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 Navy-priority 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 Kaua’i 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.
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 2-13). Weather forecasts over the nine days ranged from variable <10 knots (two days), west 15 knots (one day), southwest 20 knots (one day), northeast 20 knots (one day), east 20 knots (one day), northeast 25 knots (two days), and north 25 knots (one day). Surveys were undertaken on eight days, with one day lost due to unworkable weather conditions (i.e., forecast southwest 20 knots). Overall, we covered 850 kilometers of trackline over 51 survey hours. Survey effort was spread broadly across the southernmost part of the PMRF, and included areas to the southeast of the range, off south Kaua’i (on days when the area to the west was unworkable), and one day off eastern Kaua’i, when conditions off the south shore were unworkable (Figure 1).
There were 20 encounters (i.e., groups approached) of seven different cetacean species, and one sighting of a Hawaiian monk seal, Neomonachus schauinslandi (Table 1). Cetacean encounters included six sightings of humpback whales, six sightings of short-finned pilot whales (Globicephala macrorhynchus), three sightings of rough-toothed dolphins (Steno bredanensis), two sightings of spinner dolphins (Stenella longirostris), and one sighting each of Blainville’s beaked whales (Mesolplodon densirostris), common bottlenose dolphins (Tursiops truncatus), and pygmy killer whales (Feresa attenuata). Groups of humpback whales that were not approached were tallied throughout the day but were not included in the encounter totals.
Six of the 20 total cetacean sightings (30%) were cued by analysts interpreting acoustic detections from the Navy’s hydrophone range, including four of the six total short-finned pilot whale sightings, the Blainville’s beaked whale sighting, and the common bottlenose dolphin sighting. In total, 23,558 photographs were taken of all seven encountered cetacean species for individual and species identification. There were 16 tagging attempts, resulting in 13 tag attachments onto four different species (Table 2). Of the three failed tagging attempts, two tags were lost, and one was recovered. Tags were deployed onto eight short-finned pilot whales (SPLASH10-F tags), three humpback whales (including two SPLASH10-F tags and one Argos location-only SPOT6 tag), one Blainville’s beaked whale (SPLASH10-F tag), and one bottlenose dolphin (SPLASH10-F tag). All tags except for the Blainville’s beaked whale tag successfully transmitted location data, including high-quality Fastloc®-GPS locations from all SPLASH10-=F tags (Figures 2-13). Additionally, dive behavior data was received from all SPLASH10-F tags, with the exception of the Blainville’s beaked whale tag (Figure 14). Six of the tag deployments overlapped temporally with Phase A of the SCC, and 12 overlapped temporally with Phase B (Table 2). All odontocete tags that successfully transmitted, and one of the humpback whale tags, remained on or in close proximity to the PMRF for the duration of the SCC (Figures 2-13). 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. In addition, we collected one eDNA sample from the pygmy killer whale group, and seven biopsy samples from two different species (four from humpback whales, and three from rough-toothed dolphins). The biopsy samples have been shared with collaborators at the Southwest Fisheries Science Center for genetic analysis.
Preliminary photo-identification results are available for two species. The pygmy killer whale sighting represents only the fourth time that CRC has documented this species off Kaua’i in field efforts over 16 years, with approximately 27,000 km of survey effort off Kaua’i and Ni’ihau. A comparison of the 23 individuals from this encounter to CRC’s long-term photo-identification catalog of pygmy killer whales (Baird et al. 2024) revealed that none of the individuals documented in this encounter had been previously identified, supporting previous work indicating that pygmy killer whales off the island are not part of a resident, island-associated population. The Blainville’s beaked whale encounter was only the 10th encounter of this species off Kaua’i or Ni’ihau by CRC. All five individuals were photo-identified and compared to CRC’s long-term photo-identification catalog (Baird 2019; McSweeney et al. 2007), two of which were re-sightings of individuals seen off Kaua’i in 2019 and 2021, including a previously satellite tagged adult male.
Citation:
Baird, R.W., A.E. Harnish, R.D. Andrews, J.K. Lerma, M.A. Mohler, J.E. Phipps, and S.D. Mahaffy. 2024. Small-Boat Surveys and Satellite Tagging of Cetaceans on the Pacific Missile Range Facility, Kaua’i, in February 2024. Field survey report to U.S. Pacific Fleet by HDR, under Federal contract number N62470-20-D-0016, Task Order No. 24F0102. May 2024.
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