Abstract. A multinational oceanographic and acoustic sea experiment was carried out in the summer of 2014 off the western coast of the island of Sardinia, Mediterranean Sea. During this experiment, an underwater glider fitted with two hydrophones was evaluated as a potential tool for marine mammal population density estimation studies. An acoustic recording system was also tested, comprising an inexpensive, off-the-shelf digital recorder installed inside the glider. Detection and classification of sounds produced by whales and dolphins, and sometimes tracking and localization, are inherent components of population density estimation from passive acoustics recordings. In this work we discuss the equipment used as well as analysis of the data obtained, including detection and estimation of bearing angles. A human analyst identified the presence of sperm whale (Physeter macrocephalus) regular clicks as well as dolphin clicks and whistles. Cross-correlating clicks recorded on both data channels allowed for the estimation of the direction (bearing) of clicks, and realization of animal tracks. Insights from this bearing tracking analysis can aid in population density estimation studies by providing further information (bearings), which can improve estimates.

Abstract. A multinational oceanographic and acoustic sea experiment was carried out in the summer of 2014 off the western coast of the island of Sardinia, Mediterranean Sea. During this experiment, an underwater glider was evaluated as a potential tool for recording marine mammal sounds for population density estimation studies. To this end, an acoustic recording system was also tested, comprising two hydrophones connected to an off-the-shelf voice recorder installed inside the glider. Analysis of the recorded acoustic data by a human analyst indicated the presence of sperm whale (Physeter macrocephalus) regular clicks as well as dolphin clicks and whistles. Further analysis of the data consisted in cross-correlating clicks recorded on both data channels for the estimation of the direction (bearing) of clicks, and realization of animal tracks. Insights from this bearing tracking analysis is expected to aid in population density estimation studies by providing further information on animal movement and location.