Bob, for most of us, Tilapia overpopulation is not a potential problem. The fish all die each winter and must be restocked in the late spring annually. Local legend is that the small Tilapia do not die, only the large ones, but even those who tell this tale know the truth. The Tilapia get sluggish from the cold long before they would die from it. Slow-swimming small Tilapia become a favored item in the menu of the bass, and only the largest ones, too big to eat, are left alone long enough to float up on your shore.
As for competing with other fish, adult Tilapia are mostly vegetarians, feeding on plants, including at least some varieties of filamentous algae, and filter feeding on plankton. They will consume invertebrates who practically crawl into their mouths, but eat few if any fish. (We have had several caught on worms and crickets being fished on the bottom for bluegill.)
In commercial operations in tropical climates, the biggest problem is that since size offers no advantage in feeding and because reproduction is relatively efficient, Tilapia ponds become filled with many small fish and no large ones of commercial size.
My Tilapia, by the way, are entering their first spawn and tractor-tire sized beds are scattered in the shallows.
Lou
