The Nonindigenous Occurrences section of the NAS species profiles has a new structure. The section is now dynamically updated from the NAS database to ensure that it contains the most current and accurate information. Occurrences are summarized in Table 1, alphabetically by state, with years of earliest and most recent observations, and the tally and names of drainages where the species was observed. The table contains hyperlinks to collections tables of specimens based on the states, years, and drainages selected. References to specimens that were not obtained through sighting reports and personal communications are found through the hyperlink in the Table 1 caption or through the individual specimens linked in the collections tables.

Ctenopharyngodon idella
Ctenopharyngodon idella
(Grass Carp)

Copyright Info
Ctenopharyngodon idella (Valenciennes in Cuvier and Valenciennes, 1844)

Common name: Grass Carp

Synonyms and Other Names: white amur, silver orf; Ctenopharyngodon laticeps Steindachner, 1866, Leuciscus idella Valenciennes in Cuvier and Valenciennes, 1844, Ctenopharyngodon idellus

Taxonomy: available through www.itis.govITIS logo

Identification: Grass Carp is a large member of the minnow family with a body which is moderately compressed laterally. Its mouth is terminally located on a wide head and eyes are small and low on the head. It lacks barbels. It is olive-brown on the dorsal side, with silver sides and a white belly. Scales are large with dark edging. The dorsal fin origin is anterior to the pelvic fin origin and it has a short caudal peduncle. It differs from goldfish (Carassius auratus) and common carp (Cyprinus carpio) in having a shorter dorsal fin (only 7-8 rays) and from Hypophthalmichthys species (Bighead and Silver carps) in having fewer anal rays (9 or fewer) and fewer but larger lateral scales.

Distinguishing characteristics were given in Berg (1949), Shireman and Smith (1983), and Page and Burr (1991). Keys that include this species and photographs or illustrations were provided in most of the more recently published state and regional fish books (e.g., Robison and Buchanan 1988; Etnier and Starnes 1993; Jenkins and Burkhead 1994; Pflieger 1997).

Size: 125 cm.

Native Range: Eastern Asia from the Amur River of eastern Russia and China south to West River of southern China (Lee et al. 1980 et seq.; Shireman and Smith 1983).

Hydrologic Unit Codes (HUCs) Explained
Interactive maps: Point Distribution Maps

Nonindigenous Occurrences:

Table 1. States with nonindigenous occurrences, the earliest and latest observations in each state, and the tally and names of HUCs with observations†. Names and dates are hyperlinked to their relevant specimen records. The list of references for all nonindigenous occurrences of Ctenopharyngodon idella are found here.

