Foi investigada a alimentação de espécimes adultos de Geophagus brasiliensis (Quoy e Gaimard, 1824) (Osteichthyes, Cichlidae) por meio da análise de 149 conteúdos gástricos, obtidos de amostragens trimestrais efetuadas no reservatório de Capivari (28º8'34"S/48º58'55"W) Paraná-Brasil, nos anos de 1996 e 1998. O espectro alimentar foi avaliado pelos métodos de freqüência de ocorrência e volumétrica e Índice Alimentar (IAi). Variações espaço-temporais na dieta foram investigadas aplicando-se análises de variância (ANOVA) unifatoriais de modelos nulos sobre os escores dos eixos de uma análise correspondência com remoção do efeito do arco (DCA), nos quais foram ordenados os anos, os locais de amostragem e as estações do ano em relação aos recursos alimentares consumidos. Os resultados indicaram uma dieta onívora, composta predominantemente por frutos/sementes, detritos, sedimentos, invertebrados aquáticos e escamas de peixe, sendo frutos/sementes o recurso mais consumido. A composição da dieta apresentou diferenças espaço-temporais significativas, ocorrendo o consumo de recursos com maiores disponibilidades, caracterizando o oportunismo trófico da espécie.

Feeding habitats and trophic overlap of the freshwater stingrays Potamotrygon falkneri e Potamotrygon motoro (Chondrichthyes, Potamotrygonidae) in the upper Paraná river floodplain, Brazil. Feeding habits and trophic overlap of freshwater stingrays Potamotrygon falkneri e Potamotrygon motoro were evaluated in the upper Paraná river floodplain. Samples were collected during periods of drought (August/2004) and flood (January/2005) near Mutum island. Fishhook, harpoon and long line were used to capture the individuals and a total of 49 stomach contents of P. falkneri and 16 of P. motoro were analyzed. Diet composition was analyzed by the relative occurrence and volumetric frequencies. The trophic overlap was quantified by the index of niche overlap of Pianka. Results indicated that both species predominantly consumed mollusks during the flood season, while in the drought season the diet of P. falkneri was composed mainly by fish and P. motoro for aquatic insects. The values of the index of niche overlap varied from 0.38, in drought (moderate), to 0.94 in flood (accentuated). The seasonal variation of the composition of the diets was attributed to fluctuations in the availability of food resources in the floodplain.

Aspects of the feeding ecology of a small characin, Astyanax paranae, were studied during 1996/1997 and 1998/1999 in the Alagados Reservoir, Paraná, Brazil (25º01'50.0'' S; 050º03'41.9'' W). Fishes were quarterly captured from the reservoir's riverine and lacustrine zones and stomachs contents of 711 adult individuals were analyzed by volumetric method. Species' feeding spectrum and spatial, temporal and sexual variations on diet were evaluated. Data matrix was summarized by detrented correspondence analysis (DCA) and the axes scores from DCA were used as variables in one-way ANOVA of null models to test diet variations. Astyanax paranae fed on detritus/sediment, plant matter, algae and aquatic and terrestrial invertebrates. The timespace prevalence of detritus/sediment and plant matter on diet characterized the feeding habit as detritivorous tending to herbivory. Significant differences on food items proportions occurred between the sampling months and sampling sites and were related to resources availability, characterizing the species trophic opportunism.Aspectos da ecologia alimentar de um pequeno caracídeo, Astyanax paranae, foram estudados durante 1996/1997 e 1998/1999 no reservatório de Alagados, Paraná, Brasil (25º01'50,0'' S; 50º03'41,9'' W). Os peixes foram capturados trimestralmente nas zonas fluvial e lacustre do reservatório e os conteúdos gástricos de 711 espécimes adultos foram analisados através do método volumétrico. Foram avaliados o espectro alimentar da espécie e alterações espaciais, temporais e entre os sexos na dieta. A matriz de dados foi sumarizada através da análise de correspondência com remoção do efeito do arco (DCA) e os escores dos eixos resultantes da DCA utilizados como variáveis em análises de variância (ANOVA) unifatoriais de modelos nulos para testar diferenças na dieta. Astyanax paranae consumiu detrito/sedimento, vegetais, algas e invertebrados aquáticos e terrestres. O predomínio espaço-temporal de detrito/sedimento e vegetais na dieta indicou hábito alimentar detritívoro com tendência a herbivoria. Diferenças significativas na proporção dos itens alimentares ocorreram entre os meses e locais amostrados, tendo sido relacionadas à disponibilidade dos recursos, caracterizando o oportunismo trófico da espécie.

