Variação espacial e temporal na estrutura e composição de assembléias de peixes bentônicos em um trecho do Alto rio Madeira, Rondônia
This study aimed to evaluate the structure and composition of benthic fishes assemblages in a 450 km stretch of the Madeira River, Rondônia State, Brazil. The study was undertaken through an annual hydrologic cycle (from November 2008 to October 2009). The existence of a longitudinal gradient in spe...
| Autor principal: | Ribeiro, Ariana Cella |
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| Grau: | Dissertação |
| Idioma: | por |
| Publicado em: |
Instituto Nacional de Pesquisas da Amazônia - INPA
2020
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| Acesso em linha: |
https://repositorio.inpa.gov.br/handle/1/11244 http://lattes.cnpq.br/5748850237295780 |
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This study aimed to evaluate the structure and composition of benthic fishes assemblages in a 450 km stretch of the Madeira River, Rondônia State, Brazil. The study was undertaken through an annual hydrologic cycle (from November 2008 to October 2009). The existence of a longitudinal gradient in species richness was evaluated, as well as putative effects of limnological characteristics on the assemblages composition. Three sampling areas were established having the rapids of Jirau and Teotônio as natural barriers: 1) upstream Jirau; 2) between Jirau and Teotônio and 3) downstream Teotônio. Bottom trawl nets were used to perform 135 samplings, of which 33 brought no fish and 24 had only one fish each. A total of 577 specimens belonging to 73 species were captured, 27 of which representing single registers. Siluriformes (55 species, 82% of total richness) predominated in the samplings, followed by Gymnotiformes (16 species, 17%), as would be expected for benthic fish communities in Amazonia. The species richness and the number of organisms caught were higher in dry season (62 species, 469 specimens) in comparison with the high water season (31 species, 108 specimens). No increase in species richness was observed from upstream to downstream sampling sites. Notwithstanding, significant differences in assemblages composition occurred between the three areas by means of species substitution and differences in species abundances. There was no significant relationship between species richness and the environmental variables tested (dissolved oxygen, electric conductivity, depth, turbidity, river width, current speed, hydrologic period -dry and rainy- and the position of Jirau and Teotônio rapids), with only the fish abundance showing significant effects. The species composition in the sampling stretch differed significantly in relation to the position of Teotônio rapids, to the hydrological period, and to water conductivity. This indicates the existence of discontinuities in benthic fish assemblages’ composition along the Madeira River, where the Teotônio rapid constitutes and important division to the aquatic landscape. The benthic fish assemblages in the rapids stretch of Madeira River showed high species richness associated with very low fish abundance. The particular environmental conditions in this stretch of the river (high water flow, turbidity and turbulence) possibly limits the maintenance of large populations of benthic fishes and restricts the occurrence of some species that typically occur in river channels of the Amazonian lowlands. |