2. Silver carp: In the upper waters, it feeds on phytoplankton such as diatoms and green algae.
3. Bighead carp: It lives in the middle and upper waters and feeds on zooplankton such as Daphnia.
4. Black herring: It lives in the middle and lower reaches and mainly feeds on benthic animals such as snails, mussels and mussels.
5. Grass carp: It lives in the middle and lower layers of waters and on the banks with many aquatic plants, and mainly feeds on aquatic plants and reeds.
6. In the Northern Song Dynasty, the four big fish continued to develop into a wider regional culture, and the culture gradually flourished along the Yangtze River and the Pearl River. According to the records of Zhou Mi (1232 ~ 1298) Guixin magazine, the capture, transportation, screening and sales of the fry of the four big fish have reached the professional level. Moreover, the polyculture technology of the four major fish was produced in the Song Dynasty and quickly popularized. Polyculture technology not only makes full use of aquaculture resources, but also enriches the product structure of fish farmers and reduces production risks.
7.* * * Same features: The four major fishes belong to CYPRINIDAE and CYPRINIDAE. Because these four kinds of fish have the same characteristics of rapid growth and strong disease resistance, they are suitable for people to eat fish. Moreover, the growth inflection point age of the four big fish is 2-3 years older than their sexual maturity age, and they will continue to grow after sexual maturity.