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Freshwater Conservation of the Great Lakes

Asian Carp Threaten Great Lakes

Nature Conservancy scientist helps develop pioneering DNA screening method that detects the presence of Asian carp in Lake Michigan.

By Melissa Molenda

Recent media coverage about detection of the aquatic invasive species Asian carp in the Chicago Sanitary & Ship Canal, including a new detection at Calumet Harbor near Lake Michigan, prompted questions about The Nature Conservancy's role in combating this threat.

Partners in Science & Action

In partnership with colleagues at the University of Notre Dame, The Nature Conservancy's Great Lakes Aquatic Invasive Species Director, Lindsay Chadderton, has helped develop and pioneer a new genetic surveillance method that can detect the presence of Asian carp in habitats that traditional fishing tools cannot effectively sample. recently asked Lindsay to provide his insights into developments around the Asian carp issue, the eDNA sampling, and the role of The Nature Conservancy in its partnership with Notre Dame.

Lindsay Chadderton, Aquatic Ecologist.

What's the latest news about the location of Asian carp related to Lake Michigan?

Lindsay Chadderton:

We have detected the DNA of Asian carp in water samples taken directly downstream of the last lock on the Calumet-Saganashkee (Cal-Sag) Canal less than 10 miles from Lake Michigan and also above the O'Brien Dam in the Calumet Harbor near Lake Michigan. These sites are both above the electric barrier that was designed to prevent carp from invading the Great Lakes. Repeated detections on separate sampling trips give us confidence that these results are real and most likely result from the presence of Asian carp. We have also recently detected silver carp DNA directly below the Wilmette pumping stations on the shoreline of Lake Michigan, in North Chicago, although as yet we have only sampled that area on one occasion.

Who do you report your results to, and what do they do with them?

Lindsay Chadderton:

I'm part of the eDNA research group based at Notre Dame. We are working with the U.S. Army Corps of Engineers (USACE) and supply our results to the Corps. They then pass the results onto the relevant management agency partners. USACE is responsible for maintaining the electric barriers, canal, and the lock and dam systems.

Does the eDNA mean that Asian carp are in Lake Michigan?

Lindsay Chadderton:

Our advice to the Corps and federal agencies is that the most plausible explanation of the eDNA signature is that there were Asian carp present at or immediately upstream of where we have detected their DNA. So yes, it is an "early warning" that an undetermined number of Asian carp have likely entered Lake Michigan.

Does The Nature Conservancy support control methods used so far?

Lindsay Chadderton:

Yes, The Nature Conservancy believes that the federal and state agencies are responding appropriately to this threat. The long-term use of the electrical barriers is an essential measure needed to prevent a significant number of the invaders from establishing a self-supporting population in the Great Lakes. Other control methods such as the use of rotenone certainly help and are necessary measures to take.

How does the eDNA sampling procedure work?

Lindsay Chadderton:

All organisms shed DNA, and fish slough cells from their gills, in mucus, urine, feces, or attached to scales. These cells are held in suspension in water or in the case of carp feces they actually float. We can potentially collect these cells in water samples, that are filtered and any DNA present is extracted off the filter paper. We can then amplify this DNA and screen for the presence of either bighead or silver carp using standard genetic techniques. It is similar to how a crime lab might screen for a person's DNA.

Is all lost if some Asian carp enter the Great Lakes?

Lindsay Chadderton:

No, but really it's a numbers game. There's a lag in time between when they get here and how quickly they can reproduce to establish a long-term population. The more fish that get through, the more likely that they will reproduce and the populations will grow. But, if we can prevent any further introductions and then target any fish that might have gotten through, we may be able to prevent them from successfully breeding and establishing a self sustaining population.

What measure should be taken in light of the DNA findings?

Lindsay Chadderton:

I think all options have to be considered to contain these fish and prevent movement into Lake Michigan. We are talking with our partners to better understand the practicality of all ideas, and hydrologic and economic implications of such actions.

What's next for our involvement?

Lindsay Chadderton:

We will continue to contribute to eDNA surveillance efforts aimed at determining the extent of the invasion above the electric barrier. And, if we can secure additional resources, we will try to determine their entry points and best way to control their movement. At the same time, we are looking to transition these tools to the state and federal agencies involved so they can scale up their surveillance efforts.

About the Author

Melissa Soule is a marketing manager for The Nature Conservancy.

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