Common Knowledge on the Prevention and Treatment of Fish Diseases Every Fish Keeper Must Know

Aquaculture is a high-input, high-output farming industry. In the production process, how well fish diseases are controlled is directly related to farming yield and profitability, so doing a good job of fish disease prevention and treatment in aquaculture is particularly important. So-called fish disease prevention and treatment means the prevention and treatment of fish diseases during the fishery farming process. In fish disease prevention and treatment work, the key is prevention, with prevention as the priority. If prevention work is not done well, once a fish disease occurs, not only is a large amount of medicine and time needed for treatment, but it also seriously affects the normal growth of fish and causes major economic losses. Based on the aquaculture situation in Jinggu County, the following common fish disease prevention and treatment methods are mainly introduced.

1. Enteritis disease

Fish affected: grass carp, common carp, tilapia, with a small number of silver carp and bighead carp occurring.

Symptoms: The abdomen of the diseased fish is swollen, the anus is red and swollen, and when the abdomen is gently pressed, a pale yellow or bloody purulent liquid flows out from the anus. When the abdomen is cut open, abdominal dropsy can be seen, the intestinal wall is congested and inflamed; in mild cases the foregut or hindgut appears red, and in severe cases the entire intestine is purplish red. The intestine generally contains no food and is filled with pale yellow mucus or bloody pus. The body color of the diseased fish becomes dark, it loses appetite, moves slowly, and swims alone away from the school.

Prevention: 1. Strengthen feeding management, pay attention to keeping the water quality fresh, and routinely remove leftover grass stems and residue that the fish have not eaten. 2. Before stocking fingerlings, soak them in 10 ppm bleaching powder for 20-30 minutes. During the disease season, splash bleaching powder over the whole pond once every half month at 1 ppm.

Treatment: 1. Add 25 grams of crushed garlic and 300 grams of table salt per kilogram of feed and feed twice a day. 2. Use 50 grams of Changyanling fish medicine mixed into the feed and feed twice a day, with 3 days as one treatment course.

2. Saprolegniasis.

Fish affected: Generally speaking, any fish with wounds may develop saprolegniasis.

Symptoms: The zoospores of the fungus penetrate wounds on the fish body, absorb nutrients, and rapidly grow into hyphae. One end of the hyphae extends into the muscle, spreads and expands, forming gray-white cotton-like masses visible to the naked eye. Because the hyphae wrap around and adhere to the cell tissue of the fish wound, the fish tissue becomes necrotic. At the same time, as the hyphae increase day by day, the burden on the fish body becomes too heavy, causing abnormal swimming, loss of appetite, and death from gradual emaciation day and night.

Prevention: 1. Disinfect and clear the fish pond with quicklime, and try to avoid injuring the fish body during netting and transport. 2. Try to avoid using injured broodstock for breeding.

Treatment: 1. Splash a mixture of 0.4 kilograms of table salt and 0.4 kilograms of baking soda per cubic meter of water over the whole pond. 2. Splash a mixture of 5 kilograms of sweet flag, 3 kilograms of table salt, and 20 kilograms of human urine per mu over the whole pond. 3. Splash formalin at 0.5 ppm over the whole pond.

3. Bacterial gill rot

Cause: Bacterial gill rot is divided into two types: caused respectively by Cytophaga columnaris and Cytophaga columnaris.

Symptoms: The fish body turns dark, breathing is difficult and the fish floats at the water surface, the gills swell, are pale in color, and show severe anemia. In acute infection they appear purplish red, with much mucus, filth, and bacterial plaques; the gills rot, but generally the diseased fish dies before defects appear.

Epidemic pattern: In densely stocked aquaculture water bodies, tilapia is prone to gill rot, which causes the fish to die.

Prevention: 1. Discharge sewage promptly, refill with fresh water, and where conditions permit appropriately raise the water temperature. For still water, EM (effective microorganisms) can be splashed over the whole pond to inhibit the reproduction and infection of harmful bacteria. 2. Splash quicklime over the whole pond to make the pond water reach a concentration of 2.3-3.0 grams per cubic meter.

Treatment: 1. Splash chlorine preparations over the whole pond, such as trichloroisocyanuric acid (strong chlorine powder) at 0.3 grams per cubic meter or sodium dichloroisocyanurate (Youlüjing) at 0.5 grams per cubic meter, with continuous treatment for 3 days as one course. 2. Splash potassium permanganate over the whole pond to make the pond water reach a concentration of 2.3-3.0 grams per cubic meter. 3. Splash formalin over the whole pond to make the pond water reach a concentration of 30 grams per cubic meter.