Control techniques of common diseases and enemy pests in freshwater crayfish culture

There are few diseases of freshwater lobster under natural conditions. with the expansion of high-density artificial culture, freshwater lobster culture is also facing the risk of disease outbreak. Therefore, we should adhere to the principle of "giving priority to prevention" and do a good job in disease prevention and control.

(1) Prevention of diseases 1. Before thorough disinfection and stocking, the ponds should be thoroughly cleared and disinfected to kill pathogens and enemy organisms. The inflow of water should be filtered to prevent enemy creatures from entering the pool. Exotic shrimp seedlings should be sterilized in 1: 3% salt water and then put into the pond. And feed, net gear should also be routinely disinfected. 2. Keep the water quality fresh and often flush with new water, or be equipped with an aerator to keep the dissolved oxygen in the pool water above 3 mg per liter; sprinkle the whole pool with quicklime (20 grams per ton of water) every month to keep the pH value at 7: 8. 3. To feed scientifically, it is better to use artificial mixed pellet feed to achieve "four fixed" feeding. The residual feeding or the malignant change of water quality and bottom in the pond are mostly caused by excessive feeding. When the dissolved oxygen in the water is low, the water quality deteriorates or bad weather (such as thunderstorm muggy days, continuous cloudy days), it is necessary to reduce feeding or stop feeding. (2) Prevention and control of common diseases and enemies. 1. Bacterial diseases. (1) Brown spot. The shell of shrimp is infected by many kinds of bacteria due to trauma, which destroys the stratum corneum, epidermis and chitin layer of shrimp shell and forms dark brown patches on the shell. The disease can generally shed and heal itself when molting again, but it can also cause shrimp death in severe cases. (2) septicemia. The blood and internal organs of shrimp are infected by bacteria, including Vibrio, Monospora and Gram-negative bacteria. Prevention and treatment of bacterial diseases: mainly to improve water quality and pond environment, free from severe stimulation and trauma, focusing on prevention. When conditions permit, disinfection and fungicides can also be applied to inhibit bacteria in shrimp ponds. 2. Fungal diseases (1) water mold. Because the fungi invade the dead eggs of crayfish, they multiply and make the eggs give birth to white-haired "water mildew". In severe cases, fungi can also infect the surrounding good eggs, forming even patches of white mold. The routine prevention and control of water mildew can be tried. (2) crayfish plague. The disease is caused by a fungal infection whose suitable growth temperature is no more than 18 ℃. When the water temperature is higher than 21 ℃, the fungal growth is inhibited. Therefore, crayfish will not get the disease as long as the water temperature during stocking and fishing is above 21 ℃. 3. The enemies of crayfish, such as cormorants and gulls, are the great enemies of shrimp ponds, which can be intimidated by sound or visual interference; fish such as perch, snakehead, catfish and mandarin can prey on shrimp, especially when molting, crayfish suffer more, so crayfish should be strictly removed from the pond. If you want mixed culture, you can only keep the fish in the cage (sealed cage) of the pond water. Water nutria, turtles, snakes, frogs and other amphibians can also devour crayfish or their young shrimp, which can be isolated by trapping or adding barriers around the pond. Many aquatic insects or their larvae can also harm juvenile crayfish, which can be prevented or trapped or suffocated by various methods, but special care should be paid to the application of pesticides such as pesticides in shrimp ponds, because shrimps are also arthropods and are very sensitive to some pesticides. When the harm to birds is serious, a net cover can be used on the surface of the pond to prevent the harmful birds from entering the pond to eat shrimp.