The Last of the Pure Greenbacks?

This fall, researchers at the University of Colorado released a study that revealed startling news about Colorado’s state fish, the greenback cutthroat trout.  Specifically, the genetic research indicates that the last wild population of the federally protected species resides in a four-mile stretch of Bear Creek, a small tributary to the Arkansas River west of Colorado Springs. 


Pure greenback cutthroat trout from Bear Creek. Source: Colorado DOW

The new findings may come as a shock to anglers who fished other streams looking to snag a greenback. “We’ve known for some time that the trout in Bear Creek were unique,” said Doug Krieger, senior aquatic biologist for Colorado Parks and Wildlife and the Greenback Cutthroat Trout Recovery Team leader. “But we didn’t realize they were the only surviving greenback population.”


Click on the image of Doug to watch a Colorado Parks & Wildlife video on the Bear Creek greenbacks.
Source: Colorado Parks & Wildlife

Using mitochondrial DNA extracted from wild trout and from museum specimens collected as many as 150 year ago, Drs. Jessica Metcalf and Andrew Martin of CU’s Department of Ecology and Evolutionary Biology compared DNA of native wild greenbacks to that of modern-day cutthroat species.  Their analysis estimated that only 750 greenbacks remain.

Cutthroat trout are considered one of the most diverse fish species in North America and evolved into 14 recognized subspecies in western U.S. drainages over thousands of years.  Four lineages were previously identified in Colorado: the greenback, the Colorado River cutthroat, the Rio Grande cutthroat, and the extinct yellowfin cutthroat.


Cumulative numbers (in millions of fish) of cutthroat trout, rainbow trout and brook trout stocked in Colorado waters from 1885 to 1953 by state and federal agencies. Private interests also stocked fish around the state, but their efforts were generally smaller in scale, and much less well docu- mented. Dates of museum collections used in this study are indicated by arrowheads. Source: Metcalf, et al. 2012

Due to the widespread propagation and stocking of trout over the last 150 years, the distribution and diversity of cutthroat trout have changed dramatically.  The first documented movement of fish occurred in 1873, after Colorado native trout saw dramatic declines due to overfishing, mining pollution and agricultural practices in the mid 1800s. 

Greenbacks were native to the South Platte River basin, and were actually declared extinct in the 1930’s before being “rediscovered” in 1953.  According to the study, the Bear Creek population survived because a hotel operator trying to promote a tourist route to Pike’s Peak stocked them there in the 1880s.  Interestingly, the last remaining pure greenbacks survive in stream outside their native range.  While the stocking and propagating of fish contributed to declines of cutthroat trout in their native ranges, it also appears to have inadvertently prevented the extinction of the greenback.


Native ranges of Colorado’s six distinct lineages of cutthroat trout follow major drainage basins. Colors indicate different native species. Source: Colorado Parks & Wildlife


“With the insight afforded by the historical data, we now know with a great deal of certainty what cutthroat trout strains were here in Colorado before greenbacks declined in the early 20th century,” said Dr. Martin. “And we finally know what a greenback cutthroat trout really is.”

The study has triggered a thorough re-evaluation of the taxonomy, classification, and range of cutthroat trout in Colorado.  The re-evaluation will likely cause greenbacks to be listed as “endangered” rather than “threatened” as they are currently listed.

Scott Willoughby of the Denver Post wrote that the findings arrive with “good news, bad news, and a dash of indifference” for the angling community.  “Purely from an outdoorsman’s perspective, the delineation between hooking into a genetically compromised greenback hybrid in Rocky Mountain National Park and the offspring of a pure Bear Creek greenback — fishing is prohibited in Bear Creek — is likely to remain negligible.”

The “good news” is that greenbacks are still alive.  The “bad news” is that species previously thought to be pure greenbacks are actually hybrid species, disappointing any anglers who thought they had nabbed a pure greenback.  With his “point of indifference” Willoughby misses an opportunity to rally sportsmen to support the conservation efforts needed to bring pure greenbacks back to sustainable population levels.

 This highlights a perplexing theme regarding sportsmen and conservation, where many seem to care more about the sport than the species on which it depends.  Recall the National Wildlife Federation study cited in my first post that found only 59% of sportsmen agree that global warming is occurring.  Sportsmen have an obligation to ensure that that the fish and wildlife we value, especially the rare species we covet, remain healthy and vibrant.

The startling evidence of this latest research should not be considered a point of indifference, but a call to action to increase awareness of the need for conservation.  To this end, the Cutthroat Trout Recovery Team is working with Colorado State University to further reexamine the physical characteristics of Colorado cutthroats.  The results of this examination will be used to clarify the evolutionary relationships among native cutties.  In turn, this ongoing research will inform a decision process on how to move forward with conservation efforts.

Already, a protected broodstock of Bear Creek cutthroats is being propagated in the Colorado Parks and Wildlife’s hatchery system.  The offspring will be used to establish wild populations in the future.  With adequate support from sportsmen, perhaps pure greenbacks will prosper and we can enjoy the thrill of angling this beautiful and unique species. Without support from anglers, we may lose the opportunity to see them in the wild ever again.


2 thoughts on “The Last of the Pure Greenbacks?

  1. adrianne

    How ironic that a hotel owner in the 1880s could accidentally prove to be an environmental steward in 2012. I love stories like that. If anything, it proves that the success of restoration efforts — even the scientific ones — often rests on chance and coincidence. I’ll keep my fingers crossed that serendipity continues to go the way of the greenback. Nice post!


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