Professor William Sanderson, or Bill as he likes to be known, wades into the shallows of the Dornoch Firth as the sun breaks over the ragged skyline of the Scottish Highlands, turning the waters gold. Something in the water catches his eye and he stoops to pick it up. “This is a European native oyster,” he explains. “They used to be very abundant in this site thousands of years ago right up to the 1800s.”
The shell in his hand is flatter and rounder than the faster growing Pacific oysters common in European restaurants today. It is also very rare, having been fished almost to extinction in British waters during the Industrial Revolution.
“Rail networks opened up urban markets, and what had been localized oyster fisheries suddenly found markets for many millions in the major cities like London, Paris,” explains Sanderson, who is based at Heriot-Watt University in Edinburgh. At the time, oysters were considered a “poor man’s food” and sold as street food, says Sanderson. “You could even pay your rent in oysters in Edinburgh if you wanted to.”
The popularity of the European oyster was its downfall. Since the 19th century, native oyster populations have declined by 95% in the UK.
But there is a glimmer of hope for the indigenous oysters of the UK. Beneath these waters is a marine rewilding project that has transformed the Dornoch Firth, a narrow strip of water off the northeast coast of Scotland. The Dornoch Environmental Enhancement Project, or DEEP, began in 2014 and has to date seen the successful reintroduction of 20,000 European oysters on the firth’s bed. The aim is to increase that number to a self-sustaining population of 4 million by 2025.
A spirited revival
The project is the result of an unlikely partnership. On the banks of the Dornoch sit the old buildings of the Glenmorangie Distillery, a scotch whisky maker which has called the firth its home for over 170 years. “They were expanding their warehouses and the business was booming, and they wanted to know how to reduce the environmental footprint and improve their surroundings,” Sanderson recounts.
Part of Glenmorangie’s sustainability drive is an anaerobic digestor built in 2017 to clean the waste produced by the distillery, such as barley from the fermentation process.
“Traditionally, we have discharged waste into the firth,” says Edward Thom, the distillery manager. “What we now do is remove 97% of the waste product prior to it being discharged. The remaining 3% is then cleaned by the oyster beds that we’re currently planting as part of the DEEP project.”
Oysters are able to filter about 240 liters of seawater a day, which cleans any organic byproduct from the distillery, and their presence also acts as a habitat builder for other species.
“The oysters create the structure on the seabed, create the nooks and crannies for the things to live in amongst,” Sanderson explains. “We’re starting to see increased numbers of certain fish species and certain crab species associated with these habitats.”
Furthermore, research has shown that oyster beds can act as carbon sinks, sequestering carbon from the water column and burying it in the seabed below.
The DEEP project is just one of 19 now up and running around Europe, and the first to rebuild an oyster habitat that had been completely destroyed. Through the combined benefits of increasing biodiversity, filtering water and sequestering carbon, Sanderson believes this kind of work can have a real impact.
“Restoring oyster beds is as profound as restoring ancient forests,” he says.
But even though the project has made remarkable progress, Sanderson admits he still feels some apprehension before diving in the freezing waters to check on the oysters.
“Every time we go down, it’s always a bit of an anxious moment for me,” he says. “I feel like an expectant father … and every year I come back with a grin on my face because the oysters are getting bigger and bigger.”