Consistent edge effect patterns revealed using continuous surveys across an Eastern Mediterranean no-take marine protected area

Abstract

Because marine protected areas (MPAs) are not equally effective across their areas, monitoring should progress from dichotomic (within vs. outside) to a finer spatial resolution. Here, we examine the effect of an Eastern Mediterranean no-take MPA on fishes across the MPA and into fished areas, using three methods: underwater visual censuses, acoustic surveys, and towed-diver surveys. The Eastern Mediterranean includes non-indigenous species, so the effect of the MPA was also evaluated for its resistance to invasion. The fine-scale analysis revealed ecological phenomena that could not be captured by dichotomic sampling, such as the edge effect, a reduction of fish biomass along the MPA periphery. Despite their differences, all three methods revealed similar spatial patterns. The fine-scale analysis did not support a biotic resistance of the MPA to non-indigenous species. Our study supports the prevalence of edge effects even in well-enforced no-take MPAs and highlights the need for continuous monitoring to reveal these patterns.