Tracking large marine predators in three dimensions: the Realtime Acoustic Tracking System

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A RATS buoy at sea.

Terry Hammar (WHOI AOP&E) recovers a RATS buoy.

Principal Investigators:  Mark Baumgartner (WHOI Biology) and Lee Freitag (WHOI AOP&E)

Engineering Support:  Jim Partan (WHOI AOP&E), Keenan Ball (WHOI AOP&E), and Ken Prada (WHOI AOP&E retired)

The foraging behavior of top marine predators is difficult to observe because it nearly always occurs below the sea surface.  The advent of archival tags that are attached to animals and record depth-of-dive information has improved our understanding of one-dimensional (1D) diving behavior.  However, foraging behavior is not 1D, it is three-dimensional (3D).  Recent advances in tagging technology has begun the transition from 1D to 3D observations, however the resulting instrumentation cannot separate motions of the tagged animal from that of the ocean and it cannot provide 3D location data in real-time.  We have developed a system with which marine predators can be tracked unambiguously in 3D and in real time.  The system consists of a free-floating array of GPS-linked hydrophone buoys that allow the position of an animal equipped with an acoustic transmitter to be determined based on acoustic time-of-arrival information.  The time-of-arrival data is relayed from the buoys to a mother ship immediately upon receipt of each acoustic pulse from the transmitter (nominally received once per second) so that a position can be determined continuously in real time.  The Realtime Acoustic Tracking System (RATS) was designed to examine the foraging behavior of baleen whales, but it can be applied to tracking the short-term movements of other large marine predators as well.

Support for this project provided by a Cecil H. and Ida M. Green Technology Innovation Award and the National Fish and Wildlife Foundation.

Publications and Presentations
Baumgartner, M.F., L. Freitag, J. Partan, K. Ball and K. Prada. 2008. Tracking large marine predators in three dimensions: the Real-time Acoustic Tracking System. IEEE Journal of Oceanic Engineering 33:146-157.

van der Hoop, J.M. and M.F. Baumgartner.  2010.  Estimating swimming paths of tagged baleen whales using an acoustic tracking system.  The American Cetacean Society's 12th International Conference.  Seaside, California.  November 12-14, 2010


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Last updated April 18, 2011
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