Invasive American signal crayfish discovered in Huddersfield Narrow Canal

AN INVASIVE American signal crayfish has been discovered on the banks of the Huddersfield Narrow Canal.

Which is causing concern, Janet Friend reports.

This was found dead with a cracked shell measuring 20cm long and 3cm wide, near the Tollemache Arms in Greenfield.

Larger size

Due to the larger size and thicker claws, it is an American signal crayfish, that are brown-red in colour and have bright red undersides with a small white or turquoise mark on top, near the claw hinge, which matches the description of the one found, and grows much larger than the native English species, the white claw crayfish.

The image is by Dominic Bamber who found the creature.

England's native crayfish are in a state of fast decline it is told, with their numbers having reduced by more than 50 per cent since the 1970s. Part of this decline continues as a result of the introduction of the American signal crayfish, which are aggressive, breed faster and damage canal banks with their burrowing, according to Canal & River Trust.

They were brought over to England from North America in the 1960s, when they were bred on farms for restaurants to serve as a delicacy. But the species managed to escape the farms and quickly spread throughout the UK.

Burrow two metres

Explaining why the crustaceans are so dangerous to England and its native species, a spokesman for the trust explained:

"Drawn to mainly still or slow-flowing freshwater habitats, signal crayfish can burrow two metres  deep into waterway banks, causing extensive damage and leaving canals vulnerable to collapse.

"They are able to cross land, and break through natural and artificial barriers.

"As opportunistic omnivores, signal crayfish aren't fussy about what they eat.

"However, the species that has suffered the most is our native white-clawed crayfish, which is now protected and heading towards extinction.

"It also carries a fungal disease called 'crayfish plague', which is fatal for the white-clawed, and can be spread by wet footwear and equipment."

Because of the risk they pose to the native species, it is illegal to release or allow the escape of American signal crayfish, but it is also illegal to keep them and an application for trapping must be made to the relevant environmental protection agency.