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Translocation of individuals in Kalloni Gulf, Greece

In total, 28 juvenile individuals were detected growing under unfavorable conditions in Kalloni Gulf because of its very shallow position in two public beaches where they were threatened with being crushed by bathers. Finally, the partners of the UAEGEAN translocated the individuals in a sanctuary area where many other healthy P.nobilis were recorded.

20 of the individuals were transplanted in the sediment (Fig. 1b), while the remaining 8 were placed inside a weighted and protected cage (Fig. 1d). Additionally, one P.nobilis juvenile individual (2.9 cm shell width) which was detected growing on an experimental artificial surface (settlement plate) (Fig. 1c), was carefully removed in order not to damage its byssus, then placed inside the protective cage.

Public beach with very shallow waters in Kalloni Gulf where P. nobilis juveniles were detected (a) and translocated in a protected area (b); P. nobilis juvenile (2.9 cm width) recruited on an artificial experimental surface in Kalloni Gulf (c), placed in the weighted protected cage and translocated in a sanctuary area (d). Photos: Papadakis O., Papadimitriou E.

Follow up of juvenile individuals in Kalloni Gulf, Greece

In total, 40 juvenile P. nobilis individuals, recruited in 2022, have been tagged at a single site in Kalloni Gulf, Lesvos Island, since November 2022 in order to monitor their survival and growth rate.

Within 7 months (between 11 November 2022 and 06 June 2023), the average shell width growth of the juvenile individuals was 1.0cm, with a median of 1cm. The minimum shell width during the initial measurement was 2,5cm and the maximum 5,5cm, while during the last measurement, the minimum shell width was 3,4cm and the maximum 6,4cm.

Throughout the entire 5 month monitoring period, 15 of the individuals died (mortality rate 37,5%), while some others showed, slow valve-closing reflex. Molecular analysis showed the presence of Haplosporidium pinnae in dead juveniles’ tissue samples.

Installation of the larvae collectors to assist successful recruitment

Larval collectors had been installed by CSIC-IMEDEA and CSIC-IEO on key-points along the Mallorcan coast, PN Cabrera, and Menorca and in Ebro Delta by IRTA where historical recruitment is high. Data from all partner´s larval collectors will be compiled and used to evaluate the evolution of natural recruitment at monitored sites. Number of larvae and size will be used to estimate timing and patterns in yearly recruitment and predict the trajectory of future natural recruitment. A high-resolution regional hydrodynamic model will be used to simulate backward trajectories from sites where recruitment is recorded, to identify the potential origin and possible source populations of larvae transported by ocean currents over the basin during the recruitment period.

IMEDEA and IEO-CSIC collectors installation in Balearic Islands (Spain)

ACTION C.1: Installation of larvae collectors

The objective of this action is to place larval collectors designed to collect fan mussel larvae that settle directly from the pelagic larval stage unto the mesh in the collectors, which will indicate larval availability and potential recruitment in the benthos. When recruits are obtained, it will be possible to work with them in captivity maintenance (Action C7) and repopulation of study areas which are free of the parasite and considered as adequate for reintroduction (Action C4, D1).

Starting in spring 2017, but also in 2018, 2019 and 2020, the members of PINNARCA and collaborators installed larvae collectors in more than 10 stations of Spain, France, Italy and Greek coasts, to check the events of reproduction of P. nobilis, and try to detect the occurrence of adults that could produce the seeds. This 2023 spring, fan mussel larvae collectors are being placed in different hot-spots of Spain, France, Italy and Greece, before the breeding season (April-May) and will be collected after the breeding season (October-November). Juveniles found will be transferred to areas where the disease hasn’t been observed (e.g. Fangar Bay) or maintained in tanks.


IRTA collectors in Alfacs Bay, Ebro Delta (Spain)

The design of collectors is based on García-March and Vicente (2006) using mesh-bags and has been used successfully by the consortium (see Cabanellas (2009), Kersting y García-March (2017), Kersting, Hendriks (2019)). Each device will consist of a plastic mesh bag (ca. 5 mm opening) filled with onion mesh, nylon fishing thread or fishing net attached underneath a subsurface buoy and anchored to a mooring on the seafloor with a rope. Depending on the additional research question of the participants in this action the collectors will be placed at various depths but always covering a 5-8 m depth range to allow comparison of obtained data.

