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<br />EXECUTIVE SUMMARY <br /> <br />This 2-year study of an 84 mile reach of the Green River near Vernal, Utah, <br />was conducted to characterize selected backwaters of the Green River at Island <br />Park, Jensen, and Ouray limnologically and to describe some aspects of trophic <br />interactions of these backwaters. This report describes limnological <br />conditions prevailing in selected backwaters that are documented nursery areas <br />for larval endangered Colorado squawfish. Food habits of young fish in these <br />backwaters were investigated to determine the extent of dietary overlap and <br />possible competition for available food resources. <br /> <br />Flows in the Green River differed substantially between 1987 and 1988. <br />Average flows from July 1 to October 31, 1987, were 1,983 ft3/sec, but only <br />1,532 ft3/sec for the same period in 1988. In addition, daily fluctuations <br />after mid-August 1988 were of lower magnitude and frequency than during the <br />similar period in 1987. limnological data collected from the Green River and <br />backwaters at Island Park, Jensen, and Ouray suggest an upstream to downstream <br />trend in abiotic and biotic characteristics in both the river and backwaters <br />in this reach of river. Average seasonal water temperature was higher <br />downstream than upstream, and warmer in the backwaters than at nearby river <br />sites. Average water temperatures at all sites were higher in 1988 compared <br />to 1987, probably due to the lower average river flow in 1988. Average water <br />temperatures in the main river in 1987 increased from 17.1 .C at Island Park <br />to 19.7 .C at Ouray, and increased from 17.5 .C to 20.4 .C in 1988. In <br />backwaters, average water temperatures in 1987 increased from 19.7 .C at <br />Island Park to 22.0 .C at Ouray, while in 1988, average water temperatures at <br />these same sites were 21.3 .C and 22.9 .C, respectively. <br /> <br />2 <br />