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Light traps are devices utilized in biomonitoring studies across various aquatic environments. Although light traps are used globally, few studies report their efficacy in capturing fish larvae in the Neotropics. To address this gap, this study aimed to assess the efficacy of light traps in capturing larvae of six fish species commonly found in Neotropical rivers. Additionally, we aimed to evaluate the effect of light color on larval capture. To accomplish this, we selected larvae from six species: Cyprinus carpio, Ctenopharingodon idella, Piaractus mesopotamicus, Pimelodus maculatus, Prochilodus lineatus, and Rhamdia quelen. Each experiment lasted seven days, and six types of traps were tested, including those without light (control) and those with light (green, red, yellow, white, and blue), and installed in triplicate. A total of 18 traps were randomly positioned in earthen ponds containing the six species of interest. Each species was assessed separately in six experiments. Larvae were counted, measured, and identified daily according to their developmental stage. The light traps collected 30,498 larvae, whereas the control traps only collected 39 larvae by the end of the experiment. Larvae from species of the Cypriniformes order were the most captured, while those from the Siluriformes order were least captured. The light traps exhibited selectivity in capturing larvae at different developmental stages, which varied according to species. Traps installed with green lights captured a greater number of larvae and were more efficient at capturing larvae from a wider variety of species. In contrast, traps installed with red light led to the capture of fewer larvae. Therefore, by their ability to attract a greater number of larvae, compared to control, and selectively capture larvae at different developmental stages at variable rates, depending on light source, light traps can be a valuable tool in biomonitoring and managing fish larvae in Neotropical environments.

Abstract The southern region of Brazil is rich in hydric and biogeographic resources, contributing to the formation of distinct ichthyofaunistic niches and facilitating the isolation of some species. Despite the great ecological importance, there are few cytogenetic and molecular studies on the ichthyofauna of these basins. Therefore, specimens of Ancistrus abilhoai and Hemiancistrus fuliginosus were analyzed by combining cytogenetic and mitochondrial markers. Cytogenetic analysis revealed a diploid number of 2n = 48 for A. abilhoai and 2n = 56 for H. fuliginosus and Sites rDNA (by fluorescent in situ hybridization-FISH) were identified with 18S and 5S probes in synteny in pair 16 of A. abilhoai. At the same time in H. fuliginosus, these sites are located in separate pairs. Considering the Ancistrus cluster, based on COI molecular data, specimens of A. abilhoai were close to A. cirrhosushaving as sister group A. multispinis and A. brevipinnis. Regarding Hemiancistrus, H. fuliginosus specimens showed the same haplotype as the sequences of this species, available in the database, forming a distinct clade with H. aspidolepis as a sister group. The results of our work helped to better define the taxonomic status of A. abilhoai and H. fuliginosus, species endemic to southern Brazil and which have few studies within their respective genera.

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Abstract This study investigated injuries sustained by Pimelodus maculatus caused by transient operating conditions in a Brazilian hydroelectric power plant. Fish (n = 43) that inhabited the tailrace and appeared on the water surface after changes in the operating conditions were evaluated (IF). Additionally, fish (n = 10) captured using longline in the vicinity of the tailrace were used for comparisons (NF). Blood samples were evaluated for cortisol, glucose, and lactate concentrations. Tissue samples (gill, liver, brain, and muscle) were analyzed for oxidative stress biomarkers (TBARS, protein carbonyl content, and catalase activity) and histology (gill, liver, and spleen). The most prominent findings in IF were barotraumas with intra-abdominal hemorrhage and swim bladder rupture. Cortisol and glucose concentrations were lower for IF when compared to NF. IF also suffered from oxidative stress, as indicated by increased TBARS in the liver and brain, as well as increased protein carbonyl content in the gills and liver. The main histological alterations induced by the adverse conditions were circulatory disorders, such as telangiectasia and gill aneurysm, hepatic congested veins, and hemorrhage in the liver and spleen. The abrupt drop of pressure resulting from changes in the operating conditions of the turbines caused barotraumas and oxidative stress, which were the leading causes of fish mortality

Copyright of Neotropical Ichthyology is the property of Neotropical Ichthyology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Intersecciones en Antropología is the property of Universidad Nacional del Centro de la Provincia de Buenos Aires, Facultad de Ciencias Sociales and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

We report the occurrence of an invasive alien species, palometa Serrasalmus maculatus, in the Patos Lagoon drainage. Primary occurrence data were based on three specimens captured and preserved as vouchers in scientific collections. Additionally, we searched for secondary records from unpublished scientific sources, public agencies reports and media news to find additional reports. We discussed the possible pathways of invasion, suggesting as the vector of introduction transpositions from the Uruguay River basin. Ecological implications for ichthyofauna, environmental impacts and risk of other events of invasion in the adjoining basins are discussed. [ABSTRACT FROM AUTHOR]

