The Contrecoeur Islands are situated in the St. Lawrence River, approximately 75 km downstream from Montréal, near the village of Contrecoeur. There are 29 islands spread over a 10 km stretch, from Île au Dragon in the west to Île au Coeur de Pierre in the east. In spring, some islands are completely submerged. The islands are almost completely vegetated with grasses (mostly Canary Grass) and areas of emergent grass link some of the islands. Vegetation in the shallower marshes is comprised of cattails, rushes and arrowheads. A small Red Ash grove remains on one of the islands.
The Contrecoeur Islands are a globally significant breeding site for Ring-billed Gulls, with an average of 11,761 pairs breeding throughout the 1990's. This is over 1% of the global population. Black Tern, Common Tern, Herring Gull, and Great Black-backed Gull also nest on the islands.
This site is a good breeding area for dabbling ducks. In particular, Gadwall nest on the islands in high densities. This site is also an important spring staging area for Bufflehead and Common Goldeneye. More than 2% of the total St. Lawrence River population of these two species may stage on the Contrecoeur archipelago.
The site has a diversity of marsh-breeding birds, including: American Bittern, Common Moorhen, Black Tern, Pied-billed Grebe, Virginia Rail, Marsh Wren and Swamp Sparrow. In addition, Savannah Sparrow, Song Sparrow, and Willow Flycatcher are common in tall grass and shrubby areas. Almost a third of the province's breeding population of Wilson's Phalarope occur in the archipelago, and there are also small populations of Nelson's Sharp-tailed Sparrow and Sedge Wren. Great Blue Herons also raise young here. In late summer, emergent grasses on the north shore of St. Ours Island are a roost for thousands of swallows. Between one and three Caspian Terns have been seen in the breeding season, but breeding has not been confirmed.
Accidental or purposeful human disturbance and red fox predation could both potentially affect the health of this colony.
This zone is rich in aquatic vegetation beds and wetlands in the island area. Its is a area presenting a great potential for spawning for many species of fish, including the northern pike, the walleye black, the brown bullhead, the smallmouth bass and the yellow perch. Some other species, such as lake sturgeon, use spawning ground located in fast flowing waters. More than 53 species are found in this area. Various species are targeted by commercial and sport fishing, including the American shad, which attracts many anglers during the spawning period in late May and early June. The region is also home to the copper redhorse, endangered specie endemic to Québec; the lake sturgeon which is considered as threatened in Québec; and the American eel, a species of least concern.
The destruction of spawning and aquatic habitats in wetlands threatens the reproductive success of the ichthyofauna. The cases are multiple and include artificialization of the shoreline, the agriculture practiced on islands, the presence of resorts, the recreational and commercial boating (bank erosion by waves). In addition, some species, such as walleye, are affected by the decrease in water quality, mainly created by industrial activities in the region as well as municipal and agricultural pollution. The rainbow smelt, once abundant in this area, has disappeared because of the destruction of its spawning sites in small tributaries.
Major species present:
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 :
Narrow leaf cattail