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<br />e <br /> <br />COLORADO SQUAWFISH AND HUMPBACK CHUB <br />POPULATION AND HABITAT MONITORING <br /> <br />Charles G. Prewitt, Edmund J. Wick, <br />Darrell E. Snyder and David Langlois <br /> <br />PROGRAM NARRATIVE OBJECTIVES <br /> <br />To monitor reproductive success and year class ab~ndance of Colorado <br /> <br />squawfish and humpback chubs in trend zones; develop identification <br /> <br />keys; and to monitor habitat status in trend zones known to contain <br /> <br />Colorado squawfish and humpback chubs. <br /> <br />INTRODUCTION <br /> <br />e <br /> <br />The diminishing distribution and abundance of the Colorado squawfish <br /> <br />~tychochei1us 1ucius) and humpback chub (Gila cypha) in Colorado have <br /> <br />been documented several times over the past 5 years (Holden and <br /> <br />Stalnaker 1975; Kidd 1975, 1977; Prewitt et a1 1975, 1977, 1978; <br /> <br />Wi1tzius 1978). The decline of the Colorado squawfish was recently sum- <br /> <br />marized by Seetha1er (1978). <br /> <br />Dew~tering, water impoundments, reservoir evaporation, and irrigation <br /> <br />diversions have led to changes in the river morphology, water tempera- <br /> <br />tures, and water chemistry of the Colorado River system. Also, by intent <br /> <br />or accident man has introduced a number of non-native species that inter- <br /> <br />act with the Colorado squawfish (and humpback chubs). Because of these <br /> <br />habitat changes, in 1973 both the Colorado squawfish and humpback chub <br /> <br />e <br /> <br />2 <br />