Edomaesushi | Sushiblog－Sushiuniversity

The general rule is to only eat oysters in months that contain the letter “R”.

In other words, avoid them from May to August.

It’s won’t hurt you to eat Magaki (Japanese oyster), which has its spawning season in the summer, but in the months with no R in the name, the glycogen concentration is low, so you can’t get the full-bodied texture that you get in winter. In addition, almost all amino acids such as glutamic acid, glycine, alanine, arginine, which are important components for delicious flavor, are known to accumulate from winter through spring, and conversely, they decrease in the summer, which is the spawning season. You cannot expect the same deliciousness from oysters in summer as you can from months that contain the letter R.

Furthermore, the oyster takes in large amounts of seawater and filters out the plankton for its food. Therefore, in warm seasons it fills up on large volumes of the toxic plankton that proliferates in the sea. Eating toxic plankton can make the oyster toxic and toxified oysters can cause food poisoning when consumed by humans. In addition, in the warmer months, the oyster loses its freshness faster after being harvested, increasing the likelihood of getting a bad one and risk food poisoning. Therefore, it’s best to not go out of your way to eat oysters in summer.

On the other hand, one certain oyster is actually in season in summer.

Iawagaki (Rock oyster) is known as the summer oyster. This type is close to the Magaki, and it lives attached to reefs at depths of 2 to 20 m, deeper than the intertidal zone and facing the open sea. A large Iwagaki has a shell length of 10 cm, a shell height of 20 cm or more and weighs more than 1 kg. However, the edible part is small compared to the size of the shell. It is an oviparous hermaphrodite. Growth is slow at a rate of around 5 cm in one year, around 7 cm in two years. It takes three to four years to reach 10 cm or more and grow big enough to harvest.

The glycogen volume in Iwagaki is high from March to July, peaking around May, and it then decreases from September to October. The main production areas are the Sea of Japan on the coasts of Akita, Yamagata, Niigata, and Tottori. Many of the Iwagaki in circulation are harvested from the wild, unlike Magaki, which is almost all farmed.

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Revision date: February 1, 2022

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A lesson on how the price of Nigiri sushi is determined

In order to prosper, a business wants to sell products at as high a price as possible. So how does a chef determine the price of nigiri sushi?

Naturally, the cost price is what it costs the restaurant for the ingredients while the price on the menu is the selling price. The ratio of these two prices is called the cost rate. In the case of a sushi restaurant, the ideal cost rate is 35% or less. A restaurant operating with only Omakase will have a cost rate of 40% with a focus on the quality of the toppings.

For sushi restaurants, handling of this ratio and the yield are very important. Yield refers to the part of the purchased fish and shellfish that can actually be used. For example, when purchasing a whole fish there are bones, skin, eyes, tail and internal organs that cannot be served as sushi or sashimi. No matter how good a chef is when preparing fish, the bones and skin will remain. In other words, the yield rate is the percentage of parts that can be used as sushi or sashimi. Typical fish yield rates are as follows:

Wild Maguro (Tuna): 65~75%

Buri (Japanese amberjack): 50%

Hirame (Bastard halibut): 40%

Tai (Red seabream): 35%

Akagai (Ark shell): 25%

Mirugai (Keen’s gaper): 20%

The weight of just the topping for a single piece of nigiri sushi is 12 to 18 grams, depending on the ingredients and the policy of the restaurant. The market price for rice is said to be about US$5 per kilogram, and assuming a weight of 15 grams per Nigiri, the rice for a piece of sushi is generally said to cost about US$0.05, including vinegar and salt. Even if you count the shari (sushi rice), soy sauce, wasabi, nori, etc., it’s fair to consider the cost to be about US$0.10.

Now, let’s figure out the price of Hirame, for which 3 kilograms were bought at $60 per kilogram. Assume that the weight of one topping is 15 grams.

The yield rate of Hirame is 40%, so the chef can make 1,200 grams of sushi toppings from 3,000 grams of Hirame. (formula: 3000 g × 0.4 = 1200 g). Since the weight of one topping is 15 grams, 80 pieces of sushi can be made from 3,000 grams of Hirame (1200 g ÷ 15 g = 80 pieces).

Next, we calculate the cost of one topping. Hirame is US$60 per kilogram, so US$180 (US$60×3 = US$180) for 3 kilogram. Since this volume can yield 80 pieces, the cost of one topping is US$2.25 (US$180÷ 80 pieces = US$2.25).

Add the shari price of US$0.10 to this: US$2.25+0.1=US$2.35. In other words, the cost of one Hirame nigiri sushi is US$2.35.

If the ideal cost ratio of 35% is applied here we get 2.35÷0.35 (35%) = US$6.71. For a restaurant serving mainly Omakase, 2.35÷0.4 = US$5.88.

In summary, one piece of Hirame sushi is sold between $5.88 and $6.71.

It may feel surprisingly cheap, but if you perform these calculations with Kuromaguro or Uni, it will be $60 to $90 per piece, and then you’ll feel that it is too expensive. Therefore, the total margin is secured by setting the cost rate for Kuromaguro and Uni to 80-90%, while the cost rate for Saba and Ika is set to 10-20%.

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Revision date: January 6, 2022

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Is the combination of Chablis wine and Japanese oysters match made in heaven?

White wine is generally thought to go well with fresh seafood.

