Sludge management is of utmost importance in shrimp farming due to the potential harm caused by hydrogen sulfide present in it. Hydrogen sulfide is popularly called a silent killer
It should be maintained below 0.03 ppm to ensure the safety of the shrimp.
If the hydrogen sulfide concentration exceeds this threshold, it becomes hazardous.
In this video, I will explain the negative impacts of hydrogen sulfide on shrimp and how it is produced in ponds. Additionally, I will discuss strategies to manage sludge and minimize the impact of hydrogen sulfide on shrimp
Prolonged exposure of shrimps to hydrogen sulfide can lead to:
Less feeding, especially in the morning, as the dissolved oxygen and pH will be low. Hydrogen sulfide is more toxic at low pH.
Facilitates the release of phosphate into the water, promoting algae bloom.
Destruction of nitrifying bacteria, leading to an increase in ammonia and nitrite levels in the water, causing stress to the shrimp.
Blocks uptake of oxygen. Prolonged exposure leads to Black gills, which interfere with the shrimp's respiratory functions, causing hypoxia.
Blackening of mouthparts and shrimp legs due to direct contact with sludge, resulting in a burnt-like appearance.
Harvested shrimp suffering from these conditions may fetch a lower price in the market.
Hydrogen sulfide can cause tissue corrosiveness, irritating soft tissues in the gills, gut, stomach walls, and hepatopancreas. This can lead to a loss of appetite, and shrimp may lose their chemo-sensing abilities, resorting to sludge ingestion.
There are reports of loose shell formation due to prolonged exposure to hydrogen sulfide.
Following molting, where shrimps may stay at the pond bottom after molting, and if hydrogen sulfide levels are high, they may die.
Why is hydrogen sulfide more toxic?
To appreciate the unique properties of hydrogen sulfide (H2S), perform the following steps:
Touch the sludge with your hand and smell it. Note the distinct odor similar to rotten eggs.
Wash your hands with clean water.
After half an hour, smell your hands again. You will likely perceive the same smell, indicating that hydrogen sulfide can easily penetrate tissues, making it much more harmful than ammonia or nitrite.
Hydrogen sulfide has a high degree of lipid solubility, enabling it to pass easily through cell membranes, where it can interfere with cell functions.
In fish, hydrogen sulfide binds with hemoglobin to form sulphaemoglobin, which is an inefficient oxygen carrier, leading to oxygen transport issues.
In shrimp, hydrogen sulfide interferes with cytochrome reoxidation during respiration, making it toxic to these aquatic organisms.
When present in water, H2S readily reacts with carbon dioxide molecules to form sulfuric acid, reducing the pH. At low pH levels, hydrogen sulfide becomes more toxic.
How is it produced?
The main reason for its increase is the poor water color or plankton crash, at the start of the culture, which allows sunlight to penetrate the pond's bottom, leading to the development of benthic algae, commonly referred to as lablab. As the benthic algae die off, it accumulates in the corners of the pond. During the decomposition of lablab, hydrogen sulfide is produced, posing a significant risk to the shrimp population.
During culture, hydrogen sulfide is produced from leftover feed, shrimp fecal matter, and dead plankton during anaerobic decomposition.
The circular motion created by aerators tends to cause sludge accumulation in the middle part of the pond. If you enter the pond, you can notice bubbles coming from the bottom, and you'll also be able to smell the odor associated with it
to manage the sludge in the pond, it is essential to pump it out regularly, either through a central drain or using a sludge motor.
If it is not possible, farmers can opt for good soil probiotics like Sulphox as a preventive treatment, which should be applied regularly, at least once a week, to control hydrogen sulfide levels. In severe cases leading to shrimp mortality, a combination of Sulphox and a sediment oxidizer called Aquakem has shown positive results.
Sulphox is meticulously manufactured at our state-of-the-art fermentation unit by highly skilled aquatic microbiology professionals. It comprises three distinct bacterial species known for their exceptional adaptability:
Thiobacillus denitrificans
Paracoccus pantotrophus
Rhodococcus ruber
These bacteria exhibit remarkable capabilities to thrive across diverse salinity, pH, and oxygen conditions.
As a result of its remarkably versatile triple-action formula, Sulphox has garnered significant popularity within the Indian aquaculture industry.
In addition to using Sulphox, increasing aeration and applying lime to raise the pH of the water can further help manage hydrogen sulfide toxicity. Strict feeding also helps a lot
