Over the years I have observed a very interesting baitfish occurrence that happens in freshwater lakes. I have seen it in northern & southern lakes. Usually around Sept., when temperatures start to fall large baitfish schools migrate to deeper water.
When this happens I can see them using my Raymarine CHIRP DownVision screen and they are usually in a very depth-specific “layer”.
I call these “stratified” baitfish. Sometimes there are predetor fish above them or in them, but most of the time I just mark baitfish, no predators. This tells me that while the large baitfish schools have moved to deeper water, probably anticipation a lakes “turn-over”, the predator fish are still looking to feed along shorelines and in water less than 20′ deep on other types of food like; different minnow species, small panfish, crayfish that migrate to slightly deeper water, and other smaller invertebrates. Understanding this change in the biomass of a lake can really help in figuring out where the larger fish will be feeding.