Invasive exotic species

Eurasian water milfoils have been observed in the Grand Héron, des Seize-Îles and Laurel lakes as well as in the Baie des Soeurs.The Eurasian water milfoil is an invasive exotic plant that comes from Europe, Asia and North Africa.

This plant was introduced in North America in the 1940s and was first observed in Quebec in the 1960s.


The invasion of the water milfoil in a lake can cause various harmful consequences:

  • Reduction of the abundance and diversity of indigenous aquatic plants
  • Change in water temperature and oxygen levels dissolves in the coastline
  • Decrease in the abundance and diversity of macro-invertebrates and fish
  • Reduction of the leisurely activities such as boating, fishing and swimming
  • Significant economic devaluation of waterside properties

A few affected areas:

Lac des Seize-Îles

In 2010, the Eurasian water milfoil of the Lac des Seize-Îles were mapped out.

A total of 31 Eurasian water milfoils were observed.

It is the most abundant specie among the 14 species observed.

The Lac des Seize-Îles presents a moderate risk: the presence of the Eurasian water milfoil represents a factor that could eventually compromise the ecological integrity of the lake.



The Lac du Grand Héron

Sixteen herbariums were observed in 2011 (Map 12).

The three large-leafed bulrush herbariums and the herbarium dominated by the Eurasian water milfoil cover the greatest surface areas.

The Lac du Grand-Héron

The Baie des Soeurs

At risk: the Eurasian water milfoil represents a compromising factor for the ecological integrity of the lake.
This invasive specie occupies 74 % of the surface area of the Baie des Soeurs.

The Baie des Soeurs

The Lac Laurel

Thirty herbariums are present in the Lac Laurel.

The eight herbariums dominated by the fragrant nymphea (0,3 ha) and the four Eurasian water milfoils (0,4 ha) are the other secondary herbariums in the Lac Laurel.


All this information is taken from the Environmental Master Plan (in french)

The Lac Laurel