Taking and Importing Marine Mammals; Taking Marine Mammals Incidental to the U.S. Navy Training and Testing Activities in the Hawaii-Southern California Training and Testing Study Area
Federal RegisterOct 3, 2023
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DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
50 CFR Part 218
[Docket No. 230817-0197]
RIN 0648-BL72
Taking and Importing Marine Mammals; Taking Marine Mammals Incidental to the U.S. Navy Training and Testing Activities in the Hawaii-Southern California Training and Testing Study Area
AGENCY:
National Marine Fisheries Service (NMFS), National Oceanic and Atmospheric Administration (NOAA), Commerce.
ACTION:
Proposed rule; request for comments and information.
SUMMARY:
NMFS has received a request from the U.S. Navy (Navy) to modify the regulations and Letters of Authorization (LOAs) authorizing the take of marine mammals incidental to Navy training and testing activities conducted in the Hawaii-Southern California Training and Testing (HSTT) Study Area between 2018 and 2025. In 2021, two separate U.S. Navy vessels struck unidentified large whales on two separate occasions, one whale in June 2021 and one whale in July 2021, in waters off Southern California. The takes by vessel strike of the two whales by the U.S. Navy were covered by the existing regulations and LOAs, which authorize the U.S. Navy to take up to three large whales by serious injury or mortality by vessel strike between 2018 and 2025. The Navy reanalyzed the potential of vessel strike in the HSTT Study Area, including the recent strikes and as a result, requested two additional takes of large whales by serious injury or mortality by vessel strike for the remainder of the current regulatory period. In May 2023, a U.S. Navy vessel struck a large whale in waters off Southern California. NMFS reanalyzed the potential for vessel strike following the May 2023 strike and proposes to authorize two additional takes of large whales by serious injury or mortality by vessel strike for the remainder of the current regulatory period (two takes in addition to the three takes authorized in the current regulations). Pursuant to the Marine Mammal Protection Act (MMPA), NMFS is requesting comments on the proposed promulgation of modified regulations and associated LOAs for the Navy governing this additional incidental taking of marine mammals. NMFS will consider public comments prior to issuing any final rule and making final decisions on the issuance of the requested LOAs. Agency responses to public comments will be provided in the notice of the final decision. The Navy's activities qualify as military readiness activities pursuant to the MMPA, as amended by the National Defense Authorization Act for Fiscal Year 2004 (2004 NDAA).
DATES:
Comments and information must be received no later than November 17, 2023.
ADDRESSES:
Submit all electronic public comments via the Federal e-Rulemaking Portal. Go to
https://www.regulations.gov
and enter NOAA-NMFS-2023-0102 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).
A copy of the Navy's applications, NMFS' proposed and final rules and subsequent LOAs for the existing (2020) and previous (2018) regulations, and other supporting documents and documents cited herein may be obtained online at:
www.fisheries.noaa.gov/national/marine-mammal-protection/incidental-take-authorizations-military-readiness-activities.
In case of problems accessing these documents, please use the contact listed here (see
FOR FURTHER INFORMATION CONTACT
).
FOR FURTHER INFORMATION CONTACT:
Leah Davis, Office of Protected Resources, NMFS, (301) 427-8401.
SUPPLEMENTARY INFORMATION:
Purpose of Regulatory Action
These proposed regulations, issued under the authority of the MMPA (16 U.S.C. 1361
et seq.
), would modify the current regulations, which allow for the authorization of take of marine mammals incidental to the Navy's training and testing activities (which qualify as military readiness activities) from the use of sonar and other transducers, in-water detonations, air guns, impact pile driving/vibratory extraction, and the movement of vessels throughout the HSTT Study Area (50 CFR part 218, subpart H; hereafter “2020 HSTT regulations”).
NMFS received a request from the Navy to modify the existing regulations and LOAs to authorize two additional takes of large whales by serious injury or mortality by vessel strike over the remainder of the HSTT regulatory period. The current HSTT regulations and LOAs authorize the incidental take, by serious injury or mortality, of three large whales by vessel strike. Here, in consideration of the best available science, including updated information related to vessel strikes, NMFS analyzes and proposes to authorize the incidental serious injury or mortality by vessel strike of five large whales over the effective period of the regulations (December 2018-December 2025). The effective period remains unchanged from the existing regulations. Further, the Navy's proposed activities remain unchanged; however, this proposed rule includes two additional mitigation measures and revision of two existing mitigation measures to further reduce the probability of vessel strike. With the exception of these new mitigation measures and revisions to two existing mitigation measures, the required mitigation and monitoring measures remain unchanged.
Background
The MMPA prohibits the “take” of marine mammals, with certain exceptions. Sections 101(a)(5)(A) and (D) of the MMPA (16 U.S.C. 1361
et seq.
) direct the Secretary of Commerce (as delegated to NMFS) to allow, upon request, the incidental, but not intentional, taking of small numbers of marine mammals by U.S. citizens who engage in a specified activity (other than commercial fishing) within a specified geographical region if certain findings are made and either regulations are issued or, if the taking is limited to harassment, the public is provided with notice of the proposed incidental take authorization and the opportunity to review and submit comments.
An authorization for incidental takings shall be granted if NMFS finds that the taking will have a negligible impact on the species or stock(s) 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 such species or stocks for taking for certain subsistence uses (referred to in this rulemaking as “mitigation measures”); and requirements pertaining to the monitoring and reporting of such takings. The MMPA defines “take” to mean to harass, hunt, capture, or kill, or attempt to harass, hunt, capture, or kill any marine mammal. The Preliminary Analysis and Negligible Impact Determination section below discusses the definition of “negligible impact.”
The 2004 NDAA (Pub. L. 108-136) amended section 101(a)(5) of the MMPA to remove the “small numbers” and “specified geographical region” provisions indicated above and amended the definition of “harassment” as applied to a “military readiness activity.” The definition of harassment for military readiness activities (section 3(18)(B) of the MMPA) is (i) any act that injures or has the significant potential to injure a marine mammal or marine mammal stock in the wild (Level A Harassment); or (ii) any act that disturbs or is likely to disturb a marine mammal or marine mammal stock in the wild by causing disruption of natural behavioral patterns, including, but not limited to, migration, surfacing, nursing, breeding, feeding, or sheltering, to a point where such behavioral patterns are abandoned or significantly altered (Level B harassment). In addition, the 2004 NDAA amended the MMPA as it relates to military readiness activities such that the least practicable adverse impact analysis shall include consideration of personnel safety, practicality of implementation, and impact on the effectiveness of the military readiness activity.
The NDAA for Fiscal Year 2019 (2019 NDAA) (Pub. L. 115-232), amended the MMPA to allow incidental take rules for military readiness activities under section 101(a)(5)(A) to be issued for up to 7 years. Prior to this amendment, all incidental take rules under section 101(a)(5)(A) were limited to 5 years.
Under the MMPA implementing regulations, incidental take regulations may be modified, in whole or in part, as new information is developed and after notice and opportunity for public comment (50 CFR 216.105). An LOA must be withdrawn or suspended if, after notice and opportunity for public comment, NMFS determines that the regulations are not being substantially complied with, or the taking is having, or may have, more than a negligible impact on species or stock.
Id.
at 216.106(e). Note, in its application, Navy relied on §§ 218.76, and 218.77. These sections outline the process for modification of an LOA without modifying the applicable incidental take regulation. These sections do not apply here because the Navy requested modification of the 2020 HSTT regulations.
Summary of Request
On December 27, 2018, NMFS issued a 5-year final rule governing the taking of marine mammals incidental to Navy training and testing activities conducted in the HSTT Study Area (83 FR 66846; hereafter “2018 HSTT final rule”). Previously, on August 13, 2018, and towards the end of the time period in which NMFS was processing the Navy's request for the 2018 regulations, the 2019 NDAA amended the MMPA for military readiness activities to allow incidental take regulations to be issued for up to 7 years instead of the previous 5 years. The Navy's training and testing activities conducted in the HSTT Study Area qualify as military readiness activities pursuant to the MMPA, as amended by the 2004 NDAA. On March 11, 2019, the Navy submitted an application requesting that NMFS extend the 2018 HSTT regulations and associated LOAs such that they would cover take incidental to 7 years of training and testing activities instead of 5, extending the expiration date from December 20, 2023 to December 20, 2025. On July 10, 2020, NOAA Fisheries issued regulations to govern the taking of marine mammals incidental to the training and testing activities conducted in the HSTT Study Area over the course of 7 years, effectively extending the effective period from December 20, 2023 to December 20, 2025.
On March 31, 2022, NMFS received an adequate and complete application (2022 Navy application) from the Navy requesting that NMFS modify the existing regulations and LOAs to authorize two additional takes of large whales by serious injury or mortality by vessel strike over the remainder of the HSTT authorization period. The 2020 HSTT regulations (50 CFR part 218, subpart H) and LOAs authorize the take of marine mammals from the Navy's training and testing activities in the HSTT Study Area through December 20, 2025. These regulations and LOAs authorize the take of three large whales by serious injury or mortality by vessel strike.
The Navy's 2022 request is based upon new information regarding U.S. Navy vessel strikes off the coast of Southern California. As described in the 2022 Navy application, in 2021, two separate U.S. Navy vessels struck unidentified large whales off the coast of Southern California on two separate occasions, one whale in June 2021 and one whale in July 2021. Separately, a foreign naval vessel struck two fin whales off the coast of Southern California in May 2021.
In the 2022 Navy application, the Navy proposes no changes to the nature of the specified activities covered by the 2020 HSTT final rule. The Navy states that the level of activity within and between years would be consistent with that previously analyzed in the 2020 HSTT final rule, and all activities would be conducted within the same boundaries of the HSTT Study Area identified in the 2020 HSTT final rule. The training and testing activities (
e.g.,
equipment and sources used, exercises conducted) are identical to those described and analyzed in the 2020 HSTT final rule, and the mitigation, monitoring, and reporting measures are similar to those described and analyzed in the 2020 HSTT final rule. The only changes included in the Navy's request are for additional take by serious injury or mortality by vessel strike.
The Navy's mission is to organize, train, equip, and maintain combat-ready naval forces capable of winning wars, deterring aggression, and maintaining freedom of the seas. This mission is mandated by Federal law (10 U.S.C. 8062), which ensures the readiness of the naval forces of the United States. The Navy executes this responsibility by establishing and executing training programs, including at-sea training and exercises, and ensuring naval forces have access to the ranges, operating areas (OPAREAs), and airspace needed to develop and maintain skills for conducting naval activities.
For a summary of the training and testing activities within the HSTT Study Area, see the Navy's previous rulemaking and LOA applications submitted for HSTT Phase III activities (October 13, 2017 initial rulemaking and LOA application (hereafter “2017 Navy application”) and March 11, 2019 extension rulemaking and LOA application (hereafter “2019 Navy application”)) and the 2020 HSTT regulations that were subsequently promulgated, which can be found at:
https://www.fisheries.noaa.gov/national/marine-mammal-protection/incidental-take-authorizations-military-readiness-activities.
These activities are deemed by the Navy necessary to accomplish military readiness requirements and are anticipated to continue into the reasonably foreseeable future. The 2022 Navy application and this proposed rule cover training and testing activities that would occur over the remainder of the effective period of the current regulations, valid from the
publication date of the final rule, if issued, through December 20, 2025.
Summary of the Proposed Regulations
NMFS is proposing to modify the incidental take regulations and associated LOAs to cover the same Navy activities covered by the 2020 HSTT regulations but authorize five takes of large whales by serious injury or mortality by vessel strike (two takes in addition to the three takes authorized in the current regulations). In its 2022 application, the Navy proposes no additional changes and explains that its training and testing activities, including the level of vessel use, remain unchanged. Nearly all mitigation, monitoring, and reporting measures remain unchanged with the exception of two additional mitigation measures, revision of two existing mitigation measures, and an additional reporting measure resulting from discussions between the Navy and NMFS.
In response to the Navy's request, we focus our analysis on the new information related to vessel strike. We also review any new information that may be pertinent to our analysis of the impacts from all other activities that comprise Navy's specified activity, and our analysis of mitigation, monitoring, and reporting. Where there is any new information pertinent to the descriptions, analyses, or findings required to authorize the incidental take for military readiness activities under MMPA section 101(a)(5)(A), that information is provided in the appropriate sections below. Where there is no new information or any new information does not change our previous analysis or findings, we indicate as such and refer the reader to the original analysis in the 2018 HSTT proposed and final rule, 2020 HSTT final rule or the 2019 HSTT Final Environmental Impact Statement (FEIS)/Overseas Environmental Impact Statement (OEIS).
After reviewing all new information and as discussed below, we largely find that our previous analyses and findings remain current and applicable. For vessel strike, we provide a new analysis and propose authorizing two additional takes of large whales, for a total of five takes by serious injury or mortality by vessel strike over the 7-year period. We consider authorizing these additional takes after analyzing the best available information and after considering the effects of the entire specified activity and the total taking as required by MMPA section 101(a)(5)(A). When setting forth the permissible methods of taking pursuant to the activity and other means of effecting the least practicable adverse impact on the species or stock, we propose requiring new and modified mitigation and also consider whether to require any new or modified mitigation for the entire specified activity.
The proposed regulatory language included at the end of this proposed rule, which would be published at 50 CFR part 218, subpart H, remains largely the same as that under the HSTT 2020 regulations, except for a small number of technical changes related to the Navy's 2022 request, new and revised mitigation measures, and a new reporting measure. Therefore, in this proposed rule, we refer the reader to complete analyses described in the 2018 HSTT final rule or an updated analysis in the 2020 HSTT final rule, where appropriate.
Below is a list of the regulatory documents referenced in this proposed rule. The list indicates the short name by which the document is referenced in this proposed rule as well as the full titles of the cited documents. All of the documents can be found at:
www.fisheries.noaa.gov/national/marine-mammal-protection/incidental-take-authorizations-military-readiness-activities
and
http://www.hstteis.com/.
• NMFS June 26, 2018, Hawaii-Southern California Training and Testing (HSTT) proposed rule (83 FR 29872; 2018 HSTT proposed rule);
• NMFS December 27, 2018, Hawaii-Southern California Training and Testing (HSTT) final rule (83 FR 66846; 2018 HSTT final rule);
• NMFS September 13, 2019, Hawaii-Southern California Training and Testing (HSTT) proposed rule (84 FR 48388; 2019 HSTT proposed rule);
• NMFS July 10, 2020, Hawaii-Southern California Training and Testing (HSTT) final rule (85 FR 41780; 2020 HSTT final rule);
• Navy October 13, 2017, MMPA rulemaking and LOA application (2017 Navy application);
• Navy March 11, 2019, MMPA rulemaking and LOA extension application (2019 Navy application);
• Navy March 31, 2022, MMPA rulemaking and LOA revision application (2022 Navy application); and
• October 26, 2018, Hawaii-Southern California Training and Testing (HSTT) Final Environmental Impact Statement/Overseas Environmental Impact Statement (FEIS/OEIS) (2018 HSTT FEIS/OEIS).
Description of the Specified Activity
The Navy requests authorization to take marine mammals incidental to conducting training and testing activities. The Navy has determined that acoustic and explosives stressors are most likely to result in impacts on marine mammals that could rise to the level of harassment. In addition to take by harassment, the Navy has determined that vessel movement may result in serious injury or mortality to marine mammals. Detailed descriptions of these activities are provided in chapter 2 of the 2018 HSTT FEIS/OEIS and in the 2017 Navy application.
Overview of Training and Testing Activities
The Navy routinely trains in the HSTT Study Area in preparation for national defense missions. Training and testing activities and components covered in the 2022 Navy application are described in detail in the
Overview of Training and Testing Activities
sections of the 2018 HSTT proposed rule, the 2018 HSTT final rule, and chapter 2 (
Description of Proposed Action and Alternatives
) of the 2018 HSTT FEIS/OEIS (
http://www.hstteis.com/
). Each military training and testing activity described meets mandated Fleet requirements to deploy ready forces. The Navy proposes no changes to the specified activities described and analyzed in the 2018 HSTT final rule and subsequent 2020 HSTT final rule. The boundaries of the HSTT Study Area (see figure 2-1 of the 2019 Navy application); the dates and duration of the activities; and the training and testing activities (
e.g.,
equipment and sources used, exercises conducted) analyzed in this proposed rule are identical to those described and analyzed in the 2020 HSTT final rule and therefore, are not repeated herein. Please see the 2020 HSTT final rule for more information. The manner of vessel movement presented in this proposed rule is also identical to that analyzed in the 2020 HSTT final rule.
