Indigenous to Europe and Asia, the Cyprinidae family includes several species of freshwater fish known by the common name Carp. The very species from which the name is taken is the Common Carp (Cyprinus carpio), which belongs to the genus Cyprinus. The wild form of the species is commonly slimmer than the domesticated ones, growing up to 120 cm (47 in) and weighing more than 40 kg (88 lbs). The Koi (simply Japanese for “carp”) is a domesticated variety of the Common carp, traditionally kept for ornamental purposes in water gardens and koi ponds.
The members of the genus Carassius are generally referred to as Crucian carps. The actual fish that bear that name, the Crucian Carp (Carassius carassius), is a medium-sized species that rarely surpasses more than 1 kg (3.3 lbs) in weight; though a specimen that measures 54 cm and weighs 3 kg had been caught in the Netherlands. It is related to the earliest-known domesticated fish, the Goldfish (Carassius auratus auratus). Popularly kept as pets in aquariums, it can grow up to 58 cm (23 in) in length, weigh up to 4 kg (9.9 lbs) and, under ideal conditions, live for more than 40 years. While there are claims that the Crucian carp is the wild form of the Goldfish, it is actually the Prussian Carp (Carassius gibelio), which has a maximum length of 45 cm and weighs no more than 3 kg (6.6 lbs).
Belonging to the genus Epalzeorhynchos, the Red-tailed Black Shark (Epalzeorhynchos bicolor) has unfortunately become extinct in the wild, but is still around as aquarium fish. Named and valued for its vibrant red/orange tail and black body, it can grow up to a length of 15 cm (6 in) and has an average lifespan of 8-10 years. The Black Carp (Mylopharyngodon piceus) is the single member of the genus Mylopharyngodon, and is caught either for food or for use in Chinese medicine. It can reach up to 1 m (3 ft) in length and over 32 kg (70 lbs) in weight.
Among the species of the genus Hypophthalmichthys is the Bighead Carp (Hypophthalmichthys nobilis), which is obviously named for its big, scale-less head. It can be quite big in size as well, reportedly approaching weights up to 45 kg (100 lbs). From the same genus, the Silver Carp (Hypophthalmichthys molitrix) is also known as the Flying Carp due to its propensity for leaping out of the water. Able to leap 3 m (10 ft) into the air, it can grow to a weight of above 18 kg (40 lbs).
The Carp has been a sought-after species for a number of reasons. It was initially a major food source, although its significance in this area has declined somewhat in favor of other food fish such as salmon and trout. It has also been caught for sport or for medicinal use. Most notably, carps have been very popular as ornamental and aquarium fish. In particular, the Goldfish has long been an aquarium favorite, and the Koi is viewed in Japanese culture as a bringer of good luck. Enduring for thousands of years, the carp has not fallen out fashion owing to the many purposes that it serves.