Tennessee wildlife officials have been zapping the state’s waterways this month with boats that shock fish in about a 10 foot range. The stunned fish float to the surface, which allows for a quick annual survey of how many, and what kind of fish are around before they swim off. This year, officials are sampling for one kind of fish fairly new to Tennessee – Asian carp – which compete with native species for food, and could hurt the state’s billion-dollar sport-fishing industry.

Starting at the Mississippi River, where they can spawn, Asian carp have spread across Tennessee from west to east. One variety – bighead carp, is reported as far east as Watts Bar, near Knoxville. But Bobby Wilson, with the fish division of the state wildlife agency, says the carp don’t seem to be breeding here, at least yet.

“We’re finding a lot of them in there, but we’ve never found any evidence of reproduction. We’ve never found any little ones; we’ve only found the bigger ones. So we suspect and we hope that they are the ones that have just migrated through the various locks and the dams along the Tennessee and the Cumberland River system, from the Mississippi and the Ohio River.”

Wilson says the carp migrate anywhere there’s food – plankton – which is the same food many native fish depend on. Officials say that hurts populations of native species, and damages the state’s billion-dollar sport-fishing industry.

Still, Asian carp need long stretches of flowing water to spawn, which makes Tennessee a tough place for them to breed. Outside the Mississippi, many of the state’s rivers are broken up by dams and locks. Wilson says if the carp were to breed in the state, it would happen in Kentucky Lake, northwest of Nashville.

“If we have a period of time where there’s a lot of rain in the valley, and it washes down, they have to release water through the dams, and they can’t hold much of it back. At the right water temperature, the conditions might be right for them to successfully spawn. That’s what we fear. We have no control over that.”

Wilson says it’s hard to track the spread of Asian carp because they’re nomadic, and officials haven’t searched the fish out in past years. That changes this month, as they begin sampling the state’s waterways in hopes of documenting the carps’ spread.