Vessel Strike
Vessel strikes are not specific to any particular training or testing activity but rather, a limited, sporadic, and incidental result of Navy vessel movement within the HSTT Study Area. Vessel strikes from commercial, recreational, and military vessels are known to seriously injure and occasionally kill cetaceans (Abramson
et al.
2011; Berman-Kowalewski
et al.
2010; Calambokidis, 2012; Douglas
et al.
2008; Laggner, 2009; Lammers
et al.
2003; Van der Hoop
et al.
2012; Van der Hoop
et al.
2013; Crum
et al.
2019), although reviews of the literature on vessel strikes mainly involve collisions between commercial vessels and whales (Jensen and Silber, 2003; Laist
et al.
2001). Vessel speed, size, and mass are
all important factors in determining both the potential likelihood and impacts of a vessel strike to marine mammals (Conn and Silber, 2013; Gende
et al.
2011; Silber
et al.
2010; Vanderlaan and Taggart, 2007; Wiley
et al.
2016). For large vessels, speed and angle of approach can influence the severity of a strike.
Navy vessels transit at speeds that are optimal for fuel conservation or to meet training and testing requirements. Small craft (for purposes of this analysis, less than 18 m in length) have much more variable speeds (0-50+ knots (kn; 0-92.6 kilometers (km) per hour), dependent on the activity). Submarines generally operate at speeds in the range of 8-13 kn (14.8-24.1 km per hour), and the average speed of large Navy ships range between 10 and 15 kn (18.5 and 27.8 km per hour). While these speeds are considered averages and representative of most events, some vessels need to operate outside of these parameters for certain times or during certain activities. For example, to produce the required relative wind speed over the flight deck, an aircraft carrier engaged in flight operations must adjust its speed through the water accordingly. Also, there are other instances such as launch and recovery of a small rigid hull inflatable boat; vessel boarding, search, and seizure training events; or retrieval of a target when vessels would be dead in the water or moving slowly ahead to maintain steerage. There are a few specific events, including high-speed tests of newly constructed vessels, where vessels would operate at higher speeds. By comparison, this is slower than most commercial vessels where full speed for a container ship is typically 24 kn (44.4 km per hour; Bonney and Leach, 2010).
Large Navy vessels (greater than 18 m in length) within the offshore areas of range complexes and testing ranges operate differently from commercial vessels in ways that may reduce the probability of whale collisions. Surface ships operated by or for the Navy have multiple personnel assigned to stand watch at all times when a ship or surfaced submarine is moving through the water (underway). A primary duty of personnel standing watch on surface ships is to detect and report all objects and disturbances sighted in the water that may indicate a threat to the vessel and its crew, such as debris, a periscope, surfaced submarine, or surface disturbance. Per vessel safety requirements, personnel standing watch also report any marine mammals sighted in the path of the vessel as a standard collision avoidance procedure. All vessels proceed at a safe speed so they can take proper and effective action to avoid a collision with any sighted object or disturbance and can be stopped within a distance appropriate to the prevailing circumstances and conditions. As described in the
Standard Operating Procedures
section, the Navy utilizes Lookouts to avoid collisions, and Lookouts are also trained to spot marine mammals so that vessels may change course or take other appropriate action to avoid collisions. Should a vessel strike occur, we consider that it would likely result in incidental take in the form of serious injury and/or mortality and, accordingly, for the purposes of the analysis, we assume that any vessel strike would result in serious injury or mortality.
The Navy proposes no changes to the nature of the specified activities, the training and testing activities, the manner of vessel movement, the speeds at which vessels operate, the number of vessels that would be used during various activities, or the locations in which Navy vessel activity would be concentrated within the HSTT Study Area described in the 2018 HSTT final rule and referenced in the 2020 HSTT final rule.
Vessel Movement
Vessels used as part of the planned activities include ships, submarines, unmanned vessels, and boats ranging in size from small, 22 ft (7 m) rigid hull inflatable boats to aircraft carriers with lengths up to 1,092 ft (333 m). The average speed of large Navy ships ranges between 10 and 15 kn (18.5 and 27.8 km per hour) and submarines generally operate at speeds in the range of 8-13 kn (14.8-24.1 km per hour) while a few specialized vessels can travel at faster speeds. Small craft (for purposes of this analysis, less than 18 m in length) have much more variable speeds (0-50+ kn (0-92.6 km per hour), dependent on the activity) but generally range from 10 to 14 kn (18.5 to 25.9 km per hour). From unpublished Navy data, average median speed for large Navy ships in the HSTT Study Area from 2011-2015 varied from 5-10 kn (9.2-18.5 km per hour) with variations by ship class and location (
i.e.,
slower speeds close to the coast). While these speeds for large and small craft are representative of most events, some vessels need to temporarily operate outside of these parameters. Typical speed of Navy vessels in HSTT core high use areas from 2014-2018 were between 10 and 15 kn (18.5 and 27.8 km per hour; Starcovic and Mintz 2021). This core area is a region including the approaches to San Diego, and immediate offshore areas west of San Diego, centered north and south of San Clemente Island. A full description of Navy vessels that are used during training and testing activities can be found in the 2017 Navy application and chapter 2 (
Description of Proposed Action and Alternatives
) of the 2018 HSTT FEIS/OEIS.
The number of Navy vessels used in the HSTT Study Area varies based on military training and testing requirements, deployment schedules, annual budgets, and other dynamic factors. Most training and testing activities involve the use of vessels. These activities could be widely dispersed throughout the HSTT Study Area but would typically be conducted near naval ports, piers, and range areas. Navy vessel traffic would be especially concentrated near San Diego, California and Pearl Harbor, Hawaii. Based on historical data, we anticipate the annual number of at-sea hours by U.S. Navy vessels in the HSTT action area will be around 26,800 hours per year (Starcovic and Mintz 2021). We expect that about 25 percent of this vessel activity would occur within the Hawaii Range Complex (HRC) and 75 percent within the Southern California Range Complex (SOCAL; Mintz 2016). There is no seasonal differentiation in Navy vessel use because of continual operational requirements from Combatant Commanders. The majority of large vessel traffic occurs between the installations and the OPAREAs. The transit corridor, notionally defined by the great circle route (
e.g.,
shortest distance) from San Diego to the center of the HRC, as depicted in the 2018 HSTT FEIS/OEIS, is generally used by ships transiting between SOCAL and HRC. While in transit, ships and aircraft would, at times, conduct basic and routine unit-level activities such as gunnery, bombing, and sonar training and maintenance. Of note, support craft would be more concentrated in the coastal waters in the areas of naval installations, ports, and ranges. Activities involving vessel movements occur intermittently and are variable in duration, ranging from a few hours up to weeks. More information on Navy and non-Navy vessel traffic patterns in the HSTT Study Area may be found in several studies prepared by the Navy (Starcovic and Mintz 2021; Mintz, 2016; Mintz and Filadelfo, 2011; Mintz, 2012; Mintz and Parker, 2006).
Foreign Navies
In addition, we note that in some cases, foreign militaries may participate in U.S. Navy training or testing activities in the HSTT Study Area. The Navy does not consider these foreign
military activities as part of the “specified activity” under the MMPA, and NMFS defers to the applicant to describe the scope of its request for an authorization.
The participation of foreign navies varies from year to year, but overall is infrequent compared with Navy's total training and testing activities. The most significant joint training event is the Rim of the Pacific (RIMPAC), a multi-national training exercise held every-other-year primarily in the HRC. The participation level of foreign military vessels in U.S. Navy-led training or testing events within the HRC and within SOCAL differs greatly between RIMPAC and non-RIMPAC years. For example, in 2019 (a non-RIMPAC year), there were 0.1 foreign navy at-sea days (
i.e.,
1 day = 24 hours) within HRC and 20 foreign navy at-sea days within SOCAL (Navy 2021). Out of 56 U.S.-led training events in 2019, 4 involved foreign navy vessels, with an average time per event of 8.7 hours. In 2020, a RIMPAC year, foreign vessels participating in U.S. Navy-led events accounted for 32 at-sea days in the HRC from August through September (some of this activity occurred after the RIMPAC exercise). During RIMPAC 2022, foreign vessels operated and/or transited through the HRC for 576 hours (24 days). Even in a RIMPAC year, the days at sea for foreign militaries engaged in a Navy-led training or testing activity accounts for a very small percentage compared to the U.S. Navy activities. For instance, the 2020 foreign military participation (a RIMPAC-year) was 1.5 percent of the U.S. Navy's average days at sea (32 days out of an estimated 2,056 days at sea).
According to the U.S. Navy, consistent with customary international law, when a foreign military vessel participates in a U.S. Navy exercise within the U.S. territorial sea (
i.e.,
0 to 12 nmi (0 to 22.2 km) from shore), the U.S. Navy will request that the foreign vessel follow the U.S. Navy's mitigation measures for that particular event. When a foreign military vessel participates in a U.S. Navy exercise beyond the U.S. territorial sea but within the U.S. Exclusive Economic Zone, the U.S. Navy will encourage the foreign vessel to follow the U.S. Navy's mitigation measures for that particular event (Navy 2022a; Navy 2022b). In either scenario (
i.e.,
both within and beyond the territorial sea), U.S. Navy personnel will provide the foreign vessels participating with a description of the mitigation measures to follow. If a foreign military is not participating in a U.S. Navy training or testing exercise, foreign military vessels operating within the HSTT Study Area are expected to adhere to their own standard operating procedures and environmental mitigation measures.
According to the U.S. Navy, the May 2021 vessel strike of two fin whales by an Australian navy vessel did not occur while that vessel was participating in a U.S. Navy-led training exercise. The Royal Australian Navy vessel was adhering to its standard operating procedures at the time of the strike. The Royal Australian Navy provided a report of the incident, which is discussed below to inform our analysis.
NMFS analyzes the effects of these foreign military activities in two ways. First, effects of all past foreign military activities are captured in the baseline for the analysis, through marine mammal abundance estimates and population trends found in the SARs. Second, NMFS considers foreign military activities, including recent strikes, qualitatively in this proposed rule. For instance, in preparing this rulemaking, NMFS and the U.S. Navy discussed the nature, frequency, and control over joint or U.S. Navy-led training and testing activities with foreign entities to identify opportunities to encourage foreign militaries to adopt mitigation. NMFS and the U.S. Navy examined the Royal Australian Navy strike report for any lessons that could inform U.S. Navy strike mitigation. NMFS considered the Royal Australian Navy strikes along with other recent U.S. Navy strikes to determine whether these strikes indicate an increased risk of strike by the U.S. Navy in this region during the early summer months. NMFS also considered the species struck in this incident, fin whales, along with other literature, when considering the likelihood of certain species to be struck by the U.S. Navy. Finally, NMFS considered the fact that two fin whales were struck by the Royal Australian Navy qualitatively when considering other fin whale population and mortality trends, as well as the take proposed for authorization, as part of the negligible impact analysis.
Standard Operating Procedures
For training and testing to be effective, personnel must be able to safely use their sensors and weapon systems as they are intended to be used in a real-world situation and to their optimum capabilities. While standard operating procedures (SOPs) are designed for the safety of personnel and equipment and to ensure the success of training and testing activities, their implementation often yields additional benefits on environmental, socioeconomic, public health and safety, and cultural resources. Because standard operating procedures are essential to safety and mission success, the Navy considers them to be part of the proposed activities under NEPA and included them in the environmental analysis. We consider standard operating procedures as part of Navy's specified activity for the purposes of MMPA but also, where procedures are utilized (even in part) to reduce impacts to marine mammal species and Navy's commitment to follow the measures are practicable, certain SOPs may also be required as mitigation. Details on standard operating procedures were provided in the 2018 HSTT proposed rule; please see the 2018 HSTT proposed rule, the 2017 Navy application, and Chapter 2 (
Description of Proposed Action and Alternatives
) of the 2018 HSTT FEIS/OEIS for more information.
As stated in its 2022 application, in 2018, the Navy updated its SOPs related to vessel safety to incorporate revised procedures regarding Lookouts for certain ship classes as per the 2021 Surface Ship Navigation Department Organization and Regulations Manual (NAVDORM). The 2021 NAVDORM requires the use of three Lookouts on Navy cruisers and destroyers as compared to the previous requirement of one Lookout when a vessel was underway and not engaged in sonar training or testing. However, as discussed in the Proposed Mitigation Measures section below, the Navy informed NMFS that requiring the additional Lookouts as mitigation is not practicable because this SOP may change in response to manning issues and national security needs. Further, since submission of its 2022 application, the Navy has updated its Lookout Training Handbook and implemented other training improvements, as described in the Proposed Mitigation Measures section (September 2022).
Description of Marine Mammals and Their Habitat in the Area of the Specified Activities
Marine mammal species and their associated stocks that have the potential to occur in the HSTT Study Area are presented in table 1 along with the best/minimum abundance estimate and associated coefficient of variation value. Consistent with the 2018 HSTT final rule and 2020 HSTT final rule, the Navy anticipates the take of individuals from 38 marine mammal species by Level A harassment and Level B harassment incidental to training and testing activities from the use of sonar and other transducers, in-water detonations,
air guns, and impact pile driving/vibratory extraction activities. As described in detail later, serious injury or mortality of six species is also analyzed and proposed for authorization.
In the 2018 HSTT proposed rule and 2018 HSTT final rule, we presented a detailed discussion of marine mammals and their occurrence in the HSTT Study Area, inclusive of important marine mammal habitat (
e.g.,
ESA-designated critical habitat), biologically important areas (BIAs), national marine sanctuaries (NMSs), and unusual mortality events (UMEs). Please see these rules and the 2017 and 2019 Navy applications for additional information beyond what is provided herein. While there have been some minor changes described here, there have been no changes to important marine mammal habitat, NMSs, or ESA designated critical habitat since the issuance of the 2018 HSTT final rule that change our determination of which species or stocks have the potential to be affected by the Navy's activities or the information in the
Description of Marine Mammals and Their Habitat in the Area of the Specified Activities
section in the 2019 HSTT proposed rule and 2020 HSTT final rule. Therefore, the information presented in those sections of the 2019 HSTT proposed rule and 2020 HSTT final rule remains current and valid with the exception of the information about UMEs, BIAs, and revised humpback whale stock structures, discussed below.
On April 21, 2021, NMFS designated critical habitat for the endangered Western North Pacific Distinct Population Segment (DPS), the endangered Central America DPS, and the threatened Mexico DPS of humpback whales (86 FR 21082). Areas proposed as critical habitat include specific marine areas located off the coasts of California, Oregon, Washington, and Alaska. None of the designated critical habitat overlaps with the HSTT Study Area. One of the proposed areas, critical habitat Unit 19, would have overlapped with the SOCAL range in the HSTT Study Area but was excluded after consideration of potential national security and economic impacts of designation. NMFS, in the final rule designating critical habitat for humpback whales, identified prey species, primarily euphausiids and small pelagic schooling fishes of sufficient quality, abundance, and accessibility within humpback whale feeding areas to support feeding and population growth, as an essential habitat feature. NMFS, through a critical habitat review team (CHRT), also considered inclusion of migratory corridors and passage features, as well as sound and the soundscape, as essential habitat features. NMFS did not include either in the final critical habitat, however, as the CHRT concluded that the best available science did not allow for identification of any consistently used migratory corridors or definition of any physical, essential migratory or passage conditions for whales transiting between or within habitats of the three DPSs. The best available science also currently does not enable NMFS to identify particular sound levels or to describe a certain soundscape feature that is essential to the conservation of humpback whales. Regardless of whether critical habitat is designated for a particular area, NMFS has considered all applicable information regarding marine mammals and their habitat in the analysis supporting these proposed regulations.
NMFS has reviewed the 2022 final Stock Assessment Reports (SARs; Carretta
et al.
2023, Young
et al.
2023). For all species except humpback whale, NMFS determined that neither the SARs nor any other new information changes our determination of which species or stocks have the potential to be affected by the Navy's activities. For humpback whale, the 2022 final SARs include a revision to the humpback whale stock structure in the Pacific Ocean. In the 2020 HSTT final rule, NMFS authorized take of the CA/OR/WA stock and Central North Pacific stock of humpback whale. Given the revised stock structure, in this proposed rule, NMFS has reanalyzed the potential for take of each stock of humpback whale and determined that the Central America/Southern Mexico-CA/OR/WA, Mainland Mexico—CA/OR/WA stock, and Hawaii stocks are likely to be taken by the Navy's activities. Please refer to the 2022 Alaska and Pacific Ocean SARs for additional information about these new stocks.)
The species considered but not carried forward for analysis are two American Samoa stocks of spinner dolphins—(1) the Kure and Midway stock and (2) the Pearl and Hermes stock. There is no potential for overlap with any stressors from Navy activities and therefore there would be no incidental takes, in which case, these stocks are not considered further.
