eriocheir sinensis

Paragonimus westermani (Oriental lung fluke)
In east Asia, Eriocheir sinensis is a host of the lung fluke Paragonimus westermani. If an infected crab is eaten uncooked the parasite can infect humans, causing the disease paragonimiasis. This can be fatal if left untreated.P. westermani is most often encountered in China, Korea, Thailand, the Philippines and Laos, but it can also be found in people that have travelled to susceptible regions. Cases have been reported from many parts of the world, including South America and Africa, but the disease is rarely seen in North America or Europe. A 2005 report put the number of people infected globally at around 22 million. When Eriocheir sinensis was first reported from the River Thames in the UK in the 1930s, newspapers expressed concern that paragonimiasis could be introduced into Britain. However, this is unlikely as part of the life cycle of P. westermani requires an aquatic snail family that isn't found in Britain.A recent analysis of mitten crabs sampled from the River Thames over 17 months failed to detect the lung fluke parasite (Stentiford, 2005).

Habitat
Mitten crabs spend most of their lives in freshwater. Although they burrow in mud, mitten crabs seem to occur over many different types of river bottom. Mitten crabs certainly burrow into intertidal mud banks.Unprotected mud banks collapse when crab burrows are numerous.

Feeding
Mitten crabs are opportunistic, indiscriminate omnivores. They appear to be able to consume a wide range of aquatic plants, invertebrates and fish.

The Chinese mitten crab, Eriocheir sinensis, has been widely introduced into many regions outside of its native range in China. As a result, it has been placed on the International Union for Conservation of Nature's (IUCN) list of the world's worst 100 invasive alien species.It has conspicuous setal mats on its claws and both its British common name, Chinese mitten crab, and its scientific name, Eriocheir sinensis, which means ‘wool hand, the Chinese’, originate from this distinguishing feature. It is the only crab in Britain that has this.

Mitten crabs are a contentious invasive species. They have high reproductive rates and few natural predators capable of reducing their numbers dramatically. If alien populations are not controlled, they will continue to threaten native ecosystems, damage unprotected river banks and spread even further. Increased larval densities in estuaries will increase the risk of dispersal into new watersheds via the ballast water of shipping vessels. Therefore it is important to manage existing populations.

How could crab numbers be reduced?
Since mitten crabs are eaten in southeast Asia, commercial exploitation could potentially be used as a method of reducing crab numbers. Zoologists at the Natural History Museum have been involved in assessing whether this would be viable for the mitten crab population in the River Thames. The results of the recent study, published in 2009, concluded that the crabs are fit for human consumption and the population is large enough to be exploited.

What's the next step?
The decision of whether to start a Thames mitten crab fishery now rests with governmental organisations such as DEFRA, the Environment Agency and the London Port Health Authority. A joint meeting of the Natural History Museum and the Linnean Society of London, supported by the London Port Health Authority, is being held on 11 March 2010 to discuss the pros and cons of such a fishery.