Federal Register / Vol. 89, No. 189 / Monday, September 30, 2024 / Notices 79529 

0466 in the subject line of your 

comments. Do not submit Confidential 

Business Information or otherwise 

sensitive or protected information. 

FOR FURTHER INFORMATION CONTACT: 

Requests for additional information or 

specific questions related to collection 

activities should be directed to Lisa 

Manning, Ecologist, National Marine 

Fisheries Service, 1315 East West Hwy, 

Bldg. SSMC3, Silver Spring, MD 20910– 

3282, Phone: 301–427–8466 or 

Lisa.Manning@noaa.gov. 

SUPPLEMENTARY INFORMATION: 

I. Abstract 

The National Marine Fisheries Service 

(NMFS), Office of Protected Resources, 

is sponsoring a request for extension of 

a currently approved information 

collection. 

Under the Endangered Species Act 

(ESA), determinations whether to list 

species as endangered or threatened 

must be based on the best scientific and 

commercial data available and after 

taking into account those efforts, if any, 

being made by any State or foreign 

nation (or any of their political 

subdivisions) to protect the particular 

species. On March 28, 2003, NMFS and 

the U.S. Fish and Wildlife Service (the 

‘‘Services’’) announced a final policy on 

the criteria the Services will use to 

evaluate certain conservation efforts by 

States, Tribes, and other non-Federal 

entities when making listing 

determinations under the ESA (68 FR 

15100). The conservation efforts usually 

involve the development of a 

conservation plan or agreement, 

procedures for monitoring the 

effectiveness of the plan or agreement, 

and an annual report. 

II. Method of Collection 

NMFS does not require, but does 

accept, conservation plans and reports 

electronically. NMFS has not developed 

a form to be used for submission of 

plans or reports. In the past, NMFS has 

made plans and annual reports from 

States available through the internet and 

plans to continue this practice. 

III. Data 

OMB Control Number: 0648–0466. 

Form Number(s): None. 

Type of Review: Regular submission 

(extension of a currently approved 

information collection). 

Affected Public: Business or other forprofit organizations; State, Local or 

Tribal Governments. 

Estimated Number of Respondents: 1. 

Estimated Time per Response: 2,500 

hours to complete each agreement or 

plan that has the intention of making 

listing unnecessary; 320 hours to 

conduct monitoring for successful 

agreements; and 80 hours to prepare a 

report for successful agreements. 

Estimated Total Annual Burden 

Hours: 2,900. 

Estimated Total Annual Cost to 

Public: $100. 

Respondent’s Obligation: Voluntary. 

Legal Authority: ESA (16 U.S.C. 1533). 

IV. Request for Comments 

We are soliciting public comments to 

permit the Department/Bureau to: (a) 

Evaluate whether the proposed 

information collection is necessary for 

the proper functions of the Department, 

including whether the information will 

have practical utility; (b) Evaluate the 

accuracy of our estimate of the time and 

cost burden for this proposed collection, 

including the validity of the 

methodology and assumptions used; (c) 

Evaluate ways to enhance the quality, 

utility, and clarity of the information to 

be collected; and (d) Minimize the 

reporting burden on those who are to 

respond, including the use of automated 

collection techniques or other forms of 

information technology. 

Comments that you submit in 

response to this notice are a matter of 

public record. We will include or 

summarize each comment in our request 

to OMB to approve this information 

collection request. Before including 

your address, phone number, email 

address, or other personal identifying 

information in your comment, you 

should be aware that your entire 

comment—including your personal 

identifying information—may be made 

publicly available at any time. While 

you may ask us in your comment to 

withhold your personal identifying 

information from public review, we 

cannot guarantee that we will be able to 

do so. 

Sheleen Dumas, 

Department PRA Clearance Officer, Office of 

the Under Secretary for Economic Affairs, 

Commerce Department. 

[FR Doc. 2024–22370 Filed 9–27–24; 8:45 am] 

BILLING CODE 3510–22–P 

DEPARTMENT OF COMMERCE 

National Oceanic and Atmospheric 

Administration 

[RTID 0648–XE199] 

Takes of Marine Mammals Incidental to 

Specified Activities; Taking Marine 

Mammals Incidental to Hilcorp Alaska, 

LLC Production Drilling Support in 

Cook Inlet, Alaska 

AGENCY: National Marine Fisheries 

Service (NMFS), National Oceanic and 

Atmospheric Administration (NOAA), 

Commerce. 

ACTION: Notice; issuance of an incidental 

harassment authorization. 

SUMMARY: In accordance with the 

regulations implementing the Marine 

Mammal Protection Act (MMPA) as 

amended, notification is hereby given 

that NMFS has issued an incidental 

harassment authorization (IHA) to 

Hilcorp Alaska, LLC (Hilcorp) to 

incidentally harass marine mammals 

during production drilling support 

activities in Cook Inlet, Alaska. 

DATES: This authorization is effective 

from September 24, 2024 through 

September 23, 2025. 

ADDRESSES: Electronic copies of the 

application and supporting documents, 

as well as a list of the references cited 

in this document, may be obtained 

online at: https://

www.fisheries.noaa.gov/national/ 

marine-mammal-protection/incidentaltake-authorizations-oil-and-gas. In case 

of problems accessing these documents, 

please call the contact listed below. 

FOR FURTHER INFORMATION CONTACT: 

Reny Tyson Moore, Office of Protected 

Resources, NMFS, (301) 427–8401. 

SUPPLEMENTARY INFORMATION: 

Background 

The MMPA prohibits the ‘‘take’’ of 

marine mammals, with certain 

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

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

seq.) direct the Secretary of Commerce 

(as delegated to NMFS) to allow, upon 

request, the incidental, but not 

intentional, taking of small numbers of 

marine mammals by U.S. citizens who 

engage in a specified activity (other than 

commercial fishing) within a specified 

geographical region if certain findings 

are made and either regulations are 

proposed or, if the taking is limited to 

harassment, a notice of a proposed IHA 

is provided to the public for review. 

Authorization for incidental takings 

shall be granted if NMFS finds that the 

taking will have a negligible impact on 

the species or stock(s) and will not have 

an unmitigable adverse impact on the 

availability of the species or stock(s) for 

taking for subsistence uses (where 

relevant). Further, NMFS must prescribe 

the permissible methods of taking and 

other ‘‘means of effecting the least 

practicable adverse impact’’ on the 

affected species or stocks and their 

habitat, paying particular attention to 

rookeries, mating grounds, and areas of 

similar significance, and on the 

availability of the species or stocks for 

taking for certain subsistence uses 

(referred to in shorthand as 


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‘‘mitigation’’); and requirements 

pertaining to the monitoring and 

reporting of the takings. The definitions 

of all applicable MMPA statutory terms 

cited above are included in the relevant 

sections below. 

Summary of Request 

On August 2, 2023, NMFS received a 

request from Hilcorp for an IHA to take 

marine mammals incidental to 

production drilling support activities in 

Cook Inlet, Alaska. Following NMFS’ 

review of the application, Hilcorp 

submitted revised versions on 

September 29, 2023, December 27, 2023, 

February 29, 2024, and April 8, 2024. 

The application was deemed adequate 

and complete on April 12, 2024, and the 

notice for the proposed IHA was 

published in the Federal Register on 

July 24, 2024 (89 FR 60164). Hilcorp’s 

request is for take of 12 species of 

marine mammals, by Level B 

harassment. Neither Hilcorp nor NMFS 

expect serious injury or mortality to 

result from this activity and, therefore, 

an IHA is appropriate. 

NMFS previously issued two 

consecutive IHAs to Hilcorp for similar 

work (87 FR 62364, October 1, 2022). 

Hilcorp complied with all the 

requirements (e.g., mitigation, 

monitoring, and reporting) of the 

previous IHAs, and information 

regarding their monitoring results may 

be found in the Potential Effects of 

Specified Activities on Marine 

Mammals and their Habitat section of 

this notice. 

There are no changes from the 

proposed IHA to the final IHA other 

than the addition of some clarifying 

language and some minor typographical 

corrections. 

Description of Specified Activity 

Hilcorp plans to use three tug boats to 

tow and hold, and up to four tug boats 

to position, a jack-up rig to support 

production drilling at existing platforms 

on 6 non-consecutive days during a 1- 

year period, in middle Cook Inlet and 

Trading Bay Alaska. Tug activities will 

include one demobilization effort of a 

jack-up rig (Spartan 151 or equivalent 

rig) from an existing platform to Rig 

Tenders Dock in Nikiski, one jack-up rig 

relocation between existing platforms, 

and one remobilization effort of the 

jack-up rig from Rig Tenders Dock in 

Nikiski to middle Cook Inlet. Noise 

produced by tugs under load with a 

jack-up rig may result in take, by Level 

B harassment, of 12 marine mammal 

species. References to tugging activities 

herein refer to activities where tugs are 

under load with the rig (i.e., tugs 

towing, holding, and or positioning a 

jack-up rig). 

A detailed description of the planned 

tugging activities is provided in the 

Federal Register notice for the proposed 

IHA (89 FR 60164, July 24, 2024). Since 

that time, no changes have been made 

to the planned activities. Therefore, a 

detailed description is not provided 

here. Please refer to that Federal 

Register notice for the description of the 

specific activity. 

Comments and Responses 

A notice of NMFS’ proposal to issue 

an IHA to Hilcorp was published in the 

Federal Register on July 24, 2024 (89 FR 

60164). That notice described, in detail, 

Hilcorp’s activity, the marine mammal 

species that may be affected by the 

activity, and the anticipated effects on 

marine mammals. In that notice, we 

requested public input on the request 

for authorization described therein, our 

analyses, the proposed authorization, 

and any other aspect of the notice of 

proposed IHA, and requested that 

interested persons submit relevant 

information, suggestions, and 

comments. 

During the 30-day public comment 

period, NMFS received comments from 

Hilcorp, the Center for Biological 

Diversity (CBD), and Cook Inletkeeper. 

All relevant, substantive comments, and 

NMFS’ responses, are provided below 

and are organized by topic. The 

comments and recommendations are 

available online at: https://

www.fisheries.noaa.gov/national/ 

marine-mammal-protection/incidentaltake-authorizations-constructionactivities. Please see the comment 

submissions for full details regarding 

the recommendations and supporting 

rationale. 

Comment 1: Hilcorp requests that 

NMFS provide context for the term 

‘‘serious’’ as used in the description of 

effects that temporary threshold shifts 

(TTS) can have on marine mammals 

included in the Federal Register notice 

for the proposed IHA (89 FR 60164, July 

24, 2024) and/or edit for better accuracy. 

Response: NMFS reviewed the 

referenced text provided in the Potential 

Effects of Specified Activities on Marine 

Mammals and Their Habitat of the 

notice of proposed IHA, which is 

referenced in this notice. We 

determined the discussion was 

sufficiently clear as originally written. 

Comment 2: Hilcorp requests that 

NMFS clarify that NMFS has found 

permanent threshold shifts (PTS) to not 

be likely based on the modeling results 

provided in the Federal Register notice 

for the proposed IHA (89 FR 60164, July 

24, 2024). 

Response: NMFS concurs that PTS 

resulting from Hilcorp’s tugging 

activities is unlikely. As described in 

the Federal Register notice for the 

proposed IHA (89 FR 60164, July 24, 

2024), Hilcorp contracted SLR 

Consulting to model the extent of the 

harassment isopleths for tugs under load 

with a jack-up rig during their planned 

activities. The modeling efforts used 

detailed propagation calculations that 

accounted for local bathymetry and 

specific sound source locations and 

frequency-dependent propagation 

effects in an attempt to improve the 

representation of the influence of 

relevant environmental variables on the 

propagation of sound from Hilcorp’s 

planned activities. The results of these 

modeling efforts estimated distances to 

PTS thresholds under the mobile tug 

scenarios that are smaller than the 

overall size of the tug and rig 

configuration (i.e., less than or equal to 

8 meters (m)), making it unlikely an 

animal would remain close enough to 

the tug engines to incur PTS. For 

stationary positioning of the jack up rig, 

the PTS isopleths for both the 3-tug and 

4-tug scenarios were estimated to be up 

to 749 m for high frequency (HF) 

cetaceans and up to 102 m for all other 

species, but calculated on the 

assumption that an animal would 

remain within several hundred meters 

of the jack-up rig for the full 5 hours of 

noise-producing activity. Given the 

location of the activity is not in an area 

known to be essential habitat for any 

marine mammal species with extreme 

site fidelity, in addition to the mobile 

nature of marine mammals and the 

likelihood of avoidance, NMFS concurs 

that the occurrence of PTS is unlikely 

and thus, Level A harassment was not 

proposed or authorized for any species. 

Comment 3: Hilcorp requests that 

NMFS clarify that the required 

mitigation measures will reduce Level B 

harassment as well as the already 

insignificant potential for Level A 

harassment as a result of the specified 

activity. 

Response: As described in NMFS’ 

response to Comment 2, there is a 

discountable potential for marine 

mammals to incur PTS from the project. 

Source levels from Hicorp’s tugging 

activities are anticipated to be relatively 

low, non-impulsive, and animals would 

have to remain at very close distances 

for multiple hours to accumulate 

acoustic energy at levels that could 

damage hearing. We agree that 

mitigation measures required by NMFS 

are expected to be effective in further 

reducing the potential for Level A and 

Level B harassment and minimizing 

impacts of the specified activity. These 


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measures include the employment of 

multiple protected species observers 

(PSOs), vessel maneuvering restrictions, 

pre-clearance monitoring prior to 

commencing activities (which includes 

a measure that Hilcorp must delay any 

tugging activities should Cook Inlet 

beluga whales (CIBWs) be observed at 

any distance or if other marine 

mammals are observed within a 1.5 

kilometer (km) clearance zone) as well 

as a requirement that Hilcorp must 

conduct tugging activities with a 

favorable tide to reduce noise output. 

These required measures should reduce 

any effects of the specified activity on 

marine mammals by minimizing the 

numbers of marine mammals exposed to 

sound and by minimizing the intensity 

of any exposures. Please see the 

Mitigation section of this notice for a 

full description of the required 

mitigation measures. 

Comment 4: Hilcorp notes that some 

of the densities reported in the Federal 

Register notice for the proposed IHA (89 

FR 60164, July 24, 2024) did not match 

those included in the Hilcorp 

application. 

Response: Hilcorp correctly identified 

a typo in table 10 of the notice of 

proposed IHA (89 FR 60164, July 24, 

2024) regarding the density of minke 

whales. The table included a density of 

0.0004 individuals per kilometers 

squared (km2), whereas Hilcorp’s 

application included a density of 

0.00003 individuals per km2. That table 

(table 9 in this notice) has been 

corrected to include the correct density 

estimate of 0.00003 individuals per km2

for this species. 

Hilcorp also commented that the 

density value for CIBWs based on MML 

annual surveys for the entire Cook Inlet 

reported in table 10 in the notice for the 

proposed IHA (89 FR 60164, July 24, 

2024) (i.e., 0.07166 individuals per km2) 

does not align with other numbers 

provided in that table for CIBWs. This 

value was calculated as the average 

density of CIBWs in the entire Cook 

Inlet from 2000 through 2022 as 

indicated by table 16 in Hilcorp’s 

application and is included in table 9 of 

this notice. 

Comment 5: Hilcorp requests that 

NMFS specify that Hilcorp’s activity 

will not cause repeated, sequential 

exposure or repetitious sounds. They 

also state that the best available 

information shows no potential for any 

population level impacts. 

Response: As described in the 

Negligible Impact Analysis and 

Determination section of the notice for 

the proposed IHA (89 FR 60164, July 24, 

2024) and this notice, we describe how 

repeated, sequential exposure to 

elevated noise or repetitious sounds 

from tugs under load with a jack-up rig 

over a long duration could result in 

more significant impacts to individuals 

that could affect a population (via 

sustained or repeated disruption of 

important behaviors such as feeding, 

resting, traveling, and socializing; 

Southall et al., 2007). It is unlikely that 

any individual would be exposed to 

repeated, sequential exposures or 

repetitious sounds from Hilcop’s 

activities given the short duration of 

Hilcorp’s tugging activities (i.e., 6 nonconsecutive days over a 1-year period), 

and the low densities of marine 

mammals in the planned action area 

(see tables 10 in the notice for the 

proposed IHA (89 FR 60164, July 24, 

2024) and table 9 in this notice). 

However, the potential for some repeat, 

sequential exposure or repetitious 

sounds from Hilcorp’s tugging activities, 

though limited, does exist given that 

NMFS does not know with certainty 

that any individuals would not be 

exposed to Hilcorp’s activity more than 

once. 

Despite the small potential for limited 

repeated, sequential exposure or 

repetitive sounds from Hilcorp’s tugging 

activities, NMFS concurs with Hilcorp 

that the best available science supports 

the notion that exposure to tugging 

activities would not have impacts on the 

fitness or reproductive success of any 

individual marine mammals, much less 

population level impacts. Marine 

mammals, including CIBWs, frequent 

and use Cook Inlet despite being 

exposed to anthropogenic sounds such 

as those produced by tug boats and 

other vessels across many years. The 

absence of any pinniped haul outs or 

other known home-ranges in the 

planned action area further decreases 

the likelihood of any population level 

impacts. As described in the Description 

of Sound Sources for the Specified 

Activities section of the notice for the 

proposed IHA (89 FR 60164, July 24, 

2024), while marine mammals may be 

present in low numbers during 

Hilcorp’s tugging activities, most 

individuals, including CIBWs, are 

anticipated to be transiting through the 

area, limiting exposure duration. CIBWs 

in the area are expected to be headed to 

or from the concentrated foraging areas 

farther north near the Beluga River, 

Susitna Delta, and Knik and Turnigan 

Arms. Similarly, humpback whales 

(Megaptera novaeangliae), fin whales 

(Balaenoptera physalus), minke whales 

(Balaenoptera acutorostrata), gray 

whales (Eschrichtius robustus), killer 

whales (Orcinus orca), California sea 

lion (Zalophus californianus), and 

Steller sea lions (Eumetopias jubatus) 

are not expected to remain in the area 

of the tugs. Dall’s porpoise 

(Phocoenoides dalli), harbor porpoise 

(Phocoena phocoena), and harbor seal 

(Phoca vitulina) have been sighted with 

more regularity than many other species 

during oil and gas activities in Cook 

Inlet, but due to the transitory nature of 

these species, they are unlikely to 

remain close to a tug under load for the 

full duration of the noise-producing 

activity. Further, previous observations 

of marine mammals sighted near 

Hilcorp’s planned activities have shown 

little to no observable reactions to tugs 

under load with a jack-up rig (e.g., 

Horsley and Larson, 2023). 

Lastly, no serious injury or mortality 

is anticipated to result from this 

activity. Take by Level A harassment 

(injury) is considered unlikely and is 

not authorized because of the small 

estimated Level A harassment zones 

resulting from tugs under load with a 

jack-up rig (i.e., ≤8 m during mobile 

tugging activities and ≤749 m for 

stationary tugging activities), the mobile 

nature of both the activity itself and 

marine mammals in the project area, 

and the required mitigation and 

monitoring program. Any take that may 

potentially occur would be in the form 

of Level B harassment, likely in the form 

of avoidance of the vessels and the noise 

they produce. Please see the Negligible 

Impact Analysis and Determination 

section of the notice for the proposed 

IHA (89 FR 60164, July 24, 2024) and 

this notice for more detailed 

information regarding why population 

level impacts resulting from the 

additional noise produced by tugs under 

load with a jack-up rig are not 

anticipated. 

Comment 6: Hilcorp suggests that 

because the MMPA requires NMFS to 

use the ‘‘best scientific information 

available’’, NMFS should use the CIBW 

abundance estimate of 331 from Goetz et 

al. (2003) as described in the footnote of 

table 12 of the Federal Register notice 

for the proposed IHA (89 FR 60164, July 

24, 2024) rather than 271 from the most 

recent Stock Assessment Report (Young 

et al., 2023) when considering the 

percentage of the stock proposed to be 

authorized for taking. 

Response: As noted by Hilcorp, the 

abundance estimate provided by Goetz 

et al. (2023) is the most recent CIBW 

abundance estimate available. Footnotes 

8 and 4 in tables 2 and 12, respectively, 

of the notice of the proposed IHA (and 

table 1 and table 11 in this notice) also 

state that ‘‘in accordance with the 

MMPA, this population estimate will be 

incorporated into the CIBW SAR, which 

will be reviewed by an independent 


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panel of experts, the Alaska Scientific 

Review Group. After this review, the 

SAR will be made available as a draft for 

public review before being finalized.’’ 

Even when more recent abundance 

estimates are available, NMFS typically 

considers abundance estimates from the 

SARs to be the best available given the 

rigorous SAR review process. However, 

in this case, regardless of whether the 

number of instances of takes is 

compared to the abundance estimate in 

the current CIBW SAR or the Goetz et 

al. (2023) abundance estimate, the 

number of instances of take as a percent 

of the stock abundance is less than 6 

percent and is considered to be small 

numbers even if each instance of take 

represents a different CIBW. 

Comment 7: Hilcorp requests that 

NMFS delete the requirement of the 

proposed IHA that they must monitor 

the project area to the maximum extent 

possible based on the required number 

of PSOs, required monitoring locations, 

and environmental conditions. They 

state that Hilcorp is not required to 

‘‘monitor the project area to the 

maximum extent possible,’’ but rather is 

required to monitor certain zones, 

according to the terms of the IHA. 

Response: NMFS has revised the IHA 

to make clear that the requirement to 

‘‘monitor the project area to the 

maximum extent possible’’ does not 

refer to mitigation clearance zones but is 

rather a monitoring requirement that 

applies once operations commence. 

Specifically, we moved that 

requirement, which Hilcorp included in 

its application, to item 5(a) of the IHA, 

which addresses monitoring 

requirements during tug operations (in 

acknowledgement of the fact that 

Hilcorp will not be able to shut down 

activities once the tugs are under-load 

with the jack-up rig). We have also 

clarified in the final IHA that the 

maximum extent possible is the 

maximum distance possible. 

