基于生态通道模型的北部湾渔业管理策略的评价

An evaluation of the fisheries management strategies in Beibu Gulf: using Ecopath with Ecosim

北部湾位于南海17°00′-21°45′N，105°40′-110°10′E，为中越两国共同管辖的天然半封闭海湾。根据1997-1999年在北部湾进行的渔业资源和生态环境调查数据，利用EwE软件构建了北部湾生态系统的营养通道模型（Ecopath）。在此基础上，以30a为周期，利用Ecosim中的“渔业管理者”模拟了不同管理策略（经济效益最大化、社会效益最大化、生态效益最大化以及综合考虑三者的最佳管理）对北部湾捕捞结构的影响。结果表明：以经济利益最大化为管理策略时会提高所有渔具的捕捞努力量，除了拖网下降43.2%之外;以社会利益最大化为管理策略时模型要求极大地增加小型渔业，尤其是混合渔业的捕捞努力量将上升3.34倍;而以生态稳定性最大化为管理目标时，模型要求所有渔业的捕捞努力量都必须降低甚至停止。以经济和社会利益最大化为管理目标对不同的vulnerability（V＇s）值的反应敏感，高营养级种类减少而低营养级种增加，其中社会利益最大化时系统的营养级最低（2.78）;而生态稳定性和综合管理目标最大化则对不同的敏感度的反应较为一致。综合考虑经济、社会和生态效应的最佳管理策略能满足渔业和保育目标的平衡，有望成为最佳的管理策略。由此可见，多鱼种捕捞策略的模拟是个复杂的任务，目标功能有时互相冲突，而且易受到初始模型条件的影响。

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 muhispecies 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.