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a probable spawning site near Clifton, Colorado. A significant finding of the radio tracking study indi- cates that preferred spawning habitat for squawfish is evidently rare in the upper basin and the spawning fish will travel great distances to find these pre- ferred sites with the proper combination of depth, velocity and substrate type. Two major spawning areas have been identified; one area is the lower 20 miles of the Yampa River, and the other occurs in the Colorado River above the state line to Clifton. After spawning, movements of the adult fish are less pronounced and more sporadic. _The White and Gunnison rivers and the Upper Yampa River provide areas for feeding and growth for some fish. The Green River was found to be extremely important for young squawfish. Thousands of young squawfish, born the same year (young-of-year fish), were found in the Green River. Young-of- year squawfish were found in much lesser abundance in the Colorado River and lower Yampa River. The Green River below the mouth of the Yampa is the principal nursery area for squawfish. After the outlet works at Flaming Gorge Dam were modified to increase downstream water temperatures in 1978, the average summer water temperatures in the Green River increased to historic pre-Flaming Gorge levels, as recorded at Jensen, Utah. In subsequent years, a dramatic increase in the abundance of young-of-year squawfish occurred in the Green River from Ouray, Utah, to the confluence with the Yampa River. It was mentioned in the previously written sec- tion that virtually no young squawfish had been found in the lower Yampa River since 1968. In late 1980 fish collections in the lower Yampa River found that the non-native redside shiner was rare and was being replaced by the non-native red shiner, another minnow species of relatively small size. The 1980 collec- tions also found several young-of-year squawfish in the lower Yampa River. More young-of-year were found in the Yampa in 1981 and 1982. Young-of-year squaw- fish most commonly are found together with red shiners, but almost never with redside shiners. Evi- dently, red shiners and young squawfish are compatible when coexisting in the same habitat. Continued advancements have been made in hatchery propagation of squawfish. The Dexter, New Mexico, National Fish Hatchery is now devoted to the propaga- tion of endangered and threatened species of South- western fishes. The Dexter Hatchery provided 30,000 squawfish of 2-3 inches in length for stocking in the Colorado River below Grand Junction during Octo- ber, 1982. These hatchery-reared squawfish each had a minute magnetic tag implanted in their snout before stocking so that their subsequent movement and fate could be monitored. It was found that largemouth bass and sunfishes preyed heavily on the newly stocked squawfish where they had the opportunity. The prevalence of bass and sunfishes in the larger, deeper backwater and off-channel habitats along the Colorado River and the virtual absence of these species in the Green River, suggests why the Green River produces so many more young squawfish than does the Colorado River. 15