The monitoring requirement during 

operations is distinguished from the 

mitigation-related pre-clearance zones 

identified in item 4 of the IHA, which 

identifies the clearance zones that must 

be monitored as part of a preoperational mitigation requirement. See 

the Mitigation section of this final 

notice for additional details. 

Comment 8: Hilcorp requests that 

NMFS delete and/or modify language 

that describes NMFS’ purpose and 

alternatives considered in the agency’s 

Environmental Assessment (EA). 

Specifically they state that language 

included in the draft EA incorrectly 

states NMFS’ purpose, and that NMFS 

does not have the authority to require 

Hilcorp to use alternative technologies. 

Response: NMFS believes the 

referenced paragraph regarding NMFS’ 

purpose in the EA appropriately 

describes our intent (which includes 

evaluating the information in Hilcorp’s 

application). Therefore, NMFS has not 

deleted the referenced text as requested 

by Hilcorp. NMFS has revised the 

language referring to alternatives 

considered but eliminated from further 

consideration to clarify that NMFS does 

not have authority under the MMPA to 

prescribe that an applicant use 

alternative technologies to accomplish 

their objectives (i.e., an IHA does not 

authorize an activity, rather take of 

marine mammals incidental to an 

activity). 

Comment 9: CBD states that NMFS 

failed to seriously evaluate the assertion 

that noise from tugboats is the highest 

noise threat to CIBWs according to 

NMFS’ Recovery Plan for CIBWs 

(NMFS, 2016). 

Response: NMFS’ Recovery Plan 

(NMFS, 2016) ranks noise from tugboats 

as the most important source that could 

potentially interfere with CIBW 

recovery based on signal characteristics 

and spatio-temporal acoustic footprint. 

Specifically, NMFS (2016) identified 

propeller cavitation (the formation of 

bubbles in a liquid) and engine noise 

including azimuth/bow thruster noise 

from tug boats as concerning. However, 

notably, the Recovery Plan is 

referencing tugboat noise as a whole 

across all vessels and the entirety of 

Cook Inlet, not Hilcorp’s specified 

activity in the specified location and 

geographic region, which is likely a 

small portion of overall tugboat use in 

Cook Inlet throughout the year. The 

NMFS Alaska Regional Office (AKRO) 

issued a Biological Opinion on 

September 4, 2024, under section 7 of 

the Endangered Species Act (ESA), on 

the issuance of an IHA to Hilcorp under 

section 101(a)(5)(D) of the MMPA by the 

NMFS Office of Protected Resources, 

which addressed the impacts of the 

CIBW take NMFS is authorizing in the 

context of both the environmental 

baseline and the cumulative effects 

(including tugboats) and found that it is 

not likely to jeopardize the continued 

existence of CIBWs or to destroy or 

adversely modify their designated 

Critical Habitat. 

NMFS acknowledges that the sounds 

produced by Hilcorp’s tugging activities 

may potentially result in take, by Level 

B harassment (behavioral disturbance), 

of some marine mammals, most likely in 

the form of avoidance of the vessels and 

the noise they produce. As described in 

the Estimated Take section of the notice 

for the proposed IHA (89 FR 60164, July 

24, 2024) and this notice, the sound 

source levels of tugging activities range 

widely according to the level of 

operational effort, with full power 

output and higher speeds generating 

more propeller cavitation and hence 

greater sound source levels than lower 

power output and lower speeds. As 

such, Hilcorp will implement mitigation 

measures intended to reduce the sound 

source levels from the tugs under load. 

First, the IHA requires that Hilcorp must 

conduct tug towing rig operations with 

a favorable tide unless human safety or 

equipment integrity are at risk. This is 

in an effort to reduce the operational 

effort of the tugs under load and to 

minimize source levels from Hilcorp’s 

activities. Further, Hilcorp will only use 

bow thrusters occasionally for a short 

duration (20 to 30 seconds) to either 

push or pull a vessel in or away from 

a dock or platform, and the total tugging 

activities will be limited to (at most) 6 

days of operations out to an estimated 

maximum distance of 4,453 m around 

the noise source. Last, the IHA prohibits 

Hilcorp from initiating tugging activities 

if a CIBW is observed at any distance 

within the pre-clearance monitoring 

period. If a CIBW(s) is observed during 

those 30 minutes, operations may not 

commence until the CIBW(s) is no 

longer detected at any range or 30 

minutes have elapsed without any 

observations of CIBWs. Therefore, 

NMFS anticipates that Hilcorp would 

not initiate a tow (which would include 

the use of bow thrusters) if a CIBW is 

within the portion of the Level B 

harassment zone that is closer to the 

activity, and thus more likely to disturb 

a CIBW. Lastly, it is important to note 

that there are multiple contextual 

factors (including the signal 

characteristics and the spatio-temporal 

(space and time) acoustic footprint of 

Hilcorp’s activity as well as bearing and 

distance, predictability of source 

movement, and likelihood of 

habituation to routine vessel traffic) that 

minimize this potential and the 

likelihood of behavioral disturbance 

even if a marine mammal is exposed 

above the Level B harassment threshold. 

Based on this analysis, NMFS has made 

the determinations required by the 

MMPA and authorized take accordingly. 

Comment 10: CBD asserts that NMFS 

should defer issuance of incidental take 

of CIBWs unless and until NMFS has a 

better understanding of the reasons the 

species is failing to recover. They state 

that until it does so, NMFS has no 

rational basis for concluding that any 

amount of take constitutes a ‘‘negligible 

impact’’ to the species. Cook Inletkeeper 

also comments that NMFS should not 

authorize any take of CIBWs due to 


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uncertainty regarding trends in their 

population and the impacts that 

anthropogenic noise may have on this 

species. 

Response: NMFS shares the 

commenter’s concern regarding the 

impacts of human activities on CIBWs 

and is committed to supporting the 

conservation and recovery of the 

species. Under section 101(a)(5)(D) of 

the MMPA, NMFS considers the at-risk 

status of CIBWs (and other species) in 

both the negligible impact analysis and 

through our consideration of impact 

minimization measures that support the 

least practicable adverse impact on 

those species. For example, the IHA 

includes a requirement for Hilcorp to 

delay the commencement of tugging 

activities should CIBWs be observed at 

any distance during the pre-clearance 

monitoring period and requires that tug 

operations occur with favorable tides. 

However, section 101(a)(5)(D) also 

mandates that NMFS ‘‘shall issue’’ an 

IHA, provided the necessary findings 

are made for the specified activity for 

which incidental take is requested. 

In accordance with our implementing 

regulations at 50 CFR 216.104(c), we use 

the best available scientific evidence to 

determine whether the taking by the 

specified activity within the specified 

geographic region will have a negligible 

impact on the species or stock and will 

not have an unmitigable adverse impact 

on the availability of such species or 

stock for subsistence uses. Based on the 

scientific evidence available, NMFS 

determined that the take, by Level B 

harassment only, incidental to Hilcorp’s 

tugging of the jack-up rig, which is 

primarily acoustic in nature, transient, 

and of a low level, would have a 

negligible impact on CIBWs. Moreover, 

Hilcorp proposed and NMFS has 

required in the IHA a rigorous 

mitigation plan to further reduce 

potential impacts to CIBWs (and other 

marine mammal species/stocks) to the 

lowest level practicable. Additionally, 

the ESA Biological Opinion determined 

that the issuance of the IHA is not likely 

to jeopardize the continued existence of 

CIBWs, the Mexico Distinct Population 

Segment (DPS) of humpback whales, the 

Western DPS of Steller sea lions, and 

the Northeast Pacific stock of fin 

whales, or to destroy or adversely 

modify CIBW critical habitat. The 

Biological Opinion also outlined Terms 

and Conditions and Reasonable and 

Prudent Measures to reduce impacts, 

which have been incorporated into the 

IHA. Therefore, based on the analysis of 

potential effects, the parameters of the 

activity, and the rigorous mitigation and 

monitoring program, NMFS determined 

that the taking from the specified 

activity would have a negligible impact 

on the CIBW stock. 

Cook Inletkeeper stated that recent 

changes in survey methods calls into 

question the reliability of using the most 

recent aerial survey data to identify 

trends in population status, and that 

based upon this potential uncertainty 

and the impact that anthropogenic noise 

may have on this species, NMFS should 

not authorize any take of CIBWs. Cook 

Inletkeeper is incorrect in that survey 

methods for detecting trends in CIBW 

population have changed; the survey 

field methods are essentially unchanged 

since 2004 (Paul Wade, personal 

communication, December 11, 2023). 

The analysis methods used to detect 

trends in the CIBW population have 

been updated and implemented in 

recent studies examining the CIBW 

population, notably Sheldon and Wade 

(2019) and Goetz et al. (2023). 

Results of recent studies provide 

evidence that the CIBW population 

increased between 2004 and 2010, 

declined after 2010, and increased again 

from 2016 to 2022 (Jacobsen et al., 2020; 

Shelden and Wade, 2019; Warlick et al., 

2023; Goetz et al., 2023). While there is 

some uncertainty around CIBW 

population trend analyses, the results of 

these four studies are consistent in 

showing general trends. Thus, while 

Cook Inletkeeper is correct that some 

studies confirm a declining trend in 

CIBW abundance, recent studies, which 

NMFS considers the best scientific 

information available, suggest the 

population may now be increasing (see 

Goetz et al., 2023). Additional data in 

the coming years will help to inform 

whether the recent positive trend in the 

CIBW population will continue. 

Beyond the requirements in this IHA 

to minimize the impact of any taking 

from Hilcorp’s activity, NMFS is taking 

several proactive steps to help protect 

and better understand the species. For 

example, NMFS is supporting the 

development of a population 

consequences of disturbance (PCoD) 

model, currently being developed by 

NMFS researchers, to quantitatively 

assess the degree to which 

anthropogenic disturbance, and in 

particular noise, may impact survival 

and reproduction of CIBWs. Results of 

Phase 1 of the model were published in 

2023 (McHuron et al., 2023) and the 

Phase 2 analysis is underway. NMFS 

also continues to conduct outreach and 

education to various stakeholders to 

minimize the potential for unauthorized 

take of CIBWs. NMFS also issued Cook 

Inlet and Kodiak Marine Mammal 

Disaster Response Guidelines in 2019 

(NMFS, 2019b) and a stranding response 

plan specific to CIBWs in 2009 (NMFS, 

2009), which could inform responses 

and further reduce impacts to CIBWs. 

NMFS initiated efforts to update the 

2009 stranding response plan in 2021, 

and those efforts are ongoing. For more 

information, see NMFS’ 5-year Priority 

Action Plan (2021–2025) for CIBWs as 

part of its Species in the Spotlight 

initiative to provide immediate, targeted 

efforts to halt declines and stabilize 

populations of the species most at-risk 

of extinction in the near future (see 

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

resource/document/species-spotlightpriority-actions-2021-2025-cook-inletbeluga-whale). 

Comment 11: CBD and Cook 

Inletkeeper comment that NMFS cannot 

issue ‘‘Renewed’’ IHAs under the 

MMPA. CBD further comments that 

NMFS cannot issue ‘‘successive’’ IHAs 

without a comprehensive analysis and 

must analyze and mitigate the total take 

it is proposing to authorize across all 

two years. CBD states that the 15-day 

comment period proposed for renewals 

is also unlawful and places a burden on 

interested members of the public to 

review not only the original 

authorization and supporting 

documents but also the draft monitoring 

reports, the renewal request, and the 

proposed renewed authorization and 

then to formulate comments, all within 

15 calendar days. They assert that 

NMFS should set forth, via proposed 

regulation or policy document, its 

rationale for the Renewal process and to 

allow public comment. 

Response: The process of issuing a 

renewal IHA does not bypass the public 

notice and comment requirements of the 

MMPA. The notice of the proposed IHA 

initiated a 30-day public comment 

period and expressly notifies the public 

that under certain, limited conditions an 

applicant could seek a renewal IHA for 

an additional year. The notice describes 

the conditions under which such a 

renewal request could be considered 

and expressly seeks public comment in 

the event such a renewal is sought. 

Importantly, any such renewals (if 

issued) would be limited to where the 

activities are identical or nearly 

identical to those analyzed in the 

proposed IHA, monitoring does not 

indicate impacts that were not 

previously analyzed and authorized, 

and the mitigation and monitoring 

requirements remain the same, all of 

which allow the public to comment on 

the appropriateness and effects of a 

renewal at the same time the public 

provides comments on the initial IHA. 

Importantly, renewal IHAs are 

evaluated by NMFS on a case-by-case 

basis and are not an automatic matter of 

right. Each 1-year IHA must 


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independently satisfy the negligible 

impact standard for the authorized 

taking and include the means of 

effecting the least practicable adverse 

impact on the species or stock and its 

habitat and, where relevant, on the 

availability of such species or stock for 

taking for subsistence uses (i.e., 

mitigation). Moreover, NMFS is not 

proposing to issue a ‘‘successive’’ IHA 

for a second year. For these reasons a 

comprehensive analysis of the impacts 

of potential take across two years is not 

appropriate under the MMPA. Any 

renewal request would be evaluated 

under the appropriate statutes (e.g., 

MMPA, National Environmental Policy 

Act (EPA), and ESA) for compliance 

with relevant standards. These analyses 

would consider the environmental 

baseline at that time, including any 

impacts of the IHA we have issued. 

Should a renewal request be made, 

additional documentation would be 

required from Hilcorp that NMFS would 

make publicly available and would use 

to verify that the activities are identical 

to those in the initial IHA, are nearly 

identical such that the changes would 

have either no effect on impacts to 

marine mammals or decrease those 

impacts, or are a subset of activities 

already analyzed and authorized but not 

completed under the initial IHA. NMFS 

would also confirm, among other things, 

that the activities would occur in the 

same location; involve the same species 

and stocks; provide for continuation of 

the same mitigation, monitoring, and 

reporting requirements; and that no new 

information had been received that 

would alter the prior analysis. If new 

information has been received that 

would alter the prior analysis, that 

information would be analyzed in the 

notice of the proposed renewal IHA. A 

renewal request would also contain a 

preliminary monitoring report, 

specifically to verify that effects from 

the activities do not indicate impacts of 

a scale or nature not previously 

analyzed. Any renewal request is 

subject to an additional 15-day public 

comment period that provides the 

public an opportunity to review these 

few documents, provide any additional 

pertinent information and comment on 

whether they think the criteria for a 

renewal have been met. Between the 

initial 30-day comment period on these 

same activities and the additional 15 

days, the total comment period for a 

Renewal is 45 days. 

In addition to the IHA renewal 

process being consistent with all 

requirements under section 101(a)(5)(D), 

it is also consistent with Congress’ 

intent for issuance of IHAs to the extent 

reflected in statements in the legislative 

history of the MMPA. Through the 

provision for renewals in the 

implementing regulations, description 

of the process and express invitation to 

comment on specific potential renewals 

in the Request for Public Comments 

section of each proposed IHA, the 

description of the process on NMFS’ 

website, further elaboration on the 

process through responses to comments 

such as these, posting of substantive 

documents on the agency’s website, and 

provision of 30 or 45 days for public 

review and comment on all proposed 

initial IHAs and renewals respectively, 

NMFS has ensured that the public has 

full opportunity to meaningfully 

participate in the agency’s decisionmaking process. 

Comment 12: CBD states that NMFS’ 

small numbers determination is 

arbitrary, unlawful, unreasonable, and 

improper. They comment that NMFS’ 

determination is based on a patently 

unlawful interpretation of what 

constitutes a small number and fails to 

consider that even a relatively small 

number of takes of critical endangered 

CIBWs can be more than small 

considering the species’ highly 

imperiled status. 

In support of NMFS’ small numbers 

determination, Hilcorp recommends 

that NMFS expressly reference the 

Federal Register notice where the 

standard for small numbers is identified 

and fully explained, include that 

reference in the record, and summarize 

that explanation in this final notice of 

IHA issuance. They also request that 

NMFS clearly express its finding that 

the proposed incidental harassment 

levels constitutes a ‘‘small number’’ for 

each marine mammal stock, 

independent of NMFS’s ‘‘one-third’’ 

standard. 

Response: Our notice of the proposed 

IHA referenced an earlier rulemaking in 

which we provided a full explanation of 

the agency’s interpretation of ‘‘small 

numbers.’’ (86 FR 5322, 5438, January 

19, 2021). NMFS makes its small 

numbers findings based on an analysis 

of whether the number of individuals 

authorized to be taken annually from a 

specified activity is small relative to the 

stock or population size. This relative 

approach is consistent with the 

statement from the legislative history 

that ‘‘[small numbers] is not capable of 

being expressed in absolute numerical 

limits’’ (H.R. Rep. No. 97–228, at 19 

(September 16, 1981)), and relevant case 

law (Center for Biological Diversity v. 

Salazar, 695 F.3d 893, 907 (9th Cir. 

2012) (holding that the U.S. Fish and 

Wildlife Service reasonably interpreted 

‘‘small numbers’’ by analyzing take in 

relative or proportional terms)). Using 

such a simple approach that establishes 

equal bins corresponding to small, 

medium, and large proportions of the 

population abundance, 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. (86 

FR 5322, 5438, January 19, 2021). 

As described in the Small Numbers 

section of the Federal Register notice of 

the proposed IHA (89 FR 60164, July 24, 

2024) and this notice of issuance, NMFS 

is authorizing take of less than 2 percent 

for all stocks, except for CIBWs whose 

authorized take is 5.38 percent of the 

stock; see tables 12 and 11 in the notice 

for the proposed IHA (89 FR 60164, July 

24, 2024) and this notice, respectively). 

Here, NMFS finds the taking of 5.38 

percent of CIBWs, and 2 percent of other 

14 other stocks of marine mammals 

constitutes small numbers of marine 

mammals taken relative to the 

population size of the affected species 

or stocks. As Hilcorp’s comment letter 

points out, these percentages also fall 

under the amount upheld as small 

numbers by the U.S. District Court for 

the District of Alaska in Native Village 

of Chickaloon v. NMFS, 947 F. Supp. 2d 

1031 (D. Alaska 2013) (concluding that 

NMFS’ authorization of 10 percent of 

CIBWs constituted small numbers 

relative to the affected population size). 

This is well below NMFS’ upper limit 

of one-third as described above. Further, 

using the take numbers (which actually 

represent instances of take) to compare 

to the population abundance 

conservatively assumes (for small 

numbers purposes) that each take 

represents a different individual (rather 

than a few individuals experiencing 

multiple instances of take). Therefore, 

NMFS has deemed the taking to be of 

small numbers of marine mammals 

(relative to the relevant species or stock 

abundances). 

Finally, we disagree with CBD’s 

assertion that NMFS’ small number 

determination for CIBWs should 

consider the highly imperiled status of 

the species. The argument to establish a 

small numbers threshold on the basis of 

stock-specific context is unnecessarily 

duplicative of the required negligible 

impact finding, in which relevant 

biological and contextual factors are 

considered in conjunction with the 

amount of take, and would risk 

conflating the two standards. See Ctr. 

for Biological Diversity v. Salazar, 695 

F.3d at 907 (cautioning the U.S. Fish 

and Wildlife Service to ‘‘keep[] the 

standards distinct’’). 

Comment 13: CBD comments that 

NMFS’ negligible impact determination 

is improper and arbitrary. They state 


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that it overlooks that CIBWs are among 

the most highly endangered animals 

under the agency’s jurisdiction to 

protect. They state that NMFS has no 

rational basis for concluding that 

additional harassment by noise has a 

negligible impact on the species. 

Response: NMFS disagrees with the 

comment. In the Negligible Impact 

Analysis and Determination section of 

the notice of the proposed IHA (89 FR 

60164, July 24, 2024) and again in this 

notice, we describe how the take 

estimated and authorized for Hilcorp’s 

tugging activity will have a negligible 

impact on all of the affected species or 

stocks, including CIBWs. We discuss 

how this determination is based upon, 

among other things, the low number of 

takes of each stock that might be 

exposed briefly during 6 days of activity 

over the course of the 1-year IHA, the 

comparatively low level of behavioral 

harassment that might result from an 

instance of take that could occur within 

that year, and the likelihood that the 

mitigation measures required further 

lessen the likelihood, magnitude, or 

severity of exposures. NMFS also 

considered the status of each stock in its 

analysis. 

NMFS’ negligible impact finding 

considers a number of parameters 

including, but not limited to, the nature 

of the activities (e.g., duration, sound 

source), effects/intensity of the taking, 

the context of takes, and mitigation. For 

CIBWs, NMFS considered data from 

previous similar tugging activities. 

Hilcorp’s most recent annual marine 

mammal monitoring report indicates 

that it did not record any sightings of 

CIBWs from their rig-based monitoring 

efforts (Horsley and Larson, 2023), and 

the most recent monthly monitoring 

report that describes monitoring results 

from the May 2024 rig transiting also 

indicates no recorded sightings of 

CIBWs during transit (Weston Solutions, 

2024). Any disturbance that may occur 

is anticipated to be limited to behavioral 

changes such as increased swim speeds, 

changes in diving and surfacing 

behaviors, and alterations to 

communication signals, not the loss of 

foraging capabilities or the 

abandonment of critical habitat. Given 

these anticipated impacts, none of 

which would be expected to impact the 

fitness or reproduction of any 

individual marine mammals, much less 

adversely impact annual rates of 

recruitment or survival of CIBWs, 

NMFS’ independent evaluation of the 

best scientific evidence in this case 

supports our negligible impact 

determination. Further, the ESA 

Biological Opinion concluded that the 

proposed action is not likely to 

jeopardize the continued existence of 

CIBWs or to destroy or adversely modify 

designated CIBW critical habitat. 

Comment 14: CBD asserts that NMFS 

discounts the best available science for 

CIBWs. CBD claims that NMFS 

incorrectly stated that CIBWs are not 

known to engage in critical behaviors in 

the area where Hilcorp’s project is 

planned. 

Response: NMFS acknowledges 

observation of two potential but 

unconfirmed incidences of mating 

behavior in the Trading Bay area in 

2014, but the extent to which critical 

behaviors occur in Hilcorp’s project area 

is still unknown (Lomac-Macnair et al., 

2016). Such behaviors have not been 

reported since. Surveys by NMFS or 

McGuire et al. (2020) with concentrated 

effort on the western coast of Cook Inlet 

have not yielded a comparable sighting. 

