1. School of Science and Technology; University of New England; Armidale NSW 2351 Australia
2. George Perkins Marsh Institute; Clark University; 950 Main Street Worcester Massachusetts 01610 USA
3. Marine Mammal and Turtle Division; Southwest Fisheries Science Center; National Marine Fisheries Service; NOAA; 8901 La Jolla Shores Drive La Jolla California 92037 USA
4. Department of Mathematics and Statistics; University of Otago; P.O. Box 56 Dunedin New Zealand
5. Panama City Laboratory; Southeast Fisheries Science Center; National Marine Fisheries Service; NOAA; 3500 Delwood Beach Road Panama City Florida 32408 USA
6. Department of Biological Sciences; University of Rhode Island; 120 Flagg Rd Kingston Rhode Island 02881 USA
7. Biology Department; San Diego State University; 5500 Campanile Drive San Diego California 92182-4614 USA