Abstract
Although ariid catfishe species are known to use coastal systems during some stages of their life cycles, the energetic contribution of estuarine resources and habitat use by many species in this family are still unclear. We used stable isotope analyses to estimate the assimilation of primary carbon sources and to infer the use of estuarine and freshwater habitats by two ariid catfishes Genidens barbus (Lacepede, 1803) and Genidens genidens (Cuvier, 1829). An isotopic mixing model revealed that juveniles of both catfish species consume considerable amounts of estuarine-produced carbon sources (G. barbus: 54-87% and G. genidens: 36-84%). However, G. genidens adults rely more on freshwater-derived carbon sources (31-77%) than on estuarine sources (23-69%). These results support the hypothesis that both species occupy the estuary and assimilate organic carbon produced in this region during their early stages, but G. genidens adults consume carbon sources associated with the freshwater portion of the lagoon.
Highlights
Estuaries are biologically much more productive than their adjacent rivers and the sea
Prior studies based on the distribution and abundance of the Ariidae catfish species Genidens genidens (Cuvier, 1829) and G. barbus, which are commonly found in southwestern Atlantic estuaries (Barletta & Blaber 2007, Jalal et al 2012), described contrasting life cycle models for these species
In this work we investigate the isotopic differences of two congeneric species of catfish (G. genidens and G. barbus) that have contrasting life cycles, and which move between the estuarine and freshwater habitats of the Patos Lagoon, which have distinct isotopic baselines
Summary
Estuaries are biologically much more productive than their adjacent rivers and the sea. At Patos Lagoon (32°S), for instance, young-of-the-year Genidens barbus (Lacepède, 1803) born in summer move from the northern limit of the estuarine zone (close to the freshwater portion of the lagoon) to the southern reaches of the estuary (near its connection with the sea) in autumn and winter, and return back to the freshwater region in the following spring and summer. In this work we investigate the isotopic differences of two congeneric species of catfish (G. genidens and G. barbus) that have contrasting life cycles, and which move between the estuarine and freshwater habitats of the Patos Lagoon, which have distinct isotopic baselines. We use these tracers to infer their assimilation of primary carbon sources. Our hypothesis was that the estuarine environment provides basic food sources for both species during the initial phase of their life cycles
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