Other key behaviors, such as calving 

and feeding, are described in more 

detail below but are thought to occur 

primarily in other concentrated areas 

outside of Hilcorp’s action area. 

We are unaware of any information 

regarding areas where CIBWs are more 

likely to engage in mating behavior, 

however, what is known about calving 

suggests that it is most concentrated in 

the upper Inlet, north of Hilcorp’s 

project area. McGuire et al. (2020) 

characterizes habitat use by age class in 

northern Cook Inlet and documented 

the majority of calves in the 

northernmost parts of Cook Inlet (e.g., 

Susitna Delta) despite concentrated 

survey effort in areas along the west part 

of the Inlet heading south toward the 

Forelands. NMFS acknowledges that 

CIBWs use the area, especially in spring 

and fall months, but their habitat range 

at those times is not nearly as 

constricted as their summer habitat, 

which is concentrated in a small area 

with high anthropogenic activity. 

CIBWs may well occur in the project 

area, which is why a small amount of 

take by Level B harassment is 

authorized for this species incidental to 

Hilcorp’s jack-up rig towing. Tagging 

data, acoustic studies, and opportunistic 

sightings indicate that CIBWs continue 

to occur in the upper inlet throughout 

the winter months, in particular the 

coastal areas from Trading Bay to Little 

Susitna River, with foraging behavior 

detected in lower Knik Arm and 

Chickaloon Bay, and also detected in 

several areas of the lower inlet such as 

the Kenai River, Tuxedni Bay, Big River, 

and NW Kalgin Island (e.g., Castellote et 

al., 2020, 2021; C. Garner, pers. comm.; 

Shelden et al., 2015a, 2018). CIBWs 

were historically seen in and around the 

Kenai and Kasilof rivers during June 

aerial surveys conducted by ADFG in 

the late 1970s and early 1980s and by 

NMFS starting in 1993 (Shelden et al., 

2015b), and throughout the summer by 

other researchers and local observers. In 

recent years, sightings in and near these 

rivers have been more typical in the 

spring and fall (Ovitz, 2019). It is 

unknown if this is due to increased 

monitoring efforts in the area or an 

increase in CIBWs using this area. While 

visual sightings indicate peaks in spring 

and fall, acoustic detections indicate 

that CIBWs can be present in the Kenai 

River throughout the winter (Castellote 

et al., 2016). Despite the historic 

sightings (1970s–1990s) of CIBWs 

throughout the summer (June–August) 

in the area, recent acoustic detections 

and visual sightings indicate that there 

appears to be a steep decline in CIBWs 

presence in the Kenai River during the 

summer, despite an annual return in 

recent years of 1–1.8 million sockeye 

salmon, which are important CIBW 

prey. Further, while feeding behaviors 

may occur in Hilcorp’s project area, 

there are no known foraging hot spots 

near the project area. CIBWs are 

expected to be transiting through the 

area, headed to or from the concentrated 

foraging areas farther north near the 

Beluga River, Susitna Delta, and Knik 

and Turnigan Arms. Therefore, any 

exposures are likely to be limited in 

duration during the 6 days of tugging 

activity and would take place in a small 

portion of available foraging habitat. 

Any impacts on feeding are expected to 

be minimal. 

As described above, we have no 

reason to expect CIBWs to be 

concentrated in the path of Hilcorp’s tug 

boats for the purposes of reproductive or 

feeding behaviors, but even if one or 

more of the 15 instances in which noise 

from tugboat operations briefly 

intersects with an individual CIBW 

engaged in these behaviors, the 

anticipated short duration and low level 

disturbance of any such encounter 

would not be likely to impact 

reproductive or foraging success of any 

individuals. 

The commenter further asserts that 

NMFS’ negligible impact conclusion is 

particularly arbitrary considering the 

project will occur within a year-round 

Biologically Important Area (BIA) for 

CIBWs and also in CIWB critical habitat. 

While exposure to elevated noise levels 

associated with Hilcorp’s activities may 

result in low-level behavioral changes in 

marine mammals, NMFS’ review of the 

best available scientific evidence, as 

summarized and cited herein, 

demonstrates that these responses do 

not rise to the level of having adverse 

effects on the reproduction or survival 

of any marine mammals, much less on 


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rates of recruitment or survival of any 

species or stock, and the commenter has 

provided no evidence to the contrary. 

Further, while Hilcorp’s project area 

does overlap ESA-designated critical 

habitat for CIBWs and the CIBW small 

and resident BIA (Wild et al., 2023), the 

impacts from the project are not 

expected to occur in areas that are 

specifically important for feeding or 

reproduction for any species, including 

CIBWs, nor are they anticipated to result 

in a loss of prey or habitat. Monitoring 

data from Hilcorp’s past activities 

suggest that tugging activities do not 

discourage CIBWs from transiting 

throughout Cook Inlet and between 

critical habitat areas and that the whales 

do not abandon critical habitat areas 

(Horsley and Larson, 2023). In addition, 

large numbers of CIBWs have continued 

to use Cook Inlet and pass through the 

area, likely traveling to critical foraging 

grounds found in upper Cook Inlet (i.e., 

outside of the project area), while noiseproducing anthropogenic activities, 

including vessel use, have taken place 

during the past two decades (e.g., 

Shelden et al., 2013, 2015b, 2017, 2022; 

Shelden and Wade, 2019; Geotz et al., 

2023). 

Comment 15: CBD asserts that NMFS 

negligible impact determination for all 

species relies on mitigation measures 

that rely nearly exclusively on visual 

monitoring measures that it claims are 

‘‘known to be ineffective and 

inadequate’’ to protect marine 

mammals. 

Response: NMFS disagrees with the 

comment. Our discussion in the 

Negligible Impact Analysis and 

Determination section below contains 

the factors NMFS considered in 

reaching its negligible impact 

determinations. Although NMFS’ 

implementing regulations at 50 CFR 

216.104(c) state that NMFS may 

incorporate successful implementation 

of mitigation measures to arrive at a 

negligible impact determination, for 

issuance of the IHA for Hilcorp’s tug 

towing activities, NMFS did not rely 

upon an assumption of set level of 

effectiveness in mitigation to make our 

negligible impact determinations. While 

NMFS acknowledges that visual 

observations can be difficult in Cook 

Inlet due to the extreme tidal range, 

harsh weather, turbid waters, and 

seasonal ice presence (e.g., Castellote et 

al., 2020; Lammers et al., 2013), prior 

monitoring efforts by Hilcorp have 

shown that it is clearly possible to 

detect and identify marine mammals to 

the species several km away from the 

source, including CIBWs, 

acknowledging that visibility depends 

on several factors such as visual acuity, 

sea state, glare, light, animal behavior/ 

body type, speed of travel for vessel and 

animal, etc. (Horsley and Larson, 2023). 

NMFS does not assume total 

effectiveness of monitoring, but the 

demonstrated record of PSO sightings 

for activities in Cook Inlet illustrate that 

visual monitoring is appropriate for 

implementing mitigation in this case. 

Comment 16: CBD and Cook 

Inletkeeper comment that NMFS fails to 

ensure the least practicable adverse 

impact on CIBWs, the other species or 

stocks to be taken, and their habitats 

because NMFS failed to consider 

requiring several practicable mitigation 

measures, such as the use of passive 

acoustic monitors (PAM) and drones to 

help detect the presence of marine 

mammals, time-area restrictions, and 

requiring the use of noise-quieting 

engines. Cook Inletkeeper recommended 

that NMFS should require improved 

look-outs for marine mammals and 

additional monitoring. 

Response: We disagree with the 

commenter’s claims. NMFS has 

included measures designed to effect 

the least practicable adverse impact on 

marine mammals species and their 

habitat, and has also included 

appropriate monitoring and reporting 

requirements. For example, during 

tugging activities, Hilcorp must conduct 

pre-clearance monitoring prior to 

commencing activities and must delay 

the start of activities if marine mammals 

are within designated pre-clearance 

zones (1,500 m for non-CIBW species 

and at any distance for CIBWs). Hilcorp 

must also conduct tugging activities 

with a favorable tide to reduce noise 

output. Please see the Mitigation section 

of this notice for a full description of the 

required mitigation measures. 

The CBD states that NMFS should 

require PAM for marine mammals. The 

use of PAM for real-time mitigation 

purposes has been used in Cook Inlet for 

some studies. These efforts have 

generally not resulted in successful 

deployment of PAM or useful detections 

of marine mammals to inform mitigation 

and monitoring during the activities due 

to the environmental conditions of the 

region (Austin and Zeddies, 2012; 

Kendall et al., 2015). For example, 

background acoustic conditions, 

including flow noise from strong 

currents, large tidal changes, and 

weather along with additional noise 

from the project (e.g., vessel noise, noise 

from project equipment) made it 

difficult to detect marine mammals from 

a real-time PAM system implemented as 

part of the 2012 Apache 3D seismic 

survey program in lower- and mid-Cook 

Inlet (Austin and Zeddies, 2012; LomacMacNair et al., 2013) and during the 

2015 SAExploration Cook Inlet 3D 

seismic survey program (Kendall et al., 

2015). Further, environmental 

conditions restricted the type of PAM 

systems that could be deployed during 

these programs to a single omnidirectional hydrophone lowered from 

the side of a vessel, which restricted the 

possible range of detections. These 

factors suggest that effective PAM 

monitoring in Cook Inlet can be 

challenging (Austin and Zeddies, 2012). 

As CBD notes, academic researchers 

have begun to implement more effective 

passive acoustic monitors for research 

purposes at several places in Cook Inlet 

(e.g., Lammers et al., 2013 and 

Castellote et al., 2020 as cited by CBD). 

However, the framework used by those 

researchers is not practicable for 

Hilcorp’s planned activity. An article on 

NOAA’s website (https://

www.fisheries.noaa.gov/science-blog/ 

beluga-whale-acoustic-monitoringsurvey-post-3) illustrates the level of 

customization, expertise, and difficulty 

required to assemble a passive acoustic 

mooring to then deploy in the Inlet. 

Additionally, these instruments are 

stationary, which means to effectively 

use these monitors as a means of 

avoiding harassment of marine 

mammals during Hilcorp’s tugging 

activities, Hilcorp would need to build 

and successfully deploy dozens (or 

more) stationary monitors along a route 

of travel that is subject to change 

depending upon weather or other 

environmental and shipping 

restrictions. Additionally, the data 

stored on these types of moorings is not 

accessible until they are retrieved by the 

researcher who deployed them. In the 

future, if an established network of 

passive acoustic monitors with shared 

access to the data is available, this could 

be a useful tool for implementing 

mitigation measures, but is currently not 

practicable. 

Contrary to CBD’s assertion, NMFS 

did consider a time-area restriction; 

both the IHA and resulting ESA 

Biological Opinion require that Hilcorp 

maintain a distance of at least 2.4 km 

from the mean lower-low water line of 

the Susitna River Delta (Beluga River to 

the Little Susitna River) between April 

15 and November 15, as this is an area 

where CIBWs can aggregate for feeding. 

CBD suggested further restrictions could 

include, for example, a prohibition on 

activities in April and May at Trading 

Bay where and when CIBWs have been 

observed engaged in probable mating 

behavior (Lomac-MacNair et al., 2016); 

or a prohibition on activities from July 

through September when CIBWs have 

been observed feeding in the area. 

Hilcorp’s activity in Trading Bay would 


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be either a single day of transit or 

several hours of positioning the jack-up 

rig at an existing well site. As discussed 

in our above comment response, there 

has been one published observation of 

potential (not confirmed) mating 

behavior of CIBWs in Trading Bay in 

2014. Surveys by NMFS or McGuire et 

al. (2020) with concentrated effort on 

the western coast of Cook Inlet have not 

yielded a comparable sighting. Closure 

of the entire area for two months is not 

practicable as Hilcorp would not be able 

to access the well sites that are part of 

the intended activity. As discussed 

above and in the species-specific section 

of the proposed IHA, CIBWs are highly 

concentrated in the upper Cook Inlet 

especially in the summer months (Goetz 

et al., 2012; McGuire et al., 2020). In the 

past, CIBWs used the Kenai area in 

summer months but that trend has 

shifted in recent decades to occasional 

spring and fall sightings (Ovitz, 2019). 

Throughout the Inlet, mean group sizes 

during the summer and fall were largest 

in July and smallest in October, with the 

largest groups seen during mid-July and 

early August in the Susitna River Delta, 

while the smallest group sizes were in 

the Kenai River Delta. These patterns of 

high seasonal concentrations have 

continued to be documented since 2012 

(e.g., McGuire et al., 2020). In reflection 

of this information, NMFS, as described 

above, has imposed time area 

restrictions in the Susitna River Delta 

from April to November to reduce 

effects of Hilcorp’s activity to the 

greatest extent practicable. A closure in 

the middle Inlet during the summer 

months, in the season with longest 

daylight hours and best conditions for 

visual observations to implement 

mitigation and monitoring, is not 

warranted under the least practicable 

adverse impact standard. 

CBD states that NMFS failed to 

consider requiring noise-quieting 

engines, such as electric tugboats, which 

would have the added benefit of 

reducing air pollution and greenhouse 

gas emissions from tugs. NMFS is not 

aware of any commercially available 

seaworthy tug vessels that are used in 

tandem (e.g., three tug configuration) 

with effective quieting technologies or 

of any company or entity with electric 

tug fleets able to use them in tandem as 

required for Hilcorp’s activities. The 

eWolf, and electronic tug boat, was 

christened in San Francisco Bay in June 

2024 and was the first of its kind in U.S. 

waters. NMFS is also not aware of 

alternative technologies available that 

would allow Hilcorp to move the jackup rig to various well sites without 

generating noise, which is the primary 

activity that has the potential to take 

marine mammals by harassment. 

Further, as described in our response to 

Comment 8, NMFS does not have the 

authority under the MMPA or ESA to 

prescribe that an applicant use 

alternative technologies to accomplish 

their objectives. 

CBD also commented that NMFS 

failed to consider an alternative that 

would require the use of drones, in 

addition to PSOs, to detect the presence 

of marine mammals. Cook Inletkeeper 

similarly suggested that NMFS should 

require a combination of drone and 

visual monitoring at all times. While 

unmanned aerial vehicles (UAVs; i.e., 

drones) have been used in some 

instances to observe marine mammals, 

there are logistical reasons (including 

limited berthing availability) that this 

measure is not practicable for Hilcorp to 

implement for this project. For these 

reasons, NMFS has not required that 

Hilcorp use drones or other UASs to 

assist in detecting marine mammals 

during their planned tugging activities. 

CBD correctly notes that the 1,500 m 

pre-clearance zone for non-CIBWs is 

smaller than the Level B harassment 

zone (≤4,453 m). However, as 

mentioned in the response to Comment 

7 above, NMFS has prescribed a 

requirement for this IHA (not included 

in previous IHAs issued to Hilcorp for 

take of marine mammals incidental to 

tugging activities; 87 FR 62364, October 

14, 2022) that Hilcorp establish a preclearance zone whereby they delay new 

operational activities should CIBWs be 

observed at any distance. This measure 

provides additional protection for 

CIBWs by further limiting the potential 

that tugging activities will commence 

while CIBWs are nearby. Further, using 

the Level B harassment zone as the 

clearance zone would not be practicable 

for some non-CIBW species (e.g., 

pinnipeds, harbor species) whose 

smaller size and often cryptic behavior 

may make accurate identification 

difficult at greater distances in Cook 

Inlet’s environmental conditions. While 

underway, PSOs will observe for marine 

mammals to the greatest distance 

possible (they are not limited to 

observing within 1,500 m of the vessel). 

Any marine mammal sighted by PSOs at 

any distance is noted and reported to 

NMFS, per the reporting requirements 

of the IHAs. 

Cook Inletkeeper recommended that 

NMFS require improved look-outs (i.e., 

additional observers) and additional 

monitoring to better inform about the 

marine mammal populations and 

distributions as well as impacts from the 

proposed activities to better inform 

future activities. Hilcorp has informed 

NMFS that stationing additional PSOs 

on the tug boats or jack-up rig is not a 

practicable option for this project due to 

the limited berthing areas on the 

vessels. Cook Inletkeeper did not 

provide any recommendations for what 

additional monitoring would entail; 

however, the IHA does require that 

Hilcorp monitor and carefully record all 

observations of marine mammals, 

regardless of distance from the activity, 

as well as additional data such the 

group composition of any species 

observations, their distance and bearing 

from the source, their closest approach 

and time spent in estimated harassment 

zones, and any behavioral observations, 

including an assessment of behavioral 

responses thought to have resulted from 

the tugging activities. This information 

will be used to inform any future 

decisions regarding the issuance of IHAs 

for tugging activities, similarly as details 

documented by Hilcorp in their reports 

(e.g., Horsley and Larson, 2023) 

informed the decisions made herein. 

Lastly, Cook Inletkeeper 

recommended that NMFS not permit tug 

towing rig activities during periods of 

low visibility or at night, even to 

accommodate a favorable tide. Hilcorp’s 

ability to move the jack-up rig is limited 

by several factors, including the 

presence of favorable environmental 

conditions for safe operations, crew 

availability, and the availability of the 

tug boats, which is limited by other 

scheduled work. Hilcorp must balance 

these factors with the timing of their 

planned actions. Despite this, Hilcorp 

will only begin operations in low light 

or night conditions if necessary for 

safety purposes (e.g., incoming 

inclement weather or ice) or to 

accommodate a favorable tide. Tugs may 

work at up to 80 percent power for 

much longer durations of time when 

pulling against the strong tides in Cook 

Inlet. As sound is the primary potential 

stressor from the proposed activity, 

limiting the sound output is preferred 

and tugs moving with the tide will 

reduce engine load by as much as 60 

percent. Additionally, limited daylight, 

particularly in the shoulder seasons, 

results in at least a portion of activity 

occurring in low light or night 

conditions. As the ice-free season is 

already limited to roughly half the year, 

in order to maximize the ice-free season, 

operations in low-light or night 

conditions may be necessary. To 

mitigate this and enhance PSO’s 

visibility, PSOs are required to use 

NMFS-approved night vision devices 

(NVDs) (e.g., PVS–7s, or equivalent) and 

have magnifying lenses available for 

use. 


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Comment 17: Cook Inletkeeper asserts 

that NMFS must consider whether the 

cumulative impacts from Hilcorp’s 

proposed activities in Cook Inlet will 

have a negligible impact on the area’s 

marine mammals. Specifically, NMFS 

must consider the cumulative impacts 

of noise in Cook Inlet, including noise 

impacts from vessels and nearby 

construction, and determine what 

activities or combinations of activities 

would exceed a cumulative negligible 

impact threshold. Cook Inletkeeper 

urges NMFS to perform such an analysis 

before authorizing any ITAs for take of 

CIBWs. 

Response: Neither the MMPA nor 

NMFS’ codified implementing 

regulations call for consideration of the 

take resulting from other activities in 

the negligible impact analysis. The 

preamble for NMFS’ implementing 

regulations (54 FR 40338, September 29, 

1989) states, in response to comments, 

that the impacts from other past and 

ongoing anthropogenic activities are to 

be incorporated into the negligible 

impact analysis via their impacts on the 

baseline. Consistent with that direction, 

NMFS has factored into its negligible 

impact analysis the impacts of other 

past and ongoing anthropogenic 

activities via their impacts on the 

baseline (e.g., as reflected in the 

density/distribution and status of the 

species, population size and growth 

rate, and other relevant stressors (such 

as incidental mortality in commercial 

fisheries, Unusual Mortality Events 

(UMEs), and subsistence hunting); see 

the Negligible Impact Analyses and 

Determinations section of this notice of 

issuance). The 1989 final rule for the 

MMPA implementing regulations also 

addressed public comments regarding 

cumulative effects from future, 

unrelated activities. There, NMFS stated 

that such effects are not considered in 

making findings under section 101(a)(5) 

concerning negligible impact. In this 

case, this IHA as well as other 

incidental take authorizations (ITAs) 

currently in effect or proposed within 

the specified geographic region, are 

appropriately considered an unrelated 

activity relative to the others. The ITAs 

are unrelated in the sense that they are 

discrete actions under section 

101(a)(5)(D) issued to discrete 

applicants. 

Through the response to public 

comments in the 1989 implementing 

regulations, NMFS also indicated (1) 

that we would consider cumulative 

effects that are reasonably foreseeable 

when preparing a National 

Environmental Policy Act (NEPA) 

analysis, and (2) that reasonably 

foreseeable cumulative effects would 

also be considered under section 7 of 

the Endangered Species Act (ESA) for 

ESA-listed species, as appropriate. 

Accordingly, NMFS has prepared an EA 

that considers cumulative effects. 

Additionally, under the ESA, NMFS’ 

Biological Opinion independently 

considered the reasonably foreseeable 

cumulative effects of activities on ESAlisted species. 

Comment 18: Cook Inletkeeper raises 

concerns with Hilcorp’s record of safety 

and environmental compliance. They 

state that according to the Alaska Oil 

and Gas Conservation Commission 

(AOGCC), Hilcorp has a documented 

pattern of accidents and safety 

violations and disregard for compliance 

with the law in Alaska. They assert that 

NMFS must consider Hilcorp’s record 

and provide rigorous oversight. 

Response: It is the responsibility of 

the applicants to comply with all 

applicable laws and regulations, and to 

work with the state to obtain approval 

of their Oil Discharge Prevention and 

Contingency Plans (ODPCP). Hilcorp 

complied with the mitigation, 

monitoring, and reporting requirements 

of previously issued LOAs and IHAs 

under the MMPA (Fairweather Science, 

LLC, 2020; Korsmo et al., 2022; Horsley 

and Larson, 2023; Weston Solutions, 

2024), thus we have no reason to believe 

that the requirements of the current IHA 

will not be upheld. 

Changes From the Proposed IHA to 

Final IHA 

There are no changes from the 

proposed IHA to the final IHA other 

than the addition of some clarifying 

language and some minor typographical 

corrections. 

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 authorized 

for this activity and summarizes 

information related to the population or 

stock, including regulatory status under 

the MMPA and 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 authorized 

here, PBR and annual serious injury and 

mortality from anthropogenic sources 

are included in table 1 as gross 

indicators of the status of the species or 

stocks and other threats. 

