Various discussions regarding shrimp farms cannot disregard the importance of water quality management. Good quality water is needed as a medium to sustain shrimp life and growth. Having production targets makes it even more crucial for farmers to maintain a stable water quality.
Among multiple existing water quality parameters, four physical parameters are essential for shrimp. Temperature, DO, salinity, and pH reflect whether shrimp pond conditions are well or disruptive towards cultivation. It is even recommended to measure these parameters everyday.
Why these four parameters in particular? Should they really be measured everyday? And can other parameters be neglected? Learn more in the following article.
Temperature affects growth, survival rate (SR), oxygen consumption, molting cycle, and shrimp immunity. It is a determining factor of the rate of biochemical reactions. The recommended temperature for vannamei shrimp is 28-32°C.
What happens if the temperature is too low? Temperatures below 26°C will slow down shrimp metabolism and decrease appetite. Shrimp immunity will also be affected, making shrimp more susceptible to diseases. Clinical symptoms of shrimp disease emerge especially during long periods of rain.
What happens if the temperature is too high? Metabolism will speed up and appetite will increase, causing FCR to increase. Farmers will need to add feed ratio, but the feed will not be much absorbed, as it is used for metabolism and increased activity due to higher temperatures. Moreover, sensitivity to toxins produced by blue-green algae (BGA) will also increase.
Temperature parameters are affected by farm location and the weather around it. Areas with high rain intensity will have lower water temperature. While we cannot control weather factors, we can take other measures such as regularly checking the temperature. To anticipate significant changes in temperature, always prepare windmills or water replacement.
Dissolved oxygen (DO) plays an important role in the respiration of aquatic organisms (shrimp, planktons, microorganisms) and is affected by the weather, paddle wheels, plankton population, and metabolism of microorganisms. The ideal DO for shrimp farms is no less than 4 ppm.
What happens if the DO is too low? DO levels below 2.5 ppm cause shrimp mortality. Below 4 ppm, growth will slow down, while appetite and feed efficiency will decrease. One of the signs of a drop in DO is the appearance of shrimp swimming to the surface.
What happens if the DO is too high? There is no serious impact, but keep in mind that DO stability needs to be maintained as it can be high during the day but low during the night.
A low DO needs to be looked out for as it is caused by a high amount of decomposer microorganisms in the pond sediment. Oxygen is required for biological processes that involve bacteria such as the nitrogen, phosphate, and carbon cycles. A higher shrimp biomass will cause DO to decrease, as the ‘house’ is too crowded. This happens especially at night, when phytoplanktons do not produce oxygen. Most oxygen in the pond is produced by them, but the supply won’t suffice for intensive and super-intensive farms. Windmills or aerators are thus needed to boost oxygen supply, because phytoplanktons also use up oxygen during the night for respiration.
A low DO can be mitigated by removing dead plankton, siphoning to reduce sediment build up, or application of probiotics. Increasing DO concentration can also be done through the addition of windmills. Aeration through windmills can increase DO and reduce excess CO₂ by diffusing it back to the atmosphere.
Salinity can be defined as the level of chloride ions in water. Vannamei shrimp can adapt to a wide range of salinity, from 5 to 40 ppt, however the most ideal range is 15-30 ppt. They can also adapt to gradual decrease in salinity, but fluctuations more than 5 ppt can cause stress.
What happens if the salinity is too high? More energy is required for osmoregulation, increasing metabolism in shrimp and the required energy source. Shrimp growth will slow down, increasing FCR and making shrimp more susceptible to diseases.
What happens if the salinity is too low? Oxygen levels will decrease, the water will be murkier, and planktons will die. If the decrease is caused by dilution due to rainwater, there will be a lack of minerals, which affects molting in shrimp.
The weather is one of the factors that affect salinity fluctuations. Salinity tends to increase during hotter months, so measures can be done to ensure the cultivation water has lower salinity. Water reduces salinity as rainwater has less salt and has a lower pH. During heavy rains, the surface water can be removed, as rainwater is less dense and tends to stay on the surface.
Salinity can be adjusted by replacing water as required to regulate salinity by getting water from the sea or diluting it with fresh water.
pH affects chemical reactions in the pond. It also affects the toxicity of toxic compounds (ammonia and hydrogen sulfide). pH needs to be maintained at a stable level to prevent it from affecting shrimp metabolism and physiological conditions. The most ideal pH for shrimp farms is 7.8-8.5.
What happens if the pH is too low? Growth will slow down, appetite will decrease, and shrimp will be more susceptible to diseases and stress.
What happens if the pH is too high? pH above 10 increases the toxicity of toxic compounds (compounds from BGA, free ammonia, bacteria). Higher pH speeds up metabolism, increasing ammonia levels, which may cause shrimp mortality.
High pH can be caused by high feed input and phytoplankton density. pH tends to increase in the day as a result of photosynthetic activity of phytoplanktons which use CO₂ from the water to produce oxygen. It then decreases at night due to respiration and CO₂ production by all organisms, including phytoplanktons. High pH can be treated by increasing the alkalinity through adding lime to increase the water’s buffering capacity or by decreasing phytoplankton density.
pH fluctuations will be lessened with good alkalinity levels and buffering capacity. pH fluctuations during the day should not exceed 0.5, as stress caused by high fluctuations decreases shrimp appetite, causing slowed growth and increased risk of diseases.
These four crucial parameters need to be measured regularly. Your next step is to record the daily trends or fluctuations between the morning and evening. This process is made easier with JALA Baruno. With only IDR 3 million, you can have your own JALA Baruno. Get more information here.
Measuring these water quality variables are critical as part of water quality management to make the best decisions. Analyzing and interpreting water quality data is needed for an efficient cultivation. By monitoring water quality daily, you can avoid and anticipate problems with your shrimp farm, especially for parameters which fluctuate easily.
Measurements need to be taken daily, such as in the morning (5-6 am) and afternoon (12-2 pm). In the morning, DO and pH are at their lowest levels while CO₂ levels are at their highest. 12-2 pm is when phytoplanktons photosynthesize the most, causing DO and pH to be at their highest.
Many factors play a part in creating a successful shrimp cultivation, not just water quality management, as there are other aspects such as feed management. In water quality management itself, there are other important parameters to be measured as the four parameters discussed also affect other parameters.
Some water variables that affect one another are temperature, salinity, CO₂ levels, DO, salinity, pH, phytoplankton, alkalinity, organic matter, ammonia, nitrite, nitrate, and total bacteria. As the shrimp farm is an ecosystem, every factor plays a role and has a direct or indirect impact towards cultivation success.
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