Carla Simone Pavanelli

Diversidade da ictiofauna do Alto Rio Paraná: composição atual e perspectivas futuras

Langeani, F., Castro, R.M.C., Oyakawa, O.T., Shibatta, O.A., Pavanelli, C.S. & Casatti, L. Ichthyofauna diversity of the upper rio Parana: present composition and future perspectives. Biota Neotrop. Sep/Dez 2007 vol. 7, no. 3 http://www.biotaneotropica.org.br/v7n3/pt/abstract?article+bn03407032007. ISSN 1676-0603. A synthesis concerning fishes from Upper Parana River basin is presented, based on data from fish-collections, literature, and new field samples. Three hundred and ten species, pertaining to 11 orders and 38 families, are referred to the drainage, elevating anterior estimates. Concerning total species, 236 (76.1%) are autochthonous, 67 (21.6%) are allochthonous, and seven (2.3%) are exotic. Principal causes of occurrence of non-native species are: a) dispersal from the Lower Parana, after the construction of Itaipu dam, and b) escapes from aquaculture farms. Most species (65%) are small-sized, having less than 21 cm of length, and the great majority occurs only in headwaters and small streams. One of the best known and most studied in Brazil, Upper Parana ichthyofauna richness is far from reaching actual numbers, considering the exponential elevation of species presented herein. Indeed, in the last years various new species have been described and around 50 other species, already recognized as new, are now under description. The improvement on the knowledge about Upper Parana ichthyofauna is proportional to the number of researchers involved with studies in the area and, unequivocally, reflects recent initiatives stimulating and incrementing taxonomic research, and also improving access to fish collections and to poor or never-sampled areas. However, if we are going to maintain the number of species descriptions per year of last decade, the 50 new species already recognized, will be described only in the next ten years, a period too long. In consequence it is very important that scientific community and grant agencies find and offer initiatives in order to elevate the number of new taxa descriptions per year.

A massive invasion of fish species after eliminating a natural barrier in the upper rio Paraná basin

Based on long-term studies in the upper rio Parana basin, in addition to a broad review of literature and other information, we were able to identify 33 species of native fishes in the lower rio Parana basin that successfully colonized the upper rio Parana after Itaipu impoundment, that flooded the natural geographic barrier constituted by the Sete Quedas Falls. These species belong to six Orders, encompassing two of Myliobatiformes, six of Characiformes, 17 of Siluriformes, six of Gymnotiformes, one of Perciformes, and one of Pleuronectiformes. Extensive remarks regarding each species, including their influence upon the native assemblage, in addition to comments on other non-indigenous species, are also provided. We conclude that, in spite of its widespread neglected by environmental impact studies, massive invasion of species is a real possibility when natural barriers are suppressed by reservoirs.

Identification of Astyanax altiparanae (Teleostei, Characidae) in the Iguaçu River, Brazil, based on mitochondrial DNA and RAPD markers

Astyanax fishes are among the most important food-web components of South America rivers. In the Iguacu River basin, the Astyanax genus is represented mainly by endemic species. For millions of years, that hydrographic basin has been geographically isolated from the Parana River basin by the Iguacu Falls. Recently, a species from the Upper Parana River basin identified as Astyanax bimaculatus was revised and described as a new species named Astyanax altiparanae Garutti & Britski, 2000. Fauna endemism and geographic isolation triggered interest in investigations to evaluate the identification and genetic relatedness among two A. altiparanae populations from the Upper Parana River basin and the population identified as A. bimaculatus in the Iguacu River, upstream from the Iguacu Falls. Mitochondrial DNA sequences and RAPD markers revealed high genetic diversity within each population, as well as low genetic distance, high gene flow, and high mitochondrial DNA similarity among all three populations. In conjunction with morphological similarities, these results demonstrated that the population presently known as Astyanax bimaculatus in the Iguacu River should actually be stated as Astyanax altiparanae. Furthermore, it could be inferred that the A. altiparanae population is not endemic and most likely it was recently introduced in the Iguacu River basin, maintaining the ancestral genetic identity.

