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. .., ~~.. . ~ ~~~ ~a"" ~-(Go/'" water depth; water velocity at the river bottom, ~t 0.2, 0.6,~and 0.8 of the water depth; dominant and secondary substra{:; and water temperature. Measurements at one meter on either side of the fish ('in' and 'out') were the same except that only a 0.6 velocity was taken. Velocities were measured using a Marsh-McBirney current meter and an 8-foot wading rod. Where the measurement was taken in a countercurrent (i.e., an eddy) greater than 90 degree~ from the main directional flow, velocity was recorded as negative. Substrates was assessed as one of six categories (sand, silt, gravel, rubble, boulder, or bedrock) by P!9hing with the ~, {QQ!:, 2E wadinq rod, depending on water depth. Features providing cover (i.e., large boulders, overhanging banks) at each location were also recorded. . . . USI CUrve Developoent . Preliminary habitat suitability index (HSI) curves were developed for depth, velocity, and substrate based on the radiotagged Colorado squawfish and razorback suckers monitored during this study. Curve sets were developed from 1) nose measurements, 2) , in' measurements, and 3) 'out' measurements. Separate curve sets were developed for Colorado squawfish and razorback sucker. . Curve development followed a set procedure. Only measurements taken during the 2-hour monitoring period were used, since they represented a consistent set of measurements. These included the 2-hour observations taken in conjunction with the 24-hour monitoring. A single observation was defined as a set of measurements taken on a fish remaining stationary for 15 minutes. Thus, the measurements associated with a fish that remained stationary for 1 hour were weighted as four measurements; and measurements on a fish that was stationary for 2 hours were weighted by eight. Habitat measurements were not used to generate HSI curves if the fish was not stationary for 15 minutes. . Raw data values for depth and velocity were grouped into O.l-foot classes and the frequency in each class was plotted to reveal the distribution of the data. Velocity measurements were all converted to positive values. This was done for the following reasons: 1. ~els do not consider negative velocity and will assign negative velocities a utilization value of zero. . 2. Information does not exist to suggest that these fish would differentially utilize velocity regimes based upon whether the current is flowing upstream (as in an eddy effect) or downstream. . 3. Consideration of both negative and positive velocities considers actual microhabitat conditions. . 10 .