Detecting Asian Carp
Watch a short video of scientists at The Nature Conservancy and the University of Notre Dame describing how they detected Asian carp at the brink of Lake Michigan.
"Environmental DNA is an exciting new tool that could revolutionize how we do science in aquatic ecosystems. We have moved beyond the stage of 'experimental.' This should now be a standard tool in the toolbox for exotic species research."
- Linsay Chadderton, The Nature Conservancy's Director for Aquatic Invasive Species
How can scientists claim Asian carp are close to Lake Michigan without seeing or capturing one? By using environmental DNA (eDNA) as an early-warning tool to detect their presence, a technique that is now gaining scientific acclaim.
While eDNA has been used to detect land and marine invasive species for more than 20 years, its use on freshwater species is relatively new. The Asian carp eDNA technique was developed by a team of scientists at The Nature Conservancy and the University of Notre Dame.
This technique is now described in detail by a recent paper published in the scientific journal Conservation Letters. The paper compares eDNA to other standard methods used to hunt for exotic species in the field and offers evidence that eDNA is better than traditional methods for finding a species because it is more sensitive and can be implemented earlier with fewer traces of a species than a thriving population would provide.
"Just like it's important to have early detection of cancer, it's vitally important to have early detection of invasive species like Asian carp in the waterway," says David Lodge of the University of Notre Dame. "Only if we detect [it] early, can we hope to manage it effectively."
Evidence of Asian carp reproducing rapidly in the U.S. was first detected in the Mississippi River in the 1980s. Since their escape nearly two decades ago, bighead and silver carp have overwhelmed segments of the Mississippi and Illinois River systems by disrupting the ecological balance and competing with native species for food. Through the Illinois River, they have spread northward towards the Great Lakes.
How did the team develop the eDNA technique?
From summer 2009 through May 2010, scientists from Notre Dame and The Nature Conservancy collected and analyzed more than 1,000 two-liter samples of water from the Chicago Sanitary and Ship Canal, and other water bodies in the metropolitan area. Then, using a combination of high tech genetic tools, they sifted those samples to find traces of eDNA from Asian carp.
The research grew out of a formal partnership between the University of Notre Dame and The Nature Conservancy to develop science-based solutions to environmental problems.
Last year, working with the Conservancy under a cooperative agreement funded by the U.S. Army Corps of Engineers, the team of researchers used the eDNA technique to discover just how close two species of highly invasive Asian carp (bighead and silver) were getting to Lake Michigan.
In particular, the scientists wanted to determine if any fish made it past a pair of underwater electronic barriers [302KB PDF] designed to keep exotic invasive species from moving between the Great Lakes and Mississippi River watersheds.
The team of researchers soon discovered genetic material from Asian carp in several sections of the Chicago-area waterway system. Many of the detection points suggested that Asian carp were much closer to Lake Michigan than authorities had previously believed. Asian carp eDNA was found in Calumet Harbor, a near-shore area of Lake Michigan itself, many miles beyond the electronic underwater barrier.
The announcement led to significant media attention and numerous public policy responses, including a multi-agency government effort in December of 2009 to apply rotenone, a common pesticide used to eradicate fish populations, to some sections of the Chicago-area waterway.
In June 2010, when a live bighead carp was found in Chicago's Lake Calumet, concerns about Asian carp grew higher. Controversy caused some observers and industry interest groups to question the eDNA technique, particularly since the scientists' work had not yet been published by a peer-reviewed journal. The criticisms came despite the fact that the research had been examined thoroughly by a special U.S. Environmental Protection Agency peer-review in February 2010.
At this point, it is unknown how many Asian carp breached the electric barriers. About $74 million dollars has been appropriated to fund an Asian Carp Response Framework as a response to the detection of silver and bighead carp above the electric barriers. This combination of short- and long-term actions will be designed to prevent any further spread of Asian carp into the Great Lakes.