The stocking ratio of the four major fish has different collocation ratios according to the different conditions of Tangkou. Choose the main species to match other fish species. At present, except for the high price of herring (but the cost of herring culture is also high), the culture benefits of the four major fish are not good. It is suggested that the main culture species should choose fish with better market benefits and adopt the "80:20" model.

The concept of "80: 20" in the pond refers to improving the fish yield in the pond. 80% of the harvested fish products are composed of main fish with high economic value in the shopping mall, and 20% of the output is composed of miscellaneous fish, such as filter-feeding fish and predatory fish, which are helpful to purify the water quality and control wild miscellaneous fish and other omnivorous fish. In production practice, this 80: 20 model technology can be used to cultivate fish from fry or commercial fish from fish. Any kind of herbivorous cultured fish can account for 80% of the main cultured fish, such as crucian carp, catfish, bream, grass carp, carp, tilapia and freshwater pomfret.

Basic method:

1. Prepare fish ponds by standard methods.

2. Choose fish species with uniform specifications for main breeding (such as crucian carp and catfish). ) according to the standard method, and select the fish species (mainly silver carp) with neat specifications to be stocked in the prepared pond. At the time of harvest, the weight of main cultured fish accounts for about 80%, and cultured fish accounts for 20%. Mandarin fish, catfish, California bass or other carnivorous fish can also be stocked to control crucian carp.

3. Feeding the fish with a granular feed with complete nutrition and good characteristics according to the prescribed schedule and method, or managing the pond with a standard method, will cause less fish diseases, less oxygen increase and less water movement than the traditional polyculture system.

4. At the end of the culture cycle, all the fish can be harvested at one time, and the individuals of the main cultured fish can meet the market specifications, and the specifications are relatively uniform. In the middle of the breeding season, it is also a business choice to catch fish in places with better market prices.

Three. Selection and stocking of fish species

1. The main cultured fish suitable for 80: 20 pond culture are carp, crucian carp, bream, grass carp, herring, channel catfish, tilapia and freshwater pomfret. Fish suitable for fish culture are silver carp and bighead carp, and can also be selected from Canadian bass and mandarin fish. We take crucian carp as an example to illustrate the basic selection criteria of cultured fish.

2, the choice of stocking fish and its operation guide:

① Choose healthy, disease-free and uniform fish species;

(2) Try to choose original seeds and improved varieties;

③ During all operations, all kinds of pressures on fish should be avoided or minimized;

(4) Choose the average stocking weight that can meet the market specifications in a certain breeding period, and breed the fish with uniform specifications, that is, choose the large-sized fish with neat specifications (taking crucian carp as an example below).

—— It takes about 190 days to raise fry to 250g at the water temperature of 26℃; It takes about 120 days to propagate from 15g to 250g. It takes about 80 days to raise from 60 grams to 250 grams. According to the release time, choose the fish species.

2. Reference model of pond culture at 80: 20

Table 1. Pond 80: 20 culture mode