title: Sizing up your enemy: individual predation vulnerability predicts migratory probability.
abstract: Partial migration, in which a fraction of a population migrate and the rest remain resident, occurs in an extensive range of species and can have powerful ecological consequences. The question of what drives differences in individual migratory tendency is a contentious one. It has been shown that the timing of partial migration is based upon a trade-off between seasonal fluctuations in predation risk and growth potential. Phenotypic variation in either individual predation risk or growth potential should thus mediate the strength of the trade-off and ultimately predict patterns of partial migration at the individual level (i.e. which individuals migrate and which remain resident). We provide cross-population empirical support for the importance of one component of this model--individual predation risk--in predicting partial migration in wild populations of bream Abramis brama, a freshwater fish. Smaller, high-risk individuals migrate with a higher probability than larger, low-risk individuals, and we suggest that predation risk maintains size-dependent partial migration in this system.
authors.affiliation: National Institute of Aquatic Resources, Technical University of Denmark (DTU), Vejlsøvej 39, Silkeborg 8600, Denmark. ck@aqua.dtu.dk
authors.forename: Christian
authors.initials: C
authors.lastname: Skov
authors.forename: Henrik
authors.initials: H
authors.lastname: Baktoft
authors.forename: Jakob
authors.initials: J
authors.lastname: Brodersen
authors.forename: Christer
authors.initials: C
authors.lastname: Brönmark
authors.forename: Ben B
authors.initials: BB
authors.lastname: Chapman
authors.forename: Lars-Anders
authors.initials: LA
authors.lastname: Hansson
authors.forename: P Anders
authors.initials: PA
authors.lastname: Nilsson
mesh_terms: D025041:Animal Migration; D000818:Animals; D003530:Cyprinidae / Q000235:genetics / Q000254:growth & development / Q000502:physiology*; D003718:Denmark; D020387:Food Chain; D014644:Genetic Variation