Kai（Shellfish） | Sushiblog

What is Tokobushi abalone sushi?

a photo of Tokobushi abalone — Many people may think of Tokobushi as small abalone, but it is in fact different from abalone.

What is Tokobushi abalone?

Tokobushi abalone is widely distributed from southern Hokkaido to Kyushu and Taiwan. It inhabits the reef zones along the coasts facing the open ocean in warm seas. It is oval in shape and has a shell length of 7 cm. In the past, people thought that the Tokobushi abalone was the child of the abalone.

Abalone has four to five water absorption holes, which are tubular, while Tokobushi abalone has six to nine water absorption holes, and the holes are more numerous and larger than those of abalone. Based on the amount of Tokobushi abalone caught, Kochi, Tokushima, and Mie prefectures are the production areas.

The average wholesale price of Tokobushi abalone at the Toyosu market is around US$30 per kilogram. Since domestic catches alone cannot keep up with demand, a large number of imports, mainly from Taiwan, are also distributed. The scientific name is Sulculus diversicolor supertexta (Lischke, 1870). A substitute is Luzon Tokobushi (Haliotis(Sulculus) glabra Gmelin, 1791), which is mainly processed into canned products.

Incidentally, Kinki University, which has succeeded in the complete cultivation of bluefin tuna, has been conducting research on Tokobushi abalone cultivation since 2014. The university succeeded in artificial hatching in the same year, and is currently continuing its research with the aim of achieving complete aquaculture.

What does Tokobushi abalone sushi taste like?

a photo of Tokobushi sushi — Tokobushi abalone is also used in preparations known as “nigai (煮貝)” or ni-awabi (煮鮑)”, whole abalones cooked with fish broth and soy.

Tokobushi abalone has a strong scent and taste similar to that of abalone, but its meat is smaller and thinner than that of other types of abalone (Japanese abalone (黒鮑), disk abalone (雌貝鮑), ezo abalone (蝦夷鮑), giant abalone (真高鮑)). Tokobushi abalone is generally not eaten raw, but rather boiled or steamed. Many sushi chefs say that when heated, the taste is richer than that of abalone.

Tokobushi abalone is sold in the market throughout the year, but in many fishing areas, winter is a closed season. While abalone, which is suitable for steamed shellfish, is in season in summer, Tokobushi abalone, on the contrary, is in season in winter and is used as an alternative to abalone for steamed shellfish in winter.

However, because the catch of Tokobushi abalone is decreasing and its price is high like that of abalone, few sushi restaurants use it. Compared to abalone, Tokobushi abalone is softer and does not get tough when heated, so it is boiled in soy sauce and sake to make Tsumami.

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Revision date: April 14, 2023

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What is Turban shell (Sazae) sushi?

a photo of turban shell — Sazae is found in waters near Japan and Korea, with ornately beautiful shells distinguished by jagged little horns dotting their perimeter.

What is Turban shell (Sazae)?

Turban shell (Sazae) is found on reefs from the intertidal zone to a depth of about 10 m throughout Japan, with the exception of northern Hokkaido and Okinawa.

The maximum shell height reaches 10 cm. The shell is conical and thick, with spines on the periphery. The number and length of the spines vary greatly depending on the habitat and the individual. Male gonads are yellowish-white and female ones are green.

The summer sazae become skinny due to spawning, so winter and spring are the best seasons for them. The scientific name is Turbo sazae Fukuda, 2017.

In the past, Sazae that grew on rough shores developed magnificent spines, and it was said that they may have developed because the spines caught on rocks like a kind of spike and prevented them from being washed away. Individuals that do not develop spines at all are called Marugoshi or Tsunonashi. Young, small, and thornless specimens are called hime-sazae in the market. However, those without spines and generally rounded may be imported.

Sazae is rarely seen alive, but those that make no sound when lightly shaken or quickly close their lids when touched are fresh. In the summer, even if they are alive, the water inside may be murky, so they judge the freshness by smelling. Sazae weighing 300 g or more are tasty.

The staple food of Sazae is seaweed, and the taste and color of their shells change depending on the quality of the seaweed they eat. It is said that eating arame seaweed turns the shell whitish while eating tengusa seaweed turns it blackish brown.

What does Turban shell (Sazae) nigiri sushi taste like?

a photo of Sazae Gunkan maki — Since turban shells do not fit well with shari, they should be rolled into gunkan-maki.

