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 var. diploid
Ctenopharyngodon idella var. diploid
(Grass Carp (diploid))
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Ctenopharyngodon idella var. diploid (Valenciennes in Cuvier and Valenciennes, 1844)

Common name: Grass Carp (diploid)

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

Taxonomy: available through www.itis.govITIS logo

Identification: Originally, Grass Carp were organized in the family Cyprinidae, which includes minnows and carp. However, a taxonomic update recently placed Grass Carp in subfamily xenocipridinae within the family Xenocyprididae (Tan and Armbruster, 2018). It has a body which is moderately laterally compressed, and its mouth is terminally located on a wide head that lacks scales, with eyes that are small and low on the head.  C. idella are olive-brown on the dorsal side.  Grass Carp captured in the Great Lakes are described as having a greenish tint (Kocovsky pers comm, 2019). Scales are large with dark edging.  The dorsal fin origin is anterior to the pelvic fin origin. They differ from Goldfish (Carassius auratus) and Common Carp (Cyprinus carpio) in having a shorter dorsal fin (only 7-8 rays) and in lacking barbels. Grass Carp can be distinguished from Hypophthalmichthys spp. (Bighead Carp and Silver Carp) in having fewer anal rays (9 or fewer) and larger scales.

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 var. diploid are found here.

StateFirst ObservedLast ObservedTotal HUCs with observations†HUCs with observations†
AL198919891Guntersville Lake
CA197419978Big Chico Creek-Sacramento River; Big-Navarro-Garcia; California Region; Salton Sea; San Pablo Bay; Shasta; South Fork American; Ventura
FL197720102Kissimmee; Lower Suwannee
GA199119963Lower Oconee; Lower Savannah; Ogeechee Coastal
IL199320208Bear-Wyaconda; Chicago; Des Plaines; Flint-Henderson; Little Calumet-Galien; Lower Illinois-Lake Chautauqua; Lower Illinois-Senachwine Lake; Upper Illinois
IN201420171Little Calumet-Galien
KY201820181Lower Ohio
LA201120122Lower Grand; Lower Mississippi-Baton Rouge
MI201120207Detroit; Kalamazoo; Lake Erie; Ottawa-Stony; Raisin; St. Joseph; Tittabawassee
MN201120175Buffalo-Whitewater; Middle Minnesota; Platte-Spunk; Twin Cities; Zumbro
NY200720163Lake Erie; Lower Hudson; Middle Hudson
OH201220207Cuyahoga; Lake Erie; Lower Maumee; Mahoning; Muskingum; Sandusky; Tuscarawas
PA201420152Kiskiminetas; Upper Ohio
TN201920192Lower Clinch; Lower Duck
TX198120134Lower Trinity; Lower Trinity-Kickapoo; Upper Trinity; West Fork San Jacinto
UT201520183Lower Green; Upper Colorado-Kane Springs; Upper Lake Powell
WI201520202La Crosse-Pine; Milwaukee

Table last updated 8/11/2020

† Populations may not be currently present.

Ecology: Typical habitat includes quiet waters, such as lakes, ponds, pools, and backwaters of large rivers. 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 five 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.

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). 

The 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 Carp could 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.

Grass Carp require high flow events that allow their eggs to travel downstream for successful spawning (Kocovsky et al., 2012). Slow-moving areas can cause Grass Carp eggs to settle out of the current and perish before successful spawning. In the Great Lakes Basin, the Maumee and Sandusky Rivers of Lake Erie, and the St. Joseph and Milwaukee Rivers of Lake Michigan have suitable hydrology for successful Grass Carp spawning (Murphy and Jackson, 2013).

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. 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: Illinois, Indiana, Ohio, Pennsylvania and New York all allow triploid Grass Carp to be stocked.  While triploid Grass Carp are non-reproductive, the potential exists for stock to be contaminated with individuals capable of reproduction. Reproductively viable Grass Carp may also be illegally introduced or migrate into the Great Lakes through connecting waters (Wieringa et al., 2017).  Although prohibited in Michigan, Minnesota, and Wisconsin, illegal stocking has been documented in Michigan (Emery 1985).  Grass Carp are established in the Mississippi River (Herborg et al. 2007, Mandrak and Cudmore 2005, Rixon et al. 2005, U.S. EPA 2008) and cultured in states adjacent to the Great Lakes region.

Four juvenile Grass Carp were caught in the Sandusky River, Ohio in 2012; based on their otolith microchemistry, these four individuals were likely the result of natural reproduction occurring in the Sandusky River (Chapman, 2012). A subsequent study in 2015 collected eight eggs that were morphologically consistent with Grass Carp eggs, five of these eggs were analyzed using quantitative Polymerase Chain Reaction (qPCR) which confirmed they were fertilized Grass Carp eggs (Embke et al., 2016). In addition to evidence that natural reproduction of Grass Carp is occurring in the Sandusky River, analysis of feral grass carp captured in western Lake Erie from 2014 to 2016 found that 86.7% of individuals analyzed were reproductively viable (Wieringa et al., 2017).

Remarks: All Grass Carp stocked in the US prior to 1983 were diploid (Elder and Murphy 1997). The first triploid Carp were produced by crossing female Grass Carp and male Bighead Carp (Arystichthis nobilis) (Malone, 1982). Later, triploid Grass Carp were produced by subjecting fertilized eggs to heat, cold, or hydrostatic pressure (Clugston and Shireman, 1987). 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.

