Chinese mitten crabs are becoming increasingly common in the River Thames and other rivers in England, having arrived in ship’s ballast from Asia. Mitten crabs cause a great deal of damage by burrowing into and destroying fragile riverbanks. They prey on other species and compete with native animals such as crayfish.

The crabs can make significant inland migrations. Residents of Greenwich saw the Chinese mitten crabs coming out of the River Thames and moving towards the High Street, and other reports indicate that the crabs have been known to take up residence in swimming pools. Wikipedia

This article in The Independent suggests we should be eating this delicacy and offers a recipe steamed in ginger.

The Natural History Museum investigated how to reduce the population of mitten crabs in the Thames and became aware that this species is a popular culinary delicacy among south-east Asian populations. This offered the possibility of harvesting the crabs to supply specialist shops and restaurants in London and even, potentially, markets in Asia.

Mitten crabs are considered delicacy in Shanghai cuisine and are prized for the female crab roe. The crab meat is believed by the Chinese to have a “cooling” (yin) effect on the body.

“September is the time to eat the female crab for the extra roe that makes the crab so tasty. The extra roe is the reason why the mitten crabs are so different from ordinary crabs, and this is why they are prized as a delicacy.” The Independent