Rio Uruguay Research Articles

Isotopic trophic guild structure of a diverse subtropical South American fish community

AbstractCharacterization of food web structure may provide key insights into ecological function, community or population dynamics and evolutionary forces in aquatic ecosystems. We measured stable isotope ratios of 23 fish species from the Rio Cuareim, a fifth‐order tributary of the Rio Uruguay basin, a major drainage of subtropical South America. Our goals were to (i) describe the food web structure, (ii) compare trophic segregation at trophic guild and taxonomic scales and (iii) estimate the relative importance of basal resources supporting fish biomass. Although community‐level isotopic overlap was high, trophic guilds and taxonomic groups can be clearly differentiated using stable isotope ratios. Omnivore and herbivore guilds display a broader δ13C range than insectivore or piscivore guilds. The food chain consists of approximately three trophic levels, and most fishes are supported by algal carbon. Understanding food web structure may be important for future conservation programs in subtropical river systems by identifying top predators, taxa that may occupy unique trophic roles and taxa that directly engage basal resources.

Conservação e produção em uma área protegida: dilemas em torno da sustentabilidade

A expansão das áreas protegidas nos últimos anos pode ser compreendida como parte da globalização; a questão ambiental foi uma das primeiras preocupações necessariamente não locais da sociedade, dos estados e da institucionalidade internacional, teve como contrapartida a identificação da biodiversidade como um dos primeiros objetos da preocupação global sobre a natureza. Vou trabalhar aqui sobre a situação do território ocupado atualmente pelo Parque Nacional Esteros de Farrapos e Islas del Río Uruguay, região com uma longa história de usos, desde a ocupação estacional para a caça, a pesca e a colheita em tempos anteriores à conquista até a crescente intensi„cação da agricultura na atualidade. Neste trabalho descreve-se esse processo, apresentando a tensão conservação/produção e as tentativas de “resolvê-la”, por parte de diferentes atores sociais, discutindo-a desde a perspectiva da justiça ambiental. Por outro lado, analisarei o papel das políticas públicas ambientais em relação às desigualdades sociais.

A systematic review of diapoma (teleostei: characiformes: characidae: stevardiinae: diapomini) with descriptions of two new species from southern Brazil

Diapoma is reviewed and four species are recognized: (1) Diapoma thauma, new species, from streams of the rio Jacuí basin, state of Rio Grande do Sul; (2) D. pyrrhopteryx, new species collected from the rio Canoas and streams flowing into this basin in the states of Rio Grande do Sul and Santa Catarina, Brazil; (3) Diapoma terofali, from streams flowing into rio Uruguay in Uruguay and Rio Grande do Sul, Brazil and streams flowing into rio de la Plata, Argentina; and (4) Diapoma speculiferum, from lowland coastal streams in Rio Grande do Sul, Brazil and Uruguay. Diapoma pyrrhopteryx possess the posteroventral opercular elongation typical of D. speculiferum, type species of the genus, but which is absent in D. thauma and D. terofali. Nonetheless, all the diapomin species have the caudal pouch organ about equally developed in both sexes and the dorsal portion of the pouch opening bordered by a series of 3 to 8 elongated scales, the two derived features that characterize the group. The two previously described species, D. speculiferum and D. terofali, are redescribed. Previous hypotheses of relationships among the diapomin genera Planaltina, Diapoma and Acrobrycon are discussed on the basis of preliminary morphological information. It is proposed that the Diapomini is a monophyletic group. An identification key, information on sexual dimorphism, gonad anatomy, reproductive mode and distribution of the species of Diapoma are provided.

Bunocephalus erondinae, a new species of banjo catfish from southern Brazil (Siluriformes: Aspredinidae)

Bunocephalus erondinae, a new species of banjo catfish is described from the laguna dos Patos system, Rio Grande do Sul, Brazil. The new species differs from its congeners by the bony epiphyseal bar very wide (vs. narrow). Bunocephalus erondinae is externally most similar to Bunocephalus doriae (rio Uruguay and rio Paraná-Paraguay basins), however, differs from this species by the following characters: the bony epiphyseal bar very wide (vs. narrow); metapterygoid round, width is equal the height (vs. metapterygoid elongate, width lesser than half of height), well developed lamina in the hypohyal and anterior ceratohyal bones (vs. little developed or absent), 32 vertebrae (vs. 34-35), first procurrent caudal-fin rays well developed (vs. vestigial), vertebral parapophysis 5 distally expanded, shaped like an axe (vs. not expanded).

Are the factories of cellulose really a hazard to the Uruguay river (Argentine Republic) ecosystem?

