Sushibog is wrtten by researchers of Sushi University

What is Gyosho (fish sauce)?

Shiokara (salted fish guts) and Gyosho (fish sauce) are widely produced throughout East Asia and are very similar foods in terms of their ingredients and production methods.

Gyosho is made by preserving raw seafood in salt. It is a fermented food in which the raw materials are broken down into amino acids, mainly by the action of enzymes contained in the raw materials, and the umami is intensified. There are solid and liquid products leached from it.

The production process is not much different from that of salted fish, but salted fish is intended for long-term preservation of protein sources, whereas gyosho is produced for use as a seasoning. It is originally obtained as a byproduct of salted fish, but nowadays, it is produced only for the purpose of obtaining Gyosho.

However, most of the Shoyu produced in Japan is made from cereal grains, and the amount of gyosho produced for local consumption is minimal.

Types of Gyosho

Shottsuru

Shottsuru has long been produced in the Akita area. Sailfin sandfish (Hatahata) is the most well-known fish used, but Sardine and Pacific sand lance are also used. First, the fish’s head, entrails, and tail fins are removed, and the fish is washed in water. Then the fish is drained, and about 10 kg of fish is mixed with about 1,800 ml of rice malt and 1,800 ml of salt, packed in a wooden barrel, covered with a lid, and weighted down. After maturing in a cool, dark place for about three years, the fish is filtered and boiled to make the product.

Ishiru

Ishiru is made in the Okunoto region. There are other names such as Ishiri, Yoshiru, and Yoshiri. The fish used are sardine, round herring, horse-mackerel, etc. The meat is often processed into dried fish, and the surplus heads and entrails are used. About 30% salt is added to this, packed in miso barrels, covered with a sheet, and aged for six months to a year. After that, it is boiled and filtered to make the product.

Ishikawa Prefecture also produces “Ishiri,” which is easily mistaken for “Ishiru,” but it is made from the entrails of the Japanese common squid.

Nam pla (น้ำปลา)

Nam pla is an essential seasoning for Thai cuisine. In Thai, nam means liquid and pla means fish. In the traditional method, small marine fish, starting with sardine, are mixed with 30~40% salt by weight and placed in a large jar for maturing.

After about a year, a long, thin bamboo basket is inserted into the jar and the liquid that has leached out is drawn out and bottled to make the product. Inland, freshwater fish such as Carp and Loach are used. There is also a theory that the origin of Nam pla is to use freshwater fish.

Anchovy sauce

Gyosho, called garum, was widely used in ancient Rome around the 1st century BC. Bluefish such as mackerel would be pickled in salt, stuffed into unglazed jars, and maturing under the sun. The garum that flowed out through a hole drilled in the bottom of the jar was then used as a seasoning. In Italy, garum production stopped around the 16th century.

Anchovy sauce, a similar product made by maturing salted round herring for six months or more, grinding it, and adding spices, is now used as a secret ingredient in spaghetti and other Italian dishes.

Nước mắm

Nước mắm is mainly made from Round herring and Amberstripe scad in Vietnamese Gyosho, and Carp, Loach and Catfish fry are also used around the Mekong Delta. The cleaned fish is placed in a container with 10~15% salt by weight, stirred every morning, and salt is gradually added until it reaches a concentration of about 30%, depending on the progress of maturing. Those aged for one year or more are more delicious. Gyosho from Đảo Phú Quốc is considered the best.

Colatura

Colatura is an Italian Gyosho. It is made from nothing but round herring and salt. The round herring is first removed from the head and entrails and placed in a barrel, alternately layered with salt. Then, a wooden lid is placed on the herring, and weights are placed on top of it for maturing.

After maturing for three to four years, a hole is drilled in the bottom of the barrel and the Colatura is slowly extracted, drop by drop, over time. The slow aging process in the barrels concentrates the flavor of the fish and produces the amber-colored Colatura.

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Revision date: February 20, 2023

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What is Yellow caviar in Japan?

a photo of Yellow caviar — Rainbow trout can also be yellow using a feed that does not contain astaxanthin.

Shinanoyuki-masu (信濃雪鱒) is a cold-water fish classified in the genus Coregonus, which is related to salmon, and was not originally from Japan.

In 1975, eggs were introduced to Nagano Prefecture from former Czechoslovakia, and after 10 years of testing and research at the Nagano Prefectural Fisheries Experiment Station, the prefecture succeeded in establishing the world’s first aquaculture technology.

