Swordfish, the scientific name of Coilia elata, also known as Coilia elata and Coilia elata, is a migratory fish. Swordfish usually live in the sea, enter the river from February to March every year, and migrate upstream for reproduction. Every spring, swordfish swim up the river in groups, forming a fish season. Small in size, but abundant in quantity and high in yield, it is a common economic fish along the coast. Mainly distributed in China's Yellow Sea, Bohai Sea and East China Sea, all rivers that lead to the sea, such as Liaohe River, Haihe River, Yellow River, Yangtze River and Qiantang River, can be seen. According to the data, Coilia ectenes in China are mainly divided into two ecological groups: river-sea migratory type and lake settled type. The former is divided into several ecotypes such as Yangtze River and Qiantang River according to the water system. Yangtze river swordfish has small eyes, yellow back, white and bright scales, high gloss, round body, belly and white inside. The sea knife is blue and black on the back of the fish. The sea knife is similar to the Qiantang River knife, with red head and tail, blue back and slender figure. Lake knife is a rare "big eye" among swordfish, and its scales are white and its luster is not good.