It is recommended to prevent river crab disease in winter by clearing silt, sun, eating, drainage and disinfection.

In recent years, the disease of river crab is becoming more and more serious, which causes great loss to river crab culture. To control crab disease, we should start with prevention and start in winter. The specific measures are as follows:

Grow aquatic plants in river crab ponds

1. Remove the silt from the bottom of the pool. The sludge is mainly composed of a large amount of residual bait, organic fertilizer, dead organism and biological excrement. Excessive silt can easily lead to the deterioration of water quality in summer and autumn, and produce a large amount of organic acid, hydrogen sulfide and ammonia, which reduces the pH value of pond water and endangers the survival of river crabs, especially harmful bacteria, parasites and other pathogenic microorganisms parasitic in the silt, once the conditions are suitable, all kinds of diseases are rampant. Therefore, it is necessary to make use of the idle period of the crab pond in winter to drain the water and remove the silt from the bottom of the pond mechanically or manually.

two。 Freeze and shine on the bottom of the pool. After clearing the silt in the crab pond, clean the ditch, pump water regularly with machinery, and try to make the bottom of the pond through freezing and sunshine for a period of time (preferably up to one month), so as to improve the soil condition of the pond bottom and let some pathogens be killed after freezing and sunshine. Create a good ecological environment for the growth of river crabs in the coming year.

3. Build into the drainage system. In addition to considering adequate water sources, the physical and chemical factors of water are in line with the growth of river crabs, free from pollution and free from pathogens, but also to prevent the use of the same canal for drainage, resulting in mutual and repeated infection. Therefore, each crab pond is required to discharge the water independently. If there are conditions, it is best to build a reservoir. After the influent is precipitated, filtered or disinfected, the crab pond is introduced to prevent pathogens from being brought into the water source.

4. Do a good job of drug disinfection. 20 days before the stocking of river crab seedlings, disinfection was carried out with quicklime, bleaching powder, tea seed cake and other drugs. Dry disinfection of quicklime with 75 kilograms per mu. Disinfect with water, about 150 kg per mu, sprinkle the whole pool after raw calcareous water. Bleach disinfection, with 15 20 kg; tea seed cake disinfection, generally with water, 25-50 kg per mu, mash the tea seed cake, soak for another 1-2 days, and then sprinkle the whole pool evenly with dregs and juice. Tea seed cake disinfection has the effect of fertilizing water and promoting the shelling and growth of river crab. It is best to use tea seed cake again after disinfection with quicklime.

5. Do a good job of disinfecting crabs. Crab seedlings should be disinfected with appropriate medicine before going into the pond. Soak the commonly used 15 × 10-6 20 × 10-6 potassium permanganate solution for 20 minutes, or 10 × 10-6 concentration bleach solution for 10 minutes for 15 minutes. During disinfection, it should be flexibly mastered according to the crab species size, physique, temperature and the safe concentration of the drugs used.

6. Transplant aquatic plants. Aquatic plants can not only provide habitat and shelling environment for river crabs, but also provide fresh plant feed, reduce the content of ammonia nitrogen in water, increase dissolved oxygen and improve water quality. The abundance of aquatic plants is related to the prevention of crab disease and the improvement of survival rate. Varieties of aquatic plants: submerged plants: Ellosia, bitter grass, Elaeagnus angustifolia, small grass; floating plants: water peanut, water spinach, duckweed and so on. These plants are sown, transplanted or transplanted in winter and spring, making the crab pond coverage of about 60%.