Takes of Marine Mammals Incidental to Specified Activities; Taking Marine Mammals Incidental to the Empire Wind Project, Offshore New York
Federal RegisterApr 13, 2023
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DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
50 CFR Part 217
[Docket No. 230404-0092]
RIN 0648-BL97
Takes of Marine Mammals Incidental to Specified Activities; Taking Marine Mammals Incidental to the Empire Wind Project, Offshore New York
AGENCY:
National Marine Fisheries Service (NMFS), National Oceanic and Atmospheric Administration (NOAA), Commerce.
ACTION:
Proposed rule; proposed letter of authorization; request for comments.
SUMMARY:
NMFS has received a request from Empire Offshore Wind, LLC (Empire Wind), a 50/50 joint venture between Equinor and BP p.l.c., for Incidental Take Regulations (ITR) and an associated Letter of Authorization (LOA). The requested regulations would govern the authorization of take, by Level A harassment and/or Level B harassment, of small numbers of marine mammals over the course of 5 years (2024-2029) incidental to construction of the Empire Wind Project offshore New York in a designated lease area on the Outer Continental Shelf (OCS-A-512). Project activities likely to result in incidental take include impact pile driving, vibratory pile driving and removal, and site assessment surveys using high-resolution geophysical (HRG) equipment. As required by the Marine Mammal Protection Act (MMPA), NMFS requests comments on its proposed rule. NMFS will consider public comments prior to making any final decision on the promulgation of the requested incidental take authorization (ITA) and issuance of the LOA; agency responses to public comments will be summarized in the final notice of our decision. The proposed regulations, if issued, would be effective January 22, 2024, through January 21, 2029.
DATES:
Comments and information must be received no later than May 15, 2023.
ADDRESSES:
Submit all electronic public comments via the Federal e-Rulemaking Portal. Go to
www.regulations.gov
and enter NOAA-NMFS-2023-0053 in the Search box. Click on the “Comment” icon, complete the required fields, and enter or attach your comments.
Instructions:
Comments sent by any other method, to any other address or individual, or received after the end of the comment period, may not be considered by NMFS. All comments received are a part of the public record and will generally be posted for public viewing on
www.regulations.gov
without change. All personal identifying information (
e.g.,
name, address), confidential business information, or otherwise sensitive information submitted voluntarily by the sender will be publicly accessible. NMFS will accept anonymous comments (enter “N/A” in the required fields if you wish to remain anonymous). Attachments to electronic comments will be accepted in Microsoft Word, Excel, or Adobe PDF file formats only.
FOR FURTHER INFORMATION CONTACT:
Robert Pauline, Office of Protected Resources, NMFS, (301) 427-8401.
SUPPLEMENTARY INFORMATION:
Availability
A copy of Empire Wind's application and supporting documents, as well as a list of the references cited in this document, may be obtained online at:
https://www.fisheries.noaa.gov/national/marine-mammal-protection/incidental-take-authorizations-other-energy-activities-renewable.
In case of problems accessing these documents, please call the contact listed above (see
FOR FURTHER INFORMATION CONTACT
).
Purpose and Need for Regulatory Action
This proposed rule, if issued, would provide a framework under authority of the MMPA (16 U.S.C. 1361
et seq.
) to allow for the authorization of take of marine mammals incidental to construction of the Empire Wind Project within the Bureau of Ocean Energy Management (BOEM) Renewable Energy Lease Area OCS-A 512 and along export cable corridors to two landfall locations in New York. NMFS received a request from Empire Wind requesting 5-year regulations and a LOA that would authorize take of individuals of 17 species of marine mammals (two species by Level A harassment and Level B harassment and 17 species by Level B harassment only) incidental to Empire Wind's construction activities. No mortality or serious injury is anticipated or proposed for authorization. Please see the Estimated Take of Marine Mammals section for definitions of harassment.
Legal Authority for the Proposed Action
The MMPA prohibits the “take” of marine mammals, with certain exceptions. Sections 101(a)(5)(A) and (D) of the MMPA (16 U.S.C. 1361
et seq.
) direct the Secretary of Commerce (as delegated to NMFS) to allow, upon request, the incidental, but not intentional, taking of small numbers of marine mammals by U.S. citizens who engage in a specified activity (other than commercial fishing) within a specified geographical region if certain findings are made, regulations are promulgated (when required), and public notice and an opportunity for public comment are provided.
Authorization for incidental takings shall be granted if NMFS finds that the taking will have a negligible impact on the species or stock(s) and will not have an unmitigable adverse impact on the availability of the species or stock(s) for taking for subsistence uses (where relevant). Further, NMFS must prescribe the permissible methods of taking and other “means of effecting the least practicable adverse impact” on the affected species or stocks and their habitat, paying particular attention to rookeries, mating grounds, and areas of similar significance, and on the availability of the species or stocks for taking for certain subsistence uses (referred to as “mitigation”); and requirements pertaining to the mitigation, monitoring and reporting of the takings are set forth. The definitions of all applicable MMPA statutory terms cited above are included below.
Section 101(a)(5)(A) of the MMPA and the implementing regulations at 50 CFR part 216, subpart I provide the legal basis for proposing and, if appropriate, issuing this rule containing five-year regulations and associated LOA. As directed by this legal authority, this proposed rule also establishes required mitigation, monitoring, and reporting requirements for Empire Wind's activities.
Summary of Major Provisions Within the Proposed Rule
The major provisions within this proposed rule are as follows:
• Establish a seasonal moratorium on impact pile driving during the months of highest North Atlantic right whale (
Eubalaena glacialis
) presence in the project area (January 1-April 30);
• Require both visual and passive acoustic monitoring by trained, NOAA Fisheries-approved Protected Species Observers (PSOs) and Passive Acoustic Monitoring (PAM) operators before, during, and after the in-water construction activities;
• Require the use of sound attenuation device(s) during all impact pile driving to reduce noise levels;
• Delay the start of pile driving if a North Atlantic right whale is observed at any distance by PSOs or acoustically detected;
• Delay the start of pile driving if other marine mammals are observed entering or within their respective clearance zones;
• Shut down pile driving (if feasible) if a North Atlantic right whale is observed or if other marine mammals enter their respective shut down zones;
• Implement sound field verification requirements during impact pile driving to measure in situ noise levels for comparison against the model results;
• Implement soft-starts for impact pile driving and use the least hammer energy possible;
• Require PSOs to continue to monitor for the presence of marine mammals for 30 minutes after any impact pile driving occurs;
• Implement ramp-up for HRG site characterization survey equipment;
• Increase awareness of North Atlantic right whale presence through monitoring of the appropriate networks and Channel 16, as well as reporting any sightings to the sighting network;
• Implement various vessel strike avoidance measures; and
• Implement best management practices during fisheries monitoring surveys such as removing gear from the water if marine mammals are considered at-risk or are interacting with gear.
Under Section 105(a)(1) of the MMPA, failure to comply with these requirements or any other requirements in a regulation or permit implementing the MMPA may result in civil monetary penalties. Pursuant to 50 CF 216.106, violations may also result in suspension or withdrawal of the Letter of Authorization (LOA) for the project. Knowing violations may result in criminal penalties, under Section 105(b) of the MMPA.
National Environmental Policy Act (NEPA)
To comply with the National Environmental Policy Act of 1969 (NEPA; 42 U.S.C. 4321
et seq.
) and NOAA Administrative Order (NAO) 216-6A, NMFS must evaluate the review our proposed action (
i.e.,
promulgation of regulations and subsequent issuance of a 5-year LOA) and alternatives with respect to potential impacts on the human environment.
Accordingly, NMFS proposes to adopt the Bureau of Ocean Energy Management's (BOEM's) Environmental Impact Statement (EIS), provided our independent evaluation of the document finds that it includes adequate information analyzing the effects of promulgating the proposed regulations and LOA issuance on the human environment. NMFS is a cooperating agency on BOEM's EIS. BOEM's draft EIS (Empire Wind Draft Environmental Impact Statement (DEIS) for Commercial Wind Lease OCS-A 512) was made available for public comment on November 18, 2022 (87 FR 69330), beginning the 60-day comment period ending on January 17, 2023. The draft EIS can be found at:
https://www.boem.gov/renewable-energy/state-activities/empire-wind.
Additionally, BOEM held three virtual public hearings on December 7, 2022, December 13, 2022 and December 15, 2022.
Information contained within Empire Wind's ITA application and this proposed rule collectively provide the environmental information related to these proposed regulations and associated 5-year LOA for public review and comment. NMFS will review all comments submitted in response to this proposed rule prior to concluding the NEPA process or making a final decision on the requested 5-year ITA and LOA.
Fixing America's Surface Transportation Act (FAST-41)
This project is covered under Title 41 of the Fixing America's Surface Transportation Act, or “FAST-41”. FAST-41 includes a suite of provisions designed to expedite the environmental review for covered infrastructure projects, including enhanced interagency coordination as well as milestone tracking on the public-facing Permitting Dashboard. FAST-41 also places a 2-year limitations period on any judicial claim that challenges the validity of a Federal agency decision to issue or deny an authorization for a FAST-41 covered project. 42 U.S.C. 4370m-6(a)(1)(A).
Empire Wind's proposed project is listed on the Permitting Dashboard (
https://www.permits.performance.gov/),
where milestones and schedules related to the environmental review and permitting for the project can be found:
https://www.permits.performance.gov/permitting-project/empire-wind-energy-project.
Summary of Request
On December 7, 2021, Empire Wind submitted a request for the promulgation of regulations and issuance of an associated 5-year LOA to take marine mammals incidental to construction activities associated with implementation of the Empire Wind Project offshore of New York in BOEM Lease Area OCS-A-0512. Empire Wind's request is for the incidental, but not intentional, taking of a small number of 17 marine mammal species (comprising 18 stocks) by Level B harassment (for all 18 stocks) and by Level A harassment (for two species or stocks). Neither Empire Wind, nor NMFS, expect serious injury or mortality to result from the specified activities nor is any proposed for authorization.
In response to our comments, and following extensive information exchange with NMFS, Empire Wind submitted a final, revised application on July 28, 2022, that NMFS deemed adequate and complete on August 11, 2022. In June 2022, new scientific information was released regarding marine mammal densities (Robert and Halpin, 2022). In response, Empire Wind submitted a final addendum to the application on January 25, 2023, which included revised marine mammal densities and take estimates based on Roberts and Halpin 2022. The addendum also identified a revision to the density calculation methodology. Both of these revisions were recommended by NMFS. Empire Wind requests the regulations and subsequent LOA be valid for 5 years beginning in the first quarter of 2024 (January 22) through the first quarter of 2029 (January 21). Neither Empire Wind nor NMFS expects serious injury or mortality to result from the specified activities. Empire Wind's complete application and associated addendum are available on NMFS' website at:
https://www.fisheries.noaa.gov/action/incidental-take-authorization-empire-offshore-wind-llc-construction-empire-wind-project-ew1?check_logged_in=1.
On September 9, 2022, NMFS published a notice of receipt (NOR) of the application in the
Federal Register
(87 FR 55409), requesting comments and soliciting information related to Empire Wind's request during a 30-day public comment period. During the NOR public comment period, NMFS received comment letters from an environmental non-governmental organization (Responsible Offshore Development Alliance) and a corporate entity (Allco Renewable Energy Limited). NMFS has reviewed all submitted material and has taken these into consideration during the drafting of this proposed rulemaking.
NMFS previously issued three Incidental Harassment Authorizations (IHAs) to Equinor and its predecessors for the taking of marine mammals incidental to marine site characterization surveys (using HRG equipment) of the Empire Wind Lease Area (OCS-A 0512) and cable corridors (these were not issued to Empire Wind as this subsidiary of Equinor had not yet been established). On April 24, 2018, NMFS issued an IHA to Statoil Wind U.S. LLC, effective from April 24, 2018, through April 23, 2019 (83 FR 19532; May 3, 2018) which included Lease
Area OCS-A 512 and associated cable route corridors. Since the initial IHA was issued, Statoil Wind U.S. LLC changed the name under which the company operates to Equinor. A renewal IHA was issued to Equinor and was effective from April 25, 2019 through April 24, 2020 (84 FR 18801) which covered the same area. A new IHA was issued to Equinor on September 25, 2020 (85 FR 60424) and was effective from September 20, 2020, to September 19, 2021 which included OCS-A 512 and associated cable routes.
To date, Equinor, the parent company of Empire Wind, has complied with all IHA requirements (
e.g.,
mitigation, monitoring, and reporting) of these IHAs. Information regarding Equinor's take estimates and monitoring results may be found in the Estimated Take of Marine Mammals section, and the full monitoring reports can be found on NMFS' website:
https://www.fisheries.noaa.gov/national/marine-mammal-protection/incidental-take-authorizations-other-energy-activities-renewable.
On August 1, 2022, NMFS announced proposed changes to the existing North Atlantic right whale vessel speed regulations to further reduce the likelihood of mortalities and serious to endangered right whales from vessel collisions, which are a leading cause of the species' decline and a primary factor in an ongoing Unusual Mortality Event (87 FR 46921). Should a final vessel speed rule be issued and become effective during the effective period of this ITA (or any other MMPA incidental take authorization), the authorization holder would be required to comply with any and all applicable requirements contained within the final rule. Specifically, where measures in any final vessel speed rule are more protective or restrictive than those in this or any other MMPA authorization, authorization holders would be required to comply with the requirements of the rule. Alternatively, where measures in this or any other MMPA authorization are more restrictive or protective than those in any final vessel speed rule, the measures in the MMPA authorization would remain in place. The responsibility to comply with the applicable requirements of any vessel speed rule would become effective immediately upon the effective date of any final vessel speed rule and, when notice is published of the effective date, NMFS would also notify Empire Wind if the measures in the speed rule were to supersede any of the measures in the MMPA authorization such that they were not longer required.
Description of the Specified Activity
Overview
Empire Wind proposes to construct and operate two offshore wind projects within OCS-A 0512: Empire Wind 1 (EW 1; western portion of Lease Area) and Empire Wind 2 (EW 2; eastern portion of Lease Area) (Figure 1). Combined the two projects would produce a total of approximately 2,076 megawatts (MW) of renewable energy to New York. EW 1 (816 MW) and EW 2 (1,260 MW) will be electrically isolated and independent of each other and each will be connected to their own points of interconnection (POIs) via individual submarine export cable routes.
Empire Wind's project would consist of several different types of permanent offshore infrastructure, including wind turbine generators (WTGs) and associated foundations, offshore substations (OSSs), inter-array cables, submarine export cables and scour protection. Specifically, activities to construct the project include the installation of up to 147 WTGs and two OSSs by impact pile driving (total of 149 foundations). Additional activities would include cable installation, site preparation activities (
e.g.,
dredging), HRG surveys, installation of cofferdams or casing pipes supported by goal post piles, removal of berthing piles and performing marina bulkhead work; and conducting several types of fishery and ecological monitoring surveys. Multiple vessels would transit within the project area and between ports and the wind farm to perform the work and transport crew, supplies, and materials. All offshore cables will connect to onshore export cables, substations, and grid connections on Long Island and Brooklyn, New York. Marine mammals exposed to elevated noise levels during impact and vibratory pile driving or site characterization surveys may be taken by Level A harassment and/or Level B harassment depending on the specified activity.
Activities Not Considered in Empire Wind's Request for Authorization
During construction, Empire Wind will receive equipment and materials to be staged and loaded onto installation vessels at one or more existing third-party port facilities. Empire Wind not yet finalized the selection of all facilities, although they will include the South Brooklyn Marine Terminal (SBMT) in Brooklyn, New York. SBMT has been selected as the location for export cable landfall and the onshore substation for EW 1. Empire Wind also has leased portions of SBMT for EW 1 and EW 2 for laydown and staging of wind turbine blades, turbines, and nacelles; foundation transition pieces; or other facility parts during construction of the offshore wind farm.
The final port selection(s) for staging and construction will be determined based upon whether the ports are able to accommodate Empire Wind's schedule, workforce and equipment needs. Any port improvement construction activities to facilitate laydown and staging would be conducted by a separate entity and would serve the broader offshore wind industry in addition to the Empire Wind Project. Empire Wind would, therefore, not be the applicant for the authorization of marine mammal take incidental to these activities if an authorization for incidental take is warranted, and these activities are not analyzed further in this proposed rule.
