85244 Federal Register / Vol. 88, No. 234 / Thursday, December 7, 2023 / Notices 

Paperwork Reduction Act of 1995 

(PRA), invites the general public and 

other Federal agencies to comment on 

proposed, and continuing information 

collections, which helps us assess the 

impact of our information collection 

requirements and minimize the public’s 

reporting burden. The purpose of this 

notice is to allow for 60 days of public 

comment preceding submission of the 

collection to OMB. 

DATES: To ensure consideration, 

comments regarding this proposed 

information collection must be received 

on or before February 5, 2024. 

ADDRESSES: Interested persons are 

invited to submit written comments by 

mail to Elizabeth Reinhart, Management 

Analyst, NIST, 100 Bureau Drive, 

Gaithersburg, MD 20899, or by email to 

PRAcomments@doc.gov. Do not submit 

Confidential Business Information or 

otherwise sensitive or protected 

information. 

FOR FURTHER INFORMATION CONTACT: 

Requests for additional information or 

specific questions related to collection 

activities should be directed to Bethany 

Loftin, Interagency and iEdison 

Specialist, National Institute of 

Standards and Technology, 100 Bureau 

Drive, Gaithersburg, MD 20899, 202– 

941–7750, bethany.loftin@nist.gov. 

SUPPLEMENTARY INFORMATION: 

I. Abstract 

The Bayh-Dole Act (35 U.S.C. 18) and 

its implementing regulations (37 CFR 

401) allow for recipients of federal 

research funding (Contractors) to retain 

ownership of inventions developed 

under federal funding agreements 

(Subject Inventions). In exchange, the 

government retains certain rights to the 

Subject Invention, including a worldwide right to use by or on behalf of the 

U.S. government, and the Contractor 

also has certain responsibilities and 

obligations. Among these obligations is 

a requirement that in certain 

circumstances products embodying the 

Subject Invention or produced through 

the use of the Subject Invention be 

manufactured substantially in the 

United States. The statute also allows 

the Contractor to request a waiver of this 

obligation if reasonable but 

unsuccessful efforts were made to grant 

licenses on similar terms to potential 

licensees that would be likely to 

manufacture substantially in the United 

States or if under the circumstances 

domestic manufacture is not 

commercially feasible. This information 

collection will be utilized as a common 

form, which will allow other Federal 

agencies to request use. 

II. Method of Collection 

The form will be provided in PDF 

format. It may be submitted to funding 

agencies via email, via an attachment to 

a Domestic Manufacturing Waiver 

Request in the iEdison online reporting 

system if the agency participates in the 

iEdison online reporting system, or via 

other electronic transmission if the 

agency does not participate in the 

iEdison reporting system. 

III. Data 

OMB Control Number: 0693–XXXX. 

Form Number(s): None. 

Type of Review: Regular submission 

of a new Common Form. 

Affected Public: Business or other forprofit organizations; not-for-profit 

institutions; State, local, or Tribal 

government. 

Estimated Number of Respondents: 

10. 

Estimated Time per Response: 13 

hours. 

Estimated Total Annual Burden 

Hours: 130 hours. 

Estimated Total Annual Cost to 

Public: $6355.00 

Respondent’s Obligation: Mandatory 

to obtain benefits. 

Legal Authority: 35 U.S.C. 204. 

IV. Request for Comments 

We are soliciting public comments to 

permit the Department/Bureau to: (a) 

Evaluate whether the proposed 

information collection is necessary for 

the proper functions of the Department, 

including whether the information will 

have practical utility; (b) Evaluate the 

accuracy of our estimate of the time and 

cost burden for this proposed collection, 

including the validity of the 

methodology and assumptions used; (c) 

Evaluate ways to enhance the quality, 

utility, and clarity of the information to 

be collected; and (d) Minimize the 

reporting burden on those who are to 

respond, including the use of automated 

collection techniques or other forms of 

information technology. 

Comments that you submit in 

response to this notice are a matter of 

public record. We will include or 

summarize each comment in our request 

to OMB to approve this ICR. Before 

including your address, phone number, 

email address, or other personal 

identifying information in your 

comment, you should be aware that 

your entire comment—including your 

personal identifying information—may 

be made publicly available at any time. 

While you may ask us in your comment 

to withhold your personal identifying 

information from public review, we 

cannot guarantee that we will be able to 

do so. 

Sheleen Dumas, 

Department PRA Clearance Officer, Office of 

the Under Secretary for Economic Affairs, 

Commerce Department. 

[FR Doc. 2023–26910 Filed 12–6–23; 8:45 am] 

BILLING CODE 3510–13–P 

DEPARTMENT OF COMMERCE 

National Oceanic and Atmospheric 

Administration 

[RTID 0648–XD253] 

Takes of Marine Mammals Incidental to 

Specified Activities; Taking Marine 

Mammals Incidental To U.S. Navy 2024 

Ice Exercise Activities in the Arctic 

Ocean 

AGENCY: National Marine Fisheries 

Service (NMFS), National Oceanic and 

Atmospheric Administration (NOAA), 

Commerce. 

ACTION: Notice; proposed incidental 

harassment authorization; request for 

comments on proposed authorization 

and possible renewal. 

SUMMARY: NMFS has received a request 

from the U.S. Navy (Navy) for 

authorization to take marine mammals 

incidental to 2024 Ice Exercise 

Activities in the Arctic Ocean. Pursuant 

to the Marine Mammal Protection Act 

(MMPA), NMFS is requesting comments 

on its proposal to issue an incidental 

harassment authorization (IHA) to 

incidentally take marine mammals 

during the specified activities. NMFS is 

also requesting comments on a possible 

one-time, 1-year renewal that could be 

issued under certain circumstances and 

if all requirements are met, as described 

in Request for Public Comments at the 

end of this notice. NMFS will consider 

public comments prior to making any 

final decision on the issuance of the 

requested MMPA authorization and 

agency responses will be summarized in 

the final notice of our decision. The 

Navy’s activities are considered 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 January 8, 

2024. 

ADDRESSES: Comments should be 

addressed to Jolie Harrison, Chief, 

Permits and Conservation Division, 

Office of Protected Resources (OPR), 

NMFS and should be submitted via 

email to ITP.Davis@noaa.gov. Electronic 

copies of the application and supporting 


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Federal Register / Vol. 88, No. 234 / Thursday, December 7, 2023 / Notices 85245 

documents, as well as a list of the 

references cited in this document, may 

be obtained online at: https://

www.fisheries.noaa.gov/national/ 

marine-mammal-protection/incidentaltake-authorizations-military-readinessactivities. In case of problems accessing 

these documents, please call the contact 

listed above. 

Instructions: NMFS is not responsible 

for comments sent by any other method, 

to any other address or individual, or 

received after the end of the comment 

period. Comments, including all 

attachments, must not exceed a 25- 

megabyte file size. All comments 

received are a part of the public record 

and will generally be posted online at 

https://www.fisheries.noaa.gov/permit/ 

incidental-take-authorizations-undermarine-mammal-protection-act without 

change. All personal identifying 

information (e.g., name, address) 

voluntarily submitted by the commenter 

may be publicly accessible. Do not 

submit confidential business 

information or otherwise sensitive or 

protected information. 

FOR FURTHER INFORMATION CONTACT: 

Leah Davis, OPR, NMFS, (301) 427– 

8401. 

SUPPLEMENTARY INFORMATION: 

Background 

The MMPA prohibits the ‘‘take’’ of 

marine mammals, with certain 

exceptions. Sections 101(a)(5)(A) and 

(D) of the MMPA (16 U.S.C. 1361 et 

seq.) direct the Secretary of Commerce 

(as delegated to NMFS) to allow, upon 

request, the incidental, but not 

intentional, taking of small numbers of 

marine mammals by U.S. citizens who 

engage in a specified activity (other than 

commercial fishing) within a specified 

geographical region if certain findings 

are made and either regulations are 

proposed or, if the taking is limited to 

harassment, a notice of a proposed IHA 

is provided to the public for review. 

Authorization for incidental takings 

shall be granted if NMFS finds that the 

taking will have a negligible impact on 

the species or stock(s) and will not have 

an unmitigable adverse impact on the 

availability of the species or stock(s) for 

taking for subsistence uses (where 

relevant). Further, NMFS must prescribe 

the permissible methods of taking and 

other ‘‘means of effecting the least 

practicable adverse impact’’ on the 

affected species or stocks and their 

habitat, paying particular attention to 

rookeries, mating grounds, and areas of 

similar significance, and on the 

availability of the species or stocks for 

taking for certain subsistence uses 

(referred to in shorthand as 

‘‘mitigation’’); and requirements 

pertaining to the mitigation, monitoring 

and reporting of the takings are set forth. 

The definitions of all applicable MMPA 

statutory terms cited above are included 

in the relevant sections below. 

The 2004 NDAA (Pub. L. 108–136) 

removed the ‘‘small numbers’’ and 

‘‘specified geographical region’’ 

limitations indicated above and 

amended the definition of ‘‘harassment’’ 

as applied to a ‘‘military readiness 

activity.’’ The activity for which 

incidental take of marine mammals is 

being requested addressed here qualifies 

as a military readiness activity. 

National Environmental Policy Act 

To comply with the National 

Environmental Policy Act of 1969 

(NEPA; 42 U.S.C. 4321 et seq.) and 

NOAA Administrative Order (NAO) 

216–6A, NMFS must review our 

proposed action (i.e., the issuance of an 

IHA) with respect to potential impacts 

on the human environment. 

Accordingly, NMFS plans to adopt the 

Navy’s Environmental Assessment (EA), 

provided our independent evaluation of 

the document finds that it includes 

adequate information analyzing the 

effects on the human environment of 

issuing the IHA. The Navy’s EA was 

made available for public comment at 

https://www.nepa.navy.mil/icex/ from 

September 29, 2023 to October 13, 2023. 

We will review all comments 

submitted in response to this notice 

prior to concluding our NEPA process 

or making a final decision on the IHA 

request. 

Summary of Request 

On May 24, 2023, NMFS received a 

request from the Navy for an IHA to take 

marine mammals incidental to 

submarine training and testing activities 

including establishment of a tracking 

range on an ice floe in the Arctic Ocean, 

north of Prudhoe Bay, Alaska. 

Following NMFS’ review of the 

application, the Navy submitted a 

revised application on October 13, 2023 

that removed the request for take of 

bearded seal and included an updated 

take estimate for ringed seals. The 

application was deemed adequate and 

complete on October 19, 2023. The 

Navy’s request is for take of ringed seal 

by Level B harassment. Neither the 

Navy nor NMFS expect serious injury or 

mortality to result from this activity 

and, therefore, an IHA is appropriate. 

NMFS previously issued IHAs to the 

Navy for similar activities (83 FR 6522; 

February 14, 2018, 85 FR 6518; February 

5, 2020, 87 FR 7803; February 10, 2022). 

The Navy complied with all the 

requirements (e.g., mitigation, 

monitoring, and reporting) of the 

previous IHAs, and information 

regarding their monitoring results may 

be found in the Estimated Take section. 

Description of Proposed Activity 

Overview 

The Navy proposes to conduct 

submarine training and testing 

activities, which includes the 

establishment of a tracking range and 

temporary ice camp, and research in the 

Arctic Ocean for 6 weeks beginning in 

February 2024. Active acoustic 

transmissions may result in occurrence 

of Level B harassment, including 

temporary hearing impairment 

(temporary threshold shift (TTS)) and 

behavioral harassment, of ringed seals. 

Dates and Duration 

The specified activities would occur 

over approximately a six-week period 

between February and April 2024, 

including deployment and 

demobilization of the ice camp. The 

submarine training and testing activities 

would occur over approximately 4 

weeks during the 6-week period. The 

proposed IHA would be effective from 

February 1, 2024 through April 30, 

2024. 

Geographic Region 

The ice camp would be established 

approximately 100–200 nautical miles 

(nmi) north of Prudhoe Bay, Alaska. The 

exact location of the camp cannot be 

identified ahead of time as required 

conditions (e.g., ice cover) cannot be 

forecasted until exercises are expected 

to commence. Prior to the establishment 

of the ice camp, reconnaissance flights 

would be conducted to locate suitable 

ice conditions. The reconnaissance 

flights would cover an area of 

approximately 70,374 square kilometers 

(km2; 27,172 square miles (mi2)). The 

actual ice camp would be no more than 

1.6 kilometers (km; 1 mi) in diameter 

(approximately 2 km2 (0.8 mi2) in area). 

The vast majority of submarine training 

and testing would occur near the ice 

camp, however some submarine training 

and testing may occur throughout the 

deep Arctic Ocean basin near the North 

Pole within the larger Navy Activity 

Study Area. Figure 1 shows the 

locations of the Navy Activity Study 

Area and Ice Camp Study Area, 

collectively referred to in this document 

as the ‘‘ICEX24 Study Area’’. 

BILLING CODE 3510–22–P 


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85246 Federal Register / Vol. 88, No. 234 / Thursday, December 7, 2023 / Notices 

BILLING CODE 3510–22–C 

Detailed Description of the Specified 

Activity 

The Navy proposes to conduct 

submarine training and testing 

activities, which includes the 

establishment of a tracking range and 

temporary ice camp, and research in the 

Arctic Ocean for six weeks beginning in 

February 2024. The activity proposed 

for 2024 and that is being evaluated for 

this proposed IHA—ICEX24—is part of 

a regular cycle of recurring training and 

testing activities that the Navy proposes 

to conduct in the Arctic, under which 

submarine and tracking range activities 

would be conducted biennially. Some of 

the submarine training and testing may 

occur throughout the deep Arctic Ocean 

basin near the North Pole, within the 

Navy Activity Study Area (Figure 1). 


ddrumheller on DSK120RN23PROD with NOTICES1EN07DE23.002</GPH>

ICEX study Area 

+ ~ .. Fflhht and ----16 ,..,,.,w1,,4.,. .. Nortb Pole ~~-ii '¥'~ uarn:n, -.n1-.n 

• - Navy Activity Study Area. 

1:tt.000.cxio 

~--: . 

• c:J Ice camp StudyArea. 0 100100300400 

Dalt: t4May201t ~SJ$1tffl:v«iS 1984 NoitiM lAEAAlltb Dliilll~: ESRI, HOM USNavv 

Figure 1-- ICEX24 Study Area in the Arctic Ocean 
Federal Register / Vol. 88, No. 234 / Thursday, December 7, 2023 / Notices 85247 

Additional information about the Navy’s 

proposed training and testing activities 

in the Arctic is available in the Navy’s 

2023 Draft Supplemental Environmental 

Assessment/Overseas Environmental 

Assessment for the Ice Exercise 

Program, available at https://

www.nepa.navy.mil/icex/. Only 

activities which may occur during 

ICEX24 are discussed in this section. 

Ice Camp 

ICEX24 includes the deployment of a 

temporary camp situated on an ice floe. 

Reconnaissance flights to search for 

suitable ice conditions for the ice camp 

would depart from the public airport in 

Deadhorse, Alaska. The camp generally 

would consist of a command hut, dining 

hut, sleeping quarters, a powerhouse, 

runway, and helipad. The number of 

structures and tents would range from 

15–20, and each tent is typically 2 

meters (m) by 6 m (6.6 ft by 19.7 ft) in 

size. The completed ice camp, including 

runway, would be approximately 1.6 km 

(1 mi) in diameter. Support equipment 

for the ice camp would include 

snowmobiles, gas-powered augers and 

saws (for boring holes through ice), and 

diesel generators. All ice camp 

materials, fuel, and food would be 

transported from Prudhoe Bay, Alaska, 

and delivered by air-drop from military 

transport aircraft (e.g., C–17 and C–130), 

or by landing at the ice camp runway 

(e.g., small twin-engine aircraft and 

military and commercial helicopters). 

A portable tracking range for 

submarine training and testing would be 

installed in the vicinity of the ice camp. 

Hydrophones, located on the ice and 

extending to 30 m (90.4 ft) below the 

ice, would be deployed by drilling or 

melting holes in the ice and lowering 

the cable down into the water column. 

Hydrophones would be linked remotely 

to the command hut. Additionally, 

tracking pingers would be configured 

aboard each submarine to continuously 

monitor the location of the submarines. 

Acoustic communications with the 

submarines would be used to coordinate 

the training and research schedule with 

the submarines. An underwater 

telephone would be used as a backup to 

the acoustic communications. The Navy 

plans to recover the hydrophones; 

however, if emergency demobilization is 

required, or the hydrophones are frozen 

in place and are unrecoverable, they 

would be left in place. 

Additional information about the 

ICEX24 ice camp is located in the 2023 

Draft Supplemental Environmental 

Assessment/Overseas Environmental 

Assessment for the Ice Exercise 

Program. We have carefully reviewed 

this information and determined that 

activities associated with the ICEX24 ice 

camp, including de minimis acoustic 

communications, would not result in 

incidental take of marine mammals. 

Submarine Activities 

Submarine activities associated with 

ICEX24 generally would entail safety 

maneuvers and active sonar use. The 

safety maneuvers and sonar use are 

similar to submarine activities 

conducted in other undersea 

environments and are being conducted 

in the Arctic to test their performance in 

a cold environment. Submarine training 

and testing involves active acoustic 

transmissions, which have the potential 

to harass marine mammals. The Navy 

categorizes acoustic sources into ‘‘bins’’ 

based on frequency, source level, and 

mode of usage (U.S. Department of the 

Navy, 2013). The acoustic transmissions 

associated with submarine training fall 

within bins HF1 (hull-mounted 

submarine sonars that produce highfrequency (greater than 10 kHz but less 

than 200 kHz) signals) and M3 (midfrequency (1–10 kHz) acoustic modems 

greater than 190 dB re 1 mPa) as defined 

in the Navy’s Phase III at-sea 

environmental documentation (see 

Section 3.0.3.3.1, Acoustic Stressors, of 

the 2018 AFTT Final Environmental 

Impact Statement/Overseas 

Environmental Impact Statement, 

available at https://www.nepa.navy.mil/ 

AFTT-Phase-III/). The specifics of 

ICEX24 submarine acoustic sources are 

classified, including the parameters 

associated with the designated bins. 