The ENSO (El Niño-Southern Oscillation) phenomenon affects, through climate teleconnections, hydrometric variables of water bodies worldwide, influencing biota communities. The aim of this work is to analyze ENSO effects on water discharge, water level, cyanobacterial blooms and, consequently, on the reproduction of migratory fishes with high-frequency monitoring of ichthyoplankton data from Salto Grande, a large South American reservoir. Two highest peaks of ichthyoplankton density were observed; the first one (2015–2016) occurred during a very strong El Niño event, while the second one (2019–2020) was preceded by weak El Niño events that lasted 18 months. These results suggest that ichthyoplankton abundance may be affected by the intensity and temporal extent of the episodes. In contrast, mean fish larval and egg densities were reduced by 65% and 85%, respectively during La Niña periods. Cross-correlation function (CCF) analysis indicates that water discharge, water level, and ichthyoplankton abundance were positively related to the Oceanic Niño Index, while cyanobacteria showed an inverse relationship. Cyanobacterial density increased by 574% during La Niña compared with El Niño events. Based on an uninterrupted monitoring of ichthyoplankton over 11 years, it seems reasonable to consider ENSO as a predictive tool for the intensity of reproductive activity of migratory fishes. [ABSTRACT FROM AUTHOR]

The condition called "river disease" (MDR by its acronym in Spanish) is an intoxication in immature stages of honey bees caused by a compound from the genus Sebastiania Spreng and concentrated in the exudates of Epormenis cestri Berg. Our objective was to determine the temporal dynamics of the life cycle of E. cestri, its association with the predominant vegetation components and the influence of the Uruguay river on the size of its populations. With this aim, we selected 5 sites in the vicinity of the Uruguay river where populations of E. cestri were sampled using the Stem-tap technique modified for this purpose. The effect of landscape components on the abundance of E. cestri was evaluated using GLMM. It was determined that the hatching of the E. cestri eggs was in mid-October, finding a staggered distribution of its phenophases. In addition, we found significantly negative effects of the Espinal forest cover and the increase in the distance from the banks of the Uruguay river on the total abundance of E. cestri. This work shows some first clues for the understanding of how the components of the landscape structure the populations of E. cestri, allowing to predict the critical moment of incidence of MDR. [ABSTRACT FROM AUTHOR]

Copyright of Iheringia. Série Zoologia is the property of Fundacao Zoobotanica do Rio Grande do Sul and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This article presents a detailed petrographic, mineralogical and geochemical study of clay, silt, sand and fine gravel generated in the Paraná–Etendeka large igneous province, once united and today exposed in contrasting climatic and orographic conditions on conjugate sides of the Atlantic Ocean. The comparison between low‐relief wetter Uruguay and steeper hyper‐dry Namibia allows to investigate the influence of weathering on basalt‐derived sediments spanning in grain size from <2 μm to >2000 μm. In Namibia, as in Uruguay, X‐ray diffraction analyses of mud samples from streams draining basaltic lavas show only smectitic clay minerals. Macroscopic and microscopic observations indicate that sand is composed in variable proportions of glassy to lathwork volcanic rock fragments, plagioclase and augitic clinopyroxene with minor pigeonite, and gravel dominantly consists of volcanic clasts with chalcedony or quartz geodes occurring locally. Geochemical data highlight the strong grain‐size dependence of weathering intensity. Whereas fine gravel closely reflects source‐rock composition in both Namibia and Uruguay, and mobile elements in sand are moderately depleted, αAlE indices increase notably in silt and reach maximum in clay, with mobility sequence Na >> Ca ≥ Mg > Sr > K. Differences in sand versus mud generation potential in the two regions are prominent. Namibian rivers draining the dry Etendeka Plateau carry purely volcaniclastic sand, whereas streams draining even exclusively the Paraná lava field carry sediments containing invariably significant and even overwhelming amounts of recycled quartz, testifying to the much greater sand‐generation potential of the very‐locally‐exposed underlying, interbedded or overlying quartz‐rich sandstones and loess deposits. Smectite is dominant throughout the Uruguay River catchment, even in the lower course where sand is pure quartzose and pyroxene negligible. A comparison with basaltic provinces worldwide indicates that, especially in low‐relief wet regions where weathering is intense, basalt generates gravel, very minor sand and abundant smectite. Kaolinite forms where chemical leaching is extreme. [ABSTRACT FROM AUTHOR]

Genidens barbus is a vulnerable marine migrant catfish with low fecundity, a complex life cycle (i.e. mouth breeding), and is the target of industrial and artisanal fisheries of several countries. This species regularly migrates from marine to freshwater environments of the south‐western Atlantic.The aim of this work was to delve deeper into the migration ecology of G. barbus, characterizing both its timing and potential environmental drivers. Furthermore, aspects of the population structure and reproduction of migrants in the lower Uruguay River were studied and the presence of juveniles in the adjacent estuarine recruitment area was evaluated.Data from 11 years (2008–2018) of records of adult G. barbus captured by artisanal fisheries were used alongside relevant environmental variables that were recorded monthly. Reproductive biology (i.e. sex ratio, gonadosomatic index, fecundity, and oocyte size) was analysed for a period of 3 years (2016–2018). The juvenile abundance in the Río de la Plata estuary was evaluated seasonally.A total of 935 adult individuals of G. barbus were captured, representing a total biomass of 3,123 kg. The migration timing was from early spring to early summer. The abundance of migrants strongly increased with river discharge, suggesting that this variable regulates the upriver migration. Furthermore, pre‐ and post‐spawn females and males displaying mouth breeding were recorded during the study period, confirming G. barbus reproduction in the lower Uruguay River.The results obtained suggest that G. barbus ascend to spawn in the freshwater environments upstream from the mouth of the Uruguay River. Then, adult males incubate and carry the embryos downstream, releasing juveniles in the Río de la Plata estuary.This relevant information will help with the implementation of effective management polices (e.g. fishing restrictions during the reproductive period) for the presently unregulated fishery of this vulnerable species in the lower Uruguay River. [ABSTRACT FROM AUTHOR]