Table 1—Marine Mammal Occurrence Within the HSTT Study Area
Common name
Scientific name
Stock
Status
MMPA
ESA
Occurrence
Seasonal
absence
Stock abundance
(CV)/minimum
population
Blue whale
Balaenoptera musculus
Eastern North Pacific
Strategic, Depleted
Endangered
Southern California
—
1,898 (0.085)/1,767.
Central North Pacific
Strategic, Depleted
Endangered
Hawaii
Summer
133 (1.09)/63.
Bryde's whale
Balaenoptera brydei/edeni
Eastern Tropical Pacific
—
—
Southern California
—
unknown.
Hawaii
—
—
Hawaii
—
602 (0.22)/501.
Fin whale
Balaenoptera physalus
CA/OR/WA
Strategic, Depleted
Endangered
Southern California
—
11,065 (0.405)/7,970.
Hawaii
Strategic, Depleted
Endangered
Hawaii
Summer
203 (0.99)/101.
Humpback whale
Megaptera novaeangliae
Central America/Southern Mexico—CA/OR/WA
Strategic
Endangered
1
Southern California
Winter
1,496 (0.171)/1,284.
Mainland Mexico—CA/OR/WA
Strategic
Threatened
1
Southern California
Winter
3,477 (0.101)/3,185.
Hawai'i
—
—
1
Hawaii
Summer
11,278 (0.56)/7,265.
Minke whale
Balaenoptera acutorostrata
CA/OR/WA
—
—
Southern California
—
915 (0.792)/509.
Hawaii
—
—
Hawaii
Summer
438 (1.05)/212.
Sei whale
Balaenoptera borealis
Eastern North Pacific
Strategic, Depleted
Endangered
Southern California
—
519 (0.40)/374.
Hawaii
Strategic, Depleted
Endangered
Hawaii
Summer
391 (0.9)/204.
Gray whale
Eschrichtius robustus
Eastern North Pacific
—
—
Southern California
—
26,960 (0.05)/25,849.
Western North Pacific
Strategic, Depleted
Endangered
Southern California
—
290 (NA)/271.
Sperm whale
Physeter macrocephalus
CA/OR/WA
Strategic, Depleted
Endangered
Southern California
—
1,997 (0.57)/1,270.
Hawaii
Strategic, Depleted
Endangered
Hawaii
—
5,707 (0.23)/4,486.
Pygmy sperm whale
Kogia breviceps
CA/OR/WA
—
—
Southern California
Winter and Fall
4,111 (1.12)/1,924.
Hawaii
—
—
Hawaii
—
42,083 (0.64) 25,695.
Dwarf sperm whale
Kogia sima
CA/OR/WA
—
—
Southern California
—
unknown.
Hawaii
—
—
Hawaii
—
unknown.
Baird's beaked whale
Berardius bairdii
CA/OR/WA
—
—
Southern California
—
1,363 (0.53)/894.
Blainville's beaked whale
Mesoplodon densirostris
Hawaii
—
—
Hawaii
—
1,132 (0.99)/564.
Cuvier's beaked whale
Ziphius cavirostris
CA/OR/WA
—
—
Southern California
—
5,454 (0.27)/4,214.
Hawaii
—
—
Hawaii
—
4,431 0.41/3,180.
Longman's beaked whale
Indopacetus pacificus
Hawaii
—
—
Hawaii
—
2,550 (0.67)/1,527.
Mesoplodont beaked whales
Mesoplodon spp
CA/OR/WA
—
—
Southern California
—
3,044 (0.54)/1,967.
Common Bottlenose dolphin
Tursiops truncatus
California Coastal
—
—
Southern California
—
453 (0.06)/346.
CA/OR/WA Offshore
—
—
Southern California
—
3,477 (0.696)/2,048.
Hawaii Pelagic
—
—
Hawaii
—
unknown.
Kauai and Niihau
—
—
Hawaii
—
NA NA/97.
Oahu
—
—
Hawaii
—
NA.
4-Islands
—
—
Hawaii
—
NA.
Hawaii Island
—
—
Hawaii
—
unknown.
False killer whale
Pseudorca crassidens
Main Hawaiian Islands Insular
Strategic, Depleted
Endangered
Hawaii
—
167 (0.14)/149.
Hawaii Pelagic
—
—
Hawaii
—
2,086 (0.35)/1,567.
Northwestern Hawaiian Islands
—
—
Hawaii
—
477 (1.71)/178.
Fraser's dolphin
Lagenodelphis hosei
Hawaii
—
—
Hawaii
—
40,960 (0.7)/24,068.
Killer whale
Orcinus orca
Eastern North Pacific Offshore
—
—
Southern California
—
300 (0.1)/276.
West Coast Transient
—
—
Southern California
—
349 (N/A)/349.
Hawaii
—
—
Hawaii
—
161 (1.06)/78.
Long-beaked common dolphin
Delphinus capensis
California
—
—
Southern California
—
83,379 (0.216)/69,636.
Melon-headed whale
Peponocephala electra
Hawaiian Islands
—
—
Hawaii
—
40,647 (0.74)/23,301.
Kohala Resident
—
—
Hawaii
—
unknown.
Northern right whale dolphin
Lissodelphis borealis
CA/OR/WA
—
—
Southern California
—
29,285 (0.72)/17,024.
Pacific white-sided dolphin
Lagenorhynchus obliquidens
CA/OR/WA
—
—
Southern California
—
34,999 (0.222)/29,090.
Pantropical spotted dolphin
Stenella attenuata
Oahu
—
—
Hawaii
—
unknown.
4-Islands
—
—
Hawaii
—
unknown.
Hawaii Island
—
—
Hawaii
—
unknown.
Hawaii Pelagic
—
—
Hawaii
—
39,768 (0.51)/25,548.
Pygmy killer whale
Feresa attenuata
Tropical
—
—
Southern California
Winter & Spring
unknown.
Hawaii
—
—
Hawaii
—
10,328 (0.75)/5,885.
Risso's dolphins
Grampus griseus
CA/OR/WA
Hawaii
—
—
—
—
Southern California
Hawaii
—
—
6,336 (0.32)/4,817.
7,385 (0.22)/6,150.
Steno bredanensis
NSD
2
—
—
Southern California
—
unknown.
Rough-toothed dolphin
Hawaii
—
—
Hawaii
—
76,357 (0.41)/54,804.
Short-beaked common dolphin
Delphinus delphis
CA/OR/WA
—
—
Southern California
—
1,056,308 (0.21)/888,971.
Short-finned pilot whale
Globicephala macrorhynchus
CA/OR/WA
—
—
Southern California
—
836 (0.79)/466.
Hawaii
—
—
Hawaii
—
12,607 (0.18)/10,847.
Spinner dolphin
Stenella longirostris
Hawaii Pelagic
—
—
Hawaii
—
unknown.
Hawaii Island
—
—
Hawaii
—
665 (0.09)/617.
Oahu and 4-Islands
—
—
Hawaii
—
unknown.
Kauai and Niihau
—
—
Hawaii
—
unknown.
Kure and Midway
—
—
Hawaii
—
unknown.
Pearl and Hermes
—
—
Hawaii
—
unknown.
Striped dolphin
Stenella coeruleoalba
CA/OR/WA
—
—
Southern California
—
29,988 (0.3)/23,448.
Hawaii
—
—
Hawaii
—
35,179 (0.23)/29,058.
Dall's porpoise
Phocoenoides dalli
CA/OR/WA
—
—
Southern California
—
16,498 (0.61)/10,286.
Harbor seal
Phoca vitulina
California
—
—
Southern California
—
30,968 (NA)/27,348.
Hawaiian monk seal
Neomonachus schauinslandi
Hawaii
Strategic, Depleted
Endangered
Hawaii
—
1,465
3
(0.03)/1,431.
Northern elephant seal
Mirounga angustirostris
California
—
—
Southern California
—
187,386 (NA)/85,369.
California sea lion
Zalophus californianus
U.S. Stock
—
—
Southern California
—
257,606 (NA)/233,515.
Guadalupe fur seal
Arctocephalus townsendi
Mexico to California
Strategic, Depleted
Threatened
Southern California
—
34,187 (NA)/31,019.
Northern fur seal
Callorhinus ursinus
California
Depleted
—
Southern California
—
14,050 (NA)/7,524.
Note:
A “—” indicates that this column does not apply.
1
The Mainland Mexico-CA-OR-WA stock and the Mexico-North Pacific stock (which does not occur in the HSTT Study Area) of humpback whale comprise the Mexico DPS. The Hawai'i stock comprises the Hawai'i DPS. The Central America/Southern Mexico-CA-OR-WA stock comprises the Central America DPS.
2
NSD—No stock designation. Rough-toothed dolphin has a range known to include the waters off Southern California, but there is no recognized stock or data available for the U.S. West Coast.
3
The best official estimate of the total population size from the NMFS 2022 Stock Assessment Report (Carretta
et al.
2023) is 1,465. This estimate is based on available data through 2020 data for Kure and Midway Atolls, Nihoa Island, and the MHI, and through 2019 for all other subpopulations. More recent survey data for 2021 and 2022 indicate an increasing trend in population size. NMFS estimates a total population size for 2022 of 1,605 (NOAA 2023).
Unusual Mortality Events
An UME is defined under section 410(6) of the MMPA as a stranding that is unexpected, involves a significant die-off of any marine mammal population, and demands immediate response. From 1991 to the present, there have been 17 formally recognized UMEs affecting marine mammals in California and Hawaii and involving species under NMFS' jurisdiction. There is one UME that is applicable to our evaluation of the Navy's activities in the HSTT Study Area. The gray whale UME along the west coast of North America is active and involves ongoing investigations. At the time of publication of the 2020 HSTT final rule, there was an active UME for Guadalupe fur seal, which NMFS fully considered in its analysis (85 FR 41780, July 10, 2020). This UME was closed on September 2, 2021, and therefore, it is not discussed further beyond the information provided here. The UME was closed because conditions under which the UME was declared are no longer occurring or have become persistent. Scientists documented a reduction in strandings compared to peak UME years. The team of scientists who investigated this UME determined the cause of the UME as being due to malnutrition in Guadalupe fur seal pups and yearlings from ecological factors (
e.g.,
warm water events) in the Pacific Ocean causing suboptimal prey conditions. Please see
https://www.fisheries.noaa.gov/national/marine-life-distress/unusual-mortality-event-2015-2021-guadalupe-fur-seal-and-2015
for additional information on this UME.
Gray Whale UME
Since January 1, 2019, elevated gray whale strandings have occurred along the west coast of North America, from Mexico to Canada. As of June 25, 2023, there have been a total of 674 strandings along the coasts of the U.S., Canada, and Mexico, with 333 of those strandings occurring along the U.S. coast. Of the strandings on the U.S. coast, 135 have occurred in Alaska, 83 in Washington, 22 in Oregon, and 93 in California. Full or partial necropsy examinations were conducted on a subset of the whales. Preliminary findings in several of the whales have shown evidence of emaciation. These findings are not consistent across all of the whales examined, so more research is needed. As part of the UME investigation process, NOAA has assembled an independent team of scientists to coordinate with the Working Group on Marine Mammal Unusual Mortality Events to review the data collected, sample stranded whales, consider possible causal-linkages between the mortality event and recent ocean and ecosystem perturbations, and determine the next steps for the investigation. Please refer to:
https://www.fisheries.noaa.gov/national/marine-life-distress/2019-2023-gray-whale-unusual-mortality-event-along-west-coast-and
for more information on this UME. See the Preliminary Analysis and Negligible Impact Determination section for additional information on how NMFS has considered this UME in this proposed rule.
Biologically Important Areas
Since publication of the 2020 HSTT final rule, Kratofil
et al.
(2023) identified updated BIAs in Hawaii. The HSTT Study Area overlaps the updated BIAs for small and resident populations of the following species in Hawaii: spinner dolphin, short-finned pilot whale, rough-toothed dolphin, pygmy killer whale, pantropical spotted dolphin, melon-headed whale, false killer whale, dwarf sperm whale, Cuvier's beaked whale, common bottlenose dolphin, and Blainville's beaked whale. Further, the HSTT Study Area overlaps updated BIAs for humpback whale reproduction in Hawaii. The updated BIAs overlap critical Navy training and testing areas within the HSTT Study Area, including most of the internal Navy operating areas. Please see Kratofil
et al.
(2023) for additional details about the BIAs.
Potential Effects of Specified Activities on Marine Mammals and T heir Habitat
This section provides a discussion of the ways in which components of the specified activity may impact marine mammals and their habitat. The Estimated Take 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 section, and the Proposed Mitigation section, to draw conclusions regarding the likely impacts of these activities on the reproductive success or survivorship of individuals and whether those impacts are reasonably expected to, or reasonably likely to, adversely affect the species or stock through effects on annual rates of recruitment or
survival. In the
Potential Effects of Specified Activities on Marine Mammals and Their Habitat
section of the 2018 HSTT proposed and final rules, and as updated by the 2020 HSTT final rule, NMFS provided a description of the ways marine mammals may be affected by the same activities that the Navy will be conducting during the 7-year period analyzed in this rulemaking in the form of serious injury or mortality, physical trauma, sensory impairment (permanent and temporary threshold shifts and acoustic masking), physiological responses (particularly stress responses), behavioral disturbance, or habitat effects. We do not repeat the information here, all of which remains current and applicable, and instead summarize any new relevant information from the scientific literature. For more information we refer the reader to those rules and the 2018 HSTT FEIS/OEIS (Chapter 3, Section 3.7
Marine Mammals
), which NMFS participated in the development of via our cooperating agency status and adopted to meet our NEPA requirements.
In the
Potential Effects of Specified Activities on Marine Mammals and Their Habitat
section of the 2018 HSTT final rule, we stated that it has been speculated for some time that beaked whales might have unusual sensitivities to sonar sound due to their likelihood of stranding in conjunction with mid-frequency active sonar (MFAS) use, although few definitive causal relationships between MFAS use and strandings have been documented, and no such findings have been documented with Navy use in Hawaii and southern California. On March 25, 2022, a beaked whale (species unknown) stranded in Honaunau Bay, Hawaii. The animal was observed swimming into shore and over rocks. Bystanders intervened to turn the animal off of the rocks, and it swam back out of the Bay on its own. Locals reported hearing a siren or alarm type of sound underwater on the same day, and a Navy vessel was observed from shore on the following day. The Navy confirmed it used continuous active sonar (CAS) within 50 km (27 nmi) and 48 hours of the time of stranding, though the stranding has not been definitively linked to the Navy's CAS use.
An initial study of another deep diving odontocete, the sperm whale, found similar behavioral responses and reductions in foraging when whales were exposed to pulsed active sonar (PAS) and CAS at similar cumulative Sound Exposure Levels (SEL
cum
), even though the CAS signal had a lower source level than the PAS signal. This may indicate that animals were, in this case, responding to the cumulative energy of a signal rather than the instantaneous amplitude (Cure
et al.
2021, Isojunno
et al.
2020). If a beaked whale were inshore of a Navy vessel using either PAS or CAS MFAS, and responded by moving away from the vessel, they could find themselves in shallow water and become disoriented, as may have happened in the case of Honaunau Bay. In addition, the animal was not seen after it returned to sea, so blood tissue samples could not be obtained. There has been a growing body of literature about the impacts of new pathogens on the health and stranding of marine mammals, including beaked whales in Hawaii and other locations in the Pacific (
e.g.,
Clifton
et al.
2023 and West
et al.
2013).
New Pertinent Science Since Publication of the 2020 HSTT Final Rule
NMFS has reviewed new relevant information from the scientific literature since publication of the 2020 HSTT final rule. Summaries of the new key scientific literature reviewed since publication of the 2020 HSTT final rule are presented below. The literature generally falls into the following topic areas: Vessel Strike; Aircraft Noise; Hearing, Vocalization, and Masking; Hearing Loss (Temporary Threshold Shift (TTS) and Permanent Threshold Shift (PTS)); Behavioral Reactions; Stranding; Population Consequences of Disturbance and Cumulative Stressors; Methodology for Assessing Acoustic Impacts.
Vessel Strike
Crum
et al.
(2019) analyzed a modeling framework using encounter theory to estimate the risk of lethal commercial vessel strike to North Atlantic right whales. Seasonal mortality rates of right whales decreased by 22 percent on average after a speed rule was implemented, indicating that the rule is effective at reducing lethal collisions. The rule's effect on risk was greatest where right whales were abundant and vessel traffic was heavy but varied considerably across time and space.
Keen
et al.
