Social versus genetic measures of reproductive success in sockeye salmon, Oncorhynchus nerka Ladan Mehranvar, 1 * Michael Healey, 2 Anthony Farrell 4 and Scott Hinch 3 1 Department of Zoology, 2 Institute for Resources, Environment and Sustainability, 3 Department of Forest Sciences, University of British Columbia, Vancouver and 4 Department of Biology, Simon Fraser University, Burnaby, Canada ABSTRACT 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. Keywords: consort, dominance, genetic mating success, life span, partners, sockeye salmon, social mating success. INTRODUCTION Many conclusions concerning reproductive strategies and mate choice in animals are based on inferences about paternity and maternity derived from behavioural observations (Clutton-Brock, 1988). Females are frequently considered to be the limiting sex, creating an intense struggle among the males for access to them (Darwin, 1871). Because fighting for access to females is costly, the victor of male–male competition is often superior in quality and one which females may prefer (Cox and Leboeuf, 1977; Berglund et al., 1996). On the other hand, females may seek to mate with multiple partners for a variety of social and * Address all correspondence to Ladan Mehranvar, Department of Zoology, University of British Columbia, Vancouver, BC V6T 1Z4, Canada. e-mail: ladan@zoology.ubc.ca Consult the copyright statement on the inside front cover for non-commercial copying policies. Evolutionary Ecology Research, 2004, 6: 1167–1181 © 2004 Ladan Mehranvar