those 
assets (e.g., safety observers, evaluators) must support observing the 
mitigation zone for applicable biological resources while performing 
their regular duties.
    (ii) Mitigation zone and requirements--(A) Air-to-surface 
activities. 200 yd (182.9 m) around the intended impact location for 
air-to-surface activities using explosive medium-caliber projectiles.
    (B) Surface-to-surface activities, medium-caliber. 600 yd (548.6 m) 
around the intended impact location for surface-to-surface activities 
using explosive medium-caliber projectiles.
    (C) Surface-to-surface activities, large-caliber. 1,000 yd (914.4 
m) around the intended impact location for surface-to-surface 
activities using explosive large-caliber projectiles.
    (D) Prior to activity. Prior to the start of the activity (e.g., 
when maneuvering on station), Navy personnel must observe the 
mitigation zone for floating vegetation; if floating vegetation is 
observed, Navy personnel must relocate or delay the start of firing 
until the mitigation zone is clear. Navy personnel also must observe 
the mitigation zone for marine mammals; if marine mammals are observed, 
Navy personnel must relocate or delay the start of firing.
    (E) During activity. During the activity, Navy personnel must 
observe for marine mammals; if marine mammals are observed, Navy 
personnel must cease firing.
    (F) Commencement/recommencement conditions after a marine mammal 
sighting before or during the activity. Navy personnel must allow a 
sighted marine mammal to leave the mitigation zone prior to the initial 
start of the activity (by delaying the start) or during the activity 
(by not recommencing firing) until one of the following conditions has 
been met:
    (1) Observed exiting. The animal is observed exiting the mitigation 
zone;
    (2) Thought to have exited. The animal is thought to have exited 
the mitigation zone based on a determination of its course, speed, and 
movement relative to the intended impact location;
    (3) Clear from additional sightings. The mitigation zone has been 
clear from any additional sightings for 10 min for aircraft-based 
firing or 30 min for vessel-based firing; or for activities using 
mobile targets, the intended impact location has transited a distance 
equal to double that of the mitigation zone size beyond the location of 
the last sighting.
    (G) After activity. After completion of the activity (e.g., prior 
to maneuvering off station), Navy personnel must, when practical (e.g., 
when platforms are not constrained by fuel restrictions or mission-
essential follow-on commitments), observe for marine mammals in the 
vicinity of where detonations occurred; if any injured or dead marine 
mammals are observed, Navy personnel must follow established incident 
reporting procedures. If additional platforms are supporting this 
activity (e.g., providing range clearance), these Navy assets must 
assist in the visual observation of the area where detonations 
occurred.
    (9) Explosive missiles and rockets. Aircraft-deployed explosive 
missiles and rockets. Mitigation applies to activities using a surface 
target.
    (i) Number of Lookouts and observation platform. One Lookout must 
be positioned in an aircraft. If additional platforms are participating 
in the activity, Navy personnel positioned in those assets (e.g., 
safety observers, evaluators) must support observing the mitigation 
zone for applicable biological resources while performing their regular 
duties.
    (ii) Mitigation zone and requirements--(A) Missiles or rockets with 
0.6-20 lb net explosive weight. 900 yd (823 m) around the intended 
impact location for missiles or rockets with 0.6-20 lb net explosive 
weight.
    (B) Missiles with 21-500 lb net explosive weight. 2,000 yd (1,828.8 
m) around the intended impact location for missiles with 21-500 lb net 
explosive weight.
    (C) Prior to activity. Prior to the initial start of the activity 
(e.g., during a fly-over of the mitigation zone), Navy personnel must 
observe the mitigation zone for floating vegetation; if floating 
vegetation is observed, Navy personnel must relocate or delay the start 
of firing until the mitigation zone is clear. Navy personnel also must 
observe the mitigation zone for marine mammals; if marine mammals are 
observed, Navy personnel must relocate or delay the start of firing.
    (D) During activity. During the activity, Navy personnel must 
observe for marine mammals; if marine mammals are observed, Navy 
personnel must cease firing.
    (E) Commencement/recommencement conditions after a marine mammal 
sighting before or during the activity. Navy personnel must allow a 
sighted marine mammal to leave the mitigation zone prior to the initial 
start of the activity (by delaying the start) or during the activity 
(by not recommencing firing) until one of the following conditions has 
been met:
    (1) Observed exiting. The animal is observed exiting the mitigation 
zone;
    (2) Thought to have exited. The animal is thought to have exited 
the mitigation zone based on a determination of its course, speed, and 
movement relative to the intended impact location; or
    (3) Clear from additional sightings. The mitigation zone has been 
clear from any additional sightings for 10 min when the activity 
involves aircraft that have fuel constraints, or 30 min when the 
activity involves aircraft that are not typically fuel constrained.
    (F) After activity. After completion of the activity (e.g., prior 
to maneuvering off station), Navy personnel must, when practical (e.g., 
when platforms are not constrained by fuel restrictions or mission-
essential follow-on commitments), observe for marine mammals in the 
vicinity of where detonations occurred; if any injured or dead marine 
mammals are observed, Navy personnel must follow established incident 
reporting procedures. If additional platforms are supporting this 
activity (e.g., providing range clearance), these Navy assets will 
assist in the visual observation of the area where detonations 
occurred.
    (10) Explosive bombs--(i) Number of Lookouts and observation 
platform. One

[[Page 68360]]

