I re-read all four of the AFS studies you posted; three out of four found a negative effect on bluegill populations from the introduction of threadfin shad. One states that a "precipitous" decline in zooplankton occurred, and that the bluegill population suffered a corresponding decline in survival to the size at which they move into the littoral zone; another states that shad and bluegill did compete for food, and further that their foraging zones overlapped; the third finds that bluegill were negatively affected in more BOWs than ones in which they were positively affected. So I agree with those studies (and yes, that's meant to be funny though it's also true.) The fourth one, which comes first in your post, I had confused as being part of the gizzard shad study I was railing against; it's the study that clearly states that threadfin shad changed the size structure of phytoplankton in the lakes studied, reducing the number of larger phytoplankton and increasing the number of smaller phytoplankton, and then claims that the bluegill were not affected.

Here's the article that claims gizzard shad have no adverse effect on bluegill size:

http://www.bassresource.com/fish_biology/gizzard_shad.html

Here's the actual study Nutt references - and if I didn't like his article before, I really don't now because he simply misquotes the study below, which makes no mention whatsoever of the size structure of bluegill as affected by gizzard shad, which of course is the whole point; it notes that bluegill density was not affected, but density was never the issue:

http://afsjournals.org/doi/abs/10.1577/M02-068?journalCode=fima