Estrutura e composição da ictiofauna de riachos da bacia do Rio Grande no estado de São Paulo, sudeste do Brasil

Abstract

Eighteen 100 m long streams stretches, none of an order higher than three, were sampled in three tributaries (six stream stretches sampled in each one) of the left margin of the main channel of Rio Grande (Rios Turvo, Pardo and Sapucaí) in the State of São Paulo, southeastern Brazil. Each stream stretch had its midpoint located with a GPS satellite receiver and had its fish fauna sampled via a standardized environmental data and fish collection methodology (primarily utilizing electrofishing) with the aim of providing the following information about each stream: 1) the taxonomic composition of the fish fauna and the contribution of each species in that stream in terms of both number of individuals and biomass; 2) a photographic documentation of the live coloration of representative specimens of each collected species; and 3) the description of each sampled environment, with colored photographic illustrations and details of the main biotic and abiotic parameters. Overall 3,070 fishes were collected, belonging to six orders, 18 families, 44 genera, and 64 species, with a total biomass of 14.3 kg. Of the collected species, approximately 50% were Characiformes, 26.5% Siluriformes, 11% Perciformes, 6% Gymnotiformes, 5% Cyprinodontiformes, and 1.5% Synbranchiformes. The most abundant species in terms of total number of individuals were Astyanax altiparanae (17.4%) and Hypostomus ancistroides (9%); the species with the largest biomasses were Astyanax altiparanae (35%) and Geophagus brasiliensis (9%). In terms of abundance and biomass collected for each family, the Characidae was clearly the predominant family followed by the Loricariidae, and Cichlidae. Among the sampled stream stretches, locality SG6 with 26 species and locality PG4 with three species yielded the highest and lowest richness in terms of species numbers, respectively. This coincides with the values obtained for the ShannonWiener index of specific diversity (H´ = 1.08 and 0.26, respectively). The median species richness for all streams stretches was 12. In the species richness estimate by extrapolation for all 18 sampled stream stretches, a value of 93 species was obtained (with a standard error of three) indicating the need for an additional moderate sampling effort to reach the asymptote of the curve. Of the 64 collected species, four (approximately 6% of the total) are clearly new to science and seven other species (approximately 11% of the total) are of indefinite taxonomic status and require further analysis. Two of the captured species are certainly introduced (approximately 3% of the total). Analysis of the trophic and spatial structure of the studied fish fauna indicates that the 10 numerically dominant species in the sampled streams can be grouped, based on published data, into five guilds that are in decreasing order of numeric importance: nektonic omnivores; benthic invertivores; periphytovores; algivores and benthic omnivores. An identification key for all the species of fish collected during this study is provided.

Rapid ecological assessment of benthic indicators of water quality: a successful capacity-building experience for Brazilian postgraduate students in ecology

“…While Neotropical aquatic ecosystems tend to be dominated by siluriforms and characiforms (Castro, 1999), only the latter predominated in the present study. In general, the species identified in the present study were typical of those found in other hydrographic basins, such as those of the Rio São Francisco (Alves and Pompeu, 2010) and Rio Grande (Castro et al, 2004).…”

Diversidade da ictiofauna do Alto Rio Paraná: composição atual e perspectivas futuras

“…Esse número encontra-se dentro das estimativas de 6 a 15% de novas espécies para algumas porções do Alto Paraná, referidos recentemente por Castro et al (2003Castro et al ( , 2004Castro et al ( e 2005. Mantido o ritmo de descrições de novas espécies desta década, aproximadamente cinco por ano, levaríamos mais dez anos para descrever essas 50 espécies já reconhecidas, o que é um tempo demasiadamente longo.…”

“…sificada, além de registrar a ocorrência de várias espécies alóctones e exóticas e mostrar que cerca de 6 a 15% das espécies referidas são novas (Castro et al 2003(Castro et al , 2004(Castro et al , 2005. Resultados semelhantes têm sido obtidos também por meio da revisão de coleções ictiológicas e de outros estudos independentes, reforçando o fato de que os levantamentos realizados no Alto Paraná são incompletos (Agostinho & Gomes 2005) e mostrando a importância de se incrementar esforços de coleta na área e de se revisar o material depositado em coleções.…”

Knodus moenkhausii (Characiformes: Characidae): one fish species, three hydrographic basins - a natural or anthropogenic phenomenon?

“…Identifying this species can be difficult due to its similarity to other species of the genus and the related genera Creagrutus, Piabina, and Bryconamericus. The species was first described from the Paraguay River basin (Eigenmann & Kennedy, 1903), and later reported from the Upper Paraná [6,[24][25][26][27] and São Francisco River basins [28]. Recently, our research group collected specimens of K. moenkhausii in the Paraíba do Sul River basin as well.…”