Lookout must be positioned in an aircraft conducting the activity. If 
additional platforms are participating in the activity, Navy personnel 
positioned in those assets (e.g., safety observers, evaluators) must 
support observing the mitigation zone for applicable biological 
resources while performing their regular duties.
    (ii) Mitigation zone and requirements. 2,500 yd (2,286 m) around 
the intended target.
    (A) Prior to activity. Prior to the initial start of the activity 
(e.g., when arriving on station), Navy personnel must observe the 
mitigation zone for floating vegetation; if floating vegetation is 
observed, Navy personnel must relocate or delay the start of bomb 
deployment until the mitigation zone is clear. Navy personnel also must 
observe the mitigation zone for marine mammals; if marine mammals are 
observed, Navy personnel must relocate or delay the start of bomb 
deployment.
    (B) During activity. During the activity (e.g., during target 
approach), Navy personnel must observe the mitigation zone for marine 
mammals; if marine mammals are observed, Navy personnel must cease bomb 
deployment.
    (C) Commencement/recommencement conditions after a marine mammal 
sighting before or during the activity. Navy personnel must allow a 
sighted marine mammal to leave the mitigation zone prior to the initial 
start of the activity (by delaying the start) or during the activity 
(by not recommencing bomb deployment) until one of the following 
conditions has been met:
    (1) Observed exiting. The animal is observed exiting the mitigation 
zone;
    (2) Thought to have exited. The animal is thought to have exited 
the mitigation zone based on a determination of its course, speed, and 
movement relative to the intended target;
    (3) Clear from additional sightings. The mitigation zone has been 
clear from any additional sightings for 10 min; or for activities using 
mobile targets, the intended target has transited a distance equal to 
double that of the mitigation zone size beyond the location of the last 
sighting.
    (D) After activity. After completion of the activity (e.g., prior 
to maneuvering off station), Navy personnel must, when practical (e.g., 
when platforms are not constrained by fuel restrictions or mission-
essential follow-on commitments), observe for marine mammals in the 
vicinity of where detonations occurred; if any injured or dead marine 
mammals are observed, Navy personnel must follow established incident 
reporting procedures. If additional platforms are supporting this 
activity (e.g., providing range clearance), these Navy assets must 
assist in the visual observation of the area where detonations 
occurred.
    (11) Sinking exercises--(i) Number of Lookouts and observation 
platform. Two Lookouts (one must be positioned in an aircraft and one 
must be positioned on a vessel). If additional platforms are 
participating in the activity, Navy personnel positioned in those 
assets (e.g., safety observers, evaluators) must support observing the 
mitigation zone for applicable biological resources while performing 
their regular duties.
    (ii) Mitigation zone and requirements. 2.5 nautical miles (nmi) 
around the target ship hulk.
    (A) Prior to activity. Prior to the initial start of the activity 
(90 min prior to the first firing), Navy personnel must conduct aerial 
observations of the mitigation zone for floating vegetation and 
jellyfish aggregations; if floating vegetation or jellyfish 
aggregations are observed, Navy personnel must delay the start of 
firing until the mitigation zone is clear. Navy personnel also must 
conduct aerial observations of the mitigation zone for marine mammals; 
if marine mammals are observed, Navy personnel must delay the start of 
firing.
    (B) During activity. During the activity, Navy personnel must 
conduct passive acoustic monitoring for marine mammals and use the 
information from detections to assist visual observations. Navy 
personnel must visually observe the mitigation zone for marine mammals 
from the vessel; if marine mammals are observed, Navy personnel must 
cease firing. Immediately after any planned or unplanned breaks in 
weapons firing of longer than 2 hours, Navy personnel must observe the 
mitigation zone for marine mammals from the aircraft and vessel; if 
marine mammals are observed, Navy personnel must delay recommencement 
of firing.
    (C) Commencement/recommencement conditions after a marine mammal 
sighting before or during the activity. Navy personnel must allow a 
sighted marine mammal to leave the mitigation zone prior to the initial 
start of the activity (by delaying the start) or during the activity 
(by not recommencing firing) until one of the following conditions has 
been met:
    (1) Observed exiting. The animal is observed exiting the mitigation 
zone;
    (2) Thought to have exited. The animal is thought to have exited 
the mitigation zone based on a determination of its course, speed, and 
movement relative to the target ship hulk; or
    (3) Clear from additional sightings. The mitigation zone has been 
clear from any additional sightings for 30 minutes.
    (D) After activity. After completion of the activity (for 2 hours 
after sinking the vessel or until sunset, whichever comes first), Navy 
personnel must observe for marine mammals in the vicinity of where 
detonations occurred; if any injured or dead marine mammals are 
observed, Navy personnel must follow established incident reporting 
procedures. If additional platforms are supporting this activity (e.g., 
providing range clearance), these Navy assets will assist in the visual 
observation of the area where detonations occurred.
    (12) Explosive mine countermeasure and neutralization activities--
(i) Number of Lookouts and observation platform--(A) Smaller mitigation 
zone. One Lookout must be positioned on a vessel or in an aircraft when 
implementing the smaller mitigation zone.
    (B) Larger mitigation zone. Two Lookouts (one must be positioned in 
an aircraft and one must be on a small boat) when implementing the 
larger mitigation zone.
    (C) Additional platforms. If additional platforms are participating 
in the activity, Navy personnel positioned in those assets (e.g., 
safety observers, evaluators) must support observing the mitigation 
zone for applicable biological resources while performing their regular 
duties.
    (ii) Mitigation zone and requirements. (A) Activities using 0.1-5 
lb net explosive weight. 600 yd (548.6 m) around the detonation site 
for activities using 0.1-5 lb net explosive weight.
    (B) Activities using 6-650 lb net explosive weight. 2,100 yd 
(1,920.2 m) around the detonation site for activities using 6-650 lb 
net explosive weight (including high explosive target mines).
    (C) Prior to activity. Prior to the initial start of the activity 
(e.g., when maneuvering on station; typically, 10 min when the activity 
involves aircraft that have fuel constraints, or 30 min when the 
activity involves aircraft that are not typically fuel constrained), 
Navy personnel must observe the mitigation zone for floating 
vegetation; if floating vegetation is observed, Navy personnel must 
relocate or delay the start of detonations until the mitigation zone is 
clear. Navy personnel also must observe the mitigation zone for marine 
mammals; if marine mammals are observed, Navy personnel must relocate 
or delay the start of detonations.
    (D) During activity. During the activity, Navy personnel must 
observe the mitigation zone for marine mammals, concentrations of 
seabirds,

[[Page 68361]]

