An acoustic observatory for sperm whales in the Eastern Mediterranean Sea

Abstract

A deep-water acoustic observatory for real-time detection and 3D localization of sperm whales has been developed, deployed and operated for 3-month periods in summer 2020 and 2021 off SW Crete in the Eastern Mediterranean Sea. Detection and localization rely on receptions of regular clicks at 3 hydrophones suspended from surface buoys at depths of ∼100 m and ∼1 km apart. Travel times of significant arrivals extracted onboard the buoys are transmitted, together with other supporting data, via mobile broadband to a land-based analysis center where the data from all buoys are combined to enable detection and 3D localization of vocalizing animals exploiting direct and surface-reflected arrivals and using a Bayesian approach. The large separations between hydrophones result in small localization uncertainties for ranges up to ∼6 km, whereas, on the other hand, they pose significant challenges related, e.g., to peak association and synchronization between the buoys. The design and implementation, as well as results from the operation of the system will be presented. [Work supported by Ocean Care – SAvEWhales project.]