A VORACIOUS North American interloper could be lurking in the depths of a mountain pond on the Blorenge.

Pictures of what appear to be signal crayfish have caused concern among anglers and conservationists studying Blaenavon’s Keeper’s Pond.

The signal crayfish is a voracious predator, feeding on a variety of fish, frogs and invertebrates, as well as plants, and even eating individuals of its own species. In the 1970s, the British government introduced the signal crayfish (Pacifastacus leniusculus) from North America to UK waters for export to the lucrative Scandinavian market.

The crayfish plague had ravaged native crayfish populations in Europe and it was seen as an attractive commercial species.  Unfortunately it is also a carrier of crayfish plague and is thought to be responsible for passing the deadly disease to the native white-clawed crayfish (Austropotamobius pallipes) in the UK.

Signal crayfish soon escaped from commercial fisheries and began to outcompete the native species for habitat and food. They cause further problems by burrowing into river and canal banks causing erosion, bank collapse and sediment pollution.

The creature is lobster-like in appearance and reaches a maximum size of 18-22cm (7-9 inches). Its claws have red undersides with a small turquoise/white blotch on the upper surface at the claw hinge. The native white-clawed species rarely exceeds 10cm (4 inches).

Social media comments imply the creatures are not newcomers to the area, with one poster stating, ’These crayfish have been in Keeper’s Pond for a long long time, a lot of people have begun to realise the pond is full of them and I really hope they’re left to their own devices.’

Another suggests they are also commonplace in the area’s canals where, in the 1960s and before, these habitats were home to the native species.

A spokesperson for World Wildlife Fund Cymru stated,’The native white-clawed crayfish is threatened by the American signal crayfish, climate change, habitat loss and the impact of pollution in Wales. Unfortunately, diminishing resources mean it is more than ever a survival of the fittest; however, Wales has a head-start on the rest of the world. Our ground-breaking laws are the foundations that should put nature at the heart of everything we do.’

The Keeper’s Pond, was built in the early 19th century to provide water for Garnddyrys Forge, which started production in about 1817.