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. . Study Area This study was conducted during 1997 through 1999 and included the lower 34.5 miles of the Duchesne River, from the Lake Fork Diversion near Myton, Utah, downstream to the confluence with the Green River. Three specific monitoring sites were selected to provide a standardized, representative overview of the river and allow observation over the course of the study (Figure 1). The Myton site (RM 29.0 - 27.0) represents upper, higher gradient habitats. The Uintah site (RM 13.7 - 11.7) represents intermediate gradient with meanders and braided channels, and the Ouray site (RM 3.0 - 0.0) represents low gradient habitat. . . Methods . Sampling Larval.- Evidence of endangered fish spawning was investigated by sampling the lower river below the confluence with the Uintah River for drifting fish larvae. Shoreline and low velocity habitats from the confluence with the Uintah River to the confluence with the Green River were sampled during the spring run-off period from early May through July. This included intensive sampling using light traps, larval drift nets, dip nets and fine mesh seines. Larval light traps (Southern Concepts 7) were set overnight in low velocity habitats. . These light traps were 31.5 cm high and 22.6 cm in diameter. Samples were collected at dawn, identified and enumerated. If crews were unable to positively identify larvae or larvae were too numerous to count, the sample was preserved and submitted to the Larval Fish Laboratory (LFL) at Colorado State University for processing. Fine-mesh drift nets equipped with flow meters (General Oceanics7) were set at the margins of the river channel during all years ofthe study. Duration of drift net sets was generally 20 to 30 minutes and was adjusted according to the amount of debris carried in the water. Beginning and ending readings were taken from the flow meters for later calculation of water volume sampled. During the 1999 field season a 24-hour drift net station was established near river-mile 6.4 (Pipeline) to assess possible larval drift time periods. A bank of three larval drift nets was set in the margin of the main channel at 4-hour intervals for a duration of20 to 30 minutes. Drift net samples were preserved in alcohol for later examination in the Utah Division of Wildlife Resources (UDWR) laboratory. A fine mesh seine was used in backwaters and other low velocity areas. The seine was 4 . . . . . 3 .