1. Institute for Terrestrial and Aquatic Wildlife ResearchUniversity of Veterinary Medicine Hannover Foundation Werftstr. 6, 25761 Büsum Germany
2. Marine Mammal and Turtle DivisionSouthwest Fisheries Science CenterNational Marine Fisheries ServiceNational Oceanic and Atmospheric Administration 8901 La Jolla Shores Drive La Jolla California 92037 USA
3. Marine Mammal and Turtle DivisionSouthwest Fisheries Science CenterNational Marine Fisheries ServiceNational Oceanic and Atmospheric Administration 110 Shaffer Rd Santa Cruz California 95060 USA
4. IMARES Wageningen Institute for Marine Resource & Ecosystem Studies Ankerpark 27, 1781 AG Den Helder The Netherlands
5. Royal Belgian Institute of Natural Sciences (RBINS)Operational Directorate Nature 3de en 23ste Linieregimentsplein, B‐8400 Ostend Belgium
6. Department of BioscienceAarhus University Frederiksborgvej 399, DK‐4000 Roskilde Denmark
7. Department of Aquatic Ecology and Water Quality Management Wageningen UR, PO Box 47, 6700AA Wageningen The Netherlands