Rosie Cataldo - Staff Writer
Published January 1, 2001 | January 2001 issue
Origin: Atlantic Ocean. Entered via Erie Canal in 1921.
Problem: Attaches to and kills marine life, causing financial difficulties for fisheries and are a threat to native species.
Location: Great Lakes; hot zone is St. Mary's River, which connects Lake Superior and Lake Huron east of Michigan's Upper Peninsula.
Origin: Azov, Black and Caspian seas. Entered Duluth Harbor via ballast water in 1986.
Problem: Bottom dwelling fish that competes with native fish for food and habitat. Spine on gills and fins make them difficult for other fish to eat.
Location: Great Lakes and the Sand River in northern Wisconsin.
Origin: Caspian Sea. Spread by ballast water to the United States in the 1980s.
Problem: Attaches to hard surfaces and reproduces by the millions annually.
Location: Great Lakes, Mississippi River, St. Croix River and some inland lakes such as Lake Pepin and Lake Zumbro in Minnesota.
Origin: Azov, Black and Caspian seas. Entered via ballast water in 1990.
Problem: Bottom dweller that takes over prime native fish spawning sites. Easily identified by its underside suction disk that has a clam shell-like appearance, which helped anglers catch 120 of them in and around Lake Superior in 1998.
Location: Great Lakes.
Origin: Europe, Asia and North Africa. Believed to have been intentionally introduced for aquarium use in the 1960s.
Problem: Thick vegetation; degrades water quality, restricts swimming, fishing and boating; clogs water intakes. Depletes water oxygen levels for wildlife.
Location: In 48 states; abundant in the Great Lakes and the Twin Cities metro area.
|Spiny water flea
Origin: Great Britain, Northern Europe, Caspian Sea. Entered via ballast water in 1984.
Problem: Small crustacean competes with small fish for food and reproduces rapidly. Sharp spine makes it hard for other fish to swallow.
Location: Great Lakes and some inland lakes.