Here is a question for those of you much more knowledgeble than me. When I launch just as it’s barely breaking dawn, most mornings my sonar will have a very distinct zone of what looks like thermocline at a certain level that day. It will typically black out the sonar from that level to the bottom. On up the lake towards the Elbow this time of year, it will be much shallower and down below Spence Island it gets much deeper. It was around 30 feet up in Ballentine Sunday morning and I believe it was around 35 feet below Spence as I was running. For years and years, I have used that as my indicator of what depth to look for fish on humps and suspended and it has worked out well for me. It feels like active fish seem to like that break line.
The interesting thing is as it gets more daylight this break line typically gets deeper then fades completely. But it’s so thick just before daylight, you wouldn’t be able to see a fish down in it if you had to. My question is…What is this break line I’m seeing? Since it changes with the amount of daylight, I have always assumed it was phytoplankton but never was sure. If it is phytoplankton, where does it go once it gets to be daylight?