James,
I haven't seen any adverse effects on BG from Tilapia...in fact the opposite, the BG numbers in my ponds improved each year and now have kind of stabilized at a high level after 4 years of stocking Tilapia.
The key may be in initial stocking rates and sizes of the initial stockers. Seems to me that very high stocking rates with relatively large Tilapia might indeed work against the BG. There is some evidence from lakes in Mexico that large Tilapia that overwinter each year may have an adverse effect on quality of LMB fishing...theory being that larger Tialpia in overpopulated waters may eat fry of other game fish.
In my own case, I've reduced Tilapia stocking rates to about 5 to 7 pounds per acre and things seem to be very stable for me at that rate. One pond stocked with 2 pounds per acre last summer, didn't get the algae control I wanted.
One of the great things about Tilapia I haven't seen mentioned is what you touched on...their survival rate. Mouth brooders that protect their young like Tilapia do, should have a higher survival rate in the young. I'm hoping to get some really good data/experience in the next few months on Tilapia reproduction and growing out young fish capable of surviving in the ponds with predators.
In my own case, I'm planning to produce young Tilapia in my indoor facility, transfer them to grow out tanks and then, if necessary, transfer them again to cages in the ponds for final growing before release. By the way, my indoor facility is also stocked with Gams to determine if Tilapia will eat them. So far, they haven't.
