He said after rumours of a massive cod living in the lake surfaced, Murdoch University Fresh Water Fish group and the Department of Fisheries started electro-fishing.

But instead of the tale of the one that got away, a 15-kilogram cod came bobbling to the surface.

There were also rumours that a woman living adjacent to the lake was feeding the fish dog biscuits, which Langdon said could explain its whopping size.

"Whether this fish has been enjoying a diet of dog biscuits, or whether enjoying other local fare... maybe small ducks that have lobbed on the lake, that have found themselves inside of a cod," he said.

And like all good fishing yarns, Langdon said there could be a bigger cod at the bottom of the lake.