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Freshwater fishes [Diversity] [Biogeography] [Hydrographic units] [Water masses] [Depth] [Sediments] [Wetlands] [Local richness] [Rarity] [Conservation status] [Diversity and conservation] |
Saltwater fishes [Diversity] [Biogeography] [Salinity gradient] [Aquatic physiographic units] [Distance from the shore] [Depth] [Sediments] [Local richness] [Rarity] [Conservation status] [Diversity and conservation] |
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| Freshwater fishes of the St. Lawrence: water masses |
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The various water masses in the St. Lawrence form another large-scale longitudinal division. The brown waters of the Ottawa River flow alongside the green waters of the Great Lakes until the area downstream from Lake St. Pierre; these water masses then mix with the water masses from the tributaries. The regional species-area curve predicts the richness of several water masses fairly accurately: the Great Lakes water mass, the Ottawa River water mass and the Ottawa River-northern tributaries mixture. The richness of small local water masses, formed by the plumes of the main tributaries, is dispersed around the regional curve. However, the Lake St. Louis gyre, despite its small size, supports 58 fish species, while the regional species-area curve predicts only around 30 species. This is undoubtedly the richest ecological unit in the freshwater section of the St. Lawrence, along with perhaps the Sorel Islands. The other water masses are poorer than predicted by the curve: the water masses in the centre and south part of Lake Saint-Pierre that extend into the freshwater estuary (GRLacs2 on the graph) and the Great Lakes-southern tributaries mixture (GrLacs-Sud on the graph). Similarly, mixtures around Quebec City are also relatively poor in freshwater fish species.
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