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What is Fugu poison?

Why do people risk their lives to eat Fugu, a fish known to be deadly?

Fugu, or blowfish, is a celebrated delicacy in Japanese cuisine, but it comes with a deadly risk. Despite its exquisite taste and refined culinary presentation, Fugu contains one of the most powerful natural toxins known to humans. Understanding what makes this fish so dangerous—and how it’s safely prepared—sheds light on one of the most fascinating aspects of Japanese food culture.

In most cases, Fugu (blowfish) poison is found in non-meat parts of the fish such as the liver, ovaries, stomach, intestine, skin and eyes. There are Fugu that do not contain poison in these parts, but most of the Fugu in the waters near Japan are poisonous. A mistake in preparations that allows the meat to touch the poison of the liver or ovaries results in immediate death. Therefore, the general rule is to only eat Fugu at restaurants with an expert licensed in Fugu preparation. Cases of poisoning by Fugu are nearly always a result of an amateur trying to prepare the fish.

The toxin in Fugu is a chemical substance called tetrodotoxin and even heat from boiling or frying can’t detoxicate it. Even Torafugu (Japanese pufferfish) that we find so delicious (we eat the meat, skin and testes) has poison in the liver, ovaries and intestines. The toxicity is said to be at least 1,000 times that of potassium cyanide. They say 10 people would die from the organs of a single Torafugu. In the case of Fugu poisoning, the first poisoning symptoms occur between 20 minutes and three hours after eating the Fugu. It starts with numbness in the lips, the tip of the tongue and fingertips. This is followed by headache, stomachache and severe vomiting. The victim will stagger when trying to walk. Soon they will experience sensory paralysis, speech disturbance and difficulty breathing, accompanied by a decrease in blood pressure. After that, the entire body becomes paralyzed and the victim can no longer move even a finger. Finally, they will fade out of consciousness and eventually both breathing and heartbeat cease, resulting in death. If the consumer doesn’t notice they are experiencing poisoning symptoms, they will surely die.

The strength of the toxin of the fugu also varies depending on the season. Even on an individual basis, some fish have toxins while others don’t. It’s not possible to determine this based on appearance, so it’s better to never eat the organs and eyes, which have a high probability of containing poison.

Fugu has already been successfully farmed and is on the market. No toxins have been found in this farmed Fugu. If farmed Fugu has no toxins, it’s only natural to question what factors generate toxins in wild Fugu and apparently it‘s a cumulative effect of toxins from the food chain. Fugu’s main sources of nutrition are starfish and shellfish. Starfish and shellfish accumulate poison in the body by eating zooplankton with vibrio attached to them. This vibrio creates poisons. Then, Fugu accumulates toxins in the body by eating starfish and shellfish that have toxins accumulated in their bodies. Therefore, farmed Fugu are raised on man-made feed that doesn’t contain Fugu toxins, and since they don’t ingest Fugu toxins and there is no bioconcentration, so the Fugu does not contain poison.

Enjoying Fugu safely requires more than bravery—it requires expertise.
While the thought of eating a potentially lethal fish may seem reckless, the strict regulations and skilled craftsmanship behind Fugu preparation make it one of the safest delicacies when handled properly. As farmed Fugu becomes more common and toxin-free, the dangers may be diminishing—but the mystique surrounding this unique fish remains as strong as ever.

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Revision date: August 7, 2025

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What is Shusseuo?

During the Edo period, samurai would change their names at Genpuku (coming-of-age ceremony and career stages. Following this tradition, fish that are called by names as they grow older/larger are called “shusseuo (出世魚)”, are considered lucky and are used in cooking to celebrate milestones in life.

Shusseuo doesn’t just change in name, they also change in taste. The bigger the body, the more fat. However, young fish also have their own delicious, refreshing taste unique to their age. For example, using the young fish for deep-frying and fatty fish as sashimi is an interesting way to put it.

In addition to fish commonly referred to as “syusseuo,” there are other fish whose names change as they grow. According to “A Study of Japanese Fish Names,” there are 82 species of fish whose names change as they grow. Bluefin tuna (Maguro) and Greater amberjack (Kanpachi) are representative examples. Maguro changes from “komaji” to “meji” to “maguro” to “oomaguro.” Kanpachi changes from “mojaco” to “shiwoko” to ‘akahana’ to “kanpachi.”Fish such as konoshiro, sawara, unagi, sake, and koi are not considered “syusseuo.” It is not the case that all fish whose names change as they grow are classified as “syusseuo.” Rather, these are fish whose taste improves as they grow, undergo minimal changes over time, and were highly valued in eras when preservation and transportation technologies were not yet developed.

Incidentally, opinions are divided on whether to call Maguro “Shusseuo.” Maguro is also called “Meji” or “Chubou” when it is small, and its name changes as it grows. Fishermen distinguish between different stages of Maguro before it becomes an adult fish, but when it is sold in stores, even if it is slightly small, it seems that people tend to trust the name ‘Maguro’ and do not treat it as a fish that has “made it.”

