Search

Menu
Search
in Ecology

Surviving the collapse: unprecedented densities of the critically endangered fan mussel Pinna nobilis in a Mediterranean coastal lagoon

179 Views


Abstract

The fan mussel Pinna nobilis, the largest bivalve endemic to the Mediterranean Sea, has experienced a near-total collapse since 2016 due to mass mortality events (MMEs) primarily caused by the protozoan parasite Haplosporidium pinnae. Now listed as Critically Endangered, the species is considered functionally extinct across most of its native range. However, recent surveys in the Thau Lagoon (southern France) revealed a large resilient population, with total abundance previously estimated at over 100,000 individuals. Within this population, exceptionally high densities were recorded along the Tocs sandbank system and the adjacent Quilles sector. Densities were quantified by freediving-based 100 m² belt transects (50 m × 2 m; n = 89) across 15 stations. Our study reports unprecedented densities, with a global mean of 78.6 ± 8.7 individuals/100 m² and a maximum of 511 individuals/100 m², surpassing previously reported values. Extrapolation within a conservative 180-ha core survey area yields a total abundance exceeding 1.4 million individuals. Field observations indicate the presence of various life stages, from juveniles to large adults, suggesting ongoing recruitment and long-term survival. Together, these findings highlight the potential conservation importance of Thau lagoon as a refuge for P. nobilis and identify the Tocs-Quilles area as a major density hotspot within this lagoon refuge.

Similar content being viewed by others

RNA-Seq comparative study reveals molecular effectors linked to the resistance of Pinna nobilis to Haplosporidium pinnae parasite

Article
Open access
08 December 2022

Phytoplankton phenology paradox in an isolated tropical lagoon of the northern Red Sea

Article
Open access
26 September 2025

Phytoplankton dynamics in a shellfish farming lagoon in a deltaic system threatened by ongoing climate change

Article
Open access
21 August 2024

Data availability

The datasets used during the current study are available from the corresponding author upon request.

References

  1. Vicente, N. & Moreteau, J. C. Statut de Pinna nobilis L. en Méditerranée (mollusque eulamellibranche). inLes Espèces Marines à Protéger en Méditerranée (eds (eds Boudouresque, C. F., Avon, M. & Gravez, V.) 159–168 (GIS Posidonie, Marseille, (1991).

    Google Scholar 

  2. Zavodnik, D. & Brenko, M. & Legac, M. Synopsis on the Fan Shell Pinna nobilis L. in the eastern Adriatic Sea. in Les Espèces Marines à Protéger en Méditerranée 169–178 (GiIS Posidonie, Marseille, (1991).

    Google Scholar 

  3. Rouanet, E., Trigos, S. & Vicente, N. From youth to death of old age: the 50-year story of a Pinna nobilis fan mussel population at Port-Cros Island (Port-Cros National Park, Provence, Mediterranean Sea). Sci. Rep. Port-Cros Natl. Park. 29, 209–222 (2015).

    Google Scholar 

  4. Corriero, G. & Pronzato, R. Epibiontic sponges on the bivalve Pinna nobilis. Mar. Ecol. Prog. Ser. 35, 75–82 (1987).

    Google Scholar 

  5. Cosentino, A. & Giacobbe, S. Aspects of epizoobiontic mollusc assemblages on Pinna shells. I. Composition and structure. Cah. Biol. Mar. 48, 187–197 (2007).

    Google Scholar 

  6. Rabaoui, L., Tlig-Zouari, S. & Cosentino, A. Ben Hassine, O. K. Associated fauna on the fan shell Pinna nobilis (Mollusca: Bivalvia) in the northern and eastern Tunisian coasts. Scientia Mar. 73, 129–141 (2009).

    Google Scholar 

  7. Vicente, N. La grande nacre de Méditerranée; Pinna nobilis, un coquillage bivalve plein de noblesse (Presses universitaires de Provence, 2020).

  8. Cosentino, A. & Giacobbe, S. Aspects of epizoobiontic mollusc assemblages on Pinna shells. II. Does the Mediterranean P. nobilis represent an isle of biodiversity?. Cah. Biol. Mar. 49, 161–173 (2008).

    Google Scholar 

  9. Hernandis Caballero, S. Avances en la ecología y biología para la conservación de la especie críticamente amenazada Pinna nobilis (Linnaeus, 1758), endemismo mediterráneo. (2021).

