What is Japanese red fish?

A photo of red fish fillet
Red fish cannot be distinguished even by fish professionals when filleted.

Red fish is a common name for several species of fish. In Japan, it is most commonly applied to certain deep-sea rockfish in the genus Sebastes. Red fish means the word ‘Akauo’ (赤魚). ‘Aka’ (赤) is red, and ‘uo’ (魚) is fish.

Since there are numerous red looking fish, Splendid alfonsino (Kinmedai) and Broadbanded thornyhead (Kichiji) may also be considered Akauo.

Originally, Akauo referred to Akoudai (Sebastes matsubarae Hilgendorf, 1880). This fish is in season during the winter. It was once used as a substitute for Madai or Pacific cod (Madara), but in recent years its catch has declined dramatically and it has become an ultra-premium fish. It is also caught in the Kanto area and is still caught in Tokyo Bay. The term “Akou” for short refers to red-spotted grouper (Kijihata), which is quite confusing. Besides, Akauo is also the standard Japanese name for a species of goby family.

According to the “Guidelines for seafood names” issued by the Consumer Affairs Agency, three types of Akouo can be labeled: Golden redfish or Atlantic Ocean Perch (Taiseiyouakauo), Pacific ocean perch (Arasukamenuke), and Beaked or Deepwater redfish (Okiakauo).

In most cases, the fish sold in the market as Akauo are Pacific ocean perch (Arasukamenuke) and golden redfish (Taiseiyouakauo), which are closely related species frozen and imported from Alaska and Russia. The flesh is white without any particular flavor, and is widely used in dishes such as miso zuke, kasuzuke (pickling in sake lees), shioyaki (grilled with salt), and simmered. Pacific ocean perch (Arasukamenuke), which is caught in the waters around Japan, is also used in Nigiri sushi.

In any case, there is no doubt that red fish is a delicious fish.

*Sebastes norvegicus (Ascanius, 1772) and Sebastes marinus (Linnaeus, 1758) are the same species.

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

A photo of Salmon nigiri sushi
Salmon is by far the most popular topping at conveyor-belt sushi restaurants.

If you ask people around the world what their favorite fish is, the answer is sure to be salmon. Its flesh is tender and fatty, with few small bones, and its color is appetizing. But we don’t think most people around the world pay much attention to the type of salmon they eat. This is not surprising, since people do not have the habit of eating many kinds of fish in their daily lives. In Japan, it is common for the species offered to change with the seasons, even among fish of the same family. We sometimes sense that the season has changed based on the change in fish species. For example, seeing a Salmon (Chum, Keta, or Dog salmon) moving up the river, one senses that it is autumn.

This article explores salmon, for which we were able to confirm statistical data. Also, see below for the differences between trout and salmon.
Trout vs. Salmon: What’s the Difference?

Global demand for salmons is strong and production is growing rapidly. Currently, the global production of salmon is over 5 million tons/year. Of this, more than 4 million tons are farmed, of which roughly 3 million tons are Atlantic salmon and 1 million tons are Rainbow trout. The salmon that people around the world say they love are Atlantic salmon and Rainbow trout.

Atlantic salmon is produced in Norway, the United Kingdom, Ireland, the Faroe Islands, Iceland, Canada, the United States, Australia, and Chile. Trout salmon (Rainbow trout) is produced in Norway, Finland, Sweden, Denmark, England, Ireland, Turkey, and Chile.

Although production is low, King salmon, Silver salmon, Cherry salmon, and Brown trout are also commercially farmed. King salmon is a very delicate fish and can only be found in areas with clean water. For this reason, it is difficult to farm, and King salmon accounts for less than 1% of all salmon farmed in the world. New Zealand, Canada, and Chile are the only countries that have succeeded in commercial farming of King salmon. In New Zealand, which is a rare example from a global perspective, no antibiotics are given to the fish. Silver salmon is farmed in Peru, Japan, and other countries, with a yearly production of over 20 tons. It is used as a standard side dish for bento (lunch box) in Japan. Cherry salmon is farmed only in Japan and does not reach 30 tons/year. Masu zushi, a famous specialty of Toyama Prefecture, is made from cherry salmon.

