High quality crabs in ponds, in addition to selecting waters, pond sites, rational planning, designing crab ponds, and doing well in anti-escape facilities, must also grasp the following six key technologies.
1. Disinfection in Qingtang
In combination with winter dry pond repair, remove excess sludge, leave silt about 10 cm, and freeze-dry 10- 20 days, use the whole lime pool to splash, use 200-250 kg per acre, remove the wild, eliminate the bacteria and improve the quality.
Second, planting aquatic plants, transplanting Screws
Water grass and snails are excellent bait for river crabs. Especially the water grass is the key to the success of farming. To raise a pond crab, you must first plant a pond. The planting time is generally around the Qingming period, and the water depth is controlled at about 20 cm. The cultivated varieties are mainly Hydrilla verticillata, Carex, Elodea and so on. It is also possible to set some water-sound vocal cords to ensure that the coverage of the water plants reaches about 70%, which can play the role of shading and increase the habitat. Before and after the Qingming period, 200-300 kilograms of fresh snails were placed per acre to allow them to naturally multiply and proliferate. Its young snail shell is thin and tender, and it is a palatable natural bait for young crabs. At the same time, it can also play a role in purifying water quality.
3. Crab stocking
The crab stocking should be “three suitable” and “sustained”, that is, appropriate density, moderate specifications, timely stocking, and stocking after holding. The crab species choose the Chinese mitten crab of the Yangtze River, and the specifications are neat, the appendage is sound, and there is no disease and no injury. Especially the crab species cultivated in the local pond is suitable, and the stocking amount per acre is 500-600. The stocking specifications are preferably 100-200/kg. If the specification is too large, the clam shell is difficult; if the specification is too small, the growth base will not affect the scale of the listing. The stocking time is generally from the end of February to March. If the stocking is too early, the casualties will be greater during the wintering. If the water temperature rises too late, some river crabs will be shelled, which will affect the survival rate of the lower pond. The holding of crab species is a necessary transitional stage before stocking. Before stocking, set up a “suspension zone” in the pool. The length of the holding period depends on the water temperature and the growth in the pool. The holding area accounts for about one-fifth of the stocking area.
Four feed feed
The river crab is an omnivorous animal that eclipses animal feed. On the basis of cultivating basic bait, it is necessary to actively carry out artificial feeding work, and adhere to the scientific feeding methods of “four-set” and “four-view” and the principle of “pre-skilled, middle-green, and succulent”. In the morning and evening, each time, it is advisable to eat the feed in 1-2 hours, and often check the food field and adjust the feeding amount in time. In the early stage of stocking, animal feeds are mainly used, mainly fresh fish, snail meat, etc., and the feed of young crabs is gradually increased. Its formula is partial to animal raw materials, and the ratio is balanced to improve the immunity of juvenile crabs. In the late stage of breeding (the stage of promoting the weight gain of river crabs), plant-based concentrates and animal raw materials are added to ensure that the crabs eat well. In the whole year’s feeding management, it is important to close the two clams and carefully feed the palatability and nutrient feed to ensure the survival rate of crabs and the market rate of large-sized river crabs.
V. Water quality regulation
Water is the root of aquaculture, and water quality regulation is another important part of pond crab culture. The main focus is on four aspects: First, the water level control, the general water depth is maintained at 0.5-0.8 meters, the temperature in the middle of the culture is high, and the water depth is controlled at about 1.2 meters, which is conducive to lowering the water temperature and promoting the growth of crabs; Generally, change water once every 7-10 days. During high temperature, water is injected 10-20 cm every day, change water once every 3-4 days. When changing water, take the method of first row and backward. Third, adjust the pH, 7-10 days to splash the whole pool. One quick lime, 10-15 kg per mu, to ensure the pH of the water is between 7.0-8.5, while increasing the calcium content in the water, precipitating and purifying the water; the fourth is to occasionally spill the “active enzyme”, the amount per acre is 0.4-0.6 kg to control the absorption and absorption of harmful bacteria such as ammonia nitrogen and hydrogen sulfide in water.
Six, crab disease prevention
The prevention and treatment of crab disease is based on the principle of “prevention first, prevention and treatment combination”, and actively adopts drugs with high efficiency, low toxicity and small side effects. The main drugs used are quicklime, carapace net, river crab multi-dimensional, biological preparations, Chinese herbal medicine, etc., enhance the body structure of crabs, disinfect water bodies, control and prevent bacterial diseases and viral diseases, cure early, prevent disease and prevent disease, and reduce diseases to a minimum. degree.