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Obiective 4. Determine if flow training enhances survivorship of different size classes of bony tail. This objective had not been field tested as of FY 2001. Flow Training Hatchery-Reared Bonytail Initial findings on the effects of flow showed significant increases in mitochondrial volume and muscle fibre diameter in I-year old fish raised for 18 months in constant flow conditions (Lentsch et al. 1996). In 1997, lab experiments which tracked growth over a 12-month period of flow training showed no significant differences between groups with and with out flow training (Crowl and Rivera 2000). In both sets of experiments, I-year old fish averaged <150 nun in total length. It was suggested by the researchers that additional experiments be completed with a larger size range offish. To date, further flow training has not been conducted. Although the experiments by Crowl and Rivera showed no affects on growth, the earlier experiments did demonstrate a positive physiological response. The potential for flow training in the hatchery setting to affect behavior, growth, or survivorship is still very unclear. If any further research is to be done in this area, it would be most appropriate for it to be conducted on site at the Wahweap State Hatchery. Flow trained fish could then be released and their survivorship could be examined through our standard monitoring. CONCLUSIONS . Overall return rates ofbonytail stocked in both the Green and Colorado rivers were consistent with return rates observed for juvenile razorback and pikeminnow reintroductions. However, the recapture rates for stocked bonytail at large more than six months was lower relative to what was experienced in other native fish reintroductions. . Relative return rates and survival were highest for bonytail released at 300 nun or greater. This includes the 1996 cohort released in 1998 and all bonytail released for telemetry 1997-2000. Insufficient data was available to definitively determine the relationship of survivorship and fish size at the time of stocking. . Growth rates of small bonytail stocked in the fall (October) showed, on average, no change in total length before the onset of their first winter. Although no overall difference was observed between short-term returns for fall and spring stockings, this could indicate too short of an acclimation period prior to overwintering. . Juvenile bonytail (<150 mm) showed a strong preference for flooded tributary and backwater habitats and larger bonytail (> 150 nun) were more prevalent in flowing habitats such as runs, riffles, and eddies. 18