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: ; Second, indoor cultivation of winter management Third, broodstock feeding management Fourth, the specific operation in the broodstock cultivation pool The daily operation of the management personnel in the cultivation pool will directly affect the success or failure of broodstock feeding and cultivation. 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. Fifth, the disease prevention and treatment of overwintering broodstock The main diseases of over-wintering of large yellow croaker are in vitro injury and small echinococcosis, diseases caused by external injury, can be used 1-2ppm nitrofurazone, 1-2 times per week, small measles can be used formalin 15- The 25 ppm concentration was used once every other day for 2-3 times, or with 2 ppm of methylene blue per day for 2-3 days.
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First, broodstock selection and transport of broodstock should be selected physically strong, body-heavy, scales intact, no pathogens, no traumatic individuals, females are 2 instar fish, weighing more than 600 grams, more than 400 grams of male fish, male and female The ratio is 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.
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.
1. The feeding condition of broodstock directly affects the quality of gonadal development, the quality of eggs and the survival rate of larvae. Broiler broodstock, usually chilled fish, squid and oysters, large sand silkworm, small sand silkworm, etc., of which the small sandworm is the best, because the small sandworm is suitable for large yellow croaker swallow, but also can not finish Under the circumstances, it will not die after sinking, which will reduce the pollution in 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. 