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In the absence of definitive management measures based upon quantitative analysis of fi sheries data, it may be necessary to rely upon a multifaceted approach to developing a management scheme for these endangered species. Assuming that habitat implies presence of fish, one element of this approach is the deve10pment of relationships between riverine flows and needed habitats at critical times to the life history of each species. During 1983 a study was performed in the upper Colorado River to determine the availability of riverine habitats under different river discharges. The resul ts of this study may have signi ficance as a tool in managing riverine systems for endemic fishes. .. The purpose of this investigation was to assess the suitability of the study area for the endangered fishes by documenting changes in habitat categories with changes in river discharge. This method of assessing habi tat dynamics has not been used before, and is proposed, with refinements, for determining flow recommendations for the endangered fishes. METHODS AND MATERIALS Study Area The study area encompassed a two-mile reach of the Colorado River near Parachute, Colorado (Figure 1). It included one-entire river channel -- STUDY AREA COLORADO RIVER DRAINAGE BASIN , /' /. / . Figure 1. Location of the study area within the Colorado River drainage basin (left) and the limits of the study section between @ and @ on the Colorado River near Parachute, Colorado. The hatched area indicates an in- tensive habitat study area where a probable YOY razorback sucker was captured. 250