It commonly reaches fork lengths up to 80 cm (2 ft 7 in) and a mass of 8–10 kg (18–22 lb). It has no scales, except on the lateral line and the corselet (a band of large, thick scales forming a circle around the body behind the head). It is an important prey species for sharks and large pelagic fishes and is often used as live bait when fishing for marlin. It is a streamlined, fast-swimming pelagic fish, common in tropical waters throughout the world, where it inhabits surface waters in large shoals (up to 50,000 fish), feeding on fish, crustaceans, cephalopods, and mollusks. It is a very important species for fisheries. It is a cosmopolitan pelagic fish found in tropical and warm-temperate waters. It is otherwise known as the balaya (Sri Lanka), bakulan/kayu (North Borneo), tongkol/aya (Malay Peninsula/Indonesia), aku (Hawaii), cakalang (Indonesia), katsuo, arctic bonito, mushmouth, oceanic bonito, striped tuna or victor fish. The skipjack tuna ( Katsuwonus pelamis) is a medium-sized perciform fish in the tuna family, Scombridae, and is the only member of the genus Katsuwonus.