Limnoperna fortunei, an invasive mussel altering the structure of benthic communities, is preyed upon by several fish species in South America. To investigate the impact of predatory fish on populations of this mussel, and the effects of this top-down interaction on native macroinvertebrates, we performed an in situ experiment in the Uruguay River. By comparing benthic communities of artificial substrates colonised in treatments allowing or excluding fish access, it was demonstrated that fish significantly reduce colonisation by L. fortunei (i.e. its density, biomass and body size). In the absence of mussels (before settlement), fish preyed upon the native macroinvertebrate community inhabiting artificial substrates, reducing their densities compared to the fish exclusion treatment. However, it was found that in the presence of golden mussel (after settlement), the total density of benthic macroinvertebrates, densities of scrapers, and densities of dipterans and gastropods strongly decreased in fish exclusion treatments, suggesting a strong effect of L. fortunei in reducing the native fauna. By preying on L. fortunei, fish favoured the persistence of native macroinvertebrates. Further studies focused on predatory fish species and their efficiency in removing L. fortunei may contribute to advancing towards using native fish as mitigating agents. [ABSTRACT FROM AUTHOR]

Copyright of Revista del Museo de Antropología is the property of Museo de Antropologia - IDACOR and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Uruguay River is the most important river in western Rio Grande do Sul, separating Brazil from Argentina and Uruguay. However, its pollution is of great concern due to agricultural activities in the region and the extensive use of pesticides. In a long term, this practice leads to environmental pollution, especially to the aquatic system. The objective of this study was to analyze the physicochemical characteristics, metals and pesticides levels in water samples obtained before and after the planting and pesticides' application season from three sites: Uruguay River and two minor affluents, Mezomo Dam and Salso Stream. For biomonitoring, the free-living nematode Caenorhabditis elegans was used, which were exposed for 24 h. We did not find any significant alteration in physicochemical parameters. In the pre- and post-pesticides' samples we observed a residual presence of three pesticides (tebuconazole, imazethapyr, and clomazone) and metals which levels were above the recommended (As, Hg, Fe, and Mn). Exposure to both pre- and post-pesticides' samples impaired C. elegans reproduction and post-pesticides samples reduced worms' survival rate and lifespan. PCA analysis indicated that the presence of metals and pesticides are important variables that impacted C. elegans biological endpoints. Our data demonstrates that Uruguay River and two affluents are contaminated independent whether before or after pesticides' application season. In addition, it reinforces the usefulness of biological indicators, since simple physicochemical analyses are not sufficient to attest water quality and ecological safety. [ABSTRACT FROM AUTHOR]

The La Plata Basin (LPB) is a continental river-system, extending across five countries in South America. The study intended to discriminate limnological and water quality macroscale patterns and the determinants. Samplings were performed at 44 points, including free-flowing river stretches and reservoirs, distributed along 3000 km, from tropical (18°S) to subtropical/temperate (33°S) latitudes, in summer and winter. In situ measurements and sample analyses included the water column (13 variables) and sediments (granulometry, nutrients, 36 pesticides, 13 metals, and bioassays for acute and chronic toxicity). Both natural factors – climate gradient, geological substrate, soil, floodplains, and human interference – river damming, metropolitan areas, and intensive agriculture, strongly influenced the results. Seasonality effects were pronounced in south of the LPB, associated with higher temperature amplitude, and in north of the LPB, in terms of marked precipitation distribution. Data sets were ordinated through principal component analyses, and spatial patterns were clearly evidenced. River impoundments determined higher deepness and transparency, lower temperature amplitude, and thermal and chemical stratification. Reservoir sediments presented higher organic matter and metal concentrations, fine sand, and silt. Higher natural turbidity, suspended matter and coarse sand sediments characterized the shallower free-flowing stretches, especially in the undammed Paraguay River. Recovery of the riverine conditions (Paraná and Uruguay Rivers) occurs with distance from dams due to the river’s long courses. The variables indicating trophic conditions (phosphorus and nitrogen) were not clearly ordinated, but positioning of the most eutrophic LPB reservoir, under the influence of the São Paulo metropolis, was distinctive due to remarkably high chlorophyll a concentrations. Nutrients and conductivity were influenced by northern summer rains and tended to increase downstream, towards south latitudes. These variables were also locally influenced by urban agglomerations and by vast areas managed for commercial farming. Contamination with pesticides is widespread in LPB, but with higher incidence in the upper Paraná and middle Uruguay sub-basins. The same trend occurred for toxicity. A better understanding of macroscale processes brings a new perspective to transcend from local to a transboundary water management in the LPB.

