Rough-toothed dolphins (Steno bredanensis) are reported to form isolated communities with stable groups around some oceanic islands. Within these communities, this species exhibits cooperative foraging and care-giving behavior including the sharing of large prey. These group behaviors could be driving community level structure where there are clear differences in habitat use between island groups, and limited movement among islands. Similar social characteristics are found in other cetacean species, e.g. killer whales, where individuals remain in maternally related groups indefinitely, forming “extended matrilines” as reflected by a single mitochondrial (mt) DNA haplotype. Here we test the hypothesis that rough-toothed dolphins also form “extended matrilines” using mtDNA control region haplotypes as a marker for maternal lineages. Alternatively, we test the influence of maternal fidelity on group structure within communities. The sample collection comprises adults from Pacific Ocean Islands and the continental Atlantic USA spanning 1976-2010. We sequenced mtDNA from 4 deceased groups (3 mass strandings and 1 bycatch; 350bp; n=28 teeth samples) and 14 living groups (460bp; n=106 skin samples) identifying 22 haplotypes. Differentiation and haplotype diversity were evaluated for groups within island communities in the Hawaiian Islands (Kauai and Hawaii) and Society Islands (Moorea and Raiatea) as well as between islands communities. Our results revealed multiple matrilines in 16 of the 18 groups, allowing us to reject the hypothesis of strict matrilineal structure. Although an AMOVA detected significant differentiation between island communities, groups did not significantly partition any genetic diversity within island communities. This is consistent with permutation tests where no strong signal of matrilineal influence was identified within island communities. Our study provides evidence of genetic structure at the community level, but demonstrates negligible structure at the group level. Fine-scale analyses to evaluate kinship and temporal association patterns are underway to further our understanding of group structure for this species.

This report documents the findings of a pilot study conducted in 2013 to investigate the efficacy of ground-based surveys as a potential alternative to, or in supplementation of, aerial surveys in detecting strandings of marine mammals and sea turtles (MM/ST) on remote shorelines, in this case the island of Ni‘ihau. In this study, aerial (helicopter) and ground-based (vehicle and horseback) shoreline surveys were conducted concurrently in order to compare the efficacy of each method. Observers scanned the shorelines of Kauai and Ni‘ihau, adjacent to PMRF, for stranded and near-stranded marine mammals and sea turtles within one week after an SCC training event that involved mid-frequency active sonar in August 2013.

HDR, Inc. provided comprehensive monitoring services for an in-water pile driving construction project at Naval Base Kitsap Bangor, Washington. Using highly trained marine species observers, field technicians, and acousticians, we ensured client compliance in the face of complex regulatory requirements.

Navy Marine Species Observers (MSOs) monitored UNDET training exercises at the Pu‘uloa Underwater Range, located west of the Pearl Harbor entrance channel, on 2 and 4 April 2013. The intent of the exercises was to provide training in precision cutting for harbor clearance or salvage. The primary purpose of the MSO presence was to monitor mitigation measures conducted by Mobile Diving and Salvage Unit 1 (MDSU-1); however, visual surveys were also conducted opportunistically.

Preliminary Results from a Deep‐water Ecological Acoustic Recorder (EAR) Deployed off NW Ni‘i hau during RIMPAC‐2010

Two ecological acoustic recorders (EARs) were deployed on July 17, 2010, one at a depth of 800 meters (m) off the northwest coast (21° 59.613' N, 160° 12.167' W), and the other at a depth of 16 m off the southeast coast of Ni'ihau (21° 47.306' N, 160° 11.964' W). These two sites were selected by personnel from the Naval Facilities Engineering Command, Pacific to provide acoustic data during the 2010 Rim of the Pacific (RIMPAC) exercise in the Hawaii Range Complex.

Ecological acoustic recorders (EARs) have been deployed around the islands of Oahu and Kauai in a project sponsored by the Office of Naval Research. Detailed information on the EAR was published by Lammers et al. (2008). EARs have been deployed from February, 2009 to the present time around Oahu and from February, 2009 until April, 2011 around Kauai. From April, 2011 four EARs in the waters of Kauai have been deployed along the southern coast.

Ecological acoustic recorders (EARs) have been deployed at several locations in Hawaii and in other western Pacific locations to study the foraging behavior of deep-diving odontocetes. EARs have been deployed at depths greater than 400 m at five locations around the island of Kauai, one at Ni’ihau, two around the island of Okinawa, and four in the Marianas (two close to island of Guam, one close to the island of Saipan and another close to the island of Tinian).

In May 2011, a rare occurrence took place off the Southern California coast. For the first time since U.S. Navy-funded aerial surveys began in the area in 2008, a group of 20 sperm whales, including four calves, was seen—approximately 24 nautical miles west of San Diego.

Baseline undisturbed behavior and social patterns of blue (Balaenoptera musculus) and fin whales (B. physalus) are not well described and are needed to identify and understand potential effects of anthropogenic activities. Behavioral data for blue and fin whales were collected during line-transect and focal-follow effort. Initially observed behavior state, heading, and minimum and maximum interindividual dispersal distance were recorded during line-transect sampling. Focal groups were circled for 10-60+ minutes and videotaped from outside Snell’s sound cone to avoid disturbance. During 24,736 km of survey effort, 51 fin whale sightings (85 individuals) and 49 blue whalesightings (81 individuals) were seen. Over 7 hours of video was collected for16 blue and 15 fin focal follows. During the summer seasons, blues (n=48) were seen more commonly than fins (n=35); in fall, fins (n=16) were seen significantly more frequently than blues (n=1). Mean group size was 1.7 whales for both species. Initially observed blue behavior was usually travel (85%) or mill (11%). Observed fin whale behavior was also mostly travel (90%), mill (4%), or surface-active travel (4%). Both species were seen socializing in fall but not summer; foraging was observed in summer through fall. Mean initial dispersal for blues and fins was 9.1 and 14.2 body lengths, respectively. In summer, blues were most frequently (26%) seen headed S; in fall (n=2), they were headed only inshore (E). In summer, fin whales were most commonly headed SSW (26%) or WNW (26%); in fall, they were headed mostly NE (38%) or WSW (38%). Dive/respiration/behavioral event rates were also collected. Both species may directly compete for food based on observations of inter-specific maneuvering for a bait ball. Data represent the most extensive record of systematic undisturbed behavior on these species in SOCAL and include social interactions not previously documented in this region.

