The main hazards of cyanobacteria in penaeuscus culture ponds of Penaeus vannamei in South America and the feasibility of treating cyanobacteria

The main hazards of cyanobacteria in penaeuscus culture ponds of Penaeus vannamei in South America and the feasibility of treating cyanobacteria

Since the beginning of summer, the South American white shrimp farming industry has entered the breeding stage of high temperature, high bait, high excretion, high oxygen debt, low air pressure and other harsh environments, and in the continuous high temperature breeding environment, shrimp farming ponds are very easy to breed cyanobacteria, and even flood.

Cyanobacteria, also known as cyanobacteria, are a type of prokaryotes that contain chlorophyll and have photosynthetic properties, which are customarily called cyanobacteria in the farming community. Cyanobacteria is a widely distributed, adaptable algae, with the continuous expansion of the scale of national Penaeus monodon farming, the degree of intensification continues to increase, the negative impact of cyanobacteria on penaeus monodon farming is also becoming more and more apparent, cyanobacterial blooms after the occurrence of haphalio shrimp farming and production of accidents occur from time to time.

First, the causes of cyanobacteria

1. Eutrophication of water bodies. Due to the relative concentration of Penaeus vannamei culture area in South America, the breeding density is getting larger and larger, and after excessive bait, the excreta of shrimp accumulates too much, and the accumulation of years and months makes the aquaculture water rich in organic matter, and the water body is eutrophicated.

2. Suitable living environment for cyanobacteria such as microcysticus: from July to September, the temperature in central China, east China, south China and other places is generally 25 to 38 °C, and the pH value of penaeus monocysian culture ponds is generally between 8.0 and 9.5, and the organic matter-rich breeding ponds are most prone to cyanobacterial blooms at this time.

3. A large amount of bait has caused a serious imbalance in the proportion of nitrogen and phosphorus in the cultured water, which is also one of the important reasons for the breeding of cyanobacteria.

Second, the main harm of cyanobacteria

1. Cyanobacteria have strong phototropism, generally live in the most surface layer of water bodies, and have a very strong ability to absorb nutrients. The main harm of cyanobacteria is that once the cyanobacteria multiply in large numbers, it will lead to other dominant algae such as green algae, diatoms, etc. can not reproduce, and make the water body always take cyanobacteria as the dominant population, which makes the water source below the surface of the aquaculture water body often clear, the purification ability of the water body is very weak, and the bottom of the pond is easy to smell.

2. Once cyanobacterial water is formed, it will produce algal toxins, which have a strong toxic effect on the liver pancreas and intestines of Penaeus vannamei, often causing red liver or yellow liver and enteritis. Moreover, the accelerated consumption of dissolved oxygen in water after the proliferation and death of microcystic algae, management negligence, will form a devastating pond death. At the same time, microcystis will produce a soil flavor, which will also make farmed shrimp produce an earthy smell, affecting the commercial value of adult shrimp.

3. Cyanobacteria has a strong phosphorus collection effect, so once cyanobacterial blooms are formed, it is difficult for other single-celled algae and zooplankton to survive, and the ponds that form cyanobacterial blooms generally have high nitrite nitrogen content, which is very easy to induce farmed shrimp to suffer from bacterial diseases.

4. The generation of cyanobacterial blooms is generally related to factors such as high organic load, high nitrogen content, high pH value, high temperature and imbalance of algae nutrient salts in water bodies, and more often related to the imbalance of carbon, nitrogen and phosphorus under pond culture conditions, and in a few cases, it is also related to the lack of medium or trace elements.

Third, the traditional method of dealing with cyanobacterial outbreaks

1. Sprinkle algae killers along the edge of the pool: generally chlorine-containing preparations or copper preparations such as "copper sulfate" and complexed copper. This method has a certain effect, but the disadvantage is that the stimulation of Penaeus vannamei is great, especially the copper preparation will inhibit the growth of shrimp; in addition, once the dosage is too large, it is easy to cause inverted algae, and the toxins produced by the decomposition of cyanobacteria after a large number of deaths will further aggravate the harm to the cultivation of Penaeus vannamei, which is easy to cause accidents.

