Species group: Carp
Other common names: White Amur
Scientific name: Ctenopharyngodon idella
The Grass Carp is an herbivorous freshwater member of the Cyprinidae (Carp) family that is a cousin of the domestic Koi carp. They are native to Eastern Asia, with a native range extending from Vietnam to China and up to the Chinese-Soviet border. It is found in large, turbid rivers but when the rivers flood the fish moves onto the floodplains to graze its grasses. The Grass Carp grows very rapidly and is east to keep. It has been farmed extensively in China for centuries. In the wild they live in in lakes, ponds, pools and backwaters of large rivers, but need to spawn in fast-moving water. If raised in small pools near humans they can become very tame and will even get used to being hand-fed, raising their heads out of the water to eat from their owners' hand. If used for weed control, a specially produced sterile triploid version (it has three times the copies of each chromosome rather than the usual two) is often introduced these days as this version of the fish is sterile. Grass carp are active grazers and need to consume three times their own body weight every day. In smaller ponds their feed often needs to be supplemented with commercial feed, typically carp pellets. This frequent feeding makes them much tamer and they will get used to being fed. They will also learn to take feed from a human hand, particularly if it's in pellet form. Carp are some of the few large or farmed fish that can be kept as pets. They are intelligent and get used to being fed by humans. Indeed, they can become so used to being fed that they will actually poke their heads out of the water to be fed by hand. As a result they are some of the few fish that humans can form a bond with. A rarity for freshwater fish (most of the fish with this kind of behaviour being saltwater species).
Grass Carp have elongate, chubby, torpedo-shaped body forms. The terminal mouth is slightly oblique with non-fleshy, firm lips, and no barbels (which is unusual for a carp). 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 colour 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 8 in will reach over 18 in by the autumn, and adults often attain nearly 4 ft in length at maturity.
Grass Carp are not compatible with aquarium tanks, but can be reared in any pond or pool or slow-moving waterway. They are good for keeping duck ponds clear of vegetation and can survive in shallow water as long as it is sufficiently oxygenated. But they need deeper water to over-winter, particularly if the water is prone to freeze. It will grow happily in ponds, but the eggs are not viable there. The fish has a certain preference for some kinds of common pond weeds (such as duckweed) and it has been introduced to Europe and North America to control such weeds.
large pond, Pond Management, weed control, algae menace, blanket weed, voracious grazers
space, aggressive fish
little garlic salt, frequent hand feeding