TOLEDO, Ohio (AP) – Scientists say there’s proof that one type of invasive Asian carp is spawning in a Great Lakes tributary.

A graduate student at the University of Toledo in Ohio discovered grass carp eggs last summer in the Sandusky River, which flows into Lake Erie.

Holly Embke’s findings have been published in the Journal of Great Lakes Research.

The U.S. Geological Survey previously reported that four young grass carp taken from the river had resulted from natural reproduction.

Grass carp are not as big an environmental threat as Asian bighead and silver carp, which could reach Lake Michigan through Chicago-area waterways.

Grass carp can harm fish and waterfowl habitat by gobbling up aquatic plants. But unlike bighead and silver carp, they don’t compete with native fish or threaten to disrupt food chains.