Abstract
The drainage of the Negro River is the most important watercourse in the Patagonia ecoregion and, together with the Colorado river basin, define an ecotone, i.e., a zoogeographic transition, where coexist the Brazilian and Patagonian lineages of freshwater fishes. The Patagonia ecoregion has 29 fish species, 15 native and the remaining introduced. For this study, the ichthyofauna of seven locations in the lower course of the Negro river drainage were sampled along two years. Gillnets, coastal trawls, cast nets, river trammel nets and fishing rods were used to catch specimens. A total of 13 species belonging to nine orders and 11 families were collected. The families Atherinopsidae and Characidae show the highest species richness and one exotic species, Cyprinus carpio Linnaeus, 1758, was recorded. The origin and distribution of some species is discussed, considering the role of human action and certain environmental factors.
Highlights
South America has the richest freshwater fish fauna in the world, with more than 5,100 species which represent about one third of all freshwater fish worldwide (Reis et al 2016)
South America belongs to the Neotropical region and its freshwater fauna is distributed in 51 ecoregions defined by hydrographic limits (Abell et al 2008; Albert and Reis 2011)
Thirteen species corresponding to nine orders and 11 families were recorded (Fig. 3, Table 2): Odontesthes bonariensis (Valenciennes, 1835), O. hatcheri (Eigenmann, 1909), Cheirodon interruptus (Jenyns, 1842), Psalidodon pampa (Casciotta, Almirón & Azpelicueta, 2005), Cyprinus carpio Linnaeus, 1758, Jenynsia lineata (Jenyns, 1842), Cnesterodon decemmaculatus (Jenyns, 1842), Galaxias maculatus (Jenyns, 1842), Mugil liza (Valenciennes, 1863), Percichthys trucha (Cuvier & Valenciennes, 1840), Paralichthys brasiliensis (Ranzani, 1840), Genidens barbus (Lacepède, 1803), and Corydoras paleatus (Jenyns, 1842)
Summary
South America has the richest freshwater fish fauna in the world, with more than 5,100 species which represent about one third of all freshwater fish worldwide (Reis et al 2016). South America belongs to the Neotropical region and its freshwater fauna is distributed in 51 ecoregions defined by hydrographic limits (Abell et al 2008; Albert and Reis 2011). These ecoregions in turn form 13 basin complexes grouped by hydrologic and biogeographic units (Reis et al 2016). It should be noted that as observed in Albert and Reis (2011), there are ecoregions with high percentages of endemism, such as the Maracaibo, Titicaca, and Patagonia. The Negro river drainage is in the north of Patagonia ecoregion, within Southern Cone basin complex, and is the most important watercourse in this ecoregion (Fig. 1)
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