The staff were working clearing rubbish caught on a grill allowing water into the huge water turbines when they discovered the dead fish.
They then needed to use a crane to lift it out of the water, and once it was on the banks the team from the Austrian electricity company Verbund were stunned to discover that the catfish was an incredible 2.25 metres (7.4 feet) in length, and weighed an incredible 90 kilogrammes (over 14 stone).
Usually catfish species (Siluriformes) can grow up to 1.5 metres (5 feet), and discoveries of catfish over 2 metres (6.5 feet) in length are extremely rare.
Fish expert Peter Noebauer said that catfish have multiplied in recent years on the river, with more and more monster specimens being found like this one, which was found at Verbund's Abwinden-Asten hydroelectric plant near Linz in Upper Austria.
He said: "We are seeing more and more catfish, though I don't ever remember seeing one of this size before."
Story courtesy of Central European News