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Underhill, J. C. (1989). Distribution of Minnesota fishes and Late Pleistocene glaciation. Journal of the Minnesota Academy of Science. 55:32-37.

The fishes of Minnesota have been the focus of research for almost a century. At present the ichthyofauna totals 153 species belonging to 19 families, including 13 species which have been introduced. Because Minnesota was covered by glacial ice until at least late Wisconsinan time, species that migrated into the state from the periglacial region could have been derived from three refugia: unglaciated Alaska, the Atlantic refugium, and the lower Mississippi River refugium. The routes followed in their dispersal were dependent upon the drainage connections that existed during late Pleistocene and early Holocene time. Fish migration paths were largely determined by the formation of large glacial lakes such as Lake Agassiz, Lake Koochiching, Lake Duluth, and Lake Ontonagon. Advances and retreats of various glacial lobes controlled the size and drainage directions of the glacial lakes, allowing migration of fishes from different refugia at different times. The geologic evidence for Holocene drainage is more conjectural, and the present distribution of species can be used to infer changes in drainage during this period of time.