If you start with adults and feed them, along with what they eat from the pond naturally, I have no doubt there will be plenty big enough to eat.

I have had them several years in my pond, I do not feed them, but that does not stop them from growing rapidly and reproducing like I would have never imagined.

I have never caught one on hook and line, granted I have not tried all that hard. In my experience the hardest part of tilapia is catching one of any size. That's just me though.

If you have no predators you will have lots of babies and lots of dead (small) fish come fall. What are your goals for the pond? to raise tilapia just to eat?

Get out and fish.