1. Food and Environment Research Agency, Sand Hutton, York YO41 1LZ, UK
2. Current address: Department of Ecological Modeling, UFZ Helmholtz Centre for Environmental Research, Permoserstraße 15, 04318 Leipzig, Germany
3. Finnish Game and Fisheries Research Institute, Turku Game and Fisheries Research, Itäinen Pitkäkatu 3 A, FI-20520 Turku, Finland
4. Finnish Game and Fisheries Research Institute, Helsinki Game and Fisheries Research, P.O. Box 2, FI-00791 Helsinki, Finland