Frequently Asked Questions

The term invasive carp refers to several species of related fish that originate from Southeast Asia. As many as ten types of carp are considered invasive around the world, but in the United States and Canada invasive carp refers to four of these species: bighead carp, black carp, grass carp and silver carp. These species have different characteristics, life cycles and distribution.  

Of the four kinds of invasive carp in North America, silver carp are the most well-known because they jump out of the water when disturbed, causing injuries and boat damage and limiting on-the-water recreation in areas where they are abundant. Learn more on the differences between the four species.

Invasive carp are found throughout the Mississippi River basin and parts of the Great Lakes basin but their distribution varies by species. 

Silver carp and bighead carp are the most widespread in the Mississippi River basin, including the Illinois River where there is potential access to Lake Michigan. Grass carp are the more widespread throughout the continent and present outside the Mississippi River basin. Unlike the others, grass carp historically have been detected in all the Great Lakes except Superior and there is currently a population of grass carp in Lake Erie. Less is known about black carp compared to the others. Because they are bottom-feeders, black carp are harder to find and efforts are underway to get more thorough information on their distribution. They have been found throughout the lower Mississippi River and some tributaries, including the Illinois River.  

More specific information is available from the U.S. Geological Survey’s Nonindigenous Aquatic Species Database showing the current distribution of black carp, grass carp, silver carp, and bighead carp in North America.

Invasive carp can quickly become abundant and destructive because of their voracious feeding habits, prolific reproduction and lack of predators. They out-compete native fisheries and disrupt the entire food web in aquatic ecosystems. They jeopardize the safety and quality of our outdoor experiences, causing physical harm to anglers and boaters and diminishing opportunities for all on-the-water recreation. They can have potentially devastating economic impacts in communities supported by recreational and commercial fishing and other outdoor recreation-related businesses. They threaten our broader economic stability the more they spread.

As adults, bighead carp, black carp, grass carp and silver carp have no natural predators in North American waters. They are only susceptible to predation when they are very young and still small. White pelicans and eagles have been observed feeding on small adult invasive carp, and largemouth bass also have been observed feeding on young invasive carp. Unfortunately, invasive carp produce many offspring that in turn grow quickly. In the absence of significant natural predation, invasive carp are therefore capable of overwhelming and outcompeting native fisheries.

Invasive carp were originally imported from Southeast Asia into the southern United States in the 1970s for controlling the growth of algae and vegetation in aquaculture ponds and wastewater treatment facilities. They entered the lower Mississippi River through flooding and accidental releases. From there, they spread west into the Arkansas, Red and White Rivers, south into the delta region, northeast into the Ohio River, east and south into the Tennessee and Cumberland Rivers, northwest into the Missouri River and north up the Mississippi River. After decades of multiplying and spreading, they are now found in many of the Mississippi River’s tributaries, including the Illinois River.  

A manmade connection known as the Chicago Sanitary and Ship Canal links the Illinois River to Lake Michigan. This canal system provides the most direct potential pathway for invasive carp to enter the Great Lakes. For more than 20 years, the U.S. Army Corps of Engineers has operated an Electric Dispersal Barrier System in the upper Illinois River about 37 river miles from Lake Michigan. Using underwater electrical currents, the system is designed to deter fish movement through the Chicago area waterway. It is one of the main tools used to prevent invasive carp from entering Lake Michigan.  

Silver carp and bighead carp are abundant in the Illinois River, with the adult population front located within the Dresden Island pool about 47 river miles from Lake Michigan. Members of the Invasive Carp Regional Coordinating Committee have been able to hold the line on their advancement for more than 10 years. Black carp have been found throughout the lower Mississippi River and some tributaries, including the Illinois River. Grass carp are the most widespread throughout the continent and historically have been detected in all the Great Lakes except Superior, including a population in Lake Erie. Individual grass carp have been found in the Chicago area waterway during routine monitoring, too. 

In addition to the potential access to Lake Michigan through the manmade connection known as the Chicago Sanitary and Ship Canal, members of the Invasive Carp Regional Coordinating Committee have focused on three other areas along the 1,500-mile divide between the Mississippi River and Great Lakes basins.  

Those areas were identified in the U.S. Army Corps of Engineers' Great Lakes and Mississippi River Interbasin Study as potential pathways for invasive carp movement into the Great Lakes during intermittent high-water events. Partners constructed barriers to reduce this risk at Eagle Marsh in Fort Wayne, Indiana, in 2016 and at the Ohio & Erie Canal in Akron, Ohio, in 2020. Barrier construction began in 2024 at the third location, Little Killbuck Creek near Wooster, Ohio.

