Seasonal inundations shape the floodplain characteristics of the Pantanal, a large wetland in Central South America. In the first study combining stable carbon and nitrogen isotope analysis with classical stomach content analysis in this region, we investigated the influence of the annual inundation on diet and isotopic composition of floodplain fish. Apart from potential food items, 33 fish species from the Coqueiro Lake were analyzed, 10 of which were present during both the wet and dry season 1999. A d 13 C and d 15 N plot of the floodplain ecosystem allowed us to assess a foodchain of 3 -4 trophic levels. However, the wide overlap of nitrogen values suggested that the organisms act on trophic continua rather than on distinct levels. The foodweb was based mainly on C 3 -plant carbon. However, fish species capable of feeding on terrestrial invertebrates (e. g., Brycon microlepis) had d 13 C values above -25 ‰, indicating 13 -30 % intake of C 4 -plant based carbon during the flooding period. The novel use of vector coordinates and 2-dimensional ANOVA showed that the seasonal isotopic shifts of d 13 C and d 15 N were highly significant for some feeding guilds. d 15 N values increased from the wet to dry season in most Aquatic Sciences fish species, and these shifts were highly significant for omnivores (Astyanax bimaculatus, Triportheus nematurus, Tetragonopterus argenteus and Moenkhausia dichroura), and significant for invertivores (Gymnogeophagus balzanii and Poptella paraguayensis) and carnivores (Serrasalmus spilopleura). Average carbon isotope ratios decreased at the same time in the herbivores (Methynnis mola: 3.4 ‰) and detritivores (Psectrogaster curviventris: 5.3‰), but they did not change in the hypostomatic herbivore Sturisoma robustum. We explain these shifts by abundant and variable food sources during the inundation period and increasing carnivory and starvation during the dry season when the lake is confined to its central basin. Isotopic shifts between seasons were more prominent in less specialized species of omnivores, invertivores and some carnivores, whereas more specialized herbivores and detritivores appeared to be more influenced by changes in the carbon isotope ratio of the diet affected by biogeochemical processes such as respiration and methanogenesis. A general model for the interpretation of isotope data of floodplain fish considering different timescales is given.

The objective of the present study was to determine the composition of the diet of fish and its relation to the condition of canopy along a stream in the savanna of Central Brazil. Fish were collected monthly from April 1994 to March 1995. A total of 3872 individuals belonging to 82 species were captured and 1606 of them had their stomach content analysed. Allochthonous resources were widely used by fish. Although some fish groups do present generalist habits, most of the species can be included in well-defined trophic groups. Piscivores were abundant only during the flooding season when they occupied the stream looking for food and reproduction sites. Deforestation of the riparian forest has negative effects on the fish populations that depend on allochthonous resources. Lack of vegetation near the mouth of the river allows sand accumulation on the bottom of the stream and destruction of important microhabitats used as feeding and shelter, a fact that excluded some species from this site.Este trabalho teve como objetivo determinar a composição da dieta dos peixes e sua relação com a vegetação marginal em um córrego de cerrado no Brasil Central. Os peixes foram coletados mensalmente de abril de 1994 a março de 1995. No total, foram capturados 3872 indivíduos, distribuídos em 82 espécies, destes, 1606 foram submetidos à análise de conteúdo estomacal. Recursos alóctones foram amplamente utilizados pelos peixes. Embora existam grupos com hábitos alimentares generalistas, a maioria das espécies pôde ser incluída em grupos tróficos bem definidos. Piscívoros foram abundantes apenas no período de cheia, quando entram no córrego à procura de alimento e locais de reprodução. O desmatamento da vegetação marginal apresentou efeito negativo sobre a população de peixes que depende de recursos alóctones. A falta de vegetação, próximo à foz do córrego, facilitou assoreamento e destruição de importantes microhabitats usados para alimentação e esconderijo, fato que impediu a permanência de algumas espécies no local.

The Pantanal Biosphere Reserve contains one of the highest concentration of animal species in the Neotropics, including about 300 fish species living in diverse environments associated with wetlands in the upper Paraguai River basin. This biome spans portions of Bolivia, Brazil and Paraguay and includes the Parque Nacional do Pantanal Matogrossense (PNPM), a region of the Pantanal which has been assigned as high conservation priority in Brazil. This study reports the results of an ichthyological survey within the PNPM, where samples were taken at 12 sites during the dry season in 2001, 2010 and 2011. We record 182 species representing three classes, 10 orders and 41 fish families. We report the first occurrence of the genus Anchoviella (order Clupeiformes), in the La Plata basin. This survey will provide information for future studies concerning conservation and management plans for the PNPM as well as for the Pantanal, which is one of the largest permanent wetland areas in the world and among the most unique and important South American biomes.

Fish assemblages associated to aquatic macrophytes in wetland environments of Pantanal de Poconé, State of Mato Grosso, Brazil. Biota Neotrop. 10(2): http:// www.biotaneotropica.org.br/v10n2/en/abstract?inventory+bn02310022010. Abstract:We examined the composition, richness and biomass of fish assemblages associated with aquatic macrophytes in temporary environments of the Pantanal de Poconé, State of Mato Grosso, Brazil. The fish were captured in April 2008 in five loan boxes and five locations along Coqueiro Bay, using seine nets at three points within each site. A total of 9646 specimens were captured, distributed in seven orders, 17 families and 59 species. The fish community was composed mainly of small-sized species (Characidae) and some juveniles of medium-sized species (Erythrinidae and Gymnotidae). In this study, few species were very abundant, some showed intermediate abundance, and most had low abundance. According to an analysis of similarity (Anosim) there was no difference in species composition between the environments. Species richness, total abundance and biomass did not vary spatially. Thus, the results suggest that the similarity of the fish fauna can be attributed to flooding, since this phenomenon homogenizes the abiotic characteristics and enlarges the area for the distribution of fish. This fact seems to be very important for these small fish species, since many species need to inhabit specific sites during certain stages; for example, these environments may function as temporary refuges. This aspect may ensure the survival of many individuals until they reach a stage in life where predation is significantly reduced. Resumo: Este estudo avaliou a composição, riqueza e a biomassa das assembléias de peixes associadas às macrófitas aquáticas em ambientes temporários do Pantanal de Poconé -MT. A coleta foi realizada em abril de 2008, em cinco caixas de empréstimo e cinco locais na baía do Coqueiro, por meio de rede de cerco, em três pontos dentro de cada local. Foram capturados 9646 exemplares, distribuídos em sete ordens, 17 famílias e 59 espécies. A comunidade de peixes foi composta principalmente por espécies de pequeno porte (Characidae) e alguns juvenis de espécies de médio porte (Erythrinidae e Gymnotidae). Poucas espécies foram muito abundantes, algumas apresentaram abundância intermediária e a maioria apresentou baixa abundância. A análise de similaridade (Anosim) mostrou que não existe diferença na composição de espécies entre os ambientes. A riqueza de espécie e a biomassa dos peixes também não diferiram espacialmente. Desta forma, nossos resultados sugerem que a similaridade da ictiofauna é uma conseqüência da inundação, uma vez que esta permite a homogeneização das características abióticas e amplia a área de distribuição dos peixes. Este fato aparenta ser de grande importância para estes pequenos peixes, considerando que muitas espécies necessitam de lugares específicos em determinados estágios, como, por exemplo, esses ambientes temporários que podem servir de refúgio. Este aspec...

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