Morphological aspects in the ontogeny of Salminus hilarii Valenciennes, 1850 (Ostaryophysi: Characidae) / Aspectos Morfológicos na ontogenia de Salminus hilarii Valenciennes, 1850 (Ostaryophysi: Characidae)

This study compared various morphological characteristics of S. hilarii, in order to verify possible variations over the life of the fish. It was used individuals collected from the Tietê river basin (sub-basins of Sorocaba, Jacaré Pepira and Corumbataí rivers) and from the Rio Grande basin (sub-basins of Pardo and Mogi Guaçu rivers). For the analysis we used 15 relative values of morphological attributes. Measures of S. hilarii were taken from samples with a range of size ranging between 49-430 mm standard length. The relative values were first analyzed by an array of Principal Component Analysis of correlation (PCA). Subsequently the most important attributes of PCA were correlated with standard length, using the Pearson correlation coefficient. The PCA revealed eight most important characteristics, and six showed a significant correlation with standard lengths (relative height, depth ratio, relative area of caudal fin, relative head length, eye diameter relative height and relative mouth height), indicating common variations along the fishs growth besides indicating an adaptation to the conditions of the environment it occupies. On the other hand some characteristics have not changed, maintaining typical morphological patterns of fish that occupy the middle water and piscivorous predators.(AU)

Este trabalho comparou várias características morfológicas de S. hilarii, com a finalidade de verificar possíveis variações ao longo da vida do peixe. Foram utilizados indivíduos coletados nas bacias dos rios Tietê (sub-bacias dos rios Sorocaba, Jacaré Pepira e Corumbataí) e da bacia do rio Grande (sub-bacias dos rios Mogi Guaçu e Pardo). Para as análises foram utilizados 15 valores relativos de atributos morfológicos. As medidas de S. hilarii foram tomadas a partir de exemplares com uma amplitude de tamanho variando entre 49 a 430 mm de comprimento padrão. Os valores relativos foram analisados primeiramente por uma Análise de Componentes Principais (PCA). Posteriormente os atributos mais importantes da PCA foram correlacionados com o comprimento padrão, utilizando o coeficiente de correlação de Pearson. A análise de componentes principais revelou oito características mais importantes sendo que seis mostraram correlação significativa com os comprimentos padrão (altura relativa, razão de profundidade, área relativa da nadadeira caudal, comprimento relativo da cabeça, diâmetro relativo do olho, altura relativa da boca, indicando variações comuns ao longo do crescimento do peixe, além de, indicar uma adequação para as condições dos ambientes que ocupa. Por outro lado, outras características não mudaram, mantendo padrões morfológicos típicos de peixes que ocupam a meia água e de predadores piscívoros.(AU)

Morphological aspects in the ontogeny of Salminus hilarii Valenciennes, 1850 (Ostaryophysi: Characidae) / Aspectos Morfológicos na ontogenia de Salminus hilarii Valenciennes, 1850 (Ostaryophysi: Characidae)

Abstract This study compared various morphological characteristics of S. hilarii, in order to verify possible variations over the life of the fish. It was used individuals collected from the Tietê river basin (sub-basins of Sorocaba, Jacaré Pepira and Corumbataí rivers) and from the Rio Grande basin (sub-basins of Pardo and Mogi Guaçu rivers). For the analysis we used 15 relative values of morphological attributes. Measures of S. hilarii were taken from samples with a range of size ranging between 49-430 mm standard length. The relative values were first analyzed by an array of Principal Component Analysis of correlation (PCA). Subsequently the most important attributes of PCA were correlated with standard length, using the Pearson correlation coefficient. The PCA revealed eight most important characteristics, and six showed a significant correlation with standard lengths (relative height, depth ratio, relative area of caudal fin, relative head length, eye diameter relative height and relative mouth height), indicating common variations along the fish’s growth besides indicating an adaptation to the conditions of the environment it occupies. On the other hand some characteristics have not changed, maintaining typical morphological patterns of fish that occupy the middle water and piscivorous predators.

Resumo Este trabalho comparou várias características morfológicas de S. hilarii, com a finalidade de verificar possíveis variações ao longo da vida do peixe. Foram utilizados indivíduos coletados nas bacias dos rios Tietê (sub-bacias dos rios Sorocaba, Jacaré Pepira e Corumbataí) e da bacia do rio Grande (sub-bacias dos rios Mogi Guaçu e Pardo). Para as análises foram utilizados 15 valores relativos de atributos morfológicos. As medidas de S. hilarii foram tomadas a partir de exemplares com uma amplitude de tamanho variando entre 49 a 430 mm de comprimento padrão. Os valores relativos foram analisados primeiramente por uma Análise de Componentes Principais (PCA). Posteriormente os atributos mais importantes da PCA foram correlacionados com o comprimento padrão, utilizando o coeficiente de correlação de Pearson. A análise de componentes principais revelou oito características mais importantes sendo que seis mostraram correlação significativa com os comprimentos padrão (altura relativa, razão de profundidade, área relativa da nadadeira caudal, comprimento relativo da cabeça, diâmetro relativo do olho, altura relativa da boca, indicando variações comuns ao longo do crescimento do peixe, além de, indicar uma adequação para as condições dos ambientes que ocupa. Por outro lado, outras características não mudaram, mantendo padrões morfológicos típicos de peixes que ocupam a meia água e de predadores piscívoros.

