Influence of seasonal variability on the trophic structure of pelagic communities

Seasonal variations in hydrodynamic conditions play a critical role prey availability at the base of food web and thus have implications for trophic interactions higher levels. Here we use combination stomach content analysis (SCA) stable isotope (SIA) to investigate predator-prey structure pelagic fish community Bay Biscay (BoB) spring late summer 2020 2021. We found that guilds were more influenced by intra-specific affinities rather than seasonal variability. Main comprised set species belonging different positions (TPs), from low TP class Thaliacea (salps) mid Engraulis encrasicolus . Vertically migrating meso- macrozooplankton (mainly copepods krill) also played an important as source showing high overlap among most species. No differences detected between with fish, squids chaetognaths top TPs, whereas krill, meso-zooplankton salps had lowest values. However, TPs estimated using both SCA SIA approaches consistently lower spring, likely due densities and, thus, spring. When analyzing ontogenic changes predator’s size, significant positive relationships when was but not SCA. Overall, our results reveal new insights into dynamics BoB.