Increase of inbreeding by stocking on wild population assessed by using individual-based life history model

個体ベース生活史モデルを用いて，種苗放流が天然個体群に与える遺伝的影響を検討した。モデルでは，自然死亡，漁獲死亡，放流個体数等を考慮し，放流個体数，種苗生産時の親魚数，親魚の性比，漁獲死亡及び親魚の由来による遺伝的影響の差違を比較した。親魚数を雄 10 雌90，雄5 雌5 としたとき，雄 50 世代目における近交係数は，親魚数を雄50雌50としたときに比べそれぞれ5倍および27倍高くなった。親魚に天然個体を用いる場合は，過度の漁獲死亡係数が遺伝的多様性に影響を与えることが示された。
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 more when 50 male and 50 female at the 50th generation, and the coefficient of inbreeding increases about five times at the 50th 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.