COMMON
NAME: Grass Carp
Sometimes a grass carp may be referred to as a white amur.
SCIENTIFIC NAME: Ctenopharyngodon idella
Grass carp belong to the Cyprinidae family, the minnows and
the carps. Its genus Ctenopharyngodon is made up of the
Greek word "ktenos" meaning "comb", the Greek word "pharynx"
meaning "throat", and the Greek word "odous" meaning
"teeth". Referring to this fish's pharyngeal teeth. The
grass carp was first described by Valenciennes in 1844.
DISTRIBUTION: Grass carp are natively from eastern
Asia from the Amur River in Russia to the West River in
southern China. Currently the grass carp's range has
significantly increased. It has been introduced into about
70 countries around the world including the United States.
The grass carp can now be found in 45 states.
DESCRIPTION: The grass carp has an oblong body, a
round belly and a broad head. Above its color is a silvery
dark grey and the sides are lighter with a gold sheen and
the belly is whitish. The dorsal fin begins in front of the
fish's pelvic fins. It has large scales that resemble a
chain link fence. There are no teeth in the grass carp's jaw
but it does have pharyngeal teeth. The maximum-recorded
length of a grass carp is 5 feet and the maximum-recorded
weight is 100 pounds.
PATHWAYS/HISTORY: In 1963 the grass carp was
introduced into aquaculture facilities in Alabama and
Arkansas. The first report of these fish escaping into open
waters was in 1984 from the facility in Arkansas. Though
stocking had been made in Arkansas into lakes that were open
to stream systems. By 1970 there were reports of grass carp
being caught in the Mississippi River and the Missouri
River. From here the grass carp was being sighted all over
it was being continually stocked into new waters. Now there
are recorded grass carp sightings in Alabama, Arizona,
Arkansas, California, Colorado, Connecticut, Delaware,
Georgia, Hawaii, Idaho, Illinois, Indiana, Iowa, Kansas,
Kentucky, Louisiana, Maryland, Massachusetts, Michigan,
Minnesota, Mississippi, Missouri, Nebraska, Nevada, New
Hampshire, New Jersey, New Mexico, New York, North Carolina,
North Dakota, Ohio, Oklahoma, Oregon, Pennsylvania, South
Carolina, South Dakota, Tennessee, Texas, Utah, Virginia,
Washington, West Virginia, Wisconsin, and Wyoming.
Established populations of grass carp can be found in
Arkansas, Kentucky, Illinois, Louisiana, Missouri,
Mississippi, Tennessee, Texas and Minnesota.
DISPERSAL/SPREAD: Originally grass carp were
introduced into farm ponds to control aquatic vegetation.
They have escaped these ponds due to flooding and moved into
open waters. Stocking of grass carp is very common. Some
stocking have occurred in lakes with access to rivers and
streams, this has allowed the grass carp to spread into new
waters. Federal and state agencies have participated in
stockings as well as private pond owners. Escapees from
these introductions have contributed to the rapid range
expansion of the grass carp.
MANAGEMENT: To try to control the spread of grass
carp all 50 states have restrictions on their use. There was
an effort to try to create all female populations so that no
breeding would take place. These females were still fertile
so if there happened to be an accidental introduction of a
male, they could become a reproducing population. Since then
scientists have tried to create triploid individuals that
would be sterile and therefore they would be unable to
breed. Alaska, Oregon, Montana, North Dakota, Minnesota,
Wisconsin, Michigan, Massachusetts, Vermont, Maine, Maryland
and Rhode Island all prohibit any form of grass carp.
Hawaii, Iowa, Kansas, Missouri, Oklahoma, Arkansas,
Mississippi and Alabama have no restrictions at all on grass
carp. All of the remaining states have some form of
restrictions regarding grass carp as of 1994.
SPECIAL INTEREST: Grass carp are legal to stock in
Indiana as long as they are triploid, unable to breed. Visit
the Indiana Department on Fish and Wildlife's website for a
list of Indiana dealers who sell triploid grass carp.
LIFE CYCLE BIOLOGY AND LIFE HISTORY: The grass
carp can occur in lakes, ponds, pools and backwaters of
large rivers. It prefers to have large standing or
slow-flowing water with vegetation. They are a hearty
species that can tolerate temperatures from freezing to over
100o F., brackish water, and low oxygen situations. Female
carp release their eggs when the water temperature is
between 18o F and 23o F, and when the water level is rising.
The eggs must remain suspended until they hatch to survive.
The maximum age of a grass carp is 21 years old. Grass carp
primarily eat aquatic vegetation but they will eat detritus,
insects and other invertebrates if vegetation is scarce.
Because they eat aquatic plants grass carp are frequently
stocked as a biological control of vegetation.
RISKS/IMPACTS: In large numbers grass carp can
remove all aquatic vegetation from the water. If they do so
they eradicate habitat for invertebrates and juvenile
fishes. It also eliminates the food base for other fishes
and it remove all the forage for waterfowl. In a lesser
density of grass carp they can be selective feeders, which
increases the toxic plants availability. This can result in
algae blooms that can reduce the oxygen level in the water.
They also compete with invertebrates and fishes for food.
They have the ability alter the plant community, which can
in turn completely change the invertebrate community and the
fish community. One more risk that grass carp pose is that
it may be carrying a parasite or disease that could be
transmitted to our native fishes.
REFERENCES:
- Agbayani, Eli. Ctenopharyngodon idella: Grass Carp. 19 May
2004. Fishbase. 27 May 2004.
- Asian Carp. 11 Nov. 2002. U.S. Fish and Wildlife Service.
27 May 2004.
- Ctenopharyngodon idella. 21 Nov. 2003. Gulf States Marine
Fisheries Commission. 27 May 2004.
- Grass Carp. Florida's Fish and Wildlife Conservation
Commission. 27 May 2004.
- Nico, Leo and Pam Fuller. Ctenopharyngodon idella. 1 April
2001. U.S. Geological Survey. 27 May
2004.
- Seng, Phil, and Gwen White. Indiana Aquatic Nuisance
Species Management Plan. 1 Oct. 2003.
Indiana Department of Natural Resources. 27 May 2004.
