The bluefin tuna goes by different names in Japanese depending on its age. It starts out as “Meji (メジ or メジマグロ),” grows into “Chubou (中坊)” and finally is called Maguro or Shibi (once it’s 50 kg or more).
Meji is less than 1 year old and weighs around 20 kg. The term “Meji” is primarily used in the Kanto region. In the Kansai region, it is called “Yokowa (ヨコワ).” Bluefin tuna have ring-like spots on their sides during their juvenile stage, which disappear as they mature. The regional name for the juvenile stage, “Yokowa” (where “Yoko” means “side” and ‘wa’ means “ring”), derives from these spots.
Chubou is an old word for relatively low-class Buddhist priests who were treated as errand boys. I guess it was meant to imply that these boys were even weaker than tuna. At this stage, the fish are between 2-5 years old and weigh about 40kg.
Anything larger than that is called Maguro. The biggest is 3m long and 600kg or more. Especially large tuna is called Shibi. “Shibi” comes from the Japanese characters for “4-days”, which is how long the fish takes to mature.
From late November, Meji fixed net fishing begins in Himi and Sado in the Hokuriku region. Similarly, fishing starts in Shiogama and Kamaishi in the Sanriku rerion, with the peak season for Meji fishing occurring from December to February. In early summer, Chubou begins to be caught off the Sanriku coast, reaching its peak season from May to July. This spring’s tuna schools migrate through the Boso Peninsula and cross the Pacific Ocean. The juvenile bluefin tuna fishing season from spring to early summer comes to an end.
Meji has a unique scent and taste that sets it apart from full-grown tuna. The color is similar to the skipjack rather than bluefin. On the other hand, Chubou has a lighter color and it isn’t as rich, but the flavor is young, refreshing tuna. That is why Meji is considered to be a completely separate sushi topping and Chubou is presented to be a type of tuna.
Related contents: TYPES OF TUNA
We hope this information will be helpful.
Revision date: June 9, 2025
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