Colonização ictiofaunística do Reservatório de Itaipu e áreas adjacentes

Samples were taken from November 1983 to October 1989 in sites along the main body of the Itaipu reservoir and its area of influence to evaluate the impacts of this reservoir on ichthyofauna and to provide information about the colonization process in the dammed area. The ichthyofaunistic similarity between the sites was analysed during the studied period. Spatial and temporal variations of the ichthyofaunistic diversity were also done, using Shannon-Winer Index of Diversity, eveness and species richness, comparing the results with those obtained before the damming. After Itaipu Reservoir formation, it was observed significative alteration in specific abundance and ichthyofauna structure of the Parana River, with an increase in species number in ali tributaries of the reservoir, and a high replacement in species. Diversity and species richness were higher in the dammed stretch of the Parana river and in its tributaries of the left side after the Itaipu reservoir formation. Among the sampled sites, the highest values of the diversity index were registered in Parana River upstream and downstream the reservoir, Iguatemi river and Arroio Guacu. Based on information of similarity in species composition and abundance in the sampled area, five site groups could be identified.

Temporal and spatial distribution of the ichthyofauna in two streams of the upper Rio Parana basin

The temporal and spatial distribution of the ichthyofauna was assessed in two streams, Caracu and Sao Pedro, affluents of the Rio Parana, from March 1991 through February 1992. Samples were taken along the streams, using sieves (three sites on the Caracu and two on the Sao Pedro), and gill nets (two sites on the Sao Pedro). A total of 6,664 specimens belonging to 71 species were captured. CPE was calculated for each fishing gear. The data for cumulative frequency indicated that only the mouths of streams did not reach an asymptote. Constancy analysis showed that occasional and accessory species predominated. The spectrum of spatial diversity indicated that diversity increased toward the mouth of streams and temporal diversity increased in the high water season. The results of correspondence analysis for sieved fishes and Sorensen similarity for netted ones showed that the sites located at the same position on the streams were more similar than between adjacent sites in the same stream.

The Canal da Piracema at Itaipu Dam as a fish pass system

The Canal da Piracema is the longest (nearly 10 km) fish pass system in the world. The construction of this fish pass was somehow controversial, because it connected two distinct ichthyofaunistic provinces. This study evaluated the ichthyofauna present in the Canal da Piracema and the abundance and distribution of long-distance migratory fish species along this fish pass system (evaluated possible selectivity). The Canal da Piracema was shown to be difficult to sample because of its environmental heterogeneity: artificial ponds, ladders and nature-like fish pass. To solve this problem, we used several fishing gears, adequate for the several biotopes present (unstructured and structured littoral were sampled with seining nets and electrofishing; lentic were sampled with gillnets and longlines (deeper areas); and rapid water areas were sampled with cast nets). The ichthyofauna of the Canal da Piracema followed the pattern for South America and the Parana River, with a predominance of Characiformes and Siluriformes. The most representative families were Characidae, Anostomidae, Pimelodidae and Loricariidae. We captured 116 species (17 were long-distance migratory) during the period studied. Small-sized species were predominant in unstructured and structured littoral areas, especially Bryconamericus exodon and Apareiodon affinis.The most abundant species was Hypostomus spp. in lentic areas, followed by Iheringichthys labrosus. Hoplias aff. malabaricus predominated in deeper lentic areas. Long-distance migratory species were abundant in rapid waters; they were Prochilodus lineatus and Leporinus elongatus. The sharp reduction in the number of species, including migratory ones, is an indication that the Canal da Piracema is selecting the species that ascend it. Therefore, the search for information on the efficiency of the various fish passes present in the Canal da Piracema is fundamental, to facilitate upward movements of fish. If this is reached, this polemic fish pass has the potential to contribute to the conservation of fish stocks in Itaipu Reservoir and upstream stretches, because of the presence of spawning and development (nurseries) areas for migratory species.

