1 site selection for crab culture technology 1. 1 The water source is sufficient and the water quality is suitable for crab culture technology. As long as the water quality is suitable and the water quantity is sufficient, crab culture can generally be used as the water source. If there is industrial wastewater discharge nearby, we must pay attention to it, and we must analyze the water quality to see if there are any substances harmful to river crabs. The key to water quality is to control the critical point (ccp), and the possible hazards include chemical pollution and biological pollution. The World Trade Organization has put forward the standards of aquaculture wastewater, which can be used as the critical limit of water quality. According to China's "Fishery Water Quality Standard" and "Pollution-free Food Freshwater Aquaculture Water Quality (NY 505 1-200 1)" standards, determine whether the water quality is applicable. At the same time, fully collect local hydrology, meteorology, topography, soil quality and other related information. It is necessary to fully combine the injection and discharge measures of crab production in each season to determine whether the water source is sufficient. Crab culture technology 1.2 The terrain is suitable and the transportation is convenient. Crab culture technology should not unilaterally pursue flatness and openness and occupy fertile land. As far as possible, choose lakes and reservoirs without factories and pollution, and build contiguous pollution-free crab breeding bases. This terrain conforms to the principle of developing pollution-free farming, which can not only make full use of the terrain, but also save investment and get twice the result with half the effort. The soil quality of the construction site should ensure that the bottom of the crab pond built on it does not leak, and the excavated soil should be suitable for building a solid dam, without leakage or collapse. The location of the farm should not be too far away from the traffic line to facilitate the transportation of breeding materials and products. Chinese mitten-handed crab culture technology 2 pond construction Chinese mitten-handed crab culture technology 2. 1 area Chinese mitten-handed crab culture technology pond artificial culture should also choose a larger water surface. Large area, large force, automatic oxygen increase, conducive to convection between the upper and lower water layers, improve the dissolved oxygen status of the lower water body, and help the harmful gases at the bottom escape in time. Generally, a pond of about 65,438+0 hectares is more suitable. 2.2 Deep-water crab culture technology The crab pond needs a certain depth and water storage capacity. The pond has a deep water depth, a large storage capacity, and the water temperature is not easy to change, and the water quality is relatively stable, which is not easy to be affected by drought and is conducive to the growth of crabs. But the water in the pool is too deep for the growth of river crabs and aquatic plants. Practice has proved that the water depth of 0.5- 1.5m is suitable for water conservation all the year round. Drainage and irrigation facilities in crab ponds should be improved, with high irrigation and low drainage, and drainage and irrigation should be separated, so that every crab pond can be irrigated and drained, crabs can't escape, drought and flood can ensure harvest, and stable and high yield can be achieved. 2.3 The terrain should be rectangular in the east-west direction, which is conducive to feeding management and net catching, with long sunshine and large windward area. 2.4 Anti-escaping river crabs climb very fast and have strong escape ability. Usually, a reed, a branch or a small hole in a crab pond can be a channel for crabs to escape. A few crabs often set up a "crab ladder" beside the escape wall to help other crabs escape. Therefore, it is necessary to have solid and reliable escape prevention equipment around the adult crab pond to prevent crabs from escaping. Generally, cement light-proof wall, calcium-plastic board, iron sheet, nylon film, glass and linoleum are used to prevent escape. 3. Preparation for stocking 3. 1 Cleaning and disinfecting the pond In the crab pond, there are often wild fish, water snakes, water voles, aquatic insects and other pests and various pathogens, which not only consume dissolved oxygen in the water, but also attack the river crabs and compete for feed, so it is necessary to clean the pond. At present, the commonly used drugs for cleaning and disinfecting pools mainly include quicklime, bleaching powder and tea residue. Generally, the pond is cleaned 10- 15 days before the crab species are stocked. There are two methods for pond cleaning: dry pond cleaning and water pond cleaning. If the pond is cleaned by dry lime, the dosage per hectare is 975- 1 125 kg, which will splash all over the pond after melting. Quicklime cleaning pond can not only kill harmful organisms in water, but also improve the soil quality at the bottom of the pond and increase the calcium content in water, which plays an important role in the growth and development of river crabs. In addition, before cleaning the pond, weeds should be removed from the pond, and excess silt should be dug up to keep the crab pond clean and hygienic. 3.2 Planting aquatic plants is not only a place for river crabs to inhabit, avoid enemies and shed their shells, but also has the function of purifying water quality and is also a good feed that river crabs like to eat. After the pond is disinfected, the water in the pond is kept at 20-30cm. When the water temperature rises gradually and the pond-clearing medicine disappears, aquatic plants can be planted immediately. 3.2. 1 Aquatic plants mainly include submerged organisms such as Kuroshio, Elodea, and Swallowwort. From the quality of aquatic plants, it is better to choose Kuroshio and Elodea, followed by Sophora alopecuroides; From the growing season, Elodea nuttallii is the best, and spring and autumn are the best growing seasons. You can plant early and grow early, so that crab species can be released as soon as possible, raised early and managed early. 