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 Juvenile
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| Ctenopharyngodon idella Valenciennes, 1844 |
The Grass Carp, (Ctenopharyngodon idella), also known as the White Amur, is a herbivorous, freshwater fish. It is cultivated in China for food but was introduced in the United States for aquatic weed control. It is a species of carp native to Siberia and northern China.[1] The name White Amur derives from the Amur river, where the species is believed to originate.
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Appearance and anatomy
White amur have an elongate, chubby body form that is torpedo shaped. The terminal mouth is slightly oblique with non-fleshy, firm lips, and no barbels.[1] The complete lateral line contains 40 to 42 scales. Broad, ridged pharyngeal teeth are arranged in a 2, 4-4, 2 formula. The dorsal fin has 8 to 10 soft rays, and the anal fin is set closer to the tail than most cyprinids. Body color is dark olive, shading to brownish-yellow on the sides with a white belly and large slightly outlined scales. The grass carp grows very rapidly, and young fish stocked in the spring at 20 cm (8 inches) will reach over 45 cm (18 inches) by fall, and adults often attain nearly 1.2 m (4 feet) in length and over 18 kg (70-90 pounds) in weight. They grow 10 pounds a year at least. They eat up to 3 times their own body weight daily. They thrive in small lakes and backwaters that provide an abundant supply of fresh water vegetaion.
Ecology
This species occurs in lakes, ponds, pools and backwaters of large rivers, preferring large, slow-flowing or standing water bodies with vegetation.[1] In the wild, grass carp spawn on riverbeds in fast-moving rivers.[1] Adults of the species feed exclusively on aquatic plants. They feed on higher aquatic plants and submerged grasses, but may also take detritus, insects, and other invertebrates.[1]
Relationship to humans
The species was deliberately introduced into the United States in 1963 for aquatic weed control. It was introduced into New Zealand along with stocks of goldfish but the distribution is carefully controlled to prevent it from becoming a more widespread pest. When used for weed control, often the fish introduced to the pond or stream are sterile, triploid fish. The process for producing triploid fish involves shocking eggs with rapid change in temperature. The young are then tested for triploidy before being sold. Bait often consists of vegetables or fruits that are native to the area.[2] These fish are also a food fish, and may be steamed, pan fried, broiled, or baked.[1]
References
- ^ a b c d e f "Ctenopharyngodon idella". FishBase. Ed. Ranier Froese and Daniel Pauly. May 2007 version. N.p.: FishBase, 2007.
- ^ Triploid Grass Carp in New York Ponds. New York State Department of Environmental Conservation.
