FRESH WATER PEARL MUSSEL Margaritifera margaritifera


What an exotic fascinating creature that we once again have discovered and exploited across the globe to the brink of extinction. Similar to the surprise I got upon hearing from Kevin Corcoran, biologist & author, about the wonders of the Gearagh (last weeks blogpost), this story really captured my attention!

Clean, well oxygenated water is of paramount importance for the survival of our oceans and rivers inhabitants. River pollution has caused havoc in our rivers over the past 50 years. Slowly the awareness of what we flush down the river is changing. In the case of the fresh water pearl mussel another ancient inhabitant on the river Lee it is critical.

This bivalve mollusc has a life span of 100 -125 years! It is dependent on migratory fish like the Wild Atlantic Salmon and the fresh water trout for propagation. This master stroke of mother Nature really grabs me. At that time of the year when the salmon and trout are making their up way to their natal streams to spawn, Margaritifera releases tiny little eggs that attach themselves to the gills of the fish. This causes no harm whatsoever, it simply allows the tiny mollusc larvae a safe haven for it to grow in its formative weeks. The mature salmon and trout have several months now in the shallow streams to reproduce before they begin their return journey to sea. These few incubating months allow the baby pearl mussel to grow. Once the fishes have spawned and begin to filter back down stream, the tiny mussel detaches itself from the gills and with its minuscule tentacles, it positions itself on the river bed. There it can remain for up to 125 years!

The form is ovular. Incredibly similar in size and shape to the stones on the riverbed. Perfect adaptation. If undisturbed it will grow to be about human palm size. The colour is practically identical with that of the gravel bed. Mother Nature simply a master colourist. A tiny slit allows its interior mussel to extrude and manoeuvre its way along the river bed. I quote Kevin Corcoran again: “when the fish had free passage on the entire river Lee system there used to be hundreds of thousands of these mussels. You could find them in ‘mother clusters’. Sadly that day is long gone!”

The major shift from a free flowing natural river to a slow moving, reservoir-waterscape has wiped out this ancient exotic mussel. Those few that have been found and identified by specialists like Kevin Corcoran and biologists that work for Ecofact are 60 years plus in age. Sadly there are no young fresh water pearl mussels in the upper Lee catchment presently. Pollution and the absence of host fish have clearly wiped them out.

I will finish with a quotation from a rather exotic jewelry website I came across who predominantly sell farmed pearls as the natural ones are practically extinct :

Pearls have long been associated by many cultures with mystery, elegance, beauty, and the power of nature.  Pearls are also associated with the moon and it’s believed they offer protection to those that wear them.

Well the contradiction is as plain as daylight! We are it seems by nature creatures of destruction!

For further detailed information on the fresh water pearl mussel please visit : (




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