Uruguay River Basin Research Articles

Papel do judiciário nos remanejamentos de populações atingidas por hidrelétricas no Sul do Brasil

A implantação de usinas hidrelétricas significa o realocamento compulsório de famílias ribeirinhas atingidas pelo empreendimento. Muitas famílias já foram desapropriadas em nome de um desenvolvimento econômico, que exige melhor infraestrutura, para a qual a energia elétrica é essencial. A luta pelos direitos humanos e sociais dessas famílias, protagonizada por essas e pelo Movimento dos Atingidos por Barragens, contraria o interesse das empresas responsáveis, bem como o próprio Estado que, mesmo não sendo responsável direto pelos remanejamentos, constitui a Parceria Público Privada para a construção desses grandes empreendimentos. O objetivo central desse trabalho é verificar a atuação do judiciário nesse processo dos remanejamentos dos atingidos por hidrelétricas na bacia do rio Uruguai, no Sul do país, desde a década de 1980.

Desempeño hidrológico y Propiedades físico mecánicas de Hormigones Porosos elaborados con áridos de la Provincia de Entre Ríos

Los antecedentes vinculados al estudio de hormigones porosos en la República Argentina son escasos. Especialmente en nuestra región (Entre Ríos, cuenca del Río Uruguay) prácticamente no se dispone de información específica. Por ello, este trabajo se orientó a caracterizar las propiedades mecánicas e hidrológicas de hormigones porosos construidos con materiales locales. Se avanzó en el diseño de distintas mezclas, con porosidades variables hasta un máximo del 25%. La resistencia a compresión se ubicó entre 9 y 39 Mpa, y la resistencia a tracción por flexión entre 1,4 y 2,4 Mpa, cuyos valores concuerdan con los reportados por la bibliografía. Se determinaron las tasas de infiltración de probetas limpias (Io en mm/h), las cuales están comprendidas entre 7000 mm/h y 44.000 mm/h, y su variación en función del grado de colmatación, observando una drástica reducción hasta alcanzar la colmatación total (Ic en mm/h) con tasas comprendidas entre 20 y 45 mm/h.

Contextos geomorfológicos y tecno-económicos del registro arqueológico del bajo río Uruguay (margen izquierda). Resultados preliminares de nuevas prospecciones


 
 
 Este trabajo propone ampliar el conocimiento relacionado con la ocupación del espacio y con las estrategias de asentamiento, tecnología y subsistencia generadas por los grupos cazadores-recolectores complejos que habitaron la margen izquierda del bajo río Uruguay durante el Holoceno tardío (ca. 1900 – 500 años AP). Para ello presentamos y discutimos una serie de datos arqueológicos recientemente obtenidos a través de prospecciones y sondeos y mediante el análisis de colecciones locales. Los sitios arqueológicos del área presentan registros de explotación de recursos acuáticos y terrestres, manufactura y uso de alfarería y artefactos líticos tallados y picados/pulidos. Estos fueron ubicados mayoritariamente en formas naturalmente elevadas del paisaje como son los cordones arenosos y los albardones que, en conjunto con las densidades artefactuales evidenciadas y la variabilidad cronológica de los mismos, conduce a que las mencionadas poblaciones desarrollaron un patrón de asentamiento de baja movilidad de manera similar al esquema “campamento central”. Los resultados de las prospecciones y de los análisis de la composición sedimentológica de los sitios señalan la ausencia de estructuras construidas. Sin embargo, existen similitudes tecnológicas, estilísticas y económicas que permiten relacionar las ocupaciones en la margen oriental del bajo río Uruguay con distintas unidades arqueológicas correspondientes a grupos cazadores-recolectores complejos identificadas en la margen derecha del río Uruguay y en el Paraná medio e inferior. Finalmente, a partir de estilos cerámicos corrugados y pintados también se ha identificado en el área la presencia de grupos guaraníes, asociada a contextos de cazadores-recolectores, aunque también se manifiesta en ocupaciones exclusivamente realizadas por grupos guaraníes.
 