Marine mammal abundance estimates 

presented in this document represent 

the total number of individuals that 

make up a given stock or the total 

number estimated within a particular 

study or survey area. NMFS’ stock 

abundance estimates for most species 

represent the total estimate of 

individuals within the geographic area, 

if known, that comprises that stock. For 

some species, this geographic area may 

extend beyond U.S. waters. All managed 

stocks in this region are assessed in 

NMFS’ U.S. 2022 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/marinemammal-stock-assessments. 


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TABLE 1—SPECIES 1 WITH ESTIMATED TAKE FROM 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

Order Artiodactyla—Cetacea—Mysticeti (baleen whales) 

Family Eschrichtiidae: 

Gray Whale ...................... Eschrichtius robustus ............. Eastern N Pacific ................... -, -, N 26,960 (0.05, 25,849, 2016) .. 801 131 

Family Balaenidae: 

Family Balaenopteridae 

(rorquals): 

Fin Whale ......................... Balaenoptera physalus ........... Northeast Pacific .................... E, D, Y UND 5 (UND, UND, 2013) ...... UND 0.6 

Humpback Whale ............. Megaptera novaeangliae ........ Hawai1i .................................... -, -, N 11,278 (0.56, 7,265, 2020) .... 127 27.09 

Mexico-North Pacific .............. T, D, Y N/A6 (N/A, N/A, 2006) ........... UND 0.57 

Western North Pacific ............ E, D, Y 1,084 (0.088, 1,007, 2006) .... 3.4 5.82 

Minke Whale .................... Balaenoptera acutorostrata .... Alaska ..................................... -, -, N N/A7 (N/A, N/A, N/A) ............. UND 0 

Odontoceti (toothed whales, dolphins, and porpoises) 

Family Delphinidae: 

Killer Whale ...................... Orcinus orca ........................... Eastern North Pacific Alaska 

Resident.

-, -, N 1,920 (N/A, 1,920, 2019) ....... 19 1.3 

Eastern North Pacific Gulf of 

Alaska, Aleutian Islands 

and Bering Sea Transient.

-, -, N 587 (N/A, 587, 2012) ............. 5.9 0.8 

Pacific White-Sided Dolphin.Lagenorhynchus obliquidens North Pacific ........................... -, -, N 26,880 (N/A, N/A, 1990) ........ UND 0 

Family Monodontidae (white 

whales): 

Beluga Whale ................... Delphinapterus leucas ............ Cook Inlet ............................... E, D, Y 279 8 (0.061, 267, 2018) ........ 0.53 0 

Family Phocoenidae (porpoises): 

Dall’s Porpoise ................. Phocoenoides dalli ................. Alaska ..................................... -, -, N UND 9 (UND, UND, 2015) ...... UND 37 

Harbor Porpoise ............... Phocoena phocoena .............. Gulf of Alaska ......................... -, -, Y 31,046 (0.21, N/A, 1998) ....... UND 72 

Order Carnivora—Pinnipedia 

Family Otariidae (eared seals 

and sea lions): 

CA Sea Lion ..................... Zalophus californianus ........... U.S ......................................... -, -, N 257,606 (N/A, 233,515, 2014) 14,011 >321 

Steller Sea Lion ................ Eumetopias jubatus ................ Western .................................. E, D, Y 49,837 10 (N/A, 49,837, 2020) 299 267 

Family Phocidae (earless 

seals): 

Harbor Seal ...................... Phoca vitulina ......................... Cook Inlet/Shelikof Strait ........ -, -, N 28,411 (N/A, 26,907, 2018) ... 807 107 

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

(https://marinemammalscience.org/science-and-publications/list-marine-mammal-species-subspecies/; Committee on Taxonomy (2022)). 2Endangered Species Act (ESA) status: Endangered (E), Threatened (T)/MMPA status: Depleted (D). 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. 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. 5The best available abundance estimate for this stock is not considered representative of the entire stock as surveys were limited to a small portion of the stock’s 

range. Based upon this estimate and the Nmin, the PBR value is likely negatively biased for the entire stock. 6Abundance estimates are based upon data collected more than 8 years ago and, therefore, current estimates are considered unknown. 7 Reliable population estimates are not available for this stock. Please see Friday et al. (2013) and Zerbini et al. (2006) for additional information on numbers of 

minke whales in Alaska. 8On June 15, 2023, NMFS released an updated abundance estimate for endangered Cook Inlet beluga whales (CIBWs) in Alaska (Goetz et al., 2023). Data collected during NOAA Fisheries’ 2022 aerial survey suggest that the whale population is stable or may be increasing slightly. Scientists estimated that the population 

size is between 290 and 386, with a median best estimate of 331. In accordance with the MMPA, this population estimate will be incorporated into the CIBW SAR, 

which will be reviewed by an independent panel of experts, the Alaska Scientific Review Group. After this review, the SAR will be made available as a draft for public 

review before being finalized. 9The best available abundance estimate is likely an underestimate for the entire stock because it is based upon a survey that covered only a small portion of the 

stock’s range. 10 Nest is best estimate of counts, which have not been corrected for animals at sea during abundance surveys. 

As indicated above, all 12 species 

(with 15 managed stocks) in table 1 

temporally and spatially co-occur with 

the activity to the degree that take could 

occur. In addition, the northern sea otter 

may be found in Cook Inlet, Alaska. 

However, northern sea otters are 

managed by the U.S. Fish and Wildlife 

Service and are not considered further 

in this document. 

A detailed description of the species 

likely to be affected by Hilcorp’s tugging 

activities, including a brief introduction 

to the affected stock as well as available 

information regarding population trends 

and threats, and information regarding 

local occurrence, were provided in the 

Federal Register notice of the proposed 

IHA (89 FR 60164, July 24, 2024). Since 

that time, we are not aware of any 

changes in the status of these species 

and stocks; therefore, detailed 

descriptions are not provided here. 

Please refer to that Federal Register 

notice for these descriptions. Please also 

refer to NMFS’ website (https://

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

generalized species accounts. 

Marine Mammal Hearing 

Hearing is the most important sensory 

modality for marine mammals 


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underwater, and exposure to 

anthropogenic sound can have 

deleterious effects. To appropriately 

assess the potential effects of exposure 

to sound, it is necessary to understand 

the frequency ranges marine mammals 

are able to hear. Not all marine mammal 

species have equal hearing capabilities 

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

and Ketten, 1999; Au and Hastings, 

2008). To reflect this, Southall et al. 

(2007, 2019) recommended that marine 

mammals be divided into hearing 

groups based on directly measured 

(behavioral or auditory evoked potential 

techniques) or estimated hearing ranges 

(behavioral response data, anatomical 

modeling, etc.). Subsequently, NMFS 

(2018) described generalized hearing 

ranges for these marine mammal hearing 

groups. Generalized hearing ranges were 

chosen based on the approximately 65 

decibel (dB) threshold from the 

normalized composite audiograms, with 

the exception for lower limits for lowfrequency cetaceans where the lower 

bound was deemed to be biologically 

implausible and the lower bound from 

Southall et al. (2007) retained. Marine 

mammal hearing groups and their 

associated hearing ranges are provided 

in table 2. Specific to this action, gray 

whales, fin whales, minke whales, and 

humpback whales are considered lowfrequency (LF) cetaceans, beluga 

whales, pacific white-sided dolphins, 

and killer whales are considered midfrequency (MF) cetaceans, harbor 

porpoises and Dall’s porpoises are 

considered high-frequency (HF) 

cetaceans, Steller sea lions and 

California sea lions are otariid 

pinnipeds (OW), and harbor seals are 

phocid pinnipeds (PW). 

TABLE 2—MARINE MAMMAL HEARING GROUPS

[NMFS, 2018] 

Hearing group Generalized hearing range * 

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

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

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

cruciger & L. australis).

275 Hz to 160 kHz. 

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

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

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

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

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

For more detail concerning these 

groups and associated frequency ranges, 

please see NMFS (2018) for a review of 

available information. 

Potential Effects of Specified Activities 

on Marine Mammals and Their Habitat 

The effects of underwater noise from 

Hilcorp’s tugging activities have the 

potential to result in harassment of 

marine mammals in the vicinity of the 

project area. The notice of proposed IHA 

(89 FR 60164, July 24, 2024) included a 

discussion of the effects of 

anthropogenic noise on marine 

mammals and the potential effects of 

underwater noise from tugging activities 

on marine mammals and their habitat. 

That information and analysis is 

referenced in this final IHA 

determination and is not repeated here; 

please refer to the notice of proposed 

IHA (89 FR 60164, July 24, 2024). 

Estimated Take of Marine Mammals 

This section provides an estimate of 

the number of incidental takes 

authorized through the IHA, which will 

inform NMFS’ consideration of ‘‘small 

numbers,’’ 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 will be by Level B 

harassment only, as use of the acoustic 

sources (i.e., tugging activities) may 

result in disruption of behavioral 

patterns of individual marine mammals. 

We note here that given the slow, 

predictable, and generally straight path 

of tug towing, holding, and positioning, 

the likelihood of a resulting disruption 

of marine mammal behavioral patterns 

that would qualify as harassment is 

considered relatively low; however, at 

the request of the applicant, we have 

quantified the potential take from this 

activity, analyzed the impacts, and 

authorized take. The required mitigation 

and monitoring measures are expected 

to minimize the potential for take and, 

if take were to occur, the severity of the 

taking to the extent practicable. Based 

on the nature of the activity (e.g., the 

very small area ensonified above the 

Level A harassment threshold), Level A 

harassment is neither anticipated nor 

authorized. 

No serious injury or mortality is 

anticipated or authorized for this 

activity. Below we describe how the 

take numbers are estimated. 

To determine whether Level B 

harassment is expected to result from 

acoustic exposure, NMFS considers the 

received levels a marine mammal is 

expected to be exposed to as compared 

to the relevant NMFS Level B 

harassment thresholds, as well as 

multiple contextual factors that can 

impact whether a marine mammal’s 

behavioral patterns are likely to be 

disrupted (e.g., bearing and distance, 

predictability of source movement, 

whether habituation in a noisier/busy 

area is likely); specifically, whether any 

contextual factors would be expected to 

lower the likelihood of behavioral 

disturbance even when a marine 

mammal is exposed above the Level B 

harassment threshold. Where the take of 

marine mammals is considered likely or 

is requested by the applicant, generally 

speaking, we estimate take by 

considering: (1) acoustic thresholds 

above which NMFS believes the best 

available science indicates marine 

mammals will be behaviorally harassed 

(absent relevant contextual factors) or 

incur some degree of permanent hearing 

impairment where relevant; (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 


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contribute to a basic calculation to 

provide an initial prediction of potential 

takes, additional information that can 

qualitatively inform take estimates is 

also sometimes available (e.g., previous 

monitoring results or average group 

size). Below, we describe the factors 

considered here in more detail and 

present the take estimates. 

Acoustic Thresholds 

NMFS recommends the use of 

acoustic thresholds that identify the 

received level of underwater sound 

above which exposed marine mammals 

would be reasonably expected to be 

behaviorally harassed (equated to Level 

B harassment) or to incur PTS of some 

degree (equated to Level A harassment). 

Level B Harassment—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., Richardson et al., 1995; 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 support the estimation 

of the onset of Level B harassment and 

to quantify likely Level B harassment. 

Acknowledging the consideration of 

contextual factors noted above, NMFS 

generally predicts that marine mammals 

are likely to be behaviorally disturbed in 

a manner considered to be Level B 

harassment when exposed to 

underwater anthropogenic noise above 

root-mean-squared pressure received 

levels (root mean square [RMS] sound 

pressure level [SPL]) of 120 dB 

(referenced to 1 micropascal (re 1 mPa)) 

for continuous sources (e.g., tugging, 

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 thresholds are expected to 

include any likely takes by TTS as, in 

most cases, the likelihood of TTS occurs 

at distances from the source smaller 

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. 

Hilcorp’s planned activity includes 

the use of continuous sources (tugging 

activities), and therefore the RMS SPL 

threshold of 120 dB is applicable. 

Level A harassment—NMFS’ 

Technical Guidance for Assessing the 

Effects of Anthropogenic Sound on 

Marine Mammal Hearing (Version 2.0) 

(Technical Guidance, 2018) identifies 

dual criteria to assess auditory injury 

(Level A harassment) to five different 

marine mammal groups (based on 

hearing sensitivity) as a result of 

exposure to noise from two different 

types of sources (impulsive or nonimpulsive). Hilcorp’s planned activity 

includes the use of non-impulsive 

sources (i.e., tugging activities). 

The thresholds identifying the onset 

of PTS are provided in table 3 below. 

The references, analysis, and 

methodology used in the development 

of the thresholds are described in 

NMFS’ 2018 Technical Guidance, which 

may be accessed at: https://

www.fisheries.noaa.gov/national/ 

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

Take by Level A harassment is 

considered unlikely for this action 

because of the small estimated Level A 

harassment zones resulting from tugs 

under load with a jack-up rig (i.e., <1 m) 

(as described below), the mobile nature 

of both the activity itself and marine 

mammals in the project area, and the 

required mitigation and monitoring 

program (see the Mitigation and 

Monitoring sections of this notice). 

TABLE 3—THRESHOLDS IDENTIFYING THE ONSET OF 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. 

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

High-Frequency (HF) 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. 

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 (TL) coefficient. 

The sound field in the project area is 

the existing background noise plus 

additional noise resulting from the 

planned project. Marine mammals are 

expected to be affected via sound 

generated by the primary components of 

the project (i.e., tugging activities). 

Calculation of the area ensonified by the 

planned action is dependent on the 

background sound levels at the project 


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79542 Federal Register / Vol. 89, No. 189 / Monday, September 30, 2024 / Notices 

site, the source levels of the planned 

activities, and the estimated TL 

coefficients for the planned activities at 

the site. These factors are addressed 

below. 

Sound Source Levels of Tugging 

Activities. The project includes three to 

four tugs under load with a jack-up rig. 

Hilcorp conducted a literature review of 

underwater sound emissions of tugs 

under various loading efforts. The 

sound source levels for tugs of various 

horsepower (2,000 to 8,200) under load 

can range from approximately 164 dB 

RMS to 202 dB RMS. This range largely 

relates to the level of operational effort, 

with full power output and higher 

speeds generating more propeller 

cavitation and hence greater sound 

source levels than lower power output 

and lower speeds. Tugs under tow 

produce higher source levels than tugs 

transiting with no load because of the 

higher power output necessary to pull 

the load. The amount of power the tugs 

expend while operating is the best 

predictor of relative sound source level. 

Several factors will determine the 

duration that the tugboats are towing the 

jack-up rig, including the origin and 

destination of the towing route (e.g., Rig 

Tenders Dock, an existing platform) and 

the tidal conditions. The power output 

will be variable and influenced by the 

prevailing wind direction and velocity, 

the current velocity, and the tidal stage. 

Unless human safety or equipment 

integrity are at risk, transport will be 

timed with the tide to minimize towing 

duration and power output. 

Hilcorp’s literature review identified 

no existing data on sound source levels 

of tugs towing jack-up rigs. Accordingly, 

for this analysis, Hilcorp considered 

data from tug-under-load activities, 

including berthing and towing 

activities. Austin and Warner (2013) 

measured 167 dB RMS for tug towing 

barge activity in Cook Inlet. Blackwell 

and Greene (2002) reported berthing 

activities in the POA with a source level 

of 179 dB RMS. Laurinolli et al. (2005) 

measured a source level of 200 dB RMS 

for anchor towing activities by a tugboat 

in the Strait of Juan de Fuca, WA. The 

Roberts Bank Terminal 2 study (2014) 

repeated measurements of the same tug 

operating under different speeds and 

loading conditions. Broadband 

measurements from this study ranged 

from approximately 162 dB RMS up to 

200 dB RMS. 

The rig manager for Hilcorp, who is 

experienced with towing jack-up rigs in 

Cook Inlet, described operational 

conditions wherein the tugs generally 

operate at half power or less for the 

majority of the time they are under load 

(pers. Comm., Durham, 2021). Transits 

with the tide (lower power output) are 

preferred for safety reasons, and effort is 

made to reduce or eliminate traveling 

against the tide (higher power output). 

The Roberts Bank Terminal 2 study 

(2014) allowed for a comparison of 

source levels from the same vessel 

(Seaspan Resolution tug) at half power 

versus full power. Seaspan Resolution’s 

half-power (i.e., 50 percent) berthing 

scenario had a sound source level of 180 

dB RMS. In addition, the Roberts Bank 

Terminal 2 Study (2014) reported a 

mean tug source level of 179.3 dB RMS 

from 650 tug transits under varying load 

and speed conditions. 

The 50 percent (or less) power output 

scenario will occur during the vast 

majority of tug towing jack-up rig 

activity. Therefore, based on Hilcorp’s 

literature review, a source level of 180 

dB RMS was found to be an appropriate 

proxy source level for a single tug under 

load based on the Roberts Bank 

Terminal 2 study. If all three tugs were 

operating simultaneously at 180 dB 

RMS, the overall source emission levels 

will be expected to increase by 

approximately 5 dB when 

logarithmically adding the sources (i.e., 

to 185 dB RMS). To further support this 

level as an appropriate proxy, a sound 

source verification (SSV) study 

performed by JASCO Applied Sciences 

(JASCO) in Cook Inlet in October 2021 

(Lawrence et al., 2022) measured the 

sound source level from three tugs 

pulling a jack-up rig in Cook Inlet at 

various power outputs. Lawrence et al. 

(2022) reported a source level of 167.3 

dB RMS for the 20 percent-power 

scenario and a source level of 205.9 dB 

RMS for the 85 percent-power scenario. 

Assuming a linear scaling of tug power, 

a source level of 185 dB RMS was 

calculated as a single point source level 

for three tugs operating at 50 percent 

power output. Because the 2021 Cook 

Inlet SSV measurements by JASCO 

represent the most recent best available 

data, and because multiple tugs may be 

operating simultaneously, the analyses 

presented below use a mean tug sound 

source level scenario of 185 dB RMS to 

calculate the 120-dB isopleths for three 

tugs operating at 50 percent power 

output. In practice, the load condition of 

the three tugs is unlikely to be identical 

at all times, so sound emissions will be 

dominated by the single tug in the group 

that is working hardest at any point in 

time. 

Further modeling was done to 

account for one additional tug working 

for 1 hour at 50 percent power during 

jack-up rig positioning, a stationary 

activity. This is equivalent in terms of 

acoustic energy to three tugs operating 

at 180.0 dB RMS (each of them) for 4 

hours, joined by a fourth tug for 1 hour, 

increasing the source level to 186.0 dB 

RMS only during the 1-hour period (the 

logarithmic sum of four tugs working 

together at 180.0 dB RMS). A sound 

exposure level (SEL) of 185.1 dB was 

used to account for the cumulative 

sound exposure when calculating Level 

A harassment by adding a 4th tug 

operating at 50 percent power for 20 

percent of the 5-hour period. This is 

equivalent in terms of acoustic energy to 

three tugs operating at 185.0 dB for 4 

hours, joined by a fourth tug for 1 hour, 

increasing the source level to 186.0 dB 

only during the 1-hour period. The use 

of the 20 percent duty cycle was a 

computational requirement and, 

although equal in terms of overall 

energy and determination of impacts, 

should not be confused with the actual 

instantaneous SPL (see section 6.2.1.1 of 

Hilcorp’s application for additional 

computational details). 

In summary, Hilcorp proposed to use 

a source level of 185.0 dB RMS to 

calculate the stationary 120-dB isopleth 

where three tugs were under load for 4 

hours with a 50 percent power output 

and a source level of 186.0 dB RMS to 

calculate the stationary 120-dB isopleth 

where four tugs were under load for 1 

hour with a 50 percent power output. 

Further, Hilcorp proposed to use a 

source level of 185.1 dB SEL to calculate 

the stationary Level A harassment 

isopleths where three tugs were 

underload for 4 hours and then one tug 

joined for 1 additional hour. Lastly, 

Hilcorp proposed to use the 185.0 dB 

RMS level to model the mobile Level A 

harassment isopleths for three tugs 

under load with a 50 percent power 

output. NMFS concurs that Hilcorp’s 

proposed source levels are appropriate. 

Underwater Sound Propagation 

Modeling. Hilcorp contracted SLR 

Consulting to model the extent of the 

harassment isopleths for tugs under load 

with a jack-up rig during their planned 

activities. Cook Inlet is a particularly 

complex acoustic environment with 

strong currents, large tides, variable sea 

floor and generally changing conditions. 

Accordingly, Hilcorp applied a more 

detailed propagation model than the 

‘‘practical spreading loss’’ approach that 

uses a factor of 15. The objective of a 

more detailed propagation calculation is 

to improve the representation of the 

influence of some environmental 

variables, in particular by accounting for 

bathymetry and specific sound source 

locations and frequency-dependent 

propagation effects. 

Modeling was conducted using the 

dBSea software package. The fluid 

parabolic equation modeling algorithm 

was used with 5 Pade ́ terms to calculate 


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the TL between the source and the 

receiver at low frequencies (1/3-octave 

bands, 31.5 Hz up to 1 kHz). For higher 

frequencies (1 kHz up to 8 kHz) the ray 

tracing model was used with 1,000 

reflections for each ray. Sound sources 

were assumed to be omnidirectional and 

modeled as points. The received sound 

levels for the project were calculated as 

follows: (1) One-third octave source 

spectral levels were obtained via 

reference spectral curves with 

subsequent corrections based on their 

corresponding overall source levels; (2) 

TL was modeled at one-third octave 

band central frequencies along 100 

radial paths at regular increments 

around each source location, out to the 

maximum range of the bathymetry data 

set or until constrained by land; (3) The 

bathymetry variation of the vertical 

plane along each modeling path was 

obtained via interpolation of the 

bathymetry dataset which has 83 m grid 

resolution; (4) The one-third octave 

source levels and transmission loss were 

combined to obtain the received levels 

as a function of range, depth, and 

frequency; and (5) The overall received 

levels were calculated at a 1-m depth 

resolution along each propagation path 

by summing all frequency band spectral 

levels. 

