The scientific name of hairy crabs is Eriocheir sinensis, and the catering industry is known as the story of "a crab on a mat covers a hundred flavors". In 2005, an epoch-making event happened in the history of hairy crabs in Sichuan Province, that is, authentic hairy crabs from Sichuan climbed the beach at the end of August and participated in the Shanghai National Hairy Crab Exhibition, winning the gold medal in one fell swoop. Now it has become a hot commodity in Hongkong, Singapore, Taiwan Province and other places, and has become a fashionable and delicious food in the mouth of gourmets. For many years, hairy crabs have been the main course at high-end banquets. Recently, the person in charge of the wholesale market of Chengdu Aquatic Center told the author that the bigger the specifications of hairy crabs, the thicker the crab yellow and the richer the crab meat, and the higher its price. The current market situation is that the price of hairy crabs with specifications of 100 ~ 150g is 60 ~100g; The price of specifications above 250 grams reaches 400 yuan/kg; The price of specifications below 100g is only 30~40 yuan/kg. With the improvement of people's quality of life, hairy crabs began to go out of the high-end banquet territory and enter the homes of ordinary people.
In recent years, hairy crab farming has developed rapidly in various places. Hairy crabs are mainly cultivated in Longquanyi District, chenghua district, Jintang County, Mianyang, Xichang and Qionghai in Sichuan. Among them, Xichang Qionghai is the largest, with more than 600 hectares (nearly 10,000 mu) of aquaculture water. However, due to the unreasonable breeding mode and unscientific management measures of some farmers (farms) and the rising feed price, hairy crabs have small specifications, poor quality, low selling price and low breeding efficiency. Therefore, in order to enhance the competitiveness of hairy crabs in the market, it is necessary to change the previous "hairy crabs" into "crabs", optimize the breeding mode, improve management measures, and do everything possible to improve the listing specifications and quality of hairy crabs, thus improving the sales price and economic benefits. High-quality, efficient and pollution-free breeding techniques of hairy crabs are introduced as follows:
First, create a good environment.
Simulating natural ecological environment is an effective way to improve the quality of pollution-free breeding of hairy crabs. The pond area should not be too small, generally 2~ 10 hectare is appropriate to stabilize the water environment, and the water depth in the deep water area is required to reach 2 meters in high temperature season. The crab pond is made into a ditch or a mound in the middle forms a shoal, and the area of the ditch accounts for 15%~25% of the pond area. The water source is reliable and pollution-free, and the water quality conforms to the Water Quality Standard for Pollution-free Food Freshwater Culture (NY505 1-200 1), so it can be charged and discharged. The periphery of the pond is made of black calcium-plastic board, with the buried depth of 10cm, fixed with bamboo piles every 0.7 ~ 1m, and equipped with network card to prevent the enemy from invading the crab pond. The inner slope of the pond bank is paved with thick plastic film to save water. Crab species were released about 15 days ago. Clean the pond thoroughly, with 65 ~ 70kg of quicklime per mu in dry pond, and quicklime125 ~150kg per mu in clear water. After melting, sprinkle the pond. There are three functions of quicklime: one is to kill wild fish and enemy creatures; The second is to improve the soil quality of the bottom (or silt); The third is to increase the calcium content in the water and improve the water quality of the pond.
After cleaning the pool, replenish fresh water in time and plant aquatic plants. Aquatic plants are not only places for crabs to inhabit, feed, avoid enemies and shed their shells, but also important sources of vitamins, crude fiber and minerals in food, and can purify water quality. Aquatic plants include floating plants (Alternanthera philoxeroides, water spinach, duckweed, etc. ) and submerged plants (Elodea, Sophora alopecuroides, black algae, etc. ), each accounting for 1/3 of the total area, emergent plants (reed, wormwood, etc. Appropriate transplantation, the submerged plant area is shielded by network card to protect the germination of aquatic plants, and the coverage area of aquatic plants reaches the pond area. Be careful not to plant aquatic plants in the middle of the pool to avoid affecting the distribution of wind waves and crabs. When the aquatic plants grow to 3-4 cm, live molluscs such as snails, mussels and mussels are put in, with the dosage of 250-300 kg per mu, so that they can reproduce naturally, which not only purifies the water quality, but also provides palatable high-protein feed for fresh animals for crabs.
Second, optimize the breeding mode.