 

GENETIC IMPLICATIONS OF RESTOCKING PROGRAMS ON WILD POPULATIONS OF STREAKED PROCHILOD <i>Prochilodus lineatus<i>

Genetic diversity of wild and farmed populations is crucial, both for conservation of fish resources and fish culture development. To infer the genetic diversity and population structure of Streaked prochilod Prochilodus lineatus, individuals were sampled between 2007-2009 from four fish farms and from the Upper Uruguay River Basin, both in southern Brazil. Population structure was identified in both farmed and wild individuals through seven microsatellite loci. Bayesian analysis indicated three main groups, including two from fish farms. Pairwise genetic differentiation showed spatial structure between and within wild and farmed populations; however, the sampling design did not allow testing temporal structure according to isolation-by-time (IBT), which means that populations can breed within the same geographic distribaution, but reproduce at different times. Cultivated individuals presented lower diversity, allelic richness and effective population size, but higher inbreeding rates, compared to wild populations. These characteristics constitute warning signs against indiscriminate restocking of natural Prochilodus lineatus populations, a species sensitive to fragmented habitats, with farmed fish.

Río Uruguay. Una síntesis arqueológica

La cuenca del río Uruguay se extiende a través de Brasil, Argentina y Uruguay y es una de las redes fluviales fundamentales para la ocupación humana del sudeste de Sudamérica. Desde sus nacientes hasta su desembocadura y desde el Pleistoceno final hasta la actualidad, este río presenta evidencias arqueológicas y etnohistóricas de ocupaciones indígenas. En este marco, este artículo constituye una síntesis regional de la historia de estas ocupaciones y del desarrollo de las investigaciones arqueológicas en los tres países mencionados. Primero, se expone el contexto ambiental y los estudios arqueológicos realizados. Posteriormente, se presentan los sitios arqueológicos y los artefactos más relevantes para la transición Pleistoceno-Holoceno, Holoceno temprano y Holoceno medio. Por último, se caracteriza el registro arqueológico Taquara-Itararé, Goya-Malabrigo y guaraní correspondiente al Holoceno tardío. La información presentada permite reconocer al río Uruguay y sus afluentes como el escenario de una compleja dinámica poblacional, caracterizada por la articulación de un gran número de poblaciones, cultural y lingüísticamente diversas, durante más de 12.000 años.

High resolution AMS 14C dates for late Pleistocene Fishtail technology from the Tigre site, Uruguay river basin, South America

The basin of the Uruguay middle river has contributed important advances related to knowledge of the early settlement of southeastern South America. This paper presents recent progress of the research on the Paleoamerican period that is being carried out in the Tigre site (Uruguay), where a cultural component with Fishtail points, bifaces, preforms and other artifacts dated at ∼ 12,800 and 12,200 cal BP was found. The presence of silicified limestone (silcrete) in the Tigre site indicates mobility ranges of 190–350 km to obtain this lithic resource. The data presented here allow to have an accurate discussion of the chronological period occupied by Fishtail groups on the plains of Uruguay; and to recognize the late stages of the Fishtail point manufacturing process used by these human groups, one of the most successful adaptations during the end of the Pleistocene in South America.

Reconstructing biogeographic temporal events in the evolution of the livebearer fish genus Jenynsia based on total evidence analysis (Cyprinodontiformes: Anablepidae)

The current distribution of the Neotropical ichthyofauna has been widely affected by the main geological events that occurred in South and Central America. However, robust biogeographic information is still scarce or absent for most fish families. The biogeographic relationships of the most diverse anablepid genus, Jenynsia, are herein analysed, using temporal and spatial approaches based on a total evidence dataset, including 167 morphological characters and seven nuclear genes, totalling 6075 bp. A time calibrated analysis recovered the origin of Jenynsia at the Miocene and the diversification of its two subgenera between the Late Miocene and Early Pliocene. This result combined with the analysis of reconstruction of ancestral states indicates that the ancestor of Jenynsia colonized the Paranean Sea, and the current distribution of the species of the genus is probably a result of geological events, including: (1) ancient connections between Iguaçu and upper Uruguay River basins; (2) sea level variation along the Pliocene in the South American Atlantic coast; and (3) the decrease of the Paranean Sea along the Pliocene and Pleistocene.

Redescription of Corydoras undulatus Regan, 1912 (Siluriformes: Callichthyidae), with comments on the identity of Corydoras latus Pearson, 1924.

