Journal of Aquaculture Research & Development

Production of wild phenotypes under fish culture conditions for liberation into rivers

International Conference on Aquaculture & Fisheries

July 20-22, 2015 Brisbane, Australia

Schreck, Carl B 1, Billman E J, Unrein J, Chitwood R, Whitman L D, Schroeder R K, Sharpe C S, Kimmel C, McGibben N, Brignon B, Munakata A, Cogliati K and Noakes D L G

Posters-Accepted Abstracts: J Aquac Res Development

Abstract:

Fish culture can be a useful for reestablishing depleted populations of endangered fishes. It is also useful for providing study animals for release into the wild when wild stocks are unavailable for such purposes. We present findings from research on juvenile Chinook salmon Oncorhynchus tshawytscha, Steelhead trout Oncorhynchus mykiss and bull trout Salvelinus confluentus, demonstrating that special diets, feeding strategies, fish densities and temperature in-tank structure are all viable tools that result in phenotypes that match those of wild fish more closely than those reared under typical aquaculture conditions. For example, wild fish can display considerable variation in downstream-movement life history tactics. Chinook salmon reared in circular tanks self-sort into surface and bottom oriented groups starting just after per os feeding begins. Morphometric analysis suggests that the surface phenotype is similar in shape to wild fall migrants and parr from downstream sites. The benthic phenotype fish are similar to wild spring migrants and fish collected concurrently up-river. Bone structure analysis of the head suggests that these differences rest with the jaw. Plasma sodium, gill Na/K ATPase and boldness analyses also revealed early effects of rearing conditions. Behavioral tests found that minute (<0.5oC) temperature decrease results in downstream movement by various species of anadromous salmonids. Similar downstream movement was displayed by surface-oriented laboratory Chinook in the fall (concurrent with timing of the fall out migration of wild Chinook; bottom-oriented Chinook had significantly less movement at this time. We suggest that downstream movement of juveniles soon after emergence is associated with differentiation in the expression of life history variation. This contention is also supported by movement studies in large artificial streams and in a small tributary stream. Structure in rearing tanks also affects performance of bull trout. Fish reared with some simple structure had significantly larger brains, were bolder and were better predators like wild fish that were also tested than fish reared in typical hatchery troughs. Body shape, coloration and fin condition are strongly influenced by feeding tactic, structure and density.