The health of our Great Lakes and the plants, animals and people that rely on them are threatened by four invasive Asiatic carp species:
Their most likely introduction to the Great Lakes is through the Chicago Area Waterway System (CAWS.) Current barriers are insufficient in stopping the invaders. As a new barrier system is devised and installed, learn about the problem and test your creativity by designing your own method of keeping them out of the Great Lakes!
The following information was transcribed from an activity lesson plan. Contact Joseph Gruzalski at firstname.lastname@example.org for more information or to request a PDF version of the design challenge. Check out our travelling trunks (including an invasive carp-specific trunk) available to borrow from the Paul H. Douglas Center for Envrionmental Education here.
Meet the Carp
The term "Asian carp" can be confusing. It's not just one kind of fish. It's more of an umbrella term that includes many different species. In China, four carp species have been aquafarmed for food and medicine for over 1,000 years. These are collectively known as the "Four Domesticated Fish." These same four species have all been seperately introduced into the Mississippi River watershed. Out of their native range they are invasive; they reproduce quickly, outcompete native fish for food, and have no natural predators to control their numbers. Since their introduction in the 1970's, they have been rapidly destroying habitat and moving north towards the Great Lakes.
The Hungry Hungry Carp
Bighead carp devour planktons, a diverse collection of tiny aquatic organisms. Although small in size, planktons' role in the Great Lakes is critical: nearly every organisms in the lakes are directly or indirectly dependent on planktons for food. Both bighead and silver carp are planktivores, they use their large mouths to gulp up massive quanitites of them. This threatens the entire food web and in turn our 7 billion dollar fishing industry.
See Carp. See Carp Fly!Silver carp are known for their areial acrobatics. They can leap over 10 feet out of water when startled by sounds like a boat motor. This transforms the area above the water into a danger zone; their jumping habits introduce the risk of getting struck by a fish that can be over 3 feet long and weigh over 60 pounds! This can seriously harm people and destroy costly equipment that get in the fish's way.
Mussel-ing Their Way into the Great Lakes
Molluscivores. Mollusc-eaters. Black carp threaten our native mussels and clams. There are over 40 species of Great Lakes mussels; most are considered endangered or are restricted to protected areas. The abundance of invasive zebra and quagga mussels could help black carp establish and quickly spread throughout the region. If they infect our streams, their eating habits could decimate remaining populations of endangered native mussels whose very existence is at stake.
Aquatic Plants are Greener on the Other Side (the side without grass carp)Like their name suggests, grass carp are herbivores. Similar to their cousins, they are voracious eaters. They can weigh over 110 pounds and consume 40% of their body weight in plants every day. This quality makes our Great Lakes wetlands and organisms dependent on underwater vegetation especially at risk. This is the only species of invasive carp currently found breeding within the Great Lakes watershed, where it has been discovered spawning in Lake Erie tributaries. Establishment may be imminent.
Our Great Lakes
They hold over 20% of the world's liquid freshwater. They have over 4,500 miles of coast. They're critical to the 34 million people who live around them. These five lakes provide us food. They provide us water. They provide us enjoyment. They are also habitat to many other species who depend on them to survive.
What's a watershed?
A watershed is a land area where all of the water in it eventually drains to the same spot. The Great Lakes watershed includes parts Canadian provinces Ontario and Quebec as well as 8 American states: Illinois, Indiana, Michigan, Ohio, Minnesota, New York, Pennsylvania, and Wisconsin. Water makes its way to the Great Lakes, travels through them and empties into the Atlantic Ocean through the St. Lawrence River.
The Mississippi River watershed borders the Great Lakes watershed to the south and west. This watershed is the fourth largest in the world. It empties all of its water into the Gulf of Mexico through the Mississippi River. The CAWS (Chicago Area Waterway System) connects this watershed to the Great Lakes by a series of dredged canals and streams. A fish can now swim from the Mississippi River and enter Lake Michigan, something that would have been impossible before human alteration of the waterways.
Monitoring for Invasive Carp
Organisms constantly drop bits of their DNA. Fish leave blood and tissue in the water as they swim. This "environmental DNA" or eDNA can be analyzed in water samples to determine what species have been in the water. The University of Notre Dame helped perfect the method, and testing for eDNA is now a standard practice for detecting the presence of invasive carp species. Biologists collect water samples in the field and analyze them for carp DNA in a lab. Although eDNA cannot tell us where the species is specifically or how many there are, it is very useful. It gives us a strong warning of a new threat and could ultimately help prevent invasives establish in a new area.
Barriers to Stop the Carp
The Army Corps of Engineers have installed two barriers in the CAWS to block the carps' connection between the Mississippi River watershed and Lake Michigan. These "electric dispersal barriers" produce an underwater electric field that shocks fish as they try to swim through. The first of these barriers has operating since 2002 and a second one was installed in 2013. Although they are a strong deterrent, both big and small invasive carp have been found on the other side of the barriers.
Because occasional carp make their way past the electric barriers and into the streams and lakes within miles from Lake Michigan, plans are in progress to introduce new ways to stop intruders. Scientists, engineers, and designers are working on solving this connection crisis right now. The final draft of a report to construct a new barrier system at Brandon Road has been approved by the Army Corps of Engineers and now awaits Congressional approval. Check out the project's website for updates here.
Part of what makes solving this problem especially tricky is that the waterway needs to stop invasive species from going upstream, while at the same time allowing for boat and ship traffic to continue passing through.
Last updated: September 10, 2020