Interview with Lindsay Chadderton, the Scientist Who Discovered the Asian Carp DNA Beyond the Barrier

You may not have heard of Lindsay Chadderton, but you've probably heard of one of his recent discoveries: Asian carp DNA found beyond an electric barrier on the Chicago Sanitary and Ship Canal, meant to keep the voracious, invasive fish out of the Great Lakes. His find has unleashed a wave of concern and action, including a massive fish kill to repair the barrier that netted a single dead carp and a subsequent netting operation that failed to pull in more of the fish. There also have been calls for closing a lock system to shipping, to make sure no more of the fish make it to the lakes, where they could out-compete native species and devastate the fishery.

Chadderton, Great Lakes aquatic invasives species director for The Nature Conservancy, took a break the other day to discuss the double helix with Treehugger.

TREEHUGGER: So you're the one that discovered the Asian carp DNA beyond the electric barrier. Tell me how that came about?

LINDSAY CHADDERTON: I am working as part of a collaboration between the Nature Conservancy and Centre for Aquatic Conservation at the University of Notre Dame. I have been part of the team that has developed this new DNA detection tool from its inception, and my role most recently has been to lead the field survey program.

TH: What was your reaction when you discovered that the barrier had apparently been breached? Were you surprised?

LC: Disappointment, and I guess an element of disbelief. I think we were all a little shocked and we went back over the data to make certain it was correct.

Having said that, I wasn't totally surprised. I think, largely, because all our results and data indicates that these fish were probably testing the electric barrier much earlier than people thought, and due to maintenance issues and the flooding associated with Hurricane Ike last year, it seems possible that fish could have bypassed the barrier.

TH: How significant do you think the find is?

LC: It is very significant, and our results have serious implications for the Great Lakes.

Unfortunately, we cannot tell how many fish have produced the DNA plume we have detected, but we have to assume that any fish present, if left to their own devices, are capable of establishing a self-supporting population. And while we don't know how they might respond in the Great Lakes, we do know from their history of invasions elsewhere in the U.S. and world that they are capable of reaching extremely high densities and having dramatic negative impacts on the ecology and food webs of the invaded waters.

TH: Is it likely there are many more Asian carp that have made it beyond the barrier, in your view?

LC: We have found DNA along the Cal Sag branch of the canal, suggesting there are a number of fish in the system, and there are still some areas of the canal that we haven't yet had a chance to survey or that we are still analyzing data from. So yes, there is potential we could find other areas with fish, but hopefully not.

TH: What do you think of the actions that have transpired since the DNA find, including the massive fish kill along six miles of the canal that came up with one dead Asian carp, and the netting operation by the Army Corps that didn't find any?

LC: The management agencies are taking these incursions very seriously and the rotenone treatment of the canal below the barrier was necessary as the barrier is critical to keeping further fish from moving upstream.

You see, it is a numbers game, and the more fish that get through, the harder it will be to stop them and the more likely it is that they can establish a self-supporting population.

So it's important that the barrier is maintained and the rotenone treatment was a necessary pre-requisite to enable critical maintenance to be carried out.

It was nice to see one Asian carp captured to validate our research results, as there has and I think continues to be a significant level of skepticism about our technique as this is really the first time it has been deployed on such an issue.

Credit: The Nature Conservancy.

As for the netting operations recently carried out in the upper most area where we have found Asian carp, it was a good start, but I think it needs and warrants much more of a fishing effort that uses a wider variety of techniques and innovations.

If the decision is made to close down the lock and dams, this will have major economic repercussions, and therefore it seems only right that every effort is made to try and catch these fish and reduce their numbers using whatever tools can be deployed.

The trouble is, we are trying to eradicate hopefully a small number of specific fish which requires a very different approach to that used by commercial fishers, who want to crop the most abundant and easy fish, or general fish ecologists, who typically want a relative measure of abundance or species richness.

These fish need to be systematically hunted down, and given the size of the values we are trying to protect, we need to accept a level of non-target impact and also be prepared to manipulate field conditions so they are more conducive to catching these fish.

More from TreeHugger:
Asian Carp Fever Grips Great Lakes
Was it Worth It? One Asian Carp Found After Six Miles of River Poisoned in Illinois

Tags: Chicago | Fish