Asian carp may be swimming their way into the US Great Lakes. Or not. As the New York Times reports, DNA from the invasive species has been found in Lake Michigan, but how that DNA arrived in those waters is still a matter of debate.
A water sample taken from Sturgeon Bay last May came back positive for carp DNA, but repeat samples from November have come back negative. Asian carp are common in the Mississippi and Ohio river basins.
While some researchers tell the Times that the most likely source of Asian carp DNA is the fish itself, others note that carp DNA could originate from scales that sloughed off the fish or from its feces and traveled into the lake. Additionally, birds that fed on the fish may have dropped feces containing DNA from their meal into the water or boats that were in carp-infested rivers could have transferred DNA from there into the lake.
"A single positive hit would be less worrisome were there not other clues that at least some carp have sneaked into the lakes," the Times says, noting that carp have been sighted in a river that feeds into Lake Michigan and that they were caught in Lake Erie back in the late 1990s, though that was thought to be a chance happening.
Researchers, the Times notes, will be heading back to Sturgeon Bay in May for additional sampling.