Hairtail, also known as saury and toothfish, is a trichiuridae animal of Perciformes. As the name implies, hairtail is flat on its side, silvery gray, with light gray dorsal fin and pectoral fin with tiny spots, black tail, big mouth, and gradually tapering towards the tail like a thin whip. The head length is twice the height and the total length is about 1 m. Hairtail is widely distributed in the western Pacific Ocean and the Indian Ocean, and can be seen in all coastal provinces in China, with the highest yield in the East China Sea.

Hairtail is a fierce carnivorous fish with sharp teeth, long dorsal fin, small pectoral fin and degenerated scales. When swimming, it moves forward by swinging its body instead of paddling with its fins, so it moves very freely.

Professor Xin, a fish research expert at the Institute of Oceanography, Chinese Academy of Sciences, told the reporter that the so-called scaleless fish and scaly fish are just different species, and their nutritional value is not much different. Generally speaking, most scaleless fish live in the deep sea above 500 meters, mainly in the order Anguilla, such as sea eel, sea eel and so on. Among freshwater fish, only loach and eel belong to scaleless fish. Professor Wang also said that many people think that saury and hairtail in marine fish are scaleless fish. In fact, they are scaleless fish, but their scales are small and difficult to be found.