User blog comment:LuffyPirateKing/Chapter 621 Prediction../@comment-3242083-20110410131147

Hm, the idea that Arlong sold out Tiger is nice, but your reason for it is a bit lacking (or maybe not enough explained).

A reason I would buy:

Tiger, after liberating his kind, stopped his aggressive ways. His goal is achieved (freedom for his people). Much to Arlongs disappointment, who believes that they will lose their newfound freedom as fast as they gained it, if they don't make the first strike. But what should he do about it? Fisher Tiger is the hero of his race, and Queen Otohime herself welcomes his change of heart. Arlongs words would fall on deaf ears, thats for sure. Disappointed in his former idol, Arlong's admiration for the great Fishman turns into hate. He must prove that the humans need to be dominated, in order to ensure the safety of his people, of his kind.

It is decided, Tiger needs to die by the hand of the humans. Everyone should witness how their great hero falls due to their naive passiveness.

But anyway, I like the idea of betrayal, especially because it would be so unlikely for Arlong to do something like that (at first glance)