Side imaging question

Okay hopefully this question will be a good one. Let me start off By saying that I fish the river a lot and Fish for catfish quite often. With that being said most fish are facing into current at all time including catfish. Now if Im going up or downstream looking at my si wouldnt it be possible to point out if a group of fish consist of large fish or small fish??? That may be a dumb question but its worth asking. I know that with 2d sonar you can't go by that because a large fish could be on the outside of yor sonar cone and still appear small but with my 997 with si it shoots a beam if Im thinking correctly. Am I crazy?? I know that with crappie and even large shad they show up as just very small specks but 2 days ago while playing around with the 997 in the river I marked some very large flecks that were much longer than the shad and fish I was marking at the creek mouths. Sorry if this is a stupid question.

Not a stupid question at all and I believe your analogy is correct relative to the size of the fish on SI..

Some of my instructional pieces have Side Images of both small and large fish.

Small fish (crappies): Using Humminbird Side Imaging to target fall crappies

Large fish (musky): Humminbird Side Imaging and suspended muskies

I included some other fish pics (of primarily larger fish...musky, cats, sturgeon) below. I think it's pretty easy to discern small from large, especially when you start to consider the prominent sonar shadows cast by larger fish.

if you see the white spots stop and fish them that will tell you what is there if you catch anything