Shells on the coast after the storm ; (the noble pen shell or fan mussel )

Dead shells appeared on the Slovenian coast in Strunjan. It is a natural process, as part of the population always dies. They were brought by Tramontana. Once the shell is dead, it is no longer firmly attached to the seabed. Therefore, storms or increased sea waves uproot it and throw it ashore. These shells did not die due to protozoa or bacteria.
Tramontána is a short-lived transient wind that blows from the north in the Adriatic. It blows in all seasons. It can be a strong and dangerous wind. It usually turns into a bora. It can reach speeds of up to 200 km / h. In Slovenia, tramontana means a strong (hurricane) north wind that blows from the Alps to Venice, across Trieste and the Slovenian Littoral and Istria. With hurricane force, it can knock down trees, uncover roofs on houses, destroy boats or even capsize them.
The collection of these shells is also prohibited in Slovenia, and the penalty for their destruction or collection is 584 euros or up to five years in prison.

Pinna nobilis, common name the noble pen shell or fan mussel, is a large species of Mediterranean clam.
The bivalve shell is usually 30–50 cm (1.0–1.6 ft) long, but can reach 120 cm (4 ft). Its shape differs depending on the region it inhabits. Like all pen shells, it is relatively fragile to pollution and shell damage. The inside of the shell is lined with brilliant mother-of-pearl.
This species is endemic to the Mediterranean Sea, where it lives offshore at depths ranging between 0.5 and 60 m (1.6 and 196.9 ft). It could be found buried beneath soft-sediment areas (fine sand, mud, often anoxic).
In 2016, there was an outbreak of a disease that caused the mortality of 99% of population in Spain. The cause of the disease is a newly discovered pathogen, Haplosporidium pinnae and it is posing a serious threat to the survival of the species. By 2019, mortality spots have been detected in Greece, Croatia, Turkey, Tunisia, France and Morocco. In the Trieste area, considerable efforts have also been made to conserve the deposits since 2020. In the past, Pinna nobilis has been threatened with extinction, due in part to fishing, incidental killing by trawling and anchoring, and the decline in seagrass fields; pollution kills eggs, larvae, and adult mussels. Such threats, however, have been very localised and have not led to such a widespread and rapid population decline. The pathogen, which is still present in the environment, will make recovery a challenge, so continuing declines are expected. The percentage of population size reduction over the last ten years is over 80%. In December 2019, Pinna Nobilis has entered the IUCN Red List as critically endangered.
The noble pen shell has been listed as an endangered species in the Mediterranean Sea. The European Council Habitats Directive 92/43/EEC, on conservation of natural habitats and the wild fauna and flora, proclaims that P. nobilis is strictly protected (by the Annex IV of EEC, 1992) – all forms of deliberate capture or killing of fan mussel specimens are prohibited by law.
As part of the Costa Concordia disaster recovery effort in Italy in 2012, a group of about 200 Pinna nobilis was relocated to a nearby area due to the threat posed by subsequent engineering work.
(https://en.wikipedia.org/wiki/Pinna_nobilis)