A team of fish experts braved the cold water on Wednesday, 8 November to remove carp, dace roach, bream and perch, before rehoming them in another section of the canal.
Once this is done, more than 2.5 million litres of water, the equivalent of six and a half Olympic sized swimming pools, will be drained. Engineers will use clay to secure 100 metres of the waterway walls, which will help to prevent water leaking from the canal.
The project is part of a £38million programme of repairs to canals and rivers across Wales and England being carried out by us over the winter months.
Kevin Phillips, waterway supervisor, said: "The Monmouthshire & Brecon Canal is one of the most popular attractions in the Brecon Beacons, enjoyed by boaters, wildlife enthusiasts, runners, walkers and more. But at over two centuries old it needs plenty of care and attention. This is a good example of the type of work our charity has to do to make sure it's in top condition for everyone who uses it, visits or lives on it.
"The fish rescue looks quite unusual. A method known as electrofishing is being used, which will see teams wading through the water in wet suits and passing a small electric current through the water. This effectively tickles the fish so that they temporarily stop swimming and can be gently netted and rehomed."