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mile reach if not the upper Colorado River. Thus, if not representative of backwaters as a whole, they are representative of backwaters with features attractive to adult squawfish. The four secondary and three main-single, channel segments sampled with transects were not necessarily areas of high squawfish use; some were known to have been used, others were not. How representative our transect sites were of fast and slow runs throughout the reach is unknown. At the time of study design and selection of transect sites, it was not known that eddies and pools were the most preferred habitats types; in retrospect, it is clear that these important types were under sampled. Thus, we draw what conclusions we can regarding flows needed to maintain adequate depth within the various habitat types, recognizing the limitations of our sample. The one eddy we sampled maintained depth that exceeded summer and winter suitability criteria at all flows studied (Table 4). For the pool, the deepest point was sufficient for summer use at all flows, but average depth was suitable only at flows of 1,240 cfs or greater. For winter use, the deepest point was suitable at flows of 810-900 cfs but flows had to be greater than 5,020 cfs to provide an average depth that was adequate. Scouring of the bed in 1991, however, resulted in maximum depths in the pool that later met or exceeded the suitability criteria at all flows studied. Of the two backwaters studied, backwater No. I had less than suitable depth at all flow levels typical of summer or winter conditions and higher spring flows in 1991 failed to improve condi- tions there. Backwater No.2, on the other hand, did benefit from the 1991 spring flows: in 1990, both maximum and average depths were less than adequate at both upper and midway sites during all flows typical of summer or winter conditions. But in 1991, average depth at the midway transect was very close to being suitable for summer use at flows of 1,630 cfs, and maximum depth there met the criteria at flows of 810 cfs. For winter use, maximum depth in 1991 at the midway transect in backwater No. 2 met or exceeded the suitability minimum at all flows studied, and average depth did so at flows of 900 cfs. During low summer flows when runs are preferred, maximum depth was suitable at all flows for fast runs at two secondary and two main-single channel sites. Average depth was greatly improved at one secondary-channel site after the bed was scoured in spring of 1991. For slow runs, maximum depth during the lower flows was less than adequate at one secondary channel transect but was more than adequate at a different one. At a main-single, channel transect that bisected a slow run, maximum depth was also suitable at the lower flows. Depth in Relation to The Summer-Winter Flow Recommendations In a previous section, we found that flows of 1,630 cfs provided the best combination of habitats (total weighted area) preferred during summer (backwaters, pools and eddies). We therefore recommended a flow of 1,630 cfs for the top of the 15-mile reach during summer (August- October). During years of below average precipitation when it would be difficult to meet this recommendation, 1,240 cfs would still provide sufficient flows such that Colorado squawfish would continue using their normally preferred habitats. During drought years fish would be forced to modify their behavior but 810 cfs would result in significantly more total weighted area of slow and fast runs than would 557 cfs. During winter, habitat preferences change somewhat and flows in the reach are higher on average than during summer. However, flows of 1,630 cfs were also found to provide the greatest total weighted area of preferred winter habitat. 43