Yea, what they said.
Other than perhaps disrupting previous April fishing patterns, slowly rising water levels are not damaging to fish spawning success.
What is damaging is if we have an excessive rain event and the water levels rise especially high... and the TVA is forced to pull the plug and drop water levels dramatically at the peak of the spawn. That can potentially wipe out a full year-class of crappie or bass. Fortunately that hasn't happened in a long time.
I'm sure TVA water management officials are aware of the potential impact the water levels have on the fishery, but I also understand that their top priority has to be protecting lives and property. If we had been smart enough to NOT build our cities (cough, cough - Chattanooga) in the flood plain, it wouldn't be an issue.
But we did ... emoDoh