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We assessed the impact of a modified flood pulse on the trophic ecology of Ilisha amazonica by analyzing diet and resource assimilation through stable isotope analysis (δ13C and δ15N). Collections were conducted monthly between December 2020 and November 2021 in the Xingu River, Amazon. Stomach and muscle tissue were extracted for analysis, and both allochthonous and autochthonous resources were collected. Stomach contents of 247 specimens were analyzed and identified. The water flow regime influenced the consumption of aquatic insects, as well as the trophic niche breadth and feeding intensity of I. amazonica. Based on isotopic composition, the primary carbon sources in the species' diet originated autochthonous items, and the species exhibited a higher trophic position during the flood period. These results highlight the influence of the flood pulse, in a reduced flow environment, on the trophic dynamics of I. amazonia. Our results emphasize the importance of comprehending the interplay between consumers and resources, in areas with human influence, where impacts are practically unknown. [ABSTRACT FROM AUTHOR] more...

This study investigates the geochemical characteristics and evolutionary implications of sediments at the confluence of the Xingu and Amazon Rivers. The main objective is to understand sediment mixing, mobility, and weathering processes through geochemical proxies. Samples were collected from various sections of the lower Xingu River, focusing on its interaction with the Amazon River. Analytical techniques such as X-ray diffraction (XRD), X-ray fluorescence (XRF), and inductively coupled plasma mass spectrometry (ICP-MS) were employed to analyze major and trace elements. The results reveal significant spatial variations in mineralogical and textural patterns, with sediments forming distinct groupings based on their location. The data suggest that the lower Xingu River is strongly influenced by sediment inputs from the Amazon River, particularly affecting sediment composition and chemical weathering processes. This research highlights the critical interactions between river systems and their implications for the evolution of the Amazon basin, especially regarding sediment contributions from various geological sources. Even though the Xingu River drains cratonic regions at higher elevations, the geochemistry of the bottom sediments confirms that the bedload is derived from heterogeneous sources with primarily intermediate igneous compositions and has undergone substantial recycling during river transport. [ABSTRACT FROM AUTHOR] more...

Stocking density has a significant influence on animal homeostasis, and so is a crucial factor in the management of organisms in captivity and an important role in ex situ conservation of endangered species. Hypancistrus zebra is an endemic fish species from the Xingu River, Brazil—considered Critically Endangered since the early 2000s due to fishing pressure and, more recently, due to habitat changes resulting from the construction of the Belo Monte Hydroelectric Dam. The implementation of appropriate management in captivity is of utmost importance for its conservation, particularly in enhancing ex situ breeding techniques. This study aimed to evaluate the growth of juvenile H. zebra in aquaria with three different stocking density levels. The juveniles were distributed between three treatments, each with three replicates. We found no correlation between biomass and aquarium volume. The highest correlation coefficients were found between growth rates and densities related to the number of individuals per shelter area. Mortality rate was directly related to the initial number of fish in the aquariums, with larger populations showing higher mortality rates. The treatment with lower stocking density displayed the highest growth rate, while the treatment with higher density had the lowest growth rate, with a 23.38% difference between them. [ABSTRACT FROM AUTHOR] more...

In this study, we aimed to identify the factors that drive the patterns in beta diversity of fish assemblages on the beaches of the Volta Grande do Xingu, a river stretch under the influence of Belo Monte dam. Fishes were collected using a trawl net in 28 sandy beaches during the low water period of 2021 (each beach was sampled once during this period). Measurements of environmental variables were carried out on-site, while spatial variables were obtained using Asymmetric Eigenvector Maps (AEM). Using the Bray–Curtis dissimilarity index, we calculated beta diversity and conducted a distance-based redundancy analysis (db-RDA) with the dissimilarity matrix to assess its relationship between beta diversity and environmental and spatial variables. Additionally, we performed a variance partition to quantify the pure and shared contributions of the explanatory matrices to our response matrix. The results revealed low beta diversity among the sampled beaches, and that this beta diversity was explained in part by the spatial variables and pH. Our findings underscore the influence of spatial structure on the assembly of local communities, indicating that dispersion processes and spatial connectivity are relevant mechanisms that contribute to the beta diversity of beach fish communities under influence of a reduced flow by a Hydropower Plant. [ABSTRACT FROM AUTHOR] more...

Lula’s presidency in Brazil offers great hope for the environment but plans for hydroelectric dams in Amazonia represent an area of concern. The Belo Monte hydroelectric power plant that Lula promoted in his previous administrations and still defends illustrates the contradictions. In 2015 Belo Monte diverted water from the Xingu River through a canal that, since 2019, has left a 130-km river stretch with less than 30% of its natural annual discharge. This has compromised the food security of three Indigenous groups and of traditional non-indigenous river-dwelling people dependent on the river’s fish and turtles. Endemic (and threatened) species and unique ecosystems are now being eliminated. The pending renewal of Belo Monte’s operating license poses a test for the Lula administration’s socioenvironmental commitment. We offer suggestions for improved governance for existing dams like Belo Monte but conclude that no more large dams should be built in Amazonia. more...

