In 1835, the sea lamprey was first observed in Lake Ontario. Due to Niagara Falls, lampreys were unable to spread further into other Great Lakes. Unfortunately, the improvements conducted in the early 1900s to the Welland Canal infrastructure, a bypass of Niagara Falls, were enough for the lampreys to begin their invasion.
First was Lake Eerie in 1921, Lake Huron
in 1936, Lake Michigan in 1937, and finally Lake Superior
a year later.