Speed of Steelheads' Change a Surprise

Article excerpt

Byline: The Register-Guard

Researchers at Oregon State University say they are surprised by the speed of evolution and natural selection that takes place among salmonids in adapting to hatcheries.

The effect of hatcheries on steelhead is so profound, a recent study shows, that in just one generation traits are selected that allow fish to survive and prosper in the hatchery environment, at the cost of their ability to thrive and reproduce in a wild environment.

The findings were published last week in Proceedings of the National Academy of Sciences. They confirm that a primary effect of hatcheries is a change in fish genetics, as opposed to a temporary environmental effect.

"We've known for some time that hatchery-born fish are less successful at survival and reproduction in the wild," Michael Blouin, a professor of zoology at Oregon State University, said in a news release. "However, until now, it wasn't clear why. What this study shows is that intense evolutionary pressures in the hatchery rapidly select for fish that excel there, at the expense of their reproductive success in the wild."

Hatcheries are efficient at producing fish for harvest, the researchers said, but this and other studies continue to raise concerns about the genetic impacts that hatchery fish may have when they interbreed with wild salmon and steelhead, and whether or not they will help wild salmonid runs to recover.

The findings were based on a 19-year genetic analysis of steelhead in Oregon's Hood River. It examined why hatchery fish struggle to reproduce in wild river conditions, which has been made clear in previous research. Some of the possible causes explored were environmental effects of captive rearing, inbreeding among close relatives, and unintentional "domestication selection," or the ability of some fish to adapt to the unique hatchery environment.

The study confirmed that domestication selection was at work.

When thousands of smolts are born in the artificial environment of a hatchery, those that survive best are the ones that can deal, for whatever reason, with hatchery conditions. …