A redescription of Corydoras undulatus Regan, 1912 is presented. The original description of C. undulatus is very succinct, as is its diagnosis, which is based only on external morphology. Additional information in the scientific literature on this species is scarce. Specimens from the distribution area of this species were analyzed; Paraná and Paraguay river basins in Argentina, Uruguay river basin in Argentina, Brazil and Uruguay, and the Laguna dos Patos system in Brazil. Morphological analysis, principal component analysis (PCA), meristic comparison and osteological description were performed. Corydoras undulatus can be distinguished from its congeners mainly by having the following combination of characters: mesethmoid short, with anterior tip short, smaller than 50% of the entire bone length; posterior margin of the pectoral-fin spine with nearly all serrations directed towards origin of spine; pectoral-fin spine with conical serrations; and its peculiar color pattern. The analysis of the material from the different basins did not indicate relevant morphological differences, suggesting that the species presents a wide distribution in La Plata and Laguna dos Patos drainages. The shared geographic distribution between these two systems is also present in other fish species. The current work presents data about the type locality, taxonomy, osteology, distribution and ontogenetic variation of color pattern in C. undulatus. Comments on the identity of a very similar congener, Corydoras latus, will also be provided.

Analysis of the Basin of the Uruguay River Through Automated Geomorphometric Classification of the Landforms Elements

The present work aims to determine the landforms, from the automated classification generating geomorphons for the Uruguay River basin, identifying the distribution of these elements in the high, medium and low course. The landforms elements called geomorphons were obtained analyzing the textural similarity of the Digital Elevation Models (DEM), which present variations more or less gray levels between neighboring cells. After the generation of the landforms elements, the data were organized in Geographic Information Systems (GIS) to define the area and percentage of each unit, as well as the occurrence of elements in each sector of the river.

Contribution of Anthropogenic Climate Change to April–May 2017 Heavy Precipitation over the Uruguay River Basin

Anthropogenic climate change has increased the risk of the April-May 2017 extreme rainfall in the Uruguay River basin, which has caused extensive flood and major socio-economic impacts, by at least twofold with a most-likely increase of about five.

Geographic variation of Moenkhausia bonita (Characiformes: Characidae) in the rio de la Plata basin, with distributional comments on M. intermedia

ABSTRACT Moenkhausia bonita occurs in numerous additional localities from the Bermejo, Paraná, Paraguay, and Uruguay river basins. Given that this finding greatly expands the distributional range of M. bonita, we carried out an intraspecific comparison, using multivariate methods for 18 morphometric and eight meristic characters taken from a comprehensive sample of 536 specimens. All localities were distributed in four major geographic groups as follows: Bermejo, Paraná, Paraguay, and Uruguay. Results of the morphometric comparisons showed significant differences among the studied groups except between the Paraguay and Uruguay groups. Statistical differences in meristic values were found for most between-group comparisons, especially in those resulting from discriminant canonical analyses (DCA). Specimens from the Bermejo basin were the most distinct group in most morphological comparisons. However, the overall subtle differences found in body morphology likely reflect intraspecific variation within M. bonita and seem to be mainly influenced by spatial and environmental features of drainages. As M. bonita was previously identified as M. intermedia in the río de La Plata basin, distributional comments on the latter species in that basin are provided.

Seasonal and longitudinal variation in fish assemblage structure along an unregulated stretch of the Middle Uruguay River

ABSTRACT Diversity patterns and their causes remain important questions, especially for ecosystems that preserve natural conditions. This is the case of fish diversity in large Neotropical rivers. In this context, we investigated fish diversity patterns along an extensive unregulated river section (ca. 450 km) in the Middle Uruguay River Basin. Sampling was conducted seasonally between May 2017 and March 2018, at six sites (patches) with contrasting environmental conditions. We collected 3,008 individuals belonging to 90 species. Nine were migratory, which summed relevant biomass in local assemblages (20 to 60%). We observed spatial variation in assemblage structure, but weak seasonal effects. Overall, biomass was similar among sites, but richness tended to increase downstream. Migratory fishes showed opposed trends, with higher richness and biomass upstream, particularly catfishes (Siluriformes). Ordination analyses separated sites in three groups based on variations in composition and abundance, and revealed associations between these groups and specific hydro-geomorphic conditions (i.e., flow, depth, channel width and the presence of riparian vegetation). Our study revealed that fish diversity distributes heterogeneously along the main channel, where hydro-geomorphic patches select for distinct assemblages along riverine gradients.

