The north Wales mussel population has been under threat

Proposals have been drawn up by the owners of Conwy Marina, who have to remove hundreds of tonnes of mud every year to keep their berths clear for boats.

The marina has to be dredged each year to remove silt which been washed in by the tide.

At the moment, it is dumped out at sea, but the marina owners want to start pumping it into the river instead.

Experts advising them have said this is the best way to preserve the River Conwy's finely balanced eco-system.

They say studies have shown that taking the mud away from the river has been upsetting that balance.

But some of Conwy's mussel fishermen have claimed the marina is just trying to cut down the cost of taking the mud out to sea.

They are worried extra silt will pollute the mussel beds and put an 800-year-old industry in danger.

Last year it was revealed that scientists in north Wales were planning to introduce ageing shellfish to potential partners in an effort to stop them dying out.

Using dating agency-style methods, conservation groups are hoping to revitalise the declining population of the freshwater pearl mussel.

The mussels breed successfully in the dense beds of Scotland and Ireland, but are disappearing in their traditional grounds in Gwynedd and Conwy.

The shellfish have become so scattered that they have little chance to breed.

As a result, the youngest mussels are middle-aged, their numbers are dropping and thousands are living solitary lives in empty beds.

The Environment Agency, Countryside Council for Wales and English Nature are planning to relocate isolated individual mussels and encourage them to breed.

The freshwater pearl mussel is said to have been a factor in the first Roman invasion of Britain in 55BC by Julius Caesar, who valued the pearls produced by them.

Pearl fishing, although now illegal, has been cited as one factor in reducing the density of populations and causing the present-day breeding problems.

David Fraser, from English Nature, added that reduced water quality could also be a reason for their decline.

The mussels live between 80 and 100 years and can grow up to 15cm in length.