This paper considers the probable consequences due to the installation of a cellulose pulp mill, related to the health risk of the human population and the nearby environment. The authors tried to be objective from the scientific point of view, revising recent world literature on the chemical and physical properties of the gaseous and liquid effluents. Relevant evidences were considered in view of the authors' professional experience on the laboratory handling of some chemicals involved and related to the damage that would be produced. It is concluded that the industrialisation process of that populated region, associated with the human progress, must be seriously evaluated in this particular case. It is remarked that the geographical place selected for the installation of a cellulose mill, on the riverside of the Rio Uruguay, is neither appropriate nor legally correct, because the effects will be more evident after decades of the operation of that kind of factory.

Spatial and temporal variability of the frequency of extreme daily rainfall regime in the La Plata Basin during the 20th century

We analyzed trends, interdecadal variability, and the quantification of the changes in the frequency of daily rainfall for two thresholds: 0.1 mm and percentile 75th, using high quality daily series from 52 stations in the La Plata Basin (LPB). We observed increases in the annual frequencies in spatially coherent areas. This coherence was more marked in austral summer, autumn, and spring, during which the greatest increases occurred in southern Brazil, especially during extreme events. In winter, the low and middle basins of the Rio Uruguay and Rio Parana showed negative trends, some of which were significant. Interdecadal variability is well defined in the region with more pronounced positive jumps west of the basin between 1950 and 2000. This variability was particularly more marked during periods of extreme rainfall in summer, autumn, and spring, unlike in winter when extreme daily rainfall in the lower Rio Parana basin decreased by up to 60%. The changes in the past century during extreme rainfall produced modifications in the annual rainfall cycle. The annual cycle of both indices was broader during the last period which is mainly explained by the strong decreases in winter.

Four new species of Hisonotus (Siluriformes: Loricariidae) from the upper rio Uruguay, southeastern South America, with a review of the genus in the rio Uruguay basin

Four new species of Hisonotus are described from the upper course of the rio Uruguay basin in Brazil: Hisonotus iota from the rio Chapecó drainage; Hisonotus leucophrys from rio Rancho Grande and rio Ariranhas; Hisonotus megaloplax from the rio Passo Fundo drainage; and Hisonotus montanus from the rio Canoas drainage. The species Epactionotus aky, described from the arroyo Yabotí-Guazú drainage in Argentina, is transferred to Hisonotus and rediagnosed. Hisonotus candombe is considered a junior synonym of H. ringueleti. The new taxa, together with H. nigricauda, H. ringueleti, H. charrua, and H. aky represent the genus Hisonotus in the rio Uruguay basin. A taxonomic key for Hisonotus in the rio Uruguay basin is provided. Their distributions are discussed under biogeographic patterns previously proposed for the rio Uruguay basin.

Nove espécies novas do gênero Rineloricaria (Siluriformes, Loricariidae) do rio Uruguai, do sul do Brasil

Nove espécies novas de Rineloricaria do alto e médio rio Uruguai são descritas nos Estados do Rio Grande do Sul e Santa Catarina, Brasil. Rineloricaria misionera Rodriguez & Miquelarena, 2005 é a única espécie atualmente conhecida desta bacia. As novas espécies são diagnosticadas principalmente pela disposição das placas no abdome, padrão de colorido, extensão da área nua anterior no focinho e comprimento das nadadeiras. As espécies aqui descritas são endêmicas do rio Uruguai. Rineloricaria anitae e R. tropeira são restritas aos afluentes dos rios Canoas e Pelotas; R. zaina é amplamente distribuída da confluência dos rios Canoas com o rio Pelotas até o rio Ibicuí; R. anhanguapitan é restrita a bacia do Passo Fundo; R. capitonia ocorre no alto rio Ijuí; R. stellata é conhecida dos rios Buricá, Ijuí, Piratini e Ibicuí; R. setepovos e R. reisi são descritas do rio Piratini e R. sanga é conhecida apenas dos arredores do município de Iraí. São apresentados comentários sobre a diversidade de espécies no rio Uruguai e em relação à variação de placas no abdome.

Characidium heirmostigmata, a new characidiin fish (Characiformes: Crenuchidae) from the upper rio Paraná basin, Brazil

Characidium heirmostigmata new species is described from the rio Ivaí drainage, upper rio Paraná basin, Paraná State, Brazil. The new species is diagnosed among its congeners by the possession of eight to 11 incomplete oblique dark bars on the body sides, extending upwards and downwards from the lateral line, independently of the eight or nine dorsal transverse bars usually present in species of Characidium. The new species is similar to Characidium serrano from the upper rio Uruguay basin, but differs by meristic and morphometric traits.

