If a thermocline is present in a lake, is it present throughout the lake or can it just be in certain parts of it? Reason I ask, I was fishing Saturday night in one of the river channels in a lake, and there was that "line" on my fishfinder at 20ft, and alot of fish arches all around this line, and none on the bottom. I took this to be the thermocline. But then every other area I fished the line wasn't present and I was seeing fish arches along the bottom. Just wondering if I in fact saw the thermocline or if it could have been something else, maybe a school of bait fish or something? Water temps were high 80's.