Abstract Aim The aim was to analyze the incidence of microplastics in the diet of fish in the middle Uruguay River. Methods The present work analyzed the gastrointestinal content of two species: Astyanax lacustris and Iheringichthys labrosus. Results This study provides the first evidence of synthetic materials, such as fibres and plastics in the gastrointestinal tract of fish species in the Middle Uruguay River basin. A sample of sixty-one A. lacustris and twenty-nine I. labrosus were examined to highlight the ingestion of microplastics in the middle section of the Uruguay River in Brazil. In the A. lacustris, eleven fibres and two fragments were found in their gastrointestinal contents, corresponding to 18.1% of the specimens, while in the I. labrosus, twelve fibres and one fragment were found, corresponding to 34.5% of the specimens analyzed. Blue staining was also prevalent in the occurrence of microplastics. Conclusions These data are the first record of microplastics in this zone and represent a baseline for this contamination for future studies.

Unravelling the effect of climate variability on species biology has been one of the main goals of ecological studies. Environmental factors such as river discharge and temperature have being proposed as triggers of reproductive cycle in fish. In temperate climates, fish reproduction is affected mainly by temperature, while is influenced by flood pulses in large tropical rivers. We evaluated the influence of temperature and river discharge as triggers of Iheringichthys labrosus' reproduction. We studied the following reproductive variables: gonadosomatic index (GSI), hepatosomatic index (HSI) and condition factor (K). Females of I. labrosus were examined in a time series of ten years along three sites located in Lower Uruguay River at the beginning (last week of November‐first week of December, spring) and by the end of the reproductive period (middle‐end of April, autumn). Generalised linear models detected a positive effect of mean winter temperature and site on the spring mature female GSI. Site was significant in addition to the interaction between temperature and site. Moreover, the effect of winter temperature was stronger than water discharge in triggering reproductive timing of I. labrosus, contrary to the model proposed for other species in tropical systems. Additionally, a literature review suggested a latitudinal gradient on reproduction, occurring earlier and prolonged with decreasing latitude (and increasing temperature). In this study, we stated the effect of temperature on the life history in a Neotropical fish using a multifaceted approach, particularly important in the current context of global climate warming. [ABSTRACT FROM AUTHOR]

This paper presents the results of the investigations that defined the formation of the sedimentary deposits and the chronological sequence of the Foz do Chapecó archaeological area in the Volta Grande of the Upper Uruguay River, Southern Brazil. This research was undertaken to contribute to the definition of the diachronic, sedimentary and stratigraphic context of the archaeological occupations. To achieve these goals a geoarchaeological prospection by land and water was conducted, focusing on the valley bottoms, in the whole Volta Grande area. It comprehended the characterization of surface sedimentary deposits, the exposure and analysis of stratigraphic profiles, and sedimentological analysis. Four superficially exposed deposits were identified: i.e., fluvial conglomerates, fine sediments with sandy texture, clay colluviums and current and recent alluvial deposits. Six interesting points for the opening of stratigraphic profiles were identified, and subsequently resulted in the identification of sedimentary facies associated with river-bed, colluvial and colluvial-alluvial deposits. Three of these points presented a clear sequence of archaeological levels in the stratigraphic context. The results indicated that the local sediments are predominantly composed of a variable mixture of silt and clay, with sands occurring predominantly in an interdigitated form. The stratigraphic structure of the identified layers led to the establishment of 7 sedimentary facies, associated with colluvium (Cm), colluvium-alluvium (Sm) and alluvium and fluvial channels (Sm, Fl, Gms, Gt, Gp, Gh). The radiocarbon dating gives an age between 12.0 and 0.3 cal kBP, indicating that the filling of the local valley occurred during the end of the Pleistocene and throughout the Holocene by means of both fluvial and colluvial systems. Nine distinct archaeological levels, with a clear stratigraphic, chronological, and technological characterization were identified. The pre-ceramic archaeological sequence shows the following chronology: the oldest occupation occurred between 12.0 and 11.0 cal kBP (Cm facies); this was followed by an occupation between 10.5 and 9.5 cal kBP (Cm, Gt, Gp and Gh facies in three archaeological sites with eleven 14C data), then an occupation between 8.7 and 8.5 cal kBP (Cm facies), another between 5.7 and 5.5 cal kBP, one more between 4.8 and 4.6 cal kBP (Cm facies), and the last between 3.4 and 3.3 cal kBP (Cm and Sm facies). The ceramic phase seems to form a single dense component with the anthropogenic soil formation, and was dated between 0.5 and 0.3 cal kBP (Sm facies). These data present a previously unpublished chronostratigraphic sequence that is unique for the context of open-air sites in inner southern Brazil. • This research presents a unique example of a well-documented archaeological settlement in an open-air, multi-component site situated in a riverine setting in inland Southern Brazil. • It marks the first geoarchaeological study in Southern Brazil's subtropical oxidic environments, utilizing an integrated approach that includes sedimentology, stratigraphy, radiocarbon dating, and the spatial distribution of archaeological features. • The study's sedimentary sequence aids in reconstructing the paleo-environments of the Upper Uruguay River region. • The findings suggest that prehistoric cultural dynamics throughout the Holocene in Southern Brazil were more complex than previously understood. [ABSTRACT FROM AUTHOR]

