I did not see the photo, but he said 26kg, so I said 'how big', and he again said 26kg. I cannot tell you any more than that. It sounds like a fishy story, but he said the fisherman is an honest bloke and he saw the fish in a photo.
When I was a kid, and I am talking about the 1960's, I saw a tuna jumping in the middle of Yowie Bay out from the public wharf, and it was a minimum of 4 foot long, probably closer to 5. Anything is possible, as in the 1920's and 30's, 20 pound snapper were being caught in Gymea Bay.