What is Gasutoro?


a photo of Gastoro
Image credit: © Copyright National Research Institute of Far Seas Fisheries, Japan Fisheries Research and Education Agency

Gasutoro (ガストロ) is widely distributed throughout the temperate and subarctic regions of the Southern Hemisphere, but is not known to be found in the Northern Hemisphere. It is found in the open ocean around Australia and New Zealand, at depths of about 200 meters. It has the English name “Butterfly Tuna (Gasterochisma melampus Richardson, 1845)” because of its large, butterfly-like abdominal fins.

It is mostly caught as bycatch in longline fisheries that catch southern bluefin tuna. This is due to the overlap in habitat with southern bluefin tuna.

It is often thought to taste similar to tuna, a popular sashimi fish, perhaps due to the inclusion of maguro and tuna names in its name, such as “Uroko maguro” and “Butterfly tuna,” but it actually does not resemble tuna very much.

It has a refreshing flavor more like swordfish tuna. The best way to eat it raw is marinated with soy sauce, which takes about 15 minutes for the whole saku (fillet).

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Revision date: January 28, 2023

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What is Himokyu-maki?

a photo of Himokyu maki
Himokyumaki (Hosomaki) using the mantle of ark shell and cucumber as fillings.

Edomae sushi rolls are made with grilled nori. In Tokyo, this is called nori-maki. Himokyu-maki (ひもきゅう巻) is norimaki filled with Akagai mantle wrapped in. The mantle has a stronger sea smell and slight bitterness than the Akagai body itself, and some people actually prefer the mantle. The crunchy texture and umami bring out maximum harmony with the refreshing fragrance and texture of the cucumber. This is a true nori-maki masterpiece. Make sure to give it a try when Akagai is in season.

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Revision date: January 27, 2023

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What is Tazuna-maki?

a photo of Tazunamaki
Tazunamaki made by long-established Kizushi (㐂寿司)

In general, Tazuna-maki (手綱巻き) refers to thinly sliced sayori, shrimp, kohada, and omelets, arranged diagonally and rolled with sushi rice. It is called Tazunamaki because the surface of the diagonally arranged finished product looks like the pattern of a horse’s reins.

The ingredients used for Tazuna-maki are almost always fixed, and the four main colors are: red from the shrimp, silvery white from the sayori or kohada, green from the cucumber, and yellow from the omelet. As a precaution in preparation, the sayori should be used after a quick wash in salted water, or furthermore, it should be kobujime (salted or vinegared fish marinated between sheets of kelp). Cucumbers should also be slightly wilted in salted water to help them adhere to the sushi rice.

On the other hand, Tazuna-maki made by sushi chefs, consists of kohada and kuruma prawns rolled alternately on a bed of sushi rice. This seems like Kansai’s oshizushi, but it is another old Edo-style work (Edomae shigoto).

The balance between the sweetness of the shiba shrimp oboro and the sourness of the kohada is wonderfully balanced, and the taste is so delicious that one can never get tired of it no matter how many times one eats it.

Related contents: Kizushi Tazunamaki

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Revision date: January 25, 2023

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What is Chawan-mushi at a sushi restaurant?

a photo of chawan-mushi
It is typically topped with Kamaboko, Shiitake mushrooms, Ginkgo nuts, and shrimp.

Chawan-mushi (Savory steamed egg custard) is made from eggs and dashi (soup stock) and garnished with shrimp and ginkgo nuts. It is steamed in a cup and often served as a cold or hot appetizer. It is a standard item at the sushi restaurant.

Unlike other egg custard, it is not sweet but it has a savory flavor packed with umami from dashi and topping ingredients. It is velvety feeling on the palate is irresistible.

Then why do sushi restaurants serve chawan-mushi?

That is because sushi is a cold dish, so they basically serve something warm as a garnish.

Another reason is that the ingredients used for chawan-mushi (茶碗蒸し), such as shrimp, shiitake mushrooms, eggs, and kamaboko, are either used daily at sushi restaurants or are readily available at market stores that sell sushi items.

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Revision date: January 20, 2023

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How to eat soups at a sushi restaurant

a photo of eating soup
How to eat shirumono which is soup in a bowl.

A sushi meal is often completed with clear soup or miso soup. Interestingly, the ingredients in the soup differ depending on the sushi restaurant or the day.

Put all four fingers of your left hand under the bottom of the bowl and place your thumb, gently on the rim. The key is to smell the aroma first. Next hold the rim of the bowl right up to your mouth, and do not make any slurping noises. Then eat between the soup and the ingredients alternately.

Turn the lid over and place it on the right side of the bowl. Do not place the lids on top of each other as this may scratch them. Make sure to drop the water drops from the inside of the lid into the soup.

When asked “Could we serve you a soup bowl now?” at a high-class sushi restaurant, it sometimes is a sign that the Omakase course is about to end. If there are any additional sushi toppings you would like to eat, this is the right time to order. And occasions like having a client dinner imply that your meal has reached the budget you informed in advance.

