Document: MIC-3-84-12

Hatchery or wild: Effects of habitat enrichment on brain structures in rainbow trout (Oncorhynchus mykiss).

MARCHETTI, M.P.* and G.A.NEVITT

University of California, Davis. Davis CA 95616 USA ¹

Abstract:
Previous work has clearly demonstrated significant changes in fish behavior when individuals are raised in a hatchery environment versus rearing in a natural setting. The present study examined brain morphology of hatchery and wild-reared rainbow trout (Oncorhynchus mykiss) for differences in brain size. We examined two populations of wild fish and two hatchery strains. Using multiple analysis of covariance (MANCOVA) and analysis of covariance (ANCOVA) with standard length, sexual maturity and age, we found wild-reared fish have significantly larger brains per body size overall, and were specifically larger in the following regions: optic tectum, telencephalon, olfactory bulb and olfactory nerve. These results suggest the importance of early rearing environment on the natural development of fish brains. The hatchery fish we examined have reduced neurobiological structures but it may be possible to alter the hatchery rearing environment to more closely mirror a natural environment and thus lessen the negative impact hatchery fish have on dwindling wild stocks. This work has profound implications for the management, stocking and restoration of declining fish populations worldwide. The work also suggests the possibility of an index of salmonid brain morphology that would provide concrete comparisons of hatchery and wild fish brains and essentially provide an asessment tool for evaluation of improved hatchery procedures.

Keywords: hatchery, salmonid, restoration, brain

This abstract is being presented at: 1:45 PM in session:
Oral Session #62: Freshwater Fish Ecology.