The trophic ecology of marine catfishes in south-eastern Brazil

Abstract

AbstractThe stable isotope ratios of carbon (δ13C) and nitrogen (δ15N) and total mercury concentrations (THg) of the three marine catfish speciesAspistor luniscutis,Bagre bagreandGenidens genidenswere evaluated to understand their trophic relationship in northern Rio de Janeiro state, south-eastern Brazil. The δ13C was similar among the three marine catfishes, whereas δ15N was similar inA. luniscutisandB. bagreand lower inG. genidens. THg was higher inG. genidensand lower inB. bagre. The greater assimilation of Sciaenidae fishes and squids byA. luniscutisandB. bagreresulted in smaller isotopic niche areas and trophic diversity but higher isotopic niche overlap, trophic redundancy and evenness. ForG. genidens, the similar assimilation of all prey items resulted in the broadest isotopic niche among the marine catfishes. The higher mercury content inG. genidensis consistent with an increased important contribution of prey with a higher Hg burden. The bioaccumulation process was indicated by significant correlations of δ15N and THg with total length and total mass. Additionally, a significant correlation between THg and δ15N reflected the biomagnification process through the food web.