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I I I I I I I I I I I I I I I I I I I Table 2. DutTy Tunnel species composition (fish over 150 mm) for total catch and estimated numbers in the Representative Reach and Surveyed Site, September 1998. DUFFY REPRESENTATIVE REPRESENTATIVE SURVEYED REACH REACH slm Species N % EST. % EST. % Total fish 1388 3574 948 Flannelmouth Sucker 81 5.8% 258 7.2% 56 3.9% Bluehead Sucker 56 4.0% 178 5.0% 23 4.6% White Sucker* (WSWX') 930 67.0% 2121 59.3% 602 63.1% Roundtail Chub 43 3.1% 137 3.8% 23 2.5% Chamiel Catfish 44 3.2% 140 3.9% 13 1.4% Carp 42 3.0% 134 3.7% 16 1.8% Northern Pike 46 3.3% 147 4.1% 63 6.7% Smallmouth Bass 124 8.9% 395 11.1% 122 13.0% Cmppie 1 0.1% ne. n.e. Colorado Pikeminnow* 20 1.4% 64 1.8% 30 3.2% Green Sunfish 1 0.1% ne. ne. Native species 200 14.4% 637 17.8% 132 13.9% Nonnative species 1188 85.6% 2937 0.8 816 86.0% Density and Biomass Estimation The total fish density estimated at Sevens RR was 950/km (Table 3) and the total fish estimate for Duffy RR was 4111km (Table 4). The total fish density estimate was significantly higher at Sevens RR compared to Duffy RR (Table 5) and indicates a larger population oftlannelmouth sucker, bluehead sucker, roundtail chub, and channel catfish at Sevens. However, total fish density estimates were not significantly different between Sevens SS and Duffy SS. Sevens SS had significantly more catfish and tlannelmouth sucker and significantly fewer WSWX than Duffy SS. Table 3. Density estimate, 95% C.L (% of est.), and biomass estimate for the Representative Reach (RR) and Surveyed Site (SS) at Sevens, Yampa River, September 1998. SEVENS REPRESENTATIVE REACH SURVEYED STUDY SITE No./km 95%C.I KG/HA No./km 95%C.I KG/HA Total fish 950 8% 148 893 19% 134 Flannelmouth S. 351 11% 61 250 20% 37 Bluehead S. 256 21% 20 125 104% 9 *White S. 158 20% 23 253 57% . 26 . Roundtail Chub 64 36% 7 84 80% 8 Channel Catfish 63 25% 20 78 49% 19 Carp 32 62% 16 59 120% 30 Northern Pike 15 128% 1 . 19 NR 1 Smallmouth Bass 11 185% 1 22 159% 2 C. pikeminnow 1 NR 1 3 NR 1 11