ST. PAUL (AP) - Minnesota's fight to stop the spread of invasive Asian carp is going high tech.

Scientists have launched a new underwater spying campaign. They're implanting 120 ordinary local fish with transmitters to track their movements to get better prepared for when invasive carp species inevitably arrive.

Researchers have set up an underwater network of about 50 receivers, scattered in the Mississippi, Minnesota and St. Croix rivers. When any tagged fish comes within a third of a mile of a receiver, the signals will be recorded. When researchers dredge up the devices, they'll learn which individual fish passed by, and when.

Downstream, hundreds of Asian carp have been implanted with the same devices, so as they migrate upriver, their signals will be a calling card.