"I would say there's at least some evidence for Asian carp being present in southern Lake Michigan, " Jerde said.

WSJ: Report: Asian carp may have reached Great Lakes

Between September 2009 and October 2011, Jerde and his colleagues collected more than 2, 800 water samples from parts of the Great Lakes and tributary rivers.

WSJ: Report: Asian carp may have reached Great Lakes

But the Jerde team's paper, published online Thursday by the Canadian Journal of Fisheries and Aquatic Sciences, argues that the likeliest explanation remains the presence of live Asian carp.

WSJ: Report: Asian carp may have reached Great Lakes