Lake Michigan now has joined Lake Erie as a fishery where Asian carp DNA has been discovered.
A single positive sample for silver carp was found in Sturgeon Bay this past summer, according to the Wisconsin Department of Natural Resources (DNR), which conducted the research along with the University of Notre Dame and The Nature Conservancy.
The water sample wasn’t screened for the presence of carp DNA until recently. It was collected originally in a search for evidence of Eurasian ruffe, another exotic fish species.
Is the finding cause for concern? That’s debatable. But it is reason enough to begin regular sampling of Sturgeon Bay.
“When we start talking about evidence for Asian carp in a system and the use of DNA, we talk about repeated sampling events and repeated detections,” said Chris Jerde, a Notre Dame scientist.
This latest discovery was from just one of 50 water samples taken in Sturgeon Bay and 282 total from the state’s portion of Lake Michigan.
But Jerde added that if Asian carp DNA were commonly spread by bird feces, boat hulls, and other means besides live fish, other positive samples would be noted from across the Great Lakes.
"We can talk about alternative pathways (for DNA to get into a water body), but we still have thousands of negative detections throughout the Great Lakes and we have one positive here."
DNR’s Bob Wakeman added, “It is what it is. We just need to clarify what it means.”
Despite the discovery of positive DNA in Lake Erie and even a couple of live carp over the years, no evidence has been found of a breeding population.