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Table 6.-Number of backwaters sampled and percent of backwaters containing at least one Colorado squawfish, Interagency Standardized Monitoring Program, 1986-1992. Reach 1 Reach 2 Reach 3 Reach 4 Percent Percent Percent Percent Number of with Number of with Number of with Number of with Backwaters Colorado Backwaters Colorado Backwaters Colorado Backwaters Colorado Year Sampled squawfish Sampled squawfish Sampled squawfish Sampled squawfish 1986 24 75.0 11 63.6 28 85.7 42 66.7 1987 34 44.1 11 18.2 35 80.0 40 50.0 1988 43 69.8 10 10 42 97.6 42 73.8 1989 43 51.2 11 9.1 48 95.8 42 40S 1990 37 48.6 14 7.1 46 76.1 42 71.4 1991 34 58.8 20 5.0 34 70.6 40 77S 1992 41 43.9 15 6.7 47 51.1 40 67S The descriptive histograms did not show any major differences in backwater size between backwaters that contained Colorado squawfish and those that contained none. With a few exceptions, the frequency distributions for both backwater categories followed basically the same pattern. Independent t-tests were conducted on 22 data sets (t-tests could not be done for Reach 2 for 1988 through 1992 because only one backwater contained a Colorado squawfish or for Reach 3 in 1988 because only one backwater did not contain any Colorado squawfish). Significant differences were found in five of those data sets-Reach 1 in 1989, Reach 3 in 1989, and Reach 4 in 1989, 1990, and 1991. The backwaters containing Colorado squawfish were significantly larger than those that did not contain any in four of those cases and significantly smaller in one case (Reach 3, 1989). In cases where significant differences were not found, average surface area of backwaters containing Colorado squawfish was larger in 13 cases and smaller in four cases. Of 23 cases when ANOVA could be conducted significant differences were found in four instances. Three of these instances found significantly higher catch rates in larger backwaters (Reach 1, 1989 and 1990, Reach 4, 1991) and one found significantly lower catch rates in the larger backwaters (Reach 4, 1989). As would be expected in this type of data, variability was very high among the four categories in most years. Correlations between gmean CPE for Colorado squawfish and backwater surface area were generally very weak and not significant (Table B-10). Only one significant relationship was found-Reach 4, 1991 (r=.72). The maximum depth of the sampled backwaters was partitioned into 15-cm increments for the descriptive histograms and into four categories for ANOVA- < 35 cm, 35 to 49 cm, 50 to 76 cm, and > 76 cm. There was no discernable difference in patterns between depths of backwaters containing Colorado squawfish and those that did not. However, t-tests found significant differences in maximum depth between the two categories in four instances-Reach 3 in 1986 and 1989 and Reach 4 in 1986 and 1989. Backwaters containing Colorado squawfish were significantly deeper in three of these cases and significantly shallower in one case. Significant differences in gmean CPE among the four depth categories were found with ANOVA in three cases-Reach 3 in 1989 and Reach 4 in 1986 and 1988. Catch rates were significantly higher in the deeper backwater categories in two cases and significantly lower in the higher categories in one of those cases (Reach 4, 1988). As observed with backwater size, there was considerable variation among the various categories in most 15