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. AC marking to have yet another uniquely marked batch of larvae for release into the river. Personnel at Ouray Hatchery noted complete mortality oflarvae marked with AC. We investigated potential reasons for mortalities by conducting additional tests with seven-day-old fathead minnow, Pimephales promelas, larvae and older razorback suckers and did not observe mortalities. Thus, we reached no conclusions regarding reasons for mortality of razorback suckers marked at Ouray Hatchery (Appendix III). We did not attempt marking additional larvae with AC. We present release and field sampling information for each year separately because protocols changed with flow level and as we gained more information about the behavior of these systems relative to entrainment. Basic summary data are presented to assist reader understanding of the different release sites, conditions, and techniques used each year (Table 1). . . . . . 2004 In 2004, Green River peaks flows were low (161 cubic meters per second [m3/secD (Figure 2) and river-flood plain connections, including those at Thunder Ranch and Stewart Lake, were non-existent. Thus, 2004 sampling was conducted primarily to determine drift rates for beads and larvae, assess cross-channel mixing of beads downstream from release sites, and to evaluate whether beads were adequate surrogates for hatchery-reared razorback sucker larvae in main channel drift. Such information was deemed useful to guide sampling designs in years when flows were high enough to create a river-flood plain connection. Beads and marked larvae were released downstream from the island at Razorback Bar on 26 May, which was mostly a river right location. Two conical drift nets (four m long, 500 micron mesh size) equipped with General Oceanics (GO) Model2030R mechanical flow meters and cod-end capture buckets were . . . . 21 .