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Survival estimates and growth rates were impressive when predation by, and ~ competition with, the large number of nonnative fish were considered. Each study site was occupied by high numbers of nonnative fish in the spring at the time of stocking. Several years of above average flow preceding the study provided conditions that allowed non-native fish populations to build up in each site (Birchell et al. 2002). During razorback sucker sampling in the fall, nonnative fish were removed from the sites and ~ estimates were calculated using catch effort decline. There were an estimated 5357.4 kg (458,474 fish) of nonnative fish in Baeser Bend, 2708.2 kg (310,565 fish) in The Stirrup and 711.4 kg (86,122 fish) in Above Brennan (Birchell et.al 2002). These results ~ indicate age-1 razorback sucker are very capable of competing with and avoiding predation by large numbers of nonnative fish. Razorback sucker survival was dramatically reduced during the second year of the study. Below average spring flows and summer drought created water conditions in The Stirrup and Baeser Bend that were lethal for all fish species. At The Stirrup, low ~ spring flows resulted in a brief connection duration that did not sufficiently fill the site. As a result, stagnant water remaining from the previous year was not adequately freshened and nighttime dissolved oxygen levels became lethal for razorback sucker ~ sometime in the early summer (4 June - 13 July). Unlike The Stirrup, Baeser Bend and Above Brennan filled during river-floodplain connection in all years. Late summer water depths were nearly the same in each site, however, an estimated 50 - 75% of the razorback sucker in Baeser Bend were lost. Late summer fish kills were not observed at Above Brennan. Differences in connection configurations between the two sites may explain why fish kills occurred at Baeser 21