Biology Letters
Restricted accessAnimal behaviour

Migration confers survival benefits against avian predators for partially migratory freshwater fish

Christian Skov

Christian Skov

National Institute of Aquatic Resources, Technical University of Denmark (DTU), Vejlsøvej 39, Silkeborg 8600, Denmark

[email protected]

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,
Ben B. Chapman

Ben B. Chapman

Department of Biology/Aquatic Ecology, Lund University, Ecology Building, Lund 22362, Sweden

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,
Henrik Baktoft

Henrik Baktoft

National Institute of Aquatic Resources, Technical University of Denmark (DTU), Vejlsøvej 39, Silkeborg 8600, Denmark

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,
Jakob Brodersen

Jakob Brodersen

Department of Fish Ecology and Evolution, Centre of Ecology, Evolution and Biochemistry, EAWAG Swiss Federal Institute of Aquatic Science and Technology, Seestrasse 79, Kastanienbaum 6047, Switzerland

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Christer Brönmark

Christer Brönmark

Department of Biology/Aquatic Ecology, Lund University, Ecology Building, Lund 22362, Sweden

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Lars-Anders Hansson

Lars-Anders Hansson

Department of Biology/Aquatic Ecology, Lund University, Ecology Building, Lund 22362, Sweden

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Kaj Hulthén

Kaj Hulthén

Department of Biology/Aquatic Ecology, Lund University, Ecology Building, Lund 22362, Sweden

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and
P. Anders Nilsson

P. Anders Nilsson

Department of Biology/Aquatic Ecology, Lund University, Ecology Building, Lund 22362, Sweden

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    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.

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