The deaths of thousands of crabs along the Thanet coast remains an unsolved mystery.

Weeks after a tide of dead adult velvet swimming crabs covered the beaches and rock pools from Westbook to Birchington, the Environment Agency admits it is no closer to an answer.

The investigation has focused on three possible cause - a vicious virus, freezing cold weather or pollution.

Ian Humphreyes for the Environment Agency said: "We shared the public’s concern about this serious incident and wanted to find out as quickly as possible what had happened to the crabs. Pollution was quickly ruled out as miles of coastline were affected but no other species killed."

This incident is not unheard of, but uncommon – around three years ago swimming crabs from the rocky shores around Thanet were virtually wiped out until last summer, by when their numbers had recovered.

Mr Humphreyes said: "It is possible the severe cold weather at the time might have disproportionately affected this species, a view supported by local environmentalists. However, disease is an equally likely cause and needed to be considered."

Experts in fish and shellfish diseases were contacted at CEFAS (Centre for Environment, Fisheries & Aquaculture Science) and two officers from Weymouth examined crabs collected by the Environment Agency.

The CEFAS officers dissected the crabs on the seafront and samples of crab tissue (heart, muscle, and stomach) were removed and preserved for later analysis. The possibility of a species specific virus as the cause is being considered.

Mr Humphreyes added: "This work is still ongoing but no obvious disease agent has yet been identified.

"The mystery of the dead crabs remains unsolved and we can only hope that they recover quickly. A survey by Canterbury City Council has already shown that there are still live swimming crabs present off-shore around north Kent, which is positive news for this attractive species."

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