The grass carp Ctenopharyngodon idellus is a native Chinese freshwater fish with a broad distribution in China, and has now been introduced to more than 100 countries. The fish is widely cultivated for food. Production in China reached 4.08 million tons in 2009 and constitutes 21.4% of the total freshwater cultured fish annual output. Grass carp represent the largest freshwater aquaculture product in the world. Under natural conditions, the grass carp is basically herbivorous, feeding on certain aquatic weeds.