(2019) compared vessel traffic patterns in the Southern California Bight, San Francisco, and the Pacific Northwest and found fin whales had a higher risk of nighttime vessel strikes with the nighttime risk being double daytime risk. The authors concluded that the shipping lanes contained 14 percent of all traffic volume and contributed 13 percent of all strike risk similar to conclusions reached by Rockwood
et al.
(2017). However, the authors also point out that a California Current Ecosystem (CCE) wide shipping speed reductions would not be practicable. Instead, they proposed 24-hour speed restrictions around and within shipping lanes would be more effective and feasible than nighttime only speed restrictions elsewhere. Keen
et al.
(2019b) reported high fin whale habitat suitability throughout the Southern California Bight, in particular inshore in winter and in southern portions of the Bight, which include HSTT SOCAL Study Area.
Leaper (2019) estimated that a global 10 percent reduction in shipping speeds could result in a reduction of underwater sound associated with shipping by approximately 40 percent and vessel strike risk by around 50 percent by 2050. The vessel strike risk reduction done by the author is highly variable based solely on the relationship between ship speed and risk, qualitative in its findings, and speculative.
Redfern
et al.
(2019) compared risk of vessel strike to baleen whales around the Santa Barbara Channel based on 8 years of shipping data (2008-2015). Species evaluated include blue whales, fin whales, and humpback whales using available spatial habitat models and satellite tagging results. Spatial habitat modeling data included the years 1991, 1993, 1996, 2001, 2005, 2008, and 2009. The authors defined collision risk based on the co-occurrence of whales and ships for various management scenarios focused on adding shipping routes, expanding existing area to be avoided, and reducing shipping speed associated with these areas. Encounter rate theory was used to predict relative mortality resulting from vessel strikes by estimating (a) the encounter rate; (b) the number of encounters that result in a collision; and (c) the probability that a collision is lethal (Martin
et al.
2016, Rockwood
et al.
2017, Crum
et al.
2019). The authors concluded that expanding the existing areas to be avoided and speed reductions within shipping lanes and their approaches would be the most effective solutions. Ship speeds declined in the Bight from 2008 to 2015 because California air pollution regulations and economic factors made slow‐steaming strategies more favorable, therefore reduction in risk from slowing ships was greatest in 2008 and lowest in 2015.
Rockwood and Jahncke (2019) estimated that humpback whale mortality from January to April in Southern California alone was 6.5 whales (1.63/month), based upon modeling using updated abundance
estimates for humpback whales off Southern California. When added to the estimated mortality from July to November, the total estimated annual humpback mortality from vessel strikes in California alone was 23.4 deaths (16.9 + 6.5). This study did not include information for January to April for fin or blue whales and did not estimate humpback mortality in central or Northern California. Thus, even this updated study may underestimate whale mortality. The author's focus was exclusively on shipping approaches to San Francisco Bay (Northern California) and Los Angeles/Long Beach (Southern California) based on Rockwood
et al.
2017 with new local fine scale analysis. The paper postulated potential mortality from models, not actual reported strikes. The model is used to predict whale mortality based on factors listed in Rockwood
et al.
2017. In the model results, cargo vessels, especially container ships, accounted for more than half of the predicted mortality for all whale species in both Northern and Southern California with oil tankers accounting for the second highest mortality. The author's recommendation concludes with commercial industry-wide shipping speed reduction recommendations given the model is biased on mortality as a function of speed. In summary, Rockwood and Jahncke (2019) only addresses commercial shipping strike risk associated with major California commercial ports, and therefore, the paper may have limited applicability to how the Navy trains and tests in SOCAL.
Sèbe
et al.
(2019) assesses previous publications on whale vessel strike risk methodology and proposed a systematic approach to addressing the issue called the Formal Safety Assessment: (1) identification of hazards, (2) assessment of risks, (3) risk control options, (4) cost-benefit assessment, and (5) recommendations for decision-making. The authors provided a case study based on data from Rockwood
et al.
(2017). No new data analysis is presented in the paper. Caveats to Sèbe
et al.
(2019) are similar to those mentioned for Rockwood
et al.
(2017, 2019): older marine mammal data that may not be reflective of current or future distribution and focus on limited navigation within shipping approaches by commercial ships means that this study may have somewhat limited applicability to how the Navy trains and tests in SOCAL.
Szesciorka
et al.
(2019) concluded that while whales have some cues to avoid ships, this is true only at close range, under certain oceanographic conditions and if the whale is not otherwise distracted by feeding, breeding, or other behaviors. The paper is based on a single blue whale reaction observed in the Santa Barbara Channel, north of, and outside of, SOCAL. The blue whale was tagged as part of the U.S. Navy-funded Southern California Behavioral Response Study (SOCAL BRS) 2010-2015 and exposed to simulated MFAS when a closest point of approach of 93 m from a passing commercial container ship was noted. The whale was only tagged for a couple of hours before tag detachment. As other published papers report from the SOCAL BRS and as cited in the 2018 HSTT FEIS/OEIS, there can be significant individual variation in response to anthropogenic sources, which in this case would include vessel transit.
Blondin
et al.
(2020) estimated blue whale vessel strike risk in the Southern California Bight by combining predicted daily whale distributions with continuous vessel movement data for 4 years (2011, 2013, 2015, 2017). The study focuses on the northern Southern California Bight associated with the commercial vessel traffic separation zone through Santa Barbara Channel approaching the Port of Los Angeles/Long Beach. This area is north of and outside of SOCAL. The authors found that vessel traffic activity across years (2011, 2013, 2015, 2017) was variable and whale spatial probability was also variable based on inter-annual fluctuations in environmental conditions. Similar to previous monitoring efforts in Southern California, blue whales are typically in higher concentrations north of SOCAL from July-November (Mate
et al.
2018), and Blondin
et al.
(2021) also picked up on this seasonal variability in their analysis. Oceanographic conditions favorable for krill development and concentration (
i.e.,
cool water periods) would lead to increased blue whale occurrence and higher strike risk as evidenced during the higher number of blue whale strikes in 2007 (Berman-Kowalewski
et al.
2010). Finally, the coarse level of data analyzed by the authors does not account for short-term patchy prey conditions influencing blue whale occurrence and may result in overestimation of average risk.
Redfern
et al.
(2020) revised their 2019 assessments of vessel strike risk off California using interannual variability of risk across multiple years for blue whale, fin whale and humpback whale. The authors showed higher concentrations of both blue and fin whales along the Central California coast as compared to within SOCAL. Magnitude of vessel strike risk was influenced by the ship traffic scenario. In addition, interannual species variability (1991, 1993, 1996, 2001, 2005, 2008, and 2009) also influenced the magnitude of vessel strike risk, but did not change whether nearshore or offshore scenarios had higher risk. The author's conclusions were similar to Redfern
et al.
(2019). Figure 2 from Redfern
et al.
(2020) illustrates mean blue whale, fin whale, and humpback whale vessel strike risk for California based on data through 2009. Results from more recent NMFS surveys in 2014 and 2018 may or may not change this assessment in the future.
Rockwood
et al.
(2020b) calculated expected blue whale and humpback whale mortality for hypothetical compliance scenarios by imposing speed caps within and adjacent to vessel traffic lanes leading to the Port of San Francisco in Central California, 400 miles (643.7 km) north of SOCAL. Rookwood
et al.
(2020a) had already demonstrated this area off Central California had concentrated krill prey with associated higher distributions of blue whales and humpback whales. Rookwood
et al.
(2020b) used better temporal resolution density data than previous modeling efforts reported by Rookwood
et al.
(2017). Biological data analysis for Rookwood
et al.
(2020b) was based on regional monthly krill and whale surveys from 2004-2017. Rockwood
et al.'
s (2020b) overall modeling conclusions were that lower commercial ship speeds within the vessel traffic lanes could potentially reduce whale mortality from vessel strike. The authors acknowledge that local changes in whale abundance can have strong effects on both inter-annual and long-term patterns of ship-strike mortality.
Bernknopf
et al.
(2021) examined the socioeconomic benefits of using remotely-sensed information instead of in situ observations for determining blue whale occurrence in the eastern North Pacific Ocean. Their analysis used blue whale spatial distribution through 1991-2009 projects as representative of 2017 densities (Becker
et al.
2012) combined with automatic identification system (AIS) derived measures of civilian commercial vessel traffic to predict blue whale vessel strike risk, called the Reference Case by the authors. The authors then compared estimated blue whale strike risk in a second analysis that, instead of using empirically measured blue whale observations converted into spatial habitat maps, used satellite tracking and environmental data to identify the spatial and temporal distribution of blue
whales, called the Counterfactual Case by the authors (Hazen
et al.
2017). Estimated mean fatal strikes to blue whales for the Reference Case based on empirical density data from 1991-2009 ranged from 0.0490 to 2.5877 (max. values >1.000 between June to October) (see Table 2 in Bernknopf
et al.
2021). Estimated mean fatal strikes to blue whales for the Counterfactual Case based on environmental estimates of blue whale density in 2017 ranged from 0.0286 to 2.1556 (max. values >1.000 between August to October). An important caveat to this research is that the two approaches result in different strike risks due to using different blue whale density estimates.
Barkaszi
et al.
(2021) designed a model to estimate risks to large whales from shipping associated with offshore wind development along the U.S. Atlantic Coast. A key caveat for the model is that it is based on civilian vessel types associated with wind energy construction (
e.g.,
tugs, service craft,
etc.
) with relatively fixed, direct routes to offshore wind sites. Therefore, while lower vessel speeds can reduce mortality, prediction and implementation of reduced speed zones are a far more complex challenge (Barkaszi
et al.
2021). Vessel speed has less effect on strike risk over a fixed distance with fixed target density when there are no behavioral components considered (Yin
et al.
2019). Vessel speed has a significant effect on strike risk only when behavioral components are considered, thus the ability for the user to input animal or vessel aversion is an important variable that can provide insights to the encounter risk based on vessel speeds.
Cusato (2021) discusses the merits of vessel traffic separation changes or mandatory commercial ship speed reductions in the Santa Barbara Channel to reduce the risk of vessel strikes to large whales. The author compares it to similar restrictions on the U.S. East Coast for North Atlantic right whales. The paper is a policy discussion rather than an analysis of current biological distribution of large whales and associated risk. Cusato (2021) focuses on reducing risk from commercial ships in the current vessel traffic separation scheme within the Santa Barbara Channel. Speed restrictions in the Channel would need to be implemented through either Federal regulations or Federal statute. The author also correctly points out legitimate concerns that operating large vessels at slow speeds in certain conditions could pose a safety risk because large vessels are more difficult to control and steer at slower speeds.
Hausner
et al.
(2021) examined tradeoffs of blue whale vessel strikes and speed reduction mitigation over a 17-year period from 2002 to 2018 in the Southern California Bight under two management scenarios verses a “fixed strategy” that implements speed reductions for a fixed time period each year. The two management strategies were (1) a “daily strategy” implementing speed reductions in response to whale habitat conditions on a daily basis, and (2) a “seasonal strategy” implementing speed reductions in response to whale habitat conditions on a seasonal basis. The period of the author's data analysis also covers the abnormal marine heat wave along the U.S. West Coast (2014-2016). The study's focus was exclusively with the traffic separation lanes leading from the Santa Barbara Channel to the Ports of Los Angeles and Long Beach, a narrow corridor north of and outside of SOCAL. The daily and seasonal management strategies were more effective in reducing blue whale strike risk in the Santa Barbara channel than the fixed strategy. The daily management strategy had the highest protective effect. This apparent difference in strategies also applied during and after the 2014-2016 marine heat wave where the daily strategy added even extra protection. The authors acknowledged that interannual variation on blue whale presence in the shipping lanes added some variability to their analysis. In addition, their study only considered blue whales sighted within the Traffic Separation Scheme, as opposed to the broader region where vessels transit through or a blue whale could occur.
Ransome
et al.
(2021) documented 40 vessel strikes to large whales in the Eastern Tropical Pacific Ocean between 1905 and 2017 off the coasts of 10 Central and South American countries (Mexico to Columbia). The authors concluded that vessel strikes to large whales are more prolific in this region than previously reported. For instance, the author's findings of 40 vessel strikes was over three times greater than previous reporting and still is likely under reporting total whale strikes. The majority of whale strikes occurred from the 1950s onward with the growth of modern shipping and whale watching. Humpback whales were the most commonly struck species (45 percent) although 30 percent of the species were not identified in their data.
Rockwood
et al.
(2021), similar to Rockwood
et al.
(2020b), calculated potential whale strike mortalities using AIS vessel data and whale density data to estimate mortality under several management scenarios within the commercial shipping lanes passing through Santa Barbara Channel and San Pedro Channel to and from the Ports of Los Angeles and Long Beach. While the Santa Barbara Channel is approximately 100 miles (160.9 km) north of SOCAL, Rockwood
et al.'
s study area also included the southern vessel traffic approach to Los Angeles and Long Beach which did extend into the northeast coastal portion of SOCAL. Recent whale surveys were not available for this effort, so the authors used long-term average blue, fin, and humpback whale densities from Becker
et al.
(2016). The author's model also predicted a higher level of whale vessel strikes from commercial ships than Rockwood
et al.
(2017), although the authors acknowledged that for the 2020 publication they included more vessel classes than for the 2017 publication.
Silber
et al.
(2021) examined the risk to gray whales from commercial shipping in the North Pacific. Vessel strike risk was highest for gray whales including the Western North Pacific Distinct Population Segment (WNP DPS) along most of the migratory routes. Highest risk to the WNP DPS of gray whales was outside of the SOCAL in the western Bering Sea, along the east coast of the Kamchatka peninsula (Russia), and coastlines of Japan. For both Eastern North Pacific and WNP DPSs of gray whales, the greatest vessel strike risk along the U.S. West Coast was from Washington to Central California.
Helm
et al.
(2023) looked at strike risk to foraging humpback whales surfacing around large cruise ships transiting Glacier Bay National Park, Alaska. The authors concluded that the probability of foraging humpback whales remaining near the surface after first sightings was relatively high. While this puts humpback whales at increased risk of ship strike, it also allows shipboard observers more time to spot whales in order to maneuver the ship to avoid a strike.
Lookout Effectiveness
A recent study by Oedekoven and Thomas (2022) was designed to evaluate the effectiveness of Navy Lookouts at detecting marine mammals before they entered a defined set of mitigation zones (
i.e.,
200, 500, and 1,000 yd (182.9, 457.2, and 914.4 m)) during MFAS training activities. This study also compared Lookout effectiveness with that of trained marine mammal observers. Lookout teams were comprised of varying numbers of Lookouts depending on the type of ship and the training activity that was occurring (noting that the data was
collected prior to the Navy's change in its SOPs to require the use of three Lookouts on Navy cruisers and destroyers.) Marine mammal observer teams consisted of two dedicated observers. Results of this study indicate that Navy Lookout Teams, which include Lookouts and other crew members, have approximately an 80 percent chance of failing to detect a pod of large baleen whales (rorquals) before they come closer than a mitigation range of 200 yd (182.9 m), compared with a 49 percent chance for trained marine mammal observers. The probability of a pod remaining undetected by Lookouts was greater for larger mitigation zones (
i.e.,
85 percent at 500 yd (457.2 m); 91 percent at 1,000 yd (914.4 m)). These values require some level of interpretation with regard to the numerical results. For instance, the study's statistical model assumed that Navy ships moved in a straight line at a set speed for the duration of the field trials, and that animals could not move in a direction perpendicular to a ship. Violation of this model assumption would underestimate Lookout effectiveness for some data points. The values for both Navy Lookouts and the Marine Mammal Observers include animals under the water that would not have been available for detection by a Lookout. This study suggests that detection of marine mammals is less certain than previously assumed at certain distances.
Hearing, Vocalization, and Masking
Branstetter
et al.
(2021) measured underwater, masked hearing thresholds for frequencies between 0.5 and 80 kilohertz (kHz) in two killer whales. Critical ratios computed from the threshold measurements ranged from 16 to 32 decibels (dB). For communication signals in the 1.5-15 kHz range, killer whales would require the signal to be up to 26 dB above background Gaussian noise to be detected. The authors noted that ambient background noise in the marine environment is not Gaussian, the tones used in this study do not contain as much frequency information as biologically relevant signals, and the temporal and spectral characteristics of actual signals and noise may result in some degree of release from masking. These results are consistent with critical ratio measurements from other odontocete species, despite differences in hearing ability and head size.
Fournet
et al.