For example, every Frenchman knows that Chablis wine and Belon oysters go together like peanut butter and jelly. The soil of Chablis is made of the stratum that dates back to the Kimmeridgian age and a unique characteristic is that the soil is rich in fossils of small oysters and shellfish. That is why oysters and Chablis wine are said to be the perfect pairing. However, surely there are Japanese people who sense the fishy odor when having Chablis wine and Japanese oysters (Magaki) together. Therefore, some people say that sake is definitely preferred over wine.

The reason for this is that the types of oysters in France and Japan differ.

Famous for its Belon brand name, the oyster native to Europe has a flat, rounded shell. It belongs to the genus Ostrea. To be honest, Belon oysters aren’t sweet and don’t have a distinguished flavor compared to Japanese oysters, and the salty fragrance of the sea is dulled, so it can seem less flavorful.

Meanwhile, the Japanese oyster is elongated and shaped like a raindrop. It is characterized by a smell like it swallowed the whole ocean. This is the main species farmed in Japan. It belongs to the genus Crassostrea. The taste is as if the umami components of the sea have all been concentrated together in one little shell.

Going back to pairing Chablis wine with oysters, it’s common sense in the world of flavors that items with basically similar components pair well together.

The issue lies in how wine is made. Chablis wine contains lactic acid because it is made through forced mal-lactic fermentation. Because it contains this lactic acid, it is partially fighting against the Belon oyster, which has a high glycogen content. In addition, lactic acid is called “warm organic acid”, and it has the property of becoming delicious at warm temperatures. Oysters are eaten cold, so they aren’t good for taking advantage of “warm organic acids”.

Therefore, it can be said that rather than Chablis wine, it goes well with cold organic acid white wine that is delicious when cooled to 7 or 8 degrees, for example, German Franken wine.

So then, what should be done when pairing oysters with Chablis wine?!

If you insist on pairing oysters with Chablis wine, go all out and add squeezed lemon so the citric acid will work to mask the lactic acid and succinic acid, in turn making the wine taste good even when cold. Citric acid is a “cold organic acid” that becomes delicious when cooled, and oysters rich in glycogen go well with “cold organic acid”. Cold acid-based white wine is abundant in the refreshing “cold organic acids” known as malic acid and tartaric acid. Oysters lack this cold organic acid (malic acid and tartaric acid), so adding the citric acid of lemon creates an exquisite harmony.

However, in France there was a time when a disease spread that caused the death of the Belon oyster, nearly rendering it extinct. Therefore, since the Japanese oyster has been transplanted so many times, it is said that nowadays, at least 90% are Japanese oysters hybrids of Japanese oysters.

That means the question remains among Japanese as to whether the combination of Chablis wine and oysters really is a match made in heaven or not. Personally, we’ve never heard of oysters served without lemon, so the fishy smell really isn’t an issue at all in the end.

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Revision date: January 6, 2022

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What is Toro Katsuo (Torogatsuo)?

In recent years, sushi menus have seen an explosion of creative names, many of which begin with the word “Toro.” But what exactly is “Toro katsuo (Torogatsuo),” and does it truly deserve the prestigious Toro label?

Toro is an absolute at sushi restaurants and it’s only natural to aspire to such a position. That’s why there are so many sushi dish names that start with “Toro”. The most laissez-faire of these is Toro salmon. In this case the definition of Toro is ignored in an attempt to promote sales. Just as bad is Toro katsuo (pronounced “Toro-gatsuo” in Japanese).

Katsuo is born in the warm southern seas. When it reaches about two years old it migrates north in pursuit of Iwashi and other small fish. There are two routes taken by the Katsuo that come to the seas around Japan. One of the routes rides the Kuroshio Current (a warm current) from around the Philippines, passing by Taiwan and the Ryukyus Islands, arriving in southern Kyushu. From there the Katsuo rarely heads toward the Sea of Japan and instead the majority moves northward on the Pacific Ocean side. The Katsuo migration schedule may shift depending on the temperature of the seawater and how the schools of Iwashi and Aji (which the Katsuo feeds on) are migrating that year. The first group appears around Ishigaki Island about January, then in the seas off the shores of Kyushu and Shikoku between February and March. It then moves to the seas off of the Izu and Boso peninsulas between April and June. It reaches the open seas off the southern coast of Sanriku and Hokkaido between July and September.

Another route follows the Ogasawara ocean current from below the equator in the seas off the shore of Papua New Guinea and the seas around Micronesia to the Ogasawara Islands, along the Seven Islands of Izu and approaching the open seas off the Boso Peninsula. The route then goes northward to join with the routes mentioned above.

It’s the Modori-gatsuo that begins reverse migration toward the south at the beginning of autumn when the water temperatures start to drop. Katsuo has a strong appetite before returning south in preparation for the long trip. Unlike the light-flavored Hatsu-gatsuo, the Modori-gatsuo has plenty of fat and its body fattens up quite a bit. The main fishing locations for Modori-gatsuo are in the northern Pacific, such as the waters off the shore of Sanriku. This is the season when it is truly worthy of the name Toro katsuo when served raw, and nothing else should be called by the same name.

When served at its peak in early autumn, Modori-gatsuo truly lives up to the name “Torogatsuo”—a seasonal delicacy that offers the richness and depth sushi lovers crave.

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Revision date: july 18, 2025

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What is Warisu?

