Worldwide there are 12 species of billfish—a group of large predatory fish whose upper jaws bear a long, bony spear- or sword-shaped bill. They include marlins, spearfish and sailfish (family Istiophoridae), as well as swordfish (family Xiphiidae). In different seasons of the year, six species of these fast-swimming fish follow the Kuroshio Current into the waters around Taiwan.