  10. Trigos, S., Garcia-March, J., Vicente, N., Medialdea, J. & Torres, J. Utilization of muddy detritus as organic matter source by the fan mussel Pinna nobilis. Mediterranean Mar. Sci. 15, 667–674 (2014).

    Google Scholar 

  11. Pensa, D. et al. Population status, distribution and trophic implications of Pinna nobilis along the South-eastern Italian coast. npj Biodivers. 1, 1–10 (2022).

    Google Scholar 

  12. Combelles, S., Moreteau, J. C. & Vicente, N. Contribution a la connaissance de l’écologie de Pinna nobilis L. (Mollusque: Eulamellibranche). Sci Rep. Port-Cros ntl Park. 12, 29–43 (1986).

    Google Scholar 

  13. Butler, A., Vicente, N. & de Gaulejac, B. Ecology of the pterioid bivalves Pinna bicolor Gmelin and Pinna nobilis L. Mar. Life. 3, 37–45 (1993).

    Google Scholar 

  14. Hendriks, I., Cabanellas-Reboredo, M., Bouma, T., Deudero, S. & Duarte, C. Seagrass Meadows Modify Drag Forces on the Shell of the Fan Mussel Pinna nobilis. Estuaries Coasts. 34, 60–67 (2011).

    Google Scholar 

  15. Vázquez-Luis, M., March, D., Elvira, Á. P., Alvarez-Berastegui, D. & Deudero, S. Spatial distribution modelling of the endangered bivalve Pinna nobilis in a Marine Protected Area. Mediterranean Mar. Sci. 15, (2014).

  16. Coppa, S. et al. Self-organisation in striped seagrass meadows affects the distributional pattern of the sessile bivalve Pinna nobilis. Sci. Rep. 9, 7220. https://doi.org/10.1038/s41598-019-43214-6 (2019).

    Google Scholar 

  17. Basso, L. et al. The Pen Shell, Pinna nobilis: A Review of Population Status and Recommended Research Priorities in the Mediterranean Sea. Adv. Mar. Biol. 71, 109–160 (2015).

    Google Scholar 

  18. Deudero, S., Vázquez-Luis, M. & Álvarez, E. Human stressors are driving coastal benthic long-Lived sessile fan mussel Pinna nobilis population structure more than environmental stressors. PLOS ONE. 10, e0134530 (2015).

    Google Scholar 

  19. Öndes, F., Kaiser, M. & Güçlüsoy, H. Human impacts on the endangered fan mussel, Pinna nobilis. Aquatic Conserv.: Mar. Freshw. Ecosyst. 30, (2019).

  20. Deudero, S. &Vázquez-Luis, M. Marine protected areas effectively maintain endemic Pinna nobilis populations. In CIESM Congress 2016 (Kiel, Germany) abstract 0502 (2016).

  21. Catanese, G. et al. Haplosporidium pinnae sp. nov., a haplosporidan parasite associated with mass mortalities of the fan mussel, Pinna nobilis, in the Western Mediterranean Sea. J. Invertebr. Pathol. 157, 9–24 (2018).

    Google Scholar 

  22. Katsanevakis, S. et al. The cryptogenic parasite Haplosporidium pinnae invades the Aegean Sea and causes the collapse of Pinna nobilis populations. Aquatic Invasions 14, (2019).

  23. Panarese, R. et al. Haplosporidium pinnae associated with mass mortality in endangered Pinna nobilis (Linnaeus 1758) fan mussels. J. Invertebrate Pathol. 164, (2019).

  24. Grau, A. et al. Wide-Geographic and long-term analysis of the role of pathogens in the decline of Pinna nobilis to critically endangered species. Front. Mar. Sci. 9, (2022).

  25. Carella, F. et al. Multipathogen infections and multifactorial pathogenesis involved in noble pen shell (Pinna nobilis) mass mortality events: Background and current pathologic approaches. Vet. Pathol. 60, 1–18 (2023).

    Google Scholar 

  26. Kersting, D. et al. Pinna nobilis. The IUCN Red List of Threatened Species 2019. 10.2305/IUCN.UK.2019-3.RLTS.T160075998A160081499.en (2019).

