Laserfiche WebLink
stocking (Allendorf 1993; Kapuscinski et al. 1993). Captive rearing results in a <br />gain in total offspring but there may be a simultaneous reduction in the effective <br />population size (Ryman and Laikre 1991) A reduction in effective population size <br />will be accompanied by loss of genetic heterozygosity. This is true if the <br />absolute size of the wild population is small. Ryman and Laikre (1991) strongly <br />recommend that the risk of losing genetic variability through captive breeding <br />should be carefully considered even if only a single introduction is to be made. <br />Precautions that will be taken during propagation and stocking are summarized in <br />Box 8. <br />Box 8. Precautions to be taken during propagation and stocking <br />listed and candidate fish. (Listed in priority order) <br />1. Precautions must be taken to prevent escapement of fish from <br />refugia or captive propagation facilities. <br />2. Stocking of captive-reared fish will be conducted only in locations <br />where it can be demonstrated that such stocking will not adversely <br />affect indigenous fish populations or stocks of the same or <br />different species. <br />3. Reintroduction (i.e., experimental, augmentation, and <br />restoration stocking) will be restricted to habitat that will <br />support a viable population, to historic habitats and experimental <br />plants in "closed basins". <br />4. All captive-reared fish will be marked before initial release <br />and stocked as equal family lots from pedigreed matings so that <br />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 species is known sufficiently well to predict the likelihood <br />of stocking success. <br />6. Any proposed stocking will be described in a reintroduction <br />plan that is approved by the Recovery Team and Regional Director, <br />and covered by a U.S. Fish and Wildlife Service Permit (section <br />10 (a)(I)(A) Recovery Permit). <br />H. Effective Population Size in Captive Propagation The effective population size <br />(N°) as a key parameter in conservation of genetic diversity. The rate of <br />inbreeding and the loss of genetic heterozygosity is proportional to the inverse <br />of the effective population size (Ryman and Laikre 1991). The effective <br />0 19