Baseline undisturbed behavior and social patterns of blue (Balaenoptera musculus) and fin whales (B. physalus) are not well described and are needed to identify and understand potential effects of anthropogenic activities in the SCB. In 2008-2012, 72,467 km of aerial line transect and focal-follow effort was conducted in the SCB. Initially observed location, group size, behavior state, heading, and minimum and maximum inter-individual dispersal distance were recorded. Focal groups were circled for 10-60+ minutes and videotaped from outside the plane’s sound cone to avoid disturbance. A total of 122 fin whale sightings (208 individuals) and 65 blue whale sightings (104 individuals) were made. Behavior, occurrence and distribution were related to season, location, bathymetry, and time of day. Blue whales were seen only from summer-fall and concentrated primarily close to shore (

Baseline undisturbed behavior/social patterns of blue/fin whales are not well described and are needed to identify and understand potential effects of anthropogenic activities. Behavioral data were collected during aerial effort. Initially observed behavior state, heading, minimum/maximum inter-individual dispersal distance were recorded during line-transect sampling. During the summer seasons, blues were seen more than fins; in fall, fins were seen more. Initially observed blue behavior was usually travel or mill. Observed fin behavior was mostly travel, mill, or surface-active travel. Both species were seen socializing in fall but not summer; foraging was observed in summer through fall. In summer, blues were seen headed S; in fall, headed inshore. In summer, fins were headed SSW or WNW; in fall, they were headed NE or WSW. Data represent the most extensive record of systematic undisturbed behavior on these species in SOCAL and include social interactions not previously documented in this region.

Baseline undisturbed behavior and social patterns of blue (Ba/aenoptera musculus) and fin whales (8. physa/us) are not well described and are needed to identify and understand potential effects of anthropogenic activities. Behavioral data for blue and fin whales were collected during aerial survey line-transect and focal-follow effort. Initially-observed behavior state, group size, heading, and minimum and maximum inter-individual dispersal distance were recorded during line-transect sampling and / or subsequent verification circling by the aircraft. Focal groups were circled for 3- 60+ minutes and videotaped from outside Snell's sound cone to avoid disturbance. During 24,736 km of survey effort, 51 fin whale sightings (86 individuals) and 49 blue whale sightings (84 individuals) were seen . Over 7 hours of video was collected for 16 blue and 15 fin focal follows. During the summer, blues (n=48) were seen more commonly than fins (n=35); in fall, fins (n=16) were seen much more frequently than blues (n= 1 ). Mean group size was 1. 7 whales for both species. Initially observed blue behavior was usually travel (85%) or mill (11%). Observed fin whale behavior was also mostly travel (87%), mill (6%), or surface-active travel (3%). Both species were seen socializing (e.g., touching) in fall but not summer; foraging was observed in summer through fall. Mean initial dispersal for blues and fins was 8 and 16 body lengths, respectively. In summer, blues were most frequently (26%) seen headed S; in fall (n=2), they were headed only inshore (E). In summer, fin whales were most commonly headed SSW (26%) or WNW (26%); in fall, they were headed mostly NE (38%) or WSW (38%). Both species directly compete for food based on observations of inter-specific maneuvering for a bait ball. Data represent the most extensive record of systematic undisturbed behavior on these species in SOCAL and include social interactions not previously documented in this region. Dive / respiration / behavioral event rates were also collected and are currently being analyzed. Bacon, C., M.A. Smultea, B. Wursig, K. Lomac-MacNair, and J. Black.

Fifteen aerial surveys (72,647 km) occurred during 2008-2012 to monitor occurrence, abundance, and behavior of marine mammals in the Southern California Bight (SCB) on behalf of the U.S. Navy. Thirty-six (2%) of 2,151 total sightings of at least 11 species were mixed-species associations (i.e., at least two different species swimming together/interacting). Little is known about these associations. Risso’s dolphins were most frequently associated with another marine mammal species (19 [7%] of 238 total Risso’s sightings) as follows: with sperm whales (1x), California sea lions (CaSL) (3x), and bottlenose (7x), northern right whale (NRWD) (4x), long-beaked common (1x), unidentified (1x), and common dolphin sp. (2x). Up to 3 species occurred together on 3 different occasions: (1) sperm whales/Risso’s/NRW dolphins, (2) Risso’s/unidentified dolphins/CaSL, and (3) Pacific white-sided/common dolphins with CaSL. The most unusual mixed species sighting was 24 sperm whales (including 4 calves) with 11 Risso’s and ~50 NRW dolphins: Risso’s repeatedly charged adult sperm whales’ heads who responded by dropping their lower jaw, perhaps related to kleptoparasitism. Potential reasons for mixed-species associations include increased protection from predators via dilution, increased prey detection/consumption, and “play” (i.e., fin whale calf touching NRWD). Data include interactions not previously documented in the SCB among these socially complex animal groups.

Effects of mixed-species associations (MSA [at least two different species swimming together and / or inte racting]) on cetacean behavior rarely have been quantified, but are important for identifying and differentiating potential anthropogenic impacts . Baseline marine mammal behavior was assessed during 83 ,005 km of U.S. Navy supported aerial line-transect surveys in the Southern California Bight during 2008-2013.

Effects of mixed-species associations (MSA [at least two differentspecies swimming together and/or interacting]) on cetacean behavior rarely have been quantified, but are important for identifying and differentiating potential anthropogenic impacts. Baseline marine mammal behavior was assessed during 77,390 km of U.S. Navy supported aerial line-transect surveys in the Southern California Bight during 2008-2013. Multinomial logistic regression was used to assess effects of MSA on group size, maximum nearest neighbor distance (a “cohesion” index, in body lengths), behavior state, and heading. Two percent (43) of 2,330 sightings were MSA involving 13 species (5 baleen whales, 7 toothed whales, 1 pinniped). Behavior and group size of some species differed significantly in MSA vs. non-MSA. MSA were predominated by Risso’s dolphins (44%; 19 of 43 MSA). Risso’s dolphins were most frequently associated with bottlenose dolphins (37% of 19 Risso’s MSA groups) followed by northern right whale dolphins (NRWD; 3% of 19). Risso’s dolphins tended to change headings more often in MSA (p

This study investigates mixed-species associations among marine mammals in the Southern California Bight, focusing specifically on Risso's dolphins (Grampus griseus). Over a six-year period, aerial surveys were conducted to record the frequency and nature of these associations, revealing that Risso's dolphins were the most commonly observed species in mixed interactions. The results indicate a significant decline in the proportion of Risso's dolphins involved in such associations compared to historical records, possibly due to an increase in their relative abundance. The findings underline the importance of monitoring mixed-species associations to understand marine mammal dynamics and ecological interactions.

