The "red body" of Penaeus vannamei is a "symptom" after the disease, especially after the virus or bacterial disease of Penaeus vannamei, or the stress response of Penaeus vannamei to its changes after the change of water environment factors, which generally shows that the tentacles and appendages are red, and then develops into the phenomenon that the head breastplate and tail fan turn red, or even the whole shrimp body turns red. At present, the symptoms of red body generally have the following three phenomena:
First, emphasize "red body"
1. When various physical and chemical factors in the water environment suddenly change (especially water temperature, salinity and PH value), the tentacles of white shrimp turn red, and the tip of tail fan turns red, or sometimes the tentacles, tail fan and even appendages turn red due to artificial fishing and pesticide application. This is a common phenomenon that white shrimp adapts to its own changes. We call it: pressure red body. This phenomenon will disappear in a short time with the stability of water factors. However, it is worth noting that during the stress period, the disease resistance of white shrimp drops sharply, and it is easily attacked by bacteria, viruses or enemy organisms, making it secondary to bacterial and viral diseases.
2. Stress red blood cells can occur in the whole reproductive period. It often happens after sudden temperature change, heavy rain, application of pesticides and a large number of water changes. It usually happens in hot and rainy summer.
3, stress red body:
(1) keep the water body relatively stable in hot and rainy summer, and biological agents such as Bacillus concentrated and stachys easily. It should be used to keep the water body transparent. After the rainstorm, the weather changed suddenly and the water quality changed little.
(2) Immediately after the rainstorm, start the aerator to break the phenomenon of water stratification, and use quicklime and double-effect bottom net to prevent the water body from mutating due to the rainstorm.
(3) The amount of water discharged and exchanged should not be too large (especially the speed of adding water should not be too fast), and it is best not to exceed 10% of the total amount at a time. Meanwhile, pay attention to the changes of water temperature, salinity and PH value.
(4) After various physical and chemical factors change, drugs should be used appropriately to prevent the occurrence of diseases, but the drugs selected should not be too irritating, and some mild and non-irritating drugs, such as granular zinc bromide, should be selected.
(5) Probiotics, concentrated Bacillus, synbiotics and other biological agents are commonly used in aquaculture water, which can not only degrade ammonia nitrogen in water and adjust water quality, but also indirectly supplement the deficiency of various trace elements in white shrimp and improve the disease resistance of the body. At the same time, special VC for aquatic products, Yikang and Shangganning are added. Adding it to feed can improve the immune ability of the body and enhance its adaptability to the environment.
Second, the red blood cell group of Vibrio parahaemolyticus.
1, this disease is mainly manifested as red appendages, especially swimming feet, which is also known as "red leg disease" customarily. The activity of sick shrimp is weakened. At the edge of the pool, the water surface flows slowly or sinks, sometimes rotating or swimming vertically, resulting in slow response, loss of appetite or stopping eating. The diseased shrimp has yellowish gills, hard shell, no obvious variation of hepatopancreas, no symptoms of dark spots on the body, thinner hemolymph, fewer blood cells, and slow or no coagulation.
2. The disease occurs in shrimp culture areas all over the country, with a high incidence rate and a mortality rate of over 90%. This disease mostly occurs in the high temperature season after July, especially in ponds where shrimps are raised all the year round. Pools with incomplete dredging and poor disinfection are prone to occur. Some farmers unilaterally pursue yield per mu, and the stocking density is too high, which greatly increases the incidence of the disease. According to the author's understanding, more than 85% of the polycythemia of Penaeus vannamei is Vibrio parahaemolyticus.
The occurrence of this disease will also be affected by various physical and chemical factors. When the temperature is relatively high and changeable, there is more seasonal rainfall, and various physical and chemical factors in the water change frequently, the probability of the disease is high, which is why the disease often occurs after July.
3, prevention and control measures
(1) Clean the pond thoroughly before stocking. In the high temperature and rainy season, 0.5ppm of concentrated Bacillus or 0.5ppm of probiotics are regularly applied to the aquaculture water, and 0. 10- 15 ppm of aquatic pesticides or 0.1-0. 15ppm of PV mycotoxin are sprayed in the whole pond every15 days.
(2) Suitable for stocking and scientific feeding. Pay attention to patrol the pond in the popular season to observe the activity, feeding and body color of prawns.
(3) When the water temperature and water quality change greatly after the rainstorm, quicklime or granular zinc bromide should be properly used to maintain the stability of the water body, so as to reduce the stress reaction of prawns.
(4) After the onset, the whole pool is sprayed with aquatic toxin with the dosage of 0.2ppm (after spraying, the aerator is started 1-2 hours), and then 0.2ppm of Toxoplasma PV or 0.3ppm of Bikang are sprayed on the next day, and 0.4-0.5ppm of Bacillus or 0.4ppm of Synbiotics are sprayed on the whole pool three days later. At the same time of external use, oral bait: fluoxetine 1.5g+Vc2g+ Yikang 5g/kg, feeding for 5-7 days or until the condition improves.
Third, viral red blood cells.
1 Also known as Taula syndrome, it is mainly characterized by red beard and red tail of sick shrimp, especially red tail fan, so it is also called "red tail disease". The body color turns to tea red, and the sick shrimp does not eat or eat less, and flows slowly on the water surface, and dies after being fished out of the water surface. The crustacean of the sick shrimp becomes soft and easily separated from the muscle. A long-lasting disease is that crustaceans have irregular black spots, basically.
2. The occurrence of viral polycythemia is greatly influenced by the change of water environment, which generally occurs within 1-2 days after the rapid change of water environment. When the water temperature is 26-28℃, the size of shrimp is generally 6-9cm, the water color of diseased shrimp ponds is generally strong, the transparency is generally within 20cm, the PH value is higher than 9.0, and the ammonia nitrogen is above 0.5ppm.
3, prevention and control measures
(1) Before stocking, the pond should be thoroughly cleaned by comprehensive cleaning method. During the whole culture stage, especially after white shrimp culture 1 month, 0.3ppm of probiotics, 0.3-0.4ppm of concentrated Bacillus or 0.2-0.3ppm of synbiotics should be sprayed on the whole pond regularly to improve the aquatic environment of the shrimp pond, and at the same time, every 15 days.
(2) Strengthen the virus detection of the strain, use gene chip and PCR technology to detect the virus carried by the strain, and cut off the virus from the source and bring it into the culture environment.
(3) In the popular season, sprinkle 0.25ppm of hydrocortisone or 0.2ppm of chlorpromazine or 0.2ppm of granular zinc bromide in the pool every half month.
(4) After the onset of the disease, spray 0.2ppm hydrocortisone in the whole pool first, the next day 1 time (pay attention to start the aerator), and then spray 0.4ppm concentrated Bacillus, 0.5ppm probiotics or 0.3ppm synbiotics three days later. While disinfecting and improving the water quality, feed bait: add 2 g of shrimp poison buster+5g of Yikang+5 g of VCG+3g of Gansuning or 3 g of Kangdujia+5 g of Yikang+2 g of VCG+5 g of Shangganning to each kilogram of feed, and feed continuously for 5-7 days or until the disease is cured.