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Oklahoma Invasive Species
Oklahoma State University

Grass Carp/White Amur
Ctenopharyngodon idella

grass carp
Country of Origin: Originally, grass carp are native to large rivers in Asia, ranging from the Amur River in China and Siberia, as well as south of the West River in China and Thailand. 
History: The grass carp is thought to have been first released in Arkansas reservoirs during the 1960s with the hope that it would control prolific plant growth. Because the animal's ferocious appetite and this method of aquatic plant control was successful until the mid 1980s.
Intended Use: Grass carp were introduced as a method of control for aquatic plant populations.
Mode of Invasion:

Grass carp have been legally introduced into at least 35 states.  Most of these introductions have been the introduction of triploid (sterile) grass carp into ponds and small reservoirs; however, populations of Diploid (non-sterile) grass carp have been established by grass carp that have escaped from experiments in Lake Conroe.  Also illegal stockings have contributed to grass carp invasion.

Species Description:

The grass carp has an oblong body with fairly large scales on the whole body except for the head which has no scales and no barbels.  Grass carp are silvery to olive colored.  The grass carp typically reaches sizes of 65 to 80 pounds in its native habitat.  Although much larger individuals have been reported, some even reaching 400 pounds.

Map of Occurrence:

map

Effects of Invasion: It is not commonly known that grass carp are omnivorous as well as herbaceous. Reports show that they feed on more than 50 different food items, including aquatic plants, algae, invertebrates and vertebrates.  Due to this fact, grass carp are potentially harmful to populations of native species of fish, invertebrates, and aquatic plants.  In fact, major reductions of aquatic plants and their complete elimination can be caused by foraging activities of grass carp.
Control:

Many states only legalize triploid (sterile) grass carp to be stocked in fisheries. This is a precaution to keep the populations low.  The grass carp threat is thought to be so severe due to their invasive nature that in Texas, any angler who catches a grass carp in an area where triploid (sterile) carp are not known to exist, the fisherman must immediately remove the intestines of the fish.

References:

Texas Parks and Wildlife
http://www.tpwd.state.tx.us/huntwild/wild/species/gcarp/

 

GRI: Geological Resources Institute
http://www.gri.msstate.edu/lwa/invspec/grass_carp.php

 

The USGS website http://nas.er.usgs.gov/queries/FactSheet.asp?speciesID=51