Bonito

Bonito is a type of tuna, which is a member of the mackerel family, and one of the most important fish in Japanese cuisine. Rarely eaten fresh, the dark, oily meat is dried into very hard cubes, which must be ground or shaved with a special tool before use. Bonito shavings form the base for many Japanese sauces and stocks (such as dashi, made with bonito and seaweed).

Bonito flakes
It can be bought in flakes, also known as katsuobushi, which have a strong, salty flavor and a tan color. The flakes are frequently sprinkled over boiled or steamed vegetables and into soups. It is an English word for the Japanese Katsuo.