The Rivière Sainte-Marguerite begins its 100 kilometer journey from Lac Sainte-Marguerite, at an altitude of 678 meters, in the Monts Valin. Clear and narrow, it then flows through a steep, wild valley between the municipalities of Sacré-Coeur and Saguenay, first in a north-westerly direction, then south-westerly for 15 kilometers before turning abruptly south-easterly. It then runs along the Saguenay Fjord for 60 kilometers before emptying into Sainte-Marguerite Bay.
The history of sport salmon fishing on the Saint-Marguerite River began in 1860, when a private club was formed, whose assets are held today by the Corporation de pêche Sainte-Marguerite. In 1980, the river was incorporated as a zec, and the Association de la rivière Sainte-Marguerite became the salmon-fishing manager, ending the exclusive management rights of the Corporation de la rivière Sainte-Marguerite. In 1995, the Centre interuniversitaire de recherche sur le saumon atlantique moves to the river's banks.
The Sainte-Marguerite River is divided into three branches, with some 100 pools in 10 sectors, including 7 sectors with restricted access. Some pools are privately owned by the Corporation de pêche Sainte-Marguerite or by local residents. Fishing is mostly done by wading or by boat, depending on the pit. Route 172 runs along the river for some 55 kilometers, in sectors 1 to 4. There are also salmon-watching sites.
The river also offers exceptional habitat for sea trout.