Guest commentary: Fish eDNA suggests Asian carp closing in on Great Lakes

By Andy Mahon/Central Michigan University

CMU biology professor Andy Mahon and a research team introduce a new screening method to detect the abundance of invasive species in water. (courtesy photo/Central Michigan University)

It all started with a simple question. In late 2008, while sitting around after work with a group of colleagues, Lindsay Chadderton from The Nature Conservancy asked, “Do you think there’s fish DNA in water?”

Pausing for a moment, I answered, “Sure, why not … why do you ask?” He went on to describe a scientific paper, new at the time, which tracked animals in water using their DNA. Chadderton suggested we try doing something similar to track invasive species in the Great Lakes.

That’s how our work got started; utilizing the common genetic technique, including Polymerase Chain Reaction screening, to track down and help control the spread of invasive species in the Great Lakes. The findings of our research, recently published in two peer-reviewed scientific journals (the Canadian Journal of Fisheries and Aquatic Sciences and PLOS ONE, the electronic journal of the Public Library of Science), demonstrate how the use of environmental DNA technology can serve as a surveillance and early warning tool to recognize dangerous species in small enough quantities for us to take action before they impact the Great Lakes.

Andy Mahon is an assistant professor of biology at Central Michigan University’s Institute for Great Lakes Research.

Our study began in early 2009 in Morris, Ill., an area at the time known to have large numbers of Asian carp. Back then, few people knew much about Asian carp. There were few news stories about these invasive species. No federal lawsuits had been filed to stop their movements. No multi-agency task forces had been formed to halt their invasion north into Lake Michigan.

Gathering these first samples in an area with one of the world’s largest populations of Asian carp, we hypothesized that if our testing couldn’t find their DNA there, our research wasn’t worth pursuing.  Our tests worked … really worked! We detected the DNA of both species we were searching for – bighead carp and silver carp. This success answered that initial question that got us started: Yes, there is fish DNA in water. We continued our use of this surveillance method to detect Asian carp.

Our research group – me and colleagues from the University of Notre Dame and The Nature Conservancy – has since collected more than 2,800 water samples from throughout the Great Lakes basin.

The bad news from our findings: 64 samples collected in the Chicago Area Waterway System and in the western basin of Lake Erie indicate the presence of Asian carp DNA in the Great Lakes. These positive samples were found within a few miles of where bighead carp were recovered near Lake Michigan in 2010 and from Lake Erie’s Sandusky Bay in 2000.

It’s this pattern, finding our positive detections so close to those locations where fish have been previously caught (and not all over the basin in random locations), that convinced us the DNA we are detecting is coming from live fish and not from other sources (bird excrement, boats, sewage outflows, etc.). If these other potential origins of the fish’s genetic materials were the source for the DNA discovered, we’d be seeing a different pattern in our detections.

Now the good news from our findings: While we picked up some Asian carp DNA in the Great Lakes basin, only a small percentage of the samples we took came back positive for the presence of Asian carp environmental DNA. This tells us the Asian carp invasion into the Great Lakes isn’t widespread -- yet.

We started the DNA studies to provide management agencies with another monitoring tool to assist them in keeping invasive species out of the Great Lakes. But this tool is not a silver bullet. It is another very effective tool to help in early detection and prevention.

Having an answer to that simple question of whether there is fish DNA in water, we now have a better picture of where Asian carp are in the Great Lakes basin. With continued vigilance -- and the combined efforts of local, state and federal partners -- we are optimistic it will be possible to keep these harmful invasive carp from becoming established in the Great Lakes.