Warisu is diluted vinegar, typically used for gently curing fish in the Sujime process. It is less acidic than undiluted vinegar, making it suitable for preserving delicate textures and flavors. Warisu refers to the vinegar used in Sujime.

The fish is first washed in water, then soaked in vinegar. When working with blue-backed fish, the smell of the fish’s fat is removed from the surface with vinegar that has been used once before (and thus has a low acidity). This is called Suarai. When preparing fish with Sujime, cooled Warisu is used, made either with a 10 to 3 ratio of vinegar to ice, or the same ratio of vinegar to cold water. Vinegar with a high acidity that hasn’t been cut with water only soaks the surface of the fish (denaturing it) and the vinegar does not penetrate to the inside. In addition, if the temperature of vinegar is high, such as during summer, the skin and body of the fish soften. That’s why the vinegar is diluted (acidity is between ph 3.3 and ph 3.7) and used as chilled Warisu.

How sushi chefs adjust vinegar for each type of fish

In traditional sushi preparation, vinegar is not just a preservative—it’s a seasoning tool carefully adjusted by skilled sushi chefs. The choice and dilution of vinegar used in warisu (diluted vinegar for curing) are not fixed; they vary depending on the type of fish, its condition, and even the individual preferences of the guest.

Different fish call for different vinegars. White-fleshed fish such as sea bream or flounder are delicate in flavor and low in fat. Using vinegar that’s too acidic can overpower their subtle sweetness. For these, chefs commonly use warisu made with rice vinegar, which offers gentle acidity and a clean finish that enhances the natural umami of the fish without masking it.

In contrast, blue-backed fish like mackerel or sardines are bolder in character, with strong aromas and rich oils. These require a more assertive approach. Chefs often reach for aged sake lees vinegar (akazu), which has deep complexity from long fermentation. However, because akazu can be quite sharp, it’s usually blended with rice vinegar to strike a balance—removing odor while drawing out flavor.

Fatty fish, such as toro, salmon, or yellowtail, pose a different challenge. Their richness can linger heavily on the palate, so vinegar is used to “cut” the fat and refresh the mouth. In such cases, a slightly stronger warisu—sometimes incorporating grain vinegar—provides the right amount of acidity to balance the richness and keep the dining experience light and pleasant.

But the decision doesn’t end with fish type alone. The condition of the fish also plays a vital role. Factors like the fishing method, season, and time since catch can all influence fat content and firmness. For instance, freshly caught mackerel in the morning may be mild, but by afternoon its oils begin to rise to the surface—prompting chefs to adjust the acidity accordingly. A winter yellowtail (kanburi), with its intense fattiness, might call for a bold akazu blend to bring out deeper umami.

Beyond the fish itself, experienced chefs also fine-tune vinegar based on the guest’s palate. An elderly customer might prefer a milder, smoother vinegar base, while a guest who enjoys bolder flavors or is pairing their meal with sake may appreciate a vinegar with more depth and presence. Some international guests, who may not be familiar with the distinct aroma of fermented vinegar, are served fish cured in blends that are gentler and more neutral in scent.

Ultimately, this level of customization reflects the spirit of sushi itself: it is not a standardized dish, but a conversation between chef and guest, expressed one piece at a time.

At the highest level of craftsmanship, chefs seek to create umami synergy—a phenomenon where the amino acids in vinegar (especially akazu) combine with the natural inosinate in fish to create a flavor experience greater than the sum of its parts. For example, a well-aged flounder paired with a carefully blended vinegar can produce profound depth, richness, and lingering satisfaction. In the language of food science, it’s a case of 1 + 1 = 3.

This thoughtful approach to vinegar usage is one of the quiet but essential reasons why great sushi tastes so perfectly balanced.

After the Sujime of the topping is finished, it is important to place it in the refrigerator and allow the meat to mature slowly. The unsaturated fats in oily fish are particularly prone to oxidation, which leads to unpleasant smells and off-flavors if the fish is not properly chilled and managed. For fish with strong fat, that fat oxidizes faster than the meat can mature, so it must be done very carefully.

What is Meki? Substitute for Kuruma ebi?

Japan leads the world in shrimp consumption by far. Most of the shrimp is imported, but it is a little known fact that shrimp is called “Meki” among importers and sushi restaurants in Japan. It is said to be a remnant from a time when much of the imported shrimp came from Mexico (pronounced “Mekishiko” in Japanese).

Shrimp can be caught within 45 degrees north or south of the equator. The caught shrimp is quick-frozen on site and then sent to Japan. Mexico was early in advanced refrigeration technology so when it became impossible to catch shrimp in the seas around Japan in the 1970s, a large volume of shrimp was already being imported from Mexico. It was around that time that importers shortened the phrase “Shrimp imported from Mexico” to “Meki”.

After that the major source of shrimp imports switched to Taiwan, which started shrimp aquaculture, and it is now also imported from Thailand, Indonesia and China. The name “Meki” stuck in the industry, despite the fact that shrimp is now mainly imported from other places in Asia.

Imported shrimp is categorized by body color tones, either brown, pink or white. The color is combined with the place of origin or country name and that is what each type of fish is called at the distribution stage. For example, they may be called Mexico brown or Guiana pink.

