Compare the upper jaw line of these spotted bass pictures with that of this "mystery" fish caught.
Notice how the upper jaw line of the "mystery" fish ends well beyond the rear edge of the eye. In the spotted bass, this line ends before or just at the rear edge of the eye.
The slope of the head of the "mystery" fish is exaggerated by camera angle, basically having the camera pointed upwarded in the picture hides some of the head in that angle.
Let's do a little test. I pulled some pictures of spotted bass, smallmouth bass and largemouth bass from the internet and crop out the head only. Let's see if head slope and jaw structure can tell in these pics based on different camera angle and how the fish was held.
Pic 1 - Spotted, Smallmouth or Largemouth?
Pic 2 - Spotted, Smallmouth or Largemouth?
Pic 3 - Spotted, Smallmouth or Largemouth?
Pic 4 - Spotted, Smallmouth or Largemouth?
Pic 5 - Spotted, Smallmouth or Largemouth?
Pic 6 - Spotted, Smallmouth or Largemouth?
Pic 7 - Spotted, Smallmouth or Largemouth?
Pic 8 - Spotted, Smallmouth or Largemouth?
Also, Largemouth Bass could develop rows of lateral spots on the belly during spawning. Again, let's play this game...
Pic 9 - Spotted or Largemouth?
Pic 10 - Spotted or Largemouth?
Pic 11 - Spotted or Largemouth?
Pic 12 - Spotted or Largemouth?
Pic 13 - Spotted or Largemouth?