Comparative feeding ecology of four syntopic Hypostomus species in a Brazilian southeastern river

Abstract Though their broad distribution in most Brazilian rivers, scarce studies concerning ecological interactions on Hypostomus species are available. This study observes the diet, the trophic interactions and some morphological aspects of four syntopic species of Hypostomus. These fishes were studied at the superior part of the Corumbataí river, at São Paulo state, southeastern Brazil. Analyses focused feeding patterns, their amplitude and whether there happens some food items overlap among the species. Fish were caught using cast nets at some points of the river. Species were chosen according to their local abundance and, so there were four main species: H. albopunctatus, H. ancistroides, H. regani and H. strigaticeps. Nine food items were found: sediments, fungi, diatoms, green algae, Tecamoeba, vegetal debris and invertebrates. There were not significant differences for the feeding pattern among the four Hypostomus species. The feeding niche amplitude has been larger for H. albopunctatus influenced by a larger amount of vegetal debris and invertebrates. Elevated niche overlap was found to happen among the species and also for their trophic morphology. Results may suggest that there is a similar pattern in food taken between four species of Hypostomus analyzed since all consume similar environmental resources and have similar anatomical features. However, a different intake insect larvae and plant material in H. albopunctatus diet indicate differences in local and how this species may be exploring their food compared to the others.(AU)

Resumo Apesar de sua grande distribuição em todos rios brasileiros, poucos estudos estão disponíveis sobre as interações ecológicas do gênero Hypostomus. Neste estudo nós examinamos a dieta, as interações tróficas e a morfologia de quatro espécies sintópicas de Hypostomus sp. no trecho superior do rio Corumbataí, estado de São Paulo no sudeste do Brasil. As análises focaram o padrão alimentar, a amplitude e sobreposição de nicho alimentar e a correlação entre a dieta com características da morfologia. A captura dos exemplares foi realizada com o uso de redes de arremesso (tarrafa) ao longo do leito do rio. O critério adotado para a escolha baseou-se nas espécies de maior abundância no local, chegando a quatros espécies principais: H. albopunctatus, H. ancistroides, H. regani e H. strigaticeps. Foram encontrados nove itens alimentares: sedimento grosso e fino, hifas de fungos, diatomáceas, algas verdes, algas azuis, Tecamoeba, restos de material vegetal e invertebrados, não havendo diferenças significativas no padrão alimentar entre as quatro espécies de Hypostomus. A amplitude de nicho alimentar foi maior para H. albopunctatus influenciada por um maior consumo de material vegetal e invertebrados. Foram encontrados altos valores de sobreposição de nicho alimentar além de uma similaridade entre a dieta e a morfologia trófica entre as espécies consideradas. Os resultados sugerem que exista um padrão semelhante na tomada de alimento entre as quatros espécies de Hypostomus analisadas, uma vez que, todas consomem recursos alimentares semelhantes e possuam características anatômicas semelhantes. No entanto, uma ingestão diferenciada de larvas de insetos e material vegetal na dieta de H. albopunctatus indicam diferenças nos locais e na forma como esta espécie pode estar explorando o seu alimento em comparação com as demais.(AU)

Comparative feeding ecology of four syntopic Hypostomus species in a Brazilian southeastern river / Ecologia alimentar comparativa de quatro espécies simpátricas de Hypostomus em um rio do sudoeste brasileiro

Abstract Though their broad distribution in most Brazilian rivers, scarce studies concerning ecological interactions on Hypostomus species are available. This study observes the diet, the trophic interactions and some morphological aspects of four syntopic species of Hypostomus. These fishes were studied at the superior part of the Corumbataí river, at São Paulo state, southeastern Brazil. Analyses focused feeding patterns, their amplitude and whether there happens some food items overlap among the species. Fish were caught using cast nets at some points of the river. Species were chosen according to their local abundance and, so there were four main species: H. albopunctatus, H. ancistroides, H. regani and H. strigaticeps. Nine food items were found: sediments, fungi, diatoms, green algae, Tecamoeba, vegetal debris and invertebrates. There were not significant differences for the feeding pattern among the four Hypostomus species. The feeding niche amplitude has been larger for H. albopunctatus influenced by a larger amount of vegetal debris and invertebrates. Elevated niche overlap was found to happen among the species and also for their trophic morphology. Results may suggest that there is a similar pattern in food taken between four species of Hypostomus analyzed since all consume similar environmental resources and have similar anatomical features. However, a different intake insect larvae and plant material in H. albopunctatus diet indicate differences in local and how this species may be exploring their food compared to the others.