and individual foraging seabirds; if marine mammals, concentrations of 
seabirds, or individual foraging seabirds are observed, Navy personnel 
must cease detonations.
    (E) Commencement/recommencement conditions after a marine mammal 
sighting before or during the activity or a sighting of seabird 
concentrations or individual foraging seabirds during the activity. 
Navy personnel must allow a sighted animal to leave the mitigation zone 
prior to the initial start of the activity (by delaying the start) or 
during the activity (by not recommencing detonations) until one of the 
following conditions has been met:
    (1) Observed exiting. The animal is observed exiting the mitigation 
zone;
    (2) Thought to have exited. The animal is thought to have exited 
the mitigation zone based on a determination of its course, speed, and 
movement relative to detonation site; or
    (3) Clear from additional sightings. The mitigation zone has been 
clear from any additional sightings for 10 min when the activity 
involves aircraft that have fuel constraints, or 30 min when the 
activity involves aircraft that are not typically fuel constrained.
    (F) After activity. After completion of the activity (typically 10 
min when the activity involves aircraft that have fuel constraints, or 
30 min when the activity involves aircraft that are not typically fuel 
constrained), Navy personnel must observe for marine mammals in the 
vicinity of where detonations occurred; if any injured or dead marine 
mammals are observed, Navy personnel must follow established incident 
reporting procedures. If additional platforms are supporting this 
activity (e.g., providing range clearance), these Navy assets must 
assist in the visual observation of the area where detonations 
occurred.
    (13) Explosive mine neutralization activities involving Navy 
divers--(i) Number of Lookouts and observation platform--(A) Smaller 
mitigation zone. Two Lookouts (two small boats with one Lookout each, 
or one Lookout must be on a small boat and one must be in a rotary-wing 
aircraft) when implementing the smaller mitigation zone.
    (B) Larger mitigation zone. Four Lookouts (two small boats with two 
Lookouts each), and a pilot or member of an aircrew must serve as an 
additional Lookout if aircraft are used during the activity, when 
implementing the larger mitigation zone.
    (C) Divers. All divers placing the charges on mines will support 
the Lookouts while performing their regular duties and will report 
applicable sightings to their supporting small boat or Range Safety 
Officer.
    (D) Additional platforms. If additional platforms are participating 
in the activity, Navy personnel positioned in those assets (e.g., 
safety observers, evaluators) must support observing the mitigation 
zone for applicable biological resources while performing their regular 
duties.
    (ii) Mitigation zone and requirements--(A) Activities under 
positive control using 0.1-20 lb net explosive weight. 500 yd (457.2 m) 
around the detonation site during activities under positive control 
using 0.1-20 lb net explosive weight.
    (B) Activities under positive control using 21-60 lb net explosive 
weight charges. 1,000 yd (914.4 m) around the detonation site during 
all activities using time-delay fuses (0.1-29 lb net explosive weight) 
and during activities under positive control using 21-60 lb net 
explosive weight charges.
    (C) Prior to activity. Prior to the initial start of the activity 
(e.g., when maneuvering on station for activities under positive 
control; 30 min for activities using time-delay firing devices), Navy 
personnel must observe the mitigation zone for floating vegetation; if 
floating vegetation is observed, Navy personnel must relocate or delay 
the start of detonations or fuse initiation until the mitigation zone 
is clear. Navy personnel also must observe the mitigation zone for 
marine mammals; if marine mammals are observed, Navy personnel must 
relocate or delay the start of detonations or fuse initiation.
    (D) During activity. During the activity, Navy personnel must 
observe the mitigation zone for marine mammals, concentrations of 
seabirds, and individual foraging seabirds (in the water and not on 
shore); if marine mammals, concentrations of seabirds, or individual 
foraging seabirds are observed, Navy personnel must cease detonations 
or fuse initiation. To the maximum extent practicable depending on 
mission requirements, safety, and environmental conditions, Navy 
personnel must position boats near the mid-point of the mitigation zone 
radius (but outside of the detonation plume and human safety zone), 
must position themselves on opposite sides of the detonation location 
(when two boats are used), and must travel in a circular pattern around 
the detonation location with one Lookout observing inward toward the 
detonation site and the other observing outward toward the perimeter of 
the mitigation zone. If used, Navy aircraft must travel in a circular 
pattern around the detonation location to the maximum extent 
practicable. Navy personnel must not set time-delay firing devices 
(0.1-29 lb net explosive weight) to exceed 10 minutes.
    (E) Commencement/recommencement conditions after a marine mammal 
sighting before or during the activity or a sighting of seabird 
concentrations or individual foraging seabirds during the activity. 
Navy personnel must allow a sighted animal to leave the mitigation zone 
prior to the initial start of the activity (by delaying the start) or 
during the activity (by not recommencing detonations) until one of the 
following conditions has been met:
    (1) Observed exiting. The animal is observed exiting the mitigation 
zone;
    (2) Thought to have exited. The animal is thought to have exited 
the mitigation zone based on a determination of its course, speed, and 
movement relative to the detonation site; or
    (3) Clear from additional sightings. The mitigation zone has been 
clear from any additional sightings for 10 min during activities under 
positive control with aircraft that have fuel constraints, or 30 min 
during activities under positive control with aircraft that are not 
typically fuel constrained and during activities using time-delay 
firing devices.
    (F) After activity. After completion of an activity (for 30 min), 
the Navy must observe for marine mammals for 30 minutes. Navy personnel 
must observe for marine mammals in the vicinity of where detonations 
occurred; if any injured or dead marine mammals are observed, Navy 
personnel must follow established incident reporting procedures. If 
additional platforms are supporting this activity (e.g., providing 
range clearance), these Navy assets must assist in the visual 
observation of the area where detonations occurred.
    (14) Maritime security operations--anti-swimmer grenades--(i) 
Number of Lookouts and observation platform. One Lookout must be 
positioned on the small boat conducting the activity. If additional 
platforms are participating in the activity, Navy personnel positioned 
in those assets (e.g., safety observers, evaluators) must support 
observing the mitigation zone for applicable biological resources while 
performing their regular duties.
    (ii) Mitigation zone and requirements. 200 yd (182.9 m) around the 
intended detonation location.
    (A) Prior to activity. Prior to the initial start of the activity 
(e.g., when maneuvering on station), Navy personnel must observe the 
mitigation zone for floating vegetation; if floating vegetation is 
observed, Navy personnel

[[Page 68362]]

