中文摘要：

网围养殖虽有良好的经济社会效益，但生态环境胁迫效应亦较强。以网箱养殖对东太湖生态环境的胁迫效应分析为基础，对1984年～2003年湖区网围养殖的生态环境成本做出测算。结果显示：①近年来网围养殖的生态环境成本占其产值20％强；②20世纪90年代以来湖区生态环境成本快速攀升，90年代中后期更是进入高成本持续阶段；③成本结构中，水资源供给成本、水体自净能力下降和天然渔业资源损失几项最多。最后，笔者提出推行产权制度改革，提倡轮种轮养和生态养殖，强化规划先导，生态环境成本内部化以及实施生态补偿等对策以有效减缓东太湖的生态环境成本。

英文摘要：

Tai Lake is known as a land of fish and rice, but has experienced worsening problems with water in recent years. East Tai Lake, a long and narrow bay in the southeastern part of the lake, plays an important role in water supply, flood discharge and aquatic breeding for the surrounding area. Thus, water security issues in this region have long attracted attention from both researchers and the public. Pen fish- farming in East Tai Lake was started in 1984 and developed rapidly during the 1990s. The pollution caused by unused food and excrement led to severe eutrophication in the lake. The ecosystem services were impaired, including water regulation, water supply, and waste treatment. Environmental cost accounting of the pen fish-farming industry is valuable for assessing the sustainable development of the East Tai Lake region. We describe 6 categories of environmental impacts and calculate the external costs of pen fish-farming in East Tai Lake from 1984 to 2003. The results show that the total external costs of pen fish-farming in East Tai Lake were about 1/5 of the gross production value of aquatics breeding in recent years （47 million RMB in 2003）. External costs increased remarkably in the 1990s （by around 30% per year）, with the highest level of gross costs in the late 1990s. The three categories of water supplement loss, degradation of water self-purification ability and natural fishery losses contributed 85.9 % of total external costs. As a result, pen fish-farming was an economically irrational choice from the perspective of the whole society, with an unequal tradeoff between environmental costs and economic benefits, whereas it was a rational choice from the perspective of farmers. In conclusion, we propose several countermeasures for reducing pollution caused by pen fish-farming, including market-oriented property rights institutions, ecological payment mechanisms for farmers, development of ecological rotation culture techniques, and effective integrated lake region planning.