Resumo Apesar de sua grande distribuição em todos rios brasileiros, poucos estudos estão disponíveis sobre as interações ecológicas do gênero Hypostomus. Neste estudo nós examinamos a dieta, as interações tróficas e a morfologia de quatro espécies sintópicas de Hypostomus sp. no trecho superior do rio Corumbataí, estado de São Paulo no sudeste do Brasil. As análises focaram o padrão alimentar, a amplitude e sobreposição de nicho alimentar e a correlação entre a dieta com características da morfologia. A captura dos exemplares foi realizada com o uso de redes de arremesso (tarrafa) ao longo do leito do rio. O critério adotado para a escolha baseou-se nas espécies de maior abundância no local, chegando a quatros espécies principais: H. albopunctatus, H. ancistroides, H. regani e H. strigaticeps. Foram encontrados nove itens alimentares: sedimento grosso e fino, hifas de fungos, diatomáceas, algas verdes, algas azuis, Tecamoeba, restos de material vegetal e invertebrados, não havendo diferenças significativas no padrão alimentar entre as quatro espécies de Hypostomus. A amplitude de nicho alimentar foi maior para H. albopunctatus influenciada por um maior consumo de material vegetal e invertebrados. Foram encontrados altos valores de sobreposição de nicho alimentar além de uma similaridade entre a dieta e a morfologia trófica entre as espécies consideradas. Os resultados sugerem que exista um padrão semelhante na tomada de alimento entre as quatros espécies de Hypostomus analisadas, uma vez que, todas consomem recursos alimentares semelhantes e possuam características anatômicas semelhantes. No entanto, uma ingestão diferenciada de larvas de insetos e material vegetal na dieta de H. albopunctatus indicam diferenças nos locais e na forma como esta espécie pode estar explorando o seu alimento em comparação com as demais.

Comparative feeding ecology of four syntopic Hypostomus species in a Brazilian southeastern river.

Though their broad distribution in most Brazilian rivers, scarce studies concerning ecological interactions on Hypostomus species are available. This study observes the diet, the trophic interactions and some morphological aspects of four syntopic species of Hypostomus. These fishes were studied at the superior part of the Corumbataí river, at São Paulo state, southeastern Brazil. Analyses focused feeding patterns, their amplitude and whether there happens some food items overlap among the species. Fish were caught using cast nets at some points of the river. Species were chosen according to their local abundance and, so there were four main species: H. albopunctatus, H. ancistroides, H. regani and H. strigaticeps. Nine food items were found: sediments, fungi, diatoms, green algae, Tecamoeba, vegetal debris and invertebrates. There were not significant differences for the feeding pattern among the four Hypostomus species. The feeding niche amplitude has been larger for H. albopunctatus influenced by a larger amount of vegetal debris and invertebrates. Elevated niche overlap was found to happen among the species and also for their trophic morphology. Results may suggest that there is a similar pattern in food taken between four species of Hypostomus analyzed since all consume similar environmental resources and have similar anatomical features. However, a different intake insect larvae and plant material in H. albopunctatus diet indicate differences in local and how this species may be exploring their food compared to the others.

Morphological aspects in the ontogeny of Salminus hilarii Valenciennes, 1850 (Ostaryophysi: Characidae).

This study compared various morphological characteristics of S. hilarii, in order to verify possible variations over the life of the fish. It was used individuals collected from the Tietê river basin (sub-basins of Sorocaba, Jacaré Pepira and Corumbataí rivers) and from the Rio Grande basin (sub-basins of Pardo and Mogi Guaçu rivers). For the analysis we used 15 relative values of morphological attributes. Measures of S. hilarii were taken from samples with a range of size ranging between 49-430 mm standard length. The relative values were first analyzed by an array of Principal Component Analysis of correlation (PCA). Subsequently the most important attributes of PCA were correlated with standard length, using the Pearson correlation coefficient. The PCA revealed eight most important characteristics, and six showed a significant correlation with standard lengths (relative height, depth ratio, relative area of caudal fin, relative head length, eye diameter relative height and relative mouth height), indicating common variations along the fish's growth besides indicating an adaptation to the conditions of the environment it occupies. On the other hand some characteristics have not changed, maintaining typical morphological patterns of fish that occupy the middle water and piscivorous predators.

