1. Norwegian Institute for Nature Research (NINA), Fakkelgården; 2624 Lillehammer Norway
2. Centre for Ecological and Evolutionary Synthesis (CEES), Department of Biosciences; University of Oslo, P. O. Box 1066 Blindern; 0316 Oslo Norway
3. Norwegian University of Life Sciences; Faculty of Environmental Sciences and Natural Resource Management, P. O. Box 5003 NMBU, 1432; Ås Norway
4. National Oceanic and Atmospheric Administration, National Marine Fisheries Service; Northwest Fisheries Science Center, Fish Ecology, 2725 Montlake Boulevard East; Seattle WA 98112 U.S.A.