the amazon Basin is an unquestionable biodiversity hotspot, containing the highest freshwater biodiversity on earth and facing off a recent increase in anthropogenic threats. The current knowledge on the spatial distribution of the freshwater fish species is greatly deficient in this basin, preventing a comprehensive understanding of this hyper-diverse ecosystem as a whole. Filling this gap was the priority of a transnational collaborative project, i.e. the AmazonFish project -https://www.amazon-fish.com/. Relying on the outputs of this project, we provide the most complete fish species distribution records covering the whole Amazon drainage. The database, including 2,406 validated freshwater native fish species, 232,936 georeferenced records, results from an extensive survey of species distribution including 590 different sources (e.g. published articles, grey literature, online biodiversity databases and scientific collections from museums and universities worldwide) and field expeditions conducted during the project. This database, delivered at both georeferenced localities (21,500 localities) and sub-drainages grains (144 units), represents a highly valuable source of information for further studies on freshwater fish biodiversity, biogeography and conservation.Scientific Data | (2020) 7:96 | https://doi.collections from Peru 25,26 and by initiating sampling campaigns in detected gaps in Colombia, Peru and Brazil. All these spatial gaps in the database will also be prioritized in future updates through literature and web-based sources checking. Researchers holding fish distribution data from any of the current gaps or under-sampled areas (Fig. 2) and that wish to share these data are welcome to join the project. This information will be included with the complete source, after validation, in the next update of the database.

ABSTRACT. Fish assemblages from two sandy beaches in the lower Purus river (Amazonas, Brazil) were compared. Four sampling groups were represented by: day and night samples in sandy beach inside the Reserva Biológica de Abufari (biological reserve) and day and night samples in the Reserva de Desenvolvimento Sustentável Piagaçu-Purus (sustainable development reserve). Samples were collected during low water levels (November) in 2007. The fish were sampled by means of seines with mesh size of 5 mm between opposing knots, 11 m long and 6 m wide. A total of 112 fish species belonging to nine orders and 27 families was captured. The vast majority of the dominant forms consisted of small fishes (< 100 mm SL) or juveniles. Samples collected in Abufari at night presented more specimens (3,540), higher richness (84 spp.), larger total biomass (76,614 g) and higher diversity (H'= 2.57) than the other groups. The composition of fish assemblages was significantly different among all analyzed groups (ANOSIM, p < 0.0001, R= 0.71). NMDS analysis also clustered all species in four distinct groups according to species composition per period and site. SIMPER analyses showed that 80% of variation of species composition among the groups examined was due to 12 species. However, fish composition did not show any correlation with the abiotic factors examined. Different levels of use in both reserves may explain differences in fish composition. KEYWORDS.Amazon fish, nictemeral, protected areas, diversity, abundance. RESUMO. Assembleias de peixes de duas praias no baixo rio Purus, Amazonas, Brasil. Foram comparadas as assembleias de peixes de duas praias arenosas localizadas no baixo rio Purus (Amazonas, Brasil). As amostragens foram delineadas representando quatro situações:amostras diurna e noturna na praia da Reserva Biológica de Abufari e amostras diurna e noturna na praia da Reserva de Desenvolvimento Sustentável Piagaçu-Purus. As coletas foram realizadas durante o período de seca (novembro) de 2007. Os peixes foram coletados utilizando rede de cerco com malha de 5 mm entre nós opostos, 11 m de comprimento e 6 m de altura. Um total de 112 espécies de peixes foram coletados pertencentes a nove ordens e 27 famílias. A grande maioria das formas dominantes compreendeu peixes de pequeno porte (< 100 mm CP) ou juvenis. A praia de Abufari a noite apresentou mais espécimes (3.540), maior riqueza (84 spp.), maior biomassa total (76.614 g) e maior diversidade (H' = 2,57) do que os demais grupos. A composição das assembleias de peixes foi significativamente diferente entre as quatro situações analisadas (ANOSIM, p < 0,0001, R = 0,71). Análises de NMDS também agruparam todas as espécies em quatro grupos distintos de acordo com a composição por período e local. A análise de SIMPER revelou que 80% da variação na composição entre os grupos analisados foi devido a 12 espécies. Entretanto, a composição de peixes não mostrou correlação com os fatores abióticos analisados. Diferentes níveis de uso de ambas as reservas são apontados como possíveis cau...