Details of source use for submarine 

training are also classified. Any ICEXspecific acoustic sources not captured 

under one of the at-sea bins were 

modeled using source-specific 

parameters. 

Aspects of submarine training and 

testing activities other than active 

acoustic transmissions are fully 

analyzed within the 2023 Draft 

Supplemental Environmental 

Assessment/Overseas Environmental 

Assessment for the Ice Exercise 

Program. We have carefully reviewed 

and discussed with the Navy these other 

aspects, such as vessel use, and 

determined that aspects of submarine 

training and testing other than active 

acoustic transmissions would not result 

in take of marine mammals. These other 

aspects are therefore not discussed 

further, with the exception of potential 

vessel strike, which is discussed in the 

Potential Effects of Specified Activities 

on Marine Mammals and Their Habitat 

section. 

Research Activities 

Personnel and equipment proficiency 

testing and multiple research and 

development activities would be 

conducted as part of ICEX24. 

Unmanned underwater vehicle testing 

and various acoustic/communication 

sources (i.e., echosounders, and 

transducers) involve active acoustic 

transmissions, which have the potential 

to harass marine mammals. Most 

acoustic transmissions that would be 

used in research activities for ICEX24 

are considered de minimis. The Navy 

has defined de minimis sources as 

having the following parameters: low 

source levels, narrow beams, downward 

directed transmission, short pulse 

lengths, frequencies above (outside) 

known marine mammal hearing ranges, 

or some combination of these factors 

(U.S. Department of the Navy, 2013). 

NMFS reviewed the Navy’s analysis and 

conclusions on de minimis sources and 

finds them complete and supportable. 

Parameters for scientific devices with 

active acoustics, including de minimis 

sources, are included in table 1. 

Additional information about ICEX24 

research activities is located in table 1– 

1 of the Navy’s IHA application as well 

as table 2–2 of the 2023 Draft 

Supplemental Environmental 

Assessment/Overseas Environmental 

Assessment for the Ice Exercise 

Program, and elsewhere in that 

document. The possibility of vessel 

strikes caused by use of unmanned 

underwater vehicles during ICEX24 is 

discussed in the Potential Effects of 

Vessel Strike subsection within the 

Potential Effects of Specified Activities 

on Marine Mammals and Their Habitat 

section. 

TABLE 1—PARAMETERS FOR SCIENTIFIC DEVICES WITH ACTIVE ACOUSTICS

Research institution Source name Frequency range 

(kHz) 

Source level 

(dB) Pulse length Source type 

Woods Hole Oceanic Institute LRAUV+ ........................ 10 and 25 ...................... 185 or less .................... 14 and 3000 ms ............ Unmanned Underwater 

Vehicle. 

Naval Postgraduate School ..... Echosounder ................. 38 to 200 ....................... 221 ................................ 0.5 ms ........................... Sonar. 


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TABLE 1—PARAMETERS FOR SCIENTIFIC DEVICES WITH ACTIVE ACOUSTICS—Continued 

Research institution Source name Frequency range 

(kHz) 

Source level 

(dB) Pulse length Source type 

Massachusetts Institute of 

Technology Lincoln Lab.

Echosounder ................. 115 and 200 .................. 227 or less .................... 1 ms .............................. Sonar. 

Naval Postgraduate School ..... Geospectrum M72, 

Geospectrum M71, 

ITC 1007.

0.13, 0.8, and 5 ............ 190 or less .................... maximum length sequence of 20 min on 

and 40 min off.

Transducer. 

Note: dB = decibels; kHz = kilohertz; LRAUV = Long Range Autonomous Underwater Vehicle; min = minutes; ms = millisecond(s). 

Proposed mitigation, monitoring, and 

reporting measures are described in 

detail later in this document (please see 

Proposed Mitigation and Proposed 

Monitoring and Reporting). 

Description of Marine Mammals in the 

Area of Specified Activities 

Sections 3 and 4 of the application 

summarize available information 

regarding status and trends, distribution 

and habitat preferences, and behavior 

and life history of the potentially 

affected species. NMFS fully considered 

all of this information, and we refer the 

reader to these descriptions, instead of 

reprinting the information. Additional 

information regarding population trends 

and threats may be found in NMFS’ 

Stock Assessment Reports (SARs; 

https://www.fisheries.noaa.gov/ 

national/marine-mammal-protection/ 

marine-mammal-stock-assessments) 

and more general information about 

these species (e.g., physical and 

behavioral descriptions) may be found 

on NMFS’ website (https://

www.fisheries.noaa.gov/find-species). 

Table 2 lists all species or stocks for 

which take is expected and proposed to 

be authorized for this activity, and 

summarizes information related to the 

population or stock, including 

regulatory status under the MMPA and 

Endangered Species Act (ESA) and 

potential biological removal (PBR), 

where known. PBR is defined by the 

MMPA as the maximum number of 

animals, not including natural 

mortalities, that may be removed from a 

marine mammal stock while allowing 

that stock to reach or maintain its 

optimum sustainable population (as 

described in NMFS’ SARs). While no 

serious injury or mortality is anticipated 

or proposed to be authorized here, PBR 

and annual serious injury and mortality 

from anthropogenic sources are 

included here as gross indicators of the 

status of the species or stocks and other 

threats. 

Marine mammal abundance estimates 

presented in this document represent 

the total number of individuals that 

make up a given stock or the total 

number estimated within a particular 

study or survey area. NMFS’ stock 

abundance estimates for most species 

represent the total estimate of 

individuals within the geographic area, 

if known, that comprises that stock. For 

some species, this geographic area may 

extend beyond U.S. waters. All managed 

stocks in this region are assessed in 

NMFS’ U.S. Alaska SARs (Young et al. 

2023). All values presented in table 2 

are the most recent available at the time 

of publication and are available online 

at: https://www.fisheries.noaa.gov/ 

national/marine-mammal-protection/ 

marine-mammal-stock-assessments. 

TABLE 2—SPECIES LIKELY IMPACTED BY THE SPECIFIED ACTIVITIES 1

Common name Scientific name Stock 

ESA/MMP a 

status; strategic (Y/N) 2

Stock abundance 

(CV, Nmin, most recent 

abundance survey) 3

PBR Annual 

M/SI 4

Ringed Seal ........................... Pusa hispida ......................... Arctic .................................... T, D, Y UND 5 (UND, UND, 2013) .... UND 6,459 

1 Information on the classification of marine mammal species can be found on the web page for The Society for Marine Mammalogy’s Committee on Taxonomy 

(https://marinemammalscience.org/science-and-publications/list-marine-mammal-species-subspecies/; Committee on Taxonomy (2022)). 2Endangered Species Act (ESA) status: Endangered (E), Threatened (T)/MMPA status: Depleted (D). Under the MMPA, a strategic stock is one for which the level 

of direct human-caused mortality exceeds PBR or which is determined to be declining and likely to be listed under the ESA within the foreseeable future. Any species 

or stock listed under the ESA is automatically designated under the MMPA as depleted and as a strategic stock. 3 NMFS marine mammal stock assessment reports online at: https://www.fisheries.noaa.gov/national/marine-mammal-protection/marine-mammal-stock-assessmentreports-region. CV is coefficient of variation; Nmin is the minimum estimate of stock abundance. 4These values, found in NMFS’s SARs, represent annual levels of human-caused mortality plus serious injury from all sources combined (e.g., commercial fisheries, ship strike). Annual M/SI often cannot be determined precisely and is in some cases presented as a minimum value or range. A CV associated with estimated 

mortality due to commercial fisheries is presented in some cases. 5A reliable population estimate for the entire stock is not available. Using a sub-sample of data collected from the U.S portion of the Bering Sea, an abundance estimate of 171,418 ringed seals has been calculated, but this estimate does not account for availability bias due to seals in the water or in the shorefast ice zone at the 

time of the survey. The actual number of ringed seals in the U.S. portion of the Bering Sea is likely much higher. Using the Nmin based upon this negatively biased 

population estimate, the PBR is calculated to be 4,755 seals, although this is also a negatively biased estimate. 

As indicated in table 2, ringed seals 

(with one managed stock) temporally 

and spatially co-occur with the activity 

to the degree that take is reasonably 

likely to occur. While beluga whales 

(Delphinapterus leucas), gray whales 

(Eschrichtius robustus), bowhead 

whales (Balaena mysticetus), and 

spotted seals (Phoca largha) may occur 

in the ICEX24 Study Area, the temporal 

and/or spatial occurrence of these 

species is such that take is not expected 

to occur, and they are not discussed 

further beyond the explanation 

provided here. Bowhead whales are 

unlikely to occur in the ICEX24 Study 

Area between February and April, as 

they spend winter (December to April) 

in the northern Bering Sea and southern 

Chukchi Sea, and migrate north through 

the Chukchi Sea and Beaufort Sea 

during April and May (Young et al. 

2023). On their spring migration, the 

earliest that bowhead whales reach 

Point Hope in the Chukchi Sea, well 

south of Point Barrow, is late March to 

mid-April (Braham et al. 1980). 

Although the ice camp location is not 

known with certainty, the distance 

between Point Barrow and the closest 

edge of the Ice Camp Study Area is over 

200 km (124.3 mi). The distance 

between Point Barrow and the closest 

edge of the Navy Activity Study Area is 

over 50 km (31 mi), and the distance 

between Point Barrow and Point Hope 

is an additional 525 km (326.2 mi; 

straight line distance); accordingly, 

bowhead whales are unlikely to occur in 

the ICEX24 Study Area before ICEX24 

activities conclude. Beluga whales 

follow a migration pattern similar to 


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bowhead whales. They typically 

overwinter in the Bering Sea and 

migrate north during the spring to the 

eastern Beaufort Sea where they spend 

the summer and early fall months 

(Young et al. 2023). Though the beluga 

whale migratory path crosses through 

the ICEX24 Study Area, they are 

unlikely to occur in the ICEX24 Study 

Area between February and April. (Of 

note, the ICEX24 Study Area does 

overlap the northernmost portion of the 

North Bering Strait, East Chukchi, West 

Beaufort Sea beluga whale migratory 

BIA (April and May), though the data 

support for this BIA is low, the 

boundary certainty is low, and the 

importance score is moderate. Given the 

spring migratory direction, the 

northernmost portion of the BIA is 

likely more important later in the April 

and May period, and overlap with this 

BIA does not imply that belugas are 

likely to be in the ICEX24 Study Area 

during the Navy’s activities.) Gray 

whales feed primarily in the Beaufort 

Sea, Chukchi Sea, and Northwestern 

Bering Sea during the summer and fall, 

but migrate south to winter in Baja 

California lagoons (Young et al. 2023). 

Typically, northward migrating gray 

whales do not reach the Bering Sea 

before May or June (Frost and Karpovich 

2008), after the ICEX24 activities would 

occur, and several hundred kilometers 

south of the ICEX24 Study Area. 

Further, gray whales are primarily 

bottom feeders (Swartz et al. 2006) in 

water less than 60 m (196.9 ft) deep 

(Pike 1962). Therefore, on the rare 

occasion that a gray whale does 

overwinter in the Beaufort Sea (Stafford 

et al. 2007), we would expect an 

overwintering individual to remain in 

shallow water over the continental shelf 

where it could feed. Therefore, gray 

whales are not expected to occur in the 

ICEX24 Study Area during the ICEX24 

activity period. Spotted seals may also 

occur in the ICEX24 Study Area during 

summer and fall, but they are not 

expected to occur in the ICEX24 Study 

Area during the ICEX24 timeframe 

(Muto et al. 2020). 

Further, while the Navy initially 

requested take of bearded seals 

(Erignathus barbatus), which do occur 

in the ICEX24 Study Area during the 

project timeframe, NMFS does not 

expect that bearded seals would occur 

in the areas near the ice camp or where 

submarine activities involving active 

acoustics would occur, and therefore 

incidental take is not anticipated to 

occur and has not been proposed for 

authorization. Bearded seals are not 

discussed further beyond the 

explanation provided here. The Navy 

anticipates that the ice camp would be 

established 100–200 nmi (185–370 km) 

north of Prudhoe Bay in water depths of 

800 m (2,625 ft) or more, and also that 

submarine training and testing activities 

would occur in water depths of 800 m 

(2,625 ft) or more. Although acoustic 

data indicate that some bearded seals 

remain in the Beaufort Sea year round 

(MacIntyre et al. 2013, 2015; Jones et al. 

2014), satellite tagging data (Boveng and 

Cameron 2013; ADF&G 2017) show that 

large numbers of bearded seals move 

south in fall/winter with the advancing 

ice edge to spend the winter in the 

Bering Sea, confirming previous visual 

observations (Burns and Frost 1979; 

Frost et al. 2008; Cameron and Boveng 

2009). The southward movement of 

bearded seals in the fall means that very 

few individuals are expected to occur 

along the Beaufort Sea continental shelf 

in February through April, the 

timeframe for ICEX24 activities. The 

northward spring migration through the 

Bering Strait, begins in mid-April 

(Burns and Frost 1979). 

In the event some bearded seals were 

to remain in the Beaufort Sea during the 

season when ICEX24 activities will 

occur, the most probable area in which 

bearded seals might occur during winter 

months is along the continental shelf. 

Bearded seals feed extensively on 

benthic invertebrates (e.g., clams, 

gastropods, crabs, shrimp, bottomdwelling fish; Quakenbush et al. 2011; 

Cameron et al. 2010) and are typically 

found in water depths of 200 m (656 ft) 

or less (Burns 1970). The Bureau of 

Ocean Energy Management (BOEM) 

conducted an aerial survey from June 

through October that covered the 

shallow Beaufort and Chukchi Sea shelf 

waters and observed bearded seals from 

Point Barrow to the border of Canada 

(Clarke et al. 2015). The farthest from 

shore that bearded seals were observed 

was the waters of the continental slope 

(though this study was conducted 

outside of the ICEX24 time frame). The 

Navy anticipates that the ice camp will 

be established 185–370 km (100–200 

nmi) north of Prudhoe Bay in water 

depths of 800 m (2,625 ft) or more. The 

continental shelf near Prudhoe Bay is 

approximately 55 nmi (100 km) wide. 

Therefore, even if the ice camp were 

established at the closest estimated 

distance (100 nmi from Prudhoe Bay), it 

would still be approximately 45 nmi (83 

km) distant from habitat potentially 

occupied by bearded seals. Empirical 

evidence has not shown responses to 

sonar that would constitute take beyond 

a few km from an acoustic source, and 

therefore, NMFS and the Navy 

conservatively set a distance cutoff of 10 

km (6.2 mi). Regardless of the source 

level at that distance, take is not 

estimated to occur beyond 10 km (6.2 

mi) from the source. Although bearded 

seals occur 20 to 100 nmi (37 to 185 km) 

offshore during spring (Simpkins et al. 

2003, Bengtson et al. 2005), they feed 

heavily on benthic organisms (Hamilton 

et al. 2018; Hjelset et al. 1999; Fedoseev 

1965), and during winter bearded seals 

are expected to select habitats where 

food is abundant and easily accessible 

to minimize the energy required to 

forage and maximize energy reserves in 

preparation for whelping, lactation, 

mating, and molting. Bearded seals are 

not known to dive as deep as 800 m 

(2,625 ft) to forage (Boveng and 

Cameron, 2013; Cameron and Boveng 

2009; Cameron et al. 2010; Gjertz et al. 

2000; Kovacs 2002), and it is highly 

unlikely that they would occur near the 

ice camp or where the submarine 

activities would be conducted. This 

conclusion is supported by the fact that 

the Navy did not visually observe or 

acoustically detect bearded seals during 

the 2020 or 2022 ice exercises. 

In addition, the polar bear (Ursus 

maritimus) may be found in the ICEX24 

Study Area. However, polar bears are 

managed by the U.S. Fish and Wildlife 

Service and are not considered further 

in this document. 

Ringed Seal 

Ringed seals are the most common 

pinniped in the ICEX24 Study Area and 

have wide distribution in seasonally 

and permanently ice-covered waters of 

the Northern Hemisphere (North 

Atlantic Marine Mammal Commission 

2004), though the status of the Arctic 

stock of ringed seals is unknown (Young 

et al. 2023). Throughout their range, 

ringed seals have an affinity for icecovered waters and are well adapted to 

occupying both shore-fast and pack ice 

(Kelly 1988c). Ringed seals can be found 

further offshore than other pinnipeds 

since they can maintain breathing holes 

in ice thickness greater than 2 m (6.6 ft; 

Smith and Stirling 1975). Breathing 

holes are maintained by ringed seals’ 

sharp teeth and claws on their fore 

flippers. They remain in contact with 

ice most of the year and use it as a 

platform for molting in late spring to 

early summer, for pupping and nursing 

in late winter to early spring, and for 

resting at other times of the year (Young 

et al. 2023). 

Ringed seals have at least two distinct 

types of subnivean lairs: haul-out lairs 

and birthing lairs (Smith and Stirling 

1975). Haul-out lairs are typically 

single-chambered and offer protection 

from predators and cold weather. 

Birthing lairs are larger, multiVerDate Sep<11>2014 20:23 Dec 06, 2023 Jkt 262001 PO 00000 Frm 00046 Fmt 4703 Sfmt 4703 E:\FR\FM\07DEN1.SGM 07DEN1

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chambered areas that are used for 

pupping in addition to protection from 

predators. Ringed seals pup on both 

land-fast ice as well as stable pack ice. 

