DENVER — Fifty years ago, few biologists or anglers lost much sleep over the fate of Colorado’s four native trout subspecies. The fish, whose incredible beauty mirrored the wilderness they inhabited, were little more than relics recalled by a few old timers.

At that time, tiny populations of two natives - the Rio Grande and greenback cutthroats - were barely holding on in remote streams of Colorado’s mountains. Another, the Colorado River cutthroat, was holding its own but faced a myriad of threats. And one, the yellowfin greenback, was already extinct.

Today, the three remaining subspecies are making a remarkable comeback, thanks to cooperative efforts between the Colorado Division of Wildlife, other state and federal agencies and citizens’ groups.

An integral part of that comeback has been the Division’s recovery and conservation plans to establish secure, pure strains of Colorado’s remaining native trout and self-sustaining populations in their historic home ranges. "Our cutthroat trout are part of Colorado’s wildlife heritage and are the only trout species that inhabited the state historically," said Tom Nesler, the DOW’s threatened and endangered aquatic species coordinator.

"It is clearly reflected in our statewide fish-management policy to protect our remaining three native cutthroat subspecies by restoring and enhancing populations to suitable habitats whenever possible," Nesler said. "We mean not only to secure these native fish from decline but expect to feature them as unique fishery opportunities where feasible and compatible with conservation efforts."

The longest running of these recovery plans was mandated by the Endangered Species Act in 1973 and has been successful in bringing the greenback cutthroat, native to the South Platte and Arkansas drainages, back from the edge of extinction.

Greenbacks on the brink of recovery By 1937, the greenback cutthroat, which is found only along the Front Range, was thought to be extinct. Like all native trout, this once abundant fish with its distinctive crimson gill slash and belly had been hit hard by habitat degradation, overfishing competition from non-native trout, and hybridization with rainbow trout.

Two tiny populations were found in remote areas of Larimer and Boulder counties, and broodstocks were developed to allow the species to be restored into waters that were reclaimed from other species.

By 1978, the greenback’s status was upgraded from endangered to threatened. Today, 18 conservation populations - meaning secure and self-sustaining populations of pure or nearly pure strains of the species - have been established in the South Platte River drainage and another four have been established in the Arkansas drainage.

Nearly all recovery populations are open to fishing with regulations that allow take by flies and lures only and immediate return to the water.

Colorado River cutthroat numbers higher than expected

The greenback’s West Slope cousin, the Colorado River cutthroat, is the latest native trout to receive attention. The Division, U.S. Fish and Wildlife Service, Wyoming and Utah signed a five-year agreement last year to restore the species to a portion of its native range.

To date, the effort has paid off better than anyone expected, with what are thought to be conservation populations located in 123 streams and 28 lakes, already exceeding the Division’s long term goals of 111 conservation populations in streams and 15 in lakes. Based on this early success, the Division is considering revising upward its long-term goals for recovery populations to 163 streams and 73 lakes, Nesler said.

Nevertheless, a coalition of conservation groups in early August filed a notice of intent to sue U.S. Fish and Wildlife for failure to act within 90 days of their petition to list the Colorado River cutthroat as threatened under the Endangered Species Act.

Regulations are in place to protect Colorado River cutthroats where it is deemed necessary, according to Gunnison-based Division biologist Dan Brauch. Some populations are in areas with no public access, and special regulations are not needed, he said.

Down south, the Rio Grande cutthroat is faring well enough that the Colorado populations were the basis for denial of a petition requesting U.S. Fish and Wildlife to list the subspecies under the Endangered Species Act. The subspecies had previously been state-listed as threatened but removed as populations were discovered and restored.

The Rio Grande cutthroat conservation program is being carried out by the Division, in cooperation with the U.S. Forest Service and New Mexico’s Fish and Game Department. And like the Colorado River subspecies, Division biologists continue to revise targets to promote expansion of cutthroat populations in the Rio Grande drainage where suitable habitat exists or can be restored, Nesler said.

As of this year, there are 76 known populations of Rio Grande cutthroats in the basin - 50 of those are historic populations and 26 are transplants, according to Division records. Of those, seven populations are secure and expanding, 15 are secure and stable, 16 are stable but at risk, 21 are declining and at risk, and six populations’ status is unknown.

Forty-seven Rio Grande cutthroat populations are genetically pure and ten are slightly hybridized. Based upon stability and genetic purity, 38 populations would be considered conservation populations under draft federal guidelines.

Regulations protecting Rio Grande cutthroats are in place on 24 waterways on public lands. Twenty-six streams on private land hold populations of Rio Grande cutthroats and are not open to public fishing.

Despite being denied a federal listing, conservationists have filed a lawsuit to force the federal government to add the Rio Grande cutthroat to the Endangered Species list as threatened across its historic range. However, Colorado’s cutthroat experts disagree with efforts for federal protection.