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<br />Box 8. Precautions to be taken during propagation and when stocking- <br />endangered fish into the Upper Colorado River Basin. These <br />precautions are in priority order. <br />1. Precautions must be taken to prevent escapement of endangered fish <br />from refugia or captive propagation facilities. <br />2. Stocking of captive-reared endangered fish will be conducted only <br />in locations of the upper basin where it can be demonstrated that <br />such stocking will not adversely and significantly affect any <br />indigenous fish populations or stocks of the same or different <br />species. <br />3. Supplemental stocking (i.e., experimental, augmentation, and <br />restoration stocking) will be restricted to locations with suitable <br />habitat that will support a viable population or stock, or to <br />historic habitats. <br />4. All captive-reared endangered fish will be marked before initial <br />release and stocked as equal family lots from pedigreed matings <br />so that an adequate evaluation of stocking can be made. <br />5. Large-scale augmentation or restoration stocking will be done only <br />when knowledge of life history and ecological requirements of the <br />target endangered species is known sufficiently well to predict the <br />likelihood of stocking success. <br />6. Any proposed stocking of endangered Colorado River fishes will be <br />described in a stocking plan that is approved by the Program and <br />is covered by a Federal Fish and Wildlife Permit or a supplemental <br />permit. <br />The effective population size can be calculated using the following <br />formula (Lande and Barrowclough 1987): <br />_ 4N (males) X 4N (females) <br />N e N (males) + N (females) <br />Exact estimates of the effective population size are complicated. For <br />example, the formula given above for the effect of sex ratios assumes <br />random mating, constant population size through time, and variance in <br />fertility that approaches the Poisson distribution. By non-random <br />matings of paired individuals and equalizing the sizes of family lots, <br />the effective population size can be maximized (Allendorf 1993). <br />The effective population size should be maximized in every hatchery <br />generation to reduce the risk of loss of within population genetic <br />variation (Kapuscinski et al. 1993). Strategies for conserving genetic <br />diversity in captive-reared endangered fish are summarized in Box 9. <br />32 <br /> <br />1 <br />1 <br /> <br />1 <br /> <br />1 <br /> <br /> <br /> <br /> <br /> <br /> <br />1 <br /> <br /> <br />1 <br />