Fish Migrate to Escape Predators

Mar. 1, 2013 — By individually tagging fish in a lake and following their movements, a research team has shown that migration is a very effective defence against being eaten.

Each year billions of animals make annual migrations to escape adverse environmental conditions. Migration is a spectacular and important biological phenomenon, but studying what drives animals to make these arduous journeys is extremely difficult. Food and climate are classic explanations for animal migration, but the idea that animals migrate to escape predators is less well studied. Senior scientist Christian Skov, DTU Aqua and colleagues from Lund University, Sweden and Eawag, Switzerland now present direct evidence that migrants benefit by evading predators.

The biologists tagged more than 2000 individual fish (roach, Rutilus rutilus) in two Danish lakes over 4 years and monitored migratory behaviour using passive telemetry. Next, they calculated the predation vulnerability of fish with differing migration strategies, by recovering data from passive integrated transponder tags of fish eaten by cormorants (Phalacrocorax carbo spp.) at communal roosts close to the lakes. The results are published in Biology Letters.

Continued:  http://www.sciencedaily.com/releases/2013/03/130301034605.htm