Hydroacoustic records of humpback whales and spinner dolphins, Ogasawara Islands, Japan (23-26 February 2025)

This dataset contains ~3 days of continuous hydroacoustic data from a moored underwater sound recorder, Soundtrap ST600 (sampling at 96 kHz, UTC timestamp, 23-26 Feb 2025). The dataset was collected during an instrument testing campaign. It is potentially valuable for bioacoustical studies, as abundant snapping shrimp sounds, humpback whale calls, and transient spinner dolphin sounds were recorded (more than 100 were sighted next to the mooring at retrieval). In addition, acoustic release, Ascent AR, collected water temperature, tilt, noise, and water pressure (1 sample per minute). Location: Japan, Ogasawara Islands, Anijima (Takinoura Bay) Deployment: 23 Feb 2025 (local afternoon) The hydroacoustic mooring was deployed from a boat with 50 kg of weights as anchor (40 kg gym disks + 10 kg diver belt). GPS (Marker 021, 3:33 pm LT): N 027 deg 07.206’ E 142 deg 12.018’ ~13 m water depth The operator heard humpback whales already during the drop (on the handheld DJI camera). On return to port, 3.5 km away, observers saw n=3 humpback whales (mother, calf + escort). Retrieval: 26 Feb 2025 (local morning) The mooring was recovered after a storm with strong winds, by using an acoustic release as a test and diving to pick up the anchor (~14 m), i.e., nothing was left on the seafloor. More than a hundred spinner dolphins were around and above the mooring just before deployment as the observers entered the bay. Before arriving (~8 am LT), observers saw 2 humpback whales (they were close to a small Hitomaru Island, between Nishijima Island and Takinoura bay). Sensor and file metadata: Soundtrap ST600 (Ocean Instruments, NZ), #6462, high gain, 96 kHz, UTC timestamp files: 6462.YYMMDDhhmmss.wav Ascent AR, #580383 (Innovasea, Vemco, Canada) files: VUE_Export_Ogasawara.csv (raw: AAR_***.csv, AAR_***.vrl) The overview plot: The experimental data is visualized in "data_summary_Feb2025.png". The overview of data includes a long-term spectrogram (LTS), time series recorded by the release, and the number of humpback whales sighted on deployment days (whale-sighting data credit: Dr. K. Tsujii, Ogasawara Whale Watching Association - https://x.com/owa_ogasawara). The plot shows that during the storm (Feb 24, 2025), the mooring experienced increased tilt and a reduction in high-frequency noise (presumably due to quieter snapping shrimps). As we understand, the Ogasawara Whale Watching Association's whale count was skipped on some days due to bad weather.