Takes of Marine Mammals Incidental to Specified Activities; Taking Marine Mammals Incidental to Geophysical Surveys in the Atlantic Ocean

DEPARTMENT OF COMMERCE

National Oceanic and Atmospheric Administration

RIN 0648-XE283

Takes of Marine Mammals Incidental to Specified Activities; Taking Marine Mammals Incidental to Geophysical Surveys in the Atlantic Ocean

AGENCY:

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

ACTION:

Notice; issuance of five incidental harassment authorizations.

SUMMARY:

In accordance with the regulations implementing the Marine Mammal Protection Act (MMPA) as amended, notification is hereby given that we have issued incidental harassment authorizations (IHA) to five separate applicants to incidentally harass marine mammals during geophysical survey activities in the Atlantic Ocean.

DATES:

These authorizations are effective for one year from the date of effectiveness.

FOR FURTHER INFORMATION CONTACT:

Ben Laws, Office of Protected Resources, NMFS, (301) 427-8401.

SUPPLEMENTARY INFORMATION:

Availability

Electronic copies of the applications and supporting documents, as well as a list of the references cited in this document, may be obtained online at:

www.fisheries.noaa.gov/action/incidental-take-authorization-oil-and-gas-industry-geophysical-survey-activity-atlantic.

In case of problems accessing these documents, please call the contact listed above.

Background

Section 101(a)(5)(D) of the MMPA (16 U.S.C. 1361

et seq.

) directs 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 specific geographic region if certain findings are made and notice of a proposed authorization is provided to the public for review.

An authorization for incidental takings shall be granted if NMFS finds that the taking will have a negligible impact on the species or stock(s), will not have an unmitigable adverse impact on the availability of the species or stock(s) for subsistence uses (where relevant), and if the permissible methods of taking and requirements pertaining to the mitigation, monitoring and reporting of such takings are set forth.

NMFS has defined “negligible impact” in 50 CFR 216.103 as an impact resulting from the specified activity that cannot be reasonably expected to, and is not reasonably likely to, adversely affect the species or stock through effects on annual rates of recruitment or survival.

The MMPA states that the term “take” means to harass, hunt, capture, or kill, or attempt to harass, hunt, capture, or kill any marine mammal.

Except with respect to certain activities not pertinent here, the MMPA defines “harassment” as any act of pursuit, torment, or annoyance which (i) has the potential to injure a marine mammal or marine mammal stock in the wild (Level A harassment); or (ii) has the potential to disturb a marine mammal or marine mammal stock in the wild by causing disruption of behavioral patterns, including, but not limited to, migration, breathing, nursing, breeding, feeding, or sheltering (Level B harassment).

Summary of Requests

In 2014, the Bureau of Ocean Energy Management (BOEM) produced a Programmatic Environmental Impact Statement (PEIS) to evaluate potential significant environmental effects of geological and geophysical (G&G) activities on the Mid- and South Atlantic Outer Continental Shelf (OCS), pursuant to requirements of the National Environmental Policy Act (NEPA). BOEM's PEIS and associated Record of Decision are available online at:

www.boem.gov/Atlantic-G-G-PEIS/.

G&G activities include geophysical surveys in support of hydrocarbon exploration, as are planned by the five IHA applicants discussed herein.

In 2014-15, we received multiple separate requests for authorization for take of marine mammals incidental to geophysical surveys in support of hydrocarbon exploration in the Atlantic Ocean. The applicants are companies that provide services, such as geophysical data acquisition, to the oil and gas industry. Upon review of these requests, we submitted questions, comments, and requests for additional information to the individual applicant companies. As a result of these interactions, the applicant companies provided revised versions of the applications that we determined were adequate and complete. Adequate and complete applications were received from ION GeoVentures (ION) on June 24, 2015, Spectrum Geo Inc. (Spectrum) on July 6, 2015, and from TGS-NOPEC Geophysical Company (TGS) on July 21, 2015.

We subsequently posted these applications for public review and sought public input (80 FR 45195; July 29, 2015). The comments and information received during this public review period informed development of the proposed IHAs (82 FR 26244; June 6, 2017), and all letters received are available online at

www.fisheries.noaa.gov/action/incidental-take-authorization-oil-and-gas-industry-geophysical-survey-activity-atlantic.

Following conclusion of this opportunity for public review, we received revised applications from Spectrum on September 18, 2015, and from TGS on February 10, 2016. We received additional information from ION on February 29, 2016. We also received adequate and complete applications from two additional applicants: WesternGeco, LLC (Western) on February 17, 2016, and CGG on May 26, 2016. Full details regarding these timelines were described in our

Federal Register

Notice of Proposed IHAs (82 FR 26244; June 6, 2017).

On June 26, 2018, Spectrum notified NMFS of a modification to their survey plan. Spectrum's letter and related information is available online, as is their preceding adequate and complete application. The descriptions and analyses contained herein were complete at the time we received notification of the modification. Therefore, we present those descriptions and analyses, including those related to Spectrum's request (as detailed in their 2015 application), intact as originally developed. However, we provide detail regarding Spectrum's modified survey plan, our evaluation of the modification to the specified activity, and our finding that the determinations made in regard to Spectrum's previously proposed specified activity remain appropriate and valid in a standalone section entitled “Spectrum Survey Plan Modification” at the end of this notice.

All issued authorizations are valid for the statutory maximum of one year. All applicants plan to conduct two-dimensional (2D) marine seismic surveys using airgun arrays. Generally speaking, these surveys may occur within the U.S. Exclusive Economic Zone (EEZ) (

i.e.,

to 200 nautical miles (nmi)) from Delaware to approximately Cape Canaveral, Florida, and corresponding with BOEM's Mid- and South Atlantic OCS planning areas, as well as additional waters out to 350 nmi from shore. Please see the applications for specific details of survey design. The use of airgun arrays is expected to

produce underwater sound at levels that have the potential to result in harassment of marine mammals. Multiple cetacean species with the expected potential to be present during all or a portion of the planned surveys are described below.

Because the specified activity, specific geographic region, and planned dates of activity are substantially similar for the five separate requests for authorization, we have determined it appropriate to provide a joint notice for issuance of the five authorizations. However, while we provide relevant information together, we consider the potential impacts of the specified activities independently and make determinations specific to each request for authorization, as required by the MMPA.

Description of the Specified Activities

In this section, we provide a generalized discussion that is broadly applicable to all five requests for authorization, with project-specific portions indicated.

Overview

The five applicants plan to conduct deep penetration seismic surveys using airgun arrays as an acoustic source. Seismic surveys are one method of obtaining geophysical data used to characterize the subsurface structure, in this case in support of hydrocarbon exploration. The planned surveys are 2D surveys, designed to acquire data over large areas in order to screen for potential hydrocarbon prospectivity. To contrast, three-dimensional surveys may use similar acoustic sources but are designed to cover smaller areas with greater resolution (

e.g.,

with closer survey line spacing). A deep penetration survey uses an acoustic source suited to provide data on geological formations that may be thousands of meters (m) beneath the seafloor, as compared with a survey that may be intended to evaluate shallow subsurface formations or the seafloor itself (

e.g.,

for hazards).

An airgun is a device used to emit acoustic energy pulses into the seafloor, and generally consists of a steel cylinder that is charged with high-pressure air. The firing pressure of an array is typically 2,000 pounds per square inch (psi). Release of the compressed air into the water column generates a signal that reflects (or refracts) off of the seafloor and/or subsurface layers having acoustic impedance contrast. When fired, a brief (~0.1 second (s)) pulse of sound is emitted by all airguns nearly simultaneously. The airguns do not fire during the intervening periods, with the array typically fired on a fixed distance (or shot point) interval. This interval may vary depending on survey objectives, but a typical interval for a 2D survey in relatively deep water might be 25 m (approximately every 10 s, depending on vessel speed). Vessel speed when towing gear is typically 4-5 knots (kn). The return signal is recorded by a listening device and later analyzed with computer interpretation and mapping systems used to depict the subsurface. In this case, towed streamers contain hydrophones that would record the return signal.

Individual airguns are available in different volumetric sizes, and for deep penetration seismic surveys are towed in arrays (

i.e.,

a certain number of airguns of varying sizes in a certain arrangement) designed according to a given company's method of data acquisition, seismic target, and data processing capabilities. A typical large airgun array, as was considered in BOEM's PEIS (BOEM, 2014a), may have a total volume of approximately 5,400 cubic inches (in

3

). The notional array modeled by BOEM consists of 18 airguns in three identical strings of six airguns each, with individual airguns ranging in volume from 105-660 in

3

. Sound levels for airgun arrays are typically modeled or measured at some distance from the source and a nominal source level then back-calculated. Because these arrays constitute a distributed acoustic source rather than a single point source (

i.e.,

the “source” is actually comprised of multiple sources with some pre-determined spatial arrangement), the highest sound levels measurable at any location in the water will be less than the nominal source level. A common analogy is to an array of light bulbs; at sufficient distance the array will appear to be a single point source of light but individual sources, each with less intensity than that of the whole, may be discerned at closer distances. In addition, the effective source level for sound propagating in near-horizontal directions (

i.e.,

directions likely to impact most marine mammals in the vicinity of an array) is likely to be substantially lower than the nominal source level applicable to downward propagation because of the directional nature of the sound from the airgun array. The horizontal propagation of sound is reduced by noise cancellation effects created when sound from neighboring airguns on the same horizontal plane partially cancel each other out.

Survey protocols generally involve a predetermined set of survey, or track, lines. The seismic acquisition vessel (source vessel) will travel down a linear track for some distance until a line of data is acquired, then turn and acquire data on a different track. In addition to the line over which data acquisition is desired, full-power operation may include run-in and run-out. Run-in is approximately 1 kilometer (km) of full-power source operation before starting a new line to ensure equipment is functioning properly, and run-out is additional full-power operation beyond the conclusion of a trackline (typically half the distance of the acquisition streamer behind the source vessel) to ensure that all data along the trackline are collected by the streamer. Line turns typically require two to three hours due to the long, trailing streamers (approximately 10 km). Spacing and length of tracks vary by survey. Survey operations often involve the source vessel, supported by a chase vessel. Chase vessels typically support the source vessel by protecting the hydrophone streamer from damage (

e.g.,

from other vessels) and otherwise lending logistical support (

e.g.,

returning to port for fuel, supplies, or any necessary personnel transfers). Chase vessels do not deploy acoustic sources for data acquisition purposes; the only potential effects of the chase vessels are those associated with normal vessel operations.

Dates and Duration

All issued IHAs are valid for the statutory maximum of one year from the date of effectiveness. The IHAs are effective upon written notification from the applicant to NMFS, but not beginning later than one year from the date of issuance or extending beyond two years from the date of issuance. However, the expected temporal extent of survey activity varies by company and may be subject to unpredictability due to inclement weather days, equipment maintenance and/or repair, transit to and from ports to survey locations, and other contingencies. Spectrum originally planned a 6-month data acquisition program (February through July), consisting of an expected 165 days of seismic operations. This plan has been modified and now consists of an estimated 108 days of operations. Please see “Spectrum Survey Plan Modification” for further information. TGS plans a full year data acquisition program, with an estimated 308 days of seismic operations. ION plans a six-month data acquisition program (July through December), with an estimated 70 days of seismic data collection. Western plans a full year data acquisition program, with an estimated 208 days of seismic operations. CGG plans a six-month data acquisition program (July through

December), with an estimated 155 days of seismic operations. Seismic operations typically occur 24 hours per day.

Specific Geographic Region

The planned survey activities would occur off the Atlantic coast of the United States, within BOEM's Mid-Atlantic and South Atlantic OCS planning areas (

i.e.,

from Delaware to Cape Canaveral, FL), and out to 350 nmi (648 km) (see Figure 1, reproduced from BOEM, 2014a). The seaward limit of the region is based on the maximum constraint line for the extended continental shelf (ECS) under the United Nations Convention on the Law of the Sea. Until such time as an ECS is established by the United States, the region between the U.S. EEZ boundary and the ECS maximum constraint line (

i.e.,

200-350 nmi from shore) is part of the global commons, and BOEM determined it appropriate to include this area within the area of interest for geophysical survey activity.

The specific survey areas differ within this region; please see maps provided in the individual applications (Spectrum: Figure 1; Western: Figures 1-1 to 1-4; TGS: Figures 1-1 to 1-4; ION: Figure 1; CGG: Figure 3) (however, please see “Spectrum Survey Plan Modification” for further information). The specific geographic region has not changed compared with what was described in our Notice of Proposed IHAs (82 FR 26244; June 6, 2017), nor has substantive new information regarding the region become available. Therefore, we do not reprint that discussion here; for additional detail regarding the specific geographic region, please see our Notice of Proposed IHAs.

BILLING CODE 3510-22-P

EN07DE18.000

BILLING CODE 3510-22-P

Detailed Description of Activities

Survey descriptions, as summarized from specific applications, are provided here. Please see Table 1 for a summary of airgun array characteristics. With the exception of Spectrum, the planned surveys have not changed from those described in our Notice of Proposed IHAs (82 FR 26244; June 6, 2017) Please see “Spectrum Survey Plan Modification” for further information. For full detail, please see the individual IHA applications and our Notice of Proposed IHAs. Note that all applicants expect there to be limited additional operations associated with equipment testing, startup, line changes, and repeat coverage of any areas where initial data quality is sub-standard. Therefore, there

could be some small amount of use of the acoustic source not accounted for in the total estimated line-km for each survey; however, this activity is difficult to quantify in advance and would represent an insignificant increase in effort.

ION

—ION's survey is planned to occur from Delaware to northern Florida (~38.5° N to ~27.9° N) (see Figure 1 of ION's application), and consists of ~13,062 km of survey line. The acoustic source planned for deployment is a 36-airgun array with a total volume of 6,420 in

3

. The array would consist of airguns ranging in volume from 40 in

3

to 380 in

3

. The airguns would be configured as four identical linear arrays or “strings” (see Figure 3 of ION's application). The four airgun strings would be towed at 10-m depth, and would fire every 50 m or 20-24 s, depending on exact vessel speed. ION provided modeling results for their array, including notional source signatures, 1/3-octave band source levels as a function of azimuth angle, and received sound levels as a function of distance and direction at 16 representative sites in the survey area. For more detail, please see Figures 4-6 and Appendix A of ION's application.

Spectrum

—Spectrum's survey was originally planned to occur from Delaware to northern Florida (see Figure 1 of Spectrum's application), consisting of ~21,635 km of survey line. This plan has been modified and now consists of ~13,766 km of operations. Please see “Spectrum Survey Plan Modification” for further information). The acoustic source planned for deployment is a 32-airgun array with a total volume of 4,920 in

3

. The array would consist of airguns ranging in volume from 50 in

3

to 250 in

3

. The airguns would be configured as four subarrays, each with eight to ten airguns (see Figure 2 in Appendix A of Spectrum's application). The four airgun strings would be towed at 6 to 10-m depth, and would fire every 25 m or 10 s, depending on exact vessel speed. Spectrum provided modeling results for their array, including notional source signatures, 1/3-octave band source levels as a function of azimuth angle, and received sound levels as a function of distance and direction at 16 representative sites in the survey area. For more detail, please see Appendix A of Spectrum's application.

As stated above, Spectrum notified NMFS on June 26, 2018, of a modification to their survey plan. Please see “Spectrum Survey Plan Modification” for further information.

