That's good that you know that. This summer, if you see a thermocline set up again, try fishing deeper than the depth where it sets up. Note where you catch fish - below the thermocline or above the thermocline. That will help you determine what depth to set the trap too. Remember fish will normally swim up to take a bait, but rarely swim down more than a foot or so to take a bait.
Also below the thermocline, the O2 levels are typically reduced unless you have tremendous clarity in the water.