StateFirst ObservedLast ObservedTotal HUCs with observations†HUCs with observations†
AL1976202231Alabama-Coosa; Bear; Black Warrior-Tombigbee; Cahaba; Guntersville Lake; Lower Black Warrior; Lower Choctawhatchee; Lower Conecuh; Lower Coosa; Lower Elk; Lower Tallapoosa; Lower Tombigbee; Middle Alabama; Middle Chattahoochee-Lake Harding; Middle Chattahoochee-Walter F; Middle Coosa; Middle Tallapoosa; Middle Tennessee-Elk; Middle Tombigbee-Chickasaw; Middle Tombigbee-Lubbub; Mobile Bay; Mobile-Tensaw; Noxubee; Perdido Bay; Sepulga; Sipsey Fork; Upper Black Warrior; Upper Choctawhatchee; Upper Conecuh; Upper Tallapoosa; Wheeler Lake
AZ197020238Brawley Wash; Canyon Diablo; Lower Salt; Lower Verde; Middle Gila; Rillito; Upper Santa Cruz; Yuma Desert
AR1968202240Bayou Bartholomew; Bayou Macon; Bayou Meto; Beaver Reservoir; Big; Bodcau Bayou; Bull Shoals Lake; Cache; Cadron; Dardanelle Reservoir; Elk; Fourche La Fave; Frog-Mulberry; Illinois; Lake Conway-Point Remove; Little Missouri; Little River Ditches; Lower Arkansas-Maumelle; Lower Black; Lower Little Arkansas, Oklahoma; Lower Mississippi-Greenville; Lower Mississippi-Helena; Lower Mississippi-Memphis; Lower Neosho; Lower Ouachita-Smackover; Lower St. Francis; Lower Sulpher; Lower White; Lower White-Bayou Des Arc; McKinney-Posten Bayous; North Fork White; Ouachita Headwaters; Poteau; Robert S. Kerr Reservoir; Spring; Strawberry; Upper Black; Upper Ouachita; Upper Saline; Upper White-Village
CA1974199711Big Chico Creek-Sacramento River; Big-Navarro-Garcia; California Region; Lower Sacramento; Salton Sea; San Francisco Bay; San Pablo Bay; Shasta; South Fork American; Ventura; Whitewater River
CO1985201915Clear; Colorado Headwaters; Colorado Headwaters-Plateau; Fountain; Lower Gunnison; Lower Yampa; Middle South Platte-Cherry Creek; North Platte; Republican; Rio Grande Headwaters; San Luis; South Platte; St. Vrain; Upper Arkansas; Upper South Platte
CT198520172Housatonic; New England Region
DE198620064Brandywine-Christina; Chincoteague; Delaware Bay; Mid Atlantic Region
FL1972202432Alafia; Apalachee Bay-St. Marks; Big Cypress Swamp; Blackwater; Caloosahatchee; Cape Canaveral; Charlotte Harbor; Chipola; Choctawhatchee Bay; Daytona-St. Augustine; Escambia; Everglades; Florida Panhandle Coastal; Florida Southeast Coast; Hillsborough; Kissimmee; Lake Okeechobee; Lower Choctawhatchee; Lower Ochlockonee; Lower St. Johns; Lower Suwannee; Manatee; Myakka; Oklawaha; Peace; Pensacola Bay; South Atlantic-Gulf Region; St. Andrew-St. Joseph Bays; Tampa Bay; Upper St. Johns; Western Okeechobee Inflow; Withlacoochee
GA1972202228Altamaha; Brier; Conasauga; Coosawattee; Cumberland-St. Simons; Etowah; Little; Lower Flint; Lower Ocmulgee; Lower Oconee; Lower Savannah; Middle Chattahoochee-Lake Harding; Middle Chattahoochee-Walter F; Middle Flint; Middle Tennessee-Chickamauga; Ogeechee Coastal; Oostanaula; Satilla; Savannah; South Atlantic-Gulf Region; Spring; Upper Chattahoochee; Upper Coosa; Upper Flint; Upper Ocmulgee; Upper Oconee; Upper Savannah; Upper Tallapoosa
HI196820132Hawaii; Kauai
ID198920077Blackfoot; Brownlee Reservoir; Idaho Falls; Palouse; Pend Oreille Lake; Spokane; Upper Snake-Rock
IL1971202335Bear-Wyaconda; Big Muddy; Cache; Cahokia-Joachim; Chicago; Copperas-Duck; Des Plaines; Flint-Henderson; Kankakee; La Moine; Lake Michigan; Little Calumet-Galien; Little Wabash; Lower Fox; Lower Illinois; Lower Illinois-Lake Chautauqua; Lower Illinois-Senachwine Lake; Lower Kaskaskia; Lower Ohio; Lower Ohio-Bay; Lower Rock; Lower Sangamon; Lower Wabash; Mackinaw; Middle Kaskaskia; Middle Wabash-Busseron; Peruque-Piasa; Pike-Root; Salt; The Sny; Upper Fox; Upper Illinois; Upper Mississippi-Cape Girardeau; Vermilion; Wabash