(2021) measured call amplitudes from male bearded seals in the Beaufort Sea under different ambient noise conditions. The results showed that estimated source levels of seal calls increased with ambient noise up to approximately 100-105 dB root-mean-squared (rms), above which no further Lombard effect was observed. This suggests that masking of bearded seal mating calls may occur, resulting in reduced communication range, which could reduce the ability of bearded seals to detect one another, mate, and reproduce.
Mercado (2021) aimed to characterize how units within humpback whale songs were systematically varied using a large dataset of recordings from off the coast of Kona, Hawaii. The data showed that narrowband, reverberant units repeated at regular time intervals and dominated most song sessions, while broadband units were less predictable and occupied frequency bands that did not overlap with the narrowband units. The persistent production of narrowband units at regular time intervals resulted in consistent reverberation, which could either function to increase the range at which the song can be detected, or listen for fluctuations in echoes to indicate the presence of whale-sized targets.
Rey-Baquero
et al.
(2021) collected theodolite and passive acoustic data on humpback whales in a pristine environment along the Colombian Pacific for 2 months. When acoustic data (n=34 files) were analyzed for unit duration and inter-unit interval before and after boats passed, song unit lengths were shorter and more variable when boats were present. The second aim of this study was to model the whales' communication space during ambient noise or one to two boats traveling slowly. The most common peak frequency of this stock's song (350 Hz) was used in the model, and, along with a whale's location along the coast, informed calculations of transmission loss. However, the source level of “typical whale-watching boats” (145 dB re 1 uPa (decibels referenced to 1 micropascal) at 1 m; (Erbe
et al.
2012)) and humpback whales (153 dB re 1 uPa at 1 m; (Au
et al.
2006)) were taken from previous studies. Authors found that the infrequent addition of ecotour boat noise could temporarily reduce the “very audible area” (>10 dB SNR) in their song's commonly used peak frequency (350 Hz) by 63 percent.
Ruscher
et al.
(2021) measured aerial behavioral hearing thresholds in a Hawaiian monk seal (
Neomonachus schauinslandi
). The results showed a hearing range between 0.1 and 33 kHz with relatively poor sensitivity compared to Phocinae seals. The most sensitive thresholds were 40 dB re 20 μPa measured at 800 Hz and 3.2 kHz. The resulting audiogram was most similar to the northern elephant seal, which is the only other species of Monachinae seal with audiogram data (Reichmuth
et al.
2013). This study suggested that hearing sensitivity of Monachinae seals is substantially reduced compared to other species within their functional hearing group (phocid carnivores in air; PCA); therefore, the use of the PCA weighting function to predict auditory impacts is likely conservative for Hawaiian monk seals.
Sills
et al.
(2021) measured underwater auditory detection thresholds in a male Hawaiian monk seal, and the range of most sensitive hearing was between 0.2 and 33 kHz. Peak hearing sensitivity of 73 dB re 1 μPa was observed at 1.6 kHz. The audiogram for this individual was similar but narrower and elevated compared to the hearing group (phocid carnivores in water; PCW) composite audiogram used to assess impacts to this species. Underwater vocalizations were also measured, and 6 call types were identified, which had peak energy between 55 and 400 Hz. The number of calls produced per minute fluctuated seasonally and peaked in the breeding season with the highest call rates recorded in December.
Sweeney
et al.
(2022) examined the difference between noise impact analyses using unweighted broadband sound pressure levels (SPLs) and analyses using auditory weighting functions. The recordings used to conduct parallel analyses in three marine mammal species groups were from a shipping route in Canada. Since shipping noise was predominantly in the low-frequency spectrum, bowhead whales perceived similar weighted and unweighted SPLs while narwhals and ringed seals experienced lower SPLs when auditory weighting functions were used. The data provide a real-world example to support the use of weighting functions based on hearing sensitivity when estimating audibility and potential impact of vessel noise on marine mammals.
A study by von Benda-Beckmann
et al.
(2021) modeled the effect of pulsed and continuous 1-2 kHz active sonar on sperm whale echolocation clicks and found that the presence of upper harmonics in the sonar signal increased masking of clicks produced in the search phase of foraging compared to buzz clicks produced during prey capture. Different levels of sonar caused intermittent to continuous masking (120 to 160 dB re 1 μPa2, respectively), but varied based on click level, whale orientation, and prey target strength. CAS resulted in a greater percentage of
time that echolocation clicks were masked compared to PAS.
Kastelein
et al.
(2021c) compared the ability of harbor porpoises to detect signals in constant-amplitude noise with amplitude-modulated noise. Underwater, behavioral hearing thresholds were measured from harbor porpoises at 4 kHz under three conditions: ambient noise (control), sinusoidally amplitude modulated (SAM) masking noise, and Gaussian (constant amplitude) masking noise. Both masker types were centered at 4 kHz with a one-third octave bandwidth and were tested at various SPLs. The SAM noise was also tested at modulation rates from 1-90 hertz (Hz). The 4 kHz hearing test signals were 0.5, 1, and 2 seconds in duration. The results showed that, compared to Gaussian noise, up to 14.5 dB of masking release (from “dip listening”) was observed in lower-modulation rate (1-5 Hz) SAM noise. The effect of masking on communication space is often modeled using constant-amplitude noise, whereas most Navy sources contain gaps, more like amplitude-modulated noise. This study suggests that the signal duration, masker level, and masker modulation rate and depth should be considered when modeling the effect of noise on signal detection.
Isojunno
et al.
(2021) used data from 15 tagged sperm whales (Isojunno
et al.
2020) to evaluate odontocete echolocation behavior as a function of received sonar exposures. Statistical analysis revealed small reductions in the number of buzzes and movement during sonar, but the most apparent change in echolocation behavior was a Lombard effect observed during higher sea states (increased surface noise). No behavioral changes in orientation relative to the sonar source were observed that would suggest an anti-masking strategy for spatial release from masking. Theoretical modeling of masking potential in terms of detection range revealed that search phase clicks would likely be masked during both PAS and CAS, but the buzz clicks would not. For regular search phase clicks to be continuously masked, SELs would have to be equal to or greater than 160 and 173 dB re 1 μPa
2
s (dB referenced to 1 micropascal squared seconds) for PAS and CAS, respectively. Overall, the data showed more evidence for masking by increases in ambient noise (surface noise from higher sea states), than for sonar. This result could be due, in part, to the 1-2 kHz narrowband sonar masker, which is not comparable to broadband maskers such as ambient noise or shipping noise.
Matthews and Parks (2021) reviewed the existing literature on North Atlantic right whale acoustic behavior and summarize information on acoustic behavior of the Southern right whale, North Pacific right whale, and bowhead whale. The authors reviewed primary literature on whale vocalizations, anatomical modeling, and behavioral responses to playbacks to conclude that the North Atlantic right whale might have a hearing range of 20 Hz to 22 kHz. However, vocalization data cannot be used to directly estimate audible range since there are many examples of mammals (including marine mammals) that vocalize with energy below the frequency of best hearing, and calls can also contain high-frequency harmonics that are above the upper limit of hearing. The anatomical model developed by Ketten (1994) was used by Parks
et al.
(2007) to estimate a functional hearing range of 15 Hz to 18 kHz for this species.
Jacobson
et al.
(2022) modeled the probability of Blainville's beaked whale group vocal periods (GVPs) on the Pacific Missile Range Facility during periods of no naval activity, naval activity without hull-mounted MFAS, and naval activity with hull-mounted MFAS. Data were collected from bottom-mounted hydrophones on the range before, during, and after six Submarine Commanders Course (SCC) exercises. At an MFAS received level of 150 dB re 1 μPa rms (root mean square), the probability of GVP detection decreased by 77 percent (95 percent CI: 67 percent-84 percent) compared to periods when general training activity was ongoing and by 87 percent (95 percent CI: 81 percent-91 percent) compared to baseline conditions. This study found a greater reduction in p(GVP) with MFAS than observed in a prior study of Blainville's beaked whales at the Atlantic Undersea Test and Evaluation Center (AUTEC) (Moretti
et al.
2014). The authors suggest that this may be due to the baseline period in the AUTEC study including naval activity without MFAS, potentially lowering the baseline p(GVP), or due to differences in the residency of the populations at each range.
Branstetter and Sills (2022) reviewed direct laboratory (
i.e.,
psychoacoustic) studies of marine mammal hearing in noise. Psychoacoustic studies of auditory masking in marine mammals were described in detail and categorized by the type of signal and masker (
e.g.,
tone in white noise), and specific conditions under which masking is reduced (
i.e.,
release from masking). Specifically, comodulation masking release, or the reduction in masking due to amplitude or frequency modulation differences between the signal and noise, and spatial release from masking, or the reduction in masking due to spatial separation between signal and noise and the directional hearing ability of the listener, are discussed. Finally, energetic masking, or the ability of the listener to detect a signal was compared to informational masking, or the ability of the listener to comprehend the signal was reviewed. The authors point out that while the body of scientific evidence thus far shows that processes of the ear result in energetic masking, more research on informational masking is needed to develop realistic communication space models. This is because current communication space models are based on 50 percent signal detection rather than some threshold of successful signal recognition or interpretation by the listener.
Hearing Loss (TTS and PTS)
Houser (2021) reviews existing literature on the relationship between auditory threshold shift and tissue destruction in mammals. According to small terrestrial mammal literature, TTSs of approximately 30-50 dB measured 24 hours after sound exposure induced progressive tissue damage despite the return of normal hearing thresholds. Although large TTSs allow for full recovery of hearing, pathological tissue destruction may occur; however, smaller-magnitude TTSs are unlikely to result in tissue damage. The author concludes that the current criteria of 40 dB of TTS measured within minutes of the noise exposure as the onset of injury is likely to encompass recoverable auditory threshold shift without tissue damage. This publication supports the use of current definitions of auditory injury in marine mammals.
Kastelein
et al.
(2022a) measured underwater behavioral hearing thresholds in two California sea lions at 0.6, 0.85, and 1.2 kHz before and after exposure to a one-sixth-octave noise band centered at 0.6 kHz for 60-minutes. Hearing tests were also conducted at 1, 1.4, and 2 kHz after exposure to a one-sixth-octave noise band centered at 1 kHz for 60-minutes. For the 0.6 kHz exposure, the maximum TTS was 7.5 dB (6.7 dB mean) for a 210 dB cumulative SEL (SEL
cum
) exposure at the hearing test frequency one-half octave above the center frequency of the fatiguing stimulus (0.85 kHz), which recovered after approximately 12 minutes. For the 1 kHz exposure, the maximum TTS was 10.6 dB (9.6 dB mean) after a 195 dB SEL
cum
exposure at the hearing test frequency one-half octave above the center frequency of the fatiguing
stimulus (1.4 kHz). Mean threshold shift (TS) greater than 6 dB (mean = 8.0 dB, min = 7.2 dB, max = 8.5 dB) was also observed after exposure to the 1 kHz fatiguing stimulus at 195 dB SEL
cum
for the 1 kHz hearing test frequency. For this exposure frequency, hearing recovered within 24 minutes. The results of this study show individuals exhibiting onset of TTS in water at lower received levels than the otariid thresholds in “Criteria and Thresholds for U.S. Navy Acoustic and Explosive Effects Analysis (Phase III)” (Navy, 2017).
Kastelein
et al.
(2022b) measured underwater behavioral hearing thresholds in two California sea lions at 8, 11.3, and 16kHz before and after exposure to a one-sixth-octave noise band centered at 8 kHz for 60-minutes. Hearing tests were also conducted at 32 kHz after exposure to a one-sixth-octave noise band centered at 16 kHz for 60-minutes. For the 8kHz exposure, the maximum TTS was 20.2 dB (18 dB mean) for a 190 dB SEL
cum
exposure at the hearing test frequency one-half octave above the center frequency of the fatiguing stimulus (11.3 kHz), which recovered after approximately 12 minutes. For the 16 kHz exposure, the maximum TTS was 19.7 dB (16.3 dB mean) after a 207 dB SEL
cum
exposure at the hearing test frequency one-half octave above the center frequency of the fatiguing stimulus (22.4 kHz). For these exposure frequencies and scenarios, hearing recovered within 72 minutes or less. The results of this study show TTS onset in-water occurred at lower received levels than what the current otariid criteria in “Criteria and Thresholds for U.S. Navy Acoustic and Explosive Effects Analysis (Phase III”) (Navy, 2017) suggest.
Kastelein
et al.
(2021a) measured underwater behavioral hearing thresholds at 0.5, 0.71, and 1 kHz in one harbor porpoise before and after exposure to one-sixth-octave band noise centered at 0.5 kHz. Maximum TTS was 8.9 dB (mean = 7.6 dB) at the 0.5 kHz hearing test frequency after a 205-dB SEL
cum
exposure. For the 0.71 and 1 kHz hearing test frequencies, no mean TTS > 6 dB was observed. However, at 0.71 kHz, maximum TTS was 6.5 dB (mean = 5.8 dB) was observed after a 205-dB SEL
cum
exposure. At 1 kHz, a maximum of 6.3 dB of TTS (mean = 5.7 dB) occurred after 206-dB SEL
cum
exposures. All shifts < 5 dB recovered within 12 minutes and shifts > 6 dB recovered within 60 minutes. These results are consistent with the criteria and thresholds described in “Criteria and Thresholds for U.S. Navy Acoustic and Explosive Effects Analysis (Phase III)” (Navy, 2017).
Kastelein
et al.
(2021b) measured behavioral, underwater hearing thresholds at 2, 2.8, and 4.2 kHz in two sea lions before and after exposure to band-limited noise centered at 2 kHz. Sea lion hearing was also tested at 4.2, 5.6, 8 kHz before and after exposure to noise centered at 4 kHz. Maximum TTS was 24.1 dB (22.4 dB mean) at the 5.6 kHz test frequency after a 205-dB SEL
cum
exposure centered at 4 kHz. Threshold shifts greater than or equal to 6 dB occurred at 187, 181, and 187 dB SEL
cum
for 4.2, 5.6, and 8 kHz test frequencies respectively. After exposure to the 2-kHz noise, maximum TTS of 11.1 dB (10.5 dB mean) occurred for 203 dB SEL
cum
at the 2 kHz test frequency. Threshold shifts greater than or equal to 6 dB occurred at SEL
cum
of 192, 186, and 198 dB for test frequencies 2, 2.8, and 4.2 kHz respectively. These data suggest that one-half octave above the exposure frequency is the most sensitive to noise exposure. TTS between 6 and 10 dB recovered within 60 minutes, 10-15 dB of TTS recovered within 120 min, and TTS up to 24.1 dB recovered after 240 minutes. The results of this study show individuals exhibiting onset of TTS in-water at lower received levels than the current otariid criteria (“Criteria and Thresholds for U.S. Navy Acoustic and Explosive Effects Analysis (Phase III)” (Navy, 2017)).
Kastelein
et al.
(2020a) measured underwater, behavioral hearing thresholds in one harbor porpoise before and after exposure to playbacks of one-sixth-octave band noise centered at 1.5 kHz and a 6.5 kHz continuous wave. Following exposure to the 1.5 kHz noise band at 201 dB SEL
cum,
a maximum of a 7.8 dB, 9.8 dB, and 7 dB TTS was observed for 1.5, 2.1, and 3 kHz hearing frequencies respectively. After exposure to the 6.5 kHz continuous wave at 184 dB SEL
cum
, a maximum of a 7.5, 16.7, and 11.8 dB TTS was observed for 6.5, 9.2, and 13 kHz hearing frequencies respectively. For the 6.5 kHz exposure, a mean TTS > 6 dB was observed for the 178 and 180 dB SEL
cum
when the hearing test frequency was 9.2 kHz, and for the 180 dB SEL
cum
when the hearing test frequency was 13 kHz. The results of this study show that the animal incurred onset of TTS at higher received levels than what the current HF cetacean criteria in “Criteria and Thresholds for U.S. Navy Acoustic and Explosive Effects Analysis (Phase III)” (Navy, 2017) indicate for both 1.5 and 6.5 kHz.
Kastelein
et al.
(2020b) measured underwater, behavioral hearing thresholds in two harbor seals before and after exposure to playbacks of one-sixth-octave band noise centered at 0.5, 1, and 2 kHz. Hearing tests were conducted at the center frequency, one-half octave above, and 1 octave above center frequency. No TTS > 6 dB was observed for any hearing frequency after 204, 210, or 211 dB SEL
cum
exposures to the 0.5 kHz noise band. For the 1 kHz exposure frequency, max TTS of 7.4 dB (6.1 mean) was observed after a 207 dB SEL
cum
exposure at a hearing frequency of 1.4 kHz. For this exposure frequency, no other test condition produced TTS > 6 dB; although, a 5.9 dB shift (at 1.4 kHz) occurred at 206 dB SEL
cum.