Sazae flesh is firm and is not easy to make nigiri. It also looks unattractive. In addition, the strong aroma of the sea and the thick umami make the nigiri sushi lose its sense of unity. However, some love the wild flavor and umami of Sazae.

When making nigiri sushi, it is best to put a fine Kakushi boucho on the inside to make it easier to eat. Fresh entrails can be boiled quickly and topped with a pleasantly bitter taste and rich flavor.

a photo of sazae tsuboyaki — For grilling Tsuboyaki, the entire shell can be placed directly onto hot charcoal, eventually coaxing juices to boil from the shell’s interior, at which point soy sauce and sake are poured directly into the shell.

Japanese people may prefer Sazae-no-tsuboyaki, which has the aroma of burnt soy sauce and the scent of the sea from the turban shells.

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Revision date: April 1, 2023

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What is Baigai sushi?

a photo of Baigai — Baigai is often used for Tsumami and sushi topping in sushi restaurants.

What is Baigai?

There are several species of shells called Baigai. Among them, the whitish Baigai such as Kagabai (Buccinum bayani Jousseaume,1883), Echubai (Buccinum striatissimum Sowerby,1899), Ooechubai (Buccinum tenuissimum Kuroda in Teramachi,1933), and other whitish Baigai, collectively called Shirobai.

Kagabai lives in depths of 200 to 500 m from the Noto Peninsula to Hokkaido, with shells reaching 15 cm in height, while Echubai (Finely-striated buccinum) is caught in the Sea of Japan west of the Noto Peninsula, at depths of 200 to 500 m, with shells reaching 15 cm in height. Ooechubai (Finely-striated buccinum) is endemic to the Sea of Japan north of Shimane, living at depths of 400 to 1,000 meters, and reaching a shell height of 25 cm. Ooechubai is considered the most delicious of the Shirobai, and the larger the size, the more expensive.

What does Baigai nigiri sushi taste like?

a photo of Baigai nigiri sushi — It is not familiar as sushi topping in the Kanto region, but is often found at sushi restaurants in Kanazawa.

As the name “Shirobai” (Shiro means white) shows, the meat is pure white and shiny like white porcelain. After the characteristic crunchy texture of the shellfish, sweetness and bitterness spread softly in the mouth.

If you are worried about the hardness of the meat in Nigiri sushi, it might be better to taste it as sakamushi (sake steamed). It becomes moderately tender and easy to make nigiri. To enhance the light flavor, you can also boil it quickly in kombu dashi (kelp stock) during preparation.

It is not familiar as sushi topping in the Kanto region, but is often found at sushi restaurants in Kanazawa and other areas. As a side note, from the sound “bai (bai means double)” in Baigai, it is considered a fortunate food, as it doubles the amount of good fortune.

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Revision date: March 22, 2023

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What is Aka-nishi-gai (Ko-naganishi) sushi?

a photo of Top shell (Aka-nishi) — This is Aka-nishi (Top shell) nigiri.

What is Aka (aka means red)-nishi-gai (gai means shell)?

There are three typical types of shellfish called Aka-nishi-gai: Naganishi, Ko-naganishi, and Aka-nishi. Yonaki-gai (夜泣貝), enthusiastically favored in Hiroshima and Yamaguchi prefectures, is the Naganishi (Fusinus perplexus (A.Adams,1864)) caught in the Seto Inland Sea. It is no longer caught in large quantities, and Ko-naganishi (Fusinus ferrugineus Kuroda & Habe,1961) from the Sea of Japan is used as a substitute. This shellfish is a smaller version of the Naganishi, and has a unique astringent taste in its entrails.

Aka-nishi (Top shell) is a carnivorous shell commonly found in tidal flats of inner bays in Japan, and in the Kanto region, it is a natural enemy of oysters and clams rather than a target for fishing. Its flesh is softer than that of the turban shell (Sazae), and some say it is tastier. In recent years, large quantities of frozen top shell has been imported cheaply from Turkey and Bulgaria, which face the Black Sea, so when you hear “Aka-nishi-gai” at conveyor belt sushi restaurants, you are probably talking about this. Aka-nishi-gai is considered an invasive alien species in the local market.

What does Aka-nishi-gai (Ko-naganishi) sushi taste like?

