Temporal and spatial patterns of freshwater decapods associated with aquatic vegetation from floodplain rivers

Abstract

The presence of freshwater decapods may be considered dependent on the habitat and vegetation characteristics in floodplain rivers. Water level can influence the availability of macrophytes and the associated species composition of freshwater decapods. Changes in the sex ratios, abundances and body sizes of Macrobrachium borellii, Palaemon argentinus and Trichodactylus borellianus were investigated focusing on the type (floating, emergent) and the presence/absence of macrophytes in the Middle Paraná River floodplains. Organisms were sampled and analysed from river sites with floating, emergent vegetation and vegetation-free waters during different hydrological periods. The presence of macrophytes and some environmental variables during different hydrological and seasonal periods affected the variations in the species composition of decapods. M. borellii and T. borellianus tended to increase with the increase in floating vegetation in high waters, while P. argentinus was abundant in emergent vegetation and vegetation-free waters in low waters. Macrophytes provide food and shelter for freshwater decapods, influencing the species abundance according to the ecological response of each species. Variations in macrophytes composition due to water-level fluctuations modify the abundance of freshwater decapods, altering the species composition of decapod assemblages. Floodplain rivers are complex systems that act as macrofactors that regulate other factors that impact species composition.