Copyright of Revista Eletrônica em Gestão, Educação e Tecnologia Ambiental is the property of Revista Eletronica em Gestao, Educacao e Tecnologia Ambiental and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The origin of resources supporting metazoan biomass in rivers has long been a subject of debate. The river wave concept (RWC) postulates that the energetic basis of food webs varies along its spatial–temporal location with respect to flow pulses. According to the RWC, river flow determines carbon assimilation in food webs, but this may also depend on river geomorphology. However, studies testing this theory are scarce, particularly those from large subtropical rivers. To analyse the origin of fish biomass in areas of differing geomorphology, we combined stable isotope analysis with standardised measurements of biomass of a diverse fish assemblage along the lower Uruguay River. Furthermore, using 14 years of monitoring data, we tested for relationships between the biomass of species dominantly fuelled by allochthonic resources and the river flow. Fish biomass was dominantly allochthonous-derived along most of the studied sites. At all trophic levels, autochthonous-derived fish biomass was the highest in an upstream anabranch functional process zone (FPZ) (fuelling 54% of the total biomass), while allochthonous-derived biomass prevailed downstream, in the widest sections of an unconstrained lowland FPZ (fuelling 64–72% of the total biomass). Moreover, the dominant species that derived most of its biomass from allochthonous resources (Prochilodus lineatus) increased its biomass following flood pulses. This study supports the RWC statements that, at a spatial scale, local river geomorphology affects fuelling sources for food webs (probably by determining contrasting resource availability scenarios) and, at a temporal scale, increases in the allochthonous fraction of biomass are driven by flood pulses. [ABSTRACT FROM AUTHOR]

The La Plata River basin, the second largest drainage basin in South America, supports important fisheries, in which the sábalo Prochilodus lineatus is the leading species measured as extracted volumes. To characterize the population structure of the sábalo in the middle and lower regions of the La Plata River basin, cytochrome b DNA sequences of 121 samples collected in La Plata, Paraná and Uruguay rivers were used. Results suggest the presence of at least two populations: one that we called "southern population" uses the La Plata River and the lower sections of the Paraná and Uruguay rivers and another population (called here "northern population") in the middle section of the Uruguay and Paraná rivers. The southern population would have a larger effective population size and coalescence-based analyses reveal an asymmetric gene flow, mainly from north to south. A striking result is that samples from the middle sections of the Paraná and Uruguay rivers are more alike to each other than they are to the other samples of their respective rivers. This similarity could be explained by historical reasons, probably as a consequence of the proximity that both rivers had until 100,000 years ago. The presence of different management units being exploited by the continental fisheries of three countries demands coordination at a regional level in order to maintain a sustainable fishery. [ABSTRACT FROM AUTHOR]

The Crenicichla mandelburgeri species complex from the Middle Paraná shows parallel evolution of ecomorphs to the unrelated C. missioneira species complex from the Uruguay River. In this article, we describe a new species from the C. mandelburgeri species complex that has evolved a parallel morphology and ecology to an unrelated species from the C. missioneira species complex (C. celidochilus). The new species is a pelagic predator that feeds predominantly on fishes and together with C. celidochilus is the only known pelagic species in the large riverine genus Crenicichla. The new species is endemic solely to a small tributary (the Urugua-í) of the Middle Paraná River where it is sympatric and partly syntopic with two other closely related endemic species that, however, differ strongly in their ecomorphologies (one is a generalistic invertivore and the other a specialized molluscivore). Mitochondrial DNA phylogeny finds the new species nested within the widespread C. mandelburgeri. Reduced genome-representation ddRAD analyses, however, demonstrate that this new species is of a hybrid origin and shares ancestry with C. ypo, one of the two studied sympatric species. [ABSTRACT FROM AUTHOR]

As part of an ongoing taxonomic revision of the genus Heptapterus from the Laguna dos Patos and Uruguay River drainages and Atlantic coastal streams of southern Brazil and Uruguay, two new species closely related to Heptapterus mustelinus were identified. Both species are endemic to small tributaries of the Uruguay River. The two new species are distinguished from each other and from other species of Heptapterus by arrangement of cephalic and trunk laterosensory systems, number of vertebrae and number of dorsal, pectoral and anal‐fin rays. Phylogenetic analyses of mitochondrial DNA (coI and cytb) sequence data further supports distinctiveness of the two new species. [ABSTRACT FROM AUTHOR]

