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Colorado squawfish adults were captured in all 4 strata, but were rare. Only one razorback sucker was collected, (Stratum 4, May 1981). Humpback chub was only found in Stratum 3, Whirlpool Canyon (August). Qnly 2 humpback chub were collected, but two other individuals in the sa,Te collection appeared to have humpback charactertistics. Exotic species in the Green River were numerically dominated by the red shiner which comprised 25% or more of total fishes in each of the four strata. Other relatively common cyprinids included fathead minnow, sand shiner, redside shiner, and carp. Incidental species included one smallmouth bass from Stratum 3 and one white sucker from Stratum 4. Two introduced salmonids, brown trout and rainbow trout, were found occasionally in Strata 3 and 4, Catch/effort data indicated that electrofishing was most effective in capturing juvenile and adult flannelmouth and bluehead suckers, carp and channel catfish (Tables 7 and 8). Electrofishing was also more effective in collecteg juvenile channel catfish than adults. Seines were more effective for all size classes of the smaller cyprinids,'and' the YOY of larger species. Catch rates in trammel nets (fish/h) were generally quite low (less than 0.1 fish/h). Trammel nets were most effective for adult bluehead and flannelmouth suckers, adult roundtail chub and adult channel catfish (Tables 11 and 12). Of the 19 species collected in the Green River during standardized sampling, 17 species were found in Strata 3 and 4 and only 13 in Strata 1 and 2 (Table 6). This difference may be due to the presence of more pools, eddies and backwaters in the upper 2 strata, however, all four, species not found in the two lower strata occurred in very low numbers (i.e. one smallmouth bass in Stratum 3; one razorback sucker in Stratum 4; a few brown and rainbow trout in both strata). The two salmonids were probably recruitment from Jones Hole Creek and/or Flaming Gorge reservoir, (since they are introduced there) rather than any direct reflection to habitat. Habitat Preferences - All Species Habitat preferences may be inferred from conditions measured at points of fish captures but caution should be used when interpreting relative number of fishes collected in different habitats (Figure 8). Since these data include all gear types in all strata, habitat types are not uniformly represented in all strata. With the concurrence of NPS a more complete analysis of these data will be made later in 1982 using a number of variables including habitat type, water depth, water velocity and substrate type. Shoreline habitats generally contained more fishes than other habi- tats, which is logical since a diversity of microhabitats were present. Adults of all species combined exceeded young and juveniles in shorelines (all three rivers; Figure 8). Eighteen of 19 species collected in the Green River, 18 of 23 species collected in the Yampa River, and all 11 species from the Little Snake River were captured from shorelines (Figure 9). 43