Thermocline And Understanding It

By Perry Hensley

First, let me state that I am still learning and although I have fished for crappie most of my life, I have been trying to dig into where and now why crappie do what they do. Let’s start with the word, stratification, which basically means there are 3 stages of depth in a lake.

First, there is what is known as the Epilimnion Layer. This layer will be found in the upper or shallower layer of the lake, which has the most oxygen content believed to be caused by the growth of vegetation in and around the lake.

Second we have what is known as the Metalimnion Layer and this layer while not having as much oxygen it does however have adequate levels to hold crappie. As a bonus this layer also has the most drastic temperature change of any other layer that will be described here. Needless to say this is my favorite layer.

Finally the Third layer known as the Hypolimnion has the least oxygen content and is much cooler than any other layer and doesn’t hold many fish if any due to those conditions.

Here is the kicker though, as confusing as it can be to some Anglers you can find the thermocline on your depth finder/sonar unit. If you will notice on your unit, most aquatic life will be showing up starting at a certain depth band. For instance, looking at your down imaging with your sensitivity set higher than normal you will see a cloudy layer with most of the fish being in that cloudy range. This is the thermocline.

With fall and winter arriving, along with those cooler water temps, your lake may go through what is called the turnover. The turnover simply is when oxygen levels in the lake will flip-flop, or the thermocline will disappear or become a much deeper or larger layer in the water column. In some cases the oxygen will even out from the top to the bottom. Putting the fish in a wider depth band as mentioned above.

In closing I recommend that you research all the characteristics and patterns of the fish you target in your own lakes. Do some homework to maximize your angling abilities.

As always, I encourage everyone to get out there and make those memories with that friend or loved one and enjoy all that the creator has given us.

God Bless and Tight lines,
Perry Hensley Sr.