Dispersal strategies of juvenile pike (Esox lucius L.): influences and consequences for body size, somatic growth and trophic position.

Abstract

Individual variability in dispersal strategies, where some individuals disperse and others remain resident, is a common phenomenon across many species. Despite its important ecological consequences, however, the mechanisms and individual advantages of dispersal remain poorly understood. Here, riverine Northern pike (Esox lucius) juveniles (young-of-the-year and age 1+ year) were used to investigate the influence of body size and trophic position (at capture) on the dispersal from off-channel natal habitats, and the subsequent consequences for body sizes, specific growth rate and trophic position (at recapture). Individuals that dispersed into the river (‘dispersers’) were not significantly different in body size or trophic position than those remaining on nursery grounds (‘stayers’). Once in the river, however, the dispersers grew significantly faster than stayers and, on recapture, were significantly larger, but with no significant differences in their trophic positions. Early dispersal into the river was therefore not facilitated by dietary shifts to piscivory and the attainment of larger body sizes of individuals whilst in their natal habitats. These results suggest that there are long-term benefits for individuals dispersing early from natal areas via elevated growth rates and, potentially, higher fitness, with the underlying mechanisms potentially relating to competitive displacement.