Abstract: In order to study environmental effects of crab culture in different ponds in reclamation zones of the Gucheng Lake and screen an optimal ecological pattern of crab culturing, the operation of crab culture and variation of the water environment during the culturing period were monitored and a model was constructed to estimate the carrying capacity of the ponds. Results show that under the current pattern of crab culturing , the waters in the ponds and the water supplying rivers fell in Grade Ⅳ andⅤof the “Standard for Surface Water Environmental Quality” (GB3838-2002), and were obviously lower than that in the Gucheng Lake, which was in Grade III. In the former, total nitrogen (TN) and total phosphorus(TP) were the main polluting factors. In the ponds, the community structures of phytoplankton, zooplankton and benthos were simple, and dominated mainly by Cryptomonas ehrenberg, Diaphanosoma and Bellamya. The Margalef species richness index (D) was significantly and positively related with crab output(P<0.05). Based on the current pattern, the largest crab carrying capacity of the ponds is 9855 ind•hm^-2. Based on comparative analysis of the ponds under the current pattern and under the pattern of comprehensive crab culture in pond environment, economic benefit and carrying capacity, an optimal ecological pattern of crab culture is recommended to be (9000±750) ind•hm^-2 in juvenile crab input rate, 0.47 -0.53 in food coefficient, about 70% in aquatic plant coverage (Vallisneria spiraslis 40%, Elodea nuttallii 20%, H.verticallata 10%); and 6000-7500 kg•667hm-2 in snail input rate.

Key words: reclamation zones of Gucheng Lake, crab, environmental effects, production pattern