Abstract
The northern Humboldt Current system(NHCS) is the most productive eastern boundary upwellingsystem (EBUS) in terms of fish productivity despite havinga moderate primary production compared with otherEBUS. To understand this apparent paradox, an updatedvision of the trophic relationships in the NHCS is required.Using δ13C and δ15N as a proxy of foraging habitat andtrophic position, respectively, we focused on thirteen relevanttaxonomic groups from zooplankton to air-breathingtop predators collected off Peru from 2008 to 2011. Estimates of trophic position (TP) for the anchovetaEngraulis ringens were high (3.4–3.7), in accordance withprevious studies showing zooplankton as a major contributorto anchoveta diet and challenging the often-cited shortfood chain hypothesis for this ecosystem. The squat lobster,Pleuroncodes monodon, a little studied consumer had similarδ15N values that of anchoveta, and thus similar trophicposition. However, their differing δ13C values indicate thattheir foraging habitat do not fully overlap, which could alleviatepotential competition between these species. Giventhe current high biomass of squat lobsters in the ecosystem,we encourage that future research focus on this speciesand its role in the diet of top predators. The presentstudy provides first estimates of the relative TP of importanttaxonomic groups in the NHCS, which are needed torevisit anchoveta-centred ecosystem models for this region.Further work using amino acid compound specific stableisotope analyses is now required to confirm these TPestimates.