Resource partitioning allows for interspecific coexistence and is frequently reported for similar species. Here, we predicted the existence of resource partitioning among species of Astyanax that co-occur in the Low Iguaçu River and tributaries in Brazil. A total of 848 stomachs of five species of Astyanax were analyzed. Algae, terrestrial plant and fruit/seed were the most consumed resources. Astyanax bifasciatus and A. dissimilis had predominantly herbivorous diets, A. gymnodontus and A. lacustris were omnivorous, and A. minor was mainly algivorous. Permutational analysis of variance showed the species had different diets, and similarity percentage analysis indicated that fruit/seed and terrestrial plant contributed the most to this differentiation. A paired comparison indicated that the trophic breadth of A. gymnodontus differed from that of other species. The food overlap was low for 55% of Astyanax pairs. These results showed alignment with the niche theory, in which differentiation in the use of food resources facilitates the coexistence of species and minimizes competition. These adjustments to coexistence become relevant in the context of endemic species in a highly isolated basin under intense threat (dams, species introduction, deforestation, and pollution) as is the case for the Iguaçu River basin.

The population structure, condition and reproductive period of Astyanax paranae adult individuals inhabiting a small reservoir were investigated. The fishes were quarterly captured from the riverine and lacustrine zones of the Alagados Reservoir, Paraná, Brazil, during 1996/1997 and 1998

Abstract:This study aimed to evaluate population abundance patterns and the main events in the reproductive cycle of Loricariichthys platymetopon at Saraiva Lagoon, Ilha Grande National Park, MS-PR, Brazil. Monthly samplings were conducted from October 2004 to September 2005 in three sections of the lagoon: entrance, middle and end, which resulted in the capture of 175 individuals. Spatial and temporal variation in abundance was obtained through CPUE (number of captured individuals/1000 m 2 of gillnets in 12 hours). The reproductive tactics considered were: duration, time and location of spawning, oocyte diameter and fecundity. The highest relative abundance was recorded in February, in the middle section of the lagoon, and the reproductive period lasted from September to February. The prevalence of females with spent ovaries and at rest in the following months indicated that reproductive activity ceased during autumn and winter. We observed that reproduction was high at the end section of the lagoon. The recorded mean oocyte diameter was 1.67 (SD ± 0.76) mm, mean absolute fecundity was 962.1 (SD ± 382.48) oocytes, and relative fecundity was 7.60 (SD ± 2.25) oocytes/g and 5.13 (SD ± 0.75) oocytes/cm. These tactics, probably are related to the settlement of L. platymetopom in Saraiva A variação espaço-temporal na abundância foi avaliada através da CPUE (nº de indivíduos capturados/1000 m 2 rede em 12 h de exposição). As táticas reprodutivas avaliadas foram duração, época e local de desova, diâmetro de ovócitos e fecundidade. A maior abundância relativa foi registrada em fevereiro, na região média da lagoa e o período reprodutivo estendeu-se de setembro a fevereiro. A prevalência de fêmeas com ovários esgotados e em repouso nos meses subseqüentes indicou que a atividade reprodutiva cessou no outono e inverno. Observou-se que a reprodução foi acentuada na região final da lagoa. O diâmetro médio de ovócitos registrado foi 1,67 (SD ± 0,76) mm, a fecundidade absoluta média 962,1 (SD ± 382,48) ovócitos e a fecundidade relativa 7,60 (SD ± 2,25) ovócitos/g e 5,13 (SD ± 0,75) ovócitos/cm. Essas táticas muito provavelmente, devem estar relacionadas à ocupação da lagoa Saraiva por L. platymetopom, bem como de outros biótopos da planície de inundação do alto rio Paraná. Palavras-chave: peixes, distribuição, diâmetro de ovócitos, fecundidade, período reprodutivo.