2. Sprinkle products with "erythromycin thiocyanate soluble powder" and similar ingredients. On the one hand, at this stage, erythromycin is a banned drug, it is strictly forbidden to use in aquatic products, more importantly, erythromycin is a bacteriostatic antibiotic, which is easy to produce bacterial resistance, inhibiting the disappearance of the drug effect for one or two days after the cyanobacteria return to growth, which makes it costly and can not play much effect.

3. Cyanobacteria can die by changing the water a lot. Due to the poor ability of cyanobacteria to adapt to the new environment, once the water environment suddenly changes, causing discomfort, it will cause a large number of deaths and form inverted algae. The disadvantage of this method is that the sudden change of physical and chemical indicators in the aquaculture water body will also cause an emergency response to Penaeus vannamei in South American, resulting in a decrease in the immunity of the shrimp, and abnormal molting, or infection with various diseases during molting.

4. South China can be in the shrimp breeding pond to raise an appropriate amount of unisexual tilapia, central China, East China and other regions of freshwater aquaculture Penaeus vannamei can be appropriately raised silver carp, the use of tilapia to eat part of the cyanobacteria and diseased shrimp, the use of silver carp to control the number of branches, is conducive to the normal growth of algae, the control of cyanobacteria plays a certain effect.

Fourth, the feasibility of treating cyanobacteria at this stage

In the process of pond culture, the occurrence and development of cyanobacterial blooms are mainly controlled by regulating the nutrient salt balance of single-celled algae, accelerating nitrogen circulation, and promoting the growth and reproduction of other algae. Using the principle of "promoting nitrogen with phosphorus", sprinkling "calcium superphosphate" or "potassium dihydrogen phosphate" in the whole tank, combined with the use of "Bacillus", if necessary, using the principle of "carbon promoting nitrogen", with the use of "polyorganic acids", and as appropriate, supplement potassium, calcium, sodium, magnesium, phosphorus, manganese, iron, zinc, copper and other medium elements and trace elements, at the same time can be used in the downwind area of the breeding pond using "copper sulfate" and "ferrous sulfate" mixture (5: 3) for killing, you can also sprinkle "polyacrylamide" and "polyaluminum chloride" in the whole pool for killing, you can also sprinkle "polyacrylamide" and "polyaluminum chloride" in the whole pool. Flocculants such as "polymeric iron sulfate" and "potassium aluminum sulfate dodecahydrate" precipitate cyanobacteria, and then use granular strong oxidation substances such as "potassium persulfate" and "potassium perferrate" to oxidize and decompose the precipitated cyanobacteria. Here's how.

1. On the first day, choose to drain part of the pond water (preferably at the downwind outlet) at noon on a sunny day, quickly use the "benzalamine solution" into the pool to kill the cyanobacteria, and then increase the water level to the original water depth at night, depending on the death of the cyanobacteria, consider reusing the "benzalabroamine solution" as appropriate, and the floating debris after the cyanobacteria is killed should be fished out of the pond as much as possible.

2. The next day first use "potassium persulfate", after 2 to 4 hours after the use of "bacillus" + "polyorganic acids" + "amino acid fertilizer paste" the whole pool sprinkling, not only can decompose the toxins produced by cyanobacteria after death, but also for diatoms, green algae to become the dominant population of the pond again, otherwise even if the cyanobacteria is killed by drugs after a part of the strong reproductive ability of cyanobacteria will soon become the dominant population.

Treatment of cyanobacteria will cause stress on farmed shrimp, the more cyanobacteria the greater the stress, it is best to detect early and deal with it; abnormally elevated pH is the main feature of cyanobacteria outbreaks, and early detection and early treatment after mastering this feature can effectively solve the problem of cyanobacteria in the breeding pond.