Empire Wind is not planning on detonating any unexploded ordnance (UXO) or munitions and explosives of concern (MEC) during the effective period of the proposed rule, if issued. Hence, Empire Wind did not analyze or request take associated with this activity as it would not occur. Other means of removing UXO/MEC may occur (
e.g.,
lift and shift). As UXO/MEC detonation would not occur, it is not discussed further in this analysis.
Dates and Duration
Empire Wind anticipates that activities with the potential to result in harassment of marine mammals would occur throughout all five years of the proposed regulations which, if promulgated, would be effective from January 22, 2024 through January 21, 2029.
The estimated schedule, including dates and duration, for various activities is provided in Table 1. Detailed information about the activities themselves may be found in the Detailed Description of the Specific Activity subsection.
Empire Wind anticipates that 96 WTG monopiles will be installed in 2025 and the remaining 51 WTG monopiles will be installed in 2026. Specifically, installation of WTG monopiles is expected to begin in the second quarter of 2025 and end in the fourth quarter of 2025 for both EW 1 and EW 2. Installation of monopile foundations would resume in EW 2 in the second quarter of 2026 and end in the fourth quarter of that year. OSS foundation installation would occur in 2025 for both EW 1 and EW 2; however, topside work on the EW 2 OSS would occur in 2026 and 2025 and 2026 (EW 2). While Empire Wind currently anticipates adherence to this schedule, it is possible
that foundations could be installed in later time periods (but within the 5-year effective period of the LOA) should permitting or scheduling delays occur).
Installation of foundation piles would not occur from January 1-April 30 in any given year. In addition, impact pile driving is not planned from December 1 through December 31 but could only occur if unanticipated delays due to weather or technical problems arise that necessitate extending pile driving into December in which case Empire Wind would notify NOAA Fisheries and BOEM in advance writing by September 1 that circumstances are expected to necessitate pile driving in December. Given this uncertainty, Empire Wind has included December into its analysis to be precautionary; however, pile driving is currently planned for May through November. Each monopile pile will require up to 3.5 hours of impact pile driving and each pin pile will require up to 5 hours of impact pile driving.
Either cofferdams or casing pipe and goal post installation may occur as part of cable landfall activities, but not both. EW 1 cable landfall work would occur sometime between Q1 to Q4 in 2024 while EW 2 cable landfall work would occur sometime between Q1 2024-Q4 2025. Depending on the construction method chosen, each cable landfall site would require 7-30 days of work. Exact dates and durations could shift depending on factors such as weather delays, procurement, or contracting issues
The anticipated activity schedule for all activities is shown in Table 1. Empire Wind anticipates that WTGs in EW 1 would become operational late in Q2 or early Q3 in 2026 while those in EW 2 would become operational in Q4 of 2027. Turbines would be commissioned individually by personnel on location, so the number of commissioning teams would dictate how quickly turbines would become operational.
Table 1—Estimated Activity Schedule To Construct and Operate the Empire Wind Project
Project activity
Expected timing EW 1
Expected timing EW 2
Submarine Export Cables
Q3 2024; Q3 2025
Q3-Q4 2025.
Offshore Substation Jacket Foundation and Topside
Q2
1
-Q4 2025
Q2
1
-Q4 2025; Q2
1
-Q4 2026.
2
Monopile Foundation Installation
Q2
1
-Q4 2025
Q2
1
-Q4 2025; Q2
1
-Q4 2026.
WTG Installation
Q4 2025-Q2 2026
Q4 2026-Q3 2027.
Interarray Cables
Q2-Q4 2025
Q2-Q3 2026.
HRG Surveys
Q1 2024-Q4 2028
Q1 2024-Q4 2028.
Cable Landfall Construction
Q1-Q4 2024
3
Q1 2024-Q4 2025.
3
Marina Activities
n/a
Q1-Q4 2024.
Barnum Channel Cable Bridge Construction
n/a
Q4 2024-Q2 2025.
Note:
Project activities are anticipated to start no earlier than Q1 2024.
1
Impact driving of foundation piles is prohibited between January 1 and April 30. During Q2 such activities could not start until May 1.
2
EW 2 OSS jacket installation is planned for 2025, only EW 2 topside work is planned for 2026.
3
While cable landfall construction could occur at any time during the time period identified would only occur for approximately 30 days.
Specific Geographic Region
Empire Wind would conduct activities in state waters and Federal waters within the designated Lease Area OCS-A 0512 (which covers approximately 321 square kilometers (km
2
; 79,350 acres) and New York state waters (See Figure 1)). The Lease Area is located in the New York Bight, approximately 14 miles (mi; 12 nautical miles (nm); 22 km) south of Long Island, New York, and 19.5 mi (16.9 nm; 31.4 km) east of Long Branch, New Jersey. The New York Bight is a section of the northwestern Atlantic Ocean that extends along the United States East Coast between Cape May, New Jersey in the southwest, to Montauk Point, New York in the northeast. It includes the waters over the continental shelf and offshore to the shelf break. It is part of the larger Mid-Atlantic Bight, which spans from Cape Hatteras, North Carolina to Cape Cod, Massachusetts. A number of estuaries drain into the New York Bight and provide spawning and nursery areas for many of the diadromous and marine species that utilize the New York Bight. Important geological features of the area include the Hudson Shelf Valley and Hudson Canyon, which provide habitat for deep-sea coral that shelters benthic invertebrates and fish. Nutrient-rich water created by water-column stratification from spring through fall, known as the cold pool, plays an essential role in the ecosystem and supports high biodiversity and phytoplankton productivity. The average temperature of the cold pool has increased due to changes to ocean circulation. The cold pool has been decreasing over the last several decades with the smallest sizes associated with warmer years while area fish distributions have shifted north or offshore (Zoidis
et al.,
2021). The geology and geomorphology in the New York Bight region are diverse with glacial deposits as a result of the Pleistocene Epoch sea level falls and rises, and more recent Flandrian transgression of sea level (Messina and Stoffer, 1996). Analysis of geophysical and geotechnical survey data collected across the Lease Area indicates the current geological conditions underlying the Lease Area are generally flat.
Water depths vary within the Lease Area from 24 m (78 ft) to 44 m (144 ft), with deeper water depths in the southeast portion of the Lease Area. From June to September, the average temperature of the upper (10-15 m) water column is higher, which can lead to a surface layer of increased sound speeds (Kusel
et al.
2022). This creates a downward refracting environment in which propagating sound interacts with the seafloor more than in a well-mixed environment. Increased wind mixing combined with a decrease in solar energy during winter, from December through March, results in a sound speed profile that is more uniform with depth.
Sediments in the project area are characterized as predominantly sands and fine sands in the New York Bight area, which includes the Lease Area and most of the submarine export cable routes, to predominantly clays and silts in New York Bay, which includes a section of the EW 1 submarine export cable route. Impact pile driving would occur in a continental shelf environment characterized by predominantly fine to coarse grained sandy seabed sediments, with some clay content.
The EW 1 submarine export cable route exits the Lease Area from the northwestern edge of the Lease Area and will travel northwest through Raritan Bay to the EW 1 export cable landfall in
Brooklyn, New York. Current geological conditions underlying the EW 1 submarine export cable route trend with shoaling towards the shore, and with more significant variation in the bathymetry closer to shore, where dredging patterns influence the seabed. Water depths vary along the EW 1 submarine export cable route from 5.9 m (19.4 ft) to 31.7 m (104.0 ft). Several channels exist along the submarine export cable route, both natural and anthropogenic. The general gradient along the cable is less than 1 degree, although isolated gradients of up to five degrees exist along the near shore portion of the route.
The EW 2 submarine export cable route exits the Lease Area from the central portion of the Lease Area and travels in a northwestern direction in a relatively straight line until turning north to the EW 2 export cable landfall in Long Beach, New York. Conditions along the EW 2 submarine export cable route exhibit a general trend of shoaling towards the shore. Water depth variations range, in the current surveyed and interpreted portion of the route, from 21.5 m (70 ft) to 35.5 m (116 ft). The slope gradient along the EW 2 submarine export cable route reaches a maximum of 1 degree.
Impact pile driving activities to install monopile and the piled jacket foundations will occur within the proposed WTG and offshore substation layout within EW 1 (Figure 3 in application). The WTGs and offshore substations will be located in the Wind Farm Development Area (WFDA), which is a subset of the Lease Area. EW 1 is located in the northwest portion of the WFDA. Additionally, impact pile driving activities to install monopile and the piled jacket foundations will occur within the proposed WTG and offshore substation layout within EW 2 (Figure 3 in application). EW 2 is located in the southeast portion of the WFDA.
Cable Landfall activities for EW 1 would occur at the South Brooklyn Marine Terminal in Brooklyn, NY along the waterfront and adjacent to 1st Avenue/2nd Avenue (Figure 1 in Application). The EW 1 submarine export siting corridor itself begins on the northern edge of the EW 1 portion of the WFDA and extends northwest for approximately 40 nm (74 km). EW 2 landfall locations would occur at one of the following locations: Landfall A (Riverside Boulevard); EW 2 Landfall B (Monroe Boulevard); EW 2 Landfall C (Lido Beach West Town Park); or Landfall E (Laurelton Boulevard). The final location is still being determined. The EW 2 submarine export siting corridor itself begins on the northwest corner of the EW 2 portion of the WFDA and extends northwest for approximately 26 nm (48 km).
All marina activities, both the berthing pile removal and bulkhead work, would be conducted at the Onshore Substation C location along inshore Long Island on the Wreck Lead Channel. Wreck Lead Channel adjoins Reynolds Channel. Reynolds Channel's median salinity is 30-32 practical salinity units (PSU) and dissolved oxygen levels range from 6-12 milligrams per decilitre (mg/dL), decreasing seasonally with warming temperatures. The sediments in the New York Bight, outer harbor, and barrier islands region are composed primarily of sand, gravel, silt, and clay. Currents in the area are minimal and are expected to be similar to those reported at Rockaway Inlet, which vary between 0.0 and 1.0 knots.
BILLING CODE 3510-22-P
EP13AP23.110
BILLING CODE 3510-22-C
Detailed Description of Specific Activity
Below, we provide detailed descriptions of Empire Wind's activities, explicitly noting those that are anticipated to result in the take of marine mammals and for which incidental take authorization is requested. Additionally, a brief explanation is provided for those activities that are not expected to result in the take of marine mammals.
WTG and OSS Foundation Installation
As described above, Empire Wind would construct two independent
projects under these proposed regulations: EW 1 and EW 2. In total, 147 WTGs would be installed. Turbine size includes either 9.6 or 11-m diameter piles driven to a penetration depth of 38 m or 55 m respectively. Both of the 9.6-m and 11-m piles would be installed using a 5,500 kilojoule (kJ) impact pile driver, although only up to 5,225 kJ would be necessary for the 9.6-m piles and up to 2,500 kJ would be used for 11-m piles. Empire Wind anticipates installing up to 57 WTG monopile foundations and 1 OSS jacket foundation for EW 1 and up to 90 WTG monopile foundations and 1 OSS jacket foundation for EW 2. Only one foundation is proposed to be installed via pile driving at a given time (
i.e.,
no concurrent foundation-specific pile driving activities are proposed) and there would be no overlap in pile driving activities between EW 1 and EW 2. WTGs turbines would be installed in clearly marked rows aligned with the dominant trawl directions when feasible. Minimum spacing of no less than 0.65 nm (1.2 km) in a north-south orientation will be maintained between WTGs. Additionally, the layout maintains a 1 nm setback from existing shipping lanes.
Monopile installation techniques are as follows. Once the installation vessel is in place, the steel pile is lifted into a vertical position and lowered onto the seabed. The steel pile is then driven into the seabed. Pile driving is conducted with the use of a large crane mounted hydraulic impact hammer being dropped, or driven, onto the top of a foundation pile, and driving it into the ground to a penetration depth of up to 38 m for 9.6-m piles and 55 m for 11-m piles. Each monopile pile will require a maximum of up to 3.5 hours of impact pile driving. All monopiles would be installed using impact hammers capable of reaching 5,500 kJ of energy. Typically, 9.6-m piles would require a maximum energy level of 2,300 kJ; however, there may be positions (up to 17) wherein the pile is difficult to drive due to seabed conditions. These difficult-to-drive piles would require hammer energies up to 5,225 kJ. Typically, 11-m piles require an energy level of up to 2,500 kJ. An additional hammer energy schedule was generated for difficult-to-drive monopiles (the difficult-to-drive hammer energy schedule was generated only for the 9.6-m diameter scenario as larger diameter monopiles could not be driven in difficult-to-drive conditions).
Installation of each monopile will include a 20-minute soft-start where lower hammer energy is used at the beginning of each pile installation. Following pile driving, the transition piece and secondary ancillary equipment are installed onto the steel pile. Only one foundation is proposed to be installed via pile driving at a given time and there will be no overlap in pile driving activities between EW 1 and EW 2.
Installation of the OSS foundations would be similar to WTG foundation installation. Pin piles (2.5 m) for jacket foundations would be installed via impact driving and would require the installation of up to 12 pin piles per OSS. Once the installation vessel is in place, the jacket structure is lifted from the vessel and lowered onto the seabed. The support piles are placed in the jacket structure and then driven into the seabed. The piles will be driven using the same methodology as described for monopiles. Each pin pile will require a maximum of up to 4.2 hours of impact pile driving. Pin piles at both OSSs would require use of a hammer with an energy level of 4,000 kJ. However, the maximum energy level would be 3,200 kJ at each location. The OSS 1 location would have a penetration depth of 56 m while OSS 2 would have a penetration depth of 47 m. Installation of each pin pile would include a 20-minute soft-start where lower hammer energy is used at the beginning of each pile installation. Following pile driving of the pin piles, the jacket structure is secured to the driven piles.
Seabed preparation will include installation of a filter layer prior to monopile installation and an armor layer after cable installation on each WTG location. The filter layer and armor layer are rock layers installed on the seabed to prevent scour due to flow increase around the monopiles. This activity would not have any impacts on marine mammals.
Foundation installation is scheduled for May through November in 2025 and 2026. Pile driving in December would not occur unless unforeseen circumstances arise. Foundation installation pile driving would not occur January 1-April 30 of any year. Pile driving would occur during daylight hours, only extending into night if Empire Wind starts installing a pile 1.5 hours prior to civil sunset.
Installation of WTG monopile foundations and OSS pin piles are anticipated to result in the take of marine mammals due to noise generated during pile driving. Therefore, Empire Wind has requested, and NMFS proposes to authorize, take (by Level A harassment and Level B harassment) of marine mammals incidental to foundation installation.
Cable Landfall Construction
To connect the offshore export cable to the onshore cable, Empire Wind proposes to conduct construction related activities at two cable landfall sites. The export cable landfall for the EW 1 export cables will occur at SBMT, located along the Brooklyn waterfront and adjacent to 1st Avenue/2nd Avenue. The cable landfall site for EW2 has not yet been chosen but will occur somewhere between Jones Beach to Long Beach, NY. Installation of the export cable landfall will be accomplished using a horizontal directional drilling (HDD) methodology. HDD operations for an export cable landfall originate from an onshore landfall location and exit a certain distance offshore, which is determined by the water depth contour, as well as total length considerations. To support this installation, both onshore and offshore work areas are required. The onshore work areas are typically located within the landfall parcels. Target transition depths of landfall HDD paths vary by the length of the HDD, up to approximately 80 ft (24 m). Once the onshore work area is set up, the HDD activities commence using a rig that drills a borehole underneath the surface. Once the drill for the HDDs exits onto the seafloor, the ducts in which the submarine cable will be installed are floated out to sea and then pulled back onshore within the drilled borehole. The offshore exit locations require some seafloor preparation to collect any drilling fluids that localize during HDD completion. Preparation will include excavation of pits at each offshore exit location. To facilitate the retaining of drilling fluids, Empire Wind may utilize a casing pipe supported by goal posts on the exit side from a jack-up barge or cofferdams (but not both). The jack-up barge will also house the drill rig.
