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the Virgin River, the source of the Dexter broodstock. The majority of the genetic <br />variation was distributed within sampling locations (individuals) (98.74%) rather than <br />between sites (1.26%). This finding indicated that over the 19-year life of the captive <br />propagation program at Dexter, genetic drift has acted on all populations, which resulted <br />in a low level of divergence between captive and wild populations and the upper and <br />lower Virgin River. The effects of drift were mitigated in the broodstock at Dexter by the <br />transfer of wild fish in 2002, 2004 and 2005. The slight divergence is indicative of the <br />need to maintain active gene flow between groups of fish if the intent is to manage the <br />Virgin River and the Dexter population as one stock. In addition, as Hedrick (1999) <br />points out, statistically significant differences do not necessarily indicate meaningful <br />biological differences, especially when the differences are so slight. <br />The Dexter populations were moderately different than the Moapa River <br />population based on an FsT value that ranged from 0.098 to 0.118 (P < 0.001). The level <br />of difference was approximately the same as that between the Virgin River populations <br />and the Moapa River population. This is not surprising since the Dexter broodstock <br />originated from the Virgin River populations and had no input from the Moapa River. <br />Genetic variation <br />Based on published data for 13 freshwater species, DeWoody and Avise (2000) <br />derived a mean heterozygosity value per species of H = 0.54 (0.25 S.D.) and a mean <br />allelic richness value across loci per species of A = 9.1 (6.1 S.D.). In the present study, <br />the estimate of heterozygosity for every population was higher than the mean value per <br />freshwater species, and mean allelic richness across loci for every population fell within <br />17