91340 Federal Register / Vol. 89, No. 223 / Tuesday, November 19, 2024 / Notices 

22See Amended Final, 86 FR at 50326. 

publication of the final results of this 

review in the Federal Register. If a 

timely summons is filed at the U.S. 

Court of International Trade, the 

assessment instructions will direct CBP 

not to liquidate relevant entries until the 

time for parties to file a request for a 

statutory injunction has expired (i.e., 

within 90 days of publication). 

Cash Deposit Requirements 

The following cash deposit 

requirements will be effective for all 

shipments of the subject merchandise 

entered, or withdrawn from warehouse, 

for consumption on or after the 

publication date of the final results of 

this administrative review, as provided 

by section 751(a)(2)(C) of the Act: (1) the 

cash deposit rate for the companies 

under review will be equal to the 

weighted-average dumping margin 

established in the final results of this 

review, except if the rate is de minimis 

(i.e., less than 0.50 percent), in which 

case the cash deposit rate will be zero; 

(2) for previously reviewed or 

investigated companies not covered by 

this review, the cash deposit rate will 

continue to be the company-specific rate 

published for the most recentlycompleted segment of this proceeding in 

which they were examined; (3) if the 

exporter is not a firm covered in this 

review, a prior review, or the LTFV 

investigation, but the producer is, the 

cash deposit rate will be the rate 

established for the most recentlycompleted segment of this proceeding 

for the producer of the merchandise; 

and (4) the cash deposit rate for all other 

producers or exporters will continue to 

be 7.00 percent,22 the all-others rate 

established in the Amended Final. 

These cash deposit requirements, when 

imposed, shall remain in effect until 

further notice. 

Notification to Importers 

This notice also serves as a 

preliminary reminder to importers of 

their responsibility under 19 CFR 

351.402(f)(2) to file a certificate 

regarding the reimbursement of 

antidumping and/or countervailing 

duties prior to liquidation of the 

relevant entries during this review 

period. Failure to comply with this 

requirement could result in Commerce’s 

presumption that reimbursement of 

antidumping and/or countervailing 

duties occurred and the subsequent 

assessment of double antidumping 

duties, and/or an increase in the amount 

of antidumping duties by the amount of 

the countervailing duties. 

Notification to Interested Parties 

We are issuing and publishing these 

results in accordance with sections 

751(a)(1) and 777(i)(1) of the Act, and 19 

CFR 351.213 and 351.221(b)(4). 

Dated: November 6, 2024. 

Abdelali Elouaradia, 

Deputy Assistant Secretary for Enforcement 

and Compliance. 

Appendix I 

List of Topics Discussed in the Preliminary 

Decision Memorandum 

I. Summary 

II. Background 

III. Scope of the Order 

IV. Discussion of the Methodology 

V. Recommendation 

Appendix II 

List of Companies Not Selected for 

Individual Examination 

1. Balkrishna Steel Forge Pvt. Ltd. 

2. CD Industries (Prop. Kisaan Engineering 

Works Pvt. Ltd.) 

3. Echjay Forgings Private Limited 

4. Fivebros Forgings Private Limited 

5. Goodluck India Limited; Goodluck 

Engineering Co. 

6. Jai Auto Pvt. Ltd 

7. Jay Jagdamba Limited 

8. Jay Jagdamba Forgings Private Limited 

9. Kisaan Die Tech Private Limited 

10. Pradeep Metals Limited 

11. R.N. Gupta & Company Limited 

[FR Doc. 2024–26887 Filed 11–18–24; 8:45 am] 

BILLING CODE 3510–DS–P 

DEPARTMENT OF COMMERCE 

National Oceanic and Atmospheric 

Administration 

[RTID 0648–XE398] 

Takes of Marine Mammals Incidental to 

Specified Activities; Taking Marine 

Mammals Incidental to a Marine 

Geophysical Survey in the Northwest 

Gulf of Mexico 

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 University of Texas at Austin 

(UT) for authorization to take marine 

mammals incidental to a marine 

geophysical survey in coastal waters off 

Texas in the northwest (NW) Gulf of 

Mexico (GOM). 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 

the Request for Public Comments 

section 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. 

DATES: Comments and information must 

be received no later than December 19, 

2024. 

ADDRESSES: Comments should be 

addressed to Jolie Harrison, Chief, 

Permits and Conservation Division, 

Office of Protected Resources, National 

Marine Fisheries Service and should be 

submitted via email to 

ITP.wachtendonk@noaa.gov. Electronic 

copies of the application and supporting 

documents, as well as a list of the 

references cited in this document, may 

be obtained online at: https://

www.fisheries.noaa.gov/national/ 

marine-mammal-protection/incidentaltake-authorizations-research-and-otheractivities. In case of problems accessing 

these documents, please call the contact 

listed below. 

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: 

Rachel Wachtendonk, Office of 

Protected Resources, NMFS, (301) 427– 

8401. 

SUPPLEMENTARY INFORMATION: 

Background 

The MMPA prohibits the ‘‘take’’ of 

marine mammals, with certain 

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

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

seq.) direct the Secretary of Commerce 

(as delegated to NMFS) to allow, upon 

request, the incidental, but not 


ddrumheller on DSK120RN23PROD with NOTICES1
Federal Register / Vol. 89, No. 223 / Tuesday, November 19, 2024 / Notices 91341 

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 monitoring and 

reporting of the takings. The definitions 

of all applicable MMPA statutory terms 

used above are included in the relevant 

sections below and can be found in 

section 3 of the MMPA (16 U.S.C. 1362) 

and NMFS regulations at 50 CFR 

216.103. 

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. This action 

is consistent with categories of activities 

identified in Categorical Exclusion B4 

(IHAs with no anticipated serious injury 

or mortality) of the Companion Manual 

for NAO 216–6A, which do not 

individually or cumulatively have the 

potential for significant impacts on the 

quality of the human environment and 

for which we have not identified any 

extraordinary circumstances that would 

preclude this categorical exclusion. 

Accordingly, NMFS has preliminarily 

determined that the issuance of the 

proposed IHA qualifies to be 

categorically excluded from further 

NEPA review. 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 July 25, 2024, NMFS received a 

request from UT for an IHA to take 

marine mammals incidental to a marine 

geophysical survey in coastal waters off 

Texas in the NW GOM. The application 

was deemed adequate and complete on 

September 24, 2024. UT’s request is for 

take of bottlenose dolphins, Atlantic 

spotted dolphins, and rough-toothed 

dolphins by Level B harassment only. 

Neither UT nor NMFS expect serious 

injury or mortality to result from this 

activity and, therefore, an IHA is 

appropriate. 

Description of Proposed Activity 

Overview 

Researchers from UT propose to 

conduct a low-energy marine seismic 

survey using airguns as the acoustic 

source from the research vessel (R/V) 

Brooks McCall (McCall) or similar 

vessel operated by TDI-Brooks 

International. The proposed survey 

would occur within Texas State waters 

in the NW GOM from approximately 

January to April 2025. The proposed 

survey would occur within the 

Exclusive Economic Zone (EEZ) of the 

United States and in Texas State waters, 

in water depths less than 30 meters (m). 

To complete this high resolution 3D 

(HR3D) seismic survey, the McCall 

would tow a 2-airgun array with a total 

discharge volume of ∼210 cubic inches 

(in3) at a depth of 3–4 m, with a shot 

interval of 12.5 m (5–10 seconds (s)) as 

the primary acoustic source. The airgun 

array receiver would consist of four 25- 

m-long solid-state hydrophone 

streamers, spaced 10 m apart. 

Approximately 4,440 km of seismic 

acquisition is proposed. The airgun 

array would introduce underwater 

sounds that may result in take, by Level 

B harassment, of marine mammals. 

The purpose of the proposed survey is 

to study the geologic section beneath the 

GOM for secure, long-term, large-scale 

carbon dioxide storage and enhanced 

hydrocarbon recovery. 

Dates and Duration 

The proposed survey is anticipated to 

take place from January to April 2025. 

The survey is expected to last 23 days, 

including approximately 20 days of 

seismic operations and 3 days of transit 

and equipment deployment. 

Specific Geographic Region 

The proposed survey would occur 

within approximately lat. 27.1–29.6° N, 

long. 93.6–97.4° W, the EEZ of the 

United States and in Texas State waters, 

in water depths less than 30 m. The 

primary study area is around the 10 m 

isobaths, and if no suitable sites are 

within Texas State waters, the alternate 

study area is on the outer continental 

shelf within the 30 m isobaths. The 

region where the survey is proposed to 

occur is depicted in figure 1; the 

tracklines could occur anywhere within 

the polygon shown in figure 1. The 

McCall would likely mobilize and 

demobilize from the nearest available 

port. 


ddrumheller on DSK120RN23PROD with NOTICES1
91342 Federal Register / Vol. 89, No. 223 / Tuesday, November 19, 2024 / Notices 

Detailed Description of the Specified 

Activity 

The procedures to be used for the 

proposed survey would be similar to 

those used during previous seismic 

surveys by UT and would use 

conventional seismic methodology. The 

survey would involve one source vessel, 

the McCall, or similar vessel operated 

by TDI-Brooks. During the low-energy 

HR3D seismic survey, the McCall would 

tow two Generator-Injector (GI) airguns 

with a total discharge volume of 210 in3. 

The airgun array would be deployed at 

a depth of about 3–4 m below the 

surface, spaced about 2 m apart, and 

have a shot interval of 12.5 m (about 5– 

10 s). The receiving system would 

consist of four 25-m solid-state 

hydrophone streamers, spaced 10 m 

apart and towed at a depth of 2 m. As 

the airguns are towed along the survey 

lines, the hydrophone streamer would 

transfer data to the on-board processing 

system. Approximately 4,440 km of 

seismic acquisition are planned. The 

survey would take place in water depths 

less than 30 m. 

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 1 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 

(M/SI) 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 


ddrumheller on DSK120RN23PROD with NOTICES1EN19NO24.000</GPH>

-• l!tollllllitv~ k<!IWIII~ :nitllil (Ult► 

1:!N~t-MIH 

•-1Ni<llll:ll:al1\111\1$ 

3l>llllli:iellll!li!N, 

1$~(11'\) 

Figure 1 -- Location of the Proposed Seismic Survey in the NW GOM 

~ 
Federal Register / Vol. 89, No. 223 / Tuesday, November 19, 2024 / Notices 91343 

stocks in this region are assessed in 

NMFS’ U.S. Atlantic and Gulf of Mexico 

SARs. All values presented in table 1 

are the most recent available at the time 

of publication (including from the draft 

2023 SARs) and are available online at: 

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

national/marine-mammal-protection/ 

marine-mammal-stock-assessments. 

TABLE 1—SPECIES 1 LIKELY AFFECTED BY THE SPECIFIED ACTIVITIES

Common name Scientific name Stock 

ESA/ 

MMPA 

status; 

strategic 

(Y/N) 2

Stock abundance 

(CV, Nmin, most 

recent abundance 

survey) 3

PBR Annual 

M/SI 4

GOM 

population 

abundance 5

Odontoceti (toothed whales, dolphins, and porpoises) 

Family Delphinidae: 

Atlantic spotted dolphin.Stenella frontalis ............. GOM ................................ -/-; N 21,506 (0.26; 

17,339; 2018).

166 .......................... 6 36 7 12,240 

Rough-toothed dolphin.Steno bredanensis .......... GOM ................................ -/-; N unk (n/a; unk; 2018) undetermined .......... 39 4,853 

Bottlenose dolphin .... Tursiops truncatus .......... GOM Western Coastal .... -/-; N 20,759 (0.13; 

18,585; 2018).

167 .......................... 36 7 151,886 

Northern GOM Continental Shelf.-/-; N 63,280 (0.11; 

57,917; 2018).

556 .......................... 5 65 

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/). 2ESA status: Endangered (E), Threatened (T)/MMPA status: Depleted (D). A dash (-) indicates that the species is not listed under the ESA or designated as depleted under the MMPA. Under the MMPA, a strategic stock is one for which the level of direct human-caused mortality exceeds PBR or which is determined to be 

declining and likely to be listed under the ESA within the foreseeable future. Any species or stock listed under the ESA is automatically designated under the MMPA 

as depleted and as a strategic stock. 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. In some cases, CV is not applicable. 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. 5 Model-predicted stock abundance for Atlantic spotted dolphins and bottlenose dolphins from the most recent GOM density models (Garrison et al., 2023). Stock 

abundance for rough-toothed dolphins was taken from Roberts et al. (2016) density models, as Garrison et al. (2023) did not create a model for this species. 6 M/SI is a minimum count and does not include projected mortality estimates for 2015–2019 due to the DWH oil spill. 

7This estimate includes both coastal and continental shelf bottlenose dolphins from other stocks. 

As indicated above, all three species 

(with four managed stocks) in table 1 

temporally and spatially co-occur with 

the activity to the degree that take is 

reasonably likely to occur. All species 

that could potentially occur in the 

proposed survey areas are included in 

table 2 of the IHA application. While the 

additional 11 species listed in table 2 of 

UT’s application have been infrequently 

sighted in the survey 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. Species or stocks that 

only occur in deep waters (>200 m) 

within the GOM are unlikely to be 

observed during this survey where the 

maximum water depth is 30 m, and 

thus, the following species or stocks 

will not be considered further: offshore 

stock of bottlenose dolphins, 

pantropical spotted dolphin, spinner 

dolphin, striped dolphin, Clymene 

dolphin, Fraser’s dolphin, Risso’s 

dolphin, melon-headed whale, pygmy 

killer whale, false killer whale, killer 

whale, and short-finned pilot whale. 

Bottlenose Dolphin 

Bottlenose dolphins are cosmopolitan, 

occurring in tropical, subtropical, and 

temperate waters around the world 

(Wells and Scott 2018). The bottlenose 

dolphin is the most widespread and 

common delphinid in coastal waters of 

the GOM (Wu ̈rsig et al., 2000; Wu ̈rsig 

2017). While there are multiple stocks of 

bottlenose dolphins in the GOM, only 

the Northern GOM Continental Shelf 

and GOM Western Coastal stocks 

overlap with the study area, with the 

shelf stock assumed to occur in waters 

>20 m and the coastal stock assumed to 

occur in waters <20 m. Fall sightings 

have been made throughout the 

northern Gulf but primarily on the shelf, 

including within survey waters. Five 

sightings totaling 12 animals were made 

during a UT geophysical survey on the 

Texas shelf during March 2024, which 

is within the proposed study area. All 

sightings were made in water <20 m 

deep (RPS 2024). 

There are 31 bay, sound, and estuary 

(BSE) stocks in the northern GOM, 

which are small, resident populations of 

bottlenose dolphins that live inshore or, 

occasionally, close to shore or in passes, 

and are genetically discrete. There are 

two of the BSE stocks that occur near 

the survey area, the West Bay stock and 

the Galveston Bay/East Bay/Trinity Bay 

stock. These areas in and near West Bay 

and Galveston Bay, along with 

numerous other ones along the coast of 

Texas, have been identified as yearround Biologically Important Areas 

(BIAs) for resident bottlenose dolphins 

(LeBrecque et al., 2015). Due to the 

distance that the survey will occur off 

the coast (between 1 and 115 km) and 

general expectation that BSE dolphins 

are most likely to occur in inshore 

waters and around passes into inshore 

waters, we do not expect the survey to 

encounter any BSE stocks of bottlenose 

dolphins. 

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.). On October 24, 2024, 

NMFS published (89 FR 84872) the final 

Updated Technical Guidance, which 

includes updated thresholds and 

weighting functions to inform auditory 

injury estimates, and has replaced the 

2018 Technical Guidance used 

previously (NMFS 2018). The updated 

hearing groups are presented below 

(table 2). The references, analysis, and 

methodology used in the development 


ddrumheller on DSK120RN23PROD with NOTICES1

I I I I 
91344 Federal Register / Vol. 89, No. 223 / Tuesday, November 19, 2024 / Notices 

of the hearing groups are described in 

NMFS’ 2024 Technical Guidance, which 

may be accessed at: https://

www.fisheries.noaa.gov/national/ 

marine-mammal-protection/marinemammal-acoustic-technical-guidance. 

TABLE 2—MARINE MAMMAL HEARING GROUPS

[NMFS, 2024] 

Hearing group ∧ Generalized hearing 

range * 

Underwater: 

Low-frequency (LF) cetaceans (baleen whales) .................................................................................................................. 7 Hz to 36 * kHz.+

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

Very High-frequency (VHF) cetaceans (true porpoises, Kogia, river dolphins, Cephalorhynchid, Lagenorhynchus 

cruciger & L. australis).

