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. . flown. The selected study sites will represent the general habitat conditions found in the Gunnison River as well as specific sites known to be important to Colorado squawfish and razorback sucker. Habitat types that can not be identified directly from the photographs (e.g. eddies, runs, riffles, and pools) will be drawn on photographs from prior trips to allow quantification of these specific habitat types. Number and area of each habitat type will be calculated for each flight. EXPANSION OF ONGOING PROJECT Title: Flow effects on humpback chub populations in Black Rocks Scope of Work Number: G Tasks: 10 Cooperating Agencies: Fish and Wildlife Service Wildlife FY 94 Cost: $40,000 Study Summary: The study focuses on the Black Rocks population of humpback chubs in the Colorado River about 35 miles below the Gunnison River confluence. It is designed to address the effect of high spring flows on successful reproduction and recruitment of humpback chub, as well as the effect of seasonal flow events on the formation of critical habitat and the invasion/proliferation of non-native species. The study will also assess the effeces of flows on the invasion of roundtail chubs into Black Rocks and the potential impact of hybridization. Title: Impact of flows and geomorphology on food web dynamics of the Colorado River native fish community: a river-wide, interdisciplinary, ecosystem approach to flow recommendations. Scope of Work Number: H Tasks: 2, 9, 11, 12 Cooperating Agencies: Fish and Wildlife Service, Utah State University, Ecosystem Research Institute. FY 94 Cost: $130,640 Study Summary: Determination of the key limiting factors for each population of endangered fish is a prerequisite to designing and implementing appropriate management activities for species recovery, The precise factors that now limit population size are poorly understood. Currently, there is not even a theory as to why bony tail disappeared. For humpbacks, population size and number are probably limited by availability of sites containing their specialized habitat type, For razorbacks, the key limiting factor apparently involves an unknown mechanism affecting reproductive success, For squawfish, however, it is unclear which factor primarily limits their number: (1) Inadequate reproductive success, (2) Adequate reproduction but low survival, (3) Inadequate reproductive success 9