I don't want to rely too heavily on this forum, and I don't want to monopolize it. So I carefully went through Reef Fish from the beginning, page by page, up to odd-shaped fishes. I looked primarily for the distinctive black spot in front of the tail. I did not find any fish I consider a match.
These are the fish I found with similar black spots -- silver porgy, spottail pinfish, Latin grunt and butter hamlet.
Is it any of these? Which one? Why does it not look like my photo?
Molasses Reef, buoy M1, Key Largo, Florida, Monday, November 1, 2010, depth 32 feet, 85 degrees Fahrenheit.