Fish diversity along spatial gradients in the Itaipu Reservoir, Paraná, Brazil

Abstract

Local and turnover patterns of fish diversity in the Itaipu Reservoir were evaluated and related to a longitudinal or river-dam gradient (composed of riverine, transitional, and lacustrine zones) and to transversal or upstream-downstream gradients of the tributaries (composed of lotic and lentic stretches of tributaries and reservoir shores). Thirteen stations were sampled quarterly during 2 years. A total of 85 fish species were caught. Local (alpha) and turnover (beta) patterns of fish diversity showed significant differences in reservoir spatial gradients. Along the longitudinal gradient, total and alpha-diversity were the highest in the riverine and transitional zones of the reservoir and lowest in the lacustrine zone. Along the transversal gradient, total and alpha-diversity increased from the lotic stretches of the tributaries to the reservoir shores. The lotic and lentic stretches of the tributaries presented the highest beta-diversity values, indicating heterogeneity in species compositions among the sub-basins. We conclude with recommendations for reservoir management based on the results of this study.

Influence of limnological zones on the spatial distribution of fish assemblages in three Brazilian reservoirs

“…The fish fauna of a freely flowing river constitutes the initial assemblage of the newly formed reservoir. Therefore, the remaining species are often concentrated in tributary mouths, which are more similar to the original habitat than other parts of the reservoir, where their ability to compete and survive is lower (Irz et al, 2002;Oliveira et al, 2004). We observed this pattern in São Simão, where the riverine zone had more native species than the lacustrine zone.…”

“…According to this researcher, although predators be successful in high-visibility environments, predation rates may also be higher in places with lower visibility, but with high abundance of prey. Similar to São Simão, greater species richness has been reported in the riverine zone of other Brazilian reservoirs (Oliveira et al, 2004;Gubiani et al, 2010;Terra et al, 2010) as well as in reservoirs of other countries (Gido et al, 2002;Prchalová et al, 2009;Freedman et al, 2013). The riverine zone can be considered a quasi ecotone, because of the overlap of fluctuating riverine and lacustrine conditions .…”

“…The riverine zone can be considered a quasi ecotone, because of the overlap of fluctuating riverine and lacustrine conditions . These environments have a wide range of exploitable microhabitats and high rates of primary productivity, which contribute to greater species richness and fish diversity than in other areas (Eadie and Keast, 1984;Cecílio et al, 1997;Irz et al, 2004;Oliveira et al, 2004). Furthermore, lacustrine zones often have chemical or thermal stratification creating microhabitats that are severe environmental filters for many species (Oliveira et al, 2003;Agostinho et al, 2008).…”

“…Freshwater fish species respond differently to these riverine/lacustrine zones because the differing habitat types control the spatial distribution of fish species and the resulting fish assemblages (Holmgren and Appelberg, 2000;Irz et al, 2002;Terra et al, 2010). For example, riverine zones tend to support more native species (Oliveira et al, 2005;Agostinho et al, 2007;Gao et al, 2010) and rare species (Oliveira et al, 2003), whereas lacustrine zones tend to support fewer species (Oliveira et al 2004;Agostinho et al, 2007). If reservoir riverine and lacustrine zones support markedly different fish assemblages, it would be wise to manage them differently if managers desire to conserve or rehabilitate native fish assemblages and control invasive non-native species.…”

Interannual variations of the fish assemblage in the transitional zone of the Three Gorges Reservoir: persistence and stability

“…Habitats in reservoirs vary longitudinally, allowing the division of three distinct zones: riverine, transitional and lacustrine (Thornton et al 1990). Studies on the fish assemblages in reservoirs suggest that transitional zone, which is an ecotone between the river upstream and the lacustrine zone of the reservoir, is important for the management of reservoirs (Carvalho et al 1998;Oliveira et al 2004Oliveira et al , 2005Agostinho et al 2008). The transitional zone has relatively higher fish density and diversity than others possibly by reason of its higher light penetration and primary productivity (Carvalho et al 1998;Oliveira et al 2004;Santos et al 2010;Terra et al 2010).…”