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17 areas in the Dolores could explain the correspondingly high percentage of non-natives. The reverse would be true for the Gunnison, with a majority of flowing habitat types contributing to a high percentage of native species. Species Composition by Stratum Gunnison River Stratum Q. Seventeen species and two hybrids were caught from stratum Q during this study. Twelve non-native, three endemic and two native species were collected from this stratum; however, endemics comprised 51% of the total catch. Roundtail chub (37.6%), bluehead sucker (18.3%) and flannelmouth sucker (13.2%) were the most common fishes. Sand shiner (8.2%) and fathead minnow (7.8%) were the most numerous non-native species caught in stratum Q. Eight Colorado squawfish (0.15% of the total catch) were captured in stratum Q, more squawfish than were observed in other strata sampled in the Gunnison River. All squawfish captured in stratum Q were found below Redlands Diversion (RM 3.0), several of which were captured by either Northwest Fisheries Research or the Colorado Division of Wildlife (DOW). Area and hour CPE values for each species in each stratum are shown in Tables 4 and 5. CPE values were lowest in stratum Q when compared to the other Gunnison River strata. "The total area CPE was 6.20 fish/10m2 and the total hour CPE was 54.81 fishllO hr. The presence of a dam (Redlands Diversion) within the stratum could affect fish concentrations in the reach, thus explaining the relatively low ePE values. Stratum R. Fewer species were found in stratum R than the other Gunnison River strata. Thirteen species (eight non-native, three endemic and two native) were collected from stratum R during this study. Natives comprised 68.1% of the total catch. Bluehead sucker (43.5%), roundtail chub (16.2%) and fathead minnow (11.7%) were the most frequently encountered fishes. Two Colorado squawfish were observed during electrofishing by GJFS -personnel on 23 July 1981 at RM 22.1, and on 20 May 80 at RM 27.7. Another large adult squawfish was captured by DOW personnel on 26 August 81 at RM 26.7, and this field team observed a second squawfish at this same time and location during electrofishing efforts. Small fish were more prevalent in stratum R than the other two Gunnison River strata. The total area CPE was 39.18 fish/10m2 (Table 4). Larger fish were also quite abundant in stratum R as indicated by a total hour CPE of 123.72 fish/l0 hr (Table 5). Stratum S. Stratum S contained the greatest number of species of the three Gunnison strata. Eighteen species including thirteen exotic, three endemic and two native were found in stratum S. Endemic species accounted for a large portion (38.3%) of the total catch. Bluehead sucker (31.7%), roundtail chub (24.2%) and flannelmouth sucker (14.1%) were the most abundant fish in the total catch. Sand shiner (8.1%) and fathead minnow (7.7%) were the most common non-native species.