In 1983, full-scale production began on a private-sector basis, and the fish was named Shinanoyuki-masu (shinano means ‘Nagano prefecture’, yuki means ‘snow’, and masu means ‘trout’), an appropriate nickname for its silvery-white appearance reminiscent of snow.

The neighboring Saku Aquaculture and Fisheries Cooperative Association also sell sturgeon roe under the name Golden caviar after separating the muscle-like roe into pieces and marinating them in salt. However, this is not a Golden caviar, but rather a Yellow caviar.

Generally, River trout, Char, Yamame, and Amago, which grow only in rivers and lakes, do not take red pigments, so their eggs themselves remain yellow. Yellow is also associated with roes but can also come from an albino fish. Rainbow trout is almost always orange, but can also be yellow using a feed that does not contain astaxanthin.

These are what we call Yellow caviar in Japan.

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Revision date: February 18, 2023

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What is Tsukudani?

a photo of Tsukudani — Assorted Tsukudani

Tsukudani (佃煮) is a type of processed food made by simmering small fish caught at the seashore or lakeshore in seasonings. Tsukudani is boiled down in a seasoning solution consisting mainly of soy sauce and sugar, so it can be kept for a long time. In addition to the sterilizing effect of heating, the osmotic pressure created by the salt in the soy sauce reduces the water content in the tissue. This reduces the proliferation of bacteria and thus preserves the fish.

The marine products used to make Tsukudani include small fish such as Spiny goby (Haze), Pacific sand lance (Konago), Half mouth sardine (Shirasu), Crucian carp (Funa), Bitterling (Tanago), and Japanese smelt (Wakasagi); diced Bonito (Katsuo) and Tuna (Maguro); shellfish such as Baby clam (Asari), Orient clam (Hamaguri), and Bloody clam (Akagai); crustaceans such as Shrimp (Ebi) and Mysid (Ami); and seaweeds such as Kombu and Nori. Shio-kombu is also a type of Tsukudani.

For Tsukudani, the freshest ingredients are chosen. If small fish are used that are not fresh, their flesh will fall apart and the seasoning will become cloudy, reducing the value of the product.

When making Tsukudani, the first step is to bring water, soy sauce, sugar, and other seasonings to a boil in an iron cauldron. The ingredients are then placed in the pot and simmered over low heat to allow the liquid to absorb into the tissues of the ingredients. After the simmering process, the Tsukudani is removed from the cauldron and cooled quickly by blowing air through a fan or similar device. The reason for this is that prolonged heat will cause the quality of the product to deteriorate.

The name Tsukudani is said to have originated with fishermen on Tsukuda Island (佃島) during the Edo period (1603-1868), a small island at the mouth of the Sumida River, which flows into Edo Bay. It was named Tsukuda Island after a group of fishermen from the village of Tsukuda in Settsu (摂津), who were invited to settle there when the Edo shogunate was established.

Since Edo’s traditional fishing industry was underdeveloped then, Tokugawa Ieyasu is said to have introduced advanced fishing techniques from the west to supply food for the urban population of Edo.

Tsukuda Island fishermen delivered fish to Edo Castle and the lords. On the other hand, small fish that had no commercial value were seasoned and processed for their use.

Their taste became so well known that they came to be called Tsukuda-ni (ni means simmer) after the name of the land. Tsukudani was a way to make effective use of small fish without discarding them and preserving them.

These Tsukudani were brought back to the country as souvenirs by the samurai on the “Sankinkotai (duty of alternate-year attendance in Edo)”. Eventually, local producers began to follow their example, and it spread throughout the country.

Tsukudani has several variations. Shigure-ni (時雨煮) is made by cooking flaked clams, clams, and other shellfish with soy sauce as well as sansho (Japanese pepper) and ginger. Shigure-hamaguri (時雨蛤) is a specialty of Kuwana, Mie Prefecture. Kanro-ni (甘露煮) is soy sauce with more syrup added and boiled down until there is no more liquid. Ame-ni (飴煮) is made by adding sake and mirin to soy sauce, simmering the ingredients in the seasoning liquid, and then adding more syrup. In the past, Ame-ni was often made with river fish such as crucian carp. In recent years, sugar and syrup have been used in Tsukudani, and the distinction between Kanro-ni and Ame-ni seems to have become ambiguous.

