Tunas vary considerably, both within and among species. Tunas are elongated, robust, and streamlined fishes; they have a rounded body that tapers to a slender tail base and a forked or crescent-shaped tail. In colour, tunas are generally dark above and silvery below, often with an iridescent shine.
Skipjack are the smallest and most abundant of the major commercial tuna species. They have a streamlined body that is mostly without scales. Their backs are dark purple-blue and their lower sides and bellies are silver with four to six dark bands. Skipjack can live as long as eight to 10 years.
They are found mainly in the tropical areas of the Atlantic, Indian and Pacific Oceans, with the greatest abundance seen near the equator. Skipjack usually swim near the surface at night and can dive up to 850 feet during the day. Large schools of adult skipjack tuna often mix with juvenile yellowfin and bigeye tuna. They can breed year-round.
It grows up to 1 m (3 ft) in length.