河蟹过度放养对湖泊底栖动物群落的影响

THE IMPACT OF OVERSTOCKING OF MITTEN CRAB,ERIOCHEIR SINENSIS, ON LACUSTRINE ZOOBENTHIC COMMUNITY

通过对河蟹养殖的代表湖泊黄湖与参照水体即黄湖围栏外、天然捕捞湖泊龙感湖以及鱼类放养湖泊牛山湖的比较研究 ,探讨河蟹过度放养对湖泊底栖动物群落结构和功能的影响。结果表明 ,河蟹影响底栖动物群落的途径有两条 ,一是直接摄食 ,二是破坏沉水植物的间接作用。在蟹苗放养强度约 1kg·hm-2 的条件下 ,底栖动物的种类多样性明显下降 ,密度和生产量减少 6 0 %以上 ,其中对小型螺类的影响尤甚。作者认为目前最适的养殖模式应是河蟹与非草食性鱼类的轮作经营。

To examine the impact of mitten crabs (Eriocheir sinensis) on zoobenthic community, a comparative study was conducted along Changjiang River in 1998-1999 between crab-overstocking-lake, Huanghu Lake, and the reference waters, viz. unstocked vicinity of Huanghu Lake, natural-fishing-lake, Longganhu Lake, and fish-stocking-lake, Niushanhu Lake. The parameters include species composition, body size, standing crop, functional feeding group and production. The results showed that the species diversity of Huanghu was substantially lower than that of the references. Due to the extinction of submerged macrophytes, small scrappers on the plants were greatly decreased in Huanghu, and subsequently, big gastropods, Bellamya, feeding on the bottom, became dominant. Under the stocking density of about 1kg·hm -2 of crab larvae or juveniles, zoobenthic density and production were reduced by more than 60%. Inferentially, zoobenthos are affected by mitten crabs in two ways, i.e. direct feeding on benthos, and indirect effect through damage of submerged macrophytes. Considering that the method of capacity estimation of mitten crabs has not yet been established, the authors are of the opinion that mitten crabs and planktonivorous fishes should be in rotation of stocking for the purpose of sustainable utilization of natural resources.