La Mauricie National Park of Canada

A Land of Lakes and Brooks

Brook Trout
© Parks Canada/Jacques Pleau

La Mauricie National Park represents a landscape of rounded hills and deep valleys characteristic of the Lower Laurentian Mountains. The glaciation receded approximately 10,000 years ago, leaving behind accumulations of sand and gravel, forming eskers and moraines. Following the thaw, the Champlain Sea flooded the southeast portion of the park and the Saint-Maurice River valley for a short period, leaving behind numerous clay terraces.

The departure of the glacier ice resulted in the formation of more than 150 lakes of varying sizes and characteristics. Small lakes in bogs, with dark acid water, are generally situated in higher altitudes, and the large, deep clearwater lakes follow the valley bottoms. They are all interconnected by a network of brooks or small cascading rivers that ultimately flow into the Matawin and Saint-Maurice rivers.

Shortly after the retreat of the glaciers, the majority of the water bodies were isolated from the large rivers by an uplifting of the earth’s crust, creating natural barriers for the fish. This phenomenon explains why originally the Eastern Brook Trout was the only species found in most of the streams and lakes. The invasion of the Champlain Sea at this same period permitted the Arctic Char, Ninespine Stickleback and Spoonhead Sculpin to colonise the low altitude lakes that form the network of lac à la Pêche, Isaïe, Français and Berubé lakes. These characteristics of the territory and the quality of angling brought about the founding of prestigious fish and game clubs as of 1883.

Today, there are some 19 new species of fish that have been voluntarily or involuntarily introduced by man. Generally, the most accessible water bodies are those that have received the most new species (18 in lac à la Pêche, 9 in Wapizagonke Lake and 8 in Édouard Lake). The introduction of these species has had a dramatic effect on the indigenous ones, particularly the Brook Trout. Without the presence of the Laurentian and Shawinigan Clubs, the situation would have undoubtedly been worse.

Among the treasures of the park are four large lakes in the Lac du Caribou sector that contain only Brook Trout. Français Lake supports the only Arctic Char population. The Brook Trout is still the dominant species in most of the lakes, particularly in the northern portion of the park.

The park waters are principally acidic or neutral. They support a low biological productivity characteristic of young lakes also called oligotrophic. The natural acidity is accentuated by acid rains. This phenomenon is particularly important and probably has more effect on the smaller head lakes than on large water bodies.

Beginning in 1849, the presence of forest exploitation is noted on the territory. For 120 years, logging and log driving were in activity on the majority of the park waters. Traces of this era are visible everywhere: old dams, logging roads, accumulations of logs on lake bottoms, eroded sediments, dragged streams to permit the passage of logs and stone piles to orient the flow of water. The impact of these activities on the natural environment was certainly a major one, but rests unknown to this date.

Man has profoundly modified the aquatic environment. The recent disappearance of 38 populations of Brook Trout are proof of this. Keeping this in mind, we are attempting to understand the state of our resources and develop conservation strategies required for the protection and maintenance of the natural characteristics of this territory.

To do this, it is therefore necessary to first establish a realistic historical profile in order to identify the natural components of the local biodiversity. Next it is essential to recognize the stresses that threaten, perturb or modify their evolution, be they internal or external to the park. Lastly, we must determine the measures that will be used to diminish the negative effects on the resources, correct unacceptable situations, and restore habitats and populations of major conservation interests. The ultimate objective is to permit this network of lakes, rivers, forests, as well as the living organisms that inhabit them to prevail safe from human influence for the benefit of present and future generations.

If you would like to know more:

• Lakes: A Look Beneath the Surface
• The Bedrock of an Ancient Mountain Chain
• Where the Southern and Northern Forests Meet
• Typical and Varied Wildlife
• A Place Birds Can Call Home
• A Land of Lakes and Brooks