How to adjust the water in the crab pond during high temperature? The aquatic plants in the crab pond are very dirty. How to remove them?

At present, the output of crab culture is getting higher and higher, and the pollution caused by high-yield culture will exceed the self-purification ability of crab pond itself, which will seriously affect the improvement of crab output, quality and benefit in the future and restrict the sustainable development of crab culture. Xiang Yang Town, Yixing City is located in the upper reaches of Taihu Lake with developed economy. Pollution caused by industry, agriculture, life and aquaculture seriously affects the water quality of crab culture. The crab culture area in Xiang Yang Town is17000× 667m2, so the water cannot be changed normally. Therefore, we discuss the crab pond from the perspective of sustainable development of crab culture and water saving and emission reduction of aquaculture. Implemented in 2007, 4 farmers participated in the implementation, with a total area of 154×667 square meters, with remarkable results. In 2009, it grew to 1, 7 1 household, with a total area of 235 1×667 square meters. The average yield of 667 square meters is 89.6 kilograms of river crabs and 32.5 kilograms of freshwater shrimps, and there are a certain number of silver carp, bighead carp and mandarin fish. Output value of 667 square meters is 7 1 17 yuan, and profit of 667 square meters is 39 12 yuan. It has achieved good economic and social benefits and has great promotion value. Now its operation technology is introduced as follows. 1 culture technology 1. 1 pond conditions The crab ponds are all old ponds that have been cultivated for many years, with a field board in the middle and deep ditches around, with the water depth of 1.3 ~ 1.8m, the average water depth of 1.4m and the mud depth. There must be a reservoir around the crab pond. The reservoir is rebuilt by farmers according to the crab pond and its surrounding conditions. The shape of the reservoir is not limited. The water depth is 1 ~ 2m, and the total area accounts for 15.3% of the crab pond area on average. The main function of the reservoir is equivalent to a wetland. Through the water exchange between the crab pond and the reservoir, the water quality of the crab pond is purified and the water is stored for later use. The outside river water can be purified by the reservoir and injected into the crab pond, which can effectively avoid the crab pond. The water quality of all implemented pond water sources is poor, the water source of the outer river is eutrophic or seriously aging, and occasionally industrial sewage flows in, so it is very difficult to use water in the crab pond. After the crab pond is dried in the sun in winter, the excess silt is removed, and the silt depth is controlled at 10 ~ 15 cm. After 5 ~ 7 days of exposure and freezing, the sludge should be sprinkled with 150 kg of quicklime every 667 square meters to improve the bottom quality of the crab pond and achieve the purpose of disinfection. At the same time, the pond bank is renovated to ensure that the crab pond does not leak and maintain the aquaculture water level. Remove the silt and sundries in the reservoir, and clean the pond with quicklime 100kg/667 m2 to kill wild fish, pests and pathogens. 1.2 Planting, management and release of aquatic plants. We planted Elodea and yellow grass before we put them in the pond for feeding snails and crabs. At the same time, according to the growth of aquatic plants, suitable Sophora alopecuroides seeds should be replanted in March, and some black algae should be transplanted in May to give full play to the advantages of various aquatic plants, and the area of aquatic plants should be controlled at about 65%. From March to May, some harmful algae and sundries are often attached to the stems and leaves of aquatic plants, which affects the normal growth of aquatic plants. Biological agents such as EM-active bacteria can be used to remove them. From the end of May to the beginning of June, the head of Elodea nuttallii should be cut by stages with a drag knife, accounting for about 20% of the total area of the crab pond, and the cut weeds should be fished out in time. The area of mowing weeds should not be too large at a time, and the interval between mowing should not be too long or too short, and the interval should be controlled at about 5 days, so that the environment and water quality of the crab pond can be relatively stable when mowing grass. Put live snails in stages, about 300kg/667 square meters before March and about 200kg/667 square meters in June. The aquatic plants planted in the reservoir are mainly Sophora alopecuroides and Hydrilla verticillata (the above aquatic plants grow vigorously at high temperature in summer and have strong water purification ability), and some emergent plants are planted in the surrounding shallow waters, and the area of aquatic plants is controlled at about 80%; According to the need of water purification, snails in the reservoir can also be released several times. Generally, in summer, the total amount of snails in the reservoir is controlled at about 1000kg/667 square meters, which makes the reservoir have the function of a natural wetland. 1.3 fry stocking and selecting high-quality fry. Choose local high-quality crab species and shrimp fry to match with silver carp, bighead carp and mandarin fish. The average number of released crabs in the implementation area is 965 /667m2, and the specification is 155/kg; Shrimp 1 1.6kg, specification 1255 fish/kg; Silver carp 7.2, 7/ kg in size; 5 silver carp, size 6/kg; 6.5 mandarin fish, size 200/ kg. About 1k freshwater shrimp and 15 silver carp of the same specification were put into the 667m2 reservoir, which was mainly used to observe the water quality of the reservoir. 