Recruitment failure can attributable to multiple causes. Tilapia stockers used from all male stocks? Predator pressure too high on released fry can also be an issue. Tilapia themselves are not a good predator but bass and even other sunfish can get the job done if density high.

I breed Tilapia in tanks and have done so in ponds many years ago. They are hard to keep from breeding to be sure. My females in the absence of larger adults will start holding before 2" long. It is not a big deal to see females on nest as they do a lot of courting before spawning really gets underway.

Aquaculture
Cooperative Research / Extension
Lincoln University of Missouri