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National Marine Conservation Areas of Canada

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Canada’s National Marine Conservation Areas System Plan

St. Lawrence Estuary

The Water

East of Quebec City, the St. Lawrence River becomes a 370 km long funnel-shaped tidal estuary, 48 km wide at its mouth. Depths average more than 200 m, with the Laurentian Channel reaching depths in excess of 300 m as it extends down the middle of the estuary. Submarine cliffs dominate the north shore, while wide shallow subtidal platforms are common along the south shore. The Saguenay Fjord is a 104-km long inland extension of the St. Lawrence, 200-300 m deep and with strong tidal currents at its mouth. A fresh water layer overlies a deeper layer that is distinctly marine. Opposite the mouth of the Saguenay River, the estuary floor rises abruptly from 350 m to 25 m, bringing nutrient-rich waters to the surface which are mixed with The Waters of the Saguenay and St. Lawrence rivers, leading to high biological productivity. Tides range from 2.5 m in the east to 5 m in the west and are discernable as far as Montreal. The open water season lasts 7-8 months, open pack ice covering the estuary during the winter, though currents keep the mouth of the Saguenay River open year-round.

The Coast

Canadian Shield rocks form spectacular scenery along the north shore, with bedrock cliffs indented by numerous deep valleys and gorges, as well as the steep-sided Saguenay Fjord where the cliffs reach 450 m in height. A straight low rocky shore, strewn with offshore islands and interspersed with extensive mud flats and salt marshes dominates the south coast.

The Wildlife

Some 65 freshwater, anadromous and marine fish species make up the fish fauna of the region, including Atlantic cod, Greenland halibut, herring, capelin and Atlantic salmon. The diversity of marine life found along the underwater cliffs and shelves of this region make it one of the most interesting diving destinations in Eastern Canada. Some of the greatest densities of nesting common eiders in North America, as well as some of the highest concentrations of black-crowned night herons, great blue herons and double-crested cormorants in Eastern Canada are found here. Important concentrations of migrating snow geese, sea ducks and shorebirds stage in the marsh and mud flat areas while gulls and terns concentrate in the upwelling areas. This is also one of the best whale watching areas in the country - harbour porpoise, minke, fin, humpback and blue whales and harbour and grey seals are common. This is also home to the only southern group of belugas, an endangered population of 500-700 individuals.


This region is represented by the Saguenay–St. Lawrence Marine Park (1138 km²), established in 1998 under the Saguenay–St. Lawrence Marine Park Act. In 1990, the governments of Canada and Quebec signed a federal-provincial agreement providing for the establishment of the marine park at the confluence of the Saguenay River and St. Lawrence Estuary. The agreement stipulates that both levels of government retain their respective jurisdictions over the area and will work towards its protection. Specific, complementary legislation was adopted at the federal and provincial levels to officially establish the park and provide for its management. (For details on the establishment process, see The NMCA Program.)

Last Updated: 2013-05-10 To the top
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