In 1970s, silver carp were brought to the US for aquaculture. Now the jumping fish threaten a $20 billion Great Lakes industry

Silver carp that were brought to the US in the 1970s for aquaculture and water-treatment facilities have spread across the Mississippi River basin and are now raising concerns about the Great Lakes. Hundreds of the invasive fish have been detected in the Illinois River about 80 miles from Lake Michigan, while their established population front is even closer.

The discovery has renewed concerns about what could happen if silver carp establish a reproducing population in the Great Lakes. The fish consume large amounts of microscopic plankton that form the base of aquatic food webs, potentially putting pressure on native fish populations.

The threat also extends beyond the ecosystem. Silver carp are known for jumping out of the water when startled by boat motors and other disturbances. Their behavior has made some waterways with large carp populations hazardous for recreational boaters.


The Great Lakes boating industry is estimated to be worth about $20 billion, while the region's fishery is valued at nearly $5.1 billion. An established silver carp population could therefore affect both the ecology of the lakes and the industries that depend on them.

How silver carp reached the US

Silver carp were introduced to the United States in the 1970s for use in aquaculture and water-treatment facilities. The fish were valued for their ability to consume algae and other organisms in the water.

Over time, silver carp escaped into connected waterways and spread through the Mississippi River basin.

The Illinois Waterway has become the main pathway of concern because it connects the Mississippi River basin with waterways around Chicago that eventually reach Lake Michigan.

Federal and state agencies have spent years trying to prevent the fish from moving farther upstream.

Hundreds of young fish found near Lake Michigan

The Illinois Department of Natural Resources recently detected several hundred silver carp in the Marseilles Pool of the Illinois River. The fish were between 4 and 6 inches long and were found about 80 miles from Lake Michigan.

The discovery represents the farthest upstream that small invasive carp have been recorded since monitoring began 16 years ago.

The presence of young fish is significant because it could indicate that silver carp are reproducing nearby or successfully colonizing new areas at an early life stage.

Officials suspect there could be spawning grounds farther upstream and are monitoring the area. Recent flooding and water temperatures created conditions favorable for carp spawning.

The established adult silver carp population front, however, remains in the Dresden Island Pool, about 47 river miles from Lake Michigan. Officials have not found evidence of silver carp reproduction above that location.

Individual fish have occasionally been detected farther upstream, but extensive monitoring has not identified a reproducing population near Lake Michigan.

Why the Great Lakes are vulnerable

Silver carp are filter feeders that consume phytoplankton and zooplankton. Those organisms sit near the bottom of aquatic food webs and are particularly important to young native fish.

A large silver carp population can therefore compete with native species for food.

Research on the Upper Mississippi River System has found a negative relationship between silver carp abundance and adult native sport-fish abundance. Researchers identified competition for zooplankton during early life stages as a likely explanation.

Scientists have also examined whether silver carp could actually survive in the Great Lakes.

Much of Lake Michigan has relatively low productivity compared with rivers and reservoirs where silver carp thrive. That could limit the amount of food available to the fish.

But researchers have found that the entire lake does not need to provide ideal conditions for an invasion to succeed.

River mouths, productive nearshore areas and other zones with higher concentrations of algae could provide enough food for silver carp to survive and grow. These areas could serve as refuges for an invading population.

Lake Erie presents another concern because it is generally more productive. Research has found that both silver carp and bighead carp could encounter sufficient food there.

The bigger question is whether enough fish could reach the Great Lakes, find suitable habitat and reproduce successfully.

The fish that can jump into boats

Silver carp are also unusual among invasive species because they can create a direct hazard for people on the water.

The fish can leap out of the water when startled by boat motors and other disturbances. USGS reports that silver carp can jump as high as 10 feet.

In heavily invaded waterways, the behavior has created problems for recreational boaters. Large carp can strike passengers, damage equipment or land inside boats.

A fish weighing several dozen pounds can become a serious hazard when it suddenly leaves the water.

That behavior could affect how people use parts of the Great Lakes and their connecting waterways if silver carp become established.

$1.15 billion project is designed to stop them

Federal and state agencies are spending heavily to prevent silver carp from reaching Lake Michigan because removing an established population would be far more difficult.

The main defense is being developed at Brandon Road Lock and Dam near Joliet, Illinois, a strategic point between the established carp population and Lake Michigan.

The Brandon Road Interbasin Project has an estimated cost of about $1.15 billion.

The project is designed to use several deterrents at the same location, including an electric barrier, underwater acoustic equipment and a bubble curtain. Other systems are intended to prevent fish from moving alongside commercial barges and to push fish away from the lock area.

An electric barrier system has already operated farther upstream near Romeoville for more than two decades.

But construction of the Brandon Road project was paused earlier this month after the U.S. Army Corps of Engineers ordered the work to stop. Conservation groups say they have not received a clear explanation for the decision.

Michigan's Department of Natural Resources said it was working to understand the reason for the pause as part of a federal administrative review and reaffirmed its support for completing the project.

Millions of pounds of carp are being removed

Authorities are also trying to reduce the number of invasive carp before they reach the barriers.

More than 7 million pounds of invasive carp were removed from the Illinois River during 2025, according to the federal partnership coordinating the response.

The strategy is intended to reduce population density and limit the number of fish moving toward the invasion front.

Silver carp are not the only invasive carp species being monitored.

Bighead carp also consume plankton and occupy much of the same river system. Black carp feed on mollusks and are spreading through parts of the Mississippi basin.

Grass carp present a different concern because individual fish have already been found in most of the Great Lakes, while natural reproduction has been documented in tributaries of Lake Erie.

Silver carp remain a particular concern because their established population sits along a direct aquatic pathway toward Lake Michigan and their feeding behavior could put pressure on native fish.

The invasion is not inevitable

Despite the growing concern, officials have not found evidence of a self-sustaining silver carp population near Lake Michigan.

The established population front has remained in roughly the same area for more than a decade. Extensive monitoring continues, and agencies have so far been able to detect and respond to fish found farther upstream.

That gives authorities an opportunity that was not available with some earlier Great Lakes invasions.

Zebra mussels, quagga mussels and round gobies were already spreading by the time the full scale of their ecological effects became clear. With silver carp, managers know where the main source population is, understand the potential invasion route and have identified Brandon Road as a key point where the fish can potentially be stopped.

The stakes extend beyond the Great Lakes ecosystem.

If silver carp establish a reproducing population, they could compete with native fish for food, alter aquatic food webs and create new hazards for people using the waterways.

For now, the fish remain outside the Great Lakes. But with young silver carp detected just 80 miles from Lake Michigan, efforts to keep them out are facing a new test.