Recent advances in aquatic hatcheries with a variety of fish and shell
fish made a large scale stocking of artificially produced seeds into n
atural fishing grounds possible. When the genetic properties of the st
ocking population are different from the wild population, displacement
of the gene in the wild population will gradually occur by the gene o
f the stocking population through reproduction. In this study, we inve
stigate the change of the composition of both genes, in terms of the r
ate of stocking and fitness of the individuals of each genotype, using
a simple mathematical model. When the fitness is equal in each genoty
pe 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 te
rm that the gene of the wild becomes 1% (Genetic Displacement Time, GD
T) is 49 generations. When the fitness of the hybrid between wild and
stocking individuals is smaller that both parents, GHT and GDT are muc
h smaller.