Picture by Chad Thomas, Texas State University-San Marcos
China (Valenciennes in Cuvier and Valenciennes 1844).
Etymology/Derivation of Scientific Name
Ctenopharyngodon: Cteno, comb; pharynx, throat; odon, tooth, referring to comblike pharyngeal teeth; and idella: presumably derived from the Greek idios, distinctive or peculiar (Scharph 2005).
Leuciscus idella Valenciennes in Cuvier and Valenciennes 1844:362.
Maximum size: 1,250 mm (49.2 in) (Guillory 1980; Page and Burr 1991).
Coloration: Silvery pale-gray color with scales of dorsum and sides having prominent dark edges, producing cross-hatched pattern (Robison and Buchanan 1988).
Counts: Pharyngeal teeth 2,4-4,2 or 2,5-4,2 (Page and Burr 1991) with prominent parallel grooves (Hubbs et al. 2008); fewer than 10 dorsal fin soft rays (Hubbs et al. 2008); 37-47 lateral line scales; 6 or 7 scale rows above lateral line; 8 (rarely 9) dorsal fin soft rays; 9 (rarely 8 or 10) anal fin soft rays; 15-20 pectoral fin soft rays (Robison and Buchanan 1988).
Body shape: Elongate, stout body; blunt head (Robison and Buchanan 1988).
Mouth position: Terminal (Robison and Buchanan 1988).
Morphology: Breeding males develop tubercles on pectoral fins (Robison and Buchanan 1988). Intestine long with several loops (Goldstein and Simon 1999).
Distribution (Native and Introduced)
U.S. distribution: Widely distributed throughout much of the United States and Canada (Guillory and Gasaway 1978; Pflieger 1978; Guillory 1980). Species found in every U.S. state, except AK, ME, MT, RI, and VT, inhabits Lake Erie and ponds in MT and AB (Scharpf 2005). Introduced into the United States in 1963 at Auburn, Alabama and Stuttgart, Arkansas; spread rapidly as a result of widely scattered research projects, agency stockings to solve aquatic weed problems, interstate importation by individuals from private hatcheries, and natural dispersal from stocking sites (Greenfield 1973; Guillory and Gasaway 1978; Guillory 1980). Pflieger (1978) reported that no evidence for natural reproduction of this species was found in Missouri; Greenfield (1973) and Guillory (1980) reported that the species was not known to be established at most areas of stocking. However, Hargrave and Gido (2004) presented evidence of natural reproduction of the grass carp in the Red and Washita rivers (Lake Texoma, Oklahoma-Texas), and previous publications reported natural reproduction in the lower and upper Mississippi, Illinois, and Missouri rivers, and in the Trinity River, Texas (Conner et al. 1980; Pflieger and Grace 1987; Zimpfer et al. 1987; Brown and Coon 1991; Howells 1994; Raibley et al. 1995; Elder and Murphy 1997; Howard and Murphy 1997; Hargrave and Gido 2004).
Texas distribution: Found widely scattered in the Canadian, Red, Sabine, Trinity, and Rio Grande basins; introduced from Asia and rapidly extending its range in the state, primarily from initial stockings (Hubbs et al. 1991). Juveniles captured in Lake Texoma (Oklahoma-Texas), evidenced natural reproduction in the Red and Washita rivers (Hargrave and Gido 2004). Reproduction documented in the Trinity River (Howells 1994; Elder and Murphy 1997).
[Additional literature noting collection of this species from Texas locations includes, but is not limited to the following: Bettoli et al. (1993); Gido et al. (2002).]
Abundance/Conservation status (Federal, State, Non-governmental organizations)
No information at this time.
Macrohabitat: Ponds, lakes, rivers. In native range (Pacific slope of Asia from Amur River of China and Siberia south to West River in southern China and Thailand), inhabits low gradient stretches of large rivers (Guillory 1980). Juveniles are found in lakes closely connected to rivers, or reservoirs into which the rivers empty (Stanley et al. 1978).
Mesohabitat: Prefer areas with submergent vegetation (Bain et al. 1990). Found in deep holes in river beds, during the winter (Cudmore and Mandrak 2004). Tolerant of a wide range of environmental conditions: water temperatures 0-35°C
(32-95°F); salinities up to 10 ppt; oxygen concentrations as low as .0005 ppt (Guillory and Gasaway 1978; Guillory 1980); preferred temperature of 35°C (Galloway and Kilambi 1984). Species is capable of surviving and migrating through brackish waters to at least 12 ppt, but not for extended periods (Kilambi 1980; Abdusamadov 1987). Temperature required for survival of larvae ranges from 19-30°C (66.2-86.0°F). Within two days post-hatching, larvae move from flowing water to areas characterized by quiet water in which aquatic or submerged terrestrial vegetation is present (Stanley et al. 1978).