Ontogeny of feeding by Astyanax paris in streams of the Uruguay River Basin, Brazil

espanolEstudiamos la ontogenia de la alimentacion de Astyanax paris, un pez caracido insectivoro de los arroyos de la cuenca del rio Uruguay, en el sureste de Brasil. Las diferencias de la composicion de la dieta en funcion del tamano se analizaron mediante el analisis de varianza multivariante con permutaciones (PERMANOVA). Se muestrearon seis arroyos durante 12 meses y se obtuvieron 20 especimenes para analizar el contenido del estomago. Los individuos mas pequenos (longitud estandar ≤ 25 mm) consumieron principalmente insectos acuaticos. A medida que aumentaba el tamano corporal, se pasaba gradualmente a una dieta compuesta principalmente por insectos terrestres. En consecuencia, la ontogenia de los habitats de alimentacion cambia la posicion de las especies en las redes troficas de los arroyos. EnglishWe studied the ontogeny of feeding by Astyanax paris, an insectivorous characid fish from streams of the Uruguay River Basin in southern Brazil. Size–based differences in diet composition were evaluated using permutational multivariate analysis of variance (PERMANOVA). Six streams surveyed over twelve months yielded twenty specimens for analysis of stomach contents. Smaller individuals (SL ≤ 25 mm) consumed mainly aquatic insects. As body size increased, there was a gradual shift to a diet dominated by terrestrial insects. Ontogeny of feeding habitats thus changes the species’ position in stream food webs.

PROCAUDOTESTIS CORDIFORMIS SP. NOV. (DIGENEA: APOCREADIIDAE), PARASITE OF RHINELEPIS STRIGOSA (OSTEICHTHYES: LORICARIIDAE) FROM URUGUAY RIVER BASIN, URUGUAY

Procaudotestis cordiformis sp. nov. (Digenea: Apocreadiidae) is described from specimens collected in the loricariid catfish Rhinelepis strigosa (Osteichthyes: Loricariidae) from Uruguay River basin, Uruguay. The new species is morphologically similar to the only species known of the genus, Procaudotestis uruguayensis Szidat, 1954. P. cordiformis is proposed for specimens with the following features: a heart-like body form, pharynx disproportionately larger, testes more anteriorly located, ovary and anterior testis with overlapping fields, vitellaria less extended in relation to body length and with fields not confluent posteriorly, and eggs wider than those described for P. uruguayensis. An amended diagnosis of the genus Procaudotestis is proposed.

Ontogeny of feeding by Astyanax paris in streams of the Uruguay River Basin, Brazil

espanolEstudiamos la ontogenia de la alimentacion de Astyanax paris, un pez caracido insectivoro de los arroyos de la cuenca del rio Uruguay, en el sureste de Brasil. Las diferencias de la composicion de la dieta en funcion del tamano se analizaron mediante el analisis de varianza multivariante con permutaciones (PERMANOVA). Se muestrearon seis arroyos durante 12 meses y se obtuvieron 20 especimenes para analizar el contenido del estomago. Los individuos mas pequenos (longitud estandar ≤ 25 mm) consumieron principalmente insectos acuaticos. A medida que aumentaba el tamano corporal, se pasaba gradualmente a una dieta compuesta principalmente por insectos terrestres. En consecuencia, la ontogenia de los habitats de alimentacion cambia la posicion de las especies en las redes troficas de los arroyos. EnglishWe studied the ontogeny of feeding by Astyanax paris, an insectivorous characid fish from streams of the Uruguay River Basin in southern Brazil. Size–based differences in diet composition were evaluated using permutational multivariate analysis of variance (PERMANOVA). Six streams surveyed over twelve months yielded twenty specimens for analysis of stomach contents. Smaller individuals (SL ≤ 25 mm) consumed mainly aquatic insects. As body size increased, there was a gradual shift to a diet dominated by terrestrial insects. Ontogeny of feeding habitats thus changes the species’ position in stream food webs.

