Maguro まぐろ (tuna) is one of the most commercially valuable fish, and is highly sought-after at fish auctions. They are impressive wild animals: capable of reaching 3 meters in length, and weighing hundreds of kilograms. Their exposure to cold waters result in relatively high fat build-up, commonly around internal organs where they function as insulation.
The flesh of the tuna is divided, generally, into three categories:
Akami あかみ - deep red lean tuna (further divided into Senaka 背中, Sekami 背神, and Seshimo 背しもwhose grade is arranged in descending order)
Chu-toro 中とろ - medium fat tuna
Oo-toro 大トロ - fatty tuna
Other parts of the tuna are (though rarely found in most restaurants):
Kama-Toro かまとろ - back cheek
Hoho-niku ほほ肉 - Cheek
Noten ほてん - Top of the head
Depending on the chefs, some prefer to serve Oo-toro as sashimi as their rich flavours are best enjoyed independently, whilst Chu-toro served as sushi so that neither one of the components overpower the other.
Ways in which Tuna can be served:
Tekka-Don 鉄火丼 (raw tuna slices over a bowl of rice) is named as such because of the intense red appearance of the dish.
Akami-Shoyu Tsuke 赤み醤油漬け (red lean tuna marinated in tuna) is prepared by marinating slices of Akami in soya sauce for minutes. This accentuates the ruby red appearance of the fish slices. This was often done so during the Edo period where there was lack of refrigeration.
Toro Kama no Sumiyaki トロかまの炭焼き (grilled tuna collarbone) is a luxurious item that can be found in few menus.