Time runs out for the Thames eel
January 21 2010 Paul Eccleston
The eel is fast disappearing from London’s River Thames and may soon be gone completely.
New research by the Zoological Society of London (ZSL) shows that numbers have crashed by 97 per cent in the past five years.
In 2005 1500 eels were caught in traps in the river’s tributaries but last year the number plummeted to just 50.
The figures are in line with the general decline of the European eel (Anguilla Anguilla) across Europe and which it has seen it placed in the IUCN Red List as a critically endangered species – one step away from extinct in the wild.
The eel was once so plentiful in the Thames that it became a staple food for the city’s East End poor because it was cheap and easy to catch. Along with equally cheap mashed potato and green liquor – the water residue from stewed eels – jellied eels became a traditional food of London’s cockneys.
The latest figures were revealed by the ZSL’s annual Tidal Thames Conservation Project which traps and counts eels before freeing them. It seems to confirm fears by conservationists that the eel is failing to return to the river in sufficient numbers to guarantee future populations.
After being declared biologically dead in the 1960s because of pollution, the Thames is now cleaner than it has been for centuries and marine life has staged a dramatic recovery – excluding the eel.
Matthew Gollock, ZSL’s Tidal Thames Conservation Project Manager, said: “Eels are mysterious creatures at the best of times but we are very concerned about the rapid disappearance of the species in the Thames.
“It’s difficult to say what is going on – it could be due to a number of potential factors including changes in oceanic currents due to climate change, man made structures such as dams and the presence of certain diseases and parasites.
“Other rivers in the UK are also seeing a European eel population decline – so it seems to be a worrying trend.”
He said there was a need to find out why the declines were happening, in order to save the fish and help other species in the estuary’s food web who would be affected by its disappearance, such as birds which feed on it.
“Time appears to be running out for eels in the River Thames and this could have a domino effect on other species in the Thames,” Dr Gollock said.
“The Thames is a very urban, developed estuary. It’s much healthier than it was 50 years ago, but there is constant pressure on it.
“It’s quite a precarious ecosystem and the fast removal of any species – whether it is a fish or a plant – is going to upset the balance,” he said.
The European eel is a complex and mysterious species which is believed to start its life in the Sargasso Sea where it drifts on oceanic currents before reaching European shores up to 4 years later.
From here, as elvers, they migrate into our river systems where they can spend up to 50 years, feeding and growing before returning to the Sargasso to spawn and die.
Scientists still do not know the causes of the eel’s dramatic population decline but it is thought to be a number of factors including: loss of habitat, pollution, disease and over fishing.
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