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<br />( <br /> <br />o <br />o <br />(":) <br />(,p1 <br />00 <br />...... <br /> <br />In conjunction with early life history research and <br />secondary channel research elements characterize <br />relative abundance of non-native fishes in <br />backwaters and secondary channels. <br /> <br />Determine food habits and food availability of <br />native and nonnative fishes in backwaters and <br />secondary channels and evaluate for dietary <br />overlap. <br /> <br />compare <br />native <br />without <br /> <br />growth and survival of YOY and juvenile <br />fishes in backwater habitats with and <br />predators and/or competitors. <br /> <br />Develop flow recommendations that minimize non- <br />native species survival and growth and do no <br />negatively impact native species. <br /> <br />Research Need: Nonnative fish species have been implicated in the <br />decline of native fishes of the Colorado River and <br />other systems. The successful introduction and <br />establishment of nonnative fishes in concert with <br />habitat alteration has coincided with the decline <br />in distribution and abundance of native species, in <br />particular the Colorado squawfish and razorback <br />( sucker. <br /> <br />The effects of predation and competition by <br />nonnative species on Colorado squawfish and other <br />native species needs to be addressed in the San <br />Juan River. In addition, the effect of flow on the <br />nonnative species component of the fish fauna needs <br />to be addressed to determine its usefulness as a <br />potential management tool for controlling nonnative <br />species. Preliminary research conducted during <br />1987-1990 indicated that flows were a possible <br />factor controlling the abundance of nonnative <br />species. <br /> <br />Methods: <br /> <br />During FY 92 studies addressing the first three <br />objectives would be implemented. Channel catfish <br />distribution and movement studies would be <br />conducted in conjunction with other adult and <br />juvenile fish sampling programs, using similar <br />methods. Food habitats of potential non-native <br />. predators such as channel catfish would be assessed <br />under differing flow regimes by taking stomach <br />samples from fish collected during other study <br />elements. In addition, stomach contents of museum <br />specimens collected during 1987-1990 would be <br />analyzed. In conjunction with other study element <br /> <br />". <br /> <br />(. <br /> <br />19 <br />