Should I stay or should I go? Understanding the shapeshifting rainbow trout/steelhead.

Published online
23 Sep 2015
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Reeves, G.
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Publication language
USA & Oregon


Steelhead are the sea-going form of Oncorhynchus mykiss. Rainbow trout, also O. mykiss, remain in freshwater. Each form, or life-history, can produce offspring of the other, but the mechanism for this and potential effects that climate change may have on the species are poorly understood. Forest Service scientist Gordie Reeves, along with colleagues from other federal agencies and Oregon State University, conducted a series of studies to better document the biological processes that affect the life-history expression of O. mykiss. They found that standard metabolic rate and lipid levels play important roles: those fish with higher metabolisms and lower lipid levels tended to be steelhead, while those with lower metabolisms and higher lipid levels tended to be resident rainbows. Reeves' findings challenge the existing theory that faster growing individuals of the species tend to be seagoing steelhead. The research examined the effects of water temperature on life-history expression within the species. These findings offer clues about how climate change may affect the rainbow/steelhead ratio in the years ahead. This research informs habitat improvement efforts and protection for steelhead populations, which are listed under the Endangered Species Act. It provides context, revealing how their life-history is interconnected with that of rainbow trout, which are not listed.

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