Acoustic monitoring of cetaceans using static and dynamic devices in the central Mediterranean Sea

Mediterranean cetacean populations face many threats from increased human activities, such as ship traffic, overfishing, bycatch, chemical pollution, marine litter and underwater noise. Here, we investigated cetacean diversity using acoustic recorders installed in static and dynamic devices in the central Mediterranean Sea, where a floating offshore wind farm will soon be developed. Therefore, acoustic recorders were installed in a seafloor mooring and in a wave glider. Acoustic data from the seafloor mooring were acquired from 18th February to 27th April 2022, with 50% duty cycle and 192 kHz sampling rate. A total of 9,473 acoustic files of 300 sec (69 days, similar to 790 hours, similar to 1 TB) were collected. Subsequently, a wave glider was launched in the same area from 10th to 25th October 2022. Acoustic data were acquired continuously with the same sampling rate used previously, storing a total of 2,974 recordings of 460 sec (15 days, similar to 380 hours, similar to 360 GB). In this study, a preliminary data analysis involved spectrogram visualization and audio listening of a subsample of both datasets, at broadband and low-frequency, to identify cetacean vocalizations and anthropogenic noise sources. The acoustic signals of delphinids, sperm whale, fin whale and different anthropogenic noise sources were identified in the study area. Passive acoustics resulted a powerful tool to monitor cetacean diversity using both static and dynamic devices, providing valuable information for the establishment of conservation actions in a poorly investigated area of the Mediterranean basin.