1. Norwegian Institute for Nature Research, The Polar Environmental Centre, N-9296 Tromsø, Norway, National Veterinary Institute and Norwegian School of Veterinary Science, P.O. Box 8156 Dep., N-0033 Oslo, Norway, Norwegian Institute for Air Research, The Polar Environmental Centre, N-9296 Tromsø, Norway, SINTEF Fisheries and Aquaculture, 7465 Trondheim, Norway, Department of Zoology, University of Melbourne, Victoria 3010, Australia, Institute of Marine Research, Sykehusveien 23, NO-9019 Tromsø, Norway,...