Ko-naganishi is a member of the family Fasciolariidae that inhabits the Sea of Japan from Mutsu Bay to Kyushu, where it grows to a shell length of about 8 cm. In Ishikawa Prefecture, it is caught in Nanao Bay (七尾湾) and is often used in sushi toppings. Its season is from September to November. The color of this shellfish is bright red, which is derived from its name. The texture is chewy and the aroma of the sea fills the mouth, and at Nigiri sushi, it is served in Gunkan maki, which some tourists come for.　In Nanao, Ko-naganishi is called Aka-nishi-gai (赤西貝) instead of the standard Japanese name Aka-nishi (Rapana venosa (Valenciennes,1846)), which is a little confusing at times.

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Revision date: March 20, 2023

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Abalone around the world

a photo of abalone — Apart from Australia and New Zealand, Mexico, South Africa, South Korea, and the United States have seen a marked decrease in the catch of abalone, as in Japan.

California Abalone

About seven species of large abalone live off the coasts of California and Mexico, and are consumed locally as abalone steaks. Some of these are distributed to the seafood-loving Japanese market.

Red abalone (Haliotis (Nordotis) rufescens Swainson, 1822) has a reddish surface and a greenish-blue interior. It is as large as Japan’s largest species, the Giant abalone (Haliotis madaka (Habe 1977)), but has a much thicker and heavier shell. For a while, attempts were made to cultivate this species in Japan, but without success.

Pink abalone (Haliotis (Nordotis) corrugata) has a shell about the size of Disk abalone (Haliotis gigantea Gmelin 1791), but much thicker, more circular in shape, and characterized by strong corrugations. The surface of the shell is green and the radial ribs are separated by growth lines. The flesh is tough and is more valuable as a beautiful ornament than as a foodstuff. It is found in shallow waters along with the Green abalone (Haliotis (Nordotis) fulgens).

Green abalone range from point conception, California, to Bahia de Magdalena, Mexico. The oval-shaped shell protects the abalone from predators. The shell is usually brown and marked with many low, flat-topped ribs which run parallel to the 5 to 7 open respiratory pores that are elevated above the shell’s surface. The inside of the shell is an iridescent blue and green.

Black abalone (Haliotis cracherodii Leach, 1814) grows to about 12 cm in length and has a black shell. The blackish-blue shell has five to nine holes (respiratory pores) used to breathe, remove waste, and reproduce. They once numbered in the millions along the California coast, but are now endangered. Threaded abalone (Haliotis assimilis Dall, 1878.) from California is close to Japanese abalone in flavor and firmness.

Australian Abalone

Roe’s abalone (Haliotis roei Gray 1826) was the most common abalone on the market from early on. The shell is more rounded than that of Tokobushi (Haliotis supertexta Lischke 1870), and the spiral expansion is not as rapid as in Tokobushi. The shell is also characterized by the presence of numerous deep spiral grooves on the surface. Greenlip abalone (Schismotis pulcherrima, Gmelin, 1791) is rarely used as boiled shellfish or steamed in sake.

Atlantic Ocean Abalone

Although large abalone is not distributed in the Atlantic Ocean as they are in Japan and California, the Mediterranean Sea is home to the Ear shell (Haliotis tuberculata Linnaeus 1758), which is a slightly larger version of Tokobushi. It is rarely imported from France and other countries.

Asian Abalone

Large species of abalone are distributed in waters where large brown algae grow. Therefore, only small species live in the tropical areas of Asia, where coral reefs are well developed. Even so, small species are used as substitutes for Tokobushi in canned foods and bento dishes, such as Glistening abalone (Haliotis glabra Gmelin 1791) from the Philippines, Sheep’s ear abalone (Haliotis ovina Gmelin 1791) from Taiwan, and Ass’s ear abalone (Haliotis asinina Linnaeus 1758) from Hong Kong.

Chilean Abalone

Chilean abalone (Concholepas concholepas (Bruguie, 1789) ) is listed as Loco-gai in the Japanese product label and as Awabi-modoki in the illustrated book. The name of this species suggests an intention to associate it with abalone, but it belongs to the family Muricidae, which is not related to abalone.

It is native to the coasts of Chile and Peru. The shell is about 8 cm long and plate-shaped. It has a lid of keratin that is not found on real abalones. In rare cases, you can see that it is dyed in a light purple color, etc., because it is a unique characteristic of the family Muricidae, which becomes purple when the secreted mucus comes into contact with air.

When it was first imported to Japan, it was labeled as “awabi” in supermarkets and restaurants, and there was some fuss about the mislabeling, but even when sliced, there is no epipodial tentacle characteristic of awabi, and the difference can be seen.