TGS

—TGS's survey is planned to occur from Delaware to northern Florida (see Figure 1-1 of TGS's application), and consists of ~58,300 km of survey line. The survey plan consists of two contiguous survey grids with differently spaced lines (see Figures 1-1 to 1-4 of TGS's application), and would involve use of two source vessels operating independently of one another at a minimum of 100 km separation distance. The acoustic sources planned for deployment are 40-airgun arrays with a total volume of 4,808 in

3

. The array would consist of airguns ranging in volume from 22 in

3

to 250 in

3

. The airguns would be configured as four identical strings (see Figure 3 in Appendix B of TGS's application). The four airgun strings would be towed at 7-m depth, and would fire every 25 m or 10 s, depending on exact vessel speed. More detail regarding TGS's acoustic source and modeling related to TGS's application is provided in Appendix B of TGS's application.

Western

—Western's survey is planned to occur from Maryland to northern Florida (see Figure 1-1 of Western's application), and consists of ~27,330 km of survey line. The survey plan consists of a survey grid with differently spaced lines (see Figures 1-1 to 1-4 of Western's application). The acoustic source planned for deployment is a 24-airgun array with a total volume of 5,085 in

3

. The airguns would be configured as three identical strings. The three airgun strings would be towed at 10-m depth, and would fire every 37.5 m (approximately every 16 s, depending on vessel speed). More detail regarding Western's acoustic source and modeling related to Western's application is provided in Appendix B of Western's application.

CGG

—CGG's survey is planned to occur from Virginia to Georgia (see Figure 3 of CGG's application), and consists of ~28,670 km of survey line. The acoustic source planned for deployment is a 36-airgun array with a total volume of 5,400 in

3

. The array would consist of airguns ranging in volume from 40 in

3

to 380 in

3

. The airguns would be configured as four identical strings (see Figure 2 of CGG's application). The four airgun strings would be towed at 7-m depth, and would fire every 25 m or 10 s, depending on exact vessel speed. More detail regarding CGG's acoustic source and modeling related to CGG's application is provided in CGG's application.

Table 1—Survey and Airgun Array Characteristics

Company

Total planned

survey km

Total

volume

(in

3

)

Number of guns

Number of strings

Nominal source output

(downward)

1

0-pk

pk-pk

rms

Shot interval

(m)

Tow depth

(m)

ION

13,062

6,420

36

4

257

263

4

247

50

10

Spectrum

13,766

4,920

32

4

266

272

243

25

6-10

TGS

58,300

4,808

40

4

255

(

3

)

240

25

7

Western

27,330

5,085

24

3

(

3

)

262

235

37.5

10

CGG

28,670

5,400

36

4

(

3

)

259

3 4

243

25

7

BOEM

2

n/a

5,400

18

3

247

(

3

)

233

n/a

6.5

1

See “Description of Active Acoustic Sound Sources,” later in this document, for discussion of these concepts.

2

Notional array characteristics modeled and source characterization outputs from BOEM's PEIS (2014a) provided for comparison.

3

Values not given; however, SPL (pk-pk) is usually considered to be approximately 6 dB higher than SPL (0-pk) (Greene, 1997).

4

Value decreased from modeled 0-pk value by minimum 10 dB (Greene, 1997).

Comments and Responses

We published a Notice of Proposed IHAs in the

Federal Register

on June 6, 2017 (82 FR 26244), beginning a 30-day comment period. In that notice, we requested public input on the requests for authorization described therein, our analyses, the proposed authorizations, and any other aspect of the Notice of Proposed IHAs for the five separate specified geophysical survey activities, and requested that interested persons submit relevant information, suggestions, and comments. We further specified that, in accordance with the requirements of the MMPA, we would only consider comments that were relevant to marine mammal species that occur in U.S. waters of the Mid- and South Atlantic and the potential effects of the specified geophysical survey activities on those species and their habitat. We also noted that comments

indicating general support for or opposition to hydrocarbon exploration or any comments relating to hydrocarbon development (

e.g.,

leasing, drilling) were not relevant to the proposed actions and would not be considered. We requested that comments indicate whether they were general to all of the proposed authorizations or specific to one or more of the five separate proposed authorizations, and that comments should be supported by data or literature citations as appropriate. Following requests to extend the public comment period, we determined it appropriate to do so by an additional 15 days (82 FR 31048; July 5, 2017). Including the 15-day extension, the public comment period concluded on July 21, 2017. Comments received after the close of the comment period were not considered.

During the 45-day comment period, we received 117,294 total comment letters. Of this total, we determined that approximately 3,196 comment letters represented unique submissions, including 73 letters from various organizations or individuals acting in an official capacity (

e.g.,

non-governmental organizations, representatives and members of the oil and gas industry, state and local government, members of Congress, members of academia) and 3,103 unique submissions from private citizens. We note that the 73 letters represent approximately 330 organizations or individuals, as many letters included multiple co-signers. The remaining approximately 114,118 comment letters followed one of 20 different generic template formats, in which respondents provided comments that were identical or substantively the same. We consider each of the 20 different templates to represent a single unique submission that is included in the value cited above (3,196). Separately, we received 15 petitions, with a total of 99,423 signatures. Of these, one petition (595 signatures) expressed support for issuance of the proposed IHAs, while the remainder expressed opposition to issuance of the proposed IHAs or, more generally, to oil and gas exploration and/or development in the U.S. Atlantic Ocean.

NMFS has reviewed all public comments received on the proposed issuance of the five IHAs. All relevant comments and our responses are described below. Comments indicating general support for or opposition to hydrocarbon exploration but not containing relevant recommendations or information are not addressed here. Similarly, any comments relating to hydrocarbon development (

e.g.,

leasing, drilling)—including numerous comments received that expressed concern regarding the risks of oil spills or of potential future industrialization on the U.S. Atlantic coast—are not relevant to the proposed actions and therefore were not considered and are not addressed here. We also provide no response to specific comments that addressed species or statutes not relevant to our proposed actions under section 101(a)(5)(D) of the MMPA (

e.g.,

comments related to sea turtles), nor do we respond to comments more appropriately directed at BOEM pursuant to their authority under the Outer Continental Shelf Lands Act (OCSLA) to permit the planned activities. For those comments germane to the proposed IHAs, we outline our comment responses by major categories. Recurring comments are noted below as having been submitted by “several” or “many” commenters to avoid repetition. The 73 letters from various organizations or individuals acting in an official capacity, and representatives of each of the 20 form letter templates, are available online at:

www.fisheries.noaa.gov/action/incidental-take-authorization-oil-and-gas-industry-geophysical-survey-activity-atlantic.

Remaining comments are part of our administrative record for these actions but are not available online.

General Comments

A large majority of commenters, including all of those following one of the 20 templates, expressed general opposition towards geophysical airgun surveys in the U.S. Atlantic Ocean. We reiterate here that NMFS's proposed actions concern only the authorization of marine mammal take incidental to the planned surveys—jurisdiction concerning decisions to allow the surveys rests solely with BOEM, pursuant to their authority under the OCSLA. Further, NMFS does not have discretion regarding issuance of requested incidental take authorizations pursuant to the MMPA, assuming (1) the total taking associated with a specified activity will have a negligible impact on the affected species or stock(s); (2) the total taking associated with a specified activity will not have an unmitigable adverse impact on the availability of the species or stock(s) for subsistence uses (not relevant here); (3) the total taking associated with a specified activity is small numbers of marine mammals of any species or stock; and (4) appropriate mitigation, monitoring, and reporting of such takings are set forth, including mitigation measures sufficient to meet the standard of least practicable adverse impact on the affected species or stocks. A large volume of the comments received request that NMFS not issue any of the IHAs and/or express disdain for NMFS's proposal to issue the requested IHAs, but without providing information relevant to NMFS's decisions. These comments appear to indicate a lack of understanding of the MMPA's requirement that NMFS shall issue requested authorizations when the above listed conditions are met; therefore, these comments were not considered.

In general, commenters described the close linkages between their local and state economies to a healthy ocean, contending that the planned surveys could have substantial impacts on, for example, commercial and recreational fishing, wildlife viewing, outdoor recreation, and businesses dependent on these activities. Commenters suggested that NMFS should undertake analyses unrelated to the proposed actions (

i.e.,

issuance of requested IHAs), such as a cost-benefit analysis of hydrocarbon exploration and development compared to the economic benefits of coastal tourism and healthy fisheries. Many commenters also noted that over 120 municipalities and cities and 1,200 elected officials on the Atlantic coast have passed resolutions or otherwise formally opposed hydrocarbon exploration and/or development in the region. We also received comments expressing general opposition to oil and gas exploration activity from the Business Alliance for Protecting the Atlantic Coast, which stated that the comments were submitted on behalf of 41,000 businesses and 500,000 commercial fishing families. While NMFS recognizes the overwhelming opposition expressed by the public to oil and gas exploration and/or development in the U.S. Atlantic Ocean that it has received, we remain appropriately focused on consideration of the best available scientific information in support of our analyses pursuant to the MMPA, specific to the five IHAs considered herein.

Multiple commenters focused on specific, rather than general, issues that are not germane to our consideration of requested action under the MMPA. For example, the Northwest Atlantic Marine Alliance (NAMA) and other groups provided comments related to potential impacts on commercial fisheries, and the New Jersey Council of Diving Clubs expressed concern regarding potential impacts of the planned surveys on recreational divers. Recommendations were provided concerning mitigating potential impacts. We reiterate that NMFS's proposed action—the issuance

of IHAs authorizing incidental take of marine mammals—necessarily results in impacts only to marine mammals and marine mammal habitat. Effects of the surveys more broadly are the purview of BOEM, which has jurisdiction under OCSLA for permitting the actual surveys, as opposed to authorizing take of marine mammals incidental to a permitted survey. Therefore, we do not address comments such as these.

Multiple groups stated that NMFS should consider impacts and protection for other species in the action area, such as Atlantic sturgeon, other fish species, invertebrates, plankton, and sea turtles. Some of these comments specifically referenced the importance of the area offshore Cape Hatteras as home to a diverse assemblage of non-marine mammal species, including sharks, turtles, seabirds, and other fish species. The NAMA provided comments relating to Essential Fish Habitat (EFH) (as designated pursuant to the Magnuson Stevens Fishery Conservation and Management Act (MSA), as amended by the Sustainable Fisheries Act of 1996 (Pub. L. 104-267)), including concerns regarding effects to EFH resulting from the planned surveys. Because NMFS's proposed action is limited to the authorization of marine mammal take incidental to the planned surveys, effects of the surveys on aspects of the marine environment other than marine mammals and their habitat are not relevant to NMFS's analyses under the MMPA. Pursuant to guidance from NMFS's Office of Habitat Conservation concerning EFH and MMPA incidental take authorizations, we have determined that the issuance of these IHAs will not result in adverse impacts to EFH, and further, that issuance of these IHAs does not require separate consultation per section 305(B)(2) of the MSA. We do not further address potential impacts to EFH.

The MMPA does require that we evaluate potential effects to marine mammal habitat, which includes prey species (

e.g.,

zooplankton, fish, squid). However, consideration of potential effects to taxa other than marine mammals and their prey, or consideration of effects to potential prey species in a context other than the import of such effects on marine mammals, is not relevant to our action under the MMPA. We have appropriately considered effects to marine mammal habitat. Separately, BOEM evaluated effects to all relevant aspects of the human environment (including marine mammals and other taxa) through the analysis presented in their PEIS (available online at:

www.boem.gov/Atlantic-G-G-PEIS/

), and effects to all potentially affected species that are listed under the Endangered Species Act (ESA) and any critical habitat designated for those species were addressed through consultation between BOEM and NMFS pursuant to section 7 of the ESA. That Biological Opinion, which evaluated both BOEM's (issuing permits for the five surveys) and NMFS's (issuing IHAs associated with the five permitted surveys) proposed actions, is available online at:

www.fisheries.noaa.gov/action/incidental-take-authorization-oil-and-gas-industry-geophysical-survey-activity-atlantic.

We do not further address taxa other than marine mammals and marine mammal prey.

Marine Mammal Impacts

Comment:

Many commenters expressed concern regarding the perceived lack of information regarding the affected marine mammal stocks and the impacts of the surveys on marine mammal individuals and populations and their habitat (direct and indirect; short- and long-term).

Response:

NMFS acknowledges that, while there is a growing body of literature on the affected marine mammal stocks and regarding the impacts of noise on individual marine mammals, data gaps do remain, particularly with regard to potential population-level impacts and cumulative impacts. However, NMFS must use the best available scientific information in analyses supporting its determinations pursuant to the MMPA, and has done so here. While NMFS does not take lightly the potential effects of surveys on marine mammal populations, these surveys, with the robust suite of required mitigation and monitoring, are expected to have a negligible impact on the affected species and stocks.

Comment:

Many commenters expressed general concern regarding impacts to both individual marine mammals and potential population-level harm, including impacts to important behaviors and chronic stress stemming from acoustic disturbance. More specifically, this included: Potential displacement from preferred feeding, breeding, and migratory habitats, which could lead to long-term and large-scale habitat avoidance or abandonment; impacts to mating, vocalizing, and other key marine mammal behaviors; communication interference between cow-calf pairs, which could lead to stranding increases and juvenile deaths; hearing loss hindering recruitment and marine mammals' ability to locate mates and find food.

Response:

NMFS has carefully reviewed the best available scientific information in assessing impacts to marine mammals, and recognizes that the surveys have the potential to impact marine mammals through threshold shifts, behavioral effects, stress responses, and auditory masking. However, NMFS has determined that the nature of such potentially transitory exposure—any given location will be exposed to survey noise only relatively briefly and infrequently—means that the potential significance of the authorized taking, including potential long-term avoidance, is limited. NMFS has also prescribed a robust suite of mitigation measures, such as time-area restrictions and extended distance shutdowns for certain species, that are expected to further reduce the duration and intensity of acoustic exposure, while limiting the potential severity of any possible behavioral disruption.

Comment:

Many commenters described impacts to “millions of marine mammals,” expressing concern that NMFS would allow such a level of impacts, or stating concern that NMFS would allow killing of marine mammals. Similarly, many commenters refer to taking or killing “138,000 marine mammals.”

Response:

Many of these comments were written with reference to the acoustic exposure analysis provided in BOEM's PEIS, which is not directly related to the specific surveys that are the subject of NMFS's analysis. In fact, the more specific figure commonly cited (

i.e.,

138,000) represents the number of incidents of Level A harassment estimated by BOEM in their analysis using now-outdated guidance (

i.e.,

180-dB root mean square (rms) with no consideration of frequency sensitivity) that the best available science indicates does not reflect when Level A harassment should be expected to occur. Certain non-governmental organizations have incorrectly suggested the information represents animals killed. In addition, BOEM's programmatic analysis was based on a vastly greater amount of survey activity occurring per year over a period of nine years, versus the five surveys considered herein. Regardless, NMFS cannot issue the authorizations unless the total taking expected to occur as a result of each specified activity is determined to result in a negligible impact to the affected species or stocks. The best available science indicates that Level B harassment, or disruption of behavioral patterns, is likely to occur, and that a limited amount of auditory injury, or permanent threshold shift (PTS) (Level A harassment) may occur for a few

species. No mortality is expected to occur as a result of the planned surveys, and there is no scientific evidence indicating that any marine mammal could experience mortality as a direct result of noise from geophysical survey activity. Authorization of mortality may not occur via IHAs, and such authorization was neither requested nor proposed. Finally, we emphasize that an estimate of take numbers alone is not sufficient to assess impacts to a marine mammal population. Take numbers must be viewed contextually with other factors, as explained in the “Negligible Impact Analyses and Determinations” section of this Notice.