Well-known brown-toned shrimp include Ushi ebi (Black tiger shrimp) and Mexico brown (Yellowleg shrimp). Pink-toned types include Guiana pink (Pink spotted shrimp) and Nigeria pink ebi (Southern pink shrimp). White-toned shrimp include Taisho ebi (Fleshly prawn), Banana ebi (Banana Prawn) , Eedeavour ebi (Eedeavour prawn) and Vannamei ebi (Whiteleg shrimp). There are many sushi restaurants that use pink and brown-toned sushi that turn into a nice red color when boiled. While the meat of white-toned shrimp is soft, it turns a whitish color when boiled and doesn’t look very appetizing. However, due to the splendid, large tail, it is perfect for tempura or fried prawns.

Next, We will touch on the characteristics of shrimp that is typically imported to Japan. All these types are actually related to the Kuruma prawn, which is representative of premium shrimp and a familiar ingredient of sushi. In other words, these imports are alternatives to make up for the shrimp consumption in Japan that can’t be covered by the Kuruma prawn. Normally the head is removed, it is frozen, packed in large lots, and then embarks on the distribution channel in Japan.

There are about 27 species of kuruma prawns (Penaeus japonicus Spence Bate, 1888). The following is a list.

Crystal shrimp: Farfantepenaeus brevirostris (Kingsley, 1878)

Witch Shrimp: Farfantepenaeus Burukovsky, 1972

Northern pink shrimp: Farfantepenaeus duorarum (Burkenroad, 1939)

Indian white prawn (Shonanebi): Fenneropenaeus indicus (H.Milne Edwards, 1837)

Caramote Prawn: Penaeus kerathurus (Forskål, 1775)

Western king prawn (Futomizoebi): Penaeus latisulcatus Kishinouye, 1896

Redspot King Prawn: Penaeus longistylus Kubo, 1943

Aloha Prawn (Terao-kurumaebi): Penaeus marginatus J.W.Randall, 1840

Western White Shrimp (Tenjiku-kurumaebi): Penaeus occidentalis Streets, 1871

San Paulo Shrimp: Penaeus (Melicertus) paulensis Pérez Farfante, 1967

Redtail Prawn (Akaoebi): Penaeus penicillatus Alcock, 1905

Southern White Shrimp: Penaeus schmitti Burkenroad, 1936

Green Tiger Prawn (Kumaebi): Penaeus semisulcatus De Haan, 1844

Northern White shrimp: Penaeus setiferus (Linnaeus, 1767)

－: Penaeus silasi Muthu & Motoh, 1979

Blue Shrimp (Paradise prawn or Theshinoebi): Penaeus stylirostris Stimpson, 1874

Southern Brown Shrimp: Penaeus subtilis Pérez Farfante, 1967

The following is a list of those commonly used in sushi restaurants and Japanese restaurants in Japan.

Guiana pink (Redspotted shrimp, Spotted pink shrimp /Farfantepenaeus brasiliensis (Latreille, 1817))

For more information, go here.

Taisho ebi (Fleshly prawn /Fenneropenaeus chinensis (Osbeck, 1765))

It is found from the Indian Ocean to the Pacific Ocean, the Malay Archipelago and Australia. The species is of considerable commercial importance in the Yellow Sea, East China Sea and Korean Bight, where it is trawled. It is sold in Korea, China, Japan and Hong Kong. This is a large shrimp that reaches up to 25 cm in body length. The appearance is similar to the Kuruma ebi, but without any special pattern. The edge of the abdomen is a dark brown color. There are 28 known species related to the Kuruma ebi. In the Toyosu market, those with a striped pattern are Kuruma ebi, and those without are Taisho ebi. In Japanese it’s been dubbed “Korai ebi” is due to the fact that it is often caught in the waters off the west coast of the Korean peninsula. The soft meat has a sweetness that makes this shrimp delicious. The number of wild Taisho ebi has decreased drastically in recent years. The coloring is lighter than Kuruma prawn and Black tiger shrimp, but darker than other white-toned shrimp. This type has a long history compared to other imported frozen shrimp and such high volumes were imported from China that it was called Chinese Taisho. It accounted for the majority of the market share until farmed Black tiger shrimp started to appear on the market.

Banana ebi (Banana Prawn /Penaeus merguiensis De Man, 1888)

It found around the northern coast of Australia from the New South Wales-Queensland border to Shark Bay in Western Australia, it is mainly caught by trawlers between Exemouth Gulf, Western Australia and Brisbane, with the bulk of the catch coming from the Gulf of Carpentaria. It weighs between 18 to 30 g per shrimp and is colored like a banana. The meat is soft and has a sweetness. Sometimes it is also sold as Taisho ebi. The body is thinner and slenderer than the Black tiger shrimp. It is available year round with peak supply in April.

Mexico brown (Yellowleg shrimp, Brown shrimp /Farfantepenaeus californiensis (Holmes, 1900))

For more information, go here.

Vannamei ebi (Whiteleg shrimp, Pacific white shrimp/Litopenaeus vannamei (Boone, 1931))

For more information, go here.

Ushi ebi (Black tiger shrimp, Giant tiger prawn/Penaeus monodon Fabricius, 1798)

For more information, go here.

Australia tiger (Brown tiger prawn /Penaeus esculentus Haswell, 1879)

The Australian tiger (Brown tiger prawn) is endemic to Australia and is found at depths of 15~20 meters along the coast except in the southern part of the country. Its main locality is the Gulf of Carpentaria on the northern coast of Australia. It reaches 25 cm in length but is generally 15~20 cm long.

