Shrimp may show signs of stress before farmers notice mortality. Reduced feeding, unusual swimming and gathering near pond edges can indicate changes in water quality or shrimp health. Recognising these changes early can help farmers investigate the problem before losses increase.
The key is to connect what the shrimp are doing with when the behaviour begins and when mortality appears.
Behavioural Changes Farmers Should Watch
- Reduced feed consumption: Shrimp may eat less when dissolved oxygen is low, water conditions deteriorate or health problems develop.
- Surface swimming: Shrimp gathering near the surface, especially before sunrise, can indicate low dissolved oxygen.
- Edge swimming: Unusual gathering near pond edges may signal environmental stress and should prompt water-quality checks.
- Weak movement: Sluggish swimming or reduced responsiveness can indicate stress or illness.
- Sudden feeding changes: A sharp decline after normal feeding warrants investigation, particularly if other warning signs appear.
These signs are not specific to one disease. Their significance depends on the pond's normal behaviour, current water conditions and whether the changes affect a few shrimp or a large portion of the population.
Why the Timing of Mortality Matters
Before sunrise: Dissolved oxygen often reaches its lowest level overnight because shrimp, algae and other organisms continue consuming oxygen while photosynthesis stops. Surface swimming or distress during this period should prompt an immediate dissolved oxygen measurement.
Sudden mortality: Rapid losses can result from severe oxygen depletion, acute water-quality changes or infectious disease. Check dissolved oxygen immediately, review other water parameters and seek technical assistance if mortality continues.
Reduced feeding followed by mortality: When feed consumption declines for several days before deaths appear, investigate earlier changes in water quality, weather, pond management and shrimp health. The sequence provides useful clues but does not establish a diagnosis.
Mortality spreading across the pond: Record where the first deaths appeared and how the affected area changes. Poor circulation, local oxygen depletion and infectious conditions are among the possibilities; the distribution alone cannot confirm the cause.
What Should Farmers Do First?
- Measure dissolved oxygen, particularly when shrimp show early-morning distress or surface swimming.
- Check pH, temperature and salinity and review other relevant water-quality parameters.
- Inspect feeding trays to establish whether feed consumption has changed.
- Record the first signs and mortality, including the time, location and progression.
- Seek professional diagnosis if mortality persists or increases. Laboratory testing may be needed to identify infectious causes.
If dissolved oxygen is critically low, activate emergency aeration immediately and follow the farm's response procedure. Avoid applying treatments without identifying the likely cause.
Why Daily Records Matter
Record feed consumption, water-quality readings, unusual behaviour, mortality, weather changes and management interventions every day. Comparing these records can reveal whether abnormal behaviour began hours or days before mortality and help an aquaculture professional investigate the cause.
The takeaway: Shrimp behaviour can provide an early warning, while mortality timing helps narrow the investigation. Neither can confirm a disease on its own. Observe the change, measure the water, record the timing and investigate promptly.
