Availability of sedimentary organic matter for benthic fishes of the upper Paraná river floodplain

This work aims to investigate the hypothesis that sedimentary organic matter presents concentration variations in accordance to the size of sediment particles and to proximity with the river's margin. This organic matter is known as a feeding source for benthonic fishes. Sampling of the sediment was carried out in dry and rainy periods, at three Parana River floodplain subsystems. Three sampling points were established: right margin, center and left margin. The samples (n=88) were submitted to granulometric fractionation ( 200µm). Low variability in organic matter concentration was observed for samples from the center of the subsystems. Particles, smaller than 70µm, had high variability in organic matter concentration. The rainy period was shown to affect concentration of organic matter adhered to the sediment fractions in transversal section at the sampled environments. With support of literature, the experiment lead to the conclusion that fish species which ingest particles of detritus < 70µm obtain more organic matter of sediment.