Prevention and Control Methods and Technical Key Points for Protozoan Diseases in Large Yellow Croaker

(1) Pathogen: Cryptocaryon irritans (Crypjocaryonirrions).

(2) Symptoms: Small white spots appear on the body surface and gills of diseased fish. These small white spots are white vesicles formed by the parasitism of the parasite, irritation of the host, and the secretion of large amounts of mucus and proliferation of epidermal cells in the surrounding tissues. In severe cases, the body surface tissues are destroyed. If bacteria invade, it can cause skin inflammation, scale loss, fin membrane rot and splitting, corneal damage, and blindness. The diseased fish ultimately die due to loss of appetite, emaciation, slow swimming, and difficulty breathing.

(3) Prevention and control methods: ① Sprinkle 0.3×0.000001 sodium dichloroisocyanurate throughout the pond, which has a certain effect. ② Sprinkle 25×0.000001 formalin throughout the pond, then change half of the water the next day and apply the medication once more. ③ Soak the diseased fish in 17×0.000001 to 20×0.000001 copper sulfate for 40 to 60 minutes, once a day, for 3 to 5 consecutive days.