Model Inputs. Bathymetry data used 

in the model was collected from the 

NOAA National Centers for 

Environmental Information (AFSC, 

2019). Using NOAA’s temperature and 

salinity data, sound speed profiles were 

computed for depths from 0 to 100 m for 

May, July, and October to capture the 

range of possible sound speed 

depending on the time of year Hilcorp’s 

work could be conducted. These sound 

speed profiles were compiled using the 

Mackenzie Equation (1981) and are 

presented in table 8 of Hilcorp’s 

application (available at https://

www.fisheries.noaa.gov/action/ 

incidental-take-authorization-hilcorpalaska-llc-oil-and-gas-activities-cookinlet-alaska-0). Geoacoustic parameters 

were also incorporated into the model. 

The parameters were based on substrate 

type and their relation to depth. These 

parameters are presented in table 9 of 

Hilcorp’s application (available at 

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

incidental-take-authorization-hilcorpalaska-llc-oil-and-gas-activities-cookinlet-alaska-0). 

Detailed broadband sound 

transmission loss modeling in dBSea 

used the source level of 185 dB RMS 

calculated in one-third octave band 

levels (31.5 Hz to 64,000 Hz) for 

frequency dependent solutions. The 

frequencies associated with tug sound 

sources occur within the hearing range 

of marine mammals in Cook Inlet. 

Received levels for each hearing marine 

mammal group based on one-third 

octave auditory weighting functions 

were also calculated and integrated into 

the modeling scenarios of dBSea. For 

modeling the distances to relevant PTS 

thresholds, a weighting factor 

adjustment was not used; instead, the 

data on the spectrum associated with 

their source was used and incorporated 

the full auditory weighting function for 

each marine mammal hearing group. 

The tugs towing the jack-up rig 

represent a mobile sound source, while 

tugs holding and positioning the jack-up 

rig on a platform are more akin to a 

stationary sound source. In addition, 

three tugs will be used for towing 

(mobile) and holding and positioning 

(stationary) and up to four tugs could be 

used for positioning (stationary). 

Consequently, sound TL modeling was 

undertaken for the various stationary 

and mobile scenarios for three and four 

tugs to generate the distances to the 120- 

dB (relevant Level B) and Level A 

harassment isopleths. 

For acoustic modeling of the 

stationary Level A harassment isopleths, 

two locations representative of where 

tugs will be stationary while they 

position the jack-up rig were selected in 

middle Cook Inlet near the Tyonek 

platform and in lower Trading Bay 

where the production platforms are 

located. To account for the mobile 

scenarios, the acoustic model calculated 

the Level A harassment isopleths along 

a representative route from the Rig 

Tenders dock in Nikiski to the Tyonek 

platform, the northernmost platform in 

Cook Inlet (representing middle Cook 

Inlet), as well as from the Tyonek 

Platform to the Dolly Varden platform in 

lower Trading Bay, then from the Dolly 

Varden platform back to the Rig Tenders 

Dock in Nikiski. Note that this route is 

representative of a typical route the tugs 

may take; the specific route is not yet 

known, as the order in which platforms 

will be drilled with the jack-up rig is not 

yet known. The locations represent a 

range of water depths from 18 to 77 m 

found throughout the project area. 

For mobile Level B harassment and 

stationary Level B harassment with 

three tugs, the average distance to the 

120 dB RMS threshold was based on the 

assessment of 100 radials at 25 locations 

across seasons (May, July, and October) 

and represented the average 120-dB 

isopleth for each season and location 

(table 4). The result is a mobile and 

stationary 120-dB isopleth of 3,850 m 

when three tugs are used (table 4). For 

four stationary tugs, the average 

distance to the 120 dB threshold was 

based on 100 radials at two locations, 

one in Trading Bay and one in middle 

Cook Inlet, across seasons (May, July, 

and October) and represents the average 

120-dB isopleth for each season and 

location. The result is a stationary 120- 

dB isopleth of 4,453 m when four tugs 

are in use (table 5). NMFS concurs that 

3,850 m and 4,453 m are appropriate 

estimates for the extent of the 120-dB 

isopleths for Hilcorp’s towing, holding, 

and positioning activities when using 

three and four tugs, respectively, for the 

purpose of predicting the number of 

potential takes by Level B harassment. 

TABLE 4—AVERAGE DISTANCES TO THE 120-dB THRESHOLD FOR THREE TUGS TOWING (MOBILE) AND HOLDING AND

POSITIONING FOR 4 HOURS (STATIONARY) 

Location 

Average distance to 120-dB threshold (m) Season 

average 

distance to 

120-dB 

threshold 

(m) 

May July October 

M1 .................................................................................................................... 4,215 3,911 4,352 4,159 

M2 .................................................................................................................... 3,946 3,841 4,350 4,046 

M3 .................................................................................................................... 4,156 3,971 4,458 4,195 

M4 .................................................................................................................... 4,040 3,844 4,364 4,083 

M5 .................................................................................................................... 4,053 3,676 4,304 4,011 

M6 .................................................................................................................... 3,716 3,445 3,554 3,572 

M7 .................................................................................................................... 2,947 2,753 2,898 2,866 

M8 .................................................................................................................... 3,270 3,008 3,247 3,175 


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TABLE 4—AVERAGE DISTANCES TO THE 120-dB THRESHOLD FOR THREE TUGS TOWING (MOBILE) AND HOLDING AND

POSITIONING FOR 4 HOURS (STATIONARY)—Continued 

Location 

Average distance to 120-dB threshold (m) Season 

average 

distance to 

120-dB 

threshold 

(m) 

May July October 

M9 .................................................................................................................... 3,567 3,359 3,727 3,551 

M10 .................................................................................................................. 3,600 3,487 3,691 3,593 

M11 .................................................................................................................. 3,746 3,579 4,214 3,846 

M12 .................................................................................................................. 3,815 3,600 3,995 3,803 

M13 .................................................................................................................. 4,010 3,831 4,338 4,060 

M14 .................................................................................................................. 3,837 3,647 4,217 3,900 

M15 .................................................................................................................. 3,966 3,798 4,455 4,073 

M16 .................................................................................................................. 3,873 3,676 4,504 4,018 

M18 .................................................................................................................. 5,562 3,893 4,626 4,694 

M20 .................................................................................................................. 5,044 3,692 4,320 4,352 

M22 .................................................................................................................. 4,717 3,553 4,067 4,112 

M24 .................................................................................................................. 4,456 3,384 4,182 4,007 

M25 .................................................................................................................. 3,842 3,686 4,218 3,915 

M26 .................................................................................................................. 3,690 3,400 3,801 3,630 

M27 .................................................................................................................. 3,707 3,497 3,711 3,638 

M28 .................................................................................................................. 3,546 3,271 3,480 3,432 

M29 .................................................................................................................. 3,618 3,279 3,646 3,514 

Average ............................................................................................................ 3,958 3,563 4,029 3,850 

TABLE 5—AVERAGE DISTANCES TO THE 120-dB THRESHOLD FOR FOUR TUGS POSITIONING (STATIONARY) FOR 1 HOUR

Location 

Average distance to 120-dB threshold (m) Season 

average 

distance to 

120-dB 

threshold 

(m) 

May July October 

Trading Bay ..................................................................................................... 4,610 3,850 4,810 4,423 

Middle CI .......................................................................................................... 4,820 4,130 4,500 4,483 

Average ............................................................................................................ 4,715 3,990 4,655 4,453 

The average Level A harassment 

distances for the stationary, four tug 

scenario were calculated assuming a 

SEL of 185.1 dB for a 5-hour exposure 

duration (table 6). For the mobile, three 

tug scenario, the average Level A 

harassment distances were calculated 

assuming a SEL of 185.0 dB with an 18- 

second exposure period (table 7). This 

18-second exposure was derived using 

the standard TL equation (Source 

Level¥TL = Received Level) for 

determining threshold distance (R [m]), 

where TL = 15Log10. In this case, the 

equation was 185.0 dB¥15Log10 = 173 

dB. Solving for threshold distance (R) 

yields a distance of approximately 6 m, 

which was then used as the preliminary 

ensonified radius to determine the 

duration of time it would take for the 

ensonified area of the sound source 

traveling at a speed of 2.06 m/s (4 knots) 

to pass a marine mammal. The duration 

(twice the radius divided by speed of 

the source) that the ensonified area of a 

single tug would take to pass a marine 

mammal under these conditions is 6 

seconds. An 18-second exposure was 

used in the model to reflect the time it 

would take for three ensonified areas 

(from three consecutive individual tugs) 

to pass a single point that represents a 

marine mammal (6 seconds + 6 seconds 

+ 6 seconds = 18 seconds). 

TABLE 6—AVERAGE DISTANCES TO THE LEVEL A HARASSMENT THRESHOLDS FOR FOUR STATIONARY TUGS UNDER LOAD

WITH A JACK-UP RIG FOR 5 HOURS

Location Season 

Average distance (m) to Level A harassment threshold by 

functional hearing group 

LF MF HF PW OW 1

Trading Bay ......................... May ..................................... 107 77 792 64 ........................

Trading Bay ......................... July ..................................... 132 80 758 66 ........................

Trading Bay ......................... October ............................... 105 75 784 79 ........................

Middle Cook Inlet ................ May ..................................... 86 85 712 78 ........................

Middle Cook Inlet ................ July ..................................... 95 89 718 80 ........................

Middle Cook Inlet ................ October ............................... 82 86 730 80 ........................


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TABLE 6—AVERAGE DISTANCES TO THE LEVEL A HARASSMENT THRESHOLDS FOR FOUR STATIONARY TUGS UNDER LOAD

WITH A JACK-UP RIG FOR 5 HOURS—Continued 

Location Season 

Average distance (m) to Level A harassment threshold by 

functional hearing group 

LF MF HF PW OW 1

Average ............................... ............................................. 102 82 749 75 0 

1The Level A harassment distances are smaller than the footprint of the tugs. 

TABLE 7—AVERAGE DISTANCES TO THE LEVEL A HARASSMENT THRESHOLDS FOR THREE MOBILE TUGS UNDER LOAD

WITH A JACK-UP RIG ASSUMING AN 18-SECOND EXPOSURE DURATION

Location Season 

Average distance (m) to Level A threshold by functional hearing group 

LF 1 MF 1 HF PW 1 OW 1

M2 ....................................... May ..................................... ........................ ........................ 10 ........................ ........................

M2 ....................................... July ..................................... ........................ ........................ 5 ........................ ........................

M2 ....................................... October ............................... ........................ ........................ 10 ........................ ........................

M11 ..................................... May ..................................... ........................ ........................ 10 ........................ ........................

M11 ..................................... July ..................................... ........................ ........................ 5 ........................ ........................

M11 ..................................... October ............................... ........................ ........................ 10 ........................ ........................

M22 ..................................... May ..................................... ........................ ........................ 10 ........................ ........................

M22 ..................................... July ..................................... ........................ ........................ 5 ........................ ........................

M22 ..................................... October ............................... ........................ ........................ 10 ........................ ........................

Average ............................... ............................................. 0 0 8 0 0 

1The Level A harassment distances are smaller than the footprint of the tugs. 

Tugs are anticipated to be towing the 

jack-up rig between platforms and 

considered a mobile sound source for 6 

hours in a single day per jack-up rig 

move. Tugs are anticipated to be towing 

the jack-up rig and considered a mobile 

source during demobilization and 

mobilization to/from Rig Tenders Dock 

in Nikiski for 9 hours. One jack-up rig 

move between platforms is planned 

during the IHA period. Tugs are 

anticipated to be holding or positioning 

the jack-up rig at the platforms or Rig 

Tenders Dock during demobilization 

and mobilization and are considered a 

stationary sound source for 5 hours in 

the first day and 5 hours in the second 

day if a second attempt to pin the jackup rig is required due to the first 

pinning event being unsuccessful. A 

second attempt was built into the 

exposure estimate for each pinning 

event; three total pinning events are 

anticipated during the IHA period for 

production drilling. 

The ensonified area for a location-tolocation transport for production 

drilling represents a rig move between 

two production platforms in middle 

Cook Inlet and/or Trading Bay and 

includes 6 mobile hours over an average 

distance of 16.77 km in a single day and 

5 stationary hours on the first day and 

5 stationary hours on a second day. The 

5 stationary hours are further broken 

into 4 hours with three tugs under load 

and 1 hour with four tugs under load. 

One location-to-location jack-up rig 

move is planned for the IHA period. 

The ensonified area for production 

drilling demobilization and 

mobilization represents a rig move from 

a production platform in middle Cook 

Inlet to Rig Tenders Dock in Nikiski and 

reverse for mobilization and includes 9 

mobile hours over a distance of up to 

64.34 km in a single day and 5 

stationary hours on the first day and 5 

stationary hours on a second day, which 

are further broken into the same three 

tugs working for 4 hours and four tugs 

working for 1 hour as mentioned above. 

A summary of the estimated Level A 

and Level B harassment distances and 

areas for the various tugging scenarios is 

provided in table 8. 

TABLE 8—AVERAGE DISTANCES AND AREAS TO THE ESTIMATED LEVEL A AND LEVEL B HARASSMENT THRESHOLDS FOR

THE VARIOUS TUGGING SCENARIOS

Activity 

Level A harassment distance (m)/area 

(km2) 

Level B 

harassment 

distance (m)/area 

(km2 LF MF HF PW OW ) 

Demobilization/Mobilization 

3 Tugs Towing a Jack-Up Rig—Mobile .................................................. (1) (1) 8/1.07 (1) (1) 3,850/541.96 

3 Tugs Towing a Jack-Up Rig—Stationary for up to 4 hours ................ 102/0.03 82/0.02 749/1.76 75/0.02 (1) 3,850/46.56 

4 Tugs Towing a Jack-Up Rig—Stationary for up to 1 hour .................. 102/0.03 82/0.02 749/1.76 75/0.02 (1) 4,453/62.30 

Location-to-Location 

3 Tugs Towing a Jack-Up Rig—Mobile .................................................. (1) (1) 8/0.28 (1) (1) 3,850/175.6 

3 Tugs Towing a Jack-Up Rig—Stationary for up to 4 hours ................ 102/0.03 82/0.02 749/1.76 75/0.02 (1) 3,850/46.56 

4 Tugs Towing a Jack-Up Rig—Stationary for up to 1 hour .................. 102/0.03 82/0.02 749/1.76 75/0.02 (1) 4,453/62.30 

1The Level A harassment distances are smaller than the footprint of the tugs. 


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Marine Mammal Occurrence 

In this section we provide information 

about the occurrence of marine 

mammals, including density or other 

relevant information that informed the 

take calculations. 

Densities for marine mammals in 

Cook Inlet were derived from NMFS’ 

Marine Mammal Laboratory (MML) 

aerial surveys, typically flown in June, 

from 2000 to 2022 (Rugh et al., 2005; 

Shelden et al., 2013, 2015b, 2017, 2019, 

2022; Goetz, et al. 2023). While the 

surveys are concentrated for a few days 

in summer annually, which may skew 

densities for seasonally present species, 

they represent the best available longterm dataset of marine mammal 

sightings available in Cook Inlet. 

Densities were calculated by summing 

the total number of animals observed 

during the MML surveys and dividing 

the number sighted by the approximate 

area of Cook Inlet. For CIBWs, several 

correction factors were applied to the 

density estimates to address perception, 

availability, and proximity bias; 

correction factors were not applied to 

the non-CIBW density estimates. For 

CIBWs, densities were derived for the 

entirety of Cook Inlet as well as for 

middle and lower Cook Inlet; for nonCIBW marine mammals densities 

account for both lower and upper Cook 

Inlet. There are no density estimates 

available for California sea lions and 

Pacific white-sided dolphins in Cook 

Inlet, as they were so infrequently 

sighted. Average densities across survey 

years are presented in table 9. 

TABLE 9—AVERAGE DENSITIES OF MARINE MAMMAL SPECIES IN COOK INLET 1

Species Density 

(individuals per km2) 

Humpback whale ................................................................................................................................................................. 0.00185 

Minke whale ......................................................................................................................................................................... 0.00003 

Gray whale ........................................................................................................................................................................... 0.00007 

Fin whale ............................................................................................................................................................................. 0.00028 

Killer whale .......................................................................................................................................................................... 0.00061 

Beluga whale (Entire Cook Inlet) ......................................................................................................................................... 0.07166 

Beluga whale (Middle Cook Inlet) ....................................................................................................................................... 0.00658 

Beluga whale (Lower Cook Inlet) ........................................................................................................................................ 0.00003 

Beluga whale (North Cook Inlet) 2 ....................................................................................................................................... 0.00166 

Beluga whale (Lower Cook Inlet) 2 ...................................................................................................................................... 0.00000 

Beluga whale (Trading Bay) 2 .............................................................................................................................................. 0.01505 

Dall’s porpoise ..................................................................................................................................................................... 0.00014 

Harbor porpoise ................................................................................................................................................................... 0.00380 

Pacific white-sided dolphin .................................................................................................................................................. 3 N/A 

Harbor seal .......................................................................................................................................................................... 0.26819 

Steller sea lion ..................................................................................................................................................................... 0.00669 

California sea lion ................................................................................................................................................................ 3 N/A 

1 Density estimates are derived from MML surveys unless otherwise identified. 

2 Density estimates are derived from the Goetz et al. (2012a) habitat-based model. 3 Density estimates are not available in Cook Inlet for this species. 

CIBW densities estimated from the 

MML surveys across regions are low, 

however, there is a known effect of 

seasonality on their distribution. Thus, 

densities derived directly from these 

summer surveys might underestimate 

the density of CIBWs in lower Cook 

Inlet at other ice-free times of the year. 

Therefore, additional CIBW densities 

were considered as a comparison of 

available data. The other mechanism for 

arriving at CIBW density considered 

here is the Goetz et al. (2012a) habitatbased model. This model is derived 

from sightings and incorporates depth 

soundings, coastal substrate type, 

environmental sensitivity index, 

anthropogenic disturbance, and 

anadromous fish streams to predict 

densities throughout Cook Inlet. The 

output of this model is a density map 

of Cook Inlet, which predicts spatially 

explicit density estimates for CIBW. 

Using the resulting grid densities, 

average densities were calculated for 

two regions applicable to Hilcorp’s 

operations (table 9). The densities 

applicable to the area of activity (i.e., the 

North Cook Inlet Unit density for 

middle Cook Inlet activities and the 

Trading Bay density for activities in 

Trading Bay) are provided in table 9 

above and were carried forward to the 

exposure estimates as they were deemed 

to likely be the most representative 

estimates available. Likewise, when a 

range is given, the higher end of the 

range was used out of caution to 

calculate exposure estimates (i.e., 

Trading Bay in the Goetz model has a 

range of 0.004453 to 0.015053; 0.015053 

was used for the exposure estimates). 

Take Estimation 

Here we describe how the information 

provided above was synthesized to 

produce a quantitative estimate of the 

take that could occur and is authorized. 

As described above, Hilcorp’s tugging 

activity considers a total of three rig 

moves across 6 days (one 2-day 

location-to-location jack-up rig move, 

one 2-day demobilization effort, and one 

2-day mobilization effort). For the 

location-to-location move, Hilcorp 

assumed 6 hours of mobile (towing) and 

5 hours of stationary (holding and 

positioning) activities on the first day, 

and 5 hours of the stationary activity (4 

hours with three tugs and 1 hour with 

four tugs) on the second day to account 

for two positioning attempts (across 2 

days). For the demobilization and 

mobilization efforts, Hilcorp assumed 9 

hours of mobile and 5 hours of 

stationary (4 hours with three tugs and 

1 hour with four tugs) activities on the 

first day, and 5 hours of stationary (4 

hours with three tugs and 1 hour with 

four tugs) activities on the second day 

(across 2 days for each effort, for a total 

of 4 days of tugs under load with a jackup rigs). 

Potential take by Level A harassment 

was quantified by multiplying the 

ensonified Level A harassment areas per 

tugging activity scenario for each 

functional hearing group (table 8) by the 

estimated marine mammal densities 

(table 9) to get an estimate of exposures 

per day. This value was then multiplied 

by the number of days per move and the 

number of moves of that type of activity 

scenario. The estimated exposures by 

activity scenario were then summed to 

result in a number of exposures for all 

tugging activities. Based on this 


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analysis, only Dall’s porpoise, harbor 

porpoise, and harbor seals had potential 

estimated take by Level A harassment 

that was greater than zero: 0.001, 0.018, 

and 0.006, respectively. For mobile 

tugging, the distances to the PTS 

thresholds for HF cetaceans and phocids 

are smaller than the overall size of the 

tug and rig configuration (i.e., 8 m and 

0 m, respectively), making it unlikely an 

animal will remain close enough to the 

tug engines to incur PTS. For stationary 

positioning of the jack up rig, the PTS 

isopleths for both the 3-tug and 4-tug 

scenarios are up to 749 m for HF 

cetaceans and up to 102 m for all other 

species, but calculated on the 

assumption that an animal would 

remain within several hundred meters 

of the jack-up rig for the full 5 hours of 

noise-producing activity. Given the 

location of the activity is not in an area 

known to be essential habitat for any 

marine mammal species with extreme 

site fidelity over the course of 2 days, 

in addition to the low exposure 

estimates for take by Level A 

harassment (i.e., ≤0.18 for all species), 

the mobile nature of marine mammals, 

and the general tendencies of most 

marine mammals to avoid loud noises, 

the occurrence of PTS is unlikely and 

thus not authorized for any species. 

The ensonified Level B harassment 

areas calculated per activity scenario 

(three tug stationary, four tug stationary, 

and three tug mobile for the location-tolocation move and the demobilization 

and mobilization efforts) for a single day 

(see table 8) were multiplied by marine 

mammal densities to estimate takes by 

Level B harassment per day, 

acknowledging that there are contextual 

factors that make take less likely to 

result from this activity. This was then 

multiplied by the number of days per 

move and the number of moves of that 

type of activity scenario to arrive at the 

number of estimated exposures above 

120 dB per activity type. These 

exposures by activity scenario were then 

summed to result in a number of 

exposures for all Hilcorp’s tugging 

activities during the IHA period (table 

10). As exposure estimates were 

calculated based on specific potential 

rig moves or well locations, the density 

value for CIBWs that was carried 

through the estimate was the higher 

density value for that particular location 

(table 9; i.e., 0.00658 for locations in 

middle Cook Inlet and 0.01505 for 

locations in Trading Bay). There are no 

estimated exposures based on this 

method of calculation for California sea 

lions and Pacific white-sided dolphins 

because the assumed density of these 

species in the project area is 0.00 

animals per km2. Table 10 also indicates 

the number of takes, by Level B 

harassment, authorized. For species 

where the total calculated exposures 

above the Level B harassment threshold 

is less than the estimated group size for 

that species, NMFS adjusted the take 

authorized up to the anticipated group 

size. Explanations for species for which 

take authorized is greater than the 

calculated take are included below. 