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Revision date: February 17, 2023

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What is Brown trout sushi?

a photo of Brown trout — Brown trout is a popular target in controlled fishing areas.

What is Brown trout?

In Europe, the word “Trout” often refers to Brown trout. It has been transplanted to many parts of the world as an angling target fish.

Since the 1860s, it has been transplanted to all parts of the world and has become established in natural waters. It appears to have been transplanted to Japan in the 1930s via the U.S. mixed with Brook trout eggs, and natural reproduction has been confirmed in Lake Chuzenji, Lake Ashi, and the upper reaches of the Katsura River.

Body shape is similar to Rainbow trout, etc. The body color is grayish blue with relatively large black spots on the dorsal surface of the body and near the base of the dorsal fin, and whitish-orange spots below the lateral line. 1-5 years in freshwater, then become smolt and descend to the sea, spending 6 months to 5 years in the ocean. The descending type is also called Seatrout. Some spend their entire lives in freshwater areas such as rivers and lakes. It reaches a maximum length of 0.7 m.

What does Brown trout sushi taste like?

Brown trout is said to have less fat and a lighter flavor than rainbow trout, and when eaten as sashimi, it should be frozen completely before eating, since it is a freshwater fish, it is possible that parasites may be hidden in it. It also has a fishy odor unique to river fish, so it is necessary to quickly remove the blood. However, we have never heard of a sushi restaurant serving brown trout nigiri. Brown trout and Rainbow trout hybrids are sold as Shinshu-salmon (信州サーモン), and their market price is over 2,000 yen per kilogram. Shinshu-salmon nigiri is commonly eaten in Nagano and other places in Japan.

In Europe, where it originated, it is a high-grade fish that is delicious to eat. It is farmed mainly in France and Austria for eating purposes. However, compared to Rainbow trout, it grows more slowly and is more difficult to farm, so there are only a few companies that provide it. Hence, it is expensive. The main way to eat trout is to cook it. Incidentally, Schubert’s song “The Trout” was inspired by the brown trout.

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Revision date: February 16, 2023

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What is the thought behind Toro?

a photo of Toro block — Marbled toro block

Toro salmon, Toro Katsuo, Toro Sawara, Toro saba, Buri toro, Beni toro, and Toro, the original maguro, have all been added to the list, and the number of fish calling themselves Toro, other than maguro, is increasing.

In other words, the word Toro is becoming increasingly generic.

Anyone who has endured the advertising onslaught of the modern era knows that word “toro” always seems to make its way into marketing materials. The word is meant to convey a luxury ingredient, and the “gotta-eat-it” mentality that drives sales.

For example, Toro saba (Saba means ‘mackerel’) is a fatty mackerel. Speaking of fatty mackerel in Japan, the first thing that comes to mind is Norwegian mackerel (Atlantic mackerel). It was once criticized for being too fatty for some unintelligible reason.

In Norway, the amount of mackerel that can be caught in a year is strictly regulated by each fishing boat, so they only catch mackerel when it is fatty and the price is high. Japanese chub mackerel has a peak fat content of 20-25%, while Norwegian mackerel has a peak fat content of 25-30%.

When we looked at the Norwegian Seafood Council’s website to confirm this fact, strangely enough, they do not use a single word Toro mackerel.

The term “fatty” is often used to describe the meat and taste of the fish. This term, of course, implies a high fat content, but the real message we wanted to convey was supposed to be “tasty”. This is because fat contains many flavor compounds. However, literally fatty fish is appreciated and it has become a first-class citizen.

The increase in fatty farmed fish and imported fish such as Northern mackerel may have played a role in this trend, and at the bottom of it all, as with the Toro worship of tuna, there has been a major shift in Japanese eating habits in the postwar period.

In this naming, we cannot help but feel the commercial spirit and skill of the company, which has successfully turned what could be a disadvantage into an advantage by combining changing tastes with the sense of luxury that the word “Toro” possesses.

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Revision date: February 15, 2023

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What is Beni toro?

a photo of Fresh fillet of Benizake — Fresh fillet of Benizake (Sockeye salmon)

Toro was originally used for bluefin tuna (and later for all tuna), but Beni toro was probably the first example of the term being applied to a fish other than tuna.