Context: Hydrological dynamics are crucial in fish ecology. Aims: To evaluate the effect of the flood pulse on the feeding ecology of Doras higuchii in the reduced-flow section of the Belo Monte dam, Xingu River, Brazil. Methods: Collections were conducted between December 2020 and November 2021. The fish were measured and had their stomachs removed. Muscle tissue was also extracted for stable-isotope analysis. Stomach contents were inspected to assess diet, testing the influence of hydrological periods by using GLM. In addition, we evaluated the effect of the flood pulse on the δ13C and isotopic ratios of individuals Results: In total, 362 specimens of D. higuchii were analysed, highlighting a diet mainly on the basis of sediment (74.9%) and aquatic insects (24.8%), not varying between periods characterising the species as a specialist for having detritivorous habit, as well as the extension of the trophic niche. There was variation in food intensity, with higher average food consumption in the flood period. The isotopic composition (δ13C and δ15N) also did not differ between periods. Finally, δ15N did not vary by length class. Conclusions: This information helps understand the interface between environmental and biological factors in an environment affected by a hydroelectric dam. Implications: Our results may help fill gaps in knowledge about the diet of doradid fishes. Exploring what fish eat is important to understand how changes in the environment can affect their lives. In this study, we looked into the diet of an Amazonian catfish in a river affected by the construction of a dam. We found that the catfish mostly fed on sediment and aquatic insects, and these feeding habits were not strongly influenced by changes in the local water levels. [ABSTRACT FROM AUTHOR] more...

Summary: The Neotropics have vast river catchments with untapped hydroelectric potential, but there are multiple expected negative impacts of dams, including those on local food security and livelihoods. Yet, monitoring of dam effects on subsistence is rare, particularly during initial implementation. Our study assessed changes in human fish consumption near the Belo Monte Dam in the Brazilian Amazon during the period 2012–2021, which covers construction, operation and a severe El Niño-induced drought. Over time, fish became less common and were consumed in smaller amounts, even though fewer people shared meals. The largest changes occurred between 2013 and 2016 (post-construction but prior to full operation), resulting in a downward trend in fish consumption, particularly during the drought season. Adding more fish species to the diet did not increase consumption per person. These changes in fish consumption suggest that they stem from environmental impacts of the project (e.g., reduced river level), despite secondary effects from climatic events. These findings underscore the urgent need for comprehensive assessments of the social and ecological impacts of large infrastructure projects in the Amazon, along with sustainable and equitable management strategies to ensure food security and meet the needs of local communities. [ABSTRACT FROM AUTHOR] more...

As a result of Belo Monte Hydroelectric installation, hundreds of indigenous and peasant families were dispossessed from banks and islands in the middle Xingu River, in Pará. These social groups that lost their im-material reproduction bases became politically articulated and established, at the end of 2016, a Riparian Council, which started to fight in the licensing arena to regain fractions of expropriated territory. In this article, the objective is to discuss this political struggle process in its geographical dimension, starting from a qualitative methodology, with obtainment and interpretation of bibliographic and documentary material, besides field information. [ABSTRACT FROM AUTHOR] more...

The trauma that resulted from the construction of large hydroelectric dams in the Amazon is marked by major social and environmental restructuring, plunder, and impacts, on Indigenous Lands, Conservation Units, and residents on the outskirts of cities, or through the country roads. In general, the effects caused by the Belo Monte HPP gain prominence and production, and one of them composes the objective of this article: to analyze the impacts on the fishing territory. Having as the methodological path the bibliographic review, field, and relative work with the fishermen of the Fishing Colony Z-57. It appears that the installation of the plant ended up deleteriously altering the systemic and cultural relations, under which the fishing territory is expressed. Compromising it, translating into low fishing stocks in the communities; a decrease of up to 70% in fisheries production, and, consequently, an increase in pain and economic costs for carrying out the activity. It was evident that the legal frameworks and the licensing instruments, all the judicialization resulting from these infrastructure projects, and the struggle imposed on their installation, were not capable of safeguarding the interests of society - fishermen, specifically - in the face of the despoliation effect of the construction of the hydroelectric dam on the fishing territory. more...

The Volta Grande do Xingu (VGX) in the Amazon Forest of Brazil was chosen to analyze the land use and land cover changes (LULCC) from 2000 to 2017, with the aim of assessing the most suitable classification method for the area. Three parametric (Mahalanobis distance, maximum likelihood and minimum distance) and three non-parametric (neural net, random forest and support vector machine) classification algorithms were tested in two Landsat scenes. The accuracy assessment was evaluated through a confusion matrix. Change detection of the landscape was analyzed through the post-classification comparison method. While maximum likelihood was more capable of highlighting errors in individual classes, support vector machine was slightly superior when compared with the other non-parametric options, these being the most suitable classifiers within the scope of this study. The main changes detected in the landscape were from forest to agro-pasture, from forest/agro-pasture to river, and from river to non-river, resulting in rock exposure. The methodology outlined in this research highlights the usefulness of remote sensing tools in follow-up observations of LULCC in the study area (with the possibility of application to the entire Amazon rainforest). Thus, it is possible to carry out adaptive management that aims to minimize unforeseen or underestimated impacts in previous stages of environmental licensing. [ABSTRACT FROM AUTHOR] more...

Abstract Social predation—when groups of predators coordinate actions to find and capture prey—is a common tactic among mammals but comparatively rare in fishes. We report the unexpected social predation by electric eels, an otherwise solitary predator in the Amazon rainforest. Observations made in different years and recorded on video show electric eels herding, encircling shoals of small nektonic fishes, and launching joint predatory high‐voltage strikes on the prey ball. These findings challenge the hypothesis that electric eels may have a single foraging strategy and extend our knowledge on social predation to an organism that employs high‐voltage discharge for hunting. Thereby offering a novel perspective for studies on the evolutionary interplay between predatory and escape tactics. more...

