Influence of Marine Protected Areas on parasitic prevalence: the case of the isopod Anilocra physodes as a parasite of the fish Lithognathus mormyrus

The effectiveness of Marine Protected Areas ( MPA s) on the conservation of species, habitats, and processes has been largely studied. However, although parasites play a key role in the ecology of marine ecosystems, the effect of MPA s on host‐parasite relationships remains poorly understood. In order to characterize prevalence and host specificity of the widely distributed parasitic isopod Anilocra physodes , as well as the effect of MPA s on these parameters, a study based on visual census of fishes (repeated at two different study periods) and angling was conducted in the Alboran Sea (Western Mediterranean). Despite the wide diversity of potential hosts, A. physodes was only found associated with the sparid fish Lithognathus mormyrus . A significant relationship between the length of the host and the parasite was detected. While similar host densities were recorded inside and outside the MPA , parasitic prevalence was significantly lower inside the MPA . These differences among MPA s and non‐ MPA s in parasite prevalence and host availability, as well as the strong host specificity pattern, were consistent throughout time. Anthropogenic pressures, host size, and cleaning interactions are proposed to be potential factors involved in the observed lower parasitization levels inside the MPA . This study highlights that the protection status of marine areas can drive constant changes in parasitic prevalence.