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The Mountain-Prairie Region


U.S. Fish and Wildlife Service
134 Union Boulevard
Lakewood, Colorado 80228

 April 20, 2004 

 Contacts: Patty Schrader Gelatt 970-243-2778 (available 4/21)                    Susan Linner 303-275-2343
                  Diane Katzenberger 303-236-4578 

Colorado River Cutthroat Trout Will Not Be Considered for Listing Under the Endangered Species Act 

The U. S. Fish and Wildlife Service concluded today that a petition to list the Colorado River cutthroat trout as threatened or endangered under the Endangered Species Act does not provide substantial biological information to indicate that a listing may be warranted at this time. 

The Center for Biological Diversity, the Biodiversity Legal Foundation, Biodiversity Associates, Ancient Forest Rescue, Southwest Trout, Wild Utah Forest Campaign, Colorado Wild, and an individual, Mr. Noah Greenwald, petitioned the Service to list the Colorado River cutthroat trout in its occupied habitat within its known historical range. 

"While the Colorado River cutthroat trout has declined from historic levels, the most recent biological information and surveys indicate that a significant number of viable, self-sustaining, and well-distributed populations are found throughout its historical range, said Ralph Morgenweck, Director of the Service’s Mountain-Prairie Region. The hard work of our State, Federal, tribal, and private partners is paying off.  Their ongoing conservation efforts are responsible for the improved status of this native fish. Their continued efforts will ensure its long-term prosperity.” 

State agencies representing Colorado, Utah and Wyoming as well as the USDA-Forest Service, Bureau of Land Management, National Park Service, the Ute Indian Tribe, and the Service formed a task force to address range-wide conservation efforts for Colorado River cutthroat trout. The task force developed conservation measures for the species in Colorado, Utah and Wyoming. It has been implementing these measures for several years. 

In addition to reviewing the petition and supporting documentation, the Service examined information that was contained in its files or readily available. The Service found that: 

  • Colorado, Utah and Wyoming report 327 conservation populations – fish that are more than 90 percent pure Colorado River cutthroat trout. Of these, 286 populations occupy approximately 1,010 stream miles and 41 populations occupy approximately 1,124 acres of lakes. 
  • These populations include 221 core conservation populations – fish that are more than 99 percent pure Colorado River cutthroat trout – in approximately 684 stream miles and 30 core conservation populations in approximately 545 acres of lakes.
  • Fifty-three percent of existing core conservation populations are currently protected by a natural or artificial barrier to prevent intrusions by non-native fish.

With regard to the petition, the Service concurs that certain land management practices such as overgrazing and water diversions can have a negative impact on Colorado cutthroat trout habitat. However, the petition did not recognize the ongoing efforts of the State and Federal land management agencies to protect and conserve Colorado River cutthroat trout populations and habitat.  These agencies have also instituted fishing regulations and prohibited nonnative stocking near core or conservation populations. 

The Service also acknowledges that hybridization does occur in some Colorado River cutthroat trout populations. But many populations are more than 99% pure Colorado River cutthroat trout – and the states of Colorado, Wyoming and Utah have implemented policies to protect the genetic purity of the core populations.   

Whirling disease is a significant concern for trout in general, but few Colorado River cutthroat trout populations have tested positive for the disease, and the states of Colorado, Wyoming and Utah are implementing management actions to protect Colorado cutthroat trout from whirling disease. Also, the whirling disease pathogen is unlikely to proliferate in much of the habitat for the Colorado River cutthroat trout, because this species is generally found at higher elevations, where the water is too cold for the pathogen to survive. 

The Colorado River cutthroat trout is the only salmonid native to the upper Colorado River basin. It is distinguished by its red/orange slash marks on both sides of the lower jaws and relatively large spots concentrated on the posterior part of the body.  The Colorado River cutthroat trout currently occupy portions of the Colorado River drainage in Colorado, southern Wyoming and eastern Utah and may still occur in very limited areas of New Mexico and Arizona. 

For more information about this finding please visit the Service’s web site at 

The U.S. Fish and Wildlife Service is the principal Federal agency responsible for conserving, protecting and enhancing fish, wildlife and plants and their habitats for the continuing benefit of the American people. The Service manages the 95-million-acre National Wildlife Refuge System, which encompasses 544 national wildlife refuges, thousands of small wetlands and other special management areas. It also operates 69 national fish hatcheries, 63 Fish and Wildlife Management offices and 81 ecological services field stations. The agency enforces federal wildlife laws, administers the Endangered Species Act, manages migratory bird populations, restores nationally significant fisheries, conserves and restores wildlife habitat such as wetlands, and helps foreign governments with their conservation efforts. It also oversees the Federal Assistance program, which distributes hundreds of millions of dollars in excise taxes on fishing and hunting equipment to state fish and wildlife agencies.

For more information about the U.S. Fish and Wildlife Service, visit our home page at

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