Intra- and inter-specific competition and the reproductive success of sympatric Pacific salmon

Individual female Pacific salmon fight for breeding space with conspecific and heterospecific females. We evaluated the consequences of this competiti on on the reproductive success of sockeye (Oncorhynchus nerka), chum (Oncor hynchus keta), and pink salmon (Oncorhynchus gorbuscha) in the Weaver Creek spawning channel, British Columbia. We hypothesized that differences in bo dy size, relative abundance, and spawning date would influence the magnitud e of interspecific interactions. Reproductive success (survival rate of egg s to emigrating fry) of the most abundant species, sockeye, was strongly an d inversely correlated with conspecific abundance but not with the abundanc e of the other, less abundant species. Chum reproductive success was invers ely correlated with sockeye abundance but not with the abundance of the sca rce and smaller pink. Surprisingly, pink reproductive success was not corre lated with sockeye abundance and only marginally correlated with chum abund ance despite the fact that pink are smaller and spawn earlier than sockeye. Thus, intra- and inter-specific competition can substantially affect salmo n reproductive success, but the magnitude of the competitive effects may de pend on relative abundance, size, spawning date, and microhabitat preferenc es.