Two new species of Rineloricaria (Siluriformes: Loricariidae) from the rio Iguaçu basin, southern Brazil

Rineloricaria langei and R. maacki, new species, are described from upper and middle regions of the rio Iguaçu basin, a left bank tributary of the rio Paraná basin, southern Brazil. Rineloricaria langei has narrow body and is similar to R. quadrensis, which is found in coastal rivers of Rio Grande do Sul State and is distinguishable by several morphometric characters. Rineloricaria maacki is distinguishable from all other congeners by the shape and extension of the naked area of the ventral region of pectoral girdle and other morphological characters. The presence of a naked region on the abdominal surface is shared with other species from the rio Paraná and rio Uruguay basins and coastal drainages from southeastern and southern Brazil. This may indicate a close phylogenetic relationship among these species. Similarities between the two new species and species from the aforementioned drainages also suggest close biogeographic relationship between the Paraná basin and other Brazilian coastal Atlantic drainages throughout the rio Iguaçu basin.

Two new species of the genus Crenicichla Heckel, 1840 from the upper rio Uruguay drainage (Perciformes: Cichlidae)

Two new species of the genus Crenicichla from the upper rio Uruguay basin are described, Crenicichla hadrostigma and C. empheres. Both are included in the C. missioneira species group along with C. missioneira, C. minuano, C. tendybaguassu, C. igara, and C. jurubi, all occurring in the upper and middle rio Uruguay drainage. Crenicichla hadrostigma is distinguished by the conspicuous ocellated posttemporal blotch, absence of a humeral spot and lateral band, and the presence in males of nine to 16 narrow vertical bars extending from the dorsum to a horizontal line that passes through the lower edge of pectoral axilla. Crenicichla empheres is distinguished from the other species of the missioneira-group by the presence of six to eight horizontally elongate dark blotches along the middle portion of the body, slightly below the upper lateral line, absence of a lateral band, presence in males of numerous dark and irregularly arranged spots on nape, back, and sides of body, and isognathous mouth. A key to the species from rio Uruguay basin is presented.

A fast and accurate molecular method for the detection of larvae of the golden mussel Limnoperna fortunei (Mollusca: Mytilidae) in plankton samples

A fast and accurate molecular method for the detection of larvae of the golden mussel Limnoperna fortunei (Mollusca: Mytilidae) in plankton samples

A new species of Hyphessobrycon (Characiformes, Characidae) from the río Uruguay basin, Argentina

A new species of Hyphessobrycon (Characiformes, Characidae) from the rio Uruguay basin, Argentina. Hyphessobrycon isiri sp. n., is described from the no Uruguay basin. Hyphessobrycon isiri sp. n. differs from the remaining species of the genus by the presence of teeth of the inner series of the premaxilla with 5 to 11 cusps, one maxillary tooth with 7 cusps; 16 to 22 branched anal-fin rays; one humeral spot vertically elongated, and a rnidlateral stripe ending in a conspicuous caudal spot.

A new species of Microglanis (Siluriformes: Pseudopimelodidae) from upper rio Paraná basin, Brazil

Microglanis garavelloi, new species, collected in tributaries of rio Paranapanema and rio Tietê, is the first species of the genus described from upper rio Paraná basin. The new species can be distinguished from other species of Microglanis on morphometric characters, color pattern, caudal-fin shape, pectoral-spine morphology and lateral line development. Characters used specifically to distinguish M. garavelloi from M. cottoides (laguna dos Patos and rio Uruguay basins) and M. parahybae (rio Paraíba do Sul basin) include morphometrics, color pattern and pectoral-spine serration.

A new species of Microglanis (Siluriformes: Pseudopimelodidae) from the rio Uruguay drainage, Brazil

A new pseudopimelodid catfish, Microglanis malabarbai, is described from the rio Ijuí drainage, tributary of the middle rio Uruguay, Rio Grande do Sul, Brazil. The new species is distinguished from all other Microglanis species by the caudal fin color pattern, almost completely black, with a narrow vertical white band across central portions of the caudal-fin rays. Furthermore, it is distinguished from M. cottoides and M. eurystoma, both from rio Uruguay drainage, by head length, maxillary barbel length, internareal distance, and number of lateral-line pores, and from M. cibelae from the coastal drainages of northern Rio Grande do Sul and southern Santa Catarina states, by head length, maxillary barbel length, and body width. A key is presented for the species of Microglanis occurring in southern Brazil.

