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. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Duchesne River Adult fish monitoring malfunction in the radio receiver used for aerial surveys, codes for most fish located were undetected in the spring and summer of 2000. The Ouray data logger detected three fish implanted in 1999 entering the Duchesne River in February 2000. Although codes were not determined, an aerial survey on 6 March 2000 detected three fish in the Duchesne River in March. Fish were not detected in the Duchesne River in aerial flights in May, July or September 2000. Movement of implanted fish into the Duchesne River occurred prior to the onset of peak spring runoff during each year of the study. ill 1998 and 1999, fish implanted in the Duchesne River returned from the Green River in March and April. Temperatures at this time were warmer in the Duchesne than the Green river in 1998 (Figure 4). However, three fish implanted with transmitters in 1999 (codes 1,4, and 11) were recorded by the stationary telemetry station as returning to the Duchesne River in February 2000 when temperatures were colder in the Duchesne than in the Green River. Fish were not recorded by the telemetry logger as leaving, although aerial surveys did not detect fish in the river in the spring or summer. Most fish implanted in the Duchesne River appeared to remain in the local area. Once fish moved into the Green River, most were located within 22 miles either upstream or downstream from the confluence of the Duchesne River (Figure 5). Diel Movements Twenty-four hour monitoring of two individual fish was conducted in 1997 (Tables 6 and 7), Both fish 40.323 and 40.303 used occupied a range of depths and velociticies. Both fish tended to use higher velocity run habitats more often than slower velocity pool habitats. Both fish moved short distances (i.e., 0.2 and 0.9 rmi) in late afternoon and morning. The timing of fish movement past the Ouray telemetry logger showed a similar patterns to those observed during the 24 hr monitoring (Figures 6 and 7). Among individual fish that were recorded on successive days, most passed the logger during the late evening and late morning hours. Fish 40.323, remained in the vicinity of the logger 13 of 14 days between 25 May and 7 June 1998. During several days, a constant power signal during the daylight hours suggested that the fish 40.323 remained near the logger during the midday hours and moved more during the late afternoon or evening hours. Fish 40.323 left the vicinity of the Ouray logger between 25 May and 7 June 1998 between sunset and sunrise on 9 of 12 occasions. ill addition, records of fishes 40.182 and 40.392 also showed most movement between the late evening and late morning hours. 8