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   Ctenopharyngodon idella (fish)   
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    Taxonomic name: Ctenopharyngodon idella (Valenciennes in Cuvier and Valenciennes, 1844)
    Synonyms: Ctenopharingodon idella (Valenciennes, 1844), Ctenopharyngodon idellus (Valenciennes, 1844), Ctenopharyngodon laticeps (Valenciennes, 1844), Leuciscus idella (Valenciennes in Cuvier and Valenciennes, 1844), Leuciscus idella (Valenciennes, 1844), Leuciscus idellus (Valenciennes, 1844), Leuciscus tschiliensis (Valenciennes, 1844), Pristiodon siemionovii (Valenciennes, 1844), Sarcocheilichthys teretiusculus (Valenciennes, 1844)
    Common names: amur (Italian), amur bialy (Poland), amur biely (Slovak), amur i bardhe (Albanian), amurkarpfen (German), beli amur (Slovenia), belyi amur (Ukraine), bílý amur (Czech), byal amur (Bulgarian), Cá Châm Treng (Vietnamese), carpa China (Spanish), carpa do limo (Portuguese), carpa erbivora (Italian), carpa herbivora (Spanish), carpe de roseau (French), carpe herbivore (French), Chinese carp (English), Chinese graskarper (Dutch), chortofagos kyprinos (Greek), crap-de-iarba (Polish), gardd carp (English), græskarpe (Danish), graskarp (Afrikaans), gräskarp (Sweden), gräskarp (Swedish), graskarpe (Norwegian), graskarpen (Dutch), graskarper (Dutch), graskarpfen (German), grass carp (English), hullu (Kannada), hullugende (Kannada), kap makan rumput (Malay), kap rumput (Malay), Pla Chao Hea (Thai), Pla Chao Heu (Thai), pla van heu (Thai), ruohokarppi (Finland), silver orfe (English), sôgyo (Japanese), tongsan (Malay), trey srokchen (Khmer), waan ue (Cantonese), white amur (English)
    Organism type: fish
    Grass carp (Ctenopharyngodon idella) is a large cyprinid introduced worldwide as a biological control of aquatic vegetation as well as a food fish. It is a voracious feeder which is incredibly efficient at removing aquatic weeds. However they can completely eliminate vegetation from water systems, resulting in widespread ecological effects. Grass carp are also known to compete with native fish, carry parasites such as Asian tapeworm (Bothriocephalus opsarichthydis), and induce other harmful effects to introduced waters.
    Grass carp (Ctenopharyngodon idella) has an oblong, slender body, a wide scaleless head, and very short snout. It is dark gray, silver, to olive in color with lighter sides and clear to gray-brown fins. It bears large cycloid scales with dark edges. Its dorsal fin bears 7-8 rays, anal fin 7-11 rays, and caudal fin about 18 rays. They are among the largest of the minnow family reaching weights of 30-50 kg and lengths of over a meter (Cudmore & Mandrak, 2004; FishBase, 2008).
    Occurs in:
    lakes, water courses
    Habitat description
    Grass carp (Ctenopharyngodon idella) inhabit sub-tropical and temperate climates and prefer in large rivers, lakes, and reservoirs with abundant vegetation and relatively shallow waters. They are tolerant of a range of conditions may inhabit temperatures of 0-33° C, oxygen levels as low as 0.5 ppm, and salinities as great as 10 ppt, although it is reported as capable of tolerating much greater salinities (Cudmore & Mandrak, 2004; Nico et al. 2006).