1.4 water quality regulation and water circulation operation are just water exchange between crab ponds and reservoirs. When the water quality of the crab pond is poor and water needs to be changed, the upper water of the reservoir can be directly injected into the crab pond, and then the bottom water of the crab pond can be injected into the reservoir. The two water injection ports are located diagonally or opposite to the crab pond. In order to keep the water level of crab pond and reservoir relatively stable, the water exchange of crab pond and reservoir can also be carried out at the same time. For the treatment of water injection, the river water should be injected into the reservoir at a better time (to avoid industrial sewage injection, a small cage can be set near the upstream of the water injection port of the outer river, and some small fish and shrimp can be raised in the cage to judge whether the water source is polluted or not and decide whether to inject water). After the reservoir is filled with water, 2× 10e ~ 6 bleaching powder or 30× 10e ~ 6 quicklime should be used in time. Water quality management of crab ponds: Before May, the crab ponds were mainly irrigated, with an average water depth of 0.4m The pond water needs to have a certain degree of fertility, which is beneficial to the growth of shrimps and crabs. In early March, high-efficiency Feishuibao and partial fermented organic fertilizer were used to cultivate fertilizer water, and in mid-April, "bottom material" 1000g/667m2 was used to improve the bottom material of crab pond, and the transparency of pond water was controlled at about 30cm. From May to September, change the water once every five days or inject water once, and the water level will gradually rise. The high temperature season reaches the highest and the water level is maintained. Biological agents (EM, Bacillus subtilis, photosynthetic bacteria, etc. ) once every 10 ~ 15 days, and once every 20 days, the dosage is 5 ~ 10 kg/666. When the crab pond dries up, use the reservoir to fill part of the pond water as a backup water source. The method of water quality management in the reservoir is the same as that in the crab pond, which is mainly to strengthen the management of aquatic plants and snails, adjust the snail density in the reservoir in time according to the intensity of water circulation, and control the coverage rate of aquatic plants at about 80%. 1.5 scientific use of pipeline aerator adopts pipeline aerator technology, adopts vortex fan to supply air, and the power configuration is about 0.3kW/667 square meters. The blower is directly connected to the main pipe of the 3-inch photovoltaic tube, and the main pipe is fixed above the water surface in the middle of the pond with wooden stakes, and the height should not touch the water surface. The branch pipes are vertically connected with the main pipe and mutually connected, and symmetrically and evenly distributed on both sides of the main pipe. The branch pipes are PV pipes with a spacing of 6m. An aeration hole with a diameter of 1.5mm is drilled every 3m on the branch pipe, and the branch pipe is fixed at the bottom of the crab pond with small piles or cement bricks, which are evenly distributed in the whole crab pond. When the fan is started, the air is compressed by the fan and ejected from the aeration hole of the branch pipe, so that oxygen can fully contact with the pool water to achieve the purpose of increasing oxygen. It will be started from April to June from 24: 00 to 6: 00 tomorrow morning,1early October from 2 1: 00 to July to 10 at 7: 00 tomorrow morning, and the startup time will be extended in case of abnormal weather. 1.6 During the breeding period, the crab pond is fed once every evening, and the pellet feed with crude protein content above 35% is fed from March to May, and some wild fish are fed. In July and August, the pellet feed with crude protein content around 30% is fed, and the pellet feed is mainly fed in September, and the crude protein content gradually increases to above 35%. Reservoirs are generally not fed with feed. 1.7 Prevention of diseases focuses on improvement of pond environment and drug prevention. In early April and late September, spraying 1 time of "Mekening" on all parts of the pond to kill ciliates. Spraying 0.4× 10E~6 ~ 6 chlorine dioxide 1 time in mid-April, and using 0.4× 1 dibromohydantoin in June and July respectively. At the same time, through the adjustment of quicklime and the improvement of biological agents, the management of aquatic plants was strengthened, aerobic machines were used reasonably, and the breeding environment was improved. No diseases occurred during the whole breeding period. 2. As a result of culture, the shrimps are mainly caught in two stages, 1 stage is May-June, and the second stage is September-65438+February. River crabs and fish were caught in front of a dry pond. The implementation area is 235 1 × 667m2, the crab yield is 2 10 650kg, the average yield of 667m2 is 89.6kg, and the average specification is1,5 1g/ crab; It produces 76,408 kilograms of freshwater shrimp, with an average output of 32.5 kilograms of 667 square meters; ; The yield of silver carp and bighead carp is 17.5kg/667m2, and that of Siniperca chuatsi is 3.3kg/667m2. Total output value167.32 million yuan, average output value of 667 square meters 717 yuan, and profit of 667 square meters 39 12 yuan. 3. Analyze and discuss that raising crabs requires excellent water quality, sufficient dissolved oxygen and a good ecological environment. In most areas, the water quality outside the river is poor, so it is impossible to completely improve the water quality of crab ponds by changing the traditional water. So we practice the technology of circulating water in ponds to raise crabs. This reservoir has a strong function of purifying water quality. At the same time, reasonable aquatic plants, snails, silver carp and bighead carp in the crab pond can purify the water quality of the crab pond. In addition, biological agents can also transfer water and aerate the pipeline, so that the ecology of the crab pond can get a virtuous cycle, and the water quality and environment of the crab pond can be kept in a good state, which lays a foundation for the implementation of this project and has certain guiding significance for the sustainable development of crab pond culture and water-saving aquaculture of aquatic products in the future. The ratio of reservoir area to crab pond area should be determined according to factors such as crab pond conditions, stocking density and management level. Crab ponds have good conditions, low stocking density, high management level, and a small proportion of reservoir areas. On the contrary, it is necessary to increase the proportion of reservoir areas. According to the current implementation of this project, this ratio should be in the range of 15% ~ 20%, which not only saves resources but also achieves the goal. of course，