IN1977202312Blue-Sinking; Kankakee; Lake Michigan; Little Calumet-Galien; Lower Wabash; Lower White; Middle Ohio-Laughery; Middle Wabash-Busseron; Middle Wabash-Little Vermilion; Ohio Region; Vermilion; Wabash
IA1973202227Big Papillion-Mosquito; Big Sioux; Blackbird-Soldier; Boyer; Chariton-Grand; Des Moines; Flint-Henderson; Floyd; Grand; Iowa; Keg-Weeping Water; Lake Red Rock; Lower Big Sioux; Lower Cedar; Lower Des Moines; Lower Iowa; Middle Des Moines; Missouri Region; Missouri-Little Sioux; Missouri-Nishnabotna; Skunk; South Raccoon; Thompson; Upper Mississippi Region; Upper Mississippi-Iowa-Skunk-Wapsipinicon; Upper Mississippi-Skunk-Wapsipinicon; West Nodaway
KS197420107Big Nemaha; Independence-Sugar; Lower Kansas, Kansas; Middle Neosho; Neosho Headwaters; South Fork Ninnescah; Tarkio-Wolf
KY1974202221Bayou De Chien-Mayfield; Blue-Sinking; Highland-Pigeon; Kentucky Lake; Licking; Licking; Lower Cumberland; Lower Kentucky; Lower Mississippi-Memphis; Lower Ohio; Lower Ohio-Bay; Lower Ohio-Little Pigeon; Lower Tennessee; Middle Green; Middle Ohio-Laughery; North Fork Kentucky; Obion; Rolling Fork; Salt; Silver-Little Kentucky; Tradewater
LA1978202429Atchafalaya; Bayou Cocodrie; Bayou Macon; Bayou Pierre; Bayou Sara-Thompson; Bayou Teche; Black; Bodcau Bayou; Boeuf; East Central Louisiana Coastal; Lake Pontchartrain; Little; Loggy Bayou; Lower Grand; Lower Mississippi-Baton Rouge; Lower Mississippi-Greenville; Lower Mississippi-Natchez; Lower Ouachita; Lower Ouachita-Bayou De Loutre; Lower Red; Lower Red; Lower Red-Lake Iatt; Mermentau; Middle Red-Coushatta; Tensas; Tickfaw; Toledo Bend Reservoir; West Central Louisiana Coastal; West Fork Calcasieu
MD197720095Conococheague-Opequon; Mid Atlantic Region; Middle Potomac-Catoctin; Nanticoke; Potomac
MA198420053Ashuelot River-Connecticut River; New England Region; Winnipesaukee River
MI1980202111Detroit; Kalamazoo; Lake Erie; Lake Huron; Lake Michigan; Lake St. Clair; Muskegon; Ottawa-Stony; Raisin; St. Joseph; Tittabawassee
MN1977202012Buffalo-Whitewater; Cannon; East Fork Des Moines; Little Sioux; Lower St. Croix; Middle Minnesota; Platte-Spunk; Rush-Vermillion; Snake; Twin Cities; Upper St. Croix; Zumbro
MS1978201913Big Sunflower; Coles Creek; Lower Mississippi-Greenville; Lower Mississippi-Helena; Lower Mississippi-Natchez; Luxapallila; Middle Pearl-Strong; Mississippi Coastal; Tallahatchie; Tibbee; Upper Big Black; Upper Leaf; Yazoo
MO1971202224Bear-Wyaconda; Cahokia-Joachim; Independence-Sugar; Lake of the Ozarks; Lower Gasconade; Lower Mississippi-Memphis; Lower Missouri; Lower Missouri-Crooked; Lower Missouri-Moreau; Lower Osage; Lower St. Francis; Meramec; North Fabius; Peruque-Piasa; Sac; Tarkio-Wolf; The Sny; Town of Madrid-Saint Johns Bayou; Upper Black; Upper Gasconade; Upper Grand; Upper Mississippi-Cape Girardeau; Upper St. Francis; Whitewater
NE1975202211Big Papillion-Mosquito; Blackbird-Soldier; Keg-Weeping Water; Lewis and Clark Lake; Lower Platte; Middle Platte-Prairie; Missouri Region; North Fork Republican; Salt; Tarkio-Wolf; Upper Elkhorn
NV198420012Las Vegas Wash; Truckee
NH198019802Lower Androscoggin River; Saco River
NJ198920194Cohansey-Maurice; Hackensack-Passaic; Raritan; Sandy Hook-Staten Island
NM1990202228Arroyo Del Macho; Canadian Headwaters; Carrizo Wash; El Paso-Las Cruces; Jemez; Middle San Juan; Mimbres; Monument-Seminole Draws; Mora; Mustang Draw; Pecos Headwaters; Rio Grande-Albuquerque; Rio Hondo; Rio Penasco; Salt Basin; San Francisco; Tularosa Valley; Upper Canadian; Upper Gila-Mangas; Upper Pecos; Upper Pecos-Black; Upper Pecos-Long Arroyo; Upper Rio Grande; Upper San Juan; Ute; Western Estancia; Yellow House Draw; Zuni
NY1985202314Ausable River; Housatonic; Irondequoit-Ninemile; Lake Erie; Lake Ontario; Lower Genesee; Lower Hudson; Middle Hudson; Mohawk; Niagara River; Sacandaga; Seneca; Southern Long Island; Upper Susquehanna
