Most loricariids are algivorous and detritivorous and play an important role in both the grazer and detritus food chains of neotropical waters. Relationships between morphological variation and diet were analysed in six syntopic species (Rhinelepis aspera, Hypostomus regani, H. ternetzi, H. margaritifer, H. microstomus and Megalancistrus aculeatus) fished commercially in a 10 km 2 area of the Upper Paraná River upstream from the Itaipu Reservoir. Species feeding on fine grained detritus use suction to obtain food, and possess a well-developed respiratory membrane, long gill rakers, rudimentary labial and pharyngeal teeth, a thin stomach wall, and a long intestine. Species feeding on coarser material (e.g. periphyton), ingest food by scraping the substratum. Their morphological characteristics are large, strong, spatulate teeth, short gill rakers, a well-developed stomach, and a shorter intestine. The first species group is composed by R. aspera while the latter by M. aculeatus and H. microstomus. The others species had an intermediary position. 2001 The Fisheries Society of the British Isles

This study examined the diet and trophic structure of the fish fauna, over temporal and spatial scales, as affected by the impoundment of the Iguaçu River in the region of Salto Caxias, Paraná State, Brazil. Sampling was conducted before (March 1997 - February 1998) and after the impoundment (March 1999 - February 2000), at four sampling sites. The stomach contents were analyzed by the volumetric method. The species could be organized in 10 trophic guilds: algivores, carcinophages, detritivores, herbivores, aquatic insectivores, terrestrial insectivores, invertivores, omnivores, piscivores, and planktivores; the first and last guilds were represented only in the post-impoundment period. Similarity patterns and feeding changes were summarized by a non-metric Multi-dimensional Scaling (nMDS) analysis and statistically tested by a Permutational multivariate analysis of variance (PERMANOVA). Most species showed feeding changes, except for the piscivores and detritivores. These changes were related to the temporal factor (impoundment phases), such as reduced intake of benthic organisms and allochthonous food, which were usually replaced by resources from the reservoir itself (algae, microcrustaceans, and fish), simplifying the food spectrum of the fish fauna. A different indicator of food resources (IndVal) corroborated these changes in the feeding of the species. The proportions of the trophic guilds evaluated based on the catch per unit of effort (CPUE) and tested by ANOSIM were significantly different before and after the impoundment. Herbivores and piscivores were the guilds that contributed (SIMPER) to these differences, especially the high increase in biomass of the piscivore guild after the impoundment. Variations in the abundance of trophic guilds were more directly related to changes in the feeding habits of the fish fauna than to increases in the number and biomass of the species that constitute these guilds.

Most loricariids are algivorous and detritivorous and play an important role in both the grazer and detritus food chains of neotropical waters. Relationships between morphological variation and diet were analysed in six syntopic species (Rhinelepis aspera, Hypostomus regani, H. ternetzi, H. margaritifer, H. microstomus and Megalancistrus aculeatus) fished commercially in a 10 km 2 area of the Upper Paraná River upstream from the Itaipu Reservoir. Species feeding on fine grained detritus use suction to obtain food, and possess a well-developed respiratory membrane, long gill rakers, rudimentary labial and pharyngeal teeth, a thin stomach wall, and a long intestine. Species feeding on coarser material (e.g. periphyton), ingest food by scraping the substratum. Their morphological characteristics are large, strong, spatulate teeth, short gill rakers, a well-developed stomach, and a shorter intestine. The first species group is composed by R. aspera while the latter by M. aculeatus and H. microstomus. The others species had an intermediary position. 2001 The Fisheries Society of the British Isles

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at 24 sampling sites. For analytical purposes, the sampling sites were grouped into upper, middle and lower areas. The upper area of the National Park had the highest egg density and should be considered the primary spawning area. The middle area should be considered a drift area, and the lower area likely functions as a growth and feeding habitat. Statistical analyses showed that the spawning was influenced by water temperature, pH, fluviometric level and rainfall, and that larval density was influenced by pH, conductivity, dissolved oxygen and rainfall. The results also revealed that the tributaries apparently are used as migratory routes by fish, and and this shows the need to protect these sites.O objetivo deste trabalho foi estudar a ocorrência de ictioplâncton em uma região sob influência de barragens. A área de estudo está localizada na região do Parque Nacional de Ilha Grande, planície de inundação do Alto Rio Paraná. Especificamente, analisamos a distribuição temporal e espacial do ictioplâncton, identificando áreas de desova e estabelecendo relações entre a abundância de ovos e larvas de peixes e algumas variáveis limnológicas e hidrológicas. Amostras foram coletadas mensalmente entre outubro e março de 2001 a 2005 em 24 pontos de amostragem. Para fins de análise as estações de amostragens foram agrupadas em área superior, média e inferior. A parte superior da área do Parque Nacional apresentou a maior densidade de ovos e pode ser considerada como local de desova, enquanto que a área central pode ser considerada local de deriva, e a área inferior funciona como um provável local de crescimento e alimentação das larvas. As análises estatísticas mostraram que as desovas foram influenciadas pela temperatura da água, pH, nível fluviométrico e precipitação, e que a densidade de larvas foi influenciada pelo pH, condutividade, oxigênio dissolvido e precipitação. Os resultados também revelaram que os afluentes aparentemente são utilizados como rotas migratórias de peixes, e isso demonstra a necessidade de proteção destes locais.

