Trophic relations between Acestrorhynchus britskii (native) and Plagioscion squamosissimus (introduced) in a reservoir cascade system

Abstract

The objective of this study was to identify possible differences in feeding of Acestrorhynchus britskii and Plagioscion squamosissimus in the reservoir cascade of the São Francisco River. The species were obtained from samples taken along the Sobradinho, Itaparica, Moxotó, Paulo Afonso I, II, III, Paulo Afonso IV and Xingó reservoirs from September 2006 to October 2010. The diet was evaluated as the relative importance of each food item consumed (%RII). The range of length classes has been established by Sturges rule to characterize the feeding species variation. Furthermore, the nMDS, PERMANOVA and SIMPER analysis were performed to evaluate changes in relation to length class factor. The food overlap of diet and the similarity between the species were observed in order to compare similarities among the food items consumed in each reservoir. No significant interaction (PERMANOVA) between the classes of length and the food items was detected for A. britskii (P = 0.134) or P. squamosissimus (P = 0.095). By SIMPER analysis it was observed that the categories which most contributed to the A. britskii dissimilarity were Clupeiformes (49.83%) and Characiformes (49.04%), and to P. squamosissimus were mollusks (40.58%). The use of food resources by the species in this study are the result of the abundance of preferential prey in the environment, and the different predatory tactics adopted by each species as well as the different microhabitats exploited by them.