Resurvey of sea urchins and mussels at protected and harvested shores a decade after: A beyond-BACI approach

Comparing temporal patterns of distribution and abundance of target organisms between protected and harvested shores is essential to assess the extant effectiveness of marine protected areas (MPAs) and whether it is maintained through time. By means of an adapted Beyond-BACI approach, we compared the short- and long-term patterns of variation in the abundance of the sea urchin Paracentrotus lividus and the mussel Mytilus galloprovincialis at a protected shore (within the Parque Litoral Norte MPA, Portugal) and at three adjacent shores subject to intense harvesting over a decadal interval. Despite the existence of the MPA for more than 30 years, we did not obtain clear evidence of its persistent or recent effectiveness on intertidal species of commercial interest. We suggest the need for refining management options along the northern Portuguese coast, possibly by better enforcing current regulations and reconsidering the present design of protection schemes. Moreover, the adopted analytical approach may represent a methodological reference for similar investigations in systems where the perturbation of interest (protection or disturbance) would not occur at a given time during the course of the study, but has been operating since before the first sampling occasion and maintained until subsequent surveys.