If Empire Wind installs temporary cofferdams to facilitate transition of the export cable to the onshore cable, up to five cofferdams would be required (up to two cofferdams for EW 1 and three cofferdams for EW 2). Each cofferdam would be installed using vibratory driving over 3 days and removed over 3 days for a total of 6 days for each cofferdam (or 30 days total (5 cofferdams × 6 days of pile driving per cofferdam)). Empire Wind anticipates only 1 hour of pile driving would be required each day (30 hours total). The temporary offshore cofferdams will be constructed by installing up to 60 0.61-m (24-inch) steel sheet piles per cofferdam in a tight configuration around an area of up to 30 m by 30 m (100 ft by 100 ft). A total of up to five
temporary cofferdams may be constructed (two cofferdams for EW 1 and three cofferdams for EW 2). Variation in the final cofferdam design is possible, with designs ranging from 30 to 40 sheet piles per cofferdam. To be conservative, up to 60 sheet piles per cofferdam have been accounted for in the modeling (see Estimated Take of Marine Mammals section). Sheet piles would be installed with a vibratory hammer. Vibratory pile drivers install piling into the ground by applying a rapidly alternating force to the pile. This is generally accomplished by rotating eccentric weights about shafts. Each rotating eccentric produces a force acting in a single plane and directed toward the centerline of the shaft. The weights are set off-center of the axis of rotation by the eccentric arm. If only one eccentric is used, in one revolution a force will be exerted in all directions, giving the system a good deal of lateral whip. To avoid this problem, the eccentrics are paired so the lateral forces cancel each other, leaving only axial force for the pile.
Seabed preparation may also be completed with installation of a cofferdam for each HDD and an excavation pit to remove material from the cofferdam. The pit would likely be excavated using a bucket—there are no acoustic impacts from this activity if it were to occur and therefore no potential for take.
An alternative to the use of cofferdams for the cable landfall would be the use of a casing pipe supported by up to 3 goal posts. The casing pipe at each landfall location would likely be a 42″ pipe installed with a pneumatic hammer. Empire Wind estimates it would take approximately 4 hours to install the casing pipe with a strike rate of 180 strikes/minute. Each goal post would consist of two piles for a total of 18 piles at each landfall location. Each goal post pile would be installed with an impact hammer requiring up to 2,000 strikes per pile over 2 hours. In total, up to 36 hours (18 piles × 2 hours per pile) of impact pile driving to install three goal posts may occur.
For the goal post installation process, a barge with necessary support equipment is first mobilized and anchored into position. The support equipment on the barge will include at least one crane, a hydraulic impact hammer mounted at the end of the crane hook or load block, and the piles to be driven. An additional crane or similar equipment may also be located on the support barge to aid in the handling of the goal post piles. For each HDD installation, it is estimated that three goal posts will need to be installed to support the casing pipe. Therefore, for each HDD installation there could be up to ten 12-inch piles. For each goal post, a total of two 12-inch steel piles must be driven to complete a single goal post installation, with 2,000 strikes per pile. The piles are installed by attaching the hydraulic hammer to the end of the pile, and lifting the hydraulic hammer with the crane, and swinging the pile into place for the goal post installation. The hydraulic hammer then drives the pile into the subsea floor by repeated percussive blows until the pile reaches a sufficient depth where enough strength to support the casing pipe is achieved. This process is repeated until all piles necessary for the goal post are installed.
HRG Surveys
Empire Wind would conduct HRG surveys in the EW 1 and EW 2 marine environment of the approximately 321 km
2
(79,350 acres) Lease Area and along the submarine export cable route corridors, inter-array cable locations, and export cable landfall sites. The HRG survey activities will include the following equipment summarized in Table 2, or comparable sources. HRG site characterization surveys would occur annually throughout the five years the rule and LOA would be effective.
Empire Wind would conduct HRG surveys within the lease area and the export cable corridor, including the cable landfall sites. The estimated distance of the daily vessel track line was determined using the estimated average speed of the vessel and the 24-hour operational period within each of the corresponding survey segments. Empire Wind proposes to use up to three vessels to conduct the surveys. The estimated daily vessel track for all vessels is approximately 177.792 km (110.475 mi) for 24-hour operations with a daily ensonified area of 17.8 km
2
. The number of active survey vessel days ranges from 41 (in 2024) to 191 (in 2025). There would be an anticipated 483 survey days over the 5-year LOA period covering 85,872 km. The duration of each survey varies as described in Table 11 in the application. The survey schedule is based on 24-hour operations and includes estimated weather down time.
These surveys may utilize active acoustic equipment such as multibeam echosounders, side scan sonars, shallow penetration sub-bottom profilers (SBPs) (
e.g.,
Compressed High-Intensity Radiated Pulses (CHIRPs) non-parametric SBP), medium penetration sub-bottom profilers (
e.g.,
sparkers and boomers), ultra-short baseline positioning equipment, and marine magnetometers, some of which are expected to result in the take of marine mammals. Surveys would occur annually, with durations dependent on the activities occurring in that year (
i.e.,
construction years versus operational years).
Of the HRG equipment types proposed for use, only Shallow penetration sub-bottom profilers (SBPs) have the potential to result in take. SBPs would be used to map the near-surface stratigraphy (top 0 to 5 m (0 to 16 ft) of sediment below seabed). A CHIRP system emits sonar pulses that increase in frequency over time. The pulse length frequency range can be adjusted to meet project variables. These are typically mounted on the hull of the vessel or from a side pole. Boomers and sparkers would not be used during HRG surveys.
Table 2 identifies all the representative survey equipment that operate below 180 kilohertz (kHz) (
i.e.,
at frequencies that are audible and have the potential to disturb marine mammals) that may be used in support of planned geophysical survey activities. Equipment with operating frequencies above 180 kHz (
e.g.,
SSS, MBES) and equipment that does not have an acoustic output (
e.g.,
magnetometers) will also be used but are not discussed further because they are outside the general hearing range of marine mammals likely to occur in the project area. No harassment exposures can be reasonably expected from the operation of these sources; therefore, they are not considered further in this proposed action.
Table 2—Summary of Representative HRG Survey Equipment
Representative HRG equipment
a
Operating
frequencies
(kHz)
RMS source
level
Peak source
level
Primary
beamwidth
(degrees)
Pulse
duration
(milliseconds (ms))
Pulse
repetition
(Hz)
Kongsberg HiPAP 501/502 USBL
21—31
190
207
Omni
2
0.5-2
iXblue, IxSea GAPS Beacon System
8-16
188
194
Omni
10
1
Sonardyne Ranger 2 and Mini Ranger 2 USBL HPT 3000/5/7000
19-34
200
206
Omni
5
1
Reson Seabat T20P multibeam echosounder
a
200-400
221
227
90
0.253
Reson 7111
100
224
228
6
1.35
Kongsberg EM2040Quad
200-400
-
-
-
-
R2 Sonic 2026
170-450
191
221
1
1.115
R2 Sonic 2024
200-700
-
-
-
-
Klein 3900 SSS
a
445-900
200
226
1.8
0.1
EdgeTech DW106
1 to 6
194
197
Omni
<66
8
EdgeTech 424
a
4-20
180
186
122
4.8
Innomar, SES-2000 compact
85-115
232
238
4
40
1
Innomar, SES-2000 Light & Light Plus
85-115
232
238
4
40
1
Innomar, SES-2000 Standard & Standard Plus
85-115
234
240
1-3.5
60
1.5
Innomar, SES-2000 Smart
90-110
229
235
5
40
0.5
Innomar, SES-2000 Medium-70
60-80
240
246
3
40
5
Teledyne Benthos Chirp III-TTV 170
2 to 7
219
225
100
60
15
Coda Octopus 3D
240-300
-
-
-
-
20
Note:
a
Equipment specifications found in the 2016 Crocker and Fratantonio Report. Equipment selected would be the same or similar.
“-” indicates Empire Wind was unable to provide this information; however, it is not relevant to the analysis herein.
Based on the operating frequencies of some types of HRG survey equipment and the hearing ranges of the marine mammals that have the potential to occur in the Project Area, HRG survey activities will have the potential to result in Level B harassment of marine mammals. No Level A harassment is anticipated as a result of HRG survey activities.
Onshore Substation C Marina Activities
Construction activities will also be completed to facilitate the connection of the cables to Onshore Substation C, located inshore Long Island on the Wreck Lead Channel, as shown in Figure 1. Work includes removing berthing piles and bulkhead repair. Up to 130 12-inch diameter timber berthing piles would be removed using a combination of a crane and vibratory hammer, depending on the condition of the piles. Two piles would be removed each hour with up to 15 piles per day (7-8 hours per day) with approximately 130 piles removed over the course of two weeks for a total of approximately 65 hours. Vibratory installation of 24-inch z-type steel sheet piles would also occur at the marina bulkheads, consisting of 20 piles per day, with installation occurring for approximately 1 hour of noise generation time per day for 35 days.
The onshore substation will be used to transform and prepare the power received by the export cables from EW 2 for connection to the points of interconnection (POIs) in New York. SMBT Vibratory installation of sheet piles would also occur at the marina bulkheads, consisting of 20 piles per day, with installation occurring for approximately 1 hour of noise generation time per day for 35 days for a total of 700 sheet piles between Q1-Q4 for EW 1 and EW 2 in 2024 and between Q1-Q4 for EW 2 in 2025.
Barnums Channel Cable Bridge Activities
The cable bridge structure for EW 2 only requires two support columns (pile caps) located within the waterway to support the truss system, which will hold the cables above water. The support may be installed by a hammer, but other methods are under consideration. There could be up to six 1.5 ft (0.5 meter) diameter steel pipe piles per cap for a total of 12 steel pipe piles. The location is in an inland waterway near the Barrett Generation Station in an industrialized section of the island, where water depths are only 1 meter, therefore, marine mammals, including seals, are not expected. Sightings data support this assumption, as no sightings of seals have been recorded in the vicinity (OBIS 2023). No take is anticipated from this activity.
Cable Laying and Installation
Submarine export cables will be installed from specialized installation vessels/barges, which will install the cables from a turntable on the lay vessel/barge. One or several vessels might be used for the installation of the cables depending on a number of factors, such as seabed depth, depth of cable protection, distance to shore, and cable protection method to be used. There are several cable installation and burial methods being considered. Some activities will be performed before the installation of the cables, some during the installation of the cables, and some after the installation of the cables. Cable pre-lay activities may include pre-installation grapnel run, route clearance and boulder removal, pre-sweeping, dredging and pre-trenching. The cable burial methods being considered are plowing, jetting, trenching, and dredging. The equipment selected will depend on seabed conditions, the required burial depths, as well as the results of various cable burial studies. More than one installation and burial method may be selected per route and has the potential to be used pre-installation, during installation, and/or post-installation.
Installation of the submarine export cables is expected to take approximately four months for the EW 1 submarine export cables and approximately four months for the EW 2 submarine export cables. The actual installation schedule will be subject to seabed characteristics, installation vessel availability, seasonal restriction windows for protected species, and weather. Installation of the EW 1 and EW 2 submarine export cables may occur at the same time; however,
any overlap in installation activities would not occur at the same stage (
i.e.,
pre-installation activities may commence for EW 2 while the cable lay and burial for EW 1 is being completed).
The noise levels generated from cable laying and installation work are low so the potential for take of marine mammals to result is discountable. Empire Wind is not requesting, and NMFS is not proposing to authorize, take associated with cable laying activities. Therefore, cable laying activities are not analyzed further in this document.
Vessel Operation
Multiple vessels will be in use during construction and operations. Empire Wind estimates that the Project will require approximately 18 vessels for construction of EW 1 and approximately 18 vessels for construction of EW 2. Vessels including barges, tugboats, crew transfer vessels, heavy transport vessels, and various supply vessels are expected to be utilized. Helicopters may also be used to provide site support (Table 3).
Table 3—Preliminary Summary of Offshore Vessels for Construction
Foundations
Vessel
Description
Monopile
Piled Jacket
Wind
turbines
Offshore Substation Topside &
Foundation
Substation Topside & Foundation
Submarine Export
Cables
Interarray Cables
Scour
Protection
Heavy lift vessel
Vessel for installation of foundations
X
X
X
Monopile supply vessel
Vessel for transport of monopile foundations
X
Wind turbine installation vessel
Vessel for installation of wind turbine components
X
Wind turbine supply vessel
Vessel for transport of wind turbine components
X
Cable lay vessel/barge
Vessel for installation of submarine cables
X
X
Heavy transport vessel
Vessel for transport of offshore substation topside
X
X
X
Cable lay support vessel
Support vessel for cable lay operations
X
X
Pre-lay grapnel run vessel
Vessel for seabed clearance along cable routes
X
X
Fall pipe vessel
Vessel for installation of scour protection
X
X
X
X
X
X
Crew transfer vessel
Vessel for transporting workers to and from shore
X
X
X
X
X
X
Accommodation vessel
Vessel for worker accommodations
X
Construction support vessel
Vessel for general construction support
X
X
X
X
Tugboat
Vessel for transporting and maneuvering barges
X
X
X
X
X
Barge
Vessel for transport of construction materials
X
X
X
X
Safety vessel
Vessel for protection of construction areas
X
X
X
X
Fisheries and Benthic Monitoring
Empire Wind will engage in various fisheries and benthic monitoring surveys that have been designed for the Project in accordance with recommendations set forth in “Guidelines for Providing Information on Fisheries for Renewable Energy Development on the Atlantic Outer Continental Shelf” (BOEM 2019). Empire Wind would conduct a number of surveys including trawl surveys, baited underwater video surveys, and hard bottom monitoring surveys.
Because the gear types and equipment used for benthic habitat monitoring, and Habcam surveys do not have components with which marine mammals are likely to interact (
i.e.,
become entangled in or hooked by), these activities are unlikely to have any impacts on marine mammals. Only trawl surveys, in general, have the potential to result in harassment to marine mammals. Empire Wind did not propose to implement mitigation measures to avoid take of marine mammals incidental to trawl surveys; however, NMFS has included them in this proposed rule (see Proposed Mitigation). With the implementation of those measures, NMFS does not anticipate, and is not proposing to authorize, take associated with fisheries and benthic monitoring surveys.
Description of Marine Mammals in the Area of Specified Activities
Thirty-eight marine mammal species under NMFS' jurisdiction have geographic ranges within the western North Atlantic OCS (Hayes
et al.,
2022). However, for reasons described below, Empire Wind has requested, and NMFS proposes to authorize, take of 17 species (comprising 18 stocks) of marine mammals. Sections 3 and 4 of Empire Wind's application summarize available information regarding status and trends, distribution and habitat preferences, and behavior and life history of the potentially affected species (Empire Wind, 2022). NMFS fully considered all of this information, and we refer the reader to these descriptions in the application, incorporated here by reference, instead of reprinting the information. Additional information regarding population trends and threats may be found in NMFS's Stock Assessment Reports (SARs;
https://www.fisheries.noaa.gov/national/marine-mammal-protection/marine-mammal-stock-assessments
) and more
general information about these species (
e.g.,
physical and behavioral descriptions) may be found on NMFS's website (
https://www.fisheries.noaa.gov/find-species).
Of the 38 marine mammal species in the Atlantic OCS under NMFS' jurisdiction, 21 are not expected to be present or are considered rare or unexpected in the project area based on sighting and distribution data; they are, therefore, not discussed further beyond the explanation provided here. The following species are not expected to occur in the project area due to the location of preferred habitat outside the Empire Wind project area based on the best scientific information available: blue whale (
Balaenoptera musculus
), dwarf and pygmy sperm whales (
Kogia sima and K. breviceps
), northern bottlenose whale (
hyperoodon ampullatus
), cuvier's beaked whale (
Ziphius cavirostris
), four species of Mesoplodont beaked whales (
Mesoplodon densitostris, M. europaeus, M. mirus, and M. bidens
), killer whale (
Orcinus orca
), false killer whale (
Pseudorca crassidens
), pygmy killer whale (
Feresa attenuate
), melon-headed whale (
Peponocephala electra
), white-beaked dolphin (
Lagenorhynchus albirotris
), pantropical spotted dolphin (
Stenella attenuata
), Clymene dolphin (
Stenella clymene
), striped dolphin (
Stenella coeruleoalba
), spinner dolphin (
Stenella longirostris
), Fraser's dolphin (
Lagenodelphis hosei
), and rough-toothed dolphin (
Steno bredanensis
) and the hooded seal (
Cystophora cristata
).
In addition, Florida manatees (
Trichechus manatus;
a sub-species of the West Indian manatee) have been previously documented as an occasional visitor to the Northeast region during summer months. However, manatees are managed by the U.S. Fish and Wildlife Service and are not considered further in this document.
