Grass carp is one of the major freshwater aquaculture species in China and occupies an important position in the aquaculture industry. However, due to long-term artificial breeding, inbreeding, grass carp germplasm is severely declining. The specific performance is that the quality of the variety is reduced and the growth progress is slowed down. In particular, the diseases in the breeding process are serious. Hemorrhagic disease, gill disease and enteritis disease are the three major dysentery of grass carp, and often cause huge economic losses to the farmers and fishery production. Greatly hindered the healthy development of aquaculture. A technician from a fishery science and technology company in Hunan's Xiangyin County, through years of research, applied the modern genomic engineering method to develop a pure gynogenetic grass carp that has strong resistance to disease. The breeding experiments over the past few years have shown that the F1 generation of gynogenetic grass carp has three major advantages compared with ordinary grass carp: 1. Strong resistance to disease, female grass carp is not susceptible to viral diseases such as hemorrhagic disease and enteritis. The survival rate of the winter flower fingerlings is as high as 75%~80%, and the survival rate of the winter fish fillets is 90%. 2. The growth rate is improved. Compared with the common grass carp, the growth rate of the gynodiclone grass carp is higher than that of the ordinary grass carp. Fast 15%~20%; 3. The specifications are neat and the quality of the variety is improved. Due to the low incidence of gypsilon and the low mortality rate, the use of little or no medication during the breeding process has greatly reduced the cost of breeding, saved feed, and improved the breeding efficiency. The pure disease-resistant grass carp project was included in the National Spark Program in 2008. At present, it has been promoted to Hebei, Henan, Chongqing, Sichuan, Jiangsu, Zhejiang, Guangdong, Hunan, and other provinces and cities with good breeding efficiency. Widely acclaimed by farmers, seed supply in short supply. The author is the main researcher of the disease-resistant grass carp project. Through years of work experience, he has accumulated a wealth of relevant experience and technology, which will now be summarized as follows:
Fry cultivation
Before stocking, prepare the fry cultivation pool area of ​​2 mu to 3 mu, pool depth of 1.5 to 2 meters, water depth of 1.2 to 1.5 meters; the shape of the pool is rectangular; water drainage is convenient, and the bottom of the pool is loam. The fry was disinfected with fresh lime pond before going down the pond. With clear ponds, 130 kg ~ 150 kg of lime per acre, dry clear pond, 50 kg ~ 70 kg of lime per acre. When the quicklime water melts without cooling, it immediately spills from Quanchipi.
Fertilizer culture ponds can be filled with fresh water after sterilizing in clear ponds. When water is injected, they should be filtered at the inlet with sieve bowls. Water depth should be 50 cm to 60 cm. Base fertilizer should be applied in front of the fish seedlings. That is, 5 to 7 days before fry stocking, 20 to 300 kg of livestock manure per mu, or 300 to 400 kg of green manure. Through the use of basal fertilizer, the zooplankton in the water grows rapidly, and the water turns green or light brown, and fry can be released.
The stocking time for fry stocking is 5 months each year. When the water temperature is stable above 20°C, it is put on sunny days. When stocking, put the fry bag into the pool water for 10 minutes to 15 minutes to balance the water temperature. The fish fry to be put on should have strong physique, neat specifications, fresh color, plump symmetry, and active swimming. Generally, 120,000 to 150,000 tails are reared per acre; if the fish pond covers a large area, 200,000 tails can be stocked per acre.
After the fry were reared on the fish pond, the yellow soybean milk was fed on the 2nd day, 2 times a day, 8 a.m. to 9 a.m., 14 a.m. to 15 p.m. No later than 16 hours. After the first week of stocking, soybeans were used in 2kg to 3kg/mu daily, and ground soybean milk was splashed into two pools. From the second week, the amount of soybeans should be increased to 3kg-4kg/mu per day; from the third week, bean dregs or beancake paste can be added in the shallow water area around the pond.
