My county is located in Zhejiang, east of Hangzhou Bay. Seawater salinity is between 2% and 10%, which is low salinity. There are more than 5,000 acres of seawater ponds, and the natural resources are in excellent condition. We began to import large yellow croakers from Ningbo in 1999 to develop low salinity mariculture. The county's low-salinity seawater pooling techniques for large yellow croakers are summarized as follows: I. Selection of breeding sites and requirements of ponds The breeding sites can be selected to be near coastal tidal flat ponds. Coastal shrimp ponds can also be used for coastal aquaculture and breeding sites. The surrounding environment should remain quiet. Pond requirements; Sea water is easy to enter and drain, and the water exchange conditions are good (such as the pond located near the sea gate and the gate is more ideal); the deepest water level is more than 1.8 meters (2 meters above the deepwater of the river block breeding), so that the fish High-temperature period can safely cross the summer; the area should be 10-20 acres (10-30 acres can be blocked around the river), large area, can artificially cultivate large yellow croaker's growth environment close to the natural living environment, so that the cultured fish has a fast growth, shape , good body color and other characteristics, and too large area is inconvenient to manage; to facilitate drainage and fishing, the bottom of the pool should be inclined to the direction of the drainage port; pool shape is good from east to west, so that a long day of light, is conducive to fish growth . Second, prepare before stocking Trimming the pond to the old pond. Dry ponds, dredging, leveling of ponds and ponds should be done in winter to reinforce the dams. Anti-leakage in ponds, dredge into drainage channels, etc. 2. Thorough clearing ponds can be cleaned with quick-drying lime ponds of 150 kg/mu in 20-30 days before stocking to kill pathogens and predators and improve sediment quality. Can also be used bleaching powder clear pond: dry pool clear pond pond amount of 4-5 kilograms, 3 days after the water; with clear pond water depth of 13 to 15 thousand meters per meter, 4 days after the fish can be put. Drug clear pond can also be used tea seed cake. 3. The first time influent water 70-80 匣 rice, in order to increase the temperature of the water. The entrance to the gate of the pond is set with a dense net to prevent flooding of wild fish, shrimp, etc. Third, fish stocking 1. Selection of fingerlings In order for the large yellow croaker to be stocked in the same year, stocking stocks should be selected for complete body scales, no sickness, no injuries, strong physique, and consistent first-instar fingerlings; large-scale fingerlings should be selected at the same time (100 g/tail) stocking, and strive to make the specifications neat, so that all the year up to commercial fish. 2. The stocking time and density stocking time is from mid-April to May, and the pond water temperature is at least 14, and it is advised that it should be sooner rather than later. Because the temperature is low, the survival rate of the species can be improved and the growth period can be prolonged. When fish species are stocked. It is best to concentrate temporarily on the fence in the pond. Strong bait domestication and other management, about 10-15 days after the removal of the seine net pond culture. The pond stocking density is generally 500-600 tails/mu, which can be appropriately increased or decreased according to pond conditions and fish species specifications. Utilize natural local barracuda and blue crab seed. A small amount of polyculture can also be used in large yellow croaker breeding ponds, and 100 mussels of barnacles or 60 species of green crabs can be placed on mu in order to increase the efficiency of integrated breeding. 3. The species transportation is introduced from Ningbo and other places, and it can be used for continuous air transport by live water vehicles. Fish species are gradually desalinated prior to or during transportation, in order to adapt to the local bottom salinity mariculture. The desalination method is to store pre-transportation fish in barrels (80 cm in diameter and 120 cm in height) and release 150 kg of water, including 100 kg of sea water, 50 kg of fresh water, and 135 tails of 75 to 100 g/tail of rhubarb fish. After 6 hours of desalination of the inflated transport, the large yellow croaker can adapt to poor salinity (the salinity of the seedlings is 15%, to the local 7%). Or desalt by adding fresh water twice during transportation for 6 hours. Fourth, daily management 1. Feed fed feeds can choose compound feed or small trash fish, can also be used with mixed feed and dried fresh fish; Frozen Fish feed must be thawed, washed, chopped into blocks and then fed. The daily feeding amount is mainly based on the previous day's feeding conditions and the day's weather, water quality, etc., the early breeding period should be more high quality feed, and cast enough food, daily feeding rate of about lO%; mid-term (July-August) Appropriately control the amount of feeding, about 6%; later increase the amount of feeding, about 8%. The number of feedings is generally one for each day at sunrise and sunset; small tides are difficult to change water, and when the water quality is poor, they can be fed one time, or the feeding is suspended; when late cold air strikes, less or no feeding is performed. . Feeding method: You can dial the upper layer of water by hand at the fixed feeding point (preferable to select the outlet near the outlet to facilitate the discharge of residual baits etc.), and the feed is dropped from less to more. From the water you can hear the cry of the big yellow croaker, and when the sound grows small, it proves that the fish has entered the food market and has reached food. When the fish is full, the sound gradually disappears, and the feeding and eating of the fish can be observed on each feeding. 2. Water Quality Water quality requirements are fresh and not too fat. According to the tide to strengthen water change, conditional change of water every 2 days, the general change of water is 1/3, change the water in the hot season should be carried out at night. Every half a month, use lime water 10-15 g/m 3 regularly to improve water quality. 3. Patrol ponds, observations and records Every morning, evening, and evening, stick to the patrol ponds and find out if problems arise. When feeding, the large yellow croaker school of fish will appear at a fixed place to observe the fish’s feeding, growth, and disease. Observe and record water level, water temperature, salinity, transparency, etc. on a regular basis. If the fish has abnormal conditions or water quality is worse, pH, ammonia nitrogen, dissolved oxygen, etc. should be measured. 5. After catching up to the specifications of the commodity in time, it can be caught with the market demand and market conditions, because the large yellow croaker is below the water temperature of 7c. Can't winter in shallow ponds. Therefore, the catch should be completed at a water temperature of 8C or higher, and local catches should generally be taken in late December.
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