Diversity and Genetic Distance in Populations of Steindachnerina in the Upper Paraná River Floodplain of Brazil

Whereas four species of the genus Steindachnerina occur in the Paraná river basin, S. insculpta was the only endemic species of the region under analysis, which is the third lower section of the upper Paraná river. Among other factors, this species has been characterised by the absence of spots in the basal region of the dorsal fin. However, various specimens with this characteristic appeared in the region after the construction of the Itaipu Hydroelectric Plant in 1982. An analysis of the genetic variability of Steindachnerina populations with or without spots is provided. Specimens were collected in different sites of the floodplain of the upper Paraná river and samples were compared by random amplified polymorphic DNA (RAPD) technique and morphological analyses. Ninety-eight amplified loci with nine random primers were analysed in 19 specimens of each phenotype. Data for genetic distance showed great divergences between the two phenotypes and indicate two different species. Spotted specimens may be identified as S. brevipinna, found in the region downstream Sete Quedas Falls. The species must have overcome the geographical barrier during the building of the Itaipu hydroelectric dam that submerged the waterfalls and which became an obstacle between the upper and middle Paraná river some 150 km downstream. Since phenotypes do not share dominant alleles, absence of gene flow has been suggested.

Two New Species of Characidium (Characiformes: Crenuchidae) from Paraguay and Xingu River Basins. State of Mato Grosso, Brazil

Abstract Characidium nupelia, new species, is described from the upper Rio Paraguay basin, and C. xavante, new species, from the upper Rio Xingu basin, State of Mato Grosso, Brazil. The two species comprise a group diagnosed by a high number (12–18) of dark vertical bars on the body, each bar having the width of a scale. Characidium nupelia differs from C. xavante by having 12 instead of 10 scales around the caudal peduncle, a narrower interorbital distance, and a deeper caudal peduncle. Both species lack an adipose fin, have an incomplete lateral line, and have a conspicuous dark blotch on the caudal peduncle. Breeding males of the two new species present sexual hooks on some pelvic and pectoral branched fin rays. Characidium nupelia, nova espécie, é descrita da bacia do alto rio Paraguai, e C. xavante, nova espécie, da bacia do alto rio Xingu, Estado do Mato Grosso, Brasil. As duas espécies formam um grupo diagnosticado pelo elevado número (12–18) de barras verticais escuras no corpo, cada barra com a largura de uma escama. Characidium nupelia difere de C. xavante por apresentar 12 ao invés de 10 escamas circumpedunculares, distância interorbital menor e pedúnculo caudal mais alto. Ambas têm nadadeira adiposa ausente, linha lateral incompleta e uma mancha escura conspícua no pedúnculo caudal. Machos maduros das duas espécies novas apresentam ganchos sexuais em alguns raios ramificados das nadadeiras pélvica e peitoral.

Astyanax jordanensis (Ostariophysi: Characidae), a new species from the rio Iguaçu basin, Paraná, Brazil

Astyanax jordanensis, new species, is described from the rio Jacu and rio das Torres, both tributaries to the lower rio Jordao, in the rio Iguacu basin, Parana, Brazil. The new species is a member of the A. scabripinnis species complex. Astyanax jordanensis differs from its congeners by several meristic and morphometric characters. Mature males possess bony hooks in the dorsal, pectoral, pelvic, and anal fins, and mature females have a few small bony hooks on the first rays of the anal fin. The presence of these bony hooks in females and the endemism of the ichthyofauna in the rio Jordao are discussed.

A new dark-saddled species of Hypostomus (Siluriformes: Loricariidae) from the upper rio Paraguay basin

A new Hypostomus species is described from the rio Cuiaba, upper rio Paraguay basin, Mato Grosso State, Brazil. The new species is distinguished from all other Hypostomus species, with exception of young specimens of H. latifrons, by the presence of a wide dark transverse bars on laterals of body and fins; and conspicuous dark vermiculations on abdominal region. From H. latifrons it differs by having just one pre-dorsal plate surrounding supraoccipital bone and by the maintenance of the dark saddles in adults. Added to the other fish species recently described from the upper rio Paraguay basin, this work helps to highlight that the region still functions as a potential source of new species.