A good representative fish of shusseuo is the yellowtail (Buri). Its name changes as it grows and there are various forms of their names depending on the region. In the Kanto region, it changes from Wakashi (15-20cm) to Inada (30-40cm) to Warasa (60cm) and then to Buri (80cm or greater). It is said to be most delicious at 40 cm or longer and even if the body is plump, inada often has little fat.

Even if the name is the same, depending on the region, it may be referring to a different size. For example, inada is a fish up to 40 cm in Kanto but in Tohoku and Tokai, it refers to small fish of 15-20 cm. Further, although it is not related to its growth, those caught in Tohoku during summer are called “ao”. In Toyama, they are called “gan” and “gando”.

Finally, the changing names of fish demonstrate the breadth of culture. We should cherish this local diversity present in the names of our fish that capture the abundant food culture and importance of the seasons.

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Revision date: August 8, 2025

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What is Artificial caviar?

Caviar refers to salted sturgeon ovaries but in many European countries, caviar is also used as a generic term for fish roe. In its home of Russia, roe is generally called “ikura” and caviar specifically refers to black fish roe.

Caviar is one of the world’s three major delicacies and can command different prices depending on the type of sturgeon (egg size). It is ranked in the order: Beluga, Oscietra and Sevruga, all of which come from the Caspian Sea. Beluga from the Caspian Sea is designated as an endangered species and international trade is prohibited by the Washington Convention. Its population is very small and it does not lay eggs until 20 years into its lifespan, so the resource has yet to recover. This has brought the market price of Beluga up to around USD $400 for just 50 g.

What is the substitute for caviar?

Lumpfish roe is sold as a substitute for caviar. The size of each egg is about 2 mm in diameter and it is colored with squid ink. This gives it a taste and appearance similar to caviar. The market price is an astonishing USD $5 per 50 g.

The main ingredients of Lumpfish caviar are as follows:

　Lumpfish roe
　Salt
　Sugar
　Thickening agent
　Sodium benzoate
　Coloring

What is artificial caviar?

Artificial caviar is significantly cheaper than genuine caviar. It’s low in fats, lower in calories and healthier than the real thing. It is already a big hit in the U.S. The size of the eggs is a little larger than authentic caviar and the skin is thicker but most people would tell you the texture and taste is much the same. There has also been a decrease in sturgeon, and there is no sign that its price will fall in the future. The challenge is meeting the global demand through a combination of farmed caviar which has become a more stable supply in recent years, with the ever-dwindling wild caviar. The market price is reasonable at around USD $10 for 50 g.

There is a way to tell the difference between real caviar and fake caviar.

First, place the caviar on a cracker. Fake caviar (made of Lumpfish roe) has added color, and this color will bleed onto the cracker within about 30 minutes. However, the color will not transfer to the cracker from real caviar.

The main raw ingredients of artificial caviar are as follows:

　Sea urchin extract
　Oyster extract
　Gelatin
　Dextrin
　D-sorbitol
　Trehalose
　Gelling agent
　Seasoning
　Coloring

Finally, seafood with a high price, unfortunately, results in substitutes, counterfeits, and artificial products. Masquerading a fake as the real thing can result in a large profit. I will tell you that it is difficult to trick a middleman who serves professional sushi chefs or restaurants. Therefore anyone in Japan who uses seafood like this, does it knowingly, which makes the crime even worse.

What is Izumidai?

When you see “tai” on the menu at a conveyor belt sushi restaurant, it’s very likely that is not “madai” (Red sea bream). It’s a competitive industry where these conveyor belt restaurants have no problem using a variety of imitation or replacement fish if it means they can cut costs. In any case, the purpose for using different types of fish without even considering farmed cheap madai, is to further reduce costs.

First on the list is Nile tilapia. This fish was introduced from Egypt to rivers throughout the world as food in 1962. While it was farmed in large quantities in Japan, especially in Kagoshima, from the 1990s, production rapidly declined with the stagnant prices of farmed madai. However, they are extremely fertile and proliferate naturally, and started living in the thermal regions and the rivers where warm wastewater flow throughout Japan.

The commonly used names for this is “izumidai” or “chikadai”. While izumidai (Nile tilapia) is a freshwater fish, it was likely named after “tai” (sea bream) because of the similarities in appearance. In Taiwan, it is considered to be so similar in appearance and taste, that it is called “Taiwanese sea bream”. It is a popular fish for consumption on a global scale with high production and distribution volume.

However, even though has “sea bream” in the name, it is not actually related to the sea bream at all.

As an aside, at least 90% of the tilapia found in the U.S. is imported. Most of those imports come from China. It’s often said that they are raised on a large volume of antibiotics and pesticides, and they are kept fresh using high amounts of chemicals. It’s best to avoid eating it if possible. The tagline they give it is “Sushi grade tilapia is a high quality, firm fish with a mild, clean taste perfect for sashimi and sushi applications” You’ll be hard-pressed to even find kaiten sushi restaurants using this in Japan. In addition, it would never be used at restaurants that describe themselves as Edomae Sushi.