For the 2 kHz noise band, after a 201 dB SEL
cum
exposure, max TTS of 12 dB was measured one octave above the center frequency (4 kHz). For this exposure frequency, TTS > 6 dB was observed at SEL
cum
> 201, 198, and 192 dB for hearing frequencies 2, 2.8, and 4 kHz respectively. All shifts recovered within 1 hour. These results of this study show that the animal incurred lower TTS (
i.e.,
smaller threshold shifts) at higher received levels than what the current phocid pinniped criteria in “Criteria and Thresholds for U.S. Navy Acoustic and Explosive Effects Analysis (Phase III)” (Navy, 2017) indicate.
Kastelein
et al.
(2020c) measured underwater, behavioral hearing thresholds in one harbor porpoise before and after exposure to playbacks of one-sixth-octave band noise centered at 88.4 kHz. Maximum TTS of 13.6 dB was observed at 197 dB SEL
cum
for the 100 kHz hearing test frequency. No TTS > 6 dB was observed for any SEL
cum
at the 88.4 kHz test frequency. For 125 kHz, shifts > 6 dB were observed for 191, 194, and 197 dB SEL
cum
exposures, with a mean TTS of 5.4, 6.1, and 5.9 dB, respectively. The results of this study show that the animal incurred TTS at higher received levels than what the current HF cetacean criteria in “Criteria and Thresholds for U.S. Navy Acoustic and Explosive Effects Analysis (Phase III)” (Navy, 2017) suggest.
Kastelein
et al.
(2020d) measured underwater, behavioral hearing thresholds in one harbor porpoise before and after exposure to airgun impulses (“shots”). Exposure conditions varied with regard to number of airguns, number of shots, light cues, and position of the dolphin relative to the airguns. Hearing test frequencies were 2, 4, and 8 kHz, and no TTS > 6 dB was observed. The results of this study show that the animal would incur TTS onset at higher received levels than what the current HF cetacean criteria in “Criteria and Thresholds for U.S. Navy Acoustic and Explosive Effects Analysis (Phase III)” (Navy, 2017) suggest.
Kastelein
et al.
(2020e) measured underwater, behavioral hearing thresholds in two harbor seals before and after exposure to playbacks of one-sixth-octave band noise centered at 40 kHz. For the 50 kHz hearing test frequency, a maximum TTS of 30.7 dB was observed 12-16 minutes after the 189 dB SEL
cum,
and a mean TTS > 6 dB was observed for all SEL
cum
177 dB and above. The 30-dB shift recovered after 3 days. No TTS > 6 dB was observed for any SEL
cum
at the 63 kHz test frequency for either seal. At 40 kHz, mean TTS of 9.2 dB was observed after a 189-dB SEL. The results of this study show that the animal incurred TTS at lower received levels than what the current phocid criteria in “Criteria and Thresholds for U.S. Navy Acoustic and Explosive Effects Analysis (Phase III)” (Navy, 2017) suggest.
Sills
et al.
(2020) exposed one bearded seal to multiple impulsive underwater noise exposures (seismic air gun “shots”). Hearing tests were conducted at 100 Hz and 400 Hz after exposures to 2, 4, and 10 shots. After a 4-shot (191 dB SEL
cum
) exposure, max TTS of 9.4 dB was observed, but no other TTS > 6 dB was demonstrated, despite four 10-shot (194-195 dB SEL
cum
) exposures. It is possible that TTS recovered during the measurements, as quantified by a mean “first miss” of 7.5 dB for the 10-shot exposures (mean TTS was 2.2 dB). The results of this study show that the animal incurred TTS onset at lower received levels than what the current criteria in “Criteria and Thresholds for U.S. Navy Acoustic and Explosive Effects Analysis (Phase III)” (Navy, 2017) suggest. Behavioral responses were also scored and averaged across three observers. For most exposures, the seal exhibited mild/detectable responses, and all scores indicated that the seal did not move more than half his body and consistently participated in the study.
Tougaard
et al.
(2022) reviewed the most recent temporary TTS data from phocid seals and harbor porpoises and compared empirical data to the predictive exposure functions put forth by Southall
et al.
(2019), which were based on data collected prior to 2015. The authors concluded that more recent data supports the thresholds used for harbor porpoises (categorized as `very high frequency', or VHF cetaceans), which over-estimated the hearing impact for sounds above 20 kHz in frequency. Similarly, the new data for phocid seals show TTS onset thresholds that are well-above the predicted levels for sounds below 5 kHz in frequency. However, phocid seals might be more sensitive to higher frequency sound exposures than predicted, as the TTS onset data for frequencies higher than 20 kHz was below the predicted levels.
von Benda-Beckmann
et al.
(2022) assessed whether correcting for kurtosis, a measure of sound impulsiveness, improved the ability to predict TTS in a marine mammal. Two different kurtosis correction factors were tested by applying them to frequency-weighted sound exposure levels (SEL
cum
) and fitting (linear least squares) previously collected harbor porpoise TTS data to create dose-response functions, then comparing the resulting R
2
values to that of the standard function used to fit TTS growth data. TTS data from both continuous and intermittent sound exposures were used. For intermittent and continuous 1-2 kHz exposures combined, kurtosis-corrected fits were poorer (R
2
= 0.47, 0.68) than SEL
cum
-based fits (R
2
= 0.73). For intermittent exposures of different types, one of the kurtosis-corrections resulted in a better fit (R
2
= 0.84) than SEL
cum
(R
2
= 0.64), but only when a model fitting parameter denoting the relationship between SEL
cum
and risk of permanent hearing loss was specifically derived from harbor porpoise TTS growth data. The conclusions from this study were that the kurtosis-corrected SELs did not explain differences in TTS between intermittent and continuous sound exposures, likely because silent intervals provided an opportunity for hearing recovery that could not be accounted for by these models. Kurtosis might still be useful for evaluating sound exposure criteria for different types of sounds having various degrees of impulsiveness.
Behavioral Reactions
In a study by Benti
et al.
(2021), vocalizations from Northeast Atlantic herring-feeding killer whales and Northeast Pacific mammal-eating killer whales were played back to humpback whales in Norwegian waters while their behavior was monitored through animal-borne tags and visual observations. In five of six cases the humpback whales approached the fish-eating killer whales, suggesting some attraction. The response to the mammal-eating killer whales varied with the behavioral context of the humpback whales. The results suggested that the calls of the fish-eating killer whales may have acted like a dinner-bell and initiated approach and foraging behavior in the humpback whales, while the unfamiliar sounds of the mammal-eating killer whales may have been perceived as a threat in offshore waters, but led to mixed behavior during inshore herring foraging by humpback whales. These results indicated that the humpback whales were able to discriminate between the different call types and respond with different behavioral strategies.
Boisseau
et al.
(2021) exposed foraging minke whales in Icelandic waters to an acoustic deterrent device that emitted 15 kHz pure tones with a source level of 198 dB rms. Pulse length and the number of pulses in a block were randomized but average pulse length was 752 millisecond (ms) with a 10 percent duty cycle. The source was deployed from a Zodiac boat 500 m away from an animal for the first two exposures, and 1000 m away in the remaining 8 exposures (max received level of 150 dB RMS at a minimum distance of 338 m). Video-range tracking was used to track animals before, during, and after the exposures and dive duration (sec), swim speed (km/h), reoxygenation rate (blows/min), and path predictability were also examined. During the exposure, animal speed and dive duration increased, measures of path predictability increased indicating straighter paths, and reoxygenation rate decreased. Path predictability had a strong relationship with received level whereas speed and dive duration did not, which suggested those two metrics were more influenced by the presence of the exposure signal than the received sound level.
Curé
et al.
(2021) conducted controlled exposure experiments using both PAS (5 percent duty cycle) and CAS (95 percent duty cycle) to measure and score tagged sperm whale behavioral responses. No sonar control exposures resulted in significantly fewer and less severe behavioral responses than sonar exposures. No significant differences were observed between sonar types, but the presence of killer whales or pilot whales did significantly increase the number of responses. The probability of observing low and medium severity responses increased with cumulative sound exposure level (SEL, dB re 1 μPa2 s), reaching a probability of 0.5 at approximately 173 dB SEL for low severity responses. Medium severity responses reached a probability of approximately 0.35 at cumulative SELs between 179 and 189 dB. This study suggested that both PAS and CAS exposure resulted in a greater number of behavioral changes in sperm whales as compared to the vessel (control) alone, and the types of behavioral responses might differ across sonar types.
Czapanskiy
et al.
(2021) modeled energetic costs associated with behavioral response to MFAS using
datasets from 11 cetaceans' feeding rates, prey characteristics, avoidance behavior, and metabolic rates. Authors found that the short-term energetic cost was influenced more by lost foraging opportunities than increased locomotor effort during avoidance. Additionally, the model found that mysticetes incurred more energetic cost than odontocetes, even during mild behavioral responses to sonar.
Durbach
et al.
(2021) analyzed acoustic tracks from minke whales detected on the Pacific Missile Range Facility (PMRF) in Hawaii in 3 years before, during, and after major Navy training exercises. These tracks were fit using a continuous-time correlated random walk at 5-minute interpolated locations. During sonar periods, fast movement became more northerly and more directed (less turning), with less movement south and east in the direction of the training activity, and this more northerly movement continued after sonar cessation. Specifically, whales to the north of the training activity were more likely to head north, while whales that were west of the activity were more likely to head west. Headings did not appear to change for slow, undirected movement during sonar. In addition, fast movement was more likely to occur during sonar than during any other period (70 percent during vs 35-41 percent in the other periods). Finally, whales were more likely to stop calling when in the fast state although not necessarily more during sonar than in other periods; in contrast, slow moving whales were more likely to stop calling during sonar than other periods. These results demonstrated that minke whales moved faster and movements were more directed during periods of active sonar. Minke whales also avoided the locations of the ships producing the sonar and were more likely to cease calling during sonar.
Fernandez-Betelu
et al.
(2021) used passive acoustic data recorded over a 10-year time period to assess the effects of impulsive noise produced during offshore activities on coastal bottlenose dolphin occurrence. Offshore activities included seismic surveys and pile driving from wind farm construction. Echolocation detections of dolphins were compared across years with and without offshore activity and also across days with and without impulsive noise. The effect of distance from the noise-producing activities on dolphin detections was also investigated by placing recorders (CPODs) at locations expected to be the most (impact areas) and least (reference areas) impacted by noise. No consistent relationship was found between annual dolphin occurrence and impulsive noise, but significantly more detections were observed on days with impulsive noise. The results showed that dolphins were not displaced by impulsive noise levels up to 141 dB re 1 μPa and as close as 20 km (10.8 nmi) from the impact area. These results suggest that the increase in dolphin detections during far-field noise was likely due to an increase in the number and/or amplitude of echolocation vocalizations.
Hastie
et al.
(2021) studied how the number and severity of avoidance events may be an outcome of marine mammal cognition and risk assessment. Five captive grey seals were given the option to forage in a high- or low-density prey patch while continuously exposed to silence, pile driving, or tidal turbine playbacks (source levels = 148 dB re 1 μPa at 1 m) for 1 hour. One prey patch was closer to the speaker, so had a higher received level in experimental exposures. Overall, seals avoided both anthropogenic noise playback conditions with higher received levels when the prey density was limited but would forage successfully and for as long as control conditions when the prey density was higher, demonstrating a classic cognitive approach utilized with predation risk and profit balancing.
In a study by Holt
et al.
(2021a), DTAGs (miniature sound and movement recording tags) were attached with suction cups to Southern Resident Killer Whales in the Salish Sea to investigate the relationship between probability of prey capture and vessel and sound variables. The predicted probability of prey capture was lower when vessels increased their speed. Received noise level did not significantly affect the probability of prey capture. The rate of descent during dives was slower when echosounders were on. The observed effects of echosounders suggest that whales prolonged their foraging efforts to successfully hunt, which could be caused by acoustic masking or increased attention to vessels. The rate of descent increased with increasing broadband noise levels and decreasing vessel distance. Decrease prey abundance also decreased the probability of predicted prey capture.
Holt
et al.
(2021b) attached DTAGs to 23 Southern Resident Killer Whales in the San Juan Islands over 3 field seasons in order to investigate the effects of vessel distance on underwater foraging behavior. When vessels were less than 366 m away, whales (n=13) decreased the number of dives associated with prey capture and the amount of time spent in these dives. Additionally, female killer whales were more likely to stop foraging, socializing, and prey-sharing and instead start traveling when vessels approached at this distance. At the same distance from vessels, male orcas were more likely to transition from close prey capture to socializing and prey-sharing, but would not stop general foraging behavior, such as searching for prey at deeper depths. Female orcas may therefore be at greater risk than males during close vessel interactions.
Kates Varghese
et al.
(2021) analyzed the effect of two separate surveys using a 12 kHz multibeam echosounder (
i.e.,
downward directed, unlike ASW sonar) over the Southern California Antisubmarine Warfare Range (SOAR) hydrophone array on Cuvier's beaked whale foraging. The authors conducted a spatial analysis, building off a temporal analysis of a previously presented dataset (Varghese
et al.
2020). There were differences in spatial use of the SOAR for foraging between the 2 survey years. While no change in overall foraging effort was detected before, during, and after the surveys each year, some localized spatial shifts in foraging hot spots were detected during and after the survey in the second year. Because of the known heterogeneity of prey patches on SOAR, lack of evidence of avoidance of the sound source, and no observed change in overall foraging effort, the authors suggest that the observed spatial shifts were most likely due to prey dynamics.
Königson
et al.
(2021) tested the efficacy of Banana Pingers (300 ms, 59-130 kHz frequency modulated, 133-139 dB rms re 1 µPa at 1 m source level) as a deterrent for harbor porpoise in Sweden. As described previously, these pingers were designed to avoid potential pinniped responses. Authors used recorded echolocation clicks with C-PODs to measure the presence or absence of porpoise in the area. Porpoise were less likely to be detected at 0 m and within 100 m of an active pinger, but a pinger at 400 m appeared to have no effect.
In a study by Laborie
et al.
(2021), unmanned aerial vehicles (UAVs) were flown at three altitudes (25, 20, and 15 m) over Weddell seals, including adult males and females and females with pups. There was generally little response; 88 percent of the time the animals showed mild vigilance or no responses, and mothers rarely ended nursing. Agitation or escape responses only occurred in 12 percent of observations. The strongest response was in females with pups when wind speeds were lowest and therefore ambient noise levels were at their lowest. The probability of response
increased with lower altitude flights, so at altitudes over 25 m a low level of impact to Weddell seal behavior would be expected.
Manzano-Roth
et al.
(2022) found that cross seamount beaked whales reduced clusters of foraging pulses (Group Vocal Periods) during Submarine Command Course events and remained low for a minimum of 3 days after the MFA sonar activity.
An analysis subsequent to Varghese
et al.
(2020) suggested that the observed spatial shifts of Cuvier's beaked whales during multibeam echosounder activity on the Southern California Antisubmarine Warfare Range were most likely due to prey dynamics (Kates Varghese
et al.
2021).
Ramesh
et al.
(2021) explored environmental drivers and the impact of shipping noise on fin whale vocalizations in Ireland. Approximately 3 months of passive acoustic fin whale call data from spring 2016 used in the habitat model found that fin whale calls increased at night, along with signs of higher prey availability. Fin whale calls were also less likely to be detected for every 1 dB re 1 μPa/minute increase in shipping noise levels (rms). However, these results should be used cautiously since the model was more likely to predict the absence of fin whale detections, rather than their presence.
Santos-Carvallo
et al.
(2021) monitored fin whale behavior before, during, and after the presence of whale watching vessels in Caleta Chañaral de Aceituno to determine if the whale watching activity was having any adverse impacts on the fin whales. Whale watching activities were only conducted by local artisanal fishers; 39 boats have permission but less than 20 conduct the whale watching activity. Land-based observations were conducted in January and February of 2015-2018 via binocular scans and focal follow tracking using a theodolite. Groups of whales were tracked through the area with continuous sampling of position, behavior, and presence of boats for every surfacing until they were no longer visible. Behavior was classified as traveling or resting, and the groups' swim speed, reorientation, and directness index, and these were modeled relative to the number of boats and whether the time period was before, during, or after the boats were present. Most observations occurred within the presence of at least one boat, but no more than three boats at one time. Travel swim speeds increased in the after period, while reorientation increased and directness decreased during and after the presence of boats. During rest behavior, reorientation increased during the presence of boats compared to before the boats were present, and directness decreased during the presence of boats. These results indicate that when whale watching vessels were present, the fin whales changed their direction of movement more frequently, with less linear movement than occurred before the boats arrived; this behavior may represent evasion or avoidance of the boats. The increase in travel swim speeds after the boats left the area may be related to the vessel's rapid speeds when leaving, sometimes in front of animals, leading to more avoidance behavior after the boats departed.
