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INTRODUCTION Purpose The operation of Flaming Gorge Dam affects native fishes and their habitats in the Green River of the upper Colorado River basin. These effects have been characterized in spring, summer, and fall, but little is known about biological responses to dam operations in winter. This document synthesizes information from winter studies on native fishes in the Green River, together with literature from rivers and streams throughout the world. The purpose of this synthesis is to provide background .information and identify future research needs for developing winter flow recommendations for Flaming Gorge Dam that will be beneficial to native fishes. Background The Green River is regulated year around by Flaming Gorge Dam for water delivery, flood control, and power generation. At an elevation of 1,708 m, the dam is located in northeastern Utah, about 660 km upstream of the confluence with the Colorado River (Figure 1). Flaming Gorge Dam was authorized by the Colorado River Storage Project Act of 1956 (43 U.S.C. 620). Construction began in 1956, and was completed in 1964. The reservoir began filling in November, 1962, and continued through 1966, with full operation in 1967. Flaming Gorge Reservoir impounds water for about 145 km upstream to Green River, Wyoming, with a total area of about 17,000 ha, and a live storage capacity of about 3.75 million acre feet. Daily releases from Flaming Gorge Dam can range from 800 to 4,700 cfs (23 to 133 cros). Minimum releases have been established by the Utah Division of Wildlife Resources (UDWR) to provide necessary flows for the tailwater trout fishery, and maximum powerplant releases are constrained by generator output capacity and reservoir elevation. The dam also has the capacity to release up to 4,000 cfs (113 cros) through two river outlets (jet tubes), and an additional 28,800 cfs (816 cros) through the spillway. Flow regulation is ameliorated with distance downstream from the dam, and by inflow from several major tributaries, including the Yampa, White, Duchesne, San Rafael, and Price rivers. The Green River and its tributaries historically supported 13 species of fish native to the upper Colorado River basin (ryas et al. 1982). Eight warmwater species were native to the river below Flaming Gorge (Table 1), including Colorado squawfish (Ptychocheilus Lucius ,humpback chub Gila cypha), bonytail (Gila ele ans , roundtail chub (Gila robusta ,speckled dace (Rhinichth +Ls osculus ,razorback sucker (Xyrauchen texanus , IIannelmouth sucker (Catostomus lati Innis ,and bluehead sucker (Catostomus discobolus (Vanicek 1967). Following construction of Flaming Gorge 1