Captive Rearing Environment Effects Bull Trout Phenotype: Implications for Recovery Strategies

Rearing environment can influence brain development and animal behavior.  Fishes reared in conventional hatchery environments have smaller brains and brain regions than conspecifics reared in complex hatchery or wild environments.  Differences in brain size of fish can give rise to variable life history trajectories and may influence cognition and behaviors essential for survival in wild environments.  Developmental and behavioral differences may influence the success of species conservation and recovery programs when fish are reared in captivity for release into the wild.  However, few studies have concurrently evaluated brain development and behavior in ESA listed salmonids.  Using magnetic resonance imaging, we show that conventional and complex hatchery rearing environments, and wild rearing environments influence brain development in threatened bull trout (Salvelinus confluentus) and results in differential expression of “boldness” and prey acquisition; two behaviors important for post-release survival in a reintroduction program.  Our results demonstrate that early rearing environment can be manipulated to rear a fish more similar to wild conspecifics which may affect the outcome of reintroduction and recovery programs for listed species.  We are in the process of incorporating this information into a structured decision model with an adaptive framework that will evaluate all bull trout reintroduction strategies.