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INTRODUCTION <br />Three native fishes, Colorado squawfish (Ptychocheilus lucius), humpback <br />chub (Gila cy ha), and bonytail (G. elegans) are classified as endangered, and <br />the razorback sucker (Xyrauchen texanus) is rare in the upper Colorado River <br />drainage. The habitat of these fishes has been altered in recent years by <br />man-made water development projects and the fish community has been changed <br />by introduction of exotic species. <br />Striped bass were first introduced into Lake Powell on the Colorado <br />River by the Utah Division of Wildlife Resources in 1974. With the exception <br />of 1980, bass fry have been stocked annually since 1974 at Wawheap Bay and <br />from 1976-1978 at Bullfrog Bay. Inasmuch as striped bass are highly piscivorous, <br />a concern exists as to whether the adult spawners prey on native fishes while <br />in the river on their spawning migration. Two other exotic, piscivorous <br />species, walleye (Stizostedion vitreum) and channel catfish (Ictalurus punctatus), <br />are common at the head of the reservoir. <br />The objective of this study was to determine if striped bass constitute <br />a threat to survival of the native fish species in the drainage. <br />Specific objectives were to: <br />1. Sample the Colorado River at the head of Lake Powell and above <br />Cataract Canyon for adult striped bass during their spawning period. <br />2. Determine the food habits of all migratory striped bass captured. <br />3. Determine the degree of success of striped bass reproduction in <br />the Colorado River. <br />In the process of realizing these objectives, data on walleye and channel <br />catfish were also collected.