Changes in fish species composition in the middle and lower Tietê River (São Paulo, Brazil) throughout the centuries, emphasizing rheophilic and introduced species

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

doi:10.1590/s2179-975x0118

Abstract

Abstract Aim: This paper is aimed at describing the changes of fish species in the middle and lower courses of the Tietê River, emphasizing rheophilic and invasive fish species as well as identifying the causes for such alterations. Methods Data collection consisted in: intense revision of publications, dissertations and thesis regarding the subject; information at the Zoology Museum at USP (MZUSP); revision in species identification through MUZUSP collection; historical survey of introduced species based on the literature and samplings in the years of 2000 and 2001. Results The main impacts identified in the Tietê River with consequence to the ichthyofauna were: domestic and industrial pollution, deforestation, damming, course rectification, silting and species introduction. From the 80 species identified in the study area, 28 were 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) at the beginning of 20th Century. Other species such as corvina (Plagioscion squamosissimus ) have been introduced by electricity companies, which has contributed to the species composition changes. 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 and damming. Conclusions Following the building of the reservoirs there have been important 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.

Highlights

The reservoirs consist in important artificial ecosystems that alter the hydrological and ecological characteristics of a river (Tundisi, 1993), being regulated by the following factors: morphometry, seasoning, operation system, flow rate and residence time
Considering all the impact here presented, this paper describes the alterations in the composition of fish species along years, through a historical survey of species introduction and several changes as well as presenting the impacts suffered by the Tietê River in addition to the existing dams
In the 17th Century, the ciliary forest had already been damaged in the upper course of the Tietê River and more recently the dammings in the middle and lower courses of the Tietê River have strengthened the modification in the composition of fish species

Summary

Introduction

The reservoirs consist in important artificial ecosystems that alter the hydrological and ecological characteristics of a river (Tundisi, 1993), being regulated by the following factors: morphometry, seasoning, operation system, flow rate and residence time Such factors alter the physical and chemical characteristics of the water (Straškraba & Tundisi, 2000; Smith et al, 2014) and shape the structure of the fish communities (Pelicice et al, 2015). In reservoirs there is a change in the composition and structure of fish assembly, leading to a high increase of some species and decrease and even extinction of others. Agostinho et al (1992) claimed that in reservoirs there is a change in the composition and structure of fish assembly, featuring excessive increase of some species and decrease or even extinction of others. In the Três Irmãos Reservoir it is difficult to catch lambaris, Astyanax lacustris Lütken, 1875, Astyanax fasciatus (Cuvier 1819) and cará (Geophagus brasiliensis), forage species which have nearly disappeared as a consequence of the construction of the reservoir and the pressure caused by the introduced species and the increase of population of other species such as pirambeba (Serrasalmus maculatus)

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Conclusion