  27. González, R. et al. Deliverable D.2 – Report of the Status of the Followed Individuals II. Within the Action D2: Follow up of Resistant Individuals (Pinna Nobilis). LIFE Pinnarca NAT/ES/001265 ‘Protection and restoration of Pinna Nobilis populations as a response to the catastrophic pandemic started in 2016’, 27 pp. (2023).

  28. Donato, G., Vázquez-Luis, M., Nebot-Colomer, E., Lunetta, A. & Giacobbe, S. Noble fan-shell, Pinna nobilis, in Lake Faro (Sicily, Italy): Ineluctable decline or extreme opportunity? Estuar. Coast. Shelf Sci. 261, 107536 (2021).

    Google Scholar 

  29. Foulquie, M., Grandrive, R., Dalias, N. & Vicente, N. Inventaire et état de santé des populations de Pinna nobilis (L.1758) dans l’étang de Thau (Hérault, France). Marine-life (2020).

  30. Foulquié, M., Coupé, S., Vicente, N. & Bunet, R. First detection of Pinna nobilis infection by Haplosporidium pinnae in the sanctuary area of Thau lagoon, France. Mediterranean Mar. Sci. 24, 569–573. https://doi.org/10.12681/mms.32300 (2023).

    Google Scholar 

  31. Foulquié, M., Coupé, S., Vicente, N. & Bunet, R. Population status of the critically endangered fan mussel Pinna nobilis in Thau lagoon (France). Endanger. Species Res. 55, 21–36 (2024).

    Google Scholar 

  32. Karadurmuş, U., Benli, T. & Sari, M. Discovering new living Pinna nobilis populations in the Sea of Marmara. Mar. Biol. 171, (2024).

  33. Karadurmuş, U., Akkuş, M. & Sarı, M. Distribution of fan mussel (Pinna nobilis) population in the Sea of Marmara. Aquat. Conserv.: Mar. Freshw. Ecosyst. 35, e70173. https://doi.org/10.1002/aqc.70173 (2025).

    Google Scholar 

  34. Karadurmuş, U. et al. Health assessment of fan mussels in the southern part of the Sea of Marmara. Mediterranean Mar. Sci. 26, (2025).

  35. Katsanevakis, S. et al. The fan mussel Pinna nobilis on the brink of extinction in the Mediterranean. In Imperiled: The Encyclopedia of Conservation 700–709 (Elsevier, 2022). https://doi.org/10.1016/B978-0-12-821139-7.00070

  36. Labidi, S. et al. First detection of the invasive protozoan Haplosporidium pinnae in the critically endangered bivalve Pinna nobilis in the Southern Mediterranean Sea (Bizerte Lagoon, Tunis) and update of its current status. Mediterranean Mar. Sci. 24, 470–481 (2023).

    Google Scholar 

  37. Mihaljevic, Z. et al. Noble pen shell (Pinna nobilis) mortalities along the Eastern Adriatic coast with a study of the spreading velocity. J. Mar. Sci. Eng. 9, 764 (2021).

    Google Scholar 

  38. Nebot-Colomer, E. et al. Living under threat: Will one of the last Pinna nobilis populations be able to survive? Aquat. Conservation: Mar. Freshw. Ecosyst. 32, 1–13 (2022).

    Google Scholar 

  39. Nikolaou, A., Papadimitriou, E., Kiourani, E. & Katsanevakis, S. Pinna nobilis refugia breached: Ongoing mass mortality event in the Gulf of Kalloni (Aegean Sea). Mediterranean Mar. Sci. 25, 747–752 (2024).

    Google Scholar 

  40. Peyran, C., Morage, T., Nebot-Colomer, E., Iwankow, G. & Planes, S. Unexpected residual habitats raise hope for the survival of the fan mussel Pinna nobilis along the Occitan coast (Northwest Mediterranean Sea). Endanger. Species Res. 48, 123–137 (2022).

    Google Scholar 

  41. Prado, P. et al. Pinna nobilis in suboptimal environments are more tolerant to disease but more vulnerable to severe weather phenomena. Mar. Environ. Res. 163, 105220 (2021).

    Google Scholar 

  42. Zotou, M. et al. Pinna nobilis in the Greek seas (NE Mediterranean): On the brink of extinction? Mediterranean Mar. Sci. https://doi.org/10.12681/mms.23777 (2020).

