Every summer when white shrimp culture in South America enters the management stage of high temperature period, the density of shrimp cultured in the pond is large, the physiological function of shrimp is high, and the shrimp is in the peak period of growth; the amount of feed is large, the amount of residual baits and excrement in the pool is increasing, and the water pollution is worsened. , The transparency of water is reduced; Algae, bacteria and other organisms thrive, and the biomass is large. There are many factors such as thermocline and oxygen stratum stratification in the water body, easy to make the oxygen in the pond water produce oxygen deficiency and so on. In particular, when typhoons and heavy rains occur, water quality in shrimp aquaculture ponds often deteriorates, and flooding with ponds causes a large number of deaths of cultured shrimp. Diseases such as red body disease, white spot disease, and red leg disease are high, and water environment mutations make it easy for shrimp to emerge. Reactions that cause red body disease are more common. According to the above characteristics of high temperature and water quality, in order to ensure the healthy culture of white shrimp in South America, to survive the difficulties and obtain high yields and high yields, combined with the accumulation of aquaculture disease monitoring data for the past three years, the following high temperature seasonal aquaculture management points were proposed.
1 Timely water change, scientific oxygenation
Where conditions permit, according to changes in water quality, timely and appropriate replacement of new water, change the water in a small number of ways, avoid large-scale irrigation, and appropriate increase in water level, try to maintain at 1.5m or more, so that the lower and middle temperature can still Keep within 32°C. In the general shrimp farm, the daily water exchange capacity is 8% to 10% of the pool water, and if it is increased to 20%, the growth rate of the shrimp is significantly increased; the daily water exchange capacity is increased to 30%, and the growth valley of the shrimp in midsummer disappears. As the water temperature rises and the shrimp grows, the water depth must be continuously increased. Especially in the middle and later stages of the cultivation, the water level must be increased to 1.8m-2m, and the high temperature period should be maintained at more than 2.2m. For this reason, in the tide period, it is necessary to maintain the exchange of water every d; in the low tide and dry season, it is necessary to carry out mechanical drainage and irrigation, it is best to exchange water between 30% to 50%, to achieve the purpose of reducing the water temperature. When changing the water, it is best to prevent the intrusion of the fulminant virus of the shrimp. It is better to filter the water at the inlet with 80 mesh.
In summer, due to the high water temperature, stratification phenomena such as thermocline and oxygen leaching layer are prone to occur, resulting in the lack of oxygen in shrimp ponds. In view of this characteristic of high temperature pond waters, it is necessary to maintain the oxygen in the morning and at noon every day for several hours to eliminate them in time. Water stratification to avoid the formation of oxygen debt. Due to the changeable weather, we must pay attention to the weather forecast every day and make good precautions against thunderstorms and winds. We should promptly add water, turn on oxygen, or throw out particulate oxygen to prevent signs of hypoxia. Conditional ponds can be equipped with an aerator underneath, and can be used with an under-bed oxygenator at the bottom of the tube, or a pond without an aerator, and can use a water pump to agitate the lower water body. During the high temperature period, the on-site determination of the water quality of aquaculture ponds in Ninghai Changjie and other places revealed that most of the ponds had a significant oxygen layer. The dissolved oxygen in the bottom layer of the pond was less than 4 mg/L, and only 1.5 mg/L in some ponds. Oxygen status, which is one of the major causes of decreased food intake, slow growth, disease progression, and floating head death in white shrimp culture in summer.
