Structure dynamics of a fish community over ten years of formation in the reservoir of the hydroelectric power plant in upper Uruguay River/Dinamica da estrutura da comunidade ictica ao longo de dez anos da formacao do reservatorio da usina hidreletrica no Alto Rio Uruguai

• Published in: Brazilian journal of biology 2017-11, Vol.77 (4), p.710
• Main Authors: Schork, G, Zaniboni-Filho, E
• Format: Article
• Language: English
• ISSN: 1519-6984; 1678-4375
• DOI: 10.1590/1519-6984.17015

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 Ita 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 Ita 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.