    General impacts
    Grass carp (Ctenopharyngodon idella) are voracious feeders. Many of their introductions have been for the control of aquatic vegetation. However, they are known to completely eliminate aquatic plants in introduced habitats altering trophic structure and inflicting widespread detrimental effects on ecosystems. They may also feed selectively on softer plants thereby enhancing development of tougher plants. Grass carp remove macrophyte cover, eliminate spawning substrate, disturb sediment and muddy waters, reduce water quality, increase nutrients in waters accelerating eutrophication, decrease oxygen levels, and promote alagal bloom. They compete with native invertebrates and fish for food and other important resources. Reported impacts on native fishes include the reduction of bluegill, sunfish, smelt, bully, and pike populations. Grass carp are believed to impact waterfowl by reducing aquatic vegetation, an essential food source. Significant declines of gadwall (Anas stepera), American wigeon (Anas americana), and American coot (Fulica americana) have been reported following grass carp introductions. They carry diseases and parasites which are transmittable to other fish and are believed to be the main vector for Asian tapeworms (Bothriocephalus opsarichthydis) known to infect several fishes in Canada including common carp (Cyprinus carpio), golden shiner (Notemigonus crysoleucas), fathead minnow (Pimephales promelas), channel catfish (Ictalurus punctatus). One record cites grass carp as the vector for the infection of endangered woundfin (Plagopterus argentissimus) (Standish & Wattendorf 1987; Jordan, 2003; Jacobson & Kartalia, 1994; Nico et al. 2006; GSMFC, 2005; McKnight & Hepp, 1995; Mitchell, 1986; Elvira, 2001).
    Grass carp (Ctenopharyngodon idella) are used worldwide for control of aquatic vegetation as well as an important food fish. Techniques to produce triploid populations that are functionally sterile have effectively removed the threat of wild establishment and rendering them a cheaper, safer alternative to chemical and mechanical control methods. The U.S. Fish and Wildlife Service has implemented a voluntary program that certifies triploidy to would be stocked populations. Beneficial effects of grass carp on ecosystems regarding angling have been reported from some locations. Grass carp have been used in Germany and the Netherlands for their positive effects on sportfish productivity, growth and survival. Apparently, the high productivity and consumption of plants ignored by many sportfish of grass carp result in faster organic breakdown and decreased retention of nutrients by plants, as well as more aerated, sunlit waters bearing more habitable space. Grass carp have also been used to effectively eliminate malarial mosquitos (Anopheles pulcherrimus) from the Kara Kum Canal of the former Soviet Union. The mosquitos were believed to be eliminated as a result of extensive vegetation consumption by grass carp (Standish & Wattendorf 1987; Jacobson & Kartalia, 1994; Pierce, 1983; GSMFC, 2005).
    The use of grass carp as a control for aquatic vegetation is best suited in situations where total elimination of the macrophyte community is desired, as over consumption of vegetation may induce negative effects (Standish & Wattendorf 1987).
    Geographical range
    Native range: China, Russian Federation.
    Known introduced range: Afghanistan, Algeria, Argentina, Albania, Algeria, Armenia, Azerbaijan, Bangladesh, Belarus, Belgium, Bhutan, Bolivia, Brazil, Brunei Darsm, Cambodia, Canada, Colombia, Cote d' Ivoire, Croatia, Cuba, Cyprus, Czech Republic, Denmark, Egypt, Ethiopia, Fiji, Finland, Guyana, Hawaii, Honduras, Hong Kong, Hungary, India, Indonesia, Iraq, Islamic Republic of Iran, Israel, Italy, Jamaica, Japan, Kazakhstan, Kenya, Democratic People's Republic of Korea, Kyrgyzstan, Laos, Latvia, Malaysia, Mauritius, Mexico, Republic of Moldova, Mongolia, Morocco, Mozambique, Myanmar, Nepal, Netherlands, New Zealand, Nigeria, Pakistan, Panama, Peru, Philippines, Puerto Rico, La Réunion, Romania, Rwanda, Serbia and Montenegro, Singapore, Slovakia, Slovenia, South Africa, Sri Lanka, Sudan, Sweden, Taiwan, Tanzania, Thailand, Tunisia, Turkey, Turkmenistan, United Kingdom, Ukraine, United Arab Emirates, Uruguay, United States, Uzbekitsan, and Vietnam (FishBase, 2008).
