Colorado River Cutthroat Trout

Oncorhynchus clarkii pleuriticus

Historically, the Colorado River cutthroat trout (CRCT) occupied numerous tributary systems of the Colorado River upstream of the Grand Canyon. The Upper Green River system in Wyoming and Utah contains many extant populations, including remaining strongholds. Additional, but mostly scattered populations remain in the upper Colorado River, upper Gunnison, upper Dolores, upper Yampa, Little Snake, upper White, upper Duchesne, upper Escalante, and upper San Juan systems.

Robert Behnke reported on early pioneer records that CRCT reached weights of 17 to 20 pounds. If true, the fish may have grown to such large proportions in bigger lakes and larger stream systems than they typically inhabit today.

Key CSI Findings

• 16% of subwatersheds (213/1351) within historic range are occupied by CRCT
• Most populations are fragmented and restricted to smaller headwater streams
• Only 1% of populations were classified in highest Population Integrity category
• Genetically unaltered CRCT may occupy as much as 51% of currently occupied range
• The CRCT Conservation Team has identified 285 separate CRCT “conservation populations” with important genetic and life history traits
• Reintroductions into unoccupied habitat were the highest management priority. High priority reintroduction sites were identified throughout the range.

Historic Range Relief Map

In more recent years, CRCT have been pushed into higher elevation streams by the same cast of problems that plague most native trout in the West: introductions of non-native trout, habitat degradation from timber harvest and overgrazing, excessive fish harvest, and fragmentation of stream habitat by water diversions and other barriers. In 1996, Michael Young and colleagues from the U.S. Forest Service estimated that 318 populations of CRCT existed in their native range.

Strongholds for CRCT are very few and occupy limited habitat compared to most other western trouts. Two stronghold areas were identified in the CSI, both in the upper Green River drainage. One, the LaBarge Creek system, occurs in the Bridger-Teton National Forest of Wyoming. The other, the Blacks Fork drainage, occurs in the Ashley National Forest and along the Wyoming-Utah border.

Non-native trout stockings and their subsequent invasion into higher elevation habitats has been a major cause of declines and continues to have a major negative influence on remaining CRCT. Most migratory life histories and interconnected habitats have been lost. Dams and water diversions limit downstream movement, but ironically, may also serve as barriers to upstream invasion by non-native trouts. One of the most challenging needs for CRCT is the reestablishment of large, interconnected habitat areas where fluvial and adfluvial populations can exist free of non-native trout species.

Non-native species control and reintroduction efforts are the highest priority recovery actions. Existing watershed condition is relatively high throughout the historic range, with 19% of subwatersheds in the highest condition category. Protection of remaining strongholds also is vital, particularly in the face of widespread energy development on public lands. Currently, 51% of CRCT habitat in Wyoming lies in unprotected National Forest roadless areas.

We have very little data to assess lake populations and encourage various state and federal agencies to more closely monitor and report their status in the future.

Prepared by Jack E. Williams, TU, 4/23/2007

Conservation Strategies Map

(500KB JPEG)