Around 1970, a major fishery company called Kyokuyo (極洋) gave the name to a sashimi product of fatty Benizake (sockeye salmon; Oncorhynchus nerka) caught in the North Sea, which had not yet entered the spawning migration stage.

At that time, Kyokuyo adapted “ultra-low temperature freezing,” which had been developed mainly as a freezing technology for tuna, to Benizake (red salmon) caught in the Bering Sea in the North Pacific Ocean.

It took many years from application to approval due to various problems, but Beni toro became a legitimately registered trademark in 1987. The registration number is 1991889.

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Revision date: July 17, 2025

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What is Iromono?

a photo of kanapchi sashimi — The flesh of this fish is beige in color.

At sushi restaurants, sushi toppings are classified as Akami (Aka means ‘red’ and mi means ‘flesh’), Shiromi (Shiro means ‘white’), Hikarimono (Hikari means ‘silver’), and so on. These names are derived from the color of the flesh and the appearance of the fish. However, since there is no clear definition, different sushi chefs have different classifications. For example, if the fish has shiny skin, it is called Hikarimono, and if the skin is removed, it is called Shiromi.

Basically, if the flesh is white, it is called Shiromi. If it is red, it is Akami, but if it is beige, it is called Iromono (Iro means ‘colored’). It may be an obsolete term nowadays, but among older sushi chefs, it makes sense.

The fish that fall into this Iromono category include Hiramasa, Kanpachi, Buri, and Shima-aji. Sawara should also be classified as Iromono, but since Sawara is a newcomer to the Edomae sushi category, it is not classified as Iromono.

It is difficult for the ordinary person to understand what is going on. To add to the confusion, Hiramasa, Kanpachi, Buri, and Shima-aji are called Aomono (Ao means ‘blue’) because they are blue-back fish. This is used primarily as a fishing term.

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Revision date: February 11, 2023

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What is Shiokara?

a photo of Shiokara — Shiokara broadly refers to seafood fermented in their own viscera, salted and seasoned.

Generally, Shiokara (salted fish guts) is a food product made by maturing salted seafood meat and offal. This maturing is a chemical process in which proteins are converted into free amino acids by the digestive action of proteolytic enzymes contained in the offal, creating a rich umami, while the high salt content prevents spoilage. As maturing progresses, the taste becomes less salty and mellower.

Today, shiokara is rarely found in any other food than seafood, but in the past, it was also made from animal meat. As evidence, shiokara made from rabbit and deer meat is mentioned in documents (倭名類聚鈔) dating from 905 to 967.

In the Edo period (1603-1867), eating animal flesh became anathema, and shiokara made from animal flesh gradually declined, leaving only shiokara made from fish and shellfish.

In the Edo period, shiokara was called nashimono (なし物) or natsushimono (なつし物) or nanshimo (なんし物) and included fish and shellfish such as Red seabream (Tai), Horse mackerel (Aji), Pacific cod (Tara), Ark shell (Akagai), Orient clam (Hamaguri), Abalone (Awabi), Prawn (Ebi), and Crab (Kani), as well as birds such as Lark and Quail.

It is said that the term shiokara, which is still used today, took root around the end of the Edo period, and literature from that time describes shiokara being sold as Katsuo, Ami, Ebi, Ika, and others.

These days, shiokara is considered more of a luxury food than a side dish, and many shiokara products cannot be stored without refrigeration because the salt content has been reduced to less than 10% due to low-salt preference. Also, some products are seen with the addition of mirin or rice malt to suppress the salty taste.

And what I must tell you is that there are various delicacies not only in Japan but also in other countries, some of which are characterized by their odd smell and strange appearance, but are also very flavorful.

One of the most typical examples is the shiokara introduced here. It can be said that it is the top 5 stinky food in Japan.

We are fairly sure that Shiokara isn’t the type of dish that will have you coming back for more. But rest assured, Japanese cuisine has so much more to offer.

Types of shiokara in Japan

Ika-no-shiokara (salted squid guts)

Generally, Japanese common squid (Surume-ika) is used, and it is the most in-demand shiokara.

The process is to mix squid liver, commonly called “goro,” with shredded squid meat in a ratio of 1:15 to 20, add 10 to 20% salt, and allow the mixture to stand for about half a month, stirring occasionally, until the meat is broken down by enzymes to produce the characteristic umami, which is then ready to eat. There are three types of shiokara: shiro (shiro means ‘white’)-zukuri, in which the skin is removed; aka (aka means ‘red’)-zukuri, in which the skin is left on; and kuro (kuro means ‘black’)-zukuri, in which squid ink is added.

