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1 Th e average rate of dispersal for both groups of razorback suckers was very similar during the first 14 days, but differed mazkedly over time. Initial movement rates were ~4.6 km/day for both treatments. During the 15 to 29 day period, average daily movement rates for experimental razorback suckers decreased to 1:1 km/day while control suckers decreased their movement rates much less (3.5 km/day). During the 30- to 58-day period since release, experimental suckers continued to move at approximately the same rate (1.2 km/day) while the control fish had decreased their movements to 0.37 km/day. Razorback sucker movement rates decreased significantly over time (p < 0.001), but due to high within-group variation the observed treatment affect was not signif cant (p = 0.44). This attenuation in the estimated rates of daily movement are very ' similar to those observed by Day and Modde (1999) in 1995 on the Green River. Their much smaller razorback suckers (average TL 197.9 mm vs. 437.6 mm) averaged 6.8 km/day (n = 16) during the first 13 days and decreased to 2.0 km/day (n = 7) between days 13 and 28. Although the rates of dispersal of experimental and control suckers did not differ significantly over time, the average directed rates of movement (+/-km/day) were significantly different between treatments (p = 0.042). Directed rates of movement were calculated for a particular fish by defining upstream movement rates as +km/day and downstream movements rates as -km/day and then summing these within treatment and time periods. The effect of a 2-day acclimation was to significantly reduce the downstream directed movements rates of razorback suckers, as seen in Figure 6. Initial downstream directed movement rates of control fish were -4.2 km/day. This is more than double the rate (-1.9 km/day) for experimental razorbacks. During days 15 to 29, experimental razorback sucker directed movement rates had attenuated to just 0.3 km/day h ' w ile control fish were still continuing to move downstream at a rate of 3.5 km/day. Control razorback suckers required at least 30 days from the time of release to reduce their downstream directed movements to a level that was reached by experimental razorbacks after 15 days. The finding that the majority of dispersal of stocked razorback sucker occurs during the first few weeks following release has been observed in previous razorback sucker stockings (Brooks 1985, Day and Modde 1999, Marsh 1987, Mueller and Mazsh 1998, Ryden and Pfeifer 1995), as well as in other species offish. Chilton and Poarch (1997) observed that 50% of the total yeazly movements of grass carp stocked into Texas reservoirs occurred during the first 2 weeks. Hanson and Mazgenau (1992) observed that the majority of young of the year muskellunge dispersal in lakes occurs during the first 2 weeks. Cazlstein and Eriksson (1996) observed that 75% European grayling (Thymallus thymallus) stocked into an experimental stream dispersed greater than 400 m downstream during the initial 8 hours. 17