Freshwater culture techniques of Penaeus vannamei

The most suitable water temperature for survival of Penaeus vannamei is 28-32 ℃, and when the weather is sunny or dusk, the most suitable water temperature is 20 ℃ or more. Choose the high-quality seedlings with good vitality, quick reaction and transparent body. Desalination and extensive treatment was carried out before it was put into the freshwater culture pond to improve the survival rate. Control the content of salinity, PH, dissolved oxygen and other chemicals in the pond.

1. The stocking of shrimp seedlings and the selection of shrimp seedlings.

Penaeus vannamei can live in a water temperature of 15-35 ℃, but the most suitable water temperature for their growth is 28-32 ℃. The young shrimp living in this water temperature are very strong and grow very fast. Avoid stocking at noon when the water is muddy or when the sun is shining directly. Choose sunny days or evening to release seedlings. The water temperature should be above 20 ℃ when stocking.

The annual seedling release time in Huanggang area of China is around late May, and the water temperature at this time is relatively stable, generally about 25 ℃. At this time, seedling release can effectively avoid low temperature stimulation caused by cold current. During stocking, in order to reduce the temperature difference between the water temperature in the shrimp bag and that in the pond, you can first put the shrimp seedling bag into the pond for about 30 minutes.

When choosing shrimp seedlings, you should choose shrimp seedlings with good vitality, agile action, transparent shrimp body without red, and no blackening of the cheeks and black umbrellas.

2. Dilute the rough treatment of the standard

The shrimp seedlings hatched in the nursery are usually hatched in seawater with a salinity of 20 ‰. Although they have been desalinated for a short time, the survival rate will be affected if the seedlings are released directly, and if serious, it will lead to the annihilation of the whole army. In order not to affect the survival rate of Penaeus vannamei, it is necessary to carry out a gradual desalination and temporary culture treatment of shrimp seedlings in the early stage of culture.

Before releasing the seedlings, a temporary culture pond was built in the corner of the pond with colored cloth strips or earth dam to carry out desalination standard rough treatment. 500 shrimp fry per square meter were put in the temporary culture pond, and 1000 seedlings could be put in if there was oxygen-increasing equipment. Then, sea water essence or crude salt was added to the water of the temporary culture pond, and the salinity was adjusted to be similar to that in the seedling pond. At the time of seedling release, the difference of salinity in water should not exceed 3 ‰-5 ‰, the temperature difference should not exceed 3 ℃, and the PH value should be 7.8-8.6.

After 4 days of seedling release, about 3-5cm of water should be injected into the temporary pond every day to slowly reduce the salinity of the pond, while keeping the water depth in the pond at about 1m. Pay attention to adjust the PH value and water color in time. After half a month of desalination standard rough treatment, the salinity content in the temporary culture pond will be compared with that in the culture pond.

When the size of the shrimp fry in the temporary culture pond is above 2cm, stop feeding, dig several gaps in the dam of the temporary culture pond, communicate with the culture pond, and let the shrimp fry swim out on their own. The seedlings were fed on the same night when they entered the pond, and 4 days later. The first feeding amount is 5-10 grams per 10,000 tails, and the feeding times are 5-6 times a day, gradually increasing every day, increasing by 20% and 30% per day. The stocking density in the pond should be reasonable, about 100,000 tails per mu.

3. Water quality requirements

Penaeus vannamei is marine shrimp, so the salinity of the pond water of the culture pond can not exceed 5%, the PH value is between 7.5 and 9.0, and the daily change range can not exceed 0.5 units, the dissolved oxygen content is above 4mg/L, the nitrite ammonia content can not exceed 0.1mg/L, the ammonia nitrogen content can not exceed 0.02mg/L, and the hydrogen sulfide content at the bottom of the pond can not exceed 0.1mg/L.

Higher requirements for algae in the pond water, the most suitable water color is formed by green algae and diatoms tea brown or yellowish green, transparency is 25-40cm.