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Revision date: January 4, 2021

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What is Engawa?

Engawa has both a unique, crunchy texture and delightful fat distribution and is said to be the most delicious part of hirame.

But what exactly is engawa?

a photo of Engawa nigiri — Engawa is not the name of a fish, but a generic term for a specific part of a fish.

Engawa is the generally used name for the meat muscle that moves the soft ray of the dorsal and ventral fins of flatfish (such as Hirame and Makogarei). Most people in Japan think of the hirame version when they hear the word ‘engawa’.

To go into a more advanced level of detail, there are three types of muscles that move the dorsal and ventral fins in fish: the erector spinae, the depressor and the scalene muscles. These muscles are well-developed in fish that move their dorsal and ventral fins often, like flatfish and flounder. Actually, not all three of these types are always consumed. If we look at the way hirame and makogarei are cut for preparation, the slanted muscle is taken to be used for engawa while the erector spinae and depressor are left, affixed to the fin ray, etc. In other words, to be exact, engawa is the slanted muscle of the dorsal and ventral fins.

The unique, crunchy texture comes from the high content of collagen, which is a scleroprotein. “Kakushi boucho” is used to make the crunch pleasant and is one of the skills a sushi chef must perfect. The delicious flavor is related to the high amount of fat compared to body meat. There is also a sense of elegant sweetness. Only four pieces of engawa can be taken from a single flatfish, so it makes sense that foodies love it.

The name “engawa” comes from its resemblance to the unique veranda structure of Japanese-style homes. This veranda is called “engawa” in Japanese.

Incidentally, substitutions have become common at kaiten sushi (conveyor belt sushi) restaurants, and the topping is especially popular among women lately. So the question is, how is it possible to eat this valuable topping that is only rarely available at expensive sushi restaurants, so cheaply at kaiten sushi? Actually, Greenland halibut engawa and Kamchatka flounder engawa are used as substitutes to hirame engawa. The proof of this is in a menu that lists only “engawa” and not “hirame engawa”.

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Revision date: December 3, 2020

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What is the difference between Fish farming tuna and Fish fattening tuna?

While high-quality tuna toro used to be unattainable for normal people, it’s now become a much more affordable item. This is thanks to fish fattening (畜養) practices of the southern bluefin tuna, which is equivalent in quality to the Pacific bluefin tuna. The fattening method of catching young southern bluefin tuna in roll nets or something similar, and then keeping them in fish preserves until they grow big enough was developed in the 1990s in Australia.

There have been changes in the Pacific bluefin tuna as well. In the late 1990s, the southern bluefin tuna fish fattening method started to be used in the seas throughout the world, and this led to the fattening of the Pacific bluefin tuna, which became all the rage. Most of these are exported to Japan, and account for about half of the consumption of southern bluefin tuna and Pacific bluefin tuna in Japan.

As a bonus, tuna that has been fattened in this way has such a high volume of fat that it is said to be “all toro”, and it’s taken the Japan high-grade toro market by storm. Also, both southern bluefin tuna and Pacific bluefin tuna are served at kaiten-zushi (conveyor belt sushi) restaurants.

The fattening of Pacific bluefin tuna started on the east coast of Canada in the mid-seventies. In the summer, large volumes of Pacific bluefin tuna are caught in the fixed shore nets on the Atlantic seaboard, and since they have already spawned, they have slimmed down and aren’t worth much commercially. These fish are fed and fattened, and a new route to Japan has been developed, giving the fish new commercial value.

Both fish fattening and fish farming (養殖) mean to hold fish in fish preserves, but the purpose differs between the two. The purpose of fish fattening is an adjustment for fishing while the purpose of fish farming is to grow fish to a certain size. Therefore, in fish fattening, they are not fed food to promote growth, but they are in fish farming. However, even in fish fattening, if the period of time they are held for shipping adjustment stretches out too long, they are fed in order to prevent a decrease in meat quality and cannibalism. This can blur the line between fish fattening and fish farming quite a bit.

The Pacific bluefin tuna fish fattening started in Canada is similarly vague. In that case, the purpose was fattening, so it may be fair to call it fish farming. However, shipping adjustment was also one of the major objectives. What about the fish fattening of southern bluefin tuna and Pacific bluefin tuna in Australia and the Mediterranean Sea? These are in place clearly for the purpose of growing small fish, so we can call them fish farming.

In the Mediterranean, where resources are already declining, methods are used to catch natural tuna alive. The only mobile fishing gear that can catch tuna alive is purse seine nets.

The period when tuna are transported to the fattening farms is generally from May or June to July or September, but this varies depending on the country. They are then transferred to cages, where they are fattened for a relatively short period to meet Japanese market standards. The fattening period is usually six to seven months, because demand in the Japanese market peaks at the end of the year. In Croatia, the size of tuna transferred to cages is small, so the fattening period can be as long as 20 months.

