Effects of extended absence of flooding on the fish assemblages of three floodplain lagoons in the middle São Francisco River, Brazil

Abstract

In the Neotropics, a large proportion of fish communities of large rivers use floodplain as habitats for feeding, reproduction, and refuge. An evaluation was made of the effects of extended dry periods on the species richness, abundance and local extinction of fish species in three marginal lagoons in the middle São Francisco River, southeastern Brazil. The studied lagoons fail to receive river floods during the study period (1994)(1995)(1996). A gradual reduction in richness and abundance was observed in all lagoons. Migratory fish species had the highest probability to become extinct in the two lagoons that remained with large water volume. Species tolerant to low levels of dissolved oxygen had the lowest probability of local extinction in the lagoon showing an abrupt reduction in water volume. Similar changes to those observed in the current study are likely to occur in the floodplains if dams would be constructed in this segment of the river. Adequate water releases from Três Marias reservoir, located upstream, should be considered as a management tool for producing episodic flooding on the marginal lagoons of the region.Na região neotropical uma grande porção da comunidade de peixes utiliza a planície de inundação como habitat de alimentação, reprodução e refúgio. Neste trabalho, foi avaliado o efeito de um período de seca prolongado sobre a diversidade, abundância e extinção local de peixes de três lagoas marginais do médio curso do rio São Francisco. As lagoas estudadas não receberam água proveniente da cheia do rio durante o período de estudos (1994)(1995)(1996). Redução gradual na abundância e riqueza de peixes foi abservada em todas as lagoas. Nas lagoas que permaneceram com grande volume de água, espécies migradoras foram as que apresentaram maior probabilidade de extinção. Já na lagoa que apresentou abrupta redução no volume de água, espécies tolerantes a baixos níveis de oxigênio dissolvido apresentaram menor probabilidade de extinção local. Caso barragens venham a ser construídas no médio curso do rio São Francisco, mudanças similares às observadas neste estudo poderão ocorrer com maior freqüência na sua planície de inundação. Vertimentos controlados através do reservatório de Três Marias, localizado a montante, devem ser avaliados como ferramenta de manejo para produzir inundações periódicas nas lagoas marginais da região.

Fish larvae assemblages in two floodplain lakes with different degrees of connection to the Paraná River, Brazil

“…The importance of the connection of the floodplain lakes with the main river and the occurrence of floods that reach the disconnected lagoons was already evidenced in various studies of fish assemblages (Sabo & Kelso, 1991;Súarez et al, 2004;Amoros & Bornette, 2002;King et al, 2003;Petry et al, 2003Petry et al, , 2004Pompeu & Godinho, 2006;Gubiani et al, 2007). However, specific studies that showed this same pattern for fish larvae assemblages were scarce.…”

The roles of marginal lagoons in the maintenance of genetic diversity in the Brazilian migratory fishes Prochilodus argenteus and P. costatus

“…The continuous and rapid advancement of agriculture and the subsequent sediment deposition in some of the important tributaries from the central basin (Sato & Godinho, 2003) are factors that directly affect the conservation of the lagoons. Notwithstanding, Pompeu & Godinho (2006) observed a gradual reduction in fish richness and an abundance of lagoons that did not receive annual flooding because of the water flow control by the Três Marias hydroelectric dam. Local extinction with a reduction of almost 70% of the native fish fauna was also observed in a lagoon from the rio São Francisco basin (Pompeu & Alves, 2003).…”

Effects of reservoirs water level variations on fish recruitment

“…Many studies have been conducted to assess the influence of WL variations on the community of fish or other aquatic organisms (Pompeu, Godinho, 2006;Paulovits et al, 2007;Baumgärtner et al, 2008;Zohary, Ostrovsky, 2011;Dutterer et al, 2013). These studies demonstrated that both the fluctuations of water levels in natural environments (caused by annual cycle and climate change), as well as in reservoirs and other artificial water bodies, promoted impacts on the fish communities and other components of the aquatic biota, as well as in water quality parameters.…”