Scientists say they may be able to restore a once-abundant mussel bed in the Firth of Thames, which will increase local sea life.
Five National Institute of Water and Atmospheric Research scientists have spent three years researching the decline of green-lipped mussels on the western coast of the area.
The sea floor was over-fished between the 1920s and 1960s and has not recovered since.
The study reveals that even though mussels have not grown in the harbour for the past 50 years, they do survive when they are returned to the sea floor.
One of the researchers, Darren Parsons, says natural mussel beds are important because they clean the water and provide a good environment for other sea life.