Competitive Differences between Newly Emerged Offspring of Captive‐Reared and Wild Coho Salmon

We investigated competition among newly emerged fry from captive‐reared and wild female coho salmon Oncorhynchus kisutch by conducting dominance challenges and growth and survival experiments in laboratory stream channels. Newly emerged fry from captive‐reared females won a significant majority (72.7%) of dyadic dominance challenges against fry from wild females. In a growth and survival experiment conducted from emergence to 30 d postemergence, fewer captive brood fry died of apparent starvation when food was limited than wild fry, further suggesting a competitive advantage for the captive brood fry. All fry used in the study were paternal half‐sibs, so observed differences between captive brood and wild fry were attributed to the maternal parent. We hypothesize that fry coloration resulting from differences in egg color between wild and captive‐reared females may have influenced the observed competitive asymmetries. If so, such differences might be ameliorated by changes in husbandry practices such as providing more natural diets.