Because of its beautiful red legs and reddish-brown stripes, this shrimp is mainly imported to Japan with its head on. In addition to its shape and size reminiscent of Kuruma ebi, it is a high-end variety that is not so tough, sweet, and has a good taste and coloration and is used in grilled dishes and tempura.

Nigeria pink ebi (Southern pink shrimp, Candied shrimp/Farfantepenaeus notialis (Pérez Farfante, 1967))

Nigeria pink ebi (Southern pink shrimp) is found from Mauritania to Angola at depths of 20~100m. It is also found in the western Atlantic Ocean from the Caribbean coast to southern Brazil.

It inhabits bottom mud or sandy mud, and sandy patches among rocks in marine environments. Juveniles are found in estuarine environments. Also inhabits lagoons. It is often used for sushi because of the soft meat, good flavor, and nice coloring. This is one of the highest grades of imported shrimp.

Mexico ebi (Northern brown shrimp, Brown shrimp /Farfantepenaeus aztecus (Ives, 1891))

Mexico ebi (Northern white shrimp) is distributed from the Gulf of Mexico to depths of up to 30 meters along the eastern coast of North America. Juvenile shrimp grows in estuaries. It is the most important species in the Gulf of Mexico, with an average annual catch of nearly 30,000 tons. On the other hand, Southern white shrimp is distributed in shallow waters from the Caribbean Sea to southern Brazil. It is almost indistinguishable from this species in appearance, but the male and female reproductive organs differ in shape.

Maximum standard length: 22 cm. It lives in bottom mud or peat, often with sand, clay, or broken shells. Adults inhabit the marine environment. Juveniles inhabit the estuarine and marine environments. There are 13 types of brown-toned Kuruma prawn in the world and the names get confusing.

Also called Golden Shrimp, Red Shrimp, Redtail Shrimp.

King ebi (Eastern king prawn /Penaeus plebejus Hess, 1865)

Adults are found in marine environments while juveniles are found in estuarine environments. It is found over sandy bottoms at depths of 2-350 m or deeper.

Finally, the shrimp introduced in this section is consumed not only in Japan but all over the world. Judging by the images on social media, takeout sushi and the frozen shrimp sold at Costco are made from one of the types of shrimp described here. If you’re going to learn about sushi, it’s important to learn the types of shrimp used in sushi.

India ebi (Indian prawn/Madagascar white prawn/Fenneropenaeus indicus (H.Milne Edwards, 1837))

India ebi (Indian prawn) is widely distributed from the Philippines through Southeast Asia to the western Indian Ocean. It is especially important in the waters from the Indian coast to the western Indian Ocean.

It is a White species of Kuruma ebi and is similar in appearance to the Banana Prawn. Once the head is removed, it is difficult to distinguish between the two species. In Southeast Asian markets, both species are sold together.

Those distributed in East African waters have brownish bodies and reddish legs. It has a rich flavor and aroma and is very tasty. It is suitable for frying and tempura.

Also called Indian white prawn, Tugela prawn , White prawn.

Endeavour ebi (Endeavour prawn/ Metapenaeus endeavouri (Schmitt, 1926))

Endeavour ebi (Endeavour prawn) are abundant in all waters except the southern part of Australia, but can also be caught in Philippine waters. It is found at depths of 20 to 45 meters. It is said to be caught together with shiba shrimp in some waters, but unlike shiba shrimp, it does not enter brackish water.

It is about 15 cm long and weighs about 17 grams. The entire body is covered with fine hair. Its scientific name is derived from the name of a research vessel, the Endeavour, which surveyed the eastern coast of Australia.

Also called Brown prawn, Endeavour shrimp.

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Revision date: June 15, 2024

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What is Sekisaba?

Sekisaba (関サバ) and Sekiaji (関アジ) are ‘designer’ fish known for their high prices.

Of them, Sekisaba is a premium fish that can go for as high as US $50 per fish. So, what kind of fish is Sekisaba and what’s the difference between it and normal Saba (Mackerel)?

Sekisaba is a Saba caught in the Hoyo Strait with a fishing pole by a union member of the Saganoseki branch of the Oita National Federation of Fisheries Cooperative (JF Oita). In other words, Sekisaba is not a type of Saba, but a premium fish created by differentiating the fishing method.

Sekisaba started to become known all over Japan between the late 1980s and early 1990s. Until then, Sekisaba was only known as a commonplace fish that was caught incidentally with Aji and went for US $2 per fish.

However, the Saganoseki branch of JF Oita applied for the first trademark ever in the industry and then grew the brand through methods such as tagging each individual fish by hand. This resulted in recognition of its taste as “Saba that can be enjoyed even as sashimi” (while Saba is generally a fish that loses its freshness easily and not eaten raw), catapulting it to a national constituency After that, the thorough quality management and branding paid off and the price jumped to 10 times that of normal Saba.

