PROJECT DESCRIPTION
BACKGROUND
Populations of the endemic Mediterranean Fan mussel (Pinna nobilis) have been devastated by a die-off caused by the protozoan Haplosporidium pinnae, in association with mycobacterial and other bacteria diseases. The first reports of the die-off occurred in September 2016 in southeast Spain, and it has since spread throughout all Spanish Mediterranean coastal areas, reaching France, Italy, Greece, Cyprus, Croatia, Montenegro and other Mediterranean countries in a few years. To date, only Fan mussel populations from the north Adriatic Sea are known to be free of the disease. Data indicates that the protozoan is specific to the Fan mussel, leaving other invertebrates (including the congeneric species Pinna rudis) unaffected. Fan mussel mortality reaches almost 100% in affected populations.
When the Haplosporidian protozoan was identified in early 2017 as the probable cause of the die-off, the Spanish expert group monitoring the event indicated a high risk that the disease would be spread by marine currents. This, together with the characteristic biology of Fan mussels (a K strategist species that typically produces a small number of offspring with a high investment in each individual), could eventually cause the ecological, if not total, extinction of the species, representing an unprecedented process in the Mediterranean Sea. Consequently, in the National Catalogue of Endangered Species of Spain the status of Pinna nobilis was upgraded from "Endangered" to "In danger of extinction", while the species was assessed as ‘Critically Endangered’ in the IUCN Red List.
A rescue programme to maintain individuals in captivity started in November 2017, enabling the study and quick identification of the Haplosporidian parasite. Observations of fan mussels rescued from infected populations led to the hypothesis that some individuals may have some resistance to the parasite, though the disease makes them extremely vulnerable to predators.
Other pressures on the mussels include harvesting for its decorative value or as food, destruction of its habitat (Posidonia oceanica and other seagrass meadows), pollution and indiscriminate boat anchoring.
OBJECTIVES
The overall goal of LIFE PINNARCA was to prevent the extinction of the Mediterranean Fan mussel (Pinna nobilis) in the short to medium term. The project aimed to carry out urgent measures within the framework of an international collaborative consortium of experts to enable the application of coherent trans-boundary measures. The project was implemented in Spain, France, Italy and Greece,
The project’s 3 main objectives are described below.
Increasing awareness on a global scale, to reduce the possibility of vandalism and illegal collection of the remaining fan mussels, but also to call for broad public collaboration. Actions would be oriented towards schools and the general public, including the production of a video, international workshops and volunteering actions.
Gathering all existing information on the remaining populations and resistant individuals in a database integrated within the project’s website, to provide information to other countries planning mitigation and recovery actions. This objective was to be achieved by implementing a comprehensive census of areas where resistant individuals or unaffected populations were found, as well as installing larvae collectors to assist successful recruitment.
Developing active recovery actions, focused both on resistant individuals and the remaining non-resistant populations, to increase the probabilities of recovery of the species. This objective involved efforts to aggregate resistant individuals, translocate vulnerable individuals to safer areas, exchange genetic information among remaining populations, identify locations with optimal conditions to repopulate with healthy fan mussels, maintain individuals in indoor facilities, and develop active measures to improve the environments where healthy non-resistant individuals were still found.
The project was in line with the EU Habitats Directive, 7th EU Environment Action Programme (EAP), Biodiversity Strategy to 2030, and the EU Action Plan for the species.
RESULTS
The project achieved the outcomes described below.
- Improving of knowledge about the species populations within the Mediterranean Sea: 107 487 individuals are still alive in some parts of Spain, France, Italy and Greece;
- An increase to thousands of individuals in the Mar Menor reservoir could not be achieved, since only 573 remained alive in 2024. Nevertheless, a significant recruitment was observed in Thau Lagoon (22 805 individuals) and Amvrakikos Gulf (80 549 individuals);
- The rescue of the still remaining juvenile individuals (3 000 estimated in 2018) in Ebro Delta was finally implemented over 219 individuals.
- An increase in the longevity of resistant individuals in the surviving populations living in reservoirs was achieved in Thau Lagoon and Amvrakikos Gulf, where populations had an increment of longevity, but not in Spanish open waters, with only 26 and 2 individuals in open waters of Murcia Coast and Balearics Islands, respectively.
- The beneficiaries expected to find an important number of open water survivors – at least 10 to 15 new potential resistant individuals in each of the partner countries, but the poor situation of the species yielded the presence of only 28 individuals in Spanish open waters. Some individuals in reservoirs were put together in optimum open water locations, to facilitate their crossbreeding and their protection from predation and anthropic impacts.
- Reduction of anthropogenic impacts in the reservoirs was attempted, to avoid trampling by tourists in shallow waters such as in Greece, and avoid illegal anchoring of recreative boats such as in south-east Spain.
- Raising of awareness and knowledge about the species, to avoid poaching and to involve the general public in future protection surveys with volunteers, and to inform fishermen in priority areas.
- Maintenance of individuals in indoor facilities, to study the relationship between the abiotic environmental variables and survival rates, as well as better understand the limits of environmental tolerance of the parasite. Longer-term captive breeding of fan mussels (over years) or growth of juveniles from approximately 3 cm to 25 cm, achieved through improved feeding knowledge. This information helped to predict the best areas for repopulation with non-resistant individuals.
- Increased knowledge about genetic variability in different environments, comparing non-resistant fan mussels living in open seas to those few that are resistant and have survived the disease.
- Increased genetic diversity of survivor populations by translocating 248 individuals in Spain, 79 in France, 11 in Italy and 27 in Greece, although genetic diversity in reservoirs is very high and confirmed by studies.
- Enhanced understanding of the disease mechanism reveals that infection by a picornavirus species is a precursor to Haplosporidium attack due to immune system weakening.
- Discovering that 60% of resistant individuals come from hybrids with Pinna rudis due to gene movements; they are reproductive hybrids.
- Creation of a catalogue of surviving populations, made available in a public database hosted on the LIFE PINNARCA website.
- Publication of 19 scientific articles.
