Litopenaeus vannamei: Essential Management Practices for Traditional Earthen Pond Farming

In recent years, shrimp farming in Taiwan has shifted focus from pure technique to environmental stability. Cumulative organic waste—such as uneaten feed, excrement, and biological debris—can deteriorate water quality and pond sediment, leading to disease and mortality. Understanding and stabilizing the pond environment is the primary goal for increasing success rates.

I. Water Quality & Environmental Requirements

1. Water Temperature:

• Farming is generally viable within Taiwan's average temperature range; growth occurs between 23–32°C, with the optimal range being 28–30°C.
• Feeding stops below 18°C (suspension of feeding is recommended), and mortality occurs below 9°C.
• In summer, adjust water exchange to noon (peak temperature) to prevent heat stress.
• In winter, exchange water at night as temperatures drop to help maintain warmth.

2. Salinity:

• For freshwater white shrimp, salinity is typically controlled at 3 ppt in areas with sufficient water resources; the optimal range is 12–20 ppt.
• Through gradual acclimation, farming can succeed at 1–2 ppt or even lower.

3. pH Level:

• Extremely high or low values inhibit growth. It is best to maintain pH at 8.0 ± 0.3, with daily fluctuations kept within ± 0.3.
• Stable pH indicates healthy water color, allowing for normal growth.

4. Dissolved Oxygen (DO):

• Maintain above 4 ppm; do not allow it to drop below 3 ppm.
• Deploy one 1-HP paddlewheel per 0.1 hectare (increase for high-density stocking) to ensure adequate aeration day and night.

5. Transparency:

• Normal growth occurs between 20–60 cm, with 30 ± 5 cm being ideal.
• If water color becomes too dense, adjust via water exchange; maintaining proper transparency is crucial as it represents water stability.

6. Total Alkalinity:

• Ideally 180–240 mg/L; freshwater farmers should maintain at least 120 mg/L.
• Use hydrated lime $[Ca(OH)_2]$ before stocking and limestone powder $[CaCO_3]$ during the culture period.
• Supplement minerals such as magnesium-calcium fertilizer or active magnesium during each molting cycle.

7. Probiotics:

• Apply probiotics every 14 days during the first month and every 7 days from the second month onwards.
• Concentration should ideally be above $10^5$ CFU/mL.
• (Note: PBC – Comprehensive Probiotics for Aquaculture)

II. Key Criteria for Shrimp Post-Larvae (PL) Selection

Healthy post-larvae should exhibit:

1. Clear, transparent body color without organic debris.

2. Uniform body size and complete, non-deformed morphology.

3. Strong resistance to water currents when observed in a white basin.

4. Certified Lab Reports: Negative for Microsporidia, Vibrio, and viral pathogens.

III. Feed Management

1. Strategy: Use reputable, high-quality Grass Shrimp feed. Utilize multi-meal feeding to accelerate growth.

2. Scheduling: Feed 2–4 times daily, with consumption time controlled within 1–1.5 hours.

• Night: 60–70% of daily ration (including 40% at 8:00 PM).
• Day: 30–40% of daily ration.

3. Troubleshooting:

• Poor Appetite: May indicate poor water quality; stop feeding and test parameters immediately.
• Molting Cycles: Expect reduced intake; reduce feed or skip one meal.
• Disease Outbreak: Use electrolytic seawater (20kg per 0.1 hectare) for 3 consecutive days of disinfection before resuming feed.