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Yang Y.,Key Laboratory of Freshwater Fishery Germplasm Resources | Yang Y.,Shanghai Ocean University | Zhang Y.,Key Laboratory of Freshwater Fishery Germplasm Resources | Zhang Y.,Shanghai Ocean University | And 15 more authors.
Journal of Food, Agriculture and Environment | Year: 2014

Rice-crab system as a new eco-culture system has only been trailed in several areas, especially in northeast of China. In order to better understand such eco-culture system, rice-crab culture experiment was conducted to determine the diel fluctuation of water quality, i.e. dissolved oxygen (DO), water temperature (T) and pH under different crab larvae stocking density (1) rice monoculture (RM), (2) rice-crab with 500 crab larvae (RCL), (3) rice-crab with 1500 crab larvae (RCH) at four rice growth stages (tillering, jointing, flowering and filling stage). The result showed that dissolved oxygen and pH exhibited significant difference (p<0.05) at flowering and filling stage between rice-crab culture and rice monoculture, it indicated that the presence of crab decreased DO and pH. Temperature did not change significantly through rice growing seasons. The results also showed that the concentration of nitrogen was high after fertilizing and then descended rapidly, for rice utilizes nitrogen most at tillering stage. At jointing stage, concentrations of NO3-N and NO2-N showed significant difference (p<0.05). At filling stage, concentrations of NO2-N and NH4-N had significant difference (p<0.05) among treatments. PO4-P did not differ significantly (p>0.05) from each other at any rice growth stages. Concentrations of nitrogen and phosphorus in high stocking density were higher than two other treatments. Moreover, there was no significant effect of presence of crab on yield of rice paddy during the year, probably due to the mechanism of "Uninterruptible fertilization" (UPF), yield of rice-crab had a little improvement compare with rice monoculture. In general, low stocking density was considered reasonable in rice-crab culture system.

Li Y.,Shanghai Ocean University | Li Y.,Shanghai Yi Hao Aquaculture CO. | Wang A.,Shanghai Ocean University | Ma X.,Shanghai Ocean University | And 4 more authors.
Journal of Food, Agriculture and Environment | Year: 2013

To evaluate the effects on the zooplankton community in rice-crab culture system, we calculated five response variables for the zooplankton community. Crab larvae were stocked at the density of 0 ind m-2 (CK), 10 ind m-2 (LD) and 30 ind m-2 (HD). LD, HD and CK differed little in their species composition: 26 of 38 species were common, and the same five species were dominant. The average density and average biomass of each zooplankton faunal group and their annual trends displayed similar patterns, except the average density of cladocera fauna between HD and CK in September (HD > CK, P < 0.05), and the average biomass of rotifer fauna between HD and CK in September (CK > HD, P < 0.05). The diversity indices calculated for cladocera group revealed significant difference among LD, HD and CK in August (CK > LD, CK > HD, P < 0.05), and for rotifer group in September (LD > CK, HD > CK, P < 0.05). These results suggested that the zooplankton community in rice-crab culture systems was not significantly affected by the stocking density of Chinese mitten crab, but the biomass of zooplankton in LD and HD was higher than CK. Thus, the crab has positive effects on the water purification in this system. The density of crab has no effect on yields of rice and crab, but has a significant effect on the crab size. Considering the profitability and the growing performance of crab in the following year, the low density (10 ind m-2) is considered reasonable.

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