Bill,
Possibily not, but I sure don't know, would be like, do fish have personalities?
Neither the barrimundi nor pacu breed in the pond, so there is only one generation of each. They are not passing anything along. So their genetics are set, when little, they were all aggressive. To this day you can see the pacu shoulder each other out of the way. The pacu are very eager eaters and dispurse the pellets almost immediately. That gives everyone a fair shot at some food.
Long winded way of saying I would tend to believe the bigger fish come by it naturally rather than being less aggressive.
