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.

Related contents: Ezoishikagegai


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Revision date: October 5, 2021

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

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. They include a large volume of umami components, such as Succinic acid. 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

Akaneawabi- Red abalone

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

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

Aniwabai

Atsuezobora- Whelk

Awabi (Kuroawabi)-Japanese abalone

Awabimodoki (Rokogai)- Chilean abalone

Azumanishiki- Scallop

Baigai-Japanese ivory-shell

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

Etyuubai (Shirobai)-Finely-striated buccinm

Ezoawabi-Ezo-abalone

Ezobora (Matsubu)-Wheck (Ezo neptune)

Himeshakogai-Boring clam

Hioogi-Noble scallop

Hokkigai-Hen-clam

Hotate-Common scallop (Giant ezo-scallop, Frill, Fan-shell)

Ishigakigai-Bering Sea cockle

Itayagai-Japanese scailop, Frill

Iwagaki-Rock-oyster

Kaki (Magaki)-Oyster

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

Kumasarubougai

Kuriiroezobora-Whelk

Madakaawabi-Giant abalone

Megaiawabi-Disk abalone

Mirugai (Honmirugai)-Otter-shell (Keen’s gaper)

Nabaubagai-Surf clam

Namigai (shiromiru)-Japanese geoduck

Nihama (Hamaguri)-Common orient clam (Japanese hard clam, White clam)

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))

Sarubougai-Half-crenated ark, Bloody clam

Satougai-Bloody clam

Sazae-Spiny top-shell

Shirogai (Manjugai, Saragai)-Northern great tellin

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

Tokobushi-Tokobushi abalone

Torigai-Egg-cockle (Heart-shell)

Tubugai (Matsubu)-Ezo-neptune (Whelk, Winckle)

Usuhirawabi-Greenlip abalone

Yakougai-Great green turban


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Revision date: January 10, 2023