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 proper wintering measures to ensure the fish survive the colder months.
**Preparation for Winter**
1. **Wintering Pond Setup**
The ideal location for wintering ponds is on a sunny, sheltered side with good water quality, easy access to water sources, and convenient transportation. These factors help maintain stable conditions for tilapia during cold weather.
2. **Selecting Fish Species**
Choose fish that were raised in specialized autumn breeding pools, with a size of 3-4 cm. This size ensures a high survival rate during winter. Fish that are too large may not utilize the pond efficiently, while those that are too small have a lower chance of surviving. Select only healthy, injury-free, and disease-free individuals, and separate them by size to optimize pond use.
3. **Timing and Density of Fish Entry**
Fish should be moved into the wintering pond when the water temperature drops to 20-22°C. The exact timing depends on local climate conditions, but it's crucial to complete this before the first cold front arrives. If the temperature falls below 16°C, avoid moving fish, as they may already be frostbitten and will die after being placed in the pond. Choose calm, sunny days for fishing to prevent further stress on the fish.
The stocking density should be adjusted based on pond conditions and fish size, typically ranging from 30,000 to 50,000 per mu (approximately 0.067 hectares).
4. **Wintering Methods**
- **Hot Spring Water Wintering**: Using hot spring water is an efficient and cost-effective method. Dig the wintering pond near the hot spring, ensuring a water depth of 1 to 1.2 meters. Set up an inlet and outlet system to balance water flow and maintain consistent temperature. If the hot spring is extremely hot, cool it down to around 16°C before introducing it to the pond. Install nets at the inlet and outlet to prevent fish from escaping.
- **Plastic Greenhouse Wintering**: In some southern areas, tilapia can be overwintered in earthen ponds. Alternatively, plastic greenhouses provide a controlled environment, especially in regions with milder winters.
5. **Winter Management**
The wintering period is long, so a dedicated person should monitor the pond throughout. Key tasks include controlling water temperature, maintaining water quality, feeding properly, and preventing diseases.
- **Water Quality Control**: Keep the water clean and ensure dissolved oxygen levels remain above 3 mg/L. Flowing warm water helps regulate water quality. In plastic greenhouses, where water changes are difficult, only replace water when necessary or add oxygen to improve conditions.
- **Feeding Practices**: Tilapia consume energy during winter, so feeding is essential to support their health. Use nutritious feeds like rice bran and wheat bran, which are less likely to pollute the water. Adjust feeding amounts based on water quality and fish appetite.
**Fish Removal After Winter**
When removing tilapia from the pond after winter, follow these steps:
1. **Stop Feeding in Advance**: Stop feeding the fish 7 to 10 days before removal to reduce digestive stress.
2. **Net Exercise**: Pull the net and allow the fish to acclimate for two days. On the second day, release them for 2-3 hours, and on the third day, transport them in the afternoon after another net pull.
3. **Safe Transportation**: Use oxygenated nylon bags or waterwheels with pure oxygen to minimize stress and damage during transport.