The first difference between Sekisaba and normal Saba is that Sekisaba is caught carefully, one at a time. The use of ground bait is also banned so that the Sekisaba won’t eat anything but the natural diet (avoiding odor). Each fisher is only allowed to use fishing lures they make from fish skin or ragworms. Fish caught in this way are let out into a live holding tank on the ship and brought to the fishing port alive. After arriving at the port, the tank on the ship is checked, the fish size is looked at from the water surface and the approximate weight is measured. This method is called “Tsurugai”. This is because when the fish is placed on a scale, it struggles violently and can injure itself. The fish are allowed to calm down in the tank (called Ikekoshi) for a day at the fishing port. At the time of shipping, Ikejime is performed, in which a knife is put into gill parts, the spinal cord is cut, and then it is submerged into saltwater and the blood is let out. After that a processing method called Shinkeijime is performed in which a wire is inserted into the spinal cord to put the fish in a state of asphyxiation. Therefore, there is little damage to the fish, maintaining the freshness. When it is transported to the place of consumption, the temperature is kept at 5°C (41°F). This is because the fish does not lose its crunchiness compared to when it is cooled to 0°C. Even this is not easy to imitate.

The Hoyo Strait where Sekisaba is caught is rich in plankton, which the Sekisaba feeds on, and the flow of the tide is fast. The reason Sekisaba meat firms well and is fatty year-round is thanks to the good environment of the sea it is raised in.

If you come across a Sekisaba that so much work has been put into, try it as sashimi, not Nigiri sushi. This is because Saba, which has a peculiarity to it, is unpopular among some people. However, Sekisaba doesn’t have this off-taste and doesn’t taste like Mackerel, so even people who don’t care for fish should be able to find it tasty.

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Revision date: August 21, 2023

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What is Shiromi?

Hirame is a high-quality fish that goes for at least US $50 per kilogram. It can even exceed US $80 per kilogram, depending on the timing and the fish’s body.

Hirame is a typical shiromi (white meat fish) when winter is approaching and a great sushi topping to start off a meal. Also, the taste is so delicate that the original flavor can be cancelled out just by adding too much soy sauce. How the chef expresses this delicate taste is a tribute to his skill and something that foodies look forward to.

In the US, Hirame is often written as “halibut” on the menu of sushi restaurants. Technically the English name of Hirame is Bastard halibut. Hailbut (referring to Pacific halibut) is called “Ohyo” in Japanese. In Japan, the engawa of massive Ohyo is often used as a substitute for Hirame engawa at conveyor belt sushi, but the two are not confused for each other. There is no mistake that Hirame is related to halibut, but they are completely different species. Incidentally, the price of Ohyo is US $3 to $20 per kilogram. It is incomparably cheaper than Hirame.

Also, depending on the restaurant it may be represented in a variety of other ways such as fluke, flatfish and flounder. These terms refer to relatives of Hirame (鮃) or Karei (鰈), but do not indicate any certain species of fish. In other words, there is generally no distinction between Hirame and Karei in the US and to go even further, all white fish are thought to be the same species.

The delicious taste of fish is dependent on the distribution of fat and the amount of inosinic acid. Therefore, fish taste better in the seasons when they have fattened up. On the other hand, people have a hard time distinguishing between types of fish when comparing the tastes of the parts with less fat. The free amino acids in fish meat differ only slightly between different types of fish. In other words, the flavor of all fish is mostly the same. It is only the amount of fat and the amount of the umami component, inosinic acid, that differ between fish, so apparently even sushi chefs cannot distinguish between fish just by eating the back part, which has a low fat content.

This is part of the reason why in the US all white fish is all lumped into the same category and to top it off, the common consensus there is that white fish has no flavor.

At sushi restaurants in Japan, generally there are at least two types of white fish on offer. It is practically guaranteed that Hirame will be in stock in winter. The light flavor unique to this white meat that spreads with each bite maximizes the aroma and sweetness of the vinegared rice. Recently, white fish with high levels of fat such as Kinmedai and Nodoguro, have become standard, high-quality white fish.

The difference between how even these sorts of white fish are handled in the US and Japan is astonishing. That said, flavorless Hirame is not consumed as sashimi or sushi even in Japan. It is served in dishes with strong flavors, like carpaccio. It’s possible that delicious Hirame is just not available in the US.

Related contents: List of White flesh fish

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Revision date: July 16, 2022

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There are strangely two types of Ama ebi

It goes without saying, that each type of fish has its very own scientific name. However, in places like the Toyosu Fish Market, there are seafoods that end up sharing a name.

The official Japanese name of ama ebi (sweet shrimp) is “Hokkoku Akaebi” (scientific name: Pandaluseous Makarov).

In Japan, ama ebi lives naturally along the Sea of Japan coast and the coasts of Hokkaido, and the ama ebi sold at Toyosu market is caught from Toyama prefecture and northward to Hokkaido and southward. When made into nigiri sushi, it is harmonious with the acidity of the vinegared rice and the thick sweetness is irresistible. It really lives up to its “sweet” name.

However, what dominates the Toyosu Market is frozen shrimp of the same pandalidae family, called “Honhokkoku Akaebi” (scientific name: pandalus borealis kroyer) from Iceland and Greenland.

This is distributed as “Ama ebi” at the market, but strictly speaking it is a different type of shrimp. As far as appearance goes, it is impossible to tell the difference and they say that even the flavor is the same.

The majority of ama ebi used at conveyor belt sushi is produced in Greenland and imported to Japan through China. The reason for this import circumvention is that the processing to turn the shrimp into ready-made sushi toppings is done using inexpensive labor in China. The frozen ama ebi is thawed in China, processed (head, shell, etc., are removed) and then frozen again. Of course, this process diminishes the freshness of the fish. Preservatives are used to help prevent this. For example, pigment fixing agents are used in order to reduce discoloration from fading. Furthermore, acidity regulators and antioxidants are used to prevent changes in the quality and color of the meat. Ama ebi is stored in packs of 50, imported en masse to Japan, and can be used for sushi or sashimi immediately upon thawing.