Volume contents Endang Species Res 57:325-340 (2025) DOI: https://doi.org/10.3354/esr01423 copied Accounting for sampling bias reveals a decline in abundance of endangered false killer whales in the main Hawaiian Islands Janelle J. Badger Robin W. Baird Devin S. Johnson Amanda L. Bradford Sabre D. Mahaffy Michaela A. Kratofil Tori Cullins Jens J. Currie Stephanie H. Stack Erin M. Oleson ABSTRACT: We estimated abundance of the endangered main Hawaiian Islands (MHI) insular population of false killer whales Pseudorca crassidens from 1999-2022 using a modeling technique that incorporates animal availability in a capture-recapture analysis. The population was sampled using different sampling methods, resulting in yearly encounter histories of 265 individuals and 53 satellite-tagged whales. Survey effort and animal location data were separately analyzed using kernel density estimators, and the degree of overlap between these 2 processes was used to model detection probability in a Bayesian Jolly-Seber population model. This approach better addresses spatiotemporally variable sampling effort than traditional capture-recapture methods, improving the estimation of reliable abundance trends. Using simulated data, the model was robust to many sampling and ecological complications, such as variable low detectability, unequal tag deployment lengths, and variable social group sizes. Fitting the model to the MHI false killer whale data set, we found that the insular population of false killer whales remains small, with an estimated 139 individuals (95% credible interval, CRI = [114, 162]) in 2022. The population appears to be in decline throughout the study period, with a mean annual percent change of -1.09 (95% CRI = [-2.11, -0.023]) over the entire time series and -3.51 (95% CRI = [-5.08, -1.88]) since 2013, when the population was listed as endangered. Given the magnitude of the decline, identifying which of the many factors affecting this population is most responsible is key in order to guide potential management responses.

In August 2017, a marine mammal monitoring project was carried out combining boat-based field efforts and passive acoustic monitoring on and around the Pacific Missile Range Facility (PMRF). Commander, Pacific Fleet (PACFLT) funded five days of small-boat effort and the National Marine Fisheries Service funded an additional six days of effort. Information obtained was compared to previous sightings during small-boat effort by Cascadia Research Collective (CRC) off Kauai and Niihau, during 1,119 hr of effort (19,194 km) over nine different years from 2003 through 2016 (see Baird 2016)

As part of the long-term United States (U.S.) Navy-funded Marine Species Monitoring Program, from 16–24 August 2022, Cascadia Research Collective (CRC) carried out a vessel-based field effort in conjunction with passive acoustic monitoring undertaken by U.S. Navy (Navy) scientists on and around the underwater hydrophone ranges of the Pacific Missile Range Facility (PMRF).

As part of the long-term United States (U.S.) Navy-funded Marine Species Monitoring Program, from 5-13 August 2023, Cascadia Research Collective (CRC) carried out a vessel-based field effort in conjunction with passive acoustic monitoring undertaken by U.S. Navy (Navy) scientists on and around the underwater hydrophone ranges of the Pacific Missile Range Facility (PMRF).

As part of the long-term United States (U.S.) Navy-funded Marine Species Monitoring Program, from 1-14 August 2021, a combination of boat-based field effort and passive acoustic monitoring was carried out on and around the underwater hydrophone ranges of the Pacific Missile Range Facility (PMRF).

A number of species of resident and non-resident odontocetes use the waters of the Kaulakahi Channel between Kaua‘i and Ni‘ihau, overlapping with the Pacific Missile Range Facility (PMRF). Submarine Command Courses (SCCs) held at PMRF provide an opportunity to assess exposure and measure odontocete reactions to mid-frequency active sonar (MFAS) being used in realistic training scenarios. The primary goal of this assessment was to estimate MFAS received levels (RLs) for satellite tagged odontocetes and determine whether any large-scale movements occurred in response to hull-mounted surface ship MFAS exposure. Two prior reports have used odontocete satellite tag data and information on MFAS use to estimate RLs for animals tagged in 2011 through 2015.

The U.S. Navy’s marine species monitoring program addresses four general topics surrounding the impact of midfrequency active sonar (MFAS) on protected species: occurrence, exposure, response, and consequences. Occurrence of odontocete cetaceans on and around the Pacific Missile Range Facility (PMRF) has been studied for several years using a combination of satellite tags and photo-identification, demonstrating the existence of resident populations of several species of odontocetes and resulting in considerable information on diving behavior and movement patterns of these species.

The Pacific Missile Range Facility (PMRF) off the island of Kaua‘i is the site of regular United States (U.S.) Navy training, some of which involves mid-frequency active sonar (MFAS) use from different types of military sound sources. PMRF includes acoustic instrumentation which allows for passive acoustic monitoring (PAM) capabilities to detect and localize sounds such as vocalizing marine mammals. Recent boat-based studies at PMRF have utilized real-time PAM (in conjunction with the Marine Mammal Monitoring on Navy Ranges project) to detect odontocetes for vectoring a field tagging boat to groups in order to increase the likelihood of deploying satellite tags. The resulting data have allowed for an assessment of habitat use and range of several different species. Some of these boat-based tagging efforts were timed to occur just before Submarine Commanders Courses (SCCs) occurring on PMRF so that animal movements and diving behavior could be measured both before and during sonar use.

As part of the long-term United States (U.S.) Navy-funded Marine Species Monitoring Program, from 11–19 February 2024, Cascadia Research Collective (CRC) carried out a vessel-based field effort in conjunction with passive acoustic monitoring undertaken by the U.S. Navy (Navy) scientists on and around the underwater hydrophone ranges of the Pacific Missile Range Facility (PMRF). The effort was timed to occur immediately prior to the start of a Submarine Command Course (SCC) to allow for collection of movement and dive data that could be used to examine exposure and response of cetaceans to Navy mid-frequency active sonar (MFAS; see Henderson et al. 2021). Eight days of field effort were funded by the Navy, and one day of field work was funded by National Oceanic and Atmospheric Administration (NOAA) Fisheries. Wildlife Computers SPLASH10-F satellite tags were funded by the Navy for deployment on Navypriority species, and additional tags were provided by Wildlife Computers or CRC for deployment on other species (e.g., humpback whales [Megaptera novaeangliae]). Tags were programmed to collect dive behavior and Fastloc®-Global Positioning System (GPS) data from the time deployed until three and a half days after the end of the SCC and continue to transmit the dive and Fastloc®-GPS data for an additional six days. Starting on either May 2nd or May 3rd, the tags were duty cycled to transmit only every second day, to provide longer-term tracks of individual movements. During the period that tags were collecting dive and Fastloc®-GPS data, tags were programmed to try to obtain Fastloc®-GPS locations only for the 12 hours of the day when there were no or limited satellite overpasses. This programming change from previous Kauaʻi field efforts was taken to minimize temporal gaps in location data during the period that overlapped with and immediately followed the SCC. Field efforts were undertaken out of Kikiaola small boat harbor when conditions allowed for working on or near PMRF, or out of Port Allen when conditions on or near PMRF were not workable.