200 Hz to 165 kHz. 

Phocid pinnipeds (PW) (underwater) (true seals) ............................................................................................................... 40 Hz to 90 kHz. 

Otariid pinnipeds (OW) (underwater) (sea lions and fur seals) ........................................................................................... 60 Hz to 68 kHz. 

∧Southall et al., 2019 indicates that as more data become available there may be separate hearing group designations for Very Low-Frequency cetaceans (blue, fin, right, and bowhead whales) and Mid-Frequency cetaceans (sperm, killer, and beaked whales). However, at this 

point, all baleen whales are part of the LF cetacean hearing group, and sperm, killer, and beaked whales are part of the HF cetacean hearing 

group. Additionally, recent data indicates that as more data become available for Monachinae seals, separate hearing group designations may 

be appropriate for the two phocid subfamilies (Ruscher et al., 2021; Sills et al., 2021). 

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

hearing ranges may not be as broad. Generalized hearing range chosen based on ∼65 dB threshold from composite audiogram, previous analysis in NMFS 2018, and/or data from Southall et al., 2007; Southall et al., 2019. Additionally, animals are able to detect very loud sounds above 

and below that ‘‘generalized’’ hearing range. + NMFS is aware that the National Marine Mammal Foundation successfully collected preliminary hearing data on two minke whales during 

their third field season (2023) in Norway. These data have implications for not only the generalized hearing range for low-frequency cetaceans 

but also on their weighting function. However, at this time, no official results have been published. Furthermore, a fourth field season (2024) is 

proposed, where more data will likely be collected. Thus, it is premature for us to propose any changes to our current Updated Technical Guidance. However, mysticete hearing data is identified as a special circumstance that could merit re-evaluating the acoustic criteria in this document. Therefore, we anticipate that once the data from both field seasons are published, it will likely necessitate updating this document (i.e., 

likely after the data gathered in the summer 2024 field season and associated analysis are published). 

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 Active Acoustic Sound 

Sources 

This section contains a brief technical 

background on sound, the 

characteristics of certain sound types, 

and on metrics used in this proposal 

inasmuch as the information is relevant 

to the specified activity and to a 

discussion of the potential effects of the 

specified activity on marine mammals 

found later in this document. 

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 hertz 

(Hz) or cycles per second. Wavelength is 

the distance between two peaks or 

corresponding points of a sound wave 

(length of 1 cycle). Higher frequency 

sounds have shorter wavelengths than 

lower frequency sounds, and typically 

attenuate (decrease) more rapidly, 

except in certain cases in shallower 

water. Amplitude is the height of the 

sound pressure wave or the ‘‘loudness’’ 

of a sound and is typically described 

using the relative unit of the dB. A 

sound pressure level (SPL) in dB is 

described as the ratio between a 

measured pressure and a reference 

pressure (for underwater sound, this is 

1 micropascal (mPa)) and is a 

logarithmic unit that accounts for large 

variations in amplitude; therefore, a 

relatively small change in dB 

corresponds to large changes in sound 

pressure. The source level (SL) 

represents the SPL referenced at a 

distance of 1 m from the source 

(referenced to 1 mPa) while the received 

level is the SPL at the listener’s position 

(referenced to 1 mPa). 

Root mean square (RMS) is the 

quadratic mean sound pressure over the 

duration of an impulse. Root mean 

square is calculated by squaring all of 

the sound amplitudes, averaging the 

squares, and then taking the square root 

of the average (Urick, 1983). Root mean 

square 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. 

Sound exposure level (SEL; 

represented as dB re 1 mPa2¥s) 

represents the total energy contained 

within a pulse and considers both 

intensity and duration of exposure. Peak 

sound pressure (also referred to as zeroto-peak sound pressure or 0-p) is the 

maximum instantaneous sound pressure 

measurable in the water at a specified 

distance from the source and is 

represented in the same units as the 

RMS sound pressure. Another common 

metric is peak-to-peak sound pressure 

(pk-pk), which is the algebraic 

difference between the peak positive 

and peak negative sound pressures. 

Peak-to-peak pressure is typically 

approximately 6 dB higher than peak 

pressure (Southall et al., 2007). 

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 a manner similar 

to ripples on the surface of a pond and 

may be either directed in a beam or 

beams or may radiate in all directions 


ddrumheller on DSK120RN23PROD with NOTICES1
Federal Register / Vol. 89, No. 223 / Tuesday, November 19, 2024 / Notices 91345 

1Please refer to the information given previously 

(‘‘Description of Active Acoustic Sound Sources’’) 

regarding sound, characteristics of sound types, and 

metrics used in this document. 

(omnidirectional sources), as is the case 

for pulses produced by the airgun array 

considered here. 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., 

wind and waves, earthquakes, ice, 

atmospheric sound), biological (e.g., 

sounds produced by marine mammals, 

fish, and invertebrates), and 

anthropogenic (e.g., vessels, dredging, 

construction) sound. 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 sound for frequencies between 

200 Hz and 50 kHz (Mitson, 1995). In 

general, ambient sound levels tend to 

increase with increasing wind speed 

and wave height. Surf sound becomes 

important near shore, with 

measurements collected at a distance of 

8.5 km from shore showing an increase 

of 10 dB in the 100 to 700 Hz band 

during heavy surf conditions; 

Precipitation: Sound from rain and 

hail impacting the water surface can 

become an important component of total 

sound at frequencies above 500 Hz, and 

possibly down to 100 Hz during quiet 

times; 

Biological: Marine mammals can 

contribute significantly to ambient 

sound levels, as can some fish and 

snapping shrimp. The frequency band 

for biological contributions is from 

approximately 12 Hz to over 100 kHz; 

and 

Anthropogenic: Sources of 

anthropogenic sound related to human 

activity include transportation (surface 

vessels), dredging and construction, oil 

and gas drilling and production, seismic 

surveys, sonar, explosions, and ocean 

acoustic studies. Vessel noise typically 

dominates the total ambient sound 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. 

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. 

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 human 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 this 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 a given activity 

may be a negligible addition to the local 

environment or could form a distinctive 

signal that may affect marine mammals. 

Details of source types are described in 

the following text. 

Sounds are often considered to fall 

into one of two general types: Pulsed 

and non-pulsed. 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., 

NMFS, 2018; Ward, 1997 in Southall et 

al., 2007). Please see Southall et al., 

(2007) for an in-depth discussion of 

these concepts. 

Pulsed sound sources (e.g., airguns, 

explosions, gunshots, sonic booms, 

impact pile driving) produce signals 

that are brief (typically considered to be 

less than 1 second), broadband, atonal 

transients (American National 

Standards Institute (ANSI), 1986, 2005; 

Harris, 1998; National Institute for 

Occupational Health and Safety 

(NIOSH), 1998; International 

Organization for Standardization (ISO), 

2003) and occur either as isolated events 

or repeated in some succession. Pulsed 

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. 

Non-pulsed 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 nonpulsed sounds can be transient signals 

of short duration but without the 

essential properties of pulses (e.g., rapid 

rise time). Examples of non-pulsed 

sounds include those produced by 

vessels, aircraft, machinery operations 

such as drilling or dredging, vibratory 

pile driving, and active sonar systems 

(such as those used by the U.S. Navy). 

The duration of such sounds, as 

received at a distance, can be greatly 

extended in a highly reverberant 

environment. 

Airgun arrays produce pulsed signals 

with energy in a frequency range from 

about 10–2,000 Hz, with most energy 

radiated at frequencies below 200 Hz. 

The amplitude of the acoustic wave 

emitted from the source is equal in all 

directions (i.e., omnidirectional), but 

airgun arrays do possess some 

directionality due to different phase 

delays between guns in different 

directions. Airgun arrays are typically 

tuned to maximize functionality for data 

acquisition purposes, meaning that 

sound transmitted in horizontal 

directions and at higher frequencies is 

minimized to the extent possible. 

Acoustic Effects 

Here, we discuss the effects of active 

acoustic sources on marine mammals. 

Potential Effects of Underwater 

Sound 1—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 

potentially result in one or more of the 

following: Temporary or permanent 

hearing impairment; non-auditory 

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; Go ̈tz 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 


ddrumheller on DSK120RN23PROD with NOTICES1
91346 Federal Register / Vol. 89, No. 223 / Tuesday, November 19, 2024 / Notices 

level sounds. Temporary or permanent 

loss of hearing, if it occurs at all, will 

occur almost exclusively in cases where 

a noise is within an animal’s hearing 

frequency range. We first describe 

specific manifestations of acoustic 

effects before providing discussion 

specific to the use of airgun arrays. 

Richardson et al. (1995) described 

zones of increasing intensity of effect 

that might be expected to occur, in 

relation to distance from a source and 

assuming that the signal is within an 

animal’s hearing range. First is the area 

within which the acoustic signal would 

be audible (potentially perceived) to the 

animal, but not strong enough to elicit 

any overt behavioral or physiological 

response. The next zone corresponds 

with the area where the signal is audible 

to the animal and of sufficient intensity 

to elicit behavioral or physiological 

response. Third is a zone within which, 

for signals of high intensity, the 

received level is sufficient to potentially 

cause discomfort or tissue damage to 

auditory or other systems. Overlaying 

these zones to a certain extent is the 

area within which masking (i.e., when a 

sound interferes with or masks the 

ability of an animal to detect a signal of 

interest that is above the absolute 

hearing threshold) may occur; the 

masking zone may be highly variable in 

size. 

We describe the more severe effects of 

certain non-auditory physical or 

physiological effects only briefly as we 

do not expect that use of airgun arrays 

are reasonably likely to result in such 

effects (see below for further 

discussion). Potential effects from 

impulsive sound sources can range in 

severity from effects such as behavioral 

disturbance or tactile perception to 

physical discomfort, slight injury of the 

internal organs and the auditory system, 

or mortality (Yelverton et al., 1973). 

Non-auditory physiological effects or 

injuries that theoretically might occur in 

marine mammals exposed to high level 

underwater sound or as a secondary 

effect of extreme behavioral reactions 

(e.g., change in dive profile as a result 

of an avoidance reaction) caused by 

exposure to sound include neurological 

effects, bubble formation, resonance 

effects, and other types of organ or 

tissue damage (Cox et al., 2006; Southall 

et al., 2007; Zimmer and Tyack, 2007; 

Tal et al., 2015). The survey activities 

considered here do not involve the use 

of devices such as explosives or midfrequency tactical sonar that are 

associated with these types of effects. 

Auditory Injury (AUD INJ) and 

Permanent Threshold Shift (PTS)— 

NMFS defines auditory injury as 

‘‘damage to the inner ear that can result 

in destruction of tissue . . . which may 

or may not result in PTS’’ (NMFS, 

2024). NMFS defines PTS as a 

permanent, irreversible increase in the 

threshold of audibility at a specified 

frequency or portion of an individual’s 

hearing range above a previously 

established reference level (NMFS, 

2024). PTS does not generally affect 

more than a limited frequency range, 

and an animal that has PTS has incurred 

some level of hearing loss at the relevant 

frequencies; typically, animals with PTS 

are not functionally deaf (Au and 

Hastings, 2008; Finneran, 2016). 

Available data from humans and other 

terrestrial mammals indicate that a 40- 

dB threshold shift approximates PTS 

onset (see Ward et al., 1958, 1959, 1960; 

Kryter et al., 1966; Miller, 1974; Ahroon 

et al., 1996; Henderson et al., 2008). PTS 

levels for marine mammals are 

estimates, as with the exception of a 

single study unintentionally inducing 

PTS in a harbor seal (Kastak et al., 

2008), there are no empirical data 

measuring PTS in marine mammals 

largely due to the fact that, for various 

ethical reasons, experiments involving 

anthropogenic noise exposure at levels 

inducing PTS are not typically pursued 

or authorized (NMFS, 2018). 

Temporary Threshold Shift (TTS). A 

temporary, reversible increase in the 

threshold of audibility at a specified 

frequency or portion of an individual’s 

hearing range above a previously 

established reference level (NMFS, 

2018). Based on data from marine 

mammal TTS measurements (see 

Southall et al., 2007, 2019), a TTS of 6 

dB is considered the minimum 

threshold shift clearly larger than any 

day-to-day or session-to-session 

variation in a subject’s normal hearing 

ability (Finneran et al., 2000, 2002; 

Schlundt et al., 2000). As described in 

Finneran (2015), marine mammal 

studies have shown the amount of TTS 

increases with SELcum in an accelerating 

fashion: at low exposures with lower 

SELcum, the amount of TTS is typically 

small and the growth curves have 

shallow slopes. At exposures with 

higher SELcum, the growth curves 

become steeper and approach linear 

relationships with the noise SEL. 

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 (similar to those discussed in 

auditory masking, below). 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 takes place during 

a time when the animal is traveling 

through the open ocean, 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. We 

note that reduced hearing sensitivity as 

a simple function of aging has been 

observed in marine mammals, as well as 

humans and other taxa (Southall et al., 

2007), so we can infer that strategies 

exist for coping with this condition to 

some degree, though likely not without 

cost. 

Many studies have examined noiseinduced hearing loss in marine 

mammals (see Finneran (2015) and 

Southall et al. (2019) for summaries). 

TTS is the mildest form of hearing 

impairment that can occur during 

exposure to sound (Kryter, 2013). 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. For 

cetaceans, published data on the onset 

of TTS are limited to captive bottlenose 

dolphin (Tursiops truncatus), beluga 

whale, harbor porpoise, and Yangtze 

finless porpoise (Neophocoena 

asiaeorientalis) (Southall et al., 2019). 

These studies examine hearing 

thresholds measured in marine 

mammals before and after exposure to 

intense or long-duration sound 

exposures. The difference between the 

pre-exposure and post-exposure 

thresholds can be used to determine the 

amount of threshold shift at various 

post-exposure times. 

The amount and onset of TTS 

depends on the exposure frequency. 

Sounds at low frequencies, well below 

the region of best sensitivity for a 

species or hearing group, are less 

hazardous than those at higher 

frequencies, near the region of best 

sensitivity (Finneran and Schlundt, 

2013). At low frequencies, onset-TTS 

exposure levels are higher compared to 

those in the region of best sensitivity 

(i.e., a low frequency noise would need 

to be louder to cause TTS onset when 

TTS exposure level is higher), as shown 

for harbor porpoises and harbor seals 

(Kastelein et al., 2019a, 2019c). Note 

that in general, harbor seals and harbor 

porpoises have a lower TTS onset than 

other measured pinniped or cetacean 

species (Finneran, 2015). In addition, 

TTS can accumulate across multiple 

exposures, but the resulting TTS will be 


ddrumheller on DSK120RN23PROD with NOTICES1
Federal Register / Vol. 89, No. 223 / Tuesday, November 19, 2024 / Notices 91347 

less than the TTS from a single, 

continuous exposure with the same SEL 

(Mooney et al., 2009; Finneran et al., 

2010; Kastelein et al., 2014, 2015). This 

means that TTS predictions based on 

the total, cumulative SEL will 

overestimate the amount of TTS from 

intermittent exposures, such as sonars 

and impulsive sources. Nachtigall et al. 

(2018) describe measurements of 

hearing sensitivity of multiple 

odontocete species (bottlenose dolphin, 

harbor porpoise, beluga, and false killer 

whale (Pseudorca crassidens)) when a 

relatively loud sound was preceded by 

a warning sound. These captive animals 

were shown to reduce hearing 

sensitivity when warned of an 

impending intense sound. Based on 

these experimental observations of 

captive animals, the authors suggest that 

wild animals may dampen their hearing 

during prolonged exposures or if 

conditioned to anticipate intense 

sounds. Another study showed that 

echolocating animals (including 

odontocetes) might have anatomical 

specializations that might allow for 

conditioned hearing reduction and 

filtering of low-frequency ambient 

noise, including increased stiffness and 

control of middle ear structures and 

placement of inner ear structures 

(Ketten et al., 2021). Data available on 

noise-induced hearing loss for 

mysticetes are currently lacking (NMFS, 

2018). Additionally, the existing marine 

mammal TTS data come from a limited 

number of individuals within these 

species. 

Relationships between TTS and PTS 

thresholds have not been studied in 

marine mammals, and there is no PTS 

data for cetaceans. However, such 

relationships are assumed to be similar 

to those in humans and other terrestrial 

mammals. PTS typically occurs at 

exposure levels at least several dB above 

that inducing mild TTS (e.g., a 40-dB 

threshold shift approximates PTS onset 

(Kryter et al., 1966; Miller, 1974), while 

a 6-dB threshold shift approximates TTS 

onset (Southall et al., 2007, 2019). Based 

on data from terrestrial mammals, a 

precautionary assumption is that the 

PTS thresholds for impulsive sounds 

(such as impact pile driving pulses as 

received close to the source) are at least 

6 dB higher than the TTS threshold on 

a peak-pressure basis, and PTS 

cumulative sound exposure level 

thresholds are 15 to 20 dB higher than 

TTS cumulative sound exposure level 

thresholds (Southall et al., 2007, 2019). 

