Actual situation

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SPAIN

Concerning survival of P. nobilis at the wild, after different waves of the MME, a search for survivors from 2018 in Spanish coasts has produced a very discouraging result: only few isolated alive individuals have been found (2 in Columbretes Islands, 6 in Balearic Islands and 3 in Cap de Creus). It is noteworthy that two small Spanish fan mussel populations remain not severely impacted by the MME, but they are both located in paralic environments (Delta del Ebro and Mar Menor lagoon). The reason why these populations remain at least partially protected has been associated with particular salinity conditions, either lower or higher, respectively than the open sea. In the Alfacs Bay, there are evidences that salinity conditions below 36 confer certain tolerance against the parasite, whereas ranges below 30-32 in the Fangar Bay, appear to prevent the infection.

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Concerning the second population (Mar Menor lagoon), the remaining fan mussels that had survived the environmental collapse in 2016, before the arrival of the disease, suffered a severe flood episode in September 2019. The total of specimens that remain alive is unknown, but at least several docens have been located in the least affected areas.

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FRANCE

The mass mortality of fan mussels along the French coasts first appeared in the western coast of Corsica in autumn 2017. Populations of P. nobilis remain alive in coastal lagoons both in Occitania (Leucate, Thau, Fos: Rhône’s delta) and in the east coast of Corsica (Diana). In Diana a dense healthy population was observed in June 2019. In Thau lagoon, well-known populations have been monitored for several years.

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ITALY

In the Italian coast, the first description of MMEs in 2017 was reported in the Tyrrhenian Sea, in the region of Campania, in the islands of Ischia and Procida, and in the Sicilian coasts of Messina. By March 2018, the populations of Sorrento and from the islands totally disappeared. Few young individuals were observed in the south of the coast (Cilento) in 2019 and in the internal marine lakes of Phlegrean area (north of Naples). Mortality was also reported in many other Italian regions, like Sardinia and Tuscany. In Sardinia, in Oristano and in Asinara Island (north-west of Sardinia) mortality was reported since 2018, and currently no live individuals are present in these areas.

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In the western Ionian Sea (, the first evidence of mortality of P. nobilis (40% of the individuals) was reported in summer 2017. Later, in the early summer 2018, the western Ionian Sea P. nobilis populations suffered very high mortalities, with up to 100% mortality in 3 months.

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GREECE

The status of P. nobilis in the eastern Ionian Sea was assessed, based on data collected at 69 sites in 2019. Mortality rates exceeded 80% by August 2019, and kept increasing at that time. In autumn 2019, in all sites surveyed there was almost no live individual. The only locality, where mortality rates were low (40%) was the National Marine Park of Zakynthos, surveyed in August 2019. However, in 2020 the fan mussel population in NMPZ was largely affected, with only few live individuals left, mostly juveniles. Nevertheless, the eastern Ionian Sea remains under-sampled.

In a broader context, the mortality has reached practically all the Mediterranean basin in the open sea, and some sanctuary areas host P. nobilis population in particular conditions. Survivors/resistant individuals are few and far between but the monitoring and protection of those individuals is extremely important for the conservation of the species.