The Zoogeography of the Freshwater Fishes of Canada

There are 209 freshwater fish species in Canada. Of those species, 193 are native and 16 have been introduced into Canada and become established. Native freshwater fish diversity generally exhibits a latitudinal gradient and is greatest in the southern Great Lakes basin. The current distribution of freshwater fishes in Canada is the result of postglacial dispersal following the Wisconsinan glacial period and contemporary environmental factors.  Canadian fishes survived the last Ice Age in southern refugia in the Atlantic, Mississippi, Missouri, and Pacific basins, and a northern Beringian refugium, dispersed through glacial lakes and outlets following its recession, and became isolated as watersheds formed as a result of isostatic rebound. The influence of historical factors is most apparent in the strong differences in the fish fauna on either side of the continental divide. In the last 150 years, the isolation of the fish fauna in watersheds had been breached as humans introduced exotic species and transferred native species beyond their historical ranges. This human-mediated dispersal has resulted in the increasing homogenization of the Canadian fish fauna. Undoubtedly, further changes in the fish fauna will occur, likely exacerbated by climate change.