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and beetles were less abundant. Fishes collected in 1971 and 1972, in decreasing order of numerical abundance, were speckled dace, mottled sculpin, redside shiner, mountain whitefish, bluehead sucker, white sucker, flannel- mouth sucker, rainbow trout and roundtail chub. Seethaler, McAda and 6Jydoski (1976), in a report on endangered and threatened fishes of the Yampa and Green Rivers in Dinosaur National f~onu- ment from 1974 to 1976, compared their collections to Holden's from the lower Yampa River. Their observations were similar to Holden's, but they did not collect bonytail chub, largemouth bass, bluegill, green sunfish, or walleye. Species in their collections from the lower Yampa which were not collected there by Holden were Fundulus kansae (plains killifish), Gila atraria (Utah chub), and Notropis stramineus (sand shiner). Colorado squawfish were said to ascend the Yampa River when water levels were high and additional food and habitat were available. squawfish reproduction was said to have de- clined since the 1960's. Ripe humpback suckers (X rauchen texanus), also known as razorback suckers, of both sexes were reported on two spawning bars in the Yampa River. Evidence of increased hybridization between flannel- mouth and humpback suckers was also reported. Six humpback chubs were collected from the lower Yampa River in 1975 and 1976. The Yampa River was mentioned as a possible refuge for some of the large-river endemic fishes that are threatened or endangered. The major contribution of the Yarnpa to continued survival of these fishes was considered to be its effect on the Green River below the confluence of the two streams, and Seethaler et al. (1976) stated that "Our concern is that any alteration of the Yampa River or its tributaries could have a serious negative impact upon this amelior- ating effect." 18