① Pond conditions. The pond requires sufficient water, no harmful substances, convenient irrigation and drainage, flat and solid bottom, silt thickness less than 15cm, and solid ridges without any holes. The ridge of the pond is more than 40 centimeters above the water surface, and the water inlet and outlet are blocked to prevent escape. Putting water lilies or duckweeds on the surface of the pond can not only shade, but also purify the water quality as an auxiliary feed. Before the fry enter the pond, the pond should be dried, cleaned and disinfected, applied with base fertilizer and injected with new water. Fish species can only be released when the biological reproduction of feed in pond water reaches its peak. The pond area is generally 600-2000m2, and the water depth is1-1.5m ... ② Fish farming. The specifications of the stocked fish species are consistent, and the stocking density depends on the size of the fish species and the conditions such as ponds, feed and water sources. Generally, there are 5- 10 kinds of fish per square meter. Putting in large-scale fish species can improve the survival rate and increase the yield. The specifications of fish species in Xiatang should be no less than 5cm. ③ Feeding. When fingerlings first enter the pond, they should be fed some high-quality animal feed to restore their physique as soon as possible and accelerate their growth. Silurus meridionalis is an omnivorous fish, which mainly feeds on animals, such as snails, clams, snails and other shellfish, as well as fly maggots, silkworm chrysalis, earthworms, animal carcasses and leftovers. Shellfish should be broken and fed, and those with strong toughness should be broken or twisted into slurry to make food balls to improve utilization rate. Powdered feed (fish meal, bone meal, shrimp shell powder, corn meal, rice bran, wheat bran, etc.). ) It's best to feed it mixed with meat. Conditional catfish can be used according to the nutritional needs of catfish with skin whiskers.

The pellet feed with crude protein content above 30% can not only improve feed utilization rate, but also accelerate fish growth. Feeding should be on the feeding table. Feed should be fine and coarse, every morning, noon and evening 1 time, and the feeding should adhere to the "four decisions". Proper application of organic fertilizer to cultivate zooplankton can meet the feeding needs of Silurus meridionalis and reduce the feeding coefficient. ④ Daily management. Always clean the feed table to keep the water fresh and prevent the fish from lacking oxygen because of its high density. Water should be filtered to avoid parasites and other enemies. It is also necessary to prevent snakes and rats from digging holes and rising water to escape fish after rain. At ordinary times, it is necessary to check whether there are loopholes in the patrol pond and whether the fish-stopping facilities are damaged. (2) Polyculture in ponds. The mixed culture of Silurus meridionalis and other fish can make full use of water space and give full play to the pond production potential. This method can also be used to remove wild fish in the pond and control the excessive reproduction of tilapia. Silurus meridionalis can be mixed with fish such as catfish, bighead carp, carp, grass carp and tilapia, but it cannot be mixed with carnivorous fish. The specifications of polyculture fish should be appropriately large, and it is best to meet the commodity specifications of the year and can be put on the market together with catfish. The polyculture methods are as follows: ① Silurus meridionalis is the main species, and other fish are raised: generally, 3-6 southern Silurus meridionalis species with 5-6 cm are raised per square meter, and every 2-3 square meters/kloc-0 per domestic fish. (2) Give priority to other fish, supplemented by catfish with skin whiskers: in the adult fish pond where domestic fish can be fed, a catfish with a body length of 6-8 cm should be raised every 2-3 square meters, and small miscellaneous fish and aquatic insects in the water should be used as its feed, so there is no need to increase feeding. ③ Hybrid culture of catfish parent fish in fish ponds: a small number of catfish are put into fish nests according to the ratio of male to female of 65,438+0: 65,438+0 or 65,438+0: 65,438+0.2, and they are put into fish nests to lay eggs and hatch in breeding season. According to the number of Silurus meridionalis, some animals are properly raised to directly develop commercial fish in adult fish ponds. The carrying capacity of water body after breeding of Silurus meridionalis should be considered when stocking.