ABSTRACT We assessed the flood pulse effect on the diet composition, trophic niche breadth, and the amount of food intake of two Amazonian auchenipterids with different feeding strategies. Sampling was carried out quarterly (from April/2012 to January/2014) on the middle Xingu River, using gillnets. We measured specimens for standard length and total weight. The specimens’ stomachs were removed, weighed, and had their contents identified. We analyzed 360 stomachs of Auchenipterus nuchalis and 584 of Tocantinsia piresi. The diet of A. nuchalis was mainly composed of aquatic insects and crustaceans, while T. piresi fed on fruits and seeds. The diet composition of both species varied seasonally, but only T. piresi changed its trophic niche breadth in response to hydrological changes, becoming more specialist during the higher water periods (filling and flood). Both species also showed differences in their amount of food intake between hydrological periods, with A. nuchalis feeding more intensely in lower water periods (ebb and dry), while T. piresi in the higher water periods. We evidenced different responses to the hydrological periods for the related species. We emphasize that studies considering the relationship between flood pulse and feeding ecology of the organisms are essential to understanding river floodplain systems’ dynamics. more...

We assessed the flood pulse effect on the diet composition, trophic niche breadth, and the amount of food intake of two Amazonian auchenipterids with different feeding strategies. Sampling was carried out quarterly (from April/2012 to January/2014) on the middle Xingu River, using gillnets. We measured specimens for standard length and total weight. The specimens' stomachs were removed, weighed, and had their contents identified. We analyzed 360 stomachs of Auchenipterus nuchalis and 584 of Tocantinsia piresi. The diet of A. nuchalis was mainly composed of aquatic insects and crustaceans, while T. piresi fed on fruits and seeds. The diet composition of both species varied seasonally, but only T. piresi changed its trophic niche breadth in response to hydrological changes, becoming more specialist during the higher water periods (filling and flood). Both species also showed differences in their amount of food intake between hydrological periods, with A. nuchalis feeding more intensely in lower water periods (ebb and dry), while T. piresi in the higher water periods. We evidenced different responses to the hydrological periods for the related species. We emphasize that studies considering the relationship between flood pulse and feeding ecology of the organisms are essential to understanding river floodplain systems' dynamics. [ABSTRACT FROM AUTHOR] more...

Niche partitioning occurs among coexisting populations to reduce the effects of competitive exclusion among species of similar niche. The aim of the present study is to verify the trophic niche partitioning and feeding behavior between two mustelids, the Giant otter and the Neotropical otter, through the dry and rainy season hydrologic of the Lower Xingu River. Our results suggest that the diets of both mustelids are composed primarily of fish of the family Anostomidae (Headstanders). Despite extensive niche overlap, our results indicate partitioning is facilitated by differences in niche breadth, with potential implications for conservation of both species in the case of declines in prey abundance and diversity. Both species inhabit an area recently impacted by completion of the Belo Monte Hydropower Plant, resulting in large changes to the hydrologic regime. Thus, our results provide important information for conservation efforts regarding the feeding behavior and co-occurrence of both species, as well as providing a baseline for monitoring future health of these mustelid populations. The present study is the first to test the hypothesis of niche partitioning between these two mustelids outside a protected area in the Amazon. [ABSTRACT FROM AUTHOR] more...

Abstract Characidium xavante was described from two tributaries of the Culuene River drainage, in the upper Xingu River basin. New samplings recorded the species for streams from the Kaaiapó River drainage (Teles Pires River drainage, upper Tapajós River basin) with additional specimens also recorded in the Xingu River basin, Paranatinga municipality, Mato Grosso State, Brazil. The new records represent an extension of the geographical distribution of the species, that from now on fits in a pattern of distribution known to be shared with other ca. 20 species of fishes. We suggest that Characidium xavante could be classified as Least Concern (LC), according to the International Union for Conservation of Nature Standards and Petitions Committee (IUCN). more...

Abstract In the Xingu river basin, Brazil, occurs two genera of Potamotrygonidae family: Potamotrygon and Paratrygon. In this region, the taxa have significant economic importance for the ornamental fishing industry, being intensively captured, especially the species Potamotrygon leopoldi, which is endemic to this basin. In the attempt to propose a species-specific DNA marker for the species from Xingu, as well as ensuring a robust and reliable molecular identification, the present work analysed mitochondrial gene portions Cytochrome Oxidase C – subunit I (COI) and Cytochrome B (Cytb) of five species: P. leopoldi; Potamotrygon orbignyi; Potamotrygon motoro; Potamotrygon scobina and Paratrygon aiereba. We found haplotype sharing, with a total absence of reciprocal monophyly in the majority of taxa. Individuals morphologically identified as a species showed mitochondrial DNA from another, suggesting the first record of hybridization amongst freshwater stingrays of Xingu. Also, we detected a deep divergence among Paratrygon aiereba haplotypes, indicative of speciation, suggesting the possibility of a new species for the Xingu river. Therefore, although the is still confusing and controversial taxonomy of freshwater stingrays, and evidencing hybridization processes that may have shaped the evolutionary history of this Family, the genes COI and Cytb can successfully help in the their species identification. more...