Comparative feeding ecology of four syntopic Hypostomus species in a Brazilian southeastern river

Abstract Though their broad distribution in most Brazilian rivers, scarce studies concerning ecological interactions on Hypostomus species are available. This study observes the diet, the trophic interactions and some morphological aspects of four syntopic species of Hypostomus. These fishes were studied at the superior part of the Corumbataí river, at São Paulo state, southeastern Brazil. Analyses focused feeding patterns, their amplitude and whether there happens some food items overlap among the species. Fish were caught using cast nets at some points of the river. Species were chosen according to their local abundance and, so there were four main species: H. albopunctatus, H. ancistroides, H. regani and H. strigaticeps. Nine food items were found: sediments, fungi, diatoms, green algae, Tecamoeba, vegetal debris and invertebrates. There were not significant differences for the feeding pattern among the four Hypostomus species. The feeding niche amplitude has been larger for H. albopunctatus influenced by a larger amount of vegetal debris and invertebrates. Elevated niche overlap was found to happen among the species and also for their trophic morphology. Results may suggest that there is a similar pattern in food taken between four species of Hypostomus analyzed since all consume similar environmental resources and have similar anatomical features. However, a different intake insect larvae and plant material in H. albopunctatus diet indicate differences in local and how this species may be exploring their food compared to the others.

Resumo Apesar de sua grande distribuição em todos rios brasileiros, poucos estudos estão disponíveis sobre as interações ecológicas do gênero Hypostomus. Neste estudo nós examinamos a dieta, as interações tróficas e a morfologia de quatro espécies sintópicas de Hypostomus sp. no trecho superior do rio Corumbataí, estado de São Paulo no sudeste do Brasil. As análises focaram o padrão alimentar, a amplitude e sobreposição de nicho alimentar e a correlação entre a dieta com características da morfologia. A captura dos exemplares foi realizada com o uso de redes de arremesso (tarrafa) ao longo do leito do rio. O critério adotado para a escolha baseou-se nas espécies de maior abundância no local, chegando a quatros espécies principais: H. albopunctatus, H. ancistroides, H. regani e H. strigaticeps. Foram encontrados nove itens alimentares: sedimento grosso e fino, hifas de fungos, diatomáceas, algas verdes, algas azuis, Tecamoeba, restos de material vegetal e invertebrados, não havendo diferenças significativas no padrão alimentar entre as quatro espécies de Hypostomus. A amplitude de nicho alimentar foi maior para H. albopunctatus influenciada por um maior consumo de material vegetal e invertebrados. Foram encontrados altos valores de sobreposição de nicho alimentar além de uma similaridade entre a dieta e a morfologia trófica entre as espécies consideradas. Os resultados sugerem que exista um padrão semelhante na tomada de alimento entre as quatros espécies de Hypostomus analisadas, uma vez que, todas consomem recursos alimentares semelhantes e possuam características anatômicas semelhantes. No entanto, uma ingestão diferenciada de larvas de insetos e material vegetal na dieta de H. albopunctatus indicam diferenças nos locais e na forma como esta espécie pode estar explorando o seu alimento em comparação com as demais.

Variations of Salminus hilarii diet (Ostariophysi, Characidae): seasonal and ontogenetic effects.

This study described the variations seasonal and ontogenetic of Salminus hilarii diet. Samples were collected in the Sorocaba River, São Paulo, Brazil, one of the few rivers where individuals of the species still occur in a higher frequency. The preys consumed were analyzed by Importance Alimentary Index (AIi). To determine similarities between year seasons, the AIi data were analyzed by the Morisita-Horn index and reduced in cluster analysis, along with a statistical comparison made by one-way ANOSIM test (5%). The feeding activity was analyzed according to the stomach repletion index and compared among the year seasons using non parametric variance analysis Kruskal-Wallis test (5%). Comparison of prey consumed between immature and adult individuals was made by Spearman correlation (5%). A Pearson correlation (5%) was applied between the standard length of the fish and prey consumed, as well as between the mouth and prey heights. The analyzes of stomach contents showed that the diet of this species was exclusively piscivorous, with significant difference of prey consumption during the period, the same happening among adult and immature individuals. It was observed that these fishes use to swallow their prey whole and that significant correlations between size of predator and prey size can be observed. There is also correlation between the mouth height and the maximum prey depth. Salminus hilarii feeds on the available prey, and the species food composition and feeding activity depends on prey`s abundance, their size and morphology, as do the water temperatures.

Differences in the feeding of Rhamdia quelen (Siluriformes, Heptapteridae) in four distinct lotic systems.

The aim of this study was to compare the food composition of Rhamdia quelen in four distinct order rivers. It was performed at a low part at the basin of the Sorocaba river in systems classified as first (Anastácio stream), second (Nego stream), fifth (Tatuí river) and sixth (Sorocaba river) orders. Collections were performed every month between January and December of 2011. The stomach contents were examined by using the alimentary index (IAi) and compared by the non-parametric method non-metric multidimensional scale ranking (NMDS) with the Spearman rank correlation. A diet difference was observed for individuals of the smaller systems (Anastácio and Nego streams) and the larger ones (Tatui and Sorocaba rivers), represented respectively by allochthonous and autochthonous organisms compounding their diets. Marginal vegetation and its interaction with the water conditions may respond to these composition differences.

