The wels catfish (Silurus glanis) gets fairly large. But, not as large as the stories surrounding it. The record for a wels is 9ft 1.5" and weighing 317lbs.
Actually the record for a Wels is 16 1/2 foot long & 675 lbs-it was caught from the Dneiper. As far as I'm aware this is legitimate. I kept one years ago before they were banned here in England-the most phenomenal growth rate I've ever seen on a fish-looking back I was mad to even contemplate buying. I ended up donating it to London Zoo Aquarium-took the bloody thing up on the train & Tube! They contacted me several months later to inform me it had been exchanged with San Diego Sea World.
They grow bloody big - I've met a fisherman who has seen them take & eat wildfowl.