The second shelling of crabs in Jinxi Town, Kunshan City, Suzhou City, Jiangsu Province started around April 25. With the rise of air temperature and water temperature, river crabs have entered a stage of rapid growth, and the technical difficulty of breeding management has gradually increased. Now, the main points of management after the second shelling are analyzed as follows:
1. Feeding
After the second crab molting, farmers should adjust the structure and quantity of the bait in time according to the number and growth of the crabs and shrimp in their respective ponds, and regularly add calcium, phosphorus and other minerals and various vitamins to the bait. To enhance the crab physique. Generally speaking, in May, the daily food intake of river crabs should account for 6% to 10% of the pond stock. 34-40%) pellet feed and corn, soybean meal, etc. Feed twice a day, mainly once in the evening, accounting for about 70%.
2. Water Quality Control
(1) Turn on the aerator: At present, the stocking density of crab breeding ponds is high, and the breeding ponds are prone to hypoxia. After May, oxygenation measures should be taken in time according to weather changes and water quality conditions. Start the aerator early or prolong the aeration time, and turn it on at noon on a sunny day to adjust the water quality to promote water convection, increase the dissolved oxygen in the bottom pool water, and volatilize toxic substances; when the weather is hot and humid, the start-up time can be appropriately extended, and the start-up time can be appropriately reduced when the weather is cool. . For ponds without oxygen-enhancing equipment, add fresh water to keep the water quality fresh, and keep certain high-quality algae for photosynthesis to release a large amount of dissolved oxygen.
(2) Sprinkling biological preparations and biological fertilizers: Sprinkling photosynthetic bacteria, EM bacteria, amino acid products, biological fertilizers and other biological products every 10-15 days. Generally, biological fertilizer + amino acid products are applied no less than 1-2 times a month to maintain a certain degree of fertility, so that the water quality is "fat, live, tender and cool". Adjusting the water quality can prevent bacterial diseases and improve the feeding ability and immune function of shrimps and crabs.
(3) Filling with new water: Filling with new water can increase dissolved oxygen and nutrient salts, and dilute the organic matter and toxic substances in the pool water. Generally, water is added once every 7 to 10 days, and 15 to 20 cm of new water is added each time.
3. Weed maintenance
At present, all kinds of aquatic plants in the pond have entered a period of vigorous growth, and they should pay close attention to their growth. For example, if the pond mouth is full of aquatic plants, the upper 30-40 cm should be cut off in time to ensure a certain lighting area and enhance water flow. The rotten aquatic plants should be removed immediately to avoid spoiling the water quality and breeding bacteria. If the water grass in the pond is not growing well, fertilization should be applied in time, and if the water grass is scarce, it should be transplanted and replanted to ensure that the coverage rate of various types of water grass in the pond in the high temperature season is 60%-70%.
4. Disease Prevention
After the second molting of river crabs, before the rainy season, apply insecticides and disinfectants. As the water temperature gradually increases, the food intake of river crabs increases, and there will inevitably be a certain amount of residual bait, feces, etc., which will cause the water body to produce toxic and harmful substances such as nitrite and hydrogen sulfide. Therefore, after insecticide and disinfection, the substrate should be improved, the water body should be detoxified, and the water quality should be adjusted with microbial preparations to improve the pond substrate and water environment and prevent the occurrence of river crab diseases. (Kunshan City Science and Technology Home Wang Weijin)
