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<br />ECOLOGY AND CONSERVATION OF NATIVE FISHES IN THE UPPER COLORADO RIVER BASIN <br /> <br />159 <br /> <br /> <br />Figure 2.- The upper Colorado River downstream of Moab, Utah, December 1981. Photo by R A. Valdez. <br /> <br />endemic; eight are primarily large-riverwarmwater <br />inhabitants, five are coolwater or coldwater tribu- <br />tary inhabitants, and one is found in a warm stream <br />(T yus et al. 1982; Muth et al. 2000; McAda 2003; <br />Table 1). Many native fishes in the upper basin <br />have declined in range and abundance since the <br />early 1900s (Carlson and Muth 1989). Five are <br />federally endangered: Colorado pikeminnow, <br />humpback chub, bonytail, razorback sucker, and <br />Kendall Warm Springs dace. Concerns over de- <br />clines in native fish populations in the mid-1900s <br />prompted studies to assess the status and life his- <br />tory of these little-known southwestern fishes (e.g., <br />Miller 1955,1959,1961; Vanicek 1967; Holden <br /> <br />1973), and passage of the Endangered Species Act <br />of 1973, as amended (ESA; 16 U.s.e. 1531 et <br />seq.), led to initiation of more comprehensive stud- <br />ies in the late 1970s (e.g., u.s. Fish and Wildlife <br />Service 1982a). <br /> <br />Colorado Pikeminnow <br /> <br />Colorado pikeminnow is the largest minnow in <br />North America, with estimated maximum size of <br />1.8 m total length (TL) and 36 kg (Miller 1961); <br />largest confirmed weights are 12.2 and 15.5 kg <br />from the lower basin (Wallis 1951), and about 12 <br />kg from the upper basin (Figure 3). Maximum age, <br />