Acoustic seagliders for monitoring marine mammal populations

A DMON digital acoustic monitoring device has been integrated into a Seaglider with the goal of passive, persistent acoustic monitoring of cetacean populations. The system makes acoustic recordings as it travels in a sawtooth pattern between the surface and up to 1000 m depth. It includes three hydrophones, located in the center of the instrument and on each wing. An onboard real-time detector has been implemented to record continuously after ambient noise has risen above a signal-to-noise (SNR) threshold level, and the glider transmits power spectra of recorded data back to a shore-station computer via iridium satellite after each dive. The glider pilot has the opportunity to set parameters that govern the amount of data recorded, thus managing data storage and therefore the length of a mission. This system was deployed in the vicinity of the Hawaiian Islands to detect marine mammals as an alternative or complement to conventional ship-based survey methods. System design and implementation will be described and preliminary results will be presented.