Reproductive behavioral interactions between wild and captively reared coho salmon (Oncorhynchus kisutch)

Captive rearing is an evolving strategy for restoring depleted salmon populations; it involves capturing wild juvenile salmon from natural streams; rearing them in captivity to adulthood, and then releasing them as adults back into their natal streams to spawn naturally. The conservation benefit of captive rearing is that it bypasses the typically high smolt-to-adult mortality experienced by wild populations, but its success as a restoration strategy depends upon the ability of captively reared salmon to spawn and reproduce in natural streams. In an experimental channel, wild males dominated captively reared males of similar size in 86% of spawning events. Both wild and captively reared females attacked captively reared males more frequently than wild males, indicating a preference for wild over captively reared males, although the interplay between male dominance and Female mate choice was unclear. Wild females established nesting territories earlier and constructed more nests per individual than captively reared females of similar size, suggesting a competitive advantage for wild females. Nevertheless, captively reared coho salmon demonstrated the full range of behaviors shown by wild coho salmon of both sexes and the ability to spawn naturally. (C) 1997 International Council for the Exploration of the Sea.