Reconstruction of trophic pathways between plankton and the North Iberian sardine ( Sardina pilchardus ) using stable isotopes

摘要: SUMMARY: Feeding on phyto- and zooplankton by juvenile (< 1 year old) adult sardines (Sardina pilchardus) was inferred from analyses of natural abundance stable carbon nitrogen isotopes in samples the northwestern Iberian Peninsula (Spain) collected at beginning upwelling season peak spawning period sardine. Plankton were fractionated through nets 20, 200, 500, 1000 2000 µm mesh-size muscle protein individual isolated before isotopic determinations. Up to six planktonic components two sardine feeding types identified modes frequency distributions isotope values. Also, most probable pathways for flows between compartments analysed. The resulting food web revealed a relatively large degree omnivory, both plankton components, which confirms that complex trophic interactions could also occur pelagic ecosystems. Young had values clustered around single mode distribution, while displayed main modes. These are interpreted as representative extreme types: one related capture prey other unselective filter-feeding. Although include micro- (20-200 µm) mesozooplankton (200-2000 prey, phytoplankton appears be ingested mainly However, even must zoophagous achieve observed values, taking into account current assumptions enrichment levels. From differences using either or isotopes, we acquire substantial fraction their would derive phytoplankton. interpretations agree with information available this species gut contents anatomy filtering apparatus.