The Amazon rainforest has experienced rapid land-use changes over the last few decades, including extensive deforestation that can affect riparian habitats and streams. The aim of this study was to assess responses of stream fish assemblages to deforestation and land cover change in the eastern Amazon. We expected that percentage of forest in the catchment is correlated with local habitat complexity, which in turn determines fish assemblage composition and structure. We sampled 71 streams in areas with different land uses and tested for relationships between stream fish assemblages and local habitat and landscape variables while controlling for the effect of inter site distance. Fish assemblage composition and structure were correlated with forest coverage, but local habitat variables explained more of the variation in both assemblage composition and structure than landscape variables.Inter site distance contributed to variance explained by local habitat and landscape variables, and the percentage of variance explained by the unique contribution of local habitat was approximately equivalent to the shared variance explained by all three factors in the model. In these streams of the eastern Amazon, fish assemblages were most strongly influenced by features of instream and riparian habitats, yet indirect effects of deforestation on fish assemblage composition and structure were observed even though intact riparian zones were present at most sites. Long-term monitoring of the hydrographic basin, instream habitat and aquatic fauna is needed to test for potential legacy effects and time lags, as well as assess species responses to continuing deforestation and land-use changes in the Amazon. Aperfeiçoamento de Pessoal de Nível Superior (CAPES) for PROCAD/ CAPES funding (project no 88881.068425/2014-01), the graduate scholarship for TOB and senior internship scholarship for LFAM to conduct research at Texas A&M University (process 88881.119097/2016-1). The manuscript was improved during the review process by addressing the thoughtful comments from Philip Kaufmann and an anonymous reviewer.
Summary Reduced‐impact logging (RIL) has been considered as the main activity of forestry management in the Amazon. However, little is known of the effects of RIL on the region's ecosystems or in their biodiversity, and such information would be useful to inform forest management. Accordingly, this study aimed to investigate the effects of RIL on physical habitat and fish assemblages in Eastern Amazonia streams. We predicted that changes caused by RIL affect stream habitat, leading to a loss of diversity and changes in species composition with a predominance of generalist species. We sampled 13 streams in basins dominated by native vegetation without evidence of logging activity (unlogged areas) and 23 in areas that had been logged at different times between 2001 and 2011. Stream physical habitat structure was characterized using a standardized protocol, and the abundance, richness and composition of fish assemblages were assessed. Biotic and abiotic data were compared between unlogged and logged areas, and among streams in areas with different logging years. The relationship between the stream habitat structure and fish assemblages was assessed using a distance‐based linear model using a forward procedure, followed by application of the Akaike information criterion. Variations in tree canopy cover, channel morphology, water temperature and dissolved oxygen and conductivity accounted for most of the differences in habitat characteristics between unlogged and logged areas. A total of 53 fish species was collected, belonging to 20 families and 6 orders. Fish abundances did not vary consistently between streams in unlogged areas and those that had undergone RIL, and showed minor evidence of species‐specific changes in response to logging years. Likewise, there were no obvious differences in species richness, composition and biomass between logged and unlogged sites, regardless of logging years. RIL in Eastern Amazonia is performed in compliance with technical guidelines, but this practice has resulted in changes in stream physical habitat. Nonetheless, in the headwater streams that we sampled, the effects of RIL on fish assemblages were minor.
Studies on the length-weight relationship (LWR) of fishes are an important tool to describe several biological aspects of the species. Consequently, these studies are relevant due the necessity of comprehension about fish life cycle. Thus, this study aimed to establish the length-weight relationship of the ten most common fish in the Lower Nhamundá River, left tributary of the Amazon River. The capture of fish was conducted in January 2008 using gill nets. A total of 807 individuals, ten species and three Orders (Characiformes, Siluriformes and Clupeiformes) were analyzed. The parameter b varied from 2.680 to 3.698. The LWR were shown for the first time for two species: Anostomoides laticeps and Ageneiosus polystictus. Finally, this research emphasizes the importance of LWR studies in the Amazon and the use of primary data for fisheries management plans. KEYWORDS: growth pattern, alometry, fish, Amazonia.Relação peso-comprimento de dez espécies de peixes do Rio Nhamundá, Bacia Amazônica, Brasil RESUMOEstudos acerca da relação peso-comprimento em peixes são importantes ferramentas para descrever diversos aspetos biológicos das espécies. Consequentemente, estes estudos são importantes em decorrência da necessidade de compreensão do ciclo de vida dos peixes. Sendo assim, este estudo visou estabelecer a relação peso-comprimento de dez espécies mais comuns de peixes na região do baixo Rio Nhamundá, afluente da margem esquerda do Rio Amazonas. A captura dos peixes foi realizada em janeiro de 2008, utilizando redes de emalhar. Foram analisados 807 indivíduos, pertencentes a dez espécies e três Ordens (Characiformes, Siruliformes e Clupeiformes). O coeficiente alométrico "b" variou de 2,680 à 3,698. A relação peso-comprimento é apresentada pela primeira vez para duas espécies: Anostomoides laticeps e Ageneiosus polystictus. Por fim, esse estudo enfatiza a importância de estudos de relação peso-comprimento de peixes na Amazônia e o uso de dados primários para fins conservacionistas. PALAVRAS-CHAVE: padrão de crescimento, alometria, peixe, Amazônia.
