Bonito or katsuo as we call it in Japan is a fish that makes a frequent appearance in Japanese cuisine. Most of the times, we are unaware of its presence, as it is most commonly used as katsuobushi. Katsuobushi is where the katsuo is dried, fermented, smoked then shaved into whisps. The katsuo shavings are then used as toppings for foods such as okonomiyaki and also a core ingredient in dashi (what is dashi?) Katsuo is also served during meals, most commonly seared, sliced, seasoned like a carpaccio. We call that dish katsuo no tataki.
Katsuo is in season in Japan two times a year.
Katsuo just like maguro tuna, needs to constantly keep swimming in order to survive. March – May is when the younger katsuo swim upstream from Kyushu towards Hokkaido and August – September is when the katsuo swim back down to lay eggs.
Upstream katsuo hatsu katuso is leaner and best served seared katsuo no tataki. Downstream katsuo modori katsuo is fattier and the meat has more depth, since they gained muscle swimming up north and are also feeding on plankton and other aquatics from the mineral rich northern Hokkaido sea. The katsuo served in August and September, are best served as sashimi. Katsuo is also an extremely finicky fish and one can tell right away if it is not fresh by the smell and color.
This is a super ultra nerdy post about one of the hundreds of fish served in Japanese cuisine but as I was writing the Summer Sashimi post, I found myself going on and on about katsuo and decided katsuo deserved its own post.