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i II area during discharges over 325 m3/s. Wick (1997) hypothesized that reduction in peak discharges since closure of Flaming Gorge Dam has resulted in sediment storage at lower elevations in the channel and sediment transport occurring at a narrower range of lower peak flow levels. Subsequent work using in-channel load sensors at the Green River spawning site found deposition of about 20 cm of sediment occurred during the spawning season (June 1999) at flows of about 500 m3/s at the Jensen, UT stream gage (Carpenter et al. 2000). These studies support the hypothesis that during some years sediment deposition on the spawning bar could adversely affect incubating eggs or pre-emergent larvae. Synthesis of larval and adult collection data (Modde 1996; Wick 1997) suggests that a second reproductive bottleneck affecting recruitment of razorback sucker is limited access to backwater and floodplain habitats. Based on length-frequency data, Modde et al. (1996) found that the only recruitment observed since closure of Flaming Gorge Dam has occurred following high flow years. Access to backwater and floodplain habitats during high flows provides conditions needed for recruitment (Stanford 1994; Modde et al. 2001) and may mediate predation by nonnative fishes on razorback sucker juveniles (Modde 1996). High flows may directly reduce the density of nonnative cyprinids that prey on young razorback sucker (Valdez 1990; Osmundson and Kaeding 1991) and also facilitate faster growth by razorback sucker in food-rich backwaters which could reduce vulnerability and increase survival (Modde et al. 1996; Modde et al. 2001). Both of these potential bottlenecks are affected by the timing, frequency, magnitude, and duration of annual and inter-annual flows. On an annual basis, migration and spawning behavior are likely initiated by a series of cues related to the magnitude of