In anticipation of the Empire Wind Project, Equinor (prior to establishing its subsidiary, Empire Wind) conducted 12 monthly aerial digital surveys of Empire Wind Lease Area OCS-A 0512 in the New York Bight between November 2017 and October 2018 using APEM Inc.'s high-resolution camera system to capture digital still imagery. Raw counts and design-based abundance estimates of all species and incidental observations recorded during the surveys are presented here as well as information on species distribution, flight height and flight direction. The key findings from each of the monthly aerial digital surveys are summarized below. (Normandeau-APEM, 2019). Common dolphins were the most abundant marine mammal species recorded, with a peak count (n=68) in the May survey, followed by bottlenose dolphins, with a peak raw count (n=22) in the June survey. Harbor porpoises, minke whales and a single humpback whale were also recorded, as were three unidentified dolphins and three unidentified marine mammals. Marine mammals were recorded in peak numbers in spring. Equinor's required marine mammal monitoring report as part of HRG surveys covering Lease Area OCS-A 0512 and the associate export cable routes from September 20, 2020 through September 19, 2021 reported sightings of humpback whales, bottlenose dolphins, common dolphins, unidentifiable dolphin species, and harbor seals. Between April 19, 2019 through July 22, 2019, Equinor also observed fin whales, humpback whales, unidentified whales, common bottlenose dolphins, unidentifiable dolphins, and gray seals during HRG surveys. The lack of detections of any of the 22 species listed above during these surveys reinforces the fact that they are not expected to occur in the project area. As these species are not expected to occur in the project area during the proposed activities, Equinor did not request, and NMFS does not propose to authorize, take of these species, and they are not discussed further in this document.
Table 4 lists all species and stocks for which take is expected and proposed to be authorized for this action, and summarizes information related to the population or stock, including regulatory status under the MMPA and Endangered Species Act (ESA) and potential biological removal (PBR), where known. PBR is defined by the MMPA as the maximum number of animals, not including natural mortalities, that may be removed from a marine mammal stock while allowing that stock to reach or maintain its optimum sustainable population (16 U.S.C. 1362(20)), as described in NMFS's SARs. While no mortality is anticipated or proposed to be authorized, PBR and annual serious injury and mortality from anthropogenic sources are included here as gross indicators of the status of the species and other threats.
Marine mammal abundance estimates presented in this document represent the total number of individuals that make up a given stock or the total number estimated within a particular study or survey area. NMFS's stock abundance estimates for most species represent the total estimate of individuals within the geographic area, if known, that comprises that stock. For some species, this geographic area may extend beyond U.S. waters. All managed stocks in this region are assessed in NMFS's U.S. Atlantic and Gulf of Mexico SARs. All values presented in Table 4 are the most recent available at the time of publication and are available in NMFS' final 2021 SARs (Hayes
et al.,
2022) and draft 2022 SARs available online at:
https://www.fisheries.noaa.gov/national/marine-mammal-protection/draft-marine-mammal-stock-assessment-reports.
T able 4—Marine Mammal Species Likely To Occur Near the Project Area That May Be Taken by Empire Wind's Activities
Common name
Scientific name
Stock
ESA/
MMPA
status;
strategic
(Y/N)
1
Stock abundance
(CV, N
min
, most recent
abundance survey)
2
PBR
Annual
M/SI
3
Order Artiodactyla—Cetacea—Superfamily Mysticeti (baleen whales)
Family Balaenidae:
North Atlantic right whale
Eubalaena glacialis
Western Atlantic
E, D, Y
338 (0; 332; 2020)
5
0.7
8.1
Family Balaenopteridae (rorquals):
Fin whale
Balaenoptera physalus
Western North Atlantic
E, D, Y
6,802 (0.24; 5,573; 2016)
11
1.8
Sei whale
Balaenoptera borealis
Nova Scotia
E, D, Y
6,292 (1.02; 3,098; 2016)
6.2
0.8
Minke whale
Balaenoptera acutorostrata
Canadian Eastern Coastal
-, -, N
21,968 (0.31; 17,002; 2016)
170
10.6
Humpback whale
Megaptera novaeangliae
Gulf of Maine
-, -, Y
1,396 (0; 1,380; 2016)
22
12.15
Superfamily Odontoceti (toothed whales, dolphins, and porpoises)
Family Physeteridae:
Sperm whale
Physeter macrocephalus
North Atlantic
E, D, Y
4,349 (0.28; 3,451; 2016)
3.9
0
Family Delphinidae:
Atlantic white-sided dolphin
Lagenorhynchus acutus
Western North Atlantic
-, -, N
93,233 (0.71; 54,433; 2016)
544
27
Atlantic spotted dolphin
Stenella frontalis
Western North Atlantic
-, -, N
39,921 (0.27; 32,032; 2016)
320
0
Common bottlenose dolphin
Tursiops truncatus
Western North Atlantic Offshore
-, -, N
62,851 (0.23; 51,914; 2016)
519
28
Migratory Coastal
-, -, N
6,639 (0.41; 4,759; 2016)
48
12.2-21.5
Long-finned pilot whales
Globicephala melas
Western North Atlantic
-, -, N
39,215 (0.3; 30,627; 2016)
306
29
Short-finned pilot whales
Globicephala macrorhynchus
Western North Atlantic
-, -, N
28,924 (0.24; 23,637; 2016)
236
136
Risso's dolphin
Grampus griseus
Western North Atlantic
-, -, N
35,215 (0.19; 30,051; 2016)
301
34
Common dolphin (short-beaked)
Delphinus delphis
Western North Atlantic
-, -, N
172,897 (0.21; 145,216; 2016)
1,452
390
Family Phocoenidae (porpoises):
Harbor porpoise
Phocoena phocoena
Gulf of Maine/Bay of Fundy
-, -, N
95,543 (0.31; 74,034; 2016)
851
16
Order Carnivora—Superfamily Pinnipedia
Family Phocidae (earless seals):
Gray seal
4
Halichoerus grypus
Western North Atlantic
-, -, N
27,300 (0.22; 22,785; 2016)
1,458
4,453
Harbor seal
Phoca vitulina
Western North Atlantic
-, -, N
61,336 (0.08; 57,637; 2018)
1,729
339
Harp seal
6
Pagophilus grownlandicus
Western North Atlantic
-, -, N
7,600,000 (UNK, 7,100,000
426,000
178,573
1
ESA status: Endangered (E), Threatened (T)/MMPA status: Depleted (D). A dash (-) indicates that the species is not listed under the ESA or designated as depleted under the MMPA. Under the MMPA, a strategic stock is one for which the level of direct human-caused mortality exceeds PBR or which is determined to be declining and likely to be listed under the ESA within the foreseeable future. Any species or stock listed under the ESA is automatically designated under the MMPA as depleted and as a strategic stock.
2
NMFS marine mammal stock assessment reports online at:
www.fisheries.noaa.gov/national/marine-mammal-protection/marine-mammal-stock-assessments
(Hayes
et al.,
2022). CV is the coefficient of variation; Nmin is the minimum estimate of stock abundance. In some cases, CV is not applicable.
3
These values, found in NMFS' SARs, represent annual levels of human-caused mortality plus serious injury from all sources combined (
e.g.,
commercial fisheries, ship strike).
4
NMFS' stock abundance estimate (and associated PBR value) applies to the U.S. population only. Total stock abundance (including animals in Canada) is approximately 451,431. The annual M/SI value given is for the total stock.
5
On Monday, October 24, 2022, the North Atlantic Right Whale Consortium announced that the North Atlantic right whale population estimate for 2021 was 340 individuals. NMFS' website also indicates that less than 350 animals remain (
https://www.fisheries.noaa.gov/species/north-atlantic-right-whale
).
6
Harp seals are rare in the region; however, stranding data suggest this species may be present during activities that may take marine mammals.
As indicated above, all 17 species and 18 stocks in Table 4 temporally and spatially co-occur with the activity to the degree that there is a potential for take. Four of the marine mammal species for which take is requested are listed as threatened or endangered under the ESA, including North Atlantic right, fin, sei, and sperm whales. In addition to what is included in Sections 3 and 4 of Empire Wind's application (
https://www.fisheries.noaa.gov/action/incidental-take-authorization-empire-offshore-wind-llc-construction-empire-wind-project-ew1?check_logged_in=1
), the SARs (
https://www.fisheries.noaa.gov/national/marine-mammal-protection/marine-mammal-stock-assessments
), and NMFS' website (
https://www.fisheries.noaa.gov/species-directory/marine-mammals
), we provide further detail below informing the baseline for select species (
e.g.,
information regarding current Unusual Mortality Events (UME) and known important habitat areas, such as Biologically Important Areas (BIAs) (Van Parijs, 2015). There is no ESA-designated critical habitat for any species within the project area.
Under the MMPA, a UME is defined as “a stranding that is unexpected; involves a significant die-off of any marine mammal population; and demands immediate response” (16 U.S.C. 1421h(6)). As of January 24, 2023, five UMEs in total are considered active, with four of these occurring along the U.S. Atlantic coast for various marine mammal species; of these, the most relevant to the Empire Wind Project are the right whale, humpback whale, and northeast pinniped UMEs, given the prevalence of these species in the project area. More information on UMEs, including all active, closed, or pending, can be found on NMFS' website at
https://www.fisheries.noaa.gov/national/marine-life-distress/active-and-closed-unusual-mortality-events.
Below we include additional information for a subset of the species that presently have an active or recently closed UME occurring along the Atlantic coast, or for which there is information available related to areas of biological significance. For the majority of species potentially present in the specific geographic region, NMFS has designated only a single generic stock (
e.g.,
“western North Atlantic”) for management purposes. This includes the “Canadian east coast” stock of minke whales, which includes all minke whales found in U.S. waters and is also
a generic stock for management purposes. For humpback and sei whales, NMFS defines stocks on the basis of feeding locations,
i.e.,
Gulf of Maine and Nova Scotia, respectively. However, references to humpback whales and sei whales in this document refer to any individuals of the species that are found in the specific geographic region. Any areas of known biological importance (including the BIAs identified in La Brecque
et al.,
2015) that overlap spatially with the project area are addressed in the species sections below.
North Atlantic Right Whale
The North Atlantic right whale has been listed as Endangered since the ESA was enacted in 1973. They were recently uplisted from Endangered to Critically Endangered on the International Union for Conservation of Nature (IUCN) Red List of Threatened Species (Cooke, 2020). The uplisting was due to a decrease in population size (Pace
et al.,
2017), an increase in vessel strikes and entanglements in fixed fishing gear (Daoust
et al.,
2017; Davis & Brillant, 2019; Knowlton
et al.,
2012; Knowlton
et al.,
2022; Moore
et al.,
2021; Sharp
et al.,
2019), and a decrease in birth rate (Pettis
et al.,
2021; Reed
et al.,
2022). The Western Atlantic stock is considered depleted under the MMPA (Hayes
et al.
2022). There is a recovery plan (NOAA Fisheries 2005) for the North Atlantic right whale, and NMFS completed 5-year reviews of the species in 2012, 2017, and 2022 which concluded no change to the listing status is warranted.
The North Atlantic right whale population had only a 2.8 percent recovery rate between 1990 and 2011, and an overall abundance decline of 29.7 percent from 2011-2020 (Hayes
et al.
2022). Since 2010, the North Atlantic right whale population has been in decline (Pace
et al.,
2017; Pace
et al.,
2021), with a 40 percent decrease in calving rate (Kraus
et al.,
2016; Moore
et al.,
2021). North Atlantic right whale calving rates dropped from 2017 to 2020, with zero births recorded during the 2017-2018 season. The 2020-2021 calving season had the first substantial calving increase in five years, with 20 calves born, followed by 15 calves during the 2021-2022 calving season. However, mortalities continue to outpace births, and best estimates indicate fewer than 100 reproductively active females remain in the population.
The project area both spatially and temporally overlaps a portion of the migratory corridor BIA within which right whales migrate south to calving grounds generally in November and December, followed by a northward migration into feeding areas east and north of the project area in March and April (LaBrecque
et al.,
2015; Van Parijs
et al.,
2015).
In late fall (
i.e.,
November), a portion of the right whale population (including pregnant females) typically departs the feeding grounds in the North Atlantic, moves south along the migratory corridor BIA, including through the project area, to right whale calving grounds off Georgia and Florida. However, recent research indicates understanding of their movement patterns remains incomplete and not all of the population undergoes a consistent annual migration (Davis
et al.,
2017; Gowan
et al.,
2019; Krzystan
et al.,
2018). The results of multistate temporary emigration capture-recapture modeling, based on sighting data collected over the past 22 years, indicate that non-calving females may remain in the feeding grounds, during the winter in the years preceding and following the birth of a calf to increase their energy stores (Gowen
et al.,
2019).
Right whales are anticipated to occur in the proposed survey area year-round but with lower levels in the summer from July-September. (Estabrook
et al.,
2021). Recent aerial surveys in the New York Bight showed right whales near the proposed survey area with the highest sighting rate in spring, followed by winter, preferring deeper waters near the shelf break (right whales observed in depths ranging from 33-1,041 m), but were observed throughout the survey area. No right whales were observed in summer months (Normandeau Associates and APEM, 2020; Zoidis
et al.,
2021). Similarly, passive acoustic data collected from 2018 to 2020 in the New York Bight showed detections of right whales throughout the year. During the Year 3 survey period, North Atlantic right whales were detected in each month, except in February, March, and October 2020, with the most detections occurring in late fall through early spring. Seasonally, North Atlantic right whale acoustic presence was highest in the fall at sites that were closer to New York Harbor and during spring months at sites farthest from the Harbor (Zoidis
et al.,
2021).
North Atlantic right whales present in the Empire Wind project area are primarily migrating through. Some opportunistic foraging may occur although core foraging habitat is located north of the project area in Southern New England, Gulf of Maine and Gulf of St. Lawrence. Right whales feed primarily on the copepod
Calanus finmarchicus,
a species whose availability and distribution has changed both spatially and temporally over the last decade due to an oceanographic regime shift that has been ultimately linked to climate change (Meyer-Gutbrod
et al.,
2021; Record
et al.,
2019; Sorochan
et al.,
2019). This distribution change in prey availability has led to shifts in right whale habitat-use patterns within the region over the same time period (Davis
et al.,
2020; Meyer-Gutbrod
et al.,
2022; Quintano-Rizzo
et al.,
2021, O'Brien
et al.,
2022).
Elevated right whale mortalities have occurred since June 7, 2017, along the U.S. and Canadian coast, with the leading category for the cause of death for this UME determined to be “human interaction,” specifically from entanglements or vessel strikes. As of February, 2023, there have been 36 confirmed mortalities and 22 seriously injured free-swimming whales for a total of 58. The UME also considers animals with sublethal injury or illness, also known as morbidity cases. There have been 39 bringing the total number of whales in the UME to 97. 2021), likely contributing to smaller body sizes at maturation, making them more susceptible to threats and reducing fecundity (Moore
et al.,
2021; Reed
et al.,
2022; Stewart
et al.,
2022). More information about the North Atlantic right whale UME is available online at:
https://www.fisheries.noaa.gov/national/marine-life-distress/2017-2023-north-atlantic-right-whale-unusual-mortality-event.
NMFS' regulations at 50 CFR part 224.105 designated nearshore waters of the Mid-Atlantic Bight as Mid-Atlantic U.S. Seasonal Management Areas (SMAs) for right whales in 2008. These specific SMAs were developed to reduce the threat of collisions between ships and right whales around their migratory route and calving grounds. The SMA southeast of Ports of New York/New Jersey is currently active from November 1 through April 30 of each year and may be used by right whales for feeding. As noted above, NMFS is proposing changes to the North Atlantic right whale speed rule (87 FR 46921; August 1, 2022). In addition, Dynamic Management Areas (DMAs) are areas of temporary protection established by NOAA Fisheries for particular marine mammal species, in an effort to respond to movements of high-risk whale species (such as right whale). These DMAs are determined by sighting reports made through vessel traffic in the larger Northern Atlantic and are communicated through marine communication systems and published on their website. The Right Whale Sighting Advisory System, a statutory
requirement to reduce the risk of right whale collisions, is in place for any DMA. As noted above, NMFS is proposing changes to the North Atlantic right whale speed rule (87 FR 46921; August 1, 2022).
Fin Whale
Fin whales typically feed in the Gulf of Maine and the waters surrounding New England, but their mating and calving (and general wintering) areas are largely unknown (Hain
et al.
1992, Hayes
et al.
2022). Recordings from Massachusetts Bay, New York Bight, and deep-ocean areas have detected some level of fin whale singing from September through June (Watkins
et al.
1987, Clark and Gagnon 2002, Morano
et al.
