The broodstock culture of large yellow croaker is the basis for seed propagation. The breeding of brood gonads in artificial rearing plays an important role in breeding. In 1998, we conducted artificial wintering of gonads. We selected 207 female fish and 70 male fish. After wintering, we carefully cultivated. In the spring of 1999, we obtained 35 Kg of high quality eggs for the first time in 3 days of spawning. Two days after spawning, 20Kg high-quality eggs were obtained. The survival rate of the broodstock reached 95% in winter and the spawning rate reached 99.5%. Only one female fish died and it was difficult to produce. The large-yellow croaker breeding in spring 1999 achieved great success. More than 5 million fish fry were bred and the output value was nearly 2 million yuan. The economic benefits were very good. The specific operations and technical points of large yellow croaker during wintering are summarized as follows: ; First, broodstock selection and transportation The broodstock should be selected for a physically strong, physically thick, backed, scale-free, pathogen-free, non-injured individual. The female is a 2-year-old fish weighing more than 600 grams, males above 400 grams, and a male to female ratio of 3:1. For the transportation of broodstock, live water boats should be selected and transported in small winds and waves. The density depends on the length of the transportation time. Transporting for about one hour, the density can reach 70kg/m3. During the selection and transportation of cages, broodstock should be carefully handled to avoid damage caused by careless operation. After the broodstock is transported to the nursery room, it is first disinfected with 30-50ppm nitrofurazone for a short period of time, and then placed in the wintering cultivation pond. . The cultivation pond should be selected for the indoor wintering pool with quietness, good insulation performance and dark lighting. The cultivation pond area is 20-40m2, the water depth is 1.5m, and the stocking density is 3.5kg/m2. The broodstock must be warmed up 40 days before the artificial oxytocin to strengthen the gonadal development. Otherwise, even if the broodstock is raised, the hatching larvae will be difficult to open. Second, indoor cultivation of winter management 1. After the broodstock enters the pond, the large yellow croaker scales are looser than other fish and easily fall off. During the process of picking, loading into the boat, and digging into the net, some broodstock will have some damage. If scales partially fall off, and the skin will have bleeding spots, therefore, 1-2ppm nitrofurazone should be given to the breeding pool, 1-2 times a week, and the bleeding spots can be cured and disappeared after 10 days. 2. The temperature of the sea during the selection of broodstock is generally in the range of 10-12°C. After entering the room, the temperature is increased by 0.5-1°C per day, raised to 18°C, maintained for 3-5 days, and then gradually warmed up to 22°C. Then keep this. Temperature cultivation. 3. In the brooding pond, place 3-4 gas heads in a row to inflate continuously to keep enough dissolved oxygen during the overwintering process. The salinity range of wintering seawater requires between 20.0 ‰ -33 ;; although large yellow croakers adapt to a wide range of salinities, salinity is relatively stable during wintering cultivation; special attention is paid to the salinity and nursery room of broodstock cages. The difference in salinity, try to avoid the mutation. Third, broodstock feeding management 1. The feeding condition of broodstock directly affects the quality of gonadal development, the quality of eggs and the survival rate of larvae. The broodstock bait, generally chilled? Fish, squid and oysters, big sand silkworm, small sand silkworm, etc. Among them, small sand silkworm is the best, because small sand silkworm is suitable for swallowing of large yellow croaker, and it will not die after sinking under endless conditions. , can reduce the pollution of the water. 2. When the broodstock warms up to about 20°C, the food intake should be at least 3% of the body weight. The feeding time is generally based on the daily food intake and is divided into 2-3 times a day. 3. In the early period of cultivation, the amount of water changed every day is 1/3, the amount of water in the middle and later stages is 1/2, and the dirt is sucked every 2-3 days. Fourth, the specific operation of broodstock breeding pool The daily operations of managers in the cultivation pool will directly affect the success or failure of broodstock feeding and breeding. As the large yellow croaker is very timid, it is easily frightened. The noise caused by the movement of management staff in the breeding room, feeding, and the use of tools, etc., and the sudden change of light caused by the opening of the door may cause large yellow croaker not to eat or eat at one time. Ingestion may cause mad chaos, which may result in hitting the pool wall or jumping out of the pool, causing injury or death and affecting the normal development of the gonads of the broodstock. V. Disease prevention and control of wintering broodstock The major wintering disease of large yellow croaker is external wounds and small typhoid diseases. Diseases caused by extracorporeal injury can be treated with 1-2 ppm nitrofurazone, 1-2 times a week. The small melon worms can use formalin 15-25 ppm concentration every 1 day. Once, share 2-3 times, or use methylene blue 2ppm once a day for 2-3 days. Lactic Acid,Biodegradable Lactic Acid,Lactic Acid Liquid,Poly Lactic Acid SHANDONG BAISHENG BIOTECHNOLOGY COM , https://www.baishengbioproducts.com