As the name implies, grass carp eat grass and other underwater plants but will also eat insects and decaying plants. This appetite lead to its importation in the mid1970s for use in controlling nuisance vegetation in waterways and ponds. It is considered an invasive fish and is already established in most of the Mississippi River.
See the interactive map showing the spread of the invasive grass carp produced by the U.S. Geological Survey.
- Commercial fish farms and federal and state agencies use sterile grass carp to control aquatic plant growth. Before release, each fish must be tested and certified to avoid accidental release of individuals capable of reproducing.
- Grass carp can consume up to 40% of their body weight per day in aquatic vegetation.
Key ID Features: Grass carp are large fish with a torpedo-shaped body, blunt head, and moderately large scales. The scales’ dark edges give the fish a cross-hatched appearance. Its back is olive brown with silver sides and a white belly. It can reach 62 inches in length and 81 pounds.
Present in Park: No breeding populations are known to be in the Mississippi National River and Recreation Area, although individual fish have been caught in the Cottage Grove area south of the Twin Cities.
Habitat: Large warm rivers and connected lakes.
MN Status: On Minnesota Department of Natural Resources prohibited invasive species list, which means import, possession, transport, and introduction into the wild is prohibited. Unlike the silver, bighead, and black carp, it is not federally listed as injurious.