The St. Lawrence River is one of the largest watersheds colonized by the American eel Anguilla rostrata. Upstream from Québec City, eels are present in the St. Lawrence main stem and tributaries, including the Lake Ontario watershed. Recently, much concern has been raised concerning declining recruitment of young eels in Lake Ontario and declining catch of silver eels in the St. Lawrence estuary fishery, but not previous study attempted to estimate current silver eel production. This study marks the first silver eel population estimation for a large watershed;