3.2.2 Planting method: Hydrilla verticillata and Elodea nuttallii mainly reproduce asexually, and stem cutting and cutting are adopted. Grass consumption per hectare 150-250kg, row spacing 1- 1.5m: Sophora alopecuroides is a typical submerged plant with small seeds. Before planting, soak it in clear water for 10- 15 hours, rub it out with a washboard, mix the soil and sprinkle it. Sowing or drilling can be used, with 0.5 hectares per kilogram of grass seeds. 3.2.3 The planting time is March. Elodea is cleaned in the pond or in early spring. Before planting aquatic plants, apply 30-45 kilograms of compound fertilizer as base fertilizer per hectare to make them grow rapidly. 3.2.4 Coverage The coverage rate of aquatic plants can reach 30%-35%, which meets the living habits of river crabs. In the pond where submerged plants such as black algae and Sophora alopecuroides are planted, a 2-meter-wide peanut belt should be set around the pond1m. The arrangement of water peanut belt should be carried out after the crab species are stocked. 3.3 The live snail meat is delicious, and the river crab likes to eat, so it is an ideal high-quality natural feed. At the same time, snails mainly feed on plankton in the water, which can effectively reduce the plankton content in the pond and purify the water quality, which is beneficial to the growth of river crabs; Snails are cheap and widely available, which can obviously reduce the cost of breeding and improve the economic benefits of breeding. From June to July, a large number of young snails began to breed. Young snails are not only fresh and tender, but also rich in nutrition and high in utilization rate, and river crabs prefer to eat them. Pay attention to disinfection when placing snails in the pond. Strong chlorine can be used to kill bacteria and protozoa on snails, and snails should be washed when placed. Generally, 2,000-3,000 Jin of snails are put in each hectare of crab pond. 4. Breed stocking 4. 1 The selection and purchase of crab species should be based on the crab species cultivated by natural seedlings in the Yangtze River or artificially cultivated by parents in the Yangtze River system. Crab species should have complete specifications, strong physique, complete appendages, no diseases and injuries, active and agile crawling, and no attachments. Crabs purchased in the same batch should be placed in the same pond or purse seine. 4.2 stocking methods strictly control stocking. If the supporting young crabs are stocked in three levels, they can be put into large ponds around spring; After more than 20 days of stocking and twice molting, the crab seedlings can be moved from the crab seedling cultivation pond to the adult crab pond. Specifically: "one district", "three reforms" and "three adaptations". "1 area" means to set up a temporary breeding area for crab species, enclose the breeding area with nets, and put high-quality crab species into it for intensive breeding until aquatic plants in the pond account for more than 50% of the whole pond surface and snails breed to a certain extent. "Three changes", that is, winter release is changed to spring release, small size is changed to large size, and exotic crab species is changed to self-bred crab species; "Three fitness" means suitable stocking specifications, suitable stocking time and suitable stocking density. The general stocking specification is 80- 120 per kilogram, and the stocking time should be sooner rather than later. More than 80% crab species are required to be self-bred. Production practice has proved that the survival rate, disease resistance and growth specifications of self-bred crab species are obviously better than those of purchased crab species. Before stocking crabs, soak them in 6 mg/L potassium permanganate solution for 10- 15 minutes, and then put them into the temporary culture area. 4.3 Stocking density For ponds with sufficient water, rich feed and good feeding management, the stocking density is generally controlled at around 1 head /m2. 4.4 Generally, the stocking time is from the end of February to March. Crab culture should be carried out when the weather is sunny and warm and the water temperature is high to ensure the survival rate of culture. Feed feeding is the material basis for raising crabs. In the whole growth stage, on the one hand, aquatic plants and other feed organisms cultivated artificially in ponds can be used, on the other hand, most of the feed needs to be artificially fed. 5. 1 Feed sources mainly come from two aspects: one is the cultivation of basic feed such as aquatic plants and snails, and the other is artificial feeding. The coverage rate of aquatic plants is generally around 70%. Before and after Tomb-Sweeping Day, about 4,500 kilograms of snails were fed per hectare, which was increased to 1.500 kilograms per hectare in August. In artificial feeding, the management of artificial feeding is carried out according to the scientific feeding principles of "pre-sperm, middle-aged and young-sperm" and the scientific feeding methods of "four decisions" and "four views". Animal feed and crab pellet feed are mainly used in the early and late stages. In the middle stage, plant feed, aquatic plants and pumpkins are the main products. Insist on not feeding spoiled feed, and salvage residues in time to feed. 5.2 Scientific feeding should first pay attention to feed quality. Full-price feed is required, and fresh feed is not allowed. The compound feed requires comprehensive nutrition, low cost, low feed coefficient, convenient use, good attraction and no pollution to water quality. Secondly, pay attention to the feeding position of feed. Feeding places should be suitable, not too much and not too little. Often disinfect the feeding point. Third, it is necessary to determine the reasonable feeding time and frequency. Throw more at night. Generally speaking, the method of small amount and multiple feeding is worth popularizing. In the season of disease outbreak, the number of feeding can be appropriately reduced. Fourth, it is necessary to determine the reasonable feeding amount. According to different specifications, different breeding seasons, different climates, different environmental conditions and breeding conditions. Be careful not to overeat the river crab, and don't let it affect its growth because of insufficient food. In the outbreak season of the disease, it is necessary to appropriately reduce the feeding amount, which is generally about 80% of the usual. 