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from ten reaches (8 to 25 RK-long) of the Green River Basin, five from the Green River (RK 539.4 to 526.5, 513.6 to 483, 418.6 to 394.5, 185.2 to 154.6, 90 to 64), three from the Yampa River (RK 167.4 to 153, 128.8 to 112.7, 86.9 to 78.9), and two from the White River (RK 169.1 to 153, 33.8 to 0). The reaches totaled about 23% of critical habitat of Colorado pikeminnow in the Green River Basin and were chosen because they were accessible by a flat-bottom boat and represented reaches known to support Colorado pikeminnow. Sampling was conducted during spring each year from 1986 to 2000 when water levels were rising due to snow-melt runoff but were usually below peak runoff levels. A single electrofishing sampling pass was made down each shoreline, stunned Colorado pikeminnow were captured with dipnets, and electrofishing time was recorded. Captured fish were tagged, measured, and released with a protocol similar to that described above for abundance estimation sampling. Sampling effort was stratified among four to eight sub-reaches of each river reach and catch per unit effort statistics were calculated for each sub-reach sample. Variances and standard errors for catch/effort indices were calculated based on those samples. Prior to 1991, Colorado pikeminnow were tagged with a Carlin dangler tag, which were presumed subject to relatively high tag loss. Therefore, data from 1986 to 1990 was not included in analyses presented here. After 1990, tag loss was considered negligible because all Colorado pikeminnow were PIT-tagged. From 2001 to 2003 abundance estimation sampling data, we designated a sampling pass as one that conformed in space and time to when ISMP sampling was previously conducted. We calculated catch/effort statistics for Colorado pikeminnow to examine trends from 1991 to 2003. To compare abundance estimates of Colorado pikeminnow with catch/effort indices, we averaged capture rates for ISMP reaches that were within the main river reaches used for abundance estimation sampling. Those annual composite ISMP catch/effort indices for the Yampa River, White River, the middle Green River, 19