What Are Invasive Carps?

The term "invasive carp" is used to refer to four species of fish introduced into the United States in the 1960s and 1970s for use in aquaculture ponds. Through flooding and accidental releases, invasive carp found their way into the Mississippi River system and are now thriving in waters of the United States. These four species are similar, but they have unique diets and are found in different locations.

Bighead carp and silver carp are filter feeders that remove plankton from the water and are established throughout much of the Mississippi River Basin. Bighead and silver carp are often collectively referred to as bigheaded carp.

Black carp consume freshwater mussels, snails, and other mollusks. They have a limited but expanding range in the Mississippi River.

Grass carp specialize on eating submerged aquatic plants and are widely distributed in the United States, with growing numbers of reproducing populations, including in the Sandusky River in the Lake Erie watershed. Of the four species, grass carp is the only species being used as a bio-control agent for nuisance aquatic vegetation throughout much of the United States.

Where Are Invasive Carps?

The following series of maps show the expanding range of all four species of invasive carp in rivers throughout the United States. Data points shown on the maps are documented sightings or records from the USGS Nonindigenous Aquatic Species (NAS) Database. Below, the map on the left shows the spread of bighead carp (red dots) throughout rivers of the United States from 1981 to 2020. One bighead carp was captured in Lake Erie in 1995 and two were captured in 2000. The map on the right displays the expansion of silver carp (orange triangles) over a similar time period. 

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Documented bighead carp records (left) from September 1981 to May 2020 and silver carp records (right) from January 1981 to May 2020. Data source: USGS NAS Database.

The maps below show the expansion into the United States of grass carp (green squares on the left) from 1972 to 2020 and black carp (yellow diamonds on the right) from 2003 to 2020.

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Documented grass carp records (left) from November 1972 to July 2020 and black carp records (right) from March 2003 to July 2020. Data source: USGS NAS Database.

Invasive Carp Research At USGS

Invasive carp are fast growing and compete with native aquatic species for food and habitat resources. In areas where invasive carp are abundant, they harm native fish communities and interfere with commercial and recreational fishing. Silver carp are easily disturbed and will jump out of the water, often damaging boats and injuring passengers.

The USGS conducts invasive carp research focused on early detection, risk assessment, and the development of control tools and strategies. The goals are to prevent the establishment of invasive invasive carp in the Great Lakes and to reduce their impacts in the Mississippi River Basins and elsewhere.

Managers can use the information, tools, and strategies for early detection of invasive carp in order to control the population once their presence has been discovered. New detection and control tools are designed to also be effective for other invasive species and application in many different regions.

This USGS research focus addresses the goals of the Great Lakes Restoration Initiative (GLRI), a multi-agency collaboration started in 2010 to protect and restore the Great Lakes. 

As a member of the Invasive Carp Regional Coordinating Committee (ICRCC), which guides invasive carp efforts, the USGS works closely with federal and state agencies, Canada, and other partners to address high-priority invasive carp issues and to provide science for management decisions.

The USGS has gained extensive knowledge of invasive carp biology and life history over the past 30 years. Life history refers to the pattern of events related to an organism's survival and reproduction. That knowledge guides the design, development, and application of control strategies. This is essential for developing approaches in line with modern principles and practices of integrated pest management (IPM). 

IPM is a process used to solve pest problems while minimizing risks to people and the environment. Use of an integrated and adaptive approach helps managers focus monitoring and control efforts. These multiple areas of research are interrelated.

Effective management of any invasive species relies on early detection. Detection of invasive carp using traditional capture gears is difficult when their populations are small because these fish avoid nets and are sensitive to the sound of boat motors. 

Scientists perform risk assessments to estimate the likelihood that a species may invade, spread, or cause economic or ecological damage; to identify ecosystems or habitats most likely to be invaded; and to estimate other risks associated with species' invasions. Risk assessments are part of the IPM process and help managers focus their monitoring and control efforts.

In collaboration with partners, USGS scientists continue to develop and test containment and control tools and technologies for invasive carp to prevent their future spread, reduce their population levels, and minimize their effects.

The integrated pest management approach investigates options for combined implementations of tools in strategic locations.

The Future...

The negative effects of invasive invasive carp in North America are far reaching and have real potential to expand and intensify. A wide variety of organizations are working to keep these invasive fish out of the Great Lakes and other aquatic ecosystems, and control them in their current locations, including the Ohio River and Mississippi River Basins.

Contributions by the USGS to inform integrated pest management are particularly important, especially the objective evaluation of tools for control. Numerous USGS Science Centers will continue this important research, coupled with education, synthesis, publication, and other forms of knowledge transfer that inform management solutions.