The picture Kosmo posted appears to be from a 998c Si unit Rickie, so that means the catfish was marked in at least one of the Si beams. That would put the catfish off to one side or the other. If Kosmo would have also posted a screen snapshot of the Si sonar we would know which side it was off to.
Knowing it's a 998c Si unit, I don’t find the shadow strangely placed.
I'm curious to know the clues of the image posting that indicate it was his 998c SI instead of his 597ci HD DI...(orientation of the split screen? Size of the depth digits? Lake bottom presentation in the image?..)