NC1980201926Cape Fear; Chowan; French Broad-Holston; Haw; Lower Cape Fear; Lower Pee Dee; Lower Tar; Lumber; Neuse; Nolichucky; Northeast Cape Fear; Roanoke; Roanoke Rapids; Rocky; Santee; Seneca; South Fork Catawba; Upper Broad; Upper Cape Fear; Upper Catawba; Upper Dan; Upper French Broad; Upper Neuse; Upper New; Upper Pee Dee; Upper Yadkin
ND199819981Upper James
OH1980202322Ashtabula-Chagrin; Auglaize; Black-Rocky; Cuyahoga; Lake Erie; Licking; Little Miami; Little Muskingum-Middle Island; Lower Maumee; Lower Scioto; Mahoning; Middle Ohio-Laughery; Mohican; Muskingum; Ohio Brush-Whiteoak; Raccoon-Symmes; Sandusky; Scioto; Tuscarawas; Upper Great Miami, Indiana, Ohio; Upper Ohio-Shade; Upper Scioto
OK1980202213Black Bear-Red Rock; Blue; Deep Fork; Kiamichi; Lake O' The Cherokees; Lake Texoma; Lower Cimarron; Lower Cimarron-Eagle Chief; Lower North Canadian; Lower Washita; Middle Washita; Upper Little; West Cache
OR198020066Lower Columbia-Sandy; Middle Columbia-Lake Wallula; Middle Willamette; Pacific Northwest; Siletz-Yaquina; Upper Willamette
PA1992202410Brandywine-Christina; Conococheague-Opequon; French; Kiskiminetas; Lake Erie; Lower Susquehanna-Penns; Middle Allegheny-Redbank; Upper Allegheny; Upper Ohio; Upper Susquehanna-Tunkhannock
PR197220042Culebrinas-Guanajibo; Eastern Puerto Rico
SC1980202218Black; Bulls Bay; Carolina Coastal-Sampit; Coastal Carolina; Congaree; Cooper; Edisto-South Carolina Coastal; Lake Marion; Lower Broad; Lower Catawba; Lower Pee Dee; Lynches; Middle Savannah; Saluda; Santee; South Atlantic-Gulf Region; Upper Broad; Wateree
SD198020203Lewis and Clark Lake; Middle James; Vermillion
TN1978202014Buffalo; Forked Deer; Horn Lake-Nonconnah; Kentucky Lake; Loosahatchie; Lower Clinch; Lower Duck; Lower Hatchie; Lower Mississippi-Memphis; Middle Tennessee-Chickamauga; Obion; Upper Clinch, Tennessee, Virginia; Watts Bar Lake; Wolf
TX1975202442Austin-Travis Lakes; Buffalo-San Jacinto; Cedar; East Galveston Bay; Elm Fork Trinity; Lake Meredith; Lake O'the Pines; Lake Texoma; Lavaca; Lower Angelina; Lower Brazos; Lower Colorado-Cummins; Lower Nueces; Lower Sulpher; Lower Trinity; Lower Trinity-Kickapoo; Lower Trinity-Tehuacana; Lower West Fork Trinity; Middle Brazos-Lake Whitney; Middle Brazos-Palo Pinto; Middle Guadalupe; Middle Sabine; Navidad; North Corpus Christi Bay; North Fork Double Mountain Fork Brazos; North Fork Red; North Galveston Bay; Pedernales; Reagan-Sanderson; San Marcos; South Laguna Madre; Toledo Bend Reservoir; Trinity; Upper Guadalupe; Upper Neches; Upper San Antonio; Upper Trinity; West Fork San Jacinto; West Galveston Bay; West Nueces; White Oak Bayou; Yegua
UT198420196Lower Green; Lower Green-Diamond; Lower San Juan-Four Corners; Upper Colorado-Kane Springs; Upper Lake Powell; Westwater Canyon
VT202220221Richelieu River
VA1986202315Albemarle; Appomattox; Lower James; Lower Rappahannock; Middle James-Willis; Middle Potomac-Anacostia-Occoquan; Middle Potomac-Catoctin; Pamunkey; Rivanna; Shenandoah; South Fork Shenandoah; Upper Clinch, Tennessee, Virginia; Upper James; Upper Roanoke; York
WA1987200312Deschutes; Duwamish; Grays Harbor; Lake Washington; Lower Columbia-Clatskanie; Lower Columbia-Sandy; Lower Cowlitz; Lower Snake; Lower Snake-Tucannon; Middle Columbia-Hood; Pacific Northwest Region; Upper Columbia-Priest Rapids
WV198020237Cacapon-Town; Conococheague-Opequon; Kanawha; Lower Kanawha; Lower New; Upper Kanawha; Upper Ohio-Shade
WI1975202114Buffalo-Whitewater; Coon-Yellow; La Crosse-Pine; Lake Michigan; Lower St. Croix; Lower Wisconsin; Manitowoc-Sheboygan; Milwaukee; Pike-Root; Red Cedar; Rush-Vermillion; Sugar; Upper Fox; Upper Rock
WY198720193Crow; Nowood; Upper Laramie

