Thousands of oysters released into the Firth of Forth appear to be thriving again after a century-long absence from the Scottish estuary since they were lost to overfishing.

Marine experts from Heriot-Watt University who have helped reintroduce about 30,000 European flat oysters to the estuary said divers and underwater cameras showed they were doing well.

The Firth of Forth was once home to one of the largest native European oyster reefs in the north-east Atlantic, yielding up to 30 million oysters a year during the 1800s, but by the beginning of the 1900s they had been fished to local extinction.