Summary The present work presents parameters of the length–weight relationships (LWR) for 12 species of freshwater fish from rivers within the Caxiuanã National Forest, Eastern Amazon. Data coverage include the main taxonomic groups in the sampling area: Characiformes: Acestrorhynchidae, Anostomidae, Curimaridae, Erythrinidae, Hemiodontidae; Siluriformes: Auchenipteridae; Perciformes: Sciaenidae. LWR parameters are estimated for the first time for five species: Leporinus affinis, Bryconops melanurus, Pygopristis denticulata, Serrasalmus gouldingi and Triportheus albus. Relative growth patterns were evenly distributed among species, one‐third showing negative allometry (b < 3; n = 4), isometry (b = 3; n = 4) or positive allometry (b > 3; n = 4).
Studies on feeding ecology of fishes are important to understand the relationship between species and environmental seasonal variations. In tropical rivers, these relationships are mainly modeled by hydrological patterns. Thereby, this study aimed to assess the influence of fluviometric variation and life stage (juveniles and adults) in the feeding ecology of Serrasalmus gouldingi in the lower Anapu River region, located in Eastern Amazon, Pará, Brazil. Specimens were collected bimonthly, considering four different hydrological periods. We assessed the diet composition, feeding intensity and niche breadth of the species. Thirty-two dietary items were identified and grouped into ten categories. A total of 279 stomachs were analyzed, showing a predominance of fish fragments, followed by fruits and seeds. The diet composition of S. gouldingi differed only between drought and flood season, although it did not differ between juveniles and adults. An increase in feeding intensity was recorded during the rise in the water level, with a lower feeding intensity observed during transitional season. Serrasalmus gouldingi showed lower niche breadth during flood season, attributed to the high consumption of fruits and seeds, presenting an omnivorous diet with high tendency towards piscivory. Although less evident than in other Amazon watersheds, the flood pulse in the lower Anapu River region is an important factor influencing the feeding ecology of the species. KEYWORDS: Amazon basin, diet, flood pulse, niche breadth, repletion index.Ecologia alimentar de Serrasalmus gouldingi (Characiformes: Serrasalmidae) na região do baixo Rio Anapu, Amazônia Oriental, Brasil RESUMO Estudos sobre ecologia trófica dos peixes são importantes ferramentas para compreensão das relações entre as espécies e as variações sazonais no ambiente. Em rios tropicais essas relações são modeladas principalmente por variações hidrológicas. Sendo assim, o objetivo presente estudo é avaliar a influência variação fluviométrica e do estágio de vida (juvenis e adultos) na ecologia alimentar de Serrasalmus gouldingi na região do baixo Rio Anapu, Amazônia Oriental, Pará, Brasil. Os espécimes foram amostrados bimensalmente considerando quatro períodos hidrológicos distintos. Nós avaliamos a composição da dieta, intensidade alimentar e amplitude de nicho da espécie. Foram identificados trinta e dois itens alimentares agrupados em dez categorias. Um total de 279 estômagos foi analisado, registrando um predomínio no consumo de fragmento de peixes seguido por frutos e sementes. A composição na dieta de S. gouldingi diferiu apenas entre os períodos de seca e cheia, não diferindo entre juvenis e adultos. Uma maior intensidade alimentar foi observada durante o aumento do nível dos rios, com uma menor intensidade alimentar durante os períodos transicionais. Durante o período de cheia S. gouldingi também evidenciou uma menor amplitude de nicho, a qual foi atribuída ao elevado consumo de frutos e sementes. Sendo assim, a dieta de S. gouldingi foi classificada como...
This study investigates the influence of the flood pulse on the reproductive biology of the auchenipterids Tocantisia piresi (Miranda Ribeiro, 1920) and Auchenipterus nuchalis (Spix & Agassiz, 1829) from the middle Xingu River in the Brazilian state of Pará. The specimens were collected every three months between April, 2012, and January, 2014, covering four distinct periods (flood, ebb, dry, and filling). The sex ratio, size at first maturity, gonadosomatic index, and condition factor were analysed in the two species, and evaluated in the context of the different hydrological periods. A total of 897 specimens of T. piresi were collected, of which 467 were female, and 430 males, and 383 A. nuchalis (286 females and 97 males). In T. piresi, the sex ratio was biased only in the filling and ebb periods, whereas in A. nuchalis, it departed significantly from the expected ratio of 1:1 in all periods, with a predominance of females. The female T. piresi mature at a smaller size than the males, with the opposite of the pattern being recorded in A. nuchalis. In T. piresi, the breeding peak was observed during the low water periods, whereas in A. nuchalis, the peak was recorded in the flood periods. Male and female T. piresi presented similar positively allometric growth rates, whereas in A. nuchalis, growth was negatively allometric, but rates were different between genders. A higher condition factor was recorded in the females of both species during the ebb period. Overall, the results of this study reveals distinct flood pulse effects on the reproductive parameters of the two auchenipterid species studied; for A. nuchalis the spawning seems to happen at the flood period and for T. piresi at the dry season of the middle Xingu River.Keywords: Amazon, Auchenipteridae, flood pulse, fish reproduction. Influência do pulso de inundação na reprodução de
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