The situation with grass carp is different from the other kinds of invasive carp in North America because grass carp already have been detected in all of the Great Lakes except Superior and there is currently a population of grass carp in Lake Erie. The Invasive Carp Regional Coordinating Committee and other partners have made it a priority to prevent grass carp from becoming established in the Great Lakes.  

Unlike the other kinds of invasive carp, it is legal in some states to use triploid grass carp – meaning they are bred to be sterile – for controlling algae and vegetation in ponds and other small, contained waterbodies. A national inspection and certification program is aimed at making the trade in triploid grass carp as safe as possible.  

Invasive carp management varies significantly in different locations and by species, since the four kinds of invasive carp in North America have life-cycle and distribution differences among them. There are three main components to our collective activities:  

• Conducting targeted mass removal efforts to reduce the abundance of invasive carp populations, decreasing the risk of expansion and inhibiting reproductive success
• Developing deterrent technologies and barriers to block or impede invasive carp movement
• Ongoing monitoring, including in areas invasive carp haven’t yet reached, to inform management strategies and detect their spread to new areas before they can become established

A significant recent development is the beginning of the construction phase for the Brandon Road Interbasin Project. The U.S. Army Corps of Engineers and the States of Illinois and Michigan are leading the development of this state-of-the-art, multi-layered deterrent project at the Brandon Road Lock and Dam on the Illinois River near Joliet, about 40 miles from Lake Michigan. By integrating different deterrent technologies, the project is designed to create a more robust line of defense against the upstream movement of invasive species toward the Great Lakes, including invasive carp. A number of the Invasive Carp Regional Coordinating Committee members’ technology research projects over the years helped inform its design. 

Given the impacts invasive carp have had in other areas, members of the Invasive Carp Regional Coordinating Committee are concerned that invasive carp becoming established in the Great Lakes would devastate our fisheries and have major impacts on the aquatic food web, recreation and the regional economy. When it comes to invasive carp, we are continually reminded that the old adage is true: An ounce of prevention is worth a pound of cure. 

The following are a few important studies related to the potential impacts of invasive carp in the Great Lakes: 

• Potential Effects of Bigheaded Carps on Four Great Lakes Habitats - NCCOS - National Centers for Coastal Ocean Science
• Binational Ecological Risk Assessment of Bigheaded Carps for the Great Lakes Basin
• GLMRIS-Brandon Road: The Great Lakes and Mississippi River Interbasin Study - Brandon Road integrated feasibility study and environmental impact statement - Will County, Illinois
• Socio-Economic Risk Assessment of the Presence of Grass Carp in the Great Lakes Basin
• Ecological Risk Assessment of Grass Carp for the Great Lakes Basin

Eradicating invasive species is expensive, time intensive and almost always impossible in large, open aquatic ecosystems. Prevention is the most cost-effective solution, which is why the Invasive Carp Regional Coordinating Committee is leveraging resources around managing the invasive carp population in the Illinois River, blocking potential pathways for invasive carp to enter the Great Lakes and conducting ongoing monitoring. The situation with grass carp is different from the other kinds of invasive carp because they historically have been detected in all of the Great Lakes except Superior and a population exists in Lake Erie. Preventing that population from becoming self-sustaining is a priority. 

There is currently no evidence to suggest that the Great Lakes are home to self-sustaining populations of bighead carp, black carp or silver carp. The best indication of a self-sustaining population would be repeated captures of multiple year classes of both young and adult invasive carp, but intensive monitoring and fish sampling efforts have not found this to be the case. 

Great Lakes state and provincial agencies conduct intensive monitoring efforts to evaluate the status of grass carp in Lakes Huron, Michigan and Ontario, where detections have been documented, and in Lake Erie where a population exists and there is some recent evidence of reproduction. The Invasive Carp Regional Coordinating Committee and other partners have made it a priority to prevent grass carp from becoming established in the Great Lakes.  

If you catch an invasive carp in any of the Great Lakes or tributaries, please do not release the fish back into the water. Instead, freeze the fish in a sealed plastic bag, note the date and location where it was caught, and call your state or provincial natural resource agency. The same applies if you find a dead invasive carp.  

Everyone plays a role in preventing the spread of invasive carp. Educating yourself and others is key in the fight against these aquatic invaders.  

• If you catch an invasive carp, please do not release the fish back into the water. Instead, freeze the fish in a sealed plastic bag, note the date and location where it was caught, and contact your state or provincial natural resource agency. The same applies if you find a dead invasive carp.  
• Learn the difference between juvenile invasive carp and other young bait fish such as gizzard shad. Gizzard shad look very similar to young bighead carp and silver carp and can be inadvertently captured for bait and transported to new areas. Only use wild-caught baitfish in waters where they came from and don’t move live fish from one location to another. 
• Drain water from live wells and bilges before leaving any waterbody. 
• Become an ambassador for your watershed by helping others learn these simple steps.