1. Theoretical Biology Group, Centre for Ecological and Evolutionary Studies (CEES), University of Groningen, P.O. Box 11103, 9700 CC Groningen, The Netherlands
2. Department of Fish Ecology and Evolution, Eawag Centre of Ecology, Evolution and Biogeochemistry, Seestraße 79, 6047 Kastanienbaum, Switzerland
3. Department of Aquatic Ecology, Institute of Ecology and Evolution, University of Bern, Baltzerstraße 6, CH-3012 Bern, Switzerland
4. Sylvius Laboratory, Behavioural Biology, IBL, Leiden University, P.O. Box 9505, 2300 RA Leiden, The Netherlands
5. Behavioural Biology Group, Centre for Behaviour and Neurosciences, University of Groningen, P.O. Box 11103, 9700 CC Groningen, The Netherlands