The study tested the use of Artemia salina nauplii as first exogenous feeding in the larviculture of Hypancistrus sp. Moreover, we aimed to assess the quantity of prey concentrations and the stocking density during the first 30 days of feeding. Experiment I: larvae were fed with four initial prey concentrations, T100: 100, T200: 200, T300: 300 and T400: 400 A. salina nauplii/larvae/day. The quantity of A. salina nauplii increased every six days to adequate the larval growth. Experiment II: larvae were kept at four stocking densities, 1, 5, 10 and 15 larvae/L. In both experiments, the A. salina nauplii were consumed with success for the larvae. Best larvae growth and survival were observed with T400 in comparison to T100. In the Experiment II, the stocking density of 15 larvae/L showed higher ammonia (1.23 mg/L) and reduction of larvae growth and dissolved oxygen concentration (5.7 mg/L). The densities of 1 and 5 larvae/L provided the best results for growth. The stocking densities showed no differences for survival. Thus, we recommend the use of A. salina nauplii in the first feeding for larvae of Hypancistrus sp., at the initial prey concentration of 400 nauplii/larvae/day and stocking density of 5 larvae/L. [ABSTRACT FROM AUTHOR] more...

Social predation—when groups of predators coordinate actions to find and capture prey—is a common tactic among mammals but comparatively rare in fishes. We report the unexpected social predation by electric eels, an otherwise solitary predator in the Amazon rainforest. Observations made in different years and recorded on video show electric eels herding, encircling shoals of small nektonic fishes, and launching joint predatory high‐voltage strikes on the prey ball. These findings challenge the hypothesis that electric eels may have a single foraging strategy and extend our knowledge on social predation to an organism that employs high‐voltage discharge for hunting. Thereby offering a novel perspective for studies on the evolutionary interplay between predatory and escape tactics. [ABSTRACT FROM AUTHOR] more...

In 2017, indigenous and non-indigenous people from the Xingu-Araguaia region met in Mato Grosso to celebrate 10 years of partnership and collective action of the Xingu Seeds Network (XSN). This network originated from the Campaign `Y Ikatu Xingu, a social phenomenon concerning conservation and protection of the Xingu spring region. The river basin of the Xingu headwaters, 17 million hectares, is the main focus of XSN and it has lost five million hectares of forests and cerrados, which were converted into grain monoculture fields, within a very short period of time. The impact on the quality of the river water caused an environmental and health problem for the indigenous peoples of the indigenous lands. XSN has promoted innovative technological alternatives for recovery of permanent preservation areas (PPAs) or gallery forest and income generation for small farmers and local communities. The goal of this study is to analyze the environmental governance in the Xingu basin, paying particular attention to institutional arrangements of the Xingu Seeds Network. This analysis is grounded on the theoretical-methodological framework, contained in the Institutional Analysis and Development (IAD), which offers tools for understanding the strengthening process of democratic institutions in the protection of common-pool resources. These are permanent preservation areas, in Brazilian case. This study provides a reflection of governance mechanisms, based on the "Commons Theory", in regions where socioeconomic dynamics drastically modify the tropical ecosystems that are fundamental to wildlife and human life. more...

We isolated and characterized 10 new microsatellites loci for Paleosuchus trigonatus using ION TORRENT Sequencing Technology. We tested the transferability of these loci to three related species of the subfamily Caimaninae, and used these bi-parental markers to test population structure and genetic diversity of two populations of P. trigonatus impacted by hydroelectric dam construction on the Madeira (N = 16) and Xingu (N = 16) rivers. We also investigated the transferability of these markers to three related species: Paleosuchus palpebrosus (N = 5), Caiman crocodilus (N = 6) and Melanosuchus niger (N = 6). The genetic diversity of P. trigonatus was low in both the Madeira (He: 0.535 ± 0.148) and Xingu (He: 0.381 ± 0.222) populations, but the loci were sufficiently polymorphic to be used in system of mating and kinship studies in P. trigonatus. DAPC analysis with our set of microsatellites loci was able to separate the four species of Caimaninae studied and to detect a shallow genetic structure between Madeira and Xingu populations of P. trigonatus. AMOVA and STRUCTURE analyses using locprior model corroborate this shallow genetic structure. These novel molecular markers will be also useful in conservation genetics and phylogeographic studies of P. trigonatus, since they improve our ability to monitor the putative effects of dams on the loss of genetic diversity and allow us to investigate population dynamics and microevolutionary processes that occurred in the species. [ABSTRACT FROM AUTHOR] more...

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The Xingu River, located in northern Brazil, is already under the impacts of one of the most harmful projects in the history of the Amazon – the Belo Monte hydroelectric dam. A new megaproject called the ‘Volta Grande Project’, led by Canadian gold mining company Belo Sun will be situated adjacent to the same stretch of the Xingu that is dewatered by the Belo Monte complex. Various aspects of the project are controversial. There are reports that the mining company acquired public lands illegally, the affected area has high biodiversity and endemism of several taxonomic groups, and mining operations would be approximately 9.5 km from indigenous lands. Synergistic impacts of impoundment and mining operations are expected to dramatically alter the Xingu's biodiversity and ecosystem services that support indigenous people and riverine populations. Moreover, the mining activities will generate tons of toxic waste that will be stored in a high-risk tailings dam, which exposes the Xingu River to catastrophic consequences similar to those of the Doce River disaster. more...

