As part of the long-term United States Navy (Navy)-funded Marine Species Monitoring Program, from 9 to 18 February 2025, Cascadia Research Collective (CRC) carried out a vessel-based field effort in conjunction with passive acoustic monitoring undertaken by Navy scientists on and around the underwater hydrophone ranges of the Pacific Missile Range Facility (PMRF). The effort was timed to start 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. 2025). This field survey report provides a summary of small vessel-based survey methodology (Appendix I), survey effort (Figure 1), encounters (Table 1), and satellite tag deployments (Table 2; Figures 2-12). Eight days of field effort were funded by the Navy, and one day of fieldwork was funded by a grant from the National Oceanic and Atmospheric Administration. Over the nine-day period, we were able to survey eight days, covering 1,117 kilometers of trackline over 66 survey hours. Survey effort was focused on the southernmost part of the PMRF (Figure 1).
Survey effort was also conducted on a day of transit from Kauaʻi to Oʻahu at the conclusion of the effort (details not included).
There were 54 encounters with 11 species of cetaceans and one brief sighting of an unidentified delphinid that took place during an encounter with a group of short-finned pilot whales (Globicephala macrorhynchus, Table 1). Nineteen of the sightings (35 percent) were cued by analysts (from the Naval Undersea Warfare Center and Naval Information Warfare Center) interpreting acoustic detections from the Navy’s hydrophone range. Encounters included 24 sightings of rough-toothed dolphins (Steno bredanensis), 12 sightings of humpback whales (Megaptera novaeangliae), six sightings of short-finned pilot whales, three sightings each of Blainville’s beaked whales (Mesoplodon densirostris) and spinner dolphins (Stenella longirostris), one sighting of common bottlenose dolphins (Tursiops truncatus), one sighting of false killer whales (Pseudorca crassidens), one sighting of fin whales (Balaenoptera physalus), one sighting of a Kogia sp., one sighting of melon-headed whales (Peponocephala electra), and one sighting of pygmy killer whales (Feresa attenuata).
Over the course of the field effort, 26,107 photos were taken for species and individual identification. Samples collected included two eDNA samples (one from a pair of fin whales and
one from a group of pygmy killer whales), two fecal samples from short-finned pilot whales during two different encounters, one breath sample from a rough-toothed dolphin, and five biopsy samples from three species (two each from false killer whales and short-finned pilot whales and one from a rough-toothed dolphin; Table 1). Skin sub-samples of biopsy samples
have been shared with collaborators at the Southwest Fisheries Science Center for genetic analysis, while the remaining skin and blubber from biopsy samples, as well as fecal samples and the breath sample, have been archived at the University of Hawaiʻi Health and Stranding Lab.
Wildlife Computers SPLASH10-F Low Impact Minimally Percutaneous External-electronics Transmitter (LIMPET) satellite tags were programmed to collect dive behavior and Fastloc®- Global Positioning System (GPS) data from the time they were deployed until three and a half days after the end of the SCC. There were 11 tagging attempts, resulting in 10 tag attachments onto four species (Table 2). The one failed tagging attempt, during a Blainville’s beaked whale encounter, resulted in tag loss. Tags were successfully deployed onto four short-finned pilot whales (from three different groups), three rough-toothed dolphins, two false killer whales, and one Blainville’s beaked whale, and all successfully transmitted location (including high-quality Fastloc®-GPS locations) and behavior data (Table 2; Figures 2-12). Six of the tag deployments overlapped temporally with Phase A of the SCC, and all ten overlapped temporally with Phase B (Table 2). Data from all individuals have been provided to collaborating researchers with the Naval Information Warfare Center Pacific for analyses of received levels of MFAS.
Several of the species that were sighted are not commonly encountered off Kauaʻi and Niʻihau. Our encounter with fin whales was only the second sighting of this species off Kauaʻi in 17 years of CRC survey effort and was the first mother-calf pair that CRC has encountered in the Hawaiian Islands. The adult female from this encounter was compared to CRC’s Hawaiʻi fin whale photo-identification catalog but yielded no matches. Additionally, prior to this effort, CRC had only encountered Blainville’s beaked whales off Kauaʻi and Niʻihau ten times. The data collected from our three encounters with Blainville’s beaked whales over the course of this field project therefore represent a substantial increase in our understanding of this species off those islands. One individual each from the first two encounters with Blainville’s beaked whales matched to the long-term photo-identification catalog for this species, and the known individual from the second encounter had been tagged off Kauaʻi in 2021 (MdTag020 in Henderson et al. 2025). However, there were no matches between the three encounters, and no individuals from the third Blainville’s beaked whale encounter (that included a successful tag deployment) had been previously sighted. Our sightings of Northwestern Hawaiian Islands (NWHI) false killer whales and pygmy killer whales are also particularly notable, as we have only encountered NWHI false killer whales six times previously, all off Kauaʻi (Kratofil et al. 2023), and have only encountered pygmy killer whales off Kauaʻi and Niʻihau four times previously (Baird et al. 2024a, 2024b), with field efforts off the islands in 17 different years. Two of the four individuals from the NWHI false killer whale encounter were matched to the CRC long-term photoidentification catalog for this species and had been seen most recently in June 2012 and February 2020 off Kauaʻi. Five individuals from the pygmy killer whale encounter were also compared to the photo-identification catalog but yielded no matches, supporting previous work indicating that pygmy killer whales off Kauaʻi are not part of a resident, island-associated population (Baird et al. 2024a).
Citation:
Baird, R.W., A.E. Harnish, C.J. Cornforth, M.A. Mohler, D.M. Barrios, J.A. Fahlbusch, L.D. Hutcheson, S.D. Mahaffy, and M.A. Kratofil. 2025. Small-Boat Surveys and Satellite Tagging of Cetaceans on the Pacific Missile Range Facility, Kaua’i, in February 2025. Field survey report to U.S. Pacific Fleet by HDR, under Federal contract number N62470-20-D-0016, Task Order No. 24F0225.
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