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GREEN RIVER STUDY PLAN 35 February 2,2007 7: Determine spillway entrainment rates of nonnative fish at Flaming Gorge Dam. Description Spillway releases from Flaming Gorge Dam are hydrologically driven events that occur when excessive water volumes from flows into the reservoir exceed the ability to make controlled releases through the turbines and bypass tubes. Under certain circumstances, spillway releases also could be used to meet flow and temperature recommendations. Spillway releases may allow nonnative fish (especially smallmouth bass) from Flaming Gorge Reservoir to escape into the river below the dam and eventually into habitat occupied by endangered fish further downstream. The species and approximate numbers of fish that escape from the reservoir need to be determined to evaluate the risks of using spillway releases to meet the flow and temperature recommendations. The Recovery Program should coordinate with the Utah Division of Wildlife Resources (UDWR) and Reclamation to secure baseline information. It is expected that UDWR will continue to collect data as part of their annual monitoring programs, and this data can be used to determine rates of entrainment from the reservoir. Sampling immediately following spill events should also be conducted as a means to assess entrainment and escapement of nonnative species. Results of the isotope study (Project C18/19) should be evaluated in reference to reservoir entrainment rates. Hypotheses to Be Evaluated and Information Needs to Be Filled · Increased frequency of bypassing water (spills) at Flaming Gorge Dam would result in increased entrainment of reservoir nonnative fish species (Ul). · Spillway entrainment rates (information need). Implementation · Ongoing Project C18/19.-Isotope data are scheduled to be collected through 2009. These data would provide baseline information that can be used to determine rates of entrainment should spills occur in the future. Because spillway use is hydrologically driven and cannot be predicted, studies to evaluate entrainment rates cannot be scheduled. Isotope data should be collected following spill events and compared to baseline data to determine rates of entrainment. 3.4 Timeline for Recommended Studies and Integration of Information A timeline for the implementation, conduct, and completion of studies recommended in this Study Plan is presented in Table 3. The seven subject areas, as described in Section 3.3 are identified by each of the three resource categories and shown as new starts or ongoing studies.