Mediterranean coastal countries involved in tuna fattening include Algeria, Croatia, Cyprus, Greece, Libya, Malta, Spain, Tunisia, and Turkey. French tuna purse seine fishing fleets are the largest suppliers of live tuna to fattening farms in Mediterranean coastal countries.

The Kindai University Aquaculture Research Institute has succeeded in a complete farming process of taking eggs from spawning Pacific bluefin tuna, incubating them and raising adult fish. Research for a complete farming process began around 1970, so it has taken 30 years for success. These fully farmed tuna are also raised in fish preserves and fed small fish like sardines as well as artificial feed for fattening, resulting in all-toro tuna. However, even though the Kindai University tuna have been featured by the media, you never see them in the supermarket. Why is that? Even though the university has succeeded in a mass-production method, the absolute quantity is extremely low even though raising the fish takes a lot of time and effort, so the price is extremely high.

Whether they are fattened, farmed, or fished in the wild, consumers always welcome delicious, high-quality toro at a reasonable price.

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Revision date: May 28, 2025

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What is a firm difference between sushi and western fish cuisine?

In Japan, they say, “Japanese cooking means taking away and Western cooking means adding.” This concept is well-known among Japanese chefs, but it may be difficult for western chefs to understand. This is verified in the way the white Japanese sea bass, the representative fish of summer, is prepared. This is all connected to clearly explaining the irrefutable differences between sushi and western fish cuisine, which also involves differences in cultivated history and culture.

In the case of Sushi, a representative of Japanese cuisine, the decisive point is to prepare the fish in a way that removes the fishy odor characteristic of Japanese sea bass. At the same time, the finished piece should be a simple dish that can be enjoyed with only a minimal amount of nikiri soy sauce and wasabi, so as not to override the natural refreshing flavor and umami of the fish. It should let the customer imagine sea bass swimming in the summer sea. And yet, the deep flavor required for the dish is successfully brought out using only a balanced combination of vinegar rice, the topping, wasabi and soy sauce. The method is really just to take out the excessive elements of the dish.

Meanwhile, the method for making sea bass dishes in French cuisine, representative of western cooking, includes seasoning the fish with salt and pepper and saute in butter, then adding rich, creamy sauce as well as other things like herbs, caviar, black truffles, etc., creating a dish that allows enjoyment of multilayered flavor. This sort of dish beautifully makes up for the flavors that the light, white fish lacks and portrays a flavor with depth through the finished plate over the individual flavor of the sea bass. In this cuisine, it can be said that the cooking method is more important than the raw ingredients. It can be thought of as cuisine that adds many ingredients.

Comparing the two, it’s clear that the approaches are completely opposite. Another difference is how the flavors are treated. Flavors perceived through aroma can be described as “aromatic flavor”.

If this fragrant flavor were not important in sushi, then there would be no debate on whether to use wild or farmed fish. For example, sea bream is available both in the wild and as farmed fish. There is not much difference in amino acid composition and umami content between the two. So how is it that farmed sea bream and wild sea bream end up tasting so different? The reason is undoubtedly the aroma. The subtle aromatic compounds, volatile substances carried in the fish’s fat, are what define the essential flavor of the sea bream. Wild fish, having fed on a natural diet and lived in varied ocean environments, develop a more complex and refined aromatic profile. In contrast, farmed fish, raised on controlled feed in uniform conditions, lack this nuance. This means that much of the pleasure of eating sushi comes from recognizing and savoring this delicate aroma.

On the other hand, in Western fish cuisine, the culture is to combine many different aromas, as if composing a perfume, probably because people want complex flavor. In addition, in French and similar cuisines, care to serve dishes at a temperature that is warm, but not hot, in order to bring out the natural flavor of the ingredients. While cooking the dishes, the temperature is strictly controlled so that the components of the ingredients don’t change from the heat, in order to maintain the taste and aroma. This method does not neglect fragrance by any means. In sushi, the fish itself is the centerpiece, with preparation methods designed to remove distractions from its inherent character. In Western cuisine, the plate as a whole is the centerpiece, where the fish is one component in a carefully constructed harmony of flavors.

In either method, the one essential element is this “aroma”. The only true difference is how that is expressed.

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Revision date: August 11, 2025

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How can frozen tuna be thawed to still taste good?

In order to maintain the quality of tuna, when it is caught in the sea, the ikejime technique is used first, then rapid freezing is used as a matter of course. This means that the quality of the thawing technique is also important. Poor thawing conditions mean that the drip outflow volume will be too high, shrinking the meat and worsening the texture. Here I will explain a thawing method that doesn’t cause drip, uneven thawing, or loss of color.

What exactly is drip anyway?

I’m sure you’ve seen it before in any type of thawing frozen meat, but there is a red liquid that comes out of the tuna when thawing. This is called ‘drip’. This liquid includes the tuna’s umami, and when the fish loses a lot, it naturally detracts from the flavor.

First of all, we will explain the worst thawing methods. Never thaw naturally at room temperature or in the microwave. These are common methods at home, but they are out of the question.

Next we will explain the general method of thawing.