As this ama ebi caught in the North Atlantic Ocean is considerably cheaper than domestic ama ebi, the reality is that conveyor belt sushi wouldn’t survive in Japan without these imports.

What is Masuzushi?

The origin of Masuzushi dates back about 300 years. Apparently, in 1717 it was first presented as Ayu narezushi (narezushi is a traditional food, said to be the original form of sushi and made from lactic fermentation of fish) to the third-generation feudal lord, Toshioki Maeda, by Shinpachi Yoshimura, a feudal retainer of Toyama who excelled in cooking skills. Toshioki liked the dish very much and assigned the role of vinegaring Ayu to Shinpachi. After that, it is said that the same narezushi was presented to the eighth shogun of the Tokugawa shogunate, Yoshimune Tokugawa, and that Yoshimune was extremely pleased with it.

Shinpachi’s ayuzushi was made through the painstaking process of washing salt-preserved ayu with sake, then pickling it for around 12 days, removing the rice the day before it was to be served, then adding new rice that had been flavored with sake and salt.

This transformed to the present-day Masuzushi in the late Edo period, when the amount of vinegar was increased. Hayazushi, in which vinegar is added to rice for a quick meal, became popular, and Sakuramasu started to be used instead of Ayu, These factors seem to have contributed to how it transformed into the Masuzushi we see today.

It is made by first filleting fresh Sakuramasu into three pieces and removing the skin and bones, then cutting into 3 mm thick strips. These strips are sprinkled with salt and left for 3 to 5 hours before being washed with a vinegar mixture made of salt, sugar and other seasonings (water is never used for this). The type and amount of seasonings mixed with the vinegar at this time is a secret and determines the house flavor of the restaurant or family. Sakuramasu that has marinated for 1 to 2 hours in the vinegar mixture is placed on sushi rice in the container, then held down with weights to press for several hours to complete the Masuzushi.

Long ago, it was only made with Sakuramasu caught in Jinzu River, so it was made between April and July. However, due to reasons such as a dam being built upstream and water pollution, Sakuramasu produced outside the prefecture and imported Masu (trout) is used now, and it is made year-round.

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Revision date: August 3, 2021

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What is Funazushi?

Narezushi (mainly a preserved food in which fish undergoes lactic fermentation with salt and rice), in which Sushi finds its roots, can still be found even today throughout Japan. The most famous is Funazushi (鮒寿司, 鮒鮓, 鮒寿し) in Shiga prefecture.

Although it has “sushi” in the name, according to common knowledge of the day, it would be called crucian carp. The sweet and sour smell tickles your nose and it’s almost like pickled crucian carp. When you actually put it in your mouth it fills with an intense sourness and it can only be described as a really sour pickled food. However, the more you eat it, the more you somehow get used to it and in the end it becomes a favorite food that you will even crave. This effect is so mysterious that people even wonder, “Could this have been synchronized at some point with the tastes of our Japanese ancestors?”

Making Funazushi sushi is surprisingly simple. The only ingredients are crucian carp caught in Lake Biwa, rice and salt. First the internal organs are removed from the crucian carp, next it is salted and then it is shade-dried. This crucian carp is packed tightly into freshly steamed rice in a large cask. “Sushizume” refers to this precise situation, and the ingredients are packed in so there is no air inside. If air is let in, the oxygen will cause microbiota to grow. In other words, it will rot. This is the most important thing in making funazushi.

While this cask is left for eight months to two years, special microorganisms will cultivate even without oxygen. These are lactic bacteria and acetic bacteria, which work to change the entire contents into a sour flavor.

After that, the mushy rice is removed from the finished Funazushi, and only the crucian carp is consumed. However, let me reiterate, this sour flavor is intense and complicated. Comparing it to bleu cheese or camembert cheese might make it easier to understand. The taste is so intense that it makes some people sick.

Incidentally, there are records from when Hideyoshi Toyotomi advanced his army to the Korean peninsula (around 1592), that Funazushi from Oumi was presented to soldiers on the front line as a comfort food. This episode illustrates the fact that Funazushi was a dish of pride for the people of the town of Nagahama (where Toyotomi’s castle was located, now part of Shiga prefecture).

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Revision date: June 23, 2023

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What is Yamawasabi?

Horseradish is believed to have originated in Eastern Europe. It’s a cruciferous vegetable, alongside mustard, wasabi, cabbage, and broccoli. Horseradish is very fertile, and buds and roots will sprout just by cutting the root stock part to an appropriate size and soaking it in water. Once transferred to soil the roots will multiply quickly even without any other efforts.

In Europe horseradish is used as an ingredient for sauces or to accompany sausage and roast beef, or as a subtle seasoning for other dishes. In Japan most is used as an ingredient in processed foods such as wasabi powder or wasabi paste. Unlike wasabi, horseradish is characterized by its pure white root and strong spicy flavor. In Hokkaido horseradish is called “Yamawasabi” and is a common sight at home dinner tables.

Farming of Yamawasabi for food started in the Meiji era and settled in Hokkaido. Currently over 90% of the domestic production in Japan is accounted for in Hokkaido. While it is grown throughout Hokkaido, the vast Yamawasabi fields befitting Hokkaido are especially prevalent in Abashiri and Kitami.

