In this study we investigated the distribution of Macrobrachium olfersii (Wiegmann, 1836) along ~150 km of the Ribeira de Iguape river, São Paulo, Brazil. We compared the abundance and spatio-temporal distribution, and checked for differences in size and proportion of each sex in the collections, using two sampling methods. Shrimps were collected monthly at four sites (Eldorado, Sete Barros, Registro, and Iguape), from January to December 2007, using traps and sieves. We obtained a total of 23,818 individuals. The abundance was significantly higher at the Iguape-site, which was the closest to the estuary. There was a positive cross-correlation between abundance and rainfall, indicating an increase in abundance with a decrease in rainfall. The body size increased significantly upstream, suggesting a juvenile upstream migration, controlled by the rainfall regime and the amphidromous behavior of M. olfersii. More than 95% of the individuals were captured by sieving through the marginal vegetation of the river. The average size and sex ratio of each sample varied depending on the capture method: traps captured more and larger males than the sieve. Therefore, we recommend the combined use of these methods to obtain a better coverage of the population biology of freshwater shrimps.
Rocky shores are ecosystems susceptible to anthropic impact, and the absence of information in Brazil about their biota hampers characterization and conservation measures. Thus, this study analyzed the abundance, richness, diversity and dominance of anomuran and brachyuran communities in sheltered and exposed rocky shores in Anchieta and Guarapari on the coast of Espírito Santo State. It was also studied the community variation concerning the types of rocky shores during the rainy and dry seasons. The organisms were collected manually in the mediolittoral zone of the rocky shores from October 2014 to September 2015. Additionally, temperature and salinity of the water were measured and the rainfall recorded from a meteorological station. In this study, 3,156 individuals were collected, comprising 14 species. The hermit crabs Clibanarius antillensis and Calcinus tibicen were the most abundant species. The three-way ANOVA analysis revealed that there was no interaction between ecological indices and the study locations, rocky shores and seasons. The abundance of the decapod community was statistically different between locations. The richness and diversity indices were higher on the sheltered rocky shore because of the presence of rock fragments and heterogeneous sediments, they are providing higher availability of microhabitats in these areas. There was no relationship between the decapod community and environmental factors, possibly because of a small variation of these factors registered between rainy and dry seasons. It is concluded that the anomuran and brachyuran communities are probably more influenced by biological interactions and physiographic features of rocky shores than by environmental factors.
Levantamento faunístico dos crustáceos decápodes é de fundamental importância para o conhecimento das comunidades, servindo de base para a conservação da biodiversidade. O objetivo deste estudo foi analisar a fauna dos Anomura e Brachyura em dois costões rochosos, localizados em Anchieta e Guarapari, litoral do Espírito Santo, com ênfase na análise dos índices de diversidade e similaridade entre as espécies. Em cada região, foram amostrados quatro pontos (P1, P2, P3 e P4), durante o período de outubro/2014 a setembro/2015. A diversidade de Shannon Wiener e equitabilidade foram calculados, bem como, o grau de semelhança entre as espécies. Foram coletados 3.156 indivíduos (1.022 em Anchieta e 2.134 em Guarapari), sendo representados por oito famílias e 14 espécies. O maior valor de diversidade foi encontrado no P1 e P2 em Anchieta, além do P1 ter apresentado o maior valor de equitabilidade. As espécies com abundância e ocorrência semelhantes foram agrupadas com maior similaridade. Os locais estudados apresentam condições favoráveis para o desenvolvimento e estabelecimento desses crustáceos anumuros e braquiúros.
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