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

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.Keywords: dam, ichthyofauna, southern Brazil, temporal variation, Itá.Dinâmica da estrutura da comunidade íctica ao longo de dez anos da formação do reservatório da usina hidrelétrica no Alto Rio Uruguai Resumo O objetivo deste trabalho foi avaliar a estrutura da assembleia de peixes nos dez anos seguintes ao fechamento do lago da Usina Hidrelétrica de Itá. Para isto, foram realizadas coletas com periodicidade sazonal no período compreendido entre 2001 e 2010. Durante o período de estudo, foram capturados 44834 peixes, totalizando 3818,01 kg, distribuídos em 8 ordens, 24 famílias e 84 espécies. De uma forma geral, a assembleia de peixes não mostrou alterações profundas nos dez anos após a formação do lago de Itá. Poucas espécies alternam-se na dominância ao longo do tempo, enquanto muitas mostraram-se como raras no ambiente. A ictiofauna do reservatório foi dominada por espécies oportunistas, de pequeno e médio porte e que realizam curtos ou nenhum movimento migratório. Entre as mais abundantes, seis espécies foram responsáveis por mais de 50% da representatividade numérica, sendo elas: Steindachnerina brevipinna, Astyanax fasciatus, Apareiodon affinis, Hypostomus isbrueckeri, Iheringichthys labrosus e Loricariichthys anus. Destaque para aumento da representatividade deste último. Já para a biomassa, destacaram-se: Steindachneridion scriptum, Prochilodus lineatus, I. labrosus, Schizodon nasutus, Hoplia smalabaricus, Acestrorhynchus pantaneiro, Hoplias lacerdae, H. isbrueckeri e L. ...

Diets and Trophic Structure of Fish Assemblages in a Large and Unexplored Subtropical River: The Uruguay River

“…Several anthropogenic factors may affect fish assemblages, such as the agrochemical inputs from the basin, fisheries, industrial and domestic sewage [183] and habitat fragmentation caused by hydroelectric dams [27,184]. This anthropogenic intervention in freshwater ecosystems typically results in the reduction of local biodiversity and affected community structure, particularly of fish [185,186].…”

“…This anthropogenic intervention in freshwater ecosystems typically results in the reduction of local biodiversity and affected community structure, particularly of fish [185,186]. For example, the low species richness and high spatial variability in the relative representation of different trophic groups in the upper Uruguay River might well be attributed to the presence of three hydroelectric dams between sampling sites (being this, a well-known impact of dams) [27,184,187]. Unfortunately, as there is a lack of baseline information on fish trophic structure it became impossible to disentangle the anthropogenic and natural effects driving fish trophic structure along the Uruguay River gradient.…”

“…Despite that the Neotropical region represents one of the largest hotspots for freshwater fish biodiversity [18,19], the functioning of its riverine ecosystems and the biology of the vast majority of the species remains understudied [20,21]. Besides, while most Neotropical fish assemblage studies focus on tropical and subtropical rivers, with marked flow seasonality (e.g., Amazonas River, Parana River, Orinoco River [22][23][24][25]), less research effort has been made in large irregular flow rivers of southern subtropical areas (see [26][27][28]). Particularly within the La Plata River basin, most studies describing aspects of fish biology focused on the large Parana River (e.g., [29][30][31]) while its smaller tributary-a 1800 km long and 6000 m 3 /s river bearing at least 10 species of long-distance migratory fish of commercial importance-the irregular-flow subtropical Uruguay River remains largely unstudied in its total extension [32].…”

Reservoir management: an opinion to how the scientific community can contribute

“…Ichthyofauna monitoring is probably the most evident and sensitive activity addressed in reservoir studies, as this information has considerable repercussion considering mortality or any other fact involving fisheries. Riverine populations traditionally use fishing, thus ichthyofauna is always the focal point of reservoir management (Agostinho & Gomes, 2005;Schork & Zaniboni-Filho, 2017).…”

Mosaic environments shape the distribution of Neotropical freshwater ichthyoplankton

“…Watersheds worldwide exhibit an association between dam presence and variation in ichthyofaunal population structure (Agostinho, Pelicice, & Gomes, ; Angulo‐Valencia, Agostinho, Suzuki, Luz‐Agostinho, & Agostinho, ; Lima et al, ; Schork & Zaniboni‐Filho, ; Winemiller et al, ). Dam construction in response to increasing electricity demands has large‐scale impact on river systems (Suzuki, Dunham, Silva, Alves, & Pompeu, ), modifying water flow and existing environments (Agostinho, Gomes, Santos, Ortega, & Pelicice, ; Pelicice, Pompeu, & Agostinho, ; Reynalte‐Tataje, Nakatani, Fernandes, Agostinho, & Bialetzki, ).…”