Daily management During the fry cultivation, new water should be added regularly. When the fish is under the pond, the pool water is generally between 4 days and 5 days after the 50 cm to 70 cm fish fry, and 10 cm of water should be added. After that, every 3 days to 4 days will be added. Once the water is raised, the depth of the pool should be 1.5 meters. Adding new water should prevent wild fish from entering the pool. Twice a day to observe the fish fry and clear the frog eggs in time. Check whether the pool water leaks. Timely remove feed residue, surface milk foam, etc. to keep the water environment clean. After the fry under the pond after 20 days to 30 days of cultivation, grow to 3 cm or so should be divided into pool culture.
Pull net exercise before the summer fish species out of the pond, should be after 2 pull net exercise out of the pond. In general, after 20 days after the fish pond is in the pond, fish is caught in the pool with the fisheye fishnet. The time should be chosen from 8am to 9am on a sunny day. Pick up the fish in the net and pick up the wild fish. Put it back into the original pond within a few minutes. After one day interval, use the same method to set the fish around the net, lift the net, transfer the fish to the cage, slowly drag the cage so that the top water swims for 1 hour to 2 hours, and the fish is put into the pool. in. After 2 times of pulling exercise, the summer fish species are robust and can be cultured in separate ponds.
Fish breeding
The fish fry were cultured for about 30 days and their body length reached about 3 cm. At this time, they should be divided into pools and enter the fish breeding stage. The pond area is generally 2mu~3 mu, and the big one can also be 4 mu~5 mu. The pure grass carp fry fish species of 8000 to 10000 tails per acre are stocked, and the 200 to 300 tail fish species of the grass carp and the summer fish are used. After the mu, the Xiahuacaoyuxiatang can be fed with compound feed, the crude protein content is 30%, the compound feed is processed into powder and the whole pond is fed, and the feed is fed once in the afternoon and afternoon, and the feeding amount is 0.25 to 0.5 kg per day. / Million. The body length reached 8 cm, and the pellets were fed with a diameter of 1.5 mm and crude protein of 28%. After reaching a body length of 12 cm, the pellets were fed with a particle size of 2.5 mm and a protein content of 26%. Each pond is equipped with an automatic feeding bait machine, which is fed once a day in the afternoon and in the afternoon, each feeding for about 1 hour, and each time about 70% of the fish species spread, the feeding is stopped. Use 5%~10% of tender green material every day during the course of fingerling culture.
After the summer grass carp is under the pond, it is also possible to feed it with duckweed and duckweed and concentrate feed. When the grass carp grows to 7 centimeters, it is fed with chopped young grass. After 10 centimeters, the grass is fed directly to the grass. The amount of feeding depends on the growth of the fish, the feeding and the weather conditions. It is cloudy and sultry, and the weather is sunny and sunny. More feed. Conceived feed generally controlled in 3h after eating, green feed 4 hours to 5 hours is appropriate.
Water Quality Management Feeding 2 days to 3 days before the new water, add water 10 cm; from mid-July to early October, add water once every half a month, add water 20 cm to 30 cm. As the number of water injections increases, the water depth remains at 2.0 meters. In the middle of cultivation, water is added at night. After mid-September, water is added depending on changes in water quality. Generally adding water should be done in the early morning. Maintain a water clarity of about 30 centimeters during the service of fingerlings.
Precautions: Shrimp are planted in front of the pond and sterilized with 4% salt water for 5 minutes to 10 minutes. The bait should be fresh and free of moldy feed. The bait is often sterilized around the bait station; feeding for 1 day every 10 days during feeding can enhance fish hunger. Stress response ability, exercise the fish's digestive system, reduce the occurrence of hepatobiliary disease; the whole pool pull net exercise once a month, enhance the fish's constitution; fish disease prevention, in addition to thorough clear pond, from the summer flowers into the pond After that, pay attention to regulate water quality. In the epidemic season of fish disease, the limestone is splashed once a month with a dosage of 10 kg to 15 kg/mu. After feeding for about 5 months, it can be bred into winter fish fillets with specifications ranging from 100g to 150g.
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