Diet of invertebrates sampled in leaf-bags incubated in a tropical headwater stream

The diet of macroinvertebrates sampled in leaf-bags incubated in a tropical stream was analyzed on a spatial scale (one forested and one deforested area) and on a temporal scale (dry and rainy seasons). The macroinvertebrates were mostly represented by detritivores specialized in fine detritus (69%), followed by generalist detritivores (10% with a diet based on fine and coarse detritus), carnivores (10%), omnivores (8%), and one detritivore genera specialized on coarse detritus (3%). The detritivores exhibited a broad spatial and temporal distribution and were represented mainly by Ephemeroptera, Trichoptera and Diptera. Phylloicus sp. (Trichoptera) consumed mostly coarse detritus (CPOM) and can be classified as the unique specialist shredder in this stream. Carnivores were represented by Anacroneuria sp. (Plecoptera), Hetaerina sp. and Heteragrion sp. (two Odonata). Omnivory was observed for Anacroneuria sp. and Smicridea sp. (Trichoptera), which evidently varied spatially and temporally in the proportion of the food consumed. The high diversity and the wide distribution of the taxa that used organic matter as food resource demonstrated the great importance of this food item to the macroinvertebrates community in this tropical stream.

Diet of invertebrates sampled in leaf-bags incubated in a tropical headwater stream

The diet of macroinvertebrates sampled in leaf-bags incubated in a tropical stream was analyzed on a spatial scale (one forested and one deforested area) and on a temporal scale (dry and rainy seasons). The macroinvertebrates were mostly represented by detritivores specialized in fine detritus (69%), followed by generalist detritivores (10% with a diet based on fine and coarse detritus), carnivores (10%), omnivores (8%), and one detritivore genera specialized on coarse detritus (3%). The detritivores exhibited a broad spatial and temporal distribution and were represented mainly by Ephemeroptera, Trichoptera and Diptera. Phylloicus sp. (Trichoptera) consumed mostly coarse detritus (CPOM) and can be classified as the unique specialist shredder in this stream. Carnivores were represented by Anacroneuria sp. (Plecoptera), Hetaerina sp. and Heteragrion sp. (two Odonata). Omnivory was observed for Anacroneuria sp. and Smicridea sp. (Trichoptera), which evidently varied spatially and temporally in the proportion of the food consumed. The high diversity and the wide distribution of the taxa that used organic matter as food resource demonstrated the great importance of this food item to the macroinvertebrates community in this tropical stream.

Diet of invertebrates sampled in leaf-bags incubated in a tropical headwater stream

The diet of macroinvertebrates sampled in leaf-bags incubated in a tropical stream was analyzed on a spatial scale (one forested and one deforested area) and on a temporal scale (dry and rainy seasons). The macroinvertebrates were mostly represented by detritivores specialized in fine detritus (69%), followed by generalist detritivores (10% with a diet based on fine and coarse detritus), carnivores (10%), omnivores (8%), and one detritivore genera specialized on coarse detritus (3%). The detritivores exhibited a broad spatial and temporal distribution and were represented mainly by Ephemeroptera, Trichoptera and Diptera. Phylloicus sp. (Trichoptera) consumed mostly coarse detritus (CPOM) and can be classified as the unique specialist shredder in this stream. Carnivores were represented by Anacroneuria sp. (Plecoptera), Hetaerina sp. and Heteragrion sp. (two Odonata). Omnivory was observed for Anacroneuria sp. and Smicridea sp. (Trichoptera), which evidently varied spatially and temporally in the proportion of the food consumed. The high diversity and the wide distribution of the taxa that used organic matter as food resource demonstrated the great importance of this food item to the macroinvertebrates community in this tropical stream.

Diet of the ichthyofauna associated with marginal vegetation of a mangrove forest in southeastern Brazil

The objective of this study was to analyze the diet of fish species that use the mangrove vegetation for shelter and feeding in a river southeastern Brazil. The fieldwork, including collecting and underwater observations, was carried out in the dry (July and August 2004) and in the rainy season (February and March 2005) in order to assess the existence of seasonal variation in the diets. Seven kinds of food items were consumed, two of plant origin and five of animal origin. Crustaceans predominated in the diet of most species, either in the form of unidentified fragments or discriminated in eight groups. The predominance of species using mainly a single food source (crustaceans, principally Ostracoda and Tanaidacea) and the existence of seasonal variation in the diets of some species became very evident in the analysis food niche breadth, with a predominance of dietary specialists. In the Rio da Fazenda mangrove, the submersed marginal vegetation was used by the ichthyofauna as a locale for foraging, and principally as cover by bottom-feeding species. These species may be using the vegetation for protection from aerial and aquatic predators, or even from the pull of the current during the turn of the tide. In the study area, the great diversity of crustaceans constitutes an important food source for most fish species which adjusted their diet according to seasonal changes in food availability and to interactions with other species.

