# Takes of Marine Mammals Incidental to Specified Activities; Taking Marine Mammals Incidental to the Naval Base Point Loma Deperming Pier Replacement Project and the Naval Base San Diego Chollas Creek Quay Wall Repair Project in San Diego Bay, California > Briefs, arguments, decisions, and more. URL: https://www.frixlaw.com/law-library/documents/fr%3A2026-02173 ## Record - **Collection:** Federal Register - **Document type:** Notice - **Published:** February 3, 2026 - **Citation:** 91 FR 4875 ## Text DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration [RTID 0648-XF037] Takes of Marine Mammals Incidental to Specified Activities; Taking Marine Mammals Incidental to the Naval Base Point Loma Deperming Pier Replacement Project and the Naval Base San Diego Chollas Creek Quay Wall Repair Project in San Diego Bay, California AGENCY: National Marine Fisheries Service (NMFS), National Oceanic and Atmospheric Administration (NOAA), Commerce. ACTION: Notice; two proposed incidental harassment authorizations; request for comments on two proposed authorizations and possible renewals. SUMMARY: NMFS has received separate requests from the U.S. Navy (Navy) for authorization to take marine mammals incidental to the Naval Base Point Loma (NBPL) Deperming Pier Replacement Project and the Naval Base San Diego (NBSD) Chollas Creek Quay Wall Repair Project, respectively, both in San Diego Bay, California (CA). Pursuant to the Marine Mammal Protection Act (MMPA), NMFS is requesting comments on its proposals to issue separate incidental harassment authorizations (IHAs) to incidentally take marine mammals during the specified activities. NMFS is also requesting comments on a possible one-time, 1-year renewal for each IHA that could be issued under certain circumstances, provided all requirements are met, as described in Request for Public Comments at the end of this notice. NMFS will consider public comments prior to making any final decision on the issuance of the requested MMPA authorizations. Agency responses will be summarized in the final notice of our decision. DATES: Comments and information must be received no later than March 5, 2026. ADDRESSES: Comments should be addressed to the Permits and Conservation Division, Office of Protected Resources, National Marine Fisheries Service, and should be submitted via email to ITP.Graham@noaa.gov. Electronic copies of the application and supporting documents, as well as a list of the references cited in this document, may be obtained online at: https://www.fisheries.noaa.gov/national/marine-mammal-protection/incidental-take-authorizations-construction-activities. In case of problems accessing these documents, please call the contact listed below. Instructions: NMFS is not responsible for comments sent by any other method, to any other address or individual, or received after the end of the comment period. Comments, including all attachments, must not exceed a 25-megabyte file size. All comments received are a part of the public record and will generally be posted online at https://www.fisheries.noaa.gov/permit/incidental-take-authorizations-under-marine-mammal-protection-act without change. All personal identifying information ( e.g., name, address) voluntarily submitted by the commenter may be publicly accessible. Do not submit confidential business information or otherwise sensitive or protected information. FOR FURTHER INFORMATION CONTACT: Krista Graham, Office of Protected Resources, NMFS, (301) 427-8401. SUPPLEMENTARY INFORMATION: Background The MMPA prohibits the “take” of marine mammals, with certain exceptions. Section 101(a)(5)(A) and (D) of the MMPA (16 U.S.C. 1361 et seq. ) directs the Secretary of Commerce (as delegated to NMFS) to allow, upon request, the incidental, but not intentional, taking of small numbers of marine mammals by U.S. citizens who engage in a specified activity (other than commercial fishing) within a specified geographical region if certain findings are made and either regulations are proposed or, if the taking is limited to harassment, a notice of a proposed IHA is provided to the public for review. Authorization for incidental takings shall be granted if NMFS finds that the taking will have a negligible impact on the species or stock(s) and will not have an unmitigable adverse impact on the availability of the species or stock(s) for taking for subsistence uses (where relevant). Further, NMFS must prescribe the permissible methods of taking; other “means of effecting the least practicable adverse impact” on the affected species or stocks and their habitat, paying particular attention to rookeries, mating grounds, and areas of similar significance, and on the availability of the species or stocks for taking for certain subsistence uses (collectively referred to as “mitigation”); and requirements pertaining to the monitoring and reporting of the takings. The definitions of all applicable MMPA statutory terms used above are included in the relevant sections below ( see also 16 U.S.C. 1362; 50 CFR 216.103). National Environmental Policy Act To comply with the National Environmental Policy Act of 1969 (NEPA; 42 U.S.C. 4321 et seq. ) and NOAA Administrative Order (NAO) 216-6A, NMFS must review our proposed action ( i.e., the issuance of an IHA) with respect to potential impacts on the human environment. These actions are consistent with categories of activities identified in Categorical Exclusion B4 (IHAs with no anticipated serious injury or mortality) of the Companion Manual for NAO 216-6A, which do not individually or cumulatively have the potential for significant impacts on the quality of the human environment and for which we have not identified any extraordinary circumstances that would preclude this categorical exclusion. Accordingly, for both proposed IHAs, NMFS has preliminarily determined that the issuance of the proposed IHA qualifies for categorical exclusion from further NEPA review. Summary of Request On April 23, 2025, NMFS received a request from the Navy for an IHA to authorize incidental take of marine mammals during the NBPL Deperming Pier Replacement Project, which involves removing and replacing damaged fender piles at three large piers at NBPL in San Diego Bay, CA. Then, on April 30, 2025, NMFS received another request from the Navy for an IHA to authorize incidental take during the NBSD Chollas Creek Quay Wall Repair Project, which includes removing and replacing the existing quay wall and dock pilings in Chollas Creek, San Diego Bay, CA. Since both projects are proposed by the Navy and are located in San Diego Bay, CA, and the Navy has requested the authorizations be issued near concurrently, NMFS is announcing its proposals of the two IHAs and soliciting public comment within this single Federal Register notice. Following NMFS' review of the applications, the Navy submitted a revised version of both applications on November 13, 2025. Both applications were deemed adequate and complete on November 19, 2025. For the NBPL Deperming Pier Replacement Project, the Navy's request is for the take of six species of marine mammals, by Level A harassment and/or Level B harassment only; for the NBSD Chollas Creek Quay Wall Repair Project, the Navy's request is for the take of three species of marine mammals, by Level B harassment only. Neither the Navy nor NMFS expects serious injury or mortality to result from either activity; therefore, an IHA for each project is appropriate. Both IHAs would be valid for the statutory maximum of 1 year from the date of effectiveness, and would become effective upon written notification from the Navy to NMFS, but not beginning later than 1 year from the date of issuance or extending beyond 2 years from the date of issuance. Description of Proposed Activity Overview The purpose of both Navy projects is to maintain structurally sound and operational areas at both naval bases, to continue safely supporting Pacific Fleet surface ships, and to allow berth-side repair, maintenance, and storage of vessels. Both proposed projects are located at naval bases within San Diego Bay, CA, either near the mouth of the Bay at Point Loma (NBPL), or in the south-central part of the Bay, at Chollas Creek (NBSD). The Navy would remove existing piles using a dead pull, high-pressure water jetting, or a vibratory extractor, and install permanent piles using high-pressure water jetting, vibratory hammer, or an impact hammer to replace the existing piers. For the NBPL Project, the proposed activities would result in removing 192 piles and installing 192 piles over approximately 171 in-water work days. For the NBSD Project, 190 in-water work days are estimated to remove 544 piles, and 121 days to install 936 piles. Pile removal via vibratory extractor and pile installation via vibratory hammer or impact hammer have the potential to result in marine mammal harassment, and, therefore, IHAs are warranted. Dates and Duration Each proposed IHA would be valid for the statutory maximum of 1 year from the date of effectiveness. They would become effective upon written notification from the applicant to NMFS, but not beginning later than 1 year from the date of issuance or extending beyond 2 years from the date of issuance. Pile driving is expected to occur at NBPL between June 1, 2026, and May 31, 2027, for 171 days. Pile driving is expected to occur at NBSD between January 1, 2027, and December 31, 2027, for 190 days. However, project delays may occur due to several factors, including project funding, permitting requirements, equipment and/or material availability, weather-related delays, equipment maintenance and/or repair, and other contingencies. For both projects, pile removal and driving would occur only during daylight hours. Specific Geographic Region The NBPL Deperming Pier Replacement Project is located on the peninsula of Point Loma near the mouth and along the northern edge of San Diego Bay, CA. This area, known as North Bay, extends from the Bay mouth to the area offshore Downtown San Diego. The NBSD Chollas Creek Quay Wall Repair Project is located in the San Diego Bay in an area known as South-Central Bay. Specifically, the project is located at the mouth of Chollas Creek, a highly militarized area on both sides of the Creek. The U.S. Army Corps of Engineers dredges the main navigation channel into and through San Diego Bay to maintain a depth of 47 feet (ft) (14.3 meters (m)) below mean lower low water (MLLW), ensuring safe passage for private, commercial, and military vessels within the Bay (NOAA 2010). In North Bay, typical depths range from 36 to 38 ft (11.0 to 11.6 m) below MLLW to support large ship turning and anchorage (Merkel & Associates, Inc., 2008, 2009). In Central Bay, typical depths range from 11 to 12 m (35 to 38 ft) below MLLW (Merkel & Associates, 2009). BILLING CODE 3510-22-P EN03FE26.001 EN03FE26.002 EN03FE26.003 BILLING CODE 3510-22-C Detailed Description of the Specified Activity NBPL Deperming Pier Replacement Project For the NBPL Project, the Navy proposes in-water construction work at three piers: the two Magnetic Silencing Facility (MSF) piers ( i.e., the Deperming Pier and the Electromagnetic Roll Garden (ERG) Pier), and Pier 5002 North Inner Berth. Specifically, the Navy proposes to remove and replace damaged piles at the Deperming Pier and the ERG Pier, and replace plastic fender piles at Pier 5002. The MSF provides mission-critical magnetic treatment (deperming) of Navy surface vessels, and calibration and testing of magnetic signature reduction systems (degaussing), thereby significantly reducing the risk to Navy ships from magnetic mines. The project would maintain the Deperming Pier, ERG Pier, and Pier 5002 in a structurally sound, operational condition so that the Navy may safely continue to support Pacific Fleet surface ships. During construction activities at NBPL, 192 16-inch timber piles would be removed via vibratory extraction over an estimated 86 days. High-pressure water jetting or dead pull may also be used to remove piles. The installation of the 192 16-inch round fiberglass-reinforced plastic piles would be carried out using vibratory or impact hammers over 85 days. High-pressure external water jetting may be used to loosen the soil before vibratory or impact hammering. Two-inch pile sleeves made of high-density polyethylene would be slipped onto the outside of each 16-inch pile to minimize long-term pile degradation ( i.e., no pile driving is needed). Each sleeve would be bolted in place to the steel pile above the waterline. Additionally, 8-ft (2.4 m) link chains (one for each replaced piling) would be replaced to connect the pier to the piling for extra support. High-pressure water jetting or dead-pull removal methods are not likely to result in harassment and, therefore, we do not discuss these action components further. The Navy estimates that 171 days are needed to remove and install a total of 384 piles. A floating barge secured directly to the pier would remove and install between two and four piles per day. The sequence of pile removal and installation involves removing three to four piles, then installing three to four new piles. The barge would then move to the next section and repeat the process. The estimated time to remove each timber pile with a vibratory hammer is up to 5 minutes. Installation is expected to take up to 5 minutes per plastic pile using vibratory pile driving, while impact installation may require up to 600 strikes per plastic pile (see table 1). A bubble curtain or similar attenuation method is not proposed (see Proposed Mitigation section below for rationale). NBSD Chollas Creek Quay Wall Repair Project For this project, the Navy plans to repair Quay Wall Segment B at NBSD along Chollas Creek. This area experienced a catastrophic failure in 2019 due to its age (82 years), which led to undermined sheet piles and the deterioration of utility lines. The project includes demolishing the existing quay wall and associated piles, then building a new quay wall. Additionally, piles would be installed to support a small craft floating dock in the same area as the old location (within Chollas Creek) for berth-side repairs, maintenance, and vessel storage. Repairs would span approximately 1,410 ft (430 m) along the quay wall in about 30 ft (10 m) of water depth. Vibratory extraction would be used to remove the 14-inch steel H piles, 18-inch square concrete fender piles, 18-inch octagonal concrete fender piles, and 24-inch steel sheet piles. Dead pulling would be used to remove the 13-inch round plastic fender piles. Piles would only be removed if they interfere with the installation of new piles. Vibratory pile driving, impact pile driving, or high-pressure water jetting would be used to install the 24-inch sheet piles, 18-inch square concrete fender piles, 18-inch octagonal concrete guide piles, and the 13-inch round plastic fender piles. For reasons