The shishamo is found in Japan and nowhere else. More precisely, it is found along one stretch of the Pacific coast of Hokkaido, between Uchiura Bay and Akkeshi Bay, and it runs up only the rivers that empty into that stretch. The Mu River, at Mukawa, is the one people name.

The fishery lasts about a month, from the end of October. That is the whole year's opportunity, and in that month the fish is also eaten raw and as sushi, which almost nobody outside the region has done.

Most of what is sold under this name is not this fish. The catch declined, and rainbow smelt and imported capelin took the name over in the shops. The two can be told apart even dried, by the arrangement of the scales and the length of the fins, but very few people buying a packet are doing that.

It is dried overnight, pickled in rice bran, dried hard, made into fritters and tempura. For the sweet simmered version the fish is first grilled plain, then cooked down in soy sauce and sugar until the bones give way. Head, spine, roe and all, it becomes something you eat whole. The name comes from Ainu and is said to mean willow leaf, which is exactly what a thin flat silver fish looks like when it is lying on a board.