    Google Scholar 

  43. Burchaell, O. Les variations du niveau de l’étang de Thau (Hérault, France). Etude des phénomènes de surcotes-décotes au sein d’un milieu lagunaire méditerranéen. 180 p. (2000).

  44. Fiandrino, A., Giraud, A., Robin, S. & Pinatel C.Validation d’une méthode d’estimation des volumes d’eau échangés entre la mer et les lagunes. 104 (2012).

  45. Fiandrino, A. et al. Spatial patterns in coastal lagoons related to the hydrodynamics of seawater intrusion. Mar. Pollut. Bull. 119, 132–144 (2017).

    Google Scholar 

  46. Lazure, P. Etude de la dynamique de l’étang de Thau par modèle numérique tridimensionnel. Vie et milieu. 42, 137–145 (1992).

    Google Scholar 

  47. Fleury, E., Petton, S., Benabdelmouna, A. & Pouvreau, S. (eds) (coord.). Observatoire national du cycle de vie de l’huître creuse en France. Rapport annuel ECOSCOPA 2022. (2023). https://archimer.ifremer.fr/doc/00840/95240/.

  48. SMBT. Suivi oxygène 2023 de la lagune de Thau. (2023). https://www.smbt.fr/storage/2023/06/bull_24_et_25_07_2023.pdf

  49. Gerbal, M. & Verlaque, M. Macrophytobenthos de substrat meuble de l’étang de Thau (France, Méditerranée) et facteurs environnementaux associés. Oceanol. Acta. 18, 557–571 (1995).

    Google Scholar 

  50. SMBT. Document d’Objectifs Des Sites Natura 2000 de Thau. Tome 1. (2011).

  51. Katsanevakis, S. Population ecology of the endangered fan mussel Pinna nobilis in a marine lake. Endanger. Species Res. 1, 51–59 (2005).

    Google Scholar 

  52. Garcia-March, J., Garcia- Carrascosa, A., Peña Cantero, Á. & Wang, Y. G. Population structure, mortality and growth of Pinna nobilis Linnaeus, 1758 (Mollusca, Bivalvia) at different depths in Moraira bay (Alicante, Western Mediterranean). Mar. Biol. 150, 861–871 (2007).

    Google Scholar 

  53. Coppa, S., Guala, I., de Lucia, G., Massaro, G. & Bressan, M. Density and distribution patterns of the endangered species Pinna nobilis within a Posidonia oceanica meadow in the Gulf of Oristano (Italy). J. Mar. Biol. Association United Kingd. – J. MAR. BIOL. ASSN UK. 90, 885–894 (2010).

    Google Scholar 

  54. Efron, B. & Tibshirani, R. J. An Introduction to the Bootstrap (Chapman and Hall/CRC, 1994). https://doi.org/10.1201/9780429246593

  55. R Core Team. R: A language and Environment for Statistical Computing (R Foundation for Statistical Computing, 2023). https://www.R-project.org/

  56. Wickham, H. ggplot2: Elegant graphics for data analysis. in Data analysis 189–201 (Springer International Publishing, 2016). https://doi.org/10.1007/978-3-319-24277-4_9

  57. Rabaoui, L., Ben Hassine, O. K. & Tlig-Zouari, S. Distribution and habitat of the fan mussel Pinna nobilis Linnaeus, 1758 (Mollusca: Bivalvia) along the northern and eastern Tunisian coasts. Cah. Biol. Mar. 49, 67–78 (2008).

    Google Scholar 

  58. Silvestri, S., Capra, V., Cucchiaro, S. & Pivato, M. Tides, topography, and seagrass cover controls on the spatial distribution of Pinna nobilis on a coastal lagoon tidal flat. J. Geophys. Res.: Biogeosci. 127, (2022).

  59. Papadakis, O. et al. Status, distribution, and threats of the last surviving fan mussel populations in Greece. Mediterranean Mar. Sci. 24, 679–708 (2023).

    Google Scholar 

  60. Cizmek, H. & Čolić, B. Zubak Čižmek, I. Reconstructing the historical density, size, and age structure of the noble pen shell (Pinna nobilis) population: Insights from Malo Jezero Lagoon, Mljet National Park (Adriatic Sea). Water 17, 663 (2025).

