A Multiplatform Ultrasonic Event Recorder for Tagging, Towing, and Stationed Monitoring of Odontocetes

Abstract

A simple and easy to handle acoustic event recorder (A-tag) has been developed and applied to monitor the echolocation behaviour, distribution, and long-term presence of odontocetes. A-tag stores peak intensity of a biosonar pulse as well as the sound source direction calculated by the time difference of sound arrival by stereo hydrophone. “A-tag” was developed as a biologging system to observe acoustic sensing behaviour of dolphins and porpoises in the wild. Results showed the free-ranging finless porpoises scan ahead by their sonar in advance before swimming silently. The inspection distance reached several tens meters that provide long enough ‘safety margin’ for the animal before facing real risks or rewards. The frequent sound production of dolphins and porpoises was confirmed by the acoustic tagging that is helpful for passive acoustic monitoring of odontocetes. A-tag was modified for towed and fixed operation. Towed-type A-tag has been widely used for acoustic line transect to observe distribution of odontocetes. Number of individuals were observed by counting independent sound sources recorded by the stereo hydrophone. Acoustic capture-recapture model provides detection probability of A-tag that is useful to estimate total population size in the monitored area. Fixed-type A-tag has been applied for a long-term monitoring of presence and swimming direction of odontocetes. Combining with sound production rate observed by the acoustic biologging, density estimation of animals is feasible using stationed monitoring data. Patient and continuous recording of echolocation sounds by the fixed A-tag provided various types of underwater behaviour and movement of odontocetes. Now the acoustic devices made the observation of dolphins and porpoises automatic like oceanographic observation devices. Listening in the OceanListening in the Ocean Look Inside Reference tools Export citation Add to Papers Other actions About this Book Reprints and Permissions Share Share this content on Facebook Share this content on Twitter Share this content on LinkedIn