Studies of fish assemblages have demonstrated that the main channels of rivers contain ichthyofauna adapted to this environment. However, information regarding the effects of temporal and spatial variations on this ichthyofauna is scarce. Using data from benthic fish assemblages in a major tributary of the Amazon basin collected during two consecutive receding and two rising water seasons, we tested the hypothesis that there are marked variations in community composition between the receding and rising water seasons. An asymmetry in predictability was detected among samples from the receding and rising seasons. Predictability in terms of species composition was higher for receding than rising seasons. The continual disassembly and reassembly cycles (due to dispersal) of local communities across a spatially heterogeneous landscape could explain this difference. Depth and dissolved oxygen affected the distribution of some benthic fish species during the rising seasons. This study highlights the important contribution of marginal wetlands to the benthic ichthyofauna inhabiting the main channel of the Purus River, as well as other major Amazonian rivers.

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1. The seasonality of tropical rivers, induced mainly by water level changes, shapes many interrelated aspects of ecological communities and the populations they contain, including animal movement, feeding, growth, and reproductive activity.However, the role played by seasonality in structuring the diversity of tropical assemblages is not yet fully understood.2. We examined the effects of seasonality on community structure and composition of benthic fish assemblages comparing two consecutive receding and rising water seasons in a major tributary of the Amazon basin. We quantified seasonal shifts in species abundance distributions and in composition using a multivariate dispersion test, total β diversity and its decomposition into local (LCBD) and species contribution to β diversity (SCBD). Additionally, we tested for relationships between LCBD values and richness, total abundance, and environmental variables.3. Many benthic fish species were rare in terms of numerical abundance. Rarity was most pronounced in the rising seasons, which had a higher proportion of singletons. A logseries was the best-fit model for both the receding and one of the rising season's species abundance distributions, while a lognormal was selected for the second rising season. We detected variation in species composition between seasons-the rising seasons were distinct from one another in terms of species composition, as well as differing from the receding seasons.LCBD showed strong negative relationships with species richness and total abundance, particularly in the rising seasons, indicating that seasons with high uniqueness in their composition also had low richness and abundance. LCBD was negatively correlated with temperature, while depth presented a positive relationship, as observed mainly in rising seasons with colder temperatures and greater water depth. Approximately one third of the species had higher than average SCBD values and were considered major contributors to β diversity. 4. These significant seasonal differences in both species relative abundances and assemblage composition might be explained by the asymmetrical spatial use of habitats during different seasons, strongly suggesting the importance of the flood-pulse cycle for maintaining diversity in this environment.

The objective of this study was to assess if larvae of Phylloicus spp. show any preference for leaves with or without microorganisms when building cases. Two experiments were realized at municipality of Presidente Figueiredo (Amazonas – Brazil), containing leaves treated with Hydrogen peroxide (H2O2), a compost that has an antimicrobial action, and another one with untreated leaves. In the first were observed the case-building by larvae of Phylloicus spp. And in the second was tested the preference by treated or untreated leaves. The larvae were monitored during 24 hours and to statistical analysis was used the t-test. Were not observed significant differences in the number of discs used by the larvae in the first experiment (p=0.24; t=-0.73) and no preference by type of leaf in the second experiment (p=0.41; t=0.23). Therefore, we do not recommend the use of hydrogen peroxide in studies that aim to eliminate microorganisms from decomposing leaves. Uso de Folhas Tratadas com Peróxido de Hidrogênio na Construção de Abrigos por Phylloicus spp. (Trichoptera: Calamoceratidae) Resumo. O objetivo deste estudo foi avaliar se larvas de Phylloicus spp. possuem preferência por folhas com ou sem micro-organismos para a construção de abrigos. Dois experimentos foram realizados no município de Presidente Figueiredo (Amazonas – Brasil), contendo folhas tratadas com peróxido de hidrogênio (H2O2), composto que possui ação antimicrobiana, e folhas não tratadas. No primeiro observaram-se a construção de abrigos pelas larvas de Phylloicus spp. e no segundo testou-se a preferência por folhas tratadas ou não tratadas. As larvas foram monitoradas durante 24 horas e para a análise estatística foi utilizado o teste-t. Não foram observadas diferenças significativas no número de discos usados pelas larvas no primeiro experimento (p=0,24; t=-0,73) e nem na preferência pelo tipo de folha no segundo experimento (p=0,41; t=0,23). Portanto, não recomendamos o uso do peróxido de hidrogênio em estudos realizados em laboratório que visem à eliminação de micro-organismos de folhas em decomposição.

