Based on the knowledge of local artisanal fishermen and on direct observations, this study presents evidence that the giant manta ray Manta birostris uses the Paranaguá estuarine complex in south Brazil, south-western Atlantic Ocean, in a predictable seasonal pattern. Behavioural observations suggest that the estuary can act as a nursery ground for M. birostris during the summer.

To determine the fish species present in Taperoá II Reservoir, and their relevance to the local economy, this research aimed to evaluate the composition, abundance, degree of dominance and constancy of species, along with diversity, richness, evenness and similarity indices in a tropical semi-arid fish assemblage, during one year. Six 24 hour-long samplings were carried out between October 2005 and October 2006 using cast, seine and gillnets. The 889 collected individuals belonged to 11 species from 9 families. Temporal variation was observed in the capture frequency of different species, and a significant negative correlation between precipitation and number of individuals was also observed. Among the recorded families, Characidae showed a higher frequency of occurrence (38.4%), mostly due to Astyanax bimaculatus (Linnaeus, 1758) and A. fasciatus (Cuvier, 1819). Eight species were categorised as constant, two as accessory and one as accidental. Diversity index values were intermediate with low fluctuation throughout the study period, and no correlation with precipitation or water volume. However, the greatest diversity value was recorded in March 2006, when the peak of the precipitation was recorded. Evenness values showed a similar trend to the diversity index.Keywords: reservoir, ecology, community, temporal variation. Diversidade da ictiofauna do açude Taperoá II, semiárido paraibano, Brasil ResumoPara determinar as espécies de peixe presentes no Açude Taperoá II e sua relevância para a economia local, objetivou-se determinar a composição, a abundância, a dominância e a constância de espécies da ictiofauna, bem como os índices de diversidade (H'), riqueza, equitabilidade e similaridade de espécies ao longo de um ano. Foram realizadas seis coletas ao longo de 24 horas, de outubro de 2005 a outubro de 2006, utilizando-se tarrafas, redes de espera e arrasto. Foram coletados 889 indivíduos, identificados em 11 táxons específicos, distribuídos em nove famílias. A abundância das diferentes espécies variou temporalmente, com correlação negativa significativa entre a precipitação e o número de indivíduos. Dentre as famílias identificadas, Characidae apresentou a maior frequência de ocorrência (38,5%), representada pelas espécies Astyanax bimaculatus (Linnaeus, 1758) e A. fasciatus (Cuvier, 1819). Oito espécies foram consideradas constantes, duas acessórias e uma acidental. O índice de diversidade apresentou valores entre 2,11 e 2,80, e não apresentou correlação com a precipitação e o volume do açude. Entretanto, o índice de diversidade mais elevado foi registrado no mês de março de 2006, pico do período chuvoso. Os valores da equitabilidade comportaram-se de forma semelhante aos do índice de diversidade.Palavras-chave: reservatório, ecologia, comunidade, variação temporal.

Improving our knowledge on the behavior of threatened species is essential for developing effective conservation actions. The Paranaguá Estuarine Complex (PEC), southern Brazil, is the only estuary in the world where manta rays have been observed performing breaches seasonally. The exact role of this breaching behavior and the environmental factors connected to it are unknown. Our goals were to determine the spatial distribution, and the temporal and environmental factors that influence the breaching behavior of this endangered group in a dynamic estuarine habitat for the first time. Manta rays were observed breaching in the PEC during austral summer and early autumn, when the sea surface temperature (SST) and precipitation were high. Generalized additive models revealed that the presence and frequency of the breaches were both influenced by the SST and hours of daily effort, while the breaching frequency was also influenced by the wind direction and speed, percentage of moon illumination, and year. The breaches were mainly concentrated near the mouth of a river. Likely these factors influenced not only the occurrence and behavior of manta rays, but also the distribution of their food source, potentially providing optimal conditions for foraging and reproduction. Based on the coloration pattern, it is possible that the observations were of Mobula cf. birostris. These results provide valuable insights into the breaching behavior of manta rays in estuarine waters that will assist future conservation initiatives and research on their behavioral ecology, to optimize fishery management and contribute to developing sustainable ecotourism in the PEC.