Given the higher level of sound or 

longer exposure duration necessary to 

cause PTS as compared with TTS, it is 

considerably less likely that PTS could 

occur. 

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, 2019; 

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). Observed 

responses of wild marine mammals to 

loud pulsed 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). However, many 

delphinids approach acoustic source 

vessels with no apparent discomfort or 

obvious behavioral change (e.g., 

Barkaszi et al., 2012). 

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 briefly reacts to 

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, 

2005). 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; Ng and Leung, 

2003; Nowacek et al., 2004; Goldbogen 

et al., 2013a, b). Variations in dive 

behavior may reflect disruptions 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 


ddrumheller on DSK120RN23PROD with NOTICES1
91348 Federal Register / Vol. 89, No. 223 / Tuesday, November 19, 2024 / Notices 

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

2004; Madsen et al., 2006; Yazvenko et 

al., 2007). A determination of whether 

foraging disruptions affect 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. 

Visual tracking, passive acoustic 

monitoring (PAM), and movement 

recording tags were used to quantify 

sperm whale behavior prior to, during, 

and following exposure to airgun arrays 

at received levels in the range 140–160 

dB at distances of 7–13 km, following a 

phase-in of sound intensity and full 

array exposures at 1–13 km (Madsen et 

al., 2006; Miller et al., 2009). Sperm 

whales did not exhibit horizontal 

avoidance behavior at the surface. 

However, foraging behavior may have 

been affected. The sperm whales 

exhibited 19 percent less vocal, or buzz, 

rate during full exposure relative to post 

exposure, and the whale that was 

approached most closely had an 

extended resting period and did not 

resume foraging until the airguns had 

ceased firing. The remaining whales 

continued to execute foraging dives 

throughout exposure; however, 

swimming movements during foraging 

dives were 6 percent lower during 

exposure than control periods (Miller et 

al., 2009). These data raise concerns that 

seismic surveys may impact foraging 

behavior in sperm whales, although 

more data are required to understand 

whether the differences were due to 

exposure or natural variation in sperm 

whale behavior (Miller et al., 2009). 

Changes in respiration naturally vary 

with different behaviors and alterations 

to breathing rate as a function of 

acoustic exposure can be expected to cooccur 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, 

2005, 2006; Gailey et al., 2007, 2016). 

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 or amplitude of 

calls (Miller et al., 2000; Fristrup et al., 

2003; Foote et al., 2004; Holt et al., 

2012), 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). 

Cerchio et al. (2014) used PAM to 

document the presence of singing 

humpback whales off the coast of 

northern Angola and to 

opportunistically test for the effect of 

seismic survey activity on the number of 

singing whales. Two recording units 

were deployed between March and 

December 2008 in the offshore 

environment; numbers of singers were 

counted every hour. Generalized 

Additive Mixed Models were used to 

assess the effect of survey day 

(seasonality), hour (diel variation), 

moon phase, and received levels of 

noise (measured from a single pulse 

during each 10 minutes sampled period) 

on singer number. The number of 

singers significantly decreased with 

increasing received level of noise, 

suggesting that humpback whale 

communication was disrupted to some 

extent by the survey activity. 

Castellote et al. (2012) reported 

acoustic and behavioral changes by fin 

whales in response to shipping and 

airgun noise. Acoustic features of fin 

whale song notes recorded in the 

Mediterranean Sea and northeast 

Atlantic Ocean were compared for areas 

with different shipping noise levels and 

traffic intensities and during a seismic 

airgun survey. During the first 72 hours 

of the survey, a steady decrease in song 

received levels and bearings to singers 

indicated that whales moved away from 

the acoustic source and out of the study 

area. This displacement persisted for a 

time period well beyond the 10-day 

duration of seismic airgun activity, 

providing evidence that fin whales may 

avoid an area for an extended period in 

the presence of increased noise. The 

authors hypothesize that fin whale 

acoustic communication is modified to 

compensate for increased background 

noise and that a sensitization process 

may play a role in the observed 

temporary displacement. 

Seismic pulses at average received 

levels of 131 dB re 1 mPa2-s caused blue 

whales to increase call production (Di 

Iorio and Clark, 2010). In contrast, 

McDonald et al. (1995) tracked a blue 

whale with seafloor seismometers and 

reported that it stopped vocalizing and 

changed its travel direction at a range of 

10 km from the acoustic source vessel 

(estimated received level 143 dB pk-pk). 

Blackwell et al., (2013) found that 

bowhead whale call rates dropped 

significantly at onset of airgun use at 

sites with a median distance of 41–45 

km from the survey. Blackwell et al. 

(2015) expanded this analysis to show 

that whales actually increased calling 

rates as soon as airgun signals were 

detectable before ultimately decreasing 

calling rates at higher received levels 

(i.e., 10-minute cumulative sound 

exposure level (SELcum) of ∼127 dB). 

Overall, these results suggest that 

bowhead whales may adjust their vocal 

output in an effort to compensate for 

noise before ceasing vocalization effort 

and ultimately deflecting from the 

acoustic source (Blackwell et al., 2013, 

2015). These studies demonstrate that 

even low levels of noise received far 

from the source can induce changes in 

vocalization and/or behavior for 

mysticetes. 

Avoidance is the displacement of an 

individual from an area or migration 

path as a result of the presence of 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). Humpback 

whales show avoidance behavior in the 

presence of an active seismic array 

during observational studies and 

controlled exposure experiments in 

western Australia (McCauley et al., 

2000). Avoidance may be short-term, 

with animals returning to the area once 

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

1994; Goold, 1996; Stone et al., 2000; 

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., Bejder et al., 2006; Teilmann et al., 

2006). 

Forney et al. (2017) detail the 

potential effects of noise on marine 

mammal populations with high site 

fidelity, including displacement and 

auditory masking, noting that a lack of 

observed response does not imply 

absence of fitness costs and that 


ddrumheller on DSK120RN23PROD with NOTICES1
Federal Register / Vol. 89, No. 223 / Tuesday, November 19, 2024 / Notices 91349 

apparent tolerance of disturbance may 

have population-level impacts that are 

less obvious and difficult to document. 

Avoidance of overlap between 

disturbing noise and areas and/or times 

of particular importance for sensitive 

species may be critical to avoiding 

population-level impacts because 

(particularly for animals with high site 

fidelity) there may be a strong 

motivation to remain in the area despite 

negative impacts. Forney et al., (2017) 

state that, for these animals, remaining 

in a disturbed area may reflect a lack of 

alternatives rather than a lack of effects. 

Forney et al. (2017) specifically 

discuss beaked whales, stating that until 

recently most knowledge of beaked 

whales was derived from strandings, as 

they have been involved in atypical 

mass stranding events associated with 

mid-frequency active sonar (MFAS) 

training operations. Given these 

observations and recent research, 

beaked whales appear to be particularly 

sensitive and vulnerable to certain types 

of acoustic disturbance relative to most 

other marine mammal species. 

Individual beaked whales reacted 

strongly to experiments using simulated 

MFAS at low received levels, by moving 

away from the sound source and 

stopping foraging for extended periods. 

These responses, if on a frequent basis, 

could result in significant fitness costs 

to individuals (Forney et al., 2017). 

Additionally, difficulty in detection of 

beaked whales due to their cryptic 

surfacing behavior and silence when 

near the surface pose problems for 

mitigation measures employed to 

protect beaked whales. Forney et al., 

(2017) specifically states that failure to 

consider both displacement of beaked 

whales from their habitat and noise 

exposure could lead to more severe 

biological consequences. 

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 5-day 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 

1 diel cycle or recur on subsequent days 

(Southall et al., 2007). Consequently, a 

behavioral response lasting less than 1 

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. 

Stone (2015) reported data from at-sea 

observations during 1,196 seismic 

surveys from 1994 to 2010. When arrays 

of large airguns (considered to be 500 

in3 or more in that study) were firing, 

lateral displacement, more localized 

avoidance, or other changes in behavior 

were evident for most odontocetes. 

However, significant responses to large 

arrays were found only for the minke 

whale and fin whale. Behavioral 

responses observed included changes in 

swimming or surfacing behavior, with 

indications that cetaceans remained 

near the water surface at these times. 

Cetaceans were recorded as feeding less 

often when large arrays were active. 

Behavioral observations of gray whales 

during a seismic survey monitored 

whale movements and respirations 

pre-, during, and post-seismic survey 

(Gailey et al., 2016). Behavioral state 

and water depth were the best ‘‘natural’’ 

predictors of whale movements and 

respiration and, after considering 

natural variation, none of the response 

variables were significantly associated 

with seismic survey or vessel sounds. 

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 sufficiently to restore 

normal function. 


ddrumheller on DSK120RN23PROD with NOTICES1
91350 Federal Register / Vol. 89, No. 223 / Tuesday, November 19, 2024 / Notices 

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). 

For example, Rolland et al., (2012) 

found that noise reduction from reduced 

ship traffic in the Bay of Fundy was 

associated with decreased stress in 

North Atlantic right whales. 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; 

Erbe et al., 2016). 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, 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, 

significant masking could disrupt 

behavioral patterns, which in turn could 

affect fitness for survival and 

reproduction. 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 

predicting 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., 

2007; Di Iorio and Clark, 2009; Holt et 

al., 2009). Masking may be less 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. 

Masking effects of pulsed sounds 

(even from large arrays of airguns) on 

marine mammal calls and other natural 

sounds are expected to be limited, 

although there are few specific data on 

this. Because of the intermittent nature 

and low duty cycle of seismic pulses, 

animals can emit and receive sounds in 

the relatively quiet intervals between 

pulses. However, in exceptional 

situations, reverberation occurs for 

much or all of the interval between 

pulses (e.g., Simard et al., 2005; Clark 

and Gagnon 2006), which could mask 

calls. Situations with prolonged strong 

reverberation are infrequent. However, 

it is common for reverberation to cause 

some lesser degree of elevation of the 

background level between airgun pulses 

(e.g., Gedamke 2011; Guerra et al., 2011, 

2016; Klinck et al., 2012; Guan et al., 

2015), and this weaker reverberation 

presumably reduces the detection range 

of calls and other natural sounds to 

some degree. Guerra et al., (2016) 

reported that ambient noise levels 

between seismic pulses were elevated as 

a result of reverberation at ranges of 50 

km from the seismic source. Based on 

measurements in deep water of the 

Southern Ocean, Gedamke (2011) 

estimated that the slight elevation of 

background noise levels during intervals 

between seismic pulses reduced blue 

and fin whale communication space by 

as much as 36–51 percent when a 

seismic survey was operating 450–2,800 

km away. Based on preliminary 

modeling, Wittekind et al., (2016) 

reported that airgun sounds could 

reduce the communication range of blue 

and fin whales 2,000 km from the 

seismic source. Nieukirk et al., (2012) 

and Blackwell et al., (2013) noted the 

potential for masking effects from 

seismic surveys on large whales. 

Some baleen and toothed whales are 

known to continue calling in the 

presence of seismic pulses, and their 

calls usually can be heard between the 

pulses (e.g., Nieukirk et al., 2012; Thode 

et al., 2012; Bro ̈ker et al., 2013; Sciacca 

et al., 2016). Cerchio et al., (2014) 

suggested that the breeding display of 

humpback whales off Angola could be 

disrupted by seismic sounds, as singing 

activity declined with increasing 

received levels. In addition, some 

cetaceans are known to change their 

calling rates, shift their peak 

frequencies, or otherwise modify their 

vocal behavior in response to airgun 

sounds (e.g., Di Iorio and Clark 2010; 

Castellote et al., 2012; Blackwell et al., 

2013, 2015). The hearing systems of 

baleen whales are more sensitive to lowfrequency sounds than are the ears of 

the small odontocetes that have been 

studied directly (e.g., MacGillivray et 

al., 2014). The sounds important to 

small odontocetes are predominantly at 

much higher frequencies than are the 

dominant components of airgun sounds, 

thus limiting the potential for masking. 

In general, masking effects of seismic 

pulses are expected to be minor, given 


ddrumheller on DSK120RN23PROD with NOTICES1
Federal Register / Vol. 89, No. 223 / Tuesday, November 19, 2024 / Notices 91351 

the normally intermittent nature of 

seismic pulses. 

Vessel Noise 

Vessel noise from the McCall could 

affect marine mammals in the proposed 

survey areas. Houghton et al., (2015) 

proposed that vessel speed is the most 

important predictor of received noise 

levels, and Putland et al., (2017) also 

reported reduced sound levels with 

decreased vessel speed. However, some 

energy is also produced at higher 

frequencies (Hermannsen et al., 2014); 

low levels of high-frequency sound from 

vessels has been shown to elicit 

responses in harbor porpoise (Dyndo et 

al., 2015). 

Vessel noise, through masking, can 

reduce the effective communication 

distance of a marine mammal if the 

frequency of the sound source is close 

to that used by the animal, and if the 

sound is present for a significant 

fraction of time (e.g., Richardson et al., 

1995; Clark et al., 2009; Jensen et al., 

2009; Gervaise et al., 2012; Hatch et al., 

2012; Rice et al., 2014; Dunlop 2015; 

Erbe et al., 2015; Jones et al., 2017; 

Putland et al., 2017). In addition to the 

frequency and duration of the masking 

sound, the strength, temporal pattern, 

and location of the introduced sound 

also play a role in the extent of the 

masking (Branstetter et al., 2013, 2016; 

Finneran and Branstetter 2013; Sills et 

al., 2017). Branstetter et al., (2013) 

reported that time-domain metrics are 

also important in describing and 

predicting masking. 

Baleen whales are thought to be more 

sensitive to sound at these low 

frequencies than are toothed whales 

(e.g., MacGillivray et al., 2014), possibly 

causing localized avoidance of the 

proposed survey area during seismic 

operations. Many odontocetes show 

considerable tolerance of vessel traffic, 

although they sometimes react at long 

distances if confined by ice or shallow 

water, if previously harassed by vessels, 

or have had little or no recent exposure 

to vessels (Richardson et al., 1995). 

Pirotta et al., (2015) noted that the 

physical presence of vessels, not just 

ship noise, disturbed the foraging 

activity of bottlenose dolphins. There is 

little data on the behavioral reactions of 

beaked whales to vessel noise, though 

they seem to avoid approaching vessels 

(e.g., Wu ̈rsig et al., 1998) or dive for an 

extended period when approached by a 

vessel (e.g., Kasuya, 1986). 

In summary, project vessel sounds 

would not be at levels expected to cause 

anything more than possible localized 

and temporary behavioral changes in 

marine mammals, and would not be 

expected to result in significant negative 

effects on individuals or at the 

population level. In addition, in all 

oceans of the world, large vessel traffic 

is currently so prevalent that it is 

commonly considered a usual source of 

ambient sound (NSF–USGS, 2011). 

Vessel Strike 

Vessel collisions with marine 

mammals, or vessel strikes, can result in 

death or serious injury of the animal. 

Wounds resulting from vessel strike 

may include massive trauma, 

hemorrhaging, broken bones, or 

propeller lacerations (Knowlton and 

Kraus, 2001). An animal at the surface 

may be struck directly by a vessel, a 

surfacing animal may hit the bottom of 

a vessel, or an animal just below the 

surface may be cut by a vessel’s 

propeller. Superficial strikes may not 

kill or result in the death of the animal. 

These interactions are typically 

associated with large whales (e.g., fin 

whales), which are occasionally found 

draped across the bulbous bow of large 

commercial vessels upon arrival in port. 

Although smaller cetaceans are more 

maneuverable in relation to large vessels 

than are large whales, they may also be 

susceptible to strike. The severity of 

injuries typically depends on the size 

and speed of the vessel, with the 

probability of death or serious injury 

increasing as vessel speed increases 

(Knowlton and Kraus, 2001; Laist et al., 

2001; Vanderlaan and Taggart, 2007; 

Conn and Silber, 2013). Impact forces 

increase with speed, as does the 

probability of a strike at a given distance 

(Silber et al., 2010; Gende et al., 2011). 

