1. Department of Biology; University of Eastern Finland; PO Box 111 FI-80101 Joensuu Finland
2. Department of Biological and Environmental Sciences; University of Jyväskylä; PO Box 35 FI-40014 Jyväskylä Finland
3. Finnish Game and Fisheries Research Institute; Itäinen Pitkäkatu 3 FI-20520 Turku Finland