2012). These acoustic observations from both coastal and deep-ocean regions support the conclusion that male fin whales are broadly distributed throughout the western North Atlantic for most of the year (Hayes
et al.
2022).
There are no fin whale BIAs in the immediate vicinity of the project area although a small feeding BIA is located approximately 140 km to the northeast offshore of Montauk Point, from March to October (Hain
et al.,
1992; LaBrecque
et al.,
2015).
Minke Whale
Minke whales are among the most widely distributed of all the baleen whales. They occur in the North Atlantic and North Pacific, from tropical to polar waters. Generally, they inhabit warmer waters during winter and travel north to colder regions in summer, while some animals migrate as far as the ice edge. There appears to be a strong seasonal component to minke whale distribution in the survey areas, in which spring to fall are times of relatively widespread and common occurrence while during winter the species appears to be largely absent (Waring
et al.,
2016). Recent aerial surveys in the New York Bight area found that minke whales were observed throughout the survey area, with highest numbers sighting in the spring months (Normandeau Associates and APEM). Minke whales are primarily documented near the continental shelf offshore of New Jersey (Schwartz, 1962; Mead, 1975; Potter, 1979; Rowlett, 1980; Potter, 1984; Winn
et al.,
1985, DoN, 2005). Acoustic recordings of minke whales have been detected north of the Lease survey area within the New York Bight during the fall (August to December) and winter (February to May) (Biedron
et al.,
2009). Minke whales are most common off New Jersey in coastal waters in the spring and early summer as they move north to feeding ground in New England and fall as they migrate south (Geo-Marine, 2010). Geo-Marine (2010) observed four minke whales near the survey area and surrounding waters during winter and spring. A juvenile minke whale was sighted northwest of the Lease survey area near the New York Harbor in April 2007 (Hamazaki, 2002). Minke whale sightings off the coast of New Jersey were within water depths of 36 ft to 79 ft (11 m to 24 m) and temperatures ranging from 5.4 to 11.5 °C (47 °F) (Geo-Marine, 2010).
There are no minke whale BIAs in or near the project area. The closest is a feeding BIA identified in the southern and southwestern section of the Gulf of Maine from March through November, annually (LeBrecque
et al.,
2015). A migratory route for minke whales transiting between northern feeding grounds and southern breeding areas may exist to the east of the proposed project area, as minke whales may track warmer waters along the continental shelf while migrating (Risch
et al.,
2014).
Since January 2017, elevated minke whale mortalities detected along the Atlantic coast from Maine through South Carolina resulted in the declaration of a UME. However, that UME is now nonactive with closure pending. During the active phase of the UME, a total of 140 strandings had been reported with 21 occurring in New York and 11 in New Jersey. Previous minke whale UMEs occurred in 2003 and 2005 (NOAA Fisheries 2018c). Full or partial necropsy examinations were conducted on more than 60 percent of the whales. Preliminary findings in several of the whales have shown evidence of human interactions or infectious disease, but these findings are not consistent across all of the whales examined, so more research is needed. More information is available at:
https://www.fisheries.noaa.gov/national/marine-life-distress/2017-2022-minke-whale-unusual-mortality-event-along-atlantic-coast.
Humpback Whale
Humpback whales are a cosmopolitan species, found worldwide in all oceans, but were listed as endangered under the Endangered Species Conservation Act (ESCA) in June 1970. In 1973, the ESA replaced the ESCA, and humpbacks continued to be listed as endangered.
On September 8, 2016, NMFS divided the once single species into 14 distinct population segments (DPS), removed the species-level listing, and, in its place, listed four DPSs as endangered and one DPS as threatened (81 FR 62259; September 8, 2016). The remaining nine DPSs were not listed. The West Indies DPS, which is not listed under the ESA, is the only DPS of humpback whales that is expected to occur in the project area. Bettridge
et al.
(2015) estimated the size of the West Indies DPS population at 12,312 (95 percent CI 8,688-15,954) whales in 2004-05, which is consistent with previous population estimates of approximately 10,000-11,000 whales (Stevick
et al.,
2003; Smith
et al.,
1999) and the increasing trend for the West Indies DPS (Bettridge
et al.,
2015).
The project area does not overlap any designated critical habitat, nor any identified BIAs or other known important areas, for the humpback whales. A humpback whale feeding BIA extends throughout the Gulf of Maine, Stellwagen Bank, and Great South Channel from May through December, annually (LeBrecque
et al.,
2015). However, this BIA is located further east and north of, and thus does not overlap, the project area.
Four decades ago, humpback whales were infrequently sighted off the US mid-Atlantic states (USMA, New York, New Jersey, Delaware, Maryland, Virginia and North Carolina, CeTAP, 1982), but they are now regular visitors. Humpback whales are now frequently seen inside the New York-New Jersey harbor estuary and in the greater New York Bight (Brown
et al.,
2018, 2019; King
et al.,
2021; Zoidis
et al.,
2021; Smith
et al.,
2022). Based on a 2012-2018 dataset, mean occurrence was low (2.5 days), mean occupancy was 37.6 days, and 31.3 percent of whales returned from one year to the next (Brown
et al.,
2022). Sightings of mother-calf pairs are rare in the New York Bight Area, suggesting that maternally directed fidelity may not be responsible for the presence of young whales in this area (Brown
et al.,
2022).
Humpback whales belonging to the West Indies DPS typically feed in the waters between the Gulf of Maine and Newfoundland during spring, summer, and fall, but they have been observed feeding in other areas, such as off the coast of New York and New Jersey, including in close-proximity to the entrance of the Port of New York and New Jersey (Sieswerda
et al.,
2015, Brown
et al.,
2019).
Recent aerial surveys in the New York Bight observed humpback whales in the spring and winter, but sightings were reported year round in the area (Normandeau Associates and APEM, 2020). During 36 line-transect aerial surveys conducted systematically nearshore out to 120 nm from March 2017 to February 2020. Humpback whales preferred deeper waters near the shelf break, but were observed throughout the area. Additionally,
passive acoustic data recorded humpback whales in the New York Bight throughout the year, but the presence was highest in the fall and summer months (Estabrook
et al.,
2021). In addition, recent research has demonstrated a higher occurrence and foraging use of the New York Bight area by humpback whales than previously known.
Since January 2016, elevated humpback whale mortalities along the Atlantic coast from Maine to Florida led to the declaration of a UME. A total of 27 and 36 strandings have been reported in the waters off New Jersey and New York, respectively. Partial or full necropsy examinations have been conducted on approximately half of the 189 known cases (as of February 2023). Of the whales examined, about 50 percent had evidence of human interaction, either ship strike or entanglement. While a portion of the whales have shown evidence of pre-mortem vessel strike, this finding is not consistent across all whales examined and more research is needed. NOAA is consulting with researchers that are conducting studies on the humpback whale populations, and these efforts may provide information on changes in whale distribution and habitat use that could provide additional insight into how these vessel interactions occurred. More information is available at:
https://www.fisheries.noaa.gov/national/marine-life-distress/2016-2023-humpback-whale-unusual-mortality-event-along-atlantic-coast.
Since December 1, 2022, the number of humpback strandings along the mid-Atlantic coast, including New York, has been elevated. In some cases, the cause of death is not yet known. In others, vessel strike has been deemed the cause of death. As the humpback whale population has grown, they are seen more often in the Mid-Atlantic. Along the New York/New Jersey shore, these whales may be following their prey which are reportedly close to shore this winter. These prey also attract fish that are of interest to recreational and commercial fishermen. This increases the number of boats in these areas. More whales in the water in areas traveled by boats of all sizes increases the risk of vessel strikes. Vessel strikes and entanglement in fishing gear are the greatest human threats to large whales.
Phocid Seals
Since June 2022, elevated numbers of harbor seal and gray seal mortalities have occurred across the southern and central coast of Maine. This event has been declared a UME. Preliminary testing of samples has found some harbor and gray seals positive for highly pathogenic avian influenza. While the UME is not occurring in the Empire Wind project area, the populations affected by the UME are the same as those potentially affected by the project.
The above event was preceded by a different UME, occurring from 2018-2020 (closure of the 2018-2020 UME is pending). Beginning in July 2018, elevated numbers of harbor seal and gray seal mortalities occurred across Maine, New Hampshire, and Massachusetts. Additionally, stranded seals have shown clinical signs as far south as Virginia, although not in elevated numbers, therefore the UME investigation encompassed all seal strandings from Maine to Virginia. A total of 3,152 reported strandings (of all species) occurred from July 1, 2018, through March 13, 2020. Full or partial necropsy examinations have been conducted on some of the seals and samples have been collected for testing. Based on tests conducted thus far, the main pathogen found in the seals is phocine distemper virus. NMFS is performing additional testing to identify any other factors that may be involved in this UME, which is pending closure. Information on this UME is available online at:
www.fisheries.noaa.gov/new-england-mid-atlantic/marine-life-distress/2018-2020-pinniped-unusual-mortality-event-along.
There are several seal haul-out sites in New York. Harbor seals generally predominate in the onshore haul-out sites but gray seals intermix and are present as well. There are 26 known haul-out sites on Long Island, New York (CRESLI, 2019). During surveys from 2004-2019, a total of 18,321 harbor seals were documented using these sites (CRESLI, 2019). While there are no known haul-out sites directly at or near the proposed nearshore activities (
i.e.,
cable landfall construction, marine activities), harbor seals will occur throughout the New York coastline and have potential to haul out at many beach sites. The only known and consistently used gray seal haul out locations are along the sandy shoals located closer to Monomoy Refuge and on Nantucket, both in Massachusetts (Kenney and Vigness-Raposa 2010). This species has been reported with greater frequency in waters south of Cape Cod in recent years, likely due to a population rebound in the Mid-Atlantic (Kenney and Vigness-Raposa 2010).
Marine Mammal Hearing
Hearing is the most important sensory modality for marine mammals underwater, and exposure to anthropogenic sound can have deleterious effects. To appropriately assess the potential effects of exposure to sound, it is necessary to understand the frequency ranges marine mammals are able to hear. Current data indicate that not all marine mammal species have equal hearing capabilities (
e.g.,
Richardson
et al.,
1995; Wartzok and Ketten, 1999; Au and Hastings, 2008). To reflect this, Southall
et al.
(2007) recommended that marine mammals be divided into functional hearing groups based on directly measured or estimated hearing ranges on the basis of available behavioral response data, audiograms derived using auditory evoked potential techniques, anatomical modeling, and other data. Note that no direct measurements of hearing ability have been successfully completed for mysticetes (
i.e.,
low-frequency cetaceans). Subsequently, NMFS (2018) described generalized hearing ranges for these marine mammal hearing groups. Generalized hearing ranges were chosen based on the approximately 65 decibel (dB) threshold from the normalized composite audiograms, with the exception for lower limits for low-frequency cetaceans where the lower bound was deemed to be biologically implausible and the lower bound from Southall
et al.
(2007) retained. Marine mammal hearing groups and their associated hearing ranges are provided in Table 5.
Table 5—Marine Mammal Hearing Groups
[NMFS, 2018]
Hearing group
Generalized hearing range *
Low-frequency (LF) cetaceans (baleen whales)
7 Hz to 35 kHz.
Mid-frequency (MF) cetaceans (dolphins, toothed whales, beaked whales, bottlenose whales)
150 Hz to 160 kHz.
High-frequency (HF) cetaceans (true porpoises, Kogia, river dolphins, cephalorhynchid, Lagenorhynchus cruciger & L. australis)
275 Hz to 160 kHz.
Phocid pinnipeds (PW) (underwater) (true seals)
50 Hz to 86 kHz.
* Represents the generalized hearing range for the entire group as a composite (
i.e.,
all species within the group), where individual species' hearing ranges are typically not as broad. Generalized hearing range chosen based on ~65 dB threshold from normalized composite audiogram, with the exception for lower limits for LF cetaceans (Southall
et al.
2007) and PW pinniped (approximation).
The pinniped functional hearing group was modified from Southall
et al.
(2007) on the basis of data indicating that phocid species have consistently demonstrated an extended frequency range of hearing compared to otariids, especially in the higher frequency range (Hemilä
et al.,
2006; Kastelein
et al.,
2009; Reichmuth and Holt, 2013).
For more detail concerning these groups and associated frequency ranges, please see NMFS (2018) for a review of available information. Seventeen marine mammal species (14 cetacean species (6 mysticetes and 8 odontocetes) and 3 pinniped species (both phocid)) have the reasonable potential to co-occur with the proposed project activities (Table 4).
NMFS notes that in 2019, Southall
et al.
recommended new names for hearing groups that are widely recognized. However, this new hearing group classification does not change the weighting functions or acoustic thresholds (
i.e.,
the weighting functions and thresholds in Southall
et al.
(2019) are identical to NMFS 2018 Revised Technical Guidance). When NMFS updates our Technical Guidance, we will be adopting the updated Southall
et al.
(2019) hearing group classification.
Acoustic Habitat
Acoustic habitat is defined as distinguishable soundscapes inhabited by individual animals or assemblages of species, inclusive of both the sounds they create and those they hear (NOAA, 2016). All of the sound present in a particular location and time, considered as a whole, comprises a “soundscape” (Pijanowski
et al.,
2011). When examined from the perspective of the animals experiencing it, a soundscape may also be referred to as “acoustic habitat” (Clark
et al.,
2009, Moore
et al.,
2012, Merchant
et al.,
2015). High value acoustic habitats, which vary spectrally, spatially, and temporally, support critical life functions (feeding, breeding, and survival) of their inhabitants. Thus, it is important to consider acute (
e.g.,
stress or missed feeding/breeding opportunities) and chronic effects (
e.g.,
masking) of noise on important acoustic habitats. Effects that accumulate over long periods can ultimately result in detrimental impacts on the individual, stability of a population, or ecosystems that they inhabit.
Potential Effects to Marine Mammals and Their Habitat
This section includes a summary and discussion of the ways that components of the specified activity may impact marine mammals and their habitat. The Estimated Take of Marine Mammals section later in this document includes a quantitative analysis of the number of individuals that are expected to be taken by this activity. The Negligible Impact Analysis and Determination section considers the content of this section, the Estimated Take of Marine Mammals section, and the Proposed Mitigation section, to draw conclusions regarding the likely impacts of these activities on the reproductive success or survivorship of individuals and how those impacts on individuals are likely to impact marine mammal species or stocks. General background information on marine mammal hearing was provided previously (see the Description of Marine Mammals in the Area of the Specified Activities section). Here, the potential effects of sound on marine mammals are discussed.
Empire Wind has requested, and NMFS proposes to authorize, the taking of marine mammals incidental to construction activities associated with in the EW 1 and EW 2 project area. In their application, Empire Wind presented analyses of potential impacts to marine mammals from use of acoustic sources. NMFS both carefully reviewed the information provided by Empire Wind, as well as independently reviewed applicable scientific research and literature and other information to evaluate the potential effects of Empire Wind's activities on marine mammals.
The proposed activities would result in placement of up to 147 permanent monopiles foundations and two OSS jacket foundations in the marine environment. There are a variety of the types and degrees of effects to marine mammals, prey species, and habitat that could occur as a result from the project. Below we provide a brief description of the types of sound sources that would be generated by the project, the general impacts from these types of activities, and an analysis of the anticipated impacts on marine mammals from the project, with consideration of the proposed mitigation measures.
Description of Sound Sources
This section contains a brief technical background on sound, on the characteristics of certain sound types, and on metrics used in this proposal inasmuch as the information is relevant to the specified activity and to a discussion of the potential effects of the specified activity on marine mammals found later in this document. For general information on sound and its interaction with the marine environment, please see,
e.g.,
Au and Hastings (2008); Richardson
et al.
(1995); Urick (1983) as well as the Discovery of Sound in the Sea (DOSITS) website at
https://dosits.org/.
Sound is a vibration that travels as an acoustic wave through a medium such as a gas, liquid or solid. Sound waves alternately compress and decompress the medium as the wave travels. These compressions and decompressions are detected as changes in pressure by aquatic life and man-made sound receptors such as hydrophones (underwater microphones). In water, sound waves radiate in a manner similar to ripples on the surface of a pond and may be either directed in a beam (narrow beam or directional sources) or sound beams may radiate in all directions (omnidirectional sources).
