Bluefin tuna | Sushiblog－Sushiuniversity

a photo of bluefin tuna — Bluefin tuna in the fish market

There are eight types of tuna fished in the world: Pacific bluefin tuna (T. orientalis), Atlantic bluefin tuna (T. thynnus), Southern bluefin tuna (T. thynnus maccoyii), Bigeye tuna (T. obesus), Yellowfin tuna (T. albacares), Albacore (T. alalunga), Blackfin tuna (T. atlanticus) and Longtail tuna (T. tonggol).

According to 2019 statistics, approximately 2,280,000 tons of 8 types of tuna were caught that year. Of those, only 1.6 tons per year are Pacific bluefin tuna. Atlantic bluefin tuna only reaches 3.1 tons per year. Southern bluefin tuna is 1.7 tons per year. Yellowfin tuna is 1,579,000 tons per year. Bigeye tuna accounts for 392,000 tons per year. Albacore is 245,000 tons per year. There is some fluctuation from year to year, but the data has remained pretty stable over the past 20 years, except for the Yellowfin tuna. Blackfin tuna catch is extremely how and is not found at sushi restaurants as a topping except Florida. Longtail tuna is no more than a by-catch of other tuna and is the least caught species in the tuna genus.

Of these eight types, the six types used as Nigiri sushi toppings include Pacific bluefin tuna, Atlantic bluefin tuna, Southern bluefin tuna, Bigeye tuna, Yellowfin tuna and Albacore.

We have attempted to lay them out here in order of price. Incidentally, the unit price for Bluefin tuna is more than ten times that of Albacore.

an illustration of Distribution map of Pacific bluefin tuna — Distribution map of Pacific bluefin tuna

The statistics categorize Pacific bluefin tuna and Atlantic bluefin tuna separately, but Japanese sushi restaurants do not distinguish the two. In other words, the menu does not read “Pacific bluefin tuna”. Not only that, the menu actually only lists “Tuna,” so in that case you can assume it is either Bluefin tuna, Southern bluefin tuna or Bigeye tuna.

an illustration of Distribution map of Atlantic bluefin tuna — Distribution map of Atlantic bluefin tuna

Those in the industry at the Toyosu Market refer to Atlantic bluefin tuna as “Jumbo”. This is the nickname for Tuna imported from Boston and Ireland into Japan. This also makes it clear that it is not the Pacific bluefin tuna fished in Japan’s local sea waters. Southern bluefin tuna is mainly caught in the Indian Ocean and flash-frozen to negative 60℃ before being distributed all over the world. The majority of Bigeye tuna, Yellowfin tuna and Albacore are also frozen and distributed.

When the Tuna a sushi restaurant is serving is Bluefin tuna, the chef wants to emphasize that, so he or she may drum up conversation with, “We got some good Bluefin tuna in today.” Incidentally, Bluefin tuna is also called “Hon-maguro”. In Japanese “Hon” is short for “Honto,” which means “Real.” In other words, this implies that other Tuna is not the real thing.

a photo of Yellowfin tuna — Yellowfin tuna in the fish market

Yellowfin tuna is generally served at Kansai sushi restaurants, but not at Tokyo sushi restaurants. This is due to differences in Kansai and Kanto food cultures. The Ahi often consumed in Hawaii is Yellowfin tuna. Tuna caught in the inshore waters of Micronesia is either Yellowfin tuna or Bigeye tuna.

a photo of bigeye tuna — Bigeye tuna in the fish market

Yellowfin tuna and Bigeye tuna are often used for take-out sushi. If Bluefin tuna is used, this will be indicated with a label on the package making it clear that it, “Includes Bluefin tuna.” That is how expensive and delicious Bluefin tuna is. However, in this case you can be sure that the Bluefin tuna came frozen and was farmed. Also, depending on when it was fished, the akami (red meat) of the Bigeye tuna caught in the inshore of Japan are nearly on-par with the akami Bluefin tuna. Bigeye tuna is the most-consumed Tuna as Sashimi in Japan.

a photo of Albacore — Albacore in the fish market

Albacore is often served at conveyor belt sushi. Bintoro is especially popular. Bintoro is the name for the Toro part of Albacore. The meat is whiter than that of Bluefin tuna and the fat is known for being lighter.