Pace and Silber (2005) also found that 

the probability of death or serious injury 

increased rapidly with increasing vessel 

speed. Specifically, the predicted 

probability of serious injury or death 

increased from 45 to 75 percent as 

vessel speed increased from 10 to 14 

knots (kn; 26 kilometers per hour (kph)), 

and exceeded 90 percent at 17 kn (31 

kph). Higher speeds during collisions 

result in greater force of impact, but 

higher speeds also appear to increase 

the chance of severe injuries or death 

through increased likelihood of 

collision by pulling whales toward the 

vessel (Clyne, 1999; Knowlton et al., 

1995). In a separate study, Vanderlaan 

and Taggart (2007) analyzed the 

probability of lethal mortality of large 

whales at a given speed, showing that 

the greatest rate of change in the 

probability of a lethal injury to a large 

whale as a function of vessel speed 

occurs between 8.6 and 15 kn (28 kph). 

The chances of a lethal injury decline 

from approximately 80 percent at 15 kn 

(28 kph) to approximately 20 percent at 

8.6 kn (16 kph). At speeds below 11.8 

kn (22 kph), the chances of lethal injury 

drop below 50 percent, while the 

probability asymptotically increases 

toward 100 percent above 15 kn (28 

kph). 

The McCall will travel at a speed of 

4–5 kn (7–9 kph) while towing seismic 

survey gear. At this speed, both the 

possibility of striking a marine mammal 

and the possibility of a strike resulting 

in serious injury or mortality are 

discountable. At average transit speed, 

the probability of serious injury or 

mortality resulting from a strike is less 

than 50 percent. However, the 

likelihood of a strike actually happening 

is again discountable. Vessel strikes, as 

analyzed in the studies cited above, 

generally involve commercial shipping, 

which is much more common in both 

space and time than is geophysical 

survey activity. Jensen and Silber (2004) 

summarized vessel strikes of large 

whales worldwide from 1975 to 2003 

and found that most collisions occurred 

in the open ocean and involved large 

vessels (e.g., commercial shipping). No 

such incidents were reported for 

geophysical survey vessels during that 

time period. 

It is possible for vessel strikes to occur 

while traveling at slow speeds. For 

example, a hydrographic survey vessel 

traveling at low speed (5.5 kn (10 kph)) 

while conducting mapping surveys off 

the central California coast struck and 

killed a blue whale in 2009. The State 

of California determined that the whale 

had suddenly and unexpectedly 

surfaced beneath the hull, with the 

result that the propeller severed the 

whale’s vertebrae, and that this was an 

unavoidable event. This strike 

represents the only such incident in 

approximately 540,000 hours of similar 

coastal mapping activity (p = 1.9 × 10¥6; 

95 percent confidence interval = 0–5.5 

× 10¥6; NMFS, 2013). In addition, a 

research vessel reported a fatal strike in 

2011 of a dolphin in the Atlantic, 

demonstrating that it is possible for 

strikes involving smaller cetaceans to 

occur. In that case, the incident report 

indicated that an animal apparently was 

struck by the vessel’s propeller as it was 

intentionally swimming near the vessel. 

While indicative of the type of unusual 

events that cannot be ruled out, neither 

of these instances represents a 

circumstance that would be considered 

reasonably foreseeable or that would be 

considered preventable. 

Although the likelihood of the vessel 

striking a marine mammal is low, we 

propose a robust vessel strike avoidance 

protocol (see Proposed Mitigation), 

which we believe eliminates any 

foreseeable risk of vessel strike during 

transit. We anticipate that vessel 


ddrumheller on DSK120RN23PROD with NOTICES1
91352 Federal Register / Vol. 89, No. 223 / Tuesday, November 19, 2024 / Notices 

collisions involving a seismic data 

acquisition vessel towing gear, while 

not impossible, represent unlikely, 

unpredictable events for which there are 

no preventive measures. Given the 

proposed mitigation measures, the 

relatively slow speed of the vessel 

towing gear, the presence of bridge crew 

watching for obstacles at all times 

(including marine mammals), and the 

presence of marine mammal observers, 

the possibility of vessel strike is 

discountable and, further, were a strike 

of a large whale to occur, it would be 

unlikely to result in serious injury or 

mortality. No incidental take resulting 

from vessel strike is anticipated, and 

this potential effect of the specified 

activity will not be discussed further in 

the following analysis. 

Stranding—When a living or dead 

marine mammal swims or floats onto 

shore and becomes ‘‘beached’’ or 

incapable of returning to sea, the event 

is a ‘‘stranding’’ (Geraci et al., 1999; 

Perrin and Geraci, 2002; Geraci and 

Lounsbury, 2005; NMFS, 2007). The 

legal definition for a stranding under the 

MMPA is that a marine mammal is dead 

and is on a beach or shore of the United 

States; or in waters under the 

jurisdiction of the United States 

(including any navigable waters); or a 

marine mammal is alive and is on a 

beach or shore of the United States and 

is unable to return to the water; on a 

beach or shore of the United States and, 

although able to return to the water, is 

in need of apparent medical attention; 

or in the waters under the jurisdiction 

of the United States (including any 

navigable waters), but is unable to 

return to its natural habitat under its 

own power or without assistance. 

Marine mammals strand for a variety 

of reasons, such as infectious agents, 

biotoxicosis, starvation, fishery 

interaction, vessel strike, unusual 

oceanographic or weather events, sound 

exposure, or combinations of these 

stressors sustained concurrently or in 

series. However, the cause or causes of 

most strandings are unknown (Geraci et 

al., 1976; Eaton, 1979; Odell et al., 1980; 

Best, 1982). Numerous studies suggest 

that the physiology, behavior, habitat 

relationships, age, or condition of 

cetaceans may cause them to strand or 

might predispose them to strand when 

exposed to another phenomenon. These 

suggestions are consistent with the 

conclusions of numerous other studies 

that have demonstrated that 

combinations of dissimilar stressors 

commonly combine to kill an animal or 

dramatically reduce its fitness, even 

though one exposure without the other 

does not produce the same result 

(Chroussos, 2000; Creel, 2005; DeVries 

et al., 2003; Fair and Becker, 2000; Foley 

et al., 2001; Moberg, 2000; Relyea, 

2005a; 2005b, Romero, 2004; Sih et al., 

2004). 

There is no conclusive evidence that 

exposure to airgun noise results in 

behaviorally-mediated forms of injury. 

Behaviorally-mediated injury (i.e., mass 

stranding events) has been primarily 

associated with beaked whales exposed 

to mid-frequency active (MFA) naval 

sonar. MFA sonar and the alerting 

stimulus used in Nowacek et al., (2004) 

are very different from the noise 

produced by airguns. One should 

therefore not expect the same reaction to 

airgun noise as to these other sources. 

It is important to distinguish between 

energy (loudness, measured in dB) and 

frequency (pitch, measured in Hz). In 

considering the potential impacts of 

mid-frequency components of airgun 

noise (1–10 kHz, where beaked whales 

can be expected to hear) on marine 

mammal hearing, one needs to account 

for the energy associated with these 

higher frequencies and determine what 

energy is truly ‘‘significant.’’ Although 

there is mid-frequency energy 

associated with airgun noise (as 

expected from a broadband source), 

airgun sound is predominantly below 1 

kHz (Breitzke et al., 2008; 

Tashmukhambetov et al., 2008; Tolstoy 

et al., 2009). As stated by Richardson et 

al., (1995), ‘‘[. . .] most emitted [seismic 

airgun] energy is at 10–120 Hz, but the 

pulses contain some energy up to 500– 

1,000 Hz.’’ Tolstoy et al., (2009) 

conducted empirical measurements, 

demonstrating that sound energy levels 

associated with airguns were at least 20 

dB lower at 1 kHz (considered ‘‘midfrequency’’) compared to higher energy 

levels associated with lower frequencies 

(below 300 Hz) (‘‘all but a small fraction 

of the total energy being concentrated in 

the 10–300 Hz range’’ [Tolstoy et al., 

2009]), and at higher frequencies (e.g., 

2.6–4 kHz), power might be less than 10 

percent of the peak power at 10 Hz 

(Yoder, 2002). Energy levels measured 

by Tolstoy et al., (2009) were even lower 

at frequencies above 1 kHz. In addition, 

as sound propagates away from the 

source, it tends to lose higher-frequency 

components faster than low-frequency 

components (i.e., low-frequency sounds 

typically propagate longer distances 

than high-frequency sounds) (Diebold et 

al., 2010). Although higher-frequency 

components of airgun signals have been 

recorded, it is typically in surfaceducting conditions (e.g., DeRuiter et al., 

2006; Madsen et al., 2006) or in shallow 

water, where there are advantageous 

propagation conditions for the higher 

frequency (but low-energy) components 

of the airgun signal (Hermannsen et al., 

2015). This should not be of concern 

because the likely behavioral reactions 

of beaked whales that can result in acute 

physical injury would result from noise 

exposure at depth (because of the 

potentially greater consequences of 

severe behavioral reactions). In 

summary, the frequency content of 

airgun signals is such that beaked 

whales will not be able to hear the 

signals well (compared to MFA sonar), 

especially at depth where we expect the 

consequences of noise exposure could 

be more severe. 

Aside from frequency content, there 

are other significant differences between 

MFA sonar signals and the sounds 

produced by airguns that minimize the 

risk of severe behavioral reactions that 

could lead to strandings or deaths at sea, 

e.g., significantly longer signal duration, 

horizontal sound direction, typical fast 

and unpredictable source movement. 

All of these characteristics of MFA 

sonar tend towards greater potential to 

cause severe behavioral or physiological 

reactions in exposed beaked whales that 

may contribute to stranding. Although 

both sources are powerful, MFA sonar 

contains significantly greater energy in 

the mid-frequency range, where beaked 

whales hear better. Short-duration, high 

energy pulses—such as those produced 

by airguns—have greater potential to 

cause damage to auditory structures 

(though this is unlikely for highfrequency cetaceans, as explained later 

in this document), but it is longer 

duration signals that have been 

implicated in the vast majority of 

beaked whale strandings. Faster, less 

predictable movements in combination 

with multiple source vessels are more 

likely to elicit a severe, potentially antipredator response. Of additional interest 

in assessing the divergent characteristics 

of MFA sonar and airgun signals and 

their relative potential to cause 

stranding events or deaths at sea is the 

similarity between the MFA sonar 

signals and stereotyped calls of beaked 

whales’ primary predator: the killer 

whale (Zimmer and Tyack, 2007). 

Although generic disturbance stimuli— 

as airgun noise may be considered in 

this case for beaked whales—may also 

trigger antipredator responses, stronger 

responses should generally be expected 

when perceived risk is greater, as when 

the stimulus is confused for a known 

predator (Frid and Dill, 2002). In 

addition, because the source of the 

perceived predator (i.e., MFA sonar) 

will likely be closer to the whales 

(because attenuation limits the range of 

detection of mid-frequencies) and 

moving faster (because it will be on 

faster-moving vessels), any antipredator 


ddrumheller on DSK120RN23PROD with NOTICES1
Federal Register / Vol. 89, No. 223 / Tuesday, November 19, 2024 / Notices 91353 

response would be more likely to be 

severe (with greater perceived predation 

risk, an animal is more likely to 

disregard the cost of the response; Frid 

and Dill, 2002). Indeed, when analyzing 

movements of a beaked whale exposed 

to playback of killer whale predation 

calls, Allen et al., (2014) found that the 

whale engaged in a prolonged, directed 

avoidance response, suggesting a 

behavioral reaction that could pose a 

risk factor for stranding. Overall, these 

significant differences between sound 

from MFA sonar and the mid-frequency 

sound component from airguns and the 

likelihood that MFA sonar signals will 

be interpreted in error as a predator are 

critical to understanding the likely risk 

of behaviorally-mediated injury due to 

seismic surveys. 

The available scientific literature also 

provides a useful contrast between 

airgun noise and MFA sonar regarding 

the likely risk of behaviorally-mediated 

injury. There is strong evidence for the 

association of beaked whale stranding 

events with MFA sonar use, and 

particularly detailed accounting of 

several events is available (e.g., a 2000 

Bahamas stranding event for which 

investigators concluded that MFA sonar 

use was responsible; Evans and 

England, 2001). D’Amico et al., (2009) 

reviewed 126 beaked whale mass 

stranding events over the period from 

1950 (i.e., from the development of 

modern MFA sonar systems) through 

2004. Of these, there were two events 

where detailed information was 

available on both the timing and 

location of the stranding and the 

concurrent nearby naval activity, 

including verification of active MFA 

sonar usage, with no evidence for an 

alternative cause of stranding. An 

additional 10 events were at minimum 

spatially and temporally coincident 

with naval activity likely to have 

included MFA sonar use and, despite 

incomplete knowledge of timing and 

location of the stranding or the naval 

activity in some cases, there was no 

evidence for an alternative cause of 

stranding. The U.S. Navy has publicly 

stated agreement that five such events 

since 1996 were associated in time and 

space with MFA sonar use, either by the 

U.S. Navy alone or in joint training 

exercises with the North Atlantic Treaty 

Organization. The U.S. Navy 

additionally noted that, as of 2017, a 

2014 beaked whale stranding event in 

Crete coincident with naval exercises 

was under review and had not yet been 

determined to be linked to sonar 

activities (U.S. Navy, 2017). Separately, 

the International Council for the 

Exploration of the Sea reported in 2005 

that, worldwide, there have been about 

50 known strandings, consisting mostly 

of beaked whales, with a potential 

causal link to MFA sonar (ICES, 2005). 

In contrast, very few such associations 

have been made to seismic surveys, 

despite widespread use of airguns as a 

geophysical sound source in numerous 

locations around the world. 

A review of possible stranding 

associations with seismic surveys 

(Castellote and Llorens, 2016) states 

that, ‘‘[s]peculation concerning possible 

links between seismic survey noise and 

cetacean strandings is available for a 

dozen events but without convincing 

causal evidence.’’ The authors’ search of 

available information found 10 events 

worth further investigation via a ranking 

system representing a rough metric of 

the relative level of confidence offered 

by the data for inferences about the 

possible role of the seismic survey in a 

given stranding event. Only three of 

these events involved beaked whales. 

Whereas D’Amico et al., (2009) used a 

1–5 ranking system, in which ‘‘1’’ 

represented the most robust evidence 

connecting the event to MFA sonar use, 

Castellote and Llorens (2016) used a 1– 

6 ranking system, in which ‘‘6’’ 

represented the most robust evidence 

connecting the event to the seismic 

survey. As described above, D’Amico et 

al., (2009) found that 2 events were 

ranked ‘‘1’’ and 10 events were ranked 

‘‘2’’ (i.e., 12 beaked whale stranding 

events were found to be associated with 

MFA sonar use). In contrast, Castellote 

and Llorens (2016) found that none of 

the three beaked whale stranding events 

achieved their highest ranks of 5 or 6. 

Of the 10 total events, none achieved 

the highest rank of 6. Two events were 

ranked as 5: one stranding in Peru 

involving dolphins and porpoises and a 

2008 stranding in Madagascar. This 

latter ranking can only be broadly 

associated with the survey itself, as 

opposed to use of seismic airguns. An 

investigation of this stranding event, 

which did not involve beaked whales, 

concluded that use of a high-frequency 

mapping system (12-kHz multibeam 

echosounder) was the most plausible 

and likely initial behavioral trigger of 

the event, which was likely exacerbated 

by several site- and situation-specific 

secondary factors. The review panel 

found that seismic airguns were used 

after the initial strandings and animals 

entering a lagoon system, that airgun 

use clearly had no role as an initial 

trigger, and that there was no evidence 

that airgun use dissuaded animals from 

leaving (Southall et al., 2013). 

However, one of these stranding 

events, involving two Cuvier’s beaked 

whales, was contemporaneous with and 

reasonably associated spatially with a 

2002 seismic survey in the Gulf of 

California conducted by LamontDoherty Earth Observatory (L–DEO), as 

was the case for the 2007 Gulf of Cadiz 

seismic survey discussed by Castellote 

and Llorens (also involving two Cuvier’s 

beaked whales). Neither event was 

considered a ‘‘true atypical mass 

stranding’’ (according to Frantzis (1998)) 

as used in the analysis of Castellote and 

Llorens (2016). While we agree with the 

authors that this lack of evidence should 

not be considered conclusive, it is clear 

that there is very little evidence that 

seismic surveys should be considered as 

posing a significant risk of acute harm 

to beaked whales or other high 

frequency cetaceans. We have 

considered the potential for the 

proposed surveys to result in marine 

mammal stranding and, based on the 

best available information, do not 

expect a stranding to occur. 

