Marais de Saint-Étienne (QC160)

Marais de Saint-Étienne (QC160)

Saint-Étienne-de-Beauharnois, Québec

Site Description

The Saint-Étienne marsh borders the south side of the Canal de Beauharnois roughly 25 kilometres to the southwest of Montreal. The Canal de Beauharnois is another IBA and a branch of the St. Lawrence River. The Saint-Étienne marsh is an artificially created marsh, surrounded mostly by agricultural lands. A large hydro line cuts through the middle of the site.

Birds

About 90 waterbird species and 81 other bird species have been recorded in the Saint-Étienne wetlands. Not well known, but most significant are the numbers of Great Egrets, Black-crowned Night Herons and Black Terns. In the '90s, approximately 200 Black Terns were recorded during the breeding season, but this species was not observed in 2013. 90 post-breeding Black-crowned Night Herons were seen in 1999 (about 1% of the Canadian population). In 2000, 32 Great Egrets were counted here in the summer. These numbers are equivalent to about 5% of the Canadian population of Great Egrets. Another interesting breeding species is the Least Bittern. Four birds were recorded in 1992.

Conservation Issues

The growing muskrat population has damaged the dyke (by digging numerous tunnels) which has led to reduced water levels. Nonpoint source pollution caused by farming activities in the area also threatens the quality of aquatic ecosystems. Furthermore, the spread of invasive plants results in considerable pressure on native flora. For example, the common water reed is spreading on the ponds' banks and in some of the drier areas, whereas the flowering rush is invading the reservoirs. Since 2012, reservoir number 4 is leaking and invasive plants, notably flowering rush, are spreading at an alarming rate. Poaching is reported every year despite the fact that a portion of the IBA is within a No Hunting Zone.

Fish Habitat

A variety of freshwater and diadromous fish coexist in different habitats in the IBA. We found between 70 and 80 species (including historical records) in the area. Several species, such as the northern pike, the yellow perch and the common carp exploit the aquatic vegetation and the floodplains as a spawning ground, a nursery and a feeding ground. Others, such as walleye, freshwater specie with an important economic value in Canada prefer rather to spawn in fast flowing waters. A special feature of this area is the presence of salmonids introduced for sport fishing (brown trout, rainbow tout, and salmons). Salmons were introduced in the Great Lakes and some drift into the St. Lawrence River where they are sometimes caught by anglers. Brown trout and rainbow trout were also stocked in riffles (in the river) for sport fishing.

Several pressures threaten the availability of fish habitats: the creation of embankments, the artificialization of banks, the residential, commercial and industrial development as well as developing the road network, while agricultural, industrial and urban waste deteriorate the water quality. The Eastern sand darter, among others, is very vulnerable to pollution and it is now on the list of endangered species. Among the species listed at risk frequenting the site, we found the lake sturgeon, the channel darter, the bridle shiner, the American eel and some historical records mention the presence of copper redhorse, a fish endemic to Canada designated endangered. In addition, the presence of invasive species such as round goby, threatens the natural dynamics of ecosystems and the water level regulation of the Great Lakes creates risks for the availability of spawning habitats of certain species.

Major species present:
American eel
American shad
Bridle shiner
Brown trout
Channel darter
Common carp
Copper redhorse
Eastern sand darter
Lake sturgeon
Muskellunge
Northern pike
Rainbow trout
Salmon
Smallmouth bass
Walleye
Yellow perch

Plants

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

• Least Bittern12 (max.)