described for the NBPL project above, dead pull and high-pressure water jetting are not expected to have the potential to result in harassment and are not discussed further. The Navy estimates 190 days of in-water work, conducted only during daylight hours, are necessary for this project. Specifically, the Navy estimates 69 days to remove 544 piles and 121 days to install 936 piles. The sequence of pile removal/installation for this project is less certain but likely involves removing all piles, then installing all new piles. However, the contractor may opt to remove and install all piles of a similar nature ( e.g., square and octagonal piles) before moving on to another pile type ( e.g., wall sheet piles). Anywhere from 2 to 12 piles may be removed per day, during daylight hours only, with 4 to 10 piles installed per day. Vibratory pile removal is estimated to take approximately 20 minutes per pile for all pile types; vibratory pile installation is estimated to take anywhere from 1 to 20 minutes per pile, depending on the pile type, whereas impact pile installation is estimated to take 600 strikes per pile (see table 1). Table 1—NBPL and NBSD Pile Removal and Installation Method, Pile Size/Type, Location, Number, and Duration Method Pile size/type Pile location Piles/day Number of piles Number of days NBPL DEPERMING PIER Pile Removal 1 Vibratory Extraction 16-inch (41 cm) round timber Deperming Pier Edge 4 72 21 Deperming Pier Corners 2 51 26 ERG Pier Dolphin Clusters 2 38 20 ERG Pier 2 28 17 Pier 5002 2 3 2 Total 2-4 192 2 86 Pile Installation 1 Vibratory Hammer/Impact Hammer 16-inch (41 cm) round fiberglass-reinforced plastic Deperming Pier Edge Deperming Pier Corners 3 2 72 51 24 26 ERG Pier Dolphin Clusters 2 38 19 ERG Pier 2 28 14 Pier 5002 2 3 2 Totals 2-3 192 85 Total in-water pile extraction/installation days 171 NBSD CHOLLAS CREEK Pile Removal 3 Vibratory Extraction 13-inch round plastic 4 Quay wall corner to channel 7 14 2 18-inch square concrete Quay wall 5 140 28 14-inch steel H Quay wall 12 100 9 18-inch octagonal concrete Small craft dock 2 2 1 24-inch steel sheet 5 Quay wall 10 288 29 Totals 2-12 544 69 Pile Installation 1 Vibratory/Impact Hammer 13-round plastic Quay wall corner to channel 5 14 3 18-inch square concrete Quay wall 6 155 26 18-inch octagonal concrete Small craft dock 4 23 6 27.5-inch steel sheet 6 Quay wall 10 744 86 Total 4-10 936 121 Total in-water pile extraction/installation days 190 1 Vibratory pile removal/installation and impact pile installation may occur with or without high-pressure water jetting occurring either simultaneously or separately. 2 Contractor added buffer days for some locations. 3 While other methods of pile extraction are possible, vibratory extraction is the most likely method that would be used to extract piles. No Level A harassment or Level B harassment (take analysis) is conducted on the other pile extraction methods ( i.e., dead pull, water jetting). 4 These piles are anticipated to be dead pulled. 5 These piles are anticipated to be either vibratory extracted, dead pulled, or clipped at the mud-line and removed. For this IHA, we are assuming vibratory extraction for the demolition of all existing sheet piles. 6 Includes extra days as a buffer. For both projects, only in-water vibratory pile removal and vibratory and impact pile installation are anticipated to result in marine mammal harassment due to elevated underwater noise. Any above-ground activities ( e.g., repositioning equipment) are expected to result in only in-air/in-ground construction noise below levels known to affect marine mammals, and thus won't be discussed further. The underwater sound generated by these in-water activities associated with the NBPL Deperming Pier Replacement Project may result in Level A harassment and/or Level B harassment of six marine mammal species, comprising six stocks. For the NBSD Chollas Creek Quay Wall Repair Project, underwater sound may result in Level B harassment of three marine mammal species. With respect to the ambient or background underwater sound levels (SPL) for San Diego Bay, these levels are reported in the “Compendium of Underwater and Airborne Sound Data during Pile Installation and In-Water Demolition Activities in San Diego Bay, California” (NAVFAC SW, 2020). These sound levels were measured for the NBPL Fuel Pier Replacement Project at two locations. The median background underwater SPL in areas of the Bay subject to project construction noise at NBPL averaged approximately 129.6 dB (referenced to 1 micropascal (re 1 µPa)). As described in the Estimated Take section, pile removal and installation noise for the NBSD Project is likely to become indistinguishable from background noise as it diminishes to 126 dB re 1 μPa with distance from the source (NBSD IHA application, citing Dahl and Dall'Osto, 2019). Proposed mitigation, monitoring, and reporting measures are described in detail later in this document (please see Proposed Mitigation and Proposed Monitoring and Reporting). Description of Marine Mammals in the Area of Specified Activities Sections 3 and 4 of the application summarize available information regarding the status and trends, distribution and habitat preferences, and behavior and life history of the potentially affected species. NMFS fully considered all of this information, and we refer the reader to these descriptions in the application instead of reprinting the information. Additional information on population trends and threats may be found in NMFS' Stock Assessment Reports (SARs; https://www.fisheries.noaa.gov/national/marine-mammal-protection/marine-mammal-stock-assessments ), and more general information about these species ( e.g., physical and behavioral descriptions) may be found on NMFS' website ( https://www.fisheries.noaa.gov/find-species ). Furthermore, information may be found in the “U.S. Navy's Dive Distribution and Group Size Parameters for Marine Species Occurring in the U.S. Navy's Atlantic and Hawaii-California Training and Testing Study Areas” (Navy, 2024), available online at https://www.nepa.navy.mil/Portals/20/Documents/Pacific%20Fleet/HSTTEIS/HCTT/DraftEIS/TechnicalReports/AFTTHCTTDiveProfile_TR12243A.pdf. Table 2 lists all the species or stocks for which take is expected and proposed to be authorized for these activities and summarizes information related to the population or stock, including regulatory status under the MMPA and Endangered Species Act (ESA), as well as the potential biological removal (PBR), where known. The MMPA defines PBR as the maximum number of animals, not including natural mortalities, that may be removed from a marine mammal stock while allowing that stock to reach or maintain its optimum sustainable population (as described in NMFS' SARs). While no serious injury or mortality is anticipated or proposed to be authorized for either project, the PBR and annual mortality and serious injury (M/SI) from anthropogenic sources are included here as gross indicators of the status of the species or stocks and other threats. Marine mammal abundance estimates presented in this document represent the total number of individuals that make up a given stock or the total number estimated within a particular study or survey area. NMFS' stock abundance estimates for most species represent the total estimate of individuals within the geographical area, if known, that comprises that stock. For some species, this area may extend beyond U.S. waters. All managed stocks in this region are assessed in NMFS' U.S. Pacific SARs (Carretta et al., 2025). All values presented in table 2 are the most recent available at the time of publication (including from the draft 2024 SARs) and are available online at: https://www.fisheries.noaa.gov/ national/marine-mammal-protection/marine-mammal-stock-assessments. Table 2—Species, Stocks, and the Status of Marine Mammals With Estimated Take From the Specified NBPL and NBSD Activities Common name 1 Scientific name Stock ESA/ MMPA status; strategic (Y/N) 2 Stock abundance (CV, N min , most recent abundance survey) 3 PBR Annual M/S 4 Order Artiodactyla—Infraorder Cetacea—Mysticeti (baleen whales) Family Eschrichtiidae: Gray whale 5 Eschrichtius robustus Eastern North Pacific -,-,N 25,960 (0.05, 25,849, 2016) 801 131 Odontoceti (toothed whales, dolphins, and porpoises) Family Delphinidae: Common dolphin (short-beaked) 5 Delphinus delphis CA/OR/WA -,-,N 1,056,308 (0.21, 888,971, 2018) 8,889 ≥30.5 Common dolphin (long-beaked) 5 Delphinus delphis bairdii CA -,-,N 83,379 (0.216, 69,636, 2018) 668 ≥29.7 Common bottlenose dolphin 5 6 Tursiops truncatus truncatus CA coastal -,-,N 453 (0.6, 346, 2011) 2.7 ≥2.0 Order Carnivora—Pinnipedia Family Otariidae (eared seals and sea lions): California sea lion 5 6 Zalophus californianus U.S. -,-,N 257,606 (N/A, 233,515, 2014) 14,011 >321 Family Phocidae (earless seals): Harbor seal 5 6 Phoca vitulina California -,-,N 30,968 (N/A, 27,348, 2012) 1,641 43 1 Information on the classification of marine mammal species can be found on the web page for The Society for Marine Mammalogy's Committee on Taxonomy ( https://marinemammalscience.org/science-and-publications/list-marine-mammal-species-subspecies/ ). 2 Endangered Species Act (ESA) status: Endangered (E), Threatened (T); MMPA status: Depleted (D). A dash (-) indicates that the species is not listed under the ESA or designated as depleted under the MMPA. Under the MMPA, a strategic stock is one for which the level of direct human-caused mortality exceeds PBR or is determined to be declining and likely to be listed under the ESA within the foreseeable future. Any species or stock listed under the ESA is automatically designated as depleted and as a strategic stock under the MMPA. 3 NMFS marine mammal stock assessment reports online at https://www.fisheries.noaa.gov/national/marine-mammal-protection/marine-mammal-stock-assessment-reports. CV is the coefficient of variation; N min is the minimum estimate of stock abundance. In some cases, a CV is not applicable. N/A indicates data are unknown. UND (undetermined) PBR indicates data are available to calculate a PBR level, but a determination has been made that calculating a PBR level using those data is inappropriate (see the SAR for details). 4 These values, found in NMFS' SARs, represent annual levels of human-caused mortality plus serious injury from all sources combined ( e.g., commercial fisheries, ship strikes). Annual M/SI is often not precisely determined and is sometimes reported as a minimum value or a range. 5 Species occurs in the NBPL Project area; see the Marine Mammal Species at NBPL section and table 8 for further information. 6 Species occurs in the NBSD Project area; see the Marine Mammal Species at NBSD section and table 8 for further information. As indicated above, table 2 lists all six species that temporally and spatially co-occur during all or a portion of the in-water work associated with the proposed activities at NBPL to the degree that incidental take could potentially occur. Thus, the Navy has requested, and NMFS proposes to authorize, the incidental take of these six species. Table 2 also lists the three species that temporally and spatially co-occur during all or a portion of the in-water work associated with the proposed activities at NBSD to the degree that incidental take could potentially occur. Thus, for the NBSD Project, the Navy has requested, and NMFS proposes to authorize, the incidental take of California sea lions, the California coastal stock of the bottlenose dolphins, and harbor seals. NMFS has previously authorized the incidental take of Risso's dolphins ( Grampus griseus ), northern elephant seals ( Mirounga angustirostris ), and Pacific white-sided dolphins ( Lagenorhynchus obliquidens ) in past IHAs spanning over a decade for Navy projects in San Diego Bay (see the NBPL Fuel Pier Replacement projects: 78 FR 44539, July 24, 2013 (Year 1 Project); 79 FR 65378, November 4, 2014; (Year 2 Project); 80 FR 62032, October 15, 2015 (Year 3 Project); 81 FR 66628, September 28, 2016 (Year 4 Project); 82 FR 45811, and October 2, 2017 (Year 5 Project); 85 FR 33129, June 1, 2020 (NBPL Floating Dry Dock Project); 86 FR 7993, February 3, 2021 (NBPL Pier 6 Replacement Project), and 86 FR 48986, September 1, 2021 (NBPL Fuel Pier Inboard Pile Removal Project) for examples). However, based on monitoring reports for these projects, sightings of these species were rare or occurred only during an El Niño monitoring year and are not considered representative of typical species occurrences (see 88 FR 6703, February 1, 2024). Therefore, because the temporal and/or spatial occurrence of Risso's dolphins, northern elephant seals, and Pacific white-sided dolphins during in-water activities for both projects is such that incidental take is not expected to occur, the Navy did not request, and NMFS is not proposing to authorize, the incidental take of these three species, and these species are not discussed further (for either the NBPL or NBSD projects). The most frequently observed marine mammal in San Diego Bay is the California sea lion, which is considered abundant and often rests on buoys and other man-made structures found throughout the North to North Central Bay. Other species known to occur in San Diego Bay include the California coastal stock of the common bottlenose dolphin, which is seen year-round in the North Bay but sightings are sporadic and highly variable, and the harbor seal, which is relatively uncommon in the North Bay. Gray whales, which are occasionally sighted near the mouth of San Diego Bay during their winter migration, are considered rare/seasonal. Lastly, common dolphins (both short-beaked and long-beaked are occasional visitors to San Diego Bay. Recently, the Committee on Taxonomy ( https://marinemammalscience.org/science-and-publications/list-marine-mammal- species-subspecies /) determined that both the short-beaked and long-beaked common dolphin belong to the same species, and we adopt this taxonomy. However, the SARs still describe the two as separate stocks, and that stock information is presented in table 2. Sightings of common dolphins (both short-beaked and long-beaked) and gray whales are rare occurrences in San Diego Bay, especially in South-Central San Diego Bay, where Chollas Creek is located. Based on the lack of sightings as documented in the NBSD Pier 6 Replacement Project's final report (NAVFAC SW, 2024) during 172 monitoring days, the Navy is not requesting, and NMFS is not proposing to authorize, the incidental take for these three species, and they are not discussed further beyond the explanation provided here. Finally, there are no known biologically important areas (BIAs) for marine mammals near the project sites that would be relevant to the Navy's proposed activities. Marine Mammal Hearing Hearing is the most vital sensory modality for marine mammals underwater, and exposure