The flounder, also known as plaice, is a collective name for the fish of the order Platyhelminthes. The body is laterally compressed, long oval, ovoid or long tongue-shaped, the maximum body length can reach 5 M. The adult body is asymmetrical. Both eyes are located on the left or right side of the head. The mouth is slightly protruding. The fins are generally without fin spines. The dorsal and anal fins are basally long and may or may not be attached to the caudal fin. It is widely distributed in warm and hot waters of all oceans, feeding mainly on benthic invertebrates and fish. There are more than 540 species in the world, and China produces 120 species, with the main categories being flounder, turbot, plaice, sole and tongue sole, which are economic fish. They inhabit the sandy seabed in shallow waters and prey on small fish and shrimp. They are especially suitable for benthic life on the seabed. Due to their flattened body. The eyes are the same on the upward-facing side of the body, and the color of this side matches the surroundings well; the downward-facing side of their body is white. Flounder have extremely fine scales on the surface of their body. Flounder have only one dorsal fin, which extends from the head almost to the caudal fin. They live mainly in temperate waters and are an economically important fish in temperate seas.