Exploratory behavior of dispersers within a metapopulation of sockeye salmon

Abstract

In many anadromous fishes, such as salmon, most individuals return (home) to their natal habitat to spawn. However, experimental and observational studies of the homing and spawning behavior of hatchery-raised salmon have indicated that their search for high-quality spawning habitat can overcome their homing tendency. Nevertheless, the extent to which dispersal between populations is motivated by habitat selection versus navigational errors during the homing process is not well understood, especially in wild populations. Here we investigated whether dispersers between populations of stream-spawning sockeye salmon successfully homed to their natal streams before dispersing. We tracked the daily locations of all adult salmon spawning in 2 proximate streams and determined the dispersal status for each individual by comparing its chosen spawning stream with that of its parents (as determined by genetic parentage reconstruction). Dispersers were often observed in or at the mouths of their natal streams before spawning elsewhere, whereas philopatric individuals were rarely observed in or at the mouths of their non-natal streams. This result suggests that dispersers were exposed to multiple spawning habitats, potentially allowing local environmental or demographic conditions to influence patterns of dispersal within the metapopulation.