Prevention and control techniques of catfish disease in southern China

(1) The fish with blackbody disease are black and emaciated, so they stop eating. In severe cases, fish often hang upside down on the water until they die. After examination, there was a round red blood spot on the inner side of pectoral fin, the fin festered and mildew spots appeared on the back of its head. The disease is easy to be infected in the fry stage, and it is most likely to occur because of insufficient bait and poor water quality, with rapid onset and infection. Prevention and control methods: keep the water clean and do not use unfermented fertilizer; Galla Chinensis 2-4g/m3 and quicklime water 30g/L are sprinkled in the whole pool, once every other day, 2-3 times in total. (2) The fish with enteritis is emaciated and black, with swollen abdomen, wandering alone, lightly pressing the abdomen, and yellowish mucus flowing out of the anus. Abdominal cavity effusion, congestion and inflammation of intestinal wall, reddish purple, especially ulceration and shedding of intestinal mucosa in the posterior intestine can be seen by laparotomy. The disease is caused by bacteria or viruses, which mostly occurs in July and August, and mainly harms fish species and adults. Prevention and control methods: use bleaching powder hanging basket in the onset season; Spraying 1g/m3 bleaching powder in the whole pool for 2 days; Add 1 mg furazolidone to each kilogram of fish feed, and sprinkle once 1 .4-3 mg/liter of gallnut; Every 50 kg of fish is fed sulfaguanidine according to 17.5 g of medicine for 6 days, and bleached powder is sprinkled. (3) Bubbles-The sick fish floats on the water, with its belly facing the sky, and there are bubbles in its belly, so it can't sink. The main cause of the disease is that too much unfermented organic fertilizer is applied in the pond, or the water quality in the pond is aging, and there are too many cyanobacteria in the water, which makes the gas in the water too saturated under strong light, leading to fish eating bubbles by mistake. Prevention and control methods: when the transparency of the pool water is too small, it is not suitable to put fry; Injecting fresh water quickly and feeding enough live bait after onset can make some fry discharge bubbles and return to normal; For each water depth 1m, it is effective to splash the whole pond with 1.5-2kg salt. (4) After the fish is infected with water mold, the surface of the fish infected with water mold is gray, like cotton wool. After the hyphae gradually expanded, fish swam abnormally, skin mucus increased, appetite decreased, and finally lost weight and died. Most of the reasons are injuries during fishing and transportation, or frostbite at low temperature. Prevention and control methods: pay attention to the operation, do not hurt the fish, and control the water temperature in the overwintering pool above 65438 05℃; Soak fish bodies or fish eggs with malachite green of 0/0g per cubic meter/kloc; Soak the sick fish in 3%-4% salt solution 10-20 minutes; Sprinkle 1 mg bleaching powder in the whole pool per ml; Sprinkle a mixture of 0.4 ‰ salt and 0.4 ‰ baking soda in the whole pool. (5) Rotifers, large in size and individual, parasitize on skin and fins, resulting in black, thin and slow swimming. Small rotifers gather in the edges and gaps of gills, constantly sliding on gills, stimulating gill tissues, and in severe cases, turning the edges of gill filaments white and rotten, making sick fish black and emaciated, and slowly drifting away from the pool. When there are a large number of parasites, the growth and development of young fish are hindered and even die. Prevention and control methods: thoroughly clean the pond with quicklime, and do not use unfermented organic fertilizer; When the seedlings are divided into pools, transferred to pools and overwintering, they should be soaked with 8 mg/L copper sulfate; Spray the whole pool with a mixture of 0.7 g/m3 copper sulfate and ferrous sulfate (5: 2). (VI) Cercariasis Cercospora sinensis parasitizes the fins and skin of fish, causing gray-white punctate nodules or blocks in fish. It mainly harms the seedlings cultivated in soil ponds and spreads in the form of spores. The popular season is from May to July. Prevention and control methods: remove too much silt; Using quicklime can kill spores in silt; Spray 0.3- 1g/m3 crystal trichlorfon all over the body. (7) The third-generation helminthiasis, due to the movement of the third-generation worms parasitic on the fish, destroys the body surface and gill filaments of the fish, causing the fish to secrete a gray-white viscous liquid surface, which can cause a large number of deaths when seriously infected. The disease mainly harms the young Silurus meridionalis cultured in soil ponds and spreads through the host or water flow. It is popular when the water temperature is around 20℃. Control method: Dip the fish with 2-3g/m3 trichlorfon when entering the pond; 90% of the crystal trichlorfon is scattered all over the pool water at the concentration of 0.2-0.3g/m3; Spray the whole pond with 0.1-0.24g/m3 mixture of trichlorfon and surface alkali (ratio of 5: 3).