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Lower Green River! Colorado River The annual ISMP sampling for yay Colorado pikeminnow was completed during September 15-30, 2002. One group of three researchers sampled RM 110-0 of the Colorado River (reach 1) and RM 120-0 of the lower Green River (reach 3). Backwaters were sampled in 21 of 24 sub-reaches in the lower Green River and 17 of 22 sub-reaches in the Colorado River. The Sampling followed two large storm events which increased flows and sediment loads. A number of backwaters were not sampled due to large amounts of both deposited and suspended silts. This condition also effected the seining efficiency in many of the backwaters which were sampled. In the Colorado River, water temperatures ranged from 14 to 220 C in the main channel and 14 to 2r C in backwaters. In the Green River, water temperatures ranged from 19 to 220 C in the main channel and 14 to 280 C in backwaters. In the Colorado River, 25 Colorado pikeminnow were captured, measured and released. In the Green River, 22 yay Colorado pikeminnow were captured, measured and released. All fish were sorted, identified and enumerated in the field. Pikeminnow were distributed primarily in the upper 60 miles of both reaches (Figure 3). In the Colorado River, this marks a very different distribution pattern from 2001, where pikeminnow were found exclusively in the lower 55 miles of reach !. The average length of Colorado pikeminnow was 57.2 mm in the Colorado River, and 64.9 mm in the Green River. These lengths represent a 10-20 mm increase in average length from that seen in 2001, and are the largest reported since 1993 for either reach (Figure 4, Table I). Other yay native species captured included Gila spp., flannelmouth suckers, bluehead suckers, and speckled dace (Table I). The 35 Gila spp. captured in the Colorado River represents an appreciable increase over the one captured in 200 I (Table I). Ray counts were recorded for Gila spp. captured if they were large enough to allow for accurate counts. Although there was potential for capturing wild bonytail (reproduction from hatchery-reared fish) to appear in these samples, all chubs were identified as Gila spp., as species identification of chubs this size in the field is diffIcult at best. Total catches in both reaches were again dominated by nonnative cyprinids (Table I). In the Colorado River, 12 nonnative species were captured. These included red shiners (20,091), sand shiners( 4,145), fathead minnows (10,095), common carp, channel catfish, yellow bullheads, black bullheads, largemouth bass, green sunfish, white sucker, plains killifish, and Gambusia. In the Green River, seven nonnative species were captured. These included red shiners (43,606), sand shiners (2,600), fathead minnows (17,404), common carp, channel catfish, yellow bullheads, and green sunfish. The number of nonnative cyprinids captured in 2002 was extremely high compared to previous years with 34,331 found in the Colorado River and 63,610 in the Green River ,I FY 2002 Annual Report 22c Page - 5