Bakagai, Surf clam バカガイ、馬鹿貝
(Mactra sinensis)
Alternative names in English: Japanese orange clam, hen clam, round clam
The Japanese bakagai is found all over Japan, living in sandy substrates in shallow marine habitats. Main production areas are the Bay of Tokyo, the Bay of Ise, the Inland Sea, the Ariake Sea and Hokkaido. It is the same size as the hamaguri clam (ark mussel) - 4 cm wide and about 9 cm long.
[Bakagai, Aoyagi]
The Japanese name "baka-gai" literally means "idiot clam" and has its origins in the fact that when this shell lets its orange-colored foot loosely hang out, it looks like an idiot with the tongue out of the mouth. This is not politically correct, which is why it is now called “aoyagi” (青柳, "green willow") after a place outside Tokyo where it is commonly found (and the orange tongue has the form of a willow leaf).
Bakagai is a classical topping of Edomae-zushi. When the round shell is opened, the intensely orange-colored leg (peduncle) is visible. This is lightly beaten with a knife and then parboiled. When after butterflying it is put on the sushi, care is taken to keep the foot intact and have it stick up in the air like the tail of a rooster.
The most prized part of the clam are however the adductor muscles (columella) which are called kobashira ("little pillars"). Large ones are called "oboshi" ("big stars") and smaller ones "koboshi" ("small stars"). They are usually served on gunkanmaki and are an expensive and rare delicacy.
Bakagai has been a favorite since the Edo period, and continues to appeal to sushi fans today thanks to its crunchy texture, sweet flavor and concentrated umami. The best season (shun) is winter and early spring. Besides being eaten on sushi, it is also prepared as sunomono or used as an ingredient in kakiage.
In the Edo period there was another use for bakagai as shown on the ukiyo-e below: they were used in Fukagawa-meshi instead of asari clams.
[Preparing bakagai at Fukagawa]
Illustrations from Wikimedia Commons
Japanese Food Dictionary