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Título: The High River Paraná Basin: limnological and ichthyological aspects
Autor(es): AGOSTINHO, A.A.; VAZZOLER, A.E.A. de M.; THOMAZ, S.M.
Palavras-chave [PT]:

Paraná, Rio, Bacia. Limnologia. Ictiologia. Brasil.

River Paraná Basin. Limnological. Ichthyological. Brazil.

Abstract: This chapter is concerned with the limnological and ichthyological aspects of the high River Paraná, delimited by the confluence of Rivers Paranaíba and Grande up to the former Sete Quedas Waterfalls (619 km). The intensive use of the water bodies of this basin and the construction of many dams have had a great influence on the limnological characteristics which affect the structure and the functioning of the biological community that inhabit them. Among the limnological parameters, phosphorus deserves special attention since it is the main nutrient associated with the eutrofication process and it can be an indicator of anthropogenic interference. A model concerning the main routes of phosphorus in different water bodies of the basin is proposed. The flood pulses are the main forcing function that regulates the exchange between the river and its floodplain. Two hundred and twenty-one fish species were registered in the different environments of the basin. More than 20 species from other basins were introduced and, at least 17 other species were dispersed after the barrier of the former Sete Quedas Waterfalls had been submerged when the Itaipu Reservoir was formed. Piscivorous and detritivorous species are dominant in the fish assemblages of the basin alternating in importance according to the environment. The first group predominates in rivers, while the second one in lagoons and secondary channels. Information on some reproductive tatics of 71 species of teleosts is available. There is a prevalence of species with external fecundation, partial spawning, marked reproductive seasonality and shor reproductive period. The beginning of gonadal development is related to water temperature and day-length increase; spawning begins with the flood which widens the environmental areas, while the end of this period is determined by the flood peak. Information about growth parameters is restrict to only about 10% of the species: loricarids and pimelodids present low growth rates, while characids and curimatids present higher growth rates. The inverse relation between growth rate values and those of first maturity length reflects the relationship between somatic and reproductive investment. The pressure of anthropic activities, especially those related to damming and pollution, has deeply changed fishery yield and its specific composition. The integrity maintenance of the remaining free stretches of the high River Paraná is essential to the permanence of the access routes to the spawning sites, and to the floodplain, vital to the juvenile phases of development. This is still possible through the definitive suspension of the construction of Ilha Grande Reservoir and of a suitable flow manipulation of the reservoirs upstream.

AGOSTINHO, Angelo Antonio; VAZZOLER, Anna Emília Amato de Moraes; THOMAZ, Sidinei Magela. The High River Paraná Basin: limnological and ichthyological aspects. In: TUNDISI, José Galizia; BICUDO, Carlos Eduardo de Mattos; MATSUMURA-TUNDISI, Takako. Limnology in Brazil. Rio de Janeiro: ABC/SBL , 1995. p.[59]-103.

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