Mycteroperca microlepis
Lines radiate from eyes; Dusky tail has thin blue margin; Scamp Grouper (M. phenax) is very similar, but does not show those radiating lines.
I reduced picture size so they would be visible on your screen. Just click on thumbnail for 6 x 4 picture, and name for 10 x 8 full size picture or more info.
Size: 1.5-2 feet; max 3 feet;
Depth: 20-100 feet;
Audubon Field Guide; page 450; no plate;
Reef Fish ID 3rd ed; page 168-169; plate 169;
This appears to be a juvenile Gag Grouper. Photo by Rod
25 Feb 04 in about 10 feet water.
Location was offshore at Cannon Beach, Pennekamp Park, Key Largo.