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Collectors settled on the Alfacs Bay, Spain

The design of collectors is based on García-March and Vicente (2006) using mesh-bags and has been used successfully by the consortium (see Cabanellas (2009), Kersting y García-March (2017), Kersting, Hendriks (2019)). Each device will consist of a plastic mesh bag (ca. 5 mm opening) filled with onion mesh, nylon fishing thread or fishing net attached underneath a subsurface buoy and anchored to a mooring on the seafloor with a rope. Depending on the additional research question of the participants in this action the collectors will be placed at various depths but always covering a 5-8 m depth range to allow comparison of obtained data.

Monitoring P. nobilis resistant individuals in Menorca island (Spain)

Several resistant survival individuals have been found in different sites on the Balearic Islands coast, and they have been monitored up to date by CSIC-IEO (e.g., in the National Park of Cabrera). These specimens and new resistant individuals (if found) will be monitored on the source site or in the translocated sites in order to check their survival by scuba diving.


MPAs proposal in Greece as an environmental improvement in fan mussel sanctuary areas

In an effort to protect the last two remaining P. nobilis populations of Greece, new Marine Protected Areas were defined and proposed towards the conservation of the species. 

Some of these areas would be located in Kalloni Gulf (Lesvos Island) at the Aegean Sea, and others in Amvrakikos Gulf, Ionian Sea. In these areas, all fishing activities would be prohibited, while boat anchoring would also be restricted in several of them.

The matter was discussed in length between governmental departments (such as the “Ministry of Environment & Energy” & the “Natural Environment & Climate Change Agency”) and the University of The Aegean (UAEGEAN), and the final decision of the Ministry of Environment & Energy is pending.

Looking for optimal sites in Formentera island (Spain)

Optimal areas free of pathogen (sanctuary) are being explored in the Balearic Islands by the CSIC-IEO this April 2023, which may enhance the dispersal capacity and successful settlement of the P. nobilis, particularly in L’Estany des Peix (small and shallow coastal lagoon located in Formentera island).

Additionally, optimal sites for translocation of resistant individuals are being identified considering previous data on distribution, density, population dynamics, genetic connectivity of the species and protection level. New areas for the translocation of surviving individuals will be identified within the limits of the National Park of Cabrera, where there is currently the first optimal site for translocation of resistant individuals.


ACTION A.2: Location of optimum sites

The identification of optimal sites to perform conservation actions is of high importance to reach successful reintroductions/reinforcements in Pinna nobilis populations. Two kinds of situations to be considered in this action are: sanctuary areas (free of the pathogen) and areas in the Mediterranean open sea (ideal for resistant individuals).

  • In the first case, and base in updated knowledge, optimal sites will be explored taking into account environmental conditions that prevent the spread of the pathogen (i.e., salinity) but are compatible with the survival of P. nobilis (dissolved oxygen, temperature, additional impacts…).

  • On the other hand, further optimal sites will be also prospected in the Mediterranean open sea aiming to find suitable places to host P. nobilis resistant individuals (previous knowledge of high densities, MPAs…).

An additional synergy of this action with broad implications at local and European ecological level is that, once the environment extremes have been characterized, the identified optimal areas could be used for conservation projects of other endangered species. The information will be made public and there is a strong commitment within the partners of the project to use the solutions developed and applied in the project for new conservation actions during and after the LIFE PINNARCA. By this way, the ecological value of the project would be increased beyond the target species itself.

Translocation of pen shell exposed to desiccation to deeper areas

In the Alfacs Bay (Ebro Delta, Spain), the disease has only affected some parts of the bay. It is of utmost interest to search for possible survivors, which could be resistant to the disease. A large number of juveniles and also some adults have been spotted in very shallow areas of the Alfacs Bay not subjected to MMEs. These individuals are at risk due to intense human activities and desiccation in the area. This month, IRTA has performed different census of the shallow areas (<30m depth) to examine for these survivors. Finally, a total of 200 out-of-water individuals have been translocated to deeper, safer areas, with the collaboration on the Zoo of Barcelona. Three new reservoirs in the Trabucador location have been created where repopulation could be successful. A follow up of the translocated individuals will be conducted monthly from now on.

