Small-Boat Surveys and Satellite Tagging of Odontocetes on the Pacific Missile Range Facility, Kauaʻi, in August 2023

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). 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). This interim field survey report provides a summary of small boat-based survey methodology (Appendix 1), survey effort (Figure 1), encounters (Table 1), and satellite tags deployed (Table 2; Figures 2-12). Eight days of field effort were funded by the Navy, and field efforts were undertaken on seven days, with two days in the middle being lost due to conditions related to Hurricane Dora. Overall, we covered 781 km of trackline over 48 survey hours. On the first day, we coordinated with NOAA Oscar Elton Sette to increase the likelihood of being able to work with high-priority species. Survey effort was spread primarily across the southernmost tip of the PMRF (Figure 1). There were 30 encounters with six species of cetaceans (Table 1), including 12 sightings of rough-toothed dolphins (Steno bredanensis), six sightings of common bottlenose dolphins (Tursiops truncatus), four sightings of short-finned pilot whales (Globicephala macrorhynchus), four sightings of pantropical spotted dolphins (Stenella attenuata), three sightings of spinner dolphins (Stenella longirostris), and one sighting of melonheaded whales (Peponocephala electra). The pantropical spotted dolphins were the most unusual species encountered during the field project; in 15 years of CRC field effort  off Kauaʻi and Niʻihau since 2003, this species has only been encountered 12 previous times during seven different years. Seven of the 30 total cetacean sightings (18%) were cued by analysts interpreting acoustic detections from the Navy’s hydrophone range, including a short finned pilot whale sighting, three sightings of rough-toothed dolphins, two sightings of common bottlenose dolphins, and the melon headed whale sighting. In total, 19,610 photographs were taken of all six encountered cetacean species for individual and species identification. There were 11 tagging attempts, during which one tag was lost, and 10 SPLASH10-F (Fastloc®-Global Positioning System (GPS)) tags were deployed onto four different species, including six short-finned pilot whales, two common bottlenose dolphins, one melon-headed whale, and one pantropical spotted dolphin (Table 2). Location data1 were received from all 10 tags (Figures 2-11), as well as high resolution time series and/or dive behavior data (Figure 12). Four tags were deployed prior to the start of Phase A, and all tags overlapped with Phase B of the SCC (Table 2). Data from all individuals have been provided to collaborating researchers with Naval Information Warfare Center Pacific (NIWCPAC) for analyses of received levels of MFAS, and for examination of potential behavioral changes associated with MFAS exposure. All individuals remained on or in close proximity to the PMRF for the majority of their tag deployments (Figures 2-11). One biopsy sample was collected from a pantropical spotted dolphin, which will be shared with collaborators at the Southwest Fisheries Science Center and the University of Hawai‘i for analysis.



Baird, R.W., A.E. Harnish, C.J. Cornforth, J.K. Lerma, M.A. Mohler, and J.E. Phipps. 2023. Small-boat Surveys and Satellite Tagging of Odontocetes on the Pacific Missile Range Facility, Kauaʻi, in August 2023. Field survey report to U.S. Pacific Fleet by HDR, under under Federal contract number M62470-20-D-0016, Task Order No. 23F0108. November 2023.

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