to anthropogenic sound can have deleterious effects. To appropriately assess the potential effects of sound exposure, it is necessary to understand the frequency ranges that marine mammals can hear. Not all marine mammal species have equal hearing capabilities or hear over the same frequency range ( e.g., Richardson et al., 1995; Wartzok and Ketten, 1999; Au and Hastings, 2008). To reflect this, Southall et al. (2007; 2019) recommended that marine mammals be divided into hearing groups based on directly measured (behavioral or auditory evoked potential techniques) or estimated hearing ranges (behavioral response data, anatomical modeling, etc. ). Subsequently, NMFS (2018, 2024) described generalized hearing ranges for these marine mammal hearing groups. Generalized hearing ranges were chosen based on the approximately 65-decibel (dB) threshold from the normalized composite audiograms, with the exception of lower limits for low-frequency cetaceans, where the lower bound was deemed to be biologically implausible, and the lower bound from Southall et al. (2007) was retained. In October 2024, NMFS published its 2024 Updated Technical Guidance, which includes updated thresholds and weighting functions to inform auditory injury estimates and replaces the 2018 Technical Guidance referenced above. This 2024 Updated Technical Guidance represents the best available science. Marine mammal hearing groups and their associated hearing ranges are provided in table 3. Of the species potentially present in both proposed action areas, gray whales are considered low-frequency (LF) cetaceans; bottlenose dolphins and short- and long-beaked common dolphins are considered high-frequency (HF) cetaceans; California sea lions are otariid pinnipeds; and harbor seals are phocid pinnipeds. Table 3—Marine Mammal Hearing Groups [NMFS, 2024] Hearing group Generalized hearing range * Low-frequency (LF) cetaceans (baleen whales) 7 Hz to 36 kHz. High-frequency (HF) cetaceans (dolphins, toothed whales, beaked whales, bottlenose whales) 150 Hz to 160 kHz. Very High-frequency (VHF) cetaceans (true porpoises, Kogia, river dolphins, Cephalorhynchid, Lagenorhynchus cruciger & L. australis ) 200 Hz to 165 kHz. Phocid pinnipeds (PW) (underwater) (true seals) 40 Hz to 90 kHz. Otariid pinnipeds (OW) (underwater) (sea lions and fur seals) 60 Hz to 68 kHz. * Represents the generalized hearing range for the entire group as a composite ( i.e., all species within the group), where individual species' hearing ranges may not be as broad. Generalized hearing range chosen based on approximately 65 dB threshold from composite audiogram, previous analysis in NMFS (2018), and/or data from Southall et al. (2007) and Southall et al. (2019). Additionally, animals can detect very loud sounds above and below the “generalized” hearing range. Potential Effects of Specified Activities on Marine Mammals and Their Habitat This section includes a discussion of how components of the specified activities for both the NBPL and NBSD projects may affect marine mammals and their habitat. The Estimated Take of Marine Mammals section later in this document includes a quantitative analysis of the number of individuals that are expected to be taken by both the NBPL and NBSD activities. The Negligible Impact Analysis and Determination section considers the content of this section, as well as the Estimated Take of Marine Mammals section and the Proposed Mitigation section, to draw conclusions regarding the likely impacts of both of the proposed project 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. Acoustic effects on marine mammals during the specified activities for both projects are expected to result from vibratory removal/driving and impact pile driving. While marine mammals in some cases have exhibited little to no obviously detectable response to certain common or routine industrialized activities (Cornick et al., 2011; Horley and Larson, 2023) such as those that occur in San Diego Bay, it is possible that some animals may, at times, be exposed to received levels of sound above the auditory injury (AUD INJ; discussed later) and/or Level B harassment thresholds during the proposed projects. This potential exposure, in combination with the nature of planned activities ( e.g., vibratory pile removal/driving and impact pile driving), means that take by Level A harassment and/or Level B harassment could occur over the total estimated period of activities. Therefore, NMFS, in response to the Navy's NBPL Deperming Pier Replacement Project IHA application, proposes to authorize take by Level A harassment and/or Level B harassment from the proposed construction activities. Moreover, in response to the Navy's NBSD Chollas Creek Quay Wall Repair Project IHA application, NMFS proposes to authorize take by Level B harassment only from the proposed construction activities. NMFS has summarized a brief technical description of the physics of sound and relevant measurement metrics ( i.e., RMS, Peak, and SEL) (NMFS, 2024), available online at https://www.fisheries.noaa.gov/national/marine-mammal-protection/ marine-mammal-acoustic-technical-guidance. We refer readers to this document for definitions of the measurement terms and metrics used herein. There are a variety of types and degrees of effects on marine mammals, prey species, and habitats that could result from the projects. Since both projects would use the same pile-driving and removal methods, below is a brief description of the sound sources the projects would generate, the general impacts of these activities, and an analysis of the anticipated impacts on marine mammals from the projects, with consideration of the proposed mitigation measures. Description of Sound Sources for the Specified NBPL and NBSD Activities Construction Activities Impact hammers typically operate by repeatedly dropping and/or pushing a heavy piston onto a pile to drive the pile into the substrate. Sound generated by impact hammers is impulsive, characterized by rapid rise times and high peak levels, a potentially injurious combination (Hastings and Popper, 2005). Vibratory hammers install piles by vibrating them and allowing the hammer's weight to drive them into the substrate. Vibratory hammers typically produce less sound ( i.e., lower levels) than impact hammers. Peak SPLs may be 180 dB or greater, but are generally 10 to 20 dB lower than SPLs generated during impact pile driving of the same-sized pile (Oestman et al., 2009; California Department of Transportation (CALTRANS), 2015; 2020). Sounds produced by vibratory hammers are non-impulsive; compared to sounds produced by impact hammers, the rise time is slower, reducing the probability and severity of injury, and the sound energy is distributed over a greater amount of time (Nedwell and Edwards, 2002; Carlson et al., 2005). Potential Effects of Underwater Sound on Marine Mammals The introduction of anthropogenic noise into the aquatic environment from vibratory pile removal and vibratory and impact pile installation is the primary means by which marine mammals may be harassed from the Navy's specified activities at both NBPL and NBSD. Anthropogenic sounds span a broad range of frequencies and sound levels and can have highly variable impacts on marine life, from none or minor to potentially severe responses, depending on received levels, duration of exposure, behavioral context, and other factors. Broadly, underwater sound from active acoustic sources, such as those in these projects, can potentially result in one or more of the following: temporary or permanent hearing impairment, non-auditory physical or physiological effects, behavioral disturbance, stress, and masking (Richardson et al., 1995; Gordon et al., 2003; Nowacek et al., 2007; Southall et al., 2007; Götz et al., 2009). We describe the more severe effects of certain non-auditory physical or physiological effects only briefly, as we do not expect that the use of impact/vibratory hammers is reasonably likely to result in such effects (see below for further discussion). For non-auditory physical effects, for the NBPL Project, abundant California sea lions are known to haul out at docks associated with Pier 122 (~363 ft (110 m) to the north) and Pier 40 (~192 ft (58 m) to the south). They are also known to haul out at barges associated with the Everingham Brothers' Bait Barge Company that are from 541 ft to 1,003 ft (164 m to 304 m) east of the NBPL Project area. For the NBSD Project, the species is known to haul out near the NBSD security fence and navigation channel marker buoys. However, California sea lions exhibit a high tolerance to human activity (Holcomb et al., 2009) and opportunistically use almost any available structure as a haul out (NAVFAC SW and POSD, 2013). As for the NBSD Project, the relatively uncommon harbor seals also haul out on rocks, buoys, and other structures. As stated above, the nearest pinniped haul outs are a pair of active Navy docks to the north and the south of the Deperming Pier, with a pair of bait barges to the east. Harbor seals are even more uncommon with respect to the NBSD Project. Ultimately, we expect that any visual and/or other non-acoustic stressors would be limited and that any impacts on marine mammals would be acoustic in nature for both projects. Potential physiological effects from sound sources, particularly impulsive sound, can range from behavioral disturbance or tactile perception to physical discomfort, slight injury to the internal organs and the auditory system, or mortality (Yelverton et al., 1973). Non-auditory physiological effects or injuries that theoretically might occur in marine mammals exposed to high level underwater sound or as a secondary effect of extreme behavioral reactions ( e.g., change in dive profile as a result of an avoidance reaction) caused by exposure to sound include neurological effects, bubble formation, resonance effects, and other types of organ or tissue damage (Cox et al., 2006; Southall et al., 2007; Zimmer and Tyack, 2007; Tal et al., 2015). However, the Project activities considered here do not involve the use of devices such as explosives or mid-frequency tactical sonar that are associated with these types of effects. In general, animals exposed to natural or anthropogenic sound may experience physical and psychological effects, ranging in magnitude from none to severe (Southall et al., 2007, 2019). Exposure to anthropogenic noise can result in auditory threshold shifts and behavioral responses ( e.g., avoidance, temporary cessation of foraging and vocalizing, changes in dive behavior). It can also lead to non-observable physiological responses, such as increased stress hormone levels. Additional noise in a marine mammal's habitat can mask acoustic cues used in daily functions, such as communication and predator and prey detection. The degree of effect of an acoustic exposure on marine mammals is dependent on several factors, including, but not limited to, sound type ( e.g., impulsive vs. non-impulsive), signal characteristics, the species, age, and sex class ( e.g., adult male vs. mom with calf), duration of exposure, the distance between the noise source and the animal, received levels, behavioral state at time of exposure, and previous history with exposure (Wartzok et al., 2004; Southall et al., 2007). In general, sudden, high-intensity sounds can cause hearing loss, as can longer exposures to lower-intensity sounds. Moreover, any temporary or permanent loss of hearing, if it occurs at all, would occur almost exclusively for noise within an animal's hearing range. We describe below the specific manifestations of acoustic effects that may occur from the specified activities. Richardson et al. (1995) described zones of increasing effect intensity that might be expected to occur with distance from a source, assuming that the signal is within an animal's hearing range. First (at the greatest distance) is the area within which the acoustic signal would be audible (potentially perceived) to the animal but not strong enough to elicit any overt behavioral or physiological response. The next zone (closer to the receiving animal) corresponds to the area where the signal is audible to the animal and sufficiently intense to elicit behavioral or physiological responsiveness. The third is a zone within which, for high-intensity signals, the received level is sufficient to cause discomfort or tissue damage to auditory or other systems. Overlaying these zones to some extent is the area within which masking ( i.e., when a sound interferes with or masks an animal's ability to detect a signal of interest above the absolute hearing threshold) may occur; the masking zone may vary widely in size. Below, we provide additional detail regarding the potential impacts on marine mammals and their habitat from noise in general, starting with hearing impairment, as well as from the specific activities the Navy plans to conduct at both project sites, to the extent available. Hearing Threshold Shifts NMFS defines a noise-induced threshold shift (TS) as a change, usually an increase, in the audibility threshold at a specified frequency or portion of an individual's hearing range above a previously established reference level (NMFS, 2018, 2024). The amount of threshold shift is customarily expressed in dB. A TS can be permanent or temporary. As described in NMFS (2018, 2024), there are numerous factors to consider when examining the consequence of TS, including, but not limited to, the signal temporal pattern ( e.g., impulsive or non-impulsive), the likelihood an individual would be exposed for a long enough duration or to a high enough level to induce a TS, the magnitude of the TS, the time to recovery (seconds to minutes or hours to days), the frequency range of the exposure ( i.e., spectral content), the hearing frequency range of the exposed species relative to the signal's frequency spectrum ( i.e., how the animal uses sound within the frequency band of the signal; e.g., Kastelein et al., 2014), and the overlap between the animal and the source ( e.g., spatial, temporal, and spectral). Temporary Threshold Shift A temporary threshold shift (TTS) is a temporary, reversible increase in the threshold of audibility at a specified frequency or portion of an individual's hearing range above a previously established reference level (NMFS, 2024), and is not considered an AUD INJ. Based on data from marine mammal TTS measurements (see Southall et al., 2007, 2019), a TTS of 6 dB is considered the minimum threshold shift clearly larger than any day-to-day or session-to-session variation in a subject's normal hearing ability (Finneran et al., 2000, 2002; Schlundt et al., 2000). As described in Finneran (2015), marine mammal studies have shown that the amount of TTS increases with the 24-hour cumulative sound exposure level (SEL24) in an accelerating fashion: at low exposures with lower SEL24, the