Seki Saba and Seki Aji: Oita's Prized Branded Fish

Seki saba (mackerel) and seki aji (horse mackerel) are caught specifically in the Bungo Channel off Saganoseki, Oita, where strong tidal currents are credited with giving the fish firmer flesh and more consistent fat content than mackerel and horse mackerel caught elsewhere. They're caught using single-hook line fishing rather than nets, in part to avoid bruising the fish, and handled carefully from catch to sale — the whole process is built around preserving quality, not just volume.

Because of this care, seki saba and seki aji are strictly regulated brand names — fish caught outside the specific method and area can't legally be sold under those labels, similar to protected regional products elsewhere in Japan. They command noticeably higher prices than ordinary mackerel and are often served simply, as sashimi, to let the texture and fat speak for themselves. Availability and price shift with the season and catch, so it's worth confirming current status if you're chasing the real thing.