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Katsuo, Japan’s ubiquitous tuna

by Makiko Itoh

In the world of sushi and sashimi, maguro (tuna, especially bluefin tuna) currently reigns supreme. It’s so popular that large specimens of the fish fetch ridiculous, headline-grabbing prices at the Tsukiji wholesale market in Tokyo, and the species is in danger of extinction due to overfishing. But bluefin was not always the king of Japan’s culinary sea — it only became popular in the 20th century. The fish that reigned supreme before it was skipjack tuna — better known as bonito, and as katsuo in Japanese.

Katsuo is one of the most important fish on the Japanese menu. Dried and fermented it becomes katsuobushi, one of the main ingredients in dashi stock, the foundation of Japanese cooking. But katsuo is also eaten in many other ways: as tsukudani, preserved by cooking in a sweet-salty sauce; as shiokara, cured in salt; coated in flour and deep-fried; and, of course, raw or almost raw. The most popular way it’s served these days is as tataki — seared on the outside, still raw on the inside, sliced and eaten as sashimi. Katsuo tataki is a speciality of Kochi Prefecture, where it’s seared over a sweet-smelling straw fire.

Katsuo has been a perennial favorite in Japan, perhaps because it was and still is very abundant near its shores. There are records of katsuo being served to the Yamato Imperial Court in the third century, and its importance as a food is reflected by katsuobushi’s use as one of the formal offerings made at a Shinto shrine.

For a while katsuo was seen as a rather common fish: In the Kamakura Period (1192-1333), the monk Yoshida Kenko noted in his “Tsurezuregusa” collection of essays that even the poor threw away the heads. But by the Edo Period (1603-1867) katsuo had regained its status as a desirable fish. In particular hatsu-gatsuo, the “first catch” of katsuo in the late spring to early summer, was so highly prized that there was even a saying, “I’d be willing to pawn my wife for a taste of hatsu-gatsuo.” The word “hatsu-gatsuo” is considered a key word indicating the season in haiku rules, indicating early summer.

A good reason for eating katsuo in this century is that of all the meaty red-flesh types of fish used for sushi and sashimi it’s considered to be the most sustainable. Unlike bluefin tuna, which seems to share the modern Japanese problem of working (well, swimming) too long and hard and not making enough babies, katsuo spawns quite readily. So for the moment you can enjoy it free of guilt — although like other predator fish it has a moderately high amount of mercury so don’t go overboard, especially if you’re pregnant.

May is a great time for hatsu-gatsuo, especially in the Tokyo region, and preferably as tataki, sashimi or sushi. Grated raw garlic goes a lot better with uncooked katsuo than the usual grated wasabi, as do chopped green onions, grated ginger and shredded shiso leaves and myōga ginger. You may not want to pawn your spouse for a taste, but it’s certainly worth setting aside a few pennies for.

Makiko Itoh is the author of “The Just Bento Cookbook” (Kodansha USA). She writes about bentō lunches at www.justbento.com and about Japanese cooking and more at www.justhungry.com.

  • Adam Sharpe

    For mercury poisoning reasons, which is accumulating in all larger fish especially all types of tuna (bluefin is definitely dangerous), but for the fact that all populations of ocean fish are in a near catastophic decline, maybe we should do without for a couple of centruies until the populatons recover and we end pollution.