Table last updated 7/12/2024

† Populations may not be currently present.

Ecology: Typical habitat includes quiet waters, such as lakes, ponds, pools, and backwaters of large rivers, and individuals generally do not travel long distances except for the annual spawning migration (Mitzner 1978; Nixon and Miller 1978; Bain et al. 1990). Nevertheless, there are reports of juvenile Grass Carp traveling as far as 1,000 km from their original spawning grounds (Stanley et al. 1978). Shallow water is the generally preferred habitat, although deeper waters are used when temperatures decrease (Nixon and Miller 1978). A number of experimental studies have reported environmental tolerances for Grass Carp. Fry and fingerlings have been reported to tolerate water temperatures from 0-40°C (Stevenson 1965; Vovk 1979), and Stevenson (1965) reported that fingerlings in small ponds in Arkansas survived 5 months under heavy ice cover. Chilton and Muoneke (1992) reported an upper lethal temperature range for fry as 33-41°C, and for yearlings as 35-36°C. Bettoli et al. (1985) documented a thermal maximum of 39.3°C and a preferred temperature of 25.3°C. Collee et al. (1978) reported that feeding declined sharply below 14°C. Nico et al. (2005) reviewed temperature tolerance of Grass Carp and the other Chinese carps.

Oxygen consumption (per gram of body mass) increases with higher water temperature and decreases with fish age and mass (Chen and Shih 1955; Wozniewski and Opuszynski 1988). The lethal low oxygen level for juveniles was <0.5 mg/L (Negonovskaya and Rudenko 1974). The maximum pH for culture of grass carp was reported as 9.24 (Liang and Wang 1993). Egg hatching was delayed below pH 6.5 and increased mortality and deformation of larvae occurred below pH 6.0 (Li and Zhang 1992). Sensitivity to low pH decreased with age (Li and Zhang 1992). Median lethal concentration of ammonia was determined to be 1.05 mg/L (Gulyas and Fleit 1990).

Grass Carp appears to be tolerant of low levels of salinity, and may occasionally enter brackish-water areas. Fry (32-50 mm TL) survived transfer from freshwater to a salinity of 12 ppt (Chervinski 1977). Adults (2+ years) survived 10.5 ppt salinity for about 24 days and 17.5 ppt for 5 hours (Cross 1970). However, Grass Carp acclimated to 3, 5, and 7 ppt had an upper tolerance of about 14 ppt (Kilambi and Zdinak 1980). Maceina and Shireman (1980) showed that fingerlings reduce feeding at 9 ppt and stop feeding altogether at 12 ppt; thus, they predicted Grass Carpcould inhabit brackish water bodies up to 9 ppt. Maceina and Shireman (1979) reported that the species can tolerate 14 ppt for as long as 4 days, but that the upper long-term tolerance of fingerlings to saline waters was lower, about 10-14 ppt. Maceina et al. (1980) noted that oxygen consumption decreased along a salinity gradient of 0-9 ppt. Movement of Grass Carp from one river to another through a brackish-water estuary (Cross 1970) is not surprising given the species' tolerance to low levels of salinity. Avault and Merowsky (1978) reported food preference and salinity tolerance of hybrid Common Carp X Grass Carp.