amount of TTS is typically small, and the growth curves have shallow slopes. At higher SEL 24 exposures, the growth curves become steeper and approach a linear relationship with the sound exposure level (SEL). Depending on the degree (elevation of threshold in dB), duration ( i.e., recovery time), and frequency range of TTS, and the context in which it is experienced, TTS can have effects on marine mammals ranging from discountable to more impactful (similar to those discussed in auditory masking, below). For example, a marine mammal may readily compensate for a brief, relatively small amount of TTS in a non-critical frequency range that occurs while the animal is traveling through the open ocean, where ambient noise is lower and competing sounds are fewer. Alternatively, a larger amount and longer duration of TTS sustained during times when communication is critical for successful mother/calf interactions could have more severe impacts. We note that reduced hearing sensitivity, as a simple function of aging, has been observed in marine mammals, as well as in humans and other taxa (Southall et al., 2007), suggesting that strategies exist to cope with this condition to some degree, though likely not without cost. Many studies have examined noise-induced hearing loss in marine mammals (see Finneran (2015) and Southall et al. (2019) for summaries). TTS is the mildest form of hearing impairment that can occur during exposure to sound (Kryter, 2013). While experiencing TTS, the hearing threshold rises, so a sound must be louder to be heard. In terrestrial and marine mammals, TTS can last from minutes to hours (in cases of strong TTS) (Finneran, 2015). In many cases, hearing sensitivity recovers rapidly after exposure to the sound ends. For cetaceans, published data on the onset of TTS are limited to captive bottlenose dolphin ( Tursiops truncatus ), beluga whale ( Delphinapterus leucas ), harbor porpoise ( Phocoena phocoena ), and Yangtze finless porpoise ( Neophocoena asiaeorientalis ) (Southall et al., 2019). For pinnipeds in water, measurements of TTS are limited to harbor seals, northern elephant seals, bearded seals ( Erignathus barbatus ), and California sea lions (Kastak et al., 1999, 2007; Kastelein et al., 2019b, 2019c, 2021, 2022a, 2022b; Reichmuth et al., 2019; Sills et al., 2020). TTS was not observed in spotted ( Phoca largha ) and ringed ( Pusa hispida ) seals exposed to single airgun impulse sounds at levels matching previous predictions of TTS onset (Reichmuth et al., 2016). These studies examine hearing thresholds in marine mammals before and after exposure to intense or long-duration sound. The difference between the pre-exposure and post-exposure thresholds can be used to determine the amount of threshold shift at various post-exposure times. The amount and onset of TTS depend on the exposure frequency. Sounds below the region of best sensitivity for a species or hearing group are less hazardous than those near the region of best sensitivity (Finneran and Schlundt, 2013). At low frequencies, onset-TTS exposure levels are higher compared to those in the region of best sensitivity ( i.e., a low frequency noise would need to be louder to cause TTS onset when TTS exposure level is higher), as shown for harbor porpoises and harbor seals (Kastelein et al., 2019a, 2019c). Note that in general, harbor seals and harbor porpoises have a lower TTS onset than other measured pinniped or cetacean species (Finneran, 2015). In addition, TTS can accumulate across multiple exposures, but the resulting TTS would be lower than that from a single, continuous exposure with the same SEL (Mooney et al., 2009; Finneran et al., 2010; Kastelein et al., 2014, 2015). This means that TTS predictions based on the total, SEL 24 , will overestimate the amount of TTS from intermittent exposures, such as sonars and impulsive sources. Nachtigall et al. (2018) describe measurements of hearing sensitivity of multiple odontocete species (bottlenose dolphin, harbor porpoise, beluga, and false killer whale ( Pseudorca crassidens )) when a warning sound preceded a relatively loud sound. These captive animals were shown to reduce hearing sensitivity when warned of an impending intense sound. Based on these experimental observations of captive animals, the authors suggest that wild animals may dampen their hearing during prolonged exposures or if conditioned to anticipate intense sounds. Another study showed that echolocating animals (including odontocetes) might have anatomical specializations that enable conditioned hearing reduction and filtering of low-frequency ambient noise, including increased stiffness and control of middle ear structures, as well as placement of inner ear structures (Ketten et al., 2021). Data available on noise-induced hearing loss for mysticetes are currently lacking (NMFS, 2024). Additionally, the existing marine mammal TTS data come from a limited number of individuals within these species. Relationships between TTS and AUD INJ thresholds have not been studied in marine mammals, and there are no measured PTS data for cetaceans, but such relationships are assumed to be similar to those in humans and other terrestrial mammals. AUD INJ typically occurs at exposure levels at least several dB above that inducing mild TTS ( e.g., a 40-dB threshold shift approximates AUD INJ onset (Kryter et al., 1966; Miller, 1974), while a 6-dB threshold shift approximates TTS onset (Southall et al., 2007, 2019). Based on data from terrestrial mammals, a precautionary assumption is that the AUD INJ thresholds for impulsive sounds (such as impact pile driving pulses as received close to the source) are at least 6 dB higher than the TTS threshold on a peak-pressure basis, and AUD INJ cumulative sound exposure level thresholds are 15 to 20 dB higher than TTS cumulative sound exposure level thresholds (Southall et al., 2007, 2019). Given the higher level of sound or longer exposure duration necessary to cause AUD INJ as compared with TTS, it is considerably less likely that AUD INJ could occur. Auditory Injury NMFS (2024) defines AUD INJ as damage to the inner ear that can result in tissue destruction, such as loss of cochlear neuron synapses or auditory neuropathy (Houser 2021; Finneran 2024). AUD INJ may or may not result in a permanent threshold shift (PTS). PTS is subsequently defined as a permanent, irreversible increase in the threshold of audibility at a specified frequency or portion of an individual's hearing range above a previously established reference level (NMFS, 2024). PTS generally affects only a limited frequency range, and animals with PTS have some level of hearing loss at the relevant frequencies; typically, animals with PTS or other AUD INJ are not functionally deaf (Au and Hastings, 2008; Finneran, 2016). Available data from humans and other terrestrial mammals indicate that a 40-dB threshold shift approximates the onset of PTS (see Ward et al., 1958, 1959; Ward, 1960; Kryter et al., 1966; Miller, 1974; Ahroon et al., 1996; Henderson et al., 2008). However, a variety of terrestrial and marine mammal studies (see Ward et al., 1958; Ward et al., 1959; Ward, 1960; Miller et al., 1963; Kryter et al., 1966; Finneran et al., 2007; Kastelein et al., 2013) indicate that threshold shifts of up to 40 to 50 dB (measured a few minutes after exposure) may be induced without resulting in PTS. PTS levels for marine mammals are estimates; with the exception of a single study unintentionally inducing PTS in a harbor seal ( Phoca vitulina ) (Kastak et al., 2008), no empirical data measure PTS in marine mammals largely due to the fact that, for various ethical reasons, experiments involving anthropogenic noise exposure at levels inducing AUD INJ are not typically pursued or authorized (NMFS, 2024). NMFS has set the PTS onset as a threshold shift of 40 dB. However, after sound exposure ceases or between successive sound exposures, the potential for recovery from hearing loss exists. Thus, because a threshold shift is measured a few minutes after noise exposure does not mean that those initial shifts are persistent ( i.e., no recovery). When initial threshold shifts fully recover back to baseline hearing levels, these are considered TTS. PTS indicates there is no full recovery back to baseline hearing levels; however, it does not mean there is no recovery. Rather, PTS indicates incomplete recovery of hearing. Recovery depends on the initial threshold shift amount, the frequency at which the shift occurred, the temporal pattern of exposure ( e.g., exposure duration; continuous vs. intermittent exposure), and the physiological mechanisms underlying the shift ( e.g., mechanical vs. metabolic). Since recovery is complicated, our current AUD INJ onset criteria do not account for the potential for recovery. Behavioral Effects Exposure to noise can also behaviorally disturb marine mammals to a level that rises to the definition of harassment under the MMPA. Generally speaking, NMFS considers a behavioral disturbance that rises to the level of harassment under the MMPA a non-minor response. In other words, not every response qualifies as a behavioral disturbance, and for responses that do, those of higher level or longer duration have the potential to affect foraging, reproduction, or survival. Behavioral disturbance may include subtle changes ( e.g., minor or brief avoidance of an area or changes in vocalizations), more conspicuous changes in similar behavioral activities, and more sustained and/or potentially severe reactions, such as displacement from or abandonment of high-quality habitat. Behavioral responses may include changing durations of surfacing and dives, changing direction and/or speed; reducing/increasing vocal activities; changing/cessation of certain behavioral activities (such as socializing or feeding); eliciting a visible startle response or aggressive behavior (such as tail/fin slapping or jaw clapping); and avoidance of areas where sound sources are located. In addition, pinnipeds may increase their haul-out time, possibly to avoid in-water disturbance (Thorson and Reyff, 2006). Behavioral responses to sound are highly variable and context-specific, and any reactions depend on numerous intrinsic and extrinsic factors ( e.g., species, state of maturity, experience, current activity, reproductive state, auditory sensitivity, time of day), as well as the interplay between factors ( e.g., Richardson et al., 1995; Wartzok et al., 2004; Southall et al., 2007, 2019; Weilgart, 2007; Archer et al., 2010). Behavioral reactions can vary not only among individuals but also within an individual, depending on previous experience with a sound source, context, and numerous other factors (Ellison et al., 2012), and can vary depending on characteristics associated with the sound source ( e.g., whether it is moving or stationary, number of sources, distance from the source). In general, pinnipeds seem more tolerant of, or at least habituate more quickly to, potentially disturbing underwater sound than do cetaceans, and generally seem to be less responsive to exposure to industrial sound than most cetaceans. Please see Appendices B and C of Southall et al. (2007) and Gomez et al. (2016) for reviews of studies involving marine mammal behavioral responses to sound. Habituation can occur when an animal's response to a stimulus wanes with repeated exposure, usually in the absence of unpleasant associated events (Wartzok et al., 2004). Animals are most likely to habituate to predictable, unvarying sounds. It is important to note that habituation is appropriately considered as a “progressive reduction in response to stimuli that are perceived as neither aversive nor beneficial,” rather than as, more generally, moderation in response to human disturbance (Bejder et al., 2009). The opposite process is sensitization, in which an unpleasant experience leads to subsequent responses, often in the form of avoidance, at lower levels of exposure. As noted above, behavioral state may affect the type of response. For example, resting animals may show greater behavioral change in response to disturbing sound levels than highly motivated animals that are highly motivated to remain in an area for feeding (Richardson et al., 1995; Wartzok et al., 2004; National Research Council (NRC), 2005). Controlled experiments with captive marine mammals have shown pronounced behavioral reactions, including avoidance of loud sound sources (Ridgway et al., 1997; Finneran et al., 2003). Observed responses of wild marine mammals to loud pulsed sound sources ( e.g., seismic airguns) have been varied but often consist of avoidance behavior or other behavioral changes (Richardson et al., 1995; Morton and Symonds, 2002; Nowacek et al., 2007). Available studies show wide variation in response to underwater sound; therefore, it is difficult to predict specifically how any given sound in a particular instance might affect marine mammals perceiving the signal ( e.g., Erbe et al., 2019). If a marine mammal briefly reacts to an underwater sound by changing its behavior or moving a small distance, the resulting change is unlikely to be significant to the individual, let alone the stock or population. If a sound source displaces marine mammals from an important feeding or breeding area for a prolonged period, impacts on individuals and populations could be significant ( e.g., Lusseau and Bejder, 2007; Weilgart, 2007; NRC, 2005). However, there are broad categories of potential response, which we describe in greater detail here, that include alteration of dive behavior, alteration of foraging behavior, effects on breathing, interference with or alteration of vocalization, avoidance, and flight. Avoidance and Displacement Changes in dive behavior can vary widely and may consist of increased or decreased dive times and surface intervals as well as changes in the rates of ascent and descent during a dive ( e.g., Frankel and Clark, 2000; Costa et al., 2003; Ng and Leung, 2003; Nowacek et al., 2004; Goldbogen et al., 2013a, 2013b; Blair et al., 2016). Variations in dive behavior may reflect interruptions in biologically significant activities ( e.g., foraging) or they may be of little biological significance. The impact of an alteration in dive behavior resulting from acoustic exposure depends on what the animal is doing at the time of exposure and on the type and magnitude of the response. Disruption of feeding behavior can be difficult to correlate with anthropogenic sound exposure, so it is usually inferred by observed displacement from known foraging areas, the appearance of secondary indicators ( e.g., bubble nets or sediment plumes), or changes in dive behavior. As for other types of behavioral response, the frequency, duration, and temporal pattern of signal presentation, as well as differences in species sensitivity, are likely contributing factors to differences in response in