On the other hand, the catch of wild salmon has remained flat for the past 40 years at around 1 million tons/year. More than 90% of the catch consists of six species: King or Chinook salmon, Chum, Keta or Dog salmon, Pink or Humpback salmon, Silver or Coho salmon, Red or Sockeye salmon, and Steelhead trout (Rainbow trout).

Salmon mainly caught in Japan are Chum salmon (Japanese name: Sake, Akizake, Shirozake), Pink salmon (Japanese name: Karafuto-masu), King salmon (Japanese name: Masunosuke), Cherry salmon (Japanese name: Sakura-masu).

The main production areas are Hokkaido, Aomori, Iwate, Miyagi, and Niigata. Red salmon (Japanese name: Benizake) and silver salmon (Japanese name: Ginzake) are rarely caught only in Hokkaido. The catch of chum salmon, which used to be over 100,000 tons/year, has been drastically reduced to less than 50,000 tons/year. On the other hand, Alaska and Russia have recorded catches of over 400,000 tons/year and can be said to have good catches.

However, whether it is farmed or natural salmon is not even a subject of debate, except among some chefs and Japanese. In our opinion, the decision of whether to use farmed or wild should be based on the type of dish to be cooked.


From here, we get down to business.

It has long been said that pink salmon, the most abundant salmon caught in Japan, is not suitable for nigiri sushi. This is not true. It is simply because salmon in good condition was difficult to obtain in the past due to the lack of a well-developed distribution system. As proof of this, migratory pink salmon is highly valued for its rich flavor and fat. On the other hand, pink salmon that have gathered to spawn have lost their fat and are tasteless. This is a common story for all salmon.

In Japan, King salmon, Cherry salmon, farmed Atlantic salmon and Rainbow trout, and Chum salmon, which was born in Russian rivers and migrates along the Hokkaido coast, are used as sushi toppings (ingredients). There was a time around 1980 when sushi chefs used to serve red salmon, which he named Beni-toro, but there is no sign of it now. And we rarely hear of Chum salmon returning to the river where it was born in the fall to be made into Nigiri sushi. Worldwide, only a few countries, such as Russia, Canada, and Alaska in the United States, use wild pink salmon, silver salmon, and red salmon as Nigiri sushi.

We can say with certainty that Edomae Sushi restaurants do not use any salmon. As time goes by, some restaurants have begun to offer King salmon, Chum salmon, Cherry salmon, Biwa trout, and other rare sushi toppings as their main selling point, but only a few of them do so.

Chum salmon originally return to Japan in the fall, but those migrating off the coast of Japan out of season are called Keiji, Tokishirazu, and Mejika to distinguish them. The mother river is in Russia. Chum salmon originally return to Japan in the fall, but those migrating off the coast of Japan out of season are called Keiji, Tokishirazu, and Mejika to distinguish them. These are rarely found in some high-end sushi restaurants, as they have a fresh flavor and fat that is ideal for nigiri sushi. Of course, they are also delicious in other dishes. However, it should be frozen once to kill Anisakis and other fish before making sushi. This is one of the reasons why salmon has been avoided as a sushi topping.

A photo of salmon fillet
The appearance of salmon fillet

On the other hand, Atlantic salmon and Rainbow trout (known as Salmon trout or Trout salmon) are farmed at sea, exported without ever being frozen, and used for sushi at conveyor-belt sushi restaurants. The fish is already processed into fillets, so the chef only needs to remove the skin.

As a side note, salmon farming is said to have less environmental impact than other fish species. And from the perspective of the SDGs, we are moving from sea farming to land-based aquaculture. In addition, farmed salmons are being actively improved and blended with different species.

