This is only from limited experience.
Before I built my pond I fished many of the local public lakes and ponds. In none were the tilapia dominant, in an afternoon’s catch of 15 or so fish, 1 or 2 would be tilapia, most would be barbs. In all of the fishing we did we caught one predator, a cat fish. In most of the ponds/lakes catfish is the only predator, if there is one.
In a one acre pond in which I fished a lot we seldom caught any tilapia, they had been stocked and were present, we could see them at feeding time. Visiting ponds at temples where there is no fishing and people are allowed to put any animal in the water, there was never an abundance of tilapia. People feed these fish all day long and you can see big carp, catfish and tilapia.
I think that there are two factors at work, one is predation the other is a natural monitoring.
Before I stocked the predators I would see maybe one batch of fry a week, some times there would be 2 weeks in between. The predators have put a lot of pressure on the tilapia and now I see new fry almost daily. The spawning beds in my pond are shallow, 3 or 4 inches deep at the center and 4 to 6 feet wide, they seem to use the same ones over and over.
