A PROJECT to reintroduce European native oysters has unveiled the first predicted impact of the species’ return.
New research from Heriot-Watt University has found that biodiversity will likely double over a decade once oyster restoration projects are complete.
The Dornoch Environmental Enhancement Project (DEEP) seeks to reintroduce four million oysters by 2030 into the protected area of the Dornoch Firth in the Scottish highlands.
The species had become extinct, probably due to overfishing, over 100 years ago.
The project aims to improve water quality, enhance marine biodiversity and increase carbon storage.
Oyster restoration efforts are growing as more is understood about the ‘ecosystem services’ provided by reefs, which many benefits to people and the environment.
But with intact oyster reef habitats so rare, researchers have previously had limited data to work with to help predict the biodiversity benefits of this marine conservation work.
Heriot-Watt researchers studied the biodiversity of Scotland’s last remaining native oyster fishery at Loch Ryan in south-west Scotland.
The fishery has operated since 1701 and uses a rotational harvest system: different areas are fished each year and then left to repopulate for six years before they are fished again.
As well as giving the researchers a window into the past, this has allowed the team to predict what a future reef in Dornoch could look like once oysters are fully restored.
This was achieved by studying the effect of oyster reef development and biodiversity gain at different stages after the oyster habitat had been fished.
Lead author Naomi Kennon from Heriot-Watt University said: “The findings from our research in Loch Ryan are extremely exciting, demonstrating that biodiversity will likely double over a decade once oyster restoration projects are complete.
“This means the population of species will increase in a balanced way.
“Our data has also shown a link between increased shell material as the oyster population grows and increased biodiversity.”
Treatments were plots that had been harvested one year previously, two years, and six years before the study began.
The treatments were surveyed with SCUBA using a combination of video transects and photo quadrats.
Modelling was used to predict changes in the Shannon-Wiener’s Diversity index (a globally recognised and popular measure of diversity) over time since fishing.
Calum Duncan, Head of Conservation Scotland at the Marine Conservation Society, said: “We are in a climate and nature emergency and need more than ever to boost marine ecosystem recovery.
“We’re proud to be a founding partner of this visionary project which demonstrates how powerful species restoration can be.
“The study in Loch Ryan shows that increasing the complexity of the seabed allows many species to find refuge in this living reef.
“We therefore look forward to thousands more native oysters being released in the Dornoch Firth, to attract even more biodiversity to the area.”
