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Spatial Variations (All Habitats) In order to evaluate the spatial pattern exhibited by the parameters investigated in this study, means and confidence intervals (P=0.05) were calculated by averaging the three sample periods (fall 1994, spring 1995, and fall 1995). The spring 1994 data was not included in this analysis because only four strata were sampled. Significant differences for all habitats combined, as well as for riffles or runs, were initially determined by a one-way ANOVA followed by the Tukeys HSD which determined significant differences between specific stratum. All data were plotted by stratum with mean values and 95% confidence intervals. A summary of the stratum characteristics and locations can be seen in Table 3 and Figure 1. Physical Parameters-The mean substrate diameter (D50) showed significant changes by river stratum. The general pattern was a reduction in substrate size (D16 and D50) from stratum 11 downstream to stratum 6. Substrate size then increased to approximately 100 mm in stratum 3 only to decrease in stratum 2 and reaching its lowest value in stratum 1. Inspection of the mean and 95% confidence interval for these strata can be seen in Figure 27. The stratum sampled in the Gunnison River had a mean D50 of 78 mm and a D16 of 37 mm and was similar to strata 7 and 8 and strata 3 and 4, respectively in the Colorado River. 180 140 120 E100 E 80 SO f 40 20 0 -20 STRATA COLORADO RIVER Mean Particle Diameter: D50 1 ± ! T 1 S7 S2 53 S4 S5 SS S7 88 s9 sio's11 GuNN COLORADO RIVER Mean Depth to Embeddedness 12 10 E 8 D 8 m 2 4 STRATA Figure 27. The spatial distribution of substrate sizes within Figure 28. The spatial distribution of depth to embeddedness the Colorado and Gunnison rivers. and percent embeddedness within the Colorado and Gunnison rivers. 26