Think I'll chime in on this one.
Here's our experiences, based on 35+ years of using threadfin shad in client lakes and ten years using tilapia, in Texas.
I was hesitant to use tilapia because of what I believed to be true. What I thought was that people would stock them into existing, overcrowded bass lakes. Tilapia would reproduce prolifically, then die off every fall and leave an overcrowded bass lake with more mass, with even less food than when they started. Then, there'd be a mess to clean up in the fall. That's not what happens. We've learned that when we stock ten pounds per surface acre into a bass-crowded lake, we see an increase in survival rates of young of the year bluegills every fall. When we stock 20 pounds per surface acre, we see algae control, and we see increased survival rates of young of the year bluegill, going into the fall. As the water temperature begins to decrease in the fall, tilapia become sluggish and game fish gorge themselves on those tilapia. The few big ones which die are quickly cleaned up by buzzards, and on some client lakes, bald eagles eat them. Stomach contents of bass studied in lakes with tilapia suggest larger bass don't necessarily feed on small tilapia. I believe small tilapia feed the smaller bass and simply by sheer numbers allow bluegill survival rates to rise. This management strategy certainly doesn't preclude bass harvest. That has to happen for long term growth rates.
Threadfin shad live in a totally different niche than tilapia. They live in open water and are filter feeders. They need plankton in order to have reasonable survival rates and to become enough mass to be substantial. Threadfins are primarily preyed on by intermediate-sized bass.
So, I see them as two completely different tools. I've not seen any evidence that threadfins assist in survival rates of young bluegills.
But, every trophy bass lake we manage has threadfin shad.
