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<br />93 <br />Two native suckers, Catostomus discobolus and Catostomus latipinnis <br />were abundant throughout both rivers in the Monument (Tables 2 and 31. <br />Numbers of these two species were approximately equal in the Yampa and Green <br />rivers downstream to Echo Park, but Catostomus discobolus was noticeably <br />more abundant further downstream (Table 3). Gila spp. (including G. robusta) <br />occurred throughout the monument, but were uncommon in the Green River below <br />Whirlpool Canyon. Rhinichthys osculus and Gila robusta were abundant in <br />seine hauls throughout both rivers in the monuments. <br />Two introduced species, Cyprinus carpio and Ictalurus punctatus? <br />were common in trammel net and electrofishing samples throughout the <br />monument (Table 3). Both these species- reached weights in excess of 5 kg. <br />Rhinichthys osculus and Notropis lutrensis were abundant in seine hauls <br />throughout both rivers. Pimephales promelas was widespread in both rivers, <br />but was abundant only in occasional seine samples from backwaters. Notropis <br />stramineus and Richardsonius balteatus were common in the Green River, but <br />were uncommon-to-rare in the Yampa. <br />Occurrence of fishes found in the present study was generally similar <br />to that reported by Holden and Stalnaker (1975a, 1975b), Seethaler et al. (1979), <br />and Tyus et al. (1981a). Gila elegans was reported abundant in the Green River <br />at Echo Park in 1964-66 (Vanicek et al. 1970), but Holden and Stalnaker (1975b) <br />found the species to be rare. No G. elegans were found in 1981, and the <br />species appears to be extirpated in DNM. G. cypha were rare in 1981, as <br />was reported by Holden and Stalnaker (1975b) from 1968-71. The five G. cypha <br />collected in 1981 were found in deep pools or eddies adjacent to boulders <br />where water velocity was < 0.5 ft/sec. Xyrauchen texanus was found in spawning <br />condition in May 1981 from the identical riffle where found by McAda i:n 1975 <br />(McAda and Wydoski 1980). Ptychocheilus lucius was rare; however, a radio- <br />telemetry study (Tyus et al. 1981b) discovered spawning Colorado squawfish in <br />the lower 32 km of Yampa canyon in early July 1981 at which time the species <br />was locally common. <br />Results of the Yampa River Study are preliminary since data analysis <br />has just begun. The final report is due in January 1982 and will include <br />information for all fish species, with emphasis on endangered fishes. Infor- <br />mation from radiotelemetry and larval collections will be used to explore <br />spawning of Colorado squawfish. The largest task has yet to be addressed: <br />combining all FWS studies so that the upper Colorado River Basin can be placed <br />in perspective regarding the most important habitats for endangered fishes. <br />When this is done it appears the Yampa River may be proven a critical link.