Estuary of St. Lawrence

, Ilnu Museum in Mashteuiatsh, Saguenay–Lac-Saint-Jean The culture of the First Nations in Canada was largely based on birch, and the Birch bark canoe provided these hunting peoples with the mobility essential to this way of life. After crossing the Gulf of St. Lawrence, the itinerary of the first Europeans: whalers, fishermen, explorers and navigators enters the waters of the Estuary, where the most difficult manoeuvres of the voyage begin: reefs, shoals, diagonal currents, fog and the presence of shallow channels, often narrow and winding, not to mention winter and ice and its unpredictable and fearsome storms. Throughout its history, the estuary of St. Lawrence River is not easily domesticated. St. Lawrence Pilots From Les Escoumins ensure the safe efficient passage of the vessels under their care. ==Fluvial estuary==

Running for about 160 km, the fluvial estuary or estuarine section of the river extends from the outlet of lake Saint-Pierre to the RCM L'Islet; the portion of the river under the power of freshwater tides. The average depth of the main channel varies from 13 to 40 m, with pools of 21 m in Trois-Rivières-Ouest and 60 m in Quebec City. The waters of the streams and rivers that flow into the river differ from those of the St. Lawrence in terms of temperature, chemical composition and suspended solids. The main rivers of the fluvial estuary, on the south shore, are the Bécancour, Chaudière, Rivière du Sud rivers, on the north shore: St. Maurice Champlain, Batiscan, Sainte-Anne, Jacques-Cartier, Saint-Charles, Montmorency rivers and several secondary watercourses. The waters retain their distinctiveness over a relatively long course before mixing. Those in the Rivière des Outaouais keep their properties up to 25 km downstream from the mouth of the Saint-Maurice. Downstream of Grondines, the currents of the rising tide (flood) reverse the direction of the river's flow. The result is an increasingly homogeneous stirring and mixing of fresh water from different sources. Between Saint-Augustin-de-Desmaures and Île aux Grues, from 2008 to 2012, three plants characteristic of the St. Lawrence freshwater estuary and in a precarious situation were monitored annually: Victorin's gentian (Gentianopsis virgata ssp. victorinii), Victorin's water-hemlock (Cicuta maculata var. victorinii) and Parker's Buckwheat (Eriocaulon parkeri). ==Middle estuary==

, Saint-Laurent-de-l'Île-d'Orléans 2000 Running for about 195 km, the middle estuary of the St. Lawrence extends, according to the authors, from the eastern tip of Île d'Orléans or Saint-Jean-Port-Joli, to the mouth of the Saguenay River. This estuary section widens rapidly from a few kilometres to 10 km, then to 20 km upstream of Île aux Coudres and the archipelago of L'Isle-aux-Grues. ==Maritime estuary==

, Maritime estuary of St. Lawrence River, Tadoussac Among the deepest and largest estuaries in the world, running for about 300 km, the maritime Estuary of the St. Lawrence extends from the mouth of Saguenay River at Tadoussac to Pointe-des-Monts where the Gulf begins. The Whale Route Along the shore, the Whale Route (Route 138), stretches from Tadoussac to Labrador. This national road is one of the best places in the world to observe marine mammals. There, the two bodies of water that mix off the coast of Tadoussac give the Maritime Estuary characteristics that distinguish it from other reaches of the St. Lawrence: nutrient-rich surface waters throughout the summer and upwellings of deep, cold water that favour the formation of krill (euphausiids). Those organisms rise towards the surface near the shore, providing vast food stores for whales as large Baleen whales, as many others variety of whales and seals. It is home to the southernmost Beluga whale population in the world. This section is connected to the Gulf of St. Lawrence, an enclosed sea leading to the Atlantic Ocean by Cabot Strait and the Strait of Belle-Isle. == Fauna and flora ==

Habitats The zone of contact between fresh and salt water corresponds to a region of high concentrations of suspended matter causing a zone of maximum turbidity (MTZ) of a length that can vary from , depending on the flow of the river. This zone of maximum turbidity is located between Île d'Orléans (salinity greater than 0 PSU) and Île aux Coudres (salinity below 10 PSU). The mechanisms of estuarine circulation associated with this environment make it a privileged site of primary and secondary production which shelters many fish nurseries. High environmental turbidity provides shelter against predators while larvae are maintained under optimum temperature and salinity conditions. Large variations in salinity and turbidity result in a wide variety of physicochemical conditions and planktonic communities on the river. An emblematic species is the beluga (beluga whale), but many other species are present. An identification guide for marine fishes of the estuary and northern Gulf of St. Lawrence was completed in 2008. == See also ==