his range looks very capped, should fold against this sizing. u can bluff catch lower bets.

villian can also randomly show up with AQ or AK ( not that often )

To me its pretty weird that he doesn't cbet such a flop, I think fish will generally cbet their bluffs quite frequently in this spot, especially the kind that like to 3bet more than just the nuts. They also love to check value hands, even those they have no business trapping. His big river sizing is a second red flag that this fish has something like a trapped overpair or of course 99. There are fish who could do this sort of thing with a bluff but I think it is much more likely that you are beat. I do expect them to bet the turn a lot with overpairs a lot however. Ultimately I do not think it is good to play the guessing game with fish (i.e., does he frequently bluff all these x,y,z combos that he needs to for me to call profitably?), the money is made by recognizing common lines or narrowing their range in a logical fashion. You are also getting a very punishing price here which makes calling even worse. Also do not post results in the OP as it can skew analysis.

I think from the fish 99 is the single most likely hand for this line, followed by 22 if he 3b it, then maybe AA. All hands the fish sees as so strong they want to really enjoy with some oddball low ev line.
I agree 100% with reg3000. It's an odd line to bluff with, why not bluff earlier, then why wait til it looks like you're weak and use a massive sizing when a small one would likely be very +ev anyway.
The big thing with a fish as opposed to a reg here is as r3000 points out, fish can't help but slowplay big hands. It's like they'd rather use x-x-pot and win 1/3 stack from your bluff catchers because it's "clever" or "tricky" than B-B-B and win a whole stack from all your value.

Also FWIW, you'll smash the fish by exploiting the way they overvalue mediocre hands when you have clear value, bot by trying to make light call downs.