Colorado River Cutthroat Trout
Colorado River cutthroat trout have a bright yellow-gold body with a brassy-green back and orange belly, medium to large spots concentrated on the caudal peduncle and dorsal region (though spotting varies by region) and absent on the pectoral, pelvic, and anal fins, and 180-200 lateral line scales.
About This Species
Colorado River cutthroat trout, Oncorhynchus clarkii pleuriticus, are one of three recognized subspecies of native trout found in Colorado. They historically occupied portions of the Colorado River drainage in Wyoming, Colorado and Utah. Widespread introductions of non-native salmonids over the last century have served to limit current distributions primarily to isolated headwater streams and lakes. As such, the Colorado River cutthroat trout is designated as a species of special concern in Colorado, and significant resources have been dedicated to conservation of the subspecies.
Researching and Protecting Cutthroat Trout
There are four native subspecies of cutthroat trout in Colorado: the Colorado River Cutthroat, the Rio Grande Cutthroat, the Snake River Cutthroat and the native Greenback Cutthroat trout. Colorado researchers are also currently attempting to find the thought-extinct Yellowfin Cutthroat trout. All subspecies of cutthroat trout are the subject of conservation efforts and research by multiple state and federal agencies.
The beautiful and vibrant cutthroat trout gets its name from the red slash under its jaw. The cutthroat's medley of colors and spots make it one of the most cherished fish among Colorado anglers. Colorado is home to three subspecies of native cutthroat: the Rio Grande, Colorado River and the renowned greenback, which was designated Colorado's state fish in 1994. But, despite its iconic stature, the plight of the cutthroat has been both challenging and uncertain. For decades, cutthroat trout populations have declined throughout the western United States.
Working with a consortium of state and federal wildlife agencies, Trout Unlimited and other conservation groups, Colorado Parks and Wildlife (CPW) has developed an aggressive conservation strategy to help restore native cutthroat populations. A key component of cutthroat conservation is egg-collection, hatchery and stocking programs.
Genetic research led by University of Colorado scientists has produced several fascinating discoveries about Colorado's native cutthroat trout - including the location of the last surviving wild population of the federally protected greenback cutthroat trout.
Researchers analyzed DNA extracted from wild trout and from museum specimens collected from sites around Colorado and New Mexico as far back as 1856, then used that genetic data as a baseline for understanding the current distribution of Colorado's native cutthroat trout.
In addition to identifying the one remaining "true" greenback population, researchers identified two distinct genetic lineages within the range of Colorado River cutthroat trout, one in northwest Colorado and the other centered around the Gunnison River basin. Further research will be needed to understand the relationship between these two lineages.
In all, six lineages of cutthroat appear to have evolved in Colorado, with native ranges that roughly correspond to major drainage basins in the state. The greenback cutthroat trout, Colorado's state fish, was native to the drainages of the South Platte, while the long extinct yellowfin cutthroat trout of Twin Lakes actually appears to have been the native trout of the Arkansas River Basin. Rio Grande cutthroat trout still can be found in streams that drain into the San Luis Valley, while a lineage that used to call the San Juan basin home appears to be extinct as well. More research will be required to resolve whether the remaining two lineages that can be found across Colorado’s western slope are indeed two distinct subspecies – that work is ongoing.
Given that additional lineages of our native cutthroat trout were identified with the DNA testing, we wanted to determine if these lineages displayed different physical characteristics as well. This is particularly important since it has been argued that genetics should not be the sole factor in determining taxonomic distinctions, and that morphological traits (visual characteristics) are often better suited for discriminating taxa. A recent comprehensive study examined the relationship between the differences implied by the DNA and the morphology of these fish. Indeed, it appears that these new lineages can also be identified by examining morphological traits as well.
A key element of cutthroat trout conservation involves the ability to take fertilized eggs from wild populations. Progeny from these operations are used for founding new populations in waters that have been cleared of nonnative fish that otherwise replace cutthroat trout or hybridize with them. Where habitats home to pure cutthroat trout have been invaded by nonnative salmonids, it important to replicate those populations before they wink out. Improving methods for obtaining fertilized eggs in the wild will facilitate those efforts.
Like many coldwater fish species, cutthroat trout will face numerous additional challenges in a warming climate (see Dan Isaak's climate blog). State and federal researchers teamed up with Dr. Kurt Fausch of Colorado State University to develop a robust approach for synthesizing the myriad factors that will influence the persistence of remaining 121 individual conservation populations of Rio Grande cutthroat trout to 2080. Recently published as a featured paper in the North American Journal of Fisheries Management titled “Predicting persistence of Rio Grande Cutthroat Trout populations in an uncertain future”, the study found that although streams are predicted to warm by 2080, less than 10% of populations will be adversely affected. In contrast, nearly 65% are predicted to be extirpated (or nearly so) by nonnative trout that have already invaded or are expected to soon. Many populations will require the help of managers if they are to persist well into the 21st century. A manual for running the model can be found by clicking the link below.
Trappers Lake historically was home to Colorado’s premier wild Colorado River cutthroat trout fishery. Unfortunately, a variety of factors have served to suppress the current population as well as marginalize the value of the fishery due to introgression with Yellowstone cutthroat trout. Recent genetic surveys have revealed that the remaining cutthroat trout are a hybrid swarm. Reduced cutthroat trout numbers have been attributed to a burgeoning brook trout population that is now being thinned by fall trapping efforts. In addition, whirling disease invaded the population in the late 1990s, and has now firmly established itself suppressing recruitment of cutthroat trout further. In an effort to control the spread of the disease, anglers are reminded to decontaminate their gear after fishing at Trappers Lake particularly before heading into the higher elevation lakes such as Little Trappers Lake that remain free of the parasite.