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Essays to improve feeding of P. nobilis in ex-situ conditions are being carried out

This action aims to address the knowledge gap in the feeding behavior of Pinna nobilis. It consolidates findings from prior studies conducted in natural habitats and during ex situ maintenance. The next step involves examining current advancements and protocols for locating in situ individuals and refining feeding practices within the culture systems at the Aquarium of the University of Murcia. Ensuring appropriate feeding practices is vital for maintaining this species effectively in ex-situ systems and, consequently, for its survival. Finally, findings on feeding recommendations will be published by the Murcia University Aquarium and IMEDMAR-UCV.

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Phytoplankton cultivation system at the University of Murcia Aquarium.

Specimens of Pinna nobilis in the IMEDMAR aquariums where the experiments are carried out.

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19 Pinna sp. were retrieved from the collectors in Calpe this 2023

Monitoring recruitment of populations of sessile bivalves with pelagic larvae is a powerful tool to detect the presence of healthy, reproductive adult populations. It also is an indicator for the natural recovery potential of the species and reduces efforts when searching for newly recruited individuals as the collector bags concentrate the larval potential and reduce mortality associated with benthic populations.

The LIFE PINNARCA project provides the means to support a large part of the monitoring network and has helped expanding the sites were recruitment is monitored. In 2022, a positive identification was made in Catalunya 1.25 Pinna nobilis per bag in Meda gran and 0.5 in Cadaquès - s’Arenella at less than 1 m depth. In the marine reserve of the Columbretes islands 4 P. rudis were found at 15 m depth between 12 collectors (personal comm Diego Kersting), but no P. nobilis.

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Retrieved individuals in Calpe

This year, in total many bags were deployed and information is being processed. In the Balearic islands, no recruits were found, even if this year an extensive effort was done on part of the local government with the deployment of 75 collectors. In Calpe 19 Pinna sp. Individuals were retrieved by IMEDMAR-UCV, mostly outside the actual collectors, at 2 sites in 3 and 6 replicate collectors. On average 3.00 ± 1.53 (SD) and 1.67 ± 0.52 (SD) individuals were found per site. Identification to species levels is currently underway.

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IEO and IRTA carried out visual census in shallow areas in Ebro Delta

A distance sampling survey was conducted for estimating the abundance of the species in the Alfacs bay (Spain). In contrast to Fangar Bay, where fan mussels are more confined to a specific zone, their widespread presence along the entire perimeter of Alfacs Bay made necessary the implementation of a Distance Sampling methodology. This method involves quantifying the distance along perpendicular transects and observing each individual (whether alive or dead) within a detailed description of its habitat, aiming to estimate the densities of the species in all the bay areas as accurate as possible.

A total of 73 walking transects extending from the shoreline to a depth of ca. 1.2 meters was conducted with the collaboration of Forestal Catalana (Catalan Government) in summer 2022-2023 who used their own funds. The survey covered the entire Alfacs Bay, starting from the north coast and extending southward through the Trabucador sandbar to the Banya peninsula. Additionally, 75 underwater transects were conducted by the Balearic IEO-CSIC in September 2022 and 2023, reaching depths of up to 3 meters. The IEO-CSIC sampling was conducted in the context of the project ESMARES_PINNA_C2A5T3 financed by the Spanish Government. The depth limit of 2-3 meters was established, as it is presumed that the habitat beyond this range is no longer suitable for fan mussels and no individuals have been never observed.

Distance sampling consisted in a series of transects perpendicular to the coast. The methodology consisted of traveling with scuba through systematic transects, perpendicular to the coast, divided in a succession of sections, each of them 40 m long. At the beginning of each transect and every 20 m of each section, the depth, visibility, and composition of the algal community and the sediment were noted. In the case of finding a specimen of P. nobilis, the state, size, depth of the individual, visibility, algal composition and composition of the sediment around the individual were recorded. Each underwater transect began with the theoretical coordinate of the end of the fordable transect, following the same course and this methodology was followed until the end of the ideal habitat for the survival of P. nobilis. If at the end of the section the habitat was no longer suitable for the survival of P. nobilis, the transect was finished.

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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.

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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.

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Collection of Pinna nobilis from the Mar Menor coastal lagoon

The collection of Pinna nobilis specimens from their natural habitat, followed by their maintenance in laboratory conditions, should be performed, taking into account the specific requirements of each individual (Cortes Melendreras and Giménez Casalduero, 2020). The objective is to develop protocols for the collection, translocation, and ex situ maintenance of P. nobilis specimens from the Mar Menor, ensuring optimal health, growth, and reproductive potential. This action will be conducted in close collaboration with the University of Murcia's aquarium, which will handle the outsourcing.

Transport of Pinna nobilis from the Mar Menor coastal lagoon in a portable cooler.

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Installation and recovery 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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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.

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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.

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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.

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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.

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Translocation of pen shell exposed to desiccation to deeper areas in Alfacs Bay