Lentfer (1972) found that ringed seals 

north of Barrow, Alaska (which would 

be west of the ice camp), build their 

subnivean lairs on the pack ice near 

pressure ridges. They are also assumed 

to occur within the sea ice in the 

proposed ice camp area. Ringed seals 

excavate subnivean lairs in drifts over 

their breathing holes in the ice, in 

which they rest, give birth, and nurse 

their pups for 5–9 weeks during late 

winter and spring (Chapskii 1940; 

McLaren 1958; Smith and Stirling 

1975). Snow depths of at least 50–65 

centimeters (cm; 19.7–25.6 in) are 

required for functional birth lairs (Kelly 

1988b; Lydersen 1998; Lydersen and 

Gjertz 1986; Smith and Stirling 1975), 

and such depths typically occur only 

where 20–30 cm (7.9–11.8 in) or more 

of snow has accumulated on flat ice and 

then drifted along pressure ridges or ice 

hummocks (Hammill 2008; Lydersen et 

al. 1990; Lydersen and Ryg 1991; Smith 

and Lydersen 1991). Ringed seal 

birthing season typically begins in 

March, but the majority of births occur 

in early April. About a month after 

parturition, mating begins in late April 

and early May. 

In Alaskan waters, during winter and 

early spring when sea ice is at its 

maximal extent, ringed seals are 

abundant in the northern Bering Sea, 

Norton and Kotzebue Sounds, and 

throughout the Chukchi and Beaufort 

Seas (Frost 1985; Kelly 1988c), 

including in the ICEX24 Study Area. 

Passive acoustic monitoring (PAM) of 

ringed seals from a high-frequency 

recording package deployed at a depth 

of 240 m (787 ft) in the Chukchi Sea, 

120 km (74.6 mi) north-northwest of 

Barrow, Alaska, detected ringed seals in 

the area between mid- December and 

late May over a four year study (Jones 

et al. 2014). With the onset of the fall 

freeze, ringed seal movements become 

increasingly restricted and seals will 

either move west and south with the 

advancing ice pack, with many seals 

dispersing throughout the Chukchi and 

Bering Seas, or remain in the Beaufort 

Sea (Crawford et al. 2012; Frost and 

Lowry 1984; Harwood et al. 2012). Kelly 

et al. (2010a) tracked home ranges for 

ringed seals in the subnivean period 

(using shorefast ice); the size of the 

home ranges varied from less than 1 

km2 (0.4 mi2) up to 27.9 km2 (10.8 mi2; 

median of 0.62 km2 (0.2 mi2) for adult 

males and 0.65 km2 (0.3 mi2) for adult 

females). Most (94 percent) of the home 

ranges were less than 3 km2 (1.2 mi2) 

during the subnivean period (Kelly et al. 

2010a). Near large polynyas, ringed 

seals maintain ranges up to 7,000 km2

(2.702.7 mi2) during winter and 2,100 

km2 (810 mi2) during spring (Born et al. 

2004). Some adult ringed seals return to 

the same small home ranges they 

occupied during the previous winter 

(Kelly et al. 2010a). The size of winter 

home ranges can vary by up to a factor 

of 10 depending on the amount of fast 

ice; seal movements were more 

restricted during winters with extensive 

fast ice, and were much less restricted 

where fast ice did not form at high 

levels (Harwood et al. 2015). Ringed 

seals may occur within the ICEX24 

Study Area throughout the year and 

during the proposed specified activities. 

Since June 1, 2018, elevated ice seal 

strandings (bearded, ringed and spotted 

seals) have occurred in the Bering and 

Chukchi seas in Alaska. This event was 

declared an Unusual Mortality Event 

(UME), but is currently considered nonactive and is pending closure. Given 

that the UME is non-active, it is not 

discussed further in this document. 

Critical Habitat 

Critical habitat for the ringed seal was 

designated in May 2022 and includes 

marine waters within one specific area 

in the Bering, Chukchi, and Beaufort 

Seas (87 FR 19232; April 1, 2022). 

Essential features established by NMFS 

for conservation of the ringed seal are 

(1) snow-covered sea ice habitat suitable 

for the formation and maintenance of 

subnivean birth lairs used for sheltering 

pups during whelping and nursing, 

which is defined as waters 3 m (9.8 ft) 

or more in depth (relative to Mean 

Lower Low Water (MLLW)) containing 

areas of seasonal landfast (shorefast) ice 

or dense, stable pack ice, which have 

undergone deformation and contain 

snowdrifts of sufficient depth to form 

and maintain birth lairs (typically at 

least 54 cm (21.3 in) deep); (2) sea ice 

habitat suitable as a platform for basking 

and molting, which is defined as areas 

containing sea ice of 15 percent or more 

concentration in waters 3 m (9.8 ft) or 

more in depth (relative to MLLW); and 

(3) primary prey resources to support 

Arctic ringed seals, which are defined to 

be small, often schooling, fishes, in 

particular, Arctic cod (Boreogadus 

saida), saffron cod (Eleginus gracilis), 

and rainbow smelt (Osmerus dentex), 

and small crustaceans, in particular, 

shrimps and amphipods. 

The proposed ice camp study area 

was excluded from the ringed seal 

critical habitat because the benefits of 

exclusion due to national security 

impacts outweighed the benefits of 

inclusion of this area (87 FR 19232; 

April 1, 2022). However, as stated in 

NMFS’ final rule for the Designation of 

Critical Habitat for the Arctic 

Subspecies of the Ringed Seal (87 FR 

19232; April 1, 2022), the area proposed 

for exclusion contains one or more of 

the essential features of the Arctic 

ringed seal’s critical habitat, although 

data are limited to inform NMFS’ 

assessment of the relative value of this 

area to the conservation of the species. 

As noted above, a portion of the ringed 

seal critical habitat overlaps the larger 

proposed ICEX24 Study Area. However, 

as described later and in more detail in 

the Potential Effects of Specified 

Activities on Marine Mammals and 

Their Habitat section, we do not 

anticipate physical impacts to any 

marine mammal habitat as a result of 

the Navy’s ICEX activities, including 

impacts to ringed seal sea ice habitat 

suitable as a platform for basking and 

molting and impacts on prey 

availability. Further, this proposed IHA 

includes mitigation measures, as 

described in the Proposed Mitigation 

section, which would minimize or 

prevent impacts to sea ice habitat 

suitable for the formation and 

maintenance of subnivean birth lairs. 

Marine Mammal Hearing 

Hearing is the most important sensory 

modality for marine mammals 

underwater, and exposure to 

anthropogenic sound can have 

deleterious effects. To appropriately 

assess the potential effects of exposure 

to sound, it is necessary to understand 

the frequency ranges marine mammals 

are able to hear. Not all marine mammal 

species have equal hearing capabilities 

(e.g., Richardson et al., 1995; Wartzok 

and Ketten, 1999; Au and Hastings, 

2008). To reflect this, Southall et al. 

(2007, 2019) recommended that marine 

mammals be divided into hearing 

groups based on directly measured 

(behavioral or auditory evoked potential 

techniques) or estimated hearing ranges 

(behavioral response data, anatomical 

modeling, etc.). Note that no direct 

measurements of hearing ability have 

been successfully completed for 

mysticetes (i.e., low-frequency 

cetaceans). Subsequently, NMFS (2018) 

described generalized hearing ranges for 

these marine mammal hearing groups. 

Generalized hearing ranges were chosen 

based on the approximately 65 decibels 

(dB) threshold from the normalized 

composite audiograms, with the 

exception for lower limits for lowfrequency cetaceans where the lower 

bound was deemed to be biologically 

implausible and the lower bound from 

Southall et al. (2007) retained. Marine 

mammal hearing groups and their 


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associated hearing ranges are provided 

in table 3. 

TABLE 3—MARINE MAMMAL HEARING GROUPS

[NMFS, 2018] 

Hearing group Generalized hearing 

range * 

Low-frequency (LF) cetaceans (baleen whales) .................................................................................................................. 7 Hz to 35 kHz. 

Mid-frequency (MF) cetaceans (dolphins, toothed whales, beaked whales, bottlenose whales) ........................................ 150 Hz to 160 kHz. 

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

australis).

275 Hz to 160 kHz. 

Phocid pinnipeds (PW) (underwater) (true seals) ................................................................................................................ 50 Hz to 86 kHz. 

Otariid pinnipeds (OW) (underwater) (sea lions and fur seals) ............................................................................................ 60 Hz to 39 kHz. 

* Represents the generalized hearing range for the entire group as a composite (i.e., all species within the group), where individual species’ 

hearing ranges are typically not as broad. Generalized hearing range chosen based on ∼65 dB threshold from normalized composite audiogram, 

with the exception for lower limits for LF cetaceans (Southall et al. 2007) and PW pinniped (approximation). 

The pinniped functional hearing 

group was modified from Southall et al. 

(2007) on the basis of data indicating 

that phocid species have consistently 

demonstrated an extended frequency 

range of hearing compared to otariids, 

especially in the higher frequency range 

(Hemila ̈ et al., 2006; Kastelein et al., 

2009; Reichmuth and Holt, 2013). 

For more detail concerning these 

groups and associated frequency ranges, 

please see NMFS (2018) for a review of 

available information. 

Potential Effects of Specified Activities 

on Marine Mammals and Their Habitat 

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 of Marine Mammals 

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 of Marine Mammals 

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 survival. 

Description of Sound Sources 

Here, we first provide background 

information on marine mammal hearing 

before discussing the potential effects of 

the use of active acoustic sources on 

marine mammals. 

Sound travels in waves, the basic 

components of which are frequency, 

wavelength, velocity, and amplitude. 

Frequency is the number of pressure 

waves that pass by a reference point per 

unit of time and is measured in Hz or 

cycles per second. Wavelength is the 

distance between two peaks of a sound 

wave; lower frequency sounds have 

longer wavelengths than higher 

frequency sounds and attenuate 

(decrease) more rapidly in shallower 

water. Amplitude is the height of the 

sound pressure wave or the ‘loudness’ 

of a sound and is typically measured 

using the dB scale. A dB is the ratio 

between a measured pressure (with 

sound) and a reference pressure (sound 

at a constant pressure, established by 

scientific standards). It is a logarithmic 

unit that accounts for large variations in 

amplitude; therefore, relatively small 

changes in dB ratings correspond to 

large changes in sound pressure. When 

referring to sound pressure levels (SPLs; 

the sound force per unit area), sound is 

referenced in the context of underwater 

sound pressure to 1 microPascal (mPa). 

One pascal is the pressure resulting 

from a force of one newton exerted over 

an area of 1 square meter. The source 

level (SL) represents the sound level at 

a distance of 1 m from the source 

(referenced to 1 mPa). The received level 

is the sound level at the listener’s 

position. Note that all underwater sound 

levels in this document are referenced 

to a pressure of 1 mPa. 

Root mean square (RMS) is the 

quadratic mean sound pressure over the 

duration of an impulse. RMS is 

calculated by squaring all of the sound 

amplitudes, averaging the squares, and 

then taking the square root of the 

average (Urick 1983). RMS accounts for 

both positive and negative values; 

squaring the pressures makes all values 

positive so that they may be accounted 

for in the summation of pressure levels 

(Hastings and Popper 2005). This 

measurement is often used in the 

context of discussing behavioral effects, 

in part because behavioral effects, 

which often result from auditory cues, 

may be better expressed through 

averaged units than by peak pressures. 

When underwater objects vibrate or 

activity occurs, sound-pressure waves 

are created. These waves alternately 

compress and decompress the water as 

the sound wave travels. Underwater 

sound waves radiate in all directions 

away from the source (similar to ripples 

on the surface of a pond), except in 

cases where the source is directional. 

The compressions and decompressions 

associated with sound waves are 

detected as changes in pressure by 

aquatic life and man-made sound 

receptors such as hydrophones. 

Even in the absence of sound from the 

specified activity, the underwater 

environment is typically loud due to 

ambient sound. Ambient sound is 

defined as environmental background 

sound levels lacking a single source or 

point (Richardson et al. 1995), and the 

sound level of a region is defined by the 

total acoustical energy being generated 

by known and unknown sources. These 

sources may include physical (e.g., 

waves, earthquakes, ice, atmospheric 

sound), biological (e.g., sounds 

produced by marine mammals, fish, and 

invertebrates), and anthropogenic sound 

(e.g., vessels, dredging, aircraft, 

construction). A number of sources 

contribute to ambient sound, including 

the following (Richardson et al. 1995): 

• Wind and waves: The complex 

interactions between wind and water 

surface, including processes such as 

breaking waves and wave-induced 

bubble oscillations and cavitation, are a 

main source of naturally occurring 

ambient noise for frequencies between 

200 Hz and 50 kHz (Mitson, 1995). 

Under sea ice, noise generated by ice 

deformation and ice fracturing may be 

caused by thermal, wind, drift, and 

current stresses (Roth et al. 2012); 

• Precipitation: Sound from rain and 

hail impacting the water surface can 

become an important component of total 

noise at frequencies above 500 Hz, and 

possibly down to 100 Hz during quiet 


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times. In the ice-covered ICEX24 Study 

Area, precipitation is unlikely to impact 

ambient sound; 

• Biological: Marine mammals can 

contribute significantly to ambient noise 

levels, as can some fish and shrimp. The 

frequency band for biological 

contributions is from approximately 12 

Hz to over 100 kHz; and 

• Anthropogenic: Sources of ambient 

noise related to human activity include 

transportation (surface vessels and 

aircraft), dredging and construction, oil 

and gas drilling and production, seismic 

surveys, sonar, explosions, and ocean 

acoustic studies. Shipping noise 

typically dominates the total ambient 

noise for frequencies between 20 and 

300 Hz. In general, the frequencies of 

anthropogenic sounds are below 1 kHz 

and, if higher frequency sound levels 

are created, they attenuate rapidly 

(Richardson et al. 1995). Sound from 

identifiable anthropogenic sources other 

than the activity of interest (e.g., a 

passing vessel) is sometimes termed 

background sound, as opposed to 

ambient sound. Anthropogenic sources 

are unlikely to significantly contribute 

to ambient underwater noise during the 

late winter and early spring in the 

ICEX24 Study Area as most 

anthropogenic activities would not be 

active due to ice cover (e.g. seismic 

surveys, shipping; Roth et al. 2012). 

The sum of the various natural and 

anthropogenic sound sources at any 

given location and time—which 

comprise ‘‘ambient’’ or ‘‘background’’ 

sound—depends not only on the source 

levels (as determined by current 

weather conditions and levels of 

biological and shipping activity) but 

also on the ability of sound to propagate 

through the environment. In turn, sound 

propagation is dependent on the 

spatially and temporally varying 

properties of the water column and sea 

floor, and is frequency-dependent. As a 

result of the dependence on a large 

number of varying factors, ambient 

sound levels can be expected to vary 

widely over both coarse and fine spatial 

and temporal scales. Sound levels at a 

given frequency and location can vary 

by 10–20 dB from day to day 

(Richardson et al. 1995). The result is 

that, depending on the source type and 

its intensity, sound from the specified 

activity may be a negligible addition to 

the local environment or could form a 

distinctive signal that may affect marine 

mammals. 

Underwater sounds fall into one of 

two general sound types: impulsive and 

non-impulsive (defined in the following 

paragraphs). The distinction between 

these two sound types is important 

because they have differing potential to 

cause physical effects, particularly with 

regard to hearing (e.g., Ward, 1997 in 

Southall et al. 2007). Please see Southall 

et al. (2007) for an in-depth discussion 

of these concepts. 

Impulsive sound sources (e.g., 

explosions, gunshots, sonic booms, 

impact pile driving) produce signals 

that are brief (typically considered to be 

less than one second), broadband, atonal 

transients (ANSI 1986; Harris 1998; 

NIOSH 1998; ISO 2016; ANSI 2005) and 

occur either as isolated events or 

repeated in some succession. Impulsive 

sounds are all characterized by a 

relatively rapid rise from ambient 

pressure to a maximal pressure value 

followed by a rapid decay period that 

may include a period of diminishing, 

oscillating maximal and minimal 

pressures, and generally have an 

increased capacity to induce physical 

injury as compared with sounds that 

lack these features. There are no pulsed 

sound sources associated with any 

planned ICEX24 activities. 

Non-impulsive sounds can be tonal, 

narrowband, or broadband, brief or 

prolonged, and may be either 

continuous or non-continuous (ANSI 

1995; NIOSH 1998). Some of these nonimpulsive sounds can be transient 

signals of short duration but without the 

essential properties of pulses (e.g., rapid 

rise time). Examples of non-impulsive 

sounds include those produced by 

vessels, aircraft, machinery operations 

such as drilling or dredging, vibratory 

pile driving, and active sonar sources 

(such as those planned for use by the 

Navy as part of the proposed ICEX24 

activities) that intentionally direct a 

sound signal at a target that is reflected 

back in order to discern physical details 

about the target. 

Modern sonar technology includes a 

variety of sonar sensor and processing 

systems. In concept, the simplest active 

sonar emits sound waves, or ‘‘pings,’’ 

sent out in multiple directions, and the 

sound waves then reflect off of the target 

object in multiple directions. The sonar 

source calculates the time it takes for 

the reflected sound waves to return; this 

calculation determines the distance to 

the target object. More sophisticated 

active sonar systems emit a ping and 

then rapidly scan or listen to the sound 

waves in a specific area. This provides 

both distance to the target and 

directional information. Even more 

advanced sonar systems use multiple 

receivers to listen to echoes from several 

directions simultaneously and provide 

efficient detection of both direction and 

distance. In general, when sonar is in 

use, the sonar ‘pings’ occur at intervals, 

referred to as a duty cycle, and the 

signals themselves are very short in 

duration. For example, sonar that emits 

a 1-second ping every 10 seconds has a 

10 percent duty cycle. The Navy’s most 

powerful hull-mounted mid-frequency 

sonar source used in ICEX activities 

typically emits a 1-second ping every 50 

seconds representing a 2 percent duty 

cycle. The Navy utilizes sonar systems 

and other acoustic sensors in support of 

a variety of mission requirements. 