Comparação da eficiência relativa de dois apetrechos de coleta de peixes em praias no baixo rio Purus, Amazonas, Brasil Cleber DUARTE¹, Cláudia Pereira de DEUS 2 , Lúcia RAPP PY-DANIEL 3 RESUMOApesar das praias serem consideradas um dos sete mais importantes habitats aquáticos da Amazônia, poucos trabalhos foram realizados quanto ao levantamento de sua ictiofauna, principalmente quando utilizados diferentes apetrechos de coleta. Este trabalho teve como objetivo comparar a eficiência relativa de dois apetrechos, rede de cerco e malhadeira, ambos utilizados de forma ativa (arrasto), em três praias localizadas no baixo rio Purus. A rede de cerco apresentou maior número de espécies e indivíduos capturados, no entanto, a malhadeira apresentou maiores valores de biomassa total, representada principalmente por Siluriformes. A baixa similaridade da fauna de peixes capturada (38%) foi devido à exclusividade de espécies coletadas com cada apetrecho, 41 com rede de cerco e 32 com malhadeira. O presente trabalho mostra a importância de se utilizar diferentes apetrechos de coleta como forma de diminuir a seletividade inerente de cada um desses aparelhos, melhorando a efetividade de amostragens em ambientes pouco estudados. PALAVRAS-CHAVE: Ictiofauna, riqueza de espécies, malhadeira, rede de cerco. Comparison of the relative efficiency of two fishing gears in sandy beaches in lower Purus river, Amazonas, Brazil ABSTRACTDespite representing one of the seven most important aquatic habitats in the Amazon, little has been done concerning fish inventories on sandy beaches, especially related to the fishing gear used in these environments. This study aims to compare the relative efficiency of two fishing gears, seine and gill-net, used actively (trawling), on three sandy beaches on the lower reaches of Rio Purus. Seining resulted in a larger number of species and specimens, whereas for total biomass, gill-nets showed larger values, mainly represented by Siluriformes. Low similarity between samples (38%) was due to different catches of each gear: 41 species collected only with seine and 32 only with gill-net. The present study strengthens the importance of using different fishing gears in experimental fisheries as a way to overcome the inherent selectivity of each gear, and thus improving the efficacy of sampling in poorly-known environments.

Despite the high number of fish species described for the Amazon region, the ichthyofauna that inhabits the depths of the main channels of large tropical rivers is one of the least known. In order to know the diversity patterns of these fish in whitewater rivers of the Central Amazon, we used data from the main channel benthic fish assemblage of the Japurá, Purus and Madeira rivers and tested the hypothesis that there are marked spatial and seasonal differences in the composition of the fish community among them. For this, we used a multivariate dispersion test, total β diversity and its decomposition into local (LCBD) and species contribution to β diversity (SCBD). Additionally, we tested for relationships between LCBD values and richness, total abundance, and environmental variables. We categorized species with higher SCBD values into resident or migratory to investigate the potential importance of floodplains to benthic fish assemblage of the main channel of whitewater rivers. Our results corroborate the proposed hypothesis, showing that there are seasonal and inter-river differences in benthic ichthyofauna, being more evident for the Purus River. LCBD showed strong negative relationships with species richness and total abundance, particularly in the Japurá and Madeira rivers in rising season, indicating that rivers and season with high uniqueness in their composition also had low richness and abundance. LCBD was negatively correlated with conductivity and pH, which increased with declining these environmental variables, as observed mainly in Japurá River in both seasons. Approximately one third of the species had higher than average SCBD values and were considered major contributors to β diversity, as well as classified as migratory. This demonstrates the importance of conducting studies that use spatial and seasonal variables, in addition to including the background fish fauna in conservation studies, expanding the protected area and taking into account the different patterns of diversity between rivers. Furthermore, these differences in assemblage composition might be explained by the asymmetrical spatial use of habitats during different seasons, strongly suggesting the importance of the flood-pulse cycle for maintaining diversity in this environment.