O presente trabalho objetivou analisar a dieta das espécies de peixes que utilizam a vegetação do mangue do Rio da Fazenda como local de abrigo e alimentação em um rio do sudeste do Brasil. O trabalho de campo, incluindo coleta e observação subaquática das espécies, foi realizado na estação seca (julho e agosto de 2004) e na chuvosa (fevereiro e março de 2005) com o objetivo de verificar a existência de variação sazonal na dieta. Sete tipos de itens alimentares foram consumidos pelas espécies, dois de origem vegetal e cinco de origem animal. Os crustáceos predominaram na dieta da maioria das espécies, seja na forma de fragmentos não identificados ou discriminados em oito grupos. O predomínio de espécies utilizando essencialmente uma única fonte alimentar (crustáceos, principalmente Ostracoda e Tanaidacea) e a existência de variação sazonal na dieta de algumas espécies ficaram bem evidentes na análise de amplitude do nicho alimentar, com um predomínio de espécies especialistas. No mangue do Rio da Fazenda, a vegetação marginal submersa foi utilizada pela ictiofauna como local de forrageamento e, principalmente, como cobertura para espécies que buscavam alimento no substrato do fundo. Estas espécies podem estar utilizando a vegetação como proteção contra predadores aéreos e aquáticos, ou mesmo contra o arraste no período de mudança das marés. Na área de estudo, a grande diversidade de crustáceos constituiu uma importante fonte de alimento para a maioria das espécies, as quais ajustaram sua dieta em função de variações sazonais na oferta e em função das interações com outras espécies.

Diet of the ichthyofauna associated with marginal vegetation of a mangrove forest in southeastern Brazil

The objective of this study was to analyze the diet of fish species that use the mangrove vegetation for shelter and feeding in a river southeastern Brazil. The fieldwork, including collecting and underwater observations, was carried out in the dry (July and August 2004) and in the rainy season (February and March 2005) in order to assess the existence of seasonal variation in the diets. Seven kinds of food items were consumed, two of plant origin and five of animal origin. Crustaceans predominated in the diet of most species, either in the form of unidentified fragments or discriminated in eight groups. The predominance of species using mainly a single food source (crustaceans, principally Ostracoda and Tanaidacea) and the existence of seasonal variation in the diets of some species became very evident in the analysis food niche breadth, with a predominance of dietary specialists. In the Rio da Fazenda mangrove, the submersed marginal vegetation was used by the ichthyofauna as a locale for foraging, and principally as cover by bottom-feeding species. These species may be using the vegetation for protection from aerial and aquatic predators, or even from the pull of the current during the turn of the tide. In the study area, the great diversity of crustaceans constitutes an important food source for most fish species which adjusted their diet according to seasonal changes in food availability and to interactions with other species.

O presente trabalho objetivou analisar a dieta das espécies de peixes que utilizam a vegetação do mangue do Rio da Fazenda como local de abrigo e alimentação em um rio do sudeste do Brasil. O trabalho de campo, incluindo coleta e observação subaquática das espécies, foi realizado na estação seca (julho e agosto de 2004) e na chuvosa (fevereiro e março de 2005) com o objetivo de verificar a existência de variação sazonal na dieta. Sete tipos de itens alimentares foram consumidos pelas espécies, dois de origem vegetal e cinco de origem animal. Os crustáceos predominaram na dieta da maioria das espécies, seja na forma de fragmentos não identificados ou discriminados em oito grupos. O predomínio de espécies utilizando essencialmente uma única fonte alimentar (crustáceos, principalmente Ostracoda e Tanaidacea) e a existência de variação sazonal na dieta de algumas espécies ficaram bem evidentes na análise de amplitude do nicho alimentar, com um predomínio de espécies especialistas. No mangue do Rio da Fazenda, a vegetação marginal submersa foi utilizada pela ictiofauna como local de forrageamento e, principalmente, como cobertura para espécies que buscavam alimento no substrato do fundo. Estas espécies podem estar utilizando a vegetação como proteção contra predadores aéreos e aquáticos, ou mesmo contra o arraste no período de mudança das marés. Na área de estudo, a grande diversidade de crustáceos constituiu uma importante fonte de alimento para a maioria das espécies, as quais ajustaram sua dieta em função de variações sazonais na oferta e em função das interações com outras espécies.