Acoustic Impacts 

Please refer to the information 

provided previously regarding sound, 

characteristics of sound types, and 

metrics used in this document. 

Anthropogenic sounds cover a broad 

range of frequencies and sound levels 

and can have a range of highly variable 

impacts on marine life, from none or 

minor to potentially severe responses, 

depending on received levels, duration 

of exposure, behavioral context, and 

various other factors. The potential 

effects of underwater sound from active 

acoustic sources can include one or 

more of the following: temporary or 

permanent hearing impairment, nonauditory physical or physiological 

effects, behavioral disturbance, stress, 

and masking (Richardson et al. 1995; 

Gordon et al. 2004; Nowacek et al. 2007; 

Southall et al. 2007; Gotz et al. 2009). 

The degree of effect is intrinsically 

related to the signal characteristics, 

received level, distance from the source, 

and duration of the sound exposure. In 

general, sudden, high level sounds can 

cause hearing loss, as can longer 

exposures to lower level sounds. 

Temporary or permanent loss of hearing 

will occur almost exclusively for noise 

within an animal’s hearing range. In this 

section, we first describe specific 

manifestations of acoustic effects before 

providing discussion specific to the 

proposed activities in the next section. 

Permanent Threshold Shift—Marine 

mammals exposed to high-intensity 

sound, or to lower-intensity sound for 

prolonged periods, can experience 

hearing threshold shift (TS), which is 

the loss of hearing sensitivity at certain 

frequency ranges (Finneran 2015). TS 

can be permanent (PTS), in which case 

the loss of hearing sensitivity is not 

fully recoverable, or temporary (TTS), in 

which case the animal’s hearing 

threshold would recover over time 

(Southall et al. 2007). Repeated sound 

exposure that leads to TTS could cause 

PTS. In severe cases of PTS, there can 

be total or partial deafness, while in 

most cases the animal has an impaired 

ability to hear sounds in specific 

frequency ranges (Kryter 1985). 

When PTS occurs, there is physical 

damage to the sound receptors in the ear 

(i.e., tissue damage), whereas TTS 


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represents primarily tissue fatigue and 

is reversible (Southall et al. 2007). In 

addition, other investigators have 

suggested that TTS is within the normal 

bounds of physiological variability and 

tolerance and does not represent 

physical injury (e.g., Ward 1997). 

Therefore, NMFS does not consider TTS 

to constitute auditory injury. 

Relationships between TTS and PTS 

thresholds have not been studied in 

marine mammals—PTS data exists only 

for a single harbor seal (Phoca vitulina; 

Kastak et al. 2008)—but are assumed to 

be similar to those in humans and other 

terrestrial mammals. PTS typically 

occurs at exposure levels at least several 

dB above (a 40-dB threshold shift 

approximates PTS onset; e.g., Kryter et 

al. 1966; Miller, 1974) those inducing 

mild TTS (a 6-dB threshold shift 

approximates TTS onset; e.g., Southall 

et al. 2007). Based on data from 

terrestrial mammals, a precautionary 

assumption is that the PTS thresholds 

for impulse sounds (such as impact pile 

driving pulses as received close to the 

source) are at least six dB higher than 

the TTS threshold on a peak-pressure 

basis and PTS cumulative sound 

exposure level (SEL) thresholds are 15 

to 20 dB higher than TTS cumulative 

SEL thresholds (Southall et al. 2007). 

Temporary Threshold Shift—TTS is 

the mildest form of hearing impairment 

that can occur during exposure to sound 

(Kryter, 1985). While experiencing TTS, 

the hearing threshold rises, and a sound 

must be at a higher level in order to be 

heard. In terrestrial and marine 

mammals, TTS can last from minutes or 

hours to days (in cases of strong TTS). 

In many cases, hearing sensitivity 

recovers rapidly after exposure to the 

sound ends. 

Marine mammal hearing plays a 

critical role in communication with 

conspecifics, and interpretation of 

environmental cues for purposes such 

as predator avoidance and prey capture. 

Depending on the degree (elevation of 

threshold in dB), duration (i.e., recovery 

time), and frequency range of TTS, and 

the context in which it is experienced, 

TTS can have effects on marine 

mammals ranging from discountable to 

serious. For example, a marine mammal 

may be able to readily compensate for 

a brief, relatively small amount of TTS 

in a non-critical frequency range that 

occurs during a time where ambient 

noise is lower and there are not as many 

competing sounds present. 

Alternatively, a larger amount and 

longer duration of TTS sustained during 

time when communication is critical for 

successful mother/calf interactions 

could have more serious impacts. 

Currently, TTS data only exist for four 

species of cetaceans (bottlenose dolphin 

(Tursiops truncatus), beluga whale, 

harbor porpoise (Phocoena phocoena), 

and Yangtze finless porpoise 

(Neophocoena asiaeorientalis)) and 

three species of pinnipeds (northern 

elephant seal (Mirounga angustirostris), 

harbor seal, and California sea lion 

(Zalophus californianus)) exposed to a 

limited number of sound sources (i.e., 

mostly tones and octave-band noise) in 

laboratory settings (Finneran 2015). TTS 

was not observed in trained spotted and 

ringed seals exposed to impulsive noise 

at levels matching previous predictions 

of TTS onset (Reichmuth et al. 2016). In 

general, harbor seals and harbor 

porpoises have a lower TTS onset than 

other measured pinniped or cetacean 

species. Additionally, the existing 

marine mammal TTS data come from a 

limited number of individuals within 

these species. There are no data 

available on noise-induced hearing loss 

for mysticetes. For summaries of data on 

TTS in marine mammals or for further 

discussion of TTS onset thresholds, 

please see Southall et al. (2007), 

Finneran and Jenkins (2012), and 

Finneran (2015). 

Behavioral effects—Behavioral 

disturbance may include a variety of 

effects, including subtle changes in 

behavior (e.g., minor or brief avoidance 

of an area or changes in vocalizations), 

more conspicuous changes in similar 

behavioral activities, and more 

sustained and/or potentially severe 

reactions, such as displacement from or 

abandonment of high-quality habitat. 

Behavioral responses to sound are 

highly variable and context-specific and 

any reactions depend on numerous 

intrinsic and extrinsic factors (e.g., 

species, state of maturity, experience, 

current activity, reproductive state, 

auditory sensitivity, time of day), as 

well as the interplay between factors 

(e.g., Richardson et al. 1995; Wartzok et 

al. 2003; Southall et al. 2007; Weilgart, 

2007; Archer et al. 2010). Behavioral 

reactions can vary not only among 

individuals but also within an 

individual, depending on previous 

experience with a sound source, 

context, and numerous other factors 

(Ellison et al. 2012), and can vary 

depending on characteristics associated 

with the sound source (e.g., whether it 

is moving or stationary, number of 

sources, distance from the source). 

Please see Appendices B–C of Southall 

et al. (2007) for a review of studies 

involving marine mammal behavioral 

responses to sound. 

Habituation can occur when an 

animal’s response to a stimulus wanes 

with repeated exposure, usually in the 

absence of unpleasant associated events 

(Wartzok et al. 2003). Animals are most 

likely to habituate to sounds that are 

predictable and unvarying. It is 

important to note that habituation is 

appropriately considered as a 

‘‘progressive reduction in response to 

stimuli that are perceived as neither 

aversive nor beneficial,’’ rather than as, 

more generally, moderation in response 

to human disturbance (Bejder et al. 

2009). The opposite process is 

sensitization, when an unpleasant 

experience leads to subsequent 

responses, often in the form of 

avoidance, at a lower level of exposure. 

As noted, behavioral state may affect the 

type of response. For example, animals 

that are resting may show greater 

behavioral change in response to 

disturbing sound levels than animals 

that are highly motivated to remain in 

an area for feeding (Richardson et al. 

1995; NRC 2003; Wartzok et al. 2003). 

Controlled experiments with captive 

marine mammals have shown 

pronounced behavioral reactions, 

including avoidance of loud sound 

sources (Ridgway et al. 1997; Finneran 

et al. 2003). Observed responses of wild 

marine mammals to loud impulsive 

sound sources (typically seismic airguns 

or acoustic harassment devices) have 

been varied but often consist of 

avoidance behavior or other behavioral 

changes suggesting discomfort (Morton 

and Symonds 2002; see also Richardson 

et al. 1995; Nowacek et al. 2007). 

Available studies show wide variation 

in response to underwater sound; 

therefore, it is difficult to predict 

specifically how any given sound in a 

particular instance might affect marine 

mammals perceiving the signal. If a 

marine mammal does react briefly to an 

underwater sound by changing its 

behavior or moving a small distance, the 

impacts of the change are unlikely to be 

significant to the individual, let alone 

the stock or population. However, if a 

sound source displaces marine 

mammals from an important feeding or 

breeding area for a prolonged period, 

impacts on individuals and populations 

could be significant (e.g., Lusseau and 

Bejder 2007; Weilgart 2007; NRC 2003). 

However, there are broad categories of 

potential response, which we describe 

in greater detail here, that include 

alteration of dive behavior, alteration of 

foraging behavior, effects to breathing, 

interference with or alteration of 

vocalization, avoidance, and flight. 

Changes in dive behavior can vary 

widely, and may consist of increased or 

decreased dive times and surface 

intervals as well as changes in the rates 

of ascent and descent during a dive (e.g., 

Frankel and Clark 2000; Costa et al. 


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2003; Ng and Leung, 2003; Nowacek et 

al. 2004; Goldbogen et al. 2013). 

Variations in dive behavior may reflect 

interruptions in biologically significant 

activities (e.g., foraging) or they may be 

of little biological significance. The 

impact of an alteration to dive behavior 

resulting from an acoustic exposure 

depends on what the animal is doing at 

the time of the exposure and the type 

and magnitude of the response. 

Disruption of feeding behavior can be 

difficult to correlate with anthropogenic 

sound exposure, so it is usually inferred 

by observed displacement from known 

foraging areas, the appearance of 

secondary indicators (e.g., bubble nets 

or sediment plumes), or changes in dive 

behavior. As for other types of 

behavioral response, the frequency, 

duration, and temporal pattern of signal 

presentation, as well as differences in 

species sensitivity, are likely 

contributing factors to differences in 

response in any given circumstance 

(e.g., Croll et al. 2001; Nowacek et al. 

2004; Madsen et al. 2006; Yazvenko et 

al. 2007). A determination of whether 

foraging disruptions incur fitness 

consequences would require 

information on or estimates of the 

energetic requirements of the affected 

individuals and the relationship 

between prey availability, foraging effort 

and success, and the life history stage of 

the animal. 

Variations in respiration naturally 

vary with different behaviors and 

alterations to breathing rate as a 

function of acoustic exposure can be 

expected to co-occur with other 

behavioral reactions, such as a flight 

response or an alteration in diving. 

However, respiration rates in and of 

themselves may be representative of 

annoyance or an acute stress response. 

Various studies have shown that 

respiration rates may either be 

unaffected or could increase, depending 

on the species and signal characteristics, 

again highlighting the importance in 

understanding species differences in the 

tolerance of underwater noise when 

determining the potential for impacts 

resulting from anthropogenic sound 

exposure (e.g., Kastelein et al. 2001, 

2005b, 2006; Gailey et al. 2007). 

Marine mammals vocalize for 

different purposes and across multiple 

modes, such as whistling, echolocation 

click production, calling, and singing. 

Changes in vocalization behavior in 

response to anthropogenic noise can 

occur for any of these modes and may 

result from a need to compete with an 

increase in background noise or may 

reflect increased vigilance or a startle 

response. For example, in the presence 

of potentially masking signals, 

humpback whales and killer whales 

have been observed to increase the 

length of their songs (Miller et al. 2000; 

Fristrup et al. 2003; Foote et al. 2004), 

while right whales have been observed 

to shift the frequency content of their 

calls upward while reducing the rate of 

calling in areas of increased 

anthropogenic noise (Parks et al. 2007). 

In some cases, animals may cease sound 

production during production of 

aversive signals (Bowles et al. 1994). 

Avoidance is the displacement of an 

individual from an area or migration 

path as a result of the presence of a 

sound or other stressors, and is one of 

the most obvious manifestations of 

disturbance in marine mammals 

(Richardson et al. 1995). For example, 

gray whales are known to change 

direction—deflecting from customary 

migratory paths—in order to avoid noise 

from seismic surveys (Malme et al. 

1984). Avoidance may be short-term, 

with animals returning to the area once 

the noise has ceased (e.g., Bowles et al. 

1994; Goold, 1996; Morton and 

Symonds, 2002; Gailey et al. 2007). 

Longer-term displacement is possible, 

however, which may lead to changes in 

abundance or distribution patterns of 

the affected species in the affected 

region if habituation to the presence of 

the sound does not occur (e.g., 

Blackwell et al. 2004; Bejder et al. 

2006). 

A flight response is a dramatic change 

in normal movement to a directed and 

rapid movement away from the 

perceived location of a sound source. 

The flight response differs from other 

avoidance responses in the intensity of 

the response (e.g., directed movement, 

rate of travel). Relatively little 

information on flight responses of 

marine mammals to anthropogenic 

signals exist, although observations of 

flight responses to the presence of 

predators have occurred (Connor and 

Heithaus 1996). The result of a flight 

response could range from brief, 

temporary exertion and displacement 

from the area where the signal provokes 

flight to, in extreme cases, marine 

mammal strandings (Evans and England 

2001). However, it should be noted that 

response to a perceived predator does 

not necessarily invoke flight (Ford and 

Reeves 2008), and whether individuals 

are solitary or in groups may influence 

the response. 

Behavioral disturbance can also 

impact marine mammals in more subtle 

ways. Increased vigilance may result in 

costs related to diversion of focus and 

attention (i.e., when a response consists 

of increased vigilance, it may come at 

the cost of decreased attention to other 

critical behaviors such as foraging or 

resting). These effects have generally not 

been demonstrated for marine 

mammals, but studies involving fish 

and terrestrial animals have shown that 

increased vigilance may substantially 

reduce feeding rates (e.g., Beauchamp 

and Livoreil, 1997; Fritz et al. 2002; 

Purser and Radford 2011). In addition, 

chronic disturbance can cause 

population declines through reduction 

of fitness (e.g., decline in body 

condition) and subsequent reduction in 

reproductive success, survival, or both 

(e.g., Harrington and Veitch 1992; Daan 

et al. 1996; Bradshaw et al. 1998). 

However, Ridgway et al. (2006) reported 

that increased vigilance in bottlenose 

dolphins exposed to sound over a fiveday period did not cause any sleep 

deprivation or stress effects. 

Many animals perform vital functions, 

such as feeding, resting, traveling, and 

socializing, on a diel cycle (24-hour 

cycle). Disruption of such functions 

resulting from reactions to stressors 

such as sound exposure are more likely 

to be significant if they last more than 

one diel cycle or recur on subsequent 

days (Southall et al. 2007). 

Consequently, a behavioral response 

lasting less than one day and not 

recurring on subsequent days is not 

considered particularly severe unless it 

could directly affect reproduction or 

survival (Southall et al. 2007). Note that 

there is a difference between multi-day 

substantive behavioral reactions and 

multi-day anthropogenic activities. For 

example, just because an activity lasts 

for multiple days does not necessarily 

mean that individual animals are either 

exposed to activity-related stressors for 

multiple days or, further, exposed in a 

manner resulting in sustained multi-day 

substantive behavioral responses. 

For non-impulsive sounds (i.e., 

similar to the sources used during the 

proposed specified activities), data 

suggest that exposures of pinnipeds to 

received levels between 90 and 140 dB 

re 1 mPa do not elicit strong behavioral 

responses; no data were available for 

exposures at higher received levels for 

Southall et al. (2007) to include in the 

severity scale analysis. Reactions of 

harbor seals were the only available data 

for which the responses could be ranked 

on the severity scale. For reactions that 

were recorded, the majority (17 of 18 

individuals/groups) were ranked on the 

severity scale as a 4 (defined as 

moderate change in movement, brief 

shift in group distribution, or moderate 

change in vocal behavior) or lower; the 

remaining response was ranked as a 6 

(defined as minor or moderate 

avoidance of the sound source). 

Additional data on hooded seals 

(Cystophora cristata) indicate avoidance 


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responses to signals above 160–170 dB 

re 1 mPa (Kvadsheim et al. 2010), and 

data on gray seals (Halichoerus grypus) 

and harbor seals indicate avoidance 

response at received levels of 135–144 

dB re 1 mPa (Go ̈tz et al. 2010). In each 

instance where food was available, 

which provided the seals motivation to 

remain near the source, habituation to 

the signals occurred rapidly. In the same 

study, it was noted that habituation was 

not apparent in wild seals where no 

food source was available (Go ̈tz et al. 

2010). This implies that the motivation 

of the animal is necessary to consider in 

determining the potential for a reaction. 

In one study that aimed to investigate 

the under-ice movements and sensory 

cues associated with under-ice 

navigation of ice seals, acoustic 

transmitters (60–69 kHz at 159 dB re 1 

mPa at 1 m) were attached to ringed seals 

(Wartzok et al. 1992a; Wartzok et al. 

