I'd never seen this on a walleye before.

[Sluggo]

Looks like a lateral line that's incurred some sort of trauma. Crazy!

The trauma being the vicious, eye-crossing hookset by 5575 as riverview mentions above

 

[tikkalover]

Ah yes. I call those the Babe Winkelman hook sets. #$%^&>

 

[DonC]

I know right! Like I said there definitely wasn't blood on the outside of its skin anyways, tried wiping it off.
I had just ran my hand down it before the pic. Just odd I thought.

An obvious republican walleye