Animal Nutrition

The importance of water quality in shrimp farming

The importance of water quality in shrimp farming: parameters and control strategies

Shrimp farming is a profitable business. As a steadily rising market, especially in developed countries, shrimps have a high added value, being considered fancy foods.

Precisely for this reason, one of the biggest concerns of shrimp farmers is the quality of the product. Rapid growth and healthy development of crustaceans are essential to maintain the business profitable.

To do so, an essential factor is to guarantee the quality of the environment where the shrimps are raised, that is, the water of the tanks.

When water has poor quality, the animals are exposed to various types of physical, chemical and biological stresses, which will negatively impact the rates of growth, reproduction and survival of shrimp. In addition to favoring the appearance of diseases that often kill the entire group.

Therefore, it is necessary to understand the quality parameters to be controlled to ensure a healthy aquatic environment and favorable to the good development of the shrimps.

Water quality in shrimp farming: everything starts in the water abstraction

The process of water abstraction starts with a filtration for the removal of impurities and possible predators. This can be done with sand filters combined with a mesh bag.

Then, a water treatment process is also required to lower the concentrations of iron, ammonia, hydrogen sulfide, and carbon dioxide before the water is pumped to the breeding site.

It is further recommended that chlorine disinfection is performed at a concentration of 30 ppm for a period of 48 hours together with aeration (dissolved oxygen content of at least 4 mg/L), which helps dissipate chlorine and to decrease the levels of iron and ammonia in the water.

One should wait a period of 7 days before the stocking of the breeding site for all this water preparation.

Water quality parameters: understand the importance of it

The presence of pollutants, whether in the form of solid particles or gases, in the water of shrimp farms, should be monitored through toxicity testing.

This type of test analyzes the response of aquatic animals to the content of certain toxic substances such as ammonia, nitrite and nitrate. It is important to note that these substances will be tolerated at different levels depending on the species being raised.

The toxicity test will show the starting point in which the mentioned substances begin to cause stress in the shrimp.

According to studies found in the literature, the water quality parameters measured daily in shrimp farms are the level of dissolved oxygen, temperature and salinity. Once a week, the pH, ammonia and nitrate levels and turbidity are measured.

See more about each of these parameters:

Temperature: it has an influence on the metabolism of crustaceans. In addition, it controls the solubility of the dissolved gases in the water, the chemical reactions and the toxicity of the ammonia. It should be between 31 and 33 °C. If higher than that, there is a great risk of diseases development caused by Vibrios. When the water temperature reaches more than 34 °C, the amount of feed should be decreased, vitamin C added and aeration of the water increased.

Dissolved oxygen: the most critical parameter. If its level is too low, the growth of the shrimp will be slow. A minimum level of dissolved oxygen of 4 to 5 ppm is recommended.

Salinity: high levels of salinity reduce the level of dissolved oxygen. Therefore, the optimum concentration should be around 15 – 23 ppt.

pH: extreme pH rate causes stress in the shrimp, resulting in soft shell and low survival rate. The breeding water pH should be in the range of 7.5 to 8.5. If it is less than 7.5, it can be used CaCO3 in the water at a dose of 10 – 20 kg/1000 m³ to increase it. On the other hand, when higher than 8.5, it is possible to lower the pH with molasses at doses of 3 kg/1000 m³, combined with microbial products or vitamin C.

Ammonia: it is the main product of crustacean protein catabolism. Elevated levels of ammonia reduce the blood’s ability to carry oxygen. The non-ionized form of ammonia (NH+4) is characterized as the most toxic one. The recommended NH+4 levels should be around 0.1 mg/L, while the total ammonia content should not exceed 1 mg/L.

Nitrite: it is extremely toxic to shrimp and its presence above the allowed limit leads to the animal’s death. Its presence should be limited to between 0 and 0.5 mg/L.

Turbidity: it is the measurement of the loss of water transparency due to the presence of suspended particles. The optimum level of turbidity should be between 35 and 45 cm deep.

And how is it possible to keep the breeding water clean?

In breeding sites where the water is not renewed, it is inevitable that there will be accumulation of waste in the lower part of it. In such cases, it is necessary to avoid that this waste is scrambled, as water pollution would occur, leading to a decrease in quality.

To clean the debris that accumulate in the bottom of the breeding sites, the ideal is that, once a year, the water is drained to remove the residues.

In breeding sites where water is not renewed, there may be a high proliferation of plankton.

It is necessary to be careful, however, not to kill the planktons when the pH of the water is high, because when they decompose, toxic gases such as ammonia can be generated. Therefore, it is always important to monitor the pH of the water.

Conclusion

Controlling water quality is one of the main guidelines for making shrimp farming a profitable business as it has the potential to be.

For this, parameters such as pH, dissolved oxygen, temperature and level of toxic substances, among others, must be constantly monitored and, if it is proved that they are outside the allowed range, corrective actions must be taken.

Keeping water clean and with all parameters within the normal range is an essential step in shrimp farming that will have rapid growth and healthy development.

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