Movements and Spatial Use of Satellite‐tagged Odontocetes in the Western Main Hawaiian Islands: Results of Fieldwork Undertaken off O‘ahu in October 2010 and Kaua‘i in February 2011

Although considerable information is available on residency patterns and spatial use of odontocetes in the eastern half of the Hawai‘i Range Complex (HRC), much less is known about odontocetes in the western half of the HRC. In the second year of a three-year effort in the western main Hawaiian Islands we undertook surveys off Kaua‘i and Ni‘ihau in July/August 2011, to examine spatial use and residency patterns using satellite tags, to provide visual verification of acoustically-detected odontocetes on the Pacific Missile Range Facility (PMRF), and to obtain individual identification photographs and biopsy samples for assessment of population identity and structure.

As part of an assessment of habitat use and movements of odontocetes being undertaken in the western half of the main Hawaiian Islands (see Baird et al. 2011, 2012), field operations funded by Commander, U.S. Navy Pacific Fleet were undertaken off of Kaua‘i in January 2012. There were two primary goals of these operations: 1) providing species verification for acoustic detections by the Marine Mammal Monitoring on Navy Ranges (M3R) project on the Pacific Missile Range Facility (PMRF) hydrophone range (see Moretti et al. 2012); and 2) deploying satellite tags prior to a Submarine Commanders Course (SCC) training event to be undertaken off Kaua‘i in February 2012.

Here we combine results of field efforts funded through the U.S. Navy’s Living Marine Resources Program (through a three-year grant from the Naval Postgraduate School) as well as additional field time in the study area in 2011 and 2012 funded through the Pacific Islands Fisheries Science Center and Commander, Pacific Fleet. We also utilize results from research efforts in the eastern main Hawaiian Islands, off Lāna‘i, Maui, and Hawai‘i Island, to help interpret results from photo-identification and satellite tagging.

A joint project in February 2013 of the Pacific Missile Range Facility (PMRF) combined passive acoustic monitoring and boat-based field efforts. There were 1,010 kilometers (km) (55.9 hours [hr]) of small-vessel field effort over the course of the 8-day project. Of the 55.9 hr of survey effort, 64.2 percent was spent within the PMRF instrumented hydrophone range boundaries, and 14.8 percent of the effort was in depths greater than 1,000 meters (m).

A joint project in July and August 2013 on and around the Pacific Missile Range Facility (PMRF) combined passive acoustic monitoring and boat-based field efforts. There were 671 kilometers (36.6 hours [hr]) of small-vessel survey effort over the course of the 8-day project, with 55.1 percent of time (20.2 hr) spent within the PMRF instrumented hydrophone range boundaries. A total of 33.0 hr of acoustic monitoring coincided with the small-vessel field effort.

A joint project in February 2014 on and around the Pacific Missile Range Facility (PMRF) was carried out utilizing combined passive acoustic monitoring and boat-based field efforts. There were 1,287 kilometers (km) (66.3 hours [hr]) of small-vessel survey effort over the course of the 10 day project, with 44.6 percent of search time (29.6 hr) spent within the PMRF instrumented hydrophone range boundaries. A total of 81.7 hr of acoustic monitoring was undertaken during the field effort. There were 26 sightings of five species of odontocetes, six of which were directed by acoustic detections from the Marine Mammal Monitoring on Navy Ranges (M3R) system.

A joint project in February 2015 on and around the Pacific Missile Range Facility (PMRF) was carried out utilizing combined boat-based field efforts and passive acoustic monitoring from the Marine Mammal Monitoring on Navy Ranges (M3R) system. There were 1,132 kilometers (63.4 hours [hr]) of small-vessel survey effort over the course of the 13-day project. Weather conditions precluded field operations on 4 days, and strong westerly winds and/or range operations limited access to PMRF on seven additional days, with only 15.1 percent of search time (9.6 hr) spent within the range boundaries.

As part of a long-term U.S. Navy-funded marine mammal monitoring program, in February 2016 a combining boat-based field effort and passive acoustic monitoring was carried out on and around the Pacific Missile Range Facility (PMRF). The U.S. Navy funded five days of small-boat effort and the National Marine Fisheries Service funded an additional two days of effort. There were 859 kilometers (49 hours) of small-vessel survey effort over the course of the seven day project.

As part of a long-term U.S. Navy-funded marine mammal monitoring program, in August 2017 a combination of boatbased field effort and passive acoustic monitoring was carried out on and around the Pacific Missile Range Facility (PMRF) off Kaua‘i prior to a Submarine Command Course scheduled for mid-August 2017. The U.S. Navy funded five days of small-boat effort and the National Marine Fisheries Service funded an additional six days of effort. There were 1,113 kilometers (77.4 hours) of small-vessel survey effort over the course of the 11 day project.

As part of a long-term U.S. Navy-funded marine mammal monitoring program, in August 2018 a combination of vessel-based field effort and passive acoustic monitoring was carried out on and around the Pacific Missile Range Facility (PMRF) Kaua‘i prior to a Submarine Commander Course scheduled for mid-August 2018. The purpose of the monitoring effort was to assess the spatial movement patterns and habitat use of cetaceans that are exposed to mid-frequency active sonar and how those patterns influence exposure and potentially responses.

As part of a long-term U.S. Navy-funded marine mammal monitoring program, in February 2020 a combination of vesselbased field effort and passive acoustic monitoring was carried out on and around the Pacific Missile Range Facility (PMRF) off Kaua‘i prior to a Submarine Command Course scheduled for mid-February 2020. The purpose of the monitoring effort was to assess the spatial movement patterns and habitat use of cetaceans that are exposed to midfrequency active sonar and how those patterns influence exposure and potentially responses. Results from this effort were compared with previous Cascadia Research Collective (CRC) survey effort and photo-identification and tag data from Kaua‘i, based on surveys in 11 different years since 2003.

In Hawai'i fishermen use a variety of hook and line methods to catch tuna associated with pantropical spotted dolphins. In response to reports of dolphins being hooked in fisheries, the National Marine Fisheries Service (NMFS) proposed recategorizing two fisheries ("charter vessel" and "trolling, rod and reel") in 2011 from Category III (those having a remote likelihood of serious injury/mortality) to Category II (those having occasional serious injury/mortality). After reviewing comments received in response to the proposal, NMFS did not re-categorize the fisheries, in part because of statements that fishing effort around dolphins may have been overestimated and that many vessels just trolled near dolphins, not through groups. We used photo-identification of individually distinctive vessels fishing in association with dolphin groups and observations on the number and behavior of vessels with dolphins to examine the extent and nature of interactions between fishing vessels and spotted dolphins off Hawai'i Island. Since 2010, 34.5% of spotted dolphin encounters had fishing vessels present within the group envelope of the dolphins (mean=3.7, SD=3.5, range=1-19, n=57 of 165 encounters). Two primary fishing methods were used, either trolling through groups of dolphins or repeatedly transiting through a group at high speed to the advancing front of the group and stopping and fishing as the group passed by, with some vessels alternating methods during encounters. Since 2010, 133 different vessels were documented fishing in association with dolphins; of these, 38 (28.6%) were documented on two or more occasions, and 26 were documented in two or more years. A mark-recapture abundance estimate of the number of vessels fishing in association with spotted dolphins in 2012 and 2013 was 322 (CV=0.05). In 2015 NMFS recognized three distinct island-associated populations of spotted dolphins in Hawai'i, including one off Hawai'i Island, thus the population of dolphins involved in these interactions is smaller than originally expected. While many factors likely influence the probability of boats fishing associated with dolphin groups, continued reports of occasional hooking combined with the relatively large number of vessels "fishing" dolphins suggest the fisheries categories should be re-evaluated.

