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News & Releases
Mountain-Prairie Region


Return of the Native


August 14, 2014

Greenback Cutthroat Trout in bucket before release. Credit: USFWS
Greenback cutthroat trout in bucket before release. Credit: Theo Stein / USFWS

Bucket by bucket, the rarest trout in North America reclaimed a small piece of its former range on a beautiful August morning high in the Colorado Rockies.

The greenback cutthroat trout is nothing short of a miracle fish. The only native trout of the South Platte basin, the greenback was extirpated from its northeastern Colorado home during the 20th Century and had been reduced to a single population hanging on in tiny Bear Creek on the slope of Pikes Peak.

On August 8, a group of biologists and researchers gathered to release 1,200 hatchery-raised greenbacks into Zimmerman Lake, jumpstarting the process of restoring a symbol of Colorado’s natural heritage to its rightful place. It’s an improbable story, as dependent on the passion of people devoted to wild trout as on the indomitable survival instinct of a species that survived for more than a century in a tiny stream.

With origins from the Pacific Ocean, cutthroat trout are considered to be one of the most diverse fish species in North America and a symbol of wildness in the American West. For thousands of years, cutthroat trout evolved across the western U.S. into 14 recognized subspecies, including the giant yellowfin cutthroat, an Arkansas Basin strain that once grew to prodigious size in Twin Lakes near Leadville, which is now extinct.

Greenback cutthroat trout were first listed as endangered prior to the passage of the Endangered Species Act. Recovery efforts with trout identified by experts as greenbacks helped convince the Service to downgrade the fish to threatened in 1979. Wildlife managers and the recovery team continued restoring native cutthroats to the South Platte drainage to meet the goals of the Greenback Recovery Plan, moving along a track that suggested recovery benchmarks might soon be met and the threatened designation lifted.

Then came a 2012 study by a team of researchers from the University of Colorado, Colorado Parks and Wildlife and the National Park Service, which compared cutthroat DNA from museum specimens collected in the late 1880s with cutthroat DNA from current populations. Researchers determined that most of the streams that were believed to contain greenbacks  actually contained descendants of West Slope transplants. Further sleuthing through historic records revealed that these were survivors of an ambitious and entirely ad-hoc trout restoration effort that lasted for several decades around the turn of the 20th Century.

But the big news was the announcement that the several hundred diminutive trout hanging on in Bear Creek, trout recognized as unique by CPW biologists for over a decade, were in fact the last surviving population of greenbacks.

Fast forward to today – greenbacks are now being raised in three Colorado hatcheries, including the Leadville National Fish Hatchery. While the Service reviews the greenback’s status under the Endangered Species Act, the Greenback Recovery Team is busy identifying South Platte waters where they can continue the recovery process.

Although the genetic “labels” associated with the species and individual populations of the species have changed over time, recovery efforts have protected the cutthroats and their habitats. Thanks to those efforts, the pieces to the genetic puzzle are still largely intact.

Sitting in the Arapaho-Roosevelt National Forest in the shadow of rugged cliffs, Zimmerman Lake has become a key tool in the greenback trout recovery program. The isolated lake has an abundance of scuds and other aquatic insects, perfect for growing trout.

Anglers can try to land one of these rare four-inch long jewels, but will be required to return the fish back to the water unharmed. In a couple of years, the greenbacks planted in Zimmerman Lake this summer will grow into brood stock – whose eggs and milt will be harvested for future projects designed to return this native to its ancestral home along the Front Range.

To view more photos from this event visit our Flickr gallery: Zimmerman Lake Photos

– FWS –

U.S. Fish and Wildlife Service

Office of External Affairs

Mountain-Prairie Region

134 Union Blvd

Lakewood, CO 80228


303-236-3815 FAX



Theo Stein


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The mission of the U.S. Fish and Wildlife Service is working with Others to conserve, protect, and enhance fish, wildlife, plants and their habitats for the continuing benefit of the American People.
Last modified: August 14, 2014
All Images Credit to and Courtesy of the U.S. Fish and Wildlife Service Unless Specified Otherwise.
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