I
Ian Cloke
Guest
Plight of the white-clawed crayfish
In early autumn 1979 a prison break began. Under cover of darkness the escapee slipped past his captors and away into the chilly English night.
Disorientated but determined, the north American signal crayfish scrabbled across the foreign terrain in search of fresh water.
The break-out was inevitable. Signals are fearsome among crayfish - stubborn and aggressive with large, versatile claws and a formidable climbing ability. The wire mesh covering the pond was bound to be conquered sooner or later.
During the 1980s, thousands of signals escaped trout farms in the south of England. At that time, white-clawed crayfish - the only species of freshwater crayfish native to the British Isles - thrived in the UK's waterways. Three decades later, they would be decimated.
National stronghold
Stephanie Peay, an ecologist and freshwater crayfish specialist, has spent much of her career studying white claws.
"Most people don't know native crayfish were so abundant, mainly because they're nocturnal, but in the 70s they were absolutely everywhere," she said.
"Back then, if you waded into any gently-flowing stream or river in the country and turned over a few rocks, chances are you'd find a white claw.
"They're not cute or cuddly, but they certainly are very interesting animals, and people are usually very surprised at how large they are. They love clean, limestone streams and could often be found under all the biggest and best stones."
In Cumbria, this is still the case - the county is a national stronghold for what remains of a once-numerous species, whose current dilemma can be traced directly back to the "great escapes" of the 1970s and 80s.
White claws are no match for the invaders. Beefy and aggressive, and twice the size of the native species, signals have the physical advantage when competing for food and habitats. But their most devastating weapon has nothing to do with size.
As the current flows around a signal, it often disturbs a colony of tiny spores clinging to its shell. These are easily dislodged and quickly swept away. Some embed themselves in rushes or reeds, others travel uninterrupted for miles.
continues...........
In early autumn 1979 a prison break began. Under cover of darkness the escapee slipped past his captors and away into the chilly English night.
Disorientated but determined, the north American signal crayfish scrabbled across the foreign terrain in search of fresh water.
The break-out was inevitable. Signals are fearsome among crayfish - stubborn and aggressive with large, versatile claws and a formidable climbing ability. The wire mesh covering the pond was bound to be conquered sooner or later.
During the 1980s, thousands of signals escaped trout farms in the south of England. At that time, white-clawed crayfish - the only species of freshwater crayfish native to the British Isles - thrived in the UK's waterways. Three decades later, they would be decimated.
National stronghold
Stephanie Peay, an ecologist and freshwater crayfish specialist, has spent much of her career studying white claws.
"Most people don't know native crayfish were so abundant, mainly because they're nocturnal, but in the 70s they were absolutely everywhere," she said.
"Back then, if you waded into any gently-flowing stream or river in the country and turned over a few rocks, chances are you'd find a white claw.
"They're not cute or cuddly, but they certainly are very interesting animals, and people are usually very surprised at how large they are. They love clean, limestone streams and could often be found under all the biggest and best stones."
In Cumbria, this is still the case - the county is a national stronghold for what remains of a once-numerous species, whose current dilemma can be traced directly back to the "great escapes" of the 1970s and 80s.
White claws are no match for the invaders. Beefy and aggressive, and twice the size of the native species, signals have the physical advantage when competing for food and habitats. But their most devastating weapon has nothing to do with size.
As the current flows around a signal, it often disturbs a colony of tiny spores clinging to its shell. These are easily dislodged and quickly swept away. Some embed themselves in rushes or reeds, others travel uninterrupted for miles.
continues...........