Three very basic rules of Gizzard Shad. (These rules are subject to change due to the million or so variables you can have in a body of water)

1. Your largemouth bass will do a
little better.
2. You bluegill, redears and other lepomids will do a lot worse.
Thanks, Bruce--that information helps. I realize the shad out-compete the lepomids with sheer numbers, but why wouldn't the bass do quite a bit better?
In reference to what ewest said, yes, no LMB can swallow the largest g-shad, but if there are enough mature LMB, can they devour most of the shad before they get that size?
I know I'm oversimplifying things, and I don't have any scientific data.
SO FAR, though, our BG, CNBG, and RES are doing a little worse with the presence of g-shad and our LMB are doing a lot better.
We didn't stock the g-shad, but it's working ok right now. Of course, the goal for that pond is not growing trophy-sized lepomids.