1992b). An acoustic tracking system 

then was installed in the ice to receive 

the acoustic signals and provide realtime tracking of ice seal movements. 

Although the frequencies used in this 

study are at the upper limit of ringed 

seal hearing, the ringed seals appeared 

unaffected by the acoustic 

transmissions, as they were able to 

maintain normal behaviors (e.g., finding 

breathing holes). 

Seals exposed to non-impulsive 

sources with a received sound pressure 

level within the range of calculated 

exposures for ICEX activities (142–193 

dB re 1 mPa), have been shown to 

change their behavior by modifying 

diving activity and avoidance of the 

sound source (Go ̈tz et al. 2010; 

Kvadsheim et al. 2010). Although a 

minor change to a behavior may occur 

as a result of exposure to the sources in 

the proposed specified activities, these 

changes would be within the normal 

range of behaviors for the animal (e.g., 

the use of a breathing hole further from 

the source, rather than one closer to the 

source, would be within the normal 

range of behavior; Kelly et al. 1988). 

Adult ringed seals spend up to 20 

percent of the time in subnivean lairs 

during the winter season (Kelly et al. 

2010a). Ringed seal pups spend about 

50 percent of their time in the lair 

during the nursing period (Lydersen and 

Hammill 1993). During the warm season 

ringed seals haul out on the ice. In a 

study of ringed seal haulout activity by 

Born et al. (2002), ringed seals spent 25– 

57 percent of their time hauled out in 

June, which is during their molting 

season. Ringed seal lairs are typically 

used by individual seals (haulout lairs) 

or by a mother with a pup (birthing 

lairs); large lairs used by many seals for 

hauling out are rare (Smith and Stirling 

1975). If the non-impulsive acoustic 

transmissions are heard and are 

perceived as a threat, ringed seals 

within subnivean lairs could react to the 

sound in a similar fashion to their 

reaction to other threats, such as polar 

bears (their primary predators). 

Responses of ringed seals to a variety of 

human-induced sounds (e.g., helicopter 

noise, snowmobiles, dogs, people, and 

seismic activity) have been variable; 

some seals entered the water and some 

seals remained in the lair. However, 

according to Kelly et al. (1988), in all 

instances in which observed seals 

departed lairs in response to noise 

disturbance, they subsequently 

reoccupied the lair. 

Ringed seal mothers have a strong 

bond with their pups and may 

physically move their pups from the 

birth lair to an alternate lair to avoid 

predation, sometimes risking their lives 

to defend their pups from potential 

predators (Smith 1987). If a ringed seal 

mother perceives the proposed acoustic 

sources as a threat, the network of 

multiple birth and haulout lairs allows 

the mother and pup to move to a new 

lair (Smith and Hammill 1981; Smith 

and Stirling 1975). The acoustic sources 

from these proposed specified activities 

are not likely to impede a ringed seal 

from finding a breathing hole or lair, as 

captive seals have been found to 

primarily use vision to locate breathing 

holes and no effect to ringed seal vision 

would occur from the acoustic 

disturbance (Elsner et al. 1989; Wartzok 

et al. 1992a). It is anticipated that a 

ringed seal would be able to relocate to 

a different breathing hole relatively 

easily without impacting their normal 

behavior patterns. 

Stress responses—An animal’s 

perception of a threat may be sufficient 

to trigger stress responses consisting of 

some combination of behavioral 

responses, autonomic nervous system 

responses, neuroendocrine responses, or 

immune responses (e.g., Seyle 1950; 

Moberg 2000). In many cases, an 

animal’s first and sometimes most 

economical (in terms of energetic costs) 

response is behavioral avoidance of the 

potential stressor. Autonomic nervous 

system responses to stress typically 

involve changes in heart rate, blood 

pressure, and gastrointestinal activity. 

These responses have a relatively short 

duration and may or may not have a 

significant long-term effect on an 

animal’s fitness. 

Neuroendocrine stress responses often 

involve the hypothalamus-pituitaryadrenal system. Virtually all 

neuroendocrine functions that are 

affected by stress—including immune 

competence, reproduction, metabolism, 

and behavior—are regulated by pituitary 

hormones. Stress-induced changes in 

the secretion of pituitary hormones have 

been implicated in failed reproduction, 

altered metabolism, reduced immune 

competence, and behavioral disturbance 

(e.g., Moberg, 1987; Blecha, 2000). 

Increases in the circulation of 

glucocorticoids are also equated with 

stress (Romano et al. 2004). 

The primary distinction between 

stress (which is adaptive and does not 

normally place an animal at risk) and 

‘‘distress’’ is the cost of the response. 

During a stress response, an animal uses 

glycogen stores that can be quickly 

replenished once the stress is alleviated. 

In such circumstances, the cost of the 

stress response would not pose serious 

fitness consequences. However, when 

an animal does not have sufficient 

energy reserves to satisfy the energetic 

costs of a stress response, energy 

resources must be diverted from other 

functions. This state of distress will last 

until the animal replenishes its 

energetic reserves sufficient to restore 

normal function. 

Relationships between these 

physiological mechanisms, animal 

behavior, and the costs of stress 

responses are well-studied through 

controlled experiments and for both 

laboratory and free-ranging animals 

(e.g., Holberton et al. 1996; Hood et al. 

1998; Jessop et al. 2003; Krausman et al. 

2004; Lankford et al. 2005). Stress 

responses due to exposure to 

anthropogenic sounds or other stressors 

and their effects on marine mammals 

have also been reviewed (Fair and 

Becker, 2000; Romano et al. 2002b) and, 

more rarely, studied in wild populations 

(e.g., Romano et al. 2002a). These and 

other studies lead to a reasonable 

expectation that some marine mammals 

will experience physiological stress 

responses upon exposure to acoustic 

stressors and that it is possible that 

some of these would be classified as 

‘‘distress.’’ In addition, any animal 

experiencing TTS would likely also 

experience stress responses (NRC, 

2003). 

Auditory masking—Sound can 

disrupt behavior through masking, or 

interfering with, an animal’s ability to 

detect, recognize, or discriminate 

between acoustic signals of interest (e.g., 

those used for intraspecific 

communication and social interactions, 

prey detection, predator avoidance, 

navigation) (Richardson et al. 1995). 

Masking occurs when the receipt of a 

sound is interfered with by another 

coincident sound at similar frequencies 

and at similar or higher intensity, and 

may occur whether the sound is natural 

(e.g., snapping shrimp, wind, waves, 


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precipitation) or anthropogenic (e.g., 

shipping, sonar, seismic exploration) in 

origin. The ability of a noise source to 

mask biologically important sounds 

depends on the characteristics of both 

the noise source and the signal of 

interest (e.g., signal-to-noise ratio, 

temporal variability, direction), in 

relation to each other and to an animal’s 

hearing abilities (e.g., sensitivity, 

frequency range, critical ratios, 

frequency discrimination, directional 

discrimination, age or TTS hearing loss), 

and existing ambient noise and 

propagation conditions. 

Under certain circumstances, marine 

mammals experiencing significant 

masking could also be impaired from 

maximizing their performance fitness in 

survival and reproduction. Therefore, 

when the coincident (masking) sound is 

anthropogenic, it may be considered 

harassment when disrupting or altering 

critical behaviors. It is important to 

distinguish TTS and PTS, which persist 

after the sound exposure, from masking, 

which occurs during the sound 

exposure. Because masking (without 

resulting in TS) is not associated with 

abnormal physiological function, it is 

not considered a physiological effect, 

but rather a potential behavioral effect. 

The frequency range of the potentially 

masking sound is important in 

determining any potential behavioral 

impacts. For example, low-frequency 

signals may have less effect on highfrequency echolocation sounds 

produced by odontocetes but are more 

likely to affect detection of mysticete 

communication calls and other 

potentially important natural sounds 

such as those produced by surf and 

some prey species. The masking of 

communication signals by 

anthropogenic noise may be considered 

as a reduction in the communication 

space of animals (e.g., Clark et al. 2009) 

and may result in energetic or other 

costs as animals change their 

vocalization behavior (e.g., Miller et al. 

2000; Foote et al. 2004; Parks et al. 

2007b; Di Iorio and Clark, 2009; Holt et 

al. 2009). Masking can be reduced in 

situations where the signal and noise 

come from different directions 

(Richardson et al. 1995), through 

amplitude modulation of the signal, or 

through other compensatory behaviors 

(Houser and Moore, 2014). Masking can 

be tested directly in captive species 

(e.g., Erbe 2008), but in wild 

populations it must be either modeled 

or inferred from evidence of masking 

compensation. There are few studies 

addressing real-world masking sounds 

likely to be experienced by marine 

mammals in the wild (e.g., Branstetter et 

al. 2013). 

Masking affects both senders and 

receivers of acoustic signals and can 

potentially have long-term chronic 

effects on marine mammals at the 

population level as well as at the 

individual level. Low-frequency 

ambient sound levels have increased by 

as much as 20 dB (more than three times 

in terms of SPL) in the world’s ocean 

from pre-industrial periods, with most 

of the increase from distant commercial 

shipping (Hildebrand 2009). All 

anthropogenic sound sources, but 

especially chronic and lower-frequency 

signals (e.g., from vessel traffic), 

contribute to elevated ambient sound 

levels, thus intensifying masking. 

Potential Effects of Sonar on Prey— 

Ringed seals feed on marine 

invertebrates and fish. Marine 

invertebrates occur in the world’s 

oceans, from warm shallow waters to 

cold deep waters, and are the dominant 

animals in all habitats of the ICEX24 

Study Area. Although most species are 

found within the benthic zone, marine 

invertebrates can be found in all zones 

(sympagic (within the sea ice), pelagic 

(open ocean), or benthic (bottom 

dwelling)) of the Beaufort Sea (Josefson 

et al. 2013). The diverse range of species 

include oysters, crabs, worms, ghost 

shrimp, snails, sponges, sea fans, 

isopods, and stony corals (Chess and 

Hobson 1997; Dugan et al. 2000; Proctor 

et al. 1980). 

Hearing capabilities of invertebrates 

are largely unknown (Lovell et al. 2005; 

Popper and Schilt 2008). Outside of 

studies conducted to test the sensitivity 

of invertebrates to vibrations, very little 

is known on the effects of anthropogenic 

underwater noise on invertebrates 

(Edmonds et al. 2016). While data are 

limited, research suggests that some of 

the major cephalopods and decapods 

may have limited hearing capabilities 

(Hanlon 1987; Offutt 1970), and may 

hear only low-frequency (less than 1 

kHz) sources (Offutt 1970), which is 

most likely within the frequency band 

of biological signals (Hill 2009). In a 

review of crustacean sensitivity of high 

amplitude underwater noise by 

Edmonds et al. (2016), crustaceans may 

be able to hear the frequencies at which 

they produce sound, but it remains 

unclear which noises are incidentally 

produced and if there are any negative 

effects from masking them. Acoustic 

signals produced by crustaceans range 

from low frequency rumbles (20–60 Hz) 

to high frequency signals (20–55 kHz) 

(Henninger and Watson 2005; Patek and 

Caldwell 2006; Staaterman et al. 2016). 

Aquatic invertebrates that can sense 

local water movements with ciliated 

cells include cnidarians, flatworms, 

segmented worms, urochordates 

(tunicates), mollusks, and arthropods 

(Budelmann 1992a, 1992b; Popper et al. 

2001). Some aquatic invertebrates have 

specialized organs called statocysts for 

determination of equilibrium and, in 

some cases, linear or angular 

acceleration. Statocysts allow an animal 

to sense movement and may enable 

some species, such as cephalopods and 

crustaceans, to be sensitive to water 

particle movements associated with 

sound (Goodall et al. 1990; Hu et al. 

2009; Kaifu et al. 2008; Montgomery et 

al. 2006; Popper et al. 2001; Roberts and 

Breithaupt 2016; Salmon 1971). Because 

any acoustic sensory capabilities, if 

present at all, are limited to detecting 

water motion, and water particle motion 

near a sound source falls off rapidly 

with distance, aquatic invertebrates are 

probably limited to detecting nearby 

sound sources rather than sound caused 

by pressure waves from distant sources. 

Studies of sound energy effects on 

invertebrates are few, and identify only 

behavioral responses. Non-auditory 

injury, PTS, TTS, and masking studies 

have not been conducted for 

invertebrates. Both behavioral and 

auditory brainstem response studies 

suggest that crustaceans may sense 

frequencies up to 3 kHz, but best 

sensitivity is likely below 200 Hz 

(Goodall et al. 1990; Lovell et al. 2005; 

Lovell et al. 2006). Most cephalopods 

likely sense low-frequency sound below 

1 kHz, with best sensitivities at lower 

frequencies (Budelmann 2010; Mooney 

et al. 2010; Offutt 1970). A few 

cephalopods may sense higher 

frequencies up to 1,500 Hz (Hu et al. 

2009). 

It is expected that most marine 

invertebrates would not sense the 

frequencies of the sonar associated with 

the proposed specified activities. Most 

marine invertebrates would not be close 

enough to active sonar systems to 

potentially experience impacts to 

sensory structures. Any marine 

invertebrate capable of sensing sound 

may alter its behavior if exposed to 

sonar. Although acoustic transmissions 

produced during the proposed specified 

activities may briefly impact 

individuals, intermittent exposures to 

sonar are not expected to impact 

survival, growth, recruitment, or 

reproduction of widespread marine 

invertebrate populations. 

The fish species located in the ICEX24 

Study Area include those that are 

closely associated with the deep ocean 

habitat of the Beaufort Sea. Nearly 250 

marine fish species have been described 

in the Arctic, excluding the larger parts 

of the sub-Arctic Bering, Barents, and 

Norwegian Seas (Mecklenburg et al. 

2011). However, only about 30 are 


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known to occur in the Arctic waters of 

the Beaufort Sea (Christiansen and Reist 

2013). Largely because of the difficulty 

of sampling in remote, ice-covered seas, 

many high-Arctic fish species are 

known only from rare or geographically 

patchy records (Mecklenburg et al. 

2011). Aquatic systems of the Arctic 

undergo extended seasonal periods of 

ice cover and other harsh environmental 

conditions. Fish inhabiting such 

systems must be biologically and 

ecologically adapted to surviving such 

conditions. Important environmental 

factors that Arctic fish must contend 

with include reduced light, seasonal 

darkness, ice cover, low biodiversity, 

and low seasonal productivity. 

All fish have two sensory systems to 

detect sound in the water: the inner ear, 

which functions very much like the 

inner ear in other vertebrates, and the 

lateral line, which consists of a series of 

receptors along the fish’s body (Popper 

and Fay 2010; Popper et al. 2014). The 

inner ear generally detects relatively 

higher-frequency sounds, while the 

lateral line detects water motion at low 

frequencies (below a few hundred Hz) 

(Hastings and Popper 2005). Lateral line 

receptors respond to the relative motion 

between the body surface and 

surrounding water; this relative motion, 

however, only takes place very close to 

sound sources and most fish are unable 

to detect this motion at more than one 

to two body lengths distance away 

(Popper et al. 2014). Although hearing 

capability data only exist for fewer than 

100 of the approximately 32,000 fish 

species known to exist, current data 

suggest that most species of fish detect 

sounds from 50 to 1,000 Hz, with few 

fish hearing sounds above 4 kHz 

(Popper 2008). It is believed that most 

fish have their best hearing sensitivity 

from 100 to 400 Hz (Popper 2003). 

Permanent hearing loss has not been 

documented in fish. A study by 

Halvorsen et al. (2012) found that for 

temporary hearing loss or similar 

negative impacts to occur, the noise 

needed to be within the fish’s 

individual hearing frequency range; 

external factors, such as developmental 

history of the fish or environmental 

factors, may result in differing impacts 

to sound exposure in fish of the same 

species. The sensory hair cells of the 

inner ear in fish can regenerate after 

they are damaged, unlike in mammals 

where sensory hair cells loss is 

permanent (Lombarte et al. 1993; Smith 

et al. 2006). As a consequence, any 

hearing loss in fish may be as temporary 

as the timeframe required to repair or 

replace the sensory cells that were 

damaged or destroyed (Smith et al. 

2006), and no permanent loss of hearing 

in fish would result from exposure to 

sound. 

Fish species in the ICEX24 Study 

Area are expected to hear the lowfrequency sources associated with the 

proposed specified activities, but most 

are not expected to detect the higherfrequency sounds. Only a few fish 

species are able to detect mid-frequency 

sonar above 1 kHz and could have 

behavioral reactions or experience 

auditory masking during these 

activities. These effects are expected to 

be transient, and long-term 

consequences for the population are not 

expected. Fish with hearing 

specializations capable of detecting 

high-frequency sounds are not expected 

to be within the ICEX24 Study Area. If 

hearing specialists were present, they 

would have to be in close vicinity to the 

source to experience effects from the 

acoustic transmission. Human-generated 

sound could alter the behavior of a fish 

in a manner that would affect its way of 

living, such as where it tries to locate 

food or how well it can locate a 

potential mate; behavioral responses to 

loud noise could include a startle 

response, such as the fish swimming 

away from the source, the fish 

‘‘freezing’’ and staying in place, or 

scattering (Popper 2003). Auditory 

masking could also interfere with a 

fish’s ability to hear biologically 

relevant sounds, inhibiting the ability to 

detect both predators and prey, and 

impacting schooling, mating, and 

navigating (Popper 2003). If an 

individual fish comes into contact with 

low-frequency acoustic transmissions 

and is able to perceive the 

transmissions, they are expected to 

exhibit short-term behavioral reactions, 

when initially exposed to acoustic 

transmissions, which would not 

significantly alter breeding, foraging, or 

populations. Overall effects to fish from 

ICEX24 active sonar sources would be 

localized, temporary, and infrequent. 

