THE FUTURE OF THE COLORADO CUTTHROAT TROUT
Over millennia one of America's most spectacular native trout, the Colorado River Cutthroat, has specialized to thrive in unique conditions of the upper Colorado River Basin waters. Within each basin and stream the Colorado River Cutthroat co-evolved with the indigenous aquatic flora and fauna and even with the hydrodynamic conditions of the streams themselves. Among these unique waters are a handful of cold High Uinta headwater streams. As one of only two native trout in the High Uinta Wilderness, the Colorado River Cutthroat is essential to this thriving natural ecosystem. (The other native trout of the Uintas is the Bonneville Cutthroat; both of these are Utah's only wild native trout. (See HUPC Review 8/97).
The pre-Columbian distribution of the Colorado River Cutthroat included all the cool water streams and rivers of the upper Colorado basin above present day Glen Canyon Dam. Under natural conditions individual Colorado River Cutthroat moved free ly between breeding populations, ensuring great genetic diversity. Despite the reproductive potential of the Colorado River Cutthroat, scientific studies indicate that the current populations are increasingly isolated and occupy a scant 5% of the historic range. Due to the increasing isolation of the remaining populations in small high elevation streams, most populations are below levels that biologists feel are necessary to maintain genetic integrity and population viability. Small isolated groups are highly vulnerable to localized extinction due to both anthropogenic causes as well as significant natural events.
The reasons for this dramatic range and population reduction are multi-faceted and clearly attributable to human activity. Of primary concern in the High Uintas Wilderness and surrounding roadless areas are the stocking and spread of non-native trout and degradation of stream conditions due to livestock grazing. Non-natives compete with the Colorado River Cutthroat at many levels. Brook trout are primary predators of the Cutthroat, devouring many of the fry and young fish before they reach sexual maturity. In addition, Brook trout reach sexual maturity at an earlier age and breed during the fall when stream flows have stabilized and consequently have a distinct reproductive advantage over the native cutthroat trout.
Rainbow trout, on the other hand, impact the Colorado River Cutthroat mainly by hybridization. Cross breeding accounts for genetic impurity in many remaining populations. Compounding the problem is the erosion of stream conditions due to overgrazing of riparian areas, which results in the loss of streamside plants that prevent soil erosion and provide valuable shade in the heat of summer.
The result is lack of undercut banks, elevated stream temperatures, widened stream channels, and heavy siltation of the gravel beds required for reproduction. If the native cutthroats weren't confined to such fragmented and disjunct habitats in nearl invisible population numbers, they may be able to withstand some of this competition. But as it stands now, and likely will for decades to come, these two species are deeply threatened with broad scale extirpation.
The Colorado River Cutthroat, along with Utah's other native trout, the Bonneville Cutthroat, is currently undergoing formal analysis for listing as a threatened and endangered species. The management practices of the Utah Division of Wildlife Resources and the Forest Service have been less than adequate to ensure the survival of these species. Minimalistic and piecemeal in their approach, the Ashley National Forest and UDWR have recently proposed to use two fish poisons, rotenone and antimycin, in isolated stretches of streams just outside the eastern end of the High Uintas Wilderness. This approach requires removing the native cutthroat prior to poisoning and after neutralization and introduction of downstream fish barriers returning the natives to these waters. (See associated article .)
It is imperative for the survival of the Colorado River and Bonneville Cutthroats that a more widespread and long-term approach be taken to protect remaining populations. (See August 1997 HUPC Review.) HUPC has proposed a more productive approach:broaden the geographic and time scale to include a 10 year view of eradicating non-native fisheries within the High Uintas Wilderness and adjacent roadless areas. This process should be initiated immediately by establishing native trout refugia on basins and drainages within the High Uintas Wilderness, and ending all non-native stocking within these refugia. Clearly this is a difficult problem that cannot be adequately addressed by small steps that address the symptoms but not the root causes of the problem.