Monmouthshire and Brecon Canal gets £2m of repairs
More than £2m will be spent to improve the 200-year-old Monmouthshire and Brecon Canal by the end of winter.
Work will be carried out to prevent leaks in the canal at Llangynidr in Powys, while the Goytre Wharf aqueduct near Abergavenny will also be repaired.
Thousands of fish will be relocated during the work using a harmless process called electrofishing, during which a low voltage stuns them.
The Canal & River Trust in Wales is funding the maintenance.
The charity said the work at Llangynidr would involve draining a length of the canal.
Before that happens the fish will have to be temporarily stunned and scooped up in big nets to be moved to safety.
The canal, which dates back to 1812, is now home to a flourishing array of wildlife and the electrofishing is expected to reveal a large number of fish, including roach, perch, carp and bream.
Nick Worthington, waterway manager at the trust, said while the Monmouthshire and Brecon Canal was one of the "real gems of the UK's canal system", it was not an easy one to take care of.
"It requires constant maintenance to keep it running smoothly, a job made all the more challenging when it's built half way up a hill," he added.