That's a single mark. Bait would be more of a ball shape or a longer flatter line. That's probably a decent size fish since it is showing some yellow in the mark showing that the fish is giving a stronger return in the middle of the mark. The fish was probably not coming up to check a lure but living in that space due to temprature. Looks to be about 70 down over 200 which could indicate a decent temp for a salmon. Hard to say without a temp from a probe.