Biologists regroup after trout goof
October 11, 2007
DENVER ” State and federal biologists, still smarting from research showing that they may have been protecting the wrong fish the past 20 years, are regrouping in their efforts to restore the rare greenback cutthroat trout to Colorado waters.
State biologist Tom Nesler had hoped to see the fish removed from the endangered species list during his career. He concedes that might not happen if it turns out some of the greenback populations biologists thought they were saving are actually the similar but more common Colorado River cutthroat trout.
A three-year study led by University of Colorado researchers, published in August, found that out of nine fish populations believed to be descendants of original greenbacks, five were actually Colorado River cutthroat trout.
The recovery effort was thought to be near its goal of establishing 20 self-sustaining greenback populations.
“Hey, science happens,” said Nesler with a shrug as he discussed the findings.
Not that Nesler, chairman of the greenback recovery team, takes the study lightly. He and other members of the team ” which includes four federal agencies, agencies from three states, an Indian tribe and a conservation group ” are doing further testing and review.
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Greenback cutthroat trout were historically found in the drainages of the Arkansas and South Platte rivers in Colorado, east of the Continental Divide, and a small part of Wyoming. The Colorado River cutthroat trout is native to the upper Colorado River basin, west of the divide.
Greenbacks were declared extinct in 1937 due to overfishing, pollution from mines and competition from nonnative fish. But researchers said remnant populations were found in tributaries in the 1950s. The fish was added to the federal endangered species list in 1978.
Under the state-federal recovery program, biologists used fish they believed to be descendants of pure greenback cutthroat trout as brood stock. New fish, raised in hatcheries, were released in different waters, Nesler said, not where the remnant populations were.
As team members huddle to chart the course forward, they’re also trying to explain why what they thought were greenbacks weren’t. In a letter to the state natural resources chief, four Colorado legislators denounced “this significant scientific blunder” as a waste of taxpayer dollars.
The Colorado Division of Wildlife has spent an average of $320,000 annually for the past five years to restore the greenback. Most of the money has come from state lottery revenue; no state tax dollars have been used.
In 1998, officials projected it would cost $634,000 to restore the greenback, with the money coming from a variety of sources. It’s not clear how much of that has been spent. Figures for the recovery project before 1998 weren’t available.
Biologists and researchers have suggested that the Colorado River cutthroat trout once thought to be greenbacks might have been stocked in various spots in the late 1800s or early 1900s by early settlers.
The team will recommend to the U.S. Fish and Wildlife Service, the agency responsible for endangered species, how to proceed.
Meanwhile, it has been thrown another curve.
Tests on a batch of fish not examined during the study produced results Nesler said he can’t explain: two tests showed they were Colorado River cutthroat trout ” but a third showed they were greenbacks.
The results could be an anomaly or say something about either the testing or the fish. They hope to have the answer after testing more fish.
“As a scientist, I know this kind of stuff happens,” Nesler said. “That’s why we didn’t immediately rush to embrace this (research), but we didn’t throw it out.”
Nesler and Bruce Rosenlund of the U.S. Fish and Wildlife Service said the recovery team has taken measured steps all along. The state and federal agencies helped pay for the university study and have always worked with outside scientists.
It also was the first time that geneticists told the team that DNA tests could tell greenback and Colorado River cutthroat trout apart, Nesler said. “Up until a year ago, no one could tell us the difference between the two,” he said.
University of Colorado professor Andrew Martin, the study’s principal investigator, said he believes some of the previous science the team relied on wasn’t the best, but he didn’t give examples.
“I think overall the (Colorado Division of Wildlife) and Fish and Wildlife Service did a superb job in what they were trying to do,” Martin said. “The problem was with some of the science and how the science was evaluated.”
Robert Behnke, a retired Colorado State University professor and expert on trout, said he has questions about the new research.
“The genetic work might be superb,” he said, but the study claims to sweep “doubt and uncertainty under the carpet.”
“Science is not about proof and certainty, it’s about testable hypotheses,” he said.