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Among the native species assemblage, only 2 of 470 flannelmouth suckers were collected in the most upstream river segment (RM 1-6). Beginning with RM 7, they became quite abundant and uniformly distributed throughout the river segments downstream to RM 30. Bluehead suckers were captured in very low numbers, but were collected in every river segment. Only three roundtail chubs were collected during the 15 day sampling period. Two were captured in the uppermost river segment and the other in the most downstream segment. Mottled sculpin and speckled dace were incidental captures throughout the entire 30 mile reach of river, but were not captured in portion to their true abundance or in relation to the larger fish species. Population Estimates by River Seqrnent Estimates of population size (N) with the 95% confidence limits (95% CI), density (N/ha), biomass (kg/ha), and density (N/ha) of fish (by species) ~ 35 cm (14 inches) for each of four river study segments are given in Table 4. Brown trout density and biomass estimates for the first two river segments downstream from Bradfield Bridge were greater than those for the upper reach of river. The highest brown trout density and biomass estimates occurred in the third river segment (RM 17 - RM 25), while the lowest occurred in the most downstream segment (RM 25 - RM 30) . Dolores River rainbow trout density and biomass estimates were the highest in the most upstream segment (RM 1 - RM 12) between the dam and Bradfield Bridge. Density and biomass estimate for the stream-reared rainbow trout were similar for the lower three river segments, i.e., RM 12 - RM 17, RM 17 - RM 25, and RM 25 - RM 30). McPhee Lake rainbow trout and kokanee salmon density and biomass estimates were the highest in the most upstream segment (RM 1 - RM 12) and decreased dramatically in the three lower river segments (Table 4). More than 6000 lake rainbows and 1200 kokanee salmon were estimated to be in the most upstream study reach. In comparison, the estimates of lake rainbow trout and kokanee salmon occurring in the three lower study reaches combined were 499 and 63, respectively. Flannelmouth sucker density and biomass estimates were the highest in the second and fourth river segments below the dam. These fish were the most unifOrmly distributed among all the river segments of the six species for which population estimates were calculated. Bluehead suckers and roundtail chubs were the least abundant of the fish species large enough to be efficiently collected with electrofishing equipment. It was surprising that so few roundtail chub and bluehead suckers were captured. The relative abundance of both species was much greater in the uppermost river reach during fish trapping and electrofishing operations in July and August 1991 (Nehring 1992). However, the summer of 1991 was at the end of a four year drought, while the Dolores River drainage has experienced above normal precipitation and run-off during the 1992 and 1993 water years. The longitudinal distribution of the roundtail chub may have been pushed downstream in 1992 and 1993 as a result of the colder water temperatures and high levels and extended duration of the spring run-off, especially in 1993. Smallmouth bass were not marked and returned to the water for the purpose of conducting a population estimate. Instead, all smallmouth bass collected were removed from the stream and killed at the time of capture. However, 70% of the smallmouth captured were taken on the first electrofishing pass through the river, making it possible to complete a two-pass removal Seber-LeCren population estimate (Seber and LeCren 1967). The smallmouth bass population estimate was' 25 with 95% confidence limits of :t 12, indicating the number of bass that migrated out of McPhee Reservoir during the managed spill was quite small. -5-