CHARACTERIZING THE TROPHIC DYNAMICS OF SMALL PELAGIC FISHES ACROSS THE NORTH IBERIAN UPWELLING SYSTEM BY STABLE ISOTOPE AND FATTY ACID ANALYSES

Small pelagic fishes (SPF) are important for the functioning of marine food webs, as they link basal resources with top consumers. Therefore, understanding the feeding ecology and trophic relationships of coexisting SPF at local scales may improve the strategic management of marine resources. This study represents the first effort to investigate the feeding patterns of the most abundant SPF (sardine, anchovy, mackerel and chub mackerel) across different regions in northern Spain (NE Atlantic) using bulk isotope analysis (δ13C, δ15N), compound-specific isotope analysis of amino acids (δ15N), and the fatty acid (FA) composition of lipids. The results imply large zonal variability and diet plasticity across species, largely unrelated to changes in local plankton availability. Furthermore, low mobility of East Cantabrian fishes was indicated by their C and N isotopic baselines. However, low resource competition among co-occurring species across zones can be deduced from the comparison of trophic position (TP) estimates and FA profiles, with mackerels occupying the highest TP. Overall, this work shows the importance of: i) integrating multiple biochemical tracers, and ii) the use of more sensitive trophic indicators (amino acid δ15N and neutral lipid FA), instead of traditional methods (bulk δ15N and total lipid FA), to strengthen ecological interpretation of the fish dietary preferences and TP estimates. Finally, this contribution advances our understanding of the pelagic food web dynamics and nutrient cycling in highly productive systems.

Presentation Preference: Oral

Primary Presenter: RITA GARCIA SEOANE, Spanish National Research Council (CSIC) (rita.garcia@ieo.csic.es)

Authors:

RITA GARCIA SEOANE, Spanish National Research Council (CSIC)  (rita.garcia@ieo.csic.es)

INES G. VIANA, Spanish National Research Council (CSIC)  (ines.viana@ieo.csic.es)

ANTONIO BODE, Spanish National Research Council (CSIC)  (antonio.bode@ieo.csic.es)

HILARY CLOSE, University of Miami  (hclose@miami.edu)