Because of its low yield per unit area, it is limited to improve breeding efficiency only by improving quality. It can make full use of crab pond resources, increase the yield of interplanting varieties and improve the overall efficiency without affecting the feeding and growth of hairy crabs. Production practice has proved that the following four intercropping modes are the main modes of increasing efficiency in crab ponds at present.
1. Intercropping mode of freshwater shrimp: Intercropping freshwater shrimp in crab pond can not only eat the residual erbium and organic matter at the bottom of the pond, but also reduce the pollution at the bottom of the pond, and freshwater shrimp itself is a high-quality natural erbium material for hairy crabs. Generally, 0.5~ 1 kg of shrimps with eggs are released per mu in May, or 40,000 shrimps with eggs 1~ 1.5 cm are released per mu in early July. Considering the production cost, it is better to release shrimp with eggs. By the end of the year, we can harvest 10~ 15 kg of high-quality commercial shrimp per mu without increasing bait.
2. Interplanting method of ACIPENSER sinensis: Hairy crabs are fed in large quantities during the whole growth period, and their feces are easy to fatten the pond water, and ACIPENSER sinensis is a kind of "fat fish". Intercropping in crab ponds can not only promote the growth of ACIPENSER sinensis, but also purify the water quality. In mid-May, 35-40 paddlefish with the specification of15-20 cm/tail were planted per mu, and 20-25 kg of commercial paddlefish could be produced by the end of the year.
3. Interplanting method of Pelteobagrus fulvidraco: Pelteobagrus fulvidraco is an omnivorous fish, which can eat residual bait and small miscellaneous fish in crab ponds, thus purifying water quality and improving feed efficiency. The first fry of Pelteobagrus fulvidraco are spring-sown fish with the specification of 120~ 160/kg, which can be released in March. Per mu 100~ 150; Second, the summer flowers of that year, with specifications of 3~5 cm, were put in at the end of May and the beginning of June, with about 300 tails per mu. By the end of the year, about 15 kg of commercial fish can be collected.
4. Intercropping Siniperca chuatsi: Siniperca chuatsi is a carnivorous fish, and its requirements for water quality and environment are similar to those of hairy crabs. Siniperca chuatsi in the pond mainly feeds on small miscellaneous fish and shrimp in the pond, which reduces the biological oxygen consumption and improves the feed efficiency, and at the same time transforms the low-value fish in the pond into high-grade fish to achieve the purpose of increasing efficiency. The release time of Siniperca chuatsi fry is in early June, and the specification is about 5 cm. Putting 15~20 fish per mu can produce 8~ 10 kg of commercial mandarin fish by the end of the year.
Third, raise high-quality crab species.
Pollution-free hairy crab varieties cultivated by natural crab seedlings in the Yangtze River system are selected. This crab is gray, shiny, energetic, fast growing and rarely precocious. When stocking, select individuals with neat specifications, strong physique and no disease or injury, with specifications of 100~ 150 heads/kg, and stock 500~600 heads per mu. The density is too small, it is difficult to improve the population yield, the density is too large, and the individual specifications are too small. The stocking time should be from late February to early March, when the weather is sunny and warm and the water temperature is high. Before stocking, the crabs were soaked in 3%~5% salt solution for disinfection for 65438 05 minutes. When stocking, the crab pond is temporarily kept in the middle fence, accounting for 1/5~ 1/3 of the whole pond area, which is not only conducive to centralized feeding management in early spring, but also conducive to the growth and reproduction of large aquatic plants and snails. The temporary support time is generally April-May. After molting for the first time, the crab removed the fence and entered the whole pond for culture.
Fourth, feed enough.
Hairy crabs are omnivorous animals, so it is necessary to ensure adequate animal feed as well as adequate plant feed. In the process of artificial feeding, the feed should be fresh and palatable, and the deteriorated feed should not be fed. Early and late (March-May and 9-65438+1October), small miscellaneous fish, mussel meat, aquatic insects and other animal feeds. Or mainly commercial feed for adult crabs, and in the middle period (June-August). When using crab commercial feed, we should grasp the quality of feed and choose pollution-free high-quality feed. Generally, the crabs are fed twice a day, and the feeding amount accounts for 8%~ 10% of the crab's weight, and the whole day is13 in the morning and 2/3 in the evening. The specific feeding amount depends on the specifications, quantity, water temperature, weather and environmental conditions of crabs. Feed at fixed points, mainly in shallow waters with aquatic plants, to ensure that all crabs can eat well.
Verb (abbreviation of verb) regulates the water quality of pond.