Means of Introduction: Both authorized and unauthorized stockings of Grass Carp have taken place for biological control of vegetation. This species was first imported to the United States in 1963 to aquaculture facilities in Auburn, Alabama, and Stuttgart, Arkansas (Guillory and Gasaway 1978). The Auburn stock came from Taiwan, and the Arkansas stock was imported from Malaysia (Courtenay et al. 1984). The first release of this species into open waters took place at Stuttgart, Arkansas, when fish escaped the Fish Farming Experimental Station (Courtenay et al. 1984). However, many of the early stockings in Arkansas were in lakes or reservoirs open to stream systems, and by the early 1970s there were many reports of Grass Carp captured in the Missouri and Mississippi rivers (Pflieger 1975, 1997). During the past few decades, the species has spread rapidly as a result of widely scattered research projects, stockings by federal, state, and local government agencies, legal and illegal interstate transport and release by individuals and private groups, escapes from farm ponds and aquaculture facilities; and natural dispersal from introduction sites (e.g., Pflieger 1975; Lee et al. 1980 et seq.; Dill and Cordone 1997). Some of the agencies that have stocked grass carp in the past include the Arkansas Game and Fish Commission, the Tennessee Valley Authority, the U.S. Fish and Wildlife Service, the Delaware Division of Fish and Wildlife, the Florida Game and Fresh Water Fish Commission, the Iowa Conservation Commission, the New Mexico Department of Fish and Game, and the Texas Parks and Wildlife Department. The species also has been stocked by private individuals and organizations. In some cases, Grass Carp have escaped from stocked waterbodies and appeared in nearby waterbodies. Stocking of Grass Carp as a biological control against nuisance aquatic plants in ponds and lakes continues. For instance, Pflieger (1997) stated that thousands of Grass Carp are reared and sold by fish farmers in Missouri and Arkansas.

Status: Grass Carp have been recorded from 45 states; there are no reports of introductions in Alaska, Maine, Montana, Rhode Island, and Vermont. It is known to have established populations in a number of states in the Mississippi River basin. Breeding populations have been recorded for the Mississippi River in Kentucky (Conner et al. 1980; Burr and Warren 1986), the Illinois and upper Mississippi rivers of Illinois and Missouri (Raibley et al. 1995), the lower Missouri River in Missouri (Raibley et al. 1995), the Mississippi River or its tributaries in the states of Arkansas (Conner et al. 1980), Louisiana (Conner et al. 1980; Zimpfer et al. 1987), Tennessee (Etnier and Starnes 1993), and presumably Mississippi (Courtenay et al. 1991). It is also established in the Ohio River in Illinois (Burr, personal communication); it was listed as established in Minnesota (Courtenay et al. 1991, but see Courtenay 1993), and in the Trinity River of Texas (Waldrip 1992; Webb et al. 1994; Elder and Murphy 1997). Courtenay (1993) listed Grass Carp as established in eight states, Arkansas, Kentucky, Illinois, Louisiana, Missouri, Mississippi, Tennessee, and Texas; an additional one, Minnesota, was included in an earlier listing of states with established populations (Courtenay et al. 1991). Stone (1995) listed this species as being established in Wyoming; however, Stone (personal communication) clarified his earlier report by stating that, as of early 1997, there is no evidence of natural reproduction in that state. Similar to a few other authors, he used the term 'established' to indicate that grass carp populations have persisted for many years, presumably because of their long life span and because of long-term maintenance of wild populations through continued stockings. Pearson and Krumholz (1984) mentioned several records from the Ohio River, including river mile 963 on the Illinois-Kentucky border and from the Falls of the Ohio, at Louisville, along the Kentucky-Ohio border. They also stated that the species had been stocked in many private ponds and lakes in the Ohio River basin. Sigler and Sigler (1996) stated that this species is no longer found in Utah, but they provide no details. Harvest of Grass Carp by commercial fishermen in the Missouri and Mississippi rivers of Missouri has exhibited a general climb. In 1996, the most recent available data, there was a record reported harvest, about 44,000 pounds, 8 percent of the total commercial fish harvest (J. W. Robinson, personal communication). Starnes et al. (2011) report Grass Carp as stocked and occassionally occurring in the lower Potomac River and C&O Canal near Plummers Island. Chapman et al. (2013) provided evidence for successful reproduction of Grass Carp in the Sandusky River in 2011.

Impact of Introduction:
Summary of species impacts derived from literature review. Click on an icon to find out more...