This study investigated the population parameters, condition and diet of Oligosarcus paranensis at Fiú and Mourão Reservoirs, located in Paraná State, Brazil. The fishes were collected quarterly between 1996/1997 and 1998/1999 using gillnets. Food items were quantified by volumetric method. The specimens at Fiú showed comparatively smaller length and worse condition. Sex ratio was statistically equal to 1:1 at Mourão, whereas there was a significant predominance of males at Fiú. Sex ratio also varied among size classes. Allometric growth prevailed among the studied groups. The diet consisted mainly of fishes and was complemented with invertebrates and plant matter in both reservoirs. There was a change in the feeding pattern as the standard length increased. Fishes changed from invertivores to piscivores, except for males in Mourão, for which a reverse trend occurred.

ABSTRACT. This study investigated the assemblages attributes (composition, abundance, richness, diversity and evenness) and the most representative genera of Odonata, Anisoptera at Água Boa and Perobão Streams, Iguatemi River basin, Brazil. Both are first order streams with similar length that are impacted by riparian forest removal and silting. Quarterly samplings were conducted from March to December 2008 in the upper, intermediate and lower stretch of each stream. The Mantel test was used to check the influence of spatial autocorrelation on the Odonata composition. Spatial variations in the composition were summarized by the Principal Coordinates Analysis (PCoA) using Mantel test residuals. The effects of spatial correlation on richness and abundance were investigated by the spatial correlogram of Moranʼs I coefficients. The most representative genera in each stream were identified by the Indicator Value Method. The spatial variations in the attributes of the assemblages were assessed using analysis of variance of null models. We collected 500 immature individuals of 23 genera and three families. Among the attributes analyzed only the composition and abundance showed significant spatial differences, with the highest mean abundance found in the Perobão Stream. Miathyria and Zenithoptera were the indicator genera of the Água Boa Stream and Erythrodiplax, Libellula, Macrothemis, Progomphus and Tramea were the indicator genera of the Perobão Stream. KEYWORDS.Aquatic invertebrates, Iguatemi River basin, lotic environments, odonatofauna.RESUMO. Assembleia de imaturos de Odonata (Insecta, Anisoptera) em riachos sul-matogrossenses: implicações espaciais. Este trabalho investigou atributos de assembleias (composição, abundância, riqueza, diversidade e equitabilidade) e os gêneros mais representativos de Odonata, Anisoptera nos riachos Água Boa e Perobão, bacia do rio Iguatemi, MS, Brasil. Os riachos são de primeira ordem, apresentam extensão similar e são impactados pela remoção da mata ripária e assoreamento. As amostragens foram realizadas trimestralmente de março a dezembro/2008 nos trechos superior, intermediário e inferior de ambos os riachos. O teste de Mantel foi utilizado para verificar a influência da autocorrelação espacial sobre a composição de Odonata. Variações espaciais na composição foram sumarizadas através da Análise de Coordenadas Principais (PCoA) utilizando-se os resíduos do teste de Mantel. Os efeitos da correlação espacial na riqueza e abundância foram investigados através do correlograma espacial dos coeficientes do I de Moran. Para identificar os gêneros mais representativos em cada riacho foi utilizado o Método do Valor Indicador. As variações espaciais dos atributos das assembleias foram avaliadas por meio de análises de variância de modelos nulos. Foram coletados 500 indivíduos imaturos distribuídos em 23 gêneros e três famílias. Dentre os atributos analisados, apenas a composição e abundância apresentaram diferenças espaciais significativas, sendo o maior valor médio do último atributo regi...