Now an exotic Chinese crab which preys on British native species is on the verge of taking over the country's major waterways, environmental experts have warned.
A study showed invading mitten crabs, which can grow to the size of a dinner plate, cou
ld threaten other marine life.
Newcastle University researchers have warned there could be a population explosion of the creatures.
The study authors predict the mitten crab – so called because its claws are coated with small clumps of dark brown fur, or mittens – has the potential to establish itself in all major estuaries in several years time.
Mitten crabs are already present in some British waterways, including the Thames, Humber and Tyne rivers and parts of the North Sea and Channel coasts.
A member of the research team, Dr Matt Bentley, said: "The pattern of the spread in the UK since the 1970s mirrors the spread in mainland Europe and in the Baltic region which experienced a major outbreak.
"This is a fairly good indication that the UK is set for a similar situation."
The study, published in the academic journal Biological Invasions, says a nationwide monitoring and trapping system for the crab should be introduced.
