A numerical simulation on the dispersion of swimming crab (Portunus trituberculatus MEIRS) megaropae is carried out in Hiuchi-Nada, the central part of the Seto Inland Sea. The calculated dispersal pattem of megaropae in the 3-dimensional numerical model well reproduces the observed one. The vertical migration of swimming crab megaropae plays an important role in their retum process from offshore to the nearshore region.
