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Crucian carp is a small fish of crucian carp. Carassius auratus is flat, tall and thick, with round abdomen, short head, blunt nose and mouth, and small eyes, which are located above the head side. The gill harrow is long, the gill filaments are slender, the scales are large, the dorsal fin is long, the outer edge is straight, the caudal fin is bifurcated, the back is gray-black, the abdomen is silvery white, and the fins are gray. In different growing waters, the body color is different.

Carassius auratus is widely distributed in Europe and Asia. In China, it is distributed in other rivers and lakes except the Qinghai-Tibet Plateau. Crucian carp is a typical bottom fish, which has strong adaptability to the environment and strong tolerance to water temperature, pH and salinity.

Crucian carp is an omnivorous fish. Under natural conditions, it usually feeds on zooplankton, phytoplankton, zoobenthos and organic debris. Under the condition of artificial breeding, compound feed is generally the main feed, and natural bait in water is also eaten.

Generally, crucian carp matures at 1 winter age; The breeding season is from March to July, and the eggs are sticky and attached to aquatic plants and other objects.

Carassius auratus is one of the important freshwater economic cultured fish in China. Since 1980s, the scale and potential of crucian carp breeding in China have been increasing after the excellent varieties of crucian carp such as allogynogenetic crucian carp, Fangzheng crucian carp and Pengze crucian carp were widely promoted in China.

Since 2005, the annual output of crucian carp in China has been maintained at more than 2 million tons, reaching 2.749 million tons in 2020, showing a steady growth trend year by year. The successful breeding of allogynogenetic crucian carp "Zhongke No.3", allogynogenetic crucian carp "Zhongke No.5", Changfeng crucian carp, Xiangyun crucian carp and hybrid golden crucian carp plays an important role in promoting the renewal of crucian carp breeding varieties and the rapid development of crucian carp industry.

Crucian carp can be found almost everywhere in rivers, lakes, reservoirs, ponds, mountain ponds, swings, ditches, swamps and large and small water bodies full of weeds. Crucian carp is one of the typical bottom fishes with strong adaptability.

It can survive in water with pH value of 4 or 9, even in spring water, sewage and mineral-bearing industrial and mining wastewater, and has strong tolerance to water temperature, pH value and salinity. In addition, it can resist severe cold (such as-10℃ to-15℃) and has strong endurance in hot summer climate and low oxygen environment.