Uplifting resources management in conservation: mid-term studies are able to capture the dynamic patterns of site-fidelity and seasonal abundance of coastal cetacean populations

Mid-to long-term research is pivotal for conservation and coastal management yet often undervalued by policymakers and funding bodies. Continuous marine monitoring may be needed to define animal residency patterns and abundance—key information for effective conservation strategies. Here, we used an eight-year (2016–2023) dataset on coastal bottlenose dolphins at Tiber River estuary (Mediterranean Sea, Italy) to examine site-fidelity and estimate population abundance. The work aimed to (1) compare results with a previous, shorter-term study (2017–2020) and (2) test whether extended datasets enhance understanding of population dynamics. Longitudinal photo-identification analysis and site-fidelity metrics (occurrence, monthly/yearly rates, resight rate, periodicity, relative span-time) confirmed three site-fidelity clusters: residents, partially-residents and transients. A first-order Markov chain model revealed a high misclassification risk for partially-residents in short-term studies. Kernel density estimations showed distinct spatial use, with a more coastal occurrence of residents. The updated abundance estimate aligns with previous findings but with a narrowed confidence interval, indicating population stability and improved statistical robustness. These results support the need of multi-year studies for reliable ecological insights and population assessments. We urge policymakers to support longer-term research efforts and consider our findings in future local conservation actions targeting coastal dolphins, key species in marine ecosystems.