Hello BMG,
Thats definately a fingermark......
Once the fish has died and sometimes when they grow to a larger size they tend to lose their dark spot on their back...........hence why in northern Australia they are called golden snapper. It looks like in that photo that fish has been bled and put on ice, thats why it wouldn't have a spot on it...
Here is a pic of a fingermark caught off a wreck east of mackay
Cheers dan...