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Table 3. Depth and mean water velocities recorded at locations of radio- telemetered Colorado squawfish during the spawning season, Yampa River, Colorado. n = number of fish. Year n Number of contacts Mean depth (m) Mean velocity (m/s) Resting-Staginq 1981 6 68 2.23 0.43 1984 7 45 2.26 0.50 1984 5 147 1.89 0.17 Mean 2.13 0.37 Deposition-Fertilization 1981 5 84 1.05 0.49 1983 5 30 0.91 0.51 1984 5 45 0.87 0.45 Mean 0.94 0.48 Colorado squawfish adults were observed in a variety of habitats (Ty~~s et al. 1984) during the remainder of the year, usually in eddies and runs along shorelines and over sand and silt substrates (Tyus et al. 1984). Radio- telemetry indicated the fish, at times, selected drop-offs next to sand bars, both in runs and eddies. In 1984 and 1985, fish habitat utilization data for use in the PHABSIM model (Bovee 1986) were evaluated by collecting depth, velocity, and substrate data 1 to 2 m inshore (shallow) and offshore (deeper) from the signal source. Visual observations in shallow water indicated that Colorado squawfish selected sheltered habitats behind boulders or other cover. In deeper waters, the fish were most often located in eddies, where their movements suggested heavy use of the eddy-run interface (Figure 5). Depth and velocity measurements taken at the locations of 84 fish differed from the adjacent measurements (Student's t) with respect to inshore depths (P < 0.04; means = 1.8 m, 1.46 m) and offshore velocities (P < 0.006; means = 0.3 m/s, 0.53 m/s). There was no difference between depth and velocity measurements taken at fish locations (means = 1.8 m, 0.30 m/s) when these were compared with offshore depths and inshore velocities (means = 1.85 m, 0.25 m/ s). Mean inshore and offshore depths (1.46 m, 1.85 m) and velocities (0.25 m/s, 0.53 m; s) were different (P < 0.02 and P < 0.002, respectively). These results indicate •that Colorado squawfish utilize habitats that are relatively heterogenous with respect to water depth and velocity profiles. In this respect, microhabitat data recorded at the fish may not reflect the mean cell depths and velocities that are input variables for the PHABSIM model 152