Lindsay Chadderton is director of the Conservancy’s Great Lakes Aquatic Invasive Species program.
Most of the stories we tell at The Nature Conservancy have a happy ending — a precious piece of land is saved from future development or rare species are brought back from the brink of extinction. While the project I’ve been working on — a tool to find out if invasive carp are close to invading Lake Michigan — certainly is a success from a scientific point of view, the results have qualified our celebration. Our research indicates that one of the most infamous of these species, Asian carp, have entered the lake. If the carp thrive, they may pose a threat to the other Great Lakes.
I’ve been working with my colleagues at the University of Notre Dame to develop a sensitive, early detection screening tool to search for signs of silver and bighead carp in the canals south of Chicago. Scientists have documented at least 180 non-native aquatic species that have established populations in the Great Lakes, and of those, about 20 species have become invasive, causing significant ecological and economic harm. Our goal is to monitor their movement and prevent these invasive species from becoming established in Lake Michigan. We know from working on other aquatic invasives that the earlier we can detect a new invasion, the better chance we have of controlling an emerging population.
Asian carp have been known to disrupt the ecological balance of similar freshwater systems, such as the Mississippi River, harming humans and the biological integrity of the river as well. The DNA we found suggests a number of Asian carp are present in the Chicago canals that connect to Lake Michigan, but we really can’t tell the extent of their population at this point. Our sampling is similar to driving on a dirt road when all you can see is a dust cloud — you know at least one vehicle came in front of you to create the cloud, but you can’t tell how many were there. We are, in effect, sampling a dust cloud or plume produced by the fish.
Regardless of how many Asian carp we may be dealing with, taken together all our results speak for themselves — Asian carp have made it to Lake Michigan, leaving behind a trail of evidence. How we deal with this is another issue, but for me and the team at Notre Dame, the debate now needs to shift how we respond to this discovery, and not the merits of the method.
Sadly, this also means the battle to keep Asian carp out of the Great Lakes is really just beginning. This isn’t likely to give us a traditional happy ending, but a satisfactory celebration of some sorts would be a welcome outcome.
(Image: Asian carp at Chicago’s Shedd Aquarium. Credit: kate.gardiner/Flickr through a Creative Commons license.)