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MANAGEMENT BRIEFS Upon reaching the Green and Colorado River con- fluence (54 km), six fish (4 acclimated, 2 control) swam up the Colorado River; 9 (82%) of the 11 fish detected downstream of the confluence were control fish. Moment by the site-acclimated group averaged 66 km (maximum 126 km), whereas con- trols averaged 71 km (maximum 122 km). Large Backwater We followed 58 fish for a month and accounted for 1,121 contacts. Fish dispersed following re- lease, but 21 remained in the backwater for at least 1 month. Twenty-two fish (16 pond-reared, 6 flow- conditioned) moved downstream, whereas 6 fish (5 flow-conditioned, 1 pond-reared) went up- stream. Most (95%) fish entering the river were found in small backwaters by the end of week 4. Site-acclimated and reference pond-reared fish dis- persed an average of 8.8 and 6.6 km, respectively, whereas the site-acclimated and reference flow- conditioned groups dispersed 3.6 and 0.2 km. We detected a maximum movement of 49 km down- stream and 9 km upstream by the end of week 4. Average poststocking dispersal from the release point varied among pond-reared fish released in the reservoir (3.7 km, N = 19), small-backwater fish (69.5 km, N = 20), and large-backwater fish (7.6 km, N = 28) (Table 2). A Kruskal-Wallis analysis of the three test groups showed that dis- persal was greatest in fish released from the small backwater (X2 = 39.5, df = 2, P < 0.01). Flow combined with the lack of adequate cover aggra- vated downstream dispersal or drift. We detected no statistical difference in dispersal distance between reference and site-acclimated fish at any release site (Table 2). Acclimation pe- riods of less than 7 d appeared to have negligible influence on short-term dispersal. However, flow- conditioned fish had significantly lower dispersal rates than did pond-reared fish (Wilcoxon two- sample test; Z = -2.298; P = 0.0216, N = 30). Discussion Reintroduction of endangered fish into their his- torical ranges is a relatively recent management tool. Typically, recovery programs use existing conventional culturing and stocking techniques that have served the recreational fishery; however, there is growing evidence that some endangered species are not surviving this reintroduction for- mat. Hatchery-produced fish have been shown to exhibit problems with physical and behavioral stress, disorientation, and occasionally starvation that affects performance and survival (Miller 273 1954; Wedemeyer et al. 1990; Hanson and Mar- genau 1992). In contrast, recent research on anad- romous salmonid culturing techniques has shown that innovative hatchery procedures can increase the postrelease survival of smolts (Berejikian et al. 2000; Maynard et al. 1995). Our site-acclimation tests proved inconclusive and possibly were influenced by small sample size or short acclimation period. Previous studies dem- onstrated that handling and transportation stress can alter blood chemistry, behavior, and fish per- formance for days and even weeks (Carmichael et al. 1984a, 1984b; Olla et al. 1995; Waring et al. 1996) and that handling or environmentally in- duced stresses are cumulative and can lead to chronic fatigue or death (Wydoski et al. 1976; Schreck 1981; Schister and Bergersen 2000). Site acclimation has become a critical component of many terrestrial reintroduction programs (Fritts et al. 1997; Biggins et al. 1998). The pronounced and prolonged drift (>68 km/ month) witnessed in the small-backwater test on the Green River added to growing evidence that pond-reared fish perform poorly in streams and are prone to downstream drift. Research has shown that initial exposures of pond-reared trout to flow can lead to physiological fatigue (Poston et al. 1967; Barton et al. 1986; Clearwater and Pank- hurst 1997). Alternatively, fish exercised for pe- riods beyond 2 weeks exhibited increased stamina, higher food conversions, improved growth rates, better circulation, and greater heart and muscle mass (Cresswell and Williams 1983; Leon 1986; 7obling 1994; Davison 1997). Barrett and Mc- Keown (1988) suggested that exercise training not only increased stamina but presumably improved the ability of steelhead Oncorhynchus mykiss to avoid or escape predators. Although flow condi- tioning is commonly used in culturing salmonids (Davison 1997), we were unable to find similar approaches for catostomids or other warmwater fish. Our data suggests that razorback suckers con- ditioned to flow 2 months before release remained closer to the release site than pond-reared fish and performed similarly to the wild-captured fish used in earlier telemetry studies (McAda and Wydoski 1980; Valdez and Masslich 1989). We propose that flow conditioning improved swimming perfor- mance while reducing overall stress and the chanc- es of chronic fatigue, and we assume that increased performance leads to improved survivability (cf. Barrett and McKeown 1988).