Sound travels in water more efficiently than almost any other form of energy, making the use of acoustics ideal for the aquatic environment and its inhabitants. In seawater, sound travels at roughly 1500 meters per second (m/s). In-air, sound waves travel much more slowly, at about 340 m/s. However, the speed of sound can vary by a small amount based on
characteristics of the transmission medium, such as water temperature and salinity. Sound travels in water more efficiently than almost any other form of energy, making the use of acoustics ideal for the aquatic environment and its inhabitants. In seawater, sound travels at roughly 1500 m/s. In-air, sound waves travel much more slowly, at about 340 m/s. However, the speed of sound can vary by a small amount based on characteristics of the transmission medium, such as water temperature and salinity.
The basic components of a sound wave are frequency, wavelength, velocity, and amplitude. Frequency is the number of pressure waves that pass by a reference point per unit of time and is measured in Hz or cycles per second. Wavelength is the distance between two peaks or corresponding points of a sound wave (length of one cycle). Higher frequency sounds have shorter wavelengths than lower frequency sounds, and typically attenuate (decrease) more rapidly, except in certain cases in shallower water. The intensity (or amplitude) of sounds are measured in decibels (dB), which are a relative unit of measurement that is used to express the ratio of one value of a power or field to another. Decibels are measured on a logarithmic scale, so a small change in dB corresponds to large changes in sound pressure. For example, a 10-dB increase is a ten-fold increase in acoustic power. A 20-dB increase is then a 100-fold increase in power and a 30-dB increase is a 1000-fold increase in power. However, a ten-fold increase in acoustic power does not mean that the sound is perceived as being ten times louder. Decibels are a relative unit comparing two pressures, therefore a reference pressure must always be indicated. For underwater sound, this is 1 microPascal (μPa). For in-air sound, the reference pressure is 20 microPascal (μPa). The amplitude of a sound can be presented in various ways; however, NMFS typically considers three metrics. In this proposed rule, all decibel levels referenced to 1μPa.
Sound exposure level (SEL) represents the total energy in a stated frequency band over a stated time interval or event, and considers both amplitude and duration of exposure (represented as dB re 1 μPa
2
-s). SEL is a cumulative metric; it can be accumulated over a single pulse (for pile driving this is often referred to as single-strike SEL; SEL
ss
), or calculated over periods containing multiple pulses (SEL
cum
). Cumulative SEL represents the total energy accumulated by a receiver over a defined time window or during an event. The SEL metric is useful because it allows sound exposures of different durations to be related to one another in terms of total acoustic energy. The duration of a sound event and the number of pulses, however, should be specified as there is no accepted standard duration over which the summation of energy is measured.
Root mean square (rms) is the quadratic mean sound pressure over the duration of an impulse. Root mean square is calculated by squaring all of the sound amplitudes, averaging the squares, and then taking the square root of the average (Urick, 1983). Root mean square accounts for both positive and negative values; squaring the pressures makes all values positive so that they may be accounted for in the summation of pressure levels (Hastings and Popper, 2005). This measurement is often used in the context of discussing behavioral effects, in part because behavioral effects, which often result from auditory cues, may be better expressed through averaged units than by peak pressures.
Peak sound pressure (also referred to as zero-to-peak sound pressure or 0-pk) is the maximum instantaneous sound pressure measurable in the water at a specified distance from the source, and is represented in the same units as the rms sound pressure. Along with SEL, this metric is used in evaluating the potential for PTS (permanent threshold shift) and TTS (temporary threshold shift).
Sounds can be either impulsive or non-impulsive. The distinction between these two sound types is important because they have differing potential to cause physical effects, particularly with regard to hearing
(e.g.,
Ward, 1997 in Southall
et al.,
2007). Please see NMFS
et al.
(2018) and Southall
et al.
(2007, 2019) for an in-depth discussion of these concepts. Impulsive sound sources (
e.g.,
airguns, explosions, gunshots, sonic booms, impact pile driving) produce signals that are brief (typically considered to be less than one second), broadband, atonal transients (ANSI, 1986, 2005; Harris, 1998; NIOSH, 1998; ISO, 2003) and occur either as isolated events or repeated in some succession. Impulsive sounds are all characterized by a relatively rapid rise from ambient pressure to a maximal pressure value followed by a rapid decay period that may include a period of diminishing, oscillating maximal and minimal pressures, and generally have an increased capacity to induce physical injury as compared with sounds that lack these features. Impulsive sounds are typically intermittent in nature.
Non-impulsive sounds can be tonal, narrowband, or broadband, brief or prolonged, and may be either continuous or intermittent (ANSI, 1995; NIOSH, 1998). Some of these non-impulsive sounds can be transient signals of short duration but without the essential properties of pulses (
e.g.,
rapid rise time). Examples of non-impulsive sounds include those produced by vessels, aircraft, machinery operations such as drilling or dredging, vibratory pile driving, and active sonar systems.
Sounds are also characterized by their temporal component. Continuous sounds are those whose sound pressure level remains above that of the ambient sound, with negligibly small fluctuations in level (NIOSH, 1998; ANSI, 2005), while intermittent sounds are defined as sounds with interrupted levels of low or no sound (NIOSH, 1998). NMFS identifies Level B harassment thresholds based on if a sound is continuous or intermittent.
Even in the absence of sound from the specified activity, the underwater environment is typically loud due to ambient sound, which is defined as environmental background sound levels lacking a single source or point (Richardson
et al.,
1995). The sound level of a region is defined by the total acoustical energy being generated by known and unknown sources. These sources may include physical (
e.g.,
wind and waves, earthquakes, ice, atmospheric sound), biological (
e.g.,
sounds produced by marine mammals, fish, and invertebrates), and anthropogenic (
e.g.,
vessels, dredging, construction) sound. A number of sources contribute to ambient sound, including wind and waves, which are a main source of naturally occurring ambient sound for frequencies between 200 Hz and 50 kHz (ICES, 1995). In general, ambient sound levels tend to increase with increasing wind speed and wave height. Precipitation can become an important component of total sound at frequencies above 500 Hz, and possibly down to 100 Hz during quiet times. Marine mammals can contribute significantly to ambient sound levels, as can some fish and snapping shrimp. The frequency band for biological contributions is from approximately 12 Hz to over 100 kHz. Sources of ambient sound related to human activity include transportation (surface vessels), dredging and construction, oil and gas drilling and production, geophysical surveys, and sonar. Vessel noise typically dominates the total ambient sound for frequencies between 20 and 300 Hz. In general, the frequencies of anthropogenic sounds are below 1 kHz and, if higher frequency sound levels are created, they attenuate rapidly.
The sum of the various natural and anthropogenic sound sources that comprise ambient sound at any given location and time depends not only on the source levels (as determined by current weather conditions and levels of biological and human activity) but also on the ability of sound to propagate through the environment. In turn, sound propagation is dependent on the spatially and temporally varying properties of the water column and sea floor, and is frequency-dependent. As a result of the dependence on a large number of varying factors, ambient sound levels can be expected to vary widely over both coarse and fine spatial and temporal scales. Sound levels at a given frequency and location can vary by 10-20 dB from day to day (Richardson
et al.,
1995). The result is that, depending on the source type and its intensity, sound from the specified activity may be a negligible addition to the local environment or could form a distinctive signal that may affect marine mammals. Human-generated sound is a significant contributor to the acoustic environment in the project location.
Potential Effects of Underwater Sound on Marine Mammals
Anthropogenic sounds cover a broad range of frequencies and sound levels and can have a range of highly variable impacts on marine life, from none or minor to potentially severe responses, depending on received levels, duration of exposure, behavioral context, and various other factors. Broadly, underwater sound from active acoustic sources such as those in the Empire Wind Project can potentially result in one or more of the following: temporary or permanent hearing impairment, non-auditory physical or physiological effects (
e.g.,
stress), behavioral disturbance, and masking (Richardson
et al.,
1995; Gordon
et al.,
2003; Nowacek
et al.,
2007; Southall
et al.,
2007; Götz
et al.,
2009). Non-auditory physiological effects or injuries that theoretically might occur in marine mammals exposed to high level underwater sound or as a secondary effect of extreme behavioral reactions (
e.g.,
change in dive profile as a result of an avoidance reaction) caused by exposure to sound include neurological effects, bubble formation, resonance effects, and other types of organ or tissue damage (Cox
et al.,
2006; Southall
et al.,
2007; Zimmer and Tyack, 2007; Tal
et al.,
2015).
In general, the degree of effect of an acoustic exposure is intrinsically related to the signal characteristics, received level, distance from the source, and duration of the sound exposure, in addition to the contextual factors of the receiver (
e.g.,
behavioral state at time of exposure, age class, etc). In general, sudden, high level sounds can cause hearing loss as can longer exposures to lower level sounds. Moreover, any temporary or permanent loss of hearing will occur almost exclusively for noise within an animal's hearing range. We describe below the specific manifestations of acoustic effects that may occur based on the activities proposed by Empire Wind.
Richardson
et al.
(1995) described zones of increasing intensity of effect that might be expected to occur, in relation to distance from a source and assuming that the signal is within an animal's hearing range. First (at the greatest distance) is the area within which the acoustic signal would be audible (potentially perceived) to the animal but not strong enough to elicit any overt behavioral or physiological response. The next zone (closer to the receiving animal) corresponds with the area where the signal is audible to the animal and of sufficient intensity to elicit behavioral or physiological responsiveness. The third is a zone within which, for signals of high intensity, the received level is sufficient to potentially cause discomfort or tissue damage to auditory or other systems. Overlaying these zones to a certain extent is the area within which masking (
i.e.,
when a sound interferes with or masks the ability of an animal to detect a signal of interest that is above the absolute hearing threshold) may occur; the masking zone may be highly variable in size.
Below, we provide additional detail regarding potential impacts on marine mammals and their habitat from noise in general, as well as from the specific activities Empire Wind plans to conduct, to the degree it is available (noting that there is limited information regarding the impacts of offshore wind construction on marine mammals or cetaceans).
Hearing Threshold Shift
Marine mammals exposed to high-intensity sound, or to lower-intensity sound for prolonged periods, can experience hearing threshold shift (TS), which NMFS defines as a change, usually an increase, in the threshold of audibility at a specified frequency or portion of an individual's hearing range above a previously established reference level, expressed in decibels (NMFS, 2018). Threshold shifts can be permanent (permanent threshold shift; PTS), in which case there is an irreversible increase in the threshold of audibility at a specified frequency or portion of an individual's hearing range, or temporary (temporary threshold shift; TTS), in which there is reversible increase in the threshold of audibility at a specified frequency or portion of an individual's hearing range and the animal's hearing threshold would fully recover over time (Southall
et al.,
2019). Repeated sound exposure that leads to TTS could cause PTS.
When PTS occurs, there can be physical damage to the sound receptors in the ear (
i.e.,
tissue damage), whereas TTS represents primarily tissue fatigue and is reversible (Henderson
et al.,
2008). In addition, other investigators have suggested that TTS is within the normal bounds of physiological variability and tolerance and does not represent physical injury (
e.g.,
Ward, 1997; Southall
et al.,
2019). Therefore, NMFS does not consider TTS to constitute auditory injury.
Relationships between TTS and PTS thresholds have not been studied in marine mammals, and there is no PTS data for cetaceans, but such relationships are assumed to be similar to those in humans and other terrestrial mammals. Noise exposure can result in either a permanent shift in hearing thresholds from baseline (PTS; a 40 dB threshold shift approximates a PTS onset;
e.g.,
Kryter
et al.,
1966; Miller, 1974; Henderson
et al.,
2008) or a temporary, recoverable shift in hearing that returns to baseline (a 6 dB threshold shift approximates a TTS onset;
e.g.,
Southall
et al.,
2019). Based on data from terrestrial mammals, a precautionary assumption is that the PTS thresholds, expressed in the unweighted peak sound pressure level metric (PK), for impulsive sounds (such as impact pile driving pulses) are at least 6 dB higher than the TTS thresholds and the weighted PTS cumulative sound exposure level thresholds are 15 (impulsive sound) to 20 (non-impulsive sounds) dB higher than TTS cumulative sound exposure level thresholds (Southall
et al.,
2019). Given the higher level of sound or longer exposure duration necessary to cause PTS as compared with TTS, PTS is less likely to occur as a result of these activities, but it is possible and a small amount has been proposed for authorization for several species.
TTS is the mildest form of hearing impairment that can occur during exposure to sound, with a TTS of 6 dB considered the minimum threshold shift clearly larger than any day-to-day or session-to-session variation in a subject's normal hearing ability (Schlundt
et al.,
2000; Finneran
et al.,
2000; Finneran
et al.,
2002). While experiencing TTS, the hearing threshold
rises, and a sound must be at a higher level in order to be heard. In terrestrial and marine mammals, TTS can last from minutes or hours to days (in cases of strong TTS). In many cases, hearing sensitivity recovers rapidly after exposure to the sound ends. There is data on sound levels and durations necessary to elicit mild TTS for marine mammals but recovery is complicated to predict and dependent on multiple factors.
Currently, TTS data only exist for four species of cetaceans (bottlenose dolphin, beluga whale (
Delphinapterus leucas
), harbor porpoise, and Yangtze finless porpoise (
Neophocoena asiaeorientalis
)) and six species of pinnipeds (northern elephant seal (
Mirounga angustirostris
), harbor seal, ring seal, spotted seal, bearded seal, and California sea lion (
Zalophus californianus
)) that were exposed to a limited number of sound sources (
i.e.,
mostly tones and octave-band noise with limited number of exposure to impulsive sources such as seismic airguns or impact pile driving) in laboratory settings (Southall
et al.,
2019). There is currently no data available on noise-induced hearing loss for mysticetes. For summaries of data on TTS or PTS in marine mammals or for further discussion of TTS or PTS onset thresholds, please see Southall
et al.
(2019), and NMFS (2018).
Recent studies with captive odontocete species (bottlenose dolphin, harbor porpoise, beluga, and false killer whale) have observed increases in hearing threshold levels when individuals received a warning sound prior to exposure to a relatively loud sound (Nachtigall and Supin, 2013, 2015, Nachtigall
et al.,
2016 a,b,c, Finneran, 2018, Nachtigall
et al.,
2018). These studies suggest that captive animals have a mechanism to reduce hearing sensitivity prior to impending loud sounds. Hearing change was observed to be frequency dependent and Finneran (2018) suggests hearing attenuation occurs within the cochlea or auditory nerve. Based on these observations on captive odontocetes, the authors suggest that wild animals may have a mechanism to self-mitigate the impacts of noise exposure by dampening their hearing during prolonged exposures of loud sound, or if conditioned to anticipate intense sounds (Finneran, 2018, Nachtigall
et al.,
2018).
Marine mammal hearing plays a critical role in communication with conspecifics, and interpretation of environmental cues for purposes such as predator avoidance and prey capture. Depending on the degree (elevation of threshold in dB), duration (
i.e.,
recovery time), and frequency range of TTS, and the context in which it is experienced, TTS can have effects on marine mammals ranging from discountable to serious depending on the degree of interference of marine mammals hearing. For example, a marine mammal may be able to readily compensate for a brief, relatively small amount of TTS in a non-critical frequency range that occurs during a time where ambient noise is lower and there are not as many competing sounds present. Alternatively, a larger amount and longer duration of TTS sustained during time when communication is critical (
e.g.
, for successful mother/calf interactions, consistent detection of prey) could have more serious impacts.
Behavioral Effects
Exposure of marine mammals to sound sources can result in, but is not limited to, no response or any of the following observable responses: Increased alertness; orientation or attraction to a sound source; vocal modifications; cessation of feeding; cessation of social interaction; alteration of movement or diving behavior; habitat abandonment (temporary or permanent); and, in severe cases, panic, flight, stampede, or stranding, potentially resulting in death (Southall
et al.,
2007). A review of marine mammal responses to anthropogenic sound was first conducted by Richardson (1995). More recent reviews (Nowacek
et al.,
2007; DeRuiter
et al.,
2012 and 2013; Ellison
et al.,
2012; Gomez
et al.,
2016; Southall
et al.,
2021)) address studies conducted since 1995 and focused on observations where the received sound level of the exposed marine mammal(s) was known or could be estimated. Gomez
et al.
(2016) conducted a review of the literature considering the contextual information of exposure in addition to received level and found that higher received levels were not always associated with more severe behavioral responses and vice versa. Southall
et al.