Effects of Acoustics on Physical and 

Foraging Habitat—Unless the sound 

source is stationary and/or continuous 

over a long duration in one area, neither 

of which applies to ICEX24 activities, 

the effects of the introduction of sound 

into the environment are generally 

considered to have a less severe impact 

on marine mammal habitat compared to 

any physical alteration of the habitat. 

Acoustic exposures are not expected to 

result in long-term physical alteration of 

the water column or bottom topography 

as the occurrences are of limited 

duration and would occur 

intermittently. Acoustic transmissions 

also would have no structural impact to 

subnivean lairs in the ice. Furthermore, 

since ice dampens acoustic 

transmissions (Richardson et al. 1995) 

the level of sound energy that reaches 

the interior of a subnivean lair would be 

less than that ensonifying water under 

surrounding ice. For these reasons, it is 

unlikely that the Navy’s acoustic 

activities in the ICEX24 Study Area 

would have any effect on marine 

mammal habitat. 

Potential Effects of Vessel Strike 

Because ICEX24 would occur only 

when there is ice coverage and 

conditions are appropriate to establish 

an ice camp on an ice floe, no ships or 

smaller boats would be involved in the 

activity. Vessel use would be limited to 

submarines and unmanned underwater 

vehicles (hereafter referred to together 

as ‘‘vessels’’ unless noted separately). 

The potential for vessel strike during 

ICEX24 would therefore only arise from 

the use of submarines during training 

and testing activities, and the use of 

unmanned underwater vehicles during 

research activities. Depths at which 

vessels would operate during ICEX24 

would overlap with known dive depths 

of ringed seals, which have been 

recorded to 300 m (984.3 ft) in depth 

(Gjertz et al. 2000; Lydersen 1991). Few 

authors have specifically described the 

responses of pinnipeds to vessels, and 

most of the available information on 

reactions to boats concerns pinnipeds 

hauled out on land or ice. No 

information is available on potential 

responses to submarines or unmanned 

underwater vehicles. Brueggeman et al. 

(1992) stated ringed seals hauled out on 

the ice showed short-term escape 

reactions when they were within 0.25– 

0.5 km (0.2–0.3 mi) from a vessel; ringed 

seals would likely show similar 

reactions to submarines and unmanned 

underwater vehicles, decreasing the 

likelihood of vessel strike during 

ICEX24 activities. 

The Navy has kept strike records for 

over 20 years and has no records of 

individual pinnipeds being struck by a 

vessel as a result of Navy activities and, 

further, the smaller size and 

maneuverability of pinnipeds make a 

vessel strike unlikely. Also, NMFS has 

never received any reports indicating 

that pinnipeds have been struck by 

vessels of any type. Review of 

additional sources of information in the 

form of worldwide ship strike records 

shows little evidence of strikes of 

pinnipeds from the shipping sector. 

Further, a review of seal stranding data 

from Alaska found that during 2020, 9 

ringed seal strandings were recorded by 

the Alaska Marine Mammal Stranding 

Network. Within the Arctic region of 

Alaska, 7 ringed seal strandings were 


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recorded. Of the 9 strandings reported 

in Alaska (all regions included), none 

were found to be caused by vessel 

collisions (Savage 2021). 

Vessel speed, size, and mass are 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). 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. For 

most of the research and training and 

testing activities during the specified 

activity, submarine and unmanned 

underwater vehicle speeds would not 

typically exceed 10 knots during the 

time spent within the ICEX24 Study 

Area, which would lessen the already 

extremely unlikely chance of collisions 

with marine mammals, specifically 

ringed seals. 

Based on consideration of all this 

information, NMFS does not anticipate 

incidental take of marine mammals by 

vessel strike from submarines or 

unmanned underwater vehicles. 

Other Non-Acoustic Impacts 

Deployment of the ice camp could 

potentially affect ringed seal habitat by 

physically damaging or crushing 

subnivean lairs, which could potentially 

result in ringed seal injury or mortality. 

March 1 is generally expected to be the 

onset of ice seal lairing season, and 

ringed seals typically construct lairs 

near pressure ridges. As described in the 

Proposed Mitigation section, the ice 

camp and runway would be established 

on a combination of first-year ice and 

multi-year ice without pressure ridges, 

which would minimize the possibility 

of physical impacts to subnivean lairs 

and habitat suitable for lairs. Ice camp 

deployment would begin mid-February, 

and be gradual, with activity increasing 

over the first five days. So in addition, 

this schedule would discourage seals 

from establishing birthing lairs in or 

near the ice camp, and would allow 

ringed seals to relocate outside of the ice 

camp area as needed, though both 

scenarios are unlikely as described 

below in this section. Personnel on onice vehicles would observe for marine 

mammals, and would follow established 

routes when available, to avoid 

potential disturbance of lairs and habitat 

suitable for lairs. Personnel on foot and 

operating on-ice vehicles would avoid 

deep snow drifts near pressure ridges, 

also to avoid potential lairs and habitat 

suitable for lairs. Implementation of 

these measures are expected to prevent 

ringed seal lairs from being crushed or 

damaged during ICEX24 activities, and 

are expected to minimize any other 

potential impacts to sea ice habitat 

suitable for the formation of lairs. Given 

the proposed mitigation requirements, 

we also do not anticipate ringed seal 

injury or mortality as a result of damage 

to subnivean lairs. 

ICEX24 personnel would be actively 

conducting testing and training 

operations on the sea ice and would 

travel around the camp area, including 

the runway, on snowmobiles. Although 

the Navy does not anticipate observing 

any seals on the ice given the lack of 

observations during previous ice 

exercises (U.S. Navy, 2020), as a general 

matter, on-ice activities could cause a 

seal that would have otherwise built a 

lair in the area of an activity to be 

displaced and therefore, construct a lair 

in a different area outside of an activity 

area, or a seal could choose to relocate 

to a different existing lair outside of an 

activity area. However, in the case of the 

ice camp associated with ICEX24, 

displacement of seal lair construction or 

relocation to existing lairs outside of the 

ice camp area is unlikely, given the low 

average density of structures (the 

average ringed seal ice structure density 

in the vicinity of Prudhoe Bay, Alaska 

is 1.58 structures per km2 (table 4)), the 

relative footprint of the Navy’s planned 

ice camp (2 km2; 0.8 mi2), the lack of 

previous ringed seal observations on the 

ice during ICEX activities, and proposed 

mitigation requirements that would 

require the Navy to construct the ice 

camp and runway on first-year or 

multiyear ice without pressure ridges 

and would require personnel to avoid 

areas of deep snow drift or pressure 

ridges (see the Proposed Mitigation 

section for additional information about 

the proposed mitigation requirements). 

This measure, in combination with the 

other mitigation measures required for 

operation of the ice camp are expected 

to avoid impacts to the construction and 

use of ringed seal subnivean lairs, 

particularly given the already low 

average density of lairs, as described 

above. 

TABLE 4—RINGED SEAL ICE STRUCTURE DENSITY IN THE VICINITY OF THE PRUDHOE BAY, ALASKA

Year Ice structure density 

(structures per km2) Source 

1982 ........................................................................................................................................ 3.6 Frost and Burns 1989. 

1983 ........................................................................................................................................ 0.81 Kelly et al. 1986. 

1999 ........................................................................................................................................ 0.71 Williams et al. 2001. 

2000 ........................................................................................................................................ 1.2 Williams et al. 2001. 

Average Density ...................................................................................................................... 1.58 

Given the required mitigation 

measures and the low density of ringed 

seals anticipated in the Ice Camp Study 

Area during ICEX24, we do not 

anticipate behavioral disturbance of 

ringed seals due to human presence. 

The Navy’s activities would occur 

prior to the late spring to early summer 

‘‘basking period,’’ which occurs 

between abandonment of the subnivean 

lairs and melting of the seasonal sea ice, 

and is when the seals undergo their 

annual molt (Kelly et al. 2010b). Given 

that the ice camp would be demobilized 

prior to the basking period, and the 

remainder of the Navy’s activities occur 

below the sea ice, impacts to sea ice 

habitat suitable as a platform for basking 

and molting are not anticipated to result 

from the Navy’s ICEX24 activities. 

Our preliminary determination of 

potential effects to the physical 

environment includes minimal possible 

impacts to marine mammals and their 

habitat from camp operation or 

deployment activities, given the 

proposed mitigation and the timing of 

the Navy’s proposed activities. In 

addition, given the relatively short 

duration of submarine testing and 

training activities, the relatively small 

area that would be affected, and the lack 

of impacts to physical or foraging 

habitat, the proposed specified activities 

are not likely to have an adverse effect 

on prey species or marine mammal 

habitat, other than potential localized, 

temporary, and infrequent effects to fish 

as discussed above. Therefore, any 

impacts to ringed seals and their habitat, 

as discussed above in this section, are 

not expected to cause significant or 


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long-term consequences for individual 

ringed seals or the population. Please 

see the Negligible Impact Analysis and 

Determination section for additional 

discussion regarding the likely impacts 

of the Navy’s activities on ringed seals, 

including the reproductive success or 

survivorship of individual ringed seals, 

and how those impacts on individuals 

are likely to impact the species or stock. 

Estimated Take of Marine Mammals 

This section provides an estimate of 

the number of incidental takes proposed 

for authorization through this IHA, 

which will inform NMFS’ consideration 

of the negligible impact determinations 

and impacts on subsistence uses. 

Harassment is the only type of take 

expected to result from these activities. 

For this military readiness activity, 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 the behavioral patterns are 

abandoned or significantly altered 

(Level B harassment). 

Authorized takes would be by Level B 

harassment only, in the form of 

behavioral reactions and/or TTS for 

individual marine mammals resulting 

from exposure to acoustic 

transmissions. Based on the nature of 

the activity, Level A harassment is 

neither anticipated nor proposed to be 

authorized. As described previously, no 

serious injury or mortality is anticipated 

or proposed to be authorized for this 

activity. Below we describe how the 

proposed take numbers are estimated. 

For acoustic impacts, generally 

speaking, we estimate take by 

considering: (1) acoustic thresholds 

above which NMFS believes the best 

available science indicates marine 

mammals will be behaviorally harassed 

or incur some degree of permanent 

hearing impairment; (2) the area or 

volume of water that will be ensonified 

above these levels in a day; (3) the 

density or occurrence of marine 

mammals within these ensonified areas; 

and, (4) the number of days of activities. 

We note that while these factors can 

contribute to a basic calculation to 

provide an initial prediction of potential 

takes, additional information that can 

qualitatively inform take estimates is 

also sometimes available (e.g., previous 

monitoring results or average group 

size). Below, we describe the factors 

considered here in more detail and 

present the take estimates. 

Acoustic Thresholds 

NMFS recommends the use of 

acoustic thresholds that identify the 

received level of underwater sound 

above which exposed marine mammals 

would be reasonably expected to be 

behaviorally harassed (equated to Level 

B harassment) or to incur PTS of some 

degree (equated to Level A harassment). 

Level B Harassment—In coordination 

with NMFS, the Navy developed 

behavioral thresholds to support 

environmental analyses for the Navy’s 

testing and training military readiness 

activities utilizing active sonar sources; 

these behavioral harassment thresholds 

are used here to evaluate the potential 

effects of the active sonar components of 

the proposed specified activities. 

Though significantly driven by received 

level, the onset of behavioral 

disturbance from anthropogenic noise 

exposure is also informed to varying 

degrees by other factors related to the 

source or exposure context (e.g., 

frequency, predictability, duty cycle, 

duration of the exposure, signal-to-noise 

ratio, distance to the source), the 

environment (e.g., bathymetry, other 

noises in the area, predators in the area), 

and the receiving animals (hearing, 

motivation, experience, demography, 

life stage, depth) and can be difficult to 

predict (e.g., Southall et al., 2007, 2021, 

Ellison et al., 2012). 

The Navy’s Phase III proposed 

pinniped behavioral threshold was 

updated based on controlled exposure 

experiments on the following captive 

animals: Hooded seal, gray seal, and 

California sea lion (Go ̈tz et al. 2010; 

Houser et al. 2013a; Kvadsheim et al. 

2010). Overall exposure levels were 

110–170 dB re 1 mPa for hooded seals, 

140–180 dB re 1 mPa for gray seals, and 

125–185 dB re 1 mPa for California sea 

lions; responses occurred at received 

levels ranging from 125 to 185 dB re 1 

mPa. However, the means of the 

response data were between 159 and 

170 dB re 1 mPa. Hooded seals were 

exposed to increasing levels of sonar 

until an avoidance response was 

observed, while the grey seals were 

exposed first to a single received level 

multiple times, then an increasing 

received level. Each individual 

California sea lion was exposed to the 

same received level ten times. These 

exposure sessions were combined into a 

single response value, with an overall 

response assumed if an animal 

responded in any single session. 

Because these data represent a doseresponse type relationship between 

received level and a response, and 

because the means were all tightly 

clustered, the Bayesian biphasic 

Behavioral Response Function for 

pinnipeds most closely resembles a 

traditional sigmoidal dose-response 

function at the upper received levels 

and has a 50 percent probability of 

response at 166 dB re 1 mPa. 

Additionally, to account for proximity 

to the source discussed above and based 

on the best scientific information, a 

conservative distance of 10 km is used 

beyond which exposures would not 

constitute a take under the military 

readiness definition of Level B 

harassment. 

Level A harassment—NMFS’ 

Technical Guidance for Assessing the 

Effects of Anthropogenic Sound on 

Marine Mammal Hearing (Version 2.0) 

(Technical Guidance, 2018) identifies 

dual criteria to assess auditory injury 

(Level A harassment) to five different 

marine mammal groups (based on 

hearing sensitivity) as a result of 

exposure to noise from two different 

types of sources (impulsive or nonimpulsive). The Navy’s activities 

include the use of non-impulsive (active 

sonar) sources. 

These thresholds are provided in the 

table below. The references, analysis, 

and methodology used in the 

development of the thresholds are 

described in NMFS’ 2018 Technical 

Guidance, which may be accessed at: 

https://www.fisheries.noaa.gov/ 

national/marine-mammal-protection/ 

marine-mammal-acoustic-technicalguidance. 

For previous ICEXs, the Navy’s PTS/ 

TTS analysis began with mathematical 

modeling to predict the sound 

transmission patterns from Navy 

sources, including sonar. These data 

were then coupled with marine species 

distribution and abundance data to 

determine the sound levels likely to be 

received by various marine species. 

These criteria and thresholds were 

applied to estimate specific effects that 

animals exposed to Navy-generated 

sound may experience. For weighting 

function derivation, the most critical 

data required were TTS onset exposure 

levels as a function of exposure 

frequency. These values can be 

estimated from published literature by 

examining TTS as a function of sound 

exposure level (SEL) for various 

frequencies. 

Table 5 below provides the weighted 

criteria and thresholds used in previous 

ICEX analyses for estimating 

quantitative acoustic exposures of 

marine mammals from the specified 

activities. 


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TABLE 5—ACOUSTIC THRESHOLDS IDENTIFYING THE ONSET OF BEHAVIORAL DISTURBANCE, TTS, AND PTS FOR NONIMPULSIVE SOUND SOURCES 1

Functional hearing group Species Behavioral criteria 

Physiological criteria 

TTS threshold SEL 

(weighted) 

PTS threshold SEL 

(weighted) 

Phocid Pinnipeds (Underwater) ................... Ringed seal ....... Pinniped Dose Response Function 2 .......... 181 dB SEL cumulative ... 201 dB SEL cumulative. 

1The threshold values provided are assumed for when the source is within the animal’s best hearing sensitivity. The exact threshold varies based on the overlap of 

the source and the frequency weighting. 2See Figure 6–1 in the Navy’s IHA application. 

Note: SEL thresholds in dB re: 1 μPa2 s. 

Marine Mammal Occurrence and Take 

Calculation and Estimation 

In previous ICEX analyses, the Navy 

has performed a quantitative analysis to 

estimate the number of ringed seals that 

could be harassed by the underwater 

acoustic transmissions during the 

proposed specified activities using 

marine mammal density estimates 

(Kaschner et al. 2006 and Kaschner 

2004), marine mammal depth 

occurrence distributions (U.S 

Department of the Navy, 2017), 

oceanographic and environmental data, 

marine mammal hearing data, and 

criteria and thresholds for levels of 

potential effects. Given the lack of 

recent density estimates for the ICEX 

Study Area and the lack of ringed seal 

observations and acoustic detections 

during ICEXs in the recent past 

(described in further detail below), 

NMFS expects that the ringed seal 

density relied upon in previous ICEX 

analyses was an overestimate to a large 

degree, and that the resulting take 

estimates were likely overestimates as 

well. Please see the notice of the final 

IHA for ICEX 22 for additional 

information on that analysis (87 FR 

7803; January 10, 2022). 

For ICEX24, rather than relying on a 

density estimate, the Navy estimated 

take of ringed seals based on an 

occurrence estimate of ringed seals 

within the ICEX Study Area. Ringed seal 

presence in the ICEX Study Area was 

obtained using sighting data from the 

Ocean Biodiversity Information SystemSpatial Ecological Analysis of 

Megavertebrate Populations (OBIS– 

SEAMAP; Halpin et al. 2009). The ICEX 

Study Area was overlaid on the OBIS– 

SEAMAP ringed seal sightings map that 

included sightings for years 2000 to 

2007 and 2013. Sighting data were only 

available for the mid-to-late summer 

and fall months. Due to the paucity of 

winter and spring data, the average 

number of individual ringed seals per 

year was assumed to be present in the 

ICEX Study Area during ICEX24; 

therefore, it is assumed that three ringed 

seals would be present in the ICEX 

Study Area. 