Comment:

Several commenters referenced studies showing that noise from airgun surveys can travel great distances underwater, leading to concern that the surveys would impact marine mammals throughout the specific geographic region at all times. Some commenters then suggested that this would result in there being no available habitat for displaced animals to escape to.

Response:

NMFS acknowledges that relatively loud, low-frequency noise (as is produced by airgun arrays) has the potential to propagate across large distances. However, propagation and received sound levels are highly variable based on many biological and environmental factors. For example, while one commonly cited study (Nieukirk

et al.,

2012) described detection of airgun sounds almost 4,000 km from the acoustic source, the sensors were located within the deep sound channel (SOFAR), where low-frequency signals may travel great distances due to the advantageous propagation environment. While sounds within this channel are unlikely to be heard by most marine mammals due to the depth of the SOFAR channel—which is dependent primarily on temperature and water pressure and therefore variable with latitude—it is arguable whether sounds that travel such distances may be heard by whales as a result of refraction to shallower depths (Nieukirk

et al.,

2012; McDonald

et al.,

1995). Regardless, while the extreme propagation distances cited in some comments may not be realistic in terms of effects on mysticetes, we acknowledge that contraction of effective communication space for whales that vocalize and hear at frequencies overlapping those emitted by airgun arrays can occur at distances on the order of tens to hundreds of kilometers. However, attenuation to levels below the behavioral harassment criterion (

i.e.,

160 dB rms) will likely always occur over much shorter distances and, therefore, we do not agree with the contention that essentially the entire specific geographic region would be ensonified to a degree that marine mammals would find it unsuitable habitat. Rather, it is likely that displacement would occur within a much smaller region in the vicinity of the acoustic source (

e.g.,

within 5-10 km of the source, depending on season and location). Overall, the specific geographic region and marine mammal use of the area is sufficiently large that, although displacement may occur, the region offers enough habitat for marine mammals to seek temporary viable habitat elsewhere, if necessary. Many of the affected species occupy a wide portion of the region, and it is expected that individuals of these species can reasonably find temporary foraging grounds or other suitable habitat areas consistent with their natural use of the region. Further, although the planned surveys would cover large portions of the U.S. Mid- and South Atlantic, they will only be transitory in any given area. Therefore, NMFS does not expect displacement to occur frequently or for long durations. Importantly, for species that show high site fidelity to a particular area (

e.g.,

pilot whales around Cape Hatteras) or to bathymetric features (

e.g.,

sperm whales and beaked whales), NMFS has required additional time-area restrictions to reasonably minimize these impacts.

Comment:

The Bald Head Island Association commented that many bottlenose dolphin populations are depleted, and risks from the surveys are too great.

Response:

NMFS acknowledges that coastal bottlenose dolphin stocks are depleted under the MMPA, and we described the 2013-2015 Unusual Mortality Event affecting these stocks in our Notice of Proposed IHAs. NMFS is requiring a year-round closure to all survey activity out to 30 km offshore, including a 20-km distance beyond which encountered dolphins would generally be expected to be of the offshore stock and a 10-km buffer distance that is expected to encompass all received sound levels exceeding the 160-dB rms Level B harassment criterion. In consideration of this mitigation requirement, NMFS believes that impacts to coastal bottlenose dolphins will be minimal.

Comment:

The New York State Department of Environmental Conservation expressed concern about impacts from the surveys to animals in the New York Bight, noting that even though the surveys would not be occurring in the vicinity of New York Bight many of the same animals that use the New York Bight for certain life history strategies would also be found in certain times of year in the specific geographic region.

Response:

Although unrelated to our analyses and necessary findings pursuant to the MMPA, we note that in requesting the opportunity to conduct review of the proposed surveys pursuant to the Coastal Zone Management Act, New York did not demonstrate that the surveys would have reasonably foreseeable effects on New York's coastal uses or resources. Therefore, New York's request was denied. However, we acknowledge that some of the same animals that may occur in the New York Bight could also occur at other times of year within the survey region and, therefore, be affected by the specified activities. However, as detailed elsewhere in this document, we have found for each specified activity and each potentially affected species or stock that the taking would have a negligible impact.

Comment:

The Natural Resources Defense Council (NRDC) submitted comments on behalf of itself and over thirty other organizations, including the Center for Biological Diversity, Defenders of Wildlife, Earthjustice, The Humane Society of the United States, Sierra Club,

et al.

Hereafter, we refer to this collective letter as “NRDC.” NRDC and other commenters assert that the surveys will drive marine mammals into shipping lanes, thereby increasing their risk of ship strike.

Response:

As an initial matter, we address overall themes in NRDC's 85-page comment letter. In addition to mischaracterizing the literature, likely impacts to marine mammals, and NMFS's analyses in multiple places—which we attempt to correct throughout our responses—the letter repeatedly makes use of undefended or off-point assertions (

e.g.,

that NMFS's findings are “arbitrary and capricious” and “non-conservative”). While we have attempted to clarify and correct individual mischaracterizations in our specific responses to comments, we broadly address the issue here. NRDC's 16 assertions that NMFS's analyses and/or conclusions are “arbitrary and capricious” or just “arbitrary” are unfounded. Similarly, NRDC claims that NMFS's approaches or decisions are “non-conservative,” or should be more “conservative,” at least 15 times, with no indication of what standard they are seeking to attain. While NRDC may disagree with the issuance of the IHAs or the underlying activities themselves, we believe the administrative record for these IHAs amply demonstrates that NMFS used the best available science

during our administrative process to inform our analyses and satisfy the standards under section 101(a)(5)(D).

With regard to this specific comment, the surveys are largely not occurring in or near any shipping lanes, as they will occur a minimum of 30 km offshore. NMFS is not aware of any scientific information suggesting that the surveys would drive marine mammals into shipping lanes, and disagrees that this would be a reasonably anticipated effect of the specified activities.

Comment:

Comments submitted jointly by Oceana and the International Fund for Animal Welfare (hereafter, “Oceana”) and, separately, by Sea Shepherd Legal discuss particular concerns regarding potential impacts to large whales. The comments cite studies showing modified singing behavior and habitat avoidance among fin whales in response to airguns; that sperm whales in the Gulf of Mexico have shown decreased buzz rates around airguns; that singing among humpback whales declined in response to airgun noise; etc.

Response:

NMFS reviewed all cited studies in making its determinations for both the proposed and final IHAs, and agrees that there are multiple studies documenting changes in behavior and/or communication amongst large whales in response to airgun noise, sometimes at significant distance. Changes in vocalization associated with exposure to airgun surveys within migratory and non-migratory contexts have been observed (

e.g.,

Castellote

et al.,

2012; Blackwell

et al.,

2013; Cerchio

et al.,

2014). The potential for anthropogenic sound to have impacts over large spatial scales is not surprising for species with large communication spaces, like mysticetes (

e.g.,

Clark

et al.,

2009); however, not every change in a vocalization would necessarily rise to the level of a take, much less have meaningful consequences to the individual or for the affected population. As noted previously, the planned surveys are expected to be transient and would not result in any sustained impacts to such behaviors for baleen whales. We also acknowledge that exposure to noise from airguns may impact sperm whale foraging behavior (Miller

et al.,

2009). However, our required mitigation—including time-area restrictions designed to protect certain habitat expected to be of importance for foraging sperm whales, in addition to standard shutdown requirements expected to minimize the severity and duration of any disturbance—when considered in context of the transient nature of the impacts possible for these surveys lead us to conclude that effects to large whales will be no greater than a negligible impact and will be mitigated to the level of least practicable adverse impact.

Comment:

Several industry commenters stated, in summary, that there is no scientific evidence that geophysical survey activities have caused adverse consequences to marine mammal stocks or populations, and that there are no known instances of injury to individual marine mammals as a result of such surveys, stating that similar surveys have been occurring for years without significant impacts. One stated that surveys have been ongoing in the Gulf of Mexico for years and have not resulted in any negative impacts to marine mammals, including reducing fitness in individuals or populations. Referring to other regions, the commenters stated that bowhead whale numbers have increased in the Arctic despite survey activity. CGG noted that there is no “empirical evidence” of surveys causing injury or mortality to marine mammals, and that previous surveys resulted in less take than authorized. Another group added that BOEM has spent $50 million on protected species and noise research over four decades with no evidence of adverse effects.

Response:

Disruption of behavioral patterns (

i.e.,

Level B harassment) has been documented numerous times for marine mammals in the presence of airguns (in the form of avoidance of areas, notable changes in vocalization or movement patterns, or other shifts in important behaviors; see “Potential Effects of the Specified Activity on Marine Mammals and Their Habitat”). Further, lack of evidence for a proposition does not prove it is false. In this case, there is growing scientific evidence demonstrating the connections between sub-lethal effects, such as behavioral disturbance, and population-level effects on marine mammals (

e.g.,

Lusseau and Bedjer, 2007; New

et al.,

2014). Disruptions of important behaviors, in certain contexts and scales, have been shown to have energetic effects that can translate to reduced survivorship or reproductive rates of individuals (

e.g.,

feeding is interrupted, so growth, survivorship, or ability to bring young to term is compromised), which in turn can adversely affect populations depending on their health, abundance, and growth trends.

Based on the available evidence, a responsible analysis of potential impacts of airgun noise on marine mammal individuals and populations cannot assume that such effects cannot occur. In reality, conclusive statements regarding population-level consequences of acoustic stressors cannot be made due to insufficient investigation, as such studies are exceedingly difficult to carry out and no appropriate study and reference populations have yet been established. For example, a recent report from the National Academy of Sciences noted that, while a commonly-cited statement from the National Research Council (“[n]o scientific studies have conclusively demonstrated a link between exposure to sound and adverse effects on a marine mammal population”) remains true, it is largely because such impacts are very difficult to demonstrate (NRC, 2005; NAS, 2017). Population‐level effects are inherently difficult to assess because of high variability, migrations, and multiple factors affecting the populations. However, NMFS has carefully considered the available evidence in determining the most appropriate suite of mitigation measures and in making the necessary determinations (see “Negligible Impact Analyses and Determinations”).

Comment:

NRDC states that NMFS must consider that behavioral disturbance can amount to Level A harassment, or to serious injury or mortality, if it interferes with essential life functions through secondary effects, stating that displacement from migration paths can result in heightened risk of ship strike or predation, especially for right whales. In a similar vein, Oceana expressed concern about the presence of additional ships in the Atlantic, risking serious injury to marine mammals from ship strike or entanglement. Relatedly, NRDC noted that NMFS's conclusion that ship strikes will not occur indicates an assumption that required ship-strike avoidance procedures will be effective. NRDC disagrees that the ship-strike avoidance measures will be effective.

Response:

NMFS acknowledges that sufficient disruption of behavioral patterns could theoretically, likely in connection with other stressors, result in a reduction in fitness and ultimately injury or mortality. However, such an outcome could likely result only from repeated disruption of important behaviors at critical junctures, or sustained displacement from important habitat with no associated compensatory ability. No such outcome is expected as a result of these surveys, which will be transient in any given area within the large overall region, and which avoid some of the most important habitat. Effects such as those suggested by NRDC would not be expected for

right whales, as the surveys are required to avoid migratory pathways (80 km from coast), or achieve comparable protection provided through implementation of a NMFS-approved mitigation and monitoring plan at distances between 47-80 km offshore (see “Mitigation” for more information).

Although the primary stressor to marine mammals from the specified activities is acoustic exposure to the sound source, NMFS takes seriously the risk of vessel strike and has prescribed measures sufficient to avoid the potential for ship strike to the extent practicable. NMFS has required these measures despite a very low likelihood of vessel strike; vessels associated with the surveys will add a discountable amount of vessel traffic to the specific geographic region (

i.e.,

each survey will operate with roughly 2-3 vessels) and, furthermore, vessels towing survey gear travel at very slow speeds (

i.e.,

roughly 4-5 kn).

NMFS's required vessel strike avoidance protocol is expected to further minimize any potential interactions between marine mammals and survey vessels. Please see “Vessel Strike Avoidance” for a full description of requirements, which include: Vessels must maintain a 10 kn speed restriction when in North Atlantic right whale critical habitat, Seasonal Management Areas, or Dynamic Management Areas; vessel operators and crews must maintain a vigilant watch for all marine mammals and must take necessary actions to avoid striking a marine mammal; vessels must reduce speeds to 10 kn or less when mother/calf pairs, pods, or large assemblages of cetaceans are observed near a vessel; and vessels must maintain minimum separation distances.

Comment:

NRDC stated that NMFS did not properly consider potential impacts of masking to marine mammals. For example, NRDC notes that NMFS addresses masking in the general consequences discussion of its negligible impact analysis, but disagrees with NMFS's conclusion that consequences are appropriately categorized as “medium” rather than “high” for mysticetes, citing the distances at which vocal modifications to distant sounds have been detected in low-frequency cetaceans and newly-described low-level communication calls between humpback whales and their calves, which they suggest have dire implications for right whales. NRDC also states that NMFS incorrectly thinks masking is co-extensive with the modeled 160-dB rms behavioral harassment zones, and suggests that NMFS should take a modeling approach to better assess potential masking. Relatedly, another commenter stated a belief that NMFS assumes that there is no potential for masking during the interpulse interval, when in fact there is noise during that period due to multipath arrivals.

Response:

NMFS disagrees that the potential impacts of masking were not properly considered. NMFS acknowledges our understanding of the literature NRDC cites regarding the greater sensitivity of low-frequency cetaceans to airgun survey noise via the designation of these effects as “medium,” but fundamentally, the masking effects to any one individual whale from one survey operating far offshore are expected to be minimal. Masking is referred to as a chronic effect because one of the key harmful components of masking is its duration—the fact that an animal would have reduced ability to hear or interpret critical cues becomes much more likely to cause a problem the longer it is occurring. Also, inherent in the concept of masking is the fact that the potential for the effect is only present during the times that the animal and the source are in close enough proximity for the effect to occur (and further this time period would need to coincide with a time that the animal was utilizing sounds at the masked frequency) and, as our analysis (both quantitative and qualitative components) indicates, because of the relative movement of whales and vessels, we do not expect these exposures with the potential for masking to be of a long duration within a given day. Further, because of the relatively low density of mysticetes, the time-area restrictions, and large area over which the vessels travel, we do not expect any individual whales to be exposed to potentially masking levels from these surveys more than a few days in a year.

NMFS recognizes that masking may occur beyond the 160-dB zone and, further, that the primary concern is when numerous sources, many of which may be at distances beyond their 160-dB isopleth, contribute to higher background noise levels over extended time periods and significant portions of an individual's acoustic habitat. However, as noted above, any masking effects of these single surveys operating far offshore (with no expectation that any of the five would be in close enough proximity to one another to contemporaneously expose animals to noise from multiple source vessels) are expected to be limited and brief, if present. Further, we recognize the presence of multipath arrivals, especially the farther the receiver is from the ship, but given the reduced received levels at distance, combined with the short duration of potential masking and the lower likelihood of extensive additional contributors to background noise this far offshore and within these short exposure periods, we believe that the incremental addition of the seismic vessel is unlikely to result in more than minor and short-term masking effects, likely occurring to some small number of the same individuals captured in the estimate of behavioral harassment.