any given circumstance ( e.g., Croll et al., 2001; Nowacek et al., 2004; Madsen et al., 2006; Yazvenko et al., 2007). A determination of whether foraging disruptions incur fitness consequences would require information on, or estimates of, the energetic requirements of the affected individuals, the relationship between prey availability, foraging effort, and success, and the animal's life history stage. Respiration rates vary naturally with different behaviors, and alterations in breathing rate, as a function of acoustic exposure, can be expected to co-occur with other behavioral reactions, such as a flight response or an alteration in diving. However, respiration rates in and of themselves may be representative of annoyance or an acute stress response. Various studies have shown that respiration rates may either be unaffected or could increase, depending on the species and signal characteristics, again highlighting the importance of understanding species differences in the tolerance of underwater noise when determining the potential for impacts resulting from anthropogenic sound exposure ( e.g., Kastelein et al., 2001; 2005; 2006; Gailey et al., 2007). For example, harbor porpoise respiration rates increased in response to pile driving sounds at and above a received broadband SPL of 136 dB (zero-peak SPL: 151 dB re 1 μPa; SEL of a single strike (SEL ss ): 127 dB re 1 μPa 2 -s) (Kastelein et al., 2013). Avoidance is the displacement of an individual from an area or migration path due to the presence of a sound or other stressors, and is one of the most obvious manifestations of disturbance in marine mammals (Richardson et al., 1995). Avoidance may be short-term, with animals returning to the area once the noise has ceased ( e.g., Bowles et al., 1994; Goold, 1996; Stone et al., 2000; Morton and Symonds, 2002; Gailey et al., 2007). Longer-term displacement is possible, however, which may lead to changes in the abundance or distribution patterns of the affected species in the affected region if habituation to the sound does not occur ( e.g., Blackwell et al., 2004; Bejder et al., 2006; Teilmann et al., 2006). A flight response is a dramatic change in normal movement, with directed, rapid movement away from the perceived location of a sound source. The flight response differs from other avoidance responses in its intensity ( e.g., directed movement and travel rate). Relatively little information exists on the flight responses of marine mammals to anthropogenic signals, although observations of flight responses to the presence of predators have been made (Connor and Heithaus, 1996; Bowers et al., 2018). The result of a flight response could range from brief, temporary exertion and displacement from the area where the signal provokes flight to, in extreme cases, marine mammal strandings (England et al., 2001). However, it should be noted that response to a perceived predator does not necessarily invoke flight (Ford and Reeves, 2008), and whether individuals are solitary or in groups may influence the response. Behavioral disturbance can also affect marine mammals in more subtle ways. Increased vigilance may incur costs from the diversion of attention ( i.e., when a response requires heightened vigilance, it may come at the expense of reduced attention to other critical behaviors, such as foraging or resting). These effects have generally not been demonstrated in marine mammals, but studies of fishes and terrestrial animals have shown that increased vigilance may substantially reduce feeding rates ( e.g., Beauchamp and Livoreil, 1997; Fritz et al., 2002; Purser and Radford, 2011). In addition, chronic disturbance can cause population declines through reductions in fitness ( e.g., declines in body condition) and subsequent reductions in reproductive success, survival, or both ( e.g., Harrington and Veitch, 1992; Daan et al., 1996; Bradshaw et al., 1998). However, Ridgway et al. (2006) reported that increased vigilance in bottlenose dolphins exposed to sound over a 5-day period did not result in sleep deprivation or stress. Many animals perform vital functions, such as feeding, resting, traveling, and socializing, on a diel cycle (24-hour cycle). Disruption of such functions resulting from reactions to stressors, such as sound exposure, is more likely to be significant if it lasts more than one diel cycle or recurs on subsequent days (Southall et al., 2007). Consequently, a behavioral response lasting less than one day and not recurring on subsequent days is not considered particularly severe unless it could directly affect reproduction or survival (Southall et al., 2007). Note that there is a difference between multi-day substantive ( i.e., meaningful) behavioral reactions and multi-day anthropogenic activities. For example, just because an activity lasts multiple days does not necessarily mean that individual animals are exposed to activity-related stressors for multiple days, or, further, exposed in a manner that results in sustained, multi-day, substantive behavioral responses. Physiological Stress Responses An animal's perception of a threat may be sufficient to trigger stress responses that include some combination of behavioral, autonomic nervous system, neuroendocrine, and immune responses ( e.g., Selye, 1950; Moberg, 2000). In many cases, an animal's first and sometimes most economical response (in terms of energetic costs) is behavioral avoidance of the potential stressor. Autonomic nervous system responses to stress typically involve changes in heart rate, blood pressure, and gastrointestinal activity. These responses have a relatively short duration and may or may not have a significant long-term effect on an animal's fitness. Neuroendocrine stress responses often involve the hypothalamus-pituitary-adrenal system. Virtually all neuroendocrine functions that are affected by stress—including immune competence, reproduction, metabolism, and behavior—are regulated by pituitary hormones. Stress-induced changes in pituitary hormone secretion have been implicated in reproductive failure, altered metabolism, reduced immune competence, and behavioral disturbances ( e.g., Moberg, 1987; Blecha, 2000). Increases in glucocorticoid levels are also associated with stress (Romano et al., 2004). The primary distinction between stress (which is adaptive and does not normally place an animal at risk) and “distress” is the cost of the response. During a stress response, an animal uses its glycogen stores, which can be quickly replenished once the stress is alleviated. In such circumstances, the cost of the stress response would not pose serious fitness consequences. However, when an animal does not have sufficient energy reserves to satisfy the energetic costs of a stress response, energy resources must be diverted from other functions. This state of distress will last until the animal replenishes its energy reserves to a sufficient level to restore normal function. Relationships between these physiological mechanisms, animal behavior, and the costs of stress responses are well-studied through controlled experiments and for both laboratory and free-ranging animals ( e.g., Holberton et al., 1996; Hood et al., 1998; Jessop et al., 2003; Krausman et al., 2004; Lankford et al., 2005; Ayres et al., 2012; Yang et al., 2022). Stress responses to exposure to anthropogenic sounds or other stressors, and their effects on marine mammals, have also been reviewed (Fair and Becker, 2000; Romano et al., 2002b) and, more rarely, studied in wild populations ( e.g., Romano et al., 2002a). For example, Rolland et al. (2012) found that noise reduction from reduced ship traffic in the Bay of Fundy was associated with decreased stress in North Atlantic right whales. In addition, Lemos et al. (2022) observed a correlation between higher levels of fecal glucocorticoid metabolite concentrations (indicative of a stress response) and vessel traffic in gray whales. Yang et al. (2022) studied behavioral and physiological responses in captive bottlenose dolphins exposed to playbacks of “pile-driving-like” impulsive sounds, finding significant changes in cortisol and other physiological indicators, but only minor behavioral changes. These and other studies lead to a reasonable expectation that some marine mammals will experience physiological stress responses upon exposure to acoustic stressors, and that some of these responses may be classified as “distress.” In addition, any animal experiencing TTS would likely also experience stress responses (NRC, 2005); however, distress is unlikely to result from these projects based on observations of marine mammals during previous, similar construction projects in San Diego Bay. Vocalizations and Auditory Masking Since many marine mammals rely on sound to find prey, moderate social interactions, and facilitate mating (Tyack, 2008), noise from anthropogenic sound sources can interfere with these functions, but only if the noise spectrum overlaps with the hearing sensitivity of the receiving marine mammal (Southall et al., 2007; Clark et al., 2009; Hatch et al., 2012). Chronic exposure to excessive, though not high-intensity, noise could cause masking at specific frequencies for marine mammals that rely on sound for vital biological functions (Clark et al., 2009). Acoustic masking is when other noises, such as from human sources, interfere with an animal's ability to detect, recognize, or discriminate between acoustic signals of interest ( e.g., those used for intraspecific communication and social interactions, prey detection, predator avoidance, navigation) (Richardson et al., 1995; Erbe et al., 2016). The frequency range of the potentially masking sound is important in determining any potential behavioral impacts. For example, low-frequency signals may have less effect on high-frequency echolocation sounds produced by odontocetes but are more likely to affect the detection of mysticete communication calls and other potentially important natural sounds such as those produced by surf and some prey species. The masking of communication signals by anthropogenic noise may be considered as a reduction in the communication space of animals ( e.g., Clark et al., 2009), and may result in energetic or other costs as animals change their vocalization behavior ( e.g., Miller et al., 2000; Foote et al., 2004; Parks et al., 2007; Di Iorio and Clark, 2010; Holt et al., 2009). Masking can be reduced in situations where the signal and noise come from different directions (Richardson et al., 1995), through amplitude modulation of the signal, or through other compensatory behaviors, including modifications of the acoustic properties of the signal or the signaling behavior (Hotchkin and Parks, 2013). Masking can be tested directly in captive species ( e.g., Erbe, 2008), but in wild populations it must be either modeled or inferred from evidence of masking compensation. Few studies have addressed real-world masking sounds likely to be experienced by marine mammals in the wild ( e.g., Branstetter et al., 2013). Masking occurs in the frequency band that the animals use, and is more likely to occur in the presence of broadband, relatively continuous noise sources such as vibratory pile removal or installation. The energy distribution of pile-driving sound spans a broad frequency spectrum and is expected to fall within the audible range of marine mammals present in the project areas. Since noises generated from the proposed construction activities are mostly concentrated at low frequencies (<2 kHz), these activities likely have less effect on mid-frequency echolocation sounds produced by odontocetes (toothed whales). However, lower-frequency noises are more likely to affect the detection of communication calls and other potentially important natural sounds, such as surf and prey noise. Low-frequency noise may also affect communication signals when they occur near the noise band, thereby reducing the communication space of animals ( e.g., Clark et al., 2009) and increasing stress levels ( e.g., Holt et al., 2009). Unlike TS, masking, which can occur over large temporal and spatial scales, can potentially affect the species at population, community, or even ecosystem levels, in addition to individual levels. Masking affects both senders and receivers of signals, and at higher levels and for longer durations could have long-term chronic effects on marine mammal species and populations. However, the noise generated by the Navy's proposed activities would occur only intermittently, across an estimated 171 and 190 days, respectively, at both proposed activity locations (NBPL and NBSD) during the authorization periods, in a relatively small area focused around the proposed construction sites. Thus, while the Navy's proposed activities may mask some acoustic signals relevant to the daily behavior of marine mammals, the short-term duration and limited areas affected make it very unlikely that the fitness of individual marine mammals would be affected. The ability of a noise source to mask biologically important sounds depends on the characteristics of both the noise source and the signal of interest ( e.g., signal-to-noise ratio, temporal variability, direction), in relation to each other and to an animal's hearing abilities ( e.g., sensitivity, frequency range, critical ratios, frequency discrimination, directional discrimination, age, or TTS hearing loss), and existing ambient noise and propagation conditions (Hotchkin and Parks, 2013). Marine mammals vocalize for different purposes and across multiple modes, such as whistling, echolocation click production, calling, and singing. Changes in vocalization behavior in response to anthropogenic noise can occur across any of these modes and may result from a need to compete with increased background noise, or may reflect increased vigilance or a startle response. For example, in the presence of potentially masking signals, humpback whales ( Megaptera novaeangliae ) and killer whales ( Orcinus orca ) have been observed to increase the length of their songs (Miller et al., 2000; Fristrup et al., 2003) or vocalizations (Foote et al., 2004), respectively, while North Atlantic right whales ( Eubalaena glacialis ) have been observed to shift the frequency content of their calls upward while reducing the rate of calling in areas of increased anthropogenic noise (Parks et al., 2007). Fin whales ( Balaenoptera physalus physalus ) have also been documented to lower the bandwidth, peak frequency, and center frequency of their vocalizations in the presence of increased background noise from large vessels (Castellote et al., 2012). Other alterations to communication signals have also been observed. For example, gray whales, in response to playback experiments that exposed them to vessel noise, have been observed to increase their vocalization rate and produce louder signals during periods of increased outboard engine