Alterations in fish species composition in the middle and lower courses of the Tietê River (São Paulo, Brazil) throughout the years, emphasizing rheophilic and introduced species

Welber Senteio Smith, Marta Severino Stefani, Evaldo Luiz Gaeta Espindola, Odete Rocha

Resumo


Aim: This paper aimed at describing the alterations of fish species in the middle and lower courses of the Tietê River, emphasizing rheophilic and invasive fish species as well as identifying such alteration causes. Methods: Data were obtained through intense revision of publications, dissertations and thesis accomplished in the study area, information search at the Zoology Museum at USP, revision in species identification, historical survey of introduced and collected species in the years of 2000 and 2001. Results: the main impacts identified in the Tietê River with consequence to the ichthyofauna were: domestic pollution, industrial pollution, deforestation, damming, course rectification, silting and species introduction. From the 80 species identified in the study area, 13 were found to be invasive. Many fish species have been introduced in the Tietê River since the late 19th Century with carpa (Cyprinus carpio) being the first one, followed by the introduction of black bass (Mycropterus salmonoides). Other species such as corvina (Plagioscion squamosissimus) have been introduced by companies in the electricity business, which has contributed to the alteration of species composition. Migratory species as dourado (Salminus brasiliensis), pacú (Piaractus mesopotamicus) and pintado (Pseudoplatystoma corruscans), which used to be abundant have become rare or absent after the construction of reservoirs, mainly because reservoirs in cascade have been built. Piracanjuba (Brycon orbignyanus), typically herbivore species, had its stock decreased due to the lack of ciliary vegetation. Conclusions: Following the building of the reservoirs there have been profound alterations in the composition of ichthyofauna, leading to the nearly complete absence of migratory species and the prevalent species are the ones which adapted to the new conditions. In addition to the damming, lack of ciliary vegetation and pollution also caused alterations in the ichthyological community.

Palavras-chave


ichthyofauna; reservoir; environmental impacts; migratory species; invasive species

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