Practical Experience Sharing on Cage Culture of Grass Carp

Grass carp mainly feeds on grass. It often inhabits places with lush aquatic plants and is a middle-to-lower-layer fish. Its optimum growth temperature is 20-30°C, and it has a large food intake. Above 32°C or below 15°C, its growth rate slows markedly and its food intake decreases. When the water temperature is below 10°C, it stops feeding and enters a state of winter dormancy, with half of them dying. It likes to live in places with abundant dissolved oxygen and fresh water quality, and does not like fertile water. When the dissolved oxygen in the water is below 2 mg/L, although the water temperature is very good, its appetite also declines; when the dissolved oxygen is below 1 mg/L, it stops feeding and begins to gasp at the surface due to oxygen deficiency; at 0.9 mg/L it dies. Therefore, grass carp cages should be placed in places with smooth water flow, lean water quality, and pure water quality, and it is advisable to use floating cages made into fully enclosed cages extending 50 cm above the water surface for culture. Cages should be small. 

Fry and fingerling stocking density: the fry stocking density is 300-500 fish per sq m of water surface, and the fingerling stocking density is 30-50 fish per sq m of water surface (individuals of 100-500 g, especially those of 500 g have fewer diseases and the most remarkable growth rate). They can be directly raised to market-size fish.

Feeding and management: Cage culture of grass carp generally starts from summer fry, with a body length of more than 3 cm. At this time, the fry have already been raised for more than 20 days after hatching, and their food is plankton. In the absence of sufficient plankton, they should be fed crushed high-quality high-protein bait as well as aquatic earthworms, small duckweed, and rootless duckweed. When feeding, domestication is needed first, that is, first sprinkle a little powder feed in the cage to lure the fish up, and each time it is sprinkled, a scramble must be formed, and there are always a few fish that cannot get any. The scramble for food is intense, letting them taste the deliciousness of the bait, and after a few days a habit is formed, and feeding is gradually increased. When feeding rootless duckweed and small duckweed, the amount put in must be sufficient, and when it is eaten up, put in more, and do not feed at night. When grass carp grow to more than 6 cm, they can eat tender aquatic plants; when they grow to more than 10 cm, they can eat tender aquatic and terrestrial grasses, vegetable leaves, etc., and they are even more fond of insects and bran. Before the Beginning of Autumn, they must be fed enough; after the Beginning of Autumn, the weather changes greatly, so limit it to being eaten up in 5-6 hours, otherwise they will become ill. What is not eaten up must be taken out of the cage. Before the Beginning of Autumn, they must be fed to satiety; June to July is exactly when they put on fat. August to September has high water temperature, and the fish cannot stand being too full.