AMAre project title
Noble Pen Shell (Pinna nobilis) survey
Book icon AMAre Project
Funded under the Interreg MED Programme (2014 - 2020), the AMAre (Actions for Marine Protected Areas) project is conceived to aid Mediterranean countries in the conservation and management of designated marine protected areas by developing shared methodologies and geospatial tools for assessment, monitoring, analyses and effective stakeholders' engagements.

Info icon Description
If you are a diver, a snorkeler or even a swimmer, you certainly know the noble pen shell (also known as fan mussel, or as nakkra or nakkra tal-ħarir colloquially). It is an emblematic Mediterranean endemic species and is also the largest bivalve (a two valved hinged shelled mollusc) in the Mediterranean Sea. Its shell can reach more than one metre in total length. It usually lives in sandy bottoms in coastal areas, and is generally associated with seagrass meadows and can be found up to a depth of 60m. This noble pen shell used to be extensively collected for ornamental purposes which led to its inclusion in the list of protected species under the EU Habitats Directive 92/43/EEC and in the protocol for specially protected areas and biodiversity under the Barcelona Convention. Apart from its intrinsic beauty, the noble pen shell plays an important ecological role by filtering water and retaining large amounts of organic matter and suspended detritus, thus helping to reduce turbidity. Interestingly, it also hosts a particular shrimp and a pea crab which normally only live inside animals and generally provide a kind of symbiotic mutualistic association.

SOS icon Mass Mortality Event
Unfortunately, in the past two years a mass mortality event of the noble pen shell was detected in the western Mediterranean Sea. The cause is very likely to be a recently identified parasite.
Dead molluscs are recognised as they are found on the bottom, open and empty, though in some cases they can still be anchored to the bottom. Unhealthy individuals affected by the parasite, but still living, close their valve very slowly and show a lack of response to stimuli. Survey QR code

Write icon Action
To better understand the mass mortality event and devise an action plan, YOUR HELP IS NEEDED. So please fill the quick online questionnaire:

Warning! Don’t confuse the Noble Pen Shell (Pinna nobilis) with the Rough Pen Shell (Pinna rudis). Distinguishing features include:
  • Pinna rudis is usually not longer than 40cm;
  • The shell of Pinna rudis is thicker and has between 5 to 10 radial ribs with big spines on them;
  • Young Pinna nobilis have no ribs and the spines are crowded on the shell surface;
  • The mantle border is usually white and iridescent in Pinna rudis and pink in Pinna nobilis;
  • Nacre lobes in the inner side of the valves are of similar size in Pinna rudis;
  • Pinna rudis is commonly found among boulders or in crevices and less often in soft sediments like Pinna nobilis.
This survey is conducted on behalf of the AMARe project by the Physical Oceanography Research Group (Dept. of Geosciences, University of Malta). For further info please contact Monica Previati ( or Aldo Drago ( who is the local responsible for AMAre in Malta.
Pinna nobilis image
Pinna rudis image
Results thumbnail
View results
Video thumbnail
Watch video
Leaflet thumbnail
Download leaflet