Second, strict feeding Because the feed coefficient of Penaeus vannamei is low, it is generally 1.5-2.0, so it is not appropriate to feed it too much. If the daily feeding amount is 150 g/ 10,000 pieces without considering the basic bait (red worms) in the pond before the shrimp grows less than 2 cm, the feeding amount will gradually increase with the growth of the shrimp at any time, and the standard is to eat it all within 2 hours after feeding. Feeding management should be relatively reasonable, not only to eat well, but also to take into account the feeding environment and save costs. Generally, we should insist on: 1. Feeding frequency is reduced (not less than 4 times a day); 2. Feed more after the evening and before the morning; 3. When the water temperature is higher than 32℃, feed less when the water quality becomes worse; 4. Feed less prawns on the day of molting, and feed more prawns 1 day after molting; 5. Feed more competitive creatures (tadpoles) in the pond (this problem is more common this year). The amount and time of feeding should be flexible. Generally, there are more basic bait in the pond at the initial stage of breeding, so you can feed less. In the medium term, high-quality special feed for prawns should be selected; In order to promote the later growth, some crushed and cleaned fresh snails should be fed in Wujiang area to improve the problem of thin shell and light color in the process of light culture of seawater shrimp.
Third, timely oxygenation For Litopenaeus vannamei, the requirement for dissolved oxygen is high, and the general breeding requirement is 3-5 mg/L, so special attention should be paid to the problem of oxygenation. Therefore, we advocate that the aerator should be started after the prawn grows to 3cm, and the start-up time should be gradually increased from the initial 2 hours a day. After the prawn grows to 6cm, it should be started at least 10 hour every day, especially at noon on sunny days. Because our city is a freshwater aquaculture, generally speaking, under the condition that the water quality of pond water is not very bad, we should try not to change water or change water less, strengthen feeding management, adjust photosynthetic bacteria and extend the start-up time of aerator, which not only improves the water quality, but also helps to enhance the vitality and survival rate of Penaeus vannamei, which was well verified in East Taihu Lake last year. Of course, it is necessary to equip every 5 mu with a 3KW aerator. In addition, in order to ensure the color of Penaeus vannamei and improve the survival rate of transportation, it is best to apply some salt and adjust the salinity in the later stage.
Fourth, disease prevention Penaeus vannamei (especially Brazilian species) has strong disease resistance, but it does not mean that it is not sick. Viral, bacterial and other nutritional and fungal diseases should be actively prevented and treated in time. Such as routine rotten tail, black cheeks, brown spots, red legs and so on. , as long as the use of universal sterilization disinfectant. The emphasis here is on viral diseases, the main symptoms of which are emaciation, shell softening and dark color of sick shrimp; The stomach is not full, the activity is poor, the attachments increase, and obvious white spots appear on the yellow cheeks, swollen cheeks and head and breastplate. Shrimp may not get sick after being infected with virus, but environmental pressure can induce virus, and primary infection of bacteria can also cause virus infection. At present, there is no specific method for shrimp virus, but the vertical transmission is cut off by freshwater culture, which is an important way for virus transmission, greatly reducing the incidence rate and giving priority to prevention.