A second test of water from the US Great Lakes has indicated the presence of Asian carp DNA, the Associated Press reports. A 2010 sample also came up positive.
Four different types of imported Asian carp escaped a number of years ago and have been moving into the Mississippi River and its tributaries, according to the AP. The presence of two species in particular — bighead and silver carp — in US waterways is worrisome as they voraciously eat plankton and may out-compete native species. An electric barrier near Chicago is supposed to block their migration into the Great Lakes, and the AP says that if the fish reach the lakes, they could threaten a $7 billion fishing industry.
However, two tests have now indicated the presence of carp DNA in Lake Michigan. Still, researchers say that the presence of DNA does not mean the fish are there as fish DNA could be found in the droppings of birds that ate them as well as in mucus, scales, and waste from the fish that may travel.
"One sample is a smoke detector," Chris Jerde, a University of Notre Dame biologist tells the AP. "A couple of more samples is a fire."
The AP notes that the work was carried out by Notre Dame researchers along with scientists from Central Michigan University and the Nature Conservancy.