6. Disease control 6. 1 Water quality adjustment "three adjustments" measures should be taken during the whole breeding period. New adjustment: new water injection, water injection every 5-7 days 1 time, 10- 15 days, water injection every 6-9 cm in high temperature season and water change every 3 15 days. Optimization: that is, adjust the pH value to control the pH value between 7.5 and 8.5. Using quicklime once every 10- 15 days, the dosage is per hectare per m depth 150kg, which not only improves the pH value, but also increases the calcium ion concentration in the water, which is convenient for the river crab to absorb. Regulation: photosynthetic bacteria are used to regulate the water body, the dosage is 75-90 kg per hectare, once every half month, mixed with soil and applied to the bottom or diluted with water and sprinkled all over the pond. Through these three adjustments, it is especially required that the dissolved oxygen should be kept above 5 mg/L, the transparency should be kept above 40cm, and the pH value should be kept above 7.5, so as to truly achieve the purpose of "clean, fresh, fresh and refreshing". While adjusting the water quality, we should also adjust the water level according to the three stages of "shallow before, deep in the middle and stable after". The water depth shall be controlled at 0.5-0.6m in March-May, 1.2- 1.5m, 9-65438+1October 1m in June-August, and the water level shall be appropriately deepened in high temperature season to prevent the growth of river crabs from being affected by excessive water temperature. 6.2 To strengthen the disease prevention and control of river crabs, we must follow the principle of "prevention first, combining prevention with control", adhere to the principle of ecological prevention first, supplemented by drug prevention, and vigorously promote the ecological culture technology of river crabs, so as to achieve the goal of not getting sick or getting sick less, and not using drugs or using drugs less. That is, drugs with high efficiency, low toxicity, no side effects or little side effects are used for auxiliary prevention and treatment. The main drugs used are quicklime, chlorine dioxide, strong chlorine essence, zinc sulfate and Chinese herbal medicines. Dosage standard: quicklime per hectare 1o- 15kg, sprinkled with water; Chlorine dioxide is 3kg per hectare, and water is spilled; Zinc sulfate 0.2g/m3, sprayed with chemical water (all used at water depth 1m). Chinese herbal medicine 1- 1.5 kg is added to each 100 kg feed to make medicine, and the medicine is continuously fed for 5-7 days. Control methods: first, the combination of pest control (pest control first, then pest control); Second, the combination of oral administration and external use; Third, the combination of traditional Chinese and western medicine; Fourth, cross-use different drugs; Fifth, use drugs in advance to prevent it. Planting aquatic plants and transplanting snails are two important technical keys to improve the water and sediment environment. The application of photosynthetic bacteria to control the growth and reproduction of harmful bacteria has obvious effects. 7 Daily management 7. 1 Daily work mainly includes "six inspections and six diligence", that is, checking whether the activities of river crabs are normal and patrolling the pond frequently, and insisting on patrolling the pond once in the morning, noon and evening; Check whether the crab water is short of oxygen, do a good job of cleaning and hygiene regularly, and improve the water quality; Check whether there are enemy creatures in the pool and remove them frequently; Check whether there are soft-shelled crabs in the crab pond, protect them frequently, and put in more palatable animal feed to restore physical strength as soon as possible and enhance the ability to resist enemies; Check whether the river crab is sick, and frequently prevent and treat crab diseases; Check the escape prevention facilities in the crab pond and maintain them regularly. In addition, in daily work, it is necessary to keep the environment in the crab pond quiet and comfortable, not to interfere too much with the feeding and molting process of river crabs, and to eat lightly and clean lightly to improve the survival rate of molting crabs. At the same time, it is necessary to do a good job in the archives of aquaculture ponds. 7.2 Routine detection: regularly detect the biological characteristics of cultured river crabs and the hydration index of aquaculture ponds, and make records. The contents include: collection, treatment and preservation of water samples. General sampling should be able to represent the comprehensiveness of the crab pond waters, preferably in the morning; The sampling times can be determined as required; The sampling depth should be determined according to the water depth, and one layer should be collected at regular intervals and stored at low temperature. The analysis items of fishery water quality should mainly consider the physical and chemical factors that are most closely related to crab culture. Conventional standard analysis method is the main method of water quality analysis at present. 8 River crab fishing 8. 1 fishing time When the proportion of river crabs with mature gonads reaches 80%, it is generally better to fish with 10. 8.2 There are three kinds of fishing methods: cage fishing, running water fishing and bamboo foil fishing. Among them, cage fishing is the most practical fishing method. Running water fishing method: install net basket fishing gear at the water inlet, open the water outlet to let the water flow out, and the river crab will climb into the basket with the water flow. Pay attention to two points: first, you can't catch all the water at once. You should add water when the depth of the pool is 0.2-0.3m, and then drain it, and so on for many times; Another point is that after the water in the pool is released, the river crabs all come out and climb ashore to the escape wall at night. At this point, you can capture them manually.