In period of 3 years (2008-2010), 4 survey trips were carried out in mangrove ecosystem Dong Rui (Quang Ninh province), Hung Hoa (Nghe .An province), Long Son (Ba Ria - Vung Tau province) and cape Ca Mau national Park (Ca Mau province). The research results showed that the total of 992 aquatic species were determined in four surveyed mangrove forests. Among them, there are 221 species of mangrove trees, 4 species of sea grass, 50 species of sea weed, 293 species of plankton, 161 species of fishes, 112 species of crustacean, 146 species of mollusca, 5 species of echinoderm, 44 familie of fish egg-larva, 17 families of shrimp larva-instar. The total fisheries biomass and Maximum Sustainable Yield (MSY) is estimated 36,173 tons and 18,086 tons respectively in four surveyed mangrove forests (the total of 48,284 hectares). Meanwhile, the total biomass of the economically important.species is estimated 25,039 tons occupying 70 percent of the total fisheries biomass in four surveyed mangrove forests.