Speculation about the decline of pure cutthroat trout due to hybridization has been around since the ’50s. Meantime, we’ve rotenoned lakes, bashed brains, and written at length about the ills of pure trout populations mingling with introduced species and diluting the gene pools. Turns out our worst fears are unfounded, at least according to a new paper by scientists at the U.S. Forest Service Rocky Mountain Research Station and National Genomics Center for Wildlife and Fish Conservation.

Using genetic analyses of markers known as “single nucleotide polymorphisms,” the scientists analyzed 3,865 cutthroat from 129 streams in Montana and Idaho and found that more than 70 percent of fish sampled showed no signs of hybridization.

“This is a better situation than anyone concerned or interested in these fish could have hoped for,” said lead author, Kevin McKelvey. “We found that most of the fish in the streams we sampled were not hybrids.”

The paper appeared this week in Ecology and Evolution and goes on to say that pure cutthroat populations are more widespread than originally thought. And that pure westslope cutts, specifically, are less inclined to mate with introduced rainbow trout and create hybrid swarms, or groups of hybridized fish that continue to breed with each other until all fish are hybrids. Westslopes, of course, are the state fish of both Montana and Idaho, and have previously been petitioned for listing under the Endangered Species Act.

So why are hybrids not as widespread as so many people had predicted?

“That is not currently resolved, but most likely it is linked to environmental conditions and we will continue research to help address this question,” McKelvey concluded.

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Tom Bie
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Tom Bie is the founder, editor, and publisher of The Drake. He started the magazine in 1998 as an annual newsprint publication based in Jackson Hole, Wyoming. He then moved it to Steamboat, Colorado (1999), Boulder, Colorado (2001), and San Clemente, California (2004), as he took jobs as managing editor at Paddler, Senior Editor at Skiing, and Editor-in-Chief at Powder, respectively. Tom and The Drake are now both based in Denver, Colorado, where The Drake is finally all grows up(Swingers, 1996) to a quarterly magazine.

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Author: Tom Bie

Tom Bie is the founder, editor, and publisher of The Drake. He started the magazine in 1998 as an annual newsprint publication based in Jackson Hole, Wyoming. He then moved it to Steamboat, Colorado (1999), Boulder, Colorado (2001), and San Clemente, California (2004), as he took jobs as managing editor at Paddler, Senior Editor at Skiing, and Editor-in-Chief at Powder, respectively. Tom and The Drake are now both based in Denver, Colorado, where The Drake is finally all grows up(Swingers, 1996) to a quarterly magazine.

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