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JJI. PROTECTION F NATIVE AND WILD TROUT The primary management goal in dealing with WD in Colorado is to maintain the long-term integrity of naturally-repr9ducing populations of native cutthroat trout and wild trout. Two management programs associated with these trout populations include Wild Trout and Gold Medal fisheries. The three native subspecies of cutthroat trout are a resource unique to Colorado, with the greenback being found nowhere else. Populations of these trout found in adjoining river basins offer unique recreational fishing opportunities. From the conservation perspective, the greenback cutthroat is federally and state listed as threatened, and the Colorado River cutthroat has declined and is a likely candidate for federal listing. Rio Grande cutthroat are considered a "species of special concern." Recent research into WD effects on trout have demonstrated an equal or greater vulnerability of the Colorado River cutthroat compared with other salmonids. In 1995, brook trout and native Colorado River cutthroat trout were found to suffer far greater mortality than wild Colorado River rainbow trout when exposed to the same conditions in tests in the Colorado River. This vulnerability may be translated into potential impacts to self-sustaining populations of cutthroat trout that are similar to those documented for rainbow trout, i.e., failure of recruitment and greatly diminished, or lost, year classes. Already in a precarious ecological status, further spread of the WD parasite into Colorado's native cutthroat trout habitats will put these subspecies at greater risk and further jeopardize their potential for recovery. In some sections of the upper Colorado River, negative population level effects have been documented on brown trout (Walker and Nehring 1995; Nehring 1996), although in other sections containing WD, biomass of brown trout showed increases. Wild Trout and Gold Medal trout fisheries that are officially designated by the CWC represent quality fishing experiences that are highly desired by the public for their environmental setting, high quality and productive habitat, and availability of large- to trophy-size trout. These fisheries are sustained by introduced populations of primarily rainbow and brown trout, but they also include nonnative cutthroat trout, brook trout, and other gamefish species. Catch-and- release and limited harvest regulations are used to maintain these trout populations. Before the spread of WD, most trout populations under Gold Medal and Wild Trout management were largely self-sustaining. Dimensions of the Native Cutthroat/Wild Trout Resource The habitat occupied by native cutthroat trout is limited. Right now, 137 populations of native cutthroat are found in 11 of the 15 major watersheds in Colorado. They occupy 96 streams totaling almost 600 stream miles and 41 lakes encompassing 450 surface acres (Table 2). Under the most optimistic conditions, 296 streams totaling almost 1,600 miles and 61 lakes encompassing 1,000 surface acres (current plus potential habitat) might be suitable for native cutthroat restoration. This expansion is implied in the recovery and conservation plans and would have to be accomplished over many years. 10