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I <br />INTRODUCTION <br />In the upper Colorado River drainage three native fishes, <br />)lorado squawfish (Ptychocheilus lucius), humpback chub (Gila c ha), <br />and bonytail (G. elegans) are classified as endangered, and the razor <br />k sucker (Xyrauchen texanus) is rare. The habitat of these fishes <br />been altered in recent years by man-made water development projects, <br />the fish community has been changed by introduction of exotic <br />sbecies. <br />Striped bass were first introduced into Lake Powell on the. <br />Colorado River by the Utah Division of Wildlife Resources in 1974. <br />Bass fry were stocked annually from 1974-79 at Wawheap Bay and from <br />1976-78 at Bullfrog Bay. Inasmuch as striped bass are highly <br />pJscivorous, a concern existed as to whether the adult spawners <br />y on native fishes while on their spawning migration in the river. <br />Striped bass, an anadromous coastal species, moves upstream <br />in rivers and estuaries to spawn in freshwater during the spring <br />d early summer. Spawning occurs at temperatures of 10 to 25°C, <br />st frequently at 15.6 to 17.8°C (Hardy, 1978). Spawning is usually <br />st concentrated within the first 40 river km above salt water, <br />t distance traveled by spawning fish in individual rivers is <br />ighly variable (Hardy, 1978). In the Hudson River, spawning occurs <br />imarily between river km 25-62 (Rathjen and Miller, 1957). In the <br />noke River, North Carolina, major spawning grounds are approximately <br />009 - 217 km upriver (Hardy, 1978). Mature striped bass may move <br />stream as much as 320 km above salt water (Raney, 1954).