Common carp

The common carp, known scientifically as Cyprinus carpio, is a widespread freshwater fish.

It thrives in eutrophic waters, which are environments rich in nutrients, such as large rivers and lakes. While native to Europe and Asia, humans have introduced them to almost every part of the world. This global spread has made them a complex species. In many places, they are farmed for food through aquaculture. However, they are also considered one of the world's 100 worst invasive species. This is because they can out-compete native fish populations in new habitats.

Physiologically, the common carp is built for life on the water's bottom.

They are benthic feeders, meaning they search for food in the sediment. To find prey, they use two pairs of barbels near their mouths. These barbels act as sensors to feel for insects, worms, or plant tubers. The carp creates suction to pull up mud and sediment. It then mouths the contents to identify food by taste and size. While they have no oral teeth, they possess ten pharyngeal teeth in their throat. These teeth are used to crush or grind food items before they pass through the intestines.

Common carp are highly adaptable to various environmental conditions.

They prefer slow-moving or standing water with soft, vegetative sediments. They can tolerate a wide pH range from 6.5 to 9.0. They are also quite salt tolerant compared to other freshwater fish. Research shows they can withstand salinity levels of at least 12 g/L. If oxygen levels in the water become very low, they can gulp air at the surface to survive. They can even survive winter in frozen-over ponds as long as some liquid water remains below the ice.

Humans have shaped the carp through domestication for thousands of years.

Records of carp farming date back to Roman times. In Europe, monks helped spread carp farming between the 13th and 16th centuries. This long history of breeding has created many different varieties. For example, the ornamental koi carp originated in the Niigata region of Japan in the 1820s.

Other varieties were bred specifically for food. These include the mirror carp, which has large, shiny scales, and the leather carp, which has very few scales.

Genetic mutations have led to these distinct physical appearances.

The mirror carp phenotype is caused by a mutation at specific scale trait loci. This involves the S and N alleles. A mirror carp has a genotype of "ssnn," meaning it is all recessive. This mutation affects the fibroblast growth factor receptor, known as Fgfr1A1. In contrast, the leather carp is also recessive at the S locus but is heterozygous at the N locus. This specific genetic combination results in a body with almost no scales at all.

Common carp are also known for their impressive size and longevity.

While wild carp are typically slimmer, domesticated versions grow much larger. Domesticated carp can reach a maximum length of 1.3 meters and weigh over 30 kilograms. The largest recorded common carp was caught in France in 2013 and weighed 15.8 kilograms.

They are also very long-lived. One documented wild carp in North America lived to be 64 years old. Their reproductive capacity is equally massive. A single female can lay 300,000 eggs in one spawn, and over a million eggs in a single year.

In the wider ecosystem, the common carp plays many roles. They are omnivores that eat plants, seeds, insects, and even other fish remains. Because they root through the bottom, they often stir up sediment. This process increases water turbidity, or cloudiness. Their eggs and young fry are often eaten by many different predators. These include birds like herons and ospreys, as well as mammals like otters and mink. By changing the water and competing for food, they significantly impact the balance of the freshwater systems they inhabit.