Category: Nimono (cooked fish).
Season: from mid-winter to spring.
Shirauo first arrive at fish markets in late January and remain in season until May, and specimens that are about two inches in length are used for sushi. Five or six of these tiny fish are arranged onto shari to form a piece of nigiri.
Typically shirauo are salted then steamed for a few minutes (which turns them from translucent to white) then quickly chilled before being served. Another preparation method involves a quick boil followed by an overnight simmer.
In either case, this traditional Edomae fish can be served with a pinch of oboro and a brush of nikiri.