In this study, we analysed gauging stations in the Paraná and Uruguay Rivers, two rivers with excessive run-off which is used for energy and irrigation. We studied their statistical structure and applied spectral techniques to monthly streamflow in order to represent temporal and spatial variability. We also explored the relationship of some of these series with El Niño Southern Oscillation (ENSO) variability. Given these conditions, climatic coherence studies between pairs of stations in the Paraná network, especially for the most frequent waves (less than 2 years), turned out to be redundant. Furthermore, we observed that series for stations in the Paraná River fit to common theoretical distributions, where normality is absent, making this kind of analysis to be redundant as well. The exploratory analysis for this streamflow network, and its extensive records, suggest that in order to improve hydroclimatological studies, reference stations can be selected for each river. [ABSTRACT FROM AUTHOR]

The article presents a study which examines the contribution of anthropogenic climate change to the risk of the April-May 2017 extreme precipitation in the Uruguay River basin, which resulted to extensive flood and major socioeconomic impacts. Data and methods used in the study are described, including anomalous precipitation, Climate Prediction Center's Global Unified Precipitation data, and sea surface temperature and sea ice coverage.

Copyright of Animal Biodiversity & Conservation is the property of Museu de Ciencies Naturals de Barcelona and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Flooding is a natural disaster which affects thousands of riverside, coastal, and urban communities causing severe damage. River flood mapping is the process of determining inundation extents and depth by comparing historical river water levels with ground surface elevation references. This paper aims to map flood hazard areas under the influence of the Uruguay River, Itaqui (southern Brazil), using a calibration digital elevation model (DEM), historic river level data and geoprocessing techniques. The temporal series of maximum annual level records of the Uruguay River, for the years 1942 to 2017, were linked to the Brazilian Geodetic System using geometric leveling and submitted for descriptive statistical analysis and probability. The DEM was calibrated with ground control points (GCPs) of high vertical accuracy based on post-processed high-precision Global Navigation Satellite System surveys. Using the temporal series statistical analysis results, the spatialization of flood hazard classes on the calibrated DEM was assessed and validated. Finally, the modeling of the simulated flood level was visually compared against the flood area on the satellite image, which were both registered on the same date. The free DEM calibration model indicated high correspondence with GCPs (R2=0.81 ; p<0.001). The calibrated DEM showed a 68.15 % improvement in vertical accuracy (RMSE = 1.00 m). Five classes of flood hazards were determined: extremely high flood hazard, high flood hazard, moderate flood hazard, low flood hazard, and non-floodable. The flood episodes, with a return time of 100 years, were modeled with a 57.24 m altimetric level. Altimetric levels above 51.66 m have a high potential of causing damage, mainly affecting properties and public facilities in the city's northern and western peripheries. Assessment of the areas that can potentially be flooded can help to reduce the negative impact of flood events by supporting the process of land use planning in areas exposed to flood hazard. [ABSTRACT FROM AUTHOR]

Copyright of Brazilian Journal of Biology is the property of Instituto Internacional de Ecologia and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Biological corridors are connections which link habitats in a regional scale, allowing the gene flow between populations. The Uruguay River comprises riverside and insular riparian forests along subtropical to temperate zones passing through different biogeographic provinces. The aim of this study was to characterise the spider fauna from the Uruguay River islands highlighting their connection role for the spider community of riparian forest. Spiders were studied from surveys in a fluvial island of the southern course of the river with nine campaigns being carried out from September 2007 to September 2009. Three complementary collecting methods were used: G-Vac, night hand collecting and pitfall traps. A total of 58 samples were taken in each campaign. A total of 33 families, 145 species/morphospecies and 8 guilds were registered. Theridiidae and space web weavers showed the highest abundance and species richness. Web weavers were predominant in the spider community evidencing the importance of the forest vegetation heterogeneity in spider diversity. Fifteen species have been recorded for the first time for Uruguay. Additional data of previous surveys in the northern islands of the river were analysed and compared. Several species confirm the role of the Uruguay River as a biological corridor from the upper to lower course of the river. The riparian forests from the islands constitute a southernmost intromission of Paranaense biota between Chaco and Pampa regions along the river. The results obtained are an important input for the conservation of these areas. Knowing the biodiversity, as well as its dynamics and the flow of biota that exists in these environments, would allow planning the management from a regional point of view. [ABSTRACT FROM AUTHOR]

Otolith core-to-edge Sr:Ca ratio was determined by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) to analyze the salinity-habitat migration history of the silverside, Odontesthes bonariensis , within the Uruguay River (freshwater) and Río de la Plata Estuary (estuarine water) (Plata Basin, South America). Regular core-to-edge oscillations in Sr:Ca suggest that the silverside makes annual migrations between freshwater (<1 PSU) and brackish (>1 PSU) habitats, with no evidence of marine incursion or non-migratory individuals. Empirical equations that represent the relationship between conductivity/salinity and otolith Sr:Ca ratio were used to identify where in an otolith an individual transitioned between freshwater and brackish habitats. In most specimens, the first migration between habitats likely occurred within the first year of life. Average numbers of changes between stable Sr:Ca signatures (sites with different salinities) determined by Change-Point analysis were similar from Uruguay River (8.9 ± 3.7) and Río de la Plata Estuary (7.5 ± 2.5) for comparable age fish (p < 0.05), suggesting that habitat use is similar in both collection sites. [ABSTRACT FROM AUTHOR]

