Thermocline

[Stump bumper]

I was out for about two hours yesterday around PC and saw a clear thermocline set up at 30 feet. My question is when that is 10 to 20 feet thick on the depth finder is all that shad I am seeing at 35-50 feet? I know a lot of it is plankton and the yellow and red in the therocline looks a lot different then shad balls above it, but sure does look like a lot of shad below it. At one point I was in 80 feet of water and the depth finder was reading 38 feet because of the shad or whatever was in the thermocline.