Overwintering conservation of tilapia in soil ponds

Tilapia, commonly known as: African crucian carp, tilapia, Vietnamese fish, Nanyang crucian carp and so on. It originally refers to the species of mouth-hatched non-crucian carp with Mozambique as the model producing area: Mozambique mouth-hatched non-crucian carp (scientific name: Oreochromis mossambicus), which is now the common name of several species of fish belonging to several genera of Sparidae and mouth-hatched non-crucian carp; collectively called Tilapia in English. At present, it is the focus of scientific research and cultivation of freshwater farmed fish in the world aquaculture, and is known as one of the main sources of animal protein in the future. Usually live in fresh water, can also live in salt water with different salt content, can also live in the shallow water of lakes, rivers, ponds. It has strong adaptability, can reproduce in narrow waters, can even grow in rice fields, and has strong adaptability to water with less dissolved oxygen. The vast majority of tilapia are omnivorous and often draw plants and fragments in water.

There are many ways to protect tilapia overwintering, but some of them are limited by resource conditions, or have no hot spring or thermal drainage, and some have complex equipment and large investment. In order to explore a mass conservation method with low investment and simple equipment. Its main facilities and technologies are:

1. Construction of overwintering ponds: tilapia overwintering ponds should be built in low-lying areas away from the wind and against the sun and close to the river. In the place where the soil is solid, dig a soil pool of 4 ~ 5 meters, 1 ~ 2 meters wide and 2 ~ 3 meters deep, and the water of the river can gradually infiltrate into the soil pool through the gaps in the soil layer to keep the water fresh and have sufficient oxygen content.

two。 Thermal insulation facilities: bamboo scaffolding is made of bamboo on the surface of the pool, which is covered with two layers of plastic film, like a greenhouse for cultivating vegetable seedlings. The height of the pool surface and the film is about 0.1 m ~ 0.8 m, and the space is too large to keep warm. When blowing the northwest wind, the wind shield should be made of reeds or grass curtains on the west and north sides of the overwintering pond. In the frost and snow weather, the film should be covered with grass curtains. If the temperature drops in case of a cold wave, 2 ~ 4 electric lights with 100 ~ 200 watts should be hung in the plastic shed to increase the water temperature. In short, the temperature of the pond water should be kept at about 15 ℃ ~ 16 ℃, so that the fish species can survive the winter safely.

3. Fish species into the pond: before entering the pond, the fish species should be watered and soaked in the overwintering pond for 3 ~ 5 days to eliminate the effect of pollutants on the pond water. The time for fish to enter the pond is generally in the first ten days of November, and the water temperature is about 16 ℃. It is easy to suffer frost injury too late. Before entering the pond, the fish should be soaked in 4% salt water for 3 to 5 minutes to disinfect the fish to prevent infectious diseases. The density of fish species is 5 kg ~ 7.5 kg per cubic meter.

4. Overwintering management: special personnel should be assigned to manage the whole overwintering period. At the same time, we should pay attention to the change of water temperature, the change of water quality and the dynamics of fish.

(1) feeding: a small amount of feeding can be given during the overwintering period, usually once in 10 to 15 days, the feeding amount is about 1% of the weight of overwintering fish, but when the water temperature exceeds 16 ℃, it can be fed once a day, such as sugar lees, rapeseed cakes and so on. And grasp flexibly according to the feeding situation, so that the fish can eat well, so as to improve the survival rate of overwintering and reduce the loss.

(2) daylighting: throughout winter, as long as it is a sunny day, remove the grass curtain covered in the greenhouse from 9 to 15:00 and increase the temperature by daylighting. The snow on the scaffolding should be swept away in time on a snowy day to prevent the scaffolding from collapsing.

(3) Prevention and treatment of fish disease: tilapia overwintering for a long time, we should pay attention to observe whether there is fish disease, once found to be treated in time. During the overwintering period, water mildew is the most common, which mostly occurs after entering and before leaving the pool. Water mildew is a common disease caused by epiphytic fungi such as water mold, Pythium and so on. A kind of grayish-white, soft cotton hair attached to the fish can be seen with the naked eye. Injured fish are extremely susceptible to infection, especially in winter and early spring. Treatment can be treated with 0.1 mg ~ 0.2 mg / L alkaline green or 1 mg / L copper sulfate solution sprinkled throughout the pool, which is effective. If there is a lack of oxygen in the pond, the floating head of fish can be replaced with new water.