Non-Native Species
These fish have been introduced, either intentionally or accidentally, into the Great Lakes. Also called "exotic" or "nonindigenous" species, these newcomers can cause trouble by changing the ecological balance of the lakes and, sometimes, crowding out native species. Some non-native species are ecologically harmless and or even beneficial, but others cause great harm.
For example, the sea lamprey (shown in the illustration) is a predator that attaches itself to a fish, rasps a hole with its large sucking disk, and sucks blood and body tissues until it becomes satiated or the victim dies. Sea lampreys have caused great damage to the lake trout, whitefish, and burbot populations in the Great Lakes. Before the lamprey invasion of Lake Superior (prior to 1952), the lake trout harvest averaged about 4.5 million pounds; by 1960, it was less than 500,000 pounds.
For more information about these non-native species, see the Wisconsin Sea Grant nonindigenous species Web site.
See also Lake Michigan, Lake Superior, Lake Huron, Lake Erie, or the complete listing.
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copyright 1998 University of Wisconsin Sea Grant Institute
Brook Trout illustration copyright 1998 Gina Mikel
lamprey mouth image copyright Great Lakes Sea Grant Network Graphics Library
Lamprey feeding on lake trout image from the Great Lakes Fishery Commission
Last updated 05 February 2002 by Seaman