The trading price of Chilean abalone is about one-fifth that of abalone. It is a popular ingredient in conveyor-belt sushi, Chinese cuisine, etc. under the name Chile-awabi, but actually that name cannot be used.

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Revision date: February 22, 2023

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What is Ishigakigai sushi?

Ishigakigai is a shellfish found from Kashimanada northward, Hokkaido, from the Kuril Islands to the Aleutian Islands and even on the west coast of North America. It lives off of plankton in the shallow sandy mud bottoms of the sea at depths of about 50 meters.

Aquaculture in Hirota Bay, Iwate Prefecture, has been successful and it started to appear at the Tsukiji Fish Market starting in about 2008, distributed as Ishigakigai. According to brokers, someone in the business at Tsukiji Fish Market misheard “Ishikage” as “Ishigaki” and the name stuck in the market. While Torigai meat looks black, Ishigakigai looks whiter, so it is also called “Shirotorigai”. The official name is “Ezoishikagegai”.

It starts to become common at the market when the Japanese rainy season ends, at the beginning of summer every year, which is around the end of the Torigai season. It then disappears from the market at the end of summer. A number of sushi restaurants start using it as a substitute for Torigai all at the same time, so Ishigakigai nigiri sushi suddenly started appearing on menus. Frankly, it is somewhat conservative as a nigiri topping but is known for the crunchy texture when biting into it. It also has strong sweetness and umami, which goes exquisitely with Shari. The sushi chef slaps the meat in his hand directly before serving to stiffen it–a way to increase the crunchy texture characteristic of shellfish. Naturally this texture is evidence of its freshness.

As the season of availability is short and the production sites are limited, Ishigakigai often fetches a high price. Those up for sale at the Toyosu Market go for $2 to $4 each. Wild-caught Ishigakigai is rarely found on the market, but when they are, the price is double that of the farmed version.

A relative of the Torigai, the Ishigakigai is rich in amino acids such as taurine, glycine and arginine. It is also resilient and can live for days, even outside its shell.

What is Shiromiru?

The official name of Mirugai is “Mirukui”. The part of the Mirugai that is used as a sushi topping is the siphon that bulges out from the shell. The siphon is separated from the shell and then this is cut through longways, from top to bottom. One Mirugai can only produce four pieces of sushi. It is also nearly extinct from overfishing. While it can still be caught in the Seto Inland Sea and Mikawa Bay, there are fishing limits, which means it is an ultra-high-priced sushi topping.

However, most conveyor belt sushi restaurants offer Mirugai at reasonable prices. The topping on these is quite white. In conclusion, this shellfish is actually Shiromiru (also known as Namigai or Japanese geoduck) and is mainly found in Aichi and Chiba. As the name suggests, the siphon is larger than Mirugai and whiter (“shiro” means “white” in Japanese). There is a certain flavor that is peculiar to shellfish that live in sandy terrain, which some people like and some people hate. However, at less than half the price of Mirugai, it makes a decent substitute.

Unfortunately, the number of Shiromiru is also declining. Now, in order to fulfill demand, Pacific geoduck is being imported from places like Canada and the U.S. and is also called Shiromiru at the Toyosu Market.

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Revision date: July 8, 2021

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List of Shellfish (Kai)

Shellfish has been a traditional sushi topping started off with the origin of Edomae sushi. Its distinctive texture is fascinating, but the thing is, all kinds are expensive. As a sushi topping, it is placed between rich and light in flavor, and functions as a palate refresher.

The texture, flavor and fragrance differ greatly depending on the type and most people either love or hate Shellfish toppings.

A characteristic of the taste of shellfish is that it is both refreshing and rich. This is presumably due to succinic acid. It is known that if succinic acid is removed from the shellfish extract component, the umami of shellfish also disappears. However, the umami of shellfish is not due to succinic acid alone, but to the synergistic effects of amino acids such as glutamic acid, glycine, alanine, arginine, and betaine, which are present in the extract, and adenylic acid, a nucleic acid-related substance.

Kai is another topping type that has been eaten as Nigiri sushi since it was invented. Hamaguri is essentially a type of shellfish, but when in the Nigiri sushi world, it is generally lightly seared and then marinated in broth, so it is classified as Nimono.

*Japanese terms will be italicized on sushi ingredients page.

