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<br />vi <br /> <br />. <br /> <br />ABSTRACT <br /> <br />Distribution, Abundance and Life History <br /> <br />of the Fishes of the Upper <br /> <br />Colorado River Basin <br /> <br />by <br /> <br />Paul Bernard Holden, Doctor of Philosophy <br /> <br />Utah State University, 1973 <br /> <br />Major Professor: Dr. ClS:ir B. Stalnaker <br />Department: Wildlife Science <br /> <br />Knowledge concerning the distribution and abundance of fishes in <br /> <br />the upper Colorado River basin is lacking. This study was undertaken <br /> <br />. <br /> <br />to determine status of the fish fauna in that area. Introduced species <br /> <br />outnumbered native species 19 to 10. Abundance of introduced species <br /> <br />r <br />increased steadily since 1900 as did introduction of new species. I Four <br /> <br />endemic species--Colorado squawfish (ptychocheilus lucius), bol'lYiJail <br />chub (~ elegans), humpback chub (Gila cypha), and humpback sucker <br />(Xyrauchen texanus )--were rare and endangered. Areas which supported <br /> <br />reproduction of these rare forms were the lower Yampa River, Desolation <br /> <br />Canyon of the middle Green River, and the lower Green River in Canyon- <br />lands National Park. Major reasons for the decline of the native fauna <br /> <br />were considered to be alteration of habitat by high dams and introduction <br />of exotic species~ Delineation of spa'Wrling periods, movement of tagged <br />fish and taxonomy of juvenile chubs (Q.!!! spp.) were also studied. <br /> <br />i. <br /> <br />(65 pages) <br />