title: Migration costs drive convergence of threshold traits for migratory tactics.
abstract: Partial migration of some, but not all, members of a population is a common form of migration. We evaluated how migration costs influence which members migrate in 10 populations of two salmonid species. The migratory patterns of both species were evaluated based on the size at maturity for resident males, which is the threshold trait that determines the migratory tactics used within a population. In both species, this size was smaller in males located further from the sea, where migration costs are presumably higher. Moreover, the threshold sizes at maturity in males were correlated between both species. Our results suggest that migration costs are a significant convergent selective force on migratory tactics and life-history traits in nature.
authors.affiliation: Division of Marine Bioresource and Environmental Science, Graduate School of Fisheries Sciences, Hokkaido University, , Hakodate 041-8611, Japan, Hokkaido National Fisheries Research Institute, Fisheries Research Agency, , Sapporo 062-0922, Japan.
authors.forename: Genki
authors.initials: G
authors.lastname: Sahashi
authors.forename: Kentaro
authors.initials: K
authors.lastname: Morita
mesh_terms: D025041:Animal Migration; D000818:Animals; D049628:Body Size; D008297:Male; D045483:Rivers; D012487:Salmonidae / Q000502:physiology*; D012641:Selection, Genetic; D012741:Sexual Maturation
keywords: alternative migratory tactics; life-history traits diversity; migration distance; partial migration; salmonid fish; selection