A wave glider for passive acoustic monitoring of cetaceans in the Mediterranean Sea

Abstract

A Wave Glider is a surface and remotely operable oceanographic platform equipped with multi-parameter sensors, including a towed array hydrophone. Here, we tested the potential use of this autonomous vehicle to acquire high quality acoustic data and provide information on the spatial distribution of different cetacean species in the Mediterranean Sea, including elusive species such as deep-diving whales. This autonomous vehicle was launched from the island of Minorca (Spain) to Apulia (Italy), crossing the southern Tyrrhenian Sea, the Strait of Sicily, the Ionian Sea and the lower Adriatic Sea for about 1,600 nautical miles. Acoustic data were acquired continuously from the 30 th September to the 17 th December 2022. Data collection was set at a sampling rate of 192 kHz, storing files of 460 sec in the flac format. A total of 10,695 recordings (about 1.3 TB) were acquired. A preliminary data analysis involved spectrogram visualization and audio listening of a subsample of the dataset (3,565 files), both broadband and low-frequency, to identify cetacean vocalizations and anthropogenic noise sources. The acoustic signals of delphinids, sperm whales, fin whales and different anthropogenic noise sources were identified during the route traveled by this autonomous surface vehicle.