Duobao fish (scientific name: Scophthalmus maximus) belongs to Scophthalmus. It is a marine benthic fish belonging to the genus Scophthalmus of the family Scoliotidae of the bony fish class. Commonly known as European flounder, it is called "Duobao Fish" in China.

In natural waters, adult fish can grow up to 75cm. The body is very flat, oblong, oval or long tongue-shaped. Young fish's eyes are on both sides of the body, and adult fish's body is asymmetrical left and right. One eye gradually turns left or right, and both eyes are located on the left or right side of the head. The mouth is slightly prominent. Fins are generally spineless. The dorsal fin and the anal fin are long in base, connected or not connected with the caudal fin. Both eyes are on the upward side of the body, and the color of this side is well matched with the surrounding environment; Their downward side is white. There are extremely fine scales on the surface of the body.

Duobao fish are widely distributed in warm and hot seas, and mainly feed on benthic invertebrates and fish. Habitat in the sandy bottom of shallow sea, preying on small fish and shrimp. Their flat bodies are especially suitable for benthic life on the seabed.

Native to the Atlantic Ocean of Europe, it is recognized as one of the high-quality flounder in the world. If artificial breeding is carried out, its growth period is obviously shortened, and it can reach about 500 ~ 600 g in the same year under suitable conditions. The male of Duobao fish reaches sexual maturity in one year, and the female fish reaches sexual maturity in two years. The natural maturity period is from May to August every year. Under the condition of controlled temperature and light, mature eggs can be obtained all year round, and artificial insemination is used for artificial reproduction.