Eels are vanishing from the Thames

Eel numbers in the Thames have crashed by 98% in 5 years. Photo credit ZSL

January 2010. Eel populations in the River Thames have crashed to alarmingly low levels, conservationists have revealed.

Over the last five years scientists from the Zoological Society of London (ZSL) have recorded a 98 per cent drop in the number of European eels within the river.

50 eels caught in 2009 - 1,500 in 2005
Every year, ZSL's Tidal Thames Conservation Project carefully places eel traps on a number of the river's tributaries. Last year less than 50 eels were seen in the traps, marking a stark contrast to 2005 when around 1,500 eels were captured. Conservationists are now concerned that the eel, which has been sold as an iconic East London dish for centuries, is not returning to the river.

Extraordinary migration
Scientists believe that European eels originate from the Sargasso Sea in the Atlantic Ocean and can spend up to three years travelling to their designated waters in Europe. They remain in catchments, such as the Thames, for up to 20 years before they make their mammoth 6,500km return voyage back to the Sargasso Sea to spawn and die.

Matthew Gollock, ZSL's Tidal Thames Conservation Project Manager, says: "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."

First fish to re-colonise the Thames after the pollution
European eels and flounder were the first two fish species to re-colonise the Thames River after the Estuary was considered biologically dead in the 1960s. Conservationists believe that any serious and rapid collapse of the eel population could have a knock on effect for other species in the river.

Matthew says: "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. We need to understand why this decline is occurring so we can be in with a chance of saving this extraordinary animal."

Eel monitoring for 2010 begins in April.