Arranz
et al.
(2021) conducted a noise exposure experiment which compared behavioral reactions of resting short-finned pilot whale mother-calf pairs during controlled approaches by a tour boat with two electric (136-140 dB) or petrol engines (139-150 dB). Approach speed (<4 kn (7.4 km per hour)), distance of passes (60 m (65.6 yd)), and vessel features other than engine noise remained the same between the two experimental conditions. Behavioral data was collected via unmanned aerial vehicle (UAV) and activity budgets were calculated from continuous focal follows. Mother pilot whales rested less, and calves nursed less, in response to both types of boat engines compared to control conditions (vessel >300 m (328 yd), stationary in neutral). However, they found no significant impact on whale behaviors when the boat approached with the quieter electric engine, while resting behavior decreased 29 percent and nursing decreased 81 percent when the louder petrol engine was installed in the same vessel.
Hiley
et al.
(2021) exposed groups of harbor porpoises to “startle sounds”, which were 200-ms in duration and were band limited (5.5-20.5 kHz) with a peak frequency of 10.5 kHz and a source level of 176 dB re 1 µPa. There were 13 exposure sequences in which the startle sound was repeated for 15 minutes at a 0.6 percent duty cycle, and 11 control sequences in which vessels operated but no startle sounds were played. Despite a larger distance between porpoise groups and vessels during sound exposure trials (152 m) as compared to control trials (90 m), avoidance responses during exposures were significant whereas no avoidance was observed for controls. Porpoises avoided the area where sound exposures took place for approximately 30-60 minutes, and no long-term exclusion effect was observed.
Pellegrini
et al.
(2021) examined how boat presence impacts a unique subspecies of bottlenose dolphin (
Tursiops truncatus gephyreus,
Lahille's bottlenose) that vocalizes while foraging cooperatively with local fishermen who cast nets onto dolphin-herded fish while standing in coastal waters in Brazil. Dolphin vocalizations changed in response to the number, type, and speed of boats within 250 m. When more than one boat was present, dolphins produced fewer whistles and had a lower click rate and a longer whistle duration; initial and maximum frequency increased as well, especially when group size or calf presence increased. Whistles were longer duration when boat speed increased as well.
Martin
et al.
(2022) exposed a wild Cape fur seal breeding colony in Africa to playback recordings of boat noise and sea-side car traffic. Focal groups of at least six seals were approached by an experimenter who crawled within 6 m to avoid disturbing the seals. Seals were exposed to low (60-64 dB re 20 µPa rms SPL, broadcast at 6 m), medium (64-70 dB, broadcast at 3 m), or high (70-80 dB, broadcast at 1 m) levels, depending on the individual's distance to the speaker. No behavioral differences were found between low, medium, and high-level groups. Video recorded behavioral analysis demonstrated that mother-pup pairs spent less time nursing (15-31 percent) and more time awake (13-26 percent), vigilant (7-31 percent), and mobile (2-4 percent) during boat noise conditions compared to control conditions. Mothers were more vigilant (26 percent) than pups (7 percent) to medium levels of boat noise.
Jones‐Todd
et al.
(2021) analyzed the movement of seven Blainville's beaked whales tagged at (AUTEC) relative to MFAS use during the SCC training event. Data from these tags was previously reported by Joyce
et al.
(2019). A continuous time correlated random walk movement model accounted for location accuracy by modeling 100 track imputations for each tag and arranged samples in equal time intervals. The probability of whale presence within the boundary of the instrumented range (on range), and outside the boundary of the instrumented range (off range) was modeled relative to the time since the last MFAS transmission. Results show there was a higher probability that whales on the range would go off range when there were MFAS transmissions, and that whales off the range would stay off the range when there were MFAS transmissions. These results indicate a response to MFAS that lasted for 3 days since transition rates on-off and off-on the range returned to baseline levels
after that amount of time. There was also variability in transition rates and time spent on/off range between individuals, which highlights the need to analyze a larger sample size of whales.
Durban
et al.
(2022) tested new methods of observing behavioral responses of groups of small delphinids to sonar, where the use of tags is challenging, and the response of the group is more salient than that of the individual. They tested the use of a land-based observation platform coupled with a drone and multiple acoustic recorders to observe the vocal behavior, group cohesion, group size, and group behavior before, during, and after a simulated sonar exposure. In a group of short-beaked common dolphins, the authors found the number of whistles and sub-groups to increase during the exposure period, but the directivity of the tracked subgroup did not change much.
Königson
et al.
(2022) tested the efficacy of Banana Pingers (300 ms, 59-130 kHz frequency modulated, 133-139 dB
rms
re 1 µPa at 1 m source level) as a deterrent for harbor porpoise in Sweden. As described previously, these pingers were designed to avoid potential pinniped responses. Authors used recorded echolocation clicks with C-PODs to measure the presence or absence of porpoise in the area. Porpoise were less likely to be detected at 0 m and within 100 m of an active pinger, but a pinger 400 m appeared to have no effect.
Miller
et al.
(2022) investigated the risk disturbance hypothesis that an animal's response decision is a trade-off between perceived risk and the cost of a missed opportunity (the reward of foraging). The authors predicted that species that are more vulnerable to predation would be more likely to respond to both predator sounds and anthropogenic stressors. Using data collected from 2008 to 2017 during the 3S project in Norway, changes in foraging duration during killer whale playbacks and changes in foraging duration during mid-frequency sonar were positively correlated across the four species examined (listed in order of increasing sensitivity to foraging disruption: sperm whales, long-finned pilot whales, humpback whales, and northern bottlenose whales). This suggests that tolerance of predation risk may play a role in sensitivity to sonar disturbance.
Paitach
et al.
(2022) tested the efficacy of Banana Pingers (300 ms, 50-120 kHz frequency modulated, 145 dB +/− 3 dB at 1 m source level) as a deterrent and entanglement mitigation for Franciscana dolphins in Brazil. These pingers were designed to emit sound outside of the best hearing range for pinnipeds and were therefore less likely to incite a “dinner bell” effect. Authors used recorded echolocation clicks with C-PODs to measure the presence or absence of dolphins in the area. Dolphins were 19 percent and 15 percent less likely to be detected nearby and within 100 m of an active pinger respectively, but dolphins 400 m from the pinger did not appear to avoid it. While a reduction in vocalizations does not always equate to a reduction in presence, this species has been previously seen departing from areas with active pingers. Authors did not witness any habituation to the pinger during the length of the experiment (64 days), and although they recorded fewer dolphins in the area over time, they believe this was due to seasonality rather than habitat displacement.
Siegal
et al.
(2022) used Dtag data from 15 northern bottlenose whales tagged during 3S efforts off Norway (2013-2016) to estimate body density (to represent body condition by lipid energy stores) using hydrodynamic models and obtain foraging and anti-predator indicators based on vocal behavior and dive metrics. The authors compared relative anti-predator/foraging indices to body condition and found that relative anti-predator to foraging indices typically did not depend on body condition. This finding is inconsistent with the needs/assets hypothesis; an individual in poor condition would accept more risk (
i.e.,
engage in less anti-predator behavior) for foraging opportunities, whereas healthy animals can afford to be more risk averse (
i.e.,
have a relatively higher anti-predator to foraging index ratio). The authors suggest that this result may be due to an insufficient range of body conditions in the data set to determine a relationship, or a selection of bolder individuals in the tagging effort. The authors also suggest that animals in good condition may take greater predation risks because they may successfully flee. Three of the 15 whales were exposed to sonar (presented in prior 3S publications). The authors compared foraging and anti-predator metrics pre- and post-exposure, showing that all three animals increased their anti-predator index and reduced their foraging index.
Stanistreet
et al.
(2022) used passive acoustic recordings during a multinational navy activity to assess marine mammal acoustic presence and behavioral response to especially long bouts of sonar lasting up to 13 consecutive hours, occurring repeatedly over 8 days (median and maximum SPL = 120 dB and 164 dB). Cuvier's beaked whales and sperm whales substantially reduced how often they produced clicks during sonar, indicating a decrease or cessation in foraging behavior. Few previous studies have shown sustained changes in foraging or displacement of sperm whales, but there was an absence of sperm whale clicks for 6 consecutive days of sonar activity. Sperm whales returned to baseline levels of clicks within days after the activity, but beaked whale detection rates remained low even 7 days after the exercise. In addition, there were no detections from a Mesoplodon beaked whale species within the area during and at least 7 days after the sonar activity. Clicks from northern bottlenose whales and Sowerby's beaked whales were also detected but were not frequent enough at the recording site used to compare clicks between baseline and sonar conditions.
Benhemma-Le Gall
et al.
(2021) compared harbor porpoise presence and foraging activity between periods of baseline and construction at two Scottish offshore windfarms with arrays of echolocation click detectors (C-PODs). Noise levels were measured with calibrated noise recorders, and vessel presence was tracked with AIS data. Authors found an 8-17 percent decline in porpoise presence compared to baseline, with more porpoises (more buzzing) further from vessels, construction sites, and related higher levels of noise. The probability of porpoise occurrence by source vessels decreased by 9-23 percent without piling activity, and by 40-54 percent during pile driving. Porpoises were displaced up to 12 km (6.5 nmi) from pile driving and 4 km (2.2 nmi) from construction vessels. At an average vessel distance of 2 km (1.1 nmi), porpoise occurrence decreased by up to 35 percent. Outside piling hours, porpoise detection decreased by 17 percent (0.26), and foraging (buzzes) decreased by up to 41.5 percent (0.03) with increasing noise levels (159 and 155 dB re 1 µPa, respectively). During piling activities, porpoise occurrence began lower (0.16, 102 dB) but occurrence still decreased by 9 percent (0.07), and foraging (buzzes, beginning at 0.76, 104 dB) also decreased by 61.8 percent (0.15) with increasing noise levels (161 and 155 dB re 1 µPa, respectively).
Kastelein
et al.
(2022c) recorded pile driving sounds 100 m from construction for an offshore windfarm turbine, and six versions of the sound were created with varying frequency content using low-pass filters at 44.1, 6.3, 3.2, 1.5, 1.0,
and 0.5 kHz, at levels of 135 dB re 1 µPa
2
s. When authors played these impulsive sounds back to a single harbor porpoise in a pool, she increased swim speed, respiration rate, distance from the transducer, and occasionally jumped in response to the sounds with higher frequencies present (
i.e.,
the sounds with a wider bandwidth, especially sounds low-pass filtered at 44.1 and 6.3 kHz). However, the porpoise still moved away from the three most narrowband sounds, just not as far. Results indicate that frequency weighting of SEL may improve prediction of harbor porpoise behavioral responses, and authors present the argument that weighted SELs should be used for reporting behavioral response threshold levels for criteria.
Todd
et al.
(2022) detected harbor porpoises with C-PODS before, during, and after pile driving for an oil and gas platform from 2015-2020. Pile driving single strike SEL at 750 m was 160-164 dB re 1 µPa
2
s. Porpoise detections significantly decreased at the beginning of the construction project, but detections appeared to return to baseline levels within 5 months. According to the authors, the lack of significant trend over years indicated that porpoises returned to the area and did not experience habitat displacement for the entire 5-year period.
Physiological Responses and Stress
Elmegaard
et al.
(2021) exposed two captive harbor porpoises to sonar sweeps (6-9 kHz, 500 msec duration, 50-100 msec rise time, varying received levels (RL)) and pulsed sounds (50 msec duration, peak frequency 40 kHz, half power bandwidth of ~5 kHz, rise time < 5 msec, varying RL) to investigate startle reflex and changes in heart rate. The sonar exposures did not elicit startle responses; the initial two to three exposures induced bradycardia (a slow heart rate), with subsequent habituation. This habituation was conserved after a 3-year pause in exposures. The authors suggest that the initial bradycardia allows “a prolonged breath-hold to assess the nature of a novel stimuli or flee in crypsis if needed;” in naïve wild cetaceans, the reduced peripheral perfusion caused by this response may reduce N
2
diffusion from supersaturated tissues during dive ascents, increasing risk of decompression sickness. Startle responses to the pulse exposures were directly correlated to RL. The 50 percent motor-startle probability threshold was around 130 dB re 1 μPa (rms50). This is ~85 dB above hearing threshold and is similar to that observed in bottlenose dolphins (~90 dB over hearing threshold) (Gotz
et al.
2020). No significant change in heart rate was observed. The authors suggest that the parasympathetic cardiac dive response may override any transient sympathetic response, or that diving mammals may not have the cardiac startle response seen in terrestrial mammals in order to maintain volitional cardiovascular control at depth.
Fahlman
et al.
(2021) reviews decompression theory and the mechanisms dolphins have evolved to prevent high N2 levels and gas emboli (
i.e.,
bends-like symptoms) in normal conditions. However, in times of high stress, the selective gas exchange hypothesis states that this mechanism can break down. In addition, circulating microparticles may be useful biomarkers for decompression stress in cetaceans.
Yang
et al.
(2021) measured cortisol concentrations in blood samples of two captive bottlenose dolphins and found significantly higher levels after exposure to high sound level (140 dB re 1 μPa) impulsive noise playbacks, compared to control and low sound levels (0 and 120 dB re 1 μPa, respectively). Six cytokine gene transcriptions were also measured in blood samples and two (IL-10 and IFN-γ) showed significant changes at high sound level exposure, compared to control and low sound levels. Results suggest that repeated exposures or sustained stress response to impulsive sounds may increase an affected individual's susceptibility to pathogens, affect growth and reproduction,
etc.
In addition, no avoidance behavior was observed during the trials, indicating that stress-induced physiological changes could be present despite the absence of behavioral changes.
Williams
et al.
(2022) measured physiological and behavioral responses in narwhals in the Arctic during seismic airgun impulse exposure compared to control conditions. Responses were measured using heart rate-accelerometer-depth recorders and changes in locomotor, cardiovascular, and respiratory responses were observed following exposure. Airgun SELs, as received at 10 m depth during sound source verifications, were approximately 152 dB re 1 µPa
2
s at 1 km (0.5 nmi) range and decreased to approximately 120 dB re 1 µPa
2
s at 10 km (5.4 nmi) dives. The response to seismic and vessel noise was a reduction in gliding descents and prolonged periods of high intensity activity associated with periods of elevated stroke frequencies. Noise exposure also resulted in periods of prolonged and intense bradycardia (
i.e.,
slowed heart rate). An increase in post-dive respiratory rates occurred during recovery from noise-exposed dives compared to control dives.
Stranding
Danil
et al.
(2021) document the findings of NOAA's investigation of the strandings of three coastal bottlenose dolphins in 2015 at Silver Strand Training Complex in NOAA Technical Memorandum NMFS-SWFSC-641. On October 21, 2015, two dolphins were found stranded dead near each other on the beach. Because a Navy major training exercise (MTE) was underway, these strandings met the criteria of an Uncommon Stranding Event in accordance with the Southern California Stranding Response Plan in the Navy's Phase 2 LOA for HSTT. A third decomposed dolphin was found in the same area 10 days later. Examination of the dolphins resulted in findings indicative of severe acute trauma, including lower jaw subcutaneous hemorrhage, emphysema, and cervical blubber hemorrhage. Additional signs of injury to the cerebrum and heart, or lipids in the lungs were also discovered. No hemorrhage was found near the ears. At least two of the dolphins showed signs of feeding before stranding, and all were in robust condition. There were no external signs of strike or entanglement. These observations and lack of others did not clearly determine the cause of the acute trauma. Based on previous case studies, the investigators determined that underwater detonation, peracute underwater entrapment (
i.e.,
fisheries interaction), or sonar were the most plausible causes. The Navy notes that sonar has not been associated with these kinds of symptoms before, nor has there ever been any association between dolphin mortality and sonar. No anti-submarine (ASW) sonar or explosive use was associated with the Navy MTE; however, unit level training with MF1 sonar occurred on October 19 (for 35 minutes) and October 20 (62 minutes in total), with sonar use as close as 6 nmi (11.1 km) to the stranding location. No known squid or bait fishing efforts within U.S. waters occurred in the vicinity preceding the strandings. The Navy notes that it is unknown what fishing efforts occurred in Mexican territorial waters immediately south of the stranding location.
Wang
et al.