    Google Scholar 

  61. Gascoigne, J. & Lipcius, R. Allee effects in marine systems. Mar. Ecol. Prog Ser. 269, 49–59 (2004).

    Google Scholar 

  62. Coupé, S. et al. The characterization of toll-like receptor repertoire in Pinna nobilis after mass mortality events suggests adaptive introgression. Ecol. Evol. 13, e10383 (2023).

    Google Scholar 

Download references

Acknowledgements

We thank Simone Richard (Mediterranean Institute of Oceanography) for her valuable advice on statistical analysis, the team of the Côte agathoise Marine Protected Area, the Syndicat Mixte du Bassin de Thau and the Sète Agglopôle Méditerranée’s Brigade bleue for the technical assistance during field surveys. This work was supported by the European projects LIFE20-NAT-ES-PINNARCA/001265, LIFE24-NAT-ES-PINNACARE/101216239 and by the Maud Fontenoy, Forvia and UEM Foundations.

Author information

Authors and Affiliations

  1. Institut océanographique Paul Ricard, Ile des Embiez, 83140, Six-Fours-les- Plages, France

    Mathieu Foulquié, Yaël Hatret, Nardo Vicente & Robert Bunet

  2. Aix Marseille Univ., CNRS, IRD, MIO, Université de Toulon, 83130, La Garde, France

    Mathieu Foulquié & Stéphane Coupé

  3. Faculté des Sciences – Aix-Marseille Université, 13009, Marseille, France

    Ambre Bailet

  4. Aix-Marseille Université, CNRS, IRD, Avignon Univ. France, Institut Méditerranéen de Biodiversité et Ecologie marine et continentale (IMBE), 84916, Avignon, France

    Nardo Vicente

Authors

  1. Mathieu Foulquié
    View author publications

    Search author on:PubMed Google Scholar

  2. Ambre Bailet
    View author publications

    Search author on:PubMed Google Scholar

  3. Yaël Hatret
    View author publications

    Search author on:PubMed Google Scholar

  4. Nardo Vicente
    View author publications

    Search author on:PubMed Google Scholar

  5. Stéphane Coupé
    View author publications

    Search author on:PubMed Google Scholar

  6. Robert Bunet
    View author publications

    Search author on:PubMed Google Scholar

Contributions

MF, SC, NV and RB designed and supervised the study. MF and AB conducted the field work. MF, YH, RB, NV and SC analyzed the data and wrote the manuscript. All authors read and approved the final manuscript.

Corresponding author

Correspondence to
Robert Bunet.

Ethics declarations

Competing interests

The authors declare no competing interests.

Ethics approval

No experimentation involving killing of P. nobilis individuals was performed.

Additional information

Publisher’s note

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Supplementary Information

Below is the link to the electronic supplementary material.

Supplementary Material 1 (download DOCX )

Rights and permissions

Open Access This article is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License, which permits any non-commercial use, sharing, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if you modified the licensed material. You do not have permission under this licence to share adapted material derived from this article or parts of it. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by-nc-nd/4.0/.

Reprints and permissions

About this article

Cite this article

Foulquié, M., Bailet, A., Hatret, Y. et al. Surviving the collapse: unprecedented densities of the critically endangered fan mussel Pinna nobilis in a Mediterranean coastal lagoon.
Sci Rep (2026). https://doi.org/10.1038/s41598-026-48614-z

Download citation

  • Received:

  • Accepted:

  • Published:

  • DOI: https://doi.org/10.1038/s41598-026-48614-z

Keywords

  • Noble pen shell, fan mussel

  • Pinna nobilis
  • Critically endangered species
  • Densities
  • Abundance
  • Coastal lagoons
  • Conservation

Source: Ecology - nature.com

Gradient compression drives divergent sediment bacterial and fungal assembly from river to sea

Spatiotemporal monitoring and assessment of green oak leaf-roller outbreaks in Zagros forests using Sentinel-2 data and the BFAST algorithm

This portal is not a newspaper as it is updated without periodicity. It cannot be considered an editorial product pursuant to law n. 62 of 7.03.2001. The author of the portal is not responsible for the content of comments to posts, the content of the linked sites. Some texts or images included in this portal are taken from the internet and, therefore, considered to be in the public domain; if their publication is violated, the copyright will be promptly communicated via e-mail. They will be immediately removed.

Back to Top
Close