Table 6 provides range to effects for 

active acoustic sources proposed for 

ICEX24 to phocid pinniped-specific 

criteria. Phocids within these ranges 

would be predicted to receive the 

associated effect. Range to effects can be 

important information for predicting 

acoustic impacts, but also in 

determining adequate mitigation ranges 

to avoid higher level effects, especially 

physiological effects, to marine 

mammals. 

TABLE 6—RANGE TO BEHAVIORAL DISTURBANCE, TTS, AND PTS IN THE ICEX24 STUDY AREA

Source/exercise 

Range to effects (m) 

Behavioral 

disturbance TTS PTS 

Submarine Exercise ..................................................................................................................... 10,000 a 5,050 130 b

aEmpirical evidence has not shown responses to sonar that would constitute take beyond a few km from an acoustic source, which is why 

NMFS and the Navy conservatively set a distance cutoff of 10 km. Regardless of the source level at that distance, take is not estimated to occur 

beyond 10 km from the source. bThe distance represents the range to effects for all ICEX24 activities. 

Though likely conservative given the 

size of the ICEX Study Area in 

comparison to the size of the anticipated 

Level B harassment zone (10,000 m), 

Navy estimated that three ringed seals 

may be taken by Level B harassment per 

day of activity within the ICEX Study 

Area. Navy anticipates conducting 

active acoustic transmissions on 42 

days, and therefore requested 126 takes 

by Level B harassment of ringed seals (3 

seals per day × 42 days = 126 takes by 

Level B harassment; Table 7). NMFS 

concurs and proposes to authorize 126 

takes by Level B harassment. Modeling 

for the three previous ICEXs (2018, 

2020, and 2022), which employed 

similar acoustic sources, did not result 

in any estimated takes by PTS; 

therefore, particularly in consideration 

of the fact that total takes were likely 

overestimated for those ICEX activities 

given the density information used in 

the analyses (NMFS anticipates that the 

density of ringed seals is actually much 

lower) and the relatively small range to 

effects for PTS (130 m), the Navy did 

not request, and NMFS is not proposing 

to authorize, take by Level A harassment 

of ringed seal. 

TABLE 7—QUANTITATIVE MODELING RESULTS OF POTENTIAL EXPOSURES FOR ICEX ACTIVITIES

Species Level B 

harassment 

Level A 

harassment Total 

Ringed seal .................................................................................................................................. 126 0 126 


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During monitoring for the 2018 IHA 

covering similar military readiness 

activities in the ICEX22 Study Area, the 

Navy did not visually observe or 

acoustically detect any marine 

mammals (U.S. Navy, 2018). During 

monitoring for the 2020 IHA covering 

similar military readiness activities in 

the ICEX22 Study Area, the Navy also 

did not visually observe any marine 

mammals (U.S. Navy, 2020). Acoustic 

monitoring associated with the 2020 

IHA did not detect any discernible 

marine mammal vocalizations 

(Henderson et al. 2021). The monitoring 

report states that ‘‘there were a few very 

faint sounds that could have been 

(ringed seal) barks or yelps.’’ However, 

these were likely not from ringed seals, 

given that ringed seal vocalizations are 

generally produced in series (Jones et al. 

2014). Henderson et al. (2021) expect 

that these sounds were likely iceassociated or perhaps anthropogenic. 

While the distance at which ringed seals 

could be acoustically detected is not 

definitive, Henderson et al. (2021) states 

that Expendable Mobile ASW Training 

Targets (EMATTs) ‘‘traveled a distance 

of 10 nmi (18.5 km) away and were 

detected the duration of the recordings; 

although ringed seal vocalization source 

levels are likely far lower than the 

sounds emitted by the EMATTs, this 

gives some idea of the potential 

detection radius for the cryophone. The 

periods when the surface anthropogenic 

activity is occurring in close proximity 

to the cryophone are dominated by 

those broadband noises due to the 

shallow hydrophone placement in ice 

(only 10 cm down), and any ringed seal 

vocalizations that were underwater 

could have been masked.’’ During 

monitoring for the 2022 IHA covering 

similar military readiness activities in 

the ICEX24 Study Area, the Navy also 

did not visually observe any marine 

mammals (U.S. Navy, 2022). With the 

exception of PAM conducted during 

activities for mitigation purposes (no 

detections), PAM did not occur in 2022 

because the ice camp ice flow broke up, 

and therefore, Navy had to relocate 

camp. Given the lost time, multiple 

research projects were canceled, 

including the under-ice PAM that the 

Naval Postgraduate School was 

planning to conduct. 

Proposed Mitigation 

In order to issue an IHA under section 

101(a)(5)(D) of the MMPA, NMFS must 

set forth the permissible methods of 

taking pursuant to the activity, and 

other means of effecting the least 

practicable impact on the species or 

stock and its habitat, paying particular 

attention to rookeries, mating grounds, 

and areas of similar significance, and on 

the availability of the species or stock 

for taking for certain subsistence uses. 

NMFS regulations require applicants for 

incidental take authorizations to include 

information about the availability and 

feasibility (economic and technological) 

of equipment, methods, and manner of 

conducting the activity or other means 

of effecting the least practicable adverse 

impact upon the affected species or 

stocks, and their habitat (50 CFR 

216.104(a)(11)). The 2004 NDAA 

amended the MMPA as it relates to 

military readiness activities and the 

incidental take authorization process 

such that ‘‘least practicable impact’’ 

shall include consideration of personnel 

safety, practicality of implementation, 

and impact on the effectiveness of the 

military readiness activity. 

In evaluating how mitigation may or 

may not be appropriate to ensure the 

least practicable adverse impact on 

species or stocks and their habitat, as 

well as subsistence uses where 

applicable, NMFS considers two 

primary factors: 

(1) The manner in which, and the 

degree to which, the successful 

implementation of the measure(s) is 

expected to reduce impacts to marine 

mammals, marine mammal species or 

stocks, and their habitat, as well as 

subsistence uses. This considers the 

nature of the potential adverse impact 

being mitigated (likelihood, scope, 

range). It further considers the 

likelihood that the measure will be 

effective if implemented (probability of 

accomplishing the mitigating result if 

implemented as planned), the 

likelihood of effective implementation 

(probability implemented as planned); 

and 

(2) The practicability of the measures 

for applicant implementation, which 

may consider such things as cost, 

impact on operations, and, in the case 

of a military readiness activity, 

personnel safety, practicality of 

implementation, and impact on the 

effectiveness of the military readiness 

activity. 

The proposed IHA requires that 

appropriate personnel (including 

civilian personnel) involved in 

mitigation and training or testing 

activity reporting under the specified 

activities must complete Arctic 

Environmental and Safety Awareness 

Training. Modules include: Arctic 

Species Awareness and Mitigations, 

Environmental Considerations, 

Hazardous Materials Management, and 

General Safety. 

Further, the following general 

mitigation measures are required to 

prevent incidental take of ringed seals 

on the ice floe associated with the ice 

camp (further explanation of certain 

mitigation measures is provided in 

parentheses following the measure): 

• The ice camp and runway must be 

established on first-year and multi-year 

ice without pressure ridges. (This will 

minimize physical impacts to subnivean 

lairs and impacts to sea ice habitat 

suitable for lairs); 

• Ice camp deployment must begin no 

later than mid-February 2024, and be 

gradual, with activity increasing over 

the first 5 days. Camp deployment must 

be completed by March 15, 2024. (Given 

that mitigation measures require that the 

ice camp and runway be established on 

first-year or multi-year ice without 

pressure ridges, as well as the average 

ringed seal lair density in the area, and 

the relative footprint of the Navy’s 

planned ice camp (2 km2 0.8 mi2), it is 

extremely unlikely that a ringed seal 

would build a lair in the vicinity of the 

ice camp. Additionally, based on the 

best available science, Arctic ringed seal 

whelping is not expected to occur prior 

to mid-March, and therefore, 

construction of the ice camp will be 

completed prior to whelping in the area 

of ICEX24. Further, as noted above, 

ringed seal lairs are not expected to 

occur in the ice camp study area, and 

therefore, NMFS does not expect ringed 

seals to relocate pups due to human 

disturbance from ice camp activities, 

including construction); 

• Personnel on all on-ice vehicles 

must observe for marine and terrestrial 

animals; 

• Snowmobiles must follow 

established routes, when available. Onice vehicles must not be used to follow 

any animal, with the exception of 

actively deterring polar bears if the 

situation requires; 

• Personnel on foot and operating onice vehicles must avoid areas of deep 

snowdrifts near pressure ridges. (These 

areas are preferred areas for subnivean 

lair development); 

• Personnel must maintain a 100 m 

(328 ft) avoidance distance from all 

observed marine mammals; and 

• All material (e.g., tents, unused 

food, excess fuel) and wastes (e.g., solid 

waste, hazardous waste) must be 

removed from the ice floe upon 

completion of ICEX24 activities. 

The following mitigation measures are 

required for activities involving acoustic 

transmissions (further explanation of 

certain mitigation measures is provided 

in parentheses following the measure): 

• Personnel must begin passive 

acoustic monitoring (PAM) for 

vocalizing marine mammals 15 minutes 

prior to the start of activities involving 

active acoustic transmissions from 


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submarines. (This PAM would be 

conducted for the area around the 

submarine in real time by technicians 

on board the submarine.); 

• Personnel must delay active 

acoustic transmissions if a marine 

mammal is detected during pre-activity 

PAM and must shutdown active 

acoustic transmissions if a marine 

mammal is detected during acoustic 

transmissions; and 

• Personnel must not restart acoustic 

transmissions until 15 minutes have 

passed with no marine mammal 

detections. 

Ramp up procedures for acoustic 

transmissions are not required as the 

Navy determined, and NMFS concurs, 

that they would result in impacts on 

military readiness and on the realism of 

training that would be impracticable. 

The following mitigation measures are 

required for aircraft activities to prevent 

incidental take of marine mammals due 

to the presence of aircraft and associated 

noise. 

• Fixed wing aircraft must operate at 

the highest altitudes practicable taking 

into account safety of personnel, 

meteorological conditions, and need to 

support safe operations of a drifting ice 

camp. Aircraft must not reduce altitude 

if a seal is observed on the ice. In 

general, cruising elevation must be 305 

m (1,000 ft) or higher; 

• Unmanned Aircraft Systems (UAS) 

must maintain a minimum altitude of at 

least 15.2 m (50 ft) above the ice. They 

must not be used to track or follow 

marine mammals; 

• Helicopter flights must use 

prescribed transit corridors when 

traveling to or from Prudhoe Bay and 

the ice camp. Helicopters must not 

hover or circle above marine mammals 

or within 457 m (1,500 ft) of marine 

mammals; 

• Aircraft must maintain a minimum 

separation distance of 1.6 km (1 mi) 

from groups of 5 or more seals; and 

• Aircraft must not land on ice within 

800 m (0.5 mi) of hauled-out seals. 

Based on our evaluation of the 

applicant’s proposed measures, as well 

as other measures considered by NMFS, 

NMFS has preliminarily determined 

that the proposed mitigation measures 

provide the means of effecting the least 

practicable impact on the affected 

species or stocks and their habitat, 

paying particular attention to rookeries, 

mating grounds, and areas of similar 

significance. 

Proposed Monitoring and Reporting 

In order to issue an IHA for an 

activity, section 101(a)(5)(D) of the 

MMPA states that NMFS must set forth 

requirements pertaining to the 

monitoring and reporting of such taking. 

The MMPA implementing regulations at 

50 CFR 216.104(a)(13) indicate that 

requests for authorizations must include 

the suggested means of accomplishing 

the necessary monitoring and reporting 

that will result in increased knowledge 

of the species and of the level of taking 

or impacts on populations of marine 

mammals that are expected to be 

present while conducting the activities. 

Effective reporting is critical both to 

compliance as well as ensuring that the 

most value is obtained from the required 

monitoring. 

Monitoring and reporting 

requirements prescribed by NMFS 

should contribute to improved 

understanding of one or more of the 

following: 

• Occurrence of marine mammal 

species or stocks in the area in which 

take is anticipated (e.g., presence, 

abundance, distribution, density); 

• Nature, scope, or context of likely 

marine mammal exposure to potential 

stressors/impacts (individual or 

cumulative, acute or chronic), through 

better understanding of: (1) action or 

environment (e.g., source 

characterization, propagation, ambient 

noise); (2) affected species (e.g., life 

history, dive patterns); (3) co-occurrence 

of marine mammal species with the 

activity; or (4) biological or behavioral 

context of exposure (e.g., age, calving or 

feeding areas); 

• Individual marine mammal 

responses (behavioral or physiological) 

to acoustic stressors (acute, chronic, or 

cumulative), other stressors, or 

cumulative impacts from multiple 

stressors; 

• How anticipated responses to 

stressors impact either: (1) long-term 

fitness and survival of individual 

marine mammals; or (2) populations, 

species, or stocks; 

• Effects on marine mammal habitat 

(e.g., marine mammal prey species, 

acoustic habitat, or other important 

physical components of marine 

mammal habitat); and 

• Mitigation and monitoring 

effectiveness. 

The Navy has coordinated with NMFS 

to develop an overarching program, the 

Integrated Comprehensive Monitoring 

Program (ICMP), intended to coordinate 

marine species monitoring efforts across 

all regions and to allocate the most 

appropriate level and type of effort for 

each range complex based on a set of 

standardized objectives, and in 

acknowledgement of regional expertise 

and resource availability. The ICMP was 

created in direct response to Navy 

requirements established in various 

MMPA regulations and ESA 

consultations. As a framework 

document, the ICMP applies by 

regulation to those activities on ranges 

and operating areas for which the Navy 

is seeking or has sought incidental take 

authorizations. 

The ICMP is focused on Navy training 

and testing ranges where the majority of 

Navy activities occur regularly, as those 

areas have the greatest potential for 

being impacted by the Navy’s activities. 

In comparison, ICEX is a short duration 

exercise that occurs approximately 

every other year. Due to the location and 

expeditionary nature of the ice camp, 

the number of personnel on site is 

extremely limited and is constrained by 

the requirement to be able to evacuate 

all personnel in a single day with small 

planes. As such, the Navy asserts that a 

dedicated ICMP monitoring project is 

not feasible as it would require 

additional personnel and equipment, 

and NMFS concurs. However, the Navy 

is exploring the potential of 

implementing an environmental DNA 

(eDNA) study on ice seals. 

Nonetheless, the Navy must conduct 

the following monitoring and reporting 

under the IHA. Ice camp personnel must 

generally monitor for marine mammals 

in the vicinity of the ice camp and 

record all observations of marine 

mammals, regardless of distance from 

the ice camp, as well as the additional 

data indicated below. Additionally, 

Navy personnel must conduct PAM 

during all active sonar use. Ice camp 

personnel must also maintain an 

awareness of the surrounding 

environment and document any 

observed marine mammals. 

In addition, the Navy is required to 

provide NMFS with a draft exercise 

monitoring report within 90 days of the 

conclusion of the specified activity. A 

final report must be prepared and 

submitted within 30 calendar days 

following receipt of any NMFS 

comments on the draft report. If no 

comments are received from NMFS 

within 30 calendar days of receipt of the 

draft report, the report shall be 

considered final. The report, at 

minimum, must include: 

• Marine mammal monitoring effort 

(dedicated hours); 

• Ice camp activities occurring during 

each monitoring period (e.g., 

construction, demobilization, safety 

watch, field parties); 

• Number of marine mammals 

detected; 

• Upon observation of a marine 

mammal, record the following 

information: 

Æ Environmental conditions when 

animal was observed, including relevant 

weather conditions such as cloud cover, 


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snow, sun glare, and overall visibility, 

and estimated observable distance; 

Æ Lookout location and ice camp 

activity at time of sighting (or location 

and activity of personnel who made 

observation, if observed outside of 

designated monitoring periods); 

Æ Time and approximate location of 

sighting; 

Æ Identification of the animal(s) (e.g., 

seal, or unidentified), also noting any 

identifying features; 

Æ Distance and location of each 

observed marine mammal relative to the 

ice camp location for each sighting; 

Æ Estimated number of animals (min/ 

max/best estimate); and 

Æ Description of any marine mammal 

behavioral observations (e.g., observed 

behaviors such as traveling), including 

an assessment of behavioral responses 

thought to have resulted from the 

activity (e.g., no response or changes in 

behavioral state such as ceasing feeding, 

changing direction, flushing). 

Also, all sonar usage will be collected 

via the Navy’s Sonar Positional 

Reporting System database. The Navy is 

required to provide data regarding sonar 

use and the number of shutdowns 

during ICEX24 activities in the Atlantic 

Fleet Training and Testing (AFTT) 

Letter of Authorization 2024 annual 

classified report. The Navy is also 

required to analyze any declassified 

underwater recordings collected during 

ICEX24 for marine mammal 

vocalizations and report that 

information to NMFS, including the 

types and nature of sounds heard (e.g., 

clicks, whistles, creaks, burst pulses, 

continuous, sporadic, strength of signal) 

and the species or taxonomic group (if 

determinable). This information will 

also be submitted to NMFS with the 

2024 annual AFTT declassified 

monitoring report. 

Finally, in the event that personnel 

discover an injured or dead marine 

mammal, personnel must report the 

incident to OPR, NMFS and to the 

Alaska regional stranding network as 

soon as feasible. The report must 

include the following information: 

• Time, date, and location (latitude/ 

longitude) of the first discovery (and 

updated location information if known 

and applicable); 

• Species identification (if known) or 

description of the animal(s) involved; 

• Condition of the animal(s) 

(including carcass condition if the 

animal is dead); 

• Observed behaviors of the 

animal(s), if alive; 

• If available, photographs or video 

footage of the animal(s); and 

• General circumstances under which 

the animal(s) was discovered (e.g., 

during submarine activities, observed 

on ice floe, or by transiting aircraft). 

