Donal Hickey: Sewage pollution and the pearl mussel
The catchments of the Munster Blackwater and river Araglen, in north Cork, are among the pearl mussel's remaining habitats. Picture: Larry Cummins
The odds of finding a pearl in a pearl mussel are reckoned at around 10,000/1. But, such has been decline in this critically endangered species in our rivers, you’d be lucky to find a mussel, never mind a pearl.
Numbers have dropped so much that it would be simply untenable to catch them: better to protect what little remains of the species.
They are extremely sensitive to changes in their environment and are declining in Ireland and internationally due to deteriorating river quality, especially pollution from poorly treated sewage.
Which explains why the EPA, in its latest report, has been telling Uisce Eireann (UE) to take urgent action to prevent the flow of sewage into waters where the mussel is present. The catchments of the Munster Blackwater and river Araglen, in north Cork, are among its remaining habitats.
These mussels, which can live to be more than 100 years, are an ‘indicator species’ as they tell us a lot about the health of a river: they thrive in pristine, fast-flowing water and clean river beds.
Once widespread, they are now found in very few catchments. Ireland is believed to have almost half of Europe’s pearl mussel population, with the Blackwater catchment accounting for a sizeable portion of that.
An EU-protected species, the mussels are very sensitive to polluted water which can be caused by artificial fertiliser, farm slurry, sewage, or industrial waste. River bed silt also kills the mussels.
Newmarket, County Cork-based IRD Duhallow has been involved in a number of projects to protect the mussel, with the cooperation of the community and local farmers Along the river Allow, they have installed silt traps in farm drains which capture the silt before it can enter the river to kill incubating salmon eggs and the mussel.
Earth entering water from eroding river banks can also cause siltation. However, some farmers have fenced flood-prone land, allowing the vegetation to grow, with the roots helping to stabilise the banks.
The EPA has identified 12 towns and villages where sewage treatment must improve to protect mussel habitat. Most of these places are in County Cork, including Mallow, Boherbue, and Inchigeelagh, and Kilgarvan, in Kerry.
In 2023, the EPA prosecuted UE for discharging poorly treated sewage in Boherbue. Improvements have been completed in six of the dozen areas, but it could be 2030 before upgrade works start in the remaining areas.
Not happy with the rate of progress, the EPA says urgent action is needed to progress necessary upgrading.
Finally, only a small percentage of pearls rarely found in the mussels meet the needs of the jewellery industry… better to leave them alone.