Mix 30 g of salt with 1000 cc of warm water at 40℃ to create a saltwater mixture.
Place the frozen block of tuna in this 40℃ saltwater, submerge for one to two minutes and then drain the water.
Wash any remaining salt off the surface of the block of fish with fresh water and remove moisture from the surface with paper towels.
Wrap the fish in clean paper towels, wrap with plastic over that and leave it in the refrigerator for about a day to thaw naturally.
Cut from the block directly before consuming.

Now for the thawing method used by professionals, such as sushi chefs.

The first three steps are the same as the general thawing method above.

Place block in an air-tight plastic bag. Push out as much air as possible before sealing the bag.
Prepare ice water in a bowl or container and submerge the plastic bag in the water for one hour. Normally the bag will float, so it must be weighed down with something.
Remove the thawed tuna from the plastic bag and remove moisture with paper towels.
Wrap the fish in clean paper towels, wrap with plastic over that and leave it in the refrigerator for about a day to mature.

After thawing, the meat of the tuna may have shrunk. This is called ‘chijire’. The reason for this is, after the tuna is caught, it is frozen before rigor mortis begins, so the rigor mortis process starts once the fish is thawed. Therefore, this is proof of freshness. The meat of tuna for which ‘chijire’ has begun is tough and isn’t yet matured. However, amateurs can’t tell if ‘chijire’ is happening or not. That’s why it’s better to let the fish mature in the refrigerator for half a day to one day. Please use these explanations for your own reference.

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Revision date: October 2, 2020

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What’s the trick to distinguishing which conveyor belt sushi restaurants are better?!

There is only one trick to distinguishing between conveyor belt sushi restaurants (kaiten-zushi), and that is to try eating the tuna as your first dish.

Why is that, you ask?

The most commonly used ingredient at kaiten-zushi is tuna. At kaiten-zushi, the tuna is imported and frozen nearly 100% of the time. The most famous is the Southern blue-fin tun, but you’ll also find Boston bluefin tuna, Canadian tuna farmed in fish preserves, inland sea tuna from Turkey and Spain, New Zealand offshore tuna, Atlantic tuna, etc. Also, the season of each type of tuna and the timing of high-volume catch differ, which makes the prices fluctuate greatly.

Therefore, the biggest task of a kaiten-zushi chain buyer is to decide where to import tuna from. Looking for high cost-performance, they watch fluctuations in the market every single day without fail, check the flavor in detail and constantly change the locality.

In other words, the chain restaurant purchaser’s efforts are concentrated on tuna. Restaurants that serve tuna that has lost its fat, is watery or rubbery, clearly either have a purchaser with a poor eye, or poor thawing skills. Therefore, if you are disappointed with that first tuna plate, then reign in your expectations for other toppings. On the other hand, if you enjoy the tuna then you’ll have a lot of other toppings to look forward to.

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Revision date: August 17, 2020

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What is Imitation crab?

One of the common ingredients of sushi rolls is imitation crab. In Japan this is called kanikama (カニカマ), in Europe, it’s called surimi and in the US it’s also called fake crab.

I’m sure everyone reading this has tried it before, but what is imitation crab made of?

It seems kanikama was invented in Japan. In the early 1970s, Sugiyo, a fish paste manufacturer, in a failed attempt to develop artificial jellyfish, ended up with a product that had a texture exactly like crab and shifted development to that instead.

What’s the Difference Between Surimi and Kanikama?

Surimi and kanikama are related but not the same. Surimi refers to the base ingredient—a white fish paste made by washing and mincing fish such as Alaska pollock. It is a versatile ingredient used in various processed seafood products like fish balls, kamaboko (steamed fish cake), and imitation crab.

Kanikama, on the other hand, is a finished product made from surimi. The word is short for “kani kamaboko,” meaning “crab-flavored fish cake” in Japanese. It’s processed to look and taste like real crab meat, often with added flavorings, coloring, and shaping to mimic crab leg texture. In short, surimi is the raw material, while kanikama is one of the products made from it.

So while all kanikama is made from surimi, not all surimi becomes kanikama.

The “kani” of “kanikama” means “crab”. “Kama” is an abbreviation of kamaboko, which is boiled fish paste, fish sausage, or fish cake. Its official name is “crab-like kamaboko”. The main ingredient is minced fish meat mashed into a paste. One of the whitefish used is in Alaska pollack. But it contains no crab. Therefore, to bring out the crab flavor, crab extract, which is a combination of ingredients extracted from crab shells and meat, salt, etc., is added. In this way, the crab-like taste can be reproduced without the use of crab meat. However, those who are allergic to crab or other crustaceans cannot eat kanikama containing crab extract. Also, the red color of the crab-like appearance is made with paprika dye, etc.

Is Imitation Crab Vegetarian or Vegan?

Despite being called “fake crab,” imitation crab is not suitable for vegetarians or vegans. Its main ingredient, surimi, is made from minced white fish, making it an animal-based product.

