Isotopic niche of the catfishes Bagre bagre and Genidens barbus in a coastal area of south-eastern Brazil

Abstract: The isotopic niche of Bagre bagre and Genidens barbus target of commercial fisheries in a marine coastal area from northern Rio de Janeiro State (~21ºS), south-eastern Brazil was compared to evaluate the feeding assimilation and the trophic relationship. The mean isotopic values of the catfishes and their food items in the δ13C-δ15N space were coherent with their respective trophic positions. The relative contributions of the food items highlighted the shrimp Xiphopenaeus kroyeri as the most assimilated item in the diet of B. bagre, while for G. barbus the model highlighted the fish Porichthys porosissimus. The absence of niche overlap together with the trophic evenness point to a reduced feeding overlap between B. bagre and G. barbus in northern Rio de Janeiro State.