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The humpback chub persists in isolated locations, with largest <br />numbers reported from the lower 13 km of the Little Colorado River and <br />nearby mainstream Colorado River (Kaeding and Zimmerman 1983; C.O. <br />Minckley, in press), and in Black Rocks area of Ruby Canyon and Westwater <br />Canyon of the upper Colorado River (Valdez and Clemmer 1982; Kaeding et <br />al., in press). Smaller numbers are known to occur in the Green and Yampa <br />rivers (Holden and Stalnaker 1975a, 1975b; Valdez and Clemmer 1982; Tyus <br />et al. 1982). Cataract Canyon of the Colorado River may also support <br />humpback chub (Valdez and Williams, in press), but the genetic purity of <br />that population is uncertain because about 7,300 juvenile hatchery- <br />reared humpback chubs (derived from upper Colorado River Black Rocks <br />adults) were introduced there in 1981 (J. Valentine, Utah Division of <br />Wildlife Resources, written communication). <br />The distribution and status of humpback chub in the upper Green and <br />lower Yampa rivers (i.e., Dinosaur National Monument, DNM) are not well <br />documented, partly because some early workers collectively referred to <br />Colorado River chubs as "bonytails" or Gila species (e.g., Bosley 1960), <br />and some reported the presence of morphologically intermediate forms <br />(e.g., Holden and Stalnaker 1970). Chub remains in Indian sites dating <br />more than 1000 years old (Leach 1970) indicate that these fish were <br />present at that time, and may have been eaten by native Americans. <br />Earliest documentation of suspected humpback chubs in DNM may be <br />traced to isolated captures in survey studies associated with closure of <br />Flaming Gorge Dam in 1963 (Bosley 1960; see Vanicek et al. 1970 for review <br />of unpublished data). More recent studies also noted the rare presence of <br />the species in DNM, most captures occurring in the confluence area of the <br />3