Science Says

Wild steelhead remain the best hope for the future of the species.

by Scott Sadil

Epigenetics is not a word I generally use to hold up my end of the conversation. 

Nor, for that matter, is phenotype, methylation, somatic, genomics, or a host of other scientific terms used in a recent paper published by researchers from the Center for Reproductive Biology, School of Biological Sciences, at Washington State University.

But I do have some familiarity with, and interest in, steelhead – the West Coast’s sea-going version of rainbow trout, Oncorhyncus mykiss.

The WSU paper, published May 18 in Environmental Epigenetics under a title that would make even this long sentence blush, details research that shows how alterations in the “epigenetic programming” of hatchery-raised steelhead could account for their reduced fertility, diminished vigor, and lower survival rates compared to wild fish.

The research establishes a link between feeding practices that promote faster growth, as well as other environmental factors in fish hatcheries, and epigenetic changes found in the sperm and red blood cells of steelhead.

Epigenetics gets at the fact that although the genetic makeup of steelhead raised in either hatcheries or the wild remains the same (little different, for that matter, than yours and mine), measurable molecular and cellular changes are affected by different environmental conditions. 

“Despite being genetically very similar, steelhead trout raised under hatchery conditions don’t have the same level of health and survivability of wild-raised fish,” says Michael Skinner, co-author of the study. “This research provides a molecular explanation for why we are seeing these differences.

Implications of the study, however, reach far beyond the anecdotal evidence that many Northwest steelheaders already share about the perceived deficiencies of hatchery steelhead – how some of these fish, when hooked, can behave like listless dogs

Epigenetic changes, it turns out, are “heritable” – that is, they can be passed on from one generation to the next. This means that anywhere there are hatchery fish breeding with wild populations of steelhead – virtually everywhere in the Columbia River basin – you are altering the native, indigenous fish, a trajectory that doesn’t bode well for the future, and may tell us why so many steelhead populations are in such a sorry state today.

Wild steelhead populations have passed through eons of changes. They exist because of the species’s ability to adapt to changes in climate, changes in ocean conditions, changes in rainfall and river flows and every other challenge nature throws its way.

The return of steelhead to the North Fork of the Toutle River, following the annihilation caused by the explosion forty-one years ago of Mount St. Helens, seemed nothing short of a miracle. The reintroduction of hatchery fish to this watershed, years later, appeared woefully short-sighted at best.    

I’m happy to point out, however, that in 2014 the North Fork of the Toutle was designated a wild steelhead gene bank, ending the release of hatchery fish.

A growing number of fisheries biologists, anyway, have been arguing, for a long time now, that hatcheries don’t help.

Now the science says it may be a lot worse than that.


Gray’s Angling Editor Scott Sadil suspects he became a writer, not a scientist, because his seventh-grade English teacher, Miss Walters, was a lot cuter than his biology teacher, Mr. Webb.