Hairy crab scientific name of the Chinese mitten crab, the catering industry has "a crab on the seat of the hundred flavors cover" of the good news. 2005, Sichuan Province, a hairy crab in the history of epoch-making significance of the big event, that is, the authentic Sichuan production of hairy crabs, the end of August! "Climb" into the Shanghai Tang, to participate in the National Hairy Crab Exhibition held in Shanghai, won the gold medal in one fell swoop, and now it has become Hong Kong, Singapore, Taiwan and other places of the sought-after goods, has become a fashionable delicacy in the mouth of the delicious. Over the years, hairy crabs have been the main dishes at high-grade banquets. Recently, Chengdu Aquatic Products Center Wholesale Market told the author that the larger the hairy crab specifications, the thicker the crab meat, the more abundant, the higher its price. The current market situation is, specification 100 ~ 150 grams of hairy crabs, selling price of 60 ~ 100 yuan / kg; specification 250 grams or more selling price of 400 yuan / kg; and specification 100 grams of the following, selling price of only 30 ~ 40 yuan / kg. With the improvement of people's quality of life, hairy crabs have begun to get out of the high-grade banquets territory, into the homes of ordinary people.
In recent years, hairy crab farming around the rapid development. Sichuan hairy crab farming in Chengdu Longquanyi District, Chenghua District, Jintang County, as well as Mianyang, Xichang Qionghai and other places. Among them, Xichang Qionghai has the largest scale, with more than 600 hectares (nearly 10,000 mu) of aquaculture surface. However, due to some farmers (farms) breeding mode is unreasonable, management measures are not scientific, coupled with feed and other price increases aggravate the cost, resulting in hairy crab specifications small, poor quality, selling price is low, breeding efficiency is not high. Therefore, in order to enhance the competitiveness of hairy crabs in the market, it is necessary to change the previous "hairy crabs" to "raising big crabs", optimize the breeding mode, improve the management measures, and do everything possible to improve the listing specifications and quality of hairy crabs, so as to improve the selling price and economic benefits. Hairy crab quality and efficient pollution-free farming techniques are introduced as follows:
A, create an excellent environment
Simulation of the natural ecological environment is an effective way to improve the quality of the pollution-free culture of hairy crabs. Pond area should not be too small, generally 2 to 10 hectares appropriate for the stability of the water environment, the depth of water required in the hot season deep water can reach 2 meters. Crab ponds made into a ditch or the center of a mound, forming a shallow, ditch area of 15% to 25% of the area of the pool. The water source is reliable and pollution-free, and the water quality is in line with the standard of Water Quality for Freshwater Aquaculture of Pollution-Free Food (NY5051-2001), which can be irrigated and drained. The periphery of the pool is made of black calcium-plastic boards as anti-escape boards, 10 cm into the soil, fixed with bamboo stakes at intervals of 0.7~1 meter, plus net cards to prevent enemy invasion of the pool, and the inner slope of the ridges is lined with thick plastic film to retain water. About 15 days before crab stocking. Thoroughly clear the pool, dry pool per mu with quicklime 65 ~ 70 kg, with water to clear the pool with 125 ~ 150 kg, after dissolving the whole pool splashing. Lime has three functions: one is to kill wild fish and hostile organisms; two is to improve the bottom of the pond (or silt) soil quality; three is to increase the content of calcium in the water to improve the quality of pond water.
After clearing the pond, add new water and plant water plants in time. Water plants are both crab habitat, foraging, enemy avoidance and moulting place, but also an important source of food vitamins, crude fiber and minerals, but also purify the water quality. The types of water plants include floating plants (water peanuts, water spinach, duckweed, etc.) and submerged plants (Edongrass, bitter grass, black algae, etc.) each accounted for 1/3 of the total area, and the appropriate transplantation of water-supporting plants (reeds, Artemisia, etc.), submerged plant area with net card separation netting, protection of water plants sprouting, water plants cover an area of the pond area of 60% ~ 70%. Note that the middle of the pond is not planted with water plants, so as not to affect the wind and waves and crab distribution. To be water plants grow to 3 ~ 4 cm, put snails, clams and small mussels and other live shellfish mollusks, 250 ~ 300 kg per acre, so that their natural reproduction, both to purify the water quality, but also for the crab to provide mouth-filling live animal high-protein feed.
