Fish assemblage structure in tributaries of the Meia Ponte River, Goiás, Brazil

DNA barcode and minibarcode identification of freshwater fishes from Cerrado headwater streams in Central Brazil

The extraordinary species diversity of the Neotropical freshwater fish fauna is world renown. Yet, despite rich species diversity, taxonomic and genetic resources for its Cerrado ichthyofauna remain poorly developed. We provide a reference library of 149 DNA barcodes for 39 species/lineages of Cerrado headwater stream fishes from the Brazilian Distrito Federal and nearby areas and test the utility of distance-based criteria, tree-based criteria and minibarcodes for specimen identification. Mean Kimura 2-parameter genetic distances within species to orders ranged 1·8-12·1%. However, mean intraspecific v. congeneric-interspecific distances (0·9-1·3%) overlapped extensively and distance-based barcoding failed to achieve correct identifications due to c. 4-12·1% error rates and 19·5% ambiguous identifications related to the presence of singletons. Overlap was reduced and best-match success rates improved drastically to 83·5% when Characidium barcodes representing potential misidentifications or undescribed species were removed. Tree-based monophyly criteria generally performed similarly to distance methods, correctly differentiating up to c. 85% of species/lineages despite neighbour-joining and Bayesian tree errors (random lineage-branching events, long-branch attraction). Five clusters (Ancistrus aguaboensis, Characidium spp., Eigenmannia trilineata, Hasemania hanseni and Hypostomus sp. 2) exhibited deep intraspecific divergences or para-/polyphyly and multiple Barcode Index Number assignments indicative of putative candidate species needing taxonomic re-examination. Sliding-window analyses also indicated that a 200 bp minibarcode region performed just as well at specimen identification as the entire barcode gene. Future DNA barcoding studies of Distrito Federal-Cerrado freshwater fishes will benefit from increased sampling coverage, as well as consideration of minibarcode targets for degraded samples and next-generation sequencing.

Assessment of fish assemblages in streams of different orders in the Upper Paraná River basin, Central Brazil

The aim of this study was to test whether the richness observed and the biomass per trophic group of fish assemblages vary depending on the order (1st and 2nd) of the streams located in three different basins of the Upper Paraná River Basin, Central Brazil. Samples were collected between April and September, 2009, in 27 streams of the Meia Ponte, Piracanjuba and Santa Maria River basins. A total of 4,879 specimens were collected distributed in 59 species and 19 families. The statistical analyses carried out indicate that the observed richness and biomass of omnivore fish were influenced by the interaction of two factors: stream order and basin. The 2nd order streams located in the Santa Maria basin presented significant differences in the observed richness and omnivore biomass when compared to i) 1st order streams in the same basin (only richness) or in the Piracanjuba and Meia Ponte basin; ii) 2nd order streams in the Piracanjuba (only omnivore biomass) and Meia Ponte Rivers basins. Results are discussed considering the influence of geomorphic processes on fish assemblages and food availability.

Structure and integrity of fish assemblages in streams associated to conservation units in Central Brazil

This study aims to characterize the spatial and seasonal distribution of the fish assemblage and evaluate the integrity of streams in a sustainable use area that includes integral protection conservation units in Distrito Federal, Central Brazil (Cerrado biome). For the study, 12 stretches of 8 streams were sampled in 2008 (dry season) and 2009 (wet season). For that evaluation was estimated the Physical Habitat Index (PHI), vegetation cover (VC), pH, dissolved oxygen, turbidity, and conductivity. We recorded 22 species, about eight undescribed species, by a total of 2,327 individuals. The most representative families in number of species were Characidae (31.8%), Loricariidae (31.8%), and Crenuchidae (13.6%). Knodus moenkhausii was the most abundant species with 1,476 individuals, added to Astyanax sp., Phalloceros harpagos, and Hasemania sp. they represent over 95% of the total abundance. The species Astyanax sp. (occurring in 79.2% of the stretches) and K. moenkhausii (50.0%) were considered constant in both seasons. The longitudinal gradient (River Continuum) exerts a strong influence on the studied assemblage. According to CCA, the variables that structure the fish assemblage are based on aspects related to water volume and habitat complexity. No seasonal variation in richness, diversity, abundance, and mass were detected. A cluster analysis suggests a separation of species composition between the stretches of higher and lower orders, which was not observed for seasonality. The streams were considered well preserved (mean PHI 82.9±7.5%), but in some stretches were observed anthropogenic influence, detected in the water quality and, mainly, on the riparian vegetation integrity. The exotic species Poecilia reticulata was sampled in the two stretches considered most affected by anthropogenic activities by PHI, conductivity, and VC.

