Salmon are running upstream!
You can ? observe it up close at "Totorodo"

Salmon are born in rivers, grow large in the sea, and eventually return up their hometown rivers.
Fry recovered from their eggs in rivers descend to the sea in spring with melted snow, and travel back and forth between the Bering Sea in summer and the Gulf of Alaska in winter.
Almost four years later, the mature salmon migrate south from the Bering Sea along the Kuril Islands, returning to their hometown rivers to spawn from September to November.

Fishway observation room and torodo
Address: 127 Aikawa Makubetsu Nakagawa-gun, Hokkaido
Open: End of April to November from 9 a.m. to 5 p.m. (depending on the season)