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Revision date: March 1, 2024

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What is Futomaki?

A photo of Futomaki
Futomaki contain multiple ingredients.

Sushi made by spreading vinegared rice on a sheet of dried laver and rolling it up with ingredients is called “Makizushi” in Kansai and “Norimaki” in Kanto, and the two are basically the same.

In Kanto, sushi rolls are distinguished by their thickness as “Hosomaki (thin rolls),” “Nakamaki (medium rolls),” or “Futomaki (thick rolls),” but in Kansai, the term “Makizushi” often refers to “thick rolls.

Hosomaki, such as Kanpyomaki (Dried Gourd Shavings Sushi Roll), Tekkomaki (Tuna roll), and Kappamaki (Cucumber roll), generally contain only one type of ingredient, while Futomaki (太巻き) contains multiple ingredients such as kanpyo, tamagoyaki, shiitake mushrooms, and cucumbers.

The size of the nori used differs depending on the thickness of the roll. Hosomaki uses a sheet of nori cut in half, Nakamaki uses one half to one sheet of nori, and Futomaki uses one or more sheets of nori. The basic size of nori is 21 cm in length and 19 cm in width per sheet, and each sheet weighs about 3 g. This size is called “Zenkei”.

The filling and hearty Futomaki satisfies your appetite. It has a slight sweetness, intricate flavors, and pleasant textures. Everything appealing about sushi is packed into a roll of Futomaki.

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Revision date: January 16, 2023

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Do you know what kind of Tuna you’re eating at a sushi restaurant?

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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What is Moshio?

a photo of moshio
Natural salt with a pleasant taste

The “Mo” of “Moshio (藻塩)” means “seaweed (海藻)” and “shio” means “salt (塩).” The only ingredient in Moshio is Hondawara, a type of seawater and seaweed. It is also called Mojio.

The way it is made is extremely primitive. First, Hondawara (Gulfweed), etc. is soaked in seawater then wrung out and dried multiple times over 2 to 3 days. This creates a brown-colored seawater infused with the umami and color of Hondawara. In the end, Hondawara is dried and grilled, then the charcoal ash is mixed with the seawater infused with the umami and color. This is left for a day, where the ash naturally sinks to the bottom, completing the dark-brown seawater. Moshio is made by boiling down this seawater. This is said to be the origin of salt-making far longer ago than the manufacturing method of using salt farms.

According to a sushi chef at a Michelin Star restaurant, there are two types of Shari and each will either bring out the best of either Akami or the Shiromi. When pursuing ideal Shari to go well with a variety of toppings, this chef happened to come across Moshio. This led to a lot of trial and error, and eventually he came up with a fully universal type of Shari. Perhaps switching to Moshio is a good idea.

It is characteristic in that there is no sharp spiciness and it has a very mellow flavor, so it brings out the taste of the elements of seafood, etc. The color is a light beige and the salt can be called a concentration of umami made from nothing but seawater and seaweed.

Related contents: Nikkei Style

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Revision date: January 7, 2023

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What is Venerupin?

a photo of oyster As this is an extremely lethal toxin, there are reports of cases of poisoning in some types of oysters and Asari (short-necked clams). The source of the Venerupin is said to be the intake of toxic dinoflagellate. This only occurs in early Spring in Nagai, Kanagawa prefecture and Lake Hamana in Shizuoka prefecture and in one instance over 100 people died. However, as there have been no incidents of poisoning since 1950, it’s still not clear if the shellfish actually become toxic or not.

In most cases, the toxic symptoms appear within one to two days and start with abdominal pain, vomiting, constipation, etc., followed by blood spots on the skin and bleeding from the mouth and nose. Liver function also significantly decreases and the patient suffers from mental derangement. They then fall into a coma and die within a few days.

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Revision date: January 5, 2023

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What is Geso?

Geso is not the name of a fish or shellfish.

a photo of squid

Geso refers to the 10 arms/tentacles of a squid.

A photo of Geta
The appearance of Geta (wooden clogs)

The reason squid arms came to be called “Geso” is that the shoes that are removed before entering the indoors in Japan are referred to as “Gesoku”. The name comes from a time when restaurants used to hold onto their customers geta (wooden clogs) and the cloak would tie them with a string in 10-pair units.

a photo of geso nigiri

Geso can be lightly boiled or grilled. For large squid, a butcher knife is inserted at the tip of the arm to peel off the skin membrane, and then the tips of the arms are cut off so the sizes match. When Nitsume or other sauce is applied and it is made into Nigiri, it has an excellent springy texture and scent of the sea. It is also used as Tsumami when drinking alcohol. In my personal opinion, the Geso child of Sumiika is nice and soft and worlds above any others.

a photo of gesoThis is one of the sushi terms that even most of the general public in Japan knows well.

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Revision date: July 2, 2024

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