The family Cyprinidae, from the Ancient Greek κυπρῖνος (kuprīnos "carp") , consists of the carps, the true minnows, and their relatives (e.g. the barbs). They are commonly called cyprinids or carp and minnow family. It is the largest family of fresh-water fish, with over 2,400 species in about 220 genera. The family belongs to the order Cypriniformes, of whose genera and species the cyprinids make up two-thirds.
The fish in this family are native to North America, Africa, and Eurasia. The largest cyprinid in this family is the Giant Barb (Catlocarpio siamensis), which may grow up to 3 m (10 ft). The largest North American species is the Colorado Pikeminnow (Ptychocheilus lucius), of which individuals up to 6 ft (1.8 m) long and weighing over 100 pounds (45 kg) have been recorded.
On the other hand, many species are smaller than 5 cm (2 in). As of 2008, the smallest known freshwater fish is indeed a cypriniform, Danionella translucida, reaching 12 mm at the longest. All fish in this family are egg-layers and the breeding habits of most is one of non-guarding of the eggs, however, there are a few species that build nests and/or guard the eggs. The bitterling-like cyprinids (Acheilognathinae) are notable for depositing their eggs in bivalves where the young grow up until able to fend for themselves.
Cyprinids are highly important food fish; they are fished and farmed across Eurasia. In land-locked countries in particular, cyprinids are often the major species of fish eaten, although the prevalence of inexpensive frozen fish products made this less important now than it was in earlier times. Nonetheless, in certain places they remain popular for food as well as recreational fishing, and have been deliberately stocked in ponds and lakes for centuries for this reason.
Several cyprinids have been introduced to waters outside their natural range to provide food, sport, or biological control for some pest species. The Common Carp (Cyprinus carpio) and the Grass Carp (Ctenopharyngodon idella) are the most important of these, for example in Florida. In some cases, these have become invasive species that compete with native fishes or disrupt the environment, carp in particular can stir up the riverbed reducing the clarity of the water making it difficult for plants to grow.
Numerous cyprinids have become important in the aquarium hobby, most famously the Goldfish, which was bred in China from the Prussian Carp (Carassius (auratus) gibelio). First imported into Europe around 1728, it was much fancied by Chinese nobility as early as 1150 AD and after it arrived there in 1502, also in Japan. In the latter country, from the 18th century onwards the Common Carp was bred into the ornamental variety known as koi – or more accurately nishikigoi (錦鯉), as koi (鯉) simply means "Common Carp" in Japanese.
Other popular aquarium cyprinids include danionins, rasborines and true barbs. Larger species are bred by the thousands in outdoor ponds, particularly in Southeast Asia, and trade in these aquarium fishes is of considerable commercial importance. The small rasborines and danionines are perhaps only rivalled by characids and poecilid livebearers in their popularity for community aquaria.
One particular species of these small and undemanding danionines is the Zebrafish (Danio rerio). It has become the standard model species for studying developmental genetics of vertebrates, in particular fish.
Habitat destruction and other causes have reduced the wild stocks of several cyprinids to dangerously low levels; some are already entirely extinct. In particular, Leuciscinae from southwestern North America have been hit hard by pollution and unsustainable water use in the early-mid 20th century; most globally extinct Cypriniformes species are in fact Leuciscinae from the southwestern United States and northern Mexico.
The massive diversity of cyprinids has hitherto foiled attempts to resolve their phylogeny in sufficient detail to make assignment to subfamilies more than tentative in many cases. It is obvious that some rather distinct lineages exist – for example, Cultrinae and Leuciscinae, regardless of their exact delimitation, are rather close relatives and stand apart from Cyprininae –, but the overall systematics and taxonomy of the Cyprinidae remain a subject of considerable debate. A large number of genera are incertae sedis, too equivocal in their traits and/or too little-studied to permit assignment to any one subfamily with even a reasonable degree of certainty.
Part of the solution seems the realization that the rasborines seem to merely assemble minor lineages that have little shifted from their evolutionary niche, or co-evolved, for millions of years. The core group apparently not just looks much like small delicate rasborines but is quite exactly that. These are among the most basal lineages of living cyprinids. Other "rasborines" apparently are distributed across the divere lineages of cyprinids however.
The validity and circumscription of proposed subfamilies like Garrinae, Labeoninae or Squaliobarbinae also remains doubtful. The latter however appear to correspond to a distinct lineage. The sometimes-seen grouping of the large-headed carps (Hypophthalmichthyinae) with Xenocypris on the other hand seems quite in error. More likely, the latter is part of the Cultrinae.
The Barbidae and the disputed Labeoninae might be better treated as part of the Cyprininae, forming a close-knit group whose internal relationships are still little known. However, as noted above, how Garra and various other minor lineages tie into this is still ill-resolved. Therefore such a radical move, though reasonable, is probably premature.
The Tench (Tinca tinca), a significant food species farmed in western Eurasia in large numbers, is very singular. It has been allied with the Leuciscinae most often, but even when these were rather loosely circumscribed it always stood apart. A cladistic analysis of DNA sequence data of the S7 ribosomal protein intron 1 supports the view of its distinctness. It also suggests that it may be closer to the small East Asian Aphyocypris, Hemigrammocypris and Yaoshanicus. They would have diverged roughly at the same time from cyprinids of east-central Asia, perhaps as a result of the Alpide orogeny that vastly changed the topography of that region in the late Paleogene, when their divergence presumably occurred.
Subfamily Labeoninae (disputed: in Barbinae, Cyprininae, Garrinae?)
Subfamily Psilorhynchinae – mountain carps
Subfamily Squaliobarbinae (sometimes included in Cyprininae or Leuciscinae)