The Japanese knife used for filleting fish in sushi preparation is the deba bōchō, commonly shortened to deba.
A deba is a thick, broad-bladed Japanese kitchen knife designed for fish work. Its weight lets a cook remove a fish’s head and cut through tougher areas near the spine and ribs, while its single-bevel edge helps separate flesh from bones during filleting. The blade is usually used with controlled cuts rather than forceful chopping through large mammal bones.
The knife first appeared during Japan’s Edo period in Sakai, a historic knife-making center. Larger hon-deba, meaning “true deba,” are suited to substantial fish; smaller ko-deba versions are useful for smaller specimens. Carbon-steel blades remain traditional, though stainless-steel versions are widely available.
A deba is often confused with a yanagiba. The yanagiba is the long, narrow sashimi knife used to slice finished fillets into clean portions, whereas the deba performs the earlier structural work of breaking down the fish. Nakiri and usuba knives are primarily vegetable knives.