Looking for the surviving optimal areas for the threatened species Pinna nobilis in a highly anthropized coastal lagoon (Mar Menor, SE Spain)

Pinna nobilis, an endemic bivalve species in the Mediterranean Sea, is critically endangered mainly due to the devastating impact of the protozoan parasite Haplosporidium pinnae. The population within the Mar Menor lagoon (Murcia, Spain) represents one of only two surviving populations along the Spanish coast. This relict population has witnessed a significant decline since 2016, primarily due to eutrophication episodes and other anthropogenic impacts affecting the lagoon. It is imperative to identify the most suitable zones for the survival of this species, where adult individuals could be translocated from affected areas to enhance their chances of survival. In the present study, we identify these zones through a Multi-Criteria Evaluation considering several factors that pose a threat to the species. This evaluation was complemented using Geographic Information Systems based multi-criteria decision analysis (GIS-MCDA). A total of 18 factors were weighted and combined, resulting in a surface area of 307.92 hectares (2.28% of the lagoon) with over 70% high suitability for species survival.