Entanglement—Entanglements occur 

when marine mammals become 

wrapped around cables, lines, nets, or 

other objects suspended in the water 

column. During seismic operations, 

numerous cables, lines, and other 

objects primarily associated with the 

airgun array and hydrophone streamers 

will be towed behind the McCall near 

the water’s surface. However, we are not 

aware of any cases of entanglement of 

marine mammals in seismic survey 

equipment. There are no meaningful 

entanglement risks posed by the 

proposed survey, and entanglement 

risks are not discussed further in this 

document. 

Anticipated Effects on Marine Mammal 

Habitat 

Effects to Prey—Marine mammal prey 

varies by species, season, and location 

and, for some, is not well documented. 

Fish react to sounds which are 

especially strong and/or intermittent 

low-frequency sounds, and behavioral 

responses such as flight or avoidance 

are the most likely effects. However, the 

reaction of fish to airguns depends on 

the physiological state of the fish, past 

exposures, motivation (e.g., feeding, 

spawning, migration), and other 

environmental factors. Several studies 

have demonstrated that airgun sounds 

might affect the distribution and 

behavior of some fishes, potentially 

impacting foraging opportunities or 

increasing energetic costs (e.g., Fewtrell 

and McCauley, 2012; Pearson et al., 

1992; Skalski et al., 1992; Santulli et al., 

1999; Paxton et al., 2017), though the 

bulk of studies indicate no or slight 

reaction to noise (e.g., Miller and 

Cripps, 2013; Dalen and Knutsen, 1987; 

Pena et al., 2013; Chapman and 


ddrumheller on DSK120RN23PROD with NOTICES1
91354 Federal Register / Vol. 89, No. 223 / Tuesday, November 19, 2024 / Notices 

Hawkins, 1969; Wardle et al., 2001; Sara 

et al., 2007; Jorgenson and Gyselman, 

2009; Blaxter et al., 1981; Cott et al., 

2012; Boeger et al., 2006), and that, most 

commonly, while there are likely to be 

impacts to fish as a result of noise from 

nearby airguns, such effects will be 

temporary. For example, investigators 

reported significant, short-term declines 

in commercial fishing catch rate of 

gadid fishes during and for up to 5 days 

after seismic survey operations, but the 

catch rate subsequently returned to 

normal (Engas et al., 1996; Engas and 

Lokkeborg, 2002). Other studies have 

reported similar findings (Hassel et al., 

2004). 

Skalski et al., (1992) also found a 

reduction in catch rates—for rockfish 

(Sebastes spp.) in response to controlled 

airgun exposure—but suggested that the 

mechanism underlying the decline was 

not dispersal but rather decreased 

responsiveness to baited hooks 

associated with an alarm behavioral 

response. A companion study showed 

that alarm and startle responses were 

not sustained following the removal of 

the sound source (Pearson et al., 1992). 

Therefore, Skalski et al., (1992) 

suggested that the effects on fish 

abundance may be transitory, primarily 

occurring during the sound exposure 

itself. In some cases, effects on catch 

rates are variable within a study, which 

may be more broadly representative of 

temporary displacement of fish in 

response to airgun noise (i.e., catch rates 

may increase in some locations and 

decrease in others) than any long-term 

damage to the fish themselves (Streever 

et al., 2016). 

SPLs of sufficient strength have been 

known to cause injury to fish and fish 

mortality and, in some studies, fish 

auditory systems have been damaged by 

airgun noise (McCauley et al., 2003; 

Popper et al., 2005; Song et al., 2008). 

However, in most fish species, hair cells 

in the ear continuously regenerate and 

loss of auditory function likely is 

restored when damaged cells are 

replaced with new cells. Halvorsen et 

al., (2012) showed that a TTS of 4–6 dB 

was recoverable within 24 hours for one 

species. Impacts would be most severe 

when the individual fish is close to the 

source and when the duration of 

exposure is long; both of which are 

conditions unlikely to occur for this 

survey that is necessarily transient in 

any given location and likely result in 

brief, infrequent noise exposure to prey 

species in any given area. For this 

survey, the sound source is constantly 

moving, and most fish would likely 

avoid the sound source prior to 

receiving sound of sufficient intensity to 

cause physiological or anatomical 

damage. In addition, ramp-up may 

allow certain fish species the 

opportunity to move further away from 

the sound source. 

A comprehensive review (Carroll et 

al., 2017) found that results are mixed 

as to the effects of airgun noise on the 

prey of marine mammals. While some 

studies suggest a change in prey 

distribution and/or a reduction in prey 

abundance following the use of seismic 

airguns, others suggest no effects or 

even positive effects in prey abundance. 

As one specific example, Paxton et al., 

(2017), which describes findings related 

to the effects of a 2014 seismic survey 

on a reef off of North Carolina, showed 

a 78 percent decrease in observed 

nighttime abundance for certain species. 

It is important to note that the evening 

hours during which the decline in fish 

habitat use was recorded (via video 

recording) occurred on the same day 

that the seismic survey passed, and no 

subsequent data is presented to support 

an inference that the response was longlasting. Additionally, given that the 

finding is based on video images, the 

lack of recorded fish presence does not 

support a conclusion that the fish 

actually moved away from the site or 

suffered any serious impairment. In 

summary, this particular study 

corroborates prior studies indicating 

that a startle response or short-term 

displacement should be expected. 

Available data suggest that 

cephalopods are capable of sensing the 

particle motion of sounds and detect 

low frequencies up to 1–1.5 kHz, 

depending on the species, and so are 

likely to detect airgun noise (Kaifu et al., 

2008; Hu et al., 2009; Mooney et al., 

2010; Samson et al., 2014). Auditory 

injuries (lesions occurring on the 

statocyst sensory hair cells) have been 

reported upon controlled exposure to 

low-frequency sounds, suggesting that 

cephalopods are particularly sensitive to 

low-frequency sound (Andre et al., 

2011; Sole et al., 2013). Behavioral 

responses, such as inking and jetting, 

have also been reported upon exposure 

to low-frequency sound (McCauley et 

al., 2000b; Samson et al., 2014). Similar 

to fish, however, the transient nature of 

the survey leads to an expectation that 

effects will be largely limited to 

behavioral reactions and would occur as 

a result of brief, infrequent exposures. 

A review article concluded that, while 

laboratory results provide scientific 

evidence for high-intensity and lowfrequency sound-induced physical 

trauma and other negative effects on 

some fish and invertebrates, the sound 

exposure scenarios in some cases are 

not realistic to those encountered by 

marine organisms during routine 

seismic operations (Carroll et al., 2017). 

The review finds that there has been no 

evidence of reduced catch or abundance 

following seismic activities for 

invertebrates, and that there is 

conflicting evidence for fish with catch 

observed to increase, decrease, or 

remain the same. Further, where there is 

evidence for decreased catch rates in 

response to airgun noise, these findings 

provide no information about the 

underlying biological cause of catch rate 

reduction (Carroll et al., 2017). 

In summary, impacts of the specified 

activity on marine mammal prey species 

will likely generally be limited to 

behavioral responses, the majority of 

prey species will be capable of moving 

out of the area during the survey, a 

rapid return to normal recruitment, 

distribution, and behavior for prey 

species is anticipated, and, overall, 

impacts to prey species will be minor 

and temporary. Prey species exposed to 

sound might move away from the sound 

source, experience TTS, experience 

masking of biologically relevant sounds, 

or show no obvious direct effects. 

Mortality from decompression injuries 

is possible in close proximity to a 

sound, but only limited data on 

mortality in response to airgun noise 

exposure are available (Hawkins et al., 

2014). The most likely impacts for most 

prey species in the survey area would be 

temporary avoidance of the area. The 

proposed survey would move through 

an area relatively quickly, limiting 

exposure to multiple impulsive sounds. 

In all cases, sound levels would return 

to ambient once the survey moves out 

of the area or ends and the noise source 

is shut down and, when exposure to 

sound ends, behavioral and/or 

physiological responses are expected to 

end relatively quickly (McCauley et al., 

2000b). The duration of fish avoidance 

of a given area after survey effort stops 

is unknown, but a rapid return to 

normal recruitment, distribution, and 

behavior is anticipated. While the 

potential for disruption of spawning 

aggregations or schools of important 

prey species can be meaningful on a 

local scale, the mobile and temporary 

nature of this survey and the likelihood 

of temporary avoidance behavior 

suggest that impacts would be minor. 

Acoustic Habitat—Acoustic habitat is 

the soundscape—which encompasses 

all of the sound present in a particular 

location and time, as a whole—when 

considered from the perspective of the 

animals experiencing it. Animals 

produce sound for, or listen for sounds 

produced by, conspecifics 

(communication during feeding, mating, 

and other social activities), other 

animals (finding prey or avoiding 


ddrumheller on DSK120RN23PROD with NOTICES1
Federal Register / Vol. 89, No. 223 / Tuesday, November 19, 2024 / Notices 91355 

predators), and the physical 

environment (finding suitable habitats, 

navigating). Together, sounds made by 

animals and the geophysical 

environment (e.g., produced by 

earthquakes, lightning, wind, rain, 

waves) make up the natural 

contributions to the total acoustics of a 

place. These acoustic conditions, 

termed acoustic habitat, are one 

attribute of an animal’s total habitat. 

Soundscapes are also defined by, and 

acoustic habitat influenced by, the total 

contribution of anthropogenic sound. 

This may include incidental emissions 

from sources such as vessel traffic, or 

may be intentionally introduced to the 

marine environment for data acquisition 

purposes (as in the use of airgun arrays). 

Anthropogenic noise varies widely in its 

frequency content, duration, and 

loudness and these characteristics 

greatly influence the potential habitatmediated effects to marine mammals 

(please see also the previous discussion 

on masking under Acoustic Effects), 

which may range from local effects for 

brief periods of time to chronic effects 

over large areas and for long durations. 

Depending on the extent of effects to 

habitat, animals may alter their 

communications signals (thereby 

potentially expending additional 

energy) or miss acoustic cues (either 

conspecific or adventitious). For more 

detail on these concepts see, e.g., Barber 

et al., 2010; Pijanowski et al., 2011; 

Francis and Barber, 2013; Lillis et al., 

2014. 

Problems arising from a failure to 

detect cues are more likely to occur 

when noise stimuli are chronic and 

overlap with biologically relevant cues 

used for communication, orientation, 

and predator/prey detection (Francis 

and Barber, 2013). Although the signals 

emitted by seismic airgun arrays are 

generally low frequency, they would 

also likely be of short duration and 

transient in any given area due to the 

nature of these surveys. As described 

previously, exploratory surveys such as 

these cover a large area but would be 

transient rather than focused in a given 

location over time and therefore would 

not be considered chronic in any given 

location. 

Based on the information discussed 

herein, we conclude that impacts of the 

specified activity are not likely to have 

more than short-term adverse effects on 

any prey habitat or populations of prey 

species. Further, any impacts to marine 

mammal habitat are not expected to 

result in significant or long-term 

consequences for individual marine 

mammals, or to contribute to adverse 

impacts on their populations. 

Estimated Take of Marine Mammals 

This section provides an estimate of 

the number of incidental takes proposed 

for authorization through the IHA, 

which will inform NMFS’ consideration 

of ‘‘small numbers,’’ the negligible 

impact determinations, and impacts on 

subsistence uses. 

Harassment is the only type of take 

expected to result from these activities. 

Except with respect to certain activities 

not pertinent here, section 3(18) of the 

MMPA defines ‘‘harassment’’ as any act 

of pursuit, torment, or annoyance, 

which (i) has the potential to injure a 

marine mammal or marine mammal 

stock in the wild (Level A harassment); 

or (ii) has the potential to disturb a 

marine mammal or marine mammal 

stock in the wild by causing disruption 

of behavioral patterns, including, but 

not limited to, migration, breathing, 

nursing, breeding, feeding, or sheltering 

(Level B harassment). 

Authorized takes would be by Level B 

harassment only, in the form of 

disruption of behavioral patterns for 

individual marine mammals resulting 

from exposure to sound from low energy 

seismic airguns. Based on the nature of 

the activity, i.e., use of a low energy 2- 

airgun array, auditory injury (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 likely 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 proposed 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 auditory 

injury of some degree (equated to Level 

A harassment). 

Level B Harassment—Though 

significantly driven by received level, 

the onset of behavioral disturbance from 

anthropogenic noise exposure is also 

informed to varying degrees by other 

factors related to the source or exposure 

context (e.g., frequency, predictability, 

duty cycle, duration of the exposure, 

signal-to-noise ratio, distance to the 

source), the environment (e.g., 

bathymetry, other noises in the area, 

predators in the area), and the receiving 

animals (hearing, motivation, 

experience, demography, life stage, 

depth) and can be difficult to predict 

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

et al., 2012). Based on what the 

available science indicates and the 

practical need to use a threshold based 

on a metric that is both predictable and 

measurable for most activities, NMFS 

typically uses a generalized acoustic 

threshold based on received level to 

estimate the onset of behavioral 

harassment. NMFS generally predicts 

that marine mammals are likely to be 

behaviorally harassed in a manner 

considered to be Level B harassment 

when exposed to underwater 

anthropogenic noise above root-meansquared pressure received levels (RMS 

SPL) of 120 dB (referenced to 1 

micropascal (re 1 mPa)) for continuous 

(e.g., vibratory pile driving, drilling) and 

above RMS SPL 160 dB re 1 mPa for nonexplosive impulsive (e.g., seismic 

airguns) or intermittent (e.g., scientific 

sonar) sources. Generally speaking, 

Level B harassment take estimates based 

on these behavioral harassment 

thresholds are expected to include any 

likely takes by TTS as, in most cases, 

the likelihood of TTS occurs at 

distances from the source less than 

those at which behavioral harassment is 

likely. TTS of a sufficient degree can 

manifest as behavioral harassment, as 

reduced hearing sensitivity and the 

potential reduced opportunities to 

detect important signals (conspecific 

communication, predators, prey) may 

result in changes in behavior patterns 

that would not otherwise occur. 

UT’s proposed survey includes the 

use of impulsive seismic sources (e.g., 

GI-airguns) and therefore, the 160 dB re 

1 mPa (rms) criteria is applicable for 

analysis of Level B harassment. 

Level A harassment—NMFS’ 

Technical Guidance for Assessing the 

Effects of Anthropogenic Sound on 

Marine Mammal Hearing (Version 2.0) 

(Technical Guidance, 2018) identifies 

dual criteria to assess auditory injury 


ddrumheller on DSK120RN23PROD with NOTICES1
91356 Federal Register / Vol. 89, No. 223 / Tuesday, November 19, 2024 / Notices 

(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). UT’s proposed survey 

includes the use of impulsive seismic 

sources (i.e. airguns). 

These thresholds are provided in the 

tables below. The references, analysis, 

and methodology used in the 

development of the thresholds are 

described in NMFS’ 2018 Updated 

Technical Guidance, which may be 

accessed at: https://

www.fisheries.noaa.gov/national/ 

marine-mammal-protection/marinemammal-acoustic-technical-guidance. 

TABLE 3—NMFS’ 2018 1 THRESHOLDS IDENTIFYING THE ONSET OF PERMANENT THRESHOLD SHIFT

[PTS] 

Hearing group 

PTS onset acoustic thresholds * 

(received level) 

Impulsive Non-impulsive 

Low-Frequency (LF) Cetaceans ............................................ Cell 1: Lpk,flat: 219 dB; LE,LF,24h: 183 dB ............................ Cell 2: LE,LF,24h: 199 dB. 

High-Frequency (HF) Cetaceans .......................................... Cell 3: Lpk,flat: 230 dB; LE,MF,24h: 185 dB ........................... Cell 4: LE,MF,24h: 198 dB. 

Very High-Frequency (VHF) Cetaceans ............................... Cell 5: Lpk,flat: 202 dB; LE,HF,24h: 155 dB ........................... Cell 6: LE,HF,24h: 173 dB. 

Phocid Pinnipeds (PW) (Underwater) ................................... Cell 7: Lpk,flat: 218 dB; LE,PW,24h: 185 dB ........................... Cell 8: LE,PW,24h: 201 dB. 

Otariid Pinnipeds (OW) (Underwater) ................................... Cell 9: Lpk,flat: 232 dB; LE,OW,24h: 203 dB .......................... Cell 10: LE,OW,24h: 219 dB. 

* Dual metric acoustic thresholds for impulsive sounds: Use whichever results in the largest isopleth for calculating PTS onset. If a non-impulsive sound has the potential of exceeding the peak sound pressure level thresholds associated with impulsive sounds, these thresholds should also be considered. 

