The link between fish behavior and water stratification
If you're an impoundment striper fisherman you must know and understand the thermocline to be successful. The thermocline can be found by measuring the water temperature at various depths with a recording thermometer.
The thermocline is a thin layer of water in a lake which is sandwiched between the upper layer of water (the epilimnion) and the lower, colder layer of water (hypolimnion). During the summer months, surface water is heated by the sun and the surface temp could be 80 degrees or more. This floats over a layer of colder more denser water called the hypolimnion. Now, between these 2 layers you have a thin layer in which the water temp drops fairly substantially. This will be the thermocline. The temp at this level may be high 60's and up in about the middle of spring.
This is the home and feeding area for the larger fish. The thermocline layer also has more oxygen and an available food supply.
The hypolimnion layer is the colder water on a typical lake, but is almost devoid of oxygen because of plant and animal decomposition. If the surface temperature is 75 degrees, then the hypolimnion will usually be anywhere from 39 degrees to 55 degrees.
In the summer the stripers cant take the high surface temperatures of the upper layer and the underoxygenated properties of the lower stratum. So hence the necessity of finding the lakes thermocline.
Each fall a lake will "turn over" the cooler top layers will displace the bottom layers and recirculate. The shallow coves are among the first to cool and the bass will begin to relate to shallow structure.
Also fish dont have eyleids and light refracts differntly at dawn and dusk so they are then more likly to surface and feed.
In shallow lakes with an average depth of 15 feet usually no thermocline will develop.
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