An update of the amazon prawn (Macrobrachium amazonicum) distribution in the low course of the São Francisco river (northeast Brazil)

The prawn Macrobrachium amazonicum has been considered a successful colonizing species of freshwater environments beyond its native range; however, information on the distribution of the species in rivers in northeastern Brazil is doubtful or incomplete. This study updates the presence of the Amazon River prawn Macrobrachium amazonicum in the Sao Francisco River (northeast Brazil) where eight areas were sampled downstream from the Xingo Hydroelectric Plant (Alagoas/Sergipe) up to the mouth of the river, between April 2014 and February 2016. The specimens were sampled using manual trawls and artisanal traps. Hydrological data were obtained using a multi-parameter probe. Only 258 specimens were found in Piranhas, Pao de Acucar, and Belo Monte, which are regions far from the mouth of the river. They were found in shallow (3.96 ± 1.01 m), warm (26.15 ± 1.18 °C), and oxygenated fresh waters (5.70 ± 1.14 mg L-1) with low turbidity (71.33 ± 6.43 mg L-1) and slight alkalinity (7.26 ± 0.53), always associated with the aquatic vegetation. The presence of M. amazonicum has not yet been evaluated in relation to possible impacts on local native diversity. Therefore, studies addressing the interaction of this species with native species are necessary to understand whether or not it poses a risk to endemic species.