Maintaining good water quality is particularly important for raising crabs. Generally, it is required that the water quality is fresh, the dissolved oxygen is above 5mg/L, the pH value is between 7.5 and 8.5, and the water transparency is above 40cm. Changing water plays an important role in maintaining good water quality and increasing dissolved oxygen, which depends on water temperature, season, water quality and crab growth. Generally, water is changed once in spring and autumn. Change water every time 1/3 or1/4; In summer, the water temperature is high. Change the water every 5-7 days and deepen it by 30-40 cm each time. In addition, the transparency of the pool water is less than 40 cm, so it is necessary to change the water frequently; The crab's food intake is obviously reduced, and it climbs out of the water during the day, indicating that the water quality is deteriorating and should be replaced immediately; If it doesn't rain for a long time, change the water frequently when the water quality is aging. Change the water first, then pour it. In addition, quicklime commonly used in crab ponds has the functions of disinfection, sterilization, adjustment of water quality and pH value, and increase of calcium. But the water level in the crab pond is shallow, and there are aquatic plants and fresh snails. Therefore, the spraying amount of quicklime in crab pond should not be too much at a time, generally 2.5-5 kg per mu, and it is required to be sprayed in water without aquatic plants, and the spraying times are 3-4 times a month.
Sixth, do a good job in daily management.
Four checks: check the water quality, crab feeding, crab growth and whether the escape prevention facilities are in good condition; Four diligence: diligent inspection of ponds, diligent weeding, diligent cleaning of food, diligent keeping of breeding records; Four defenses: against enemy harm, escape, theft and deterioration of water quality.
Seven, strengthen disease prevention and control.
Pollution-free cultivation of hairy crabs should not use more drugs, especially drugs with high toxicity and residue. In the treatment of diseases, it is necessary to prescribe the right medicine and treat it comprehensively, and the hairy crabs with uncertain symptoms should not be treated indiscriminately, so as not to cause phytotoxicity.
1. rotten gills: the abdomen and appendages of the sick crab rot, the anus is red and swollen, the activity is slow, and the food intake is reduced, resulting in death. Prevention and treatment: to prevent injuries during the fishing and transportation of hairy crabs; Sprinkle fresh quicklime to make the concentration of pool water 15 μ l/L, once every 7 days, 2~5 times in a row.
2. Edema: The abdomen, navel and back shell of the sick crab are swollen and transparent, crawling on the edge, stopping eating, and finally dying in the surrounding shallow water. Control method: spray 0.5~ 1 μ l/L oxytetracycline or nitrofurazone in the whole pool; According to 0. 1 ~ 0.2g oxytetracycline or erythromycin per kilogram of crabs, feeding with bait, every 7 days is a course of treatment.
3. Incomplete molting: Cracks appeared at the joint between the shell and abdomen of the sick crab, and it died because it could not molt its old shell. Control method: every cubic meter of water 10g quicklime slurry splashes all over the pond, and chitin and ecdysone are added to the feed.
4. Ciliate disease: The body surface of the sick crab is covered with many brown or yellow-green villi, and it moves slowly, and a large number of people die within a few days. Prevention and control methods: change water or add new water to keep the water fresh; Disinfect with 10μ l/L formalin.
5. Polyconchocerciasis: There is more dirt in the crab, and there are white spot worms in the navel of the crab. The activity and feeding ability of the sick crab gradually weaken, leading to death. Control method: spray with 5~ 10 μ l/L formalin in the whole pond.
6. parasitic diseases of crab slaves: crab slaves live in the abdomen of crabs and absorb the body fluids of crabs for a living. The crab slave is seriously ill. Crab meat stinks and can't be eaten. Control method: If crab slave parasitism is found, the mixed solution of 0.5 μ l/L copper sulfate and 0.2 μ l/L ferrous sulfate can be sprinkled all over the pond.
7. Enemy damage: the first is mouse damage. Water voles are harmful to hairy crabs. Effective rodenticides such as zinc phosphide can be placed around the crab culture environment, and at the same time, rodent cages, mousetraps, electric cats and other rodent control tools can be placed. The second is frog injury. Frogs eat a lot of crab species and young crabs, which is very harmful. Before the hairy crabs are released, the frog eggs and tadpoles in the pond should be thoroughly cleaned to prevent frogs from entering their feeding environment. Once found, it should be killed in time. The third is the water centipede. Also known as water catcher, it is the larva of lice, which is harmful to crab species and first-stage young crabs. The pond must be thoroughly cleaned and filtered before breeding. If water centipedes are found, they can be trapped with lights or killed with special fishing nets.