Stress in Shrimp Farming —
The Hidden Trigger Behind Disease Outbreaks
Shrimp living in an unstable environment will experience a decline in immune response. This condition leads to a reduction in total hemocytes and decreased production of defense molecules such as lysozyme enzymes, phenoloxidase, and antimicrobial peptides. As a result, stressed shrimp become more vulnerable to pathogen infections
Minimize stress
Boost immunity
Prevent disease
Behind Clear Water
The Role of Autotroph and Heterotroph Bacteria
Optimal water quality in shrimp farming depends on more than routine parameter control. It requires a balanced microbial ecosystem. Two key functional groups, autotrophic and heterotrophic bacteria — play complementary roles in maintaining a stable and healthy pond environment. Disrupting this balance can increase shrimp stress, compromise immune function, and elevate the risk of disease outbreaks.
Autotrophic Bacteria
— Supporting Nitrogen Cycling and Oxygenation
Chemoautotrophs (e.g., Nitrosomonas, Nitrobacter) oxidize ammonia (NH₃) into nitrite (NO₂⁻) and subsequently into nitrate (NO₃⁻), reducing toxicity and helping to maintain water quality.
Photoautotrophs (e.g., cyanobacteria such as Oscillatoria and Anabaena) produce oxygen via photosynthesis, supporting stable dissolved oxygen levels in the water.
Heterotrophic Bacteria
— Degrading Organic Matter and Controlling Pathogens
Probiotic Bacillus species (e.g., B. subtilis, B. licheniformis) decompose organic waste, produce digestive enzymes, and inhibit pathogens through the production of antimicrobial compounds.
Pseudomonas species degrade organic material and produce biosurfactants, which help improve water clarity.
Lactobacillus plantarum lowers local pH in the shrimp's digestive tract, creating an unfavorable environment for intestinal pathogens and reducing their growth.
| Main Impact | Explanation | |
|---|---|---|
Dominance of autotrophs, minimal heterotrophs | • Organic matter accumulation | Feed waste and shrimp feces are not decomposed properly, accumulating as sludge → deteriorates water quality |
| • Nitrate buildup | High nitrification (NO₃⁻) leads to elevated pH → causes osmotic stress in shrimp | |
| • Dissolved oxygen fluctuations | Autotrophs (cyanobacteria) produce oxygen during the day, but consume large amounts at night | |
Dominance of heterotrophs, minimal autotrophs | • Persistent ammonia/nitrite levels | Low chemoautotroph activity → NH₃/NO₂⁻ remain high → increases toxicity |
| • General oxygen depletion | Organic degradation by heterotrophs requires high oxygen → risk of hypoxia | |
| • Opportunistic pathogen growth | Organic-rich conditions support Vibrio spp. and other pathogenic microbes | |
Cyanobacteria bloom (photoautotroph explosion) | • Sharp pH fluctuations | Intense photosynthesis raises pH during the day and drops it at night |
| • Cyanotoxin risk | Some cyanobacteria produce toxins harmful to shrimp and beneficial plankton | |
Heterotrophic bloom (bacterial explosion) | • High water turbidity | High bacterial density → reduces light penetration and affects gill respiration |
| • Increased BOD | Higher BOD → lowers dissolved oxygen, increases shrimp stress and mortality risk |
Carrying Capacity
The Hidden Limit in Shrimp Farming
Every shrimp pond has a limit — this is called its carrying capacity, or the maximum number of shrimp that can be raised without causing negative impacts on health and performance. Exceeding this limit disrupts the pond ecosystem and directly affects shrimp welfare.
Dissolved Oxygen (DO) Drops Rapidly
Increase oxygen demand. Low DO stresses shrimp, reduces feeding, weakens immunity, and can cause mortality.
Water Quality Declines
High stocking increases waste, releasing toxins like ammonia, nitrite, and hydrogen sulfide that can harm shrimp and disrupt pond balance.
Sludge Accumulates Faster
Excess waste forms sludge that releases harmful gases and harbors bacteria, creating a risky environment, especially when oxygen is low
Exceeding carrying capacity
Low DO
Increased toxins
Sludge build-up
Shrimp stress and disease
Diseases
When Immunity Falls, Disease Rises
EHP (Enterocytozoon hepatopenaei)
EHP is a microsporidian parasite that infects the hepatopancreas of shrimp. The disease it causes is called hepatopancreatic microsporidiosis. EHP does not cause direct mortality in shrimp, but chronic infection disrupts the function of the hepatopancreas, which is the organ responsible for digestion and nutrient absorption.
Shrimp infected with EHP often show slow growth and uneven size due to suboptimal nutrient absorption from feed. Clinical signs visible in EHP-infected shrimp include size variation and the hepatopancreas may be atrophied or pale. Severe EHP infection is sometimes associated with white feces (White Feces Syndrome) when accompanied by other opportunistic infections.
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Regional Disease Spread
This map represents disease spread in shrimp farming