Introduction In order to rationally use resources to protect the Yangcheng Lake water environment and restore the ecological balance of the lake, in 2002, we developed grass and crabs on the 140,000-million Yangcheng Lake Lianhuayu crab base in Yangchenghu Town Crab King Aquatic Products Co., Ltd., Xiangcheng District. , Spiral standardized ecological farming, control of the development of rich lakes in the Lake District, the breeding situation is introduced as follows. 1. Basic conditions and main technologies The area of ​​the net culture area is 0 to 90,000 mu, each of which covers 90 mu. 0 to 50,000 mu is a resource conservation area. According to the principles of lake ecology, the ecological aquaculture operating rules shall be formulated, and ecological aquaculture shall be implemented in the net enclosure area to maintain and repair natural resources. 1.1 Control the crab density to reduce the amount of feed and control the eutrophication of water quality. It is stipulated that 4500 to 5250 crabs per hm2 should be placed in the net enclosure area, which is about 42% lower than the original density. 1.2 Rehabilitation of ecologically suitable plants is an ideal place for growth and palatable natural food for crabs. Water plants can also purify water and eliminate excess nutrients in the water. Therefore, in addition to controlling the density of crabs in the area surrounding the crabs, it is also recommended to transplant the chard , Elodea and other aquatic plants to restore the ecology, so that the coverage of water plants in the lake reaches 2/3 or so. 1.3 Putting the snail net around the breeding area requires that before and after the Ching Ming, live 3,000 to 3,750 kg of live snails per hm2 to adsorb and precipitate suspended particles in water to purify the water. 1.4 Rotation culture To maintain the shape of the Yangcheng Lake grass-type lakes, a "product"-shaped rotation culture is also adopted in the area surrounding the fences, that is, each shed area is protected by 1/2 area of ​​the fence each year, and the 1/2 water surface of the river crabs is interlocked. Accelerate the restoration and regeneration of fishery resources and enhance the self-purification of the lake's water bodies. 1.5 Feed Structures Protect planted plants and put snails on the ground to provide peculiar natural baits for river crabs. From June to August in the peak season, supplemented with animal feed snails, oyster meat, and small trash fish, as well as vegetable feed corn , barley, squash, potatoes, etc., to ensure crab food needs and nutritional needs. 1.2.6 Disease Prevention and Control The aquaculture area adopts biological prevention as the main focus, and the biologically active agent—the water quality improver. During the peak period of cultivation, a course of treatment with allicin, iodine preparations, etc., was administered monthly to prevent bacterial diseases and trembling diseases of crabs. 2 Results 2.1 Water Quality On May 9 and July 31, 2002, two representative sites were selected in the central location of the net-preserved crab area, and the water quality was monitored according to the pollution-free index. 2.2 Harvesting 2.2.1 The total output of the production area of ​​the netting area is 2.43 million kg of Yangcheng Lake sluice, with an average yield of 27 kg per mu, and a total yield of 6.75 million kg of green shrimp, with an average yield of 7.5 kg per mu. 2.2.2 The average price of crabs is 82 yuan/kg, the average price of green prawn is 30 yuan/kg, and the total output value is 219.51 million yuan. 2.2.3 The total cost of materialization for materialization is RMB 597.78 million, the benefit is RMB 159.732 million, and the average yield per mu is RMB 17,748. 3 Analysis and Conclusions 3.1 Effect of Ecological Aquaculture on Water Quality This aquaculture technology makes full use of the mutually beneficial complementary relationship between crabs, snails and grass from the perspective of the balance between energy and material flow of lakes to achieve the purpose of protecting the water quality of Yangcheng Lake and enhancing its self-purification capacity. . The data in Tables 1 and 2 indicates that the water quality in both the early aquaculture period in early and early July at the end of July was basically the same. The ecologically cultivated crabs in the net enclosure did not cause aquaculture pollution. Therefore, we believe that the ecological implementation is ecological. The aquaculture model conforms to the status of Yangcheng Lake's resources and plays a role in restoring the ecology and controlling the eutrophication of the lake. 3.2 Changes in the total amount of N and P in the aquaculture process According to the results of water quality analysis, the P content in water increases slightly as the water temperature rises and crab activity increases, but the change in N content decreases accordingly. The threshold is adjusted from 0 to 8 mg/l. N and P are respectively one of the three elements of plant growth. N, P inorganic nutrients decomposed by the excrement of crabs, animal carcasses, and rotten leaves are absorbed by aquatic plants for a long time, which promotes the reproduction and growth of aquatic plants in the lake area and expands. Improving the coverage of aquatic weeds in water bodies provides a good shelling, habitat and growth environment for crabs, providing palatable natural foods, maintaining the coordinated growth of crabs and aquatic plants, and achieving the reproduction, recycling, and reuse of resources. Therefore, the content of N and P in water is stabilized and the development of eutrophication in the lake is controlled. 3.3 Standardization of ecologically-controlled crab rearing in the net enclosure, which stipulates the technical operation of Yangcheng Lake to raise crabs, better controls the breeding density and production inputs, and achieves the goal of zero pollution. It promoted the restoration and recycling of Yangcheng Lake resources and enhanced the self-purification capability of the Lake District. 3.4 Crop rotation is beneficial to conservation of grass and grass to restore the ecological Yangcheng Lake is a water-grass-type lake. Due to the large number of crabs and grazing resources that have been kept around the net for many years, a farming culture technique is adopted for this purpose, ie, 1/2 per year per net. The area turns grass, grass, and crabs, so that resources are fully maintained and restored, and ecological balance is promoted. Improved water environment.
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