Using complementary visual approaches to investigate residency, site fidelity and movement patterns of the dusky grouper (Epinephelus marginatus) in a Mediterranean marine protected area

Abstract Assessing individuals’ abundance, residency (presence at a site within certain period) and fidelity (tendency to return the same in subsequent seasons or years) is crucial for evaluating improving effectiveness of spatial conservation/management measures regarding ecologically socio-economically valuable species. Using underwater visual census (UVC) photo-identification (photo-ID) techniques, we estimated dusky grouper, Epinephelus marginatus , two protected sites Tavolara-Punta Coda Cavallo Marine Protected Area (Sardinia, Italy) summers 2017–2018. The scope spatio-temporal resolution study was extended by involving volunteer recreational divers photo collection. Grouper mean densities varied significantly across sampling dates, with significant variability between 2 years investigated sites. At least 94 grouper visited 2017–2018 based on analysis 968 high-quality photos using semi-automated software photo-identify individuals. Overall, most frequently sighted recorded 32 different days 21 individuals (22%) identified 2017 were re-sighted 2018. participation helped detect inter-site (3.5–4 km apart) movements female male, supporting previous findings occurrence reproduction-related movements. This provides novel insights into site-fidelity patterns its small-scale probably related reproduction. Specifically, provide indications that effective protection from fishing should encompass entire area used reproductive