1, because it can make full use of the water surface. If we put the fry directly into lakes and oceans, it will be "fish diving". I don't know where they swam, but there are still many enemies who will hurt them, and not many can really grow up. In addition, natural bait is hard to find and grows fast. Now if the fry were kept in cages, there would be no such problems. Because the container is a cage, unlike pond culture, the mesh of the cage is unobstructed with lake water or seawater. With the breeze blowing, the water quality inside and outside the cage is exchanged, and the fish in the cage have fresh oxygen just like in a lake or ocean. Small fish, shrimp and plankton in lakes and oceans are not restricted by cages, and can enter and leave freely, and can still be used as food for some fish. For example, in Bailianhe Reservoir in Hubei Province, silver carp and bighead carp fry feeding on plankton were raised in a cage of 8 square meters without feeding bait. It only took 75 days, that is, 1.236 kg of fish, which was more than 1.3 cm long. Another example is the Yangtze River Fisheries Research Institute 1977 cage culture of silver carp and bighead carp, which are not fed. A year later, the net fish yield per mu was 33,633 Jin, which was more than 20 times higher than that of intensive culture in ponds, which not only provided more fresh fish for the market, but also saved a lot of land and fertilizer.

2. Keeping other fish in cages is just to feed the bait. At present, different synthetic granular baits, such as grass carp, are generally prepared according to the fish species raised. The formula of bait should include rape straw, soybean straw, bean cake, rice bran, silkworm chrysalis, bone meal, salt and so on. If the ingredients synthesized in these articles are properly prepared, the fish can grow 1 kg per1kg. According to foreign data, the maximum annual output of catfish cultured in cages has reached 480 kilograms per cubic meter.

3. Fish are kept in cages, not afraid of other fierce fish; After breeding, it can be caught at any time, and it can be listed without hard fishing. It seems to be a living fish bank. In addition, cage fish culture can also observe the ecological activities of fish, conduct scientific research, find fish diseases in time and prevent them.