must relocate or delay the start of detonations until the mitigation 
zone is clear. Navy personnel also must observe the mitigation zone for 
marine mammals; if marine mammals are observed, Navy personnel must 
relocate or delay the start of detonations.
    (B) During activity. During the activity, Navy personnel must 
observe the mitigation zone for marine mammals; if marine mammals are 
observed, Navy personnel must cease detonations.
    (C) Commencement/recommencement conditions after a marine mammal 
sighting before or during the activity. Navy personnel must allow a 
sighted marine mammal to leave the mitigation zone prior to the initial 
start of the activity (by delaying the start) or during the activity 
(by not recommencing detonations) until one of the following conditions 
has been met:
    (1) Observed exiting. The animal is observed exiting the mitigation 
zone;
    (2) Thought to have exited. The animal is thought to have exited 
the mitigation zone based on a determination of its course, speed, and 
movement relative to the intended detonation location;
    (3) Clear from additional sightings. The mitigation zone has been 
clear from any additional sightings for 30 min; or
    (4) Detonation location transit. The intended detonation location 
has transited a distance equal to double that of the mitigation zone 
size beyond the location of the last sighting.
    (D) After activity. After completion of the activity (e.g., prior 
to maneuvering off station), Navy personnel must, when practical (e.g., 
when platforms are not constrained by fuel restrictions or mission-
essential follow-on commitments), observe for marine mammals in the 
vicinity of where detonations occurred; if any injured or dead marine 
mammals are observed, Navy personnel must follow established incident 
reporting procedures. If additional platforms are supporting this 
activity (e.g., providing range clearance), these Navy assets will 
assist in the visual observation of the area where detonations 
occurred.
    (15) Underwater demolition multiple charge--mat weave and obstacle 
loading exercises--(i) Number of Lookouts and observation platform. Two 
Lookouts (one must be positioned on a small boat and one must be 
positioned on shore from an elevated platform). If additional platforms 
are participating in the activity, Navy personnel positioned in those 
assets (e.g., safety observers, evaluators) must support observing the 
mitigation zone for applicable biological resources while performing 
their regular duties.
    (ii) Mitigation zone and requirements. 700 yd (640.1 m) around the 
intended detonation location.
    (A) Prior to activity. Prior to the initial start of the activity, 
or 30 min prior to the first detonation, the Lookout positioned on a 
small boat must observe the mitigation zone for floating vegetation and 
marine mammals; if floating vegetation or marine mammals are observed, 
Navy personnel must delay the start of detonations until the mitigation 
zone is clear. For 10 min prior to the first detonation, the Lookout 
positioned on shore must use binoculars to observe the mitigation zone 
for marine mammals; if marine mammals are observed, Navy personnel must 
delay the start of detonations.
    (B) During activity. During the activity, Navy personnel must 
observe the mitigation zone for marine mammals; if marine mammals are 
observed, Navy personnel must cease detonations.
    (C) Commencement/recommencement conditions after a marine mammal 
sighting before or during the activity. Navy personnel must allow a 
sighted marine mammal to leave the mitigation zone prior to the initial 
start of the activity (by delaying the start) or during the activity 
(by not recommencing detonations) until one of the following conditions 
has been met:
    (1) Observed exiting. The animal is observed exiting the mitigation 
zone;
    (2) Thought to have exited. The animal is thought to have exited 
the mitigation zone based on a determination of its course, speed, and 
movement relative to the detonation location; or
    (3) Clear from additional sightings. The mitigation zone has been 
clear from any additional sightings for 10 min (as determined by the 
Navy shore observer).
    (D) After activity. After completion of the activity (for 30 min), 
the Lookout positioned on a small boat must observe for marine mammals 
in the vicinity of where detonations occurred; if any injured or dead 
marine mammals are observed, Navy personnel must follow established 
incident reporting procedures. If additional platforms are supporting 
this activity (e.g., providing range clearance), these Navy assets must 
assist in the visual observation of the area where detonations 
occurred.
    (16) Vessel movement. The mitigation will not be applied if: the 
vessel's safety is threatened; the vessel is restricted in its ability 
to maneuver (e.g., during launching and recovery of aircraft or landing 
craft, during towing activities, when mooring); the vessel is operated 
autonomously; or when impracticable based on mission requirements 
(e.g., during Amphibious Assault--Battalion Landing exercise).
    (i) Number of Lookouts and observation platform. One Lookout must 
be on the vessel that is underway.
    (ii) Mitigation zone and requirements--(A) Whales. 500 yd (457.2 m) 
around whales.
    (B) Marine mammals other than whales. 200 yd (182.9 m) around all 
other marine mammals (except bow-riding dolphins and pinnipeds hauled 
out on man-made navigational structures, port structures, and vessels).
    (iii) During the activity. When underway, Navy personnel must 
observe the mitigation zone for marine mammals; if marine mammals are 
observed, Navy personnel must maneuver (which may include reducing 
speed as the mission or circumstances allow) to maintain distance.
    (iv) Incident reporting procedures. If a marine mammal vessel 
strike occurs, Navy personnel must follow the established incident 
reporting procedures.
    (v) Post-strike alerts. Navy personnel must send alerts to Navy 
vessels of increased risk of strike following any reported Navy vessel 
strike in the HSTT Study Area.
    (vi) Large whale aggregation alerts. Navy personnel must issue 
real-time notifications to Navy vessels of large whale aggregations 
(four or more whales) within 1 nmi (1.9 km) of a Navy vessel in the 
area between 32-33 degrees North and 117.2-119.5 degrees West.
    (17) Towed in-water devices. Mitigation applies to devices that are 
towed from a manned surface platform or manned aircraft. The mitigation 
will not be applied if the safety of the towing platform or in-water 
device is threatened.
    (i) Number of Lookouts and observation platform. One Lookout must 
be positioned on a manned towing platform.
    (ii) Mitigation zone and requirements. 250 yd (228.6 m) around 
marine mammals.
    (iii) During the activity. During the activity (i.e., when towing 
an in-water device), Navy personnel must observe the mitigation zone 
for marine mammals; if marine mammals are observed, Navy personnel must 
maneuver to maintain distance.
    (18) Small-, medium-, and large-caliber non-explosive practice 
munitions. Mitigation applies to activities using a surface target.
    (i) Number of Lookouts and observation platform. One Lookout must

[[Page 68363]]

