Animal migration is a wide-spread phenomenon that has fascinated humans since before the beginning of science. This fascination has lead to numerous studies on migrations patterns in almost all kinds of organism groups, from microscopic dinoflagellates to the largest baleen whales, with the vast majority of these studies describing and explaining the patterns and underlying mechanisms of the migrations. It has become clear that the patterns of animal migration to a great extent are shaped by the dynamics of their surrounding ecosystem. As migration ultimately leads to a temporal and spatial variation in the presence and absence of species, it is logical to expect that migration will in turn have feed-back effects on ecosystem dynamics. However, only recently focus has been paid to the potential effects of migration on ecosystem dynamics, and studies including both how animals are affected by and themselves affect ecosystem dynamics are rare.

Results/Conclusions

In this talk, I present novel empirical results showing that variation in ecosystem dynamics shape seasonal migration of cyprinid fish and that the fish migration in turn has feed-back effects on lake ecosystem structure and dynamics. In a six-year study on roach migrating from their home lake during autumn or early winter to seek predation refuge in streams we found that the migrating proportion of the population increased with temperature during summer. Moreover, the timing of migration depended on temperature during fall, most likely due to variation in the trade-off between predation risk and potential growth rate. We also found that the mean size of zooplankton in the lake increased with the proportion of fish being out of the lake during winter, most likely as a consequence of decreased predation pressure. These results significantly contribute to our understanding of the interplay between migration and ecosystem dynamics, and should be seen in light of altered animal migration pattern in a globally warmer future.