Monitoring the reserve effect of a coastal no-take area in the northeast Atlantic along the first ten years of implementation

Marine Protected Areas (MPAs) have been widely implemented to protect habitats and species and promote sustainable fisheries. In 2011 several coastal areas were closed to fishing in a southwestern Portuguese MPA (SACVMP – ‘Sudoeste Alentejano’ and ‘Costa Vicentina’ Marine Park), including the Pessegueiro Island no-take area. To assess its effectiveness, experimental fishing surveys were conducted in an early protection period (2011–2013) and nearly a decade later (2019–2021), in the no-take area and two control areas. Fish were sampled using bottom otter trawl (sandy habitats) and trammel nets (rocky and sandy bottoms) in winter and summer. Spatial and temporal comparisons were performed for both the overall fish assemblage (abundance, biomass, species richness, and structure) and the dominant commercial species (abundance, biomass, size, and juvenile proportion). Results showed generally positive trends over time, particularly in the no-take area for larger-bodied commercial species. Scorpaena porcus and Trisopterus luscus specimens with legal landing size increased in abundance, while Phycis phycis specimens were significantly bigger inside the protected area. Larger sizes of legal landing size specimens of the endangered and protected species Raja undulata inside the no-take area also highlight its importance. However, increasing differences among areas over time suggest that a steady state may not yet have been reached after ten years of protection, and the likely reasons for this are discussed. Nonetheless, these results provide evidence of a reserve effect in a relatively small no-take area within the first decade of implementation.