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SPECIES CODE COMMON NAME SCIENTIFIC NAME STATUS. I I I I I I I I I I I I I I I I I I I Table 4. (Continued) Family: Poeciliidae (Jivebearers) GA mosquitofish (Gambusia affinis) NN Family: Esocidae (pikes) NP northern pike (Esox lucius) NN Family: Salmonidae (trouts) BR brown trout KS kokanee salmon RB rainbow trout (Sa/mo trutta) (Oncorhynchus nerka kennerlyi) (Oncorhynchus mykiss) NN NN NN Family: Serranidae (sea basses) SB striped bass (Morone saxatilis) NN UN unclassified a Scientific names tram Robins et a/. 1980, except for Oncorhynchus mykiss. b NA = native to the drainage, EN = endemic to the drainage, NN = non-native, introduced. It is also noted that small numbers (fewer than 25) of the crayfish, Orconectes virilis, were found in the Colorado River above the confluence and in Cataract Canyon. These crustaceans may be invading this area since they were not reported below Grand Junction in 1981 (Valdez at al. 1982). They may pose an additional predation or competition threat to the young endangered fish. 4.2 Fish Composition by Year As a percentage of total numbers by year, the eight native species made up only 3 to 11 % of the catch, while the six endemics alone made up only about 3 to 8% of the catch (Table 5). The non- native fish accounted for 89 to 97% of all fish caught from 1985 to 1988. These results show that the native ichthyofauna of the mainstem Upper Colorado River Basin was overshadowed by non-native species in all years of this investigation. Table 5. Number and percentage of native, endemic, and non-native fishes captured by year, 1985-1988. ORIGIN 1985 1986 1987 1988 N. p. N P N P N P Native 935 4.41 1,215 9.65 2,634 10.81 2,702 3.11 (Endemic) (827) (3.90) (1,012) (8.03) (1,764) (7.24) (2,477) (2.85) Non-Native 20.274 95.59 11.380 90.35 21.725 89.19 84.216 96.89 Totals: 21,209 12,595 24,359 86,918 a N = number, P = percentage of total 24