Fish in Danish lakes substantially reduce their risk of being eaten by making annual migrations. Thus, predation — alongside food and weather — may drive such movements.

Credit: JAKOB BRODERSEN

Christian Skov at the Technical University of Denmark in Silkeborg and his team implanted 2,219 roach (Rutilus rutilus, pictured) with tags during a 4-year period, and monitored individuals' migratory behaviour. Most of the tags recovered from a nearby colony of cormorants (Phalacrocorax carbo) were from fish that were last recorded as being in lakes. Roach that spent most time in the lakes during winter were substantially more likely to be eaten by cormorants than those that moved to streams.

This study provides direct evidence that animals can benefit from migration by reducing their risk from predators.

Biol. Lett. 9, 20121178 (2013)