Seasonal migration in a freshwater fish: causes and consequences – Biologisk Institut - Københavns Universitet

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Seasonal migration in a freshwater fish: causes and consequences

Speaker: Professor Christer Brönmark, Department of Biology, Lund University

Host: Associate Professor Dean Jacobsen, Freshwater Biology Section, BIO-UCPH

In this project we study the causes and consequences of seasonal migration in a freshwater cyprinid fish, the roach Rutilus rutilus, in lakes in Sweden and Denmark. In the autumn, roach migrate from the lake into streams and wetlands and then return to the lake in early spring. We have shown that this migration is driven by a seasonal change in a cost/benefit trade-off, where the predation costs and growth benefits change seasonally in the lake and stream habitats. The migration is partial and individual properties such as size, condition and personality affects an individual’s migratory drive. Differences in the density and biomass of migratory roach among years may further have repercussions on the dynamics of the whole ecosystem, specifically by affecting the zooplankton dynamics during spring. At present, we are investigating how differences in immune defence affect migratory propensity and overwinter survival.