Trophic Ecology of Arapaima sp. in a ria lake—river–floodplain transition zone of the Amazon

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.

Trophic ecology of speckled peacock bass Cichla temensis Humboldt 1821 in the middle Negro River, Amazon, Brazil

“…These results contrast with patterns observed in other predatory fish in the Amazon region where adult fish focus on a higher variety of food resources (Carvalho et al, 2017). These results contrast with patterns observed in other predatory fish in the Amazon region where adult fish focus on a higher variety of food resources (Carvalho et al, 2017).…”

Population recovery, seasonal site fidelity, and daily activity of pirarucu (Arapaima spp.) in an Amazonian floodplain mosaic

“…Fish movement patterns, at a local scale, can be explained by both abiotic conditions and resource availability (Winemiller & Jepsen, 1998). For pirarucu, lateral migration provides a source of high-quality food, since the flooded forest supports both the main fish prey of adults, such as detritivorous and omnivorous fish species (Carvalho et al, 2018;Castello, 2008), and the insects, fish larvae, and other small organisms that constitute the bulk of the fingerling diet (Carvalho et al, 2018;Junk et al, 1989;Queiroz, 2000). Calm sheltered shallows within the flooded forests also provide the preferred nesting sites for adults to spawn.…”

Fishery yields vary with land cover on the Amazon River floodplain

“…C 3 plants (tree seeds, fruits and leaves and non-gramineous aquatic macrophytes) and algae (periphyton and phytoplankton) are the main sources of carbon supporting fish biomass (e.g. Carvalho et al, 2017;Davis, Blanchette, Pusey, Jardine, & Pearson, 2012;Hladyz, Nielsen, Suter, & Krull, 2012;Lewis, Hamilton, Rodriguez, Saunders, & Lasi, 2001; Mortillaro et al, 2015;Roach, 2013). For some species, such as the economically important tambaqui (Colossoma macropomum, Characidae), fruits and seeds constitute the major food source during high waters (Oliveira, Martinelli, Moreira, Soares, & Cyrino, 2006).…”

“…The diets of many freshwater fishes naturally vary with age, season and location within the system (Carvalho et al, 2017;Welcomme, Winemiller, & Cowx, 2006;Winemiller et al, 2014), potentially allowing fish to adapt their feeding behaviours to the habitats that replace natural vegetation. Habitat changes may also cause fish to exhibit compensatory responses at the community level (e.g.…”