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Each cluster was numbered and 9 clusters were selected from strata 1, 11 from strata 2, 3 from strata 3,2 from strata 4, 12 from strata 6, and 13 from strata 8 in 1996. The rest will be sampled in 1997 (Table 2). Table 1 . The river mile and location of sample strata (river reaches) in the Yampa River, Colorado, 1996. I Strata I River Mile I Description I 1 0-20 Echo Park to Harding Hole 2 20-45.0 Harding Hole to Deerlodge Park ., 45.0-51.0 Deerlodge Park to Little Snake River Confluence .) 4 51.0-55.6 Little Snake River Confluence to Cross Mountain 5 55.6-58.8 Cross mountain Canyon 6 58.8-88.7 Cross Mountain Canyon to Juniper Canyon 7 88.7-91.0 Juniper Canyon 8 91.0-124.0 Juniper Canyon to Round Bottom Habitat features were determined for a riffle:run sequence using cross sectional profiles. Cross sections were made between headpins on both sides of the channel and measured the bed profile and water surface elevations and also depth, velocity and substrate at 25 to 30 points. The first cross section was placed at the most suitable hydraulic control in the cluster. Cross sections upstream of the control were positioned to describe the lower run, middle run, pool or upper run, lower riffle, and at the shallowest part of the rime. Cross sectional measurements were taken in September during the low flow period. Only one stage-discharge measurement was taken at each cross section. The range of concern for habitat availability was at flows of less than about 200 to 300 cfs. Therefore, as long as field readings were within this range, only one calibration flow was considered necessary. Habitat types were defined by a certain combination of depths and velocity. Instead of assigning suitability values for depth and velocity for a species and life stage, we characterized the river into six discrete habitat types. Three of these habitat types are considered usable by adult Colorado squawfish and three of them are not (Table 3). Class I and Class II pools (over 2m and 1 m, respectively), were used by Wick and Hawkins (1986) in their habitat suitability model for adult Colorado squawfish. Their determination was that adult CS were 2.5 times more likely to be caught fi-om pools over 2 m deep than in pools between 1 and 2 m of depth. They also reported that pools less than 25 square meters were considered unused. Habitat use information obtained by radio tracking during the study was also used to validate the criteria used to define usable habitats 17