Survey of fish species from the Lower Roosevelt River, Southwestern Amazon basin

Abstract

This study presents an inventory of the ichthyofauna of the lower Roosevelt River sub-basin and its associated tributaries. Fish sampling with fishing nets and measurements of environmental parameters of water occurred in November/2012 (rising water), February/2013 (flooding), May/2013 (falling water) and August/2013 (drought). Depth mean was 8.86 m, water transparency was 0.6 m, conductivity was 22.7 µS.cm-1, pH was 6.59, dissolved oxygen was 7.63 mg.l-1 and temperature was 28°C. The total estimated capture area was 68,829.6 m2 during 2,880 hours. The catch per unit Effort (CPUE) was 0.37 individuals m-2.day-1. Species were spatially aggregated in all sampling points and river water levels. A total of 5,183 individuals distributed in 7 orders, 29 families, 104 genders and 188 species were sampled in this survey. The diversity index was 4.121 and equitability index was 0.789. The Characiforms order was the most abundant with 106 species, followed by Siluriforms with 63 species and Cichliforms with 23 species. The most abundant species was Serrasalmus rhombeus (Linnaeus, 1766) with 327 individuals (5.9%), followed by Chalceus epakros (Cope, 1870) with 309 individuals (5.6%) and Acestrorhynchus microlepis (Schomburgk, 1841) with 250 individuals (4.5%). Trophicity was characterized by omnivorous (28.6%), piscivorous (14.3%), carnivorous (13.8%) and detritivorous (12.8%). According to IBAMA's regulation, 29.25% of captured species presents ornamental potential.

Fish fauna of moderate altitude from first order stream in upper Rio Machado, Rondônia, Brazil

“…This region is also the type locality of many recently described fish species (Fisch-Müller et al, 2005;Wingert & Malabarba, 2011;Ohara & Lima, 2015;Ohara & Marinho, 2016;Bockmann & Reis, 2021;Marinho et al, 2021). The majority of these species seem to have very restricted distribution, since they were not recorded during previous surveys in the Rio Machado basin (e.g., Perin et al, 2007;Casatti et al, 2013;Costa et al, 2017), in other rivers of the Rio Madeira basin (e.g., Rapp Py-Daniel et al, 2007;Araújo et al, 2009;Pedroza et al, 2012;Queiroz et al, 2013a, b;Vieira et al, 2016;Anjos et al, 2019;Oliveira et al, 2020), or in neighboring drainages (Ohara & Loeb, 2016;Ohara et al, 2017). A similar pattern with restricted species has also been mentioned to the Chapada dos Parecis, regarding small fishes from the upper Rio Machado/Guaporé (Rio Madeira basin), upper Rio Juruena (Rio Tapajós basin), and upper Rio Paraguai (Ohara & Lima, 2015).…”

“…Most of this ichthyofaunal diversity is located within the Amazon basin, where more than 2,400 valid fish species are included (Reis et al, 2016;Jézéquel et al, 2020). In the Rio Madeira, the largest tributary of the Rio Amazonas, about 1,000 fish species are registered (Queiroz et al, 2013a based on collecting efforts concentrated on the Brazilian territory, in the lower and middle portions of the basin and its main tributaries (Rapp Py-Daniel et al, 2007;Perin et al, 2007;Camargo & Giarrizzo, 2007;Pedroza et al, 2012;Queiroz et al, 2013a, b;Costa et al, 2017;Anjos et al, 2019;Oliveira et al, 2020). However, the fish fauna of moderate altitude from headwaters of main rivers of Rondônia State remains practically unknown.…”