Tsubu-uni (salted and preserved sea urchin)

a photo of Tsubu-uni — Tsubu-uni is a food product processed from fresh sea urchin to make it last longer.

Tsubu-uni is a specialty of Yamaguchi Prefecture and was invented around 1887, using Bafun uni, Aka uni, and Murasaki uni as ingredients.

The process begins by rinsing the gonads removed from the sea urchin. The product is then sprinkled with about 10% salt, packed in a bottle containing about 20% alcohol, shaken well, and aged for about half a month. The resulting product has a low salt content of about 8%, but can be stored at room temperature for about a year because of its alcohol content of about 9%.

Shuto (salted bonito guts)

Shuto (酒盗) is a shiokara made from bonito entrails. It is a specialty of Kochi Prefecture and is said to have been named by Yamauchi Toyosuke. Fatty bonito that has been frozen for a long time will become discolored, so bonito caught from spring to summer, when it has less fat, is the best material for shuto.

Among the removed internal organs, the pyloric appendage, stomach, and intestines are rinsed and aged with 30% salt. The one made with meat and offal is called “Tataki”, while the one made with only the stomach and intestines is called “Hantou (飯盗)”. It is also called Japanese anchovy and has a distinctive smell.

Konowata (salted sea cucumber guts)

a photo of Konowata — Konowata is salted sea cucumber intestines and is one of the three major delicacies in Japan.

Konowata is a shiokara, the digestive tract of sea cucumbers (海鼠).

When making dried or pickled sea cucumbers, the digestive tract is removed, washed, and soaked in 30% salt. The value of konowata is diminished when it is torn off and the yield is only about 1%, making konowata especially expensive among shiokara. The moment you put it in your mouth, you can smell the mellow aroma of the sea, and it is characterized by its unique sticky texture.

Mefun (salted salmon guts)

Mefun is a shiokara made from Salmon’s kidney.

The removed kidneys are washed in salt water, sprinkled with salt, hardened, then washed in thin salt water to reduce the salt content to about 12% and dried in the shade. The fish is then packed in containers and aged for about six months before being made into a product. The product has a maturing smell peculiar to salted fish.

Uruka (salted ayu guts)

Uruka is the shiokara of ayu fish entrails. There are ko-uruka made with ayu fish ovaries, shiro-uruka made with testes, kiri-uruka made with chopped meat mixed with the entrails, and shibu-uruka made with entrails other than ovaries and testes.

The process is the same for all ingredients: add about 30% salt, remove the leaching liquid, repeat the process of adding more salt, and let the product mature for about one year.

Sukugarasu (salted orange-spotted spinefoot)

In Okinawa, shiokara is called karasu. Kara means spicy and su means salt. Suku refers to the juvenile orange-spotted spinefoot, which are caught around the new moon of the sixth lunar month, when they gather in large schools on coral reefs.

The fish is matured in a dark place with 30% salt added to the fish. The fish is ready to eat within 2 to 3 days after being marinated, but the longer maturing fish is considered tastier. In Okinawa, shiokara of bonito entrails is called Watagarasu, shiokara of squid is called Ichagarasu, and shiokara of sea urchin is called Gashagarasu.

Ganzuke (salted fiddler crab)

A specialty of the Ariake Sea coast of Saga Prefecture, it is mainly made from fiddler crab and is said to have been invented around the 18th century by the lord of the Nabeshima feudal lord at that time.

The process involves removing the abdomen, mashing the fiddler crab with a mortar, adding about 30% salt, chili peppers, and other seasonings, and maturing the mixture for about three months.

Types of shiokara in Southeast Asia

Jeotgal (젓갈)

On the Korean peninsula, shiokara is called jeotgal or jeot, and there are over 40 varieties. Among them, 새우젓 made with small shrimp and 멸치젓 made with half mouth sardine are consumed in large quantities because they are essential for kimchi (김치) production.

鮭

The Fujian Han Chinese in Taiwan refer to the shiokara as 鮭 or 鹸鮭. Ingredients include shrimp, small fish, and crab.

Mắm

In Vietnam, shiokara, fish sauce, and narezushi are collectively called mắm, all of which are produced with the main purpose of flavoring dishes.