In regard to some of the specific examples NRDC raised, we acknowledge that vocal modifications of low-frequency cetaceans in response to distant sound sources have been detected. However, as discussed elsewhere in this Notice, not every behavioral change or minor vocal modification rises to the level of a take or has any potential to adversely impact marine mammal fitness, and NRDC has not demonstrated why it believes the short duration exposures that low-frequency cetaceans might be exposed to a few times a year from a survey should constitute a “high” versus “medium” consequence in NMFS's assessment framework.

Similarly, NMFS is also aware of the Videsen

et al.

(2017) paper reporting the lower-level communication calls between humpback mother-calf pairs and noting the increased risk of cow-calf separation with increases in background noise. We first note that only neonates were tagged and measured in this study (

i.e.,

circumstances could change with older calves). Further, while vocalizations between these pairs are comparatively lower level than between adults, the cow and neonate calf are in regular close proximity (as evidenced by the extent of measured sound generated by rubbing in this study), which means that the received levels for cow-calf communication are higher than they would be if the animals were separated by the distance typical between adults—in other words, it is unclear whether these lower-level, but close proximity, communications are comparatively more susceptible to masking. Assuming that right whale cow-calf pairs use the same lower-level communication calls, we first note that across all five surveys, modeled results estimate that 19 right whales may intercept with the tracklines of the surveys such that they are potentially taken and, further, as described in the “Negligible Impact Analyses and Determinations” section and based on available demographic information, it should be expected that no more than four exposures could be of adult females with calves (not

specifically neonates). Again, when this very low likelihood of encountering cow-calf pairs is combined with the fact that any individuals (or cow-calf pairs) would not be expected to be exposed on more than a couple/few days in a year, NRDC has not demonstrated how the consequences of these activities would be “catastrophic,” for right whales, and we believe our analysis supports a “medium” consequence rating.

Last, in response to the suggestion that we utilize a model, such as the model NMFS used for assessing similar potential impacts in the Gulf of Mexico, to assess impacts to communication space from the surveys evaluated here—it is neither necessary nor an appropriate use of those tools. As noted above, the combination of the modeled take estimates, along with a qualitative evaluation of the temporal and spatial footprint of the activities within the large action area and dispersed marine mammal distributions, makes it clear that masking effects, if any, would be highly limited for these activities. In the Gulf of Mexico, NMFS used the referenced model in the context of a five-year rule to programmatically assess the chronic impacts of an entire seismic program in a mature and active hydrocarbon-producing region, with a significantly greater amount of effort than is contemplated in these five surveys, overlaid in an area with already otherwise high ambient noise. Use of the model is comparatively expensive and time-consuming, and produces a relatively gross-scale comparison of predicted annual averages (or other duration) of accumulated sound energy (which can also be interpreted in the context of the communication space of any species). This sort of analysis can be helpful in understanding relative chronic effects when higher and longer-term overall levels of activity and impacts are being evaluated across areas with notably variable levels of activities and/or ambient noise, and can potentially inform decisions regarding time-area mitigation. Here, however, any impacts to communication space from any individual survey are expected to be minimal; in addition to being unnecessary, the lack of granularity in the suggested model (which is appropriate at larger and denser scales of impacts, and which can be improved with improvement of the available input data) is such that its application to these activities would not produce useful information.

Comment:

The South Carolina Environmental Law Project, on behalf of the Business Alliance for Protecting the Atlantic Coast, commented that chronic stress is possible from the specified activities and that likely stress effects would be exacerbated due to their contention that avoidance is impossible.

Response:

As described in our Notice of Proposed IHAs, NMFS recognizes that stress from acoustic exposure is one potential impact of these surveys, and that chronic stress can have fitness, reproductive, etc. impacts at the population-level scale. However, we believe the possibility for chronic stress is low given the transitory and intermittent nature of the sound source (

i.e.,

acoustic exposure in specific areas will not be long lasting). The potential for chronic stress was evaluated in making the determinations presented in NMFS's negligible impact analyses.

Comment:

An individual stated that NMFS did not account for long-term impacts to species, writing that it is impossible to accurately account for impacts without looking at the effects of sound disturbance on energy balance (

e.g.,

when disturbance results in additional time spent traveling and/or foraging in less optimal habitats, the result may be a negative energy balance). The commenter stated further that this negative energy balance could have effects both individually and cumulatively for a population, and that the cumulative effect of behavioral disturbance could be equivalent to a certain amount of lethal takes.

Response:

NMFS acknowledges that the concerns raised are theoretically possible, but in this case, with limited duration of individual surveys or of overlap of multiple surveys, and modeled take estimates suggesting that individuals would rarely be impacted by any given survey more than a few days in a year, frequent and long-term displacement is not expected. Therefore, NMFS does not anticipate behavioral disruptions sufficient to negatively impact individual energy balances, much less to a degree where long-term effects resulting in impacts to recruitment or survival would occur. For example, while the available evidence indicates sensitivity to disruption of foraging efficiency for sperm whales exposed to airgun noise (Miller

et al.,

2009), a recent bioenergetic modeling exercise showed that infrequent, minor disruptions in foraging—as are expected in this case—are unlikely to be fatal (Farmer

et al.,

2018). The authors conclude that foraging disruptions would have to be relatively frequent to lead to terminal starvation, but continual minor disruptions can cause substantial reductions in available reserves. Given the temporary, infrequent nature of exposure likely to result from the planned surveys, in conjunction with the planned mitigation, which includes effort restrictions in areas expected to be of importance for sperm whale foraging, it is unlikely that either continual minor disruptions or less frequent, but more severe disruptions would occur.

Comment:

One individual cited Schnitzler

et al.

(2017) in stating that the varied anatomy of individual sperm whale ears indicates that “tolerable” sound levels may not be the same for different animals.

Response:

NMFS acknowledges that actual individual responses to noise exposure will vary based on a variety of factors, including individual anatomy but more likely because of individual context and experience. However, sufficient scientific information does not exist to assess differential impacts to specific individuals. Therefore, NMFS uses generic acoustic thresholds in order to predict potential responses to noise exposure. However, NMFS has required a sufficiently robust suite of mitigation measures to provide reasonable certainty of general reduction of takes and of intensity and/or duration of acoustic exposures for individual sperm whales.

Comment:

The Bald Head Island Association noted that many marine mammals have washed up on their beaches in recent years, including a beaked whale and juvenile dolphin after offshore airgun surveys. Sea Shepherd Legal claimed that NMFS did not adequately address the potential for stranding events, noting several studies that they claim link strandings with airgun surveys. They also noted that NMFS did not acknowledge a January 2017 mass stranding of false killer whales when considering impacts to species.

Response:

Marine mammals are known to strand for a variety of reasons, such as infectious agents, biotoxicosis, starvation, fishery interaction, ship strike, unusual oceanographic or weather events, sound exposure, or combinations of these stressors sustained concurrently or in series (

e.g.,

Geraci

et al.,

1999). However, the cause or causes of most strandings are unknown (

e.g.,

Best, 1982). Stranding events are known to occasionally happen as a result of sound exposure,

e.g.,

Southall

et al.,

2006, 2013; Jepson

et al.,

2013; Wright

et al.,

2013, with stranding thought to occur subsequent to the exposure, as a result of non-auditory physiological effects or injuries, which theoretically might occur as a secondary effect of extreme behavioral reactions (

e.g.,

change in dive profile as a result of an avoidance reaction). However, such events are typically associated with use of military

tactical sonar, which has very different characteristics than airgun noise.

NMFS is unaware of any information linking possible strandings on Bald Head Island, or in any other location on the East Coast, with offshore airgun survey activity, and does not expect the planned surveys to have any potential to result in stranding events or the type of injuries or effects that could lead to stranding events, given the required mitigation and operational protocols. In support of its position, Sea Shepherd Legal cites two review articles (Gordon

et al.,

2003; Compton

et al.,

2008) that make general statements regarding the potential effects of airgun noise and/or review best practices in mitigation—NMFS reviewed these papers and discussed them in our Notice of Proposed IHAs. Sea Shepherd also cites a third document (Engel

et al.,

2004) questioning whether such surveys may be responsible for coincident strandings of humpback whales in Brazil in 2002, and notes NMFS's discussion of a 2002 beaked whale stranding event that was contemporaneous with and reasonably associated spatially with an airgun survey in the Gulf of California. However, unlike for strandings associated with use of military sonar, no conclusive causal link was made, and these observations remain based on spatial and/or temporal coincidence. NMFS here acknowledges the 2017 stranding of false killer whales in Florida referenced by Sea Shepherd Legal, for which no cause was found.

However, as a precaution NMFS has modified its reporting requirements to include protocols relating to minimization of additional harm to live-stranded (or milling) marine mammals. Addition of these protocols does not imply any change to our determination that stranding events are unlikely, nor does it imply that a stranding event that does occur is necessarily the result of the specified activities. However, we recognize that regardless of the cause of a stranding event, it is appropriate to take action in certain circumstances to avoid additional harm. Please see “Monitoring and Reporting” for more information.

Marine Mammal Impacts—Habitat

Comment:

Many commenters expressed concern regarding potential impacts to marine mammal prey and/or food webs from the planned surveys. NRDC specifically provided numerous citations in claiming that the surveys could impact marine mammal prey through the following: (1) Cause severe physical injury and mortality; (2) damage hearing and sensory abilities of fish and marine invertebrates; (3) impede development of early life history stages; (4) induce stress that physically damages marine invertebrates and compromises fish health; (5) cause startle and alarm responses that interrupt vital behaviors; (6) alter predator avoidance behavior that may reduce probability of survival; (7) affect catchability of prey species; (8) mask important biological sounds essential to survival; (9) reduce reproductive success, potentially jeopardizing long-term sustainability of fish populations; (10) interrupt feeding behaviors and induce other species-specific effects that may increase risk of starvation, reduce reproduction, and alter community structure; and (11) compromise orientation of fish larvae with potential ecosystem-level effects. Additionally, many commenters cited a recent publication by McCauley

et al.

(2017) as evidence that the surveys could potentially impact zooplankton and consequently marine mammal food webs.

In contrast, the International Association of Geophysical Contractors, American Petroleum Institute, and National Ocean Industries Association (hereafter, “the Associations”) stated that McCauley

et al.

(2017) “purports to demonstrate, but fails to prove, that seismic survey air sources negatively impact zooplankton.” The Associations cite small sample size, variability in the baseline and experimental data, and the “large number of speculative conclusions that appear to be inconsistent with the data collected over a two-day period” in stating that the research “creates no reasonable implication regarding the potential effects of seismic surveys on marine mammals.”

Response:

NMFS strongly disagrees with NRDC's contention that we ignored effects to prey species; in fact, we considered relevant literature (including that cited by NRDC) in finding that the most likely impact of survey activity to prey species such as fish and invertebrates would be temporary avoidance of an area, with a rapid return to recruitment, distribution, and behavior anticipated. While there is a lack of specific scientific information to allow an assessment of the duration, intensity, or distribution of effects to prey in specific locations at specific times and in response to specific surveys, NMFS's review of the available information does not indicate that such effects could be significant enough to impact marine mammal prey to the extent that marine mammal fitness would be affected. A more detailed discussion is provided in “Potential Effects of the Specified Activities on Marine Mammals and Their Habitat.”

In summary, fish react to sounds which are especially strong and/or intermittent low-frequency sounds, and behavioral responses such as flight or avoidance are the most likely effects. However, the reaction of fish to airguns depends on the physiological state of the fish, past exposures, motivation (

e.g.,

feeding, spawning, migration), and other environmental factors. While we agree that some studies have demonstrated that airgun sounds might affect the distribution and behavior of some fishes, potentially impacting foraging opportunities or increasing energetic costs (

e.g.,

Fewtrell and McCauley, 2012; Pearson

et al.,

1992; Skalski

et al.,

1992; Santulli

et al.,

1999; Paxton

et al.,

2017), other studies have shown no or slight reaction to airgun sounds (

e.g.,

Pena

et al.,

2013; Wardle

et al.,

2001; Jorgenson and Gyselman, 2009; Cott

et al.,

2012). Most commonly, though, the impacts of noise on fish are temporary. Investigators reported significant, short-term declines in commercial fishing catch rate of gadid fishes during and for up to five days after survey operations, but the catch rate subsequently returned to normal (Engas

et al.,

1996; Engas and Lokkeborg, 2002); other studies have reported similar findings (Hassel

et al.,

2004).

As discussed by NRDC, however, even temporary effects to fish distribution patterns can impact their ability to carry out important life-history functions. SPLs of sufficient strength have been known to cause injury to fish and fish mortality and, in some studies, fish auditory systems have been damaged by airgun noise (McCauley

et al.,

2003; Popper

et al.,

2005; Song

et al.,

2008). However, in most fish species, hair cells in the ear continuously regenerate and loss of auditory function likely is restored when damaged cells are replaced with new cells. Halvorsen

et al.

(2012b) showed that a TTS of 4-6 dB was recoverable within 24 hours for one species. Impacts would be most severe when the individual fish is close to the source and when the duration of exposure is long—both of which are conditions unlikely to occur during these surveys, which will be transient in any given location and likely result in brief, infrequent noise exposure to prey species in any given area. For these surveys, the sound source is constantly moving, and most fish would likely avoid the sound source prior to receiving sound of sufficient intensity to cause physiological or anatomical damage. In addition, ramp-up may

allow certain fish species the opportunity to move further away from the sound source.

Available data suggest that cephalopods are capable of sensing the particle motion of sounds and detect low frequencies up to 1-1.5 kHz, depending on the species, and so are likely to detect airgun noise (Kaifu

et al.,

2008; Hu

et al.,

2009; Mooney

et al.,

2010; Samson

et al.,

2014). Auditory injuries (lesions occurring on the statocyst sensory hair cells) have been reported upon controlled exposure to low-frequency sounds, suggesting that cephalopods are particularly sensitive to low-frequency sound (Andre

et al.,

2011; Sole

et al.,

2013). Behavioral responses, such as inking and jetting, have also been reported upon exposure to low-frequency sound (McCauley

et al.,

2000b; Samson

et al.,

2014). Similar to fish, however, the transient nature of the surveys leads to an expectation that effects will be largely limited to behavioral reactions and would occur as a result of brief, infrequent exposures.

With regard to potential impacts on zooplankton, McCauley

et al.

(2017) found that exposure to airgun noise resulted in significant depletion for more than half the taxa present and that there were two to three times more dead zooplankton after airgun exposure compared with controls for all taxa, within 1 km of the airguns. However, the authors also stated that in order to have significant impacts on

r

-selected species such as plankton, the spatial or temporal scale of impact must be large in comparison with the ecosystem concerned, and it is possible that the findings reflect avoidance by zooplankton rather than mortality (McCauley

et al.,

2017). In addition, the results of this study are inconsistent with a large body of research that generally finds limited spatial and temporal impacts to zooplankton as a result of exposure to airgun noise (

e.g.,

Dalen and Knutsen, 1987; Payne, 2004; Stanley

et al.,

2011).

A modeling exercise was conducted as a follow-up to the McCauley

et al.

(2017) study (as recommended by McCauley

et al.

