The term "exotic species" refers to an organism that is introduced into an ecosystem where it is not naturally present (or "native").
Most exotic species are introduced by humans, both intentionally and unintentionally. The Common carp is a dramatic example of an introduced exotic species, as it was deliberately imported to this country and placed in our waters a long time ago
. The destructively prolific Zebra Mussel, on the other hand, was introduced accidentally, probably from ballast water discharged into a North American harbor by a European ocean tanker.
While the impact of an exotic species varies from harmless to beneficial to highly destructive, it can rarely be predicted. Like the carp, most exotic species spread very quickly, because their natural foes and competitors do not exist in their new habitat. They can often overwhelm, and even completely eliminate, native species, and are nearly impossible to remove once established.
Even exhaustively researched attempts to control an introduction for beneficial purposes have proven to be risky. As recently as 1994, for example, the Asian Black carp, an especially large and voracious variety being researched as a control for the Zebra Mussel, escaped on flood waters into several Southern rivers, before the successful development of a sterile strain.
For specific information on the identification and range of several exotic species presently of concern in Minnesota waters and elsewhere, as well as steps you can and must legally take to prevent their spread, refer to the Minnesota Department of Natural Resources web pages on invasive aquatic species