For example, mắm tôm, a shiokara paste of small shrimp, is made by adding about 20-30% salt to freshly caught shrimp, grinding them in a blender, and then spreading them on winnows and drying them in the sun for 2-3 days before maturing them in a container. It will be ready to eat in about a month, but those that have been around for more than a year are considered tasty.

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Revision date: February 13, 2023

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What is Biwa trout sushi?

a photo of Biwa masu — Biwa masu (Biwa trout) nigiri served at Kyogoku zushi.

What is Biwa trout (salmon)?

Biwa trout is a species of fish native to Lake Biwa, but is also found in Lake Kizaki, Lake Chuzenji, Lake Ashi, and other lakes through transplantation. The Japanese name for Biwa trout is Biwa masu (琵琶鱒). As indicated by its scientific name, Oncorhynchus masou subsp., it is considered to be a subspecies of Satsukimasu (Red-spotted masu trout). It reaches up to 60 cm, and the spots on the body are pale orange and disappear with growth. The adult one has a silver colored body.

It has also been farmed in Japan for a long time. There is even a famous Biwa trout farm near Lake Biwa in Shiga Prefecture that has been in operation since 1878.

An interesting fact about Biwa trout is that it is a landlocked variety of Pacific Salmon while being anadromous as it moves between the freshwater lake Biwa and surrounding rivers according to the water temperature as part of its life cycle.

What does Biwa trout sushi taste like?

The natural Biwa trout season is from June to early September. At this time of year, it has no peculiar flavor and has large amounts of fat with refined sweetness. When you put it in your mouth, only the delicious flavor of the fat spreads out as if it were melting softly. The rich flavor of trout can also be fully enjoyed as a sushi topping.

Sushi restaurants in Shiga prefecture, such as Kyogoku-zushi, serve Biwa masu nigiri sushi during the summer months. Ordinary Ikura is red in color because salmon go down to the sea and feed on crabs and shrimps, taking in red pigment. Biwa masu, on the other hand, grows only in lakes, so it does not take in any pigment and its eggs remain golden. Kyogoku-zushi also offers this Golden Ikura sushi. Both are rarely seen at sushi restaurants in Tokyo.

On June 21, 2025, an international academic journal published a new scientific name, “Oncorhynchus biwaensis,” for this salmon species, which is endemic to Lake Biwa.

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Revision date: July 1, 2025

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What are the important points when using ice to kill small fish?

a photo of Korijime — the general practice for small fish is to kill them all together with cold seawater using Korijime.

When it comes to large volumes of small fish like Aji and Iwashi, it’s impossible to use Ikejime for each individual fish. Therefore, the general practice for small fish is to kill them all together with cold seawater using Korijime (“kori” is the Japanese word for “ice”).

Here we will explain the important points of Korijime (氷締め).

The ice is important to maintain freshness. However, this does not mean that more ice is better. The amount of ice used must be adjusted depending on the state of the fish. When Ikejime is performed on live fish and then the fish is put directly on ice, it is killed too early. Also, if ice is only applied to certain parts, only that part will cool, changing the color of the meat. So, rather than directly cooling fish that haven’t yet reached rigor mortis after death, the environment around the fish is cooled.

On the other hand, the fish that have been killed lose their freshness quickly so plenty of ice is applied then in order to prevent changes in the temperature of the fish’s body. Although plenty of ice is necessary, ice is heavy so using so much that it would leave indentations on the fish’s body would be inexcusable. You can tell whether the fisherman is used to handling the fish depending on how much ice is used.

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Revision date: February 4, 2023

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What is Sashimi?

a photo of sashimi — A plate of assorted sashimi

Sashimi (刺身) is made by removing the inedible head, bones, skin, fins, and tail from raw fish, etc., and cutting them into small, easy-to-eat pieces.

It is considered the ultimate washoku dish, but why is such a simple and uncooked dish regarded so highly? In Japan, ingredients that are fresh enough to eat raw are considered more valuable, and sashimi preparation in particular requires substantial labor and technique.

Its preparation begins when the fish is first taken out of the sea. The fishermen perform Ikejime, a technique that shuts off the fish’s neurotransmission in order to preserve freshness and texture while the fish matures.

