Michael McCarthy: Mussels land man in hot water

Nature notebook

You want to know a first? A man has been prosecuted for damaging mussels. Not the sort you find clinging to a breakwater, or steaming in a plate of moules marinière. (Tip: eat them with frites – as in moules frites. Never tried it? Brilliant combination. The French aren't daft.) No, that beast is the saltwater mussel, Mytilus edulis. What we are talking about is a different animal entirely, a freshwater cousin: Margaritifera margaritifera. Not just the freshwater mussel, but as you will realise if you know that margarita is the lovely Latin word for pearl, the freshwater pearl mussel.

The Romans knew perfectly well that pearls didn't just come from oysters, but were also found in this small bivalve which inhabits fast-flowing clear rivers; and when in the summer of 55BC Julius Caesar, the Proconsul of Gaul, looked across the Channel and decided to have a go at conquering the island over the way, one of his considerations was very probably that Britannia was known to house a magnificent freshwater pearl fishery.

Not any more, alas. Commercial overexploitation down the centuries, followed by pollution, have pushed pearl mussels to the brink of extinction in Britain, and now they are found only in a few rivers in Cumbria and Northumbria and over the border in Scotland. They are now rightly protected by more Acts and schedules than you can shake a stick at and it is an offence to remove, handle or disturb them, which is why last week, for the first time ever, a man was fined for mussel damage. Jason Phizacklea, 36, of Holmrook, Cumbria, was given a 12-month conditional discharge and ordered to pay costs of £2,350 after admitting damaging mussel beds in Cumbria's River Irt, by driving an excavator into the river. In bygone days the Irt was famous for its black pearls, but the thousands of mussels which used to provide them have been reduced to a pathetic relict population of only about 200.

It just shows that environmental laws have teeth. Speaking of teeth, you may be wondering if the freshwater mussel could be eaten (were it still plentiful) like its marine cousin. I haven't a clue. Ask the French. They'll eat anything.

Horse chestnut blues

Anybody noticed that autumn has come to the horse chestnut trees, at least in the south of England, two months early? All the leaves are brown (as the Mamas and the Papas sang in 'California Dreaming') while the leaves of all the other trees are still resolutely green.

This has been happening for a few years now and it is because of a small insect pest, the leaf-miner moth, Cameraria ohridella, which arrived here around 2001 and has rapidly spread.

It looks as if we're stuck with it. You can find out more on the Forestry Commission website: http://www.forestry.gov.uk/fr/INFD-68JJRC.