Scotland's gamekeepers are teaming up with specialist police wildlife crime officers to fight illegal freshwater pearl mussel fishing.

The mussels, Margaritifera margaretifera, are protected under the Wildlife and Countryside Act and are often found on the bed of salmon rivers where they can live for up to 80 years.

Seventy two of Scotland's rivers support reproducing populations and represent some of the world's most important sites for the survival of the mollusc.

In 2011, they joined giant pandas and Javan rhinos on a list of 365 of the world's most endangered species.

In the 12th century Alexander I, King of Scots, was said to have the best pearl collection of any man living, but from the 16th century onwards there was commercialisation of the fishery and from the 19th century there signs of a growing shortage.

There is evidence that pearl mussels have become extinct from an average of two rivers every year in Scotland since 1970.

As well as fishing, pollution is also a cause of their decline and a case in March saw directors of A&C Construction fined £11 000 for causing irreversible damage to hundreds of pearl mussels in the River Lyon while working on the Inverinian Hydro Scheme.

Now the SGA has signed an agreement with the National Wildlife Crime Unit (NWCU) in order to build intelligence that can help tackle illegal fishing.

Gamekeepers and ghillies often work around the remote rivers containing mussels and guidelines have been set out to encourage confidential reporting of suspicious activity to police.

Amongst activity they will be looking out for is wild camping sites by rivers containing mussels, suspicious vehicles, people wading through mussel rivers or individuals using glass bottom buckets to survey beds.

Discarded shells can also be a clue, although it is understood many modern fishers dispose of shells away from the banks.

SGA Chairman Alex Hogg said: "This is an important initiative and the SGA is delighted to offer the assistance of its members. Many of them are working these rivers and I know some have contacted police after seeing suspicious activity.

"This agreement gives people the information to help and gives them the confidence that they can engage freely with the police, knowing the information will be treated confidentially.

"I would encourage as many of our members as possible to get involved for the good of the remaining freshwater pearl mussel stock in Scotland."

Charlie Everitt, Investigative Support Officer of NWCU said it was important that wildlife crime officers engaged with those who could offer vital information.

"We recognise that the only way we can start to identify illegal pearl fishers is with the help of the rural workers and the NWCU are very grateful for the Scottish Gamekeepers Association's support and assistance of their members.

"Pearl fishing can happen in the remotest parts of Scotland and the only way the police may ever hear about it is if members of the public working in those locations inform them."