Index). Spearman correlation analysis, a glm and CCA were performed between biotic and abiotic variables, and we used the CPUE as a measure of fish abundance. Results: Eleven taxa of fish were recorded, four of which were predated by adult "trahira". Insects and other items were also common in the stomachs of juveniles. According to statistical analysis, it was observed that the highest consumption of cichlids was correlated with its increase in CPUE in the environment, while no relationship was observed for A. bimaculatus, C. bimaculatum and S. notonota abundances. The environmental factors as nutrients, transparency and water volumn were related to selection of species by trahira. Conclusions: Intrinsic characteristics of preys as swimming speed, food habit and the food preference of the predator possibly be the main factors to selection of species. Other mechanisms as heterogeneity of habitat and environmental factors can also influence the consumption of prey by trahira.

AimTo determine the composition and biomass of functional groups around the vertical and temporal gradient correlated with environmental conditions and apply the index Q in a water-supply reservoir.MethodsWater samples were collected monthly (n = 92) between 2009 and 2011 in two points of the dam for physicochemical and biological analysis.ResultsThe pH, dissolved oxygen and water temperature showed significant differences between the photic and aphotic zones (p<0.05). The vertical variation of dissolved oxygen and water temperature, showed a profile of stratification. The phytoplankton community was represented by 11 functional groups: S1, M, H1, Lo, P, F, SN, J, W2, MP and R.ConclusionsThe vertical variations were less pronounced than the temporal variations in the phytoplankton community. The Q index pointed out poor water quality, corresponding to the current state of eutrophication in the reservoir and it was sensitive to responsive to environmental and hydrodynamic changes in these systems, demonstrating to be an appropriate tool for monitoring and evaluating the quality of water in tropical semi-arid reservoirs.

ResumoAs regiões semiáridas do Nordeste brasileiro sofrem com os prolongados períodos de estiagem, afetando a qualidade da água e a produtividade pesqueira. Os estudos têm demonstrado que as alterações entre períodos de chuva e estiagem têm profundas influências sobre os organismos dos ambientes aquáticos das regiões semiáridas e em especial sobre a ictiofauna. Apesar disto, poucos são os estudos que tentam conhecer e elucidar a ecologia de peixes do semiárido. O objetivo do presente artigo foi conhecer a diversidade e alguns aspectos da estrutura populacional de espécies de peixes, a fim de avaliar a importância da formação das poças para a conservação das espécies e da produtividade pesqueira. Foi encontrado um total de 13 espécies de peixes, das quais uma espécie é exótica (Oreochromis niloticus). A abundância de espécies foi altamente variável entre os meses de coleta, embora a riqueza tenha revelado baixa flutuação. As espécies de importância econômica apresentaram tamanho médio acima de 7cm de comprimento padrão e 57,9% dos indivíduos estiveram em atividade reprodutiva. Os resultados demonstraram que o período de estiagem afeta a comunidade de peixes, sendo que as poças parecem ser locais importantes para a conservação da diversidade e da produtividade pesqueira. AbstractFish diversity in pools of an intermittent river in a semiarid region of Paraíba, Brazil. Prolonged periods of drought cause alterations in water quality and productivity of fisheries in semiarid regions of Brazil. Changes between periods of rain and drought affect aquatic organisms, especially fish. However, there are few studies that have attempted to understand and elucidate the ecology of fish in these semiarid regions. The purpose of this study was to investigate the diversity, and some aspects of population structure of fish species in these areas, in order to evaluate the importance of shallow pond formations in the conservation of these taxa and the productivity of these fisheries. We recorded 13 fish species, of which one was exotic (Oreochromis niloticus). Species abundance was highly variable among months, while variability of richness was low. The average size of the fish, which is important for the local economy, was over 7cm long, and 57.9% of individuals were Revista Biotemas, 25 (3), setembro de 2012 162 M. M. L. Cardoso et al.reproductively active at the moment of capture. The results show that the dry season affects the structure of the fish community and that the pools are important sites for the conservation of the diversity and productivity of these fisheries.

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Role of the rain and macrophytes on temporal and spatial pattern of ichthyoplankton in the Caatinga Biome, Brazil Papel da chuva e das macrófitas no padrão temporal e espacial do ictioplâncton no Bioma Caatinga, Brasil

Climate change is affecting the global hydrological cycle, causing drastic changes in precipitation patterns. Extreme climatic events are becoming more frequent and intense than in the past, leading to water-level fluctuations and affecting aquatic ecosystems. Semiarid regions are very susceptible to changing climate. We analyzed a 10 years dataset from a tropical semiarid reservoir during extreme hydrological events (heavy rains and prolonged drought), and evaluated phytoplankton functional responses to environmental conditions. We found, as hypothesized, that phytoplankton functional structure change in a temporal scale due to water–volume fluctuation induced by the rainfall pattern. Depth and inorganic material acted as environmental filters selecting phytoplankton groups. High water level seems to improve water quality and low water level worsen it. Colonial and filamentous cyanobacteria dominate the wet period; however, it may have a critical threshold during severe periods of drought, which will lead to dominance of groups well adapted to low light conditions and with mixotrophic metabolism. Phytoplankton functional approaches can simplify phytoplankton identification and reflect better the environmental conditions than the taxonomic approach. Therefore, these approaches can help to understand the shifts in aquatic ecosystems under extreme hydrological events and predict functional response of phytoplankton being an important tool to water management and conservation. Supplementary Information The online version contains supplementary material available at 10.1007/s10750-023-05241-3.

Avaliou-se o uso de ração alternativa com resíduos agroindustriais na alimentação de tilápia nilótica (Oreochromis niloticus) e carpa comum (Cyprinus carpio), em sistema de policultivo, conduzido em dois viveiros escavados, situados no assentamento Estiva do Geraldo, município de Lucena-PB. Para a coleta dos dados biométricos as amostras foram compostas de 5% dos indivíduos estocada em cada viveiro, sendo esta mesma porcentagem utilizada para calcular a biomassa e reajustar a quantidade de ração ao peso dos indivíduos, aos 30, 60, 90, 120 e 150 dias de cultivo. Foram realizados dois tratamentos: Ração Alternativa, à base de restos de hortifrutigranjeiros, varredura de cevada, raspa de mandioca, farelo de coco, sangue in natura, fosfato bicálcico, premix mineral e vitamínico; e Ração Comercial. A tilápia apresentou melhor desempenho produtivo quando alimentada com a ração comercial. Enquanto que com a carpa ocorreu o inverso, cresceram mais no viveiro em que se aplicou a ração alternativa. Conclui-se que, a ração alternativa foi mais eficiente para a carpa que para a tilápia, mas analisando os lucros que seriam obtidos pela venda dos peixes, vê-se que são muito semelhantes, em virtude da ração alternativa ser muito mais barata, e poder ser preparada com facilidade em regime de aquicultura familiar.

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