AIM: The present study analyzed the spatial variation in fish species richness and composition in streams of the Ivinhema River basin, Upper Paraná basin, determining the relationship between local and regional descriptors of the fish assemblage organization; METHOD: From 2001 to 2011 we sampled 200 stream stretches, using different sampling methods. Local species richness and composition were analyzed using univariate and multivariate methods to detect patterns of variation in the fish assemblage organization; RESULTS: We identified 111 fish species in the streams, and estimated the occurrence of 117 fish species (CIα0.05 = 111 to 123) with lower species richness in headwater streams compared to the lower parts of the basin. The fish species recorded were predominantly of small size, and the mean size increased from the headwaters to the river mouth. The four most common species are widely distributed in the basin. However, 24 species are allocthonous to the Upper Paraná basin, and two species (Chaetobranchopsis australis and Apistogramma commbrae) are recorded here for the first time in the Upper Paraná basin. Altitude was the main determinant of local fish species richness and composition, and a discontinuity in assemblage organization (richness, composition, fish size) was detected at approximately 430 m a.s.l.; CONCLUSION: Streams of the Ivinhema River basin are inhabited mainly by small-sized fishes; and longitudinal variation, interacting with local characteristics, determines the fish assemblage patterns.

Aim: This study aimed to evaluate influence of hydrological variation, ontogeny and interspecific variation in the feeding activity and diet composition for P. nattereri and S. marginatus in floodplain of Negro River, South Pantanal. Methods: The samples were taken with the use of gillnets and cast nets of different sizes, from October/2005 to August/2008. Results: We sampled 748 specimens, 442 of P. nattereri and 306 of S. marginatus. We identified 31 items in the dry and 14 in the flood season for P. nattereri, and 29 items in the dry and eight in the flood season for S. marginatus. For both species, fish was the predominant food item in both seasons. The PERMANOVA results showed that the diet varied significantly between the two species (p<0.001), during ontogenetic development (p<0.001) and seasonally (p=0.024). The ancova results suggests that the intensity of food intake was higher in the dry season (p<0.001) for both species. The niche breadth varied only between studied species with S. marginatus presenting higher niche breadth than P. nattereri. Conclusion: Piranhas feed more during dry season, probably because in this period food is more varied and abundant, due to the concentration of fish in the main river channel. There were ontogenetic changes in the diet, with no feeding overlap between the two species, probably because of differences in preference for some items and differences in feeding behavior displayed during hunting attacks.Keywords: Serrasalminae, diet, feeding overlap, trophic ontogeny, Nhecolândia.Resumo: Objetivos: Este trabalho tem como objetivo avaliar a influência da variação hidrológica, da ontogenia e da variação interespecífica na atividade alimentar e composição da dieta de P. nattereri e S. marginatus na planície de inundação do Rio Negro, Pantanal Sul. Métodos: As amostragens foram realizadas com o uso de redes de espera e tarrafas com diversas malhagens no período de outubro/2005 e agosto/2008. Resultados: Foram coletados um total de 748 indivíduos, 442 de P. nattereri e 306 indivíduos de S. marginatus. Identificamos 31 itens alimentares no período da seca e 14 na cheia para P. nattereri e 29 itens alimentares no período da seca e oito na cheia para S. marginatus. Para ambas as espécies, peixes foi o item predominante em ambas as estações. Os resultados da PERMANOVA mostraram que a dieta variou significativamente entre as espécies (p<0,001), durante o desenvolvimento ontogenético (p<0,001) e sazonalmente (p=0,024). Os resultados da ANCOVA sugerem que a intensidade da tomada de alimento foi maior na estação seca (p<0,001), para ambas as espécies. A amplitude de nicho 382 Ferreira, FS. et al.Acta Limnologica Brasiliensia variou entre as espécies estudadas, S. marginatus apresentou uma amplitude de nicho maior do que P. nattereri. Conclusão: As piranhas se alimentam mais durante a seca, provavelmente porque neste período o alimento é mais variado e abundante, devido a concentração de peixes no canal principal do rio. Houve mudanças ontogenéticas na dieta, sem sobreposiç...

Abstract:The Porto Murtinho Pantanal lies at the limit of the Upper Paraguay River basin, and despite its biogeographical importance, several aspects of the ecology of the fish assemblage are not known. Monthly samples of fish associated with aquatic macrophytes were taken from February 2009 through January 2011. A total of 46,327 individuals were collected, belonging to 144 species. Characiformes and Siluriformes were the predominant orders, and Odontostilbe pequira, O. paraguayensis and Bryconamericus exodon were the most abundant species. Two species, Cynopotamus sp. and Pimelodus mysteriosus, were recorded for the first time in the Pantanal, and a new occurrence record of Cichla piquiti was observed, representing an approximately 400 km range expansion in your distribution area in the Pantanal.

The objective of this study was to provide a comprehensive list of the fish fauna of headwater streams of the Miranda River in the Upper Paraguay River Basin. Our primary data set was constructed from sampling of fish using a rectangular sieve, trawl, and gill nets from 2004 to 2015. Our secondary data were derived from published reports conducted in the Miranda River Basin, in addition to taxonomic and distribution data from other studies conducted in the basin. All data were compiled, which in the end encompassed a period from 1999 to 2015. The datasets yielded a total of 143 species, 104 from the primary data (72.7%) and 39 from the secondary data (27.3%). Species were distributed among seven orders and 30 families were found in the Miranda River Basin. Characiformes and Siluriformes were the predominant orders, and the families Characidae and Loricariidae had the greatest number of species. Our results indicate a greater number of species compared to other studies of the Upper Paraguay Basin headwaters, likely due to the longer time frame covered by our primary and secondary datasets.

