Linking small pelagic dietary shifts with ecosystem changes in the Gulf of Lions

摘要: Since 2008, a severe decrease in size and body condition together with demographic truncation has been observed the sardine (secondarily anchovy) population of Gulf Lions (NW Mediterranean Sea). In parallel, sprat biomass, which was negligible before, increased tenfold. All these changes have strongly affected regional fisheries. Using trophic isotopic data from contrasting periods low versus high growth condition, we investigated potential diet interspecific feeding interactions through time. Evidence resource partitioning found between both anchovy 2004 2005. 2010, niches 3 species tended to overlap, suggesting higher risk competition for food resources. Moreover, wider niche indicates variability individual diets. Anchovy varied time, proportion large copepods or cladocerans (1994 2007, respectively) dominance small present (2011-2012). Furthermore, an important reduction prey diversity also identified during most recent period. Our results support hypothesis that pelagic fish growth, ultimately biomass could be due bottom-up control characterized by availability increasing competition.