be positioned on the platform conducting the activity. Depending on the 
activity, the Lookout could be the same as the one described for 
``Weapons firing noise'' in paragraph (a)(5)(i) of this section.
    (ii) Mitigation zone and requirements. 200 yd (182.9 m) around the 
intended impact location.
    (A) Prior to activity. Prior to the start of the activity (e.g., 
when maneuvering on station), Navy personnel must observe the 
mitigation zone for floating vegetation; if floating vegetation is 
observed, Navy personnel must relocate or delay the start of firing 
until the mitigation zone is clear. Navy personnel also must observe 
the mitigation zone for marine mammals; if marine mammals are observed, 
Navy personnel must relocate or delay the start of firing.
    (B) During activity. During the activity, Navy personnel must 
observe the mitigation zone for marine mammals; if marine mammals are 
observed, Navy personnel must cease firing.
    (C) Commencement/recommencement conditions after a marine mammal 
sighting before or during the activity. Navy personnel must allow a 
sighted marine mammal to leave the mitigation zone prior to the initial 
start of the activity (by delaying the start) or during the activity 
(by not recommencing firing) until one of the following conditions has 
been met:
    (1) Observed exiting. The animal is observed exiting the mitigation 
zone;
    (2) Thought to have exited. The animal is thought to have exited 
the mitigation zone based on a determination of its course, speed, and 
movement relative to the intended impact location;
    (3) Clear from additional sightings. The mitigation zone has been 
clear from any additional sightings for 10 min for aircraft-based 
firing or 30 min for vessel-based firing; or
    (4) Impact location transit. For activities using a mobile target, 
the intended impact location has transited a distance equal to double 
that of the mitigation zone size beyond the location of the last 
sighting.
    (19) Non-explosive missiles and rockets. Aircraft-deployed non-
explosive missiles and rockets. Mitigation applies to activities using 
a surface target.
    (i) Number of Lookouts and observation platform. One Lookout must 
be positioned in an aircraft.
    (ii) Mitigation zone and requirements. 900 yd around the intended 
impact location.
    (A) Prior to activity. Prior to the initial start of the activity 
(e.g., during a fly-over of the mitigation zone), Navy personnel must 
observe the mitigation zone for floating vegetation; if floating 
vegetation is observed, Navy personnel must relocate or delay the start 
of firing until the mitigation zone is clear. Navy personnel also must 
observe the mitigation zone for marine mammals; if marine mammals are 
observed, Navy personnel must relocate or delay the start of firing.
    (B) During activity. During the activity, Navy personnel must 
observe the mitigation zone for marine mammals; if marine mammals are 
observed, Navy personnel must cease firing.
    (C) Commencement/recommencement conditions after a marine mammal 
sighting prior to or during the activity. Navy personnel must allow a 
sighted marine mammal to leave the mitigation zone prior to the initial 
start of the activity (by delaying the start) or during the activity 
(by not recommencing firing) until one of the following conditions has 
been met:
    (1) Observed exiting. The animal is observed exiting the mitigation 
zone;
    (2) Thought to have exited. The animal is thought to have exited 
the mitigation zone based on a determination of its course, speed, and 
movement relative to the intended impact location; or
    (3) Clear from additional sightings. The mitigation zone has been 
clear from any additional sightings for 10 min when the activity 
involves aircraft that have fuel constraints, or 30 min when the 
activity involves aircraft that are not typically fuel constrained.
    (20) Non-explosive bombs and mine shapes. Non-explosive bombs and 
non-explosive mine shapes during mine laying activities.
    (i) Number of Lookouts and observation platform. One Lookout must 
be positioned in an aircraft.
    (ii) Mitigation zone and requirements. 1,000 yd (914.4 m) around 
the intended target.
    (A) Prior to activity. Prior to the initial start of the activity 
(e.g., when arriving on station), Navy personnel must observe the 
mitigation zone for floating vegetation; if floating vegetation is 
observed, Navy personnel must relocate or delay the start of bomb 
deployment or mine laying until the mitigation zone is clear. Navy 
personnel also must observe the mitigation zone for marine mammals; if 
marine mammals are observed, Navy personnel must relocate or delay the 
start of bomb deployment or mine laying.
    (B) During activity. During the activity (e.g., during approach of 
the target or intended minefield location), Navy personnel must observe 
the mitigation zone for marine mammals and, if marine mammals are 
observed, Navy personnel must cease bomb deployment or mine laying.
    (C) Commencement/recommencement conditions after a marine mammal 
sighting prior to or during the activity. Navy personnel must allow a 
sighted marine mammal to leave the mitigation zone prior to the initial 
start of the activity (by delaying the start) or during the activity 
(by not recommencing bomb deployment or mine laying) until one of the 
following conditions has been met:
    (1) Observed exiting. The animal is observed exiting the mitigation 
zone;
    (2) Thought to have exited. The animal is thought to have exited 
the mitigation zone based on a determination of its course, speed, and 
movement relative to the intended target or minefield location;
    (3) Clear from additional sightings. The mitigation zone has been 
clear from any additional sightings for 10 min; or
    (4) Target transit. For activities using mobile targets, the 
intended target has transited a distance equal to double that of the 
mitigation zone size beyond the location of the last sighting.
    (b) Mitigation areas. In addition to procedural mitigation, Navy 
personnel must implement mitigation measures within mitigation areas to 
avoid or reduce potential impacts on marine mammals.
    (1) Mitigation areas for marine mammals in the Hawaii Range Complex 
for sonar, explosives, and vessel strikes--(i) Mitigation area 
requirements--(A) Hawaii Island Mitigation Area (year-round)--(1) MF1 
surface ship hull-mounted mid-frequency active sonar, MF4 dipping 
sonar, or explosives. Except as provided in paragraph (b)(1)(i)(A)(2) 
of this section, Navy personnel must not conduct more than 300 hours of 
MF1 surface ship hull-mounted mid-frequency active sonar or 20 hours of 
MF4 dipping sonar annually, or use explosives that could potentially 
result in takes of marine mammals during training and testing.
    (2) National security exception. Should national security require 
conduct of more than 300 hours of MF1 surface ship hull-mounted mid-
frequency active sonar or 20 hours of MF4 dipping sonar, or use of 
explosives that could potentially result in the take of marine mammals 
during training or testing, Naval units must obtain permission from the 
appropriate designated Command authority prior to commencement of the 
activity. Navy personnel must provide NMFS with advance notification 
and include the

[[Page 68364]]

