1. Institute of Marine Research and Hjort Centre for Marine Ecosystem Dynamics; N-5817 Bergen Norway
2. Institute of Marine Research; N-5817 Bergen Norway
3. Centre for Ecological and Evolutionary Synthesis (CEES), Department of Biosciences; University of Oslo; PO Box 1066 Blindern N-0316 Oslo Norway
4. Institute of Marine Research; Austevoll Research Station; N-5392 Storebø Norway