Rivulidae includes non-annual fish of perennial habitats and annual fish of temporary wetlands. The objective of this research was to investigate the trophic strategy of Atlantirivulus riograndensis in a perennial environment. Sampling occurred in an environmental conservation unit in the Pampa biome, Brazil. Quantification of the diet followed the volumetric method. Consumption of autochthonous material as the main food source of the species followed the pattern of Rivulidae. Species is zooplanktonic when young. Food spectrum is broadened and insectivorousness increases with ontogeny, revealing a specialist trend in the feeding strategy of A. riograndensis. The most diverse feeding occurs in the spring and summer seasons in which the presence of larger fish was more frequent than in other seasons. The increased consumption of microcrustaceans in the fall was related to smaller individuals, captured in greater quantities in this post-reproductive period. The lowest diversity of dietary items occurs during the winter and may reflect the lower diversity of food resources available in this season or the transition from juvenile to adult diet, with consumption of autochthonous Diptera by medium sized fish.Rivulidae inclui peixes não anuais de habitats perenes e peixes anuais de alagados temporários. O objetivo desta pesquisa foi investigar a estratégia trófica de Atlantirivulus riograndensis em um ambiente perene. A amostragem ocorreu em uma unidade de conservação ambiental no bioma Pampa, Brasil. A quantificação da dieta seguiu o método volumétrico. O consumo de material autóctone como principal recurso alimentar da espécie seguiu o padrão da família Rivulidae. A espécie é zooplanctívora quando juvenil. O espectro alimentar é ampliado e a tendência à insetivoria aumenta com a ontogenia, revelando traços especialistas na estratégia alimentar de A. riograndensis. A alimentação mais diversificada ocorreu na primavera e no verão, estações em que a presença dos peixes maiores foi frequente que em outras estações. O aumento no consumo de microcrustáceos no inverno foi relacionado aos indivíduos menores, capturados em maior quantidade neste período pós-reprodutivo. A menor diversidade de itens alimentares ocorreu durante o inverno e pode refletir uma menor diversidade de recursos alimentares disponíveis nesta época do ano ou a transição da dieta de juvenil para adulto, com consumo de Diptera autóctone por peixes de tamanho médio.

The ichthyofauna of streams in the Neotropical region is not yet fully known. This study aims to investigate the ichthyofauna composition of six streams of the Ijuí River sub-basin, Rio Grande do Sul State, inserted in the Uruguay River basin, as to contribute to the knowledge of fishes species richness and distribution in the south of Brazil. Sampling was carried out between July 2015 and May 2016, bimonthly, using the technique of electric fishing to collect the fishes. Spatial variations (per sampled stream) in the ichthyofauna composition were tested with a permutational multivariate analysis of variance. In total, we collected 5,029 individuals from 55 species, 13 families and five orders. From these species, 17 are endemic to the Uruguay River basin. Five species alone represented approximately 70% of the ichthyofauna abundance sampled. Our hypothesis that the fish community composition is not homogeneous along the streams sampled was confirmed and we observed that species complexity increases from the upstream closest area to the downstream according to the river continuum concept.

Ontogeny of feeding by Astyanax paris in streams of the Uruguay River Basin, Brazil. We 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. ResumenOntogenia de la alimentación de Astyanax paris en los arroyos de la cuenca fluvial del río Uruguay, en Brasil. Estudiamos la ontogenia de la alimentación de Astyanax paris, un pez carácido insectívoro de los arroyos de la cuenca del río Uruguay, en el sureste de Brasil. Las diferencias de la composición de la dieta en función del tamaño se analizaron mediante el análisis de varianza multivariante con permutaciones (PERMANOVA). Se muestrearon seis arroyos durante 12 meses y se obtuvieron 20 especímenes para analizar el contenido del estómago. Los individuos más pequeños (longitud estándar ≤ 25 mm) consumieron principalmente insectos acuáticos. A medida que aumentaba el tamaño corporal, se pasaba gradualmente a una dieta compuesta principalmente por insectos terrestres. En consecuencia, la ontogenia de los hábitats de alimentación cambia la posición de las especies en las redes tróficas de los arroyos.

ABSTRACT. Atlantirivulus riograndensis (Costa & Lanés, 2009) is a fish registered to the basin of Patos lagoon and the adjacent coastal plains in southern states of Rio Grande do Sul and Santa Catarina, Brazil, found in shallow water courses with that have large quantities of aquatic vegetation and forest edges. The objective of this study was to investigate the reproductive strategy and tactics of this species including the sex ratio, the length at first maturity, spawning type, fecundity and the possible associations among reproduction and abiotic factors. Sampling of specimens occurred in perennial wetlands within the Banhado dos Pachecos wildlife refuge, in the city of Viamão, state of Rio Grande do Sul, Brazil, which is a conservation unit that belongs to an area of environmental protection in the Pampa Biome. The capture of 30 A. riograndensis specimens per month occurred from January to December of 2012. A total of 188 females and 172 males were captured and the total sex ratio was 1:1 in the sampled population. Sexual maturity of the species occurs after 13.59 and 11.92 mm (SL) for females and males, respectively. Both a multiple spawning and a long reproductive period (since August to March) were confirmed by the presence of post-ovulatory follicles that were observed through histological analysis and the values of the gonadosomatic index in females considered spawning capable. The average absolute fecundity of the species is of 19.33 (± 6.18) vitellogenic oocytes in mature ovaries. No significant relationship was found between mean GSI and the abiotic data. Reproductive tactics presented by A. riograndensis indicate a species with an opportunistic reproductive strategy, following the pattern of other species of the Rivulidae family. KEYWORDS.Atlantirivulus riograndensis, gonadal development, multiple spawning, fecundity. (Costa & Lanés, 2009) é uma espécie de peixe registrada para a bacia da laguna dos Patos e planícies costeiras adjacentes, nos estados do Rio Grande do Sul e sul de Santa Catarina, Brasil, encontrada em corpos d'água rasos, com grande quantidade de vegetação aquática e em bordas de mata. O objetivo deste estudo consistiu em investigar a estratégia e as táticas reprodutivas desta espécie, incluindo a proporção sexual, o comprimento de primeira maturação, o tipo de desova, a fecundidade e possíveis associações entre a reprodução e fatores abióticos. As amostragens de exemplares da espécie ocorreram em um banhado perene no Refúgio da Vida Silvestre Banhado dos Pachecos, município de Viamão, estado do Rio Grande do Sul, Brasil, que constitui uma área de proteção ambiental em uma unidade de conservação no bioma Pampa. A captura de trinta indivíduos de A. riograndensis por mês, ocorreu de janeiro a dezembro de 2012. Foram amostradas 188 fêmeas e 172 machos e a proporção sexual total foi de 1:1 na população amostrada. A maturação sexual da espécie ocorre a partir de 13,59 e 11,92 mm (CP) para fêmeas e machos, respectivamente. As análises histológicas demonstraram uma desova parcelada com a pr...

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