Flounder is mainly produced in the northern part of the Yellow Sea and the Bohai Sea, such as Zhuanghe in Liaoning, Qinhuangdao in Hebei, Penglai and Shidao in Shandong, preferably from Qinhuangdao. April to June is the peak season for flounder production. The body is long and flat on the side, generally about 20 cm in length, about 200 grams in weight, with large and prominent eyes. Both eyes are on the right side of the head, and the upper eyes are high on the midline of the back of the head. The slits on both sides are slightly unequal in length, and both foreheads have sharp and thin teeth. The edge of the front operculum is free, the lateral line is complete, there is no curvature above the pectoral fin, and the eye side is covered with weak comb scales. The body is yellowish brown or dark brown, without Brindle. The side without eyes is white with round scales. The scales on the head and between the eyes are small and dense. The dorsal fin extends from the eyes to the tip of the caudal stalk; the pectoral fins are one pair and smaller; the abdominal fins start from the back of the pectoral fin to the tip of the tail; the caudal fin is double Truncate shape and long tail handle.