Pinna nobilis is undergoing one of the most dramatic events suffered by an endangered species. An emerging disease has relegated its populations to coastal lagoons or estuaries with salinities beyond the 36.5–39.7 psu range. The Mar Menor is one of two such locations on the Spanish coastline. Poor environmental conditions and eutrophication and anoxia events, that became critical in 2016, 2019 and 2021, have reduced its population in >99 %. In this work, the spatial distribution of the species within the lagoon and the factors determining its survival along the successive crises of eutrophication are studied using a two-stage (presence/absence estimation and density modelling) Species Distribution Model. A potential area of 200.97 ha and an average density of 1.05 ind.100 m2 is estimated for 2020. The viability of the Mar Menor population depends on management actions designed both for the species and to improve the lagoon environmental state.This research was supported by the EU LIFE Programme Project “Protection and restoration of Pinna nobilis populations as a response to the catastrophic pandemic started in 2016” (LIFE PINNARCA) [grant number LIFE20 NAT/ES/001265] and the Biodiversity Foundation of the Ministry for Ecological Transition and the Demographic Challenge Project RECUPERA PINNA [grant number IRTA1-21T]. This research was supported by the Dirección General del Mar Menor, Consejería de Agua, Agricultura, Ganadería, Pesca y Medio Ambiente (CARM), Project “Proyecto para la cría ex situ de Pinna nobilis y creación del Banco de Especies protegidas y singulares del Mar Menor”
