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94 nun (range = 74-125 nun) in total length and 9.5 g (range = 3-18 g). In 1996,45 age-O razorback sucker were collected earlier (August) and averaged 65.9 nun (range = 44-83 nun) in total length and 3.8 g (1-6 g). In 1995 two razorback sucker adults were collected, while none were collected in 1996. Inunature Colorado squawfish (total length ranges 175-207 nun, and 115-155 nun in 1995 and 1996, respectively), flannelmouth sucker and roundtail chub were also collected in both 1995 and 1996. Speckled dace were identified only in 1996, but may have been present in 1995. The percentage offish collected over time was not uniform during the draining period in 1996. Adult fishes, with the exception of green sunfish, were collected at the outlet structure throughout the draining process (Figure 16). Most channel catfish were actually caught midway through the draining process in 1996. In addition, red shiner were also collected throughout the draining process, although most were taken during the last few days of draining. Age-O yearclass of the most abundant nonnative fishes and fathead minnows showed little tendency to move into the drainage outlet until the last few days of draining. Native species showed different tendencies, flannelmouth sucker and Colorado squawfish moved to the drainage outlet earlier in the draining process as well as later, whereas, most razorback sucker did not move into the drainage outlet until the last days of draining. Discussion Suitability of Old Charley Wash as a nursery site Old Charley Wash provided a favorable environment for fish, particularly age-O fishes during years when spring flows inundated the wetland. Water quantity and quality existed throughout the spring and summer to support age-O and adult fishes. Water loss through evaporation and seepage would have created an adverse environment for fishes had not water from the Green River been supplemented during the low flow year of 1994. Water temperatures in the main channel were similar to Old Charley Wash after mid-June during the low flow year of the study, but during the two high flow years, water temperatures in Old Charley Wash were consistently higher than main channel temperatures. Later in the spring or summer, when most backwaters begin appearing in the Jensen and Ouray areas of the river (i.e. 109m3/s [Pucherelli et al. 1988]), warmer habitats would become available to fish in the main channel. However, until river flows receded sufficiently to allow the appearance of backwaters, Old Charley Wash and other floodplain habitats provided the best thermal environment for growth of larval and juvenile fish in the Green River. Zooplankton densities in surface waters from Old Charley Wash were much higher than in backwaters in the Middle Green River in 1994. Peak zooplankton densities in Old Charley Wash were 43 organismsll an 54 organismsll in 1995 and 1996, respectively. Greater zooplankton densities in Old Charley Wash coincided with larval razorback sucker appearance in the Green River during the three years of this study (i.e. peak and post peak flows, Muth et al. 1997). Grabowski and Hiebert (1989) reported that zooplankton Green River backwaters varied from 0.44 zooplanktonll in Island Park to 1.5 zooplanktonll in Ouray. Mabey (1993) reported zooplankton densities of 7.1/1 and 1.5/1 (using a 63 mu mesh, compared to 243 mu mesh used in this study) in a riverine backwater near Ouray in July and August, respectively, compared to 311.4/1 and 690.2/1 during the same time in Old Charley Wash. In main channel habitats Mabey (1993) reported only 1.3 and 0.3 zooplanktersll in July and August, respectively. Based on invertebrate densities, Cooper and Severn (1994) concluded that offchannel wetlands were more 39