種苗放流による遺伝子のおきかわりに関する数理モデル A Model of Gene Displacement by Stocking Activities

Recent advances in aquatic hatcheries with a variety of fish and shellfish made a large scale stocking of artificially produced seeds into natural fishing grounds possible. When the genetic properties of the stocking population are different from the wild population, displacement of the gene in the wild population will gradually occur by the gene of the stocking population through reproduction. In this study, we investigate the change of the composition of both genes, in terms of the rate of stocking and fitness of the individuals of each genotype, using a simple mathematical model. When the fitness is equal in each genotype and the rate of stocking is 10%, the term that the gene of the wild becomes half (Genetic Halving Time, GHT) is 8 generations, and the term that the gene of the wild becoms 1% (Genetic Displacement Time, GDT) is 49 generations. When the fitness of the hybrid between wild and stocking individuals is smaller that both parents, GHT and GDT are much smaller.