information (e.g., sonar hours or explosives usage) in its annual 
activity reports submitted to NMFS.
    (B) 4-Islands Region Mitigation Area (November 15-April 15 for 
active sonar; year-round for explosives)--(1) MF1 surface ship hull-
mounted mid-frequency active sonar or explosives. Except as provided in 
paragraph (b)(1)(i)(B)(2) of this section, Navy personnel must not use 
MF1 surface ship hull-mounted mid-frequency active sonar or explosives 
that could potentially result in takes of marine mammals during 
training and testing.
    (2) National security exception. Should national security require 
use of MF1 surface ship hull-mounted mid-frequency active sonar or 
explosives that could potentially result in the take of marine mammals 
during training or testing, Naval units must obtain permission from the 
appropriate designated Command authority prior to commencement of the 
activity. Navy personnel must provide NMFS with advance notification 
and include the information (e.g., sonar hours or explosives usage) in 
its annual activity reports submitted to NMFS.
    (C) Humpback Whale Special Reporting Areas (December 15-April 15). 
Navy personnel must report the total hours of surface ship hull-mounted 
mid-frequency active sonar used in the special reporting areas in its 
annual training and testing activity reports submitted to NMFS.
    (D) Humpback Whale Awareness Notification Message Area (November-
April)--(1) Seasonal awareness notification message. Navy personnel 
must issue a seasonal awareness notification message to alert ships and 
aircraft operating in the area to the possible presence of 
concentrations of large whales, including humpback whales.
    (2) Vessel instruction. To maintain safety of navigation and to 
avoid interactions with large whales during transits, Navy personnel 
must instruct vessels to remain vigilant to the presence of large whale 
species (including humpback whales).
    (3) Awareness notification message use. Platforms must use the 
information from the awareness notification message to assist their 
visual observation of applicable mitigation zones during training and 
testing activities and to aid in the implementation of procedural 
mitigation.
    (ii) [Reserved]
    (2) Mitigation areas for marine mammals in the southern California 
portion of the study area for sonar, explosives, and vessel strikes--
(i) Mitigation area requirements--(A) San Diego Arc, San Nicolas 
Island, and Santa Monica/Long Beach Mitigation Areas (June 1-October 
31)--(1) MF1 surface ship hull-mounted mid-frequency active sonar. 
Except as provided in paragraph (b)(2)(i)(A)(2) of this section, Navy 
personnel must not conduct more than a total of 200 hours of MF1 
surface ship hull-mounted mid-frequency active sonar in the combined 
areas, excluding normal maintenance and systems checks, during training 
and testing.
    (2) National security exception. Should national security require 
conduct of more than 200 hours of MF1 surface ship hull-mounted mid-
frequency active sonar in the combined areas during training and 
testing (excluding normal maintenance and systems checks), Naval units 
must obtain permission from the appropriate designated Command 
authority prior to commencement of the activity. Navy personnel must 
provide NMFS with advance notification and include the information 
(e.g., sonar hours) in its annual activity reports submitted to NMFS.
    (3) Explosives in San Diego Arc Mitigation Area. Except as provided 
in paragraph (b)(2)(i)(A)(4) of this section, within the San Diego Arc 
Mitigation Area, Navy personnel must not use explosives that could 
potentially result in the take of marine mammals during large-caliber 
gunnery, torpedo, bombing, and missile (including 2.75-inch rockets) 
activities during training and testing.
    (4) National security exception. Should national security require 
use of explosives that could potentially result in the take of marine 
mammals during large-caliber gunnery, torpedo, bombing, and missile 
(including 2.75-inch rockets) activities during training or testing 
within the San Diego Arc Mitigation Area, Naval units must obtain 
permission from the appropriate designated Command authority prior to 
commencement of the activity. Navy personnel must provide NMFS with 
advance notification and include the information (e.g., explosives 
usage) in its annual activity reports submitted to NMFS.
    (5) Explosives in San Nicolas Island Mitigation Area. Except as 
provided in paragraph (b)(2)(i)(A)(6) of this section, within the San 
Nicolas Island Mitigation Area, Navy personnel must not use explosives 
that could potentially result in the take of marine mammals during mine 
warfare, large-caliber gunnery, torpedo, bombing, and missile 
(including 2.75-inch rockets) activities during training.
    (6) National security exception. Should national security require 
use of explosives that could potentially result in the take of marine 
mammals during mine warfare, large-caliber gunnery, torpedo, bombing, 
and missile (including 2.75-inch rockets) activities during training in 
the San Nicolas Island Mitigation Area, Naval units must obtain 
permission from the appropriate designated Command authority prior to 
commencement of the activity. Navy personnel must provide NMFS with 
advance notification and include the information (e.g., explosives 
usage) in its annual activity reports submitted to NMFS.
    (7) Explosives in the Santa Monica/Long Beach Mitigation Area. 
Except as provided in paragraph (b)(2)(i)(A)(8) of this section, within 
the Santa Monica/Long Beach Mitigation Area, Navy personnel must not 
use explosives that could potentially result in the take of marine 
mammals during mine warfare, large-caliber gunnery, torpedo, bombing, 
and missile (including 2.75-inch rockets) activities during training 
and testing.
    (8) National security exception. Should national security require 
use of explosives that could potentially result in the take of marine 
mammals during mine warfare, large-caliber gunnery, torpedo, bombing, 
and missile (including 2.75-inch rockets) activities during training or 
testing in the Santa Monica/Long Beach Mitigation Area, Naval units 
must obtain permission from the appropriate designated Command 
authority prior to commencement of the activity. Navy personnel must 
provide NMFS with advance notification and include the information 
(e.g., explosives usage) in its annual activity reports submitted to 
NMFS.
    (B) Santa Barbara Island Mitigation Area (year-round)--(1) MF1 
surface ship hull-mounted mid-frequency active sonar or explosives. 
Except as provided in paragraph (b)(2)(i)(B)(2) of this section, Navy 
personnel must not use MF1 surface ship hull-mounted mid-frequency 
active sonar during training or testing, or explosives that could 
potentially result in the take of marine mammals during medium-caliber 
or large-caliber gunnery, torpedo, bombing, and missile (including 
2.75-inch rockets) activities during training.
    (2) National security exception. Should national security require 
use of MF1 surface ship hull-mounted mid-frequency active sonar during 
training or testing, or explosives that could potentially result in the 
take of marine mammals during medium-caliber or large-caliber gunnery, 
torpedo, bombing,

[[Page 68365]]

and missile (including 2.75-inch rockets) activities during training, 
Naval units must obtain permission from the appropriate designated 
Command authority prior to commencement of the activity. Navy personnel 
must provide NMFS with advance notification and include the information 
(e.g., sonar hours or explosives usage) in its annual activity reports 
submitted to NMFS.
    (C) Spring Large Whale Awareness Notification Message--(1) 
Awareness notification message. Navy personnel must issue an awareness 
notification message to alert ships and aircraft operating in the area 
to the possible presence of concentrations of large whales, including 
blue whales, fin whales, and humpback whales.
    (2) Applicable period. This message must apply to a period that is 
based on predicted oceanographic conditions for a given year.
    (3) Marine mammals and vessel transit. To maintain safety of 
navigation and to avoid interactions with large whales during transits, 
Navy personnel must emphasize to vessels that when a marine mammal is 
spotted, this may be an indicator that additional marine mammals are 
present nearby, and increased vigilance and awareness of Navy personnel 
is warranted.
    (4) Platform use of message. Platforms must use the information 
from the awareness notification messages to assist their visual 
observation of applicable mitigation zones during training and testing 
activities and to aid in the implementation of procedural mitigation.
    (D) Gray Whale (November-March) and Fin Whale (November-May) 
Awareness Notification Message Areas--(1) Seasonal awareness message. 
Navy personnel must issue a seasonal awareness notification message to 
alert ships and aircraft operating in the area to the possible presence 
of concentrations of large whales, including gray whales, and fin 
whales.
    (2) Marine mammals and vessel transit. To maintain safety of 
navigation and to avoid interactions with large whales during transits, 
Navy personnel must instruct vessels to remain vigilant to the presence 
of large whale species.
    (3) Platform use of message. Platforms must use the information 
from the awareness notification messages to assist their visual 
observation of applicable mitigation zones during training and testing 
activities and to aid in the implementation of procedural mitigation.
    (ii) [Reserved]


Sec.  218.75  Requirements for monitoring and reporting.