2 Adjust water quality and improve bottoms
The ideal water color for the cultured Penaeus vannamei is yellow-green or yellow-brown formed by green algae or diatoms. Chlorophyte or diatom is a kind of benign biological community in the micro-ecological environment of ponds and has a net effect on water quality. At the middle and later stages of aquaculture, the general pond water color changes and the water color is deep, which is mainly due to the lack of magnesium ions required for the propagation of green algae or diatoms. Every 10 to 15 days, Quanhui Dianbai spills 210E-6-310E-6 concentration of calcium hydrogen phosphate once, and dolomite powder of 2010E-6 concentration once can regulate the balance of nutrient salts in the culture water environment and supplement calcium and magnesium in the water body. Phosphorus content. Generally every 3 ~ 5d Quanchiposa zeolite powder once, the amount of 10 ~ 15kg per mu, sunny morning, dissolved after the spill; every 7 ~ 10d, use once beneficial microorganisms. At present, commonly used biological agents are photosynthetic bacteria, EM crude, fish and shrimp auxin (CBS), live water treasure (Bacillus), etc., commonly used bottom modifier is zeolite powder, excellent net or (1 +1) bottom net , granular oxygen, etc., photosynthetic bacteria can be used together with zeolite powder, Bacillus should be used on a sunny morning, use should be activated at the same time aerator or oxygen. The suitable pH value of P. vannamei is 7.8-8.5. However, there was a peak of 9.2 in the middle and late breeding period. Therefore, special attention should be paid to the regulation of the pH value in the breeding process, which should not be too high, otherwise it will increase the toxicity of ammonia nitrogen and inhibit the growth of shrimp. For the pond with high pH (pH: 8.6-9.0), use "Greenway" (composite polybasic organic acid salt, dosage 110E-6-210E-6 concentration), acetic acid (110E-6-210E-6 concentration). Such as Quanchiposa, adjust the pH; for high pH (pH: greater than 9.0), low transparency, high algae density of the pond, first use "Greenway" 110E-6 ~ 210E-6 concentration, after 2h, Then use the composite ferrate cesium 0.1510E-6 ~ 0.310E-6 concentration Quanchiposa. If the sudden drop of heavy rain or continuous cloudy causes the pH value to drop below 7.5, then Quanchipi will throw lime 6-8kg per mu.
During the cultivation of Penaeus vannamei, the demand for dissolved oxygen in the water increases with the growth of shrimp, so the time for starting the aerator should be extended gradually. For intensive fish ponds and high-density, high-yield aquaculture ponds, When necessary, it needs to be turned on for 24 hours to ensure that the pool water-soluble oxygen is above 5mg/L, the dissolved oxygen in the bottom of the pond is above 3mg/L, the minimum is not less than 1.2mg/L, and the dissolved oxygen value fluctuates, which indicates that the organic matter in the water is too much. To adjust the color in time. Therefore, it is necessary to purchase a rapid water quality analyzer and monitor the pH, dissolved oxygen, ammonia and other changes of the pool water at any time to ensure that the shrimp is safe.
In the later period of culture, the transparency of pool water should be maintained at 35-60cm. If the transparency is less than 20cm, change the water, add water or apply zeolite powder or quicklime. If the transparency is too large, apply nitrogen fertilizer and phosphate fertilizer.
3 Feed high-quality feed and control feed volume
Penaeus vannamei feed should be fed with fresh, high-quality Penaeus vannamei full-rate feed. In summer, shrimps have large food intake, rapid digestion, and increased daily feeding rates. They should adopt a small number of meal feeding methods. Prawns have the habit of nocturnal emission, nocturnal activity is frequent, and the appetite is vigorous; during the daytime, the appetite is weakened. Therefore, bait is mainly fed before sunrise and after sunset, accounting for 70% to 80% in the morning and evening, 20% to 30% in the daytime, and try to avoid high temperatures. Daily feeding should be based on the weather, water quality, shrimp health and activity. Generally, it is based on the principle of checking the food baits without leaving residual baits. If you eat within 1 to 1.5 hours after feeding, it is better. When the weather is hot or there is thunderstorm, you can feed less or not, which can reduce the feed coefficient and reduce the water body. Pollution pressure.
