1. Institute of Marine Research , PO Box 1870, N-5817 Bergen , Norway
2. Baltic Sea Centre, Stockholm University , 106 91 Stockholm , Sweden
3. Department of Aquatic Resources, Institute of Coastal Research, Swedish University of Agricultural Sciences , 750 07 Uppsala , Sweden
4. Centre for Environment, Fisheries and Aquaculture Science, Lowestoft Laboratory , Pakefield Road, Lowestoft, Suffolk NR33 0HT , UK
5. Department of Aquatic Resources, Institute of Marine Research, Swedish University of Agricultural Sciences , SE-453 30 Lysekil , Sweden
6. Swedish Institute for the Marine Environment (SIME), University of Gothenburg , 405 30 Gothenburg , Sweden