Here are some photos of a couple of fish that were badly injured at some point. We can only guess as to what caused the damage.
Both fish took off strong and seemed unaware of their injuries.
All of these photos were pulled from the video we took while measuring and releasing the fish.
Pic 1: 39" northern that seemed to be injured quite recently. Prop from a boat perhaps? The fish was not bleeding at all when I handled it.
Pic 2: 39" northern; same fish
Pic 3: 39" northern; same fish
Pic 4: 41.5" muskie with a wound back towards the tail. This injury was healing very nicely. It had hardened over the wound completely.