Structure dynamics of a fish community over ten years of formation in the reservoir of the hydroelectric power plant in upper Uruguay River.

E Zaniboni-Filho,G Schork

doi:10.1590/1519-6984.17015

Abstract

The objective of this study was to evaluate the structure of the fish assemblage in the ten years following the closing of the lake of the Itá Hydroelectric Power Plant. Seasonal collections were conducted from 2001 to 2010. During this period, 44,834 fish were captured, totaling 3,818.01 kg, among 8 orders, 24 families and 84 species. In general, profound changes were not observed in the fish assemblage in the ten years after the formation of the Itá lake. Few species changed in dominance over time, while many were rare in the environment. The ichthyofauna in the reservoir was dominated by small and medium size opportunist species that conduct short or no migratory movements. Among the most abundant, six species were responsible for more than 50% of the numeric representation: Steindachnerina brevipinna, Astyanax fasciatus, Apareiodon affinis, Hypostomus isbrueckeri, Iheringichthys labrosus and Loricariichthys anus. The increase in the representation of the later species stood out. The biomass was dominated by Steindachneridion scriptum, Prochilodus lineatus, I. laborsus, Schizodon nasutus, Hoplias malabaricus, Acestrorhynchus pantaneiro, Hoplias lacerdae, H. isbrueckeri and L. anus. Despite the presence of large migrators in the region of the reservoir, their vulnerability was revealed by the low numeric abundance and accidental capture. The k-dominance curve of numerical abundance and biomass indicates a moderately disturbed community, in which the representation of small species was also important to the amounts of biomass.

Highlights

Electrical energy production in Brazil still depends essentially on hydroelectricity, which is responsible for approximately 65% of the national energy supply (Brasil, 2015)
The Itá hydroelectric power plant is located between the municipalities of Itá (SC) and Aratiba (RS) and was the first large power plant built on the upper portion of the Uruguay River (Zaniboni-Filho et al, 2008), initiating operations in March 2000
Composing a cascading system of dams above the Itá hydroelectric power plant, there is the Machadinho hydroelectric dam, built in the bed of the Uruguay River, the Barra Grande hydroelectric power plant on the Pelotas River and the Campos Novos hydroelectric power plant built on the Canoas River

Summary

Introduction

Electrical energy production in Brazil still depends essentially on hydroelectricity, which is responsible for approximately 65% of the national energy supply (Brasil, 2015). The construction of dams for hydroelectric energy generation is among the main anthropogenic impacts on Brazilian watersheds, substantially modifying most of the country’s large rivers. The interruption in the natural flow of the rivers damages their hydrological connectivity (Vannote et al, 1980), causing a series of changes so intense that a new ecosystem is formed (Baxter, 1977). This substitution of lotic waters for lentic waters causes changes in the water retention time, in the size of the sediments and nutrients and in various limnological variables (Souza-Filho, 2009; Ribeiro-Filho et al, 2011). The main changes described for the ichthyofauna in reservoirs include the proliferation of opportunist species and the decline of species with greater ecological demands (Agostinho et al, 1999)

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