Young Eels Get A Helping Hand

To climb up the weir at Osterley Lock

On behalf of the Zoological Society of London (ZSL) and The Environment Agency, a company caled Frog Environmental has designed a revolutionary new eel pass structure to allow juvenile eels, also known as elvers, to travel through the weir alongside Osterley Lock on the Grand Union Canal.

BBC London reporter Yvonne Hall spoke to ecologist Leela O’Dea (video).

Leela O’Dea, Technical Director for Frog Environmental, explains: “This totally new and bespoke structure will be the final piece in the jigsaw enabling more baby eels migrating along the River Thames to reach the freshwater environment of the River Brent, where they can feed and grow to become adult eels.

“Sadly the previous eel pass installed two years ago wasn’t strong enough to withstand the force of the water and debris passing over the weir alongside Osterley Lock, the final barrier to overcome on the Grand Union Canal before it connects with the River Brent.

Eels spawn in the Sargasso Sea in the western Atlantic and are carried towards European waters by ocean currents. After approximately 1 to 2 years, the young eels arrive in Europe and head up estuaries, including the Thames estuary. They spend up to 20 years in rivers, before migrating back out to sea to breed.

Over the last 30 years the number of elvers joining the adult population of European eels in our rivers has declined. In 2008 the International Union for Conservation of Nature (IUCN) classified the species as Critically Endangered and in 2005, ZSL set up its European eel monitoring programme to assess the presence of migrating juvenile eels in London, identify restrictions to their movements and gather long term data on elvers entering the River Thames catchment.

With strength in mind and to avoid a further failure, the inner structure of this new eel pass is made of a single piece of polypropylene, an extremely strong plastic that is both chemically and heat resistant. Reinforced with steel it offers deflection and better protection from trees and other debris moving through the weir.

February 4, 2015