1. Department of Aquatic Resources, Institute of Coastal Research, Swedish University of Agricultural Sciences, Skolgatan 6, SE-742 42 Öregrund, Sweden
2. Department of Aquatic Resources, Swedish University of Agricultural Sciences, Box 7018, SE-750 07 Uppsala, Sweden
3. Lammi Biological Station, University of Helsinki, Pääjärventie 320, FI-16900 Lammi, Finland
4. Ecosystems and Environment Research Programme, Faculty of Biological and Environmental Sciences, University of Helsinki, P.O. Box 65, FI-00014 Helsinki, Finland
5. Department of Environmental and Biological Sciences, University of Eastern Finland, P.O. Box 111, FI-80101 Joensuu, Finland
6. Natural Resources Institute Finland, Aquatic Population Dynamics, P.O. Box 2, FI-00791 Helsinki, Finland