Chasing Pinna nobilis Survivors: Current Status in Spanish Open Coastal Waters

The largest and endemic bivalve of the Mediterranean Sea, Pinna nobilis, is on the brink of extinction after a mass mortality event (MME) that has affected its populations since autumn 2016. Since then, different actions have been performed to improve the conservation status of P. nobilis. The monitoring of survivors in open coastal systems along the Spanish Mediterranean coast showed, after an 8-year period since the start of the MME (2017-2024), that the geographical distribution of the survivors in open sea is currently concentrated in a few regions, with focal points of specimen density in Cap de Creus (Catalonia) and Menorca (Balearic Islands). During the exhaustive monitoring of individuals of P. nobilis, the active participation of citizen science became decisive, locating almost half of the survivors. Most individuals were found in marine protected areas, mainly in Posidonia oceanica meadows in the upper 15 m. As a safety measure, several survivors were translocated to safer areas, while evaluation of the impact of the translocation showed no demonstrable effects. The knowledge acquired during these years has highlighted the necessity for collaborative monitoring, specifically to understand the current critical situation of P. nobilis and to implement effective conservation measures for this emblematic species.