1. Tromsø Department, Institute of Marine Research Norwegian, PO Box 6404, 9294 Tromsø, Norway
2. Bergen Department, Institute of Marine Research Norwegian, PO Box 1870, 5817 Bergen, Norway
3. Department of Biology, University of Bergen, P.O. Box 7803, N-5020 Bergen, Norway
4. Runde Environmental Centre, Rundavegen 237, 6096 Runde, Norway