Experts say spiny water fleas discovered in a northern Wisconsin lake could spread to many lakes where the European crustacean would threaten native organisms.
University of Wisconsin-Madison graduate student Pieter Johnson discovered the fleas in Gile Flowage, a large lake in Iron County near Lake Superior.
The spiny water flea has big black eyes, a bulbous sac sitting above its head, and a long, barbed, whip-like tail.
The fleas have been living in the Great Lakes for more than 15 years, but hadn't previously been found in the state's inland waters.
The fleas compete with and eat native zooplankton -- the food of young sport fish like walleye and perch and small foraging fish, like minnows.
Johnson says that, although the exact impact of the flea on the food chain is not yet know, it has the potential to hurt fisheries and reduce the number of game fish.
The species can move from lake to lake in bait buckets, boats' live wells and bilges.
Wisconsin natural resource workers hope to stop any spread by alerting boaters and anglers about the problem.