What's up with the noble pen shells of Blanes?

What are the noble pen shells?

The noble pen shell (Pinna nobilis) is the largest bivalve mollusc of the Mediterranean sea and one of the World’s largest. It can reach over a meter long. However it lives half buried in the sand, so it is difficult to appreciate its actual length. It is found between 2 and 50m deep in soft-sediment areas overgrown by the seagrasses Posidonia oceanica, Cymodocea nodosa, Zostera marina and Zostera noltii. It feeds on plankton by filtering the surrounding water which it contributes to its transparency. Its predators are sea stars and carnivorous snails. Remarkably, while being alive it already offers a habitat to sponges and worms that colonise its outer shell and, inside, small crabs and shrimps are often found.

Since ancient times its byssus, the turf that keeps it ancored to the sea bed have been greatly appreciated. Till present it is still used to producte the sea silk, an outstanding fabric for its resistance, flexibility and golden colour. More information >>        

Present state

LEVEL OF PROTECTION: strict protection status according to the European Council Directive (92/43/EEC). Fishing is banned.
THREATS:
-Poaching: its shells are appreciated for their size
-Death due to the impact of boat's anchors
-Parasite of the gender Haplosporidium: once it reaches the digestive system it causes its death. First cases were reported during 2016 and presently it is at the category of massive mortality affecting the Mediterranean coast of Spain (ïncluding the Balearic islands) and some populations of France and Italy

Punta Santa Anna (Blanes, Spain)

The Project

In this scenario members of S’Agulla wonder about what is the state of the known population of noble pen shells at Santa Anna Point (Blanes, Spain).
Surveys were carried out between July 2018 - June 2019.

First exploration >>
January 2019 >>
May 2019 >>
June 2019 >>

Results

  1. No nobel shell pens (Pinna nobilis) have been found
  2. Bits of dead juvenile shells of a smaller species Pinna rudis have been found
  3. The grassland of Posidonia oceanica presents a strong regression, especially close to the port's breakwater. This is particularlý serious because this plant offers a habitat for many fish species and prevents the movement of sand during storms. More information >>


In this grassland of Posidonia oceanica S'Agulla had a control point set before the construction of the extension of the port. This is what's left... Do you see the four nails that are nailed to the sea bottom?

 

Anchoring weight of the buoys to mark the uses of the beach. Couldn't they have put it a little further into the sandy area?

Conclusions
Although no noble shell pens have been found, there is news about some being found alive in the southern waters of Tarragona (Spain). Hope they will be able to expando to the rest of the Meditarranean shore.
On the other hand, it is og big concern the strong recession of the extension of the grassland of Posidonia oceanica. Moreover, it is really demoralising to observe that actions to manage the coastline, as the deployment of buoys, do not take into consideration the location of marine grasslands when placing them. If measure are not taking shortly, nothing will be left at Santa Anna Point.

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