Grass carp

The grass carp (Ctenopharyngodon idella) is a species of large herbivorous freshwater fish in the family Cyprinidae, native to the Pacific Far East, with a native range stretching from northern Vietnam to the Amur River on the Sino-Russian border. This Asian carp is the only species of the genus Ctenopharyngodon.

Grass carp are resident fish of large turbid rivers and associated floodplain lakes/wetlands with a wide range of temperature tolerance, and spawn at temperatures of 20 to 30 °C (68 to 86 °F). It has been cultivated as a food fish in China for centuries, being known as one of the "Four Great Domestic Fish" (Chinese: 四大家鱼), but was later introduced to Europe and the United States for aquatic weed control, becoming the fish species with the largest reported farmed production globally, over five million tonnes per year.

Habitat

Grass carp inhabit lakes, ponds, pools and backwaters of large rivers, preferring large, slow-flowing or standing water bodies with abundant vegetation. In the wild, grass carp spawn in fast-moving rivers, and their eggs, which are slightly heavier than water, develop while drifting downstream, kept in suspension by turbulence. Grass carp require long rivers for the survival of the eggs and very young fish, and the eggs are thought to die if they sink to the bottom.

Adult grass carps feed primarily on aquatic plants, both higher aquatic plants and submerged terrestrial vegetation, but may also eat detritus, insects and other invertebrates. They eat up to three times their own body weight daily, and thrive in small lakes and backwaters that provide an abundant supply of vegetation.

According to one study, grass carp live 5–9 years, with the oldest surviving 11 years. In Silver Lake, Washington, a thriving population of grass carp is passing the 15-year mark.

Behaviour

Grass carp is one of the most common freshwater farmed fish in China, being one of the Four Domestic Fish (四大家鱼) alongside the black carp, silver carp, and bighead carp. Its meat is tender, with little bones. Many Chinese cuisine has grass carp as a featured dish, such as Cantonese cuisine. In some Asian countries, it is believed that ingestion of raw bile or entire gall bladders of the grass carp may improve visual acuity and health. However, it may in fact cause severe poisoning.