Rescuers were shocked when they netted a massive fish in the waters of Welsh Harp Reservoir.

Two contractors brought in to help the Canal and River Trust look stunned as they hold up the immense mirror carp found last week.

The fish was among thousands removed before a clean-up operation to completely drain the reservoir and remove tonnes of litter.

It’s estimated that more than 100,000 fish will have been rescued since the operation began last Friday (December 22).

The fish have been temporarily rehomed to different locations including Blythe Waters in the Midlands.

Ham & High: The partially drained Welsh Harp Reservoir during the fish rescue operationThe partially drained Welsh Harp Reservoir during the fish rescue operation (Image: Canal and River Trust)

The fish rehoming is part of a five-month, £2 million programme of essential maintenance work over the winter months in “one of the capital’s most important urban wildlife spaces”.

It includes repairing the chains and rods that operate the reservoir’s sluices, repainting the Valve House Tower and fully draining the water to remove any litter left behind.

The Welsh Harp Reservoir is home to thousands of aquatic creatures, but despite the size of one of its inhabitants, there is a strict no fishing rule in the lake, a special site of scientific interest (SSSI).

Ham & High: The fish rescue operation at Welsh Harp ReservoirThe fish rescue operation at Welsh Harp Reservoir (Image: Canal and River Trust)

John Ellis, the Canal & River Trust national fisheries and angling manager, said: “Before the reservoir is fully drained, we’re carrying out a fish rescue, employing specialist contractors.

“The fish will be caught in nets and then placed in large containers of oxygenated water where they can recover for a few minutes, before being rehomed at various locations on the trust’s network.

“We expect to rescue thousands of fish from Brent Reservoir, including roach, perch, bream, carp and pike.

“When the reservoir has refilled with water, we plan to restock it with native fish species, including roach and perch, beginning in the spring and completed next autumn and winter.

“Whilst the reservoir is drained we are going to take the opportunity carry out a series of improvements to enhance the SSSI.

“As well as using specialist contractors to remove rubbish, we’ll carry out vegetation management and we’ll install 14 new tern rafts to provide island habitats for common terns, one of the species of water bird that lives on the reservoir.”

Tickets are on sale for a once-in-a-lifetime opportunity to see “beneath the surface” and see the sluice gates up-close during a Brent Reservoir Open Day event on February 3.