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<br />~~,. <br /> <br />difficult to prove in natural environments, and especially in large rivers like <br />the Green River. In-depth studies of competition could be very expensive and <br />result in little insight. This project will approach the topic of fish <br />competition in Colorado squawfish nursery habitats by using a stepwise procedure. <br />First, we would determine if fish predation in back.waters has an impact on the <br />structure and function of benthic and plank.tonic communities. If not, we would <br />anticipate that resource sharing between fishes is not limiting. However, if a <br />significant shift in food organisms occurs, this would demonstrate that the food <br />base is impacted, thus implying resource competition. <br /> <br />If competition between fishes is thus expected, i.e., food resources are limiting <br />the fish community, we would design specific studies to evaluate exploitive and <br />interference competition~ For example, inter- and intraspecific competition <br />would be evaluated using fish inclosures in which foods eaten in the absence of <br />other species (preferences) would be compared with the foods eaten in the <br />presence of others. <br /> <br />An additional product of this work would include an evaluation of riverine flows <br />on selected backwater habitats. <br /> <br />VI. Task Description (FY 1992(: <br /> <br />A series of exclosures will be constructed at randomly-chosen locations in <br />backwater in the Ouray area. These would be designed to exclude or admit fishes. <br />Benthos and plankton will be monitored by core an net sampling for about 100 <br />days, i.e., during the period when Colorado squawfish are present. Sampling <br />frequency will De a function of water temperature, and samples will range form <br />one per week to three per day. <br /> <br />Data collected will allow the computation of invertebrate densities, changes in <br />ccxranunity structure, and production estimates for the dominant invertebrate <br />species in the system. Preliminary studies will be conducted to generate growth <br />rates for invertebrates and additional growth information will be made form size- <br />class distributions. <br /> <br />Fish collections will also be made a bi-weekly intervals to document the use of <br />the area by various species. Fish biomass will be estimated by determining the <br />relative numbers and weights by species. <br /> <br />VII. Study Schedule: <br /> <br />Field collections, July-October 1992. Laboratory ID and analysis, October-March <br />1993. Report preparation, March-May 1993. <br /> <br />VIII. FY-l Work <br /> <br />Description of work: field collections, species ID. <br /> <br />- Deliverables: NA <br />Budget <br />- Labor (l/2@13,l@FF,4@4,2@3)_ $14,500 <br />- Travel <br />Equipment <br />- Other <br />Total <br /> <br />400 <br />200 <br /> <br />$lS,lOO <br /> <br />FY-2 Work <br /> <br />Brief Description: Species ID, analysis, report. <br />- Deliverables: Report of findings, recommendations. <br />- Budget estimate: $4,000 <br /> <br />C29 <br />