I have caught most of my bigger fish (not speaking this year) in deeper water, more like 9'-10' trolling. I am talking about fish in the 17" plus range.
As far as spawning in tree tops, when T-Bend was a pretty new lake the bass would spawn in the tree tops in 40' of water. Now not all of them just some. Can't tell you much about crappie in tree tops though.
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