Pearl mussels under threat from illegal fishermen

The freshwater pearl mussel, coveted by Julius Caesar and Scottish kings, is under threat from illegal fishermen who are plundering Scotland's riverbeds to remove them.

The endangered mussel was once found in more than 160 rivers. This number has now been reduced to 50 colonies in a dozen Scottish waterways.

The decline is so dramatic that Scottish Natural Heritage is concerned that the species may disappear altogether within the next 25 years. Scientists are monitoring the surviving colonies – and keeping their location secret.

A flourishing black market continues to add to the pressures of pollution and climate change on the species, despite protective legislation that makes it an offence, punishable by a £5,000 fine, to harm, kill or trade in any part of the mussel.

A number of opportunistic fishermen are still willing to break the 1998 ban to find the Scottish mussels, which make up almost 60 per cent of the world's remaining stocks.

John Ralston, a wildlife crime expert with Scottish Natural Heritage, said the pearls could fetch thousands of pounds on the black market.

"We are trying to find exactly the extent of the market that still exists for freshwater pearls but the indications are that there is a flourishing trade in illegally fished pearls, which are either exported abroad or sold to jewellers in this country through the back door," he said. "As recently as New Year's Day we found evidence on the river Dee in Aberdeenshire that people had been fishing for pearls. Unfortunately, up until now it has been quite difficult to catch these people because the areas where the mussels can be found are quite remote.

"However, we are now stepping up our efforts to crack down on illegal fishing and, along with recruiting more people to patrol the important sites, we are also pushing for the judicial system to treat wildlife crimes like this much more seriously."

The attraction of the pearls can be traced back more than two thousand years. The Roman historian Suetonius described Julius Caesar's desire for them as being one of the reasons for his invading Britain in 55BC.

The Scottish crown jewels also feature them, including the giant Kellie pearl – the largest found in Britain. Alexander I, the 12th-century king of Scotland, was said to have the best collection of freshwater pearls in the world.

Although the pearl mussel can live for more than 100 years, it does not usually mature and start reproducing for more than 10 years. The adult mussels spawn on riverbeds and their fertilised eggs are ingested by migrating salmon and sea trout as they return to the rivers in which they were spawned to breed.

The mussel larvae attach themselves to the gills of the fish and live as a parasite before gradually transforming into tiny mussels and falling to the seabed. Of the 210 million spat a female mussel produces in her lifetime, scientists estimate that only two survive to become adult mussels.

Iain Sime, freshwater advisory officer at Scottish Natural Heritage, said: "Freshwater pearl mussels are among Scotland's rarest and most complex species and their presence is an indicator of the health of our rivers.There is still a major problem with illegal fishing of pearl mussels and we need to raise awareness about this problem if the species is to survive."