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1 1 and the flood plain was confined. In valley reaches, channel gradient was lower, substrate was mostly sand, and the flood plain was relatively broad. Although more widespread historically, most razorback suckers now occur in relatively low-gradient reaches of the Green River from upstream of Jensen downstream to near the White River confluence (Fig. 1). METHODS Fish sampling, adults.-Basinwide sampling for adult razorback suckers was conducted in the lower Yampa, and the middle and lower Green rivers, both at sites that previously yielded razorback sucker adults (summarized in Muth 1995) and at other locations. In 1996, 1998, and 1999 sampling in the Yampa River was near the suspected spawning bar in the lower kilometer of the river in Echo Park (McAda and Wydoski 1980). Three reaches of the middle Green River received most of the 1996 to 1999 Basinwide sampling effort. Sampling in the most upstream reach was near Escalante Ranch (Escalante reach, river km (RK) 486 to 515; now called Thunder Ranch) and was focused near or on the suspected spawning azeas at RK 494.3 and 501.5 and near the mouths of Cliff Creek and Brush Creek and the Helley Pump. Sampling in the second middle Green River reach (RK to 446 to 486} near Jensen (Jensen reach) occurred near Jensen Bridge, Kane Hollow, Red Wash, Spring Hollow, and Walker Hollow, but most effort was expended near Ashley Creek, Sportsmans Drain, and Stewart Lake Drain. In the third reach of the middle Green River reach near Ouray (Ouray reach, RK 399 to 446), sampling occurred mostly neaz the inlet or outlet of Old Charlie Wash and the mouth of the Duchesne River. Adult Basinwide sampling in the lower Green River was limited to the San Rafael River confluence in 1997, but was more extensive in 1998 and 1999. Most effort in the Green River valley reach (RK 151 to 193) occurred in or near the mouth of the San Rafael River, a suspected spawning area. 3