Specially-trained dogs have been drafted in to help sniff out an invasive species in Devon.
The dogs can detect American signal crayfish, which can have a devastating impact on native wildlife.
South West Water and South West Lakes have teamed up with Sequor Ecology Detection Dogs as part of the ongoing control programme at Burrator and Roadford reservoirs.
The water company said it was hoping to reduce the numbers of the species.
Sid the black labrador and River the cocker spaniel started searching for the unwanted visitors, which shelter among rocks, tree roots and in burrows along river banks, last autumn.
Since then 200 traps have been set and about 6,000 invasive crayfish have been captured and killed.
Dog handler Lucy Wilde from Seqour Ecology Detection Dogs, said: “The early identification from the dogs allows us to quickly pinpoint areas where traps can be laid, helping to minimise the impact of the species on the environment.”
The American Signal Crayfish eats a wide range of invertebrates and small fish, and carries crayfish plague, which destroys the native white clawed crayfish population.
But South West Water’s biosecurity and invasives manager, Kate Hills told the BBC that they would never completely eradicate crayfish from the reservoirs.
“Our hope is to reduce the numbers to reduce the impact on the environment,” she said.
“Invasive non-native species are one of the top five threats to biodiversity and American Signal Crayfish are recognised as one of the worst.”
The American signal crayfish was brought into the UK in the 1970s as a commercial species but soon escaped from fisheries.
The species is now found in 80% of rivers in England and Wales, according to the Environment Agency.
Ms Hills said the creatures were causing concern for water companies across the UK.
She said: “South West Water know that we are really lucky to only have two reservoirs with American crayfish in them.
“Here at Burrator and another at Roadford. We know up country it’s a much bigger problem for other water companies.
“We are monitoring the population here and are grateful to local anglers who report when they see crayfish and they are using the wash down facilities we provide to help prevent their spread. “
As well as being voracious predators the American crayfish burrows can cause river bank erosion.