Wait a minute! Something's fishy

Experts confused two trout species in stocking program

Kevin Vaughan, Rocky Mountain News

Published September 6, 2007 at midnight

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Wildlife experts had the right idea - they just had the wrong fish.

For decades, Colorado officials have worked to restore the threatened greenback cutthroat trout to the Front Range. But somewhere along the line, someone mistook Colorado River cutthroats for greenback cutthroats, and officials have been inadvertently populating lakes and streams with the wrong fish ever since.

That conclusion, reached in a new study led by researchers at the University of Colorado, has the potential to radically reshape an expensive program under way since the early 1970s to restore Colorado's official state fish to its native habitat.

Using DNA analysis, researchers recently found that five of nine "relic" populations of what were believed to be greenback cutthroats were actually Colorado River cutthroats, a closely related subspecies native to the Western Slope.

"This was a very surprising result," said Jessica Metcalf, a researcher at CU who led the study. "It's not at all what we expected."

She had expected to confirm what researchers had thought for decades - that those nine populations were made up of greenback cutthroats.

The greenback, named for the brilliant crimson slashes behind its jaw, became Colorado's state fish in 1994.

Native to the South Platte and Arkansas river drainages on the Front Range, its numbers diminished radically in the late 1800s and early 1900s, and by 1937 it was believed to be extinct.

However, in the 1950s, several small populations were discovered, and in 1973 the greenback cutthroat was declared an endangered species.

State, federal and private organizations launched an effort to restore the greenback cutthroat, using sperm and eggs from what were believed to be the nine relic populations to reproduce new generations in hatcheries.

Those fish were then introduced in the greenback cutthroat's native range.

The last version of the recovery plan for the greenback cutthroat, written in 1998, said $634,000 more was needed to complete restoration of the population.

But the new study, published in the online edition of the journal Molecular Ecology, found that five of those nine relic populations were Colorado River cutthroats.

"Greenbacks and Colorado River cutthroats - our feeling for a long time has been that they were very, very closely related and indistinguishable, in fact, in their morphology, other than the fact that one's on the east side of the Continental Divide and one's on the west side of the Divide," said Bruce Rosenlund of the U.S. Fish and Wildlife Service.

Only the development of DNA technology allowed researchers to differentiate between the two.

Now, he said, it is time to see how the scientific community responds to the findings - and which populations should be used in the ongoing restoration.

One expert said he is skeptical of the findings.

Robert Behnke, a retired Colorado State University professor who originally identified some of the native populations, questioned Wednesday whether researchers fully understand that "what's left are tiny fragments of what was here over 100 years ago. The genetic data is not wrong, but it is misinterpreted," he said.

But Metcalf said additional research bore out the conclusion.

She and others who worked on the project, perplexed by their original findings, started looking at everything from historical stocking records to diaries and journals from people who ran fish hatcheries a century ago.

What they found was that stocking was widespread, and they concluded that Colorado River cutthroat were probably moved from the Western Slope to the Front Range as part of that effort in the late 1800s and early 1900s.

vaughank@RockyMountainNews.com or 303-954-5019

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