    (a) Unauthorized take. Navy personnel must notify NMFS immediately 
(or as soon as operational security considerations allow) if the 
specified activity identified in Sec.  218.70 is thought to have 
resulted in the mortality or serious injury of any marine mammals, or 
in any Level A harassment or Level B harassment take of marine mammals 
not identified in this subpart.
    (b) Monitoring and reporting under the LOAs. The Navy must conduct 
all monitoring and reporting required under the LOAs, including abiding 
by the HSTT Study Area monitoring program. Details on program goals, 
objectives, project selection process, and current projects are 
available at www.navymarinespeciesmonitoring.us.
    (c) Notification of injured, live stranded, or dead marine mammals. 
The Navy must consult the Notification and Reporting Plan, which sets 
out notification, reporting, and other requirements when dead, injured, 
or live stranded marine mammals are detected. The Notification and 
Reporting Plan is available at https://www.fisheries.noaa.gov/national/marine-mammal-protection/incidental-take-authorizations-military-readiness-activities.
    (d) Changes in Lookout Policies. The Navy must report changes in 
its Lookout policies to NMFS as soon as practicable after a change is 
made.
    (e) Annual HSTT Study Area marine species monitoring report. The 
Navy must submit an annual report of the HSTT Study Area monitoring 
describing the implementation and results from the previous calendar 
year. Data collection methods must be standardized across range 
complexes and study areas to allow for comparison in different 
geographic locations. The report must be submitted to the Director, 
Office of Protected Resources, NMFS, either within 3 months after the 
end of the calendar year, or within 3 months after the conclusion of 
the monitoring year, to be determined by the Adaptive Management 
process. This report will describe progress of knowledge made with 
respect to intermediate scientific objectives within the HSTT Study 
Area associated with the Integrated Comprehensive Monitoring Program 
(ICMP). Similar study questions must be treated together so that 
progress on each topic can be summarized across all Navy ranges. The 
report need not include analyses and content that does not provide 
direct assessment of cumulative progress on the monitoring plan study 
questions. As an alternative, the Navy may submit a multi-Range Complex 
annual Monitoring Plan report to fulfill this requirement. Such a 
report will describe progress of knowledge made with respect to 
monitoring study questions across multiple Navy ranges associated with 
the ICMP. Similar study questions must be treated together so that 
progress on each topic can be summarized across multiple Navy ranges. 
The report need not include analyses and content that does not provide 
direct assessment of cumulative progress on the monitoring study 
question. This will continue to allow the Navy to provide a cohesive 
monitoring report covering multiple ranges (as per ICMP goals), rather 
than entirely separate reports for the HSTT, Gulf of Alaska, Mariana 
Islands, and Northwest Study Areas.
    (f) Annual HSTT Study Area training exercise report and testing 
activity report. Each year, the Navy must submit two preliminary 
reports (Quick Look Report) detailing the status of authorized sound 
sources within 21 days after the anniversary of the date of issuance of 
each LOA to the Director, Office of Protected Resources, NMFS. Each 
year, the Navy must submit detailed reports to the Director, Office of 
Protected Resources, NMFS, within 3 months after the 1-year anniversary 
of the date of issuance of the LOA. The HSTT annual Training Exercise 
Report and Testing Activity Report can be consolidated with other 
exercise reports from other range complexes in the Pacific Ocean for a 
single Pacific Exercise Report, if desired. The annual reports must 
contain information on major training exercises (MTEs), Sinking 
Exercise (SINKEX) events, and a summary of all sound sources used, 
including within specific mitigation reporting areas, as described in 
paragraph (e)(3) through (5) of this section. The analysis in the 
detailed reports must be based on the accumulation of data from the 
current year's report and data collected from previous reports. The 
detailed reports must contain information identified in paragraphs 
(e)(1) through (7) of this section.
    (1) MTEs. This section of the report must contain the following 
information for MTEs conducted in the HSTT Study Area.
    (i) Exercise information (for each MTE).
    (A) Exercise designator.
    (B) Date that exercise began and ended.
    (C) Location.
    (D) Number and types of active sonar sources used in the exercise.
    (E) Number and types of passive acoustic sources used in exercise.

[[Page 68366]]

    (F) Number and types of vessels, aircraft, and other platforms 
participating in exercise.
    (G) Total hours of all active sonar source operation.
    (H) Total hours of each active sonar source bin.
    (I) Wave height (high, low, and average) during exercise.
    (ii) Individual marine mammal sighting information for each 
sighting in each exercise where mitigation was implemented:
    (A) Date, time, and location of sighting.
    (B) Species (if not possible, indication of whale/dolphin/
pinniped).
    (C) Number of individuals.
    (D) Initial Detection Sensor (e.g., sonar, Lookout).
    (E) Indication of specific type of platform observation was made 
from (including, for example, what type of surface vessel or testing 
platform).
    (F) Length of time observers maintained visual contact with marine 
mammal.
    (G) Sea state.
    (H) Visibility.
    (I) Sound source in use at the time of sighting.
    (J) Indication of whether animal was less than 200 yd (182.9 m), 
200 to 500 yd (182.9 to 457.2 m), 500 to 1,000 yd (457.2 m to 914.4 m), 
1,000 to 2,000 yd (914.4 m to 1,828.8 m), or greater than 2,000 yd 
(1,828.8 m) from sonar source.
    (K) Whether operation of sonar sensor was delayed, or sonar was 
powered or shut down, and how long the delay.
    (L) If source in use was hull-mounted, true bearing of animal from 
the vessel, true direction of vessel's travel, and estimation of 
animal's motion relative to vessel (opening, closing, parallel).
    (M) Lookouts must report, in plain language and without trying to 
categorize in any way, the observed behavior of the animal(s) (such as 
animal closing to bow ride, paralleling course/speed, floating on 
surface and not swimming, etc.) and if any calves were present.
    (iii) An evaluation (based on data gathered during all of the MTEs) 
of the effectiveness of mitigation measures designed to minimize the 
received level to which marine mammals may be exposed. This evaluation 
must identify the specific observations that support any conclusions 
the Navy reaches about the effectiveness of the mitigation.
    (2) SINKEXs. This section of the report must include the following 
information for each SINKEX completed that year.
    (i) Exercise information (gathered for each SINKEX).
    (A) Location.
    (B) Date and time exercise began and ended.
    (C) Total hours of observation by Lookouts before, during, and 
after exercise.
    (D) Total number and types of explosive source bins detonated.
    (E) Number and types of passive acoustic sources used in exercise.
    (F) Total hours of passive acoustic search time.
    (G) Number and types of vessels, aircraft, and other platforms 
participating in exercise.
    (H) Wave height in feet (high, low, and average) during exercise.
    (I) Narrative description of sensors and platforms utilized for 
marine mammal detection and timeline illustrating how marine mammal 
detection was conducted.
    (ii) Individual marine mammal observation (by Navy Lookouts) 
information for each sighting where mitigation was implemented.
    (A) Date/Time/Location of sighting.
    (B) Species (if not possible, indicate whale, dolphin, or 
pinniped).
    (C) Number of individuals.
    (D) Initial detection sensor (e.g., sonar or Lookout).
    (E) Length of time observers maintained visual contact with marine 
mammal.
    (F) Sea state.
    (G) Visibility.
    (H) Whether sighting was before, during, or after detonations/
exercise, and how many minutes before or after.
    (I) Distance of marine mammal from actual detonations (or target 
spot if not yet detonated): Less than 200 yd (182.9 m), 200 to 500 yd 
(182.9 to 457.2 m), 500 to 1,000 yd (457.2 m to 914.4 m), 1,000 to 
2,000 yd (914.4 m to 1,828.8 m), or greater than 2,000 yd (1,828.8 m).
    (J) Lookouts must report, in plain language and without trying to 
categorize in any way, the observed behavior of the animal(s) (such as 
animal closing to bow ride, paralleling course/speed, floating on 
surface and not swimming etc.), including speed and direction and if 
any calves were present.
    (K) The report must indicate whether explosive detonations were 
delayed, ceased, modified, or not modified due to marine mammal 
presence and for how long.
    (L) If observation occurred while explosives were detonating in the 
water, indicate munition type in use at time of marine mammal 
detection.
    (3) Summary of sources used. This section of the report must 
include the following information summarized from the authorized sound 
sources used in all training and testing events:
    (i) Total annual hours or quantity (per the LOA) of each bin of 
sonar or other acoustic sources (e.g., pile driving and air gun 
activities); and
    (ii) Total annual expended/detonated ordinance (missiles, bombs, 
sonobuoys, etc.) for each explosive bin.
    (4) Humpback Whale Special Reporting Area (December 15-April 15). 
The Navy must report the total hours of operation of surface ship hull-
mounted mid-frequency active sonar used in the special reporting area.
    (5) HSTT Study Area Mitigation Areas. The Navy must report any use 
that occurred as specifically described in these areas. Information 
included in the classified annual reports may be used to inform future 
adaptive management of activities within the HSTT Study Area.
    (6) Geographic information presentation. The reports must present 
an annual (and seasonal, where practical) depiction of training and 
testing bin usage (as well as pile driving activities) geographically 
across the HSTT Study Area.
    (7) Sonar exercise notification. The Navy must submit to NMFS 
(contact as specified in the LOA) an electronic report within 15 
calendar days after the completion of any MTE indicating:
    (i) Location of the exercise;
    (ii) Beginning and end dates of the exercise; and
    (iii) Type of exercise.
    (g) Seven-year close-out comprehensive training and testing 
activity report. This report must be included as part of the 2025 
annual training and testing report. This report must provide the annual 
totals for each sound source bin with a comparison to the annual 
allowance and the 7-year total for each sound source bin with a 
comparison to the 7-year allowance. Additionally, if there were any 
changes to the sound source allowance, this report must include a 
discussion of why the change was made and include the analysis to 
support how the change did or did not result in a change in the 2018 
HSTT FEIS/OEIS and final rule determinations. The draft report must be 
submitted within 3 months after the expiration of this subpart to the 
Director, Office of Protected Resources, NMFS. NMFS must submit 
comments on the draft close-out report, if any, within 3 months of 
receipt. The report will be considered final after the Navy has 
addressed NMFS' comments, or 3 months after the submittal of the draft 
if NMFS does not provide comments.