TABLE 10—CALCULATED EXPOSURES AND TOTAL AUTHORIZED TAKE BY LEVEL B HARASSMENT, BY SPECIES AND STOCK, 

FOR HILCORP’S TUGGING ACTIVITIES

Scenario 

Location-to-location Demobilization/mobilization Total 

calculated 

Level B 

harassment 

exposures 

Total 

authorized 

take by 

Level B 

harassment 

3 Mobile 

tugs 

3 Stationary 

tugs 

4 Stationary 

tugs 

3 Mobile 

tugs 

3 Stationary 

tugs 

4 Stationary 

tugs 

Level B Harassment Area (km2) ................... 175.67 46.56 62.30 541.96 46.56 62.30 

Species Calculated Exposures above the Level B Harassment threshold 

Humpback whale ........................................... 0.324 0.029 0.010 2.001 0.057 0.019 2.440 3 

Minke whale .................................................. 0.005 0.000 0.000 0.031 0.001 0.000 0.037 3 

Gray whale .................................................... 0.012 0.001 0.000 0.072 0.002 0.001 0.088 3 

Fin whale ....................................................... 0.048 0.004 0.001 0.299 0.009 0.003 0.364 2 

Killer whale .................................................... 0.108 0.009 0.003 0.663 0.019 0.006 0.808 10 

Beluga whale ................................................. 1.900 0.168 0.056 7.133 0.204 0.068 9.529 15 

Dall’s porpoise ............................................... 0.024 0.002 0.001 0.148 0.004 0.001 0.180 6 

Harbor porpoise ............................................ 0.667 0.059 0.020 4.117 0.118 0.039 5.020 12 

Pacific white-sided dolphin ............................ 0.000 0.000 0.000 0.000 0.000 0.000 0.000 3 

Harbor seal .................................................... 47.112 4.163 1.392 290.699 8.325 2.785 354.476 355 

Steller sea lion .............................................. 1.175 0.104 0.035 7.253 0.208 0.069 8.844 9 

California sea lion ......................................... 0.000 0.000 0.000 0.000 0.000 0.000 0.000 2 

During annual aerial surveys 

conducted in Cook Inlet from 2000 to 

2016, humpback group sizes ranged 

from 1 to 12 individuals, with most 

groups comprised of 1 to 3 individuals 

(Shelden et al., 2013). Three humpback 

whales were observed in Cook Inlet 

during SAExploration’s seismic study in 

2015: two near the Forelands and one in 

Kachemak Bay (Kendall and Cornick, 

2015). In total, 14 sightings of 38 

humpback whales (ranging in group size 

from 1 to 14) were recorded in the 2019 

Hilcorp lower Cook Inlet seismic survey 

in the fall (Fairweather Science, 2020). 

Two sightings totaling three individual 

humpback whales were recorded near 

Ladd Landing north of the Forelands on 

the recent Harvest Alaska CIPL 

Extension Project (Sitkiewicz et al., 

2018). Based on documented 

observations from the CIPL Extension 

Project, which is the data closest to the 

specific geographic region, NMFS has 

authorized, three takes by Level B 

harassment for humpback whales, 

which is slightly greater than the 

calculated exposures using the methods 

described above (0.2440 takes by Level 

B harassment, table 10). 

Minke whales usually travel in groups 

of two to three individuals (NMFS, 

2023b). During Cook Inlet-wide aerial 

surveys conducted from 1993 to 2004, 

minke whales were encountered three 

times (1998, 1999, and 2006), all were 

observed off Anchor Point (Shelden et 

al., 2013, 2015b, and 2017). Several 

minke whales were recorded off Cape 

Starichkof in early summer 2013 during 

exploratory drilling (Owl Ridge, 2014), 

suggesting this location is regularly used 

by minke whales year-round. During 

Apache’s 2014 survey, a total of two 

minke whale groups (three individuals) 

were observed. One sighting occurred 

southeast of Kalgin Island while the 

other sighting occurred near Homer 

(Lomac-MacNair et al., 2014). 

SAExploration noted one minke whale 

near Tuxedni Bay in 2015 (Kendall and 

Cornick, 2015). Eight sightings of eight 

minke whales were recorded in the 2019 

Hilcorp lower Cook Inlet seismic survey 


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(Fairweather Science, 2020). Based on 

these observations of group size and 

consistency of sightings in Cook Inlet, 

NMFS has authorized three takes by 

Level B harassment for minke whales 

(table 10). This is higher than the 

exposure estimate (i.e., 0.037, table 10) 

to allow for the potential occurrence of 

a group, or several individuals, during 

the project period. 

During Apache’s 2012 seismic 

program, nine sightings of a total of nine 

gray whales were observed in June and 

July (Lomac-MacNair et al., 2013). In 

2014, one gray whale was observed 

during Apache’s seismic program 

(Lomac-MacNair et al., 2014) and in 

2015, no gray whales were observed 

during SAExploration’s seismic survey 

(Kendall and Cornick, 2015). No gray 

whales were observed during the 2018 

CIPL Extension Project (Sitkiewicz et 

al., 2018) or during the 2019 Hilcorp 

seismic survey in lower Cook Inlet 

(Fairweather Science, 2020). The 

greatest densities of gray whales in Cook 

Inlet occur from November through 

January and March through May; the 

former are southbound, the latter are 

northbound (Ferguson et al., 2015). 

Based on this information, NMFS has 

authorized three takes by Level B 

harassment for gray whales. This is 

higher than the exposure estimate (i.e., 

0.088, table 10) to allow for the potential 

occurrence of a group, or several 

individuals, particularly during the fall 

shoulder season during the higher 

density periods mentioned above. 

Fin whales most often travel alone, 

although they are sometimes seen in 

groups of two to seven individuals. 

During migration they may be in groups 

of 50 to 300 individuals (NMFS, 2010). 

During the NMFS aerial surveys in Cook 

Inlet from 2000 to 2018, 10 sightings of 

26 estimated individual fin whales were 

recorded in lower Cook Inlet (Shelden et 

al., 2013, 2015b, and 2017; Shelden and 

Wade, 2019). Wild et al. (2023) 

identified areas south of the mouth of 

Cook Inlet as a fin whale feeding BIA 

from June to September with an 

importance score of 1 and an intensity 

score of 1 (see Harrison et al. 2023 for 

more details regarding BIA scoring). As 

such, the potential for fin whales to 

occupy waters adjacent to the BIA 

during that time period and near the 

specified area may be higher. Acoustic 

detections of fin whales were recorded 

during passive acoustic monitoring in 

the fall of 2019 (Castellote et al., 2020) 

Additionally, during seismic surveys 

conducted in 2019 by Hilcorp in lower 

Cook Inlet, 8 sightings of 23 fin whales 

were recorded in groups ranging in size 

from 1 to 15 individuals (Fairweather 

Science, 2020). The higher number of 

sightings in a single year relative to the 

multi-year NMFS aerial surveys flown 

earlier in season each year suggests fin 

whales may be present in greater 

numbers in the fall. Given the possible 

presence of fin whales in the project 

area, NMFS has authorized two takes by 

Level B harassment for fin whales 

during Hilcorp’s planned activities. 

Killer whale pods typically consist of 

a few to 20 or more animals (NMFS, 

2023c). During seismic surveys 

conducted in 2019 by Hilcorp in lower 

Cook Inlet, 21 killer whales were 

observed. Although also observed as 

single individuals, killer whales were 

recorded during this survey in groups 

ranging in size from two to five 

individuals (Fairweather Science, 2020). 

One killer whale group of two 

individuals was observed during the 

2015 SAExploration seismic program 

near the North Foreland (Kendall and 

Cornick, 2015). Based on recent 

documented sightings, observed group 

sizes, and the established presence of 

killer whales in Cook Inlet, NMFS has 

authorized 10 takes by Level B 

harassment for killer whales. This will 

account for two sightings with a group 

size of five individuals, which 

represents the upper end of recorded 

group size in recent surveys conducted 

in Cook Inlet. 

The total calculated exposures for 

CIBW was calculated to be 9.529 

individuals based on recorded densities 

and estimated durations that tugs will 

be under load with a jack-up rig (table 

10). The 2018 MML aerial survey 

(Shelden and Wade, 2019) reported a 

median beluga group size estimate of 

approximately 11 whales, although 

estimated group sizes were highly 

variable (ranging from 2 to 147 whales) 

as was the case in previous survey years 

(Boyd et al., 2019). The median group 

size during 2021 and 2022 MML aerial 

surveys was 34 and 15, respectively, 

with variability between 1 and 174 

between the years (Goetz et al., 2023). 

Additionally, vessel-based surveys in 

2019 found CIBW groups in the Susitna 

River Delta (roughly 24 km north of the 

Tyonek Platform) that ranged from 5 to 

200 animals (McGuire et al., 2022). 

Based on these observations, NMFS 

increased the estimated take calculated 

above and has authorized 15 takes by 

Level B harassment for CIBWs to 

account for 1 group of 15 individuals, 

the lower end of the 2022 median group 

size, or 2 observations of smaller-sized 

groups. While large groups of CIBWs 

have been seen in the Susitna River 

Delta region, they are not expected near 

Hilcorp’s specified activity because 

groups of this size have not been 

observed or documented outside river 

deltas in upper Cook Inlet; however, 

smaller groups (i.e., around the 2022 

median group size) could be traveling 

through to access the Susitna River 

Delta and other nearby coastal locations. 

Dall’s porpoises are usually found in 

groups averaging between 2 and 12 

individuals (NMFS, 2023d). During 

seismic surveys conducted in 2019 by 

Hilcorp in lower Cook Inlet, Dall’s 

porpoises were recorded in groups 

ranging from two to seven individuals 

(Fairweather Science, 2020). The 2012 

Apache survey recorded two groups of 

three individual Dall’s porpoises 

(Lomac-MacNair et al., 2014). NMFS has 

authorized six takes by Level B 

harassment for Dall’s porpoises. This is 

greater than the estimated exposure 

estimate for this species (0.180, table 

10), but will allow for at least one group 

at the higher end of documented group 

size or a combination of small groups 

plus individuals. 

Harbor porpoises are most often seen 

in groups of two to three (NMFS, 

2023e); however, based on observations 

during project-based marine mammal 

monitoring, they can also occur in larger 

group sizes. Shelden et al. (2014) 

compiled historical sightings of harbor 

porpoises from lower to upper Cook 

Inlet that spanned from a few animals 

to 92 individuals. The 2018 CIPL 

Extension Project that occurred in 

middle Cook Inlet reported 29 sightings 

of 44 individuals (Sitkiewicz et al., 

2018). NMFS has authorized 12 takes by 

Level B harassment for harbor porpoises 

to allow for multiple group sightings 

during the specified activity. These 

authorized takes are greater than the 

exposure estimate calculated (5.020, 

table 10) but will account for the 

possibility of a couple sightings of small 

groups of harbor porpoises during 

Hilcorp’s 6 days of tugging activity. 

Recent data specific to Pacific whitesided dolphins within Cook Inlet are 

lacking, and the calculated exposure 

estimate is zero based on the paucity of 

sightings of this species in this region 

(table 10). However, Pacific-white sided 

dolphins have been observed in Cook 

Inlet. During an aerial survey in May 

2014, Apache observed three Pacific 

white-sided dolphins near Kenai. No 

large groups of Pacific white-sided 

dolphins have been reported within 

Cook Inlet, although acoustic detections 

of several Pacific white-sided dolphins 

were recorded near Iniskin Bay during 

Hilcorp’s 3D seismic survey in 2020. 

Prior to this, only one other survey in 

the last 20 years noted the presence of 

Pacific white-sided dolphins (three 

animals) within Cook Inlet. As a result 

of the dearth of current data on this 

species, an accurate density for Pacific 


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white-sided dolphins in the specific 

project region has not been generated. 

However, based on the possibility of 

this species in the project area, NMFS 

has authorized three takes by Level B 

harassment for Pacific white-sided 

dolphins, the maximum number of 

Pacific white-sided dolphins that have 

been recorded in the somewhat recent 

past are present in Cook Inlet. This is 

consistent with NMFS’ IHA for 

Hilcorp’s previous tugging activities (87 

FR 62364, October 14, 2022). 

Harbor seals are often solitary in 

water but can haul out in groups of a 

few to thousands (Alaska Department of 

Fish and Game (ADF&G), 2022). Given 

their presence in the study region, 

NMFS has authorized 355 takes by 

Level B harassment for harbor seals, 

which is commensurate with the 

calculated exposure estimate based on 

harbor seal densities and Hilcorp’s 

estimated durations for tugging 

activities (table 10). 

Steller sea lions tend to forage 

individually or in small groups (Fiscus 

and Baines, 1966) but have been 

documented feeding in larger groups 

when schooling fish were present 

(Gende et al., 2001). Steller sea lions 

have been observed during marine 

mammal surveys conducted in Cook 

Inlet. In 2012, during Apache’s 3D 

Seismic survey, three sightings of 

approximately four individuals in upper 

Cook Inlet were reported (LomacMacNair et al., 2013). Marine mammal 

observers associated with Buccaneer’s 

drilling project off Cape Starichkof 

observed seven Steller sea lions during 

the summer of 2013 (Owl Ridge, 2014). 

During SAExploration’s 3D Seismic 

Program in 2015, four Steller sea lions 

were observed in Cook Inlet. One 

sighting occurred between the West and 

East Forelands, one occurred near 

Nikiski, and one occurred northeast of 

the North Foreland in the center of Cook 

Inlet (Kendall and Cornick, 2015). 

During NMFS CIWB aerial surveys from 

2000 to 2016, 39 sightings of 769 

estimated individual Steller sea lions in 

lower Cook Inlet were reported (Shelden 

et al., 2017). During a waterfowl survey 

in upper Cook Inlet, an observer 

documented an estimated 25 Steller sea 

lions hauled out at low tide in the Lewis 

River on the west side of Cook Inlet (K. 

Lindberg, pers. comm., August 15, 

2022). Hilcorp reported one sighting of 

two Steller sea lions while conducting 

pipeline work in upper Cook Inlet 

(Sitkiewicz et al., 2018). Commensurate 

with exposure estimates shown in table 

10, NMFS has authorized nine takes by 

Level B harassment for Steller sea lions. 

While California sea lions are 

uncommon in the specific geographic 

region, two were seen during the 2012 

Apache seismic survey in Cook Inlet 

(Lomac-MacNair et al., 2013). California 

sea lions in Alaska are typically alone 

but may be seen in small groups usually 

associated with Steller sea lions at their 

haulouts and rookeries (Maniscalco et 

al., 2004). Despite the estimated 

exposure estimate being zero due to the 

lack of sightings during aerial surveys, 

NMFS has authorized two takes by 

Level B harassment for California sea 

lions to account for the potential to see 

up to two animals over the course of the 

season. This is consistent with NMFS 

authorization for Hilcorp’s previous 

tugging activities (87 FR 62364, October 

14, 2022). 

Mitigation 

In order to issue an IHA under section 

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

set forth the permissible methods of 

taking pursuant to the activity, and 

other means of effecting the least 

practicable impact on the species or 

stock and its habitat, paying particular 

attention to rookeries, mating grounds, 

and areas of similar significance, and on 

the availability of the species or stock 

for taking for certain subsistence uses. 

NMFS regulations require applicants for 

ITAs 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, as well as 

subsistence uses. This considers the 

nature of the potential adverse impact 

being mitigated (likelihood, scope, 

range). It further considers the 

likelihood that the measure will be 

effective if implemented (probability of 

accomplishing the mitigating result if 

implemented as planned), the 

likelihood of effective implementation 

(probability implemented as planned), 

and; 

(2) The practicability of the measures 

for applicant implementation, which 

may consider such things as cost and 

impact on operations. 

There is a discountable potential for 

marine mammals to incur PTS from the 

project, as source levels are relatively 

low, non-impulsive, and animals would 

have to remain at very close distances 

for multiple hours to accumulate 

acoustic energy at levels that could 

damage hearing. Therefore, we do not 

believe there is reasonable potential for 

Level A harassment and we are not 

authorizing it. Hilcorp will implement a 

number of mitigation and related 

monitoring measures designed to reduce 

the potential for and severity of Level B 

harassment and further reduce the 

already insignificant potential for Level 

A harassment. 

The tugs towing a jack-up rig are not 

able to shut down while transiting, 

holding, or positioning the rig. Hilcorp 

will maneuver the tugs towing the jackup rig such that they maintain a 

consistent speed (approximately 4 knots 

[7 km/hr]) and avoid multiple changes 

of speed and direction to make the 

course of the vessels as predictable as 

possible to marine mammals in the 

surrounding environment, 

characteristics that are expected to be 

associated with a lower likelihood of 

disturbance. 

Hilcorp will use two NMFS-approved 

PSOs to observe and implement 

clearance zone procedures as described 

below (i.e., pre-clearance monitoring). If 

a marine mammal(s) is observed within 

the relevant clearance zone during the 

pre-clearance monitoring period, 

tugging activities will be delayed, unless 

the delay interferes with the safety of 

working conditions. The pre-clearance 

zones include a distance of 1.5 km for 

non-CIBWs and any distance for CIBWs 

(note: transitioning from towing to 

positioning without shutting down will 

not be considered commencing a new 

operational activity). The 1.5 km 

clearance zone is consistent with 

previous authorizations for tugging 

activities (87 FR 62364, October 14, 

2022), and was determined to be 

appropriate as it is approximately twice 

as large as the largest Level A 

harassment zone (table 9) and is a 

reasonable distance within which 

cryptic species (e.g., porpoises, 

pinnipeds) could be observed. The 

larger clearance zone for CIBWs is a new 

measure aimed to further minimize any 

potential impacts from tugs under load 

with a jack-up rig on this species. 

During daylight hours, for 30 minutes 

prior to commencing new operational 

activities, or if there is a 30-minute 

lapse in operational activities, two PSOs 

will observe and implement clearance 

zones procedures as described below 

(i.e., pre-clearance monitoring); Note: 

transitioning from towing to positioning 


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without shutting down will not be 

considered commencing a new 

operational activity. If no marine 

mammals are observed within the 

relevant clearance zones described 

above during this 30 minute preclearance monitoring period, tugging 

activities may commence. If a CIBW(s) 

is observed at any distance during those 

30 minutes, operations may not 

commence until the PSO(s) confirm that 

the CIBW(s) or any other CIBW(s) has 

not been observed for 30 minutes, 

unless the delay interferes with the 

safety of working conditions. If a nonCIBW marine mammal(s) is observed 

within the relevant clearance zone (i.e., 

1.5 km) during the 30 minute preclearance monitoring period, tugging 

activities will not commence until the 

PSO(s) observe that the non-CIBW 

animal(s) is outside of and on a path 

away from the clearance zone, or 30 

minutes have elapsed without observing 

the non-CIBW marine mammal. 

During nighttime hours or low/nolight conditions, NVDs shown to be 

effective at detecting marine mammals 

in low-light conditions (e.g., Portable 

Visual Search-7 model, or similar) will 

be provided to PSOs to aid in their 

monitoring of marine mammals. Every 

effort will be made to observe that the 

relevant clearance zone is free of marine 

mammals by using night-vision devices 

and or the naked eye, however it may 

not always be possible to see and clear 

the entire clearance zones prior to 

nighttime transport. Prior to 

commencing new operational activities 

during nighttime hours or if there is a 

30-minute lapse in operational activities 

in low/no-light conditions, the two 

PSOs will observe and implement 

clearance zone procedures as described 

below while using NVDs (i.e., preclearance monitoring). If a marine 

mammal(s) is observed during the 30 

minute pre-clearance monitoring period, 

operations may not commence until the 

PSO(s) observe that one of the following 

conditions is met, unless the delay 

interferes with the safely of working 

conditions: (1) the animal(s) is outside 

of the observable area; or (2) 30 minutes 

have elapsed without observing the 

marine mammal. If no marine mammals 

are observed during the 30 minute preclearance monitoring period, tugs may 

commence towing, positioning, or 

holding the jack-up rig. 

Hilcorp will operate with the tide, 

resulting in a low power output from 

the tugs towing the jack-up rig, unless 

human safety or equipment integrity are 

at risk. Due to the nature of tidal cycles 

in Cook Inlet, it is possible that the most 

favorable tide for the towing operation 

will occur during nighttime hours. 

Hilcorp will only operate the tugs 

towing the jack-up rigs at night if the 

nighttime operations result in a lower 

power output from the tugs by operating 

with a favorable tide. 

Out of concern for potential 

disturbance to CIBWs in sensitive and 

essential habitat, Hilcorp will maintain 

a distance of 2.4 km from the mean 

lower-low water (MLLW) line of the 

Susitna River Delta (Beluga River to the 

Little Susitna River) between April 15 

and November 15. The dates of 

applicability of this exclusion area have 

been expanded based on new available 

science, including visual surveys and 

acoustic studies, which indicate that 

substantial numbers of CIBWs continue 

to occur in the Susitna Delta area 

through at least mid-November (M. 

Castellote, pers. comm., T. McGuire, 

pers. comm.). In addition, Hilcorp will 

coordinate with local Tribes as 

described in its Stakeholder Engagement 

Plan (see appendix C in Hilcorp’s 

application), notify the communities of 

any changes in the operation, and take 

action to avoid or mitigate impacts to 

subsistence harvests. 

For transportation of a jack-up rig to 

or from the Tyonek platform, in 

addition to the two PSOs stationed on 

the rig during towing, one additional 

PSO will be stationed on the Tyonek 

platform to monitor for marine 

mammals. The PSO will be on-watch for 

at least 1 hour before tugs are expected 

to arrive (scheduled to approach the 

estimated 120-dB isopleth). 

