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I I I I I I I I I I I I I I I I I I I To quantify fish habitat availability, maps were made of the river at a given flow that delineated the surface area for sixteen habitat types based on depth and velocity criteria. Pools had a velocity of zero to 0.15 mlsec and had five differing depths from very shallow (< 0.2m) to deep (>2m). The velocity of runs ranged from 0.15 to 0.6 m1sec and depths were the same as give for pools Riffles had velocity ranging from 0.6 to 1.5 m1sec and rapids had velocities over 1. 5 m1sec. The fish sampling effort will attempt to determine which habitat type is more or less suitable for each species and size offish collected during the base flow period. This will indicate which habitats are useable and which are not. Fish composition for each study will be compared to its habitat composition. As more sites are sampled correlations will be examined to determine if similar river section with similar habitat composition have similar species composition. As more empirical fish data is collected it may be necessary to adjust the number and criteria of habitat types used in the analysis. Habitat diversity and composition will be calculated in each study site at an optimal base flow. The flow model will be used to determine how habitat diversity and composition are affected as flows drop. RESULTS SPECIES COMPOSITION Y AMP A RIVER FISH SAMPLES Species composition offish over 15 cm captured by electrofishing were similar at the Sevens station between years even though the 1999 electrofishing site was about half the distance it was in 1998 (Table 1). Flannelmouth sucker was the most common fish caught in both years at 46% of the total in 1998 and 47% in 1999 (Table 1). The next most common fish was bluehead sucker (about 20% in both years) followed by white sucker (about 10% in both years). The next most common fish in 1998 were roundtail chub, catfish, the white- 27