Sec.  218.76  Letters of Authorization.

    (a) To incidentally take marine mammals pursuant to the regulations 
in

[[Page 68367]]

this subpart, the Navy must apply for and obtain LOAs in accordance 
with Sec.  216.106 of this chapter.
    (b) LOAs, unless suspended or revoked, may be effective for a 
period of time not to exceed December 20, 2025.
    (c) If an LOA expires prior to December 20, 2025, the Navy may 
apply for and obtain a renewal of the LOA.
    (d) In the event of projected changes to the activity or to 
mitigation, monitoring, or reporting (excluding changes made pursuant 
to the adaptive management provision of Sec.  218.77(c)(1)) required by 
an LOA issued under this subpart, the Navy must apply for and obtain a 
modification of the LOA as described in Sec.  218.77.
    (e) Each LOA must set forth:
    (1) Permissible methods of incidental taking;
    (2) Geographic areas for incidental taking;
    (3) Means of effecting the least practicable adverse impact (i.e., 
mitigation) on the species or stocks of marine mammals and their 
habitat; and
    (4) Requirements for monitoring and reporting.
    (f) Issuance of the LOA(s) must be based on a determination that 
the level of taking is consistent with the findings made for the total 
taking allowable under the regulations in this subpart.
    (g) Notice of issuance or denial of the LOA(s) must be published in 
the Federal Register within 30 days of a determination.


Sec.  218.77  Renewals and modifications of Letters of Authorization.

    (a) An LOA issued under Sec. Sec.  216.106 of this chapter and 
218.76 for the activity identified in Sec.  218.70(c) may be renewed or 
modified upon request by the applicant, provided that:
    (1) The planned specified activity and mitigation, monitoring, and 
reporting measures, as well as the anticipated impacts, are the same as 
those described and analyzed for the regulations in this subpart 
(excluding changes made pursuant to the adaptive management provision 
in paragraph (c)(1) of this section); and
    (2) NMFS determines that the mitigation, monitoring, and reporting 
measures required by the previous LOA(s) were implemented.
    (b) For LOA modification or renewal requests by the applicant that 
include changes to the activity or to the mitigation, monitoring, or 
reporting measures (excluding changes made pursuant to the adaptive 
management provision in paragraph (c)(1) of this section) that do not 
change the findings made for the regulations or result in no more than 
a minor change in the total estimated number of takes (or distribution 
by species or stock or years), NMFS may publish a notice of planned LOA 
in the Federal Register, including the associated analysis of the 
change, and solicit public comment before issuing the LOA.
    (c) An LOA issued under Sec. Sec.  216.106 of this chapter and 
218.76 may be modified by NMFS under the following circumstances:
    (1) Adaptive management. After consulting with the Navy regarding 
the practicability of the modifications, NMFS may modify (including 
adding or removing measures) the existing mitigation, monitoring, or 
reporting measures if doing so creates a reasonable likelihood of more 
effectively accomplishing the goals of the mitigation and monitoring.
    (i) Possible sources of data that could contribute to the decision 
to modify the mitigation, monitoring, or reporting measures in an LOA 
include:
    (A) Results from the Navy's monitoring from the previous year(s);
    (B) Results from other marine mammal and/or sound research or 
studies; or
    (C) Any information that reveals marine mammals may have been taken 
in a manner, extent, or number not authorized by the regulations in 
this subpart or subsequent LOAs.
    (ii) If, through adaptive management, the modifications to the 
mitigation, monitoring, or reporting measures are substantial, NMFS 
will publish a notice of planned LOA in the Federal Register and 
solicit public comment.
    (2) Emergencies. If NMFS determines that an emergency exists that 
poses a significant risk to the well-being of the species or stocks of 
marine mammals specified in LOAs issued pursuant to Sec. Sec.  216.106 
of this chapter and 218.76, an LOA may be modified without prior notice 
or opportunity for public comment. Notice would be published in the 
Federal Register within 30 days of the action.


Sec. Sec.  218.78-218.79  [Reserved]

[FR Doc. 2023-21499 Filed 10-2-23; 8:45 am]
BILLING CODE 3510-22-P`