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.”