noise (Dahlheim and Castellote, 2016). Alternatively, in some cases, animals may cease sound production during the production of aversive signals (Bowles et al., 1994; Wisniewska et al., 2018). Under certain circumstances, marine mammals that experience significant masking could also be impaired in maximizing their performance fitness for survival and reproduction. Therefore, when the coincident (masking) sound is human-made, it may be considered harassment if it disrupts or alters critical behaviors. It is important to distinguish TTS and PTS, which persist after the sound exposure, from masking, which occurs during the sound exposure. Because masking (without resulting in TS) is not associated with abnormal physiological function, it is not considered a physiological effect but rather a potential behavioral effect (though not necessarily one associated with harassment). Therefore, under certain circumstances, marine mammals whose acoustic sensors or environment are severely masked could also be impaired in maximizing their performance fitness for survival and reproduction. Airborne Acoustic Effects Pinnipeds occurring near either project site could be exposed to airborne sounds associated with construction activities, depending on their distance from these activities, which could cause behavioral harassment. Airborne noise would primarily be an issue for pinnipeds that are swimming or hauled out near either project site, within the range of noise levels elevated above the airborne acoustic harassment criteria. Although pinnipeds are known to haul out regularly on man-made objects, we believe that incidents of take resulting solely from airborne sound are unlikely due to the proximity between the proposed project areas and the known haul out sites ( e.g., on docks associated with Pier 122 and Pier 40 for the NBPL project, and on the security fencing and barges associated with the Everingham Brothers' Bait Barge Company for the NBSD project) in San Diego Bay. Cetaceans are not expected to be exposed to airborne sounds that would result in harassment as defined under the MMPA. We recognize that pinnipeds in the water may be exposed to airborne sound that could result in behavioral harassment when they lift their heads above the water or when they haul out. Most likely, airborne sound would cause behavioral responses similar to those discussed above in relation to underwater sound. For instance, anthropogenic sound could cause hauled-out pinnipeds to exhibit changes in their normal behavior, such as a reduction in vocalizations, or to flush from haulouts, temporarily abandon the area, and/or move further from the source. However, these animals previously would have been “taken” because of exposure to underwater sound above the behavioral harassment thresholds, which are, in all cases, larger than those associated with airborne sound. Thus, the behavioral harassment of these animals is already accounted for in these estimates of potential take. Therefore, we do not believe that authorization of additional incidental take resulting from airborne sound for pinnipeds is warranted for either project, and airborne sound is not discussed further here. Potential Effects on Marine Mammal Habitat The Navy's proposed activities for both projects could have localized, temporary impacts on marine mammal habitat, including prey, due to increased in-water noise levels. Increased noise levels may affect the acoustic habitat and adversely affect marine mammal prey in the vicinity of the project areas (see discussion below). Elevated levels of underwater noise would ensonify the project areas where both fishes and mammals occur and could affect foraging success. Additionally, marine mammals may avoid the area during the proposed construction activities; however, any displacement due to noise is expected to be temporary and not to result in long-term effects on individuals or populations. The total area likely impacted by the Navy's proposed activities at NBPL and NBSD is relatively small compared to the available habitat within and outside of San Diego Bay. Avoidance by potential prey ( i.e., fish) of the immediate areas due to increased noise is possible. The duration of fish and marine mammal avoidance of this area after construction stops is unknown, but a rapid return to normal recruitment, distribution, and behavior is anticipated. Any behavioral avoidance by fish or marine mammals of either disturbed area would still leave significantly large areas of fish and marine mammal foraging habitat in the nearby vicinity. The proposed projects would occur within the same footprint as existing marine infrastructure. The nearshore and intertidal habitats where the proposed projects would occur are in industrialized areas with relatively high marine vessel traffic. Temporary, intermittent, and short-term habitat alteration may result from increased noise levels during the proposed construction activities. Effects on marine mammal habitat would be limited to temporary displacement from pile removal and installation noise, and effects on prey species would be similarly limited in time and space. Water Quality Temporary and localized reduction in water quality would occur as a result of in-water construction activities. Most of this effect would occur during the removal and installation of piles, when bottom sediments are disturbed, and may temporarily increase suspended sediment in the project area. During pile extraction, sediment attached to the pile moves vertically through the water column causing a sediment plume. However, since currents are so strong in the area, following the completion of sediment-disturbing activities, suspended sediment in the water column should dissipate and quickly return to background levels across all construction scenarios. Turbidity in the water column can reduce dissolved oxygen levels and irritate the gills of prey fish in the proposed project areas. Studies of the effects of turbid water on fish (marine mammal prey) suggest that concentrations of suspended sediment can reach thousands of milligrams per liter before an acute toxic reaction is expected (Burton, 1993). However, turbidity plumes associated with the projects would be temporary and localized, and fish in the proposed project areas would be able to move away from and avoid the areas where plumes may occur. Overall, the water quality in the immediate area that is likely impacted by the proposed construction activities for both projects is relatively small compared to the available marine mammal habitat within and surrounding San Diego Bay. Therefore, it is expected that water quality impacts on prey fish species due to turbidity, and therefore on marine mammals, would be minimal and temporary. Potential Effects on Prey Sound may affect marine mammals by altering the abundance, behavior, or distribution of prey species ( e.g., crustaceans, cephalopods, fishes, zooplankton). Marine mammal prey varies by species, season, and location, and for some, it is not well documented. Studies regarding the effects of noise on known marine mammal prey are described here. Fishes use the soundscape and components of sound in their environment to perform important functions such as foraging, predator avoidance, mating, and spawning ( e.g., Zelick et al., 1999; Fay, 2009). Depending on their hearing anatomy and peripheral sensory structures, which vary among species, fishes hear sounds using pressure- and particle-motion sensitivity and detect the motion of surrounding water (Fay et al., 2008). The potential effects of noise on fishes depends on the overlapping frequency range, distance from the sound source, water depth of exposure, and species-specific hearing sensitivity, anatomy, and physiology. Key impacts on fishes may include behavioral responses, hearing damage, barotrauma (pressure-related injuries), and mortality. Fish react to especially strong and/or intermittent low-frequency sounds, and behavioral responses such as flight or avoidance are the most likely effects. Short-duration, sharp sounds can cause overt or subtle changes in fish behavior and local distribution. The reaction of fish to noise depends on their physiological state, past exposures, motivation ( e.g., feeding, spawning, migration), and other environmental factors. Hastings and Popper (2005) identified several studies that suggest fish may relocate to avoid certain areas of sound energy. Additional studies have documented effects of pile driving on fishes ( e.g., Scholik and Yan, 2001, 2002; Popper and Hastings, 2009). Several studies have demonstrated that impulse sounds might affect the distribution and behavior of some fishes, potentially impacting foraging opportunities or increasing energetic costs ( e.g., Fewtrell and McCauley, 2012; Pearson et al., 1992; Skalski et al., 1992; Santulli et al., 1999; Paxton et al., 2017). However, some studies have shown no or slight reaction to impulse sounds ( e.g., Peña et al., 2013; Wardle et al., 2001; Jorgenson and Gyselman, 2009; Cott et al., 2012). More commonly, though, the impacts of noise on fishes are temporary. SPLs of sufficient strength have been known to cause injury to fishes and fish mortality (summarized in Popper et al., 2014). However, in most fish species, hair cells in the ear continuously regenerate, and loss of auditory function is likely restored when damaged cells are replaced with new cells. Halvorsen et al. (2012b) showed that a TTS of 4-6 dB was recoverable within 24 hours in one species. Impacts would be most severe when the individual fish is near the source, and the exposure duration is long. Injury caused by barotrauma can range from slight to severe and can cause death, and is most likely for fish with swim bladders. Barotrauma injuries have been documented during controlled exposure to impact pile driving (Halvorsen et al., 2012a; Casper et al., 2013, 2017). Fish populations in the proposed project area that serve as prey for marine mammals could be temporarily affected by noise from pile removal and installation. The frequency range in which fishes generally perceive underwater sounds is 50 to 2,000 Hz, with peak sensitivities below 800 Hz (Popper and Hastings, 2009). Fish behavior or distribution may change, especially in response to strong and/or intermittent sounds that could harm fish. High underwater SPLs have been documented to alter behavior, cause hearing loss, and injure or kill individual fish by causing serious internal injury (Hastings and Popper, 2005). Zooplankton is a food source for several marine mammal species, as well as a food source for fish that are then preyed upon by marine mammals. Population effects on zooplankton could indirectly affect marine mammals. Data are limited on the effects of underwater sound on zooplankton species, particularly sound from construction (Erbe et al., 2019). Popper and Hastings (2009) reviewed information on the effects of human-generated sound and concluded that no substantive data are available on whether sound levels from pile driving, seismic activity, or other human-made sources would have physiological effects on invertebrates. Any such effects would be limited to the area very near (1 to 5 m) the sound source and would result in no population effects because of the relatively small area affected at any one time and the reproductive strategy of most zooplankton species (short generation, high fecundity, and very high natural mortality). No adverse impact on zooplankton populations is expected from the specified activities, due in part to their large reproductive capacity and naturally high levels of predation and mortality. Any mortalities or impacts that might occur would be negligible. The greatest potential impact on marine mammal prey during construction would occur during impact pile driving. Vibratory pile removal/installation may elicit behavioral responses in fishes, such as temporary avoidance of the area, but is unlikely to cause injuries to fishes or have persistent effects on local fish populations. In-water construction activities would only occur during daylight hours, allowing fish to forage and transit the project area in the evening. Construction would also have minimal permanent and temporary impacts on benthic invertebrate species, a marine mammal prey source. Additionally, the proposed project areas are low-quality habitats, as both areas are already highly developed and experience high levels of anthropogenic noise from regular naval operations and other vessel traffic. Potential Effects on Foraging Habitat The proposed projects are not expected to result in any habitat-related effects that could cause significant or long-term negative consequences for individual marine mammals or their populations, since removal and installation of in-water piles would be temporary and intermittent. The areas affected by these projects are relatively small compared to the available habitat just outside the project areas, and neither project would affect any areas of particular importance. Any behavioral avoidance by fish of the disturbed areas would still leave significantly large areas of fish and marine mammal foraging habitat in the nearby vicinity. As described in the preceding, the potential for the Navy's construction at NBPL or NBSD to affect the availability of prey to marine mammals or to meaningfully impact the quality of physical or acoustic habitat is considered to be insignificant. Therefore, the impacts of the projects are not likely to adversely affect marine mammal foraging habitat in the proposed project areas. In summary, given the relatively small areas being affected, as well as the temporary and mostly transitory nature of the proposed construction activities, any adverse effects from the Navy's NBPL or NBSD activities on prey habitat or prey populations are expected to be minor and temporary. The most likely impact on fishes at the project sites would be temporary avoidance of the area. Any behavioral avoidance by fish of the disturbed areas would still leave significantly large areas of fish and marine mammal foraging habitat in the nearby vicinity. Thus, we preliminarily conclude that the impacts of the specified activities at both the NBPL and NBSD are not likely to have more than short-term adverse effects on any prey habitat or populations of prey species. Further, any impacts on marine mammal habitat are not expected to result in significant or long-term consequences for individual marine mammals or to contribute to adverse impacts on their populations. Estimated Take of Marine Mammals This section provides an estimate of the number of incidental takes proposed for authorization under both IHAs, which will inform NMFS' consideration of “small numbers,” the negligible impact determinations, and impacts on subsistence uses. Harassment is the only type of take expected to result from these activities. Except for