Native Oyster Restoration
Native oysters are “ecosystem engineers”, filtering and cleaning water, sequestering carbon and contributing substantially to inshore biodiversity by creating reefs that become fish spawning grounds and nurseries.
Loch Craignish once supported a large population of native oysters but owing to human predation all but a few have gone. In the largest project of its kind in the UK, we plan to restore 1 million native oysters to the Loch Craignish seabed in order to restore biodiversity and create a community fishery in the long-run. So far, by the end of 2023, we’ve restored 350,000.
Pictures (from right): Oyster restoration with our local community; a goby in one of our newly restored oyster beds; oyster spat on the bottom of our boat. All images taken at Loch Craignish.
Our juvenile native oysters are sourced from Morecambe Bay Hatchery weighing around 1 gramme. We grow them in our floating nursery until they weigh approximately 12 grammes. At this point they’re big enough to survive some degree of predation from starfish and crabs on the seabed.
After conducting baseline surveys to identify the best release sites with the right substrate, shelter and depth, at a low spring tide our community volunteers broadcast them by hand into the shallows.
We survey the oysters on the seabed annually to see how they’re doing. As a result we know that the newly-formed oyster reefs are already contributing to biodiversity as we’re seeing a 1/3 more species in these areas. We’re also seeing “spat” showing that the oysters are breeding and multiplying – a crucial step towards our goal of creating a sustainable oyster population in Loch Craignish.
.jpg)
THE HISTORY OF NATIVE OYSTERS
Once native oysters were common and the food of the masses and in the Firth of Forth, outside Edinburgh, 30 million were harvested annually in the 1800s. As a result of human predation, pollution and disease, globally, an estimated 85% of native oyster beds have disappeared. In recognition of their importance for ecosystem health, efforts are now being made to restore native oysters worldwide.
The native oyster (Ostrea edulis) is distinct from the oysters which you normally buy in fishmongers and restaurants. These are non-native Pacific oysters (Crassostrea gigas) and are grown commercially in farms. The native oyster is more slow-growing and generally a far superior beast.
"It's so empowering to restore native oysters and to know we can make a difference." Hannah, Loch Craignish