Two new species of Bryconamericus Eigenmann (Characiformes: Characidae) from southern Brazil

Two new species of Bryconamericus are described from southern Brazil: B. patriciae, from the headwaters of rio Pelotas (rio Uruguay drainage) and rio das Antas (laguna dos Patos drainage) and B. ecai from lower rio Taquari drainage. Bryconamericus patriciae differs from other Bryconamericus species from southern South America, by the following combination of characters: body depth (25.5-30.3% SL); head length (25.2-27.6% SL); pelvic-fin length (11.0-14.4% SL); branched anal-fin rays 14-18; teeth of outer row of premaxilla regularly implanted; teeth of inner row of premaxilla pentacuspid; teeth compressed distally; and males with bony hooks on pelvic and anal fins. Bryconamericus ecai differs from other Bryconamericus species from southern South America by the following combination of characters: body depth (33.1-36.9% SL); eye diameter (31.1-33.9% HL); snout length (26.8-32.4% HL); branched anal-fin rays 15-18; teeth of outer row of premaxilla regularly implanted; teeth of inner row of premaxilla tricuspid or pentacuspid; teeth compressed distally; and males with bony hooks on pelvic and anal fins.

Austrolebias varzeae, a new annual fish from the upper rio Uruguay basin, southern Brazil (Cyprinodontiformes: Rivulidae)

Austrolebias varzeae n. sp. is described from rio da Várzea floodplains, upper rio Uruguay basin, southern Brazil. It seems to be closely related to A. carvalhoi (Myers), with which it shares a similar color pattern of male and an apomorphic morphology of the autopalatine. The new species differs from A. carvalhoi by having more anal-fin rays in males and more caudal-fin rays. Austrolebias varzeae is distinguished from all other species of the genus by a unique color pattern, in which there are three distinctively darker and narrower bars on the anterior portion of male flank. Putative close relationships between A. varzeae and A. carvalhoi suggest a closely related biogeographic history between upper Uruguay and upper Iguaçu River basins, corroborated by a biogeographic pattern of the anablepid genus Jenynsia.

Austrolebias arachan (Cyprinodontiformes, Rivulidae), a new species of annual fish from northeastern Uruguay

The annual fish Austrolebias arachan is described from temporary ponds of Rio Tacuari (Los Patos-Merin system) and Rio Negro (Rio Uruguay drainage) basins. Austrolebias arachan is easily distinguished from otherAustrolebias species by the combination of the following characters: body of males dark brown to black, with light narrow yellow vertical bands, dorsal fin dark brown with vertically elongated light yellow dots in the proximal half, pectoral fin light grey with margin black; females with anterior anal fin rays elongated, forming a triangular-shaped fin. Both sexes with pelvic fins joined to each other in different degrees; two to four parietal neuromasts; three pectoral radials in most individuals. The new species is closely related to A. adloffi species group and to A. viarius.

Long‐term flow forecasts based on climate and hydrologic modeling: Uruguay River basin

This paper describes a procedure for predicting seasonal flow in the Rio Uruguay drainage basin (area 75,000 km2, lying in Brazilian territory), using sequences of future daily rainfall given by the global climate model (GCM) of the Brazilian agency for climate prediction (Centro de Previsão de Tempo e Clima, or CPTEC). Sequences of future daily rainfall given by this model were used as input to a rainfall‐runoff model appropriate for large drainage basins. Forecasts of flow in the Rio Uruguay were made for the period 1995–2001 of the full record, which began in 1940. Analysis showed that GCM forecasts underestimated rainfall over almost all the basin, particularly in winter, although interannual variability in regional rainfall was reproduced relatively well. A statistical procedure was used to correct for the underestimation of rainfall. When the corrected rainfall sequences were transformed to flow by the hydrologic model, forecasts of flow in the Rio Uruguay basin were better than forecasts based on historic mean or median flows by 37% for monthly flows and by 54% for 3‐monthly flows.

Bryconamericus pyahu sp. n. (Characiformes, Characidae), a new species from the río Iguazú basin, in Argentina

A new species of the genus Bryconamericus is described from rio Uruguay basin in Misiones, Argentina. Bryconamericus uporas is distinguished by the following combination of characters: low body depth (28.9-32.2 in % of SL); all teeth of upper jaw broadest distally; premaxillary teeth of the inner series with seven cusps; premaxillary teeth of the outer row with five cusps, and maxillary teeth with five or seven cusps. Also, the new species has 18-20 branched anal-fin rays, large subcircular black humeral spot, wide black lateral band, light violet upper half of flank, and lower half silvery. The new species was collected in the headwaters of the arroyos Once Vueltas, Toro, Fortaleza, and Yaboti-Mini. Those streams were born in the sierras, having rocky and sandy bottom, with clear and rapid water.