there was a good discussion about golden shiner not long ago, so look for it on the board.
gizzard shad can look, grey, greenish to blue dorsally, silvery below. there is a large black spot present behind the gill cover. Gizzard have a rounded snout, if you scrape you finger nail along the snout of a gizzard shad (in an attempt to open the fishes mouth) your finger nail will be below the fishes eye before its mouth opens.
Threadfin shad are colored very much the same, with the black spot also but the snout is much more pointed. if you do the finger nail test you will notice that the treadfin has a much more upturned mouth. its mouth kind of looks like it opens upward.
dont be fooled by the long thread that comes off the dorsal fin, this is present on both species.
After rereading this I wish I could be more descriptive, I'm not exactly a wordsmith. I can email some pics if you like.
