On the lookout for the endangered, only to find the invasive

Among the most worrisome threats to Mediterranean Sea habitats are the range expansions of invasive species and declines of native species. An ongoing (disease-related) mass mortality event has brought the native Mediterranean fan mussel (Pinna nobilis) to the brink of extinction. Using nylon-mesh collectors, Kersting and Hendriks assessed larval P nobilis recruitment at selected sites in the Columbretes and Balearic islands, in the northwest Mediterranean. Before the mortality event, which had begun in 2016, P nobilis juveniles were very common in our samples; in 2020, however, not a single juvenile was collected. Recently, and to their surprise, another bivalve species appeared in their samples: the pearl oyster (Pinctada imbricata radiata), a Lessepsian invader (that is, from the Red Sea via the Suez Canal) that was first reported (as adults) on the mainland coast of Spain in 2019. However, the larval recruits of this invasive oyster were detected in the Balearic Islands almost a year earlier in 2018.