<Kai－Shell>

Agemakigai－ Chinese razor clam

Akaawabi－ Blacklip abalone

Akagai－Ark shell, Bloody clam (Anadara broughtonii (Schrenck, 1867))

Akaneawabi－ Red abalone

Akanishi (Akanishigai)－ Top shell, Rock shell, Rapa whelk (Rapana venosa (Valenciennes,1846))

Akoyagai－Japanese pearl-oyster (Pinctada martensi (Dunker, 1880))

Amerikaubagai－Atlantic surf clam (Spisula solidissima (Dillwyn, 1817))

Aniwabai

Aoyagi (Bakagai)－Rediated trough-shell (Surf-clam)

Asari － Japanese clam, Baby clam, Manila clam, Japanese littleneck clam (Ruditapes philippinarum (Adams and Reeve,1850))

Atsuezobora－ Whelk

Awabi (Kuroawabi)－Japanese abalone

Awabimodoki (Rokogai)－ Chilean abalone

Azumanishiki－ Scallop

Baigai－Japanese ivory-shell

Chousenbora－whelk (Neptunea arthritica cumingii (Bernardi, 1857))

Echubai (Shirobai)－Finely-striated buccinm (Buccinum striatissimum Sowerby,1899)

Ezoawabi－Ezo-abalone (Haliotis discus subsp. hannai Ino, 1953)

Ezobora (Matsubu)－Wheck (Ezo neptune)

Himeshakogai－Boring clam

Hioogi (Hiougigai)－Noble scallop (Mimachlamys nobilis (Reeve,1852))

Hokkigai－Sakhalin surf clam, Hen-clam (Pseudocardium sachalinense (Schrenck,1862))

Hotate－Common scallop, Giant ezo-scallop, Frill, Fan-shell (Mizuhopecten yessoensis (Jay, 1857))

Ishigakigai－Bering Sea cockle

Itayagai－Japanese scailop, Frill

Iwagaki－Rock-oyster

Kaki (Magaki)－Oyster

Kagabai (Shirobai)－(Buccinum bayani Jousseaume,1883)

Kobashira－The adductor of bakagai shellfish (Rediated trough-shell)

Konakanishi－(Fusinus ferrugineus Kuroda & Habe,1961)

Kumasarubougai

Kuriiroezobora－Whelk

Kuroawabi－Japanese abalone (Haliotis discus subsp. discus)

Madakaawabi－Giant abalone (Haliotis madaka (Habe, 1977))

Mategai－Razor clam (Solen strictus Gould, 1861)

Megaiawabi－Disk abalone

Mirugai (Honmirugai)－Otter-shell, Keen’s gaper (Tresus keenae (Kuroda & Habe, 1950))

Moegiigai－New Zealand mussel (Perna canaliculus (Gmelin, 1791))

Nabaubagai－Surf clam

Namigai (shiromiru)－Japanese geoduck

Nihama (Hamaguri)－Common orient clam, Japanese hard clam, White clam (Meretrix lusoria (Röding, 1798))

Nakanishi－(Fusinus perplexus (A.Adams,1864))

Ooechubai (Shirobai)－(Buccinum tenuissimum Kuroda in Teramachi,1933)

Oomategai－Giant jacknife clam, Giant razor-shell

Oomizogai－Alaska razor, Dall’s razor clam

Onisazae

Osagawabai

Rokogai (Awabimodoki)－Chilean abalone, Baranacle rock-shell (Concholepas concholepas (Bruguie, 1789))

Saragai－Northern great tellina clam (Megangulus venulosus (Schrenck, 1861))

Sarubougai－Half-crenated ark, Bloody clam (Anadara kagoshimensis (Tokunaga, 1906))

Satougai－Bloody clam

Sazae－Turban shell, Spiny top-shell (Turbo (Batillus) sazae H.Fukuda, 2017)

Shirogai (Manjugai, Saragai)－Northern great tellin

Sudaregai－Well-carved venus (Paphia euglypta (Philippi, 1847))

Tairagi (Tairagai)－Pen-shell (Fan-shell)

Tokobushi－Tokobushi abalone (Haliotis diversicolor Reeve, 1846)

Torigai－Egg-cockle, Heart-shell (Fulvia (Fulvia) mutica (Reeve, 1844))

Tubugai (Matsubu)－Ezo-neptune, Whelk, Winckle (Neptunea polycostata Scarlato,1952)

Usuhirawabi－Greenlip abalone

Yakougai－Great green turban

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Revision date: September 4, 2024

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