MPR’s Dan Kraker looks into the ongoing battle to control sea lamprey in the Great Lakes. It was one of the earliest aquatic nonnative species to invade the U.S., long before zebra mussels and Asian carp garnered headlines. Its also been one of the most destructive, wiping out lake trout populations.

The sea lamprey, fittingly known as the "vampire of the Great Lakes," look like a giant leech. About 18 inches long, an inch in diameter, with a circular mouth lined with rows of teeth that suction to the sides of fish. And it has a needle-sharp, rasping tongue that bores a hole through the scales, so it can suck out the blood and fluids.