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Squawfish Population Viability Analysis --July 1993 Page 26 decade (one generation) the problem of local inbreeding will be alleviated. As previously mentioned, fidelity to the natal area is unproven and it is extremely difficult to believe that that gene flow in such a mobile animal would not eliminate the risk of such local inbreeding in the Upper Colorado River Basin. Nonetheless, ongoing genetic analysis will soon shed light on this issue. 2.12 The Genetics of Hatchery Populations There seem to be no immediate plans to introduce on a continuing basis large numbers of hatchery-reared fish into areas presently populated by the Colorado squawfish. The introductions to date are unlikely to have done much to change the genetic composition of local Colorado squawfish populations. First, the introductions have not been wide or comprehensive enough in either space or time. Second, even if the introduced hatchery stock has different gene frequencies, the associated traits would likely be maladaptive and would be subject to strong selection pressure. Nonetheless, the genetics of hatchery populations must be given serious consideration in the future. 2.13 Discussion and Conclusion to Genetic Analysis Genetic studies and genetic analyses are important to our understanding of the viability and the recovery of the Colorado squawfish. The foregoing analysis laid out the connections that genetics has to demography, to ecology, and to spatial distribution (histo'rical and present) of the Colorado squawfish. At this point, genetics do not seem to be of overriding importance to viability or to recovery. Appendix This appendix outlines how Slatkin's (1985) method of determining gene flow from the frequency of rare alleles ("private alleles") can possibly be used for quantifying gene flow in the Colorado squawfish. Using an island migration model, Slatkin found a correlation between p(1), the proportion of alleles that are present in only one of a number of populations, and the number of migrants per generation, Nm, where N is the population size of each patch and m is the fraction of migrants exchanged.(see Figure AI) The logic behind this is fairly simple; a greater proportion of private alleles indicates less genetic mixing between populations caused by a lower migration rate. The important value of Nm is 1 as this is the 'magic number' of breeding migrants per generation above which the risk of local inbreeding is avoided. Looking at Figure 1, a p(1) value of approximately 0.07 or less would indicate safety from inbreeding.