How to raise fish in courtyard fish ponds

The whole production process of pond culture in China can be roughly divided into three main stages: artificial propagation of fry (see artificial propagation of fish), fry propagation (see fry propagation) and edible fish propagation.

1. The specifications of stocked fish species should be determined according to the factors such as the better growth stage of different fish species, local climate conditions, aquaculture technology level, yield and economic benefits. Common fish species in China are grass carp 1500 ~ 800g, herring/kloc-500g, silver carp/300g, bighead carp/500g, herring 15 ~ 50g and carp 15 ~ 50g. The key points of aquaculture technology are as follows.

2, polyculture and close culture

That is, fish with different habits, different feeding habits or the same species but different specifications are mixed and planted in the same pond reasonably and densely, which is the core of pond culture technology in China. Silver carp and bighead carp live in the upper water, grass carp and bream live in the middle and lower water, and herring, herring, carp, crucian carp and non-crucian carp live in the bottom water.

When these different kinds of fish are mixed in the same pond, compared with a single fish, it can not only increase the stocking amount per unit area of the pond, but also make full use of various bait resources in the pond because of the different types of bait needed by various fish, resulting in a mutually beneficial relationship.

Such as herring and carp eat snails, clams and other benthic animals; Grass carp and Megalobrama amblycephala are herbivores, but their ability to digest cellulose is poor. Feces contain a large number of undigested stem and leaf cells, which can fertilize water, cultivate plankton and provide rich suspended organic matter. Silver carp and bighead carp feed on plankton. If these fish are mixed, these bait resources can be fully utilized to prevent eutrophication of water bodies.

In addition, carp, crucian carp, herring and non-crucian carp all have the characteristics of feeding on debris. They turn over the pond mud when foraging, which can accelerate the decomposition of organic matter and improve the production conditions of the pond. In polyculture, there are also contradictions among various fish, such as competing for food and occupying living space. Usually, some measures can be taken to avoid or alleviate it, such as controlling the stocking amount of some fish, harvesting some fish in advance, stocking fish of different specifications and so on.

Mixed culture of fish of the same species and different specifications can produce large-scale fish species at the same time as edible fish, thus reducing the pond for breeding fish species and expanding the breeding area of edible fish. In a reasonable density range, as long as the water temperature is appropriate, the water quality is good, the proportion of mixed fish and the specifications of stocked fish are appropriate, the bait is of high quality and sufficient, and the feeding management is meticulous. The higher the stocking density, the higher the yield.

Due to the differences in climate, fish species and bait resources, various types of polyculture have been formed in China. Silver carp, bighead carp and grass carp are the most common, followed by bighead carp and grass carp, which are more common in the Pearl River Delta. Both herring and grass carp are equally important, and polyculture with herring is more common in Taihu Lake area. Carp is the main species in North China, Northeast China and Northwest China.

3. Circular capture and release

That is to say, after a complete release, after a period of feeding, some adult fish that meet the commercial specifications are caught in batches, and then the fish are properly replenished. By adopting this method, the unit water body in the pond can always maintain an appropriate density, so as to avoid that the water body can not be fully utilized due to the lack of fish species in the initial stage of stocking, and the growth of fish is inhibited due to the relative shrinkage of the growth and living space of fish in the later stage of breeding, thus obtaining a higher yield per unit area.

Extended data

During the day, the oxygen produced by phytoplankton in the downwind and dissolved from the air in the fish pond is always more than that in the upwind, and the greater the wind, the greater the difference in dissolved oxygen content between the upper and lower parts. On the other hand, at night, because there are more plankton and organic matter in the downwind of the fish pond than in the upwind, and the oxygen consumption is large at night, the dissolved oxygen in the upwind is more than in the downwind.

Replenish fresh water regularly. In the case of high-density culture, there are a lot of residual bait and dirt in fish ponds, and anaerobic fermentation produces harmful substances such as ammonia nitrogen and hydrogen sulfide, which makes the water body worse, especially in hot summer, and the water quality changes faster. Therefore, regular water injection is one of the most commonly used and economical methods to regulate water quality. Generally, fresh water is added once every 7 days-10, and water is added every time 15cm-20cm.

When the deterioration of the pool water is serious, it is appropriate to take measures to change the water and maintain good water quality conditions. The ponds where silver carp and bighead carp are mainly raised should be grass green or brown with a transparency of 20 cm -30 cm; The pond with grass and carp is lighter in color than the pond with silver carp and bighead carp, so fresh water is poured every 7 days-10, and the water level is raised 15 m -20 cm each time. Fish ponds should try to keep the highest water level in summer.

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