Field Notes: a Northwest nature blog
One of the reasons many of us live in the Pacific Northwest is the natural wonders that amaze us all. On this blog Seattle Times writers and photographers will share their explorations of the natural world from snowcaps to whitecaps. Write us at firstname.lastname@example.org with your own sightings, questions and wonders to share.
Study: Hatcheries drive rapid evolutionary change in fish
Posted by Hal Bernton
Wind River steelhead. John McMillan, photo
Researchers have found that intense evolutionary pressures exerted on hatchery fish can alter their traits in just one generation, improving their prospects for survival in the confines of concrete rearing ponds but reducing their ability to reproduce successfully in the wild.
These findings by four Oregon scientists were based on a 19-year genetic analysis of steelhead in Oregon's Hood River, and published last week in the Proceedings of the National Academy of Sciences.
"We expected to see some of these changes after multiple generations," said Mark Christie, an Oregon State University post-doctoral research associate and lead author of the study. "To see these changes happen in a single generation was amazing. Evolutionary change doesn't always take thousands of years."
The study builds on concerns that hatchery fish, as they interbreed with wild salmon and steelhead, weaken efforts to rebuild natural runs. The study found that the hatcheries actually impact the genetics of the fish, rather than creating temporary environmental effects on the steelhead.
But it's not clear just what specific traits are being passed on to the hatchery fish. They could, for example, be picking up traits that enable them to better survive the crowding in rearing ponds, or perhaps traits that affect their growth rates, according to Christie.
"The next research is to focus on exactly what these traits are," said Christie, who worked on the study with two other OSU scientists, Melanie Marine and Michael Blouin, and Oregon Department of Fish and Wildlife biologist Rod French.
The researchers say it is important to find the mechanisms that reduce the fitness of these fish in the wild to determine if, when and how captive breeding programs should be applied for conservation and management purposes.
If hatcheries affect only a few genetic traits, then it might be possible to figure out a way to breed hatchery fish that don't have those traits and could better survive in the wild, Christie said. But if the research shows that hundreds of traits are affected by the hatcheries, then that task would be difficult.
The researchers also caution that it is unclear how much the study of the Hood River steelhead can be widened to determine the effects of other hatcheries or other salmon species.
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