Comprehensive disease prevention for aquaculture in summer

To increase resistance and reduce the risk of disease in farmed aquatic animals, especially in hot summers or sudden rains, aquaculture farmers need to implement good environmental management measures to suit the ecological needs of the animals and to be stable throughout the farming season, specifically as follows:

1. Prevent organic pollution in ponds

- Determining the exact food ration and feeding many meals a day is a necessary measure to reduce organic waste in the pond by reducing the amount of excess food and food decomposed in the pond water environment.

- Regular use of microbial products can stabilize algae and reduce organic matter in the pond slowly but very effectively. On the other hand, it is necessary to limit the use of antibiotics and chemicals, because if used regularly, the drugs can destroy beneficial microorganisms at the bottom of the pond, reducing the process of converting suspended organic matter and settling at the bottom of the pond.

- Preventing pond bank erosion and preventing rainwater from carrying organic waste into the pond is also a necessary measure. Using tarpaulin to cover the pond bank also aims to achieve this purpose. The water source taken into the pond must be filtered, especially when farming in estuaries, where there is a large amount of alluvium in the water.

- Applying polyculture, rotational farming and integrated farming models can help farmers manage the environment appropriately and sustainably.

2. Transparency management

The clarity of aquaculture water mainly depends on the density of plankton in the pond. When the clarity is too low, it is often due to the plankton growing too thickly, causing the pH and DO indicators to fluctuate greatly, causing shock to the aquatic products in the pond. On the contrary, when the clarity is high, the oxygen content is often low and bottom algae are at risk of strong outbreaks, competing for space and oxygen at night, causing shock to shrimp and fish. The best clarity of water in a pond for black tiger shrimp farming is 30 - 40cm. To have suitable and stable clarity, farmers need to:

- Use organic, inorganic, and microbial fertilizers to color the water before stocking.

- Periodically use CaCO3 or CaMg(CO3)2 lime to stabilize pH and hardness in saltwater aquaculture ponds to ensure stable growth of plankton throughout the farming season.

- Use microbial preparations (EM) to regularly and fully supply nutrients and CO2 for stable algae growth.

- When the clarity is too low due to strong growth of plankton, it is necessary to change part of the water or turn off the aerator to force the algae into the corner of the pond in the direction of the wind, use formalin at a concentration of 4-10 ppm to kill some of the algae in that corner of the pond, then operate the water fan back to normal.

3. Salinity management

- In the pond, after prolonged heavy rains, salinity stratifies, so it is necessary to change the surface water and take bottom water to stabilize salinity, avoiding shock to farmed aquatic products.

- Use local freshwater sources to reduce salinity in aquaculture ponds during the dry season, when salinity is high, sometimes up to 50‰.

4. pH management

High or low pH of water not only adversely affects the health of farmed aquatic animals but also kills aquatic ecosystems in the pond, causes algae to die and negatively impacts the environment and health of aquatic animals. pH of pond water also affects the toxicity of NH3 and H2S gases to the life of farmed aquatic animals.

In shrimp ponds, when the pH is higher than the allowable limit, you can sprinkle sugar (Sucrose) into the pond to reduce the pH due to the fermentation of sugar by microorganisms. In an emergency, you can spray some types of organic acids into the pond to reduce the pH when necessary.

5. Management of Ammonia (NH3) gas

The presence of NH3 gas in the aquaculture system is completely detrimental to the life of livestock. It can inhibit the process of NH3 excretion and NH3 accumulation in the body leading to poisoning of livestock. Severe cases can cause death, mild cases can cause shock, increase the amount of NH3 in the blood, affecting the functioning of the circulatory, respiratory, hepatopancreas and nervous systems. To manage the NH3 content in the pond, avoid adverse effects on the health of aquaculture, it is necessary to take the following measures:

- Periodically use biological products in intensive ponds with long farming cycles to reduce excess nitrogen content in pond water.

- Stabilize pond water pH within the range of 7.5 - 8.5 (salt water) to inhibit the conversion between different forms of nitrogen.

- Some highly oxidizing disinfectants can be periodically used to remove toxic gases produced in the pond (Iodine, BKC, H2O2 ...)

When necessary and conditions permit, it is necessary to quickly replace pond water with new water source to urgently reduce NH3 content in the pond.

6. Hydrogen Sulfide (H2S) Gas Management

To avoid the phenomenon of shrimp and fish being shocked or dying due to H2S, in aquaculture there are some following measures:

- Increase water circulation and aeration so that H2S can escape.

- When raising shrimp and fish in mangrove forests, it is necessary to remove all waste and mud after each farming cycle and compact the pond bottom thoroughly.

- When there are signs of fish and shrimp being poisoned by H2S, you can change the water urgently to save the livestock, then find a way to eliminate the source of this toxic gas.

According to TTKNQG - LY