Disease prevention and control of California perch

First, prevention and treatment of common fish diseases: California perch has strong disease resistance and rarely occurs. However, fish species are easy to be infected with water mildew and parasitized by rotifers, oblique tube worms and other protozoa, and cause death in serious cases. Therefore, prevention should be given priority to, and prevention should be combined. 1. Fish can be bathed before stocking: (1) soak in 3-5% salt water or methylene blue for about 15 minutes and then go into the pond to prevent rotifer, water mold and vertical scale disease. (2) soaking in 15~20ppm potassium permanganate (1000 kg water plus 15 kg potassium permanganate) for about 15 minutes can prevent the parasitism of protozoan parasites. 2. Sprinkle medicine regularly. 0.7ppm copper sulfate and ferrous sulfate mixture or insecticides such as insecticide can be used to kill insects, and then disinfected with fungicides such as chlorine dioxide. Each time the fish will be damaged after pulling the net, disinfect the fish with 0.2 ppm chlorine dioxide; if you are infected with water mold, do not use malachite green, but should use methylene blue or salt and baking soda mixture to treat. When it is found that the pool water is too fertile and the water quality deteriorates, sprinkle quicklime appropriately. 3. Oral bait regularly. Starting from June, once a month, the medicine will be mixed into the California perch feed, 3-5 days as a course of treatment. Oxytetracycline 5g / 50kg fish, furazolidone 5g / 50kg fish per day. In addition, special vitamins for aquatic products are often added to improve disease resistance. Second, the main characteristics of fulminant disease and its prevention and treatment techniques 1, the main characteristics of fulminant disease: (1) the main symptoms of the disease are rotting on both sides of the body surface, accompanied by hyperemia at the base of the fin, and the diseased fish swim slowly on the surface of the water. You can't get under water when you're alarmed. Microscopic examination of the focus found no parasites, anatomy found visceral inflammation, a small amount of ascites, liver enlargement, yellowing, necrosis. (2) the disease comes fiercely, and diseased fish will cause a large number of diseases and deaths in three days. Prevention and treatment is difficult, external sterilization drugs combined with internal administration of antibiotics and antiviral drugs, there is no obvious effect. (3) the disease mainly harms fish species and adults cultivated in high-density cages. The incidence of cages in the affected waters is often up to 100%, and the mortality rate is also very high, even wiped out. 2. Analysis of the cause of the disease we preliminarily believe that the disease is caused by lack of nutrition, decreased disease resistance and secondary bacterial infection. Because: (1) California perch cage culture mainly fed frozen fish, because frozen fish contains a large number of "vitamin decomposing enzymes", California perch will cause vitamin deficiency after eating. In addition, when the fish were fed, the thawing was not complete, the California perch was indigestible after eating, and the histamine produced by the protein decomposition of frozen fish combined with free amino acids during storage and transportation to produce "erosive hormone", damaging the internal organs. (2) the cage setting in the aquaculture area is unreasonable, and the cage interval is too small; the cage culture area has been cultured for many years, and the bottom quality is poor; the culture density in the cage is too large, which is easy to cause the outbreak of cross infection. 3, prevention and control methods: (1) it is best to feed fresh fish, such as frozen fish must be thawed thoroughly, and disinfect with 3% salt water or dysentery before feeding. (2) vc and multivitamins for aquatic products are often added, and the addition amount is 1-3 ‰ of the weight of feed fish. (3) the cage setting and stocking density should be reasonable, and the cage and aquaculture waters should be disinfected regularly. (4) to clean the net clothes thoroughly on a regular basis to avoid blocking the mesh such as dirt, residual feeding and attachments, resulting in poor internal and external water flow, and avoiding dead fish and residual feeding sinking into the bottom of the box and causing pollution. (5) after the onset of the disease, vc and multivitamins can be taken orally, combined with external chlorine dioxide and trichloroisocyanuric acid, which can be effective in three days. The specific method is to add 25g of aquatic special vc and multivitamins per 50kg fish day to improve the disease resistance of the fish. The concentration of chlorine dioxide in the cage was about 3 times that of the conventional dosage, and the aquaculture waters outside the cage were disinfected with trichloroisocyanuric acid 0.3mg/l.