Please welcome Eyoyo Underwater Fishing Cameras.https://amzn.to/3siEgXn
Food options can change drastically in winter on some bodies of water. If they were accustomed to asst hatches and their active nymphs during warm water, lack of hatches will send them elsewhere in winter. Worms in the muckier areas or scuds in the heavier weeds may be what they're after. Check stomach contents and go from there
I'm finding gills @ one spot over featureless bottom in 9'; flats adjacent to the shallow weedline. Without the camera I would have never known gills were using this area. Search unlikely spots & they might be there.
exactly townie.i would put money on that featureless bottom being a soft sticky mucky one that is loaded with bugs/grubs/larva.