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whether there are differences between fish in the lower and upper reaches of the Virgin <br />River need to be addressed to assist in making informed management decisions. <br />DeMarais et al. (1992) found that the Moapa River was a "distinctive population" <br />of Virgin River chub based on morphology, allozymes and mitochondrial DNA. In 1993, <br />DeMarais et al. found that there was no genetic structure, spatial or temporal, within the <br />mainstem Virgin River using three allozyme loci. The present study provides an analysis <br />of population structure using microsatellite markers. These nuclear markers generally are <br />more variable than allozymes and provide greater resolution for determining subtle <br />differences within and between populations (Christiakov et al. 2006). <br />It is also important to compare the genetic character of samples of wild and captive <br />populations. The genetic composition of captive populations may diverge from wild <br />donor populations, even over a few generations, due to founder effect, genetic drift or <br />selection for traits that are advantageous to survival in captivity (Williamson 2001). <br />DeMarais et al. (1993) found differences between the first generation of captive-bred fish <br />at Dexter and the source population: a shift in allele frequency had. occurred at one locus <br />or gene, and the loss of a relatively rare allele at another. Augmentation of wild stocks <br />with captive populations that are genetically different can have deleterious effects <br />(Hindar et al. 1991). The present study includes an assessment of samples from Dexter <br />compared to wild fish collected from the Virgin and Moapa Rivers. This study will <br />provide the Virgin River Resource Management and. Recovery Program (VRRMRP) <br />with essential data for integrating genetic management strategies into annual planning for <br />the species.