Abstract
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.
Highlights
Autonomous underwater vehicles (AUVs) such as gliders are being used ever more frequently as a tool in ocean research
A glider was fitted with two hydrophones and an inexpensive, off-the-shelf acoustic recording system for use in studies related to marine mammal population density estimation
Even though the experiment described here was opportunistic and by no means designed as a density estimation experiment, this was the first time a glider fitted with two sensors was used to monitor marine mammals
Summary
Autonomous underwater vehicles (AUVs) such as gliders are being used ever more frequently as a tool in ocean research. A glider moves through the water column in a seesaw pattern by controlling its buoyancy, enabling it to glide forward with the use of horizontally mounted wings. Given their mode of operation, gliders provide a platform that is acoustically very quiet, making them well-suited for passive acoustic monitoring of marine mammals. Increasing amounts of marine mammal recordings are being obtained by fitting gliders with hydrophones (e.g., Klinck et al, 2012; Baumgartner et al, 2013). The ability of gliders to perform and report real-time detections of four different kinds of baleen whales and their different call types has been tested successfully by Baumgartner et al (2013)
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