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normal 24-hour releases usually ranged between 600 and 800 cfs, producing stage changes in the nursery area of <0.1 m at the upper end and <0.01 m and the lower end. These fluctuations did not alter physical morphology of backwaters studied in the Ouray Backwater Complex. These stage changes had only minimal affect on backwater habitats and were limited to the upper end of the nursery area. In contrast to flow fluctuations, the formation of ice jams, as observed in the 1999-2000 winter, had far greater affect on backwater nurseryhabitats. Ice jams increased stage by 0.75-1.50 m, and transformed many backwater habitats into flow-through areas. In association with backwater transformation to flow-through environments, fish may be flushed into the surrounding system and incur increased risk of injury, predation, and metabolic cost associated with the search for another suitable nursery area (Haines et al. 1998; Muth et al. 2000). The role of fluctuating winter flows from Flaming Gorge in the creation of ice jams is unclear to us. Valdez and Cowdell (1999) speculated that fluctuating winter flows dismantle ice cover which facilitates the formation of frazil ice, and potentially results in ice jams that increase river stage several meters thus inundating many backwaters. However, Hayse et al. (2000) found that fluctuating winter flows did not dismantle ice cover or promote formation of frazil ice and ice jams. Whatever the cause, it is likely that ice jams format several locations on the middle Green River nursery area in most years (Valdez and Cowdell 1999; Hayes et al. 2000). Winter Sampling for Age-0 Colorado pikeminnow Prior to ice formation, the most effective method for catching age-0 Colorado pikeminnow was seining. Seining was most effective when backwaters were warm and became less efficient as temperatures cooled. Colorado pikeminnow that occupied backwaters on the first pass during autumn sampling often vacated them prior to subsequent passes, especially when slush ice was found in the backwaters. During ice cover, all gear types were ineffective for capturing age-0 Colorado pikeminnow. Over the three year study period, only one young-of-year Colorado pikeminnow was captured under ice xiii