The Japanese term for skipjack tuna often used in sushi and sashimi is katsuo.
Skipjack tuna, scientifically known as Katsuwonus pelamis, is a major food fish in Japan. It may be served raw in sushi or sashimi, lightly seared in katsuo tataki, or cooked and preserved for other Japanese dishes.
Katsuo is not the same menu term as maguro. Maguro generally refers to tuna, especially tuna of the genus Thunnus, while katsuo specifically names skipjack tuna. Hamachi means young yellowtail, and sake or shake refers to salmon, so neither is a synonym.
Seasonality also affects Japanese names and preferences. Skipjack moving north in summer may be called hatsugatsuo, or “first katsuo,” while fish returning south in autumn may be called modorigatsuo. These seasonal fish can differ noticeably in fat content and flavor.