Historical Changes in Large River Fish Assemblages of the Americas

Abstract

<em>Abstract.</em>—The upper Colorado River basin supports a native ichthyofauna of 14 species or subspecies that have been impacted by poor land-use practices, altered flows, physical habitat fragmentation, competition and predation from nonnative fish species, and degraded water quality. Five taxa are federally endangered, including the large-river species, Colorado pikeminnow <em>Ptychocheilus lucius</em>, humpback chub <em>Gila cypha</em>, bonytail <em>G. elegans</em>, razorback sucker <em>Xyrauchen texanus</em>, and a warm-stream subspecies, Kendall Warm Springs dace <em>Rhinichthys osculus thermalis</em>. Two recovery programs, formed through cooperative agreements among federal, state, tribal, and private agencies and stakeholders, coordinate activities in the upper basin that have helped to resolve water resource issues, implement management actions to minimize or remove threats, and conserve endangered species. A cooperative biological management program among state and federal agencies works to protect the Kendall Warm Springs dace. Conservation agreements have also been established for the other native fish species. Continued public and institutional support for these programs is vital to species recovery and to the balance between long-term species conservation and human demands on the Colorado River system.