Its hard to tell how big a fish is in a photo.
I caught a 5 lb bass and it looks a lot smaller then the bass my son caught that was the same size. I am 6' 1" and 260 lbs, my son is 5' 11" and 135 lbs. I've also heard people look at finger sizes, saying each joint is 1", well that is wrong too. Mine are longer then that, and as far as thickness, it depends on what you do for a liveing. I am a Elevator mechanic and you could squeze a quarter through my wedding ring.
So I hope he got the Perch weighed on a cirtified scale & in front of witnesses. That is the only way to know the fish story is true.
It is a very impressive Perch, and it looks to me like it can be 6 lbs.
Mike