Aha! You're thinking of tilapia. Very popular in the US because it's so mild.
Triggerfish are found worldwide, as far as I know. There are several members of the family. The one I'm talking about is the Queen Triggerfish, found in the Atlantic, with a range from North Carolina to Brazil.
They're called triggerfish because when they raise their dorsal fin the first spine locks in place. If you touch the second spine like a trigger, however, it releases the locking action.
The Queen Triggerfish is found primarily on, and near, reefs, where it dines on barnacles, which is what gives it its sweet flavor.
Most people spoil garden things by over-boiling them... if they are overboiled they have neither any sweetness or beauty. Hannah Glasse 1745