River Colne project helps streamline fish migration

A project to help critically endangered European eels navigate their way along the River Colne in Stanwell, has been completed by locally-based environmental charity Groundwork South in partnership with the Environment Agency.

Until recently, barriers at Hithermoor Weir meant the eels and coarse fish, such as roach, chub and bream, were unable to migrate up and downstream.

But now, thanks to an £8,000 grant from Grundon Waste Management through the Landfill Communities Fund (LCF), and matched funding from the Heritage Lottery Fund, work has transformed the area by creating a fish ladder for coarse fish and climbing support for juvenile eels.

Work in progress at Hithermoor Weir to transform the area by creating a fish ladder for coarse fish and climbing support for juvenile eels
Work in progress at Hithermoor Weir to transform the area by creating a fish ladder for coarse fish and climbing support for juvenile eels

Tom White, project manager (Colne Rivers) Groundwork South, said: “The weir would have housed the original millwheel dating back to when a water mill stood on the river. Although the wheel itself is now long gone, it had left a physical barrier which was impossible for the eels and fish to pass.

“We worked out how to make it easier for the fish to ascend the barrier, pouring in concrete to provide a shallower gradient slope and adding stone baffles to help slow down the flow, making the water deeper and providing resting places for the fish.

“We also installed specially-designed eel tiles which enable the young eels to wind their way in and out and effectively gives them their own ladder to climb up the slope.”

The work is part of a bigger project to monitor barriers on both the River Colne and other local rivers, with a view to understanding if the eels and coarse fish can regain full connectivity with the River Thames and the Upper Colne.

Work at Hithermoor Weir has been completed, including the installation of specially-designed eel tiles which enable the young eels to climb the weir
Work at Hithermoor Weir has been completed, including the installation of specially-designed eel tiles which enable the young eels to climb the weir

Anthony Foxlee-Brown, Head of Marketing and Communications at Grundon Waste Management, said: “Preserving the countryside and the creatures that live there is something very close to our hearts and when we were asked to contribute towards this project through the LCF, we were very happy to do so. The fact the European eel is a critically endangered species means every single one helped to survive is a victory and we are very proud to have contributed towards their future success.”

The eels spawn in the Sargasso Sea, an area of the North Atlantic Ocean, before undertaking what is recognised as one of the most impressive feats of animal migration as the eel’s offspring are thought to drift towards Europe on the Gulf Stream, a journey that can take a couple of years.

Once here, these metamorphose into virtually transparent glass eels and then, as they migrate up freshwater rivers and streams such as the River Colne they gradually darken in colour and are known as elvers. Once in their freshwater habitat, they take on the name yellow eels and can stay in place for more than 20 years before eventually deciding to to go back to the Sargasso Sea to spawn, at which point they are known as silver eels.

Alongside the eels, Tom says the improvements will also help coarse fish breeding, adding: “Although coarse fish don’t have a huge migratory range, it is very important that they can swim freely from one area of the river to the next. If they are unable to do so, then they are unable to access the different types of habitat they require to complete their lifecycle.”

Given the historic nature of the location, the team worked closely with the local landowner to ensure the development was in keeping with the area. Although privately-owned on one side, the river is a popular location for members of the Bath Road Piscatorial Society, which has permissive access to allow fishing.

The completed works at Hithermoor Weir have enabled eels and coarse fish, such as roach, chub and bream, to once again migrate up and down the River Colne
The completed works at Hithermoor Weir have enabled eels and coarse fish, such as roach, chub and bream, to once again migrate up and down the River Colne
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