In Hawaiian waters fishermen use the association between pantropical spotted dolphins (Stenella attenuata) and yellowfin tuna (Thunnus albacares) to catch tuna. Targeting fishing effort around or in spotted dolphin groups has the potential to lead to bycatch, and anecdotal reports of hooking dolphins exist. We recorded information on fishing vessels associated with spotted dolphin groups from 2008 through 2018 to inform discussions about potential bycatch. Associations occurred from Oʻahu to Hawaiʻi Island, but were most prevalent off Hawaiʻi Island, where 29.7 % of spotted dolphin groups had fishing vessels present

We assess spatiotemporal overlap between false killer whales and nearshore fisheries in Hawai‘i to identify fisheries and regions where interactions are most likely to occur. Interactions with fisheries was cited as the greatest threat to this population's viability as a result of growing evidence over recent decades. We used false killer whale location data from 38 satellite tag deployments (2007–2018) and commercial fishery catch logs from a corresponding period to develop fishery overlap indices (FOIs) from a perspective that should reflect the experience of local fishermen

Currently a single stock of short-finned pilot whales is recognized in Hawaiian waters, with an estimated abundance of over 12,000 individuals in the EEZ. However, preliminary genetic results suggest that pilot whales around the main Hawaiian Islands are reproductively isolated from those elsewhere in the tropical Pacific. Since the type and extent of anthropogenic interactions varies both among the main Hawaiian Islands and offshore, we test the hypothesis that there is only a single stock of this species in Hawai‘i using a combination of association analyses of photo-identification data and movement/habitat use analyses from satellite tags. Photographs over 13 years included over 6,500 identifications of 868 distinctive individuals. Satellite tag data from 64 deployments averaged 37 days (max=228 days). Combining tag and association analyses indicate individuals do not mix freely among the islands and suggest the existence of three socially isolated but partially overlapping insular communities and an offshore population. The ranges of the three insular communities are from Ni‘ihau to western O‘ahu, from O‘ahu to Lana‘i, and primarily off Hawai‘i Island. Tagged individuals from these insular communities (n=61 deployments) remained an average of 57.5 km from their tagging location, with a grand mean of depth used and distance from shore of 1,564 m and 15.2 km, respectively. Evidence for an offshore population comes from three individuals tagged in two isolated social clusters with mean distances from their tagging locations of 249 km, with a grand mean of depth used and distance from shore of 4,336 m and 81.1 km (max=381 km) respectively. Anthropogenic interactions vary among the population ranges, with long-line fishing in offshore waters, Navy activities primarily off Ni‘ihau, Kaua‘i and O‘ahu, and vessel-based whale watching and swim-with operations primarily off Hawai‘i Island. As each community is exposed to different anthropogenic threats they should be managed independently.

Dwarf sperm whales (Kogia sima) have been studied rarely at sea. We used photo-identification, boat- and drone-based behavioral observations, and citizen science photo contributions to examine site fidelity, spatial use, and behavior in Hawaiʻi. Sighting rates were highest in island slope (500–1,000 m) waters. Over 40% of photo-identified individuals were linked by association in the same social network. More than half of the very distinctive individuals were seen more than once, and 28.5% were seen in multiple years, with one individual seen 14 times over a 15-year span. Resighted individuals and those in the main cluster of the social network were found in significantly shallower water than individuals that were not resighted or that were in isolated clusters. Distances between resighting locations suggest small home ranges. This suggests an insular slope-dwelling population that overlaps with an offshore population. Evidence of unsuccessful predatory attempts by large sharks was recorded on four individuals, and linear wounds consistent with interactions with line fisheries were documented on three individuals. Surface and subsurface behavior recorded by drone revealed vigilance behavior likely to minimize predation risk. Lessons learned from this study can be applied elsewhere to increase knowledge of this poorly known and difficult-to-study species.

Unique morphological and acoustic characteristics of beaked whales (Mesoplodon sp.) off the west coast of Baja California, Mexico

Acoustic point-transect distance-sampling surveys have recently been used to estimate the density of beaked whales. Typically, the fraction of short time “snapshots” with detected beaked whales is used in this calculation. Beaked whale echolocation pulses are only intermittently available, which may affect the best choice of snapshot length. The effect of snapshot length on density estimation for Cuvier's beaked whale (Ziphius cavirostris) is investigated by sub-setting continuous recordings from drifting hydrophones deployed off southern and central California. Snapshot lengths from 20 s to 20 min are superimposed on the time series of detected beaked whale echolocation pulses, and the components of the density estimation equation are estimated for each snapshot length. The fraction of snapshots with detections, the effective area surveyed, and the snapshot detection probability all increase with snapshot length. Due to compensatory changes in these three components, density estimates show very little dependence on snapshot length. Within the range we examined, 1–2 min snapshots are recommended to avoid the potential bias caused by animal movement during the snapshot period and to maximize the sample size for estimating the effective area surveyed.

Passive acoustic monitoring was conducted in the Navy’s Southern California Range Complex from January 2013 to June 2017 to detect marine mammal sounds. High-frequency Acoustic Recording Packages (HARPs) recorded sounds between 10 Hz and 100 kHz at four locations: west of San Clemente Island (1,000 m depth, site H), south of San Clemente Island (1200 m depth, site N), northwest of San Clemente Island (900 m depth, site M) and west of La Jolla, California (500 m depth, site P).

We present progress on the development of methods to investigate the potential impacts of sonar and other anthropogenic activities on calling animals. The basis for this effort is previously collected PAM data from four sites in the years 2006 to 2015. Recording effort at these sites varied between 674 and 2,284 days per site, resulting in 19 years of cumulative acoustic recording during 79 instrument deployments and 227 TB of acoustic recordings. As part of the work in this progress report, automated routines have been established and/or modified to detect and classify acoustic signals of blue whales (Balaenoptera musculus) and Cuvier’s beaked whales (Ziphius caviostris) as well as Mid-Frequency Active (MFA) sonar pings and explosions.

