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<br />" <br /> <br />(HQD in which 11 habitat variables, including baseflow and annual change in discharge, thought to <br />influence trout populations were subjectively rated. The predictions were significantly correlated <br />with actual measures of biomass. The Delphi rating schedules used in this technique apparently <br />resolved much of the nonlinearity usually ObselVed in relationships between habitat d~~criptors and <br />fish biomass. However, Bowlby and Rolf (1986) were not as successful in using the method in <br />Ontario streams because trout density changed within stream segments when habitat variables <br />remained the same. Other biophysical indices of habitat quality have been proposed (cf., Osborne <br />et al. 1992); they have been used to establish relative influences of stream regulation in different <br />streams, but to my knowledge they have not been used to examine incremental effects of flow. <br />A general (simple application in different streams) incremental flow - biomass model that is <br />statistically precise (repeatable) and accurate (describes reality) is likely not attainable, especially in <br />large rivers like the Upper Colorado where ecosystem structure and function is complex and poorly <br />known. It is feasible, however, to approach the problem from a multidisciplinary perspective, where <br />strong inferences about how the endangered fishes are likely to respond to reregulated flow regimes <br />can be derived from process-oriented studies that demonstrate key biophysical relationships. <br />Linking hydrology, geomorphology and limnology in an ecosystem context is the key (Stanford <br />and Ward 1992a), and I recommend below (Section VI) a new approach for reaching an ecosystem <br />level of understanding with respect to flow provision in potamon reaches of the Upper Colorado <br />River Basin. <br /> <br />Flow RelPmes Recommended to Protect and Enhance Endang:ered Fishes in the Upper Colorado <br />River Basin <br />In this section I attempt a very concise presentation of the flow recommendations that were <br />made by the U.S. Fish and Wildlife SelVice to provide context for my summary of problems with <br />these recommendations, which follows in the next section. Flow recommendations have not been <br />made for the Gunnison, White and Dolores Rivers, major tributaries that have considerable potential <br /> <br />52 <br />