1. Greeneridge Sciences, Inc., 5266 Hollister Avenue, Santa Barbara, California 93111, USA
2. Marine Physical Laboratory, Scripps Institution of Oceanography, University of California, San Diego, La Jolla, California 92093, USA
3. Marine Mammal Laboratory, Alaska Fisheries Science Center, National Marine Fisheries Service, National Oceanic and Atmospheric Administration, 7600 Sand Point Way Northeast, Seattle, Washington 98115, USA
4. Applied Physics Laboratory, University of Washington, Seattle, Washington 98105, USA
5. Centre for Research into Ecological and Environmental Modelling, School of Mathematics and Statistics, University of St Andrews, The Observatory, Buchanan Gardens, St Andrews, Fife KY16 9LZ, Scotland