Grass carp

What it is

This fish has a torpedo-shaped body that is chubby and elongated. Its colour ranges from dark olive to brownish-yellow on the sides, with a white belly. The scales are large and slightly outlined. It lacks barbels and has firm, non-fleshy lips. The dorsal fin holds eight to ten soft rays, while the anal fin sits closer to the tail than in many related species. Adults typically measure between 60 and 100 centimetres, though they can reach two metres in length and weigh up to 45 kilograms.

Where it lives

Native to the Pacific Far East, its natural home stretches from northern Vietnam to the Amur River on the border of China and Russia. It inhabits large, turbid rivers and associated floodplain lakes or wetlands. Humans have introduced it to many nations, including the United States, New Zealand, and various European countries. In the wild, it prefers slow-flowing or standing water bodies rich in vegetation. It tolerates a wide range of temperatures but requires specific conditions for reproduction.

How it lives

Adults feed primarily on aquatic plants, including submerged terrestrial vegetation. They may also consume detritus, insects, and other invertebrates. These fish eat up to three times their own body weight each day. They thrive in small lakes and backwaters where vegetation is abundant. Young fish grow very rapidly, often reaching over 45 centimetres by autumn if stocked in spring. Lifespan is typically five to nine years, though some individuals survive past fifteen years in favourable conditions.

Breeding and life cycle

Spawning occurs in fast-moving rivers when water temperatures reach 20 to 30 degrees Celsius. The eggs are slightly heavier than water and must remain suspended in turbulence to survive. If they sink to the bottom, they likely die. This requirement for long, flowing rivers limits natural reproduction in many introduced areas. Maturation takes about five years. Recent research has developed methods to shorten breeding cycles using surrogate host fish.

Fish and people

Farmers in China have cultivated this species for centuries as one of the Four Great Domestic Fish. It is valued for its tender meat and low bone content. Globally, it is the most farmed fish species by tonnage. Authorities also introduce sterile triploid individuals to control aquatic weeds in places like New Zealand and the Netherlands. Anglers find them challenging due to their vegetarian diet and wariness, but they are strong fighters. Some traditions involve consuming raw bile for health, though this poses poisoning risks.

Status and threats

The species has established self-reproducing populations in only a few major rivers outside its native range. In the United States, it is present in 45 states and reproduces in the Great Lakes Basin. While useful for weed control, unauthorized releases have raised ecological concerns. Management often relies on stocking sterile fish to prevent uncontrolled spread. Conservation efforts focus on regulating introductions and monitoring existing populations to balance agricultural benefits with environmental protection.

Relatives and look-alikes

It is the only living member of the genus Ctenopharyngodon. Extinct relatives include Ctenopharyngodon orientalis and Ctenopharyngodon xiejiaensis from the Miocene era. Another extinct species, Ctenopharyngodon hermi, was found in Turkey. It is often grouped with other Asian carps such as the black carp, silver carp, and bighead carp. These related species share similar habitats and are also significant in aquaculture and invasive species discussions.

Questions people ask about Grass carp

Good reading and sources

• Grass carp on WikipediaEncyclopedia
• More photos on Wikimedia CommonsPhotos
• Wikidata recordOpen data