Variations of Salminus hilarii diet (Ostariophysi, Characidae): seasonal and ontogenetic effects / Variações na dieta de Salminus hilarii(Ostariophysi, Characidae): efeitos da sazonalidade e ontogenia

This study described the variations seasonal and ontogenetic of Salminus hilarii diet. Samples were collected in the Sorocaba River, São Paulo, Brazil, one of the few rivers where individuals of the species still occur in a higher frequency. The preys consumed were analyzed by Importance Alimentary Index (AIi). To determine similarities between year seasons, the AIi data were analyzed by the Morisita-Horn index and reduced in cluster analysis, along with a statistical comparison made by one-way ANOSIM test (5%). The feeding activity was analyzed according to the stomach repletion index and compared among the year seasons using non parametric variance analysis Kruskal-Wallis test (5%). Comparison of prey consumed between immature and adult individuals was made by Spearman correlation (5%). A Pearson correlation (5%) was applied between the standard length of the fish and prey consumed, as well as between the mouth and prey heights. The analyzes of stomach contents showed that the diet of this species was exclusively piscivorous, with significant difference of prey consumption during the period, the same happening among adult and immature individuals. It was observed that these fishes use to swallow their prey whole and that significant correlations between size of predator and prey size can be observed. There is also correlation between the mouth height and the maximum prey depth. Salminus hilarii feeds on the available prey, and the species food composition and feeding activity depends on prey`s abundance, their size and morphology, as do the water temperatures.(AU)

Este estudo descreve as variações na dieta de Salminus hilariiem relação aos efeitos da sazonalidade e da ontogenia. As coletas foram realizadas no rio Sorocaba, São Paulo, Brasil, um dos poucos rios onde a espécie ainda é encontrada com frequência. As presas consumidas foram analisadas pelo índice de importância alimentar (AIi). Para determinar similaridades entre as estações do ano, os dados do AIi foram analisados pelo índice de Morisita-Horn e reduzidos em uma análise de agrupamento, em associação com uma comparação estatística realizada pelo teste one-way ANOSIM (5%). A atividade alimentar foi analisada pelo índice de repleção estomacal e comparada entre as estações do ano usando o teste de variância não paramétrico de Kruskal-Wallis (5%). A comparação das presas consumidas entre os indivíduos imaturos e adultos foi feita pela correlação de Spearman (5%). Uma correlação de Pearson (5%) foi aplicada entre o comprimento padrão do peixe e da presa, assim como entre a altura da boca e a altura da presa. As análises dos conteúdos estomacais mostraram que a dieta dessa espécie foi exclusivamente piscívora, com diferença significativa do tipo de presas consumidas ao longo do ano e entre adultos e imaturos. Foi observado que esta espécie engole as presas inteiras com correlações significativas entre o tamanho do predador e presa e, também entre a altura da boca e altura da presa. Salminus hilarii consome as presas disponíveis no ambiente sendo que, a composição da dieta e a atividade alimentar dependem da abundância, tamanho e morfologia das presas, além da temperatura da água.(AU)

Differences in the feeding of Rhamdia quelen (Siluriformes, Heptapteridae) in four distinct lotic systems / Diferenças na alimentação de Rhamdia quelen em quatro diferentes ordens de sistemas lóticos

The aim of this study was to compare the food composition of Rhamdia quelen in four distinct order rivers. It was performed at a low part at the basin of the Sorocaba river in systems classified as first (Anastácio stream), second (Nego stream), fifth (Tatuí river) and sixth (Sorocaba river) orders. Collections were performed every month between January and December of 2011. The stomach contents were examined by using the alimentary index (IAi) and compared by the non-parametric method non-metric multidimensional scale ranking (NMDS) with the Spearman rank correlation. A diet difference was observed for individuals of the smaller systems (Anastácio and Nego streams) and the larger ones (Tatui and Sorocaba rivers), represented respectively by allochthonous and autochthonous organisms compounding their diets. Marginal vegetation and its interaction with the water conditions may respond to these composition differences.(AU)

Este estudo teve como objetivo comparar a alimentação de Rhamdia quelenem quatro diferentes ordens de sistemas lóticos. O estudo foi realizado em um trecho da parte baixa da bacia do rio Sorocaba, em sistemas de primeira (Anastácio stream), segunda (Nego stream), quinta (Tatuí river) e sexta (Sorocaba river) ordens. As coletas foram realizadas mensalmente entre janeiro a dezembro de 2011. Os conteúdos estomacais foram analisados pelo índice alimentar (IAi) e comparados pelo método de escalonamento multidimencional não-metrico (NMDS), juntamente com a correlação de Spearman. Foi percebida uma diferença na dieta dos indivíduos dos sistemas menores, córregos Anastácio e Nego e os rios maiores, rios Tatuí e Sorocaba. Nos córregos Nego e Anastácio houve maior incidência de itens de origem alóctone na dieta, enquanto que nos rios Tatuí e Sorocaba foi observado o inverso. A diferença nos itens consumidos pode depender da ordem dos sistemas lóticos e da interação entre a vegetação marginal com o sistema aquático.(AU)

