A new eel pass structure to help baby eels known as elvers to grow has been installed at Osterley weir in the River Brent.

It will allow the young fish to travel through the weir, alongside Osterley Lock on the Grand Union Canal, Brentford , making for an easier journey migrating upstream from the Thames.

The passage was set up as part of the The Zoological Society of London (ZSL) eel conservation programme, along with ecology experts, frog environmental, on Thursday (Jan 22).

Leela O’Dea, technical director for frog environmental, said: “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.

Osterley weir eel pass

“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.

“These creatures undertake the most incredible journey in the hope of reaching freshwater where they can thrive and grow, so it’s vital that we enable them to complete the very last section of that journey by installing successful eel passes."

The new eel pass is stronger and is made out polypropylene, a strong plastic, and reinforced with steel to offer better protection from debris moving through the weir.

Eels spend up to 20 years in the rivers before migrating back out to sea to breed but the number of elvers is declining rapidly.

In 2008 they were classified as critically endangered species.

On the River Brent, ZSL been working with the Environment Trust, which set up an eel recovery programme three years ago, and the Canal and River Trust.

During this time four eel passes have been installed, and since April 2014 almost 63,000 juvenile eels have been recorded in the river by a team of 20 Citizen Science volunteers.

Joe Pecorelli, of ZSL’s UK & Europe conservation programme, added: "One of the contributory factors causing the decline are barriers that prevent eels migrating upstream and accessing habitat in our rivers. 

“We hope this new pass over Osterley weir will make a huge difference to eels travelling to the River Brent and we are very grateful to the SITA Trust for funding this work.”