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rearing habitat to be limited, and may have contributed to the small -, number of YOY squawfish collected. At the flow levels electrofishing efforts were completed, few backwater habitats were observed. How- ~ ever, at lower flow levels during fall YOY seining, backwater habitats did not appear limiting in the braided channel area of the river. There may be a threshold in discharge, or range of discharge, at which backwater formation is most prevalent. Survival of young Colorado squawfish in the San Juan River, Utah may be controlled in large part by the co-occurrence of fry emergence and discharge levels that result ~ in backwater formation. It seems likely that most of the squawfish reproduction in the San Juan River, Utah occurs in the braided channel area. Generally cobble substrate was most predominant in upstream areas, and sand substrate increased downstream. Lack of backwaters in upstream areas would probably result in most young fish being swept downstream, given the high gradients and water velocities. There ~ appeared to be a lack of YOY habitat in the lower canyon area, but if young fish were carried as far as Lake Powell, physical conditions there may be suitable for their survival. A problem with survival in Lake Powell, however, for young squawfish would appear to be the greater prevalence of predators (e.g., smallmouth, largemouth, and striped bass, walleye). Backwater areas preferred by YOY squawfish ~ have been described as having zero velocity and less than 1,5 feet in depth over a silt substrate (Miller et al. 1982). Holden (1977) de- scribed preferred backwaters as having little or no current, depth _ over one foot and silt substrate. Previous data on fishes' relative abundances (CPUE) from back- water habitats in the San Juan River, Utah did not exist in sufficient quantities to make meaningful comparisons with 1987 data. Standard- ized sampling of backwaters, however, indicated lower relative abundances of exotic species than had been anticipated. Relative abundances of exotics may have been influenced by the abnormally high flows during spring and summer. Flow conditions during this study ~ appeared more similar to pre-Navajo Dam flow regimes than post-Navajo Dam flow regimes. Mean monthly flows during January though July 1987 were well above the mean monthly flows under post-Navajo Dam condi- tions. Flow regime changes since dam completion (i.e., habitat changes) may have had direct impacts on squawfish reproduction and recruitment, and indirect impacts by producing conditions more favor- able to competing exotics. The results of our fall YOY seining gave us the impression that relatively high discharges in the summer (i.e., into July) may be more conducive to reproduction of endemic fishes (such as the Colorado squawfish) and less conducive to reproduction of exotic fishes. This concept has been suggested by Haynes et al. (1985): high late spring flow accompanied by rapid heat accumulation ~ provide high quantity and quality spawning areas and satisfactory incubation and growth conditions for squawfish eggs and larvae, and _ may suppress non-native fishes' reproductive success. Habitat preferences of juvenile squawfish (60-200 mm) have been - described as "an intermediate phase in the shift from the backwater ~ requirements of YOY to the deeper, main channel eddy and shoreline - 41 -