Detailed Explanation of Key Technical Points for Silver Carp Disease Prevention and Control

Silver carp, also known as white carp, water carp, jumping carp, silver fish, etc., is one of the excellent fish species more suitable for farming, with the characteristics of fast growth, few diseases, and high yield. It is mostly polycultured with grass carp and common carp, and is a major freshwater aquaculture fish in China. Let us take a look together at the common disease prevention and control techniques for silver carp!

Branchiomycosis (Gill Rot Disease)

[Disease characteristics] Sick fish have darkened body color, stay alone away from the school, and stop feeding. Gill filaments rot and carry mud, the inner epidermis of the operculum is congested, and is often corroded into round transparent small holes, commonly known as "open skylight". After grass carp gill lamellae are infected with Myxococcus, the affected tissue shows varying degrees of rotting, ulceration, and invasive bleeding. Farmed fish such as black carp, grass carp, and bighead carp can all develop this disease, with grass carp being the most severely affected. It is generally rare below 15°C water temperature and begins to spread at around 20°C.

[Preventive measures] For a water depth of 1 m, splash 50 ml of "Sterilizing Red" per mu over the whole pond, once every 15 days. Or add 0.5% "Fish Health Joy No. 2" to the bait and feed once every 15 days. Before stocking fry and fingerlings, dilute "Fry and Fingerling Soaking Agent" at a ratio of 1:5000 and bathe the fish for 3-5 minutes.

[Treatment methods] For a water depth of 1 m, splash 100-125 ml of "Sterilizing Red" per mu over the whole pond; the effect is better when combined with "Fish Health Joy No. 2". If the condition is severe or an explosive disease outbreak occurs, add 1.5% "Fish Health Joy No. 1" to the bait and feed, with 3-5 days as one treatment course.

Silver Carp Tetracapsuloides Disease

[Disease characteristics] Caused by Tetracapsuloides parasitic in the gallbladder of silver carp. Tetracapsuloides infects silver carp fry in June and July, remains in a metamorphic stage in the fish body during the overwintering period, and forms the first batch of mature spores in the late overwintering period. It often occurs concurrently with saprolegniasis and chilodonelliasis, causing mass mortality of sick fish. When only a small number are parasitic, symptoms are not obvious. In severe cases, sick fish become emaciated, body color darkens, the eye ring shows punctate congestion or exophthalmos, the fin base and abdomen are yellow, the liver is pale yellow or pale, the gallbladder is extremely enlarged and filled with yellow or yellowish-brown bile, the intestine is filled with yellow viscous material, and individual sick fish have ascites in the body cavity.

[Prevention and control methods] 1. Thoroughly clear the pond with quicklime, which can kill spores in the pond bottom sludge. 2. Strictly implement quarantine systems. 3. Strengthen feeding management. Enhance fish body resistance. 4. Promptly remove diseased individuals and bury them deep in places far from water sources.

Lepidorthosis (Scale Protrusion Disease)

[Disease characteristics] Sick fish have rough body surfaces, with some scales protruding outward in a pinecone shape, edema at the scale base, and accumulation of translucent or blood-tinged exudate inside. Fin rot, congestion at the fin ray base, abdominal swelling, and exophthalmos. Sick fish swim slowly, have difficulty breathing, turn abdomen upward, and die after 2-3 days. This disease mainly harms common carp, crucian carp, grass carp, and silver carp, and spreads every spring.

[Preventive measures] In winter, after each netting harvest, for a water depth of 1 m, splash 50 ml of "Sterilizing Red" per mu over the whole pond.

[Treatment methods] For a water depth of 1 m, splash 100-125 ml of "Sterilizing Red" per mu over the whole pond; in severe cases, use continuously 2-3 times, or add 1.5% "Fish Health Joy No. 1" to the bait and use continuously for 3 days.

Dactylogyriasis

[Disease characteristics] The pathogen is Dactylogyrus. In severe cases, sick fish have swollen gill filaments, increased mucus, and difficulty breathing, which can cause mass mortality of fry and fingerlings.

[Prevention and control methods] 1. Splash 0.3-0.7 ppm of 90% trichlorfon crystals over the whole pond. 2. Splash "Chong Sao Jing" at 130 ml-170 ml per mu per meter over the whole pond; in severe cases, use again the next day.

Carp Pox Disease

[Disease characteristics] In the early stage, white small spots appear on the body surface of sick fish, covered with white blocky mucus. As the disease progresses, the number of white spots continuously increases, the epidermis at the lesion site gradually thickens, and paraffin-like growths form, resembling pox, hence the name "carp pox disease". It mainly harms 2-year-old common carp before and after overwintering, and 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 severe, and the incidence rate has gradually increased.

[Preventive measures] After the beginning of spring, for a water depth of 1 m, splash 50 ml of "Sterilizing Red" or 200-400 ml of "High-efficiency Sterilizing Iodine" diluted per mu over the whole pond, once a week.

[Treatment methods] After the fish begin to feed, add 0.2% "Ultra-concentrated Photosynthetic Bacteria" and 0.3% vitamin Vc to the bait to improve fish body immunity.