The ayu (アユ, 鮎, 香魚) or sweetfish, Plecoglossus altivelis, is an amphidromous fish, the only species in the genus Plecoglossus and in family Plecoglossidae. It is a relative of the smelts and is placed in the order Osmeriformes. Native to the Palearctic ecozone, it occurs in rivers, lakes, and coastal waters of western Hokkaidō in Japan southward to the Korean Peninsula, China, and Taiwan. The name "sweetfish" is due to the sweetness of its flesh. In refer… (More on Ayu)