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~t '.' .~ Fishery Early in the planning stages of developing environmental studies below Glen Canyon Dam, the '''Lee's Ferry Fishery" was singled out as a resource that warranted special attention. The biological subteam recommended that the Fish and Wildlife Service's Instream Flow Methodology be applied to this 15-mi1e section of the Colorado River. This methodology can predict available fish habitat at varying flow increments (i.e., 5,000 cfs., 15,000 cfs., 40,000 cfs., etc.). Specifically, the amount of usable fish habitat can be expressed as a function of velocity, depth, and substrate (compOsition of streambed). Eleven cross-sections were selected in a study reach located approximately 5 miles below Glen Canyon Dam. Each cross-section was selected to predict specific habitat types. At three different flows, each one of the cross-sections was surveyed for overall depth, water velocity, and bottom substrate. Since we are predicting fish habitat over a wide spectrum of available flow (1,000 to 40,000 cfs.), we correspondingly selected representative flows for our study. Recently, the last set of measurements was taken at a flow of approximately 26,000 cfs. The other two measurements were taken earlier this year at 2,000 and 16,000 cfs. Although existing fish habitat data are available for velocities, depths, and substrate, we are supplementing these data with our own study designed to ,develop fish preferences for this specific habitat area. Through the use of divers and surface observation, we will be able to predict the probability of finding a specific fish species at a given combination of these hydraulic criteria. We anticipate that this study will be completed by early 1981. At that time, possible impacts to this important fishery resource could be quantified and used in selecting a size.