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Tetra Tech I I I I I I I I I I I I I I I 'I I I I sucker fry. Small (< 6cm) sunfish, rainbow trout (5 and 18 em), red shiner (<7 em), largemouth bass (<8 cm), yellow bullhead (<14 cm), channel catfish (<13 em) and bonytail (<8 cm) were all aggressive predators of 10-50 mm razorback sucker. Yes, Razorback Sucker Can Recruit Naturally in the Wild! Tim L. Welkerl, Paul B. Holden I, Kirk Dahlel, and Jim E. Heinrich2 I BIO-WEST, Inc.; 2Nevada Division of Wildlife We have studied the ecology and life history characteristics of the Lake Mead razorback sucker (Xyrauchen texanus) population for the past 7 years. A major emphasis of this research has been to examine the age structure of this population to determine its age relative to existing wild populations of razorback sucker and to identify patterns of recruitment. Ages calculated nonlethally for 57 wild razorback sucker during this study indicate that the Lake Mead population is relatively young with a current average age of approximately 16 years. Additionally, the capture of one 5-year-old and seven 4-year-old sub adult fish in 2003 shows that natural recruitment has occurred recently in the lake. A comparison of the years all aged razorback sucker were spawned with historical Lake Mead water elevations provides some evidence that a combination of small, annual lake- level fluctuations and larger, multi-year changes in lake elevation may influence razorback sucker recruitment. The long-term lake-level changes may promote growth of terrestrial vegetation that, when inundated by the lake, provides increased protective cover for larval and juvenile razorback sucker, resulting in the limited recruitment documented in Lake Mead. The fact that the recently aged sub-adult fish were apparently spawned in 1997 and 1998, at a time when large amounts of protective cover were inundated, generally supports this theory. Flow-through connection at the Above Brennan and Bonanza Bridge Bottomlands Carey, Jason In April of 2000 Above Brennan and Bonanza Bridge Bottomlands were reconfigured to connect to the Green River with a flow-through condition. Previously the bottomlands were configured with a notch at the downstream end that only provided a backwater condition in the bottomland during connection with the river. The flow-through configuration was created by constructing notches at the upstream ends of the bottom lands. The gradient of the river now causes flows to pass through the bottomland and exit through the notches at the downstream of the bottomlands. The flow-through condition has potential to capture magnitudes greater numbers of drifting larvae in the bottomland than a backwater condition. However, the potential 20