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Invasive Asian Carp Are Spawning in Louisville

Byron Hopkins holds a bighead carp the crew caught in its nets as part of a fishing event called Carp Madness in Western Kentucky in 2013.
Byron Hopkins holds a bighead carp the crew caught in its nets as part of a fishing event called Carp Madness in Western Kentucky in 2013.

Invasive Asian carp have been in the Ohio River for several years, and a federal report released earlier this month revealed the carp are spawning in Louisville. This is the furthest known upstream point on the Ohio River where the invasive species has an established population.

“When [Asian carp] spawn, they actually go to the main channel, right where the strongest currents are, maybe below a dam or a ripple,” said Kevin Irons of the Illinois Department of Natural Resources. In Louisville’s case, that spot is right below the McAlpine Lock and Dam.

The actual spawning is “not all that impressive,” according to Irons. If you were to stare into the churning waters, you might see male carp wrapped around females just before they release gametes into the river. But what is impressive is carp virility and their single-minded pursuit of reproduction.

“They essentially become numb to everything else but the spawning,” Irons said. “There was one time on the Illinois River, where I saw them just chopped up by barges. They failed to jump away or flee from other things.”

And one large bighead carp can have more than two million eggs, most of which are released during a spawning event.

“Maybe only one percent of those would survive to one year, but you have enough fish and you just broadcast so many eggs…because there are other fish that will eat them when they’re small,” Irons said.

“So you just saturate the environment, and that’s their strategy to survive. And they’re good at it.”

So, there are known carp spawning spots, and once the carp begin spawning, they reproduce quickly. This is one of the reasons that the invasive animal is proving so tough to contain or eradicate, and has overrun several major waterways in the Midwest. But carp are fairly picky about when and where they spawn, and Irons said there’s ongoing research about these spawning areas, like the area under Louisville’s McAlpine Lock and Dam.

“If we prevent them from getting to that spot, we know they just don’t spawn haphazardly,” he said. “So, they may either not spawn that year or wait for another time.”

Scientists are experimenting with using water cannons, nets and loud sounds on some popular carp spawning areas. Efforts are also increasing to attack the carp once they’re full-grown—by encouraging commercial fishing, eating them, or processing them into fertilizer or pet food.

But for now, a visit to the McAlpine Lock and Dam at the right time of year could be an educational lesson in Asian carp spawning.