That's a good question. I suppose it wouldn't take too long to figure that out - provided PT will import the histories.
I would think a lot of fish would change their names for 2 reasons:
1) because they can and would think it's cool - not because they are aware they're fish
2) because TP, Mayhem, sjay and JD will be showing up at their tables so often they become paranoid
I remember one guy I was chasing around for 3 hours. I was on very table he was on and I kept following him as he moved. Eventually he asked why I was following him everywhere - I told him that I thought he was following me! He said he wasn't... lol - I miss that guy...