Understanding the distribution of cetacean species and their populations over space and time is relevant to conservation, management, and mitigation goals. Geographic differences in Blainville’s beaked whale (Mesoplodon densirostris) frequency-modulated (FM) echolocation pulses are investigated as a potential tool for population-level discrimination.

Passive acoustic monitoring (PAM) provides extensive datasets to examine the behavioral response of cetaceans to anthropogenic sound. Using broadband passive acoustic monitoring, the full range of cetacean sounds and the sounds of naval and other anthropogenic sources are recorded. We have been collecting high-frequency PAM data in the Southern California (SOCAL) region since 2006. Within this dataset are many instances of anthropogenic sound as well as cetacean presence at the locations of naval training.

This ongoing project will study explosions recorded by passive acoustic monitoring in the Southern California (SOCAL) region between 2009 and 2012, and provide a description of their characteristics and frequency of occurrence. In this region, explosions are used both by the Navy as part of training exercises, and by the commercial fishing industry as a deterrent for marine mammals

Marine ambient sound was recorded on autonomous high-frequency acoustic recording packages (bandwidth 10 Hz to 100 kHz) during long term deployments at multiple sites across the North Pacific, from the high latitude Aleutian Islands to tropical Palmyra Atoll in depths of 600–1 000 m. Most intertropical but no temperate locations showed a distinct diel pattern in ambient sound. The soundscape at each location was unique, yet there was a similar recurring sound of unknown origin in lower latitude locations. This sound had a peak frequency around 3–5 kHz and was recorded only for several hours after sunset. Additionally, at some locations, a broadband acoustic signal with bandwidth up to 60 kHz was recorded at night with crepuscular peaks. Both sound patterns were lunar dependent with lower acoustic levels during full moon phases. Site-specific diel and seasonal acoustic patterns have been observed for various odontocete species. Correlations between odontocete presence and levels of ambient sound are investigated. [Work supported by NOAA-Pacific Islands Fisheries Science Center, US Navy-N45/PACFLT, ONR, Pacific Life, Ocean Foundation, University of California, San Diego.]

Mesoscale oceanographic features are a major force in structuring the marine environment through processes such as eddy-induced upwelling, and as such effect distribution and aggregation patterns of all organisms along the food chain. It has been shown that top pelagic predators such as cetaceans react to these environmental changes in different ways. We present analysis of frequency-modulated (FM) echolocation pulses of Cuvier’s beaked whale (Ziphius cavirostris), Blainville’s beaked whale (Mesoplodon densirostis), and an unknown beaked whale species producing FM pulse type “BWC,” possibly ginkgo-toothed beaked whale (M. ginkgodens), at five locations in the central Pacific. The recordings were collected at Pearl and Hermes Reef (Northwestern Hawaiian Islands), Kona (Main Hawaiian Islands), Wake Atoll, Tinian, and Saipan (Northern Mariana Islands) between 2008 and 2015, ranging from 4 to 8 years per site. All three beaked whale species were present at all sites in different proportions throughout the recording periods, with a strong nocturnal pattern only for the “BWC” pulse type, yet without seasonal pattern. We examine the varying presence in the context of remotely sensed oceanographic data, including sea surface height deviation, temperature, and salinity, as well as chlorophyll a and derived primary productivity.

Evidence from strandings and anecdotal reports indicate that a number of odontocete species interact with near-shore fisheries in Hawai'i. In the absence of observer programs in these fisheries, we evaluated mouthline injuries from known resident populations of false killer whales and pygmy killer whales, to assess the viability of this method to document injuries associated with hook and line fishery interactions. All individuals with mouthlines visible were selected from photo-ID catalogs and scored for presence of mouthline injuries consistent with fisheries interactions. Ninety-seven false killer whales and 47 pygmy killer whales had ≥50% of the mouthline visible using fair to excellent quality photos, with a mean of 67% and 59% mouthline visible, respectively. Preliminary analysis suggests that main Hawaiian Islands insular false killer whales have high rates of mouthline injuries- 20% of adult and sub-adult individuals with ≥50% mouthline visible have injuries consistent with fisheries interactions, supporting studies using dorsal fin injuries that indicate individuals from this population regularly interact with fisheries. Pygmy killer whales also appear to interact with fisheries at high rates. Of adult and sub-adult individuals off Hawai'i and O'ahu with ≥50% of the mouthline visible, 31% have injuries consistent with fisheries interactions. Since pygmy killer whales feed primarily at night, and there are few reports of them depredating lines, mouthline injury analysis provides new insight into fisheries interactions for this species. Scars on pygmy killer whales heal white and are easier to detect than healed injuries on false killer whales, thus a greater proportion of individuals with such injuries may be detected for pygmy killer whales. With both species, the proportion of mouthline visible increased the likelihood of mouthline injuries being detected. Injury rates are negatively biased, since those individuals scored as having no mouthline injury may not have had their entire mouthline visible. Further efforts will aim to identify injury rates in short-finned pilot whales and rough-toothed dolphins. An examination of differences in injury rates between age classes, and multi-species comparisons will also be undertaken to better understand fisheries interactions.

The overall goal of this study was to include the 2018 survey data in the previous 1991–2014 modeling dataset in order to improve SMDs for the CCE study area. Specific objectives included: Generating multi-year average density surfaces for the Navy and others to use in their long-term (2–7 year) environmental planning efforts; and Providing updated abundance and “minimum population size (Nmin)” estimates as defined in the Guidelines for Assessing Marine Mammal Stocks (National Oceanic and Atmospheric Administration 2016).

The objectives of our study were two-fold: (1) develop spatially-explicit density estimates for winter/spring to support management applications, and (2) compare model-predicted density and distribution patterns to previously developed summer/fall model results in the context of species ecology. We used a well-established Generalized Additive Modeling framework to develop cetacean SDMs based on 20 California Cooperative Oceanic Fisheries Investigations (CalCOFI) shipboard surveys conducted during winter and spring between 2005 and 2015.

The Hawaiian Islands Cetacean and Ecosystem Assessment Survey (HICEAS) 2017 was conducted in waters within the United States (U.S.) Exclusive Economic Zone (EEZ) around the Hawaiian Archipelago (henceforth “Hawaiian EEZ” for brevity) from 6 July through 1 December 2017 (Yano et al. 2018). The primary objective of this line-transect survey was to collect cetacean sighting data to support the derivation of cetacean density estimates using both design-based analyses and habitat modeling techniques.