Each fish has its peak, which is referred to as shun (season), and chefs train for years to develop their ability to determine whether a fish is fresh and its peak. The carefully selected fish is cut into smaller pieces in one stroke with a sashimi boucho (knife), which creates a smooth surface. If the meat is cut with an unsharp knife, it will be crushed and the result will be watery and tasteless.

The chefs pursue pleasing texture, ease of eating, and delicious flavors by varying the thickness of cuts and cutting techniques, depending on the type of seafood they work with.

It is popularly served with soy sauce and condiments such as wasabi, and such garnishes as shiso and shredded daikon radish.

As an aside, sushi restaurants offer a variety of sashimi cuisine. You can order them as assortments, not to mention as single dishes of tuna, sea bream, squid, horse mackerel, or shellfish among others. If the shop has seasonal fish in stock, it might be a good idea to leave your order to the chef.

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Revision date: February 3, 2023

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What is Longtail tuna (koshinaga maguro) sushi?

An illustration of longtail tuna (© 2023 – Fishing Spots)

What is Longtail tuna (Koshinaga maguro)?

Longtail tuna inhabits continental shell and ocean waters in warm temperate and tropical regions of the Ind-west pacific. The dark blue-backed fish is recognized by their short pectoral fins and slender body. Its tail is long compared to other tuna. It is also distinguished by the presence of elongated, colorless spots on the underside and belly, between the pectoral and anal fins. As the name suggests, it is characterized by a rather long tail from the tail fins to the tail.

It reaches a maximum length of 1.5 m and up to 32 kg in weight. It is caught by longline fishing in Southeast Asia and Australia.

The Japanese name is Koshinaga maguro (腰長鮪). It is caught in small numbers in Kagoshima, Nagasaki, and Okinawa prefectures, but its numbers are small and it is the least caught species of the tuna genus, so it is traded only in its place of origin and rarely appears on the market. In addition, juvenile tuna look similar to bluefin tuna, yellowfin tuna, and albacore. Therefore, they are sometimes confused in the market.

What does Longtail tuna (Koshinaga maguro) sushi taste like?

In northern Kyushu and Sanin regions where bonito are not caught, however, it is an autumn treat. Most of its flesh is red meat, and its taste is refreshing so it is eaten as sashimi. However its fat is not sweet and has little acidity, so it is not suitable for nigiri sushi. In Australia and Southeast Asia, it is eaten as steak or sauteed.

Its scientific name is Thunnus tonggol (Bleeker, 1851).

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Revision date: February 2, 2023

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What is Blackfin tuna (Taiseiyou maguro) sushi?

An illustration of Blackfin tuna (Image credit: Duane Raver Jr.)

What is Blackfin tuna (Taiseiyou maguro)?

Blackfin tuna is one of the smallest members of the species of Tuna belonging to the genus called Thunnus and family of Scombridae. The English name blackfin tuna comes from its black pectoral fins and other fins. It is known by various interesting names like Blackfinned Albacore, Bermuda and football due to its typical football like appearance.

The Japanese name is Taiseiyou maguro (大西洋鮪). There is also a species called Taiseiyou Kuro-maguro (Atlantic bluefin tuna), which is very confusing. It is not distributed in the Japanese market.

The range of distribution of these tuna is restricted as they can only be spotted in the West Atlantic Ocean, encompassing the Gulf of Mexico, southern Brazil and the Caribbean Sea. This is unique for a species of Tuna to have a limited range but it probably has something to do with the Blackfin Tuna’s preference to migrate to temperate waters above 20℃. It is especially common in the Gulf of Mexico, where it is a favorite target of sports fishermen.

It can be identified by a dark-blue to black stripe across its back usually with a golden hue under it and a silver belly. It is the smallest in the Tuna family reaching lengths of about 1 m and weight of 20 kg. It is at its peak during autumn, winter, and spring in Florida Keys. Only 0.4 tons per year of blackfin tuna is caught in the world.

What does Blackfin tuna (Taiseiyou maguro) sushi taste like?

Though it doesn’t quite measure up to world-class bluefin, yellowfin or bigeye tuna in food value, it is very good in its own right. The top preparation method with fresh blackfin is undoubtedly sushi or sashimi, as it yields an incredible flavor and texture when raw, but it also excels on the grill or is seared over high heat. It also makes a delectable tuna salad.

Its scientific name is Thunnus atlanticus (Lesson, 1831).

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Revision date: February 2, 2023

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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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