The greenback cutthroat trout was supposed to be a U.S. conservation success story. Wildlife managers spent more than 2 decades rearing the endangered species and restocking it in mountain streams in Colorado. There's just one problem: A new genetic analysis finds that conservationists have been helping the wrong fish.
The greenback cutthroat trout (Oncorhynchus clarkii stomias) once lived throughout thousands of kilometers of rivers and streams on the eastern slopes of the Colorado Rockies. Its life changed drastically, however, after mining, pollution, and competition from other species that were stocked in its habitat for recreational fishing. In 1937, the greenback was declared extinct.
But beginning in 1953, several populations were discovered in the headwaters of the South Platte River and Arkansas River in Colorado. The U.S. Fish and Wildlife Service added the subspecies to the federal list of endangered species in 1978. To help it recover, wildlife managers first removed non-native fish from greenback habitat. Then they took eggs and sperm from surviving greenbacks and reared fish in hatcheries. Last year, the Colorado Division of Wildlife reached the target of 20 self-sustaining populations--or so they thought.
The bad news comes from a study by researchers at the University of Colorado, Boulder, and colleagues. While surveying the genetics of the greenback trout, they discovered that only four populations actually consisted of greenback trout. The rest were Colorado River cutthroat trout (O. c. pleuriticus), a species that looks very similar, the team reported online 28 August in Molecular Ecology. That means managers had been accidentally stocking streams with Colorado River cutthroat, which are not listed as endangered.
Instead of being fully recovered, the greenback inhabits just a dozen kilometers of streams. Moreover, the genetic diversity of the greenback population in the eastern Rockies is low compared to other subspecies of cutthroat, perhaps enough to have led to inbreeding. "Now there's no way they are coming off the list" anytime soon, says lead author Jessica Metcalf.
Biologist Kevin Rogers of the Colorado Division of Wildlife in Steamboat Springs agrees. ""It's certainly discouraging," he says. "We've got guys who have spent the last 20 years of their careers doing what they thought were good things for [the] greenback." Rogers says the agency is still digesting the information and hopes to figure out how to proceed with conservation efforts by next year.
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