We’re talking about freshwater pearl mussels, of course. But there’s an even more alarming statistic to accompany the fact that half of all the world’s population of pearl mussels lives in Scotland: since 1970, pearl mussels have been vanishing from Scottish rivers at the rate of two rivers each year. In roughly two-thirds of the rivers previously known to have harbored the endangered Margaritifera margaritifera species, pearl mussels are now assessed as ‘extinct’ (no mussels present) or ‘functionally extinct’ (adult mussels are present, but they aren’t breeding). Frightfully sobering statistics, indeed.
Why is this happening?
Unchecked land use, pollution, engineering works along rivers, declining populations of symbiotic species, and exploitation by poachers have wreaked havoc on the perilously threatened species and are the most significant contributing factors in their decline and disappearance – so much so, that Scotland’s pearl mussels are now classified alongside giant pandas and Javan rhinos as among the most endangered species in the world (International Union for Conservation of Nature). To remove a pearl mussel from a Scottish river has been a UK criminal offense since 1998, but illegal fishing continues to this day.
The decline is particularly pronounced in the Scottish West Highlands and Western Isles, though waterways like our namesake River Spey serve as last bastions of hope. Other internationally significant strongholds of the species occur in Ireland, Norway, Finland and Sweden, but numbers are dwindling throughout this range. In central Europe, populations are down 95 percent from previous records. The pearl mussel is a bedrock species, helping to filter and maintain water purity – foundational to the success of a freshwater ecosystem. Its decline is reverberating throughout the food chain.
What can be done?
Understanding and awareness are the first two steps. We must work to catalogue the sizes, densities and age structures of extant pearl mussel groups, so that shifts in populations can be better recognized and recorded. Of equal importance is the dissemination of facts. The more people know and the more they are galvanized into action, the better chance we have of enacting conservation and reintroduction programs to turn this tale around. The freshwater pearl mussel is a fascinating creature, and one we hope will be around for centuries to come. If you want to get involved, drop Spey a note. We’d be delighted to share with you our plans for championing this endangered species.
Spey would like to thank Dr. Peter Cosgrove of Alba Ecology for contributing to the substance of this article and for his continued efforts in protecting Scottish rivers.