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Rate of Loss of Genetic Variability The rate of genetic loss per generation by drift can be defined as: 1 2 (EN) For Example: EN = 4 The rate of genetic loss/generation = 12.5 EN = 50 The rate of genetic loss/generation = 1.0~ EN = 100 The rate of genetic loss/generation = 0.5~ EN = 250 The rate of genetic loss/generation = 0.2~ The effective population size is inversely related to the rate of loss of variation by genetic drift. Founding Broodstocks from wild or Free Roaming Populations Considerations for founding broodstocks from free roaming populations are basically the same as those that apply to captive broodstocks. If possible, new broodstocks should be founded on a minimum of 100 paired matings. Wild broodstocks should be founded over a period of 3 consecutive years, which facilitates obtaining the required number of paired matings. Management plans should be developed that allow for crossing all 3 year classes with one another as they mature. If possible, gametes should be collected over the entire course of the spawning season to insure maximum genetic variation. Regardless of how a wild broodstock is managed at the hatchery, unintentional selection will gradually adapt these fish to the hatchery environment. Improved hatchery performance is not an indication of potential for improved performance in the wild. In virtually all situations,- it is likely that adaptation to the hatchery environment will result in decreased potential for performance in the wild. When electrophoretic analysis and other baseline data indicate that the variability of wild broodstocks is being lost due to adaptation to the hatchery environment, infusion of new genetic material from the original wild population should be considered. 1-9