Based on our evaluation of our 

proposed measures and consideration of 

public comments, NMFS has 

determined that the required mitigation 

and related monitoring measures (see 

below for additional descriptions) 

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, and on the availability of 

such species or stock for subsistence 

uses. 

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. 

Hilcorp will abide by all monitoring 

and reporting measures contained 

within the IHA and their Marine 

Mammal Monitoring and Mitigation 

Plan (see appendix D of Hilcorp’s 

application). A summary of those 

measures and additional requirements 

from NMFS is provided below. 

Hilcorp must monitor the project area 

once tugging activities are underway to 

the maximum distance possible based 

on the required number of PSOs, 

required monitoring locations, and 

environmental conditions. PSOs must 

also conduct monitoring for marine 

mammals during the pre-clearance 

monitoring periods, through 30 minutes 

post-completion of any tugging activity 

each day, and after each stoppage of 30 

minutes or greater. 

A minimum of two NMFS-approved 

PSOs must be stationed on the tug or 

jack-up rig for monitoring purposes for 

the entirety of jack-up rig towing, 


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holding, and positioning operations and 

pre-clearance monitoring. PSOs must be 

independent of the activity contractor 

(for example, employed by a 

subcontractor) and have no other 

assigned tasks during monitoring 

periods. At least one PSO must have 

prior experience performing the duties 

of a PSO during an activity pursuant to 

a NMFS-issued ITA or Letter of 

Concurrence. Other PSOs may 

substitute other relevant experience 

(including relevant Alaska Native 

traditional knowledge), education 

(degree in biological science or related 

field), or training for prior experience 

performing the duties of a PSO. 

PSOs must also have the following 

additional qualifications: 

(a) The ability to conduct field 

observations and collect data according 

to assigned protocols; 

(b) Experience or training in the field 

identification of marine mammals, 

including the identification of 

behaviors; 

(c) Sufficient training, orientation, or 

experience with the tugging operation to 

provide for personal safety during 

observations; 

(d) Sufficient writing skills to record 

required information including but not 

limited to the number and species of 

marine mammals observed; dates and 

times when tugs were under load with 

the jack-up rig; dates, times, and reason 

for implementation of mitigation (or 

why mitigation was not implemented 

when required); and marine mammal 

behavior; and 

(e) The ability to communicate orally, 

by radio or in person, with project 

personnel to provide real-time 

information on marine mammals 

observed in the area as necessary. 

PSOs must be positioned aboard the 

tug or the jack-up-rig at the best 

practical vantage points that are 

determined to be safe, ideally an 

elevated stable platform from which a 

single PSO would have an unobstructed 

360-degree view of the water or a total 

360-degree view between all PSOs onwatch. Generally, one PSO will be on 

the port side and one PSO will be on the 

starboard side. Additionally, when 

towing the jack-up rig to the Tyonek 

platform, an additional PSO must be 

stationed on the Tyonek platform 1 hour 

before tugs are expected to arrive (i.e., 

scheduled to approach the estimated 

120-dB isopleth) to monitor for marine 

mammals. PSOs may use a combination 

of equipment to scan the monitoring 

area and to verify the required 

monitoring distance from the project 

site, including the naked eye, 7 by 50 

binoculars, and NMFS approved NVDs 

for low light and nighttime operations. 

PSOs must be in communication with 

all vessel captains via VHF radio and/ 

or cell phones at all times and alert 

vessel captains to all marine mammal 

sightings relative to the vessel location. 

Hilcorp must submit interim monthly 

reports for all months in which tugging 

activities occur. Monthly reports will be 

due 14 days after the conclusion of each 

calendar month, and must include a 

summary of marine mammal species 

and behavioral observations, delays, and 

tugging activities completed (i.e., tugs 

towing, holding, or positioning the jackup rig). They also must include an 

assessment of the amount of tugging 

remaining to be completed, in addition 

to the number of CIBWs observed 

within estimated harassment zones to 

date. 

A draft final summary marine 

mammal monitoring report must be 

submitted to NMFS within 90 days after 

the completion of the tug towing jackup rig activities for the year or 60 

calendar days prior to the requested 

issuance of any subsequent IHA for 

similar activity at the same location, 

whichever comes first. The draft 

summary report must include an overall 

description of all work completed, a 

narrative regarding marine mammal 

sightings, and associated marine 

mammal observation data sheets (data 

must be submitted electronically in a 

format that can be queried such as a 

spreadsheet or database). Specifically, 

the summary report must include: 

• Date and time that monitored 

activity begins or ends; 

• Activities occurring during each 

observation period, including (a) the 

type of activity (towing, holding, 

positioning), (b) the total duration of 

each type of activity, (c) the number of 

attempts required for positioning, (d) 

when nighttime operations were 

required, and (e) whether towing against 

the tide was required; 

• PSO locations during marine 

mammal monitoring; 

• Environmental conditions during 

monitoring periods (at the beginning 

and end of the PSO shift and whenever 

conditions change significantly), 

including Beaufort sea state, tidal state, 

and any other relevant weather 

conditions including cloud cover, fog, 

sun glare, overall visibility to the 

horizon, and estimated observable 

distance; 

• Upon observation of a marine 

mammal, the following information: 

Æ Name of PSO who sighted the 

animal(s) and PSO location and activity 

at time of sighting; 

Æ Time of sighting; 

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

genus/species, lowest possible 

taxonomic level, or unidentified), PSO 

confidence in identification, and the 

composition of the group if there is a 

mix of species; 

Æ Distance and location of each 

observed marine mammal relative to the 

tug boats for each sighting; 

Æ Estimated number of animals (min/ 

max/best estimate); 

Æ Estimated number of animals by 

cohort (adults, juveniles, neonates, 

group composition, etc.); 

Æ Animal’s closest point of approach 

and estimated time spent within the 

harassment zone; 

Æ Description of any marine mammal 

behavioral observations (e.g., observed 

behaviors such as feeding or traveling), 

including an assessment of behavioral 

responses thought to have resulted from 

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

in behavioral state such as ceasing 

feeding, changing direction, flushing, or 

breaching); 

• Number of marine mammals 

detected within the harassment zones, 

by species; and 

• Detailed information about 

implementation of any mitigation (e.g., 

delays), a description of specific actions 

that ensued, and resulting changes in 

behavior of the animal(s), if any. 

If no comments are received from 

NMFS within 30 days, the draft 

summary report will constitute the final 

report. If comments are received, a final 

report addressing NMFS comments 

must be submitted within 30 days after 

receipt of comments. 

In the event that personnel involved 

in Hilcorp’s tugging activities discover 

an injured or dead marine mammal, 

Hilcorp must report the incident to the 

Office of Protected Resources, NMFS 

(PR.ITP.MonitoringReports@noaa.gov, 

itp.tyson.moore@noaa.gov), and to the 

Alaska Regional Stranding Coordinator 

as soon as feasible. If the death or injury 

was clearly caused by the specified 

activity, Hilcorp must immediately 

cease the specified activities until 

NMFS is able to review the 

circumstances of the incident and 

determine what, if any, additional 

measures are appropriate to ensure 

compliance with the IHA. Hilcorp must 

not resume their activities until notified 

by NMFS. The report must include the 

following information: 

• Time, date, and location (latitude 

and 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); 


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• 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. 

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 all the species 

listed in table 10, except CIBWs, given 

that many of the anticipated effects of 

this project on different marine mammal 

stocks are expected to be relatively 

similar in nature. For CIBWs, there are 

potentially meaningful differences in 

anticipated responses to activities, 

impact of expected take on the 

population, or impacts on habitat; 

therefore, we provide a separate 

independent detailed analysis for 

CIBWs following the analysis for other 

species for which we authorize take. 

NMFS has identified several key 

factors to assess whether potential 

impacts associated with a specified 

activity should be considered negligible. 

These include (but are not limited to) 

the type and magnitude of taking, the 

amount and importance of the available 

habitat for the species or stock that is 

affected, the duration of the anticipated 

effect on the individuals, and the status 

of the species or stock. The potential 

effects of the specified activity on 

humpback whales, minke whales, gray 

whales, fin whales, killer whales, Dall’s 

porpoises, harbor porpoises, Pacific 

white-sided dolphins, Steller sea lions, 

harbor seals, and California sea lions are 

discussed below. These factors also 

apply to CIBWs; however, an additional 

analysis for CIBWs is provided in a 

separate sub-section below. 

Tugs under load with the jack-up rig, 

as outlined previously, have the 

potential to disturb or displace marine 

mammals, and the number of authorized 

takes that could potentially result from 

Hilcorp’s activities have been identified 

above in the Estimated Take section. 

Hilcorp’s planned activities and 

associated impacts will occur within a 

limited, confined area of the affected 

species or stocks’ range over a total of 

6 days between September 24, 2024, and 

September 23, 2025. The intensity and 

duration of take by Level B harassment 

will be minimized through use of 

mitigation measures described herein. 

In addition, NMFS does not anticipate 

that serious injury or mortality will 

occur as a result of Hilcorp’s planned 

activity given the nature of the activity, 

even in the absence of required 

mitigation. 

Exposures to elevated sound levels 

produced during tugs under load with 

the jack-up rig may cause behavioral 

disturbance of some individuals within 

the vicinity of the sound source. 

Behavioral responses of marine 

mammals to tugs under load with the 

jack-up rig are expected to be mild, 

short term, and temporary. Effects on 

individuals that are taken by Level B 

harassment, as enumerated in the 

Estimated Take of Marine Mammals 

section, on the basis of reports in the 

literature as well as monitoring from 

other similar activities conducted by 

Hilcorp (Horsley and Larson, 2023), will 

likely be limited to behavioral response 

such as increased swimming speeds, 

changing in directions of travel and 

diving and surfacing behaviors, 

increased respiration rates, or decreased 

foraging (if such activity were occurring) 

(Ridgway et al., 1997; Nowacek et al., 

2007; Thorson and Reyff, 2006; Kendall 

and Cornick, 2015; Goldbogen et al., 

2013b; Blair et al., 2016; Wisniewska et 

al., 2018; Piwetz et al., 2021). Marine 

mammals within the 120-dB isopleths 

may not present any visual cues they are 

disturbed by activities, or they could 

become alert, avoid the area, leave the 

area, or have other mild responses that 

are not observable such as increased 

stress levels (e.g., Rolland et al. 2012; 

Bejder et al., 2006; Rako et al., 2013; 

Pirotta et al., 2015; Pe ́rez-Jorge et al., 

2016). They may also exhibit increased 

vocalization rates (e.g., Dahlheim, 1987; 

Dahlheim and Castellote, 2016), louder 

vocalizations (e.g., Frankel and Gabriele, 

2017; Fournet et al., 2018), alterations in 

the spectral features of vocalizations 

(e.g., Castellote et al., 2012), or a 

cessation of communication signals 

(e.g., Tsujii et al., 2018). However, as 

described in the Potential Effects of 

Specified Activities on Marine 

Mammals and Their Habitat section of 

the Federal Register notice of the 

proposed IHA (89 FR 60164, July 24, 

2024), marine mammals observed near 

Hilcorp’s planned activities have shown 

little to no observable reactions to tugs 

under load with a jack-up rig (Horsley 

and Larson, 2023). 

Tugs towing, holding, and positioning 

a jack-up rig are slow-moving as 

compared to typical recreational and 

commercial vessel traffic. Assuming an 

animal is stationary, exposure from the 

moving tug configuration (which 

comprises most of the tug activity being 

considered) will be on the order of 

minutes in any particular location. The 

slow, predictable, and generally straight 

path of this activity is expected to 

further lessen the likelihood that sound 

exposures at the expected levels will 

result in the harassment of marine 

mammals, though the potential takes 

based on straight calculations have 

nonetheless been considered in the 

analysis. Also, this slow transit along a 

predictable path is planned in an area 

of routine vessel traffic where many 

large vessels move in slow straight-line 

paths, and some individuals are 

expected to be habituated to these sorts 

of sounds. While it is possible that 

animals may swim around the project 

area, avoiding closer approaches to the 

boats, we do not expect them to 

abandon any intended path. Further, 

most animals present in the region will 

likely be transiting through the area; 

therefore, any potential exposure is 

expected to be brief. Based on the 

characteristics of the sound source and 

the other activities regularly 

encountered in the area, it is unlikely 

Hilcorp’s planned activities will be of a 

duration or intensity expected to result 

in impacts on reproduction or survival. 

Further, most of the species present in 

the region will only be present 

temporarily based on seasonal patterns 

or during transit between other habitats. 

These temporarily present species will 

be exposed to even shorter periods of 


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noise-generating activity, further 

decreasing the impacts. Most likely, 

individual animals will simply move 

away from the sound source and be 

temporarily displaced from the area. 

Takes also have the potential to occur 

during important feeding times. 

However, the project area represents a 

small portion of available foraging 

habitat and impacts on marine mammal 

feeding for all species should be 

minimal. 

We anticipate that any potential 

reactions and behavioral changes are 

expected to subside quickly when the 

exposures cease and, therefore, we do 

not expect long-term adverse 

consequences from Hilcorp’s planned 

activities for individuals of any species. 

The intensity of Level B harassment 

events will be minimized through use of 

mitigation measures described herein, 

which were not quantitatively factored 

into the take estimates. Hilcorp will use 

PSOs to monitor for marine mammals 

before commencing any tugging activity, 

which will minimize the potential for 

marine mammals to be present within 

the 120-dB isopleth when tugs are under 

load, further reducing the likely amount 

of any potential Level B harassment. 

Further, given the absence of any major 

rookeries or areas of known biological 

significance for marine mammals (e.g., 

foraging hot spots) within the estimated 

harassment zones (other than critical 

habitat and a BIA for CIBWs as 

described below), we predict that 

potential takes by Level B harassment 

will have an inconsequential short-term 

effect on individuals and will not result 

in population-level impacts. 

Theoretically, repeated, sequential 

exposure to elevated noise from tugs 

under load with a jack-up rig over a long 

duration could result in more severe 

impacts to individuals that could affect 

individual fitness or reproductive 

success (via sustained or repeated 

disruption of important behaviors such 

as feeding, resting, traveling, and 

socializing; Southall et al., 2007). 

Alternatively, marine mammals exposed 

to repetitious sounds may become 

habituated, desensitized, or tolerant 

after initial exposure to these sounds 

(reviewed by Richardson et al., 1995; 

Southall et al., 2007). Cook Inlet is a 

regional hub of marine transportation 

and is used by various classes of vessels, 

including containerships, bulk cargo 

freighters, tankers, commercial and 

sport-fishing vessels, and recreational 

vessels. Off-shore vessels, tug vessels, 

and tour boats represent 86 percent of 

the total operating days for vessels in 

Cook Inlet (BOEM, 2016). Given that 

marine mammals still frequent and use 

Cook Inlet despite being exposed to 

anthropogenic sounds such as those 

produced by tug boats and other vessels 

across many years, and that it is 

unlikely that any individual would be 

exposed to repeated, sequential 

exposures or repetitious sounds from 

Hilcop’s activities, no impacts to the 

reproduction or survival of any marine 

mammal individuals from the 

additional noise produced by tugs under 

load with a jack-up rig are anticipated. 

The absence of any pinniped haul outs 

or other known home-ranges in the 

planned action area further decreases 

the likelihood of any more severe 

energetic impacts that might affect 

reproduction or survival. 

Hilcorp’s planned activities are also 

not expected to have significant adverse 

effects on any marine mammal habitat 

as no physical impacts to habitat are 

anticipated to result from the specified 

activities and any impacts to marine 

mammal habitat (i.e., elevated sound 

levels) will be temporary. In addition to 

being temporary and short in overall 

duration, the acoustic footprint of the 

planned activity is small relative to the 

overall distribution of the animals in the 

area and their use of the area. 

Additionally, the habitat within the 

estimated acoustic footprint is not 

known to be heavily used by marine 

mammals. 

Impacts to marine mammal prey 

species are also expected to be minor 

and temporary and to have, at most, 

short-term effects on foraging of 

individual marine mammals, and likely 

no effect on the populations of marine 

mammals as a whole. Overall, as 

described above, the area anticipated to 

be impacted by Hilcorp’s planned 

activities is very small compared to the 

available surrounding habitat and does 

not include habitat of particular 

importance to marine mammals. The 

most likely impact to prey will be 

temporary behavioral avoidance of the 

immediate area. When tugs are under 

load with the jack-up rig, it is expected 

that some fish will temporarily leave the 

area of disturbance (e.g., Nakken, 1992; 

Olsen, 1979; Ona and Godo, 1990; Ona 

and Toresen, 1988), thus impacting 

marine mammals’ foraging 

opportunities in a limited portion of 

their foraging range. But, because of the 

relatively small area of the habitat that 

may be affected, and lack of any 

foraging habitat of particular 

importance, the impacts to marine 

mammal habitat are not expected to 

cause significant or long-term negative 

consequences. 

Finally, Hilcorp will minimize 

potential exposure of marine mammals 

to elevated noise levels by delaying 

tugging activities if CIBWs are observed 

at any distance or if non-CIBW marine 

mammals are observed within 1.5 km 

during the pre-clearance monitoring 

period. Hilcorp will also implement 

vessel maneuvering measures to reduce 

the likelihood of disturbing marine 

mammals during any periods when 

marine mammals may be present near 

the vessels. Lastly, Hilcorp will also 

reduce the impact of their activity by 

conducting tugging operations with 

favorable tides whenever feasible. 

In summary and as described above, 

the following factors (with additional 

analyses for CIBWs included below) 

primarily support our determinations 

that the impacts resulting from the 

activities described for this IHA are not 

expected to affect any individual marine 

mammal’s fitness for survival or 

reproduction, and thus is not expected 

to adversely affect the species or stocks 

through effects on annual rates of 

recruitment or survival: 

• No takes by mortality, serious 

injury, or Level A harassment are 

anticipated or authorized; 

• Exposure, and resulting impacts, 

will likely be brief given the short 

duration of the specified activity and 

the transiting behavior of marine 

mammals in the action area; 

• Marine mammal densities are low 

in the project area; therefore, there will 

not be substantial numbers of marine 

mammals exposed to the noise from the 

project compared to the affected 

population sizes; 

• Take will not occur in places and/ 

or times where take is more likely to 

accrue to impacts on reproduction or 

survival, such as within ESA-designated 

or proposed critical habitat, BIAs (other 

than for CIBWs as described below), or 

other habitats critical to recruitment or 

survival (e.g., rookery); 

• The project area represents a very 

small portion of the available foraging 

area for all potentially impacted marine 

mammal species; 

• Take will only occur within middle 

Cook Inlet and Trading Bay—a limited, 

confined area of any given stock’s home 

range; 

• Monitoring reports from previous 

projects where tugs were under load 

with a jack-up rig in Cook Inlet have 

documented little to no observable 

effect on individuals of the same species 

impacted by the specified activities; 

• The required mitigation is expected 

to be effective in reducing the effects of 

the specified activity by minimizing the 

numbers of marine mammals exposed to 

sound and the intensity of the 

exposures; and 

• The intensity of anticipated takes 

by Level B harassment is low for all 

stocks consisting of, at worst, temporary 


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modifications in behavior, and will not 

be of a duration or intensity expected to 

result in impacts on reproduction or 

survival. 

Cook Inlet Beluga Whales. For CIBWs, 

we further discuss our negligible impact 

findings in addition to the findings 

discussed above for all species in the 

context of potential impacts to this 

endangered stock based on our 

evaluation of the take authorized (table 

10). 

All tugging activities will be done in 

a manner implementing best 

management practices to preserve water 

quality, and no work will occur around 

creek mouths or river systems leading to 

prey abundance reductions. In addition, 

no physical structures will restrict 

passage, though impacts to the acoustic 

habitat are relevant and discussed here. 

While the specified activity will occur 

within CIBW Critical Habitat Area 2, 

and the CIBW small and resident BIA 

(see the Description of Marine Mammals 

in the Area of Specified Activities 

section in the notice for the proposed 

IHA; 89 FR 60164, July 24, 2024), 

monitoring data from Hilcorp’s 

activities suggest that the presence of 

tugs under load with a jack-up rig do 

not discourage CIBWs from transiting 

throughout Cook Inlet and between 

critical habitat areas and that the whales 

do not abandon critical habitat areas 

(Horsley and Larson, 2023). In addition, 

large numbers of CIBWs have continued 

to use Cook Inlet and pass through the 

area, likely traveling to critical foraging 

grounds found in upper Cook Inlet, 

while noise-producing anthropogenic 

activities, including vessel use, have 

taken place during the past two decades 

(e.g., Shelden et al., 2013, 2015b, 2017, 

2022; Shelden and Wade, 2019; Geotz et 

al., 2023). These findings are not 

surprising as food is a strong motivation 

for marine mammals. As described in 

Forney et al. (2017), animals typically 

favor particular areas because of their 

importance for survival (e.g., feeding or 

breeding), and leaving may have 

significant costs to fitness (reduced 

foraging success, increased predation 

risk, increased exposure to other 

anthropogenic threats). Consequently, 

animals may be highly motivated to 

maintain foraging behavior in historical 

foraging areas despite negative impacts 

(e.g., Rolland et al., 2012). 

Generation of sound may result in 

avoidance behaviors that will be limited 

in time and space relative to the larger 

availability of important habitat areas in 

Cook Inlet; however, the area ensonified 

by sound from the specified activity is 

anticipated to be small compared to the 

overall available critical habitat for 

CIBWs to feed and travel. Therefore, the 

specified activity will not create a 

barrier to movement through or within 

important areas. We anticipate that 

disturbance to CIBWs will manifest in 

the same manner as other marine 

mammals described above (i.e., 

increased swimming speeds, changes in 

the direction of travel and dive 

behaviors, increased respiration rates, 

decreased foraging (if such activity were 

occurring), or alterations to 

communication signals). We do not 

believe exposure to elevated noise levels 

during transit past tugging activity will 

have adverse effects on individuals’ 

fitness for reproduction or survival. 