ACTION C.4: Translocation of individuals

This action will be carried out in two levels. In the first level, because most individuals that needed urgent translocation have already been moved, this has become a maintenance task for juveniles in reservoirs and for punctual movement of new survivors that could be found after the end of the project.

In the second level, until enough resistant fan mussels are found and capable to achieve reproduction naturally, periodical translocation of individuals may have to be conducted among the different reservoirs periodically (once every several few years) and indefinitely, either to maintain a high genetic diversity, or to recover the populations in case any of them could collapse by natural or anthropogenic causes. This artificial recovery of areas optimal for fan mussels, would be an artificial adaptation of metapopulation theory, necessary to avoid the extinction of the species, until the numbers of resistant individuals could increase to safety values for the species.

Reproduction assays and tank maintenance of healthy individuals in IMEDMAR-UCV (Calpe, Valencia) and UA installations (Murcia)

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Two replicate actions with 20 individuals each is being carried out at the marine station of IMEDMAR-UCV in Calpe and the installations of Murcia Aquarium (subcontracted by UA). The individuals will be maintained during the entire project in closed circuits. Both institutions have experience in the maintenance of fan mussels in captivity. The objective of the action is to develop culture protocols to maximize the possibilities of captive reproduction, while ensuring the long-term survival of stabled individuals. Once reproduction in captivity is achieved, it will be possible to apply the same methodologies learned to the few resistant individuals, to produce seed with a higher potential of being resistant to the disease. The seed could be released in open waters to recover fan mussel populations. A common protocol will be used for the evaluation of growth rates and maturation degree of individuals in order to establish the best possible diet for the captive maintenance of the species.

On the other hand, different food types and quantities are being tested in Calpe, including phytoplankton gel (Isochrysis, Tetraselmis and Phaeodactylum), rotifers and Artemia nauplii. Furthermore, experiments of enrichment of Rotifers and Artemia, with high quality fatty acids, vitamins, antibiotics, when necessary, are being conducted. The condition and status of the individuals is being periodically evaluated by endoscopy and by the calculation of bioenergetic models (dynamic energy budget model) from faeces and pseudofaeces production, oxygen consumption, etc. Tank conditions (variable water temperatures, nutrients, nature of the sediment -porosity and type-, light cycles and wavelength) is being also modified and adapted to improve the microcosm conditions in the closed circuits.

Shallow census in the Fangar Bay

The Fangar Bay was recently hit by Storm Gloria (January 2020), which decimated hundreds of individuals due to reduced salinity and high turbidity. In a census after the event, only 12 individuals of Pinna nobilis were found alive (see Prado et al., 2020). However, an inner region of the bay has also been observed to host individuals in the recent past and a follow up of the healthy individuals in these shallow areas is being carried out in order to assess the survival of the species in this region, where there is no evidence of disease.

Additionally, some pen shells from IMEDMAR-UCV were returned to their natural habitat after having been part of reproduction assays in controlled tanks, and another group of individuals was removed from the area for the continuation of these experiments in captivity.

At the same time, the production of a professional video describing the main objectives of the LIFE PINNARCA project has been carried out these days in order to record the Fangar Bay census and the reproduction assays, among other things.

Revision of possible emerged P. nobilis at the Alfacs Bay


A large number of juveniles have been observed in a very shallow sandbar area of the Alfacs Bay. Estimated abundance in 2018 was over 3,000 juveniles. Last year, many of them were translocated after being found fully emerged at low tide conditions. The aim of this action is to find new individuals in extreme circumstances and areas where to translocate the survivors. These sub-optimal sites are adjacent deeper and safer zones, at least at 80 cm depth.

First follow up of translocated individuals in Ebro Delta this 2023


Monitoring of juvenile individuals transplanted to deeper areas adjacent to the main sand bar of the Alfacs Bay (Ebro Delta, Spain) is being conducted monthly. At each sampling time, the survival and growth of individuals and the physicochemical variables of the area are being recorded. For salinity and temperature, which are likely to be the most determinant variables influencing the dispersal of the Haplosporidian parasite, recording is conducted in continuum using a Hobo data logger.

Implementation of sedimentation fances in Alfacs Bay (Ebro Delta, Spain)

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