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Donkin on Fishing - Scotland


December 2007 - Fishing on Skye and freshwater mussels

Travelling towards the highlands of Scotland on the M9, I can never drive past Sterling castle, perched on its granite crag, without thinking of the great armies that came this way over the past 2,000 years.

This natural thoroughfare between the Clyde and Forth estuaries was the ideal place for Scottish armies to draw their line in the sand. You need only consult a map to look at the number of battle sites here, the most famous of all at Bannockburn in 1314.

Among the first of these forays by foreign invaders was that made by the Romans some time after their invasion of Britain in the last half of the century before the birth of Christ. Why on Earth did Julius Caesar want to come so far and what, you may ask, has any of this to do with fishing?

The clue is to be found in the classic history of the Caesars written by Suetonius. Pearls seem to have been the lure that prompted his (Julius Caesar's) invasion of Britain, wrote Suetonius. He would sometimes weigh them in the palm of his hand to judge their value.

These, I hasten to add, were not oyster pearls but the pearls of freshwater mussels then found throughout Britain but now found rarely outside Scotland in the British Isles. Those pictured above were photographed on a trip to the River Dee in April 2011. 

On some of my earliest salmon fishing visits to the River Tay I stayed in a small village called Spittalfield not far from the great beech hedge at Meikleour. Just behind our cottage was the site of a large Roman camp not more than a few hundred yards from the river where the Romans had constructed a ford.

This must have been one of the most northerly Roman camps in the British Isles. Did they come here for the pearls? The dark blue Tay pearl was prized all over Europe in the 19th century. Back in the late 1970s I saw a pearl fisher working the river with his glass-bottomed bucket. It is a sight that has passed in to history.

Today the freshwater mussel is an endangered species, protected under the Wildlife and Countryside Act. So it should be. The mussel is a remarkable animal that lives to a great age - up to 140 years. It plays an important role in the ecosystem of salmon rivers where it has lived in happy symbiosis with migrating fish for thousands of years.

Mussel reproduction is a hit and miss affair. At what seems like a good time the male ejects sperm on the off chance that some will be inhaled by a female mussel. She releases her eggs in late summer, most of which are swept away. But a small fraction of them manage to attach themselves on to the gills of trout and salmon and hitch a lift to the headwaters of their streams. In time the tiny mussels fall in to the silt where they begin their purifying work. A single adult mussel filters up to 50 litres of water a day.

According to Peter Cosgrove, a Scottish-based scientist who has studied the mussel lifecycle, an adult female might produce more than 200m larvae in her lifetime to replace two adults.

Their food is fish waste so you can see how important they are to the health of a river. But mussels are slow growing and many of the surviving populations are no longer viable for breeding.

The silting of rivers has wrecked some populations and illegal harvesting continues, sometimes among people who regard what they do as a birthright, supplementing a small agricultural wage with the occasional lucrative discovery. Moreover declining salmon and sea trout runs have deprived the baby mussels of their early host.

I heard the story of the mussels from Derek Dowsett whose company The Three Esses* runs the salmon fishing for most of the river Snizort on the Isle of Skye. On its day, after a good spate, the Snizort can be a productive salmon river. This year, with 193 salmon and 80 sea trout, it recorded its best season since 1993.

I visited the river before this year's spates, another case of bad timing. I didn't see a salmon but I did see freshwater pearl mussels that are becoming all too rare a sight these days. A survey in Scotland carried out during the late 1990s found that mussels were extinct or nearing extinction in a 101 of the 155 rivers with mussel populations a century ago. Evidence of breeding populations was found in only 17 rivers.

Given that Scotland has up to half of the world's viable freshwater pearl mussels, we can see how threatened these creatures have become. They depend on migratory fish and who knows to what extent the fish benefit from the mussels? So next time you're casting a fly and you spot those empty shell cases by the river bank, spare a thought for those mussels. They're helping to keep your river clean and that's worth more than any pearl.


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