The optimum temperature of the crab during the growing season is 20～28°C. Grasping all the feeding and management work during this period is the key to raising the output, specifications, quality and economic benefits of crab cultivation. According to the years of experience of farmers, the main The technical measures are described as follows:
1. Pay attention to shell management
Before the first shell, shallow water should be used to enhance the light, increase the water temperature, and start eating early to feed small trash fish or high-quality pellet feeds to ensure that the first time the oyster shell is smooth, and the survival rate and the final growing standard are improved. the goal of. Outside the crab pond spilled medicine, fertilization should avoid the relative concentration period of crab shell, while grasping the law of crab shell, forecasting the next peak of the shell. The crab pool disinfection should be carried out after the water changes in the week before the peak of the clam shell, and add about 1% of locust nutrient and (feed grade) calcium dihydrogen phosphate and fructooligosaccharides, vitamin C, Sanhuang powder, etc. in the feed. The amount of feeding should be reduced during the peak period of clams, and attention should be paid to keeping the environment relatively quiet.
2. Control crab pond moss
The appropriate fertilizer for the early period, to maintain a certain degree of fat crab pond, transparency 30 to 40 cm, weaken the light necessary for the growth of moss, change the Qing Ming before a snail into the Qingming before and after two launches. In the early stages of moss germination, copper sulfate and moss net can be used for drug control, but it is necessary to pay attention to the effects of moss-killing drugs on the growth of aquatic plants, and to add water in time after the drug is used. For small ponds, it is best to remove them manually during the growing season.
3. Planting plants in time
Aquatic grass not only provides natural feed for crabs, but also regulates water temperature, provides shelter, absorbs nitrogen, phosphorus, and heavy metals in water bodies, prevents eutrophication of water bodies, and controls water pollution. Crab ponds need to be diversified, with submerged plants (Elodea, Vallisneria, etc.) as the dominant species, floating plants (water peanuts, water spinach, Qingping, etc.) as supplements, and a small amount of emergent plants (Artemisia, reeds). Wait). The distribution of aquatic plants in the crab pond should be sparse and dense, and the water grass coverage rate should be maintained at 60% to 70% during the growth period of the crabs. If it is too dilute, it should be replanted or transplanted in a timely manner. The excessive density must be manually removed, and the high temperature and flood season should be paid special attention. Crab pond water grass management.
4 timely release snail
The artificial release of snails not only provides a good source of natural animal protein for river crabs, but also purifies the water quality of the bottom water bodies. The first time of snail feeding was earlier. Normally, 150-200 kg of live snails were released per acre before Chingming. This will help snails adapt to the pond environment early and produce young snails for early feeding. From June to August, it will be supplemented once again (150-200 kg/mu). The two inputs can prevent the large amount of one-time input, resulting in lean water in the early stage and large-scale reproduction of the moss and affect the growth of crabs.
5. Reasonably feed bait
According to the reasonable matching of the nutritional requirements of crabs at various stages, the principle is: before and after the refined, the middle green, with prime ingredients, green sperm combination. The ratio of animal and vegetable diets was 60:40 before mid-June, 45: from late June to mid-August, and 65:35 from late-February until mid-October. Meiyu and high temperature seasons should reduce the amount of artificial feeding and can control about 30% of the normal feeding amount to prevent crabs from overeating. Formulated feed should be added to the feed enzyme preparations to increase the exogenous enzyme assisted digestion. The corresponding increase in feeding points, mainly feeding in the evening, so that feed can be eaten in time by the crab, the loss of small loss, high absorption and conversion rate, the relative reduction in pollution, is conducive to water quality management and disease prevention.
6. increase the crab pool dissolved oxygen
Crabs are mainly benthic and live for a long time in the water with the lowest dissolved oxygen at the bottom of the water body. Therefore, it is particularly important to increase the dissolved oxygen in the water in the crab pond. Crab pond should maintain a reasonable depth of water. Conditional installation of micro-aeration facilities at the bottom should be installed; new water should be gradually added during the early period, and the amount of water intake and the number of water changes should be increased from June to September (1 to 4 hours on sunny days, cloudy days). In the middle of the night or in the early hours of the morning, it will form micro-flows in the water for a certain period of time to keep the water fresh; during the periods of plum rain or high temperature, when the pressure is low, the light is insufficient, and the water quality is poor, in addition to the normal influent water, the chemical is injected in time according to the change in water quality. Oxygen booster (granular oxygen, sediment modification, etc., generally used in the evening).
7. Pay attention to regulating water quality
Before the end of May, the transparency of the water should be maintained at 30-40 cm. After May, it should be more than 50 cm in the summer and the water quality should be kept fresh in the middle and later periods. From July to August, change the water every 7 to 10 days, change the water 30 centimeters each time, change the water once every week from September to October, and change the water by 1/3 each time. In addition to conventional water quality management, special attention should be paid to changes in the pH of the water during the rainy season, and prompt lime sprinkling should be adjusted. After 6 months, the content of other minerals required for calcium and crab in the water should be reduced and should be added to the feed.
8. Use biological agents
Microbiological preparations include EM bacteria, photosynthetic bacteria, and so on. From July to September, crab ponds need to be splashed by the whole pond 4 times. They should be used on the premise of starting aerobic facilities at about 10:00 a.m. on sunny days, or within 1 to 2 hours after use. With particulate oxygen (granular oxygen, etc.). In the hot season (July to August), the sprinkling method throws mud into the bottom of the pool, which not only improves the underlying body of water, but also avoids the effects on the aquatic plants. Microbiological preparations cannot be performed at the same time as disinfectants, antibiotics, and the like.
9. Prevent and control diseases
Advocate eco-healthy breeding, adhere to prevention, prevention and control, rational use of various types of drugs, avoid using illegal drugs. From the end of April to the beginning of May, the surface ciliates of the crabs were killed with fibrin nets or shellfish nets, etc., and were used 7 days before the oyster shell, and the water was changed two days later. 5 to 6 months of use of bromochlorohydrin disinfection, 0.3 grams of medication per cubic meter of water. From July to September, EM microbial preparations were taken orally, usually after oral administration of EM, orally, 1% for dry materials and 2% to 3% for fresh materials, each for 3 days. At the same time, we must prevent predators such as water snakes, frogs, cockroaches, rats, birds, crawfish, and jaundice.
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