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<br />. <br /> <br />EXECUTIVE SUMMARY <br /> <br />. <br /> <br />. <br /> <br />The razorback sucker, Xyrauchen texanus was formerly widespread throughout <br /> <br />warmwater reaches of the Colorado River Basin, but is currently federally listed as endangered <br /> <br />due to negative impacts from physical habitat alteration and introduction and proliferation of <br /> <br />nonnative fishes. Flood plain wetlands are presumed important habitat for early life stages of <br /> <br />razorback sucker. Therefore, the Upper Colorado River Basin Endangered Fish Recovery <br /> <br />Program initiated actions to 1) identify key flood plain areas and breach levees to increase river <br /> <br />connections to them and 2) develop and implement flow recommendations to enhance those <br /> <br />connections. <br /> <br />. <br /> <br />. <br /> <br />I <br /> <br />We released semi-buoyant beads and marked razorback sucker larvae into the Green <br /> <br />River during spring run-off in 2004, 2005, and 2006 to evaluate drift characteristics of larvae and <br /> <br />beads into flood plain wetlands. Based on drift rates and capture patterns, our findings from <br /> <br />2004 main channel only sampling suggested that beads and tetracycline-marked fish larvae were <br /> <br />reasonable surrogates for one another based on similarities in drift capture patterns, We also <br /> <br />captured substantial numbers of unmarked, wild-produced razorback sucker larvae in 2004. This <br /> <br />demonstrated that stocked adult fish were successfully reproducing and that another spawning <br /> <br />area may exist downstream from Razorback Bar (now named "Escalante Bar"), an hypothesis <br /> <br />later verified by independent sampling of ripe adult fish. <br /> <br />Based on 2004 and 2005 captures of two different colored beads released on different <br /> <br />sides ofthe river, complete cross-channel mixing of drift particles did not occur until at least 22 <br /> <br />kilometers (lan) downstream of release sites over the range of flows we tested. Mixing is likely <br /> <br />to occur more quickly at higher flows. This conclusion was supported by the collection of a <br /> <br />greater number of orange beads released upstream and on the opposite side of the river of <br /> <br />. <br /> <br />. <br /> <br />. <br /> <br />. <br /> <br />IX <br /> <br />. <br />