Crabs, commonly known as crabs, also known as hairy crabs, velvet crabs, etc. Is a crustacean, Fang Crab. The head and chest are square and generally 6 to 7 cm long, usually green. The chela feet are strong, densely fuzzed, and the legs are flat and long. The wild river crabs are located in mudflats on banks of rivers and lakes, and are produced in all parts of China's north and south coasts. Due to its unique freshwater growth and breeding habits in the sea, it provides natural conditions for artificial breeding. The artificial breeding method is now described as follows:
1 Build a site. It is necessary to select a crab cultivation pond with good water quality, sufficient water supply, convenient irrigation and drainage, and sufficient sunshine. The terrain to be excavated should be neat, and the east-west rectangle should be the best. Pool depth of 1.5 meters, water depth of 0.8 meters. Because crabs have a strong ability to climb. Will also make holes to escape. Therefore, it is necessary to make a wall at 20 to 30 cm below the bottom of the pool, with a height of 150 to 180 cm. Above the brick or cement board as a gargle, to be "factory" shape, a width of 15 cm, to prevent crabs climbing to escape. The wall surface should be smoothed with cement, and the aluminum mesh screen should be used to prevent escape. In the bottom of the pool, we must use soil to make a long, ridge-like hillock. We plant some white water-pepper and water-pepper plants to house the river crab camp. The water and grass cover should reach about 70%. If you can't grow grass, you can fish some water plants on the edge of the pool. Can also play the same role in planting aquatic plants.
2 Yunmiao. According to the characteristics of crabs breeding in the sea and growing to fresh water, artificial breeding must carry seedlings in the distance. At present, although artificial breeding crabs have made major breakthroughs, they are still limited to key research units and cannot meet the needs of a wide range of breeding. China's Yangtze River Port is a natural breeding site for crabs. More than 20 provinces and cities across the country have purchased crab seedlings from there and shipped them back for stocking. However, crabs must be given in order to improve their survival rate. Jiangsu Aquatic Technology Promotion Station, after repeated research and trials, finally succeeded in researching double-layer plastic bags for oxygenation and water transportation. That is, in a double-layer plastic bag, 3 to 5 kg of water is loaded, and the salinity is controlled at about 4%. Then, each bag is loaded with 100 to 150 g of crab seed and then filled with oxygen, and the oxygen volume is 10 to 12 liters. Finally, the inside and outside two layers of plastic bags are fastened and put into cartons. One person can bring 10 bags at a time, that is, 1500 grams, transport 400 kilometers, walk for 8 to 13 days, and the survival rate can still reach 80%. Achieved 95%, it is a cost-effective, easy-to-use method of transporting crabs.
3 Stocking. 40 days before purchasing crab seedlings. To disinfect the rearing tank with quicklime and bleaching powder, generally use 10kg of lime per 0.1mu, 0.5kg of bleaching powder, and throw it into the water in the pool (usually stay 3~6cm deep), and mix it repeatedly to completely eliminate pests and water. . Then let the water drain away and rinse once with clean water. Continue to sterilize with sunlight. 15 to 20 days before the emergence of the seedlings, water can be filled. Usually can be purchased from 5 to 6 months. The newly shipped crabs should not be placed in the pool immediately, but should be placed in a holding tank or holding pond for half an hour. When the internal and external temperatures are close, open the plastic bags and pour the crabs into the pool. Usually 0.1 to 100,000 per 0.1 mu can be stocked, 300 to 600 grams are required. Water quality and feed conditions are good, and the density can be appropriately larger. When the crabs are cast, the pool water should be lighter, about 0.5 meters deep, to increase the water temperature. Reduce death and promote growth. After a week of raising, the water level is increased day by day until the depth reaches 0.8 meters. One year old young crabs can be released for every 0.1 mu and will be released from April to May.
4 feeding. Crabs have more complex food and feeds, mainly animal and vegetable feeds. Animal feedstuffs are mainly small fish, snails, fish flesh, livestock and poultry blood, turtles, fish meal, etc., which are crushed into a paste; soybean feed, corn flour, wheat flour, bran, rice bran, etc. Generally half of the animal and vegetable feed is better, and a small amount of green grass and other green feed is required, and the mixture is mixed and fed. The feed for the early crabs is mainly fed with fish and shrimp. Feeding materials in peacetime should adhere to the principle of “four lookes†(see the season, see the weather, see the color of the water, see the feeding behavior of river crabs), and “four settings†(positioning, quantitative, timing, and qualitative). Time is from 8 to 10 in the morning and from 3 to 5 in the afternoon. Generally, the amount of feed can be eaten within two hours with each feed dropped. The amount of feeding will gradually increase with the growth of crabs. Generally, 0.5 kg will be fed every 10 kg of crabs. The water plants in the pond can both feed and shade and prevent heatstroke. It is indispensable for feeding crabs. Pay attention to them.
5 Management. Crabs like to live in fresh water and aquatic plants, and are particularly sensitive to oxygen deficiency. Therefore, the feeding ponds must always inject new water. Change the water every 10 to 15 days in the early stage and change the water in the 2 to 3 days in the summer and high temperature season. Each change of water volume is 2/3 of the pool water. Smelly pool sludge should be removed in stages. If the pool is too fat, there may be some kinds of water peanuts and other aquatic plants in the pool. In this way, the crabs can be hidden in the water, and they can avoid killing each other. At the same time, aquatic plants can also absorb nutrients in the pool, increase the amount of dissolved oxygen, prevent deterioration of water quality, and promote the growth of crabs. There are also more predators in river crabs, and prevention and control work must be strengthened. Its main predators are rats, water snakes, water birds, frogs and otters. According to reports, a rat kills or kills 10 crabs a day. It is the most vicious enemy. A variety of effective methods must be used to eradicate rats and prevent rats. When water snakes, water birds, frogs, and otters are found to be harmful, they must be rushed and driven in time to ensure normal growth of crabs.
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