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complex-channel segments (Osmundson and Kaeding 1990). The complex segments provide a greater diversity of habitats for Colorado squawfish to utilize for feeding, resting, and other activities. High spring flows are important in maintaining these aYeas. High spring flows are also important to successful reproduction of Colorado squawfish. McAda and Kaeding (1989) reported higher reproductive success in the Colorado River during years of moderately high flow. The Fish and Wildlife Service conducted fall surveys to determine relative abundance of young-of-the-year (YOY) Colorado squawfish in the Colorado River from 1982 to 1985 (Archer et al. 1985). F~eginning in 1986, similar surveys were conducted by the states of Utah and Co]orado as part of the Interagency Standardized Monitoring Program (ISMP). ]:SMP divided the river into two reaches (1, RM 0- 110 and 2, RM 140-170), based on the known distribution of Colorado squawfish (Archer et al. 1985). McAda and Kaeding (1989) used the FWS and ISMP data to compare relative abundance off: YOY Colorado squawfish in fall with maximum- annual discharge (mean-daily flow on the highest day) the previous spring (Figure 8). They found a parabolic relation in reach 1--the highest relative abundance of YOY Colorado squawfish occurred in 1985 and 1986 when spring flows peaked at 32,800 and 38,200 cfs at the stateline gage (peak flows at Cisco were 34,100 and 43,200 cfs). Relative abundance was lower in years that had lower and substantially Higher peak discharges (Figure 8). McAda and Kaeding (1989) found no clear relation in reach 2 for the years they studied, but Osmundson and Kaeding (1~~90) showed a positive relation between relative abundance of age-0 Colorado :>quawfish and maximum-annual discharge for about the same reach during 1986 to 1989. It is not yet clear whether spring runoff itself or another variable c:Losely related to spring runoff is responsible for 25