title: Migration confers survival benefits against avian predators for partially migratory freshwater fish.
abstract: The importance of predation risk in shaping patterns of animal migration is not well studied, mostly owing to difficulties in accurately quantifying predation risk for migratory versus resident individuals. Here, we present data from an extensive field study, which shows that migration in a freshwater fish (roach, Rutilus rutilus) that commonly migrates from lakes to streams during winter confers a significant survival benefit with respect to bird (cormorant, Phalacrocorax carbo spp.) predation. We tagged over 2000 individual fish in two Scandinavian lakes over 4 years and monitored migratory behaviour using passive telemetry. Next, we calculated the predation vulnerability of fish with differing migration strategies, by recovering data from passive integrated transponder tags of fish eaten by cormorants at communal roosts close to the lakes. We show that fish can reduce their predation risk from cormorants by migrating into streams, and that probability of being preyed upon by cormorants is positively related to the time individuals spend in the lake during winter. Our data add to the growing body of evidence that highlights the importance of predation for migratory dynamics, and, to our knowledge, is one of the first studies to directly quantify a predator avoidance benefit to migrants in the field.
authors: National Institute of Aquatic Resources, Technical University of Denmark (DTU), , Vejlsøvej 39, Silkeborg 8600, Denmark. ck@aqua.dtu.dk
authors: Christian
authors: C
authors: Skov
authors: Ben B
authors: BB
authors: Chapman
authors: Henrik
authors: H
authors: Baktoft
authors: Jakob
authors: J
authors: Brodersen
authors: Christer
authors: C
authors: Brönmark
authors: Lars-Anders
authors: LA
authors: Hansson
authors: Kaj
authors: K
authors: Hulthén
authors: P Anders
authors: PA
authors: Nilsson
mesh_terms: D025041:Animal Migration; D000818:Animals; D001717:Birds / Q000502:physiology; D003530:Cyprinidae / Q000502:physiology*; D003718:Denmark; D056145:Freshwater Biology / Q000379:methods*; D060106:Lakes; D016014:Linear Models; D011157:Population Dynamics; D011235:Predatory Behavior; D012307:Risk Factors; D012621:Seasons; D013045:Species Specificity; D016019:Survival Analysis; D013997:Time Factors