Now you may know what kind of salmons you are eating. For your reference.

Related contents:
Learn more about salmon

How salmon fillet are made in factory

What is Mochigatsuo?

A photo of Modori-gatsuo
Modori-gatsuo are those that migrate southward from off Sanriku to the Boso Peninsula from mid-September to late October.

In Japan, bonito is called variously Hatsugatsuo, Modorigatsuo, Mayoigatsuo, Netsukigatsuo, and so on. The quality of the fish is unique depending on the season and size, and bonito lovers will be able to enjoy a variety of flavors throughout the year. Now, bonito, a popular fish since the Edo period, has recently been given a new name, Mochigatsuo, which we have never heard of, and we would like to dig deeper into it.

A photo of bonito
The quality of bonito cannot be determined until it has been sliced.

As a general rule, one cannot identify a bonito just by looking at it, and even marketers and sushi chefs cannot tell its quality until they try to slice it. In particular, Hatsugatsuo (Noborigatsuo) has greater individual differences than Modori-gatsuo (Kudarigatsuo), and may even be inedible raw due to its distinctive odor. It is called Ishigatsuo or Gorigatsuo. Its flesh is noticeably firmer than normal fish in terms of elasticity. Its flesh is white, pink, or brownish. It also smells very bloody, almost like iron. The cause is currently unknown.

Because of its high hemoglobin and myoglobin content, bonito has a stronger bloody smell than other fish, even if it is not fresh. This richness is due to the high content of nitrogen compounds such as creatine and histidine, in addition to the umami substance inosinic acid. This is the reason for the unparalleled love of bonito.

A photo of Kenken gatsuo
The fishermen in the town of Susami, Wakayama Prefecture, immediately ikejime each bonito they catch on board, drain the blood out of the fish, and bring it back to the port in a container with its head in seawater ice.

On the other hand, bonito is a representative fish that loses its freshness quickly and is usually flash-frozen immediately after being caught. However, thanks to the tremendous efforts of fishermen, we can now eat fresh bonito. For example, fishermen in the town of Susami, Wakayama Prefecture, immediately ikejime each bonito they catch on board, drain the blood out of the fish, and bring it back to the port in a container with its head in seawater ice for the day’s auction. Kenkengatsuo is the result of thorough techniques for preserving freshness. The same is true of Taru-gatsuo from Hachijojima Island in Tokyo, for example. However, by the time the raw bonito arrives at the sushi restaurant to be made into Nigiri sushi, 12 hours have passed since the fish was caught. This time is critical to the quality of the fish.

So what kind of bonito is Mochi-gatsuo?

Hatsugatsuo has a refreshing, spring breeze-like flavor. Some of them are called “Mochigatsuo”, a type of bonito whose flesh is elastic and has the texture of freshly pounded rice cakes. Originally, bonito is caught far offshore, but in the spring, it comes much closer to land, so it can be brought to port before it becomes rigor mortis. Not all bonito are Mochi-gatsuo, however, and only a few are part of the same school, making them extremely rare. According to one theory, they are eaten before rigor mortis, which occurs four to five hours after the catch. Its season is from March to June, and it is consumed locally, as it is difficult to ship to distant places.

The name is also wonderful, as it compares the flesh of the bonito to a Mochi (rice cake). So far, the name “Mochigatsuo” is only used in Wakayama and Shizuoka regions. If you have a chance, you would like to try it.

Related contents:

Bonito (Katsuo)

Quality Improvement of Frozen Bonito


A photo of bonito sashimi
Frozen bonito begins to mature after thawing.

Large fishing vessels sail the Pacific Ocean year-round in pursuit of bonito (Skipjack tuna). The fishing method is divided into pole-and-line fishing and purse seine fishing. Pole-and-line fishing involves spreading live bait such as Japanese anchovy to attract schools of skipjack tuna, which are then caught in large numbers with the rod in a short period. Because of the need to keep live bait for a long period, this fishing method was limited to the waters around Japan for many years. Still, recent technological advances have also made pole-and-line fishing possible in southern waters.

