Abstract:The Beibu Gulf, located in 17°00′~21°45′N, 105°40′~110°10′E and surrounded by China and Vietnam, is a natural semi-closed sea in South China Sea. Historically, the Beibu Gulf supported various commercial, recreational, and artisanal fisheries. Many fisheries are now depleted or had experienced substantial declining. In this paper we developed a mass balance model using Ecopath with Ecosim for the Gulf of Beibu ecosystem in the Northern South China Sea. Input data were mainly from the information collected in trawl surveys during October 1998 to September 1999. Using the Ecosim model, we evaluated how the ecosystem may respond to change in fisheries over next 30 years. We considered four fishery management scenarios, which maximized three independent objective functions (fishery profits, employment, and ecosystem) and the combination of the above three objectives (Big compromise) were simulated with different vulnerability settings. The results suggest that policy simulation aimed to maximize the economic will increasing all fishing effort of all fishing sector except demersal trawl should be reduced 43.2%, and social strategy were suggested increasing small-scale fishing effort to satisfy social benefits, especially for miscellaneous will increase 3.48 times on current level, maximize ecological suggested all fishing sector should be reduced drastically or stop. Furthermore, policy simulations aimed to maximize the economic and social goal tend to be sensitive to vulnerability settings, whereas maximize ecologic stability and the compromise scenarios were generally consistent. The maximization of social and economical goals results in the complexity of ecosystem being decreased, high trophic levels species being depleted, and low trophic level species being increased. The maximization of the social strategy has the lowest trophic level 2.78 of all the strategies considered in this study. A trade-offs analysis indicates that Big compromise′ strategy would be optimal one which to balances fishery and resource conservation. These results indicate that developing multispecies harvesting strategies is a complex task and management goals focusing on different areas are likely to conflict each other., and the initial model conditions can influence the results also.