Abstract The golden mussel, Limnoperna fortunei, is an Asian freshwater bivalve introduced in South America in the beginning of the 1990’s, probably through ballast water releases in La Plata River estuary. It dispersed north through Paraná, Uruguay and Paraguay Rivers. The study evaluated the macroscale (18° to 34° S; 45° to 60° W) distribution of L. fortunei (larval stages) in the main rivers and reservoirs of La Plata Basin. Samplings were performed through 68 µm vertical plankton net hauls. Limnological variables were simultaneously determined. Larvae abundance correlated significantly with oxygen (positively) in summer, with temperature (positively) in winter and with total phosphorus and total nitrogen (both negatively) in winter. We expected densities to decrease towards north (latitudinal gradient) and increase in lentic conditions (reservoirs). Despite maximum density was found near the introduction point (La Plata River) similar value was also observed 2,000 km north (Paraguay River). The first hypothesis was refuted. The second hypothesis was partially accepted. Abundances were consistently higher in summer. Higher trophic conditions and fast flow seem to inhibit population growth. Food resources (chlorophyll a) locally influenced temporal variation. Limnoperna fortunei is widely distributed in La Plata basin, reaching high larval densities superior to 10,000 ind. m-3, in all major sub-basins. The species exhibits a high intrinsic dispersal ability (free planktonic larvae), wide tolerance to environmental factors and dispersion is potentialized by natural dispersion processes (e.g. fauna displacement) and human facilitation (e.g. commercial navigation).

ABSTRACT The construction of hydroelectric power plants has many social and environmental impacts. Among them, the impacts on fish communities, which habitats are drastically modified by dams, with consequences across the ecosystem. This study aimed to assess the influence of water level (WL) variations in the reservoirs of the Itá and Machadinho hydroelectric plants on the recruitment of fish species from the upper Uruguay River in southern Brazil. The data analyzed resulted from the WL variation produced exclusively by the hydroelectric plants generation and were collected between the years 2001 and 2012. The results showed significant correlations between the abundance of juvenile fish and the hydrological parameters only for some reproductive guilds. The species that spawn in nests showed, in general, a clear preference for the stability in the WL of the reservoirs, while the species that spawn in macrophytes or that release demersal eggs showed no significant correlation between the abundance of juvenile fish and hydrological parameters. A divergence of results between the two reservoirs was observed between the species that release semi-dense eggs; a positive correlation with a more stable WL was only observed in the Machadinho reservoir. This result can be driven by a wider range of WL variation in Machadinho reservoir.

ABSTRACT A new species of Astyanax belonging to the Astyanax scabripinnis complex is described from dos Touros River, tributary of the Pelotas River, Uruguay River basin. Astyanax taurorum sp. nov. is distinguished from other species of the Astyanax scabripinnis species complex by having two humeral spots, the first vertically elongated; teeth of inner row of premaxilla with three to five cusps; 2-3 (modes 2 or 3) maxillary teeth; 20-23 (mode 22) branched anal-fin rays; 13-15 (mode 14) gill rakers on lower branch of the first branchial arch; 20-23 (mode 21) total gill rakers in first branchial arch; 33-36 (mode 35) perforated lateral line scales. Astyanax taurorum sp. nov. is similar to Astyanax paris; nevertheless, it can be readily distinguished from it by having a smaller head depth (73.6-83.1% vs. 86.4-95.6%) and smaller interorbital width (24.1-28.0% vs. 30.8-32.8%). In addition, it differs from A. paris by the presence a posttemporal hook-shaped posterodorsal margin.

ABSTRACT System for hydrological forecasting and alert running in an operational way are important tools for floods impacts reduction. The present study describes the development and results evaluation of an operational discharge forecasting system of the upper Uruguay River basin, sited in Southern Brazil. Developed system was operated every day to provide experimental forecasts with special interest for Barra Grande and Campos Novos hydroelectric power plants reservoirs inflow, with 10 days in advance. We present results of inflow forecasted for floods occurred between July 2013 to July 2016, the period which the system was operated. Forecasts results by visual and performance metrics analysis showed a good fit with observations in most cases, with possibility of floods occurrence being well predicted with antecedence of 2 to 3 days. Comparing the locations, it was noted that the sub-basin of Campos Novos, being slower in rainfall-runoff transformation, is easier forecasted. The difference in predictability between the two basins can be observed by the coefficient of persistence, which is positive from 12h in Barra Grande and from 24h to Campos Novos. These coefficient values also show the value of the rainfall-runoff modeling for forecast horizons of more than one day in the basins.

