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Exact estimates of the effective population size are complicated. For example, the formula given above for the effect of sex ratios assumes random mating, constant population size through time, and variance in fertility that approaches to Poisson distribution. Effective population size can be maximized by non-random matings of paired individuals and equalizing the sizes of family lots (Allendorf 1993). The effective population size should be maximized in every hatchery generation to reduce the risk of loss of within-population genetic variation (Kapuscinski et al. 1993). Strategies for conserving genetic diversity in captive-reared fish are summarized in Box 9. Box 9. Strategies for conserving genetic diversity of endangered and candidate fish. 1. The genetic diversity of wild fish stocks should be characterized by genetic markers. 2. Captive propagation and stocking should be considered temporary management tools to facilitate development of self-sustaining wild fish stocks. 3. Broodstocks should be developed from an appropriate donor source in an artificial genetic refuge that offers maximum control. 4. Appropriate breeding strategies should be used to maintain genetic diversity similar to the wild donor stock or population. 5. The genetic diversity of captive broodstocks and their progeny will be monitored and compared to the genetic diversity of wild stocks. 6. The number of captive-reared fish that are to be stocked should be limited to prevent potential risks to severely depleted wild stocks from genetic swamping. The rate of inbreeding ( Q F) can be calculated if the N is known using the formula: 1 j?F= 2N By applying this formula, the estimated rate of inbreeding for an effective population size of 50 (equal sexes) is 1 %. For an effective population size of 10 (equal sexes), the estimated rate of inbreeding is 5%. Therefore, it is advantageous to use as many adult fish as possible in developing broodstocks. 21