The use of crab ponds for large-scale crab breeding, due to shallow ponds, large differences in the size of ponds, crabs, density control is difficult, aquaculture production is late and difficult to grow aquatic plants and other reasons, the results are often high incidence of crab, small specifications , Low economic efficiency, regular loss and so on. In order to do a good job of production, after practice summarizing, we now introduce the technology of large-scale crabs for crab breeding ponds as follows: I. Preparation for holding ponds When crabs are harvested for sale, select 1 or 2 corner ponds as holding pools, with an area of ​​approx. For 15% of the crabs, the bottom sludge is removed after the crabs are sold. If the pond is too low, it must be raised to 1.2m or more. Plastic film or calcium plastic plates are placed around the holding tanks to prevent the crabs from escaping when young crabs are caught. The pond water was added to the water level above the crab cultivation, and after 2 days, the small crab hole to be burrowed was excavated, and bleaching powder was used to clean the pond with 25 kg/mu water to kill the small crab species and wild fish in the pond. Pathogens; After 5 days, the pool water was drained, fresh water was replenished, and plants such as Elodea were transplanted, and 300 kg/mu of snails were stocked to prepare for the preservation of the crabs. 2. After the flat crabs of the crab breeding pond are all sold, they will be raised to 1.2m or more in the middle of the pond, and they will be restored in the middle. During the leveling process, the size of the excavated pond crabs within 160 animals per kg was reserved for breeding crabs. If the number of crab species is insufficient, the large-scale species of crabs can be removed by using a grounding cage in the pond circulation ditch before the ponds of the crab species are irrigated with clear water. The crab species need to be soaked with oxygen for 30 minutes at a concentration of 5g/L to 10g/L potassium permanganate solution and then put into a holding pond for breeding. The amount of temporary conservation is calculated based on 400 animals/mu. In order to improve the comprehensive benefits, it is possible to raise 3kg/mu~5kg/mu of green shrimp and 3~5cm body length of carp fry 8/mu~10/mu. Large-sized carp species with individual weight of 0.3kg Mu - 15 tails/mu. Third, the planting of aquatic plants Planting aquatic plants is a key measure for the breeding of crabs and ponds. The species of planted aquatic plants are mainly Elodea and Vallisneria. Elodea grows well within 25°C, but it is not tolerant to high temperatures and must be controlled at a later stage to prevent death. Vallisneria grows slowly in the early stages and is easily eaten by crabs. . The water level for planting plants must be controlled within 30cm. 1. Elodea transplantation Elodea was cut into small pieces of 5cm, and sown in shallow water to avoid floating. The spreading density was 100 pieces/m2 to 200 pieces/m2, and the spreading width was 6m to 8m with an interval of 2m. After transplanting, application of 10kg/mu compound fertilizer promotes the growth of aquatic plants. The roots of the transplanted plants are well developed, and they are not easily floated after being fed by the crabs. The plants spread in the form of strips are dependent on each other and are conducive to shading in the hot season and can control the pond water temperature. In order to prevent Elodea from growing too fast, before the end of June, the water level can be controlled within 70cm to suppress the height of aquatic plants. In mid-July, Elodea grows at a high temperature, and then the water level in the pool is deepened to over 1.0m. Lezao forms a “dense forest†under water, and the surface water body is ventilated and lighted to enable the water in the lower water layer of the pool to circulate, maintain good water quality, control the water temperature, and achieve the effect of ecological crab cultivation. 2. The planting of Vallisneria is to cultivate the time of the growth of Vallisneria. It can be planted after the crab pond is replanted. The method is to use 0.5kg/mu ~ 1.0kg/mu bittergrass species soaked for 2 days to 3 days after mixing soil all over the country, ring ditch planted Elodea, and then irrigation clear pond. After 20 days to 25 days, the toxicity of the drug disappeared, and the pool water was drained and replaced with fresh water to maintain a water depth of about 20 cm to 30 cm. At this time, Vallisneria has begun to sprout, in order to prevent the crabs from feeding after being put into the holding tank, they can trap the plastic film along the circular ditch in the pool to adjust the water level and the water quality in the pool center, in the direction of the water inlet and the direction of the drainage. Bury one into the drain and place an internet bag to change the water. In order to promote the rapid growth of Vallisneria, 75kg/mu compound fertilizer or urea can be applied 2 to 3 times. The early water level is relatively stable at 20cm to 30cm, allowing the growth of A. turfgrass to have sufficient light, and then slowly growing to 10cm. Raise the water level so that the coverage of Vallisneria reaches 70% of the total area of ​​the pool water. When the Vallisneria grows to about 30cm, remove the plastic film from the fence. Other crabs like to eat water plants, such as Rotary Hydrilla, alfalfa grass, goldfish and other algae, which can be used to plant their rhizomes. IV. Production Management in Crab Aquiculture 1. Water Management In the early stage of cultivation, crab seedlings are cultured in temporary holding pools. Due to excessive stocking density, water must be changed every 3 days to 5 days. Each time the water volume is changed to 1 /4 to keep the water cool. One month later, the toxicity of Datang's drugs disappeared, and the aquatic plants grew to the ground. At the both ends of the holding tank, one opening was opened along the direction of the circulation ditch, and the crab was allowed to enter the pond for breeding. In order to avoid the juvenile crabs from affecting growth for a long period of time in the holding tank, a flush can be used at the exit of the holding tank at night to drain the water and stimulate the crabs to enter into the big pond. The depth of crab culture is generally controlled in the shallow water area 1.2m ~ 1.5m, the water depth of the circulation ditch 2.0m ~ 2.5m, change the water every spring in the second half of the spring, change the water every 3 days ~ 5 days in the summer, autumn weekly Change the water once, change the amount of water every time is 1/4, keep the pH of the pool water at 7.5-8.5, and the dissolved oxygen content is 5.0mg/L. 2. The feed is mainly animal feed, supplemented by plant feed. The feeding amount is 5% to 8% of the crab body weight. From March to June and from September to October, the feeding amount of small fish should account for 70% of the total amount of feed; from mid-July to mid-August, due to the high temperature, the food intake of crabs decreased, and the feeding amount of small fish decreased. It can reduce to 50% of the total amount of feed, and increase the amount of plant feed such as wheat, soybeans, corn, and broad beans. Each time the crab shells were adjusted, the amount of feed was adjusted. In rainy days and crab shells, the amount of feed was reduced as appropriate. 3. Disease prevention and control methods are generally used after the first insecticide sterilization method, from May to June, can be used 0.3ppm of zinc sulfate and trichloroisocyanuric acid Quanchiposa 1 times; into the hot season, should try to avoid the use of insecticide, Bactericidal drugs and spilled lime, bacteriophage, vibrio anguillarum, bud bacillus and other microbial preparations can be used to improve the micro-ecological environment of aquaculture water, inhibit the breeding of harmful bacteria, or increase the number of water changes and water exchange, regulate water quality, and prevent diseases. happened. V. Harvesting crab ponds The above method is adopted to raise river crabs. The crab trap rate can reach 80% or more. The product crab crab pool specifications are as follows: male crabs reach 200g/, and female crabs reach 150g/pc. The same economic benefits.
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