Combating mass extinctions: Discovering new Pinna nobilis populations in the Sea of Marmara

Abstract Pinna nobilis is one of the largest bivalve species in the Mediterranean Sea. The situation of the species is critical as it faces widespread mass extinctions in various parts of the Mediterranean Sea. The Sea of Marmara offers a unique environment for fan mussel populations, with some areas hosting alive communities. This study aims to discover new populations of P. nobilis in the Sea of Marmara that are known to be not affected by mass extinctions. An area of 28,200 m 2 at 47 stations along the 105 km coastline in the southern part of the Sea of Marmara was scanned by underwater visual counting method. A total of 544 alive fan mussels were recorded during the underwater surveys, ranging in shell height from 11.8 to 31.4 cm. The mean density was estimated as 5.3 ind·100 m − 2 , and recorded very high densities which reached 18.8 ind·100 m − 2 among the stations. The hotspots of the population were distributed from the shoreline to a 10 m depth range and 100 m distance from the shoreline in sandy and seagrass meadow habitats. The presence of juveniles provided evidence of successful recruitment and settlement. The distribution pattern and recorded mortalities were attributed to hydrodynamic factors and intense human activities. This study provides key insights into the mechanisms of resilience and survival among fan mussels' mass death events and offers valuable guidance for potential conservation strategies in other affected regions.