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Cultivation and Reproduction of Tilapia Progeny
Tilapia breeding does not require artificial stimulation or water manipulation. As long as the water temperature remains consistently above 20°C, mature male and female broodstock can naturally reproduce when placed in the same breeding pond. When the temperature is stable between 25-29°C, fry can be produced every 30-50 days. In southern China, tilapia typically spawns five to six times a year, and under controlled temperature conditions, it can breed throughout the year.
**Breeding Pond Conditions**
1. **Location**: The breeding pond should be located near a water source for easy water exchange, in a quiet area, and accessible for transportation. It’s ideal to choose a pond close to the broodstock during winter to minimize stress and damage caused by relocation.
2. **Area and Water Level**: A typical breeding pond ranges from 2 to 6 acres. Too large an area makes fry collection difficult, while too small a size leads to unstable water quality and temperature fluctuations. The water level should be maintained at 1.4–1.5 meters during normal conditions. During breeding, reduce it to 0.8–1.2 meters, and increase it slightly to 1.2–1.4 meters during summer heat.
3. **Pool Shape and Bottom**: Rectangular ponds with east-west and north-south orientation are preferred. Shallow beaches along the edges help broodstock spawn. The bottom should be flat or slightly concave, with sandy soil being ideal. Avoid weeds near the shallow areas, as they hinder fry collection.
**Pond Cleaning and Disinfection**
Before introducing broodstock, the pond must be thoroughly cleaned and disinfected. Drain all water, remove unwanted fish, weeds, and debris, especially within 1.6 meters of the pond bottom. Ensure the pond edges and drainage systems are secure. Sun-drying the bottom for 10–15 days helps eliminate pathogens. Two weeks before stocking, refill the pond with 10–20 cm of water and apply disinfectants like tea pods, bleaching powder, or quicklime. Quicklime and tea pods are most effective. Apply 40–50 kg/mu of tea pods, 150–200 kg/mu of quicklime, and 15–20 kg/mu of bleaching powder (30% available chlorine).
**Water Quality Management**
After disinfection, use a net to check the pond for remaining debris. Refill the water through a fine mesh filter, regularly cleaning the mesh. Apply base fertilizers such as 300–600 kg of fermented manure or 500–800 kg of green manure per acre. Maintain a tea-green or yellow-green water color. If using green manure, turn it regularly until fully decomposed, then sterilize for 7–10 days before releasing fish.
**Broodstock Stocking**
1. **Selection**: Broodstock must be purebred, fast-growing, and healthy. Choose individuals over 250 grams, with males slightly larger. They should have full scales, bright coloration, no injuries, and conform to taxonomic standards.
2. **Stocking Timing and Procedure**: Introduce broodstock when the water temperature is stable above 20°C. In Guangdong, this usually happens in mid-March, but with greenhouses, it can start as early as mid-February. Stock on sunny days, ensuring enough fish are introduced at once. Soak broodstock in disinfectant for 3–5 minutes before placing them in the pond. Handle gently to avoid injury. After stocking, treat with 0.3 ppm chlorine dioxide to prevent infections.
3. **Density and Sex Ratio**: Stocking density depends on oxygen levels and pond size. For a normal pond, 1500–2000 fish per mu is common. Without aeration, 600–800 fish per acre at 300–500 grams is acceptable. A sex ratio of 2.5:1 to 4:1 is ideal, as males are more aggressive and may overbreed if not properly managed.
**Care and Management**
After wintering, broodstock need extra care. Combine feeding with fertilization to support gonad development. Feed 3–4% of their body weight daily, using a balanced diet rich in protein (over 35%). Common feeds include soybean meal, fish meal, corn, and peanut meal. Pellets are recommended for better nutrition.
Monitor the pond daily for frog eggs and predators. Maintain good water quality by replacing water when necessary or adding lime. Apply lime every two weeks at 10–15 kg/mu, and use microbial agents to improve the aquatic environment.
**Broodstock Spawning**
When the water reaches 22°C, broodstock begin spawning. Fertilized eggs hatch in the female’s mouth at 25°C, and fry emerge after 5–6 days. At 28–30°C, hatching occurs in 4–5 days. From spawning to fry release, the process takes about 10–15 days. Monitor the pond daily for fry activity and harvest promptly to maximize yield.
**Harvesting Fry**
Fry are best collected in the morning or evening using hand nets or small trawls. Collect 4–5 times daily to ensure all fry are removed. Handle fry gently to avoid stress. Transfer them to a rearing pond for further growth.
**Important Notes**
1. Before moving broodstock to the breeding pond, gradually acclimate them to the new temperature. Stop feeding three days prior and introduce new water slowly to avoid shock.
2. Water quality is crucial. Avoid overly thick or thin water. Use lime regularly and replace old water in hot seasons. Microbial agents can help maintain balance and increase oxygen levels.
3. Feeding is essential for successful breeding. Provide high-quality feed with sufficient protein to support reproduction and increase fry production.
4. During summer, high temperatures can reduce spawning. Separate males and females until the temperature drops below 30°C, then pair them again for more efficient fry collection. This helps manage seedling quantity and improves breeding success.