Wild oysters, once the gastronomic delight of kings as much as they were the staple diet of paupers, have returned to the Firth of Forth for the first time in almost a century.

The native oyster, ostrea edulis, is thought to have disappeared from the Forth in 1920, but out of the blue, two have made their way on to rocks somewhere on the south shore of Firth near Edinburgh, prompting jigs of delight from environmentalists and the smacking of lips from gourmands.

They were discovered by Liz Ashton, an aquaculturalist, after she heard rumours that they had been sighted around the estuary, even though an extensive marine survey in 1997 found no evidence of oysters. Taking advantage of a very low tide, she went to investigate and after walking for an hour along the shoreline, came across the pair, 100 yards (91 metres) apart.

“I was ecstatic, I jumped up and down and cheered,” she said. “I phoned my supervisor and told her the good news. Then I measured them and took their photographs, and then left them there to let the tide wash over them.”

Dr Ashton’s joy is partly explained by her deep interest in the native oyster. Overfishing has all but wiped the creature out across Europe, but she and a team from the Institute of Aquaculture at Stirling University are working on a project devoted to re-establish oysters in the Firth of Forth.

The two oysters were almost certainly members of a larger bed (or colony) that remained hidden when surveys of the estuary were carried out. If numbers could be increased, the oysters would promote bio-diversity, providing a habitat and food for little crabs and lobsters, and improving water quality, because the animals are “filter feeders”, taking impurities out of the water.

These highly desirable outcomes depended on the behaviour of humans, Dr Ashton said. “We need to try and restore them. I wouldn’t want people going down there and eating them straight away.”

Her warning was timely. Edinburgh’s restaurant trade has been yearning to supply local oysters for generations. “It’s wonderful news and it would be very interesting to compare them with oysters we serve now,” said Tia Millar, co-director of Fisher’s restaurants in Leith and Edinburgh.

Fisher’s is obliged to use West Coast shellfish and its menu includes oysters in their shells and grilled oysters, although Ms Millar’s preferred method — perfect for a Forthside picnic — is to cook oysters on a barbecue and then when the shells pop, eat them “in their delicious nectar”.

Ms Millar is part of a gastronomic tradition in the city. Long before Mr Pickwick was handing out barrels of oysters to his friends in London, Edinburgh was knee-deep in the creatures, its population reportedly eating its way through millions every year.

Edinburgh’s oysters enjoyed world renown but Scots kept the best of the crop for themselves. Adam Smith even founded an oyster club, which counted the philosophers David Hume and Adam Fergusson among its members. James Boswell and Samuel Johnson dined in a reputable laigh shop, or oyster house, near the law courts; in the nearby Cowgate gentlemen could season their fun with side of orders of oysters and porter.

James Hogg, the novelist, was baffled by the sheer quantities consumed: “What desperate breedy beasts eisters must be, for the they tell me that Embro devours a hunder thousand ever day ... That is only about two oysters for every three mouths.”

As the end loomed for the oysters, the Victorians showed no mercy. Local recipes for Oyster Kromeskies and Oyster Custard from the 1890s, used 24 oysters in each serving and no true Musselburgh Pie was complete without a least a dozen to sweeten the taste of the meat.

“There was a lack of effective management,” Dr Ashton said. “We should learn from that.”

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