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the desired stable base flow of 51 m3/sec (+ 12.5 % Pucherelli et al. 1990 , Tyus and Karp 1991, U. S. Fish and Wildlife Service 1992), releases were usually decreased to as low as 22.3 m3/sec soon after prescribed high spring flows ended because Yampa River dischazge was usually high. Dam releases were increased later in summer after Yampa River dischazge declined and when Green River discharge at Jensen fell below target levels. Summer discharge manipulations altered thermal regimes in the regulated reach (see later section) because dischazge level and water temperature aze inversely correlated in the Green River downstream of Flaming Gorge Dam (Vanicek et al. 1970). Composition and reproductive status of the fish community in the regulated reach, 1962- 1996.--Community composition and reproductive status of fish in the Green River upstream of the Yampa River, as documented in previous studies, has changed dramatically since construction of Flaming Gorge Dam (Table 1). Limited sampling during pre-impoundment investigations in the present-day reservoir basin area suggested that eleven native and six introduced fishes, and one catostomid hybrid inhabited that reach prior to 1960. All native fishes, including endangered Colorado pikeminnow, bonytail Gila elegans, humpback chub Gila cypha, and razorback sucker Xyrauchen texanus, inhabited the reach and likely reproduced there. During reservoir filling from 1963 to 1967, sampling detected only seven native and eight introduced taxa in the study azea. The limited reproduction noted for only a few species occurred in 1965 when reservoir dischazge was relatively low and warm and only in downstream reaches. Notable was the near absence of reproduction by native fishes in the regulated reach after normal dam operations commenced in 1967. Following penstock modifications that warmed reservoir releases in June 1978, sampling detected a total of nine native and 13 introduced taxa and two hybrid sucker combinations. With the exception of raze native or incidental non-native taxa, most fishes reproduced in the regulated reach. Natives mountain whitefish Prosopium williamsoni, mountain sucker Catostomus platyrhynchus, and mottled sculpin Cottus bairdi re-appeazed in collections, and first 14