Odontesthes bonariensis

Odontesthes bonariensis is native to subtropical and temperate South America east of the Andes where it ranges from around the Río Negro basin in Argentina, north throughout most of the northern half of that country, to the Río de la Plata Basin in south Brazil, Paraguay and Uruguay.[3][6][8] In coastal Atlantic parts of South America it ranges at least from the southernmost Buenos Aires Province in Argentina to Rio Grande do Sul State (Lagoa dos Patos) in Brazil.[3][8] It has been introduced to many places outside its native range, including Argentina (in parts of the country where not native), Bolivia, Brazil (in parts of the country where not native), Chile, Peru, Morocco (where probably not established), Italy (only Lake Nemi), Israel (failed to become established) and Japan.[4][11][12][13]

O. bonariensis is highly adaptable and can live in a wide range of habitats. This includes both stagnant and flowing waters, such as rivers, streams, channels, lakes, reservoirs, estuaries and coastal lagoons.[2][3][4] In much of its range it is particularly common in Pampas lakes that generally are less than 4 m (13 ft) deep.[14] The species is able to live in fresh, brackish and salt water (salinity up to 3.5%),[11] but not in hypersaline conditions.[14] The water temperature can range at least from 7 to 30 °C (45–86 °F); in short periods they can even survive in waters where the surface has frozen.[11][15] Temperatures of 32 °C (90 °F) are lethal to most individuals,[14] and when above 25 °C (77 °F) they often perish due to increases of the parasitic Lernaea copepods (also a primary reason for failed introduction attempts of O. bonariensis in some countries), the bacteria Aeromonas hydrophila and algal blooms.[7]

Overall the species is widespread and common, but global warming can increase the temperature and salinity in some placed inhabited by O. bonariensis, representing a threat to these local populations.[16][17]

This species is considered an excellent food fish, and it is of major economic importance in both its native range and where introduced.[4][7] Many thousand tonnes are caught each year.[4] It is also considered a good game fish. It is sometimes kept in aquaculture due to its ability to live in a wide range of environments, the ease of breeding it in captivity and its fast growth.[7] In Lake Titicaca where introduced they are typically caught when around 20 cm (8 in) long and 100 g (3.5 oz) in weight, but those caught in its native Argentina typically are around 27 cm (11 in) long and weigh 300 g (11 oz).[11] However, some populations, notably the one in Lake Titicaca, contain levels of metals from pollution that exceed the internationally recommended safety thresholds for human consumption.[21]

Although it has significantly aided the local economy in many places where introduced, it has become invasive in some places, causing serious problems to the native species. It is one of the causes of the major declines in Orestias pupfish and Trichomycterus catfish in Bolivia, Peru (notably Lake Titicaca where O. cuvieri has become extinct and relatives declined) and Chile.[4][22] Another vulnerable habitat where it has been introduced is the Iguazu River at the Argentina–Brazil border.[23] Odontesthes hatcheri replaces O. bonariensis in the southern half of Argentina (roughly equalling Patagonia),[6] but the latter has been translocated to certain southern regions where the two hybridize. This offspring is viable and some native populations of O. hatcheri have become "diluted".[13]