In this study, winter and spring density estimates for the entire CCE study area were made from SWFSC summer and fall model predictions (temporal extrapolation) and CalCOFI winter and spring model predictions (spatial extrapolation) for short-beaked common dolphin ( Delphinus delphis delphis ), Pacific white-sided dolphin ( Lagenorhynchus obliquidens ), Dall's porpoise ( Phocoenoides dalli ), and fin whale ( Balaenoptera physalus ).

For the last five months, Dr. Will Gough has been working at the Marine Mammal Research Program (MMRP) on a number of goals that will build capacity within Hawaii and advance the Navy’s goals related to the long-term health of protected marine mammal species. These goals relate to Dr. Gough’s expertise working with accelerometry-based biologging tags and include: setting up infrastructure at the MMRP to maintain large quantities of tag data, collecting novel data and expanding existing datasets through field efforts, training members of the Navy and MMRP to work effectively with accelerometry data and biologging devices, develop training materials and short-form workshops to disseminate knowledge of accelerometry data processing and analysis more broadly within the Hawaiian community, and use new and existing datasets to answer questions of relevance to the Navy and other organizations tasked with monitoring and management of protected species.

For the period of funding, Dr. Will Gough has been working at the Marine Mammal Research Program (MMRP) on a number of goals that will build capacity within Hawaii and advance the Navy’s goals related to the long-term health of protected marine mammal species. These goals relate to Dr. Gough’s expertise working with accelerometry-based biologging tags and include: setting up infrastructure at the MMRP to maintain large quantities of tag data, collecting novel data and expanding existing datasets through field efforts, training members of the Navy and MMRP to work effectively with accelerometry data and biologging devices, develop training materials and short-form workshops to disseminate knowledge of accelerometry data processing and analysis more broadly within the Hawaiian community, and use new and existing datasets to answer questions of relevance to the Navy and other organizations tasked with monitoring and management of protected species.

Rapid progress and affordability of photographic technology with increasing improvements in image resolution have facilitated advancements in efficiency and alternative approaches in data collection for marine mamma ls. We report these recent improvements by comparing marine mammal photographs taken during 2008-2013 aerial surveys of 16 marine mammal species in the Southern California Bight, shore-based studies of bottlenose dolphins (Tursiops truncatus) in Galveston Bay, Texas (2011 - 2013), and gray whales (Eschrichtius robustus) off Sakhalin Island, Russia (2004 -2010).

Rapid progress and affordability of photographic technology with increasing improvements in image resolution have facilitated advancements in efficiency and alternative approaches in data collection for marine mammals. We report these recent improvements by comparing marine mammal photographs taken during 2008-2013 aerial surveys of 16 marine mammal species in the Southern California Bight, shorebased studies of bottlenose dolphins (Tursiops truncatus) in Galveston Bay, Texas (2011-2013), and gray whales (Eschrichtius robustus) off Sakhalin Island, Russia (20042010). Various Canon and Nikon high-definition cameras ranging from 8.2-36.3 MP resolution and 70-1600 mm lenses with image stabilization were used during the studies. Results of these photographic comparisons demonstrate the evolution of digital photography advancements with the successful capture of individuals, as well as detailed information for behavioral ecology studies. For example, (1) individual identification of marine mammal species from aircraft not previously reported (Risso’s dolphins (Grampus griseus), killer whales (Orcinus orca), and blue and fin whales (Balaenoptera musculus and B. physalus)), (2) shore-based individual identification of bottlenose dolphins up to 500 m and of gray whales up to 2 km from shore, (3) instantaneous differentiation/confirmation of short-beaked vs. long-beaked common dolphins (Delphinus delphis and D. capensis) from 1,500-ft altitude with a 36 MP camera, (4) reduced proportion of “unidentified” dolphin and whale species, and (5) potential tracking of the behavior, social associations and durations, and relative position within the group of some individually identified delphinids and other species not previously studied in this manner. High- definition digital photography reduces costs and acquisition/processing time from earlier “tried and true” analog photography. This facilitates, advances, and compliments the efficacy of data collection for population and behavioral ecology studies on marine mammals, most recently allowing capture of individual identification images at distances of up to 2 km away.

In marine ecosystems, cetaceans are large mobile predators that depend on maximizing foraging efficiency. Their presence within a habitat can therefore be strongly related to the modulation of local prey by oceanographic conditions. Understanding how cetaceans are impacted by prey responses to the physical environment is challenging due to the difficulty of collecting presence data of cetaceans and their prey over long, comparable time periods. We used passive and active acoustic recordings collected from moorings within the San Diego Trough, along with physical oceanographic sampling (i.e. in situ, satellite-derived, and ocean general circulation model measurements), to elucidate relationships between cetaceans, their prey, and the physical environment. Our results show that the predator-prey dynamics of some cetaceans within the San Diego Trough are influenced by seasonal changes in the physical oceanographic conditions and processes that shape their prey resources. Specifically, common dolphin Delphinus delphis foraging activity increased during conditions associated with increased presence of diel vertically migrating fish prey. Blue whale Balaenoptera musculus foraging-associated acoustic activity increased during periods with increased presence of mid-water crustacean zooplankton and was replaced with breeding-associated acoustic activity during conditions associated with the waning of mid-water crustacean zooplankton. Fin whale B. physalus foraging-associated calling activity was more complex to model, most likely because these animals have a generalist diet and occupy this area year-round. Our results highlight environmental conditions and features relevant to cetaceans inhabiting this region and may aid in developing better spatially explicit management actions.

The abundance of two remote and broadly-distributed populations of false killer whales (Pseudorca crassidens) in Hawaiian waters was estimated using sighting data collected from ship-based, line-transect surveys conducted by NOAA Fisheries within the central Pacific between 1986−2017, including the three Hawaiian Islands Cetacean and Ecosystem.

The Hawaiian Islands Cetacean and Ecosystem Assessment Survey (HICEAS) is a recurring ship-based, line-transect survey designed to estimate cetacean abundance in the entirety of the Hawaiian EEZ.

Since the closure of a power plant in the southern part of San Diego Bay, a collaborative monitoring effort among the Navy, the National Marine Fisheries Service (NMFS) and others has been underway to better understand changes in the movement and behavior of the green sea turtle so that the Navy and this turtle can continue to share the resources in the bay. San Diego Bay is home to one of the largest U.S. Navy complexes in the world and California’s second largest incorporated city. Today, more than 25 percent of the U.S. Navy fleet is homeported in San Diego. Maintaining readiness in this ecosystem without causing harm to the natural resources is an ongoing challenge. There are a variety of threatened and endangered species that rely on the San Diego Bay ecosystem at different stages of their lives. One of these is the East Pacific green sea turtle. The East Pacific green sea turtle is a federally threatened species in San Diego Bay. While the majority of the population has traditionally lived in the quieter south part of the bay, the turtles may be venturing into areas more frequently used for U.S. Navy, recreational, and commercial activities. An increased presence of turtles outside of the southern portion of the bay may have potential implications for management of this species, as there is a higher likelihood of boat strikes and other potentially adverse human interactions.

