A species of crab that originates in Asia and can cause massive amounts of damage to riverbanks has been discovered in the Dee estuary.
Environment Agency Wales has been following up reports that Chinese mitten crabs were being caught in the Dee by commercial fishermen as a “by catch” as they netted for flat fish.
Further investigations have been carried out and the capture of an adult mitten crabs in the Greenfield area indicates that this alien species has become established in the estuary.
Mitten crabs cause a huge amount of damage to the tidal and lower freshwater sections of rivers as they burrow into riverbanks causing them to collapse and silt up.
Further pressure is also put on our wildlife as the crabs out compete native species.
They must spend the juvenile part of their life cycle in freshwater but must return to the sea to breed. Although mitten crabs can be eaten - they are a delicacy in Asia - they can also cause problems for human health as they can act as a host for a parasitic lung fluke that can cause infection via undercooked meat.
The crabs can grow to at least 80mm and live for five years.