From The Denver Post (Bruce Finley):

The biologists have purged this gulch of all other fish competitors.

But the first pure greenback cutthroat trout dropped into chilly streams Monday morning simply quivered at edges of eddies.

These captive-bred 1-year-olds — 960 of them — are thought to be hardier than the 4,000 hatchlings that Colorado Parks and Wildlife biologists put in Herman Gulch last year. State crews conducted a survey last week and found no evidence any of the hatchlings survived the hard winter.

A whole lot of people really want the greenback cutthroats to make it in their ancestral home.

So on Monday morning, an expanding cutthroats recovery team coordinated by CPW mobilized, with more than 50 volunteers from Trout Unlimited and other conservation groups hauling 20-pound bags of the 5-inch fish into the high-country basin…

Most understood this is something of an ecological longshot because greenback cutthroats — listed as threatened on the nation’s endangered species roster — have all but disappeared. After all, evolution is all about change, and species come and go.

Greenback cutthroats originated in the South Platte River Basin headwaters. They disappeared as humans settled the region, mining for gold that turned water toxic, stocking streams with nonnative fish in hopes of promoting tourism.

State wildlife managers declared greenback cutthroats extinct in the 1930s. But they rediscovered them in 1953 and celebrated them in 1994 as Colorado’s official state fish. However, the fish that Colorado wildlife officials touted as the state fish was a different species of cutthroat trout.

In 2012, University of Colorado genetics scientists determined that only a few greenback cutthroats survived in the wild, by a fluke, southwest of Colorado Springs, in the Arkansas River Basin. Back in the 1870s, aspiring hotel resort operator Joseph Jones had captured some greenbacks from South Platte headwaters and plopped them into Bear Creek near his property. CU scientists verified that only the descendants of those fish carried the true greenback cutthroat genes.

CPW officials now are working intensely, gathering genetic material from Bear Creek fish and breeding tens of thousands of greenback cutthroats in hatcheries created to stock Colorado streams with trout that compete with native species.

CPW crews already have transplanted some greenback cutthroats successfully into Zimmerman Lake, west of Fort Collins.

“This would be the first steam,” CPW aquatic biologist Boyd Wright said Monday, directing the transplanting operation along 3 miles of streams. “And this is a fish that evolved in streams.”

[…]

If this second attempt at getting greenback cutthroats to survive in Herman Gulch fails, CPW officials said they’ll try once more next year. State crews this year also are planning to drop cutthroats into Dry Gulch, to the west of this site, and into Rock Creek in South Park.

But much depends on how the fish respond in this ideal habitat, a basin considered ecologically healthy.