(2017)), in order to assess the potential for impacts on ocean ecosystem dynamics and zooplankton population dynamics (Richardson

et al.,

2017). Richardson

et al.

(2017) found that for copepods with a short life cycle in a high-energy environment, a full-scale airgun survey would impact copepod abundance up to three days following the end of the survey, suggesting that effects such as those found by McCauley

et al.

(2017) would not be expected to be detectable downstream of the survey areas, either spatially or temporally. However, these findings are relevant for zooplankton with rapid reproductive cycles in areas where there is a high natural replenishment rate resulting from new water masses moving in, and the findings may not apply in lower-energy environments or for zooplankton with longer life-cycles. In fact, the study found that by turning off the current, as may reflect lower-energy environments, the time to recovery for the modelled population extended from several days to several weeks.

However, while potential impacts to zooplankton are of obvious concern with regard to their follow-on effects for higher-order predators, the survey area is not an important area for feeding for taxa that feed directly on zooplankton,

i.e.,

mysticetes. In the absence of further validation of the McCauley

et al.

(2017) findings, if we assume a worst-case likelihood of severe impacts to zooplankton within approximately 1 km of the acoustic source, the large spatial scale and expected wide dispersal of survey vessels does not lead us to expect any meaningful follow-on effects to the prey base for odontocete predators. While the large scale of effect observed by McCauley

et al.

(2017) may be of concern, especially in a more temperate environment, NMFS concludes that these findings indicate a need for more study, particularly where repeated noise exposure is expected—a condition unlikely to occur in relation to these planned surveys. We do not offer further comment with regard to the specific criticisms of the Associations, other than to say that their dismissal of the study seems to reflect an unsubstantiated opinion.

Overall, prey species exposed to sound might move away from the sound source, experience TTS, experience masking of biologically relevant sounds, or show no obvious direct effects. Mortality from decompression injuries is possible in close proximity to a sound, but only limited data on mortality in response to airgun noise exposure are available (Hawkins

et al.,

2014). The most likely impacts for most prey species in a given area would be temporary avoidance of the area. The surveys are expected to move through an area relatively quickly, limiting exposure to multiple impulsive sounds. In all cases, sound levels would return to ambient once a survey ends and the noise source is shut down and, when exposure to sound ends, behavioral and/or physiological responses are expected to end relatively quickly (McCauley

et al.,

2000b). The duration of fish avoidance of a given area after survey effort stops is unknown, but a rapid return to normal recruitment, distribution, and behavior is anticipated. While the potential for disruption of spawning aggregations or schools of important prey species can be meaningful on a local scale, the mobile and temporary nature of the surveys and the likelihood of temporary avoidance behavior suggest that impacts would be minor.

Comment:

A group of scientists (C.W. Clark, S.D. Kraus, D.P. Nowacek, A.J. Read, M. Rekdahl, A.N. Rice, H. Rosenbaum, and R.S. Schick) submitted a collective comment letter. Hereafter, we refer to this letter as “Nowacek

et al.”

Nowacek

et al.

and NRDC stated that it is inappropriate to conclude that these surveys will not impact marine mammal acoustic habitat, since the production of airgun noise is known to increase ambient noise, thereby negatively impacting habitat. NRDC further states that NMFS has failed to adequately account for impacts to acoustic habitat. In support of their statements, Nowacek

et al.

submitted the results of a sound field modeling exercise in which they considered energy produced from seven shots of a 40-element array at 6 m depth (other important source details were not provided) across one-third-octave bands spanning the 71-224 Hz frequency range. Resulting sound fields were concatenated at 1-s resolution for two different water depths (50 and 200 m) (commenters submitted animations associated with this exercise; these are available upon request and are part of our administrative record for these actions). They wrote that these animations highlight the dynamic nature of the marine environment, especially the low-frequency sound field, and the large area over which sound levels are increased above ambient levels but below current regulatory harassment thresholds. The commenters then correctly note that consideration of likely takes is limited to just a portion of the area over which airgun noise extends into the marine environment. Nowacek

et al.

also recommended that NMFS produce a quantitative methodology for assessing the region's acoustic environment, the proportional contributions from each of the natural and anthropogenic noise inputs, and create mechanisms to mitigate these lower-level noise exposures.

Response:

The commenters' claims that NMFS concluded that there “would be no impact to the quality of the acoustic habitat” or suggested that “there is no basis for acoustic habitat impacts” are erroneous. NMFS made no such statements, but rather

acknowledged in our Notice of Proposed IHAs that it was likely that there would be impacts to acoustic habitat, particularly for low-frequency cetaceans. In fact, we explicitly considered this likelihood in our preliminary negligible impact analyses, finding that “consequence” of the surveys should be considered as higher for mysticete whales than for other species for this reason.

NMFS addressed potential effects to habitat, including acoustic habitat, and acknowledges that the surveys will increase noise levels in the vicinity of operating source vessels. However, following consideration of the available information, NMFS concludes that these impacts will not significantly affect ambient noise levels or acoustic communication space over long time periods, especially in the context of any given exposed individual. As described previously, exploratory surveys such as these cover a large area but would be transient rather than focused in a given location over time and therefore would not be considered as contributing meaningfully to chronic effects in any given location. Given these conclusions, a separate quantitative analysis of potential impacts to acoustic habitat, as is suggested by Nowacek

et al.,

is not warranted. In contrast, we did develop and perform such analysis for a different assessment of much more extensive geophysical survey activity (see Appendix K in BOEM, 2017) to be conducted over a period of ten years, versus the limited amount of survey activity to be conducted over a period of one year here.

We acknowledge and appreciate the commenters' scientific expertise, but there are relevant statutory and regulatory requirements that inform NMFS in the scope of analysis relevant to a finding of negligible impact. Please see also our response to a previous comment above, in which NRDC makes similar charges regarding the impacts of masking. Finally, regarding terminology used in the comments (

i.e.,

“primary constituent elements”), the discussion in this document pertains specifically to the MMPA and not components related to critical habitat designated under the ESA.

Comment:

The Sierra Club Marine Group noted that Cape Hatteras has a very unique morphology, and that these features support upwelling that supports significant biodiversity, including beaked whales. The commenters stated that impacts to this habitat provide a compelling reason to deny the IHAs.

Response:

As described in our Notice of Proposed IHAs, NMFS concurs that Cape Hatteras provides important habitat for a diverse assemblage of species, particularly for species such as sperm whales, beaked whales, pilot whales, and other species that show high site fidelity to the area. Accordingly, NMFS has designed a time-area restriction encompassing the area referenced in the comment that precludes survey effort within the area for a three-month period (January to March; Stanistreet

et al.,

2018); the restriction is defined specifically to benefit beaked whales, sperm whales, and pilot whales, with the specific timing intended as the most appropriate for sperm whales. We also require mitigation to reduce the intensity and duration of exposure for these species—particularly for acoustically sensitive species, such as beaked whales, for which shutdown is required at an extended distance of 1.5 km. Separately, NMFS has required year-round closures of similar high-relief habitats further offshore that are predicted to host relatively high densities of beaked whales. In addition, the North Atlantic right whale closure will protect portions of the area referenced by the commenters, as it extends out to 90 km from the coastline (

i.e.,

80 km plus a 10 km buffer, see “Mitigation”) and is in effect from November through April (or comparable protection provided through implementation of a NMFS-approved mitigation and monitoring plan at distances between 47-80 km offshore), whereas the seasonal restriction off of Cape Hatteras is in effect from January through March. NMFS believes these restrictions provide a high degree of protection to these species and the habitat they utilize around Cape Hatteras, while meeting the MMPA's least practicable adverse impact standard. When the contextual factor addressing required mitigation is considered, the outcome is a negligible impact to affected species.

Comment:

An individual states that the surveys have the potential to impair the Chesapeake Bay, and that such impairment would have wider ecological and economic repercussions beyond the scope of impacting marine mammals. Similarly, one group mentioned that impacts from the surveys could ripple into smaller bays and inlets elsewhere along the East Coast, and impact species long after surveys are complete.

Response:

NMFS's action is authorizing the taking of marine mammals pursuant to section 101(a)(5)(D); therefore, impacts of the survey on aspects of the environment other than marine mammals and their habitat are not relevant to NMFS's analysis conducted pursuant to the MMPA. However, the authorization of marine mammal take incidental to the planned surveys would not impact marine mammals of the Chesapeake Bay or of other coastal bays and estuaries. Surveys may not operate closer than 30 km to shore at any time.

North Atlantic Right Whale

Comment:

Many commenters expressed concern regarding the North Atlantic right whale and potential impacts of the specified activities, given their declining population size, an ongoing Unusual Mortality Event (UME), declining calf production, and annual exceedances of the calculated potential biological removal value (see “Description of Marine Mammals in the Area of the Specified Activities—North Atlantic Right Whale” for further discussion of these issues). Some commenters noted additional concern regarding potential survey overlap with biologically important areas. Others highlighted concerns regarding increased risk of ship strike and/or entanglement with survey vessels, in addition to the potential for acoustic and behavioral effects.

Response:

NMFS appreciates the concerns expressed by commenters regarding right whales. As an agency, NMFS is working to address the numerous issues facing right whales, including continued work to reduce deaths due to ship strike and entanglement in fishing gear and ongoing investigation of the UME, as well as other measures to investigate and address the status of the species. The best available scientific information shows that the majority of right whale sightings in the southeast occur in right whale calving areas from roughly November through April, with individual right whales migrating to and from these areas through mid-Atlantic shelf waters. Because of these concerns regarding right whales, NMFS is requiring closure of these areas (out to 90 km from shore) to survey activity from November 1 to April 30 (or that comparable protection is achieved through implementation of a NMFS-approved mitigation and monitoring plan at distances between 47-80 km offshore). This measure is expected to largely avoid disruption of behavioral patterns for right whales and to minimize overall acoustic exposures. Therefore, NMFS believes that this restriction provides for migratory passage to and from calving grounds as well as avoiding impacts to the whales while on the grounds. In addition, NMFS re-evaluated potential right whale takes using the best available

scientific information (

i.e.,

Roberts

et al.,

2017) and in consideration of the revised time-area restriction. The result of this analysis shows that takes of right whales will be minimal.

Comment:

NRDC and, separately, Nowacek

et al.

state that airgun surveys have been linked to significant reductions in the probability of calf survival in western Pacific gray whales (another endangered baleen whale population), claiming that these findings indicate that similar surveys off the southeastern U.S will have significant negative effects on the whales that occur anywhere in the region.

Response:

Commenters cite a preliminary report (Cooke

et al.,

2015) that documented a reduction in calf survival that they suggested may be related to disruption of foraging from airgun survey activity and pile driving in Russia due to presumed avoidance of foraging areas. However, a more recent analysis (Cooke

et al.,

2017) invalidated these findings, showing that this was a sampling effect, as those calves that were assumed dead in the 2015 study have since been observed alive elsewhere. The new study found no significant annual variation in calf survival. Johnson

et al.

(2007) had previously reported that foraging gray whales exposed to airgun sounds during surveys in Russia did not experience any biologically significant or population-level effects.

Comment:

J.J. Roberts and P.N. Halpin of the Duke University Marine Geospatial Ecology Lab (hereafter, “MGEL”) provided two comments related to right whales. First, the commenters stated, in summary, that the time-area restriction included in our Notice of Proposed IHAs for the specific purpose of avoiding impacts to the North Atlantic right whale would not be sufficient to achieve its stated purpose. The commenters noted multiple lines of scientific evidence that right whales occur beyond the area defined in the Notice of Proposed IHAs (

i.e.,

a 20-nmi coastal strip, superseded by either critical habitat or seasonal management areas, and buffered by a distance of 10 km; this equates roughly to a 47-km coastal strip). The commenters also reiterated concern regarding an error associated with the right whale take estimates for two applicants (TGS and Western). Finally, the commenters noted that they were developing updated density models for the right whale; these revised models more than double the survey effort utilized by the models in the region south of Cape Hatteras, while additional new data boost coverage in non-summer seasons. As stated by the commenters, collectively these data allow for a notable upgrade in right whale density model performance in the regions and seasons addressed here. The commenters noted that, while the revised models have not been through formal peer review, they utilize the same methodology as the Roberts

et al.

(2016) publication, which has been peer reviewed.

Response:

We agree with these comments, and addressed them through use of the revised North Atlantic right whale models (Roberts

et al.,

2017) in developing new exposure estimates for all five applicant companies. Importantly, in agreement with the statements of the commenters and with the outputs of the revised models, we revised the time-area restriction by increasing the standoff distance from shore to 90 km (

i.e.,

80 km plus a 10 km buffer) (or requiring that comparable protection is achieved through implementation of a NMFS-approved mitigation and monitoring plan at distances between 47-80 km offshore). As stated by MGEL and other commenters, Norris

et al.

(2014) reported acoustic detections of right whales in the southeast beyond the previous 47 km limit, while Foley

et al.

(2011) documented a right whale birth beyond the previous limit. The right whale model produced by Roberts

et al.

(2016) explicitly included distance from shore as a predictor in the model; right whale densities significantly above zero were predicted beyond the proposed 47 km limit. The revised model retains distance from shore as a predictor and, in the region north of Cape Fear, indicates that right whale density peaks at about 50 km offshore during the winter and is moderate to about 80 km from shore, beyond which limit density is predicted as dropping off rapidly. Please see “Estimated Take—North Atlantic Right Whale” and “Mitigation” for additional discussion.

Comment:

Nowacek

et al.

commented that NMFS should perform a quantitative evaluation of right whale health and reproductive rates, including mortality and sublethal effects of entanglement. They noted that tools such as the Population Consequences of Disturbance (PCOD) model could be used to perform such an analysis. However, Nowacek

et al.

provided their own modeling example, including a health assessment of five North Atlantic right whales, which they described in their comment letter. Nowacek

et al.'

s analysis showed that a small decrement in health that could be linked to stress caused by chronic noise exposure can result in negative consequences for individual right whales.

Response:

NMFS appreciates the attention given to this issue by the commenters, and finds the analysis provided in their letter useful. As noted by many commenters, the primary threats to the right whale remain ship strike and entanglement in fishing gear. However, NMFS considered this analysis and its conclusions in its determination to revisit the acoustic exposure analysis conducted for right whales and in reconsidering the most appropriate habitat-based mitigation requirements related to right whales. Following these new analyses, NMFS finds that predicted takes of right whales have been substantially reduced and that potential impacts to the right whale have been reduced to the level of least practicable adverse impact. While it is likely not possible to completely avoid acoustic exposures of North Atlantic right whales, NMFS finds that such exposures will be minimized and that, importantly, the impact of acoustic exposures will be minimized by avoiding entirely the habitat expected to be important for right whales for calving and migratory behavior (or that comparable protection is achieved through implementation of a NMFS-approved mitigation and monitoring plan at distances between 47-80 km offshore). In the event that right whales are encountered outside these areas, the expanded shutdown requirement will minimize the severity and/or duration of acoustic exposures. Finally, while exposures of right whales at levels below those expected to result in disruption of behavioral patterns but above the level of ambient noise may occur, NMFS does not consider such potential exposures as likely to constitute “chronic noise exposure,” as a result of the relatively brief duration of any given survey in any particular location; therefore, it is unlikely that the specified activities could result in impacts such as those assessed through the analysis of Nowacek

et al.

Comment:

One commenter described the relationship between noise and stress shown by Rolland

et al.

