They are found in rivers in tropical and subtropical South America (freshwater stingrays in Africa, Asia and Australia are in another family, Dasyatidae).

They are generally brownish, greyish or black, often with a mottled, speckled or spotted pattern, have disc widths ranging from 31 to 200 centimetres (1.0–6.6 ft) and venomous tail stingers.

River stingrays feed on a wide range of smaller animals and the females give birth to live young.

[4][5] The largest freshwater species in this family are the discus ray (Paratrygon aiereba) and short-tailed river stingray (Potamotrygon brachyura), which grow up to 1.5–1.6 m (4.9–5.2 ft) in disc width.

[3] Members of Potamotrygonidae are predators and feed on a wide range of animals such as insects, worms, molluscs, crustaceans and fish (even spiny catfish).

[1] Like other Elasmobranchs, male freshwater stingrays are easily recognized by their pair of claspers, modifications of the pelvic fins used when mating.

[25] The stings are typically highly painful and are occasionally fatal to humans, especially people living in rural areas that only seek professional medical help when the symptoms have become severe.

[18] A study at the Butantan Institute, São Paulo, Brazil, revealed that the composition of freshwater stingray venom varies according to sex and age, even between individuals of the same species.

[27] Accidents occur when the rays are stepped on or when the fins are touched, the defensive behavior consists of turning the body, moving the tail and introducing the stinger into the victim.

Initial symptoms include severe pain, erythema and edema, then necrosis occurs which results in sagging tissue in the affected area and forms a deep ulcer, which develops slowly.

[29] In the Río de la Plata region, the meat of P. brachyura is particularly prized and locally the species is called raya fina (fine ray).

[26] Several species are commonly bred in captivity, especially at East and Southeast Asian fish farms, which produce thousands of offspring each year.

[18] Some captive farms produce hybrids (both intentionally to get offspring with new patterns and unintentionally because of a lack of males), but this practice is generally discouraged.

[29] Zoos and public aquariums in Europe and North America have initiated programs, including studbooks, for several Potamotrygonidae species.

For example, the Guaíra Falls disappeared after the completion of the Itaipu Dam, allowing Potamotrygon amandae (formerly misidentified as P. motoro) and P. falkneri to spread into the upper Paraná basin.

[38] In contrast, dams threaten some species such as P. magdalenae by isolating populations and preventing gene flow,[39] and others such as P. brachyura generally avoid lentic habitats, including the reservoirs created by river impoundment.

[12] In addition to the large numbers caught for food (hundred of tons per year in the Brazilian Amazon alone),[29] many are killed because of the risk their stings represent to locals and tourists.

[7] Initially Brazil completely banned all exports of wild-caught freshwater stingrays for the aquarium trade, but have since introduced quotas for some species.