C and N stable isotope ratios in fishes from marine protected areas and areas open to fishing

Here, we assess whether fishery exploitation affects the trophic structure of carnivorous fishes. We censused fishes and analysed the stable isotope ratios of C and N of species targeted by fishermen in areas open to fishing and marine protected areas in the Mediterranean Sea and the north-eastern Atlantic Ocean. Results demonstrated a major impact of fishing on the biomass and the size structure of nektobenthic carnivorous fishes. However, those changes did not modify the diversity of the trophic resources used by the assemblage, the pattern of resource partitioning between species or the degree of trophic redundancy. These results add to recent evidence suggesting that marine protected areas implemented in fished seascapes may fail to restore the original structure of the food webs that once existed in pre-fished ecosystems, because regional decimation and extinction of highly mobile predators prevents recovering the original diversity of predators at local scales, even at no-take areas. If so, more strict local fishing regulations are unlikely to restore the original diversity of high trophic level carnivores and restoration goals should be reframed in terms of an objective that is less unrealistic than restoring the pre-fished condition while still recovering aspects of the historical trophic structure.Funding provided by: Organismo Autónomo de Parques NacionalesCrossref Funder Registry ID: http://dx.doi.org/10.13039/100015865Award Number: 1588/2015Fish were captures in shallow rocky bottoms of marine protected areas and areas open to fishing and the stable isotope ratios of C and N in muscle assessed