Bath's Prior Park crayfish damage to 'cost millions'
Invasive crayfish have caused millions of pounds of damage to a historical beauty spot in Bath.
As many as 100,000 American signal crayfish have been burrowing into three 250-year-old dams and banks surrounding the lakes at Prior Park.
One of the lakes has already been drained to relieve pressure on the most seriously-damaged middle dam.
The National Trust, which owns the site, says the repair works and "crayfish-proofing" will cost £2.2m.
It is thought the large and aggressive species - Pacifastacus leniusculus - arrived in the park about 18 years ago from the River Avon but the problems have only emerged in the last decade.
Simon Ford, National Trust wildlife adviser in the South West, said: "They create what are actually quite small holes - almost the size of a mouse hole - and they burrow in and so one or two would be no problem.
"But here we could have 10,000, even 100,000, and when you start to multiply it to that level, then you start to see the problems that we have."
Tom Bowden, general manager for the National Trust in Bath, said the repaired dams would have a "crayfish-proof barrier" using concealed concrete and timber to prevent the creatures from causing further damage.
Signal crayfish were introduced to the UK in the 1970s for food but have since spread to the UK's river systems, devastating native crayfish populations and damaging riverbanks.