In Hokkaido, Yamawasabi is eaten as an accompaniment to white rice. Grated Yamawasabi is sprinkled on rice and there are also jars of “Soy sauce-marinated Yamawasabi” sold as a normal item at supermarkets. Besides on rice, it is also indispensable to Hokkaido cuisine as seasoning for hiyayakko (cold tofu) and sashimi.

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Revision date: June 28, 2021

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What is Rendaku?

In Japanese, when a compound word is made out of two individual words, and the first consonant of the second word changes from a “clear sound” to a “fuzzy sound”, it is called “Rendaku”. For example, Edomae (江戸前) + sushi (寿司) changes to Edomaezushi (江戸前寿司). However, the correct pronunciation is only generalized among Japanese people, so in this book we chose the most commonly searched version of each compound word.

Examples of Rendaku (連濁):

Nigiri (握り) + sushi (寿司)→Nigirizushi (握り寿司)

Inari (稲荷) + sushi (寿司)→Inarizushi (稲荷寿司)

Masu (鱒) + sushi (寿司)→Masuzushi (鱒寿司)

Kaiten (回転) + sushi (寿司)→Kaitenzushi (回転寿司)

Kuro (黒) + tai (鯛)→Kurodai (黒鯛)

Ma (真) + tako (蛸)→Madako (真蛸)

Aka (赤) + kai (貝)→Akagai (赤貝)

Tori (鳥) + kai (貝)→Torigai (鳥貝)

Shiromi (白身) + sakana (魚)→Shiromizakana (白身魚)

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Revision date: June 9, 2021

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What is Shiojime?

Generally, saltwater fish grow in seawater, and their bodies naturally contain a certain concentration of salt. Because seawater has a higher salinity than the fish’s internal fluids, the water in their bodies is constantly being drawn out by osmotic pressure. As this water is lost, the internal salt concentration increases. To compensate, saltwater fish actively drink large amounts of seawater and excrete the excess salt through specialized cells in their gills and kidneys. This complex osmoregulation mechanism helps them maintain a balance, which is why their flesh typically contains a high percentage of water.

This high moisture content sometimes gives the impression that the fish is “somehow watery” or lacking in firmness. However, once the fish is cooked—especially through gentle heating—the texture becomes soft and fluffy, enhancing its natural qualities.

Therefore, when preparing fish for cooking, it is often sprinkled with salt approximately 30 minutes to one hour beforehand. This process, commonly practiced by sushi chefs as well, is called Shiojime (塩締め), or salting.

Shiojime serves several purposes. First, it draws out excess moisture through the process of osmosis, which in turn concentrates the fish’s natural umami (savory) flavor.

Additionally, by removing moisture, Shiojime helps eliminate the fishy odor (commonly caused by compounds like trimethylamine), allowing the clean, delicate flavor of the fish to shine through.

Another important benefit of Shiojime is that it helps control bacteria. When salt is applied to the fish, it creates a salty (hypertonic) environment that draws water out of the bacteria on the surface. Without enough water, the bacteria can’t survive or grow. In addition, salt lowers the water activity in the fish, which makes it harder for microbes to multiply. This helps keep the fish safe to eat and slows down spoilage, making it last longer.

In traditional sushi preparation, Shiojime is often followed by Sujime (vinegar curing). The amount of vinegar that penetrates the fish depends significantly on the prior conditions established during Shiojime, making it a delicate and finely tuned process that requires experience and attention to detail.

Ultimately, Shiojime is a time-honored technique that delivers numerous benefits—enhancing flavor, improving texture, reducing odors, and increasing safety—while showcasing the depth of Japanese culinary knowledge.

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Revision date: June 12, 2025

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What is Karami?

Sashimi essentials such as wasabi, ginger, karami-daikon, etc., are collectively called “Karami”. The term Karami comes from the Japanese word 辛味, which literally means “spicy” or “pungent taste.” In the context of sashimi, it refers not to intense heat like chili peppers, but to a sharp, aromatic pungency that stimulates the palate, cuts through richness, and neutralizes fishy odors. This quality is why karami ingredients—such as wasabi, ginger, or grated daikon—are used alongside raw fish: they enhance flavor while making the dish feel cleaner and more refreshing.

Originally Karami was a type of Tsuma. From the mid to late Edo period, Karashi (mustard) was mainly used for karami in sashimi. Eventually, due to the influence of Edomae sushi, wasabi became the norm. Wasabi was favored not only for its refreshing heat but also for its antibacterial properties and its ability to complement the delicate flavors of raw fish. For sashimi such as bonito and sardines, wasabi isn’t enough to offset the peculiar aroma. In some cases, it is better to use ginger, which works on the root components of the odor. These types of fish have the best flavor once spring has passed, and interestingly enough, wasabi is least prevalent in summertime, while ginger is in peak season. Mother nature seems to know what she’s doing.

Historically, karami was considered a type of tsuma, but today it is classified as a type of yakumi (condiment). Tsuma refers to the decorative and edible garnishes that accompany sashimi, serving both aesthetic and functional purposes—enhancing presentation, adding contrasting textures, and refreshing the palate between bites. Over time, karami came to be recognized not just as a garnish but as a form of yakumi (condiment), whose primary role is to add flavor, mask unwanted odors, and balance the taste of the fish rather than to decorate the plate.

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Revision date: August 12, 2025

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