An increasing percentage of eDNA samples, taken near Lake Michigan, are turning up positive for carp. But what does that really mean?

There is a general consensus among environmental groups, as well as state and federal government agencies, that Asian carp are knocking on the door of the Great Lakes — or rather, the electric barrier in Chicago that is meant to zap any fish that get too close to Lake Michigan — but there remains much debate about whether or not the barrier is effective.

Recent environmental DNA (eDNA) testing in the Little Calumet River and Lake Calumet upstream of the barrier found that, out of 114 samples taken, 17 came back positive — or nearly 15 percent. That is a big jump from the 34 positives out of 2,378 samples (only 1.5 percent) taken from upstream waters last year. The recent samples were taken over the course of one day. So does this mean that more and more carp are secretly sneaking past the barrier, edging closer to the Great Lakes and the region’s $US 7 billion sport-fishing industry? Not necessarily, according to the U.S. Army Corps of Engineers.

“At present, eDNA evidence cannot verify whether live Asian carp are present, whether the DNA may have come from a dead fish, or whether water containing Asian carp DNA may have been transported from other sources such as bilge water, storm sewers or fish-eating birds.” –Army Corps of Engineers

Proponents of more drastic measures to stop the carp point to the increasing number of positive samples as mounting evidence that the fish are thwarting authorities, but the Corps of Engineers has played down the results. The nature of eDNA testing — which detects cells from tissue, mucus, feces, and urine — only allows researchers to know that a carp (alive or dead) has probably been in the area.

For now, that means the controversy over Chicago’s barrier will likely continue, as will the debate about taking further measures to stop the carp.

Have any news about Asian carp, invasive species, or the Great Lakes? Comment below or send me an e-mail at codi@circleofblue.org.

–Codi Yeager-Kozacek
Circle of Blue Reporter

Codi Yeager-Kozacek is a reporter for Circle of Blue based out of Enterprise, Alabama. She studied journalism and biology as an undergraduate at West Virginia University and graduated summa cum laude from the university’s Perley Isaac Reed School of Journalism. She has done research at the College of the Bahamas Gerace Research Center on San Salvador Island, Bahamas, and her study on coastal dune plants is currently pending publication in the Bahamas Natural History Proceedings. Her interests include food security and ecology. She co-writes The Stream, Circle of Blue’s daily digest of international water news trends. Email: Codi Yeager-Kozacek  :: Follow on Twitter :: More Articles