The bonito caught in the waters around Japan is called Higashi-no-mono. This follows sardines and other fish that serve as bait and come north from the waters around the Philippines. The bonito called Nanpo-mono also approaches the waters around Japan from off Micronesia and other areas. This one is mainly caught by large vessel purse seine fishing. In purse seine fishing, the bonito rub against each other before being hauled on board, easily damaging the flesh. As a result, the fish may be less fresh and damaged than when caught pole-and-line fishing.

Vessels that take skipjack are equipped with sophisticated refrigeration facilities. There is a pool of brine solution, a salt solution with a concentration of about 20%, on board. The flash-frozen skipjack is called B1. After being thawed and filleted, the fish is rigor mortis, which means it is extremely fresh and is distributed as high-quality frozen skipjack for raw consumption. Of course, they are also very expensive. In addition, when caught, the blood is removed and the fish is flash-frozen, called S1, and is distributed as a higher quality product than B1.

Only carefully selected skipjack and those frozen under strict freezing conditions are marketed as B1, while skipjack that is frozen in the same freezer but not according to B1 standards is distinguished from B1 and referred to as B. Incidentally, B1 and B are caught by pole-and-line fishing. There is another type of frozen bonito called PS. This is not caught by pole-and-line fishing but by purse seine fishing. It is not in as good condition as pole-and-line fishing, but it is handled with care and has few scratches.

In summary, Bonito (skipjack) originally deteriorated quickly and was difficult to distribute fresh, but improvements in freezing technology and other factors have ensured that the quality is close to fresh.

How is the taste of vinegar determined?

A photo of Rice vinegar
The vinegar used for Vinegared rice is basically rice vinegar or red vinegar. Mizkan, which contributed greatly to the development of Edomae sushi, is still a famous vinegar manufacturer.

When we think of vinegar, a sour taste immediately comes to mind, but vinegar is not only sour, it also contains a variety of ingredients and has a mild taste. There are also many different types of vinegar, each with its unique flavor. Just as beer is made from barley and wine from grapes, vinegar has a variety of flavors, aromas, and richness depending on the ingredients.

Acetic acid is the predominant acidity, with other organic acids such as gluconic and citric acid also present. It also contains lactic acid, succinic acid, tartaric acid, malic acid, and citric acid, each with a different taste. Lactic acid has an astringent taste, while citric acid has a refreshing sour taste. These mix to form a complex sour taste. Adding even more variety to the sourness are the ingredients that the raw materials originally contained, such as sweetness, umami, richness, and aroma. Rice vinegar is particularly rich in carbohydrates and proteins, while black vinegar is rich in amino acids and various organic acids. These diverse flavors combine to create the flavor of vinegar.

By the way, we believe that what is required of vinegar used for sushi rice (vinegared rice) are two contradictory characteristics: refreshing and full-bodied. When sushi chefs prioritize richness, they use red vinegar or black vinegar with high amino acid content. However, this is a far cry from the light and refreshing taste that was originally sought in nigiri sushi. Therefore, sushi chefs try to solve the contradictory problem by mixing kinds of vinegar.

Various studies have also found amino acids such as glutamic acid, peptides, fat, glycogen, and alliin as substances that strengthen the richness. To make delicious nigiri sushi, the ingredients of sushi toppings and condiments must also be taken into consideration. It is not enough to focus only on vinegar. Of course, sushi chefs are not food researchers, so they have never conducted a quantitative analysis of amino acid content.

According to papers on the taste of vinegar by Masao Fujimaki, professor emeritus at the University of Tokyo, Ryuzo Ueda, associate professor at Osaka University, and Hiroshi Masai of Mizkan, amino acids exhibit a variety of flavors and are closely related to the unique taste of various foods. It is said that there are more than 20 kinds of amino acids that make up proteins, and 17 kinds of free amino acids exist in vinegar, which affects the taste of each vinegar.