Two, optimize the breeding mode
Hairy crab farming due to its low yield, only by improving the quality to improve the breeding efficiency is limited, we can make full use of the crab pool resources, increase the growth of crab feeding does not affect the production of aquaculture varieties to improve the overall efficiency. Production practice has proved that the following four types of aquaculture mode for the current crab pool efficiency of the main mode.
1. set of shrimp mode: crab pool set of shrimp can feed on the bottom of the pool residual erbium and organic matter, reduce the bottom of the pool pollution, shrimp itself is also a high-quality natural erbium crab. Generally in May, each mu put 0.5 ~ 1 kg of shrimp eggs, or in early July each mu put 1 ~ 1.5 cm shrimp seedlings 40,000 tails, taking into account the cost of production, in order to put eggs shrimp effect is better. In the case of no increase in baiting, by the end of the year each mu can be harvested high-quality commercial shrimp 10 ~ 15 kg.
2. set of spoonbill sturgeon mode: crab feeding throughout the growth period are more, its feces are easy to make the pond water quality fertilizer, and spoonbill sturgeon is "fertilizer fish", crab pond set of not only promote sturgeon growth, but also play a role in purifying the water quality. mid-May each mu put specifications of 15-20 cm / tail spoonbill sturgeon seedlings 35~40 tails, the end of the year can produce 20~25 kilograms of commercial sturgeon.
3. Set up yellow catfish mode: yellow catfish is omnivorous fish, can ingest crab pool residual bait, small fish, etc., play a role in purifying the water quality, improve the efficiency of the bait. Pelteobagrus fulvidraco fry a spring piece of fish species, specifications 120~160 tail/kg, can be put in March. Put 100~150 tails per mu; the second is the summer flower of the year, specifications 3~5 cm, put in the end of May and early June, put about 300 tails per mu. To the end of the year can generally collect about 15 kg of commercial fish.
4. Cultivation of Mandarin fish mode: Mandarin fish is a carnivorous fish, the water quality and environmental requirements are similar to those of hairy crabs, the pool of Mandarin fish in the pool mainly feed on small fish and shrimp in the pool to reduce biological oxygen consumption and improve the feed efficiency, and at the same time will be converted to high-grade fish in the pool of low-value fish, to achieve the purpose of increasing efficiency. Siniperca chuatsi fry are released in early June, and their size is about 5 centimeters. Each mu put 15~20 tail, the end of the year can produce 8~10 kg of commercial Mandarin fish.
Three, stocking high-quality crab species
The use of the Yangtze River system of natural crab fry cultivated pollution-free hairy crab species. This kind of crab has greenish gray body color, glossy, strong vitality, fast growth, and seldom appear precocious. When stocking, choose the neat specification, healthy body, no disease or injury of the individual, specification 100~150/kg, 500~600 per mu stocking, density is too small, group production is difficult to improve, density is too large, individual specification is small. Stocking time in late February ~ early March is appropriate, choose the weather is warm and sunny, the water temperature is high. Before stocking, the crab species are sterilized by soaking in 3%~5% salt water for 15 minutes. When stocking first in the middle of the crab pool fence a piece of 1/5 ~ 1/3 of the area of the whole pool for temporary feeding, not only is conducive to the early spring of the centralized feeding management, but also conducive to the growth of large areas of aquatic grass and snail reproduction. Tentative time is generally to April ~ May, the crab molted the first shell after the removal of the fence, into the whole pool culture.
Four, feeding adequate feed
Hairy crabs are omnivores, not only to ensure adequate animal feed, but also supplemented with plant feed, in the process of artificial feeding, the feed should be fresh and palatable, can not be fed spoiled feed, before and after (March ~ May and September ~ October) to the animal feed small miscellaneous fish, mussels, aquatic insects, etc., or adult crabs, mainly commercial feed, medium-term (June ~ August) to plant-based feeds. In the middle period (June~August), the plant-based feeds such as bran, cereals, vegetables and water plants are mainly used. When using crab commercial feed, it is necessary to grasp the quality of feed and choose pollution-free and high-quality feed. Generally feeding twice a day, feeding amount of 8%~10% of the crab body weight, early morning feeding 1/3 of the whole day bait, evening feeding 2/3, the specific amount of feeding depending on the specifications of the crab, the number of water temperature, weather, environmental conditions and other flexible control. Fixed-point feeding, mainly placed in the shallow water with water plants, to ensure that all the crabs can eat and eat well.
