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~~ Larval collections were made in late July 1981 and sent to the Larval Fish Laboratory, Colorado State University, for sorting and id- entification. Beginning in September, the young-of-the-year collections for the larger Colorado squawf ish were made using the same sampling design, with the exception that fishes were identified in the field instead of shipped to a con-tractor and a one-quarter inch mesh seine was used for all collections. Movements and Habitat Preferences of Young Colorado~Squawf ish Preliminary sampling conducted by the Vernal station in October 1979 indicated that young-of-the-year Colorado squawf ish exhibited a diel (24 hour) movement pattern. In 1980, studies were initiated to further examine potential habitat preferences for backwater areas and to explore movement patterns. Sample sites were selected in strata A, C and F, since young-of-the-year Colorado squawf ish were more abundant in those strata in 1979. Each stratum was scheduled for sampling during pre-runoff, runoff, and post-runoff river stages to coincide with the standardized sampling program. Each site was sampled for four days. Each day was divided into three, 8-hour periods; in turn, these 8-hour periods were divided into two, 4-hour periods (Figure A-4, Appendices). The selected backwater was sampled during each 8-hour period by systematic sampling using a random start. Sampling alternated between the two halves of an 8-hour period. For example, if sampling on the first day included time periods A-1, B-1 and C-2, then sampling on the second day would be done during periods A-2, B-2 and C-1. Sampling on the third day included the same periods as sampled on the first day. Data were recorded in the same manner as were other collections except all Colorado squawf ish were fin-clipped before release. All habitat types found in proximity to a selected backwater were sampled with a one-quarter inch mesh seine at the same time with comparable effort. This allowed comparisons of the abundance of young Colorado squawf ish in backwaters with other habitat types. On October 9, 1980, the Vernal field office initiated a small study in cooperation with the Bureau fo Reclamation and the Fish and Wildlife Service's Division of Ecological Services. The objectives of this study were two: 1) to determine if peaking power type releases from Flaming Gorge Dam would have a measurable effect on backwater habitat (important for young-of-the-year Colorado squawf ish) as far downriver as Ouray, Utah; and 2) to evaluate any potential effects on movement or habitat preferences of young-of-the-year Colorado squawf ish. In order to monitor any effects, a Large backwater was selected at river mile 255.4 (408.6 km) in Stratum F. Samples of fish populations were made as stated for the diel investigations. Depths and relative size of the backwater and depth of the river was recorded each time fish samples were taken. Noted effects were compared with the U.S. Geological Survey (USGS) stream discharge monitoring station at Jensen, Utah.