The importance of high-level predators in marine protected area management: Consequences of their decline and their potential recovery in the Mediterranean context

Abstract

High-level predators have been depleted in the oceans worldwide following centuries of selective fishing. There is widespread evidence that high-level predators’ extirpation may trigger trophic cascades leading to the degradation of marine ecosystems. Restoration of large carnivores to former levels of abundance might lead to ecosystem recovery, but very few pristine ecosystems are left as baselines for comparison. Marine protected areas (MPAs) can trigger initial rapid increases of high-level predator abundance and biomass. Nevertheless, long term protection is needed before the ecosystem's carrying capacity for large carnivores is approached and indirect effects on lower trophic levels are observed. The Mediterranean is probably very far from its pristine condition, due to a long history of fishing. Today small to medium-sized consumers (e.g. sea breams) are the most abundant predators shaping coastal benthic communities, while historical reconstructions depict abundant populations of large piscivores and sharks inhabiting coastal areas. Mediterranean MPAs are following a promising trajectory of ecosystem recovery, as suggested by a strong gradient of fish biomass increase. Consistent monitoring methods to assess relative variations of high-level predators, together with food-web models aimed at disentangling the indirect effects of their recovery, could be useful tools to help set up appropriate management strategies of MPAs.

Keywords

• high-level predator, top predator, trophic cascades, MPAs, ecosystem shift, overfishing, baseline, ecosystem recovery