Articles | Volume 13, issue 2
Ocean Sci., 13, 273–288, 2017

Special issue: REP14-MED: A Glider Fleet Experiment in a Limited Marine...

Ocean Sci., 13, 273–288, 2017

Research article 11 Apr 2017

Research article | 11 Apr 2017

Marine mammal tracks from two-hydrophone acoustic recordings made with a glider

Elizabeth T. Küsel1, Tessa Munoz1, Martin Siderius1, David K. Mellinger2, and Sara Heimlich2 Elizabeth T. Küsel et al.
  • 1Northwest Electromagnetics and Acoustics Research Laboratory, Portland State University, 1900 SW 4th Ave, Portland, OR 97201, USA
  • 2Cooperative Institute for Marine Resources Studies, Oregon State University, 2030 Marine Science Drive, Newport, OR 97365, USA

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.

Short summary
An ocean glider was tested during the REP14-MED experiment off the western coast of the island of Sardinia as a platform for recording sounds produced by whales and dolphins using two sensors. Sperm whale clicks as well as dolphin clicks and whistles were identified in the recordings. Automatically detected sperm whale clicks were used to estimate animal tracks. Such information is useful for marine mammal density estimation studies that use passive acoustics.