---Thursday, 7 November, 2002, 11:10 GMT Fake date for 'alien' crayfish
Crayfish alien to British waters are being lured into traps using sex chemicals. Underwater baskets have been laced with natural pheromones produced by the creatures to attract a mate.
UK scientists are using the bait in a conservation exercise to catch North American signal crayfish.
The larger, more aggressive species is regarded as a threat to the native British crayfish.
It is under threat from pollution, habitat loss and competition from its trans-Atlantic cousin.
Novel approach
Researchers are discussing the first results of the scheme at an international conference in Nottingham.
"Although pheromones have been used in pest management for a number of years on land, this is one of the first attempts to use them to improve trapping success in the water," said the Environment Agency's Peter Sibley.
The local breed
Work began in March last year when a Newcastle University scientist started collecting pheromones from female crayfish in the laboratory. Tests have since been carried out in rivers and ponds.
"Results so far suggest that using pheromones with established trapping methods could be a viable option for controlling this species," said Paul Stebbing.
"Female crayfish pheromones only attract the males so we are now working with male pheromones in an attempt to capture the females as well."
Fungal disease
American crayfish have been thriving in British waters for many years.
They were introduced into the UK for restaurant food in the 1970s and some later escaped.
Signal crayfish often walk overland in their search for a home and are known to colonise freshwaters, killing or displacing native crayfish. They are also blamed for damaging river banks.
The introduced crayfish carry a fungal disease, known as crayfish plague, which can spread rapidly among the more vulnerable native species.
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