Negligible Impact Analysis and 

Determination 

NMFS has defined negligible impact 

as an impact resulting from the 

specified activity that cannot be 

reasonably expected to, and is not 

reasonably likely to, adversely affect the 

species or stock through effects on 

annual rates of recruitment or survival 

(50 CFR 216.103). A negligible impact 

finding is based on the lack of likely 

adverse effects on annual rates of 

recruitment or survival (i.e., populationlevel effects). An estimate of the number 

of takes alone is not enough information 

on which to base an impact 

determination. In addition to 

considering estimates of the number of 

marine mammals that might be ‘‘taken’’ 

through harassment, NMFS considers 

other factors, such as the likely nature 

of any impacts or responses (e.g., 

intensity, duration), the context of any 

impacts or responses (e.g., critical 

reproductive time or location, foraging 

impacts affecting energetics), as well as 

effects on habitat, and the likely 

effectiveness of the mitigation. We also 

assess the number, intensity, and 

context of estimated takes by evaluating 

this information relative to population 

status. Consistent with the 1989 

preamble for NMFS’ implementing 

regulations (54 FR 40338; September 29, 

1989), the impacts from other past and 

ongoing anthropogenic activities are 

incorporated into this analysis via their 

impacts on the baseline (e.g., as 

reflected in the regulatory status of the 

species, population size and growth rate 

where known, ongoing sources of 

human-caused mortality, or ambient 

noise levels). 

Underwater acoustic transmissions 

associated with ICEX24, as outlined 

previously, have the potential to result 

in Level B harassment of ringed seals in 

the form of TTS and behavioral 

disturbance. No take by Level A 

harassment, serious injury, or mortality 

are anticipated to result from this 

activity. Further, at close ranges and 

high sound levels approaching those 

that could cause PTS, seals would likely 

avoid the area immediately around the 

sound source. 

NMFS anticipates that take of ringed 

seals by TTS could occur from the 

submarine activities. TTS is a temporary 

impairment of hearing and can last from 

minutes or hours to days (in cases of 

strong TTS). In many cases, however, 

hearing sensitivity recovers rapidly after 

exposure to the sound ends. This 

activity has the potential to result in 

only minor levels of TTS, and hearing 

sensitivity of affected animals would be 

expected to recover quickly. Though 

TTS may occur as indicated, the overall 

fitness of the impacted individuals is 

unlikely to be affected given the 

temporary nature of TTS and the minor 

levels of TTS expected from these 

activities. Negative impacts on the 

reproduction or survival of affected ring 

seals as well as impacts on the stock are 

not anticipated. 

Effects on individuals that are taken 

by Level B harassment by behavioral 

disturbance could include alteration of 

dive behavior, alteration of foraging 

behavior, effects to breathing, 

interference with or alteration of 

vocalization, avoidance, and flight. 

More severe behavioral responses are 

not anticipated due to the localized, 

intermittent use of active acoustic 

sources and mitigation using PAM, 

which would limit exposure to active 

acoustic sources. Most likely, 

individuals would be temporarily 

displaced by moving away from the 

sound source. As described previously 

in the Acoustic Impacts section, seals 

exposed to non-impulsive sources with 

a received sound pressure level within 

the range of calculated exposures, (142– 

193 dB re 1 mPa), have been shown to 

change their behavior by modifying 

diving activity and avoidance of the 

sound source (Go ̈tz et al. 2010; 

Kvadsheim et al. 2010). Although a 

minor change to a behavior may occur 

as a result of exposure to the sound 

sources associated with the proposed 

specified activity, these changes would 

be within the normal range of behaviors 

for the animal (e.g., the use of a 

breathing hole further from the source, 

rather than one closer to the source). 

Further, given the limited number of 

total instances of takes and the 

unlikelihood that any single individuals 

would be taken repeatedly, multiple 

times over sequential days, these takes 

are unlikely to impact the reproduction 

or survival of any individuals. 

The Navy’s proposed activities are 

localized and of relatively short 

duration. While the total ICEX24 Study 

Area is large, the Navy expects that most 

activities would occur within the Ice 

Camp Study Area in relatively close 

proximity to the ice camp. The larger 

Navy Activity Study Area depicts the 

range where submarines may maneuver 

during the exercise. The ice camp 

would be in existence for up to 6 weeks 

with acoustic transmission occurring 

intermittently over approximately 4 

weeks. 

The project is not expected to have 

significant adverse effects on marine 

mammal habitat. The project activities 

are limited in time and would not 


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modify physical marine mammal 

habitat. While the activities may cause 

some fish to leave a specific area 

ensonified by acoustic transmissions, 

temporarily impacting marine 

mammals’ foraging opportunities, these 

fish would likely return to the affected 

area. As such, the impacts to marine 

mammal habitat are not expected to 

cause significant or long-term negative 

consequences. 

For on-ice activity, Level A 

harassment, Level B harassment, serious 

injury, and mortality are not 

anticipated, given the nature of the 

activities, the lack of previous ringed 

seal observations, and the mitigation 

measures NMFS has proposed to 

include in the IHA. The ringed seal 

pupping season on the ice lasts for 5 to 

9 weeks during late winter and spring. 

As stated in the Potential Effects of 

Specified Activities on Marine 

Mammals and Their Habitat section, 

March 1 is generally expected to be the 

onset of ice seal lairing season. The ice 

camp and runway would be established 

on first-year ice or multi-year ice 

without pressure ridges, as ringed seals 

tend to build their lairs near pressure 

ridges. Ice camp deployment will begin 

no later than mid-February, and be 

gradual, with activity increasing over 

the first 5 days. Ice camp deployment 

will be completed by March 15, before 

the pupping season. Displacement of 

seal lair construction or relocation to 

existing lairs outside of the ice camp 

area is unlikely, given the low average 

density of lairs (the average ringed seal 

lair density in the vicinity of Prudhoe 

Bay, Alaska is 1.58 lairs per km2 (Table 

4) the relative footprint of the Navy’s 

planned ice camp (2 km2; 0.77 mi2), the 

lack of previous ringed seal observations 

on the ice during ICEX activities, and 

mitigation requirements that require the 

Navy to construct the ice camp and 

runway on first-year or multi-year ice 

without pressure ridges and require 

personnel to avoid areas of deep snow 

drift or pressure ridges. 

Given that mitigation measures 

require that the ice camp and runway be 

established on first-year or multi-year 

ice without pressure ridges, where 

ringed seals tend to build their lairs, it 

is extremely unlikely that a ringed seal 

would build a lair in the vicinity of the 

ice camp. This measure, together with 

the other mitigation measures required 

for operation of the ice camp, are 

expected to avoid impacts to the 

construction and use of ringed seal 

subnivean lairs, particularly given the 

already low average density of lairs, as 

described above. Given that ringed seal 

lairs are not expected to occur in the ice 

camp study area, NMFS would not 

expect ringed seals to relocate pups due 

to human disturbance from ice camp 

activities. 

Additional mitigation measures 

would also prevent damage to and 

disturbance of ringed seals and their 

lairs that could otherwise result from 

on-ice activities. Personnel on on-ice 

vehicles would observe for marine 

mammals, and would follow established 

routes when available, to avoid 

potential damage to or disturbance of 

lairs. Personnel on foot and operating 

on-ice vehicles would avoid deep snow 

drifts near pressure ridges, also to avoid 

potential damage to or disturbance of 

lairs. Further, personnel would 

maintain a 100 m (328 ft) distance from 

all observed marine mammals to avoid 

disturbing the animals due to the 

personnel’s presence. Implementation of 

these measures would prevent ringed 

seal lairs from being crushed or 

damaged during ICEX24 activities. 

In summary and as described above, 

the following factors primarily support 

our preliminary determination that the 

impacts resulting from this activity are 

not expected to adversely affect any of 

the species or stocks through effects on 

annual rates of recruitment or survival: 

• No Level A harassment (injury), 

serious injury, or mortality is 

anticipated or proposed for 

authorization; 

• Impacts would be limited to Level 

B harassment, primarily in the form of 

behavioral disturbance that results in 

minor changes in behavior; 

• TTS is expected to affect only a 

limited number of animals and is 

expected to be minor and short term; 

• The number of takes proposed to be 

authorized are low relative to the 

estimated abundances of the affected 

stock, even given the extent to which 

abundance is significantly 

underestimated; 

• Submarine training and testing 

activities would occur over only 4 

weeks of the total 6-week activity 

period; 

• There would be no loss or 

modification of ringed seal habitat and 

minimal, temporary impacts on prey; 

• Physical impacts to ringed seal 

subnivean lairs would be avoided; and 

• Mitigation requirements for ice 

camp activities would prevent impacts 

to ringed seals during the pupping 

season. 

Based on the analysis contained 

herein of the likely effects of the 

specified activity on marine mammals 

and their habitat, and taking into 

consideration the implementation of the 

proposed monitoring and mitigation 

measures, NMFS preliminarily finds 

that the total marine mammal take from 

the proposed activity will have a 

negligible impact on all affected marine 

mammal species or stocks. 

Unmitigable Adverse Impact Analysis 

and Determination 

In order to issue an IHA, NMFS must 

find that the specified activity will not 

have an ‘‘unmitigable adverse impact’’ 

on the subsistence uses of the affected 

marine mammal species or stocks by 

Alaskan Natives. NMFS has defined 

‘‘unmitigable adverse impact’’ in 50 CFR 

216.103 as an impact resulting from the 

specified activity: (1) That is likely to 

reduce the availability of the species to 

a level insufficient for a harvest to meet 

subsistence needs by: (i) Causing the 

marine mammals to abandon or avoid 

hunting areas; (ii) Directly displacing 

subsistence users; or (iii) Placing 

physical barriers between the marine 

mammals and the subsistence hunters; 

and (2) That cannot be sufficiently 

mitigated by other measures to increase 

the availability of marine mammals to 

allow subsistence needs to be met. 

Impacts to marine mammals from the 

specified activity would mostly include 

limited, temporary behavioral 

disturbances of ringed seals; however, 

some TTS is also anticipated. No Level 

A harassment (injury), serious injury, or 

mortality of marine mammals is 

expected or proposed for authorization, 

and the activities are not expected to 

have any impacts on reproductive or 

survival rates of any marine mammal 

species. 

The specified activity and associated 

harassment of ringed seals would not be 

expected to impact marine mammals in 

numbers or locations sufficient to 

reduce their availability for subsistence 

harvest given the short-term, temporary 

nature of the activities, and the distance 

offshore from known subsistence 

hunting areas. The specified activity 

would occur for a brief period of time 

outside of the primary subsistence 

hunting season, and though seals are 

harvested for subsistence uses off the 

North Slope of Alaska, the ICEX24 

Study Area is seaward of known 

subsistence hunting areas. (The Study 

Area boundary is approximately 50 km 

from shore at the closest point, though 

exercises will occur farther offshore.) 

The Navy proposes to provide 

advance public notice to local residents 

and other users of the Prudhoe Bay 

region of Navy activities and measures 

used to reduce impacts on resources. 

This includes notification to local 

Alaska Natives who hunt marine 

mammals for subsistence. If any Alaska 

Natives express concerns regarding 

project impacts to subsistence hunting 

of marine mammals, the Navy would 


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further communicate with the 

concerned individuals or community. 

The Navy would provide project 

information and clarification of the 

mitigation measures that will reduce 

impacts to marine mammals. 

Based on the description of the 

specified activity, the measures 

described to minimize adverse effects 

on the availability of marine mammals 

for subsistence purposes, and the 

proposed mitigation and monitoring 

measures, NMFS has preliminarily 

determined that there will not be an 

unmitigable adverse impact on 

subsistence uses from the Navy’s 

proposed activities. 

Endangered Species Act 

Section 7(a)(2) of the Endangered 

Species Act of 1973 (ESA; 16 U.S.C. 

1531 et seq.) requires that each Federal 

agency insure that any action it 

authorizes, funds, or carries out is not 

likely to jeopardize the continued 

existence of any endangered or 

threatened species or result in the 

destruction or adverse modification of 

designated critical habitat. To ensure 

ESA compliance for the issuance of 

IHAs, NMFS consults internally 

whenever we propose to authorize take 

for endangered or threatened species, in 

this case with NMFS’ Alaska Regional 

Office (AKRO). 

NMFS OPR is proposing to authorize 

take of ringed seals, which are listed 

under the ESA. OPR has requested a 

section 7 consultation with the AKRO 

for the issuance of this IHA. The Navy 

has also requested a section 7 

consultation with AKRO for ICEX Study 

Area activities. OPR will conclude the 

ESA consultation prior to reaching a 

determination regarding the proposed 

issuance of the authorization. 

Proposed Authorization 

As a result of these preliminary 

determinations, NMFS proposes to issue 

an IHA to the Navy for conducting 

submarine training and testing activities 

in the Arctic Ocean beginning in 

February 2024, provided the previously 

mentioned mitigation, monitoring, and 

reporting requirements are incorporated. 

A draft of the proposed IHA can be 

found at: https://

www.fisheries.noaa.gov/national/ 

marine-mammal-protection/incidentaltake-authorizations-military-readinessactivities. 

Request for Public Comments 

We request comment on our analyses, 

the proposed authorization, and any 

other aspect of this notice of proposed 

IHA for the proposed ICEX24 activities. 

We also request comment on the 

potential renewal of this proposed IHA 

as described in the paragraph below. 

Please include with your comments any 

supporting data or literature citations to 

help inform decisions on the request for 

this IHA or a subsequent renewal IHA. 

On a case-by-case basis, NMFS may 

issue a 1-time, 1-year renewal IHA 

following notice to the public providing 

an additional 15 days for public 

comments when (1) up to another year 

of identical or nearly identical activities 

as described in the Description of 

Proposed Activity section of this notice 

is planned or (2) the activities as 

described in the Description of 

Proposed Activity section of this notice 

would not be completed by the time the 

IHA expires and a renewal would allow 

for completion of the activities beyond 

that described in the Dates and Duration 

section of this notice, provided all of the 

following conditions are met: 

• A request for renewal is received no 

later than 60 days prior to the needed 

renewal IHA effective date (recognizing 

that the renewal IHA expiration date 

cannot extend beyond 1 year from 

expiration of the initial IHA); and 

• The request for renewal must 

include the following: 

(1) An explanation that the activities 

to be conducted under the requested 

renewal IHA are identical to the 

activities analyzed under the initial 

IHA, are a subset of the activities, or 

include changes so minor (e.g., 

reduction in pile size) that the changes 

do not affect the previous analyses, 

mitigation and monitoring 

requirements, or take estimates (with 

the exception of reducing the type or 

amount of take); and 

(2) A preliminary monitoring report 

showing the results of the required 

monitoring to date and an explanation 

showing that the monitoring results do 

not indicate impacts of a scale or nature 

not previously analyzed or authorized. 

• Upon review of the request for 

renewal, the status of the affected 

species or stocks, and any other 

pertinent information, NMFS 

determines that there are no more than 

minor changes in the activities, the 

proposed renewal timeframe does not 

significantly alter the agency’s initial 

impact findings, the mitigation and 

monitoring measures will remain the 

same and appropriate, and the findings 

in the initial IHA remain valid. 

Dated: December 4, 2023. 

Catherine Marzin, 

Acting Director, Office of Protected Resources, 

National Marine Fisheries Service. 

[FR Doc. 2023–26913 Filed 12–6–23; 8:45 am] 

BILLING CODE 3510–22–P 

DEPARTMENT OF COMMERCE 

National Oceanic and Atmospheric 

Administration 

Evaluation of Sapelo Island National 

Estuarine Research Reserve; Notice of 

Public Meeting; Request for Comments 

AGENCY: Office for Coastal Management, 

National Ocean Service, National 

Oceanic and Atmospheric 

Administration, Department of 

Commerce. 

ACTION: Notice of public meeting and 

opportunity to comment. 

SUMMARY: The National Oceanic and 

Atmospheric Administration (NOAA), 

Office for Coastal Management, will 

hold an in-person public meeting to 

solicit input on the performance 

evaluation of the Sapelo Island National 

Estuarine Research Reserve. NOAA also 

invites the public to submit written 

comments. 

DATES: NOAA will hold an in-person 

public meeting on Wednesday, February 

7, 2024, at 6:30 p.m. eastern. NOAA will 

consider all relevant written comments 

received by Friday, February 16, 2024. 

ADDRESSES: Comments may be 

submitted by one of the following 

methods: 

• In-Person Public Meeting: Provide 

oral comments during the in-person 

public meeting on Wednesday, February 

7, 2024, at 6:30 p.m. eastern at the 

Sapelo Island Visitor Center, 1766 

Landing Road Southeast, Darien, GA 

31305. 

• Email: Send written comments to 

Ralph Cantral, Evaluator, NOAA Office 

for Coastal Management, at 

Ralph.Cantral@noaa.gov. Include 

‘‘Comments on Performance Evaluation 

of Sapelo Island National Estuarine 

Research Reserve’’ in the subject line of 

the message. 

NOAA will accept anonymous 

comments; however, the written 

comments NOAA receives are 

considered part of the public record, 

and the entirety of the comment, 

including the name of the commenter, 

email address, attachments, and other 

supporting materials, will be publicly 

accessible. Sensitive personally 

identifiable information, such as 

account numbers and Social Security 

numbers, should not be included with 

the comments. Comments that are not 

related to the performance evaluation of 

the Sapelo Island National Estuarine 

Research Reserve or that contain 

profanity, vulgarity, threats, or other 

inappropriate language will not be 

considered. 


ddrumheller on DSK120RN23PROD with NOTICES1