东太湖河蟹网围养殖的环境效应

通过对东太湖网围养蟹区内外的生态环境因子的观测分析和养蟹区N、P等营养物质的平衡估算,结果表明,草型湖泊适合河蟹的养殖;不投饵时,养蟹有助于减轻湖泊内的营养负荷;而投饵的利用和转化率很低,多数饵料沉积于湖底或进入湖水中,从而影响湖泊生态环境。与湖泊小面积高密度养鱼相比较,网围养蟹的万元利润污染只有养鱼的1/14,利润却是养鱼的1.8倍。因此低密度网围养蟹是兼顾东太湖渔业资源开发和环境保护的有效方式。

Impacts of Pen Crab Farming on Evironment in East Taihu Lake

Pen crab farming has become a main part of inland water fishery in China in the past ten years. However, its influences on lake environment is unclear till now. In 1997, a research was carried out to show to what degree and how the pen crab farming of different pattern may impact on the water quality, hydrobiological communities and sediment environment by comparing these factors inside and outside pens in East Taihu Lake. The results showed that the impacts of the crab farming both with bait casting and without on factors of water quality, planktonic community and the water vegetation were not obvious, because of the dilution of huge amount of water. But it was apparent on the sediment quality that was characterized by a sharp increase of total nitrogen, phosphorus and organic carbon inside the pen as much bait not utilized effectively had deposited. The number and biomass of benthonic molluscs decreased rapidly by prey of crabs. It has been also known that the crab farming without bait casting had a net output of nutrient from lake and that the crab farming with bait casting had a big net input of nutrient to lake as the utilization rate of bait was very low. It was obvious that pen crab farming of low density without bait casting was the best pattern in obtaining modest fishery production while keeping a good environment. However, it was still needed to control and plan the farming scientifically as it may result in such influences as the physical clog against current and accumulation of pollution.