The Project KNOWHALE: Improving Knowledge On Fin Whale Acoustic Occurrence And Behaviour In The Central Mediterranean Sea

The scarce information available on fin whales (Balaenoptera physalus) in the Central Mediterranean Sea limits the understanding of key bio-ecological activities of the endangered Mediterranean population. This work is part of a collaborative effort within the project “KNOWhale” and aims to expand knowledge about the species’ acoustic behavior and seasonal distribution. Acoustic data were collected from three different recording areas. Site-1, located in the Ionian Sea: OBS/H, 2065 m depth, 100 Hz sampling frequency (fs), operating continuously between May 2017 - January 2018; Site-2, South Adriatic Sea (EMSO-ERIC regional facility): Silence-LP recorder, 700 m depth, 64 kHz fs, 50% duty cycle, November 2022 – June 2023; Site-3, Sicily Channel: SoundTrap ST600 recorder, 157 m depth, 192 kHz fs, 50% duty cycle, February - April 2022. Fin whales 20Hz calls were detected at all sites using custom automatic detector, with calls occurring in 17, 122 and 16.54 hours respectively in Site-1 (0,29% detection rate), Site-2 (4,35% detection rate), and Site-3 (2.14% detection rate). Our results show for the first time the acoustic presence of fin whales in the Adriatic Sea over several months and attest to their monthly occurrence in data-deficient regions. This work provides essential baseline knowledge for conservation purposes in the Central Mediterranean Sea.