Although data demonstrate that 

CIBWs are not abandoning the planned 

project area during anthropogenic 

activities, results of an expert elicitation 

(EE) at a 2016 workshop, which 

predicted the impacts of noise on CIBW 

survival and reproduction given a 

specific amount of lost foraging 

opportunities, helped to inform our 

assessment of impacts on this stock. The 

2016 EE workshop used conceptual 

models of an interim population 

consequences of disturbance (PCoD) for 

marine mammals (NRC, 2005; New et 

al., 2014; Tollit et al., 2016) to help in 

understanding how noise-related 

stressors might affect vital rates 

(survival, birth rate and growth) for 

CIBW (King et al., 2015). NMFS (2016b) 

suggests that the main direct effects of 

noise on CIBWs are likely to be through 

masking of vocalizations used for 

communication and prey location and 

habitat degradation. The 2016 workshop 

on CIBWs was specifically designed to 

provide regulators with a tool to help 

understand whether chronic and acute 

anthropogenic noise from various 

sources and projects are likely to be 

limiting recovery of the CIBW 

population. The full report can be found 

at https://www.smruconsulting.com/ 

publications/ with a summary of the 

expert elicitation portion of the 

workshop below. 

For each of the noise effect 

mechanisms chosen for the EE, the 

experts provided a set of parameters and 

values that determined the forms of a 

relationship between the number of 

days of disturbance a female CIBW 

experiences in a particular period and 

the effect of that disturbance on her 

energy reserves. Examples included the 

number of days of disturbance during 

the period April, May, and June that 

would be predicted to reduce the energy 

reserves of a pregnant CIBW to such a 

level that she is certain to terminate the 

pregnancy or abandon the calf soon after 

birth, the number of days of disturbance 

in the period April–September required 

to reduce the energy reserves of a 

lactating CIBW to a level where she is 

certain to abandon her calf, and the 

number of days of disturbance where a 

female fails to gain sufficient energy by 

the end of summer to maintain herself 

and her calf during the subsequent 

winter. Overall, median values ranged 

from 16 to 69 days of disturbance 

depending on the question. However, 

for this elicitation, a ‘‘day of 

disturbance’’ was defined as any day on 

which an animal loses the ability to 

forage for at least one tidal cycle (i.e., it 

forgoes 50–100 percent of its energy 

intake on that day). The day of 

disturbance considered in the context of 

the report is notably more severe than 

any Level B harassment expected to 

result from these activities, which as 

described is expected to be comprised 

predominantly of temporary 

modifications in the behavior of 

individual CIBWs (e.g., faster swim 

speeds, longer dives, decreased sighting 

durations, alterations in 

communication). Also, NMFS has 

authorized 15 instances of take, with the 

instances representing disturbance 

events within a day—this means that 

either 15 different individual CIBWs are 

disturbed on no more than 1 day each, 

or some lesser number of individuals 

may be disturbed on more than 1 day, 

but with the product of individuals and 

days not exceeding 15. Given the overall 

authorized take, and the short duration 

of the specified activities (i.e., 6 days), 

it is unlikely that any one CIBW will be 

disturbed on more than a couple of 

days. Lastly, even if a CIBW was 

exposed every day of Hilcorp’s planned 

activities, these activities are only 

planned for 6 days, and thus do not fall 

into the expected range of days of 

disturbance expected to elicit an effect 

on energy reserves as determined by the 

experts as described above (i.e., 16 to 19 

days). Further, Hilcorp will implement 

mitigation measures specific to CIBWs 

whereby they will not begin tugging 

activities should a CIBW be observed at 

any distance. While Level B harassment 

(behavioral disturbance) is authorized, 

this measure, along with other 

mitigation measures described herein, 

will limit the severity of the effects of 

that Level B harassment to behavioral 

changes such as increased swim speeds, 

changes in diving and surfacing 

behaviors, and alterations to 

communication signals, not the loss of 

foraging capabilities. Finally, take by 

mortality, serious injury, or Level A 

harassment of CIBWs is not anticipated 

or authorized. 

In summary and as described above, 

the additional following factors 

primarily support our determination 


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that the impacts resulting from this 

activity are not expected to adversely 

affect the CIBWs through effects on 

annual rates of recruitment or survival: 

• The area of exposure will be limited 

to habitat primarily used for transiting, 

and not areas known to be of particular 

importance for feeding or reproduction; 

• The activities are not expected to 

result in CIBWs abandoning critical 

habitat nor are they expected to restrict 

passage of CIBWs within or between 

critical habitat areas; and 

• Any disturbance to CIBWs is 

expected to be limited to temporary 

modifications in behavior, and will not 

be of a duration or intensity expected to 

result in impacts on reproduction or 

survival. 

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 

required monitoring and mitigation 

measures, NMFS finds that the total 

marine mammal take from the planned 

specified 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 section 101(a)(5)(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 (see 

86 FR 5322, January 19, 2021). 

Additionally, other qualitative factors 

may be considered in the analysis, such 

as the temporal or spatial scale of the 

activities. 

For all stocks whose abundance 

estimate is known, the amount of 

authorized taking is less than one-third 

of the best available population 

abundance estimate (in fact it is less 

than 2 percent for all stocks, except for 

CIBWs whose authorized take is for up 

to 5.38 percent of the stock; see table 

11). The numbers of animals authorized 

to be taken are small relative to the 

relevant species or stock abundances 

even if each estimated take occurred to 

a new individual. 

TABLE 11—AUTHORIZED TAKE AS A PERCENTAGE OF STOCK ABUNDANCE

Species 

Total amount 

of take 

authorized 

Stock Abundance 

(Nbest 1) 

Percent of 

stock 

Humpback whale .................................. 3 Hawaii (Hawaii DPS) .......................................................... 11,278 0.03 

Mexico-North Pacific (Mexico DPS) .................................... 1 N/A N/A 

Western North Pacific ......................................................... 1,084 0.28 

Minke whale ......................................... 3 Alaska ................................................................................. 2 N/A N/A 

Gray whale ........................................... 3 Eastern Pacific .................................................................... 26,960 0.01 

Fin whale .............................................. 2 Northeast Pacific ................................................................. 3 UND N/A 

Killer whale ........................................... 10 Eastern North Pacific Alaska Resident ............................... 1,920 0.52 

Eastern North Pacific Gulf of Alaska, Aleutian Islands, 

and Bering Sea Transient.

587 1.7 

Beluga whale ........................................ 15 Cook Inlet ............................................................................ 4 279 5.38 

Dall’s porpoise ...................................... 6 Alaska ................................................................................. 5 UND N/A 

Harbor porpoise ................................... 12 Gulf of Alaska ..................................................................... 31,046 0.04 

Pacific white-sided dolphin ................... 3 North Pacific ........................................................................ 26,880 0.01 

Harbor seal ........................................... 365 Cook Inlet/Shelikof .............................................................. 28,411 1.29 

Steller sea lion ..................................... 9 Western U.S ........................................................................ 6 49,932 0.02 

California sea lion ................................ 2 U.S ...................................................................................... 257,606 <0.01 

1Abundance estimates are based upon data collected more than 8 years ago and, therefore, current estimates are considered unknown. 2 Reliable population estimates are not available for this stock. Please see Friday et al. (2013) and Zerbini et al. (2006) for additional information on numbers of minke whales in Alaska. 3The best available abundance estimate for this stock is not considered representative of the entire stock as surveys were limited to a small 

portion of the stock’s range. 4On June 15, 2023, NMFS released an updated abundance estimate for endangered CIBWs in Alaska (Goetz et al., 2023). Data collected 

during NOAA Fisheries’ 2022 aerial survey suggest that the whale population is stable or may be increasing slightly. Scientists estimated that the 

population size is between 290 and 386, with a median best estimate of 331. In accordance with the MMPA, this population estimate will be incorporated into the CIBW SAR, which will be reviewed by an independent panel of experts, the Alaska Scientific Review Group. After this review, 

the SAR will be made available as a draft for public review before being finalized. When the number of instances of takes is compared to this 

median abundance, the percent of the stock authorized is 4.53 percent. 5The best available abundance estimate is likely an underestimate for the entire stock because it is based upon a survey that covered only a 

small portion of the stock’s range. 6 Nest is the best estimate of counts, which have not been corrected for Steller sea lions at sea during abundance surveys. 

Abundance estimates for the MexicoNorth Pacific stock of humpback whales 

are based upon data collected more than 

8 years ago and, therefore, current 

estimates are considered unknown 

(Young et al., 2023). The most recent 

minimum population estimates (NMIN) 

for this population include an estimate 

of 2,241 individuals between 2003 and 

2006 (Martinez-Aguilar, 2011) and 766 

individuals between 2004 and 2006 

(Wade, 2021). NMFS’ Guidelines for 

Assessing Marine Mammal Stocks 

suggest that the NMIN estimate of the 

stock should be adjusted to account for 

potential abundance changes that may 

have occurred since the last survey and 

provide reasonable assurance that the 

stock size is at least as large as the 

estimate (NMFS, 2023a). The abundance 

trend for this stock is unclear; therefore, 

there is no basis for adjusting these 

estimates (Young et al., 2023). 

Assuming the population has been 

stable, and that the 4 authorized takes 

of humpback whale will all be of the 

Mexico-North Pacific stock, this 

represents small numbers of this stock 

(0.18 percent of the stock assuming a 

NMIN of 2,241 individuals and 0.52 

percent of the stock assuming an NMIN

of 766 individuals). 


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A lack of an accepted stock 

abundance value for the Alaska stock of 

minke whale did not allow for the 

calculation of an expected percentage of 

the population that will be affected. The 

most relevant estimate of partial stock 

abundance is 1,233 minke whales in 

coastal waters of the Alaska Peninsula 

and Aleutian Islands (Zerbini et al., 

2006). Given three authorized takes by 

Level B harassment for the stock, 

comparison to the best estimate of stock 

abundance shows, at most, less than 1 

percent of the stock is expected to be 

impacted. 

There is no stock-wide abundance 

estimate for Northeast Pacific fin 

whales. However, Young et al. (2022) 

estimate the minimum stock size for the 

areas surveyed is 2,554. Given two 

authorized takes by Level B harassment 

for the stock, comparison to the 

minimum population estimate shows, at 

most, less than 1 percent of the stock is 

expected to be impacted. 

The Alaska stock of Dall’s porpoise 

has no official NMFS abundance 

estimate for this area, as the most recent 

estimate is greater than 8 years old. As 

described in the 2022 Alaska SAR 

(Young et al., 2023) the minimum 

population estimate is assumed to 

correspond to the point estimate of the 

2015 vessel-based abundance computed 

by Rone et al. (2017) in the Gulf of 

Alaska (N = 13,110; CV = 0.22). Given 

six authorized takes by Level B 

harassment for the stock, comparison to 

the minimum population estimate 

shows, at most, less than 1 percent of 

the stock is expected to be impacted. 

Based on the analysis contained 

herein of the planned activity (including 

the required mitigation and monitoring 

measures) and the anticipated take of 

marine mammals, NMFS finds that 

small numbers of marine mammals will 

be taken relative to the population sizes 

of the affected species or stocks. 

Unmitigable Adverse Impact Analysis 

and Determination 

In order to issue an IHA, NMFS must 

find that the specified activity will not 

have an ‘‘unmitigable adverse impact’’ 

on the subsistence uses of the affected 

marine mammal species or stocks by 

Alaskan Natives. NMFS has defined 

‘‘unmitigable adverse impact’’ in 50 CFR 

216.103 as an impact resulting from the 

specified activity: (1) That is likely to 

reduce the availability of the species to 

a level insufficient for a harvest to meet 

subsistence needs by: (i) Causing the 

marine mammals to abandon or avoid 

hunting areas; (ii) Directly displacing 

subsistence users; or (iii) Placing 

physical barriers between the marine 

mammals and the subsistence hunters; 

and (2) That cannot be sufficiently 

mitigated by other measures to increase 

the availability of marine mammals to 

allow subsistence needs to be met. 

Hilcorp’s tugging activities will occur 

offshore and north of Kenai and the 

Village of Salmatof. The last ADF&G 

subsistence survey conducted in Kenai 

was in 1998 (Fall et al., 2000). In the 

greater Kenai area, an estimated 13 

harbor seals and no sea lions were 

harvested in 1988 by an estimated 10 

households. In the Kenai area, estimated 

harbor seal harvest has ranged between 

13 (1998) and 35 (1997) animals. In 

1996, two sea lions and six harbor seals 

were harvested. No sea otters have been 

reported harvested in Kenai. ADF&G 

Community Subsistence Information 

System harvest data are not available for 

Salamatof, so Hilcorp assumes the 

subsistence harvest patterns are similar 

to other communities along the road 

system on the southern Kenai 

Peninsula, namely Kenai. 

Tugging activities at the Tyonek 

platform in the North Cook Inlet Unit in 

middle Cook Inlet will occur 

approximately 10 km from the Native 

Village of Tyonek. Tyonek, on the 

western side of middle Cook Inlet, has 

a subsistence harvest area that extends 

south from the Susitna River to Tuxedni 

Bay (Stanek et al., 2007). Moose and 

salmon are the most important 

subsistence resources measured by 

harvested weight (Stanek, 1994). In 

Tyonek, harbor seals were harvested 

between June and September by 6 

percent of the households (Jones et al., 

2015). Seals were harvested in several 

areas, encompassing an area stretching 

32 km along the Cook Inlet coastline 

from the McArthur Flats north to the 

Beluga River. Seals were searched for or 

harvested in the Trading Bay areas as 

well as from the beach adjacent to 

Tyonek (Jones et al., 2015). 

Seal hunting occurs opportunistically 

among Alaska Natives who may be 

fishing or traveling in upper Cook Inlet 

near the mouths of the Susitna River, 

Beluga River, and Little Susitna River. 

Hilcorp’s tugging activities may overlap 

with subsistence hunting of seals. 

However, these activities typically occur 

along the shoreline or very close to 

shore near river mouths, whereas most 

of Hilcorps’s tugging is in the middle of 

the Inlet and rarely near the shoreline or 

river mouths. 

Any harassment to marine mammals 

will be limited to minor behavioral 

changes (e.g., increased swim speeds, 

changes in dive behaviors and 

communication signals, temporary 

avoidance near the tugs) and is 

anticipated to be short-term, mild, and 

not result in any abandonment or 

behaviors that would make the animals 

unavailable to Alaska Natives. 

To further minimize any potential 

effects of their action on subsistence 

activities, Hilcorp has outlined their 

communication plan for engaging with 

subsistence users in their Stakeholder 

Engagement Plan (see appendix C of 

Hilcorp’s application). This includes 

using traditional/subsistence knowledge 

to inform planning for the activity. 

Hilcorp is required to abide by this plan 

and update the plan accordingly. 

Based on the description of the 

specified activity, the measures 

described to minimize adverse effects 

on the availability of marine mammals 

for subsistence purposes, and the 

required mitigation and monitoring 

measures, NMFS has determined that 

the authorized harassment will not have 

an unmitigable adverse impact on the 

availability of marine mammal species 

or stocks for taking for subsistence uses. 

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, in 

this case with the NMFS AKRO. 

Four marine mammal species (fin 

whale, humpback whale (Mexico DPS), 

beluga whale (Cook Inlet), and Steller 

sea lion (Western DPS)) occur in the 

project area and are listed as threatened 

or endangered under the ESA. The 

NMFS AKRO issued a Biological 

Opinion under section 7 of the ESA on 

the issuance of an IHA to Hilcorp under 

section 101(a)(5)(D) of the MMPA by 

NMFS Office of Protected Resources. 

The Biological Opinion concluded that 

the action is not likely to jeopardize the 

continued existence of these species and 

is not likely to destroy or adversely 

modify their critical habitat. 

National Environmental Policy Act 

To comply with the NEPA of 1969 (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. NMFS prepared an 

EA and analyzed the potential impacts 

to marine mammals that would result 

from Hilcorp’s planned activities. A 

Finding of No Significant Impact 


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(FONSI) was signed on September 4, 

2024. Copies of the EA and FONSI are 

available at https://

www.fisheries.noaa.gov/national/ 

marine-mammal-protection/incidentaltake-authorizations-oil-and-gas. 

Authorization 

NMFS has issued an IHA to Hilcorp 

for the potential harassment of small 

numbers of 12 marine mammal species 

incidental to Hilcorp’s use of tugs to 

tow, hold, and position a jack-up rig in 

support of their oil and gas activities in 

Cook Inlet, Alaska from September 24, 

2024 through September 23, 2025, that 

includes the previously explained 

mitigation, monitoring and reporting 

requirements. 

Dated: September 24, 2024. 

Kimberly Damon-Randall, 

Director, Office of Protected Resources, 

National Marine Fisheries Service. 

[FR Doc. 2024–22293 Filed 9–27–24; 8:45 am] 

BILLING CODE 3510–22–P 

DEPARTMENT OF COMMERCE 

National Oceanic and Atmospheric 

Administration 

[RTID 0648–XE225] 

Takes of Marine Mammals Incidental to 

Specified Activities; Taking Marine 

Mammals Incidental to the Army Corps 

of Engineers Baker Bay Pile Dike 

Repair Project 

AGENCY: National Marine Fisheries 

Service (NMFS), National Oceanic and 

Atmospheric Administration (NOAA), 

Commerce. 

ACTION: Notice; issuance of an incidental 

harassment authorization. 

SUMMARY: In accordance with the 

regulations implementing the Marine 

Mammal Protection Act (MMPA) as 

amended, notification is hereby given 

that NMFS has issued an incidental 

harassment authorization (IHA) to the 

Army Corps of Engineers (ACOE) to 

incidentally harass marine mammals 

during construction activities associated 

with the Baker Bay pile dike repair 

project in Baker Bay, Oregon. There are 

no changes from the proposed 

authorization in this final authorization. 

DATES: This authorization is effective 

from August 1, 2025 to July 31, 2026. 

ADDRESSES: Electronic copies of the 

application and supporting documents, 

as well as a list of the references cited 

in this document, may be obtained 

online at: https://

www.fisheries.noaa.gov/action/ 

incidental-take-authorization-armycorps-engineers-baker-bay-pile-dikerepair-project-baker. In case of problems 

accessing these documents, please call 

the contact listed below. 

FOR FURTHER INFORMATION CONTACT: 

Craig Cockrell, Office of Protected 

Resources, NMFS, (301) 427–8401. 

SUPPLEMENTARY INFORMATION: 

Background 

The MMPA prohibits the ‘‘take’’ of 

marine mammals, with certain 

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

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

seq.) direct the Secretary of Commerce 

(as delegated to NMFS) to allow, upon 

request, the incidental, but not 

intentional, taking of small numbers of 

marine mammals by U.S. citizens who 

engage in a specified activity (other than 

commercial fishing) within a specified 

geographical region if certain findings 

are made and either regulations are 

proposed or, if the taking is limited to 

harassment, a notice of a proposed IHA 

is provided to the public for review. 

Authorization for incidental takings 

shall be granted if NMFS finds that the 

taking will have a negligible impact on 

the species or stock(s) and will not have 

an unmitigable adverse impact on the 

availability of the species or stock(s) for 

taking for subsistence uses (where 

relevant). Further, NMFS must prescribe 

the permissible methods of taking and 

other ‘‘means of effecting the least 

practicable adverse impact’’ on the 

affected species or stocks and their 

habitat, paying particular attention to 

rookeries, mating grounds, and areas of 

similar significance, and on the 

availability of the species or stocks for 

taking for certain subsistence uses 

(referred to in shorthand as 

‘‘mitigation’’); and requirements 

pertaining to the monitoring and 

reporting of the takings. The definitions 

of all applicable MMPA statutory terms 

cited above are included in the relevant 

sections below. 

Summary of Request 

On September 8, 2022, NMFS 

received a request from the ACOE for an 

IHA to take marine mammals incidental 

to pile driving and removal at the mouth 

of the Columbia River in Oregon. 

Following NMFS’ review of the 

application, the ACOE submitted two 

revised versions on March 4, 2024 and 

May 1, 2024. The application was 

deemed adequate and complete on June 

10, 2024. The ACOE’s request is for take 

of eight species of marine mammals by 

Level B harassment and, for harbor seal 

(Phoca vitulina), Level A harassment. 

Neither ACOE nor NMFS expect serious 

injury or mortality to result from this 

activity and, therefore, an IHA is 

appropriate. 

Description of Activity 

ACOE is planning to conduct pile 

dike repairs in the Baker Bay system, 

located in the Columbia River estuary. 

There are a variety of activities that will 

occur during this project. Take of 

marine mammals is expected to occur 

only during the construction of the 

material offload facility and the 

installation of the marker piles. 

Vibratory and impact pile driving will 

introduce underwater sounds that may 

result in take, by Level A and Level B 

harassment, of marine mammals. It is 

expected to take up to 12 nonconsecutive days to complete the pile 

driving activities from August through 

October. 

A detailed description of the planned 

construction project is provided in the 

Federal Register notice for the proposed 

IHA (89 FR 60385, July 25, 2024). Since 

that time, no changes have been made 

to the planned activities. Therefore, a 

detailed description is not provided 

here. Please refer to that Federal 

Register notice for the description of the 

specific activity. 

Comments and Responses 

A notice of NMFS’ proposal to issue 

an IHA to the ACOE was published in 

the Federal Register on July 25, 2024 

(89 FR 60385). That notice described, in 

detail, the ACOE’s activity, the marine 

mammal species that may be affected by 

the activity, and the anticipated effects 

on marine mammals. In that notice, we 

requested public input on the request 

for authorization described therein, our 

analyses, the proposed authorization, 

and any other aspect of the notice of 

proposed IHA, and requested that 

interested persons submit relevant 

information, suggestions, and 

comments. During the 30-day public 

comment period, NMFS did not receive 

any public comments. 

Description of Marine Mammals in the 

Area of Specified Activities 

Sections 3 and 4 of the application 

summarize available information 

regarding status and trends, distribution 

and habitat preferences, and behavior 

and life history of the potentially 

affected species. NMFS fully considered 

all of this information, and we refer the 

reader to these descriptions, instead of 

reprinting the information. Additional 

information regarding population trends 

and threats may be found in NMFS’ 

Stock Assessment Reports (SARs; 

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

national/marine-mammal-protection/ 

marine-mammal-stock-assessments) 


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