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" It is recognized that the six populations of humpback chub vary considerably in size, from about 400 to 5,000 adults. The larger populations are considered "core populations". A core population is an independent self-sustaining population sufficiently large to maintain genetic and demographic viahility. A core population may serve as a center of dispersal from which new populations are established or existing populations are augmented. Core populations are sufficiently large and viable to protect against extreme demographic and environmental variabi lity. A core population may consist of two or more geographically proximate populations (e.g., Black Rocks and Westwater Canyon). In case of a catastrophe, multiple or redundant core populations preserve species viability." Despite a current downward trend (not statistical) in adult humpback chub population estimates in the past few years, if the estimates of all humpback chub populations were summed there would be between 5,000 and 10,000 adults in the Colorado River Basin. The current population trend may be caused by recent drought during the late 1990's and early part of2000, although there is some indication that some of the population declines may have been occurring before the drought conditions. Reduced stream flows have also allowed for an expansion of nonnative fish species which compete with and prey upon the native fishes. UPPER COLORADO RIVER BASIN GENETICS MANAGEMENT PLAN The Upper Colorado River Endangered Fish Recovery Program (Recovery Program) philosophy and mission for genetics management of endangered fishes are to: I. Maintain the genetic integrity of wild endangered fish stocks in the upper basin; and 2. Maintain genetic diversity in captive broodstocks that is similar to the stock used as founders. The goals of this genetics management plan are to: I. Conserve genetic diversity of wild endangered fish populations while implementing recovery efforts that will maintain, enhance, or reestablish viable wild populations by removing or significantly reducing factors that caused population declines; 2. Maintain genetic diversity in captive-reared endangered fish broodstock that is similar to that of the wild population used as founders; and 3. Produce genetically diverse fish for augmentation efforts. According to the current Genetics Management Plan (Czapla 1999), the humpback chub was assigned "Priority 3" among the four endangered species because the populations were considered stable but small and localized in deep canyon river reaches. Within the species, DRAFT HBC Genetics Management Plan-3 OCG:g