The papers on the taste of vinegar

Rice vinegar is composed mainly of more than 10 amino acids, including glutamic acid, arginic acid, and aspartic acid. Among them, glutamic acid produces a delicious taste. Glutamic acid not only makes vinegar tasty but also works synergistically with the umami component to make nigiri sushi even tastier. Furthermore, the amino acid also acts on the slight sweetness of the vinegar and makes the overall taste milder and milder. In this respect, it can be said that the taste of rice vinegar is determined by the amount of amino acids present in the vinegar.

Although the amount of rice used as a raw material and the characteristics of the alcohol added during the production process are also important factors in increasing amino acids, at least standing fermentation (or static Fermentation) is a particularly important condition. Therefore, we surveyed Japanese vinegar manufacturers that use standing fermentation. Many sushi chefs use these vinegars. However, which vinegar is used as the main ingredient and what it is mixed with is, of course, a trade secret. And for fish preparation, vinegar made from brewing alcohol and containing almost no amino acids produced by fast fermentation is more refreshing. Again, it is not just a matter of focusing on the amount of amino acids.


List of Japanese Vinegar Manufacturers using Standing fermentation

Marusho vinegar (合名会社 丸正酢醸造元)

Establishment: 1879

TEL: +81-735-52-0038

Address:271 Tenma, Nachikatsuura-cho, Higashimuro-gun, Wakayama prefecture 〒649-5331

HP: Marusho vinegar

#standing fermentation


Kobara vinegar (合名会社 河原酢造)

Establishment: 1823

TEL: +81-779-66-3275

Address:8-25 Yoshi, Ono-shi, Fukui prefecture 〒912-0401

HP: Kobara vinegar

Products: Yuuki Junmai vinegar Robai

#standing fermentation


Totsuka Vinegar Brewery (戸塚醸造店)

Establishment: 2005

TEL: +81-554-56-7431


253 Natsukari, Tsuru-shi, Yamanashi prefecture

HP: Totsuka Vinegar Brewery

#standing fermentation


Okuno zyouzou (株式会社 奥野醸造)

Establishment: –

TEL: +81-224-51-8891

Address:44 Aza Hayashi, Oaza Irimada, Shibata-cho, Shibata-gun, Miyagi prefecture 〒989

HP: Okuno zyouzou

Products: Junmai vinegar

#standing fermentation


Tobaya vinegar (株式会社とば屋酢店)

Establishment: 1710

TEL: +81-770-56-1514

Address:6-2, Higashiichiba 34, Obama City, Fukui Prefecture 〒917-0232

HP: Tobaya vinegar

Contact: support@tobaya.com

Products: Junmai brewed vinegarTsubonosu

#standing fermentation


Takano vinegar (株式会社高野酢造)

Establishment: –

TEL: +81-76-273-1188

Address:103, Tsurugi Okuni-machi Ho, Hakusan City, Ishikawa prefecture 〒920-2133

HP: Takano vinegar

Contact: https://takano-su.co.jp/inquiry/inquiry.php

Products: Hakubai

#standing fermentation


Tankai vinegar (淡海酢有限会社)

Establishment: –

TEL: +81-740-36-0018

Address:1403 Katsuno, Takashima-shi, Shiga prefecture〒520-1121

HP: Tankai vinegar

Products: Rice vinegar Ginjo

#standing fermentation


Mikura vinegar (株式会社トーエー)


TEL: +81-5979-3-1660

Address: 2266 Atawa, Mihama-cho, Minamimuro-gun, Mie prefecture 〒519-5204

HP: Mikura vinegar

Contact: https://mikurasu.jp/en/contact

Products: White Vinegar Gekka, Red Vinegar Akane

#standing fermentation


Onomichi vinegar (尾道造酢株式会社)

