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Gorge Dam is located on the Green Ri ver near one of these canyons; the reservoir extends upstream 147 km (91 mi) to within 8 km (5 mi) of the town of Green River, Wyoming, In general, the water coming down the Green River from the Wyoming Wind River Mountains is low in dissolved minerals and carries little silt but picks up considerable silt, alkali and other dissolved constituents from the desert area before entering the reservoir. The inflow reservoir area (Fig. 1) is directly affected by the substantial water contributions of the Green and Black's Fork rivers. The inflow area has the lowest gradient and is the shallowest portion ofthe reservoir, with a maximum depth of 24 meters. Strong prevailing winds result in extensive mixing of the water column and limit thermal stratification, Reservoir water temperatures are highest in this portion, and heavy blooms of phytoplankton occur in the summer. Turbidity is high in the spring, During years of normal inflow, sport fish in the area exhibit the best growth and length-weight relationship. Here the Utah chub population exhibited its most rapid expansion and highest total population levels, Concurrent with early ongoing fishery investigations, decisions were made to reduce rainbow stocking as the main management program in this area in favor of brown trout, The open hills aquatic environment (Fig. 1) is surrounded by low, rolling: sagebrush covered hills. Considering total biomass this area is the most productive portion of the reservior. The lake consists of extensive littoral bays and gravel and shale shelves at both shallow and mid-depths. The water is well mixed by prevailing winds. Maximum depth is approximately 61 m (200 ft), and the effects of water fluctuation are moderate, Turbidity and color are not major factors influencing water quality. Generally the area is most popular with anglers and appears to be prime habitat as evidenced by sport fish populations, Rainbow trout growth and length-weight relationships are intermediate for the reservoir as a whole and excellent for similar western reservoirs. The canyon reservoir portion is characterized by a considerable volume of the storage being deep water, 61 to 122 m (200 to 400 ft). The area has stepping rock ledges or vertical fractured walls with a severely limi ted littoral zone, Mixing by wind is very limited because the twisting deep canyons, 152 to over 400 III (500-1,300 ft), provide extensive protection, Extremely soft water tributaries empty into this portion, The effects of fluctuation are minimal, and waters of the area are the most transparent and generally show lowest production of the reservoir. Sport fish populations reach high levels of abundance, but growth rate and length-weight relationships are the lowest ofthe reservoir, During at least some years, considerable down-reservoir migration of trout to this area is evident. Therefore, original management stocking practices were changed during the early years of impoundment to provide maintenance stocking at a lower rate per hectare here than the other two aquatic environments, The third feature of Flaming Gorge Reservoir relates to the control of undesirable fish species within the drainage above Flaming Gorge Dam by the introduction of rotenone prior to dam closure. This project encompassed 720km (445mi) of the Green River and its tributaries and resulted in the reduction offish life at all trophic levels, From the standpoint of fish populations,the channel catfish (Ictalurus punctatus), humpback sucker (Xyrauchen texanus) and the Colorado squawfish (Ptychlocheilus lucius) have not since been found in the reservoir (Tables 1,2). It should be noted that the two native species require a lotic environment, Prior to impoundment, the five most abundant species were redside shiner (Richardsonius balteatus hydrophlox), speckled dace (Rhinichythys osculus), flannelmouth sucker (Catostomus latipinnis), roundtail 5