Variations of Salminus hilarii diet (Ostariophysi, Characidae): seasonal and ontogenetic effects / Variações na dieta de Salminus hilarii(Ostariophysi, Characidae): efeitos da sazonalidade e ontogenia.

AbstractThis study described the variations seasonal and ontogenetic of Salminus hilarii diet. Samples were collected in the Sorocaba River, São Paulo, Brazil, one of the few rivers where individuals of the species still occur in a higher frequency. The preys consumed were analyzed by Importance Alimentary Index (AIi). To determine similarities between year seasons, the AIi data were analyzed by the Morisita-Horn index and reduced in cluster analysis, along with a statistical comparison made by one-way ANOSIM test (5%). The feeding activity was analyzed according to the stomach repletion index and compared among the year seasons using non parametric variance analysis Kruskal-Wallis test (5%). Comparison of prey consumed between immature and adult individuals was made by Spearman correlation (5%). A Pearson correlation (5%) was applied between the standard length of the fish and prey consumed, as well as between the mouth and prey heights. The analyzes of stomach contents showed that the diet of this species was exclusively piscivorous, with significant difference of prey consumption during the period, the same happening among adult and immature individuals. It was observed that these fishes use to swallow their prey whole and that significant correlations between size of predator and prey size can be observed. There is also correlation between the mouth height and the maximum prey depth. Salminus hilarii feeds on the available prey, and the species food composition and feeding activity depends on prey`s abundance, their size and morphology, as do the water temperatures.

ResumoEste estudo descreve as variações na dieta de Salminus hilariiem relação aos efeitos da sazonalidade e da ontogenia. As coletas foram realizadas no rio Sorocaba, São Paulo, Brasil, um dos poucos rios onde a espécie ainda é encontrada com frequência. As presas consumidas foram analisadas pelo índice de importância alimentar (AIi). Para determinar similaridades entre as estações do ano, os dados do AIi foram analisados pelo índice de Morisita-Horn e reduzidos em uma análise de agrupamento, em associação com uma comparação estatística realizada pelo teste one-way ANOSIM (5%). A atividade alimentar foi analisada pelo índice de repleção estomacal e comparada entre as estações do ano usando o teste de variância não paramétrico de Kruskal-Wallis (5%). A comparação das presas consumidas entre os indivíduos imaturos e adultos foi feita pela correlação de Spearman (5%). Uma correlação de Pearson (5%) foi aplicada entre o comprimento padrão do peixe e da presa, assim como entre a altura da boca e a altura da presa. As análises dos conteúdos estomacais mostraram que a dieta dessa espécie foi exclusivamente piscívora, com diferença significativa do tipo de presas consumidas ao longo do ano e entre adultos e imaturos. Foi observado que esta espécie engole as presas inteiras com correlações significativas entre o tamanho do predador e presa e, também entre a altura da boca e altura da presa. Salminus hilarii consome as presas disponíveis no ambiente sendo que, a composição da dieta e a atividade alimentar dependem da abundância, tamanho e morfologia das presas, além da temperatura da água.

Differences in the feeding of Rhamdia quelen (Siluriformes, Heptapteridae) in four distinct lotic systems / Diferenças na alimentação de Rhamdia quelen em quatro diferentes ordens de sistemas lóticos

AbstractThe aim of this study was to compare the food composition of Rhamdia quelen in four distinct order rivers. It was performed at a low part at the basin of the Sorocaba river in systems classified as first (Anastácio stream), second (Nego stream), fifth (Tatuí river) and sixth (Sorocaba river) orders. Collections were performed every month between January and December of 2011. The stomach contents were examined by using the alimentary index (IAi) and compared by the non-parametric method non-metric multidimensional scale ranking (NMDS) with the Spearman rank correlation. A diet difference was observed for individuals of the smaller systems (Anastácio and Nego streams) and the larger ones (Tatui and Sorocaba rivers), represented respectively by allochthonous and autochthonous organisms compounding their diets. Marginal vegetation and its interaction with the water conditions may respond to these composition differences.

