Habitat-specific response of fish assemblages in a small fully protected urban MPA

Abstract This study aims at assessing the reserve effect on fish assemblage in a small urban fully protected and highly enforced Marine Protected Area (MPA), Larvotto MPA (Monaco, Mediterranean Sea). The data about fish density, size, and biomass was collected by underwater visual census in the MPA and unprotected areas in two habitats, artificial rocky substrates and Posidonia oceanica meadows. On artificial rocky substrates, we recorded significantly higher fish biomass within the MPA compared to unprotected areas, while no significant difference was detected on Posidonia, with this suggesting the habitat-specific responses of fish assemblages to protection. Here we highlight the potential effectiveness of highly enforced small-sized urban MPAs, such as the Larvotto MPA, in generating ecological benefits, and speculate about their potential role in supporting networks of MPAs. This study supports increased attention to urban MPAs in conservation efforts, emphasizing the need for efficient management strategies in the face of ongoing coastal expansion.