California Aquatic Invasive Species (AIS)
University of California
California Aquatic Invasive Species (AIS)

Invasive Fish Species

Grass Carp

Scientific Name

Ctenopharyngodon idella - Visit ITIS for full scientific classification. 


  • Large, freshwater fish.
  • Elongated body, with a wide scale-less head.
  • Olive brown color on back, silvery sides, white to yellow belly, dark fins, and a gray head.
  • Scales are large with dark edges. Long, serrated teeth in throat for chopping and grinding aquatic vegetation.
  • Sexually mature at about 2 feet and 10 pounds, but not uncommon for them to reach lengths greater than 3 feet long, and weigh over 60 pounds.
  • Possible for individuals to reach nearly 100 pounds.
  • Because they aggressively eat aquatic plants, they are sometimes used for weed control. If sighted, find out if they were placed there.
  • Commonly found in shallow areas of rivers, but also found in quiet waters of ponds, irrigation canals, and lakes.
  • Grass Carp can tolerate extreme environmental conditions including: low oxygen levels, brackish water, and temperatures ranging from 32-100 degrees F. 
Invasion Pathways and Distribution
  • In 1963, Grass Carp were introduced to control aquatic plants in a fish farm in Arkansas.
  • They spread from the Arkansas River to the Mississippi River, and are now found and continue to spread throughout the U.S.
  • Asian Carp can spread through fish farming activities, legal and illegal stocking, accidental inclusion in shipments, escape or release to open waters, and natural dispersal.
  • Native to China and Russia.
  • See USGS for a map of current U.S. distribution. 
Life History
  • Mating season begins in the summer when the water is warmer than 65 degrees F.
  • Females migrate to areas of moderate water flow in order to release their eggs into the water column.
  • Enormous reproductive capabilities.
  • Possible for females to release over 1 million eggs in a single season. 
  • Compete with native fishes for resources.
  • Aggressively eats aquatic plants, which physically alters habitat.
  • Habitat changes affect native fishes, birds and invertebrates.
  • If aquatic plants are not around they will dig in sediment causing bank erosion, impacting the habitat for native species.
  • Grass Carp can also carry diseases that can spread to native fishes. 
References and Useful Links

For references by category and links to other useful AIS sites see our LEARN MORE page.

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