Additionally, some varieties of imitation crab contain additives like crab extract, which is derived from real crab shells or meat. This makes them unsuitable not only for vegetarians and vegans, but also for those with shellfish allergies.

However, in recent years, plant-based alternatives to imitation crab have been developed. These vegan-friendly products are made from ingredients such as soy, konjac (a root vegetable), or starches, and are designed to mimic the taste and texture of traditional kanikama without using any animal-derived ingredients. Always check labels carefully if you follow a vegetarian or vegan diet.

Incidentally, some kanikama sold in the US and Europe actually contain real crab.

It has now become a staple not only in sushi rolls, but also in sandwiches or on baguettes and even on takeout salads. It’s become even more popular than it is within Japan.

What’s the difference between Tobiko and Masago?

Tobiko and Masago often appear on sushi rolls around the world, but do you know the real difference between them? Whether you’re a sushi lover or just curious about what’s on your plate, this article explains everything from texture and flavor to nutritional value and even food fraud behind these colorful fish roes.

The tiny red balls around the outside of the rice on California rolls are Tobiko (飛び子). Specifically, they have salted roe of flying fish and are known for the plump, crunchy texture. This crunchy texture comes from the skin, which is relatively tough, even compared to other fish eggs. As the roe is made up of small eggs of only 1 to 2 mm, each one bursts as you bite, without leaving the outer skin in your mouth, so you can enjoy a nice texture that you won’t find with any other fish roe. Unlike the orange-colored tobiko sold in stores, natural tobiko has a pale golden color with a sense of transparency. Therefore, some processors have dubbed it “golden caviar”.

The main production areas are Indonesia and Peru, and in small quantities, Taiwan as well. The eggs from Indonesia are smaller than those from Peru. If you don’t like the skin remaining in your mouth then the Indonesian tobiko is recommended. Meanwhile, Peruvian roe has larger eggs and thus the skin is tougher, giving it an excellent firmness.

Freshly harvested flying fish roe gives you not only the satisfying popping texture like bubble wrap, but also a sense of the subtle aroma unique to fish roe. This combined with the saltiness of the sea gives you the same sort of umami found in tarako and ikura. Also, Tobiko sold at stores has even more added flavor. This is used for making hand-rolled sushi at home.

In fact, it is a registered trademark of a seafood processing company called Kanetoku (かね徳), located in Hyogo prefecture, Japan. It isn’t hard to see that it’s an abbreviated version of the Japanese “Tobiuo no ko”.

Tobiko is rich in nutrients such as the minerals and vitamins potassium, phosphorus, vitamin E, vitamin C and niacin. Also, since it has a natural pigment composition called astaxanthin, which gives tobiko its bright color, it has antioxidative effects and is effective in strengthening the immune system. While Ikura has 272 kcal per 100 g, Tobiko only has 74 kcal per 100 g, adding a health factor to its charm.

What is flying fish?

Flying fish are found in the subtropical to temperate waters of the Pacific Ocean, Indian Ocean, and the Atlantic Ocean. They travel along the surface of the sea and eat zooplankton. Over 50 types of flying fish have been identified around the world. More than 30 of these have been identified in Japan, of which 4 types are used as food. Since the meat is white, low in fat, and has little odor, it is prepared in various ways such as sashimi, minced, grilled with salt, and fried. In Kyushu, flying fish is called “ago,” and it is dehydrated to be used as soup stock, called “dashi” in Japanese. Ago dashi has a refined and refreshing sweetness and a deep flavor, and it is considered to be on the higher-end of dashi stock.

The dorsal side of the flying fish is a vibrant dark blue, and the ventral side is silver The pectoral fin is considerably longer at about 30-40 cm long. It uses it pectoral fins to fly over the water’s surface to escape from its natural enemies, such as tuna Depending on the breed, it can fly an average of 200 m in one go. The larger the species, the longer distance it can fly and the longest can be up to even 600 m. Furthermore, the flying fish has no stomach and its other digestive organs are short and straight, which makes its body lighter and ideal for extended flight.

Flying fish contains a lot of a nutrient called Niacin which can help prevent hangovers. Additionally, it is rich in vitamin E, which works to prevent the oxidation of unsaturated fatty acids in the body, and as such is a good fish for preventing lifestyle-related diseases such as arteriosclerosis and myocardial infarction.

On the other hand, an orange-colored tobiko is often seen at conveyor belt sushi restaurants, etc., but this is the roe of a fish called capelin (カペリン), which is similar to shishamo smelt. A salted version of this is used for sushi rolls in the US and other places, where it is called masago. Compared to tobiko, the grains are smaller and the texture is a bit chewier. It is mainly rich in EPA (Omega-3 fatty acids) and collagen.

“Masago (真砂子)” actually means “fine sand” and therefore is used for foods that depict that image. In other words, it refers to broken-up fish roe and doesn’t indicate a specific type of fish. Dishes made using capelin roe can be called masago, but please keep in mind that dishes with broken-up tarako or kazunoko are also called masago.

What is capelin?

