A fish-based index of large river quality for French Guiana (South America): method and preliminary results

Growing pressures from development activities, oil aquatic environments in South American Countries, have created an urgent need for tools to measure the quality of aquatic systems. The index of biotic integrity, based oil fish assemblages, elaborated in North America, constitutes a basis for the development of these tools. However, its direct application is problematic in regions having a rich and diverse ichthyofauna and where the knowledge of fish species ecology is incomplete. The response of taxonomic or trophic groups is often unknown and the selection of fish assemblage metrics cannot be based on previous knowledge, as in intensely studied regions. This work proposes a method, similar to the approach recently pursued in Europe, based on comparing the variability of fish assemblages in reference Situations with their variability influenced by human-induced perturbations. The method was developed from 53 samples of 27 reaches in 7 hydrographic basins of French Guiana. For each of 28 fish assemblage descriptors, stepwise Multiple linear regressions with 28 habitat variables were carried out. The residuals of the models obtained were used as candidate metrics independent of natural environmental factors. Nine metrics showing significant differences , between reference and disturbed samples were selected to constitute the index. The index was validated by analysing a temporal data series obtained from a reach disturbed by dam Construction

Tropical headwater streams and the role of non-native species on fish assemblage’s diversity

Non-native species cause several impacts on freshwater biodiversity, but studies focusing on the Neotropical stream’s biota are still incipient. We used a data set of 586 headwater stream’s fish assemblages from the Brazilian Upper Paraná ecoregion to test whether the presence/absence of non-native species affect: species richness (S), functional diversity (MPD) and taxonomic diversity (Δ+). We compared diversity patterns of fish assemblages formed only by native species against those of assemblages formed by native and non-native species (Scenario 1); then, we removed non-native species from their original assemblages and recalculated their diversity values to compare them with those of fish assemblages formed only by native species again (Scenario 2). We also investigated: (1) whether non-native’s fish assemblages are associated with land use, topographic and watercourse connectivity variables; (2) fish ecological traits-environment relationship. In Scenario 1, S was higher in assemblages with the presence of non-native species, while in Scenario 2, both S and MPD were higher in assemblages where non-native species were removed. Non-native species were not directly related to land use, topographic or connectivity variables and most of them had a similar response to the environment when compared with native species. Findings show that non-native fish species are related to high-rich assemblages in headwaters, and they increase species richness and the functional redundancy of assemblages, decreasing functional diversity. Moreover, in most cases, native and non-native species seem to respond similarly to the environmental influence on their occurrence

Diversidade biológica da comunidade de peixes no baixo rio das Mortes, Mato Grosso, Brasil Biological diversity of the fish assemblage in the Lower das Mortes River, Mato Grosso, Brazil

O rio das Mortes é um dos principais cursos d’água do estado de Mato Grosso e o maior afluente, da margem esquerda, do rio Araguaia, sendo que a seção baixa do mesmo está inserida na planície do Bananal. Este estudo objetiva caracterizar ecologicamente a comunidade de peixes considerando um período sazonal: cheia e seca. A comunidade de peixes em estudo apresenta altos valores de diversidade (4,783 bits/indivíduos do Índice de Shannon-Wiener), riqueza de espécies (66 espécies amostradas) e abundância de indivíduos (659 indivíduos) durante o período de seca, onde as espécies mais abundantes foram Pygocentrus nattereri Kner, 1858 e Boulengerella cuvieri (Agassiz, 1829). Ageneiosus inermis (Linnaeus, 1766) e Rhaphiodon vulpinus Agassiz, 1829 foram mais abundantes na época cheia. A interação entre a comunidade de peixes e a planície de inundação apresenta um padrão comparável a este observado em planícies de inundação na região Neotropical.<br>The das Mortes River is one of the main water courses of the Mato Grosso State and the largest tributary of the Araguaia River on it’s left bank. Its low section is located in the Bananal floodplain. This study aims to characterize the fish assemblage of this river during high and low waters. Fish assemblage during low waters was characterized by high diversity (4.783 bits/individuals of the Shannon-Wiener index), species richness (69 species sampled) and abundance (659 individuals), where the most abundant species were Pygocentrus nattereri Kner, 1858 and Boulengerella cuvieri (Agassiz, 1829). Ageneiosus inermis (Linnaeus, 1766) and Rhaphiodon vulpinus Agassiz, 1829 were abundant at high waters. Interaction between the fish assemblage and the floodplain have similar pattern to that observed in other Neotropical floodplains

Microsatellite analysis of the parental contribution of Piaractus mesopotamicus to the production of offspring in the semi-natural system of reproduction

The objective of this study was to evaluate the genetic diversity and the parental contribution of Piaractus mesopotamicus in the production of offspring in the semi-natural system of reproduction. Twenty parental fishes (eleven males and nine females) and the total of 100 larvae were evaluated by microsatellite marker. The parents and offspring had thirty-one alleles and heterozygosity of 0.550 and 0.563, respectively. The females were fertilised by two up to six males while the males fertilised three up to five females. The contribution of the females and males to the offspring were 66.6 and 58%, respectively. Such results indicated no loss in the genetic variability in the offspring, and the parents had multiple paternity and reasonable contribution to the offspring production.<br>O objetivo deste trabalho foi avaliar a diversidade genética e a contribuição parental de Piaractus mesopotamicus na produção de descendência no sistema seminatural de reprodução. Vinte peixes parentais (onze machos e nove fêmeas) e o total de 100 larvas foram avaliados por meio do marcador microssátelite. Os parentais e a progênie tiveram trinta e um alelos e heterozigosidade de 0,550 e 0,563, respectivamente. As fêmeas foram fertilizadas por dois até seis machos enquanto machos fertilizaram três até cinco fêmeas. A contribuição de fêmeas e machos para a descendência seja 66,6 e 58,0%, respectivamente. Tais resultados não indicam diminuição da variabilidade genética na progênie e os parentais apresentaram paternidade múltipla e razoável contribuição à produção de descendência