    Management information
    Preventative measures: Most of the United States have some form of regulation regarding the introduction of Ctenopharyngodon idella (Allen, 1987). Introduced populations should be securely contained. Grass carp migrate and are capable of dispersing long distances and establishing potentially harmful populations. They are known to leap fish barriers, so they should only be introduced to systems where escape is impossible. Also, stocking densities should be kept as low as possible to prevent adverse ecological effects (Jordan, 2003)

    Chemical: The use of food pellets containing 1.0% anitmycin, a respiratory poison, were found to be readily consumed by and lethal to Ctenopharyngodon idella in studies (Kroon, 2005).

    Biological: Induced tripoloidy, and the resultant sterilization, in grass carp provides an effective means of controlling Ctenopharyngodon idella. By inhibiting the second maturation division of meiosis in fertilized eggs, an extra chromosome set is retained in the second polar body, thereby producing a triploid zygote. This may be accomplished by cold shocks, which result in 50-100% triploidy with survival less than 20%, heat shocks yeilding about 87% triploids and up to 50% survival, or by hydrostatic pressure treatments of 7000 to 8000 psi, which consistently result in nearly 100% triploids with only 30% mortality. Upon proper seperation of diploids, these methods provide completely sterile populations that can be used for the control of vegetation or aquaculture without risking wild establishments. The U.S. Fish and Wildlife Service has implemented a voluntary program that certifies triploidy to would be stocked populations, thereby providing an impartial means of ensuring low incidence of diploidy (Allen, 1987; Jacobson, 1994).

    Ctenopharyngodon idella feed on a wide range of aquatic vegetation, and are capable of consuming 40-300% of their body mass per day of plant material depending on their age and size. Fry consume planktonic crustaceans, rotifers, and insect larvae, while adults are completely vegetarian. Active feeding occurs at 7-8°C and intensive feeding requires 20°C. They are found to prefer softer, low fiber plants. Studies have found them to preferentially consume or have demonstrated themselves as an effective control for species: Eurasian watermilfoil (Myriophyllum spicatum), hydrilla (Hydrilla verticillata), pondweed (Potamoeton diversifolius), fanwort (Cabomba caroliniana), water hyacinth (Eichhornia crassipes), musk grass (Chara spp.), elodea (Elodea canadensis), Brazilian elodea (Egeria densa), southern naiad (Najas quadalupensis), coastal arrowhead (Sagittaria graminea), eastern bladderwort (Utricularia gibba), watermeal (Woffia spp.), and duckweeds (Lemna spp. and Spirodela spp.). (Jordan, 2003; Cudmore, 2004; Pierce, 1983).
    Sexual. Oviparous, external fertilization. Spawning occurs in summer months prompted by rising water levels of about 20cm or more and water temperatures of around 20° C. Grass carp migrate long distances to seek turbulent waters in which to spawn. Eggs are pelagic and left to drift downstream, hatching in 2-3 days. They must remain suspended during their incubation and are very much dependant on adequate oxygen flow, therefore usually require long river streches of turbulent rising waters. Since they require these conditions for spawning, they are not able to reproduce in many introduced habitats. Grass carp have a tremendous reproductive capacity with females producing 500,000-700,000 eggs and over 1,000,000 eggs in its native range (FishBase, 2008; DPIF, 2004; GSMFC, 2005; Tu, 2003).
    Lifecycle stages
    Eggs hatch within 2-3 days. Pelagic larvae emerge and seek shelter in vegetated areas of flood plains, reservoirs, and lakes. They may winter in deep holes within riverbeds. Males reach sexual maturity around the age of two years, while females take about three. Grass carp and may live as long as 30-50 years (FishBase, 2008; DPIF, 2004; Pierce, 1983)
    Reviewed by: Pam Fuller USGS/BRD, Nonindigenous Aquatic Species Program. Florida Integrated Science Center. USA
    Compiled by: National Biological Information Infrastructure (NBII) & IUCN/SSC Invasive Species Specialist Group (ISSG)
    Last Modified: Friday, 8 April 2005

ISSG Landcare Research NBII IUCN University of Auckland