Country & Coast

Like most people I am extremely partial to moules-frites, a more-ish bowl of mussels steamed in a rich liquor of white wine, shallots and parsley and served with a plate of fries.

The French usually get credited with its invention but apparently it originated in Belgium.

I have sometimes gathered mussels from one corner of the Yorkshire coast - those who know where to find them jealously guard the location - and made an English version of moules by using cider instead of wine, and fresh chives snipped from the garden.

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September and October are the best months because the young ones laid down in spring have grown to an edible size of around 50mm.

A few years back, I was surprised to learn that another variety of mussel is present in Yorkshire, one which I would not dare to gather for eating.

The type we find on the coast is the blue mussel (Mytilus edulis), but the other member of the family is the pearl mussel (Margaritifera margaritifera), and it is found in freshwater.

Its pearl is a ball of calcium carbonate secreted by the mussel in response to irritation from a piece of grit or twig that finds its way inside the shell. Over many years - some mussels can live for a century - the pearls grows bigger as they envelop the source of irritation, and sometimes appear translucent.

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They were once gathered by so-called pearl fishers and sold in shops, but pearl mussels are now so rare that collecting them is illegal.

In Yorkshire, sadly, they are in danger of being wiped out altogether unless the habitat around their last remaining population on the River Esk is preserved.

There are few rivers more unspoilt than the Esk, since for much of its 25-mile-long course to the sea at Whitby it meanders secretively beneath overhanging trees.

It may very well be one of England’s least-polluted rivers, however the Esk’s waters are not as brilliantly crystal clear as you might be led to expect. They resemble the colour of tea due to its origins high on Westerdale Moor, where the peaty sediment is easily washed away.

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The murkiness is not helped by the livestock which graze on its riverbanks churning up mud which runs off into the water, and for years the North York Moors National Park and the Environment Agency have been carrying out a project with farmers to restore the banks so that they do not crumble into the Esk.

That is because silt is the enemy of the pearl mussel, blocking up spaces between river gravels and preventing oxygenated water from reaching the mussel beds.

In order to help the mussels breed, scientists have been artificially attaching microscopic young pearl mussels to the gills of salmon and trout where, quite remarkably, they are nurtured before being released onto the river bed.

Another strand of the project involves breeding the Esk’s pearl mussels in fish tanks, and when they are old enough they will be reintroduced to the River Esk to hopefully save the endangered colony.

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