Overwintering Cold-Protection Management Technical Measures for Tilapia Aquaculture

Tilapia has the characteristics of being omnivorous, easy to raise, fast-growing, quick to reach market size, low in cost, and less prone to disease, making it an excellent species widely cultured in our province. However, this fish is a tropical and subtropical species, and whenever a strong cold front moves south and the water temperature drops to around 10°C, there is a risk of freezing to death and cold injury. As the weather gradually turns cold, cold-protection work must therefore be done well to protect tilapia through the winter safely. 

1. Choose the fish pond well. 

It is best to choose ponds beside a village, ponds in front of a house, ponds on the outskirts of towns, and ponds beside sugarcane fields, bamboo groves, or trees. These ponds generally have houses, trees, and other natural windbreaks on the west and north sides to block cold wave attacks, so the water temperature changes less, which is beneficial for overwintering. A pond area of 2 to 3 mu is best, as it has a small wind-exposed surface. After the pond is chosen, first carry out pond clearing and disinfection to eliminate all pathogens and harmful organisms, creating conditions for both fish species to overwinter safely. 

2. Fill with water in good time. 

Increasing the water depth to raise the pond water temperature is the most basic work for protecting cultured fish through the winter safely. According to many years of investigation, wherever the water depth is above 2.5 m and there are trees for wind shelter, the insulation requirement is basically met, so pond water must be stored in sufficient quantity as early as possible so that the water depth reaches above 2.5 m. For water surfaces where drainage and irrigation are inconvenient, a “fish bed” can be dug on the west and north sides of the pond so that the water depth meets the cold-protection overwintering requirement; when a cold wave strikes, the fish in the pond all gather in the “fish bed” to keep out the cold and warm up. 

3. Build windproof and cold-proof sheds. 

For ponds that have no houses, bamboo, or trees for wind shelter, windproof and cold-proof sheds should especially be built well. For the windproof and cold-proof sheds, straw or sugarcane leaves can be used to make grass mats each 3 m × 4 m, and then bamboo frames are used to fix them on the west and north sides of the pond, and the grass mats are tied firmly to block cold wave intrusion. For the windproof shed, the grass mats should be laid obliquely over the west and north water surfaces of the pond, with the front end about 67 cm from the water surface and the back end close to the pond edge. Some straw should also be placed under the shed, so that when a cold wave strikes, the fish can gather under the shed among the scattered grass to warm up and keep out the cold. 

For the broodstock preservation pond for tilapia, use bamboo poles or thin steel bars to build a semicircular frame at the pond edge, and cover the frame with plastic film to make a cold-proof greenhouse. On clear days, the film should be opened from 10:00 in the morning to 15:00 in the afternoon to achieve ventilation and light transmission, ensuring the broodstock overwinter safely. 

4. Dig drainage ditches. 

Around the overwintering fish pond, dig a drainage ditch 0.5 m deep and 0.7 m wide. This work is very important, because when cold waves move south continuously, they often cause low-temperature weather with continuous drizzle. Rainwater is lower in temperature than the pond water, and after the drainage ditch is dug, the rainwater can be drained out of the pond, keeping the pond water temperature stable.