1. School of Marine and Atmospheric Sciences; Stony Brook University; Stony Brook NY 11794-5000 USA
2. School of Aquatic and Fishery Sciences; University of Washington; Seattle WA 98195-5020 USA
3. Fisheries Centre; University of British Columbia; Vancouver BC Canada V6T 1Z4
4. Department of Biology; University of Washington; Seattle WA 98195-1800 USA
5. NERC Sea Mammal Research Unit; Gatty Marine Laboratory; University of St Andrews; St Andrews Fife KY16 8LB UK
6. Institut de Recherche pour le Développement; UMR EME-212, Centre de Recherche Halieutique Méditerranéenne et Tropicale; BP 171, 34203 Séte Cedex France
7. Department of Fisheries and Wildlife; Oregon State University; Corvallis OR 97331-4501 USA
8. University of Maryland; Center for Environmental Science; Cambridge MD 21613 USA
9. Department of Applied Mathematics and Statistics; University of California; Santa Cruz CA 95064 USA
10. CSIRO Marine and Atmospheric Research; Hobart Tasmania 7000 Australia
11. Institute of Marine and Antarctic Science; University of Tasmania; Sandy Bay Tasmania Australia
12. School of Marine Sciences; University of Maine; Walpole ME 04573 USA