Patterns in fish species composition and assemblage structure in the upper Salado River lakes, Pampa Plain, Argentina

The Pampa Plain, in the central region of Argentina, is mostly drained by the Salado River. The fish fauna of this river is mostly known from field collections in lower reach lakes. Consequently, we aimed to explore the composition and structure of the fish assemblages in the upper Salado River lakes. Patterns in dominance and persistence of species and assemblage level attributes were correlated with environmental and human activity-derived (NO3:NH4) variables. Overall, 19,913 individuals of 17 species included in 5 orders and 11 families were collected. Several species are first records for the upper Salado River lakes. There was a marked proliferation of species in the family Characidae. Conversely, the remainder 10 families were only represented by one or two species. The species composition along the study lakes changed slightly but their relative contribution to the total fish collected (dominance) varied greatly. Rather few species were present in all collections suggesting an important interannual variability in assemblage stability. The gradient in water conductivity was an important factor for the persistence of particular species in the lakes. The gradients in water conductivity and NO3:NH4 ratio were associated with particular fish communities dominated by different groups of species. These results suggest that even when broad management and conservation strategies should encompass the system as a whole, lake-specific approaches must also be addressed. Overall, our results highlight that human impacts on surface waters may interact with environmental factors to influence the dynamics of fish species and the structure of their communities.

Ictiofauna dos córregos do Parque Nacional de Brasília, bacia do Alto Rio Paraná, Distrito Federal, Brasil Central

O objetivo do presente estudo foi realizar o inventário da fauna íctica dos córregos do Parque Nacional de Brasília no Distrito Federal e caracterizar a estrutura da comunidade íctica ao longo dos cursos d'água. Foram amostrados córregos das sub-bacias do Bananal e Santa Maria/Torto na região hidrográfica do Alto Rio Paraná. Esses cursos d'água apresentam bom estado de preservação, evidenciado na integridade de suas características ambientais naturais e na manutenção dos componentes biológicos nativos. Um total de 8.614 indivíduos, distribuídos em quatro ordens e nove famílias, foram coletados. A ordem com maior número de espécies foi a Characiformes, seguida por Siluriformes. Das 28 espécies encontradas 11 são novas para a ciência. Apenas a espécie exótica Poecilia reticulata foi encontrada. Astyanax sp. e Hyphessobrycon balbus foram as espécies com maior distribuição na área de estudo e Knodus moenkhausii apresentou a maior abundância (64,5% dos indivíduos). Nos trechos com maiores larguras e profundidades foram encontrados maiores valores de riqueza de espécies e abundância de indivíduos.

Composição e diversidade da ictiofauna em riachos do Cerrado, bacia do ribeirão Ouvidor, alto rio Paraná, Goiás, Brasil

Este estudo tem como objetivo descrever ecologicamente a ictiofauna quanto à riqueza, abundância, diversidade de Shannon-Wiener, uniformidade, relação riqueza/abundância e constância. As amostragens da ictiofauna foram realizadas bimestralmente de agosto de 2004 a junho de 2005 num trecho de 50 m de comprimento em nove afluentes e na calha principal do ribeirão Ouvidor, bacia do Alto Paraná. A coleta dos peixes foi realizada utilizando-se a pesca elétrica. Foram coletados 4049 indivíduos distribuídos em 35 espécies, seis ordens e 14 famílias. As espécies mais abundantes na bacia foram Astyanax cf. fasciatus Cuvier, 1819 (762 indivíduos), Poecilia reticulata Peters, 1859 (725) e Astyanax altiparanae Garutti & Britski, 2000 (650). A correlação encontrada entre a largura da calha e a riqueza sugere que riachos largos apresentam maior riqueza que estes estreitos. Apenas a diversidade de Shannon-Wiener variou significativamente entre os riachos amostrados. Astyanax cf. fasciatus e Rhamdia quelen Quoy & Gaimard, 1824 estiveram presentes em todos os trechos considerados, enquanto que a maior quantidade de espécies constantes foi encontrada no riacho Santo Antônio.