Fighting Invasive Carp: USGS Science for Detection, Deterrents and Removal

The four invasive carp. Bighead and silver carp are sometimes called bigheaded carp, for their large heads. Photographs by Ryan Hagerty and Sam Stukel, U.S. Fish and Wildlife Service.

Four unwanted fish

Invasive species are non-native organisms whose introduction causes, or is likely to cause, economic or environmental harm, or harm to the health of people, animals or plants. The four invasive carp were brought to the United States from China for specific jobs, and all escaped between the 1970s and 1990s:

They are now established in the Mississippi River Basin and several of its subbasins — the Illinois, Ohio, Missouri and Tennessee/Cumberland. Naturally reproducing grass carp also live in the upper Colorado River and Lake Erie, where agencies are working to reduce them.

Established ranges of the four carp, from the USGS Nonindigenous Aquatic Species Database.

Why act now

• Native fish: bighead and silver carp have harmed native fish throughout the Illinois River.
• The Great Lakes: they have spread through the whole Illinois River and could reach the Great Lakes through the Chicago Area Waterway System, threatening a fishery worth $7 billion a year.
• The Southeast: dense populations in Kentucky Lake and the Tennessee and Cumberland Rivers threaten fisheries and boating.
• Lake Erie: reproducing grass carp could destroy water plants, setting off a cascade of harm — more wave erosion and harmful algal blooms that pollute water supplies.
• Mussels: black carp, spreading up the Mississippi and into the Missouri, Ohio and Illinois, threaten native and endangered mussels.

The immediate goal: stop all invasive carp from spreading into southeastern rivers and the Great Lakes, and reduce or eradicate grass carp in the Great Lakes.

USGS science in action

The USGS develops tools for managers within an integrated pest management framework — combining biological, chemical, cultural and physical tools to increase the chance of success while limiting ecological, economic and cultural harm.

• Detection: environmental DNA (eDNA) to detect carp in spawning areas, and sonar, with state and university partners, to count carp before and after removal. The Nonindigenous Aquatic Species database is the most complete record of aquatic invasive species in the country.
• Structured decision making: processes that found information gaps and guided action, leading to local management plans for grass carp in the Great Lakes and silver carp in the Tennessee and Cumberland Rivers.
• Population modeling: the SEIcarP model, built with the Fish and Wildlife Service and universities for the Illinois River and being adapted for other Mississippi subbasins, uses fish movement and harvest data to guide population reduction.
• Egg drift modeling: the Fluvial Egg Drift Simulator predicts where carp eggs and larvae end up; it has identified spawning areas for grass carp in Lake Erie tributaries and silver carp in the Illinois River.
• Deterrents: silver carp avoid certain noises, such as outboard motors, so USGS and university researchers identified sound patterns that repel silver and bighead carp and built an Acoustic Deterrent System — a 105-foot steel structure with 16 speakers, installed with the Army Engineer Research and Development Center in February 2021 in the lock approach of Lock and Dam 19 near Keokuk, Iowa. Other work tests a bioacoustic fish fence of bubbles, light and sound, and carbon dioxide captured from ethanol production, which carp avoid; the USGS led the registration of Carbon Dioxide-Carp as an aquatic pesticide.
• Baits: food-based attractants to raise capture rates, tested for algae in Illinois River backwaters (2014–2016) and for grass carp in Lake Erie (2021), and research on whether feeding sounds attract other carp.
• Pesticides: particles sized like the food bighead and silver carp prefer, which in lab tests killed them at high rates with little or no harm to native fish.
• Mass removal: a modified Unified Method, from China, using sonar and underwater sound to herd carp; it has removed hundreds of thousands of pounds of carp from backwaters of the Illinois, Mississippi, Missouri and Tennessee/Cumberland Rivers.
• Tracking: the FISHTRACK database of carp movements from acoustic, radio and satellite telemetry, used to target harvests, test barriers and improve models; in the Great Lakes, telemetry guides grass carp removal.

The Acoustic Deterrent System installed near Keokuk, Iowa, February 2021. Photograph by Mark Cornish, U.S. Army Corps of Engineers.

Field trials have included carbon dioxide and sound deterrents at Emiquon Preserve, Illinois (2016–17); temporary sound deterrents in the Chicago Area Waterway System during maintenance of its electric barrier; a model of sound at Brandon Road Lock and Dam on the Illinois River to plan a speaker array; new sound signals tested on wild fish in the Wabash River (2019); carbon dioxide injected into a navigation lock (2019), whose registration the EPA approved that year; and, from 2020, monitoring at Lock and Dam 19 and at Barkley Dam on the Cumberland River.

Silver (left) and bighead (right) carp collected in the Illinois River. Photograph by the U.S. Geological Survey.

Fish and Wildlife Service crews net leaping silver carp in the Fox River. Photograph by Ryan Hagerty, U.S. Fish and Wildlife Service.

Sources

Based on U.S. Geological Survey, "Science and Innovation for Battling Invasive Carp," Fact Sheet 2022–3012, USGS; a work of the United States government in the public domain. The photographs and maps are restored from the fact sheet's PDF.