Tilapia winter conservation measures
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Tilapia is a tropical fish that gradually becomes inactive when water temperatures drop below a certain threshold. In most regions outside of southern China, where natural winter survival is possible, farmers must implement artificial overwintering techniques to ensure the fish survive the colder months.
**Preparation for Winter**
1. **Wintering Pond Setup**
The ideal location for a wintering pond is a sunny and sheltered area with good water quality, easy access to water sources, and convenient transportation. These factors help maintain stable water conditions and reduce stress on the fish.
2. **Selecting Fish Stock**
Choose tilapia fry that are around 3–4 cm in size from autumn-raised stocks, as they have a higher survival rate during winter. Larger fish may not utilize the pond efficiently, while smaller ones may be too fragile to survive. Ensure the fish are healthy, free from injuries or diseases, and have smooth skin. Separate them by size and place them in appropriately sized pools for better management.
3. **Timing and Stocking Density**
Fish should be moved into the wintering pond when the water temperature drops to 20–22°C. This timing varies depending on the local climate, but it's crucial to move them before the first cold snap. If the water is below 16°C, the fish may already be damaged and won’t survive. Choose calm, sunny days for catching and transferring fish to avoid frostbite.
The stocking density should be adjusted based on pond conditions and fish size—typically 30,000 to 50,000 fish per mu (approximately 667 square meters).
4. **Overwintering Methods**
- **Hot Spring Water Overwintering**: Using hot spring water is an effective method, as it requires minimal investment and provides consistent warmth. Dig the pond near the hot spring, maintain a water depth of 1–1.2 meters, and ensure balanced inflow and outflow to regulate temperature. If the water is too hot, cool it down before introducing it to the pond. Install inlet and outlet systems to prevent fish from getting trapped.
- **Plastic Greenhouse Overwintering**: In some southern regions, tilapia can be overwintered in earth ponds, while in other areas, plastic film greenhouses are used. These structures provide insulation and help maintain a stable environment.
5. **Winter Management**
The overwintering period is long, so someone must monitor the pond throughout. Key tasks include controlling water temperature, maintaining water quality, feeding properly, and preventing disease.
- **Water Quality Control**: Keep the water clean and oxygen-rich, with dissolved oxygen above 3 mg/L. Flowing warm water helps maintain water quality, while greenhouse ponds may require partial water changes or oxygenation if conditions worsen.
- **Feeding Practices**: Tilapia need proper nutrition during winter to build energy reserves. Use high-quality feed such as rice bran or wheat bran, which don’t easily pollute the water. Adjust feeding amounts based on water quality and fish behavior.
6. **Removing Fish from the Pond After Winter**
When preparing to release the fish after winter:
- Stop feeding them 7–10 days before removal to allow digestion.
- Gradually exercise the fish by pulling nets and releasing them over a few days. On the third day, they can be transported in the afternoon.
- Use oxygenated nylon bags or waterwheels with pure oxygen for safe transport to minimize stress and damage.
By following these steps, tilapia can survive the winter successfully and be ready for the next growing season.