Note: Peak sound pressure (Lpk) has a reference value of 1 μPa, and cumulative sound exposure level (LE) has a reference value of 1μPa2s. In this table, thresholds are abbreviated to reflect American National Standards Institute standards (ANSI, 2013). However, peak sound pressure is defined by ANSI as incorporating frequency weighting, which is not the intent for this Technical Guidance. Hence, the subscript ‘‘flat’’ is being included to indicate peak sound pressure should be flat 

weighted or unweighted within the generalized hearing range. The subscript associated with cumulative sound exposure level thresholds indicates the designated marine mammal auditory weighting function (LF, MF, and HF cetaceans, and PW and OW pinnipeds) and that the recommended accumulation period is 24 hours. The 

cumulative sound exposure level thresholds could be exceeded in a multitude of ways (i.e., varying exposure levels and durations, duty cycle). When possible, it is 

valuable for action proponents to indicate the conditions under which these acoustic thresholds will be exceeded. 1 UT previously used modeling based on NMFS’ 2018 technical guidance in order to calculate their isopleths. Based on the outcome of these comparisons/analyses 

using the Updated 2024 Technical Guidance, the low-frequency cetacean isopleth is slightly higher using the updated guidance, and the high-frequency cetacean and 

very-high frequency cetacean are the same as those calculated using the 2018 Technical Guidance. Therefore, the isopleths based on the 2018 Technical Guidance 

will be used as the basis for take numbers and mitigation zones for this IHA. 

Ensonified Area 

Here, we describe operational and 

environmental parameters of the activity 

that are used in estimating the area 

ensonified above the acoustic 

thresholds, including source levels and 

transmission loss coefficient. 

When the Technical Guidance was 

initially published (NMFS, 2016), in 

recognition of the fact that ensonified 

area/volume could be more technically 

challenging to predict because of the 

duration component in the new 

thresholds, we developed a user 

spreadsheet that includes tools to help 

predict a simple isopleth that can be 

used in conjunction with marine 

mammal density or occurrence to help 

predict takes. We note that because of 

some of the assumptions included in the 

methods used for these tools, we 

anticipate that isopleths produced are 

typically going to be overestimates of 

some degree, which may result in some 

degree of overestimation of Level A 

harassment take. However, these tools 

offer the best way to predict appropriate 

isopleths when more sophisticated 3D 

modeling methods are not available, and 

NMFS continues to develop ways to 

quantitatively refine these tools and will 

qualitatively address the output where 

appropriate. 

The proposed survey would entail the 

use up to two 105 in3 airguns with a 

maximum total discharge of 210 in3 at 

a tow depth of 3–4 m. UT used 

modeling by Lamont-Doherty Earth 

Observatory (L–DEO), which determines 

the 160 dBrms radius for the airgun 

source down to a maximum depth of 

2,000 m. Received sound levels have 

been predicted by L–DEO’s model 

(Diebold et al., 2010) as a function of 

distance from the 2-airgun array. This 

modeling approach uses ray tracing for 

the direct wave traveling from the array 

to the receiver and its associated source 

ghost (reflection at the air-water 

interface in the vicinity of the array), in 

a constant-velocity half-space (infinite 

homogeneous ocean layer, unbounded 

by a seafloor). 

The proposed low-energy survey 

would acquire data with up to two 105- 

in3 GI guns, towed in-line, at a depth of 

3–4 m. The shallow-water radii are 

obtained by scaling the empirically 

derived measurements from the GOM 

calibration survey to account for the 

differences in volume and tow depth 

between the calibration survey (6,600 

in3 at 6 m tow depth) and the proposed 

survey (210 in3 at 4 m tow depth). A 

simple scaling factor is calculated from 

the ratios of the isopleths calculated by 

the deep-water L–DEO model, which are 

essentially a measure of the energy 

radiated by the source array. 

L–DEO’s methodology is described in 

greater detail in UT’s IHA application. 

The estimated distances to the Level B 

harassment isopleth for the proposed 

airgun configuration are shown in table 

4. 

TABLE 4—PREDICTED RADIAL DISTANCES FROM THE R/V MCCALL SEISMIC SOURCE TO ISOPLETH CORRESPONDING TO

LEVEL B HARASSMENT THRESHOLD

Airgun configuration Max tow depth 

(m) 

Water depth 

(m) 

Predicted 

distances 

(in m) to 

the Level B 

harassment 

threshold 

2 105-in3 airguns ......................................................................................................................... 4 <100 1,750 


ddrumheller on DSK120RN23PROD with NOTICES1
Federal Register / Vol. 89, No. 223 / Tuesday, November 19, 2024 / Notices 91357 

TABLE 5—MODELED RADIAL DISTANCE

TO ISOPLETHS CORRESPONDING TO

LEVEL A HARASSMENT THRESHOLDS

[NMFS 2018] 

High 

frequency 

cetaceans 

PTS SELcum ............................. 0 

PTS Peak ................................. * 1.5 

* The largest distance of the dual criteria 

(SELcum or Peak) was used to estimate 

threshold distances and potential takes by 

Level A harassment. 

Table 5 presents the modeled Level A 

harassment isopleths for the highfrequency cetacean hearing group based 

on L–DEO modeling incorporated in the 

companion user spreadsheet, for the 

low-energy surveys with the shortest 

shot interval (i.e., greatest potential to 

cause auditory injury or PTS based on 

accumulated sound energy) (NMFS 

2018). Although NMFS’ 2024 Updated 

Technical Guidance was finalized on 

October 24, 2024 (89 FR 84872), there 

was no meaningful change in the 

auditory injury (Level A harassment) 

isopleths, so the values based on the 

2018 guidance was used here. 

Predicted distances to Level A 

harassment isopleths, which vary based 

on marine mammal hearing groups, 

were calculated based on modeling 

performed by L–DEO using the Nucleus 

software program and the NMFS user 

spreadsheet, described below. The 

acoustic thresholds for impulsive 

sounds contained in the NMFS 

Technical Guidance were presented as 

dual metric acoustic thresholds using 

both SELcum and peak sound pressure 

metrics (NMFS, 2024). As dual metrics, 

NMFS considers onset of PTS (Level A 

harassment) to have occurred when 

either one of the two metrics is 

exceeded (i.e., metric resulting in the 

largest isopleth). The SELcum metric 

considers both level and duration of 

exposure, as well as auditory weighting 

functions by marine mammal hearing 

group. 

The SELcum for the 2-airgun array is 

derived from calculating the modified 

farfield signature. The farfield signature 

is often used as a theoretical 

representation of the source level. To 

compute the farfield signature, the 

source level is estimated at a large 

distance (right) below the array (e.g., 9 

km), and this level is back projected 

mathematically to a notional distance of 

1 m from the array’s geometrical center. 

However, it has been recognized that the 

source level from the theoretical farfield 

signature is never physically achieved at 

the source when the source is an array 

of multiple airguns separated in space 

(Tolstoy et al., 2009). Near the source (at 

short ranges, distances <1 km), the 

pulses of sound pressure from each 

individual airgun in the source array do 

not stack constructively as they do for 

the theoretical farfield signature. The 

pulses from the different airguns spread 

out in time such that the source levels 

observed or modeled are the result of 

the summation of pulses from a few 

airguns, not the full array (Tolstoy et al., 

2009). At larger distances, away from 

the source array center, sound pressure 

of all the airguns in the array stack 

coherently, but not within one time 

sample, resulting in smaller source 

levels (a few dB) than the source level 

derived from the farfield signature. 

Because the farfield signature does not 

take into account the large array effect 

near the source and is calculated as a 

point source, the farfield signature is not 

an appropriate measure of the sound 

source level for large arrays. See UT’s 

application for further detail on acoustic 

modeling. 

Auditory injury is unlikely to occur 

for high-frequency cetaceans, given the 

very small modeled zones of injury for 

those species (all estimated zones are 

less than 10 m for high-frequency 

cetaceans), in the context of distributed 

source dynamics. 

In consideration of the received sound 

levels in the near-field as described 

above, we expect the potential for Level 

A harassment of high-frequency 

cetaceans to be de minimis, even before 

the likely moderating effects of aversion 

and/or other compensatory behaviors 

(e.g., Nachtigall et al., 2018) are 

considered. We do not anticipate that 

Level A harassment is a likely outcome 

for any high-frequency cetacean and do 

not propose to authorize any take by 

Level A harassment for these species. 

The Level A and Level B harassment 

estimates are based on a consideration 

of the number of marine mammals that 

could be within the area around the 

operating airgun array where received 

levels of sound ≥160 dB re 1 mPa rms 

are predicted to occur. The estimated 

numbers are based on the densities 

(numbers per unit area) of marine 

mammals expected to occur in the area 

in the absence of seismic surveys. To 

the extent that marine mammals tend to 

move away from seismic sources before 

the sound level reaches the criterion 

level and tend not to approach an 

operating airgun array, these estimates 

likely overestimate the numbers actually 

exposed to the specified level of sound. 

Marine Mammal Occurrence 

In this section we provide information 

about the occurrence of marine 

mammals, including density or other 

relevant information which will inform 

the take calculations. 

For the proposed survey area in the 

NW GOM, UT determined that the best 

source of density data for marine 

mammal species that might be 

encountered in the project area was 

habitat-based density modeling 

conducted by Garrison et al., (2023). 

The Garrison et al., (2023) data provides 

abundance estimates for marine 

mammal species in the GOM within 40 

km2 hexagons (∼3.9 km sides and ∼7 km 

across from each side) on a monthly 

basis. To calculate expected densities 

specific to the survey area, UT 

calculated the mean of the predicted 

densities from the cells within the 

combined survey area (primary and 

alternate survey area) for each species 

and month. The highest mean monthly 

density was chosen for each species 

from the months of January to April (i.e., 

the months within which the survey is 

expected to occur). 

Rough-toothed dolphins were not 

modeled by Garrison et al., (2023) due 

to a lack of sightings, so habitat-based 

marine mammal density estimates from 

Roberts et al., (2016) were used. The 

Roberts et al., (2016) models consisted 

of 10 km x 10 km grid cells containing 

average annual densities for U.S. waters 

in the GOM. The combined survey area 

was used to select grid cells from the 

Roberts et al., (2016) dataset, and the 

mean of the selected grid cells for 

rough-toothed dolphins was calculated 

to estimate the annual average density 

of the species in the survey area. 

Estimated densities used and Level B 

harassment ensonified areas to inform 

take estimates are presented in table 6. 

TABLE 6—MARINE MAMMAL DENSITIES

AND TOTAL ENSONIFIED AREA OF

ACTIVITIES IN THE PROPOSED SURVEY AREA

Species 

Estimated 

density 

(#/km2) 

Level B 

ensonified 

area 

(km2) 

Atlantic spotted 

dolphin ........... b 0.0043 1,522 

Bottlenose dolphin a ............. b 0.8596 1,522 

Rough-toothed 

dolphin ........... c 0.0037 1,522 

aBottlenose dolphin density estimate does 

not differentiate between coastal and shelf 

stocks. b Density calculated from Garrison et al., 

(2023). c Density calculated from Roberts et al., 

(2016). 


ddrumheller on DSK120RN23PROD with NOTICES1
91358 Federal Register / Vol. 89, No. 223 / Tuesday, November 19, 2024 / Notices 

Take Estimation 

Here we describe how the information 

provided above is synthesized to 

produce a quantitative estimate of the 

take that is reasonably likely to occur 

and proposed for authorization. In order 

to estimate the number of marine 

mammals predicted to be exposed to 

sound levels that would result in Level 

B harassment, radial distances from the 

airgun array to the predicted isopleth 

corresponding to the Level B 

harassment threshold was calculated, as 

described above. Those radial distances 

were then used to calculate the area(s) 

around the airgun array predicted to be 

ensonified to sound levels that exceed 

the harassment thresholds. The area 

expected to be ensonified on 1 day was 

determined by multiplying the number 

of line km possible in 1 day by two 

times the 160-dB radius plus adding 

endcaps to the start and beginning of the 

line. The daily ensonified area was then 

multiplied by the number of survey 

days (20 days). The highest mean 

monthly density for each species was 

then multiplied by the total ensonified 

area to calculate the estimated takes of 

each species. 

No takes by Level A harassment are 

expected or proposed for authorization. 

Estimated takes for the proposed survey 

are shown in table 7. 

TABLE 7—ESTIMATED TAKE PROPOSED FOR AUTHORIZATION

Common name Stock 

Estimated 

Level B 

take 

Proposed 

authorized 

Level B 

take 

Stock 

abundance 1

Percent of 

stock 

Atlantic spotted dolphin ............................. GOM ......................................................... 7 2 26 21,506 0.12 

Bottlenose dolphin 3 .................................. GOM Western Coastal ............................. 1,309 1,309 20,759 6.31 

Northern GOM Continental Shelf ............. 63,280 2.07 

Rough-toothed dolphin .............................. GOM ......................................................... 6 2 14 4,853 0.29 

1Stock abundance for Atlantic spotted dolphins and bottlenose dolphins was taken from Garrison et al., (2023). Stock abundance for roughtoothed dolphins was taken from Roberts et al., (2016), as Garrison et al., (2023) did not create a model for this species. 2Proposed take increased to mean group size from Maze-Foley and Mullin (2006). 

3Estimated take for bottlenose dolphins is not apportioned to stock, as density information does not differentiate between coastal and shelf 

dolphins. However, based on the proposed survey depths, we expect that most of the takes would be from the coastal stock, but some takes 

could be from the shelf stock. Percent of stock was calculated as if all takes proposed for authorization accrued to the single stock with the lowest population abundance. 

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 

(latter not applicable for this action). 

NMFS regulations require applicants for 

incidental take authorizations to include 

information about the availability and 

feasibility (economic and technological) 

of equipment, methods, and manner of 

conducting the activity or other means 

of effecting the least practicable adverse 

impact upon the affected species or 

stocks, and their habitat (50 CFR 

216.104(a)(11)). 

In evaluating how mitigation may or 

may not be appropriate to ensure the 

least practicable adverse impact on 

species or stocks and their habitat, as 

well as subsistence uses where 

applicable, NMFS considers two 

primary factors: 

(1) The manner in which, and the 

degree to which, the successful 

implementation of the measure(s) is 

expected to reduce impacts to marine 

mammals, marine mammal species or 

stocks, and their habitat. This considers 

the nature of the potential adverse 

impact being mitigated (likelihood, 

scope, range). It further considers the 

likelihood that the measure will be 

effective if implemented (probability of 

accomplishing the mitigating result if 

implemented as planned), the 

likelihood of effective implementation 

(probability implemented as planned); 

and, 

(2) The practicability of the measures 

for applicant implementation, which 

may consider such things as cost, and 

impact on operations. 

Vessel-Visual Based Mitigation 

Monitoring 

Visual monitoring requires the use of 

trained observers (herein referred to as 

visual protected species observers 

(PSOs)) to scan the ocean surface 

visually for the presence of marine 

mammals. PSOs shall establish and 

monitor a pre-start clearance zone and, 

to the extent practicable, a Level B 

harassment zone (Table 4). These zones 

shall be based upon the radial distance 

from the edges of the acoustic source 

(rather than being based on the center of 

the array or around the vessel itself). 

During pre-start clearance (i.e., before 

ramp-up begins), the pre-start clearance 

zone is the area in which observations 

of marine mammals within the zone 

would prevent airgun operations from 

beginning (i.e., ramp-up). The pre-start 

clearance zone encompasses the area at 

and below the sea surface out to a radius 

of 200 meters from the edges of the 

airgun array. 

During survey operations (e.g., any 

day on which use of the acoustic source 

is planned to occur, and whenever the 

acoustic source is in the water, whether 

activated or not), a minimum of two 

PSOs must be on duty and conducting 

visual observations at all times during 

daylight hours (i.e., from 30 minutes 

prior to sunrise through 30 minutes 

following sunset). Visual monitoring 

must begin no less than 30 minutes 

prior to ramp-up and must continue 

until 1 hour after use of the acoustic 

source ceases or until 30 minutes past 

sunset. Visual PSOs must coordinate to 

ensure 360 degree visual coverage 

around the vessel from the most 

appropriate observation posts, and must 

conduct visual observations using 

binoculars and the naked eye while free 

from distractions and in a consistent, 

systematic, and diligent manner. 

PSOs shall establish and monitor a 

pre-start clearance zone and to the 

extent practicable, a Level B harassment 

zone. These zones shall be based upon 

the radial distance from the edges of the 

acoustic source (rather than being based 

on the center of the array or around the 

vessel itself). Any observations of 

marine mammals by crew members 

shall be relayed to the PSO team. During 

good conditions (e.g., daylight hours, 

Beaufort sea state (BSS) 3 or less), visual 

PSOs shall conduct observations when 

the acoustic source is not operating for 


ddrumheller on DSK120RN23PROD with NOTICES1
Federal Register / Vol. 89, No. 223 / Tuesday, November 19, 2024 / Notices 91359 

comparison of sightings rates and 

behavior with and without use of the 

acoustic source and between acquisition 

periods, to the maximum extent 

practicable. 

