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The battle to save the Spanish Mediterranean coast’s last noble pen shell populations continues

Nacres a la Badia dels Alfacs. Font: IRTA (CC BY-NC 4.0)
Nacres a la Badia dels Alfacs. Font: IRTA (CC BY-NC 4.0)

Coordinated by IRTA with the cooperation of the University of Alicante, a new project is being carried out to save the noble pen shells of the Ebro Delta and the Mar Menor, the two locations where the species can still be found in Spanish waters

The main threat to these bivalves is a deadly parasite that appears to be less virulent in conditions of extremely high or extremely low salinity

The Institute of Agrifood Research and Technology (IRTA) and the University of Alicante (UA) will be working together on a new project to save the noble pen shell (Pinna nobilis) in two characteristic areas of the Spanish Mediterranean, the Ebro Delta (in Catalonia) and the Mar Menor (in Murcia). Funded by the Biodiversity Foundation of Spain’s Ministry for the Ecological Transition and the Demographic Challenge (MITECO) and the Barcelona Zoo Foundation, the Recupera Pinna project has the main objective of determining the status of the current noble pen shell populations and taking a real census of them, helped by volunteers from the two areas through the citizen science platforms NACRANET and Sea Watchers. Once the populations’ status has been established, specimens in locations where they are at risk will be moved to safe sites.

Habitat loss, trawling and eutrophication have all spelled danger for the noble pen shell, as has the fact that it is highly prized by collectors. Since 2016, however, the main threat to its survival as a species has been the appearance of Haplosporidium pinnae, a protozoan parasite of unknown origin which causes death in close to 100% of cases. In the Ebro Delta, there are noble pen shell populations in the Fangar Bay and the Alfacs Bay. “Unfortunately, only 12 of the Fangar Bay’s 533 specimens survived Storm Gloria,” says IRTA researcher Patricia Prado. “The Alfacs bay was not directly affected by the storm, but many of its noble pen shells have died because of the parasite, particularly in the outer part of the bay,” she continues.

Exemplar de nacra a la Badia dels Alfacs. Font: IRTA (CC BY-NC 4.0)
Individual of a noble pen shell at Badia dels Alfacs. Source: IRTA (CC BY-NC 4.0)

Scientists have found that marine environment conditions make the parasite more virulent.“When the seawater temperature rises above 13.5ºC, the parasite becomes very capable of developing and infecting specimens; that happens in spring and, in particular, in summer,” explains Prado. Furthermore, the level of salinity optimal for noble pen shells is also ideal for the parasite, which is why the specimens worst affected are those found close to the connection with the open sea, where the mean salinity level is between 36.5 and 39 ppt. The populations that remain healthy live in the inner part of the Alfacs Bay, where the salinity level is low due to the delta’s oceanographic dynamics causing an inflow of fresh water from rice fields, which acts as a boundary for the parasite. Thanks to the new project and a partnership agreement with the Barcelona Zoo Foundation, the researchers will not only have six new instruments for measuring salinity and temperature, so as to ensure the safety of new sites for the noble pen shells, but will also enjoy the support of the Foundation’s technical staff when working in the field.

Environmental imbalance is the danger threatening the Mar Menor’s noble pen shells

The main problem in the Mar Menor is poor water quality. “Midway through 2015, extreme eutrophication took place there and the lack of oxygen caused many specimens to die,” states UA researcher Francisca Giménez. “We hope this project will enable us to find new specimens, identify critical zones, and move specimens from areas where they are at risk to safer locations,” she adds. The Mar Menor’s first noble pen shell populations appeared in the 1980s, when the lagoon was artificially connected with the sea, resulting in a drop in its salinity level. The noble pen shell subsequently became a key species in the lagoon, occupying 65% of its area until 2014. Besides extreme environmental conditions, the bivalves are also threatened by illegal fishing and other pathogens, such as the bacteria Vibrio mediterranei sp.

In Spain, the noble pen shell is classified as critically endangered. It is one of the species prioritized by the MITECO, which is already coordinating conservation work with expert researchers from the different autonomous communities. Nonetheless, the experts warn that ensuring the noble pen shell’s survival will require further measures besides its inclusion in the Catalogue of Threatened Wildlife of Catalonia. “We need cooperation and coordination with the different users of the marine environment, such as the tourism industry, fishermen and bivalve producers, to protect the specimens in the bays from being hit by boats or vandalized, as well as to identify any new specimens that may appear in fishing grounds or infrastructures,” the researchers conclude.

The project “Recupera Pinna” counts with the support of Fundación Biodiversidad, from the Ministery for Ecological Transition and the Demographic Challenge.