Spawning season: In the Trinity River, Texas reproduction occurred in May – July, possibly as early as April (Elder and Murphy 1997). Fish begin moving into spawning areas as water temperatures reach 15-17°C (59.0-62.6°F) and spawning usually occurs above 18°C (64.4°F), with peaks at 20-22°C (68.0-71.6°F) (Stanley et al. 1978; Chilton and Muoneke 1992).
Spawning habitat: Species is an open substratum spawner – broadcast spawner discharging ova and sperm in large numbers (Simon 1999). In large rivers or canals, where current velocity exceeds 0.6 m/s (2.0 ft/s) and having well-vegetated, flooded lowlands (Stanley et al. 1978; Hargrave and Gido 2004). Turbulent areas at the confluence of rivers or below dams are focal points for reproduction (Stanley et al. 1978). Results of an experiment conducted at Econfina Creek, Florida, showed that eggs were sufficiently transported by a current of 0.23 m/s (0.75 ft /s); theoretically, hatching could occur at this flow rate if river is long enough (Leslie et al. 1982). Some prairie streams, such as the Trinity, Washita, and Red rivers (U.S.A.) have suitable environmental conditions for spawning of this species (Elder and Murphy 1997; Hargrave and Gido 2004).
Reproductive strategy: Nonguarder; pelagophil (Simon 1999; Balon 1981). Once appropriate water temperature is reached, spawning seems to be initiated after a sudden rise (>1.2 m (3.9 ft) within a 12-hour period) in water level, usually after heavy rains (Greenfield 1973; Zimpfer et al. 1987; Chilton and Muoneke 1992). During natural spawning, males generally outnumber females by about two to one. Fish typically swim into the strongest current in mid-stream, where swimming and chasing occur; the male then pushes his head against belly of female and leans to one side; this is believed to be the time when eggs and milt are released and fertilization takes place (Chilton and Muoneke 1992).
Fecundity: Females are highly fecund, producing on average 1 million eggs per year (Stanley 1976). Abdusamadov (1987) reported average absolute individual fecundity of 756,000 eggs (range 210,500-1,230,700 eggs from females 4-8 years, 630-880 mm (24.8-34.6 in) in length, from the Terek region of the Caspian Basin). Fecundities of females in the Trinity River, Texas were variable, ranging from 607 eggs/kg – 361,080 eggs/kg, with a mean of 85,528 eggs/kg; significant increase in fecundity with total length for length classes <900 mm (35.4 in) (Elder and Murphy 1997). Upon release from ovaries, eggs are small, measuring 2.0-2.5 mm (0.07-0.10 in) in diameter (Chilton and Muoneke 1992). Eggs are semipelagic, and require temperature ranging from 19-30°C (66.2-86.0°F) and well oxygenated water for successful incubation; hatching was observed at 26-28 hours at 24°C (75.2°F), in Arkansas (Stanley et al. 1978). Hatching occurs in 24-30 hours at 25°C (77°F) (Greenfield 1973).
Age/size at maturation: Highly variable; from 1-10 (Greenfield 1973; Abdusamadov 1987; Chilton and Muoneke 1992) or 11 years; females range from 580-670 mm (22.8-26.4 in) SL while males mature an average of one year earlier from 510-600 mm (20.1-23.6 in) SL (Shireman and Smith 1983). Temperature required for sexual maturation ranges from 19-30°C (66.2-86.0°F) (Stanley et al. 1978).
Migration: Capable of extensive migrations once released in open systems (Guillory and Gasaway 1978; Bain et al. 1990), though larger individuals tend to move more than smaller individuals (Bain et al. 1990). Grass carp undergo spawning migration, usually in large shoals (Greenfield 1973).
Longevity: Usually 5-11 years, with some individuals reaching15 years old; specimen from North Dakota found to be >33 years old (Cudmore and Mandrak 2004).
