"Double-backed crucian carp", CYPRINIDAE, belongs to Qihe crucian carp and double-backed crucian carp. Because it is produced in Qihe River, it is also called Qihe crucian carp. Double-backed crucian carp is produced in the middle and lower reaches of Qihe River. Surrounded by mountains on three sides and facing the water on one side, the green hills are faint, beautiful and picturesque. It is the place where Luo Guanzhong, the author of Romance of the Three Kingdoms, lived in his later years.

Double-backed crucian carp is different from ordinary freshwater crucian carp. The scales of common crucian carp are generally gray-black, and the color of double-backed crucian carp is slightly golden yellow, similar to carp; Generally, crucian carp is flat and thin, while double-backed crucian carp has a wide back and a full body; Generally, crucian carp is diploid fish, while double-backed crucian carp is a rare natural triploid fish. Generally, the growth rate of crucian carp is slow, but the growth rate of double-backed crucian carp is fast, which is 2.5 times that of ordinary crucian carp and the back thickness is twice that of ordinary crucian carp, so it is called double-backed crucian carp.

Double-backed crucian carp is not only broad-backed, but also generally strong. Generally, the weight of crucian carp is relatively light, only about 500 grams, while the double-backed crucian carp is about 2500 grams, which is a unique variety of crucian carp.

Double-backed crucian carp "ten fish and nine females" have a large number of females. Men have a prominent position and are typical polygamous families. This is extremely rare in many fish families.