In order to inventory the species richness and fish fauna composition along the Ivinhema river basin, 232 stretches of rivers and streams were sampled from 2000 to 2018, using a rectangular sieve, trawls, gillnets, cast nets, and electrofishing. A total of 141 species was caught in the basin, including seven orders and 35 families. For the recorded species, 42 are from the upper Paraná river, 51 from lower Paraná river, 27 from other basins, two from other continents, and the origin for 19 species are unknown/not reported. Six species are registred for the first time in the upper Paraná river basin: Astyanax abramis, Moenkhausia oligolepis, Serrapinnus kriegi, Curimatopsis myersi, Pyxiloricaria menezesi, and Cichlasoma dimerus. This is the first complete survey of the ichthyofauna in lotic environments along the whole Ivinhema river basin, containing relevant information for comparing studies and serving as reference data that can contribute to the management and implementation of politics for conservation of the basin. This survey also increases 24 species on the list of the most complete inventory in the upper Paraná river published in 2007.

The Neotropical region hosts 4225 freshwater fish species, ranking first among the world's most diverse regions for freshwater fishes. Our NEOTROPICAL FRESHWATER FISHES data set is the first to produce a large‐scale Neotropical freshwater fish inventory, covering the entire Neotropical region from Mexico and the Caribbean in the north to the southern limits in Argentina, Paraguay, Chile, and Uruguay. We compiled 185,787 distribution records, with unique georeferenced coordinates, for the 4225 species, represented by occurrence and abundance data. The number of species for the most numerous orders are as follows: Characiformes (1289), Siluriformes (1384), Cichliformes (354), Cyprinodontiformes (245), and Gymnotiformes (135). The most recorded species was the characid Astyanax fasciatus (4696 records). We registered 116,802 distribution records for native species, compared to 1802 distribution records for nonnative species. The main aim of the NEOTROPICAL FRESHWATER FISHES data set was to make these occurrence and abundance data accessible for international researchers to develop ecological and macroecological studies, from local to regional scales, with focal fish species, families, or orders. We anticipate that the NEOTROPICAL FRESHWATER FISHES data set will be valuable for studies on a wide range of ecological processes, such as trophic cascades, fishery pressure, the effects of habitat loss and fragmentation, and the impacts of species invasion and climate change. There are no copyright restrictions on the data, and please cite this data paper when using the data in publications.

Astyanax lineatus was previously known only from the Paraguay river basin and we report the first record from the Paraná river basin near the municipality of Sidrolândia, Mato Grosso do Sul state, Brazil. The species was found in Lajeado Stream, a tributary of the Anhanduí River, which belongs to the Pardo River sub-basin of the Paraná river basin.

ABSTRACT. Population structure and reproductive aspects of Corydoras aeneus (Siluriformes, Callichthyidae) in streams of the River Ivinhema Basin, Upper Paraná River. Despite of increase of studies about biology of small fish species, the knowledge of basic aspects of biology great portion of species still is incipient. Thereat, the aim of this study was analyze the population structure and the reproductive aspects of Corydoras aeneus (Gill, 1858) in streams of the Ivinhema River Basin, Upper Paraná River. The samplings were performed from 2008 to 2011 at fifty seven sites distributed in basin. They were analyzed 684 individuals, including 213 females, 190 males and 281 obtained only the dada of standard length. The maximum standard length registered for analyzed population was 50.19 mm for females and 45.24 mm for males, so females were larger than males. The sex ratio was 52.7% females and of 47.1% males, no significant variation (Χ 2 = 1.313; p = 0.252) between sex. How much the Lengthweight relationship both sexes presented isometric growth. The highest proportion of mature females was observed in from October to December, although were observed mature females in others months of year. It was observed that 50% of females were sexually mature at 33.54 mm. Mean fecundity was estimated 359.47 eggs, and presented total spawning. The recruitment pattern no presented a unimodal period, although the more intensity was observed from October to December. The asymptotic length was estimated at 54.59 mm and growth rate at 1.1 year -1 . The growth performance index was estimated to 3.51, the longevity at 2.72 years and the mortality rate at 1.48 year -1 . KEYWORDS. Length-weight relationship, fecundity, mortality, sex-ratio. RESUMO.Apesar do crescente número de estudos sobre biologia de espécies de peixes de pequeno porte, o conhecimento dos aspectos básicos da biologia da maioria das espécies ainda é incipiente. Com isso, o objetivo desse estudo foi descrever alguns aspectos populacionais e reprodutivos de Corydoras aeneus (Gill, 1858) em riachos da bacia do rio Ivinhema, Alto rio Paraná. As amostragens foram realizadas entre 2008 e 2011 em 57 riachos distribuídos na bacia. Foram analisados 684 indivíduos, sendo 213 fêmeas e 190 machos, além de 281 exemplares analisados apenas quanto aos dados de comprimento padrão. O comprimento padrão máximo da população analisada foi de 50,19 mm para as fêmeas e de 45,24 mm para machos; Desta forma, as fêmeas foram maiores que os machos. A proporção sexual foi de 52,7% para fêmeas e de 47,1% para os machos, sem variação significativa entre os sexos (Χ 2 = 1,313; p = 0,252). Quanto à relação peso/comprimento ambos os sexos apresentaram a crescimento isométrico. As maiores frequências de fêmeas maduras foram observadas nos meses de outubro a dezembro, embora tenham sido observadas fêmeas maduras em outros meses do ano. Estimou-se que 50% das fêmeas estão sexualmente maduras com 33,54 mm de comprimento padrão. A fecundidade média foi estimada em 359,47 oócitos, sendo que a população a...