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<br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br /> <br />INTRODUCTION <br /> <br />Establislunent of instream flows is generally considered to be a valuable tool tor <br />maintaining declining native fish populations (Espegren 1998) and also for recovery of <br />threatened and endangered species (McAda 2003). Most instream flow recommendations are <br />based on a modeling process that employs a hydraulic model to simulate flow conditions and <br />a species habitat suitability index that predicts habitat availability or quality. The level of <br />confidence in the models output is a function of the validation process that compared model <br />output with field observations, In most situations the model projections are outside the range <br />of the empirical data. <br /> <br />In 1998 the COOW established a research project to gather population and habitat <br />data for non-endangered native fish, for the purpose of making biologically justified in stream <br />flow recommendations. Anderson and Stewart (2003) designed a meso-habitat instream flow <br />method that used a 2-0 modeling methodology. Channel topography was surveyed at six <br />study sites on three rivers, The methodology included development of meso-habitat <br />suitability ratings based on density and biomass population estimates, Flows were simulated <br />with a 2-0 flow model. <br /> <br />The drought of record for several rivers in Colorado occurred in 2002, Extreme low <br />base flows occurred just at the completion of the instream tlow study for the Yampa and <br />Colorado rivers, Since the populations of the target native fishes were quantified using mark <br />and recapture electro-fishing during the years 199~ to 2001 on the Yampa River and 1999 to <br />2001 on the Colorado River, a baseline data set had been recently established, These flows <br />provided the opportunity to empirically demonstrate the response of the fish community to a <br />season of unusually low flows, This data could also be used to validate or calibrate the <br />biomass model from the in stream flow study made data from prior years, <br /> <br />This report also compiled available geomorphic and hydrologic data tor rivers with <br />recent tishery infonnation, The objective of this synthesis was to present hypotheses about <br />relationships between native fish stocks and habitat availability between rivers and within <br />rivers over time. These hypotheses could be refined or tested by future research, <br /> <br />The Study Objectives: <br /> <br />I. Sample fish populations at the Yampa River study sites of Lily Park, Ouffy, Sevens and <br />in the Colorado River at the Com Lake and Clifton sites, <br /> <br />2, Compare post-2002 (drought) population data to baseline population data, <br /> <br />3, Refine the biomass model made in the instream flow study based on results found in <br />2003, <br /> <br />4, Present hypotheses about the intluences of macro- or meso-habitat availability on <br />standing stocks of blue head sucker, tlannelmouth sucker and roundtail chub based on <br />existing hydrologic and fish community structures, <br />