Visual PSOs may be on watch for a 

maximum of 4 consecutive hours 

followed by a break of at least 1 hour 

between watches and may conduct a 

maximum of 12 hours of observation per 

24-hour period. 

Pre-Start Clearance and Ramp-Up 

Ramp-up (sometimes referred to as 

‘‘soft start’’) means the gradual and 

systematic increase of emitted sound 

levels from an airgun array. The intent 

of pre-start clearance observation (30 

minutes) is to ensure no marine 

mammals are observed within the prestart clearance zone prior to the 

beginning of ramp-up. The intent of the 

ramp-up is to warn marine mammals of 

pending seismic survey operations and 

to allow sufficient time for those 

animals to leave the immediate vicinity 

prior to the sound source reaching full 

intensity. A ramp-up procedure, 

involving a stepwise increase in the 

number of airguns firing and total array 

volume until all operational airguns are 

activated and the full volume is 

achieved, is required at all times as part 

of the activation of the airgun array. All 

operators must adhere to the following 

pre-start clearance and ramp-up 

requirements: 

• The operator must notify a 

designated PSO of the planned start of 

ramp-up as agreed upon with the lead 

PSO; the notification time should not be 

less than 60 minutes prior to the 

planned ramp-up in order to allow PSOs 

time to monitor the pre-start clearance 

zone for 30 minutes prior to the 

initiation of ramp-up (pre-start 

clearance). 

• Ramp-ups shall be scheduled so as 

to minimize the time spent with the 

source activated prior to reaching the 

designated run-in. 

• One of the PSOs conducting prestart clearance observations must be 

notified again immediately prior to 

initiating ramp-up procedures and the 

operator must receive confirmation from 

the PSO to proceed. 

• Ramp-up may not be initiated if any 

marine mammal is within the pre-start 

clearance zone. If a marine mammal is 

observed within the pre-start clearance 

zone during the 30 minutes preclearance period, ramp-up may not 

begin until the animal(s) has been 

observed exiting the zone or until an 

additional time period has elapsed with 

no further sightings (15 minutes for 

small delphinids and 30 minutes for all 

other species). 

• Ramp-up must begin by activating 

one GI airgun for no less than 5 minutes 

and then activating the second airgun. 

The operator must provide information 

to the PSO documenting that 

appropriate procedures were followed. 

• PSOs must monitor the pre-start 

clearance zone during ramp-up, and 

ramp-up must cease and the source 

must be shut down upon detection of a 

marine mammal within the pre-start 

clearance zone. Once ramp-up has 

begun, observations of marine mammals 

for which take authorization is granted 

within the pre-start clearance zone does 

not require shutdown. 

• If the acoustic source is shut down 

for brief periods (i.e., less than 30 

minutes) for reasons other than 

implementation of prescribed mitigation 

(e.g., mechanical difficulty), it may be 

activated again without ramp-up if PSOs 

have maintained constant observation 

and no detections of marine mammals 

have occurred within the pre-start 

clearance zone. For any longer 

shutdown, pre-start clearance 

observation and ramp-up are required. 

Ramp-up may occur at times of poor 

visibility (e.g., BSS 4 or greater), 

including nighttime, if appropriate 

visual monitoring has occurred with no 

detections of marine mammals in the 30 

minutes prior to beginning ramp-up. 

Acoustic source activation may only 

occur at night where operational 

planning cannot reasonably avoid such 

circumstances. 

• Testing of the acoustic source 

involving all elements requires rampup. Testing limited to individual source 

elements or strings does not require 

ramp-up but does require a 30-minute 

pre-start clearance period. 

Shutdown Procedures 

The shutdown of an airgun array 

requires the immediate de-activation of 

all individual airgun elements of the 

array. Any PSO on duty will have the 

authority to call for shutdown of the 

airgun array. The operator must also 

establish and maintain clear lines of 

communication directly between PSOs 

on duty and crew controlling the airgun 

array to ensure that shutdown 

commands are conveyed swiftly while 

allowing PSOs to maintain watch. The 

shutdown requirement will be waived 

for small dolphins. As defined here, the 

small dolphin group is intended to 

encompass those members of the Family 

Delphinidae most likely to voluntarily 

approach the source vessel for purposes 

of interacting with the vessel and/or 

airgun array (e.g., bow riding). This 

exception to the shutdown requirement 

applies solely to specific genera of small 

dolphins—Steno, Stenella, and 

Tursiops. As Tursiops, Stenella, and 

Steno are the only species expected to 

potentially be encountered, there is no 

shutdown requirement included in the 

proposed IHA for species for which take 

is proposed to be authorized. UT must 

implement shutdown if a marine 

mammal species for which take was not 

authorized or a species for which 

authorization was granted but the 

authorized takes have been met 

approaches the Level B harassment 

zone. 

We include this small dolphin 

exception because shutdown 

requirements for these species under all 

circumstances represent practicability 

concerns without likely commensurate 

benefits for the animals in question. 

Small dolphins are generally the most 

commonly observed marine mammals 

in the specific geographic region and 

would typically be the only marine 

mammals likely to intentionally 

approach the vessel. As described 

above, auditory injury is extremely 

unlikely to occur for high-frequency 

cetaceans (e.g., delphinids), as this 

group is relatively insensitive to sound 

produced at the predominant 

frequencies in an airgun pulse while 

also having a relatively high threshold 

for the onset of auditory injury (i.e., 

permanent threshold shift). 

A large body of anecdotal evidence 

indicates that small dolphins commonly 

approach vessels and/or towed arrays 

during active sound production for 

purposes of bow riding with no 

apparent effect observed (e.g., Barkaszi 

et al., 2012; Barkaszi and Kelly, 2018). 

The potential for increased shutdowns 

resulting from such a measure would 

require the McCall to revisit the missed 

track line to reacquire data, resulting in 

an overall increase in the total sound 

energy input to the marine environment 

and an increase in the total duration 

over which the survey is active in a 

given area. 

Vessel Strike Avoidance Mitigation 

Measures 

Vessel personnel should use an 

appropriate reference guide that 

includes identifying information on all 

marine mammals that may be 

encountered. Vessel operators must 

comply with the below measures except 

under extraordinary circumstances 

when the safety of the vessel or crew is 

in doubt or the safety of life at sea is in 

question. These requirements do not 

apply in any case where compliance 

would create an imminent and serious 

threat to a person or vessel or to the 

extent that a vessel is restricted in its 

ability to maneuver and, because of the 

restriction, cannot comply. 


ddrumheller on DSK120RN23PROD with NOTICES1
91360 Federal Register / Vol. 89, No. 223 / Tuesday, November 19, 2024 / Notices 

Vessel operators and crews must 

maintain a vigilant watch for all marine 

mammals and slow down, stop their 

vessel, or alter course, as appropriate 

and regardless of vessel size, to avoid 

striking any marine mammal. A single 

marine mammal at the surface may 

indicate the presence of submerged 

animals in the vicinity of the vessel; 

therefore, precautionary measures 

should always be exercised. A visual 

observer aboard the vessel must monitor 

a vessel strike avoidance zone around 

the vessel (separation distances stated 

below). Visual observers monitoring the 

vessel strike avoidance zone may be 

third-party observers (i.e., PSOs) or crew 

members, but crew members 

responsible for these duties must be 

provided sufficient training to (1) 

distinguish marine mammals from other 

phenomena and (2) broadly to identify 

a marine mammal as a right whale, 

other whale (defined in this context as 

sperm whales or baleen whales other 

than right whales), or other marine 

mammals. 

Vessel speeds must be reduced to 10 

kn (18.5 kph) or less when mother/calf 

pairs, pods, or large assemblages of 

cetaceans are observed near a vessel. 

The vessel must maintain a minimum 

separation distance of 500 m from 

baleen whales. If a baleen whale is 

sighted within the relevant separation 

distance, the vessel must steer a course 

away at 10 knots or less until the 500- 

m separation distance is established. If 

a whale is observed but cannot be 

confirmed as a species other than a 

baleen whale, the vessel operator must 

assume that it is a baleen whale and 

take appropriate action. All vessels must 

maintain a minimum separation 

distance of 100 m from sperm whales. 

All vessels must, to the maximum 

extent practicable, attempt to maintain a 

minimum separation distance of 50 m 

from all other marine mammals, with an 

understanding that at times this may not 

be possible (e.g., for animals that 

approach the vessel). 

When marine mammals are sighted 

while a vessel is underway, the vessel 

shall take action as necessary to avoid 

violating the relevant separation 

distance (e.g., attempt to remain parallel 

to the animal’s course, avoid excessive 

speed or abrupt changes in direction 

until the animal has left the area). If 

marine mammals are sighted within the 

relevant separation distance, the vessel 

must reduce speed and shift the engine 

to neutral, not engaging the engines 

until animals are clear of the area. This 

does not apply to any vessel towing gear 

or any vessel that is navigationally 

constrained. 

Based on our evaluation of the 

applicant’s 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. 

Vessel-Based Visual Monitoring 

As described above, PSO observations 

would take place during daytime airgun 

operations. During seismic survey 

operations, two visual PSOs would be 

on duty at all times during daytime 

hours. The operator will work with the 

selected third-party observer provider to 

ensure PSOs have all equipment 

(including backup equipment) needed 

to adequately perform necessary tasks, 

including accurate determination of 

distance and bearing to observed marine 

mammals. SIO must use dedicated, 

trained, and NMFS-approved PSOs. At 

least one visual PSO aboard the vessel 

must have a minimum of 90 days at-sea 

experience working in those roles, 

respectively, with no more than 18 

months elapsed since the conclusion of 

the at-sea experience. One visual PSO 

with such experience shall be 

designated as the lead for the entire 

protected species observation team. The 

lead PSO shall serve as primary point of 

contact for the vessel operator and 

ensure all PSO requirements per the 

IHA are met. To the maximum extent 

practicable, the experienced PSOs 

should be scheduled to be on duty with 

those PSOs with appropriate training 

but who have not yet gained relevant 

experience. The PSOs must have no 

tasks other than to conduct 

observational effort, record 

observational data, and communicate 

with and instruct relevant vessel crew 

with regard to the presence of marine 

mammals and mitigation requirements. 

PSO resumes shall be provided to 

NMFS for approval. Monitoring shall be 

conducted in accordance with the 

following requirements: 

• PSOs shall be independent, 

dedicated, trained visual PSOs and must 

be employed by a third-party observer 

provider. 

• PSOs shall have no tasks other than 

to conduct observational effort, collect 

data, and communicate with and 

instruct relevant vessel crew with regard 

to the presence of protected species and 

mitigation requirements (including brief 

alerts regarding maritime hazards). 

• PSOs shall have successfully 

completed an approved PSO training 

course appropriate for their designated 

task. 

• NMFS must review and approve 

PSO resumes accompanied by a relevant 

training course information packet that 

includes the name and qualifications 

(i.e., experience, training completed, or 

educational background) of the 


ddrumheller on DSK120RN23PROD with NOTICES1
Federal Register / Vol. 89, No. 223 / Tuesday, November 19, 2024 / Notices 91361 

instructor(s), the course outline or 

syllabus, and course reference material 

as well as a document stating successful 

completion of the course. 

• PSOs must successfully complete 

relevant training, including completion 

of all required coursework and passing 

(80 percent or greater) a written and/or 

oral examination developed for the 

training program. 

• PSOs must have successfully 

attained a bachelor’s degree from an 

accredited college or university with a 

major in one of the natural sciences, a 

minimum of 30 semester hours or 

equivalent in the biological sciences, 

and at least one undergraduate course in 

math or statistics. 

• The educational requirements may 

be waived if the PSO has acquired the 

relevant skills through alternate 

experience. Requests for such a waiver 

shall be submitted to NMFS and must 

include written justification. Requests 

shall be granted or denied (with 

justification) by NMFS within 1 week of 

receipt of submitted information. 

Alternate experience that may be 

considered includes, but is not limited 

to (1) secondary education and/or 

experience comparable to PSO duties; 

(2) previous work experience 

conducting academic, commercial, or 

government-sponsored protected 

species surveys; or (3) previous work 

experience as a PSO; the PSO should 

demonstrate good standing and 

consistently good performance of PSO 

duties. 

• For data collection purposes, PSOs 

shall use standardized electronic data 

collection forms. PSOs shall record 

detailed information about any 

implementation of mitigation 

requirements, including the distance of 

animals to the airgun array and 

description of specific actions that 

ensued, the behavior of the animal(s), 

any observed changes in behavior before 

and after implementation of mitigation, 

and if shutdown was implemented, the 

length of time before any subsequent 

ramp-up of the airgun array. If required 

mitigation was not implemented, PSOs 

should record a description of the 

circumstances. At a minimum, the 

following information must be recorded: 

Æ Vessel name, vessel size and type, 

maximum speed capability of vessel; 

Æ Dates (MM/DD/YYYY) of 

departures and returns to port with port 

name; 

Æ PSO names and affiliations, PSO ID 

(initials or other identifier); 

Æ Date (MM/DD/YYYY) and 

participants of PSO briefings; 

Æ Visual monitoring equipment used 

(description); 

Æ PSO location on vessel and height 

(meters) of observation location above 

water surface; 

Æ Watch status (description); 

Æ Dates (MM/DD/YYYY) and times 

(Greenwich Mean Time/UTC) of survey 

on/off effort and times (GMC/UTC) 

corresponding with PSO on/off effort; 

Æ Vessel location (decimal degrees) 

when survey effort began and ended and 

vessel location at beginning and end of 

visual PSO duty shifts; 

Æ Vessel location (decimal degrees) at 

30-second intervals if obtainable from 

data collection software, otherwise at 

practical regular interval; 

Æ Vessel heading (compass heading) 

and speed (knots) at beginning and end 

of visual PSO duty shifts and upon any 

change; 

Æ Water depth (meters) (if obtainable 

from data collection software); 

Æ Environmental conditions while on 

visual survey (at beginning and end of 

PSO shift and whenever conditions 

changed significantly), including BSS 

and any other relevant weather 

conditions including cloud cover, fog, 

sun glare, and overall visibility to the 

horizon; 

Æ Factors that may have contributed 

to impaired observations during each 

PSO shift change or as needed as 

environmental conditions changed 

(description) (e.g., vessel traffic, 

equipment malfunctions); and 

Æ Vessel/Survey activity information 

(and changes thereof) (description), 

such as airgun power output while in 

operation, number and volume of 

airguns operating in the array, tow 

depth of the array, and any other notes 

of significance (i.e., pre-start clearance, 

ramp-up, shutdown, testing, shooting, 

ramp-up completion, end of operations, 

streamers, etc.). 

• Upon visual observation of any 

marine mammals, the following 

information must be recorded: 

Æ Sighting ID (numeric); 

Æ Watch status (sighting made by 

PSO on/off effort, opportunistic, crew, 

alternate vessel/platform); 

Æ Location of PSO/observer 

(description); 

Æ Vessel activity at the time of the 

sighting (e.g., deploying, recovering, 

testing, shooting, data acquisition, 

other); 

Æ PSO who sighted the animal/ID; 

Æ Time/date of sighting (GMT/UTC, 

MM/DD/YYYY); 

Æ Initial detection method 

(description); 

Æ Sighting cue (description); 

Æ Vessel location at time of sighting 

(decimal degrees); 

Æ Water depth (meters); 

Æ Direction of vessel’s travel 

(compass direction); 

Æ Speed (knots) of the vessel from 

which the observation was made; 

Æ Direction of animal’s travel relative 

to the vessel (description, compass 

heading); 

Æ Bearing to sighting (degrees); 

Æ Identification of the animal (e.g., 

genus/species, lowest possible 

taxonomic level, or unidentified) and 

the composition of the group if there is 

a mix of species; 

Æ Species reliability (an indicator of 

confidence in identification) (1 = 

unsure/possible, 2 = probable, 3 = 

definite/sure, 9 = unknown/not 

recorded); 

Æ Estimated distance to the animal 

(meters) and method of estimating 

distance; 

Æ Estimated number of animals (high/ 

low/best) (numeric); 

Æ Estimated number of animals by 

cohort (adults, yearlings, juveniles, 

calves, group composition, etc.); 

Æ Description (as many 

distinguishing features as possible of 

each individual seen, including length, 

shape, color, pattern, scars or markings, 

shape and size of dorsal fin, shape of 

head, and blow characteristics); 

Æ Detailed behavior observations 

(e.g., number of blows/breaths, number 

of surfaces, breaching, spyhopping, 

diving, feeding, traveling; as explicit 

and detailed as possible; note any 

observed changes in behavior); 

Æ Animal’s closest point of approach 

(meters) and/or closest distance from 

any element of the airgun array; 

Æ Description of any actions 

implemented in response to the sighting 

(e.g., delays, shutdown, ramp-up) and 

time and location of the action; 

Æ Photos (Yes/No); 

Æ Photo Frame Numbers (List of 

numbers); and 

Æ Conditions at time of sighting 

(Visibility; BSS). 