The shape of capelin is very similar to shishamo smelt, but the scales are very fine, barely visible to the eye. The body is a bluish silver color with an average length of 12-16 cm, but can grow up to 20 cm.

It is found in a wide area from the Arctic Ocean to the frigid sea regions and also migrates to the Sea of Okhotsk on the coast of Hokkaido. The time they spawn depends on the region. The season for Canadian capelin is June to mid-July, and the season for Icelandic and Norwegian capelin is mid-February to mid-March.

They are also known as Komochi Shishamo (Shishamo with child) and are known to have a wonderful balance of fat and roe. Compared to shishamo smelt, they are leaner and have a lighter texture. Shishamo smelt is not caught in great numbers, so capelin started to be imported as a substitute for it for Japanese homes and izakaya (Japanese bar/restaurants).

Capelin rush to the coastal area in large groups to lays eggs on the sandy bottom of the beach during spawning season. The amount of eggs it lays at one time is about 5,000 to 6,000. It has spherical, adhesive demersal eggs with a diameter of around 1 mm. The eggs hatch around spring tide about 2 weeks after spawning The total length of larvae immediately after hatching is 4-5 mm, and it is thought that they leave the coastal area by utilizing waves at high tide and reach a total length of around 10 cm in the first year of life.

Capelin is a healthy fish that can be eaten in its entirety, and boasts 7 nutrients (DHA, EPA, calcium, zinc, potassium, vitamin B2, collagen). Moreover, since the sugar content is only 0.5 g per fish, about 1/3 of the amount normally contained in fish, it is perfect for those who are dieting.

If you come across wholesale Tobiko and Masago, it was likely purchased at the Toyosu Market. The reason for the ambiguous expression here is that you will rarely find nigiri sushi with tobiko or masago at sushi restaurants with counters. There may be some sushi restaurants that have tobiko or masago on their standard menu, but there are fewer than ten of those restaurants in Tokyo. In other words, in Japan, tobiko and masago are mainly used for kaiten-zushi (conveyor belt sushi) and izakaya restaurants.

Finally, we’ll let you in on a not-so-pleasant secret. Flying fish and capelin roe is actually a light yellow or beige color. However, you’ll find it in bright red, orange, yellow and lately even green or black. Of course, these are colored by either natural pigments or synthetic coloring. Furthermore, tobiko is sometimes mixed with the cheaper capelin or herring roe. Unfortunately, food fraud is common in seafood products that are consumed in high quantities.

In summary, while Tobiko and Masago may look similar on your sushi roll, they come from different fish, have unique textures, and vary in price, flavor, and nutrition. The next time you enjoy sushi, you’ll know exactly what you’re tasting.

If you’d like to learn more about sushi ingredients and how they’re used in Japan, check out our other articles on Ikura, Tarako, or Ago-dashi. And don’t forget to always check the labels—looks can be deceiving!

What makes a “good” sushi restaurant?

It is probably cutting fish just before serving. For a big size fish, keep its skin on the meat during the process of preparing and cutting into half, and at every serving use sogigiri* as much as customers eat. Protected by the skin, the fish flesh will expose to air for the first time as it is cut. The skin blocks the oxidation process significantly because the fat in fish centers right under the skin in general. Needless to say, even with any amazing fish, it loses flavor if the fat gets oxidized.

＊Sogigiri－A method of cutting makes a slice thinner with a greater surface, by holding the knife diagonally and cutting in line with the cutting board. Usually used for white fish with firm flesh because it is easier to be eaten when served thin.

Hirazukuri－A method of cutting gives thickness to each slice so that the texture of sashimi can be enjoyable. This is used for akami like tuna.

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We hope this information will be helpful.

Revision date: April 1, 2020

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Why do they say that the quality and price of tuna is determined by the processing after the fish is caught?

Why is only tuna brought into certain ports high-priced, even though all of the tuna is caught in the seas near Japan? This is because the level of stress caused to the fish when it is caught has a huge impact on the quality, including taste, color and texture. In other words, the same fish may be delicious or taste unpleasant depending on how the fisher handles the fish directly after catching it. Naturally, everyone ends up wanting the fish from the ports with fisherman who are skilled in this practice*. Furthermore, it is individuals who process the fish. The quality changes drastically depending on who caught it.

*This is a method of cutting off the medulla oblongata and aorta of a fish, essentially keeping the body alive while killing the fish. There is also a method of inserting a thin wire, like a piano wire, into the backbone. This technique paralyzes the nerves while at the same time suppressing the putrefied substance that comes from the spinal cord. Using the ikejime method extends the time until rigor mortis starts, and makes it easier to maintain freshness, while at the same time preventing raw fish odor and damage to the body by inserting a butcher knife into the base of the tail to drain the blood and keep oxidized blood from running throughout the body.

What is the ideal temperature for sushi toppings?

Tokyo Health Centers stipulate that refrigerated cases where sushi toppings are stored should be kept at 5℃ or lower. This is to maintain the temperature of the toppings at below 10°C at which point bacterial growth is slowed.