This study addressed the feeding ecology of fish fauna from a first-order stream located in a rural area. The purposes were to evaluate the influence of interspecific, seasonal and spatial factors on the diet, examine the dietary overlap, and determine the predominant food sources. Sampling was conducted in December 2007, September 2008, and March 2009, in three 50-m stretches of Itiz stream (upstream, intermediate, and downstream), through electrofishing. A total of 1,102 stomach contents were analyzed from 14 species, by the volumetric method. In general, allochthonous resources were predominant in the diets. Astyanax aff. fasciatus, Astyanax aff. paranae, Astyanax bockmanni, and Bryconamericus aff. iheringi consumed a higher proportion of plant remains, and Bryconamericus stramineus consumed predominantly Hymenoptera. The diets of Cetopsorhamdia iheringi, Characidium aff. zebra, Imparfinis schubarti, and Trichomycterus sp. consisted of aquatic insects, especially immature forms of Trichoptera, Ephemeroptera, Plecoptera, and Diptera. Hypostomus ancistroides, Hisonotus sp., Poecilia reticulata, and Rineloricaria aff. pentamaculata exploited mainly detritus, while Rhamdia quelen used a variety of items, predominantly terrestrial insects. Detrended Correspondence Analysis (DCA) showed a clear distinction among the species, with different morphology and feeding tactics. The Multi-Response Permutation Procedure (MRPP) supported this differentiation, and also indicated significant spatial and temporal variations in the dietary composition; the Indicator Value Method (IndVal) indicated the main items that contributed to these differences. The diet overlap among species was low (< 0.4) to around 78% of pairs, and the mean value did not vary significantly among the sites or between hydrological periods within each site. According to the null model of Pianka's index, the values for dietary overlap were significantly higher than expected at random, showing evidence of resource sharing. This was related to the availability of allochthonous resources, highlighting the importance of riparian vegetation as a source of these resources for maintaining the fish fauna of the stream.Este estudo abordou a ecologia alimentar da ictiofauna de um riacho de primeira ordem situado em área rural. Os objetivos foram verificar a influência dos fatores interespecíficos, sazonais e espaciais sobre a dieta, avaliar a sobreposição alimentar, além de determinar os recursos alimentares predominantes. As amostragens foram realizadas em dezembro/2007, setembro/ 2008 e março/2009, em três pontos do riacho Itiz (montante, intermediário e foz) com extensões de 50 m, através de pesca elétrica. Foram analisados 1102 conteúdos estomacais referentes a 14 espécies de acordo com o método volumétrico. De forma geral observou-se que a maior contribuição na dieta das espécies foi de recursos alóctones. Astyanax aff. fasciatus, Astyanax aff. paranae, Astyanax bockmanni, Bryconamericus aff. iheringi, consumiram maior proporção de vegetal e Bryconamericus stram...

The objective of this study was to assess the abundance, attributes of assemblages, and spatial and temporal distributions of fish larvae and their relationships with some abiotic variables in two floodplain lakes with different degrees of connection to the Paraná River in Ilha Grande National Park, PR, Brazil. Four sampling sites were chosen, two in each floodplain lake. Night samples were taken with plankton nets during three spawning seasons (monthly, from October to March) from 2001 to 2005. The highest diversity and abundance were recorded at Saraiva Lake, with 25 taxa being identified. In Xambrê Lake, only sedentary species were captured, and the most abundant species were Plagioscion squamosissimus and Hypophthalmus edentatus. The greatest abundance of larvae was found in the second spawning season. In the Saraiva Lake, the most abundant species were Moenkhausia aff. intermedia, Hyphessobrycon sp., and Bryconamericus stramineus, but larvae of known migratory species were also documented. In this lake, the greatest abundance of larvae was found in the third spawning. Larvae abundance was influenced by water temperature and conductivity. The high diversity and abundance recorded in Saraiva Lake may be a result of its connectivity with the Paraná River, and the low diversity and abundance observed at Xambrê Lake are likely due to its isolation from the river. This work shows the importance of these lagoons for fish development, for both sedentary and migratory species. Both lagoons may be considered to have extreme ecological importance and they are also extremely susceptible to impacts, so any careless disturbance may cause irreversible damage.Este trabalho teve por objetivo avaliar a abundância, os atributos da assembleia e a distribuição espacial e temporal de larvas de peixes, bem como a relação dessas variáveis com alguns fatores abióticos, em duas lagoas com diferentes graus de conexão com o rio Paraná, Parque Nacional de Ilha Grande, PR, Brasil. As amostragens foram realizadas em quatro locais, dois em cada lagoa. As coletas foram realizadas mensalmente à noite durante três períodos de desova (outubro a março) de 2001 a 2005, com o auxílio de redes de plâncton. A maior diversidade e abundância foram verificadas na lagoa Saraiva, sendo identificados 25 táxons. Na lagoa Xambrê somente foram capturadas espécies sedentárias e as mais abundantes foram Plagioscion squamosissimus e Hypophthalmus edentatus. Nessa lagoa as maiores ocorrências foram verificadas no período II. Na lagoa Saraiva as maiores capturas foram de Moenkhausia aff. intermedia, Hyphessobrycon sp. e Bryconamericus stramineus, entretanto, larvas de espécies migradoras também foram registradas. Nessa lagoa, as maiores ocorrências foram no período III. A abundância de larvas foi influenciada pela temperatura da água e pela condutividade elétrica. A elevada diversidade e abundância registradas na lagoa Saraiva podem ser atribuídas a sua conectividade com o rio Paraná, enquanto que a baixa diversidade e abundância observadas na lagoa Xambrê pode...

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