If we compare the section of the belly area between the Japanese ocean’s blue fin tuna and the Atlantic Ocean’s tuna, the abdominal cavity is different. The one from the Atlantic Ocean’s blue fin tuna is divided into two parts, the fatty belly part and the back side reddish tuna meat part whereas the Japanese blue fin tuna’s abdominal cavity doesn’t have bones that breaks into two parts. That’s why there is a transitional piece of flesh called “Chutoro” in Japan.

Now think of the tuna’s belly and the cut after the tuna is divided between various sushi clients. The belly is divided into two sides, a left and right side and the fish has a center cut, a cut towards the tail and towards the head. It a matter of piecing the various portions for suitable sushi chefs. The size of a fish really does matter given the fish has an optimum size.

Don’t be surprised that the body structure of blue fin tuna found in the oceans surrounding Japan differs from those found in other parts of the world. Japanese tuna are like Japanese people, and imported tuna look like “gaijin” with a different physiology; a bigger body, heavier bone structure and taste.

Blue fin tuna that are caught around Japan are naturally suitable for Japanese taste, and less fatty compared to others. However, as Japanese tastes have been influenced by western food culture, more Japanese are favoring fattier tuna. It is all a matter of price, experience and knowing the difference.