Autonomous Detection of Baleen Whales Using Wave Gliders



Autonomous platforms provide a persistent monitoring capability that cannot be replicated by conventional methods for assessing marine mammal occurrence.  Traditional visual surveys are expensive, inefficient, and limit the time scales of study, whereas passive acoustic monitoring from autonomous platforms allows round-the-clock monitoring over time scales of months to years and offers the possibility of real-time reporting of detection data.  We have recently integrated (1) detection and classification software for low-frequency baleen whale calls, (2) the WHOI-built DMON acoustic recording and processing instrument, and (3) several autonomous platforms that operate silently (electric ocean gliders, profiling floats, and “stretch hose” moorings) to allow baleen whale calls to be detected, classified, and reported in near real time to a shore-based computer via a satellite communication link.  With support from the WHOI Marine Mammal Center, we plan to extend this capability to a new class of autonomous platform, the Liquid Robotics wave glider, which has unique capabilities and challenges.  Unlike all other autonomous platforms, the wave glider’s endurance is theoretically unlimited, so it can remain at sea indefinitely while collecting and relaying information.  However, because it remains at the surface and uses fins for propulsion, its operation is plagued by wave and mechanical noise; therefore, low-frequency acoustic monitoring from this platform is challenging.  We plan to leverage recent developments in the WHOI Acoustic Communications group to integrate a DMON instrument in a wave glider and test a towed hydrophone that will substantially reduce this noise and its impact on baleen whale call detections.  With this novel capability, we plan to ultimately deploy wave gliders in remote and harsh environments, such as the Bering Sea, to monitor the occurrence and distribution of endangered baleen whales.