A step back on the conservation of a highly threatened species: opposite signs of recovery on Pinna nobilis population from Mar Menor lagoon

The endemic species Pinna nobilis is the most endangered Mediterranean bivalve, facing nearly extinction all over the Mediterranean Sea, hosting its last reservoirs in highly impacted coastal lagoons. Thus, knowledge about the populations' conservation status in these ecosystems is essential. In 2019, the Mar Menor lagoon’s population was considered as a highly vulnerable population (Nebot-Colomer et al., 2021) due to several ecological disasters. The present study represents a continuation of the previous work, which aims to evaluate the resilience of the population, by assessing its reproductive success and maintenance of the population. To do so, between 2019 to 2022, we installed between 23-45 larvae collectors, monitored 13 permanent individual’s plots, and conducted visual searches and censuses. Overall, densities remained stable over years, although the number of individuals alive monitored in permanent plots decrease each year. Moreover, none of the methodologies carried out detected the incorporation of recruits in the population. Our results pointed out to opposite signs of recovery of the species, increasing its vulnerability to future disturbances. Therefore, urgent management and conservation actions focused on restoring the ecosystem and protecting P. nobilis individuals are needed to avoid this population extinction