Euthynnus affinis



Binomial: Euthynnus affinis
English: Mackerel Tuna
Japanese: Suma-Katsuo



sashimi, tataki

m_katsuo01This is Suma. Euthynnus affinis, or mackerel tuna. Amongst all Tuna family, I think it’s the tastiest. The flesh is dark red. The taste is rich and juicy. So tasty.

It’s got black dots on the belly under the pectoral fin. When you see those dots, whatever you do, DO NOT throw away the fish!

Katsuwonus_pelamisThis is common Katsuo, or skipjack tuna, Katsuwonus pelamis. This is the fish that has captured the Japanese fondness. It’s got the distinct stripes on the belly. They migrate from the tropics to subarctic waters in a large school, while Suma moves in small groups in tropical to sub-tropical waters. They migrate from the south to the north along Japan’s coast. We call them “the first katsuo”. The taste is refreshing and light. In the fall, they come back down the coast from the north. They carry fats now. We call them “returning Katsuo”. The taste is rich and juicy. So tasty.

This is called Mackerel Bonito, or Striped Bonito. Sarda orientalis. It’s got sharp teeth. The flesh is soft and watery, and pale pinkish in color. It’s not considered as delicacy as others but the taste is good. Especially at the end of summer when they start putting on some fats, the taste is just as good as other tunas. But sushi chefs don’t serve it usually because it can’t hold the shape of its own, it’s quick to go bad, and the color does not look like Katsuo. You should cook it to appreciate it.


Probably this fish makes me the happiest when catch it. Not only because it’s delicious, but also this fish is migratory and it’s a luck to encounter them unless you are chasing them particularly.
Among all tunas, I think this is the tastiest. Very rich in flavor. Full of essential amino acids and unsaturated fats. Because of that, the fishmeat is really fast to go bad. Lucky to be a fisherman to know exactly how fresh the fish is.
When we cut sashimi out of tuna, we remove the bloody meat which runs alongside of the spine, because it’s too fishy. But you don’t have to do that with this bonito family, even the bloody parts and the guts are tasty. But because it has a distinct flavor, it goes well with garlic, ginger, onions and other rather strong herbs and spices.

Tataki is a kind of sashimi. Grill just the surface of the fillet with skin on in open flame, traditionally straw flame, put it in iced water to stop the heat from reaching inside, and slice thick to sashimi. Tataki method removes the extra moisture and harshness of the flavor, condenses the taste, and adds smoky flavor.

  1. Daz

    Interestingly, in Australia we go out of our way to avoid these tuna and sometimes you can’t get away and all you can catch are these fish.
    You’ve sparked my interest and I’d like to try some one day soon.

    • Totos

      Yes, please do Daz.
      It’s such a delicious fish. This fish is the heart of Japanese cuisine.
      It’s just that it goes bad quickly. Even when you close it with Ike-Jime, it’s only good till the day after. It will lose flavor in the 2nd day. It will be no good sashimi on the 3rd day. And this fish is only good in sashimi. Try it with soy sauce, ginger and other herbs.

  2. philip

    After reading your page, I feel that I should treat these as a fish for the table and not for bait.


  3. scott

    can you put up a video of you filleting a tuna for sashimi? and is there a specific part of the fish that is best for sashimi? cheers

  4. Nelson

    Totos! Thank you for your article! I am just returning from the sea of Cortez from a week long sailing trip and we caught one of these. My shipmates thought it was bonito and wanted to throw it back but when I saw the dots I knew it was Suma. Luckily I read your article on Katsuo. They didn’t believe me until I made tataki and they’re all believers now.

    • Totos

      Hi Nelson.
      Thank you very much for your great feedback!
      I’m glad that more people appreciate this fish.

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