Establishment: 1582

TEL: +81-848-37-4597

Address: 1-5-2 Kubo, Onomichi City, Hiroshima prefecture 〒722-0045

HP: Onomichi vinegar

Contact: https://kakuhoshisu-onomiti.com/contact.php

Products: Rice vinegar, Pure Red vineager

#standing fermentation


Imakawa vinegar (今川酢造)

Establishment: 1923

TEL: +81-76-241-4020

Address: 3-19-1 Nomachi, Kanazawa City, Ishikawa prefecture 〒921-8031

HP: Imakawa vinegar

Contact: https://www.imakawa.com/inquiry/

Products: Marusan Junmai vinegar

#standing fermentation


Iio Jozo (株式会社飯尾醸造)

Establishment: 1893

TEL: +81- 772-25-0015

Address: 373 Odasyukuno, Miyazu-shi, Kyoto-fu 〒626-0052

HP: Iio Jozo

Contact: fujisu@iio-jozo.co.jp

Products: Pure rice vinegar Fujisu, Pure rice vinegar Premium

#Stationary fermentation


Yokoi vinegar (横井醸造工業株式会社)

Establishment: 1937

TEL: +81- 3522-1111

Address: 4-2-17 Shinkiba, Koto-ku, Tokyo 〒136-0082

HP: Yokoi vinegar

Contact: https://yokoi-vinegar.com/contact-us

Products: Kinsho etc.

#standing fermentation


Kisaichi Brewing (私市醸造株式会社)

Establishment: 1922

TEL: +81- 47-443-2511

Address: 6-7-45 Higashi-Michinobe, Kamagaya-shi, Chiba prefecture 〒273-0115

HP: Kisaichi Brewing

Contact: https://kisa1.com/contact/

Products: THE EDOMAE Sushi vinegar

#standing fermentation


Murayama vinegar (村山造酢株式会社)

Establishment: about 1720

TEL: +81-75-761-3151

Address: 3-2, Ohashi Higashi-iru, Sanjo-dori, Higashiyama-ku, Kyoto 〒605-0005

HP: Murayama vinegar

Products: Chidori

#standing fermentation


Mizkan (株式会社 Mizkan)

Establishment: 1804

TEL: +81-569-21-3331

Address: 2-6 Nakamura-cho, Handa, Aichi prefecture 〒475-8585

HP: Mizkan

Contact: https://www.mizkanholdings.com/en/inquiry/

#standing fermentation


Kokonoesaika (株式会社九重雜賀)

Establishment: 1908

TEL: +81-736-66-3160

Address: 142-1, Momoyama-cho Moto, Kinokawa-shi, Wakayama prefecture 〒649-6122

HP: Kokonoesaika

Contact: https://kokonoesaika.co.jp/contacts/

Products: Saika Ginjo Red vinegar

#standing fermentation


Koutarou vinegar (有限会社林孝太郎造酢)

Establishment: –

TEL: +81-75-451-2071

Address: 455 Michimasa-cho, Higashi-iru, Teranouchi-agaru, Shinmachi-dori, Kamigyo-ku, Kyoto-shi, Kyoto 〒602-0004

HP: Koutarou vinegar

Products: Rice vinegar

#standing fermentation


Shoubun vinegar (株式会社庄分酢)

Establishment: 1711

TEL: +81-944-88-1535

Address: 548 Enokizu, Okawa City, Fukuoka Prefecture 〒831-0004

HP: Shoubun vinegar

Products: Shoubun Rice vinegar

#standing fermentation


Ishikawa  Industory (石川工業株式会社)

Establishment: 1928

TEL: +81-985-74-0046

Address: 3792 Kamitashima, Sadowara-cho, Miyazaki City, Miyazaki Prefecture 〒880-0301

HP: Ishikawa Industory

Products: Yamato vinegar

#standing fermentation


Related contents:

Types of vinegar

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