However, sushi chefs will remove the topping from the refrigerator and leave it standing out for a while (in the case of tuna, the fat will melt at around 23℃). They do this because if the topping is cold, it becomes difficult to taste the essential nature of the fish. The temperature of the shari is best at human skin temperature (around 36℃) to maximize the taste and sweetness of the rice. However, the ideal temperature differs very slightly depending on the topping.

Some of Japan’s top sushi chefs pay meticulous attention to temperature—down to the exact degree. Hideshi Namba, the head chef of Sushi Nanba in Hibiya, is renowned for controlling both the topping (neta) and the sushi rice (shari) temperatures to within 1°C. He uses a laser thermometer to ensure that each piece is served at the most flavorful combination of warmth and texture.

For example, he serves fatty tuna (toro) with the topping at around 24°C and the rice at around 40°C, enhancing the melting of fat and the release of umami. Shellfish like scallop or clam are served cooler to preserve delicacy, while kuruma prawn is carefully matched to body temperature—approximately 38°C—for maximum sweetness and a harmonious mouthfeel.

You can check the general guidelines below for the ideal temperature range of common sushi toppings. This data was obtained from professional cookbooks.

Sushi Topping	Ideal Temperature	Description
White Fish (Tai, Hirame)	Approx. 18–22°C	Delicate flavor and aroma are best preserved at slightly cool room temperature.
Squid (Sumii-ka, Aori-ika)	Approx. 20°C	Sweetness and texture stand out at this temperature. Too cold makes it too firm.
Shellfish (Scallop, Akagai)	Approx. 20–23°C	Room temperature enhances sweetness and ocean aroma.
Salmon (including Toro Salmon)	Approx. 23–25°C	Fat melts smoothly, creating a rich mouthfeel when served slightly warm.
Tuna (Chutoro, Otoro)	Approx. 23–26°C	High fat content melts around this range, maximizing umami and texture.
Silver-skinned Fish (Aji, Saba)	Approx. 20–23°C	Vinegared fish benefit from being served close to room temperature for balance.
Sea Urchin (Uni)	Approx. 18–20°C	Too warm dulls aroma; too cold mutes sweetness. Slightly cool is ideal.
Salmon Roe (Ikura)	Approx. 15–18°C	Cooler temperature preserves the firm texture and prevents melting.
Kuruma Prawn	Approx. 36°C (body temperature)	Served warm, just like the sushi rice, for harmony and natural sweetness.
Conger Eel (Anago)	Approx. 40–42°C	Served warm to bring out the aroma and sweetness of the sauce and fat.

Overseas, there are laws that state that sushi must be served at 10℃ or lower. This ignores that sushi is best enjoyed at skin temperature. Serving it straight out of the refrigerator makes it no better than purchasing takeout sushi from the supermarket.

When does Kinmedai taste the best?

No one is more sensitive to the changing of the seasons than sushi lovers. This must be because the taste of sushi toppings is directly tied to the seasons. There are terms to describe this such as Hashiri (early season), Sakari (in-season), and Nagori (late season). In Japanese culinary tradition, these three terms capture the evolving flavors of seasonal ingredients. Recognizing where a sushi topping stands within this cycle allows diners to appreciate not just its taste, but its fleeting character.

There is nothing that says a sushi topping is less delicious because it has a lower fat content. For example, everyone wants to get in there and be the first to eat early season (走り) toppings. It’s obvious that these would all be toppings with leaner profiles. But early-season toppings have a liveliness that you can’t find in other foods, and some believe that eating these types of food will give you new vitality.

Once a fish is in peak-season (さかり又は旬), we eat it as sushi. This is because the fish has grown as it approaches breeding season, gradually gaining more fat, and at this stage in its development it has a richer flavor.

And the ‘late season (名残)’ perhaps means that since the season is about to end, we need to get our fill now. While we may feel a bit sad that the season is ending, we can look forward to it coming around again the next year.

On the other hand, there are sushi toppings that don’t seem to fit into the seasons, although the seasonal dishes are one of the important reasons that Japanese food was registered under UNESCO World Heritage.

Those are deep sea fish such as Largehead hairtail, Japanese bluefish, Pollack and Splendid alfonsino.

Deep sea fish live at least 200 m below the surface of the ocean. For example, Splendid alfonsino lives at a depth of between 100 to 800 m deep, so it would generally be thought of as in-season in the winter when it has the highest fat content. However, except just before and after spawning season, the flavor of the Splendid alfonsino doesn’t change much throughout the year. Therefore, even high-end sushi restaurants always keep it in the topping case and it’s a popular choice.

Therefore, Splendid alfonsino is never actually “in-season”.

Since very little light reaches the deep sea, the water temperature remains more or less constant. In other words, there aren’t really seasonal (temperature) changes. The concept of season may not exist there.

Even so, you can think of it as especially delicious in the winter between December and February, when it has a higher fat content. Otherwise you might start to think of it as a fish that is “in-season” all year round, like salmon, and that just doesn’t feel quite as splendid.

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