The back of the body is blue-black, the belly is silvery white, and the most obvious feature is that the pectoral fin is extremely long and exceeds the anal fin, so it is called longfin tuna. It is widely distributed in the tropical and temperate waters of the three major oceans, in the latitudes between 45 and 50 degrees north and between 30 and 40 degrees south, but is rarely found between 10 degrees north and south of the equator. The body length is generally between 40 and 100 cm. The temperature range for its habitat is between 10 and 28 degrees Celsius, and the optimum water temperature is cold waters between 10 and 20 degrees Celsius. Taiwanese call it "Chuanzai". Its scientific name is Thunnus alalunga. It is mainly distributed in the equator. It is almost not produced in tropical and subtropical areas. It is a shallow-water fish. Taiwan catches it in the deep sea.