Reporting 

UT shall submit a draft 

comprehensive report on all activities 

and monitoring results within 90 days 

of the completion of the survey or 

expiration of the IHA, whichever comes 

sooner. The report must describe all 

activities conducted and sightings of 

marine mammals, must provide full 

documentation of methods, results, and 

interpretation pertaining to all 

monitoring, and must summarize the 

dates and locations of survey operations 

and all marine mammal sightings (dates, 

times, locations, activities, associated 

survey activities). The draft report shall 

also include geo-referenced timestamped vessel tracklines for all time 

periods during which airgun arrays 

were operating. Tracklines should 


ddrumheller on DSK120RN23PROD with NOTICES1
91362 Federal Register / Vol. 89, No. 223 / Tuesday, November 19, 2024 / Notices 

include points recording any change in 

airgun array status (e.g., when the 

sources began operating, when they 

were turned off, or when they changed 

operational status such as from full 

array to single gun or vice versa). 

Geographic Information System files 

shall be provided in Environmental 

Systems Research Institute shapefile 

format and include the UTC date and 

time, latitude in decimal degrees, and 

longitude in decimal degrees. All 

coordinates shall be referenced to the 

WGS84 geographic coordinate system. 

In addition to the report, all raw 

observational data shall be made 

available. The report must summarize 

data collected as described above in 

Proposed Monitoring and Reporting. A 

final report must be submitted within 30 

days following resolution of any 

comments on the draft report. 

Reporting Injured or Dead Marine 

Mammals 

Discovery of injured or dead marine 

mammals—In the event that personnel 

involved in the survey activities 

discover an injured or dead marine 

mammal, UT shall report the incident to 

the Office of Protected Resources (OPR), 

NMFS and the NMFS, Southeast 

Regional Stranding Coordinator 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 was discovered. 

Vessel strike—In the event of a strike 

of a marine mammal by any vessel 

involved in the activities covered by the 

authorization, UT shall report the 

incident to OPR, NMFS, and the NMFS 

Southeast Regional Stranding 

Coordinator as soon as feasible. The 

report must include the following 

information: 

• Time, date, and location (latitude/ 

longitude) of the incident; 

• Vessel’s speed during and leading 

up to the incident; 

• Vessel’s course/heading and what 

operations were being conducted (if 

applicable); 

• Status of all sound sources in use; 

• Description of avoidance measures/ 

requirements that were in place at the 

time of the strike and what additional 

measure were taken, if any, to avoid 

strike; 

• Environmental conditions (e.g., 

wind speed and direction, BSS, cloud 

cover, visibility) immediately preceding 

the strike; 

• Species identification (if known) or 

description of the animal(s) involved; 

• Estimated size and length of the 

animal that was struck; 

• Description of the behavior of the 

marine mammal immediately preceding 

and following the strike; 

• If available, description of the 

presence and behavior of any other 

marine mammals present immediately 

preceding the strike; 

• Estimated fate of the animal (e.g., 

dead, injured but alive, injured and 

moving, blood or tissue observed in the 

water, status unknown, disappeared); 

and 

• To the extent practicable, 

photographs or video footage of the 

animal(s). 

Negligible Impact Analysis and 

Determination 

NMFS has defined negligible impact 

as an impact resulting from the 

specified activity that cannot be 

reasonably expected to, and is not 

reasonably likely to, adversely affect the 

species or stock through effects on 

annual rates of recruitment or survival 

(50 CFR 216.103). A negligible impact 

finding is based on the lack of likely 

adverse effects on annual rates of 

recruitment or survival (i.e., 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). 

To avoid repetition, the discussion of 

our analysis applies to Atlantic spotted 

dolphins, bottlenose dolphins, and 

rough-toothed dolphins, given that the 

anticipated effects of this activity on 

these different marine mammal stocks 

are expected to be similar. There is little 

information about the nature or severity 

of the impacts, or the size, status, or 

structure of any of these species or 

stocks that would lead to a different 

analysis for this activity. 

NMFS does not anticipate that serious 

injury or mortality would occur as a 

result of UT’s planned survey, even in 

the absence of mitigation, and no 

serious injury or mortality is proposed 

to be authorized. As discussed in the 

Potential Effects of Specified Activities 

on Marine Mammals and Their Habitat 

section above, non-auditory physical 

effects and vessel strike are not expected 

to occur. NMFS expects that all 

potential take would be in the form of 

Level B behavioral harassment in the 

form of temporary avoidance of the area 

or decreased foraging (if such activity 

was occurring), responses that are 

considered to be of low severity, and 

with no lasting biological consequences 

(e.g., Southall et al., 2007, 2021). These 

low-level impacts of behavioral 

harassment are not likely to impact the 

overall fitness of any individual or lead 

to population level effects of any 

species. As described above, auditory 

injury (Level A harassment) is not 

expected to occur given the estimated 

small size of the Level A harassment 

zones. 

In addition, the maximum expected 

Level B harassment zone around the 

survey vessel is 1,750 m. Therefore, the 

ensonified area surrounding the vessel 

is relatively small compared to the 

overall distribution of animals in the 

area and their use of the habitat. 

Feeding behavior is not likely to be 

significantly impacted as prey species 

are mobile and are broadly distributed 

throughout the survey area; therefore, 

marine mammals that may be 

temporarily displaced during survey 

activities are expected to be able to 

resume foraging once they have moved 

away from areas with disturbing levels 

of underwater noise. Because of the 

short duration (20 survey days) and 

temporary nature of the disturbance and 

the availability of similar habitat and 

resources in the surrounding area, the 

impacts to marine mammals and marine 

mammal prey species are not expected 

to cause significant or long-term fitness 

consequences for individual marine 

mammals or their populations. 


ddrumheller on DSK120RN23PROD with NOTICES1
Federal Register / Vol. 89, No. 223 / Tuesday, November 19, 2024 / Notices 91363 

Additionally, the acoustic ‘‘footprint’’ 

of the proposed survey would be very 

small relative to the ranges of all marine 

mammals that would potentially be 

affected. Sound levels would increase in 

the marine environment in a relatively 

small area surrounding the vessel 

compared to the range of the marine 

mammals within the proposed survey 

area. The seismic array would be active 

24 hours per day throughout the 

duration of the proposed survey. 

However, the very brief overall duration 

of the proposed survey (20 survey days) 

would further limit potential impacts 

that may occur as a result of the 

proposed activity. 

There are no rookeries, mating, or 

calving grounds known to be 

biologically important to marine 

mammals within the planned survey 

area and there are no feeding areas 

known to be biologically important to 

marine mammals within the survey 

area. There is no designated critical 

habitat for any ESA-listed marine 

mammals within the project area. 

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 serious injury or mortality is 

anticipated or authorized; 

• No auditory injury (Level A 

harassment) is anticipated or proposed 

to be authorized; 

• The proposed activity is temporary 

and of relatively short duration (23 days 

total with 20 days of planned survey 

activity); 

• The anticipated impacts of the 

proposed activity on marine mammals 

would be temporary behavioral changes 

due to avoidance of the ensonified area, 

which is relatively small (see tables 4 

and 5); 

• The availability of alternative areas 

of similar habitat value for marine 

mammals to temporarily vacate the 

survey area during the proposed survey 

to avoid exposure to sounds from the 

activity is readily abundant; 

• The potential adverse effects on fish 

or invertebrate species that serve as prey 

species for marine mammals from the 

proposed survey would be temporary 

and spatially limited and impacts to 

marine mammal foraging would be 

minimal; and 

• The proposed mitigation measures 

are expected to reduce the number and 

severity of takes, to the extent 

practicable, by visually detecting marine 

mammals within the established zones 

and implementing corresponding 

mitigation measures (e.g., delay; rampup). 

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. 

Small Numbers 

As noted previously, only take of 

small numbers of marine mammals may 

be authorized under sections 

101(a)(5)(A) and (D) of the MMPA for 

specified activities other than military 

readiness activities. The MMPA does 

not define small numbers and so, in 

practice, where estimated numbers are 

available, NMFS compares the number 

of individuals taken to the most 

appropriate estimation of abundance of 

the relevant species or stock in our 

determination of whether an 

authorization is limited to small 

numbers of marine mammals. When the 

predicted number of individuals to be 

taken is fewer than one-third of the 

species or stock abundance, the take is 

considered to be of small numbers. 

Additionally, other qualitative factors 

may be considered in the analysis, such 

as the temporal or spatial scale of the 

activities. 

The number of takes NMFS proposes 

to authorize is below one-third of the 

modeled abundance for all relevant 

populations (specifically, take of 

individuals is less than 7 percent of the 

most appropriate abundance estimate 

for each stock, see table 6). This is 

conservative because this approach 

assumes all takes are of different 

individual animals, which is likely not 

the case. Some individuals may be 

encountered multiple times in a day, 

but PSOs would count them as separate 

individuals if they cannot be identified. 

Based on the analysis contained 

herein of the proposed activity 

(including the proposed mitigation and 

monitoring measures) and the 

anticipated take of marine mammals, 

NMFS preliminarily finds that small 

numbers of marine mammals would be 

taken relative to the population size of 

the affected species or stocks. 

Unmitigable Adverse Impact Analysis 

and Determination 

There are no relevant subsistence uses 

of the affected marine mammal stocks or 

species implicated by this action. 

Therefore, NMFS has determined that 

the total taking of affected species or 

stocks would not have an unmitigable 

adverse impact on the availability of 

such species or stocks for taking for 

subsistence purposes. 

Endangered Species Act 

Section 7(a)(2) of the ESA of 1973 (16 

U.S.C. 1531 et seq.) requires that each 

Federal agency insure that any action it 

authorizes, funds, or carries out is not 

likely to jeopardize the continued 

existence of any endangered or 

threatened species or result in the 

destruction or adverse modification of 

designated critical habitat. To ensure 

ESA compliance for the issuance of 

IHAs, NMFS consults internally 

whenever we propose to authorize take 

for endangered or threatened species. 

No incidental take of ESA-listed 

species is proposed for authorization or 

expected to result from this activity. 

Therefore, NMFS has determined that 

formal consultation under section 7 of 

the ESA is not required for this action. 

Proposed Authorization 

As a result of these preliminary 

determinations, NMFS proposes to issue 

an IHA to UT for conducting marine 

geophysical surveys in coastal waters off 

Texas in the NW GOM from 

approximately January to April 2025, 

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/ 

incidental-take-authorizations-researchand-other-activities. 

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 marine 

geophysical survey. 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 one-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 


ddrumheller on DSK120RN23PROD with NOTICES1
91364 Federal Register / Vol. 89, No. 223 / Tuesday, November 19, 2024 / Notices 

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). 

• 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). 

(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 

mitigation and monitoring measures 

will remain the same and appropriate, 

and the findings in the initial IHA 

remain valid. 

Dated: November 12, 2024. 

Kimberly Damon-Randall, 

Director, Office of Protected Resources, 

National Marine Fisheries Service. 

[FR Doc. 2024–26903 Filed 11–18–24; 8:45 am] 

BILLING CODE 3510–22–P 

DEPARTMENT OF COMMERCE 

National Oceanic and Atmospheric 

Administration 

[RTID 0648–XE444] 

Atlantic Highly Migratory Species; 

Advisory Panel 

AGENCY: National Marine Fisheries 

Service (NMFS), National Oceanic and 

Atmospheric Administration (NOAA), 

Commerce. 

ACTION: Notice; solicitation of 

nominations. 

SUMMARY: NMFS solicits nominations 

for the Atlantic Highly Migratory 

Species (HMS) Advisory Panel (AP). 

NMFS consults with and considers the 

comments and views of the HMS AP 

when preparing and implementing 

Fishery Management Plans (FMPs) or 

FMP amendments for Atlantic tunas, 

swordfish, sharks, and billfish. 

Nominations are being sought to fill 

approximately one-third (12) of the seats 

on the HMS AP, each with a 3-year 

appointment. NMFS will consider 

individuals with definable interests in 

recreational and commercial fishing and 

related industries, including those from 

the environmental community, 

academia, and non-governmental 

organizations, for membership on the 

HMS AP. 

DATES: Submit nominations on or before 

December 19, 2024. 

ADDRESSES: You may submit 

nominations and requests for the 

Advisory Panel Statement of 

Organization, Practices, and Procedures 

by email to HMSAP.Nominations@

noaa.gov. Include in the subject line the 

following identifier: ‘‘HMS AP 

Nominations.’’ 

FOR FURTHER INFORMATION CONTACT: 

Anna Quintrell at 301–427–7861 or via 

email at HMSAP.Nominations@

noaa.gov. 

SUPPLEMENTARY INFORMATION: HMS 

fisheries (tunas, swordfish, sharks, and 

billfish) are managed under the 2006 

Consolidated HMS FMP and its 

amendments pursuant to the authority 

of the Magnuson-Stevens Fishery 

Conservation and Management Act 

(Magnuson-Stevens Act; 16 U.S.C. 1801 

et seq.) and consistent with the Atlantic 

Tunas Convention Act (16 U.S.C. 971 et 

seq.). HMS implementing regulations 

are at 50 CFR part 635. 

The Magnuson-Stevens Act requires 

NMFS to establish an AP for each HMS 

FMP (16 U.S.C. 1854(g)(1)(A)–(B)). 

Since the inception of the AP in 1998, 

NMFS has consulted with and 

considered the comments and views of 

AP members when preparing and 

implementing HMS FMPs or FMP 

amendments. In this notice, NMFS 

solicits nominations for the HMS AP. 

Nominations are being sought to fill 

approximately one-third (12) of the seats 

on the HMS AP for 3-year 

appointments. NMFS will consider 

individuals with definable interests in 

recreational and commercial fishing and 

related industries, including those from 

the environmental community, 

academia, and non-governmental 

organizations for membership on the 

HMS AP as described below. 

Procedures and Guidelines 

Nomination Procedures for 

Appointments to the AP 

Nomination packages should include: 

1. The name and contact information, 

including mailing address, email 

address, and phone number of the 

nominee; 

2. A description of the nominee’s 

interest in HMS or HMS fisheries, or in 

particular species of tunas, swordfish, 

sharks, or billfish; 

3. A statement of the nominee’s 

background and/or qualifications; 

4. A list of outreach resources that the 

nominee has at their disposal to 

communicate qualifications for HMS AP 

membership; and 

5. A written commitment that the 

nominee shall actively participate in 

good faith in the meetings and tasks of 

the HMS AP. 

Advisory Panel members will be 

required to comply with applicable 

rules of conduct, including all ethics 

requirements. Qualification for 

membership includes experience in one 

or more of the following: 

1. HMS recreational fisheries; 

2. HMS commercial fisheries; 

3. Fishery-related industries (e.g., 

marinas, bait and tackle shops); 

4. The scientific community working 

with HMS; and/or 

5. Representation of a private, nongovernmental, regional, national, or 

international organization that 

represents marine fisheries, or 

environmental, governmental, or 

academic interests regarding HMS. 

HMS AP Tenure 

Members are appointed for 3-year 

terms. Approximately one-third of the 

members’ terms expire on December 31 

of each year. NMFS is seeking 

nominations for terms beginning 

January 2025 and expiring December 

2027. 

Members can serve a maximum of 

three consecutive terms (a total of 9 

consecutive years). Afterwards, a 

member must then sit off the HMS AP 

for a single year before becoming 

eligible to apply for a new term. 

Participants 

NMFS will accept nominations for the 

HMS AP that allow for representation 

from commercial and recreational 

fishing interests, academic/scientific 

interests, and the environmental/nongovernmental organization community, 

for individuals who are knowledgeable 

about HMS and/or HMS fisheries. 

Current representation on the HMS AP, 

as shown in table 1, consists of 12 

members representing commercial 

interests, 12 members representing 

recreational interests, 4 members 

representing environmental interests, 4 

academic representatives, and the 

ICCAT Advisory Committee Chair. 


ddrumheller on DSK120RN23PROD with NOTICES1