Hotate-gai scallop literally means ‘the shellfish with the standing sail’, referring to its style of crossing the seabed by opening and closing its shell. This large bivalve is taken mainly in Hokkaido and Tohoku where it is sometimes called akita-gai or ogi-gai, the fan-shaped shellfish. The heel of the hotate-gai is called kaibashira.
Hotate-gai are served as sashimi, grilled, sautéed in butter and go well with soups both Japanese and fusion. On the West coast of Aomori you can also find scallop ramen, which is generally rather roughly presented, but tastes fantastic.
The hamaguri Venus clam was the first shellfish ever eaten in Japan. This spring speciality is caught in clean sea-water, on the northern coast west of Hokuriku, and in Tokyo Bay, Ise Bay, the Seto Island Sea, and the Ariake sea. They are best between December and March.
Chestnut-shaped - hamaguri means ‘beach chestnut’ - it features large in Hina matsuri Girls' Festival cuisine to suggest chastity (never opened) and also fidelity (its two halves perfectly matched). Hamaguri need to be washed well to remove the sand, then are often grilled in the shell with yuzu citrus, steamed in sake as sakamushi. or in suimono soups.
These can be particularly delicate when served in a high-class ryotei restaurant. On the other hand they can be quite rustic and down to earth, as in the photograph below, taken at a seaside 'restaurant' at Chirihama Nagisa Beach in Hakui, Ishikawa Prefecture. Actually, it was more shack than restaurant, but the soup was excellent.
The i-gai or muru-gai mussel, taken mainly in Hokkaido and the Inland Sea, from winter to early spring, has a venerable history. It gets a mention in the Heian-period diary Tosa Nikki, where it is described as ‘sushi’, although it is not eaten that way today. It is mainly included in misoshiru, sunomono and as shoyu-yaki grilled with shoyu.
The taira-gai fan shell or sea pen is more correctly called the tairagi. It is famed for its resemblance to a piece of Heian-era headgear, the eboshi a sort of signal, spiked dunce’s hat. In season from autumn to early spring, it is taken in Tokyo Bay, Ise Bay, and the Seto Inland Sea. It is eaten as sashimi, sunomono, shioyaki, teriyaki, furai and sautéed in butter.
The baka-gai surf clam or hen clam is known as aoyagi, as it was often harvested in Tokyo’s Aoyagi-mura village. The original name – used in Kansai and elsewhere – means ‘idiot shellfish’. The flesh is said to resemble a face, with a red mark signifying a lolling tongue. In Chiba, they don't even bother with the -kai suffix, meaning 'shellfish'. They just call it 'The Idiot'. in Tokyo it occurs often in Edomaezushi, elsewhere as sashimi and sushi.