We spend a lot of money to control sea lampreys. The U.S. and Canada spend $21 million dollars a year to keep them in check. The invasive fish drills holes into big fish like trout and salmon, and drinks their blood and body fluids. A single lamprey can kill 40 pounds of fish. Managers are always looking for new ways to control the blood suckers and keep tabs on where they are in the Great Lakes system. Now, scientists are testing the idea of using environmental DNA – or eDNA. It’s a tool that’s