The migrating route of Inshore bluefin tuna and fishing place!

Tuna caught in the coastal regions of the Japan Sea is notable as the best bluefin tuna in January. Iki, a small island in Kyushu area is one of the famous ports for tuna.

In February and March, the tuna auction market becomes slack due to rough weather. Just a few tunas from Nachikatsuura where is also the famous port for tuna are on the market.

In March and April, tunas become thin because their eggs need many nutrients.

In May, large tuna is seldom seen in the Tsukiji Fish Market. Even if there is, its body is really thin. “Kinkaimono” which means a shore-fish is generally considered as high-class tuna, but in this season, imported tuna is useful instead.

It is said that Pacific Bluefin tunas spawn around Japanese waters between Taiwan and Okinawa in April and May. And then, they go up to fertile, north sea along the eastern coast of Japan.

In June, “Chubo” which is young and small tuna is taken hugely off the coast of the Sea of Japan. The school of Chubo begin moving northward in this season.

In July and August, tunas can be seen occasionally but their bodies are still thin. Instead, Boston Tuna which is caught in the Atlantic Ocean and nicknamed “Jumbo” is on the market. Its fresh is softer than “Kinkaimono” and it doesn’t have medium-fatty part which “Kinkaimono” has.

In September, Boston Tunas are at their best with plenty of fat on them. The best season of Boston Tuna is limited and ends in October. But fortunately, Japanese tunas come into season.

The school of tunas split up into two groups, the one takes Pacific Ocean route and another takes the Japan Sea route and both of them move northward along the Japanese Islands. Some of them reach the Tsugaru Strait where and the season of Tuna begins from September to next January. Oma town and Toi town is famous nationwide for its catch of tuna from the Tsugaru Strait. The flavor of tuna in September is still weak but it becomes stronger in October. In November, feed of tunas such as Pacific saury or Japanese common squid with plenty of fat increase and flavor of tuna also gets stronger. In December, the peak season comes around.

A catch of tuna falls off in January and it enters the final season. The temperature of sea water gets cold and feed of tuna, squids decrease and the fishing season in this area ends.


We hope this information will be helpful.

Revision date: August 20, 2018

Tuna is allowed to rest before it is used.

Once a bluefin tuna is caught, it arrives in Tsukiji fish market within a day or two. However, that fish is not used as a sushi topping that day. No mater how good the tuna is, it starts out very stiff and is not in a state where it should be eaten. The meat is hard and the white muscle lines are left in your mouth. The odor and acidic taste of the red meat is strong and the unique sweetness of the fish is nowhere to be found. After it has rested the muscles soften, bringing out the fat.

Then, when the sushi chef gets the tuna, he first separates the red, lean meat and the fatty toro portion, rewraps them separately and, seals them in plastic and puts them on ice. Next is waiting for the “young” meat, not yet suitable for eating, to mature. The number of days the fish will be rested depends on the size of the fish and the temperature. The smaller the cut and the warmer the temperature, the shorter the rest time. Generally the time is from 3-14 days.

This “young” fish not ready for consumption is a fresh, deep color but as it matures the color darkens, the fat is brought out and becomes a fleshy color. Proper care must be taken because if it’s rested for too long, the color changes too quickly.


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Revision date: August 13, 2018

What is “Hagashi”?

There is a part on the tuna belly called “Sunazuri” or “Zuri” (gizzards). Normally “Jabara,” with the diagonal white lines is the king of tuna, but the fatty tuna is spoiled if the white lines are left in your mouth. Instead, the knife cuts along those lines, gently removing the fish meat from them, making “Hagashi.” If the chef is not skilled, this cut will take time and extra meat is left behind. This is delicate work, making for a delicious and satisfying experience.


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Revision date: May 7, 2018

Strong belief that fish is only about freshness

In some cases, the strong belief that fish is only about freshness, may prevent you from tasting the true value of the fish. For example, slicing up a fish that was just swimming, in front of the customer. The umami flavor is weak at first so while the texture is tough (a unique, crunchy feeling), the flavor is lacking. But the idea that freshness is equivalent to deliciousness continues still. This is a typical case of faith in freshness overtaking the actual taste.


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Revision date: April 16, 2018

Why is freshly-caught fish allowed to age?

The most delicious time to eat fish differs depending on if it is served as sashimi, as sushi, or boiled. Fresh does not necessarily mean delicious. For example, Japanese Amberjack should be used in sashimi 3-5 days after being caught, in sushi a week after being caught and it can be used in a stew or boiled once it turns black around the edges. This is because the inosine acid, which is responsible for the umami taste, increases after rigor mortis ends and understanding the timing of the peak in flavor is up to the skill of the sushi chef.


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Revision date: March 12, 2018

Isn’t it true that fish is all about the freshness??

It’s a well-known fact among professional chefs that some fish don’t rely solely on freshness. Of course there is importance in freshness, but that’s just one element. It’s generally understood that flavor and taste improve with time (maturity).

The umami* found in the meat of the fish is essentially inosinic acid and glutamic acid. After a certain amount of time has passed after a fish has died, the body stiffens and not long after that the rigor lets up. The inosinic acid, which the umami is composed of, comes after the fish has stiffened. It then accumulates in the process of the body relaxing. This is the same in beef and pork in which there is no umami in the meat unless it is hung and matured for a time.

Therefore, ikizukuri sashimi that is still twitching usually won’t have the taste or depth of umami. However, the firm texture of sashimi is also an undeniable enjoyable aspect. It is not all about the umami.

*Glutamic acid, Inosinic acid and Guanylic acid are representative components of umami. Guanylic acid is found in kelp and vegetables (tomato, Chinese cabbage, green tea, etc.) as well as Parmesan cheese, inosinic acid is found in fish (bonito, macheral, sea bream, etc.) and meat (pork, chicken, etc.) while Guanylic acid is abundant in mushrooms (especially dried shiitake mushrooms).


We hope this information will be helpful.

Revision date: July 17, 2017