Abstract In this paper the authors describe the limnological approaches, the sampling methodology, and strategy adopted in the study of the Xingu River in the area of influence of future Belo Monte Power Plant. The river ecosystems are characterized by unidirectional current, highly variable in time depending on the climatic situation the drainage pattern an hydrological cycle. Continuous vertical mixing with currents and turbulence, are characteristic of these ecosystems. All these basic mechanisms were taken into consideration in the sampling strategy and field work carried out in the Xingu River Basin, upstream and downstream the future Belo Monte Power Plant Units. more...

Abstract In the Tapajos-Xingu interfluve, one of the largest birds of prey, the Harpy Eagle, is under intense anthropogenic pressure due to historical and recent reductions in forest cover. We studied prey availability and use by Harpy Eagle on six breeding territories on the low- and mid-Xingu River, between 2013 and 2015. We evaluated food resource availability using the environmental-surveys database from two methods: terrestrial surveys (RAPELD method) and fauna rescue/flushing before vegetation suppression for the Belo Monte Hydroelectric Complex construction. Harpy Eagle diet was identified by prey remains sampled around six nest trees. Eighteen species of mammals, birds and reptiles comprised the prey items. Most prey species were sloths, primates and porcupines, which have arboreal habits and are found in forested areas, but two species, hoatzin and iguana, are usually associated with riverine habitats. The proportion of prey from each species predated on the nest best studied was different from estimated availability (χ2 = 54.23; df = 16; p < 0.001), however there was a positive correlation (rs = 0.7; p < 0.01) between prey species consumed and abundance available, where the predation was more on species more abundant. Continuous monitoring of the Harpy Eagle diet at these nests could evidence changes in the assemblage of prey species available for Harpy Eagles, due to changes in the seasonal flood pulse of the Xingu River to be caused by the operation of the hydroelectric dam, and changes in habitat features by forest reduction around breeding territories. We believe that it is important to consider the protection of remnants of forested areas in the landscape matrix surrounding the breeding territories to maintain the food resource availability and allow all pairs to successfully reproduce. more...

Abstract Reported here is the first evidence of plastic ingestion by freshwater fishes in the Amazon. Plastic bags, bottles, fishing gear, and other products are entering Amazonian water bodies and degrade into meso- and micro-plastic particles that may be ingested, either directly or indirectly via food chains, by fishes. Examination of stomach contents from 172 specimens of 16 serrasalmid species from lower Xingu River Basin revealed consumption of plastic particles by fishes in each of three trophic guilds (herbivores, omnivores, carnivores). Overall, about one quarter of specimens and 80% of species analyzed had ingested plastic particles ranging from 1 to 15 mm in length. Fourier transform infrared spectroscopy indicated 12 polymer types, including 27% identified as polyethylene, 13% polyvinyl chloride, 13% polyamide, 13% polypropylene, 7% poly(methyl methacrylate), 7% rayon, 7% polyethylene terephtalate, and 13% a blend of polyamide and polyethylene terephtalate. Dimensions of ingested plastic particles varied among trophic guilds, even though the frequency and mass of ingested particles were not significantly different among fishes with different feeding habits. Highlights • First report on plastic ingestion by Amazon fishes. • Plastic debris are ingested by fishes regardless of trophic guild. • No difference in number or mass of plastic eaten. • No difference in size of microplastics. • Difference in size of mesoplastics across guilds. [ABSTRACT FROM AUTHOR] more...

Due to the toxicity and high environmental persistence of organochlorine pesticides in aquatic organisms, turtles have been studied as environment biomonitors. These animals are important sources of protein for the riverside and indigenous peoples of the Brazilian amazon. In the present study, organochlorine pesticide contamination was investigated in Podocnemis unifilis. Liver, muscle and fatty tissue samples were removed from 50 specimens collected from five sampling points located in the Xingu River basin. Fourteen organochlorine pesticides were analysed via gas chromatography with an electron capture detector (CG-ECD). Eight organochlorine pesticides were detected with average concentrations of ∑DDT, ∑Endossulfan and ∑HCH which were 26.17 ± 26.35, 14.38 ± 23.77 and 1.39 ± 8.46 ng g−1 in moisture content, respectively. DDT compounds were the most predominant, with a greater concentration of pp′-DDT in the liver and pp′-DDD in the muscle. Significant differences were noted between the types of tissues studied, and the concentration of OCPs varied between sampling sites. [ABSTRACT FROM AUTHOR] more...

Dreissenidae is one of the most economically and ecologically important families of freshwater and estuarine mollusks. Fourteen extant species and three genera are currently recognized: Congeria contains three species from karst caves along the eastern Adriatic coast and one from the Orinoco River of Venezuela, Dreissena contains six species native to Eastern European rivers and estuaries , and Mytilopsis contains three species from the Gulf of Mexico, Caribbean, and northwestern coast of South America and one from the Tocantins River of Brazil. Previous molecular phylogenetic studies have examined all species except those from South American rivers, and found each genus to be monophyletic with Congeria and Mytilopsis forming a clade sister to Dreissena . We present the first multilocus phylogeny of Dreissenidae inclusive of South American riverine species. Bayesian and maximum likelihood analyses of a 3085 bp alignment consisting of mitochondrial (COI and 16S) and nuclear (18S and 28S) gene regions found Neotropical species to be consistently and strongly supported as sister to all other dreissenids, although incomplete sequencing of the single Orinoco specimen obscured Neotropical monophyly. Our intergeneric relationships are inconsistent with an extensive fossil record suggesting that dreissenids originated in Europe approximately 30 My before dispersing to the Western Hemisphere. Fossil-calibrated analyses indicated that Neotropical dreissenids diverged from European lineages in the mid to late Eocene (∼39.3 Ma), and Brazilian and Guiana shield populations diversified during the Oligocene to Miocene. We erect the new genus Rheodreissena for all Neotropical freshwater dreissenids and present haplotype data indicative of at least three species. Widespread anthropogenic alteration of the middle Xingu River and lower Amazon threatens the persistence of these endemic, poorly studied mussels and may facilitate introduction beyond their native range. [ABSTRACT FROM AUTHOR] more...