Fifth, the regulation of pond water quality
Maintaining good water quality is especially important for crab farming. The general requirements of water quality is fresh, dissolved oxygen in more than 5 mg / liter, pH value in 7.5 ~ 8.5, water transparency of more than 40 cm. Water change to maintain good water quality, increase dissolved oxygen has a greater role, depending on the pool water temperature, season, water quality conditions and crab growth. Generally, change water once every half month in spring and fall. Each time the water change 1/3 or 1/4; summer water temperature is higher, every 5~7 days to change the water, each time to deepen 30~40 cm. In addition, the pool water transparency is less than 40 cm, the need for diligent water change; crab feeding significantly reduced, away from the water during the day crawling, indicating deterioration of water quality, should immediately change the water; in a long drought without rain, water quality aging, to diligent water change. Change water first row after irrigation. In addition, the crab pool commonly used quicklime with disinfection, sterilization, water quality and pH adjustment and increase the role of calcium, but the crab pool water level is shallow, and planted water plants and put fresh snails, so the crab pool splash quicklime can not be too much of a one-time dosage, generally 2.5 ~ 5 kg per acre can be required to splash in the surface of the water without water plants, splash the number of times per month, 3 ~ 4 times.
Sixth, good daily management
Four check: check the water quality, check the crab eating situation, check the crab growth, check the escape facilities are intact; four diligent: diligent pond inspection, diligent weed removal, diligent clean food, diligent breeding records; four prevention: anti-enemy, anti-escape, anti-stealing, anti-water quality deterioration.
Seven, strengthen the disease prevention and control
Hairy crab pollution-free culture should not be more drugs, especially high toxicity, high residue drugs should be banned. In the treatment of disease should be symptomatic, comprehensive treatment, can not determine the disease of hairy crabs can not be indiscriminate drug, so as not to cause drug damage.
1. Gill rot disease: the sick crab abdomen and appendages rot, anus red and swollen, slow activity, feeding decreased, resulting in death. Prevention and treatment: prevent trauma during crab fishing and transportation; splash fresh quicklime to make the concentration of pool water become 15 microliters/liter every 7 days for 2~5 times.
2. Edema disease: the sick crab abdomen, umbilicus and dorsal shell below the swollen and transparent, creeping edge, stop feeding, and finally die in the surrounding shallow water. Prevention and treatment methods, with 0.5 ~ 1 microliter / liter of oxytetracycline or furacilin sprinkled all over the pool; 0.1 ~ 0.2 grams of oxytetracycline or erythromycin per kilogram of crabs, mixed with bait feeding, every 7 days for a course of treatment.
3. Molting disease: cracks appear at the junction of the back edge of dorsal armor and abdomen of the diseased crabs, and the crabs die because they can't molt their old shells. Prevention and control methods: each cubic meter of water with about 10 grams of quicklime slurry sprinkled throughout the pool, add chitin and ecdysone in the feed.
4. Ciliopathy: the diseased crab's body surface is covered with many brown or yellow-green hairs, slow action, and a large number of deaths within a few days. Prevention and treatment methods: change or refill new water, keep water quality fresh; disinfect by splashing with 10 microliters/liters of formalin.
5. Polycysticercosis: the crab body has more dirt, there are white dotted worms in the umbilicus, and the activity and feeding ability of the diseased crabs is gradually weakened, resulting in death. Prevention and treatment methods: 5~10 microliters/liter formalin splashing the whole pool.
6. Crab slave parasitism: Crab slaves parasitize the abdomen of crabs and live by absorbing the body fluids of crabs. Crab slave parasitism is a serious disease of the crab meat odor, inedible. Prevention and control methods: found crab slave parasites, available 0.5 microliters / liter of copper sulfate and 0.2 microliters / liter of ferrous sulfate mixture sprinkled all over the pool.
7. Enemies: one is the rat. Water rats are harmful to hairy crabs, can be placed around the crab environment such as zinc phosphide and other effective rodenticide, at the same time, placed in the rat cage, rat clips, electric cats and other rodent extermination tools. Secondly, frogs are harmful. Frogs devour crab species and young crabs in large quantities, which is extremely harmful. Before stocking hairy crabs, frog eggs and tadpoles should be thoroughly cleaned up in the pool and frogs should be strictly prevented from entering into the feeding environment, and once found, they should be killed in time. Third, water centipede. Also known as water clip, is the larvae of the dragon louse, the crab species and the first phase of the juvenile crabs are more harmful, in the breeding before the pool must be thoroughly cleaned, filtered into the water. If you find the water centipede, you can use light trapping, but also special small fishing nets to catch and kill.