Fish diversity of the headwaters and streams of the Upper Paraná River System in the State of São Paulo, Brazil

Abstract

The so called upper Paraná River system includes the whole Paraná River drainage basin upriver from the former Sete Quedas falls (now drowned by the Itaipu Reservoir) and encompass large sized tributaries like the Rivers Grande, Paranaíba, Tietê and Paranapanema. Geographically , the drainage basin approximately 900.000 km2 includes the north of Paraná State, the south of Mato Grosso do Sul, the majority of São Paulo State (west of the Serra do Mar), the south of Minas Gerais, the south of Goiás and a small area of eastern Paraguay adjacent to Mato Grosso do Sul. In the São Paulo State, according to our estimates, the upper Paraná system contains 22 families and approximately 170 described fish species, including the largest rivers of the State. These large rivers main channels are inhabited by medium to large size fish species. Associated to these large rivers there is a huge number of streams and headwaters, inhabited primarily by small size fish species, with restrict geographical distributions, with a small or inexistent commercial value and greatly dependent of the riparian vegetation for food, shelter and reproduction. Small size fish species like those are approximately 50% of the described freshwater fish species of South America and shown a high degree of geographical endemism. The study of the small freshwater fish species systematics, evolution and general biology is, without doubt, the great challenge and main frontier of the South American ichthyology in the end of this century. Unfortunately, these fish species are also the most threatened by harmful human activities like deforesting and extensive use of fertilizers and pesticides associated of intensive agricultural activities, since as a whole, they are heavily dependent on the allochthonous organic matter imported from the riparian vegetation to survive. Inside the São Paulo section of the upper Paraná system, our estimates indicate that the Pontal do Paranapanema, Alto Paranapanema, Peixe, Aguapeí, Baixo Tietê and São José dos Dourados drainage basins (as defined in the BIOTASP synthesis map - "Mapa Sintese do Estado de São Paulo" - see Fig. 2 of the Project) are poorly sampled for fishes. The Médio Paranapanema, Turvo-Grande, Baixo Pardo-Grande, Sapucaí-Grande and Piracicaba-Capivari-Junduaí drainage basins are moderately sampled and only the Tietê¬-Sorocaba, Tietê-Jacareí, Tietê-Batalha, Mogi-Guaçu and Pardo drainage basins are reasonably well sampled for fishes. That means that of the 16 drainage basins composing the São Paulo upper Paraná system portion, in terms of ichthyofauna, six are poorly sampled, five are moderately sampled and five are well sampled, meaning that about 70% of the São Paulo upper Paraná drainage basins are not satisfactorily explored for fishes in scientific terms... (AU)