An extremely rare and threatened species of giant mussel has been discovered on the seabed near Valentia Island in Co Kerry.
The fan mussel – or Atrina fragilis – is critically endangered.
It was discovered by divers from Sea Synergy Marine Awareness, Research and Activity Centre, and environmental coalition Fair Seas, who were studying the native European flat oyster population in the Portmagee Channel Special Area of Conservation.
They did not disturb the mussel on the seabed, but on a visual examination estimate that it measures 25 centimetres wide by 20 centimetres tall, with another two-thirds of the mussel buried in the silt.
This fan mussel is one of the largest and one of the rarest bivalve molluscs in Europe.
The only other live sightings in Irish waters were in Northern Ireland off Rathlin Island in 2007 and 1971. Shells from the mussels have previously washed up in Cork harbour and in Daingean Uí Chuis in west Kerry.
The mussel was widely sought-after by Victorian shell-collectors, and expensive gloves and stockings were once made from its silky threads.
“We know very little about this mussel,” Elis Martinelli, Marine Programme and Operations Manager with Sea Synergy said.
“They live in soft sediment with up to two-thirds of their shell buried, they’re estimated to live from anywhere between 10 and 100 years. They were far more common more than a century ago but they are fragile creatures, vulnerable to trawling, dredging and pollution, and have become incredibly rare. The last sighting in Irish waters was almost 20 years ago, off Northern Ireland, so this find is extremely significant.”
Jack O’Donovan Trá, Marine Biologist and Communications Officer with Fair Seas, also took part in the dive.
“The fan mussel is an extraordinarily rare aquatic animal and it’s amazing to find it so close to the Kerry coast. On-the-ground projects such as those being run by Sea Synergy and partners are vital because of the lack of detailed marine habitat surveys by government agencies,” he said.
Pictured are Jack O’Donovan Trá, Communications Officer, Fair Seas; Elis Martinelli, Marine Programme and Operations Manager, Sea Synergy; and Lukas Werner, Research Officer, Sea Synergy. Picture: Sea Synergy
He added: “Supporting projects such as these are direct actions that will lead to a deeper understanding of our native and threatened ecosystems. It also highlights why we need management plans and dedicated surveys of Ireland’s protected sites to ensure these ecosystems can recover and thrive.”
The Sea Synergy Oyster Project, developed in collaboration with Portmagee Tidy Towns, began following the discovery of an exceptionally large native oyster by local fisherman Brendan Murphy in 2020.
Since then, scientific research, extensive shoreline and snorkelling surveys have recorded 1,605 living native oysters, including unusually large individuals, and helped map their distribution throughout the channel.
In 2026, the project entered a new phase, expanding into deeper waters through SCUBA-based biodiversity and oyster surveys with Inbhear Sceine Kerry Sub Aqua Club.
The project has been supported by the Heritage Council, the National Parks and Wildlife Service, and Fair Seas.
Fair Seas is a coalition of leading environmental non-governmental organisations and networks. It is campaigning for strong and ambitious marine protected areas legislation committing to effectively protecting 30% of the seas around Ireland by 2030, with 10% strictly protected.
The group’s membership includes Irish Wildlife Trust, BirdWatch Ireland, Sustainable Water Network, Irish Whale and Dolphin Group, Streamscapes, Irish Environmental Network and Coastwatch.