NC Crappie, I can't answer that.
I know back in the late '90's. We would fish under and around Ebenezer bridge at night with star-fire lights submerged about 10 ft. Water under bridge was 20 to 30 ft. deep fish were always about 14-16 ft. deep. We would troll in under bridge towards cove side ( not big water side of bridge) we could always fill coolers with 11-13" fish at that same depth as under bridge, fish would be in that 14-16 ft. depth , hugging the bank fall off's in to deeper waters. So as far as if they move to the open water I don't know. IMO, I think they hold on structure in that goldilocks zone of PH and TEMP. near deep water in case of drastic temp. changes and PH changes. Under the bridge they're just moving thru, I would think that bait fish are moving out of open water as wind blows their bait in big coves. But I don't know