Key points of Management in the Middle and late stage of Shrimp

In the middle and later stage of shrimp ponds with a body length of 7-8 cm, due to the increase of feeding amount, shrimp excreta gradually accumulated, coupled with the joint effects of dead algae, residual bait, oxidation and decomposition of organic matter at the bottom of the pond, great changes have taken place in pond water quality, sediment, microorganisms and so on.

The specific changes of water environment and prawns in the middle and later stages were as follows: ph gradually increased, water color changed from clear green and yellowish green to brown, tea green, transparency decreased, turbidity increased; the bottom of the pond was blackened and smelly, and the number and species of harmful microorganisms increased. The tail fan and tentacles of shrimp are red, and even the phenomenon of rotten tail and broken beard appears. In some shrimp ponds, there are slow growth, weak physique, poor sensitivity, failed shelling, parasitism of ciliates, lack of food, enteritis and yellow Gill disease. there are also some shrimp ponds, floating heads, soft shells, red legs, rotten eyes, carapace ulcers and other symptoms. Based on the experience of shrimp culture for many years, the author summarized the key points of management in the middle and later stage of shrimp culture.

Stabilize water color and reduce water turbidity. The reason for the change of pond water color in the middle and later stage of shrimp culture is mainly due to the lack of magnesium ions needed for the reproduction and growth of green algae. You can sprinkle dolomite powder 20-25 × 10-6 and use it once every 7-10 days to stabilize the water color. In order to reduce the turbidity of the water body, photosynthetic bacteria 10-15 × 10-6 were used to pour wine in the whole pond and used once every 7 days. At the same time, the aquaculture water body should be disinfected regularly and the whole pond should be disinfected twice every 10-15 days. For the first time, the whole pool of dibromohydantoin disinfectant was sprinkled with dibromohydantoin disinfectant in the morning according to the treatment concentration, and the second time it was sprinkled with organic iodine and quaternary amine salt 0.2 × 10 ~ (- 6) in the second morning. if the turbidity of suspended organic matter in water was high, the concentration of disinfectant could be increased appropriately.

Adjust the balance of nutrients in aquaculture water environment and supplement the contents of calcium, magnesium and phosphorus in water. Sprinkle 2-3 × 10-6 calcium hydrogen phosphate and 20 × 10-6 dolomite powder in the whole pool every 10-15 days.

Improve the environment of pond bottom and control ph value. Every 10-15 days sprinkle beneficial microbial preparation 0.3 × 10-6, or every 5 days sprinkle zeolite powder as the main raw material of the substrate improver once, each time the dosage is 10-15 × 10-6, if the sudden rainstorm or continuous cloudy days cause the ph value to drop below 7.5, then the whole pool sprinkles quicklime 5-8 kg per 667 square meters.

Reasonably add water and change water. The amount of water exchange is controlled at about 10 cm on the first day, and can be gradually increased to 20 cm, 30 cm and 50 cm on the second, third and fourth day. In this way, it can not only improve the water quality, but also promote the shelling growth of prawns. If the water level is insufficient, the water level should be deepened in time and oxygen-increasing equipment should be purchased in order to increase the production and scale of aquaculture. Facts have proved that the higher the output of shrimp culture is, the larger the specification is, the more obvious the economic benefit is.

Feed reasonably and reduce the feed coefficient. The material is usually fed four times a day. The feeding time in the morning must be arranged 1-2 hours after sunrise, and it is best when the dissolved oxygen in the water reaches more than 4 mg per liter. Feed once at 6-hour intervals. Control the amount of feed, generally shrimp in 45 minutes to 1 hour to finish the feed is appropriate.

Improve the immune ability and anti-stress ability of shrimp. The feed was supplemented with immune polysaccharides 1 ‰, biological enzyme active additives 2 ‰, vitamin C1-2 ‰, vitamin b 10.5 ‰, 2 meals per day for 2 days a week, and allicin 0.5 ‰-1 ‰ in high temperature season.

Check the health status of prawns regularly. If it is found that prawns eat less bait or sick shrimp floating head to the side, the general shrimp pond shrimp disease infection rate has reached more than 20%. Therefore, diseased shrimps that are found to have infected diseases but eat normally and do not float their heads to the side should be treated in time. In the middle and later stages of shrimp culture, 200-300 prawns must be randomly sampled around the pond every 3-5 days to see if it is normal. In the case of shrimp disease can be induced by sudden increase or reduction of shrimp, such as heavy rain and wind in the sudden climate change period, and after water intake and water change, spin net sampling should be used as soon as possible.