Oysters reintroduced to Scotland’s Firth of Forth as part of a marine restoration project are thriving, according to new research. A year after being released, their survival rate is high – about 88 per cent – and many have grown faster than anticipated.
Scientists from Heriot-Watt University recently dived at two sites in the east-coast estuary to monitor the condition of European flat oysters relocated from Loch Ryan Oyster Fishery on the west coast of Scotland. Their observations indicate how well the marine molluscs are adapting to their new environment.
“One oyster has grown 2.1cm in one year, which is hugely promising,” says Dr Naomi Kennon of Heriot-Watt University, adding, “there is much higher growth than we expected.”
European flat oysters have declined by about 85 per cent worldwide. Once abundant in the Firth of Forth, overfishing and deteriorating water quality drove them to local extinction in the early 1900s.
The return of oysters to the Firth of Forth after a century-long absence is thanks to Restoration Forth, a marine conservation project that has brought 46,780 oysters to the estuary since 2023. Here, the animals play a crucial role in restoring the ecosystem.
“Oysters are incredible underwater engineers,” explains Kennon. “They filter water, store carbon and enhance biodiversity by providing shelter for countless marine species.” Based on studies of how oyster reefs recover after harvesting, Kennon believes the restoration effort could double local biodiversity over the next ten years.
More than 1,500 community volunteers have contributed to the project, which is supported by several partners, including the Marine Conservation Society (MCS). Caitlin Godfrey from the MCS describes working with volunteers as “one of the real positives” of Restoration Forth. “This success is only possible thanks to the incredible support from volunteers, local communities, and partners who share our vision for ocean recovery,” she says.
That support will be needed again, with further oyster releases planned for spring 2026. Oysters are now also being raised locally by Forth Marine Hatchery, which will significantly increase the number of oysters available for reintroduction to the Firth of Forth.
Over time, it is hoped the oysters will establish self-sustaining reefs. "That would be fantastic,” says Kennon.
Top image: oysters being deployed in the Firth of Forth. Credit: Maverick Photo Agency
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