Shima-aji, or Japanese “striped jack,” is a common point of confusion for many sushi eaters.
The Shima means “striped” and aji is Japanese “horse mackerel,” or “jack.” But Shima-aji and aji make two very different types of sushi.
Aji would be more familiar to those who have eaten the more common saba (mackerel), which is a bit more fatty and oily with a “fishier” finish. The Shima variety is quite a bit leaner and more delicate, closer to Kanpachi.
Shima-aji tastes like a cross between saba (mackerel) and Kanpachi (greater amberjack, like leaner yellowtail).
It’s light and buttery with very tender flesh and just a bit of fat. When very fresh, it has a firm texture and finishes with sweet notes.