Eel culture must prevent Gill nephritis

Gill nephritis is a disease that does great harm to eel. The epidemic period of the disease is long, which can occur from December to May of the following year. The mortality rate of small eel species can reach more than 50% during the overwintering period. The disease of large size eel is later than that of small size eel, and the disease usually occurs from February to March. If the disease is more serious in autumn, the harm of Gill nephritis in winter is more serious. When the water temperature begins to rise from February to March, it is easy to be complicated with water mildew disease, red fin disease, red spot disease and so on. The disease generally does not occur in ponds with salt in water, even if the disease is much lighter than that in freshwater ponds. Warm water eel culture and circulation filter eel culture generally do not occur this disease.

Symptoms: the anterior Gill thickened, the posterior Gill space narrowed, and the appearance was normal in the early stage of the disease, but the eel became thinner and thinner, with depression from the center of the abdomen to the anus, obvious ribs and slightly protruding liver. With the development of the disease, the pectoral fin, anal fin, anus are red, Gill water mold. When the disease is serious, the Gill filaments are all adhered, the Gill filaments are stick-shaped, even turn white, rot, Gill is generally dark red, sometimes bleeding, blood clots are covered on the gills, and the kidneys are enlarged.

Prevention and treatment: due to the unknown etiology, there is no ideal treatment at present. ① should prevent other diseases during the autumn feeding period, such as using furans to prevent red fin disease and Gill rot disease, enhance the physique of eel and reduce the inducing factors. ② was divided into ponds in advance (from the end of September to the beginning of October), and continued feeding after the ponds, delaying the time of stopping feeding. ③ overwintering eels should be regularly sprinkled with methylene blue or disinfected with salt water to prevent the disease from being caused by water mildew. Micronutrients such as vitamins and minerals should be added to the feed fed by ④ before overwintering in order to enhance the physique of overwintering eel. ⑤ oral tetracycline, mixed with 5.5mg per kilogram of feed, can prevent and cure the disease. ⑥ uses saline medicine bath with a concentration of 0.5% Mel 0.7%. The medicine bath time is from December of that year to February of the following year, and after the water temperature rises, it is gradually transferred to fresh water, which also has a certain effect.