A newly released study says Asian carp may be reproducing in more places and for longer periods than previously thought.

That's a bad sign for natural resource managers looking for ways to stop the invasive fish from reaching more rivers and keep them out of the Great Lakes.

Several varieties of have infested the and many of its tributaries. Scientists say they may be out-competing for food.

A Purdue University study released Tuesday says the aggressive fish are spawning in waters that had been considered too narrow or with currents too slow for their offspring to survive.

Scientist Reuben Goforth says it's uncertain whether eggs laid in those outlying areas will survive to adulthood. But he says findings illustrate the carps' ability to adapt.