Grass Carp

Ctenopharyngodon idella

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Image of grass carp
Joseph R. Tomelleri. Used with permission.
Other Common Name
White Amur
Family

Cyprinidae (minnows) in the order Cypriniformes (carps, minnows, and loaches)

Description

A large member of the minnow family. Grass carp are large and  thick-bodied, silvery, with a broad, blunt head, a short, pointed dorsal fin, and a terminal, transverse mouth. Both dorsal and anal fins lack spines at the leading edge. The scales appear cross-hatched, similar to those of a common carp. The anal fin is closer to the tail fin than in native minnows.

Size

Total length: 12 to 24 inches; maximum length 48 inches. Weight: up to 50 pounds or more.

Habitat and conservation

Native to eastern Asia; introduced to the United States as early as 1963, it quickly dispersed and spread from its points of introduction. Today it is found in large rivers and in natural and artificial impoundments. It is stocked in ponds and lakes to control vegetation, but it commonly removes too much vegetation and instead deteriorates the habitat for game fish.

Foods

Herbivorous, feeding on a variety of plant matter. The young feed mainly on small crustaceans and other invertebrates, but when they're about 8 inches long they shift mostly to aquatic vegetation, though a wide variety of plant and animal material is also eaten, including filamentous algae. This species has a voracious appetite and can eat more than the equivalent of its body weight in a day. Interestingly, their digestive system is not very efficient, so about half of the food is passed through undigested.

image of Grass Carp Distribution Map
Distribution in Missouri

Widely distributed in the Missouri, Mississippi, and St. Francis rivers. Occasionally found in nearly any stream in the state, but most of these are the result of escape from impoundments where they have been stocked.

Status

Grass carp are harvested commercially. As a sport fish, this active, strong-swimming fish will jump spectacularly to avoid a seine. An exotic fish, its introduction to our state is controversial. Also called "white amur," from its native range in the Amur River, one of the largest rivers in the world, which forms the border between Russia and eastern China.

Life cycle

Individuals can live up to 20 years. Spawning apparently occurs May through July, in the channels of large rivers, and the eggs hatch while they are carried along in suspension by the river currents. Larval grass carp have been collected as far as 5 miles above the mouths of tributary streams. Lower reaches of tributaries and overflows of big rivers apparently serve as nursery areas. Grass carp can grow from 5 to 26 inches in a single year. By their third summer of life, they can be 24 to 34 inches long, and weigh 6 to 14 pounds.

Human connections

Thousands of pounds of grass carp are commercially harvested from the Missouri and Mississippi rivers annually. It makes about 5 percent of the commercial fish harvest in the Missouri River. In its native range in Asia, it is a highly valued food fish, where it is raised in ponds. In our country, it is principally used to control aquatic vegetation in lakes and ponds.

Ecosystem connections

Introducing grass carp into our country was and is controversial because of the possible harmful effects on native species and habitats. Their populations and distribution have not yet stabilized, so their effect is still unknown.