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252 The Southwestern Naturalist vol. 36, no. 2 WYO '" -'''_00','''_'''-'''-'''- ...-... Cross Mountain , Yampa Canyon Canyon N I ~ , :rlo 0 10 20 Km <(:-1 !-'O :J U WYOMING COLORADO FIG. 1-Map of Little Snake River, Colorado. Hatched area denotes known spawning area of Colorado squawfish on the Yampa River. m3/s on 27 June. By 6 July, flows declined to 5 m3/s. During August and September, flows were at base levels of 0.2 to 0.3 m3 Is. In October, flow increased to 0.85 m3/s. Two radiotagged Colorado squawfish were contacted by radiotelemetry in the Little Snake River. Thl!se fish were implanted in September 1987 on the Yampa River 3 km above the Little Snake confluence to investigate winter habitat use and timing of spring migration. One fish (824 mm total length; TL) was found in the Little Snake River on 24 and 25 May in a large (10 by 50 m) eddy below an island at RK 9.2. On 8 June, it was located below another island at RK 10.8. After flows declined on the Little Snake River, this fish was located in the Yampa River on 26 June and migrated to the Yampa Canyon spawning area by 6 July (H. Tyus, pers. comm.). We located this fish after it migrated back to its Yampa River over-wintering area above the Lit- tle Snake River- Yampa River confluence on 2 October. The other Colorado squawfish was ob- served 8 June moving upstream in main-channel run habitat. Water temperature was 190C in the Little Snake River and 160C in the Yampa River. This fish was located in the Yampa River moving downstream on 27 and 30 June, and then radio contact was lost. Sampling for adult fishes in the Little Snake River was initiated during spring runoff and con- tinued into baseflow periods in July and October. A total of 308 adult and large juvenile fish was collected by trammel net (50.0 by 2.5 m, 25-mm mesh), seine (3 by 1 m, 5-mm mesh), and angling on five sampling trips. Among the specimens col- lected were seven suspected humpback chub, two suspected humpback chub x Colorado roundtail chub, Gila robusta robusta, hybrids, and one Col- orado squawfish. Suspected humpback chub (216 to 320 mm TL) were collected from eddies that ranged from 1.0 to 1.3 m deep with sand and boulder substrates. Two of the suspected hump- " " ~ ~ -....