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<br />· J.vos \[tL\k~N~~ <br /> <br />American Fisheries Society Symposium 45:157-204,2005 <br />@ 2005 by the American Fisheries Society <br /> <br />~5S3 <br /> <br />Ecology and Conservation of Native Fishes in the <br />Upper Colorado River Basin <br /> <br />RICHARD A. V ALDEZ* <br /> <br />SWCA, Inc., 172 W 12755., Logan, Utah 84321, USA <br /> <br />ROBERTT. MUTH <br /> <br />Upper Colorado River Endangered Fish Recovery Program, <br />44 Union Boulevard, Suite 120, Lakewood, Colorado 80228, USA <br /> <br />Abstract.- The upper Colorado River basin supports a native ichthyofauna of 14 species <br />or subspecies that have been impacted by poor land-use practices, altered flows, physical <br />habitat fragmentation, competition and predation from nonnative fish species, and <br />degraded water quality. Five taxa are federally endangered, including the large-river species, <br />Colorado pikeminnow Ptychocheilus Lucius, humpback chub Gila cypha, bonytail G. eLegans, <br />razorback sucker Xyrauchen texanus, and a warm-stream subspecies, Kendall Warm Springs <br />dace Rhinichthys oscuLus thermaLis. Two recovery programs, formed through cooperative <br />agreements among federal, state, tribal, and private agencies and stakeholders, coordinate <br />activities in the upper basin that have helped to resolve water resource issues, implement <br />management actions to minimize or remove threats, and conserve endangered species. A <br />cooperative biological management program among state and federal agencies works to <br />protect the Kendall Warm Springs dace. Conservation agreements have also been <br />established for the other native fish species. Continued public and institutional support <br />for these programs is vital to species recovery and to the balance between long-term species <br />conservation and human demands on the Colorado River system. <br /> <br />Introduction <br /> <br />The upper Colorado River basin lies within the <br />states of Colorado, Wyoming, Utah, and New <br />Mexico (Figure 1). Upper basin drainage area is <br />about 289,540 km2, or less than half the total area <br />of the Colorado River system; average annual his- <br />toric upper basin discharge is about 93% of aver- <br />age total basin volume (i.e., 12.93 million acre-feet <br />of 13.90 million acre-feet). The upper basin in- <br />cludes the upper Colorado River, Green River, and <br />San Juan River subbasins. Evidence suggests that <br />the Colorado River in the upper basin has been in <br />its present course for more than 5 million years <br />and flowed into one or more closed basins near <br /> <br />. Corresponding author: valdezra@aol.com <br /> <br />the upper end of present-day Grand Canyon <br />(Minckley et al. 1986). About 5 million years ago <br />(i.e., late Miocene/early Pliocene), the river began <br />carving its way through the Colorado Plateau form- <br />ing Grand Canyon, and joined with a lower, more <br />dispersed drainage within the last 2-3 million years <br />(McKee et al. 1967; Luchitta 1990). The ances- <br />tral upper Colorado River consisted primarily of a <br />single large river and tributaries in contrast to more <br />dispersed smaller tributaries in the lower basin. Fish <br />species that evolved in the upper basin were mostly <br />large riverine forms and those that evolved in the <br />lower basin were small stream forms. Connection <br />between these two ancestral basins, marked by the <br />river cutting through Grand Canyon, allowed for <br />inter-basin movement of the larger, more mobile <br />species, particularly from the upper basin. These <br /> <br />157 <br />