A wave glider for passive acoustic monitoring of cetaceans and anthropogenic sources in the central Mediterranean Sea

Passive acoustic monitoring has become a widely used method to study cetaceans, especially for populations facing escalating threats from noisy human activities, including shipping traffic, fishing industry and marine constructions. Here, we conducted a study using an autonomous surface vehicle to explore the distribution and acoustic behavior of cetaceans and to characterize anthropogenic sound sources in the central Mediterranean Sea. A wave glider equipped with a single-towed acoustic recorder was deployed from 13th September 2022 to 3rd March 2023. The recording yielded 19,115 files of 460s each (approximately 2 TB), a third of which was kept for a preliminary analysis based on spectrogram visualization and audio listening. The results showed that nearly half of the dataset contained delphinid signals (Delphinidae), followed by sperm whales (Physeter macrocephalus) and fin whales (Balaenoptera physalus), with notable hotspots in the southern Tyrrhenian and the Ionian Sea. Moreover, the almost continuous detection of anthropogenic sources highlighted the widespread acoustic impact of human activities in the area. These findings demonstrate the value of passive acoustics in the use of autonomous vehicles as a versatile tool for large-scale and long-term monitoring, offering a promising approach to support conservation efforts for vulnerable species while advancing strategies to mitigate human impacts on marine ecosystems.