(2012) for right whales, stating that the planned surveys could increase stress in right whales.

Response:

While NMFS concurs that the findings of Rolland

et al.

(2012) indicate a connection between noise exposure and stress in right whales, the number of vessels associated with the surveys is unlikely to contribute to significant additive vessel traffic and associated vessel noise as compared with vessel activity already occurring in the region. Rolland

et al.

(2012)

measured vessel density in an area with much more concentrated activity (

i.e.,

shipping lanes in the Bay of Fundy) than what would occur in the activity area. While noise from the surveys, whether due to use of the airgun arrays or from the vessels themselves, may cause stress responses in exposed animals, NMFS finds it unlikely that such responses will significantly impact individual whales as chronic noise exposure is not expected.

Comment:

Several groups commented on additional data NMFS should have considered in assessing impacts to North Atlantic right whales. For example, the Marine Mammal Commission (MMC) recommended that we consult with NMFS's Northeast Fisheries Science Center regarding results of their most recent acoustic analysis, which they contend may provide insight on occurrence of right whales at different distances from shore. Similarly, Nowacek

et al.

recommended that NMFS should consider more recent data from the Atlantic Marine Assessment Program for Protected Species (AMAPPS) surveys or right whale surveys in the southeast curated by the North Atlantic Right Whale Consortium. NRDC stated that NMFS must use additional data sources in calculating right whale densities, noting that recent passive acoustic studies have detected whales further offshore and with broader seasonality than previously expected.

Response:

NMFS agrees with these comments, and has considered these various sources of newer data, including by revising acoustic exposure estimates for right whales by using the latest density models for right whales (Roberts

et al.,

2017). These revised models incorporate the southeast U.S. right whale survey data as well as the AMAPPS data. While the revised model does not directly incorporate acoustic data—we note that NRDC offers no suggestions as to how this might be accomplished—it was validated through comparison with passive acoustic monitoring data (Davis

et al.,

2017). While this validation work does suggest that the revised model may underestimate right whale presence in certain locations or seasons—for example, acoustic data indicate that the model may underestimate the presence of whales relatively far from shore during the winter in the region north of Cape Hatteras—we developed an extended right whale closure (out to 90 km from shore) (or we require that comparable protection is achieved through implementation of a NMFS-approved mitigation and monitoring plan at distances between 47-80 km offshore) in an effort to reasonably encompass the likelihood of increased whale presence at greater distances from shore than have previously been expected.

Comment:

Sea Shepherd Legal stated that NMFS ignored the “Cetacean & Sound Mapping platform (“CetSound”)” when discussing biologically important areas for North Atlantic right whales.

Response:

Though NMFS did not give specific reference to “CetSound” in our Notice of Proposed IHAs, we did in fact incorporate and consider information available through NOAA's CetSound website (

cetsound.noaa.gov

), including information relating to BIAs, as discussed by LaBrecque

et al.

(2015).

Cumulative Impacts and Related Issues

Comment:

Many commenters expressed concern regarding “cumulative,” “aggregate” and “synergistic” impacts. Commenters stated that NMFS did not adequately address cumulative or aggregate impacts from the five surveys, which are planned to occur within the same broad geographic region and which could overlap temporally. Some commenters referenced the large amount of survey effort described in BOEM's PEIS, erroneously ascribing the potential cumulative impacts associated with that level of effort—associated with nine years of surveys in support of an active oil and gas program in the Atlantic—to the significantly smaller amount of activity contemplated in our five separate proposed IHAs. Commenters urged the agency to review cumulative impacts using a risk-averse approach, considering such impacts in the context of effects to both species and ecosystems, as well as across time and geographic extent. As discussed in a previous comment response, some commenters cited studies demonstrating potential long-range propagation of airgun signals as reason for additional consideration of cumulative impacts. Similarly, some commenters claimed a need to consider takes in the aggregate and to consider potential takes from other sources. Nowacek

et al.

specified that NMFS should assess aggregate impacts in addition to cumulative impacts, highlighting available tools to do so. One commenter suggested that a cumulative noise management plan should be developed. Commenters such as Nowacek

et al.

decry our independent consideration of the effects of each individual specified activity under the MMPA as “completely without basis in science or logic.” Similarly, NRDC claims that failing to consider the total impact of all five surveys in the negligible impact assessment does not satisfy NMFS's legal obligations and is “contrary to common sense and principles of sound science.” NRDC also states that NMFS's negligible impact determination underestimates impacts to marine mammal species and populations because it fails to consider the effects of other anticipated activities on the same marine mammal populations. Finally, some commenters acknowledged that the MMPA does not require consideration of cumulative impacts but stated that NMFS must do so in this case given the unprecedented scale of these surveys in the Atlantic.

Response:

Cumulative impacts (also referred to as cumulative effects) is a term that appears in the context of NEPA and the ESA, but it is defined differently in those different contexts. Neither the MMPA nor NMFS's codified implementing regulations address consideration of other unrelated activities and their impacts on populations. However, the preamble for NMFS's 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 environmental baseline. Consistent with that direction, NMFS here has factored into its negligible impact analyses 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)). In addition, the context aspect of our assessment framework also considers these factors. See the “Negligible Impact Analyses and Determinations” section of this notice.

Our 1989 final rule for the MMPA implementing regulations also addressed public comments regarding cumulative effects from future, unrelated activities. There we stated that such effects are not considered in making findings under section 101(a)(5) concerning negligible impact. We indicated that NMFS would consider cumulative effects that are reasonably foreseeable when preparing a NEPA analysis; and also that reasonably foreseeable cumulative effects would be considered under section 7 of the ESA for ESA-listed species.

In this case, we deem each of these IHAs a future, unrelated activity relative to the others. Although these IHAs are all for surveys that will be conducted for

a similar purpose, they are unrelated in the sense that they are discrete actions under section 101(a)(5)(D), issued to discrete applicants.

Here, we recognize the potential for cumulative impacts, and that the aggregate impacts of the five surveys will be greater than the impacts of any given survey. The direct aggregate impacts of multiple surveys were addressed through the associated NEPA analyses: In BOEM's PEIS, which addressed the impacts of a significantly greater amount of survey activity that may be permitted by BOEM, and which NMFS adopted as the basis for its Record of Decision; as well as in NMFS's tiered Environmental Assessment, which supported a Finding of No Significant Impact (FONSI) for the issuance of the five IHAs here.

In our FONSI, NMFS's assessment was focused on whether the predicted level of take from the five surveys, when considered in context, would have a meaningful biological consequence at a species or population level. NMFS, therefore, assessed and integrated other contextual factors (

e.g.,

species' life history and biology, distribution, abundance, and status of the stock; mitigation and monitoring; characteristics of the surveys and sound sources) in determining the overall impact of issuance of the five IHAs on the human environment. Key considerations included the nature of the surveys and the required mitigation. In all cases, it is expected that sound levels will return to previous ambient levels once the acoustic source moves a certain distance from the area, or the surveys cease, and it is unlikely that the surveys will all occur at the same time in the same places, as the area within which the surveys will occur is very large and some will occur for less than six months. In other words, we would not expect the duration of a sound source to be greater than moderate and intermittent in any given area. Surveys have been excluded from portions of the total area deemed to result in the greatest benefit to marine mammals. These restrictions will not only reduce the overall numbers of take but, more importantly, will eliminate or minimize impacts to marine mammals in the areas most important to them for feeding, breeding, and other important functions. Therefore, these measures are expected to meaningfully reduce the severity of the takes that do occur by limiting impacts that could reduce reproductive success or survivorship.

In summary, NMFS finds that when the required mitigation and monitoring is considered in combination with the large spatial extent over which the activities are spread across for comparatively short durations (less than one year), the potential impacts are both temporary and relatively minor. Therefore, NMFS does not expect aggregate impacts from the five surveys to marine mammals to affect rates of recruitment or survival, either alone or in combination with other past, present, or ongoing activities. The cumulative impacts of these surveys (

i.e.,

the incremental impact of the action when added to other past, present, and reasonably foreseeable future actions) were addressed as required through the NEPA documents cited above and, as noted, supported a FONSI for the five IHAs. These documents, as well as the relevant Stock Assessment Reports, are part of NMFS's Administrative Record for this action, and provided the decision-maker with information regarding other activities in the action area that affect marine mammals, an analysis of cumulative impacts, and other information relevant to the determinations made under the MMPA.

Separately, cumulative effects were analyzed as required through NMFS's required intra-agency consultation under section 7 of the ESA, which concluded that NMFS's action of issuing the five IHAs was not likely to jeopardize the continued existence of listed marine mammals and was not likely to adversely affect any designated critical habitat.

We note that section 101(a)(5)(D) of the MMPA requires NMFS to make a determination that the take incidental to a “specified activity” will have a negligible impact on the affected species or stocks of marine mammals, and will not result in an unmitigable adverse impact on the availability of marine mammals for taking for subsistence uses. We believe the “specified activity” for which incidental take coverage is being sought under section 101(a)(5)(D) is appropriately defined and described by the IHA applicant, just as with applications submitted for section 101(a)(5)(A) incidental take regulations. Here there are five specified activities, with a separate applicant for each. NMFS must make the necessary findings for each specified activity.

Comment:

Several commenters discussed a recent report from the National Academy of Sciences concerning cumulative impacts to marine mammals (“Approaches to Understanding the Cumulative Effects of Stressors on Marine Mammals”; NAS, 2017), suggesting that NMFS should have reviewed this report in addressing cumulative impacts.

Response:

NMFS acknowledges the importance of this new report, which was not available at the time of writing for our Notice of Proposed IHAs. We reviewed this report and considered its findings in relation to our considerations pursuant to NEPA as well as with regard to its general findings for marine mammals. Behavioral disturbance or stress may reduce fitness for individual animals and/or may exacerbate existing declines in reproductive health and survivorship. For example, stressors such as noise and pollutants can induce responses involving the neuroendocrine system, which controls reactions to stress and regulates many body processes (NAS, 2017). As an example, Romano

et al.

(2004) found that upon exposure to noise from a seismic watergun, bottlenose dolphins had elevated levels of a stress-related hormone and, correspondingly, a decrease in immune cells. Population-level impacts related to energetic effects or other impacts of noise are difficult to determine, but the addition of other stressors can add considerable complexity due to the potential for interaction between the stressors or their effects (NAS, 2017). When a population is at risk NAS (2017) recommends identifying those stressors that may feasibly be mitigated. In this case, we have done so by prescribing a comprehensive suite of mitigation measures that both specifically tailors real-time detection and mitigation requirements to the species most sensitive to noise from airguns or to additional stressors in general (due to overall vulnerability of the stock), and includes habitat-based mitigation that restricts survey effort in the areas and times expected to be most important for the species at greatest risk of more severe impacts from the specified activities (or requires comparable protection via other methods).

Acoustic Thresholds

Comment:

NRDC and several other commenters criticized NMFS's use of the 160-dB rms Level B harassment threshold, stating that the threshold is based on outdated information and that current research shows that behavioral impacts can occur at levels below the threshold. Criticism of our use of this threshold also focused on its nature as a step function,

i.e.,

it assumes animals don't respond to received noise levels below the threshold but always do respond at higher received levels. Several organizations also suggest that reliance on this threshold results in consistent underestimation of impacts. Commenters urged the agency to provide additional technical acoustic guidance regarding thresholds for behavioral harassment and stated that

no determinations regarding the proposed IHAs can be made until such new guidance has been developed. NRDC specifically stated that NMFS should employ specific thresholds for which species-specific data are available, and then create generalized thresholds for other species, and that the thresholds should be expressed as linear risk functions where appropriate to account for intraspecific and contextual variability. NRDC and others suggested that NMFS must revise the threshold as suggested in Nowacek

et al.

(2015), which recommended a dose function centered on 140 dB rms. TGS suggested that NMFS should re-evaluate take estimates using the approach described in Wood

et al.

(2012).

Response:

NMFS acknowledges that the 160-dB rms step-function approach is simplistic, and that an approach reflecting a more complex probabilistic function may more effectively represent the known variation in responses at different levels due to differences in the receivers, the context of the exposure, and other factors. Certain commenters suggested that our use of the 160-dB threshold implies that we do not recognize the science indicating that animals may react in ways constituting behavioral harassment when exposed to lower received levels. However, we do recognize the potential for Level B harassment at exposures to received levels below 160 dB rms, in addition to the potential that animals exposed to received levels above 160 dB rms will not respond in ways constituting behavioral harassment. These comments appear to evidence a misconception regarding the concept of the 160-dB threshold. While it is correct that in practice it works as a step-function,

i.e.,

animals exposed to received levels above the threshold are considered to be “taken” and those exposed to levels below the threshold are not, it is in fact intended as a sort of mid-point of likely behavioral responses (which are extremely complex depending on many factors including species, noise source, individual experience, and behavioral context). What this means is that, conceptually, the function recognizes that some animals exposed to levels below the threshold will in fact react in ways that are appropriately considered take, while others that are exposed to levels above the threshold will not. Use of the 160-dB threshold allows for a simplistic quantitative estimate of take, while we can qualitatively address the variation in responses across different received levels in our discussion and analysis.

NRDC consistently cites reports of changes in vocalization, typically for baleen whales, as evidence in support of a lower threshold than the 160-dB threshold currently in use. A mere reaction to noise exposure does not, however, mean that a take by Level B harassment, as defined by the MMPA, has occurred. For a take to occur requires that an act have “the potential to disturb by causing disruption of behavioral patterns,” not simply result in a detectable change in motion or vocalization. Even a moderate cessation or modification of vocalization might not appropriately be considered as being of sufficient severity to result in take (Ellison

et al.,

2012). NRDC claims these reactions result in biological consequences indicating that the reaction was indeed a take but does not provide a well-supported link between the reported reactions at lower received levels and the claimed consequences. In addition, NRDC fails to discuss documented instances of marine mammal exposure to received levels greater than 160 dB that did not elicit any response. Just a few examples are presented here:

• Malme

et al.

(1985) conducted a study consisting of playback using a stationary or moving single airgun and humpback whales. No clear overall signs of avoidance of the area were recorded for feeding/resting humpback whales exposed to received levels up to 172 dB. Although startle responses were observed when the airgun was first turned on, likely due to the novelty of the sound, increasing received levels did not result in increasing probability of avoidance. In three instances, whales actually approached the airgun.

• Malme

et al.

(1988) conducted a controlled exposure experiment involving a moving single airgun and gray whales. From this study, the authors predicted a 0.5 probability that whales would stop feeding and move away from the area when received levels reached 173 dB and a 0.1 probability of feeding interruption at a received level of 163 dB. However, whale responses were highly variable, with some whales remaining feeding with received levels as high as 176 dB.

• McCauley

et al.

(1998, 2000a, 2000b) report observations associated with an actual seismic survey (array volume 2,678 in

3

) and controlled approaches of humpback whales with a single airgun. When exposed to the actual seismic survey, avoidance maneuvers for some whales began at a range of 5-8 km from the vessel; however, in three trials whales at a range beyond 5 km showed no discernible effects on movement patterns. In addition, some male humpback whales were attracted to the single airgun (maximum received level of 179 dB). Overall, McCauley

et al.

(2000a) found no gross disruption of humpback whale movements in the region of the source vessel, based on encounter rates.

• Malme

et al.

