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a <br />*****DRAFT***** <br />Introduction <br />The Colorado River Fishery Project of the U. S. Fish and Wildlife <br />Service has studied the Colorado squawfish (Ptychocheilus Lucius) and <br />razorback sucker (Xyrauchen texan«s) populations of the upper Colorado <br />River since 1979. These studies include the routine sampling of the <br />larval-fish community using fine-mesh (0.5-mm) hand nets, as well as <br />sampling of the small-fish community using small-mesh (3 and 6-mm) <br />seines. In this report,~.we compare the captures of larval, post-larval <br />age-0, and adult-size Colorado squawfish from adjacent Colorado River <br />reaches immediately upstream and downstream from the confluence with the <br />Gunnison River, Mesa County, Colorado. We also summarize our records on <br />the capture of adult-size razorback suckers from these river reaches. <br />No information is provided on the occurrence of larval or post-larval <br />-- - age-0 razorback suckers because reliable techniques that would tallow us <br />to distinguish these li`e stages from those of other Colorado River <br />species of catostomids (suckers) have yet to be developed. <br />N~thods <br />Samples of larval fishes are collected from low-velocity shoreline <br />areas during July, August and September--when larval Colorado squawfish <br />are normally present. Samples are collected at intervals of 3 to 5 <br />river miles, and approximately 10 minutes of effort is expended to <br />collect each sample. All samples are preserved in the field and <br />identified later by the Larval Fish Laboratory (CSU, rr"ort Collins). <br />Sampling with small-mesh seines occurs during September, and has <br />recently been conducted during August and October as well. At that <br />2 <br />