certain activities not pertinent here, section 3(18) of the MMPA defines “harassment” as any act of pursuit, torment, or annoyance, which (i) has the potential to injure a marine mammal or marine mammal stock in the wild (Level A harassment); or (ii) has the potential to disturb a marine mammal or marine mammal stock in the wild by disrupting behavioral patterns, including, but not limited to, migration, breathing, nursing, breeding, feeding, or sheltering (Level B harassment). Authorized takes would predominantly be by Level B harassment for both the NBPL and NBSD Projects, as using acoustic sources ( i.e., vibratory and impact pile driving) can potentially disrupt behavioral patterns for individual marine mammals. There is also some potential for AUD INJ (Level A harassment) to result for six species of marine mammals incidental to the NBPL Project. As for the NBSD Project, due to the location within South-Central San Diego Bay in Chollas Creek, AUD INJ is not anticipated to occur for any of the three species for which harassment is proposed for authorization due to the low noise energy marine mammals may be exposed (resulting in very small distances to the Level A harassment threshold as described below). The proposed mitigation and monitoring measures for both projects are expected to minimize the amount and severity of the taking to the extent practicable. As previously described, no serious injury or mortality is anticipated or proposed to be authorized for either proposed activity. Below, we describe how the proposed take numbers are estimated. For acoustic impacts, generally speaking, we estimate take by considering (1) acoustic criteria above which NMFS believes the best available science indicates that there is some reasonable potential for marine mammals to be behaviorally harassed or incur some degree of AUD INJ; (2) the area or volume of water that would be ensonified above these levels in a day; (3) the density or occurrence of marine mammals within these ensonified areas; and, (4) the number of days of activities. While these factors can contribute to a basic calculation to provide an initial prediction of potential takes, additional information that can qualitatively inform take estimates is also sometimes available ( e.g., previous monitoring results or average group size). Below, we describe the factors considered here in more detail and present the proposed take estimates. Acoustic Criteria NMFS recommends the use of acoustic criteria that identify the received level of underwater sound above which exposed marine mammals would reasonably expect to be behaviorally harassed (equated to Level B harassment) or incur AUD INJ of some degree (equated to Level A harassment). Below, we describe the thresholds used by the Navy and NMFS for this analysis. Level B Harassment Though significantly driven by the received level, the onset of behavioral disturbance from anthropogenic noise exposure is also informed to varying degrees by other factors. These factors are related to the source or exposure context ( e.g., frequency, predictability, duty cycle, duration of the exposure, signal-to-noise ratio, distance to the source), the environment ( e.g., bathymetry, other noises in the area, predators in the area), and the receiving animals (hearing, motivation, experience, demography, life stage, depth) and can be difficult to predict ( e.g., Southall et al., 2007; Ellison et al., 2012). Based on available science and the practical need to use a threshold based on a predictable, measurable metric for most activities, NMFS typically uses a generalized acoustic threshold based on the received level to estimate the onset of behavioral harassment. NMFS generally predicts that marine mammals are likely to be behaviorally harassed in a manner considered to be Level B harassment when exposed to underwater anthropogenic noise above root-mean-squared sound pressure levels (RMS SPL) of 120 dB re 1 μPa for continuous ( e.g., vibratory pile driving, drilling) and above RMS SPL 160 dB re 1 μPa for non-explosive impulsive ( e.g., seismic airguns) or intermittent ( e.g., scientific sonar) sources. Level B harassment take estimates based on these behavioral harassment thresholds potentially include TTS, as, in most cases, TTS likely occurs at distances from the source less than those at which behavioral harassment may occur. TTS of sufficient degree can manifest as behavioral harassment and reduced hearing sensitivity, and the potential reduction in opportunities to detect important signals (conspecific communication, predators, prey) may result in behavior patterns that would not otherwise occur. The Navy's proposed activities for projects at NBPL and NBSD include continuous (vibratory pile driving) and impulsive (impact pile driving) sources. As previously discussed, the Navy has measured and reported background noise in San Diego Bay (NAVFAC SW, 2020) above 120 dB re 1 μPa. Therefore, the RMS SPL thresholds of 129.6 dB and 160 dB re 1 μPa are applicable to the NBPL Project, and the thresholds of 126 dB and 160 dB re 1 μPa are applicable to the NBSD Project. Level A Harassment NMFS' Updated Technical Guidance for Assessing the Effects of Anthropogenic Sound on Marine Mammal Hearing (Version 3.0) (NMFS, 2024) identifies dual criteria to assess AUD INJ (Level A harassment) to five different underwater marine mammal groups (based on hearing sensitivity) as a result of exposure to noise from two different types of sources (impulsive or non-impulsive). It includes updated thresholds and updated weighting functions for each hearing group, provided in table 4 below. The references, analysis, and methodology used to develop the criteria are described in NMFS' 2024 Updated Technical Guidance, available at: https://www.fisheries.noaa.gov/national/marine-mammal-protection/marine-mammal-acoustic-technical-guidance-other-acoustic-tools. Table 4—Thresholds Identifying the Onset of Auditory Injury Hearing group AUD INJ onset acoustic thresholds * (received level) Impulsive Non-impulsive Low-Frequency (LF) Cetaceans Cell 1: L pk,flat : 222 dB; L E, LF,24h : 183 dB Cell 2: L E, LF,24h : 197 dB. High-Frequency (HF) Cetaceans Cell 3: L pk,flat : 230 dB; L E, HF,24h : 193 dB Cell 4: L E, HF,24h : 201 dB. Very High-Frequency (VHF) Cetaceans Cell 5: L pk,flat : 202 dB; L E, VHF,24h : 159 dB Cell 6: L E, VHF,24h : 181 dB. Phocid Pinnipeds (PW) (Underwater) Cell 7: L pk,flat : 223 dB; L E, PW,24h : 183 dB Cell 8: L E, PW,24h : 195 dB. Otariid Pinnipeds (OW) (Underwater) Cell 9: L pk,flat : 230 dB; L E, OW,24h : 185 dB Cell 10: L E, OW,24h : 199 dB. * Dual metric criteria for impulsive sounds: Use whichever criterion results in the larger isopleth for calculating AUD INJ onset. If a non-impulsive sound has the potential of exceeding the peak sound pressure level criteria associated with impulsive sounds, the PK SPL criteria are recommended for consideration for non-impulsive sources. Note: Peak sound pressure level ( L p,0-pk ) has a reference value of 1 µPa, and weighted cumulative sound exposure level ( L E,p ) has a reference value of 1 µPa 2 s. In this table, criteria are abbreviated to better reflect International Organization for Standardization (ISO) standards (ISO, 2017). The subscript “flat” is being included to indicate that peak sound pressures are flat weighted or unweighted within the generalized hearing range of marine mammals underwater ( i.e., 7 Hz to 165 kHz). The subscript associated with cumulative sound exposure level criteria indicates the designated marine mammal auditory weighting function (LF, HF, and VHF cetaceans, and PW and OW pinnipeds) and that the recommended accumulation period is 24 hours. The weighted cumulative sound exposure level criteria could be exceeded in a multitude of ways ( i.e., varying exposure levels and durations, duty cycle). When possible, action proponents should indicate the conditions under which these criteria would be exceeded. Ensonified Area Here, we describe the operational and environmental parameters of the activity used to estimate the area ensonified above the acoustic thresholds, including source levels and the transmission loss coefficient. The sound field in the project areas is the existing background noise plus additional construction noise from the proposed project. Marine mammals are expected to be affected via sound generated by the primary components of the project ( i.e., vibratory pile removal, vibratory pile driving, and impact pile driving). The source levels assumed for both removal and installation activities are based on reviews of measurements of piles of the same or similar types and dimensions available in the scientific literature and from similar coastal construction projects. The source level for the piles and activities ( i.e., installation or removal) at both NBPL and NBSD is presented in table 5. Table 5—Proxy Sound Source Levels for Pile Sizes and Driving Methods Method Pile size/type Peak SPL (dB re 1µPa) 1 RMS SPL (dB re 1µPa) 1 SEL (dB re 1µPa) 1 Source NBPL DEPERMING PIER REPLACEMENT PROJECT Pile Removal Activities Vibratory Extraction 16-inch round timber 162 Naval Submarine Base New London Monitoring Report (NAVFAC Mid-Atlantic, 2022); NMFS interim proxy level (2024). Pile Installation Activities Vibratory Pile Driving 16-inch round plastic 162 Naval Submarine Base New London Monitoring Report (NAVFAC Mid-Atlantic, 2022); NMFS interim proxy level (2024). Impact Hammer 196 182 170 NBSD CHOLLAS CREEK QUAY WALL REPAIR PROJECT Pile Removal Activities Vibratory Extraction 14-inch steel H 150 California Department of Transportation (Caltrans, 2020); Chevron Long Wharf (Richmond, CA). 24-inch steel sheet 160 Caltrans (2020); Berth 23 (Port of Oakland). 18-inch square concrete 155 NAVFAC SW (2024); NBSD Pier 6 Pier Replacement. 2 18-inch octagonal concrete 155 NAVFAC SW (2024); NBSD Pier 6 Pier Replacement. 2 Pile Installation Activities Vibratory Pile Driving 13-inch round plastic 159 NAVFAC SW (2024); NBSD Pier 6 Pier Replacement. 3 18-inch octagonal concrete 155 NAVFAC SW (2024); NBSD Pier 6 Replacement. 2 27.5-inch steel sheet 160 Caltrans (2020); Berth 23 (Port of Oakland). Impact Hammer 18-inch octagonal concrete 185 170 160 NMFS Interim Proxy Level based on Caltrans (2020). 2 18-inch square concrete 185 170 160 NMFS Interim Proxy Level based on Caltrans (2020). 1 As measured, or calculated, at 10 m (33 ft). 2 20-inch square concrete piles used as a proxy; based on the maximum value between 56-61 m of 149.5 dB (rounded to 150 dB) @61 m, and back-calculated to the source (10 m). 3 12-inch round plastic piles used as a proxy; based on an RMS average of 159.4 dB and back-calculated to the source (10 m). Data show that the 12-inch plastic proxy source level is louder than the 20-inch concrete pile proxy source due to reverberation from the lighter plastic pile. Transmission loss (TL) is the decrease in acoustic intensity as an acoustic pressure wave propagates out from a source. TL parameters vary with frequency, temperature, sea conditions, current, source and receiver depth, water depth, water chemistry, bottom composition, and topography. The general formula for underwater TL is: TL = B * Log 10 (R 1 /R 2 ), where: TL = transmission loss in dB B = transmission loss coefficient; for practical spreading equals 15 R 1 = the distance of the modeled SPL from the driven pile, and R 2 = the distance from the driven pile of the initial measurement. This formula neglects loss due to scattering and absorption, which is assumed to be zero here. The degree to which underwater sound propagates away from a sound source depends on various factors, most notably the water bathymetry and the presence or absence of reflective or absorptive conditions, including in-water structures and sediments. Spherical spreading occurs in a perfectly unobstructed (free-field) environment not limited by depth or water surface, resulting in a 6 dB reduction in sound level for each doubling of distance from the source (20*log[range]). Cylindrical spreading occurs in an environment in which sound propagation is bounded by the water surface and sea bottom, resulting in a reduction of 3 dB in sound level for each doubling of distance from the source (10*log[range]). A practical spreading value of 15 is often used in shallow-water coastal conditions, such as those found in the NBPL and NBSD projects. In these environments, sound waves repeatedly reflect off the surface and bottom, reflecting an expected propagation environment between spherical and cylindrical spreading-loss conditions. Therefore, the default coefficient of 15 is used to calculate distances to the Level A harassment and Level B harassment thresholds. Assuming practicable spreading and other assumptions regarding the source characteristics and operational logistics ( e.g., source level, number of strikes per pile, number of piles per day), the Navy calculated distances to the Level A harassment and Level B harassment thresholds and associated ensonified areas. Because an ensonified area associated with Level A harassment is more technically challenging to predict given the accounting for a cumulative energy component that changes over time, to assist applicants in assessing the potential for Level A harassment without the need for complex modeling, NMFS developed an optional User Spreadsheet tool to accompany the 2024 Updated Technical Guidance (see https://www.fisheries.noaa.gov/national/marine-mammal-protection/marine-mammal-acoustic-technical-guidance-other-acoustic-tools ). This relatively simple tool can be used to calculate a Level A harassment isopleth distance for use in conjunction with marine mammal density or occurrence data to predict the amount of take that may occur incidental to an activity. We note that, because of some of the assumptions in the methods underlying this spreadsheet tool, we anticipate that the resulting isopleths would typically be overestimates, which may lead to an overestimate of potential exposures from Level A harassment. However, this optional tool offers a practical alternative for estimating isopleth distances when more sophisticated modeling methods are unavailable or are impractical. For stationary sources such as impact or vibratory pile driving and removal, the optional User Spreadsheet tool predicts the distance at which, if a marine mammal remained at that distance for the duration of the activity within 24 hours, it would be expected to incur AUD INJ. Inputs used in the optional User Spreadsheet tool are contained within table 6. Table 6—User Spreadsheet Input Parameters Used for Calculating Level A Harassment Isopleths Equipment type Vibratory pile removal 16″ round timber 1 13″ round plastic 2 3 18″ square concrete 2 18″ octagonal concrete 2 14″ steel H 2 24″ steel sheet 2 4 Vibratory pile installation 16″ round plastic 1 13″ round plastic 2 5 18″ octagonal concrete (small float) 2 5 27.5″ steel sheet 2 Impact pile installation 16″ round plastic 1 18″ square concrete 2 5 18″ octagonal concrete 2 5 Spreadsheet Tab Used A.1) Vibratory pile driving. A.1) Vibratory pile driving. E.1) Impact pile driving. Source Level (dB re: 1 µPa 162 RMS Dead pull 155 RMS 155 RMS 150 RMS 160 RMS 162 RMS 159 RMS 155 RMS 160 RMS 196 Peak 182 RMS 170 SEL 185 Peak 170 RMS 160 SEL 185 Peak 170 RMS 160 SEL. Weighting Factor Adjustment (kH) 2.5 2.5 2 Activity Duration within 24 Hours 5 min/pile * 4 piles = 20 min 20 min/ pile * 5 piles = 100 min 20 min/ pile * 2 piles = 40 min 20 min/ pile * 12 piles = 240 min 20 min/ pile * 10 piles = 200 min 5 min/ pile * 4 piles = 20 min 1 min/ pile * 5 piles = 5 min 20 min/ pile * 4 piles = 80 min 20 min/ pile * 10 piles = 200 min Strikes per Second 0.01 0.01 Number of strikes per pile 600 600 Number of piles per day 4 7 5 2 12 10 3 5 4 10 3 6 4 Propagation (xLogR) 15 15 15 Distance of SPL Measurement 10 10 10 Acoustic threshold (dB RMS) 129.6 dB 126 dB 129.6 dB 126 dB 160 dB. 1 NBPL Deperming Pier Replacement Project. See table 6-4 in the application. 