(1983, 1984) conducted playback experiments with gray whales involving a single airgun and a full array (2,000-4,000 in

3

). For playback of the array, it was estimated that probability of avoidance during migration (including moving inshore and offshore to avoid the area or to pass the noise source at a greater distance then would normally occur) was 0.1 at 164 dB; 0.5 at 170 dB; and 0.9 at levels greater than 180 dB.

These examples are related only to baleen whales, for which NRDC provides examples of vocalization changes in response to noise exposure. Although associated received levels are not available, a substantial body of evidence indicates that delphinids are significantly more tolerant of exposure to airgun noise. Based on review of monitoring reports from many years of airgun surveys, many delphinids approach acoustic source vessels with no apparent discomfort or obvious behavioral change (Barkaszi

et al.,

2012; Stone, 2015a). Behavioral observations of gray whales during an airgun survey monitored whale movements and respirations pre-, during-, and post-seismic survey (Gailey

et al.,

2016). Behavioral state and water depth were the best `natural' predictors of whale movements and respiration and, after considering natural variation, none of the response variables were significantly associated with survey or vessel sounds.

Overall, we reiterate the lack of scientific consensus regarding what criteria might be more appropriate. Defining sound levels that disrupt behavioral patterns is difficult because responses depend on the context in which the animal receives the sound, including an animal's behavioral mode when it hears sounds (

e.g.,

feeding, resting, or migrating), prior experience, and biological factors (

e.g.,

age and sex). Other contextual factors, such as signal characteristics, distance from the source, and signal to noise ratio, may also help determine response to a given received level of sound. Therefore, levels at which responses occur are not necessarily consistent and can be difficult to predict (Southall

et al.,

2007; Ellison

et al.,

2012; Bain and Williams, 2006).

There is currently no agreement on these complex issues, and NMFS followed the practice at the time of submission and review of these applications in assessing the likelihood

of disruption of behavioral patterns by using the 160-dB threshold. This threshold has remained in use in part because of the practical need to use a relatively simple threshold based on available information that is both predictable and measurable for most activities. We note that the seminal review presented by Southall

et al.

(2007) did not suggest any specific new criteria due to lack of convergence in the data. NMFS is currently evaluating available information towards development of guidance for assessing the effects of anthropogenic sound on marine mammal behavior. However, undertaking a process to derive defensible exposure-response relationships is complex (

e.g.,

NMFS previously attempted such an approach, but is currently re-evaluating the approach based on input collected during peer review of NMFS (2016)). A recent systematic review by Gomez

et al.

(2016) was unable to derive criteria expressing these types of exposure-response relationships based on currently available data.

NRDC consistently cites Nowacek

et al.

(2015) in public comments, suggesting that this paper is indicative of a scientific consensus that NMFS is missing or ignoring. We note first that while NRDC refers to this paper as a “study” (implying that it presents new scientific data or the results of new analyses of existing scientific data), the paper in fact makes policy recommendations rather than presenting any new science. The more substantive reviews presented by Southall

et al.

(2007) and Gomez

et al.

(2016) were unable to present any firm recommendations, as noted above. Other than suggesting a 50 percent midpoint for a probabilistic function, Nowacek

et al.

(2015) offer minimal detail on how their recommended probabilistic function should be derived/implemented or exactly how this midpoint value (

i.e.,

140 dB rms) was derived (

i.e.,

what studies support this point). In contrast with elements of a behavioral harassment function that NRDC indicates as important in their comments, Nowacek

et al.

(2015) does not make distinctions between any species or species groups and provide no quantitative recommendations for acknowledging that behavioral responses can vary by species group and/or behavioral context. In summary, little substantive support is provided by Nowacek

et al.

(2015) for the proposal favored by NRDC and it is treated in that paper as a vague recommendation with minimal support offered only in a one-page supplementary document rather than well-supported scientific consensus, as the commenter suggests.

NMFS disagrees that establishing species-specific thresholds is practical (

i.e.,

this approach would make assessments unnecessarily onerous by creating numerous thresholds to evaluate). Additionally, there is scientific evidence that grouping thresholds by broad source category (Gomez

et al.,

2016) or taxonomic group (NMFS, 2018) is supportable. NMFS currently uses data/thresholds from surrogate species/groups to represent those species/groups where data are not available.

Overall, while we agree that there may be methods of assessing likely behavioral response to acoustic stimuli that better capture the variation and context-dependency of those responses than the simple step-function used here, there is no agreement on what that method should be or how more complicated methods may be implemented by applicants. NMFS is committed to continuing its work in developing updated guidance with regard to acoustic thresholds, but pending additional consideration and process is reliant upon an established threshold that is reasonably reflective of available science.

In support of exploring new methods for quantitatively predicting behavioral harassment, we note NMFS's recently published proposed incidental take regulations for geophysical surveys in the Gulf of Mexico (83 FR 29212; June 22, 2018), which propose using the modeling study first published in BOEM's associated EIS (Appendix D in BOEM, 2017) to estimate take. This study evaluated potential disruption of behavioral patterns that could result from a program of airgun surveys, using both the 160-dB step function and a probabilistic risk function similar to that suggested by Nowacek

et al.

(2015), but with a midpoint set at 160 dB for the majority of species, rather than 140 dB. This function, described in Wood

et al.

(2012), includes for most species a 10 percent probability of behavioral harassment at 140 dB, with subsequent steps of 50 percent at 160 dB and 90 percent at 180 dB. Of note, use of this generic function resulted in lower numbers of estimated takes than did use of the 160-dB step function. Therefore, while use of the probabilistic risk function may allow for more specific quantitative consideration of contextual issues and variation in individual responses, our use of the 160-dB step function is conservative in that the number of resulting takes is higher. NMFS will continue to explore quantitative refinement of the behavioral harassment threshold where there is available information to support methodologies that better reflect the variation in individual responses. However, the current threshold allows for an appropriate, and often conservative, enumeration of predicted takes by Level B harassment, which support robust negligible impact and small numbers analyses.

Comment:

Nowacek

et al.

stated that use of the 160-dB threshold would be specifically problematic for beaked whales, as these species demonstrate behavioral response at levels below 160 dB rms and occupy certain areas of the specific geographic region in high densities.

Response:

Please see our previous comment response regarding use of the 160-dB threshold for behavioral harassment. With regard to the expected significance of takes by harassment specifically for beaked whales, we acknowledge that beaked whales are documented as being a particularly behaviorally sensitive species in response to noise exposure. This information is considered in our negligible impact analyses (“Negligible Impact Analyses and Determinations”) and informed our evaluation of the mitigation necessary to satisfy the least practicable adverse impact standard (“Mitigation”). We require implementation of three year-round closures of submarine canyon areas expected to provide important habitat for beaked whales, a seasonal closure of the area off of Cape Hatteras cited by the commenters, and have required expanded shutdown requirements for beaked whales. Additionally, regarding the specific levels at which they are behaviorally harassed by exposure to noise from airguns, we note that there are no data on beaked whale responses to airgun noise, and their hearing sensitivity in the frequency range of signals produced by airguns is notably lower than their sensitivity in the frequency range of the sonar sources for which data is available indicating that they have responded at lower levels (in other words, noise from an airgun must be louder than a sonar pulse for them to hear it as the same level).

Comment:

NRDC and others stated that if NMFS does not revise existing behavioral harassment thresholds, it should use the acoustic threshold for continuous noise (

i.e.,

120 dB rms) rather than the threshold for intermittent sound sources (

i.e.,

160 dB rms). NRDC contends that, as a result of reverberation and multipath arrivals, the impulsive signal produced by airguns is more similar to a continuous noise at greater distances from the source and,

therefore, use of the 120-dB “continuous” noise threshold is more appropriate than the 160-dB threshold for intermittent sound sources.

Response:

NMFS acknowledges that as airgun shots travel through the environment, pulse duration increases because of reverberation and multipath propagation. However, we disagree that the 120-dB rms threshold for continuous noise—which was based on behavioral responses of baleen whales to drilling (Malme

et al.,

1984; Richardson

et al.,

1990)—is more appropriate than the intermittent noise threshold of 160-dB rms for evaluating potential behavioral harassment resulting from airgun noise. The 160-dB threshold was derived from data for mother-calf pairs of migrating gray whales (Malme

et al.,

1983, 1984) and bowhead whales (Richardson

et al.,

1985, 1986) behaviorally responding when exposed specifically to noise from airguns. The Richardson

et al.

(1985, 1986) studies included controlled approaches with a full-scale airgun array firing at 7.5 km from the animals. Thus, behavioral responses observed in these studies account for changes in the pulse duration associated with propagation.

In addition, there is a prevalent misconception in comments from NRDC and others regarding Level B harassment, as defined by the MMPA. NRDC cites multiple observations of behavioral reactions or of changes in vocal behavior in making statements supporting their overall recommendation that behavioral harassment thresholds be lower. However, these observations do not necessarily constitute evidence of disruption of behavioral patterns (Level B harassment) rather than simple reactions to often distant noise, which may provoke a reaction when discernable above ambient noise levels.

For example, changes in mysticete vocalization associated with exposure to airgun surveys within migratory and non-migratory contexts have been observed (

e.g.,

Castellote

et al.,

2012; Blackwell

et al.,

2013; Cerchio

et al.,

2014). The potential for these changes to occur over large spatial scales is not surprising for species with large communication spaces, like mysticetes (

e.g.,

Clark

et al.,

2009), although not every change in a vocalization would necessarily rise to the level of a take.

Comment:

NRDC claims that NMFS misapplies the MMPA's statutory definition of harassment by adopting a probability standard other than “potential” in setting thresholds for auditory injury, stating that a take estimate based on “potential” should either count take from the lowest exposure level at which hearing loss can occur or establish a probability function that accounts for variability in the acoustic sensitivity of individual marine mammals. Instead, NRDC states that NMFS derived auditory injury thresholds from average exposure levels at which tested marine mammals experience hearing loss, which discounts instances of hearing loss at lower levels of exposure. The comment goes on to state that for purposes of take estimation, thresholds based on mean or median values will lead to roughly half of an exposed cohort experiencing the impacts that the threshold is designed to avoid, at levels that are considered “safe,” therefore resulting in substantial underestimates of auditory injury. NRDC makes similar statements with regard to the 160-dB threshold for Level B harassment.

Response:

The technical guidance's (NMFS, 2018) onset thresholds for temporary threshold shift (TTS) for non-impulsive sounds encompass more than 90 percent of available TTS data (

i.e.,

for mid-frequency cetaceans, only two data points are below the onset threshold, with maximum point only 2 dB below), and in some situations 100 percent of TTS data (

e.g.,

high-frequency cetaceans; although this group is data-limited). Thus, the technical guidance thresholds provide realistic predictions, based on currently available data, of noise-induced hearing loss in marine mammals. For impulsive sounds, data are limited to two studies, and NMFS directly adopted the TTS onset levels from these two studies for the applicable hearing groups.

Our

Federal Register

notice announcing the availability of the original technical guidance (81 FR 51694; August 4, 2016; NMFS, 2016), indicated that onset of auditory injury (PTS) equates to Level A harassment under the MMPA. We explained in that notice that because the acoustic thresholds for PTS conservatively predict the onset of PTS, they are inclusive of the “potential” language contained in the definition of Level A harassment. See 81 FR 51697, 51721.

Regarding Level B harassment, based on the language and structure of the definition of Level B harassment, we interpret the concept of “potential to disturb” as embedded in the assessment of the behavioral response that results from an act of pursuit, torment, or annoyance (collectively referred to hereafter as an “annoyance”). The definition refers to a “potential to disturb” by causing disruption of behavioral patterns. Thus, an analysis that indicates a disruption in behavioral patterns establishes the “potential to disturb.” A separate analysis of “potential to disturb” is not needed. In the context of an authorization such as this, our analysis is forward-looking. The inquiry is whether we would reasonably expect a disruption of behavioral patterns; if so, we would conclude a potential to disturb and therefore expect Level B harassment. We addressed NRDC's concerns regarding the scientific support for the Level B harassment threshold in a previous comment response.

Comment:

The Center for Regulatory Effectiveness (CRE) does not agree with NMFS's use of the technical acoustic guidance (NMFS, 2016, 2018) for purposes of evaluating potential auditory injury. CRE claims that (1) NMFS's use of the guidance conflicts with Executive Order 13795 (“Implementing an America-First Offshore Energy Strategy”); (2) the guidance violates the Office of Management and Budget's (OMB) Peer Review Bulletin and Guidance Document Bulletin and implementing Memoranda; (3) violates Information Quality Act (IQA) guidelines; and (4) violates Executive Orders 12866 (“Regulatory Planning and Review”) and 13771 (“Reducing Regulation and Controlling Regulatory Costs”). Regarding the IQA, CRE states that NMFS does not have an OMB-approved Information Collection Request (ICR) associated with the guidance, and is therefore violating the IQA. The CRE also claims that NMFS's use of the guidance violates the MMPA requirement that all mitigation requirements be practicable, as the guidance supposedly requires monitoring and reporting requirements and other mitigation requirements that are impossible to comply with.

Response:

NMFS disagrees that use of the technical guidance results in any of the claims listed by CRE. First, the use of the technical guidance does not conflict with Executive Order 13795. Section 10 of the Executive Order called for a review of the technical guidance (NMFS, 2016) as follows: “The Secretary of Commerce shall review for consistency with the policy set forth in Section 2 of this order and, after consultation with the appropriate Federal agencies, take all steps permitted by law to rescind or revise that guidance, if appropriate.” To assist the Secretary in the review of the technical guidance, NMFS solicited public comment via a 45-day public comment period (82 FR 24950; May 31, 2017) and hosted an interagency consultation meeting with representatives from ten federal agencies (September 25, 2017). NMFS

provided a summary of comments and recommendations received during this review to the Secretary, and per the Secretary's approval, issued a revised version of the technical guidance in June 2018 (83 FR 28824; NMFS, 2018).

Second, NMFS did comply with the OMB Peer Review Bulletin and IQA Guidelines in development of the technical guidance. The technical guidance was classified as a Highly Influential Scientific Assessment and, as such, underwent three independent peer reviews, at three different stages in its development, including a follow-up to one of the peer reviews, prior to its dissemination by NMFS. In addition, there were three separate public comment periods. Responses to public comments were provided in a previous

Federal Register

notice (81 FR 51694; August 4, 2016). Detailed information on the peer reviews and public comment periods conducted during development of the guidance are included as an appendix to the guidance, and are detailed online at:

www.cio.noaa.gov/services_programs/prplans/ID43.html.

Furthermore, the technical guidance is not significant for purposes of Executive Orders 12866 or 13771 or OMB's Bulletin entitled, “Agency Good Guidance Practices” for significant guidance documents. 72 FR 3432 (January 25, 2007). Nevertheless, the technical guidance follows the practices and includes disclaimer language suggested by the OMB Bulletin to communicate effectively to the public about the legal effect of the guidance. Finally, with regard to the claim that NMFS's use of the technical guidance violates the MMPA requirement that all mitigation requirements be practicable, as the guidance supposedly requires monitoring and reporting requirements and other mitigation requirements that are impossible to comply with, we reiterate that mitigation and monitoring requirements associated with an MMPA authorization or ESA consultation or permit are independent management decisions made in accordance with statutory and regulatory standards in the context of a proposed activity and comprehensive effects analysis and are beyond the scope of the technical guidance. The technical guidance does not mandate mitigation or monitoring. Finally, there is no collection of information requirement associated with the technical guidance, so no ICR is required.

