We assessed the genetic impact of stocking on natural populations by using individual-based life-cycle models. We constructed models that used include density-dependent mortality at the early life stage, natural mortality, fishing mortality, and the number of released fish. We varied these variables by using random numbers. We focused on the genetic impact of the number of released fish, the number of parent fish producing seedlings that were released, the sex ratio of the parent fish, fishing mortality, and the methods to select the parents of the seedlings. When brood stock size in hatchery is 5 male and 5 female, is the coefficient of inbreeding is about 27 times comparing th more when 50 male and 50 female at the 50 generation, and the coefficient of inbreeding th increases about five times at the 50 generation, when the sex ratio of the parents changes from 50 males and 50 females to 10 males and 90 females. When parents are selected from wild populations at random, extreme fishing mortality may also reduce genetic diversity. (??????????????????????????????????????????????? ???????????????????????????????????????????????? ???????????????????????????? 10 ?90??5 ?5 ??????? 50 ???? ??????????????50?50????????????5????27????????????? ????????????????????????????????????????)