In conclusion, you may have never been aware of the types of Tuna consumed at sushi restaurants. The types of Tuna that go better with spicy sauces are generally Yellowfin tuna and Albacore. For the same reason, Yellowfin tuna and Albacore are often used in Sushi rolls. But when made into Nigiri sushi, you can’t help but to be conscious of the type of tuna because the flavor and aroma are apparent. Also, when Bluefin tuna is served raw, you can expect top-level fragrance.

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Revision date: January 11, 2023

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There are three elements that make good quality Kuromaguro（Bluefin tuna）.

They are decidedly, color, fragrance and texture.

First of all, color does not simply refer to the color of the cross-section when the fish is cut with a butcher knife.

It refers to how long the fish maintains its “characteristic coloring”. After all, tuna darkens as time passes, eventually turning a burnt-brown color. The true, visual charm of Kuromaguro is the eye-awakening red color that catches your attention when the sushi is placed on a counter or plate. This wonderful coloring is a characteristic of tuna caught through longline fishing or single‐hook fishing. On the other hand, it is said that those caught in round haul nets don’t hold their color and don’t last long. When frozen tuna is thawed, it turns brown within a day. This focus on color is based more on Japanese restaurants that serve sashimi at tables that are located farther away from where the food is being prepared, than on sushi. Incidentally, Mebachi, despite also being tuna, holds its color longer than Kuromaguro does and is suitable for take-out sushi. Minamimaguro is a darker red color than Kuromaguro, but it also loses its color quicker. Kihada maintains its color best.

Next, where does Kuromaguro’s appealing fragrance come from?

The truth is that the source of fish flavor components is still being researched and there are a lot of unknowns. What we do know is that this fragrance is made up of many volatile compounds, but since there are only trace amounts of each one, they are difficult to analyze.

Yet, in the case of expensive Kuromaguro, every measure possible is taken to make sure this fragrance is maintained. Kuromaguro is a migratory fish that gets around by swimming at high speeds in the surface layer of the sea. It needs strong muscles to swim this fast. it also needs to circulate blood throughout its entire body in order to vigorously move those muscles. When a tuna violently struggles to resist and twists its body to avoid being caught, the proteins in its muscles (myosin and myoglobin) rapidly react with oxygen and start to degenerate. This causes Yake and the oxidized odor of tuna. It is important to catch the tuna while causing it as little stress as possible, quickly remove the organs and then use ice to rapidly cool the entire body. If this process is delayed then the pleasant fragrance will transform into an odor. In other words, the scent of Kuromaguro all depends on how it is processed after being caught.

The meat of Kuromaguro that is properly processed emits a unique aroma with a slightly acidic taste when you put it in your mouth. That fragrance lingers for a long time and it combines beautifully with the acetic acid of the sushi rice to go straight to your nose. Then, the moment the fish has disappeared down your throat, the scent of the iron and a subtle acidic taste linger very nicely. This experience is only possible with the exceptional Kuromaguro.

As for the texture, this is determined by the fat distribution of the tuna.

Especially in winter, the Harakami cross-section of Kuromaguro is marbled, much like the Ribulose of Wagyu beef. The melting point for the fat of high-quality tuna is low, and it starts to dissolve even at human skin temperature. This is why sushi chefs who are particular about the sense of unity between shari (sushi rice) and tuna, say, “Shari should be skin temperature.”

There are many chefs who say that the umami of Kuromaguro is in the fat. In the first place, Kuromaguro is one of the fattier fish, and especially between autumn and winter, the Kuromaguro that fed on Surumeika and Sanma has exceptional Harakami. The organs of both Surumeika and Sanma are rich, full-bodied and delicious, even when grilled and eaten by humans. In other words, it is the Surumeika and Sanma that the tuna feeds on that determine the quality of meat. As an example of the meat quality of tuna being affected by what that tuna fed on, Kuromaguro in the Atlantic ocean that has fed on Nishin may exhibit the scent of Nishin when made into sashimi.

However, having a high fat content is not the most important factor. For example, farmed Kuromaguro is fed a high-protein diet so that it will be fatty regardless of the season. Yet, the fat is tougher than that of the wild fish and it’s not something that leaves you wanting a lot more. In comparison, the fat of wild Kuromaguro has a fine texture throughout, immediately melts in your mouth and is digested easily. As sushi chefs know, the fresh fish seems to suction to their hands when making the nigiri sushi. In the same way, it has a smoothness that seems to suction to your tongue when you put it in your mouth. Once you’ve swallowed, it leaves you craving more.

This is the depth of wild Kuromaguro.

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We hope this information will be helpful.

Revision date: July 2 2022