(2021) states that results demonstrate that some individuals of different species display clear yet varied responses, some of which have negative implications, while others appear to tolerate high levels, and that responses may not be fully predictable with simple acoustic exposure metrics (
e.g.,
received sound level). Rather, the authors state that differences among species and individuals along with contextual aspects of exposure (
e.g.,
behavioral state) appear to affect response probability. Behavioral responses to sound are highly variable and context-specific. Many different variables can influence an animal's perception of and response to (nature and magnitude) an acoustic event. An animal's prior experience with a sound or sound source affects whether it is less likely (habituation) or more likely (sensitization) to respond to certain sounds in the future (animals can also be innately predisposed to respond to certain sounds in certain ways) (Southall
et al.,
2019). Related to the sound itself, the perceived nearness of the sound, bearing of the sound (approaching vs. retreating), the similarity of a sound to biologically relevant sounds in the animal's environment (
i.e.,
calls of predators, prey, or conspecifics), and familiarity of the sound may affect the way an animal responds to the sound (Southall
et al.,
2007; DeRuiter
et al.,
2013). Individuals (of different age, gender, reproductive status,
etc.
) among most populations will have variable hearing capabilities, and differing behavioral sensitivities to sounds that will be affected by prior conditioning, experience, and current activities of those individuals. Often, specific acoustic features of the sound and contextual variables (
i.e.,
proximity, duration, or recurrence of the sound or the current behavior that the marine mammal is engaged in or its prior experience), as well as entirely separate factors such as the physical presence of a nearby vessel, may be more relevant to the animal's response than the received level alone.
Overall, the variability of responses to acoustic stimuli depends not only on the species receiving the sound and the sound source, but also on the social, behavioral, or environmental contexts of exposure (
e.g.,
DeRuiter
et al.,
2012). For example, Goldbogen
et al.
(2013) demonstrated that individual behavioral state was critically important in determining response of blue whales to sonar, noting that some individuals engaged in deep (greater than 50 m) feeding behavior had greater dive responses than those in shallow feeding or non-feeding conditions. Some blue whales in the Goldbogen
et al.
(2013) study that were engaged in shallow feeding behavior demonstrated no clear changes in diving or movement even when received levels were high (~160 dB re 1µPa) for exposures to 3-4 kHz sonar signals, while deep feeding and non-feeding whales showed a clear response at exposures at lower received levels of sonar and pseudorandom noise. Southall
et al.
2011 found that blue whales had a different response to sonar exposure depending on behavioral state, more pronounced when deep
feeding/travel modes than when engaged in surface feeding.
With respect to distance influencing disturbance, DeRuiter
et al.
(2013) examined behavioral responses of Cuvier's beaked whales to MF sonar and found that whales responded strongly at low received levels (89-127 dB
re 1µPa
) by ceasing normal fluking and echolocation, swimming rapidly away, and extending both dive duration and subsequent non-foraging intervals when the sound source was 3.4-9.5 km away. Importantly, this study also showed that whales exposed to a similar range of received levels (78-106 dB
re 1µPa
) from distant sonar exercises (118 km away) did not elicit such responses, suggesting that context (in this case, distance) may moderate reactions. Thus, distance from the source is an important variable in influencing the type and degree of behavioral response and this is variable is independent of the effect of received levels (
e.g.,
DeRuiter
et al.,
2013; Dunlop
et al.,
2017a; Dunlop
et al.,
2017b; Falcone
et al.,
2017; Dunlop
et al.,
2018; Southall
et al.,
2019).
Ellison
et al.
(2012) outlined an approach to assessing the effects of sound on marine mammals that incorporates contextual-based factors. The authors recommend considering not just the received level of sound, but also the activity the animal is engaged in at the time the sound is received, the nature and novelty of the sound (
i.e.,
is this a new sound from the animal's perspective), and the distance between the sound source and the animal. They submit that this “exposure context,” as described, greatly influences the type of behavioral response exhibited by the animal. Forney
et al.
(2017) also point out that an apparent lack of response (
e.g.,
no displacement or avoidance of a sound source) may not necessarily mean there is no cost to the individual or population, as some resources or habitats may be of such high value that animals may choose to stay, even when experiencing stress or hearing loss. Forney
et al.
(2017) recommend considering both the costs of remaining in an area of noise exposure such as TTS, PTS, or masking, which could lead to an increased risk of predation or other threats or a decreased capability to forage, and the costs of displacement, including potential increased risk of vessel strike, increased risks of predation or competition for resources, or decreased habitat suitable for foraging, resting, or socializing. This sort of contextual information is challenging to predict with accuracy for ongoing activities that occur over large spatial and temporal expanses. However, distance is one contextual factor for which data exists to potentially quantitatively inform a take estimate. Other factors are often considered qualitatively in the analysis of the likely consequences of sound exposure, where supporting information is available.
Friedlaender
et al.
(2016) provided the first integration of direct measures of prey distribution and density variables incorporated into across-individual analyses of behavior responses of blue whales to sonar, and demonstrated a five-fold increase in the ability to quantify variability in blue whale diving behavior. These results illustrate that responses evaluated without such measurements for foraging animals may be misleading, which again illustrates the context-dependent nature of the probability of response.
The following subsections provide examples of behavioral responses that give an idea of the variability in behavioral responses that would be expected given the differential sensitivities of marine mammal species to sound, contextual factors, and the wide range of potential acoustic sources to which a marine mammal may be exposed. Behavioral responses that could occur for a given sound exposure should be determined from the literature that is available for each species, or extrapolated from closely related species when no information exists, along with contextual factors.
Avoidance and Displacement
Avoidance is the displacement of an individual from an area or migration path as a result of the presence of a sound or other stressors and is one of the most obvious manifestations of disturbance in marine mammals (Richardson
et al.,
1995). For example, gray whales or humpback whales are known to change direction—deflecting from customary migratory paths—in order to avoid noise from airgun surveys (Malme
et al.,
1984; Dunlop
et al.,
2018). Avoidance is qualitatively different from the flight response, but also differs in the magnitude of the response (
i.e.,
directed movement, rate of travel, etc.). Avoidance may be short-term, with animals returning to the area once the noise has ceased (
e.g.,
Bowles
et al.,
1994; Goold, 1996; Stone
et al.,
2000; Morton and Symonds, 2002; Gailey
et al.,
2007; Dähne
et al.,
2013; Russel
et al.,
2016; Malme
et al.,
1984). Longer-term displacement is possible, however, which may lead to changes in abundance or distribution patterns of the affected species in the affected region if habituation to the presence of the sound does not occur (
e.g.,
Blackwell
et al.,
2004; Bejder
et al.,
2006; Teilmann
et al.,
2006; Forney
et al.,
2017). Avoidance of marine mammals during the construction of offshore wind facilities (specifically, impact pile driving) has been documented previously noted in the literature, with some significant variation in the temporal and spatial degree of avoidance effects, and with most studies focused on harbor porpoises as one of the most common marine mammals in European waters (
e.g.,
Tougaard
et al.,
2009; Dähne
et al.,
2013; Thompson
et al.,
2013; Russell
et al.,
2016; Brandt
et al.,
2018).
Available information on impacts to marine mammals from pile driving associated with offshore wind is limited to information on harbor porpoises and seals, as the vast majority of this research has occurred at European offshore wind projects where large whales and other odontocete species are uncommon. Harbor porpoises and harbor seals are considered to be behaviorally sensitive species (
e.g.,
Southall
et al.,
2007) and the effects of wind farm construction in Europe on these species has been well documented. These species have received particular attention in European waters due to their abundance in the North Sea (Hammond
et al.,
2002; Nachtsheim
et al.,
2021). A summary of the literature on documented effects of wind farm construction on harbor porpoise and harbor seals is described below.
Brandt
et al.
(2016) summarized the effects of the construction of eight offshore wind projects within the German North Sea (
i.e.,
Alpha Ventus, BARD Offshore I, Borkum West II, DanTysk, Global Tech I, Meerwind Süd/Ost, Nordsee Ost, and Riffgat) between 2009 and 2013 on harbor porpoises, combining PAM data from 2010-2013 and aerial surveys from 2009-2013 with data on noise levels associated with pile driving. Results of the analysis revealed significant declines in porpoise detections during pile driving when compared to 25-48 hours before pile driving began, with the magnitude of decline during pile driving clearly decreasing with increasing distances to the construction site. During the majority of projects, significant declines in detections (by at least 20 percent) were found within at least 5-10 km of the pile driving site, with declines at up to 20-30 km of the pile driving site documented in some cases. Similar results demonstrating the long-distance displacement of harbor porpoises (18-25 km) and harbor seals (up to 40 km) during impact pile driving have also been observed during the construction at multiple other European wind farms
(Haleters
et al.,
2015; Lucke
et al.,
2012; Dähne
et al.,
2013; Tougaard
et al.,
2009; Bailey
et al.,
2010).
While harbor porpoises and seals tend to move several kilometers away from wind farm construction activities, the duration of displacement has been documented to be relatively temporary. In two studies on impact driving at Horns Rev II in the North Sea near Denmark, harbor porpoise returned within 1-2 days following cessation of pile driving (Tougaard
et al.,
2009, Brandt
et al.,
2011). Similar recovery periods have been noted for harbor seals off of England during the construction of four wind farms (Carroll
et al.,
2010; Hamre
et al.,
2011; Hastie
et al.,
2015; Russell
et al.,
2016; Brasseur
et al.,
2010). For example, although there was no significant displacement during construction as a whole, Russell
et al.
(2016) found that displacement did occur during active pile driving at predicted received levels between 168 and 178 dB re 1µPa
(p-p)
; however seal distribution returned to the pre-piling condition within two hours of cessation of pile driving. In some cases, an increase in harbor porpoise activity has been documented inside wind farm areas following construction (
e.g.,
Lindeboom
et al.,
2011). Other studies have noted longer term impacts after impact pile driving. Near Dogger Bank in Germany, harbor porpoises continued to avoid the area for over two years after construction began (Gilles
et al.
2009). Approximately ten years after construction of the Nysted wind farm, harbor porpoise abundance had not recovered to the original levels previously seen, although the echolocation activity was noted to have been increasing when compared to the previous monitoring period (Teilmann and Carstensen, 2012). However, overall, there are no indications for a population decline of harbor porpoises in European waters (
e.g.,
Brandt
et al.,
2016). Notably, where significant differences in displacement and return rates have been identified for these species, the occurrence of secondary project-specific influences such as use of mitigation measures (
e.g.,
bubble curtains, acoustic deterrent devices (ADDs)) or the manner in which species use the habitat in the project area are likely the driving factors of this variation.
NMFS notes the aforementioned studies from Europe involve pile driving much smaller piles than Empire Wind proposes to install and therefore we anticipate noise levels from impact pile driving to be louder. For this reason, we anticipate that the greater distances of displacement observed in harbor porpoise and harbor seals documented in Europe are likely to occur off of New York. However, we do not anticipate any greater severity of response due to harbor porpoise and harbor seal habitat use off of New York or population level consequences, similar to European findings. In many cases, harbor porpoises and harbor seals are resident to the areas where European wind farms have been constructed. However, off of New York, harbor porpoises are transient (with higher abundances in winter when impact pile driving would not occur) and a very small percentage of the large harbor seal population are only seasonally present with no rookeries established. In summary, we anticipate that harbor porpoise and harbor seals will likely respond to pile driving by moving several kilometers away from the source but return to typical habitat use patterns when pile driving ceases.
Some avoidance behavior of other marine mammal species has been documented to be dependent on distance from the source. As described above, DeRuiter
et al.
(2013) noted that distance from a sound source may moderate marine mammal reactions in their study of Cuvier's beaked whales (an acoustically sensitive species), which showed the whales swimming rapidly and silently away when a sonar signal was 3.4-9.5 km away while showing no such reaction to the same signal when the signal was 118 km away even though the received levels were similar. Tyack
et al.
(1983) conducted playback studies of SURTASS low frequency active (LFA) sonar in a gray whale migratory corridor off California. Similar to North Atlantic right whales, gray whales migrate close to shore (approximately +2 kms) and are low frequency hearing specialists. The LFA sonar source was placed within the gray whale migratory corridor (approximately 2 km offshore) and offshore of most, but not all, migrating whales (approximately 4 km offshore). These locations influenced received levels and distance to the source. For the inshore playbacks, not unexpectedly, the louder the source level of the playback (
i.e.,
the louder the received level), whale avoided the source at greater distances. Specifically, when the source level was 170 dB rms and 178 dB rms, whales avoided the inshore source at ranges of several hundred meters, similar to avoidance responses reported by Malme
et al.
(1983, 1984). Whales exposed to source levels of 185 dB rms demonstrated avoidance levels at ranges of +1 km. Responses to the offshore source broadcasting at source levels of 185 and 200 dB, avoidance responses were greatly reduced. While there was observed deflection from course, in no case did a whale abandon its migratory behavior.
The signal context of the noise exposure has been shown to play an important role in avoidance responses. In a 2007-2008 Bahamas study, playback sounds of a potential predator—a killer whale—resulted in a similar but more pronounced reaction in beaked whales (an acoustically sensitive species), which included longer inter-dive intervals and a sustained straight-line departure of more than 20 km from the area (Boyd
et al.,
2008; Southall
et al.,
2009; Tyack
et al.,
2011). Empire Wind does not anticipate, and NMFS is not proposing to authorize take of beaked whales and, moreover, the sounds produced by Empire Wind do not have signal characteristics similar to predators. Therefore we would not expect such extreme reactions to occur. Southall
et al.
2011 found that blue whales had a different response to sonar exposure depending on behavioral state, more pronounced when deep feeding/travel modes than when engaged in surface feeding.
One potential consequence of behavioral avoidance is the altered energetic expenditure of marine mammals because energy is required to move and avoid surface vessels or the sound field associated with active sonar (Frid and Dill, 2002). Most animals can avoid that energetic cost by swimming away at slow speeds or speeds that minimize the cost of transport (Miksis-Olds, 2006), as has been demonstrated in Florida manatees (Miksis-Olds, 2006). Those energetic costs increase, however, when animals shift from a resting state, which is designed to conserve an animal's energy, to an active state that consumes energy the animal would have conserved had it not been disturbed. Marine mammals that have been disturbed by anthropogenic noise and vessel approaches are commonly reported to shift from resting to active behavioral states, which would imply that they incur an energy cost.
Forney
et al.
(2017) detailed the potential effects of noise on marine mammal populations with high site fidelity, including displacement and auditory masking, noting that a lack of observed response does not imply absence of fitness costs and that apparent tolerance of disturbance may have population-level impacts that are less obvious and difficult to document. Avoidance of overlap between disturbing noise and areas and/or times of particular importance for sensitive
species may be critical to avoiding population-level impacts because (particularly for animals with high site fidelity) there may be a strong motivation to remain in the area despite negative impacts. Forney
et al.
(2017) stated that, for these animals, remaining in a disturbed area may reflect a lack of alternatives rather than a lack of effects.
A flight response is a dramatic change in normal movement to a directed and rapid movement away from the perceived location of a sound source. The flight response differs from other avoidance responses in the intensity of the response (
e.g.,
directed movement, rate of travel). Relatively little information on flight responses of marine mammals to anthropogenic signals exist, although observations of flight responses to the presence of predators have occurred (Connor and Heithaus, 1996; Frid and Dill, 2002). The result of a flight response could range from brief, temporary exertion and displacement from the area where the signal provokes flight to, in extreme cases, beaked whale strandings (Cox
et al.,
2006; D'Amico
et al.,
2009). However, it should be noted that response to a perceived predator does not necessarily invoke flight (Ford and Reeves, 2008), and whether individuals are solitary or in groups may influence the response. Flight responses of marine mammals have been documented in response to mobile high intensity active sonar (
e.g.,
Tyack
et al.,
2011; DeRuiter
et al.,
2013; Wensveen
et al.,
2019), and more severe responses have been documented when sources are moving towards an animal or when they are surprised by unpredictable exposures (Watkins 1986; Falcone
et al.,
2017). Generally speaking, however, marine mammals would be expected to be less likely to respond with a flight response to either stationery pile driving (which they can sense is stationery and predictable) or significantly lower-level HRG surveys, unless they are within the area ensonified above behavioral harassment thresholds at the moment the source is turned on (Watkins, 1986; Falcone
et al.,
2017).
