To identify fish species by observing their faces and colors.

A look at the specifications of fish species the specifications of the same kind of fish in the same pond should be neat and uniform, with little difference in body length and weight. On the contrary, the overall survival rate of poor fish species with large individual gap and uneven quality is often very low due to predation, mixed germplasm, poor feeding and other reasons.

Second, look at the body color of fish species. The body color of fish species is bright and full of luster. Generally speaking, the back of high-quality silver carp should be silver-gray, the side and abdomen of high-quality grass carp should be silver-white; the body color of high-quality grass carp is light golden yellow, and the grayish-black reticulated scales are more obvious, and the stronger the fish is, the more obvious the light golden yellow is; the body color of high-quality bighead carp is mostly light golden yellow, and the black markings are not very obvious. If the body color of the fish is dark, or even black, it means that the fish is weak fry or diseased fish; the luster of the body surface of the fish is caused by the mucus layer covered by the body surface of the fish, which is the first barrier for the fish to defend itself against diseases. On the other hand, the diseased fish or weak fish fry lack mucus layer and have no luster on the body surface.

The third look at the activity of high-quality fish species: lively action, strong clustering, quickly diving into the bottom of the water in groups when frightened, strong grabbing power, strong reverse water, when the fish are dense, head down, you can only see the tail constantly swinging, while the weak fry or sick fish with poor physique move slowly, do not cluster, swim alone, the grabbing power is weak, and the reverse water is poor.

Four-sampling randomly selected fish species to check their advantages and disadvantages, high-quality fish species beat violently when leaving the water, the individual is fat, the head is small and the back is thick, the body color is smooth, the muscle is moist, the scales and fins are intact, the Gill cover is not open, the tail is not bent, and there are no parasites and scars on the body surface. the body shape is normal and without deformity. On the contrary, weak fry or diseased fish have weak activity, incomplete scales and fins, hyperemia, thin fish body, large head and small tail, thin back, such as knife blade, even "no belly", "sticky net" and so on.