Food habits: Herbivore, particulate feeder, browser; feeds on macrophytes, but consumes insects and small fish when vegetation is unavailable (Greenfield 1973; Chilton and Muoneke 1992; Goldstein and Simon 1999). Feeding strongly affected by temperature; fish begin active feeding as temperatures rise above 7-8°C (44.6-46.4°F), with peak consumption at 20-26°C (68.0-78.8°F) (Chilton and Muoneke 1992). Larvae begin feeding on rotifers at 2-4 days, changing to larger zooplankton in about a week (Stanley et al. 1978). Adults feed on a variety of plants (Kilambi 1980), consuming filamentous algae, aquatic vascular plants, and terrestrial plant material (Pflieger 1978). Bain et al. (1990) reported that the aquatic weed, Hydrilla, was a preferred food. Mean percent composition of diet for individual fish in the Trinity River, Texas was 87% terrestrial detritus, 8% aquatic vegetation, 4.5% terrestrial grasses, and <1% algae and invertebrates (Elder and Murphy 1997).
Growth/Population structure: In the Trinity River, Texas growth rates were variable, apparently highest during the first year (>200 mm, 7.87 in), remaining above 100 mm (3.94 in) per year through age 7, beginning to decline at age 9; mean annual growth after the first year was about 107 mm (4.21 in) per year. Females represented 63% of the sample; overall, the lengths and weights of females were significantly greater than those of males (Elder and Murphy 1997). Juveniles collected from Lake Texoma (Oklahoma-Texas) ranged in length from 15.2-60 mm (0.60-2.36 in) TL (Hargrave and Gido 2004). Growth is highly variable, individuals can attain the size of 1.5 m in length in river waters within 5-6 years (Greenfield 1973). . Grass carp tend to grow larger in larger areas (i.e. larger ponds), even when stocking densities are identical (Chilton and Muoneke 1992). In the Terek region of the Caspian Basin, the ratio of females to males was 1:1.2 (Abdusamadov 1987)
Phylogeny and morphologically similar fishes
The genus Ctenophayngodon is monotypic (Guillory 1980). Both the goldfish (Carassius auratus) and the common carp (Cyprinus carpio) differ from Ctenopharyngodon idella in having a long dorsal fin, deeper body, and spinous rays in the dorsal and anal fins; further, C. carpio has barbels, and C. auratus lacks dark-edged scales (Page and Burr 1991). C. idella larvae, as well as C. auratus and C. carpio larvae, exhibit a large preanal length relative to total length (>65%). However, C. idella larvae may be distinguished from that of the latter species by the presence of 30-33 preanal myomeres. Larger larvae develop only 7-9 dorsal fin soft rays; C. auratus and C. carpio develop more than 15 (Fuiman et al.1983). For description of larval C. idella see Soin and Sukhanova (1972), Conner et al. (1980); and Shireman and Smith (1983).
In an effort to develop a sterile form of the grass carp, hybridization with the common carp (Cyprinus carpio) was attempted, but fertile hybrids were produced (Chilton and Muoneke 1992).
The Asian tapeworm (Bothriocephalus opsarichthydis), native to China and the Amur River basin, was first reported in several native North American fish species in the 1970’s following introduction of the parasite via the infected grass carp (Hoffman and Schubert 1984; Cudmore and Mandrak 2004).
Lernaea cyprinacea reported from this species in Arkansas (Stevenson 1965); B. opsarichthydis (listed as B. acheilognahti), reported from Puerto Rico (Bunkley-Williams and Williams 1994). Shireman and Smith (1983), Hoffman and Schubert (1984), and Cudmore and Mandrak (2004) list diseases and parasites of C. idella.
Commercial or Environmental Importance
Grass carp were introduced in the U.S. in an effort to control nuisance plant growth, but in some ecosystems it may negatively impact aquatic plants and invertebrate foods that provide beneficial habitat for desired species (Taylor 1984; Chilton and Muoneke 1992; Fuller et al. 1999; Cole 2006). In Lake Conroe, Texas, stocking of this species and the resultant removal of vegetation altered the invertebrate and fish communities (Bettoli et al. 1991).
A survey of fourteen Missouri fisherman found that most grass carp were caught in trammel nets or hoop nets, and a few were caught on trot lines. Fisherman generally agreed that grass carp are easy to clean, yield a large amount of usable flesh, have good flavor, and are more readily marketable than common carp (Pflieger 1978). Alabama fisherman reported the grass carp to be an excellent sportfish, with outstanding eating qualities (Greenfield 1973).
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