Between 2003 and 2005, vertebrae of 151 Xingu River Potamotrygon leopoldi (Potamotrygonidae) (75 males and 76 females) were analysed to derive a growth curve for this species. The disc width (WD) was significantly different between sexes, with females measuring 149–700 mm WD and males 109–500 mm WD. The average percentage error for vertebrae readings of the whole sample was 2·7%. The marginal increment ratio (RMI) showed an increasing trend with the highest value in November, decreasing from December on. The majority of vertebrae displaying RMI zero, occurred in September, but the annual periodicity of ring deposition throughout the year was not conclusive. Tetracycline (TCN) injected specimens were held in captivity for 13 months and displayed a fluorescent mark in vertebrae confirming a yearly periodicity of band pair formation with the translucent ring deposited in September–October. The Akaike information criterion (AIC) showed that, among the seven models considered, the best fit was obtained for the von Bertalanffy modified with W0 (where W0 = WD at birth) for both sexes. Growth parameters for females were: W0 = 149 mm; W∞ = 763·06 mm; k = 0·12 year– 1, whereas for males: W0 = 109 mm; W∞ = 536·4 and k = 0·22 year−1. Maximal ages were 7·2 years in males and 14·3 years in females. The species shows sexual dimorphism expressed in the growth pattern, size at maturity, longevity and asymptotic sizes. Concern for sustainability is raised due to the construction of the Belo Monte Hydroelectric Power Plant (2015 and 2016) in the State of Pará causing changes to the habitat of this species, which is endemic to the Xingu River and two of its tributaries. [ABSTRACT FROM AUTHOR] more...

The Belo Monte Hydroelectric dam on the Xingu River in the Brazilian Amazon will be the third largest dam in the world in power generating capacity (11 GW). Its construction has brought negative socioeconomic and environmental impacts for local fishers that far outweigh the benefits. We used a qualitative case study approach to explore perceptions among fishers in a community downstream from the dam of the impact of Belo Monte on their livelihoods and their fisheries. We found that fishers, who, although they were not displaced were neither consulted nor compensated, have been severely impacted by the dam, and that fishermen and fisherwomen are differentially affected. More attention needs to be given to downstream communities and the impacts they experience. [ABSTRACT FROM AUTHOR] more...

Palms show clear niche segregation patterns along topographic gradients in tropical forests, with some species associated to terra firme and others to seasonally flooded areas. The aim of this study was to quantitatively describe the fine-scale spatial variation within a palm community, tracking the changes in species' abundance along environmental gradients associated with a perennial stream the eastern Amazon. The study of palm communities was based on 60 forest plots in which all adult palms were counted. We found a total of 566 palms in a community containing 11 species. Furthermore, we found a significant separation in the palm community between seasonally-flooded and terra firme forests. We found a gradient with various densities of the three most abundant palm species within the first 100 m away from the flooded area. Other species were located exclusively in the terra firme forest. The abundance of the six most common species were distributed in relation to humidity gradients from floodplains to terra firme, with palm distribution from the most flood-tolerant to the least flood-tolerant palm species as follows: Euterpe oleracea, Attalea phalerata and Socratea exorrhiza (species with floodplain affinity), Astrocaryum gynacanthum, Astrocaryum aculeatum, Attalea maripa (species with terra firme affinity) more...

Here we present new records of the mouse opossum Marmosa (Stegomamosa) lepida (Thomas, 1888) collected in the recently flooded region of the Xingu River during the construction of the Belo Monte hydropower dam in the state of Pará, Brazil. This taxon is rarely captured, and it has often been misidentified as other similar genera of arboreal marsupials, such as Gracilinanus. Our specimens were identified morphologically and genetically using partial DNA of the mitochondrial cytochrome b gene. The new records increase the known distribution by about 250 km to the southeast. [ABSTRACT FROM AUTHOR] more...

A new Diaptomidae species is presented from the Neotropical region. It was found in two Amazonian lakes, Ressaca and Arapujá, both in Pará State, Brazil. The lakes are 400 km apart and threatened by the building of reservoirs for hydropower generation and pollution by human settlements. The new species resembles N. paraensis Dussart & Robertson, 1984, but it can be distinguished from this species and other congeners in having a special process on the fifth leg basis of the male, by the place of insertion of lateral spine in the last segment of right P5 of male, the shape and relationship between length and width of segments of male and female P5 exopodite 2 with stout inner process bearing short setules and outer small spine, exopodite 3, with two terminal setae, outer smaller; endopodite 1-segmented with one subterminal seta and oblique comb of spinules, the presence of a line of dorsal spinules at the distal margin of thoracic somites in both sexes. A brief comparison with other Notodiaptomus species is presented in the discussion. [ABSTRACT FROM AUTHOR] more...

