Common Spring Fish Disease Prevention and Control Methods and Technical Key Points

1. Gill rot disease

Pathogen: Myxococcus.

Symptoms: The diseased fish has a darkened body color, stays away from the school, and stops feeding. The gill filaments are rotten and covered with mud, the inner epidermis of the operculum is congested, and it is often corroded into round transparent small holes, commonly known as "open skylight". After grass carp gill lamellae are infected with Myxococcus, the tissue in the affected area shows varying degrees of rot, ulceration, and invasive hemorrhage. Cultured fish such as black carp, grass carp, and bighead carp can all develop this disease, especially causing the greatest harm to grass carp. Below a water temperature of 15°C, it is generally rare; it begins to become epidemic at around 20°C.

Prevention: At a water depth of 1 m, use 50 ml of "Shajunhong" per 1 mu of water surface (1 mu = 667 sq m) and splash it over the entire pond, using it once every 15 days. Or add 0.5% "Yukangle No. 2" to the bait and feed it once every 15 days. Before stocking fry and fingerlings, dilute "Miaozhong Paojiji" at a ratio of 1:5000 and bathe them in the medicated solution for 3-5 minutes.

Treatment: At a water depth of 1 m, use 100-125 ml of "Shajunhong" per 1 mu of water surface and splash it over the entire pond; the effect is better when used together with "Yukangle No. 2". If the condition is severe or an explosive disease occurs, 1.5% "Yukangle No. 1" can be added to the bait for feeding, with 3-5 days as one treatment course.

2. Scale protrusion disease

Pathogen: Pseudomonas punctata.

Symptoms: The body surface of the diseased fish is rough, some scales protrude outward in a pinecone-like shape, the scale bases are edematous, and semi-transparent or blood-tinged exudate accumulates inside. The fins are rotten, the fin bases are congested, the abdomen is swollen, and the eyeballs protrude. The diseased fish swims slowly, has difficulty breathing, turns belly-up, and dies after lasting 2-3 days. This disease mainly harms common carp, crucian carp, grass carp, and silver carp, and is epidemic every spring.

Prevention: In winter, after each netting and harvest of fish, at a water depth of 1 m, use 50 ml of "Shajunhong" per 1 mu of water surface and splash it over the entire pond.

Treatment: At a water depth of 1 m, use 100-125 ml of "Shajunhong" per 1 mu of water surface and splash it over the entire pond; if the condition is severe, use it 2-3 times consecutively, or add 1.5% "Yukangle No. 1" to the bait and use it for 3 consecutive days.

3. Carp pox disease

Pathogen: Virus.

Symptoms: In the early stage of the disease, small white spots appear on the body surface of the diseased fish, covered with white blocky mucus. As the disease progresses, the number of white spots continuously increases, and the epidermis at the lesion gradually thickens, forming paraffin-like growths that resemble pox, hence the name "carp pox disease". It mainly harms 2-year-old common carp before and after overwintering. It occurs frequently from autumn to early winter and in spring, when the water temperature is 10-15°C. In recent years, due to the development of high-density cage culture technology, this disease has become increasingly serious, and the incidence rate has gradually risen.

Prevention: After the beginning of spring, at a water depth of 1 m, use 50 ml of "Shajunhong" or 200-400 ml of "High-efficiency Sterilizing Iodine" per 1 mu of water surface, dilute it, and splash it over the entire pond, using it once a week.

Treatment: After the fish begin to feed, add 0.2% "Ultra-concentrated Photosynthetic Bacteria" and 0.3% vitamin Vc to the bait to improve the fish's immunity.

4. Saprolegniasis

Pathogen: Saprolegnia.

Symptoms: Commonly known as white hair disease or skin mold disease. If the fish body is injured due to careless handling or transport, or frostbitten due to low temperature, or if primary lesions are caused by parasite or bacterial infections, mold spores invade through the fish wounds, absorb nutrients from the skin, rapidly reproduce at the injured lesion, spread and expand, and grow into cotton-wool-like hyphae. The hyphae adhere to the wound tissue, causing skin ulceration and tissue necrosis. As the lesion expands, the fish swims abnormally, appetite decreases, and it dies weak and diseased. This disease occurs mostly in low water temperature seasons below 20°C, and is most epidemic in early spring and late winter. In densely stocked overwintering ponds, fish are susceptible to this disease in spring when the pond water is clear and lean or when the fish are in a starved state.

Prevention: Before fry enter the pond, dilute "Miaozhong Paojiji" at a ratio of 1:5000 and bathe them in the medicated solution for 3 minutes; after they enter the pond, use "Shajunhong" at a dosage of 50 ml per 1 mu of water surface at a water depth of 1 m and splash it over the entire pond.

Treatment: At a water depth of 1 m, use 100-125 ml of "Shajunhong" per 1 mu of water surface and splash it over the entire pond.

5. Ichthyophthiriasis

Pathogen: Ichthyophthirius multifiliis.

Symptoms: When a large number of the parasites are present, white dot-like cysts can be seen with the naked eye covering the fish's body surface, fins, and gills, so it is also called "white spot disease". In severe infections, because the parasites invade the fish skin and gill surface tissues, they cause tissue hyperplasia at the lesion and secrete large amounts of mucus, forming a white film that covers the lesion surface, and the fins rot.

Prevention: Before stocking, at a water depth of 1 m, use 50 g of "Yuchongmie 2B" per 1 mu of water surface, dissolve it in 2000 times water, and splash it over the entire pond for disinfection; or dilute "Miaozhong Paojiji" at a ratio of 1:5000 and bathe the fry and fingerlings for 3-5 minutes.

Treatment: After the disease occurs, at a water depth of 1 m, use 50 g of "Yuchongmie 2B" per 1 mu of water surface, dissolve it in 2000 times water, and splash it over the entire pond for disinfection, then use it once more after 2 days. In severe infections, "Yukangle No. 1" can be added to the bait at a ratio of 1.5% and fed continuously for 3-5 days.