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, Sandy. 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.

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., editors. 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.

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.

Elder, H.S., and B.R. Murphy. 1997. Grass carp (Ctenopharyngodon idella) in the Trinity River, Texas. Journal of Freshwater Ecology 12(2):281-289.

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

Fuller, P.L. 2003. Freshwater aquatic vertebrate introductions in the United States: patterns and pathways. In G.M. Ruiz and J.T. Carlton (eds.), Invasive Species: Vectors and Management Strategies (pp. 123-151). Island Press.

Gherardi, F., S. Gollasch, D. Minchin, S. Olenin, and V.E. Panov. 2009. Alien invertebrates and fish in European inland waters. In J.A. Drake (ed.), DAISIE Handbook of Alien Species in Europe (pp. 81-92). Dordrecht: Springer.

Global Invasive Species Database. IUCN-World Conservation Union—Invasive Species Specialist Group. 27 January 2011. http://www.issg.org/database/

Guillory, V. and R.D. Gasaway. 1978. Zoogeography of the grass carp in the United States. Transactions of the American Fisheries Societ 107:105-112

Herborg, L.-M., N.E. Mandrak, B.C. Cudmore, and H.J. MacIsaac. 2007. Comparative distribution and invasion risk of snakehead (Channidae) and Asian carp (Cyprinidae) species in North America. Canadian Journal of Fisheries and Aquatic Sciences 64: 1723-1735.

Jenkins, R.E., and N.M. Burkhead. 1994. Freshwater Fishes of Virginia. American Fisheries Society, Bethesda, MD.

Kilambi, R.V., and A. Zdinak. 1980. The effects of acclimation on the salinity tolerance of grass carp. Journal of Fish Biology 16:171-175.

Kolar, C. S., D. C. Chapman, W. R. Courtenay Jr., C. M. Housel, and J. D. Williams. 2005. Asian Carps of the Genus Hypophthalmichthys (Pisces, Cyprinidae) ? A Biological Synopsis and Environmental Risk Assessment. U.S. Fish and Wildlife Service.

Lee, D.S., C.R. Gilbert, C.H. Hocutt, R.E. Jenkins, D.E. McAllister, and J.R. Stauffer, Jr. 1980. Atlas of North American freshwater fishes. North Carolina State Museum of Natural History, Raleigh, NC.

Maceina, M.J., and J.V. Shireman. 1979. Grass carp: effects of salinity on survival, weight loss, and muscle tissue water content. Progressive Fish Culturist 41:69-72

Mandrak, N. E. 1989. Potential Invasion of the Great-Lakes by Fish Species Associated with Climatic Warming. Journal of Great Lakes Research 15:306-316.

Mandrak, N. E., and B. Cudmore. 2005. Risk assessment for Asian carps in Canada. Research Document 2004/103. Fisheries and Oceans Canada.

Menhinick, E. F. 1991. The freshwater fishes of North Carolina. North Carolina Wildlife Resources Commission. 227 pp.

Mettee, M.F., P.E. O'Neil, and J.M. Pierson. 1996. Fishes of Alabama and the Mobile Basin. Oxmoor House, Inc., Birmingham, AL.

Mitzner, L. 1978. Evalulation of biological control of nuisance aquatic vegetation by grass carp. Transactions of the American Fisheries Society 107:135-145.

Nixon, D.E., and R.L. Miller. 1978. Movements of grass carp, Ctenopharyngodon idella, in an open reservoir system as described by radiotelemetry. Transactions of the American Fisheries Society 107:146-148.

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Rixon, C.A.M., I.C. Duggan, N.M.N. Bergeron, A. Ricciardi, and H.J. MacIsaac. 2005. Invasion risks posed by the aquarium trade and live fish markets on the Laurentian Great Lakes. Biodiversity and Conservation 14: 1365-1381.

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Stanley, J. G. 1976. Reproduction of the grass carp (Ctenopharyngodon idella) outside its native range. Fisheries 1:7-10.

Stanley, J.G., W.W. Miley, and D.L. Sutton. 1978. Reproductive requirements and likelihood for naturalization of escaped grass carp in the United States. Transactions of the American Fisheries Society 103:587-592.

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W. Stone, pers. comm. - New York Dept. Environmental Conservation, Delmar, NY.

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Zhang, L. N., X. Li, W. Lu, H. X. Shen, and Y. K. Luo. 2011. Quality predictive models of grass carp (Ctenopharyngodon idellus) at different temperatures during storage. Food Control 22:1197-1202.

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Author: Nico, L.G., P.L. Fuller, P.J. Schofield, M.E. Neilson, E. Baker, C. Narlock, and R. Sturtevant

Revision Date: 9/12/2019

Citation Information:
Nico, L.G., P.L. Fuller, P.J. Schofield, M.E. Neilson, E. Baker, C. Narlock, and R. Sturtevant, 2020, Ctenopharyngodon idella var. diploid (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=2947, Revision Date: 9/12/2019, Access Date: 8/14/2020

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. [2020]. Nonindigenous Aquatic Species Database. Gainesville, Florida. Accessed [8/14/2020].

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