This paper discusses elements of the drama experienced in relation to the process of deterritorialization and resistance by the peasant families of the villages of Ressaca, Ilha Fazenda and Garimpo do Galo in the Volta Grande of Xingu due to the construction of the Belo Monte hydroelectric and Volta Grande of Xingu Mining project. Besides the work of direct observation and frequent dialogues with the local residents, interviews were conducted, of which 11 were recorded, in the period between May and July, 2012. It was possible to observe a process of deterritorialization of drastic consequences in which corporations naturalize the consequences in the lives of the people under the argument that the ultimate goal is the common good. This manifestation is emphasized insofar as the State supports the reproduction of the discourse that local populations are barriers to the development and justify the actions that overlap the local way of life, even though they amplify social problems. [ABSTRACT FROM AUTHOR] more...

Trait-based approaches for studying community assembly have improved understanding of mechanisms; however, the challenge of interpreting process from pattern is complicated by the possibility of multiple mechanisms operating simultaneously. Different traits may influence the assembly process in different ways. Analysing patterns of functional diversity among co-occurring species for each trait individually may aid interpretation of complex assembly processes; yet, few studies have tested whether patterns vary depending on trait function., We used tropical fish assemblages from the Xingu River, Brazil to test whether traits associated with resource acquisition play a stronger role in niche segregation relative to other traits. First, a null modelling approach was used to determine how trait distributions within local assemblages deviated from expectations under random assembly. Then, correlations between functional traits and stable isotope ratios (δ13C, δ15N) were used as a measure of a trait's association with trophic structure. Finally, we used mixed effects models to test whether traits having higher correlations with trophic structure also had greater deviation from null expectations. In addition, we explored how well stable isotopes explain multivariate functional trait variation and compared our correlation-based approach for organizing traits with previous categorical approaches., A significant relationship was found between a trait's deviation from null expectations and its correlation with isotopic patterns. Traits strongly associated with trophic structure had greater dispersion from the assemblage mean and were more evenly spaced than weakly associated traits. Traits strongly associated with trophic structure also were more clustered because trophic diversification tended to occur around some basic feeding strategies, such as benthic grazing or capturing food items from the water column. Based on redundancy analysis, isotopic ratios explained a low (11·6%) but significant portion of trait variation., In this study system, traits strongly associated with trophic ecology were more influential in niche differentiation among coexisting species compared to weakly associated traits. These results suggest that certain traits may respond to assembly mechanisms in predictable ways despite the complex, multidimensional nature of the assembly process. Methods designed to identify differential trait response will be critical to developing a general theory of trait-based community assembly., A is available for this article. [ABSTRACT FROM AUTHOR] more...

The essay reflects on the construction of the Tucuruí Hydroelectric Power Plant, in the Tocantins River, Brazil, and compares it to the Belo Monte plant, currently being raised on the Xingu River. The first was planned and built during the military dictatorship in Brazil (1964-1985) and the second, during a period considered democratic. The author criticizes the lack of transparency and the evidences of corruption in the history of Tucuruí, problems that seem to rise again with Belo Monte, thirty years later. He concludes that the federal government, responsible for both works, continues to disregard the adverse effects of large infrastructure projects in the Amazon. more...

Darrell Posey (1947-2001) made his mayor ethnobiological studies between Mebêngôkre-Kayapó, a Jê speaking people who inhabits territories officially recognized by Brazilian State in the region of the upper and middle Xingú river. Based on the analysis of Posey's work on the Kayapó; on documentary research in the Guilherme de La Penha Archives, in the Goeldi Museum; and on testimonies of indigenous people and researchers who were his colleagues in this institution, the article discusses the scientific and political legacy of Posey, considering his contributions to ethnobiology and current discussions on the protection of traditional knowledge. more...

Substrate complexity is strongly related to biodiversity in aquatic habitats. We illustrate a novel framework, based on Structure-from-Motion photogrammetry (SfM) and Multi-View Stereo (MVS) photogrammetry, to quantify habitat complexity in freshwater ecosystems from Unmanned Aerial Vehicle (UAV) and underwater photography. We analysed sites in the Xingu river basin, Brazil, to reconstruct the 3D structure of the substrate and identify and map habitat classes important for maintaining fish assemblage biodiversity. From the digital models we calculated habitat complexity metrics including rugosity, slope and 3D fractal dimension. The UAV based SfM-MVS products were generated at a ground sampling distance (GSD) of 1.20⁻2.38 cm while the underwater photography produced a GSD of 1 mm. Our results show how these products provide spatially explicit complexity metrics, which are more comprehensive than conventional arbitrary cross sections. Shallow neural network classification of SfM-MVS products of substrate exposed in the dry season resulted in high accuracies across classes. UAV and underwater SfM-MVS is robust for quantifying freshwater habitat classes and complexity and should be chosen whenever possible over conventional methods (e.g., chain-and-tape) because of the repeatability, scalability and multi-dimensional nature of the products. The SfM-MVS products can be used to identify high priority freshwater sectors for conservation, species occurrences and diversity studies to provide a broader indication for overall fish species diversity and provide repeatability for monitoring change over time. more...

