Sex‐biased dispersal in a salmonid fish: implications for growth rate and survival

Abstract

I tested the hypothesis that dispersal is sex‐biased in an unexploited population of brook trout (Salvelinus fontinalis Mitchill). Based on the assumptions that trout are promiscuous and that reproductive success is limited primarily by either number of mates (males) or fecundity (females), I predicted that males would disperse greater distances than females. I also tested the hypothesis that trout populations comprise stationary and mobile individuals, predicting that males have greater mobility than females. Based on a 5‐year, mark‐recapture study of almost 1000 fish, there was strong support for the hypothesis of male‐biased dispersal. On average, males dispersed 2·5 times as far as females; during the spawning period only, male dispersal exceeded that by females almost four‐fold. Both sexes were heterogeneous with respect to movement, with a lower incidence of mobility among females than males. Sex differences in dispersal may have been responsible for sex biases in seasonal growth. Importantly, growth rate was positively associated with survival, independent of the effects of body size. Sex‐biased dispersal may (1) reduce mate competition among male kin, (2) decrease the probability that males will reproduce with related females, and (3) have important implications for life history.