Austrolebias queguay (Cyprinodontiformes, Rivulidae), a new species of annual killifish endemic to the lower Uruguay river basin

In this article we describe a new species of the annual fish genusAustrolebiasfrom the lower Uruguay river basin. The fusion of the urogenital papilla to the first anal fin ray in males and the pigmentation pattern, indicates a close relationship with the clade formed byA.bellottii,A.melanoorus, andA.univentripinnis. The new species can be differentiated from those by the following combination of characters: presence of well-defined light bands contrasting with the sides of the body, the distal portion of the anal fin dark gray, pelvic fins dark bluish green and bases united at about 50–80% on their medial margins, pectoral fins with iridescent blue sub-marginal band, and general coloration of body bluish green. The new species can only be found in wetlands of the Queguay river, an area included in the Uruguayan protected areas system and represents so far the only annual fish species endemic to the lower Uruguay river basin.

Long-Term Variations of Water Runoff and Suspended Sediment Yield in the Parana and Uruguay Rivers

The hydroclimatic conditions of water runoff formation and the hydrography of Parana and Uruguay river basins in the South America are considered. A survey of the recent studies of the hydrological regime of these rivers is given. Observation data are used to evaluate the long-term average values of water runoff and suspended sediment yield in the Parana and Uruguay and their variations along the rivers. Characteristics of many-year runoff variations in the rivers were evaluated. A climate-induced increase was identified in the Parana and Uruguay water runoff, and the corresponding present-day trends in river runoff variations in both rivers were evaluated. The total water runoff and suspended sediment yield of the Parana and Uruguay into La Plata estuary were calculated. Water balance of the drainage basin of La Plata estuary was characterized.

Presence of Lutzomyia longipalpis and Nyssomyia whitmani in Entre Rios, Argentina.

ABSTRACTThe objective of this study was to evaluate the presence of Lutzomyia longipalpis in the Argentine city of Concordia, in the province of Entre Rios, without record of this species despite previous samplings, but with canine cases of visceral leishmaniasis and Lu. longipalpis reports both, from Northern Argentine localities and from the city of Salto, Uruguay, located just across the river and the international border. This study confirms the presence of Lu. longipalpis and Nyssomyia whitmani, related to the risk of visceral and tegumentary leishmaniasis, respectively, in Concordia-Entre Rios. The presence of Lu. longipalpis confirms the ongoing dispersal along the Uruguay river basin. The presence of these species in the study area alerts about the risk of transmission of Leishmania spp.

Cultura e Política e a Opção dos Atingidos por Hidrelétricas

A construção de usinas hidrelétricas ocasiona impactos sociais, pois é necessária a realocação de famílias ribeirinhas para a implantação do empreendimento. Por isso, objetiva-se pesquisar esse processo, compreendendo a influência da cultura política na tomada de decisão dos cidadãos atingidos na bacia do Rio Uruguai sobre as modalidades de remanejamento. O protocolo adotado é o quantitativo, apresentando uma análise descritiva dos dados do Projeto “Avaliação dos Resultados e Proposição de Modelo de Elaboração de Programas de Remanejamento da População Atingida por Empreendimentos Hidrelétricos (2010-2014)”. Os principais resultados indicam que as variáveis participação, confiança interpessoal e institucional impactam na opção pela modalidade de remanejamento.

Assessing the Viability of Reintroduction of Locally Extinct Migratory Fish Brycon orbignyanus: Successful Growth, Dispersal and Maturation

The reintroduction of threatened fish species in areas where wild populations have been depleted due to anthropogenic impacts is an increasingly popular conservation tool and mitigation policy. Despite the importance of fish reintroduction for conservation purposes, little is known about its efficiency. Here, we assessed the viability of reintroduction of the endangered migratory fish, Brycon orbignyanus, in an area of the Upper Uruguay River basin where the species has not been reported for more than 30 years. We released 4000 yearling juveniles in the Pelotas River in 2014 and maintained 400 juveniles in captivity as a control population. After three years, a total of 13 individuals was recaptured, of which, 10 were considered sexually mature with first maturation being recorded in animals larger than 42 cm in total body length. The age–length comparison with a control population growth curve showed that recaptured fish were slightly bigger than those in captivity. Furthermore, important ecological attributes as schooling behavior and dispersal capacity were recorded for all recaptured individuals. Combined, our results suggest that the re-establishment of a self-sustained population of locally extinct species B. orbignyanus in the Pelotas River may be successful if sustained over time and supported by conservation policies.