Three species of mud crabs Scylla olivacea, S. paramamosain and S. serrata of the genus Scylla were recorded in the Pak Phanang mangrove swamps, Thailand. The details reproductive traits, size at sexual maturity and age class were investigated to manage the fishery. For male, gonad development was classified into three stages: 1) Immature (Spermatogonia), 2) Maturing (Spermatocytes) and 3) Mature (Spermatids & Spermatozoa). In female, five distinct ovarian development stages were showed such as proliferation (immature), previtellogenesis (developing), primary vitellogenesis (early...