I am interested in how prey perceive and respond to stress induced by their natural predators. During my Masters project in Aquatic Ecology at Lund University, I empirically tested how perceived predation risk affects the migratory propensity of a partial migratory fish, the roach (Rutilus rutilus). In the investigated lake and similar systems, parts of the cyprinid fish populations are migrating into lake-connected streams in autumn, when temperature drops and the abundance of food decline (zooplankton). This migratory pattern can be explained by a trade-off between predator avoidance and growth potential, where lake habitat offers an overall better growth potential but possess a greater risk due to relatively higher number of pisciviorous birds and fish. Through a combined field and laboratory study in the season of 2013/2014 we were able to show that a key-predator (pike) within the lake-habitat acts as a strong driver on the migratory decision. Roach reared in mesocosms together with pike, and, hence, perceived greater environmental risk, had higher probability to migrate than conspecifics living in a predator-free environment prior to the migratory season.
In this season we are taking this hypothesis of predator-driven migratory plasticity to the next level by studying the underlying physiological mechanism. More specifically we study how changes in cortisol affects migratory behaviour in roach. During the autumn 2015 nearly 600 individual roach from the lake habitat were caught and their physiological stress levels manipulated using small-sized implants, containing either cortisol, metyrapone (a cortisol inhibitor) or sham (cacao butter). Further, we inserted a small PIT-tag and by the use of passive telemetry we are now following the migratory pattern of individual fish.
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