Aerial surveys provide a valuable platform to record and document behavior of marine mammals above and below the sea surface. This approach is advantageous in avoiding disturbance from the observational platform while circling outside the sound cone of the plane. Since 2008, the U.S. Navy has instituted a marine mammal monitoring program in southern California from several platforms, including aerial surveys, and has successfully captured previously undocumented behaviors and species interactions during the aerial effort. This included focal behavioral interactions between sperm whales, northern right whale dolphins, and Risso's dolphins on 14 May 2011, 24 nm west of San Diego, CA. This -1.5-hour encounter was documented in detail with high- definition digital photographs and video as the group traveled NE along the edge of a steep underwater drop-off. Risso's dolphins initiated charges towards the heads of the sperm whales on multiple occasions, followed by fast retreats. Sperm whale adults responded by displaying an open lower jaw. Risso's dolphins appeared to direct this behavior only toward adult sperm whales that had recently surfaced from long (> 20 min) dives; it was not directed toward the four calves in the group. Northern right whale dolphins intermingled with the Risso's dolphins and sperm whales, although they did not approach sperm whales as closely or abruptly as the Risso's dolphins. While similar apparently aggressive Risso's dolphin behavior has been documented toward other cetacean species, this is the first known occurrence of head-on charging by Risso's dolphins, accompanied by the elicited jaw display response from sperm whales. The interaction may be similar to aggressive pilot whales behavior towards sperm whales, and may function in acquiring regurgitated sperm whale food, or other needs by the Risso's dolphins.

The present study provides new and current estimates of cetacean density for the six most commonly encountered cetacean species off southern California based on sighting data collected during 37 quarterly CalCOFI cruises from 2004 to 2013. The current study resulted from a high survey repetition rate that allowed for the examination of inter-annual and seasonal trends in density as well as temporal and spatial patterns of distribution for six common cetacean species off southern California: blue whales, fin whales, humpback whales, short-beaked common dolphins, Pacific white-sided dolphins, and Dall’s porpoise.

Cetacean distribution, density and abundance in the Southern California Bight were assessed through visual and acoustic surveys during five California Cooperative Oceanic Fisheries Investigations (CalCOFI) cruises from August 2012-November 2013. Visual monitoring incorporated standard line-transect protocol during all daylight transits while acoustic monitoring employed a towed hydrophone array during transits and sonobuoys at oceanographic sampling stations. Visual effort included 584 observation hours covering 10,900 kilometers yielding 565 sightings of 15 identified cetacean species.

Spatial and temporal distribution patterns, density and abundance of cetaceans in the southern California Bight were assessed through visual and acoustic surveys during five California Cooperative Oceanic Fisheries Investigations (CalCOFI) cruises from August 2011 – July 2012. Visual monitoring incorporated standard line-transect protocol during all daylight transits while acoustic monitoring employed a towed hydrophone array during transits and sonobuoys at oceanographic sampling stations.

This report summarizes small boat based research conducted on cetaceans off southern California by the Scripps Institution of Oceanography (SIO) in collaboration with Southwest Fisheries Science Center (SWFSC) from August 2009 – July 2010. The primary objectives of this research were to use sighting, photo-identification, biopsy and acoustical sampling techniques to assess the occurrence, distribution and population structure of small cetaceans in a region that is subject to frequent naval exercises; this information is needed to evaluate possible effects from Mid Frequency Active Sonar (MFAS) trials and ultimately for the development of appropriate management protocols.

Trends in cetacean density and distribution off southern California were assessed through visual line-transect surveys during thirty-seven California Cooperative Oceanic Fisheries Investigations (CalCOFI) cruises from July 2004–November 2013. From sightings of the six most commonly encountered cetacean species, seasonal, annual and overall density estimates were calculated. Blue whales (Balaenoptera musculus), fin whales (Balaenoptera physalus) and humpback whales (Megaptera novaeangliae) were the most frequently sighted baleen whales with overall densities of 0.91/1000km2 (CV=0.27), 2.73/1000km2 (CV=0.19), and 1.17/1000km2 (CV=0.21) respectively. Species specific density estimates, stratified by cruise, were analyzed using a generalized additive model to estimate long-term trends and correct for seasonal imbalances. Variances were estimated using a non-parametric bootstrap with one day of effort as the sampling unit. Blue whales were primarily observed during summer and fall while fin and humpback whales were observed year-round with peaks in density during summer and spring respectively. Short-beaked common dolphins (Delphinus delphis), Pacific white-sided dolphins (Lagenorhynchus obliquidens) and Dall’s porpoise (Phocoenoidesdalli) were the most frequently encountered small cetaceans with overall densities of 705.83/1000km2 (CV=0.22), 51.98/1000km2 (CV=0.27), and 21.37/1000km2 (CV=0.19) respectively. Seasonally, short-beaked common dolphins were most abundant in winter whereas Pacific white-sided dolphins and Dall’s porpoise were most abundant during spring. There were no significant long-term changes in blue whale, fin whale, humpback whale, short-beaked common dolphin or Dall’s porpoise densities while Pacific white-sided dolphins exhibited a significant decrease in density across the ten-year study. The results from this study were fundamentally consistent with earlier studies, but provide greater temporal and seasonal resolution. Keywords: Cetaceans; Line transect; Density; Abundance; Distribution; Trends; Southern California; CalCOFI

Using a network of drifting acoustic buoys in controlled exposure experiments, we investigated the effects of mid-frequency (3–4 kHz) active sonar (MFAS) on whistle production in short-beaked (Delphinus delphis delphis) and long-beaked common dolphins (Delphinus delphis bairdii) in southern California. Given the complexity of acoustic behavior exhibited by these group-living animals, we conducted our response analysis over varying temporal windows (10 min– 5 s) to describe both longer-term and instantaneous changes in sound production. We found that common dolphins exhibited acute and pronounced changes in whistle rate in the 5 s following exposure to simulated Navy MFAS.

The first cetacean circovirus, beaked whale circovirus (BWCV), was recently reported in a Longman’s beaked whale (Indopacetus pacificus) stranded in Hawai‘i and represents an emergent disease with unknown population impacts. In other species, circovirus infection may cause mortality or opportunistic co-infection by other pathogens. We report on a targeted surveillance of stranded cetaceans in the Pacific basin, including archived beaked whale species, strandings where pathological findings suggested disease presence, mass stranded animals, and additional individuals to represent a broad range of Hawaiian cetacean species. Archived tissues primarily from the brain, kidney, liver, lung, spleen, and lymph nodes of individuals stranded between 2000 and 2020 (n=30) were tested by PCR for the presence of BWCV.