Daniel Sibley, 21, of Blaby, Leicestershire, landed the 108lb 4oz (49kg) ‘beast’ while carp fishing with his friend Aaron Johnson on Sunday.
The fish, caught at Bluebell Lakes, near Oundle, Northamptonshire, is thought to be one of the heaviest ever landed on a rod and line in Britain.
Mr Sibley said: “I was exhausted. It took me for a right merry dance!
“After the fish took my line I realised what it was. I just had to get straight in and try to get some line back because I had half a reel’s worth of line out.
“I don’t think it realised it was hooked at first, but as soon as I started to put some pressure on it took off. Because I was using just 8lb line I had to let it have as much as it needed.”
Mr Sibley had to get into the water during his epic battle with the fish.
“I found myself out of my depth a few times. I was doggy-paddling until I could touch the bottom again,” he said.
“I wondered whether it was ever going to tire, but eventually it did.”
Aaron helped Daniel land the monster fish and it took two landing nets to bring the fish ashore.
“I got a couple of handshakes and a couple of beers handed to me. Aaron was jumping round for joy. Everybody mucked in to help us and we got some nice snaps. It was so slimy – like holding an eel, but so much bigger!”
Daniel, who began fishing aged seven, was using just a small, size 12 hook on his 8lb line.
“I’m pretty sure that nobody’s caught a fish that size on the tackle I was using,” he said.
After posing for photos with the fish, he returned it back in the water where it swam away unharmed. He said he had named the fish Big Al in tribute to his friend, Alan Thompson, who died last year.
Nick Simmonds, secretary of the British Record (Rod-Caught) Fish Committee, said no records had been kept for the Wels catfish since October 2000 because it was a non-native species. Before records were suspended, the largest catfish caught was listed at 62lb (28kg).