ResumoEste estudo teve como objetivo comparar a alimentação de Rhamdia quelenem quatro diferentes ordens de sistemas lóticos. O estudo foi realizado em um trecho da parte baixa da bacia do rio Sorocaba, em sistemas de primeira (Anastácio stream), segunda (Nego stream), quinta (Tatuí river) e sexta (Sorocaba river) ordens. As coletas foram realizadas mensalmente entre janeiro a dezembro de 2011. Os conteúdos estomacais foram analisados pelo índice alimentar (IAi) e comparados pelo método de escalonamento multidimencional não-metrico (NMDS), juntamente com a correlação de Spearman. Foi percebida uma diferença na dieta dos indivíduos dos sistemas menores, córregos Anastácio e Nego e os rios maiores, rios Tatuí e Sorocaba. Nos córregos Nego e Anastácio houve maior incidência de itens de origem alóctone na dieta, enquanto que nos rios Tatuí e Sorocaba foi observado o inverso. A diferença nos itens consumidos pode depender da ordem dos sistemas lóticos e da interação entre a vegetação marginal com o sistema aquático.

Reproductive biology of the smooth butterfly ray Gymnura micrura.

This study provides the first detailed information on the reproductive biology of the smooth butterfly ray Gymnura micrura. A total of 905 individuals were sampled, 377 of which were used for the reproductive study. Juveniles accounted for 75% of the sample, but all life cycle stages were present in the study area. The disc width at which 50% were mature (W(D50))was estimated at 269 and 405 mm for males and females, respectively. The W(D50V) (based on the onset of vitellogenesis) was estimated at 359 mm. Uterine fecundity (mean ±s.d. = 3·8 ± 1·3; range: 1-6) was positively correlated with female size. A 3564% gain in mean wet mass was observed from egg to full-term embryo in utero. Size at birth ranged from 135 to 175 mm W(D) (19·5 to 55·0 g), with a mean of 165·1 mm W(D) (43·3 g). The embryo sex ratio was not significantly different from 1:1. The ovaries of pregnant females were undergoing vitellogenesis during gestation, with females ready to ovulate soon after parturition. Gymnura micrura may have an asynchronous reproductive cycle, with females reproducing continuously throughout the year.

Biological aspects of Schizodon nasutus Kner, 1858 (Characiformes, Anostomidae) in the low Sorocaba river basin, São Paulo state, Brazil.

Four biological aspects of Schizodon nasutus in the low Sorocaba river basin, São Paulo, Brazil were analysed. These were accomplished during the year seasons. The fish diet and the feeding activity were investigated by studying the repletion index, which showed no significant differences between seasons. The food items analysed by frequency of occurrence and dominance showed a predominance of vegetable items in the diet. The reproduction, analysed by using the gonadosomatic index, indicated that the reproductive period occurs during the summer period when temperatures are higher and rainfalls are more intense. The amount of accumulated fat and condition factor varied according to reproduction, especially for females.

Biological aspects of Schizodon nasutus Kner, 1858 (Characiformes, Anostomidae) in the low Sorocaba river basin, São Paulo state, Brazil / Aspectos da biologia de Schizodon nasutus Kner, 1858 (Characiformes, Anostomidae) no trecho inferior da bacia do rio Sorocaba, estado de São Paulo, Brasil

Four biological aspects of Schizodon nasutus in the low Sorocaba river basin, São Paulo, Brazil were analysed. These were accomplished during the year seasons. The fish diet and the feeding activity were investigated by studying the repletion index, which showed no significant differences between seasons. The food items analysed by frequency of occurrence and dominance showed a predominance of vegetable items in the diet. The reproduction, analysed by using the gonadosomatic index, indicated that the reproductive period occurs during the summer period when temperatures are higher and rainfalls are more intense. The amount of accumulated fat and condition factor varied according to reproduction, especially for females.(AU)

Foram analisados quatro aspectos da biologia de Schizodon nasutus no trecho inferior da bacia do rio Sorocaba, estado de São Paulo, Brasil. Esses aspectos foram abordados durante as estações do ano. Na dieta da espécie, a atividade alimentar averiguada pelo índice de repleção estomacal não mostrou diferença significativa entre as estações. Os itens alimentares analisados pela frequência de ocorrência e dominância mostraram a predominância de itens de origem vegetal na dieta. A reprodução, analisada pela relação gonadossomática, indicou que o período reprodutivo ocorre durante o verão, quando há aumento de temperatura da água e das chuvas. A quantidade de gordura acumulada e o fator de condição variaram de acordo com a reprodução, principalmente para as fêmeas.(AU)

Biological aspects of Schizodon nasutus Kner, 1858 (Characiformes, Anostomidae) in the low Sorocaba river basin, São Paulo state, Brazil / Aspectos da biologia de Schizodon nasutus Kner, 1858 (Characiformes, Anostomidae) no trecho inferior da bacia do rio Sorocaba, estado de São Paulo, Brasil

Four biological aspects of Schizodon nasutus in the low Sorocaba river basin, São Paulo, Brazil were analysed. These were accomplished during the year seasons. The fish diet and the feeding activity were investigated by studying the repletion index, which showed no significant differences between seasons. The food items analysed by frequency of occurrence and dominance showed a predominance of vegetable items in the diet. The reproduction, analysed by using the gonadosomatic index, indicated that the reproductive period occurs during the summer period when temperatures are higher and rainfalls are more intense. The amount of accumulated fat and condition factor varied according to reproduction, especially for females.