Comment:

Several groups raised concerns regarding use of the technical acoustic guidance (NMFS, 2016, 2018), claiming that the guidance is not based on the best available science and underestimates potential auditory injury. NRDC specifically cited many supposed issues with the guidance, including adoption of “erroneous” models, broad extrapolation from a small number of individuals, and disregarding “non-linear accumulation of uncertainty.” NRDC suggests that NMFS retain the historical 180-dB rms Level A harassment threshold as a “conservative upper bound” or conduct a “sensitivity analysis” to “understand the potential magnitude” of the supposed errors. Oceana stated that NMFS should not make a decision about the proposed IHAs while the technical guidance is under review.

Response:

The original 2016 technical guidance and revised 2018 guidance is a compilation, interpretation, and synthesis of the scientific literature that provides the best available information regarding the effects of anthropogenic sound on marine mammals' hearing. The technical guidance was classified as a Highly Influential Scientific Assessment and, as such, underwent three independent peer reviews, at three different stages in its development, including a follow-up to one of the peer reviews, prior to its dissemination by NMFS. In addition, there were three separate public comment periods, during which time we received and responded to similar comments on the guidance (81 FR 51694), and more recent public and interagency review under Executive Order 13795. While new information may help to improve the guidance in the future, and NMFS will review the available literature to determine when revisions are appropriate, the final guidance reflects the best available science and all information received through peer review and public comment. Given the systematic development of the guidance, which was also reviewed multiple times by both independent peer reviewers and the public, NRDC's use of the phrase “arbitrary and capricious” is unreasonable.

The guidance updates the historical 180-dB rms injury threshold, which was based on professional judgement (

i.e.,

no data were available on the effects of noise on marine mammal hearing at the time this original threshold was derived). NMFS does not believe the use of the technical guidance provides erroneous results. The 180-dB rms threshold is plainly outdated, as the best available science indicates that rms SPL is not even an appropriate metric by which to gauge potential auditory injury (whereas the scientific debate regarding behavioral harassment thresholds is not about the proper metric but rather the proper level or levels and how these may vary in different contexts). NRDC's advice to return to use of the 180-dB threshold is inconsistent with its criticism of the 160-dB rms criterion for Level B harassment. However, as we said in responding to comments criticizing the Level B harassment criterion, development of an updated threshold(s) is complicated by the myriad contextual and other factors that must be considered and evaluated in reaching appropriate updated criteria. See our response to comment on the Level B harassment threshold.

Sound Field Modeling

Comment:

The MMC noted differences in the estimated Level B harassment radii provided in ION and Spectrum's applications, noting that since the largest discrepancies were observed at shallow water sites, it is likely that geoacoustic properties were responsible. Although both ION and Spectrum used sediment data from cores collected during the Ocean Drilling Program, the data was based on samples from different sites and potentially different assumptions as to sediment attenuation. The MMC provided related recommendations: (1) NMFS should determine whether ION's or Spectrum's estimated zones are the most appropriate and require that both companies use the same set of zones; (2) NMFS should require each of the five companies to conduct sound source verification (SSV) in waters less than 100 m and use that data to inform and adjust the extent of Level B harassment zones as necessary; and (3) NMFS should determine the appropriate baseline geoacoustic model for the region in concert with BOEM, ION, and Spectrum, and then require this in future IHAs for similar activities in the region.

Response:

NMFS appreciates the MMC's attention to this matter, but disagrees that it is necessarily appropriate to require use of the same data or approaches to modeling sound fields when there is not clearly a “most appropriate” approach. Sound field modeling for both ION and Spectrum was conducted by experts in the field. We appropriately approved both applicants' applications as adequate and complete, determining that both used appropriate data inputs and acceptable modeling approaches. Subsequently, both applications were made available for public review in order to better inform NMFS's preparation of proposed IHAs; no such concerns were raised. Importantly, we recognize that there is no model or approach that is always the most appropriate and that there may be multiple approaches that may be

considered acceptable. Having determined that both applicants used appropriate data and acceptable modeling approaches, it would be inappropriate to require one to change their approach to conform to the other because of differences in the results. Given our confidence in the data inputs and modeling approaches used, we find that a requirement to conduct SSV studies is not warranted, despite discrepancies in modeling results. As is appropriate, NMFS would consider the appropriateness of data inputs and modeling approaches for any future applications but, in keeping with our response here, will not necessarily enforce use of one dataset or modeling approach when others may be considered as equally representative of the best available scientific data and techniques.

Comment:

One individual suggested that, because the representative airgun array used in BOEM's sound field modeling was characterized as having a source level lower than that of arrays planned for use by the applicants, use of BOEM's sound field modeling could lead to an underestimate of takes.

Response:

Numerous factors combine in the sound field modeling provided by BOEM to result ultimately in estimates of sound fields at different locations. BOEM's modeling was performed to be reasonably representative of the types of sources that would be used in future surveys, recognizing that actual sources may vary somewhat from what was considered in the sound field modeling. We disagree that these minor differences would have meaningful impacts on the ultimate result of the exposure estimation process, and find that the modeling provided by BOEM was reasonably representative of what would occur during actual surveys and, therefore, acceptable to use for informing the take estimates for these surveys.

Comment:

One individual stated that NMFS does not fully consider the implications of different weather phenomena in acoustic propagation, and that in failing to account for variations in ocean and weather conditions, the average estimates of propagation and take are biased downward. The same individual also claimed that NMFS did not adequately consider ocean floor sediment composition in modeling expected sound fields, and states again that this would likely result in higher numbers of take.

Response:

While NMFS acknowledges that discrete weather phenomena could result in propagation being more or less efficient than anticipated under a seasonal average scenario (

i.e.,

one element of propagation modeling is the use of sound velocity profiles that are season-specific within the specific geographic region), the commenter provides no basis for concluding that such phenomena would lead overall to the estimated takes being biased downward. Further, the sound field modeling approaches taken by the applicants (and in BOEM's PEIS) follow state-of-science approaches and are reasonable when considering the need to model propagation year-round and over a wide geographic area. The commenter provides no specific recommendation for how the suggestion should be accomplished. With regard to sediment composition, the applicants' sound field modeling considered sediment characteristics at 15 representative modeling sites throughout the region, and the commenter does not provide any evidence to back the claim that variability in actual sediment composition would result in bias to take estimates in a particular direction or provide any specific recommendation to remedy the perceived flaw.

Comment:

Ocean Conservation Research (OCR) noted that NMFS did not consider a secondary transmission path in the mixed layer above the marine thermocline that behaves as a surface duct, stating that, while the propagation in this transmission path is dependent on the wavelength of the source, the angle of incidence, the depth of the mixed layer, and the surface conditions, the attenuation characteristics are more consistent with the cylindrical spreading model. OCR goes on to claim that, assuming cylindrical propagation of surface ducted noise, typical airgun noise would require 13 km to attenuate to a received level of 180 dB rms.

Response:

Although OCR is correct to point out that the mechanism of sound propagation is complex in the ocean environment, with the potential formation of a surface duct as a result of the mixed layer above the permanent thermocline, the conclusion derived by OCR that typical airgun noise would require 13 km to attenuate to a received level of 180 dB rms is unsupported.

First, oceanographic conditions in the mid-Atlantic region do not support a persistent surface duct, which usually occurs after a storm or consistently cool and windy weather. A reduction of surface wind velocity and the warming of the surface water will quickly break down a surface duct and cause the downward refraction of a shallow source (

e.g.,

source from an airgun array) due to a negative sound velocity profile above the thermocline.

Second, as stated above, the formation of a surface duct requires strong wind gusts and a high sea state, which are not ideal conditions for conducting a seismic survey given the need to tow a large array of airguns and long streamers. Thus, even if a surface duct is formed, it is very unlikely that a seismic survey would continue under such conditions.

Third—as OCR correctly pointed out—sound propagation in a surface duct is dependent on the wavelength of the source, the angle of incidence, the depth of the mixed layer, and the surface conditions. Among these parameters, the depth of the mixed layer is typically determined by the wind speed and sea state. While relatively low wind speed may support a weak, shallow surface duct, such a duct cannot support propagation of airgun sound, which is predominantly low-frequency. Jensen

et al.

(2011) provide the following equation that determines the cutoff frequency (frequency below which sound will not propagate) given the depth of an isothermal surface layer:

EN07DE18.001

where

f

0

is the cutoff frequency in Hz and

D

is the depth in meters of an isothermal surface layer. As an example, for a cutoff frequency to be around 100 Hz, the surface duct needs to be at least 150 m deep. In general, shallow ducts (

D

<50 m) are more common, but they are only effective waveguides for frequencies above 530 Hz, which also suffer high scattering loss due to the rough sea surface under these weather conditions.

Finally, most acoustic rays from an airgun array are emitted at very steep angles to be contained within the surface duct waveguide.

For these reasons, we do not believe surface ducts in the mid-Atlantic region, if they exist, would contribute noticeably to propagation for sound emitted from airguns.

Comment:

NRDC stated that NMFS used unrealistic and non-conservative assumptions about spreading loss, bottom composition, and reverberation in its propagation analysis and claimed that the analysis does not represent the best available science. NRDC stated that, for propagation loss, NMFS incorrectly assumed that normal propagation conditions would apply, such as not accounting for surface ducting (and BOEM only assumed moderate surface ducting in 3 of 21 modeled areas). Furthermore, NRDC stated that low-

frequency propagation along the seabed can spread in a planar manner, and can propagate with more efficiency than indicated by cylindrical propagation. Finally, NRDC asserted that NMFS cannot accept the assumptions in three applications (CGG, TGS, and WesternGeco) that proposed surveys will cover areas with soft or sandy bottoms. NRDC claims that NOAA's own models indicate that there is a likelihood of coral bottom habitat in the survey area, and many hard-bottom habitat areas were not modeled by BOEM and consequently incorporated by NMFS.

Response:

Regarding sound propagation in a surface duct, please refer to the above response to a similar comment from OCR. As stated earlier, oceanographic conditions in the mid-Atlantic region do not support a persistent surface duct, particularly for low-frequency sound propagation. Therefore, the modeling of a moderate surface duct for airgun noise propagation is a conservative measure. Also as stated earlier, frequency and launch angle of the source play a major role in surface ducting. This information is clearly stated by D'Spain

et al.

(2006) with regard to the 2000 beaked whale stranding in the Bahamas,

i.e.,

that the surface duct “. . . effectively traps mid to high frequency sound radiated by acoustic sources within the duct, such as surface ship sonars . . .” and that “[a]t low frequencies, the sound is no longer effectively trapped by the duct because the acoustic wavelength. . . . is too large in comparison to the duct thickness.”

NRDC's statement that “low-frequency propagation along the seabed can spread in a planar manner . . . can propagate with significantly greater efficiency than cylindrical propagation would indicate” is incorrect. Any acoustic wave can be approximated for plane wave propagation at sufficiently far range (

R

) for a region (

W

) such that

W

≤ (λ

R

)

1/2

, where λ is the wavelength. This plane wave approximation has no bearing on the efficiency of sound propagation.

Finally, substrate types for propagation modeling are based on grain size, porosity, and shear velocity, etc., and “coral bottom” is not one of them. In fact, the roughness of the coral habitat would cause severe bottom loss due to scattering. Based on published literature, bottom types of the region are mostly composed of sand (

e.g.,

Stiles

et al.,

2007; Kaplan, 2011). Therefore, the use of sand and clay for propagation modeling is appropriate. The acoustic modeling provided by BOEM (2014a) appropriately and reasonably accounts for variability in bottom composition throughout the planned survey area.

Comment:

Some groups noted that the different approaches taken to acoustic modeling make it difficult to compare takes. Specifically, TGS, CGG, and Western relied on the acoustic modeling provided in BOEM's PEIS, while ION and Spectrum performed their own modeling. In addition, Spectrum and ION used a restricted suite of sound velocity profiles, matching the seasons when they intend to conduct their planned surveys. The comment letter from Nowacek

et al.

adds an assertion that this difficulty in comparing takes is problematic when NMFS is trying to assess whether the activities impact only small numbers or cause negligible impacts, and state that they “can find no evidence in the Notice that NMFS took account of these significant problems when attempting to evaluate the impacts of the IHAs.”

Response:

As stated in a previous response to an MMC comment, NMFS disagrees that the different approaches taken to sound field modeling constitute a problem at all, much less a significant one. BOEM's PEIS provides a sound analysis of expected sound fields in a variety of propagation conditions, including water depth, bottom type, and season, for a representative airgun array. ION and Spectrum conducted similar sound field modeling, but with the added advantage of modeling the specific array planned for use and limiting use of sound velocity profiles to the time period when the survey is planned to occur. No commenter provided any rational basis for disputing that these methods are appropriate or that they used the best available information and modeling processes. Regardless of differences in the sound field modeling processes, one would not expect that the take estimates are directly comparable, precisely because the surveys are planned for different locations, using different sound sources, and, for some companies, operating at different times of year. We disagree the various modeling approaches cause some problem for conducting appropriate negligible impact and/or small numbers analyses; both of these findings are appropriately made in consideration of a given specified activity. Therefore, comparison of the take numbers across IHAs is not a relevant consideration. We disagree that differences in approaches across the applications are arbitrary. On the contrary, we carefully evaluated each applicant's approaches to take estimation and, while they are indeed different in some respects, each applicant uses accepted approaches. Unlike NRDC, we recognize that there is no model or approach that is always the most appropriate and that there may be multiple approaches that may be considered acceptable. Far from “parroting” the applicants' assessments, as NRDC implies, NMFS made substantial changes where necessary, including complete revision of North Atlantic right whale take estimates for all applicants, revision of take estimates for all species using the best available density data (

i.e.,

Roberts

et al.,

2016) for ION and Spectrum, and revised assessment of potential Level A harassment for all applicants. NMFS strongly disagrees that “grossly inconsistent” data or methods were used for any applicant in the analyses described herein.

Comment:

One individual noted that it is not apparent how NMFS accounted for high-frequency sounds, which has implications for potential takes by Level A harassment for species that hear better at higher frequencies. The commenter wrote that airguns produce pulses with most energy at low frequencies (around 10 Hz), but that these pulses contain significant energy at frequencies up to more than 100 kHz, claiming that high-frequency hearing specialists can be affected at distances of 70 km or more. The commenter cited Bain and Williams (2006) in support of the latter claim.

Response:

In considering the potential impacts of higher-frequency components of airgun noise on marine mammal hearing, one needs to account for energy associated with these higher frequencies and determine what energy is truly “significant.” Tolstoy

et al.

(2009) conducted empirical measurements, demonstrating that sound levels (

i.e.,

one-third-octave and spectral density) associated with airguns were at least 20 dB lower at 1 kHz compared to higher levels associated with lower frequencies (below 300 Hz). These levels were even lower at higher frequencies beyond 1 kHz. Thus, even though high-frequency cetaceans may be more susceptible to noise-induced hearing loss at higher frequencies, it does not mean that a source produces a sufficiently loud sound at these higher frequencies to induce a PTS (

i.e.,

auditory injury). For example, Bain and Williams (2006) indicated “airguns produced energy above ambient levels at all frequencies up to 100 kHz (the highest frequency measured), although the peak frequency was quite low.” However, a finding that airgun signals contain energy “above ambient” and are detectable at frequencies up to 100 kHz does not mean that these levels are

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