(2021) conducted an auditory-evoked potential (AEP) hearing test on a single stranded 19-year-old male melon-headed whale in the 9.5—181 kHz frequency range. Tone pip trains were presented underwater at a depth of 0.3 m and 1 m distance from the whale, and AEPs were recorded by suction cup electrodes on the skin surface. Hearing was measured in this
individual after it had been stranded and during attempted rehabilitation in a concrete pool. Eighteen frequencies were measured once, and eight frequencies were measured twice, yielding an audiogram that showed elevated hearing thresholds (compared to the pygmy killer whale) between 10 and 100 kHz. There are no data from normal-hearing individuals of the melon-headed whale species to which this study's data can be compared.
Population Consequences of Disturbance and Cumulative Stressors
Southall
et al.
(2021) provided updated guidance and methods to assess the severity of behavioral responses by marine mammals to several types of anthropogenic noise sources. The criteria developed in the 2007 effort were updated by explicitly distinguishing between captive and field studies, decoupling their respective severity scales, and splitting the severity scale into three categories of foraging, survival, and reproduction. In addition, the updated guidance changed the categorization of noise sources and began to consider long term consequences of exposures rather than just immediate responses. Additional and consistent metrics to be reported in behavioral response studies are recommended, including subject-specific metrics (
e.g.,
functional hearing group, age class, sex, behavioral state, presence of calf), exposure context metrics (
e.g.,
exposure type, range to source, source and animal depth, presence of other species or other noise sources), and noise exposure metrics (
e.g.
exposure duration, rise time, number of exposures, SPL [rms and p-p], SEL, SNR). The authors then applied the severity scale to acute exposure studies using sonar sources, continuous (industrial) sources, pile driving sources, and airgun sources. For the long-term exposure analysis, a set of factors developed by Bejder and Samuels (2003) were applied to long-term studies on whale-watching and other long-term exposure or multi-exposure datasets. These factors included metrics of short-term impacts and long-term survival measures, characteristics of the studies, and sources of anthropogenic disturbance. The applied examples of scoring both acute and long-term studies of behavioral response provide a framework for other researchers to apply the same metrics to their own studies.
Migrating humpback whale mother-calf pairs' responses to seismic surveys were modeled by Dunlop
et al.
(2021) using both a forwards and backward approach. While a typical forwards approach can determine if a stressor would have population-level consequences, authors demonstrated that working backwards through a population consequences of disturbance (PCoD) model can be used to assess the “worst case” scenario for an interaction of a target species and stressor. Assumptions for the extreme scenario were likely exaggerated (
e.g.,
in area for > 48 hours, exposed to > 3 air gun events) but lack data to inform humpback nursing behavior and calf survivability during acoustic stressors. The results demonstrated that migrating whales would not likely experience enough of a delay as a result of disturbance to result in population consequences, but whales disturbed in breeding or resting areas would be more vulnerable to consequences of disturbance.
Greenfield
et al.
(2020) demonstrated that bottlenose dolphins who had been injured from boat strike or entanglement experienced a decline in their social network's preferred associations, and as a result were more vulnerable to predation and less fecund.
Hin
et al.
(2021) used a previously published energy budget model for pilot whales (Hin
et al.
2019) to examine how lost foraging days affect individuals in a population at carrying capacity. In this model, depletion of prey is dependent on whale density, and prey density limits the energy available for growth, reproduction, and survival. The authors assumed extreme disturbance events for this study: consecutive days of no foraging affecting all individuals in a population. The undisturbed whale population was regulated through the effect of prey availability on calf survival and pregnancy rates and on age at first reproduction of females. During a disturbance event, population decline was generally attributed to loss of lactating females and calves due to reduced body condition. The subsequent increase in prey density and per capita prey availability, however, resulted in improved body condition in the population overall and decreased age at first calf. As disturbance duration was increased (~40 days of no foraging), the population would enter extreme decline towards extinction.
Murray
et al.
(2021) conducted a cumulative effects assessment on Northern and Southern Resident killer whales, which involved both a Pathways of Effects conceptual model and a Population Viability Analysis quantitative simulation model. Authors found that both populations were highly sensitive to prey abundance and were also impacted by the interaction of low prey abundance with vessel strike, vessel noise, and polychlorinated biphenyls contaminants. However, more research is needed to validate the mechanisms of vessel disturbance and environmental contaminants.
Pirotta
et al.
(2020) reformulated their previous dynamic energy budget model (Pirotta
et al.
2018) to investigate the state-dependent life history strategies of female long-finned pilot whales and trade-offs between their body condition (
i.e.,
ability to offset starvation during pregnancy and provide milk), prey availability, and decision to reproduce in situations with and without disturbance. Many whales in this model attempted to reproduce young, and while that had no cost in situations without disturbance, young mothers would starve and die when foraging was prevented by some disturbance event or because resources were low (winter). Whale reproductive strategies resulted in lower lifetime reproductive output, compared to the model used in Hin
et al.
(2019).
Pirotta
et al.
(2021) integrated different sources of data (
e.g.,
controlled exposure data, activity monitoring, telemetry tracking, and prey sampling) into a bioenergetic model, which was used to predict effects from sonar on a blue whale's daily energy intake. Approximately half of the simulated whales had no change in daily net energy intake because they either had no response or were not exposed. However, the other half experienced a decrease in net energy intake. A portion (11 percent) of those simulated whales had negative net energy even after brief (
e.g.,
6-30 min) or weak (
e.g.,
160-180 dB re 1 μPa source level) events, which indicated that they would not be able to cover that day's energetic cost. This dichotomy in results was due to the variation in activity budgets, lunging rates and ranging patterns between tagged whales. This evidence suggests that context can influence the predicted costs of disturbance even more than body size or prey density distribution on a daily scale (although prey availability and abundance affected behavioral patterns).
Pirotta
et al.
(2022) evaluated potential long-term effects of changing environmental conditions and military sonar by modeling vital rates of Eastern North Pacific blue whales. Previous work from Pirotta
et al.
(2021) was used as a foundation for incorporating the most recent best available science into the vital rate model presented in this study. Using data and underlying models of behavioral patterns, energy budgets, body condition, contextual responses to noise, and prey resources, the model predicted female vital rates
including survival (age at death), and reproductive success (number of female calves). The model simulation results showed that “[e]nvironmental changes were predicted to severely affect vital rates, while the current regime of sonar activities was not.” The case study used an annual sonar regime in SOCAL based on the description of the action in the Navy's 2018 HSTT FEIS/OEIS. Additional military sonar scenarios were modeled, and a ten-fold increase in sonar activity combined with a shift in geographical location to overlap with main feeding areas of blue whales resulted in a moderate decrease in lifetime reproductive success (Cohen's d = 0.47). However, there was no effect on survival (Cohen's d = 0.05).
Pirotta (2022) covered the development of bioenergetic models [“any mechanistic model where the principles of metabolic ecology are used to describe how an individual animal acquires energy from food resources (
i.e.,
energy intake) and allocates assimilated energy to various life history functions (
i.e.,
energy costs, including maintenance and survival, growth and reproduction)”] with a focus on applications to marine mammals. This article provided a thorough overview of the history of marine mammal bioenergetic models, defined relevant terminology, and explained the differences between general types of models.
McHuron
et al.
(2021) developed a state-dependent behavioral and life history model to predict the probability of Western gray whale mother-calf pair survival with and without acoustic disturbance and with or without adequate prey availability on their summer foraging grounds. Pregnant mother movement, feeding behavior, fat mass and fetal length were input data for the model. Since prey availability was co-dependent on whales having access to high-density offshore areas by mid-July, nearshore seismic surveys had no impact on population fecundity or mother-calf survival. This model overcomes a key challenge in PCoD literature by providing a link between behavioral responses and vital rates; authors recommend focusing on species that are data rich to accurately characterize the biology of the focal species, metrics of fitness, and key qualities of their environment.
Joy
et al.
(2022) presented a hypothetical case study for fin whales off Southern California exposed to stationary single-ship 53C sonar events over the course of a year, using the Navy's Phase 3 behavioral response function (BRF). Two model runs were compared: using α = 0.05 (average 20-minute movement disruption) and α= 0.99 (average 3 days movement disruption). When animals returned to baseline behavior after a short disturbance (α = 0.05), there was less regional displacement and thus more instances of behavioral disturbance over the course of a year. When animals returned to baseline behavior after a longer period (α=0.99), there were fewer instances of behavioral disturbances over the course of a year due to cumulative displacement from habitat near the sonar source.
Keen
et al.
(2021) reviewed 15+ years of PCoD modeling and identified the most critical factors for determining long-term impacts to populations. Critical factors include life-history traits, disturbance source characteristics, and environmental conditions. No specific model or quantitative assessment was proposed.
Methodology for Assessing Acoustic Impacts
Palmer
et al.
(2022) recorded North Atlantic right whale upcalls using 10 Marine Autonomous Recording Units deployed in Cape Cod Bay from February to May 2009. A modified equation was provided for determining the effective survey area, including a Lombard coefficient, for single sensor applications. The authors state manual annotation or verification is nearly always used to confirm automated detector outputs prior to near-real-time conservation measures due to limitations in automatic detector capabilities.
Aircraft Noise
Kuehne
et al.
(2020) measured in-air and underwater sound from low-altitude EA-18G Growler flights in the immediate vicinity of Ault Field at Naval Air Station Whidbey Island (NASWI). Data were collected by two in-air recorders and one hydrophone placed just off the runway at a depth of 30 meters. The underwater 10-flight average sound measurement was 134 ± 3 dB re 1 μPa rms in the highest 1-second window. The results showed that the peak frequency range of the Growler overflight noise both in air and underwater was between 50 and 1,000 Hz, which is typically a frequency range with high background noise underwater, particularly in areas with large amounts of vessel traffic (Erbe
et al.
2012). The study did not include behavioral observations of wildlife, and the authors' conclusions about potential impacts to wildlife were unsupported by data from the study. In a separate effort, Kuehne and Olden (2020) relied on volunteers to identify military aircraft noise in recordings taken on land on the Olympic Peninsula. This study also did not examine impacts to or responses by wildlife to aircraft.
We reiterate that NMFS reviewed the Navy's analysis and conclusions that aircraft noise will not result in incidental take of marine mammals, and finds the analysis and conclusions complete and supportable, as stated in the 2018 HSTT final rule. Please see section 3.7 (Marine Mammals) of the 2018 HSTT FEIS/OEIS for additional information.
Conclusion for New Pertinent Science Since Publication of the 2020 HSTT Final Rule
Having considered the best scientific information available, specifically new relevant information published since the 2020 HSTT final rule, we have preliminarily determined that there is no new information that substantively affects our analysis of impacts on marine mammals and their habitat that appeared in the 2020 HSTT final rule, all of which remains applicable and valid for our assessment of the effects of the Navy's activities during the 7-year period of this rulemaking.
Estimated Take of Marine Mammals
This section indicates the number of takes that NMFS is proposing for authorization, which are based on the amount of take that NMFS anticipates could occur or is likely to occur, depending on the type of take and the methods used to estimate it, as described below. NMFS coordinated closely with the Navy in the development of their incidental take application and preliminarily agrees that the methods the Navy has put forth described herein, in the 2019 HSTT proposed rule, 2020 HSTT final rule, and in the 2018 HSTT proposed and final rules to estimate take (including the model, thresholds, and density estimates), and the resulting numbers are based on the best available science and appropriate for authorization, with the exception of that of humpback whales, discussed further below. The number and type of incidental takes that could occur or are likely to occur annually remain identical to those authorized in the 2018 HSTT regulations and 2020 HSTT regulations, with the exception of proposed takes by serious injury or mortality by vessel strike and harassment takes of humpback whale stocks in Southern California (due to the new stock structure).
Takes are predominantly in the form of harassment, but a small number of serious injuries or mortalities could
occur. For military readiness activities, the MMPA defines “harassment” as (i) any act that injures or has the significant potential to injure a marine mammal or marine mammal stock in the wild (Level A harassment); or (ii) any act that disturbs or is likely to disturb a marine mammal or marine mammal stock in the wild by causing disruption of natural behavioral patterns, including, but not limited to, migration, surfacing, nursing, breeding, feeding, or sheltering, to a point where such behavioral patterns are abandoned or significantly altered (Level B harassment).
Proposed authorized takes would primarily be in the form of Level B harassment, as use of the acoustic and explosive sources (
i.e.,
sonar, air guns, pile driving, explosives) and is more likely to result in the disruption of natural behavior patterns to a point where they are abandoned or significantly altered (as defined specifically at the beginning of this section but referred to generally as behavioral disturbance) or TTS for marine mammals. There is also the potential for Level A harassment in the form of auditory injury and/or tissue damage (the latter from explosives only) to result from exposure to the sound sources utilized in training and testing activities. Additionally, serious injuries or mortalities of mysticetes (except for sei whales, minke whales, Bryde's whales, Central North Pacific stock of blue whales, Hawaii stock of fin whales, Western North Pacific stock of gray whales, and sperm whales) could occur through vessel strike. Proposed mitigation and monitoring measures are expected to minimize the severity of the taking to the extent practicable.
Generally speaking, for acoustic impacts, NMFS estimates the amount and type of harassment by considering: (1) acoustic thresholds above which NMFS believes the best available science indicates marine mammals would experience behavioral disturbance or incur some degree of temporary or permanent hearing impairment; (2) the area or volume of water that will be ensonified above these levels in a day or event; (3) the density or occurrence of marine mammals within these ensonified areas; and (4) and the number of days of activities or events.
Acoustic Thresholds
Using the best available science, NMFS, in coordination with the Navy, has established acoustic thresholds that identify the most appropriate received level of underwater sound above which marine mammals exposed to these sound sources could be reasonably expected to experience a disruption in behavior patterns to a point where they are abandoned or significantly altered or to incur TTS (equated to Level B harassment) or permanent threshold shift (PTS) of some degree (equated to Level A harassment). Thresholds have also been developed to identify the pressure levels above which animals may incur non-auditory injury from exposure to pressure waves from explosive detonation.
We described the acoustic thresholds and the methods used to determine thresholds, none of which have changed, in detail in the
Acoustic Thresholds
section of the 2018 HSTT final rule; please see the 2018 HSTT final rule for detailed information. Further, in the 2020 HSTT final rule, we described new relevant information from the scientific literature since publication of the 2018 HSTT final rule. Since publication of the 2020 HSTT final rule, a number of additional studies have published, including several associated with TTS in harbor porpoises and seals (
e.g.,
Kastelein
et al.
2020d; Kastelein
et al.
2021a and 2021b; Sills
et al.
2020). NMFS is aware of these recent papers, summarized above in the
New Pertinent Science Since Publication of the 2020 HSTT Final Rule
section. NMFS is currently working with the Navy to update NMFS' Technical Guidance for Assessing the Effects of Anthropogenic Sound on Marine Mammal Hearing Version 2.0 (Acoustic Technical Guidance; NMFS 2018) to reflect relevant papers that have been published since the 2018 update on our 3-5 year update schedule in the Acoustic Technical Guidance. First, we note that the recent peer-reviewed updated marine mammal noise exposure criteria by Southall
et al.
(2019) provide identical PTS and TTS thresholds and weighting functions to those provided in NMFS' Acoustic Technical Guidance.
NMFS will continue to review and evaluate new relevant data as it becomes available and consider the impacts of those studies on the Acoustic Technical Guidance to determine what revisions or updates may be appropriate. However, any such revisions must undergo peer and public review before being adopted, as described in the Acoustic Technical Guidance methodology. While some of the relevant data may potentially suggest changes to TTS/PTS thresholds for some species, any such changes would not be expected to change the predicted take estimates in a manner that would change the necessary determinations supporting the issuance of these regulations, and the data and values used in this proposed rule reflect the best available science.
Navy's Acoustic Effects Model
The Navy proposes no changes to the Acoustic Effects Model as described in the 2018 HSTT final rule (and incorporated by reference in the 2020 HSTT final rule), and there is no new information that would affect the applicability or validity of the model. Please see the 2018 HSTT final and proposed rules and Appendix E of the 2018 HSTT FEIS/OEIS for detailed information.
Range to Effects
The Navy proposes no changes from the 2018 HSTT final rule (and subsequent 2020 HSTT final rule) to the type and nature of the specified activities to be conducted during the 7-year period analyzed in this proposed rule, including equipment and sources used and exercises conducted. NMFS has reviewed and will continue to review and evaluate new relevant data as it becomes available and consider the impacts of those studies on the Acoustic Technical Guidance to determine what revisions/updates may be appropriate. However, any such revisions must undergo peer and public review before being adopted, as described in the Acoustic Guidance methodology. While some of the relevant data may potentially suggest changes to TTS/PTS thresholds for some species (
e.g.,
Kastelein
et al.
(2020a) shows onset of TTS incurred by a harbor porpoise at higher received levels than would have been anticipated based on the existing criteria, while Kastelein
et al.
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