2 NBSD Chollas Creek Quay Wall Repair Project. See table 1-4 in the application. 3 These piles are anticipated to be dead pulled. 4 These piles are anticipated to be either vibratory extracted, dead pulled, or clipped at the mud-line and removed. For this IHA, we are assuming vibratory extraction for the demolition of all existing sheet piles. 5 Vibratory and/or impact pile driving are the most likely methods that would be used to install piles. High-pressure water jetting may be used either separately from or in conjunction with impact pile installation. Using the practical spreading model and source assumptions identified in table 6, the Navy calculated, and NMFS has carried forward into this analysis, the distances to the Level A harassment and Level B harassment thresholds for marine mammals for both the NBPL and the NBSD projects (table 7). Table 7—Calculated Distances to the Level A Harassment and Level B Harassment Thresholds by Marine Mammal Hearing Group and Activity Site, activity, pile size/type Level A harassment zone (m) All marine mammals Level B harassment zone (m) LFC Gray whales HFC bottlenose, common dolphins OW CSL PW Harbor seals NBPL DEPERMING PIER Pile Removal Activities Vibratory Extraction 16″ round timber 5.2 2.0 2.2 6.7 1,445 Pile Installation Activities Vibratory Hammer 16″ round plastic 5.2 2.0 6.7 2.2 1,455 Impact Hammer 16″ round plastic 242.5 30.9 80.3 215.4 293 NBSD CHOLLAS CREEK 1 Pile Removal Activities Vibratory Extraction 14″ steel H 1.6 1.9 5.5 398 Vibratory Extraction 18″ octagonal concrete 1.1 1.2 3.6 858 Vibratory Extraction 18″ square concrete 2.0 2.2 6.6 858 Vibratory Extraction 24-steel sheet 6.8 7.6 22.7 1,848 Pile Installation Activities Vibratory Driving 13″ round plastic 0.5 0.6 1.8 1,685 Vibratory Driving 18″ octagonal concrete (small float) 1.1 1.2 3.6 858 Vibratory Driving 27.5″ steel sheet 6.8 7.6 22.7 1,848 Impact Driving 18″ octagonal concrete 6.7 17.3 46.4 46 Impact Driving 18″ square concrete 8.7 22.7 60.8 46 Abbreviations: LCF = Low-Frequency Cetacean; HFC = High-Frequency Cetacean; OW = Otariid; PW = Phocid; CSL = California sea lions. Marine Mammal Occurrence In this section, we provide information on the anticipated occurrence of marine mammals present in the project areas during the proposed NBPL and NBSD Projects. This occurrence information then informs the take calculations in the following section (see Take Estimation and table 9). For all species, the best available scientific information was considered to estimate occurrence. First, the Navy considered density data contained within the U.S. Navy Marine Species Density Database for the Hawaii-Southern California Training and Testing Study Area technical report (U.S. Navy, 2024), which includes San Diego Bay. However, the Navy determined that a density-based approach would overestimate take as evidenced in previous monitoring reports (NAVFAC SW 2016, 2017a, 2017b, 2018a, 2018b). To more accurately inform take estimates, the Navy reviewed IHA applications and monitoring reports for previous projects at both NBPL and NBSD to develop more site-specific occurrence estimates for each species. Except for California sea lions, the average number of observations of marine mammals during the NBPL Fuel Pier Replacement Project monitoring periods, years 2-5 (2015-2018), was used by the Navy to estimate the expected average number of individuals observed daily for the current NBPL Project (NAVFAC SW 2016, 2017a, 2017b, 2018a, 2018b). The Navy also used observations presented in the final monitoring report for the NBSD Pier 6 Replacement Project (NAVFAC SW, 2024) to estimate the expected average number of individuals observed daily for the current NBSD Project. Except for California sea lions, the average daily occurrence per species over the NBPL Fuel Pier's 4 years was deemed to provide a reasonably representative daily occurrence estimate. As for California sea lions, due to the close proximity of the NBPL Project to the Everingham Brothers' Bait Barge, which sea lions regularly use as a haul-out location, the Navy used the highest number of individuals observed per day (from the NBPL Fuel Pier monitoring period year 2, 2015) to estimate the expected number of individuals observed per day for the current NBPL Project ( i.e., 25.09 sea lions expected to be observed daily). Table 8—Estimated Occurrence of Marine Mammal Species Species/location Relative occurrence in north and south-central San Diego Bay Expected number of individuals observed/day Naval Base Point Loma California sea lion Abundant 25.09 Harbor seal Relatively Uncommon 0.56 Bottlenose dolphin Sporadic 1.29 Short-beaked common dolphin Occasional 0.10 Long-beaked common dolphin Occasional gray whale Rare/Seasonal 0.02 Naval Base San Diego California sea lion Abundant 1.38 Harbor seal Relatively Uncommon 0.01 Bottlenose dolphin Sporadic 0.5 Take Estimation In this section, we describe how the project scope, ensonified area, and species occurrence information provided above are used to produce a quantitative estimate of the take that could occur and is proposed for authorization. We first describe the take estimation process for the NBPL Project, then for the NBSD Project. NBPL Deperming Pier Replacement Project To calculate the estimated take that may occur incidental to the NBPL Project, the Navy used the following methods, and we have carried them forward in this analysis. In summary, the Navy calculated estimated exposures at each pier for each activity using the following equation: # of individuals/day × days per pier and activity × ensonified area The number of individuals per day used in the calculations is found in table 8. The number of days used in the calculations is as follows: Vibratory pile extraction: Deperming Pier 47 days, ERG Pier 37 days, and Pier 5002 2 days; Vibratory pile driving: Deperming Pier 50 days, ERG Pier 33 days, and Pier 5002 2 days; and Impact pile driving: Deperming Pier 50 days, ERG Pier 33 days, and Pier 5002 2 days. The Navy then summed the exposure estimates across the three piers to obtain a total exposure estimate for each species. Please see section 6.9 and Appendix B of the NBPL IHA application for a detailed description of exposure estimates and take calculations, and tables of all of the calculations for each species, at each pier, and for each pile method (vibratory pile extraction, vibratory pile driving, and impact pile driving). Because take by both behavioral harassment and AUD INJ could occur incidentally to impact pile driving, the Navy allocated the total exposures for this activity by Level A harassment and Level B harassment at each of the three piers. To do so, the Navy identified the Level A harassment area percentage relative to the Level B harassment area at each pier for impact pile driving using the following equation: Level A harassment ensonified area (km 2 )/Level B harassment ensonified area (km 2 ) = Level A harassment ensonified area percentage Using impact pile driving for California sea lions at the Deperming Pier as an example, the Level A harassment ensonified area (0.025390 km 2 ) divided by the Level B harassment ensonified area (0.201349 km 2 ) equals 10.61 percent. The Navy then multiplied each species' total impact pile driving exposure estimates at each pier by the Level A harassment ensonified area percentage: Impact pile driving exposure estimate at each pier × Level A harassment ensonified area percentage = Level A take at each pier Again, using impact pile driving on California sea lions at the Deperming Pier as an example, the exposure estimate for the species (1,254.50 individuals) multiplied by the Level A harassment ensonified area percentage (10.61 percent) equals 158.19 Level A takes. The Navy then summed the results from all three piers to obtain the total requested amount of Level A harassment take. Using the example above, 159.18 + 106.46 + 5.04 equals 270 California sea lion Level A harassment takes. To calculate Level B harassment for each species at each pier, the Navy conducted a similar process, accounting for the ensonified area already considered in the Level A harassment calculations. The Navy used the following formula to estimate the Level B harassment ensonified area percentage: Level B harassment ensonified area (km 2 )−Level A harassment ensonified area (km 2 )/Level B harassment ensonified area (km 2 ) = Level B harassment ensonified area percentage Again, using impact pile driving on California sea lions at the Deperming Pier as an example, the Level B harassment ensonified area (0.201349 km 2 ) minus the Level A harassment ensonified area (0.025390 km 2 ) divided by the Level B harassment ensonified area (0.201349 km 2 ) equals 87.39 percent. The Navy then multiplied the total species' impact pile driving exposure estimates by the Level B harassment ensonified area percentage for each species at each pier to obtain the requested amount of takes by Level B harassment using the following formula: Exposure estimate per pier × Level B harassment ensonified area percentage = Level B take per pier Again, using impact pile driving on California sea lions at the Deperming Pier as an example, the exposure estimate for the species (1,254.50) multiplied by the Level B harassment ensonified area (87.39 percent) equals 1,096 takes of Level B harassment. The Navy then summed the takes by Level B harassment per species at each of the three piers. (see table 9). Of note, for the NBPL Project, the Navy combined sighting information/species occurrence for the short- and long-beaked common dolphins, as both species are difficult to differentiate in the wild. For the take estimates, we have authorized a single amount of take for both species combined. We also note a minor discrepancy in the calculations for the combined short- and long-beaked common dolphins, specifically for impact pile driving at the ERG Pier. We calculated 0.08 Level A harassment exposures for the species, whereas the application shows 1.00 Level A harassment exposure; and we calculated 3.22 Level B harassment exposures, whereas the application shows 2.30 Level B harassment exposures. This error, when carried through and using standard rounding at the end ( i.e., where a number of five or greater is rounded up), resulted in the Navy calculating 2 takes by Level A harassment and 18 takes by Level B harassment for the combined short- and long-beaked common dolphins, whereas we calculated 0 takes by Level A harassment and 18 takes by Level B harassment for the combined species. NMFS confirmed with the Navy that our calculations are correct (K. LeRoy, pers. comm., January 16, 2026); therefore, they are applied in this proposed IHA. See table 9 below for the estimated takes by Level A harassment and Level B harassment proposed to be authorized for the NBPL Project. NBSD Chollas Creek Quay Wall Repair Project To calculate the estimated takes by Level B harassment that may occur incidental to the NBSD Project, the Navy used the following formula, and we have carried forward this analysis: N × D = Estimated takes by Level B Exposure Where: N = the average number of individuals observed/day, and D = the total days of pile extraction/installation (190 days). See table 9 for the number of takes by Level B harassment proposed to be authorized. As described above, the Navy did not request, and NMFS does not propose, to authorize take by Level A harassment for any of the three species that may occur in the NBSD Chollas Creek area—California sea lions, bottlenose dolphins, and harbor seals. Based on the best available science, NMFS generally finds the Navy's estimates of the types and amounts of take for each species and each project to be a reasonable representation of the amount of take that could occur from the project. NMFS has identified the minor discrepancy in the NBPL Project take estimation section for short- and long-beaked common dolphins discussed above and has carried forward our calculations. Table 9 below summarizes the number of takes by Level A harassment and/or Level B harassment, and the total proposed take per stock as a percentage of stock abundance for both projects. Table 9—Proposed Authorized Take by Level A Harassment and Level B Harassment and as a Percentage of Stock Abundance for the NBPL Project and NBSD Project Common name Stock Stock abundance 1 Avg. number of indiv./day NBPL NBSD NBPL IHA proposed take Level A Level B Total proposed take Percent of stock NBSD IHA proposed take Level A Level B Total proposed take Percent of stock CA sea lion CA breeding stock 257,606 25.09 1.38 270 4,291 4,561 1 1.77 0 262 262 0.10 Bottlenose dolphin CA coastal stock 453 1.29 0.5 3 221 224 1 2 49.39 0 95 95 20.97 Harbor seal CA stock 30,968 0.56 0.01 30 96 106 1 0.41 0 2 2 0.00 Short-beaked common dolphin CA/OR/WA stock 1,056,308 0.10 0 18 18 0.00 Long-beaked common dolphin CA stock 83,379 Gray whale Eastern N Pacific 25,960 0.02 0 4 4 0.02 1 The values presented here are based on if all takes were to a different individual. This is not likely the case, however, for California sea lions, harbor seals, and bottlenose dolphins due to their presumed persistence at a location ( i.e., repeated takes of the same individual may occur across multiple days). 2 The percentage of the stock for the California coastal stock of bottlenose dolphins presented here is a simplistic calculation that considers each take is of a unique individual, which is not likely the case. Please see the Small Numbers section for more rationale. Proposed Mitigation To issue an IHA under section 101(a)(5)(D) of the MMPA, NMFS must set forth the pe [Text truncated at 120,000 characters. The full text is on the page linked above.] --- Source: Frix Law Library, https://www.frixlaw.com/law-library/documents/fr%3A2026-02173. Public record. Not legal advice.