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.
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 also 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.
