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<br />have been examined in the Lower Colorado River Basin at Lake Mohave are food <br />~ limitation and predation (Horn et.al 1994, Peepuls and Mickey 1992, 1990, and Marsh <br />and Langhorst 1988). Poor water quality, insufficient stocking densities to overcome <br /> <br />predation and stress from stocking are additional possibilities suggested for this study. <br />Limited food supply is unlikely to reduce larval survival in floodplain wetlands <br />because zooplankton densities are typically higher in floodplain wetland habitats than <br />~ main channel and backwater habitats (Birchell et.al 2002, Wydoski and Wick 1998, and <br />Cooper and Severn 1994). However, zooplankton data were not collected, therefore, <br />no definitive evidence exists suggesting adequate quantities and proper sized <br />~ zooplankton were available for consumption by larval razorback sucker at the time of <br />stocking. <br />Predation is a more plausible explanation for larval razorback sucker mortality <br />during this study. Johnson et al. (1993) determined larval razorback sucker were <br />predator naive and were not likely to survive with high numbers of nonnative fish. <br />~ Although nonnative fish densities for each site at the time of stocking must be <br />estimated, densities were likely much higher at The Stirrup than at Baeser Bend. Four <br />months after stocking larval razorback sucker there were an estimated 2708.2 kg (3 <br />~ tons) or 310,600 nonnative fish in The Stirrup (Birchell et al. 2002). Species <br />composition consisted of 53.2% fathead minnow, 35.6% black bullhead, 6% green <br />sunfish, 3.8% red shiner and 1.3% carp. Nonnative fish densities were lower at Baeser <br />Bend because a significant portion of the nonnative fish population perished during the <br />summer of 2000. In addition to nonnative fish, odonate nymphs are present in the <br />~ study sites and may also prey on larval razorback sucker. Under laboratory conditions <br />23 <br /> <br />