Silverbait is one of China's most expensive aquatic products. It is known as a treasure on the table and has long enjoyed a good reputation both at home and abroad. It is a hot spot for aquaculture in recent years. The following is a summary of the technology for breeding large whitebait in Dashui surface ponds.

Living habits habits. Silverfish live in the middle and lower layers of the pond, except in the absence of oxygen, rarely found in the upper activities; when disturbed, drilled into the sediment. The juveniles have a strong phototaxis and can use light to induce aggregation at night, which can be used to examine their growth and feeding conditions. Adult fish do not have phototaxis.

Breeding habits. In ponds, large silverfish can develop to mature gonads and spawn themselves. The development of gonads and oviposition characteristics of large whitebait in ponds is basically the same as that of natural whitewater fish. In the middle and lower reaches of the Yangtze River, the peak of the spawning season is from late December to early January. In hard-bottom ponds with aquatic plants, spawning is more concentrated and the fertilization rate can reach 80% to 90%.

Intake habits. Juvenile fish were exposed at the age of 10 days after they were filmed. The feed was rotifers. Afterwards, the larger and more readily available zooplankton was used as food. The order was nauplii, copepods, cladocera, and copepods. Silverfish are carnivorous and feed on small fish and shrimp.

Pond conditions

The old pond was chosen to require fresh water, no pollution, sheltered from the sun, and convenient drainage. Single pond area of ​​3 acres ~ 4.5 acres, set the pool area of ​​4.5 acres to 9 acres, the pool depth of more than 2 meters, the pool weeks amount of water plants, the bottom mud thickness of 0.2 meters. Do not breed with carnivorous and omnivorous fish.

Seedling stocking and cultivation preparation

Seedling stocking pool. After the fish ponds of the rearing fish are pulled through the net to properly turn the surface sediment several times, the pool water is poured into a stocking tank decontaminated by dredging. Because of the low temperature during the start of eating, the quality of pond water is difficult to cultivate, especially when the rotifer density is low. The use of fish pond water and fertilizer and the input of rotifer dormant eggs can rapidly increase the bait density in the stocking pond. This work should be completed two weeks before stocking, and the water depth should be 0.6 meters before stocking.

Seedling source. For the first time, the seedlings needed for feeding can be collected in natural waters, and artificial insemination can be performed on site to obtain fertilized eggs (the fertilized eggs are sold in the fish farm). Fertilized eggs can be hatched in the indoor water, when the water temperature is maintained at 4 °C ~ 6 °C, 30 days to 40 days film, the hatching rate is higher, better stocking effect. Controlling hatching time has important production significance. After the egg seedlings emerged at the end of the second month, it is easier to obtain foods to eat, which will help improve the survival rate of the seedlings.

Stocking method. In the embryo of the fish eggs, the stocking effect is better than that of the fry. One week before filming, the eggs were hatched into the pool and 20,000 eggs per acre were placed. From September to October, 30 kg of big whitebait could be caught. If the stocking amount is too large, the juvenile fish will have insufficient feed. Water depth of 1 meter to 1.5 meters is appropriate.

Cultivate technology. Fishes feed on rotifers and nauplii. Ten days after hatching, they ate and three days after eating, they died without food. Therefore, the stocking pond should be given enough fertilizer in advance to ensure that there is enough food during the start of food. The fully fermented manure is applied, and lime water is properly applied. After 10 days to 15 days, the water color turns thick and the rotifers can reach a considerable density.

Juvenile fish staple foods no juvenile, Cladocera, copepods and Chironomid larvae. In this period, fertilization can be done. The fertilizer amount should be controlled according to the water color and the water temperature. The transparency of the pool water should be as large as 40 cm or more and the water depth should be kept at 2 meters.

Adult fish culture

Supply enough food. During the adult period (above 40 mm in length), the food intake is large, and the growth is significantly accelerated. It is necessary to diligently fertilize the plankton to maintain the density of the plankton, apply the fermented fermented fertilizer, and also use a small amount of soy milk (250 g to 500 g soybeans per mu per day). Depending on the water quality, it is flexible.

Attention to food conversion. There was a conversion period for the diet of the giant whitebait. When fish and shrimp were found in the silver fish gut with a body length of approximately 80 mm from the feeding of Cladocera and copepods to meat-feeding, it was indicated that the diet was being transformed, and small fish should be promptly introduced. Shrimp, and maintaining a certain density, can greatly promote the growth of large silverfish. In the Yangtze River Valley, the amount of egg-feeding shrimp was introduced in May, and the hatched shrimp just caught the turn of the big silverfish.

Prevent floating heads. Large silver fishes require higher dissolved oxygen than ordinary fish. When they are mixed, they always float first. When the water temperature is 20°C, floating heads appear. If no immediate emergency measures are taken, large numbers of deaths can occur. The method of preventing floating heads is to reduce the amount of fertilizers and not to overfeed the food organisms. If the water is too fat, replace the fresh water as soon as possible, if necessary, use an aerator or oxygen booster to increase oxygen.

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