4 Scientific disease prevention and rational drug use
During the high temperature season, the shrimps have poor feeding ability and the body's metabolic level is reduced. In addition, the deterioration of the water environment and the breeding of pathogenic organisms can easily cause shrimp disease. There are mainly diseases such as stress red body disease, bacterial red body disease, enteritis disease, white spot disease, fixed ciliate disease, muscle necrosis disease, dead bottom disease. Every 25 to 30 days to the detection of colleges and universities or research institutes to detect diseases such as 1 times, so that no disease prevention, early treatment and early control of disease. Once a disease or detected shrimp has been detected as carrying a virus or germ, control measures should be promptly taken. As far as possible to do regular water disinfection, the use of dibromohydantoin, bromochlorohydantoin, etc. is generally used for the prevention of water disinfection, the amount of 0.1510E-6 ~ 0.310E-6 concentration / time, interval 10d. The treatment of water disinfection can use complex povidone iodine (amount 0.210E-6 concentration / time), "water toxic net" (complex quaternary ammonium salt, iodine, dosage 0.1510E-6 ~ 0.310E-6 concentration / time), Sodium dichloroisocyanurate (dosage of 110E-6 concentration/time), chlorine dioxide (amount of 0.1510E-6 to 0.310E-6 concentration/time), etc., interval 5-7 days. When using disinfecting agents, aerators or oxygenating agents should be activated at the same time, and they should not be used simultaneously with microbial preparations; keep the pond water quality stable and fresh, and adopt multiple methods to increase dissolved oxygen in the water (mechanical oxygenation and chemical oxygenation, etc.) The water body is in an oxygen-rich state (DO>6mg/L), which reduces the etiology of shrimp virus disease; regular use of immune enhancer improves the shrimp's own immunity. Long-term addition of immune polysaccharides (1 to 3 calories in feed) can be added to the feed, and high-stabilized vitamin C (3 to 5 calories in feed) and allicin can be added to the feed during the high-temperature period. Add 2% of the amount of feed, add egg white package); can use regular liver and liver protection herbs, enhance shrimp disease resistance. During the middle and later stages of shrimp aquaculture, generally, 200 to 300 prawns are randomly sampled around the pond every 3 to 5 days to observe whether they are normal or not. In the case of sudden increase or decrease of feed in shrimp, when the climate abruptly changes during the following periods of heavy rain and windy winds, in the case of shrimp disease that can be induced after water intake or water exchange, it is necessary to use a rotary screen for sampling as soon as possible.
5 Prevent shrimp from floating, so as not to flood ponds
In the hot season, it is necessary to stick to the morning and the evening to inspect the ponds, observe the growth activities of the shrimps and the surviving of the bait, and determine the type and quantity of the bait on the day. Before midnight and before dawn, the oxygen in the shrimp pond is at its lowest point, which is the most dangerous time for the shrimp to suffer death from floating head, such as the discovery of prawns, white shrimp floating head, and the gathering of small trash fish to the pond edge (this is the symptom of shrimp floating). It is necessary to start the aerator or change the water in time.
The high temperature of the water can easily lead to algae growth (diatoms: the optimum temperature is 23 to 30°C, and over 30°C easily causes algae growth; green algae: the optimal water temperature is 25 to 33°C, and over 33°C easily causes algal blooms). Bare algae is prone to cause bad water and oxygen deficiency, which causes the shrimp to reduce the stress, weaken the vitality, reduce the immunity, and the virus is easy to invade and the disease is easily stained. In particular, attention should be paid to sudden drops of heavy rain when the surface temperature of the water falls sharply and the temperature at the bottom is still relatively high, resulting in convection of the upper and lower aquifers, bringing water and organic matter with low dissolved oxygen to the water surface, accelerating the decomposition of organic matter, consuming oxygen in the water, and generating large amounts of With harmful substances such as carbon dioxide, hydrogen sulfide, and ammonia, a large number of phytoplankton in the pond died, and the water quality changed from the original high-fertilizer water to severely deficient oxygen, and the water quality deteriorated seriously, resulting in serious floating heads of shrimps and a flooding phenomenon that caused a large number of deaths. Once it occurs, the following methods can be taken: 4 kg per acre with water and mix thoroughly Quanchiposa; each acre with 1kg alum plus appropriate amount of water and mix thoroughly to the whole pond spilled; per acre with lime 5kg dissolved into a slurry Quanchiposa; after 3d Bacteria Bacillus subtilis percolate into the bottom of the pond; open more aerators or spill oxygenation preparations to prevent shrimp hypoxia.
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