Various authors (e.g., Shireman and Smith 1983; Chilton and Muoneke 1992; Bain 1993) have reviewed the literature on Grass Carp; most also discuss actual and potential impacts caused by the species' introduction. Shireman and Smith (1983) concluded that the effects of Grass Carp introduction on a water body are complex and apparently depend on the stocking rate, macrophyte abundance, and community structure of the ecosystem. They indicated that numerous contradictory results are reported in the literature concerning Grass Carp interaction with other species. Negative effects involving Grass Carp reported in the literature and summarized by these authors included interspecific competition for food with invertebrates (e.g., crayfish) and other fishes, significant changes in the composition of macrophyte, phytoplankton, and invertebrate communities, interference with the reproduction of other fishes, decreases in refugia for other fishes, and so on. In their overview, Chilton and Muoneke (1992) reported that Grass Carp seem to affect other animal species by modifying preferred habitat, an indirect effect. However, they also indicated that grass carp may directly influence other animals through either predation or competition when plant food is scarce. In his review, Bain (1993) stated that Grass Carp have significantly altered the food web and trophic structure of aquatic systems by inducing changes in plant, invertebrate, and fish communities. He indicated that effects are largely secondary consequences of decreases in the density and composition of aquatic plant communities. Organisms requiring limnetic habitats and food webs based on phytoplankton tend to benefit from the presence of Grass Carp. On the other hand, Bain reported that declines have occurred in the diversity and density of organisms that require structured littoral habitats and food chains based on plant detritus, macrophytes, and attached algae. Removal of vegetation can have negative effects on native fish, such as elimination of food sources, shelter, and spawning substrates (Taylor et al. 1984). Hubert (1994) cited a study that found vegetation removal by Grass Carp lead to better growth of Rainbow Trout (Oncorhynchus mykiss) due to increases in phytoplankton and zooplankton production, but it also lead to higher predation on Rainbow Trout by Double-crested Cormorants (Phalacrocorax auritus) due to lack of cover, and changes in diet, densities, and growth of native fishes. Although Grass Carp are often used to control selected aquatic weeds, these fish sometimes feed on preferred rather than on target plant species (Taylor et al. 1984). Van der Lee et al. (2017) report that Grass Carp can consume up to 27.6 kg of vegetation per kg of fish per year. Increases in phytoplankton populations is a secondary effect of Grass Carp presence. A single Grass Carp can digest only about half of the approximately 45 kg of plant material that it consumes each day. The remaining material is expelled into the water, enriching it and promoting algal blooms (Rose 1972). These blooms can reduce water clarity and decrease oxygen levels (Bain 1993). In addition to the above, Grass Carp may carry several parasites and diseases known to be transmissible or potentially transmissible to native fishes. For instance, it is believed that Grass Carp imported from China were the source of introduction of the Asian tapeworm Bothriocephalus opsarichthydis (Hoffman and Schubert 1984; Ganzhorn et al. 1992). As such, the species may have been responsible indirectly for the infection of the endangered Woundfin Plagopterus argentissimus (by way of the red shiner Cyprinella lutrensis) (Moyle 1993). Wittmann et al. (2014) performed a meta-analysis of ecological effects of Grass Carp, finding an overall negative impact to biota (primarly through negative effects on macrophytes, with mixed results in other taxonomic groups) and an alteration of water quality (primarily change in conductivity and salinity) in stocked areas.

Remarks: In an article by Sandy Bauers of the Philadelphia Inquirer (1995), it is reported that Philadelphia is taking precautions to ensure that the release carp are sterile. The fish are sterilized by subjecting fertilized eggs to extreme heat or extreme cold. The result is a triploid fish rather than a normal diploid fish. Before the fish are shipped off to be stocked in area lakes, each specimen undergoes two mandatory blood tests by the US Fish and Wildlife Service and the diploid fish are removed.

DeVaney et al. (2009) performed ecological niche modeling to examine the invasion potential for Grass Carp and three other invasive cyprinids (Common Carp Cyprinus carpio, Black Carp Mylopharyngodon piceus, and Tench Tinca tinca). The majority of the areas where Grass Carp have been collected, stocked, or have become established had a high predicted ecological suitability for this species. Wittmann et al. (2014) used multiple machine learning methods to examine potential distribution of Grass Carp in the Great Lakes, finding suitable predicted habitat in all lakes but Superior.

References: (click for full references)

Bain, M. 1993. Assessing impacts of introduced aquatic species: grass carp in large systems. Environmental Management 17:211-224.

Bain, M.B., D.H. Webb, M.D.Tangedal, and L.N. Mangum. 1990. Movements and habitat use by grass carp in a large mainstream reservoir. Transactions of the American Fisheries Society 119:553-561.

