Title: Use of Wave Gliders in Acoustic Tracking of Humpback Whales

The Society for Marine Mammalogy: 20th Biennial Conference

A proof-of-concept experiment was conducted during February 2013 to track singing humpback whales using a sparse array of hydrophones deployed on autonomous, wave-powered vehicles. Three Liquid Robotics Inc.® Wave Gliders®, each equipped with a hydrophone and VHF radio transmitter, held station at 1km intervals in a linear array off the Kohala coast of Hawai'i Island. A team of experienced shore-based observers collected data including 1.) whale location data using a theodolite. Visual tracking data was used to ground-truth the acoustic results; 2.) whale behavior, using quantitative behavioral sampling; and 3.) environmental conditions, using standardized observational protocols. The team also listened to and made digital recordings of real-time sounds from the hydrophone array. Using xBat software, acoustic data were subsequently analyzed using standard hyperbolic cross-fixing location methods to determine localizations of singing whales. These acoustic localizations matched the visual whale sighting positions well, with differences in ranges and bearings of ~ 4%. This study constitutes the first use of a hydrophone array deployed with multiple autonomous vehicles to acoustically track marine mammals. Propelled by wave energy and serving as a platform for solar-powered instrumentation, Wave Gliders are persistent, ecologically friendly, quiet, and can be operated at the relatively low cost compared to traditional manned research vessels. Unlike moorings, these autonomous vehicles have an advantage in that they can be directed to change array geometry, thereby removing left-right ambiguity and autonomously sent to remote areas without needing installation of bottom-mounted fixed gear. This technology has the potential to dramatically al alter how the world's oceans are studied and monitored.