Mediterranean Marine Reserves: Fish Indices as Tests of Protection Efficiency

Abstract. The fish assemblages of a strictly protected area and of a neighbouring fished area, located off a Mediterranean urbanized coast (Carry‐le‐Rouet, France), were compared in order to select the most evident, constant, and easily recorded indices of the ‘reserve effect’. Visual censusing was repeated simultaneously at both sites eight time a year during 3 years along four permanent transects layed on shallow rocky bottoms (9–14 m). Overall species richness was 16% higher in the reserve, but differences in average instantaneous richness were only marginally significant. The most contrasting results were shown by the occurrence frequency, abundance, and demographic structure of two types of target species. The type A target species group comprises 16 large meso‐ and macrocarnivores particularly threatened by spearfishing, including the common nectobenthic sparids Diplodus spp. Type B target species are represented by two small territorial fishes particularly impacted by angling: the serranid Serranus cabrilla and the terminal phase males of the labrid Coris julis . The size structure of Diplodus spp., S. cabrilla , and C.julis subpopulations strongly argues for the role of protected areas as a reservoir of large spawners. Fishing pressure is assumed to modify the social conditions of the C. julis local populations and to induce earlier sex change.