A new government study says live Asian carp don't have to be present for their DNA to turn up in the environment.
The report released Wednesday by three federal agencies identifies six other ways that genetic material from bighead and silver carp might have reached waterways in the Chicago area and western Lake Erie.
It says the DNA may have come from storm sewers, fisheries sampling gear, fish-eating birds, dead fish carcasses, barges and sediments. The report says carp DNA from those sources could remain in place for several days.
Asian carp DNA has been found in dozens of water samples beyond an electric barrier meant to prevent the invasive fish from reaching the Great Lakes, where scientists say they could destabilize ecosystems and out-compete native fish for food.