Wildlife including 600 fish have been relocated from one side of a motorway to the other.
National Highways will temporarily divert a brook so they can carry out a number of upgrades to junction 28 of the M25, near Brentwood in Essex.
To protect the area’s biodiversity, environmental specialists gathered and relocated over 12 species of fish, including a 50cm long European eel.
Some relocated wildlife, such as the eel, are considered threatened species.
Diverting the brook will allow National Highways to begin installation of steel girders to aid construction of new bridges.
Zach Pepper, project lead for the junction upgrade, said the brook would be returned to its natural course once work in the area was finished.
“We want to deliver the essential improvements to this busy junction while protecting the wildlife and biodiversity around us,” he said.
The upgraded junction was expected to be open for traffic in the summer of 2025.
Improvements include a new two-lane loop road, a wider anti-clockwise carriageway and relocation of some entry and exit slip roads.
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