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<br />( <br /> <br />l~ <br />..... <br />~\ <br /> <br />( <br /> <br />'- <br /> <br />San Juan Seven Year Research Plan <br /> <br />WORK STATEMENT/PROTOCOL <br /> <br />NON-NATIVE PISH RESEARCH <br /> <br />Background: <br />Nonnative fish species have been implicated in the decline of nati~e fishes of <br />the Colorado River and other systems. A combination of lab and field oriented <br />studies has demonstrated resource overlap in diet and habitat use of native and <br />nonnative species, predation on native species by nonnatives, and an apparent <br />inferior competitiveness by native species when sympacric with nonnatives in <br />selected habitats. The successful introduction and establishment of nonnative <br />fishes in concert with habitat alteration (primarily flow related) has coincided <br />with the decline in distribution and abundance of native species, in particular <br />the Colorado squawfish and razorback sucker. . <br /> <br />Research efforts in the San Juan River during 1987-1990 have documented the <br />CUrrent distribution and abundance of fishes in the river below Navajo Darn and <br />reservoir downstream to Lake Powell. During that period, a high flow year was <br />followed by an apparent decline in the abundance of nonnative species. <br />Subsequent low flow years coincided with an increase in nonnative fish numbers <br />in backwater collections, implying greater survival of nonnatives and/or lower <br />survival of natives. Potential nonnative predator species are few and dominated <br />by channel catfish. Potential impacts of predation on native species has not been <br />investigated on the San Juan River. Potential nonnative competitors include the <br />red shiner and fathead minnow. Other than previously collected data on fish <br />community structure in various habitat types, the role of common resource use by <br />native and nonnative species in the San Juan River has not been investigated. <br /> <br />This segment of San Juan River fishery investigations will address the impacts <br />of predation by nonnative predators and commonality in resource use between <br />native and nonnative fish species under differing flow scenarios. <br /> <br />Objectives: <br />1) In conjunction with the adult monitoring/research element determine <br />distribution, abundance and movement of channel catfish <br /> <br />2) Determine food habits of potential squawfish predators (i.e. channel <br />catfiSh) in suspected rearing areas and habitats. <br /> <br />3) In conjunction with early life history research and secondary channel <br />research elements characterize relative abundance of non-native fishes <br />in backwaters and secondary channels. <br /> <br />4) Determine food habits and food availability of native and nonnative <br />fishes in backwaters and secondary channels and evaluate for dietary <br />overlap. <br /> <br />5) Compare growth and survival of YOY and juvenile native fishes in <br />backwater habitats with and without predators and/or competitors. <br /> <br />6) <br /> <br />Develop flow recommendations that minimize non. native species survival <br />and growth and do no negatively impact native species. <br /> <br />A26 <br />