Copyright of Revista Metropolitana de Sustentabilidade is the property of Revista Metropolitana de Sustentabilidade - RMS and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The primary aims of this paper were to provide the first inventory of carabid beetles collected in five different anthropogenic habitat types of the Lower Delta of the Paraná River, to describe their main ecological characteristics and to provide information on their distribution range in ecoregions, subregions and ecosystem complexes of Argentina and across the Neotropical region. Species were grouped according to six classes of distributions in relation to their presence in the Delta of the Paraná River. In addition, rarefaction curves were built in order to compare the seasonal species richness. We collected 1486 individuals belonging to 48 species. The southernmost distribution limit of 50% of the species is located south of the Delta region. Moreover, 21% of the species are confined to the Delta and Islands of the Parana and Uruguay Rivers ecoregion and to localities within the neighbouring ecoregions of Espinal and Pampa. Most (63%) of the species were zoophagous and 25% were either omnivorous or seed eaters; 52% were hydrophilous, 44% mesophilous and one was xerophilous. The high number of species found in this ecoregion emphasising its importance as a biodiversity hotspot of South American carabids. Human activities have led to changes in the landscape of the Delta Islands which could favour the establishment of mesophilous and xerophilous species from other ecoregions. Seasonal carabid richness is higher in the warm seasons (spring and summer) compared with the cold seasons (autumn and winter). Although, the highest absolute richness was found in the most anthropised habitat types, secondary forests had exclusive species, showing the importance of preserving the ecological mosaic of the landscape. [ABSTRACT FROM AUTHOR]

Copyright of Comechingonia: Revista de Arqueología is the property of Comechingonia and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Comechingonia: Revista de Arqueología is the property of Comechingonia and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Neotropical Ichthyology is the property of Neotropical Ichthyology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Multivariate floristic analyses of Butia yatay palm groves and gallery forest associated with the Uruguay River basin of Entre Rios Province (Argentina) were performed, including vegetation stands of Rio Grande do Sul State (Brazil). Several new phytosociological associations were identified. These include Eugenio myrcianthis-Butietum yatay association, which represents palm groves on sandy soils evolved from ancient river deposits, and Bignonio callistegioidis-Terminalietum australis association, which represents some gallery forests on regular floodplains of the Uruguay River. Both are placed in the new Pampean alliance Guettardo uruguensis-Bution yatay, which is part of the Dyckio brevifoliae-Terminalietalia australis order and Sebastianio schottiae-Terminalietea australis class, which has been described for Brazil. [ABSTRACT FROM AUTHOR]

Este trabajo presenta los resultados de las investigaciones arqueológicas realizadas en el Parque Nacional El Palmar, Colón (provincia de Entre Ríos). Se debe destacar que, en la zona comprendida por estos estudios, hasta el momento no se habían realizado trabajos arqueológicos sistemáticos. Como resultado se detectaron siete sitios y trece hallazgos arqueológicos aislados, todos en posición superficial. Los conjuntos se componen de materiales líticos; cinco de ellos presentan alfarería, mientras que en ninguno se registraron restos arqueofaunísticos. Se sintetizan los resultados del análisis de los materiales recolectados con el fin de lograr una primera caracterización de la tecnología prehispánica. Se discute la funcionalidad de los sitios y se propone un esquema preliminar de ocupación del espacio. Se postula que los sitios corresponden a campamentos de actividades múltiples y talleres del Holoceno tardío. Estos restos evidencian la ocupación humana de albardones, playas y médanos, además de la explotación predominante de guijarros fluviales silíceos.This paper presents the results of intensive surveys conducted in El Palmar National Park, Colón, Entre Ríos province. No prior systematic archaeological work had been done in the area covered by the research. As a result of the surveys, seven sites and thirteen isolated archaeological finds, all in a superficial position, were detected. All of the assemblages are composed of lithic materials; five included pottery, while none registered archaeofaunal remains. This article summarizes the results of the analysis of the materials collected in order to produce an initial characterization of the technology. The functionality of the sites is discussed, as well as a preliminary outline of spatial occupation in the study area. It is proposed that the sites correspond to late Holocene multi-activity camps and workshops. The remains are evidence of the human occupation of levees, beaches and dunes, as well as the predominant exploitation of siliceous river gravel.

The distribution and abundance of fish eggs and larvae was analyzed in three sections of the Upper Uruguay river, in a stretch of 290 km. Samples were collected monthly from October, 2001 to March, 2002 during 48-h cycles at 6-h intervals between each sampling. Surface and bottom samples were collected with a 0.5-mm mesh cylindroconical net. Fishes from the Upper Uruguay river were reproductively active mainly from October to January, and this activity was more intense at the Ligeiro and Chapecó tributaries and Chapecó main river. It was observed that the tributaries are important spawning grounds and larval nursery sites, indicating the importance of preserving such environments.Foram analisadas a distribuição e abundância de ovos e larvas de peixes em três seções do Alto rio Uruguai, num trecho de 290 km. As coletas foram realizadas mensalmente no período de outubro de 2001 a março de 2002, durante um ciclo de 48 horas com intervalos de 6 horas entre as amostragens. Foram feitas coletas de superfície e fundo, nas margens e no canal central do rio, utilizando-se redes de plâncton do tipo cônicocilíndricas de malha 0,5mm. As maiores ocorrências foram verificadas entre os meses de outubro a janeiro, sendo que a atividade reprodutiva foi mais intensa nos tributários Ligeiro e Chapecó e no rio Uruguai, na foz do rio Chapecó. Foi observado neste estudo que alguns tributários se destacam como locais de desova e desenvolvimento de larvas de peixe, indicando a importância de se preservar estes ambientes.