River Dee's pearl mussels get a helping hand – or gill

They were hunted to near-extinction. Now a £3.5m project aims to let the Scottish molluscs flourish again

Tracy McVeigh

Saturday 13 August 201622.48 BST

The sun shines on clear river water running through a valley in the Cairngorms, bringing the stones on the river bed into colourful focus. Here and there are dark shadows, half-buried clusters of dull black shells, lined and gouged by decades of shifting water and gravel: the pearl mussels of the river Dee.

The pearl mussel is one of the most ancient invertebrates on the planet, a freshwater shellfish that has helped to shape the history of Britain. One pearl mussel in every 1,000 or 5,000 – no one can be sure – lives up to its name and contains a lustred treasure. Julius Caesar’s biographer, Suetonius, cites a desire for pearls as one of the reasons why the Romans invaded Britain in 55BC.

But pearl hunting, pollution and habitat destruction have almost led to the mussel’s extinction. It has been illegal to pearl fish and to sell or buy a Scottish pearl since 1998, but their numbers remain perilously low. This week or the next, some of the remaining female mussels along all 86 miles of the Dee will spawn – all at once. On just one day a year, they release millions of tiny larvae, or glochidia, into the water.

Read more

Cumbria's pearl mussels at risk of being wiped out

There is concern that one of Europe's largest mussel populations is at risk of being wiped out due to a demand on the natural water supply.

Cumbria's freshwater pearl mussels are as endangered as the giant panda but consumer needs, along with severe weather patterns, are putting them at risk.

Fiona Trott has been to Ennerdale to find out more.

Video

Deadly crayfish close in on rare pearl mussels

By NEIL POORAN
Published on Sunday 19 February 2012 00:27

THEY have dwelt in Scotland’s waterways since the last Ice Age and were, according to Roman historians, the reason why Julius Caesar invaded Britain.

But the freshwater pearl mussel, already critically endangered, is facing a potentially terminal threat from another foreign invader.

American signal crayfish released into the wild have spread through the nation’s rivers in recent decades and now directly threaten the remaining colonies of the rare molluscs.

Scottish Natural Heritage (SNH), the government’s countryside protection agency, says crayfish are now just 20 miles away from a prime colony of freshwater pearl mussels in the Tay.

Anglers are being encouraged to protect the mussel beds from being destroyed. The Tay Fisheries Board is urging fishermen and other river users to avoid anything which could help spread the crayfish, such as eggs which have attached to fishing gear. They also stress the need to kill any adult crayfish found and never return them to the water.

The warning follows SNH-supervised experiments which have demonstrated that crayfish will attack colonies when they eventually invade mussel habitat.

Scottish Natural Heritage’s freshwater adviser, Dr Colin Bean, said they now had evidence of a “mortal” threat to the mussel beds.

“Upstream in the River Earn, there are crayfish around Comrie,” he said. “You get mussels as far down as Perth. They haven’t clashed yet on the Tay, but there is a threat given how fast they spread. It’s not far away.”

Scotland is home to half the world’s population of freshwater pearl mussels. They have been harvested close to extinction on the off-chance they might contain a pearl, and are sensitive to pollution.

The precise location of surviving colonies is publicised as little as possible to give the mussel numbers a chance to recover.

But Bean said that after identifying the risk, SNH wanted to look into what would happen when the creatures met.

He said: “We put the two of them in tanks, looking at the behaviour of the crayfish.

Read on:  http://www.scotsman.com/news/environment/deadly_crayfish_close_in_on_rare_pearl_mussels_1_2125804