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<br /> <br /> <br /> <br />I <br /> <br /> <br />1 <br /> <br />u <br />1 <br />Box 9. Strategies for conserving genetic diversity of endangered fish <br />in the Upper Colorado River Basin. <br />1. The genetic diversity of wild endangered fish stocks should be <br />characterized by genetic markers. <br />2. Captive propagation and stocking should be considered temporary <br />management tools to facilitate development of self-sustaining <br />wild endangered fish stocks. <br />3. Broodstocks should be developed from an appropriate donor source <br />in an artificial genetic refuge that offers maximum control. <br />4. Appropriate breeding strategies should be used to maintain genetic <br />diversity similar to the wild donor stock or population. <br />5. The genetic diversity of captive broodstocks and their progeny <br />will be monitored and compared to the genetic diversity of wild <br />stocks. <br />6. The number of captive-reared fish that are to be stocked should be <br />limited to prevent potential risks to severely depleted wild stocks <br />from genetic swamping. <br />The rate of inbreeding ( F) can be calculated if the Ne is known using <br />the formula: <br />'6' F= 1 <br />2 Ne <br />By applying this formula, the estimated rate of inbreeding for an <br />effective population size of 50 (equal sexes) is 1 %. For an effective <br />population size of 10 (equal sexes), the estimated rate of inbreeding is <br />5%. Therefore, it is advantageous to use as many adult fish as possible <br />in developing broodstocks. <br /> <br />1 <br /> <br /> <br />1 <br />J <br />It has been suggested that a minimum effective population size of 50 is <br />required to prevent inbreeding depression (Soule 1980) and a minimum <br />effective population size of 500 is required to reduce long-term genetic <br />drift (Franklin 1980). The acceptability of the "50" value is empirical <br />from broad experience of animal breeders. Animal breeders have not <br />encountered problems when the rate of inbreeding was 1% or lower per <br />generation. However, some animal breeders will allow inbreeding to <br />increase between 2% and 3%. A maximum of 1% in the inbreeding rate is <br />recommended for wild populations (Simberloff 1988). The acceptability of <br />the "500" value was proposed for genetic drift based on one trait in a <br />fruit fly. Both values of this "50/500" rule have been disputed and no <br />magic numbers or specific rules appear to be valid for propagation of <br />animals (Simberloff 1988). Inbreeding is of particular importance <br />because it has been demonstrated that a consequence of inbreeding <br />depression in brother-sister matings for some species will result in <br />33