Trophic strategies of three predatory pelagic fish coexisting in the north-western Mediterranean Sea over different time spans

Abstract

Understanding the trophic ecology of marine predators is pivotal to assess their ecological role in the ecosystems and develop management actions. Despite the ecological importance of predatory pelagic fish species, the trophic role that individual species play within marine communities in many marine basins, such the Mediterranean Sea, remains unclear. In the present study, we aimed to provide new integrative information about the trophic ecology at different temporal scales of Atlantic bonito (Sarda sarda), little tunny (Euthynnus alletteratus) and swordfish (Xiphias gladius) in the north-western Mediterranean Sea. To quantify the trophic habits of these three species, we used stable isotopic analysis and isotopic mixing models from different tissues that integrate trophic information at different temporal scales (~1 month for liver, ~ several months for muscle, >1 year for fin). We found clear and consistent differences in the trophic habits among the three species and time spans within the same species. Although preying mainly on clupeiforms, Atlantic bonito and little tunny present a temporal segregation in the species preference, with Atlantic bonito preying mainly on European sardine and round sardinella at long-term, while little tunny preyed mainly on European anchovy. In the other hand, swordfish shows a more generalist trophic strategy with high preference for demersal prey. This study emphasises the utility of this integrative approach for trophic studies due to its capacity for monitoring trophic habits over different time spans.