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roundtail and humpback chub also provide the nursery areas for YOY. Scour channel backwaters foamed in runoff deposited sediments, which are preferred by squawfish (Trammel 1997) are at such a premium in Westwater Carryon that they could be of little import to YOY humpback chubs. Additionally, Westwater Canyon YOY chubs vacate low velocity habitats for main channel habitats (shorelines, shoreline eddies and rifles) earlier in development than Colorado squawfish, similar to the findings bf researchers in the Grand Canyon of the Colorado River and the Little Colorado River (Rich Valdez ,personal communication). The early life stages of Colorado River Gila spp. are not easily identified to species. Two species, roundtail chub and humpback chub are commonly found in Westwater Canyon. The last documented collection of a bonytail came in 1984 ten miles upstream of Westwater Canyon in the -Black Rocks area (Kaeding et al. 1986 ). Based on the findings of this study and others (McAda et al. 1994, Valdez et al. 1982) we know YOY chubs are found in the presence of adult fish - lazval chubs do not drift downstream as far as Colorado squawfish. And based on the distribution of adults chubs -humpbacks likely drift less than roundtails. Humpback chub are not common outside of Westwater Canyon and the Black Rocks (Valdez et al. 1982) area of the- Colorado River. Therefore an assumption was made in the YOY analyses -discrepancies in catch statistics from samples collected immediately upstream of Westwater and from those collected within the canyon itself were due to the presence of humpback chub in Westwater Canyon. Juvenile and adult life stages were sampled within Westwater Canyon to determine the stability of both: the humpback and roundtail chub. populations. Life history and population structure information has been included due to the general lack of this type of information in the RIP literature. .. •.~5:. . DRAFT r ~ . , 2