The crabs first appeared in Europe in 1912
A crab which has invaded the River Thames and endangers native species could be exported to China as seafood, the Natural History Museum has said.
The Chinese mitten crab can also cause structural damage as it burrows into riverbanks leading to their collapse.
They threaten local species by competing with them for food and space.
Experts are trying to reduce their numbers and are testing the crabs to see if they are safe for export to China where they are a delicacy.
Paul Clark, marine biologist at London's Natural History Museum, said: "They are testing to see how much mercury and cadmium are in the meat of the crabs.
"If the crabs were to pass then we could perhaps take the next step to see if we can fish.
"If it fails there will be no fishing at all and we will have to think of perhaps another way of depleting the population."
The mitten crabs could have arrived in England in the ballast water of international shipping.
They were first seen in Europe in Germany in 1912 and from there spread throughout the continent invading waterways from Scandinavia in the north to France and Portugal in the south.