Foram analisados quatro aspectos da biologia de Schizodon nasutus no trecho inferior da bacia do rio Sorocaba, estado de São Paulo, Brasil. Esses aspectos foram abordados durante as estações do ano. Na dieta da espécie, a atividade alimentar averiguada pelo índice de repleção estomacal não mostrou diferença significativa entre as estações. Os itens alimentares analisados pela frequência de ocorrência e dominância mostraram a predominância de itens de origem vegetal na dieta. A reprodução, analisada pela relação gonadossomática, indicou que o período reprodutivo ocorre durante o verão, quando há aumento de temperatura da água e das chuvas. A quantidade de gordura acumulada e o fator de condição variaram de acordo com a reprodução, principalmente para as fêmeas.

Diet and feeding activity of Acestrorhynchus lacustris (Lütken, 1875) (Characiformes, Acestrorhynchidae) in the water reservoir at Ribeirão Claro, SP.

A. lacustris is a widely distributed species in the São Francisco and Paraná river basins, mainly in lentic waters. Specimens were captured monthly, over a whole year in a reservoir built by damming the Ribeirão Claro stream (SP). The stomach contents analyses showed a predominantly piscivorous diet. Feeding activity showed to be clearly less intense during winter, when all the sampling groups were compared. Despite the fact that the diet of A. lacustris presents a high diversity of prey-species, the prey size, their abundance and also behavior possibly determined a certain preference for some of them.

Diet and feeding activity of Acestrorhynchus lacustris (Lütken, 1875) (Characiformes, Acestrorhynchidae) in the water reservoir at Ribeirão Claro, SP / Dieta e atividade alimentar de Acestrorhynchus lacustris (Lütken, 1875) (Characiformes, Acestrorhynchidae) no reservatório de captação de água do Ribeirão Claro, SP

A. lacustris is a widely distributed species in the São Francisco and Paraná river basins, mainly in lentic waters. Specimens were captured monthly, over a whole year in a reservoir built by damming the Ribeirão Claro stream (SP). The stomach contents analyses showed a predominantly piscivorous diet. Feeding activity showed to be clearly less intense during winter, when all the sampling groups were compared. Despite the fact that the diet of A. lacustris presents a high diversity of prey-species, the prey size, their abundance and also behavior possibly determined a certain preference for some of them.

O peixe cachorro, Acestrorhynchus lacustris, encontra-se amplamente distribuído nas bacias do rio São Francisco e do alto rio Paraná, sobretudo nos locais de caráter lêntico. Ao longo de um ano, foram capturados mensalmente exemplares desta espécie no reservatório de captação de água do Ribeirão Claro. A análise do conteúdo estomacal dos exemplares capturados revelou uma dieta predominantemente piscívora. Durante o inverno, foi constatada uma diminuição acentuada da atividade alimentar do peixe-cachorro. Apesar de apresentar uma diversidade relativamente alta de espécies-presa, foi observada certa predileção por algumas, cujo tamanho, abundância e comportamento, foram os prováveis fatores determinantes.

Diet and feeding activity of Acestrorhynchus lacustris (Lütken, 1875) (Characiformes, Acestrorhynchidae) in the water reservoir at Ribeirão Claro, SP

A. lacustris is a widely distributed species in the São Francisco and Paraná river basins, mainly in lentic waters. Specimens were captured monthly, over a whole year in a reservoir built by damming the Ribeirão Claro stream (SP). The stomach contents analyses showed a predominantly piscivorous diet. Feeding activity showed to be clearly less intense during winter, when all the sampling groups were compared. Despite the fact that the diet of A. lacustris presents a high diversity of prey-species, the prey size, their abundance and also behavior possibly determined a certain preference for some of them.

O peixe cachorro, Acestrorhynchus lacustris, encontra-se amplamente distribuído nas bacias do rio São Francisco e do alto rio Paraná, sobretudo nos locais de caráter lêntico. Ao longo de um ano, foram capturados mensalmente exemplares desta espécie no reservatório de captação de água do Ribeirão Claro. A análise do conteúdo estomacal dos exemplares capturados revelou uma dieta predominantemente piscívora. Durante o inverno, foi constatada uma diminuição acentuada da atividade alimentar do peixe-cachorro. Apesar de apresentar uma diversidade relativamente alta de espécies-presa, foi observada certa predileção por algumas, cujo tamanho, abundância e comportamento, foram os prováveis fatores determinantes.