Katsuo

Skipjack tuna is one of the most important and versatile fish in Japanese cooking, but it is not usually available fresh in the West, since once killed it goes off very quickly. It grows to about 1 m/3 ft long and weighs up to 20 kg/44 lb in tropical to subtropical seas, coming up on the warm current in large shoals to the Japanese coasts in spring. Katsuo is a handsome fish, with a deep blue-mauve back and silvery white belly with a few black stripes. In the same katsuo group are frigate mackerel, round frigate mackerel and striped bonito; these are slightly smaller than skipjack tuna.