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Centre du lac Saint-Pierre (QC115)


Centre du lac Saint-Pierre (QC115)

Sorel, Québec

Latitude 46.203°N
Longitude 72.818°W
Altitude 15m
Area 180.65km²

Site Description

Saint-Pierre Lake is a widening of the St. Lawrence River situated approximately 75 km downstream from Montreal. The lake is shallow and rarely deeper than 3 m except where waters of the St. Lawrence River directly flow through. Aquatic plant communities thrive and are well distributed - wild celery often dominates. This is an important stopover site for diving and dabbling ducks, Greater Snow Geese and Canada Geese.

This IBA solely includes the central portion of Lac St-Pierre; islands and adjacent areas have been designated as unique Important Bird Areas.


During fall migration, a large number of ducks (mostly divers) use Lac St. Pierre. During the 1980s, 15,041 ducks (both dabbling and diving) were present on the lake, which makes Lac St. Pierre a continentally significant waterfowl site. Goldeneye (mostly Common Goldeneye) are the most abundant duck, with up to approximately 7,000 individuals present in fall. Scaup, both Greater and Lesser, are the second most common duck species with up to 2,100 being recorded.

Conservation Issues

Water quality is a major issue for the conservation of the habitats and biodiversity of the Lac Saint-Pierre?s IBAs. Surface water quality tests often fail for metals such as lead, chromium, aluminium, copper, and iron. Sediments in the bottom of Lac St-Pierre are frequently over the PCBs and lead safety limits set for dredging operations. Fertilizers and other chemicals used by farmers are found in the surrounding watersheds and have a major impact on the water quality. There has also been some evidence of contamination from pentachlorophenol, hexachlorocenzene, and DDT, but few studies have been done on the potential effects of bio-accumulation on birds. The Double-crested Cormorant population levels have increased due to the creation of artificial islets in the center of the lake (whose purpose is to break up the ice during winter). The growth of the Double-crested Cormorant population may be a cause of the decline in Yellow Perch abundance and it may threaten the Great Blue Heron population nesting on La Grande Île. In 2008, the ministère du Développement durable, de l'Environnement, de la Faune et des Parcs of Québec implemented an egg-oiling program to prevent further growth of the local population of Double-crested Cormorant and a lethal control pilot project was launched in 2012. Dredging the seaway alters fish habitat, water currents and flows, and water quality. Oil spills are a constant threat because of the site?s close proximity to the St. Lawrence Seaway. Boating activities are also increasing in popularity and may be a source of disturbance to waterfowl and other birds. The site is part of the Lac Saint-Pierre Biosphere Reserve, as designated by UNESCO. It is also recognized as a wetland of international importance under the RAMSAR Convention. The site is included in the Lac Saint-Pierre Priority Intervention Zone.

Fish Habitat

The Lake Saint-Pierre is one of the largest freshwater wetland in Quebec. This area is exploited by several fishes considered at risk, which include the lake sturgeon, the copper redhorse, the striped bass, the eastern sand darter, the channel darter and the American shad. The largest known population of bridle shiner, a species whose status is “at concern” in Canada, has been reported in this area.

The availability in habitats has decreased primarily because of wetlands draining to extend the surface available for agriculture and to control of the water levels. The shoreline is eroded by waves created by commercial shipping and pleasure crafts, while dredging of the channel alters the water flow and the structure of habitats. The implementation of an agricultural industry in the watershed, the presence of many industries upstream of Lake Saint-Pierre, the density of population and the presence of resorts are responsible for the degradation of water quality. The population of walleye, a fish very sensitive to pollution, appears to be declining in the past few years. This is also the case for the yellow perch, historically the most important commercial species in the lake.

Major species present:
American eel
Bridle shiner
Brown bullhead
Copper redhorse
Lake sturgeon
Northern pike
Yellow perch


Habitats in this area are characterized by high sedimentation. The contributions of many tributaries, such as Richelieu and Saint-François rivers, are largely responsible for the suspended material. This sedimentation promotes the formation of marshes and wet meadows. We found there vast submerged meadows dominated by Wild celery and Eurasian water-milfoil. Emergent marshes are colonized by bulrushes, arrowhead and cattails. Several duck species forage in these areas, including the scaup that is fond of Wild celery.

Shoreline erosion, whether due to natural factors (wind, cycles of freezing and thawing, no ice to protect the banks in spring) or human (waves caused by passing ships), threatens riparian habitats. Variations in the water level in the river corridor affect the ecology of plant and animal species that live there. A significant and prolonged decrease of immersion banks could affect flora by promoting the growth of plant species over land, nature and even shrubby tree. In addition, the spread of invasive species exerts considerable pressure on the native flora of these habitats.

Major species present :
Wild celery
Eurasian water-milfoil
Narrow leaf cattail
Broad-leafed cattail
Sessilefruit arrowhead
Broad-leafed arrowhead
American bulrush
Great bulrush

IBA Criteria Habitats Land Uses Potential or Ongoing Threats Conservation Status
Number Year Season