1. Department of Biological and Environmental Sciences Göteborg University Box 461 405 30 Göteborg Sweden
2. Smedjebacksvägen 13 SE‐771 90 Ludvika Sweden
3. National Oceanic and Atmospheric Administration National Marine Fisheries Service Northeast Fisheries Science Center Milford Laboratory 212 Rogers Avenue Milford Connecticut06460 USA
4. Department of Marine Sciences University of Connecticut 1080 Shennecossett Road Groton Connecticut06340 USA