Temporal variation in fish community in the tailrace at Três Marias Hydroelectric Dam, São Francisco River, Brazil

Abstract

Damming rivers to generate hydroelectric energy causes a series of changes in the environment, including impacts on the ichthyofauna. Knowledge of the fish community immediately downstream from a hydroelectric dam can help to reduce the negative effects of dam operation, such as fish entrance into the draft tube during turbines maintenance. We evaluated the temporal variation in fish community composition and abundance, near Três Marias Hydroelectric Dam (TMD), and its relationship with abiotic variables. Samples (n = 18) were carried out using gill nets in the tailrace of the dam, over the course of a hydrological year, at six time points during a 24-hour period. Abiotic data were also sampled to assess the relationship with the biotic data. In the tailrace, Characiformes showed the highest richness, while Siluriformes were the most abundant. Of the 33 species sampled, six were migratory. The fish community was significantly different between the dry and wet seasons, with higher abundances during the wet season. In the wet season, the frequency of migratory species in the community rose from 0.7 to 18.3%, and Pimelodus maculatus accounted for 14.5% of the overall abundance. We observed that Characiformes captures occurred mainly in the morning, with peak activity between 5:00 and 9:00 h. Siluriformes showed greater nocturnal activity and were largely captured between 17:00 and 21:00 h. Synchronizing operational maneuvers that represent high risk to the fish with periods of low abundance in the tailrace, i.e., during months of low precipitation, may be a measure to reduce the impact of the operation on the downstream fish community.O barramento de rios para implantação de hidrelétricas causa uma série de modificações no ambiente, gerando impactos sobre a ictiofauna. O conhecimento sobre a comunidade de peixes encontrada imediatamente à jusante pode auxiliar na redução de impactos gerados pela sua operação. Assim, avaliamos as variações temporais na comunidade de peixes próxima à Usina Hidrelétrica de Três Marias quanto à composição de espécies, abundância e suas relações com variáveis abióticas. Foram realizadas 18 coletas com redes de emalhar no canal de fuga da usina, durante um ano hidrológico, em seis horários ao longo de 24 h, quando também foram obtidos dados abióticos. Foi observado que no canal de fuga da usina, Characiformes apresentou uma maior riqueza, enquanto os Siluriformes foram os mais abundantes. Das 33 espécies coletadas seis eram migradoras. A comunidade de peixes foi significativamente diferente entre os meses de seca e chuva, com maior abundância no período de chuva. Neste período, a frequência das espécies migradoras na comunidade subiu de 0,7 para 18,3%, sendo que Pimelodus maculatus representou 14,5% da abundância. A maior captura de Characiformes se deu no período da manhã com pico de atividade de 5:00 às 9:00 h. Os Siluriformes apresentaram maior atividade à noite, principalmente das 17:00 às 21:00 h. Conciliar manobras que oferecem mais riscos para os peixes com o período de menor abun...

The impact of a hydroelectric dam on Neotropical fish communities: A spatio‐temporal analysis of the Trophic Upsurge Hypothesis

“…It resulted in an earlier ecological response, characterised by contrasting patterns amongst some of the main taxonomic families compared to upstream sites. In particular, the proportionately higher increase in biomass relative to abundance—the converse of reservoir sites—is consistent with the explanation of large migratory fish impeded by the dam and corresponds with changes in the relative abundance of respective fish families (Barthem, Ribeiro, & Petrere, 1; Granzotti, Miranda, Agostinho, & Gomes, ; Loures & Pompeu, ). Perhaps more striking was the overall comparatively weak increase in richness, abundance and biomass that were significantly lower than all upstream sites, except the river site LOT + 98.…”

Factors Influencing Movements of Two Migratory Fishes within the Tailrace of a Large Neotropical Dam and their Implications for Hydropower Impacts

“…Silva () also described that most of the migratory movements of Curimba ( P. lineatus ) at the fish ladder of the Igarapava Dam in Brazil occurred during the day while is expected to have predominantly nocturnal habits, remaining hidden during the daylight (Santos et al , ). Moreover, this result agrees with observations by Loures and Pompeu () in the same study site, where captures of Characiformes and Siluriformes were greater in diurnal and nocturnal periods, respectively.…”

Seasonal and diel changes in fish distribution in a tropical hydropower plant tailrace: evidence from hydroacoustic and gillnet sampling

“…Many species of this order have demersal habit, including the two most abundant species found in wet season: Franciscodoras marmoratus (Reinhardt,) and Pimelodus maculatus Lacépède (Santos et al . ; Kirchheim & Goulart ; Loures & Pompeu ).…”

“…Water physico‐chemical parameters did not account for fish abundance variation in the TMHP tailrace. Abundance in the tailrace estimated by gillnets catches was positively correlated with total discharge and precipitation (Loures & Pompeu ). By contrast, abundance estimated by hydroacoustics was negatively correlated with total discharge, but positively with fish catches in the nets.…”