The Amazon region is the final frontier and central focus of Brazilian hydro development, which raises a range of environmental concerns. The largest project in the Amazon is the planned Belo Monte Complex on the Xingu river. If constructed it will be the second biggest hydroelectric plant in Brazil, third largest on earth. In this study, we analyse the private and social costs, and benefits of the Belo Monte project. Furthermore, we present risk scenarios, considering fluctuations in the project’s feasibility that would result from variations in total costs and power. For our analysis, we create three scenarios. In the first scenario Belo Monte appears feasible, with a net present value (NPV) in the range of US$670 million and a rate of return in excess of the 12% discount rate used in this analysis. The second scenario, where we varied some of the project costs and assumptions based on other economic estimates, shows the project to be infeasible, with a negative NPV of about US$3 billion and external costs around US$330 million. We also conducted a risk analysis, allowing variation in several of the parameters most important to the project’s feasibility. The simulations brought together the risks of cost overruns, construction delays, lower-than-expected generation and rising social costs. The probability of a positive NPV in these circumstances was calculated to be just 28%, or there is a 72% chance that the costs of the Belo Monte dam will be greater than the benefits. Several WCD recommendations are not considered in the project, especially those related to transparency, social participation in the discussion, economic analysis and risk assessment, and licensing of the project. This study underscores the importance of forming a participatory consensus, based on clear, objective information, on whether or not to build the Belo Monte dam. more...

Baited remote underwater video (BRUV) systems are being used in marine ecosystems as a nonextractive, cost-effective method of assessing the fish fauna with minimal species bias. This technique has had limited applications in freshwater ecosystems. Rheophilic fish assemblages of the Xingu River, a clearwater Amazonian river in Northern Brazil, were sampled with BRUV systems. Two-hour video recordings were collected using five different bait treatments (sardine, croaker, cat food, sweet corn, and no bait) in two lotic habitat categories (rocky and sandy bottoms). A total of 2460 fish from 56 taxa and 13 families were recorded from the 80 BRUV deployments. Significantly different fish assemblages, species richness, and abundance were detected between habitat types and among treatments. Our results suggest that the use of crushed sardines as a standardized bait optimizes the sampling recording the highest species richness, relative abundance, and number of exclusive species of rheophilic fish in clearwater Amazonian rivers. The data also highlight the unique fish diversity of the Xingu River prior to the expected large-scale environmental degradation resulting from the forthcoming operation of the Belo Monte hydroelectric power plant. [ABSTRACT FROM AUTHOR] more...

Despite growing interest in trait-based approaches to community assembly, little attention has been given to seasonal variation in trait distribution patterns. Mobile animals can rapidly mediate influences of environmental factors and species interactions through dispersal, suggesting that the relative importance of different assembly mechanisms can vary over short time scales. This study analyzes seasonal changes in functional trait distributions of tropical fishes in the Xingu River, a major tributary of the Amazon with large predictable temporal variation in hydrologic conditions and species density. Comparison of observed functional diversity revealed that species within wet-season assemblages were more functionally similar than those in dry-season assemblages. Further, species within wet-season assemblages were more similar than random expectations based on null model predictions. Higher functional richness within dry season communities is consistent with increased niche complementarity during the period when fish densities are highest and biotic interactions should be stronger; however, null model tests suggest that stochastic factors or a combination of assembly mechanisms influence dry-season assemblages. These results demonstrate that the relative influence of community assembly mechanisms can vary seasonally in response to changing abiotic conditions, and suggest that studies attempting to infer a single dominant mechanism from functional patterns may overlook important aspects of the assembly process. During the prolonged flood pulse of the wet season, expanded habitat and lower densities of aquatic organisms likely reduce the influence of competition and predation. This temporal shift in the influence of different assembly mechanisms, rather than any single mechanism, may play a large role in maintaining the structure and diversity of tropical rivers and perhaps other dynamic and biodiverse systems. [ABSTRACT FROM AUTHOR] more...

A new species of ergasilid copepod, Ergasilus xinguensis n. sp., is described from females found on the gills of two cichlid fishes, Geophagus argyrostictus (Kullander, 1991) (type host) and G. altifrons (Heckel, 1840), from the Brazilian Amazon. The new species can be distinguished from congeners by the unique combination of the following characteristics: the cephalothorax is not inflated and is slightly constricted, the first antennulary segment bears 3 setae, maxillule with 3 unequal outer setae without minute process medially, maxilla has a large syncoxa with one seta near its basis, first and fourth legs are with a 3-segmented endopod, base of the exopod in leg 2 with a conspicuous bluntly-pointed projection and caudal ramus with two rows of curved conical spinules on ventral surface. The new species is the second member of Ergasilus von Nordmann, 1832 found on cichlids of the genus Geophagus (Heckel). [ABSTRACT FROM AUTHOR] more...

Diaphorocleidus altamirensis sp. nov., parasitic on the gills of Argonectes robertsi Langeani, 1999 from the Xingu River, northern Brazil, is described. The new species differs from its six congeners by the morphology of the male copulatory organ (which comprises a coil of six rings), by the midventral vagina, and by the presence of only one pair of eyespots. It is the first species of Diaphorocleidus Jogunoori, Kritsky & Venkatanarasaiah, 2004 described from hemiodontid fishes. In addition, new host and geographical records of seven species of dactylogyrids found on fish from the Xingu River are reported. [ABSTRACT FROM AUTHOR] more...