Trophic Ecology of Arapaima sp. in a ria lake—river–floodplain transition zone of the Amazon |
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| Authors: | Felipe Carvalho Michael Power Bruce R Forsberg Leandro Castello Eduardo G Martins Carlos E C Freitas |
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| Affiliation: | 1. Freshwater Biology and Inland Fisheries, National Institute of Amazonian Research, Manaus, Brazil;2. Department of Biology, University of Waterloo, Waterloo, ON, Canada;3. Department of Fish and Wildlife Conservation, Virginia Polytechnic Institute and State University, Blacksburg, VA, USA;4. Department of Fishery Sciences, Federal University of Amazonas, Manaus, Brazil |
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| Abstract: | Neotropical floodplains are usually productive systems that are maintained by the nutrient, detritus and sediment inputs provided by the main river channel flood pulse. Ria lakes represent a special feature and habitat in the Amazonian floodplains, being characterised by a dendritic morphology and dependence on terrestrial inputs provided by an intricate stream network. Our objective was to evaluate the trophic ecology of the arapaima (Arapaima sp.). We combined stomach content analysis with measurements of carbon and nitrogen stable isotope values from dorsal muscle to infer the ontogenetic changes in trophic level and isotopic niche width in floodplain and ria lakes. Arapaima diet was dominated by fish from low trophic positions. While most of the stomachs sampled in the study ria lake were full, empty stomachs predominated in samples taken in the floodplain lakes. These differences indicate that ria lakes may provide better feeding grounds for arapaima during the dry season, presumably because ria lakes are interconnected with a large stream network and the main river channel year round. Nitrogen stable isotope results further indicated an ontogenetic dietary shift in arapaima, with piscivory increasing as a function of length in both environments. Carbon stable isotope analysis indicated that energy sources used by arapaima varied by environment, with arapaima using a greater diversity of food sources in ria lakes than in floodplain lakes. Information about the main carbon sources is useful for fishery management because stakeholders may choose to conserve key vegetal groups to ensure the productivity and diversity of aquatic ecosystems. |
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| Keywords: | fisheries management osteoglossidae stable isotopes threatened species tropical fishes |
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