The freshwater pearl mussel remains one of the planet's rarer species with Scotland holding a significant quantity of the world population. The European Union recognised the need to protect stocks which resulted in directives demanding member states to safeguard the species. The Margaritera margaritifera species was duly afforded protection under the Wildlife and Countryside Act 1981 and it remains an offence to possess or disturb them without a licence.
The main threats to this mollusc come from pollution and pearl fishing. While mini hydro-schemes remain attractive to landowners and communities as an alternative energy source, their installation has caused problems when not carefully managed with silt running off into rivers and swamping pearl mussel colonies. A recent case in Glen Lyon saw the contractors for one such installation convicted and fined for causing pollution that disturbed pearl mussels. However, greater scrutiny at planning stages and discussion at industry events should now help to spread best practice and prevent further incidents.
The pearl fisher remains a risk to small, local mussel populations. Looking for a pearl within the mollusc, the shells are picked off the river bed and prised apart thereby killing the specimen: on average, one shell in a hundred may contain a pearl. A small colony of mussels attempting to gain a foothold in a waterway could be wiped out in a single visit.
The summer often sees a drop in river levels making mussels more accessible and thereby susceptible to pearl fishing. The UK National Wildlife Crime Unit (NWCU) is keen to learn of anyone who may be fishing mussels from Scottish rivers. Charles Everitt, Scottish Investigative Support Officer with the NWCU, said, "We continue to seek information on the small number of pearl fishers in Scotland and would be very interested in learning of any incidents of pearl fishing or any events along pearl mussel rivers that appear 'out of the ordinary' or strange. Empty shells discarded on the river bank can be a sign of pearl fishing. The pearl fisher will often be in waders and examining the river bed through a glass-bottomed bucket or receptacle, occasionally reaching down or using an implement to pluck mussels off the river bed. Descriptions of individuals and vehicle registration numbers are always useful. Only with the help of landowners and rural operators around Scotland's rivers can we provide this species with the protection it demands to ensure its future."
Although submerged beneath the waterline, the freshwater pearl mussel undertakes an essential role in filtering water to benefit salmon and general river welfare. It remains in the interest of everyone to ensure its survival.