Chinese hairy crab invaders threaten Scotland’s rivers (Wired UK)


Chinese mitten crab, Eriocheir sinensis, on the banks of the River Thames, London

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Scotland’s rivers are being invaded by
Chinese hairy crabs, which poses an ecological
threat to local wildlife. After remains of the South-East Asian
beast were found in Glasgow’s River Clyde, researchers of the
Natural Histroy Museum and Royal Holloway, University of London,
are worried of the effect the incursion will have on salmon and
trout.

The Chinese hairy crab, also known as the mitten crab, has been
branded by the International Union for Conservation of Nature as one of the 100
worst alien species in the world. The crustacean is already present
in many of England’s waterways, having first appeared in the Thames
as early as 1935. Since then they have slowly crawled their way
across the lower reaches of the British Isles, making it as far as
the Tyne. But their relentless march north appears to have
continued as remains found in the Clyde two weeks ago prove they
have made it through the Scottish border.

According to the Scottish Environment Protection Agency (SEPA),
non-native species are the second biggest threat to native plants
and animals after habitat loss. Environmental damage is estimated
to cost £244 million to the Scottish economy annually through the
damage caused to local horticulture and aquaculture, and even
infrastructure. How much of this is due to invasive species isn’t
clear, but the SEPA is worried either way.


Remains discovered on the Clyde river in the Dalmarnock district of Glasgow

Willie Yeomans


Jo Long, senior conservation policy officer at the SEPA, said:
“While the remains of an adult Chinese mitten crab have been found
in the River Clyde, we do not yet know whether there is a breeding
population in the wider Clyde estuary.”

The remains are currently being studied to determine if they are
parts of a dead crab, or the shedded exoskeleton. If the latter,
the chances of there being a growing population are significantly
higher. But even this chance is no reassurance for some.

Either way it’s not necessarily good news for us,” Clyde
River Foundation catchment manager Willie Yeomans told South China Morning Post

“However many of these there are, whether it is one hundred
or one, it is bad for the river.”

The damage mitten crabs do to the environment is caused by
their habit of burrowing into riverbanks to make their
homes. Dr Paul Clark, an expert on Chinese hairy crabs
at the Natural History Museum, said the crustaceans have caused
extensive damage to the River Thames.

“Mitten crabs are burrowing away into the
riverbanks at Syon Park, London, and in dense numbers, the banks
are collapsing,” Dr Clark said. “Downstream, Chiswick Eyot, an
uninhabited island, is slowly eroded by the mitten
crab.”

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26 September 2014 | 1:56 pm – Source: wired.co.uk

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