skipjack Katsuwonus pelamis, a cosmopolitan fish of the tuna family, common in the warm waters of the Indo-Pacific and Atlantic, but less so in the Mediterranean. It accounts for over a third of the world catch of tuna.
Normal length around 60 cm (24"), maximum just over 1 m (40"). The distinctive parallel dark blue stripes running along the sides of its belly account for many vernacular names, including the Australian striped tuna and, more picturesquely, watermelon (a name used also in the USA).