Diving and Foraging
Changes in dive behavior in response to noise exposure can vary widely. They may consist of increased or decreased dive times and surface intervals as well as changes in the rates of ascent and descent during a dive (
e.g.,
Frankel and Clark, 2000; Costa
et al.,
2003; Ng and Leung, 2003; Nowacek
et al.;
2004; Goldbogen
et al.,
2013a, 2013b). Variations in dive behavior may reflect interruptions in biologically significant activities (
e.g.,
foraging) or they may be of little biological significance. Variations in dive behavior may also expose an animal to potentially harmful conditions (
e.g.,
increasing the chance of ship-strike) or may serve as an avoidance response that enhances survivorship. The impact of a variation in diving resulting from an acoustic exposure depends on what the animal is doing at the time of the exposure, the type and magnitude of the response, and the context within which the response occurs (
e.g.,
the surrounding environmental and anthropogenic circumstances).
Nowacek
et al.
(2004) reported disruptions of dive behaviors in foraging North Atlantic right whales when exposed to an alerting stimulus, an action, they noted, that could lead to an increased likelihood of ship strike. The alerting stimulus was in the form of an 18 minute exposure that included three 2-minute signals played three times sequentially. This stimulus was designed with the purpose of providing signals distinct to background noise that serve as localization cues. However, the whales did not respond to playbacks of either right whale social sounds or vessel noise, highlighting the importance of the sound characteristics in producing a behavioral reaction. Although source levels for the proposed pile driving activities may exceed the received level of the alerting stimulus described by Nowacek
et al.
(2004), proposed mitigation strategies (further described in the Proposed Mitigation section) will reduce the severity of response to proposed pile driving activities. Converse to the behavior of North Atlantic right whales, Indo-Pacific humpback dolphins have been observed to dive for longer periods of time in areas where vessels were present and/or approaching (Ng and Leung, 2003). In both of these studies, the influence of the sound exposure cannot be decoupled from the physical presence of a surface vessel, thus complicating interpretations of the relative contribution of each stimulus to the response. Indeed, the presence of surface vessels, their approach, and speed of approach, seemed to be significant factors in the response of the Indo-Pacific humpback dolphins (Ng and Leung, 2003). Low frequency signals of the Acoustic Thermometry of Ocean Climate (ATOC) sound source were not found to affect dive times of humpback whales in Hawaiian waters (Frankel and Clark, 2000) or to overtly affect elephant seal dives (Costa
et al.,
2003). They did, however, produce subtle effects that varied in direction and degree among the individual seals, illustrating the equivocal nature of behavioral effects and consequent difficulty in defining and predicting them.
Disruption of feeding behavior can be difficult to correlate with anthropogenic sound exposure, so it is usually inferred by observed displacement from known foraging areas, the cessation of secondary indicators of foraging (
e.g.,
bubble nets or sediment plumes), or changes in dive behavior. As for other types of behavioral response, the frequency, duration, and temporal pattern of signal presentation, as well as differences in species sensitivity, are likely contributing factors to differences in response in any given circumstance (
e.g.,
Croll
et al.,
2001; Nowacek
et al.;
2004; Madsen
et al.,
2006a; Yazvenko
et al.,
2007; Southall
et al.,
2019b). An understanding of the energetic requirements of the affected individuals and the relationship between prey availability, foraging effort and success, and the life history stage of the animal can facilitate the assessment of whether foraging disruptions are likely to incur fitness consequences (Goldbogen
et al.,
2013; Farmer
et al.,
2018; Pirotta
et al.,
2018; Southall
et al.,
2019; Pirotta
et al.,
2021).
Impacts on marine mammal foraging rates from noise exposure have been documented, though there is little data regarding the impacts of offshore turbine construction specifically. Several broader examples follow, and it is reasonable to expect that exposure to noise produced during the 5-years the proposed rule would be effective could have similar impacts.
Visual tracking, passive acoustic monitoring, and movement recording tags were used to quantify sperm whale behavior prior to, during, and following exposure to air gun arrays at received levels in the range 140-160 dB at distances of 7-13 km, following a phase-in of sound intensity and full array exposures at 1-13 km (Madsen
et al.,
2006a; Miller
et al.,
2009). Sperm whales did not exhibit horizontal avoidance behavior at the surface. However, foraging behavior may have been affected. The sperm whales exhibited 19 percent less vocal (buzz) rate during full exposure relative to post exposure, and the whale that was approached most closely had an extended resting period and did not resume foraging until the air guns had ceased firing. The remaining whales continued to execute foraging dives throughout exposure; however, swimming movements during foraging dives were six percent lower during exposure than control periods (Miller
et al.,
2009). Miller
et al.
(2009) noted that
more data are required to understand whether the differences were due to exposure or natural variation in sperm whale behavior.
Balaenopterid whales exposed to moderate low-frequency signals similar to the ATOC sound source demonstrated no variation in foraging activity (Croll
et al.,
2001), whereas five out of six North Atlantic right whales exposed to an acoustic alarm interrupted their foraging dives (Nowacek
et al.,
2004). Although the received SPLs were similar in the latter two studies, the frequency, duration, and temporal pattern of signal presentation were different. These factors, as well as differences in species sensitivity, are likely contributing factors to the differential response. Though the area ensonified by the HRG sources is significantly smaller than from construction, the source levels of both the proposed construction and HRG activities exceed the source levels of the signals described by Nowacek
et al.,
(2004) and Croll
et al.,
(2001), and noise generated by Empire Wind's activities at least partially overlap in frequency with the described signals. Blue whales exposed to mid-frequency sonar in the Southern California Bight were less likely to produce low frequency calls usually associated with feeding behavior (Melcón
et al.,
2012). However, Melcón
et al.
(2012) were unable to determine if suppression of low frequency calls reflected a change in their feeding performance or abandonment of foraging behavior and indicated that implications of the documented responses are unknown. Further, it is not known whether the lower rates of calling actually indicated a reduction in feeding behavior or social contact since the study used data from remotely deployed, passive acoustic monitoring buoys. Results from the 2010-2011 field season of a behavioral response study in Southern California waters indicated that, in some cases and at low received levels, tagged blue whales responded to mid-frequency sonar but that those responses were mild and there was a quick return to their baseline activity (Southall
et al.,
2011; Southall
et al.,
2012b, Southall
et al.,
2019b).
Information on or estimates of the energetic requirements of the individuals and the relationship between prey availability, foraging effort and success, and the life history stage of the animal will help better inform a determination of whether foraging disruptions incur fitness consequences. Foraging strategies may impact foraging efficiency, such as by reducing foraging effort and increasing success in prey detection and capture, in turn promoting fitness and allowing individuals to better compensate for foraging disruptions. Surface feeding blue whales did not show a change in behavior in response to mid-frequency simulated and real sonar sources with received levels between 90 and 179 dB
re 1
μ
Pa,
but deep feeding and non-feeding whales showed temporary reactions including cessation of feeding, reduced initiation of deep foraging dives, generalized avoidance responses, and changes to dive behavior (DeRuiter
et al.,
2017; Goldbogen
et al.,
2013b; Sivle
et al.,
2015). Goldbogen
et al.
(2013b) indicate that disruption of feeding and displacement could impact individual fitness and health. However, for this to be true, we would have to assume that an individual whale could not compensate for this lost feeding opportunity by either immediately feeding at another location, by feeding shortly after cessation of acoustic exposure, or by feeding at a later time. There is no indication that individual fitness and health would be impacted, particularly since unconsumed prey would likely still be available in the environment in most cases following the cessation of acoustic exposure.
Similarly, while the rates of foraging lunges decrease in humpback whales due to sonar exposure, there was variability in the response across individuals, with one animal ceasing to forage completely and another animal starting to forage during the exposure (Sivle
et al.,
2016). In addition, almost half of the animals that demonstrated avoidance were foraging before the exposure but the others were not; the animals that avoided while not feeding responded at a slightly lower received level and greater distance than those that were feeding (Wensveen
et al.,
2017). These findings indicate the behavioral state of the animal and foraging strategies play a role in the type and severity of a behavioral response. For example, when the prey field was mapped and used as a covariate in examining how behavioral state of blue whales is influenced by mid-frequency sound, the response in blue whale deep-feeding behavior was even more apparent, reinforcing the need for contextual variables to be included when assessing behavioral responses (Friedlaender
et al.,
2016).
Vocalizations and Auditory Masking
Marine mammals vocalize for different purposes and across multiple modes, such as whistling, production of echolocation clicks, calling, and singing. Changes in vocalization behavior in response to anthropogenic noise can occur for any of these modes and may result directly from increased vigilance (also see the
Potential Effects of Behavioral Disturbance on Marine Mammal Fitness
section) or a startle response, or from a need to compete with an increase in background noise (see Erbe
et al.,
2016 review on communication masking), the latter of which is described more below.
For example, in the presence of potentially masking signals, humpback whales and killer whales have been observed to increase the length of their songs (Miller
et al.,
2000; Fristrup
et al.,
2003; Foote
et al.,
2004) and blue increased song production (Di Iorio and Clark, 2009), while North Atlantic right whales have been observed to shift the frequency content of their calls upward while reducing the rate of calling in areas of increased anthropogenic noise (Parks
et al.,
2007). In some cases, animals may cease or reduce sound production during production of aversive signals (Bowles
et al.,
1994; Thode
et al.,
2020; Cerchio
et al.,
(2014); McDonald
et al.,
(1995)). Blackwell
et al.
(2015) showed that whales increased calling rates as soon as air gun signals were detectable before ultimately decreasing calling rates at higher received levels.
Sound can disrupt behavior through masking, or interfering with, an animal's ability to detect, recognize, or discriminate between acoustic signals of interest (
e.g.,
those used for intraspecific communication and social interactions, prey detection, predator avoidance, or navigation) (Richardson
et al.,
1995; Erbe and Farmer, 2000; Tyack, 2000; Erbe
et al.,
2016). Masking occurs when the receipt of a sound is interfered with by another coincident sound at similar frequencies and at similar or higher intensity, and may occur whether the sound is natural (
e.g.,
snapping shrimp, wind, waves, precipitation) or anthropogenic (
e.g.,
shipping, sonar, seismic exploration) in origin. The ability of a noise source to mask biologically important sounds depends on the characteristics of both the noise source and the signal of interest (
e.g.,
signal-to-noise ratio, temporal variability, direction), in relation to each other and to an animal's hearing abilities (
e.g.,
sensitivity, frequency range, critical ratios, frequency discrimination, directional discrimination, age, or TTS hearing loss), and existing ambient noise and propagation conditions. Masking these acoustic signals can disturb the behavior of individual animals, groups of animals, or entire populations. Masking can lead to behavioral changes including vocal changes (
e.g.,
Lombard
effect, increasing amplitude, or changing frequency), cessation of foraging or lost foraging opportunities, and leaving an area, to both signalers and receivers, in an attempt to compensate for noise levels (Erbe
et al.,
2016) or because sounds that would typically have triggered a behavior were not detected. In humans, significant masking of tonal signals occurs as a result of exposure to noise in a narrow band of similar frequencies. As the sound level increases, though, the detection of frequencies above those of the masking stimulus decreases also. This principle is expected to apply to marine mammals as well because of common biomechanical cochlear properties across taxa.
Therefore, when the coincident (masking) sound is man-made, it may be considered harassment when disrupting behavioral patterns. It is important to distinguish TTS and PTS, which persist after the sound exposure, from masking, which only occurs during the sound exposure. Because masking (without resulting in threshold shift) is not associated with abnormal physiological function, it is not considered a physiological effect, but rather a potential behavioral effect.
The frequency range of the potentially masking sound is important in determining any potential behavioral impacts. For example, low-frequency signals may have less effect on high-frequency echolocation sounds produced by odontocetes but are more likely to affect detection of mysticete communication calls and other potentially important natural sounds such as those produced by surf and some prey species. The masking of communication signals by anthropogenic noise may be considered as a reduction in the communication space of animals (
e.g.,
Clark
et al.,
2009; Matthews
et al.,
2016) and may result in energetic or other costs as animals change their vocalization behavior (
e.g.,
Miller
et al.,
2000; Foote
et al.,
2004; Parks
et al.,
2007; Di Iorio and Clark, 2009; Holt
et al.,
2009). Masking can be reduced in situations where the signal and noise come from different directions (Richardson
et al.,
1995), through amplitude modulation of the signal, or through other compensatory behaviors (Houser and Moore, 2014). Masking can be tested directly in captive species (
e.g.,
Erbe, 2008), but in wild populations it must be either modeled or inferred from evidence of masking compensation. There are few studies addressing real-world masking sounds likely to be experienced by marine mammals in the wild (
e.g.,
Branstetter
et al.,
2013; Cholewiak
et al.,
2018).
The echolocation calls of toothed whales are subject to masking by high-frequency sound. Human data indicate low-frequency sound can mask high-frequency sounds (
i.e.,
upward masking). Studies on captive odontocetes by Au
et al.
(1974, 1985, 1993) indicate that some species may use various processes to reduce masking effects (
e.g.,
adjustments in echolocation call intensity or frequency as a function of background noise conditions). There is also evidence that the directional hearing abilities of odontocetes are useful in reducing masking at the high-frequencies these cetaceans use to echolocate, but not at the low-to-moderate frequencies they use to communicate (Zaitseva
et al.,
1980). A study by Nachtigall and Supin (2008) showed that false killer whales adjust their hearing to compensate for ambient sounds and the intensity of returning echolocation signals.
Impacts on signal detection, measured by masked detection thresholds, are not the only important factors to address when considering the potential effects of masking. As marine mammals use sound to recognize conspecifics, prey, predators, or other biologically significant sources (Branstetter
et al.,
2016), it is also important to understand the impacts of masked recognition thresholds (often called “informational masking”). Branstetter
et al.
(2016) measured masked recognition thresholds for whistle-like sounds of bottlenose dolphins and observed that they are approximately 4 dB above detection thresholds (energetic masking) for the same signals. Reduced ability to recognize a conspecific call or the acoustic signature of a predator could have severe negative impacts. Branstetter
et al.
(2016) observed that if “quality communication” is set at 90 percent recognition the output of communication space models (which are based on 50 percent detection) would likely result in a significant decrease in communication range.
As marine mammals use sound to recognize predators (Allen
et al.,
2014; Cummings and Thompson, 1971; Curé
et al.,
2015; Fish and Vania, 1971), the presence of masking noise may also prevent marine mammals from responding to acoustic cues produced by their predators, particularly if it occurs in the same frequency band. For example, harbor seals that reside in the coastal waters off British Columbia are frequently targeted by mammal-eating killer whales. The seals acoustically discriminate between the calls of mammal-eating and fish-eating killer whales (Deecke
et al.,
2002), a capability that should increase survivorship while reducing the energy required to attend to all killer whale calls. Similarly, sperm whales (Curé
et al.,
2016; Isojunno
et al.,
2016), long-finned pilot whales (Visser
et al.,
2016), and humpback whales (Curé
et al.,
2015) changed their behavior in response to killer whale vocalization playbacks; these findings indicate that some recognition of predator cues could be missed if the killer whale vocalizations were masked. The potential effects of masked predator acoustic cues depends on the duration of the masking noise and the likelihood of a marine mammal encountering a predator during the time that detection and recognition of predator cues are impeded.
Redundancy and context can also facilitate detection of weak signals. These phenomena may help marine mammals detect weak sounds in the presence of natural or manmade noise. Most masking studies in marine mammals present the test signal and the masking noise from the same direction. The dominant background noise may be highly directional if it comes from a particular anthropogenic source such as a ship or industrial site. Directional hearing may significantly reduce the masking effects of these sounds by improving the effective signal-to-noise ratio.
Masking affects both senders and receivers of acoustic signals and, at higher levels and longer duration, can potentially have long-term chronic effects on marine mammals at the population level as well as at the individual level. Low-frequency ambient sound levels have increased by as much as 20 dB (more than three times in terms of SPL) in the world's ocean from pre-industrial periods, with most of the increase from distant commercial shipping (Hildebrand, 2009; Cholewiak
et al.,
2018). All anthropogenic sound sources, but especially chronic and lower-frequency signals (
e.g.,
from commercial vessel traffic), contribute to elevated ambient sound levels, thus intensifying masking.
In addition to making it more difficult for animals to perceive and recognize acoustic cues in their environment, anthropogenic sound presents separate challenges for animals that are vocalizing. When they vocalize, animals are aware of environmental conditions that affect the “active space” (or communication space) of their vocalizations, which is the maximum area within which their vocalizations can be detected before it drops to the level of ambient noise (Brenowitz, 2004; Brumm
et al.,
2004; Lohr
et al.,
2003).
Animals are also aware of environmental conditions that affect whether listeners can discriminate and recognize their vocalizations from other sounds, which is more important than simply detecting that a vocalization is occurring (Brenowitz, 1982; Br
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