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. .. " e . -. - , "..,~::..~ e here and at other stations downstream in Dinosaur National Monu- ment. Morphological characters of this fish were intermediate between the two parental species and agreed with the description by Hubbs and Miller (1953). In 1965, young-of-the-year of the following species were collected: Colorado chub, flannelmouth sucker, bluehead sucker, speckled dace, carp, redside shiner, and fathead minnow (Table 5). In 1964, fathead minnows and redside shiners were observed in spawn- ing condition, but no young-of-the-year were collected. Echo Park (65 miles below dam).-Species number increased con- siderably here from that found upstream. Although three distinct sampling stations were recognized at Echo Park (Green River above the mouth of the Yampa River, Green River below the mouth of the Yampa, and Yampa River immediately above its mouth), no major difference:; in species composition among these three locations were apparent. Three more native species-Colorado squawfish, humpback sucker, and mottled sculpin-were collected in addition to those found upstream (Table 4). In general, the native species were more abundant at Echo Park and at the other two downstream stations in the Monu- ment than at the stations above Echo Park, One humpback chub was collected here in 1963 and was identified by Dr. R. R. Miller as "Ap- parently representing Gila cypha", (letter to Earl M. Semingsen, Oc- tober 23, 1963). Exotic species taken that were not found upstream in the Green River were white sucker, green sunfish, and walleye. Rainbow trout were still present below the Yampa mouth, but in greatly reduced numbers. One brown trout taken here in 1966 was probably washed out of Jones Hole Creek in a severe flash flood in early July. Successful reproduction of all native fishes except the humpback sucker was apparent (Table 5). It was not known whether the hump- back chub reproduced during these years since the young of this extra- ordinary fish have not been identified (Miller, 1964). All young- of-the-year and juvenile Gila taken .in the present study, therefore, were identified as G, robusta. Reproduction was also noted for carp, reds ide shiner, fathead minnow, white sucker, channel catfish, and black bullhead, No reproduction of any species was observed in the Green River immediately above the mouth of the Yampa River in 1964 and 1966. Island Park (77 miles below dam) and Split Mountain (87 miles below dam) .-Species composition and relative abundance were very similar to that found at Echo Park (Table 4). One brown trout taken at Split Mountain in 1966 was probably a refugee from the Jones Hole flash flood. Reproduction of all native fishes collected here, except the 308 ".--._,.,......- ~~---.'_'~'-.o_' ~~ ___~_. ..... - .'-- --_.-_--,.--~'----~ + .r ,