Ichthyofauna of streams from the lower Iguaçu River basin, Paraná State, Brazil

Abstract

Abstract:The drainages of the Iguaçu River basin, as well as the main channel of the river, have peculiar characteristics resulting from geomorphological processes in this area, including the formation of the Iguaçu River Falls. This slope in the lower portion of the basin is a biogeographical barrier to many organisms. In this study was inventoried the fish fauna of streams of the lower Iguaçu River basin, evaluating possible differences in the species composition upstream and downstream of this biogeographical barrier. Sampling were conducted between 2004 and 2013, in five streams, three upstream and two downstream of the Iguaçu River Falls, using electrofishing. The nMDS analysis was run to investigate possible groupings of similar fauna between the streams sampled. The scores of this test were tested as to the significance of groupings with the Hotelling T 2 test. The indicator value method (IndVal) was used to detect the distribution of species among the groups of the streams upstream and downstream of the Iguaçu River Falls. We collected 18,908 individuals of six orders, 11 families, and 40 species. Siluriformes and Characiformes had the highest species richness; Cyprinodontiformes presented the highest abundance. Considering the species recorded, 21 are considered natives to the Iguaçu River basin, including 15 endemic, wich were found only in streams upstream of the falls. Additional 18 species were verified only in the streams downstream of such barrier. Four species were common to both stretches. The axis 1 of the nMDS separated two groups: streams upstream (S1, S2 and S3) and streams downstream of the Iguaçu River Falls (S4 and S5). The indicator species analysis also indicated a distinction between the groups of streams, that were significantly different (Hotelling's T 2 = 234.36, p ˂ 0.0001). The number of endemic species in the streams upstream of the Falls (15 spp.) evidences a significant effect of isolation promoted by the Iguaçu River Falls, and confirms the role of this barrier in the vicariant processes and endemism typical of this basin. These results emphasize the importance of conserving these ecosystems, once the extinction of species in this region means the irreversible loss of them. Resumo: As drenagens da bacia do rio Iguaçu, bem como o canal principal do rio, possuem características peculiares resultantes de processos geomorfológicos dessa área, incluindo a formação das Cataratas do rio Iguaçu. Esse desnível na porção inferior da bacia constitui uma barreira biogeográfica para muitos organismos. Neste trabalho inventariamos a fauna de peixes de riachos na porção do baixo rio Iguaçu, avaliando possíveis diferenças na composição de espécies acima e abaixo dessa barreira biogeográfica. Entre 2004 e 2013, foram amostrados cinco riachos, sendo três localizados acima das Cataratas do Iguaçu e dois abaixo, por meio de pesca elétrica. Para investigar possíveis padrões de agrupamentos de fauna similares entre os riachos amostrados foi

Fish fauna in forested and rural streams from an ecoregion of high endemism, lower Iguaçu River basin, Brazil

“…These findings distinguish the fish fauna of headwaters of Iguaçu River basin from others similar streams of Paraná River system, with higher species richness (Araújo et al 2011, Marceniuk et al 2011, Hoffmann et al 2015, Vidotto-Magnoni et al 2015, Cetra et al 2016, Frota et al 2016a). Lower fish richness was also verified by Larentis et al (2016) to those that flows downstream it. This low richness, similar to our results, highlights the abrupt differentiations of the fish fauna between the Iguaçu drainage below falls and their upstream reaches, above the falls (Garavello et al 1997, Zawadzki et al 1999.…”

“…For example, many previous studies already demonstrated that this pattern not occur only in low Iguaçu system (Bifi et al 2006, Baumgartner et al 2012, Larentis et al 2016, Table 2. List of fish species and their respective occurrences at sampling site in eight streams of lower Iguaçu River basin.…”

“…While others similar large tributaries from upper Paraná River system (e.g., Paranapanema, Tietê, Grande) include more than 150 fish species (Langeani et al 2007, Duke Energy 2008, the inventories along Iguaçu River basin have not exceeded much more than one hundred species, added those introduced (Baumgartner et al 2012). Its low species richness is more evident in smaller spatial scales, where local fish assemblages of streams have presented between six to 12 species (Vitule & Abilhoa 2003, Bifi et al 2006, Abilhoa et al 2008, Neves et al 2015, Larentis et al 2016, while others streams with similar magnitude from Paraná system, between 13 to 41 species (Castro et al 2003, Delariva & Silva 2013, Cetra et al 2012, Vidotto-Magnoni et al 2015.…”

“…The construction of the low Iguaçu dam at its last segment above the falls (ANEEL 2017), has imminent potential to negative impacts, both on the endemic fishes and on the boundaries of Iguaçu National Park (UNESCO 2012). Furthermore, the fish fauna located upstream, at headwater regions of lower Iguaçu River basin, has been impacted by agricultural activities (Larentis et al 2016, Nimet et al 2017 and remaining under sampled when compared with reservoirs of its principal channel (Baumgartner et al , 2012.…”

“…To the south of the hydrographical divisor of these there basins are streams that flows to lower Iguaçu River, whose ichthyofauna have been only recently studied (Neves et al 2015, Larentis et al 2016. Due to the historical process of land use and occupation, these streams present different percentages of vegetal cover among their watersheds.…”