They are loose too. The wdfw and Odwf claim the grass carp are sterile and contained in land locked lakes, but I see them regularly in the Columbia and willamette. I don't think they can damage the river habitat, but it is another lesson to leave mother nature alone. Landlocked lakes, and the white Amure is out and loose in the rivers. Never introduce a species to solve a problem.
Grass carp are a completely different species than common carp.