In traditional fish farming, the ratio of "fat fish" to "edible fish" is 6: 4; Intensive feeding with bait can increase the number of polyculture of "eating fish", and the ratio is generally 4:6. Silver carp and bighead carp are polyculture with grass carp as the main body, and the polyculture ratio is 2: 1 or 2: 2; Silver carp and bighead carp were polycultured mainly with grass carp and bighead carp, and the ratio of grass carp and bighead carp was 1:3 or 1:4, and the ratio of grass carp and bighead carp to silver carp and bighead carp was 1. Among them, the allowable amount of grass carp is 10 ~ 15 kg per square meter of water surface; The allowable quantity of silver carp is 20 ~ 30 kg per 100 square meter of water surface; The maximum allowable food intake of bighead carp is 4.5 ~ 6.0 kg per 100 square meter of water surface. The proportion of other fish with carp as the main body is 6:4 or 7:3, and the allowable amount of carp is 90 ~ 180 per 100 square meter of water. Due to the strong predation of carp, the collocation specification of carp should be controlled at 25g/ fish in ponds that mainly take care of grass carp, and the number of carp per 100 square meter should not exceed 15. In ponds dominated by herring, the collocation quantity of herring is generally 30 per 100 square meter of water. The allowable intake of crucian carp is150 ~ 220; No matter what kind of fish is the main one, if crucian carp and white crucian carp are mixed, the number of mixed culture of white crucian carp with specifications of 40-50g/ tail is 30-45 and that of mixed culture of silver crucian carp with specifications of 15-20g/ tail is 60-90 per square meter of water surface. In addition, tilapia is a good collocation fish, the specification is 5 ~ 10g, and the collocation amount is generally 45 ~ 75 fish per1100m2 water surface.
(3) polyculture mode
At present, there are mainly the following polyculture modes in pond culture:
1. A fish polyculture model with herbivorous fish as the main body, in which grass is fed to herbivorous fish and silver carp and bighead carp are fed. Using the feces of grass carp and bighead carp. This polyculture mode is mainly composed of aquatic plants and green bait, and some fine bait can be added appropriately. Because the source of bait is easy to solve and the yield and economic benefit are good, this polyculture model is more common in China.
2. The polyculture mode of filter-feeding fish is mainly silver carp and bighead carp, and other fish, especially non-crucian carp, silver carp and other fish with strong feeding ability, are appropriately polyculture. This model is mainly based on fertilization and feeding grass at the same time. Because of the wide source and low cost of fertilizer, this model is mainly used in pond culture in many areas of China.
3. The polyculture mode of omnivorous fish is mainly carp or crucian carp. The former is more common in the north, while the latter is more common in the south. The type of carp breeding is mainly concentrated feed, and the breeding cost is high; Fertilization is the main breeding type of crucian carp, and the breeding cost is low.
4. Fish polyculture mode with carnivorous fish as the main body. Herring is the main fish in this polyculture model. Because the natural resources of snails and meretrix meretrix are few, and the pellet bait of herring has not been completely solved, this culture mode is rare.