Bonito that are heading up north along the Japanese islands called noborigatsuo, which has a moderate amount of fat and light taste. Bonito that are going down south are modorigatsuo, very fatty and best eaten with green long onions and ginger. It loses freshness easily, so it was not used for sushi until after the Showa Period began.
Trivia 1 : Along with disk abalone, benito cannot be judged its quality by appearances. Whether it is thin or fat, you won't know until you actually cut it open. Especially around April, its quality changes dramatically each day.
Trivia 2 : Grained ginger served together with bonito fish is common to get rid of the smell of bonito fish. However the bonito fish in a great condition matches with various flavor such as karashi mustard and wasabi. Recently there are more places serve bonito fish with karashi mustard.