Social versus genetic measures of reproductive success in sockeye salmon, Oncorhynchus nerka

In this paper, we assess the relationship between behavioural (social) and genetic mating success in sockeye salmon (Oncorhynchus nerka) and the frequency of multiple genetic partnering in both sexes. We introduced groups of 13 ripe adults (7 males, 6 females) into four spawning arenas in the Weaver Creek spawning channel, British Columbia, and monitored their behaviour until spawning was complete. Genetic fingerprints of adults and offspring were determined with microsatellites. Both males and females spawned with up to four different partners. Only 4 of 24 females mated predominantly with a single male. Behavioural measures of reproductive success in males (social dominance, time as consort, number of female partners) were strongly correlated with genetic reproductive success (proportion of offspring sired and number of females mated with) but explained only 33–40% of the variance in reproductive success. Only longevity (spawning life index) was correlated with indices of female reproductive success. Behaviour provides a practical means to assess reproductive success in males but will underestimate the reproductive success of some subordinate males. Female reproductive success is more difficult to assess, because most females spawn all their eggs and there are no obvious behavioural or genetic attributes that can be used as indices of success.