Bauers, S. 1995. Debate on Fish that Can't Scale Back. The Philadelphia Inquirer, City & Region Section. Published on 4 June, 1995.

Becker, G.C. 1983. Fishes of Wisconsin. University of Madison Press, Madison, WI.

Berg, L.S. 1949. Freshwater fishes of the USSR and adjacent countries. Izdatel'vesto Akademii Nauk SSSR, Moscow.

Chapman, D.C., J.J. Davis, J.A. Jenkins, P.M. Kocovsky, J.G. Miner, J. Farver, and P.R. Jackson. 2013. First evidence of grass carp recruitment in the Great Lakes Basin. Journal of Great Lakes Research 39(4):547-554. http://dx.doi.org/10.1016/j.jglr.2013.09.019

Chilton, III, E.W. and M.I. Muoneke. 1992. Biology and management of grass carp (Ctenopharyngodon idella, Cyprinidae) for vegetation control: a North American perspective. Reviews in Fish Biology and Fisheries 2:283-320.

Courtenay, W.R., Jr., D.A. Hensley, J.N. Taylor, and J.A. McCann. 1984. Distribution of exotic fishes in the continental United States. Pages 41-77 in W.R. Courtenay, Jr., and J.R. Stauffer, Jr., eds. Distribution, biology and management of exotic fishes. Johns Hopkins University Press, Baltimore, MD.

Cross, D.G. 1970. The tolerance of grass carp Ctenopharyngodon idella (Val.) to seawater. Journal of Fish Biology 2:231-233.

Cross, F.B., and J.T. Collins. 1995. Fishes in Kansas. University of Kansas Natural History Museum. Lawrence, KS.

Crossman, E.J., S.J. Nepszy, and P. Krause. 1987. The first record of grass carp, Ctenopharyngodon idella, in Canadian waters. Canadian Field-Naturalist 101(4):584-586.

Cudmore-Vokey, B., and E.J. Crossman. 2000. Checklists of the fish fauna of the Laurentian Great Lakes and their connecting channels. Canadian Manuscript Report of Fisheries and Aquatic Sciences 2550. Fisheries and Oceans Canada, Burlington, Ontario.

DeVaney, S.C., K.M. McNyset, J.B. Williams, A.T. Peterson, and E.O. Wiley. 2009. A tale of four "carp": invasion potential and ecological niche modeling. PLoS ONE 4(5): e5451.

Dill, W.A., and A.J. Cordone. 1997. History and status of introduced fishes in California, 1871-1996. California Department of Fish and Game Fish Bulletin, volume 178.

Etnier, D.A., and W.C. Starnes. 1993. The fishes of Tenneessee. University of Tennessee Press, Knoxville, TN.

Freidhoff, J., pers. comm.- Buffalo State College, Buffalo, NY

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FishBase Summary

Author: Nico, L.G., P.L. Fuller, P.J. Schofield, M.E. Neilson, A.J. Benson, and J. Li

Revision Date: 1/15/2020

Peer Review Date: 2/2/2016

Citation Information:
Nico, L.G., P.L. Fuller, P.J. Schofield, M.E. Neilson, A.J. Benson, and J. Li, 2024, Ctenopharyngodon idella (Valenciennes in Cuvier and Valenciennes, 1844): U.S. Geological Survey, Nonindigenous Aquatic Species Database, Gainesville, FL, https://nas.er.usgs.gov/queries/factsheet.aspx?SpeciesID=514, Revision Date: 1/15/2020, Peer Review Date: 2/2/2016, Access Date: 7/12/2024

This information is preliminary or provisional and is subject to revision. It is being provided to meet the need for timely best science. The information has not received final approval by the U.S. Geological Survey (USGS) and is provided on the condition that neither the USGS nor the U.S. Government shall be held liable for any damages resulting from the authorized or unauthorized use of the information.


The data represented on this site vary in accuracy, scale, completeness, extent of coverage and origin. It is the user's responsibility to use these data consistent with their intended purpose and within stated limitations. We highly recommend reviewing metadata files prior to interpreting these data.

Citation information: U.S. Geological Survey. [2024]. Nonindigenous Aquatic Species Database. Gainesville, Florida. Accessed [7/12/2024].

Contact us if you are using data from this site for a publication to make sure the data are being used appropriately and for potential co-authorship if warranted.

For general information and questions about the database, contact Wesley Daniel. For problems and technical issues, contact Matthew Neilson.