Since the first confirmed records of mass mortality events (MME) in the Aegean Sea in 2018, Pinna nobilis populations in Greek seas have been decimated. To bolster recovery efforts, this study aimed to assess the status of fan mussel populations in the Aegean and Ionian seas and investigate potential recolonization through natural recruitment. From May 2022 to May 2023, 163 independent underwater visual surveys were conducted across various locations and depths along the Greek coastline. A total of 4348 P. nobilis individuals was recorded, of which 87.3% were found dead and 12.7% were alive. The sole surviving fan mussel populations were located in the semi-enclosed gulfs of Amvrakikos in the Ionian Sea and of Kalloni in the Aegean Sea, with estimated recent mortality rates (excluding potential poaching) of 7.7% and 6.3%, respectively. To track potential new recruitment, a network of larvae collectors was deployed in multiple locations. Additionally, an ocean circulation model (OCM) was developed to predict the export and fate of larvae from the surviving populations in the Marmara Sea towards the Aegean Sea. Beyond the MME, this study identified several other threats, which significantly endanger fan mussel survival. The findings of this study underscore the urgent need to implement protection measures and restoration actions to enhance the chances of P. nobilis survival and recovery in the Greek seas.

The endemic Mediterranean fan mussel Pinna nobilis is on the brink of extinction due to an infectious disease that has caused an ongoing Mediterranean Mass Mortality Event (MME) since 2016. Currently, healthy P. nobilis populations can only be found in a few refuges, mainly transitional waters such as coastal lagoons and estuaries. In the eastern Mediterranean, the only remaining fan mussel population is located in the Gulf of Kalloni (Lesvos Island, Greece). This study reports on a severe mortality event that occurred during summer 2023, leaving the population decimated and limited mainly to young individuals. The estimated density of live individuals dropped from 1.22 to 0.23 individuals per 100 m², indicating an 81% population decline within approximately three months. The significant reduction in the P. nobilis population in the Gulf of Kalloni highlights the ongoing threat of MMEs. Continuous monitoring of P. nobilis and environmental variables, such as temperature and salinity, enhanced protection from anthropogenic pressures, and research into disease resistance mechanisms are crucial for the conservation of this critically endangered species.

Coastal and island destinations increasingly rely on data-driven governance to manage seasonality, resource scarcity, overtourism, and climate risk. This article analyzes 30 official documents issued between 2017 and 2025 by nine Spanish and Portuguese Sustainable Tourism Observatories in the UN Tourism INSTO network. Rather than treating observatory language as verified policy implementation, the study uses computational content analysis to measure institutional discourse about monitoring and action. The Actionability Index (ActI), action-share, and log-ratio metrics are interpreted as exploratory, compositional text indicators, not direct evidence of governance effectiveness. Results show a negative document-level association between monitoring intensity and the ActI (r = −0.3951, p = 0.0307, alpha = 0.05), but denominator coupling and report-genre heterogeneity require a restrained interpretation: the pattern signals a monitoring-action imbalance that warrants follow-up validation rather than causal proof of a governance failure. Quartile-based profile labels are treated as sample-internal descriptors, with Barcelona interpreted as a boundary case whose action discourse is concentrated around tourism carrying capacity. A pre/post-2020 comparison is reported only as an unbalanced descriptive contrast. The contribution is a transparent, reproducible framework for auditing whether monitoring intelligence is connected to actionable discourse, together with explicit limits and validation priorities for future work.