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<br />20 <br /> <br />Yampa-Green River Study Area <br /> <br />General <br /> <br />A total of 1,326 seine and dip net samples were taken in the Yampa River <br />during 1980-1984 (Table 1) and 19 fish species were collected (Table 6). <br />Virtually 100% of the fish sampled were cyprinids and catostomids. During <br />1981-1982, non-native fishes predominated, constituting 51% and 56% of the <br />total catch, respectively. Red shiners, sand shiners and fathead minnows <br />were the dominant non-native species collected. Unidentified Gila spp. and <br />speckled dace were the most common native species. In 1983, native fishes <br />constituted 82% of all individuals collected, predominated by Gila spp., <br />speckled dace, and bluehead suckers. <br /> <br />A 267-mm (TL) humpback chub was collected by gill net in upper Cross <br />Mountain Canyon (August 1980); representing a range extension for this <br />species. <br /> <br />Thirteen fish species were collected in 420 drift-net samples at the <br />Yampa River sites (1983-1984), while 8 species were collected in 155 <br />drift-net samples at the Green River (state line) site in 1984 (Tables 1, 7, <br />and 8). Almost all fish collected were cyprinids, catostomids and <br />ictalurids. In 1983, 4,495 individu~ls, mostly larvae (juvenile and adult <br />forms contributed less than 5%), were collected at both Yampa River sites <br />combined (Table 7). Total catch at Harding Hole was almost twice the Box <br />Elder catch. Twelve species were collected at Harding Hole, of which sand <br />shiner, white sucker (Catostomus commersoni), and mottled sculpin (Cottus <br />bairdi) were exclusive to this site. Ten species were sampled at Box Elder; <br />red shiner was the only species exclusive to this locality. Native species, <br />represented by Gila spp., speckled dace and bluehead suckers, were far more <br />abundant than non=natives at both sites and accounted for 83% of the total <br />combined catch. Channel catfish was the predominant non-native species <br />collected at both sites, but were sampled in substantial numbers only at Box <br />Elder (i.e., 514 individuals=34% of total catch). <br /> <br />In 1984, 9 species were collected by drift-net sampling at Box Elder, <br />while 8 species were collected at State Line. A total of 3,607 individuals, <br />predominantly larvae, were sampled at both sites combined. The catch at <br />State Line was less than one-third the Box Elder catch. Redside shiner and <br />sand shiner were exclusive to Box Elder and fathead minnow was exclusive to <br />State Line. Native fishes (same species) were again far more abundant than <br />non-natives and accounted for 65% and 72% of the total catch in the Yampa and <br />Green rivers, respectively. As in 1983, channel catfish was the most <br />commonly collected non-native species. <br /> <br />~ <br />