Reported declines of the grooved carpet-shell clam ( Ruditapes decussatus ) across southwestern Europe and the Mediterranean: insights from expert knowledge
Abstract
The grooved carpet-shell clam ( Ruditapes decussatus ) is a native clam species that inhabits estuaries, lagoons, and coastal flats along the Mediterranean Sea and the northeast Atlantic. This highly prized bivalve is an ecosystem engineer that provides major ecological functions, including water filtration and sediment bioturbation. A decline in production has recently been observed in several areas of southwestern European and the Mediterranean region; however, data documenting this phenomenon remain scarce and are largely unpublished. To address this knowledge gap, we conducted a study based on official statistics, the expertise of 24 marine ecosystem experts from eight countries covering 17 coastal sites, and a preliminary literature map. This approach enabled the development of an expert-informed regional perspective on the reported declines of R. decussatus , as well as a synthesis of the regulatory measures and restoration actions implemented across the study area. The findings indicate a sharp decline in both production (−32 to −100%) and stocks (≈ −80%) over the past two decades. The onset of the decline varied among sites, occurring between 2003 and 2024. According to the participating experts, the main suspected drivers of the decline were disease, overfishing, competition with alien species, and climate change. The most common regulatory measures were minimum conservation reference sizes, closed fishing seasons, and licenses. Only a few restoration projects were identified, focusing on restocking through seeding, the collection of natural broodstock, harvesting natural spat or substrate modification. This study provides a preliminary overview of the seemingly widespread decline of R. decussatus across the southwestern European and Mediterranean region and highlights the need for coordinated research to elucidate the causes of this reported decline, as well as for restoration actions to support the recovery of this native species.
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BibTeX
@article{derolez2026reported,
title = {{Reported declines of the grooved carpet-shell clam ( Ruditapes decussatus ) across southwestern Europe and the Mediterranean: insights from expert knowledge}},
author = {Valerie Derolez and Rocco Auriemma and Kruno Bonačić and Diego Borme and Nathalie Caill-Milly and Stefano Carboni and Fiz da Costa and João G. Ferreira and Marta Rocha and Paolo Magni and Francisco Maia and Borut Mavrič and Walid Medhioub and Alice Newton and Roberto Pastres and Valentina Pitacco and Sofia Reizopoulou and Carlos Saavedra and Florence Sanchez and Elsa Vázquez and Satoshi Watanabe and Franck Lagarde},
journal = {Aquatic Living Resources},
year = {2026},
month = nov,
doi = {10.1051/alr/2026022},
url = {https://hal.science/hal-05854011v1},
note = {CC BY},
}
RIS
TY - JOUR
TI - Reported declines of the grooved carpet-shell clam ( Ruditapes decussatus ) across southwestern Europe and the Mediterranean: insights from expert knowledge
AU - Valerie Derolez
AU - Rocco Auriemma
AU - Kruno Bonačić
AU - Diego Borme
AU - Nathalie Caill-Milly
AU - Stefano Carboni
AU - Fiz da Costa
AU - João G. Ferreira
AU - Marta Rocha
AU - Paolo Magni
AU - Francisco Maia
AU - Borut Mavrič
AU - Walid Medhioub
AU - Alice Newton
AU - Roberto Pastres
AU - Valentina Pitacco
AU - Sofia Reizopoulou
AU - Carlos Saavedra
AU - Florence Sanchez
AU - Elsa Vázquez
AU - Satoshi Watanabe
AU - Franck Lagarde
PY - 2026
DA - 2026/11/05
JO - Aquatic Living Resources
DO - 10.1051/alr/2026022
UR - https://hal.science/hal-05854011v1
AB - The grooved carpet-shell clam ( Ruditapes decussatus ) is a native clam species that inhabits estuaries, lagoons, and coastal flats along the Mediterranean Sea and the northeast Atlantic. This highly prized bivalve is an ecosystem engineer that provides major ecological functions, including water filtration and sediment bioturbation. A decline in production has recently been observed in several areas of southwestern European and the Mediterranean region; however, data documenting this phenomenon remain scarce and are largely unpublished. To address this knowledge gap, we conducted a study based on official statistics, the expertise of 24 marine ecosystem experts from eight countries covering 17 coastal sites, and a preliminary literature map. This approach enabled the development of an expert-informed regional perspective on the reported declines of R. decussatus , as well as a synthesis of the regulatory measures and restoration actions implemented across the study area. The findings indicate a sharp decline in both production (−32 to −100%) and stocks (≈ −80%) over the past two decades. The onset of the decline varied among sites, occurring between 2003 and 2024. According to the participating experts, the main suspected drivers of the decline were disease, overfishing, competition with alien species, and climate change. The most common regulatory measures were minimum conservation reference sizes, closed fishing seasons, and licenses. Only a few restoration projects were identified, focusing on restocking through seeding, the collection of natural broodstock, harvesting natural spat or substrate modification. This study provides a preliminary overview of the seemingly widespread decline of R. decussatus across the southwestern European and Mediterranean region and highlights the need for coordinated research to elucidate the causes of this reported decline, as well as for restoration actions to support the recovery of this native species.
SN - 0990-7440
SN - 1765-2952
ER -