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these fishes may occur. Although the incidence of fish predation was <br />deemed low, channel catfish were noted to consume whole fish and fish eggs <br />in DNM (Tyus and Nikirk, In press), and humpback chub remains were found <br />in channel catfish stomachs from the Little Colorado River (W.L. Minckley, <br />Arizona State University, personal communication). Observations of "bite- <br />shaped" abrasions on some chubs in DNM is further indication of adverse <br />impacts that channel catfish may have on the native fishes (there are no <br />other piscivorous fish in that system to have caused such abrasions). Few <br />common carp were captured syntopically with humpback chub, however, their <br />abundance throughout DNM suggests that this introduced species may have <br />some negative impact on native fishes. We emphasize that flows and other <br />factors (e.g., temperature) that may favor potential competitors, such as <br />channel catfish, need to be immediately evaluated for input into recovery <br />efforts for the endangered Colorado River fishes. <br />The humpback chub persists only in a few isolated populations in the <br />Colorado River basin, and some planned water development projects may <br />further jeopardize the survival of this species. Loss or reduction of <br />spring runoff in the Yampa River could reduce the availability of spawning <br />habitat or otherwise alter their formation, and interfere with spawning <br />cues. Alteration of the existing natural flow regimen of the Yampa River <br />may also promote hybridization, as has been suggested in some altered <br />river systems (Valdez and Clemmer 1982), or may result in proliferation of <br />introduced competitor and predator fishes. Efforts should be made to <br />protect flows of the Yampa River to aid recovery of the species to a less <br />endangered status. <br />16