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<br />METHODS <br /> <br />Specimens for diet analyses were selected from samples of small fish <br />provided by the U.S. Fish and Wildlife Service (Vernal, Utah). These samples were <br />part of collections taken in backwaters throughout 520 km of the mainstem Green <br />River during summer (30 June-27 August) and fall (22 September-10 December) 1987. <br />The study area extended from the confluence of the Green and Yampa rivers at RK 555 <br />(river kilometers above confluence of the Green and Colorado rivers) in Echo Park, <br />Dinosaur National Monument, Colorado, to RK 35 at Turks Head, Canyonlands National <br />Park, Utah. Upper and lower reaches were divided at RK 346, Sand Wash, Utah. Each <br />river reach contained areas known for high catches of yay Colorado squawfish <br />(Haines and Tyus 1990, Tyus and Haines 1991) and included segments of moderately <br />high gradient (1.3-2.1 m/km) dominated by rocky substrates and segments of low <br />gradient (0.2-0.4 m/km) with primarily sand and silt substrates. The river was <br />further divided into 8-km sections starting from a random location within each <br />reach. <br /> <br />Backwaters were defined as shallow (typically < 0.5 m maximum depth), <br /> <br /> <br />ephemeral embayments with negligible water velocity adjacent to the main river <br /> <br />channel. Substrates in these habitats consisted of silt and sand or silt and mud <br /> <br />sometimes overlaying or interspersed with gravel or cobble. Backwaters had little <br /> <br /> <br />or no rooted aquatic vegetation, but many had dense mats of algae. Two backwaters <br /> <br />were sampled in each 8-km section during daylight (between 1000 and 1800 h) at <br /> <br />weekly intervals. Each backwater sample consisted of several pooled seine hauls <br /> <br /> <br />using a 1-m-square seine (0.8-mm-square mesh) in summer and a 3-m by 1-m seine <br /> <br />4 <br />