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Île Deslauriers (QC126)


Île Deslauriers (QC126)

Varennes, Québec

Latitude 45.713°N
Longitude 73.441°W
Altitude 20m
Area 0.96km²

Site Description

Île Deslauriers is part of the Varennes Archipelago in the St. Lawrence River, just east of Montréal and directly north of the town of Varennes. The western part of the island contains mounds of sediment from dredging of the river. In spring, about 30% of the island becomes submerged.

Vegetation on the island consists of short grasses, and Black Mustard and dandelions grow on the spoil piles. Aquatic vegetation is composed of arrowhead, Sago Pondweed and Spiked Water-milfoil.


An extremely large Ring-billed Gull colony is located on Île Deslauriers. Over the past two decades, the colony has substantially increased in size. At last count in 2000, 51,667 pairs (5% of the global Ring-billed Gull population) nested on the island, which makes this colony the largest in Québec as well as one of the largest in Canada, and represents over 5% of the world's population.

A population of Black-crowned Night-Herons has recently become established on the island and has shown a large increase in recent years. In 1994, 28 pairs nested on the island, and in 1997 there were 49 pairs. Compared to other nearby islands, Île Deslauriers hosts large numbers of breeding Gadwall and other waterfowl species. A Bank Swallow colony is also located on the northeast part of the island.

Conservation Issues

Accidental or purposeful human disturbance and red fox predation could both potentially affect the health of this colony.

Fish Habitat

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:
American eel
American shad
Brown bullhead
Copper redhorse
Lake sturgeon
Northern pike
Spottail shiner
Yellow perch


The sector is characterized by clear, alkaline and slow flowing water. Theses conditions promote dense plant bed that can cover up to 50% of the water bodies. Submerged plant beds are dominated by wild celery and Eurasian water-milfoil, while emergent marshes are filled with 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, freezing and thawing cycles, absence of ice protecting the river banks in spring) or human actions (waves caused by ships), all threaten the riparian habitat. Water level fluctuations affect the ecology of plant and animal species that live there. A significant and prolonged decrease of bank immersion could affect flora by promoting more land species such as shrubs or even trees. In addition, the spread of invasive species exerts considerable pressures on the native flora of these habitats.

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

IBA Criteria Habitats Land Uses Potential or Ongoing Threats Conservation Status
Ring-billed Gull
Number Year Season
25,000 - 50,0002017Summer